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Sample records for irradiated tio2 suspensions

  1. Wavelength-sensitive photocatalytic degradation of methyl orange in aqueous suspension over iron(III)-doped TiO2 nanopowders under UV and visible light irradiation.

    PubMed

    Wang, X H; Li, J-G; Kamiyama, H; Moriyoshi, Y; Ishigaki, T

    2006-04-06

    Well-crystallized iron(III)-doped TiO2 nanopowders with controlled Fe3+ doping concentration and uniform dopant distribution, have been synthesized with plasma oxidative pyrolysis. The photocatalytic reactivity of the synthesized TiO2 nanopowders with a mean particle size of 50-70 nm was quantified in terms of the degradation rates of methyl orange (MO) in aqueous TiO2 suspension under UV (mainly 365 and 316 nm) and visible light irradiation (mainly 405 and 436 nm). The photodecomposition of MO over TiO2 nanopowders followed a distinct two-stage pseudo first order kinetics. Interestingly, the photocatalytic reactivity depends not only on the iron doping concentration but also on the wavelength of the irradiating light. Under UV irradiation, nominally undoped TiO2 had much higher reactivity than Fe3+ -doped TiO2, suggesting that Fe3+ doping (> 0.05 at. %) in TiO2 with a mean particle size of approximately 60 nm was detrimental to the photocatalytic decomposition of methyl orange. Whereas, under visible light irradiation, the Fe3+ -doped TiO2 with an intermediate iron doping concentration of approximately 1 at. % had the highest photocatalytic reactivity due to the narrowing of band gap so that it could effectively absorb the light with longer wavelength. A strategy for improving the photocatalytic reactivity of Fe3+ -doped TiO2 used in the visible light region is also proposed.

  2. Rapid photocatalytic destruction of pentachlorophenol in F-Si-comodified TiO(2) suspensions under microwave irradiation.

    PubMed

    Yang, Shaogui; Fu, Hongbo; Sun, Cheng; Gao, Zhanqi

    2009-01-30

    A novel photocatalysis material, F-Si-comodified TiO(2) (FST) powder, was synthesized by ultrasound-assisted hydrolysis. The prepared material was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible absorption spectroscopy, respectively. XRD analysis indicated that the phase of FST was pure anatase and Si atoms suppressed the growth of titania crystalline, XPS spectra showed that FST was composed of Ti, O, Si and F element, the band gap energy of FST calculated according to the spectrum of UV-vis absorption was 3.26 eV. The electron spin resonance (ESR) spin-trapping technique using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin-trap reagent has been applied to detect free radical intermediates generated from FST. ESR results showed the concentration of the active species (OH) on FST is higher than those on F-doping TiO(2) (FT), Si-modifying TiO(2) (ST) and P25 titania. The degradation of pentachlorophenol (PCP) in the microwave-assisted photocatalysis (MAPC) process was faster than other processes including microwave-assisted direct photolysis (MADP), microwave process alone (MP) and dark process (DP). The photocatalytic activity of FST is much higher than that of ST, FT and P25 titania. It may be attributed to its strong capacity of absorption to the UV-vis irradiation and more hydroxyl radical on surface of FST. In MPAC process, 40 mg L(-1) PCP was completely degraded in 20 min and its corresponding mineralization efficiency was 71%, the pH of solutions decreased from 10.3 to 6.47 and the dechlorination was completed in 12 min. The intermediates products of PCP in MAPC process identified by GC/MS were trichlorophenols (TCP), tetrachlorophenols (TTCP) and tetrachlorocatechol (TTCC) and the possible mechanism of PCP degradation is proposed.

  3. Water - Based TiO2 Suspensions: A Raman Study

    NASA Astrophysics Data System (ADS)

    Rangel, Roberto; Chipara, Dorina; Yust, Brian; Padilla, Desiree; Chipara, Mircea

    The antibacterial features of TiO2 are under scrutiny due to the UV radiation, which contributes to the generation of reactive oxygen species, mainly in water environments. A study of TiO2 suspensions in water and broth is reported. TiO2 has a low solubility in water. TiO2 (anatase), with average diameter of 15 nm from Nanostructured & Amorphous Materials, Inc. has been added to the fluid (water, broth) and the mixture was stirred for 1-10 h, followed by a 10-60 minutes sonication. The suspension was left to sediment for 1 day before measurements. Quasistable suspensions of TiO2 in water and broth were investigated by Raman spectroscopy using a Renishaw InVia spectrometer operating at 532 and 785 nm. The spectra of the nanofiller have been simulated by a collection of Breit-Wigner Fano line shapes and the effect of the preparation conditions (stirring and sonication time) on the parameters of Raman lines are reported. The differences are explained by observing that the sonication destroys the agglomerates of anatase resulting in a better dispersion of nanoparticles and consequently a longer sedimentation time. Sample preparation/storage have been done both under dark and UV light conditions.

  4. UV irradiation induced transformation of TiO2 nanoparticles in water: aggregation and photoreactivity.

    PubMed

    Sun, Jing; Guo, Liang-Hong; Zhang, Hui; Zhao, Lixia

    2014-10-21

    Transformation of nanomaterials in aqueous environment has significant impact on their behavior in engineered application and natural system. In this paper, UV irradiation induced transformation of TiO2 nanoparticles in aqueous solutions was demonstrated, and its effect on the aggregation and photocatalytic reactivity of TiO2 was investigated. UV irradiation of a TiO2 nanoparticle suspension accelerated nanoparticle aggregation that was dependent on the irradiation duration. The aggregation rate increased from <0.001 nm/s before irradiation to 0.027 nm/s after 50 h irradiation, resulting in aggregates with a hydrodynamic diameter of 623 nm. The isoelectric point of the suspension was lowered from 7.0 to 6.4 after irradiation, indicating less positive charges on the surface. ATR-FTIR spectra displayed successive growth of surface hydroxyl groups with UV irradiation which might be responsible for the change of surface charge and aggregation rate. UV irradiation also changed the photocatalytic degradation rate of Rhodamine B by TiO2, which initially increased with irradiation time, then decreased. Based on the photoluminescence decay and photocurrent collection data, the change was attributed to the variation in interparticle charge transfer kinetics. These results highlight the importance of light irradiation on the transformation and reactivity of TiO2 nanomaterials.

  5. Aggregation of stabilized TiO2 nanoparticle suspensions in the presence of inorganic ions.

    PubMed

    Shih, Yang-Hsin; Liu, Wei-Szu; Su, Yuh-Fan

    2012-08-01

    The present study aims to evaluate the effect of inorganic ions on the aggregation kinetics of stabilized titanium dioxide (TiO(2) ) nanoparticle (NP) suspension, an NP mode widely used in consumer goods and in aquatic environments. The point of zero charge of stabilized TiO(2) NPs was approximately pH 6.5. The particle size of the stabilized TiO(2) NP suspensions increased with the increase in salt concentrations. The additional salts caused the shift of zeta potentials of TiO(2) suspensions to a lower value. The TiO(2) NPs aggregated more obviously in the presence of anions than cations, and the effect of divalent anions was larger than that of monovalent anions. The critical coagulation concentration (CCC) values for commercial TiO(2) NP suspensions with positive surfaces were estimated as 290 and 2.3 meq/L for Cl(-) and SO 42-, respectively. These CCC values of stabilized TiO(2) NP suspensions are higher than those of TiO(2) NP powders, indicating greater stability of the commercial stabilized TiO(2) NP suspensions. The effects of commercial TiO(2) NP suspensions still need to be explored and defined. Derjaguin-Landau-Verwey-Overbeek (DLVO) analysis can explain the aggregation behaviors of stabilized TiO(2) NP suspensions. Such an understanding can facilitate the prediction of NP fate in the environment.

  6. TiO2-promoted mineralization of organic sunscreens in water suspension and sodium dodecyl sulfate micelles.

    PubMed

    Ricci, Andrea; Chrétien, Michelle N; Maretti, Luca; Scaiano, J C

    2003-05-01

    The photostability of the widely used UVB sunscreen agents 2'-ethylhexyl-2-cyano-3-phenylcinnamate (1), 2-hydroxy-4-methoxybenzophenone (2), octyl salicilate (3), and 2'-ethylhexyl-4-methoxycinnamate (4) has been investigated under UVA irradiation in the absence and presence of TiO2, an inorganic filter commonly employed in combination with organic filters in sunscreen preparations. In the absence of TiO2, 1-3 are photostable and 4 undergoes the expected E-Z isomerization; the presence of TiO2 caused mineralization of the organic filters and, surprisingly, the process is noticeably faster in the presence of surfactant than in sunscreen and water suspensions. The results indicate that in water suspension, mineralization is likely to occur on or near the TiO2 particle surface; when the organic sunscreens are segregated in the micelle core, reactive radicals, produced during TiO2-promoted degradation of the micellar system, may participate in sunscreen degradation. In addition, a pre-fluorescent probe for carbon-centered radical detection, 4-(3-hydroxy-2-methyl-4-quinolineoxy)-2,2,6,6-tetramethylpiperidine-1-oxyl free radical or QT (5), was employed to demonstrate that carbon-centered radicals are evolved during micelle degradation and may participate in the mineralization of sunscreens.

  7. Properties of TiO2/Au nanocomposite produced by pulsed laser irradiation of mixture of individual colloids

    NASA Astrophysics Data System (ADS)

    Ghorbani, Vahideh; Dorranian, Davoud

    2016-12-01

    TiO2/Au nanocomposite was produced by irradiating the mixture of Au and TiO2 nanoparticle suspensions with the second harmonic beam of Nd:YAG pulsed laser. TiO2 and Au nanoparticles were produced by laser ablation method separately. Titanium dioxide and gold nanoparticles were prepared by ablation of a high purity titanium and gold plates in deionized water, respectively. The fundamental wavelength of a Nd:YAG laser operating at 1064 nm with pulse width of 7 ns and 10 Hz repetition rate was employed to produce nanoparticles. Targets was placed on the bottom of water contain. The synthesized Au and TiO2 colloidal solutions were mixed in equal volumetric ratio and irradiated with the 532 nm laser. The laser spot size was 6 mm on the solution surface, and the laser fluence during the post-irradiation was at 2 J/cm2. Irradiation was done using 5000 pulses at 10 Hz repetition rate and 7 ns pulse width. Results show that the absorption spectrum of nanocomposite is similar to TiO2 spectrum with a surface plasmonic absorption peak at about 530 nm. Both lattice structure of TiO2 and Au nanoparticles appears in the lattice structure of nanocomposite.

  8. Photocatalytic degradation of methylene blue under UV light irradiation on prepared carbonaceous TiO2.

    PubMed

    Ramli, Zatil Amali Che; Asim, Nilofar; Isahak, Wan N R W; Emdadi, Zeynab; Ahmad-Ludin, Norasikin; Yarmo, M Ambar; Sopian, K

    2014-01-01

    This study involves the investigation of altering the photocatalytic activity of TiO2 using composite materials. Three different forms of modified TiO2, namely, TiO2/activated carbon (AC), TiO2/carbon (C), and TiO2/PANi, were compared. The TiO2/carbon composite was obtained by pyrolysis of TiO2/PANi prepared by in situ polymerization method, while the TiO2/activated carbon (TiO2/AC) was obtained after treating TiO2/carbon with 1.0 M KOH solution, followed by calcination at a temperature of 450°C. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TG-DTA), Brunauer-Emmet-Teller (BET), and UV-Vis spectroscopy were used to characterize and evaluate the prepared samples. The specific surface area was determined to be in the following order: TiO2/AC > TiO2/C > TiO2/PANi > TiO2 (179 > 134 > 54 > 9 m(2) g(-1)). The evaluation of photocatalytic performance for the degradation of methylene blue under UV light irradiation was also of the same order, with 98 > 84.7 > 69% conversion rate, which is likely to be attributed to the porosity and synergistic effect in the prepared samples.

  9. Alternating current electrophoretic deposition (EPD) of TiO2 nanoparticles in aqueous suspensions.

    PubMed

    Chávez-Valdez, A; Herrmann, M; Boccaccini, A R

    2012-06-01

    TiO(2)-nanostructured coatings from aqueous suspensions have been successfully prepared by the application of alternating current (AC) instead of direct current (DC) during electrophoretic deposition (EPD). No organic additives in suspension were required for successful EPD. The quality of the AC-EPD TiO(2) coatings in terms of homogeneity and extent of microcracking, upon drying, observed by SEM, was superior to that of DC-EPD coatings made from the same type of suspensions. The main difference between AC- and DC-EPD was the suppression of bubble formation. The absence of water electrolysis at the electrodes can be explained by the particular distribution of the electric field during AC mode, which prevents the nucleation of bubbles. The preparation of TiO(2) coatings from aqueous suspension and without the aid of organic stabilizers opens the possibility for co-deposition of sensitive materials such as biomolecules and even cells for biomedical applications, given the high biocompatibility of TiO(2). The deposition of TiO(2) coatings from aqueous suspensions is also attractive from environmental and economical points of view.

  10. TiO2 nanoparticles suppress Escherichia coli cell division in the absence of UV irradiation in acidic conditions.

    PubMed

    Zhukova, Lyudmila V; Kiwi, John; Nikandrov, Vitaly V

    2012-09-01

    TiO(2) nanoparticles (NPs) activated by UV irradiation are known to have a bactericidal effect. In this study we report the details of TiO(2) NPs influence on the colony-forming capacity of E. coli in the dark at pH 4.0-4.5. At this pH the bacterial cells are negatively charged and TiO(2) NPs present a positive charge. A 60 min contact between E. coli with TiO(2) at concentrations of 0.02-0.2 mg/mL led to a reduction of E. coli cell number from 10(8) to 10(4)CFU/mL. After the reduction the system remains unchanged during the subsequent incubation. The observed reduction was a function on the initial E. coli concentration. In the presence of 0.04 mg/mL TiO(2) the colony-forming units (CFU) reduction after 60 min was of four-five orders of magnitude when the initial concentration was 10(8) cells/mL. But when starting with an E. coli concentration of 10(7) cells/mL the cell number reduction was less than one order of magnitude. Less than one order of magnitude cell number reduction was also observed for suspensions of E. coli 10(8) cells/mL and 0.002 mg/mL of TiO(2). The bacteria number reduction was always accompanied by the formation of cell aggregates. During cell incubation with TiO(2), the pH of the suspension increased, but did not reach the TiO(2) isoelectric point (IEP). E. coli cells stained with the fluorescent dye acridine orange (AO) showed that the fluorescence of single cells remained unchanged after incubation in the presence of TiO(2). The color change of fluorescence was revealed only in aggregated cells. This suggests changes in the physiologic state of E. coli incorporated into the aggregates. Aggregates of E. coli occur due to the electrostatic interaction between TiO(2) NPs and the bacterial cell surface. A hypothesis is suggested in this study to explain the CFU reduction and the retention of a certain irreducible number of cells capable of further division in the suspension in the presence of TiO(2) in the dark.

  11. Characteristics of dye-sensitized solar cell with TiO2 anode under UV irradiation

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Kwei; Hsiao, Chih-Chen; Weng, Hao-Wei

    2016-03-01

    The anatase phase crystalline quality of commercial TiO2 (P25) nanoparticle sintered in air and N2 is improved. Compared DSSC with air-sintered TiO2 anode, DSSC with N2-sintered TiO2 anode has better performance mainly from high optical absorption efficiency. Under UV irradiation, organic contaminants adsorbed on TiO2 are dissociated by the photocatalysis, and the dye adsorption is enhanced. The DSSC performance with UV-treated/N2-sintered TiO2 anode is further improved.

  12. Photodegradation of crystal violet in TiO(2) suspensions using UV-vis irradiation from two microwave-powered electrodeless discharge lamps (EDL(-2)): products, mechanism and feasibility.

    PubMed

    Ju, Yongming; Fang, Jiande; Liu, Xiaowen; Xu, Zhencheng; Ren, Xiuwen; Sun, Cheng; Yang, Shaogui; Ren, Qian; Ding, Youchao; Yu, Kai; Wang, Lianhong; Wei, Zhongbo

    2011-01-30

    Aqueous crystal violet (CV) solutions containing P25-TiO(2) photocatalyst were irradiated with ultraviolet-visible (UV-vis) light from two microwave-powered electrodeless discharge lamps (EDL(-2)). The results demonstrated that approximately 94.4% of CV was effectively removed after 3 min of irradiation, with a pseudo-first order kinetic constant of 0.838 min(-1). According to 32 kinds of products, a five-step degradation pathway of CV was proposed. Further investigations showed that (1) three kinds of N-demethylated products and 4-dimethylaminobenzophenone (DLBP) were the main intermediates; (2) malachite green (MG) and leuco-crystal violet could not be generated by N-demethylation and phototransformation reactions, respectively; (3) bis(4-(dimethylamino)phenyl)methanone preferentially generated via decomposition of the conjugated structure of CV could be further N-demethylated into DLBP. Moreover, the unique degradation pathways of CV and MG were ascribed to the different substituents on the conjugated structures. Additionally, the cost and kinetic constant of different processes was also evaluated, and the results indicated the feasibility of this method for treatment of CV in field situations.

  13. Degradation of organic gases using ultrasonic mist generated from TiO2 suspension.

    PubMed

    Sekiguchi, Kazuhiko; Noshiroya, Daisuke; Handa, Misako; Yamamoto, Keisuke; Sakamoto, Kazuhiko; Namiki, Norikazu

    2010-09-01

    The photocatalytic degradation of organic gases with mist particles that were formed by ultrasonic atomization of a TiO(2) suspension was performed with three different ultraviolet light sources. Three aromatic volatile organic compounds (VOCs; toluene, p-xylene, and styrene) and aldehydes (formaldehyde and acetaldehyde) were chosen as model organic gases for the degradation experiment. Under UV(365) irradiation, toluene was decomposed by a photocatalytic reaction on the surface of mist particles. Under UV(254+185) irradiation, the removal efficiency and mineralization ratio of the VOC gases were higher than those under UV(365) or UV(254) irradiation. Under UV(254+185) irradiation, it was found that VOC gases were immediately degraded and converted to water-soluble intermediates by not only direct photolysis but also oxidation by OH radical, since the removal efficiency of several organic gases depended on the reaction rate with OH radical and the primary effect of generated ozone was to complete the mineralization of the intermediates. On the other hand, water-soluble aldehyde gases were rapidly trapped by mist particles before reaction on their surface. Furthermore, water-soluble intermediates that formed via the decomposition of VOC gases were completely trapped in the mist and were not detected at the reactor exit. Therefore, notable secondary particle generation was not observed, even under UV(254+185) irradiation. Based on these results as well as the size distribution of the mist droplets, it was found that primarily submicron-scale droplets contributed to the photocatalytic reaction. Lastly, we propose a mechanism for the degradation of organic gaseous pollutants on the surface of mist particles.

  14. Microwave irradiation induced band gap tuning of MoS2-TiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Shakya, Jyoti; Mohanty, T.

    2016-05-01

    The MoS2-TiO2 nanocomposites have been synthesized by sol-gel method and characterized by different microscopic and spectroscopic techniques. The crystallinity of these nanocomposites has been confirmed by X-ray diffraction (XRD) analysis. The Raman spectrum of MoS2-TiO2 nanocomposites consists of three distinct peaks (E1 g, E1 2g and A1g) which are associated with TiO2 and MoS2. The morphological study is carried out by scanning electron microscope. The effect of microwave irradiation on the band gap of MoS2-TiO2 nanocomposites has been investigated; it is observed that the microwave irradiation causes decrease in the band gap of MoS2-TiO2 nanocomposites. The microwave treated MoS2-TiO2 thin films offers a novel process route in treating thin films for commercial applications.

  15. Remediation of 17-α-ethinylestradiol aqueous solution by photocatalysis and electrochemically-assisted photocatalysis using TiO2 and TiO2/WO3 electrodes irradiated by a solar simulator.

    PubMed

    Oliveira, Haroldo G; Ferreira, Leticia H; Bertazzoli, Rodnei; Longo, Claudia

    2015-04-01

    TiO2 and TiO2/WO3 electrodes, irradiated by a solar simulator in configurations for heterogeneous photocatalysis (HP) and electrochemically-assisted HP (EHP), were used to remediate aqueous solutions containing 10 mg L(-1) (34 μmol L(-1)) of 17-α-ethinylestradiol (EE2), active component of most oral contraceptives. The photocatalysts consisted of 4.5 μm thick porous films of TiO2 and TiO2/WO3 (molar ratio W/Ti of 12%) deposited on transparent electrodes from aqueous suspensions of TiO2 particles and WO3 precursors, followed by thermal treatment at 450 (°)C. First, an energy diagram was organized with photoelectrochemical and UV-Vis absorption spectroscopy data and revealed that EE2 could be directly oxidized by the photogenerated holes at the semiconductor surfaces, considering the relative HOMO level for EE2 and the semiconductor valence band edges. Also, for the irradiated hybrid photocatalyst, electrons in TiO2 should be transferred to WO3 conduction band, while holes move toward TiO2 valence band, improving charge separation. The remediated EE2 solutions were analyzed by fluorescence, HPLC and total organic carbon measurements. As expected from the energy diagram, both photocatalysts promoted the EE2 oxidation in HP configuration; after 4 h, the EE2 concentration decayed to 6.2 mg L(-1) (35% of EE2 removal) with irradiated TiO2 while TiO2/WO3 electrode resulted in 45% EE2 removal. A higher performance was achieved in EHP systems, when a Pt wire was introduced as a counter-electrode and the photoelectrodes were biased at +0.7 V; then, the EE2 removal corresponded to 48 and 54% for the TiO2 and TiO2/WO3, respectively. The hybrid TiO2/WO3, when compared to TiO2 electrode, exhibited enhanced sunlight harvesting and improved separation of photogenerated charge carriers, resulting in higher performance for removing this contaminant of emerging concern from aqueous solution.

  16. Microwave assisted rapid and complete degradation of atrazine using TiO(2) nanotube photocatalyst suspensions.

    PubMed

    Zhanqi, Gao; Shaogui, Yang; Na, Ta; Cheng, Sun

    2007-07-16

    A technology, microwave-assisted photocatalysis on TiO(2) nanotubes, which can be applied to degrade atrazine rapidly and completely, was investigated. TiO(2) nanotubes were prepared, and confirmed by XRD, TEM and ESR. Microwave-assisted photocatalytic degradation of atrazine in aqueous solution was investigated. The result indicates that atrazine is completely degraded in 5min and the mineralization efficiency is 98.5% in 20min, which is obviously more efficient than that by the traditional photocatalytic degradation methods. It may be attributed to the intense UV radiation generated by electrodeless discharge lamps under microwave irradiation, the increased number of OH, additional defect sites on TiO(2) under the irradiation of microwave and larger specific surface area of TiO(2) nanotubes which could adsorb more organic substances to degrade than TiO(2) nanoparticles. Along with the degradation of atrazine, the concentrations of Cl(-) and NO(3)(-) increase gradually. In 20min [Cl(-)] and [NO(3)(-)] are 3, 27.8mg/L, respectively, which are close to their stoichiometric values. The major intermediates of atrazine were identified by HPLC/MS and possible degradation pathways of atrazine in microwave-assisted photocatalysis on TiO(2) nanotubes were proposed.

  17. Study of gamma irradiation effect on commercial TiO2 photocatalyst.

    PubMed

    Bello Lamo, M P; Williams, P; Reece, P; Lumpkin, G R; Sheppard, L R

    2014-07-01

    The aim of this work is to understand the effect of gamma irradiation on commercial TiO2 photocatalyst for water treatment applications. Previous studies concluded that gamma-irradiation is able to modify the electronic properties of TiO2 based photocatalysts and consequently their photocatalytic performance. However, there are some discrepancies in the literature where on one hand a significant enhancement of the material properties is reported and on the other hand only a weak effect is observed. In this study a surface effect on TiO2 is confirmed by using low and medium gamma irradiation doses.

  18. Highly Crystalline Nanoparticle Suspensions for Low-Temperature Processing of TiO2 Thin Films.

    PubMed

    Watté, Jonathan; Lommens, Petra; Pollefeyt, Glenn; Meire, Mieke; De Buysser, Klaartje; Van Driessche, Isabel

    2016-05-25

    In this work, we present preparation and stabilization methods for highly crystalline TiO2 nanoparticle suspensions for the successful deposition of transparent, photocatalytically active TiO2 thin films toward the degradation of organic pollutants by a low temperature deposition method. A proof-of-concept is provided wherein stable, aqueous TiO2 suspensions are deposited on glass substrates. Even if the processing temperature is lowered to 150-200 °C, the subsequent heat treatment provides transparent and photocatalytically active titania thin layers. Because all precursor solutions are water-based, this method provides an energy-efficient, sustainable, and environmentally friendly synthesis route. The high load in crystalline titania particles obtained after microwave heating opens up the possibility to produce thin coatings by low temperature processing, as a conventional crystallization procedure is in this case superfluous. The impact of the precursor chemistry in Ti(4+)-peroxo solutions, containing imino-diacetic acid as a complexing ligand and different bases to promote complexation was studied as a function of pH, reaction time and temperature. The nanocrystal formation was followed in terms of colloidal stability, crystallinity and particle size. Combined data from Raman and infrared spectroscopy, confirmed that stable titanium precursors could be obtained at pH levels ranging from 2 to 11. A maximum amount of 50.7% crystallinity was achieved, which is one of the highest reported amounts of anatase nanoparticles that are suspendable in stable aqueous titania suspensions. Decoloring of methylene blue solutions by precipitated nanosized powders from the TiO2 suspensions proves their photocatalytic properties toward degradation of organic materials, a key requisite for further processing. This synthesis method proves that the deposition of highly crystalline anatase suspensions is a valid route for the production of photocatalytically active, transparent

  19. Antimicrobial photodisinfection with Zn(II) phthalocyanine adsorbed on TiO2 upon UVA and red irradiation

    NASA Astrophysics Data System (ADS)

    Mantareva, Vanya; Eneva, Ivelina; Kussovski, Vesselin; Borisova, Ekaterina; Angelov, Ivan

    2015-01-01

    The light exposure on a daily basis has been well accepted as a competitive method for decontamination of wastewater. The catalytic properties of TiO2 offer a great potential to reduce the transmission of pathogens in the environment. Although the titanium dioxide shows high activity against pathogens, its general usage in water cleaning is limited due to the insufficient excitation natural light (about 3% of the solar spectrum). A hydrophobic dodecylpyridyloxy Zn(II)-phthalocyanine with four peripheral hydrocarbon chains of C12 (ZnPcDo) was immobilized on a photocatalyst TiO2 anatase (P25). The resulted greenish colored nanoparticles of phthalocyanine were characterized by the means of absorption, fluorescence and infrared spectroscopy. The laser scanning confocal fluorescence microscopy was used to visualize the phthalocyanine dye by the red fluorescence emission (650 - 740 nm). The intensive Q-band in the far red visible spectral region (~ 690 nm) suggested a monomeric state of phthalocyanine on TiO2 nanoparticles. Two pathogenic bacterial strains (methicillin-resistant Staphylococcus aureus - MRSA and Salmonella enteritidis) associated with wastewater were photoinactivated with the suspension of the particles. The effective photoinactivation was observed with 1 g.L-1 TiO2 anatase at irradiation with UVA 364 nm as with UVA 364 nm and LED 643 nm. The gram-negative Salmonella enteritidis was fully photoinactivated with ZnPcDo-TiO2 and TiO2 alone at UVA 346 nm and at irradiation with two light sources (364 nm + 643 nm). The proposed conjugate appears as an useful composite material for antibacterial disinfection.

  20. Synergistic effects between TiO2 and carbon nanotubes (CNTs) in a TiO2/CNTs system under visible light irradiation.

    PubMed

    Wu, Chung-Hsin; Kuo, Chao-Yin; Chen, Shih-Ting

    2013-01-01

    This study synthesized a TiO2/carbon nanotubes (CNTs) composite via the sol-gel method. The surface characteristics of the TiO2/CNTs composite were determined by X-ray diffraction, transmission electron microscopy, specific surface area analyser, ultraviolent (UV)-vis spectroscopy, X-ray photoelectron spectroscopy and Raman spectrometer. The photocatalytic activity ofthe TiO2/CNTs composite was evaluated by decolourizing C.I. Reactive Red 2 (RR2) under visible light irradiation. Furthermore, the effects of calcination temperature, pH, RR2 concentration, and the TiO2/CNTs composite dosage on RR2 decolourization were determined simultaneously. The optimal calcination temperature to generate TiO2 and the TiO2/CNTs composite was 673 K, as the percentage of anatase crystallization at this temperature was highest. The specific surface area of the TiO2/CNTs composite and TiO2 were 45 and 42 m2/g, respectively. The band gap of TiO2 and the TiO2/CNTs composite was 2.97 and 2.71 eV by UV-vis measurements, respectively. Experimental data indicate that the Ti-O-C bond formed in the TiO2/CNTs composite. The RR2 decolourization rates can be approximated by pseudo-first-order kinetics; moreover, only the TiO2/CNTs composite had photocatalytic activity under visible light irradiation. At pH 7, the RR2 decolourization rate constant of 0.5, 1 and 2 g/L TiO2/CNTs addition was 0.005, 0.0015, and 0.0047 min(-1), respectively. Decolourization rate increased as pH and the RR2 concentration decreased. The CNTs functioned as electron acceptors, promoting separation of photoinduced electron-hole pairs to retard their recombination; thus, photocatalytic activity of the TiO2/CNTs composite exceeded that of TiO2.

  1. Photocatalytic degradation of nonionic surfactant, Brij 35 in aqueous TiO2 suspensions.

    PubMed

    Eng, Yong Yong; Sharma, Virender K; Ray, Ajay K

    2010-03-01

    The photocatalytic oxidation of nonionic surfactant, Brij 35 in aqueous TiO2 suspensions was investigated as a function of catalysts loading, light intensity (I), initial Brij 35 concentration [Brij](0), dissolved oxygen concentration [p(O2)], and pH. A monolithic swirl-flow photoreactor was used that allowed to perform a systematic analysis of rates at various loadings of TiO22 in order to distinguish "kinetic" and "transport" limited regimes for the photocatalytic degradation of Brij 35 in TiO2 suspensions. The optimal catalyst loading was determined to be 0.1 g L(-1) TiO2 at a neutral pH. The true kinetic dependences of the photocatalytic degradation on I and [Brij](0) were determined. A small increase in oxidation rate was observed with an increase in the partial pressure of the oxygen [p(O2)] in the system. The rates as a function of [Brij](0) and [p(O2)] were interpreted using a Langmuir-Hinshelwood model. The complete photocatalytic degradation of Brij 35 was obtained in acidic to basic pH range, however, the removal of Brij 35 removal and subsequent decrease in TOC levels were more efficient at a neutral pH than acidic or basic pH.

  2. Synthesis and electrorheological effect of Cr doped TiO2 nanorods with nanocavities in silicone oil suspensions

    NASA Astrophysics Data System (ADS)

    Almajdalawi, S.; Pavlinek, V.; Mrlik, M.; Cheng, Q.; Sedlacik, M.

    2013-02-01

    Titanium dioxide (TiO2) nanorods with nanocavities doped with chromium (Cr) were synthesized by hydrothermal method. The morphology of prepared nanorods was determined by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). The electrorheological (ER) behaviour of suspensions based on TiO2 was investigated under the steady shear, and the yield stress was chosen as a suitable tool for a comparison of ER performance. Some optimum in level of Cr doping of TiO2 was found.

  3. A spectroscopic study of dyes decomposition by irradiated nanocrystalline TiO2

    NASA Astrophysics Data System (ADS)

    Rosu, M. C.; Suciu, R. C.; Kasco, I.; Dreve, S. V.; Indrea, E.; Silipas, T. D.

    2009-08-01

    The photocatalytic activity of the TiO2 films prepared by wet-chemical techniques and deposited on the ITO glass was tested by examining the decomposition of violet gentian (VG), methylen blue (MB) and methyl green (MG) aqueous solutions under UV light illumination. The photodegradation processes of dyes have been studied using UV-VIS spectrophotometry and spectrofluorimetry. The comparative results of the present study demonstrate the capability of UV irradiation of the TiO2/ITO photocatalytic system to degrade studied organic dyes from aqueous solutions.

  4. Effect of sunlight irradiation on photocatalytic pyrene degradation in contaminated soils by micro-nano size TiO2.

    PubMed

    Chang Chien, S W; Chang, C H; Chen, S H; Wang, M C; Madhava Rao, M; Satya Veni, S

    2011-09-01

    The enhanced catalytic pyrene degradation in quartz sand and alluvial and red soils by micro-nano size TiO(2) in the presence and absence of sunlight was investigated. The results showed that the synergistic effect of sunlight irradiation and TiO(2) was more efficient on pyrene degradation in quartz sand and red and alluvial soils than the corresponding reaction system without sunlight irradiation. In the presence of sunlight irradiation, the photooxidation (without TiO(2)) of pyrene was very pronounced in alluvial and red soils and especially in quartz sand. However, in the absence of sunlight irradiation, the catalytic pyrene degradation by TiO(2) and the photooxidation (without TiO(2)) of pyrene were almost nil. This implicates that ultra-violet (UV) wavelength range of sunlight plays an important role in TiO(2)-enhanced photocatalytic pyrene degradation and in photooxidation (without TiO(2)) of pyrene. The percentages of photocatalytic pyrene degradation by TiO(2) in quartz sand, alluvial and red soils under sunlight irradiation were 78.3, 23.4, and 31.8%, respectively, at 5h reaction period with a 5% (w/w) dose of the amended catalyst. The sequence of TiO(2)-enhanced catalytic pyrene degradation in quartz sand and alluvial and red soils was quartz sand>red soil>alluvial soil, due to different texture and total organic carbon (TOC) contents of the quartz sand and other two soils. The differential Fourier transform infrared (FT-IR) spectra of degraded pyrene in alluvial soil corroborate that TiO(2)-enhanced photocatalytic degradation rate of degraded pyrene was much greater than photooxidation (without TiO(2)) rate of degraded pyrene. Based on the data obtained, the importance for the application of TiO(2)-enhanced photocatalytic pyrene degradation and associated organic contaminants in contaminated soils was elucidated.

  5. Evolution of damage fraction due to dense ionizing irradiation on TiO2 film

    NASA Astrophysics Data System (ADS)

    Kumar, Avesh; Kanjilal, D.; Mohanty, T.

    2013-10-01

    The evolution of damage fraction during dense ionizing irradiation at various fluences using 100 MeV Ag ion is studied. Irradiation induced modification of surface roughness and surface potential of titanium dioxide nanocrystalline thin films are estimated. TiO2 thin films deposited on Si (1 0 0) substrate were irradiated by 100 MeV Ag ion beam with varying fluences. Ion bombardment generates point and extended defects in TiO2 thin films due to dense electronic excitation. The surface morphology and surface roughness of irradiated and pristine thin films were measured using atomic force microscopy. The changes in surface potential of pristine as well as Ag ion beam irradiated thin films were measured from contact potential difference between TiO2 thin film (one electrode) of unknown work function and Au (reference electrode) of known work function using scanning Kelvin probe microscopy. The defect size and damage fraction are calculated from exponential fitting of variation of both contact surface potential difference and roughness exponent with fluence.

  6. TiO2 films photocatalytic activity improvements by swift heavy ions irradiation

    NASA Astrophysics Data System (ADS)

    Rafik, Hazem; Mahmoud, Izerrouken; Mohamed, Trari; Abdenacer, Benyagoub

    2014-08-01

    TiO2 thin films synthesized by sol-gel on glass substrates are irradiated by 90 MeV Xe ions at various fluences and room temperature under normal incidence. The structural, electrical, optical and surface topography properties before and after Xe ions irradiation are investigated. X-ray diffraction (XRD) reveals that the crystallinity is gradually destroyed, and the films become amorphous above 5×1012 ions/cm2. The band gap is not affected by Xe ions irradiation as evidenced from the optical measurements. By contrast, the conductivity increases with raising Xe fluence. The energy band diagram established from the electrochemical characterization shows the feasibility of TiO2 films for the photo-electrochemical chromate reduction. Xe ion irradiation results in enhanced photocatalytic activity in aquatic medium, evaluated by the reduction of Cr(VI) into trivalent state. TiO2 films irradiated at 1013 Xe/cm2 exhibit the highest photoactivity; 69% of chromate (10 ppm) is reduced at pH 3 after 4 h of exposure to sunlight (1120 mW cm-2) with a quantum yield of 0.06%.

  7. Comparative study on toxicity of ZnO and TiO2 nanoparticles on Artemia salina: effect of pre-UV-A and visible light irradiation.

    PubMed

    Bhuvaneshwari, M; Sagar, Bhawana; Doshi, Siddharth; Chandrasekaran, N; Mukherjee, Amitava

    2017-02-01

    This study evaluated the toxicity potential of ZnO and TiO2 nanoparticles under pre-UV-A irradiation and visible light condition on Artemia salina. The nanoparticle suspension was prepared in seawater medium and exposed under pre-UV-A (0.23 mW/cm(2)) and visible light (0.18 mW/cm(2)) conditions. The aggregation profiles of both nanoparticles (NPs) and dissolution of ZnO NPs under both irradiation conditions at various kinetic intervals (1, 24, 48 h) were studied. The 48-h LC50 values were found to be 27.62 and 71.63 mg/L for ZnO NPs and 117 and 120.9 mg/L for TiO2 NPs under pre-UV-A and visible light conditions. ZnO NPs were found to be more toxic to A. salina as compared to TiO2 NPs. The enhanced toxicity was observed under pre-UV-A-irradiated ZnO NPs, signifying its phototoxicity. Accumulation of ZnO and TiO2 NPs into A. salina depends on the concentration of particles and type irradiations. Elimination of accumulated nanoparticles was also evident under both irradiation conditions. Other than ZnO NPs, the dissolved Zn(2+) also had a significant effect on toxicity and accumulation in A. salina. Increased catalase (CAT) activity in A. salina indicates the generation of oxidative stress due to NP interaction. Thus, this study provides an understanding of the toxicity of photoreactive ZnO and TiO2 NPs as related to the effects of pre-UV-A and visible light irradiation.

  8. Influence of laser irradiating energy on optical properties and morphology of TiO2 films

    NASA Astrophysics Data System (ADS)

    Guo, Fang; Xu, Junqi; Su, Junhong; Dang, Shaokun

    2013-12-01

    The optical thin film parts are important components used in the laser systems. In practice, the electromagnetic field generated by the laser will make complex and diverse changes on the films, but the fundamental related with properties changing is not clear. For the purpose of recognizing the variation of TiO2 films irradiated by the laser, TiO2 films were prepared on K9 substrates at the same experimental conditions with the exception that the irradiating laser energy was different to investigate effects about the film's properties and morphology between the before and after irradiation. The following film's factors: transmittance, refractive index, extinction coefficient, film thickness and laser-induced damage threshold (LIDT) are included in experimental results, also, morphology and roughness by an Atomic Force Microscope (AFM) and a Taylor Surf CCI 2000 non-contact instrument are needed. The result showed that irradiating laser can decrease TiO2 films' transmittance and roughness, and increases the films' refractive index and LIDT. Furthermore, the results indicated that different laser energy cause the different morphology of films.

  9. Aggregation of TiO2-graphene nanocomposites in aqueous environment: Influence of environmental factors and UV irradiation.

    PubMed

    Hua, Zulin; Zhang, Jianan; Bai, Xue; Ye, Zhengfang; Tang, Zhiqiang; Liang, Lu; Liu, Yuqi

    2016-01-01

    The aggregation kinetics of TiO2-graphene nanocomposites in aqueous solution affected by solution pH, salt types (NaCl, CaCl2) and concentrations of electrolytes, and stability induced by UV irradiation was investigated in this study. The zeta potentials and hydrodynamic diameter of the nanoparticles were used as bases to assess the aggregation behavior, and stability of nanocomposites exposed to UV irradiation was expressed in terms of supernatant concentration. The aggregation of TiO2-graphene nanoparticles in aqueous media followed the colloidal theory. TiO2-graphene nanoparticles were significantly aggregated in the presence of a diavalent cation compared with monovalent cation because the former was more capable of effective charge screening and neutralization. The calculated Hamaker constant of the TiO2-graphene nanocomposites in aqueous solution prepared in the lab was 2.31×10(-20)J. The stability of this composite nanoparticles was between those of pure TiO2 and graphene. A known intensity of UV irradiation was beneficial in the formation of TiO2-graphene nanoparticle aggregates. However, prolonged UV irradiation may stabilize the nanoparticles. These results provided critical information about the colloidal properties of the new TiO2-graphene nanocomposites and were useful in predicting the fate and transport of TiO2-graphene nanocomposites in natural water environments.

  10. The surface of root canal irradiated by Nd:YAG laser with TiO2

    NASA Astrophysics Data System (ADS)

    Ebihara, Arata; Anjo, Tomoo; Takeda, Atsushi; Suda, Hideaki

    2004-05-01

    The aim of this study was to determine the appropriateness of Nd:YAG laser irradiation for root canal preparation. Tooth crowns were removed from single-rooted human teeth and a quartz optical fiber (diameter 400 μm) was inserted into the root canal orifice towards the apical foramen. The length of the fiber within the root canal was measured, and the irradiating length determined. Root canals were then filled with 3% TiO2 emulsion solution (a photosensitizer) and irradiated using a pulsed Nd:YAG laser at 600 mJ/pulse (pulse frequency; 5 or 10 pps). During laser irradiation, the fiber was moved coronally from the apical region towards the canal orifice at a rate of 1 mm/s. Contact microradiographs (CMR) were taken before and after laser irradiation. Each root was then halved longitudinally, and the root canal surface observed by scanning electron microscopy (SEM). The CMR images of the tooth revealed that the root canal was slightly enlarged as a result of treatment. Carbonization of the root canal dentin was not seen, but a smear layer and melted dentin were observed by SEM. Nd:YAG laser irradiation using TiO2 emulsion solution appears to be a useful tool for root canal preparation.

  11. Photocatalytic degradation of commercial methyl parathion in aqueous suspension containing La-doped TiO2 nanoparticles.

    PubMed

    Chen, Hao; Shen, Min; Chen, Ruiwen; Dai, Ke; Peng, Tianyou

    2011-10-01

    The photocatalytic degradation of a commercial methyl parathion (MP) under UV irradiation was investigated in aqueous suspension containing lanthanum-doped mesoporous TiO2 nanoparticles (La/m-TiO2) as photocatalyst. The rate of photodecomposition of MP was measured using UV-Vis spectrophotometry, and its mineralization was followed using ion chromatography (IC). The identification of possible intermediate products was carried out using several powerful analytical techniques such as gas chromatography-pulsed flame photometric detector (GC-PFPD) and high performance liquid chromatography-mass spectroscopy (HPLC-MS). Under our conditions, complete disappearance of 20 mg/L of MP occurred within 2 h of illumination, whereas complete mineralization of MP was not achieved through IC analysis. There was a single intermediate product found in the research, which was identified to be methyl paraoxon, owing to the substitution of S by the O atom in the MP molecule. Based on the experimental facts, it is concluded that MP was mainly attacked not by OH radicals but photo-generated holes (h+), resulting from the good adsorption of MP on the catalyst surfaces due to the enhanced adsorption by La doping.

  12. Hydrogen irradiation on TiO2 nano-thin films

    NASA Astrophysics Data System (ADS)

    Heidari, Sh.; Mohammadizadeh, M. R.; Mahjour-Shafiei, M.; Larijani, M. M.; Malek, M.

    2015-10-01

    Titanium dioxide thin films were coated on soda-lime glass substrates using spray pyrolysis method with a thickness of 152 ± 10 nm. The films were irradiated with hydrogen ions at room temperature at various beam energies and fluences. Optimized incident beam energy and beam fluence were obtained to improve photocatalytic and hydrophilicity properties of TiO2 thin films by narrowing the band gap. Samples were characterized by scanning electron microscopy to study the surface morphology and by UV-Vis absorption spectroscopy to measure the band gap. The optical band gap of H-doped anatase TiO2 thin films irradiated with hydrogen beam with energies of 2 and 4 keV and a fluence of 1015 ions/cm2 was narrowed from 3.34 eV (before irradiation) to 3.04 and 2.92 eV (after irradiation), respectively. The irradiated sample with energy of 4 keV with a fluence of 1015 ions/cm2 has the best improvement. This is attributed to the contraction of the band gap and to the increase in surface active site. Furthermore, it was observed that photocatalytic and hydrophilicity properties of this sample were improved, as well.

  13. Electrospun nanofibers of Bi-doped TiO2 with high photocatalytic activity under visible light irradiation.

    PubMed

    Xu, Jie; Wang, Wenzhong; Shang, Meng; Gao, Erping; Zhang, Zhijie; Ren, Jia

    2011-11-30

    Bi-doped TiO(2) nanofibers with different Bi content were firstly prepared by an electrospinning method. The as-prepared nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence spectra (PL), and UV-vis diffuse reflectance spectroscopy (DRS). The results indicated that Bi(3+) ions were successfully incorporated into TiO(2) and extended the absorption of TiO(2) into visible light region. The photocatalytic experiments showed that Bi-doped TiO(2) nanofibers exhibited higher activities than sole TiO(2) in the degradation of rhodamine B (RhB) and phenol under visible light irradiation (λ>420 nm), and 3% Bi:TiO(2) samples showed the highest photocatalytic activities.

  14. Shape-dependent bactericidal activity of TiO2 for the killing of Gram-negative bacteria Agrobacterium tumefaciens under UV torch irradiation.

    PubMed

    Aminedi, Raghavendra; Wadhwa, Gunveen; Das, Niranjan; Pal, Bonamali

    2013-09-01

    This paper demonstrated the relative bactericidal activity of photoirradiated (6W-UV Torch, λ > 340 nm and intensity = 0.64 mW/cm(2)) P25-TiO2 nanoparticles, nanorods, and nanotubes for the killing of Gram-negative bacterium Agrobacterium tumefaciens LBA4404 for the first time. TiO2 nanorod (anatase) with length of 70-100 nm and diameter of 10-12 nm, and TiO2 nanotube with length of 90-110 nm and diameter of 9-11 nm were prepared from P-25 Degussa TiO2 (size, 30-50 nm) by hydrothermal method and compared their biocidal activity both in aqueous slurry and thin films. The mode of bacterial cell decomposition was analyzed through transmission electron microscopy (TEM), Fourier transform-infrared (FT-IR), and K(+) ion leakage. The antimicrobial activity of photoirradiated TiO2 of different shapes was found to be in the order P25-TiO2 > nanorod > nanotube which is reverse to their specific surface area as 54 < 79 < 176 m(2) g(-1), evidencing that the highest activity of P25-TiO2 nanoparticles is not due to surface area as their crystal structure and surface morphology are entirely different. TiO2 thin films always exhibited less photoactivity as compared to its aqueous suspension under similar conditions of cell viability test. The changes in the bacterial surface morphology by UV-irradiated P25-TiO2 nanoparticles was examined by TEM, oxidative degradation of cell components such as proteins, carbohydrates, phospholipids, nucleic acids by FT-IR spectral analysis, and K(+) ion leakage (2.5 ppm as compared to 0.4 ppm for control culture) as a measure of loss in cell membrane permeability.

  15. Effects of electron beam irradiation on the photoelectrochemical properties of TiO2 film for DSSCs

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Bin; Park, Dong-Won; Jeun, Joon-Pyo; Oh, Seung-Hwan; Nho, Young-Chang; Kang, Phil-Hyun

    2012-08-01

    iO2 has been widely utilized for various industrial applications such as photochemical cells, photocatalysts, and electrochromic devices. The crystallinity and morphology of TiO2 films play a significant role in determining the overall efficiency of dye-sensitized solar cells (DSSCs). In this study, the preparation of nanostructured TiO2 films by electron beam irradiation and their characterization were investigated for the application of DSSCs. TiO2 films were exposed to 20-100 kGy of electron beam irradiation using 1.14 MeV energy acceleration with a 7.46 mA beam current and 10 kGy/pass dose rates. These samples were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS) analysis. After irradiation, each TiO2 film was tested as a DSSC. At low doses of electron beam irradiation (20 kGy), the energy conversion efficiency of the film was approximately 4.0% under illumination of simulated sunlight with AM 1.5 G (100 mW/cm2). We found that electron beam irradiation resulted in surface modification of the TiO2 films, which could explain the observed increase in the conversion efficiency in irradiated versus non-irradiated films.

  16. Photocatalytic degradation of methylene blue and inactivation of gram-negative bacteria by TiO2 nanoparticles in aqueous suspension

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The photocatalytic degradation of methylene blue (MB) and inactivation of Gram-negative bacteria E. coli K12 and P. aeruginosa by TiO2 nanoparticles in aqueous suspension were studied. TiO2 resulted in significant reduction in MB absorption and a shift of MB absorption peak from 664 nm to 658 nm aft...

  17. Photocatalytic Oxidation of Propylene on Pd-Loaded Anatase TiO2 Nanotubes Under Visible Light Irradiation.

    PubMed

    Li, Chen; Zong, Lanlan; Li, Qiuye; Zhang, Jiwei; Yang, Jianjun; Jin, Zhensheng

    2016-12-01

    TiO2 nanotubes attract much attention because of their high photoelectron-chemical and photocatalytic efficiency. But their large band gap leads to a low absorption of the solar light and limits the practical application. How to obtain TiO2 nanotubes without any dopant and possessing visible light response is a big challenge nowadays. Orthorhombic titanic acid nanotubes (TAN) are a special precursor of TiO2, which possess large Brunauer-Emmett-Teller (BET) surface areas and strong ion exchange and adsorption capacity. TAN can transform to a novel TiO2 with a large amount of single-electron-trapped oxygen vacancies (SETOV) during calcination, while their nanotubular structure would be destroyed, and a BET surface area would decrease remarkably. And interestingly, SETOV can lead to a visible light response for this kind of TiO2. Herein, glucose was penetrated into TAN by the vacuum inhalation method, and TAN would dehydrate to anatase TiO2, and glucose would undergo thermolysis completely in the calcination process. As a result, the pure TiO2 nanotubes with visible light response and large BET surface areas were obtained. For further improving the photocatalytic activity, Pd nanoparticles were loaded as the foreign electron traps on TiO2 nanotubes and the photocatalytic oxidation efficiency of propylene was as high as 71 % under visible light irradiation, and the photostability of the catalyst kept over 90 % after 4 cyclic tests.

  18. Photocatalytic Oxidation of Propylene on Pd-Loaded Anatase TiO2 Nanotubes Under Visible Light Irradiation

    NASA Astrophysics Data System (ADS)

    Li, Chen; Zong, Lanlan; Li, Qiuye; Zhang, Jiwei; Yang, Jianjun; Jin, Zhensheng

    2016-05-01

    TiO2 nanotubes attract much attention because of their high photoelectron-chemical and photocatalytic efficiency. But their large band gap leads to a low absorption of the solar light and limits the practical application. How to obtain TiO2 nanotubes without any dopant and possessing visible light response is a big challenge nowadays. Orthorhombic titanic acid nanotubes (TAN) are a special precursor of TiO2, which possess large Brunauer-Emmett-Teller (BET) surface areas and strong ion exchange and adsorption capacity. TAN can transform to a novel TiO2 with a large amount of single-electron-trapped oxygen vacancies (SETOV) during calcination, while their nanotubular structure would be destroyed, and a BET surface area would decrease remarkably. And interestingly, SETOV can lead to a visible light response for this kind of TiO2. Herein, glucose was penetrated into TAN by the vacuum inhalation method, and TAN would dehydrate to anatase TiO2, and glucose would undergo thermolysis completely in the calcination process. As a result, the pure TiO2 nanotubes with visible light response and large BET surface areas were obtained. For further improving the photocatalytic activity, Pd nanoparticles were loaded as the foreign electron traps on TiO2 nanotubes and the photocatalytic oxidation efficiency of propylene was as high as 71 % under visible light irradiation, and the photostability of the catalyst kept over 90 % after 4 cyclic tests.

  19. Effect of Erbium on the Photocatalytic Activity of TiO2 /Ag Nanocomposites under Visible Light Irradiation.

    PubMed

    Prakash, Natarajan; Karthikeyan, Rajan; Thangaraju, Dheivasigamani; Navaneethan, Mani; Arivanandhan, Mukannan; Koyama, Tadanobu; Hayakawa, Yasuhiro

    2015-10-05

    Erbium co-doped TiO2 /Ag catalysts are synthesized by using a simple, one-step solvothermal method and characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Raman analysis, X-ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. The catalysts exhibit anatase crystal structures with increased visible light absorption compared with pure TiO2 . Enhanced photocatalytic activity is observed with Er co-doped TiO2 /Ag nanocomposites for Rhodamine B degradation under visible light irradiation. The photocatalytic activity of 1 % Er co-doped TiO2 /Ag is much higher than that of TiO2 /Ag, TiO2 /Er, pure TiO2 , and commercial Degussa P25. The kinetics of the degradation process are studied and the pseudo-first-order rate constant (k) and half-life time (t1/2 ) of the reaction are calculated. The enhanced activity might be accredited to the efficient separation of electron-hole pairs by silver and higher visible light absorption of TiO2 induced by Er.

  20. Effect of UV irradiation on wear protection of TiO2 and Ni-doped TiO2 coatings

    NASA Astrophysics Data System (ADS)

    Wan, Yong; Sun, Baojian; Xu, Zhen; Chao, Wenliu

    2012-03-01

    The relationship between UV photoinduced hydrophilicity and tribological performance of the thin films of pure and Ni-doped TiO2 was investigated in this paper. The films were prepared on a glass substrate by sol-gel and spin coating process from specially formulated ethanol sols. The chemical structure and morphologies of the films surface were observed with X-ray photoelectron spectroscopy (XPS), X-ray Diffraction (XRD) and atomic force microscope (AFM). The tribological properties of obtained thin films, when sliding against steel ball, were evaluated on a one-way reciprocating friction tester. It is clearly observed that UV irradiation resume the hydrophobicility of the films of pure and Ni-doped TiO2, however greatly worsen their wear protection properties.

  1. The effect of TiO2 nanoparticles and UV irradiation on photocatalytic degradation of Imidaclopride.

    PubMed

    Ahmari, Hadi; Zeinali Heris, Saeed; Hassanzadeh Khayyat, Mohammad

    2017-03-13

    Imidaclopride is an insecticide widely used for pest control in agriculture around the world. It acts on the central nervous system of insects, while posing lower toxicity to mammals. This is an organic material made of Pyridinium, Dihydroimidazol and Nitramide. This structure poses a threat to the environment and humans. Until now, different types of methods have been used for elimination of this organic pollution. Recently, advance oxidation processes (AOPs) is presented as a proposed method to remove this organic pollution. Photocatalytic degradation is also used as an efficient method for destruction of organic structures. In this study, the effect of TiO2 nanoparticle as a photocatalyst activated by UV irradiation is investigated. The new design of the reactor was prepared with coaxial cylinders in which the inner cylinder rotated at constant speed. The reactor worked in two batch and continuous modes. The results show that the UV irradiation is more effective than activated TiO2 nanoparticle, as the designed reactor with UV irradiation eliminated Imidaclopride in less than 2 hours.

  2. Photocatalytic activity of tungsten-doped TiO2 with hydrothermal treatment under blue light irradiation.

    PubMed

    Putta, Thapanan; Lu, Ming-Chun; Anotai, Jin

    2011-09-01

    Tungsten doping and hydrothermal treatment were found to significantly improve the visible-light photoactivity of TiO(2) synthesized by the sol-gel method. It was observed that TiO(2) doped with a 0.5% W:Ti mole ratio and treated with 4 h of hydrothermal curing showed photoactivity under blue light irradiation equal to 74% of the commercial Degussa P-25 under UV irradiation, i.e., 0.01 mM 2-chlorophenol was completely removed in 120 and 90 min, respectively. Light absorptivity and photocatalytic activity under blue light irradiation were not dependent on the crystallite structure of the TiO(2). The oxidation kinetics under blue light irradiation can be effectively explained by the Langmuir-Hinshelwood model with an apparent reaction rate constant and a Langmuir constant of 3.60 × 10(-4) mM min(-1) and 206.53 mM(-1), respectively.

  3. Comparative toxicity of nano-scale TiO2, SiO2 and ZnO water suspensions.

    PubMed

    Adams, L K; Lyon, D Y; McIntosh, A; Alvarez, P J J

    2006-01-01

    TiO2, SiO2 and ZnO are common additives with improved applications at the nanoscale. The antibacterial activity of TiO2, which has important ecosystem health implications, is well understood. However, less attention has been paid to the antibacterial activity of SiO2 and ZnO despite them also producing reactive oxygen species. This paper explores the relative toxicity of TiO2, SiO2 and ZnO water suspensions towards bacteria (B. subtilis, E. coli) and the eukaryotic Daphnia magna. These three photosensitive nanomaterials were hazardous to all test organisms, with toxicity increasing with particle concentration. Toxicity of the three compounds decreased from ZnO to TiO2 to SiO2 and Daphnia were most susceptible to their effects. Nominal particle size did not affect the toxicity of these compounds. Antibacterial activity was noted under both dark and light conditions indicating that mechanisms additional to ROS production were responsible for growth inhibition. These results highlight the need for caution during the use and disposal of such manufactured nanomaterials to prevent unintended environmental impacts, as well as the importance of further research on the mechanisms and factors that increase toxicity to enhance risk management.

  4. Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation.

    PubMed

    Miao, Guang; Ye, Feiyan; Wu, Luoming; Ren, Xiaoling; Xiao, Jing; Li, Zhong; Wang, Haihui

    2015-12-30

    This study investigates selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation. The TiO2/SiO2 adsorbents were prepared and then characterized by N2 adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO2/SiO2 were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO2/0.7SiO2 adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO2 served as the photocatalytic sites for DBT oxidation, while SiO2 acted as the selective adsorption sites for the corresponding oxidized DBT using TiO2 as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO2/SiO2; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO2/SiO2 was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO2/0.7SiO2 adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions.

  5. The effect of erbium on the adsorption and photodegradation of orange I in aqueous Er3+-TiO2 suspension.

    PubMed

    Liang, Chun-Hua; Hou, Mei-Fang; Zhou, Shun-Gui; Li, Fang-Bai; Liu, Cheng-Shuai; Liu, Tong-Xu; Gao, Yuan-Xue; Wang, Xu-Gang; Lü, Jia-Long

    2006-12-01

    Pure TiO(2) and erbium ion-doped TiO(2) (Er(3+)-TiO(2)) catalysts prepared by the sol-gel method were characterized by means of XRD and diffusive reflectance spectra (DRS). The XRD results showed that erbium ion doping could enhance the thermal stability of TiO(2) and inhibit the increase of the crystallite size, and the DRS results showed that the optical absorption edge slightly shifted to red direction owing to erbium ion doping and the Er(3+)-TiO(2) catalysts had three typical absorption peaks located at 490, 523 and 654 nm owing to the transition of 4f electron from (4)I(15/2) to (4)F(7/2), (2)H(11/2) and (4)F(9/2). With a purpose of azo dyes degradation, orange I was used as a model chemical. And the adsorption isotherm, degradation and mineralization of orange I were investigated in aqueous suspension of pure TiO(2) or Er(3+)-TiO(2) catalysts. The results showed that Er(3+)-TiO(2) catalysts had higher adsorption equilibrium constants and better adsorption capacity than pure TiO(2). The adsorption equilibrium constants (K(a)) of Er(3+)-TiO(2) catalysts were about twice of that of pure TiO(2). The maximum adsorption capacity (Q(max)) of 2.0% Er(3+)-TiO(2) catalyst was 13.08x10(-5)mol/g, which was much higher than that of pure TiO(2) with 9.03x10(-5)mol/g. Among Er(3+)-TiO(2) catalysts, 2.0% Er(3+)-TiO(2) catalyst achieved the highest Q(max) and K(a) values. The kinetics of the orange I degradation using different Er(3+)-TiO(2) catalysts were also studied. The results demonstrated that the degradation and mineralization of orange I under both UV radiation and visible light were more efficient with Er(3+)-TiO(2) catalyst than with pure TiO(2), and an optimal dosage of erbium ion at 1.5% achieved the highest degradation rate. The higher photoactivity under visible light might be attributable to the transitions of 4f electrons of Er(3+) and red shifts of the optical absorption edge of TiO(2) by erbium ion doping.

  6. Adsorption and Photocatalyzed Oxidation of Methylated Arsenic Species in TiO2 Suspensions

    PubMed Central

    XU, TIELIAN; CAI, YONG; O’SHEA, KEVIN E.

    2008-01-01

    Monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) are used as herbicides in the agriculture industry. We have demonstrated that MMA and DMA are readily degraded upon TiO2 photocatalysis. DMA is oxidized to MMA as the primary oxidation product, which is subsequently oxidized to inorganic arsenate, As(V). The adsorption of MMA and DMA on TiO2 surface was measured as a function of initial arsenic concentration and solution pH. The pH of the solution influences the adsorption and photocatalytic degradation to a similar degree, due to the speciation of the arsenic substrates and surface charge of TiO2 as a function of pH. The mineralization of MMA and DMA by TiO2 photocatalysis follows the Langmuir–Hinshelwood kinetic model. Addition of tert-butyl alcohol, a hydroxyl radical scavenger, during TiO2 photocatalysis dramatically reduces the rate of degradation, indicating that •OH is the primary oxidant. For dilute solutions, TiO2 may also be applicable as an absorbent for direct removal of a variety of arsenic species, namely As(III), As(V), MMA, and DMA, all of which are strongly adsorbed, thus eliminating the need for a multistep treatment process. PMID:17822119

  7. TiO2 film/Cu2O microgrid heterojunction with photocatalytic activity under solar light irradiation.

    PubMed

    Zhang, Junying; Zhu, Hailing; Zheng, Shukai; Pan, Feng; Wang, Tianmin

    2009-10-01

    Coupling a narrow-band-gap semiconductor with TiO(2) is an effective method to produce photocatalysts that work under UV-vis light irradiation. Usually photocatalytic coupled-semiconductors exist mainly as powders, and photocatalytic activity is only favored when a small loading amount of narrow-band-gap semiconductor is used. Here we propose a heavy-loading photocatalyst configuration in which 51% of the surface of the TiO(2) film is covered by a Cu(2)O microgrid. The coupled system shows higher photocatalytic activity under solar light irradiation than TiO(2) and Cu(2)O films. This improved performance is due to the efficient charge transfer between the two phases and the similar opportunity each has to be exposed to irradiation and adsorbates.

  8. Study on the indoor volatile organic compound treatment and performance assessment with TiO2/MCM-41 and TiO2/quartz photoreactor under ultraviolet irradiation.

    PubMed

    Tsai, Chia-Wei; Chang, Chang-Tang; Chiou, Chyow-San; Shie, Je-Lueng; Chang, Yu-Min

    2008-10-01

    Volatile organic compounds (VOCs) are the cause of indoor air pollution and are readily emitted from furniture and cleaning agents. In Taiwan, the concentrations of indoor VOCs range roughly from 1 to 10 ppm. It is important to effectively reduce indoor VOC emissions and establish the implementation of long-term, low-cost, controlled techniques such as those found in the ultraviolet/titanium dioxide (UV/TiO2) control systems. This study evaluates the performance of a photoreactor activated by visible irradiation and packed with TiO2/quartz or TiO2/mobile catalytic material number 41 (MCM-41). The photocatalysts tested include commercial TiO2 (Degussa P-25) and synthesized TiO2 with a modified sol-gel process. The UV light had a wavelength of 365 nm and contained an 8-W, low-pressure mercury lamp. Reactants and products were analyzed quantitatively by using gas chromatography with a flame-ionization detector. It is important to understand the influence of such operational parameters, such as concentration of pollutant, temperature, and retention time of processing. The indoor concentrations of VOCs varied from 2 to 10 ppm. Additionally, the temperatures ranged from 15 to 35 degrees C and the retention time tested from 2 to 8.2 sec. The results show that quartz with TiO2 had a better photoreductive efficiency than quartz with MCM-41. The toluene degradation efficiency of 77.4% with UV/TiO2/quartz was larger than that of 54.4% with the UV/TiO2/MCM-41 system under 10-min reaction time. The degradation efficiency of the UV/TiO2 system decreased with the increasing concentrations of indoor VOCs. The toluene degradation efficiency at 2 ppm was approximately 5 times greater than that at 10 ppm. The photoreduction rate of the VOCs was also evaluated with the Langmuir-Hinshewood model and was shown to be pseudo-first-order kinetics.

  9. Fine surface modification of aluminum by laser irradiation with TiO2-Ni composite powder

    NASA Astrophysics Data System (ADS)

    Akanuma, Masanobu; Tanaka, Hiroyuki; Sato, Takanori; Ikeda, Masayuki

    1999-09-01

    Surface modification experiments on aluminum were performed using CO2 laser beam irradiation on a surface on which an alloying powder had been pre-placed. Using TiO2 particles coated with Ni as a new material for laser alloying, a hard and uniformly-structured alloyed layer was achieved on the Al substrate. The effects of additive Ni on the hardness and structure of the alloyed layer were then investigated. With an increase in Ni content in the alloying powder, the hardness of the alloyed layer increased. This hardening in the alloyed layer was caused by the crystallization of intermetallic compounds. The optimum alloyed layer was obtained, when the weight ratio of TiO2 to Ni was about 1:1. The thickness of the alloyed layer was 0.6 - 0.7 mm, and the surface roughness about Rz 70 micrometers. It mainly consisted of Al+Al3Ni eutectic matrix and Al3Ti dendrites. The micro Vickers hardware of the alloyed layer was Hv200+/- 50. According to the sliding friction test, and specific wear volume was smaller than that of tempered carbon steel under high sliding speed and heavy load conditions.

  10. Reversible manipulation of the adhesive forces of TiO2/polybenzoxazine nanoassembled coatings through UV irradiation and thermal treatment

    NASA Astrophysics Data System (ADS)

    Wang, Sheng-Feng; Kao, Tzu-Hao; Cheng, Chih-Chia; Chang, Chi-Jung; Chen, Jem-Kun

    2015-12-01

    In this study we mixed TiO2 nanoparticles (NPs) with 3-phenyl-3,4-dihydro-2H-1,3-benzoxazine (BA), as a precursor to a polybenzoxazine (PBA), to generate nanocomposite surfaces possessing low surface free energies. Because of extreme phase separation between the TiO2 NPs and BA, their mixtures featured nanoassembled structures on their surfaces. After thermal curing, we obtained PBA/TiO2 nanoassembled (PTN) surfaces possessing various TiO2 contents. The mixing of 30 wt% TiO2 NPs into the PBA matrix generated a superhydrophobic surface (static water contact angle: >150° with a sliding angle of approximately 1°). We could convert this superhydrophobic TiO2/PBA nanoassembled surface, through photocatalytic oxidation, into a highly hydrophilic surface (static water contact angle: ca. 0°). Interestingly, we could convert the hydrophilic surface back into a superhydrophobic surface through heat treatment. Thus, both UV irradiation and oven treatment induced changes in the surface chemistry of these materials. Furthermore, we could tune the adhesive force of the PTN surfaces by varying the UV irradiation time, without significant changes in the static water contact angle. As a result, we could transport a water droplet among PTN surfaces that had been subjected to UV irradiation for various lengths of time.

  11. Fabrication of TiO2/Ag2O heterostructure with enhanced photocatalytic and antibacterial activities under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Liu, Bingkun; Mu, Lilong; Han, Bing; Zhang, Jingtao; Shi, Hengzhen

    2017-02-01

    TiO2/Ag2O heterostructure prepared by a facile in situ precipitation route was used as an effective visible light-driven photocatalyst for degradation of methylene blue (MB) and inactivation of E. coli. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) revealed that Ag2O nanoparticles were well distributed on the surface of TiO2 microspheres. The TiO2/Ag2O composite with optimal mass ratio of TiO2 and Ag2O displayed extremely good photodegradation ability and antibacterial capability under visible light irradiation, which was mainly ascribed to the synergistic effect between Ag2O and TiO2, including highly dispersed smaller Ag2O particles, increased visible light absorption and efficient separation of photo-induced charge carriers. Meanwhile, the roles of the radical species in the photocatalysis process were investigated. Our results showed that the TiO2/Ag2O could be used as a dual functional material in water treatment of removing the organic pollutant and killing the bacterium at the same time.

  12. Enhanced photocatalytic hydrogen evolution activity of CuInS2 loaded TiO2 under solar light irradiation

    NASA Astrophysics Data System (ADS)

    Li, Changjiang; Xi, Zhenhao; Fang, Wenzhang; Xing, Mingyang; Zhang, Jinlong

    2015-03-01

    In this paper, p-n type CuInS2/TiO2 particles were prepared in ethylenediamine by the solvothermal method. The microstructural properties of the synthesized p-n type catalysts were characterized by X-ray diffraction (XRD) in order to confirm the existence of crystalline CuInS2 on the surface of TiO2, which was also confirmed by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) images provided the detailed morphological properties about the CuInS2/TiO2 heterostructure. UV-vis diffuse reflectance spectroscopy (UV-vis DRS) was used to investigate the optical properties of the CuInS2/TiO2 particles. The DRS results indicated that both the p-n type structure and CuInS2 acting as a sensitizer can enhance significantly the absorption of UV and visible light. The photocatalytic activities of the CuInS2/TiO2 particles were evaluated by hydrogen evolution reactions using Xe-lamp irradiation as a simulated solar light source. The greatly enhanced photocatalytic activity of hydrogen evolution under simulated solar light is about ~7 fold higher than that of pure commercial TiO2 (Degussa P25).

  13. Photocatalytic degradation of a widely used insecticide Thiamethoxam in aqueous suspension of TiO2: adsorption, kinetics, product analysis and toxicity assessment.

    PubMed

    Mir, Niyaz A; Khan, A; Muneer, M; Vijayalakhsmi, S

    2013-08-01

    This paper deals with the study of photocatalyzed degradation of an insecticide, Thiamethoxam in aqueous suspension of TiO2. The adsorption of Thiamethoxam on TiO2 surface under dark conditions was also investigated in order to find out equilibrium adsorption constant. The degradation kinetics was studied using spectrophotometric method under various conditions such as substrate concentration, type of catalyst, catalyst dosage, pH, and in the presence of electron acceptors such as hydrogen peroxide, potassium bromate, and ammonium persulphate under continuous purging of atmospheric oxygen, and the degradation rates were found to be strongly influenced by these parameters. The results manifested that the photocatalysis of Thiamethoxam follows pseudo-first-order kinetics. The toxicity assessments of the irradiated samples were carried out using human erythrocytes as a model system under in vitro conditions. GC-MS study showed the formation of several intermediate products which were characterised based on their molecular mass and mass fragmentation pattern. A probable mechanism for the formation of various products formed during the photocatalytic process of Thiamethoxam was also proposed.

  14. Photocatalytic degradation of chloramphenicol in an aqueous suspension of silver-doped TiO2 nanoparticles.

    PubMed

    Shokri, Mohammad; Jodat, Akbar; Modirshahla, Nasser; Behnajady, Mohammad A

    2013-01-01

    In this work, silver-doped TiO2 (Ag/TiO2) nanoparticles were synthesized using a photodeposition technique. The prepared Ag/TiO2 nanoparticles were characterized using TEM, SEM, XRD, and EDX techniques. The characterization of Ag/TiO2 nanoparticles using SEM and EDX techniques revealed the dispersion of Ag metal on the surface of TiO2. The photocatalytic activity of Ag/TiO2 and bare TiO2 in the presence of ultraviolet irradiation was investigated in the removal of chloramphenicol (CAP) as an antibiotic. CAP is a broad-spectrum antibiotic exhibiting activity against both Gram-positive and Gram-negative bacteria, as well as other groups of microorganisms. However, it is, in certain susceptible individuals, associated with serious toxic effects in humans including bone marrow depression, particularly severe in the form of fatal aplastic anaemia. The effects of the operational factors, such as doping content of Ag, photocatalyst dosage and calcination temperature were evaluated in the catalytic activity of Ag/TiO2. The results showed that the photocatalytic efficiency of TiO2 nanoparticles for the degradation of CAP, can be significantly improved by deposition an optimum amount of Ag nanoparticles (0.96 wt%) in the calcination temperature 300 degrees C. It was found that 900 mg/L of Ag/TiO2 is the optimum dosage in the removal of CAP with 20 mg/L initial concentration. The highest removal efficiency of CAP (-100%) at the optimum conditions was observed in 20 min. A mineralization study under optimum conditions showed about 88% reduction in total organic carbon after 120 min of irradiation time.

  15. Photocatalytic hydrogen generation over lanthanum doped TiO2 under UV light irradiation.

    PubMed

    Liu, Y; Xie, L; Li, Y; Qu, J L; Zheng, J; Li, X G

    2009-02-01

    TiO2 nanoparticles doped with different amount of lanthanum were obtained by sol-gel approach and followed annealing at different temperature. The crystal size of TiO2 doped with lanthanum was smaller than that of pure TiO2. Photocatalytic activity of TiO2 doped with lanthanum for water splitting into H2 was investigated. The photocatalytic activity of TiO2 doped with lanthanum for water splitting into H2 is higher than that of pure TiO2. It was found that the optimal photocatalyst was TiO2 doped with 2 wt% lanthanum and calcined at 600 degrees C for 4 h which had hydrogen generation rate 700.6 micromol h(-1).

  16. The effect of titanium dioxide (TiO2) nano-objects, and their aggregates and agglomerates greater than 100nm (NOAA) on microbes under UV irradiation.

    PubMed

    Yamada, Ikuho; Nomura, Kazuki; Iwahashi, Hitoshi; Horie, Masanori

    2016-01-01

    Today, nanoparticles are used in many products. One of the most common nanoparticles is titanium dioxide (TiO2). These particles generate reactive oxygen species (ROS) upon UV irradiation. Although nanoparticles are very useful in many products, there are concerns about their biological and ecological effects when released into the environment. Thus, it was assessed that the effect of TiO2 nano-objects, and their aggregates and agglomerates greater than 100nm (NOAA) on microbes under UV irradiation by using Escherichia coli and Saccharomyces cerevisiae. ROS generation was evaluated by adding TiO2 nanoparticles and methylene blue to distilled water. We also assessed growth inhibition by adding TiO2 nanoparticles and microbes in minimal agar medium. Moreover, microbial inactivation was assessed by adding TiO2 nanoparticles and microbes to PBS. Upon UV irradiation, TiO2-NOAAs decomposed methylene blue and generated ROS. TiO2-NOAAs also decomposed methylene blue in minimal agar medium under UV irradiation; however, they did not inhibit microbial growth. Surprisingly, TiO2-NOAAs in the medium protect microbes from UV irradiation as colony formation was observed only near TiO2-NOAAs. In PBS, TiO2-NOAAs did not inactivate microbes but instead protected microbes from lethal UV irradiation. These results suggest that the amount of ROS generated by TiO2-NOAAs is not enough to inactivate microbes. In fact, our results suggest that TiO2-NOAAs may protect microbes from UV irradiations.

  17. Photocatalytic degradation of nitrotoluene in aqueous TiO2 suspension.

    PubMed

    Vohra, Muhammad Shariq; Tanaka, Keiichi

    2002-01-01

    TiO2-mediated photocatalytic degradation process was employed to treat aqueous 2-, 3- and 4-NT (nitrotoluene) pollutants. The NT disappearance and TOC removal rates for three isomers showed no significant differences. Three hydroxylated aromatic intermediates resulting from the photocatalytic degradation of 4-NT were identified; this suggested two (initial) degradation pathways. Formation of acetic acid, formic acid, and formaldehyde was also noted. The mineralization products included NH4+, NO3- and CO2. N2 bubbling or the presence of a positive hole acceptor during 4-NT degradation resulted in a high 4-aminotoluene formation. This indicated an effective reduction of 4-NT's nitro group to amino moiety. Generally, Pt-loaded TiO2 (Pt-TiO2) had no influence on the disappearance rate of 4-NT. However, the use of Pt-TiO2 along with a higher light intensity source resulted in an accelerated TOC removal.

  18. Efficient degradation of benzene over LaVO4/TiO2 nanocrystalline heterojunction photocatalyst under visible light irradiation.

    PubMed

    Huang, Hanjie; Li, Danzhen; Lin, Qiang; Zhang, Wenjuan; Shao, Yu; Chen, Yibin; Sun, Meng; Fu, Xianzhi

    2009-06-01

    A nanocrystal heterojunction LaVO4TiO2 visible light photocatalyst has been successfully prepared by a simple coupled method. The catalyst was characterized by powder X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectra, photoluminescence, and electrochemistry technology.The results showed that the prepared nanocomposite catalysts exhibited strong photocatalytic activity for decomposition of benzene under visible light irradiation with high photochemical stability. The enhanced photocatalytic performance of LaVO4/TiO2 may be attributed to not only the matched band potentials but also interconnected heterojunction of LaVO4 and TiO2 nanoparticles.

  19. Photocatalysis effect of nanometer TiO2 and TiO2-coated ceramic plate on Hepatitis B virus.

    PubMed

    Zan, Ling; Fa, Wenjun; Peng, Tianyou; Gong, Zhen-Kui

    2007-02-01

    The photocatalysis effect of nanometer TiO2 particles and TiO2-coated ceramic plate on Hepatitis B virus surface antigen (HBsAg) was investigated. The ELISA (enzyme-linked immunosorbent assay) standard method was used to assess the efficiency of TiO2 material to destroy the HBsAg. The research has shown that the suspension of TiO2 (0.5g/L) can destroy most of the HBsAg under the irradiation of mercury lamp, with the light intensity of 0.6mW/cm(2) at 365nm wavelength, or under the sunlight irradiation for a few hours. TiO2-coated ceramic plates can also destroy the HBsAg under the irradiation of mercury lamp, with the light intensity of 0.05mW/cm(2) at 365nm wavelength or under the room daylight for a few hours.

  20. Photocatalytic Degradation of NOM for Power Plant Feedwater using Coating and Suspension of TiO2.

    PubMed

    Emam, Eman A

    2016-08-01

    This study investigated the effectiveness of coating and suspension of Degussa P25 TiO2 photocatalyst to remove natural organic matter (NOM) from surface water for use as power plant feedwater. The catalyst yield, transmittance intensity and X-ray pattern as a function of the number of coatings were characterized. In addition, P25 coating photocatalytic activity was studied. The photocatalytic activity also of P25 suspension with different catalyst concentrations and the reusing of the catalyst without and with regeneration was investigated. Results obtained show that the P25 coatings were transparent with good adhesion to the glass substrate. P25 suspension was found to be more effective in the NOM photodegradation and gave a higher rate constant compared to P25 coating. The maximum rate constants were 0.028 and 0.015 min(-1) at 0.7 g/L P25 suspension and 4 coatings, respectively. After four runs without regeneration and three runs with regeneration of P25 reusing, the photoactivity to remove NOM was still significant.

  1. Self-doped Ti(3+)-TiO2 as a photocatalyst for the reduction of CO2 into a hydrocarbon fuel under visible light irradiation.

    PubMed

    Sasan, Koroush; Zuo, Fan; Wang, Yuan; Feng, Pingyun

    2015-08-28

    Self-doped TiO2 shows visible light photocatalytic activity, while commercial TiO2 (P25) is only UV responsive. The incorporation of Ti(3+) into TiO2 structures narrows the band gap (2.90 eV), leading to significantly increased photocatalytic activity for the reduction of CO2 into a renewable hydrocarbon fuel (CH4) in the presence of water vapour under visible light irradiation.

  2. Simultaneous and synergistic conversion of dyes and heavy metal ions in aqueous TiO2 suspensions under visible-light illumination.

    PubMed

    Kyung, Hyunsook; Lee, Jaesang; Choi, Wonyong

    2005-04-01

    This study reports synergistic effects in the simultaneous conversion of dyes and heavy metal ions in aqueous TiO2/dye/metal ion systems (ternary components) under visible light (lambda > 420 nm). TiO2/Cr(VI)/Acid Orange 7 (AO7), TiO2/Cr(VI)/Rhodamine B (RhB), TiO2/Ag+/AO7, and TiO2/Ag+/RhB were chosen as test systems. Although dyes can be degraded in TiO2 suspensions under visible light, their removal rates were markedly enhanced in the presence of metal ions. Similarly, the reduction rates of metal ions in visible-light-illuminated TiO2 suspensions were negligible, but they were highly accelerated with dyes present. In particular, the synergistic effect in the ternary system of TiO2/Cr(VI)/AO7 was outstanding. The presence of dissolved oxygen increased the photoreduction rate of Cr(VI) despite the fact that Cr(VI) and O2 are competing electron acceptors. This is ascribed to in-situ photogenerated H2O2 from O2, which acts as a reductant of Cr(VI). RhB and Ag+ ions could be also converted simultaneously under visible light both in the presence and absence of TiO2. The visible-light-induced reduction of Ag+ did not occur at all in TiO2/Ag+ system, but it was enabled in both TiO2/Ag+/ RhB and TiO2/Ag+/AO7 to generate Ag particles. On the other hand, the binary systems of Cr(VI)/AO7, Ag+/AO7, and Ag+/RhB show significant visible-light activities for the conversion of both dye and metal ion. In this case, metal ions and dyes seem to form complexes that induce intracomplex electron transfers upon visible-light absorption. The Cr(VI)/RhB system, however, exhibited insignificant visible-light reactivity.

  3. Photo-catalytic degradation of toxic dye amaranth on TiO(2)/UV in aqueous suspensions.

    PubMed

    Gupta, Vinod K; Jain, Rajeev; Mittal, Alok; Saleh, Tawfik A; Nayak, Arunima; Agarwal, Shilpi; Sikarwar, Shalini

    2012-01-01

    The photo-catalytic degradation of an azo dye - Amaranth (AM) - has been investigated in TiO(2)/UV aqueous suspensions. The results obtained from the experiments during H(2)O(2)/TiO(2) addition show that the highest decolorization rate is provided by the combination of (UV+TiO(2)+H(2)O(2)). The decolorization efficiencies were 17%, 26%, 38% and 64% in the runs UV, UV+H(2)O(2), UV+TiO(2) and (UV+TiO(2)+H(2)O(2)) after approximately 100 min illumination periods, respectively. The observed dye degradation rates followed pseudo-first order kinetics with respect to the substrate concentration under the experimental conditions used. Different experimental conditions, such as temperature, pH and presence of electron acceptor were investigated. The temperature effect was investigated at the range of 293-313 K and it was observed that decolorization rate increased by the increase in temperature. Chemical oxygen demand and dye absorbance of the photodegraded dye solution substantially decreased. Effect of pH was also investigated and it was observed that the lower the pH the higher the degradation. In addition, an enhancement in the photodegradation rate was observed by the addition of hydrogen peroxide as an electron acceptor. The adsorption trends of Amaranth at various initial concentrations followed the Langmuir isotherm trend. This work adds to the global discussion on the role of the advanced oxidation processes in water treatment.

  4. Influence of anatase and rutile phase in TiO2 upon the photocatalytic degradation of methylene blue under solar irradiation in presence of activated carbon.

    PubMed

    Matos, J; Montaña, R; Rivero, E; Escudero, A; Uzcategui, D

    2014-01-01

    The influence of activated carbon (AC) on the photocatalytic activity of different crystalline TiO2 phases was verified in the photocatalytic degradation of methylene blue under UV and solar irradiation. The results showed a volcano trend with a maximum photoactivity for the crystalline phase ratio of anatase:rutile equal to 80:20 both under UV or solar irradiation. By contrast, in presence of AC the photocatalytic activity of the binary materials of TiO2/AC followed an exponential trend, increasing as a function of the increase in anatase proportion in the TiO2 framework. The increase in the photoactivity of the binary material TiO2/AC relative to neat TiO2 was up to 22 and about 17 times higher under UV and visible irradiation, respectively. The present results suggest that AC interacts more efficiently with anatase phase than with rutile phase.

  5. Mechanism and pathways of chlorfenapyr photocatalytic degradation in aqueous suspension of TiO2.

    PubMed

    Cao, Yongsong; Yi, Lei; Huang, Lu; Hou, Ying; Lu, Yitong

    2006-05-15

    The light-induced degradation of chlorfenapyr under UV was investigated in aqueous solutions containing TiO2 as photocatalyst. The photocatalytic degradation of chlorfenapyr followed pseudo-first-order degradation kinetics (Ct = C0e(-kt)). The study focused on the identification of possible intermediate products during the degradation, using gas chromatography mass-spectrometry (GC-MS) and 1HNMR. Six aromatic intermediates were identified by several techniques during the treatment and some of them were further confirmed by matching authentic standards. Structure analysis of the degradation products suggested two degradation pathways: (1) The aliphatic ether group was cleaved from chlorfenapyr to form pyrrole-alph-carboxylic acid, then the pyrrole group was broken to form 4-chloroglycine; (2) Chlorfenapyr was debrominated and the aliphatic ether group was cleaved from the pyrrole group, which was further broken to form 4-chlorophenylglycine. The glycine was degraded into 4-chlorobenzoic acids, which was further broken into inorganic ions and CO2.

  6. Degradation of polycyclic aromatic hydrocarbons in crumb tyre rubber catalysed by rutile TiO2 under UV irradiation.

    PubMed

    Yu, Kai; Huang, Linyue; Lou, Lan-Lan; Chang, Yue; Dong, Yanling; Wang, Huan; Liu, Shuangxi

    2015-01-01

    The polycyclic aromatic hydrocarbons (PAHs) in crumb tyre rubber were firstly degraded under UV irradiation in the presence of rutile TiO2 and hydrogen peroxide. The effects of light intensity, catalyst amount, oxidant amount, initial pH value, co-solvent content, and reaction time on degradation efficiency of typical PAHs in crumb tyre rubber were studied. The results indicated that UV irradiation, rutile TiO2, and hydrogen peroxide were beneficial to the degradation of PAHs and co-solvent could accelerate the desorption of PAHs from crumb tyre rubber. Up to 90% degradation efficiency of total 16 PAHs could be obtained in the presence of rutile TiO2 (1 wt%) and hydrogen peroxide (1.0 mL) under 1800 µW cm(-2) UV irradiation for 48 h. The high molecular weight PAHs (such as benz(a)pyrene) were more difficult to be degraded than low molecular weight PAHs (such as phenanthrene, chrysene). Moreover, through the characterization of reaction solution and degradation products via GC-MS, it was proved that the PAHs in crumb tyre rubber were successfully degraded.

  7. Photocatalytic performance of Fe-doped TiO2 nanoparticles under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Ali, T.; Tripathi, P.; Azam, Ameer; Raza, Waseem; Ahmed, Arham S.; Ahmed, Ateeq; Muneer, M.

    2017-01-01

    The present work focuses on the synthesis, characterization and photocatalytic activity of a nanosized Fe-doped TiO2 photocatalyst. The samples were synthesized by the sol–gel method and characterized by using techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), UV–visible spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy and Fourier-transform infrared (FTIR). The powder XRD spectra revealed that the synthesized samples are pure and crystalline in nature and show a tetragonal anatase phase of TiO2. The Raman spectroscopy also confirmed the formation of an anatase phase structure in both pure and Fe-doped TiO2 nanoparticles (NPs). The UV–visible and PL spectra illustrated the red shift in Fe-doped TiO2 NPs. The FTIR spectra indicated the vibrational band of the Ti–O lattice. The photocatalytic experimental results demonstrate that Fe-doped TiO2 NPs effectively degrade MB under visible-light illumination. Interestingly, the prepared TiO2 NPs with a dopant concentration of 3.0 mole% showed the maximum photocatalytic activity under investigation.

  8. The effect of full/partial UV-irradiation of TiO2 films on altering the behavior of fibrinogen and platelets.

    PubMed

    Chen, Jiang; Zhao, Ansha; Chen, Huiqing; Liao, Yuzhen; Yang, Ping; Sun, Hong; Huang, Nan

    2014-10-01

    Titanium oxide (TiO2) thin film is a potential candidate for the surface modification of blood-contacting devices. It has previously been reported that ultraviolet light (UV) irradiation could alter the biocompatibility of TiO2 films. However, the effect of UV-irradiated TiO2 films on blood compatibility has rarely been reported. This study attempts to determine: (1) whether UV-irradiation of TiO2 films enhances their blood compatibility, (2) the interaction between UV-irradiated TiO2 films, fibrinogen (Fgn), and platelets, especially how Fgn and platelets respond to the geometry of the partially UV-irradiated TiO2 film surface. Anatase TiO2 films were subjected to full and partial UV-irradiation. Full UV-irradiation improved the blood compatibility of TiO2 films by almost completely inhibiting the adhesion and activation of platelets, strongly suppressing the adsorption and conformational change of Fgn, and preventing the formation of fibrin fibers. Additionally, hemolysis was not observed. After partial UV-irradiation, the regions where Fgn adsorption was reduced (Fgn-dark regions) were formed at regions where UV-irradiation had occurred, but were extended in comparison with the UV-irradiated regions, which could be related to the generation and diffusion of reactive oxygen species (ROS) on the UV-irradiated TiO2 surface. It is worthwhile to study how ROS altered the nature of TiO2 films, thereby enhancing their blood compatibility. Furthermore, platelets were found adhering to the Fgn-adsorbed regions (Fgn-bright regions) selectively, suggesting that the inhibition of platelet adhesion could be related to the suppression of Fgn adsorption on the UV-irradiated TiO2 surface. It was also noted that platelet surface coverage (Sp) was not linearly correlated with Fgn-bright region surface coverage (Sf), which indicated that the adhesion and spreading of platelets were regulated by both Sf and the geometry of Fgn.

  9. Photocatalytic degradation of Orange G on nitrogen-doped TiO2 catalysts under visible light and sunlight irradiation.

    PubMed

    Sun, Jianhui; Qiao, Liping; Sun, Shengpeng; Wang, Guoliang

    2008-06-30

    In this paper, the degradation of an azo dye Orange G (OG) on nitrogen-doped TiO2 photocatalysts has been investigated under visible light and sunlight irradiation. Under visible light irradiation, the doped TiO2 nanocatalysts demonstrated higher activity than the commercial Dugussa P25 TiO2, allowing more efficient utilization of solar light, while under sunlight, P25 showed higher photocatalytic activity. According to the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis spectra analyses, it was found that both the nanosized anatase structure and the appearance of new absorption band in the visible region caused by nitrogen doping were responsible for the significant enhancement of OG degradation under visible light. In addition, the photosensitized oxidation mechanism originated from OG itself was also considered contributing to the higher visible-light-induced degradation efficiency. The effect of the initial pH of the solution and the dosage of hydrogen peroxide under different light sources was also investigated. Under visible light and sunlight, the optimal solution pH was both 2.0, while the optimal dosage of H2O2 was 5.0 and 15.0 mmol/l, respectively.

  10. Rapid photo-degradation of 2-chlorophenol under visible light irradiation using cobalt oxide-loaded TiO2/reduced graphene oxide nanocomposite from aqueous media.

    PubMed

    Sharma, Ajit; Lee, Byeong-Kyu

    2016-01-01

    The photocatalytic removal of 2-chlorophenol (2-CP) from water environment was investigated by TiO2-RGO-CoO. Cobalt oxide-loaded TiO2 (TiO2-CoO) supported with reduced graphene oxide (RGO) was synthesized using a sol-gel method and then annealed at 500 °C for 5 min. The material characteristics were analyzed by UV-Vis analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. Incorporation of cobalt oxide and RGO into the TiO2 system (TiO2-RGO-CoO) lowered the band gap energy to 2.83 eV, which greatly enhanced the visible light absorption. The TiO2-RGO-CoO photocatalyst showed complete removal of 20 mg/L 2-CP within 8 h with the addition of 0.01% H2O2 under 100 W visible light irradiation. The photo-degradation efficiency of 2-CP (10 mg/L) was 35.2, 48.9, 58.9 and 98.2% for TiO2, TiO2-RGO, TiO2-CoO and TiO2-RGO-CoO, respectively, in the presence of visible light irradiation at solution pH of 6.0. The TiO2-RGO-CoO photocatalyst retained its high removal efficiency even after five photocatalytic cycles.

  11. CO2 gas detection properties of a TIO2/Al2O3 heterostructure under UV light irradiation

    NASA Astrophysics Data System (ADS)

    Karaduman, Irmak; Demir, Mehmet; Yıldız, Dilber Esra; Acar, Selim

    2015-05-01

    Al/TiO2/p-Si and Al/TİO2/Al2O3/p-Si samples were prepared using the atomic layer deposition method (ALD) and their gas sensing properties were investigated. The electrical properties of the samples were studied using a two probe method in the temperature range 25-230 °C and at room temperature UV conditions. The TiO2/Al2O3 heterojunction sample exhibited an excellent gas sensing response to CO2 gas at room temperature and improved the effect of UV light irradiation. The results showed that heterostructures helped to improve the gas sensor properties, affected the sensing at room temperature and thus guided the design of photocatalysts. The TiO2/Al2O3 heterojunction prepared using this method can be used as a material for semiconductor gas sensors detecting poisonous gases like CO2 at room temperature with high sensitivity and selectivity.

  12. Photocatalytic Antibacterial Effects Are Maintained on Resin-Based TiO2 Nanocomposites after Cessation of UV Irradiation

    PubMed Central

    Cai, Yanling; Strømme, Maria; Welch, Ken

    2013-01-01

    Photocatalysis induced by TiO2 and UV light constitutes a decontamination and antibacterial strategy utilized in many applications including self-cleaning environmental surfaces, water and air treatment. The present work reveals that antibacterial effects induced by photocatalysis can be maintained even after the cessation of UV irradiation. We show that resin-based composites containing 20% TiO2 nanoparticles continue to provide a pronounced antibacterial effect against the pathogens Escherichia coli, Staphylococcus epidermidis, Streptococcus pyogenes, Streptococcus mutans and Enterococcus faecalis for up to two hours post UV. For biomaterials or implant coatings, where direct UV illumination is not feasible, a prolonged antibacterial effect after the cessation of the illumination would offer new unexplored treatment possibilities. PMID:24146793

  13. Strong out-of-plane magnetic anisotropy in ion irradiated anatase TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Stiller, M.; Barzola-Quiquia, J.; Esquinazi, P.; Spemann, D.; Meijer, J.; Lorenz, M.; Grundmann, M.

    2016-12-01

    The temperature and field dependence of the magnetization of epitaxial, undoped anatase TiO2 thin films on SrTiO3 substrates was investigated. Low-energy ion irradiation was used to modify the surface of the films within a few nanometers, yet with high enough energy to produce oxygen and titanium vacancies. The as-prepared thin film shows ferromagnetism which increases after irradiation with low-energy ions. An optimal and clear magnetic anisotropy was observed after the first irradiation, opposite to the expected form anisotropy. Taking into account the experimental parameters, titanium vacancies as di-Frenkel pairs appear to be responsible for the enhanced ferromagnetism and the strong anisotropy observed in our films. The magnetic impurities concentrations was measured by particle-induced X-ray emission with ppm resolution. They are ruled out as a source of the observed ferromagnetism before and after irradiation.

  14. Parameters Influencing the Photocatalytic Activity of Suspension-Sprayed TiO2 Coatings

    NASA Astrophysics Data System (ADS)

    Toma, Filofteia-Laura; Berger, Lutz-Michael; Shakhverdova, Irina; Leupolt, Beate; Potthoff, Annegret; Oelschlägel, Kathrin; Meissner, Tobias; Gomez, José Antonio Ibáñez; de Miguel, Yolanda

    2014-10-01

    Photocatalytic properties of titania have been studied very intensively for a variety of applications, including air and water purification. In order to clarify the influence of the phase composition and other parameters, thermal spraying with suspensions was applied to produce photocatalytically active titania coatings starting from two commercially available anatase and rutile submicron powders. Aqueous suspensions containing 40% solids by weight were sprayed with an HVOF process using ethylene as the fuel gas. The spray parameters were chosen in order to produce mechanically stable coatings and to preserve a high content of the initial crystalline phases of the powders. The coating microstructures, phase compositions, and surface properties were characterized. The photocatalytic performance was evaluated by degradation of the pink dye Rhodamine B (RB) using two techniques: degradation of an aqueous solution of RB and discoloration of impregnated RB. All the coatings exhibited photocatalytic activity to varying degrees, depending on the phase composition as well as other factors, namely, the coating microstructure, surface morphology, surface hydroxylation, light absorption, and interaction with the pollutant.

  15. Cotton fabric coated with nano TiO 2-acrylate copolymer for photocatalytic self-cleaning by in-situ suspension polymerization

    NASA Astrophysics Data System (ADS)

    Jiang, Xue; Tian, Xiuzhi; Gu, Jian; Huang, Dan; Yang, Yiqi

    2011-08-01

    Two kinds of nano TiO 2-polyacrylate hybrid dispersions, TBM-w and TBM-e were synthesized by in-situ suspension polymerization and solution polymerization respectively, in order to fix the nano TiO 2 on fabrics. The photocatalytic self-cleaning fabrics have received much attention in recent years for its water-saving and environment-protection advantages. However, the fixation of the photocatalyst on fabrics is still a key problem that inhibits industrialization of these eco-friendly fabrics. The cotton fabric was treated by the two hybrid dispersions. The photocatalytic self-cleaning property was characterized. Infrared spectroscopy, burning loss test and thermogravimetry showed that some copolymer chains entangled with the nano TiO 2. Transmission electron microscope illustrated that there was a polymeric layer on the surface of nano TiO 2. The average diameter of TBM-w was smaller than that of TBM-e based on size analysis. The photocatalytic decoloration of the grape syrup indicated that the fabric with TiO 2-polymer hybrid had excellent self-cleaning property.

  16. In situ Fenton reagent generated from TiO2/Cu2O composite film: a new way to utilize TiO2 under visible light irradiation.

    PubMed

    Zhang, Yong-Gang; Ma, Li-Li; Li, Jia-Lin; Yu, Ying

    2007-09-01

    TiO2/Cu2O composite is prepared by a simple electrochemical method and coated on glass matrix through a spraying method. The obtained composite is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of TiO2/Cu2O composite films with different ratio of TiO2 and Cu2O on photodegradation of the dye methylene blue under visible light is investigated in detail. It is found that the photocatalytic activity of TiO2/Cu2O composite film with the presence of FeSO4 and EDTA is much higher than that for the similar system with only TiO2 and Cu2O film respectively. Without the presence of FeSO4 and EDTA, there is no degradation for methylene blue. The exploration of the optimized parameters for the degradation of methylene blue by using TiO2/Cu2O composite film as catalyst under visible light was also carried out. The most significant factor is the amount of Ti02 in the composite, and the second significant factor is the concentration of FeSO4. During the degradation of methylene blue under visible light, TiO2/Cu2O composite film generates H202, and Fenton regent is formed with Fe2+ and EDTA, which is detected in this study. The mechanism for the great improvement of photocatalytic activity of TiO2/Cu2O composite film under visible light is proposed by the valence band theory. Electrons excitated from TiO2/Cu2O composite under visible light are transferred from the conduction band of Cu2O to that of Ti02. The formed intermediate state of Ti 3+ ion is observed by X-ray photoelectron spectroscopy (XPS) on the TiO/Cu2O composite film. Additionally, the accumulated electrons in the conduction band of TiO2 are transferred to oxygen on the TiO2 surface for the formation of O2- or O2(2-), which combines with H+ to form H2O2. The evolved H202 with FeSO4 and EDTA forms Fenton reagentto degrade methylene blue. Compared to the traditional Fenton reagent, this new kind of in situ Fenton reagent generated from TiO2/Cu2O composite film does not need to supply H202. It is expected to be easily recycled, which may reduce second pollution and the cost of wastewater treatment. Moreover, this TiO/Cu2O composite film with FeSO4 and EDTA provides a new way to take advantage of TiO2 under visible light.

  17. Photodecolorization of Rhodamine B on tungsten-doped TiO2/activated carbon under visible-light irradiation.

    PubMed

    Li, Youji; Zhou, Xiaoming; Chen, Wei; Li, Leiyong; Zen, Mengxiong; Qin, Shidong; Sun, Shuguo

    2012-08-15

    Tungsten-doped TiO(2)/activated carbon catalysts have been prepared by a supercritical-pretreatment-assisted sol-gel process. The structural features of the photocatalysts have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV/Vis diffuse-reflectance spectroscopy (DRS), electron dispersive X-ray (EDX), photoluminescence spectroscopy, and Brunauer-Emmett-Teller (BET) analysis. The results revealed that a W-TiO(2) layer was coated on the AC surface, and had higher surface area and smaller crystallite size than TiO(2)/AC obtained by a similar route. The W dopant was responsible for narrowing the band gap of TiO(2) and shifting its optical response from the ultraviolet (UV) to the visible-light region. The photocatalytic performances of the supported catalysts have been evaluated for the degradation of Rhodamine B (RhB) solution under visible-light irradiation. Compared with bulk W-TiO(2), the photoactivity was obviously enhanced when it was coated onto AC. In addition, it was found that the reactivity showed a significant relationship with the amount of W dopant, and the photoactivity order of the catalysts from weak to strong showed good agreement with their PL intensities. The effects of TiO(2) content, tungsten ion content, catalyst amount, pH, and initial RhB concentration have been examined as operational parameters. The photocatalytic reactions followed pseudo-first-order kinetics and are discussed in terms of the Langmuir-Hinshelwood model.

  18. TiO2 coated Au/Ag nanorods with enhanced photocatalytic activity under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Zhou, Na; Polavarapu, Lakshminarayana; Gao, Nengyue; Pan, Yanlin; Yuan, Peiyan; Wang, Qing; Xu, Qing-Hua

    2013-05-01

    A facile method was used to prepare uniform Au NR/TiO2 and Au/Ag NR/TiO2 core-shell composite nanoparticles. Au/Ag NR/TiO2 nanoparticles were found to display significantly enhanced visible light photo-catalytic activity compared to Au NR/TiO2 and the commercially available TiO2 nanoparticles. The enhancement mechanism was ascribed to injection of hot electrons of photo-excited Au/Ag NRs to TiO2, which was confirmed by 633 nm laser induced reduction of silver ions on the surface of Au/Ag NR/TiO2 composite nanoparticles.A facile method was used to prepare uniform Au NR/TiO2 and Au/Ag NR/TiO2 core-shell composite nanoparticles. Au/Ag NR/TiO2 nanoparticles were found to display significantly enhanced visible light photo-catalytic activity compared to Au NR/TiO2 and the commercially available TiO2 nanoparticles. The enhancement mechanism was ascribed to injection of hot electrons of photo-excited Au/Ag NRs to TiO2, which was confirmed by 633 nm laser induced reduction of silver ions on the surface of Au/Ag NR/TiO2 composite nanoparticles. Electronic supplementary information (ESI) available: The details of experimental procedures, SEM and TEM images of various nanoparticles prepared, photographs of the samples, control experiments, reusability test, wavelength dependent photocatalytic activities of Au/Ag/TiO2 nanoparticles, and UV-Vis spectra of a Ag nanoparticle formed on the surface of Au/Ag/TiO2 under visible light irradiation. See DOI: 10.1039/c3nr00517h

  19. Observation of photoexcitation of Fe-oxide grown on TiO2(100) by visible light irradiation

    NASA Astrophysics Data System (ADS)

    Kawauchi, Taizo; Nagatsuka, Naoki; Fukutani, Katsuyuki

    2016-12-01

    Electronic excitation of materials is of fundamental and technological importance and interest in terms of photoinduced phase transition, photovoltaics, and photocatalysis. In the present study, photoexcitation of Fe2 O 3 epitaxially grown on rutile TiO2(100) was investigated with conversion electron Mössbauer spectroscopy (CEMS) under dominantly visible-light irradiation. 57Fe was deposited on the substrate at a substrate temperature of 973 K, and the resulting film was characterized by RHEED and XPS. After deposition of Fe on TiO2(100), it was found that Fe was oxidized to Fe 3+, and the structure was analyzed to be the rhombohedral phase of Fe2 O 3. While the CEMS spectrum without light irradiation showed a quadrupole splitting of 0.80 mm/s with an isomer shift of +0.25 mm/s, an additional component with a quadrupole splitting of 0.85 and an isomer shift of +0.67 mm/s was observed under light irradiation. The latter component corresponds to a reduced state of Fe at the octahedral site surrounded by oxygen atoms. The lifetime of this photoexcited state is discussed.

  20. Confirmation of hydroxyl radicals (•OH) generated in the presence of TiO2 supported on AC under microwave irradiation.

    PubMed

    Zhang, Zhaohong; Yu, Fengyang; Huang, Lirong; Jiatieli, Jianaerguli; Li, Yuanyuan; Song, Lijun; Yu, Ning; Dionysiou, Dionysios D

    2014-08-15

    In order to study the degradation mechanism of technology of microwave (MW) combined with TiO2 supported on activated carbon (TiO2/AC), the reactive oxygen species (ROS) was explored through oxidation of 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). Furthermore, 2,6-di-tert-butyl-4-methylphenol (BHT), Mannitol (MT) and Vitamin C (VC) were used as radical scavengers to confirm the generation of the hydroxyl radicals ((•)OH). In addition, the influence of some parameters such as TiO2 mass ratio content, irradiation time, material dose, DPCI concentration and MW power on the determination of (•)OH were examined. The results showed that the (•)OH could be generated under MW combined with loaded TiO2/AC. Also, anatase TiO2/AC can generate more (•)OH radicals than rutile TiO2/AC under MW irradiation. This work would provide new mechanistic insights on the enhanced degradation effect of organic pollutants in water using the supported TiO2/AC coupled with MW technology.

  1. Efficient Photocatalytic Disinfection of Escherichia coli O157:H7 using C70-TiO2 Hybrid under Visible Light Irradiation

    NASA Astrophysics Data System (ADS)

    Ouyang, Kai; Dai, Ke; Walker, Sharon L.; Huang, Qiaoyun; Yin, Xixiang; Cai, Peng

    2016-05-01

    Efficient photocatalytic disinfection of Escherichia coli O157:H7 was achieved by using a C70 modified TiO2 (C70-TiO2) hybrid as a photocatalyst under visible light (λ > 420 nm) irradiation. Disinfection experiments showed that 73% of E. coli O157:H7 died within 2 h with a disinfection rate constant of k = 0.01 min‑1, which is three times that measured for TiO2. The mechanism of cell death was investigated by using several scavengers combined with a partition system. The results revealed that diffusing hydroxyl radicals play an important role in the photocatalytically initiated bacterial death, and direct contact between C70-TiO2 hybrid and bacteria is not indispensable in the photocatalytic disinfection process. Extracellular polymeric substances (EPS) of bacteria have little effect on the disinfection efficiency. Analyses of the inhibitory effect of C70-TiO2 thin films on E. coli O157:H7 showed a decrease of the bacterial concentration from 3 × 108 to 38 cfu mL‑1 in the solution with C70-TiO2 thin film in the first 2 h of irradiation and a complete inhibition of the growth of E. coli O157:H7 in the later 24 h irradiation.

  2. Efficient Photocatalytic Disinfection of Escherichia coli O157:H7 using C70-TiO2 Hybrid under Visible Light Irradiation

    PubMed Central

    Ouyang, Kai; Dai, Ke; Walker, Sharon L.; Huang, Qiaoyun; Yin, Xixiang; Cai, Peng

    2016-01-01

    Efficient photocatalytic disinfection of Escherichia coli O157:H7 was achieved by using a C70 modified TiO2 (C70-TiO2) hybrid as a photocatalyst under visible light (λ > 420 nm) irradiation. Disinfection experiments showed that 73% of E. coli O157:H7 died within 2 h with a disinfection rate constant of k = 0.01 min−1, which is three times that measured for TiO2. The mechanism of cell death was investigated by using several scavengers combined with a partition system. The results revealed that diffusing hydroxyl radicals play an important role in the photocatalytically initiated bacterial death, and direct contact between C70-TiO2 hybrid and bacteria is not indispensable in the photocatalytic disinfection process. Extracellular polymeric substances (EPS) of bacteria have little effect on the disinfection efficiency. Analyses of the inhibitory effect of C70-TiO2 thin films on E. coli O157:H7 showed a decrease of the bacterial concentration from 3 × 108 to 38 cfu mL−1 in the solution with C70-TiO2 thin film in the first 2 h of irradiation and a complete inhibition of the growth of E. coli O157:H7 in the later 24 h irradiation. PMID:27161821

  3. Effect of irradiation on deposition of CdS in fabricating co-axial heterostructure of TiO2 nanotube arrays via chemical deposition

    NASA Astrophysics Data System (ADS)

    Pan, Rongjun; Wu, Yucheng; Li, Zhenglin; Fang, Zhijie

    2014-02-01

    Highly-ordered TiO2 nanotube arrays were synthesized electrochemically. Effect of irradiation on deposition of CdS in fabricating co-axial heterogeneous structure via chemical deposition was investigated. The field emission measurements revealed that irradiation with higher energy will help to achieve not only more CdS, but also neater and more intimate heterostructure through exerting influences on ion migration into the tubes and attachment of ions onto the tube walls. The XRD measurements revealed that the deposited nanotubes are composed of anatase TiO2, metallic Ti, and CdS. The optical characterization revealed that the photoabsorption and absorption activity are correlated with the energy of irradiation. The photoelectrochemical measurements revealed that the photocurrent density are also correlated with the energy of the irradiation. The stability of the obtained structures was governed by the contact between CdS and TiO2 as well as the amount of CdS.

  4. Synthesis of TiO2 nanorod-decorated graphene sheets and their highly efficient photocatalytic activities under visible-light irradiation.

    PubMed

    Lee, Eunwoo; Hong, Jin-Yong; Kang, Haeyoung; Jang, Jyongsik

    2012-06-15

    The titanium dioxide (TiO(2)) nanorod-decorated graphene sheets photocatalysts with different TiO(2) nanorods population have been synthesized by a simple non-hydrolytic sol-gel approach. Electron microscopy and X-ray diffraction analysis indicated that the TiO(2) nanorods are well-dispersed and successfully anchored on the graphene sheet surface through the formation of covalent bonds between Ti and C atoms. The photocatalytic activities are evaluated in terms of the efficiencies of photodecomposition and adsorption of methylene blue (MB) in aqueous solution under visible-light irradiation. The as-synthesized TiO(2) nanorod-decorated graphene sheets showed unprecedented photodecomposition efficiency compared to the pristine TiO(2) nanorods and the commercial TiO(2) (P-25, Degussa) under visible-light. It is believed that this predominant photocatalytic activity is due to the synergistic contribution of both a retarded charge recombination rate caused by a high electronic mobility of graphene and an increased surface area originated from nanometer-sized TiO(2) nanorods. Furthermore, photoelectrochemical study is performed to give deep insights into the primary roles of graphene that determines the photocatalytic activity.

  5. Cu doped TiO2/GF for photocatalytic disinfection of Escherichia coli in bioaerosols under visible light irradiation: Application and mechanism

    NASA Astrophysics Data System (ADS)

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2014-03-01

    This study investigated the role of Cu as a doping agent to enhance photocatalytic activity of TiO2 in Cu-doped TiO2/glass fibers (Cu-TiO2/GF) used for disinfection of Escherichia coli (E. coli) in aerosols under visible light irradiation. Glass fiber was used as a substrate to immobilize TiO2 for disinfection of E. coli in bioaerosols. Cu in the prepared photocatalyst acted as an intermediate agent for the transfer of photo-generated electrons from the valence band to the conduction band of TiO2. Cu dopants increased the electron-hole pair separation efficiency, inhibited their recombination leading to a lifetime increase of the generated electrons, and thus improved photocatalytic activity even under visible light irradiation. Cu also defected the TiO2 lattice by producing Ti3+ ions, which can increase the electron-hole separation capacity of the photocatalyst, thereby increasing photocatalytic capacity. The optimal Cu content in Cu/TiO2 to enhance the photocatalytic activity of TiO2 was 5 wt.%. Among three humidity conditions (dry (40 ± 5%), moderate (60 ± 5%) and humid (80 ± 5%)), the moderate condition showed the highest disinfection efficiency of E. coli. When the 5% Cu-TiO2/GF was used under a moderate level of humidity, the highest disinfection efficiency and disinfection capacity of E. coli were identified as 87.8% and 23 CFU/s cm2, respectively.

  6. Self-doped Ti3+-TiO2 as a photocatalyst for the reduction of CO2 into a hydrocarbon fuel under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Sasan, Koroush; Zuo, Fan; Wang, Yuan; Feng, Pingyun

    2015-08-01

    Self-doped TiO2 shows visible light photocatalytic activity, while commercial TiO2 (P25) is only UV responsive. The incorporation of Ti3+ into TiO2 structures narrows the band gap (2.90 eV), leading to significantly increased photocatalytic activity for the reduction of CO2 into a renewable hydrocarbon fuel (CH4) in the presence of water vapour under visible light irradiation.Self-doped TiO2 shows visible light photocatalytic activity, while commercial TiO2 (P25) is only UV responsive. The incorporation of Ti3+ into TiO2 structures narrows the band gap (2.90 eV), leading to significantly increased photocatalytic activity for the reduction of CO2 into a renewable hydrocarbon fuel (CH4) in the presence of water vapour under visible light irradiation. Electronic supplementary information (ESI) available: Experimental details, XPS, XRD and SEM images. See DOI: 10.1039/c5nr02974k

  7. Photocatalytic degradation of non-steroidal anti-inflammatory drugs with TiO2 and simulated solar irradiation.

    PubMed

    Méndez-Arriaga, Fabiola; Esplugas, Santiago; Giménez, Jaime

    2008-02-01

    The aim of this work is to evaluate and compare the degradation achieved for three non-steroidal anti-inflammatory drugs (NSAIDs) by heterogeneous TiO2 photocatalytic means in aqueous solution at laboratory scale. The selected pharmaceutical compounds were diclofenac (DCF), naproxen (NPX) and ibuprofen (IBP). These compounds were used in their sodium salt chemical form. Previous experiments (adsorption, photolysis and thermodegradation) were developed to evaluate non-catalytic degradation for each NSAID. Photocatalytic experiments were carried out in a Xe-lamp reactor in order to study the influences of different operational conditions (catalyst load, temperature and dissolved oxygen concentration). These results showed that the optimum amount of TiO2, to achieve maximum degradation, of IBP was 1g/L. In contrast, the maximum degradation for DCF or NPX was observed at a TiO2 loading of 0.1g/L. Temperature had a significant effect only for NPX degradation, achieving almost 99% phototransformation. No significant differences were observed for DCF and IBP at 20, 30 and 40 degrees C. Dissolved oxygen concentration was an important parameter to increase the degradation for NPX and IBP. However, it was observed that its rate of mineralization did not increase. Intermediate metabolites were detected in all cases. Hydroxyl metabolites were the most important residual compounds after the photocatalytic treatment of IBP. The inhibition percentage of bioluminescence from Vibro fischeri--as a toxicity parameter--increased during the irradiation time due to the residual concentration of the hydroxyl metabolites generated. However, after 120 min, in experiments with 40 mg/L of dissolved oxygen, a decrease of the % inhibition was observed. Only photocatalytic treatment of IBP drives to a satisfactory biodegradability index BOD5/COD (between 0.16 and 0.42) and, only in this case, a post-biological treatment could be suggested.

  8. Synthesis and characterization of low-cost g-C3N4/TiO2 composite with enhanced photocatalytic performance under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Senthil, R. A.; Theerthagiri, J.; Selvi, A.; Madhavan, J.

    2017-02-01

    The influence of g-C3N4 in TiO2 photocatalyst on photodegradation of organic pollutant in aqueous solution has been investigated in the present study. The g-C3N4 was synthesized from low cost urea and used as precursor to synthesize g-C3N4/TiO2 composite by wet impregnation method. The synthesized g-C3N4 and g-C3N4/TiO2 composite photocatalysts were thoroughly characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy. The photocatalytic performance of pure g-C3N4, pure TiO2 and g-C3N4/TiO2 composite photocatalysts were evaluated for the photodegradation of acid orange 7 (AO7) under visible light irradiation. The photocatalytic experiments demonstrated that the g-C3N4/TiO2 composite photocatalyst showed much better photocatalytic degradability of AO7 than the pure TiO2 and g-C3N4. This may be due to the increased absorption of light in the visible region and also by a lower recombination of charge-carriers. Further, the photoelectrochemical measurements of g-C3N4/TiO2 revealed the faster migration of photo-induced charge-carriers. This study demonstrates that g-C3N4/TiO2 composite can be a good candidate for environmental remediation of polluted waters.

  9. Comparative study of photocatalytic activities of magnetically separable WO3/TiO2/Fe3O4 nanocomposites and TiO2, WO3/TiO2 and TiO2/Fe3O4 under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Fallah Shojaei, Abdollah; Shams-Nateri, Ali; Ghomashpasand, Maryam

    2015-12-01

    In this study WO3/TiO2/Fe3O4 nanocomposite particles with different amount of WO3 content (1, 3, 5, 8 and 10 wt.%) were prepared via sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface areas, diffuse reflectance spectra (DRS) and the vibration sample magnetometry (VSM) were used to characterize the nanocomposites. The photocatalytic activity of the nanoparticles was tested by degrading direct blue 71 dye solution under visible light irradiation. The enhanced photocatalytic activity is attributed to the electron-hole separation and transformation among the semiconductors. The effect of the initial dye concentration, catalyst dosage and the photocatalytic reaction apparent rate constant kapp were also investigated. On the other hand the WO3/TiO2/Fe3O4 nanocomposites could be readily recovered from the reaction solution by using a permanent magnetic bar and their photocatalytic activity was studied after six cycles of repetitive recycling. Then, this nanocomposite can be used as highly efficient and reusable photocatalyst.

  10. Reinvestigation of the photocatalytic reaction mechanism for Pt-complex-modified TiO2 under visible light irradiation by means of ESR spectroscopy and chemiluminescence photometry.

    PubMed

    Nishikawa, Masami; Sakamoto, Hodaka; Nosaka, Yoshio

    2012-10-04

    A plausible reaction mechanism for a visible light photocatalyst of TiO(2) modified with platinum(IV) chloride (PtCl) was proposed on the basis of the measurements with electron spin resonance (ESR) spectroscopy and chemiluminescence photometry. Under visible light (λ > 500 nm) irradiation, the deposited Pt(IV) chloride is charge-separated into Pt(3+) and Cl radical by the excitation of the ligand-to-metal charge transfer. The Pt(3+) gives an electron to the conduction band of TiO(2), which has Pt(3+) return to Pt(4+). The electron in the conduction band reduces the oxygen molecule into O(2)(-). The presence of Pt(3+) and O(2)(-) has been elucidated in the present study. Moreover, valence band holes of TiO(2) were detected by ESR spectroscopy under visible light irradiation. Therefore, besides being used to oxidize organic compounds, the photogenerated Cl radicals likely receive electrons from the TiO(2) valence band by visible light excitation, producing the valence band holes. Because the valence band holes have a stronger oxidation power than Cl radicals, the excitation of valence band electrons to Cl radicals would be the origin of the high photocatalytic activity of the PtCl-modified TiO(2) under visible light irradiation.

  11. Effect of UV irradiation on the aggregation of TiO2 in an aquatic environment: Influence of humic acid and pH.

    PubMed

    Wang, Peifang; Qi, Ning; Ao, Yanhui; Hou, Jun; Wang, Chao; Qian, Jin

    2016-05-01

    The behavior of photoactive TiO2 nanoparticles in an aquatic environment under UV irradiation was investigated. When there was no UV light irradiation, the attachment of humic acid (HA) onto the TiO2 nanoparticles improved their stability due to an increase in the electrostatic and steric repulsions between the particles. However, our study demonstrated that UV light clearly influenced the aggregation of TiO2 nanoparticles. Half an hour of UV irradiation caused the particles to aggregate from 331.0 nm to 1505.0 nm at a pH of 3.0. Similarly, the particles aggregated from 533.2 nm to 1037.0 nm at a pH of 6.5 and from 319.0 nm to 930.0 nm at a pH of 9.0. The aggregation continued with increased irradiation time, except for the condition at pH 3.0, which demonstrated disaggregation. Furthermore, we determined that the photocatalytic degradation of the HA dominated the behavior of TiO2 in our study. From the results of HA removal and 3DEEM fluorescence spectra data for the solution, a change in the HA was in accordance with the size change of the TiO2. The results illustrated that the UV irradiation affected the behavior of light-active nanomaterial (such as TiO2) in an aquatic system, thus influencing their bioavailability and reactivity.

  12. Photocatalytic decomposition of crotamiton over aqueous TiO(2) suspensions: determination of intermediates and the reaction pathway.

    PubMed

    Fukahori, Shuji; Fujiwara, Taku; Ito, Ryusei; Funamizu, Naoyuki

    2012-09-01

    The photocatalytic degradation of crotamiton in aqueous solution using TiO(2) was investigated. To investigate the effect of initial pH, the photodegradation behaviors of three types of pharmaceuticals were compared (crotamiton, clofibric acid, sulfamethoxazole). The degradation rates of crotamiton in the pH range 3-9 were nearly equal, but those of clofibric acid and sulfamethoxazole were affected by pH. At pH>6.5, TiO(2) particles, clofibric acid and sulfamethoxazole had negative charge, therefore, the repulsive force between TiO(2) particles and anionic pharmaceuticals occurred and a low reaction rate at high pH was observed. The effect of UV intensity and TiO(2) concentration on photodegradation efficiency was also investigated. Linear and logarithmical relationships between UV intensity, TiO(2) concentration and the reaction rate constant were confirmed. Furthermore, the structures of photodegradation intermediates formed concomitantly with the disappearance of crotamiton were estimated. Seven intermediates were characterized by LC/MS/MS analyses, and it was assumed that the photocatalytic degradation of crotamiton was initiated by the attack of electrophilic hydroxyl radicals on aromatic rings and alkyl chains.

  13. Biomolecule-controlled hydrothermal synthesis of C-N-S-tridoped TiO2 nanocrystalline photocatalysts for NO removal under simulated solar light irradiation.

    PubMed

    Wang, Yawen; Huang, Yu; Ho, Wingkei; Zhang, Lizhi; Zou, Zhigang; Lee, Shuncheng

    2009-09-30

    In this study, C-N-S-tridoped titanium dioxide (TiO(2)) nanocrystals were synthesized by using a facile hydrothermal method in the presence of a biomolecule l-cysteine. This biomolecule could not only serve as the common source for the carbon, sulfur and nitrogen tridoping, but also could control the final crystal phases and morphology. The resulting materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption and UV-vis diffuse reflectance spectroscopy. XPS analysis revealed that S was incorporated into the lattice of TiO(2) through substituting oxygen atoms, N might coexist in the forms of N-Ti-O and Ti-O-N in tridoped TiO(2) and most C could form a mixed layer of carbonate species deposited on the surface of TiO(2) nanoparticles. The photocatalytic activities of the samples were tested on the removal of NO at typical indoor air level in a flow system under simulated solar light irradiation. The tridoped TiO(2) samples showed much higher removal efficiency than commercial P25 and the undoped counterpart photocatalyst. The enhanced visible light photocatalytic activity of C-N-S-tridoped TiO(2) nanocrystals was explained on the basis of characterizations. The possible formation process of the monodispersed C-N-S-tridoped anatase TiO(2) nanocrystals was also proposed. This study provides a new method to prepare visible light active TiO(2) photocatalyst.

  14. Photocatalytic degradation of organic reactive dyes over MnTiO3/TiO2 heterojunction composites under UV-visible irradiation.

    PubMed

    Sivakumar, Santhanam; Selvaraj, Ayyasamy; Ramasamy, Anaipalayam Kandasamy

    2013-01-01

    In this study, the photocatalytic degradation of organic reactive dyes have been investigated using MnTiO3/TiO2 heterojunction composites in the presence of electron acceptors under UV-Visible light irradiation. This MnTiO3/TiO2 heterojunction composites were prepared by annealing different mass ratios of pyrophanite MnTiO3 (3-11 wt%) and TiO2 at 300°C. All the MnTiO3/TiO2 heterojunction composites were characterized by spectral techniques like X-ray diffraction (XRD), scanning electron microscope (SEM) and diffused reflectance UV-visible spectroscopic analysis (DRS). Among them, 9 wt% MnTiO3/TiO2 heterojunction composites exhibited higher photocatalytic activity for the degradation of Reactive Blue 4 (RB 4). The photocatalytic efficiency of 9 wt% MnTiO3/TiO2 heterojunction composites was further enhanced by the addition of substantial amount of electron acceptors like hydrogen peroxide (H2O2) and ammonium peroxydisulfate ([NH4]2S2O8). The presence of oxidants (electron acceptors) facilitates the fast degradation of dye solution even in higher concentration upto 200 mg/L. The photocatalytic activity of MnTiO3/TiO2 heterojunction composites was also studied for the degradation of other four different structured reactive dyes. The extent of mineralization of these organic reactive dyes during photocatalytic degradation was estimated from COD analysis. MnTiO3/TiO2 heterojunction composites was also found to have good photostability in the presence of oxidants.

  15. Synthesis of activated charcoal supported Bi-doped TiO2 nanocomposite under solar light irradiation for enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Chandraboss, V. L.; Kamalakkannan, J.; Senthilvelan, S.

    2016-11-01

    In this study, activated charcoal (AC) supported bismuth (Bi)-doped Titanium dioxide (TiO2) nanocomposite was synthesized by precipitation method. The photocatalytic activity of AC-Bi/TiO2 was investigated for the degradation of methylene blue (MB) in aqueous solution under solar light irradiation. The incorporation of Bi3+ into the TiO2 lattice shifts the absorbance of TiO2 to the visible region then the addition of high adsorption capacity activated charcoal to improve the efficiency of TiO2. AC-Bi/TiO2 is found to be more efficient than Bi/TiO2 and undoped TiO2 for the degradation of MB under solar light irradiation. Surface morphology and bulk composition of the composite was obtained using high resolution-scanning electron microscopy with energy dispersive X-ray analysis. The crystal structure evolution and elemental composition were analyzed by combining Fourier transform-Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The ultraviolet-visible (UV-vis) absorption spectra show that the absorption edge for the composite with Bi3+ has red shift as compared with that of undoped TiO2. UV-vis diffuse reflectance spectra demonstrated a decrease in the direct band gap of AC-Bi/TiO2. BET surface area, pore radius and pore volume of the materials were calculated by applying the BET equation to the sorption isotherms. The production of hydroxyl radicals (rad OH) on the surface of solar light irradiated materialswere detected by photoluminescence technique using coumarin as a probe molecule. The mechanism of photocatalytic effect of the AC-Bi/TiO2 was proposed for the degradation of MB under solar light irradiation.

  16. Variation of cell spreading on TiO2 film modified by 775 nm and 388 nm femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Tsukamoto, M.; Shinonaga, T.; Sato, Y.; Chen, P.; Nagai, A.; Hanawa, T.

    2014-03-01

    Titanium (Ti) is one of the most used biomaterials in metals. However, Ti is typically artificial materials. Thus, it is necessary for improving the biocompatibility of Ti. Recently, coating of the titanium dioxides (TiO2) film on Ti plate has been proposed to improve biocompatibility of Ti. We have developed coating method of the film on Ti plate with an aerosol beam. Periodic structures formation on biomaterials was also a useful method for improving the biocompatibility. Direction of cell spreading might be controlled along the grooves of periodic microstructures. In our previous study, periodic nanostructures were formed on the film by femtosecond laser irradiation at fundamental wave (775 nm). Period of the periodic nanostructures was about 230 nm. In cell test, cell spreading along the grooves of the periodic nanostructures was observed although it was not done for the film without the periodic nanostructures. Then, influence of the period of the periodic nanostructures on cell spreading has not been investigated yet. The period might be changed by changing the laser wavelength. In this study, the periodic nanostructures were created on the film with femtosecond laser at 775nm and 388 nm, respectively. After cell test, cell spreading along the grooves of the periodic nanostructures was observed on 775 nm and 388nm laser irradiated areas. Distribution of direction of cell spreading on laser irradiated area was also examined. These results suggested that controlling the cell spreading on periodic nanostructures with period of 230 nm was better than that with period of 130 nm.

  17. Enhanced photocatalytic activity of bismuth-doped TiO2 nanotubes under direct sunlight irradiation for degradation of Rhodamine B dye

    NASA Astrophysics Data System (ADS)

    Natarajan, Thillai Sivakumar; Natarajan, Kalithasan; Bajaj, Hari C.; Tayade, Rajesh J.

    2013-05-01

    Bismuth-doped TiO2 nanotubes (Bi-TNT) were successfully synthesized by combination of sol-gel and hydrothermal methods. The synthesized photocatalyst was efficiently used for degradation of rhodamine B (RhB) dye under direct sunlight irradiation. Subsequent characterization of synthesized photocatalysts was carried out using PXRD, SEM, TEM, EDX, FT-IR, Raman, N2 adsorption, TPD-NH3, UV-Vis DRS, XRF and ICP techniques. The surface area of the TiO2 nanoparticles increased after tubular structure formation (TiO2 nanoparticles—114.21 m2/g, TiO2 nanotube—191.93 m2/g). The degradation studies revealed that initial rate of photocatalytic degradation of RhB dye using Bi-TNT was 5.56, 4.16, 1.30 and 2.38 times higher as compared to TNP, Bi-TNP, TNT and Degussa P-25 TiO2 (P-25), respectively, under direct sunlight irradiation. The enhanced photocatalytic activity of Bi-TNT may be due to the increase in the surface area and Bi doping, which leads to effective separation of photogenerated carriers. The degradation was confirmed by chemical oxygen demand, total organic carbon and total inorganic carbon analysis of the degraded dye solutions. The probable degradation mechanism of RhB dye has also been proposed using liquid chromatography-mass spectrometry analysis of degraded samples.

  18. Enhancement of Electrical Properties of TiO2- x Oxide Semiconductor by d-Orbital Ordering Using Swift Heavy Ni-Ion Irradiation at Room Temperature

    NASA Astrophysics Data System (ADS)

    Cho, S. H.; Jun, B. H.; Chung, K. B.

    2017-02-01

    The electrical properties of radiofrequency (RF)-sputtered TiO2- x films have been investigated as a function of Ni-ion irradiation dose at room temperature. The prepared TiO2- x films were irradiated with 130-MeV swift heavy Ni ions in the range from 5 × 1011 ions/cm2 to 1 × 1013 ions/cm2. Increasing the Ni-ion irradiation dose dramatically enhanced the mobility in the TiO2- x films from 2.2 cm2/V s to 1.24 × 102 cm2/V s, while the carrier concentration did not vary. To explain this change in the electrical properties of the TiO2- x films, we investigated various physical properties, namely the physical structure, molecular orbital ordering in the conduction band, and shallow/deep trap states in the band-edge area below the conduction band. We suggest that the improvement in mobility originates from the ordering of the Ti 3 d orbital in the conduction band. In addition, increase of the Ni-ion irradiation dose changed two distinct band-edge states below the conduction band.

  19. Fabrication of Fe-doped TiO2 nanoparticles and investigation of photocatalytic decolorization of reactive red 198 under visible light irradiation.

    PubMed

    Moradi, Halimeh; Eshaghi, Akbar; Hosseini, Seyed Rahman; Ghani, Kamal

    2016-09-01

    In this research, Fe-doped TiO2 nanoparticles with various Fe concentrations (0. 0.1, 1, 5 and 10wt%) were prepared by a sol-gel method. Then, nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDX), BET surface area, photoluminescence (PL) spectroscopy and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the nano-particles was evaluated through degradation of reactive red 198 (RR 198) under UV and visible light irradiations. XRD results revealed that all samples contained only anatase phase. DRS showed that the Fe doping in the titania induced a significant red shift of the absorption edge and then the band gap energy decreased from 3 to 2.1eV. Photocatalytic results indicated that TiO2 had a highest photocatalytic decolorization of the RR 198 under UV irradiation whereas photocatalytic decolorization of the RR 198 under visible irradiation increased in the presence of Fe-doped TiO2 nanoparticles. Among the samples, Fe-1wt% doped TiO2 nanoparticles showed the highest photocatalytic decolorization of RR198 under visible light irradiation.

  20. A facile approach for TiO2-based superhydrophobic-superhydrophilic patterns by UV or solar irradiation without a photomask.

    PubMed

    Yanqing, Zhu; Jifu, Shi; Qizhang, Huang; Leilei, Wang; Gang, Xu

    2017-02-16

    A novel and facile approach to produce TiO2-based superhydrophobic-superhydrophilic patterns by UV or solar irradiation without a photomask is presented. The fabricated superhydrophobic-superhydrophilic patterns with excellent mechanical properties have long lifetimes in outdoor applications or other UV environments because of a self-supply of low surface tension material.

  1. Photocatalytic inactivation of bacteria from spoiled raw chicken carcasses in aqueous suspensions by TiO2 nanoparticles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bacterial spoilage is a major cause of reduced shelf life of fresh poultry; therefore, decreasing contamination by spoilage bacteria could increase the shelf life of these products. Titanium dioxide (TiO2) nanoparticles in the presence of UVA light possess antibacterial activities towards several ba...

  2. Fullerene-C60 derivatives prevent UV-irradiation/ TiO2-induced cytotoxicity on keratinocytes and 3D-skin tissues through antioxidant actions.

    PubMed

    Kato, Shinya; Aoshima, Hisae; Saitoh, Yasukazu; Miwa, Nobuhiko

    2014-05-01

    Microcorpuscular titanium dioxide (TiO2), a useful sunscreen agent, photocatalyzes generation of reactive oxygen species (ROS). We assessed protective effects of fullerene-C60 derivatives or microcolloidal platinum (Pt) against ultraviolet ray (UV)-irradiation in the presence of TiO2 in vitro. UV-irradiation (8 J/cm2, mixed UVA and UVB) in the presence of 15 ppm TiO2 on HaCaT keratinocytes decreased cell viability as quantified by WST-1 assay, and increased both intracellular ROS and cell-membrane-lipid peroxidation, as quantified by nitroblue-tetrazolium (NBT) assay and diphenyl-1-pyrenylphosphine (DPPP) assay, respectively, whereas all of three phototoxicity-related symptoms were appreciably repressed almost to UV-unirradiational levels by pretreatment with polyvinylpyrrolidone-entrapped fullerene-C60 (C60/PVP) or fullerene-C60 dissolved in squalane (C60/Sqn) in a dose-dependent manner of C60, but scarcely by PVP alone or Sqn alone. In contrast, Pt repressed intracellular ROS generation, but did not prevent either peroxidation of cell-membrane-lipid or cell mortality. Then in the epidermis of 3-dimensional human skin tissue model, UV-irradiation in the presence of TiO2 extensively induced two symptoms such as ROS-generation around perinuclear regions and membrane-lipid peroxidation, both of which were repressed by C60/PVP or C60/Sqn, whereas Pt did not prevent membrane-lipid peroxidation adequately. Thus the advantageous application of the lipophilic antioxidant fullerene-C60 which effectively protects cell membrane against peroxidation. In conclusion, fullerene-C60 can be expected to serve as an antioxidant for scavenging of TiO2-photocatalyzed ROS in the skin surface, and therefore provide a functional improvement of TiO2-containing sunscreens.

  3. Enhancement of photocatalytic activity of TiO2 by plasma irradiation

    NASA Astrophysics Data System (ADS)

    Kajita, Shin; Yoshida, Tomoko; Ohno, Noriyasu; Ishida, Tomoya; Kitaoka, Daiki

    2016-10-01

    In this study, plasma irradiations to titanium were conducted to enhance the photocatalytic activity of titanium oxide. When titanium is exposed to He plasmas, various morphology changes occur as forming nano-bubbles near the surface. Photocatalytic activity of the oxidized helium plasma irradiated titanium samples with nano-cones and microstructures were assessed by the hydrogen production from aqueous methanol solution. It is shown that the He plasma irradiation increases the photocatalytic activity more than double. Moreover, nitrogen mixture plasma irradiation to titanium (oxide) was conducted for doping nitrogen, which has been regarded as method to create visible light reactivity. It is shown from X-ray photoelectron spectroscopy (XPS) analysis that nitrogen doping has been successfully conducted under specific conditions.

  4. Catalytic damage of bovine serum albumin by metronidazole under ultrasonic irradiation in the presence of nano-sized TiO2 powder

    NASA Astrophysics Data System (ADS)

    Wang, J.; Wang, Z. G.; Jin, X. D.; Guo, Y. W.; Gao, J. Q.; Li, K.; Wang, B. X.; Li, Y.

    2012-05-01

    In previous work, it was found that the bovine serum albumin (BSA) could obviously be damaged by nano-sized TiO2 powder as a sonocatalyst under ultrasonic irradiation. In this work, metronidazole (MTZ) was adopted as a sensitizer to intensify the damage of BSA molecules. It was found that the damage degree of BSA molecules in the presence of MTZ was more serious than in the absence of MTZ. That is, under ultrasonic irradiation combined with nano-sized TiO2 powder, the addition of MTZ could remarkably aggravate the damage to BSA molecules. Meanwhile, the damage degree was also affected by some influence factors, such as ultrasonic irradiation time, ultrasonic irradiation power, MTZ concentration, solution acidity, ionic strength and solution temperature. In addition, the damage site of BSA molecules was also estimated by synchronous fluorescence spectra. It was found that the damage site of BSA molecules was mainly at tyrosine (Tyr) residue.

  5. [TiO2-Induced Photodegradation of Levofloxacin by Visible Light and Its Mechanism].

    PubMed

    Guo, Hong-sheng; Liu, Ya-nan; Qiao, Qi; Wei, Hong; Dong, Cheng-xing; Xue, Jie; Li, Ke-bin

    2015-05-01

    Levofloxacin is an emerging pollutant. Single levofloxacin and TiO2 have no visible-light activity. However, photodegradation of levofloxacin dramatically enhanced in the presence of TiO2 under visible light irradiation. Considering this finding, he photodegradation of levofloxacin over TiO2 was investigated under visible light irradiation. Effects of TiO2 dosage, levofloxacin concentration, and solution pH on levofloxacin photodegradation were examined by monitoring its concentration decay with time. The results showed that levofloxacin photodegradation fitted the Langmuir-Hinshelwood kinetic model. Solution pH, TiO2 dose, and levofloxacin concentration had significant effects on the photodegradation rates. In addition, batch adsorption experiments revealed that adsorption of levofloxacin on TiO2 conformed to the pseudo-second-order kinetics and the Langmuir isotherm. DRS spectrum of levofloxacin-adsorbed TiO2 suggested that a surface complex was formed between levofloxacin and TiO2. Addition of radical scavengers and N2-degassing affecting levofloxacin photodegradation indicated that the superoxide ion radical was mainly active species. UV-Vis spectra of a deaerated TiO2 and levofloxacin suspensions further confirmed that the electron injection into TiO2 conduction band took place under visible light irradiation. Based on these results, a charge-transfer mechanism initiated by photoexcitation of TiO2/ levofloxacin surface complex was proposed for levofloxacin photocatalytic degradation over TiO2 under visible light. This study indicates that the charge-transfer-complex-mediated photocatalytic technique has promising applications in the removal of colorless organic pollutants.

  6. Photocatalytic antibacterial effects on TiO2-anatase upon UV-A and UV-A/VIS threshold irradiation.

    PubMed

    Wu, Yanyun; Geis-Gerstorfer, Jürgen; Scheideler, Lutz; Rupp, Frank

    2016-01-01

    Photocatalysis mediated by the anatase modification of titanium dioxide (TiO2) has shown antibacterial effects in medical applications. The aim of this study was to investigate the possibility of expanding the excitation wavelengths for photocatalytic antibacterial effects from ultraviolet (UV) into the visible light range. After deposition of salivary pellicle and adhesion of Streptococcus gordonii on anatase, different irradiation protocols were applied to induce photocatalysis: ultraviolet A (UV-A) > 320 nm; ultraviolet/visible (UV-A/VIS) light > 380 nm and > 390 nm; and VIS light 400-410 nm. A quartz crystal microbalance with dissipation (QCM-D) tests and microscopic examination were used to observe the photoinduced antibacterial effects. Salivary pellicle could be photocatalytically decomposed under all irradiation protocols. In contrast, effective photocatalytic attack of bacteria could be observed by UV-A as well as by UV-A/VIS at 380 nm < λ < 390 nm only. Wavelengths above 380 nm show promise for in situ therapeutic antifouling applications.

  7. Efficient Performance of Electrostatic Spray-Deposited TiO2 Blocking Layers in Dye-Sensitized Solar Cells after Swift Heavy Ion Beam Irradiation.

    PubMed

    Sudhagar, P; Asokan, K; Jung, June Hyuk; Lee, Yong-Gun; Park, Suil; Kang, Yong Soo

    2011-12-01

    A compact TiO2 layer (~1.1 μm) prepared by electrostatic spray deposition (ESD) and swift heavy ion beam (SHI) irradiation using oxygen ions onto a fluorinated tin oxide (FTO) conducting substrate showed enhancement of photovoltaic performance in dye-sensitized solar cells (DSSCs). The short circuit current density (Jsc = 12.2 mA cm(-2)) of DSSCs was found to increase significantly when an ESD technique was applied for fabrication of the TiO2 blocking layer, compared to a conventional spin-coated layer (Jsc = 8.9 mA cm(-2)). When SHI irradiation of oxygen ions of fluence 1 × 10(13) ions/cm(2) was carried out on the ESD TiO2, it was found that the energy conversion efficiency improved mainly due to the increase in open circuit voltage of DSSCs. This increased energy conversion efficiency seems to be associated with improved electronic energy transfer by increasing the densification of the blocking layer and improving the adhesion between the blocking layer and the FTO substrate. The adhesion results from instantaneous local melting of the TiO2 particles. An increase in the electron transport from the blocking layer may also retard the electron recombination process due to the oxidized species present in the electrolyte. These findings from novel treatments using ESD and SHI irradiation techniques may provide a new tool to improve the photovoltaic performance of DSSCs.

  8. Chemistry of NOx on TiO2 Surfaces Studied by Ambient Pressure XPS: Products, Effect of UV Irradiation, Water, and Coadsorbed K(.).

    PubMed

    Rosseler, Olivier; Sleiman, Mohamad; Montesinos, V Nahuel; Shavorskiy, Andrey; Keller, Valerie; Keller, Nicolas; Litter, Marta I; Bluhm, Hendrik; Salmeron, Miquel; Destaillats, Hugo

    2013-02-07

    Self-cleaning surfaces containing TiO2 nanoparticles have been postulated to efficiently remove NOx from the atmosphere. However, UV irradiation of NOx adsorbed on TiO2 also was shown to form harmful gas-phase byproducts such as HONO and N2O that may limit their depolluting potential. Ambient pressure XPS was used to study surface and gas-phase species formed during adsorption of NO2 on TiO2 and subsequent UV irradiation at λ = 365 nm. It is shown here that NO3(-), adsorbed on TiO2 as a byproduct of NO2 disproportionation, was quantitatively converted to surface NO2 and other reduced nitrogenated species under UV irradiation in the absence of moisture. When water vapor was present, a faster NO3(-) conversion occurred, leading to a net loss of surface-bound nitrogenated species. Strongly adsorbed NO3(-) in the vicinity of coadsorbed K(+) cations was stable under UV light, leading to an efficient capture of nitrogenated compounds.

  9. Efficient Performance of Electrostatic Spray-Deposited TiO2 Blocking Layers in Dye-Sensitized Solar Cells after Swift Heavy Ion Beam Irradiation

    PubMed Central

    2011-01-01

    A compact TiO2 layer (~1.1 μm) prepared by electrostatic spray deposition (ESD) and swift heavy ion beam (SHI) irradiation using oxygen ions onto a fluorinated tin oxide (FTO) conducting substrate showed enhancement of photovoltaic performance in dye-sensitized solar cells (DSSCs). The short circuit current density (Jsc = 12.2 mA cm-2) of DSSCs was found to increase significantly when an ESD technique was applied for fabrication of the TiO2 blocking layer, compared to a conventional spin-coated layer (Jsc = 8.9 mA cm-2). When SHI irradiation of oxygen ions of fluence 1 × 1013 ions/cm2 was carried out on the ESD TiO2, it was found that the energy conversion efficiency improved mainly due to the increase in open circuit voltage of DSSCs. This increased energy conversion efficiency seems to be associated with improved electronic energy transfer by increasing the densification of the blocking layer and improving the adhesion between the blocking layer and the FTO substrate. The adhesion results from instantaneous local melting of the TiO2 particles. An increase in the electron transport from the blocking layer may also retard the electron recombination process due to the oxidized species present in the electrolyte. These findings from novel treatments using ESD and SHI irradiation techniques may provide a new tool to improve the photovoltaic performance of DSSCs. PMID:27502653

  10. Surface interactions and degradation of a fluoroquinolone antibiotic in the dark in aqueous TiO2 suspensions

    DOE PAGES

    Peterson, Jonathan W.; Gu, Baohua; Seymour, Michael D.

    2015-06-15

    Fluoroquinolone antibiotics (FQs) are important drugs used in human and veterinary medicine. Their detection in natural waters and waste water treatment plants, along with increased resistance to FQs among some bacteria, have generated an increased interest in the fate of these drugs in the environment. Partitioning of FQs between an aqueous solution and attendant substrates depends, in part, on the surface reactivity of the adsorbent, commonly a function of particle size, surface charge, and functional groups. In this paper, this study investigated the surface interactions between the FQ drug ofloxacin (OFL) and titanium oxide (TiO2), a common catalyst and widely-observedmore » constituent in many consumer products. Raman and fluorescence spectroscopic techniques, as well as LC/MS, were used to determine the OFL moieties present on TiO2 surfaces and in attendant solutions. Raman spectra indicate that the C==O (ketone) group of the quinolone core, the NH+ of the piperazinyl ring, and CH3 of benzoxazine core are the most active in sorption onto the TiO2 surface. Raman spectra also show that the sorbed benzoxazine–quinolone core and piperazinyl moieties are readily desorbed from the surface by re-suspending samples in water. Importantly, we found that OFL could be degraded by reacting with TiO2 even in the dark. Complementary LC/MS analysis of the attendant supernatants indicates the presence of de-piperazinylated and de-carboxylated OFL breakdown products in supernatant solutions. Together, both Raman and LC/MS analyses indicate that TiO2 breaks the compound into piperazinyl and carboxylate groups which attach to the surface, whereas de-carboxylated and hydroxylated quinolone moieties remain in solution. Finally, the present study thus identifies the sorption mechanisms and breakdown products of OFL during dark reactions with TiO2, which is critically important for understanding the fate and transport of OFL as it enters the soil and aquatic environment.« less

  11. Photocatalytic degradation of 5-nitro-1,2,4-triazol-3-one NTO in aqueous suspension of TiO2. Comparison with Fenton oxidation.

    PubMed

    Le Campion, L; Giannotti, C; Ouazzani, J

    1999-03-01

    5-nitro-1,2,4-triazol-3-one (NTO) is a powerful insensitive explosive, present in industrial waste waters. A remediation method based on photochemical decomposition and Fenton oxidation of NTO has been evaluated by monitoring the mineralization of 14C-labelled NTO. The TiO2-catalyzed photodegradation (lambda > 290 nm, TiO2 0.4 g/l, NTO 150 mg/l)) leads to the complete mineralization of NTO in 3 hours. This degradation involves a simultaneous denitrification and ring scission of NTO leading to nitrites, nitrates and carbon dioxide. No significant photo-degradation of NTO was detected in the absence of the catalyst. Long term irradiation over one week, leads to a complete degradation of concentrated NTO (5 g/l), suggesting that this method could be useful to clean-up NTO wastes. Fenton oxidation offers an efficient cost-effective method for NTO remediation. This reaction is faster that the TiO2 catalyzed photolysis and find application on the mineralization of high concentrations of NTO (15 g/l). Fenton oxidation provokes ring cleavage and subsequent elimination of the two carbon atoms of NTO as CO2. During this reaction, the nitro group is completely transformed into nitrates.

  12. New insight into singlet oxygen generation at surface modified nanocrystalline TiO2--the effect of near-infrared irradiation.

    PubMed

    Buchalska, Marta; Labuz, Przemysław; Bujak, Łukasz; Szewczyk, Grzegorz; Sarna, Tadeusz; Maćkowski, Sebastian; Macyk, Wojciech

    2013-07-14

    The generation of singlet oxygen in aqueous colloids of nanocrystalline TiO2 (anatase) modified by organic chelating ligands forming surface Ti(IV) complexes was studied. Detailed studies revealed a plausible and to date unappreciated influence of near-infrared irradiation on singlet oxygen generation at the surface of TiO2. To detect (1)O2, direct and indirect methods have been applied: a photon counting technique enabling time-resolved measurements of (1)O2 phosphorescence, and fluorescence measurements of a product of singlet oxygen interaction with Singlet Oxygen Sensor Green (SOSG). Both methods proved the generation of (1)O2. Nanocrystalline TiO2 modified with salicylic acid appeared to be the most efficient photosensitizer among the tested materials. The measured quantum yield reached the value of 0.012 upon irradiation at 355 nm, while unmodified TiO2 colloids appeared to be substantially less efficient generators of singlet oxygen with the corresponding quantum yield of ca. 0.003. A photocatalytic degradation of 4-chlorophenol, proceeding through oxidation by OH˙, was also monitored. The influence of irradiation conditions (UV, vis, NIR or any combination of these spectral ranges) on the generation of both singlet oxygen and hydroxyl radicals has been tested and discussed. Simultaneous irradiation with visible and NIR light did not accelerate OH˙ formation; however, for TiO2 modified with catechol it influenced (1)O2 generation. Singlet oxygen is presumably formed according to Nosaka's mechanism comprising O2˙(-) oxidation with a strong oxidant (hole, an oxidized ligand); however, the energy transfer from NIR-excited titanium(iii) centers (trapped electrons) plays also a plausible role.

  13. Enhanced Photocatalytic Activity for H2 Evolution under Irradiation of UV–Vis Light by Au-Modified Nitrogen-Doped TiO2

    PubMed Central

    Zhao, Weirong; Ai, Zhuyu; Dai, Jiusong; Zhang, Meng

    2014-01-01

    Background Purpose Photocatalytic water splitting for hydrogen evolution is a potential way to solve many energy and environmental issues. Developing visible-light-active photocatalysts to efficiently utilize sunlight and finding proper ways to improve photocatalytic activity for H2 evolution have always been hot topics for research. This study attempts to expand the use of sunlight and to enhance the photocatalytic activity of TiO2 by N doping and Au loading. Methods Au/N-doped TiO2 photocatalysts were synthesized and successfully used for photocatalytic water splitting for H2 evolution under irradiation of UV and UV–vis light, respectively. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and photoelectrochemical characterizations. Results DRS displayed an extension of light absorption into the visible region by doping of N and depositing with Au, respectively. PL analysis indicated electron-hole recombination due to N doping and an efficient inhibition of electron-hole recombination due to the loaded Au particles. Under the irradiation of UV light, the photocatalytic hydrogen production rate of the as-synthesized samples followed the order Au/TiO2 > Au/N-doped TiO2 > TiO2 > N-doped TiO2. While under irradiation of UV–vis light, the N-TiO2 and Au/N-TiO2 samples show higher H2 evolution than their corresponding nitrogen-free samples (TiO2 and Au/TiO2). This inconsistent result could be attributed to the doping of N and the surface plasmonic resonance (SPR) effect of Au particles extending the visible light absorption. The photoelectrochemical characterizations further indicated the enhancement of the visible light response of Au/N-doped TiO2. Conclusion Comparative studies have shown that a combination of nitrogen doping and Au loading enhanced the visible light response of TiO2 and

  14. Combined cytotoxic effect of UV-irradiation and TiO2 microbeads in normal urothelial cells, low-grade and high-grade urothelial cancer cells.

    PubMed

    Imani, Roghayeh; Veranič, Peter; Iglič, Aleš; Kreft, Mateja Erdani; Pazoki, Meysam; Hudoklin, Samo

    2015-03-01

    The differentiation of urothelial cells results in normal terminally differentiated cells or by alternative pathways in low-grade or high-grade urothelial carcinomas. Treatments with traditional surgical and chemotherapeutical approaches are still inadequate and expensive, as bladder tumours are generally highly recurrent. In such situations, alternative approaches, using irradiation of the cells and nanoparticles, are promising. The ways in which urothelial cells, at different differentiation levels, respond to UV-irradiation (photolytic treatment) or to the combination of UV-irradiation and nanoparticles (photocatalytic treatment), are unknown. Here we tested cytotoxicity of UV-irradiation on (i) normal porcine urothelial cells (NPU), (ii) human low-grade urothelial cancer cells (RT4), and (iii) human high-grade urothelial cancer cells (T24). The results have shown that 1 minute of UV-irradiation is enough to kill 90% of the cells in NPU and RT4 cultures, as determined by the live/dead viability assay. On the other hand, the majority of T24 cells survived 1 minute of UV-irradiation. Moreover, even a prolonged UV-irradiation for 30 minutes killed <50% of T24 cells. When T24 cells were pre-supplemented with mesoporous TiO2 microbeads and then UV-irradiated, the viability of these high-grade urothelial cancer cells was reduced to <10%, which points to the highly efficient cytotoxic effects of TiO2 photocatalysis. Using electron microscopy, we confirmed that the mesoporous TiO2 microbeads were internalized into T24 cells, and that the cell's ultrastructure was heavily compromised after UV-irradiation. In conclusion, our results show major differences in the sensitivity to UV-irradiation among the urothelial cells with respect to cell differentiation. To achieve an increased cytotoxicity of urothelial cancer cells, the photocatalytic approach is recommended.

  15. Facile synthesis of flake-like TiO2/C nano-composites for photocatalytic H2 evolution under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Yan, Baolin; Zhou, Juan; Liang, Xiaoyu; Song, Kainan; Su, Xintai

    2017-01-01

    The production of H2 by photocatalytic water splitting has become a promising approach for clean, economical, and renewable evolution of H2 by using solar energy. In spite of tremendous efforts, the present challenge for materials scientists is to build a highly active photocatalytic system with high efficiency and low cost. Here we report a facile method for the preparation of TiO2/C nano-flakes, which was used as an efficient visible-light photocatalyst for H2 evolution. This composite material was prepared by using a phase-transfer strategy combined with salt-template calcination treatment. The results showed that anatase TiO2 nanoparticles with the diameter of ∼10 nm were uniformly dispersed on the carbon nano-flakes. In addition, the samples prepared at 600 °C (denoted as T600) endowed a larger surface area of 196 m2 g-1 and higher light absorption, resulting in enhanced photocatalytic activity. Further, the T600 product reached a high H2 production rate of 57.2 μmol h-1 under visible-light irradiation. This unusual photocatalytic activity arose from the positive synergetic effect between the TiO2 and carbon in this hybrid catalyst. This work highlights the potential of TiO2/C nano-flakes in the field of photocatalytic H2 evolution under visible-light irradiation.

  16. Efficient photodegradation of dyes using light-induced self assembly TiO(2)/β-cyclodextrin hybrid nanoparticles under visible light irradiation.

    PubMed

    Zhang, Xu; Wu, Feng; Deng, Nansheng

    2011-01-15

    A novel β-cyclodextrin (β-CD) grafted titanium dioxide (TiO(2)/β-CD) was synthesized through photo-induced self assembly methods, and its structure was characterized. The TiO(2)/β-CD hybrid nanomaterial showed high photoactivity under visible light irradiation (λ ≥ 400 nm and/or λ ≥ 420 nm) and simulated solar irradiation (λ ≥ 365 nm). Photodegradation of Orange II followed the Langmuir-Hinshelwood kinetics model. The initial rate R(0) of Orange II degradation increased by 6.9, 2.6 and 1.9 times in the irradiation conditions of λ ≥ 420nm, λ ≥ 400nm and λ ≥ 365 nm, respectively. β-CD increased the lifetimes of the excited states of the unreactive guests and facilitated the electron transfer from the excited dye to the TiO(2) conduction band, which enhanced the dye pollutant degradation. Superoxide radicals were shown to be the main reactive species that caused the degradation of Orange II under visible irradiation.

  17. Mechanistic Features of the TiO2 Heterogeneous Photocatalysis of Arsenic and Uranyl Nitrate in Aqueous Suspensions Studied by the Stopped-Flow Technique.

    PubMed

    Meichtry, Jorge M; Levy, Ivana K; Mohamed, Hanan H; Dillert, Ralf; Bahnemann, Detlef W; Litter, Marta I

    2016-03-16

    The dynamics of the transfer of electrons stored in TiO2 nanoparticles to As(III) , As(V) , and uranyl nitrate in water was investigated by using the stopped-flow technique. Suspensions of TiO2 nanoparticles with stored trapped electrons (etrap (-) ) were mixed with solutions of acceptor species to evaluate the reactivity by following the temporal evolution of etrap (-) by the decrease in the absorbance at λ=600 nm. The results indicate that As(V) and As(III) cannot be reduced by etrap (-) under the reaction conditions. In addition, it was observed that the presence of As(V) and As(III) strongly modified the reaction rate between O2 and etrap (-) : an increase in the rate was observed if As(V) was present and a decrease in the rate was observed in the presence of As(III) . In contrast with the As system, U(VI) was observed to react easily with etrap (-) and U(IV) formation was observed spectroscopically at λ=650 nm. The possible competence of U(VI) and NO3 (-) for their reduction by etrap (-) was analyzed. The inhibition of the U(VI) photocatalytic reduction by O2 could be attributed to the fast oxidation of U(V) and/or U(IV) .

  18. Role of oxygen active species in the photocatalytic degradation of phenol using polymer sensitized TiO2 under visible light irradiation.

    PubMed

    Zhang, Dongdong; Qiu, Rongliang; Song, Lin; Eric, Brewer; Mo, Yueqi; Huang, Xiongfei

    2009-04-30

    The role of dissolved oxygen, and of active species generated by photo-induced reactions with oxygen, in the photocatalytic degradation of phenol was investigated using polymer [poly-(fluorene-co-thiophene) with thiophene content of 30%, so-called PFT30] sensitized TiO2 (PFT30/TiO2) under visible light irradiation. The photoluminescent (PL) quantum yield of PFT30/TiO2 was about 30% of that of PFT30/Al(2)O(3), proving that electron transfer took place between the polymer and TiO2. The result that photocatalytic degradation of phenol was almost stopped when the solution was saturated with N(2) proved the importance of O(2). Addition of NaN(3), an effective quencher of singlet oxygen ((1)O(2)), caused about a 40% decrease in the phenol degradation ratio. Addition of alcohols caused about a 60% decrease in the phenol photodegradation ratio, indicating that the hydroxyl radicals (OH), whose presence was confirmed by electron spin resonance (ESR) spectroscopy, was the predominant active species in aqueous solution. In anhydrous solution, singlet oxygen ((1)O(2)) was the predominant species. These results indicate that oxygen plays a very important role in the photocatalytic degradation of phenol.

  19. Design of composite photocatalyst of TiO2 and Y-zeolite for degradation of 2-propanol in the gas phase under UV and visible light irradiation.

    PubMed

    Kamegawa, Takashi; Ishiguro, Yasushi; Kido, Ryota; Yamashita, Hiromi

    2014-10-13

    Hydrophobic Y-zeolite (SiO2/Al2O3 = 810) and TiO2 composite photocatalysts were designed by using two different types of TiO2 precursors, i.e., titanium ammonium oxalate and ammonium hexafluorotitanate. The porous structure, surface property and state of TiO2 were investigated by various characterization techniques. By using an ammonium hexafluorotitanate as a precursor, hydrophobic modification of the Y-zeolite surface and realizing visible light sensitivity was successfully achieved at the same time after calcination at 773 K in the air. The prepared sample still maintained the porous structure of Y-zeolite and a large surface area. Highly crystalline anatase TiO2 was also formed on the Y-zeolite surface by the role of fluorine in the precursor. The usages of ammonium hexafluorotitanate were effective for the improvement of the photocatalytic performance of the composite in the degradation of 2-propanol in the gas phase under UV and visible light (λ > 420 nm) irradiation.

  20. Antibacterial activities of Nd doped and Ag coated TiO2 nanoparticles under solar light irradiation.

    PubMed

    Bokare, Anuja; Sanap, Avinash; Pai, Mrinal; Sabharwal, Sushma; Athawale, Anjali A

    2013-02-01

    Nanosized (8-9 nm) Nd doped and Ag coated TiO(2) nanoparticles have been synthesized by sol-gel method. The physicochemical properties of these particles were investigated by X-ray diffraction (XRD), diffuse reflectance UV-visible (DRUV) spectra and Brunauer-Emmett-Teller (BET) surface area analysis. The antibacterial activities of the samples were studied for Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) both, under the light and dark conditions. The results reveal that the extent of activity shows the order as undoped TiO(2)

  1. Effects of dissolved organic matter on adsorbed Fe(II) reactivity for the reduction of 2-nitrophenol in TiO2 suspensions.

    PubMed

    Zhu, Zhenke; Tao, Liang; Li, Fangbai

    2013-09-01

    Dissolved organic matter (DOM) is widespread in aquatic and terrestrial environments. Iron is the most abundant transition metal in the Earth's crust. The biogeochemistry of iron and the strength of Fe(II) as a reducing agent while adsorbed on minerals are affected by DOM. This study investigated the effects of Fe(II)/DOM interactions on the reduction of 2-nitrophenol (2-NP) in TiO2 suspensions. Kinetic measurements demonstrated that rates (k) of 2-NP reduction by adsorbed Fe(II) species are affected by adding DOM (denoted O-DOM), and the obtained k values under the impact of the Fe(II)/DOM interaction with different molecular weight DOM fractions [including MW<3500Da (L-DOM), 350014000Da (H-DOM)] showed significant differences. The enhanced rates of 2-NP reduction contributed to increases in the amount of adsorbed Fe(II) species and negative shifts in peak oxidation potential values (EP) in CV tests. For different molecular weight DOM fractions, increases in k (O-DOMsuspension containing the H-DOM fraction as compared the other two DOM fractions, which would further enhance the reduction rate of 2-NP. These findings promote a general understanding of Fe(II)/DOM interactions and their impact on the fate of contaminants in actual subsurface environments.

  2. Fabrication of a TiO2@porphyrin nanofiber hybrid material: a highly efficient photocatalyst under simulated sunlight irradiation

    NASA Astrophysics Data System (ADS)

    La, Duong Duc; Rananaware, Anushri; Phuong Nguyen Thi, Hoai; Jones, Lathe; Bhosale, Sheshanath V.

    2017-03-01

    The solar spectrum consists of 8% UV radiation, while 45% of solar energy is from visible light. It is therefore desirable to fabricate a hybrid material which is able to harvest energy from a wide range of photons from the sun for applications such as solar cells, photovoltaics, and photocatalysis. In this study we report on the fabrication of a TiO2@porphyrin hybrid material by surfactant-assisted co-assembly of monomeric porphyrin molecules with TiO2 nanoparticles. The obtained TiO2@porphyrin composite shows excellent integration of TiO2 particles with diameters of 15–30 nm into aggregated porphyrin nanofibers, which have a width of 70–90 nm and are several µm long. SEM, XPS, XRD, FTIR, UV–Vis and fluorescence spectroscopy were employed to characterize the TiO2@TCPP hybrid material. This material exhibits efficient photocatalytic performance under simulated sunlight, due to synergistic photocatalytic activities of the porphyrin aggregates in visible light and TiO2 particles in the UV region. A plausible mechanism for photocatalytic degradation is also proposed and discussed.

  3. Methylene blue photocatalytic mineralization under visible irradiation on TiO2 thin films doped with chromium

    NASA Astrophysics Data System (ADS)

    Diaz-Uribe, Carlos; Vallejo, William; Ramos, Wilkendry

    2014-11-01

    We studied changes in structural, optical and photocatalytic properties of TiO2 thin films due to doping process with chromium. Powders of undoped TiO2 and chromium-doped TiO2 (Cr:TiO2) were synthesized by sol-gel method and, thin films were deposited by doctor blade method. The properties of the thin films were studied by X-ray diffraction (XRD), infrared spectroscopy (IR) and diffuse reflectance. The XRD patterns indicated that doping process changed the crystalline phases radio of TiO2 thin films, furthermore, the optical analysis showed that band gap value of Cr:TiO2 thin films was 31% fewer than undoped TiO2 thin films. Along, Langmuir-Hinshelwood model was used to obtain kinetic information of the photo-mineralization process; results indicated that photocatalytic activity of Cr:TiO2 thin films were four times better than undoped TiO2 thin films; finally the synergic effect was tested by addition of the H2O2, photocatalytic yield was improved from 26% to 61% when methylene blue photo-mineralization was assisted with slightly amount of H2O2.

  4. Structural and photocatalytic studies of hydrothermally synthesized Mn2+-TiO2 nanoparticles under UV and visible light irradiation

    NASA Astrophysics Data System (ADS)

    Kamble, Ravi; Sabale, Sandip; Chikode, Prashant; Puri, Vijaya; Mahajan, Smita

    2016-11-01

    Pure TiO2 and Mn2+-TiO2 nanoparticles have been prepared by simple hydrothermal method with different Mn2+ concentrations. Obtained samples were analysed to determine it’s structural, optical, morphological and compositional properties using x-ray diffraction, UV-DRS, Raman, photoluminescence, XPS, TEM and EDS analysis. The EDS micrograph confirms the existence of Mn2+ atoms in TiO2 matrix with 0.86, 1.60 and 1.90 wt%. The crystallite size as well as band gap decreases with increase in Mn2+ concentration. The average particle size obtained from TEM was found 8-11 nm which is in good agreement with XRD results. Raman bands at 640, 518 and 398 cm-1 further confirmed pure phase anatase in all samples. XPS shows the proper substitutions of few sites of Ti4+ ions by Mn2+ ions in the TiO2 host lattice. The intensity of PL spectra for Mn2+-TiO2 shows a gradual decrease in the peak intensity with increasing Mn2+ concentration in TiO2, it implies lower electron-hole recombination rate as Mn2+ ions increases. The obtained samples were further studied for its photocatalytic activities using malachite green dye under UV light and visible light.

  5. Carbon coating stabilized Ti(3+)-doped TiO2 for photocatalytic hydrogen generation under visible light irradiation.

    PubMed

    Fu, Gao; Zhou, Peng; Zhao, Meiming; Zhu, Weidong; Yan, Shicheng; Yu, Tao; Zou, Zhigang

    2015-07-28

    Self-doping by Ti(3+) is a useful method to expand the light response of TiO2 into the visible light region. However, to obtain a stable Ti(3+)-doped TiO2 seems to be a challenge due to the easy oxidation of Ti(3+) during the heterogeneous reaction. Here, we propose a simple carbon coating route to stabilize the Ti(3+)-doped TiO2, in which both the Ti(3+) and precursor of the carbon coating layer were in situ formed from the hydrothermal hydrolysis of titanium isopropoxide. The carbon coated Ti(3+)-doped TiO2 exhibited excellent stability for photocatalytic hydrogen production. Based on electron paramagnetic resonance (EPR) analysis, the proposed stabilizing mechanism is that the conductive carbon coating layer as a barrier layer prevents the H2O and O2 from diffusing into the surface of the photocatalyst, which can oxidize the surface O vacancies and Ti(3+) in TiO2. Our findings offer a simple route to prepare a highly stable TiO2-based photocatalyst with visible light response.

  6. Efficient photocatalytic degradation of organic pollutants by magnetically recoverable nitrogen-doped TiO2 nanocomposite photocatalysts under visible light irradiation.

    PubMed

    Hamzezadeh-Nakhjavani, Sahar; Tavakoli, Omid; Akhlaghi, Seyed Parham; Salehi, Zeinab; Esmailnejad-Ahranjani, Parvaneh; Arpanaei, Ayyoob

    2015-12-01

    Preparation of novel nanocomposite particles (NCPs) with high visible-light-driven photocatalytic activity and possessing recovery potential after advanced oxidation process (AOP) is much desired. In this study, pure anatase phase titania (TiO2) nanoparticles (NPs) as well as three types of NCPs including nitrogen-doped titania (TiO2-N), titania-coated magnetic silica (Fe3O4 cluster@SiO2@TiO2 (FST)), and a novel magnetically recoverable TiO2 nanocomposite photocatalyst containing nitrogen element (Fe3O4 cluster@SiO2@TiO2-N (FST-N)) were successfully synthesized via a sol-gel process. The photocatalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM) with an energy-dispersive X-ray (EDX) spectroscopy analysis, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and vibrating sample magnetometer (VSM). The photocatalytic activity of as-prepared samples was further investigated and compared with each other by degradation of phenol, as a model for the organic pollutants, in deionized (DI) water under visible light irradiation. The TiO2-N (55 ± 1.5%) and FST-N (46 ± 1.5%) samples exhibited efficient photocatalytic activity in terms of phenol degradation under visible light irradiation, while undoped samples were almost inactive under same operating conditions. Moreover, the effects of key operational parameters, the optimum sample calcination temperature, and reusability of FST-N NCPs were evaluated. Under optimum conditions (calcination temperature of 400 °C and near-neutral reaction medium), the obtained results revealed efficient degradation of phenol for FST-N NCPs under visible light irradiation (46 ± 1.5%), high yield magnetic separation and efficient reusability of FST-N NCPs (88.88% of its initial value) over 10 times reuse.

  7. Effect of surface pretreatment of TiO2 films on interfacial processes leading to bacterial inactivation in the dark and under light irradiation.

    PubMed

    Rtimi, Sami; Nesic, Jelena; Pulgarin, Cesar; Sanjines, Rosendo; Bensimon, Michael; Kiwi, John

    2015-02-06

    Evidence is presented for radio-frequency plasma pretreatment enhancing the amount and adhesion of TiO2 sputtered on polyester (PES) and on polyethylene (PE) films. Pretreatment is necessary to attain a suitable TiO2 loading leading to an acceptable Escherichia coli reduction kinetics in the dark or under light irradiation for PES-TiO2 and PE-TiO2 samples. The amount of TiO2 on the films was monitored by diffuse reflectance spectroscopy and X-ray fluorescence. X-ray electron spectroscopy shows the lack of accumulation of bacterial residues such as C, N and S during bacterial inactivation since they seem to be rapidly destroyed by TiO2 photocatalysis. Evidence was found for Ti(4+)/Ti(3+) redox catalysis occurring on PES-TiO2 and PE-TiO2 during the bacterial inactivation process. On PE-TiO2 surfaces, Fourier transform infrared spectroscopy (ATR-FTIR) provides evidence for a systematic shift of the na(CH2) stretching vibrations preceding bacterial inactivation within 60 min. The discontinuous IR-peak shifts reflect the increase in the C-H inter-bond distance leading to bond scission. The mechanism leading to E. coli loss of viability on PES-TiO2 was investigated in the dark up to complete bacterial inactivation by monitoring the damage in the bacterial outer cell by transmission electron microscopy. After 30 min, the critical step during the E. coli inactivation commences for dark disinfection on 0.1-5% wt PES-TiO2 samples. The interactions between the TiO2 aggregates and the outer lipopolysaccharide cell wall involve electrostatic effects competing with the van der Waals forces.

  8. Degradation of microcystin-LR by highly efficient AgBr/Ag3PO4/TiO2 heterojunction photocatalyst under simulated solar light irradiation

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Utsumi, Motoo; Yang, Yingnan; Li, Dawei; Zhao, Yingxin; Zhang, Zhenya; Feng, Chuanping; Sugiura, Norio; Cheng, Jay Jiayang

    2015-01-01

    A novel photocatalyst AgBr/Ag3PO4/TiO2 was developed by a simple facile in situ deposition method and used for degradation of mirocystin-LR. TiO2 (P25) as a cost effective chemical was used to improve the stability of AgBr/Ag3PO4 under simulated solar light irradiation. The photocatalytic activity tests for this heterojunction were conducted under simulated solar light irradiation using methyl orange as targeted pollutant. The results indicated that the optimal Ag to Ti molar ratio for the photocatalytic activity of the resulting heterojunction AgBr/Ag3PO4/TiO2 was 1.5 (named as 1.5 BrPTi), which possessed higher photocatalytic capacity than AgBr/Ag3PO4. The 1.5 BrPTi heterojunction was also more stable than AgBr/Ag3PO4 in photocatalysis. This highly efficient and relatively stable photocatalyst was further tested for degradation of the hepatotoxin microcystin-LR (MC-LR). The results suggested that MC-LR was much more easily degraded by 1.5 BrPTi than by AgBr/Ag3PO4. The quenching effects of different scavengers proved that reactive h+ and •OH played important roles for MC-LR degradation.

  9. Photodegradation of Organic Pollutants on TiO2 P25 Surfaces Investigated by Transmission FTIR Spectroscopy Under In Situ UV-Vis Irradiation

    NASA Astrophysics Data System (ADS)

    Mino, Lorenzo; Negri, Chiara; Zecchina, Adriano; Spoto, Giuseppe

    2016-09-01

    A new transmission FTIR set-up has been developed to investigate photocatalytic reactions under in situ UV-Vis illumination and in controlled atmosphere. This system was employed to study the evolution of the surface species during the photodegradation of phenol and oxalic acid on TiO2 P25. As far as phenol is concerned, dosage from the gas phase on the activated oxide surface resulted in dissociative adsorption for coverages below the monolayer and in physisorption beyond this limit. Experiments under UV irradiation showed no relevant photocatalytic activity in absence of O2, the only spectroscopic consequence being the increase of a monotonic IR absorption, covering nearly the whole MIR range, related to UV-generated free conduction electrons. Only the contemporary addition of O2 and H2O to the TiO2/phenol system allowed us to observe an efficient photodegradation reaction and to highlight the IR manifestations of some of the photodegradation products which are formed. In particular, oxalic acid appeared to be the main intermediate product adsorbed at the oxide surface during phenol photodegradation. For this reason the photoreactivity of pure oxalic acid on TiO2 under UV irradiation was also investigated.

  10. Dopamine sensitized nanoporous TiO2 film on electrodes: photoelectrochemical sensing of NADH under visible irradiation.

    PubMed

    Wang, Guang-Li; Xu, Jing-Juan; Chen, Hong-Yuan

    2009-04-15

    Dopamine-coordinated photoactive TiO(2) nanoporous films with a wide excitation range of light in the visible region (up to 580 nm) were prepared and used for sensitive detection of NADH. Colloidal TiO(2) was firstly covered on an indium-tin oxide (ITO) electrode surface and sintered at 450 degrees C to form a nanoporous TiO(2) film, then the electrode was dipped in a dopamine solution to form a dopamine-TiO(2) charge transfer complex via coordinating dopamine with undercoordinated titanium atoms on the electrode surface. This charge transfer complex provided an anodic photocurrent under visible light and the photocurrent could be largely enhanced by NADH. The photocurrent enhancement might be due to the electron transfer between NADH and the holes localized on dopamine. A new photoelectrochemical methodology for sensitive detection of NADH at a relatively low potential was developed. The detection limit of NADH was 1.4x10(-7) M, and the detection range could extend up to 1.2x10(-4) M. The dopamine-TiO(2) modified electrode exhibits its major advantages such as effective electronic transducer, fast response and easy fabrication for photoelectrochemical determination of NADH. This strategy largely reduces the destructive effect of UV light and the photogenerated holes of illuminated TiO(2) to biomolecules and opens a new avenue for the applications of TiO(2) in photoelectrochemical biosensing.

  11. Facile synthesis of TiO2/microcrystalline cellulose nanocomposites: photocatalytically active material under visible light irradiation

    EPA Science Inventory

    Doped TiO2 nanocomposites were prepared in situ by a facile and simple synthesis utilizing benign and renewable precursors such as microcrystalline cellulose (MC) and TiCl4 through hydrolysis in alkaline medium without the addition of organic solvents. The as-prepared nanocompos...

  12. Online detection of reactive oxygen species in ultraviolet (UV)-Irradiated nano-TiO2 suspensions by continuous flow chemiluminescence.

    PubMed

    Wang, Dabin; Zhao, Lixia; Guo, Liang-Hong; Zhang, Hui

    2014-11-04

    Reactive oxygen species (ROS) play very important roles in the photocatalytic reactions of semiconductors. Using a continuous flow chemiluminescence (CFCL) system, we developed three methods for the selective, sensitive, and online detection of O2(• -), •OH, and H2O2 generated during ultraviolet (UV) irradiation of nano-TiO2 suspensions. TiO2 nanoparticles were irradiated in a photoreactor and pumped continuously into a detection cell. To detect O2(• -), luminol was mixed with TiO2 before it entered the detection cell. For the detection of short-lived •OH, phthalhydrazide was added into the photoreactor to capture •OH, and then mixed with H2O2/K5Cu(HIO6)2 to produce chemiluminescence (CL). To detect H2O2, an irradiated TiO2 suspension was kept in darkness for 30 min, and then mixed with luminol/K3Fe(CN)6 to produce CL. The selectivity of each method for a particular ROS was verified by using specific ROS scavengers. For a given ROS, a comparison between CL and conventional method showed good agreement for a series of TiO2 concentrations. The sensitivity of CL method was approximately 3-, 1200-, and 5-fold higher than the conventional method for O2(• -), •OH, and H2O2, respectively. To demonstrate the utility of the methods, ROS in three different types of TiO2 suspensions was detected by CFCL. It was found that photodegradation efficiency of Rhodamine B correlated the best (R(2) > 0.95) with the amount of photogenerated •OH, implying that •OH was the major oxidant in Rhodamine B photodegradation reaction. CFCL may provide a convenient tool for the studies on the reaction kinetics of ROS-participated decomposition of environmental contaminants.

  13. Highly recoverable TiO2-GO nanocomposites for stormwater disinfection.

    PubMed

    Wang, Gen; Feng, Wenjun; Zeng, Xiangkang; Wang, Zhouyou; Feng, Chuanping; McCarthy, David T; Deletic, Ana; Zhang, Xiwang

    2016-05-01

    A highly recoverable titanium dioxide-graphene oxide (TiO2-GO) composite was developed by a facile method of ultrasonic treatment of GO nanosheets and TiO2 nanoparticles, which should overcome the separation problem of nanosized TiO2 from treated water. Separability of the prepared samples was systematically investigated by gravity settling experiments. The samples' photocatalytic activity for stormwater disinfection was also studied under the irradiation of a solar simulator. The results demonstrated that TiO2-GO showed high efficient separability due to its accelerated settling behaviour. Zeta-potential analysis showed that the accelerated sedimentation of the catalyst was attributed to the aggregation of TiO2-GO resulting from the electrostatic attraction between TiO2 and GO. The TiO2-GO composite with a mass ratio of 100:2 (TiO2-2%GO) achieved both higher separability and good photocatalytic activity for stormwater disinfection. Its suspension became clear (turbidity < 50 NTU) after 8 h of sedimentation, while 99.5% of E.coli were deactivated in 90 min. The TiO2-GO composite exhibited excellent durability; no apparent change in the separability of TiO2-2%GO was observed after 10 treatment cycles (15 h in total), while only slight decrease in the photocatalytic activity was noted. In conclusion, the developed TiO2-GO composite showed promising results for stormwater disinfection.

  14. Photocatalytic decomposition of selected estrogens and their estrogenic activity by UV-LED irradiated TiO2 immobilized on porous titanium sheets via thermal-chemical oxidation.

    PubMed

    Arlos, Maricor J; Liang, Robert; Hatat-Fraile, Melisa M; Bragg, Leslie M; Zhou, Norman Y; Servos, Mark R; Andrews, Susan A

    2016-11-15

    The removal of endocrine disrupting compounds (EDCs) remains a big challenge in water treatment. Risks associated with these compounds are not clearly defined and it is important that the water industry has additional options to increase the resiliency of water treatment systems. Titanium dioxide (TiO2) has potential applications for the removal of EDCs from water. TiO2 has been immobilized on supports using a variety of synthesis methods to increase its feasibility for water treatment. In this study, we immobilized TiO2 through the thermal-chemical oxidation of porous titania sheets. The efficiency of the material to degrade target EDCs under UV-LED irradiation was examined under a wide range of pH conditions. A yeast-estrogen screen assay was used to complement chemical analysis in assessing removal efficiency. All compounds but 17β-estradiol were degraded and followed a pseudo first-order kinetics at all pH conditions tested, with pH 4 and pH 11 showing the most and the least efficient treatments respectively. In addition, the total estrogenic activity was substantially reduced even with the inefficient degradation of 17β-estradiol. Additional studies will be required to optimize different treatment conditions, UV-LED configurations, and membrane fouling mitigation measures to make this technology a more viable option for water treatment.

  15. Synthesize and characterize of Ag3VO4/TiO2 nanorods photocatalysts and its photocatalytic activity under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Zou, Xuejun; Dong, Yuying; Zhang, Xiaodong; Cui, Yubo

    2016-03-01

    In this paper, in order to expand the light response range of TiO2, Ag3VO4/TiO2 nanorods photocatalysts were fabricated by a simple sol-gel method with microwave and hydrothermal method. The as-prepared samples were characterized by XRD, SEM, DRS, XPS and N2 adsorption-desorption. Meanwhile, their photocatalytic properties were investigated by the degradation of toluene under visible light irradiation. The degradation conversation of toluene had gotten to about 70% in 1% Ag3VO4/TiO2 nanorods after reaction 4 h. The predominant photocatalytic activity can be attributed to its strong absorption in visible light region and excellent charge separation characteristics. By using in situ FTIR, benzyl alcohol and benzaldehyde species could be observed during the reaction and the formed intermediates would be partially oxidized into CO2 and H2O. Electron spin resonance confirmed that OHrad and O2rad - were involved in the photocatalytic degradation of toluene.

  16. Effect of Ar ion irradiation on the room temperature ferromagnetism of undoped and Cu-doped rutile TiO2 single crystals

    NASA Astrophysics Data System (ADS)

    Xu, Nan-Nan; Li, Gong-Ping; Lin, Qiao-Lu; Liu, Huan; Bao, Liang-Man

    2016-11-01

    Remarkable room-temperature ferromagnetism was observed both in undoped and Cu-doped rutile TiO2 single crystals (SCs). To tune their magnetism, Ar ion irradiation was quantitatively performed on the two crystals in which the saturation magnetizations for the samples were enhanced distinctively. The post-irradiation led to a spongelike layer in the near surface of the Cu-doped TiO2. Meanwhile, a new CuO-like species present in the sample was found to be dissolved after the post-irradiation. Analyzing the magnetization data unambiguously reveals that the experimentally observed ferromagnetism is related to the intrinsic defects rather than the exotic Cu ions, while these ions are directly involved in boosting the absorption in the visible region. Project supported by the National Natural Science Foundation of China (Grant No. 11575074), the Open Project of State Key laboratory of Crystal Material, Shandong University, China (Grant No. KF1311), the Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, China (Grant No. LZUMMM2012003), the Open Project of Key Laboratory of Beam Technology and Material Modification of Ministry of Education, Beijing Normal University, China (Grant No. 201204), and the Fundamental Research Funds for the Central Universities, China (Grant No. lzujbky-2015-240).

  17. TiO2 coated Au/Ag nanorods with enhanced photocatalytic activity under visible light irradiation.

    PubMed

    Zhou, Na; Polavarapu, Lakshminarayana; Gao, Nengyue; Pan, Yanlin; Yuan, Peiyan; Wang, Qing; Xu, Qing-Hua

    2013-05-21

    A facile method was used to prepare uniform Au NR/TiO2 and Au/Ag NR/TiO2 core-shell composite nanoparticles. Au/Ag NR/TiO2 nanoparticles were found to display significantly enhanced visible light photo-catalytic activity compared to Au NR/TiO2 and the commercially available TiO2 nanoparticles. The enhancement mechanism was ascribed to injection of hot electrons of photo-excited Au/Ag NRs to TiO2, which was confirmed by 633 nm laser induced reduction of silver ions on the surface of Au/Ag NR/TiO2 composite nanoparticles.

  18. Feasibility of Silver Doped TiO2/Glass Fiber Photocatalyst under Visible Irradiation as an Indoor Air Germicide

    PubMed Central

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2014-01-01

    This study investigated the feasibility of using Ag-TiO2 photocatalyst supported on glass fiber (Ag-TiO2/GF) prepared by a sol-gel method as an indoor air germicide. An experimental model was designed to investigate the bacterial disinfection efficiency of Staphylococcus (Staph), the most popular bacterium in hospitals in Korea, by the Ag-TiO2/GF photocatalyst. The silver content in Ag/TiO2 was altered from 1 to 10% to investigate the optimal ratio of Ag doped on TiO2/glass fiber (TiO2/GF) for photocatalytic disinfection of Staph. This study confirmed that Ag in Ag-TiO2/GF could work as an electron sink or donor to increase photocatalytic activity and promote the charge separation of electron-hole pairs generated from TiO2 after photon absorption. Ag also acts as an intermediate agent for the transfer of photo-generated electrons from the valence band of TiO2 to an acceptor (O2 gas) to promote photo-oxidation processes. The photocatalytic disinfection activity of Ag-TiO2/GF under visible light increased with the increase in silver content up to 7.5% and then slightly decreased with further increasing silver content. The highest disinfection efficiency and disinfection capacity of Staph using 7.5% Ag-TiO2/GF were 75.23% and 20 (CFU∙s−1∙cm−2) respectively. The medium level of humidity of 60% ± 5% showed better photocatalytic disinfection than the lower (40% ± 5%) or higher (80% ± 5%) levels. PMID:24658408

  19. Feasibility of silver doped TiO2/glass fiber photocatalyst under visible irradiation as an indoor air germicide.

    PubMed

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2014-03-20

    This study investigated the feasibility of using Ag-TiO2 photocatalyst supported on glass fiber (Ag-TiO2/GF) prepared by a sol-gel method as an indoor air germicide. An experimental model was designed to investigate the bacterial disinfection efficiency of Staphylococcus (Staph), the most popular bacterium in hospitals in Korea, by the Ag-TiO2/GF photocatalyst. The silver content in Ag/TiO2 was altered from 1 to 10% to investigate the optimal ratio of Ag doped on TiO2/glass fiber (TiO2/GF) for photocatalytic disinfection of Staph. This study confirmed that Ag in Ag-TiO2/GF could work as an electron sink or donor to increase photocatalytic activity and promote the charge separation of electron-hole pairs generated from TiO2 after photon absorption. Ag also acts as an intermediate agent for the transfer of photo-generated electrons from the valence band of TiO2 to an acceptor (O2 gas) to promote photo-oxidation processes. The photocatalytic disinfection activity of Ag-TiO2/GF under visible light increased with the increase in silver content up to 7.5% and then slightly decreased with further increasing silver content. The highest disinfection efficiency and disinfection capacity of Staph using 7.5% Ag-TiO2/GF were 75.23% and 20 (CFU∙s-1∙cm-2) respectively. The medium level of humidity of 60% ± 5% showed better photocatalytic disinfection than the lower (40% ± 5%) or higher (80% ± 5%) levels.

  20. A mechanistic study of TiO2 nanoparticle toxicity on Shewanella oneidensis MR-1 with UV-containing simulated solar irradiation: Bacterial growth, riboflavin secretion, and gene expression.

    PubMed

    Qiu, Tian A; Meyer, Ben M; Christenson, Ky G; Klaper, Rebecca D; Haynes, Christy L

    2017-02-01

    Toxicity of nanomaterials to ecological systems has recently emerged as an important field of research, and thus, many researchers are exploring the mechanisms of how nanoparticles impact organisms. Herein, we probe the mechanisms of bacteria-nanoparticle interaction by investigating how TiO2 nanoparticles impact a model organism, the metal-reducing bacterium Shewanella oneidensis MR-1. In addition to examining the effect of TiO2 exposure, the effect of synergistic simulated solar irradiation containing UV was explored in this study, as TiO2 nanoparticles are known photocatalysts. The data reveal that TiO2 nanoparticles cause an inhibition of S. oneidensis growth at high dosage without compromising cell viability, yet co-exposure of nanoparticles and illumination does not increase the adverse effects on bacterial growth relative to TiO2 alone. Measurements of intracellular reactive oxygen species and riboflavin secretion, on the same nanoparticle-exposed bacteria, reveal that TiO2 nanoparticles have no effect on these cell functions, but application of UV-containing illumination with TiO2 nanoparticles has an impact on the level of riboflavin outside bacterial cells. Finally, gene expression studies were employed to explore how cells respond to TiO2 nanoparticles and illumination, and these results were correlated with cell growth and cell function assessment. Together these data suggest a minimal impact of TiO2 NPs and simulated solar irradiation containing UV on S. oneidensis MR-1, and the minimal impact could be accounted for by the nutrient-rich medium used in this work. These measurements demonstrate a comprehensive scheme combining various analytical tools to enable a mechanistic understanding of nanoparticle-cell interactions and to evaluate the potential adverse effects of nanoparticles beyond viability/growth considerations.

  1. Photocatalytic degradation kinetics, mechanism and ecotoxicity assessment of tramadol metabolites in aqueous TiO2 suspensions.

    PubMed

    Αntonopoulou, Μ; Hela, D; Konstantinou, I

    2016-03-01

    This study investigated for the first time the photocatalytic degradation of three well-known transformation products (TPs) of pharmaceutical Tramadol, N-desmethyl-(N-DES), N,N-bidesmethyl (N,N-Bi-DES) and N-oxide-tramadol (N-OX-TRA) in two different aquatic matrices, ultrapure water and secondary treated wastewater, with high (10 mg L(-1)) and low (50 μg L(-1)) initial concentrations, respectively. Total disappearance of the parent compounds was attained in all experiments. For initial concentration of 10 mg L(-1), the target compounds were degraded within 30-40 min and a mineralization degree of more than 80% was achieved after 240 min of irradiation, while the contained organic nitrogen was released mainly as NH4(+) for N-DES, N,N-Bi-DES and NO3(-) for N-OX-TRA. The degradation rates of all the studied compounds were considerably decreased in the wastewater due to the presence of inorganic and organic constituents typically found in effluents and environmental matrices which may act as scavengers of the HO(•). The effect of pH (4, 6.7, 10) in the degradation rates was studied and for N-DES-TRA and N,N-Bi-DES-TRA, the optimum pH value was 6.7. In contrast, N-OX-TRA showed an increasing trend in the photocatalytic degradation kinetic in alkaline solutions (pH 10). The major transformation products were identified by high resolution accurate mass spectrometry coupled with liquid chromatography (HR-LC-MS). Scavenging experiments indicated for all studied compounds the important role of HO(•) in the photocatalytic degradation pathways that included mainly hydroxylation and further oxidation of the parent compounds. In addition, Microtox bioassay (Vibrio fischeri) was employed for evaluating the ecotoxicity of photocatalytically treated solutions. Results clearly demonstrate the progressive decrease of the toxicity and the efficiency of the photocatalytic process in the detoxification of the irradiated solutions.

  2. Design of polyoxometallate-titania composite film (H3PW12O40/TiO2) for the degradation of an aqueous dye Rhodamine B under the simulated sunlight irradiation.

    PubMed

    Lu, Nan; Zhao, Yahui; Liu, Hongbo; Guo, Yihang; Yuan, Xing; Xu, Hui; Peng, Huifang; Qin, Hongwei

    2012-01-15

    A series of polyoxometallate/titania (H(3)PW(12)O(40)/TiO(2)) composite films with different H(3)PW(12)O(40) loadings (6.3%, 7.7%, 14.7% and 16.7%) were prepared by a modified sol-gel-hydrothermal route followed by a spin-coating method. The smooth films are constructed by the well-distributed H(3)PW(12)O(40)/TiO(2) sphere with particle size in the range from 80 to 100 nm, and the bandgap of the composite films is somewhat narrower compared with as-prepared pure TiO(2) film. As a novel photocatalytic material, the photocatalytic performances of the H(3)PW(12)O(40)/TiO(2) composite films were evaluated by the degradation and mineralization of an aqueous dye Rhodamine B (RB) under solar simulating Xe lamp irradiation (320 nm<λ<780 nm), and the enhanced photocatalytic activity in comparison to pure TiO(2) film as well as the H(3)PW(12)O(40)/TiO(2) and Degussa P25 TiO(2) powder was obtained. Additionally, the composite films can be reused at least for three times without losing their catalytic activity.

  3. UV/TiO2 and UV/TiO2/chemical oxidant processes for the removal of humic acid, Cr and Cu in aqueous TiO2 suspensions.

    PubMed

    Jung, J-T; Choi, J-Y; Chung, J; Lee, Y-W; Kim, J-O

    2009-03-01

    The objective of this study was to investigate the treatment efficiency of UV/TiO2 and UV/TiO2/chemical oxidant processes for the removal of humic acid and hazardous heavy metals in aqueous TiO2 suspensions. The reaction rate (k) of humic acid and hazardous heavy metals by UV/TiO2 was higher than that of UV illumination alone or TiO2 alone. The removal efficiency for humic acid and Cr(VI) at acid or neutral pH values was higher than that at basic pH values. However, the removal efficiency for Cu(II) at acid pH values was smaller compared with that at neutral or basic pH values. The reaction rate (k) of humic acid and hazardous heavy metals in the TiO2 concentration range of 0.1-0.3 g l(-1) increased with increasing TiO2 dosage. However, amounts higher than a TiO2 dosage of 0.3 g l(-1) reduced the removal efficiency for humic acid and hazardous heavy metals because of the shielding effect on the UV light penetration in the aqueous solution caused by the presence of excessive amounts of TiO2. The addition of oxidants to the UV/TiO2 system showed an increase in degradation efficiency for the treatment of humic acid and hazardous heavy metals. The optimal concentration of oxidants was: H2O2 50 mg l(-1), O3 20 g m(-3) and K2S2O8 50 mg l(-1), respectively. The degradation efficiency of UV/TiO2/oxidant systems for the removal of humic acid and hazardous heavy metals was much greater when H2O2 was used as the oxidant.

  4. Enhanced nitrogen selectivity for nitrate reduction on Cu-nZVI by TiO2 photocatalysts under UV irradiation

    NASA Astrophysics Data System (ADS)

    Krasae, Nalinee; Wantala, Kitirote

    2016-09-01

    The aims of this work were to study the effect of Cu-nZVI with and without TiO2 on nitrate reduction and to study the pathway of nitrate reduction utilizing to nitrogen gas. The chemical and physical properties of Cu-nZVI and Cu-nZVI/TiO2 such as specific surface area, crystalline phase, oxidation state of Cu and Fe and morphology were determined by N2 adsorption-desorption Brunauer-Emmett-Teller (BET) analytical technique, X-ray diffraction (XRD), X-ray Absorption Near Edge Structure (XANES) technique and Transmittance Electron Microscopy (TEM). The full factorial design (FFD) was used in this experiment for the effect of Cu-nZVI with and without TiO2, where the initial solution pH was varied at 4, 5.5, and 7 and initial nitrate concentration was varied at 50, 75, and 100 ppm. Finally, the pathway of nitrate reduction was examined to calculate the nitrogen gas selectivity. The specific area of Cu-nZVI and Cu-nZVI/TiO2 was found to be about 4 and 36 m2/g, respectively. The XRD pattern of Fe0 in Cu-nZVI was found at 45° (2θ), whereas Cu-nZVI/TiO2 cannot be observed. TEM images can confirm the position of the core and the shell of nZVI for Fe0 and ferric oxide. Cu-nZVI/TiO2 proved to have higher activity in nitrogen reduction performance than that without TiO2 and nitrate can be completely degraded in both of solution pH of 4 and 7 in 75 ppm of initial nitrate concentration. It can be highlighted that the nitrogen gas selectivity of Cu-nZVI/TiO2 greater than 82% was found at an initial solution pH of 4 and 7. The main effects of Cu-nZVI with and without TiO2 and the initial nitrate concentration on nitrate reduction were significant. The interaction between solution pH and initial nitrate concentration and the interaction of all effects at a reaction time of 15 min on nitrate reduction were also significant.

  5. Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

    NASA Astrophysics Data System (ADS)

    Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

    2017-02-01

    TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.

  6. The preparation of vanadium-doped TiO 2-montmorillonite nanocomposites and the photodegradation of sulforhodamine B under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Chen, Ke; Li, Jingyi; Wang, Wenxi; Zhang, Yumin; Wang, Xiaojing; Su, Haiquan

    2011-06-01

    The photodegradation of sulforhodamine B on vanadium-doped TiO 2-montmorillonite (TiO 2-MMT) nanocomposites was investigated under visible light irradiation. V-TiO 2-MMT nanocomposites with different amounts of MMT were prepared by a sol-gel process. The microstructure and properties of V-TiO 2-MMT were characterized by XRD, TEM, XPS, DRS, nitrogen adsorption isotherms, and FTIR. These analytic results indicated that the different Ti/MMT ratios exerted a great influence on their microstructures and their photocatalytic activities. The average sizes of V-TiO 2-MMT were smaller than those of pure TiO 2 and V-TiO 2. And the layered structure of MMT was completely destroyed in the V-TiO 2-MMT with the relatively high ratio of Ti/MMT (240, 120, 80, 60 mmol/g), but it retained the partial MMT layered structure and had an enlargement of some basal space of MMT in V-TiO 2-MMT with the relatively low ratio of Ti/MMT (30, 24 mmol/g). V-TiO 2-MMT/120 (120 denotes the ratio of Ti/MMT is 120 mmol/g. The names of other catalysts followed the same convention.) and V-TiO 2-MMT/30 had relatively higher photocatalytic activity in comparison to the others. Besides, in the preparation process, we selected V-TiO 2-MMT/120 using different washing media to examine the effect of washing medium on the photocatalytic activity. The result indicated that it was critical to choose a proper washing medium to obtain an optimal photocatalytic activity.

  7. Degradations of acetaminophen via a K2S2O8-doped TiO2 photocatalyst under visible light irradiation.

    PubMed

    Lin, Justin Chun-Te; de Luna, Mark Daniel G; Aranzamendez, Graziel L; Lu, Ming-Chun

    2016-07-01

    Acetaminophen (ACT) is a mild analgesic commonly used for relief of fever, headache and some minor pains. It had been detected in both fixed factory-discharged wastewaters, and diverse sources, e.g. surface waters during festival events. Degradation of such trace emergent pollutants by titanium dioxide (TiO2) photocatalysts is a common approach; however, the band gap that can be utilized in the UV range is limited. In order to extend downward the energy required to excite the photocatalytic material, doping with potassium peroxodisulfate (K2S2O8) by a sol-gel method was done in this work. The visible-light active photocatalyst was tested on the degradation of ACT under four parameters including: initial ACT concentration, catalyst dose, initial pH, and system temperature. Optimal conditions, which achieved 100% ACT degradation, were obtained by using 0.1 mM ACT initial concentration, catalyst dose of 1 g L(-1), initial pH of 9.0 and system temperature of 22 °C at the end of 9-h irradiation. Meanwhile, three types of degradation kinetic models (i.e. zero, pseudo first and second order) were tested. The feasible model followed a pseudo-first order model with the computed constant (kapp) of 7.29 × 10(-3) min(-1). The present study provides a better photocatalytic degradation route by K2S2O8-modified TiO2 in comparison with pristine TiO2, in wastewater treatment dealing with ACT and other persistent organic pollutants.

  8. Modification of the microstructure and electronic properties of rutile TiO2 thin films with 79 MeV Br ion irradiation

    NASA Astrophysics Data System (ADS)

    Rath, Haripriya; Dash, P.; Singh, U. P.; Avasthi, D. K.; Kanjilal, D.; Mishra, N. C.

    2015-12-01

    Modifications induced by 79 MeV Br ions in rutile titanium dioxide thin films, synthesized by dc magnetron sputtering are presented. Irradiations did not induce any new XRD peak corresponding to any other phase. The area and the width of the XRD peaks were considerably affected by irradiation, and peaks shifted to lower angles. But the samples retained their crystallinity at the highest fluence (1 × 1013 ions cm-2) of irradiation even though the electronic energy loss of 79 MeV Br ions far exceeds the reported threshold value for amorphization of rutile TiO2. Fitting of the fluence dependence of the XRD peak area to Poisson equation yielded the radius of ion tracks as 2.4 nm. Ion track radius obtained from the simulation based on the thermal spike model matches closely with that obtained from the fluence dependence of the area under XRD peaks. Williamson-Hall analysis of the XRD spectra indicated broadening and shifting of the peaks are a consequence of irradiation induced defect accumulation leading to microstrains, as was also indicated by Raman and UV-Visible absorption study.

  9. Effect of size of TiO2 nanoparticles applied onto glass slide and porcine skin on generation of free radicals under ultraviolet irradiation

    NASA Astrophysics Data System (ADS)

    Popov, Alexey P.; Haag, Stefan; Meinke, Martina; Lademann, Jürgen; Priezzhev, Alexander V.; Myllylä, Risto

    2009-03-01

    Titanium dioxide (TiO2) nanoparticles are extensively used today in sunscreens and coatings as protective compounds for human skin and material surfaces from UV radiation. In this paper, such particles are investigated by electron paramagnetic resonance spectroscopy as sources of free radicals under UV irradiation. The surface density of a placebo with embedded particles corresponds to the recommendations of dermatologists (2 mg cm-2). It is revealed that if applied onto glass, small particles 25 nm in diameter produce an increased amount of free radicals compared to the larger ones of 400 nm diam and the placebo itself. However, if applied onto porcine skin in vitro, there is no statistically distinct difference in the amount of radicals generated by the two kinds of particles on skin and by the skin itself. This proves that although particles as part of sunscreens produce free radicals, the effect is negligible in comparison to the production of radicals by skin in vitro.

  10. Influence of parameters on the photocatalytic degradation of phenolic contaminants in wastewater using TiO2/UV system.

    PubMed

    Saratale, Rijuta G; Noh, Hyun S; Song, Ji Y; Kim, Dong S

    2014-01-01

    The photocatalytic degradation of phenol in aqueous suspension using commercial TiO2 powder (Degussa P-25) irradiated with UV light was investigated. Photodegradation was compared using a photocatalyst (TiO2 alone), direct photolysis (UV alone) and TiO2/UV in a single batch reactor with mercury lamp irradiation. The study focused on the influence of various operating parameters on phenol treatment efficiency, including catalyst dosage, initial concentration of phenol, temperature, pH and change in pH were systematically investigated. The highest phenol degradation rate was obtained at pH 9.0, temperature 60°C and catalyst dose of 2 g L(-1) with higher mineralization efficiency (in terms of TOC reduction). Experimental results showed that under optimized conditions the phenol removal efficiency was 98% and 100% for the TiO2/UV and TiO2/UV/H2O2 system, respectively. No significant effect on addition of chloride and metal ions was observed. Photodegradation of phenol followed first-order kinetics. To test whether the phenol removal was possible for wastewater using a TiO2/UV system, the degradation study was conducted with the real obtained wastewater. The removal of phenol from obtained wastewater and the synthetic wastewater containing phenol was comparable. The TiO2/UV system developed here is expected to be useful for the treatment of wastewater containing phenol.

  11. Evolution of structural and magnetic properties of Co-doped TiO2 thin films irradiated with 100 MeV Ag7+ ions

    NASA Astrophysics Data System (ADS)

    Mohanty, P.; Singh, V. P.; Mishra, N. C.; Ojha, S.; Kanjilal, D.; Rath, Chandana

    2014-08-01

    In continuation to our earlier studies where we have shown room temperature ferromagnetism observed in TiO2 and Co-doped TiO2 (CTO) thin films independent of their phase (Mohanty et al 2012 J. Phys. D: Appl. Phys. 45 325301), here the modifications in structure and magnetic properties in CTO thin films using 100 MeV Ag7+ ion irradiation are reported. Owing to the important role of defects in tailoring the magnetic properties of the material, we vary the ion fluence from 5 × 1011 to 1 × 1012 ions cm-2 to create post-deposition defects. While the film deposited under 0.1 mTorr oxygen partial pressure retains its crystallinity showing radiation-resistant behaviour even at a fluence of 1 × 1012 ions cm-2, films deposited under 1 to 300 mTorr oxygen partial pressure becomes almost amorphous at the same fluence. Using Poisson's law, the diameter of the amorphized region surrounding the ion path is calculated to be ˜4.2 nm from the x-ray diffraction peak intensity ((1 1 0) for rutile phase) as a function of ion fluence. The saturation magnetization (Ms) decreases exponentially similar to the decrease in x-ray peak intensity with fluence, indicating magnetic disordered region surrounding the ion path. The diameter of the magnetic disordered region is found to be ˜6.6 nm which is larger than the diameter of the amorphized latent track. Therefore, it is confirmed that swift heavy ion irradiation induces a more significant magnetic disorder than the structural disorder.

  12. Preparation and solar-light photocatalytic activity of TiO2 composites: TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite

    NASA Astrophysics Data System (ADS)

    Li, Y.; Li, S. G.; Wang, J.; Li, Y.; Ma, C. H.; Zhang, L.

    2014-12-01

    Three TiO2 loaded composites, TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite, were prepared in order to improve the solar-light photocatalytic activity of TiO2. The results showed that the photocatalytic activity could obviously be enhanced by loading appropriate amount of inorganic mineral materials. Meanwhile, TiO2 content, heat-treatment temperature and heat-treatment time on the photocatalytic activity were reviewed. Otherwise, the effect of solar light irradiation time and dye concentration on the photocatalytic degradation of Acid Red B was investigated. Furthermore, the degradation mechanism and adsorption process were also discussed.

  13. H(2)O(2)-sensitized TiO(2)/SiO(2) composites with high photocatalytic activity under visible irradiation.

    PubMed

    Zou, Jian; Gao, Jiacheng

    2011-01-30

    TiO(2)/SiO(2) composite photocatalysts were prepared by depositing of TiO(2) onto nano-SiO(2) particles. X-ray diffraction (XRD), transmission electron micrograph (TEM), Raman spectrometer, UV-Vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FT-IR) were employed to characterize the properties of the synthesized TiO(2)/SiO(2) composites. These results indicated that the products without calcination were amorphous, and calcination could enhance the crystallinity of TiO(2). Increases in the amount of TiO(2) would decrease the dispersion in the composites. H(2)O(2)-sensitized TiO(2)/SiO(2) composite photocatalysts could absorb visible light at wavelength below 550 nm. The photocatalytic activity of as-prepared catalysts was characterized by methyl-orange degradation. The results showed the uncalcined composite photocatalysts with amorphous TiO(2) exhibited higher photocatalytic activity under visible light, and the activity of catalysts with TiO(2) content over 30% decreased with increasing of TiO(2) content. Increases in the calcination temperature and TiO(2) content promote the formation of bulk TiO(2) and result in a decrease in activity.

  14. For the inactivation of mold spores by UVC irradiation, with ozone acting as a promoter, TiO2 nanoparticles may act better as a "sun block" than as a photocatalytic disinfectant.

    PubMed

    Gong, Jia-You; Chen, Yen-Chi; Huang, Yi-Ting; Tsai, Ming-Chien; Yu, Kuo-Pin

    2014-09-01

    Fungal spores are known as critical indoor allergens, and indoor air purification techniques including photocatalytic disinfection using titanium dioxide (TiO2), ultraviolet germicidal irradiation (UVGI) and ozonation, have been considerably investigated. However, most of the research is in regard to photocatalytic disinfection, focused on the anti-bacterial efficacy of TiO2 nanoparticles (NPs). Furthermore, some research even showed that the photocatalytic antifungal efficacy of TiO2 NPs may not be that significant. Thus, investigating the reasons behind the non-significant antifungal efficacy of TiO2 photocatalytic disinfection and enhancing the antifungal efficacy is indispensable. In this study, ozone was employed to improve the photocatalytic antifungal efficacy of the TiO2 NPs and nano-metal supported on TiO2 NPs. The commercial TiO2 NPs (Degussa (Evonik) P25) served as a good support, and incipient wetness impregnation was successfully exploited to prepare oxidized nano-metals (Ag, Cu and Ni) in this study. There were two surfaces (quartz and putty) used in the inactivation experiments of Aspergillus niger spores which were manipulated under two conditions: exposed to ultraviolet (UVC) light , and exposed to UVC and ozone simultaneously. The SEM images demonstrated that the spores were sheltered from UVC light in the microcracks between TiO2 agglomerates. When irradiating with UVC, the A. niger spores on the two testing surfaces, without TiO2 NPs, were inactivated faster than those with TiO2 NPs, implying a "sun block" effect of this material and a lower photocatalytic antifungal efficacy than UVGI. On both surfaces, the inactivation rate constants (k) of A. niger spores exposed to UVC and ozone simultaneously (on quartz: k = 2.09-6.94 h(-1), on putty: k = 3.17-6.66 h(-1)) were better than those exposed to only UVC (on quartz: k = 1.80-5.89 h(-1); on putty: k = 2.97-3.98 h(-1)), indicating ozone can enhance the UVGI antifungal efficacy.

  15. Photocatalytic degradation of three azo dyes using immobilized TiO2 nanoparticles on glass plates activated by UV light irradiation: influence of dye molecular structure.

    PubMed

    Khataee, A R; Pons, M N; Zahraa, O

    2009-08-30

    In order to discuss the effect of chemical structure on photocatalysis efficiency, the photocatalytic degradation of three commercial textile dyes (C.I. Acid Orange 10 (AO10), C.I. Acid Orange 12 (AO12) and C.I. Acid Orange 8 (AO8)) with different structure and different substitute groups has been investigated using supported TiO(2) photocatalyst under UV light irradiation. All the experiments were performed in a circulation photochemical reactor equipped with a 15-W UV lamp emitted around 365nm. The investigated photocatalyst was industrial Millennium PC-500 (crystallites mean size 5-10nm) immobilized on glass plates by a heat attachment method. SEM images of the immobilized TiO(2) nanoparticles showed the good coating on the plates, after repeating the deposition procedure three times. Our results indicated that the photocatalytic decolorization kinetics of the dyes were in the order of AO10>AO12>AO8. Photocatalytic mineralization of the dyes was monitored by total organic carbon (TOC) decrease, changes in UV-vis spectra and ammonium ion formation. The dye solutions could be completely decolorized and effectively mineralized, with an average overall TOC removal larger than 94% for a photocatalytic reaction time of 6h. The nitrogen-to-nitrogen double bond of the azo dyes was transformed predominantly into NH(4)(+) ion. The kinetic of photocatalytic decolorization of the dyes was found to follow a first-order rate law. The photocatalysis efficiency was evaluated by figure-of-merit electrical energy per order (E(EO)).

  16. A novel P/Ag/Ag2O/Ag3PO4/TiO2 composite film for water purification and antibacterial application under solar light irradiation.

    PubMed

    Zhu, Qi; Hu, Xiaohong; Stanislaus, Mishma S; Zhang, Nan; Xiao, Ruida; Liu, Na; Yang, Yingnan

    2017-01-15

    TiO2-based thin films have been intensively studied in recent years to develop efficient photocatalyst films to degrade refractory organics and inactivate bacteria for wastewater treatment. In the present work, P/Ag/Ag2O/Ag3PO4/TiO2 composite films on the inner-surface of glass tube were successfully prepared via sol-gel approach. P/Ag/Ag2O/Ag3PO4/TiO2 composite films with 3 coating layers, synthesized at 400°C for 2h, showed the optimal photocatalytic performance for rhodamine B (Rh B) degradation. The results indicated that degradation ratio of Rh B by P/Ag/Ag2O/Ag3PO4/TiO2 composite film reached 99.9% after 60min under simulated solar light, while just 67.9% of Rh B was degraded by pure TiO2 film. Moreover, repeatability experiments indicated that even after five recycling runs, the photodegradation ratio of Rh B over composite film maintained at 99.9%, demonstrating its high stability. Photocatalytic inactivation of E. coli with initial concentration of 10(7)CFU/mL also showed around 100% of sterilization ratio under simulated solar light irradiation in 5min by the composite film. The radical trapping experiments implied that the major active species of P/Ag/Ag2O/Ag3PO4/TiO2 composite films were photo-generated holes and O2(-) radicals. The proposed photocatalytic mechanism shows that the transfer of photo-induced electrons and holes may reduce the recombination efficiency of electron-hole pairs and potential photodecomposition of composite film, resulting in enhanced photocatalytic ability of P/Ag/Ag2O/Ag3PO4/TiO2 composite films.

  17. Microcystin-LR removal from aqueous solutions using a magnetically separable N-doped TiO2 nanocomposite under visible light irradiation.

    PubMed

    Pelaez, Miguel; Baruwati, Babita; Varma, Rajender S; Luque, Rafael; Dionysiou, Dionysios D

    2013-10-03

    The performance of magnetically separable N-doped TiO2 was found to be significantly improved when compared with non-magnetic N-doped TiO2 for the removal of cyanotoxin microcystin-LR from aqueous medium. The observed enhanced photocatalytic activity may be related to the presence of ferrite nanoparticles in the composition of the magnetically separable composite N-doped TiO2.

  18. Oxidative potential of ultraviolet-A irradiated or nonirradiated suspensions of titanium dioxide or silicon dioxide nanoparticles on Allium cepa roots.

    PubMed

    Koce, Jasna Dolenc; Drobne, Damjana; Klančnik, Katja; Makovec, Darko; Novak, Sara; Hočevar, Matej

    2014-04-01

    The effect of ultraviolet-A irradiated or nonirradiated suspensions of agglomerates of titanium dioxide (TiO(2)) or silicon dioxide (SiO(2)) nanoparticles on roots of the onion (Allium cepa) has been studied. The reactive potential of TiO(2) nanoparticles, which have photocatalytic potential, and the nonphotocatalytic SiO(2) nanoparticles with the same size of agglomerates was compared. The authors measured the activity of antioxidant enzymes glutathione reductase, ascorbate peroxidase, guaiacol peroxidase, and catalase as well as lipid peroxidation to assess the oxidative stress in exposed A. cepa roots. A wide range of concentrations of nanoparticles was tested (0.1-1000 µg/mL). The sizes of agglomerates ranged in both cases from 300 nm to 600 nm, and the exposure time was 24 h. Adsorption of SiO(2) nanoparticles on the root surface was minimal but became significant when roots were exposed to TiO(2) agglomerates. No significant biological effects were observed even at high exposure concentrations of SiO(2) and TiO(2) nanoparticles individually. Plants appear to be protected against nanoparticles by the cell wall, which shields the cell membrane from direct contact with the nanoparticles. The authors discuss the need to supplement conventional phytotoxicity and stress end points with measures of plant physiological state when evaluating the safety of nanoparticles.

  19. Role of Interparticle Charge Transfers in Agglomerated Photocatalyst Nanoparticles: Demonstration in Aqueous Suspension of Dye-Sensitized TiO2.

    PubMed

    Park, Yiseul; Kim, Wooyul; Monllor-Satoca, Damián; Tachikawa, Takashi; Majima, Tetsuro; Choi, Wonyong

    2013-01-03

    The interparticle charge transfer within the agglomerates of TiO2 nanoparticles in slurries markedly enhanced the dye-sensitized production of H2 under visible light. By purposely decoupling the light absorbing part of Dye/TiO2 from the active catalytic center of Pt/TiO2, the role of bare TiO2 nanoparticles working as a mediator that connects the above two parts in the agglomerates was investigated systematically. The presence of mediator in the agglomerate facilitated the charge separation and the electron transfer from Dye/TiO2 to Pt/TiO2 through multiple grain boundaries and subsequently produced more hydrogen. The dye-sensitized reduction of Cr(VI) to Cr(III) was also enhanced when Dye/TiO2 nanoparticles were agglomerated with bare TiO2 nanoparticles. The charge recombination between the oxidized dye and the injected electron was retarded in the presence of bare TiO2 nanoparticles, and this retarded recombination on Dye/TiO2 was confirmed by using transient laser spectroscopy. This phenomenon can be rationalized in terms of an interparticle Fermi level gradient within the agglomerates, which drives the charge separation.

  20. Reactive dyes decolouration by TiO2 photo-assisted catalysis.

    PubMed

    Lizama, C; Yeber, M C; Freer, J; Baeza, J; Mansilla, H D

    2001-01-01

    The photocatalytic degradation of three reactive azo dyes (yellow-2, orange-16 and red-2) and one anthraquinone reactive dye (blue-19) was studied. The reactions were carried out in a reactor with recirculation using TiO2 immobilised on glass Raschig rings (system A) and compared with a batch system using the catalyst in aqueous suspension (system B). Both reaction systems were irradiated with a 125 W, lambda > 254 nm lamp. The suspended TiO2 system was also studied using a 125 W 360 nm lamp (system C). Kinetic studies indicated a rapid colour removal, following the order B > A > C. The same trend was observed in COD and TOC removal profiles. The energy consumption per order of magnitude of catalytic degradation of the dyes was lower in the batch reactor (system B) than in the reactor with recirculation and immobilised TiO2 (system A).

  1. Microcystin-LR removal from aqueous solutions using a magnetically separable N-doped TiO2 nanocomposite under visible light irradiation

    EPA Science Inventory

    The performance of magnetically separable N-doped TiO2 was found to be significantly improved when compared with a non-magnetic N-doped TiO2 for the aqueous removal of cyanotoxin Microcystin-LR. The observed enhanced photocatalytic activity may be related to the presence of ferri...

  2. Photocatalytic and antibacterial properties of medical-grade PVC material coated with TiO2 film.

    PubMed

    Lin, Huaxiang; Xu, Ziting; Wang, Xuxu; Long, Jinlin; Su, Wenyue; Fu, Xianzhi; Lin, Qun

    2008-11-01

    The TiO(2) film was coated on poly vinyl chloride (PVC) surface by dip-coating process from TiO(2)-PVC-THF suspension. The morphology and crystal structure of the as-synthesized samples were characterized by SEM and XRD. The photocatalytic properties were measured by the photodegradation reaction of RhB and the anti-adhesion and anti-bacteria for Escherichia coli. The results show that the resultant TiO(2) film is well-conglutinated on PVC surface and has the same crystal structure as the original TiO(2) powder. The TiO(2)/PVC shows excellent photocatalytic activity for the degradation of aqueous RhB and the activity increases with increasing reaction time and tends toward stable after accumulative illumination for 11.5 h. The TiO(2) film shows good bacterial anti-adhesion activity following photo-activation and sterilization property under UV irradiation. The E. coli can be killed completely after UV irradiation for 1.5 h.

  3. Disinfection of B. SUBTILIS Cells in Suspension Using Ultraviolet Light Emitting Diodes (leds) in the Presence of TiO2

    NASA Astrophysics Data System (ADS)

    Province, Dennis W.; O'Neil, Shannon; Higgins, Keri; Smith, Paul J.; Dooley, Kristin; Curtis, Joey; Grippo, Adam M.; Rino, John W.; Allen, Susan D.

    2011-06-01

    The concentration of vegetative Bacillus subtilis (B. subtilis) in phosphate buffered saline decreased when subjected to ultraviolet (UV) light from light emitting diodes (LEDs) in the presence of 0.01% Degussa P25 titanium dioxide (TiO2) as compared to a sample that contained bacteria only, a sample of bacteria that contained 0.01% TiO2, and bacteria that was subjected to the same UV light but no TiO2. The starting concentration of each sample was on the order of 104 colony forming units per milliliter (CFU/mL) and the time required for complete kill was less than 100min when the peak wavelength was 370 nm for the four LED light source at a total LED power of 0.8 milliWatts (mW), decreasing to less than 75 min for a total LED power of 3 mW. Changing the peak wavelength by 7 nm to 377 nm decreased the kill of vegetative B. subtilis to less than 1 log at 100 min for 5 mW total LED power. This work was performed under Federal Contract W9113M-09-C-0136 in support of the Radiance Technologies, Inc., prime contract from US Army SMDC, Huntsville, AL.

  4. Highly antibacterial activity of N-doped TiO2 thin films coated on stainless steel brackets under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Cao, Shuai; Liu, Bo; Fan, Lingying; Yue, Ziqi; Liu, Bin; Cao, Baocheng

    2014-08-01

    In this study, the radio frequency (RF) magnetron sputtering method was used to prepare a TiO2 thin film on the surface of stainless steel brackets. Eighteen groups of samples were made according to the experimental parameters. The crystal structure and surface morphology were characterized by X-ray diffraction, and scanning electron microscopy, respectively. The photocatalytic properties under visible light irradiation were evaluated by measuring the degradation ratio of methylene blue. The sputtering temperature was set at 300 °C, and the time was set as 180 min, the ratio of Ar to N was 30:1, and annealing temperature was set at 450 °C. The thin films made under these parameters had the highest visible light photocatalytic activity of all the combinations of parameters tested. Antibacterial activities of the selected thin films were also tested against Lactobacillus acidophilus and Candida albicans. The results demonstrated the thin film prepared under the parameters above showed the highest antibacterial activity.

  5. Properties of the surface of ceramic formed under laser irradiation of Al2O3-TiO2 compacts

    NASA Astrophysics Data System (ADS)

    Márquez Aguilar, P. A.; Vlasova, M.; Escobar Martínez, A.; Tomila, T.; Stetsenko, V.

    2014-04-01

    The phase formation in the laser irradiation area from xAl2O3-yTiO2 compacts and the properties of the surface layer have been investigated by the XRD, IR, and SEM methods. Main phases precipitating from eutectic melt are tialite, corundum, and rutile. A high temperature on the surface of specimens leads to the development of dissociation processes of these compounds and molecules of the gaseous medium. As dissociation products fly apart and pass through different temperature zone, there are formed different metal oxides, metal hydroxides, and thermolysis products. When these different oxides are deposited on the surface of the ceramic, they form layers with different adhesion degrees.

  6. Efficient dechlorination of chlorinated solvent pollutants under UV irradiation by using the synthesized TiO2 nano-sheets in aqueous phase.

    PubMed

    Ndong, Landry Biyoghe Bi; Ibondou, Murielle Primaelle; Miao, Zhouwei; Gu, Xiaogang; Lu, Shuguang; Qiu, Zhaofu; Sui, Qian; Mbadinga, Serge Maurice

    2014-05-01

    Titanium dioxide (TiO2), which is the widely used photo-catalyst, has been synthesized by simple hydrothermal solution containing tetrabutyl titanate and hydrofluoric acid. The synthesized product has been applied to photo-degradation in aqueous phase of chlorinated solvents, namely tetrachloroethene (PCE), trichloroethene (TCE) and 1,1,1-trichloroethane (TCA). The photo-degradation results revealed that the degradation of these harmful chemicals was better in UV/synthesized TiO2 system compared to UV/commercial P25 system and UV only system. The photo-catalytic efficiency of the synthesized TiO2 was 1.4, 1.8 and 3.0 folds higher compared to the commercial P25 for TCA, TCE and PCE degradation, respectively. Moreover, using nitrobenzene (NB) as a probe of hydroxyl radical (·OH), the degradation rate was better over UV/synthesized TiO2, suggesting the high concentration of ·OH generated in UV/synthesized TiO2 system. In addition, ·OH concentration was confirmed by the strong peak displayed in EPR analysis over UV/synthesized TiO2 system. The characterization result using XRD and TEM showed that the synthesized TiO2 was in anatase form and consisted of well-defined sheet-shaped structures having a rectangular outline with a thickness of 4 nm, side length of 50 nm and width of 33 nm and a surface 90.3 m(2)/g. XPS analysis revealed that ≡Ti-F bond was formed on the surface of the synthesized TiO2. The above results on both photocatalytic activity and the surface analysis demonstrated the good applicability of the synthesized TiO2 nano-sheets for the remediation of chlorinated solvent contaminated groundwater.

  7. Fabrication of bidirectionally doped β-Bi2O3/TiO2-NTs with enhanced photocatalysis under visible light irradiation.

    PubMed

    Li, Deyi; Zhang, Yonggang; Zhang, Yalei; Zhou, Xuefei; Guo, Sujin

    2013-08-15

    Stable β-Bi2O3/TiO2-NTs photocatalyst with excellent visible-light-activity is successfully prepared by bidirectional doping. Stake structure of the TiO2-NTs provides a larger specific surface area and makes the contact area between the TiO2-NTs and β-Bi2O3 much larger; The stake structure of TiO2-NTs not only leads to a firmer combination of TiO2-NTs and β-Bi2O3, but also makes them dope one another deeply. The modification of Bi species into TiO2-NTs can form Bi-O-Ti chemical absorption bonds, then a localized impurity level is generated within the band gap. Electrons can be excited and transferred from the Bi(3+) impurity level to the conduction band (CB) of TiO2, similar to narrowing the band-gap of TiO2-NTs, resulting in a red shift of the absorption edge and an enhancement in visible-light activity. During annealing, Bi atoms are partially replaced by Ti atoms. The lattice of β-Bi2O3 is compressed around the Ti impurity, making the lattice dislocate and distort. This dislocation and distortion leads to an increase in the β-Bi2O3 valance band (VB), from 2.02 to 2.28 eV. Accordingly, the weak oxidability of β-Bi2O3 is improved, and its photocatalytic ability is further enhanced. Moreover, this lattice dislocation and distortion changes the Bi-O distances, thus remarkably improving the stability of the β-Bi2O3/TiO2-NTs.

  8. Enhanced photocatalytic degradation of rhodamine B under visible light irradiation on mesoporous anatase TiO2 microspheres by codoping with W and N

    NASA Astrophysics Data System (ADS)

    Zheng, Jian; Xiong, Feng-Qiang; Zou, Mingming; Thomas, Tiju; Jiang, Heng; Tian, Ying; Yang, Minghui

    2016-04-01

    Mesoporous anatase TiO2 microspheres were prepared via solvothermal method. Ammonium tungstate was used as the W source, and ammonia gas flowing in an ammonothermal reactor as the N source for codoping. TiO2:(W,N) mesoporous microspheres, which were prepared from solvothermal treatment at 160 °C for 16 h and thermal ammonolysis at 500 °C for 2 h after calcination, have high specific surface area of 106 m2 g-1. XPS results indicate the presence of NO, Ni and W6+ in the codoped mesoporous TiO2 microspheres. Monodoping with N shifts the absorption band edge of anatase TiO2 from ultraviolet region to visible region. Although codoping with W makes the visible light absorbance decrease a little, the photocatalytic degradation of a cationic dye rhodamine B (RhB) on mesoporous TiO2:(W,N) microspheres is increased to 1.7 times of that on mesoporous TiO2:N microspheres. This may due to decreasing recombination centers by W-doping charge compensation.

  9. Degradation of surfactant wastewater under microwave irradiation in the presence of activated carbon assisted with nano-sized TiO2 or nano-sized ZnO.

    PubMed

    Zhang, Z; Xu, D; Shen, M; Wu, D; Chen, Z; Ji, X; Li, F; Xu, Y

    2011-01-01

    An improved method treating surfactant wastewater by the addition of semiconductor material such as nano-sized TiO2 or ZnO to activated carbon (AC) with microwave (MW) irradiation was proposed so as to assist efficient degradation of organic pollutants. A series of degradation experiments of sodium dodecyl benzene sulfonate (SDBS) were carried out under MW irradiation in the presence of AC/TiO2 or AC/ZnO. The influences of catalyst dose, irradiation time, initial SDBS concentration and solution acidity on the degradation were assessed in detail. The results showed that the addition of TiO2 or ZnO obviously promoted the degradation and AC/TiO2 system displayed higher catalytic activity under MW irradiation. Thus the method of MW irradiation with AC/TiO2 or AC/ZnO revealed many advantages of rapid degradation rate, short irradiation time, low cost, no residual intermediates and no secondary pollution in applications.

  10. Studies on photocatalytic activity of the synthesised TiO2 and Ag/TiO2 photocatalysts under UV and sunlight irradiations.

    PubMed

    Vaithiyanathan, R; Sivakumar, T

    2011-01-01

    Photocatalytic decolorisation and degradation of Reactive Red 120 (RR 120) has been investigated under UV (365 nm) and solar light as radiation sources using synthesised nano titania catalyst prepared via sol-gel method. The study encompassed calcination of synthesised titania catalyst at a range of temperature up to 1,000°C. The effects of calcination temperature on titania catalyst have been evaluated on the decolorisation of RR 120. The analysis revealed complete decolorisation of dye solution in 100 min under UV light with the TiO2 catalyst calcined at 200°C. Only a maximum of 47% dye decolorisation was achieved under sunlight in 4 h with no improvement even after prolonged irradiation. In an endeavour to improve the catalytic activity, bare titania was modified with silver metal and a comprehensive study on the characteristics of silver modified catalyst was made. The result was an enhancement of the rate of decolorisation of dye under both UV and solar light sources. All the catalysts were characterised by XRD and BET analyses. Optimisation of the degradation of RR 120 has been carried out using the unmodified catalyst by varying the amount of catalyst, substrate concentration, pH of dye solution. Effects of addition of small amounts of various oxidants such as H2O2, KBrO3 and (NH4)2S2O8 have also been studied. Pseudo first order kinetics was observed in the photocatalytic decolorisation of dye. The mineralisation of RR 120 was monitored by TOC analysis.

  11. H2O2 and/or TiO2 photocatalysis under UV irradiation for the removal of antibiotic resistant bacteria and their antibiotic resistance genes.

    PubMed

    Guo, Changsheng; Wang, Kai; Hou, Song; Wan, Li; Lv, Jiapei; Zhang, Yuan; Qu, Xiaodong; Chen, Shuyi; Xu, Jian

    2017-02-05

    Inactivating antibiotic resistant bacteria (ARB) and removing antibiotic resistance genes (ARGs) are very important to prevent their spread into the environment. Previous efforts have been taken to eliminate ARB and ARGs from aqueous solution and sludges, however, few satisfying results have been obtained. This study investigated whether photocatalysis by TiO2 was able to reduce the two ARGs, mecA and ampC, within the host ARB, methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa, respectively. The addition of H2O2 and matrix effect on the removal of ARB and ARGs were also studied. TiO2 thin films showed great effect on both ARB inactivation and ARGs removal. Approximately 4.5-5.0 and 5.5-5.8 log ARB reductions were achieved by TiO2 under 6 and 12mJ/cm(2) UV254 fluence dose, respectively. For ARGs, 5.8 log mecA reduction and 4.7 log ampC reduction were achieved under 120mJ/cm(2) UV254 fluence dose in the presence of TiO2. Increasing dosage of H2O2 enhanced the removal efficiencies of ARB and ARGs. The results also demonstrated that photocatalysis by TiO2 was capable of removing both intracellular and extracellular forms of ARGs. This study provided a potential alternative method for the removal of ARB and ARGs from aqueous solution.

  12. Photo(electro)catalytic Activity of Cu2+-Modified TiO2 Nanorod Array Thin Films under Visible Light Irradiation

    NASA Astrophysics Data System (ADS)

    Kerkez, Özge; Boz, İsmail

    2014-05-01

    In the present study, a two-step method was applied to synthesise Cu2+-modified TiO2 nanorod array thin films for photocatalytic processes. TiO2 nanorod array thin films were synthesised by a hydrothermal method and then modified with an ultrasonic-assisted sequential cation adsorption method. The samples were characterised by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and inductively coupled plasma mass spectroscopy (ICP-MS) analysis. The photoelectrochemical properties of the samples were evaluated by linear sweep voltammetry and Mott-Schottky analysis; photocatalytic activities were tested by methylene blue degradation under visible light. The photocurrent density of the TiO2/FTO sample modified with 50 mM Cu2+ solution was 26 times higher than that of the unmodified TiO2/FTO sample. Additionally, methylene blue degradation efficiency under visible light was increased 40% with respect to the efficiency of the unmodified sample. The mechanism of the photocatalytic activity enhancement of Cu2+-modified TiO2 nanorod films was discussed.

  13. Efficient photodegradation of methyl violet dye using TiO2/Pt and TiO2/Pd photocatalysts

    NASA Astrophysics Data System (ADS)

    Saeed, Khalid; Khan, Idrees; Gul, Tamanna; Sadiq, Mohammad

    2017-02-01

    Titanium oxide supported palladium (TiO2/Pd) and titanium oxide supported platinum (TiO2/Pt) nanoparticles were prepared from their precursors through the incipient wetness method. The TiO2/Pd and TiO2/Pt nanoparticles were characterized by scanning electron microscopy (SEM), and energy dispersive X-rays (EDX), while the photodegradation study of methyl violet was performed by UV/VIS spectrophotometry. The morphological study shows that the Pd and Pt were well deposited on the surface of TiO2, which was confirmed by EDX. Both TiO2/Pd and TiO2/Pt nanoparticles were used as photocatalysts for the photodegradation of methyl violet in aqueous media under UV-light irradiation. The photodegradation study revealed that the TiO2/Pd and TiO2/Pt nanoparticles degraded about 95 and 78% of dye within 20 min, respectively. The effect of various parameters such as catalyst dosage, concentration of dye, and medium on the photocatalytic degradation was examined. The activity of recovered TiO2/Pd and TiO2/Pt nanoparticles was studied.

  14. Enhanced photocatalytic activity of S-doped TiO2-ZrO2 nanoparticles under visible-light irradiation.

    PubMed

    Tian, Guohui; Pan, Kai; Fu, Honggang; Jing, Liqiang; Zhou, Wei

    2009-07-30

    Porous nanocrystalline S-doped TiO2-ZrO2 visible-light photocatalysts were prepared through a one-step method. The resulting materials were characterized by X-ray diffraction (XRD), N(2) adsorption-desorption measurements, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra (DRS), Fourier transform infrared spectra (FT-IR) and electron paramagnetic resonance (ESR). It was found that modification by ZrO2 could effectively inhibit phase transformation, enhance visible-light absorption, and possess more surface hydroxyl groups. The photocatalytic activity of S-doped TiO2-ZrO2 was higher than that of unmodified S-doped TiO2 and Degussa P25. The enhanced photocatalytic activity could be attributed to the higher specific area, smaller crystal size, porous structure and more surface hydroxyl groups in the catalyst.

  15. Influences of different TiO 2 morphologies and solvents on the photovoltaic performance of dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Lee, Kun-Mu; Suryanarayanan, Vembu; Ho, Kuo-Chuan

    The effects of TiO 2 photoelectrode's surface morphology and different solvents on the photovoltaic performance of dye-sensitized solar cells (DSSCs) were studied. By successive coating of TiO 2 suspension, composed of low and high molecular weight poly(ethylene)glycol (PEG) as a binder, double layered TiO 2 photoelectrodes with four different structures were obtained. Among the DSSCs with different TiO 2 electrodes, DSSC with P2P1 electrode (P2 and P1 correspond to PEG molecular weights of 20,000 and 200,000, respectively) showed higher performance under identical film thickness at a constant irradiation of 100 mW cm -2, which may be correlated with large pore size and high surface area of the corresponding TiO 2 electrode. This was confirmed by electrochemical impedance spectroscopy (EIS) analysis of the DSSC and the transient photovoltage measurement of electrons in the TiO 2 electrode. Among the different solvents investigated here, the DSSC containing acetonitrile showed high conversion efficiency and the order of performance of the DSSCs with different solvents were AN > MPN > PC > GBL > DMA > DMF > DMSO. Better correlation was observed between the donor number of solvents and photoelectrochemical parameters of the DSSCs containing different solvents rather than the measured viscosity and dielectric constant of solvents. The reasons for the low performance of the DSSCs containing DMA, DMSO and DMF, respectively, were due to the negative shift of TiO 2 conduction band and the desorption of dye molecules from the TiO 2 photoelectrode by those solvents.

  16. Influence of process parameters on the photodegradation of synthesized azo pyridone dye in TiO2 water suspension under simulated sunlight.

    PubMed

    Dostanić, Jasmina M; Loncarević, Davor R; Banković, Predrag T; Cvetković, Olga G; Jovanović, Dusan M; Mijin, Dusan Z

    2011-01-01

    Photocatalytic degradation of synthesized azo pyridone dye (5-(4-sulpho phenylazo)-6-hydroxy-4-methyl-3-cyano-2-pyridone), in aqueous solutions by simulated sunlight in the presence of commercial TiO(2), Aeroxide P25, was studied. The reaction kinetics analysis showed that photodegradation exhibits pseudo first-order kinetics according to Langmuir-Hinshelwood model. The effects of various process parameters on the photocatalytic degradation were investigated. The optimal catalyst content and pH were determined. A decrease in the reaction rate was observed upon the increase of the initial dye concentration. Degradation of the dye was enhanced by hydrogen peroxide, but it was inhibited by ethanol. The influence of temperature was studied, and the energy of activation was determined. According to total organic carbon (TOC) analysis, 54% of TOC remained when 100% of the dye was decolorized. Although the intermediates were not determined in this study, the TOC results clearly indicate their presence during the reaction. In addition, photocatalytic degradation of simulated dyehouse effluents, containing tested azo pyridone dye and associated auxiliary chemicals was investigated.

  17. One pot synthesis of nanosized anion doped TiO2: Effect of irradiation of sound waves on surface morphology and optical properties

    NASA Astrophysics Data System (ADS)

    Sharotri, Nidhi; Sud, Dhiraj

    2015-08-01

    Commercialization of AOP's for remediation of pollutants from environmental matrix required the process to be operated by solar light. Semiconductor TiO2 has emerged as an effective and preferred photocatalyst in the field of environmental photocatalysis due to its; (i) biological and chemical inertness (ii) resistance to chemical and photo corrosion, (iii) can absorb natural UV light due to appropriate energetic separation between its valence and conduction band. However, unfortunately the optical band gap of TiO2 (3.0-3.23 eV) with absorption cut off ˜ 380 nm, enables it to harness only a small fraction (˜ 5%) of the entire solar spectrum. One of the current areas of research is modification of TiO2 photocatalyst. In present paper one pot greener synthesis from titanium isopropoxide and hydroxylamine hydrochloride has been used as titanium and nitrogen precursor under ultrasonic waves. The as synthesized TiO2 nanomaterials were dried at 100°C and further calcinated at different temperatures. The effect of reaction parameters such as ultrasonication time on the yield, surface morphology, spectroscopic data and optical properties was also investigated. The results confirm that the anatase phase is a main phase with a crystallite size of 35-77 nm and the calculated band gap of nanomaterials varies from 2.10-3.1 eV.

  18. Mesoporous nitrogen-doped TiO2 for the photocatalytic destruction of the cyanobacterial toxin microcystin-LR under visible light irradiation.

    PubMed

    Choi, Hyeok; Antoniou, Maria G; Pelaez, Miguel; De la Cruz, Armah A; Shoemaker, Jody A; Dionysiou, Dionysios D

    2007-11-01

    The presence of the harmful cyanobacterial toxins in water resources worldwide drives the development of an innovative and practical water treatment technology with great urgency. This study deals with two important aspects: the fabrication of mesoporous nitrogen-doped TiO2 (N-TiO2) photocatalysts and their environmental application for the destruction of microcystin-LR (MC-LR) under visible light. In a nanotechnological sol-gel synthesis method, a nitrogen-containing surfactant (dodecylammonium chloride) was introduced as a pore templating material for tailor-designing the structural properties of TiO2 and as a nitrogen dopant for its visible light response. The resulting N-TiO2 exhibited significantly enhanced structural properties including 2-8 nm mesoporous structure (porosity 44%) and high surface area of 150 m2/g. Red shift in light absorbance up to 468 nm, 0.9 eV lower binding energy of electrons in Ti 2p state, and reduced interplanar distance of crystal lattices proved nitrogen doping in the TiO2 lattice. Due to its narrow band gap at 2.65 eV, N-TiO2 efficiently degraded MC-LR under visible spectrum above 420 nm. Acidic condition (pH 3.5) was more favorable for the adsorption and photocatalytic degradation of MC-LR on N-TiO2 due to electrostatic attraction forces between negatively charged MC-LR and +6.5 mV charged N-TiO2. Even under UV light, MC-LR was decomposed 3-4 times faster using N-TiO2 than control TiO2. The degradation pathways and reaction intermediates of MC-LR were not directly related to the energy source for TiO2 activation (UV and visible) and nature of TiO2 (neat and nitrogen-doped). This study implies a strong possibility for the in situ photocatalytic remediation of contaminated water with cyanobacterial toxins and other toxic compounds using solar light, a sustainable source of energy.

  19. Comparison of the killing effects between nitrogen-doped and pure TiO2 on HeLa cells with visible light irradiation

    NASA Astrophysics Data System (ADS)

    Li, Zheng; Pan, Xiaobo; Wang, Tianlong; Wang, Pei-Nan; Chen, Ji-Yao; Mi, Lan

    2013-02-01

    The killing effect of nitrogen-doped titanium dioxide (N-TiO2) nanoparticles on human cervical carcinoma (HeLa) cells by visible light photodynamic therapy (PDT) was higher than that of TiO2 nanoparticles. To study the mechanism of the killing effect, the reactive oxygen species produced by the visible-light-activated N-TiO2 and pure-TiO2 were evaluated and compared. The changes of the cellular parameters, such as the mitochondrial membrane potential (MMP), intracellular Ca2+, and nitrogen monoxide (NO) concentrations after PDT were measured and compared for N-TiO2- and TiO2-treated HeLa cells. The N-TiO2 resulted in more loss of MMP and higher increase of Ca2+ and NO in HeLa cells than pure TiO2. The cell morphology changes with time were also examined by a confocal microscope. The cells incubated with N-TiO2 exhibited serious distortion and membrane breakage at 60 min after the PDT.

  20. Comparison of the killing effects between nitrogen-doped and pure TiO2 on HeLa cells with visible light irradiation

    PubMed Central

    2013-01-01

    The killing effect of nitrogen-doped titanium dioxide (N-TiO2) nanoparticles on human cervical carcinoma (HeLa) cells by visible light photodynamic therapy (PDT) was higher than that of TiO2 nanoparticles. To study the mechanism of the killing effect, the reactive oxygen species produced by the visible-light-activated N-TiO2 and pure-TiO2 were evaluated and compared. The changes of the cellular parameters, such as the mitochondrial membrane potential (MMP), intracellular Ca2+, and nitrogen monoxide (NO) concentrations after PDT were measured and compared for N-TiO2- and TiO2-treated HeLa cells. The N-TiO2 resulted in more loss of MMP and higher increase of Ca2+ and NO in HeLa cells than pure TiO2. The cell morphology changes with time were also examined by a confocal microscope. The cells incubated with N-TiO2 exhibited serious distortion and membrane breakage at 60 min after the PDT. PMID:23433090

  1. Tubular nitrogen-doped TiO2 samples with efficient photocatalytic properties based on long-lived charge separation under visible-light irradiation: synthesis, characterization and reactivity.

    PubMed

    Hirose, Yoshikazu; Itadani, Atsushi; Ohkubo, Takahiro; Hashimoto, Hideki; Takada, Jun; Kittaka, Shigeharu; Kuroda, Yasushige

    2017-03-27

    A nitrogen-doped TiO2 sample was prepared at 413 K by direct hydrothermal treatment of titanium isopropoxide in an aqueous solution of NH3. This new material has a large specific surface area of ca. 220 m(2) g(-1) because of its tubular structure and it exhibits a prominent absorption feature in the region between 400 and 650 nm. It responds strongly to light in the visible region, which is key to its potential performance as a photocatalyst that may improve the efficiency for utilization of solar energy. Actually, this sample exhibits very efficient activity in the decomposition of CH3COOH under visible light among the samples prepared. This effective photocatalysis of the present sample was substantiated by characteristic spectroscopic features, such as: (1) an optical absorption band with λ > 400 nm because of the doped nitrogen species; (2) the formation of EPR-active, long-lived N˙ and O2(-) species, as well as N2(-) species, under visible-light irradiation in the O2 or N2 adsorption process at 300 K by way of the monovalent nitrogen ions in the bulk (both substitutional and interstitial); (3) the existence of IR-active O2 species adsorbed on the nitrogen-doped TiO2 sample even without light irradiation; and (4) an XPS N1s band around 399.6 eV that is assignable to the N(-) species. The amounts of N˙ and O2(-) species formed in the nitrogen-doped TiO2 sample under visible-light irradiation correlated well with the levels of reactivity observed in the decomposition of CH3COOH on the samples with varying amounts and types of doped nitrogen species. We conclude that the photoactive N˙ and O2(-) species created in the present sample are responsible for the decomposition of organic materials assisted by visible light irradiation. These features may be attributable to the interface between the sample's tubular structure and anatase with poor crystallinity, which probably causes the resistance to the recombination of electron-hole pairs formed by irradiation.

  2. P-doped TiO2 nanoparticles film coated on ground glass substrate and the repeated photodegradation of dye under solar light irradiation

    NASA Astrophysics Data System (ADS)

    Lv, Yingying; Yu, Leshu; Zhang, Xiaolan; Yao, Jinyan; Zou, Ruyi; Dai, Zheng

    2011-04-01

    The convenient reuse of photocatalysts is essential to the practical application in the degradation of organic pollutant. In this study, compact P-doped TiO2 film coated on ground glass substrate was easily achieved by layer-by-layer assembly technique. Thus such an elaborate complex system exhibited very convenient in recycling photocatalyst in the degradation of dye with high catalytic activity. The excellent performance of P-TiO2 film coated on ground glass substrates endows the assembled route potential in purifying waste water.

  3. Two methods for microwave irradiation synthesis of TiO2–ZnO–graphene ternary hybrids with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Darvishi, Motahareh; Jamali-Paghaleh, Mina; Jamali-Paghaleh, Fatemeh; Seyed-Yazdi, Jamileh

    2017-01-01

    In this study, graphene–zinc oxide–titanium dioxide (RGO–ZnO–TiO2) ternary hybrids are successfully synthesized by two methods called ‘one step’ and ‘two steps’, by using a simple microwave treatment of a solution containing graphene oxide, ZnO, TiO2, water and ethanol. Their morphology, structure, and photocatalytic performance in degradation of methylene blue, were characterized by scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffraction analysis, Fourier transform infrared and UV–vis analysis. The results show that RGO–ZnO–TiO2 (GZT) hybrids (containing 7% graphene mass ratio) improve photodegradation efficiency 1.39- and 1.8-fold, compared with RGO–ZnO (GZT0) (containing 7% graphene mass ratio) and pure ZnO, because of reduction of electron–hole recombination in ZnO due to introduction of TiO2. Furthermore, we found that the photocatalytic activity in the ‘one step’ method is higher than in ‘two steps’.

  4. Design of self-cleaning TiO2 coating on clay roofing tiles

    NASA Astrophysics Data System (ADS)

    Hadnadjev, Milica; Ranogajec, Jonjaua; Petrovic, Snezana; Markov, Sinisa; Ducman, Vilma; Marinkovic-Neducin, Radmila

    2010-07-01

    The phenomenon of heterogeneous photocatalysis takes place in the degradation process of many organic contaminants on solid surfaces. Photocatalysis is based on the excitation of the semiconductor by irradiation with supraband gap photons and the migration of electron-hole pairs to the surface of the photocatalysts, leading to the reaction of the holes with adsorbed H2O and OH- to form hydroxyl radicals. Due to the stability and photosensitivity of TiO2 semiconductors, this system is well studied and is of great interest from an ecological and industrial point of view for use in the field of building materials. Clay roofing tiles, due to their long-term exploitation, are subject to physical, chemical and biological degradation that leads to deterioration. Ceramic systems have a high percentage of total porosity and considering their non-tolerance of organic coating, the use of surface active materials (SAM) that induce porosity in TiO2 coatings is of vital significance. Photocatalytic coatings applied on clay roofing tiles under industrial conditions were designed by varying the quantity of TiO2 (mass/cm2) on the tile surface (thin and thick TiO2 layer). The positive changes in specific surface area and mesopore structure of the designed coatings were made by the addition of PEG 600 as a surface active material. It was shown that a thin photocatalytic layer (0.399 mg suspension/cm2 tile surface), applied onto ceramic tiles under industrial conditions, had better photocatalytic activity in methylene blue decomposition, hydrophilicity and antimicrobial activity than a thick photocatalytic coating (0.885 mg suspension/cm2).

  5. Synthesis of surface molecular imprinted TiO2/graphene photocatalyst and its highly efficient photocatalytic degradation of target pollutant under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Lai, Cui; Wang, Man-Man; Zeng, Guang-Ming; Liu, Yun-Guo; Huang, Dan-Lian; Zhang, Chen; Wang, Rong-Zhong; Xu, Piao; Cheng, Min; Huang, Chao; Wu, Hai-Peng; Qin, Lei

    2016-12-01

    The molecular imprinted TiO2/graphene photocatalyst (MIP-TiO2/GR) was successfully prepared with bisphenol A (BPA) as the template molecule (target pollutant) and o-phenylenediamine (OPDA) as functional monomers by the surface molecular imprinting method. The combination between BPA and OPDA led to the formation of the precursor, and the subsequent polymerization of OPDA initiated by ultraviolet radiation can ensure the realization of MIP-TiO2/GR. The samples were characterized by SEM, EDS, XRD, BET, UV-vis DRS and Zeta potential. In addition, adsorption capacities, adsorption selectivity and visible light photocatalytic performances of MIP-TiO2/GR and non-imprinted TiO2/graphene (NIP-TiO2/GR) were evaluated. Moreover, the effects of pH and initial BPA concentration on removal efficiency of BPA were also investigated. The results showed that MIP-TiO2/GR exhibited better adsorption capacity and adsorption selectivity towards the template molecule compared to NIP-TiO2/GR due to the imprinted cavities on the surface of MIP-TiO2/GR. Moreover, the photocatalytic activity of MIP-TiO2/GR toward the target molecules was stronger than that of NIP-TiO2/GR as a result of large adsorption capacity to target molecules and narrow band gap energy on MIP-TiO2/GR. Therefore, modifying the photocatalyst by the surface molecular imprinting is a promising method to improve the molecule recognition and photocatalytic efficiency of photocatalyst for target pollutant.

  6. Photoinduced underwater superoleophobicity of TiO2 thin films.

    PubMed

    Sawai, Yusuke; Nishimoto, Shunsuke; Kameshima, Yoshikazu; Fujii, Eiji; Miyake, Michihiro

    2013-06-11

    The photoinduced wettabilities of water, n-hexadecane, dodecane, and n-heptane on a flat TiO2 surface prepared by a sol-gel method-based coating were investigated. An amphiphilic surface produced by UV irradiation exhibited underwater superoleophobicity with an extremely high static oil contact angle (CA) of over 160°. The TiO2 surface almost completely repelled the oil droplet in water. A robust TiO2 surface with no fragile nanomicrostructure was fabricated on a Ti mesh with a pore size of approximately 150 μm. The fabricated mesh was found to be applicable as an oil/water separation filter.

  7. Photocatalytic performance of the SiO2 sphere/ n-type TiO2/ p-type CuBiS2 composite catalysts coated with different contents of Ag nanoparticles under ultraviolet and visible light irradiations

    NASA Astrophysics Data System (ADS)

    Abdullah, Hairus; Kuo, Dong-Hau

    2016-08-01

    Photocatalytic performance of the SiO2 sphere/ n-type TiO2/ p-type CuBiS2 composite catalysts with different contents of silver nanoparticles (abbreviated as SiO2/ n-TiO2/ p-CuBiS2/Ag) toward the photodegradation of Acid Black 1 ( AB 1) dye under ultraviolet (UV) and visible light was investigated. The composite catalyst spheres were analyzed their crystal structure, microstructure, optical absorbance capabilities, and photodegradation capabilities of AB 1 dye. The best photodegradation performances of the 20 mg composite powder with only ~5 mg photoactive catalysts showed the degradation of AB 1 dye in 5 min under UV and 60 min under visible light irradiations. The concept of composite catalyst with numerous nano p- n diodes and its photodegradation mechanism were proposed.

  8. Photocatalytic degradation properties of V-doped TiO2 to automobile exhaust.

    PubMed

    Wang, Tong; Shen, Dongya; Xu, Tao; Jiang, Ruiling

    2017-05-15

    To improve the photocatalytic degradation properties of titanium dioxide (TiO2) used as raw materials for purifying automobile exhaust (AE), the vanadium (V)-doped TiO2 samples were prepared. The photocatalytic degradation efficiencies of V-doped TiO2 to each component in AE were evaluated under ultraviolet (UV) and visible light irradiation, respectively. Results indicated that the photocatalytic activity of V-doped TiO2 to AE was higher than that of pure TiO2, and the optimal V dopant content of TiO2 was 1.0% under UV light irradiation. The degradation efficiencies of V-doped TiO2 to NOx and HC were higher than those to CO2 and CO in AE because of the reversible reaction between CO2 and CO. In addition, it was found that the photocatalytic degradation efficiencies of V-doped TiO2 to each component in AE were also increased under visible light irradiation. The V-doped TiO2 also showed higher degradation efficiencies to NOx and HC than those to CO2 and CO under visible light irradiation. The V doped TiO2 presented higher photocatalytic activity to CO2 than that to CO, but the reversible reaction between CO and CO2 was not found under visible light irradiation. The photocatalytic reactions of pure and V-doped TiO2 samples to each component in AE followed the first order kinetic pathway under the two light irradiations. It is concluded that the V doping is a feasible method to improve the photocatalytic degradation properties of TiO2 to AE for air purification, developing a sustainable environmental purification technology based on TiO2 materials.

  9. Visible light photocatalytic activity of TiO2 nanoparticles hybridized by conjugated derivative of polybutadiene

    NASA Astrophysics Data System (ADS)

    Liu, Guoquan; Liu, Longchen; Song, Jinran; Liang, Jiudi; Luo, Qingzhi; Wang, Desong

    2014-05-01

    A series of conjugated polymer/TiO2 (CP/TiO2) nanocomposites were prepared from TiO2 and commercial polybutadiene. The as-prepared CP/TiO2 nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman Spectroscopy, UV-vis diffuse reflectance spectroscopy (UV-vis DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of CP/TiO2 nanocomposites were investigated by monitoring the degradation of methyl orange aqueous solution under visible light irradiation. The effects of preparation conditions (such as the mass ratio of PB to TiO2 in suspensions for PB/TiO2 preparation, heat-treatment temperature and time) of CP/TiO2 nanocomposites on their visible light photocatalytic activity were investigated. The results show that the CP/TiO2 nanocomposites have excellent visible light photocatalytic activity. As the content of conjugated polymer on the TiO2 surface, heat-treatment temperature and time increase, the visible light photocatalytic activity increases at first and then decreases. The visible light photocatalytic mechanism of the CP/TiO2 nanocomposites has been discussed.

  10. Modification of TiO2 by Bimetallic Au-Cu Nanoparticles for Wastewater Treatment

    PubMed Central

    Hai, Zibin; Kolli, Nadia EL; Uribe, Daniel Bahena; Beaunier, Patricia; José-Yacaman, Miguel; Vigneron, Jackie; Etcheberry, Arnaud; Sorgues, Sébastien; Colbeau-Justin, Christophe; Chen, Jiafu; Remita, Hynd

    2016-01-01

    Au, Cu and bimetallic Au-Cu nanoparticles were synthesized on the surface of commercial TiO2 compounds (P25) by reduction of the metal precursors with tetrakis (hydroxymethyl) phosphonium chloride (THPC) (0.5 % in weight). The alloyed structure of Au-Cu NPs was confirmed by HAADF-STEM, EDS, HRTEM and XPS techniques. The photocatalytic properties of the modified TiO2 have been studied for phenol photodegradation in aqueous suspensions under UV-visible irradiation. The modification by the metal nanoparticles induces an increase in the photocatalytic activity. The highest photocatalytic activity is obtained with Au-Cu/TiO2 (Au/Cu 1:3). Their electronic properties have been studied by time resolved microwave conductivity (TRMC) to follow the charge-carrier dynamics. TRMC measurements show that the TiO2 modification with Au, Cu and Au-Cu nanoparticles plays a role in charge-carrier separations increasing the activity under UV-light. Indeed, the metal nanoparticles act as a sink for electron, decreasing the charge carrier recombination. The TRMC measurements show also that the bimetallic Au-Cu nanoparticles are more efficient in electron scavenging than the monometallic Au and Cu ones. PMID:27274844

  11. Modification of TiO2 by Bimetallic Au-Cu Nanoparticles for Wastewater Treatment.

    PubMed

    Hai, Zibin; Kolli, Nadia El; Uribe, Daniel Bahena; Beaunier, Patricia; José-Yacaman, Miguel; Vigneron, Jackie; Etcheberry, Arnaud; Sorgues, Sébastien; Colbeau-Justin, Christophe; Chen, Jiafu; Remita, Hynd

    2013-09-28

    Au, Cu and bimetallic Au-Cu nanoparticles were synthesized on the surface of commercial TiO2 compounds (P25) by reduction of the metal precursors with tetrakis (hydroxymethyl) phosphonium chloride (THPC) (0.5 % in weight). The alloyed structure of Au-Cu NPs was confirmed by HAADF-STEM, EDS, HRTEM and XPS techniques. The photocatalytic properties of the modified TiO2 have been studied for phenol photodegradation in aqueous suspensions under UV-visible irradiation. The modification by the metal nanoparticles induces an increase in the photocatalytic activity. The highest photocatalytic activity is obtained with Au-Cu/TiO2 (Au/Cu 1:3). Their electronic properties have been studied by time resolved microwave conductivity (TRMC) to follow the charge-carrier dynamics. TRMC measurements show that the TiO2 modification with Au, Cu and Au-Cu nanoparticles plays a role in charge-carrier separations increasing the activity under UV-light. Indeed, the metal nanoparticles act as a sink for electron, decreasing the charge carrier recombination. The TRMC measurements show also that the bimetallic Au-Cu nanoparticles are more efficient in electron scavenging than the monometallic Au and Cu ones.

  12. The Study of Femtosecond Laser Irradiation on GaAs Solar Cells With TiO2/SiO2 Anti-Reflection Films

    NASA Astrophysics Data System (ADS)

    Hua, Yinqun; Shi, Zhiguo; Wu, Wenhui; Chen, Ruifang; Rong, Zhen; Ye, Yunxia; Liu, Haixia

    Femtosecond laser ablation on GaAs solar cells for space power has been investigated. In particular, we studied the effects of laser energy and laser number on the ablation of solar cells. Furthermore, the morphologies and microstructure of ablation were characterized by the non-contact optical profilometer and scanning electron microscope (SEM). The photovoltaic properties were tested by the volt ampere characteristic test system. The abaltion threshold of the TiO2/SiO2 anti-reflection film of GaAs solar cells was obtained from the linear fit of the dependence of the square diameter of the ablated area with the natural logarithm of the femtosecond laser pulse energy, the resulting threshold of the laser fluence is about 0.31J/cm2, and the corresponding energy is 5.4uJ. The ablation depth showed nonlinear dependence of energy. With the fixed energy 6uJ and the increasing laser number, the damage degree increases obviously. Furthermore, the electric properties also suffer a certain degradation. Among all the evaluated electric properties, the photoelectric conversion efficiency (η) degraded remarkably.

  13. Photoassisted NO reduction with NH3 over TiO2 photocatalyst.

    PubMed

    Tanaka, Tsunehiro; Teramura, Kentaro; Arakaki, Kyoko; Funabiki, Takuzo

    2002-11-21

    Photoassisted selective catalytic reduction of NO with ammonia (photo-SCR) at low temperature over irradiated TiO2 in a flow reactor was confirmed to proceed efficiently and the adsorbed ammonia reacted with NO under irradiation of TiO2.

  14. Improvement of Ultrasonic Disinfection Power Using TiO2 Photocatalyst

    NASA Astrophysics Data System (ADS)

    Dadjour, Mahmoud Farshbaf; Ogino, Chiaki; Matsumura, Susumu; Nakamura, Shinichi; Shimizu, Nobuaki

    2005-03-01

    The disinfection power of an ultrasonic system was enhanced using TiO2-photocatalyst in the irradiating solutions. Cultures of Legionella were used in the irradiation system with and without TiO2. A significant decrease in the concentration of viable cells was observed during irradiation in the presence of TiO2. The rate of cell killing was higher in the presence of TiO2 than it was with Al2O3, and was proportional to the amount of TiO2 used in the irradiating samples. There was no significant effect of cell concentration on the rate of cell killing in the range of 103 to 107 CFU/ml. Addition of OH radical scavengers such as glutathione, ascorbic acid and histidine to the irradiating solutions reduced the rate of disinfection, thus indicating the primary role of OH radicals in this process.

  15. Thin wetted film cylindrical flow photo reactor for the degradation of Procion blue H-B dye over TiO2 and ZnO.

    PubMed

    Neelavannan, M G; Basha, C Ahmed

    2011-01-01

    A thin wetted film cylindrical flow reactor was fabricated for photocatalytic oxidation of Procion blue H-B dye in textile washwater with the suspensions of TiO2 and ZnO. The disappearance of colour and organic reduction were studied in terms of the removal of colour and chemical oxygen demand (COD). Operating parameters such as effect of pH, UV irradiation with and without catalyst, initial concentration of dye and effect of flow rate were studied and kinetics of Procion blue H-B dye has been studied over TiO2 and ZnO surfaces. Since adsorption is the prerequisite condition for decolorization/degradation of dye molecules in the presence of heterogeneous catalysis, the Langmuir and Freundlich isotherms were examined to verify the adsorption intensity. The results clearly demonstrated that, the optimum loading of the photocatalyst was found to be 300 and 400 mg/L of TiO2 and ZnO, respectively. The maximum COD reduction efficiency was 68% for TiO2 and 58% for ZnO. On the other hand, the colour removal efficiency was found to be 74% and 69%, respectively for TiO2- and ZnO-assisted systems under optimum conditions. Conclusively, these two semiconductors could degrade Procion blue H-B dye at different time intervals and both isotherms fit well.

  16. Saturable absorption in aqueous suspensions of detonation nanodiamonds under irradiation with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Mikheev, G. M.; Vanyukov, V. V.; Mogileva, T. N.; Puzyr', A. P.; Bondar', V. S.; Svirko, Y. P.

    2015-12-01

    The phenomenon of saturable absorption has been observed in aqueous suspensions of detonation nanodiamonds (DNDs) with 34, 50, and 110 nm sized clusters of nanoparticles under irradiation with 795-nm laser pulses of 120-fs duration. The saturable absorption intensity has been studied as a function of the DND concentration in suspension. At a concentration of 2 wt % of DNDs with 50-nm average cluster size, the saturable absorption intensity amounts to 950 GW/cm2.

  17. Comparison study on photocatalytic oxidation of pharmaceuticals by TiO2-Fe and TiO2-reduced graphene oxide nanocomposites immobilized on optical fibers.

    PubMed

    Lin, Lu; Wang, Huiyao; Jiang, Wenbin; Mkaouar, Ahmed Radhi; Xu, Pei

    2017-03-08

    Incorporating reduced graphene oxide (rGO) or Fe(3+) ions in TiO2 photocatalyst could enhance photocatalytic degradation of organic contaminants in aqueous solutions. This study characterized the photocatalytic activities of TiO2-Fe and TiO2-rGO nanocomposites immobilized on optical fibers synthesized by polymer assisted hydrothermal deposition method. The photocatalysts presented a mixture phase of anatase and rutile in the TiO2-rGO and TiO2-Fe nanocomposites. Doping Fe into TiO2 particles (2.40eV) could reduce more band gap energy than incorporating rGO (2.85eV), thereby enhancing utilization efficiency of visible light. Incorporating Fe and rGO in TiO2 decreased significantly the intensity of TiO2 photoluminescence signals and enhanced the separation rate of photo-induced charge carriers. Photocatalytic performance of the synthesized nanocomposites was measured by the degradation of three pharmaceuticals under UV and visible light irradiation, including carbamazepine, ibuprofen, and sulfamethoxazole. TiO2-rGO exhibited higher photocatalytic activity for the degradation of pharmaceuticals under UV irradiation, while TiO2-Fe demonstrated more suitable for visible light oxidation. The results suggested that the enhanced photocatalytic performance of TiO2-rGO could be attributed to reduced recombination rate of photoexcited electrons-hole pairs, but for TiO2-Fe nanocomposite, narrower band gap would contribute to increased photocatalytic activity.

  18. Photodegradation of nalidixic acid assisted by TiO(2) nanorods/Ag nanoparticles based catalyst.

    PubMed

    Petronella, F; Diomede, S; Fanizza, E; Mascolo, G; Sibillano, T; Agostiano, A; Curri, M L; Comparelli, R

    2013-05-01

    Two different nanosized TiO2-based catalysts supported onto glass with tailored photocatalytic properties upon irradiation by UV light were successfully employed for the degradation of nalidixid acid, a widely diffused antibacterial agent of environmental relevance known to be non-biodegradable. Anatase rod-like TiO2 nanocrystals (TiO2NRs) and a semiconductor oxide-noble metal nanocomposite TiO2 NRs/Ag nanoparticles (NPs), synthesized by colloidal chemistry routes, were cast onto glass slide and employed as photocatalysts. A commercially available catalyst (TiO2 P25), also immobilized onto a glass slide, was used as a reference material. It was found that both TiO2 NRs/Ag NPs composite and TiO2 NRs demonstrated a photocatalytic efficiency significantly higher than the reference TiO2 P25. Specifically, TiO2 NRs/Ag NPs showed a photoactivity in nalidixic acid degradation 14 times higher than TiO2 P25 and 4 times higher than bare TiO2 NRs in the first 60min of reaction. Several by-products were identified by HPLC-MS along the nalidixic acid degradation, thus getting useful insight on the degradation pathway. All the identified by-products resulted completely removed after 6h of reaction.

  19. TiO2 coated microfluidic devices for recoverable hydrophilic and hydrophobic patterns

    NASA Astrophysics Data System (ADS)

    Lee, Jin-Hyung; Kim, Sang Kyung; Park, Hyung-Ho; Kim, Tae Song

    2015-03-01

    We report a simple method for modifying the surfaces of plastic microfluidic devices through dynamic coating process with a nano-colloidal TiO2 sol. The surface of the thermoplastic, cyclic olefin copolymer (COC) was coated with the TiO2 film, that displayed an effective photocatalytic property. The hydrophilic surface is obtained in the TiO2-coated zone of a microfluidic channel, and TiO2 coated surface degradation can be reversed easily by UV irradiation. The present work shows a photocatalytic activity concerning the effect of TiO2 coating density, which is controlled by the number of coating cycles. The hydrophilized surface was characterized by the contact angle of water and the TiO2 coated COC surface reduced the water contact angle from 85° to less than 10° upon UV irradiation. The photocatalytic effect of the layer that was coated five times with TiO2 was excellent, and the super-hydrophilicity of the TiO2 surface could be promptly recovered after 10 months of storage at atmospheric conditions. The COC microfluidic devices, in which TiO2 has been freshly deposited and aged for 10 months, were capable of generating water-in oil-in water (W/O/W) double emulsions easily and uniformly by simple control of the flow rates for demonstration of excellent hydrophilic patterning and recovery of the TiO2 coated in the microchannels.

  20. Photocatalytical removal of fluorouracil using TiO2-P25 and N/S doped TiO2 catalysts: A kinetic and mechanistic study.

    PubMed

    Koltsakidou, Α; Antonopoulou, M; Εvgenidou, Ε; Konstantinou, I; Giannakas, A E; Papadaki, M; Bikiaris, D; Lambropoulou, D A

    2017-02-01

    In the present study, the photocatalytic activity of TiO2-based photocatalysts toward degradation and mineralization of the anti-cancer drug 5-fluorouracil (5-FU) in aqueous phase was investigated under simulated solar and visible irradiation. Commercial TiO2 (P25) and N/S-doped TiO2 catalysts synthesized by a simple sol-gel method were used as photocatalysts. TiO2 P-25 was found to be the most photoactive catalyst for the removal of 5-FU, under simulated solar irradiation. Among N/S-doped TiO2 catalysts, the one with molar Ti:N/S ratio equal to 0.5 was the most efficient under simulated solar irradiation. In contrast, under visible irradiation the catalyst with equimolar Ti:N/S ratio showed the highest performance for the removal of 5-FU. Scavenging experiments revealed that HO radicals and h(+) were the major reactive species mediating photocatalytic degradation of 5-FU using TiO2 P-25 and N/S-doped TiO2 catalysts, under simulated solar irradiation. On the other hand, the essential contribution of (1)O2 and O2(-) in the degradation of 5-FU under visible light was proved. The transformation products (TPs) of 5-FU, were identified by LC-MS-TOF suggesting that defluorination followed by hydroxylation and oxidation are the main transformation pathways, under all the studied photocatalytic systems.

  1. Effects of TiO2 nanoparticles on ROS production and growth inhibition using freshwater green algae pre-exposed to UV irradiation.

    PubMed

    Fu, Ling; Hamzeh, Mahsa; Dodard, Sabine; Zhao, Yuan H; Sunahara, Geoffrey I

    2015-05-01

    This study investigated the possibility that titanium dioxide nanoparticles (nano-TiO2) toxicity in Pseudokirchneriella subcapitata involves reactive oxygen species (ROS) production, using the dichlorodihydrofluorescein (DCF) assay. Algae were exposed to nano-TiO2 under laboratory fluorescent lamps supplemented with UV irradiation for 3h, with or without a UV filter. Results showed that nano-TiO2 increased ROS production in UV-exposed cells, with or without a UV filter (LOEC values were 250 and 10mg/L, respectively). Sublethal effects of nano-TiO2 on UV pre-exposed algae were also examined. Toxicity studies indicated that exposure to nano-TiO2 agglomerates decreased algal growth following 3h pre-exposure to UV, with or without a UV filter (EC50s were 8.7 and 6.3mg/L, respectively). The present study suggests that the growth inhibitory effects of nano-TiO2 in algae occurred at concentrations lower than those that can elevate DCF fluorescence, and that ROS generation is not directly involved with the sublethal effects of nano-TiO2 in algae.

  2. Photocatalytic antibacterial performance of TiO2 and Ag-doped TiO2 against S. aureus. P. aeruginosa and E. coli

    PubMed Central

    Gupta, Kiran; Singh, R P; Pandey, Ashutosh

    2013-01-01

    Summary This paper reports the structural and optical properties and comparative photocatalytic activity of TiO2 and Ag-doped TiO2 nanoparticles against different bacterial strains under visible-light irradiation. The TiO2 and Ag-doped TiO2 photocatalysts were synthesized by acid catalyzed sol–gel technique and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis spectroscopy and photoluminescence (PL). The XRD pattern revealed that the annealed sample of TiO2 has both anatase and rutile phases while only an anatase phase was found in Ag-doped TiO2 nanoparticles. The decreased band-gap energy of Ag-doped TiO2 nanoparticles in comparison to TiO2 nanoparticles was investigated by UV–vis spectroscopy. The rate of recombination and transfer behaviour of the photoexcited electron–hole pairs in the semiconductors was recorded by photoluminescence. The antimicrobial activity of TiO2 and Ag-doped TiO2 nanoparticles (3% and 7%) was investigated against both gram positive (Staphylococcus aureus) and gram negative (Pseudomonas aeruginosa, Escherichia coli) bacteria. As a result, the viability of all three microorganisms was reduced to zero at 60 mg/30 mL culture in the case of both (3% and 7% doping) concentrations of Ag-doped TiO2 nanoparticles. Annealed TiO2 showed zero viability at 80 mg/30 mL whereas doped Ag-TiO2 7% showed zero viability at 40 mg/30 mL culture in the case of P. aeruginosa only. PMID:23844339

  3. Photocatalytic antibacterial performance of TiO2 and Ag-doped TiO2 against S. aureus. P. aeruginosa and E. coli.

    PubMed

    Gupta, Kiran; Singh, R P; Pandey, Ashutosh; Pandey, Anjana

    2013-01-01

    This paper reports the structural and optical properties and comparative photocatalytic activity of TiO2 and Ag-doped TiO2 nanoparticles against different bacterial strains under visible-light irradiation. The TiO2 and Ag-doped TiO2 photocatalysts were synthesized by acid catalyzed sol-gel technique and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectroscopy and photoluminescence (PL). The XRD pattern revealed that the annealed sample of TiO2 has both anatase and rutile phases while only an anatase phase was found in Ag-doped TiO2 nanoparticles. The decreased band-gap energy of Ag-doped TiO2 nanoparticles in comparison to TiO2 nanoparticles was investigated by UV-vis spectroscopy. The rate of recombination and transfer behaviour of the photoexcited electron-hole pairs in the semiconductors was recorded by photoluminescence. The antimicrobial activity of TiO2 and Ag-doped TiO2 nanoparticles (3% and 7%) was investigated against both gram positive (Staphylococcus aureus) and gram negative (Pseudomonas aeruginosa, Escherichia coli) bacteria. As a result, the viability of all three microorganisms was reduced to zero at 60 mg/30 mL culture in the case of both (3% and 7% doping) concentrations of Ag-doped TiO2 nanoparticles. Annealed TiO2 showed zero viability at 80 mg/30 mL whereas doped Ag-TiO2 7% showed zero viability at 40 mg/30 mL culture in the case of P. aeruginosa only.

  4. Reaction pathways of dimethyl phthalate degradation in TiO2-UV-O2 and TiO2-UV-Fe(VI) systems.

    PubMed

    Yuan, Bao-ling; Li, Xiang-zhong; Graham, Nigel

    2008-05-01

    The photocatalytic degradation of dimethyl phthalate (DMP) in aqueous TiO2 suspension under UV illumination has been investigated using oxygen (O2) and ferrate (Fe(VI)) as electron acceptors. The experiments demonstrated that Fe(VI) was a more effective electron acceptor than O2 for scavenging the conduction band electrons from the surface of the catalyst. Some major intermediate products from DMP degradation were identified by HPLC and GC/MS analyses. The analytical results identified dimethyl 3-hydroxyphthalate and dimethyl 2-hydroxyphthalate as the two main intermediate products from the DMP degradation in the TiO2-UV-O2 system, while in contrast phthalic acid was found to be the main intermediate product in the TiO2-UV-Fe(VI) system. These findings indicate that DMP degradation in the TiO2-UV-O2 and TiO2-UV-Fe(VI) systems followed different reaction pathways. An electron spin resonance analysis confirmed that hydroxyl radicals existed in the TiO2-UV-O2 reaction system and an unknown radical species (most likely an iron-oxo species) is suspected to exist in the TiO2-UV-Fe(VI) reaction system. Two pathway schemes of DMP degradation in the TiO2-UV-O2 and TiO2-UV-Fe(VI) reaction systems are proposed. It is believed that the radicals formed in the TiO2-UV-O2 reaction system preferably attack the aromatic ring of the DMP, while in contrast the radicals formed in the TiO2-UV-Fe(VI) reaction systems attack the alkyl chain of DMP.

  5. New evidence for TiO2 uniform surfaces leading to complete bacterial reduction in the dark: critical issues.

    PubMed

    Nesic, Jelena; Rtimi, Sami; Laub, Danièle; Roglic, Goran M; Pulgarin, Cesar; Kiwi, John

    2014-11-01

    This study presents new evidence for the events leading to Escherichia coli reduction in the absence of light irradiation on TiO2-polyester (from now on TiO2-PES. By transmission electron microscopy (TEM) the diffusion of TiO2 NP's aggregates with the E. coli outer lipo-polyssacharide (LPS) layer is shown to be a prerequisite for the loss of bacterial cultivability. Within 30 min in the dark the TiO2 aggregates interact with E. coli cell wall leading within 120 min to the complete loss of bacterial cultivability on a TiO2-PES 5% TiO2 sample. The bacterial reduction was observed to increase with a higher TiO2 loading on the PES up to 5%. Bacterial disinfection on TiO2-PES in the dark was slower compared to the runs under low intensity simulated sunlight light irradiation. The interaction between the TiO2 aggregates and the E. coli cell wall is discussed in terms of the competition between the TiO2 units collapsing to form TiO2-aggregates at a physiologic pH-value followed by the electrostatic interaction with the bacteria surface. TiO2-PES samples were able to carry repetitive bacterial inactivation. This presents a potential for practical applications. X-ray photoelectron spectroscopy (XPS) evidence was found for the reduction of Ti4+ to Ti3+ contributing to redox interactions between TiO2-PES and the bacterial cell wall. Insight is provided into the mechanism of interaction between the E. coli cell wall and TiO2 NP's. The properties of the TiO2-PES surface like percentage atomic concentration, TiO2-loading, optical absorption, surface charge and crystallographic phases are reported in this study.

  6. Solar-driven photocatalytic treatment of diclofenac using immobilized TiO2-based zeolite composites.

    PubMed

    Kovacic, Marin; Salaeh, Subhan; Kusic, Hrvoje; Suligoj, Andraz; Kete, Marko; Fanetti, Mattia; Stangar, Urska Lavrencic; Dionysiou, Dionysios D; Bozic, Ana Loncaric

    2016-09-01

    The study is aimed at evaluating the potential of immobilized TiO2-based zeolite composite for solar-driven photocatalytic water treatment. In that purpose, TiO2-iron-exchanged zeolite (FeZ) composite was prepared using commercial Aeroxide TiO2 P25 and iron-exchanged zeolite of ZSM5 type, FeZ. The activity of TiO2-FeZ, immobilized on glass support, was evaluated under solar irradiation for removal of diclofenac (DCF) in water. TiO2-FeZ immobilized in a form of thin film was characterized for its morphology, structure, and composition using scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX). Diffuse reflectance spectroscopy (DRS) was used to determine potential changes in band gaps of prepared TiO2-FeZ in comparison to pure TiO2. The influence of pH, concentration of hydrogen peroxide, FeZ wt% within the composite, and photocatalyst dosage on DCF removal and conversion efficiency by solar/TiO2-FeZ/H2O2 process was investigated. TiO2-FeZ demonstrated higher photocatalytic activity than pure TiO2 under solar irradiation in acidic conditions and presence of H2O2.

  7. Synthesis and characterization of Ag doped TiO2 heterojunction films and their photocatalytic performances

    NASA Astrophysics Data System (ADS)

    Demirci, Selim; Dikici, Tuncay; Yurddaskal, Metin; Gultekin, Serdar; Toparli, Mustafa; Celik, Erdal

    2016-12-01

    In this study, undoped and silver (Ag) doped titanium dioxide (TiO2) films were successfully synthesized by sol-gel spin coating technique on the Si substrates. Photocatalytic activities of the TiO2 films with different Ag content were investigated for the degradation of methylene blue (MB) under UV light irradiation. The crystal phase structure, surface morphology, chemical and optical properties of Ag-doped TiO2 films were characterized using an X-ray diffractometer (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-vis spectrophotometer, and FTIR spectrophotometer. The results showed that the Ag-doped TiO2 films calcined at 500 °C had the crystalline anatase phases and the surface morphologies with some cracks. Ag substitution into TiO2 matrix enhanced the photocatalytic activity of TiO2 films under UV light irradiation as compared to the undoped TiO2 film. Furthermore, the results indicated that the 0.7% Ag doped TiO2 film exhibited a superior photocatalytic activity than that of undoped and other Ag-doped TiO2 films. This study demonstrated the potential of an application of Ag doped films to efficiently treat dissolved organic contaminants in water.

  8. Photocatalytic degradation of azo dyes using Au:TiO2, gamma-Fe2O3:TiO2 functional nanosystems.

    PubMed

    Jagadale, Tushar; Kulkarni, Manjusha; Pravarthana, D; Ramadan, Wegdan; Thakur, Pragati

    2012-02-01

    We report photocatalytic degradation studies on Navy Blue HE2R (NB) dye on significant details as a representative from the class of azo dyes using functional nanosystems specifically designed to allow a strong photocatalytic activity. A modified sol-gel route was employed to synthesize Au and gamma-Fe2O3 modified TiO2 nanoparticles (NPs) at low temperature. The attachment strategy is better because it allows clear surface of TiO2 to remain open for photo-catalysis. X-ray diffraction, Raman and UV-VIS spectroscopy studies showed the presence of gold and iron oxide phases along-with the anatase TiO2 phase. TEM studies showed TiO2 nanocomposite particles of size approximately 10-12 nm. A detailed investigation on heterogeneous photocatalytic performance for Navy Blue HE2R dye was done using the as-synthesized catalysts Au:TiO2 and gamma-Fe2O3:TiO2 in aqueous suspension under 8 W low-pressure mercury vapour lamp irradiation. Also, the photocatalytic degradation of Amranth and Orange G azo dyes were studied. The surface modified TiO2 NPs showed significantly improved photocatalytic activity as compared to pure TiO2. Exposure of the dye to the UV light in the presence of pure and gold NPs attached TiO2 catalysts caused dye degradation of about approximately 20% and approximately 80%, respectively, in the first couple of hours. In the presence of gamma-Fe2O3 NPs attached TiO2, a remarkable approximately 95% degradation of the azo dye was observed only in the first 15 min of UV exposure. The process parameters for the optimum catalytic activity are established which lead to a complete decoloration and substantial dye degradation, supported by the values of the Chemical Oxygen Demand (COD) approximately 93% and Total Organic Carbon (TOC) approximately 65% of the treated dye solution after 5 hours on the employment of the UV/Au:TiO2/H2O2 photocatalytic process.

  9. Photocatalytic degradation of phenol by visible light-responsive iron-doped TiO2 and spontaneous sedimentation of the TiO2 particles.

    PubMed

    Nahar, Mst Shamsun; Hasegawa, Kiyoshi; Kagaya, Shigehiro

    2006-12-01

    Fe-doped TiO2 was prepared by the calcination of Fe(x)TiS(2) (x=0, 0.002, 0.005, 0.008, 0.01) and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectra. All the Fe-doped TiO2 were composed of an anatase crystal form and showed red shifts to a longer wavelength. The activity of the Fe-doped TiO2 for the degradation of phenol was investigated by varying the iron content during UV (365nm) and visible light (405nm and 436nm) irradiation. The degradation rate depended on the Fe content and the Fe-doped TiO2 was responsive to the visible light as well as the elevated activity toward UV light. The molar ratio of 0.005 was the optimum for both the UV and visible light irradiations. The result was discussed on the basis of the balance of the excited electron-hole trap by the doped Fe(3+) and their charge recombination on the doped Fe(3+) level. The Fe-doped TiO2 (x=0.005) was more active than P25 TiO2 under solar light irradiation. The suspended Fe-doped TiO2 spontaneously precipitated once the stirring of the reaction mixture was terminated.

  10. Selective aerobic oxidation mediated by TiO(2) photocatalysis.

    PubMed

    Lang, Xianjun; Ma, Wanhong; Chen, Chuncheng; Ji, Hongwei; Zhao, Jincai

    2014-02-18

    TiO2 is one of the most studied metal oxide photocatalysts and has unparal-leled efficiency and stability. This cheap, abundant, and non-toxic material has the potential to address future environmental and energy concerns. Understanding about the photoinduced interfacial redox events on TiO2 could have profound effect on the degradation of organic pollutants, splitting of H2O into H2 and O2, and selective redox organic transformations. Scientists traditionally accept that for a semiconductor photocatalyst such as TiO2 under the illumination of light with energy larger than its band gap, two photocarriers will be created to carry out their independent reduction and oxidation processes. However, our recent discoveries indicate that it is the concerted rather than independent effect of both photocarriers of valence band hole (hvb(+)) and conduction band electron (ecb(-)) that dictate the product formation during interfacial oxidation event mediated by TiO2 photocatalysis. In this Account, we describe our recent findings on the selective oxidation of organic substrates with O2 mediated by TiO2 photocatalysis. The transfer of O-atoms from O2 to the corresponding products dominates the selective oxidation of alcohols, amines, and alkanes mediated by TiO2 photocatalysis. We ascribe this to the concerted effect of both hvb(+) and ecb(-) of TiO2 in contribution to the oxidation products. These findings imply that O2 plays a unique role in its transfer into the products rather than independent role of ecb(-) scavenger. More importantly, ecb(-) plays a crucial role to ensure the high selectivity for the oxygenation of organic substrates. We can also use the half reactions such as those of the conduction band electron of TiO2 for efficient oxidation reactions with O2. To this end, efficient selective oxidation of organic substrates such as alcohols, amines, and aromatic alkanes with O2 mediated by TiO2 photocatalysis under visible light irradiation has been achieved. In

  11. Diversity of TiO2 nanopowders' characteristics relevant to toxicity testing

    NASA Astrophysics Data System (ADS)

    Novak, Saša; Lorenzetti, Martina; Drame, Anja; Vidmar, Janja; Ščančar, Janez; Filipič, Metka

    2016-05-01

    In this study, the physicochemical properties of several commercial ultrafine TiO2 powders and their behaviour in the as-received form and colloidal suspensions were analysed. Besides the particle size, the morphology and agglomeration state of the dry powders, dispersibility, ζ-potential and sedimentation in water and in phosphate-buffered saline (PBS) were studied. Also, leaching of ions from the powders during ageing in physiological solution and the ability of the photoactivated powders to decompose organic substances were evaluated. The examined TiO2 powders revealed diversified characteristics when dispersed in water. In general, while in dry conditions the particle size appeared in the nano-range (down to 32 nm), the particles were agglomerated in aqueous suspensions at pH 7 and only a minor amount showed dimensions below 200 nm, but none below 100 nm. The inherent pH of the 3 % suspensions varies from 3.7 to 7.5 and the surface charge at these pH values varied from highly positive to highly negative values. In PBS, the surface charge is negative and relatively low for all the samples, which resulted in agglomeration. Five out of six powders exhibited significant photocatalytic activity when exposed to UV irradiation. This also includes one cosmetic-grade powder. Furthermore, during the immersion in aqueous media at physiological temperature, the powders released foreign ions, which might also contribute to the results of cytotoxicity tests. The results revealed the major role of the particle surface charge and its impact on particle dispersion or agglomeration. Due to the high ionic strength in the liquids relevant for cell-surface interaction tests, for all the examined titania powders the nanoparticulate character was lost. However, the presence of impurities and photocatalysis might further contribute to the results of cytotoxicity tests.

  12. Investigation of photocatalytic degradation of phenol by Fe(III)-doped TiO2 and TiO2 nanoparticles

    PubMed Central

    2014-01-01

    In this study Fe (III)-doped TiO2 nanoparticles were synthesized by sol–gel method at two atomic ratio of Fe/Ti, 0.006 and 0.034 percent. Then the photoactivity of them was investigated on degradation of phenol under UV (<380 nm) irradiation and visible light (>380 nm). Results showed that at appropriate atomic ratio of Fe to Ti (% 0.034) photoactivity of Fe(III)–doped TiO2 nanoparticles increased. In addition, the effects of various operational parameters on photocatalytic degradation, such as pH, initial concentration of phenol and amount of photocatalyst were examined and optimized. At all different initial concentration, highest degradation efficiency occurred at pH = 3 and 0.5 g/L Fe(III)–doped TiO2 dosage. With increase in initial concentration of phenol, photocatalytic degradation efficiency decreased. Photoactivity of Fe (III)-doped TiO2 under UV irradiation and visible light at optimal condition (pH = 3 and catalyst dosage = and 0.5 g/L) was compared with P25 TiO2 nanoparticles. Results showed that photoactivity of Fe(III)-doped TiO2 under visible light was more than P25 TiO2 photoactivity, but it was less than P25 TiO2 photoactivity under UV irradiation. Also efficiency of UV irradiation alone and amount of phenol adsorption on Fe(III)-doped TiO2 at dark condition was investigated. PMID:25105016

  13. Investigation of photocatalytic degradation of phenol by Fe(III)-doped TiO2 and TiO2 nanoparticles.

    PubMed

    Hemmati Borji, Saeedeh; Nasseri, Simin; Mahvi, Amir Hossein; Nabizadeh, Ramin; Javadi, Amir Hossein

    2014-01-01

    In this study Fe (III)-doped TiO2 nanoparticles were synthesized by sol-gel method at two atomic ratio of Fe/Ti, 0.006 and 0.034 percent. Then the photoactivity of them was investigated on degradation of phenol under UV (<380 nm) irradiation and visible light (>380 nm). Results showed that at appropriate atomic ratio of Fe to Ti (% 0.034) photoactivity of Fe(III)-doped TiO2 nanoparticles increased. In addition, the effects of various operational parameters on photocatalytic degradation, such as pH, initial concentration of phenol and amount of photocatalyst were examined and optimized. At all different initial concentration, highest degradation efficiency occurred at pH = 3 and 0.5 g/L Fe(III)-doped TiO2 dosage. With increase in initial concentration of phenol, photocatalytic degradation efficiency decreased. Photoactivity of Fe (III)-doped TiO2 under UV irradiation and visible light at optimal condition (pH = 3 and catalyst dosage = and 0.5 g/L) was compared with P25 TiO2 nanoparticles. Results showed that photoactivity of Fe(III)-doped TiO2 under visible light was more than P25 TiO2 photoactivity, but it was less than P25 TiO2 photoactivity under UV irradiation. Also efficiency of UV irradiation alone and amount of phenol adsorption on Fe(III)-doped TiO2 at dark condition was investigated.

  14. Fabrication of TiO2/MoS2@zeolite photocatalyst and its photocatalytic activity for degradation of methyl orange under visible light

    NASA Astrophysics Data System (ADS)

    Zhang, Weiping; Xiao, Xinyan; Zheng, Lili; Wan, Caixia

    2015-12-01

    TiO2/MoS2@zeolite composite photocatalysts with visible-light activity were fabricated via a simple ultrasonic-hydrothermal synthesis method, using TiCl4 as Ti source, MoS2 as a direct sensitizer, glycerol water solution with certain dispersion agent as hydrolytic agent, and zeolite as carrier. The structure, morphology, composition, optical properties, and specific surface area of the as-prepared photocatalysts were characterized by using XRD, FTIR, SEM-EDS, TEM, XPS, UV-vis, PL and BET analyzer, respectively. And the photocatalytic degradation of methyl orange (MO) in aqueous suspension has been employed to evaluate the photocatalytic activity and degradation kinetics of as-prepared photocatalysts with xenon lamp as irradiation source. The results indicate that: (1) TiO2/MoS2@zeolite composite photocatalysts exhibit enhanced photocatalytic activities for methyl orange (MO) degradation compared to Degussa P25; (2) photocatalytic degradation of MO obeys Langmuir-Hinshelwood kinetic model (pseudo-first order reaction), and its degradation rate constant (kapp) (2.304 h-1) is higher than that of Degussa P25 (0.768 h-1); (3) the heterostructure consisted of zeolite, MoS2 and TiO2 nanostructure could provide synergistic effect for degradation of MO due to the efficient electron transfer process and better absorption property of TiO2/MoS2@zeolite composite photocatalyst.

  15. Comparing Cr, and N only doping with (Cr,N)-codoping for enhancing visible light reactivity of TiO2

    SciTech Connect

    Li, Yuan; Wang, Wei; Qiu, Xiaofeng; Meyer III, Harry M; Paranthaman, Mariappan Parans; Eres, Gyula; Zhang, Zhenyu; Gu, Baohua

    2011-01-01

    The photoreactivity of titania (TiO2) nanoclusters with varying levels of N or Cr-doping, or (Cr,N)-codoping, was systematically investigated using photodegradation of methyl orange in aqueous suspensions. The shifting of the TiO2 absorption edge into the visible spectral region that is primarily attributable to band gap narrowing was found to be a reliable metric for estimating the photoreactivity of the doped nanoclusters. Compared to the weak response with undoped and N-doped TiO2, Cr-doping and (Cr, N)-codoping were found to significantly enhance photodegradation of methyl orange under visible light. The initial reaction rates increase from about 0 to above 1.6 10-2 min-1 when the doping concentration of Cr in TiO2 increases from 0 to 5%. In stark contrast, under UV irradiation, doping is not only ineffective but detrimental to the photoreactivity, and all doping including N or Cr only and (Cr, N)-codoping were found to reduce photoreactivity.

  16. Ultrasound-mediated gene transfection: A comparison between cells irradiated in suspension and attachment status

    NASA Astrophysics Data System (ADS)

    Zhang, Yiwei; Azuma, Takashi; Sasaki, Akira; Yoshinaka, Kiyoshi; Takagi, Shu; Matsumoto, Yoichiro

    2012-10-01

    Sonoporation, in the presence of microbubbles, is a promising nonviral gene transfection method. Although the mechanism is not yet fully understood, shock waves emitted by cavitation bubbles have been known to play an important role in creating pores on cell membranes. This work investigates the gene transfection efficiency and influencing parameters of cells in two different statuses: attachment and suspension based on the fact that cells in suspension have more bubbles surrounding them and that shock wave has distinct effects on hit objects whether the object is attached to a rigid wall or not. Fibroblast cells (NIH3T3), both in attachment and suspension, and green fluorescent protein (GFP) plasmid were exposed to variations in acoustic pressure (0.6-1.2 MPa) and 10% duty cycle at fixed settings of 2 MHz central frequency, 5 kHz pulse repetition frequency and 1 minute insonation time, in the presence of 10% v/v microbubbles (Sonazoid, a commercialized product of ultrasound contrast agent). The transfection efficiency and cell viability are compared for two statuses and a distribution map of GFP transfected cells as well as viable cells over the well bottom is given for attachment status. The results show that cells irradiated in suspension status has higher transfection ratio as well as viability than those irradiated in attachment status with the same intensity and that the transfected cells of attachment status experiment are highly concentrated near the center of the well.

  17. Oxidation of sulfamethoxazole and related antimicrobial agents by TiO2 photocatalysis.

    PubMed

    Hu, Lanhua; Flanders, Phillip M; Miller, Penney L; Strathmann, Timothy J

    2007-06-01

    The widespread detection of pharmaceutically active compounds, including many synthetic antimicrobial agents, in aquatic environments is raising public health concerns. As a result, there is growing interest in the development of innovative technologies to efficiently transform these compounds to non-toxic and pharmaceutically inactive byproducts. This work examines the photocatalytic degradation of sulfamethoxazole (SMX) and related sulfonamide antimicrobial agents in aqueous suspensions of nanophase titanium dioxide (TiO(2)). Experimental results demonstrate that SMX is mineralized by TiO(2) irradiated with ultraviolet-A light (UVA: 324

  18. Antifungal activity of TiO2 photocatalysis against Penicillium expansum in vitro and in fruit tests.

    PubMed

    Maneerat, Chamorn; Hayata, Yasuyoshi

    2006-03-15

    The antifungal activity of TiO2 photocatalytic reaction in the form of TiO2 powder and TiO2 coated on a plastic film against Penicillium expansum was investigated in vitro and in fruit tests. The mixture of P. expansum conidial suspension and TiO2 powder was added to potato dextrose agar (PDA) plates for vitro test. The TiO2 photocatalytic reaction reduced conidial germination of the fungal pathogen. It was found that the ability of the TiO2 photocatalytic reaction to suppress P. expansum growth correlated to the amount of TiO2 added. Lower numbers of viable colonies of P. expansum were observed with increasing amount of TiO2. Regardless of the kind of selected fruit inoculated with P. expansum, both TiO2 powder and TiO2-coated film exhibited antifungal activity to control fruit rot. Development of Penicillium rot in apple was significantly (P = 0.05) retarded by the TiO2 photocatalytic reaction. Similarly the TiO2 photocatalytic reaction was the only treatment where no tomato fruit rot was noticeable after 1 week of storage. TiO2-coated film also decreased brown lesions and Penicillium rot infection in lemons. The mean severity fruit rot scores (browning and softening flesh) were 3.2 and 1.9 for uncoated and TiO2-coated film, respectively. Our findings suggest that "TiO2 photocatalytic reaction" shows antifungal activity against P. expansum which may have potential for postharvest disease control.

  19. Photocatalytic inactivation of Flavobacterium and E. coli in water by a continuous stirred tank reactor (CSTR) fed with suspended/immobilised TiO2 medium.

    PubMed

    Cohen-Yaniv, Vered; Narkis, Nava; Armon, Robert

    2008-01-01

    A photocatalytic continuous stirred tank reactor (CSTR) was built at laboratory scale to inactivate two environmental bacteria strains (Flavobacterium and E. coli) in tap water. Several parameters were found to impact reactor efficiency. Bacterial initial concentration is an important factor in inactivation rate. After 30 minutes of irradiation at 10(8)-10(9) CFU mL(-1) starting concentration, a >5 log reduction was achieved while at 10(4)-10(6) CFU mL(-1) only a 2 log reduction was observed. Water hardness and pH have an important influence on the photocatalytic inactivation process. Soft water, with low Ca(+2) and Mg(+2) at low pH approximately 5.3 resulted in increased inactivation of Flavobacterium reaching >6 orders of magnitude reduction. E. coli and Flavobacterium at pH 5 were inactivated by 3 logs more as compared to pH 7 under similar conditions. pH below TiO2 isoelectric point (approximately 5.6) supports better contact between bacteria and anatase particles resulting in superior inactivation. TiO2 powder suspension was compared with immobilised powder in sol-gel coated glass beads in order to exclude the need for particles separation from the treated water. TiO2 suspension was more effective by 3 orders of magnitude when compared to coated glass beads. An interesting observation was found between the two bacterial strains based on their hydrophobicity/hydrophilicity balance. The more hydrophobic Flavobacterium compared to E. coli was inactivated photocatalytically by >3 logs more then E. coli in the first 30 minutes of irradiation interval. The results indicate the importance of the parameters involved in the contact between TiO2 particles and microorganisms that govern the successful inactivation rate in CSTR.

  20. Enhancement of stability of aqueous suspension of alumina nanoparticles by femtosecond laser irradiation

    SciTech Connect

    Seo, Youngsang; Ha, Jeonghong; Kim, Dongsik; Choi, Tae-Youl; Jeong, Dae-Yong; Lee, Seung Yong

    2015-09-21

    In this work, we report substantially enhanced colloidal stability of aqueous nanoparticle suspensions by ultrashort laser pulse irradiation. A Ti:Sapphire femtosecond laser (wavelength: 800 nm; pulse duration: 50 fs at full width at half maximum) was used to modify the electrochemical properties of nanoparticle suspensions at laser fluences below the particle ablation threshold. The colloidal stability of the suspension was evaluated by zeta potential and dynamic light scattering (DLS). The DLS results along with the images from transmission electron microscopy revealed that the laser irradiation caused no distinct morphological change to the individual alumina particles, but a substantial portion of the clustered particles was fragmented by the laser pulses, decreasing the apparent size of the suspended particles. Also, X-ray photoelectron spectroscopy analysis indicates that the laser irradiation modified the surface chemistry of the alumina particles. The stabilizing capability of the proposed technique was turned out to be better than that of conventional ultrasonic treatments. The stability of the laser-treated sample with no added surfactant was maintained for up to 30 days, without requiring an additional homogenizing process such as magnetic stirring.

  1. Effects of TiO2 coating dosage and operational parameters on a TiO2/Ag photocatalysis system for decolorizing Procion red MX-5B.

    PubMed

    Lin, Yu-Chih; Lee, Ho-Shan

    2010-07-15

    In this study, titanium dioxide (TiO(2)) powder was coated onto the surface of a dendritic silver (Ag) carrier to synthesize TiO(2)/Ag for decolorizing Procion red MX-5B (MX-5B), and related operation factors were also studied. The results showed that even without ultraviolet-A (UVA) irradiation, the Ag carrier from the TiO(2)/Ag catalyst had oxidizing ability, which could effectively degrade MX-5B color, but TiO(2) was ineffective. In addition, TiO(2) from TiO(2)/Ag demonstrated photocatalysis performance when irradiated, and the Ag carrier further showed an electron-scavenging ability to mitigate electron-hole pair recombination, which can improve the photocatalytic efficacy. With the oxidization and electron-scavenging ability of Ag and the photocatalysis ability of TiO(2), TiO(2)/Ag can decolor MX-5B more efficiently than TiO(2). The heavier Ag carrier also improves the solid-liquid separation of nano-TiO(2), making TiO(2)/Ag more suitable for application in slurry systems of photocatalytic water treatment. When the TiO(2)/Ag coating ratio was 50% by weight, there was a sufficient amount of TiO(2) on Ag's surface with a good distribution, and it exhibited a good photocatalysis decolorizing effect. In a study of how operational factors impact the decolorizing of MX-5B in the TiO(2)/Ag photocatalysis system with UVA irradiation (UVA-TiO(2)/Ag), the decolorization efficiency was optimal when the solution was maintained at pH 6.35. The addition of 0.01 M hydrogen peroxide (H(2)O(2)) aided the photocatalysis decolorization efficiency, although excessive H(2)O(2) reacted with hydroxyl free radicals and decreased the active groups in the system, thereby reducing the photocatalysis activity. An operating temperature of 40 degrees C was conducive to MX-5B decolorization, which was better than operating at room temperature.

  2. Temperature-boosted photocatalytic H2 production and charge transfer kinetics on TiO2 under UV and visible light.

    PubMed

    Kim, Gonu; Choi, Hee Joon; Kim, Hyoung-Il; Kim, Jaehong; Monllor-Satoca, Damián; Kim, Minju; Park, Hyunwoong

    2016-10-05

    This study investigates the effect of reaction temperature (298-353 K) on photocatalytic H2 production in bare and platinized TiO2 (Pt/TiO2) suspensions containing various organic hole scavengers (EDTA, methanol, and formic acid) under UV (λ > 320 nm) and visible light (λ > 420 nm for ligand-to-metal charge transfer). H2 production rates are enhanced ∼7.8- and ∼2.5-fold in TiO2 and Pt/TiO2 suspensions, respectively, with EDTA under UV by simply elevating the reaction temperature from 298 K to 323 K (ΔT = 25 °C). Such a temperature-boosted increase in H2 production is always observed, regardless of the TiO2 crystalline structure (anatase, rutile, and an anatase/rutile mixture), type of hole scavenger, and irradiation wavelength range. It is estimated that approximately 90% of incident photons are utilized in H2 production, for which the activation energy is 25.5 kJ mol(-1). Detailed photoelectrochemical analyses show the positive relationship between reaction temperature and photocurrent generation, with charge carrier mobility and interfacial charge transfer improving at higher temperatures. Other possible factors, such as H2 solubility and mass transport, play a limited role.

  3. Non-UV based germicidal activity of metal-doped TiO2 coating on solid surfaces.

    PubMed

    Liu, Li-fen; Barford, John; Yeung, King Lun; Si, Grace

    2007-01-01

    A stain-based screening method was developed to screen different catalyst coatings for their germicidal activity. A Baclight dead/live bacteria viability kit (invitrogen, molecular probes) was used for staining the cell. The screening was carried out following a standard procedure. This included loading cell suspension to solid surface and maintaining contact for 30 min, then staining with a mixture containing dyes. The stained cells were observed using an epifluorescent microscope and photographed with a CCD camera under UV. Metal-doped TiO2 coatings on Al plates were prepared and tested for non-UV germicidal activity without using UV. It was tested using model microorganisms such as Bakers Yeast (Saccharomyces cerevisiae), Bacillus subtilis, Pseudomonas putida, and Escherichia coli. On the basis of the germicidal activity of catalyst and the degree of damage caused to the cells, the stained cells may appear green (viable), green with red or yellow nuclei and yellow (compromised) or red (nonviable). According to their stained color, cells were counted to calculate the percentage of dead, live, and compromised cells. Compromised cells are cells that grow very slowly after reculturing indicating a degree of reversible cell damage. Screening the germicidal activity using this staining method is accurate and efficient, and requires less time than the culture-based method. A modification to the procedure for measuring germicidal activity of rough surfaces or fibrous coatings was developed. Both TiO2 and metal-doped TiO2 (Ag, Pt, Au, Cu) possess non-UV based germicidal activity. The germicidal activity of TiO2 was found to be related with its wetting property and can be improved by UV irradiation before testing. It is not greatly affected by contact time, indicating a fast acting germicidal activity.

  4. TiO2@carbon core/shell nanofibers: Controllable preparation and enhanced visible photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Shao, Changlu; Zhang, Zhenyi; Zhang, Mingyi; Mu, Jingbo; Guo, Zengcai; Liu, Yichun

    2011-07-01

    TiO2@carbon core/shell nanofibers (TiO2@C NFs) with different thinkness of carbon layers (from 2 to 8 nm) were fabricated by combining the electrospinning technique and hydrothermal method. The results showed that a uniform graphite carbon layer was formed around the electrospun TiO2 nanofiber via C-O-Ti bonds. By adjusting the hydrothermal fabrication parameters, the thickness of carbon layer could be easily controlled. Furthermore, the TiO2@C NFs had remarkable light absorption in the visible region. The photocatalytic studies revealed that the TiO2@C NFs exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the pure TiO2 nanofibers under visible light irradiation, which might be attributed to high separation efficiency of photogenerated electrons and holes based on the synergistic effect between carbon as a sensitizer and TiO2 with one dimension structure. Notably, the TiO2@C NFs could be easily recycled due to their one-dimensional nanostructural property.TiO2@carbon core/shell nanofibers (TiO2@C NFs) with different thinkness of carbon layers (from 2 to 8 nm) were fabricated by combining the electrospinning technique and hydrothermal method. The results showed that a uniform graphite carbon layer was formed around the electrospun TiO2 nanofiber via C-O-Ti bonds. By adjusting the hydrothermal fabrication parameters, the thickness of carbon layer could be easily controlled. Furthermore, the TiO2@C NFs had remarkable light absorption in the visible region. The photocatalytic studies revealed that the TiO2@C NFs exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the pure TiO2 nanofibers under visible light irradiation, which might be attributed to high separation efficiency of photogenerated electrons and holes based on the synergistic effect between carbon as a sensitizer and TiO2 with one dimension structure. Notably, the TiO2@C NFs could be easily recycled due to their

  5. Antibacterial effect of visible light reactive TiO2/Ag nanocomposite thin film on the orthodontic appliances.

    PubMed

    Yun, Kwidug; Oh, Gyejeong; Vang, Mongsook; Yang, Hongso; Lim, Hyunpil; Koh, Jeongtae; Jeong, Woonjo; Yoon, Dongjoo; Lee, Kyungku; Lee, Kwangmin; Park, Sangwon

    2011-08-01

    This study evaluated the antibacterial effect of a visible light reactive TiO2/Ag nanocomposite thin film on dental orthodontic wire (STS 304 wire). The growth of S. mutans and A. actinomycetemcomitans was suppressed on the specimens coated with TiO2/Ag compared to the uncoated specimens. The antibacterial effect of the TiO2/Ag nanocomposite thin film was improved under visible light irradiation.

  6. Mechanochemical Synthesis of TiO2 Nanocomposites as Photocatalysts for Benzyl Alcohol Photo-Oxidation

    PubMed Central

    Ouyang, Weiyi; Kuna, Ewelina; Yepez, Alfonso; Balu, Alina M.; Romero, Antonio A.; Colmenares, Juan Carlos; Luque, Rafael

    2016-01-01

    TiO2 (anatase phase) has excellent photocatalytic performance and different methods have been reported to overcome its main limitation of high band gap energy. In this work, TiO2-magnetically-separable nanocomposites (MAGSNC) photocatalysts with different TiO2 loading were synthesized using a simple one-pot mechanochemical method. Photocatalysts were characterized by a number of techniques and their photocatalytic activity was tested in the selective oxidation of benzyl alcohol to benzaldehyde. Extension of light absorption into the visible region was achieved upon titania incorporation. Results indicated that the photocatalytic activity increased with TiO2 loading on the catalysts, with moderate conversion (20%) at high benzaldehyde selectivity (84%) achieved for 5% TiO2-MAGSNC. These findings pointed out a potential strategy for the valorization of lignocellulosic-based biomass under visible light irradiation using designer photocatalytic nanomaterials. PMID:28335221

  7. Photocatalytic oxidation of propylene on La and N codoped TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Jinfeng; Li, Haiyan; Zong, Lanlan; Li, Qiuye; Wang, Xiaodong; Zhang, Min; Yang, Jianjun

    2015-02-01

    Lanthanum- and nitrogen-codoped TiO2 photocatalysts was synthesized using orthorhombic nanotubes titanic acid as the precursor by a simple impregnation and subsequent calcination method. The morphology, phase structure, and properties of La- and N-codoped TiO2 were well characterized by transmission electron microscopy, X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectra. The La-/N-codoped TiO2 showed excellent photoactivity of propylene oxidation compared with the single-doped TiO2 and La-/N-codoped P25 TiO2 nanoparticles under visible light irradiation. The origin of the enhancement of the visible light-responsive photocatalytic activity was discussed in detail.

  8. Synthesis and Photocatalytic Activity of Anatase TiO2 Nanoparticles-coated Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Xie, Yi; Heo, Sung Hwan; Yoo, Seung Hwa; Ali, Ghafar; Cho, Sung Oh

    2010-03-01

    A simple and straightforward approach to prepare TiO2-coated carbon nanotubes (CNTs) is presented. Anatase TiO2 nanoparticles (NPs) with the average size ~8 nm were coated on CNTs from peroxo titanic acid (PTA) precursor even at low temperature of 100 °C. We demonstrate the effects of CNTs/TiO2 molar ratio on the adsorption capability and photocatalytic efficiency under UV-visible irradiation. The samples showed not only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO) dye molecules. These properties facilitated the great enhancement of photocatalytic activity of TiO2 NPs-coated CNTs photocatalysts. The TiO2 NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO2.

  9. A study of bactericidal effect and optimization of pathogenic bacteria using TiO2 photocatalyst.

    PubMed

    Kim, Tae-Young; Park, Seung-Shik; Kim, Seung-Jai; Cho, Sung-Young

    2011-02-01

    The photocatalytic degradation of Salmonella choleraesuis subsp. and Vibrio parahaemolyticus in water by TiO2 catalysts was investigated in a batch reactor. After 30 min of irradiation with UV light in the presence of 1 mg/ml of TiO2, death ratio of S. choleraesuis subsp. and V. parahaemolyticus was 60% and 83%, respectively. And complete killing of the cells was achieved after 3 h of illumination in the presence of TiO2. We established the response surface methodology to investigate the effect of principal parameters on the pathogenic bacteria sterilization such as TiO2 concentration, pH and temperature. By applying response surface analysis to the bactericidal effect of S. almonella choleraesuis subsp. and V. parahaemolyticus, we found that the cell death ratio was influenced significantly by the first order term of TiO2 concentration.

  10. Water-phase strategy for synthesis of TiO2-graphene composites with tunable structure for high performance photocatalysts

    NASA Astrophysics Data System (ADS)

    Hu, Changyuan; Chen, Fei; Lu, Tiewen; Lian, Chengjiang; Zheng, Shizheng; Hu, Quanhong; Duo, Shuwang; Zhang, Rongbin

    2014-10-01

    The controllable synthesis of strongly coupled TiO2/graphene composites has been a long-standing challenge for developing advanced photocatalysts. Here, we report a facile water-phase protocol for synthesis of TiO2-graphene composites using GO aqueous suspension and TiO2 aqueous nanosols as precursors. By controlling the ratio of GO to TiO2, both high-/low-dense TiO2 nanoparticles across graphene and graphene-TiO2-graphene sandwich structured composites are successfully achieved through electrostatic attraction between negatively charged GO nanosheets and positively charged TiO2nanosols. The TiO2-graphene composites show an enhanced photocatalytic activity for the degradation of methylene blue (MB) under UV light. Interestingly, the sandwich structured TiO2-graphene composite exhibits the best photocatalytic activity and the highest photocurrent density, which is 12.2 and 35.46 times as that of pure TiO2, respectively. The outstanding photocatalytic activity of sandwich structured composite is likely due to the following two reasons, two-channel electron conduction path between TiO2 and graphene, as well as the better adsorption capability of MB molecule.

  11. Visible-light-induced photoelectrochemical behaviors of Fe-modified TiO2 nanotube arrays.

    PubMed

    Xu, Zhihua; Yu, Jiaguo

    2011-08-01

    Fe-modified TiO(2) nanotube arrays (TiO(2) NTs) were prepared by annealing amorphous TiO(2) NTs whose surface was covered with Fe(3+) by a dip-coating procedure, and characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-visible reflectance spectroscopy. The photoelectrochemical properties were evaluated by the photocurrent response and photoelectrocatalytic (PEC) degradation of methylene orange (MO) and 4-chlorophenol in water under visible-light irradiation (λ > 420 nm). The results showed that a Fe-modified TiO(2) NTs electrode exhibited a larger photocurrent response and higher PEC activity for the degradation of organic pollutants than a pure TiO(2) NTs electrode. At a bias potential of 0.4 V, the photocurrent response of a 0.5 M Fe-modified TiO(2) NTs electrode exceeded that of a pure TiO(2) NTs electrode by a factor of about 10, and the PEC degradation rates of MO and 4-chlorophenol on a 0.5 M Fe-modified TiO(2) NTs electrode exceeded those on a pure TiO(2) NTs electrode by a factor of about 2.5. The larger photocurrent response and higher PEC activity of Fe-modified TiO(2) NTs could be attributed to the enhancement of separation of charge-carriers at the external electric field and the extension of the light response range of TiO(2) to the visible-light region with the narrowing of the band gap.

  12. Synthesis and photo-degradation application of WO3/TiO2 hollow spheres.

    PubMed

    Lv, Kezhen; Li, Jie; Qing, Xiaoxia; Li, Wenzhang; Chen, Qiyuan

    2011-05-15

    A WO(3)/TiO(2) composite, hollow-sphere photocatalyst with average diameter of 320 nm and shell thickness of 50 nm was successfully prepared using a template method. UV-vis diffuse reflectance spectra illustrated that the main absorption edges of the WO(3)/TiO(2) hollow spheres were red-shifted compared to the TiO(2) hollow spheres, indicating an extension of light absorption into the visible region of the composite photocatalyst. The WO(3) and TiO(2) phases were confirmed by X-ray diffraction analysis. BET isotherms revealed that the specific surface area and average pore diameter of the hollow spheres were 40.95 m(2)/g and 19 nm, respectively. Photocatalytic experiments indicate that 78% MB was degraded by WO(3)/TiO(2) hollow spheres under visible light within 80 min. Under the same conditions, only 24% MB can be photodegraded by TiO(2). The photocatalytic mineralization of MB, catalyzed by TiO(2) and WO(3)/TiO(2), proceeded at a significantly higher rate under UV irradiation than that under visible light, and more significant was the increase in the apparent rate constant with the WO(3)/TiO(2) composite semiconductor material which was 3.2- and 3.5-fold higher than with the TiO(2) material under both UV and visible light irradiation. The increased photocatalytic activity of the coupled nanocomposites was attributed to photoelectron/hole separation efficiency and the extension of the wavelength range of photoexcitation.

  13. Photodecomposition of tetrabromobisphenol A in aqueous humic acid suspension by irradiation with light of various wavelengths.

    PubMed

    Han, Sang Kuk; Yamasaki, Toshihide; Yamada, Ken-ichi

    2016-03-01

    The reactive species generated in aqueous 3,3',5,5'-tetrabromobisphenol A (TBBPA)/humic acid (HA) suspensions above the TBBPA pKa (∼7.4), under various light-irradiation conditions, namely ambient and ultraviolet light, were investigated using electron paramagnetic resonance (EPR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS). We confirmed that singlet oxygen and OH radicals are the key reactive oxygen species generated at wavelengths greater than 400 and 300 nm, respectively. The amount of 2,6-dibromo-p-benzosemiquinone anion radicals (2,6-DBSQ(•-)) formed under irradiation at 400 nm increased linearly with respect to irradiation time; the initial reaction rate was 7.03 × 10(-9) mol g(-1) HA s(-1). The rate increased with increasing pH and light intensity. LC-MS and EPR spectroscopy showed that tribromohydroxybisphenol A was formed under irradiation at 300 nm via reaction of OH radicals with TBBPA. This study, for the first time, shows that the main byproducts formed during irradiation at wavelengths above 300 nm are 2,6-DBSQ(•-) and tribromohydroxybisphenol A, generated from singlet oxygen ((1)O2) and OH radicals, respectively. Photodecomposition of TBBPA in the environment may occur by formation of (1)O2 and OH radicals.

  14. Antibacterial and photocatalytic activity of TiO2 and ZnO nanomaterials in phosphate buffer and saline solution.

    PubMed

    Ng, Alan Man Ching; Chan, Charis May Ngor; Guo, Mu Yao; Leung, Yu Hang; Djurišić, Aleksandra B; Hu, Xu; Chan, Wai Kin; Leung, Frederick Chi Chung; Tong, Shuk Yin

    2013-06-01

    We studied antibacterial and photocatalytic activity of anatase TiO2 and ZnO in phosphate buffer and saline solution. We found that the different anions in the suspension medium (chloride and phosphate) significantly affected the following suspension properties: the stability of nanoparticle suspension, the release of metal ions from the nanoparticles, and the production of the reactive oxygen species by the nanoparticles. As a result, antibacterial activity and photocatalytic dye degradation were also affected. However, the effect of the suspension medium was different for ZnO and TiO2. Obtained results are discussed.

  15. Structural and photocatalytic studies of Mn doped TiO2 nanoparticles.

    PubMed

    Chauhan, Ruby; Kumar, Ashavani; Chaudhary, Ram Pal

    2012-12-01

    Mn-doped TiO(2) nanoparticles (Ti(1-)(x)Mn(x)O(2); where x=0.00-0.10) were synthesized by sol-gel method. The synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and UV-Vis spectrometer. The SEM and TEM micrographs revealed the agglomerated spherical-like morphology and measurements show that the size of crystallites is in the range of 10-20 nm. Optical measurements indicated a red shift in the absorption band edge after Mn doping. Direct allowed band gap of undoped and Mn-doped TiO(2) nanoparticles measured by UV-Vis spectrometer were 3.00 and 2.95 eV at 300 °C, respectively. Photocatalytic activities of TiO(2) and Mn doped TiO(2) were evaluated by irradiating the sample solution of methylene blue (MB) dye under ultraviolet and visible light exposure. It was found that Mn-doped TiO(2) bleaches MB much faster than undoped TiO(2) upon its exposure to the visible light as comparison to ultraviolet light. The experiment demonstrated that the photodegradation efficiency of Mn-doped TiO(2) was significantly higher than that of undoped TiO(2) upon its exposure to visible light.

  16. Enhancement in photo-induced hydrophilicity of TiO2/CNT nanostructures by applying voltage

    NASA Astrophysics Data System (ADS)

    Abdi, Yaser; Khalilian, Maryam; Arzi, Ezatollah

    2011-06-01

    Carbon nanotube (CNT) arrays were synthesized by plasma-enhanced chemical vapour deposition on a silicon substrate. Cabbage-like TiO2 nanostructures on the CNTs were produced by atmospheric-pressure chemical vapour deposition. Scanning electron microcopy was used to study the morphology of the TiO2/CNT structures while x-ray diffraction and Fourier transform infrared (FTIR) spectroscopy were used to verify the characteristics of the prepared nanostructures. Their hydrophilicity under UV and visible light was investigated and compared with the activity of thin films of TiO2. The TiO2/CNTs showed a highly improved photocatalytic activity in comparison with the TiO2 film. The excellent visible-light-induced hydrophilicity of the TiO2/CNTs was attributed to the generation of electron-hole pairs by visible light excitation with a low recombination rate. The results of this study showed that the fabricated cabbage-like TiO2/CNT nanostructures have a super-hydrophilic surface without further UV irradiation. Electrical measurements showed that a p-n junction was formed at the interface of the TiO2/CNTs. Consequently, a super-hydrophilic surface was achieved by applying an electric bias voltage. Visible-light- and electro-induced hydrophilicity of the obtained nanostructure was reported in this work.

  17. Structuring a TiO2-based photonic crystal photocatalyst with Schottky junction for efficient photocatalysis.

    PubMed

    Chen, Huan; Chen, Shuo; Quan, Xie; Zhang, Yaobin

    2010-01-01

    Facile and effective approaches were developed to fabricate the inverse TiO2/Pt opals Schottky structures on the Ti substrate. The as-prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and diffuse reflectance UV-vis spectra (DRS), respectively. The results indicate that these samples were of ordered network, which was built by the Pt skeleton frame and the outer TiO2 layer. The TiO2 layer was identified as anatase with the preferential orientation of (101) plane. The experiments of short-circuit photocurrent (SCPC) and photocatalytic degradation of phenol were also conducted under the UV irradiation in order to evaluate the photoactivity of the samples. By tuning the red edge of photonic stop-band overlapping the absorption maximum of anatase (at 360 nm), both the UV absorption and the carrier separation of the samples were improved. The kinetic constant using the optimal inverse TiO2/Pt opals (0.992 h(-1)) was about 1.5 times as great as that of the disordered inverse TiO2/Pt opals (TiO2/Pt-mix) and was 3.3 times as great as that of pristine TiO2 nanocrystalline film (TiO2-nc) on Ti substrate.

  18. Photocatalytic degradation of p-chlorophenol by hybrid H₂O₂ and TiO₂ in aqueous suspensions under UV irradiation.

    PubMed

    Nguyen, Anh Thu; Juang, Ruey-Shin

    2015-01-01

    In this study, TiO2 particles were used as photocatalysts for the degradation of aqueous p-chlorophenol (p-CP) under UV irradiation. The effect of TiO2 dose (0-3 g/L), initial p-CP concentration, H2O2 concentration (2-45 mM), solution pH (4.6-9.5), and UV light intensity on the degradation of p-CP were examined. Four oxidative degradation processes, which utilized UV alone (direct photolysis), H2O2/UV, TiO2/UV, and H2O2/TiO2/UV, were compared in a batch photoreactor with a 100-W high-pressure mercury lamp. The photodegradation of p-CP could be described by the pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. Moreover, the apparent degradation rate constants increased considerably from 3.5 × 10(-)(3) min(-)(1) (direct photolysis) to 19.9 × 10(-)(3) min(-)(1) (H2O2/TiO2/UV system).

  19. Degradation product analysis from the photocatalytic oxidation/reduction of 2,4-dichlorophenol in the presence of mesoporous silica encapsulated TiO2 particles and TiO2 dispersions (presentation)

    EPA Science Inventory

    Thin films of Degussa P-25 TiO2 encapsulated in an SBA-15 mesoporous silica matrix were prepared. The TiO2/SBA-15 thin film structure was verified using transmission electron microscopy (TEM) and small angle X-ray diffraction (XRD). During irradiation with 350 nm light, the TiO...

  20. Organic photovoltaic devices with colloidal TiO2 nanorods as key functional components.

    PubMed

    Loiudice, Anna; Rizzo, Aurora; De Marco, Luisa; Belviso, Maria R; Caputo, Gianvito; Cozzoli, P Davide; Gigli, Giuseppe

    2012-03-21

    We report on a novel approach to integrate colloidal anatase TiO(2) nanorods as key functional components into polymer bulk heterojunction (BHJ) photovoltaic devices by means of mild, all-solution-based processing techniques. The successful integration of colloidal nanoparticles in organic solar cells relies on the ability to remove the long chain insulating ligands, which indeed severely reduces the charge transport. To this aim we have exploited the concomitant mechanisms of UV-light-driven photocatalytic removal of adsorbed capping ligands and hydrophilicization of TiO(2) surfaces in both solid-state and liquid-phase conditions. We have demonstrated the successful integration of the UV-irradiated films and colloidal solutions of TiO(2) nanorods in inverted and conventional solar cell geometries, respectively. The inverted devices show a power conversion efficiency of 2.3% that is a ca. three times improvement over their corresponding cell counterparts incorporating untreated TiO(2), demonstrating the excellent electron-collecting property of the UV-irradiated TiO(2) films. The integration of UV-treated TiO(2) solutions in conventional devices results in doubled power conversion efficiency for the thinner active layer and in maximum power conversion efficiency of 2.8% for 110 nm thick devices. In addition, we have demonstrated, with the support of device characterizations and optical simulations, that the TiO(2) nanocrystal buffer layer acts both as electron-transporting/hole-blocking material and optical spacer.

  1. Ag Nanorods Coated with Ultrathin TiO2 Shells as Stable and Recyclable SERS Substrates

    PubMed Central

    Ma, Lingwei; Huang, Yu; Hou, Mengjing; Xie, Zheng; Zhang, Zhengjun

    2015-01-01

    TiO2-coated Ag nanorods (Ag@TiO2 NRs) have been fabricated as multifunctional surface-enhanced Raman scattering (SERS) substrates. Uniform TiO2 shells could sufficiently protect the internal Ag NRs against oxidation and sulfuration, thus the temporal stability of SERS substrates was markedly improved. Meanwhile, due to the synergetic effect between crystalline TiO2 and Ag, the nanocomposites could clean themselves via photocatalytic degradation of the adsorbed molecules under ultraviolet irradiation and water dilution, making the SERS substrates renewable. Such Ag@TiO2 NRs were shown to serve as outstanding SERS sensors featuring high sensitivity, superior stability and recyclability. PMID:26486994

  2. Photoresponse and Donor Concentration of Plasma-Sprayed TiO2 and TiO2-ZnO Electrodes

    NASA Astrophysics Data System (ADS)

    Ye, F.-X.; Ohmori, A.; Li, C.-J.

    2005-12-01

    The photoelectrochemical characteristics of plasma-sprayed porous TiO2, TiO2-5%ZnO, and TiO2-10%ZnO electrodes in 0.1 N NaOH solution were studied through a three-electrode cell system. The microstructure, morphology, and composition of the electrodes were analyzed using an electron probe surface roughness analyzer (ERA-8800FE), scanning electron microscopy, and x-ray diffraction. The results indicate that the sprayed electrodes have a porous microstructure, which is affected by the plasma spray parameters and composition of the powders. The TiO2-ZnO electrodes consist of anatase TiO2, rutile TiO2, and Zn2Ti3O8 phase. The photoresponse characteristics of the plasma-sprayed electrodes are comparable to those of single-crystal TiO2, but the breakdown voltage is close to 0.5 V (versus that of a saturated calomel electrode). The short-circuit photocurrent density ( J SC) increases with a decrease of donor concentration, which was calculated according to the Gartner-Butler model. For the lowest donor concentration of a TiO2-5%ZnO electrode sprayed under an arc current of 600 A, the short-circuit J SC is approximately 0.4 mA/cm2 higher than that of the TiO2 electrodes under 30 mW/cm2 xenon light irradiation. The J SC increases linearly with light intensity.

  3. Overall kinetics of heterogeneous elemental mercury reactions on TiO2 sorbent particles with UV radiation

    EPA Science Inventory

    A system consisting of a photochemical reaction was used to evaluate the kinetic parameters, such as reaction order and rate constant for the elemental mercury uptake by TiO2 in the presence of uv irradiation. TiO2 particles generated by an aerosol route were used in a fixed bed...

  4. Mesoporous anatase TiO2 nanocups with plasmonic metal decoration for highly active visible-light photocatalysis.

    PubMed

    Lu, Jianwei; Zhang, Peng; Li, Ang; Su, Fengli; Wang, Tuo; Liu, Yuan; Gong, Jinlong

    2013-07-04

    This communication describes a method for facile synthesis of mesoporous anatase TiO2 nanocup crystals. The novel cuplike morphology of TiO2 decorated with gold (Au-TiO2) yields remarkably high photocatalytic activity for degradation of methylene blue under visible light irradiation.

  5. Water treatment by TiO2 photocatalysis and/or ultrasound: degradations of phenyltrifluoromethylketone, a trifluoroacetic-acid-forming pollutant, and octan-1 -ol, a very hydrophobic pollutant.

    PubMed

    Théron, P; Pichat, P; Petrier, C; Guillard, C

    2001-01-01

    TiO2 photocatalysis and ultrasound are advanced oxidation processes for water treatment. Our study aimed at showing, via the purposely chosen title compounds, that these techniques can be complementary. For C6H5COCF3 (PTMK), the photocatalytic removal rate was higher than the ultrasonic (515 kHz) removal rate in the presence of TiO2 in the dark, whereas it was the opposite for octan-1-ol under the conditions employed. Simultaneous UV and ultrasound irradiation of the TiO2 suspension led, for PTMK, to a removal rate about equal to the sum of the removal rates observed for separate irradiations, and decreased by a factor of approximately 20% for octan- 1 -ol as if the photocatalytic degradation was suppressed by the dominant distribution of octan-1-ol to the cavitation bubbles. This distribution was substantiated by the large detrimental effect of octan- 1-ol on the PTMK ultrasonic removal rate. The concurrent use of both techniques allowed a faster removal of both pollutants in binary mixtures. The amount of CF3COOH from PTMK was approximately eight times lower in sonicated, than in UV-irradiated, TiO2 suspensions. Several intermediate products showed the occurrence of chemical transformations occurring in and/or on the cavitation bubbles. COD decline and CO2 formation were initially higher for ultrasonic than for photocatalytic treatment. However, complete mineralization (except for CF3COOH) was achieved more rapidly by photocatalysis and even more rapidly by simultaneous use of both techniques.

  6. Self-doped TiO2-x nanowires with enhanced photocatalytic activity: Facile synthesis and effects of the Ti3+

    NASA Astrophysics Data System (ADS)

    Wang, Junpeng; Yang, Ping; Huang, Baibiao

    2015-11-01

    Synthesis of Ti3+ self-doped TiO2 with high stability is very necessary to understand the role of Ti3+ defects in photocatalytic process. In this study, we report a simple strategy for preparing stable Ti3+ self-doped TiO2 nanowires with Ti2O3 as precursors. Raman and XPS spectrum confirmed the existence of Ti3+ and oxygen vacancies. Compared with the pure TiO2, the photocatalytic activity of the Ti3+ self-doped TiO2 enhanced under UV light irradiation, however, neither pure TiO2 nor the self-dope TiO2 samples exhibit photocatalytic activity while irradiated under visible light, though the self-doped TiO2 have an enhanced absorption in visible region. On the basis of the experimental results, the possible mechanism of Ti3+ in photocatalytic process is proposed.

  7. Modification of the photocatalytic activity of TiO2 by β-Cyclodextrin in decoloration of ethyl violet dye

    PubMed Central

    Velusamy, Ponnusamy; Pitchaimuthu, Sakthivel; Rajalakshmi, Subramanian; Kannan, Nagarathinam

    2012-01-01

    The photocatalytic decoloration of an organic dye, ethyl violet (EV), has been studied in the presence of TiO2 and the addition of β-Cyclodextrin (β-CD) with TiO2 (TiO2-β-CD) under UV-A light irradiation. The different operating parameters like initial concentration of dye, illumination time, pH and amount of catalyst used have also been investigated. The photocatalytic decoloration efficiency is more in the TiO2-β-CD/UV-A light system than TiO2/UV-A light system. The mineralization of EV has been confirmed by Chemical Oxygen Demand (COD) measurements. The complexation patterns have been confirmed with UV–Visible and FT-IR spectral data and the interaction between TiO2 and β-CD have been characterized by powder XRD analysis and UV–Visible diffuse reflectance spectroscopy. PMID:25685468

  8. High photocatalytic activity of immobilized TiO2 nanorods on carbonized cotton fibers.

    PubMed

    Wang, Bin; Karthikeyan, Rengasamy; Lu, Xiao-Ying; Xuan, Jin; Leung, Michael K H

    2013-12-15

    In this study, TiO2 nanorods were successfully immobilized on carbon fibers by a facile pyrolysis of natural cotton in nitrogen atmosphere followed by a one-pot hydrothermal method. Carbonized cotton fibers (CCFs) and TiO2-CCFs composites were characterized using field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffractometer (XRD), diffuse reflectance UV-vis spectroscopy (DRS) and photoluminescence (PL) spectroscopy. Results implied that the band gap narrowing of TiO2 was achieved after integration of CCFs. Dye adsorption isotherm indicated that the maximum dye adsorption capacity (qm) of CCFs-1000 (13.4 mg/g) was 2 times higher than that of cotton fibers and qm of TiO2-CCFs-1000 (9.0mg/g) was 6-7 times higher than that of TiO2 nanorods. Photocatalytic activity of TiO2 nanorods prepared with 3 mL Ti(OBu)4 showed the highest photocatalytic activity. TiO2-CCFs-1000 exhibited higher activity than TiO2 immobilized on CCFs-400, CCFs-600 and CCFs-800. Good photostability of TiO2-CCFs-1000 was found for dye degradation under visible light irradiation. The enhancement of photocatalytic dye degradation was due to the high adsorptivity of dye molecules, enhanced light adsorption and effective separation of electron-hole pairs. This work provides a low-cost and sustainable approach to immobilize nanostructured TiO2 on carbon fibers for environmental remediation.

  9. Spiky TiO2/Au nanorod plasmonic photocatalysts with enhanced visible-light photocatalytic activity.

    PubMed

    Sun, Hang; Zeng, Shan; He, Qinrong; She, Ping; Xu, Kongliang; Liu, Zhenning

    2017-03-21

    A facile approach for the preparation of spiky TiO2/Au nanorod (NR) plasmonic photocatalysts has been demonstrated, which is through in situ nucleation and growth of spiky TiO2 onto AuNRs. Different aspect ratios of AuNRs in 2.5, 2.7, 4.1 and 4.5 have been applied to prepare spiky TiO2/AuNR nanohybrids to achieve tunable and broad localized surface plasmon resonance (LSPR) bands. All spiky TiO2/AuNR nanohybrids exhibit enhanced light harvesting by extending visible light absorption range by both transverse and longitudinal LSPR bands and decreasing light reflectance by their unique spiky structures. Compared to the bare AuNRs, commercial TiO2 (P25) and spiky TiO2/Au nanosphere photocatalysts, the spiky TiO2/AuNR photocatalysts exhibit significantly enhanced visible light photocatalytic activity in Rhodamine B (RhB) degradation due to their simultaneous enhancement in the light harvesting, charge utilization efficiency, and substrate accessibility. In particular, the spiky TiO2/AuNR-685 photocatalysts show the best photocatalytic activity with ∼98.9% of the RhB degraded within 90 min under the irradiation of 420-780 nm, which could be ascribed to the most extended visible light absorption range and sufficient photon energy of TiO2/AuNR-685 photocatalysts within this irradiation region. The bio-inspired nanostructure, as well as the facile and scalable fabrication approach, will open a new avenue for the rational design and preparation of high-performance photocatalysts for pollutant removal and water splitting.

  10. Optical properties of hierarchical-nanostructured TiO2 and its time-dependent photo-degradation of gaseous acetaldehyde

    NASA Astrophysics Data System (ADS)

    Ahn, Kyun; Kim, Min-Sun; Kim, Soon-Hyun; Hyun Kim, Jae; Jeong, Se-Young; Kim, Jong-Pil; Sung Jin, Jong; Cho, Chae-Ryong

    2013-12-01

    The TiO2 hierarchical nanostructures (HNs) composed of rutile TiO2 nanowires on anatase TiO2 nanofibers had higher photocatalytic activities of 62% and 48% than the commercial TiO2 nanoparticles (˜21 nm diameter) in the continuous flow mode and closed-circulation mode, respectively, leading to an efficient degradation of gaseous acetaldehyde under UV-light irradiation. This behavior may be attributed to the effective TiO2 HNs with specific surface area of 85.1 m2/g and lower radiative recombination of self-trapped excitons, enabling an effective electron-hole separation.

  11. Stability of TiO2 Nanoparticles in Deionized Water with ZrP Nanoplatelets.

    PubMed

    Liu, Zhuowei; Chen, Ying; Mo, Songping; Cheng, Zhengdong; Li, Huawel

    2015-04-01

    The stability of nanofluid is an important property that needs to be researched. In our study, a novel method using Zirconium phosphate (ZrP) discotic colloid to disperse nanoparticles was proposed for improving stability. TiO2 nanofluid was prepared by dispersing TiO2 nanoparticles into exfoliated a-ZrP suspensions at different concentrations. Scanning electron microscopy and X-ray diffraction were used to characterize the shape, average size, and components of primary ZrP nanoplatelets. The absorbance of the suspensions was measured by a UV-VIS spectrophotometer. The results show that the stability first increased, and then decreased with increasing ZrP concentration at 1 wt.% TiO2. The effect was optimal at 2 wt.% ZrP. Thus, the hindrance of nanoplatelets in the aggregation and sedimentation of nanoparticles is the main reason for improving the stability of nanofluids.

  12. Rubber sheet strewn with TiO2 particles: photocatalytic activity and recyclability.

    PubMed

    Sriwong, Chaval; Wongnawa, Sumpun; Patarapaiboolchai, Orasa

    2012-01-01

    A new method for the preparation of rubber sheet strewn with titanium dioxide particles (TiO2-strewn sheet) is presented. This simple and low cost method is based on the use of TiO2 powder (Degussa P25) being strewn onto the sheet made from rubber latex (60% HA) through a steel sieve. The characteristic of the TiO2-strewn sheet was studied by using scanning electron microscopy/energy dispersive X-ray spectrometer (SEM/EDS) and X-ray diffractometer (XRD) techniques. The photocatalytic activity of TiO2-strewn rubber sheet was evaluated using Indigo Carmine (IC) dye as a model for organic dye pollutant in water. The results showed that the TiO2-strewn sheet could degrade IC dye solution under UV light irradiation. The effects of pH, initial concentration, and the intensity of UV light on the photodegradation were also investigated. Kinetics of the photocatalytic degradation was of the first-order reaction. The used TiO2-strewn sheet can be recovered and reused. The recycling uses did not require any cleaning between successive uses and no decline in the photodegradation efficiency was observed compared with freshly prepared TiO2-strewn sheet.

  13. Thiourea-Modified TiO2 Nanorods with Enhanced Photocatalytic Activity.

    PubMed

    Wu, Xiaofeng; Fang, Shun; Zheng, Yang; Sun, Jie; Lv, Kangle

    2016-02-01

    Semiconductor TiO2 photocatalysis has attracted much attention due to its potential application in solving the problems of environmental pollution. In this paper, thiourea (CH4N2S) modified anatase TiO2 nanorods were fabricated by calcination of the mixture of TiO2 nanorods and thiourea at 600 °C for 2 h. It was found that only N element was doped into the lattice of TiO2 nanorods. With increasing the weight ratio of thiourea to TiO2 (R) from 0 to 8, the light-harvesting ability of the photocatalyst steady increases. Both the crystallization and photocatalytic activity of TiO2 nanorods increase first and then decrease with increase in R value, and R2 sample showed the highest crystallization and photocatalytic activity in degradation of Brilliant Red X3B (X3B) and Rhodamine B (RhB) dyes under visible light irradiation (λ > 420 nm). The increased visible-light photocatalytic activity of the prepared N-doped TiO2 nanorods is due to the synergistic effects of the enhanced crystallization, improved light-harvesting ability and reduced recombination rate of photo-generated electron-hole pairs. Note that the enhanced visible photocatalytic activity of N-doped nanorods is not based on the scarification of their UV photocatalytic activity.

  14. Light-induced antifungal activity of TiO 2 nanoparticles/ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Haghighi, N.; Abdi, Y.; Haghighi, F.

    2011-09-01

    Antifungal activity of TiO2/ZnO nanostructures under visible light irradiation was investigated. A simple chemical method was used to synthesize ZnO nanowires. Zinc acetate dihydrate, Polyvinyl Pyrrolidone and deionized water were used as precursor, capping and solvent, respectively. TiO2 nanoparticles were deposited on ZnO nanowires using an atmospheric pressure chemical vapor deposition system. X-ray diffraction pattern of TiO2/ZnO nano-composite has represented the diffraction peaks relating to the crystal planes of the TiO2 (anatase and rutile) and ZnO. TiO2/ZnO nanostructure antifungal effect on Candida albicans biofilms was studied and compared with the activity of TiO2 nanoparticles and ZnO nanowires. The high efficiency photocatalytic activity of TiO2 nanoparticles leads to increased antifungal activity of ZnO nanowires. Scanning electron microscope was utilized to study the morphology of the as prepared nanostructures and the degradation of the yeast.

  15. Fullerene C70 decorated TiO2 nanowires for visible-light-responsive photocatalyst

    NASA Astrophysics Data System (ADS)

    Cho, Er-Chieh; Ciou, Jing-Hao; Zheng, Jia-Huei; Pan, Job; Hsiao, Yu-Sheng; Lee, Kuen-Chan; Huang, Jen-Hsien

    2015-11-01

    In this study, we have synthesized C60 and C70-modified TiO2 nanowire (NW) through interfacial chemical bonding. The results indicate that the fullerenes (C60 and C70 derivatives) can act as sinks for photogenerated electrons in TiO2, while the fullerene/TiO2 is illuminated under ultraviolet (UV) light. Therefore, in comparison to the pure TiO2 NWs, the modified TiO2 NWs display a higher photocatalytic activity under UV irradiation. Moreover, the fullerenes also can function as a sensitizer to TiO2 which expand the utilization of solar light from UV to visible light. The results reveal that the C70/TiO2 NWs show a significant photocatalytic activity for degradation of methylene blue (MB) in visible light region. To better understand the mechanism responsible for the effect of fullerenes on the photocatalytic properties of TiO2, the electron only devices and photoelectrochemical cells based on fullerenes/TiO2 are also fabricated and evaluated.

  16. Synthesis of natural cellulose-templated TiO2/Ag nanosponge composites and photocatalytic properties.

    PubMed

    Yu, Dong-Hui; Yu, Xiaodan; Wang, Changhua; Liu, Xian-Chun; Xing, Yan

    2012-05-01

    In this paper, TiO(2)/Ag sponge-like nanostructure composites have been prepared by the surface sol-gel method with the template of natural cellulose, which is relatively simple, low-cost, and environmentally friendly. The Ag nanoparticles are deposited on the TiO(2) nanosponges through UV irradiation photoreduction of silver nitrate solutions. The physicochemical properties of as-prepared composites are characterized by XRD, BET, SEM, TEM, XPS and UV-vis DRS techniques. The UV-light photocatalytic activities of the composites are evaluated through the photodegradation of two model organic molecules including RhB and salicylic acid. The experimental results show that the photocatalytic activities of TiO(2)/Ag nanosponge composites are superior to that of P25, pure TiO(2) nanoparticle aggregates synthesized by the hydrothermal method and pure TiO(2) nanosponge. The superior activities of TiO(2)/Ag nanosponge composite photocatalysts can be attributed to the unique nanosponge morphology, uniform dispersion of Ag nanoparticles, and strong interaction between Ag and TiO(2) nanosponges.

  17. TiO2 nanoparticles versus TiO2-SiO2 nanocomposites: A comparative study of photo catalysis on acid red 88

    NASA Astrophysics Data System (ADS)

    Balachandran, K.; Venckatesh, Rajendran; Sivaraj, Rajeshwari; Rajiv, P.

    2014-07-01

    A novel, simple, less time-consuming and cost-effective wet chemical technique was used to synthesis TiO2 nanoparticles and TiO2-SiO2 nanocomposites using Titanium tetra isopropoxide (TTIP) as a precursor relatively at low temperature in acidic pH. Titania sol was prepared by hydrolysis of TTIP and was mixed with silicic acid and tetrahydrofuran mixture. The reaction was carried out under vigorous stirring for 6 h and dried at room temperature. The resulting powders were characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope (TEM). The grain size of the particles was calculated by X-ray diffraction, surface morphology and chemical composition was determined from scanning electron microscopy-energy dispersive spectroscopy, metal oxide stretching was confirmed from FT-IR spectroscopy, band gap was calculated using UV-Visible spectroscopy. Surface area of the composite as calculated by BET analyzer and it was found to be 65 and 75 m2/g for TiO2 and TiO2-SiO2 respectively. The photocatalytic experiments were performed with aqueous solution of acid red 88 with TiO2 and TiO2-SiO2 batch studies for 4 h irradiation, direct photolysis of TiO2 and TiO2-SiO2 contributed 94.2% and 96.5% decomposition in solar radiation for the optimized concentration of acid red 88.

  18. TiO2 nanoparticles versus TiO2-SiO2 nanocomposites: a comparative study of photo catalysis on acid red 88.

    PubMed

    Balachandran, K; Venckatesh, Rajendran; Sivaraj, Rajeshwari; Rajiv, P

    2014-07-15

    A novel, simple, less time-consuming and cost-effective wet chemical technique was used to synthesis TiO2 nanoparticles and TiO2-SiO2 nanocomposites using Titanium tetra isopropoxide (TTIP) as a precursor relatively at low temperature in acidic pH. Titania sol was prepared by hydrolysis of TTIP and was mixed with silicic acid and tetrahydrofuran mixture. The reaction was carried out under vigorous stirring for 6h and dried at room temperature. The resulting powders were characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction, scanning electron microscope (SEM) and transmission electron microscope (TEM). The grain size of the particles was calculated by X-ray diffraction, surface morphology and chemical composition was determined from scanning electron microscopy-energy dispersive spectroscopy, metal oxide stretching was confirmed from FT-IR spectroscopy, band gap was calculated using UV-Visible spectroscopy. Surface area of the composite as calculated by BET analyzer and it was found to be 65 and 75 m(2)/g for TiO2 and TiO2-SiO2 respectively. The photocatalytic experiments were performed with aqueous solution of acid red 88 with TiO2 and TiO2-SiO2 batch studies for 4h irradiation, direct photolysis of TiO2 and TiO2-SiO2 contributed 94.2% and 96.5% decomposition in solar radiation for the optimized concentration of acid red 88.

  19. Controlled synthesis and photocatalysis of sea urchin-like Fe3O4@TiO2@Ag nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhao, Yilin; Tao, Chengran; Xiao, Gang; Wei, Guipeng; Li, Linghui; Liu, Changxia; Su, Haijia

    2016-02-01

    Based on the synergistic photocatalytic activities of nano-sized TiO2 and Ag, as well as the magnetic properties of Fe3O4, a sea urchin-like Fe3O4@TiO2@Ag nanocomposite (Fe3O4@TiO2@Ag NCs) is controllably synthesized with tunable cavity size, adjustable shell layer of TiO2 nanofiber, higher structural stability and larger specific surface area. Here, Fe3O4@TiO2@Ag NCs are obtained with Fe3O4 as the core and nanofiber TiO2/Fe3O4/Ag nanoheterojunctions as the shell; and Ag nanoparticles with diameter of approximately 4 nm are loaded both on TiO2 nanofibers and inside the cavities of sea urchin-like Fe3O4@TiO2 nanocomposites uniformly. Ag nanoparticles lead to the production of more photogenerated charges in the TiO2/Fe3O4/Ag heterojunction via LSPR absorption, and enhance the band-gap absorption of TiO2, while the Fe3O4 cocatalyst provides the active sites for oxygen reduction by the effective transfer of photogenerated electrons to oxygen. So the photocatalytic performance is improved due to the synergistic effect of TiO2/Fe3O4/Ag nanoheterojunctions. As photocatalysts under UV and visible irradiation, the as-synthesized nanocomposites display enhanced photocatalytic and recycling properties for the degradation of ampicillin. Moreover, they present better broad-spectrum antibiosis under visible irradiation. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, makes this multifunctional nanostructure a promising candidate for antibiosis and remediation in aquatic environmental contamination in the future.Based on the synergistic photocatalytic activities of nano-sized TiO2 and Ag, as well as the magnetic properties of Fe3O4, a sea urchin-like Fe3O4@TiO2@Ag nanocomposite (Fe3O4@TiO2@Ag NCs) is controllably synthesized with tunable cavity size, adjustable shell layer of TiO2 nanofiber, higher structural stability and larger specific surface area. Here, Fe3O4@TiO2@Ag NCs are obtained with Fe3O4 as the

  20. Controlled fabrication of porous double-walled TiO2 nanotubes via ultraviolet-assisted anodization

    NASA Astrophysics Data System (ADS)

    Ali, Ghafar; Kim, Hyun Jin; Kim, Jae Joon; Cho, Sung Oh

    2014-03-01

    Double-walled TiO2 nanotubes with porous wall morphologies are fabricated by anodization under ultraviolet (UV) irradiation. TiO2 formed by anodization of Ti is activated to generate electrons and holes by UV and the anodization process is influenced by the photo-generated charges. As a consequence, morphologies of the fabricated TiO2 nanotubes can be adjusted by controlling the UV illumination. Double-walled TiO2 nanotubes or single-walled nanotubes can be selectively formed by switching on/off the UV illumination. The thickness of the inner and outer walls of the double-walled nanotubes can be tailored by changing the UV power. Due to their larger surface areas compared to single-walled nanotubes, the porous double-walled nanotubes exhibit an enhanced photo-degradation rate for methylene blue (MB). The mechanism of the porous double-walled TiO2 nanotubes is proposed based on the photoactive semiconducting property of the as-growing TiO2 nanotubes under UV.Double-walled TiO2 nanotubes with porous wall morphologies are fabricated by anodization under ultraviolet (UV) irradiation. TiO2 formed by anodization of Ti is activated to generate electrons and holes by UV and the anodization process is influenced by the photo-generated charges. As a consequence, morphologies of the fabricated TiO2 nanotubes can be adjusted by controlling the UV illumination. Double-walled TiO2 nanotubes or single-walled nanotubes can be selectively formed by switching on/off the UV illumination. The thickness of the inner and outer walls of the double-walled nanotubes can be tailored by changing the UV power. Due to their larger surface areas compared to single-walled nanotubes, the porous double-walled nanotubes exhibit an enhanced photo-degradation rate for methylene blue (MB). The mechanism of the porous double-walled TiO2 nanotubes is proposed based on the photoactive semiconducting property of the as-growing TiO2 nanotubes under UV. Electronic supplementary information (ESI) available

  1. Fabrication of TiO2/ZnS nanocomposites for solar energy mediated photocatalytic application

    NASA Astrophysics Data System (ADS)

    Prasannalakshmi, P.; Shanmugam, N.

    2017-03-01

    In the present work, we demonstrate the photocatalytic properties of nanosized TiO2, and different levels of ZnS-loaded TiO2/ZnS composites, for the degradation of the organic dyes brilliant green (BG), and methylene blue (MB) under solar light irradiation. For this process, TiO2 and the composites were synthesized by a sol-gel method. Further, the prepared products were subjected to structural, optical, and morphological characterizations. The results of the photocatalytic activity imply that for the samples studied, TiO2 loaded with an optimum level of zinc (0.25 M), and sulfur (0.5 M) is better able to actively degrade both BG and MB, due to its enhanced BET surface area, reduced band gap, and low charge transfer resistance.

  2. Fabrication of TiO2/ZnS nanocomposites for solar energy mediated photocatalytic application.

    PubMed

    Prasannalakshmi, P; Shanmugam, N

    2017-03-15

    In the present work, we demonstrate the photocatalytic properties of nanosized TiO2, and different levels of ZnS-loaded TiO2/ZnS composites, for the degradation of the organic dyes brilliant green (BG), and methylene blue (MB) under solar light irradiation. For this process, TiO2 and the composites were synthesized by a sol-gel method. Further, the prepared products were subjected to structural, optical, and morphological characterizations. The results of the photocatalytic activity imply that for the samples studied, TiO2 loaded with an optimum level of zinc (0.25M), and sulfur (0.5M) is better able to actively degrade both BG and MB, due to its enhanced BET surface area, reduced band gap, and low charge transfer resistance.

  3. Molecular design of TiO2 for gigantic red shift via sublattice substitution.

    PubMed

    Shao, Guosheng; Deng, Quanrong; Wan, Lin; Guo, Meilan; Xia, Xiaohong; Gao, Yun

    2010-11-01

    The effects of 3d transition metal doping in TiO2 phases have been simulated in detail. The results of modelling indicate that Mn has the biggest potential among 3d transition metals, for the reduction of energy gap and the introduction of effective intermediate bands to allow multi-band optical absorption. On the basis of theoretical formulation, we have incorporated considerable amount of Mn in nano-crystalline TiO2 materials. Mn doped samples demonstrate significant red shift in the optical absorption edge, with a secondary absorption edge corresponding to theoretically predicted intermediate bands/states. The gigantic red shift achievable in Mn-doped TiO2 is expected to extend the useful TiO2 functionalities well beyond the UV threshold via the optical absorption of both visible and infrared photon irradiance.

  4. Photocatalytic activity and characterization of sol-gel-derived Ni-doped TiO2-coated active carbon composites

    NASA Astrophysics Data System (ADS)

    Bhosale, R. R.; Pujari, S. R.; Lande, M. K.; Arbad, B. R.; Pawar, S. B.; Gambhire, A. B.

    2012-11-01

    Ni-doped, TiO2-coated active carbon (Ni-TiO2/AC) were prepared by a sol-gel method. The effect of supports, including TiO2 and active carbon (AC), on the molecular structure and photocatalytic activity of nickel oxide for complete decomposition of methylene blue has been examined with respect to the content of Ni on the catalyst surface. The photocatalytic activities of the Ni-TiO2/AC composites were evaluated in the decomposition of methylene blue solution under visible-light irradiation. The results indicate that Ni-TiO2/AC has a higher efficiency in decomposition of methylene blue than TiO2 and TiO2/AC. This was attributed to the different functions of active carbon and nickel species. First, nanosize TiO2 particles on composites were not reunited, possible because active carbon retards transformation of anatase into rutile and decrease the crystallite size. Second, production of high concentrations of organic compound near Ni-TiO2. Third, carbon in active carbon causes some of the TiO2 to reduce to Ti3+ ions, which prevents electron-hole pair recombination. It was found that the addition of Ni to TiO2 sol could suppress the grain growth of TiO2 crystals and increase the hydroxyl content on the surface of TiO2/AC. The photocatalytic efficiency and activity of the composites remained good, even after three cycles.

  5. Synthesis and characterization of LaFeO3/TiO2 nanocomposites for visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Dhinesh Kumar, R.; Thangappan, R.; Jayavel, R.

    2017-02-01

    LaFeO3/TiO2 nanocomposites were successfully synthesized by hydrothermal method. The as-prepared nanoparticles were characterized by TGA, XRD, HRSEM, EDS, TEM, VSM and UV-Vis techniques. Thermal stability of the material was studied by thermal analysis. XRD studies confirm the orthorhombic and rutile phase for pure LaFeO3 and TiO2 nanoparticles. The LaFeO3/TiO2 composite shows the coexistence of LaFeO3 and TiO2 phases with no extra peaks. Morphological analysis shows the spherical nanoparticles and the average particle size of LaFeO3, TiO2 and LaFeO3/TiO2 was around 60 nm. The LaFeO3/TiO2 nanocomposites show a significant shift in the UV-vis absorption spectra in comparison with both TiO2 and LaFeO3 nanoparticles. The photocatalytic activity of the samples were tested for the degradation of methyl orange (MO) in aqueous solutions under visible light irradiations for 180 min. The LaFeO3/TiO2 composite exhibits enhanced visible light photocatalytic properties in comparison with that of LaFeO3 nanoparticles.

  6. TiO2-BASED Composite Films for the Photodegradation of Oxytetracycline

    NASA Astrophysics Data System (ADS)

    Li, Hui; Guan, Ling-Xiao; Feng, Ji-Jun; Li, Fang; Yao, Ming-Ming

    2015-02-01

    The spread of the antibiotic oxytetracycline (OTC) has been thought as a threat to the safety of drinking water. In this paper, the photocatalytic activity of the nanocrystalline Fe/Ca co-doped TiO2-SiO2 composite film for the degradation of OTC was studied. The films were characterized by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), N2 adsorption/desorption isotherms, photoluminescence (PL) spectra, and UV-Vis diffraction reflectance absorption spectra (DRS). The FE-SEM results indicated that the Fe/Ca co-doped TiO2-SiO2 film was composed of smaller nanoparticles compared to pure TiO2 or TiO2-SiO2 film. The BET surface area results showed that the specific surface area of the pure TiO2, TiO2-SiO2 and Ca2+/Fe3+ co-doped TiO2-SiO2 is 118.3 m2g-1, 294.3 m2g-1 and 393.7 m2g-1, respectively. The DRS and PL spectra revealed that the Fe/Ca co-doped TiO2-SiO2 film had strong visible light adsorption and diminished electrons/holes recombination. Experimental results showed that the Fe/Ca co-doped TiO2-SiO2 film is effective in the degradation of OTC under both UV and visible light irradiation.

  7. TiO2 Nanoparticles Produced by Electric-Discharge-Nanofluid-Process as Photoelectrode of DSSC

    NASA Astrophysics Data System (ADS)

    Chen, Sih-li; Su, Hung-ting; Chang, Ho; Jwo, Ching-song; Feng, Hsiao Ju

    2010-04-01

    Self-made TiO2 nanoparticles were used as photoelectrode material of dye sensitized solar cell. The TiO2 thin film coats through spreading nanoparticles evenly onto the ITO glass via self-made spin-heat platform, and then TiO2 thin film is soaked in the dye N-719 more than 12 h to prepare the photoelectrode device. The TiO2 nanoparticles produced by electric-discharge-nanofluid-process have premium anatase crystal property, and its diameter can be controlled within a range of 20-50 nm. The surface energy zeta potential of nanofluid is from -22 mV to -28.8 mV, it is a stable particle suspension in the deionized water. A trace of surfactant Triton X-100 put upon the surface of ITO glass can produce a uniform and dense TiO2 thin film and heating up the spin platform to 200 °C is able to eliminate mixed surfactant. Self-made TiO2 film presents excellent dye absorption performance and even doesn't need heat treatment procedure to enhance essential property. Results of energy analysis show the thicker film structure will increase the short-circuit current density that causes higher conversion efficiency. But, as the film structure is large and thick, both the open-circuit voltage and fill factor will decline gradually to lead bad efficiency of dye-sensitized solar cell.

  8. Controlled synthesis and photocatalysis of sea urchin-like Fe3O4@TiO2@Ag nanocomposites.

    PubMed

    Zhao, Yilin; Tao, Chengran; Xiao, Gang; Wei, Guipeng; Li, Linghui; Liu, Changxia; Su, Haijia

    2016-03-07

    Based on the synergistic photocatalytic activities of nano-sized TiO2 and Ag, as well as the magnetic properties of Fe3O4, a sea urchin-like Fe3O4@TiO2@Ag nanocomposite (Fe3O4@TiO2@Ag NCs) is controllably synthesized with tunable cavity size, adjustable shell layer of TiO2 nanofiber, higher structural stability and larger specific surface area. Here, Fe3O4@TiO2@Ag NCs are obtained with Fe3O4 as the core and nanofiber TiO2/Fe3O4/Ag nanoheterojunctions as the shell; and Ag nanoparticles with diameter of approximately 4 nm are loaded both on TiO2 nanofibers and inside the cavities of sea urchin-like Fe3O4@TiO2 nanocomposites uniformly. Ag nanoparticles lead to the production of more photogenerated charges in the TiO2/Fe3O4/Ag heterojunction via LSPR absorption, and enhance the band-gap absorption of TiO2, while the Fe3O4 cocatalyst provides the active sites for oxygen reduction by the effective transfer of photogenerated electrons to oxygen. So the photocatalytic performance is improved due to the synergistic effect of TiO2/Fe3O4/Ag nanoheterojunctions. As photocatalysts under UV and visible irradiation, the as-synthesized nanocomposites display enhanced photocatalytic and recycling properties for the degradation of ampicillin. Moreover, they present better broad-spectrum antibiosis under visible irradiation. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, makes this multifunctional nanostructure a promising candidate for antibiosis and remediation in aquatic environmental contamination in the future.

  9. Synthesis, photoelectric properties and photocatalytic activity of the Fe2O3/TiO2 heterogeneous photocatalysts.

    PubMed

    Peng, Linlin; Xie, Tengfeng; Lu, Yongchun; Fan, Haimei; Wang, Dejun

    2010-07-28

    Fe(2)O(3)/TiO(2) heterogeneous photocatalysts with different mass ratios of Fe(2)O(3)vs. TiO(2) were synthesized by impregnation of Fe(3+) on the surface of TiO(2) microrods and calcination at 300 degrees C. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), photoluminescence spectra and X-ray diffraction (XRD) have been used to characterize the samples. The photocatalytic activities of Fe(2)O(3)/TiO(2) heterocomposites, pure Fe(2)O(3) and pure TiO(2) were evaluated by the photodegrading efficiency of Orange II under visible light (lambda > 420 nm). The experiments demonstrated that Orange II in aqueous solution was more efficiently photodegraded using Fe(2)O(3)/TiO(2) heterogeneous photocatalysts than either pure Fe(2)O(3) or TiO(2) under visible light irradiation. With an optimal mass ratio of 7:3 in Fe(2)O(3)/TiO(2) the highest rate of Orange II photodegradation was achieved under the experimental conditions. We have also compared the photoelectric properties of Fe(2)O(3)/TiO(2) heterogeneous photocatalysts with that of pure Fe(2)O(3) by surface photovoltage (SPV) and transient photovoltage (TPV) techniques. Based on the photovoltage responses, we discussed the influence of the hetero-interface between Fe(2)O(3) and TiO(2) on transfer characteristics of photogenerated charge carriers. We demonstrated that the formation of heterojunctions between Fe(2)O(3) and TiO(2) for Fe(2)O(3)/TiO(2) composites was pivotal for improving the separation and thus restraining the recombination of photogenerated electrons and holes, which accounts for the enhancement of photocatalytic activity.

  10. Removal of high concentration dimethyl methylphosphonate in the gas phase by repeated-batch reactions using TiO2.

    PubMed

    Mera, Nobuaki; Hirakawa, Tsutomu; Sano, Taizo; Takeuchi, Koji; Seto, Yasuo; Negishi, Nobuaki

    2010-05-15

    The aim of our study is to develop apparatuses that use TiO(2) for effective decontamination of air contaminated by Sarin gas. We performed photocatalytic decomposition of gaseous dimethyl methylphosphonate (DMMP) by TiO(2) and identified the oxidization products. The high activity of TiO(2) (0.01 g) was observed under UV-light irradiation and high concentration DMMP (33.5 microM) was removed rapidly. On the other hand, DMMP was not decreased under UV-light irradiation without TiO(2). This indicates that photocatalytic treatment is very effective for the removal of DMMP. Methanol, formaldehyde, formic acid, methyl formate, CO, CO(2) and H(2)O were detected as the primary products. In the gas phase, no highly poisonous substances were detected. In order to examine the performance of photocatalytic activity during long-term reactions, we performed photocatalytic decomposition by repeated-batch reactions using TiO(2). High photocatalytic activities decreased gradually. Meanwhile, the strong adsorption of TiO(2) against DMMP was observed as photocatalytic activities decreased. During the repeated-batch reactions with the sample scaled up (TiO(2): 0.1g), the total amount of removed DMMP reached 968.5 microM by both photocatalytic decomposition and the strong adsorption of TiO(2). These results suggest the possibility of removing large amounts of DMMP.

  11. Effective nitrogen doping into TiO2 (N-TiO2) for visible light response photocatalysis.

    PubMed

    Yoshida, Tomoko; Niimi, Satoshi; Yamamoto, Muneaki; Nomoto, Toyokazu; Yagi, Shinya

    2015-06-01

    The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e., with an increase of thickness, it increases to the maximum, followed by decreasing to be constant. Such variation of the reaction rate is fundamentally explained by the competitive production and annihilation processes of photogenerated electrons and holes in TiO2 films, and the optimum TiO2 thickness is estimated to be ca. 10nm. We also tried to dope nitrogen into the effective depth region (ca. 10nm) of TiO2 by an ion implantation technique. The nitrogen doped TiO2 enhanced photocatalytic activity under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1⩽x⩽2) species. In the valence band XPS spectrum of the high active sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substituting nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts.

  12. Photocatalytic Activity of Immobilized Geometries of TiO2

    NASA Astrophysics Data System (ADS)

    Koohestani, Hassan; Sadrnezhaad, Sayed Khatiboleslam

    2015-07-01

    Photocatalysts that are used for waste water treatment are often suspended in the waste water during processing and then must be removed from the water after treatment. To reduce the post-degradation expenses and time, separation is facilitated by an immobilization process. The effect of immobilized TiO2 geometries on the photocatalytic behavior of the photocatalyst is investigated in this work. Powder, fiber, film, and network-shaped TiO2 nanocatalysts were produced by using different templates. The cellulose fiber and ceramic templates were used as substrates for fiber and film/network geometry production. The products were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area measurement. The photocatalytic performance was determined by methyl orange degradation and cyanide photo-oxidation under ultraviolet irradiation. From the SEM images, the size range of the TiO2 particles in the film and in the network geometries were 20-60 nm. The nanoparticles had covered the surface of the substrate, uniformly. Removal of the cellulose substrate by heat treatment yielded hollow TiO2 fibers with diameters of 0.5-1 µm and lengths of 30 µm. The efficiencies of both photocatalytic reactions were obtained in the following order: powder > network > film > fiber geometry. The rate constant of the dye degradation reaction using powder catalyst was 0.0118 min-1. For network catalyst, it was 0.0083 min-1. Corresponding results for cyanide disinfection were 0.0055 and 0.0046 min-1. Although powder samples had higher rate constants, network geometry was preferred due to its higher immobility.

  13. Structural analysis of TiO2 and TiO2-Ag thin films and their antibacterial behaviors

    NASA Astrophysics Data System (ADS)

    Hsieh, J. H.; Yu, R. B.; Chang, Y. K.; Li, C.

    2012-01-01

    TiO2 (rutile and anatase) thin films was first prepared using reactive sputtering, in an Ar+O2 plasma. In the 2nd stage of the experiment, various amounts (3, 7, and 10 at. %) of Ag was doped into the rutile film in order to form TiO2-Ag thin films. These films were annealed for one hour in Ar atmosphere, at 300, 400, and 500 °C. The films' structures were then examined using X-ray diffractometry. FESEM (field-emission scaning electron microscopy) was used to investigate the surface emergence of Ag particles. As for the examination of optical band gaps and absorption of these films, UV-Vis-NIR photometer was used. The results show that, in as-deposited condition, the addition of Ag might disrupt the growth of crystalline structure and cause the formation of amorphous films. After annealing, it is found that the structure tends to become anatase phase which is a metastable phase between amorphous titanium oxide and rutile. More importantly, the absorption of the Ag-doped films would be enhanced in the visible-light range. Some of the enhancement is clearly due to plasmon resonance effect. The Ag-doped samples have shown some antibacterial effect in dark. When irradiated with light, the samples show a synergistic behavior combining the bactericidal effect of Ag ions and photocatalytic effect of TiO2.

  14. TiO2/carboxylate-rich porous carbon: A highly efficient visible-light-driven photocatalyst based on the ligand-to-metal charge transfer (LMCT) process

    NASA Astrophysics Data System (ADS)

    Qu, Lingling; Huang, Dongliang; Shi, Hefei; Gu, Mengbin; Li, Jilei; Dong, Fei; Luo, Zhijun

    2015-10-01

    A novel visible-light-driven photocatalyst based on TiO2/carboxylate-rich porous carbon composite (TiO2/CRPC) was successfully synthesized by low temperature carbonization process in air. Sodium gluconate plays a crucial role in the formation of TiO2/CRPC. Different functional groups of sodium gluconate play synergetic roles in the formation of TiO2/CRPC. XRD and Raman spectra studies indicated that there are two different TiO2 crystalline phases existing in TiO2/CRPC, which are anatase and brookite, and the CRPC is amorphous. Via FT-IR and XPS spectra investigations, it was demonstrated that carboxylate group, the ligand-to-metal charge transfer (LMCT) forming functional group, was solidified into the CRPC and form the LMCT complex on TiO2 surface through the fabrication of TiO2/CRPC. Compared with the pure TiO2, TiO2/CRPC exhibit enhanced absorption in the UV and visible light region around 260-600 nm. The strong absorption in the visible light region gives TiO2/CRPC advantages over pure TiO2 for the degradation of organic pollutants. TiO2/CRPC can activate O2 in air under mild conditions and exhibit excellent visible-light-driven photocatalytic activities. However, TiO2/C composite obtained by using glucose instead of sodium gluconate exhibits poor photocatalytic activity, which demonstrated that carboxylate-TiO2 complexes are responsible for the prominent photocatalytic properties of TiO2/CRPC under visible light irradiation.

  15. Sonocatalytic degradation of methylene blue with TiO2 pellets in water.

    PubMed

    Shimizu, Nobuaki; Ogino, Chiaki; Dadjour, Mahmoud Farshbaf; Murata, Tomoyuki

    2007-02-01

    A series of experiments were carried out to study the degradation of methylene blue by the irradiation of ultrasound onto TiO(2) in aqueous solution. A statistically significant decrease in the concentration of methylene blue was observed after 60 min irradiation. While the reduction was 22% of the initial concentration without H(2)O(2), addition of H(2)O(2) significantly enhanced the degradation of methylene blue for the TiO(2) containing system (85% reduction of the initial concentration). The addition of H(2)O(2) had no effect on the methylene blue degradation when the system contained Al(2)O(3). The degradation ratio of methylene blue was dependent on the amount of TiO(2) and also the specific surface area of TiO(2) in the solution. The effects of radical scavenging agents on the degradation of methylene blue were also investigated for the system with TiO(2). It was found that the radical scavenging agents dimethyl sulfoxide (DMSO), methanol, and mannitol suppressed the degradation, with DMSO being the most effective. The effect of pH on the degradation of methylene blue was further investigated. An U-shaped change in the concentration of methylene blue in the presence of TiO(2) was observed along with the change in pH values (pH 3-12), and the highest degradation ratio was observed at around pH 7. In conclusion, ultrasound irradiation of TiO(2) in aqueous solution resulted in significant generation of hydroxyl radicals, and this process may have potential for the treatment of organic dyes in wastewater.

  16. Spectroscopic study of the photofixation of SO2 on anatase TiO2 thin films and their oleophobic properties.

    PubMed

    Topalian, Z; Niklasson, G A; Granqvist, C G; Österlund, L

    2012-02-01

    Photoinduced SO(2) fixation on anatase TiO(2) films was studied by in situ Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The TiO(2) films were prepared by reactive DC magnetron sputtering and were subsequently exposed to 50 ppm SO(2) gas mixed in synthetic air and irradiated with UV light at substrate temperatures between 298 and 673 K. Simultaneous UV irradiation and SO(2) exposure between 373 and 523 K resulted in significant sulfur (S) deposits on crystalline TiO(2) films as determined by XPS, whereas amorphous films contained negligible amounts of S. At substrate temperatures above 523 K, the S deposits readily desorbed from TiO(2). The oxidation state of sulfur successively changed from S(4+) for SO(2) adsorbed on crystalline TiO(2) films at room temperature without irradiation to S(6+) for films exposed to SO(2) at elevated temperatures with simultaneous irradiation. In situ FTIR was used to monitor the temporal evolution of the photoinduced surface reaction products formed on the TiO(2) surfaces. It is shown that band gap excitation of TiO(2) results in photoinduced oxidation of SO(2), which at elevated temperatures become coordinated to the TiO(2) lattice through interactions with O vacancies and form sulfite and sulfate surface species. These species makes the surface acidic, which is manifested in nondetectable adherence of stearic acid to the modified surface. The modified films show good chemical stability as evidenced by sonication and repeated recycling of the films. The results suggest a new method to functionalize wide band gap oxide surfaces by means of photoinduced reactions in reactive gases at elevated substrate temperatures. In the case of anatase TiO(2) in reactive SO(2) gas, we here show that such functionalization yields surfaces with excellent oleophobic properties, as probed by adhesion of stearic acid.

  17. Dye-sensitized solar cells based on nanocrystalline TiO2 films surface treated with Al3+ ions: photovoltage and electron transport studies.

    PubMed

    Alarcón, H; Boschloo, G; Mendoza, P; Solis, J L; Hagfeldt, A

    2005-10-06

    Nanocrystalline TiO2 films, surface modified with Al3+, were manufactured by depositing a TiO2 suspension containing small amounts of aluminum nitrate or aluminum chloride onto conducting glass substrates, followed by drying, compression, and finally heating to 530 degrees C. Electrodes prepared with TiO2 nanoparticles coated with less than 0.3 wt % aluminum oxide with respect to TiO2 improved the efficiency of the dye sensitized solar cell. This amount corresponds to less than a monolayer of aluminum oxide. Thus, the Al ions terminate the TiO2 surface rather than form a distinct aluminum oxide layer. The aluminum ion surface treatment affects the solar cell in different ways: the potential of the conduction band is shifted, the electron lifetime is increased, and the electron transport is slower when aluminum ions are present between interconnected TiO2 particles.

  18. Spectral Sensitization of the Heterogeneous Photocatalytic Oxidation of Hydroquinone in Aqueous Solutions at Phthalocyanine-Coated TiO2 Powders.

    DTIC Science & Technology

    1979-08-01

    The photocatalyzed reaction of hydroquinone with oxygen at TiO2 (anatase) powders coated with metal-free or magnesium phthalocyanine under...irradiation with light of energy less than the TiO2 band gap is described. The behavior at the powders is correlated with current-potential curves at single...crystal n-type TiO2 electrode and an energy level scheme for the reaction is proposed. (Author)

  19. Synthesis of nanosize MCM-41 loaded with TiO 2 and study of its photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Sadjadi, M. S.; Farhadyar, N.; Zare, K.

    2009-07-01

    In recent years, nanosized mesoporous materials have received significant attention due to their impact in different processes. Several diverse applications of these materials, e.g. high density magnetic recording, magnetic fluids, magnetic refrigeration as well as in photocatalysis, solar cells, photosensors, have triggered considerable research activities in the area of nanotechnology. In this work, nanosize MCM-41 was synthesized and loaded then with TiO 2 using tetra butoxy titanium (TBT). As prepared TiO 2 loaded materials was investigated by using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR). The photocatalytic activity of the prepared TiO 2 loaded MCM-41 was finally evaluated by the degradation of methyl orange under irradiation of UV light. The result showed that TiO 2 loaded on nanosize MCM-41 has higher photocatalytic activity than that of TiO 2.

  20. Preparation of TiO2 thin films using octadecylamine Langmuir-Blodgett films and evaluation of their photocatalytic activity.

    PubMed

    Takahashi, Masashi; Sendoh, Mitsuyuki; Kobayashi, Koichi; Tajima, Kazuo

    2011-01-01

    A study was conducted to demonstrate that nanometer-thick titanium dioxide (TiO(2)) thin films could be prepared by the hydrolysis of titanium potassium oxalate using octadecylamine (ODA) Langmuir-Blodgett (LB) films as templates. The amount of TiO(2) generated in the LB film was found to be proportional to the number of deposited ODA layers, which enables precise control of the TiO(2) film thickness. After heat treatment of the LB films at 300-600°C, the photocatalytic activities of the resulting TiO(2) films were determined from the decomposition of stearic acid cast films when irradiated with UV light for different time periods. Higher photocatalytic activity was observed in TiO(2) films heat treated at lower temperatures.

  1. Facile fabrication, characterization, and enhanced photoelectrocatalytic degradation performance of highly oriented TiO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Zhao, Qidong; Li, Xinyong; Wang, Ning; Hou, Yang; Quan, Xie; Chen, Guohua

    2009-11-01

    Highly ordered TiO2 nanotube arrays were successfully fabricated using ethanol and water mixture electrolytes (40 vol% ethanol and 0.2 wt% hydrofluoric acid) by a facile electrochemical anodization method. The as-prepared nanotube arrays were grown perpendicular to the titanium substrate with about 90 nm in diameter, 20 nm in wall thickness, and around 500 nm in length. The formation mechanism of the samples is briefly discussed. A blue shift in the spectrum of UV-Vis absorption was observed with respect to a piece of the sol-gel derived TiO2 film. Moreover, photocurrent response and photoelectrocatalytic degradation of methyl orange under ultraviolet light irradiation were adopted to evaluate the photoelectrocatalytic properties of the TiO2 nanotube arrays. We demonstrate that the highly ordered TiO2 nanotube arrays possess much better photoelectrocatalytic activity than the sol-gel derived TiO2 film and good stability.

  2. Extruded expanded polystyrene sheets coated by TiO2 as new photocatalytic materials for foodstuffs packaging

    NASA Astrophysics Data System (ADS)

    Loddo, V.; Marcì, G.; Palmisano, G.; Yurdakal, S.; Brazzoli, M.; Garavaglia, L.; Palmisano, L.

    2012-11-01

    Nanostructured, photoactive anatase TiO2 sol prepared under very mild conditions using titanium tetraisopropoxide as the precursor is used to functionalise extruded expanded polystyrene (XPS) sheets by spray-coating resulting in stable and active materials functionalised by TiO2 nanoparticles. Photocatalytic tests of these sheets performed in a batch reactor in gas-solid system under UV irradiation show their successful activity in degrading probe molecules (2-propanol, trimethylamine and ethene). Raman spectra ensure the deposition of TiO2 as crystalline anatase phase on the polymer surface. The presence of TiO2 with respect to polymer surface can be observed in SEM images coupled to EDAX mapping allowing to monitor the surface morphology and the distribution of TiO2 particles. Finally thermoforming of these sheets in industrial standard equipment leads to useful containers for foodstuffs.

  3. Synthesis of TiO2-N/SnO2 heterostructure photocatalyst and its photocatalytic mechanism.

    PubMed

    Cao, Han; Huang, Shaolong; Yu, Yanlong; Yan, Yabin; Lv, Yuekai; Cao, Yaan

    2017-01-15

    A series of TiO2-N/SnO2X heterostructure photocatalysts were synthesized by a hydrolysis-deposition method. The structure, existing states of N and SnO2 heterostructure at the interface of TiO2-N/SnO2X were studied by EADX, XRD, Raman, FT-IR, XPS, and HRTEM. The band structure is investigated by both theoretical calculation and experiment characterization. It was found that the introduction of NOx surface species and SnO2 nanoparticles would enhance the absorption in visible region, increase reactive oxidative species and separate photogenerated electrons and holes efficiently. Therefore, the photocatalytic activity is improved significantly for TiO2-N/SnO2X, compared with TiO2-N and TiO2 under visible and UV light irradiation. This work may offer a new strategy to fabricate new photocatalyst with high photocatalytic performance.

  4. Formation of hydroxyl radicals and kinetic study of 2-chlorophenol photocatalytic oxidation using C-doped TiO2, N-doped TiO2, and C,N Co-doped TiO2 under visible light.

    PubMed

    Ananpattarachai, Jirapat; Seraphin, Supapan; Kajitvichyanukul, Puangrat

    2016-02-01

    This work reports on synthesis, characterization, adsorption ability, formation rate of hydroxyl radicals (OH(•)), photocatalytic oxidation kinetics, and mineralization ability of C-doped titanium dioxide (TiO2), N-doped TiO2, and C,N co-doped TiO2 prepared by the sol-gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible spectroscopy were used to analyze the titania. The rate of formation of OH(•) for each type of titania was determined, and the OH-index was calculated. The kinetics of as-synthesized TiO2 catalysts in photocatalytic oxidation of 2-chlorophenol (2-CP) under visible light irradiation were evaluated. Results revealed that nitrogen was incorporated into the lattice of titania with the structure of O-Ti-N linkages in N-doped TiO2 and C,N co-doped TiO2. Carbon was joined to the Ti-O-C bond in the C-doped TiO2 and C,N co-doped TiO2. The 2-CP adsorption ability of C,N co-doped TiO2 and C-doped TiO2 originated from a layer composed of a complex carbonaceous mixture at the surface of TiO2. C,N co-doped TiO2 had highest formation rate of OH(•) and photocatalytic activity due to a synergistic effect of carbon and nitrogen co-doping. The order of photocatalytic activity per unit surface area was the same as that of the formation rate of OH(•) unit surface area in the following order: C,N co-doped TiO2 > C-doped TiO2 > N-doped TiO2 > undoped TiO2.

  5. Photoactive TiO2 coatings obtained by Plasma Electrolytic Oxidation in refrigerated electrolytes

    NASA Astrophysics Data System (ADS)

    Franz, Silvia; Perego, Daniele; Marchese, Ottavia; Lucotti, Andrea; Bestetti, Massimiliano

    2016-11-01

    The effect of synthesis conditions on the properties of nanoporous TiO2 coatings obtained by PEO in refrigerated electrolytes have been investigated. Linear sweep voltammetry was carried out on the TiO2 coatings, in dark and under UV-C irradiation, in order to assess the photoelectrochemical behavior of samples. The largest photocurrents (0.18 mA/cm2) were measured on TiO2 coatings obtained by PEO in refrigerated aqueous solutions. UV-vis spectra revealed that lowering the processing temperature from 20 to -3.5 °C induced a blue-shift of the absorption band of the TiO2 coatings from 3.05 to 3.42 eV. The main advantage of PEO in refrigerated aqueous solutions over current approaches, based on anodic oxidation and thermal treatments, is that the synthesis of photoactive TiO2 coatings can be carried out in a relatively easy, quick and reproducible way, without annealing pre- and post-treatments. Furthermore, by controlling the solution temperature in PEO process, the photocurrent of the resulting TiO2 coating reaches quite high values.

  6. Hydrothermal synthesis spherical TiO2 and its photo-degradation property on salicylic acid

    NASA Astrophysics Data System (ADS)

    Guo, Wenlu; Liu, Xiaolin; Huo, Pengwei; Gao, Xun; Wu, Di; Lu, Ziyang; Yan, Yongsheng

    2012-07-01

    Anatase TiO2 spheres have been prepared using hydrothermal synthesis. The prepared spheres were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and UV-vis diffuse reflectance spectra (UV-vis DRS). The TiO2 consisted of well-defined spheres with size of 3-5 μm. The photocatalytic activity of spherical TiO2 was determined by degradation of salicylic acid under visible light irradiation. It was revealed that the degradation rate of the spherical TiO2 which was processed at 150 °C for 48 h could reach 81.758%. And the kinetics of photocatalytic degradation obeyed first-order kinetic, which the rate constant value was 0.01716 S-1 of the salicylic acid onto TiO2 (temperature: 150, time: 48 h). The kinetics of adsorption followed the pseudo-second-order model and the rate constant was 1.2695 g mg-1 of the salicylic acid onto TiO2 (temperature: 150, time: 48 h).

  7. Enhanced photocatalytic performances of CeO2/TiO2 nanobelt heterostructures.

    PubMed

    Tian, Jian; Sang, Yuanhua; Zhao, Zhenhuan; Zhou, Weijia; Wang, Dongzhou; Kang, Xueliang; Liu, Hong; Wang, Jiyang; Chen, Shaowei; Cai, Huaqiang; Huang, Hui

    2013-11-25

    CeO2 /TiO2 nanobelt heterostructures are synthesized via a cost-effective hydrothermal method. The as-prepared nanocomposites consist of CeO2 nanoparticles assembled on the rough surface of TiO2 nanobelts. In comparison with P25 TiO2 colloids, surface-coarsened TiO2 nanobelts, and CeO2 nanoparticles, the CeO2 /TiO2 nanobelt heterostructures exhibit a markedly enhanced photocatalytic activity in the degradation of organic pollutants such as methyl orange (MO) under either UV or visible light irradiation. The enhanced photocatalytic performance is attributed to a novel capture-photodegradation-release mechanism. During the photocatalytic process, MO molecules are captured by CeO2 nanoparticles, degraded by photogenerated free radicals, and then released to the solution. With its high degradation efficiency, broad active light wavelength, and good stability, the CeO2 /TiO2 nanobelt heterostructures represent a new effective photocatalyst that is low-cost, recyclable, and will have wide application in photodegradation of various organic pollutants. The new capture-photodegradation-release mechanism for improved photocatalysis properties is of importance in the rational design and synthesis of new photocatalysts.

  8. Photoelectrochemical Properties of CuS-GeO2-TiO2 Composite Coating Electrode

    PubMed Central

    Wen, Xinyu; Zhang, Huawei

    2016-01-01

    The ITO (indium tin oxide) conductive glass-matrix CuS-GeO2-TiO2 composite coating was generated via EPD (electrophoretic deposition) and followed by a sintering treatment at 450°C for 40 minutes. Characterizations of the CuS-GeO2-TiO2 composite coating were taken by SEM (scanning electron microscope), XRD (X-ray diffraction), EDX (energy dispersive X-ray), UV-Vis DRS (ultraviolet-visible diffuse reflection spectrum), and FT-IR (Fourier transform infrared spectroscopy). Results showed that CuS and GeO2 had dispersed in this CuS-GeO2-TiO2 composite coating (mass percentages for CuS and GeO2 were 1.23% and 2.79%, respectively). The electrochemical studies (cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization) of this CuS-GeO2-TiO2 composite coating electrode were performed in pH = 9.51 Na2CO3-NaHCO3 buffer solution containing 0.50 mol/L CH3OH under the conditions of visible light, ultraviolet light (λ = 365 nm), and dark (without light irradiation as control), respectively. Electrochemical studies indicated that this CuS-GeO2-TiO2 composite coating electrode had better photoelectrocatalytic activity than the pure TiO2 electrode in the electrocatalysis of methanol under visible light. PMID:27055277

  9. Photocatalytic properties of silver nanoparticles decorated nanobranched TiO2 nanofibers.

    PubMed

    Yi, Chuan; Nirmala, R; Barakat, Nasser A M; Navamathavan, R; Kim, Hak-Yong

    2011-08-01

    In this study, nanobranched TiO2 nanofibers and silver loaded nanobranched TiO2 nanofibers were prepared by electrospinning technique followed by TiCl4 aqueous solution treatment and silver photodeposition method. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were employed to investigate the morphology of the products. X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) were conducted on the samples to study their chemical composition as well as crystallographic structure. The photocatalytic activities of these produced nanofibers were examined with two organic dyes, methylene blue and methyl orange, under ultraviolet (UV) light irradiation. The effect of nanobranches and silver modification on TiO2 nanofibers was revealed in the photocatalysis process. The photocatalytic degradation rates of silver loaded on nanobranched TiO2 nanofibers were 1.6 and 1.7 times as that of pure TiO2 nanofibers in the presence of methylene blue and methyl orange, respectively, which indicated silver nanoparticles combined nanobranches modified on the surface of TiO2 nanofibers could enhance the photocatalytic ability.

  10. First-principles study on anatase TiO2 codoped with nitrogen and praseodymium

    NASA Astrophysics Data System (ADS)

    Gao, Pan; Wu, Jing; Liu, Qing-Ju; Zhou, Wen-Fang

    2010-08-01

    The crystal structures, electronic structures and optical properties of nitrogen or/and praseodymium doped anatase TiO2 were calculated by first principles with the plane-wave ultrasoft pseudopotential method based on density functional theory. Highly efficient visible-light-induced nitrogen or/and praseodymium doped anatase TiO2 nanocrystal photocatalyst were synthesized by a microwave chemical method. The calculated results show that the photocatalytic activity of TiO2 can be enhanced by N doping or Pr doping, and can be further enhanced by N+Pr codoping. The band gap change of the codoping TiO2 is more obvious than that of the single ion doping, which results in the red shift of the optical absorption edges. The results are of great significance for the understanding and further development of visible-light response high activity modified TiO2 photocatalyst. The photocatalytic activity of the samples for methyl blue degradation was investigated under the irradiation of fluorescent light. The experimental results show that the codoping TiO2 photocatalytic activity is obviously higher than that of the single ion doping. The experimental results accord with the calculated results.

  11. Structure and high photocatalytic activity of (N, Ta)-doped TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Le, N. T. H.; Thanh, T. D.; Pham, V.-T.; Phan, T. L.; Lam, V. D.; Manh, D. H.; Anh, T. X.; Le, T. K. C.; Thammajak, N.; Hong, L. V.; Yu, S. C.

    2016-10-01

    A hydrothermal method was used to prepare three nano-crystalline samples of TiO2 (S1), N-doped TiO2 (S2), and (N, Ta)-codoped TiO2 (S3) with average crystallite sizes (D) of 13-25 nm. X-ray diffraction studies confirmed a single phase of the samples with a tetragonal/anatase structure. A slight increase in the lattice parameters was observed when N and/or Ta dopants were doped into the TiO2 host lattice. Detailed analyses of extended X-ray absorption spectra indicated that N- and/or Ta-doping into TiO2 nanoparticles influenced the co-ordination number and radial distance (R) of Ti ions in the anatase structure. Concerning their absorption spectra, (N, Ta)-doping narrowed the band gap (Eg) of TiO2 from 3.03 eV for S1 through 2.94 eV for S2 to 2.85 eV for S3. Such results revealed the applicability of these nanoparticles in the photocatalytic field working in the ultraviolet (UV)-visible region. Among these, photocatalytic activity of S3 was the strongest. By using S3 as a catalyst powder, the degradation efficiency of methylene blue solution was about 99% and 93% after irradiation of UV-visible light for 75 min and visible-light for 180 min, respectively.

  12. TiO2 nanosized powders controlling by ultrasound sol-gel reaction.

    PubMed

    Latt, Kyaing Kyaing; Kobayashi, Takaomi

    2008-04-01

    We studied that anatase-TiO2 powders prepared from sol-gel process of titanium tetra-isopropoxide (TTIP) were developed under ultrasonic irradiation with different frequency of 28, 45 and 100 kHz. The irradiated ultrasound (US) was controlled by using semi-cylindrical reflection plate that was placed onto the vicinity of reaction vessel. The focused US influenced the reduction of particles size and increased the surface area of resultant nanosized TiO2 powders. We also examined photodegradation of rhodamine 640 dye (Rh-640) solution by the resultant TiO2 under UV light exposure. It was observed that low frequency for TiO2 photocatalyst preparation and low calcination temperature were more affected onto the photodegradation of the dye.

  13. Enhancement removal of tartrazine dye using HCl-doped polyaniline and TiO2-decorated PANI particles

    NASA Astrophysics Data System (ADS)

    Elsayed, M. A.; Gobara, Mohamed

    2016-08-01

    HCl-doped polyaniline (HCl-PANI) and titanium dioxide decorated with polyaniline (TiO2-decorated PANI) with different TiO2:PANI ratios were chemically prepared and utilized for the removal of tartrazine (TZ) dye from a synthetic aqueous solution. The mechanism of preparation of the sample suggested that aniline was adsorbed on the TiO2 surface before the polymerization process took place. Samples were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy and x-ray diffraction. The results showed that HCl-PANI and TiO2-decorated PANI have an amorphous structure. The thermal stability of the prepared samples was characterized using thermo-gravimetric (TG) analysis. HCl-PANI is stable up to 200 °C and the relative weight per cent of PANI in the TiO2-decorated PANI was 20, 25, 40 and 45%. The removal activity of TiO2-decorated PANI via TZ azo dye was investigated under UV light irradiations and compared with HCl-PANI and TiO2 particles. The results indicated the superiority of the TiO2-decorated PANI over pure HCl-PANI and TiO2. However, the excessive PANI percentage tends to form a relatively thick layer, and even aggregates on the surface of TiO2. This hinders the migration of excited electrons from the outer PANI layer to the inner TiO2 particles, which consequently leads to a decrease in the removal efficiency. A possible mechanism for the removal oxidative degradation is also mentioned.

  14. Thickness dependent activity of nanostructured TiO 2/α-Fe 2O 3 photocatalyst thin films

    NASA Astrophysics Data System (ADS)

    Akhavan, O.

    2010-12-01

    The effect of thickness of TiO 2 coating on synergistic photocatalytic activity of TiO 2 (anatase)/α-Fe 2O 3/glass thin films as photocatalysts for degradation of Escherichia coli bacteria in a low-concentration H 2O 2 solution and under visible light irradiation was investigated. Nanograined α-Fe 2O 3 films with optical band-gap of 2.06 eV were fabricated by post-annealing of thermal evaporated iron oxide thin films at 400 °C in air. Increase in thickness of the Fe 2O 3 thin film (here, up to 200 nm) resulted in a slight reduction of the optical band-gap energy and an increase in the photoinactivation of the bacteria. Sol-gel TiO 2 coatings were deposited on the α-Fe 2O 3 (200 nm)/glass films, and then, they were annealed at 400 °C in air for crystallization of the TiO 2 and formation of TiO 2/Fe 2O 3 heterojunction. For the TiO 2 coatings with thicknesses ≤50 nm, the antibacterial activity of the TiO 2/α-Fe 2O 3 (200 nm) was found to be better than the activity of the bare α-Fe 2O 3 film. The optimum thickness of the TiO 2 coating was found to be 10 nm, resulting in about 70 and 250% improvement in visible light photo-induced antibacterial activity of the TiO 2/α-Fe 2O 3 thin film as compared to the corresponding activity of the bare α-Fe 2O 3 and TiO 2 thin films, respectively. The improvement in the photoinactivation of bacteria on surface of TiO 2/α-Fe 2O 3 was assigned to formation of Ti-O-Fe bond at the interface.

  15. The preparation of nitrogen-doped TiO 2- xN x photocatalyst coated on hollow glass microbeads

    NASA Astrophysics Data System (ADS)

    Shifu, Chen; Xuqiang, Liu; Yunzhang, Liu; Gengyu, Cao

    2007-01-01

    In this paper, the effective method for nitrogen-doped TiO 2- xN x photocatalyst coated on hollow glass microbeads is described, which uses titanium tetraisopropoxide [Ti( iso-OC 3H 7) 4] as the raw materials and gaseous ammonia as a heat treatment atmosphere. The effects of heat treatment temperature and time on the photocatalytic activity of TiO 2- xN x/beads are studied. The photocatalyst is characterized by the UV-vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis and scanning electron microscopy (SEM). The results show that when the TiO 2- xN x/beads is heated at 650 °C for 5 h, the photocatalytic activity of the TiO 2- xN x/beads is the best. Compared with TiO 2, the photoabsorption wavelength range of nitrogen-doped TiO 2- xN x red shifts of about 60 nm, and the photoabsorption intensity increases as well. The photocatalytic activity of the TiO 2- xN x/beads is higher than that of the TiO 2/beads under visible light irradiation. The presence of nitrogen neither influences on the transformation of anatase to rutile, nor creates new crystal phases. When the TiO 2- xN x/beads is heated at 650 °C for 5 h, the amount of nitrogen-doped is 0.53 wt.% in the TiO 2- xN x. As the density of TiO 2- xN x/beads prepared is lower than 1.0 g/cm 3, it may float on water surface and use broader sunlight spectrum directly.

  16. Enhanced photocatalytic degradation of dyes over graphene/Pd/TiO2 nanocomposites: TiO2 nanowires versus TiO2 nanoparticles.

    PubMed

    Safajou, Hamed; Khojasteh, Hossein; Salavati-Niasari, Masoud; Mortazavi-Derazkola, Sobhan

    2017-07-15

    In this study, at first, TiO2 nanowire was prepared by an alkaline hydrothermal process. In the following, Gr/Pd/TiO2-NPs and Gr/Pd/TiO2-NWs were synthesized by a combination of hydrothermal and photodeposition methods. The properties of as prepared products were characterized using XRD, FT-IR, SEM, DRS, TEM, ICP-OES, EDS and TGA analysis. SEM results confirmed nanodimension structure for all samples. Also the band gap values obtained using DRS technique suggests that all the samples have semiconductor behavior. Using TGA analysis, the amount of graphene loaded onto the powders was confirmed. Photocatalytic degradation of rhodamine B by TiO2-NWs, Gr/Pd/TiO2-NPs and Gr/Pd/TiO2-NWs nanocomposites was compared under ultraviolet light irradiation. Results confirmed that the Gr/Pd/TiO2-NWs composite show the highest photocatalytic activity due to much higher available surface area of TiO2 substrate in nanowire structure. It is expected that the synthesis of the high surface area TiO2 nanowires, facile photodeposition of palladium into its texture, and simple conversion of GO to graphene during hydrothermal process without using strong reducing agents, could be a suitable rote for preparing different types of carbon based TiO2 nanocomposite photocatalysts.

  17. TiO2-assisted photo-catalysis degradation process of dye chemicals.

    PubMed

    Li, F B; Gu, G B; Huang, G F; Gu, Y L; Wan, H F

    2001-01-01

    The photo-catalytic degradation pathway and degradation products of methylene blue, rhodamine B, methyl orange, and malachite green in aqueous TiO2 suspension irradiated by high pressure mercury lamp by means of UV-visible absorption spectra and ion chromatography were investigated. The photo-catalysis degradation of dye solutions with charges was greatly effected by pH value owing to the electrostatic model. The photo-degradation rate of dyes anion increased with the decrease of pH value, in contrast, the photo-degradation rate of dyes cation increased with the increase of pH value. And the absorption peaks diminished with a blue shift. After illuminated for 30 minutes, a part of dye chemicals were completely mineralized and transferred into inorganic species including chloride ion, ammonium ion, nitrate ion, sulfate ion. And the addition of 100 mmol/L H2O2 promoted the formation of inorganic species. In this study, the quantity of ammonium ion was much more than that of nitrate ion. That indicated the formation of nitrate is from ammonium. The purification rate of COD in four kinds of dye solution was 71.7%-88.7%. The decrease of COD of dyes solution implies the feasibility of the environmental application of photo-catalyzed process.

  18. Enhanced retention of bacteria by TiO2 nanoparticles in saturated porous media

    NASA Astrophysics Data System (ADS)

    Gentile, Guillermina J.; Fidalgo de Cortalezzi, María M.

    2016-08-01

    The simultaneous transport of TiO2 nanoparticles and bacteria Pseudomonas aeruginosa in saturated porous media was investigated. Nanoparticle and bacterium size and surface charge were measured as a function of electrolyte concentration. Sand column breakthrough curves were obtained for single and combined suspensions, at four different ionic strengths. DLVO and classical filtration theories were employed to model the interactions between particles and between particles and sand grains. Attachment of TiO2 to the sand was explained by electrostatic forces and these nanoparticles acted as bonds between the bacteria and the sand, leading to retention. Presence of TiO2 significantly increased the retention of bacteria in the sand bed, but microorganisms were released when nanomaterial influx ceased. The inclusion of nanomaterials in saturated porous media may have implications for the design and operation of sand filters in water treatment.

  19. Electrosprayed TiO2 nanoporous hemispheres for enhanced electron transport and device performance of formamidinium based perovskite solar cells.

    PubMed

    Ye, Tao; Ma, Shaoyang; Jiang, Xi; Petrović, Miloš; Vijila, Chellappan; Ramakrishna, Seeram; Wei, Lei

    2017-01-07

    Titanium dioxide (TiO2) nanoporous hemispheres (NHSs) with a radius of ∼200 nm are fabricated by electrospraying a hydrothermally synthesized TiO2 nanoparticle (NP) suspension solution. The resulting TiO2 NHSs are highly porous, which are beneficial to the infiltration of perovskites and provide a larger contact area, as building blocks to construct a mesoporous TiO2 layer for FA0.81MA0.15Pb(I0.836Br0.15)3 based perovskite solar cells (PSCs). By varying the TiO2 NHS collecting period (15 s, 30 s, 60 s and 90 s) during the electrospraying process, the performance of PSCs changes with different TiO2 NHS distribution densities. The optimized PSC employing TiO2 NHSs (60 s) exhibits a photovoltaic conversion efficiency (PCE) as high as 19.3% with a Jsc of 23.8 mA cm(-2), a Voc of 1.14 V and a FF of 0.71. Furthermore, the PSC possesses a reproducible PCE value with little hysteresis in its current density-voltage (J-V) curves. The small perturbation transient photovoltage (TPV) measurement reveals a longer free carrier lifetime within the TiO2 NHS based PSC than that in the TiO2 NP based PSC, and the time of flight (TOF) photoconductivity measurement shows that charge mobilities in this system are also enhanced. These characteristics make TiO2 NHSs a promising electron transport material for efficient photovoltaic devices.

  20. Highly Efficient Photocatalytic Hydrogen Evolution in Ternary Hybrid TiO2/CuO/Cu Thoroughly Mesoporous Nanofibers.

    PubMed

    Hou, Huilin; Shang, Minghui; Gao, Fengmei; Wang, Lin; Liu, Qiao; Zheng, Jinju; Yang, Zuobao; Yang, Weiyou

    2016-08-10

    Development of novel hybrid photocatalysts with high efficiency and durability for photocatalytic hydrogen generation is highly desired but still remains a grand challenge currently. In the present work, we reported the exploration of ternary hybrid TiO2/CuO/Cu thoroughly mesoporous nanofibers via a foaming-assisted electrospinning technique. It is found that by adjusting the Cu contents in the solutions, the unitary (TiO2), binary (TiO2/CuO, TiO2/Cu), and ternary (TiO2/CuO/Cu) mesoporous products can be obtained, enabling the growth of TiO2/CuO/Cu ternary hybrids in a tailored manner. The photocatalytic behavior of the as-synthesized products as well as P25 was evaluated in terms of their hydrogen evolution efficiency for the photodecomposition water under Xe lamp irradiation. The results showed that the ternary TiO2/CuO/Cu thoroughly mesoporous nanofibers exhibit a robust stability and the most efficient photocatalytic H2 evolution with the highest release rate of ∼851.3 μmol g(-1) h(-1), which was profoundly enhanced for more than 3.5 times with respect to those of the pristine TiO2 counterparts and commercial P25, suggesting their promising applications in clean energy production.

  1. Preparation and Mechanism of Cu-Decorated TiO2-ZrO2 Films Showing Accelerated Bacterial Inactivation.

    PubMed

    Rtimi, Sami; Pulgarin, Cesar; Sanjines, Rosendo; Nadtochenko, Victor; Lavanchy, Jean-Claude; Kiwi, John

    2015-06-17

    Antibacterial robust, uniform TiO2-ZrO2 films on polyester (PES) under low intensity sunlight irradiation made up by equal amounts of TiO2 and ZrO2 exhibited a much higher bacterial inactivation kinetics compared to pure TiO2 or ZrO2. The TiO2-ZrO2 matrix was found to introduce a drastic increase in the Cu-dopant promoter enhancing bacterial inactivation compared to Cu sputtered in the same amount on PES. Furthermore, the bacterial inactivation was accelerated by a factor close to three, by Cu- on TiO2-ZrO2 at extremely low levels ∼0.01%. Evidence is presented by X-ray photoelectron spectroscopy for redox catalysis taking place during bacterial inactivation. The TiO2-ZrO2-Cu band gap is estimated and the film properties were fully characterized. Evidence is provided for the photogenerated radicals intervening in the bacterial inactivation. The photoinduced TiO2-ZrO2-Cu interfacial charge transfer is discussed in term of the electronic band positions of the binary oxide and the Cu TiO2 intragap state.

  2. Solvothermal-assisted synthesis of self-assembling TiO2 nanorods on large graphitic carbon nitride sheets with their anti-recombination in the photocatalytic removal of Cr(vi) and rhodamine B under visible light irradiation.

    PubMed

    Lu, Dingze; Fang, Pengfei; Wu, Wenhui; Ding, Junqian; Jiang, Lulu; Zhao, Xiaona; Li, Chunhe; Yang, Minchen; Li, Yuanzhi; Wang, Dahai

    2017-03-02

    TiO2-based nanorods (TNRs) were self-assembled on large graphitic carbon nitride (g-C3N4) sheets via the solvothermal-assisted route. The results demonstrated that the effective anchoring of TNRs (a side length of ca. 200-300 nm) was highly dispersed on the surface of whole g-C3N4 sheets. The shift in the Ti 2p XPS core level spectrum indicated an increase in the net positive charge of the Ti ions, ensuring the formation of an interface between TNRs and g-C3N4. The charge transferred from g-C3N4 sheets to TNRs effectively prevented the recombination of excited charges, which is consistent with the significant quenching of PL. The extent of visible-light-sensitive photocatalytic (PC) activity was evaluated by the removal of potassium dichromate (Cr(vi)) or the degradation of rhodamine B (RhB). The photocatalytic removal of Cr(vi) using RhB was effectively improved. The synergistic effect between the removal of Cr(vi) and degradation of RhB was revealed by multiple utilization of TNRs/g-C3N4 for PC activity. The effective suppression of the recombination of photo-induced charges and the absorption of RhB was responsible for the enhancement in the PC activity. An alternate mechanism for enhanced visible-light photocatalytic activity was also considered.

  3. Photoinduced hydroxyl radical and photocatalytic activity of samarium-doped TiO(2) nanocrystalline.

    PubMed

    Xiao, Qi; Si, Zhichun; Zhang, Jiang; Xiao, Chong; Tan, Xiaoke

    2008-01-15

    Sm(3+)-doped TiO(2) nanocrystalline has been prepared by sol-gel auto-combustion technique and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and also UV-vis diffuse reflectance spectroscopy (DRS). These Sm(3+)-doped TiO(2) samples were tested for methylene blue (MB) decomposition and *OH radical formation. The analysis of *OH radical formation on the sample surface under UV irradiation was performed by fluorescence technique with using terephthalic acid, which readily reacted with *OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. It was observed that the presence of Sm(3+) ion as a dopant significantly enhanced the photocatalytic activity for MB degradation under UV light irradiation because both the larger specific surface area and the greater the formation rate of *OH radical were simultaneously obtained for Sm(3+)-doped TiO(2) nanocrystalline. The adsorption experimental demonstrated that Sm(3+)-TiO(2) had a higher MB adsorption capacity than undoped TiO(2) and the adsorption capacity of MB increased with the increase of samarium ion content. The results also indicated that the greater the formation rate of *OH radical was, the higher photocatalytic activity was achieved. In this study, the optimum amount of Sm(3+) doping was 0.5 mol%, at which the recombination of photo-induced electrons and holes could be effectively inhibited, the highest formation rate of *OH radicals was, and thereby the highest photocatalytic activity was achieved.

  4. Improvement of optical properties of TiO2 thin film treated with electron beam.

    PubMed

    Shin, Joong-Hyeok; Lee, Byung Cheol; Woo, Hee-Gweon; Hwang, Kwang Ha; Jun, Jin

    2013-03-01

    Nanocrystalline titanium dioxide (TiO2) thin films on silicon wafer substrates were prepared by sol-gel spin coating process. The prepared thin films were treated with electron beam (1.1 MeV, 300 kGy) at air atmosphere. The effects of electron-beam (EB) irradiation on the structural and optical properties of the TiO2 thin films were investigated. The structures of all the TiO2 thin films by XRD analysis showed an anatase phase, and the phase remained unchanged within the investigating range of EB treatment. The thickness of the titania thin film decreased slightly with EB treatment whereas the porosity increased. The EB treatment of TiO2 thin film can increase the proportion of Ti3+ in Ti2p at the thin film surface. The optical transmittance of the film in the wavelength ranges of above 380 nm increased after the EB treatment while its refractive index decreased with increasing EB dose. Therefore, improvement of the optical properties could be due to the change in both surface chemistry and morphology of the TiO2 thin films affected by EB irradiation.

  5. Synthesis and photocatalytic activities of Nd-doped TiO2 mesoporous microspheres

    NASA Astrophysics Data System (ADS)

    Liu, Xijian; Sun, Yangang; Wang, Yeying; Zhang, Lijuan; Lu, Jie

    2016-11-01

    Nd-doped TiO2 mesoporous microspheres with possessing regular micro/nanostructure were synthesized by a simple and facile method. The structure and optical properties of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption isotherms and UV-Visible absorbance spectroscopy. It was revealed that Nd-doped TiO2 mesoporous microspheres are composed of primary nanoparticles with a particle size of ˜25nm. The photocatalytic activities of all the samples were evaluated by degradation methyl orange (MO) in aqueous solution as a model reaction under xenon lamp light irradiation. The results showed that the doped samples demonstrated a higher photocatalytic activity than TiO2 mesoporous microspheres, and the MO of 10mg/mL almost could be completely degraded by the Nd-doped TiO2 mesoporous sample (the dosage of Nd salt to TiO2 is 6%) under xenon lamp light irradiation within 1h.

  6. A new role for Fe3+ in TiO2 hydrosol: accelerated photodegradation of dyes under visible light.

    PubMed

    Wang, Jingyu; Liu, Zhihong; Cai, Ruxiu

    2008-08-01

    The effect of Fe3+ on the photocatalytic activity of TiO2 hydrosol prepared through a low-temperature route has been investigated under visible light irradiation. The total reactive oxygen species (ROS) level and the accumulation of Fe2+ during the photodegradation process were detected to examine the role of Fe3+. In contrastto an aqueous TiO2 dispersion where Fe3+ strongly inhibited the photoactivity of TiO2 via suppressing the reduction of O2 and decreasing the production of ROS, Fe3+ accelerated the photodegradation of all dyes examined in the hydrosol through increasing the yield of oxidative ROS. The influence of the prebound hydroxyl groups on the surface of TiO2 was compared to that of free alcohols in aqueous solution, which revealed the cooperative function of the surface hydroxyl groups. The thoroughly contrary effect of Fe3+ on the photocatalysis of TiO2 hydrosol and TiO2 powder, which are all anatase nanocrystallites but are synthesized with different procedures, was ascribed to the complexation of the hydroxyl groups bound to TiO2 surface with Fe3+. The formation of such complexes has resulted in an altered electron-transfer pathway of the dye-sensitized photocatalysis under visible light irradiation.

  7. Photoassisted and photocatalytic degradation of sulfur mustard using TiO2 nanoparticles and polyoxometalates.

    PubMed

    Naseri, Mohammad Taghi; Sarabadani, Mansour; Ashrafi, Davood; Saeidian, Hamdollah; Babri, Mehran

    2013-02-01

    The decomposition of highly toxic chemical warfare agent, sulfur mustard (bis(2-chloroethyl) sulfide or HD), has been studied by homogeneous photolysis and heterogeneous photocatalytic degradation on titania nanoparticles. Direct photolysis degradation of HD with irradiation system was investigated. The photocatalytic degradation of HD was investigated in the presence of TiO(2) nanoparticles and polyoxometalates embedded in titania nanoparticles in liquid phase at room temperature (33 ± 2 °C). Degradation products during the treatment were identified by gas chromatography-mass spectrometry. Whereas apparent first-order kinetics of ultraviolet (UV) photolysis were slow (0.0091 min(-1)), the highest degradation rate is obtained in the presence of TiO(2) nanoparticles as nanophotocatalyst. Simultaneous photolysis and photocatalysis under the full UV radiation leads to HD complete destruction in 3 h. No degradation products observed in the presence of nanophotocatalyst without irradiation in 3 h. It was found that up to 90 % of agent was decomposed under of UV irradiation without TiO(2), in 6 h. The decontamination mechanisms are often quite complex and multiple mechanisms can be operable such as hydrolysis, oxidation, and elimination. By simultaneously carrying out photolysis and photocatalysis in hexane, we have succeeded in achieving faster HD decontamination after 90 min with low catalyst loading. TiO(2) nanoparticles proved to be a superior photocatalyst under UV irradiation for HD decontamination.

  8. A one-step process for the antimicrobial finishing of textiles with crystalline TiO2 nanoparticles.

    PubMed

    Perelshtein, Ilana; Applerot, Guy; Perkas, Nina; Grinblat, Judith; Gedanken, Aharon

    2012-04-10

    Titanium oxide (TiO(2)) nanoparticles (NPs) in their two forms, anatase and rutile, were synthesized and deposited onto the surface of cotton fabrics by using ultrasonic irradiation. The structure and morphology of the nanoparticles were analyzed by using characterization methods such as XRD, TEM, STEM, and EDS. The antimicrobial activities of the TiO(2)-cotton composites were tested against Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) strains, as well as against Candida albicans. Significant antimicrobial effect was observed, mainly against Staphylococcus aureus. In addition, the combination of visible light and TiO(2) NPs showed enhanced antimicrobial activity.

  9. Porous TiO2 Assembled from Monodispersed Nanoparticles.

    PubMed

    Liu, Xu; Duan, Weijie; Chen, Yan; Jiao, Shihui; Zhao, Yue; Kang, Yutang; Li, Lu; Fang, Zhenxing; Xu, Wei; Pang, Guangsheng

    2016-12-01

    Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending on the further treating temperature. Porous TiO2 nanospheres exhibited enhanced photocatalysis activity compared to the nanoparticles.

  10. Ordered Macro/Mesoporous TiO2 Hollow Microspheres with Highly Crystalline Thin Shells for High-Efficiency Photoconversion.

    PubMed

    Liu, Yong; Lan, Kun; Bagabas, Abdulaziz A; Zhang, Pengfei; Gao, Wenjun; Wang, Jingxiu; Sun, Zhenkun; Fan, Jianwei; Elzatahry, Ahmed A; Zhao, Dongyuan

    2016-02-17

    Well ordered, uniform 3D open macro/mesoporous TiO2 hollow microspheres with highly crystalline anatase thin shells have been successfully synthesized by a simple solvent evaporation-driven confined self-assembly method. The 3D open macro/mesoporous TiO2 hollow microspheres show high energy-conversion efficiency (up to 9.5%) and remarkable photocatalytic activity (with photodegradation of 100% for methylene blue in 12 min under UV light irradiation).

  11. A practical demonstration of water disinfection using TiO2 films and sunlight.

    PubMed

    Gelover, Silvia; Gómez, Luis A; Reyes, Karina; Teresa Leal, Ma

    2006-10-01

    The scope of this study is the assessment of the efficiency of solar disinfection by heterogeneous photocatalysis with sol-gel immobilized (titanium dioxide) TiO2 films over glass cylinders. The solar disinfection process known as SODIS was considered as a reference. Spring water naturally polluted with coliform bacteria was exposed to sunlight in plastic bottles with and without TiO2 over simple solar collectors and the disinfection effectiveness was measured. Total and fecal coliforms quantification was performed by means of the chromogenic substrate method in order to obtain the efficiency of each disinfection treatment. The disinfection with TiO2 was more efficient than the SODIS process, inactivating total coliforms as well as fecal coliforms. On a sunny day (more than 1000 W m(-2) irradiance), it took the disinfection with immobilized TiO2 15 min of irradiation to inactivate the fecal coliforms to make them undetectable. For inactivation of total coliforms, 30 min was required, so that in less than half the time it takes SODIS, the treated water complies with the microbial standards for drinking water in Mexico. Another important part of this study has been to determine the bacterial regrowth in water after the disinfection processes were tested. After SODIS, bacterial regrowth of coliforms was observed. In contrast, when using the TiO2 catalyst, coliforms regrowth was not detected, neither for total nor for fecal coliforms. The disinfection process using TiO2 kept treated water free of coliforms at least for seven days after sun irradiation. This demonstration opens the possibility of application of this simple method in rural areas of developing countries.

  12. A hybridization approach to efficient TiO2 photodegradation of aqueous benzalkonium chloride.

    PubMed

    Suchithra, Padmajan Sasikala; Carleer, Robert; Ananthakumar, Solaippan; Yperman, Jan

    2015-08-15

    TiO2 get positively charged upon UV-irradiation and repel the cationic pollutants away from the surface. Hybridization of AC onto TiO2 (ACT) tends catalyst surface negatively charged besides providing highly favorable adsorptions sites for cationic pollutants. The photodegradation of benzalkonium chloride (BKC), a quaternary ammonium surfactant and a pharmaceutical, is investigated with ACT. The surface charge of the catalyst in surfactant and non-surfactant aqueous dispersion under UV-irradiation is investigated and explained. The anomalous increase in COD values at the beginning of BKC-photodegradation is explained. The intermediate products formed are identified in both solution and solid phase. Trace amount of dodecane remained adsorbed on the catalyst surface after 1h UV-irradiation, but complete mineralization of BKC is achieved with 2h UV-irradiation. We propose that BKC photodegradation starts by central fission of benzyl CN bond followed by dealkylation, and demethylation steps.

  13. Highly efficient photoelectrocatalytic removal of RhB and Cr(VI) by Cu nanoparticles sensitized TiO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Zhong, J. S.; Wang, Q. Y.; Zhou, J.; Chen, D. Q.; Ji, Z. G.

    2016-03-01

    TiO2 nanotube arrays sensitized by copper nanoparticles (TiO2 NTs/Cu) exhibited highly efficient photoelectrocatalytic removal of RhB and Cr(VI). Vertically grown anatase TiO2 NTs on Ti substrates were prepared by electrochemical anodization followed by calcinations. Subsequently, Cu nanoparticles with uniform spherical structures and size distributions were deposited on TiO2 nanotubes by a modified hydrothermal reaction. By exploiting TiO2 NTs/Cu as both photoelectrodes and photocatalysts, high photocurrent density and photoelectrocatalytic removal efficiencies of RhB and Cr(VI) were achieved under solar light irradiation. The enhancement on the photoelectrochemical performance was explained by the optoelectronic coupling between Cu nanoparticles and TiO2 NTs, which accelerated the transfer rate of electrons, and subsequently decreased the electron/hole pair recombination.

  14. Effect of Cu2O morphology on photocatalytic hydrogen generation and chemical stability of TiO2/Cu2O composite.

    PubMed

    Zhu, Lihong; Zhang, Junying; Chen, Ziyu; Liu, Kejia; Gao, Hong

    2013-07-01

    Improving photocatalytic activity and stability of TiO2/Cu2O composite is a challenge in generating hydrogen from water. In this paper, the TiO2 film/Cu2O microgrid composite was prepared via a microsphere lithography technique, which possesses a remarkable performance of producing H2 under UV-vis light irradiation, in comparison with pure TiO2 film, Cu2O film and TiO2 film/Cu2O film. More interesting is that in TiO2 film/Cu2O microgrid, photo-corrosion of Cu2O can be retarded. After deposition of Pt on its surface, the photocatalytic activity of TiO2/Cu2O microgrid in producing H2 is improved greatly.

  15. Fabrication and characterization of CdS doped TiO2 nanotube composite and its photocatalytic activity for the degradation of methyl orange.

    PubMed

    Chung, Jinwook; Kim, Seu-Run; Kim, Jong-Oh

    2015-01-01

    CdS doped TiO2 nanotube composite was fabricated by chemical bath deposition, and was characterized by the structural, spectral and photoelectrochemical properties. The results of the structural and spectral properties showed that CdS particles were successfully deposited onto the surface of TiO2 nanotube. It is demonstrated that CdS doped TiO2 nanotube composite improved the light harvesting ability. Power conversion efficiency of about 0.32% was observed. This value is about 2.9 times higher than that of pure TiO2 nanotube. The CdS doped TiO2 nanotube composite possesses relatively higher photocatalytic activity and photodegradation efficiency than that of pure TiO2 nanotube under UV light irradiation, and the degradation efficiency of methyl orange was about 42% at UV intensity of 32 W.

  16. Quantitative evaluation of local pulmonary distribution of TiO2 in rats following single or multiple intratracheal administrations of TiO2 nanoparticles using X-ray fluorescence microscopy.

    PubMed

    Zhang, Guihua; Shinohara, Naohide; Kano, Hirokazu; Senoh, Hideki; Suzuki, Masaaki; Sasaki, Takeshi; Fukushima, Shoji; Gamo, Masashi

    2016-10-01

    Uneven pulmonary nanoparticle (NP) distribution has been described when using single-dose intratracheal administration tests. Multiple-dose intratracheal administrations with small quantities of NPs are expected to improve the unevenness of each dose. The differences in local pulmonary NP distribution (called microdistribution) between single- and multiple-dose administrations may cause differential pulmonary responses; however, this has not been evaluated. Here, we quantitatively evaluated the pulmonary microdistribution (per mesh: 100 μm × 100 μm) of TiO2 in lung sections from rats following one, two, three, or four doses of TiO2 NPs at a same total dosage of 10 mg kg(-1) using X-ray fluorescence microscopy. The results indicate that: (i) multiple-dose administrations show lower variations in TiO2 content (ng mesh(-1) ) for sections of each lobe; (ii) TiO2 appears to be deposited more in the right caudal and accessory lobes located downstream of the administration direction of NP suspensions, and less so in the right middle lobes, irrespective of the number of doses; (iii) there are not prominent differences in the pattern of pulmonary TiO2 microdistribution between rats following single and multiple doses of TiO2 NPs. Additionally, the estimation of pulmonary TiO2 deposition for multiple-dose administrations imply that every dose of TiO2 would be randomly deposited only in part of the fixed 30-50% of lung areas. The evidence suggests that multiple-dose administrations do not offer remarkable advantages over single-dose administration on the pulmonary NP microdistribution, although multiple-dose administrations may reduce variations in the TiO2 content for each lung lobe. Copyright © 2016 John Wiley & Sons, Ltd.

  17. Instability of Hydrogenated TiO2

    SciTech Connect

    Nandasiri, Manjula I.; Shutthanandan, V.; Manandhar, Sandeep; Schwarz, Ashleigh M.; Oxenford, Lucas S.; Kennedy, John V.; Thevuthasan, Suntharampillai; Henderson, Michael A.

    2015-11-06

    Hydrogenated TiO2 (H-TiO2) is toted as a viable visible light photocatalyst. We report a systematic study on the thermal stability of H-implanted TiO2 using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). Protons (40 keV) implanted at a ~2 atom % level within a ~120 nm wide profile of rutile TiO2(110) were situated ~300 nm below the surface. NRA revealed that this H-profile broadened preferentially toward the surface after annealing at 373 K, dissipated out of the crystal into vacuum at 473 K, and was absent within the beam sampling depth (~800 nm) at 523 K. Photoemission showed that the surface was reduced in concert with these changes. Similar anneals had no effect on pristine TiO2(110). The facile bulk diffusivity of H in rutile, as well as its activity toward interfacial reduction, significantly limits the utilization of H-TiO2 as a photocatalyst. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. The research was performed using the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

  18. Engineered nanoparticles of titanium dioxide (TIO2): Uptake and biological effects in a sea bass cell line.

    PubMed

    Picchietti, S; Bernini, C; Stocchi, V; Taddei, A R; Meschini, R; Fausto, A M; Rocco, L; Buonocore, F; Cervia, D; Scapigliati, G

    2017-02-01

    With the rapid development of nanotechnology there has been a corresponding increase in the application of titanium dioxide nanoparticles (TiO2-NPs) in various consumer and industrial products, consequently their potential health hazards and environmental effects are considered an aspect of great concern. In the present study, in order to assess the impact of TiO2-NPs in the marine environment, the biological effects of TiO2-NPs on a sea bass cell line (DLEC) were investigated. Cells were exposed for 24 h to different concentrations of TiO2-NPs (1, 8, 40, 200 and 1000 μg/ml) or co-exposed with CdCl2 (Cd). The effects of UV light irradiation were also investigated in cells treated with TiO2-NPs and/or Cd. The internalization of TiO2-NPs and the morphological cell modifications induced by the treatments were examined by transmission and scanning electron microscopy, this latter coupled with energy dispersive X-ray spectroscopy (EDS) for particle element detection. In addition, the effects of controlled exposures were studied evaluating the cytotoxicity, the DNA damage and the expression of inflammatory genes. Our study indicates that TiO2-NPs were localized on the cell surface mainly as agglomerates revealed by EDS analysis and that they were uptaken by the cells inducing morphological changes. Photoactivation of TiO2-NPs and/or co-exposure with Cd affects ATP levels and it contributes to induce acute cellular toxicity in DLEC cells dependent on Ti concentration. The inflammatory potential and the DNA damage, this latter displayed through a caspase-3 independent apoptotic process, were also demonstrated. Overall our data suggest that the interaction of TiO2-NPs with marine water contaminants, such as cadmium, and the UV irradiation, may be an additional threat to marine organisms.

  19. Ag-loaded TiO2/reduced graphene oxide nanocomposites for enhanced visible-light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Vasilaki, E.; Georgaki, I.; Vernardou, D.; Vamvakaki, M.; Katsarakis, N.

    2015-10-01

    In this work, Ag nanoparticles were loaded by chemical reduction onto TiO2 P25 under different loadings ranging from 1 up to 4 wt% and hydrothermally deposited on reduced graphene oxide sheets. Chemical reduction was determined to be an effective preparation approach for Ag attachment to titania, leading to the formation of small silver nanoparticles with an average diameter of 4.2 nm. The photocatalytic performance of the hybrid nanocomposite materials was evaluated via methylene blue (MB) dye removal under visible-light irradiation. The rate of dye decolorization was found to depend on the metal loading, showing an increase till a threshold value of 3 wt%, above which the rate drops. Next, the as prepared sample of TiO2/Ag of better photocatalytic response, i.e., at a 3 wt% loading value, was hydrothermally deposited on a platform of reduced graphene oxide (rGO) of tunable content (mass ratio). TiO2/Ag/rGO coupled nanocomposite presented significantly enhanced photocatalytic activity compared to the TiO2/Ag, TiO2/rGO composites and bare P25 titania semiconductor photocatalysts. In particular, after 45 min of irradiation almost complete decolorization of the dye was observed for the TiO2/Ag/rGO nanocatalyst, while the respective removal efficiency was 92% for TiO2/Ag, 93% for TiO2/rGO and only 80% for the bare TiO2 nanoparticles. This simple step by step preparation strategy allows for optimum exploitation of the advanced properties of metal plasmonic effect and reduced graphene oxide as the critical host for boosting the overall photocatalytic activity towards visible-light.

  20. Structure -- Magnetic Property Correlations in TiO 2 Nanotube Arrays

    NASA Astrophysics Data System (ADS)

    Mohammad Hosseinpour, Pegah

    TiO2 nanotube arrays are promising candidates for applications such as photocatalysis and for potential employment in spin-electronic (spintronic) devices. The functionality of TiO2-based nanotubes is highly dependent on their structure (microstructure and crystallographic symmetry) and magnetic properties. Unified understanding of the influence of these factors on the electronic structure of TiO2 is of paramount importance towards engineering these materials. This Dissertation aims at investigating the correlations of the morphology, crystallinity, crystal structure, electronic structure and magnetic properties of TiO2 nanotubes, with potential relevance to their functionality. Self-ordered arrays of amorphous TiO2 nanotubes (pure and Fe-doped with cationic concentration of ~2.1 at%) were synthesized by the electrochemical anodization technique, followed by subjecting them to thermal treatments up to 450 °C to crystallize these nanostructures. A variety of probes---morphological, structural, magnetic and spectroscopic---were used to characterize the properties of these nanostructures as functions of their processing conditions and the dopant content. Structure-functionality relationships in these nanostructures were verified by examining the photodegradation rate of methyl orange (a model water pollutant) in presence of TiO2 nanotubes under UV-Visible light irradiation. Results from this Dissertation research demonstrated that post-synthesis processing conditions---specifically, the nature of the annealing environment, as well as the presence of an external dopant, can alter the crystal structure and local electronic environment in TiO2 nanotubes, with subsequent effects on the magnetic properties of these nanostructures. The fundamental knowledge obtained in this research, on the interrelations of structural-magnetic properties and their potential influence on the functionality of TiO 2-based nanotubes, can be extended to the metal oxide semiconducting systems

  1. SALDI-TOF-MS analyses of small molecules (citric acid, dexasone, vitamins E and A) using TiO2 nanocrystals as substrates.

    PubMed

    Popović, Iva A; Nešić, Maja; Vranješ, Mila; Šaponjić, Zoran; Petković, Marijana

    2016-10-01

    Surface-assisted laser desorption/ionisation time-of-flight mass spectrometry (SALDI-TOF-MS) might be the method of choice for the analysis of low mass molecules (less than m/z 500). Titanium dioxide (TiO2) nanocrystals as a substrate for SALDI-TOF-MS improve the reproducibility of the signal intensities and prevent the fragmentation of some molecules upon laser irradiation, as we have previously shown. In addition, variously shaped and sized TiO2 nanocrystals/substrates for SALDI-MS could be used for quantification of small molecules, which are otherwise difficult to detect with the assistance of organic matrices. TiO2-assisted LDI-MS spectra could be acquired with excellent reproducibility and repeatability and with low detection limit. In the current study, we analysed the spectra of dexasone, citric acid, vitamin E and vitamin A acquired with TiO2 nanocrystals of various shapes and dimensions, i.e. the colloidal TiO2 nanoparticles (TiO2 NPs), TiO2 prolate nanospheroids (TiO2 PNSs) and TiO2 nanotubes (TiO2 NTs). Various shapes and dimensions of substrates were used since these factors determine desorption and ionisation processes. The homogeneity on the target plate was compared based on signal-to-noise values of peaks of interest of analysed molecules as well as the within-day and day-to-day repeatability. In summary, the obtained results show that the applicability of individual TiO2 nanocrystals depends on the analyte. Signals which are acquired with the assistance of TiO2 PNSs have the highest sensitivity and reproducibility (the smallest standard deviation), even compared with those in the LDI mode. This implies that TiO2 PNSs could also be suitable for quantitative analyses of small molecules.

  2. Preparation and antimicrobial assay of ceramic brackets coated with TiO2 thin films

    PubMed Central

    Cao, Shuai; Wang, Ye; Cao, Lin; Wang, Yu; Lin, Bingpeng; Lan, Wei

    2016-01-01

    Objective Different methods have been utilized to prevent enamel demineralization and other complications during orthodontic treatment. However, none of these methods can offer long-lasting and effective prevention of orthodontic complications or interventions after complications occur. Considering the photocatalytic effect of TiO2 on organic compounds, we hoped to synthesize a novel bracket with a TiO2 thin film to develop a photocatalytic antimicrobial effect. Methods The sol-gel dip coating method was used to prepare TiO2 thin films on ceramic bracket surfaces. Twenty groups of samples were composed according to the experimental parameters. Crystalline structure and surface morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively; film thickness was examined with a surface ellipsometer. The photocatalytic properties under ultraviolet (UV) light irradiation were analyzed by evaluating the degradation ratio of methylene blue (MB) at a certain time. Antibacterial activities of selected thin films were also tested against Lactobacillus acidophilus and Candida albicans. Results Films with 5 coating layers annealed at 700℃ showed the greatest photocatalytic activity in terms of MB decomposition under UV light irradiation. TiO2 thin films with 5 coating layers annealed at 700℃ exhibited the greatest antimicrobial activity under UV-A light irradiation. Conclusions These results provide promising guidance in prevention of demineralization by increasing antimicrobial activities of film coated brackets. PMID:27226960

  3. Application of the Stopped Flow Technique to the TiO₂-Heterogeneous Photocatalysis of Hexavalent Chromium in Aqueous Suspensions: Comparison with O₂ and H₂O₂ as Electron Acceptors.

    PubMed

    Meichtry, Jorge M; Dillert, Ralf; Bahnemann, Detlef W; Litter, Marta I

    2015-06-09

    The dynamics of the transfer of electrons stored in TiO2 nanoparticles to Cr(VI) in aqueous solution have been investigated using the stopped flow technique. TiO2 nanoparticles were previously irradiated under UV light in the presence of formic acid, and trapped electrons (e(trap)(-)) were made to react with Cr(VI) as acceptor species; other common acceptor species such as O2 and H2O2 were also tested. The temporal evolution of the number of trapped electrons was followed by the decrease in the absorbance at 600 nm, and the kinetics of the electron-transfer reaction was modeled. Additionally, the rate of formation of the surface complex between Cr(VI) and TiO2 was determined with the stopped flow technique by following the evolution of the absorbance at 400 nm of suspensions of nonirradiated TiO2 nanoparticles and Cr(VI) at different concentrations. An approximately quadratic relationship was observed between the maximum absorbance of the surface complex and the concentration of Cr(VI), suggesting that Cr(VI) adsorbs onto the TiO2 surface as dichromate. The kinetic analyses indicate that the electron transfer from TiO2 to Cr(VI) does not require the previous formation of the Cr(VI)-TiO2 surface complex, at least the complex detected here through the stopped flow experiments. When previously irradiated TiO2 was used to follow the evolution of the Cr(VI)-TiO2 complex, an inhibition of the formation of the complex was observed, which can be related to the TiO2 deactivation caused by Cr(III) deposition.

  4. Photocatalytic oxidation of organic dyes with visible-light-driven codoped TiO2 photocatalysts

    NASA Astrophysics Data System (ADS)

    Zhang, Dongfang; Zeng, Fanbin

    2011-06-01

    A novel copper (II) and zinc (II) codoped TiO2 photocatalyst was synthesized by a modified sol-gel method using titanium (IV) isopropoxide, Zn(NO3)2 · 6H2O and copper(Il) nitrate as precursors. The samples were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and photo-luminescence spectra (PL). The XRD results showed undoped and Zn, Cu-codoped TiO2 nanoparticles mainly including anatase phase and a tiny amount of Zn- and Cu-oxides exist in the mixed system, which is attributed to the decomposition of copper and zinc nitrates in the TiO2 gel to form CuO and ZnO and randomly dispersed on the TiO2 surface. On the basis of the optical characterization results, we found that the codoping of copper (II) and zinc (II) resulted a red shift of adsorption and lower recombination probability between electrons and holes, which were the reasons for high photocatalytic activity of Zn, Cu-codoped TiO2 nanoparticles under visible light (λ > 400 nm). The photocatalytic activity of samples was tested for degradation of methyl orange (MO) in solutions. The results indicated that the visible-light driven capability of the codoped catalyst were much higher than that of the pure TiO2 catalyst under visible irradiation. Because of the synergetic effect of copper (II) and zinc (II) element, the Zn, Cu-codoped TiO2 catalyst will show higher quantum yield and enhance absorption of visible light. In the end, a key mechanism was proposed in order to account for the enhanced activity.

  5. Enhanced photodegradation of methyl orange with TiO2 nanoparticles using a triboelectric nanogenerator

    NASA Astrophysics Data System (ADS)

    Su, Yuanjie; Yang, Ya; Zhang, Hulin; Xie, Yannan; Wu, Zhiming; Jiang, Yadong; Fukata, Naoki; Bando, Yoshio; Wang, Zhong Lin

    2013-07-01

    Methyl orange (MO) can be degraded by a photocatalytic process using TiO2 under UV irradiation. The photo-generated holes and electrons can migrate to the surface of TiO2 particles and serve as redox sources that react with adsorbed reactants, leading to the formation of superoxide radical anions, hydrogen peroxide and hydroxyl radicals involved in the oxidation of dye pollution. Here, we fabricated a polytetrafluoroethylene-Al based triboelectric nanogenerator (TENG) whose electric power output can be used for enhancing the photodegradation of MO with the presence of TiO2 nanoparticles, because the TENG generated electric field can effectively boost the separation and restrain the recombination of photo-generated electrons and holes. Due to the photoelectrical coupling, the degradation percentages of MO for 120 min with and without TENG assistance are 76% and 27%, respectively. The fabricated TENGs have potential applications in wastewater treatment, water splitting, and pollution degradation.

  6. Solvothermal synthesis of hierarchical TiO2 nanostructures with tunable morphology and enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Fan, Zhenghua; Meng, Fanming; Zhang, Miao; Wu, Zhenyu; Sun, Zhaoqi; Li, Aixia

    2016-01-01

    This paper presents controllable growth and photocatalytic activity of TiO2 hierarchical nanostructures by solvothermal method at different temperatures. It is revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) that the morphology of TiO2 can be effectively controlled as rose-like, chrysanthemum-like and sea-urchin-like only changing solvothermal temperature. BET surface area analysis confirms the presence of a mesoporous network in all the nanostructures, and shows high surface area at relatively high temperature. The photocatalytic activities of the photocatalysts are evaluated by the photodegradation of RhB under UV light irradiation. The TiO2 samples exhibit high activity on the photodegradation of RhB, which is higher than that of the commercial P25. The enhancement in photocatalytic performance can be attributed to the synergetic effect of the surface area, crystallinity, band gap and crystalline size.

  7. Ethanol photocatalysis on rutile TiO2(110): the role of defects and water

    PubMed Central

    Walenta, Constantin A.; Kollmannsberger, Sebastian L.; Kiermaier, Josef; Winbauer, Andreas; Tschurl, Martin

    2015-01-01

    In this work we present a stoichiometric reaction mechanism for the photocatalytic ethanol oxidation on TiO2(110). The reaction products are analyzed either under reaction conditions or after irradiation at lower temperatures. Water is identified as a quantitative by-product, which resides in a defect site. These water molecules cause a blocking of the defect sites which results in poisoning of the catalyst. By different preparation techniques of the TiO2(110) surface, the role of surface defects is further elucidated and the role of molecular oxygen is investigated. Based on the investigation, a complete photochemical reaction mechanism is given, which provides insights into general photon driven oxidation mechanisms on TiO2. PMID:26264863

  8. Oxygen release and structural changes in TiO2 films during photocatalytic oxidation

    NASA Astrophysics Data System (ADS)

    Yoshida, Kenta; Nanbara, Takahiro; Yamasaki, Jun; Tanaka, Nobuo

    2006-04-01

    Changes in the crystal structure and grain modifications in titanium oxide (TiO2) thin films were observed during the photocatalytic oxidation of hydrocarbons. When the hydrocarbon and collodion films were irradiated, single crystalline titanium oxide transformed into polycrystals. The titanium oxide films gradually became network aggregates. These changes were analyzed with a dedicated in situ transmission electron microscope and observed three dimensionally by electron tomography. A detailed analysis of electron energy loss spectra of the samples also revealed that the changes were associated with the loss of oxygen atoms in the TiO2 crystal lattice. Correlations between the polycrystalline grain size of TiO2 and its catalyst activity were discussed based on the measured data.

  9. C ion-implanted TiO2 thin film for photocatalytic applications

    NASA Astrophysics Data System (ADS)

    Impellizzeri, G.; Scuderi, V.; Romano, L.; Napolitani, E.; Sanz, R.; Carles, R.; Privitera, V.

    2015-03-01

    Third-generation TiO2 photocatalysts were prepared by implantation of C+ ions into 110 nm thick TiO2 films. An accurate structural investigation was performed by Rutherford backscattering spectrometry, secondary ion mass spectrometry, X-ray diffraction, Raman-luminescence spectroscopy, and UV/VIS optical characterization. The C doping locally modified the TiO2 pure films, lowering the band-gap energy from 3.3 eV to a value of 1.8 eV, making the material sensitive to visible light. The synthesized materials are photocatalytically active in the degradation of organic compounds in water under both UV and visible light irradiation, without the help of any additional thermal treatment. These results increase the understanding of the C-doped titanium dioxide, helpful for future environmental applications.

  10. Enhancement of stability of N-doped TiO2 photocatalysts with Ag loading

    NASA Astrophysics Data System (ADS)

    Gao, Yuanpeng; Fang, Pengfei; Chen, Feitai; Liu, Yang; Liu, Zhi; Wang, Dahai; Dai, Yiqun

    2013-01-01

    Various contents of Ag nanoparticles were successfully introduced into the N-doped TiO2 photocatalysts via a hydrothermal procedure in the silver-ammonia solutions with different Ag concentrations. Effects of Ag loading on the structure and properties of N-doped TiO2 photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, fluorescence spectroscopy (FL), UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and N2 physical adsorption analysis. The relationship between the stability of N dopants in TiO2 lattice and the Ag loading content was investigated for the first time. The results confirm that Ag nanoparticles loading on TiO2 surfaces significantly restrain the escape of the N dopants from the oxide during the hydrothermal process, and the escape rate of N dopants decreased gradually with the increase of Ag loading amount. The dependence of photocatalytic activity on Ag content was also investigated through degradation of rhodamine B (RhB) under visible light irradiation. It was found that the photocatalytic activity increases gradually with increasing Ag content first, and then decreases after exceeding the optimal Ag content. Therefore, the photocatalytic activity of Ag/N co-modified TiO2 photocatalysts can be adjusted by the Ag content.

  11. Size-dependent optical properties of TiO2 nanostructures

    NASA Astrophysics Data System (ADS)

    Solanki, Vanaraj; Majumder, Subrata; Mishra, Indrani; Joshi, Shalik R.; Kanjilal, Dinakar; Varma, Shikha

    2013-08-01

    The size-dependent optical properties of the nanostructures created on the TiO2(110) surfaces, via low-energy ion-beam sputtering technique, have been investigated here. The crystalline nanostructures have been produced in off-normal geometry. A significant enhancement in UV and visible light absorption has been observed for TiO2 surfaces patterned with nanostructures. Moreover, this enhancement depends on the sizes of the nanostructures. Preferential sputtering of oxygen atoms, during ion beam irradiation, leads to the presence of excess Ti on the surface. Ti-rich zones thus formed can promote nucleation of self-assembled nanostructures on the TiO2(110) surface. These results have been observed in the absence of any dopant. The formation of crystalline TiO2 nanostructures and the development of Ti-rich zones on the surface, after sputtering, are responsible for the enhancement in visible absorbance seen in the present study. Although small-sized (∼10 nm) nanostructures display increased absorbance and a higher bandgap, compared to bulk TiO2, due to quantum effects, much higher absorbance with decreased bandgap is observed from larger-(∼50 nm) sized nanostructures. This enhancement in absorbance is due to the presence of well-developed (200 and 310) crystalline faces in bigger nanostructures.

  12. Comparative study of TiO2 nanoparticles applied to dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Yacoubi, Besma; Bennaceur, Jamila; Ben Taieb, S.; Chtourou, Rathowan

    2014-02-01

    Microcrystalline titanium oxide (TiO2) particles of anatase crystal phase were prepared by the sol-gel route, varying thermal treatment conditions (400 °C and 600 °C), for a comparison purpose with commercial TiO2 (P25). Structural, optical and electrical properties were investigated for dye-sensitized solar cells (DSSCs) application. Both microcrystalline TiO2 particles, synthesized by the sol-gel method and obtained from the P25 powder were used to prepare a light scattering layer of the working electrode. The obtained electrodes were then immersed in a solution of N-719 (ruthenium) dye, at the ambient temperature, during 24 h. Finally, the DSSCs were assembled, the short circuit photocurrent, the open circuit photovoltage, and the power conversion efficiency were measured using an I-V measurement system. The overall conversion efficiencies for all elaborated DSSCs were proximate. A maximum efficiency of 2.3% was achieved for the sol-gel TiO2 thin film annealed at 400 °C, under one sun irradiation, with an open circuit voltage of 0.61 V and a current density of 6.54 mA/cm2. The higher efficiency value of the sol-gel TiO2 sample, annealed at 400 °C, was attributed to the uniformity of the prepared titanium oxide substrate, which provides a better surface for the dye absorption.

  13. Photocatalytic removal of hexavalent chromium by newly designed and highly reductive TiO2 nanocrystals.

    PubMed

    Chen, Gongde; Feng, Ji; Wang, Wenshou; Yin, Yadong; Liu, Haizhou

    2017-01-01

    Hexavalent chromium Cr(VI), a highly toxic oxyanion, widely occurs in drinking water supplies. This study designed and synthesized a new type of highly reductive TiO2 nanocrystals for photochemical Cr(VI) removal, via the thermal hydrolysis of TiCl4 in the presence of diethylene glycol (DEG). Surface analyses and hydroxyl radical measurements suggested that DEG was chemically bonded on TiO2 surface that resulted in an internal hole-scavenging effect and a high electron-releasing capacity, making it advantageous to conventional TiO2 materials. Upon UV irradiation, the synthesized TiO2 photocatalyst exhibited fast Cr(VI) reduction kinetics in diverse water chemical conditions. Fast elimination of Cr(VI) was achieved on a time scale of seconds in drinking water matrices. The removal of Cr(VI) by reductive TiO2 exhibited a three-stage kinetic behavior: an initial fast-reaction phase, a lag phase resulting from surface precipitation of Cr(OH)3(s), and a final reaction phase due to surface regeneration from oxidation-reduction induced ripening process. The lag phase disappeared in acidic conditions that prevented the formation of Cr(OH)3(s). The catalyst exhibited extremely high electron-releasing capacity that can be reused for multiple cycles of Cr(VI) removal in drinking water treatment.

  14. Visible light active photocatalytic degradation of bisphenol-A using nitrogen doped TiO2.

    PubMed

    Venkatachalam, N; Vinu, A; Anandan, S; Arabindoo, Banumathi; Murugesan, V

    2006-08-01

    Nitrogen doped titania was prepared by low temperature sol-gel method using titanium precursor and nitrogen containing bases like triethylamine and tetramethyl ammonium hydroxide compounds. The materials were characterized by XRD, BET, SEM, XPS, DRS-UV, and FT-IR techniques. DRS-UV study substantially indicates shift of the absorption edge of TiO2 to lower energy region. The phase composition, crystallinity, specific surface area, and visible light activity of nitrogen doped titania depend upon the preparation conditions. Photocatalytic degradation of bisphenol-A in aqueous medium was investigated by TiO2 and nitrogen doped TiO2 under visible light irradiation in a batch photocatalytic reactor. The results indicate higher visible light activity for nitrogen doped TiO2 than commercial TiO2 (Degussa P25) for bisphenol-A degradation. The influence of various parameters such as initial concentration of bisphenol-A, catalyst loading and pH was examined for maximum degradation efficiency.

  15. Controllable synthesis of TiO2 nanoflowers and their morphology-dependent photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Ni, Jinbo; Gao, Juan; Geng, Xianya; He, Dandan; Guo, Xiaoning

    2017-03-01

    Different surface morphologies of TiO2 films were prepared through hydrothermal synthesis method on transparent fluorine-doped tin oxide (FTO) substrates by changing reaction temperatures. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray photoelectron spectrometer (XPS). As the hydrothermal temperatures increases, the surface morphologies of the TiO2 changes from nanorods (150 °C) to nanobuds (180 °C), and finally to nanoflowers (210 °C). Evolution of these structures are accompanied by great variations of optical properties and photocatalytic activities including a narrowing of band gap from 3.01 to 2.97 eV, increase of UV-visible absorption intensity and specific surface area, and photocatalytic degradation efficiencies from 88.18 to 95.56%. Under ultraviolet light (UV light) irradiation, the TiO2 nanoflowers exhibit significantly activity (95.56%) in degradation of methyl orange (MO) compared to commercial P25 (76.15%). The outstanding photocatalytic activity of the TiO2 nanoflowers can be attributed to the synergetic effect of much larger specific surface area, the larger content of oxygen vacancy, and higher intensity of absorption. These findings help to grow unique TiO2 films with desired structure and activities for photocatalyst applications.

  16. Plasmonic Effect in Au-Added TiO2-Based Solar Cell

    NASA Astrophysics Data System (ADS)

    Van Hong, Le; Cat, Do Tran; Chi, Le Ha; Thuy, Nguyen Thi; Van Hung, Tran; Tai, Ly Ngoc; Long, Pham Duy

    2016-10-01

    TiO2 nano thin films have been fabricated on fluoride tin oxide (FTO) film electrodes by hydrothermal synthesis at temperatures of 80°C, 120°C, 150°C, and 200°C for different synthesis times of 1 h, 2 h, and 3 h in 2.5 mol, 5 mol, and 7.5 mol NaOH solution. X-ray diffraction patterns and field-emission scanning electron microscopy (FESEM) images were recorded for all the film samples, and the results confirmed that TiO2 anatase phase was generally formed in nanowire form. The influence of synthesis temperature, processing time, and NaOH content on the structure and morphology of the TiO2 material was studied. Au nanoparticles with size of around 2 × 10-8 m were added into the TiO2 thin films by thermal evaporation in vacuum combined with thermal annealing. Based on photocurrent-voltage ( I- V) characteristics measured under irradiation with visible light, the short-circuit current, open-circuit voltage, and efficiency of solar cells with FTO/Au-added TiO2/(I-/I2-) electrolyte/Pt configuration were evaluated. The short-circuit current and efficiency of the Au-added solar cell were greatly improved, which is supposed to be related to a contribution of the surface plasmon resonance effect.

  17. Both enhanced biocompatibility and antibacterial activity in Ag-decorated TiO2 nanotubes.

    PubMed

    Lan, Ming-Ying; Liu, Chia-Pei; Huang, Her-Hsiung; Lee, Sheng-Wei

    2013-01-01

    In this study, Ag is electron-beam evaporated to modify the topography of anodic TiO2 nanotubes of different diameters to obtain an implant with enhanced antibacterial activity and biocompatibility. We found that highly hydrophilic as-grown TiO2 nanotubes became poorly hydrophilic with Ag incorporation; however they could effectively recover their wettability to some extent under ultraviolet light irradiation. The results obtained from antibacterial tests suggested that the Ag-decorated TiO2 nanotubes could greatly inhibit the growth of Staphylococcus aureus. In vitro biocompatibility evaluation indicated that fibroblast cells exhibited an obvious diameter-dependent behavior on both as-grown and Ag-decorated TiO2 nanotubes. Most importantly, of all samples, the smallest diameter (25-nm-diameter) Ag-decorated nanotubes exhibited the most obvious biological activity in promoting adhesion and proliferation of human fibroblasts, and this activity could be attributed to the highly irregular topography on a nanometric scale of the Ag-decorated nanotube surface. These experimental results demonstrate that by properly controlling the structural parameters of Ag-decorated TiO2 nanotubes, an implant surface can be produced that enhances biocompatibility and simultaneously boosts antibacterial activity.

  18. Synthesis of Structured Macroporous TiO2 Thin Films and Investigation on Their Photocatalytic Activities

    NASA Astrophysics Data System (ADS)

    Kamegawa, Takashi; Suzuki, Norihiko; Yamashita, Hiromi

    2011-10-01

    Synthesis of structured macroporous TiO2 thin films on quartz substrate (macro-TiO2/Q) was performed by a dip-coating method using poly(methyl methacrylate) (PMMA) microspheres as template. Obtained TiO2 thin films kept high transparency and had anatase crystalline structure. SEM observations revealed that the macropores were uniformly formed on the film surface. The size of macropores was quite similar to the diameter of PMMA microspheres as template. In comparison to the nonporous TiO2 thin films (TiO2/Q), macro-TiO2/Q exhibited twice higher photocatalytic activity for decolorization of methylene blue in water. Decomposition of acetaldehyde in gas phase also proceeded efficiently on macro-TiO2/Q. Moreover, the surface of macro-TiO2/Q was easily hydrophilized after a short period of UV light irradiation and maintained lower water contact angle in the dark for a long period as compared to those of TiO2/Q.

  19. Photoinactivation and Toxicity of Nano-sized TiO2 on Paint Microflora Using Visible Lights

    NASA Astrophysics Data System (ADS)

    Obidi, Olayide; Halverson, Larry

    2016-04-01

    Traditional TiO2 has been used as an antimicrobial additive to paints, but more recently the use of TiO2 nanoparticles (NPs) has been proposed as an alternative because of its ability to induce oxidative damage to the cell membrane of bacteria. This study focused on how photoinactivation of TiO2 NPs by fluorescent and halogen lights (400-700 nm) influenced survival of Bacillus sphaericus (Gram-positive bacterium) and Klebsiella pneumoniae (Gram-negative bacterium) isolated from spoiled paints. The loss of viability of the test organisms in the presence of TiO2 NPs determined by culturable (plate) count technique indicated a decrease in viable bacteria that was predominant after 24-h exposure. The TiO2 NPs showed higher antibacterial performance under fluorescent light than halogen light with increasing irradiation time and confirms the photokilling effect of TiO2 NPs. TiO2 NPs were also bactericidal under dark conditions, suggesting potential antibacterial applications in the paint industry.

  20. Radiation-induced catalytic degradation of p-nitrophenol (PNP) in the presence of TiO 2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Shaoqing, Yu; Jun, Hu; Jianlong, Wang

    2010-10-01

    The gamma radiation induced catalytic degradation of p-nitrophenol (PNP) in the presence of titanium dioxide (TiO 2) nanoparticles in aqueous solution was investigated. The initial concentration of PNP solution was 50 mg/L, and the additional TiO 2 doses were 0, 0.5, 1.0, and 2.0 g/L. The experimental results indicated that the PNP decomposition kinetics conformed to the modified pseudo-first order reaction equation under all applied conditions. When the TiO 2 dose was in the range of 0-2.0 g/L, the effect of additional TiO 2 on PNP decomposition rate was not obvious because PNP could be removed quite well by irradiation even in the absence of TiO 2 nanoparticles; however, the removal of total organic carbon (TOC) and total nitrogen (TN) was significantly accelerated in the presence of TiO 2 nanoparticles, the TOC removal efficiency increased from about 16% to 42%, and therefore the mineralization of PNP could be enhanced by TiO 2 nanoparticles. The inorganic nitrogen products were quantitatively measured to estimate the decomposition degree of PNP. The major aromatic intermediates, as well as carboxylic acids were identified by LCMS and IC. Possible reactions involved in radiation induced catalytic decomposition of PNP in aqueous solutions were proposed.

  1. A facile in-situ hydrothermal synthesis of SrTiO3/TiO2 microsphere composite

    NASA Astrophysics Data System (ADS)

    Wang, Hongxing; Zhao, Wei; Zhang, Yubo; Zhang, Shimeng; Wang, Zihao; Zhao, Dan

    2016-06-01

    TiO2 was successfully used as sacrificed template to synthesise SrTiO3/TiO2 microsphere composite via an in-situ hydrothermal process. The diameter of SrTiO3/TiO2 microsphere was about 700 nm with the same size of the template, and all of the microspheres were in good dispersity. The optimized reaction parameters for the phase and morphology of the as-synthesized samples were investigated. The results showed the SrTiO3/TiO2 microsphere can be synthesized at 170 °C when the concentration of sodium hydroxide was 0.1 M. Lower hydrothermal temperature hampered the formation of the SrTiO3/TiO2 composite, the higher alkali concentration, however, will destroy the morphology of products. The formation mechanism of SrTiO3/TiO2 microsphere composite was proposed and the photocatalytic properties of the samples were characterized using methylene blue solution as the pollutant under the UV light irradiation. The results indicated the proper OH- concentration will provide a channel for Sr2+ to react with Ti4+ located in the template and form the SrTiO3/TiO2 composite, and those with micro-scaled spherical morphology exhibited good photocatalytic activities.

  2. TiO2 nanofibers coated with rGO and Ag2O for promoting visible light photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Zhou, Yun; Wang, Yuan; OuYang, Xiaoping; Liu, Lixin; Zhu, Wenjun

    2017-03-01

    Due to the increase in environmental pollution, highly efficient photocatalysts with enhanced visible light photocatalytic activity have attracted considerable attention. In this work, TiO2/reduced graphene oxide (rGO)/Ag2O nanoheterostructures (NHs) based photocatalysts are successfully synthesized and a markedly higher visible light photocatalytic activity is achieved, of which at least 96% of Rhodamine B (RhB) molecules are decomposed by the TiO2/rGO/Ag2O NHs after 120 min visible light irradiation, but only 30% of RhB molecules are decomposed by pure TiO2 nanofibers (NFs). Furthermore, the influence of rGO volume ratio in TiO2/rGO/Ag2O NHs photocatalysts on visible light photocatalysis is studied, and the result shows that the sample with 5 vol% rGO exhibits the highest visible light photocatalytic activity. The much enhanced visible light photocatalytic performance of the ternary TiO2/rGO/Ag2O NHs can be ascribed to the intense visible light absorption of Ag2O, the excellent electron conductivity of 2D rGO and the matched energy level of TiO2, Ag2O, and rGO, for efficient boost of the photogenerated charge carriers transfer and separation at the interface of hierarchical TiO2/rGO/Ag2O NHs.

  3. Facile hydrothermal synthesis of TiO2-Bi2WO6 hollow superstructures with excellent photocatalysis and recycle properties.

    PubMed

    Hou, Ya-Fei; Liu, Shu-Juan; Zhang, Jing-huai; Cheng, Xiao; Wang, You

    2014-01-21

    One-dimensional mesoporous TiO2-Bi2WO6 hollow superstructures are prepared using a hydrothermal method and their photocatalysis and recycle properties are investigated. Experimental results indicate that anatase TiO2 nanoparticles are coupled with hierarchical Bi2WO6 hollow tubes on their surfaces. The TiO2-Bi2WO6 structure has a mesoporous wall and the pores in the wall are on average 21 nm. The hierarchical TiO2-Bi2WO6 heterostructures exhibit the highest photocatalytic activity in comparison with P25, pure Bi2WO6 hollow tube and mechanical mixture of Bi2WO6 tube and TiO2 nanoparticle in the degradation of rhodamine B (RhB) under simulated sunlight irradiation. The as-prepared TiO2-Bi2WO6 heterostructures can be easily recycled through sedimentation and they retains their high photocatalytic activity during the cycling use in the simulated sunlight-driving photodegradation process of RhB. The prepared mesoporous TiO2-Bi2WO6 with hollow superstructure is therefore a promising candidate material for water decontamination use.

  4. Self-cleaning cotton functionalized with TiO2/SiO2: focus on the role of silica.

    PubMed

    Pakdel, Esfandiar; Daoud, Walid A

    2013-07-01

    This manuscript aims to investigate the functionalization of cotton fabrics with TiO2/SiO2. In this study, the sol-gel method was employed to prepare titania and silica sols and the functionalization was carried out using the dip-pad-dry-cure process. Titanium tetra isopropoxide (TTIP) and tetra ethyl orthosilicate (TEOS) were utilized as precursors of TiO2 and SiO2, respectively. TiO2/SiO2 composite sols were prepared in three different Ti:Si molar ratios of 1:0.43, 1:1, and 1:2.33. The self-cleaning property of cotton samples functionalized with TiO2/SiO2 was assessed based on the coffee stain removal capability and the decomposition rate of methylene blue under UV irradiation. FTIR study of the TiO2/SiO2 photocatalyst confirmed the existence of Si-O-Si and Ti-O-Si bonds. Scanning electron microscopy was employed to investigate the morphology of the functionalized cotton samples. The samples coated with TiO2/SiO2 showed greater ability of coffee stain removal and methylene blue degradation compared with samples functionalized with TiO2 demonstrating improved self-cleaning properties. The role of SiO2 in improving these properties is also discussed.

  5. TiO2-graphene composites with exposed {001} facets produced by a one-pot solvothermal approach for high performance photocatalyst.

    PubMed

    Lu, Tiewen; Zhang, Rongbin; Hu, Changyuan; Chen, Fei; Duo, Shuwang; Hu, Quanhong

    2013-08-21

    TiO2-graphene (TOG) composites with exposed TiO2 {001} facets were prepared by a solvothermal approach without any addition of surfactants or capping agents, only using titanium isopropoxide and graphene oxide ethanol suspension as the precursors. Graphene was covered uniformly and densely with anatase TiO2 nanoparticles, exposing the {001} facets. The X-ray photoelectron spectroscopy, photoluminescence spectroscopy and photocurrent measurements show the presence of electron transfer between TiO2 and graphene. The electron transfer between TiO2 and graphene will greatly retard the recombination of photoinduced charge carriers and prolong electron lifetime, which will contribute to the enhancement of photocatalytic performance. Accordingly, the TOG composites show high photocatalytic activity of methyl orange under UV light, likely due to the effective separation of photoinduced charge, exposure of highly reactive {001} facets and great adsorptivity of dyes.

  6. The Influence of TiO2 Nanoparticles on LaFeO3/TiO2 Nanocomposites for Reduction of Aqueous Organic Dyes

    NASA Astrophysics Data System (ADS)

    Afifah, N.; Saleh, R.

    2016-11-01

    A series of Lanthanum ferrite (LaFeO3) nanoparticles over titanium dioxide (TiO2) were synthesized using sol-gel method at room temperature by varying the loading of LaFeO3 on TiO2. The magnetic properties of samples were measured using vibrating sample magnetometer and photosonocatalytic activity towards the degradation of methylene blue under light (UV or visible) and ultrasound irradiation was also evaluated. The morphology and structure of the samples were characterized by field emission scanning electron microscope, energy dispersive analysis and X-ray diffraction. Furthermore the optical properties were also characterized by UV-visible diffuse reflectance. The experimental results showed that the prepared perovskites had sphere-like shape and strong visible light absorption. LaFeO3 demonstrated ferromagnetic properties and the magnetization decreased with the incorporation of TiO2 in the samples. However, the incorporation of TiO2 increased the photosonocatalytic activity and extended the photoresponding to UV light.

  7. Tuning of optical and dielectric properties of nanoscale TiO2 using swift heavy ions

    NASA Astrophysics Data System (ADS)

    Trivedi, Sinny J.; Khan, S. A.; Joshi, U. S.

    2013-08-01

    We have investigated the influence of swift heavy ion (SHI) irradiation on the optical and dielectric properties of TiO2 thin films. Films with thickness of 80-100 nm were prepared by spin coating of sol precursor onto quartz substrates and were irradiated by 100 MeV Ag7+ ions at different fluences. The pristine sample was crystallized into single TiO2 anatase phase, exhibiting better than 80% transparency in the visible region. The optical absorption edge was found to decrease with the SHI fluence. The general behavior of the dielectric constant was found to obey Drude's theory. The effect of the SHI irradiation and fluence dependence on several optical parameters such as extinction coefficient, real and imaginary parts of dielectric constants, dispersive energy and packing density has been studied.

  8. Efficiency of Photocarrier Injection in a VO2/TiO2:Nb Heterostructure

    NASA Astrophysics Data System (ADS)

    Hiroi, Zenji; Yamauchi, Tohru; Muraoka, Yuji; Muramatsu, Takaki; Yamaura, Jun-Ichi

    2003-12-01

    The efficiency of photocarrier injection in a VO2/TiO2:Nb heterostructure is studied by measuring I-V characteristics at room temperature under ultraviolet light irradiation. It is revealed that photogenerated hole carriers in the TiO2:Nb substrate are injected and accumulated in the VO2 film by the photovoltaic effect. The surface charge density is controlled successfully in a wide range of 109-1013 cm-2 as a function of light irradiance. The maximum hole density of 9× 1018 cm-3 is attained at a light irradiance of 133 mW/cm2, which is estimated by assuming the uniform distribution of holes in the film. It is suggested that high efficiency can be achieved by utilizing the large dielectric constant of titanium oxide substrates.

  9. Optical and structural changes of TiO2/PVA nanocomposite induced laser Radiation

    NASA Astrophysics Data System (ADS)

    Shehap, A. M.; Elsayed, Khaled. A.; Akil, Dana S.

    2017-02-01

    The laser irradiation effect of on the structural and optical properties of TiO2/PVA nanocomposite at different loading of TiO2 nanoparticles as (1.25%, 2.5%, 5%, 7.5%, 10% TiO2 /PVA) was investigated. Two different types of laser sources were used Nd: YAG laser (at 266 nm) and Nitrogen laser at (337 nm). The XRD, FTIR and UV-Visible are used to reveal the structural changes and the optical parameters of the composites due to the laser irradiation. Changes of the crystalinity of the composites films were observed by XRD, where the Nd: YAG laser developed a decrease in the crystalinity of all the investigated samples, while the Nitrogen laser developed an increase of the crystalinity. IR spectroscopy showed strong reduction of -OH group as a result of both lasers. It also shows an increase in the intensity of the vibration modes at 1720 cm-1 corresponding to carbonyl formation due to the effect of Nd: YAG laser irradiation only. The intensity of the C-C bond increases after Nitrogen laser irradiation indicating the increase of crystalinity of the composites films. UV-Vis spectra indicates the photothermal effect of Nitrogen laser and the photochemical effect of Nd: YAG laser. The optical constant of the all composites samples have been calculated before and after irradiation with both two types of laser sources which coincide with the results obtained from XRD and IR studies.

  10. Carbon Single Walled Nanotubes- Electron Acceptor Molecules for Improving the Efficiency of the Photoexcitation of TiO2 for Solar-Driven Technologies

    DTIC Science & Technology

    2012-10-16

    Single walled nanotubes ( SWNTs ) are shown to be electron acceptor molecules. The PL was used to observe the buildup during UV irradiation of surface...surface. Single walled nanotubes ( SWNTs ) are shown to be electron acceptor molecules. The PL was used to observe the buildup during UV irradiation of...the TiO2 bed and through the bed containing SWNT linkers. It was found that while SWNTs are good acceptors, no added conductivity from isolated TiO2

  11. Modified microwave method for the synthesis of visible light-responsive TiO2/MWCNTs nanocatalysts.

    PubMed

    Alosfur, Firas K Mohamad; Jumali, Mohammad Hafizuddin Haji; Radiman, Shahidan; Ridha, Noor J; Yarmo, Mohd Ambar; Umar, Akrajas Ali

    2013-08-06

    Recently, TiO2/multi-walled carbon nanotube (MWCNT) hybrid nanocatalysts have been a subject of high interest due to their excellent structures, large surface areas and peculiar optical properties, which enhance their photocatalytic performance. In this work, a modified microwave technique was used to rapidly synthesise a TiO2/MWCNT nanocatalyst with a large surface area. X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller measurements were used to characterise the structure, morphology and the surface area of the sample. The photocatalytic activity of the hybrid nanocatalysts was evaluated through a comparison of the degradation of methylene blue dye under irradiation with ultraviolet and visible light. The results showed that the TiO2/MWCNT hybrid nanocatalysts degraded 34.9% of the methylene blue (MB) under irradiation with ultraviolet light, whereas 96.3% of the MB was degraded under irradiation with visible light.

  12. Modified microwave method for the synthesis of visible light-responsive TiO2/MWCNTs nanocatalysts

    PubMed Central

    2013-01-01

    Recently, TiO2/multi-walled carbon nanotube (MWCNT) hybrid nanocatalysts have been a subject of high interest due to their excellent structures, large surface areas and peculiar optical properties, which enhance their photocatalytic performance. In this work, a modified microwave technique was used to rapidly synthesise a TiO2/MWCNT nanocatalyst with a large surface area. X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller measurements were used to characterise the structure, morphology and the surface area of the sample. The photocatalytic activity of the hybrid nanocatalysts was evaluated through a comparison of the degradation of methylene blue dye under irradiation with ultraviolet and visible light. The results showed that the TiO2/MWCNT hybrid nanocatalysts degraded 34.9% of the methylene blue (MB) under irradiation with ultraviolet light, whereas 96.3% of the MB was degraded under irradiation with visible light. PMID:23919496

  13. Electrorheological behaviour under oscillatory shear of TiO2 rod-like particles prepared via microwave-assisted molten-salt synthesis

    NASA Astrophysics Data System (ADS)

    Sedlacik, M.; Mrlik, M.; Pavlinek, V.; Kozakova, Z.; Saha, P.

    2013-02-01

    Titanium dioxide (TiO2) rod-like particles were synthesized by a simple and rapid microwave-assisted molten-salt method. The X-ray diffraction analysis and electron microscopy provided information on particle composition and morphology, respectively. It was found that during the synthesis process the crystalline phase of TiO2 transformed from anatase into rutile while the morphology changed from nanospheres into micrometer sized rod-like particles. The electrorheological (ER) properties were investigated via oscillatory shear tests. It was found that TiO2 rod-like particles based silicone oil suspensions exhibited higher ER activity than those of original anatase TiO2 nanoparticles probably due to side-by-side solid friction between particles as well as shorter time of their polarization. The changes in ER properties of rod-like particle based suspensions as a function of the applied electric field strength and particles weight fraction were also investigated.

  14. Visible light photocatalytic degradation of 4-chlorophenol using vanadium and nitrogen co-doped TiO2

    NASA Astrophysics Data System (ADS)

    Jaiswal, R.; Patel, N.; Kothari, D. C.; Miotello, A.

    2013-02-01

    Vanadium and Nitrogen were codoped in TiO2 photocatalyst by Sol-gel method to utilize visible light more efficiently for photocatalytic reactions. A noticeable shift of absorption edge to visible light region was obtained for the singly-doped namely V-TiO2, N-TiO2 and codoped V-N-TiO2 samples in comparison with undoped TiO2, with smallest band gap obtained with codoped-TiO2. The photocatalytic activities for all TiO2 photocatalysts were tested by 4-chlorophenol (organic pollutant) degradation under visible light irradiation. It was found that codoped TiO2 exhibits the best photocatalytic activity, which could be attributed to the synergistic effect produced by V and N dopants.

  15. Synthesis and photocatalytic activity of N-doped TiO2 produced in a solid phase reaction

    NASA Astrophysics Data System (ADS)

    Xin, Gang; Pan, Hongfei; Chen, Dan; Zhang, Zhihua; Wen, Bin

    2013-02-01

    N-doped TiO2 was synthesized by calcining a mixture of titanic acid and graphitic carbon nitride (g-C3N4) at temperatures above 500 °C. The final samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and UV-vis diffuse reflectance spectra. The photocatalytic activity of N-doped TiO2 was studied by assessing the degradation of methylene blue in an aqueous solution, under visible light and UV light irradiation. It was found that the N-doped TiO2 displayed higher photocatalytic activity than pure TiO2, under both visible and UV light.

  16. Phosphorus-doped TiO2 catalysts with stable anatase-brookite biphase structure: synthesis and photocatalytic performance.

    PubMed

    Feng, Huajun; Zhang, Min-Hong; Yu, Liya E

    2013-07-01

    Phosphorus-doped (P-doped) TiO2 catalysts with a stable anatase-brookite biphase structure were successfully synthesized by integrating ultrasonication with phosphorus doping and Pluronic P123 surfactant. The synthesized catalysts were characterized using X-ray diffraction, transmission electron microscopy, nitrogen adsorption-desorption, Fourier transform infrared, and UV-visible diffuse reflectance spectra. Ultrasonication facilitates the appearance of brookite phase. Phosphorus doping was demonstrated an effective strategy to stabilize the anatase-brookite biphase structure and inhibits undesirable grain growth. Triblock copolymer Pluronic P123 used in the reaction facilitates the formation of catalyst particles with mesoporous structure and large surface area and prevents particles from agglomeration. The low band-gap of brookite phase enables the synthesized P-doped TiO2 catalysts outperform commercial P25 TiO2 and N-doped TiO2 in the degradation of methylene blue under both solar light and visible light irradiation.

  17. Pt deposited TiO2 catalyst fabricated by thermal decomposition of titanium complex for solar hydrogen production

    NASA Astrophysics Data System (ADS)

    Truong, Quang Duc; Le, Thanh Son; Ling, Yong-Chien

    2014-12-01

    C, N codoped TiO2 catalyst has been synthesized by thermal decomposition of a novel water-soluble titanium complex. The structure, morphology, and optical properties of the synthesized TiO2 catalyst were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity of the Pt deposited TiO2 catalysts synthesized at different temperatures was evaluated by means of hydrogen evolution reaction under both UV-vis and visible light irradiation. The investigation results reveal that the photocatalytic H2 evolution rate strongly depended on the crystalline grain size as well as specific surface area of the synthesized catalyst. Our studies successfully demonstrate a simple method for the synthesis of visible-light responsive Pt deposited TiO2 catalyst for solar hydrogen production.

  18. Increased photocatalytic activity of TiO2 mesoporous microspheres from codoping with transition metals and nitrogen

    DOE PAGES

    Mathis, John E.; Lieffers, Justin J.; Mitra, Chandrima; ...

    2015-11-06

    The composition of anatase TiO2 was modified by codoping using combinations of a transition metal and nitrogen in order to increase its photocatalytic activity and extend it performance in the visible region of the electromagnetic spectrum. The transition metals (Mn, Co, Ni, Cu) were added during the hydrothermal preparation of mesoporous TiO2 particles, and the nitrogen was introduced by post-annealing in flowing ammonia gas at high temperature. The samples were analyzed by SEM, XRD, BET, inductively-coupled plasma spectroscopy, and diffuse reflectance UV-vis spectroscopy. The photocatalytic activity was assessed by observing the change in methylene blue concentrations under both UV-vis andmore » visible-only light irradiation. As a result, the photocatalytic activity of the (Mn,N), (Co,N), (Cu,N), and Ni,N) codoped TiO2 was significantly enhanced relative to (N) TiO2.« less

  19. Ultrasound aided photochemical synthesis of Ag loaded TiO2 nanotube arrays to enhance photocatalytic activity.

    PubMed

    Sun, Lan; Li, Jing; Wang, Chenglin; Li, Sifang; Lai, Yuekun; Chen, Hongbo; Lin, Changjian

    2009-11-15

    This work presents a novel approach for preparing TiO(2) nanotube array photocatalyst loaded with highly dispersed Ag nanoparticles through an ultrasound aided photochemical route. The Ag content loaded on the array was controlled by changing the concentration of AgNO(3) solution. The Ag-TiO(2) nanotube arrays were characterized by SEM, XRD, XPS and UV-vis absorption. The effects of Ag content on the photoelectrochemical (PEC) property and photocatalytic activity of TiO(2) nanotube array electrode were studied. The results showed that Ag loading significantly enhanced the photocurrent and photocatalytic degradation rate of TiO(2) nanotube array under UV-light irradiation. The photocurrent and photocatalytic degradation rate of Ag-TiO(2) nanotube array prepared in 0.006 M AgNO(3) solution were about 1.2 and 3.7 times as that of pure TiO(2) nanotube array, respectively.

  20. Construction of dentate bonded TiO2-CdSe heterostructures with enhanced photoelectrochemical properties: versatile labels toward photoelectrochemical and electrochemical sensing.

    PubMed

    Gao, Picheng; Ma, Hongmin; Yan, Tao; Wu, Dan; Ren, Xiang; Yang, Jiaojiao; Du, Bin; Wei, Qin

    2015-01-14

    A facile synthetic route for TiO2-CdSe heterostructures was proposed based on dentate binding of TiO2 to carboxyl. Carboxyl functionalized CdSe quantum dots (CF-CdSe QDs) were successfully bonded onto TiO2 nanoparticles (NPs), which could significantly improve the photoelectrochemical (PEC) properties of TiO2 NPs. This is ascribed to the fact that CdSe QDs with a narrow band gap could be stimulated under visible light irradiation, and the energy levels of TiO2 NPs and CF-CdSe QDs are aligned with an electrolyte solution. High resolution transmission electron microscopy images revealed the heterostructures of the TiO2-CdSe composites. Ultraviolet visible spectroscopy, photoluminescence emission spectroscopy and electrochemical impedance spectroscopy analysis exhibited that the prepared TiO2-CdSe heterostructures have improved light absorption, charge separation efficiency and electron transfer ability in the visible light region. TiO2-CdSe heterostructures were used as versatile labels for fabrication of PEC and electrochemical immunosensors, and human immune globulin G (HIgG) was used as a model analyte. The immunosensor showed high sensitivity, a low detection limit and a wide linear range, which could be applied in practical serum sample analysis. The constructed TiO2-CdSe heterostructures would have potential applications in photocatalysis, aptasensors, cytosensors and other areas of nanotechnology.

  1. Synthesis of Ag-decorated porous TiO2 nanowires through a sunlight induced reduction method and its enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Yao, Yun-Chang; Dai, Xin-Rong; Hu, Xiao-Ye; Huang, Su-Zhen; Jin, Zhen

    2016-11-01

    In this work, Ag-decorated porous TiO2 nanowires were successfully synthesized via a facile and low-cost sunlight induced reduction method. The cooperation of sunlight irradiation and ethanol reduction results the formation and decoration of the Ag nanoparticles on the porous TiO2 nanowires. The structure of the Ag-decorated porous TiO2 nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Energy dispersive spectroscopy (EDS) measurements. It can be seen that the Ag nanoparticles are well dispersed within the porous TiO2 nanowires. The as-prepared Ag-decorated porous TiO2 nanowires exhibits excellent photocatalytic properties. The photocatalytic tests show that 10 ppm methylene blue can be photodegraded within 60 min. And the photodegradation ratio of the Ag-decorated porous TiO2 nanowires much higher than that of P25 and porous TiO2 nanowires. Moreover, the Ag-decorated porous TiO2 nanowires also reveal good photocatalytic activity towards to other organic pollutions, such as phenol and R6G. Therefore, it is believed that the Ag-decorated porous TiO2 nanowires can be used as a potential high performance photocatalyst in wastewater treatment.

  2. UV and visible light synergetic photodegradation using rutile TiO2 nanorod arrays based on a p-n Junction.

    PubMed

    Ji, Tao; Cui, Ze; Zhang, Wenlong; Cao, Yunjiu; Zhang, Yongfang; He, Shu-Ang; Xu, Mingdong; Sun, Yangang; Zou, Rujia; Hu, Junqing

    2017-03-27

    Herein, we report a photocatalytic heterojunction device of rutile TiO2 nanorod arrays based on a p-n silicon junction (TiO2@PN) and its full absorption of ultraviolet and visible light for synergistic photodegradation. The fabricated TiO2@PN had excellent photocatalytic degradation of methyl orange (MO) under irradiation of a 300 W Xe lamp, and its pseudo-first-order rate constant k was 0.221 h(-1), which was greatly higher than that for TiO2 nanorod arrays based on an n-p silicon junction (TiO2@NP, 0.078 h(-1)) and glass (TiO2@G, 0.032 h(-1)). The higher photocatalytic performance of TiO2@PN could be attributed to the fact that the photovoltage (PV) of the p-n junction promotes separation of the electron-hole pairs of the TiO2, and the holes are thus left within the TiO2 nanorods to produce a strong oxidant of hydroxyl radicals (˙OH). Moreover, this heterojunction device could be easily fabricated in a large size for easy recovery and recycling, which shows its promise in the solar-driven degradation of environmental pollution.

  3. Photodegradation of organic matter in fresh garbage leachate using immobilized nano-sized TiO2 as catalysts.

    PubMed

    Chen, C; Xie, Q; Hu, B Q; Zhao, X L

    2014-01-01

    Two immobilized nano-sized TiO2 catalysts, TiO2/activated carbon (TiO2/AC) and TiO2/silica gel (SG) (TiO2/SG), were prepared by the sol-gel method, and their use in the photocatalytic degradation of organic matter in fresh garbage leachate under UV irradiation was investigated. The influences of the catalyst dosage, the initial solution pH, H2O2 addition and the reuse of the catalysts were evaluated. The degradation of organic matter was assessed based on the decrease of the chemical oxygen demand (COD) in the leachate. The results indicated that the degradation of the COD obeyed first-order kinetics in the presence of both photocatalysts. The degradation rate of COD was found to increase with increasing catalyst dosage up to 9 g/L for TiO2/AC and 6 g/L for TiO2/SG, above which the degradation began to attenuate. Furthermore, the degradation rate first increased and then decreased as the solution pH increased from 2 to 14, and the degradation rate increased as the amount of H2O2 increased to 2.93 mM, after which it remained constant. No obvious decrease in the rate of COD degradation was observed during the first four repeated uses of the photocatalysts, indicating that the catalysts could be recovered and reused. Compared with TiO2/AC, TiO2/SG exhibited higher efficiency in photocatalyzing the degradation of COD in garbage leachate.

  4. Wastewater treatment by sonophotocatalysis using PEG modified TiO2 film in a circular Photocatalytic-Ultrasonic system.

    PubMed

    Hu, Xiaohong; Zhu, Qi; Gu, Zhibin; Zhang, Nan; Liu, Na; Stanislaus, Mishma S; Li, Dawei; Yang, Yingnan

    2017-05-01

    TiO2 photocatalyst film recently has been utilized as the potential candidate for the wastewater treatment, due to its high stability and low toxicity. In order to further increase the photocatalytic ability and stability, different molecular weight of polyethylene glycol (PEG) were used to modify TiO2 structure to synthesize porous thin film used in the developed Photocatalytic-Ultrasonic system in this work. The results showed that PEG2000 modified TiO2 calcinated under 450°C for 2h exhibited the highest photocatalytic activity, attributed to the smallest crystallite size and optimal particle size. Over 95.0% of rhodamine B (Rh B) was photocatalytically degraded by optimized PEG2000-TiO2 film after 60min of UV irradiation, while only about 50.8% of Rh B was decolored over pure TiO2 film. Furthermore, optimized PEG2000-TiO2 film was used in a circular Photocatalytic-Ultrasonic system, and the obtained synergy (0.6519) of sonophotocatalysis indicated its extremely high efficiency for Rh B degradation. In this Photocatalytic-Ultrasonic system, larger amount of PEG2000-TiO2 coated glass beads, stronger ultrasonic power and longer experimental time could result to higher degradation efficiency of Rh B. In addition, repetitive experiments showed that about 97.2% of Rh B were still degraded in the fifth experiment by sonophotocatalysis using PEG2000-TiO2 film. Therefore, PEG2000-TiO2 film used in Photocatalytic-Ultrasonic system has promising potential for wastewater treatment, due to its excellent photocatalytic activity and high stability.

  5. Fabrication of In2S3 nanoparticle decorated TiO2 nanotube arrays by successive ionic layer adsorption and reaction technique and their photocatalytic application.

    PubMed

    Zhang, Zhenrong; Tang, Yanhong; Liu, Chengbin; Wan, Long

    2014-06-01

    In2S3 nanoparticle (NP) decorated self-organized TiO2 nanotube array (In2S3/TiO2 NT) hybrids were fabricated via simple successive ionic layer adsorption and reaction (SILAR) technique. The In2S3 NPs in a size of about 15 nm were found to deposit on the top surface of the highly oriented TiO2 NT while without clogging the tube entrances. The loading amount of In2S3 NPs on the TiO2 NT was controlled by the cycle number of SILAR deposition. Compared with the bare TiO2 NT, the In2S3/TiO2 NT hybrids showed stronger absorption in the visible light region and significantly enhanced photocurrent density. The photocatalytic activity of the In2S3/TiO2 NT photocatalyst far exceeds that of bare TiO2 NT in the degradation of typical herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) under simulated solar light. After 160-min irradiation, almost 100% 2,4-D removal is obtained on the 7-In2S3/TiO2 NT prepared through seven SILAR deposition cycles, much higher than 26% on the bare TiO2 NT. After 10 successive cycles of photocatalytic process with total 1,600 min of irradiation, In2S3/TiO2 NT maintained as high 2,4-D removal efficiency as 95.1% with good stability and easy recovery, which justifies the potential of the photocatalytic system in application for the photocatalytic removal of organic pollutants such as herbicides or pesticides from water.

  6. TiO2/WO3 photoactive bilayers in the UV-Vis light region

    NASA Astrophysics Data System (ADS)

    Vasilaki, E.; Vernardou, D.; Kenanakis, G.; Vamvakaki, M.; Katsarakis, N.

    2017-04-01

    In this work, photoactive bilayered films consisting of anatase TiO2 and monoclinic WO3 were synthesized by a sol-gel route. Titanium isopropoxide and tungsten hexachloride were used as metal precursors and deposition was achieved by spin-coating on Corning glass substrates. The samples were characterized by X-ray diffraction, photoluminescence, UV-Vis, and Raman spectroscopy, as well as field emission scanning electron microscopy. The prepared immobilized catalysts were tested for their photocatalytic performance by the decolorization of methylene blue in aqueous matrices, under UV-Vis light irradiation. The annealing process influenced the crystallinity of the bilayered films, while the concentration of the tungsten precursor solution and the position of the tungsten trioxide layer further affected their photocatalytic performance. In particular, the photocatalytic performance of the bilayered films was optimized at a concentration of 0.1 M of the WO3 precursor solution, when deposited as an overlying layer on TiO2 by two annealing steps ( 76% methylene blue decolorization in 300 min of irradiation versus 59% in the case of a bare TiO2 film). In general, the coupled layer catalysts exhibited superior photoactivity compared to that of bare TiO2 films with WO3 acting as an electron trap, resulting, therefore, in a more efficient electron-hole separation and inhibiting their recombination.

  7. Fabrication of SnO2-TiO2 core-shell nanopillar-array films for enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Cheng, Hsyi-En; Lin, Chun-Yuan; Hsu, Ching-Ming

    2017-02-01

    Immobilized or deposited thin film TiO2 photocatalysts are suffering from a low photocatalytic activity due to either a low photon absorption efficiency or a high carrier recombination rate. Here we demonstrate that the photocatalytic activity of TiO2 can be effectively improved by the SnO2-TiO2 core-shell nanopillar-array structure which combines the benefits of SnO2/TiO2 heterojunction and high reaction surface area. The SnO2-TiO2 core-shell nanopillar-array films were fabricated using atomic layer deposition and dry etching techniques via barrier-free porous anodic alumina templates. The photocatalytic activity of the prepared films was evaluated by methylene blue (MB) bleaching under 352 nm UV light irradiation. The results show that the photocatalytic activity of TiO2 film was 45% improved by introducing a SnO2 film between TiO2 and ITO glass substrate and was 300% improved by using the SnO2-TiO2 core-shell nanopillar-array structure. The 45% improvement by the SnO2 interlayer is attributed to the SnO2/TiO2 heterojunction which separates the photogenerated electron-hole pairs in TiO2 for MB degradation, and the high photocatalytic activity of the SnO2-TiO2 core-shell nanopillar-array films is attributed to the three dimensional SnO2/TiO2 heterojunction which owns both the carrier separation ability and the high photocatalytic reaction surface area.

  8. Improved Treatment of Photothermal Cancer by Coating TiO2 on Porous Silicon.

    PubMed

    Na, Kil Ju; Park, Gye-Choon

    2016-02-01

    In present society, the technology in various field has been sharply developed and advanced. In medical technology, especially, photothermal therapy and photodynamic therapy have had limelight for curing cancers and diseases. The study investigates the photothermal therapy that reduces side effects of existing cancer treatment, is applied to only cancer cells, and dose not harm any other normal cells. The photothermal properties of porous silicon for therapy are analyzed in order to destroy cancer cells that are more weak at heat than normal ones. For improving performance of porous silicon, it also analyzes the properties when irradiating the near infrared by heterologously junction TiO2 and TiO2NW, photocatalysts that are very stable and harmless to the environment and the human body, to porous silicon. Each sample of Si, PSi, TiO2/Psi, and TiO2NW/PSi was irradiated with 808 nm near-IR of 300, 500, and 700 mW/cm2 light intensity, where the maximum heating temperature was 43.8, 61.6, 67.9, and 61.9 degrees C at 300 mW/cm2; 54.1, 64.3, 78.8, and 68.9 degrees C at 500 mW/cm2; and 97.3, 102.8, 102.5, and 95 0C at 700 mW/cm2. The time required to reach the maximum temperature was less than 10 min for every case. The results indicate that TiO2/PSi thin film irradiated with a single near-infrared wavelength of 808 nm, which is known to have the best human permeability, offers the potential of being the most successful photothermal cancer therapy agent. It maximizes the photo-thermal characteristics within the shortest time, and minimizes the adverse effects on the human body.

  9. Photocatalytic degradation of pharmaceutical wastes by alginate supported TiO2 nanoparticles in packed bed photo reactor (PBPR).

    PubMed

    Sarkar, Santanu; Chakraborty, Sudip; Bhattacharjee, Chiranjib

    2015-11-01

    In recent years deposal of pharmaceutical wastes has become a major problem globally. Therefore, it is necessary to removes pharmaceutical waste from the municipal as well as industrial effluents before its discharge. The convectional wastewater and biological treatments are generally failed to separate different drugs from wastewater streams. Thus, heterogeneous photocatalysis process becomes lucrative method for reduction of detrimental effects of pharmaceutical compounds. The main disadvantage of the process is the reuse or recycle of photocatalysis is a tedious job. In this work, the degradation of aqueous solution of chlorhexidine digluconate (CHD), an antibiotic drug, by heterogeneous photocatalysis was study using supported TiO2 nanoparticle. The major concern of this study is to bring down the limitations of suspension mode heterogeneous photocatalysis by implementation of immobilized TiO2 with help of calcium alginate beads. The alginate supported catalyst beads was characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDAX) as well as the characteristic crystalline forms of TiO2 nanoparticle was confirmed by XRD. The degradation efficiency of TiO2 impregnated alginate beads (TIAB) was compared with the performance of free TiO2 suspension. Although, the degradation efficiency was reduced considerably using TIAB but the recycle and reuse of catalyst was increased quite appreciably. The kinetic parameters related to this work have also been measure. Moreover, to study the susceptibility of the present system photocatalysis of other three drugs ibuprofen (IBP), atenolol (ATL) and carbamazepine (CBZ) has been carried out using immobilized TiO2. The continuous mode operation in PBPR has ensured the applicability of alginate beads along with TiO2 in wastewater treatment. The variation of residence time has significant impact on the performance of PBPR.

  10. TiO2-TiO2 composite resistive humidity sensor: ethanol crosssensitivity

    NASA Astrophysics Data System (ADS)

    Ghalamboran, Milad; Saedi, Yasin

    2016-03-01

    The fabrication method and characterization results of a TiO2-TiO2 composite bead used for humidity sensing along with its negative cross-sensitivity to ethanol vapor are reported. The bead shaped resistive sample sensors are fabricated by the drop-casting of a TiO2 slurry on two Pt wire segments. The dried bead is pre-fired at 750°C and subsequently impregnated with a Ti-based sol. The sample is ready for characterization after a thermal annealing at 600°C in air. Structurally, the bead is a composite of the micron-sized TiO2 crystallites embedded in a matrix of nanometric TiO2 particle aggregates. The performance of the beads as resistive humidity sensors is recorded at room temperature in standard humidity level chambers. Results evince the wide dynamic range of the sensors fabricated in the low relative humidity range. While the sensor conductance is not sensitive to ethanol vapor in dry air, in humid air, sensor's responses are negatively affected by the contaminant.

  11. Double-Shelled TiO2 Hollow Spheres Assembled with TiO2 Nanosheets.

    PubMed

    Zhang, Chao; Zhou, Yuming; Zhang, Yiwei; Zhao, Shuo; Fang, Jiasheng; Sheng, Xiaoli; Zhang, Tao; Zhang, Hongxing

    2017-02-08

    High-quality double-shelled TiO2 hollow spheres (DHS-Ti) assembled with TiO2 nanosheets have been synthesized for the first time through a simple hydrothermal treatment of sSiO2 @TiO2 (TiO2 -coated solid SiO2 spheres). The double-shelled structure shows a high BET surface area up to 417.6 m(2)  g(-1) . Anatase DHS-Ti of high crystallinity can be obtained without structural collapse by calcination treatment. The effects of cetyl trimethylammonium bromide (CTAB) concentration, pH, and hydrothermal reaction temperature have also been investigated with a series of contrast experiments. A formation mechanism involving the in situ growth of amorphous TiO2 nanosheets followed by the redeposition of dissolved silica species is proposed. Lastly, the DHS-Ti forming strategy can be extended as a general strategy to fabricate various morphological hollow nanostructures and double-shelled Pt nanocatalysts by rationally selecting functional sSiO2 nanoparticles as core materials. This work could open up a new strategy for controllable synthesis of complex hollow structures and other functional materials.

  12. Photocatalytic characteristics for the nanocrystalline TiO2 on the Ag-doped CaAl2O4:(Eu,Nd) phosphor

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Sik; Sung, Hyun-Je; Kim, Bum-Joon

    2015-04-01

    This study investigated the photocatalytic behavior of nanocrystalline TiO2 deposited on Ag-doped long-lasting phosphor (CaAl2O4:Eu2+,Nd3+). The CaAl2O4:Eu2+,Nd3+ phosphor powders were prepared via conventional sintering using CaCO3, Al2O3, Eu2O3, and Nd2O3 as raw materials according to the appropriate molar ratios. Silver nanoparticles were loaded on the phosphor by mixing with an aqueous Ag-dispersion solution. Nanocrystalline TiO2 was deposited on Ag-doped CaAl2O4:Eu2+,Nd3+ powders via low-pressure chemical vapor deposition (LPCVD). The TiO2 coated on the phosphor was actively photo-reactive under irradiation with visible light and showed much faster benzene degradation than pure TiO2, which is almost non-reactive. The coupling of TiO2 with phosphor may result in an energy band bending in the junction region, which then induces the TiO2 crystal at the interface to be photo-reactive under irradiation with visible light. In addition, the intermetallic compound of CaTiO3 that formed at the interface between TiO2 and the CaAl2O4:(Eu2+,Nd3+) phosphor results in the formation of oxygen vacancies and additional electrons that promote the photodecomposition of benzene gas. The addition of Ag nanoparticles enhanced the photocatalytic reactivity of the TiO2/CaAl2O4:Eu2+,Nd3+ phosphor. TiO2 on the Ag-doped phosphor presented a higher benzene gas decomposition rate than the TiO2 did on the phosphor without Ag-doping under both irradiation with ultraviolet and visible light.

  13. Bifunctional ultraviolet/ultrasound responsive composite TiO2/polyelectrolyte microcapsules

    NASA Astrophysics Data System (ADS)

    Gao, Hui; Wen, Dongsheng; Tarakina, Nadezda V.; Liang, Jierong; Bushby, Andy J.; Sukhorukov, Gleb B.

    2016-02-01

    Designing and fabricating multifunctional microcapsules are of considerable interest in both academic and industrial research aspects. This work reports an innovative approach to fabricate composite capsules with high UV and ultrasound responsive functionalities that can be used as external triggers for controlled release, yet with enhanced mechanical strength that can make them survive in a harsh environment. Needle-like TiO2 nanoparticles (NPs) were produced in situ into layer-by-layer (LbL) polyelectrolyte (PE) shells through the hydrolysis of titanium butoxide (TIBO). These rigid TiO2 NPs yielded the formed capsules with excellent mechanical strength, showing a free standing structure. A possible mechanism is proposed for the special morphology formation of the TiO2 NPs and their reinforcing effects. Synergistically, their response to UV and ultrasound was visualized via SEM, with the results showing an irreversible shell rapture upon exposure to either UV or ultrasound irradiation. As expected, the release studies revealed that the dextran release from the TiO2/PE capsules was both UV-dependent and ultrasound-dependent. Besides, the biocompatibility of the capsules with the incorporation of amorphous TiO2 NPs was confirmed by an MTT assay experiment. All these pieces of evidence suggested a considerable potential medicinal application of TiO2/PE capsules for controlled drug delivery.Designing and fabricating multifunctional microcapsules are of considerable interest in both academic and industrial research aspects. This work reports an innovative approach to fabricate composite capsules with high UV and ultrasound responsive functionalities that can be used as external triggers for controlled release, yet with enhanced mechanical strength that can make them survive in a harsh environment. Needle-like TiO2 nanoparticles (NPs) were produced in situ into layer-by-layer (LbL) polyelectrolyte (PE) shells through the hydrolysis of titanium butoxide (TIBO). These

  14. Flower-like TiO2 nanostructures with exposed {001} facets: Facile synthesis and enhanced photocatalysis

    NASA Astrophysics Data System (ADS)

    Liu, Min; Piao, Lingyu; Lu, Weiming; Ju, Siting; Zhao, Lei; Zhou, Chunlan; Li, Hailing; Wang, Wenjing

    2010-07-01

    Flower-like TiO2 nanostructures with exposed {001} facets were synthesized by a low-temperature hydrothermal process from Ti powders for the first time, and they exhibited enhanced photocatalytic degradation of methylene blue dye under ultraviolet light irradiation.Flower-like TiO2 nanostructures with exposed {001} facets were synthesized by a low-temperature hydrothermal process from Ti powders for the first time, and they exhibited enhanced photocatalytic degradation of methylene blue dye under ultraviolet light irradiation. Electronic supplementary information (ESI) available: Additional FE-SEM images. See DOI: 10.1039/c0nr00050g

  15. High Mobility of Graphene-Based Flexible Transparent Field Effect Transistors Doped with TiO2 and Nitrogen-Doped TiO2.

    PubMed

    Wu, Yu-Hsien; Tseng, Po-Yuan; Hsieh, Ping-Yen; Chou, Hung-Tao; Tai, Nyan-Hwa

    2015-05-13

    Graphene with carbon atoms bonded in a honeycomb lattice can be tailored by doping various species to alter the electrical properties of the graphene for fabricating p-type or n-type field-effect transistors (FETs). In this study, large-area and single-layer graphene was grown on electropolished Cu foil using the thermal chemical vapor deposition method; the graphene was then transferred onto a poly(ethylene terephthalate) (PET) substrate to produce flexible, transparent FETs. TiO2 and nitrogen-doped TiO2 (N-TiO2) nanoparticles were doped on the graphene to alter its electrical properties, thereby enhancing the carrier mobility and enabling the transistors to sense UV and visible light optically. The results indicated that the electron mobility of the graphene was 1900 cm(2)/(V·s). Dopings of TiO2 and N-doped TiO2 (1.4 at. % N) lead to n-type doping effects demonstrating extremely high carrier mobilities of 53000 and 31000 cm(2)/(V·s), respectively. Through UV and visible light irradiation, TiO2 and N-TiO2 generated electrons and holes; the generated electrons transferred to graphene channels, causing the FETs to exhibit n-type electric behavior. In addition, the Dirac points of the graphene recovered to their original state within 5 min, confirming that the graphene-based FETs were photosensitive to UV and visible light. In a bending state with a radius of curvature greater than 2.0 cm, the carrier mobilities of the FETs did not substantially change, demonstrating the application possibility of the fabricated graphene-based FETs in photosensors.

  16. Light-controlled propulsion, aggregation and separation of water-fuelled TiO2/Pt Janus submicromotors and their ``on-the-fly'' photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Mou, Fangzhi; Kong, Lei; Chen, Chuanrui; Chen, Zhihong; Xu, Leilei; Guan, Jianguo

    2016-02-01

    In this work, water-fuelled TiO2/Pt Janus submicromotors with light-controlled motions have been developed by utilizing the asymmetrical photocatalytic water redox reaction over TiO2/Pt Janus submicrospheres under UV irradiation. The motion state, speed, aggregation and separation behaviors of the TiO2/Pt Janus submicromotor can be reversibly, wirelessly and remotely controlled at will by regulating the ``on/off'' switch, intensity and pulsed/continuous irradiation mode of UV light. The motion of the water-fuelled TiO2/Pt Janus submicromotor is governed by light-induced self-electrophoresis under the local electrical field generated by the asymmetrical water oxidation and reduction reactions on its surface. The TiO2/Pt Janus submicromotors can interact with each other through the light-switchable electrostatic forces, and hence continuous and pulsed UV irradiation can make the TiO2/Pt Janus submicromotors aggregate and separate at will, respectively. Because of the enhanced mass exchange between the environment and active submicromotors, the separated TiO2/Pt Janus submicromotors powered by the pulsed UV irradiation show a much higher activity for the photocatalytic degradation of the organic dye than the aggregated TiO2/Pt submicromotors. The water-fuelled TiO2/Pt Janus submicromotors developed here have some outstanding advantages as ``swimming'' photocatalysts for organic pollutant remediation in the macro or microenvironment (microchannels and microwells in microchips) because of their small size, long-term stability, wirelessly controllable motion behaviors and long life span.In this work, water-fuelled TiO2/Pt Janus submicromotors with light-controlled motions have been developed by utilizing the asymmetrical photocatalytic water redox reaction over TiO2/Pt Janus submicrospheres under UV irradiation. The motion state, speed, aggregation and separation behaviors of the TiO2/Pt Janus submicromotor can be reversibly, wirelessly and remotely controlled at will by

  17. Photocatalytic production of 1O2 and *OH mediated by silver oxidation during the photoinactivation of Escherichia coli with TiO2.

    PubMed

    Castro, Camilo A; Osorio, Paula; Sienkiewicz, Andrzej; Pulgarin, Cesar; Centeno, Aristóbulo; Giraldo, Sonia A

    2012-04-15

    Ag loaded TiO(2) was applied in the photocatalytic inactivation of Escherichia coli under ultraviolet (UV) and visible (Vis) light irradiations. Ag enhanced the TiO(2) photodisinfecting effect under Vis irradiation promoting the formation of singlet oxygen and hydroxyl radicals as identified by EPR analyses. Ag nanoparticles, determined on TEM analyses, undergo an oxidation process on the TiO(2)'s surface under UV or Vis irradiation as observed by XPS. In particular, UV pre-irradiation of the material totally diminished its photodisinfection activity under a subsequent Vis irradiation test. Under UV, photodegradation of dichloroacetic acid (DCA), attributed to photoproduced holes in TiO(2), was inhibited by the presence of Ag suggesting that oxidation of Ag(0) to Ag(+) and Ag(2+) is faster than the oxidative path of the TiO(2)'s holes on DCA molecules. Furthermore, photoassisted increased of Ag(+) concentration on TiO(2)'s surface enhances the bacteriostatic activity of the material in dark periods. Indeed, this latter dark contact of Ag(+)-TiO(2) and E. coli seems to induce recovering of the Vis light photoactivity promoted by the surface Ag photoactive species.

  18. Improved performance of dye-sensitized solar cell based on TiO2 photoanode with FTO glass and film both treated by TiCl4

    NASA Astrophysics Data System (ADS)

    Li, Jinlun; Zhang, Haiyan; Wang, Wenguang; Qian, Yannan; Li, Zhenghui

    2016-11-01

    The dye-sensitized solar cell (DSSC) based on TiO2 photoanode with FTO glass and TiO2 film co-treated by TiCl4 were fabricated. The effects of TiCl4 treatment on the photovoltaic performance of the DSSCs were investigated. TiCl4 treatment of the FTO glass resulted in the formation of a compact TiO2 thin layer on its surface, which could increase the electron collection efficiency. Meanwhile, TiCl4 treatment of the TiO2 film could fill gaps between nanoparticles in the TiO2 film, leading to better electron transfer. These advantages make the DSSC exhibit a highest conversion efficiency of 3.34% under a simulated solar irradiation with an intensity of 100 mW/cm2 (1 sun), increased by 38% compared with that of the untreated DSSC.

  19. Synthesis of Ag or Pt nanoparticle-deposited TiO2 nanorods for the highly efficient photoreduction of CO2 to CH4

    NASA Astrophysics Data System (ADS)

    Wang, Qingli; Dong, Peimei; Huang, Zhengfeng; Zhang, Xiwen

    2015-10-01

    Ag or Pt-deposited TiO2 nanocomposites were prepared by a simple method, in which oriented TiO2 nanorods were synthesized by a hydrothermal method and a noble metal (Ag or Pt) was deposited on TiO2 by photocatalytic reduction under UV irradiation. The oriented TiO2 nanorods with Ag or Pt nanoparticles (<20 nm) exhibited high CO2 photoreduction efficiency, with CH4 yield rates up to 16.0 ppm/g h and 10.8 ppm/g h, respectively, considerably higher than that of the pure TiO2 nanorods (4.2 ppm/g h). The improvement in the CH4 yield was attributed to the formation of a Schottky barrier and surface plasmon resonance.

  20. Ultrasound with low intensity assisted the synthesis of nanocrystalline TiO2 without calcination.

    PubMed

    Ghows, Narjes; Entezari, Mohamad H

    2010-06-01

    A novel method has been developed for the preparation of nano-sized TiO(2) with anatase phase. Nanoparticles with diameter about 6 nm were prepared at a relatively low temperature (75 degrees C) and short time. The synthesis was carried out by the hydrolysis of titanium tetra-isopropoxide (TTIP) in the presence of water, ethanol, and dispersant under ultrasonic irradiation (500 kHz) at low intensity. The results show that variables such as water/ethanol ratio, irradiation time, and temperature have a great influence on the particle size and crystalline phases of TiO(2) nanoparticles. Characterization of the product was carried out by different techniques such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and UV-vis spectroscopy.

  1. Increased biodegradability of Ultracid in aqueous solutions with solar TiO2 photocatalysis.

    PubMed

    García-Ripoll, A; Amat, A M; Arques, A; Vicente, R; López, M F; Oller, I; Maldonado, M I; Gernjak, W

    2007-06-01

    A study of solar TiO(2) photocatalytic degradation of the insecticide Ultracidtrade mark, a commercial formulation containing methidathion as the active ingredient, is described. Total elimination of methidathion can be achieved in less than 2h of irradiation, although longer solar exposures are needed for complete mineralisation of the solution (7-8h). Activated sludge respirometry shows that when methidathion is eliminated, the solution is detoxified, so further irradiation does not seem necessary. A Zahn-Wellens test also indicates improved biodegradability of the treated sample after abatement of the active ingredient. Finally, analysis of the ions formed indicates that the thiophosphate moiety of the molecule is preferentially attacked in the early stages of the reaction, while the thiadiazole ring is more sluggish to the effect of TiO(2)-photocatalysis.

  2. Photocatalytic degradation of surfactants with immobilized TiO2: comparing two reaction systems.

    PubMed

    Lizama, C; Bravo, C; Caneo, C; Ollino, M

    2005-08-01

    The photocatalytic degradation of two industrial-grade surfactants, sodium lauryl sulphate (SLS) and sodium dodecylbenzenesulphonate (SDDBS), were achieved using TiO2 immobilised on glass Raschig rings and inside a bent tube of glass, using two different photoreactors in recirculation batch mode with a black light fluorescent tube as irradiation source. The influence of parameters pH, recalculation flow, airflow and number of treatment units were determined. For comparison purposes, the energetic cost of treatment was determined for both reaction systems as the figure-of-merit EE/O, showing that titania supported on glass Raschig rings is a more efficient system than the inner coated spring with TiO2, but this condition is strongly dependent on the surfactant identity. The best conditions for surfactants elimination were used to carry out the treatment of solutions containing two commercial detergents, reaching an 80% of removal in 60 min of irradiation.

  3. Enhanced TiO2 Photocatalytic Processing of Organic Wastes for Green Space Exploration

    NASA Technical Reports Server (NTRS)

    Udom, I.; Goswami, D. Y.; Ram, M. K.; Stefanakos, E. K.; Heep, A. F.; Kulis, M. J.; McNatt, J. S.; Jaworske, D. A.; Jones, C. A.

    2013-01-01

    The effect of transition metal co-catalysts on the photocatalytic properties of TiO2 was investigated. Ruthenium (Ru), palladium, platinum, copper, silver, and gold, were loaded onto TiO2 powders (anatase and mixed-phase P25) and screened for the decomposition of rhodamine B (RhB) under broad-band irradiation. The morphology and estimated chemical composition of photocatalysts were determined by scanning electron microscopy and energy dispersive spectroscopy, respectively. Brunhauer, Emmett and Teller (BET) analysis measured mass-specific surface area(s). X-ray diffraction analysis was performed to confirm the identity of titania phase(s) present. The BET surface area of anatase TiO2/Ru 1% (9.2 sq m/gm) was one of the highest measured of all photocatalysts prepared in our laboratory. Photolyses conducted under air-saturated and nitrogen-saturated conditions revealed photodegradation efficiencies of 85 and 2 percent, respectively, after 60 min compared to 58 percent with no catalyst. The cause of low photocatalytic activity under an inert atmosphere is discussed. TiO2/Ru 1% showed a superior photocatalytic activity relative to P25-TiO2 under broad-band irradiation. A potential deployment of photocatalytic technologies on a mission could be a reactor with modest enhancement in solar intensity brought about by a trough-style reactor, with reactants and catalyst flowing along the axis of the trough and therefore being illuminated for a controlled duration based on the flow rate.

  4. TiO2/UV based photocatalytic pretreatment of wheat straw for biogas production.

    PubMed

    Alvarado-Morales, Merlin; Tsapekos, Panagiotis; Awais, Muhammad; Gulfraz, Muhammad; Angelidaki, Irini

    2016-11-16

    The present study deals with the application of an advanced oxidation process combining UV irradiation in the presence of the photocatalyst titanium dioxide (TiO2), as an effective pretreatment method of wheat straw as means for increasing its biodegradability for increased biogas production by anaerobic digestion (AD). Especially attention was paid in oxidation of the lignin in straw, besides release the sugars from the lignocellulosic structure of straw. Specifically, four different TiO2 concentrations (0.0, 0.5, 1.0, 1.5, and 2.0% (w/w) TiO2) were tested at three different irradiation times (0, 1, 2, and 3 h). Products of lignin-fraction oxidation, namely, vanillic acid, ferullic acid and acetic acid were quantified for each set of pretreatment conditions. Subsequently, biochemical methane potentials (BMPs) assays were conducted under thermophilic conditions from differentially pretreated samples and the pretreatment with the best performance was further tested in continuous mode operation. From BMP assays, 1.5% (w/w) TiO2/straw at 3 h of UV light exposure pretreatment resulted in 37% (p < 0.05) increase in methane yield and 25% in CSTRs. It was concluded that the presence of TiO2 and the products of lignin oxidation did not inhibit the AD process. Finally, a simplified energy assessment showed that all pretreatment conditions become feasible when amounts of substrate to be treated are greater than the threshold value of 1.15 g.

  5. Electrochemically synthesized ordered TiO2 and platinum nanocomposite electrode: preparation, characterization, and application to photoelectrocatalytic methanol oxidation

    SciTech Connect

    Li, Zhizhou; Cui, Xiaoli; Lin, Yuehe

    2009-04-01

    In this work, the nanocomposite electrodes consisting of Pt and TiO2 nanotubular arrays have been synthesized, and the morphologies, structural, and photo-electrochemical properties of the electrodes are characterized by SEM, XRD, and electrochemical methods. Highly ordered TiO2 nanotubular arrays can be obtained through anodization of titanium. The platinum nanoparticles are electrodeposited into TiO2 nanotubes by a chronopotentiometry method. Cyclic voltammetry and XRD measurements can confirm the presence of platinum in this nanocomposite electrode. The nanostructural electrode greatly improved performances for methanol oxidation under UV-Vis illumination compared to that without illumination. An enhancement of 58% in the current density has been observed upon illumination with UV-Vis light irradiance at an intensity of 50 mW/cm2. The improved performance of the TiO2/Pt nanocomposite electrode results from a enhanced methanol oxidation by photo-generated holes in the TiO2 nanoarrays under illumination and a synergistic effectiveness between TiO2 and Pt nanoparticles.

  6. Controlled fabrication of porous double-walled TiO2 nanotubes via ultraviolet-assisted anodization.

    PubMed

    Ali, Ghafar; Kim, Hyun Jin; Kim, Jae Joon; Cho, Sung Oh

    2014-04-07

    Double-walled TiO2 nanotubes with porous wall morphologies are fabricated by anodization under ultraviolet (UV) irradiation. TiO2 formed by anodization of Ti is activated to generate electrons and holes by UV and the anodization process is influenced by the photo-generated charges. As a consequence, morphologies of the fabricated TiO2 nanotubes can be adjusted by controlling the UV illumination. Double-walled TiO2 nanotubes or single-walled nanotubes can be selectively formed by switching on/off the UV illumination. The thickness of the inner and outer walls of the double-walled nanotubes can be tailored by changing the UV power. Due to their larger surface areas compared to single-walled nanotubes, the porous double-walled nanotubes exhibit an enhanced photo-degradation rate for methylene blue (MB). The mechanism of the porous double-walled TiO2 nanotubes is proposed based on the photoactive semiconducting property of the as-growing TiO2 nanotubes under UV.

  7. Ultra-High Speed Fabrication of TiO2 Photoanode by Flash Light for Dye-Sensitized Solar Cell.

    PubMed

    Hwang, Hyun-Jun; Kim, Hak-Sung

    2015-07-01

    In this work, a new way to fabricate nanoporous TiO2 photoanode by flash light is demonstrated. TiO2 nanoparticles are sintered on FTO glass by flash light irradiation at room temperature in ambient condition, which is dramatically simple, ultrahigh speed and one-shot large area fabrication process compared to a conventional high temperature (120 °C) thermal sintering process. The effect of the flash light conditions (flash light energy, pulse numbers and pulse duration) on the nanostructures of sintered TiO2 layer, was studied and discussed using several microscopic and spectroscopic characterization techniques such as SEM, FT-IR, XRD and XPS. The sintered TiO2 photoanodes by flash light were used in DSSC and its performance were compared with that of DSSC fabricated by conventional thermal sintering process. It was found that a flash light sintered TiO2 photoanode has efficiency which is similar to that of the thermal sintered photoanode. It is expected that the newly developed flash light sintering technique of TiO2 nanoparticles would be a strong alternative to realize the room temperature and in-situ sintering of photoanode fabrication for outdoor solar cell fabrication.

  8. Reducing cross-sensitivity of TiO2-(B) nanowires to humidity using ultraviolet illumination for trace explosive detection.

    PubMed

    Wang, Danling; Chen, Antao; Jen, Alex K-Y

    2013-04-14

    Environmental humidity is an important factor that can influence the sensing performance of a metal oxide. TiO2-(B) in the form of nanowires has been demonstrated to be a promising material for the detection of explosive gases such as 2,4,6-trinitrotoluene (TNT). However, the elimination of cross-sensitivity of the explosive detectors based on TiO2-(B) toward environmental humidity is still a major challenge. It was found that the cross-sensitivity could be effectively modulated when the thin film of TiO2-(B) nanowires was exposed to ultraviolet (UV) light during the detection of explosives under operating conditions. Such a modulation of sensing responses of TiO2-(B) nanowires to explosives by UV light was attributed to a photocatalytic effect, with which the water adsorbed on the TiO2-(B) nanowire surface was split and therefore the sensor response performance was less affected. It was revealed that the cross-sensitivity could be suppressed up to 51% when exposed to UV light of 365 nm wavelength with an intensity of 40 mW cm(-2). This finding proves that the reduction of cross-sensitivity to humidity through UV irradiation is an effective approach that can improve the performance of a sensor based on TiO2-(B) nanowires for the detection of explosive gas.

  9. Multifunctional Fe3O4-TiO2 nanocomposites for magnetic resonance imaging and potential photodynamic therapy.

    PubMed

    Zeng, Leyong; Ren, Wenzhi; Xiang, Lingchao; Zheng, Jianjun; Chen, Bin; Wu, Aiguo

    2013-03-07

    Multifunctional Fe(3)O(4)-TiO(2) nanocomposites with Janus structure for magnetic resonance imaging (MRI) and potential photodynamic therapy (PDT) were synthesized, in which Fe(3)O(4) was used as a MRI contrast agent and TiO(2) as an inorganic photosensitizer for PDT. Their morphology, structure, and MRI and PDT performance were characterized, respectively. Moreover, the location of Fe(3)O(4)-TiO(2) nanocomposites in MCF-7 cells was also investigated by the staining of Prussian blue and alizarin red, respectively. The results showed that the as-prepared Fe(3)O(4)-TiO(2) nanocomposites had good T(2)-weighted MRI performance, and the MCF-7 cells incubated with nanocomposites could be killed under the irradiation of UV light. Compared with traditional organic photosensitizers, TiO(2) inorganic photosensitizers could have more stable PDT performance due to their nanoscale size and anti-photodegradable stability. Therefore, the as-prepared Fe(3)O(4)-TiO(2) nanocomposites could have potential applications as a new kind of multifunctional agent for both MRI and PDT.

  10. Synthesis of Cu Loaded TiO2 Nanoparticles for the Improved Photocatalytic Degradation of Rhodamine B

    NASA Astrophysics Data System (ADS)

    Kavitha, V.; Ramesh, P. S.; Geetha, D.

    2016-10-01

    Copper doped Titanium dioxide TiO2 nanoparticles were synthesized by sol-gel method using titanium tetraisopropoxide and copper sulfate as precursors. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), UV-Visible spectroscopy (UV-Vis), Photoluminesce spectroscopy (PL) and atomic force microscopy (AFM). XRD analysis confirms the formation of anatase titanium dioxide and average particle size was 35nm. Cu- TiO2 exhibits a shift in the absorption edge toward visible spectrum. The rate of recombination and transfer behavior of the photoexcited electron-hole pairs in the semiconductors was recorded by photoluminescence. From SEM spherical shaped nanoparticles was observed. Comparing with pure TiO2 nanoparticles, Cu doped TiO2 photocatalyst exhibited enhanced photocatalytic activity under natural sunlight irradiation in the decomposition of rhodamine B aqueous solution. The maximum 97% of degradation efficiency of Rhodamine B was observed at 0.6% Cu-TiO2 within 180min. The photocatalytic efficiency of Rhodamine B of Cu doped TiO2 nanoparticle was higher than the pure TiO2, which could be attributed to the small crystallinity intense light absorption in Sunlight and narrow bandgap energy of Copper.

  11. Towards efficient photoinduced charge separation in carbon nanodots and TiO2 composites in the visible region.

    PubMed

    Sun, Mingye; Qu, Songnan; Ji, Wenyu; Jing, Pengtao; Li, Di; Qin, Li; Cao, Junsheng; Zhang, Hong; Zhao, Jialong; Shen, Dezhen

    2015-03-28

    In this work, photoinduced charge separation behaviors in non-long-chain-molecule-functionalized carbon nanodots (CDs) with visible intrinsic absorption (CDs-V) and TiO2 composites were investigated. Efficient photoinduced electron injection from CDs-V to TiO2 with a rate of 8.8 × 10(8) s(-1) and efficiency of 91% was achieved in the CDs-V/TiO2 composites. The CDs-V/TiO2 composites exhibited excellent photocatalytic activity under visible light irradiation, superior to pure TiO2 and the CDs with the main absorption band in the ultraviolet region and TiO2 composites, which indicated that visible photoinduced electrons and holes in such CDs-V/TiO2 composites could be effectively separated. The incident photon-to-current conversion efficiency (IPCE) results for the CD-sensitized TiO2 solar cells also agreed with efficient photoinduced charge separation between CDs-V and the TiO2 electrode in the visible range. These results demonstrate that non-long-chain-molecule-functionlized CDs with a visible intrinsic absorption band could be appropriate candidates for photosensitizers and offer a new possibility for the development of a well performing CD-based photovoltaic system.

  12. Self-assembled Bi2MoO6/TiO2 nanofiber heterojunction film with enhanced photocatalytic activities

    NASA Astrophysics Data System (ADS)

    Li, Hua; Zhang, Tianxi; Pan, Chao; Pu, Chenchen; Hu, Yang; Hu, Xiaoyun; Liu, Enzhou; Fan, Jun

    2017-01-01

    TiO2 nanofiber film (TiO2 NFF) was successfully fabricated by an ethylene glycol-assisted hydrothermal method, and then self-assembled flake-like Bi2MoO6 was grown on the surface of TiO2 nanofiber under alcohol thermal condition. The investigations indicate that the nanofiber structure of TiO2 films exhibits excellent visible light scattering property, the scattering light overlaps with the absorption band of Bi2MoO6, which can enhance the utility of incident light. The prepared Bi2MoO6/TiO2 composites show obviously enhanced photocatalytic activity for methylene blue (MB) degradation compared with pure TiO2 nanofiber under visible light irradiation (λ > 420 nm). The enhanced photocatalytic activity is primarily attributed to the synergistic effect of visible light absorption and effective electron-hole separation at the interfaces of the two semiconductors, which is confirmed by photoluminescence (PL) and electrochemical tests.

  13. Photocatalytic Functional Coating of TiO2 Thin Film Deposited by Cyclic Plasma Chemical Vapor Deposition at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Kwon, Jung-Dae; Rha, Jong-Joo; Nam, Kee-Seok; Park, Jin-Seong

    2011-08-01

    Photocatalytic TiO2 thin films were prepared with titanium tetraisopropoxide (TTIP) using cyclic plasma chemical vapor deposition (CPCVD) at atmospheric pressure. The CPCVD TiO2 films contain carbon-free impurities up to 100 °C and polycrystalline anatase phases up to 200 °C, due to the radicals and ion-bombardments. The CPCVD TiO2 films have high transparency in the visible wavelength region and absorb wavelengths below 400 nm (>3.2 eV). The photocatalytic effects of the CPCVD TiO2 and commercial sprayed TiO2 films were measured by decomposing methylene blue (MB) solution under UV irradiation. The smooth CPCVD TiO2 films showed a relatively lower photocatalytic efficiency, but superior catalyst-recycling efficiency, due to their high adhesion strength on the substrates. This CPCVD technique may provide the means to produce photocatalytic thin films with low cost and high efficiency, which would be a reasonable candidate for practical photocatalytic applications, because of the reliability and stability of their photocatalytic efficiency in a practical environment.

  14. Preparation and photocatalytic activity of B, Ce Co-doped TiO2 hollow fibers photocatalyst

    NASA Astrophysics Data System (ADS)

    Qiu, Jingping; Sun, Xiaogang; Xing, Jun; Liu, Xiaobo

    2014-07-01

    A series of B, Ce co-doped TiO2 (B, Ce-TiO2) photocatalytic materials with a hollow fiber structure were successfully prepared by template method using boric acid, ammonium ceric nitrate and tetrabutyltitanate as precursors and cotton fibers as template, followed by calcination at 500°C in an N2 atmosphere for 2 h. Scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption-desorption measurements, and UV-visible spectroscopy (UV-Vis) were employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The photocatalytic performance of the samples was studied by photodegradation phenol in water under UV light irradiation. The results showed that the TiO2 fiber materials have hollow structures, and the fiber structure materials showed better photocatalytic properties for the degradation of phenol than pure TiO2 under UV light. In the experiment condition, the photocatalytic activity of B, Ce co-doped TiO2 fibers was optimal of all the prepared samples. In addition, the possibility of cyclic usage of B, Ce co-doped TiO2 fiber photocatalyst was also confirmed, the photocatalytic activity of TiO2 fibers remained above 90% of that of the fresh sample after being used four times. The material was easily removed by centrifugal separation from the medium. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.

  15. Fabrication of TiO2-modified polytetrafluoroethylene ultrafiltration membranes via plasma-enhanced surface graft pretreatment

    NASA Astrophysics Data System (ADS)

    Qian, Yingjia; Chi, Lina; Zhou, Weili; Yu, Zhenjiang; Zhang, Zhongzhi; Zhang, Zhenjia; Jiang, Zheng

    2016-01-01

    Surface hydrophilic modification of polymer ultrafiltration membrane using metal oxide represents an effective yet highly challenging solution to improve water flux and antifouling performance. Via plasma-enhanced graft of poly acryl acid (PAA) prior to coating TiO2, we successfully fixed TiO2 functional thin layer on super hydrophobic polytetrafluoroethylene (PTFE) ultrafiltration (UF) membranes. The characterization results evidenced TiO2 attached on the PTFE-based UF membranes through the chelating bidentate coordination between surface-grafted carboxyl group and Ti4+. The TiO2 surface modification may greatly reduce the water contact angle from 115.8° of the PTFE membrane to 35.0° without degradation in 30-day continuous filtration operations. The novel TiO2/PAA/PTFE membranes also exhibited excellent antifouling and self-cleaning performance due to the intrinsic hydrophilicity and photocatalysis properties of TiO2, which was further confirmed by the photo-degradation of MB under Xe lamp irradiation.

  16. TiO2 nanoparticles co-doped with silver and nitrogen for antibacterial application.

    PubMed

    Yuan, Yali; Ding, Jianqiang; Xu, Jinsheng; Deng, Jian; Guo, Jianbo

    2010-08-01

    We have prepared a series of TiO2 nanoparticles for antibacterial applications. These TiO2 nanoparticles were prepared by the hydrolysis precipitation method with Ti(OBu)4, silver nitrate and ammonia. Crystal structure, particle size, interfacial structure and UV-visible light response of the prepared nanoparticles were characterized by X-ray diffraction measurements (XRD), Transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR) and UV-Vis diffuse reflectance spectroscopy (UV-Vis-DRs). The XRD spectra showed that all samples were anatase structure calcined at 450 degrees C for 3 hours. The Ag doping made the peak of diffraction wider. The results of TEM showed that the nanoparticles of TiO2, N-TiO2 and 1% Ag-N-TiO2 were all spherical in shape and well distributed with a mean size of 19.8 nm, 39.2 nm and 20.7 nm, respectively. N doping caused the nanoparticle size to increase, while, when the doped amount of Ag+ increased, the TiO2 particle size decreased. The FTIR revealed that Ag and N doping of TiO2 appeared to have strong absorption by -OH group and showed the characteristic absorption band of NH4+ and Ag. The UV-Vis-DRs indicated that the absorption band of Ag-N co-doped TiO2 had red shift and that the optical absorption response (between 400 nm and 700 nm) had obvious enhancement. The antibacterial properties of nanoparticles were investigated by agar diffusion method toward Escherichia coli and Bacillus subtilis. The results indicated that both Ag- and N-doped TiO2 could increase the antibacterial properties of TiO2 nanoparticles under fluorescent light irradiation. A 1% Ag-N-TiO2 had the highest antibacterial activity with a clear antibacterial circle of 33.0 mm toward Escherichia coli and 22.8 mm toward Bacillus subtilis after cultivation for 24 hours.

  17. Influence of Aqueous Inorganic Anions on the Reactivity of Nanoparticles in TiO2 Photocatalysis.

    PubMed

    Farner Budarz, Jeffrey; Turolla, Andrea; Piasecki, Aleksander F; Bottero, Jean-Yves; Antonelli, Manuela; Wiesner, Mark R

    2017-03-21

    The influence of inorganic anions on the photoreactivity and aggregation of titanium dioxide nanoparticles (NPs) was assessed by dosing carbonate, chloride, nitrate, phosphate, and sulfate as potassium salts at multiple concentrations. NP stability was monitored in terms of aggregate morphology and electrophoretic mobility (EPM). Aggregate size and fractal dimension were measured over time by laser diffraction, and the isoelectric point (IEP) as a function of anion and concentration was obtained by measuring EPM versus pH. Phosphate, carbonate, and to a lesser extent, sulfate decreased the IEP of TiO2 and stabilized NP suspensions owing to specific surface interactions, whereas this was not observed for nitrate and chloride. TiO2 NPs were exposed to UV-A radiation, and the photoreactivity was assessed by monitoring the production of reactive species over time both at the NP surface (photogenerated holes) and in the bulk solution (hydroxyl radicals) by observing their reactions with the selective probe compounds iodide and terephthalic acid, respectively. The generation of photogenerated holes and hydroxyl radicals was influenced by each inorganic anion to varying degrees. Carbonate and phosphate inhibited the oxidation of iodide, and this interaction was successfully described by a Langmuir-Hinshelwood mechanism and related to the characteristics of TiO2 aggregates. Chloride and nitrate do not specifically interact with TiO2, and sulfate creates relatively weak interactions with the TiO2 surface such that no decrease in photogenerated hole reactivity was observed. A decrease in hydroxyl radical generation was observed for all inorganic anions. Quenching rate constants for the reaction of hydroxyl radicals with each inorganic anion do not provide a comprehensive explanation for the magnitude of this decrease, which arises from the interplay of several physicochemical phenomena. This work shows that the reactivity of NPs will be strongly influenced by the makeup of

  18. CNTs threaded (001) exposed TiO2 with high activity in photocatalytic NO oxidation

    NASA Astrophysics Data System (ADS)

    Xiao, Shuning; Zhu, Wei; Liu, Peijue; Liu, Fanfan; Dai, Wenrui; Zhang, Dieqing; Chen, Wei; Li, Hexing

    2016-01-01

    A microwave-ionothermal strategy was developed for in situ synthesis of CNTs threaded TiO2 single crystal with a tunable percentage of surface exposed (001) active facets. The CNTs were used as microwave antennas to create local ``super hot'' dots to induce Ti3+ adsorption and hydrolysis, thereby leading to a good assembly of (001) facets exposed single crystalline TiO2 threaded by the CNTs in the presence of Hmim[BF4] ionic liquid. Due to the high percentage of the active (001) facets of single crystal TiO2 and the direct electron transfer property of the CNTs, the as-prepared CNTs-TiO2 composite showed a photocatalytic NO removal ratio of up to 76.8% under UV irradiation. In addition, with self-doped Ti3+, the CNTs-TiO2 composite also exhibited an enhanced activity under irradiation with either solar lights or visible lights, showing good potential in practical applications for environmental remediation.A microwave-ionothermal strategy was developed for in situ synthesis of CNTs threaded TiO2 single crystal with a tunable percentage of surface exposed (001) active facets. The CNTs were used as microwave antennas to create local ``super hot'' dots to induce Ti3+ adsorption and hydrolysis, thereby leading to a good assembly of (001) facets exposed single crystalline TiO2 threaded by the CNTs in the presence of Hmim[BF4] ionic liquid. Due to the high percentage of the active (001) facets of single crystal TiO2 and the direct electron transfer property of the CNTs, the as-prepared CNTs-TiO2 composite showed a photocatalytic NO removal ratio of up to 76.8% under UV irradiation. In addition, with self-doped Ti3+, the CNTs-TiO2 composite also exhibited an enhanced activity under irradiation with either solar lights or visible lights, showing good potential in practical applications for environmental remediation. Electronic supplementary information (ESI) available: TG, FTIR, Raman, EPR and additional photocatalytic performance data. See DOI: 10.1039/c5nr07589k

  19. A facile solvothermal approach of novel Bi2S3/TiO2/RGO composites with excellent visible light degradation activity for methylene blue

    NASA Astrophysics Data System (ADS)

    Liu, Ya; Shi, Yidan; Liu, Xiang; Li, Hexing

    2017-02-01

    In this paper, novel photocatalyst Bi2S3/TiO2/RGO composites were successfully fabricated by a facile solvothermal method. During this process, TiO2 was coupled with Bi2S3 to generate Bi2S3 sensitized TiO2 nanoparticles, and graphene oxide (GO) was reduced to reduced graphene oxide (RGO), which was uniformly covered with plenty of Bi2S3 and TiO2. The as-prepared samples were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), specific surface areas (BET), X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence (PL) spectroscopy. The results confirmed that Bi2S3 could act as an optical filter, which could be activated under visible light. And the introduction of Bi2S3 could improve the response of TiO2 nanoparticles for visible light. In addition, the Bi2S3/TiO2 in Bi2S3/TiO2/RGO composites had more uniform dispersion on the surface of graphene with less agglomeration in comparison with the Bi2S3/TiO2. Graphene can provide conductive electron channels for separation of the electrons and inhibit the recombination of electrons and holes. Furthermore, the photocatalytic activity of Bi2S3/TiO2/RGO composites was evaluated through the degradation of methylene blue (MB) under visible light irradiation. The Bi2S3/TiO2/RGO composites showed the highest photocatalytic activity among the referred photocatalysts, with about 3-fold increase in photocatalytic efficiency over TiO2 nanoparticles. The mechanism of high photocatalytic activity was also discussed.

  20. Photocatalytic investigations of TiO2-P25 nanocomposite thin films prepared by peroxotitanic acid modified sol-gel method

    NASA Astrophysics Data System (ADS)

    Oshani, Fatemeh; Marandi, Reza; Rasouli, Sousan; Farhoud, Mitra Keramati

    2014-08-01

    TiO2 thin films and TiO2-P25 nanocomposite thin films were synthesized by sol-gel method utilizing peroxotitanic acid sol (PTA). Films were obtained by three dip coatings of sol on borosilicate glasses. The crystalline size and the variation in phase of thin films were determined through X-ray diffraction. The average crystalline size of the films that was in the range of 42 nm showed a reduction in the value by increasing the rutile content. The surface morphology of the films has been characterized utilizing Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Contact-mode atomic force microscopy (AFM). The results of the morphological investigations were completely coincided with the formation of TiO2-P25 nanocomposite. The optical property of the films has been evaluated by Diffuse Reflection Spectrophotometer (DRS) at the room temperature. The obtained UV-vis spectra for both TiO2 and TiO2-P25 thin films had similar maximum wavelengths. The band gap values for the direct and indirect transitions have been measured for the TiO2 and TiO2-P25 thin films and the results showed negligible variations. The photocatalytical activity of the films was studied by photodegradation of Reactive Red 222 (RR222) under UV irradiation. The results showed that the photocatalytic efficiency of TiO2-P25 nanocomposite thin films had enhanced by the addition of rutile phase which was obviously due to the cooperation of TiO2 and P25 nanoparticles in effective charge transfer process. Additionally, photodegradation rate constant result calculations for the TiO2-P25 nanocomposite thin films can well exhibit the increase in its photocatalytic performance in comparison with TiO2 thin films.

  1. Photocatalytic thin films containing TiO2:N nanopowders obtained by the layer-by-layer self-assembling method

    NASA Astrophysics Data System (ADS)

    Rojas-Blanco, L.; Urzúa, M. D.; Ramírez-Bon, R.; Espinoza Beltrán, F. J.

    2012-01-01

    In this work, TiO2-N powders were synthesized by high-energy ball milling, using commercial titanium dioxide (TiO2) in the anatase phase and urea to introduce nitrogen into TiO2 in order to enhance their photocatalytic properties in the visible spectral region. Several samples were prepared by milling a mixture of TiO2-urea during 2, 4, 8, 12 and 24 h and characterized by spectroscopic and analytical techniques. X-ray diffraction (XRD) results showed the coexistence of anatase and high-pressure srilankite TiO2 crystalline phases in the samples. Scanning electron microscopy (SEM) revealed that the grain size of the powder samples decreases to 200 nm at 24 h milling time. UV-Vis diffuse reflectance spectroscopic data showed a clear red-shift in the onset of light absorption from 387 to 469 nm as consequence of nitrogen doping in the samples. The photocatalytic activity of the TiO2-N samples was evaluated by methylene blue degradation under visible light irradiation. It was found that TiO2-N samples had higher photocatalytic activity than undoped TiO2 samples, which could be assigned to the effect of introducing N atoms and XPS results confirm it. Using polyethylenimine (PEI), transparent thin films of TiO2-N nanoparticles were prepared by layer-by-layer self assembly method. UV-visible spectrophotometry was employed in a quantitative manner to monitor the adsorbed mass of TiO2 and PEI after each dip cycle. The adsorption of both TiO2 and PEI showed a saturation dip time of 15 min.

  2. Visible Light Photocatalysis via CdS/ TiO 2 Nanocomposite Materials

    DOE PAGES

    Srinivasan, Sesha S.; Wade, Jeremy; Stefanakos, Elias K.

    2006-01-01

    Nmore » anostructured colloidal semiconductors with heterogeneous photocatalytic behavior have drawn considerable attention over the past few years. This is due to their large surface area, high redox potential of the photogenerated charge carriers, and selective reduction/oxidation of different classes of organic compounds. In the present paper, we have carried out a systematic synthesis of nanostructured CdS- TiO 2 via reverse micelle process. The structural and microstructural characterizations of the as-prepared CdS- TiO 2 nanocomposites are determined using XRD and SEM-EDS techniques. The visible light assisted photocatalytic performance is monitored by means of degradation of phenol in water suspension.« less

  3. Heterostructured ZnFe2O4/TiO2 nanotube arrays with remarkable visible-light photoelectrocatalytic performance and stability.

    PubMed

    Xie, Shan; Ouyang, Ke; Lao, Yueming; He, Peihao; Wang, Qun

    2017-05-01

    A series of heterostructured ZnFe2O4/TiO2-nanotube arrays (NTAs) with remarkable visible-light photoelectrocatalytic (PEC) activity were successfully prepared via a two-step process of anodization and impregnation, followed by annealing. The structure and morphology of the as-prepared ZnFe2O4/TiO2-NTAs samples, PEC degradation abilities and photoelectrochemical performances, as well as long-term stabilities toward degradation of methyl orange (MO) solution under visible-light irradiation were deeply investigated. Results showed that forming a heterojunction by combination of TiO2-NTAs with ZnFe2O4 successfully extended the absorption edge of TiO2-NTAs to visible-light region. Among all the ZnFe2O4/TiO2-NTAs samples, the 2-ZnFe2O4/TiO2-NTAs sample, named ZT(2), obtained the best PEC activity and the highest photocurrent density under visible-light irradiation. Moreover, the ZT(2) sample retained a good reproducibility and high stability after 20days of PEC degradation. The outstanding visible-light PEC activity and photocurrent response of the ZT(2) sample were attributed to the proper amount of ZnFe2O4 nanoparticles loaded onto the TiO2-NTAs, which not only dramatically improved the visible-light absorption of TiO2-NTAs, but also assisted the separation of photo-induced electron-hole pairs and reduced their recombination by forming a ZnFe2O4/TiO2-NTAs heterojunction. The reaction mechanism responsible for the enhanced visible-light PEC performance of the ZnFe2O4/TiO2-NTAs heterostructure was also discussed.

  4. Preparation and characterization of transparent hydrophilic photocatalytic TiO2/SiO2 thin films on polycarbonate.

    PubMed

    Fateh, Razan; Dillert, Ralf; Bahnemann, Detlef

    2013-03-19

    Transparent hydrophilic photocatalytic TiO2 coatings have been widely applied to endow the surfaces self-cleaning properties. A mixed metal oxide (TiO2/SiO2) can enhance the photocatalytic performance improving the ability of surface adsorption and increasing the amount of hydroxyl surface groups. The present work introduces a systematic study concerning the effect of the SiO2 addition to TiO2 films on the wettability, the photocatalytic activity, the adhesion strength, and the mechanical stability of the films. Transparent hydrophilic photocatalytic TiO2/SiO2 thin films were used to coat the polycarbonate (PC) substrate which was precoated by an intermediate SiO2 layer. The TiO2/SiO2 thin film was prepared employing a bulk TiO2 powder (Sachtleben Hombikat UV 100) and different molar ratios of tetraethoxysilane in acidic ethanol. A dip-coating process was used to deposit the films onto the polycarbonate substrate. The films were characterized by UV/vis spectrophotometry, FTIR spectroscopy, ellipsometry, BET, AFM, XRD, and water contact angle measurements. The mechanical stability and the UV resistance were examined. The photocatalytic activity of the coated surface was calculated from the kinetic analysis of methylene blue photodegradation measurements and compared with the photocatalytic activity of Pilkington Activ sheet glass. The coated surfaces displayed considerable photocatalytic activity and superhydrophilicity after exposure to UV light. The addition of SiO2 results in an improvement of the photocatalytic activity of the TiO2 film reaching the highest value at molar ratio TiO2/SiO2 equal to 1:0.9. The prepared films exhibit a good stability against UV(A) irradiation.

  5. Ag/WO3-codoped TiO2 nanoparticles: relation between structure, sorption, and photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Xu, Jing Y.; Wen, Chen; Jia, Li M.; Xiao, Chang F.

    2009-07-01

    Nanostructured Ag/WO3-TiO2 particles responding to sunlight were synthesized by dissolving silver nitrate, sodium tungstate and tetrabutyl titanate precursors in a suitable solvent. The obtained powders were characterized by a series of analytical methods including X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Zeta potential measurements and UV-vis diffuse reflectance spectra (UV-vis DRS) to demonstrate their physicochemical properties. The as-prepared Ag/WO3-TiO2 samples were evaluated for their photocatalytic activity towards the degradation of methylene blue (MB) under sunlight irradiations. Both silver (Ag) and tungsten (W) species were well dispersed over TiO2 surface with less than 6.0 mol % Ag and 3.0 mol % W to Ti element and contributed to a formation of crystalline WO3. XRD analysis particularly demonstrates the existence of mixed-phase TiO2 materials, to which the improvement in photocatalytic activity is attributed. Besides, the light absorption of doped samples is prominent red shifted relative to the pure TiO2 due to the synergetic effect among the components of Ag, WO3 and TiO2 in the codoped-TiO2. The particle size of the Ag/WO3-TiO2 powders was found to be a decrease which is accompanied with the increase of the surface area. The excellent stability and dispersity of the Ag/WO3-TiO2 powders in aqueous solution could be attributed to the enhanced Zeta potential. On the other hand, the adsorption performances of different samples were tested in the removal of two dyes from aqueous solution(congo red and methylene blue). The first-order adsorption equilibrium constants were determined and the results obtained were fitted by Langmuir monolayer formation. Thus, the Langmuir adsorption isotherm parameters were estimated from the experimental data.

  6. Magnetically recoverable TiO2-WO3 photocatalyst to oxidize bisphenol A from model wastewater under simulated solar light.

    PubMed

    Dominguez, S; Huebra, M; Han, C; Campo, P; Nadagouda, M N; Rivero, M J; Ortiz, I; Dionysiou, D D

    2016-09-27

    A novel magnetically recoverable, visible light active TiO2-WO3 composite (Fe3O4@SiO2@TiO2-WO3) was prepared to enable the photocatalyst recovery after the degradation of bisphenol A (BPA) under simulated solar light. For comparison, the photocatalytic activity of other materials such as non-magnetic TiO2-WO3, Fe3O4@SiO2@TiO2, TiO2, and the commercial TiO2 P25 was also evaluated under the studied experimental conditions. The structure and morphology of the synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and electron dispersion spectroscopy (EDS). Moreover, Brunauer-Emmett-Teller (BET) surface area and magnetic properties of the samples were determined. The Fe3O4@SiO2@TiO2-WO3 and TiO2-WO3 led to a BPA degradation of 17.50 and 27.92 %, respectively, after 2 h of the simulated solar light irradiation. Even though their activity was lower than that of P25, which degraded completely BPA after 1 h, our catalysts were magnetically separable for their further reuse in the treatment. Furthermore, the influence of the water matrix in the photocatalytic activity of the samples was studied in municipal wastewater. Finally, the identification of reaction intermediates was performed and a possible BPA degradation pathway was proposed to provide a better understanding of the degradation process. Graphical abstract ᅟ.

  7. Synthesis of β-NaYF4: Yb3+, Tm3+ @ TiO2 and β-NaYF4: Yb3+, Tm3+ @ TiO2 @ Au nanocomposites and effective upconversion-driven photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Duo, Shuwang; Zhang, JieJun; Zhang, Hao; Chen, Zhong; Zhong, Cuiping; Liu, Tingzhi

    2016-12-01

    The β-NaYF4: Yb3+, Tm3+ @ TiO2 nanocomposite has been prepared by a facile hydrothermal method followed by the hydrolysis of TBOT, and then NaYF4: Yb3+, Tm3+ @ TiO2, HAuCl4 and sodium citrate were put into an oil bath for reaction to obtain the β-NaYF4: Yb3+, Tm3+ @ TiO2 @ Au core-shell nanocomposite. XRD and HRTEM show that the samples exhibit the hexagonal phase NaYF4, anatase TiO2 and cubic Au, indicating that the core-shell phases of NaYF4-TiO2 or NaYF4-TiO2-Au coexist in these samples. EDS and XPS results show the presence of Na, Y, F, Ti, O and Au elements. When TiO2 was coated on the surface of upconversion nanomaterials of NaYF4: Yb3+, Tm3+, the photocatalytic activity was improved significantly, and the β-NaYF4: Yb3+, Tm3+ @ TiO2 nanocomposite gives the highest photodegradation efficiency for MB and RhB, and decomposes about 73% of MB or 80% of RhB within 4.5 h under simulated solar light irradiation respectively. When the ultraviolet light from simulated sunlight irradiation was removed by the addition of a UV filter, the β-NaYF4: Yb3+, Tm3+ @ TiO2 nanocomposite decomposes about 42% of MB or 48% of RhB within 4.5 h. It means that the upconversion-driven photocatalytic performance (decomposes 42% of MB or 48% of RhB) is more effective than UV light-driven photocatalytic performance (31% of MB or 32% of RhB) in the photodegradation process. In addition, the β-NaYF4: Yb3+, Tm3+ @ TiO2 @ Au core-shell nanocomposite does not exhibit the better photocatalytic activity, and the optimal research will be carried out in the future.

  8. Influence of Au and TiO2 structures on hydrogen dissociation over TiO2/Au(100)

    NASA Astrophysics Data System (ADS)

    Nakamura, I.; Mantoku, H.; Furukawa, T.; Takahashi, A.; Fujitani, T.

    2012-11-01

    We performed H2-D2 exchange reactions over TiOx/Au(100) and compared the observed reaction kinetics with those reported for TiOx/Au(111) in order to clarify the influence of the Au and TiO2 structures on dissociation of H2 molecules. Low energy electron diffraction observations showed that the TiO2 produced on Au(100) was disordered, in contrast to the comparatively ordered TiO2 structure formed on Au(111). The activation energies and the turnover frequencies for HD formation over TiO2/Au(100) agreed well with those for TiO2/Au(111), clearly indicating that the hydrogen dissociation sites created over TiO2/Au(100) were the perimeter interface between stoichiometric TiO2 and Au, as was previously concluded for TiO2/Au(111). We concluded that the creation of active sites for hydrogen dissociation was independent of the Au and TiO2 structures consisting perimeter interface, and that local bonds that formed between Au and O atoms of stoichiometric TiO2 were essential for the creation of active sites.

  9. Non-metal doped TiO2 nanotube arrays for high efficiency photocatalytic decomposition of organic species in water

    NASA Astrophysics Data System (ADS)

    Szkoda, Mariusz; Siuzdak, Katarzyna; Lisowska-Oleksiak, Anna

    2016-10-01

    Titanium dioxide is a well-known photoactive semiconductor with a variety of possible applications. The procedure of pollutant degradation is mainly performed using TiO2 powder suspension. It can also be exploited an immobilized catalyst on a solid support. Morphology and chemical doping have a great influence on TiO2 activity under illumination. Here we compare photoactivity of titania nanotube arrays doped with non-metal atoms: nitrogen, iodine and boron applied for photodegradation of organic dye - methylene blue and terephtalic acid. The doped samples act as a much better photocatalyst in the degradation process of methylene blue and lead to the formation of much higher amount of hydroxyl radicals (•OH) than undoped TiO2 nanotube arrays. The use of a catalyst active under solar light illumination in the form of thin films on a stable substrate can be scaled up for an industrial application.

  10. Understanding the effect of flower extracts on the photoconducting properties of nanostructured TiO2.

    PubMed

    Ansari, S G; Bhayana, Laitka; Umar, Ahmad; Al-Hajry, A; Al-Deyab, Salem S; Ansari, Z A

    2012-10-01

    Here we report an easy method to improve the optoelectronic properties of commercially available TiO2 nanopowder using extracts of various flowers viz. Calendula Orange (CO), Calendula Yellow (CY), Dahlia Violet (DV), Dahlia Yellow (DY), Rabbit flower (RF), Sweet Poppy (SP), Sweet Williams (SW) and their Mixed Extracts (ME). Various analysis techniques such as UV-Vis, FTIR, FESEM, XRD, and Raman spectroscopy were used to characterize for elemental, structural and morphological properties of the unmixed/mixed TiO2 nanopowder. TiO2 nanopowder was also calcined at 550 degrees C. Thick films of the these unmixed/mixed powder were printed, using conventional screen printing method, on fluorine doped tin oxide (FTO) substrate with organic binders and dried at 45 degrees C. The photoconducting properties are investigated as a function of wavelength from ultra-violet (UV) to infra-red (IR) region at a constant illumination intensity. Photocurrent gradually decreases when irradiated from UV to IR region. In case of unmixed and uncalcined TiO2, conductance decreased continuously whereas when extracts are added, a flat region of conductance is observed. The overall effect of extracts (colour pigments) is seen as an increase in the photoconductance. Highest photoconductance is observed in case of DY flower extract. Anthocyanins, present in flowers are known to have antioxidative properties and hence can contribute in photoconduction by reducing the surface adsorbed oxygen. This investigation indicates the potential use of flower extracts for dye sensitized solar cell (DSSC).

  11. Photocatalytic self-cleaning TiO2 coatings on carbonatic stones

    NASA Astrophysics Data System (ADS)

    Bergamonti, Laura; Bondioli, Federica; Alfieri, Ilaria; Lorenzi, Andrea; Mattarozzi, Monica; Predieri, Giovanni; Lottici, Pier Paolo

    2016-02-01

    A self-cleaning coating based on TiO2 nanoparticles obtained by sol-gel method in an alkaline environment has been tested on different types of carbonatic stones: Botticino, Carrara and Pietra Dorata, frequently used in historic buildings. XRD and Raman measurements confirmed the nanocrystalline nature of titania in anatase form, with 5-10 nm crystal size, and evidenced a small amount of brookite. A fast photocatalytic oxidation by TiO2 coatings of the stained stones with methyl orange and methylene blue under UV lamp irradiation has been assessed. The enhancement of surface wettability due to UV-induced TiO2 hydrophilicity has been evidenced by contact angle measurements. ESEM/EDS showed a surface distribution of the coating fairly homogeneous. The coating does not introduce significant colorimetric changes of the stones and does not alter the water capillarity absorption. Thus, the alkaline nanocrystalline TiO2 is promising for self-cleaning coatings on carbonatic stones.

  12. TiO2 and Fe2O3 films for photoelectrochemical water splitting.

    PubMed

    Krysa, Josef; Zlamal, Martin; Kment, Stepan; Brunclikova, Michaela; Hubicka, Zdenek

    2015-01-09

    Titanium oxide (TiO2) and iron oxide (α-Fe2O3) hematite films have potential applications as photoanodes in electrochemical water splitting. In the present work TiO2 and α-Fe2O3 thin films were prepared by two methods, e.g., sol-gel and High Power Impulse Magnetron Sputtering (HiPIMS) and judged on the basis of physical properties such as crystalline structure and surface topography and functional properties such as simulated photoelectrochemical (PEC) water splitting conditions. It was revealed that the HiPIMS method already provides crystalline structures of anatase TiO2 and hematite Fe2O3 during the deposition, whereas to finalize the sol-gel route the as-deposited films must always be annealed to obtain the crystalline phase. Regarding the PEC activity, both TiO2 films show similar photocurrent density, but only when illuminated by UV light. A different situation was observed for hematite films where plasmatic films showed a tenfold enhancement of the stable photocurrent density over the sol-gel hematite films for both UV and visible irradiation. The superior properties of plasmatic film could be explained by ability to address some of the hematite drawbacks by deposition of very thin films (25 nm) consisting of small densely packed particles and by doping with Sn.

  13. Effect of niobium on the structure and photoactivity of anatase (TiO2) nanoparticles.

    PubMed

    Hirano, Masanori; Matsushima, Kazumasa

    2006-03-01

    Anatase-type TiO2 nanoparticles doped with 0-30 mol% niobium were directly formed from precursor solutions of TiOSO4 and NbCl5 under mild hydrothermal conditions at 120-180 degrees C for 5 h using the hydrolysis of urea. When the niobium content increased from 0 to 30 mol%, the crystallite size of anatase increased from 8.5 to 19 nm. The band gap of anatase was slightly decreased by making solid solutions with niobium. Their photocatalytic activity and adsorptivity were evaluated separately by the measurement of the concentration of methylene blue (MB) remained in the solution after maintained in the dark or under UV-light irradiation. To form anatase-type solid solutions by doping 5-15 mol% niobium into TiO2 was effective for improvement of the photoactivity of TiO2. The photocatalytic activity (the photooxidation rate) and the adsorption amount of MB for the sample containing 15 mol% niobium became more than approximately nine times and six times as much as those of the hydrothermal anatase-type pure TiO2, respectively.

  14. Synthesis of rare earth doped TiO2 nanorods as photocatalysts for lignin degradation

    DOE PAGES

    Song, Liang; Zhao, Xueyuan; Cao, Lixin; ...

    2015-09-10

    In this paper, a two-step process is developed to synthesize rare earth doped titania nanorods (RE–TiO2 NRs) as photocatalysts for efficient degradation of lignin under simulated sunlight irradiation. In this approach, protonated titanate nanotubes with layered structures were first prepared by a hydrothermal approach, and rare earth metal ions were subsequently bound to the negatively charged surface of the synthesized titanate via electrostatic incorporation. The as-synthesized RE–TiO2 NRs after calcination generally showed much higher photocatalytic efficiencies than those of undoped TiO2 NRs or the commercial P25 TiO2 photocatalyst. Using methyl orange (MO) as a probing molecule, we demonstrate that Eu–TiO2more » NRs are among the best for degrading MO, with an observed rate constant of 4.2 × 10-3 s-1. The La3+, Sm3+, Eu3+ and Er3+ doped TiO2 NRs also showed higher photocatalytic efficiencies in degrading MO than the commercial P25 TiO2. Finally, we further demonstrate that lignin can be photodegraded effectively and rapidly at room temperature under simulated sunlight through two reaction routes, which could be important in controlling ways of lignin depolymerization or the formation of reaction products.« less

  15. A hydrothermal synthesis of Pr3+ doped mesoporous TiO2 for UV light photocatalysis.

    PubMed

    Wang, Yong; Chen, Guihua; Shen, Qianhong; Yang, Hui; Li, Liquan; Song, Yanjiang

    2014-07-01

    Pr3+ doped mesoporous TiO2 photocatalysts with a different molar ratio of Pr to Ti were prepared by a hydrothermal method using triblock copolymer as the template. The as-prepared samples were systematically characterized by X-ray diffraction, N2 adsorption-desorption, X-ray photoelectron spectra, transmission electron microscopy and UV-visible diffuse reflectance spectroscopy. The characterizations indicated all the samples had mesoporous structure and narrow pore size distribution. Pr3+ doping enlarged the surface area and decreased the crystallite size. The surface area of the samples varied from 136 to 170 m2/g, and the average crystallite size ranged between 5.04 and 7.60 nm. The effect of Pr3+ doping amount on the photocatalytic activity of mesoporous TiO2 was evaluated by the degradation of methyl orange under UV light irradiation. The results showed that the suitable amount of Pr3+ doped samples exhibited the higher photocatalytic activity than mesoporous TiO2. Among the samples, 1 at.% Pr3+ doped mesoporous TiO2 showed the highest photocatalytic activity.

  16. In situ sonosynthesis of nano TiO2 on cotton fabric.

    PubMed

    Akhavan Sadr, Farid; Montazer, Majid

    2014-03-01

    Here, titanium dioxide nanoparticles (NPs) were sonosynthesized and loaded simultaneously onto the cotton fabric. Titanium tetra isopropoxide (TTIP) was used as precursor and ultrasonic irradiation was utilized as a tool for synthesis of TiO2 in low temperature with anatase structure and loading nanoparticles onto the cotton fabric. TiO2 loaded cotton fabric was characterized by XRD, FE-SEM, EDS, and XRF. Moreover, several properties of the treated cotton fabrics such as self-cleaning, UV protection, washing durability, and tensile strength were studied. The effect of variables, including TTIP concentration and sonication time, was investigated based on central composite design (CCD) and response surface methodology (RSM). The results confirmed formation of anatase TiO2 nanoparticles with 3-6 nm crystalline size loaded onto the cotton fabric at low temperature (75 °C) that led to good self-cleaning and UV-protection properties. The excellent UV-protection rating of the treated fabric maintained even after 25 home launderings indicating an excellent washing durability. Interestingly, sonochemical method had no negative influence on the cotton fabric structure. The statistical analysis indicated significant effect of both TTIP concentration and sonication time on the content of the loaded TiO2 on the fiber and self-cleaning properties of the fabric.

  17. Fe ion-implanted TiO2 thin film for efficient visible-light photocatalysis

    NASA Astrophysics Data System (ADS)

    Impellizzeri, G.; Scuderi, V.; Romano, L.; Sberna, P. M.; Arcadipane, E.; Sanz, R.; Scuderi, M.; Nicotra, G.; Bayle, M.; Carles, R.; Simone, F.; Privitera, V.

    2014-11-01

    This work shows the application of metal ion-implantation to realize an efficient second-generation TiO2 photocatalyst. High fluence Fe+ ions were implanted into thin TiO2 films and subsequently annealed up to 550 °C. The ion-implantation process modified the TiO2 pure film, locally lowering its band-gap energy from 3.2 eV to 1.6-1.9 eV, making the material sensitive to visible light. The measured optical band-gap of 1.6-1.9 eV was associated with the presence of effective energy levels in the energy band structure of the titanium dioxide, due to implantation-induced defects. An accurate structural characterization was performed by Rutherford backscattering spectrometry, transmission electron microscopy, Raman spectroscopy, X-ray diffraction, and UV/VIS spectroscopy. The synthesized materials revealed a remarkable photocatalytic efficiency in the degradation of organic compounds in water under visible light irradiation, without the help of any thermal treatments. The photocatalytic activity has been correlated with the amount of defects induced by the ion-implantation process, clarifying the operative physical mechanism. These results can be fruitfully applied for environmental applications of TiO2.

  18. Ag-Si Co-doped TiO2 photocatalyst synthesized via a nonaqueous method.

    PubMed

    Chen, Qifeng; Shi, Weimei; Xu, Yao; Wu, Dong; Sun, Yuhan

    2010-11-01

    Ag-Si/TiO2 photocatalysts were synthesized in a nonaqueous system at 140 degrees C, and then annealed at different temperatures. The obtained photocatalysts were characterized by XRD, TEM, BET, TG-DTA, XPS, as well as UV-vis DRS. The results showed that All Ag-Si/TiO2 held an anatase phase and high thermal stability and the phase transformation from anatase to rutile was retarded to about 900 degrees C. The Ag-Si/TiO2 particles were highly mono-dispersed and the particles size became smaller compared to TiO2. Additionally, UV-vis light absorption shifted to visible region after Ag doping. Si weaved into the matrix of TiO2, while Ag dispersed on the surface of TiO2 particles. The visible light photocatalytic activity was evaluated by Rhodamine B (RhB) degradation in an aqueous solution under visible light irradiation. It was found that the photccatalytic activities of the obtained Ag-Si/TiO2 samples were all higher than those of pure TiO2 and Ag/TiO2, reaching the maximum at the Ag and Si content of 0.5 mol% and 20.0 mol%, respectively. The enhanced visible photocatalytic activity may be attributed to the simultaneous effects of silver and silicon co-doping.

  19. Facile control of surface wettability in TiO2/poly(methyl methacrylate) composite films.

    PubMed

    Yang, Mengjin; Di, Zengfeng; Lee, Jung-Kun

    2012-02-15

    A facile method to produce very hydrophobic surface was developed simply using the mixture of TiO(2) nanoparticles and poly(methyl methacrylate) (PMMA). When the volume ratio of TiO(2) to PMMA is between 35 vol.% and 50 vol.%, the mixture of two hydrophilic materials became very hydrophobic. Analysis of the molecular structure by infrared spectroscopy shows that the preferential orientation and attachment of a carbonyl group of a polymer molecule to the surface of TiO(2) nanoparticles play a critical role in the appearance of the strong hydrophobicity. When this composite was exposed to UV light, PMMA on the surface of the mixture film was decomposed through a photocatalytic reaction and the very hydrophobic surface turned to the superhydrophilic one. The superhydrophilic property of UV-irradiated composite lasts as long as several months. This long lasting superhydrophilicity is ascribed to the porous structure, which provides high roughness and strong capillary interaction. Easy transition from strong hydrophobicity to superhydrophilicity in TiO(2)/PMMA composites could be applied to designing high contrast hydrophilic/hydrophobic patterns.

  20. Preparation of Fe-doped TiO2 nanoparticles immobilized on polyamide fabric

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Zhu, Hong

    2012-10-01

    A thin layer of nano-scaled Fe-doped TiO2 particles prepared by hydrothermal method is immobilized on the surface of polyamide 6 (PA6) fiber using tetrabutyl titanate as the precursor, ferric trichloride as the doping agent and chitosan as the dispersant agent. The morphology, crystal structure, thermal behavior, composition and chemical structure of PA6 fabric before and after treatments are characterized by means of scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, differential scanning calorimetry and thermal gravimetric analysis techniques. The properties of diffuse reflectance spectrum, tensile, air permeability, whiteness, yellowness and photocatalytic activity are also analyzed. It is found that the anatase phase Fe-doped TiO2 nanoparticles with crystal size of 12 nm or so are synthesized, and simultaneously grafted onto the fiber surface during the processing. Compared with the TiO2-coated fabric, the thermal stability of the Fe-doped TiO2-coated fabric changes a little. The absorption ability to ultraviolet (UV) rays and visible light is greatly improved. The breaking force and breaking elongation increase to some extent because of the shrinkage of fabric. The air permeability decreases distinctly. The color of PA6 fabric changes from white to light brownish because of the introduction of ferric trichloride. The photocatalytic activity of methylene blue decolorization is enhanced under sunlight and UV irradiation.

  1. Highly efficient low-temperature plasma-assisted modification of TiO2 nanosheets with exposed {001} facets for enhanced visible-light photocatalytic activity.

    PubMed

    Li, Beibei; Zhao, Zongbin; Zhou, Quan; Meng, Bo; Meng, Xiangtong; Qiu, Jieshan

    2014-11-03

    Anatase TiO2 nanosheets with exposed {001} facets have been controllably modified under non-thermal dielectric barrier discharge (DBD) plasma with various working gas, including Ar, H2 , and NH3 . The obtained TiO2 nanosheets possess a unique crystalline core/amorphous shell structure (TiO2 @TiO2-x ), which exhibit the improved visible and near-infrared light absorption. The types of dopants (oxygen vacancy/surface Ti(3+) /substituted N) in oxygen-deficient TiO2 can be tuned by controlling the working gases during plasma discharge. Both surface Ti(3+) and substituted N were doped into the lattice of TiO2 through NH3 plasma discharge, whereas the oxygen vacancy or Ti(3+) (along with the oxygen vacancy) was obtained after Ar or H2 plasma treatment. The TiO2 @TiO2-x from NH3 plasma with a green color shows the highest photocatalytic activity under visible-light irradiation compared with the products from Ar plasma or H2 plasma due to the synergistic effect of reduction and simultaneous nitridation in the NH3 plasma.

  2. Preparation of Pd-loaded La-doped TiO2 nanotubes and investigation of their photocatalytic activity under visible light

    NASA Astrophysics Data System (ADS)

    Zong, Lanlan; Li, Qiuye; Zhang, Jiwei; Wang, Xiaodong; Yang, Jianjun

    2013-11-01

    Orthorhombic titanic acid nanotubes (TAN) have large BET surface area and small-diameter one-dimensional nanotubular morphology, so they can work as a good supporter and a precursor of TiO2. However, in our former research, we found that calcination of TAN to anatase TiO2 would destroy the nanotubular structure and decrease the BET surface area sharply. In this work, we utilized the pillar effect of the foreign nanoparticles (La2O3) to keep the nanotubular morphology of TiO2, and obtained the anatase TiO2 nanotubes with large BET surface area. For improving the photocatalytic activity, Pd nanoparticles were loaded as the electron traps on the surface of La-doped TiO2 by photo-deposition method. The photocatalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, diffuse reflectance spectra, and N2 adsorption-desorption isotherms measurement. Their photocatalytic activities were evaluated by the removal of propylene under visible light irradiation ( λ ≥ 420 nm). The results showed that the photocatalytic activity of Pd-loaded La-doped TiO2 nanotubes improved effectively compared with that of La-doped TiO2 and pure TiO2.

  3. Low temperature synthesis of polyaniline-crystalline TiO2-halloysite composite nanotubes with enhanced visible light photocatalytic activity.

    PubMed

    Li, Cuiping; Wang, Jie; Guo, Hong; Ding, Shujiang

    2015-11-15

    A series of one-dimensional polyaniline-crystalline TiO2-halloysite composite nanotubes with different mass ratio of polyaniline to TiO2 are facilely prepared by employing the low-temperature synthesis of crystalline TiO2 on halloysite nanotubes. The halloysite nanotubes can adsorb TiO2/polyaniline precursors and induce TiO2 nanocrystals/polyaniline to grow on the support in situ simultaneously. By simply adjusting the acidity of reaction system, PANI-crystalline TiO2-HA composite nanotubes composed of anatase, a mixed phase TiO2 and different PANI redox state are obtained. The XRD and UV-vis results show that the surface polyaniline sensitization has no effect on the crystalline structure of halloysite and TiO2 and the light response of TiO2 is extended to visible-light regions. Photocatalysis test results reveal the photocatalytic activity will be affected by the pH value and the volume ratio of ANI to TTIP. The highest photocatalytic activity is achieved with the composite photocatalysts prepared at pH 0.5 and 1% volume ratio of ANI and TTIP owing to the sensitizing effect of polyaniline and the charge transfer from the photoexcited PANI sensitizer to TiO2. Moreover, the PANI-TiO2-HA composite nanotubes synthesized by one-step at pH 0.5 with 1% volume ratio of ANI to TTIP exhibit higher visible light photocatalytic activity than those synthesized by the two-step. Heterogeneous PANI-TiO2-HA composite nanotubes prepared at pH 0.5 exhibit a higher degradation activity than that prepared at pH 1.5. The redoped experiment proves that the PANI redox state plays the main contribution to the enhanced visible light catalytic degradation efficiency of PANI-TiO2-HA prepared at pH 0.5. Furthermore, the heterogeneous PANI-crystalline TiO2-HA nanotubes have good photocatalytic stability and can be reused four times with only gradual loss of activity under visible light irradiation.

  4. Visible light induced electron transfer process over nitrogen doped TiO(2) nanocrystals prepared by oxidation of titanium nitride.

    PubMed

    Wu, Zhongbiao; Dong, Fan; Zhao, Weirong; Guo, Sen

    2008-08-30

    Nitrogen doped TiO(2) nanocrystals with anatase and rutile mixed phases were prepared by incomplete oxidation of titanium nitride at different temperatures. The as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), core level X-ray photoelectron spectroscopy (CL XPS), valence band X-ray photoelectron spectroscopy (VB XPS), UV-vis diffuse reflectance spectra (UV-vis DRS), and visible light excited photoluminescence (PL). The photocatalytic activity was evaluated for photocatalytic degradation of toluene in gas phase under visible light irradiation. The visible light absorption and photoactivities of these nitrogen doped TiO(2) nanocrystals can be clearly attributed to the change of the additional electronic (N(-)) states above the valence band of TiO(2) modified by N dopant as revealed by the VB XPS and visible light induced PL. A band gap structure model was established to explain the electron transfer process over nitrogen doped TiO(2) nanocrystals under visible light irradiation, which was consistent with the previous theoretical and experimental results. This model can also be applied to understand visible light induced photocatalysis over other nonmetal doped TiO(2).

  5. Use of titanium dioxide (TiO2) photocatalysts as alternative means for Listeria monocytogenes biofilm disinfection in food processing.

    PubMed

    Chorianopoulos, N G; Tsoukleris, D S; Panagou, E Z; Falaras, P; Nychas, G-J E

    2011-02-01

    The aim of this work was to study the photocatalytic activity of titanium dioxide (TiO(2)) against Listeria monocytogenes bacterial biofilm. Different TiO(2) nanostructured thin films were deposited on surfaces such as stainless steel and glass using the doctor-blade technique. All the surfaces were placed in test tubes containing Brain Heart (BH) broth and inoculated with L. monocytogenes. Test tubes were then incubated for 10 days at 16°C in order to allow biofilm development. After biofilm formation, the surfaces were illuminated by ultraviolet A light (UVA; wavelength of 315-400 nm). The quantification of biofilms was performed using the bead vortexing method, followed by agar plating and/or by conductance measurements (via the metabolic activity of biofilm cells). The presence of the TiO(2) nanoparticles resulted in a fastest log-reduction of bacterial biofilm compared to the control test. The biofilm of L. monocytogenes for the glass nanoparticle 1 (glass surface modified by 16% w/v TiO(2)) was found to have decreased by 3 log CFU/cm(2) after 90 min irradiation by UVA. The use of TiO(2) nanostructured photocatalysts as alternative means of disinfecting contaminated surfaces presents an intriguing case, which by further development may provide potent disinfecting solutions. Surface modification using nanostructured titania and UV irradiation is an innovative combination to enhance food safety and economizing time and money.

  6. Microwave-assisted synthesis and photocatalytic properties of sulphur and platinum modified TiO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Drunka, R.; Grabis, J.; Jankovica, Dz; Krumina, A.; Rasmane, Dz

    2015-03-01

    In the present work formation of active TiO2 nanofibers in microwave synthesis and their modification with platinum were studied. Mixture of anatase and rutile nanopowder and 10M KOH solution were used as raw materials. Microwave assisted synthesis method permitted to obtain TiO2 nanofibres with a diameter of 10nm and a specific surface area up to 40.2 m2/g. In order to modify TiO2 nanofibers with platinum it was stirred in H2PtCl6 solution and illuminated with UV irradiation or reduced with sodium boronhydride. To modify titania with sulphur and prepare co-doped nanofibers platinum doped samples were extra treated in hydrogen sulphide atmosphere. Photocatalytic activity was determined by degradation of the methylene blue (MB) solution under UV and visible light irradiation. The obtained samples showed higher photocatalytic activity with respect to pure TiO2 nanofibers. The doped TiO2 nanofibers were appropriate for degradation of harmful organic compounds.

  7. Heterogeneous photocatalytic degradation of sulfamethoxazole in water using a biochar-supported TiO2 photocatalyst.

    PubMed

    Kim, Jihyun R; Kan, Eunsung

    2016-09-15

    The present study reports an effective heterogeneous photocatalytic degradation of sulfamethoxazole (SMX) in water using a biochar-supported TiO2 (biochar/TiO2). The biochar was used as a low cost and effective support for TiO2 to lower the recombination rate of electrons and electron holes during photocatalysis, allow efficient attachment of TiO2, increase adsorption capacity and help easy separation of the photocatalyst after use. The biochar/TiO2 showed much higher adsorption of SMX than the commercial TiO2 powder due to the hydrophobic interaction between the biochar and SMX. Particularly this study focused on the effects of water quality and operating conditions on the photocatalytic oxidation of SMX. The addition of low concentration of bicarbonate made drastic enhancement in SMX removal and mineralization while the final effluent showed high biotoxicity. On the contrary, the presence of nitrate exhibited slight enhancement in SMX removal efficiency. The photocatalyst loading and UV irradiation time also played their important roles in enhancement of SMX removal and mineralization. In overall the photocatalytic oxidation of SMX using the biochar/TiO2 at the selected catalyst loading and irradiation time (5 g biochar-supported TiO2 L(-1), 6 h) resulted in the high removal and mineralization of SMX and negligible toxicity.

  8. Synthesis of C-N-Y tri-doped TiO2 photo-catalyst for MO degradation and characterization

    NASA Astrophysics Data System (ADS)

    Hoseinian-Maleki, F.; Nemati, A.; Joya, Yasir F.

    2015-10-01

    In this research C-N-Y tri-doped TiO2 nanopowders were synthesized by the sol-gel method. The C-N-Y TiO2 photo-catalyst was prepared using hexamine and yttrium nitrate Hexahydrate as the dopant precursors. Methyl-orange (MO) was used to study the photocatalytic performance of the doped TiO2 under UV irradiation. The synthesized samples were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, Transmission electron microscopy, Photoluminescence and Field emission scanning electron microscopy. The tri-doped sample with 8% N, 0.4% Y and 1.5% C exhibited enhanced photocatalytic efficiencies. After 100 min of irradiation with UV light, 87% of MO was decomposed by C-N-Y tri-doped TiO2 sample. It is suggested that the co-activity of C and N could make the intra-gap localized states above the valence band of TiO2, and carbon in TiO2 structure causes carbonate species to appear. These carbonate species acted as photosensitizer on the TiO2 surface to promote photo-catalytic activity of the as synthesized sample.

  9. Correlation between dispersion properties of TiO2 colloidal sols and photoelectric characteristics of TiO2 films.

    PubMed

    Jung, Hyun Suk; Lee, Sang-Wook; Kim, Jin Young; Hong, Kug Sun; Lee, Young Cheol; Ko, Kyung Hyun

    2004-11-15

    TiO2 film for use as dye-sensitized solar cell was prepared using the TiO2 colloidal sols (unpeptized sol and peptized sol). The optical properties and photocurrent-voltage characteristics of the resultant films were investigated. The optical transmittance of TiO2 thin film prepared from the peptized colloidal sol was over 90%, while that of TiO2 film from the unpeptized sol was under 80%. The TiO2 photoelectrode prepared from the peptized colloidal sol showed low photoelectric conversion efficiency (eta), 1.30%, whereas the efficiency of photoelectrode from the unpeptized sol was 2.21%. The high optical transmittance and low conversion efficiency of TiO2 film from the peptized sol are discussed in terms of dense microstructure due to the drying nature of well-dispersed colloidal sol.

  10. Photoelectrochemical characteristics of TiO2 nanorod arrays grown on fluorine doped tin oxide substrates by the facile seeding layer assisted hydrothermal method

    NASA Astrophysics Data System (ADS)

    Sui, Mei-rong; Han, Cui-ping; Gu, Xiu-quan; Wang, Yong; Tang, Lu; Tang, Hui

    2016-05-01

    TiO2 nanorod arrays (NRAs) were prepared on fluorine doped tin oxide (FTO) substrates by a facile two-step hydrothermal method. The nanorods were selectively grown on the FTO regions which were covered with TiO2 seeding layer. It took 5 h to obtain the compact arrays with the nanorod length of ~2 μm and diameter of ~50 nm. The photoelectrochemical (PEC) properties of TiO2 NRAs are also investigated. It is demonstrated that the TiO2 NRAs indicate the good photoelectric conversion ability with an efficiency of 0.22% at a full-wavelength irradiation. A photocurrent density of 0.21 mA/cm2 is observed at 0.7 V versus the saturated calomel electrode (SCE). More evidences suggest that the charge transferring resistance is lowered at an irradiation, while the flat-band potential ( V fb) is shifted towards the positive side.

  11. Coating of TiO 2 photocatalysts on super-hydrophobic porous teflon membrane by an ion assisted deposition method and their self-cleaning performance

    NASA Astrophysics Data System (ADS)

    Yamashita, H.; Nakao, H.; Takeuchi, M.; Nakatani, Y.; Anpo, M.

    2003-05-01

    By means of an ion assisted deposition method, a TiO 2 photocatalyst was prepared at relatively lower temperature on porous Teflon sheets (PTS) that are good candidates for the coating materials with super-hydrophobic surfaces. UV light irradiation of TiO 2 photocatalyst on PTS led to the photocatalytic degradation of organic pollutants (self-cleaning), which wear off the water-repellent property of the original PTS surface. The PTS surface loading of a small amount of TiO 2 photocatalyst can keep the super-hydrophobic properties of PTS for a long time because of the photocatalytic degradation of the accumulated pollutants.

  12. Photocatalytical Antibacterial Activity of Mixed-Phase TiO2 Nanocomposite Thin Films against Aggregatibacter actinomycetemcomitans.

    PubMed

    Yeniyol, Sinem; Mutlu, Ilven; He, Zhiming; Yüksel, Behiye; Boylan, Robert Joseph; Ürgen, Mustafa; Karabuda, Zihni Cüneyt; Basegmez, Cansu; Ricci, John Lawrence

    2015-01-01

    Mixed-phase TiO2 nanocomposite thin films consisting of anatase and rutile prepared on commercially pure Ti sheets via the electrochemical anodization and annealing treatments were investigated in terms of their photocatalytic activity for antibacterial use around dental implants. The resulting films were characterized by scanning electron microscopy (SEM), and X-ray diffraction (XRD). The topology was assessed by White Light Optical Profiling (WLOP) in the Vertical Scanning Interferometer (VSI) mode. Representative height descriptive parameters of roughness R a and R z were calculated. The photocatalytic activity of the resulting TiO2 films was evaluated by the photodegradation of Rhodamine B (RhB) dye solution. The antibacterial ability of the photocatalyst was examined by Aggregatibacter actinomycetemcomitans suspensions in a colony-forming assay. XRD showed that anatase/rutile mixed-phase TiO2 thin films were predominantly in anatase and rutile that were 54.6 wt% and 41.9 wt%, respectively. Craters (2-5 µm) and protruding hills (10-50 µm) on Ti substrates were produced after electrochemical anodization with higher R a and R z surface roughness values. Anatase/rutile mixed-phase TiO2 thin films showed 26% photocatalytic decolorization toward RhB dye solution. The number of colonizing bacteria on anatase/rutile mixed-phase TiO2 thin films was decreased significantly in vitro. The photocatalyst was effective against A. actinomycetemcomitans colonization.

  13. Photocatalytical Antibacterial Activity of Mixed-Phase TiO2 Nanocomposite Thin Films against Aggregatibacter actinomycetemcomitans

    PubMed Central

    Yeniyol, Sinem; Mutlu, Ilven; He, Zhiming; Yüksel, Behiye; Boylan, Robert Joseph; Ürgen, Mustafa; Karabuda, Zihni Cüneyt; Basegmez, Cansu; Ricci, John Lawrence

    2015-01-01

    Mixed-phase TiO2 nanocomposite thin films consisting of anatase and rutile prepared on commercially pure Ti sheets via the electrochemical anodization and annealing treatments were investigated in terms of their photocatalytic activity for antibacterial use around dental implants. The resulting films were characterized by scanning electron microscopy (SEM), and X-ray diffraction (XRD). The topology was assessed by White Light Optical Profiling (WLOP) in the Vertical Scanning Interferometer (VSI) mode. Representative height descriptive parameters of roughness Ra and Rz were calculated. The photocatalytic activity of the resulting TiO2 films was evaluated by the photodegradation of Rhodamine B (RhB) dye solution. The antibacterial ability of the photocatalyst was examined by  Aggregatibacter actinomycetemcomitans suspensions in a colony-forming assay. XRD showed that anatase/rutile mixed-phase TiO2 thin films were predominantly in anatase and rutile that were 54.6 wt% and 41.9 wt%, respectively. Craters (2–5 µm) and protruding hills (10–50 µm) on Ti substrates were produced after electrochemical anodization with higher Ra and Rz surface roughness values. Anatase/rutile mixed-phase TiO2 thin films showed 26% photocatalytic decolorization toward RhB dye solution. The number of colonizing bacteria on anatase/rutile mixed-phase TiO2 thin films was decreased significantly in vitro. The photocatalyst was effective against A. actinomycetemcomitans colonization. PMID:26576430

  14. Cellular and molecular responses of E. fetida cœlomocytes exposed to TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Bigorgne, Emilie; Foucaud, Laurent; Caillet, Céline; Giambérini, Laure; Nahmani, Johanne; Thomas, Fabien; Rodius, François

    2012-07-01

    An in vitro approach using cœlomocytes of Eisenia fetida was investigated to evaluate toxicity of TiO2 nanoparticles. Cœlomocytes were exposed to well-dispersed suspension of small aggregates (130 nm) of TiO2 nanoparticles (1-25 μg/ml) during 4, 12 and 24 h. Intracellular localisation suggested that the main route of uptake was endocytosis. Cellular responses showed that TiO2 nanoparticles were not cytotoxic and had no effect on phagocytosis at any of the four concentrations for each time tested. Concerning molecular responses, an increase of fetidin and metallothionein mRNA expression was observed starting from 4 h of exposure. In contrast, expression of coelomic cytolytic factor mRNA decreased for 10 and 25 μg/ml after 4 h. Superoxide dismutase, catalase and glutathione-S-transferase expression were not modified suggesting that oxidative stress was not induced by TiO2 in our experimental conditions. This in vitro approach showed that TiO2 nanoparticles were taken up by cœlomocytes and they could modify the molecular response of immune and detoxification system.

  15. Enhanced performance of {0 0 1} facets dominated mesoporous TiO2 photocatalyst composed of high-reactive nanocrystals and mesoporous spheres

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Lu, Chunhua; Ni, Yaru; Peng, Fengping; Xu, Zhongzi

    2013-01-01

    {0 0 1} facets dominated mesoporous anatase TiO2 sheets composed of mesoporous spheres and high reactive nanocrystals with exposed {0 0 1} facets were synthesized successfully with NH4F as the capping agent by the hydrothermal and heat treatment method. The photocatalyst exhibits a high specific surface area and a higher photocatalytic activity than Degussa P25 and pure TiO2 nanosheets in the degradation of organic dyes under UV irradiation.

  16. n/p-Type changeable semiconductor TiO2 prepared from NTA

    NASA Astrophysics Data System (ADS)

    Li, Qiuye; Wang, Xiaodong; Jin, Zhensheng; Yang, Dagang; Zhang, Shunli; Guo, Xinyong; Yang, Jianjun; Zhang, Zhijun

    2007-10-01

    A novel kind of nano-sized TiO2 (anatase) was obtained by high-temperature (400-700°C) dehydration of nanotube titanic acid (H2Ti2O4(OH)2, NTA). The high-temperature (400-700°C) dehydrated nanotube titanic acids (HD-NTAs) with a unique defect structure exhibited a p-type semiconductor behavior under visible-light irradiation (λ≥420 nm, E photon=2.95 eV), whereas exhibited an n-type semiconductor behavior irradiated with UV light (λ=365 nm, E photon=3.40 eV).

  17. Effect of UV-light on the uniaxial tensile properties and structure of uncoated and TiO2 coated Bombyx mori silk fibers.

    PubMed

    Aksakal, Baki; Koç, Kenan; Yargı, Önder; Tsobkallo, Katherina

    2016-01-05

    The effect of UV-light on the uniaxial tensile properties and the structure of uncoated and TiO2 coated silk fibers in the bave form by using sol-gel method was investigated with tensile testing and FT-IR/ATR spectroscopy methods after the silk filaments were exposed to UV-light with high intensity of 760W/m(2) for different times from 0.5h to 1day. It was clearly observed that TiO2 coating considerably increased the Young's modulus of the uncoated silk single filament by around 17% before the UV-irradiation. The yield point and the post yield region disappeared on the stress-strain curves of both uncoated and TiO2 coated silk filaments after UV-irradiation time higher than 1h. Except for the Young's modulus, most of the tensile characteristics of both uncoated and TiO2 coated silk filaments decreased remarkably with increasing UV-irradiation time, e.g., after 1h irradiation, although the Young's modulus slightly changed and ultimate tensile strength decreased by only around 18% and 23%, for the uncoated and TiO2 coated silk filaments, respectively; breaking extension decreased dramatically by 67% and 72%, respectively, for uncoated and TiO2 coated silk filaments. Only the Young's modulus of TiO2 coated silk filaments which can be considered as a more stable tensile characteristic became significantly higher than that of the uncoated silk filaments with increasing UV-irradiation time. After 1day irradiation, even though the uncoated silk filaments could not be tested and completely lost of their fiber properties, the TiO2 coated silk filaments showed a stress-strain curve in initial elastic region with Young's modulus of ∼13GPa which indicates considerable protective effect of TiO2 on the silk fiber structure, especially on the β-sheet microcrystals against UV-radiation. The FT-IR/ATR spectral results showed that significant photodegradation took place in not only crystalline but also amorphous regions which were deduced from the decrease in the absorbance

  18. Effect of UV-light on the uniaxial tensile properties and structure of uncoated and TiO2 coated Bombyx mori silk fibers

    NASA Astrophysics Data System (ADS)

    Aksakal, Baki; Koç, Kenan; Yargı, Önder; Tsobkallo, Katherina

    2016-01-01

    The effect of UV-light on the uniaxial tensile properties and the structure of uncoated and TiO2 coated silk fibers in the bave form by using sol-gel method was investigated with tensile testing and FT-IR/ATR spectroscopy methods after the silk filaments were exposed to UV-light with high intensity of 760 W/m2 for different times from 0.5 h to 1 day. It was clearly observed that TiO2 coating considerably increased the Young's modulus of the uncoated silk single filament by around 17% before the UV-irradiation. The yield point and the post yield region disappeared on the stress-strain curves of both uncoated and TiO2 coated silk filaments after UV-irradiation time higher than 1 h. Except for the Young's modulus, most of the tensile characteristics of both uncoated and TiO2 coated silk filaments decreased remarkably with increasing UV-irradiation time, e.g., after 1 h irradiation, although the Young's modulus slightly changed and ultimate tensile strength decreased by only around 18% and 23%, for the uncoated and TiO2 coated silk filaments, respectively; breaking extension decreased dramatically by 67% and 72%, respectively, for uncoated and TiO2 coated silk filaments. Only the Young's modulus of TiO2 coated silk filaments which can be considered as a more stable tensile characteristic became significantly higher than that of the uncoated silk filaments with increasing UV-irradiation time. After 1 day irradiation, even though the uncoated silk filaments could not be tested and completely lost of their fiber properties, the TiO2 coated silk filaments showed a stress-strain curve in initial elastic region with Young's modulus of ∼13 GPa which indicates considerable protective effect of TiO2 on the silk fiber structure, especially on the β-sheet microcrystals against UV-radiation. The FT-IR/ATR spectral results showed that significant photodegradation took place in not only crystalline but also amorphous regions which were deduced from the decrease in the absorbance

  19. Isotropic photo-decomposition of spherical organic polymers on rutile TiO2(110) surfaces

    NASA Astrophysics Data System (ADS)

    Ishida, Nobuyuki; Iwasaki, Tamaki; Fujita, Daisuke

    2011-04-01

    We observed the photo-decomposition process of polystyrene latex (PSL) spheres on a rutile TiO2(110) single crystal surface by using atomic force microscopy. During the decomposition process, both the height and width of the PSL spheres linearly decreased with the irradiation time in a similar way from the beginning, suggesting that the PSL spheres are isotropically decomposed. This indicates that the interface between the PSL spheres and the TiO2 surface is not a dominant reaction site, as expected from normal photocatalytic reactions.

  20. Nanofabrication technique based on localized photocatalytic reactions using a TiO2-coated atomic force microscopy probe

    NASA Astrophysics Data System (ADS)

    Shibata, Takayuki; Iio, Naohiro; Furukawa, Hiromi; Nagai, Moeto

    2017-02-01

    We performed a fundamental study on the photocatalytic degradation of fluorescently labeled DNA molecules immobilized on titanium dioxide (TiO2) thin films under ultraviolet irradiation. The films were prepared by the electrochemical anodization of Ti thin films sputtered on silicon substrates. We also confirmed that the photocurrent arising from the photocatalytic oxidation of DNA molecules can be detected during this process. We then demonstrated an atomic force microscopy (AFM)-based nanofabrication technique by employing TiO2-coated AFM probes to penetrate living cell membranes under near-physiological conditions for minimally invasive intracellular delivery.

  1. A visible-light-driven composite photocatalyst of TiO2 nanotube arrays and graphene quantum dots.

    PubMed

    Chan, Donald K L; Cheung, Po Ling; Yu, Jimmy C

    2014-01-01

    TiO2 nanotube arrays are well-known efficient UV-driven photocatalysts. The incorporation of graphene quantum dots could extend the photo-response of the nanotubes to the visible-light range. Graphene quantum dot-sensitized TiO2 nanotube arrays were synthesized by covalently coupling these two materials. The product was characterized by Fourier-transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and UV-vis absorption spectroscopy. The product exhibited high photocatalytic performance in the photodegradation of methylene blue and enhanced photocurrent under visible light irradiation.

  2. Influence of TiO2 hollow sphere size on its photo-reduction activity for toxic Cr(VI) removal.

    PubMed

    Cai, Jiabai; Wu, Xueqing; Zheng, Fengying; Li, Shunxing; Wu, Yaling; Lin, Yanping; Lin, Liting; Liu, Biwen; Chen, Qiaoying; Lin, Luxiu

    2017-03-15

    After polystyrene@titanium dioxide (PS@TiO2) composite with different size was calcined at designated temperature, TiO2 hollow sphere with controllable size was obtained for high efficient photo-reduction of Cr(VI). The feature of the TiO2 hollow sphere was investigated by SEM, TEM, XRD, UV-Vis, and photoluminescence. The photo-reduction of Cr(VI) were measured for the performance assessment of the TiO2 hollow sphere, Cr(VI) was used as an electron acceptor. After irradiation for 2h, the photo-reduction rate of Cr(VI) (pH=2.82) for TiO2(450nm) was 96%, which exhibited an increase of 5% and 8% compared with TiO2(370nm) and TiO2(600nm). The absorption edges of TiO2 hollow sphere (450nm) was largest with the increasing of hollow sphere size from 370 to 600nm. The optimal hollow sphere size of TiO2 was 450nm for the photo-reduction of Cr(VI), because the light-harvesting efficiency (the best of absorption edge) and photo-generated electron-hole separation rate (the best of photo-reduction rate) of TiO2 hollow sphere were controlled by its hollow sphere size. In addition, we find that the behavior of the hydrogen production was inhibited by the coexistence Cr(VI) solution. This study can improve our understanding of the mechanism for the activity enhancement by the optimal hollow sphere size of TiO2.

  3. UV light induced photodegradation of malachite green on TiO2 nanoparticles.

    PubMed

    Chen, C C; Lu, C S; Chung, Y C; Jan, J L

    2007-03-22

    The photodegradation of malachite green (MG), a cationic triphenylmethane dye, is examined both under different pH values and amounts of TiO(2). After 15W UV-365nm irradiation for 4h, ca. 99.9% of MG was degraded with addition of 0.5gL(-1) TiO(2) to solutions containing 50mgL(-1) of the MG dye. The HPLC-PDA-ESI-MS technique was used to obtain a better understanding on the mechanistic details of this TiO(2)-assisted photodegradation of the MG dye with UV irradiation. Five intermediates of the process were separated, identified, and characterized for the first time. The results indicated that the N-de-methylation degradation of MG dye took place in a stepwise manner to yield mono-, di-, tri-, and tetra-N-de-methylated MG species generated during the processes. Under acidic conditions, the results indicated that the photodegradation mechanism is favorable to cleavage of the whole conjugated chromophore structure of the MG dye. Under basic conditions, the results showed that the photodegradation mechanism is favorable to a formation of a series of N-de-methylated intermediates of the MG dye.

  4. Niobium doping induced morphological changes and enhanced photocatalytic performance of anatase TiO2

    NASA Astrophysics Data System (ADS)

    Wu, Ming-Chung; Lin, Ting-Han; Chih, Jyun-Sian; Hsiao, Kai-Chi; Wu, Po-Yeh

    2017-04-01

    In order to develop high-performance photocatalysts that are easy to produce even in industrial quantities, we developed a facile method of preparing niobium-doped titanium dioxide (Nb:TiO2) by hydrothermal synthesis and followed by thermal annealing treatment. Niobium-ion doping has been considered as an effective way to improve Nb:TiO2 performance for applications in photocatalysis. Niobium-ion doping of anatase TiO2 induced the morphological changes of Nb:TiO2. Morphological analysis shows sub-microscale fibers at doping concentration lower than 1.00 mol % and nanoscale rods at the doping concentration higher than 1.00 mol %. For the catalyzed photodegradation of methyl orange under visible light irradiation, 0.50 mol % Nb:TiO2 shows the highest activity among the synthesized Nb:TiO2 specimens. Also, for photocatalytic hydrogen generation, its photocatalytic activity is even higher than that of commercial TiO2-P25. In this study, we demonstrated the fabrication of a series of superior Nb:TiO2 specimens. It is a reasonable alternative to commercial TiO2 materials for various applications in the decomposition of organic dyes under visible light irradiation.

  5. Radiation damage induced by swift heavy ions in TiO2 sol-gel films nanocrystallines

    NASA Astrophysics Data System (ADS)

    Hazem, R.; Izerrouken, M.; Sari, A.; Kermadi, S.; Msimanga, M.; Benyagoub, A.; Maaza, M.; Belgaid, M.; Boumaour, M.

    2013-06-01

    TiO2 films prepared by sol-gel were irradiated with 25.8 MeV Cu and 90 MeV Xe ions at room temperature under normal incidence. The irradiation with Cu and Xe ions were performed respectively at iThemba labs, South Africa and GANIL, Caen, France. The properties of radiation defects induced in TiO2 nanostructures were investigated using grazing angle X-ray diffraction (GAXRD), atomic force microscopy (AFM) and UV-visible spectrophotometry. From GAXRD analysis, it is found that anatase (1 0 1) peak intensity decrease with increasing the fluence and disappear completely above a threshold ion fluence of 5 × 1012 ion/cm2. This indicates that the crystallinity of the TiO2 film is destroyed upon irradiation due to the amorphous track formation. The track radius estimated from the Poisson's law is about 2 and 4 nm after irradiation with 25.8 MeV Cu and 90 MeV Xe ions, respectively. According to the AFM analysis, the elaborated TiO2 films are composed of particles with a triangular shape of a size in the range of 200-500 nm. It is found that the particle size increases after irradiation with both Cu and Xe ions. In addition, the root-mean-square (RMS) surface roughness for 780 nm × 780 nm area scans decreases exponentially with increasing fluence up to 1013 ions/cm2 in the case of Xe irradiation, but increases drastically above 2.68 × 1011 ions/cm2 in the case of Cu ion irradiation and reaches a mean value of ˜3 nm. The absorption measurements reveal that the optical band gap is not affected by both Xe and Cu ions irradiation.

  6. Near-uv photon efficiency in a TiO2 electrode - Application to hydrogen production from solar energy

    NASA Technical Reports Server (NTRS)

    Desplat, J.-L.

    1976-01-01

    An n-type (001) TiO2 electrode irradiated at 365 nm was tested under anodic polarization. A saturation current independent of pH and proportional to light intensity has been observed. Accurate measurements of the incident power lead to a 60 per cent photon efficiency. A photoelectrochemical cell built with such an electrode, operated under solar irradiation without concentration, produced an electrolysis current of 0.7 mA/sq cm without applied voltage.

  7. Ellipsoidal TiO2 hierarchitectures with enhanced photovoltaic performance.

    PubMed

    Peng, Wenqin; Yanagida, Masatoshi; Chen, Han; Han, Liyuan

    2012-04-23

    Hierarchical TiO(2) ellipsoids 250-500 nm in size have been synthesized on a large scale by a template-free hydrothermal route. The submicrometer-sized hierarchitectures are assembled from highly crystallized anatase nanorods about 17 nm in diameter with macroporous cavities on the outer shells. Based on the time-dependent morphological evolution under hydrothermal conditions, an oriented attachment process is proposed to explain formation of the hierarchical structures. Such hierarchical TiO(2) not only adsorbs large amounts of dye molecules due to high surface area, but also shows good light scattering caused by the submicrometer size. The TiO(2) hierarchitectures were deposited on top of a transparent TiO(2) nanocrystalline main layer to construct a double-layered photoanode for dye-sensitized solar cell (DSC) application, exhibiting enhanced light harvesting and power-conversion efficiency compared to a commercial TiO(2)-based electrode.

  8. TiO2-graphene oxide nanocomposite as advanced photocatalytic materials

    PubMed Central

    2013-01-01

    Background Graphene oxide composites with photocatalysts may exhibit better properties than pure photocatalysts via improvement of their textural and electronic properties. Results TiO2-Graphene Oxide (TiO2 - GO) nanocomposite was prepared by thermal hydrolysis of suspension with graphene oxide (GO) nanosheets and titania peroxo-complex. The characterization of graphene oxide nanosheets was provided by using an atomic force microscope and Raman spectroscopy. The prepared nanocomposites samples were characterized by Brunauer–Emmett–Teller surface area and Barrett–Joiner–Halenda porosity, X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and Transmission Electron Microscopy. UV/VIS diffuse reflectance spectroscopy was employed to estimate band-gap energies. From the TiO2 - GO samples, a 300 μm thin layer on a piece of glass 10×15 cm was created. The photocatalytic activity of the prepared layers was assessed from the kinetics of the photocatalytic degradation of butane in the gas phase. Conclusions The best photocatalytic activity under UV was observed for sample denoted TiGO_100 (k = 0.03012 h-1), while sample labeled TiGO_075 (k = 0.00774 h-1) demonstrated the best activity under visible light. PMID:23445868

  9. Ecotoxicological assessment of TiO2 byproducts on the earthworm Eisenia fetida.

    PubMed

    Bigorgne, Emilie; Foucaud, Laurent; Lapied, Emmanuel; Labille, Jérôme; Botta, Céline; Sirguey, Catherine; Falla, Jaïro; Rose, Jérôme; Joner, Erik J; Rodius, François; Nahmani, Johanne

    2011-10-01

    The increasing production of nanomaterials will in turn increase the release of nanosized byproducts to the environment. The aim of this study was to evaluate the behaviour, uptake and ecotoxicity of TiO(2) byproducts in the earthworm Eisenia fetida. Worms were exposed to suspensions containing 0.1, 1 and 10 mg/L of byproducts for 24 h. Size of TiO(2) byproducts showed aggregation of particles up to 700 μm with laser diffraction. Only worms exposed at 10 mg/L showed bioaccumulation of titanium (ICP-AES), increasing expression of metallothionein and superoxide dismutase mRNA (Real-time PCR) and induction of apoptotic activity (Apostain and TUNEL). TiO(2) byproducts did not induce cytotoxicity on cœlomocytes, but a significant decrease of phagocytosis was observed starting from 0.1 mg/L. In conclusion, bioaccumulation of byproducts and their production of reactive oxygen species could be responsible for the alteration of the antioxidant system in worms.

  10. The role of nanoparticulate agglomerates in TiO2 photocatalysis: degradation of oxalic acid

    NASA Astrophysics Data System (ADS)

    Ivanova, Irina; Mendive, Cecilia B.; Bahnemann, Detlef

    2016-07-01

    The simultaneous bimodal study of the photocatalytic oxalic acid degradation by aqueous TiO2 suspensions revealed that particular systems possess the capacity to protect a certain amount of oxalic acid from oxidation, thus hindering, to some extent, the photocatalytic reaction. While measurements of the oxalic acid concentration in the bulk liquid phase indicated full photocatalytic degradation; in situ pH-stat measurements allowed the quantification of the amount of oxalic acid remaining in the part of the nanoparticulate agglomerates where light could apparently not access. An explanation for this phenomenon takes into account the possibility of the formation of TiO2 agglomerates in which these molecules are hidden from the effect of the light, thus being protected from photocatalytic degradation. Studies of different TiO2 materials with different particle sizes allowed a deeper exploration of this phenomenon. In addition, because this property of encapsulating pollutant molecules by photocatalytic systems is found to be a reversible phenomenon, P25 appears to be more convenient and advantageous as compared to the use of large surface area photocatalysts.

  11. Sensitized TiO2 nanocomposites through HMME linkage for photodynamic effects

    NASA Astrophysics Data System (ADS)

    He, Yu Lu; Wang, Sijia; Zhang, Luwei; Xin, Jing; Wang, Jing; Yao, Cuiping; Zhang, Zhenxi; Yang, Chih-Chung

    2016-12-01

    Although TiO2 can be used to effectively generate reactive oxygen species (ROS) for photodynamic application, its absorption in the ultraviolet range makes the excitation harmful to tissue. Based on the concept of a sensitized solar cell, TiO2 nanoparticles (NPs) are sensitized by linking with the photosensitizer, HMME, to form HMME nanocomposites (NCs) for demonstrating the photodynamic effects under the illumination of white light. The HMME NCs of different composition ratios are prepared for maximizing the generation of ROS and optimizing the inactivation effect of KB cells. The material characteristics and the ROS generation capability of the HMME NCs with the optimized combination ratio show their merits in a photodynamic process under white light irradiation. The application of such NCs to KB cell experiments results in a higher inactivation efficiency when compared to pure HMME of the same concentration.

  12. Metal-semiconductor-metal TiO2 ultraviolet detectors with Ni electrodes

    NASA Astrophysics Data System (ADS)

    Kong, Xiangzi; Liu, Caixia; Dong, Wei; Zhang, Xindong; Tao, Chen; Shen, Liang; Zhou, Jingran; Fei, Yongfeng; Ruan, Shengping

    2009-03-01

    In this letter, metal-semiconductor-metal (MSM) TiO2 ultraviolet (UV) detectors with Ni electrodes have been fabricated. TiO2 thin films were prepared by sol-gel method. At 5 V bias, the dark current of the detector with Ni electrode was 1.83 nA. High photoresponse of 889.6 A/W was found under irradiation of 260 nm UV light, which was much higher than those of other wide bandgap UV detectors with MSM structure. The high photoresponse was due to the great internal gain caused by the hole trapping at interface. The rise time of the device was 13.34 ms and the fall time was 11.43 s.

  13. Using Ag-embedded TiO2 nanotubes array as recyclable SERS substrate

    NASA Astrophysics Data System (ADS)

    Ling, Yunhan; Zhuo, Yuqing; Huang, Liang; Mao, Duolu

    2016-12-01

    A simple strategy for synthesizing Ag-loaded TiO2 nanotube film for use as multifunctional photocatalyst and recyclable surface-enhanced Raman scattering (SERS) substrate is introduced. Highly aligned TiO2 nanotube arrays (TNTA) prepared via electrochemical anodization were used as a 3D rough host for silver nanoparticles. Ag deposits were sputtered in a vacuum, and it was found that their morphologies were mainly influenced by the diameters of nanotubes and the UV irradiation induced aging process, especially the self-migration of silver along the tubular wall. SERS and the self-cleaning effect were observed using Rhodamine 6G (R6G) as the probe molecule. The results showed that narrow nanotube and silver nanoparticles embedment contributed significantly to both the phenomenal SERS and recyclability.

  14. Characterization of nanostructured TiO2:Ag films: structural and optical properties

    NASA Astrophysics Data System (ADS)

    Ivanova, T.; Harizanova, A.; Koutzarova, T.; Vertruyen, B.

    2016-10-01

    TiO2:Ag nanocomposites have been prepared by sol-gel method with varying silver concentration. Different technological approaches are employed to study the formation of Ag nanoparticles in titanium dioxide matrix. The obtained thin films are either thermally treated at temperatures from 300 to 600oC or UV irradiated for 15 minutes between layer deposition. XRD and FTIR studies reveal that Ag is incorporated in TiO2 films as nanoparticles and no Ag oxide phases are detected. Optical characterization performed by UV-VIS spectroscopy confirms the formation of silver nanoparticles. The influence of thermal treatment and UV radiation on the optical and structural properties is studied.

  15. TiO2 nanopores with high sensitivity to ultraviolet light

    NASA Astrophysics Data System (ADS)

    Rodríguez, D. F.; Perillo, P. M.

    2015-04-01

    We investigated the UV photoconductivity and transient response of TiO2 nanopores on silicon substrate. Ti thin films were first deposited by radio-frequency (RF) magnetron sputtering and then anodized in glycerol electrolytes containing ammonium fluoride (NH4F). For the UV irradiation, the rise and decay curves of photocurrent are well fitted to a bi-exponential function. In both cases, the photocurrent was dominated by an initial fast response about 2 s. The ohmic I-V characteristic of the TiO2 nanopores under illumination could be ascribed to the decrease of the Schottky barrier height, to the accumulation of conduction electrons, resulted from the neutralization between photogenerated holes and negatively charged oxygen ions. These nanopores arrays could be useful in serving as photodetectors, chemical and biological sensors, and switching devices for nanoscale optoelectronics.

  16. Effects of mineral tourmaline particles on the photocatalytic activity of TiO2 thin films.

    PubMed

    Meng, Junping; Liang, Jinsheng; Ou, Xiuqin; Ding, Yan; Liang, Guangchuan

    2008-03-01

    Titania composite thin films (T/TiO2) containing tourmaline particles were prepared by a sol-gel method, using alkoxide solutions as precursor. The tourmaline particles and thin films were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and so on. The effects of tourmaline on the photocatalytic activity of TiO2 were measured with methyl orange as an objective photodegradation substance. The results showed that the photocatalytic degradation of methyl orange conformed to the first-order kinetic equation and the composite thin films had better photocatalytic activity due to the cooperation of polarity and the far infrared emission of tourmaline. The T/TiO2 thin films including 0.5 wt% tourmaline exhibited better photocatalytic activity when heat-treated at 250 degrees C for 3 h, than pure TiO2 thin films under the ultraviolet irradiation.

  17. Asymmetric photoelectric property of transparent TiO2 nanotube films loaded with Au nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Liang, Wei; Liu, Yiming; Zhang, Wanggang; Zhou, Diaoyu; Wen, Jing

    2016-11-01

    Semitransparent composite films of Au loaded TiO2 nanotubes (TNT-Au) were prepared by sputtering Au nanoparticles on highly transparent TiO2 nanotubes films, which were fabricated directly on FTO glasses by anodizing the Ti film sputtered on the FTO glasses. Compared with pure TNT films, the prepared TNT-Au films possessed excellent absorption ability and high photocurrent response and improved photocatalytic activity under visible-light irradiation. It could be concluded that Au nanoparticles played important roles in improving the photoelectrochemical performance of TNT-Au films. Moreover, in this work, both sides of TNT-Au films were researched and compared owing to theirs semitransparency. It was firstly found that the photoelectric activity of TNT-Au composite films with back-side illumination was obviously superior to front-side illumination.

  18. Toxicity of TiO2 nanoparticles on soil nitrification at environmentally relevant concentrations: Lack of classical dose-response relationships.

    PubMed

    Simonin, Marie; Martins, Jean M F; Le Roux, Xavier; Uzu, Gaëlle; Calas, Aude; Richaume, Agnès

    2017-03-01

    Titanium-dioxide nanoparticles (TiO2-NPs) are increasingly released in agricultural soils through, e.g. biosolids, irrigation or nanoagrochemicals. Soils are submitted to a wide range of concentrations of TiO2-NPs depending on the type of exposure. However, most studies have assessed the effects of unrealistically high concentrations, and the dose-response relationships are not well characterized for soil microbial communities. Here, using soil microcosms, we assessed the impact of TiO2-NPs at concentrations ranging from 0.05 to 500 mg kg(-1 )dry-soil, on the activity and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB), and nitrite-oxidizing bacteria (Nitrobacter and Nitrospira). In addition, aggregation and oxidative potential of TiO2-NPs were measured in the spiking suspensions, as they can be important drivers of TiO2-NPs toxicity. After 90 days of exposure, non-classical dose-response relationships were observed for nitrifier abundance or activity, making threshold concentrations impossible to compute. Indeed, AOA abundance was reduced by 40% by TiO2-NPs whatever the concentration, while Nitrospira was never affected. Moreover, AOB and Nitrobacter abundances were decreased mainly at intermediate concentrations nitrification was reduced by 25% at the lowest (0.05 mg kg(-1)) and the highest (100 and 500 mg kg(-1)) TiO2-NPs concentrations. Path analyses indicated that TiO2-NPs affected nitrification through an effect on the specific activity of nitrifiers, in addition to indirect effects on nitrifier abundances. Altogether these results point out the need to include very low concentrations of NPs in soil toxicological studies, and the lack of relevance of classical dose-response tests and ecotoxicological dose metrics (EC50, IC50…) for TiO2-NPs impact on soil microorganisms.

  19. Reduced TiO2-Graphene Oxide Heterostructure As Broad Spectrum-Driven Efficient Water-Splitting Photocatalysts.

    PubMed

    Li, Lihua; Yu, Lili; Lin, Zhaoyong; Yang, Guowei

    2016-04-06

    The reduced TiO2-graphene oxide heterostructure as an alternative broad spectrum-driven efficient water splitting photocatalyst has become a really interesting topic, however, its syntheses has many flaws, e.g., tedious experimental steps, time-consuming, small scale production, and requirement of various additives, for example, hydrazine hydrate is widely used as reductant to the reduction of graphene oxide, which is high toxicity and easy to cause the second pollution. For these issues, herein, we reported the synthesis of the reduced TiO2-graphene oxide heterostructure by a facile chemical reduction agent-free one-step laser ablation in liquid (LAL) method, which achieves extended optical response range from ultraviolet to visible and composites TiO(2-x) (reduced TiO2) nanoparticle and graphene oxide for promoting charge conducting. 30.64% Ti(3+) content in the reduced TiO2 nanoparticles induces the electronic reconstruction of TiO2, which results in 0.87 eV decrease of the band gap for the visible light absorption. TiO(2-x)-graphene oxide heterostructure achieved drastically increased photocatalytic H2 production rate, up to 23 times with respect to the blank experiment. Furthermore, a maximum H2 production rate was measured to be 16 mmol/h/g using Pt as a cocatalyst under the simulated sunlight irradiation (AM 1.5G, 135 mW/cm(2)), the quantum efficiencies were measured to be 5.15% for wavelength λ = 365 ± 10 nm and 1.84% for λ = 405 ± 10 nm, and overall solar energy conversion efficiency was measured to be 14.3%. These findings provided new insights into the broad applicability of this methodology for accessing fascinate photocatalysts.

  20. Photocatalytic comparison of Cu- and Ag-doped TiO2/GF for bioaerosol disinfection under visible light

    NASA Astrophysics Data System (ADS)

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2015-12-01

    Photocatalysts, TiO2/glass fiber (TiO2/GF), Cu-doped TiO2/glass fiber (Cu-TiO2/GF) and Ag-doped TiO2/glass fiber (Ag-TiO2/GF), were synthesized by a sol-gel method. They were then used to disinfect Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in bioaerosols under visible light irradiation. TiO2/GF did not show any significant disinfection effect. Both Cu and Ag acted as intermediate agents to enhance separation efficiency of electron-hole pairs of TiO2, leading to improved photocatalytic activity of Cu-TiO2/GF and Ag-TiO2/GF under visible light. Cu in Cu-TiO2/GF acted as a defective agent, increasing the internal quantum efficiency of TiO2, while Ag in Ag-TiO2/GF acted as a sensitive agent, enhancing the transfer efficiency of the electrons generated. The highest disinfection efficiencies of E. coli and S. aureus by Cu-TiO2/GF were 84.85% and 65.21%, respectively. The highest disinfection efficiencies of E. coli and S. aureus by Ag-TiO2/GF were 94.46% and 73.12%, respectively. Among three humidity conditions - 40±5% (dry), 60±5% (moderate), and 80±5% (humid) - the moderate humidity condition showed the highest disinfection efficiency for both E. coli and S. aureus. This study also showed that a Gram-negative bacterium (E. coli) were more readily disinfected by the photocatalysts than a Gram-positive bacterium (S. aureus).

  1. Synergistic effect of the combination of immobilized TiO2, UVA and ozone on the decomposition of dichloroacetic acid.

    PubMed

    Mehrjouei, Mohammad; Müller, Siegfried; Möller, Detlev

    2012-01-01

    The performance of a heterogeneous photocatalytic ozonation system (TiO(2)/UVA/O(3)) was evaluated on the degradation and mineralization of dichloroacetic acid as a contaminant in aqueous solutions by means of a planar reactor. The commercial product "Pilkington Active™ glass" was used as the immobilized TiO(2) photocatalyst and it was irradiated by near UV light in this study. The synergistic interaction between ozone and the photoactivated TiO(2) surface was discussed and highlighted. Furthermore, the influences of initial concentration and temperature on the degradation rate of dichloroacetic acid and the ozone consumption level during the oxidation process were investigated. The concentrations of dichloroacetic acid and chloride anions produced during degradation were measured using ion chromatography. The mineralization of dichloroacetic acid was evaluated by Total Organic Carbon (TOC) measurements. The degradation of dichloroacetic acid by photocatalytic ozonation showed good agreement with the kinetics of first-order reactions with respect to dichloroacetic acid.

  2. Controlled synthesis of Ag-coated TiO2 nanofibers and their enhanced effect in photocatalytic applications

    NASA Astrophysics Data System (ADS)

    Guan, Hongyu; Wang, Xiaohong; Guo, Yihang; Shao, Changlu; Zhang, Xintong; Liu, Yichun; Louh, Rong-Fuh

    2013-09-01

    Novel nanostructured Ag/TiO2 hybrid nanofibers (NFs) have been successfully prepared via a simple electrospinning process combined with silver mirror reaction. The Ag/TiO2 NFs demonstrated a unique morphology with evenly distributed Ag nanoparticles uniformly deposited onto the surface of each individual TiO2 NFs. The loading capacity and size of Ag NPs can be easily controlled by varying the silver mirror reaction time. Compared with pristine TiO2 NFs, such heterogeneous Ag/TiO2 nanocomposites exhibited preferable photocatalytic activity during photocatalytic degradation of rhodamine-B under the simulated sunlight irradiation and this enhanced photocatalytic performance was driven by combination and interaction between TiO2 and Ag NPs.

  3. P-doped TiO2 with superior visible-light activity prepared by rapid microwave hydrothermal method

    NASA Astrophysics Data System (ADS)

    Niu, Jinfen; Lu, Pan; Kang, Mei; Deng, Kunfa; Yao, Binghua; Yu, Xiaojiao; Zhang, Qian

    2014-11-01

    Phosphorous-doped anatase TiO2 powders (P-TiO2) were prepared by rapid microwave hydrothermal method. The resulting materials were characterized by XRD, SEM, XPS, DRS and N2 adsorption. P-doping decreased the band gap and enlarged the surface area of P-doped samples than that of undoped TiO2 samples. Therefore, the photocatalytic degradation of methyl blue (MB) and tetracycline hydrochloride (Tc) experiments showed that the P-TiO2 catalysts, especially the two-steps-controlling products P-TiO2-2, exhibited higher degradation efficiency than the undoped TiO2 and commercial P25 under visible-light irradiation. Hydroxyl radicals (rad OH) have been confirmed to be the active species during the photocatalytic oxidation reaction. The microwave hydrothermal method confirms to be very suitable for the synthesis of superior visible-light activity P-doped samples.

  4. Preparation and Solar Light Photocatalytic Activity of N-Doped TiO2-Loaded Halloysite Nanotubes Nanocomposites

    NASA Astrophysics Data System (ADS)

    Cheng, Zhi-Lin; Sun, Wei

    2015-10-01

    A novel method to prepare N-doped TiO2-loaded halloysite nanotubes (N-TiO2/HNTs) nanocomposites was achieved by using the chemical vapor deposition in autoclave. The N-TiO2/HNTs nanocomposites obtained by the different form of the doping N source were studied through a series of characterizations. The XRD, SEM, and TEM characterizations verified the anatase structure of TiO2 nanoparticles with the size of ca.20nm loaded on the outer surface of HNTs. The UV-vis characterization of the N-TiO2/HNTs presented a further red-shift compared to the pure N-TiO2 nanoparticles.. The XPS characterizations confirmed the N element doped into the crystal structure of TiO2 nanoparticles. The photocatalytic activities of N-TiO2/HNTs nanocomposites prepared were evaluated by degradation of phenol at room temperature under simulated solar light irradiation.

  5. Preparation, characterization and visible light photocatalytic activity of silver, nitrogen co-doped TiO2 photocatalyst

    NASA Astrophysics Data System (ADS)

    Khan, Matiullah; Ramin Gul, Sahar; Li, Jing; Cao, Wenbin; Mamalis, Athanasios G.

    2015-06-01

    TiO2 photocatalyst codoped with Silver (Ag) and Nitrogen (N) with different Ag doping concentrations is successfully synthesized by hydrothermal method. The as-synthesized samples are characterized through x-ray diffraction (XRD), Transmission electron microscopy (TEM), UV-vis. absorption spectra and x-ray photoelectron spectroscopy (XPS). The photocatalytic response is evaluated by the photodegradation of methylene blue under visible light irradiations. All synthesized samples are composed of pure anatase phase with good crystallinity. The absorption edge of codoped TiO2 is shifted towards visible light region. X-ray photoelectron spectroscopy confirmed the existence of silver and nitrogen in the codoped samples. All the codoped samples demonstrated improved photocatalytic activity compared to pure TiO2. Among the different codoped samples, the one with silver doping concentration of 4 at. % exhibited the highest photoactivity.

  6. Electrodeposited Ag nanoparticles on TiO2 nanorods for enhanced UV visible light photoreduction CO2 to CH4

    NASA Astrophysics Data System (ADS)

    Kong, Dan; Tan, Jeannie Ziang Yie; Yang, Fei; Zeng, Jieliang; Zhang, Xiwen

    2013-07-01

    We employed the double-potentiostatic methodology to electrodeposit Ag nanoparticles on oriented single-crystalline rutile TiO2 nanorods synthesized by hydrothermal method. The synthesized composites were used as the photocatalyst to reduce CO2 to CH4 under UV irradiation, and tested by SEM, XRD, TEM, XPS, UV-vis and photoluminescence. Deposition with Ag nanoparticles was observed to enhance the photocatalytic activity (≈1.5-2.64 μmol (gcatal h)-1) up to 5 times with respect to undecorated TiO2 nanorods (≈0.5 μmol (gcatal h)-1). The increase in the CH4 yield was correlated with the surface morphology and structure of TiO2 nanorods.

  7. Light-Triggered Release from Pickering Emulsions Stabilized by TiO2 Nanoparticles with Tailored Wettability.

    PubMed

    Bai, Rui-Xue; Xue, Long-Hui; Dou, Rong-Kun; Meng, Shi-Xin; Xie, Chun-Yan; Zhang, Qing; Guo, Ting; Meng, Tao

    2016-09-13

    In this work, a new strategy for developing light-triggered Pickering emulsions as smart soft vehicles for on-demand release is proposed. Initially, UV-induced tailored wettability allows anchoring of TiO2 nanoparticles at the interface to prepare stable water in oil emulsions. Such emulsions show the efficacy of microencapsulation and controlled release by demulsification due to the hydrophilic conversion of the TiO2 nanoparticles using a noninvasive light irradiation trigger. A molecule of interest is selected as a model cargo to quantitatively evaluate the as-prepared Pickering emulsions for their encapsulation and release behaviors. Moreover, light-responsive emulsion destabilization mechanism is studied as a function of particle concentration, light wavelength, and light intensity, respectively, determined by drop diameter evolution and droplet coalescence kinetics plots. For consideration of application in life sciences, Pickering emulsions sensitive to visible light are also established based on nitrogen doping of TiO2 nanoparticle emulsifiers.

  8. Composite TiO2/clays materials for photocatalytic NOx oxidation

    NASA Astrophysics Data System (ADS)

    Todorova, N.; Giannakopoulou, T.; Karapati, S.; Petridis, D.; Vaimakis, T.; Trapalis, C.

    2014-11-01

    TiO2 photocatalyst received much attention for air purification applications especially for removal of air pollutants like NOx, VOCs etc. It has been established that the activity of the photocatalyst can be significantly enhanced by its immobilization onto suitable substrates like inorganic minerals, porous silica, hydroxyapatite, adsorbent materials like activated carbon, various co-catalysts such as semiconductors, graphene, reduced graphite oxide, etc. In the present work, photocatalytic composite materials consisted of mineral substrate and TiO2 in weight ratio 1:1 were manufactured and examined for oxidation and removal of nitric oxides NOx (NO and NO2). Commercial titania P25 (Evonik-Degussa) and urea-modified P25 were used as photocatalytically active components. Inorganic minerals, namely kunipia, talk and hydrotalcite were selected as supporting materials due to their layered structure and expected high NOx adsorption capability. Al3+ and Ca2+ intercalation was applied in order to improve the dispersion of TiO2 and its loading into the supporting matrix. The X-ray diffraction analysis and Scanning Electron Microscopy revealed the binary structure of the composites and homogeneous dispersion of the photocatalyst into the substrates. The photocatalytic behavior of the materials in NOx oxidation and removal was investigated under UV and visible light irradiation. The composite materials exhibited superior photocatalytic activity than the bare titania under both types of irradiation. Significant visible light activity was recorded for the composites containing urea-modified titania that was accredited to the N-doping of the semiconductor. Among the different substrates, the hydrotalcite caused highest increase in the NOx removal, while among the intercalation ions the Ca2+ was more efficient. The results were related to the improved dispersion of the TiO2 and the synergetic activity of the substrates as NOx adsorbers.

  9. Effect of TiO2 blocking layer on TiO2 nanorod arrays based dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Sivakumar, R.; Paulraj, M.

    2016-05-01

    Highly ordered rutile titanium dioxide nanorod (TNR) arrays (1.2 to 6.2 μm thickness) were grown on TiO2 blocking layer chemically deposited on fluorine doped tin oxide (FTO) substrate and were used as photo-electrodes to fabricate dye sensitized solar cells (DSSC's). Homogeneous layer of TiO2 on FTO was achieved by using aqueous peroxo- titanium complex (PTC) solutions via chemical bath deposition. Structural and morphological properties of the prepared samples were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) measurements. TNR arrays (6.2 μm) with TiO2 blocking layer showed higher energy conversion efficiency (1.46%) than that without TiO2 blocking layer. The reason can be ascertained to the suppression of electron-hole recombination at the semiconductor/electrolyte interface by the effect of TiO2 blocking layer.

  10. Transparent, well-aligned TiO(2) nanotube arrays with controllable dimensions on glass substrates for photocatalytic applications.

    PubMed

    Tan, Lee Kheng; Kumar, Manippady K; An, Wen Wen; Gao, Han

    2010-02-01

    Transparent, well-aligned TiO(2) nanotube arrays (NTAs) with controllable dimensions are grown on glass substrates via atomic layer deposition (ALD) of TiO(2) onto free-standing porous anodic alumina (PAA) templates. Photodegradation of aqueous methylene blue (MB) solution and solid stearic acid (SA) film using TiO(2) NTAs of various wall thicknesses are investigated. The Pd functionalized TiO(2) NTAs, with a wall thickness of 15 nm and height of 200 nm, has the highest photodegradation efficiency at 76% after 4 h of UV irradiation. These functionalized NTAs are able to photodegrade MB molecules completely as no obvious demethylated byproducts are observed during the process. It also demonstrates excellent photocatalytic activity for solid contaminants such as SA film. By using the ALD technique, the nanotube wall thickness can be precisely controlled so that it is sufficiently thin to be transparent while sufficiently thick for excellent photocatalytic performances. The transparent TiO(2) NTAs on glass substrates with excellent photocatalytic properties might have potential applications in self-cleaning coating, transparent electronics, and solar cells.

  11. First-principles study on codoping effect to enhance photocatalytic activity of anatase TiO2

    NASA Astrophysics Data System (ADS)

    Bai, Yujie; Zhang, Qinfang; Zheng, Fubao; Yang, Yun; Meng, Qiangqiang; Zhu, Lei; Wang, Baolin

    2017-03-01

    Codopant is an effective approach to modify the bandgap and band edge positions of transition metal oxide. Here, the electronic structures as well as the optical properties of pristine, mono-doped (N/P/Sb) and codoped (Sb, N/P) anatase TiO2 have been systematically investigated based on density functional theory calculations. It is found that mono-doped TiO2 exhibits either unoccupied or partially occupied intermediate state within the energy gap, which promotes the recombination of electron-hole pairs. However, the presence of (Sb, N/P) codopant not only effectively reduces the width of bandgap by introducing delocalized occupied intermediate states, but also adjusts the band edge alignment to enhance the hydrogen evolution activity of TiO2. Moreover, the optical absorption spectrum for (Sb, N/P) codoped TiO2, which is favored under oxygen-rich condition, demonstrates the improvement of its visible light absorption. These findings will promote the potential application of (Sb, N/P) codoped TiO2 photocatalysis for water splitting under visible light irradiation.

  12. Removal of 4-Nitrophenol from Water Using Ag–N–P-Tridoped TiO2 by Photocatalytic Oxidation Technique

    PubMed Central

    Achamo, Temesgen; Yadav, O. P.

    2016-01-01

    Photocatalytic oxidation using semiconductor nanoparticles is an efficient, eco-friendly, and cost-effective process for the removal of organic pollutants, such as dyes, pesticides, phenols, and their derivatives in water. In the present study, nanosize Ag–N–P-tridoped titanium(IV) oxide (TiO2) was prepared by using sol–gel-synthesized Ag-doped TiO2 and soybean (Glycine max) or chickpea (Cicer arietinum) seeds as nonmetallic bioprecursors. As-synthesized photocatalysts were characterized using X-ray diffraction, Fourier transform infrared, and ultra violet (UV)–visible spectroscopic techniques. Average crystallite size of the studied photocatalysts was within 39–46 nm. Whereas doped Ag in TiO2 minimized the photogenerated electron–hole recombination, doped N and P extended its photoabsorption edge to visible region. Tridoping of Ag, N, and P in TiO2 exhibited synergetic effect toward enhancing its photocatalytic degradation of 4-nitrophenol (4-NP), separately, under UV and visible irradiations. At three hours, degradations of 4-NP over Ag–N–P-tridoped TiO2 under UV and visible radiations were 73.8 and 98.1%, respectively. PMID:27081309

  13. Development of high efficient visible light-driven N, S-codoped TiO2 nanowires photocatalysts

    NASA Astrophysics Data System (ADS)

    Zhang, Yanlin; Liu, Peihong; Wu, Honghai

    2015-02-01

    One-dimensional (1D) nanowire material (especially nonmetal doped 1D nanowires) synthesized by a facile way is of great significance and greatly desired as it has higher charge carrier mobility and lower carrier recombination rate. N, S-codoped TiO2 nanowires were synthesized using titanium sulfate as a precursor and isopropanol as a protective capping agent by a hydrothermal route. The obtained doped nanowires were characterized by XRD, SEM, HRTEM, SAED, XPS, BET and UV-vis absorption spectrum. The incorporation of N and S into TiO2 NWs can lead to the expansion of its lattice and remarkably lower its electron-transfer resistance. Photocatalytic activity measurement showed that the N, S-codoped TiO2 nanowires with high quantum efficiency revealed the best photocatalytic performance for atrazine degradation under visible light irradiation compared to N, S-codoped TiO2 nanoparticles and S-doped TiO2 nanowires, which was attributed to (i) the synergistic effect of N and S doping in narrowing the band gap, separating electron-hole pairs and increasing the photoinduced electrons, and (ii) extending the anatase-to-rutile transformation temperature above 600 °C.

  14. Morphological influence of TiO2 nanostructures (nanozigzag, nanohelics and nanorod) on photocatalytic degradation of organic dyes

    NASA Astrophysics Data System (ADS)

    Khan, Sadaf Bashir; Hou, Mengjing; Shuang, Shuang; Zhang, Zhengjun

    2017-04-01

    Hierarchical nanostructures have drawn significant attention and incredible performance in photodriven chemical conversion area due to its unique physicochemical properties. Herein, we study the morphological influence of TiO2 nanostructures on photocatalytic degradation of different organic dyes methyl blue, methyl violet and methyl orange present in industrial wastewater. Nanorod, nanohelics and nanozigzag TiO2 nanofilms were fabricated by using galancing angle deposition technique (GLAD). TiO2 nanofilms were characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD), and raman analysis. BET surface area analysis were carried out by using nitrogen adsorption desorption curves. The results show that TiO2 morphology had great influence on photocatalytic degradation of organic dyes due to difference in specific surface area and pore volume of nanostructures. The photocatalytic degradation experiments were carried out for three hours under UV-vis light irradiation. Catalysis recycling and organic dyes concentration influence were also studied. In case of high concentration of organic dyes, negligible degradation rate is observed. TiO2 nanozigzag films show better degradation performance than nanohelics and nanorod due to presence of large surface area for reaction, higher porosity with dispersion of active sites at different length scales of pores and presence of oxygen vacancies.

  15. Control of TTIP Solution for Atmospheric Pressure Plasma Jet and Deposition of TiO2 Micro-particles

    NASA Astrophysics Data System (ADS)

    Hayakawa, Masahiro; Parajulee, Shankar; Ikezawa, Shunjiro

    TiO2 deposition-methods are versatile and are expected to be more simple and easy, however, in recent years the industrial photocatalytic products have been developed enormously. In this work, photocatalytic TiO2 micro-particles are deposited using the atmospheric pressure plasma jet device. Here, deposition-method is carried out in two steps, at first, the hydrolysis reaction time has been able to control which will resolve the TTIP coagulating trouble during the transportation, by acidifying the solution with AA (Acetic acid) and DEA (Diethanolamine). An experiment was performed to measure the hydrolysis reaction time of TTIP (Titanium tetraisopropoxide) solution by He-Ne laser. Secondly, the deposition of TiO2 micro-particles was carried out using the atmospheric pressure plasma jet with the controlled TTIP solution in reaction time. Based on SEM and water contact angle measurement, it is found that the smaller the mixing ratios of TTIP and DEA the smaller the TiO2 particle size. Also, the smaller the TiO2 particles the smaller the contact angle under the UV irradiation which suffices the photocatalytic behavior.

  16. Low temperature synthesis and visible light driven photocatalytic activity of highly crystalline mesoporous TiO2 particles.

    PubMed

    Gujar, Tanaji P; Anand, Chokkalingam; Shinde, Vaishali R; Ye, Jinhua; Ariga, Katsuhiko; Vinu, Ajayan

    2010-12-01

    Mesoporous TiO2 powder materials with a high crystallinity have been prepared by evaporation induced self assembly (EISA) process using titanium tetraisopropoxide (TTIP) and pluronic P123 surfactant (EO20PO70EO20) as titanium source and structure-directing reagent, respectively. The prepared materials were characterized by low and wide-angle X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical absorption, and N2 adsorption-desorption experiments. The crystallinity of the materials was controlled by varying the calcination temperature. The resulting TiO2 materials showed highly crystalline structure with uniform particle size which increases from 11.8 to 23.8 nm with increasing the calcination temperature from 400 to 600 degrees C, respectively, whereas the specific surface area decreases from 125 to 40 m2/g. TEM and XRD results revealed that the calcination temperature of 600 degrees C is the best condition to obtain highly crystalline mesoporous TiO2. The photocatalytic activity of the TiO2 mesoporous materials with different crystallinity and textural parameters has been studied in the decomposition of methylene blue (MB) dye molecules under visible light irradiation. Among the mesoporous TiO2 materials studied, the material with the highest crystallinity, prepared at 600 degrees C, showed the best photocatalytic performance in the decomposition of MB under visible light in a short time.

  17. Zr-doped TiO2 supported on delaminated clay materials for solar photocatalytic treatment of emerging pollutants.

    PubMed

    Belver, C; Bedia, J; Rodriguez, J J

    2017-01-15

    Solar light-active Zr-doped TiO2 nanoparticles were successfully immobilized on delaminated clay materials by a one-step sol-gel route. Fixing the amount of TiO2 at 65wt.%, this work studies the influence of Zr loading (up to 2%) on the photocatalytic activity of the resulting Zr-doped TiO2/clay materials. The structural characterization demonstrates that all samples were formed by a delaminated clay with nanostructured anatase assembled on its surface. The Zr dopant was successfully incorporated into the anatase lattice, resulting in a slight deformation of the anatase crystal and the reduction of the band gap. These materials exhibit high surface area with a disordered mesoporous structure formed by TiO2 particles (15-20nm) supported on a delaminated clay. They were tested in the solar photodegradation of antipyrine, usually used as an analgesic drug and selected as an example of emerging pollutant. High degradation rates have been obtained at low antipyrine concentrations and high solar irradiation intensities with the Zr-doped TiO2/clay catalyst, more effective than the undoped one. This work demonstrates the potential application of the synthesis method for preparing novel and efficient solar-light photocatalysts based on metal-doped anatase and a delaminated clay.

  18. Photocatalytically patterned TiO2 arrays for on-plate selective enrichment of phosphopeptides and direct MALDI MS analysis.

    PubMed

    Wang, Hui; Duan, Jicheng; Cheng, Quan

    2011-03-01

    We report the development of photocatalytically patterned TiO(2) arrays for selective on-plate enrichment and direct matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis of phosphopeptides. A thin TiO(2) nanofilm with controlled porosity is prepared on gold-covered glass slides by a layer-by-layer (LbL) deposition/calcination process. The highly porous and rough nanostructure offers high surface area for selective binding of phosphorylated species. The patterned arrays are generated using an octadecyltrichlorosilane (OTS) coating in combination of UV irradiation with a photomask, followed by NaOH etching. The resulting hydrophilic TiO(2) spots are thus surrounded by a hydrophobic OTS layer, which can facilitate the enrichment of low-abundance components by confining a large volume sample into a small area. The TiO(2) arrays exhibit high specificity toward phosphopeptides in complex samples including phosphoprotein digests and human serum, and the detection can be made in the fmole range. Additional advantages of the arrays include excellent stability, reusability/reproducibility, and low cost. This method has been successfully applied to the analysis of phosphopeptides in nonfat milk. The patterned TiO(2) arrays provide an attractive interface for performing on-plate reactions, including selective capture of target species for MALDI-MS analysis, and can serve as a versatile lab-on-a-chip platform for high throughput analysis in phosphoproteome research.

  19. Photocatalytic activity of S- and F-doped TiO(2) in formic acid mineralization.

    PubMed

    Dozzi, Maria Vittoria; Livraghi, Stefano; Giamello, Elio; Selli, Elena

    2011-03-02

    Two series of doped titanium dioxide samples (S-TiO(2) and F-TiO(2)) were prepared by the sol-gel method in the presence of different amounts of dopant source (thiourea and NH(4)F, respectively), followed by calcination at 500, 600 or 700 °C, and characterised by BET, UV-vis absorption, XPS, HRTEM, XRD and EPR analyses. Reference undoped materials were prepared by the same synthetic procedure. Their photocatalytic activity under visible light was investigated employing the photocatalytic degradation of formic acid in aqueous suspension as test reaction. S-doped TiO(2) showed a photocatalytic activity quite similar to that of undoped materials. In this regard, the insertion of S, characterised by a relatively large ionic radius, into the TiO(2) crystalline structure appears rather difficult, as confirmed by XPS analysis. On the contrary, moderate F doping was beneficial in increasing the rate of formic acid photocatalytic degradation, especially for photocatalysts calcined at high temperature, consisting of highly crystalline pure anatase, in which the rate of detrimental charge carrier recombination was reduced. For both series of doped materials, high doping levels appear to limit the semiconductor photoactivity, probably due to the formation of a progressively increasing number of charge recombination centres. The EPR characterisation of the investigated doped TiO(2) samples evidenced the presence of nitrogen containing species (nitric oxide radical encapsulated in micro-void, with no photoactivity, and N(b)˙ species, active in visible light sensitisation) and of titanium reduced centres Ti(3+), due to charge imbalance consequent to dopant introduction in the TiO(2) lattice either in anionic (F(-)) or in cationic form (S(6+)).

  20. Preparation and characterization of visible-light-driven TiO2 photocatalyst Co-doped with nitrogen and erbium.

    PubMed

    Chen, Guihua; Wang, Yong; Zhang, Juihui; Wu, Chenglin; Liang, Huading; Yang, Hui

    2012-05-01

    A series of nitrogen and erbium co-doped TiO2 photocatalyst was prepared by sol-hydrothermal method. The structure and properties of the photocatalyst were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectra (DRS). The XRD and BET results showed that co-doping inhibited the increase of crystallite size and enlarged specific surface areas. XPS spectroscopy indicated nitrogen atoms were incorporated into TiO2 lattice, and erbium atoms mostly existed in the forms of Er2O3. A shift of the absorption edge to the lower energy and four absorption bands located at 654, 544, 524 and 489 nm attributed to the 4f transitions of 4I15/2 --> 4F2/9, 4I15/2 --> 4S3/2, 4I15/2 --> 2H11/2, 4I15/2 --> 4F7/2 of Er3+ were observed using DRS spectroscopy. The catalytic efficency was evaluated by the photocatalytic degradation of methyl orange (MO) under visible light irradiation. The results showed that the photocatalytic performance of the co-doped TiO2 was related with the hydrothermal temperature and the molar ratio of N/Ti, and they showed higher acitivites than pure TiO2. Results determined by fluorescence technique revealed that irradiation (lambda > 400 nm) of TiO2 photocatalyst dispersed in MO solution induces the generation of the highly active hydroxyl radicals (OH). It indicated the photocatalytic activities of TiO2 photocatalyst were correlation with the formation rate of hydroxyl radicals (OH) and other active oxygen species.

  1. Facile fabrication of transparent TiO2-C@TiO2-C free-standing film for visible-light photocatalytic application

    NASA Astrophysics Data System (ADS)

    Hu, Luyang; Zhang, Yumin; Zhang, Shanmei; Li, Benxia

    2017-02-01

    A transparent TiO2-C@TiO2-C free-standing film has been synthesized by two-step hydrothermal method and subsequent thermal annealing. The chemical composition and morphological features of the TiO2-C@TiO2-C film are characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and N2 adsorption-desorption measurement. The results indicate that the flower-like micro/nanostructure TiO2-C particle layers are intimately inhered to porous TiO2-C fibers. The fibers in film are interconnected each other to form a three-dimensional reticulate microstructure, and exhibit intense visible light absorption and high adsorptivity of dye molecules. The interaction between TiO2 and its surface carbon layer in TiO2-C particle promotes the generation of Ti-O-C bonds, which leads to effective charge transfer. Under visible-light irradiation, TiO2-C@TiO2-C film presents enhanced photocatalytic activity for degradation of methylene blue. This work may provide a new viewpoint for designing transparent photocatalytic film for promising applications in heterogeneous photocatalysis.

  2. Effects of non-polar solvent on the morphology and property of three-dimensional hierarchical TiO2 nanostructures by one-step solvothermal route

    NASA Astrophysics Data System (ADS)

    Zhou, Yi; Wu, Hongyan; Zhong, Xian; Liu, Ce

    2014-07-01

    Three-dimensional (3D) hierarchical rutile TiO2 microspheres composed of nanorods with diameter of several-tens of nanometers, with different morphologies and with average size ranging from 1.3 to 1.8 μm, were successfully synthesized through a surfactant-free solvothermal route. The effects of the solvents n-hexane, chloroform, and cyclohexane on the microstructures of 3D hierarchical TiO2 nanostructures were investigated. Results of scanning electron microscopy showed that 3D sea-urchin like hierarchical TiO2 composed of nanorods with a diameter of 10 nm can only be prepared in the cyclohexane-water system. The growth mechanism of 3D sea-urchin like hierarchical TiO2 composed of numerous nanorods was further examined and found to differ from the well-known "growth → assembly" mode. The effects of surface tension and polarity of solvents on the morphology and crystal strength of 3D hierarchical TiO2 nanostructure were also investigated. In addition, the prepared 3D sea-urchin like hierarchical TiO2 showed highest photocatalytic activity compared with other 3D hierarchical TiO2 nanostructures in this study and Degussa P25 for the degradation of Rhodamine B solution under UV light irradiation, which could be attributed to its special hierarchical superstructure, the increase of surface catalytic sites and its special composition units.

  3. Comparative Study of Two Different TiO2 Film Sensors on Response to H2 under UV Light and Room Temperature

    PubMed Central

    Peng, Xiaoying; Wang, Zhongming; Huang, Pan; Chen, Xun; Fu, Xianzhi; Dai, Wenxin

    2016-01-01

    An anatase TiO2 film sensor was prepared by a facile in-situ method on the interdigitated Au electrode deposited on the alumina substrate. The structure, morphology and the optical properties of the in-situ TiO2 film sensor were characterized by X-ray diffraction, Scanning Electron Microscopy, and UV-vis diffuse reflectance spectra. The photo-assisted gas sensitivities of the prepared film towards H2 gas were evaluated at room temperature in N2 and synthetic air atmospheres. As compared to TiO2 film sensor prepared by drop-coating method, this in-situ TiO2 film sensor exhibited a more compact structure composed of uniform TiO2 microspheres as well as a better gas sensitivity towards H2 under UV irradiation, especially in synthetic air. The photo-electrochemical measurements suggest that these improvements may be associated with the efficient charge transfer in the TiO2 interface induced by the TiO2 microsphere structure. This study might offer a feasible approach to develop photo-assisted gas sensors at ambient temperature. PMID:27509502

  4. Effect of heat treatment on morphology, crystalline structure and photocatalysis properties of TiO 2 nanotubes on Ti substrate and freestanding membrane

    NASA Astrophysics Data System (ADS)

    Fang, Dong; Luo, Zhiping; Huang, Kelong; Lagoudas, Dimitris C.

    2011-05-01

    Highly ordered titanium oxide (TiO 2) nanotubes were prepared by electrolytic anodization of titanium electrodes. Morphological evolution and phase transformations of TiO 2 nanotubes on a Ti substrate and that of freestanding TiO 2 membranes during the calcinations process were studied by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction microscopy. The detailed results and mechanisms on the morphology and crystalline structure were presented. Our results show that a compact layer exists between the tubular layer and Ti substrate at 600 °C, and the length of the nanotubes shortens dramatically at 750 °C. The freestanding membranes have many particles on their tubes during calcinations from 450 to 900 °C. The TiO 2 nanotubes on the Ti substrate transform to rutile crystals at 600 °C, while the freestanding TiO 2 membranes retain an anatase crystal with increasing temperature to 800 °C. The photocatalytic activity of TiO 2 nanotubes on a Ti substrate annealed at different temperatures was investigated by the degradation of methyl orange in aqueous solution under UV light irradiation. Due to the anatase crystals in the tubular layer and rutile crystals in the compact layer, TiO 2 nanotubes annealed at 450 °C with pure anatase crystals have a better photocatalytic activity than those annealed at 600 °C or 750 °C.

  5. Effect of silica/titania ratio on enhanced photooxidation of industrial hazardous materials by microwave treated mesoporous SBA-15/TiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Mehta, Akansha; Mishra, Amit; Sharma, Manisha; Singh, Satnam; Basu, Soumen

    2016-07-01

    In this study microwave assisted technique has been adopted for the synthesis of different weight ratios of TiO2 dispersed on Santa barbara amorphous-15 (SBA-15) support. Morphological study revealed TiO2 particles (4-10 nm) uniformly distributed on SBA-15 while increases in SBA-15 content results in higher specific surface area (524-237 m2/g). The diffraction intensity of 101 plane of anatase polymorph was seen increasing with increase in TiO2 ratio. All the photocatalysts were having a mesoporous nature and follow the Langmuir IV isotherm, SBA-15 posses the highest pore volume (0.93 cm3 g-1) which consistently decreased with TiO2 content and was lowest (0.50 cm3 g-1) in case of 5 wt% of TiO2 followed by P25 (0.45 cm3 g-1) while pore diameter increased after TiO2 incorporation due to pore strain. The photocatalytic activity of the nanocomposites were analysed for the photodegradation of alizarin dye and pentachlorophenol under UV light irradiation. The reaction kinetics suggested the highest efficiency (98 % for alizarin and 94 % for PCP) of 5 wt% TiO2 compared to other photocatalysts, these nanocomposites were reused for several cycles, which is most important for heterogeneous photocatalytic degradation reaction.

  6. Fabrication of Bi2O3/TiO2 nanocomposites and their applications to the degradation of pollutants in air and water under visible-light.

    PubMed

    Chakraborty, Ashok Kumar; Hossain, Md Emran; Rhaman, Md Masudur; Sobahan, K M A

    2014-02-01

    A nanoheterojunction composite photocatalyst Bi2O3/TiO2 working under visible-light (lambda > or = 420 nm) was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2 molar ratio. Maleic acid was employed as an organic binder to unite Bi2O3 and TiO2 nanoparticles. The SEM, TEM, XRD and diffuse reflectance spectra were utilized to characterize the prepared Bi2O3/TiO2 nanoheterojunction. The nanocomposite exhibited unusual high photocatalytic activity in decomposing 2-propanol in gas phase and phenol in aqueous phase and, evolution of CO2 under visible light irradiation while the end members exhibited low photocatalytic activity. The composite was optimized to 5 mol% Bi2O3/TiO2. The remarkable high photocatalytic efficiency originates from the unique relative energy band position of Bi2O3 and TiO2 as well as the absorption of visible light by Bi2O3.

  7. Visible-light-induced photocatalytic reduction of Cr(VI) with coupled Bi2O3/TiO2 photocatalyst and the synergistic bisphenol A oxidation.

    PubMed

    Yang, Juan; Dai, Jun; Li, Jiantong

    2013-04-01

    Coupled Bi2O3/TiO2 photocatalysts were fabricated by sol-gel and hydrothermal methods and characterized using various spectroscopy techniques. Photocatalytic reduction of Cr(VI) in aqueous solution, together with the synergistic effect of photodegradation of bisphenol A (BPA), was investigated using these coupled Bi2O3/TiO2 under visible-light irradiation. Coupling of Bi2O3 inhibited the phase transformation from anatase to rutile and extended absorption region to visible light. Bi ions did not enter TiO2 lattice and were more likely to bond with oxygen atoms to form Bi2O3 on the surface of TiO2. Photovoltage signals in visible range revealed the effective interfacial charge transfer between Bi2O3 and TiO2. Two percent Bi2O3/TiO2 exhibited the highest photocatalytic activity of visible-light-induced reduction of Cr(VI). The addition of BPA effectively increased the photocatalytic reduction of Cr(VI). Simultaneously, the presence of Cr(VI) promoted the degradation of BPA, which was demonstrated by the investigation of TOC removal yield and generated intermediates. A possible mechanism of photocatalytic reduction of Cr(VI) and degradation of BPA in Bi2O3/TiO2 system was proposed. The synergistic effect, observed between reduction of Cr(VI) and degradation of BPA, provides beneficial method for environmental remediation and purification of the complex wastewater.

  8. Optimized nanostructured TiO2 photocatalysts

    NASA Astrophysics Data System (ADS)

    Topcu, Selda; Jodhani, Gagan; Gouma, Pelagia

    2016-07-01

    Titania is the most widely studied photocatalyst. In it’s mixed-phase configuration (anatase-rutile form) -as manifested in the commercially available P25 Degussa material- titania was previously found to exhibit the best photocatalytic properties reported for the pure system. A great deal of published research by various workers in the field have not fully explained the underlying mechanism for the observed behavior of mixed-phase titania photocatalysts. One of the prevalent hypothesis in the literature that is tested in this work involves the presence of small, active clusters of interwoven anatase and rutile crystallites or “catalytic “hot-spots””. Therefore, non-woven nanofibrous mats of titania were produced and upon calcination the mats consisted of nanostructured fibers with different anatase-rutile ratios. By assessing the photocatalytic and photoelectrochemical properties of these samples the optimized photocatalyst was determined. This consisted of TiO2 nanostructures annealed at 500˚C with an anatase /rutile content of 90/10. Since the performance of this material exceeded that of P25 complete structural characterization was employed to understand the catalytic mechanism involved. It was determined that the dominant factors controlling the photocatalytic behavior of the titania system are the relative particle size of the different phases of titania and the growth of rutile laths on anatase grains which allow for rapid electron transfer between the two phases. This explains how to optimize the response of the pure system.

  9. Degradation of pesticides chlorpyrifos, cypermethrin and chlorothalonil in aqueous solution by TiO2 photocatalysis.

    PubMed

    Affam, Augustine Chioma; Chaudhuri, Malay

    2013-11-30

    Degradation of pesticides chlorpyrifos, cypermethrin and chlorothalonil in aqueous solution by TiO2 photocatalysis under UVA (365 nm) irradiation was examined. Enhancement of degradation and improvement in biodegradability index (BOD5/COD ratio) by H2O2 addition were also evaluated. UVA irradiation per se produced insignificant degradation of the pesticides. In UV/TiO2 photocatalysis (TiO2 1.5 g L(-1), pH 6 and 300 min irradiation), COD and TOC removal were 25.95 and 8.45%, respectively. In UV/TiO2/H2O2 photocatalysis (TiO2 1.5 g L(-1), H2O2 100 mg L(-1), pH 6 and 300 min irradiation), COD and TOC removal were 53.62 and 21.54%, respectively and biodegradability index improved to 0.26. Ammonia-nitrogen (NH3-N) decreased from 22 to 7.8 mg L(-1) and nitrate-nitrogen (NO3(-)-N) increased from 0.7 to 13.8 mg L(-1) in 300 min, indicating mineralization. Photocatalytic degradation followed pseudo-first order kinetics with rate constant (k) of 0.0025 and 0.0008 min(-1) for COD and TOC removal, respectively. FTIR spectra indicated degradation of the organic bonds of the pesticides. UV/TiO2/H2O2 photocatalysis is effective in degradation of pesticides chlorpyrifos, cypermethrin and chlorothalonil in aqueous solution. UV/TiO2/H2O2 photocatalysis may be applied as pretreatment of a chlorpyrifos, cypermethrin and chlorothalonil pesticide wastewater at pH 6, for biological treatment.

  10. Enhanced Photodetection from TiO2-SiO x -TiO2 One-Dimensional Device

    NASA Astrophysics Data System (ADS)

    Choudhuri, Bijit; Mondal, Aniruddha; Saha, Ardhendu

    2016-08-01

    In this work, TiO2 nanowires (NWs)/SiO x zigzag (ZZ) film/TiO2 NWs structure-based devices were fabricated using glancing angle deposition and oblique angle deposition techniques. An investigation of the optoelectronic properties of the devices will be presented. The NWs-ZZ-NWs structure showed an average of 1.6 times enhancement in absorbance value as compared to the absorbance of the structure that contains only NWs. When irradiated with white light, NWs-ZZ-NWs- and only NWs-based devices exhibited a maximum 6.3 and 2.7 times greater light-to-dark current ratio, respectively, at -3 V. The maximum photoresponsivity and internal gain at the wavelength of 370 nm were calculated to be 57 A/W and 191, respectively, for the NWs-ZZ-NWs devices. The rise and fall time for the NWs-ZZ-NWs and NW devices were 16.56 s and 8.2 s, and 8.39 s and 7.31 s, respectively.

  11. Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods.

    PubMed

    Paul, Kamal Kumar; Ghosh, Ramesh; Giri, P K

    2016-08-05

    We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390-800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min(-1), which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis.

  12. Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods

    NASA Astrophysics Data System (ADS)

    Paul, Kamal Kumar; Ghosh, Ramesh; Giri, P. K.

    2016-08-01

    We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390-800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min-1, which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis.

  13. Highly active nanocrystalline TiO(2) photoelectrodes.

    PubMed

    Paronyan, Tereza M; Kechiantz, A M; Lin, M C

    2008-03-19

    A simple method for the fabrication of highly photoactive nanocrystalline two-layer TiO(2) electrodes for solar cell applications is presented. Diluted titanium acetylacetonate has been used as a precursor for covering SnO(2):F (FTO) films with dense packed TiO(2) nanocrystallites. The nanoporous thick TiO(2) film follows the dense packed thin TiO(2) film as a second layer. For the latter, amorphous TiO(2) nanoparticles have been successfully synthesized by a sol-gel technique in an acidic environment with pH<1 and hydrothermal growth at a temperature of 200 °C. The acidic nanoparticle gel was neutralized by basic ammonia and a TiO(2) gel of pH 5 was obtained; this pH value is higher than the recently reported value of 3.1 (Park et al 2005 Adv. Mater. 17 2349-53). Highly interconnected, nanoporous, transparent and active TiO(2) films have been fabricated from the pH 5 gel. SEM, AFM and XRD analyses have been carried out for investigation of the crystal structure and the size of nanoparticles as well as the surface morphology of the films. Investigation of the photocurrent-voltage characteristics has shown improvement in cell performance along with the modification of the surface morphology, depending on pH of the TiO(2) gel. Increasing the pH of the gel from 2.1 to 5 enhanced the overall conversion efficiency of the dye-sensitized solar cells by approximately 30%. An energy conversion efficiency of 8.83% has been achieved for the cell (AM1.5, 100  mWcm(-2) simulated sunlight) compared to 6.61% efficiency in the absence of ammonia in the TiO(2) gel.

  14. Photocatalytic TiO2 nanoparticles enhanced polymer antimicrobial coating

    NASA Astrophysics Data System (ADS)

    Wei, Xiaojin; Yang, Zhendi; Tay, See Leng; Gao, Wei

    2014-01-01

    Copper (Cu) containing coatings can provide sustainable protection against microbial contamination. However, metallic Cu coatings have not been widely used due to the relatively high cost, poor corrosion resistance, and low compatibility with non-metal substrates. Titanium dioxide (TiO2) possesses antibacterial functions by its photocatalytic properties which can destroy bacteria or suppress their reproduction. TiO2 also has the function of improving the mechanical properties through particle dispersion strengthening. We have recently developed an innovative polymer based coating system containing fine particles of Cu and TiO2 nanoparticles. These polymer based coatings simultaneously display excellent antimicrobial and good mechanical properties. The results showed that the addition of TiO2 has improved the antimicrobial property under sunlight, which provides extended applications in outdoor environment. The elimination of 106 bacterial by contacting the coatings without TiO2 needs 5 h, while contacting with the Cu/TiO2- 1 wt.% TiO2 took only 2 h to kill the same amount of bacteria. The coatings also presented enhanced hardness and wear resistance after adding TiO2. The width of wear track decreased from 270 μm of the Cu-polymer coating to 206 μm of Cu/TiO2-polymer coatings with 10 wt.% TiO2. Synchrotron Infrared Microscopy was used to in-situ and in-vivo study the bacteria killing process at the molecular level. The real-time chemical images of bacterial activities showed that the bacterial cell membranes were damaged by the Cu and TiO2 containing coatings

  15. Anatase TiO2 sheet-assisted synthesis of Ti(3+) self-doped mixed phase TiO2 sheet with superior visible-light photocatalytic performance: Roles of anatase TiO2 sheet.

    PubMed

    Zhang, Xiaojie; Zuo, Guoqing; Lu, Xin; Tang, Changqing; Cao, Shuo; Yu, Miao

    2017-03-15

    On the basis of measurements, such as field emission scanning electron microscope, UV-Vis diffuse reflectance spectra, X-ray diffraction, electron paramagnetic resonance, photoluminescence spectra, and photocurrent measurements, the roles of anatase TiO2 sheet on synthesizing Ti(3+) self-doped mixed phase TiO2 nanosheets (doped TiO2 (A/R, TiO2 (A))) and on improving the performance for photocatalytic CO2 reduction were explored systematically. High surface area anatase TiO2 nanosheets (TiO2 (A)) as a substrate, structure directing agent, and inhibitor, mediated the synthesis of Ti(3+) self-doped mixed phase TiO2 nanosheets. Addition of TiO2 (A) significantly improved not only visible light absorption of doped TiO2 (A/R, TiO2 (A)), but also the efficiency of photo-excited charges separations due to the existence of interfacial regions of anatase-rutile TiO2 junctions. Finally, a possible mechanism for interfacial charge transfer at the anatase-rutile TiO2 interface and for photocatalytic CO2 reduction over Pt loaded doped TiO2 (A/R, TiO2 (A)) were proposed.

  16. Double-doped TiO2 nanoparticles as an efficient visible-light-active photocatalyst and antibacterial agent under solar simulated light

    NASA Astrophysics Data System (ADS)

    Ashkarran, Ali Akbar; Hamidinezhad, Habib; Haddadi, Hedayat; Mahmoudi, Morteza

    2014-05-01

    Silver and nitrogen doped TiO2 nanoparticles (NPs) were synthesized via sol-gel method. The physicochemical properties of the achieved NPs were characterized by various methods including X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultra violet-visible absorption spectroscopy (UV-vis). Both visible-light photocatalytic activity and antimicrobial properties were successfully demonstrated for the degradation of Rhodamine B (Rh. B.), as a model dye, and inactivation of Escherichia coli (E. coli), as a representative of microorganisms. The concentration of the employed dopant was optimized and the results revealed that the silver and nitrogen doped TiO2 NPs extended the light absorption spectrum toward the visible region and significantly enhanced the photodegradation of model dye and inactivation of bacteria under visible-light irradiation while double-doped TiO2 NPs exhibited highest photocatalytic and antibacterial activity compared with single doping. The significant enhancement in the photocatalytic activity and antibacterial properties of the double doped TiO2 NPs, under visible-light irradiation, can be attributed to the generation of two different electronic states acting as electron traps in TiO2 and responsible for narrowing the band gap of TiO2 and shifting its optical response from UV to the visible-light region.

  17. Artificial Neural Network Modelling of Photodegradation in Suspension of Manganese Doped Zinc Oxide Nanoparticles under Visible-Light Irradiation

    PubMed Central

    Abdollahi, Yadollah; Sairi, Nor Asrina; Amin Matori, Khamirul; Fard Masoumi, Hamid Reza

    2014-01-01

    The artificial neural network (ANN) modeling of m-cresol photodegradation was carried out for determination of the optimum and importance values of the effective variables to achieve the maximum efficiency. The photodegradation was carried out in the suspension of synthesized manganese doped ZnO nanoparticles under visible-light irradiation. The input considered effective variables of the photodegradation were irradiation time, pH, photocatalyst amount, and concentration of m-cresol while the efficiency was the only response as output. The performed experiments were designed into three data sets such as training, testing, and validation that were randomly splitted by the software's option. To obtain the optimum topologies, ANN was trained by quick propagation (QP), Incremental Back Propagation (IBP), Batch Back Propagation (BBP), and Levenberg-Marquardt (LM) algorithms for testing data set. The topologies were determined by the indicator of minimized root mean squared error (RMSE) for each algorithm. According to the indicator, the QP-4-8-1, IBP-4-15-1, BBP-4-6-1, and LM-4-10-1 were selected as the optimized topologies. Among the topologies, QP-4-8-1 has presented the minimum RMSE and absolute average deviation as well as maximum R-squared. Therefore, QP-4-8-1 was selected as final model for validation test and navigation of the process. The model was used for determination of the optimum values of the effective variables by a few three-dimensional plots. The optimum points of the variables were confirmed by further validated experiments. Moreover, the model predicted the relative importance of the variables which showed none of them was neglectable in this work. PMID:25538962

  18. Photocatalytic degradation of industrial pulp and paper mill effluent using synthesized magnetic Fe2O3-TiO2: Treatment efficiency and characterizations of reused photocatalyst.

    PubMed

    Subramonian, Wennie; Wu, Ta Yeong; Chai, Siang-Piao

    2017-02-01

    In this work, heterogeneous photocatalysis was used to treat pulp and paper mill effluent (PPME). Magnetically retrievable Fe2O3-TiO2 was fabricated by employing a solvent-free mechanochemical process under ambient conditions. Findings elucidated the successful incorporation of Fe2O3 into the TiO2 lattice. Fe2O3-TiO2 was found to be an irregular and slightly agglomerated surface morphology. In comparison to commercial P25, Fe2O3-TiO2 exhibited higher ferromagnetism and better catalyst properties with improvements in surface area (58.40 m(2)/g), pore volume (0.29 cm(3)/g), pore size (18.52 nm), and band gap (2.95 eV). Besides, reusability study revealed that Fe2O3-TiO2 was chemically stable and could be reused successively (five cycles) without significant changes in its photoactivity and intrinsic properties. Additionally, this study demonstrated the potential recovery of Fe2O3-TiO2 from an aqueous suspension by using an applied magnetic field or sedimentation. Interactive effects of photocatalytic conditions (initial effluent pH, Fe2O3-TiO2 dosage, and air flow-rate), reaction mechanism, and the presence of chemical oxidants (H2O2, BrO3(-), and HOCl) during the treatment process of PPME were also investigated. Under optimal conditions (initial effluent pH = 3.88, [Fe2O3-TiO2] = 1.3 g/L, and air flow-rate = 2.28 L/min), the treatment efficiency of Fe2O3-TiO2 was 98.5% higher than the P25. Based on Langmuir-Hinshelwood kinetic model, apparent rate constants of Fe2O3-TiO2 and P25 were 9.2 × 10(-3) and 2.7 × 10(-3) min(-1), respectively. The present study revealed not only the potential of using magnetic Fe2O3-TiO2 in PPME treatment but also demonstrated high reusability and easy separation of Fe2O3-TiO2 from the wastewater.

  19. Nitrogen and sulfur co-doped TiO2 nanosheets with exposed {001} facets: synthesis, characterization and visible-light photocatalytic activity.

    PubMed

    Xiang, Quanjun; Yu, Jiaguo; Jaroniec, Mietek

    2011-03-21

    Nitrogen and sulfur co-doped TiO(2) nanosheets with exposed {001} facets (N-S-TiO(2)) were prepared by a simple mixing-calcination method using the hydrothermally prepared TiO(2) nanosheets powder as a precursor and thiourea as a dopant. The resulting samples were characterized by transmission electron microscope, X-ray diffraction, N(2) adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and UV-Vis absorption spectroscopy. The electronic properties of N,S co-doped TiO(2) were studied using the first-principle density functional theory (DFT). The photocatalytic activity of N-S-TiO(2) was evaluated by degradation of 4-chlorophenol (4-CP) aqueous solution under visible light irradiation. The production of hydroxyl radicals (˙OH) on the surface of visible-light-irradiated samples was detected by photoluminescence technique using terephthalic acid as a probe molecule. The results show that nitrogen and sulfur atoms were successfully incorporated into the lattice of TiO(2), which resulted in N-S-TiO(2) samples exhibiting stronger absorption in the UV-visible range with a red shift in the band gap transition. The first-principle DFT calculations further confirm that N and S co-dopants can induce the formation of new energy levels in the band gap, which is associated with the response of N-S-TiO(2) nanosheets to visible light irradiation. Surprisingly, pure TiO(2) nanosheets show the visible-light photocatalytic activity for the degradation of 4-CP mainly due to the substrate-surface complexation of TiO(2) and 4-CP, which results in extending absorption of titania to visible light region through ligand-to-titanium charge transfer. The N-S-TiO(2) samples studied exhibited an enhanced visible-light photocatalytic activity than pure TiO(2). Especially, the doped TiO(2) sample at the nominal weight ratio of thiourea to TiO(2) powder of 2 showed the highest photocatalytic activity, which was about twice greater than that of Degussa P25. The enhanced activity of

  20. Growth of TiO2 nanoparticles under heat treatment

    NASA Astrophysics Data System (ADS)

    Bahadur, J.; Sen, D.; Mazumder, S.; Sastry, P. U.; Paul, B.

    2013-02-01

    The effect of heat treatment, on growth of NiO doped TiO2, have been investigated. The nanoparticle size has been estimated by small-angle x-ray scattering. The average particle size increases with increasing temperature. The growth of crystallite size has been probed by X-ray diffraction. A polymorphic phase transition of TiO2 is observed beyond 600°C due to growth of TiO2 nanoparticles beyond 14 nm of size.