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Sample records for irradiated tio2 suspensions

  1. 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. PMID:18555596

  2. Photocatalytic reduction of hexavalent chromium and degradation of di-n-butyl phthalate in aqueous TiO2 suspensions under ultraviolet light irradiation.

    PubMed

    Xu, X R; Li, H B; Gu, J D

    2007-09-01

    Simultaneous photocatalytic reduction of chromium(VI) to the less toxic Cr(III) and degradation of di-n-butyl phthalate (DBP) in aqueous TiO2, suspension under ultraviolet light irradiation was investigated. The batch experiments were carried out in a photoreactor equipped with 350 nm lamps. The system containing Cr(VI) and DBP showed the synergistic photocatalytic decontamination as DBP facilitated Cr(VI) reduction, whereas Cr(VI) accelerated DBP degradation. This study demonstrated for the first time that two important environmental pollutants Cr(VI) and DBP could be eliminated simultaneously using UV/TiO2 process. The intermediate products of DBP degradation were identified by gas chromatography-mass spectrometry, and the reaction mechanism was proposed. PMID:17910258

  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. 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. PMID:25013855

  5. Photocatalytic Degradation of Methylene Blue under UV Light Irradiation on Prepared Carbonaceous TiO2

    PubMed Central

    Che Ramli, Zatil Amali; 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 m2 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. PMID:25013855

  6. 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. PMID:20705323

  7. 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.

  8. 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. PMID:25238917

  9. 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

  10. Positron annihilation lifetime characterization of oxygen ion irradiated rutile TiO2

    NASA Astrophysics Data System (ADS)

    Luitel, Homnath; Sarkar, A.; Chakrabarti, Mahuya; Chattopadhyay, S.; Asokan, K.; Sanyal, D.

    2016-07-01

    Ferromagnetic ordering at room temperature has been induced in rutile phase of TiO2 polycrystalline sample by O ion irradiation. 96 MeV O ion induced defects in rutile TiO2 sample has been characterized by positron annihilation spectroscopic techniques. Positron annihilation results indicate the formation of cation vacancy (VTi, Ti vacancy) in these irradiated TiO2 samples. Ab initio density functional theoretical calculations indicate that in TiO2 magnetic moment can be induced either by creating Ti or O vacancies.

  11. Effect of Xe ion irradiation on photocatalytic performance of oblique TiO2 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Li, Zhengcao; Teng, Yi; Chen, Chienhua; Lv, Shasha; Wang, Guojing; Zhang, Zhengjun

    2015-02-01

    In this work oblique TiO2 nanowire arrays (NWs) were prepared by magnetron sputtering method and irradiated by 200 keV Xe ion with different doses. The photocatalytic activity of TiO2 was studied by degrading methyl orange dye (MO) under ultraviolet (UV) light, which indicates that the photocatalytic performance of as-deposited and irradiated TiO2 NWs. It was found that when the dose was relatively low, the Ti3+ content on the surface was increased upon irradiation, dominating the enhancement of the photocatalytic property of the TiO2 NWs. By this means, an optimization of Xe ion dose can largely improve the photocatalytic performance of TiO2 NWs.

  12. Anderson localization of light in a colloidal suspension (TiO2@silica).

    PubMed

    Jimenez-Villar, Ernesto; da Silva, Iran F; Mestre, Valdeci; de Oliveira, Paulo C; Faustino, Wagner M; de Sá, Gilberto F

    2016-06-01

    In recent years, there has been dramatic progress in the photonics field in disordered media, ranging from applications in solar collectors, photocatalyzers, random lasing, and other novel photonic functions, to investigations into fundamental topics, such as light confinement and other phenomena involving photon interactions. This paper reports several pieces of experimental evidence of localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO2@silica) in ethanol solution. We demonstrate the crossover from a diffusive transport to a localization transition regime as the nanoparticle concentration is increased, and that an enhanced absorption effect arises at localization transition. PMID:26804337

  13. Photodegradation of bisphenol-A in a batch TiO2 suspension reactor.

    PubMed

    Tsai, Wen-Tien; Lee, Mei-Kuei; Su, Ting-Yi; Chang, Yuan-Ming

    2009-08-30

    In this work, the photocatalytic behaviors of bisphenol-A (BPA), which has been listed as one of endocrine disrupting chemicals, were carried out in a batch TiO(2) suspension reactor. The photodegradation efficiency has been investigated under the controlled process parameters including initial BPA concentration (i.e., 1-50 mg L(-1)), TiO(2) dosage (i.e., 5-600 mg/200 cm(3)), initial pH (i.e., 3-11), and temperature (i.e., 10-70 degrees C). It was found that the optimal conditions in the photoreaction process could be coped with at initial BPA concentration=20 mg L(-1), TiO(2) dosage=0.5 g L(-1) (100mg/200 cm(3)), initial pH=7.0, and temperature=25 degrees C. According to the Langmuir-Hinshelwood model, the results showed that the photodegradation kinetics for the destruction of BPA in water also followed the first-order model well. The apparent first-order reaction constants (k(obs)), thus obtained from the fittings of the model, were in line with the destruction-removal efficiencies of BPA in all the photocatalytic experiments. Based on the intermediate products identified in the study, the possible mechanisms for the photodegradation of BPA in water were also proposed in the present study. PMID:19285792

  14. Interactions of ciprofloxacin (CIP), titanium dioxide (TiO2) nanoparticles and natural organic matter (NOM) in aqueous suspensions.

    PubMed

    Fries, Elke; Crouzet, Catherine; Michel, Caroline; Togola, Anne

    2016-09-01

    The aim of the present study was to investigate interactions of the antibiotic ciprofloxacin (CIP), titanium dioxide nanoparticles (TiO2 NP) and natural organic matter (NOM) in aqueous suspensions. The mean hydrodynamic diameter of particles of TiO2 NP and NOM in the suspensions ranged from 113 to 255nm. During batch experiments the radioactivity resulting from (14)CIP was determined in the filtrate (filter pore size 100nm) by scintillation measurements. Up to 72h, no significant sorption of NOM to TiO2 NP was observed at a TiO2 NP concentration of 5mg/L. When the concentration of TiO2 NP was increased to 500mg/L, a small amount of NOM of 9.5%±0.6% was sorbed at 72h. The low sorption affinity of NOM on TiO2 NP surfaces could be explained by the negative charge of both components in alkaline media or by the low hydrophobicity of the NOM contents. At a TiO2 NP concentration of 5mgL(-1), the sorption of CIP on TiO2 NP was insignificant (TiO2 NP/CIP ratio: 10). When the TiO2 NP/CIP ratio was increased to 1000, a significant amount of 53.6%±7.2% of CIP was sorbed on TiO2 NP under equilibrium conditions at 64h. In alkaline media, CIP is present mainly as zwitterions which have an affinity to sorb on negatively charged TiO2 NP surfaces. The sorption of CIP on TiO2 NP in the range of TiO2 NP concentrations currently estimated for municipal wastewater treatment plants is estimated to be rather low. The Freundlich sorption coefficients (KF) in the presence of NOM of 2167L(n)mgmg(-n)kg(-1) was about 10 times lower than in the absence of NOM. This is an indication that the particle fraction of NOM<100nm could play a role as a carrier for ionic organic micro-pollutants as CIP. PMID:26765511

  15. 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.

  16. Anderson localization of light in a colloidal suspension (TiO2@silica)

    NASA Astrophysics Data System (ADS)

    Jimenez-Villar, Ernesto; da Silva, Iran F.; Mestre, Valdeci; de Oliveira, Paulo C.; Faustino, Wagner M.; de Sá, Gilberto F.

    2016-05-01

    In recent years, there has been dramatic progress in the photonics field in disordered media, ranging from applications in solar collectors, photocatalyzers, random lasing, and other novel photonic functions, to investigations into fundamental topics, such as light confinement and other phenomena involving photon interactions. This paper reports several pieces of experimental evidence of localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO2@silica) in ethanol solution. We demonstrate the crossover from a diffusive transport to a localization transition regime as the nanoparticle concentration is increased, and that an enhanced absorption effect arises at localization transition.In recent years, there has been dramatic progress in the photonics field in disordered media, ranging from applications in solar collectors, photocatalyzers, random lasing, and other novel photonic functions, to investigations into fundamental topics, such as light confinement and other phenomena involving photon interactions. This paper reports several pieces of experimental evidence of localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core-shell nanoparticles (TiO2@silica) in ethanol solution. We demonstrate the crossover from a diffusive transport to a localization transition regime as the nanoparticle concentration is increased, and that an enhanced absorption effect arises at localization transition. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07540h

  17. Ion-irradiation enhanced epitaxial growth of sol-gel TiO2 films

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Kun; Jung, Hyun Suk; Wang, Yongqiang; Theodore, N. David; Alford, Terry L.; Nastasi, Michael

    2011-04-01

    We report the epitaxial growth of sol-gel TiO2 films by using ion-irradiation enhanced synthesis. Our present study shows that the ion-beam process can provide highly crystalline TiO2 even at 350°C. Nuclear energy deposition at amorphous/crystalline interface plays a dominant role in the epitaxial growth of the films at the reduced temperature via a defect-migration mechanism. In addition, the ion irradiation allows for increasing the film density by balancing the crystallization rate and the escape rate of organic components.

  18. Switchable optical transmittance of TiO2 submicron-diameter wire suspension-based "smart window" device

    NASA Astrophysics Data System (ADS)

    Leinberg, S.; Kisand, V.; Šutka, A.; Saal, K.; Lõhmus, R.; Joost, U.; Timusk, M.; Nõmmiste, E.

    2015-08-01

    In this paper, for the first time, a TiO2 submicron-diameter wire suspension-based smart window device is demonstrated in which combined planar and finger electrodes are utilised to reversibly change the orientation of the nanowires. Electrospun TiO2 anatase submicron-diameter wire suspensions in a viscous polydimethylsiloxane (PDMS) matrix were prepared directly from electrospun submicron-diameter fibre mats by using high-shear mixing, achieving the complete break-up of all electrospun mats and suspending TiO2 submicron-diameter wires uniformly in the PDMS matrix. Suspension was used as an active layer in an electro-optical device where a reversible change in light scattering is achieved by preparing a device consisting of an active layer and combined planar and finger electrode system. Using the constructed device, it was possible to change the alignment or spatial distribution of TiO2 submicron-diameter wires by applying a DC electric field across the planar or finger, electrodes thus changing the transmittance (ΔT = 25%) of the suspension and demonstrating the potential to use combined planar and finger electrode devices in smart window applications.

  19. Degradation of the antibiotic oxolinic acid by photocatalysis with TiO2 in suspension.

    PubMed

    Giraldo, Ana L; Peñuela, Gustavo A; Torres-Palma, Ricardo A; Pino, Nancy J; Palominos, Rodrigo A; Mansilla, Héctor D

    2010-10-01

    In the work presented here, a photocatalytic system using titanium Degussa P-25 in suspension was used to evaluate the degradation of 20mg L(-1) of antibiotic oxolinic acid (OA). The effects of catalyst load (0.2-1.5 g L(-1)) and pH (7.5-11) were evaluated and optimized using the surface response methodology and the Pareto diagram. In the range of variables studied, low pH values and 1.0 g L(-1) of TiO(2) favoured the efficiency of the process. Under optimal conditions the evolution of the substrate, chemical oxygen demand, dissolved organic carbon, toxicity and antimicrobial activity on Escherichia coli cultures were evaluated. The results indicate that, under optimal conditions, after 30 min, the TiO(2) photocatalytic system is able to eliminate both the substrate and the antimicrobial activity, and to reduce the toxicity of the solution by 60%. However, at the same time, ∼53% of both initial DOC and COD remain in solution. Thus, the photocatalytical system is able to transform the target compound into more oxidized by-products without antimicrobial activity and with a low toxicity. The study of OA by-products using liquid chromatography coupled with mass spectrometry, as well as the evaluation of OA degradation in acetonitrile media as solvent or in the presence of isopropanol and iodide suggest that the reaction is initiated by the photo-Kolbe reaction. Adsorption isotherm experiments in the dark indicated that under pH 7.5, adsorption corresponded to the Langmuir adsorption model, indicating the dependence of the reaction on an initial adsorption step. PMID:20633918

  20. 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. PMID:21762957

  1. Characterization and comparison of photocatalytic activities of prepared TiO2/graphene nanocomposites using titanium butoxide and TiO2 via microwave irradiation method

    NASA Astrophysics Data System (ADS)

    Darvishi, Motahareh; Seyed-Yazdi, Jamileh

    2016-08-01

    Photocatalysis based on TiO2 nanostructures with nanoscale hybridization of graphene, is a promising method to create highly conductive composite materials and surfaces with enhanced light absorption. In this study, graphite-oxide (GO) was produced by improved Hummers’ method followed by synthesis of TiO2/graphene nanocomposites. We used two precursors, titanium butoxide (TBO) and commercial TiO2, to produce nanocomposites in a mixture of water/ethanol and graphene-oxide, for hydrolysis of titania precursors on graphene-oxide sheets resulting in the formation of nanocomposites. Microwave irradiation is used to reduce graphene-oxide into graphene. TiO2/graphene nanocomposites in both cases demonstrate enhancement of overall photocatalytic activity compared with titania precursors which was examined by degradation of methylene blue (MB). In this study, nanocomposites were synthesized with different mass ratios of GO compare to titania precursors (i.e. GO: 1, 5 and 8 wt%). Photocatalytic performance increased with the increasing content of graphene in both cases. The reduction rate of MB for TiO2 was 62% and for TiO2/graphene (TiO2/G) (GO: 8 wt%) was 85% after 90 min, and for TBO and TBO/G (GO: 8 wt%) was 3% and 99.95%, respectively. SEM, XRD, Fourier transform infrared and UV–vis spectroscopy were used to characterize the synthesized nanocomposites. FTIR analysis demonstrates the formation of Ti–O–C bonds and confirms the formation of nanocomposites made of graphene and titania nanoparticles.

  2. 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%.

  3. 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...

  4. [Simultaneous desulfurization and denitrification by TiO2/ACF under different irradiation].

    PubMed

    Han, Jing; Zhao, Yi

    2009-04-15

    The supported TiO2 photocatalysts were prepared in laboratory, and the experiments of simultaneous desulfurization and denitrification were carried out by self-designed photocatalysis reactor. The optimal experimental conditions were achieved, and the efficiencies of simultaneous desulfurization and denitrification under two different light sources were compared. The results show that the oxygen content of flue gas, reaction temperature, flue gas humidity and irradiation intensity are most essential factors to photocatalysis. For TiO2/ACF, the removal efficiencies of 99.7% for SO2 and 64.3% for NO are obtained respectively at optimal experimental conditions under UV irradiation. For TiO2/ACF, the removal efficiencies of 97.5% for SO2 and 49.6% for NO are achieved respectively at optimal experimental conditions under the visible light irradiation. The results of five times parallel experiments indicate standard deviation S of parallel data is little. The mechanism of removal for SO2 and NO is proposed under two light sources by ion chromatography analysis of the absorption liquid. PMID:19544996

  5. 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.

  6. 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.

  7. Spectroscopic analyses on ROS generation catalyzed by TiO2, CeO2/TiO2 and Fe2O3/TiO2 under ultrasonic and visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Zou, Mingming; Kong, Yumei; Wang, Jun; Wang, Qi; Wang, Zhiqiu; Wang, Baoxin; Fan, Ping

    2013-01-01

    In this work, the TiO2, CeO2/TiO2 and Fe2O3/TiO2 powders were irradiated, respectively, by ultrasound and visible-light, and the generation of reactive oxygen species (ROS) were estimated by the method of Oxidation-Extraction Photometry (OEP). That is, the 1,5-diphenyl carbazide (DPCI) can be oxidized by generated ROS into 1,5-diphenyl carbazone (DPCO), which can be extracted by mixed solvent of benzene and carbon tetrachloride. The DPCO extract liquor displays an obvious absorbance at 563 nm wavelength. In addition, some influencing factors, such as (ultrasonic or visible-light) irradiation time, catalyst addition amount and DPCI concentration, on the generation of ROS were also reviewed. The results indicated that the quantities of generated ROS increase with the increase of (ultrasonic or visible-light) irradiation time and catalyst addition amount. Moreover, the displayed quantities of ROS are also related with DPCI concentration. And then, several radical scavengers were used to determine the kinds of the generated ROS. At last, the researches on the sonocatalytic and photocatalytic degradation of several organic dyes have also been performed. It is wished that this paper might offer some important subjects for broadening the applications of sonocatalytic and photocatalytic technologies in future environment treatment.

  8. 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.

  9. 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

    2015-10-01

    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. PMID:26274932

  10. 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. PMID:27229518

  11. Study of chromium modified TiO2 nano catalyst under visible light irradiation.

    PubMed

    Wei, Yu-Ling; Chen, Kai-Wen; Wang, H Paul

    2010-08-01

    Visible light active photocatalysts were successfully prepared by incorporating chromium into anatase TiO2 at two Cr/Ti atomic ratios (0.03% and 0.11%) by the use of a modified sol-gel process. Results show that the size of the chromium modified TiO2 particles is approximately 14-25 nm. As indicated by diffuse reflectance ultra violet/visible absorption spectra, heavier chromium dosage tends to result in greater absorption in both ultra violet and visible light. The simulation results from Cr K-edge X-ray absorption spectra suggest that Cr(0) and Cr(III), accounting for approximately 25% and 75% of total Cr, respectively, coexist in the TiO2 catalyst doped with 0.11% Cr. Cr dopant is suggested to be responsible for the phenomenon of enhanced light absorption in both ultra violet and visible regions. Further, Cr(0) can act as an electron remover because of the formation of the Schottky barrier between Cr(0) and TiO2, thus reducing the possibility of electron hole recombination. Photo-catalytic degradation of methylene blue under irradiation of blue light (with peak flux at 460 nm wavelength and a small flux near 367 nm) was considerably enhanced under appropriate reaction time (12 and 24 h) as small amount of Cr was doped into anatase titanium dioxide catalyst. After prolonged reaction time, Cr(0) was suggested to be poisoned and/or oxidized by SO4(2-), one of the final products of mineralizing methylene blue, thus loosing the capability of the electron hole separation. PMID:21125918

  12. 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.

  13. 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. PMID:26223016

  14. Efficient removal of sulcotrione and its formulated compound Tangenta® in aqueous TiO2 suspension: Stability, photoproducts assessment and toxicity.

    PubMed

    Šojić, Daniela V; Orčić, Dejan Z; Četojević-Simin, Dragana D; Banić, Nemanja D; Abramović, Biljana F

    2015-11-01

    The photocatalytic degradation of the herbicide sulcotrione (0.05 mM) and its formulated compound Tangenta® in aqueous suspensions of TiO2 Degussa P25 was examined as a function of the different operational parameters. The optimum of the catalyst loading was found to be 2.0 mg mL(-1) under UVA light. In the first stage of the reaction, the photocatalytic degradation of sulcotrione alone and in Tangenta® followed the pseudo-first order kinetics, in which the heterogeneous catalysis proceeds via OH and holes. Further, it can be concluded that degradation rate of sulcotrione alone is about two times higher compared to formulated compound. The results showed that the disappearance of sulcotrione led to the formation of three organic intermediates and ionic byproducts (Cl(-), SO4(2-), acetate and formate), whereas their mineralization was about 90% after 4 h. Tentative photodegradation pathways were proposed and discussed. Also, there was no significant toxicity observed after the irradiation of sulcotrione solution and Tangenta® formulation using TiO2 catalyst on three mammalian cell lines. PMID:25563159

  15. 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. PMID:18939773

  16. Al2O3 and TiO2 entrapped ABS membranes: Preparation, characterization and study of irradiation effect

    NASA Astrophysics Data System (ADS)

    Kamelian, Fariba Sadat; Mousavi, Seyed Mahmoud; Ahmadpour, Ali

    2015-12-01

    The present study focuses on the aluminum oxide (Al2O3) and titanium oxide (TiO2) entrapped acrylonitrile-butadiene-styrene (ABS) membranes prepared from phase inversion method. The effect of Al2O3 and TiO2 nanoparticles on the hydrophilicity, tensile strength, thermal stability, permeate flux, and rejection of wastewater pollution indices was investigated. Some of the membranes were exposed to ultraviolet (UV) irradiation. Al2O3 and TiO2 nanoparticles generally improved performance of the membranes. Thermal stability and tensile strength of the membranes were also enhanced in the presence of the nanoparticles. Increasing the nanoparticles concentration increased viscosity of the casting solutions. The UV irradiated membranes had better performance than the non-irradiated ones.

  17. 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. PMID:27456139

  18. 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.

  19. Synergistic effects of C-Cr codoping in TiO2 and enhanced sonocatalytic activity under ultrasonic irradiation.

    PubMed

    Zhang, Shujuan

    2012-07-01

    C and Cr co-doped TiO(2) (C-Cr-TiO(2)) sonocatalyst were synthesized by doping TiO(2) with glucose and CrCl(3) in a sol-gel method. The samples were characterized by X-ray diffraction, transmission electron microscopy, ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, and X-ray photoelectron emission spectroscopy (XPS). C and Cr were detected by XPS analysis. The influence of dopants on the properties and sonocatalytic activity of TiO(2) was studied. The sonodegradation products of methylene blue were analyzed by UV-vis absorption spectroscopy. The presence of C-Cr-TiO(2) catalysts substantially enhanced the sonocatalytic degradation of MB in aqueous suspensions. The possible sonocatalytic mechanisms were also discussed. PMID:22227556

  20. 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. PMID:15871279

  1. 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).

  2. 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. PMID:23177765

  3. 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. PMID:25956024

  4. Annealing of TiO2 Films Deposited on Si by Irradiating Nitrogen Ion Beams

    SciTech Connect

    Yokota, Katsuhiro; Yano, Yoshinori; Miyashita, Fumiyoshi

    2006-11-13

    Thin TiO2 films were deposited on Si at a temperature of 600 deg. C by an ion beam assisted deposition (IBAD) method. The TiO2 films were annealed for 30 min in Ar at temperatures below 700 deg. C. The as-deposited TiO2 films had high permittivities such 200 {epsilon}o and consisted of crystallites that were not preferentially oriented to the c-axis but had an expanded c-axis. On the annealed TiO2 films, permittivities became lower with increasing annealing temperature, and crystallites were oriented preferentially to the (110) plane.

  5. Influence of the ultraviolet irradiation on the properties of TiO2-polystyrene shape memory nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Wenxin; Liu, Yanju; Leng, Jinsong

    2013-08-01

    To date, majority shape adaptations of shape memory polymer (SMP) are thermo responsive. A desire for isothermal, remotely controlled shape adaptations of SMP has motivated examinations of other stimulus. We successfully construct novel TiO2-polystyrene shape memory nanocomposites and investigate influence of the ultraviolet irradiation on the shape memory effect. This material is facilely fabricated by introducing TiO2 into polystyrene SMP. The properties of TiO2-polystyrene shape memory nanocomposites are characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectra (FT-IR), dynamic mechanical analysis (DMA), and diffused reflectance spectrum (DRS). Deriving from photoelectric foundational properties of TiO2, the TiO2-polystyrene shape memory nanocomposites can absorb light energy and undergo intra-molecular or inter-molecular physical or chemical transformations. Furthermore, the results of this work provide a useful baseline upon which researchers could explore more interesting behaviors of photosensitive SMP composite and investigate other more challenging actuation problems.

  6. High performance flexible ultraviolet photodetectors based on TiO2/graphene hybrid for irradiation monitoring applications

    NASA Astrophysics Data System (ADS)

    Zhou, Chen; Wang, Xiaohong; Kuang, Xuanlin; Xu, Sixing

    2016-07-01

    This paper reports a novel ultraviolet (UV) photodetector based on a TiO2/graphene hybrid, with high responsivity (0.482 A W‑1) at 3 V bias and 330 nm irradiation, which is ~100 times higher than that based on pure TiO2. The collaboration of TiO2 and graphene in the hybrid material contributes to the high performance of the device. To be more specific, graphene provides a large surface area to load sufficient TiO2 nanoparticles, and the generated electrons are instantly collected due to the prominent electrical properties of graphene which can overcome the low quantum efficiency of pristine TiO2 caused by recombination of photo-induced electron–hole pairs. The device was fabricated on a flexible substrate using a facile spraying method that shows the possibility of broadening the future of photodetectors in wearable devices. An on-board interface circuit based on commercial IC components is implemented to collaborate with the photodetector to demonstrate a UV sensing application.

  7. 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.

  8. 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.

  9. Microwave-assisted rapid photocatalytic degradation of malachite green in TiO2 suspensions: mechanism and pathways.

    PubMed

    Ju, Yongming; Yang, Shaogui; Ding, Youchao; Sun, Cheng; Zhang, Aiqian; Wang, Lianhong

    2008-11-01

    Microwave-assisted photocatalytic (MPC) degradation of malachite green (MG) in aqueous TiO2 suspensions was investigated. A 20 mg/L sample of MG was rapidly and completely decomposed in 3 min with the corresponding TOC removal efficiency of about 85%. To gain insight into the degradation mechanism, both GC-MS and LC-ESI-MS/MS techniques were employed to identify the major intermediates of MG degradation, including N-demethylation intermediates [(p-dimethylaminophenyl)(p-methylaminophenyl)phenylmethylium (DM-PM), (p-methylaminophenyl)(p-methylaminophenyl)phenylmethylium (MM-PM), (p-methylaminophenyl)(p-aminophenyl)phenylmethylium (M-PM)]; a decomposition compound of the conjugated structure (4-dimethylaminobenzophenone (DLBP)); products resulting from the adduct reaction of hydroxyl radical; products of benzene removal; and other open-ring intermediates such as phenol, terephthalic acid, adipic acid, benzoic acid, etc. The possible degradation mechanism of MG included five processes: the N-demethylation process, adduct products of the hydroxyl radical, the breakdown of chromophores such as destruction of the conjugated structure intermediate, removal of benzene, and an open-ring reaction. To the best of our knowledge, it is the first time the whole MG photodegradation processes have been reported. PMID:18841945

  10. Probing electron density across Ar+ irradiation-induced self-organized TiO2-x nanochannels for memory application

    NASA Astrophysics Data System (ADS)

    Barman, A.; Saini, C. P.; Sarkar, P. K.; Roy, A.; Satpati, B.; Kanjilal, D.; Ghosh, S. K.; Dhar, S.; Kanjilal, A.

    2016-06-01

    The variation of electron density in TiO2-x nanochannels, exhibiting resistive switching phenomenon, produced by Ar+ ion-irradiation at the threshold fluence of 5 × 1016 ions/cm2 is demonstrated by X-ray reflectivity (XRR). The transmission electron microscopy reveals the formation of nanochannels, while the energy dispersive X-ray spectroscopy confirms Ti enrichment near the surface due to ion-irradiation, in consistent with the increase in electron density by XRR measurements. Such a variation in Ti concentration indicates the evolution of oxygen vacancies (OVs) along the TiO2-x nanochannels, and thus paves the way to explain the operation and performance of the Pt/TiO2-x/Pt-based memory devices via OV migration.

  11. Irradiance influence on the multicolor photochromism of mesoporous TiO2 films loaded with silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Crespo-Monteiro, N.; Destouches, N.; Nadar, L.; Reynaud, S.; Vocanson, F.; Michalon, J. Y.

    2011-10-01

    The photochromism of heterogeneous silver nanoparticles grown thermally in mesoporous TiO2 films is investigated under visible laser illuminations with different irradiances. At low irradiance, a selective oxidation occurs that changes the film color in accordance with the illuminant wavelength. At higher irradiance, the oxidation of large nanoparticles is going with the formation of many small nanoparticles in their vicinity, which gives the films an orangy color whatever the wavelength. This color fades after long exposure times at a laser line. The laser polarization has also an influence on the dichroism of the colored films.

  12. Effect of TiO2 addition on the microstructure and nanomechanical properties of Al2O3 Suspension Plasma Sprayed coatings

    NASA Astrophysics Data System (ADS)

    Bannier, E.; Vicent, M.; Rayón, E.; Benavente, R.; Salvador, M. D.; Sánchez, E.

    2014-10-01

    Alumina-titania coatings are widely used in industry for wear, abrasion or corrosion protection components. Such layers are commonly deposited by atmospheric plasma spraying (APS) using powder as feedstock. In this study, both Al2O3 and Al2O3-13 wt% TiO2 coatings were deposited on austenitic stainless steel coupons by suspension plasma spraying (SPS). Two commercial suspensions of nanosized Al2O3 and TiO2 particles were used as starting materials. The coatings microstructure and phase composition were fully characterised using FEG-SEM and XRD techniques. Nanoindentation technique was used to determine the coatings hardness and elastic modulus properties. Results have shown that the addition of titania to alumina SPS coatings causes different crystalline phases and a higher powder melting rate is reached. The higher melted material achieved, when titania is added leads to higher hardness and elastic modulus when the same spraying parameters are used.

  13. 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. PMID:25323028

  14. Effect of the disinfection agents chlorine, UV irradiation, silver ions, and TiO2 nanoparticles/near-UV on DNA molecules.

    PubMed

    Van Aken, Benoit; Lin, Lian-Shin

    2011-01-01

    Extracellular DNA in municipal wastewater and effluents from hospitals and R&D laboratories contains antimicrobial resistance and recombinant genes that are today considered as a new class of emerging contaminants. The objective of this research was to investigate the effect of disinfection agents on the integrity of DNA molecules by using real-time PCR. Escherichia coli cell suspensions and genomic DNA in aqueous solution were exposed to increasing doses of disinfection systems, including chlorination, UV irradiation, silver ions, and TiO2 nanoparticles/near-UV. The doses resulting in damage of DNA (16S rDNA) were determined using real-time PCR and compared with the doses resulting in the inactivation of bacterial cells. Our results showed that the disinfection agents chlorine, UV, and silver significantly inhibited the amplification of a fragment of 16S rDNA, but only when applied at doses much higher than the lethal doses for E. coli bacteria. The inactivation doses of TiO2 nanoparticles/near-UV were of the same order of magnitude for both DNA and living cells. Our results raise questions about the efficacy of disinfection processes to destroy and prevent the dispersion of DNA pollutants into the environment. In addition, the damage of DNA by high levels of disinfectants may have implications for the utilization of PCR-based methods for bacterial detection. PMID:22214074

  15. 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. PMID:25172575

  16. 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. PMID:26386660

  17. Efficient Mineralization of Toluene by W-Doped TiO2 Nanofibers Under Visible Light Irradiation.

    PubMed

    Zhang, Li; Li, Yaogang; Xie, Hongyong; Wang, Hongzhi; Zhang, Qinghong

    2015-04-01

    Toxic toluene gas caused enormous harm to human health, and the traditional method to deal with this puzzle is using physical adsorption, which just transfer the toluene from one medium to another. Photocatalysis has great potential to mineralize toluene into CO2 under visible light irradiation, but their applications have been limited by difficulties in preparing efficient photocatalysts with fine crystallite size, considerable visible light response, and large surface area to contact with toluene gas. To address this problem, we have developed a film composed of W-doped TiO2 nanofibers to mineralize toluene under visible light irradiation. The electrospinning preparation route allows incorporation of up to 50 wt% of W in substitutional positions of titanium atom in the anatase network. The W-doped TiO2 nanofibers behave finer crystallite size, stronger visible light absorbance, and larger surface area comparing with pure TiO2 nanofibers. The nanofiber structured morphology on the quartz tube promotes the reaction rates for the gas-phase photo-oxidation of toluene. The concentrations of the produced CO2 keep steady during the photodegradation process, indicating the practicality and operability for the whole experiment. This research is conducive to the development of novel photocatalytic materials to efficiently mineralize toxic gas pollutants including toluene for practical application. PMID:26353518

  18. Deposition of photocatalytically active TiO2 films by inkjet printing of TiO2 nanoparticle suspensions obtained from microwave-assisted hydrothermal synthesis.

    PubMed

    Arin, Melis; Lommens, Petra; Hopkins, Simon C; Pollefeyt, Glenn; Van der Eycken, Johan; Ricart, Susagna; Granados, Xavier; Glowacki, Bartek A; Van Driessche, Isabel

    2012-04-27

    In this paper, we present an inkjet printing approach suited for the deposition of photocatalytically active, transparent titanium oxide coatings from an aqueous, colloidal suspension. We used a bottom-up approach in which a microwave-assisted hydrothermal treatment of titanium propoxide aqueous solutions in the presence of ethylenediaminetetraacetic acid and triethanolamine was used to create suspensions containing titania nanoparticles. Different inkjet printing set-ups, electromagnetic and piezoelectric driven, were tested to deposit the inks on glass substrates. The presence of preformed titania nanoparticles was expected to make it possible to reduce the heating temperature necessary to obtain the functionality of photocatalysis which can widen the application range of the approach to heat-sensitive substrates. We investigated the crystallinity and size of the obtained nanoparticles by electron microscopy and dynamic light scattering. The rheological properties of the suspensions were evaluated against the relevant criteria for inkjet printing and the jettability was analyzed. The photocatalytic activity of the obtained layers was analyzed by following the decomposition of a methylene blue solution under UV illumination. The influence of the heat treatment temperature on the film roughness, thickness and photocatalytic activity was studied. Good photocatalytic performance was achieved for heat treatments at temperatures as low as 150 °C, introducing the possibility of using this approach for heat-sensitive substrates. PMID:22460736

  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. 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

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

    PubMed

    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 × 10(8) 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

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

    PubMed

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

    2015-11-01

    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. This study investigated the surface interactions between the FQ drug ofloxacin (OFL) and titanium oxide (TiO2), a common catalyst and widely-observed 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 CO (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. 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. PMID:26086371

  3. Sonodegradation and photodegradation of methyl orange by InVO4/TiO2 nanojunction composites under ultrasonic and visible light irradiation.

    PubMed

    Min, Yulin; Zhang, Kan; Chen, Youcun; Zhang, YuanGuang

    2012-07-01

    The InVO(4)/TiO(2) nanojunction composites with different weight ratio of 1:10, 1:25, 1:50 and 1:100 were successfully constructed using an ion impregnate method, followed by calcining temperature 400°C for 2h in Ar. The sono- and photo-catalytic activities of the InVO(4)/TiO(2) nanojunction composites were evaluated through the degradation of methyl orange (MO) in aqueous solution under ultrasonic and visible light irradiation, respectively. The experimental results determined that the (1:50) InVO(4)/TiO(2) nanojunction composite has exhibited the highest sonocatalytic activity. It can be ascribed to vectorial charge transfer at the co-excited InVO(4)/TiO(2) interface under ultrasonic irradiation, results in the complete separation of electrons and holes. Interestingly, the (1:25) InVO(4)/TiO(2) nanojunction composite displayed superior photocatalytic activity for MO degradation under visible light, indicating that InVO(4) as a narrow band gap sensitizer can expand photocatalytic activity of TiO(2) to visible region, and the charge transfer can be formed from high energy level of InVO(4) conduction band to the low energy level of TiO(2) conduction band in a present of excited InVO(4) alone under visible light irradiation. The sono- and photo-catalytic activities of the InVO(4)/TiO(2) nanojunction composites were found to be dependent significantly on different InVO(4) contents, which can be explained by the influence of charge transfer on the basis of the work functions of different catalysis mechanism. PMID:22227554

  4. 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...

  5. 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.

  6. 1.5 MeV proton irradiation effects on electrical and structural properties of TiO2/n-Si interface

    NASA Astrophysics Data System (ADS)

    Ishfaq, M.; Rizwan Khan, M.; Bhopal, M. F.; Nasim, F.; Ali, A.; Bhatti, A. S.; Ahmed, I.; Bhardwaj, Sunil; Cepek, Cinzia

    2014-05-01

    In this paper, we report the effect of 1.5 MeV proton beam irradiation dose on the structural and electrical properties of TiO2 thin films deposited on n-Si substrates. The formation and transformation of different TiO2 phases in the irradiated thin films were characterized by X-ray diffraction and X-ray photoelectron spectroscopy (XPS). X-ray diffraction measurements revealed that the as grown film was rich in Ti5O9 phase and then converted to mixed phases of TiO2 (rutile and anatase) after exposure with radiation doses up to 5 × 1014 cm-2. The XPS results revealed the formation of oxygen vacancy (negative) traps in the exposed TiO2 films, which showed strong dependence on the dose. The C-V measurements showed that proton radiations also damaged the Si substrate and created deep level defects in the substrate, which caused a shift of 0.26 ± 0.01 V in the flat band voltage (VFB). I-V measurements showed that the ideality factor increased and the rectification ratio dropped with the increase in the radiation dose. The present study showed the stability of TiO2/Si interface and TiO2 film as an oxide layer against proton radiations.

  7. Enhancement of photocatalytic degradation of polyethylene plastic with CuPc modified TiO 2 photocatalyst under solar light irradiation

    NASA Astrophysics Data System (ADS)

    Zhao, Xu; Li, Zongwei; Chen, Yi; Shi, Liyi; Zhu, Yongfa

    2008-01-01

    Solid-phase photocatalytic degradation of polyethylene (PE) plastic, one of the most common commercial plastic, over copper phthalocyanine (CuPc) modified TiO 2 (TiO 2/CuPc) photocatalyst was investigated in the ambient air under solar light irradiation. Higher PE weight loss rate, greater texture change; more amount of generated CO 2, which is the main product of the photocatalytic degradation of the composite PEC plastic can be achieved in the system of PE-(TiO 2/CuPc) in comparison with PE-TiO 2 system. The CuPc promoted charge separation of TiO 2 and enhanced the photocatalytic degradation of PE based on the analysis of surface photovoltage spectroscopy (SPS). During the photodegradation of PE plastic, the reactive oxygen species generated on TiO 2 or TiO 2/CuPc particle surfaces play important roles. The present study demonstrates that the combination of polymer plastic with TiO 2/CuPc composite photocatalyst in the form of thin film is a practical and useful way to photodegrade plastic contaminants under solar light irradiation.

  8. Photocatalytic properties of Au-deposited mesoporous SiO2-TiO2 photocatalyst under simultaneous irradiation of UV and visible light

    NASA Astrophysics Data System (ADS)

    Okuno, T.; Kawamura, G.; Muto, H.; Matsuda, A.

    2016-03-01

    Mesoporous SiO2 templates deposited TiO2 nanocrystals are synthesized via a sol-gel route, and Au nanoparticles (NPs) are deposited in the tubular mesopores of the templates by a photodeposition method (Au/SiO2-TiO2). The photocatalytic characteristics of Au/SiO2-TiO2 are discussed with the action spectra of photoreactions of 2-propanol and methylene blue. Photocatalytic activities of SiO2-TiO2 under individual ultraviolet (UV) and visible (Vis) light illumination are enhanced by deposition of Au NPs. Furthermore, Au/SiO2-TiO2 shows higher photocatalytic activities under simultaneous irradiation of UV and Vis light compared to the activity under individual UV and Vis light irradiation. Since the photocatalytic activity under simultaneous irradiation is almost the same as the total activities under individual UV and Vis light irradiation, it is concluded that the electrons and the holes generated by lights of different wavelengths are efficiently used for photocatalysis without carrier recombination.

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

    DOE PAGESBeta

    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

  10. Antireflection and self-cleaning properties of a moth-eye-like surface coated with TiO2 particles.

    PubMed

    Nakata, Kazuya; Sakai, Munetoshi; Ochiai, Tsuyoshi; Murakami, Taketoshi; Takagi, Katsuhiko; Fujishima, Akira

    2011-04-01

    Poly(ethylene terephthalate) (PET) films with a moth-eye-like surface are coated with TiO(2) particles to form self-cleaning antireflective films. The use of a TiO(2) suspension of high concentration to coat the PET surface produces a thicker TiO(2) layer with smaller pores, whereas a low concentration of a TiO(2) suspension gives a thinner layer of TiO(2) with larger pores. The PET films coated with TiO(2) particles exhibit a high transmittance of 76-95% and almost no absorption in the range of 400-800 nm. The PET films coated with a TiO(2) suspension with a concentration of ≥2 vol % exhibit superhydrophilicity after irradiation with UV light. After irradiation, the superhydrophilic nature is retained for at least 18 days. The TiO(2)-coated PET films showed the ability to decompose methylene blue under UV irradiation. PMID:21391643

  11. Dual-Wavelength Irradiation and Dox Delivery for -Cancer Cell Ablation with Photocatalytic Pr Doped TiO2 /NGO -Hybrid Nanocomposite.

    PubMed

    Jang, Hongje; Choi, Myung-Ho; Yim, Yeajee; Kim, Young-Kwan; Min, Dal-Hee

    2015-08-26

    Herein, hybrid nanocomposite of praseodymium doped TiO2 nanocrystals and graphene oxide nanosheets are prepared by facile hydrothermal treatment. As-synthesized Pr-TiO2 /NGO hybrid nanocomposite exhibits enhanced photocatalytic activity under visible light irradiation by the intact graphene oxide and doped lanthanide mediated band gap narrowing compared to TiO2 . Moreover, high payload and controlled release of doxorubicin by charge reversal of hybrid nanocomposite at endosomal pH and near-infrared irradiation mediated efficient photothermal conversion provide highly favorable features in therapeutic applications. Through the combination of these three distinctive therapeutic modalities, highly efficient trimodal cancer cell ablation is demonstrated. PMID:26085286

  12. 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. PMID:26845365

  13. In situ ATR-FTIR study of H2O and D2O adsorption on TiO2 under UV irradiation.

    PubMed

    Belhadj, Hamza; Hakki, Amer; Robertson, Peter K J; Bahnemann, Detlef W

    2015-09-21

    The adsorption of water and deuterium oxide on TiO2 surfaces was investigated in the dark as well as under UV(A) irradiation using in situ ATR-FTIR spectroscopy under oxygen and oxygen free conditions. Adsorption of H2O-D2O mixtures revealed an isotopic exchange reaction occurring onto the surface of TiO2 in the dark. Under UV(A) irradiation, the amount of both OH and OD groups was found to be increased by the presence of molecular oxygen. Furthermore, the photocatalytic formation of hydroperoxide under oxygenated condition has been recorded utilizing Attenuated Total Reflection Fourier Transformed Infrared (ATR-FTIR) spectroscopy which appeared as new band at 3483 cm(-1). Different possible mechanisms are discussed in terms of the source of hydroxyl groups formed and/or hydration water on the TiO2 surface for the photocatalytic reaction and photoinduced hydrophilicity. PMID:26266701

  14. Surface nano-texturing of silicon by picosecond laser irradiation through TiO2 nanotube arrays

    NASA Astrophysics Data System (ADS)

    Babu, K. E. Sarath Raghavendra; Duraiselvam, Muthukannan

    2015-10-01

    This article presents, nano-texturing of crystalline silicon by irradiating picosecond laser with variable spatial intensity, caused by optically non-linear TiO2 nanotube arrays (TNTA). Along with micro-scale surface structure, highly ordered laser-induced periodic surface structures (LIPSS) was observed at nano-scale. The periodicity (Λ) of the LIPSS generated was near to the laser wavelength (532 nm). Surface morphology at micro-level was characterized by optical microscopy (OM) and white light interferometer (WLI) and at the nano-scale by scanning electron microscope (SEM) and atomic force microscope (AFM). The results highlight the potential use of TNTA as a single step process to produce micro/nanostructures without any gas/liquid medium under ambient condition.

  15. Synergistic effects of high-frequency ultrasound on photocatalytic degradation of aldehydes and their intermediates using TiO2 suspension in water.

    PubMed

    Sekiguchi, Kazuhiko; Sasaki, Chie; Sakamoto, Kazuhiko

    2011-01-01

    The degradation of model substances, benzaldehyde (C(6)H(5)CHO) and formaldehyde (HCHO), were investigated under various conditions, namely, ultrasound (US) irradiation, TiO(2) photocatalysis with UV irradiation (UV/TiO(2)), and the combination of sonophotocatalysis and UV irradiation (US/UV/TiO(2)), in order to clarify the synergistic effects between US and UV/TiO(2). US and UV/TiO(2) primarily contribute to the degradation of highly hydrophobic and hydrophilic substances, respectively. However, the degradation rate was found to depend on the chemical properties and concentration of not only the substances initially present, but also their decomposition intermediates. Here, the essential information for accurately evaluating the synergistic effects on reaction rate under US/UV/TiO(2) conditions is reported, with a focus on the behavior of decomposition intermediates. PMID:20483201

  16. 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. PMID:27150776

  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) . PMID:26710930

  18. Effects of the density of carboxyl groups in organic compounds on the photocatalytic reduction of Cr(VI) in a TiO2 suspension.

    PubMed

    Lee, Seung-Mok; Cho, Il-Hyoung; Chang, Yoon-Young; Yang, Jae-Kyu

    2007-03-01

    Photocatalytic reduction (PCR) of Cr(VI) in a TiO2 suspension was studied at pH 4 in the presence of organic compounds containing different numbers of carboxyl groups. The compounds studied were glycine (Gly), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA). In all the cases, near complete Cr(VI) removal was observed after 60 minutes. During PCR process, the aqueous Cr(VI) concentration measured with both Ion Chromatography and Atomic Absorption Spectrophotometery was different in the presence of IDA and EDTA as reaction proceeded while little difference was observed in a control test. This result suggests that a greater portion of reduced Cr(III) species was possibly dissolved through complex formation with IDA (Cr(III)-IDA) and EDTA (Cr(III)-EDTA) or with reaction intermediates (Cr(III)-organic complexes) during PCR compared to the control test. As the number of carboxyl group increased Cr(VI) reduction increased and showed a good linear relationship between initial rates of Cr(VI) reduction and adsorption density of carboxyl group of the surface of TiO2. The initial rate of Cr(VI) reduction in the presence of EDTA was 5 times greater than that in control. When the PCR process was applied in the treatment of real wastewater, an effective Cr(VI) reduction was observed with addition of EDTA. PMID:17365325

  19. Electrochemically assisted photocatalytic degradation of 4-chlorophenol by ZnFe2O4-modified TiO2 nanotube array electrode under visible light irradiation.

    PubMed

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

    2010-07-01

    A well-aligned ZnFe(2)O(4)/TiO(2) composite nanotube array (ZnFe(2)O(4)/TiO(2)-NTs) electrode with visible-light activity was successfully prepared using a two-step electrochemical process of anodization and a novel cathodic electrodeposition method followed by annealing. The ZnFe(2)O(4) nanoparticles were highly dispersed inside the TiO(2)-NTs but minimized at the tube entrances. The structure and optical properties of the TiO(2) nanotubes and the derived composites have been well characterized. The composites displayed a strong photo response in the visible region and low recombination rate of the electron-hole pairs. In addition, the synthesized ZnFe(2)O(4)/TiO(2)-NTs electrode showed much higher photocurrent density in the visible region than pure TiO(2)-NTs electrode. The dramatically enhanced electrochemically assisted photocatalytic activity of the composite electrode was evaluated in the decomposition of 4-chlorophenol and dichloroacetate under visible light irradiation (420 nm < lambda < 600 nm). The improved photoelectrocatalytic (PEC) activity is derived from the synergetic effect between ZnFe(2)O(4) and TiO(2), which promoted the migration efficiency of photogenerated carriers at the interface of the composite and enhanced the efficiency of photon harvesting in the visible region. The degradation of 4-chlorophenol was monitored by measuring Cl(-) concentrations and analyzing reaction intermediates by high-performance liquid chromatography-mass spectroscopy (HPLC-MS). PMID:20527761

  20. Study of the photocatalytic activity of nanocrystalline S, N-codoped TiO2 thin films and powders under visible and sun light irradiation

    NASA Astrophysics Data System (ADS)

    Behpour, Mohsen; Atouf, Vajiheh

    2012-06-01

    Homogeneous and transparent sulfur and nitrogen (S, N)-codoped TiO2 nanocrystalline thin films were deposited on glass substrates by sol gel dip coating method using thiourea (Tu) as a source of sulfur and nitrogen. The surface structure of the films was modified by addition of different concentrations of polyethylene glycol (PEG) into the TiO2 sol. The equal powders of pure and modified TiO2 were also prepared to compare of their photocatalytic activity with films. The films and powders were characterized by different techniques like diffuse reflectance UV-Vis spectroscopy (DRS), X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX). DRS exhibited a shift in optical absorption wavelength to visible region and XRD analysis showed that only the anatase TiO2 formed in both of film and powder. The photocatalytic activity was evaluated by the degradation of methyl orange (MO) as a model. The modified TiO2 films and powders showed excellent visible-light photocatalytic ability for the degradation of MO under both irradiation of visible and sun light. So that, up to 96% MO can be decomposed in sun light only within 3 h in the presence of a modified TiO2 film consist of Tu/TiO2 molar ratio of 0.45 and 0.9 g PEG. On the other hand, MO solution was discolored completely under sun light in 75 min in the presence of the modified TiO2 powder.

  1. The effect of Er:YAG laser irradiation on hydroxyapatite-coated implants and fluoride-modified TiO2-blasted implant surfaces: a microstructural analysis.

    PubMed

    Shin, Seung-Il; Lee, Eun-Kwon; Kim, Jeong-Hyun; Lee, Ji-Hun; Kim, Sun-Hee; Kwon, Young-Hyuk; Herr, Yeek; Chung, Jong-Hyuk

    2013-05-01

    The purpose of this study was to evaluate the microscopic changes and surface roughness on hydroxyapatite (HA)-coated implants following exposure to different powers and durations of Er:YAG laser irradiation in order to determine the proper pulse energy level and irradiation time. Ten HA-coated implants and ten fluoride-modified TiO2 implants were used. The implants were divided into a control (one implant) and test group (nine implants) for each implant type. Implants in the test groups were sub-divided into three groups (three implants per group) based on the applied laser pulse energy and irradiation time. The measurement of surface roughness was performed on all implants in the test groups using a white light interferometer before and after laser irradiation. R a values were recorded and compared in order to evaluate changes in surface roughness. For HA-coated implants, the R a values increased in all test groups after laser irradiation. However, mean R a values in the fluoride-modified TiO2-blasted implant test group were decreased after irradiation. There was no statistical difference. Scanning electron microscope analysis revealed surface alterations in both the HA-coated and fluoridated TiO2-blasted implants irradiated for 1.5 min at 100 mJ/pulse, 10 Hz. When the pulse energy and irradiation time increased, greater surface alterations, including surface flattening and microfractures, were observed. In conclusion, the results of the current study suggest that no changes could be observed in both HA-coated implants and fluoride-modified TiO2-blasted implants after irradiation at an intensity of 100 mJ/pulse, 10 Hz for 1 min performed to achieve surface detoxification. PMID:22833287

  2. 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. PMID:23796307

  3. Novel Bi2MoO6/TiO2 heterostructure microspheres for degradation of benzene series compound under visible light irradiation.

    PubMed

    Li, Jinliang; Liu, Xinjuan; Sun, Zhuo; Pan, Likun

    2016-02-01

    Novel Bi2MoO6/TiO2 heterostructure microspheres were successfully synthesized via a facile solvothermal method. Their morphology, structure and photocatalytic performance in the degradation of phenol and nitrobenzene were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, electrochemical impedance spectra, UV-vis absorption spectroscopy and total organic carbon analyser, respectively. The results show that the Bi2MoO6/TiO2 heterostructures exhibit excellent photocatalytic performance with maximum phenol and nitrobenzene degradation rates of 96% and 94% and corresponding mineralization rates of 66% and 61% in 300min under visible light irradiation, respectively. The improved photocatalytic performance is mainly ascribed to the reduced electron-hole pair recombination with the introduction of TiO2. PMID:26520821

  4. Design of H3PW12O40/TiO2 nano-photocatalyst for efficient photocatalysis under simulated sunlight irradiation

    NASA Astrophysics Data System (ADS)

    Zhao, Kun; Lu, Ying; Lu, Nan; Zhao, Yahui; Yuan, Xing; Zhang, Hao; Teng, Lianghui; Li, Fu

    2013-11-01

    H3PW12O40/TiO2 (PW12/TiO2) nano-photocatalyst was successfully synthesized through a modified sol-gel-hydrothermal method. The X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectra, UV-vis diffuse reflectance spectrum (UV-vis DRS), and N2 adsorption-desorption isotherms were characterized respectively to investigate the physical and chemical properties of prepared catalysts. Under simulated sunlight (320 nm < λ < 780 nm) irradiation, the degradation of fuchsin acid, malachite green and p-nitrophenol (PNP) were carried out to evaluate the photocatalytic activity of PW12/TiO2. The results showed that the pollutants degradation followed first-order kinetics, and the kinetic constants of photocatalytic degradation of fuchsin acid, malachite green and PNP were 2.82, 4.66, and 3.48 times as great as that using pristine TiO2, respectively. The high pollutants degradation efficiency was ascribed to the synergistic effect between H3PW12O40 and TiO2, which resulted in enhanced quantum efficiency and high light harvesting efficiency. We believe this work could provide new insights into the fabrication of photocatalyst with high photocatalytic performance and facilitate their practical application in environmental issues.

  5. 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.

  6. 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

  7. 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

    2014-01-01

    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. PMID:25314607

  8. 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. PMID:26991482

  9. 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. PMID:26206125

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

    PubMed Central

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

    2015-01-01

    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 Ti4+/Ti3+ 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. PMID:25657831

  11. Rational protein modification leading to resistance of enzymes to TiO2-UV irradiation-induced inactivation.

    PubMed

    Lele, Bhalchandra S; Russell, Alan J

    2004-01-01

    Photoexcited TiO2 degrades biomolecules such as nucleic acids, cell membrane proteins, and enzymes. Stabilization of enzyme activity against the deactivation caused by the combination of TiO2-UV is essential if we are to develop novel hybrid materials exhibiting photocatalytic and biocatalytic activities useful for decontamination applications. In this paper we describe the stabilization of a model enzyme, chymotrypsin, against TiO2-UV-induced deactivation by conjugating the enzyme with UV-absorbing, carboxyl-terminated oligo[2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl methacrylate] [oligo(HBMA)-COOH]. Chymotrypsin was completely deactivated within 3 h, whereas the chymotrypsin-oligo(HBMA) conjugate retained > 50% activity even after 5 h of exposure to TiO2-UV (lambdamax 365 nm). The degree of enzyme stabilization induced by the conjugated UV absorber was 2-fold higher than that from the equivalent number of conjugated PEG chains. Spectroscopic characterizations revealed that chymotrypsin-oligo(HBMA) absorbs UV light and initially resists photoexcitation of TiO2. Modified chymotrypsin also exhibited resistance to changes in the secondary structure during the deactivation. This method of stabilizing enzymes against photodegradation could be also useful in photolithographic enzyme immobilizations for sensors and arrays or for stabilization of any UV-sensitive protein. PMID:15360310

  12. Preparation of nitrogen-substituted TiO2 thin film photocatalysts by the radio frequency magnetron sputtering deposition method and their photocatalytic reactivity under visible light irradiation.

    PubMed

    Kitano, Masaaki; Funatsu, Keisho; Matsuoka, Masaya; Ueshima, Michio; Anpo, Masakazu

    2006-12-21

    Nitrogen-substituted TiO2 (N-TiO2) thin film photocatalysts have been prepared by a radio frequency magnetron sputtering (RF-MS) deposition method using a N2/Ar mixture sputtering gas. The effect of the concentration of substituted nitrogen on the characteristics of the N-TiO2 thin films was investigated by UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The absorption band of the N-TiO2 thin film was found to shift smoothly to visible light regions up to 550 nm, its extent depending on the concentration of nitrogen substituted within the TiO2 lattice in a range of 2.0-16.5%. The N-TiO2 thin film photocatalyst with a nitrogen concentration of 6.0% exhibited the highest reactivity for the photocatalytic oxidation of 2-propanol diluted in water even under visible (lambda > or = 450 nm) or solar light irradiation. Moreover, N-TiO2 thin film photocatalysts prepared on conducting glass electrodes showed anodic photocurrents attributed to the photooxidation of water under visible light, its extent depending on wavelengths up to 550 nm. The absorbed photon to current conversion efficiencies reached 25.2% and 22.4% under UV (lambda = 360 nm) and visible light (lambda = 420 nm), respectively. UV-vis and photoelectrochemical investigations also confirmed that these thin films remain thermodynamically and mechanically stable even under heat treatment at 673 K. In addition, XPS and XRD studies revealed that a significantly high substitution of the lattice O atoms of the TiO2 with the N atoms plays a crucial role in the band gap narrowing of the TiO2 thin films, enabling them to absorb and operate under visible light irradiation as a highly reactive, effective photocatalyst. PMID:17165971

  13. Synergistic photosensitized removal of Cr(VI) and Rhodamine B dye on amorphous TiO2 under visible light irradiation.

    PubMed

    Wang, Qi; Chen, Xueshuang; Yu, Keer; Zhang, Yi; Cong, Yanqing

    2013-02-15

    Amorphous TiO(2) (Am-TiO(2)) was prepared at room temperature by hydrolysis of Ti(OBu)(4) in water without addition of strong acids or organic solvents. Results from XRD and TEM revealed that the as-prepared Am-TiO(2) was composed of amorphous structure. For the simultaneous photosensitized removal of Cr(VI) and zwitterionic Rhodamine B (RhB) dye, Am-TiO(2) exhibited more significant synergistic effect than commercial P25-TiO(2). The removal efficiencies for RhB and Cr(VI) after 100 min visible light irradiation were 97.8% and 53.5% on Am-TiO(2), respectively. While 88.2% RhB and 42.1% Cr(VI) were removed on P25-TiO(2). Decreased synergistic activities as well as smaller surface areas were observed when Am-TiO(2) was pretreated at high temperatures (200-700°C). Thus, it was the larger specific surface area rather than better crystallinity dominated the synergistic degradation dynamics under visible light irradiation with lower pH (2), greater catalyst loading amount (2g/L), proper RhB/Cr(VI) ratios (1:8) and higher light intensity (500 W). Better synergistic performance was also obtained on Am-TiO(2) than P25-TiO(2) when Cr(VI) coexists with cationic dyes, while negligible difference was observed in the presence of anionic dyes. Superior stability and simplicity of Am-TiO(2) was also exhibited in the cyclic runs. PMID:23298739

  14. 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 (10mgL(-1)) and low (50μgL(-1)) initial concentrations, respectively. Total disappearance of the parent compounds was attained in all experiments. For initial concentration of 10mgL(-1), the target compounds were degraded within 30-40min and a mineralization degree of more than 80% was achieved after 240min 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. PMID:26760268

  15. 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...

  16. 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. PMID:27469042

  17. 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.

  18. Study of Li 2TiO 3 + 5 mol% TiO 2 lithium ceramics after long-term neutron irradiation

    NASA Astrophysics Data System (ADS)

    Chikhray, Y.; Shestakov, V.; Maksimkin, O.; Turubarova, L.; Osipov, I.; Kulsartov, T.; Kuykabayeba, A.; Tazhibayeva, I.; Kawamura, H.; Tsuchiya, K.

    2009-04-01

    Given work presents the results of complex material-science studies of 1 mm diameter ceramic pebbles manufactured of Li 2TiO 3 + 5 mol% TiO 2 ceramics before and after long-time neutron irradiation. Ceramic samples were placed in specially ampoules (six items) made of stainless steel Cr18Ni10Ti which were vacuumized and filled with helium. Irradiation of ampoules was carried out in the loop channel of WWRK reactor (Almaty, Kazakhstan) during 223 days at 6 MW power. After irradiation light-colored pebbles became grey-colored due to structure changes which generation of grey-colored inclusions (lithium oxide) with low density and microhardness. There is a radiation softening of lithium ceramic and that effect is higher for lower irradiation temperature 760 K than for 920 K. The value of maximum permissible load (pebble crash limit) at that is low and comprises ˜37.9 N. The content of residual tritium is higher for ceramic irradiated at 760 K (6.6 ± 0.6 × 10 11 Bq/kg) than for ceramic irradiated at 920 K (17 ± 3 × 10 10 Bq/kg). The size change indicates that pebble increase more after irradiation at 760 K than at 920 K where the bigger portion of tritium leaves the pebble. X-ray analysis shows radiation modification of Li 2TiO 3 + 5 mol% TiO 2 phase composition and generation of new phases: LiTi 2O 4, LiTiO 2 and Li 4Ti 5O 12.

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

    PubMed

    Pham, Thanh-Dong; Lee, Byeong-Kyu

    2014-03-01

    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

  20. 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

  1. 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.

  2. 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.

  3. Does photocatalytic activity of TiO2 nanoparticles correspond to photo-cytotoxicity? Cellular uptake of TiO2 nanoparticles is important in their photo-cytotoxicity.

    PubMed

    Horie, Masanori; Sugino, Sakiko; Kato, Haruhisa; Tabei, Yosuke; Nakamura, Ayako; Yoshida, Yasukazu

    2016-05-01

    Titanium dioxide (TiO2) nanoparticles are important industrial nano-objects with wide applications, including as photocatalysts and sunscreen components. Recently, the phototoxicity of TiO2 nanoparticles has been a concern. However, phototoxicity caused by photocatalytic activity may differ between anatase and rutile nanoparticles. In the present study, we compared the phototoxicity of anatase and rutile nanoparticles. Human keratinocyte HaCaT cells were treated with stable TiO2 nanoparticle suspensions. Without UVA irradiation, TiO2 nanoparticles did not affect mitochondrial activity or cell membranes. However, exposure to rutile nanoparticle suspensions inhibited cell growth and induced HO-1 gene expression without UVA irradiation. These effects may be explained by the hydrophobic surface of rutile nanoparticles. Next, TiO2-exposed cells were irradiated with UVA for 4 h and effects of TiO2 nanoparticles on cells were examined. The rutile nanoparticles did not show any cellular effects after UVA irradiation. However, the anatase nanoparticles caused strong phototoxicity. Decreased mitochondrial activity, cell membrane damage and the induction of oxidative stress were observed in the cells exposed to anatase nanoparticles with UVA irradiation. Cellular uptake of the nanoparticles was observed in both anatase- and rutile-exposed cells. These results suggest that internalized anatase nanoparticles are important for phototoxicity. Additionally, the exposure of a 3D skin model to TiO2 nanoparticles did not result in significant toxicity. In conclusion, rutile nanoparticles used in sunscreen did not exhibit phototoxic activity. Despite the strong phototoxic activity of anatase nanoparticles in cell cultures, they demonstrated no phototoxicity using a 3D skin model. PMID:27142467

  4. 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. PMID:27135700

  5. Photocatalytic decomposition of acrylonitrile with N-F codoped TiO2/SiO2 under simulant solar light irradiation.

    PubMed

    Pang, Dandan; Qiu, Lu; Wang, Yunteng; Zhu, Rongshu; Ouyang, Feng

    2015-07-01

    The solid acid catalyst, N-F codoped TiO2/SiO2 composite oxide was prepared by a sol-gel method using NH4F as nitrogen and fluorine source. The prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV-Visible diffuse reflectance spectroscopy (UV-Vis), ammonia adsorption and temperature-programmed desorption (NH3-TPD), in situ Fourier transform infrared spectroscopy (FT-IR) and N2 physical adsorption isotherm. The photocatalytic activity of the catalyst for acrylonitrile degradation was investigated under simulant solar irradiation. The results showed that strong Lewis and Brønsted acid sites appear on the surface of the sample after N-F doping. Systematic investigation showed that the highest photocatalytic activity for acrylonitrile degradation was obtained for samples calcined at 450°C with molar ratio (NH4F to Ti) of 0.8. The degradation ratio of 71.5% was achieved with the prepared catalyst after 6-min irradiation, demonstrating the effectiveness of photocatalytic degradation of acrylonitrile with N-F codoped TiO2/SiO2 composite oxide. The photocatalyst is promising for application under solar light irradiation. Moreover, the intermediates generated after irradiation were verified by gas chromatography-mass spectrometry (GC-MS) analysis and UV-Vis spectroscopy to be simple organic acids with lower toxicity, and the degradation pathway was also proposed for acrylonitrile degradation with the prepared catalyst. PMID:26141890

  6. 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.

  7. 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. PMID:25007943

  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. 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.

  10. 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.

  11. Photodegradation of ibuprofen by TiO2 co-doping with urea and functionalized CNT irradiated with visible light - Effect of doping content and pH.

    PubMed

    Yuan, Ching; Hung, Chung-Hsuang; Li, Huei-Wen; Chang, Wei-Hsian

    2016-07-01

    Ibuprofen (IBP) is one kind of non-steroidal anti-inflammatory drugs (NSAIDs), which are classified as Pharmaceuticals and Personal Care Products (PPCPs). IBP possesses bioactive property and the substantial use of IBP results in a harmful impact on bioreceptors even in small concentrations. Accordingly, the treatment of these wastewaters is important before discharging them into the ecosystem. The photodegradation of IBP with TiO2 co-doped with functionalized CNTs (CNT-COOH and CNT-COCl) and urea, named as N-doping CNT/TiO2, irradiated with visible light of 410 nm was investigated in this study. The titanium tetrachloride was used as the precursor of Ti. The N-doping CNT-COCl/TiO2 photocatalysts exhibited a better crystalline structure and smaller crystal size than the N-doping CNT-COOH/TiO2 photocatalyst. It might largely ascribe to strong binding between acyl chloride functional group and TiO2. About 85.0%-86.0% of IBP was degraded with N-doping CNT/TiO2 within 120 min at natural condition, which obeyed the pseudo first order reaction and the rate constant was 4.45 × 10(-3)-1.22 × 10(-2) min(-1) and 5.03 × 10(-3)-1.47 × 10(-2) min(-1) for N-doping CNT-COOH/TiO2 and N-doping CNT-COCl/TiO2, respectively. The best IBP degradation of 87.9%-89.0% was found at pH 5, which indicated superoxide radicals (O2(-)) played a key role. The optimal pH was majorly dominated by the nature of IBP and N-doping CNT/TiO2. A successful synergy effect of TiO2 and dopants was exhibited and this mainly attributed to the strong binding strength by functional group of acyl chloride (COCl) and carboxylic acid (COOH). In summary, IBP could be effectively photodegraded by the fabricated N-doping CNT/TiO2 photocatalysts. PMID:27145421

  12. 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...

  13. Synthesis of Metal Ion-Doped TiO2 Nanoparticles Using Two-Phase Method and Their Photocatalytic Activity Under Visible Light Irradiation.

    PubMed

    Nguyen, Duy-Trinh; Hong, Seong-Soo

    2016-02-01

    In this study, TiO2 and metal ion-doped TiO2 nanoparticles were successfully synthesized by solvothermal reaction of titanium butoxide precursor in the presence of oleic acid, oleylamine and vapor water and they were characterized by XRD, Raman, TEM and DRS. We also investigated the photocatalytic activity of these oxides for the decomposition of Rhodamine B. From XRD and Raman results, doping of the metal ion in the crystal lattice did not change the high crystallinity of the TiO2 structure, and all the metal ions were incorporated into the structures of titania as well as replaced titanium ion or located at interstitial site. The absorption band shifted to a higher wavelength on the metal ion-doped TiO2 samples compared to the pure TiO2 sample. The Ce ion- doped TiO2 catalysts showed the higher photocatalytic activity compared to the pure TiO2 and a commercial P-25 catalysts and 1% Ce-doped TiO2 showed the highest photocatalytic activity. PMID:27433699

  14. Hybrid membrane with TiO2 based bio-catalytic nanoparticle suspension system for the degradation of bisphenol-A.

    PubMed

    Hou, Jingwei; Dong, Guangxi; Luu, Belinda; Sengpiel, Robert G; Ye, Yun; Wessling, Matthias; Chen, Vicki

    2014-10-01

    The removal of micropollutant in wastewater treatment has become a key environmental challenge for many industrialized countries. One approach is to use enzymes such as laccase for the degradation of micropollutants such as bisphenol-A. In this work, laccase was covalently immobilized on APTES modified TiO2 nanoparticles, and the effects of particle modification on the bio-catalytic performance were examined and optimized. These bio-catalytic particles were then suspended in a hybrid membrane reactor for BPA removal with good BPA degradation efficiency observed. Substantial improvement in laccase stability was achieved in the hybrid system compared with free laccase under simulated harsh industrial wastewater treatment conditions (such as a wide range of pH and presence of inhibitors). Kinetic study provided insight of the effect of immobilization on the bio-degradation reaction. PMID:25084046

  15. Nanocrystalline TiO2 by sol-gel: Characterisation and photocatalytic activity on Modica and Comiso stones

    NASA Astrophysics Data System (ADS)

    Bergamonti, Laura; Alfieri, Ilaria; Lorenzi, Andrea; Montenero, Angelo; Predieri, Giovanni; Barone, Germana; Mazzoleni, Paolo; Pasquale, Stefania; Lottici, Pier Paolo

    2013-10-01

    A self-cleaning photocatalytic coating for limestone materials, based on TiO2 nanoparticles obtained by the sol-gel process has been studied. TiO2 sol was applied directly to the surface or after a SiO2 intermediate layer. The selected test materials are the Modica and the Comiso calcarenites, limestones of Ragusa Formation outcropping in the South Eastern Sicily (Italy). SEM-EDS, XRD and Raman investigations were carried out to characterise the TiO2 nanoparticles and coating. Nanocrystalline anatase and, to a lesser extent, brookite forms are obtained. To evaluate the harmlessness of the treatment, colorimetric tests, water absorption by capillarity and crystallisation of salts measurements were performed. Photocatalytic activity of the TiO2 colloidal suspension and of the coatings (TiO2 and SiO2/TiO2) was assessed under UV irradiation through methyl orange dye degradation tests. The results show good photodegradation activity and satisfactory compatibility between the sol and the surface of the investigated limestones.

  16. Enhanced Electrorheological Performance of Nb-Doped TiO2 Microspheres Based Suspensions and Their Behavior Characteristics in Low-Frequency Dielectric Spectroscopy.

    PubMed

    Guo, Xiaosong; Chen, Yulu; Su, Ming; Li, Dong; Li, Guicun; Li, Chengdong; Tian, Yu; Hao, Chuncheng; Lei, Qingquan

    2015-12-01

    Titanium dioxide and Nb-doped titanium dioxide microspheres with the same size were fabricated by a simple sol-gel method, and the formation mechanism of Nb-doped titanium dioxide microspheres was proposed. Titanium dioxide and Nb-doped titanium dioxide microspheres were adopted as dispersed materials for electrorheological (ER) fluids to investigate the influence of the charge increase introduced by Nb doping on the ER activity. The results showed that Nb doping could effectively enhance the ER performance. Combining with the analysis of dielectric spectroscopy, it was found that the interface polarization of Nb-doped TiO2 ER fluid was larger than that of TiO2 ER fluid, which might be caused by more surface charges in Nb-TiO2 microspheres due to Nb(5+) doping and resulting in enhancement of electric field force and strengthening of fibrous structure. In addition, by comparing and analyzing the permittivity curves of Nb-TiO2/LDPE solid composite and Nb-TiO2/silicone-oil fluid composite, it could be concluded that the enhancement of permittivity at low frequency resulted from the increase of the order degree of dispersed particles in ER fluid rather than from the quasi-dc (QDC) behavior. Moreover, the absolute value of slope of permittivity curves (K) at 0.01 Hz could be utilized as the standard for judging the ability to maintain the chainlike structure. The relationships between polarizability of dispersed particles, dielectric spectrum, parameter K, and ER properties were discussed in detail. PMID:26570989

  17. 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.

  18. 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. PMID:25079650

  19. 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.

  20. 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.

  1. Electrospinning Directly Synthesized Porous TiO2 Nanofibers Modified by Graphitic Carbon Nitride Sheets for Enhanced Photocatalytic Degradation Activity under Solar Light Irradiation.

    PubMed

    Adhikari, Surya Prasad; Awasthi, Ganesh Prasad; Kim, Han Joo; Park, Chan Hee; Kim, Cheol Sang

    2016-06-21

    We report a direct approach to the fabrication of a composite made of porous TiO2 nanofibers (NFs) and graphitic carbon nitride (g-C3N4) sheets, by means of an angled two-nozzle electrospinning combined with calcination process. Different wt % amounts of g-C3N4 particles in a polymer solution from one nozzle and TiO2 precursors containing the same polymer solution from another nozzle were electrospun and deposited on the collector. Structural characterizations confirm a well-defined morphology of the TiO2/g-C3N4 composite in which the TiO2 NFs are uniformly attached on the g-C3N4 sheet. This proper attachment of TiO2 NFs on the g-C3N4 sheets occurred during calcination. The prepared composites showed the enhanced photocatalytic activity over the photodegradation of rhodamine B and reactive black 5 under natural sunlight. Here, the synergistic effect between the g-C3N4 sheets and the TiO2 NFs having anisotropic properties enhanced the photogenerated electron-hole pair separation and migration, which was confirmed by the measurement of photoluminescence spectra, cyclic voltammograms, and electrochemical impedance spectra. The direct synthesis approach that is established here for such kinds of sheetlike structure and porous NFs composites could provide new insights for the design of high-performance energy conversion catalysts. PMID:27254544

  2. Fabrication of TiO2 Thick Film for Photocatalyst from Commercial TiO2 Powder

    NASA Astrophysics Data System (ADS)

    Asteti, S. Fuji; Syarif, D. Gustaman

    2008-03-01

    Photocatalytic activity of TiO2 thick film ceramics made of commercial TiO2 powder has been studied. The TiO2 powder was nano sized one that was derived from dried TiO2 suspension. The TiO2 suspension was made by pouring some blended commercial TiO2 powder into some amount of water. The paste of TiO2 was made by mixing the nano sized TiO2 powder with organic vehicle and glass frit. The paste was spread on a glass substrate. The paste was dried at 100 °C and heated at different temperatures (400 °C and 500 °C) for 60 minutes to produce thick film ceramics. The photocatalytic activity of these films was evaluated by measuring the concentration of a solution of methylene blue where the thick films were inside after being illuminated by UV light at various periods of times. The initial concentration of the methylene blue solution was 5 ppm. Structural analyses were carried out by X-ray diffraction (XRD). The XRD analyses showed that the produced thick film ceramic had mainly crystal structure of anatase. According to the photocatalytical data, it was known that the produced thick film ceramics were photocatalyst which were capable of decomposing an organic compound such as the methylene blue.

  3. Fabrication of Fe3O4@SiO2@TiO2 nanoparticles supported by graphene oxide sheets for the repeated adsorption and photocatalytic degradation of rhodamine B under UV irradiation.

    PubMed

    Chen, Fenghua; Yan, Fufeng; Chen, Qingtao; Wang, Yongwei; Han, Lifeng; Chen, Zhijun; Fang, Shaoming

    2014-09-28

    A quaternary nanocomposite Fe3O4@SiO2@TiO2/graphene oxide (GO) was for the first time successfully synthesized in this work for the repeated use in simultaneous adsorption and photocatalytic degradation of aromatically structured chemical pollutants. The resulting sample was characterized by TEM, XRD, FTIR, TG-DTG, XPS, PL, and VSM. Its photocatalytic activity was evaluated in the photocatalytic degradation of rhodamine B (RhB) under high-pressure mercury lamp irradiation. The results showed that about 63% of RhB was absorbed onto the prepared Fe3O4@SiO2@TiO2/GO nanocomposites by just 30 minute mixing, and after 120 min high-pressure mercury lamp irradiation, about 92.03% of RhB was converted. The photocatalytic degradation followed pseudo first-order reaction with an apparent rate constant of 0.0136 min(-1). Compared with the Fe3O4@SiO2@TiO2 nanoparticles, it exhibits an excellent ability to adsorb aromatic compounds via π-π stacking and a higher photocatalytic activity due to the presence of GO. In addition, the synthesized nanomaterial exhibited good magnetic response and the reusability study suggested that the prepared nanocomposites were stable enough and maintained high degradation rate and catalyst recovery even after five cycles, verifying their potential application in water purification. PMID:25087943

  4. 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.

  5. 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. PMID:18044537

  6. Biocidal effects of photocatalytic semiconductor TiO2.

    PubMed

    Rajagopal, G; Maruthamuthu, S; Mohanan, S; Palaniswamy, N

    2006-08-15

    Photocatalytic action of the commercial TiO(2) was the subject of study on the destruction of the microbes within the biofilms. The TiO(2) powder was characterized by X-ray diffraction (XRD) for identifying its type and the particle size was determined. The biofilm was allowed to form over TiO(2) coatings over glass slides irradiated with polychromatic light for different time durations and distances. It indicates that a five-fold decrease in bacterial count due to the formation of H(2)O(2) at TiO(2)/biofilm interface. The formation of H(2)O(2) at the TiO(2)/biofilm interface is estimated and it does not destroy the entire bacterial population within the biofilm. Bacterial killing effect is supported by FT-IR analysis. PMID:16870404

  7. Acetaldehyde photochemistry on TiO2(110)

    SciTech Connect

    Zehr, Robert T.; Henderson, Michael A.

    2008-07-01

    The ultraviolet (UV) photon induced decomposition of acetaldehyde absorbed on the oxidized retile TIO2(110) surface was studied with photon stimulated desorption (PSD) and theral programmed desorption (TPD). Acetaldehyde desorbs molecularly from TiO2(110) with minor decomposition channels yielding butene on the reduced TiO2 surface and acetate on the oxidized TiO2 surface. Acetaldehyde absorbed on oxidized TiO2(110) undergoes a facile thermal reaction to form a photoactive acetaldehyde-oxygen complex. UV irradiation of the acetaldehyde-oxygen complex resulting in the ejection of methyl radical into gas phase and conversion of the surface bound fragment to formate.

  8. Acetaldehyde Photochemistry on TiO2(110)

    SciTech Connect

    Zehr, Robert T.; Henderson, Michael A.

    2008-07-01

    The ultraviolet (UV) photon induced decomposition of acetaldehyde adsorbed on the oxidized rutile TiO2(110) surface was studied with photon stimulated desorption (PSD) and thermal programmed desorption (TPD). Acetaldehyde desorbs molecularly from TiO2(110) with minor decomposition channels yielding butene on the reduced TiO2 surface and acetate on the oxidized TiO2 surface. Acetaldehyde adsorbed on oxidized TiO2(110) undergoes a facile thermal reaction to form a photoactive acetaldehyde-oxygen complex. UV irradiation of the acetaldehyde-oxygen complex initiated photofragmentation of the complex resulting in the ejection of methyl radical into gas phase and conversion of the surface bound fragment to formate.

  9. Green synthesis of Pt-doped TiO2 nanocrystals with exposed (001) facets and mesoscopic void space for photo-splitting of water under solar irradiation

    NASA Astrophysics Data System (ADS)

    Banerjee, Biplab; Amoli, Vipin; Maurya, Abhayankar; Sinha, Anil Kumar; Bhaumik, Asim

    2015-06-01

    We report a non-trivial facile chemical approach using ionic liquid ([bmim][Cl]) as a porogen for the synthesis of (001) faceted TiO2 nanocrystals having mesoscopic void space. This faceted TiO2 nanomaterial has been doped with Pt nanoclusters through chemical impregnation. The resulting Pt-doped TiO2 nanomaterials are thoroughly characterized by powder X-ray diffraction (PXRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), ultra high resolution transmission electron microscopy (UHR-TEM), energy dispersive X-ray spectrometry (EDX), UV-vis diffuse reflection spectroscopy (DRS) and N2 sorption studies. These Pt/TiO2 nanocrystals with (001) exposed facets are employed as efficient and benign catalysts for hydrogen production from pure water and methanol-water systems under one AM 1.5G sunlight illumination. The effect of platinum loading and methanol-water ratio on the photocatalytic activity of the faceted TiO2 nanocrystals are investigated and it is found that hydrogen evolution rates have been enhanced significantly upon Pt loading. Under optimized reaction conditions the highest photocatalytic activity of 11.2 mmol h-1 g-1 has been achieved over ca. 1.0 wt% Pt loaded Pt/TiO2 nanocrystals with (001) exposed facets, which is one of the highest hydrogen evolution rates over the noble metal/TiO2 system reported to date in the literature.We report a non-trivial facile chemical approach using ionic liquid ([bmim][Cl]) as a porogen for the synthesis of (001) faceted TiO2 nanocrystals having mesoscopic void space. This faceted TiO2 nanomaterial has been doped with Pt nanoclusters through chemical impregnation. The resulting Pt-doped TiO2 nanomaterials are thoroughly characterized by powder X-ray diffraction (PXRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), ultra high resolution transmission electron microscopy (UHR-TEM), energy dispersive X-ray spectrometry (EDX), UV-vis diffuse reflection spectroscopy (DRS) and N2 sorption studies. These Pt/TiO2 nanocrystals with (001) exposed facets are employed as efficient and benign catalysts for hydrogen production from pure water and methanol-water systems under one AM 1.5G sunlight illumination. The effect of platinum loading and methanol-water ratio on the photocatalytic activity of the faceted TiO2 nanocrystals are investigated and it is found that hydrogen evolution rates have been enhanced significantly upon Pt loading. Under optimized reaction conditions the highest photocatalytic activity of 11.2 mmol h-1 g-1 has been achieved over ca. 1.0 wt% Pt loaded Pt/TiO2 nanocrystals with (001) exposed facets, which is one of the highest hydrogen evolution rates over the noble metal/TiO2 system reported to date in the literature. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02097b

  10. Preparation and photocatalytic activity of bicrystal phase TiO2 nanotubes containing TiO2-B and anatase

    NASA Astrophysics Data System (ADS)

    Huang, Chuanxi; Zhu, Kerong; Qi, Mengyao; Zhuang, Yonglong; Cheng, Chao

    2012-06-01

    Bicrystal phase TiO2 nanotubes (NTS) containing monoclinic TiO2-B and anatase were prepared by the hydrothermal reaction of anatase nanoparticles with NaOH aqueous solution and a heat treatment. Their structure was characterized by XRD, TEM and Raman spectra. The results showed that the bicrystal phase TiO2 NTS were formed after calcining H2Ti4O9·H2O NTS at 573 K. The bicrystal phase TiO2 NTS exhibit significantly higher photocatalytic activity than the single phase anatase NTS and Dessuga P-25 nanoparticles in the degradation of Methyl Orange aqueous solution under ultraviolet light irradiation, which is attributed to the large surface and interface areas of the bicrystal phase TiO2 NTS.

  11. 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

  12. Superiority of solar Fenton oxidation over TiO2 photocatalysis for the degradation of trimethoprim in secondary treated effluents.

    PubMed

    Michael, I; Hapeshi, E; Michael, C; Fatta-Kassinos, D

    2013-01-01

    The overall aim of this work was to examine the degradation of trimethoprim (TMP), which is an antibacterial agent, during the application of two advanced oxidation process (AOP) systems in secondary treated domestic effluents. The homogeneous solar Fenton process (hv/Fe(2+)/H2O2) and heterogeneous photocatalysis with titanium dioxide (TiO2) suspensions were tested. It was found that the degradation of TMP depends on several parameters such as the amount of iron salt and H2O2, concentration of TiO2, pH of solution, solar irradiation, temperature and initial substrate concentration. The optimum dosages of Fe(2+) and H2O2 for homogeneous ([Fe(2+)] = 5 mg L(-1), [H2O2] = 3.062 mmol L(-1)) and TiO2 ([TiO2] = 3 g L(-1)) for heterogeneous photocatalysis were established. The study indicated that the degradation of TMP during the solar Fenton process is described by a pseudo-first-order reaction and the substrate degradation during the heterogeneous photocatalysis by the Langmuir-Hinshelwood kinetics. The toxicity of the treated samples was evaluated using a Daphnia magna bioassay and was finally decreased by both processes. The results indicated that solar Fenton is more effective than the solar TiO2 process, yielding complete degradation of the examined substrate within 30 min of illumination and dissolved organic carbon (DOC) reduction of about 44% whereas the respective values for the TiO2 process were ∼70% degradation of TMP within 120 min of treatment and 13% DOC removal. PMID:23508150

  13. The hybrid process TiO(2)/PAC: performance of membrane filtration.

    PubMed

    Ziegmann, Markus; Saravia, Florencia; Torres, Pabla A; Frimmel, Fritz H

    2010-01-01

    In investigations concerning the photocatalytic degradation by TiO(2) usually filter discs with a pore size of 0.22 mum and 0.45 mum are used for the removal of photocatalyst particles in aqueous suspensions. In this study the effective rejection of suspended particles by microfiltration in different types of membrane modules and with different membrane materials was investigated. Furthermore, Powdered Activated Carbon (PAC), which can be used to gain an increase in photocatalytic degradation rates, was investigated concerning its influence on the membrane performance. It is shown that by membrane filtration with a pore size above 0.1 mum, irrespective of the experimental conditions, no complete removal can be achieved. However, UV irradiation was found to improve the removal efficiency for all types of tested membrane materials. The addition of PAC also led to a higher performance of membrane filtration with regard to particle rejection. In long-term experiments with a hollow fibre membrane module in the presence of PAC a five-fold decrease of TiO(2) particles in the permeate could be proven. Besides, it was shown that added PAC can shield the membrane regarding the abrasivity of TiO(2), which could otherwise lead to the destruction of the membrane. Therewith PAC exhibits another crucial advantage besides its synergetic effect in photodegradation. PMID:20818066

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. Photodegradation of microcystin-LR catalyzed by metal phthalocyanines immobilized on TiO2-SiO2 under visible-light irradiation.

    PubMed

    Peng, Guotao; Fan, Zhengqiu; Wang, Xiangrong; Sui, Xin; Chen, Chen

    2015-01-01

    Microcystins (MCs) are a group of monocyclic heptapeptide toxins produced by species of cyanobacteria. Since MCs exhibit acute and chronic effects on humans and wildlife by damaging the liver, they are of increasing concern worldwide. In this study, we investigated the ability of the phthalocyanine compound (ZnPc-TiO2-SiO2) to degrade microcystin-LR (MC-LR) in the presence of visible light. X-ray diffraction (XRD) and UV-Visible diffuse reflectance spectra (UV-Vis DRS) were utilized to characterize the crystalline phase and the absorption behavior of this catalyst. According to the results, XRD spectra of ZnPc-TiO2-SiO2 powders taken in the 2θ configuration exhibited the peaks characteristic of the anatase phase. UV-Vis DRS showed that the absorption band wavelength shifted to the visible range when ZnPc was supported on the surface of TiO2-SiO2. Subsequently, several parameters including catalyst dose, MC-LR concentrations and pH were investigated. The MC-LR was quantified in each sample through high-performance liquid chromatography (HPLC). The maximum MC-LR degradation rate of 80.2% can be obtained within 300 minutes under the following conditions: catalyst dose of 7.50 g/L, initial MC-LR concentration of 17.35 mg/L, pH 6.76 and the first cycling run of the photocatalytic reaction. Moreover, the degradation process fitted well with the pseudo-first-order kinetic model. PMID:26540545

  19. 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. PMID:25444660

  20. 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. PMID:16269195

  1. 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. PMID:23701360

  2. Cr(VI) photocatalytic reduction: effects of simultaneous organics oxidation and of gold nanoparticles photodeposition on TiO2.

    PubMed

    Dozzi, Maria Vittoria; Saccomanni, Alessia; Selli, Elena

    2012-04-15

    Commercial TiO(2) samples with different phase composition and surface area were tested as photocatalysts in the photoinduced reduction of Cr(VI) in aqueous suspensions at pH 3.7 under UV-visible light irradiation. This reaction was also coupled with the simultaneous photocatalytic oxidation of the pollutant azo dye Acid Orange 8 (AO8) and of formic acid, acting as hole scavengers. The co-presence of oxidizable and reducible species ensured better separation of photogenerated charge carriers, resulting in a higher rate of both organics' oxidation and Cr(VI) reduction, especially in the case of high surface area anatase TiO(2), having the strongest affinity for Cr(VI) and AO8, as demonstrated by competitive adsorption tests. The effects on Cr(VI) photocatalytic reduction of gold nanoparticles photodeposited on TiO(2) and of the Au loading were also investigated, aiming at ascertaining if this noble metal plays a role in the electron transfer processes involved in Cr(VI) reduction. PMID:21959186

  3. 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

  4. 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.

  5. 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.

  6. 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. PMID:25867689

  7. Investigation of solid phase upon γ-irradiation of ferrihydrite-ethanol suspension

    NASA Astrophysics Data System (ADS)

    Jurkin, Tanja; Zadro, Krešo; Gotić, Marijan; Musić, Svetozar

    2011-07-01

    Ferrihydrite (FH) nanoparticles were synthesised and subjected to γ-irradiation in the form of FH-ethanol suspension. The dose rate of γ-radiation was ˜16 kGy/h and the samples were irradiated to doses of up to 2590 kGy. γ-irradiation of FH-ethanol suspensions did not cause the transformation of FH to any of the other iron oxide phases. Likewise, neither the Mössbauer and FT-IR spectroscopy nor the quantitative analysis using Energy Dispersive X-ray Spectroscopy gave any evidence of structural changes of FH upon γ-irradiation. C, H analysis showed that the C concentration in FH gradually increased with dose and was higher in γ-irradiated FH samples than in non-irradiated FH sample. This finding suggested that carbon in FH originated from ethanol degradation. The H concentration in FH gradually increased to the dose of up to 340 kGy and then slightly decreased. Magnetic measurements showed a progressive decrease in magnetisation with an increase in γ-irradiation. The results of magnetic measurements and C, H analysis suggested the carbonisation of FH surface. It was supposed that γ-irradiation of FH-ethanol suspension reductively decomposed ethanol thus generating unsaturated hydrocarbons and acetylides, which in turn formed a conjugate iron complex, thus carbonating the FH surface. The carbonisation of the FH surface prevented FH transformation to other iron oxide phases.

  8. TiO2/methylcellulose nanocomposite films for photocatalytic applications

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    TiO2/methylcellulose (MeC) nanocomposite films were obtained by wet-chemical techniques using MeC and/or additives (acetylacetone, polyethylene glycol and Triton X-100). Thin films were obtained by spin-coating the colloidal suspensions on conductive indium tin oxide (ITO) glass, followed by a heat-treatment. The effect of MeC and additives on TiO2 nanoparticles dispersion was investigated by FTIR microscopy and X-ray diffraction (for structural and morphological properties), UV-VIS absorption spectroscopy and spectrofluorimetry (for optoelectronic properties) and wet technique adhesion test (for mechanical integrity). The composite film with methylcellulose and additives has good integrity and better adhesion to ITO substrate, without losing its photocatalytic activity. The results of these experiments showed that such nanocomposite films are interesting candidate for applications in the field of photocatalytic degradation of organic pollutants.

  9. Photocatalytic oxidation of chloroform using immobilized-biogenic TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Cho, Y.; Yoo, H.

    2011-12-01

    Although commercial titanium dioxide (TiO2) nanoparticles as a suspension in water are one of the most popular photocatalysts for treatment of chlorinated organic compounds, the reuse and recovery of the nanoscale phtocatalyst is a practical challenge for application in water and groundwater treatment system. As part of efforts to overcome this practical limitation, development of immobilized TiO2 is needed. Diatom Pinnularia sp. were found to be capable of producing nanoscale TiO2 in their microscale silica shells. In order to obtain biogenic TiO2 nanoparticles from Pinnularia sp., soluble Ti was fed to the silicon-starved cells, resulting in deposition of titanium on the microscale features of the silica shells. After thermal treatment at 720 oC for 2 hr, the titanium was eventually converted to nanoscale TiO2. In order to determine the physical and chemical properties of the immobilized TiO2, material characterization such as TEM, STEM-EDS, BET and XRD analysis was carried out. In this study, a novel type of immobilized photocatalytic nanoparticles, biogenic TiO2 on silica shells was used for the mineralization of chloroform in water. Batch tests were conducted to evaluate the chloroform removal efficiency of biogenic and commercial TiO2 nanoparticles. Also, the amount of Cl- ions in water during the mineralization was measured to check mineralization of chloroform by biogenic TiO2 nanoparticles. Kinetic models were used to determine the rate of chloroform mineralization. In addition, the effect of UVA (ultraviolet-A) intensity on chloroform mineralization was investigated. The results obtained from this study could provide useful information for practical application of biogenic TiO2 in the groundwater treatment contaminated with some chlorinated organic compounds.

  10. UV/thermally driven rewritable wettability patterns on TiO2-PDMS composite films.

    PubMed

    Nakata, Kazuya; Kimura, Hiroaki; Sakai, Munetoshi; Ochiai, Tsuyoshi; Sakai, Hideki; Murakami, Taketoshi; Abe, Masahiko; Fujishima, Akira

    2010-09-01

    Composite films of TiO2 and polydimethylsiloxane (PDMS) are prepared by a sol-gel method, cured with UV irradiation, and then treated in hot water to crystallize the TiO2 in the film. The presence of anatase TiO2 contributes to the photoinduced superhydrophilicity of the film under UV irradiation. Contact angle studies reveal that the TiO2-PDMS composite film recovers its original hydrophobic state. Hydrophobic-superhydrophilic patterns are successfully formed on the films. The wettability patterns can be erased by UV irradiation and thermal treatment. New wettability patterns can be reconstructed, demonstrating that the film exhibits rewritable wettability without the need for organic chemicals. PMID:20712336

  11. 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.

  12. 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...

  13. 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

  14. 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. PMID:24220193

  15. 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...

  16. 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

  17. Samarium-doped mesoporous TiO2 nanoparticles with improved photocatalytic performance for elimination of gaseous organic pollutants

    NASA Astrophysics Data System (ADS)

    Tang, Jianting; Chen, Xiaomiao; Liu, Yu; Gong, Wei; Peng, Zhenshan; Cai, Tiejun; Luo, Lianjing; Deng, Qian

    2013-01-01

    Mesoporous TiO2 doped with different amounts of Sm were prepared via a sol-gel route with Pluronic P123 as template. The materials were characterized by X-ray diffraction, transmission electron microscopy, and N2 sorption experiments, etc. The photocatalytic activity of the mesoporous TiO2 was tested in elimination of gaseous methanol and acetone. The Sm doped mesoporous TiO2 have higher activity than those of the commercial photocatalyst (Degussa, P25) and Sm doped TiO2 counterparts without mesopore structure under ultraviolet light irradiation. A possible mechanism was proposed to account for the high photocatalytic activity of the Sm doped mesoporous TiO2. The superior activity of the Sm doped mesoporous TiO2 may be attributed to the synergic effect of the high surface area, mesopore structure and doped Sm species.

  18. Toxicity of spleen cell suspensions from heavily irradiated mice: implications for CFU-S seeding

    SciTech Connect

    Hubner, G.E.; Cronkite, E.P.; Laisue, J.A.; Van Wangenheim, K.H.; Feinendegen, L.E.

    1981-11-01

    Cell suspensions were made from spleens of mice 5 hr to 6 days after irradiation. Mice were irradiated with 800 rad. One group of mice received a transfusion of 2 x 10/sup 6/ nucleated bone marrow cells and another group no bone marrow transfusion. From 15 hr to 6 days after irradiation the toxicity of the cell suspensions varies with time and number of cells injected. As many as 20 x 10/sup 6/ spleen cells from normal mice or mice 5 hr after irradiation can be injected with no signs of toxicity. A molecular factor(s) in cooperation with cells or cell debris is responsible for the toxicity. Some characteristics of the factor(s) are described. The toxic cell suspensions caused pulmonary embolism. There was no effect of the toxic substance on pluripotent stem cells (CFU-S) in regular CFU-S assay or the ability of bone marrow to repopulate irradiated mice. Whether the emboli trap the CFU-S and influence the seeding efficiency of CFU-S in the spleen is not known.

  19. On the spray-drying deposition of TiO 2 photocatalytic films

    NASA Astrophysics Data System (ADS)

    Uzunova-Bujnova, M.; Todorovska, R.; Milanova, M.; Kralchevska, R.; Todorovsky, D.

    2009-11-01

    The photocatalytic activity of TiO 2 films deposited on different substrates by the spray-drying method using suspensions of commercially available TiO 2 (Degussa P25 or Tronox) as starting material was studied. The influence of the type of the initial TiO 2, preparation conditions (temperature of the substrate during the film deposition, temperature of the post-deposition annealing), substrate material (glass, fused silica, stainless steel and graphite), the presence of additives in the spraying suspension (polyethylene glycol, ethylene glycol and acetylacetone) and its sonication before spraying on the morphology, size of crystallites and phase composition (rutile/anatase ratio) was studied. Optimal conditions for spray deposition of the films are suggested.

  20. 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. PMID:26353576

  1. Interface actions between TiO2 and porous diatomite on the structure and photocatalytic activity of TiO2-diatomite

    NASA Astrophysics Data System (ADS)

    Xia, Yue; Li, Fangfei; Jiang, Yinshan; Xia, Maosheng; Xue, Bing; Li, Yanjuan

    2014-06-01

    TiO2-diatomite photocatalysts were prepared by sol-gel process with various pre-modified diatomite. In order to obtain diatomite with different surface characteristics, two modification approaches including calcination and phosphoric acid treatment on the micro-structure of diatomite are introduced. The photocatalysts were characterized by XRD, XPS, nitrogen adsorption-desorption isotherms and micromorphology analysis. The results indicate that, compared with pure TiO2, the anatase-to-rutile phase transition temperature of TiO2 loaded on diatomite carrier is significantly increased to nearly 900 °C, depending on the different pretreatment method of diatomite. The photocatalytic activities of different samples were evaluated by their degradation rate of methyl orange (MO) dye under UV and visible-light irradiation. The samples prepared by phosphoric acid pretreatment method exhibit the highest photocatalytic activity. After 90 min of UV irradiation, about 90% of MO is decomposed by the best effective photocatalyst. And after 8 h visible-light irradiation, nearly 60% of MO is decomposed by the same sample. Further mechanism investigation reveals that the H3PO4 pretreatment process can obviously change the surface features of diatomite carrier, cause the formation of Si-O-Ti bond, increase the binding strength between TiO2 and diatomite, restrain crystal growth of loaded TiO2, and thus form thermal-stable mesoporous structure at the granular spaces. It helps to build micro-, meso- and macro-porous hierarchical porous structure in TiO2-diatomite, and improves the charge and mass transfer efficiency during catalyzing process, resulting in the significantly increased photocatalytic activity of TiO2-diatomite pretreated by phosphoric acid.

  2. Heterostructured TiO2 Nanorod@Nanobowl Arrays for Efficient Photoelectrochemical Water Splitting.

    PubMed

    Wang, Wenhui; Dong, Jingya; Ye, Xiaozhou; Li, Yang; Ma, Yurong; Qi, Limin

    2016-03-01

    Heterostructured TiO2 nanorod@nanobowl (NR@NB) arrays consisting of rutile TiO2 nanorods grown on the inner surface of arrayed anatase TiO2 nanobowls are designed and fabricated as a new type of photoanodes for photoelectrochemical (PEC) water splitting. The unique heterostructures with a hierarchical architecture are readily fabricated by interfacial nanosphere lithography followed by hydrothermal growth. Owing to the two-dimensionally arrayed structure of anatase nanobowls and the nearly radial alignment of rutile nanorods, the TiO2 NR@NB arrays provide multiple scattering centers and hence exhibit an enhanced light harvesting ability. Meanwhile, the large surface area of the NR@NB arrays enhances the contact with the electrolyte while the nanorods offer direct pathways for fast electron transfer. Moreover, the rutile/anatase phase junction in the NR@NB heterostructure improves charge separation because of the facilitated electron transfer. Accordingly, the PEC measurements of the TiO2 NR@NB arrays on the fluoride-doped tin oxide (FTO) substrate show significantly enhanced photocatalytic properties for water splitting. Under AM1.5G solar light irradiation, the unmodified TiO2 NR@NB array photoelectrode yields a photocurrent density of 1.24 mA cm(-2) at 1.23 V with respect to the reversible hydrogen electrode, which is almost two times higher than that of the TiO2 nanorods grown directly on the FTO substrate. PMID:26779803

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

    PubMed

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

    2016-01-01

    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. PMID:26840294

  4. 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.

  5. Nanostructured TiO2 Films Attached CdSe QDs Toward Enhanced Photoelectrochemical Performance.

    PubMed

    Du, Yingying; Yang, Ping; Liu, Yunshi; Zhao, Jie; He, Haiyan; Miao, Yanping

    2016-06-01

    TiO2 films consisted of small nanoparticles were fabricated via a spinning coating method on fluorine doped in tin oxide (FTO) slide glass. After calcination, the films were subsequently sensitized by CdSe quantum dots (QDs) using mercaptopropionic acid (MPA) as a bifunctional surface modifier. Upon UV light irradiation, CdSe QDs inject electrons into TiO2 nanoparticles, thus resulting in the generation of photocurrent in QD-sensitized solar cell. The results indicate that TiO2 films sensitized by CdSe QDs have achieved 1.5-fold enhancement in photocurrent compared with pure TiO2 films, indicating that CdSe QDs can improve the photocurrent by promoting the separation of photoinduced charge carriers. In addition, the photocurrent enhances as the thickness of TiO2 films increased. Such improved photoelectrochemical performance is ascribed to the basis of improved interfacial charge transport of the TiO2-CdSe composite films. Combining QDs on TiO2 thin films is a promising and effective way to enhance the photoelectrochemical performance, which is important in QD-sensitized solar cell application. PMID:27427714

  6. 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.

  7. 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. PMID:24682063

  8. Suspensions

    NASA Astrophysics Data System (ADS)

    Braccini, Stefano

    2000-06-01

    Special suspension systems are used in gravitational wave detectors to reduce the transmission of seismic vibrations to test masses by many orders of magnitude. In ground-based interferometric antennas, this allows to detect gravitational signals even below a few tens of Hz, where seismic vibrations are very strong. The state of the art on this topic is presented. .

  9. Impact of aggregate size and structure on the photocatalytic properties of TiO2 and ZnO nanoparticles.

    PubMed

    Jassby, David; Farner Budarz, Jeffrey; Wiesner, Mark

    2012-07-01

    Aggregation of photocatalytic semiconductors was determined to reduce the generation of free hydroxyl radicals in aqueous suspensions in a fashion dependent on aggregate size and structure. Static light scattering measurements were used to follow temporal changes in the fractal dimension of aggregating TiO(2) and ZnO nanoparticles. At length scales comparable to nanoparticle size, the structure of aggregated TiO(2) nanoparticles was independent of particle stability and the associated aggregation rate, consistent with the fused nature of TiO(2) primary particles in the initial suspension. In contrast, ZnO aggregates were characterized by smaller fractal dimensions when ionic strength, and the resulting aggregation rate, were increased. The photocatalytic activity of ZnO and TiO(2) in generating free hydroxyl radicals varied with aggregate structure and size, consistent with theory that predicts reduced reactivity as aggregates become larger and more dense. PMID:22225505

  10. 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.

  11. Preparation, performance and adsorption activity of TiO2 nanoparticles entrapped PVDF hybrid membranes

    NASA Astrophysics Data System (ADS)

    Zhang, Xia; Wang, Yang; You, Yuting; Meng, Hao; Zhang, Jianghua; Xu, Xinxin

    2012-12-01

    The TiO2 nanoparticles entrapped poly(vinylidenefluoride) (PVDF) hybrid membranes were prepared through impregnating the pre-treated PVDF film in the TiO2 suspension. SEM, XRD, TG and ATR-IR analyses were used to character the hybrid membranes. The results showed that the TiO2 nanoparticles with average size about 44 nm were deposited on the surface and inner pores of PVDF films. The pre-treatment of PVDF with cetyltrimethyl ammonium bromide (CTAB) is benefit for TiO2loading. The ATR-IR spectra revealed that physical interaction played important role in the construction of hybrid membranes. The adsorption behavior of Cu2+ on the hybrid membranes was studied, and a promoted adsorption and elution efficiency of PVDF/TiO2 hybrid membranes were observed compared with that of the pristine PVDF film. Meanwhile, the surface contact angle, pure water flux and static adsorption of bovine serum albumin (BSA) on the hybrid membranes were also measured to study the effects of TiO2 nanoparticles. It was found that the TiO2 nanoparticles improved the surface hydrophilicity and permeability of PVDF membranes, and the decreasing adsorption capacity of BSA indicated the promoted antifouling ability of PVDF membranes. Such the PVDF/TiO2 hybrid membranes exhibit potential applications in the separation and pre-concentration of metal ions.

  12. Synthesis of nanostructured TiO2/SiO2 as an effective photocatalyst for degradation of acid orange

    NASA Astrophysics Data System (ADS)

    Cetinkaya, Tugrul; Neuwirthová, Lucie; Kutláková, Kateřina M.; Tomášek, Vladimír; Akbulut, Hatem

    2013-08-01

    TiO2/SiO2 composites were produced as photocatalysts both by hydrolysis of TiCl4 and from TiO2 suspension prepared by hydrolysis of TiCl4. TiO2/SiO2 composites were dried at 70 °C and calcinated at 400 °C and 600 °C to investigate the effect of calcination temperature on the phase transformation of TiO2 structure. Photocatalytic effects of produced TiO2/SiO2 composites were measured against degradation of acid orange 7 (AO7) by UV-vis spectroscopy. The chemical compositions of produced samples were studied by X-ray fluorescence (XRF) technique. The composite structures were analyzed by X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM) facilities to reveal the surface morphology and their phase structures. Energy dispersive X-ray spectroscopy (EDS) was conducted to understand the elemental surface composition of composites. Photocatalytic activity of composites normalized with surface area, and TiO2/SiO2 composite produced by TiO2 suspension prepared by hydrolysis of TiCl4 and calcinated at 600 °C indicated 40% photocatalytic degradation of AO7 after 2 h under UV radiation.

  13. 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.

  14. 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

  15. Photocatalytic degradation of N-nitrosodimethylamine: mechanism, product distribution, and TiO2 surface modification.

    PubMed

    Lee, Jaesang; Choi, Wonyong; Yoon, Jeyong

    2005-09-01

    The photocatalytic degradation (PCD) reaction of N-nitrosodimethylamine (NDMA) in water was investigated using pure and surface-modified TiO2. The PCD products of NDMA were methylamine (MA), dimethylamine (DMA), nitrite, nitrate, and ammonium, and their distribution could be changed by modifying the surface of TiO2. The PCD reaction of NDMA seems to be initiated mostly by OH radicals, not valence band holes, because the addition of excess oxalates (hole scavengers) only moderately retarded the PCD rate. The presence of oxalate, however, enabled a new reductive transformation path in which the CO2-* radicals generated from the oxalate converted NDMA into DMA. In acidic suspensions of pure TiO2, the formation of MA was highly favored over DMA and NH3, whereas all degradation products (MA, DMA, and NH3) were generated at comparable concentrations at basic pH. It is suggested that there are three parallel paths depending on the position of the initial attack of OH radical on NDMA and the product distribution is closely related with which path is favored under a specific condition. DMA production is related to the OH radical attack on the nitrosyl nitrogen. Platinum deposition, silica loading, Nafion coating, and surface fluorination were tested to investigate the effects of TiO2 surface modification on the product distribution. The surface platinization of TiO2 had little effect on the PCD reaction of NDMA under air-equilibrated conditions but accelerated the PCD reaction under deaerated conditions. An enhanced PCD reaction of NDMA was achieved with the silica-loaded TiO2 and Nafion-coated TiO2, both of which favored the formation of DMA over MA. The PCD of NDMA on surface-fluorinated TiO2 was also highly enhanced but favored the formation of MA over the formation of DMA. PMID:16190242

  16. Photocatalysis of Phenolic Compounds with Synthesized Nanoparticles TiO2/Sn2

    NASA Astrophysics Data System (ADS)

    Khuanmar, Kulyakorn; Wirojanagud, Wanpen; Kajitvichyanukul, Puangrat; Maensiri, Santi

    This study was aimed to determine the photocatalytic degradation of phenolic compounds contaminated in the pulp and paper wastewater with the synthesized nanoparticle TiO2/Sn2 and the commercial TiO2 (Sigma Aldrich). The studied phenolic compounds included 2-methoxy phenol (guaiacol), 2,6-dimethoxy phenol (syringol) and phenol. The synthesized TiO2/Sn2 was prepared by sol-gel technique, mixture of titanium solution and ethanol/polymer with 2% of tin. The characterization of the synthesized TiO2/Sn2 and the commercial TiO2 were performed by XRD, BET and SEM. The synthesized TiO2/Sn2 were: mixed phase of anatase:rutile of 85: 15, 14 nm crystalline size of anatase (101) and 47 nm rutile (110) and 65.7 m2 g-1 surface area by BET. On the other hand the commercial TiO2 (Sigma aldrich) only showed the anatase phase with particle size of 41 nm and 10.9 m2 g-1 surface area by BET. The photocatalytic degradation were tested on the individual and mixed phenolic compounds. The phenolic compound solution suspended with the catalyst was irradiated with UV light. The photocatalytic degradation of phenolic compounds by such two types was significantly different. TiO2/Sn2 presented the sequential degradation as syringol > guaiacol > phenol for both individual and mixed phenolic compounds. While the commercial TiO2 indicated the degradation as phenol>guaiacol>syringol for the individual phenolic compound and the reverse order of degradation as syringol>guaiacol>phenol for the mixed compounds.

  17. 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.

  18. Photocatalytic activity of nanosized TiO2 thin film prepared by magnetron sputtering method.

    PubMed

    Kang, Sang-Jun; Kim, Ki-Joong; Chung, Min-Chul; Jung, Sang-Chul; Boo, Su-Il; Cho, Soon Kye; Jeong, Woon-Jo; Ahn, Ho-Geun

    2011-02-01

    Nanosized TiO2 thin film on the substrate such as stainless steel plate and slide glass film were prepared by magnetron sputtering method, and these TiO2 thin films were characterized by field emission-scanning electron microscopy (FE-SEM). Photocatalytic activity for Methyl-ethyl-ketone (MEK) and acetaldehyde were measured using a closed circulating reaction system through the various ultra violet (UV) sources. From the results of SEM images, nanosized TiO2 thin film was uniformly coated on slide glass, ranging from 360 nm to 370 nm. Photocatalytic activity of MEK over TiO2 thin film on stainless steel plate did not occur by UV-A irradiation, but was efficiently decomposed by UV-B and UV-C. Also, acetaldehyde could be decomposed than MEK. The effect of sputtering conditions on their structure and photocatalytic activities were investigated in detail. PMID:21456269

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    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. Optofluidic microreactors with TiO2-coated fiberglass.

    PubMed

    Li, Lin; Chen, Rong; Zhu, Xun; Wang, Hong; Wang, Yongzhong; Liao, Qiang; Wang, Dongye

    2013-12-11

    Optofluidic microreactors are promising prospects for photocatalytic reactions. However, because the flow type in conventional designs is typically laminar, the mass transport mainly relies on diffusion, and thus the rate of mass transport is limited. Accordingly, poor mass transport reduces the photocatalytic reaction rate. To alleviate the limitation of mass transport, in this work, we proposed a novel optofluidic microreactor with TiO2-coated fiberglasses immersed in the microreaction chamber. Such a design enables enhanced mass transport by shortening the transport length and inducing the perturbation to liquid flow so as to improve the performance. We demonstrated the feasibility of the optofluidic microreactor with the TiO2-coated fiberglass by the photocatalytic water treatment of methylene blue under UV irradiation. Results showed that the proposed optofluidic microreactor yielded much higher degradation efficiency than did the conventional optofluidic microreactor as a result of enhanced mass transport. The microreactor with the TiO2-coated fiberglass showed a 2-3-fold improvement in the reaction rate constant as opposed to conventional ones. The maximal increment of the degradation efficiency can reach more than 40%. PMID:24262010

  2. 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

    2016-03-01

    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. PMID:26884248

  3. Radiolysis of aqueous 4-nitrophenol solution with Al2O3 or TiO2 nanoparticles.

    PubMed

    Follut, F; Vel Leitner, N Karpel

    2007-02-01

    Aqueous 4-nitrophenol solutions containing TiO2 or Al2O3 nanoparticles were irradiated with electron beam. 4-Nitrophenol was decomposed by the ionizing radiation process in the absence of the nanoparticles. The addition of TiO2 or Al2O3 (2 g l(-1)) before irradiation improved the removal of 4-nitrophenol, total organic carbon (TOC) but also nitrogen (TN). To identify the origin of the loss (catalysis or simply adsorption), TiO2 or Al2O3 nanoparticles were added after irradiation. Experiments show that the effect of the presence of TiO2 or Al2O3 during irradiation is just due to adsorption. PMID:17113129

  4. 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.

  5. 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.

  6. 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. PMID:26499197

  7. Enhanced retention of bacteria by TiO2 nanoparticles in saturated porous media.

    PubMed

    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. PMID:27258326

  8. 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.

  9. Pulsed-laser-deposited TiO2 nanocrystalline films supporting Au nanoparticles for visible-light-operating plasmonic photocatalysts

    NASA Astrophysics Data System (ADS)

    Yoshida, Takehito; Watanabe, Tei; Kikuchi, Fumito; Tabuchi, Takeru; Umezu, Ikurou; Haraguchi, Masanobu

    2016-05-01

    We have synthesized pulsed-laser-deposited (PLD) TiO2 nanocrystalline films supporting Au nanoparticles. Au films were deposited on the PLD TiO2 nanocrystalline films with the mass thickness of 4 nm. The as-deposited Au films had island structures. After furnace annealing at 300 °C for 180 min in air, the as-deposited island-structured Au films were balled with the mean diameter of 19 nm on the PLD TiO2 nanocrystalline films. We confirmed that the balled Au nanoparticles had the localized surface plasmonic resonance absorption band in the range of 510-600 nm. Photocatalytic activities of the Au-supporting TiO2 nanocrystalline films were evaluated by a methylene blue decomposition method. We clarified that the Au-supporting TiO2 nanocrystalline films demonstrated visible-light-driven photocatalytic activities, under the filtered (490-500 nm) Xe arc lamp irradiation.

  10. Influences of working pressure on properties for TiO2 films deposited by DC pulse magnetron sputtering.

    PubMed

    Zhang, Can; Ding, Wanyu; Wang, Hualin; Chai, Weiping; Ju, Dongying

    2009-01-01

    TiO2 films were deposited at room temperature by DC pulse magnetron sputtering system. The crystalline structures, morphological features and photocatalytic activity of TiO2 films were systematically investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and ultraviolet spectrophotometer, respectively. The results indicated that working pressure was the key deposition parameter influencing the TiO2 film phase composition at room temperature, which directly affected its photocatalytic activity. With increasing working pressure, the target self-bias decreases monotonously. Therefore, low temperature TiO2 phase (anatase) could be deposited with high working pressure. The anatase TiO2 films deposited with 1.4 Pa working pressure displayed the highest photocatalytic activity by the decomposition of Methyl Orange solution, which the degradation rate reached the maximum (35%) after irradiation by ultraviolet light for 1 h. PMID:19803076

  11. 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.

  12. Anatase TiO2 nanocrystals with exposed {001} facets on graphene sheets via molecular grafting for enhanced photocatalytic activity.

    PubMed

    Sun, Lei; Zhao, Zhenlu; Zhou, Yunchun; Liu, Li

    2012-01-21

    Owing to their extensive practical applications and fundamental importance, the controllable synthesis of well-faceted anatase TiO(2) crystal with high percentage of reactive facets has attracted increasing attention. Here, nano-sized anatase TiO(2) sheets mainly dominated by {001} facets had been prepared on graphene sheets by using a facile solvothermal synthetic route. The percentage of {001} facets in TiO(2) nanosheets was calculated to be ca. 64%. The morphologies, structural properties, growth procedures and photocatalytic activities of the resultant TiO(2)/graphene nanocomposites were investigated. In comparison with commercial P25 and pure TiO(2) nanosheets, the composite exhibited significant improvement in photocatalytic degradation of the azo dye Rhodamine B under visible light irradiation. The enhancement of photocatalytic activity and stability was attributed to the effective charge anti-recombination of graphene and the high catalytic activity of {001} facets. PMID:22159272

  13. Photoelectrochemical Properties of CuS-GeO2-TiO2 Composite Coating Electrode.

    PubMed

    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

  14. 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

  15. 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).

  16. Doping mode, band structure and photocatalytic mechanism of B-N-codoped TiO 2

    NASA Astrophysics Data System (ADS)

    Yuan, Jixiang; Wang, Enjun; Chen, Yongmei; Yang, Wensheng; Yao, Jianghong; Cao, Yaan

    2011-06-01

    The photocatalyst B and N codoped TiO 2 (B-N-TiO 2) was prepared via the sol-gel method by using boric acid and ammonia as B and N precursors. The doping mode, band structure and photocatalytic mechanism of B-N-TiO 2 were investigated well and elucidated in detail. B-N-TiO 2 showed the narrowed band gap and thus extended the optical absorption due to interstitial N and [NOB] species in the TiO 2 crystal lattice. The coexistence of interstitial N and [NOB] species in the TiO 2 crystal lattice and surface NO x species allowed the more efficient utilization of visible light. Simultaneously, interstitial [NOB] and N species and surface B 2O 3 and NO x species facilitated the separation of photo generated electrons and holes and suppress their recombination effectively. Hence, B-N-TiO 2 showed a higher photocatalytic activity than pure TiO 2, N-doped TiO 2 (N-TiO 2) and B-doped TiO 2 (B-TiO 2) under both UV and visible light irradiation.

  17. Controlled synthesis of highly dispersed TiO2 nanoparticles using SBA-15 as hard template.

    PubMed

    Zhao, Li; Yu, Jiaguo

    2006-12-01

    Highly dispersed TiO2 nanoparticles were successfully synthesized by a wet impregnation method using SBA-15 as hard template for confining the growth of TiO2 nanocrystals, and then calcined at 550 degrees C in muffle furnace for 2 h. The as-synthesized samples were characterized with Fourier transform infrared spectra (FTIR), Raman spectroscopy, diffuse reflectance UV-visible spectroscopy (UV-vis), powder X-ray diffraction (XRD), small-angle X-ray diffraction (SAXRD), nitrogen adsorption, transmission electron microscopy (TEM) and photoluminescence spectra (PL). It was found that SBA-15 contained abundant silanol groups after removal of triblock copolymers by ethanol extraction and could easily adsorb a great number of titanium alkoxide via chemisorption. After subsequent hydrolysis of the anchored Ti complexes and calcination of the amorphous TiO2, anatase TiO2 nanocrystals with spherical shape and uniform particle diameter of about 6 nm were formed. A blue shift was observed in UV-vis absorption spectra due to the quantum size effect of TiO2 nanoparticles. Moreover, the as-prepared TiO2 nanoparticles showed a high PL intensity due to an increase in the recombination rate of photogenerated electrons and holes under UV light irradiation. PMID:16989852

  18. 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.

  19. 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. PMID:22204641

  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. PMID:27430307

  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. PMID:26023896

  2. A mild synthetic route to Fe3O4@TiO2-Au composites: preparation, characterization and photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Ma, Jianqi; Guo, Shaobo; Guo, Xiaohua; Ge, Hongguang

    2015-10-01

    To prevent and avoid magnetic loss caused by magnetite core phase transitions involved in high-temperature crystallization of sol-gel TiO2, a direct and feasible low-temperature crystallization technique was developed to deposit anatase TiO2 nanoparticle shell on Fe3O4 sphere cores. To promote the photocatalytic efficiency of the obtained core-shell Fe3O4@TiO2 magnetic photocatalyst, uniformly distributed Au nanoparticles (NPs) were successfully immobilized on the core-shell Fe3O4@TiO2 spheres via a seed-mediated growth procedure. The 3 nm Au colloid absorbed on Fe3O4@TiO2 served as a nucleation site for the growth of Au NPs overlayer. The morphology, structure, composition and magnetism of the resulting composites were characterized, and their photocatalytic activities were also evaluated. In comparison to Fe3O4@TiO2, Fe3O4@TiO2-Au exhibited higher photocatalytic activity for organic degradation under UV irradiation. This enhanced mechanism may have resulted from efficient charge separation of photogenerated electrons and holes due to the Au NPs attached on the TiO2. In addition, the composites possessed superparamagnetic properties with a high saturation magnetization of 44.6 emu g-1 and could be easily separated and recycled by a magnet.

  3. 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. PMID:17904404

  4. 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. PMID:27000026

  5. Decomposition of 3-chlorophenol on nitrogen modified TiO2 photocatalysts.

    PubMed

    Mozia, Sylwia; Bubacz, Kamila; Janus, Magdalena; Morawski, Antoni W

    2012-02-15

    Photocatalytic activity of nitrogen modified TiO(2) calcined at temperatures of 100-350°C toward 3-chlorophenol (3-CP) degradation was studied. In the experiments the fluorescent UV lamp and the incandescent lamp emitting mainly Vis light were applied. The degradation efficiency was evaluated on a basis of changes of 3-CP, total organic carbon and Cl(-) concentration. A significant improvement of the photoactivity of the N-modified photocatalysts compared to the reference sample was observed. The rate of 3-CP degradation increased with the calcination temperature, and the highest efficiency was achieved for TiO(2) annealed at 350°C. After 5h of UV irradiation in the presence of TiO(2)/N-350 and reference TiO(2) the 3-CP concentration decreased for 77% and 36%, respectively. The 3-CP removal after 24h of Vis irradiation was 30% and 12% for the N-modified and reference samples, respectively. The 3-CP decomposition and mineralization were greatly influenced by pH of the solution, achieving the highest rate at pH 7 for the modified photocatalysts. An increase of the calcination temperature resulted in an increase of the rate of OH formation. The photocatalytic activity of the N-modified TiO(2) remained unchanged during repeated photocatalytic degradation cycles. PMID:22192586

  6. 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. PMID:17540502

  7. Photocatalytic enhancement of hybrid C3N4/TiO2 prepared via ball milling method.

    PubMed

    Zhou, Jianwei; Zhang, Mo; Zhu, Yongfa

    2015-02-01

    C3N4/TiO2 hybrid photocatalysts with highly enhanced photocatalytic performance were prepared by a facile ball milling method. A layered structure of g-C3N4 was formed on the surface of TiO2. The mechanochemical process can promote the dispersion of C3N4 on the surface of TiO2 particles, to form a single layer hybrid structure and a multi-layer core-shell structure. The photocatalytic activities of C3N4/TiO2 under visible and UV light irradiation were 3.0 and 1.3 times those of pure g-C3N4 and TiO2, respectively. Under visible light and UV irradiation, the photocurrent response was up to 2.5 times and 1.5 times as high as that of the pure TiO2 and C3N4, respectively. The evident performance enhancement of g-C3N4-TiO2 was mainly attributed to high separation and migration efficiency of electron-hole pairs. PMID:25553728

  8. A facile one-step solvothermal synthesis of graphene/rod-shaped TiO2 nanocomposite and its improved photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Dong, Pengyu; Wang, Yuhua; Guo, Linna; Liu, Bin; Xin, Shuangyu; Zhang, Jia; Shi, Yurong; Zeng, Wei; Yin, Shu

    2012-07-01

    orange (MO), the graphene/rod-shaped TiO2 nanocomposite with the optimized graphene content of 0.48 wt% shows good stability and exhibits a significant enhancement of photocatalytic activity compared to the bare commercial TiO2 (P25) and graphene/spherical TiO2 nanocomposite with the same graphene content. Photocurrent experiments were performed, which demonstrate that the photocurrent of the graphene/rod-shaped TiO2 nanocomposite electrode is about 1.2 times as high as that of the graphene/spherical TiO2 nanocomposite electrode. The photocatalytic mechanism of graphene/rod-shaped TiO2 nanocomposite was also discussed on the basis of the experimental results. This work is anticipated to open a possibility in the integration of graphene and TiO2 with various morphologies for obtaining high-performance photocatalysts in addressing environmental protection issues. Electronic supplementary information (ESI) available: The TEM images of as-prepared pure rod-shaped TiO2 nanocrystals and the other graphene/rod-shaped TiO2 nanocomposites, the MO adsorption isotherms, the XRD pattern, TEM image and UV-vis diffuse reflectance spectrum of graphene/spherical TiO2 nanocomposite with the graphene content of 0.48 wt%, photocatalytic degradation of MO solution over graphene/spherical TiO2 nanocomposites, and plots of ln(C0/C) versus irradiation time for graphene/rod-shaped TiO2 and graphene/spherical TiO2 nanocomposites. See DOI: 10.1039/c2nr31231j

  9. Formation mechanism of TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Yao, B. D.; Chan, Y. F.; Zhang, X. Y.; Zhang, W. F.; Yang, Z. Y.; Wang, N.

    2003-01-01

    Transmission electron microscopic observation showed that TiO2 nanotubes synthesized via a simple hydrothermal chemical process formed a crystalline structure with open-ended and multiwall morphologies. Unlike multiwalled carbon nanotubes, the TiO2 nanotube walls were not seamless. During alkali treatment, crystalline TiO2 raw material underwent delamination in the alkali solution to produce single-layer TiO2 sheets. TiO2 nanotubes were formed by rolling up the single-layer TiO2 sheets with a rolling-up vector of [001] and attracting other sheets to surround the tubes.

  10. 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. PMID:26879685

  11. Instability of hydrogenated TiO2.

    PubMed

    Nandasiri, Manjula I; Shutthanandan, Vaithiyalingam; Manandhar, Sandeep; Schwarz, Ashleigh M; Oxenford, Lucas; Kennedy, John V; Thevuthasan, Suntharampillai; Henderson, Michael A

    2015-11-19

    Hydrogenated TiO2 (H-TiO2) is touted as a viable visible light photocatalyst. We report a systematic study on the thermal stability of H-implanted TiO2 using nuclear reaction analysis (NRA), Rutherford backscattering spectrometry, ultraviolet photoelectron spectroscopy, and X-ray photoelectron spectroscopy. 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 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 at low temperatures, as well as its interfacial activity toward reduction, significantly limits the utilization of H-TiO2 as a photocatalyst. PMID:26545303

  12. 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.

  13. Comparison of electrorheological performance between urea-coated and graphene oxide-wrapped core-shell structured amorphous TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Dong, Xufeng; Huo, Shuang; Qi, Min

    2016-01-01

    Polar molecules and graphene oxide (GO) have been used as the shell materials to prepare core-shell structured particles with enhanced electrorheological (ER) properties. Nevertheless, few studies compared the ER performance and stability of the suspensions with the two kinds of shell. In this study, urea and GO are used as the shell materials to prepare TiO2/urea and TiO2/GO core-shell particles-based ER fluids, respectively. Particle characterization results indicate the two kinds of core-shell structured particles present little change in size, morphology and crystal structure compared with the bare amorphous TiO2. Some polar groups are distributed on the surface of the two kinds of core-shell structured particles, which is responsible for their improved ER performance with respect to the bare TiO2 particles. The TiO2/GO particles-based ER fluid presents higher yield stress, lower leakage current density, better sedimentation stability but lower ER efficiency than the TiO2/urea particles-based sample. The larger surface area, stronger connection with the bare TiO2 particles, and larger number of polar groups of the GO-coating is the possible reason for the different properties of TiO2/GO particles-based ER fluid compared with the TiO2/urea particles-based sample.

  14. Fabrication of silver nanoparticles with limited size distribution on TiO2 containing zeolites.

    PubMed

    Mazzocut, Andrea; Coutino-Gonzalez, Eduardo; Baekelant, Wouter; Sels, Bert; Hofkens, Johan; Vosch, Tom

    2014-09-21

    Here we present a simple route to produce well-defined photo-reduced silver nanoparticles on TiO2 containing zeolites. We used natural and artificial irradiation sources to study their effect on the particle size distribution. The samples were investigated by electron microscopy, X-ray diffraction, fluorescence microscopy and UV-Vis diffuse reflectance spectroscopy. PMID:25083739

  15. Enhanced Photocatalytic H2 Production in Core-Shell Engineered Rutile TiO2.

    PubMed

    Yang, Yongqiang; Liu, Gang; Irvine, John T S; Cheng, Hui-Ming

    2016-07-01

    A rationally designed crystalline Ti(3+) core/amorphous Ti(4+) shell configuration can reverse the population disparity between holes and electrons reaching the surface of microsized rutile TiO2 photocatalyst, thus significantly enhancing its photocatalytic activity by two orders of magnitude in terms of the hydrogen production rate under the irradiation of UV-vis light. PMID:27159036

  16. 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. PMID:22707206

  17. 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. PMID:23901536

  18. Fabrication of plasmonic AgBr/Ag nanoparticles-sensitized TiO2 nanotube arrays and their enhanced photo-conversion and photoelectrocatalytic properties

    NASA Astrophysics Data System (ADS)

    Wang, Qingyao; Qiao, Jianlei; Jin, Rencheng; Xu, Xiaohui; Gao, Shanmin

    2015-03-01

    Plasmonic photosensitizer AgBr/Ag nanospheres supported on TiO2 nanotube arrays (TiO2 NTs) are prepared by successive ionic layer adsorption and reaction (SILAR) technique followed by photoreduction methods. The structural and surface morphological properties of AgBr/Ag nanoparticles sensitized TiO2 NTs and their photoelectrochemical performance are investigated and discussed. A detailed formation mechanism of the TiO2 NTs/AgBr/Ag is proposed. The TiO2 NTs/AgBr/Ag exhibit excellent photocurrent and photoelectrocatalytic activities under visible light irradiation. Efficient utilization of solar energy to create electron-hole pairs is attributed to the significant visible light response and surface plasmon resonance of Ag nanoparticles. This finding indicates that the high photosensitivity of the TiO2 NTs-based surface plasmon resonance materials could be applied toward the development of new plasmonic visible-light-sensitive photovoltaic fuel cells and photocatalysts.

  19. 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.

  20. Enhancing photoactivity of TiO2(B)/anatase core-shell nanofibers by selectively doping cerium ions into the TiO2(B) core.

    PubMed

    Yang, Dongjiang; Zhao, Jian; Liu, Hongwei; Zheng, Zhanfeng; Adebajo, Moses O; Wang, Hongxia; Liu, Xiaotang; Zhang, Hongjie; Zhao, Jin-cai; Bell, John; Zhu, Huaiyong

    2013-04-15

    Cerium ions (Ce(3+)) can be selectively doped into the TiO2(B) core of TiO2(B)/anatase core-shell nanofibers by means of a simple one-pot hydrothermal treatment of a starting material of hydrogen trititanate (H2Ti3O7) nanofibers. These Ce(3+) ions (≈0.202 nm) are located on the (110) lattice planes of the TiO2(B) core in tunnels (width≈0.297 nm). The introduction of Ce(3+) ions reduces the defects of the TiO2(B) core by inhibiting the faster growth of (110) lattice planes. More importantly, the redox potential of the Ce(3+)/Ce(4+) couple (E°(Ce(3+)/Ce(4+))=1.715 V versus the normal hydrogen electrode) is more negative than the valence band of TiO2(B). Therefore, once the Ce(3+)-doped nanofibers are irradiated by UV light, the doped Ce(3+) ions--in close vicinity to the interface between the TiO2(B) core and anatase nanoshell--can efficiently trap the photogenerated holes. This facilitates the migration of holes from the anatase shell and leaves more photogenerated electrons in the anatase nanoshell, which results in a highly efficient separation of photogenerated charges in the anatase nanoshell. Hence, this enhanced charge-separation mechanism accelerates dye degradation and alcohol oxidation processes. The one-pot treatment doping strategy is also used to selectively dope other metal ions with variable oxidation states such as Co(2+/3+) and Cu(+/2+) ions. The doping substantially improves the photocatalytic activity of the mixed-phase nanofibers. In contrast, the doping of ions with an invariable oxidation state, such as Zn(2+), Ca(2+), or Mg(2+), does not enhance the photoactivity of the mixed-phase nanofibers as the ions could not trap the photogenerated holes. PMID:23417892

  1. 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. PMID:16949121

  2. 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

    2016-02-01

    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). PMID:26708310

  3. Comparison of the photocatalytic behavior of TiO2 coatings elaborated by different thermal spraying processes

    NASA Astrophysics Data System (ADS)

    Toma, Filofteia-Laura; Sokolov, Dmitry; Bertrand, Ghislaine; Klein, Didier; Coddet, Christian; Meunier, Cathy

    2006-12-01

    This paper proposes a comparative study on the microstructure and photocatalytic performances of titanium dioxide coatings elaborated by various thermal spraying methods (plasma spraying in atmospheric conditions, suspension plasma spraying, and high-velocity oxyfuel spraying). Agglomerated spray dried anatase TiO2 powder was used as feedstock material for spraying. Morphology and microstructural characteristics of the coatings were studied mainly by scanning electron microscopy and x-ray diffraction. The photocatalytic behavior of the TiO2-base surfaces was evaluated from the conversion rate of gaseous nitrogen oxides (NOx). It was found that the crystalline structure depended strongly on the technique of thermal spraying deposition. Moreover, a high amount of anatase was suitable for the photocatalytic degradation of the pollutants. Suspension plasma spraying has allowed retention of the original anatase phase and for very reactive TiO2 surfaces to be obtained for the removal of nitrogen oxides.

  4. 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

  5. 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.

  6. Hydrothermal synthesis of Fe-doped TiO2 nanostructure photocatalyst

    NASA Astrophysics Data System (ADS)

    Nghia Nguyen, Van; Khoa Truong Nguyen, Ngoc; Nguyen, Phi Hung

    2011-09-01

    Fe-doped TiO2 catalyst was prepared by the hydrothermal method. The resulting nanopowders were characterized by x-ray diffraction, transmission electron microscopy and Raman and UV-visible spectroscopies. The photocatalytic activity of the Fe-doped TiO2 was tested by decomposition of methylene orange with a concentration of 10 mg l‑1 in aqueous solution. The obtained results showed that methylene orange was significantly degraded after irradiation for 90 min under a halogen lamp and sunlight. The doping effect on the photocatalytic activity of the iron-doped catalyst samples are discussed.

  7. Effect of calcined atmosphere on the photocatalytic activity of P-doped TiO2

    NASA Astrophysics Data System (ADS)

    Xia, Yue; Jiang, Yinshan; Li, Fangfei; Xia, Maosheng; Xue, Bing; Li, Yanjuan

    2014-01-01

    Titanium dioxide doped with phosphorus was synthesized by the sol-gel method with H3PO4 addition. The samples were calcined at different temperatures under different atmospheres, in order to affect the Tisbnd O combination behavior in P-doped TiO2. The physicochemical properties of the prepared samples were investigated using TG-DTA, XRD, FTIR, XPS, TEM and UV-vis. The photocatalytic activity was evaluated by degradation of methyl orange (MO) dye under UV and visible-light irradiation. The results show that P-doped TiO2 calcined in different thermal atmosphere reveals entirely different performances. The XRD and UV-vis analysis reveal that the effect of P species in TiO2 is increased by calcining in reducing atmosphere. Further photocatalytic experiments also display that P-doped TiO2 calcined under carbothermal reduction atmosphere (R-PT) exhibits higher photocatalytic activity than that calcined in air (A-PT). The XPS results confirms that the calcining atmosphere changes the distribution concentration of surface and interface species in P-doped TiO2, such as surface oxygen and Ti3+ sites, resulting in the improved photocatalytic activity and enhanced reutilization performance of R-PT. Further mechanism study illustrates that the promoting photocatalytic activity of P-doped TiO2 are ascribed to the formation of Ti3+ sites rather than exceeding oxygen on the surface. And the carbothermal process helps to reserve these Ti3+ sites during high temperature calcination, resulting in the increased photocatalytic activity of P-doped TiO2, especially when the doping level of P species is relative low.

  8. 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.

  9. Photoinduced interaction between riboflavin and TiO 2 colloid

    NASA Astrophysics Data System (ADS)

    Kathiravan, A.; Renganathan, R.

    2008-12-01

    The adsorption of riboflavin on the surface of TiO 2 colloidal particles and the electron transfer process from its singlet excited state to the conduction band of TiO 2 were examined by absorption and fluorescence quenching measurements. The apparent association constants ( Kapp) were determined. The quenching mechanism is discussed involving electron transfer from riboflavin to TiO 2.

  10. 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.

  11. 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

  12. 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.

  13. 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. PMID:25855569

  14. Efficient bioconversion of rice straw to ethanol with TiO2/UV pretreatment.

    PubMed

    Kang, Hee-Kyoung; Kim, Doman

    2012-01-01

    Rice straw is a lignocellulosic biomass that constitutes a renewable organic substance and alternative source of energy; however, its structure confounds the liberation of monosaccharides. Pretreating rice straw using a TiO(2)/UV system facilitated its hydrolysis with Accellerase 1000(™), suggesting that hydroxyl radicals (OH·) from the TiO(2)/UV system could degrade lignin and carbohydrates. TiO(2)/UV pretreatment was an essential step for conversion of hemicellulose to xylose; optimal conditions for this conversion were a TiO(2) concentration of 0.1% (w/v) and an irradiation time of 2 h with a UV-C lamp at 254 nm. After enzymatic hydrolysis, the sugar yields from rice straw pretreated with these parameters were 59.8 ± 0.7% of the theoretical for glucose (339 ± 13 mg/g rice straw) and 50.3 ± 2.8% for xylose (64 ± 3 mg/g rice straw). The fermentation of enzymatic hydrolysates containing 10.5 g glucose/L and 3.2 g xylose/L with Pichia stipitis produced 3.9 g ethanol/L with a corresponding yield of 0.39 g/g rice straw. The maximum possible ethanol conversion rate is 76.47%. TiO(2)/UV pretreatment can be performed at room temperature and atmospheric pressure and demonstrates potential in large-scale production of fermentable sugars. PMID:21909680

  15. 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.

  16. Both Enhanced Biocompatibility and Antibacterial Activity in Ag-Decorated TiO2 Nanotubes

    PubMed Central

    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. PMID:24124484

  17. 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

    2016-06-01

    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.

  18. Arsenic removal from water employing heterogeneous photocatalysis with TiO2 immobilized in PET bottles.

    PubMed

    Fostier, Anne Hélène; Pereira, Maria do Socorro Silva; Rath, Susanne; Guimarães, José Roberto

    2008-05-01

    Arsenic oxidation (As(III) to As(V)) and As(V) removal from water were assessed by using TiO2 immobilized in PET (polyethylene terephthalate) bottles in the presence of natural sunlight and iron salts. The effect of many parameters was sequentially studied: TiO2 concentration of the coating solution, Fe(II) concentration, pH, solar irradiation time; dissolved organic carbon concentration. The final conditions (TiO2 concentration of the coating solution: 10%; Fe(II): 7.0 mg l(-1); solar exposure time: 120 min) were applied to natural water samples spiked with 500 microg l(-1) As(III) in order to verify the influence of natural water matrix. After treatment, As(III) and total As concentrations were lower than the limit of quantitation (2 microg l(-1)) of the voltammetric method used, showing a removal over 99%, and giving evidence that As(III) was effectively oxidized to As(V). The results obtained demonstrated that TiO2 can be easily immobilized on a PET surface in order to perform As(III) oxidation in water and that this TiO2 immobilization, combined with coprecipitation of arsenic on Fe(III) hydroxides(oxides) could be an efficient way for inorganic arsenic removal from groundwaters. PMID:18342358

  19. Synthesis of biomorphological mesoporous TiO2 templated by mimicking bamboo membrane in supercritical CO2.

    PubMed

    Li, Jinhong; Shi, Xiaoying; Wang, Lijuan; Liu, Fei

    2007-11-01

    A new approach is presented for preparing biomorphological mesoporous TiO2 templated by mimicking bamboo inner shell membrane via supercritical CO2 (SCCO2) transportation through titanium tetrabutyloxide (TTBO). The analysis of wide-angle X-ray powder diffraction (XRD) showed the prepared TiO2 in phase of anatase, and the small-angle XRD revealed the presence of mesopores without periodicity. The product exhibited the shape of crinkled films and extended in two dimensions up to centimeters. The electron microscopic observation showed that the TiO2 films were around 200 nm in thickness, and across the films there were numerous round or ellipse-shaped mesopores, being 10-50 nm in diameter, which were formed by the close packing of TiO2 particles. High-resolution transmission electron microscope (HRTEM) displayed that the single TiO2 particle size was about 12.5 nm. The UV-vis absorption spectrum was transparent in the wavelength of 320-350 nm for suspensions of the prepared mesoporous TiO2 in ethanol at the concentration of 5.0 mg/l. The mesoporous TiO2 prepared with the aid of SCCO2 exhibited an obvious blue shift compared with the TiO2 prepared by sol-gel infiltration. The possible mechanism for the formation of the mesoporous TiO2 is summarized into a biomimetic mineralization pathway. First, TTBO was transported to the membrane surface via SCCO2, and then condensed. Hydrolysis reactions between the functional groups of organic membrane and TTBO took place to form the nuclear TiO2, and the TiO2 seeds grew around the organic membrane into TiO2 mesoporous materials. The approach provides a low-cost and efficient route for the production of ceramics nanomaterials with unique structural features, which may have potential application in designing UV-selective shielding devices [S. Zhao, X.H. Wang, S.B. Xin, Q. Jiang, X.P. Liang, Rare Metal Mater. Eng. 35 (2006) 508-510]. PMID:17689547

  20. Hydrophilicity, photocatalytic activity and stability of tetraethyl orthosilicate modified TiO2 film on glazed ceramic surface

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Tian, Jie; Xu, Ruifen; Ma, Guojun

    2013-02-01

    A new, simple, and low-cost method has been developed to enhance the surface properties of TiO2 film. Degussa P25-TiO2 nanoparticles were modified by tetraethyl orthosilicate (TEOS) on glazed ceramic tiles. Effects of tetraethyl orthosilicate modification on microstructure, crystal structure, hydrophilicity, photocatalytic activity and stability of the film were investigated. The obtained results showed that P25-TiO2/TEOS particles exhibited better dispersion, higher surface area, bigger surface roughness and smaller particle size comparing to pure P25-TiO2 particles, which resulted in better hydrophilicity after 10 days in a dark place and higher photocatalytic activity under visible light irradiation. 68% of Rhodamine B was degraded by P25-TiO2/TEOS film in 25 h with the light intensity of 5000 ± 500 lx, and degradation rate reached to 82% with the light intensity of 10,000 ± 1000 lx. Furthermore, two fundamentally different systems, in which the films recycle for repetitive degradation after soaked in dye solution and for discoloration after depositing dye on the surfaces, respectively, were measured to confirm that P25-TiO2/TEOS film showed excellently stable performances. Therefore the P25-TiO2/TEOS film we obtained has good washing resistance and would be a promising candidate for practical applications.

  1. 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.

  2. 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.

  3. 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. PMID:23602671

  4. 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.

  5. Photopatterning Proteins and Cells in Aqueous Environment Using TiO2 Photocatalysis.

    PubMed

    Yamamoto, Hideaki; Demura, Takanori; Sekine, Kohei; Kono, Sho; Niwano, Michio; Hirano-Iwata, Ayumi; Tanii, Takashi

    2015-01-01

    Organic contaminants adsorbed on the surface of titanium dioxide (TiO2) can be decomposed by photocatalysis under ultraviolet (UV) light. Here we describe a novel protocol employing the TiO2 photocatalysis to locally alter cell affinity of the substrate surface. For this experiment, a thin TiO2 film was sputter-coated on a glass coverslip, and the TiO2 surface was subsequently modified with an organosilane monolayer derived from octadecyltrichlorosilane (OTS), which inhibits cell adhesion. The sample was immersed in a cell culture medium, and focused UV light was irradiated to an octagonal region. When a neuronal cell line PC12 cells were plated on the sample, cells adhered only on the UV-irradiated area. We further show that this surface modification can also be performed in situ, i.e., even when cells are growing on the substrate. Proper modification of the surface required an extracellular matrix protein collagen to be present in the medium at the time of UV irradiation. The technique presented here can potentially be employed in patterning multiple cell types for constructing coculture systems or to arbitrarily manipulate cells under culture. PMID:26554338

  6. 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

  7. Fermi level shifting of TiO2 nanostructures during dense electronic excitation

    NASA Astrophysics Data System (ADS)

    Kumar, Avesh; Jaiswal, M. K.; Kanjilal, D.; Joshi, Rakesh K.; Mohanty, T.

    2011-07-01

    Scanning Kelvin probe microscopy has been used to understand the modification of work function of TiO2 with swift heavy ion irradiation. The observed increase in contact potential difference (CPD) indicates a shift in Fermi level towards the valence band, which is due to the development of defects during the bombardment of high energy heavy ions. The change in CPD values on ion irradiation is attributed to electronic excitation induced defect concentration and surface roughness.

  8. Novel coupled structures of FeWO4/TiO2 and FeWO4/TiO2/CdS designed for highly efficient visible-light photocatalysis.

    PubMed

    Bera, Sandipan; Rawal, Sher Bahadur; Kim, Hark Jin; Lee, Wan In

    2014-06-25

    A quadrilateral disk-shaped FeWO4 nanocrystal (NC) with an average size of ∼35 nm was prepared via hydrothermal reaction. The obtained dark brown FeWO4 NC with a bandgap (Eg) of 1.98 eV was then coupled with TiO2 to form FeWO4/TiO2 composites. The valence band (VB) of FeWO4 (+2.8 eV vs NHE) was more positive than that of TiO2 (+2.7 eV); thus this system could be classified as a Type-B heterojunction. Under visible-light irradiation, 5/95 FeWO4/TiO2 (by wt %) exhibited remarkable photocatalytic activity: the amount of CO2 evolved from gaseous 2-propanol (IP) and the decomposition rate of aqueous salicylic acid (SA) were, respectively, 1.7 and 2.5 times greater than those of typical nitrogen-doped TiO2 (N-TiO2). This unique catalytic property was deduced to arise from the intersemiconductor hole transfer between the VBs of FeWO4 and TiO2. Herein, several experimental evidence were also provided to confirm the hole-transfer mechanism. To further enhance the catalytic efficiency, double-heterojunctioned FeWO4/TiO2/CdS composites were prepared by loading CdS quantum dots (QDs) onto the FeWO4/TiO2 surface. Surprisingly, the catalytic activity for evolving CO2 from IP was 2.6 times greater than that of bare FeWO4/TiO2 and 4.4 times greater than that of N-TiO2, suggesting that both holes and electrons were essential species in decomposing organic compounds. PMID:24847976

  9. 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

    2015-06-01

    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. PMID:25974749

  10. 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. PMID:25743764