Synthesis of core-shell bioaffinity chitosan-TiO₂ composite and its environmental applications.

PubMed

Xiao, Gang; Su, Haijia; Tan, Tianwei

2015-01-01

Based on the coupling of molecular imprinting, chitosan biosorption, and nano TiO2 photocatalysis technologies, a novel core-shell organic-inorganic hybrid material of surface imprinted chitosan-TiO2 composite (SICT) was prepared with methyl orange as the template. SEM, EDS, AFM, pore size analysis, and FTIR characterization results illustrated that TiO2 nano powder was successfully coated on the surface of chitosan microparticles via intermolecular hydrogen bonds to form the core-shell organic-inorganic composites with rough and porous surface morphology. SICT showed enhanced photocatalytic selectivity for methyl orange (M.O.) compared with the non-imprinted chitosan-TiO2 composites because of the existing of more suitable sites generated by surface molecular imprinting. The removal of M.O. by SICT was mainly from the photocatalytic degradation rather than simple adsorption. SICT could be reused directly without further desorption and regeneration for 10 cycles with preserving 60% of its photocatalytic efficiency. The reusability of SICT would be beneficial for the simplification of the operating steps and the cost reduction which facilitated its practical applications in wastewater treatment concerning environmental organic pollutants. Copyright © 2014 Elsevier B.V. All rights reserved.

Rational design of carbon and TiO2 assembly materials: covered or strewn, which is better for photocatalysis?

PubMed

Cui, Guan-wei; Wang, Wei-liang; Ma, Ming-yue; Zhang, Ming; Xia, Xin-yuan; Han, Feng-yun; Shi, Xi-feng; Zhao, Ying-qiang; Dong, Yu-bin; Tang, Bo

2013-07-21

The rational design of carbonaceous hybrid nanostructures is very important for obtaining high photoactivity. TiO2 particles strewn with an optimal quantity of carbon nanodots have a much higher photoactivity than that of TiO2 covered with a carbon layer, showing the importance of carbon morphology in the photocatalysis of carbonaceous hybrid nanostructures.

Degradation kinetics and mechanism of RDX and HMX in TiO2 photocatalysis.

PubMed

Choi, J K; Son, H S; Kim, T S; Stenstrom, M K; Zoh, K D

2006-02-01

This study was undertaken to examine the photocatalytic degradation of explosives hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) with a circular photocatalytic reactor, using a UV lamp as a light source and TiO2 as a photocatalyst. The effects of various parameters, such as the RDX or HMX concentration, the amount of TiO, and the initial pH, on the photocatalytic degradation rates of explosives were examined. In the presence of both UV light and TiO2 RDX and HMX were more effectively degraded than with either UV or TiO2 alone. The degradation rates were found to obey pseudo-first-order kinetics represented by the Langmuir-Hinshelwood model. Increases in the RDX and HMX degradation rates were obtained with decreasing initial concentrations of the explosives. The RDX and HMX degradation rates were higher at pH 7 than at either pH 3 or pH 11. A dose of approximately 0.7 g l(-1) of TiO2 degraded HMX more rapidly than did higher or lower TiO2 doses. RDX (20 mg l(-1)) photocatalysis resulted in an approximately 20% decrease in TOC, and HMX (5 mg l(-1)) photocatalysis resulted in a 60%, decrease in TOC within 150 minutes. A trace amount of formate was produced as an intermediate that was further mineralized by RDX or HMX photocatalysis. The nitrogen byproducts from the photocatalysis of RDX and HMX were mainly NO3- with NO2-, and NH4+. The total nitrogen recovery was about 60% from RDX (20 mg l(-1)), and 70% from HMX (5 mg l(-1)), respectively. Finally, a mechanism for RDX/HMX photocatalysis was proposed, along with supporting qualitative and quantitative evidence.

Study on the photocatalytic reaction kinetics in a TiO2 nanoparticles coated microreactor integrated microfluidics device.

PubMed

Liu, Ai-Lin; Li, Zhong-Qiu; Wu, Zeng-Qiang; Xia, Xing-Hua

2018-05-15

For study of the photocatalytic reaction kinetics in a confined microsystem, a photocatalysis microreactor integrated on a microfluidic device has been fabricated using an on-line UV/vis detector. The performance of the photocatalysis microreactor is evaluated by the photocatalytic degradation of Rhodamine B chosen as model target by using commercial titanium dioxide (Degussa P25, TiO 2 ) nanoparticles as a photocatalyst. Results show that the photocatalytic reaction occurs via the Langmuir-Hinshelwood mechanism and the photocatalysis kinetics in the confined microsystem (r = 0.359 min -1 ) is about 10 times larger than that in macrosystem (r = 0.033 min -1 ). In addition, the photocatalysis activity of the immobilized TiO 2 nanoparticles in the microreactor exhibits good stability under flowing conditions. The present microchip device offers an interesting platform for screening of photocatalysts and exploration of photocatalysis mechanisms and kinetics. Copyright © 2018 Elsevier B.V. All rights reserved.

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. Copyright © 2015 Elsevier Inc. All rights reserved.

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.

Removal of antibiotic cloxacillin by means of electrochemical oxidation, TiO2 photocatalysis, and photo-Fenton processes: analysis of degradation pathways and effect of the water matrix on the elimination of antimicrobial activity.

PubMed

Serna-Galvis, Efraim A; Giraldo-Aguirre, Ana L; Silva-Agredo, Javier; Flórez-Acosta, Oscar A; Torres-Palma, Ricardo A

2017-03-01

This study evaluates the treatment of the antibiotic cloxacillin (CLX) in water by means of electrochemical oxidation, TiO 2 photocatalysis, and the photo-Fenton system. The three treatments completely removed cloxacillin and eliminated the residual antimicrobial activity from synthetic pharmaceutical wastewater containing the antibiotic, commercial excipients, and inorganic ions. However, significant differences in the degradation routes were found. In the photo-Fenton process, the hydroxyl radical was involved in the antibiotic removal, while in the TiO 2 photocatalysis process, the action of both the holes and the adsorbed hydroxyl radicals degraded the pollutant. In the electrochemical treatment (using a Ti/IrO 2 anode in sodium chloride as supporting electrolyte), oxidation via HClO played the main role in the removal of CLX. The analysis of initial by-products showed five different mechanistic pathways: oxidation of the thioether group, opening of the central β-lactam ring, breakdown of the secondary amide, hydroxylation of the aromatic ring, and decarboxylation. All the oxidation processes exhibited the three first pathways. Moreover, the aromatic ring hydroxylation was found in both photochemical treatments, while the decarboxylation of the pollutant was only observed in the TiO 2 photocatalysis process. As a consequence of the degradation routes and mechanistic pathways, the elimination of organic carbon was different. After 480 and 240 min, the TiO 2 photocatalysis and photo-Fenton processes achieved ∼45 and ∼15 % of mineralization, respectively. During the electrochemical treatment, 100 % of the organic carbon remained even after the antibiotic was treated four times the time needed to degrade it. In contrast, in all processes, a natural matrix (mineral water) did not considerably inhibit pollutant elimination. However, the presence of glucose in the water significantly affected the degradation of CLX by means of TiO 2 photocatalysis.

A Surface Science Perspective on TiO2 Photocatalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henderson, Michael A.

2011-06-15

The field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO2 photochemistry and photocatalysis. This review highlights, from a surface science perspective, recent literature providing molecular-level insights into phonon-initiated events on TiO2 surfaces obtained in seven key scientific issues: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form.

Chemical mechanisms of photocatalytic de-soiling and de-polluting processes in indoor environments and urban surfaces

NASA Astrophysics Data System (ADS)

Sleiman, M.; Rosseler, O.; Montesinos, N.; Litter, M.; Bikiel, D.; Kirchstetter, T.; Bluhm, H.; Ahmed, M.; Salmeron, M.; Destaillats, H.

2013-12-01

Photocatalysis has been postulated as a promising approach for the de-pollution of indoor air and urban atmospheres, and for self-cleaning surfaces. Building materials and coatings containing nano-sized TiO2 photocatalytic functionalities are gaining market share, including self-cleaning building envelope materials (coatings, mortar, plaster, architectural fabrics and tiles) and indoor air purifiers. While many studies have reported good performance of photocatalysis in the removal of organic pollutants from indoor air, more information is needed to understand secondary emissions of potentially harmful byproducts from photocatalytic air cleaners. This presentation will describe analytical methods and experimental results from room-sized chamber experiments using a realistic challenge VOC mixture at low ppb levels. We will also present results from separate studies that used synchrotron-based surface spectroscopic and mass spectrometric methods to better understand the photocatalytic mechanisms that regulate the de-soiling and de-polluting activity. Two photocatalytic processes were studied: de-noxification (NOx removal) and de-soiling (removal of deposited black carbon or soot). Ambient pressure XPS was used to study surface and gas-phase species formed during adsorption of NO2 on TiO2 and subsequent UV irradiation at λ = 365 nm. The results illustrate how NOx chemistry on TiO2 surfaces can be affected by the presence of water vapor, heteroatoms present as impurities, and carbonaceous soiling. The reactivity of NOx and NO3- on surfaces leads to reduced adsorbed and gas-phase nitrogenated species. These processes need to be considered in the engineering of depolluting materials and incorporated into atmospheric models. De-soiling properties were investigated by analyzing soot oxidation on TiO2 surfaces. Model soot samples were used as surrogates of urban grime. Using laser desorption coupled with time-of-flight (TOF) mass spectrometry synchrotron ionization, we investigated the mechanisms of photocatalytic soot removal under UVA irradiation. Ancillary reflectance measurements were performed to determine the efficiency and kinetics of soot removal.

Wet-Chemical Preparation of TiO2-Based Composites with Different Morphologies and Photocatalytic Properties

PubMed Central

Xiang, Liqin; Zhao, Xiaopeng

2017-01-01

TiO2-based composites have been paid significant attention in the photocatalysis field. The size, crystallinity and nanomorphology of TiO2 materials have an important effect on the photocatalytic efficiency. The synthesis and photocatalytic activity of TiO2-based materials have been widely investigated in past decades. Based on our group’s research works on TiO2 materials, this review introduces several methods for the fabrication of TiO2, rare-earth-doped TiO2 and noble-metal-decorated TiO2 particles with different morphologies. We focused on the preparation and the formation mechanism of TiO2-based materials with unique structures including spheres, hollow spheres, porous spheres, hollow porous spheres and urchin-like spheres. The photocatalytical activity of urchin-like TiO2, noble metal nanoparticle-decorated 3D (three-dimensional) urchin-like TiO2 and bimetallic core/shell nanoparticle-decorated urchin-like hierarchical TiO2 are briefly discussed. PMID:28991208

Preparation of TiO2-ZnO and its activity test in sonophotocatalytic degradation of phenol

NASA Astrophysics Data System (ADS)

Fatimah, Is; Novitasari

2016-02-01

Synthesis of TiO2-ZnO and its activity test in Sono photocatalysis degradation of phenol has been conducted. The synthesis was performed by the sol-gel mechanism by using titanium isopropoxide and zinc acetate as precursors with the Ti: Zn ratio of 5:1. Characterization of material were conducted by x-ray diffraction analysis, surface area analysis and also diffuse reflectance UV-Visible spectrophotometry. The material obtained from the synthesis was tested in photocatalysis, Sono catalysis and Sono photocatalysis degradation of phenol solution. Results showed that material exhibited the activity of varied mechanism o- phenol degradation. In advance, the Sono photocatalysis degradation produced the synergy index of 1.169 compared to both photocatalysis and Sono catalysis.

Photo-induced transformation process at gold clusters-semiconductor interface: Implications for the complexity of gold clusters-based photocatalysis

PubMed Central

Liu, Siqi; Xu, Yi-Jun

2016-01-01

The recent thrust in utilizing atomically precise organic ligands protected gold clusters (Au clusters) as photosensitizer coupled with semiconductors for nano-catalysts has led to the claims of improved efficiency in photocatalysis. Nonetheless, the influence of photo-stability of organic ligands protected-Au clusters at the Au/semiconductor interface on the photocatalytic properties remains rather elusive. Taking Au clusters–TiO2 composites as a prototype, we for the first time demonstrate the photo-induced transformation of small molecular-like Au clusters to larger metallic Au nanoparticles under different illumination conditions, which leads to the diverse photocatalytic reaction mechanism. This transformation process undergoes a diffusion/aggregation mechanism accompanied with the onslaught of Au clusters by active oxygen species and holes resulting from photo-excited TiO2 and Au clusters. However, such Au clusters aggregation can be efficiently inhibited by tuning reaction conditions. This work would trigger rational structural design and fine condition control of organic ligands protected-metal clusters-semiconductor composites for diverse photocatalytic applications with long-term photo-stability. PMID:26947754

Photo-induced transformation process at gold clusters-semiconductor interface: Implications for the complexity of gold clusters-based photocatalysis

NASA Astrophysics Data System (ADS)

Liu, Siqi; Xu, Yi-Jun

2016-03-01

The recent thrust in utilizing atomically precise organic ligands protected gold clusters (Au clusters) as photosensitizer coupled with semiconductors for nano-catalysts has led to the claims of improved efficiency in photocatalysis. Nonetheless, the influence of photo-stability of organic ligands protected-Au clusters at the Au/semiconductor interface on the photocatalytic properties remains rather elusive. Taking Au clusters-TiO2 composites as a prototype, we for the first time demonstrate the photo-induced transformation of small molecular-like Au clusters to larger metallic Au nanoparticles under different illumination conditions, which leads to the diverse photocatalytic reaction mechanism. This transformation process undergoes a diffusion/aggregation mechanism accompanied with the onslaught of Au clusters by active oxygen species and holes resulting from photo-excited TiO2 and Au clusters. However, such Au clusters aggregation can be efficiently inhibited by tuning reaction conditions. This work would trigger rational structural design and fine condition control of organic ligands protected-metal clusters-semiconductor composites for diverse photocatalytic applications with long-term photo-stability.

Photoactive glazed polymer-cement composite

NASA Astrophysics Data System (ADS)

Baltes, Liana; Patachia, Silvia; Tierean, Mircea; Ekincioglu, Ozgur; Ozkul, Hulusi M.

2018-04-01

Macro defect free cements (MDF), a kind of polymer-cement composites, are characterized by remarkably high mechanical properties. Their flexural strengths are 20-30 times higher than those of conventional cement pastes, nearly equal to that of an ordinary steel. The main drawback of MDF cements is their sensitivity to water. This paper presents a method to both diminish the negative impact of water on MDF cements mechanical properties and to enlarge their application by conferring photoactivity. These tasks were solved by glazing MDF cement with an ecological glaze containing nano-particles of TiO2. Efficiency of photocatalytic activity of this material was tested against methylene blue aqueous solution (4.4 mg/L). Influence of the photocatalyst concentration in the glaze paste and of the contact time on the photocatalysis process (efficiency and kinetic) was studied. The best obtained photocatalysis yield was of 97.35%, after 8 h of exposure to 254 nm UV radiation when used an MDF glazed with 10% TiO2 in the enamel paste. Surface of glazed material was characterized by optic microscopy, scratch test, SEM, XRD, and EDS. All these properties were correlated with the aesthetic aspect of the glazed surface aiming to propose using of this material for sustainable construction development.

Advanced oxidation treatment of pulp mill effluent for TOC and toxicity removals.

PubMed

Catalkaya, Ebru Cokay; Kargi, Fikret

2008-05-01

Pulp mill effluent was treated by different advanced oxidation processes (AOPs) consisting of UV, UV/H2O2, TiO2-assisted photo-catalysis (UV/TiO2) and UV/H2O2/TiO2 in lab-scale reactors for total organic carbon (TOC) and toxicity removals. Effects of some operating parameters such as the initial pH, oxidant and catalyst concentrations on TOC and toxicity removals were investigated. Almost every method resulted in some degree of TOC and toxicity removal from the pulp mill effluent. However, the TiO2-assisted photo-catalysis (UV/TiO2) resulted in the highest TOC and toxicity removals under alkaline conditions when compared with the other AOPs tested. Approximately, 79.6% TOC and 94% toxicity removals were obtained by the TiO2-assisted photo-catalysis (UV/TiO2) with a titanium dioxide concentration of 0.75gl(-1) at pH 11 within 60min.

Preparation, characterization, and application of titanium nano-tube array in dye-sensitized solar cells

PubMed Central

2012-01-01

The vertically orientated TiO2 nanotube array (TNA) decorated with TiO2 nano-particles was successfully fabricated by electrochemically anodizing titanium (Ti) foils followed by Ti-precursor post-treatment and annealing process. The TNA morphology characterized by SEM and TEM was found to be filled with TiO2 nano-particles interior and exterior of the TiO2 nano-tubes after titanium (IV) n-butoxide (TnB) treatment, whereas TiO2 nano-particles were only found inside of TiO2 nano-tubes upon titanium tetrachloride (TiCl4) treatment. The efficiency in TNA-based DSSCs was improved by both TnB and TiCl4 treatment presumably due to the increase of dye adsorption. PMID:22353282

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

PubMed

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

2007-02-01

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henderson, Michael A.; Lyubinetsky, Igor

The field of heterogeneous photocatalysis has grown considerably in the decades since Fujishima and Honda's ground-breaking publications of photoelectrochemistry on TiO2. Numerous review articles continue to point to both progress made in the use of heterogeneous materials (such as TiO2) to perform photoconversion processes, and the many opportunities and challenges in heterogeneous photocatalysis research such as solar energy conversion and environmental remediation. The past decade has also seen an increase in the use of molecular-level approaches applied to model single crystal surfaces in an effort to obtain new insights into photocatalytic phenomena. In particular, scanning probe techniques (SPM) have enabledmore » researchers to take a ‘nanoscale’ approach to photocatalysis that includes interrogation of the reactivities of specific sites and adsorbates on a model photocatalyst surface. The rutile TiO2(110) surface has become the prototypical oxide single crystal surface for fundamental studies of many interfacial phenomena. In particular, TiO2(110) has become an excellent model surface for probing photochemical and photocatalytic reactions at the molecular level. A variety of experimental approaches have emerged as being ideally suited for studying photochemical reactions on TiO2(110), including desorption-oriented approaches and electronic spectroscopies, but perhaps the most promising techniques for evaluating site-specific properties are those of SPM. In this review, we highlight the growing use of SPM techniques in providing molecular-level insights into surface photochemistry on the model photocatalyst surface of rutile TiO2(110). Our objective is to both illustrate the unique knowledge that scanning probe techniques have already provided the field of photocatalysis, and also to motivate a new generation of effort into the use of such approaches to obtain new insights into the molecular level details of photochemical events occurring at interfaces. Discussion will start with an examination of how scanning probe techniques are being used to characterize the TiO2(110) surface in ways that are relevant to photocatalysis. We will then discuss specific classes of photochemical reaction on TiO2(110) for which SPM has proven indispensible in providing unique molecular-level insights, and conclude with discussion of future areas in which SPM studies may prove valuable to photocatalysis on TiO2. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. I.L. was partially supported by a Pacific Northwest National Laboratory (PNNL) Chemical Imaging Initiative project. PNNL is a multiprogram national laboratory operated for DOE by Battelle.« less

Environmental assessment of different advanced oxidation processes applied to a bleaching Kraft mill effluent.

PubMed

Muñoz, Iván; Rieradevall, Joan; Torrades, Francesc; Peral, José; Domènech, Xavier

2006-01-01

Different advanced oxidation processes (AOPs) have been applied to remove the organic carbon content of a paper mill effluent originating from the Kraft pulp bleaching process. The considered AOPs were: TiO(2)-mediated heterogeneous photocatalysis, TiO(2)-mediated heterogeneous photocatalysis assisted with H(2)O(2), TiO(2)-mediated heterogeneous photocatalysis coupled with Fenton, photo-Fenton, ozonation and ozonation with UV-A light irradiation. The application of the selected AOPs all resulted in a considerable decrease in dissolved organic carbon (DOC) content with variable treatment efficiencies depending upon the nature/type of the applied AOP. A Life Cycle Assessment (LCA) study was used as a tool to compare the different AOPs in terms of their environmental impact. Heterogeneous photocatalysis coupled with the Fenton's reagent proved to have the lowest environmental impact accompanied with a moderate-to-high DOC removal rate. On the other hand, heterogeneous photocatalysis appeared to be the worst AOP both in terms of DOC abatement rate and environmental impact. For the studied AOPs, LCA has indicated that the environmental impact was attributable to the high electrical energy (power) consumption necessary to run a UV-A lamp or to produce ozone.

Degradation mechanism and the toxicity assessment in TiO2 photocatalysis and photolysis of parathion.

PubMed

Kim, Tak-Soo; Kim, Jung-Kon; Choi, Kyungho; Stenstrom, Michael K; Zoh, Kyung-Duk

2006-02-01

The photocatalytic degradation of methyl parathion was carried out using a circulating TiO2/UV reactor. The experimental results showed that parathion was more effectively degraded in the photocatalytic condition than the photolysis and TiO2-only condition. With photocatalysis, 10mg/l parathion was completely degraded within 60 min with a TOC decrease exceeding 90% after 150 min. The main ionic byproducts during photocatalysis were measured. The nitrogen from parathion was recovered mainly as NO3-, NO2- and NH4+, 80% of the sulfur as SO4(2-), and less than 5% of the phosphorus as PO4(3-). The organic intermediates 4-nitrophenol and paraoxon were also identified, and these were further degraded. Two different bioassays (Vibrio fischeri and Daphnia magna) were used to test the acute toxicity of solutions treated by photocatalysis and photolysis. A Microtox test using V. fischeri showed that the toxicity, expressed as the relative toxicity (%), was reduced almost completely after 90 min under photocatalysis, whereas only an 83% reduction was achieved with photolysis alone. Another toxicity test using D. magna also showed that the relative toxicity disappeared after 90 min under photocatalysis, whereas there was a 65% reduction in relative toxicity with photolysis alone. The pattern of toxicity reduction parallels the decrease in parathion and TOC concentrations.

Synergetic Effect of Ultrasound, the Heterogeneous Fenton Reaction and Photocatalysis by TiO2 Loaded on Nickel Foam on the Degradation of Pollutants

PubMed Central

Qiu, Shan; Xu, Shanwen; Li, Guangming; Yang, Jixian

2016-01-01

The synergistic effect of ultrasound, the heterogeneous Fenton reaction and photocatalysis was studied using a nickel foam (NF)-supporting TiO2 system and rhodamine B (RhB) as a target. The NF-supporting TiO2 system was prepared by depositing TiO2 on the skeleton of NF repeatedly and then calcining it. To optimize the conditions and parameters, the catalytic activity was tested in four systems (ultrasound alone (US), nickel foam (NF), US/NF and NF/US/H2O2). The optimal conditions were fixed at 0.1 g/mL NF, initial 5.00 mg/L RhB, 300 W ultrasonic power, pH = 3 and 5.00 mg/L H2O2. The effects of the dissolution of nickel from NF and quenching of the Fenton reaction were studied on degradation efficiency. When the heterogeneous Fenton reaction is combined with TiO2-photocatalysis, the pollutant removal efficiency is enhanced significantly. Through this synergistic effect, 22% and 80% acetochlor was degraded within 10 min and 80 min, respectively. PMID:28773580

Municipal wastewater spiramycin removal by conventional treatments and heterogeneous photocatalysis.

PubMed

Lofrano, G; Libralato, G; Casaburi, A; Siciliano, A; Iannece, P; Guida, M; Pucci, L; Dentice, E F; Carotenuto, M

2018-05-15

This study assessed the effects and removal options of the macrolide spiramycin, currently used for both in human and veterinary medicine- with a special focus on advanced oxidation processes based on heterogeneous TiO 2 _ assisted photocatalysis. Spiramycin real concentrations were investigated on a seasonal basis in a municipal wastewater treatment plant (up to 35μgL -1 ), while its removal kinetics were studied considering both aqueous solutions and real wastewater samples, including by-products toxicity assessment. High variability of spiramycin removal by activated sludge treatments (from 9% (wintertime) to >99.9% (summertime)) was observed on a seasonal basis. Preliminary results showed that a total spiramycin removal (>99.9%) is achieved with 0.1gL -1 of TiO 2 in aqueous solution after 80min. Integrated toxicity showed residual slight acute effects in the photocatalytic treated solutions, independently from the amount of TiO 2 used, and could be linked to the presence of intermediate compounds. Photolysis of wastewater samples collected after activated sludge treatment during summer season (SPY 5μgL -1 ) allowed a full SPY removal after 80min. When photocatalysis with 0.1gL -1 of TiO 2 was carried out in wastewater samples collected in winter season (SPY 30μgL -1 ) after AS treatment, SPY removal was up to 91% after 80min. Copyright © 2017 Elsevier B.V. All rights reserved.

Understanding the superior photocatalytic activity of noble metals modified titania under UV and visible light irradiation.

PubMed

Bumajdad, Ali; Madkour, Metwally

2014-04-28

Although TiO2 is one of the most efficient photocatalysts, with the highest stability and the lowest cost, there are drawbacks that hinder its practical applications like its wide band gap and high recombination rate of the charge carriers. Consequently, many efforts were directed toward enhancing the photocatalytic activity of TiO2 and extending its response to the visible region. To head off these attempts, modification of TiO2 with noble metal nanoparticles (NMNPs) received considerable attention due to their role in accelerating the transfer of photoexcited electrons from TiO2 and also due to the surface plasmon resonance which induces the photocatalytic activity of TiO2 under visible light irradiation. This insightful perspective is devoted to the vital role of TiO2 photocatalysis and its drawbacks that urged researchers to find solutions such as modification with NMNPs. In a coherent context, we discussed here the characteristics which qualify NMNPs to possess a great enhancement effect for TiO2 photocatalysis. Also we tried to understand the reasons behind this effect by means of photoluminescence (PL) and electron paramagnetic resonance (EPR) spectra, and Density Functional Theory (DFT) calculations. Then the mechanism of action of NMNPs upon deposition on TiO2 is presented. Finally we introduced a survey of the behaviour of these noble metal NPs on TiO2 based on the particle size and the loading amount.

Enhanced near-infrared photocatalysis of NaYF4:Yb, Tm/CdS/TiO2 composites.

PubMed

Guo, Xingyuan; Di, Weihua; Chen, Changfeng; Liu, Chunxu; Wang, Xue; Qin, Weiping

2014-01-21

The previous works by our group (Chem. Commun., 2010, 46, 2304-2306; ACS Catal., 2013, 3, 405-412; Phys. Chem. Chem. Phys., 2013, 15, 14681-14688) have reported the near-infrared-driven photocatalysis of broadband semiconductor TiO2 or ZnO that was combined with upconverting luminescence particles to form a core-shell structure. However, the photocatalytic efficiency is low for this new type of photocatalysts. In this work, NaYF4:Yb,Tm/CdS/TiO2 composites for NIR photocatalysis were prepared by linking CdS and TiO2 nanocrystals on the NaYF4:Yb,Tm microcrystal surfaces. CdS and TiO2 were well interacted to form a heterojunction structure. The energy transfer between NaYF4:Yb,Tm and the semiconductors CdS and TiO2 was investigated by steady-state and dynamic fluorescence spectroscopy. The photocatalytic activities of the as-prepared composites were evaluated by the degradation of methylene blue in aqueous solution upon NIR irradiation. Significantly, it was found that the united adhesions of CdS and TiO2 on the NaYF4:Yb,Tm particle surfaces showed much higher catalytic activities than the individual adhesion of CdS or TiO2 on the NaYF4:Yb,Tm surfaces. This was attributed mainly to the effective separation of the photogenerated electron-hole pairs due to the charge transfer across the CdS-TiO2 interface driven by the band potential difference between them. The presented composite structure of upconverting luminescence materials coupled with narrow/wide semiconductor heterojunctions provides a new model for improved NIR photocatalysis.

Synthesis and characterization of TiO₂ and TiO₂/Ag for use in photodegradation of methylviologen, with kinetic study by laser flash photolysis.

PubMed

Ramos, Dayana Doffinger; Bezerra, Paula C S; Quina, Frank H; Dantas, Renato F; Casagrande, Gleison A; Oliveira, Silvio C; Oliveira, Márcio R S; Oliveira, Lincoln C S; Ferreira, Valdir S; Oliveira, Samuel L; Machulek, Amilcar

2015-01-01

This paper reports the synthesis, characterization, and application of TiO2 and TiO2/Ag nanoparticles for use in photocatalysis, employing the herbicide methylviologen (MV) as a substrate for photocatalytic activity testing. At suitable metal to oxide ratios, increases in silver surface coating on TiO2 enhanced the efficiency of heterogeneous photocatalysis by increasing the electron transfer constant. The sol-gel method was used for TiO2 synthesis. P25 TiO2 was the control material. Both oxides were subjected to the same silver incorporation process. The materials were characterized by conventional spectroscopy, SEM micrography, X-ray diffraction, calculation of surface area per mass of catalyst, and thermogravimetry. Also, electron transfers between TiO2 or TiO2/Ag and MV in the absence and presence of sodium formate were investigated using laser flash photolysis. Oxides synthesized with 2.0 % silver exhibited superior photocatalytic activity for MV degradation.

Microwave-assisted solvothermal synthesis of hierarchical TiO2 microspheres for efficient electro-field-assisted-photocatalytic removal of tributyltin in tannery wastewater.

PubMed

Zhao, Yang; Huang, Zhiding; Chang, Wenkai; Wei, Chao; Feng, Xugen; Ma, Lin; Qi, Xiaoxia; Li, Zenghe

2017-07-01

Organotin compounds have been widely used in recent decades, however, the residential tributyltin (TBT) in environment has potential harmful effects on human health due to the disruption of endocrine system even at trace level. Herein, this work reports on an effective electro-field-assisted-photocatalytic technique for removal of TBT by applying an electric field to photocatalysis of as-prepared hierarchical TiO 2 microspheres. The synthesis of catalytic materials is based on a self-assembly process induced by microwave-assisted solvothermal reaction. Hierarchical TiO 2 microspheres consisting of nanowires can be obtained in short time with this facile method and possess high surface area and superior optical properties. As the catalyst, it was found that the reaction rate constant of electro-field-assisted-photocatalytic removal (0.0488 min -1 ) of TBT exhibited almost a 9 fold improvement as compared to that of photocatalysis (0.0052 min -1 ). The proposed mechanism of electro-field-assisted-photocatalytic removal of TBT was verified by using 117 Sn-enriched TBT spike solution as an isotopic tracer. In addition, varying impacts from some key reaction conditions, such as voltage of potential, pH value and the presence of Cr and formaldehyde were also discussed. The overall satisfactory TBT removal performance of the proposed electro-field-assisted-photocatalysis procedure with hierarchical TiO 2 microspheres, which was validated using actual tannery wastewater samples from three different kinds of tanning procedures. These attributes suggest that this electro-field-assisted-photocatalysis may have broad applications for the treatment of tannery wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

Z-schematic water splitting by the synergistic effect of a type-II heterostructure and a highly efficient oxygen evolution catalyst

NASA Astrophysics Data System (ADS)

Li, Xiaoyun; Hu, Haihua; Xu, Lingbo; Cui, Can; Qian, Degui; Li, Shuang; Zhu, Wenzhe; Wang, Peng; Lin, Ping; Pan, Jiaqi; Li, Chaorong

2018-05-01

Artificial Z-scheme system inspired by the natural photosynthesis in green plants has attracted extensive attention owing to its advantages such as simultaneously wide range light absorption, highly efficient charge separation and strong redox ability. In this paper, we report the synthesis of a novel all-solid-state direct Z-scheme photocatalyst of Ag3PO4/CeO2/TiO2 by depositing Ag3PO4 nanoparticles (NPs) on CeO2/TiO2 hierarchical branched nanowires (BNWs), where the CeO2/TiO2 BNWs act as a novel substrate for the well dispersed nano-size Ag3PO4. The Ag3PO4/CeO2/TiO2 photocatalyst exhibits excellent ability of photocatalytic oxygen evolution from pure water splitting. It is suggested that the Z-scheme charge transfer route between CeO2/TiO2 and Ag3PO4 improves the redox ability. On the other hand, the cascade energy level alignment in CeO2/TiO2 BNWs expedites the spatial charge separation, and hence suppresses photocatalytic backward reaction. However, it is difficult to realize a perfect excitation balance in Ag3PO4/CeO2/TiO2 and the composite still surfers photo-corrosion in photocatalysis reaction. Nevertheless, our results provide an innovative strategy of constructing a Z-scheme system from a type-II heterostructure and a highly efficient oxygen evolution catalyst.

MoS2 embedded TiO2 nanoparticles for concurrent role of adsorption and photocatalysis

NASA Astrophysics Data System (ADS)

Pal, Arnab; Jana, Tushar K.; Chatterjee, Kuntal

2018-04-01

In this work, MoS2 embedded TiO2 nanoparticles, synthesized through hydrothermal process, was successfully employed to remove organic pollutant dye like methylene blue(MB) through adsorption and as well as through photocatalysis under visible light irradiation. The system was characterized by structural and morphological study. The adsorption and photocatalytic study of MB were evaluated with different concentrations of dye in aqueous solution. This work brings the MoS2-TiO2 nanostructure as excellent adsorbent as well as efficient photocatalyst materials which can be used for organic dye removal towards waste-water treatment.

Photocatalysis of zinc oxide nanotip array/titanium oxide film heterojunction prepared by aqueous solution deposition

NASA Astrophysics Data System (ADS)

Lee, Ming-Kwei; Lee, Bo-Wei; Kao, Chen-Yu

2017-05-01

A TiO2 film was prepared on indium tin oxide (ITO)/glass by aqueous solution deposition (ASD) with precursors of ammonium hexafluoro-titanate and boric acid at 40 °C. The photocatalysis of annealed TiO2 film increases with increasing growth time and decreases with increasing growth times longer than 60 min. A ZnO nanotip array was prepared on ZnO seed layer/TiO2 film/glass by aqueous solution deposition with precursors of zinc nitrate and ammonium hydroxide at 70 °C. The photocatalysis of ASD-ZnO/ASD-TiO2 film/ITO glass can be better than that of P25.

Photochemical degradation of triazine herbicides - comparison of homogeneous and heterogeneous photocatalysis.

PubMed

Klementova, Sarka; Zlamal, Martin

2013-04-01

Photochemical degradation of atrazine under different conditions was studied and compared, namely degradation via photocatalysis on TiO2, UV C photolysis, and homogeneous photocatalysis in the presence of added ferric ions. The reaction rate constants in heterogeneous photocatalytic reactions on TiO2 and of photolytic degradation by means of UV C light are similar, 0.018 min(-1) and 0.020 min(-1), respectively. The reaction rate constants in homogeneous photocatalytic reactions with Fe(III) added depend strongly on the Fe(III) concentration, 0.0017 min(-1) for 1.6 × 10(-6) mol l(-1) Fe(III) to 0.105 min(-1) for 3.3 × 10(-4) mol l(-1) Fe(III). In all types of reactions, dechlorination was observed; in homogeneous photocatalytic reactions and in UV C (250-300 nm) photolysis, dechlorination proceeds with a 1 : 1 stoichiometry to atrazine degradation, in photocatalytic reactions on TiO2, dechlorination measured as chloride ion release reaches only 1/5 of the substrate degradation. In photocatalytic reactions on TiO2, mineralisation of 40% carbon was observed.

Multi-applicative tetragonal TiO2/SnO2 nanocomposites for photocatalysis and gas sensing

NASA Astrophysics Data System (ADS)

Patil, S. M.; Dhodamani, A. G.; Vanalakar, S. A.; Deshmukh, S. P.; Delekar, S. D.

2018-04-01

TiO2-based mixed metal oxide heteronanostructures have multiple applications in photocatalysis and gas sensing because of their charge transport properties. In this study, we prepared tetragonal TiO2/SnO2 nanocomposites (NCs) with different weight percentages using a simple wet impregnation method. The physicochemical properties of the NCs were investigated using X-ray diffraction, Fourier transform-infrared spectroscopy, ultraviolet-visible spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and Brunauer-Emmett-Teller surface area analysis. The results showed that the surface area of the NCs increased significantly and the anatase TiO2 was sensitized after the addition of a small amount of cassiterite SnO2 NPs. We systematically studied the as-prepared NCs during the photocatalytic degradation of Congo Red dye under visible light irradiation (λ > 420 nm) and NH3 gas sensing, which demonstrated the efficient photocatalytic performance and the superior sensing response of the catalyst with a weight composition of 25% SnO2 in TiO2 (4:1) compared with the other NCs or the bare individual nanoparticles. The improved photocatalytic and gas sensing performance of the TiO2/SnO2 (4:1) NCs may be attributed to the increased active surface area, the increased adsorption of the dye and target gas molecules, as well as efficient electron-hole charge separation and transfer.

Study of pyrolysed acid and based treated coconut coir as green photocatalyst substrate

NASA Astrophysics Data System (ADS)

Asim, Nilofar; Emdadi, Zeynab; Abdullah, N. A.; Mohammad, Masita; Badiei, Marzieh; Sopian, Kamaruzzaman

2017-12-01

This study investigates the possible contribution to sustainable development by utilizing agriculture waste materials to prepare a substrate for photo-catalysis application. The photocatalytic performance of impregnated TiO2 on acid and base- treated coconut coir (CC) and their pyrolysed form have been studied. The photocatalytic performance of impregnated TiO2 on acid treated CC improved compared to bare TiO2. However, the pyrolysed samples showed higher thermal stability and porosity compared to only treated CC, their catalytic performance was decreased. It seems that impregnated TiO2 undergo interaction with treated CC during pyrolysis. More investigations to reveal exact reason of this behavior is in progress.

Preliminary trial on degradation of waste activated sludge and simultaneous hydrogen production in a newly-developed solar photocatalytic reactor with AgX/TiO2-coated glass tubes.

PubMed

Liu, Chunguang; Lei, Zhongfang; Yang, Yingnan; Zhang, Zhenya

2013-09-15

A solar fluidized tubular photocatalytic reactor (SFTPR) with simple and efficient light collector was developed to degrade waste activated sludge (WAS) and simultaneously produce hydrogen. The photocatalyst was a TiO2 film doped by silver and silver compounds (AgX). The synthesized photocatalyst, AgX/TiO2, exhibited higher photocatalytic activity than TiO2 (99.5% and 30.6% of methyl orange removal, respectively). The installation of light collector could increase light intensity by 26%. For WAS treatment using the SFTPR, 69.1% of chemical oxygen demand (COD) removal and 7866.7 μmol H2/l-sludge of hydrogen production were achieved after solar photocatalysis for 72 h. The SFTPR could be a promising photocatalysis reactor to effectively degrade WAS with simultaneous hydrogen production. The results can also provide a useful base and reference for the application of photocatalysis on WAS degradation in practice. Copyright © 2013 Elsevier Ltd. All rights reserved.

TiO2-Based Advanced Oxidation Nanotechnologies For Water Purification And Reuse

EPA Science Inventory

TiO₂ photocatalysis, one of the UV-based advanced oxidation technologies (AOTs) and nanotechnologies (AONs), has attracted great attention for the development of efficient water treatment and purification systems due to the effectiveness of TiO₂ to generate ...

Controllable synthesis of graphene-based titanium dioxide nanocomposites by atomic layer deposition.

PubMed

Meng, Xiangbo; Geng, Dongsheng; Liu, Jian; Li, Ruying; Sun, Xueliang

2011-04-22

Atomic layer deposition (ALD) was used to synthesize graphene-based metal oxide nanocomposites. This strategy was fulfilled on the preparation of TiO(2)-graphene nanosheet (TiO(2)-GNS) nanocomposites using titanium isopropoxide and water as precursors. The synthesized nanocomposites demonstrated that ALD exhibited many benefits in a controllable means. It was found that the as-deposited TiO(2) was tunable not only in its morphologies but also in its structural phases. As for the former, TiO(2) was transferable from nanoparticles to nanofilms with increased cycles. With regard to the latter, TiO(2) was changeable from amorphous to crystalline phase, and even a mixture of the two with increased growth temperatures (up to 250 °C). The underlying growth mechanisms were discussed and the resultant TiO(2)-GNS nanocomposites have great potentials for many applications, such as photocatalysis, lithium-ion batteries, fuel cells, and sensors.

The investigation of photo-induced chemiluminescence on Co2+-doped TiO2 nanoparticles and its analytical application.

PubMed

Li, Guixin; Nan, Hongyan; Zheng, Xingwang

2009-07-01

A novel space- and time-resolved photo-induced chemiluminescence (PICL) analytical method was developed based on the photocatalysis of the Co2+-doped TiO2 nanoparticles. The PICL reaction procedure under the photocatalysis of Co2+-doped TiO2 nanoparticles was investigated using cyclic voltammetry and potentiometry. Meanwhile, the effect of the electrical double layer outside the Co2+-doped TiO2 nanoparticles on the PICL was investigated by contrasting with the Co2+-doped TiO2-SiO2 core-shell nanoparticles. Significantly, the CL intensity increased apparently and the time of the CL was prolonged in the presence of procaterol hydrochloride because the mechanism of the enhanced PICL reaction may be modified. The route of the PICL was changed due to the participation of the procaterol hydrochloride enriched at the surface of the Co2+-doped TiO2-SiO2 in the PICL reaction, which prolonged the time of the CL reaction and resulted in the long-term PICL. The analytical characteristics of the proposed in-situ PICL method were investigated using the procaterol hydrochloride as the model analyte. The investigation results showed that this new PICL analytical method offered higher sensitivity to the analysis of the procaterol hydrochloride and the PICL intensity was linear with the concentration of the procaterol hydrochloride in the range from ca. 2.0 x 10(-10) to 1.0 x 10(-8) g mL(-1).

Preparation of RuO2-TiO2/Nano-graphite composite anode for electrochemical degradation of ceftriaxone sodium.

PubMed

Li, Dong; Guo, Xiaolei; Song, Haoran; Sun, Tianyi; Wan, Jiafeng

2018-06-05

Graphite-like material is widely used for preparing various electrodes for wastewater treatment. To enhance the electrochemical degradation efficiency of Nano-graphite (Nano-G) anode, RuO 2 -TiO 2 /Nano-G composite anode was prepared through the sol-gel method and hot-press technology. RuO 2 -TiO 2 /Nano-G composite was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and N 2 adsorption-desorption. Results showed that RuO 2 , TiO 2 and Nano-G were composited successfully, and RuO 2 and TiO 2 nanoparticles were distributed uniformly on the surface of Nano-G sheet. Specific surface area of RuO 2 -TiO 2 /Nano-G composite was higher than that of TiO 2 /Nano-G composite and Nano-G. Electrochemical performances of RuO 2 -TiO 2 /Nano-G anode were investigated by cyclic voltammetry, electrochemical impedance spectroscopy. RuO 2 -TiO 2 /Nano-G anode was applied to electrochemical degradation of ceftriaxone. The generation of hydroxyl radical (OH) was measured. Results demonstrated that RuO 2 -TiO 2 /Nano-G anode displayed enhanced electrochemical degradation efficiency towards ceftriaxone and yield of OH, which is derived from the synergetic effect between RuO 2 , TiO 2 and Nano-G, which enhance the specific surface area, improve the electrochemical oxidation activity and lower the charge transfer resistance. Besides, the possible degradation intermediates and pathways of ceftriaxone sodium were identified. This study may provide a viable and promising prospect for RuO 2 -TiO 2 /Nano-G anode towards effective electrochemical degradation of antibiotics from wastewater. Copyright © 2018 Elsevier B.V. All rights reserved.

Photocatalysis of sub-ppm limonene over multiwalled carbon nanotubes/titania composite nanofiber under visible-light irradiation.

PubMed

Jo, Wan-Kuen; Kang, Hyun-Jung

2015-01-01

This study was conducted under visible-light exposure to investigate the photocatalytic characteristics of a multiwalled carbon nanotube/titania (TiO2) composite nanofiber (MTCN) using a continuous-flow tubular reactor. The MTCN was prepared by a sol-gel process, followed by an electrospinning technique. The photocatalytic decomposition efficiency for limonene on the MTCN was higher than those obtained from reference TiO2 nanofibers or P25 TiO2, and the experimental results agreed well with the Langmuir-Hinshelwood model. The CO concentrations generated during the photocatalysis did not reach levels toxic to humans. The mineralization efficiency for limonene on the MTCN was also higher than that for P25 TiO2. Moreover, the mineralization efficiency obtained using the MTCN increased steeply from 8.3 to 91.1% as the residence time increased from 7.8 to 78.0s, compared to the increase in the decomposition efficiencies for limonene from 90.1 to 99.9%. Three gas-phase intermediates (methacrolein, acetic acid, and limonene oxide) were quantitatively determined for the photocatalysis for limonene over the MTCN, whereas only two intermediates (acetic acid and limonene oxide) were quantitatively determined over P25 TiO2. Other provisional gas-phase intermediates included cyclopropyl methyl ketone and 2-ethylbutanal. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation of Ag@AgCl-doped TiO2/sepiolite and its photocatalytic mechanism under visible light.

PubMed

Liu, Shaomin; Zhu, Dinglong; Zhu, Jinglin; Yang, Qing; Wu, Huijun

2017-10-01

A cube-like Ag@AgCl-doped TiO 2 /sepiolite (denoted Ag@AgCl-TiO 2 /sepiolite) was successfully synthesized via a novel method. X-ray diffraction, scanning electron microscopy, energy dispersion X-ray fluorescence, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and diffuse reflectance ultraviolet-visible spectroscopy were performed to determine the structure and physicochemical properties of Ag@AgCl-TiO 2 /sepiolite. SEM micrographs revealed that Ag@AgCl nanoparticles and TiO 2 film are well deposited on the surface of tube-like sepiolite. As a result, Ag@AgCl-TiO 2 /sepiolite exhibits a red shift relative to TiO 2 /sepiolite. Photocatalytic experiments demonstrated that the dosage of catalysts plays an important role during photocatalysis. The photoelectrochemical activities of Ag@AgCl-TiO 2 /sepiolite and TiO 2 /sepiolite were also investigated. Photocurrent responses confirmed that the ability of Ag@AgCl-TiO 2 /sepiolite to separate photo-generated electron-hole pairs is stronger than that of TiO 2 /sepiolite. Methylene Blue degradation is also improved under alkaline conditions and visible light irradiation because more OH is produced by visible light excitation. This excellent catalytic ability is mainly attributed to the formed Ag nanoparticles and the Schottky barrier at the Ag/TiO 2 interface. Active species analysis indicated that O 2 - and h + are implicated as active species in photocatalysis. Therefore, catalysts are excited to produce abundant electron-hole pairs after they absorb photons in photocatalysis. Copyright © 2017. Published by Elsevier B.V.

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. Copyright © 2014 Elsevier Ltd. All rights reserved.

Super-hydrophobic Silver-Doped TiO2 @ Polycarbonate Coatings Created on Various Material Substrates with Visible-Light Photocatalysis for Self-Cleaning Contaminant Degradation

PubMed Central

Li, Zhengjian; Sun, Zongzhao; Duan, Zhiqiang; Li, Rui; Yang, Yanli; Wang, Jingyi; Lv, Xiaoxia; Qi, Wei; Wang, Hua

2017-01-01

In the present work, a facile and efficient fabrication method has been developed for creating super-hydrophobic coatings of silver-doped TiO2@polycarbonate (TiO2 (Ag)@PC) on the substrates of different materials with photocatalytic self-cleaning performances simply by the “dipping and drying” process. The substrates were first patterned with glue and then deposited with the dopamine-capped TiO2 (Ag)@PC (DA-TiO2 (Ag)@PC) nanocomposites, followed by the further etching with dimethylbenzene. The so prepared super-hydrophobic E-DA-TiO2(Ag)@PC coatings could present the lotus leaf-like porous architectures, high adhesion stability, and especially the visible-light photocatalysis for organic contaminant degradation, thus promising the wide outdoor and indoor applications like water proofing, metal erosion protection, and surface self-cleaning. PMID:28218285

Super-hydrophobic Silver-Doped TiO2 @ Polycarbonate Coatings Created on Various Material Substrates with Visible-Light Photocatalysis for Self-Cleaning Contaminant Degradation.

PubMed

Li, Zhengjian; Sun, Zongzhao; Duan, Zhiqiang; Li, Rui; Yang, Yanli; Wang, Jingyi; Lv, Xiaoxia; Qi, Wei; Wang, Hua

2017-02-20

In the present work, a facile and efficient fabrication method has been developed for creating super-hydrophobic coatings of silver-doped TiO 2 @polycarbonate (TiO 2 (Ag)@PC) on the substrates of different materials with photocatalytic self-cleaning performances simply by the "dipping and drying" process. The substrates were first patterned with glue and then deposited with the dopamine-capped TiO 2 (Ag)@PC (DA-TiO 2 (Ag)@PC) nanocomposites, followed by the further etching with dimethylbenzene. The so prepared super-hydrophobic E-DA-TiO 2 (Ag)@PC coatings could present the lotus leaf-like porous architectures, high adhesion stability, and especially the visible-light photocatalysis for organic contaminant degradation, thus promising the wide outdoor and indoor applications like water proofing, metal erosion protection, and surface self-cleaning.

Super-hydrophobic Silver-Doped TiO2 @ Polycarbonate Coatings Created on Various Material Substrates with Visible-Light Photocatalysis for Self-Cleaning Contaminant Degradation

NASA Astrophysics Data System (ADS)

Li, Zhengjian; Sun, Zongzhao; Duan, Zhiqiang; Li, Rui; Yang, Yanli; Wang, Jingyi; Lv, Xiaoxia; Qi, Wei; Wang, Hua

2017-02-01

In the present work, a facile and efficient fabrication method has been developed for creating super-hydrophobic coatings of silver-doped TiO2@polycarbonate (TiO2 (Ag)@PC) on the substrates of different materials with photocatalytic self-cleaning performances simply by the “dipping and drying” process. The substrates were first patterned with glue and then deposited with the dopamine-capped TiO2 (Ag)@PC (DA-TiO2 (Ag)@PC) nanocomposites, followed by the further etching with dimethylbenzene. The so prepared super-hydrophobic E-DA-TiO2(Ag)@PC coatings could present the lotus leaf-like porous architectures, high adhesion stability, and especially the visible-light photocatalysis for organic contaminant degradation, thus promising the wide outdoor and indoor applications like water proofing, metal erosion protection, and surface self-cleaning.

Study on preparation of SnO2-TiO2/Nano-graphite composite anode and electro-catalytic degradation of ceftriaxone sodium.

PubMed

Guo, Xiaolei; Wan, Jiafeng; Yu, Xiujuan; Lin, Yuhui

2016-12-01

In order to improve the electro-catalytic activity and catalytic reaction rate of graphite-like material, Tin dioxide-Titanium dioxide/Nano-graphite (SnO 2 -TiO 2 /Nano-G) composite was synthesized by a sol-gel method and SnO 2 -TiO 2 /Nano-G electrode was prepared in hot-press approach. The composite was characterized by X-ray photoelectron spectroscopy, fourier transform infrared, Raman, N 2 adsorption-desorption, scanning electrons microscopy, transmission electron microscopy and X-ray diffraction. The electrochemical performance of the SnO 2 -TiO 2 /Nano-G anode electrode was investigated via cyclic voltammetry and electrochemical impedance spectroscopy. The electro-catalytic performance was evaluated by the degradation of ceftriaxone sodium and the yield of ·OH radicals in the reaction system. The results demonstrated that TiO 2 , SnO 2 and Nano-G were composited successfully, and TiO 2 and SnO 2 particles dispersed on the surface and interlamination of the Nano-G uniformly. The specific surface area of SnO 2 modified anode was higher than that of TiO 2 /Nano-G anode and the degradation rate of ceftriaxone sodium within 120 min on SnO 2 -TiO 2 /Nano-G electrode was 98.7% at applied bias of 2.0 V. The highly efficient electro-chemical property of SnO 2 -TiO 2 /Nano-G electrode was attributed to the admirable conductive property of the Nano-G and SnO 2 -TiO 2 /Nano-G electrode. Moreover, the contribution of reactive species ·OH was detected, indicating the considerable electro-catalytic activity of SnO 2 -TiO 2 /Nano-G electrode. Copyright © 2016 Elsevier Ltd. All rights reserved.

Solar Fenton and solar TiO2 catalytic treatment of ofloxacin in secondary treated effluents: evaluation of operational and kinetic parameters.

PubMed

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

2010-10-01

Two different technical approaches based on advanced oxidation processes (AOPs), solar Fenton homogeneous photocatalysis (hv/Fe(2+)/H(2)O(2)) and heterogeneous photocatalysis with titanium dioxide (TiO(2)) suspensions were studied for the chemical degradation of the fluoroquinolone ofloxacin in secondary treated effluents. A bench-scale solar simulator in combination with an appropriate photochemical batch reactor was used to evaluate and select the optimal oxidation conditions of ofloxacin spiked in secondary treated domestic effluents. The concentration profile of the examined substrate during degradation was determined by UV/Vis spectrophotometry. Mineralization was monitored by measuring the dissolved organic carbon (DOC). The concentrations of Fe(2+) and H(2)O(2) were the key factors for the solar Fenton process, while the most important parameter of the heterogeneous photocatalysis was proved to be the catalyst loading. Kinetic analyses indicated that the photodegradation of ofloxacin can be described by a pseudo-first-order reaction. The rate constant (k) for the solar Fenton process was determined at different Fe(2+) and H(2)O(2) concentrations whereas the Langmuir-Hinshelwood (LH) kinetic expression was used to assess the kinetics of the heterogeneous photocatalytic process. The conversion of ofloxacin depends on several parameters based on the various experimental conditions, which were investigated. A Daphnia magna bioassay was used to evaluate the potential toxicity of the parent compound and its photo-oxidation by-products in different stages of oxidation. In the present study solar Fenton has been demonstrated to be more effective than the solar TiO(2) process, yielding complete degradation of the examined substrate and DOC reduction of about 50% in 30 min of the photocatalytic treatment. Copyright © 2010 Elsevier Ltd. All rights reserved.

Enhanced removal of toxic Cr(VI) in tannery wastewater by photoelectrocatalysis with synthetic TiO2 hollow spheres

NASA Astrophysics Data System (ADS)

Zhao, Yang; Chang, Wenkai; Huang, Zhiding; Feng, Xugen; Ma, Lin; Qi, Xiaoxia; Li, Zenghe

2017-05-01

Owing to the acute toxicity and mobility, the Cr(VI) in tannery wastewater is a huge threat to biological and environmental systems. Herein, an effective photoelectrocatalytic reduction of Cr(VI) was carried out by applying electric field to photocatalysis of as-prepared TiO2 spheres. The synthesis of spherical TiO2 catalytic materials with hollow structure and high surface areas was based on a self-assembly process induced by a mixture of organic acetic acid and ethanol. The possible formation mechanism of TiO2 spheres was proposed and verified by acid concentration-dependent and temperature-dependent experiments. It was found that the reaction rate constant of photoelectrocatalytic reduction of Cr(VI) exhibited an almost 3 fold improvement (0.0362 min-1) as compared to that of photocatalysis (0.0126 min-1). As a result, the mechanism of photoelectrocatalytic reduction of Cr(VI) was described according to the simultaneous determination of Cr(VI), Cr(III) and total Cr in the system. In addition, the effect of pH value and voltage of potential were also discussed. Moreover, this photoelectrocatalysis with TiO2 hollow spheres exhibited excellent activity for reduction of Cr(VI) in actual tannery wastewater produced from three different tanning procedures. These attributes suggest that this photoelectrocatalysis has strong potential applications in the treatment of tannery pollutants.

Nanoscale wide-band semiconductors for photocatalytic remediation of aquatic pollution.

PubMed

Sarkar, Biplab; Daware, Akshay Vishnu; Gupta, Priya; Krishnani, Kishore Kumar; Baruah, Sunandan; Bhattacharjee, Surajit

2017-11-01

Water pollution is a serious challenge to the public health. Among different forms of aquatic pollutants, chemical and biological agents create paramount threat to water quality when the safety standards are surpassed. There are many conventional remediatory strategies that are practiced such as resin-based exchanger and activated charcoal/carbon andreverse osmosis. Newer technologies using plants, microorganisms, genetic engineering, and enzyme-based approaches are also proposed for aquatic pollution management. However, the conventional technologies have shown impending inadequacies. On the other hand, new bio-based techniques have failed to exhibit reproducibility, wide specificity, and fidelity in field conditions. Hence, to solve these shortcomings, nanotechnology ushered a ray of hope by applying nanoscale zinc oxide (ZnO), titanium dioxide (TiO 2 ), and tungsten oxide (WO 3 ) particles for the remediation of water pollution. These nanophotocatalysts are active, cost-effective, quicker in action, and can be implemented at a larger scale. These nanoparticles are climate-independent, assist in complete mineralization of pollutants, and can act non-specifically against chemically and biologically based aquatic pollutants. Photocatalysis for environmental remediation depends on the availability of solar light. The mechanism of photocatalysis involves the formation of electron-hole pairs upon light irradiations at intensities higher than their band gap energies. In the present review, different methods of synthesis of nanoscale ZnO, TiO 2 , and WO 3 as well as their structural characterizations have been discussed. Photodegradation of organic pollutants through mentioned nanoparticles has been reviewed with recent advancements. Enhancing the efficacy of photocatalysis through doping of TiO 2 and ZnO nanoparticles with non-metals, metals, and metal ions has also been documented in this report.

Application of photochemical technologies for treatment of landfill leachate.

PubMed

Meeroff, Daniel E; Bloetscher, Frederick; Reddy, D V; Gasnier, François; Jain, Swapnil; McBarnette, André; Hamaguchi, Hatsuko

2012-03-30

Because of widely varying practices in solid waste management, an all-inclusive solution to long-term management of landfill leachate is currently not available. There is a major technological need for sustainable, economical options for safe discharge of leachate to the environment. Two potential on-site pretreatment technologies, photochemical iron-mediated aeration (PIMA) and TiO(2) photocatalysis were compared for treatment of landfill leachate at laboratory scale. Results of bench scale testing of real landfill leachate with PIMA and TiO(2) photocatalysis showed up to 86% conversion of refractory COD to complete mineralization, up to 91% removal of lead, up to 71% removal of ammonia without pH adjustment, and up to 90% effective color removal with detention times between 4 and 6h, in field samples. The estimated contact times for 90% removal of COD, ammonia, lead, and color were found to be on the order of 10-200 h for PIMA and 3-37 h for TiO(2) photocatalysis. Testing with actual leachate samples showed 85% TiO(2) photocatalyst recovery efficiency with no loss in performance after multiple (n>4 uses). Pre-filtration was not found to be necessary for effective treatment using either process. Copyright © 2012 Elsevier B.V. All rights reserved.

Evaluation of solar photocatalysis using TiO2 slurry in the inactivation of Cryptosporidium parvum oocysts in water.

PubMed

Abeledo-Lameiro, María Jesús; Ares-Mazás, Elvira; Gómez-Couso, Hipólito

2016-10-01

Cryptosporidium is a genus of enteric protozoan parasites of medical and veterinary importance, whose oocysts have been reported to occur in different types of water worldwide, offering a great resistant to the water treatment processes. Heterogeneous solar photocatalysis using titanium dioxide (TiO2) slurry was evaluated on inactivation of Cryptosporidium parvum oocysts in water. Suspensions of TiO2 (0, 63, 100 and 200mg/L) in distilled water (DW) or simulated municipal wastewater treatment plant (MWTP) effluent spiked with C. parvum oocysts were exposed to simulated solar radiation. The use of TiO2 slurry at concentrations of 100 and 200mg/L in DW yielded a high level of oocyst inactivation after 5h of exposure (4.16±2.35% and 15.03±4.54%, respectively, vs 99.33±0.58%, initial value), representing a good improvement relative to the results obtained in the samples exposed without TiO2 (51.06±9.35%). However, in the assays carried out using simulated MWTP effluent, addition of the photocatalyst did not offer better results. Examination of the samples under bright field and epifluorescence microscopy revealed the existence of aggregates comprising TiO2 particles and parasitic forms, which size increased as the concentration of catalyst and the exposure time increased, while the intensity of fluorescence of the oocyst walls decreased. After photocatalytic disinfection process, the recovery of TiO2 slurry by sedimentation provided a substantial reduction in the parasitic load in treated water samples (57.81±1.10% and 82.10±2.64% for 200mg/L of TiO2 in DW and in simulated MWTP effluent, respectively). Although further studies are need to optimize TiO2 photocatalytic disinfection against Cryptosporidium, the results obtained in the present study show the effectiveness of solar photocatalysis using TiO2 slurry in the inactivation of C. parvum oocysts in distilled water. Copyright © 2016 Elsevier B.V. All rights reserved.

Solar photolysis versus TiO2-mediated solar photocatalysis: a kinetic study of the degradation of naproxen and diclofenac in various water matrices.

PubMed

Kanakaraju, Devagi; Motti, Cherie A; Glass, Beverley D; Oelgemöller, Michael

2016-09-01

Given that drugs and their degradation products are likely to occur as concoctions in wastewater, the degradation of a mixture of two nonsteroidal anti-inflammatory drugs (NSAIDs), diclofenac (DCF) and naproxen (NPX), was investigated by solar photolysis and titanium dioxide (TiO2)-mediated solar photocatalysis using an immersion-well photoreactor. An equimolar ratio (1:1) of both NSAIDs in distilled water, drinking water, and river water was subjected to solar degradation. Solar photolysis of the DCF and NPX mixture was competitive particularly in drinking water and river water, as both drugs have the ability to undergo photolysis. However, the addition of TiO2 in the mixture significantly enhanced the degradation rate of both APIs compared to solar photolysis alone. Mineralization, as measured by chemical oxygen demand (COD), was incomplete under all conditions investigated. TiO2-mediated solar photocatalytic degradation of DCF and NPX mixtures produced 15 identifiable degradants corresponding to degradation of the individual NSAIDs, while two degradation products with much higher molecular weight than the parent NSAIDs were identified by liquid chromatography mass spectrometry (LC-MS) and Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS). This study showed that the solar light intensity and the water matrix appear to be the main factors influencing the overall performance of the solar photolysis and TiO2-mediated solar photocatalysis for degradation of DCF and NPX mixtures.

Parathion degradation and toxicity reduction in solar photocatalysis and photolysis.

PubMed

Zoh, K D; Kim, T S; Kim, J G; Choi, K; Yi, S M

2006-01-01

The solar photocatalytic degradation of methyl parathion was investigated using a circulating TiO2/solar light reactor. Under solar photocatalysis condition, parathion was more effectively degraded than solar photolysis and TiO2-only conditions. With solar photocatalysis, 20 mg/L of parathion was completely degraded within 60 min with a TOC decrease of 63% after 150 min. The main ionic byproducts during photocatalysis recovered from parathion degradation were mainly as NO3-, NO2- and NH4+, 80% of the sulphur as SO4(2-), and 5% of phosphorus as PO4(3-). The organic intermediates 4-nitrophenol and methyl paraoxon were also identified, and these were further degraded in solar photocatalytic condition. Two different bioassays (Vibrio fischeri and Daphnia magna) were used to test the acute toxicity of solutions treated by solar photocatalysis and photolysis. The Microtox test using V. fischeri showed that the toxicity expressed as EC50 (%) value increased from 5.5% to >82% in solar photocatalysis, indicating that the treated solution is non-toxic, but only increased from 4.9 to 20.5% after 150 min in solar photolysis. The acute toxicity test using D. magna showed that EC50 (%) increased from 0.05 to 1.08% under solar photocatalysis, but only increased to 0.12% after 150 min with solar photolysis, indicating the solution is still toxic. The pattern of toxicity reduction parallels the decrease in TOC and the parathion concentrations.

[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.

TiO2 Hollow Spheres: One-Pot Synthesis and Enhanced Photocatalysis

NASA Astrophysics Data System (ADS)

Jia, Changchao; Cao, Yongqiang; Yang, Ping

2013-04-01

Hollow TiO2 microspheres were successfully fabricated by metal salts with low solubility in ethanol acting as intelligent templates using a simple one-pot solvothermal method. Hollow spheres with large diameter were obtained using CuSO4ṡ5H2O as templates while small ones were obtained using Sr(NO3)2 as templates. It is found that titanium precursor plays an important role for the morphology of samples. Solid TiO2 microspheres were prepared by using titanium tetrabutoxide (TBT). In contrast, bowl-like hollow microspheres were obtained by using titanium tetrachloride (TiCl4). Furthermore, the amount of H2O can stimulate the hydrolysis rate of TiCl4 to form solid spheres. Compared with solid microspheres, hollow TiO2 microspheres depending on their interior cavity structure exhibited enhanced photocatalysis efficiency for the UV-light photodegradation of methyl orange. Quantificationally, the apparent photocatalytic degradation pseudo-first-rate constant of the hollow microspheres is 1.25 times of that of the solid ones.

Defective TiO2 with oxygen vacancies: synthesis, properties and photocatalytic applications

NASA Astrophysics Data System (ADS)

Pan, Xiaoyang; Yang, Min-Quan; Fu, Xianzhi; Zhang, Nan; Xu, Yi-Jun

2013-04-01

Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the synthesis of defective TiO2 with oxygen vacancies, and the defect related properties of TiO2 including structural, electronic, optical, dissociative adsorption and reductive properties, which are intimately related to the photocatalytic performance of TiO2. In particular, photocatalytic applications with regard to defective TiO2 are outlined. In addition, we offer some perspectives on the challenge and new direction for future research in this field. We hope that this tutorial minireview would provide some useful contribution to the future design and fabrication of defective semiconductor-based nanomaterials for diverse photocatalytic applications.Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the synthesis of defective TiO2 with oxygen vacancies, and the defect related properties of TiO2 including structural, electronic, optical, dissociative adsorption and reductive properties, which are intimately related to the photocatalytic performance of TiO2. In particular, photocatalytic applications with regard to defective TiO2 are outlined. In addition, we offer some perspectives on the challenge and new direction for future research in this field. We hope that this tutorial minireview would provide some useful contribution to the future design and fabrication of defective semiconductor-based nanomaterials for diverse photocatalytic applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00476g

Advances in porous and high-energy (001)-faceted anatase TiO2 nanostructures

NASA Astrophysics Data System (ADS)

Umar, Akrajas Ali; Md Saad, Siti Khatijah; Ali Umar, Marjoni Imamora; Rahman, Mohd Yusri Abd; Oyama, Munetaka

2018-01-01

In this review, we present a summary of research to date on the anatase polymorph of TiO2 nanostructures containing high-energy facet, particularly (001) plane, with porous structure, covering their synthesis and their application in photocatalysis as well as a review of any attempts to modify their electrical, optical and photocatalytic properties via doping. After giving a brief introduction on the role of crystalline facet on the physico-chemical properties of the anatase TiO2, we discuss the electrical and optical properties of pristine anatase TiO2 and after being doped with both metal and non-metals dopants. We then continue to the discussion of the electrical properties of (001) faceted anatase TiO2 and their modification upon being prepared in the form of porous morphology. Before coming to the review of the photocatalytic properties of the (001) faceted anatase and (001) with porous morphology in selected photocatalysis application, such as photodegradation of organic pollutant, hydrogenation reaction, water splitting, etc., we discuss the synthetic strategy for the preparation of them. We then end our discussion by giving an outlook on future strategy for development of research related to high-energy faceted and porous anatase TiO2.

Photocatalytic degradation of commercially sourced naphthenic acids by TiO2-graphene composite nanomaterial.

PubMed

Liu, Juncheng; Wang, Lin; Tang, Jingchun; Ma, Jianli

2016-04-01

Naphthenic acids (NAs) are a major contributor to the toxicity in oil sands process-affected water (OSPW), which is produced by hot water extraction of bitumen. NAs are extremely difficult to be degraded due to its complex ring and side chain structure. Photocatalysis is recognized as a promising technology in the removal of refractory organic pollutants. In this work, TiO2-graphene (P25-GR) composites were synthesized by means of solvothermal method. The results showed that P25-GR composite exhibited better photocatalytic activity than pure P25. The removal efficiency of naphthenic acids in acid solution was higher than that in neutral and alkaline solutions. It was the first report ever known on the photodegradation of NAs based on graphene, and this process achieved a higher removal rate than other photocatalysis degradation of NAs in a shorter reaction time. LC/MS analysis showed that macromolecular NAs (carbon number 17-22, z value -2) were easy to be degraded than the micromolecular ones (carbon number 11-16, z value -2). Furthermore, the reactive oxygen species that play the main role in the photocatalysis system were studied. It was found that holes and ·OH were the main reactive species in the UV/P25-GR photocatalysis system. Given the high removal efficiency of refractory organic pollutants and the short degradation time, photodegradation based on composite catalysts has a broad and practical prospect. The study on the photodegradation of commercially sourced NAs may provide a guidance for the degradation of OSPW NAs by this method. Copyright © 2016 Elsevier Ltd. All rights reserved.

X-ray spectroscopies studies of the 3d transition metal oxides and applications of photocatalysis

DOE PAGES

Ye, Yifan; Kapilashrami, Mukes; Chuang, Cheng-Hao; ...

2017-02-08

Some recent advances in synchrotron based x-ray spectroscopy enable materials scientists to emanate fingerprints on important materials properties, e.g., electronic, optical, structural, and magnetic properties, in real-time and under nearly real-world conditions. This characterization, then, in combination with optimized materials synthesis routes and tailored morphological properties could contribute greatly to the advances in solid-state electronics and renewable energy technologies. In connection to this, such perspective reflects the current materials research in the space of emerging energy technologies, namely photocatalysis, with a focus on transition metal oxides, mainly on the Fe 2O 3- and TiO 2-based materials.

Mineralization enhancement of a recalcitrant pharmaceutical pollutant in water by advanced oxidation hybrid processes.

PubMed

Méndez-Arriaga, F; Torres-Palma, R A; Pétrier, C; Esplugas, S; Gimenez, J; Pulgarin, C

2009-09-01

Degradation of the biorecalcitrant pharmaceutical micropollutant ibuprofen (IBP) was carried out by means of several advanced oxidation hybrid configurations. TiO(2) photocatalysis, photo-Fenton and sonolysis - all of them under solar simulated illumination - were tested in the hybrid systems: sonophoto-Fenton (FS), sonophotocatalysis (TS) and TiO(2)/Fe(2+)/sonolysis (TFS). In the case of the sonophoto-Fenton process, the IBP degradation (95%) and mineralization (60%) were attained with photo-Fenton (FH). The presence of ultrasonic irradiation slightly improves the iron catalytic activity. On the other hand, total removal of IBP and elimination of more than 50% of dissolved organic carbon (DOC) were observed by photocatalysis with TiO(2) in the presence of ultrasound irradiation (TS). In contrast only 26% of mineralization was observed by photocatalysis with H(2)O(2) (TH) in the absence of ultrasound irradiation. Additional results showed that, in the TFS system, 92% of DOC removal and complete degradation of IBP were obtained within 240 min of treatment. The advanced oxidation hybrid systems seems to be a promising alternative for full elimination/mineralization for the recalcitrant micro-contaminant IBP.

Photocatalysis as an Effective Advanced Oxidation Process

EPA Science Inventory

Photocatalysis is generally referred to as the acceleration of a photoreaction by the presence of a semiconductor catalyst such as titanium dioxide (TiO2) or zinc oxide (ZnO). Photocatalytic materials can be prepared by using various methods such as a sol-gel process, solution pr...

HETEROGENOUS PHOTOCATALYSIS ON AEROSOL PROCESSED NANOSTRUCTURED TITANIA PARTICLES: ROLE OF PARTICLE SIZE

EPA Science Inventory

Heterogenous photocatalysis with TiO2 has been extensively investigated as a method to oxidize organic pollutants in water and air, including phenols, chlorinated hydrocarbons, and other hydrocarbons. In addition, the use of titanium dioxide as a photocatalyst has also been demon...

Immobilized TiO2 on glass spheres applied to heterogeneous photocatalysis: photoactivity, leaching and regeneration process.

PubMed

Cunha, Deivisson Lopes; Kuznetsov, Alexei; Achete, Carlos Alberto; Machado, Antonio Eduardo da Hora; Marques, Marcia

2018-01-01

Heterogeneous photocatalysis using titanium dioxide as catalyst is an attractive advanced oxidation process due to its high chemical stability, good performance and low cost. When immobilized in a supporting material, additional benefits are achieved in the treatment. The purpose of this study was to develop a simple protocol for impregnation of TiO 2 -P25 on borosilicate glass spheres and evaluate its efficiency in the photocatalytic degradation using an oxidizable substrate (methylene blue), in a Compound Parabolic Concentrator (CPC) reactor. The assays were conducted at lab-scale using radiation, which simulated the solar spectrum. TiO 2 leaching from the glass and the catalyst regeneration were both demonstrated. A very low leaching ratio (0.03%) was observed after 24 h of treatment, suggesting that deposition of TiO 2 resulted in good adhesion and stability of the photocatalyst on the surface of borosilicate. This deposition was successfully achieved after calcination of the photocatalyst at 400 °C (TiO 2 -400 °C). The TiO 2 film was immobilized on glass spheres and the powder was characterized by scanning electron microscopy (SEM), X-ray diffraction and BET. This characterization suggested that thermal treatment did not introduce substantial changes in the measured microstructural characteristics of the photocatalyst. The immobilized photocatalyst degraded more than 96% of the MB in up to 90 min of reaction. The photocatalytic activity decreased after four photocatalytic cycles, but it was recovered by the removal of contaminants adsorbed on the active sites after washing in water under UV-Vis irradiation. Based on these results, the TiO 2 -400 °C coated on glass spheres is potentially a very attractive option for removal of persistent contaminants present in the environment.

Immobilized TiO2 on glass spheres applied to heterogeneous photocatalysis: photoactivity, leaching and regeneration process

PubMed Central

Kuznetsov, Alexei; Achete, Carlos Alberto; Machado, Antonio Eduardo da Hora; Marques, Marcia

2018-01-01

Heterogeneous photocatalysis using titanium dioxide as catalyst is an attractive advanced oxidation process due to its high chemical stability, good performance and low cost. When immobilized in a supporting material, additional benefits are achieved in the treatment. The purpose of this study was to develop a simple protocol for impregnation of TiO2-P25 on borosilicate glass spheres and evaluate its efficiency in the photocatalytic degradation using an oxidizable substrate (methylene blue), in a Compound Parabolic Concentrator (CPC) reactor. The assays were conducted at lab-scale using radiation, which simulated the solar spectrum. TiO2 leaching from the glass and the catalyst regeneration were both demonstrated. A very low leaching ratio (0.03%) was observed after 24 h of treatment, suggesting that deposition of TiO2 resulted in good adhesion and stability of the photocatalyst on the surface of borosilicate. This deposition was successfully achieved after calcination of the photocatalyst at 400 °C (TiO2-400 °C). The TiO2 film was immobilized on glass spheres and the powder was characterized by scanning electron microscopy (SEM), X-ray diffraction and BET. This characterization suggested that thermal treatment did not introduce substantial changes in the measured microstructural characteristics of the photocatalyst. The immobilized photocatalyst degraded more than 96% of the MB in up to 90 min of reaction. The photocatalytic activity decreased after four photocatalytic cycles, but it was recovered by the removal of contaminants adsorbed on the active sites after washing in water under UV-Vis irradiation. Based on these results, the TiO2-400 °C coated on glass spheres is potentially a very attractive option for removal of persistent contaminants present in the environment. PMID:29527416

Selective isolation of the electron or hole in photocatalysis: ZnO-TiO2 and TiO2-ZnO core-shell structured heterojunction nanofibers via electrospinning and atomic layer deposition.

PubMed

Kayaci, Fatma; Vempati, Sesha; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi; Uyar, Tamer

2014-06-07

Heterojunctions are a well-studied material combination in photocatalysis studies, the majority of which aim to improve the efficacy of the catalysts. Developing novel catalysts begs the question of which photo-generated charge carrier is more efficient in the process of catalysis and the associated mechanism. To address this issue we have fabricated core-shell heterojunction (CSHJ) nanofibers from ZnO and TiO2 in two combinations where only the 'shell' part of the heterojunction is exposed to the environment to participate in the photocatalysis. Core and shell structures were fabricated via electrospinning and atomic layer deposition, respectively which were then subjected to calcination. These CSHJs were characterized and studied for photocatalytic activity (PCA). These two combinations expose electrons or holes selectively to the environment. Under suitable illumination of the ZnO-TiO2 CSHJ, e/h pairs are created mainly in TiO2 and the electrons take part in catalysis (i.e. reduce the organic dye) at the conduction band or oxygen vacancy sites of the 'shell', while holes migrate to the core of the structure. Conversely, holes take part in catalysis and electrons diffuse to the core in the case of a TiO2-ZnO CSHJ. The results further revealed that the TiO2-ZnO CSHJ shows ∼1.6 times faster PCA when compared to the ZnO-TiO2 CSHJ because of efficient hole capture by oxygen vacancies, and the lower mobility of holes.

TiO2 supported on reed straw biochar as an adsorptive and photocatalytic composite for the efficient degradation of sulfamethoxazole in aqueous matrices.

PubMed

Zhang, Hanyu; Wang, Zhaowei; Li, Ruining; Guo, Jialei; Li, Yan; Zhu, Junmin; Xie, Xiaoyun

2017-10-01

Heterogeneous photocatalysis namely titanium dioxide supported on reed straw biochar (acid pre-treated) (TiO 2 /pBC) was synthesized by sol-gel method. The morphology, surface area and structure of TiO 2 /pBC were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), and X-ray diffraction (XRD). Low calcination condition maintained the structure of biochar completely and prevented the agglomeration of TiO 2 particles. Due to the combination of adsorption and photocatalysis, TiO 2 /pBC performed higher removal efficiency of sulfamethoxazole (SMX) than pure TiO 2 powder under UV light irradiation. The photocatalytic degradation (PCD) of SMX was also studied with the water collected from the Yellow River. Three high concentration inorganic anions (Cl - , NO 3 - , SO 4 2- ) of the river exerted certain degree of detrimental effects on the contaminant degradation. TiO 2 /pBC showed stable photocatalytic activity after five sequential PCD cycles. The biochar was able to promote further PCD on TiO 2 by adsorbing SMX and intermediates thereby prolonging the separation lifetime of electrons (e - ) and valence band hole (h + ). The transformation intermediates of SMX were identified and three possible degradation reactions of hydroxylation, opening of isoxazole ring and cleavage of SN bond might occur during the PCD of SMX. Copyright © 2017 Elsevier Ltd. All rights reserved.

Treatment of wastewater containing Reactive Brilliant Blue KN-R using TiO2/BC composite as heterogeneous photocatalyst and adsorbent.

PubMed

Zhang, Shici; Lu, Xujie

2018-09-01

Heterogeneous photocatalysis namely titanium dioxide (TiO 2 ) supported on coconut shell biochar (BC) was synthesized by sol-gel method (calcined at 450 °C) in the paper, which was innovatively applied to the decolorization of Reactive Brilliant Blue KN-R. The transmission electron microscopy (TEM) and X-ray diffraction patterns (XRD) results demonstrated that anatase TiO 2 film was firmly immobilized on the surface and pores of BC. The photocatalysis tests under UV high pressure xenon lamp (300 W) showed highest decolorization efficiency occurred at strong acid and alkali conditions (pH = 1 and 11) reached as 99.71% and 96.99% respectively within 60 min. Therefore, the TiO 2 /BC composites demonstrated both photocatalytic and adsorption capacity on KN-R decolorized, and presented quite durable and reusable in regeneration cycles, indicating a widely application possibility in anthraquinones dyeing wastewater treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Fabrication of TiO2-modified polytetrafluoroethylene ultrafiltration membranes via plasma-enhanced surface graft pretreatment

NASA Astrophysics Data System (ADS)

Qian, Yingjia; Chi, Lina; Zhou, Weili; Yu, Zhenjiang; Zhang, Zhongzhi; Zhang, Zhenjia; Jiang, Zheng

2016-01-01

Surface hydrophilic modification of polymer ultrafiltration membrane using metal oxide represents an effective yet highly challenging solution to improve water flux and antifouling performance. Via plasma-enhanced graft of poly acryl acid (PAA) prior to coating TiO2, we successfully fixed TiO2 functional thin layer on super hydrophobic polytetrafluoroethylene (PTFE) ultrafiltration (UF) membranes. The characterization results evidenced TiO2 attached on the PTFE-based UF membranes through the chelating bidentate coordination between surface-grafted carboxyl group and Ti4+. The TiO2 surface modification may greatly reduce the water contact angle from 115.8° of the PTFE membrane to 35.0° without degradation in 30-day continuous filtration operations. The novel TiO2/PAA/PTFE membranes also exhibited excellent antifouling and self-cleaning performance due to the intrinsic hydrophilicity and photocatalysis properties of TiO2, which was further confirmed by the photo-degradation of MB under Xe lamp irradiation.

The Synthesis of a Core-Shell Photocatalyst Material YF3:Ho3+@TiO2 and Investigation of Its Photocatalytic Properties

PubMed Central

Xu, Xuan; Zhou, Shiyu; Long, Jun; Wu, Tianhu; Fan, Zihong

2017-01-01

In this paper, YF3:Ho3+@TiO2 core-shell nanomaterials were prepared by hydrolysis of tetra-n-butyl titanate (TBOT) using polyvinylpyrrolidone K-30 (PVP) as the coupling agent. Characterization methods including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) under TEM, X-ray photoelectron spectroscopy (XPS), fluorescence spectrometry, ultraviolet-visible diffuse reflectance spectroscopy, and electron spin resonance (ESR) were used to characterize the properties and working mechanism of the prepared photocatalyst material. They indicated that the core phase YF3 nanoparticles were successfully coated with a TiO2 shell and the length of the composite was roughly 100 nm. The Ho3+ single-doped YF3:Ho3+@TiO2 displayed strong visible absorption peaks with wavelengths of 450, 537, and 644 nm, respectively. By selecting these three peaks as excitation wavelengths, we could observe 288 nm (5D4→5I8) ultraviolet emission, which confirmed that there was indeed an energy transfer from YF3:Ho3+ to anatase TiO2. In addition, this paper investigated the influences of different TBOT dosages on photocatalysis performance of the as-prepared photocatalyst material. Results showed that the YF3:Ho3+@TiO2 core-shell nanomaterial was an advanced visible-light-driven catalyst, which decomposed approximately 67% of rhodamine b (RhB) and 34.6% of phenol after 10 h of photocatalysis reaction. Compared with the blank experiment, the photocatalysis efficiency was significantly improved. Finally, the visible-light-responsive photocatalytic mechanism of YF3:Ho3+@TiO2 core-shell materials and the influencing factors of photocatalytic degradation were investigated to study the apparent kinetics, which provides a theoretical basis for improving the structural design and functions of this new type of catalytic material. PMID:28772662

Exposure assessment of workplace manufacturing titanium dioxide particles

NASA Astrophysics Data System (ADS)

Xu, Huadong; Zhao, Lin; Chen, Zhangjian; Zhou, Jingwen; Tang, Shichuan; Kong, Fanling; Li, Xinwei; Yan, Ling; Zhang, Ji; Jia, Guang

2016-10-01

With the widespread use of titanium dioxide (TiO2) human exposure is inevitable, but the exposure data on TiO2 are still limited. This study adopted off-line filter-based sampling combined with real-time activity-based monitoring to measure the concentrations in a workplace manufacturing TiO2 (primary diameter: 194 ± 108 nm). Mass concentrations (MCs) of aerosol particles in the packaging workshop (total dust: 3.17 mg/m3, nano dust: 1.22 mg/m3) were much higher than those in the milling workshop (total dust: 0.79 mg/m3, nano dust: 0.31 mg/m3) and executive office (total dust: 0.44 mg/m3, nano dust: 0.19 mg/m3). However, the MCs of TiO2 were at a relatively low level in the packaging workshop (total TiO2: 46.4 μg/m3, nano TiO2: 16.7 μg/m3) and milling workshop (total TiO2: 39.4 μg/m3, nano TiO2: 19.4 μg/m3) by ICP-MS. The number concentration (NC), surface area concentration (SAC) of aerosol particles potentially deposited in alveolar (SACA), and tracheobronchial (SACTB) regions of lungs in the packaging workshop were (1.04 ± 0.89) × 105 particles/cm3, 414.49 ± 395.07, and 86.01 ± 83.18 μm2/cm3, respectively, which were all significantly higher than those of the milling workshop [(0.12 ± 0.40) × 105 particles/cm3, 75.38 ± 45.23, and 17.60 ± 9.22 μm2/cm3, respectively] as well as executive office and outdoor background ( p < 0.05). Activity-related characteristics were found in both workshops, and the time-variant characteristics showed very similar trends for 3 days in the packaging workshop. Our study provides important data of TiO2 particles exposure in the workplace.

Solar treatment (H2O2, TiO2-P25 and GO-TiO2 photocatalysis, photo-Fenton) of organic micropollutants, human pathogen indicators, antibiotic resistant bacteria and related genes in urban wastewater.

PubMed

Moreira, Nuno F F; Narciso-da-Rocha, Carlos; Polo-López, M Inmaculada; Pastrana-Martínez, Luisa M; Faria, Joaquim L; Manaia, Célia M; Fernández-Ibáñez, Pilar; Nunes, Olga C; Silva, Adrián M T

2018-05-15

Solar-driven advanced oxidation processes were studied in a pilot-scale photoreactor, as tertiary treatments of effluents from an urban wastewater treatment plant. Solar-H 2 O 2 , heterogeneous photocatalysis (with and/or without the addition of H 2 O 2 and employing three different photocatalysts) and the photo-Fenton process were investigated. Chemical (sulfamethoxazole, carbamazepine, and diclofenac) and biological contaminants (faecal contamination indicators, their antibiotic resistant counterparts, 16S rRNA and antibiotic resistance genes), as well as the whole bacterial community, were characterized. Heterogeneous photocatalysis using TiO 2 -P25 and assisted with H 2 O 2 (P25/H 2 O 2 ) was the most efficient process on the degradation of the chemical organic micropollutants, attaining levels below the limits of quantification in less than 4 h of treatment (corresponding to Q UV  < 40 kJ L -1 ). This performance was followed by the same process without H 2 O 2 , using TiO 2 -P25 or a composite material based on graphene oxide and TiO 2 . Regarding the biological indicators, total faecal coliforms and enterococci and their antibiotic resistant (tetracycline and ciprofloxacin) counterparts were reduced to values close, or beneath, the detection limit (1 CFU 100 mL -1 ) for all treatments employing H 2 O 2 , even upon storage of the treated wastewater for 3-days. Moreover, P25/H 2 O 2 and solar-H 2 O 2 were the most efficient processes in the reduction of the abundance (gene copy number per volume of wastewater) of the analysed genes. However, this reduction was transient for 16S rRNA, intI1 and sul1 genes, since after 3-days storage of the treated wastewater their abundance increased to values close to pre-treatment levels. Similar behaviour was observed for the genes qnrS (using TiO 2 -P25), bla CTX-M and bla TEM (using TiO 2 -P25 and TiO 2 -P25/H 2 O 2 ). Interestingly, higher proportions of sequence reads affiliated to the phylum Proteobacteria (Beta- and Gammaproteobacteria) were found after 3-days storage of treated wastewater than before its treatment. Members of the genera Pseudomonas, Rheinheimera and Methylotenera were among those with overgrowth. Copyright © 2018 Elsevier Ltd. All rights reserved.

Mechanism of strong visible light photocatalysis by Ag2O-nanoparticle-decorated monoclinic TiO2(B) porous nanorods

NASA Astrophysics Data System (ADS)

Paul, Kamal Kumar; Ghosh, Ramesh; Giri, P. K.

2016-08-01

We report on the ultra-high rate of photodegradation of organic dyes under visible light illumination on Ag2O-nanoparticle-decorated (NP) porous pure B-phase TiO2 (TiO2(B)) nanorods (NRs) grown by a solvothermal route. The as-grown TiO2(B) NRs are found to be nanoporous in nature and the Ag2O NPs are uniformly decorated over its surface, since most of the pores work as nucleation sites for the growth of Ag2O NPs. The effective band gap of the TiO2(B)/Ag2O heterostructure (HS), with a weight ratio of 1:1, has been significantly reduced to 1.68 eV from the pure TiO2(B) band gap of 2.8 eV. Steady state and time-resolved photoluminescence (PL) studies show the reduced intensity of visible PL and slower recombination dynamics in the HS samples. The photocatalytic degradation efficiency of the TiO2(B)/Ag2O HS has been investigated using aqueous methyl orange and methylene blue as reference dyes under visible light (390-800 nm) irradiation. It is found that photodegradation by the TiO2(B)/Ag2O HS is about one order of magnitude higher than that of bare TiO2(B) NRs and Ag2O NPs. The optimized TiO2(B)/Ag2O HS exhibited the highest photocatalytic efficiency, with 88.2% degradation for 30 min irradiation. The corresponding first order degradation rate constant is 0.071 min-1, which is four times higher than the reported values. Furthermore, cyclic stability studies show the high stability of the HS photocatalyst for up to four cycles of use. The major improvement in photocatalytic efficiency has been explained on the basis of enhanced visible light absorption and band-bending-induced efficient charge separation in the HS. Our results demonstrate the long-term stability and superiority of the TiO2(B)/Ag2O HS over the bare TiO2(B) NRs and other TiO2-based photocatalysts for its cutting edge application in hydrogen production and environmental cleaning driven by solar light photocatalysis.

Visible Light-activated TiO2 photocatalytic Films; Synthesis, Characterization and Environmental Application for the Destruction of Microcystin-LR

EPA Science Inventory

Titanium dioxide (TiO2) photocatalysis has become one of the most effective advanced oxidation technologies (AOTs) for the treatment of persistent organic contaminants. To generate hydroxyl radicals, a non-selective, reactive oxidizing species and responsible for the oxidation of...

Solar photocatalytic degradation of some hazardous water-soluble pesticides at pilot-plant scale.

PubMed

Oller, I; Gernjak, W; Maldonado, M I; Pérez-Estrada, L A; Sánchez-Pérez, J A; Malato, S

2006-12-01

The technical feasibility and performance of photocatalytic degradation of six water-soluble pesticides (cymoxanil, methomyl, oxamyl, dimethoate, pyrimethanil and telone) have been studied at pilot-plant scale in two well-defined systems which are of special interest because natural solar UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. TiO(2) photocatalysis tests were performed in a 35L solar pilot plant with three Compound Parabolic Collectors (CPCs) under natural illumination and a 75L solar pilot plant with four CPC units was used for homogeneous photocatalysis tests. The initial pesticide concentration studied was 50 mg L(-1) and the catalyst concentrations employed were 200 mg L(-1) of TiO(2) and 20 mg L(-1) of iron. Both toxicity (Vibrio fischeri, Biofix) and biodegradability (Zahn-Wellens test) of the initial pesticide solutions were also measured. Total disappearance of the parent compounds and nearly complete mineralization were attained with all pesticides tested. Treatment time, hydrogen peroxide consumption and release of heteroatoms are discussed.

Surface Plasmon Enhanced Photocatalysis of Au/Pt-decorated TiO2 Nanopillar Arrays

NASA Astrophysics Data System (ADS)

Shuang, Shuang; Lv, Ruitao; Xie, Zheng; Zhang, Zhengjun

2016-05-01

The low quantum yields and lack of visible light utilization hinder the practical application of TiO2 in high-performance photocatalysis. Herein, we present a design of TiO2 nanopillar arrays (NPAs) decorated with both Au and Pt nanoparticles (NPs) directly synthesized through successive ion layer adsorption and reaction (SILAR) at room temperature. Au/Pt NPs with sizes of ~4 nm are well-dispersed on the TiO2 NPAs as evidenced by electron microscopic analyses. The present design of Au/Pt co-decoration on the TiO2 NPAs shows much higher visible and ultraviolet (UV) light absorption response, which leads to remarkably enhanced photocatalytic activities on both the dye degradation and photoelectrochemical (PEC) performance. Its photocatalytic reaction efficiency is 21 and 13 times higher than that of pure TiO2 sample under UV-vis and visible light, respectively. This great enhancement can be attributed to the synergy of electron-sink function of Pt and surface plasmon resonance (SPR) of Au NPs, which significantly improves charge separation of photoexcited TiO2. Our studies demonstrate that through rational design of composite nanostructures one can harvest visible light through the SPR effect to enhance the photocatalytic activities initiated by UV-light, and thus realize more effectively utilization of the whole solar spectrum for energy conversion.

Role of Visible Light-Activated Photocatalyst on the Reduction of Anthrax Spore-Induced Mortality in Mice

PubMed Central

Huang, Hsin-Hsien; Wong, Ming-Show; Lin, Hung-Chi; Chang, Hsin-Hou

2009-01-01

Background Photocatalysis of titanium dioxide (TiO2) substrates is primarily induced by ultraviolet light irradiation. Anion-doped TiO2 substrates were shown to exhibit photocatalytic activities under visible-light illumination, relative environmentally-friendly materials. Their anti-spore activity against Bacillus anthracis, however, remains to be investigated. We evaluated these visible-light activated photocatalysts on the reduction of anthrax spore-induced pathogenesis. Methodology/Principal Findings Standard plating method was used to determine the inactivation of anthrax spore by visible light-induced photocatalysis. Mouse models were further employed to investigate the suppressive effects of the photocatalysis on anthrax toxin- and spore-mediated mortality. We found that anti-spore activities of visible light illuminated nitrogen- or carbon-doped titania thin films significantly reduced viability of anthrax spores. Even though the spore-killing efficiency is only approximately 25%, our data indicate that spores from photocatalyzed groups but not untreated groups have a less survival rate after macrophage clearance. In addition, the photocatalysis could directly inactivate lethal toxin, the major virulence factor of B. anthracis. In agreement with these results, we found that the photocatalyzed spores have tenfold less potency to induce mortality in mice. These data suggest that the photocatalysis might injury the spores through inactivating spore components. Conclusion/Significance Photocatalysis induced injuries of the spores might be more important than direct killing of spores to reduce pathogenicity in the host. PMID:19132100

The Photocatalysis of N,N-diethyl-m-toluamide (DEET) Using Dispersions of Degussa P-25 TiO2 Particles

EPA Science Inventory

The photocatalysis of N,N-diethyl-meta-toluamide (DEET) was examined using aqueous Degussa P-25 TiO₂ dispersions and a 350 nm high pressure Hg lamp UV reactor. Various concentrations of humic acid (HA) were added to the photocatalytic sample matrix in order to simulat...

Minimum ignition temperature of nano and micro Ti powder clouds in the presence of inert nano TiO2 powder.

PubMed

Yuan, Chunmiao; Amyotte, Paul R; Hossain, Md Nur; Li, Chang

2014-06-30

Minimum ignition temperature (MIT) of micro Ti powder increased gradually with increases in nano-sized TiO2 employed as an inertant. Solid TiO2 inertant significantly reduced ignition hazard of micro Ti powder in contact with hot surfaces. The MIT of nano Ti powder remained low (583 K), however, even with 90% TiO2. The MIT of micro Ti powder, when mixed with nano Ti powder at concentrations as low as 10%, decreased so dramatically that its application as a solid fuel may be possible. A simple MIT model was proposed for aggregate particle size estimation and better understanding of the inerting effect of nano TiO2 on MIT. Estimated particle size was 1.46-1.51 μm larger than that in the 20-L sphere due to poor dispersion in the BAM oven. Calculated MITs were lower than corresponding empirically determined values for micro Ti powder because nano-sized TiO2 coated the micro Ti powder, thereby decreasing its reaction kinetics. In the case of nano Ti powder, nano-sized TiO2 facilitated dispersion of nano Ti powder which resulted in a calculated MIT that was greater than the experimentally determined value. Copyright © 2014 Elsevier B.V. All rights reserved.

An innovative ultrasound, Fe(2+) and TiO(2) photoassisted process for bisphenol A mineralization.

PubMed

Torres-Palma, Ricardo A; Nieto, Jessica I; Combet, Evelyne; Pétrier, Christian; Pulgarin, Cesar

2010-04-01

This paper explores the degradation of a model pollutant, bisphenol A, by an advanced oxidation process that combines sonolysis, Fe(2+), and TiO(2) in a photoassisted process. Experiments were done under saturated oxygen conditions. The effect of different Fe(2+) (0.56 and 5.6 mg/L) and TiO(2) (10 and 50 mg/L) concentrations was investigated on both the elimination and mineralization of the pollutant. A pronounced synergistic effect that led to the complete and rapid elimination of dissolved organic carbon (DOC) was observed even at low catalyst loadings. In this system, almost a complete removal of DOC (93%) was observed after 4 h using 10 and 5.6 mg/L of TiO(2) and Fe(2+), respectively, whereas at the same time, only 5, 6, and 22% of DOC was removed by an individual process alone (TiO(2) photocatalysis, ultrasound, and photo-Fenton, respectively). In this system, ultrasound has the principal role of eliminating the initial substrate and providing hydrogen peroxide for the photocatalytic systems, while photo-Fenton and TiO(2) photocatalysis are mainly responsible for the transformation of the intermediates in CO(2) and H(2)O. The role of H(2)O(2) generated from the sonochemical process is also discussed. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Constructing inverse V-type TiO2-based photocatalyst via bio-template approach to enhance the photosynthetic water oxidation

NASA Astrophysics Data System (ADS)

Jiang, Jinghui; Zhou, Han; Ding, Jian; Zhang, Fan; Fan, Tongxiang; Zhang, Di

2015-08-01

Bio-template approach was employed to construct inverse V-type TiO2-based photocatalyst with well distributed AgBr in TiO2 matrix by making dead Troides Helena wings with inverse V-type scales as the template. A cross-linked titanium precursor with homogenous hydrolytic rate, good liquidity, and low viscosity was employed to facilitate a perfect duplication of the template and the dispersion of AgBr based on appropriate pretreatment of the template by alkali and acid. The as-synthesized inverse V-type TiO2/AgBr can be turned into inverse V-type TiO2/Ag0 from AgBr photolysis during photocatalysis to achieve in situ deposition of Ag0 in TiO2 matrix, by this approach, to avoid the deformation of surface microstructure inherited from the template. The result showed that the cooperation of perfect inverse V-type structure and the well distributed TiO2/Ag0 microstructures can efficiently boost the photosynthetic water oxidation compared to non-inverse V-type TiO2/Ag0 and TiO2/Ag0 without using template. The anti-reflection function of inverse V-type structure and the plasmatic effect of Ag0 might be able to account for the enhanced photon capture and efficient photoelectric conversion.

Inactivation and injury of total coliform bacteria after primary disinfection of drinking water by TiO2 photocatalysis.

PubMed

Rizzo, Luigi

2009-06-15

In this study the potential application of TiO(2) photocatalysis as primary disinfection system of drinking water was investigated in terms of coliform bacteria inactivation and injury. As model water the effluent of biological denitrification unit for nitrate removal from groundwater, which is characterized by high organic matter and bacteria release, was used. The injury of photocatalysis on coliform bacteria was characterized by means of selective (mEndo) and less selective (mT7) culture media. Different catalyst loadings as well as photolysis and adsorption effects were investigated. Photocatalysis was effective in coliform bacteria inactivation (91-99% after 60 min irradiation time, depending on both catalyst loading and initial density of coliform bacteria detected by mEndo), although no total removal was observed after 60 min irradiation time. The contribution of adsorption mechanism was significant (60-98% after 60 min, depending on catalyst loading) compared to previous investigations probably due to the nature of source water rich in particulate organic matter and biofilm. Photocatalysis process did not result in any irreversible injury (98.8% being the higher injury) under investigated conditions, thus a bacteria regrowth may take place under optimum environment conditions if any final disinfection process (e.g., chlorine or chlorine dioxide) is not used.

Photocatalysis-assisted water filtration: using TiO2-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7.

PubMed

Oza, Goldie; Pandey, Sunil; Gupta, Arvind; Shinde, Sachin; Mewada, Ashmi; Jagadale, Pravin; Sharon, Maheshwar; Sharon, Madhuri

2013-10-01

A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO2) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO2/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope-energy dispersive analysis of X-ray (SEM-EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO2/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (P<0.05) as compared to TiO2/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO2-ceramic and MWCNT/TiO2-ceramic under fluorescent light was found be 1.45×10(-2) min(-1) and 2.23×10(-2) min(-1) respectively. Further, when I-V characteristics were performed for TiO2/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network. © 2013 Elsevier B.V. All rights reserved.

Synthesis of fly ash based core-shell composites for use as functional pigment in paints

NASA Astrophysics Data System (ADS)

Sharma, Richa; Tiwari, Sangeeta

2016-04-01

Fly ash is a combustion residue, mainly composed of silica, alumina and iron oxides. It is produced by the power industries in very large amounts and usually disposed in landfills, which have represented an environmental problem in recent years1. The need to generate a market for fly ash consumption is the main reason why alternative applications have been studied. It has been applied as an additive in construction materials like cement and pavements2. The present work describes the synthesis of Flyash-Titania core-shell particles by precipitation technique using Titanium tetra isopropoxide (TTIP) which can be used for variety of applications such as NIR reflecting materials for cool coatings, Photocatalysis etc. In this work, Fly ash is used in core and Nano -TiO2 is coated as shell on it. Surfactants are used to improve the adhesion of Nano Titania shell on fly ash core. Effect on adhesion of TiO2 on Fly ash is studied by using different types of surfactant. The preparation of core shells was carried out in absence of surfactant as well as using anionic and non-ionic surfactants. The percentage of surfactant was varied to study the effect of amount of surfactant on the uniformity and size of particles in the shell using Kubelka-Munk transformed reflectance spectra. The morphology of core shell structures was studied using SEM technique. Use of anionic surfactant results in more uniform coating with reduced particle size of the shell material. The composite particles prepared by using anionic surfactant are having good pigment properties and also shows good reflectance in Near Infrared region and hence can be used as a pigment in cool coatings.

[Photocatalysis characterization of titanium dioxide supported on natural clinoplilolite].

PubMed

Fang, Songsheng; Jiang, Yinshan; Wang, Yujie; Bao, Changli; Song, Bo

2003-07-01

This paper studied preparing photocatalyst supported on natural clinoplilolite, photocatalysis degrading to methyl orange solution as photocatalysis function test, solar as light resource, explored the synthesize condition and affect factors of its catalysis activity. The capability of catalyst was evaluated by decolor rate and COD removal rate. The samples was described by XRD, IR and specific surface area. Studied result showed that catalyst prepared by combination of tetrabutyl titanate and natural clinoplilolite dryed under 120 degrees C for 6 hours then calcined under 200 degrees C had the best photocatalysis activity. Degrading rate of methyl orange solution increased with the quantity of TiO2/zeolite and additional oxidant H2O2 increasing, but superfluous H2O2 can also restrain the photocatalysis activity of titanium dioxide supported on clinoplilolite. Methyl orange solution had the best degrading rate as pH value between 2 to 5.

LC/MS/MS structure elucidation of reaction intermediates formed during the TiO2 photocatalysis of microcystin-LR

EPA Science Inventory

Microcystin-LR (MC-LR), a cyanotoxin and emerging drinking water contaminant, was treated with TiO(2) photocatalysts immobilized on stainless steel plates as an alternative to nanoparticles in slurry. The reaction intermediates of MC-LR were identified with mass spectrometry (MS)...

Uniform Gold-Nanoparticle-Decorated {001}-Faceted Anatase TiO2 Nanosheets for Enhanced Solar-Light Photocatalytic Reactions.

PubMed

Shi, Huimin; Zhang, Shi; Zhu, Xupeng; Liu, Yu; Wang, Tao; Jiang, Tian; Zhang, Guanhua; Duan, Huigao

2017-10-25

The {001}-faceted anatase TiO 2 micro-/nanocrystals have been widely investigated for enhancing the photocatalysis and photoelectrochemical performance of TiO 2 nanostructures, but their practical applications still require improved energy conversion efficiency under solar-light and enhanced cycling stability. In this work, we demonstrate the controlled growth of ultrathin {001}-faceted anatase TiO 2 nanosheets on flexible carbon cloth for enhancing the cycling stability, and the solar-light photocatalytic performance of the synthesized TiO 2 nanosheets can be significantly improved by decorating with vapor-phase-deposited uniformly distributed plasmonic gold nanoparticles. The fabricated Au-TiO 2 hybrid system shows an 8-fold solar-light photocatalysis enhancement factor in photodegrading Rhodamine B, a high photocurrent density of 300 μA cm -2 under the illumination of AM 1.5G, and 100% recyclability under a consecutive long-term cycling measurement. Combined with electromagnetic simulations and systematic control experiments, it is believed that the tandem-type separation and transition of plasmon-induced hot electrons from Au nanoparticles to the {001} facet of anatase TiO 2 , and then to the neighboring {101} facet, is responsible for the enhanced solar-light photochemical performance of the hybrid system. The Au-TiO 2 nanosheet system addresses well the problems of the limited solar-light response of anatase TiO 2 and fast recombination of photogenerated electron-hole pairs, representing a promising high-performance recyclable solar-light-responding system for practical photocatalytic reactions.

High surface area TiO2/SBA-15 nanocomposites: Synthesis, microstructure and adsorption-enhanced photocatalysis

NASA Astrophysics Data System (ADS)

Wei, J. Q.; Chen, X. J.; Wang, P. F.; Han, Y. B.; Xu, J. C.; Hong, B.; Jin, H. X.; Jin, D. F.; Peng, X. L.; Li, J.; Yang, Y. T.; Ge, H. L.; Wang, X. Q.

2018-06-01

Mesoporous SBA-15 was used to anchor TiO2 nanoparticles into the mesopores to form high surface area TiO2/SBA-15 nanocomposites, and then the influence of mesoporous-structure on the photocatalytic performance was investigated. TiO2/SBA-15 nanocomposites possessed the high specific surface area and appropriate pore size, indicating the excellent adsorption performance. TiO2/SBA-15 nanocomposites exhibited the higher photocatalytic activity to degrade dyes (methylene blue: MB) than TiO2 (removing SBA-15), which should attributed to the excellent adsorption performance of the nanocomposites. MB was absorbed to form the higher concentration near TiO2/SBA-15 photocatalysts, and the photocatalytic degradation for MB was improved.

Comparative study of the effect of pharmaceutical additives on the elimination of antibiotic activity during the treatment of oxacillin in water by the photo-Fenton, TiO2-photocatalysis and electrochemical processes.

PubMed

Serna-Galvis, Efraim A; Silva-Agredo, Javier; Giraldo, Ana L; Flórez-Acosta, Oscar A; Torres-Palma, Ricardo A

2016-01-15

Synthetic pharmaceutical effluents loaded with the β-lactam antibiotic oxacillin were treated using advanced oxidation processes (the photo-Fenton system and TiO2 photocatalysis) and chloride mediated electrochemical oxidation (with Ti/IrO2 anodes). Combinations of the antibiotic with excipients (mannitol or tartaric acid), an active ingredient (calcium carbonate, i.e. bicarbonate ions due to the pH) and a cleaning agent (sodium lauryl ether sulfate) were considered. Additionally, urban wastewater that had undergone biological treatment was doped with oxacillin and treated with the tested systems. The evolution of antimicrobial activity was monitored as a parameter of processes efficiency. Although the two advanced oxidation processes (AOPs) differ only in the way they produce OH, marked differences were observed between them. There were also differences between the AOPs and the electrochemical system. Interestingly, each additive had a different effect on each treatment. For water loaded with mannitol, electrochemical treatment was the most suitable option because the additive did not significantly affect the efficiency of the system. Due to the formation of a complex with Fe(3+), tartaric acid accelerated the elimination of antibiotic activity during the photo-Fenton process. For TiO2 photocatalysis, the presence of bicarbonate ions contributed to antibiotic activity elimination through the possible formation of carbonate and bicarbonate radicals. Sodium lauryl ether sulfate negatively affected all of the processes. However, due to the higher selectivity of HOCl compared with OH, electrochemical oxidation showed the least inhibited efficiency. For the urban wastewater doped with oxacillin, TiO2 photocatalysis was the most efficient process. These results will help select the most suitable technology for the treatment of water polluted with β-lactam antibiotics. Copyright © 2015 Elsevier B.V. All rights reserved.

Studies on adsorption, reaction mechanisms and kinetics for photocatalytic degradation of CHD, a pharmaceutical waste.

PubMed

Sarkar, Santanu; Bhattacharjee, Chiranjib; Curcio, Stefano

2015-11-01

The photocatalytic degradation of chlorhexidine digluconate (CHD), a disinfectant and topical antiseptic and adsorption of CHD catalyst surface in dark condition has been studied. Moreover, the value of kinetic parameters has been measured and the effect of adsorption on photocatalysis has been investigated here. Substantial removal was observed during the photocatalysis process, whereas 40% removal was possible through the adsorption route on TiO2 surface. The parametric variation has shown that alkaline pH, ambient temperature, low initial substrate concentration, high TiO2 loading were favourable, though at a certain concentration of TiO2 loading, photocatalytic degradation efficiency was found to be maximum. The adsorption study has shown good confirmation with Langmuir isotherm and during the reaction at initial stage, it followed pseudo-first-order reaction, after that Langmuir Hinshelwood model was found to be appropriate in describing the system. The present study also confirmed that there is a significant effect of adsorption on photocatalytic degradation. The possible mechanism for adsorption and photocatalysis has been shown here and process controlling step has been identified. The influences of pH and temperature have been explained with the help of surface charge distribution of reacting particles and thermodynamic point of view respectively. Copyright © 2015 Elsevier Inc. All rights reserved.

Degradation of imidacloprid in water by photo-Fenton and TiO2 photocatalysis at a solar pilot plant: a comparative study.

PubMed

Malato, S; Caceres, J; Agüera, A; Mezcua, M; Hernando, D; Vial, J; Fernández-Alba, A R

2001-11-01

The technical feasibility, mechanisms, and performance of degradation of aqueous imidacloprid have been studied at pilot scale in two well-defined photocatalytic systems of special interest because natural UV light can be used: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. Equivalent pilot-scale and field conditions used for both allowed adequate comparison of the degree of mineralization and toxicity achieved as well as the transformation products generated in route to mineralization by both systems. Ninety-five percent of mineralization (<2.0 mg/L) was reached after 250 min of photocatalytic treatment with Fenton and 450 min with TiO2, meaning that TOC disappears 2.4 times faster with photo-Fenton photocatalytic treatment than with TiO2. The Daphnia Magna test for final residual TOC does not reveal anytoxic behavior. Transformation products evaluated by GC-MS/AED after two SPE procedures and LC-IC were the same in both cases. The main differences between the two processes are in the amount of transformation products (TPs) generated, not in the TPs detected which were always the same. At the end of both processes low concentration (<0.1 mg/L) of 2 pyrrolidinone (transformation product) remains in the dissolution and around 1 mg/L of formate in the case of photo-Fenton.

TiO₂ sol-gel for formaldehyde photodegradation using polymeric support: photocatalysis efficiency versus material stability.

PubMed

Curcio, Monique S; Oliveira, Michel P; Waldman, Walter R; Sánchez, Benigno; Canela, Maria Cristina

2015-01-01

Photocatalysts supported on polymers are not frequently used in heterogeneous photocatalysis because of problems such as wettability and stability that affect photocatalysis conditions. In this work, we used polypropylene as support for TiO2 sol-gel to evaluate its stability and efficiency under UV radiation. We also tested the effect of the thermo-pressing PP/TiO2 system on the photocatalytic efficiency and stability under UV radiation. The films were characterized by scanning electron microscopy (SEM), UV-Vis spectroscopy and X-ray diffraction (XRD). The SEM micrographs showed that the films of TiO2 sol-gel onto PP has approximately 1.0-μm thick and regular surface and the generation of polypropylene nanowires on hot-pressed samples. XRD showed the formation of TiO2 anatase on the surface of the films made by dip-coating. All photocatalysts were tested in decontaminating air-containing gaseous formaldehyde (70 ppmv) presenting degradation of the target compound to the limit of detection. The photocatalysts showed no deactivation during the entire period tested (30 h), and its reuse after washing showed better photocatalytic performance than on first use. The photocatalyst showed the best results were tested for 360 h with no observed deactivation. Aging studies showed that the film of TiO2 causes different effects on the photostability of composites, with stabilizing effect when exposed to most energetic UVC radiation (λmax = 254 nm) and degradative effects when exposed to UVA radiation (λmax = 365 nm).

Self-sterilization using silicone catheters coated with Ag and TiO2 nanocomposite thin film.

PubMed

Yao, Yanyan; Ohko, Yoshihisa; Sekiguchi, Yuki; Fujishima, Akira; Kubota, Yoshinobu

2008-05-01

Ag/titanium dioxide (TiO(2))-coated silicon catheters were easily fabricated with Ag nanoparticles deposition on both the inside wall and the outside wall of TiO(2)-coated catheters by TiO(2) photocatalysis. This is an application of the silicon catheters coated with TiO(2), which possess a self-sterilizing and self-cleaning property combining with UV light illumination (Ohko et al., J Biomed Mater Res: Appl Biomater 2001;58:97). Ag/TiO(2)-coated silicon catheters exhibited a strong bactericidal effect even in the dark. When the 2-5 x 10(5) of colony-forming units of Escherichia coli, Pseudomonas aeruginosa, or Staphylococcus aureus were respectively applied to the surface of the Ag/TiO(2) catheters, which were loaded with approximately 15 nmol cm(-2) of Ag, 99% effective sterilization occurred in a very short time: 20 min for E. coli, 60 min for P. aeruginosa, and 90 min for S. aureus. Additionally, the Ag/TiO(2)-coated catheters possessed a strong self-cleaning property. Using UV illumination, the photocatalytic decomposition rate of methylene blue dye representing the self-cleaning capability, on an Ag/TiO(2) catheter which was loaded with 2 nmol cm(-2) of Ag, was approximately 1.2 times higher (at maximum) than that on TiO(2) coating alone. Furthermore, the Ag nanoparticles can be pre-eminently and uniformly deposited onto the TiO(2) coating, and the amount of Ag was easily controllable from a few nanomoles per square centimeter to approximately 70 nmol cm(-2) by changing the UV illumination time for TiO(2) photocatalysis. This type of catheter shows a great promise in lowering the incidence of catheter-related bacterial infections. Copyright 2007 Wiley Periodicals, Inc.

Surface passivation of nano-textured fluorescent SiC by atomic layer deposited TiO2

NASA Astrophysics Data System (ADS)

Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas; Fadil, Ahmed; Syväjärvi, Mikael; Petersen, Paul Michael; Ou, Haiyan

2016-07-01

Nano-textured surfaces have played a key role in optoelectronic materials to enhance the light extraction efficiency. In this work, morphology and optical properties of nano-textured SiC covered with atomic layer deposited (ALD) TiO2 were investigated. In order to obtain a high quality surface for TiO2 deposition, a three-step cleaning procedure was introduced after RIE etching. The morphology of anatase TiO2 indicates that the nano-textured substrate has a much higher surface nucleated grain density than a flat substrate at the beginning of the deposition process. The corresponding reflectance increases with TiO2 thickness due to increased surface diffuse reflection. The passivation effect of ALD TiO2 thin film on the nano-textured fluorescent 6H-SiC sample was also investigated and a PL intensity improvement of 8.05% was obtained due to the surface passivation.

New insight into the disinfection mechanism of Fusarium monoliforme and Aspergillus niger by TiO2 photocatalyst under low intensity UVA light.

PubMed

Pokhum, Chonlada; Viboonratanasri, Duangamon; Chawengkijwanich, Chamorn

2017-11-01

Titanium dioxide (TiO 2) photocatalytic reaction has great potential for the disinfection of harmful pathogens. However, the disinfection mechanisms of TiO 2 photocatalysis are not yet well-known for fungi and protozoa. In this work, the photocatalytic disinfection mechanism of Fusarium monoliforme and Aspergillus niger under low intensity UVA light (365nm, <10W/m 2 ) was studied at the ultrastructural level. Photocatalytic treatments showed that the photocatalytic oxidation of 10% TiO 2 based paint was efficacious in the complete disinfection of F. monoliforme under low intensity UVA light. No growth of F. monoliforme was observed on agar plate in the subsequent dark. Transmission electron microscopy (TEM) of F. monoliforme exposed to TiO 2 photocatalysis treatment showed a distinct damage to electron-dense outer cell wall, but not to an underlying electron-transparent layer cell wall. The TEM image revealed that the UVA-light only did not damage cell wall, cell membrane and cellular organelles. Unlike, A. niger was more sensitive to UVA-light. Serious destructions of cell membrane and cellular organelles were shown in A. niger exposed to UVA-light only and photocatalytic treatments. However, morphological change in A. niger cell wall was only observed in photocatalytic treatment. Changes to the outermost melanin like layer and cell wall of A. niger spore due to photocatalytic treatment were greatly apparent while the intracellular organelles of A. niger spore were not affected. Therefore, regrowth of A. niger on agar plate was expected from the germination of A. niger spore in the subsequent dark. These observations give a better understanding of the photocatalytic disinfection mechanism toward fungi. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparative study of three magnetic nano-particles (FeSO4, FeSO4/SiO2, FeSO4/SiO2/TiO2) in plasmid DNA extraction.

PubMed

Rahnama, H; Sattarzadeh, A; Kazemi, F; Ahmadi, N; Sanjarian, F; Zand, Z

2016-11-15

Recent updates on Magnetic Nano-Particles (MNPs) based separation of nucleic acids have received more attention due to their easy manipulation, simplicity, ease of automation and cost-effectiveness. It has been indicated that DNA molecules absorb on solid surfaces via hydrogen-bonding, and hydrophobic and electrostatic interactions. These properties highly depend on the surface condition of the solid support. Therefore, surface modification of MNPs may enhance their functionality and specification. In the present study, we functionalized Fe3O4 nano-particle surface utilizing SiO2 and TiO2 layer as Fe3O4/SiO2 and Fe3O4/SiO2/TiO2 and then compare their functionality in the adsorption of plasmid DNA molecules with the naked Fe3O4 nano-particles. The result obtained showed that the purity and amount of DNA extracted by Fe3O4 coated by SiO2 or SiO2/TiO2 were higher than the naked Fe3O4 nano-particles. Furthermore, we obtained pH 8 and 1.5 M NaCl as an optimal condition for desorption of DNA from MNPs. The result further showed that, 0.2 mg nano-particle and 10 min at 55 °C are the optimal conditions for DNA desorption from nano-particles. In conclusion, we recommended Fe3O4/SiO2/TiO2 as a new MNP for separation of DNA molecules from biological sources. Copyright © 2016 Elsevier Inc. All rights reserved.

First-principles study on codoping effect to enhance photocatalytic activity of anatase TiO2

NASA Astrophysics Data System (ADS)

Bai, Yujie; Zhang, Qinfang; Zheng, Fubao; Yang, Yun; Meng, Qiangqiang; Zhu, Lei; Wang, Baolin

2017-03-01

Codopant is an effective approach to modify the bandgap and band edge positions of transition metal oxide. Here, the electronic structures as well as the optical properties of pristine, mono-doped (N/P/Sb) and codoped (Sb, N/P) anatase TiO2 have been systematically investigated based on density functional theory calculations. It is found that mono-doped TiO2 exhibits either unoccupied or partially occupied intermediate state within the energy gap, which promotes the recombination of electron-hole pairs. However, the presence of (Sb, N/P) codopant not only effectively reduces the width of bandgap by introducing delocalized occupied intermediate states, but also adjusts the band edge alignment to enhance the hydrogen evolution activity of TiO2. Moreover, the optical absorption spectrum for (Sb, N/P) codoped TiO2, which is favored under oxygen-rich condition, demonstrates the improvement of its visible light absorption. These findings will promote the potential application of (Sb, N/P) codoped TiO2 photocatalysis for water splitting under visible light irradiation.

Observation the Distribution of Titanium Dioxide Nano-particles in an Experimental Tumor Tissue by a Raman Microscope

NASA Astrophysics Data System (ADS)

Bibin, Andriana B.; Kume, Kyo; Tsutumi, Kotaro; Fukunaga, Yukihiro; Ito, Shinnji; Imamura, Yoshiaki; Miyoshi, Norio

2011-12-01

One of the most important technologies of the 21st century is nanotechnology. Many researchers will have been focusing to employ nanotechnology for medical purpose. Our team was interested in focusing to the application of titanium dioxide (TiO2), as nano-particles, for medical purpose especially drug delivery for the cancer and tumor. The administrations of TiO2 nano-particle via the oral administration of the interface layer particles into the mouse transplanted squamous-cell-carcinoma (SCC) have already conducted. Histology study and Raman spectroscope data were applied to the serial section of frozen tumor tissue in order to observe the distribution of TiO2 nano-particle within the SCC tissue. We used near infrared laser Raman microscopy system, the wavelength is 785 nm. Hematoxyline & eosin stained image and the Raman microscopy system were also used for analyzing the photodynamic therapy (PDT) with 5-ALA and TiO2-particle-sol [TiO2]-ALA-treated tumor samples. As the result, we demonstrated the distribution of TiO2, where TiO2 particles were detected to be distributed in the blood vessel at the bleeding in the SCC tumor tissue. PDT with TiO2 nano-particles that is presented in the SCC-transplanted mouse tumor model can cause the enhancement of photodynamic reaction by nano-particles. Therefore, the combinations of PDT with TiO2 nano-particles may have a possibility to be introduced to the human body in near future for diagnose and PDT treatment of the tumor.

UV-induced photocatalytic degradation of aqueous acetaminophen: the role of adsorption and reaction kinetics.

PubMed

Basha, Shaik; Keane, David; Nolan, Kieran; Oelgemöller, Michael; Lawler, Jenny; Tobin, John M; Morrissey, Anne

2015-02-01

Nanostructured titania supported on activated carbon (AC), termed as integrated photocatalytic adsorbents (IPCAs), were prepared by ultrasonication and investigated for the photocatalytic degradation of acetaminophen (AMP), a common analgesic and antipyretic drug. The IPCAs showed high affinity towards AMP (in dark adsorption studies), with the amount adsorbed proportional to the TiO2 content; the highest adsorption was at 10 wt% TiO2. Equilibrium isotherm studies showed that the adsorption followed the Langmuir model, indicating the dependence of the reaction on an initial adsorption step, with maximum adsorption capacity of 28.4 mg/g for 10 % TiO2 IPCA. The effects of initial pH, catalyst amount and initial AMP concentration on the photocatalytic degradation rates were studied. Generally, the AMP photodegradation activity of the IPCAs was better than that of bare TiO2. Kinetic studies on the photocatalytic degradation of AMP under UV suggest that the degradation followed Langmuir-Hinshelwood (L-H) kinetics, with an adsorption rate constant (K) that was considerably higher than the photocatalytic rate constant (k r), indicating that the photocatalysis of AMP is the rate-determining step during the adsorption/photocatalysis process.

Photocatalytic Applications of Electrospun TiO2 Nanofibres Embedded with Bimodal Sized and Prismatic Gold Nanoparticles.

PubMed

Gopika, G; Asha, A M; Sivakumar, N; Balakrishnan, A; Nair, S V; Subramanian, K R V

2015-09-01

In this paper, we have synthesized electrospun TiO2 nanofibers embedded with bimodal sized and prismatic gold nanoparticles. The surface plasmons generated in the gold nanoparticles were used to enhance the performance of photocatalysis. The photocatalytic conversion efficiencies of these bimodal sized/prismatic gold nanoparticles when embedded in electrospun TiO2 fibres showed an enhancement of upto 60% over bare fiber systems and also show higher efficiencies than electrospun fibrous systems embedded with unimodal sized gold nanoparticles. Anisotropic bimodal gold nanoparticles show the highest degree of photocatalytic activity. This may be attributed to greater density/concentration of nanoparticles with higher effective surface area and formation of a junction between the smaller and larger nanoparticles. Such a bimodally distributed range of nanoparticles could also lead to greater trapping of charge carriers at the TiO2 conduction band edge and promoting catalytic reactions on account of these trapped charges. This enhanced photocatalytic activity is explained by invoking different operating mechanisms such as improved surface area, greater trapping, coarse plasmon resonance and band effects. Thus, a useful applicability of the gold nanoparticles is shown in the area of photocatalysis.

Morphology and thermal stability of nano titanium dioxide filled natural rubber prepared by latex mixing method

NASA Astrophysics Data System (ADS)

Hayeemasae, N.; Surya, I.; Ismail, H.

2018-02-01

This paper deals with the morphology and thermal stability of nano Titanium Dioxide (TiO2) filled natural rubber composites. This study also suggests a new method of incorporating TiO2. Aqueous dispersions of nano TiO2at the loadings of 0, 2, 4, 6 and 8 phr were dispersed in natural rubber latex, the resulting compounds were then dried prior to mixing it with other ingredients on a two-roll mill. By applying this technique, the homogeneity of the compound is significantly improved. This can be clearly seen from the morphology observed. Adding TiO2 results in shifting the decomposition temperature and char residue irrespective of the loadings of nano TiO2.

Toxicity of nanoparticles of CuO, ZnO and TiO2 to microalgae Pseudokirchneriella subcapitata.

PubMed

Aruoja, Villem; Dubourguier, Henri-Charles; Kasemets, Kaja; Kahru, Anne

2009-02-01

Toxicities of ZnO, TiO2 and CuO nanoparticles to Pseudokirchneriella subcapitata were determined using OECD 201 algal growth inhibition test taking in account potential shading of light. The results showed that the shading effect by nanoparticles was negligible. ZnO nanoparticles were most toxic followed by nano CuO and nano TiO2. The toxicities of bulk and nano ZnO particles were both similar to that of ZnSO4 (72 h EC50 approximately 0.04 mg Zn/l). Thus, in this low concentration range the toxicity was attributed solely to solubilized Zn2+ ions. Bulk TiO2 (EC50=35.9 mg Ti/l) and bulk CuO (EC50=11.55 mg Cu/l) were less toxic than their nano formulations (EC50=5.83 mg Ti/l and 0.71 mg Cu/l). NOEC (no-observed-effect-concentrations) that may be used for risk assessment purposes for bulk and nano ZnO did not differ (approximately 0.02 mg Zn/l). NOEC for nano CuO was 0.42 mg Cu/l and for bulk CuO 8.03 mg Cu/l. For nano TiO2 the NOEC was 0.98 mg Ti/l and for bulk TiO2 10.1 mg Ti/l. Nano TiO2 formed characteristic aggregates entrapping algal cells that may contribute to the toxic effect of nano TiO2 to algae. At 72 h EC50 values of nano CuO and CuO, 25% of copper from nano CuO was bioavailable and only 0.18% of copper from bulk CuO. Thus, according to recombinant bacterial and yeast Cu-sensors, copper from nano CuO was 141-fold more bioavailable than from bulk CuO. Also, toxic effects of Cu oxides to algae were due to bioavailable copper ions. To our knowledge, this is one of the first systematic studies on effects of metal oxide nanoparticles on algal growth and the first describing toxic effects of nano CuO towards algae.

Electrochemical vapor generation of selenium species after online photolysis and reduction by UV-irradiation under nano TiO2 photocatalysis and its application to selenium speciation by HPLC coupled with atomic fluorescence spectrometry.

PubMed

Liang, Jing; Wang, Qiuquan; Huang, Benli

2005-01-01

An online UV photolysis and UV/TiO2 photocatalysis reduction device (UV-UV/TiO2 PCRD) and an electrochemical vapor generation (ECVG) cell have been used for the first time as an interface between high-performance liquid chromatography (HPLC) and atomic fluorescence spectrometry (AFS) for selenium speciation. The newly designed ECVG cell of approximately 115 microL dead volume consists of a carbon fiber cathode and a platinum loop anode; the atomic hydrogen generated on the cathode was used to reduce selenium to vapor species for AFS determination. The noise was greatly reduced compared with that obtained by use of the UV-UV/TiO2 PCRD-KBH4-acid interface. The detection limits obtained for seleno-DL: -cystine (SeCys), selenite (Se(IV)), seleno-DL: -methionine (SeMet), and selenate (Se(VI)) were 2.1, 2.9, 4.3, and 3.5 ng mL(-1), respectively. The proposed method was successfully applied to the speciation of selenium in water-soluble extracts of garlic shoots cultured with different selenium species. The results obtained suggested that UV-UV/TiO2 PCRD-ECVG should be an effective interface between HPLC and AFS for the speciation of elements amenable to vapor generation, and is superior to methods involving KBH4.

MD Simulation on Collision Behavior Between Nano-Scale TiO₂ Particles During Vacuum Cold Spraying.

PubMed

Yao, Hai-Long; Yang, Guan-Jun; Li, Chang-Jiu

2018-04-01

Particle collision behavior influences significantly inter-nano particle bonding formation during the nano-ceramic coating deposition by vacuum cold spraying (or aerosol deposition method). In order to illuminate the collision behavior between nano-scale ceramic particles, molecular dynamic simulation was applied to explore impact process between nano-scale TiO2 particles through controlling impact velocities. Results show that the recoil efficiency of the nano-scale TiO2 particle is decreased with the increase of the impact velocity. Nano-scale TiO2 particle exhibits localized plastic deformation during collision at low velocities, while it is intensively deformed by collision at high velocities. This intensive deformation promotes the nano-particle adhesion rather than rebounding off. A relationship between the adhesion energy and the rebound energy is established for the bonding formation of the nano-scale TiO2 particle. The adhesion energy required to the bonding formation between nano-scale ceramic particles can be produced by high velocity collision.

The Acute Liver Injury in Mice Caused by Nano-Anatase TiO2

NASA Astrophysics Data System (ADS)

Ma, Linglan; Zhao, Jinfang; Wang, Jue; Liu, Jie; Duan, Yanmei; Liu, Huiting; Li, Na; Yan, Jingying; Ruan, Jie; Wang, Han; Hong, Fashui

2009-11-01

Although it is known that nano-TiO2 or other nanoparticles can induce liver toxicities, the mechanisms and the molecular pathogenesis are still unclear. In this study, nano-anatase TiO2 (5 nm) was injected into the abdominal cavity of ICR mice for consecutive 14 days, and the inflammatory responses of liver of mice was investigated. The results showed the obvious titanium accumulation in liver DNA, histopathological changes and hepatocytes apoptosis of mice liver, and the liver function damaged by higher doses nano-anatase TiO2. The real-time quantitative RT-PCR and ELISA analyses showed that nano-anatase TiO2 can significantly alter the mRNA and protein expressions of several inflammatory cytokines, including nucleic factor-κB, macrophage migration inhibitory factor, tumor necrosis factor-α, interleukin-6, interleukin-1β, cross-reaction protein, interleukin-4, and interleukin-10. Our results also implied that the inflammatory responses and liver injury may be involved in nano-anatase TiO2-induced liver toxicity.

Nano-Scaled Particles of Titanium Dioxide Convert Benign Mouse Fibrosarcoma Cells into Aggressive Tumor Cells

PubMed Central

Onuma, Kunishige; Sato, Yu; Ogawara, Satomi; Shirasawa, Nobuyuki; Kobayashi, Masanobu; Yoshitake, Jun; Yoshimura, Tetsuhiko; Iigo, Masaaki; Fujii, Junichi; Okada, Futoshi

2009-01-01

Nanoparticles are prevalent in both commercial and medicinal products; however, the contribution of nanomaterials to carcinogenesis remains unclear. We therefore examined the effects of nano-sized titanium dioxide (TiO2) on poorly tumorigenic and nonmetastatic QR-32 fibrosarcoma cells. We found that mice that were cotransplanted subcutaneously with QR-32 cells and nano-sized TiO2, either uncoated (TiO2−1, hydrophilic) or coated with stearic acid (TiO2−2, hydrophobic), did not form tumors. However, QR-32 cells became tumorigenic after injection into sites previously implanted with TiO2−1, but not TiO2−2, and these developing tumors acquired metastatic phenotypes. No differences were observed either histologically or in inflammatory cytokine mRNA expression between TiO2−1 and TiO2−2 treatments. However, TiO2−2, but not TiO2−1, generated high levels of reactive oxygen species (ROS) in cell-free conditions. Although both TiO2−1 and TiO2−2 resulted in intracellular ROS formation, TiO2−2 elicited a stronger response, resulting in cytotoxicity to the QR-32 cells. Moreover, TiO2−2, but not TiO2−1, led to the development of nuclear interstices and multinucleate cells. Cells that survived the TiO2 toxicity acquired a tumorigenic phenotype. TiO2-induced ROS formation and its related cell injury were inhibited by the addition of antioxidant N-acetyl-l-cysteine. These results indicate that nano-sized TiO2 has the potential to convert benign tumor cells into malignant ones through the generation of ROS in the target cells. PMID:19815711

[Study on anti-coagulant property of radio frequency sputtering nano-sized TiO2 thin films].

PubMed

Tang, Xiaoshan; Li, Da

2010-12-01

Nano-TiO2 thin films were prepared by Radio frequency (RF) sputtering on pyrolytic carbon substrates. The influences of sputtering power on the structure and the surface morphology of TiO2 thin films were investigated by X-ray diffraction (XRD), and by scanning electron microscopy (SEM). The results show that the TiO2 films change to anatase through the optimum of sputtering power. The mean diameter of nano-particle is about 30 nm. The anti-coagulant property of TiO2 thin films was observed through platelet adhesion in vitro. The result of experiment reveals the amount of thrombus on the TiO2 thin films being much less than that on the pyrolytic carbon. It also indicates that the RF sputtering Nano-sized TiO2 thin films will be a new kind of promising materials applied to artificial heart valve and endovascular stent.

Minimum ignition energy of nano and micro Ti powder in the presence of inert nano TiO₂ powder.

PubMed

Chunmiao, Yuan; Amyotte, Paul R; Hossain, Md Nur; Li, Chang

2014-06-15

The inerting effect of nano-sized TiO2 powder on ignition sensitivity of nano and micro Ti powders was investigated with a Mike 3 apparatus. "A little is not good enough" is also suitable for micro Ti powders mixed with nano-sized solid inertants. MIE of the mixtures did not significantly increase until the TiO2 percentage exceeded 50%. Nano-sized TiO2 powders were ineffective as an inertant when mixed with nano Ti powders, especially at higher dust loadings. Even with 90% nano TiO2 powder, mixtures still showed high ignition sensitivity because the statistic energy was as low as 2.1 mJ. Layer fires induced by ignited but unburned metal particles may occur for micro Ti powders mixed with nano TiO2 powders following a low level dust explosion. Such layer fires could lead to a violent dust explosion after a second dispersion. Thus, additional attention is needed to prevent metallic layer fires even where electric spark potential is low. In the case of nano Ti powder, no layer fires were observed because of less flammable material involved in the mixtures investigated, and faster flame propagation in nanoparticle clouds. Copyright © 2014 Elsevier B.V. All rights reserved.

Low-frequency ultrasound induces oxygen vacancies formation and visible light absorption in TiO2 P-25 nanoparticles.

PubMed

Osorio-Vargas, Paula A; Pulgarin, Cesar; Sienkiewicz, Andrzej; Pizzio, Luis R; Blanco, Mirta N; Torres-Palma, Ricardo A; Pétrier, Christian; Rengifo-Herrera, Julián A

2012-05-01

Low-frequency ultrasound (LFUS) irradiation induces morphological, optical and surface changes in the commercial nano-TiO(2)-based photocatalyst, Evonik-Degussa P-25. Low-temperature electron spin resonance (ESR) measurements performed on this material provided the first experimental evidence for the formation of oxygen vacancies (V(o)), which were also found responsible for the visible-light absorption. The V(o) surface defects might result from high-speed inter-particle collisions and shock waves generated by LFUS sonication impacting the TiO(2) particles. This is in contrast to a number of well-established technologies, where the formation of oxygen vacancies on the TiO(2) surface often requires harsh technological conditions and complicated procedures, such as annealing at high temperatures, radio-frequency-induced plasma or ion sputtering. Thus, this study reports for the first time the preparation of visible-light responsive TiO(2)-based photocatalysts by using a simple LFUS-based approach to induce oxygen vacancies at the nano-TiO(2) surface. These findings might open new avenues for synthesis of novel nano-TiO(2)-based photocatalysts capable of destroying water or airborne pollutants and microorganisms under visible light illumination. Copyright © 2011 Elsevier B.V. All rights reserved.

TiO2/ZnO and ZnO/TiO2 core/shell nanofibers prepared by electrospinning and atomic layer deposition for photocatalysis and gas sensing

NASA Astrophysics Data System (ADS)

Boyadjiev, Stefan I.; Kéri, Orsolya; Bárdos, Péter; Firkala, Tamás; Gáber, Fanni; Nagy, Zsombor K.; Baji, Zsófia; Takács, Máté; Szilágyi, Imre M.

2017-12-01

In the present work, core TiO2 and ZnO oxide nanofibers were prepared by electrospinning, then shell oxide (ZnO, TiO2) layers were deposited on them by atomic layer deposition (ALD). The aim of preparing ZnO and TiO2 nanofibers, as well as ZnO/TiO2 and TiO2/ZnO nanocomposites is to study the interaction between the oxide materials when a pure oxide fiber is covered with thin film of the other oxide, and explore the influence of exchanging the core and shell materials on their photocatalytic and gas sensing properties. The composition, structure and morphology of the pure and composite nanofibers were studied by SEM-EDX, TEM, XRD, FTIR, UV-vis and Raman. The photocatalytic activity of the as-prepared materials was analyzed by UV-vis spectroscopy through decomposing aqueous methyl orange under UV irradiation. The gas sensing of the nanofibers was investigated by detecting 100 ppm NH3 at 150 and 220 °C using interdigital electrode based sensors.

Synthesis of nanodimensional TiO2 thin films.

PubMed

Thakurdesai, Madhavi; Mohanty, T; John, J; Rao, T K Gundu; Raychaudhuri, Pratap; Bhattacharyya, V; Kanjilal, D

2008-08-01

Nanodimensional TiO2 has wide application in the field of photocatalysis, photovoltaic and photochromic devices. In present investigation TiO2 thin films deposited by pulsed laser deposition method are irradiated by 100 MeV Ag ion beam to achieve growth of nanophases. The nanostructure evolution is characterized by atomic force microscopy (AFM). The phases of TiO2 formed after irradiation are identified by glancing angle X-ray diffraction and Raman spectroscopy. The particle radius estimated by AFM varies from 10-13 nm. Anatase phase of TiO2 is formed after irradiation. The blue shift observed in UV-VIS absorption spectra indicates the nanostructure formation. The shape and size of nanoparticles formed due to high electronic excitation depend upon thickness of the film.

Electrical, thermal, catalytic and magnetic properties of nano-structured materials and their applications

NASA Astrophysics Data System (ADS)

Liu, Zuwei

Nanotechnology is a subject that studies the fabrication, properties, and applications of materials on the nanometer-scale. Top-down and bottom-up approaches are commonly used in nano-structure fabrication. The top-down approach is used to fabricate nano-structures from bulk materials by lithography, etching, and polishing etc. It is commonly used in mechanical, electronic, and photonic devices. Bottom-up approaches fabricate nano-structures from atoms or molecules by chemical synthesis, self-assembly, and deposition, such as sol-gel processing, molecular beam epitaxy (MBE), focused ion beam (FIB) milling/deposition, chemical vapor deposition (CVD), and electro-deposition etc. Nano-structures can have several different dimensionalities, including zero-dimensional nano-structures, such as fullerenes, nano-particles, quantum dots, nano-sized clusters; one-dimensional nano-structures, such as carbon nanotubes, metallic and semiconducting nanowires; two-dimensional nano-structures, such as graphene, super lattice, thin films; and three-dimensional nano-structures, such as photonic structures, anodic aluminum oxide, and molecular sieves. These nano-structured materials exhibit unique electrical, thermal, optical, mechanical, chemical, and magnetic properties in the quantum mechanical regime. Various techniques can be used to study these properties, such as scanning probe microscopy (SPM), scanning/transmission electron microscopy (SEM/TEM), micro Raman spectroscopy, etc. These unique properties have important applications in modern technologies, such as random access memories, display, solar energy conversion, chemical sensing, and bio-medical devices. This thesis includes four main topics in the broad area of nanoscience: magnetic properties of ferro-magnetic cobalt nanowires, plasmonic properties of metallic nano-particles, photocatalytic properties of titanium dioxide nanotubes, and electro-thermal-optical properties of carbon nanotubes. These materials and their properties are briefly reviewed in Chapter One, including the concepts of ferro-magnetism, plasmonics, photocatalysis, thermal emission, and Raman spectra of carbon nanotubes. In Chapter Two, we focus on the magnetic properties of ferro-magnetic cobalt nanowires with high crystalline quality synthesized via a low voltage electro-deposition method. The crystal structure of these Co nanowires is characterized by high resolution transmission electron microscopy and X-ray diffraction. The magnetic properties of individual nanowires and nanowire arrays are investigated by magnetic force microscope (MFM) and superconducting quantum interference device (SQUID) measurements. A theoretical model is developed to explain these experimental observations. In Chapter Three, we exploit the strong plasmon resonance of gold nanoparticles. We also demonstrate a new method for patterning SERS (surface enhanced Raman spectroscopy) aggregates of gold nanoparticles by using a focused laser beam to optically trap the nanoparticles in a water suspension. Raman spectroscopy is used to estimate the temperature in the laser spot during the in-situ aggregation, by measuring the Raman peak of the hydroxyl bond of water. In Chapter Four, we demonstrate plasmonic enhancement of photocatalytic water splitting under visible illumination by integrating strongly plasmonic Au nanoparticles with strongly catalytic TiO2. Electromagnetic simulations indicate that the near-field optical enhancement increases the electron-hole pair generation rate at the surface of the TiO2, thus increasing the amount of photo-generated charge contributing to catalysis. Our results suggest that enhancement factors many times larger than this are possible if this mechanism can be optimized. In Chapter Five, we study the Raman spectra and thermal emission spectra of individual suspended carbon nanotubes induced by electrical heating. Semiconducting and metallic devices exhibit different spectra, based on their distinctive band structures. Raman spectra and the blackbody emission background are used to fit the device temperature. In addition to the blackbody emission background, polarized peaks along the nanotube direction are observed in different ranges of the thermal emission spectra for metallic and semiconducting devices. These peaks are attributed to the transitions between Van Hove singularities that are thermally driven under these high applied bias voltages. A theoretical model is developed to calculate the thermal emission spectra based on this conclusion. In Chapter Six, we present some data of single crystal zinc oxide (ZnO) nanowires synthesized by the CVD method, including magneto-resistance measurements, optical-resistance measurements, and scanning-gate measurements. In Chapter Seven, we discuss some future work related to photocatalysis and carbon nanotubes.

The orderly nano array of truncated octahedra Cu2O nanocrystals with the enhancement of visible light photocatalytic activity

NASA Astrophysics Data System (ADS)

Wei, Xiaofeng; Pan, Jiaqi; Mei, Jie; Zheng, Yingying; Cui, Can; Li, Chaorong

2018-07-01

The orderly nano array is able to improve the light utilization efficiency and has been thought to be a promising way for advancing photocatalysis. The orderly nano array of truncated octahedra Cu2O nanocrystals have been successfully fabricated by the facile solution-based one-step reduction and self-assembly method. The results of XRD, SEM and TEM indicate that the Cu2O nano array is successfully assembled on the Si substrate. The photocatalytic activity of the Cu2O orderly nano array is investigated under visible light irradiation, and it is demonstrated to be significantly enhanced after the Cu2O is self-assembled orderly. Furthermore, the surface orderly structure of the nano array is considered as the main reason for the enhancement.

Visible light-induced photocatalytic degradation of Reactive Blue-19 over highly efficient polyaniline-TiO2 nanocomposite: a comparative study with solar and UV photocatalysis.

PubMed

Kalikeri, Shankramma; Kamath, Nidhi; Gadgil, Dhanashri Jayant; Shetty Kodialbail, Vidya

2018-02-01

Polyaniline-TiO 2 (PANI-TiO 2 ) nanocomposite was prepared by in situ polymerisation method. X-ray diffractogram (XRD) showed the formation of PANI-TiO 2 nanocomposite with the average crystallite size of 46 nm containing anatase TiO 2 . The PANI-TiO 2 nanocomposite consisted of short-chained fibrous structure of PANI with spherical TiO 2 nanoparticles dispersed at the tips and edge of the fibres. The average hydrodynamic diameter of the nanocomposite was 99.5 nm. The band gap energy was 2.1 eV which showed its ability to absorb light in the visible range. The nanocomposite exhibited better visible light-mediated photocatalytic activity than TiO 2 (Degussa P25) in terms of degradation of Reactive Blue (RB-19) dye. The photocatalysis was favoured under initial acidic pH, and complete degradation of 50 mg/L dye could be achieved at optimum catalyst loading of 1 g/L. The kinetics of degradation followed the Langmuir-Hinshelhood model. PANI-TiO 2 nanocomposite showed almost similar photocatalytic activity under UV and visible light as well as in the solar light which comprises of radiation in both UV and visible light range. Chemical oxygen demand removal of 86% could also be achieved under visible light, confirming that simultaneous mineralization of the dye occurred during photocatalysis. PANI-TiO 2 nanocomposites are promising photocatalysts for the treatment of industrial wastewater containing RB-19 dye.

Rational Design of Multifunctional Fe@γ-Fe2 O3 @H-TiO2 Nanocomposites with Enhanced Magnetic and Photoconversion Effects for Wide Applications: From Photocatalysis to Imaging-Guided Photothermal Cancer Therapy.

PubMed

Wang, Meifang; Deng, Kerong; Lü, Wei; Deng, Xiaoran; Li, Kai; Shi, Yanshu; Ding, Binbin; Cheng, Ziyong; Xing, Bengang; Han, Gang; Hou, Zhiyao; Lin, Jun

2018-03-01

Titanium dioxide (TiO 2 ) has been widely investigated and used in many areas due to its high refractive index and ultraviolet light absorption, but the lack of absorption in the visible-near infrared (Vis-NIR) region limits its application. Herein, multifunctional Fe@γ-Fe 2 O 3 @H-TiO 2 nanocomposites (NCs) with multilayer-structure are synthesized by one-step hydrogen reduction, which show remarkably improved magnetic and photoconversion effects as a promising generalists for photocatalysis, bioimaging, and photothermal therapy (PTT). Hydrogenation is used to turn white TiO 2 in to hydrogenated TiO 2 (H-TiO 2 ), thus improving the absorption in the Vis-NIR region. Based on the excellent solar-driven photocatalytic activities of the H-TiO 2 shell, the Fe@γ-Fe 2 O 3 magnetic core is introduced to make it convenient for separating and recovering the catalytic agents. More importantly, Fe@γ-Fe 2 O 3 @H-TiO 2 NCs show enhanced photothermal conversion efficiency due to more circuit loops for electron transitions between H-TiO 2 and γ-Fe 2 O 3 , and the electronic structures of Fe@γ-Fe 2 O 3 @H-TiO 2 NCs are calculated using the Vienna ab initio simulation package based on the density functional theory to account for the results. The reported core-shell NCs can serve as an NIR-responsive photothermal agent for magnetic-targeted photothermal therapy and as a multimodal imaging probe for cancer including infrared photothermal imaging, magnetic resonance imaging, and photoacoustic imaging. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced phenol-photodegradation by particulate semiconductor mixtures: interparticle electron-jump.

PubMed

Karunakaran, C; Dhanalakshmi, R; Gomathisankar, P; Manikandan, G

2010-04-15

Degradation of phenol on suspended TiO(2), ZnO, CdO, Fe(2)O(3), CuO, ZnS and Nb(2)O(5) particles under UV-A light exhibit identical photokinetic behavior; follow first-order kinetics, display linear dependence on the photon flux and slowdown with increase of pH. All the semiconductors show sustainable photocatalytic activity. Dissolved O(2) is essential for the photodegradation and oxidizing agents like H(2)O(2), Na(2)BO(3), K(2)S(2)O(8), KBrO(3), KIO(3) and KIO(4), reducing agents such as NaNO(2) and Na(2)SO(3) and sacrificial electron donors like hydroquinone, diphenyl amine and trimethyl amine enhance the degradation. However, the photocatalysis is insensitive to pre-sonication. Two particulate semiconductors present together, under suspension and at continuous motion, enhance the photocatalytic degradation up to about four-fold revealing interparticle electron-jump. 2009 Elsevier B.V. All rights reserved.

Sonophotocatalytic degradation of dye C.I. Acid Orange 7 by TiO2 and Ag nanoparticles immobilized on corona pretreated polypropylene non-woven fabric.

PubMed

Marković, Darka; Šaponjić, Zoran; Radoičić, Marija; Radetić, Tamara; Vodnik, Vesna; Potkonjak, Branislav; Radetić, Maja

2015-05-01

This study discusses the possibility of using corona pre-treated polypropylene (PP) non-woven fabric as a support for immobilization of colloidal TiO2 and Ag nanoparticles in order to remove dye C.I. Acid Orange 7 from aqueous solution. Dye removal efficiency by sonocatalysis, photocatalysis and sonophotocatalysis was evaluated on corona pre-treated fabric loaded with TiO2 nanoparticles, corona pre-treated fabric double loaded with TiO2 nanoparticles and corona pre-treated fabrics loaded with TiO2 nanoparticles before and after deposition of Ag nanoparticles. In addition, the stability of PP non-woven fabric during these processes was investigated. The substrates were characterized by SEM, EDX and AAS analyses. The change of the dye concentration was evaluated by UV-VIS spectrophotometry. Unlike sonocatalysis and photocatalysis, complete dye removal from both solution and non-woven fabric was obtained already after 240-270 min of sonophotocatalysis. Corona pre-treated PP non-woven fabric loaded with Ag nanoparticles prior to deposition of TiO2 nanoparticles provided excellent degradation efficiency and superior reusability. Sonophotocatalytic degradation of dye in the presence of all investigated samples was the most prominent in acidic conditions. Although this nanocomposite system ensured fast discoloration of dye solution, TOC values of water measured after sonophotocatalysis were not satisfactory because of PP degradation. Therefore, it is suggested to include TOC evaluation in each case study where different supports for TiO2 nanoparticles are used since these nanoparticles may guarantee the dye removal from solution but the stability of support could be problematic causing even more serious environmental impact. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation of Husk-Based Porous Carbon-TiO2 Composites for Adsorption-Photocatalytic Degradation of Toluene in Aqueous Solution

NASA Astrophysics Data System (ADS)

Shi, Ning; Zhao, Lei; Liang, Shuran; Guo, Fengnan; Zhang, Dan; Liu, Xue; Li, Menghan; Peng, Xiao; Wu, Yan

2017-12-01

In this study, PC-nanoTiO2 and PC-P25 were prepared via chemical-deposition and mixture-calcination methods, respectively. Both of PC-nanoTiO2 and PC-P25 were employed to adsorb and photocatalytic degrade toluene in aqueous solution. The characterization results show that distribution of TiO2 nanoparticles in PC-nanoTiO2 and PC-P25 were different, but their binding force between PC and TiO2 were both chemical bonds. Due to synergy of adsorption and photocatalytic degradation, both PC-nanoTiO2 and PC-P25 exhibit good effect in removing toluene in aqueous solution, and both PC-nanoTiO2 and PC-P25 could be utilized for treating wastewater generated from hazardous chemicals leakage accidents emergency.

Microbial disinfection of water with endotoxin degradation by photocatalysis using Ag@TiO2 core shell nanoparticles.

PubMed

S, Sreeja; K, Vidya Shetty

2016-09-01

The studies on photocatalytic disinfection of water contaminated with Escherichia coli using Ag core and TiO2 shell (Ag@TiO2) nanoparticles under UV irradiation showed that these nanoparticles are very efficient in water disinfection both in their free and immobilised form. Complete disinfection of 40 × 10(8) CFU/mL could be achieved in 60 min with 0.4 g/L catalyst loading and in 35 min with 1 g/L catalyst loading. Ag@TiO2 nanoparticles were found to be superior to TiO2 nanoparticles in photocatalytic disinfection of water. Kinetics of disinfection followed Chick's law, and the pseudo-first-order rate constant was 0.0168 min(-1) for a catalyst loading of 0.1 g/L. Disinfection of water and degradation of endotoxins (harmful disinfection residual) occurred simultaneously during photocatalysis thereby making the treated water safe for use. Endotoxin degradation showed a shifting order of kinetics. The rate of photocatalysis with nanoparticles immobilised in cellulose acetate film was marginally lower as compared to that of free nanoparticles. Negligible Ag ion leakage and re-growth of cells post-photo-catalytic treatment of water confirmed that complete disintegration of E. coli occurred during photocatalysis making the treated water safe for use. Therefore, Ag@TiO2 nanoparticles have a potential for large-scale application in drinking water treatment plants and household purification units.

Photocatalytic Cellulosic Electrospun Fibers for the Degradation of Potent Cyanobacteria Toxin Microcystin-LR

DTIC Science & Technology

2012-01-01

treatment applications using solar light as a renewable source of energy. Introduction The need for low cost and efficient water treatment strategies... photocatalysis with nanoparticles (such as titania, TiO2) show tremendous promise as a simple and energy efficient tech- nology for water purification and...which limits the amount of available sunlight that can be used for photocatalysis . To circumvent this issue, methods have been developed to extend

Sonocatalytic degradation of some dyestuffs and comparison of catalytic activities of nano-sized TiO2, nano-sized ZnO and composite TiO2/ZnO powders under ultrasonic irradiation.

PubMed

Wang, Jun; Jiang, Zhe; Zhang, Liqun; Kang, Pingli; Xie, Yingpeng; Lv, Yanhui; Xu, Rui; Zhang, Xiangdong

2009-02-01

Here, a novel sonocatalyst, composite TiO2/ZnO powder, was prepared through the combination of nano-sized TiO2 and ZnO powders. Because of the appropriate adsorbability to organic pollutants and special crystal interphase between TiO2 and ZnO particles, the composite TiO2/ZnO powder exhibits a high sonocatalytic activity under ultrasonic irradiation during the degradation of acid red B. Especially, the sonocatalytic activity of composite TiO2/ZnO powder with 4:1 molar proportion treated at 500 degrees C for 50 min showed obvious improvement compared with pure nano-sized TiO2 and ZnO powders. When the experimental conditions such as 10mg/L acid red B concentration, 1.0 g/L catalyst addition amount, pH=7.0, 20 degrees C system temperature, 100 min ultrasonic time and 50 mL total volume were adopted, the satisfactory degradation ratio and rate were obtained. All experiments indicate that the sonocatalytic method using composite TiO2/ZnO powder may be a more advisable choice for the treatments of non- or low-transparent organic wastewaters in future.

Rhodamine B in dissolved and nano-bound forms: Indicators for light-based advanced oxidation processes.

PubMed

Shabat-Hadas, Efrat; Mamane, Hadas; Gitis, Vitaly

2017-10-01

Rhodamine B (RhB) is a water-soluble fluorescent dye that is often used to determine flux and flow direction in biotechnological and environmental applications. In the current research, RhB in soluble (termed free) and virus-bound (termed nano-bound) forms was used as an efficiency indicator for three environmental processes. The degradation of free and nano-bound RhB by (i) direct UV photolysis and (ii) UV/H 2 O 2 advanced oxidation process (AOP) was studied in a collimated beam apparatus equipped with medium-pressure mercury vapor lamp. The degradation by (iii) solar light-induced photocatalysis was studied in a solar simulator with titanium dioxide and bismuth photocatalysts. Results showed negligible RhB degradation by direct UV and solar light, and its nearly linear degradation by UV/H 2 O 2 and photocatalysis/photosensitization in the presence of a solid catalyst. Considerable adsorption of free RhB on bismuth-based catalyst vs. no adsorption of nano-bound RhB on this catalyst or of any form of the dye on titanium dioxide produced two important conclusions. First, the better degradation of free RhB by the bismuth catalyst suggests that close proximity of a catalyst hole and the decomposing molecule significantly influences degradation. Second, the soluble form of the dye might not be the best option for its use as an indicator. Nano-bound RhB showed high potential as an AOP indicator, featuring possible separation from water after the analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

TiO2 Photocatalysis in Aromatic "Redox Tag"-Guided Intermolecular Formal [2 + 2] Cycloadditions.

PubMed

Okada, Yohei; Maeta, Naoya; Nakayama, Kaii; Kamiya, Hidehiro

2018-05-04

Since the pioneering work by Macmillan, Yoon, and Stephenson, homogeneous photoredox catalysis has occupied a central place in new reaction development in the field of organic chemistry. While heterogeneous semiconductor photocatalysis has also been studied extensively, it has generally been recognized as a redox option in inorganic chemistry where such "photocatalysis" is most often used to catalyze carbon-carbon bond cleavage and not in organic chemistry where bond formation is usually the focal point. Herein, we demonstrate that titanium dioxide photocatalysis is a powerful redox option to construct carbon-carbon bonds by using intermolecular formal [2 + 2] cycloadditions as models. Synergy between excited electrons and holes generated upon irradiation is expected to promote the overall net redox neutral process. Key for the successful application is the use of a lithium perchlorate/nitromethane electrolyte solution, which exhibits remarkable Lewis acidity to facilitate the reactions of carbon-centered radical cations with carbon nucleophiles. The reaction mechanism is reasonably understood based on both intermolecular and intramolecular single electron transfer regulated by an aromatic "redox tag". Most of the reactions were completed in less than 30 min even in aqueous and/or aerobic conditions without the need for sacrificial reducing or oxidizing substrates generally required for homogeneous photoredox catalysis.

Synthesis of novel 3D SnO flower-like hierarchical architectures self-assembled by nano-leaves and its photocatalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Yongkui; Wang, Fengping, E-mail: fpwang@ustb.edu.cn; Iqbal, M. Zubair

Highlights: • Novel 3D SnO flowers self-assembled by 2D nano-leaves were synthesized by hydrothermal method. • The SnO nano-leaf is of single crystalline nature. • The band gap of 2.59 eV of as-prepared products was obtained. • The as-synthesized material will be a promising photocatalytic material. - Abstract: In this report, the novel 3D SnO flower-like hierarchical architectures self-assembled by 2D SnO nano-leaves are successfully synthesized via template-free hydrothermal approach under facile conditions. The high-resolution transmission electron microscopy results demonstrate that the 2D nano-leaves structure is of single crystalline nature. The band gap 2.59 eV for prepared product is obtainedmore » from UV–vis diffuse reflectance spectrum. The photocatalysis of the as prepared SnO for degrading methyl orange (MO) has been studied. A good photocatalytic activity is obtained and the mechanism is discussed in detail. Results indicate that the SnO nanostructures are the potential candidates for photocatalyst applications.« less

Impact of nano and bulk ZrO2, TiO2 particles on soil nutrient contents and PGPR.

PubMed

Karunakaran, Gopalu; Suriyaprabha, Rangaraj; Manivasakan, Palanisamy; Yuvakkumar, Rathinam; Rajendran, Venkatachalam; Kannan, Narayanasamy

2013-01-01

Currently, nanometal oxides are used extensively in different industries such as medicine, cosmetics and food. The increased consumption of nanoparticles (NPs) leads the necessity to understand the fate of the nanoparticles in the environment. The present study focused on the ecotoxicological behaviour of bulk and nano ZrO2 (Zirconia) and TiO2 (Titania) particles on PGPR (plant growth promoting rhizobacteria), soil and its nutrient contents. The microbial susceptibility study showed that nano TiO2 had 13 +/- 0.9 mm (B. megaterium), 15 +/- 0.2 mm (P. fluorescens), 16 +/- 0.2 mm (A. vinelandii) and 12 +/- 0.3 mm (B. brevis) zones of inhibition. However, nano and bulk ZrO2 particles were non-toxic to PGPR. In addition, it was found that toxicity varied depends on the medium of reaction. The soil study showed that nano TiO2 was found to be highly toxic, whereas bulk TiO2 was less toxic towards soil bacterial populations at 1000 mg L(-1). In contrast, nano and bulk ZrO2 were found to be inert at 1000 mg L(-1). The observed zeta potential and hydrophobicity of TiO2 particles causes more toxic than ZrO2 in parallel with particle size. However, nano TiO2 decreases the microbial population as well as nutrient level of the soil but not zirconia. Our finding shows that the mechanism of toxicity depends on size, hydrophobic potential and zeta potential of the metal oxide particles. Thus, it is necessary to take safety measures during the disposal and use of such toxic nanoparticles in the soil to prevent their hazardous effects.

Advances in photocatalytic disinfection of bacteria: Development of photocatalysts and mechanisms.

PubMed

Wang, Wanjun; Huang, Guocheng; Yu, Jimmy C; Wong, Po Keung

2015-08-01

Photocatalysis has attracted worldwide attention due to its potential in solar energy conversion. As a "green" advanced oxidation technology, it has been extensively used for water disinfection and wastewater treatment. This article provides a review of the recent progress in solar energy-induced photocatalytic disinfection of bacteria, focusing on the development of highly efficient photocatalysts and their underlying mechanisms in bacterial inactivation. The photocatalysts are classified into TiO2-based and non-TiO2-based systems, as TiO2 is the most investigated photocatalyst. The synthesis methods, modification strategies, bacterial disinfection activities and mechanisms of different types of photocatalysts are reviewed in detail. Emphasis is given to the modified TiO2, including noble metal deposition, non-metal doping, dye sensitization and composite TiO2, along with typical non-TiO2-based photocatalysts for bacterial disinfection, including metal oxides, sulfides, bismuth metallates, graphene-based photocatalysts, carbon nitride-based photocatalysts and natural photocatalysts. A simple and versatile methodology by using a partition system combined with scavenging study is introduced to study the photocatalytic disinfection mechanisms in different photocatalytic systems. This review summarizes the current state of the work on photocatalytic disinfection of bacteria, and is expected to offer useful insights for the future development in the field. Copyright © 2015. Published by Elsevier B.V.

Highly concentrated phenolic wastewater treatment by heterogeneous and homogeneous photocatalysis: mechanism study by FTIR-ATR.

PubMed

Araña, J; Tello-Rendón, E; Doña-Rodríguez, J M; Campo, C V; Herrera-Melidán, J A; González-Díaz; Pérez-Peña, J

2001-01-01

The degradation of high phenol concentrations (1 g/L) in water solutions by TiO2 photocatalysis and the photo-Fenton reaction has been studied. From the obtained data it may be suggested that degradation of phenol by TiO2-UV takes place onto the catalyst surface by means of peroxo-compounds formation. At low phenol concentrations other mechanism, the insertion of OH. radicals, may be favored. On the other hand, highly concentrated phenol aqueous solutions treatment by the photo-Fenton reaction gives rise to the formation of polyphenolic polymers. These seem to reduce the process rate. Degradation intermediates have been identified by HPLC and FTIR. The FTIR study of the catalyst surface has shown infrared bands attributable to different chemisorbed peroxo-compounds, formates, ortho-formates and carboxylates that can inactivate the catalyst.

Influence of parameters on the heterogeneous photocatalytic degradation of pesticides and phenolic contaminants in wastewater: a short review.

PubMed

Ahmed, Saber; Rasul, M G; Brown, R; Hashib, M A

2011-03-01

In recent years, the application of heterogeneous photocatalytic water purification processes has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible-light spectrum. This paper aims to review and summarize the recent works on the titanium dioxide (TiO(2)) photocatalytic oxidation of pesticides and phenolic compounds, predominant in storm and wastewater effluents. The effects of various operating parameters on the photocatalytic degradation of pesticides and phenols are discussed. Results reported here suggest that the photocatalytic degradation of organic compounds depends on the type and composition of the photocatalyst and, light intensity, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, oxidizing agents/electron acceptors, catalyst application mode, and calcination temperature in the water environment. A substantial amount of research has focused on the enhancement of TiO(2) photocatalysis by modification with metal, non-metal and ion doping. Recent developments in TiO(2) photocatalysis for the degradation of various pesticides and phenols are also highlighted in this review. It is evident from the literature survey that photocatalysis has good potential to remove a variety of organic pollutants. However, there is still a need to determine the practical utility of this technique on a commercial scale. Copyright © 2010 Elsevier Ltd. All rights reserved.

The feasibility of using combined TiO2 photocatalysis oxidation and MBBR process for advanced treatment of biologically pretreated coal gasification wastewater.

PubMed

Xu, Peng; Han, Hongjun; Hou, Baolin; Zhuang, Haifeng; Jia, Shengyong; Wang, Dexin; Li, Kun; Zhao, Qian

2015-01-01

The study examined the feasibility of using combined heterogeneous photocatalysis oxidation (HPO) and moving bed biofilm reactor (MBBR) process for advanced treatment of biologically pretreated coal gasification wastewater (CGW). The results indicated that the TOC removal efficiency was significantly improved in HPO. Gas chromatography-mass spectrometry (GC-MS) analysis indicated that the HPO could be employed to eliminate bio-refractory and toxic compounds. Meanwhile, the BOD5/COD of the raw wastewater was increased from 0.08 to 0.49. Furthermore, in the integration of TiO2 photocatalysis oxidation and MBBR process, the effluent of COD, BOD5, TOC, NH4(+)-N and TN were 22.1 mg/L, 1.1 mg/L, 11.8 mg/L, 4.1mg/L and 13.7 mg/L, respectively, which all met class-I criteria of the Integrated Wastewater Discharge Standard (GB18918-2002, China). The total operating cost was 2.8CNY/t. Therefore, there is great potential for the combined system in engineering applications as a final treatment for biologically pretreated CGW. Copyright © 2015 Elsevier Ltd. All rights reserved.

TiO2 used as photocatalyst for rhodamine B degradation under solar radiation

NASA Astrophysics Data System (ADS)

Ariyanti, Dessy; Maillot, Mathilde; Gao, Wei

2017-07-01

Transition metal oxide photocatalysis is a relatively new method representing advanced oxidation process to be applied in industrial wastewater treatment especially for degradation of organic pollutants. We investigate TiO2 as a photocatalyst for the photocatalytic degradation of Rhodamine B (RhB) under simulated sunlight. Various parameters and their effectiveness have been studied. The effects of processing parameters including catalyst loading and feed concentration were investigated; and the degradation pathway was proposed based on the UHPLC-MS analysis. The result showed that a higher kinetic rate can be obtained by employing low catalyst loading and feed concentration, i.e., 0.5 g/L of TiO2 loading and 5 ppm of RhB concentration, respectively. For this particular system, the optimum degradation rate (k) can achieve 0.297/min. The effectiveness of solar light-TiO2 system for RhB degradation shows this method can be used for wastewater treatment.

Synergistic Effect of Atmospheric-pressure Plasma and TiO2 Photocatalysis on Inactivation of Escherichia coli Cells in Aqueous Media

NASA Astrophysics Data System (ADS)

Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Li, Jiangwei; Wang, Xingquan; Chen, Qiang; Yang, Size; Chen, Zhong; Bazaka, Kateryna; (Ken) Ostrikov, Kostya

2016-12-01

Atmospheric-pressure plasma and TiO2 photocatalysis have been widely investigated separately for the management and reduction of microorganisms in aqueous solutions. In this paper, the two methods were combined in order to achieve a more profound understanding of their interactions in disinfection of water contaminated by Escherichia coli. Under water discharges carried out by microplasma jet arrays can result in a rapid inactivation of E. coli cells. The inactivation efficiency is largely dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2, He and air microplasma arrays, O2 microplasma had the highest activity against E. coli cells in aqueous solution, and showed >99.9% bacterial inactivation efficiency within 4 min. Addition of TiO2 photocatalytic film to the plasma discharge reactor significantly enhanced the inactivation efficiency of the O2 microplasma system, decreasing the time required to achieve 99.9% killing of E. coli cells to 1 min. This may be attributed to the enhancement of ROS generation due to high catalytic activity and stability of the TiO2 photocatalyst in the combined plasma-TiO2 systems. Present work demonstrated the synergistic effect of the two agents, which can be correlated in order to maximize treatment efficiency.

Synergistic Effect of Atmospheric-pressure Plasma and TiO2 Photocatalysis on Inactivation of Escherichia coli Cells in Aqueous Media

PubMed Central

Zhou, Renwu; Zhou, Rusen; Zhang, Xianhui; Li, Jiangwei; Wang, Xingquan; Chen, Qiang; Yang, Size; Chen, Zhong; Bazaka, Kateryna; (Ken) Ostrikov, Kostya

2016-01-01

Atmospheric-pressure plasma and TiO2 photocatalysis have been widely investigated separately for the management and reduction of microorganisms in aqueous solutions. In this paper, the two methods were combined in order to achieve a more profound understanding of their interactions in disinfection of water contaminated by Escherichia coli. Under water discharges carried out by microplasma jet arrays can result in a rapid inactivation of E. coli cells. The inactivation efficiency is largely dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2, He and air microplasma arrays, O2 microplasma had the highest activity against E. coli cells in aqueous solution, and showed >99.9% bacterial inactivation efficiency within 4 min. Addition of TiO2 photocatalytic film to the plasma discharge reactor significantly enhanced the inactivation efficiency of the O2 microplasma system, decreasing the time required to achieve 99.9% killing of E. coli cells to 1 min. This may be attributed to the enhancement of ROS generation due to high catalytic activity and stability of the TiO2 photocatalyst in the combined plasma-TiO2 systems. Present work demonstrated the synergistic effect of the two agents, which can be correlated in order to maximize treatment efficiency. PMID:28004829

Effect of dissolved ozone or ferric ions on photodegradation of thiacloprid in presence of different TiO2 catalysts.

PubMed

Cernigoj, Urh; Stangar, Urska Lavrencic; Jirkovský, Jaromír

2010-05-15

Combining TiO(2) photocatalysis with inorganic oxidants (such as O(3) and H(2)O(2)) or transition metal ions (Fe(3+), Cu(2+) and Ag(+)) often leads to a synergic effect. Electron transfer between TiO(2) and the oxidant is usually involved. Accordingly, the degree of synergy could be influenced by TiO(2) surface area. With this in mind, the disappearance of thiacloprid, a neonicotinoid insecticide, was studied applying various photochemical AOPs and different TiO(2) photocatalysts. In photocatalytic ozonation experiments, synergic effect of three different TiO(2) photocatalysts was quantified. Higher surface area resulted in a more pronounced synergic effect but an increasing amount of TiO(2) did not influence the degree of the synergy. This supports the theory that the synergy is a consequence of adsorption of ozone on the TiO(2) surface. No synergy was observed in photocatalytic degradation of thiacloprid in the presence of dissolved iron(III) species performed under varied experimental conditions (concentration, age of iron(III) solution, different TiO(2) films, usage of TiO(2) slurries). This goes against the literature for different organic compounds (i.e., monuron). It indicates different roles of iron(III) in the photodegradation of different organic molecules. Moreover, TiO(2) surface area did not affect photodegradation efficiency in iron(III)-based experiments which could confirm absence of electron transfer between TiO(2) photocatalyst and iron(III). Copyright (c) 2009 Elsevier B.V. All rights reserved.

Sonocatalytic degradation of humic acid by N-doped TiO2 nano-particle in aqueous solution.

PubMed

Kamani, Hossein; Nasseri, Simin; Khoobi, Mehdi; Nabizadeh Nodehi, Ramin; Mahvi, Amir Hossein

2016-01-01

Un-doped and N-doped TiO2 nano-particles with different nitrogen contents were successfully synthesized by a simple sol-gel method, and were characterized by X-ray diffraction, field emission scanning electron microscopy, Energy dispersive X-ray analysis and UV-visible diffuse reflectance spectra techniques. Then enhancement of sonocatalytic degradation of humic acid by un-doped and N-doped TiO2 nano-particles in aqueous environment was investigated. The effects of various parameters such as initial concentration of humic acid, N-doping, and the degradation kinetics were investigated. The results of characterization techniques affirmed that the synthesis of un-doped and N-doped TiO2 nano-particles was successful. Degradation of humic acid by using different nano-particles obeyed the first-order kinetic. Among various nano-particles, N-doped TiO2 with molar doping ratio of 6 % and band gap of 2.92 eV, exhibited the highest sonocatalytic degradation with an apparent-first-order rate constant of 1.56 × 10(-2) min(-1). The high degradation rate was associated with the lower band gap energy and well-formed anatase phase. The addition of nano-catalysts could enhance the degradation efficiency of humic acid as well as N-doped TiO2 with a molar ratio of 6 %N/Ti was found the best nano-catalyst among the investigated catalysts. The sonocatalytic degradation with nitrogen doped semiconductors could be a suitable oxidation process for removal of refractory pollutants such as humic acid from aqueous solution.

Surface Properties of Titanium dioxide and its Structural Modifications by Reactions with Transition Metals

NASA Astrophysics Data System (ADS)

Halpegamage, Sandamali

Surfaces of metal oxides play a vital role in many technologically important applications. The surfaces of titanium dioxide, in particular, show quite promising properties that can be utilized in solid-state gas sensing and photocatalysis applications. In the first part of this dissertation we investigate these properties of TiO2 surfaces through a vigorous surface scientific approach. In the second part, we investigate the possibilities of modifying the TiO2 surfaces by depositing multi-component transition metal oxide monolayers so that the properties of bare TiO2 surface can be influenced in a beneficial way. For instance, via formation of new surface sites or cations that have different valance states, the chemisorption and catalytic properties can be modified. We use sophisticated experimental surface science techniques that are compatible with ultra-high vacuum technology for surface characterization. All the experimental results, except for the photocatalysis experiments, were compared to and verified by supporting DFT-based theoretical results produced by our theory collaborators. TiO2 based solid-state gas sensors have been used before for detecting trace amounts of explosives such as 2,4-dinitrololuene (DNT), a toxic decomposition product of the explosive 2,4,6-trinitrotoluene (TNT) that have very low vapor pressure. However, the adsorption, desorption and reaction mechanism were not well- understood. Here, we investigate 2,4-DNT adsorption on rutile-TiO2(110) surface in order to gain insight about these mechanisms in an atomistic level and we propose an efficient way of desorbing DNT from the surface through UV-light induced photoreactions. TiO2 exists in different polymorphs and the photocatalytic activity differs from one polymorph to another. Rutile and anatase are the most famous forms of TiO2 in photocatalysis and anatase is known to show higher activity than rutile. The photoactivity also varies depending on the surface orientation for the same polymorph. So far, a reasonable explanation as to why these differences exist was not reported. In our studies, we used high quality epitaxial rutile and anatase thin films which enabled isolating the surface effects from the bulk effects and show that it is the difference between the charge carrier diffusion lengths that causes this difference in activities. In addition to that, using different surface orientations of rutile-TiO 2, we show that the anisotropic bulk charge carrier mobility may contribute to the orientation dependent photoactivity. Moreover, we show that different surface preparation methods also affect the activity of the sample and vacuum reduction results in an enhanced activity. In an effort to modify the TiO2 surfaces with monolayer/mixed monolayer oxides, we carried out experiments on (011) orientation of single crystal rutile TiO2 with few of the selected transition metal oxides namely Fe, V, Cr and Ni. We found that for specific oxidation conditions a monolayer mixed oxide is formed for all M (M= Fe, V, Cr, Ni), with one common structure with the composition MTi2O5. For small amounts of M the surface segregates into pure TiO2(011)-2x1 and into domains of MTi2O5 indicating that this mixed monolayer oxide is a low energy line phase in a compositional surface phase diagram. The oxygen pressure required for the formation of this unique monolayer structure increases in the order of V

Constructing Ordered Three-Dimensional TiO2 Channels for Enhanced Visible-Light Photocatalytic Performance in CO2 Conversion Induced by Au Nanoparticles.

PubMed

Xue, Hairong; Wang, Tao; Gong, Hao; Guo, Hu; Fan, Xiaoli; Gao, Bin; Feng, Yaya; Meng, Xianguang; Huang, Xianli; He, Jianping

2018-03-02

As a typical photocatalyst for CO 2 reduction, practical applications of TiO 2 still suffer from low photocatalytic efficiency and limited visible-light absorption. Herein, a novel Au-nanoparticle (NP)-decorated ordered mesoporous TiO 2 (OMT) composite (OMT-Au) was successfully fabricated, in which Au NPs were uniformly dispersed on the OMT. Due to the surface plasmon resonance (SPR) effect derived from the excited Au NPs, the TiO 2 shows high photocatalytic performance for CO 2 reduction under visible light. The ordered mesoporous TiO 2 exhibits superior material and structure, with a high surface area that offers more catalytically active sites. More importantly, the three-dimensional transport channels ensure the smooth flow of gas molecules, highly efficient CO 2 adsorption, and the fast and steady transmission of hot electrons excited from the Au NPs, which lead to a further improvement in the photocatalytic performance. These results highlight the possibility of improving the photocatalysis for CO 2 reduction under visible light by constructing OMT-based Au-SPR-induced photocatalysts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

MoSe2 modified TiO2 nanotube arrays with superior photoelectrochemical performance

NASA Astrophysics Data System (ADS)

Zhang, Yaping; Zhu, Haifeng; Yu, Lianqing; He, Jiandong; Huang, Chengxing

2018-04-01

TiO2 nanotube arrays (TNTs) are first prepared by anodization Ti foils in ethylene glycol electrolyte. Then, MoSe2 deposites electrochemically on TNTs. The as-synthesized MoSe2/TiO2 composite has a much higher photocurrent density of 1.07 mA cm‑2 at 0 V than pure TNTs of 0.38 mA cm‑2, which suggests that the MoSe2/TiO2 composite film has optimum photoelectrocatalysis properties. The electron transport resistances of the MoSe2/TiO2 decreases to half of pure TiO2, at 295.6 ohm/cm2. Both photocurrent-time and Mott-Schottky plots indicate MoSe2 a p-type semiconductor characteristics. MoSe2/TiO2 composite can achieve a maximum 5 orders of magnitude enhancement in carrier density (4.650 × 1027 cm‑3) than that of pure TiO2 arrays. It can be attributed to p-n heterojunction formed between MoSe2 and TiO2, and the composite can be potentially applied in photoelectrochemical, photocatalysis fields.

Enhanced adsorbability and photocatalytic activity of TiO2-graphene composite for polycyclic aromatic hydrocarbons removal in aqueous phase.

PubMed

Bai, Hongzhen; Zhou, Jun; Zhang, Hongjian; Tang, Guping

2017-02-01

Photodegradation via titanium dioxide (TiO 2 ) has been used to remove polycyclic aromatic hydrocarbons (PAHs) from environmental media broadly. In this study, a series of TiO 2 -graphene composites (P25-GR) with different GR weight ratios were synthesized via hydrothermal reaction of graphene oxide (GO) and P25. Their structures were characterized and the proprieties were tested in aqueous phase. Phenanthrene (PHE), fluoranthene (FLAN), and benzo[a]pyrene (BaP) were selected as models of PAHs. The experiment indicated that P25-2.5%GR exhibited enhancement in both adsorption and photodegradation, ∼80% of PAHs were removed after 2h photocatalysis. The influence of photodegradation rate was studied, including PAHs initial concentration and pH. Aromatic intermediates were identified during the reaction process and the degradation pathways were portrayed. This work explored the enhanced photocatalysis performance was attributed to the PAH-selective adsorbability and the strong electron transfer ability of the composite. The analysis of the degradation intermediates confirmed that the reaction proceeded with the formation of free radicals, leading to the gradual PAH mineralization. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrospray ionization mass spectrometry of the photodegradation of naphthenic acids mixtures irradiated with titanium dioxide.

PubMed

Headley, John V; Du, Jing-Long; Peru, Kerry M; McMartin, Dena W

2009-05-01

Electrospray ionization mass spectrometry was used to study the photodegradation of an oil sands naphthenic acid (NA) mixture, a commercial Fluka NA mixture and a candidate NA, 4-Methyl-cyclohexaneaceticic acid (4-MCHAA) irradiated with TiO(2) (P25) suspension under both fluorescent and natural sunlight. Under natural sunlight irradiation over the TiO(2) suspension, approximately 75% of compounds in the NA mixtures and 100% of 4-MCHAA were degraded in 8 h. No degradation was observed under dark conditions, regardless of the presence or absence of TiO(2). The structural formula of the NAs is given by C(n)H(2n + z)O(2), where n represents the carbon number and z specifies a homologous family with 0-6 rings (z = 0 to -12). The degree of degradation was noted to vary among the NA mixtures and the candidate NA compound with more efficient degradation achieved for molecules with -z values from 0 to 6. The difference in the efficacy of the photocatalysis was likely due to the structure and size of the compounds. In the case of -z = 6 to 12, steric constraints are a key factor what hinders photocatalysis.

Excess electrons in reduced rutile and anatase TiO2

NASA Astrophysics Data System (ADS)

Yin, Wen-Jin; Wen, Bo; Zhou, Chuanyao; Selloni, Annabella; Liu, Li-Min

2018-05-01

As a prototypical photocatalyst, TiO2 is a material of scientific and technological interest. In photocatalysis and other applications, TiO2 is often reduced, behaving as an n-type semiconductor with unique physico-chemical properties. In this review, we summarize recent advances in the understanding of the fundamental properties and applications of excess electrons in reduced, undoped TiO2. We discuss the characteristics of excess electrons in the bulk and at the surface of rutile and anatase TiO2 focusing on their localization, spatial distribution, energy levels, and dynamical properties. We examine specific features of the electronic states for photoexcited TiO2, for intrinsic oxygen vacancy and Ti interstitial defects, and for surface hydroxyls. We discuss similarities and differences in the behaviors of excess electrons in the rutile and anatase phases. Finally, we consider the effect of excess electrons on the reactivity, focusing on the interaction between excess electrons and adsorbates.

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.

Photocatalytic properties of nano-structured TiO2-carbon films obtained by means of electrophoretic deposition.

PubMed

Peralta-Hernández, J M; Manríquez, J; Meas-Vong, Y; Rodríguez, Francisco J; Chapman, Thomas W; Maldonado, Manuel I; Godínez, Luis A

2007-08-17

Recent studies have shown that the light-absorption and photocatalytic efficiencies of TiO2 can be improved by coupling TiO2 nano-particles with nonmetallic dopants, such as carbon. In this paper, we describe the electrophoretic preparation of a novel TiO2-carbon nano-composite photocatalyst on a glass indium thin oxide (ITO) substrate. The objective is to take better advantage of the (e-/h+) pair generated by photoexcitation of semiconducting TiO2 particles. The transfer of electrons (e-) into adjacent carbon nano-particles promotes reduction of oxygen to produce hydrogen peroxide (H2O2) which, in the presence of iron ions, can subsequently form hydroxyl radicals (*OH) via the Fenton reaction. At the same time, *OH is formed from water by the (h+) holes in the TiO2. Thus, the *OH oxidant is produced by two routes. The efficiency of this photolytic-Fenton process was tested with a model organic compound, Orange-II (OG-II) azo dye, which is employed in the textile industry.

Outstanding visible photocatalytic activity of a new mixed bismuth titanatate material

NASA Astrophysics Data System (ADS)

Zambrano, P.; Sayagués, M. J.; Navío, J. A.; Hidalgo, M. C.

2017-02-01

In this work, a new photocatalyst based on bismuth titanates with outstanding visible photocatalytic activity was prepared by a facile hydrothermal method. The synthesised material showed visible activity as high as UV activity of commercial TiO2 P25 under the same experimental conditions for phenol degradation. A wide characterisation of the photocatalyst was performed. The material was composed of three phases; majority of Bi20TiO32 closely interconnected to Bi4Ti3O12 and amorphous TiO2. The high visible activity showed by this material could be ascribed to a combination of several features; i.e. low band gap energy value (2.1 eV), a structure allowing a good separation path for visible photogenerated electron-holes pairs and a relatively high surface area. This photocatalyst appeared as a promising material for solar and visible applications of photocatalysis.

Durable Self-Cleaning Coatings for Architectural Surfaces by Incorporation of TiO2 Nano-Particles into Hydroxyapatite Films

PubMed Central

Sassoni, Enrico; D’Amen, Eros; Roveri, Norberto

2018-01-01

To prevent soiling of marble exposed outdoors, the use of TiO2 nano-particles has been proposed in the literature by two main routes, both raising durability issues: (i) direct application to marble surface, with the risk of particle leaching by rainfall; (ii) particle incorporation into inorganic or organic coatings, with the risk of organic coating degradation catalyzed by TiO2 photoactivity. Here, we investigated the combination of nano-TiO2 and hydroxyapatite (HAP), previously developed for marble protection against dissolution in rain and mechanical consolidation. HAP-TiO2 combination was investigated by two routes: (i) sequential application of HAP followed by nano-TiO2 (“H+T”); (ii) simultaneous application by introducing nano-TiO2 into the phosphate solution used to form HAP (“HT”). The self-cleaning ability was evaluated before and after prolonged exposure to simulated rain. “H+T” and “HT” coatings exhibited much better resistance to nano-TiO2 leaching by rain, compared to TiO2 alone. In “H+T” samples, TiO2 nano-particles adhere better to HAP (having flower-like morphology and high specific surface area) than to marble. In “HT” samples, thanks to chemical bonds between nano-TiO2 and HAP, the particles are firmly incorporated in the HAP coating, which protects them from leaching by rain, without diminishing their photoactivity and without being degraded by them. PMID:29360789

Low cost synthesis of TiO2-C nanocomposite powder for high efficiency visible light photocatalysis

NASA Astrophysics Data System (ADS)

Mohapatra, A. K.; Nayak, J.

2018-04-01

Titanium dioxide-carbon nanocomposite powder was synthesized via a low cost chemical route using oleic acid and titanium tetra-isopropoxide. Since the carbon remained mainly on the surface of the TiO2 nanoparticles, the powder had black color. The composition of the powder was analyzed by X-ray photoelectron spectroscopy and the structure was studied with X-ray diffraction and transmission electron microscopy. The visible photocatalytic activity of the black TiO2 powder was investigated by studying the photo-bleaching of methylene blue under visible light. Our experimental observation showed that the black-TiO2 powder had a higher visible photocatalytic activity compared to the commercial TiO2 powder (P25 Degussa).

The Effect of TiO2 Doped Photocatalytic Nano-Additives on the Hydration and Microstructure of Portland and High Alumina Cements

PubMed Central

Pérez-Nicolás, María; Alvarez, José Ignacio

2017-01-01

Mortars with two different binders (Portland cement (PC) and high alumina cement (HAC)) were modified upon the bulk incorporation of nano-structured photocatalytic additives (bare TiO2, and TiO2 doped with either iron (Fe-TiO2) or vanadium (V-TiO2)). Plastic and hardened state properties of these mortars were assessed in order to study the influence of these nano-additives. Water demand was increased, slightly by bare TiO2 and Fe-TiO2, and strongly by V-TiO2, in agreement with the reduction of the particle size and the tendency to agglomerate. Isothermal calorimetry showed that hydration of the cementitious matrices was accelerated due to additional nucleation sites offered by the nano-additives. TiO2 and doped TiO2 did not show pozzolanic reactivity in the binding systems. Changes in the pore size distribution, mainly the filler effect of the nano-additives, accounted for the increase in compressive strengths measured for HAC mortars. A complex microstructure was seen in calcium aluminate cement mortars, strongly dependent on the curing conditions. Fe-TiO2 was found to be homogeneously distributed whereas the tendency of V-TiO2 to agglomerate was evidenced by elemental distribution maps. Water absorption capacity was not affected by the nano-additive incorporation in HAC mortars, which is a favourable feature for the application of these mortars. PMID:29036917

Photolithographically Patterned TiO2 Films for Electrolyte-Gated Transistors.

PubMed

Valitova, Irina; Kumar, Prajwal; Meng, Xiang; Soavi, Francesca; Santato, Clara; Cicoira, Fabio

2016-06-15

Metal oxides constitute a class of materials whose properties cover the entire range from insulators to semiconductors to metals. Most metal oxides are abundant and accessible at moderate cost. Metal oxides are widely investigated as channel materials in transistors, including electrolyte-gated transistors, where the charge carrier density can be modulated by orders of magnitude upon application of relatively low electrical bias (2 V). Electrolyte gating offers the opportunity to envisage new applications in flexible and printed electronics as well as to improve our current understanding of fundamental processes in electronic materials, e.g. insulator/metal transitions. In this work, we employ photolithographically patterned TiO2 films as channels for electrolyte-gated transistors. TiO2 stands out for its biocompatibility and wide use in sensing, electrochromics, photovoltaics and photocatalysis. We fabricated TiO2 electrolyte-gated transistors using an original unconventional parylene-based patterning technique. By using a combination of electrochemical and charge carrier transport measurements we demonstrated that patterning improves the performance of electrolyte-gated TiO2 transistors with respect to their unpatterned counterparts. Patterned electrolyte-gated (EG) TiO2 transistors show threshold voltages of about 0.9 V, ON/OFF ratios as high as 1 × 10(5), and electron mobility above 1 cm(2)/(V s).

Dye-sensitized TiO2-catalyzed photodegradation of sulfamethoxazole under blue or yellow light.

PubMed

Lu, Norman; Yeh, Yun-Peng; Wang, Guan-Bo; Feng, Tsung-Yao; Shih, Yang-Hsin; Chen, Dong

2017-01-01

Visible light-induced photocatalysis is potentially advantageous and could be an efficient approach to degrade contaminants because it can be used to selectively target specific wavelength for decomposition of organic contaminants in water and wastewater. This study demonstrates the photodegradation of sulfamethoxazole (SMX) using [Pt(3,3'-dicarboxy-2,2'-bpy)(1,2-benzenedithiolate)] (Complex 1)-sensitized and [Pt(4,4'-dicarboxy-2,2'-bpy)(1,2-benzenedithiolate)] (Complex 2)-sensitized titanium dioxide (TiO 2 ) under blue or yellow light (420 or 580 nm, respectively) irradiation in water. The Complex 1-sensitized TiO 2 photocatalytic oxidation of SMX reached almost 100 % removal under 420 nm irradiation for 3 h in water. In addition, the formation of hydroxyl radicals can be facilitated by bubbling O 2 during the photodegradation in which an effective decomposition of SMX was observed. Based on HPLC and UV-Vis studies of the decomposed products, it was found that SMX underwent cleavage of aromatic rings during the photodegradation process.

Three-dimensional TiO2/Au nanoparticles for plasmon enhanced photocatalysis

NASA Astrophysics Data System (ADS)

Yu, Jianyu; Zhou, Lin; Wang, Yang; Tan, Yingling; Wang, Zhenlin; Zhu, Shining; Zhu, Jia

2018-03-01

The mechanisms of plasmonic nanostructures assisted photocatalytic processes are fundamental and of great importance and interest for decades. Therefore, we adopt a unique porous structure of three-dimensional TiO2/Au nanoparticles to experimentally explore the potential mechanisms of rhodamine B (RhB) based photocatalytic degradation. The highly efficient absorbance measured across the entire ultraviolet and infrared regions shows the broadband light harvesting capability and photocatalytic activity, in which the direct bandgap transition, plasmon sensitization as well as the plasmonic photothermal effect can be beneficial for the photocatalytic reaction. The RhB photocatalytic degradation experiments were conducted systematically under solar irradiance with finely chosen optical filters. Apart from the ultraviolet-driven degradation of TiO2, the plasmon assisted photocatalytic rate of our TiO2/Au structure can be enhanced by >30% as compared to the referenced TiO2 structure (equivalent to 2-4 times promotion with respect to the same quantity of the active material TiO2). Detailed wavelength-dependent analyses have revealed that the visible-driven degradation rate can be enhanced by 10 times because of the plasmon sensitization effect; while infrared-driven degradation rate is enhanced by 4 times as well for the plasmonic photothermal effect, respectively. Our experimental results may provide a clear understanding for the wavelength-dependent plasmon enhanced photocatalytic processes.

Synthesis and energy applications of mesoporous titania thin films

NASA Astrophysics Data System (ADS)

Islam, Syed Z.

The optical and electronic properties of TiO2 thin films provide tremendous opportunities in several applications including photocatalysis, photovoltaics and photoconductors for energy production. Despite many attractive features of TiO2, critical challenges include the innate inability of TiO2 to absorb visible light and the fast recombination of photoexcited charge carriers. In this study, mesoporous TiO2 thin films are modified by doping using hydrogen and nitrogen, and sensitization using graphene quantum dot sensitization. For all of these modifiers, well-ordered mesoporous titania films were synthesized by surfactant templated sol-gel process. Two methods: hydrazine and plasma treatments have been developed for nitrogen and hydrogen doping in the mesoporous titania films for band gap reduction, visible light absorption and enhancement of photocatalytic activity. The hydrazine treatment in mesoporous titania thin films suggests that hydrazine induced doping is a promising approach to enable synergistic incorporation of N and Ti3+ into the lattice of surfactant-templated TiO2 films and enhanced visible light photoactivity, but that the benefits are limited by gradual mesostructure deterioration. The plasma treated nitrogen doped mesoporous titania showed about 240 times higher photoactivity compared to undoped film in hydrogen production from photoelectrochemical water splitting under visible light illumination. Plasma treated hydrogen doped mesoporous titania thin films has also been developed for enhancement of visible light absorption. Hydrogen treatment has been shown to turn titania (normally bright white) black, indicating vastly improved visible light absorption. The cause of the color change and its effectiveness for photocatalysis remain open questions. For the first time, we showed that a significant amount of hydrogen is incorporated in hydrogen plasma treated mesoporous titania films by neutron reflectometry measurements. In addition to the intrinsic modification of titania by doping, graphene quantum dot sensitization in mesoporous titania film was also investigated for visible light photocatalysis. Graphene quantum dot sensitization and nitrogen doping of ordered mesoporous titania films showed synergistic effect in water splitting due to high surface area, band gap reduction, enhanced visible light absorption, and efficient charge separation and transport. This study suggests that plasma based doping and graphene quantum dot sensitization are promising strategies to reduce band gap and enhance visible light absorption of high surface area surfactant templated mesoporous titania films, leading to superior visible-light driven photoelectrochemical hydrogen production. The results demonstrate the importance of designing and manipulating the energy band alignment in composite nanomaterials for fundamentally improving visible light absorption, charge separation and transport, and thereby photoelectrochemical properties.

Plant uptake-assisted round-the-clock photocatalysis for complete purification of aquaculture wastewater using sunlight.

PubMed

Bian, Zhenfeng; Cao, Fenglei; Zhu, Jian; Li, Hexing

2015-02-17

A novel reactor equipped with solar batteries, Bi2O3/TiO2 film photocatalyst, and celery plant was designed and used for purification of aquaculture wastewater. The Bi2O3/TiO2 film photocatalyst started photocatalytic degradation of organonitrogen compounds under irradiation of sunlight. Meanwhile, the solar batteries absorbed and converted excess sunlight into electric energy and then started UV lamps at night, leading to round-the-clock photocatalysis. Subsequently, the inorganic nitrogen species including NH4(+), NO2(-), and NO3(-) resulting from photocatalytic degradation of the organonitrogen compounds could subsequently be uptaken by the celery plant as the fertilizer to reduce the secondary pollution. It was found that, after 24 h circulation, both organonitrogen compounds and NO2(-) species were completely removed, while NH4(+) and NO3(-) contents also decreased by 30% and 50%, respectively. The reactor could be used repetitively, showing a good potential in practical application.

Catalytic photodegradation of pharmaceuticals - homogeneous and heterogeneous photocatalysis.

PubMed

Klementova, S; Kahoun, D; Doubkova, L; Frejlachova, K; Dusakova, M; Zlamal, M

2017-01-18

Photocatalytic degradation of pharmaceuticals (hydrocortisone, estradiol, and verapamil) and personal care product additives (parabens-methyl, ethyl, and propyl derivatives) was investigated in the homogeneous phase (with ferric ions as the catalyst) and on TiO 2 . Ferric ions in concentrations corresponding to concentrations in natural water bodies were shown to be a significant accelerator of the degradation in homogeneous reaction mixtures. In heterogeneous photocatalytic reactions on TiO 2 , lower reaction rates, but mineralisation to higher extents, were observed.

Bactericidal effect of the photocatalystic reaction of titanium dioxide using visible wavelengths on Streptococcus mutans biofilm.

PubMed

Kim, Chan-Hee; Lee, Eun-Song; Kang, Si-Mook; de Josselin de Jong, Elbert; Kim, Baek-Il

2017-06-01

The aim of this study was to determine the effect of titanium dioxide (TiO 2 ) photocatalysis induced by the application of clinically acceptable visible light at 405nm on the growth of Streptococcus mutans biofilms. S. mutans biofilms were grown on a hydroxyapatite (HA) disk and deposited in a rutile-type TiO 2 solution at a concentration of 0.1mg/mL. TiO 2 photocatalysis was measured for exposure to visible light (405nm) and ultraviolet (UV) light (254nm) produced by light-emitting diodes for 10, 20, 30, and 40min. After two treatments, the number of colonies formed in the final S. mutans biofilm on the HA disk were measured to confirm their viability, and the morphological changes of S. mutans were evaluated using scanning electronic microscopy. The bactericidal effects of 254- and 405-nm light resulted in > 5-log and 4-log reductions, respectively (p<0.05), after 20min of treatment and a>7-log reduction after 40min of treatment in both treatment groups relative to the control group. It was confirmed that the antibacterial effect could be shown by causing the photocatalytic reaction of TiO 2 in S. mutans biofilm even at the wavelength of visible light (405nm) as at the wavelength of ultraviolet light (254nm). Copyright © 2017 Elsevier B.V. All rights reserved.

A review on the application of inorganic nano-structured materials in the modification of textiles: focus on anti-microbial properties.

PubMed

Dastjerdi, Roya; Montazer, Majid

2010-08-01

Textiles can provide a suitable substrate to grow micro-organisms especially at appropriate humidity and temperature in contact to human body. Recently, increasing public concern about hygiene has been driving many investigations for anti-microbial modification of textiles. However, using many anti-microbial agents has been avoided because of their possible harmful or toxic effects. Application of inorganic nano-particles and their nano-composites would be a good alternative. This review paper has focused on the properties and applications of inorganic nano-structured materials with good anti-microbial activity potential for textile modification. The discussed nano-structured anti-microbial agents include TiO(2) nano-particles, metallic and non-metallic TiO(2) nano-composites, titania nanotubes (TNTs), silver nano-particles, silver-based nano-structured materials, gold nano-particles, zinc oxide nano-particles and nano-rods, copper nano-particles, carbon nanotubes (CNTs), nano-clay and its modified forms, gallium, liposomes loaded nano-particles, metallic and inorganic dendrimers nano-composite, nano-capsules and cyclodextrins containing nano-particles. This review is also concerned with the application methods for the modification of textiles using nano-structured materials. Copyright 2010 Elsevier B.V. All rights reserved.

Color stability of pigmented maxillofacial silicone elastomer: effects of nano-oxides as opacifiers.

PubMed

Han, Ying; Zhao, Yimin; Xie, Chao; Powers, John M; Kiat-amnuay, Sudarat

2010-01-01

This study evaluated the effects of nano-oxides on the color stability of pigmented silicone A-2186 maxillofacial prosthetic elastomers before and after artificial aging. Each of three widely used UV-shielding nano-sized particle oxides (TiO(2), ZnO, CeO(2)), based on recent survey of the industry at 1%, 2%, 2.5% concentrations were combined with each of five intrinsic silicone pigment types (no pigments, red, yellow, blue, and a mixture of the three pigments). Silicone A-2186 without nano-oxides or pigments served as control, for a total of 46 experimental groups of elastomers. In each group of the study, all specimens were aged in an artificial aging chamber for an energy exposure of 450kJ/m(2). CIE L*a*b* values were measured by a spectrophotometer. The 50:50% perceptibility (ΔE*=1.1) and acceptability threshold (ΔE*=3.0) were used in interpretation of recorded color differences. Color differences after aging were subjected to three-way analysis of variance. Means were compared by Fisher's PLSD intervals at the 0.05 level of significance. Yellow pigments mixed with all three nano-oxides at all intervals increased ΔE* values significantly from 3.7 up to 8.4. When mixed pigment groups were considered, TiO(2) at 2%, and 2.5% exhibited the smallest color changes, followed by ZnO and CeO(2), respectively (p<0.001). At 1%, CeO(2) exhibited the smallest color changes, followed by TiO(2) and ZnO, respectively (p<0.001). The smallest color differences, observed for nano-oxides groups, were recorded for CeO(2) at 1%, and TiO(2) at 2% and 2.5%. When the nano-oxides were tested at all concentrations, CeO(2) groups overall had the most color changes, and TiO(2) groups had the least. All ΔE* values of the mixed pigment groups were below the 50:50% acceptability threshold (ΔE*=1.2-2.3, below 3.0) except 2% CeO(2) (ΔE*=4.2). 1% nano-CeO(2) and 2% and 2.5% nano-TiO(2) used as opacifiers for silicone A-2186 maxillofacial prostheses with mixed pigments exhibited the least color changes when subjected to artificial aging at 450kJ/m(2). Yellow silicone pigment mixed with all three nano-oxides significantly affected color stability of A-2186 silicone elastomer. Copyright © 2010 Elsevier Ltd. All rights reserved.

Construction of AgBr nano-cakes decorated Ti3+ self-doped TiO2 nanorods/nanosheets photoelectrode and its enhanced visible light driven photocatalytic and photoelectrochemical properties

NASA Astrophysics Data System (ADS)

Deng, Xiaoyong; Zhang, Huixuan; Guo, Ruonan; Cheng, Xiuwen; Cheng, Qingfeng

2018-05-01

In the study, AgBr nano-cakes decorated Ti3+ self-doped TiO2 nanorods/nanosheets (AgBr-Ti3+/TiO2 NRs/NSs) photoelectrode with enhanced visible light driven photocatalytic (PC) and photoelectrochemical (PECH) performance has been successfully fabricated by hydrothermal reaction, followed by sodium borohydride reduction and then successive ionic layer adsorption and reaction (SILAR) treatment. Afterwards, series of characterizations were conducted to study the physicochemical properties of AgBr-Ti3+/TiO2 NRs/NSs photoelectrode. Results indicated that AgBr nano-cakes with sizes varying from 110 to 180 nm were uniformly decorated on the surface of Ti3+/TiO2 NRs/NSs to form AgBr-Ti3+/TiO2 NRs/NSs photoelectrode. Moreover, PC activity of AgBr-Ti3+/TiO2 NRs/NSs photoelectrode was measured by degradation of methylene blue (MB). It was found that AgBr-Ti3+/TiO2 NRs/NSs photoelectrode exhibited higher PC activity (98.7%) than that of other samples within 150 min visible light illumination, owing to the enhancement of visible light harvesting and effective separation of photoproduced charges. Thus, AgBr nano-cakes and Ti3+ exerted a huge influence on the PC and PECH properties of AgBr-Ti3+/TiO2 NRs/NSs photoelectrode. Furthermore, the possible enhanced visible light driven PC mechanism of AgBr-Ti3+/TiO2 NRs/NSs was proposed and confirmed.

Performance of Hybrid Photocatalytic-Ceramic Membrane System for the Treatment of Secondary Effluent

PubMed Central

Song, Lili; Zhu, Bo; Gray, Stephen; Duke, Mikel; Muthukumaran, Shobha

2017-01-01

Evaluation of an advanced wastewater treatment system that combines photocatalysis with ceramic membrane filtration for the treatment of secondary effluent was undertaken. The results showed that, after photocatalysis and ceramic membrane filtration, the removal of dissolved organic carbon and UV254 was 60% and 54%, respectively, at a concentration of 4 g/L of TiO2. Dissolved organic matter (DOM) present in the secondary effluent was characterised with a liquid chromatography-organic carbon detector (LC-OCD) technique. The results showed low removal of humics, building blocks, the other oxidation by-products and no removal of biopolymers after TiO2/UV photocatalytic treatment. This suggested that the radical non-selective oxidation mechanisms of TiO2/UV process resulted in secondary effluent in which all of the DOM fractions were present. However, the hybrid system was effective for removing biopolymers with the exception of low molecular weight (LMW) compounds acids, which accumulated from the beginning of the reaction. In addition, monitoring of the DOM fractions with LC-OCD analysis demonstrated that the reduction of the effluent aromaticity was not firmly correlated with the removal of humic substances for the combined processes. PMID:28350320

Production and Characterization of TiO2 Nanofilms for Hemocompatible and Photocatalytic Applications

NASA Astrophysics Data System (ADS)

Schvezov, C. E.; Vera, M. L.; Schuster, J. M.; Rosenberger, M. R.

2017-10-01

Titanium dioxide (TiO2) coatings are currently produced for hemocompatible and photocatalytic applications by using two techniques: sol-gel and anodic oxidation. In this review, the research advances on TiO2 nanofilms produced with these techniques are presented, with a focus on different aspects such as process parameters, morphology, roughness, crystal structure, adhesion, wear and erosion resistance, corrosion resistance, hemocompatibility, toxicity, plaque and bacterial adhesion, and heterogeneous photocatalysis of immobilized porous material. This review was presented at the 3rd Pan American Materials Congress at the 2017 TMS Annual Meeting and Exhibition in San Diego, California, USA.

Sustainable Catalysis_Energy efficient reactions and Applications

EPA Science Inventory

This book chapter discusses various catalysts for environmental remediation. Detailed information on catalysis using ferrate and ferrite oxidation, TiO2 photocatalysis, and new catalysts (i.e., graphene, perovskites and graphitic carbon nitride) is provided for the degradation of...

Inactivation of pathogenic bacteria inoculated onto a Bacto™ agar model surface using TiO2-UVC photocatalysis, UVC and chlorine treatments.

PubMed

Yoo, S; Ghafoor, K; Kim, S; Sun, Y W; Kim, J U; Yang, K; Lee, D-U; Shahbaz, H M; Park, J

2015-09-01

The aim of this study was to study inactivation of different pathogenic bacteria on agar model surface using TiO2-UV photocatalysis (TUVP). A unified food surface model was simulated using Bacto(™) agar, a routinely used microbial medium. The foodborne pathogenic bacteria Escherichia coli K12 (as a surrogate for E. coli O157:H7), Salmonella Typhimurium, Staphylococcus aureus and Listeria monocytogenes were inoculated onto the agar surface, followed by investigation of TUVP-assisted inactivation and morphological changes in bacterial cells. The TUVP process showed higher bacterial inactivation, particularly for Gram-negative bacteria, than UVC alone and a control (dark reaction). A TUVP treatment of 17·2 mW cm(-2) (30% lower than the UVC light intensity) reduced the microbial load on the agar surface by 4·5-6·0 log CFU cm(-2). UVC treatment of 23·7 mW cm(-2) caused 3·0-5·3 log CFU cm(-2) reduction. The use of agar model surface is effective for investigation of bacterial disinfection and TUVP is a promising nonthermal technique. The results showing effects of photocatalysis and other treatments for inactivation of bacterial pathogens on model surface can be useful for applying such processes for disinfection of fruit, vegetables and other similar surfaces. © 2015 The Society for Applied Microbiology.

Synthesis, characterization and sonocatalytic applications of nano-structured carbon based TiO2 catalysts.

PubMed

Choi, Jongbok; Cui, Mingcan; Lee, Yonghyeon; Kim, Jeonggwan; Yoon, Yeomin; Jang, Min; Khim, Jeehyeong

2018-05-01

In order to enhance sonocatalytic oxidation of a recalcitrant organic pollutant, rhodamine B (RhB), it is necessary to study the fundamental aspects of sonocatalysis. In this study, TiO 2 -incorporated nano-structured carbon (i.e., carbon nanotubes (CNTs) or graphene (GR)) composites were synthesized by coating TiO 2 on CNTs or GR of different mass percentages (0.5, 1, 5, and 10 wt%) by a facile hydrothermal method. The sonocatalytic degradation rates of RhB were examined for the effect of ultrasound (US) frequency and calcination temperature by using the prepared TiO 2 -NSC composites. Since US frequency affected the sonoluminescence (SL) intensities, it was proposed that there exists a correlation between the surface area or band-gap of the sonocatalysts and the degradation kinetic constants of RhB. In addition, the reusability of TiO 2 -GR composites was also investigated. Overall, the performance of TiO 2 -GRs prepared by the hydrothermal method was better than that of calcined TiO 2 -CNTs. Among TiO 2 -GRs, 5% GR incorporated media (TiO 2 -GR-5) showed the best performance. Interestingly, the kinetic constants of sonocatalysts prepared under hydrothermal conditions had a negative linear relationship with the band-gap energy for the corresponding media. Furthermore, the strongest SL intensity and highest degradation rates of RhB for both carbonaceous composites were observed at 500 kHz. The kinetic constants of calcined media decreased linearly as the specific area of the media decreased, while the band-gap energy could not be correlated with the kinetic constants. The GR combined TiO 2 composite might be a good sonocatalyst in wastewater treatment using ultrasound-based oxidation because of its high stability. Copyright © 2018 Elsevier B.V. All rights reserved.

Achieving phase transformation and structure control of crystalline anatase TiO2@C hybrids from titanium glycolate precursor and glucose molecules.

PubMed

Cheng, Gang; Stadler, Florian J

2015-01-15

Considerable efforts have focused on functional TiO2@carbonaceous hybrid nanostructured materials (TiO2@C) to satisfy the future requirements of environmental photocatalysis and energy storage using these advanced materials. In this study, we developed a two-step solution-phase reaction to prepare hybrid TiO2@C with tuneable structure and composition from the hydrothermal carbonization (HTC) of glucose. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) were used to determine the crystallite size, composition, and phase purity. The results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high resolution TEM (HRTEM) showed that the morphology of the as-synthesized TiO2@C hybrids could be controlled by varying the amount of glucose, also acting as the carbon source. Based on the observations made with different glucose concentrations, a formation mechanism of nanoparticulate and nanoporous TiO2@C hybrids was proposed. In addition, the as-synthesized TiO2@C hybrids with different compositions and structures showed enhanced adsorption of visible light and improved dye-adsorption capacity, which supported their potential use as photocatalysts with good activity. This new synthetic approach, using a nanoprecursor, provides a simple and versatile way to prepare TiO2@C hybrids with tuneable composition, structures, and properties, and is expected to lead to a family of composites with designed properties. Copyright © 2014 Elsevier Inc. All rights reserved.

A novel perovskite solar cell design using aligned TiO2 nano-bundles grown on a sputtered Ti layer and a benzothiadiazole-based, dopant-free hole-transporting material.

PubMed

Ameen, Sadia; Nazim, M; Akhtar, M Shaheer; Nazeeruddin, Mohammad Khaja; Shin, Hyung-Shik

2017-11-16

This work highlights the utilization of a novel hole-transporting material (HTM) derived from benzothiadiazole: 4-(3,5-bis(trifluoromethyl)phenyl)-7-(5'-hexyl-[2,2'-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole (CF-BTz-ThR) and aligned TiO 2 nano-bundles (TiO 2 NBs) as the electron transporting layer (ETL) for perovskite solar cells (PSCs). The aligned TiO 2 NBs were grown on titanium (Ti)-coated FTO substrates using a facile hydrothermal method. The newly designed CF-BTz-ThR molecule with suitable highest occupied molecular orbital (HOMO) favored the effective hole injection from perovskite deposited aligned TiO 2 NBs thin film. The PSCs demonstrated a power conversion efficiency (PCE) of ∼15.4% with a short circuit current density (J sc ) of ∼22.42 mA cm -2 and an open circuit voltage (V oc ) of ∼1.02 V. The efficiency data show the importance of proper molecular engineering whilst highlighting the advantages of dopant-free HTMs in PSCs.

Preparation of Fe3O4/TiO2 magnetic mesoporous composites for photocatalytic degradation of organic pollutants.

PubMed

Zhang, Hongfeng; He, Xiu; Zhao, Weiwei; Peng, Yu; Sun, Donglan; Li, Hao; Wang, Xiaocong

2017-04-01

Fe 3 O 4 /TiO 2 magnetic mesoporous composites were synthesized through a sol-gel method with tetra-n-butyl titanate as precursor and surfactant P123 as template. The as-prepared Fe 3 O 4 /TiO 2 composites were characterized by X-ray diffraction, diffuse reflectance spectroscopy, nitrogen adsorption-desorption isotherm and pore size distribution. The as-synthesized products were applied as photocatalysis for the degradation of Acid Black ATT and tannery wastewater under UV lamp irradiation. Fe 3 O 4 /TiO 2 -8 composites containing Fe 3 O 4 of 8 wt% were selected as model catalysts. The optimal catalyst dosage was 3 g/L in this photocalytic system. The magnetic Fe 3 O 4 /TiO 2 composites possessed good photocatalytic stability and durability. This approach may provide a platform to prepare a magnetic composite to optimize the catalytic ability.

GW quasiparticle bandgaps of anatase TiO2 starting from DFT + U.

PubMed

Patrick, Christopher E; Giustino, Feliciano

2012-05-23

We investigate the quasiparticle band structure of anatase TiO(2), a wide gap semiconductor widely employed in photovoltaics and photocatalysis. We obtain GW quasiparticle energies starting from density-functional theory (DFT) calculations including Hubbard U corrections. Using a simple iterative procedure we determine the value of the Hubbard parameter yielding a vanishing quasiparticle correction to the fundamental bandgap of anatase TiO(2). The bandgap (3.3 eV) calculated using this optimal Hubbard parameter is smaller than the value obtained by applying many-body perturbation theory to standard DFT eigenstates and eigenvalues (3.7 eV). We extend our analysis to the rutile polymorph of TiO(2) and reach similar conclusions. Our work highlights the role of the starting non-interacting Hamiltonian in the calculation of GW quasiparticle energies in TiO(2) and suggests an optimal Hubbard parameter for future calculations.

Hierarchical TiO2/C micro-nano spheres as high-performance anode materials for sodium ion batteries

NASA Astrophysics Data System (ADS)

Ma, Xiao; Zhang, Zhihui; Tian, Jianliya; Xu, Beibei; Ping, Qiushi; Wang, Baofeng

The hierarchical TiO2/C microspheres were obtained via a facile method of in-situ hydrolysis and spray drying. Antase TiO2 nanoparticles were coherent to microspheres TiO2/C due to the pyrolysis of carbon source (PVP). Besides, the favorable electron transfer from carbon to TiO2 improves the electronic conductivity of TiO2 via the presence of Ti-C bond within TiO2/C composite. Charge-discharge tests show that TiO2/C microspheres delivered a good rate capability of 106.1mAhg‑1 at the high current density of 5Ag‑1 and an enhanced cyclic capacity. The superior electrochemical performance could be ascribed to the porous micro-nano structure, smaller crystal size and increased conductivity. The synthesis of TiO2/C microspheres is easy to scale up for satisfying high-performance sodium storage.

Oxidative stress response of the aquatic macrophyte Hydrilla verticillata exposed to TiO2 nanoparticles.

PubMed

Okupnik, Annette; Pflugmacher, Stephan

2016-11-01

The present study investigated the effects of titanium dioxide nanoparticles (TiO 2 -NPs) on the oxidative stress response in Hydrilla verticillata. Macrophytes were exposed to different concentrations of TiO 2 -NPs (0 mg/L, 0.01 mg/L, 0.1 mg/L, 1 mg/L, and 10 mg/L) for 24 h, based on currently predicted levels of nano-TiO 2 in surface waters. In addition, TiO 2 -NPs with varying crystalline status were used to assess the potential influence of crystalline phases on oxidative stress responses. The level of hydrogen peroxide (H 2 O 2 ), reduced and oxidized glutathione (GSH and GSSG), and activities of the antioxidative enzymes peroxidase (POD), catalase (CAT), and glutathione reductase (GR) were measured and compared with a bulk counterpart. Although POD was not considered to be active, the results imply an activation of the enzymatic defense system, because increased CAT and GR activities were observed. Exposure to bulk TiO 2 revealed lower enzyme activities at all exposure concentrations, suggesting a nano-specific influence on the antioxidative defense mechanisms in H. verticillata. Moreover, all TiO 2 -NP concentrations resulted in a decreased GSH/GSSG ratio, indicating high GSH-dependent metabolic activity to protect against the destructive effects of reactive oxygen species (ROS) generated during nano-TiO 2 exposure. As the level of H 2 O 2 was solely elevated after exposure to 10 mg/L of P25, it appears plausible that the adaptive metabolic mechanisms of H. verticillata are able to cope with environmentally relevant concentrations of TiO 2 -NPs. Environ Toxicol Chem 2016;35:2859-2866. © 2016 SETAC. © 2016 SETAC.

In-situ fabrication of diketopyrrolopyrrole-carbazole-based conjugated polymer/TiO2 heterojunction for enhanced visible light photocatalysis

NASA Astrophysics Data System (ADS)

Yang, Long; Yu, Yuyan; Zhang, Jianling; Chen, Fu; Meng, Xiao; Qiu, Yong; Dan, Yi; Jiang, Long

2018-03-01

Aiming at developing highly efficient photocatalysts by broadening the light-harvesting region and suppressing photo-generated electron-hole recombination simultaneously, this work reports rational design and fabrication of donor-acceptor (D-A) conjugated polymer/TiO2 heterojunction catalyst with strong interfacial interactions by a facile in-situ thermal treatment. To expand the light-harvesting window, soluable conjugated copolymers with D-A architecture are prepared by Pd-mediated polycondensation of diketopyrrolopyrrole (DPP) and t-butoxycarbonyl (t-Boc) modified carbazole (Car), and used as visible-light-harvesting antenna to couple with TiO2 nanocrystals. The DPP-Car/TiO2 composites show wide range absorption in 300-1000 nm. To improve the interfacial binding at the interface, a facile in-situ thermal treatment is carried out to cleave the pendant t-Boc groups in carbazole units and liberate the polar amino groups (-NH-) which strongly bind to the surface of TiO2 through dipole-dipole interactions, forming a heterojunction interface. This in-situ thermal treatment changes the surface elemental distribution of TiO2, reinforces the interface bonding at the boundary of conjugated polymers/TiO2 and finally improves the photocatalytic efficiency of DPP-Car/TiO2 under visible-light irradiation. The interface changes are characterized and verified through Fourier-transform infrared spectroscopy (FT-IR), photo images, UV/Vis (solution state and powder diffuse reflection spectroscopy), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fluorescence, scanning electron microscopy(SEM) and transmission electron microscopy (TEM) techniques. This study provides a new strategy to avoid the low solubility of D-A conjugated polymers and construct highly-efficient conjugated polymer/TiO2 heterojunction by enforcing the interface contact and facilitating charge or energy transfer for the applications in photocatalysis.

Characterization of TiO2-based semiconductors for photocatalysis by electrochemical impedance spectroscopy

NASA Astrophysics Data System (ADS)

Ângelo, Joana; Magalhães, Pedro; Andrade, Luísa; Mendes, Adélio

2016-11-01

The photocatalytic activity of a commercial titanium dioxide (P25) and of an in-house prepared P25/graphene composite is assessed according to standard ISO 22197-1:2007. The photoactivity performances of bare and composite TiO2-based materials were further studied by electrochemical impedance spectroscopy (EIS) technique to better understand the function of the graphene in the composite. EIS experiments were performed using a three-electrode configuration, which allows obtaining more detailed information about the complex charge transfer phenomena at the semiconductor/electrolyte interface. The Randles equivalent circuit was selected as the most suitable for modelling the present photocatalysts. The use of the graphene composite allows a more effective charge separation with lower charge transfer resistance and less e-/h+ recombination on the composite photocatalyst, reflected in the higher values of NO conversion.

Treatment of chlorinated solvents by TiO2 photocatalysis and photo-Fenton: influence of operating conditions in a solar pilot plant.

PubMed

Rodríguez, S Malato; Gálvez, J Blanco; Rubio, Manuel I Maldonado; Ibáñez, P Fernández; Gernjak, W; Alberola, I Oller

2005-01-01

Titanium dioxide photocatalysis (using 20 0mg l(-1) of TiO2), under aerobic and anaerobic conditions, and photo-Fenton (2 and 56 mg l(-1) iron) were applied to the treatment of different NBCS (non-biodegradable chlorinated solvents), such as dichloroethane, dichloromethane and trichloromethane dissolved in water at 50 mg l(-1). All the tests were performed in a 35-l solar pilot plant with compound parabolic collectors (CPCs) under natural illumination. The two solar treatments were compared with attention to chloride release and TOC mineralisation, as the main parameters. Photo-Fenton was found to be the more appropriate treatment for these compounds, assuming volatilisation as a drawback of photocatalytic degradation of NBCS dissolved in water. In this context, several operating parameters related to NBCS degradation, e.g., treatment time, temperature, hydrogen peroxide consumption and volatility of parent compounds are discussed. The correct choice of operating conditions can very often diminish the problem of volatilisation during treatment.

Interface engineered construction of porous g-C3N4/TiO2 heterostructure for enhanced photocatalysis of organic pollutants

NASA Astrophysics Data System (ADS)

Li, Ya-Nan; Chen, Zhao-Yang; Wang, Min-Qiang; Zhang, Long-zhen; Bao, Shu-Juan

2018-05-01

A porous g-C3N4/TiO2 with hierarchical heterostructure has been successfully fabricated through a in situ assembling of small needle-like TiO2 on the surface of ultrathin g-C3N4 sheets. The ultrathin g-C3N4 sheets with carbon vacancies and rich hydroxyl groups were found to facilitate the nucleation and in situ growth of TiO2 and also to modulate the surface chemical activity of the g-C3N4/TiO2 hierarchical heterostructure. The as-designed photocatalytic heterojunction degraded Acid Orange with 82% efficiency after 10 min under simulated solar light, and possessed excellent cycle stability. Relative physical characterizations and photochemical experiments reveal that engineering the interface/surface of g-C3N4 plays a vital role in effectively constructing heterostructures of g-C3N4/TiO2, thus realizing efficient photoinduced electron-hole separation during photocatalytic process.

Facile synthesis of the Ti3+ self-doped TiO2-graphene nanosheet composites with enhanced photocatalysis.

PubMed

Qiu, Bocheng; Zhou, Yi; Ma, Yunfei; Yang, Xiaolong; Sheng, Weiqin; Xing, Mingyang; Zhang, Jinlong

2015-02-26

This study developed a facile approach for preparing Ti(3+) self-doped TiO2-graphene photocatalyst by a one-step vacuum activation technology involved a relative lower temperature, which could be activated by the visible light owing to the synergistic effect among Ti(3+) doping, some new intersurface bonds generation and graphene oxide reduction. Compared with the traditional methods, the vacuum activation involves a low temperature and low-costing, which can achieve the reduction of GO, the self doping of Ti(3+) in TiO2 and the loading of TiO2 nanoparticles on GR surface at the same time. These resulting TiO2-graphene composites show the high photodegradation rate of MO, high hydrogen evolution activity and excellent IPCE in the visible light irradiation. The facile vacuum activation method can provide an effective and practical approach to improve the performance of TiO2-graphene and other metal oxides-graphene towards their practical photocatalytic applications.

Facile synthesis of the Ti3+ self-doped TiO2-graphene nanosheet composites with enhanced photocatalysis

NASA Astrophysics Data System (ADS)

Qiu, Bocheng; Zhou, Yi; Ma, Yunfei; Yang, Xiaolong; Sheng, Weiqin; Xing, Mingyang; Zhang, Jinlong

2015-02-01

This study developed a facile approach for preparing Ti3+ self-doped TiO2-graphene photocatalyst by a one-step vacuum activation technology involved a relative lower temperature, which could be activated by the visible light owing to the synergistic effect among Ti3+ doping, some new intersurface bonds generation and graphene oxide reduction. Compared with the traditional methods, the vacuum activation involves a low temperature and low-costing, which can achieve the reduction of GO, the self doping of Ti3+ in TiO2 and the loading of TiO2 nanoparticles on GR surface at the same time. These resulting TiO2-graphene composites show the high photodegradation rate of MO, high hydrogen evolution activity and excellent IPCE in the visible light irradiation. The facile vacuum activation method can provide an effective and practical approach to improve the performance of TiO2-graphene and other metal oxides-graphene towards their practical photocatalytic applications.

Degradation of paracetamol in aqueous solutions by TiO2 photocatalysis.

PubMed

Yang, Liming; Yu, Liya E; Ray, Madhumita B

2008-07-01

In this study, photo/photocatalytic oxidation of common analgesic and antipyretic drug, paracetamol (acetaminophen), was investigated to determine the optimal operating conditions for degradation in water. UVA (365 nm) radiation alone degraded negligible amount of paracetamol, whereas paracetamol concentration decreased substantially under an irradiation of UVC (254 nm) with marginal changes in total organic carbon (TOC). In the presence of TiO2, much faster photodegradation of paracetamol and effective mineralization occurred; more than 95% of 2.0mM paracetamol was degraded within 80 min. The degradation rate constant decreased with an increase in the initial concentration of paracetamol, while it increased with light intensity and oxygen concentration. The degradation rate also increased with TiO2 loading until a concentration of 0.8 g L(-1). The degradation rate slowly increased between pH 3.5 and 9.5, but significantly decreased with increasing pH between 9.5 and 11.0. Based on the experimental data, a kinetic equation describing paracetamol photocatalytic degradation with various process parameters is obtained.

Sunscreens with Titanium Dioxide (TiO2) Nano-Particles: A Societal Experiment

PubMed Central

van de Poel, Ibo; Osseweijer, Patricia

2010-01-01

The risks of novel technologies, such as nano(bio)technology cannot be fully assessed due to the existing uncertainties surrounding their introduction into society. Consequently, the introduction of innovative technologies can be conceptualised as a societal experiment, which is a helpful approach to evaluate moral acceptability. This approach is illustrated with the marketing of sunscreens containing nano-sized titanium dioxide (TiO2) particles. We argue that the marketing of this TiO2 nanomaterial in UV protective cosmetics is ethically undesirable, since it violates four reasonable moral conditions for societal experimentation (absence of alternatives, controllability, limited informed consent, and continuing evaluation). To remedy the current way nano-sized TiO2 containing sunscreens are utilised, we suggest five complementing actions (closing the gap, setup monitoring tools, continuing review, designing for safety, and regulative improvements) so that its marketing can become more acceptable. PMID:20835397

Cellulose acetate-based SiO2/TiO2 hybrid microsphere composite aerogel films for water-in-oil emulsion separation

NASA Astrophysics Data System (ADS)

Yang, Xue; Ma, Jianjun; Ling, Jing; Li, Na; Wang, Di; Yue, Fan; Xu, Shimei

2018-03-01

The cellulose acetate (CA)/SiO2-TiO2 hybrid microsphere composite aerogel films were successfully fabricated via water vapor-induced phase inversion of CA solution and simultaneous hydrolysis/condensation of 3-aminopropyltrimethoxysilane (APTMS) and tetrabutyl titanate (TBT) at room temperature. Micro-nano hierarchical structure was constructed on the surface of the film. The film could separate nano-sized surfactant-stabilized water-in-oil emulsions only under gravity. The flux of the film for the emulsion separation was up to 667 L m-2 h-1, while the separation efficiency was up to 99.99 wt%. Meanwhile, the film exhibited excellent stability during multiple cycles. Moreover, the film performed excellent photo-degradation performance under UV light due to the photocatalytic ability of TiO2. Facile preparation, good separation and potential biodegradation maked the CA/SiO2-TiO2 hybrid microsphere composite aerogel films a candidate in oil/water separation application.

Multifunctional wall coating combining photocatalysis, self-cleaning and latent heat storage

NASA Astrophysics Data System (ADS)

Lucas, S. S.; Barroso de Aguiar, J. L.

2018-02-01

Mortars, one of the most common construction materials, have not received any substantial modification for many decades. This has changed in recent years; new compositions are now being developed, with new properties, using nano-additives, fibres and capsules. In this work, surfaces with new and innovative functionalities that promote energy savings and improve air quality have been developed and studied. Incorporation of phase change materials (PCM) and titanium dioxide (TiO2) nanoparticles in construction products is currently under study by different research groups. However, these studies only address their incorporation separately. Adding new additives into the mortar’s matrix can be complex—due to microstructural modifications that will influence both fresh and hardened state properties. Moving from a single additive to multiple additions, as in this study, increases the system’s complexity. Only with a good understanding of the microstructural properties, it is possible to add multiple additives (including nano and microparticles) to mortars, without damaging its final quality. This work demonstrates that a higher additive content is not always a guarantee of better results; lower additions can often provide a better compromise between performance and final mechanical properties. The results presented in this paper confirmed this and show that combining PCM microcapsules and TiO2 nanoparticles open a new path in the development of mortars with multiple functionalities. In this study, a new material with depolluting, self-cleaning and heat storage was created. For the development of new and innovative mortars, a proper balance of multiple additives, supported by the study of microstructural changes, can lead to an optimization of the compositions, ensuring that the mortar’s final properties are not affected.

An external template-free route to uniform semiconducting hollow mesospheres and their use in photocatalysis.

PubMed

Yang, Di; Wang, Mengye; Zou, Bin; Zhang, Gu Ling; Lin, Zhiqun

2015-08-14

Solid amorphous TiO2 mesospheres were synthesized by controlled hydrolysis of Ti-containing precursors. Subsequently, solid TiO2 mesospheres were exploited as scaffolds and subjected to a one-step external template-free hydrothermal treatment, yielding intriguing hollow anatase TiO2 mesospheres. The synthetic protocol was optimized by investigating the effect of buffer reagents and fluoride ions on the formation of hollow TiO2 spheres. The diameter of hollow mesospheres, ranging from 308 to 760 nm, can be readily tailored by varying the precursor concentration. The average thickness of a shell composed of TiO2 nanocrystals was approximately 40 nm with a mean crystal size of 12.4-20.0 nm. Such hollow TiO2 mesospheres possessed a large surface area and were employed in photocatalytic degradation of methylene blue under UV irradiation. Interestingly, the synthetic conditions were found to exert a significant influence on the photocatalytic ability of hollow TiO2 mesospheres. The correlation between the degradation ability of hollow TiO2 mesospheres and the precursor concentration as well as the hydrothermal time was scrutinized. The optimal photocatalytic performance of hollow TiO2 mesospheres was identified.

1-D and 2-D morphology of metal cation co-doped (Zn, Mn) TiO2 and investigation of their photocatalytic activity

NASA Astrophysics Data System (ADS)

Benjwal, Poonam; De, Bibekananda; Kar, Kamal K.

2018-01-01

Morphology and electronic bandgap of titania (TiO2) are considered to be the primary factors for determining the photocatalytic efficiency, as they determine the number of active sites for the photocatalytic reactions. In the present study, two different morphologies of TiO2 (nanosphere and nanorod) with varying Zn and Mn co-doping were synthesized by solvothermal and hydrothermal methods to examine their photocatalytic efficiency by methylene blue degradation. The co-doped photocatalysts were characterized by XRD, XPS, SEM, TEM, Raman, FTIR and UV-vis DRS. Further, a comparison has been made with co-doped TiO2 nanospheres and TiO2 nanorods, where Zn, Mn co-doped TiO2 nanorods show higher photocatalytic activity compared to nanospheres. This higher photocatalytic activity of co-doped TiO2 is attributed to its polymorphic phases, as they act as heterojunctions for TiO2. Further, being 1-D nanostructure, the TiO2 nanorods exhibit the straight diffusion path for charge carriers, which reduces the recombination possibilities. The obtained results suggest that the photocatalysis efficiency of TiO2 can be significantly enhanced by tailoring the shape and co-doping concentration, which enforce a new concept for developing the new nanostructures of TiO2.

Removal of aqueous chromium and environmental CO2 by using photocatalytic TiO2 doped with tungsten.

PubMed

Trejo-Valdez, M; Hernández-Guzmán, S R; Manriquez-Ramírez, M E; Sobral, H; Martínez-Gutiérrez, H; Torres-Torres, C

2018-05-15

Removal of hexavalent chromium was accomplished by using photocatalyst materials of TiO 2 doped with tungsten oxide, environmental air as oxygen supply and white light as irradiation source. Dichromate anions in concentration ranges of 50 to 1000 μg/L were removed by means of aqueous dispersions of TiO 2 doped with tungsten. The aqueous chromium analyses were performed by Differential Pulse Voltammetry technique. Additionally, mineralization of CO 2 gas was promoted by the photocatalysis process, as was clearly shown by Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) analyses obtained from the TiO 2 samples recovered after photocatalytic experiments. Results of sample analyses by Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) are presented and discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Chronic TiO2 nanoparticle exposure to a benthic organism, Hyalella azteca: Impact of solar UV radiation and material surface coatings on toxicity

EPA Science Inventory

The present study examined the chronic toxicity of TiO2 nanoparticles (nano-TiO2) to a representative benthic species, Hyalella azteca, using an industry standard, P25, and a coated nano-TiO2 used in commercial products. There is limited information on the chronic effects of nano...

A study of the uptake and biodistribution of nano-titanium dioxide using in vitro and in vivo models of oral intake

NASA Astrophysics Data System (ADS)

MacNicoll, Alan; Kelly, Mick; Aksoy, Hatice; Kramer, Evelien; Bouwmeester, Hans; Chaudhry, Qasim

2015-02-01

Certain food additives may contain a sizeable fraction of particles in the nanoscale. However, little is known about the fate, behaviour and toxicological effects of orally-ingested nanoparticles. This study investigated the uptake and biodistribution of nano- and larger-sized titanium dioxide (TiO2) using an in vitro model of gut epithelium and in vivo in rat. The results of the in vivo study showed that oral administration of 5 mg/kg body weight of TiO2 nano- or larger particles did not lead to any significant translocation of TiO2 (measured as titanium) either to blood, urine or to various organs in rat at any of the time intervals studied over a 96 h post-administration period. Different methods used for dispersing particles did not affect the uptake, and orally administered TiO2 was found excreted in the faeces over a period of time. The in vitro study provided further evidence for the lack of translocation of TiO2 across the gut epithelium model. The overall evidence from both in vivo and in vitro studies did not support that oral ingestion of nano- or larger particles of TiO2 via food would result in any significant internal exposure of the consumer to the nanoparticles. The dietary TiO2 nanoparticles are likely to be excreted in the faeces.

Sol-gel-Derived nano-sized double layer anti-reflection coatings (SiO2/TiO2) for low-cost solar cell fabrication.

PubMed

Lee, Seung Jun; Hur, Man Gyu; Yoon, Dae Ho

2013-11-01

We investigate nano-sized double layer anti-reflection coatings (ARCs) using a TiO2 and SiO2 sol-gel solution process for mono-crystalline silicon solar cells. The process can be easily adapted for spraying sol-gel coatings to reduce manufacturing cost. The spray-coated SiO2/TiO2 nano-sized double layer ARCs were deposited on mono-crystalline silicon solar cells, and they showed good optical properties. The spray coating process is a lower-cost fabrication process for large-scale coating than vacuum deposition processes such as PECVD. The measured average optical reflectance (300-1200 nm) was about approximately 8% for SiO2/TiO2 nano-sized double layer ARCs. The electrical parameters of a mono-crystalline silicon solar cell and reflection losses show that the SiO2/TiO2 stacks can improve cell efficiency by 0.2% compared to a non-coated mono-crystalline silicon solar cell. In the results, good correlation between theoretical and experimental data was obtained. We expect that the sol-gel spray-coated mono-crystalline silicon solar cells have high potential for low-cost solar cell fabrication.

Energy recovery during advanced wastewater treatment: simultaneous estrogenic activity removal and hydrogen production through solar photocatalysis.

PubMed

Zhang, Wenlong; Li, Yi; Wang, Chao; Wang, Peifang; Wang, Qing

2013-03-01

Simultaneous estrogenic activity removal and hydrogen production from secondary effluent were successfully achieved using TiO(2) microspheres modified with both platinum nanoparticles and phosphates (P-TiO(2)/Pt) for the first time. The coexistence of platinum and phosphate on the surface of TiO(2) microspheres was confirmed by transmission electron microscope, energy-dispersive X-ray and X-ray photoelectron spectroscopy analyses. P-TiO(2)/Pt microspheres showed a significantly higher photocatalytic activity than TiO(2) microspheres and TiO(2) powders (P25) for the removal of estrogenic activity from secondary effluent with the removal ratio of 100%, 58.2% and 48.5% in 200 min, respectively. Moreover, the marked production of hydrogen (photonic efficiency: 3.23 × 10(-3)) was accompanied by the removal of estrogenic activity only with P-TiO(2)/Pt as photocatalysts. The hydrogen production rate was increasing with decreased DO concentration in secondary effluent. Results of reactive oxygen species (ROS) evaluation during P-TiO(2)/Pt photocatalytic process showed that O(2)(-)and OH were dominant ROS in aerobic phase, while OH was the most abundant ROS in anoxic phase. Changes of effluent organic matter (EfOM) during photocatalysis revealed that aromatic, hydrophobic, and high molecular weight fractions of EfOM were preferentially transformed into non-humic, hydrophilic, and low MW fractions (e.g. aldehydes and carboxylic acids), which were continuously utilized as electron donors in hydrogen production process. Copyright © 2012 Elsevier Ltd. All rights reserved.

Comparison of Benzene & Toluene removal from synthetic polluted air with use of Nano photocatalyticTiO2/ ZNO process.

PubMed

Gholami, Mitra; Nassehinia, Hamid Reza; Jonidi-Jafari, Ahmad; Nasseri, Simin; Esrafili, Ali

2014-02-05

Mono aromatic hydrocarbons (BTEX) are a group of hazardous pollutants which originate from sources such as refineries, gas, and oil extraction fields, petrochemicals and paint and glue industries.Conventional methods, including incineration, condensation, adsorption and absorption have been used for removal of VOCs. None of these methods is economical for removal of pollutants of polluted air with low to moderate concentrations. The heterogeneous photocatalytic processes involve the chemical reactions to convert pollutant to carbon dioxide and water. The aim of this paper is a comparison of Benzene & Toluene removal from synthetic polluted air using a Nano photocatalytic TiO2/ ZNO process. The X-ray diffraction (XRD) patterns showed that Nano crystals of TiO2 and ZNO were in anatase and rutile phases. Toluene & benzene were decomposed by TiO2/ ZNO Nano photocatalyst and UV radiation. Kruskal-wallis Test demonstrated that there are significant differences (pvalue < 0.05) between pollutant concentrations in different operational conditions. Degradation of toluene & benzene increases with increasing UV intensity and decreasing initial concentrations. Effect of TiO2/ZNO Nano photocatalyst on benzene is less than that on toluene. In this research, Toluene & benzene removal by TiO2/ZNO and UV followed first-order reactions.

Comparison of Benzene & Toluene removal from synthetic polluted air with use of Nano photocatalyticTiO2/ ZNO process

PubMed Central

2014-01-01

Background Mono aromatic hydrocarbons (BTEX) are a group of hazardous pollutants which originate from sources such as refineries, gas, and oil extraction fields, petrochemicals and paint and glue industries. Conventional methods, including incineration, condensation, adsorption and absorption have been used for removal of VOCs. None of these methods is economical for removal of pollutants of polluted air with low to moderate concentrations. The heterogeneous photocatalytic processes involve the chemical reactions to convert pollutant to carbon dioxide and water. The aim of this paper is a comparison of Benzene & Toluene removal from synthetic polluted air using a Nano photocatalytic TiO2/ ZNO process. Results The X-ray diffraction (XRD) patterns showed that Nano crystals of TiO2 and ZNO were in anatase and rutile phases. Toluene & benzene were decomposed by TiO2/ ZNO Nano photocatalyst and UV radiation. Kruskal-wallis Test demonstrated that there are significant differences (pvalue < 0.05) between pollutant concentrations in different operational conditions. Conclusions Degradation of toluene & benzene increases with increasing UV intensity and decreasing initial concentrations. Effect of TiO2/ZNO Nano photocatalyst on benzene is less than that on toluene. In this research, Toluene & benzene removal by TiO2/ZNO and UV followed first-order reactions. PMID:24499601

Photodegradation of organic matter in fresh garbage leachate using immobilized nano-sized TiO2 as catalysts.

PubMed

Chen, C; Xie, Q; Hu, B Q; Zhao, X L

2014-01-01

Two immobilized nano-sized TiO2 catalysts, TiO2/activated carbon (TiO2/AC) and TiO2/silica gel (SG) (TiO2/SG), were prepared by the sol-gel method, and their use in the photocatalytic degradation of organic matter in fresh garbage leachate under UV irradiation was investigated. The influences of the catalyst dosage, the initial solution pH, H2O2 addition and the reuse of the catalysts were evaluated. The degradation of organic matter was assessed based on the decrease of the chemical oxygen demand (COD) in the leachate. The results indicated that the degradation of the COD obeyed first-order kinetics in the presence of both photocatalysts. The degradation rate of COD was found to increase with increasing catalyst dosage up to 9 g/L for TiO2/AC and 6 g/L for TiO2/SG, above which the degradation began to attenuate. Furthermore, the degradation rate first increased and then decreased as the solution pH increased from 2 to 14, and the degradation rate increased as the amount of H2O2 increased to 2.93 mM, after which it remained constant. No obvious decrease in the rate of COD degradation was observed during the first four repeated uses of the photocatalysts, indicating that the catalysts could be recovered and reused. Compared with TiO2/AC, TiO2/SG exhibited higher efficiency in photocatalyzing the degradation of COD in garbage leachate.

Visible Light Photocatalysis via CdS/ TiO 2 Nanocomposite Materials

DOE PAGES

Srinivasan, Sesha S.; Wade, Jeremy; Stefanakos, Elias K.

2006-01-01

Nmore » anostructured colloidal semiconductors with heterogeneous photocatalytic behavior have drawn considerable attention over the past few years. This is due to their large surface area, high redox potential of the photogenerated charge carriers, and selective reduction/oxidation of different classes of organic compounds. In the present paper, we have carried out a systematic synthesis of nanostructured CdS- TiO 2 via reverse micelle process. The structural and microstructural characterizations of the as-prepared CdS- TiO 2 nanocomposites are determined using XRD and SEM-EDS techniques. The visible light assisted photocatalytic performance is monitored by means of degradation of phenol in water suspension.« less

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

NASA Astrophysics Data System (ADS)

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

2017-03-01

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

Effects of titanium dioxide nanoparticles derived from ...

EPA Pesticide Factsheets

Increased manufacture of TiO2 nano-products has caused concern about the potential toxicity of these products to the environment and in public health. Identification and confirmation of the presence of TiO2 nanoparticles derived from consumer products as opposed to industrial TiO2 NPs warrants examination in exploring the significance of their release and resultant impacts on the environment. To this end we examined the significance of the release of these particles and their toxic effect on the marine diatom algae Thalassiosira pseudonana. Our results indicate that nano-TiO2 sunscreen and toothpaste exhibit more toxicity in comparison to industrial TiO2, and inhibited the growth of the marine diatom Thalassiosira pseudonana. This inhibition was proportional to the exposure time and concentrations of nano-TiO2. Our findings indicate a significant effect, and therefore further research is warranted in evaluation and assessment of the toxicity of modified nano-TiO2 derived from consumer products and their physicochemical properties. Submit to journal Environmental Science and Pollution Research.

Facile fabrication of transparent TiO2-C@TiO2-C free-standing film for visible-light photocatalytic application

NASA Astrophysics Data System (ADS)

Hu, Luyang; Zhang, Yumin; Zhang, Shanmei; Li, Benxia

2017-02-01

A transparent TiO2-C@TiO2-C free-standing film has been synthesized by two-step hydrothermal method and subsequent thermal annealing. The chemical composition and morphological features of the TiO2-C@TiO2-C film are characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and N2 adsorption-desorption measurement. The results indicate that the flower-like micro/nanostructure TiO2-C particle layers are intimately inhered to porous TiO2-C fibers. The fibers in film are interconnected each other to form a three-dimensional reticulate microstructure, and exhibit intense visible light absorption and high adsorptivity of dye molecules. The interaction between TiO2 and its surface carbon layer in TiO2-C particle promotes the generation of Ti-O-C bonds, which leads to effective charge transfer. Under visible-light irradiation, TiO2-C@TiO2-C film presents enhanced photocatalytic activity for degradation of methylene blue. This work may provide a new viewpoint for designing transparent photocatalytic film for promising applications in heterogeneous photocatalysis.

Fabrication and assembly of two-dimensional TiO2/WO3·H2O heterostructures with type II band alignment for enhanced photocatalytic performance

NASA Astrophysics Data System (ADS)

Xu, Tao; Wang, Yun; Zhou, Xiaofang; Zheng, Xiaoli; Xu, Qun; Chen, Zhimin; Ren, Yumei; Yan, Bo

2017-05-01

The recombination of photo-induced charges is one of the main issues to limit the large-scale applications in photocatalysis and photoelectrocatalysis. To improve the charge separation, we fabricate a novel type II 2D ultrathin TiO2/WO3·H2O heterostructures with the assistance of supercritical CO2 (SC CO2) in this work. The as-fabricated heterostructures possess high photocatalytic activity for the degradation of methyl orange(MO) and high photocurrent response under simulated solar light (AM 1.5). For the TiO2/WO3·H2O heterostructures, the MO solution could be degraded by 95.5% in 150 min, and the photocurrent density reaches to 6.5 μA cm-2, exhibiting a significant enhancement compared with pure TiO2 and WO3·H2O nanosheets.

[Photophysical properties of poly (2-methoxy-5-octyloxy)-p-phenylene vinylene/TiO2 nano-composites].

PubMed

Sun, Jian-ping; Weng, Jia-bao; Cheng, Yun-tao; Lin, Ting; Huang, Xiao-zhu

2008-12-01

The photoelectric composites of poly (2-methoxy-5-octyloxy)-p-phenylene vinylene/nanometer TiO2 (PMOCOPV/ TiO2) with different nanometer TiOz amount were synthesized through dehydrochlorination in-situ polymerization. The results of Fourier transform infrared spectroscopy and Raman spectroscopy indicated that the surface of nanometer TiO2 was coated with PMOCOPV. UV-Vis spectrum showed that the absorption of PMOCOPV/TiO2 nano-composites was strengthened in the range of violet and visible light with the contents of TiO2 increasing. The composite dimensions were observed by highly resolution transmission electron microscope, PMOCOPV/TiO2 nano-composites dispersed uniformly and possessed core-shell structure, the diameter of PMOCOPV/TiO2 was measured to be about 30 nm, and the thickness of the PMOCOPV coating was about 8-10 nm. Photoluminescence spectroscopy indicated that the maximum emission wavelength of the PMOCOPV/TiO2 was red-shifted with increasing TiO2 concentration. The fluorescence lifetime of PMOCOPV/TiO2 was about 1 ns. The intensity and lifetime of fluorescence was increased remarkably with the contents of TiO2 increasing. The mechanism of the strengthened fluorescence quantum efficiency and fluorescence intensity of PMOCOPV/TiO2 was investigated through the charge transfer, exciton dissociation and potential energy in PMOCOPV/TiO2 nano-composites.

Dimmable Electronic Ballast for a Gas Discharge Lamp

NASA Technical Reports Server (NTRS)

Raducanu, Marius; Hennings, Brian D.

2013-01-01

Titanium dioxide (TiO2) is the most efficient photocatalyst for organic oxidative degradation. TiO2 is effective not only in aqueous solution, but also in nonaqueous solvents and in the gas phase. It is photostable, biologically and chemically inert, and non-toxic. Low-energy UV light (approximately 375 nm, UV-A) can be used to photoactivate TiO2. TiO2 photocatalysis has been used to mineralize most types of organic compounds. Also, TiO2 photocatalysis has been effectively used in sterilization. This effectiveness has been demonstrated by its aggressive destruction of microorganisms, and aggressive oxidation effects of toxins. It also has been used for the oxidation of carbon monoxide to carbon dioxide, and ammonia to nitrogen. Despite having many attractive features, advanced photocatalytic oxidation processes have not been effectively used for air cleaning. One of the limitations of the traditional photocatalytic systems is the ballast that powers (lights) the bulbs. Almost all commercial off-the-shelf (COTS) ballasts are not dimmable and do not contain safety features. COTS ballasts light the UV lamp as bright as the bulb can be lit, and this results in shorter bulb lifetime and maximal power consumption. COTS magnetic ballasts are bulky, heavy, and inefficient. Several iterations of dimmable electronic ballasts have been developed. Some manifestations have safety features such as broken-bulb or over-temperature warnings, replace-bulb alert, logbulb operational hours, etc. Several electronic ballast boards capable of independently lighting and controlling (dimming) four fluorescent (UV light) bulbs were designed, fabricated, and tested. Because of the variation in the market bulb parameters, the ballast boards were designed with a very broad range output. The ballast boards can measure and control the current (power) for each channel.

In Vitro Cytotoxicity Assessment of an Orthodontic Composite Containing Titanium-dioxide Nano-particles.

PubMed

Heravi, Farzin; Ramezani, Mohammad; Poosti, Maryam; Hosseini, Mohsen; Shajiei, Arezoo; Ahrari, Farzaneh

2013-01-01

Background and aims. Incorporation of nano-particles to orthodontic bonding systems has been considered to prevent enamel demineralization around appliances. This study investigated cytotoxicity of Transbond XT adhesive containing 1 wt% titanium dioxide (TiO2) nano-particles. Materials and methods. Ten composite disks were prepared from each of the conventional and TiO2-containg composites and aged for 1, 3, 5, 7 and 14 days in Dulbecco's Modified Eagle's Medium (DMEM). The extracts were obtained and exposed to culture media of human gingival fibroblasts (HGF) and mouse L929 fibroblasts. Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results. Both adhesives were moderately toxic for HGF cells on the first day of the experiment, but the TiO2-containing adhesive produced significantly lower toxicity than the pure adhesive (P<0.05). No significant differences were found in cell viability percentages between the two groups on the other days (P>0.05). There was a significant reduction in cell toxicity with increasing pre-incubation time (P<0.001). L929 cells showed similar toxicity trends, but lower sensitivity to detect cytotoxicity of dental composites. Conclusion. The orthodontic adhesive containing TiO2 nano-particles indicated comparable or even lower toxicity than its nano-particle-free counterpart, indicating that incorporation of 1 wt% TiO2 nano-particles to the composite structure does not result in additional health hazards compared to that occurring with the pure adhesive.

Noble metal nanoparticle-decorated TiO2 nanobelts for enhanced photocatalysis

NASA Astrophysics Data System (ADS)

He, Haiyan; Yang, Ping; Jia, Changchao; Miao, Yanping; Zhao, Jie; Du, Yingying

2014-07-01

TiO2 nanobelts have been fabricated through a hydrothermal method and subsequently sulfuric-acid-corrosion-treated for a rough surface. Noble metal nanoparticles such as Ag and Au were deposited on the coarse surface of TiO2 nanobelts via a coprecipitation procedure. Ag-TiO2 nanobelts were prepared in ethanolic solution contained silver nitrate (AgNO3) and sodium hydroxide (NaOH). Au-TiO2 nanobelts were obtained in chloroauric acid (HAuCl4) using sodium borohydride (NaBH4) as the reductant. It is confirmed by the results of XRD patterns together with the SEM images that the composite of noble metal and TiO2 nanobelts were obtained successfully and the Ag or Au nanoparticles were well-dispersed on the TiO2 nanobelts. Moreover, the as-prepared Ag and Au nanoparticle-decorated TiO2 nanobelts represent an enhanced photocatalytic activity compared with pure TiO2 nanobelts, which is due to the fact that the Ag and Au nanoparticles on the surface of TiO2 nanobelts act as sinks for the photogenerated electrons and promote the separation of the electrons and holes.

The effect of nano-TiO2 photocatalysis on the antioxidant activities of Cu, Zn-SOD at physiological pH.

PubMed

Zheng, Wen; Zou, Hai-Feng; Lv, Shao-Wu; Lin, Yan-Hong; Wang, Min; Yan, Fei; Sheng, Ye; Song, Yan-Hua; Chen, Jie; Zheng, Ke-Yan

2017-09-01

Security issues of nanoparticles on biological toxicity and potential environmental risk have attracted more and more attention with the rapid development and wide applications of nanotechnology. In this work, we explored the effect and probable mechanism of nano-TiO 2 on antioxidant activity of copper, zinc superoxide dismutase (Cu, Zn-SOD) under natural light and mixed light at physiological pH. Nano-TiO 2 was prepared by sol-hydrothermal method, and then characterized by X-ray Diffraction (XRD) and Transmission electron micrographs (TEM). The Cu, Zn-SOD was purified by sephadex G75 chromatography and qualitatively analyzed by sodium dodecyl sulfate polypropylene amide gel electrophoresis (SDS-PAGE). The effect and mechanism were elucidated base on Fourier Transform Infrared Spectrometer (FT-IR), Circular Dichroism (CD), zeta potential, and electron spin resonance (ESR) methods. Accompanying the results of FT-IR, CD and zeta potential, it could be concluded that nano-TiO 2 had no effect on the antioxidant activity of Cu, Zn-SOD by comparing the relative activity under natural light at physiological pH. But the relative activity of Cu, Zn-SOD significantly decreased along with the increase of nano-TiO 2 concentration under the mixed light. The results of ESR showed the cause of this phenomenon was the Cu(II) in the active site of Cu, Zn-SOD was reduced to Cu(I) by H 2 O 2 and decreased the content of active Cu, Zn-SOD. The reduction can be inhibited by catalase. Excess O 2 ·- produced by nano-TiO 2 photocatalysis under mixed light accumulated a mass of H 2 O 2 through disproportionation reaction in this experimental condition. The results show that nano-TiO 2 cannot affect the antioxidant activity of Cu, Zn-SOD in daily life. The study on the effect of nano-TiO 2 on Cu, Zn-SOD will provide a valid theory support for biological safety and the toxicological effect mechanism of nanomaterials on enzyme. Copyright © 2017 Elsevier B.V. All rights reserved.

Immobilization of TiO2 Nanoparticles on Chlorella pyrenoidosa Cells for Enhanced Visible-Light-Driven Photocatalysis

PubMed Central

Cai, Aijun; Guo, Aiying; Ma, Zichuan

2017-01-01

TiO2 nanoparticles are immobilized on chlorella cells using the hydrothermal method. The morphology, structure, and the visible-light-driven photocatalytic activity of the prepared chlorella/TiO2 composite are investigated by various methods. The chlorella/TiO2 composite is found to exhibit larger average sizes and higher visible-light intensities. The sensitization of the photosynthesis pigment originating from chlorella cells provides the anatase TiO2 with higher photocatalytic activities under the visible-light irradiation. The latter is linked to the highly efficient charge separation of the electron/hole pairs. The results also suggest that the photocatalytic activity of the composite remains substantial after four cycles, suggesting a good stability. PMID:28772899

Angle dependence in slow photon photocatalysis using TiO2 inverse opals

NASA Astrophysics Data System (ADS)

Curti, Mariano; Zvitco, Gonzalo; Grela, María Alejandra; Mendive, Cecilia B.

2018-03-01

The slow photon effect was studied by means of the photocatalytic degradation of stearic acid over TiO2 inverse opals. The comparison of the degradation rates over inverse opals with those obtained over disordered structures at different irradiation angles showed that the irradiation at the blue edge of the stopband leads to the activation of the effect, evidenced by an improvement factor of 1.8 ± 0.6 in the reaction rate for irradiation at 40°. The rigorous coupled-wave analysis (RCWA) method was employed to confirm the source of the enhancement; simulated spectra showed an enhancement in the absorption of the TiO2 matrix that composes the inverse opal at a 40° irradiation angle, owing to an appropriate position of the stopband in relation to the absorption onset of TiO2.

Studying the Use of Photocatalytic Coatings to Increase Building/Structure Sustainability and Cleanliness at NASA Stennis Space Center

NASA Technical Reports Server (NTRS)

Underwood, Lauren

2013-01-01

TiO2 coated surfaces demonstrated both visually through photographic representation, and quantitatively, through reflectance measurements that they improved upon the current state of cleanliness upon the surfaces that they were applied to. TiO2 has the potential to both maintain and increase building s sustainability and the overall appearance of cleanliness TiO2 coated slides degraded soot under UV light compared to soot samples on plain uncoated slides under the same conditions Degradation of soot by photocatalysis was far more apparent than degradation of soot by UV light alone This demonstration provides the foundation for a laboratory model that could be used to simulate real world applications for photocatalytic materials Additional research is required to better understand the full potential of TiO2

Molecular mechanism of composite nanoparticles TiO2/WO3/GO-induced activity changes of catalase and superoxide dismutase.

PubMed

Hao, Xiaoyan; Zhang, Li; Zheng, Xin; Zong, Wansong; Liu, Chunguang

2018-06-21

More and more composite nano-photocatalysts were developed by doping, modifying and coupling, which expanded its application but resulted in pollution due to the unrecyclability. Composite photocatalyst TiO 2 /WO 3 /GO, as a model, was evaluated by exploring the molecular mechanism of TiO 2 /WO 3 /GO-induced activity changes of catalase (CAT) and superoxide dismutase (SOD). Results showed that TiO 2 /WO 3 /GO could lead to conformational and functional changes of CAT and SOD. The activity of both CAT and SOD increased depending on the exposure dose of TiO 2 /WO 3 /GO. The change skeleton structure and increase of α-helix content of CAT and SOD were certificated with UV-vis absorption and CD measurements. Intrinsic fluorescence of CAT and SOD were quenched by dynamic quenching. Micro-environment of amino acid residues of CAT and SOD became more hydrophilic, and the microenvironment of Trp residues was more vulnerable than Tyr residues with TiO 2 /WO 3 /GO exposure. In addition, inhibitory comparison between GO, TiO 2 , WO 3 and TiO 2 /WO 3 /GO was made, results showed that composite nano-photocatalyst exhibited different inhibitory compared to their parent nano-particles. Copyright © 2018. Published by Elsevier B.V.

Photocatalytic inactivation of E. coli in surface water using immobilised nanoparticle TiO2 films.

PubMed

Alrousan, Dheaya M A; Dunlop, Patrick S M; McMurray, Trudy A; Byrne, J Anthony

2009-01-01

Photocatalysis is a promising method for the disinfection of potable water in developing countries where solar irradiation can be employed, thus reducing the cost of treatment. In addition to microbial contamination, water normally contains suspended solids, dissolved inorganic ions and organic compounds (mainly humic substances) which may affect the efficacy of solar photocatalysis. In this work the photocatalytic and photolytic inactivation rates of Escherichia coli using immobilised nanoparticle TiO2 films were found to be significantly lower in surface water samples in comparison to distilled water. The presence of nitrate and sulphate anions spiked into distilled water resulted in a decrease in the rate of photocatalytic disinfection. The presence of humic acid, at the concentration found in the surface water, was found to have a more pronounced affect, significantly decreasing the rate of disinfection. Adjusting the initial pH of the water did not markedly affect the photocatalytic disinfection rate, within the narrow range studied.

Biotemplated Synthesis of Anatase Titanium Dioxide Nanoparticles via Lignocellulosic Waste Material

PubMed Central

Bagheri, Samira; Abd Hamid, Sharifah Bee

2014-01-01

Anatase titanium dioxide nanoparticles (TiO2-NPs) were synthesized by sol-gel method using rice straw as a soft biotemplate. Rice straw, as a lignocellulosic waste material, is a biomass feedstock which is globally produced in high rate and could be utilized in an innovative approach to manufacture a value-added product. Rice straw as a reliable biotemplate has been used in the sol-gel method to synthesize ultrasmall sizes of TiO2-NPs with high potential application in photocatalysis. The physicochemical properties of titanium dioxide nanoparticles were investigated by a number of techniques such as X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis (TGA), ultraviolet visible spectra (UV-Vis), and surface area and pore size analysis. All results consensually confirmed that particle sizes of synthesized titanium dioxide were template-dependent, representing decrease in the nanoparticles sizes with increase of biotemplate concentration. Titanium dioxide nanoparticles as small as 13.0 ± 3.3 nm were obtained under our experimental conditions. Additionally, surface area and porosity of synthesized TiO2-NPs have been enhanced by increasing rice straw amount which results in surface modification of nanoparticles and potential application in photocatalysis. PMID:25126547

Synergistic effect of the presence of suspended and dissolved matter on the removal of cyanide from coking wastewater by TiO2 photocatalysis.

PubMed

Pueyo, Noelia; Miguel, Natividad; Mosteo, Rosa; Ovelleiro, José L; Ormad, María P

2017-01-28

This study assesses the influence of the presence of suspended and dissolved matter on the efficiency of TiO 2 photocatalysis for the removal of cyanide from coking wastewater. Photocatalytic processes were carried out at basic pH (pH 9) with titanium dioxide (1 g/L), artificial radiation (290-800 nm) and during different time periods (20-100 min). The first assays applied in aqueous solutions achieved promising results in terms of removing cyanide. The maximum cyanide removal obtained in coking wastewater was 89% after 80 min of irradiation in the presence of suspended and dissolved matter. The presence of suspended matter composed of coal improves the efficiency of the photocatalytic process due to the synergistic effect between carbon and TiO 2 . The absence of dissolved matter also improves the process due to the minimization of the hydroxyl radical scavenging effect produced by carbonate and bicarbonate ions. On the other hand, the presence of certain species in the real matrix such as silicon increases the activity of the titanium dioxide catalyst. In consequence, the improvement achieved by the photocatalytic process for the removal of cyanide in the absence of dissolved matter is counteracted.

Photodegradation of ethylene by use of TiO2 sol-gel on polypropylene and on glass for application in the postharvest of papaya fruit.

PubMed

Lourenço, Ruth Evelyn R S; Linhares, Amanda A N; de Oliveira, André Vicente; da Silva, Marcelo Gomes; de Oliveira, Jurandi Gonçalves; Canela, Maria Cristina

2017-03-01

The papaya is a commercially important fruit commodity worldwide. Being a climacteric fruit, it is highly perishable. Thus, for the transportation of papaya fruit for long distances without loss of quality, it is necessary to avoid the autocatalytic effect of ethylene in accelerating the ripening of the fruit. This work addresses the application of heterogeneous photocatalysis to the degradation of ethylene. A TiO 2 sol-gel supported on polypropylene (PP) and on glass was used as the catalytic material, and a UV-A lamp was employed as the radiation source. Initially, a concentration of 500 ppbv ethylene was exposed to the catalyst material irradiated by UV-A radiation. A sensitive photoacoustic spectrometer was used to monitor the photocatalytic activity. The TiO 2 sol-gel supported on the glass substrate was more efficient than on the PP in degrading the ethylene. Under direct UV-A exposure, the skin appearance of 'Golden' papaya was damaged, depreciating the fruit quality and thus preventing its commercialization. However, the feasibility of the heterogeneous photocatalysis to preserve the fruit quality was achieved when ethylene was removed from the storage ambient using fans, and then, this plant hormone was degraded by a reactor set apart in a ventilation closed system.

Hybrid Processes Combining Photocatalysis and Ceramic Membrane Filtration for Degradation of Humic Acids in Saline Water

PubMed Central

Song, Lili; Zhu, Bo; Gray, Stephen; Duke, Mikel; Muthukumaran, Shobha

2016-01-01

This study explored the combined effects of photocatalysis with ceramic membrane filtration for the removal of humic acid in the presence of salt; to simulate saline wastewater conditions. The effects of operating parameters, such as salinity and TiO2 concentration on permeate fluxes, total organic carbon (TOC), and UV absorbance removal, were investigated. The interaction between the humic acids and TiO2 photocatalyst played an important role in the observed flux change during ceramic membrane filtration. The results for this hybrid system showed that the TOC removal was more than 70% for both without NaCl and with the 500 ppm NaCl concentration, and 62% and 66% for 1000 and 2000 ppm NaCl concentrations. The reduction in UV absorbance was more complete in the absence of NaCl compared to the presence of NaCl. The operation of the integrated photoreactor-ceramic membrane filter over five repeat cycles is described. It can be concluded that the overall removal performance of the hybrid system was influenced by the presence of salts, as salt leads to agglomeration of TiO2 particles by suppressing the stabilising effects of electrostatic repulsion and thereby reduces the effective surface contact between the pollutant and the photocatalyst. PMID:26938568

Enhanced Adsorption and Photocatalytic Activities of Co-Doped TiO2 Immobilized on Silica for Paraquat

NASA Astrophysics Data System (ADS)

Nghia, Nguyen Manh; Negishi, Nobuaki; Hue, Nguyen Thi

2018-01-01

We studied the adsorption and photocatalysis of paraquat in an aqueous solution with cobalt-doped TiO2 supported on mesoporous silica gel. With Co concentration increasing from 0% to 9%, it was found that the TiO2 anatase phase remained unchanged and the Co was uniformly distributed, while the band gap energy decreased from 3.32 eV to 2.64 eV. The drop in band gap energy leads to the Co-TiO2/silica gel photocatalyst oxidation of paraquat to NH4 + and NO3 - products under visible light. Relative to TiO2, the incorporation of Co into TiO2 led to an increase in the adsorption ability against the paraquat. A possible mechanism of the paraquat degradation may be that the paraquat was selectively adsorbed onto the Co-TiO2/silica gel photocatalyst before light irradiation and after that the paraquat was continuously photodecomposed.

TiO2-Based Nanomaterials for Gas Sensing-Influence of Anatase and Rutile Contributions.

PubMed

Zakrzewska, K; Radecka, M

2017-12-01

The paper deals with application of three nanomaterial systems: undoped TiO 2 , chromium-doped TiO 2 :Cr and TiO 2 -SnO 2 synthesized by flame spray synthesis (FSS) technique for hydrogen sensing. The emphasis is put on the role of anatase and rutile polymorphic forms of TiO 2 in enhancing sensitivity towards reducing gases. Anatase-to-rutile transformation is achieved by annealing of undoped TiO 2 in air at 700 °C, specific Cr doping and modification with SnO 2 . Undoped TiO 2 and TiO 2 -SnO 2 exhibit n-type behaviour and while TiO 2 : 5 at.% Cr is a p-type semiconductor. X-ray diffraction (XRD) has been applied to determine anatase-to-rutile weight ratio as well as anatase and rutile crystal size. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to characterize the structure and morphological parameters. Optical reflectometry enabled to find and compare the band gaps E g of anatase and rutile predominated compositions. Electrical properties, i.e. the electrical conductivity and values of constant phase element (CPE), have been established on the basis of impedance spectroscopy. Dynamic responses of the electrical resistance as a function of hydrogen concentration revealed that predominance of rutile in anatase/rutile mixture is beneficial for gas sensing. Partial transformation to rutile in all three material systems under study resulted in an increased sensitivity towards hydrogen. It is proposed that this effect can be explained in a similar way as in photocatalysis, i.e. by specific band alignment and electron transfer from rutile to anatase to facilitate oxygen preadsorption on the surface of anatase grains.

Heterogeneous photocatalysis using TiO2 modified with hydrotalcite and iron oxide under UV-visible irradiation for color and toxicity reduction in secondary textile mill effluent.

PubMed

Arcanjo, Gemima Santos; Mounteer, Ann H; Bellato, Carlos Roberto; Silva, Laís Miguelina Marçal da; Brant Dias, Santos Henrique; Silva, Priscila Romana da

2018-04-01

The objective of this study was to evaluate ADMI color removal from a biologically treated textile mill effluent by heterogeneous photocatalysis with UV-visible irradiation (UV-vis) using a novel catalyst composed of TiO 2 supported on hydrotalcite and doped with iron oxide (HT/Fe/TiO 2 ). Simulated biological treatment of solutions of the dyes (50 mg/L) used in the greatest amounts at the mill where the textile effluent was collected resulted in no color removal in reactive dye solutions and about 50% color removal in vat dye solutions, after 96 h, indicating that the secondary effluent still contained a large proportion of anionic reactive dyes. Photocatalytic treatments were carried out with TiO 2 and HT/Fe/TiO 2 of Fe:Ti molar ratios of 0.25, 0.5, 0.75 and 1, with varying catalyst doses (0-3 mg/L), initial pH values (4-10) and UV-vis times (0-6 h). The highest ADMI color removal with unmodified TiO 2 was found at a dose of 2 g/L and pH 4, an impractical pH value for industrial application. The most efficient composite was HT/Fe/TiO 2 1 at pH 10, also at a dose of 2 g/L, which provided more complete ADMI color removal, from 303 to 9 ADMI color units (96%), than unmodified TiO 2 , from 303 to 37 ADMI color units (88%), under the same conditions. Hydroxyl radicals were responsible for the color reduction, since when 2-propanol, an OH scavenger, was added color removal was very low. For this reason, the HT/Fe/TiO 2 1 composite performed better at pH 10, because the higher concentration of hydroxide ions present at higher pH favored hydroxyl radical formation. COD reductions were relatively low and similar, approximately 20% for both catalysts after 6 h under UV-vis, because of the low initial COD (78 mg/L). Secondary effluent toxicity to Daphnia similis (EC 50  = 70.7%) was reduced by photocatalysis with TiO 2 (EC 50  = 95.0%) and the HT/Fe/TiO 2 1 composite (EC 50  = 78.6%). HT/Fe/TiO 2 1 was reused five times and still lowered secondary effluent ADMI color below local discharge limits. Benefits of the HT/Fe/TiO 2 1 catalyst compared to TiO 2 include its lower bandgap energy (2.34 eV vs 3.25 eV), higher ADMI color removal and its magnetic nature that facilitated its recovery and would reduce treatment costs. Copyright © 2018 Elsevier Ltd. All rights reserved.

Solar-chemical treatment of groundwater contaminated with petroleum at gas station sites: ex situ remediation using solar/TiO(2) photocatalysis and Solar Photo-Fenton.

PubMed

Cho, Ii-Hyoung; Kim, Young-Gyu; Yang, Jae-Kyu; Lee, Nae-Hyun; Lee, Seung-Mok

2006-01-01

Groundwater samples contaminated by BTEX (benzene, toluene, ethylbenzene, xylene isomers and TPHs (total petroleum hydrocarbons) were treated with advanced oxidation processes (AOPs), such as TiO(2) photocatalysis and Fe(2+)/H(2)O(2) exposed to solar light (37 degrees N and 128 degrees E) with an average intensity of 1.7 mW/cm(2) at 365 nm. These AOP processes showed feasibility in the treatment of groundwater contaminated with BTEX, TPH and TOC (Total Organic Carbon). Outdoor field tests showed that the degradation efficiency of each contaminant was higher in the Fe(2+)/H(2)O(2) system without solar light compared to the TiO(2)/solar light and H(2)O(2)/solar light systems. However, the TiO(2)/solar light and the Fe(2+)/H(2)O(2)/solar light systems showed significantly enhanced efficiencies in the degradation of BTEX, TPH and TOC with the additional use of H(2)O(2). Near complete degradation of BTEX and TPH was observed within 2 and 4 hrs, respectively, however, that of TOC was slower. Without pretreatment of the groundwater, fouling of the TiO(2), due to the ionic species present, was observed within 1 hr of operation, which resulted in the inhibition of further BTEX, TPH and TOC destruction. The degradation rate of n-alkanes with carbon numbers ranging from C10 to C15 was relatively greater than that of n-alknaes with carbon numbers ranging from C16 to C20. From this work, the AOP process (Fe(2+)/H(2)O(2)/solar light and TiO(2)/H(2)O(2)/solar light) illuminated with solar light was identified as an effective ex situ technique in the remediation of groundwater contaminated with petroleum.

The detrimental influence of bacteria (E. coli, Shigella and Salmonella) on the degradation of organic compounds (and vice versa) in TiO2 photocatalysis and near-neutral photo-Fenton processes under simulated solar light.

PubMed

Moncayo-Lasso, Alejandro; Mora-Arismendi, Luis Enrique; Rengifo-Herrera, Julián Andrés; Sanabria, Janeth; Benítez, Norberto; Pulgarin, César

2012-05-01

TiO2 photocatalytic and near-neutral photo-Fenton processes were tested under simulated solar light to degrade two models of natural organic matter - resorcinol (R) (which should interact strongly with TiO2 surfaces) and hydroquinone (H) - separately or in the presence of bacteria. Under similar oxidative conditions, inactivation of Escherichia coli, Shigella sonnei and Salmonella typhimurium was carried out in the absence and in the presence of 10 mg L(-1) of R and H. The 100% abatement of R and H by using a TiO2 photocatalytic process in the absence of bacteria was observed in 90 min for R and in 120 min for H, while in the presence of microorganisms abatement was only of 55% and 35% for R and H, respectively. Photo-Fenton reagent at pH 5.0 completely removed R and H in 40 min, whereas in the presence of microorganisms their degradation was of 60% to 80%. On the other hand, 2 h of TiO2 photocatalytic process inactivated S. typhimurium and E. coli cells in three and six orders of magnitude, respectively, while S. sonnei was completely inactivated in 10 min. In the presence of R or H, the bacterial inactivation via TiO2 photocatalysis was significantly decreased. With photo-Fenton reagent at pH 5 all the microorganisms tested were completely inactivated in 40 min of simulated solar light irradiation in the absence of organics. When R and H were present, bacterial photo-Fenton inactivation was less affected. The obtained results suggest that in both TiO2 and iron photo-assisted processes, there is competition between organic substances and bacteria simultaneously present for generated reactive oxygen species (ROS). This competition is most important in heterogeneous systems, mainly when there are strong organic-TiO2 surface interactions, as in the resorcinol case, suggesting that bacteria-TiO2 interactions could play a key role in photocatalytic cell inactivation processes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Yifan; Kapilashrami, Mukes; Chuang, Cheng-Hao

Some recent advances in synchrotron based x-ray spectroscopy enable materials scientists to emanate fingerprints on important materials properties, e.g., electronic, optical, structural, and magnetic properties, in real-time and under nearly real-world conditions. This characterization, then, in combination with optimized materials synthesis routes and tailored morphological properties could contribute greatly to the advances in solid-state electronics and renewable energy technologies. In connection to this, such perspective reflects the current materials research in the space of emerging energy technologies, namely photocatalysis, with a focus on transition metal oxides, mainly on the Fe 2O 3- and TiO 2-based materials.

Photocatalytic hollow TiO2 and ZnO nanospheres prepared by atomic layer deposition.

PubMed

Justh, Nóra; Bakos, László Péter; Hernádi, Klára; Kiss, Gabriella; Réti, Balázs; Erdélyi, Zoltán; Parditka, Bence; Szilágyi, Imre Miklós

2017-06-28

Carbon nanospheres (CNSs) were prepared by hydrothermal synthesis, and coated with TiO 2 and ZnO nanofilms by atomic layer deposition. Subsequently, through burning out the carbon core templates hollow metal oxide nanospheres were obtained. The substrates, the carbon-metal oxide composites and the hollow nanospheres were characterized with TG/DTA-MS, FTIR, Raman, XRD, SEM-EDX, TEM-SAED and their photocatalytic activity was also investigated. The results indicate that CNSs are not beneficial for photocatalysis, but the crystalline hollow metal oxide nanospheres have considerable photocatalytic activity.

Photocatalytic reduction of heavy metal ions on derivatized titanium dioxide nano-particle surface studied by XAFS

NASA Astrophysics Data System (ADS)

Chen, Lin X.; Rajh, Tijana; Mićić, Olga Wang, Zhiyu; Tiede, David M.; Thurnauer, Marion

1997-12-01

Photoreduction of heavy metal ions, Cu 2- and Hg 2+, on TiO 2 nano-particle surfaces, has been investigated by XAFS measurements. The effects of TiO 2 surface modification reagents on the reaction efficiency have been studied. We observed a significant reaction efficiency enhancement when amino acid alanine was added to a mixture of 0.01 M Cu 2+ and TiO 2 nano-particles. Fifty percent of the adsorbed Cu 2+ has been reduced to Cu 0 after 1-h illumination with a UV-enhanced xenon lamp. Photoreduction of Hg 2+ on TiO 2 colloid surfaces was also investigated without and with thiolactic acid (TLA). In this case, the photoreduction efficiency for Hg 2+ was lowered. Structures of metal ion surroundings in various complexes as well as their role in photoreduction of metal ions are discussed.

Photoinduced Charge Transfer from Titania to Surface Doping Site

PubMed Central

Inerbaev, Talgat; Hoefelmeyer, James D.; Kilin, Dmitri S.

2013-01-01

We evaluate a theoretical model in which Ru is substituting for Ti at the (100) surface of anatase TiO2. Charge transfer from the photo-excited TiO2 substrate to the catalytic site triggers the photo-catalytic event (such as water oxidation or reduction half-reaction). We perform ab-initio computational modeling of the charge transfer dynamics on the interface of TiO2 nanorod and catalytic site. A slab of TiO2 represents a fragment of TiO2 nanorod in the anatase phase. Titanium to ruthenium replacement is performed in a way to match the symmetry of TiO2 substrate. One molecular layer of adsorbed water is taken into consideration to mimic the experimental conditions. It is found that these adsorbed water molecules saturate dangling surface bonds and drastically affect the electronic properties of systems investigated. The modeling is performed by reduced density matrix method in the basis of Kohn-Sham orbitals. A nano-catalyst modeled through replacement defect contributes energy levels near the bottom of the conduction band of TiO2 nano-structure. An exciton in the nano-rod is dissipating due to interaction with lattice vibrations, treated through non-adiabatic coupling. The electron relaxes to conduction band edge and then to the Ru cite with faster rate than hole relaxes to the Ru cite. These results are of the importance for an optimal design of nano-materials for photo-catalytic water splitting and solar energy harvesting. PMID:23795229

Photoinduced Charge Transfer from Titania to Surface Doping Site.

PubMed

Inerbaev, Talgat; Hoefelmeyer, James D; Kilin, Dmitri S

2013-05-16

We evaluate a theoretical model in which Ru is substituting for Ti at the (100) surface of anatase TiO 2 . Charge transfer from the photo-excited TiO 2 substrate to the catalytic site triggers the photo-catalytic event (such as water oxidation or reduction half-reaction). We perform ab-initio computational modeling of the charge transfer dynamics on the interface of TiO 2 nanorod and catalytic site. A slab of TiO 2 represents a fragment of TiO 2 nanorod in the anatase phase. Titanium to ruthenium replacement is performed in a way to match the symmetry of TiO 2 substrate. One molecular layer of adsorbed water is taken into consideration to mimic the experimental conditions. It is found that these adsorbed water molecules saturate dangling surface bonds and drastically affect the electronic properties of systems investigated. The modeling is performed by reduced density matrix method in the basis of Kohn-Sham orbitals. A nano-catalyst modeled through replacement defect contributes energy levels near the bottom of the conduction band of TiO 2 nano-structure. An exciton in the nano-rod is dissipating due to interaction with lattice vibrations, treated through non-adiabatic coupling. The electron relaxes to conduction band edge and then to the Ru cite with faster rate than hole relaxes to the Ru cite. These results are of the importance for an optimal design of nano-materials for photo-catalytic water splitting and solar energy harvesting.

Conjugated polymer/nanocrystal nanocomposites for renewable energy applications in photovoltaics and photocatalysis.

PubMed

Su, Yu-Wei; Lin, Wei-Hao; Hsu, Yung-Jung; Wei, Kung-Hwa

2014-11-01

Conjugated polymer/nanocrystal composites have attracted much attention for use in renewable energy applications because of their versatile and synergistic optical and electronic properties. Upon absorbing photons, charge separation occurs in the nanocrystals, generating electrons and holes for photocurrent flow or reduction/oxidation (redox) reactions under proper conditions. Incorporating these nanocrystals into conjugated polymers can complement the visible light absorption range of the polymers for photovoltaics applications or allow the polymers to sensitize or immobilize the nanocrystals for photocatalysis. Here, the current developments of conjugated polymer/nanocrystal nanocomposites for bulk heterojunction-type photovoltaics incorporating Cd- and Pb-based nanocrystals or quantum dots are reviewed. The effects of manipulating the organic ligands and the concentration of the nanocrystal precursor, critical factors that affect the shape and aggregation of the nanocrystals, are also discussed. In the conclusion, the mechanisms through which conjugated polymers can sensitize semiconductor nanocrystals (TiO2 , ZnO) to ensure efficient charge separation, as well as how they can support immobilized nanocrystals for use in photocatalysis, are addressed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Toxicity of Food-Grade TiO2 to Commensal Intestinal and Transient Food-Borne Bacteria: New Insights Using Nano-SIMS and Synchrotron UV Fluorescence Imaging.

PubMed

Radziwill-Bienkowska, Joanna M; Talbot, Pauline; Kamphuis, Jasper B J; Robert, Véronique; Cartier, Christel; Fourquaux, Isabelle; Lentzen, Esther; Audinot, Jean-Nicolas; Jamme, Frédéric; Réfrégiers, Matthieu; Bardowski, Jacek K; Langella, Philippe; Kowalczyk, Magdalena; Houdeau, Eric; Thomas, Muriel; Mercier-Bonin, Muriel

2018-01-01

Titanium dioxide (TiO 2 ) is commonly used as a food additive (E171 in the EU) for its whitening and opacifying properties. However, a risk of intestinal barrier disruption, including dysbiosis of the gut microbiota, is increasingly suspected because of the presence of a nano-sized fraction in this additive. We hypothesized that food-grade E171 and Aeroxyde P25 (identical to the NM-105 OECD reference nanomaterial in the European Union Joint Research Centre) interact with both commensal intestinal bacteria and transient food-borne bacteria under non-UV-irradiated conditions. Based on differences in their physicochemical properties, we expect a difference in their respective effects. To test these hypotheses, we chose a panel of eight Gram-positive/Gram-negative bacterial strains, isolated from different biotopes and belonging to the species Escherichia coli , Lactobacillus rhamnosus , Lactococcus lactis (subsp. lactis and cremoris ), Streptococcus thermophilus , and Lactobacillus sakei . Bacterial cells were exposed to food-grade E171 vs. P25 in vitro and the interactions were explored with innovative (nano)imaging methods. The ability of bacteria to trap TiO 2 was demonstrated using synchrotron UV fluorescence imaging with single cell resolution. Subsequent alterations in the growth profiles were shown, notably for the transient food-borne L. lactis and the commensal intestinal E. coli in contact with food-grade TiO 2 . However, for both species, the reduction in cell cultivability remained moderate, and the morphological and ultrastructural damages, observed with electron microscopy, were restricted to a small number of cells. E. coli exposed to food-grade TiO 2 showed some internalization of TiO 2 (7% of cells), observed with high-resolution nano-secondary ion mass spectrometry (Nano-SIMS) chemical imaging. Taken together, these data show that E171 may be trapped by commensal and transient food-borne bacteria within the gut. In return, it may induce some physiological alterations in the most sensitive species, with a putative impact on gut microbiota composition and functioning, especially after chronic exposure.

Toxicity of Food-Grade TiO2 to Commensal Intestinal and Transient Food-Borne Bacteria: New Insights Using Nano-SIMS and Synchrotron UV Fluorescence Imaging

PubMed Central

Radziwill-Bienkowska, Joanna M.; Talbot, Pauline; Kamphuis, Jasper B. J.; Robert, Véronique; Cartier, Christel; Fourquaux, Isabelle; Lentzen, Esther; Audinot, Jean-Nicolas; Jamme, Frédéric; Réfrégiers, Matthieu; Bardowski, Jacek K.; Langella, Philippe; Kowalczyk, Magdalena; Houdeau, Eric; Thomas, Muriel; Mercier-Bonin, Muriel

2018-01-01

Titanium dioxide (TiO2) is commonly used as a food additive (E171 in the EU) for its whitening and opacifying properties. However, a risk of intestinal barrier disruption, including dysbiosis of the gut microbiota, is increasingly suspected because of the presence of a nano-sized fraction in this additive. We hypothesized that food-grade E171 and Aeroxyde P25 (identical to the NM-105 OECD reference nanomaterial in the European Union Joint Research Centre) interact with both commensal intestinal bacteria and transient food-borne bacteria under non-UV-irradiated conditions. Based on differences in their physicochemical properties, we expect a difference in their respective effects. To test these hypotheses, we chose a panel of eight Gram-positive/Gram-negative bacterial strains, isolated from different biotopes and belonging to the species Escherichia coli, Lactobacillus rhamnosus, Lactococcus lactis (subsp. lactis and cremoris), Streptococcus thermophilus, and Lactobacillus sakei. Bacterial cells were exposed to food-grade E171 vs. P25 in vitro and the interactions were explored with innovative (nano)imaging methods. The ability of bacteria to trap TiO2 was demonstrated using synchrotron UV fluorescence imaging with single cell resolution. Subsequent alterations in the growth profiles were shown, notably for the transient food-borne L. lactis and the commensal intestinal E. coli in contact with food-grade TiO2. However, for both species, the reduction in cell cultivability remained moderate, and the morphological and ultrastructural damages, observed with electron microscopy, were restricted to a small number of cells. E. coli exposed to food-grade TiO2 showed some internalization of TiO2 (7% of cells), observed with high-resolution nano-secondary ion mass spectrometry (Nano-SIMS) chemical imaging. Taken together, these data show that E171 may be trapped by commensal and transient food-borne bacteria within the gut. In return, it may induce some physiological alterations in the most sensitive species, with a putative impact on gut microbiota composition and functioning, especially after chronic exposure. PMID:29740421

Application of nano-TiO2/LDPE composite film on photocatalytic oxidation degradation of dichloromethane.

PubMed

Suwannahong, Kowit; Liengcharernsit, Winai; Sanongraj, Wipada; Kruenate, Jittiporn

2012-09-01

This study focused on the photocatalytic destruction of dichloromethane (DCM) in indoor air using the nano-TiO2/LDPE composite film as an economical photocatalyst. The nano-TiO2 was dispersed in a polyethylene matrix to form composite film. The photocatalytic activity of the nano-TiO2/LDPE composite films was evaluated through the degradation of dichloromethane(DCM) under UV-C irradiance at specific wavelength of 254 nm. The percentage of nano-TiO2 contents varied from 0, 5, and 10% (wt cat./wt LDPE composite film). The results derived from the kinetic model revealed that the photocatalytic rates of 5 and 10 wt.% nano-TiO2/ LDPE composite films follow the first order reaction while the rate of the film without TiO2 followed the zero order reaction. At low concentration of DCM, the rate of photocatalytic degradation of the DCM was slower than that at high DCM concentration. The 10 wt.% of TiO2 content of the nano-TiO2/LDPE composite film yielded the highest degradation efficiency of 78%, followed by the removal efficiency of 55% for the 5 wt.% of TiO2 content of the nano-TiO2/LDPE composite film. In contrast with the composite film containing nano-TiO2, the LDPE film without adding nano-TiO2 expressed the degradation efficiency of 28%.

Structural and characteristic variation of anodic oxide on pure Ti with anodization duration

NASA Astrophysics Data System (ADS)

Mizukoshi, Yoshiteru; Ohtsu, Naofhumi; Masahashi, Naoya

2013-10-01

Change in the structural and characteristic of the anodic oxide on pure Ti with the duration of anodization time was investigated. With the progress of the anodization, the phase of the formed TiO2 successively changed from anatase phase to rutile phase. In the transition process, peak intensities of rutile TiO2 1 0 1, 1 1 1 and 2 1 1 planes of X-ray diffraction characteristically increased. The contact angles of water droplets on the anodize TiO2 were monotonously decreased with the progress of the anodization except on the characteristically oriented rutile surface. In the evaluations of acetaldehyde photocatalysis under UV illumination, the anatase TiO2 anodized for short period exhibited high activities. On the other hand, when illuminated with visible light (>422 nm), rutile-structured TiO2 formed by anodization with a long duration exhibited superior photocatalytic activities probably due to high rutile fraction and sulfur incorporation from the electrolyte.

Efficient photodegradation of organic dye using anatase TiO2 plants as catalyst

NASA Astrophysics Data System (ADS)

Bahadur, Jitendra; Pal, Kaushik

2017-11-01

Anatase TiO2 hierarchical nanostructures with higher photocatalytic activity are of special importance in various applications. We have reported the synthesis of TiO2 as water chestnut plants like morphology via facile hydrothermal method, by using Titanium (IV) butoxide (TBOT) as a precursor solution. It is found that TiO2 nanoparticles work as seed and completely convert into water chestnut plants like structure or morphology, which are composed of crystallized anatase nanocrystals. X-ray diffraction spectra confirmed the presence of anatase phase of crystallized TiO2 plants (TPs). The average life time delay for generated charge carriers in TPs was calculated to be around 2.45 ns, which reflects slow recombination of charge carriers. The prepared TPs show excellent photocatalytic performance when applied in photo degradation of Rhodamine B organic dye. The unique features exhibited by TPs make them a promising candidate for vast potential applications in field such as solar cells, photocatalysis, supercapacitor, lithium ion batteries and some related fields.[Figure not available: see fulltext.

Amoxicillin degradation from contaminated water by solar photocatalysis using response surface methodology (RSM).

PubMed

Moosavi, Fatemeh Sadat; Tavakoli, Touraj

2016-11-01

In this study, the solar photocatalytic process in a pilot plant with compound parabolic collectors (CPCs) was performed for amoxicillin (AMX) degradation, an antibiotic widely used in the world. The response surface methodology (RSM) based on Box-Behnken statistical experiment design was used to optimize independent variables, namely TiO 2 dosage, antibiotic initial concentration, and initial pH. The results showed that AMX degradation efficiency affected by positive or negative effect of variables and their interactions. The TiO 2 dosage, pH, and interaction between AMX initial concentration and TiO 2 dosage exhibited a synergistic effect, while the linear and quadratic term of AMX initial concentration and pH showed antagonistic effect in the process response. Response surface and contour plots were used to perform process optimization. The optimum conditions found in this regard were TiO 2 dosage = 1.5 g/L, AMX initial concentration = 17 mg/L, and pH = 9.5 for AMX degradation under 240 min solar irradiation. The photocatalytic degradation of AMX after 34.95 kJ UV /L accumulated UV energy per liter of solution was 84.12 % at the solar plant.

Nanoscale TiO2 films and their application in remediation of organic pollutants

EPA Science Inventory

Photocatalysis is an advanced process for treatment of air, wastewater, and drinking water, the primary advantage being its ability to mineralize many pollutants. Among several nanoscale arrangements of photocatalysts, there has been a strong push to develop them as thin films be...

Titanium Dioxide/Upconversion Nanoparticles/Cadmium Sulfide Nanofibers Enable Enhanced Full-Spectrum Absorption for Superior Solar Light Driven Photocatalysis.

PubMed

Zhang, Fu; Zhang, Chuan-Ling; Wang, Wan-Ni; Cong, Huai-Ping; Qian, Hai-Sheng

2016-06-22

In this work, we demonstrate an electrospinning technique to fabricate TiO2 /upconversion nanoparticles (UCNPs)/CdS nanofibers on large scale. In addition, the as-prepared TiO2 nanofibers are incorporated with a high population of UCNPs and CdS nanospheres; this results in Förster resonance energy-transfer configurations of the UCNPs, TiO2 , and CdS nanospheres that are in close proximity. Hence, strong fluorescent emissions for the Tm(3+) ions including the (1) G4 →(3) H6 transition are efficiently transferred to TiO2 and the CdS nanoparticles through an energy-transfer process. The as-prepared TiO2 /UCNPs/CdS nanofibers exhibit full-spectrum solar-energy absorption and enable the efficient degradation of organic dyes by fluorescence resonance energy transfer between the UCNPs and TiO2 (or CdS). The UCNPs/TiO2 /CdS nanofibers may also have enhanced energy-transfer efficiency for wide applications in solar cells, bioimaging, photodynamics, and chemotherapy. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ modification of cell-culture scaffolds by photocatalysis of visible-light-responsive TiO2 film

NASA Astrophysics Data System (ADS)

Kono, Sho; Furusawa, Kohei; Kurotobi, Atsushi; Hattori, Kohei; Yamamoto, Hideaki; Hirano-Iwata, Ayumi; Tanii, Takashi

2018-02-01

We propose a novel process to modify the cell affinity of scaffolds in a cell-culture environment using the photocatalytic activity of visible-light (VL)-responsive TiO2. The proposed process is the improved version of our previous demonstration in which ultraviolet (UV)-responsive TiO2 was utilized. In that demonstration, we showed that cell-repellent molecules on TiO2 were decomposed and replaced with cell-permissive molecules upon UV exposure in the medium where cells are being cultured. However, UV irradiation involves taking the risk of inducing damage to the cells. In this work, a TiO2 film was sputter-deposited on a quartz coverslip at 640 °C without O2 gas injection to create a rutile structure containing oxygen defects, which is known to exhibit photocatalytic activity upon VL exposure. We show that the cell adhesion site and migration area can be controlled with the photocatalytic activity of the VL-responsive TiO2 film, while the cellular oxidative stress is reduced markedly by the substitution of VL for UV.

Modeling TiO2 nanoparticle phototoxicity: The importance of chemical concentration, ultraviolet radiation intensity, and time

EPA Science Inventory

Toxicity of TiO2 nanoparticles (nano-TiO2) to aquatic organisms can be greatly increased upon the exposure to ultraviolet radiation (UV). This phenomenon has received some attention for pelagic species, however, investigations of nano-TiO2 phototoxicity in benthic organisms are s...

Phototoxicity of TiO2 Nanoparticles under Solar Radiation to Two Aquatic Species: Daphnia magna and Japanese Medaka

EPA Science Inventory

One target of development and application of TiO2 nanoparticles (nano-TiO2) is photochemical degredation of contaminants and photo-killing of microbes and fouling organisms. However, few ecotoxicological studies have focused on this aspect of nano-TiO2, specifically whether this ...

Microstructure and properties of Cu-Sn-Zn-TiO 2 nano-composite coatings on mild steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Weidong; Cao, Di; Jin, Yunxue

Cu-Sn-Zn coatings have been widely used in industry for their unique properties, such as good conductivity, high corrosion resistance and excellent solderability. To further improve the mechanical performance of Cu-Sn-Zn coatings, powder-enhanced method was applied and Cu-Sn-Zn-TiO 2 nano-composite coatings with different TiO 2 concentration were fabricated. The microstructure of Cu-Sn-Zn-TiO 2 nano-composite coatings were investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The mechanical properties of coatings including microhardness and wear resistance were studied. The results indicate that the incorporation of TiO 2 nanoparticle can significantly influence the properties of Cu-Sn-Zn coatings. The microhardness of Cu-Sn-Zn coatingmore » was increased to 383 HV from 330 HV with 1 g/L TiO 2 addition. Also, the corrosion resistance of coating was enhanced. The effects of TiO 2 nanoparticle concentration on the microstructure, mechanical properties and corrosion resistance of Cu-Sn-Zn-TiO 2 nano-composite coatings were discussed.« less

Microstructure and properties of Cu-Sn-Zn-TiO 2 nano-composite coatings on mild steel

DOE PAGES

Gao, Weidong; Cao, Di; Jin, Yunxue; ...

2018-04-18

Cu-Sn-Zn coatings have been widely used in industry for their unique properties, such as good conductivity, high corrosion resistance and excellent solderability. To further improve the mechanical performance of Cu-Sn-Zn coatings, powder-enhanced method was applied and Cu-Sn-Zn-TiO 2 nano-composite coatings with different TiO 2 concentration were fabricated. The microstructure of Cu-Sn-Zn-TiO 2 nano-composite coatings were investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The mechanical properties of coatings including microhardness and wear resistance were studied. The results indicate that the incorporation of TiO 2 nanoparticle can significantly influence the properties of Cu-Sn-Zn coatings. The microhardness of Cu-Sn-Zn coatingmore » was increased to 383 HV from 330 HV with 1 g/L TiO 2 addition. Also, the corrosion resistance of coating was enhanced. The effects of TiO 2 nanoparticle concentration on the microstructure, mechanical properties and corrosion resistance of Cu-Sn-Zn-TiO 2 nano-composite coatings were discussed.« less

Morphology control of rutile TiO2 with tunable bandgap by preformed β-FeOOH nanoparticles.

PubMed

Chen, Zheming; Wang, Feng; Balachandran, Subramanian; Li, Gen; Liu, Peng; Ding, Yanfen; Zhang, Shimin; Yang, Mingshu

2018-03-23

Rutile TiO 2 are widely used for applications of coatings, cosmetics, photoelectric devices and so on. However, effective control of well-defined morphology, size and composition of rutile TiO 2 nanoparticles from agglomeration has always been a challenge. A new synthesis strategy was proposed to prepare rutile TiO 2 with controllable morphology varied from flower-like structures to single-separated nanorods. The β-FeOOH nanoparticles were generated by the hydrolysis of FeCl 3 solution and could prevent the aggregation of TiO 2 nanocrystals at early stages of the reaction; thus, could control the morphology of rutile nanoparticles. The morphology of rutile TiO 2 nanoparticles could be controllably regulated from flower-like structures to individually separated nanorods. Meanwhile, the preformed β-FeOOH also played a role of dopant. Fe ions were substitutionally doped into the bulk lattice of TiO 2 nanocrystals and reduced the bandgap, which extended the solar radiation absorption range of rutile TiO 2 . The prepared TiO 2 may be suitable for novel UV-blue light shielding agents and many other applications in photoelectric devices, photocatalysis, and so on due to its small size, unprecedented discrete rod-like structure and unique UV-vis light permeability.

Morphology control of rutile TiO2 with tunable bandgap by preformed β-FeOOH nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Zheming; Wang, Feng; Balachandran, Subramanian; Li, Gen; Liu, Peng; Ding, Yanfen; Zhang, Shimin; Yang, Mingshu

2018-03-01

Rutile TiO2 are widely used for applications of coatings, cosmetics, photoelectric devices and so on. However, effective control of well-defined morphology, size and composition of rutile TiO2 nanoparticles from agglomeration has always been a challenge. A new synthesis strategy was proposed to prepare rutile TiO2 with controllable morphology varied from flower-like structures to single-separated nanorods. The β-FeOOH nanoparticles were generated by the hydrolysis of FeCl3 solution and could prevent the aggregation of TiO2 nanocrystals at early stages of the reaction; thus, could control the morphology of rutile nanoparticles. The morphology of rutile TiO2 nanoparticles could be controllably regulated from flower-like structures to individually separated nanorods. Meanwhile, the preformed β-FeOOH also played a role of dopant. Fe ions were substitutionally doped into the bulk lattice of TiO2 nanocrystals and reduced the bandgap, which extended the solar radiation absorption range of rutile TiO2. The prepared TiO2 may be suitable for novel UV-blue light shielding agents and many other applications in photoelectric devices, photocatalysis, and so on due to its small size, unprecedented discrete rod-like structure and unique UV-vis light permeability.

In situ glow discharge plasma electrolytic synthesis of reduced TiO2 for enhanced visible light photocatalysis

NASA Astrophysics Data System (ADS)

Feng, Guang; Wu, Botao; Qayyum Khan, Abdul; Zeng, Heping

2018-05-01

Reduced titanium dioxide (TiO2‑x) due to its extraordinary visible light absorption has been widely investigated in photodegradation and water splitting nowadays. However, conventional routes to synthesize reduced TiO2 usually demand multiple preparation steps, harsh controlled conditions or expensive facilities. Here we developed a single-step in situ approach to prepare the gray TiO2‑x nanoparticles (sub-10 nm) effectively by the glow discharge plasma electrolysis (GDPE) under atmospheric pressure. The co-existence of self-doped oxygen vacancies and Ti3+ in the generated TiO2‑x nanoparticles is demonstrated by electron paramagnetic resonance (EPR). The tunable ratio of bulk/surface defect can be realized by controlling the glow discharge power directly. It should be noticed that Ti3+ in the synthesized TiO2‑x are quite stable in ambient air. The UV–vis spectra of gray TiO2‑x show an enhanced visible light absorption, which leads to high visible-light photocatalytic activity. Moreover, the as-prepared TiO2‑x after 6 months storage still shows excellent stability during photocatalytic reactions. Owing to its simplicity and effectivity, this preparation method with GDPE should provide a large-scale production for TiO2‑x with high photoactivity.

Electronic coupling in iron oxide-modified TiO2 leads to a reduced band gap and charge separation for visible light active photocatalysis.

PubMed

Nolan, Michael

2011-10-28

In recent experiments Tada et al. have shown that TiO(2) surfaces modified with iron oxide display visible light photocatalytic activity. This paper presents first principles simulations of iron oxide clusters adsorbed at the rutile TiO(2) (110) surface to elucidate the origin of the visible light photocatalytic activity of iron oxide modified TiO(2). Small iron oxide clusters adsorb at rutile (110) surface and their presence shifts the valence band so that the band gap of the composite is narrowed towards the visible, thus confirming the origin of the visible light activity of this composite material. The presence of iron oxide at the TiO(2) surface leads to charge separation, which is the origin of enhanced photocatalytic efficiency, consistent with experimental photoluminesence and photocurrent data. Surface modification of a metal oxide is thus an interesting route in the development of visible light photocatalytic materials. This journal is © the Owner Societies 2011

Superior environment resistance of quartz crystal microbalance with anatase TiO2/ZnO nanorod composite films

NASA Astrophysics Data System (ADS)

Qiang, Wei; Wei, Li; Shaodan, Wang; Yu, Bai

2015-08-01

The precise measurement of quartz crystal microbalance (QCM) in the detection and weighing of organic gas molecules is achieved due to excellent superhydrophobicity of a deposited film composite. Photocatalysis is utilized as a method for the self-cleaning of organic molecules on the QCM for extended long-term stability in the precision of the instrument. In this paper, ZnO nanorod array is prepared via in situ methods on the QCM coated with Au film via hydrothermal process. Subsequently, a TiO2/ZnO composite film is synthesized by surface modification with TiO2 via sol-gel methods. Results show the anatase TiO2/ZnO nanorod composite film with a sharp, pencil-like structure exhibiting excellent superhydrophobicity (water contact angle of 155°), non-sticking water properties, and an autonomous cleaning property under UV irradiation. The anatase TiO2/ZnO nanorod composite film facilitates the precise measurement and extended lifetime of the QCM for the detection of organic gas molecules.

UV-driven microvalve based on a micro-nano TiO2/SiO2 composite surface for microscale flow control

NASA Astrophysics Data System (ADS)

Guo, Ting; Meng, Tao; Li, Wei; Qin, Jilong; Tong, Zhiping; Zhang, Qing; Li, Xueru

2014-03-01

This paper presents a novel ultraviolet (UV)-driven microvalve based on the concept of inserting a trimethyl chlorosilane (CTMS) modified TiO2/SiO2 composite patch of switchable wettability in a microfluidic system. A unique micro-nano hierarchical structure was designed and used to enhance the overall wetting contrast with the aim of improving the wetting-based valve performances. Field-emission scanning electron microscopy (FE-SEM) and x-ray photoelectron spectroscopy (XPS) were used to characterize the morphology and chemical composition of the surface. UV-driven wettability conversion on the patched microchannel was investigated using water column relative height tests, and the results confirmed the significant improvement of the hierarchical structure with the surface hydrophobic/hydrophilic conversion, which produced enhancements of 276% and 95% of the water-repellent and water-sucking pressures, respectively, compared with those of the single-scale TiO2 nanopatterned structure. Accordingly, a good reversible and repeated on-off performance was identified by the valve tests, highlighting the potential application of the novel microvalve in the efficient control of microscale flow.

In Vitro Cytotoxicity Assessment of an Orthodontic Composite Containing Titanium-dioxide Nano-particles

PubMed Central

Heravi, Farzin; Ramezani, Mohammad; Poosti, Maryam; Hosseini, Mohsen; Shajiei, Arezoo; Ahrari, Farzaneh

2013-01-01

Background and aims. Incorporation of nano-particles to orthodontic bonding systems has been considered to prevent enamel demineralization around appliances. This study investigated cytotoxicity of Transbond XT adhesive containing 1 wt% titanium dioxide (TiO2) nano-particles. Materials and methods. Ten composite disks were prepared from each of the conventional and TiO2-containg composites and aged for 1, 3, 5, 7 and 14 days in Dulbecco’s Modified Eagle’s Medium (DMEM). The extracts were obtained and exposed to culture media of human gingival fibroblasts (HGF) and mouse L929 fibroblasts. Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results. Both adhesives were moderately toxic for HGF cells on the first day of the experiment, but the TiO2-containing adhesive produced significantly lower toxicity than the pure adhesive (P<0.05). No significant differences were found in cell viability percentages between the two groups on the other days (P>0.05). There was a significant reduction in cell toxicity with increasing pre-incubation time (P<0.001). L929 cells showed similar toxicity trends, but lower sensitivity to detect cytotoxicity of dental composites. Conclusion. The orthodontic adhesive containing TiO2 nano-particles indicated comparable or even lower toxicity than its nano-particle-free counterpart, indicating that incorporation of 1 wt% TiO2 nano-particles to the composite structure does not result in additional health hazards compared to that occurring with the pure adhesive. PMID:24578816

Recent Progress in Photocatalysis Mediated by Colloidal II-VI Nanocrystals

PubMed Central

Wilker, Molly B; Schnitzenbaumer, Kyle J; Dukovic, Gordana

2012-01-01

The use of photoexcited electrons and holes in semiconductor nanocrystals as reduction and oxidation reagents is an intriguing way of harvesting photon energy to drive chemical reactions. This review focuses on recent research efforts to understand and control the photocatalytic processes mediated by colloidal II-VI nanocrystalline materials, such as cadmium and zinc chalcogenides. First, we highlight how nanocrystal properties govern the rates and efficiencies of charge-transfer processes relevant to photocatalysis. We then describe the use of nanocrystal catalyst heterostructures for fuel-forming reactions, most commonly H2 generation. Finally, we review the use of nanocrystal photocatalysis as a synthetic tool for metal–semiconductor nano-heterostructures. PMID:24115781

Controlled synthesis and facets-dependent photocatalysis of TiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Roy, Nitish; Park, Yohan; Sohn, Youngku; Pradhan, Debabrata

2015-04-01

Titanium dioxide (TiO2) is a wide band gap semiconductor that has been extensively used in several environmental applications including degradation of organic hazardous chemicals, water splitting to generate hydrogen, dye sensitized solar cells, self cleaning agents, and pigments. Herein we demonstrate the synthesis of TiO2 nanocrystals (NCs) with the shapes of ellipsoids, rods, cuboids, and sheets with different exposed facets using a noncorrosive and nontoxic chemical (i.e. diethanolamine) as the shape controlling agent, unlike hydrofluoric acid commonly used. The TiO2 NCs of diverse shapes with different exposed facets were tested for photocatalytic hydroxyl radical (OH•) formation, which determines their photocatalytic behavior and the results were compared with the standard P-25 Degussa. The formation rate of OH• per specific surface area was found to be >6 fold higher for rod-shaped TiO2 NCs than that of commercial Degussa P25 catalyst. The highest photocatalytic activity of rod-shaped TiO2 NCs is ascribed to the unique chemical environment of {010} exposed facets which facilitates the electron/hole separation in presence of {101} facets.

Dual functional porous anti-reflective coatings with a photocatalytic effect based on a single layer system

NASA Astrophysics Data System (ADS)

Jilavi, M. H.; Mousavi, S. H.; Müller, T. S.; de Oliveira, P. W.

2018-05-01

Anti-reflection and photocatalytic properties are desirable for improving the optical properties of electronic devices. We describe a method of fabrication a single-layer, anti-reflective (AR) thin film with an additional photocatalytic property. The layer is deposited on glass substrates by means of a low-cost dip-coating method using a SiO2-TiO2 solution. A comparative study was undertaken to investigate the effects of TiO2 concentrations on the photocatalytic properties of the film and to determine the optimal balance between transmittance and photocatalysis. The average transmittance increases from T = 90.51% to T = 95.46 ± 0.07% for the wavelengths between 380 and 1200 nm. The structural characterization indicated the formation of thin, porous SiO2-TiO2 films with a roughness of less than 7.5 nm. The quality of the samples was evaluated by a complete test program of the mechanical, chemical and accelerated weathering stability. This results open up new possibilities for cost-effective AR coatings for the glass and solar cell industries.

Construction of anatase/rutile TiO2 hollow boxes for highly efficient photocatalytic performance

NASA Astrophysics Data System (ADS)

Jia, Changchao; Zhang, Xiao; Yang, Ping

2018-02-01

Hollow TiO2 hierarchical boxes with suitable anatase and rutile ratios were designed for photocatalysis. The unique hierarchical structure was fabricated via a Topotactic synthetic method. CaTiO3 cubes were acted as the sacrificial templates to create TiO2 hollow hierarchical boxes with well-defined phase distribution. The phase composition of the hollow TiO2 hierarchical boxes is similar to that of TiO2 P25 nanoparticles (∼80% anatase, and 20% rutile). Compared with nanaoparticles, TiO2 hollow boxes with hierarchical structures exhibited an excellent performance in the photocatalytic degradation of methylene blue organic pollutant. Quantificationally, the degradation rate of the hollow boxes is higher than that of TiO2 P25 nanoparticles by a factor of 2.7. This is ascribed that hollow structure provide an opportunity for using incident light more efficiently. The surface hierarchical and well-organized porous structures are beneficial to supply more active sites and enough transport channels for reactant molecules. The boxes consist of single crystal anatase and rutile combined well with each other, which gives photon-generated carriers transfer efficiently.

[Decontamination of chemical warfare agents by photocatalysis].

PubMed

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

2009-01-01

Photocatalysis has been widely applied to solar-energy conversion and environmental purification. Photocatalyst, typically titanium dioxide (TiO(2)), produces active oxygen species under irradiation of ultraviolet light, and can decompose not only conventional pollutants but also different types of hazardous substances at mild conditions. We have recently started the study of photocatalytic decontamination of chemical warfare agents (CWAs) under collaboration with the National Research Institute of Police Science. This article reviews environmental applications of semiconductor photocatalysis, decontamination methods for CWAs, and previous photocatalytic studies applied to CWA degradation, together with some of our results obtained with CWAs and their simulant compounds. The data indicate that photocatalysis, which may not always give a striking power, certainly helps detoxification of such hazardous compounds. Unfortunately, there are not enough data obtained with real CWAs due to the difficulty in handling. We will add more scientific data using CWAs in the near future to develop useful decontamination systems that can reduce the damage caused by possible terrorism.

Heterogeneous Photocatalysis and Photoelectrocatalysis: From Unselective Abatement of Noxious Species to Selective Production of High-Value Chemicals.

PubMed

Augugliaro, Vincenzo; Camera-Roda, Giovanni; Loddo, Vittorio; Palmisano, Giovanni; Palmisano, Leonardo; Soria, Javier; Yurdakal, Sedat

2015-05-21

Heterogeneous photocatalysis and photoelectrocatalysis have been considered as oxidation technologies to abate unselectively noxious species. This article focuses instead on the utilization of these methods for selective syntheses of organic molecules. Some promising reactions have been reported in the presence of various TiO2 samples and the important role played by the amorphous phase has been discussed. The low solubility of most of the organic compounds in water limits the utilization of photocatalysis. Dimethyl carbonate has been proposed as an alternative green organic solvent. The recovery of the products by coupling photocatalysis with pervaporation membrane technology seems to be a solution for future industrial applications. As far as photoelectrocatalysis is concerned, a decrease in recombination of the photogenerated pairs occurs, enhancing the rate of the oxidation reactions and the quantum yield. Another benefit is to avoid reaction(s) between the intermediates and the substrate, as anodic and cathodic reactions take place in different places.

Analysis of protein phosphorylation by monolithic extraction columns based on poly(divinylbenzene) containing embedded titanium dioxide and zirconium dioxide nano-powders.

PubMed

Rainer, Matthias; Sonderegger, Harald; Bakry, Rania; Huck, Christian W; Morandell, Sandra; Huber, Lukas A; Gjerde, Douglas T; Bonn, Günther K

2008-11-01

The potential of an organic monolith with incorporated titanium dioxide (TiO(2)) and zirconium dioxide (ZrO(2)) nanoparticles was evaluated for the selective enrichment of phosphorylated peptides from tryptic digests. A pipette tip was fitted with a monolith based on divinylbenzene (DVB) of highly porous structure, which allows sample to pass through the monolithic bed. The enrichment of phosphopeptides was enhanced by increasing the pipetting cycles during the sample preparation and a higher recovery could be achieved with adequate buffer systems. A complete automated process was developed for enrichment of phosphopeptides leading to high reproducibility and resulting in a robust method designed to minimize analytical variance while providing high sensitivity at high sample throughput. The effect of particle size on the selectivity of phosphopeptides was investigated by comparative studies with nano- and microscale TiO(2) and ZrO(2) powders. Eleven phosphopeptides from alpha-casein digest could be recovered by an optimized mixture of microscale TiO(2)/ZrO(2) particles, whereas nine additional phosphopeptides could be retained by the same mixture of nano-structured material. When compared to conventional immobilized metal-ion affinity chromatography and commercial phosphorylation-enrichment kits, higher selectivity was observed in case of self fabricated tips. About 20 phosphopeptides could be retained from alpha-casein and five from beta-casein digests by using TiO(2) and ZrO(2) based extraction tips. Further selectivity for phosphopeptides was demonstrated by enriching a digest of in vitro phosphorylated extracellular signal regulated kinase 1 (ERK1). Two phosphorylated peptides of ERK1 could be identified by MALDI-MS/MS measurements and a following MASCOT database search.

Microstructure and antibacterial property of in situ TiO(2) nanotube layers/titanium biocomposites.

PubMed

Cui, C X; Gao, X; Qi, Y M; Liu, S J; Sun, J B

2012-04-01

The TiO(2) nanotube layer was in situ synthesized on the surface of pure titanium by the electrochemical anodic oxidation. The diameter of nano- TiO(2) nanotubes was about 70~100 nm. The surface morphology and phase compositions of TiO(2) nanotube layers were observed and analyzed using the scanning electron microscope (SEM). The important processing parameters, including anodizing voltage, reaction time, concentration of electrolyte, were optimized in more detail. The photocatalytic activity of the nano- TiO(2) nanotube layers prepared with optimal conditions was evaluated via the photodegradation of methylthionine in aqueous solution. The antibacterial property of TiO(2) nanotube layers prepared with optimal conditions was evaluated by inoculating Streptococcus mutans on the TiO(2) nanotube layers in vitro. The results showed that TiO(2) nanotube layers/Ti biocomposites had very good antibacterial activity to resist Streptococcus mutans. As a dental implant biomaterial, in situ TiO(2) nanotube layer/Ti biocomposite has better and wider application prospects. Copyright © 2012 Elsevier Ltd. All rights reserved.

Cotton fibers nano-TiO{sub 2} composites prepared by as-assembly process and the photocatalytic activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, J.H., E-mail: xiajianhan@163.com; Hsu, C.T.; Qin, D.D.

Graphical abstract: Display Omitted Highlights: ► TiO{sub 2} nanoparticles self-assemble process under the assistant of carboxylic group. ► The carboxylic group was introduced by displacement reaction. ► The loading amount of nano-TiO{sub 2} was depended on the displacement degree of C-6-OH. ► UV–Vis experiments showed these fibers had efficient photocatalysis. ► The degradation reaction Rhodamine 6G under UV light obeys zero-order rate law. -- Abstract: This paper describes photocatalytic cotton fibers produced by a TiO{sub 2} nanoparticle self-assembly process with the assistance of carboxylic groups. The carboxylic group was introduced by a displacement reaction, the molecular structure of the glucosemore » unit was studied by utilizing solid {sup 13}C NMR. The appearance of the prepared fibers was observed by scanning electron microscopy, it was found that nano-TiO{sub 2} coated uniformly on the fiber surface. The loading amount of nano-TiO{sub 2} was depended on the displacement degree of C-6-OH. UV–Vis experiments showed these coated fibers undergo photocatalysis efficiently. The degradation reaction of Rhodamine 6G under UV light obeys the zero-order rate law.« less

Species sensitivity and dependence on exposure conditions impacting the phototoxicity of TiO2 nanoparticles to benthic organisms

EPA Science Inventory

Toxicity of TiO2 nanoparticles (nano-TiO2) to aquatic organisms can be greatly increased upon the exposure to ultraviolet radiation (UV). This phenomenon has received some attention for pelagic species, however, investigations of nano-TiO2 phototoxicity in benthic organisms are s...

Application of nitrogen-doped TiO2 nano-tubes in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Tran, Vy Anh; Truong, Trieu Thinh; Phan, Thu Anh Pham; Nguyen, Trang Ngoc; Huynh, Tuan Van; Agresti, Antonio; Pescetelli, Sara; Le, Tien Khoa; Di Carlo, Aldo; Lund, Torben; Le, So-Nhu; Nguyen, Phuong Tuyet

2017-03-01

Our research aimed to improve the overall energy conversion efficiency of DSCs by applying nitrogen-doped TiO2 nano-tubes (N-TNT) for the preparation of DSCs photo-anodes. The none-doped TiO2 nano-tubes (TNTs) were synthesized by alkaline hydrothermal treatment of Degussa P25 TiO2 particles in 10 M NaOH. The nano-tubes were N-doped by reflux in various concentrations of NH4NO3. The effects of nitrogen doping on the structure, morphology, and crystallography of N-TNT were analyzed by transmission electron microscopy (TEM), infrared spectroscopy (IR), Raman spectroscopy, and X-ray photoelectron spectra (XPS). DSCs fabricated with doped N-TNT and TNT was characterized by J-V measurements. Results showed that nitrogen doping significantly enhanced the efficiency of N-TNT cells, reaching the optimum value (η = 7.36%) with 2 M nitrogen dopant, compared to η = 4.75% of TNT cells. The high efficiency of the N-TNT cells was attributed to increased current density due to the reduction of dark current in the DSCs.

Graphene quantum dots to enhance the photocatalytic hydrogen evolution efficiency of anatase TiO2 with exposed {001} facet.

PubMed

Yu, Shan; Zhong, Yun-Qian; Yu, Bao-Quan; Cai, Shi-Yi; Wu, Li-Zhu; Zhou, Ying

2016-07-27

Hydrogen evolution through photocatalysis is promising with respect to the environmental problems and challenges of energy shortage that we encounter today. In this paper, we have combined graphene quantum dots (GQDs) and {001} faceted anatase TiO2 (with an exposed percentage of 65-75%) together for effective photocatalytic hydrogen evolution. A series of characterizations including X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and UV-visible absorption spectroscopy have been carried out to study the structure of the as-prepared GQDs/{001}TiO2 composite. It turns out that GQDs could be effectively decorated on {001}TiO2 sheet without changing its intrinsic structure. With an optimum loading amount of GQDs (0.5 wt% to {001}TiO2), GQDs/{001}TiO2 exhibits a hydrogen evolution efficiency 8 times higher than that of bare {001}TiO2, which is a significantly more obvious improvement than many other photocatalytic systems relevant to GQDs and TiO2 hybrids. In addition, GQDs/{001}TiO2 could stand long-term photocatalytic experiments. Photocurrent tests show that such an improvement of the photocatalytic efficiency over GQDs/{001}TiO2 may originate from a higher charge separation efficiency. The present study could offer reference for the construction of photocatalytic hydrogen evolution systems with low cost and long term stability.

The nature of chlorine-inhibition of photocatalytic degradation of dichloroacetic acid in a TiO2-based microreactor.

PubMed

Krivec, M; Dillert, R; Bahnemann, D W; Mehle, A; Štrancar, J; Dražić, G

2014-07-28

Photocatalytic degradation of dichloroacetic acid (DCA) was studied in a continuous-flow set-up using a titanium microreactor with an immobilized double-layered TiO2 nanoparticle/nanotube film. Chloride ions, formed during the degradation process, negatively affect the photocatalytic efficiency and at a certain concentration (approximately 0.5 mM) completely stop the reaction in the microreactor. Two proposed mechanisms of inhibition with chloride ions, competitive adsorption and photogenerated-hole scavenging, have been proposed and investigated by adsorption isotherms and electron paramagnetic resonance (EPR) measurements. The results show that chloride ions block the DCA adsorption sites on the titania surface and reduce the amount of adsorbed DCA molecules. The scavenging effect of chloride ions during photocatalysis through the formation of chlorine radicals was not detected.

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

NASA Astrophysics Data System (ADS)

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

2017-01-01

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

Phosphate Changes Effect of Humic Acids on TiO2 Photocatalysis: From Inhibition to Mitigation of Electron-Hole Recombination.

PubMed

Long, Mingce; Brame, Jonathon; Qin, Fan; Bao, Jiming; Li, Qilin; Alvarez, Pedro J J

2017-01-03

A major challenge for photocatalytic water purification with TiO 2 is the strong inhibitory effect of natural organic matter (NOM), which can scavenge photogenerated holes and radicals and occlude ROS generation sites upon adsorption. This study shows that phosphate counteracts the inhibitory effect of humic acids (HA) by decreasing HA adsorption and mitigating electron-hole recombination. As a measure of the inhibitory effect of HA, the ratios of first-order reaction rate constants between photocatalytic phenol degradation in the absence versus presence of HA were calculated. This ratio was very high, up to 5.72 at 30 mg/L HA and pH 4.8 without phosphate, but was decreased to 0.76 (5 mg/L HA, pH 8.4) with 2 mM phosphate. The latter ratio indicates a surprising favorable effect of HA on TiO 2 photocatalysis. FTIR analyses suggest that this favorable effect is likely due to a change in the conformation of adsorbed HA, from a multiligand exchange arrangement to a complexation predominantly between COOH groups in HA and the TiO 2 surface in the presence of phosphate. This configuration can reduce hole consumption and facilitate electron transfer to O 2 by the adsorbed HA (indicated by linear sweep voltammetry), which mitigates electron-hole recombination and enhances contaminant degradation. A decrease in HA surface adsorption and hole scavenging (the predominant inhibitory mechanisms of HA) by phosphate (2 mM) was indicated by a 50% decrease in the photocatalytic degradation rate of HA and 80% decrease in the decay rate coefficient of interfacial-related photooxidation in photocurrent transients. These results, which were validated with other compounds (FFA and cimetidine), indicate that anchoring phosphate - or anions that exert similar effects on the TiO 2 surface - might be a feasible strategy to counteract the inhibitory effect of NOM during photocatalytic water treatment.

Large bandgap narrowing in rutile TiO2 aimed towards visible light applications and its correlation with vacancy-type defects history and transformation

NASA Astrophysics Data System (ADS)

Nair, Radhika V.; Gayathri, P. K.; Siva Gummaluri, Venkata; Nambissan, P. M. G.; Vijayan, C.

2018-01-01

Extension of photoactivity of TiO2 to the visible region is achievable via effective control over the intrinsic defects such as oxygen and Ti vacancies, which has several applications in visible photocatalysis and sensing. We present here the first observation of an apparent bandgap narrowing and bandgap tuning effect due to vacancy cluster transformation in rutile TiO2 structures to 1.84 eV from the bulk bandgap of 3 eV. A gradual transformation of divacancies (V Ti-O) to tri vacancies ({{V}Ti-O-T{{i-}}} ) achieved through a controlled solvothermal scheme appears to result in an apparent narrowing bandgap and tunability, as supported by positron annihilation lifetime and electron paramagnetic resonance spectroscopy measurements. Visible photocatalytic activity of the samples is demonstrated in terms of photodegradation of rhodamine B dye molecules.

Atomic layer deposition TiO 2-Al 2O 3 stack: An improved gate dielectric on Ga-polar GaN metal oxide semiconductor capacitors

DOE PAGES

Wei, Daming; Edgar, James H.; Briggs, Dayrl P.; ...

2014-10-15

This research focuses on the benefits and properties of TiO 2-Al 2O 3 nano-stack thin films deposited on Ga 2O 3/GaN by plasma-assisted atomic layer deposition (PA-ALD) for gate dielectric development. This combination of materials achieved a high dielectric constant, a low leakage current, and a low interface trap density. Correlations were sought between the films’ structure, composition, and electrical properties. The gate dielectrics were approximately 15 nm thick and contained 5.1 nm TiO 2, 7.1 nm Al 2O 3 and 2 nm Ga 2O 3 as determined by spectroscopic ellipsometry. The interface carbon concentration, as measured by x-ray photoelectronmore » spectroscopy (XPS) depth profile, was negligible for GaN pretreated by thermal oxidation in O 2 for 30 minutes at 850°C. The RMS roughness slightly increased after thermal oxidation and remained the same after ALD of the nano-stack, as determined by atomic force microscopy. The dielectric constant of TiO 2-Al 2O 3 on Ga2O3/GaN was increased to 12.5 compared to that of pure Al 2O 3 (8~9) on GaN. In addition, the nano-stack's capacitance-voltage (C-V) hysteresis was small, with a total trap density of 8.74 × 10 11 cm -2. The gate leakage current density (J=2.81× 10 -8 A/cm 2) was low at +1 V gate bias. These results demonstrate the promising potential of plasma ALD deposited TiO 2/Al 2O 3 for serving as the gate oxide on Ga 2O 3/GaN based MOS devices.« less

Atomic layer deposition TiO 2-Al 2O 3 stack: An improved gate dielectric on Ga-polar GaN metal oxide semiconductor capacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Daming; Edgar, James H.; Briggs, Dayrl P.

This research focuses on the benefits and properties of TiO 2-Al 2O 3 nano-stack thin films deposited on Ga 2O 3/GaN by plasma-assisted atomic layer deposition (PA-ALD) for gate dielectric development. This combination of materials achieved a high dielectric constant, a low leakage current, and a low interface trap density. Correlations were sought between the films’ structure, composition, and electrical properties. The gate dielectrics were approximately 15 nm thick and contained 5.1 nm TiO 2, 7.1 nm Al 2O 3 and 2 nm Ga 2O 3 as determined by spectroscopic ellipsometry. The interface carbon concentration, as measured by x-ray photoelectronmore » spectroscopy (XPS) depth profile, was negligible for GaN pretreated by thermal oxidation in O 2 for 30 minutes at 850°C. The RMS roughness slightly increased after thermal oxidation and remained the same after ALD of the nano-stack, as determined by atomic force microscopy. The dielectric constant of TiO 2-Al 2O 3 on Ga2O3/GaN was increased to 12.5 compared to that of pure Al 2O 3 (8~9) on GaN. In addition, the nano-stack's capacitance-voltage (C-V) hysteresis was small, with a total trap density of 8.74 × 10 11 cm -2. The gate leakage current density (J=2.81× 10 -8 A/cm 2) was low at +1 V gate bias. These results demonstrate the promising potential of plasma ALD deposited TiO 2/Al 2O 3 for serving as the gate oxide on Ga 2O 3/GaN based MOS devices.« less

Methylparaben removal using heterogeneous photocatalysis: effect of operational parameters and mineralization/biodegradability studies.

PubMed

Zúñiga-Benítez, Henry; Peñuela, Gustavo A

2017-03-01

Methylparaben (MePB) is an organic compound employed mainly in the manufacture of different personal care products. However, it has been recently listed as a potential endocrine disrupter chemical. Therefore, the main objective of this work was to evaluate the degradation of MePB in aqueous solutions using heterogeneous photocatalysis with TiO 2 and hydrogen peroxide. In this way, effects of pH and the initial concentrations of catalyst, H 2 O 2 , and pollutant on treatment were analyzed. A face centered, central composite design was used for determination of the influence of each parameter in the process and the conditions under which the pollutant suffers the highest rates of degradation were selected. In general, results indicate that combination TiO 2 /H 2 O 2 /light irradiation leads to ∼90 % of substrate removal after 30 min of reaction and that hydroxyl free radicals are the main specie responsible for organic matter elimination. Finally, in terms of mineralization and biodegradability, experimental results indicated that part of the organic matter was transformed into CO 2 and water and the photo-treatment promoted an increase in samples biodegradability.

Germination and early plant development of 10 plant species exposed to Nano TiO2 and CeO2

EPA Science Inventory

Ten agronomic plant species were exposed to different concentrations of nano-TiO2 or CeO2 (0, 250, 500 and 1000 ug/l) and followed to examine effects on germination and early seedling development. For TiO2, cabbage showed increased and corn decreased percent germination, while ...

A polymer solution technique for the synthesis of nano-sized Li 2TiO 3 ceramic breeder powders

NASA Astrophysics Data System (ADS)

Jung, Choong-Hwan; Lee, Sang Jin; Kriven, Waltraud M.; Park, Ji-Yeon; Ryu, Woo-Seog

2008-02-01

Nano-sized Li 2TiO 3 powder was fabricated by an organic-inorganic solution route. A steric entrapment route employing ethylene glycol was used for the preparation of the nano-sized Li 2TiO 3 particles. Titanium isopropoxide and lithium nitrate were dissolved in liquid-type ethylene glycol without any precipitation. With the optimum amount of the polymer, the metal cations (Li and Ti) were dispersed in the solution and a homogeneous polymeric network was formed. The organic-inorganic precursor gels were turned to crystalline powders through an oxidation reaction during a calcination process. The dried precursor gel showed the carbon-free Li 2TiO 3 crystalline form which was observed above 400 °C. The primary particle size of the carbon-free Li 2TiO 3 was about 70 nm, and the structure of the crystallized powder was porous and agglomerated. The powder compact was densified to 92% of TD at a relatively low sintering temperature of 1100 °C for 2 h.

Effect of particle size on band gap and DC electrical conductivity of TiO2 nanomaterial

NASA Astrophysics Data System (ADS)

Avinash, B. S.; Chaturmukha, V. S.; Jayanna, H. S.; Naveen, C. S.; Rajeeva, M. P.; Harish, B. M.; Suresh, S.; Lamani, Ashok R.

2016-05-01

Materials reduced to the Nano scale can exhibit different properties compared to what they exhibit on a micro scale, enabling unique applications. When TiO2 is reduced to Nano scale it shows unique properties, of which the electrical aspect is highly important. This paper presents increase in the energy gap and decrease in conductivity with decrease in particle size of pure Nano TiO2 synthesized by hydrolysis and peptization of titanium isopropoxide. Aqueous solution with various pH and peptizing the resultant suspension will form Nano TiO2 at different particle sizes. As the pH of the solution is made acidic reduction in the particle size is observed. And it is confirmed from XRD using Scherer formula and SEM, as prepared samples are studied for UV absorbance, and DC conductivity from room temperature to 400°C. From the tauc plot it was observed, and calculated the energy band gap increases as the particle size decreases and shown TiO2 is direct band gap. From Arrhenius plot clearly we encountered, decrease in the conductivity for the decrease in particle size due to hopping of charge carriers and it is evident that, we can tailor the band gap by varying particle size.

Nano-titanium dioxide induced cardiac injury in rat under oxidative stress.

PubMed

Sha, BaoYong; Gao, Wei; Wang, ShuQi; Li, Wei; Liang, Xuan; Xu, Feng; Lu, Tian Jian

2013-08-01

Heart diseases, which are related to oxidative stress (OS), negatively affect millions of people from kids to the elderly. Titanium dioxide (TiO2) has widespread applications in our daily life, especially nanoscale TiO2. Compared to the high risk of particulate matter (≤2.5μm) in air to heart disease patients, related research of TiO2 on diseased body is still unknown, which suggest us to explore the potential effects of nanoscale and microscale TiO2 to heart under OS conditions. Here, we used alloxan to induce OS conditions in rat, and investigated the response of heart tissue to TiO2 in healthy and alloxan treated rats. Compared with NMs treatment only, the synergistic interaction between OS conditions and nano-TiO2 significantly reduced the heart-related function indexes, inducing pathological changes of myocardium with significantly increased levels of cardiac troponin I and creatine kinase-MB. In contrast with the void response of micro-TiO2 to heart functions in alloxan treated rats, aggravation of OS conditions might play an important role in cardiac injury after alloxan and nano-TiO2 dual exposure. Our results demonstrated that OS conditions enhanced the adverse effects of nano-TiO2 to heart, suggesting that the use of NMs in stressed conditions (e.g., drug delivery) needs to be carefully monitored. Copyright © 2013 Elsevier Ltd. All rights reserved.

Cd/In-Codoped TiO2 nanochips for high-efficiency photocatalytic dye degradation.

PubMed

Liu, Dongliang; Huang, Peng; Liu, Yong; Wu, Zhou; Li, Dongsheng; Guo, Jun; Wu, Tao

2018-05-01

Titanium dioxide has been widely investigated in the field of photocatalysis research. However, the wide bandgap (3.2 eV) greatly limits its practical applications because only ultraviolet light can be absorbed by bare TiO2. Herein, we report a facile approach to prepare Cd/In-codoped TiO2 nanochips with the capability of visible light absorption. Such bimetallic-doped TiO2 was synthesized through a two-step process: Cd/In/S-TiO2 gels were first synthesized by mixing the preformed Cd-In-S supertetrahedral nanoclusters with a titanium source, and the subsequent pyrolytic process effectively converted the gels into Cd/In-TiO2 nanochips with a thickness of ∼2.19 nm and a uniform diameter of ∼10.60 nm. Interestingly, the absorption band of Cd/In-TiO2 nanochips was adjusted by pyrolysis temperature, which further regulated the photocatalytic efficiency of dye degradation under visible light. Current research demonstrates that doping TiO2 by multimetallic sulfide nanoclusters opens up a new door to further enrich the dopants in TiO2 and broaden their potential applications.

A Facile Method for Loading CeO2 Nanoparticles on Anodic TiO2 Nanotube Arrays.

PubMed

Liao, Yulong; Yuan, Botao; Zhang, Dainan; Wang, Xiaoyi; Li, Yuanxun; Wen, Qiye; Zhang, Huaiwu; Zhong, Zhiyong

2018-04-03

In this paper, a facile method was proposed to load CeO 2 nanoparticles (NPs) on anodic TiO 2 nanotube (NT) arrays, which leads to a formation of CeO 2 /TiO 2 heterojunctions. Highly ordered anatase phase TiO 2 NT arrays were fabricated by using anodic oxidation method, then these individual TiO 2 NTs were used as tiny "nano-containers" to load a small amount of Ce(NO 3 ) 3 solutions. The loaded anodic TiO 2 NTs were baked and heated to a high temperature of 450 °C, under which the Ce(NO 3 ) 3 would be thermally decomposed inside those nano-containers. After the thermal decomposition of Ce(NO 3 ) 3 , cubic crystal CeO 2 NPs were obtained and successfully loaded into the anodic TiO 2 NT arrays. The prepared CeO 2 /TiO 2 heterojunction structures were characterized by a variety of analytical technologies, including XRD, SEM, and Raman spectra. This study provides a facile approach to prepare CeO 2 /TiO 2 films, which could be very useful for environmental and energy-related areas.

2011 Final Report - Nano-Oxide Photocatalysis for Solar Energy Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eckstein, James N.; Suslick, Kenneth S.

2011-10-19

We have very recently discovered a new hydrogen-producing photocatalyst is BiNbO4. BiNbO4 powders prepared by solid state reaction were tested for photocatalytic activity in methanol solutions under UV irradiation. When the material is tested without the presence of a Pt co-catalyst, photocatalytic activity for H2 evolution is superior to that of TiO2. It was also found that BiNbO4 photodegrades into metallic Bi and reduced Nb oxides after use; materials were characterized by SEM, XRD, and XPS. Adding Pt to the surface of the photocatalyst increases photocatalytic activity and importantly, helps to prevent photodegradation of the oxide material. With 1 wt.more » % Pt loading, photodegradation is essentially absent. BiNbO4 photodegrades into metallic Bi and reduced Nb oxides after use; materials were characterized by SEM, XRD, and XPS. Adding Pt to the surface of the photocatalyst increases photocatalytic activity and importantly, helps to prevent photodegradation of the oxide material. With 1 wt. % Pt loading, photodegradation is essentially absent.« less

Abrasion properties of self-suspended hairy titanium dioxide nanomaterials

NASA Astrophysics Data System (ADS)

Zhang, Jiao-xia; Liu, Si; Yan, Chao; Wang, Xiao-jing; Wang, Lei; Yu, Ya-ming; Li, Shi-yun

2017-11-01

Considering the excellent solubility of pyrrolidone ring organic compounds, the synthesized N-(trimethoxysilyl) propyl- N-methyl-2-pyrrolidone chlorides was tethered onto titanium dioxide (TiO2) nanoparticles to improve dispersion of TiO2, and then polyethylene oxide (PEO) oligomer through ion exchange embraced the tethered TiO2 to obtain a novel self-suspended hairy TiO2 nanomaterials without any solvent. A variety of techniques were carried out to illustrate the structure and properties of the self-suspended hairy TiO2 nanomaterials. It was found that TiO2 nanoparticles embody monodispersity in the hybrid system though the "false reunion" phenomenon occurring due to nonpermanent weak physical cross-linking. Remarkably, self-suspended hairy TiO2 nanomaterials exhibit lower viscosity, facilitating maneuverable and outstanding antifriction and wear resistance properties, due to the synergistic lubricating effect between spontaneously forming lubricating film and nano-lubrication of TiO2 cores, overcoming the deficiency of both solid and liquid lubricants. This make them promising candidates for the micro-electromechanic/nano-electromechanic systems (MEMS/NEMS).

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

PubMed

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

2015-06-01

The thickness-controlled TiO2 thin films are fabricated by the pulsed laser deposition (PLD) method. These samples function as photocatalysts under UV light irradiation and the reaction rate depends on the TiO2 thickness, i.e., with an increase of thickness, it increases to the maximum, followed by decreasing to be constant. Such variation of the reaction rate is fundamentally explained by the competitive production and annihilation processes of photogenerated electrons and holes in TiO2 films, and the optimum TiO2 thickness is estimated to be ca. 10nm. We also tried to dope nitrogen into the effective depth region (ca. 10nm) of TiO2 by an ion implantation technique. The nitrogen doped TiO2 enhanced photocatalytic activity under visible-light irradiation. XANES and XPS analyses indicated two types of chemical state of nitrogen, one photo-catalytically active N substituting the O sites and the other inactive NOx (1⩽x⩽2) species. In the valence band XPS spectrum of the high active sample, the additional electronic states were observed just above the valence band edge of a TiO2. The electronic state would be originated from the substituting nitrogen and be responsible for the band gap narrowing, i.e., visible light response of TiO2 photocatalysts. Copyright © 2015 Elsevier Inc. All rights reserved.

Highly ordered Fe3+/TiO2 nanotube arrays for efficient photocataltyic degradation of nitrobenzene

NASA Astrophysics Data System (ADS)

Zhang, Yiyang; Gu, Di; Zhu, Lingyue; Wang, Baohui

2017-10-01

Highly ordered TiO2 nanotube arrays (TiO2 NTs) were prepared through a facile two-step electrochemical anodization, subsequently, active iron ions were introduced into the TiO2 NTs via a direct impregnation method. The XPS results showed that the iron elements existed in TiO2 NTs in the form of Fe3+ ions. Compared with the undoped TiO2 NTs, the absorption edge of Fe3+/TiO2 NTs showed an overt red shift and the photocurrent improved obviously, which indicated that Fe3+/TiO2 had a much higher photocatalytic activity. The optimal doping content was tested to be 0.1 mol/L which could make the photocatalytic activity of TiO2 NTs obviously improves under both visible and ultraviolent light. The prepared samples were adopted as photocatalyst to degrade nitrobenzene (NB). The reaction rate constants ks under UV light were in the order kone-stepTiO2NTs = 0.00338

Epitaxial Growth of Lattice-Mismatched Core-Shell TiO2 @MoS2 for Enhanced Lithium-Ion Storage.

PubMed

Dai, Rui; Zhang, Anqi; Pan, Zhichang; Al-Enizi, Abdullah M; Elzatahry, Ahmed A; Hu, Linfeng; Zheng, Gengfeng

2016-05-01

Core-shell structured nanohybrids are currently of significant interest due to their synergetic properties and enhanced performances. However, the restriction of lattice mismatch remains a severe obstacle for heterogrowth of various core-shells with two distinct crystal structures. Herein, a controlled synthesis of lattice-mismatched core-shell TiO2 @MoS2 nano-onion heterostructures is successfully developed, using unilamellar Ti0.87 O2 nanosheets as the starting material and the subsequent epitaxial growth of MoS2 on TiO2 . The formation of these core-shell nano-onions is attributed to an amorphous layer-induced heterogrowth mechanism. The number of MoS2 layers can be well tuned from few to over ten layers, enabling layer-dependent synergistic effects. The core-shell TiO2 @MoS2 nano-onion heterostructures exhibit significantly enhanced energy storage performance as lithium-ion battery anodes. The approach has also been extended to other lattice-mismatched systems such as TiO2 @MoSe2 , thus suggesting a new strategy for the growth of well-designed lattice-mismatched core-shell structures. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rough gold films as broadband absorbers for plasmonic enhancement of TiO2 photocurrent over 400–800 nm

PubMed Central

Tan, Furui; Li, Tenghao; Wang, Ning; Lai, Sin Ki; Tsoi, Chi Chung; Yu, Weixing; Zhang, Xuming

2016-01-01

Recent years have witnessed an increasing interest in highly-efficient absorbers of visible light for the conversion of solar energy into electrochemical energy. This study presents a TiO2-Au bilayer that consists of a rough Au film under a TiO2 film, which aims to enhance the photocurrent of TiO2 over the whole visible region and may be the first attempt to use rough Au films to sensitize TiO2. Experiments show that the bilayer structure gives the optimal optical and photoelectrochemical performance when the TiO2 layer is 30 nm thick and the Au film is 100 nm, measuring the absorption 80–90% over 400–800 nm and the photocurrent intensity of 15 μA·cm−2, much better than those of the TiO2-AuNP hybrid (i.e., Au nanoparticle covered by the TiO2 film) and the bare TiO2 film. The superior properties of the TiO2-Au bilayer can be attributed to the rough Au film as the plasmonic visible-light sensitizer and the photoactive TiO2 film as the electron accepter. As the Au film is fully covered by the TiO2 film, the TiO2-Au bilayer avoids the photocorrosion and leakage of Au materials and is expected to be stable for long-term operation, making it an excellent photoelectrode for the conversion of solar energy into electrochemical energy in the applications of water splitting, photocatalysis and photosynthesis. PMID:27608836

Effects of titanium dioxide nanoparticles derived from consumer products on the marine diatom Thalassiosira pseudonana.

PubMed

Galletti, Andrea; Seo, Seokju; Joo, Sung Hee; Su, Chunming; Blackwelder, Pat

2016-10-01

Increased manufacture of TiO 2 nanoproducts has caused concern about the potential toxicity of these products to the environment and in public health. Identification and confirmation of the presence of TiO 2 nanoparticles derived from consumer products as opposed to industrial TiO 2 NPs warrant examination in exploring the significance of their release and resultant impacts on the environment. To this end, we examined the significance of the release of these particles and their toxic effect on the marine diatom algae Thalassiosira pseudonana. Our results indicate that nano-TiO 2 sunscreen and toothpaste exhibit more toxicity in comparison to industrial TiO 2 and inhibited the growth of the marine diatom T. pseudonana. This inhibition was proportional to the exposure time and concentrations of nano-TiO 2 . Our findings indicate a significant effect, and therefore, further research is warranted in evaluation and assessment of the toxicity of modified nano-TiO 2 derived from consumer products and their physicochemical properties.

Cation coordination reactions on nanocrystals: surface/interface, doping control and advanced photocatalysis applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhang, Jiatao

2016-10-01

Abstract: Including the shape and size effect, the controllable doping, hetero-composite and surface/interface are the prerequisite of colloidal nanocrystals for exploring their optoelectronic properties, such as fluorescence, plasmon-exciton coupling, efficient electron/hole separation, and enhanced photocatalysis applications. By controlling soft acid-base coordination reactions between cation molecular complexes and colloidal nanocrystals, we showed that chemical thermodynamics could drive nanoscale monocrystalline growth of the semiconductor shell on metal nano-substrates and the substitutional heterovalent doping in semiconductor nanocrystals. We have demonstrated evolution of relative position of Au and II-VI semiconductor in Au-Semi from symmetric to asymmetric configuration, different phosphines initiated morphology engineering, oriented attachment of quantum dots into micrometer nanosheets with synergistic control of surface/interface and doing, which can further lead to fine tuning of plasmon-exciton coupling. Therefore, different hydrogen photocatalytic performance, Plasmon enhanced photocatalysis properties have been achieved further which lead to the fine tuning of plasmon-exciton coupling. Substitutional heterovalent doping here enables the tailoring of optical, electronic properties and photocatalysis applications of semiconductor nanocrystals because of electronic impurities (p-, n-type doping) control. References: (1) J. Gui, J. Zhang*, et al. Angew. Chem. Int. Ed. 2015, 54, 3683. (2) Q. Zhao, J. Zhang*, etc., Adv. Mater. 2014, 26, 1387. (3) J. Liu, Q. Zhao, S. G. Wang*, J. Zhang*, etc., Adv. Mater. 2015, 27-2753-2761. (4) H. Qian, J. Zhang*, etc., NPG Asia Mater. (2015) 7, e152. (5) M. Ji, M. Xu, etc., J. Zhang*, Adv. Mater. 2016, in proof. (6) S. Yu, J. T. Zhang, Y. Tang, M. Ouyang*, Nano Lett. 2015, 15, 6282-6288. (7) J. Zhang, Y. Tang, K. Lee and M. Ouyang*, Science 2010, 327, 1634. (8) J. Zhang, Y. Tang, K. Lee, M. Ouyang*, Nature 2010, 466, 91.

In Situ Fabrication of Hierarchically Branched TiO2 Nanostructures: Enhanced Performance in Photocatalytic H2 Evolution and Li-Ion Batteries.

PubMed

Yang, Guorui; Wang, Ling; Peng, Shengjie; Wang, Jianan; Ji, Dongxiao; Yan, Wei; Ramakrishna, Seeram

2017-12-01

1D branched TiO 2 nanomaterials play a significant role in efficient photocatalysis and high-performance lithium ion batteries. In contrast to the typical methods which generally have to employ epitaxial growth, the direct in situ growth of hierarchically branched TiO 2 nanofibers by a combination of the electrospinning technique and the alkali-hydrothermal process is presented in this work. Such the branched nanofibers exhibit improvement in terms of photocatalytic hydrogen evolution (0.41 mmol g -1 h -1 ), in comparison to the conventional TiO 2 nanofibers (0.11 mmol g -1 h -1 ) and P25 (0.082 mmol g -1 h -1 ). Furthermore, these nanofibers also deliver higher lithium specific capacity at different current densities, and the specific capacity at the rate of 2 C is as high as 201. 0 mAh g -1 , roughly two times higher than that of the pristine TiO 2 nanofibers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

PubMed

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

2016-01-01

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

[Effect of TiO2-SiO2-SnOx film with different firing temperatures on bond strength of low-fusing dental porcelain to pure titanium].

PubMed

Zhang, Zichuan; Zhang, Pei

2015-07-01

To evaluate the influence of TiO(2)-SiO(2)-SnOx nano-coatings with different firing temperatures on the bond strength of low-fusing dental porcelain to pure titanium. The surface of pure titanium was coated uniformly with TiO(2)-SiO(2)-SnOx nano-coatings by solution-gelatin (Sol-Gel) technology and then fired at 300 °C (group A) or 750 °C (group B) for 1 h. The specimens without any coatings were the control group (group C). There were 10 specimens in each group. Dental porcelain was sintered on the surface of titanium specimens. Surface roughness and contact angle of the coatings were also detected. The titanium-porcelain bond strength was investigated according to YY 0621-2008 standards using three-point flexure bond test. The phase composition of the TiO(2)-SiO(2)-SnOx nano-coatings was characterized by X-ray diffraction(XRD). The interface of titanium-porcelain and TiO(2)-SiO(2)-SnOx nano-coatings were observed using scanning electron microscope (SEM). No rutile phase was found in these specimens of group A and group B. The surface roughness of group A, B, C was (0.97 ± 0.06), (0.99 ± 0.03), (0.96 ± 0.07) µm, respectively. No significant difference was found among the three groups. Compared with that of group C (64.37° ± 3.01°), contact angles detected in group A (52.04° ± 3.15°) and group B (85.27° ± 4.17°) were significantly different (P < 0.05). The bond strength of titanium-porcelain in group A [(35.66 ± 2.65) MPa] was significantly increased compared with those in group B [(26.18 ± 2.22) MPa] and group C [(31.66 ± 3.52) MPa]. SEM photomicrographs of titanium-porcelain interface morphology of the specimens before porcelain sintering showed that TiO(2)-SiO(2)-SnOx nano-coatings in group A were compact and homogeneous with petty cracks and those in group B was loose and arranged disorderly. TiO(2)-SiO(2)-SnOx nano-coating fired at 300 °C is significantly effective in improving the titanium-porcelain bond strength.

Selective separation and recovery of silver and copper from mixtures by photocatalysis

NASA Astrophysics Data System (ADS)

Ding, Mali; Zhang, Weijun; Xie, Zhaofeng; Lei, Rihua; Wang, Jianfang; Gao, Wei

2017-07-01

Separation and recovery of valuable metals including silver (Ag) and copper (Cu) from electronic waste mixtures are of great economic and environmental importance. Recent years, semiconductor photocatalysts have been investigated intensively for the removal of Ag from wastewater. Few studies have been carried out on the effect of pH and co-exist metal ions such as Cu on Ag. In this study, ZnO and TiO2 were applied as photocatalysts to target on the selective recovery Ag and Cu from its mixtures under UV light. The effects of pH, catalyst, ethylene-diamine tetraacetic acid (EDTA) on the Ag and Cu photo-reduction were studied. Modeling of Ag+ and Cu2+ with and without EDTA distribution together with metal precipitations was plotted against pH to understand the chemistry involved in photocatalysis. Experimental results showed that Ag+ photo-reduction was nearly completed by ZnO and TiO2 to Ag metal, while Cu2+ photo-reduction to Cu2O only occurs by ZnO in the presence of EDTA. This work illustrates that semiconductor photocatalysts are suitable for selective recovery of Ag and Cu from wastewaters.

Antibacterial Properties of Visible-Light-Responsive Carbon-Containing Titanium Dioxide Photocatalytic Nanoparticles against Anthrax

PubMed Central

Sun, Der-Shan; Kau, Jyh-Hwa; Huang, Hsin-Hsien; Tseng, Yao-Hsuan; Wu, Wen-Shiang; Chang, Hsin-Hou

2016-01-01

The bactericidal activity of conventional titanium dioxide (TiO2) photocatalyst is effective only on irradiation by ultraviolet light, which restricts the applications of TiO2 for use in living environments. Recently, carbon-containing TiO2 nanoparticles [TiO2(C) NP] were found to be a visible-light-responsive photocatalyst (VLRP), which displayed significantly enhanced antibacterial properties under visible light illumination. However, whether TiO2(C) NPs exert antibacterial properties against Bacillus anthracis remains elusive. Here, we evaluated these VLRP NPs in the reduction of anthrax-induced pathogenesis. Bacteria-killing experiments indicated that a significantly higher proportion (40%–60%) of all tested Bacillus species, including B. subtilis, B. cereus, B. thuringiensis, and B. anthracis, were considerably eliminated by TiO2(C) NPs. Toxin inactivation analysis further suggested that the TiO2(C) NPs efficiently detoxify approximately 90% of tested anthrax lethal toxin, a major virulence factor of anthrax. Notably, macrophage clearance experiments further suggested that, even under suboptimal conditions without considerable bacterial killing, the TiO2(C) NP-mediated photocatalysis still exhibited antibacterial properties through the reduction of bacterial resistance against macrophage killing. Our results collectively suggested that TiO2(C) NP is a conceptually feasible anti-anthrax material, and the relevant technologies described herein may be useful in the development of new strategies against anthrax. PMID:28335365

Water on Graphene-Coated TiO2: Role of Atomic Vacancies

PubMed Central

2018-01-01

Beyond two-dimensional (2D) materials, interfaces between 2D materials and underlying supports or 2D-coated metal or metal oxide nanoparticles exhibit excellent properties and promising applications. The hybrid interface between graphene and anatase TiO2 shows great importance in photocatalytic, catalytic, and nanomedical applications due to the excellent and complementary properties of the two materials. Water, as a ubiquitous and essential element in practical conditions and in the human body, plays a significant role in the applications of graphene/TiO2 composites for both electronic devices and nanomedicine. Carbon vacancies, as common defects in chemically prepared graphene, also need to be considered for the application of graphene-based materials. Therefore, the behavior of water on top and at the interface of defective graphene on anatase TiO2 surface was systematically investigated by dispersion-corrected hybrid density functional calculations. The presence of the substrate only slightly enhances the on-top adsorption and reduces the on-top dissociation of water on defective graphene. However, at the interface, dissociated water is largely preferred compared with undissociated water on bare TiO2 surface, showing a prominent cover effect. Reduced TiO2 may further induce oxygen diffusion into the bulk. Our results are helpful to understand how the presence of water in the surrounding environment affects structural and electronic properties of the graphene/TiO2 interface and thus its application in photocatalysis, electronic devices, and nanomedicine. PMID:29368503

Enhanced photo-response of porous silicon photo-detectors by embeddingTitanium-dioxide nano-particles

NASA Astrophysics Data System (ADS)

Ali, Hiba M.; Makki, Sameer A.; Abd, Ahmed N.

2018-05-01

Porous silicon (n-PS) films can be prepared by photoelectochemical etching (PECE) Silicon chips n - types with 15 (mA / cm2), in 15 minutes etching time on the fabrication nano-sized pore arrangement. By using X-ray diffraction measurement and atomic power microscopy characteristics (AFM), PS was investigated. It was also evaluated the crystallites size from (XRD) for the PS nanoscale. The atomic force microscopy confirmed the nano-metric size chemical fictionalization through the electrochemical etching that was shown on the PS surface chemical composition. The atomic power microscopy checks showed the roughness of the silicon surface. It is also notified (TiO2) preparation nano-particles that were prepared by pulse laser eradication in ethanol (PLAL) technique through irradiation with a Nd:YAG laser pulses TiO2 target that is sunk in methanol using 400 mJ of laser energy. It has been studied the structural, optical and morphological of TiO2NPs. It has been detected that through XRD measurement, (TiO2) NPs have been Tetragonal crystal structure. While with AFM measurements, it has been realized that the synthesized TiO2 particles are spherical with an average particle size in the (82 nm) range. It has been determined that the energy band gap of TiO2 NPs from optical properties and set to be in (5eV) range.The transmittance and reflectance spectra have determined the TiO2 NPs optical constants. It was reported the effectiveness of TiO2 NPs expansion on the PS Photodetector properties which exposes the benefits in (Al/PS/Si/Al). The built-in tension values depend on the etching time current density and laser flounce. Al/TiO2/PS/Si/Al photo-detector heterojunction have two response peaks that are situated at 350 nm and (700 -800nm) with max sensitivity ≈ 0.7 A/W. The maximum given detectivity is 9.38at ≈ 780 nm wavelength.

Photocatalytic Oxidation of Acetone Over High Thermally Stable TiO2 Nanosheets With Exposed (001) Facets.

PubMed

Shi, Ting; Duan, Youyu; Lv, Kangle; Hu, Zhao; Li, Qin; Li, Mei; Li, Xiaofang

2018-01-01

Anatase TiO 2 (A-TiO 2 ) usually exhibits superior photocatalytic activity than rutile TiO 2 (R-TiO 2 ). However, the phase transformation from A-TiO 2 to R-TiO 2 will inevitably happens when the calcination temperature is up to 600°C, which hampers the practical applications of TiO 2 photocatalysis in hyperthermal situations. In this paper, high energy faceted TiO 2 nanosheets (TiO 2 -NSs) with super thermal stability was prepared by calcination of TiOF 2 cubes. With increase in the calcination temperature from 300 to 600°C, TiOF 2 transforms into TiO 2 hollow nanoboxes (TiO 2 -HNBs) assembly from TiO 2 -NSs via Ostwald Rippening process. Almost all of the TiO 2 -HNBs are disassembled into discrete TiO 2 -NSs when calcination temperature is higher than 700°C. Phase transformation from A-TiO 2 to R-TiO 2 begins at 1000°C. Only when the calcination temperature is higher than 1200°C can all the TiO 2 -NSs transforms into R-TiO 2 . The 500°C-calcined sample (T500) exhibits the highest photoreactivity toward acetone oxidation possibly because of the production of high energy TiO 2 -NSs with exposed high energy (001) facets and the surface adsorbed fluorine. Surface oxygen vacancy, due to the heat-induced removal of surface adsorbed fluoride ions, is responsible for the high thermal stability of TiO 2 -NSs which are prepared by calcination of TiOF 2 cubes.

Nanocomposites based on thermoplastic elastomers with functional basis of nano titanium dioxide

NASA Astrophysics Data System (ADS)

Yulovskaya, V. D.; Kuz'micheva, G. M.; Klechkovskaya, V. V.; Orekhov, A. S.; Zubavichus, Ya. V.; Domoroshchina, E. N.; Shegay, A. V.

2016-03-01

Nanocomposites based on a thermoplastic elastomer (TPE) (low-density polyethylene (LDPE) and 1,2-polybutadiene in a ratio of 60/40) with functional titanium dioxide nanoparticles of different nature, TiO2/TPE, have been prepared and investigated by a complex of methods (X-ray diffraction analysis using X-ray and synchrotron radiation beams, scanning electron microscopy, transmission electron microscopy, and X-ray energy-dispersive spectroscopy). The morphology of the composites is found to be somewhat different, depending on the TiO2 characteristics. It is revealed that nanocomposites with cellular or porous structures containing nano-TiO2 aggregates with a large specific surface and large sizes of crystallites and nanoparticles exhibit the best deformation‒strength and fatigue properties and stability to the effect of active media under conditions of ozone and vapor‒air aging.

Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

NASA Astrophysics Data System (ADS)

Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

2016-02-01

Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions.

Low-temperature electrodeposition approach leading to robust mesoscopic anatase TiO2 films

PubMed Central

Patra, Snehangshu; Andriamiadamanana, Christian; Tulodziecki, Michal; Davoisne, Carine; Taberna, Pierre-Louis; Sauvage, Frédéric

2016-01-01

Anatase TiO2, a wide bandgap semiconductor, likely the most worldwide studied inorganic material for many practical applications, offers unequal characteristics for applications in photocatalysis and sun energy conversion. However, the lack of controllable, cost-effective methods for scalable fabrication of homogeneous thin films of anatase TiO2 at low temperatures (ie. < 100 °C) renders up-to-date deposition processes unsuited to flexible plastic supports or to smart textile fibres, thus limiting these wearable and easy-to-integrate emerging technologies. Here, we present a very versatile template-free method for producing robust mesoporous films of nanocrystalline anatase TiO2 at temperatures of/or below 80 °C. The individual assembly of the mesoscopic particles forming ever-demonstrated high optical quality beads of TiO2 affords, with this simple methodology, efficient light capture and confinement into the photo-anode, which in flexible dye-sensitized solar cell technology translates into a remarkable power conversion efficiency of 7.2% under A.M.1.5G conditions. PMID:26911529

Synthesis of hierarchically meso-macroporous TiO2/CdS heterojunction photocatalysts with excellent visible-light photocatalytic activity.

PubMed

Zhao, Haixin; Cui, Shu; Yang, Lan; Li, Guodong; Li, Nan; Li, Xiaotian

2018-02-15

Photocatalysts with a hierarchically porous structure have attracted considerable attention owing to their wide pore size distribution and high surface area, which enhance the efficiency of transporting species to active sites. In this study, hierarchically meso-macroporous TiO 2 photocatalysts decorated with highly dispersed CdS nanoparticles were synthesized via hydrolysis, followed by a hydrothermal treatment. The textural mesopores and interconnected pore framework provided more accessible active sites and efficient mass transport for the photocatalytic process. The light collection efficiency was enhanced because of multiple scattering of incident light in the macropores. Moreover, the formation of a heterojunction between the CdS and TiO 2 nanoparticles extended the photoresponse of TiO 2 to the visible-light range and enhanced the charge separation efficiency. Therefore, the hierarchically meso-macroporous TiO 2 /CdS photocatalysts exhibited excellent photocatalytic activity for the degradation of rhodaming B under visible-light irradiation. Trapping experiments demonstrated that superoxide radicals (O 2 - ) and hydroxyl radicals (OH) were the main active species in photocatalysis. A reasonable photocatalytic mechanism of TiO 2 /CdS heterojunction photocatalysts was also presented. Copyright © 2017 Elsevier Inc. All rights reserved.

Degradation and detoxification of 4-nitrophenol by advanced oxidation technologies and bench-scale constructed wetlands.

PubMed

Herrera-Melián, J A; Martín-Rodríguez, A J; Ortega-Méndez, A; Araña, J; Doña-Rodríguez, J M; Pérez-Peña, J

2012-08-30

The degradation and detoxification towards the duckweed Lemna minor of 4-nitrophenol (4NP) was studied by means of bench-scale constructed wetlands (CWs), TiO(2)-photocatalysis and Fenton + photoFenton reactions. The main goal of this work was to compare the three treatment techniques to evaluate their possible combination for the efficient, low cost treatment of 4NP effluents. In CWs, adsorption on the substrate of 4NP was found to achieve 34-45%. Low concentrations (up to 100 ppm) of 4NP were successfully treated by CWs in 8-12 h. The microbial degradation of 4NP started after a lag phase which was longer with higher initial concentrations of the pollutant. The greatest degradation rate was found to occur at initial concentrations of 4NP between 60 and 90 ppm. Solar TiO(2)-photocatalysis was faster than the CWs. The greatest removals in terms of mass of 4NP removed after 6 h of irradiation were found to occur at 4NP concentrations of about 200 ppm. Fenton reaction provided complete 4NP degradation up to 500 ppm in only 30 min but TOC was removed by only about 40%. The resulting toxicities were below 20% for initial 4NP concentrations below 300 ppm. It was the Fenton + photoFenton combination (180 min in total) that provided TOC reductions up to 80% and negative L. minor growth inhibition for almost all the 4NP concentrations tested. The combination of solar TiO(2)-photocatalysis (6 h) with CWs (16 h) was able to completely treat and detoxify 4NP effluents with concentrations as high as 200 ppm of the organic. Copyright © 2012 Elsevier Ltd. All rights reserved.

Markedly Enhanced Surface Hydroxyl Groups of TiO2 Nanoparticles with Superior Water-Dispersibility for Photocatalysis

PubMed Central

Wu, Chung-Yi; Tu, Kuan-Ju; Deng, Jin-Pei; Lo, Yu-Shiu; Wu, Chien-Hou

2017-01-01

The benefits of increasing the number of surface hydroxyls on TiO2 nanoparticles (NPs) are known for environmental and energy applications; however, the roles of the hydroxyl groups have not been characterized and distinguished. Herein, TiO2 NPs with abundant surface hydroxyl groups were prepared using commercial titanium dioxide (ST-01) powder pretreated with alkaline hydrogen peroxide. Through this simple treatment, the pure anatase phase was retained with an average crystallite size of 5 nm and the surface hydroxyl group density was enhanced to 12.0 OH/nm2, estimated by thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Especially, this treatment increased the amounts of terminal hydroxyls five- to six-fold, which could raise the isoelectric point and the positive charges on the TiO2 surface in water. The photocatalytic efficiency of the obtained TiO2 NPs was investigated by the photodegradation of sulforhodamine B under visible light irradiation as a function of TiO2 content, pH of solution, and initial dye concentration. The high surface hydroxyl group density of TiO2 NPs can not only enhance water-dispersibility but also promote dye sensitization by generating more hydroxyl radicals. PMID:28772926

Assessing the effects of UVA photocatalysis on soot-coated TiO2-containing mortars.

PubMed

De la Rosa, José M; Miller, Ana Z; Pozo-Antonio, J Santiago; González-Pérez, José A; Jiménez-Morillo, Nicasio T; Dionisio, Amelia

2017-12-15

The deposition of soot on building surfaces darkens their colour and leads to undesirable black crusts, which are one of the most serious problems on the conservation of built cultural heritage. As a preventive strategy, self-cleaning systems based on the use of titanium dioxide (TiO 2 ) coatings have been employed on building materials for degrading organic compounds deposited on building surfaces, improving their durability and performance. In this study, the self-cleaning effect of TiO 2 -containing mortars coated with diesel soot has been appraised under laboratory conditions. The mortar samples were manufactured using lime putty and two different doses of TiO 2 (2.5% and 5%). The lime mortars were then coated with diesel engine soot and irradiated with ultraviolet A (UVA) illumination for 30days. The photocatalytic efficiency was evaluated by visual inspection, field emission scanning electron microscopy (FESEM) and colour spectrophotometry. Changes in the chemical composition of the soot particles (including persistent organic pollutants) were assessed by analytical pyrolysis (Py-GC/MS) and solid state 13 C NMR spectroscopy. The FESEM and colour spectrophotometry revealed that the soot-coated TiO 2 -containing mortars promoted a self-cleaning effect after UVA irradiation. The combination of analytical pyrolysis and 13 C solid state NMR showed that the UVA irradiation caused the cracking of polycyclic aromatic structures and n-alkyl compounds of the diesel soot and its transformation into methyl polymers. Our findings also revealed that the inclusion of TiO 2 in the lime mortar formulations catalysed these transformations promoting the self-cleaning of the soot-stained mortars. The combined action of TiO 2 and UVA irradiation is a promising proxy to clean lime mortars affected by soot deposition. Copyright © 2017 Elsevier B.V. All rights reserved.

Differently ordered TiO2 nanoarrays regulated by solvent polarity, and their photocatalytic performances

NASA Astrophysics Data System (ADS)

Hu, Wenyuan; Dong, Faqin; Zhang, Jing; Liu, Mingxue; He, Huichao; Wu, Yadong; Yang, Dingming; Deng, Hongquan

2018-06-01

Special TiO2 arrays with exposed facets were prepared in different solvents by low- temperature solvothermal synthesis. The morphology, phase and photocatalytic performance influenced by the various solvent polarities were characterized using field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra and electrochemical testing. The results show that differences of solvent polarity are the main force driving differences in array growth; therefore, anatase TiO2 arrays with different crystal facets can be synthesized by tuning solvent polarity. TiO2 arrays prepared in cyclohexane are the best at oxidizing methyl orange through photocatalysis, followed by arrays prepared in toluene and ethanol. Arrays prepared in toluene are the best at reducing Cr(VI) photocatalytically, followed by those prepared in cyclohexane and ethanol. These differences in photocatalytic power are due to the ratio among the different crystal facets that are exposed, which affects the migration behavior of the photogenerated electrons and holes. In addition, the probable growth mechanisms of self-assembled ordered TiO2 arrays in different solvents are described.

Impact of TiO2 on the chemical and biological transformation of formulated chiral-metalaxyl in agricultural soils.

PubMed

Huang, Junxing; Zhang, Xu; Liang, Chuanzhou; Hu, Jun

2018-04-15

The impacts of TiO 2 on the chemical and biological transformation of racemic metalaxyl wettable powder (rac-metalaxyl WP) in agricultural soils, and soil microorganisms were investigated. Under simulated solar irradiation, TiO 2 highly promoted the transformation of rac-metalaxyl WP without changing the enantiomer fraction, with the promotion amplitude (60-1280%) being dependent on TiO 2 characteristics. TiO 2 characteristics showed different influence on the transformation of rac-metalaxyl WP in soils and aqueous solutions because their characteristics changed differently in soils. The impact of the mancozeb and other co-constituents on the transformation of rac-metalaxyl WP was smaller in soil media than in aqueous solution. Autoclave sterilization changed soil properties and subsequently weakened the promotion effects of TiO 2 on the chemical transformations of rac-metalaxyl WP to 0-233%. Microorganism biomass and bacterial community were not statistically significant changed by TiO 2 exposure regardless of rac-metalaxyl WP, suggesting that the promotional effects occurred mainly through chemical processes. The results also showed TiO 2 -soil interactions may be strengthened with TiO 2 (Degussa P25) aging time in soils, which decreased its promotion amplitude from 1060% (without aging) to 880% (aging for 20 days). Intermediate formed in soil biological transformation process was different from that in TiO 2 photocatalysis process. Copyright © 2018 Elsevier B.V. All rights reserved.

The nano-TiO2 exposure can induce hepatic inflammation involving in a JAK-STAT signalling pathway

NASA Astrophysics Data System (ADS)

Hong, Jie; Hong, Fashui; Ze, Yuguan; Zhang, Yu-Qing

2016-06-01

TiO2 nanoparticles (TiO2 NPs) have unique physiochemical properties and thus are widely used in daily life. However, these nanoparticles also have potential toxic effects in humans and animals, and the issue of the security TiO2 NPs has also gained prominence. In this article, mice were administered a gavage instillation of 2.5, 5, or 10 mg/kg body weight TiO2 NPs (5-6 nm) for 90 days. We investigated whether TiO2 NPs activate the JAK-STAT signalling pathway, causing nano-TiO2-induced hepatic toxicity. The results demonstrated that with increasing doses of TiO2 NPs the body weights of the mice body decreased, and the liver index, liver dysfunction, infiltration of inflammatory cells, and hepatocyte apoptosis and necrosis increased. Moreover, liver inflammation was accompanied by increased expression of Janus kinase 2, the signal transducers and activators of transcription 3, interleukin-6, cyclooxygenase-2, neutrophil gelatinase-associated lipocalin, purinergic receptor-7, and epithelial neutrophil-activating protein-78 and decreased expression of suppressors of cytokine signalling-1, peroxisome proliferator-activated receptor-γ, and peroxisome proliferator-activated receptor gamma coactivator-1 alpha. In summary, the activation of the JAK-STAT pathway may be involved in the hepatic inflammation induced by chronic nano-TiO2 toxicity.

ESR investigation of ROS generated by H2O2 bleaching with TiO2 coated HAp.

PubMed

Saita, Makiko; Kobayashi, Kyo; Kobatashi, Kyou; Yoshino, Fumihiko; Hase, Hiriko; Nonami, Toru; Kimoto, Katsuhiko; Lee, Masaichi-Chang-il

2012-01-01

It is well known that clinical bleaching can be achieved with a solution of 30% hydrogen peroxide (H2O2) or H2O2/titanium dioxide (TiO2) combination. This study examined the hypothesis that TiO2 coated with hydroxyapatite (HAp-TiO2) can generate reactive oxygen species (ROS). ROS are generated via photocatalysis using electron spin resonance (ESR). The bleaching properties of HAp-TiO2 in the presence of H2O2 can be measured using hematoporphyrin litmus paper and extracted teeth. We demonstrate that superoxides (O2(•-)) and hydroxyl radicals (HO(•)) can be generated through excitation of anatase TiO2, rutile TiO2, anatase HAp-TiO2, and rutile HAp-TiO2 in the presence of H2O2. The combination of R HAp-TiO2 with H2O2 produced the highest level of HO(•) generation and the most marked bleaching effects of all the samples. The superior bleaching effects exhibited by R HAp-TiO2 with H2O2 suggest that this combination may lead to novel methods for the clinical application of bleaching treatments.

Effect of laser irradiation on the structural, morphological and electrical properties of polycrystalline TiO2 thin films

NASA Astrophysics Data System (ADS)

Khan, M. I.; Ali, Asghar

TiO2 thin film is deposited on glass substrate by sol-gel dip coating technique. After deposition, films were irradiated by continuous wave (CW) diode laser at an angle of 45°. XRD shows both the anatase and brookite phases of TiO2. Nano particles of regular and control sizes are appeared in SEM micrographs. Therefore, shape and size of nano particles can be control by using Laser irradiation. The average sheet resistivity of TiO2 thin film irradiated by 0, 2, 4 and 6 min are 6.72 × 105, 5.32 × 105, 3.44 × 105 and 4.95 × 105 (ohm-m) respectively, according to four point probe.

NanoE-Tox: New and in-depth database concerning ecotoxicity of nanomaterials.

PubMed

Juganson, Katre; Ivask, Angela; Blinova, Irina; Mortimer, Monika; Kahru, Anne

2015-01-01

The increasing production and use of engineered nanomaterials (ENMs) inevitably results in their higher concentrations in the environment. This may lead to undesirable environmental effects and thus warrants risk assessment. The ecotoxicity testing of a wide variety of ENMs rapidly evolving in the market is costly but also ethically questionable when bioassays with vertebrates are conducted. Therefore, alternative methods, e.g., models for predicting toxicity mechanisms of ENMs based on their physico-chemical properties (e.g., quantitative (nano)structure-activity relationships, QSARs/QNARs), should be developed. While the development of such models relies on good-quality experimental toxicity data, most of the available data in the literature even for the same test species are highly variable. In order to map and analyse the state of the art of the existing nanoecotoxicological information suitable for QNARs, we created a database NanoE-Tox that is available as Supporting Information File 1. The database is based on existing literature on ecotoxicology of eight ENMs with different chemical composition: carbon nanotubes (CNTs), fullerenes, silver (Ag), titanium dioxide (TiO2), zinc oxide (ZnO), cerium dioxide (CeO2), copper oxide (CuO), and iron oxide (FeO x ; Fe2O3, Fe3O4). Altogether, NanoE-Tox database consolidates data from 224 articles and lists altogether 1,518 toxicity values (EC50/LC50/NOEC) with corresponding test conditions and physico-chemical parameters of the ENMs as well as reported toxicity mechanisms and uptake of ENMs in the organisms. 35% of the data in NanoE-Tox concerns ecotoxicity of Ag NPs, followed by TiO2 (22%), CeO2 (13%), and ZnO (10%). Most of the data originates from studies with crustaceans (26%), bacteria (17%), fish (13%), and algae (11%). Based on the median toxicity values of the most sensitive organism (data derived from three or more articles) the toxicity order was as follows: Ag > ZnO > CuO > CeO2 > CNTs > TiO2 > FeO x . We believe NanoE-Tox database contains valuable information for ENM environmental hazard estimation and development of models for predicting toxic potential of ENMs.

TiO2/porous adsorbents: Recent advances and novel applications.

PubMed

MiarAlipour, Shayan; Friedmann, Donia; Scott, Jason; Amal, Rose

2018-01-05

This article reviews two interrelated areas of research: the first is the use of TiO 2 -supported adsorbent materials as enhanced heterogeneous photocatalysts and their application to various reactions for organic pollutant removal from air and water; the second is the combination of adsorbent materials with TiO 2 photocatalysts which aims to efficiently regenerate adsorbent materials using illumination. By reviewing both areas of research, the following topics are covered; (i) photocatalytic activation of TiO 2; (ii) related properties of photocatalytic TiO 2; (iii) shortcomings of photocatalytic processes; (iv) preparation methods of composite TiO 2 /adsorbent materials and their photocatalytic performance; (v) properties of common adsorbents and their applications for pollutant removal from air and water; (vi) adsorbent regeneration methods and their economic and operational issues; (vii) conclusions and future outlooks. This topic has not been previously reviewed to such an extent, and considerable knowledge can be gained from assembling the large number of studies on adsorption-photocatalysis combinations. As such, this review provides guidance for researchers working in the fields of environmental and chemical engineering focussing on organic pollutant removal and the engineering of new high performance photocatalytic TiO 2 -supported porous adsorbent materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Fabrication of Al2O3 coated 2D TiO2 nanoparticle photonic crystal layers by reverse nano-imprint lithography and plasma enhanced atomic layer deposition.

PubMed

Kim, Ki-Kang; Ko, Ki-Young; Ahn, Jinho

2013-10-01

This paper reports simple process to enhance the extraction efficiency of photoluminescence (PL) from Eu-doped yttrium oxide (Y2O3:Eu3+) thin-film phosphor (TFP). Two-dimensional (2D) photonic crystal layer (PCL) was fabricated on Y2O3:Eu3+ phosphor films by reverse nano-imprint method using TiO2 nanoparticle solution as a nano-imprint resin and a 2D hole-patterned PDMS stamp. Atomic scale controlled Al2O3 deposition was performed onto this 2D nanoparticle PCL for the optimization of the photonic crystal pattern size and stabilization of TiO2 nanoparticle column structure. As a result, the light extraction efficiency of the Y2O3:Eu3+ phosphor film was improved by 2.0 times compared to the conventional Y2O3:Eu3+ phosphor film.

Influence of silver nanoparticles on titanium oxide and nitrogen doped titanium oxide thin films for sun light photocatalysis

NASA Astrophysics Data System (ADS)

Madhavi, V.; Kondaiah, P.; Mohan Rao, G.

2018-04-01

Decreasing recombination of photogenerated charge carriers in photocatalysts is a critical issue for enhancing the efficiency of dye degradation. It is one of the greatest challenges to reduce the recombination of photo generated charge carriers in semiconductor. In this paper, we report that there is an enhancement of photocatalytic activity in presence of Sun light, by introducing Plasmon (silver nanoparticles (Ag)) onto the titanium oxide (TiO2) and nitrogen incorporated titanium oxide (N-TiO2) films. These silver nanoparticles facilitate the charge transport and separation of charge carriers. In this paper we find that the phase transformation accurse from rutile to anatase with increase of nitrogen flow rates. The FE-SEM analysis showed the micro structure changes to dense columnar growth with increase of nitrogen flow rates. XPS studies of the N-TiO2 thin films revealed that the substitution of N atoms within the O sites plays a crucial role in narrowing the band gap of the TiO2. This enables the absorption of visible light radiation and leads to operation of the film as a highly reactive and effective photocatalysis. The synergetic effect of silver nanoparticles on TiO2 and N-TiO2 films tailored the photocatalytic acitivity, charge transfer mechanism, and photocurrent studies. The silver nanoparticle loaded N-TiO2 films showed highest degradation of 95% compare to the N-TiO2 films. The photo degradation rate constant of Ag/N-TiO2 film was larger than the N-TiO2 films.

Dye sensitized solar cell based on environmental friendly eosin Y dye and Al doped titanium dioxide nano particles

NASA Astrophysics Data System (ADS)

Kulkarni, Swati S.; Bodkhe, Gajanan A.; Shirsat, Sumedh M.; Hussaini, S. S.; Shejwal, N. N.; Shirsat, Mahendra D.

2018-03-01

Present communication deals with the development of cost effective dye sensitized solar cell (DSSC) with eco-friendly materials. Eco-friendly Eosin Y dye was used to sensitize photo anode which was fabricated using undoped and Aluminium doped titanium dioxide (TiO2) nanoparticles. Undoped and Aluminium doped TiO2 nanoparticles were synthesized by simple and cost effective sol-gel method. Aluminium doped and undoped TiO2 nanoparticles were characterized using UV-visible, FT-IR spectroscopy, x-ray Diffraction, and Scanning Electron Micrograph with EDX. The photo-voltaic activity of the cell was studied under light irradiation of 100 milliwatt cm-2. Aluminium doped TiO2 nanoparticle photo electrode exhibits more than 60% increase in cell efficiency as compared to the undoped TiO2 nanoparticle photo electrode.

MoS2 quantum dots@TiO2 nanotube composites with enhanced photoexcited charge separation and high-efficiency visible-light driven photocatalysis

NASA Astrophysics Data System (ADS)

Zhao, Fenfen; Rong, Yuefei; Wan, Junmin; Hu, Zhiwen; Peng, Zhiqin; Wang, Bing

2018-03-01

MoS2 quantum dots (QDs) that are 5 nm in size were deposited on the surface of ultrathin TiO2 nanotubes (TNTs) with 5 nm wall thickness by using an improved hydrothermal method to form a MoS2 QDs@TNT visible-light photocatalyst. The ultrathin TNTs with high percentage of photocatalytic reactive facets were fabricated by the commercially available TiO2 nanoparticles (P25) through an improved hydrothermal method, and the MoS2 QDs were acquired by using a surfactant-assisted technique. The novel MoS2 QDs@TNT photocatalysts showed excellent photocatalytic activity with a decolorization rate of 92% or approximately 3.5 times more than that of pure TNTs for the high initial concentration of methylene blue solution (20 mg l-1) within 40 min under visible-light irradiation. MoS2 as the co-catalysts favored the broadening of TNTs into the visible-light absorption scope. The quantum confinement and edge effects of the MoS2 QDs and the heterojunction formed between the MoS2 QDs and TNTs efficiently extended the lifetime of photoinduced charges, impeded the recombination of photoexcited electron-hole pairs, and improved the visible-light-driven high-efficiency photocatalysis.

Synergistic operation of photocatalytic degradation and Fenton process by magnetic Fe3O4 loaded TiO2

NASA Astrophysics Data System (ADS)

Sun, Qiong; Hong, Yong; Liu, Qiuhong; Dong, Lifeng

2018-02-01

The magnetic Fe3O4 loaded anatase TiO2 photocatalysts with different mass ratios were successfully synthesized by a one-step convenient calcining method. The morphology and structure analysis revealed that Fe3O4 was formed in TiO2 with very fine-grained particles. After a small amount of Fe3O4 loaded onto TiO2, the photocatalytic property enhanced obviously for the degradation of organic dye. Furthermore, the photo-Fenton-like catalysis of the iron-containing samples could also be induced after the addition of hydrogen peroxide. The apparent kinetic constant of the reaction that catalyzed by Fe-TiO2 was about 5.3 and 8.3 times of that catalyzed by TiO2 or Fe3O4 only, respectively, proving an effective synergistic contribution of the photocatalysis and Fenton reaction in the composite. Compared with Fe3O4 or free Fe3+ ions, only 13% of iron in TiO2 dissolved into acidic solution (25% for Fe3O4 and 100% for Fe3+) after the reaction, which confirmed the iron had been well immobilized onto TiO2. In addition, the extremely stable photocatalytic activity in cycling experiments proved the immobilized iron had been tightly attached onto TiO2, indicating the great potential of the catalyst for practical applications.

Study of photocatalytic degradation of tributyltin, dibutylin and monobutyltin in water and marine sediments.

PubMed

Brosillon, Stephan; Bancon-Montigny, Chrystelle; Mendret, Julie

2014-08-01

This study reports on the first assessment of the treatment of sediments contaminated by organotin compounds using heterogeneous photocatalysis. Photocatalysis of organotins in water was carried out under realistic concentration conditions (μgL(-1)). Degradation compounds were analyzed by GC-ICP-MS; a quasi-complete degradation of tributyltin (TBT) in water (99.8%) was achieved after 30min of photocatalytic treatment. The degradation by photolysis was about (10%) in the same conditions. For the first time decontamination of highly polluted marine sediments (certified reference material and harbor sediments) by photocatalysis proves that the use of UV and the production of hydroxyl radicals are an efficient way to treat organotins adsorbed onto marine sediment despite the complexity of the matrix. In sediment, TBT degradation yield ranged from 32% to 37% after only 2h of irradiation (TiO2-UV) and the by-products: dibutyltin (DBT) and monobutyltin (MBT) were degraded very rapidly in comparison with TBT. It was shown that during photocatalysis of organotins in sediments, the hydroxyl radical attack and photolysis are the two ways for the degradation of adsorbed TBT. Copyright © 2014 Elsevier Ltd. All rights reserved.

Controlled preparation of M(Ag, Au)/TiO2 through sulfydryl-assisted method for enhanced photocatalysis

NASA Astrophysics Data System (ADS)

Xia, Hongbo; Wu, Suli; Bi, Jiajie; Zhang, Shufen

2017-11-01

Here a simple and effective method was explored to fabricate M/TiO2 (M = Ag, Au) composites, which required neither pre-treatment of TiO2 nor any additives as reducing agent. Using amorphous TiO2 spheres functionalized with SH groups as starting materials, the noble metallic ions (Ag, Au) can be adsorbed by TiO2 due to their special affinity with SH groups, which is beneficial to the uniform dispersion of metallic ions on the surface of TiO2. Then the adsorbed ions were reduced to form noble metal nanoparticles by heating process (95 °C) directly without additive as reduction agent. Meanwhile, the amorphous TiO2 was transformed into anatase phase during the heating process. Thus, the transformation of TiO2 along with the reduction of noble metallic ions (Ag, Au) was simultaneously carried out by heating. The XRD patterns proved the formation of anatase TiO2 after heating. The characterizations of XPS and TEM proved the formation of Ag and Au nanoparticles on the surface of TiO2. The element mapping indicated that Ag nanoparticles are dispersed uniformly on the surface of TiO2. The photocatalytic activity of the composites has been investigated by the degradation of methyl orange under visible light irradiation. The results showed that when Ag/TiO2 (2.8 wt%) was used as photocatalyst, about 98% of the MO molecules were degraded in 70 min.

Density functional theory study of atomic and electronic properties of defects in reduced anatase TiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Morita, Kazuki; Yasuoka, Kenji

2018-03-01

Anatase TiO2 nanocrystals have received considerable attention owing to their promising applications in photocatalysis, photovoltaics, and fuel cells. Although experimental evidence has shown that the performance of nanocrystals can be significantly improved through reduction, the mechanistic basis of this enhancement remains unclear. To shed a light on the chemistry of reduced anatase TiO2 nanocrystals, density functional theory were used to investigate the properties of defects and excess electrons. We demonstrated that oxygen vacancies are stable both on the surface and at the sub-surface of the nanocrystal, while titanium interstitials prefer sub-surface sites. Different defect locations possessed different excess electron structures, which contributed to deep and shallow states in the band gap of the nanocrystals. Furthermore, valence band tailing was observed, resulting in band gap narrowing. The theoretical results presented here deepen our understanding, and show the potential of defects to considerably change the macroscopic properties of anatase TiO2 nanocrystals.

Polarization-Dependent Raman Spectroscopy of Epitaxial TiO 2 (B) Thin Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jokisaari, Jacob R.; Bayerl, Dylan; Zhang, Kui

2015-12-08

The bronze polymorph of titanium dioxide, known as TiO 2(B), has promising photochemical and electronic properties for potential applications in Li-ion batteries, photocatalysis, chemical sensing, and solar cells. In contrast to previous studies performed with powder samples, which often suffer from impurities and lattice water, here we report Raman spectra from highly crystalline TiO 2(B) films epitaxially grown on Si substrates with a thin SrTiO 3 buffer layer. The reduced background from the Si substrate significantly benefits acquisition of polarization-dependent Raman spectra collected from the high-quality thin films, which are compared to nanopowder results reported in the literature. The experimentalmore » spectra were compared with density functional theory calculations to analyze the atomic displacements associated with each Raman-active vibrational mode. These results provide a standard reference for further investigation of the crystallinity, structure, composition, and properties of TiO 2(B) materials with Raman spectroscopy.« less

Minimizing of the boundary friction coefficient in automotive engines using Al2O3 and TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ali, Mohamed Kamal Ahmed; Xianjun, Hou; Elagouz, Ahmed; Essa, F. A.; Abdelkareem, Mohamed A. A.

2016-12-01

Minimizing of the boundary friction coefficient is critical for engine efficiency improvement. It is known that the tribological behavior has a major role in controlling the performance of automotive engines in terms of the fuel consumption. The purpose of this research is an experimental study to minimize the boundary friction coefficient via nano-lubricant additives. The tribological characteristics of Al2O3 and TiO2 nano-lubricants were evaluated under reciprocating test conditions to simulate a piston ring/cylinder liner interface in automotive engines. The nanoparticles were suspended in a commercially available lubricant in a concentration of 0.25 wt.% to formulate the nano-lubricants. The Al2O3 and TiO2 nanoparticles had sizes of 8-12 and 10 nm, respectively. The experimental results have shown that the boundary friction coefficient reduced by 35-51% near the top and bottom dead center of the stroke (TDC and BDC) for the Al2O3 and TiO2 nano-lubricants, respectively. The anti-wear mechanism was generated via the formation of protective films on the worn surfaces of the ring and liner. These results will be a promising approach for improving fuel economy in automotive.

Electrospinning Titanium Dioxide (TiO2) nanofiber for dye sensitized solar cells based on Bryophyta as a sensitizer

NASA Astrophysics Data System (ADS)

Asma Ilahi, Novita; Suryana, Risa; Nurrosyid, Fahru; Kusuma, N. T. Linda

2017-01-01

From an engineering and economic perspective, immobilized TiO2 nanocatalysts are preferred in a variety of applications. In this study, TiO2 polymer solution was synthesized using ethanol, acetic acid, polyvinylpyrrolidone (PVP), and titanium tetra isopropoxide (TTIP). TiO2 solution was deposited on the FTO substrate by electrospinning method to obtain nano-sized layer. Capillary of syringes given a positive DC voltage of 6 kV to produce nanofiber, then annealed at 450 °C for 3 hours. Chlorophyll has obtained from extracted moss through a chromatographic process to used for dye. TiO2 nanofiber layer manufactured with varied by time and characterized by UV-Vis and IV-meter. The result exhibited a maximum efficiency of 0,0036% and significant absorption at 350 nm-500 nm wavelength.

Electrospinning preparation of oxygen-deficient nano TiO2-x/carbon fibre membrane as a self-standing high performance anode for Li-ion batteries

PubMed Central

Li, Jing-quan; Han, Chong; Yao, Shan-shan; Zhang, Ji; Zhai, Hong-ai; Chen, Li-li; Shen, Xiang-qian; Xiao, Ke-song

2017-01-01

Improving the specific capacity and electronic conductivity of TiO2 can boost its practical application as a promising anode material for lithium ion batteries. In this work, a three-dimensional networking oxygen-deficient nano TiO2-x/carbon fibre membrane was achieved by combining the electrospinning process with a hot-press sintering method and directly used as a self-standing anode. With the synergistic effects of three-dimensional conductive networks, surface oxygen deficiency, high specific surface area and high porosity, binder-free and self-standing structure, etc., the nano TiO2-x/carbon fibre membrane electrode displays a high electrochemical reaction kinetics and a high specific capacity. The reversible capacity could be jointly generated from porous carbon, full-lithiation of TiO2 and interfacial lithium storage. At a current density of 100 mA g−1, the reversible discharge capacity can reach 464 mA h g−1. Even at 500 mA g−1, the discharge capacity still remains at 312 mA h g−1. Compared with pure carbon fibre and TiO2 powder, the TiO2-x/C fibre membrane electrode also exhibits an excellent cycle performance with a discharge capacity of 209 mA h g−1 after 700 cycles at the current density of 300 mA g−1, and the coulombic efficiency always remains at approximately 100%. PMID:28791160

Electrospinning preparation of oxygen-deficient nano TiO2-x/carbon fibre membrane as a self-standing high performance anode for Li-ion batteries

NASA Astrophysics Data System (ADS)

Jing, Mao-xiang; Li, Jing-quan; Han, Chong; Yao, Shan-shan; Zhang, Ji; Zhai, Hong-ai; Chen, Li-li; Shen, Xiang-qian; Xiao, Ke-song

2017-07-01

Improving the specific capacity and electronic conductivity of TiO2 can boost its practical application as a promising anode material for lithium ion batteries. In this work, a three-dimensional networking oxygen-deficient nano TiO2-x/carbon fibre membrane was achieved by combining the electrospinning process with a hot-press sintering method and directly used as a self-standing anode. With the synergistic effects of three-dimensional conductive networks, surface oxygen deficiency, high specific surface area and high porosity, binder-free and self-standing structure, etc., the nano TiO2-x/carbon fibre membrane electrode displays a high electrochemical reaction kinetics and a high specific capacity. The reversible capacity could be jointly generated from porous carbon, full-lithiation of TiO2 and interfacial lithium storage. At a current density of 100 mA g-1, the reversible discharge capacity can reach 464 mA h g-1. Even at 500 mA g-1, the discharge capacity still remains at 312 mA h g-1. Compared with pure carbon fibre and TiO2 powder, the TiO2-x/C fibre membrane electrode also exhibits an excellent cycle performance with a discharge capacity of 209 mA h g-1 after 700 cycles at the current density of 300 mA g-1, and the coulombic efficiency always remains at approximately 100%.

Combination of ozonation and photocatalysis for pharmaceutical wastewater treatment

NASA Astrophysics Data System (ADS)

Ratnawati, Enjarlis, Slamet

2017-11-01

The chemical oxygen demand (COD) and phenol removal from pharmaceutical wastewater were investigated using configuration of two circulation batch reactors in a series with ozonation and photocatalytic processes. The ozonation is conducted with O3/granulated activated carbon (O3/GAC), whereas photocatalysis with TiO2 that immobilized on pumice stone (PS-TiO2). The effect of circulation flow rate (10; 12; 15 L/min) and the amount PS-TiO2 (200 g, 250 g, 300 g) were examined. Wastewater of 20 L was circulated pass through the pipe that injected with O3 by the ozone generator, and subsequently flow through two GAC columns, and finally, go through photoreactor that contains photocatalyst PS-TiO2 which equipped with mercury lamp as a photon source. At a time interval, COD and phenol concentration were measured to assess the performance of the process. FESEM imaging confirmed that TiO2 was successfully impregnated on PS, as corroborated by EDX spectra. Meanwhile, degradation process indicated that the combined ozonation and photocatalytic processes (O3/GAC-TiO2) is more efficient compared to the ozonation and photocatalysis alone. For combination process with the circulation flow rate of 10 L/min and 300 g of PS-TiO2,the influent COD of around 1000 ppm are effectively degraded to a final effluent COD of 290 ppm (71% removal) and initial phenol concentration of 4.75 ppm down to 0 ppm for 4 h which this condition fulfill the discharge standards quality. Therefore, this portable prototype reactor is effective that can be used in the pharmaceutical wastewater treatment. For the future, this process condition will be developed for orientation on the industrial applications (portable equipment) since pharmaceutical industries produce wastewater relatively in the small amount.

Synthesis and characterization of a mixed phase of anatase TiO2 and TiO2(B) by low pressure chemical vapour deposition (LPCVD) for high photocatalytic activity

NASA Astrophysics Data System (ADS)

Chimupala, Y.; Hyett, G.; Simpson, R.; Brydson, R.

2014-06-01

This project is concerned with enhancing photocatalytic activity by preparing a mixed phase of nano-sized TiO2. TiO2 thin films were synthesized by using Low Pressure Chemical Vapour Deposition (LPCVD). Titanium isopropoxide and N2 gas were used as the precursor and carrier gas respectively. The effects of reaction temperature, carrier gas flow rate and deposited area were studied. TiO2 thin films with nano-sized TiO2 particles were obtained under suitable conditions and SEM, TEM, powder XRD and Raman spectroscopy were employed to characterize the phase and physical appearance of synthesized materials. Preliminary results show that a dual phase (TiO2(B) and anatase) thin film nanopowder was successfully prepared by LPCVD with needle- and polygonal plate-shape crystallites respectively. This thin film deposit produced a preferred orientation of TiO2(B) needles in the [001] direction of average crystallite size 50-80 nm in length and 5-10 nm in width, whilst the crystallite size of anatase polygonal-plates was around 200 nm. The optimal LPCVD condition for preparing this mixed phase of TiO2 was 600°C with a 1 mL/s N2 flow rate.

Laser irradiation in water for the novel, scalable synthesis of black TiOx photocatalyst for environmental remediation

PubMed Central

Zimbone, Massimo; Boutinguiza, Mohamed; Privitera, Vittorio; Grimaldi, Maria Grazia

2017-01-01

Since 1970, TiO2 photocatalysis has been considered a possible alternative for sustainable water treatment. This is due to its material stability, abundance, nontoxicity and high activity. Unfortunately, its wide band gap (≈3.2 eV) in the UV portion of the spectrum makes it inefficient under solar illumination. Recently, so-called “black TiO2” has been proposed as a candidate to overcome this issue. However, typical synthesis routes require high hydrogen pressure and long annealing treatments. In this work, we present an industrially scalable synthesis of TiO2-based material based on laser irradiation. The resulting black TiOx shows a high activity and adsorbs visible radiation, overcoming the main concerns related to the use of TiO2 under solar irradiation. We employed a commercial high repetition rate green laser in order to synthesize a black TiOx layer and we demonstrate the scalability of the present methodology. The photocatalyst is composed of a nanostructured titanate film (TiOx) synthetized on a titanium foil, directly back-contacted to a layer of Pt nanoparticles (PtNps) deposited on the rear side of the same foil. The result is a monolithic photochemical diode with a stacked, layered structure (TiOx/Ti/PtNps). The resulting high photo-efficiency is ascribed to both the scavenging of electrons by Pt nanoparticles and the presence of trap surface states for holes in an amorphous hydrogenated TiOx layer. PMID:28243557

Titanium bone implants with superimposed micro/nano-scale porosity and antibacterial capability

NASA Astrophysics Data System (ADS)

Necula, B. S.; Apachitei, I.; Fratila-Apachitei, L. E.; van Langelaan, E. J.; Duszczyk, J.

2013-05-01

This study aimed at producing a multifunctional layer with micro/nano-interconnected porosity and antibacterial capability on a rough macro-porous plasma sprayed titanium surface using the plasma electrolytic oxidation process. The layers were electrochemically formed in electrolytes based on calcium acetate and calcium glycerophosphate salts bearing dispersed Ag nanoparticles. They were characterized with respect to surface morphology and chemical composition using a scanning electron microscope equipped with the energy dispersive spectroscopy and back scattering detectors. Scanning electron microscopy images showed the formation of a micro/nano-scale porous layer, comprised of TiO2 bearing Ca and P species and Ag nanoparticles, following accurately the surface topography of the plasma sprayed titanium coating. The Ca/P atomic ratio was found to be close to that of bone apatite. Ag nanoparticles were incorporated on both on top and inside the porous structure of the TiO2 layer.

A review on mechanical properties of magnesium based nano composites

NASA Astrophysics Data System (ADS)

Tarafder, Nilanjan; Prasad, M. Lakshmi Vara

2018-04-01

A review was done on Magnesium (Mg) based composite materials reinforced with different nano particles such as TiO2, Cu, Y2O3, SiC, ZrO2 and Al2O3. TiO2 and Al2O3 nanoparticles were synthesised by melt deposition process. Cu, Y2O3, SiC and ZrO2 nanoparticles were synthesised by powder metallurgy process. Composite microstructural characteristics shows that the nano-size reinforcements are uniformly distributed in the composite matrix and also minimum porosity with solid interfacial integrity. The mechanical properties showed yield strength improvement by 0.2 percentage and Ultimate tensile strength (UTS) was also improved for all the nano-particles. But UTS was adversely affected with TiO2 reinforcement while ductility was increased. With Cu reinforcement elastic modulus, hardness and fracture resistance increased and improved the co-efficient of thermal expansion (CTE) of Mg based matrix. By Y2O3 reinforcement hardness, fracture resistance was improved and ductility reached maximum by 0.22 volume percentage of Y2O3 and decreased with succeeding increase in Y2O3 reinforcement. The readings exposed that mechanical properties were gathered from the composite comprising 2.0 weight percentage of Y2O3. Ductility and fracture resistance increased with ZrO2 reinforcement in Mg matrix. Using Al2O3 as reinforcement in Mg composite matrix hardness, elastic modulus and ductility was increased but porosity reduced with well interfacial integrity. Dissipation of energy in the form of damping capacity was resolved by classical vibration theory. The result showed that an increasing up to 0.4 volume percentage alumina content increases the damping capacity up to 34 percent. In another sample, addition of 2 weight percentage nano-Al2O3 particles showed big possibility in reducing CTE from 27.9-25.9×10-6 K-1 in Magnesium, tensile and yield strength amplified by 40MPa. In another test, Mg/1.1Al2O3 nanocomposite was manufactured by solidification process followed by hot extrusion. Results showed that strengthening effect was maintained up to 150°C and fracture characteristics of Mg composite transformed from brittle to mixed ductile mode and fully ductile in attendance of nano-Al2O3 particulates.

Identification of titanium dioxide nanoparticles in food products: induce intracellular oxidative stress mediated by TNF and CYP1A genes in human lung fibroblast cells.

PubMed

Periasamy, Vaiyapuri Subbarayan; Athinarayanan, Jegan; Al-Hadi, Ahmed M; Juhaimi, Fahad Al; Mahmoud, Mohamed H; Alshatwi, Ali A

2015-01-01

Food grade TiO2 (E171) is a synthetic additive, and widely used as a coloring agent in many foods, pharmaceutical and personal care products. A few reports have highlighted that insoluble particulates (less than 200nm) of food grade TiO2 are found in many foods and confectionary products. However, information regarding the physico-chemical properties (i.e., size and shape)-based food grade TiO2 nanotoxicity related human health issues are limited. The main goal of this study is to examine the presence of nano-sized particulates and its structural characteristics of food grade- TiO2 materials and to assess the acute cellular uptake and metabolic stress induced by these particulates in human lung fibroblast (WI-38) cells. The results of transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction studies indicated that about food grade TiO2 sample contains spherical shaped particulate forms in the nano-scale range, <100nm. The intracellular oxidative stress in human lung fibroblast cells (WI-38) was assessed through studies investigating the cellular uptake of the particles, changes in nuclear and cytoplasmic morphology, intracellular ROS, mitochondrial trans-membrane potential, the cell cycle and the expression of genes linked to metabolic stress markers. Altogether our data clearly indicate that primary metabolic stress indicators such as changes in the intracellular ROS, the dose-dependent loss of the mitochondrial membrane potential, alterations in cell cycle progression (G2/M>S>G0/G1) and changes in the TNF and CYP1A gene expression pattern are linked to cellular stress. Thus, food grade TiO2 as nano-scaled contaminants could not only be potential human health risk factors, suggesting that safety considerations with special respect to a few crucial factors such as size, and shape should be considered and regulated by food regulators. Copyright © 2014 Elsevier B.V. All rights reserved.

Atomically engineered epitaxial anatase TiO2 metal-semiconductor field-effect transistors

NASA Astrophysics Data System (ADS)

Kim, Brian S. Y.; Minohara, Makoto; Hikita, Yasuyuki; Bell, Christopher; Hwang, Harold Y.

2018-03-01

Anatase TiO2 is a promising material for a vast array of electronic, energy, and environmental applications, including photocatalysis, photovoltaics, and sensors. A key requirement for these applications is the ability to modulate its electrical properties without dominant dopant scattering and while maintaining high carrier mobility. Here, we demonstrate the room temperature field-effect modulation of the conducting epitaxial interface between anatase TiO2 and LaAlO3 (001), which arises for LaO-terminated LaAlO3, while the AlO2-terminated interface is insulating. This approach, together with the metal-semiconductor field-effect transistor geometry, naturally bypasses the gate/channel interface traps, resulting in a high field-effect mobility μ FE of 3.14 cm2 (V s)-1 approaching 98% of the corresponding Hall mobility μ Hall . Accordingly, the channel conductivity is modulated over 6 orders of magnitude over a gate voltage range of ˜4 V.

Structure of a model TiO2 photocatalytic interface

NASA Astrophysics Data System (ADS)

Hussain, H.; Tocci, G.; Woolcot, T.; Torrelles, X.; Pang, C. L.; Humphrey, D. S.; Yim, C. M.; Grinter, D. C.; Cabailh, G.; Bikondoa, O.; Lindsay, R.; Zegenhagen, J.; Michaelides, A.; Thornton, G.

2017-04-01

The interaction of water with TiO2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO2(110) interface with water. This has provided an atomic-level understanding of the water-TiO2 interaction. However, nearly all of the previous studies of water/TiO2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO2(110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O2 and H2O on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO2 photocatalysis.

Structure of a model TiO2 photocatalytic interface.

PubMed

Hussain, H; Tocci, G; Woolcot, T; Torrelles, X; Pang, C L; Humphrey, D S; Yim, C M; Grinter, D C; Cabailh, G; Bikondoa, O; Lindsay, R; Zegenhagen, J; Michaelides, A; Thornton, G

2017-04-01

The interaction of water with TiO 2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO 2 (110) interface with water. This has provided an atomic-level understanding of the water-TiO 2 interaction. However, nearly all of the previous studies of water/TiO 2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO 2 (110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O 2 and H 2 O on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO 2 photocatalysis.

Nanoplasmonically Engineered Interfaces on Amorphous TiO2 for Highly Efficient Photocatalysis in Hydrogen Evolution.

PubMed

Liang, Huijun; Meng, Qiuxia; Wang, Xiaobing; Zhang, Hucheng; Wang, Jianji

2018-04-25

The nanoplasmonic metal-driven photocatalytic activity depends heavily on the spacing between metal nanoparticles (NPs) and semiconductors, and this work shows that ethylene glycol (EG) is an ideal candidate for interface spacer. Controlling the synthetic systems at pH 3, the composite of Ag NPs with EG-stabilized amorphous TiO 2 (Ag/TiO 2 -3) was synthesized by the facile light-induced reduction. It is verified that EG spacers can set up suitable geometric arrangement in the composite: the twin hydroxyls act as stabilizers to bind Ag NPs and TiO 2 together and the nonconductive alkyl chains consisting only of two CH 2 are able to separate the two building blocks completely and also provide the shortest channels for an efficient transfer of radiation energies to reach TiO 2 . Employed as photocatalysts in hydrogen evolution under visible light, amorphous TiO 2 hardly exhibits the catalytic activity due to high defect density, whereas Ag/TiO 2 -3 represents a remarkably high catalytic efficiency. The enhancement mechanism of the reaction rate is proposed by the analysis of the compositional, structural, and optical properties from a series of Ag/TiO 2 composites.

Development and characterization of the kefiran-whey protein isolate-TiO2 nanocomposite films.

PubMed

Zolfi, Mohsen; Khodaiyan, Faramarz; Mousavi, Mohammad; Hashemi, Maryam

2014-04-01

Biodegradable kefiran-whey protein isolate (WPI)-titanium dioxide (TiO2) blend films were developed and characterized as a function of incorporating amount of TiO2 nanoparticles (1, 3 and 5% wt.). Results showed that the water vapor permeability, moisture content, moisture absorption and water solubility decreased by increasing the nano-TiO2 content. Mechanical tests revealed the plasticizing effect of TiO2 nanoparticles on the kefiran-WPI-TiO2 film. Addition of TiO2 nanoparticles to kefiran-WPI films significantly decreased tensile strength and Young's modulus, while increased its elongation at break. Differential scanning calorimetry data indicated that the glass transition temperature significantly changed by adding nano-TiO2. X-ray diffraction analysis also demonstrated that crystal type in kefiran-WPI was not affected by incorporation of TiO2 nanoparticles. A uniform distribution at 1 and 3% wt. loading levels of TiO2 nanoparticles was observed using scanning electron microscopy (SEM) micrographs. Copyright © 2014 Elsevier B.V. All rights reserved.

Characterization of manufactured TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Motzkus, C.; Macé, T.; Vaslin-Reimann, S.; Ausset, P.; Maillé, M.

2013-04-01

Technological advances in nanomaterials have allowed the development of new applications in industry, increasing the probability of finding airborne manufactured and engineered nano-objects in the workplace, as well as in ambient air. Scientific studies on health and environmental risks have indicated that airborne nano-objects in ambient air have potential adverse effects on the health of exposed workers and the general population. For regulatory purposes, ambient measurements of particulate matter are based on the determination of mass concentrations for PM10 and PM2.5, as regulated in the European Directive 2008/50/EC. However, this legislation is not suitable for airborne manufactured and engineered nano-objects. Parameters characterising ultrafine particles, such as particle number concentration and size distribution, are under consideration for future health-based legislation, to monitor workplaces and to control industrial processes. Currently, there are no existing regulations covering manufactured airborne nano-objects. There is therefore a clear, unaddressed need to focus on the toxicology and exposure assessment of nano-objects such as titanium dioxide (TiO2), which are manufactured and engineered in large quantities in industry. To perform reliable toxicology studies it is necessary to determine the relevant characteristics of nano-objects, such as morphology, surface area, agglomeration, chemical composition, particle size and concentration, by applying traceable methods. Manufacturing of nanomaterials, and their use in industrial applications, also require traceable characterisation of the nanomaterials, particularly for quality control of the process. The present study arises from the OECD WPMN sponsorship programme, supported by the French Agency for Environmental and Occupational Health Safety (ANSES), in order to develop analytical methods for the characterization of TiO2 nanoparticles in size and count size distribution, based on different techniques to characterize five different manufactured TiO2 nanoparticles. In this study, different measurement techniques have been implemented: Transmission Electron Microscopy (TEM), Scanning Mobility Particle Sizer (SMPS) and Aerodynamic Particle Sizer (APS). The TEM results lead to a relatively good agreement between data from the manufacturer and our characterizations of primary particle size. With regard to the dustiness, the results show a strong presence of agglomerates / aggregates of primary particles and a significant presence of emitted airborne nanoparticles with a diameter below 100 nm (composed of isolated primary particles and small aggregates / agglomerates formed from a few primary particles): the number proportion of these particles varies from 0 to 44 % in the measurement range 14-360 nm depending on the types of powders and corrections of measurements.

Density functional theory studies of TiO2 for photocatalysis and Li storage applications

NASA Astrophysics Data System (ADS)

Kim, Yong-Hoon; Lee, Ji Il; Lee, Dong Ki; Lee, Gyu Heon; Kang, Jeung Ku

We present two theory-experiment collaboration studies of anatase TiO2 for energy applications. First, we discuss a hydrogen-nitrogen co-doped TiO2 (HN-TiO2) as a photocatalyst, and show that the interstitially introduced HN contributes to the increase of solar-to-fuel conversion efficiency. We find that the variation of valence band maximum (VBM) of NH-TiO2 extends the photoactive spectrum to the visible light, and argue that created mid-gap states produce efficient electron and hole conduction channels. Next, we consider experimentally fabricated hierarchical TiO2 nanocrystals integrated with binder-free porous graphene (PG) network foam for a Li storage application. It was found that the TiO2-PG facilitated rapid ionic transfer during the Li-ion insertion/extraction process. We clarify the mechanisms by showing that Li ion migration into the TiO2-PG interface stabilize the binder-free oxide-graphene interface. Atomistic mechanism of Li ion insertion and migration is discussed by comparing cases between an isolated Li ion, when the crowding effect is included, and when the surface Li ions are present. We found that the supply of additional surface Li ions significantly reduce the Li insertion barrier, driving a spontaneous domino-like concerted Li insertion at the oxide surface region.

TiO2-Based Nanoheterostructures for Promoting Gas Sensitivity Performance: Designs, Developments, and Prospects

PubMed Central

Wang, Yuan; Wu, Tao; Zhou, Yun; Meng, Chuanmin; Zhu, Wenjun; Liu, Lixin

2017-01-01

Gas sensors based on titanium dioxide (TiO2) have attracted much public attention during the past decades due to their excellent potential for applications in environmental pollution remediation, transportation industries, personal safety, biology, and medicine. Numerous efforts have therefore been devoted to improving the sensing performance of TiO2. In those effects, the construct of nanoheterostructures is a promising tactic in gas sensing modification, which shows superior sensing performance to that of the single component-based sensors. In this review, we briefly summarize and highlight the development of TiO2-based heterostructure gas sensing materials with diverse models, including semiconductor/semiconductor nanoheterostructures, noble metal/semiconductor nanoheterostructures, carbon-group-materials/semiconductor nano- heterostructures, and organic/inorganic nanoheterostructures, which have been investigated for effective enhancement of gas sensing properties through the increase of sensitivity, selectivity, and stability, decrease of optimal work temperature and response/recovery time, and minimization of detectable levels. PMID:28846621

Electron transfer dynamics and yield from gold nanoparticle to different semiconductors induced by plasmon band excitation

NASA Astrophysics Data System (ADS)

Du, L. C.; Xi, W. D.; Zhang, J. B.; Matsuzaki, H.; Furube, A.

2018-06-01

Photoinduced electron transfer from gold nanoparticles (NPs) to semiconductor under plasmon excitation is an important phenomenon in photocatalysis and solar cell applications. Femtosecond plasmon-induced electron transfer from gold NPs to the conduction band of different semiconductor like TiO2, SnO2, and ZnO was monitored at 3440 nm upon optical excitation of the surface plasmon band of gold NPs. It was found that electron injection was completed within 240 fs and the electron injection yield reached 10-30% under 570 nm excitation. It means TiO2 is not the only proper semiconductor as electron acceptors in such gold/semiconductor nanoparticle systems.

Visible-Light Responsive Catalysts Using Quantum Dot-Modified TiO2 for Air and Water Purification

NASA Technical Reports Server (NTRS)

Coutts, Janelle L.; Hintze, Paul E.; Clausen, Christian A.; Richards, Jeffrey T.

2014-01-01

Photocatalysis, the oxidation or reduction of contaminants by light-activated catalysts, utilizing titanium dioxide (TiO2) as the catalytic substrate has been widely studied for trace contaminant control in both air and water applications. The interest in this process is due primarily to its low energy consumption and capacity for catalyst regeneration. Titanium dioxide requires ultraviolet light for activation due to its relatively large band gap energy of 3.2 eV. Traditionally, Hg-vapor fluorescent light sources are used in PCO reactors; however, the use of mercury precludes the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure.

Ultra-Sensitive Humidity Sensor Based on Optical Properties of Graphene Oxide and Nano-Anatase TiO2.

PubMed

Ghadiry, Mahdiar; Gholami, Mehrdad; Lai, C K; Ahmad, Harith; Chong, W Y

2016-01-01

Generally, in a waveguide-based humidity sensors, increasing the relative humidity (RH) causes the cladding refractive index (RI) to increase due to cladding water absorption. However, if graphene oxide (GO) is used, a reverse phenomenon is seen due to a gap increase in graphene layers. In this paper, this interesting property is applied in order to fabricate differential humidity sensor using the difference between RI of reduced GO (rGO) and nano-anatase TiO2 in a chip. First, a new approach is proposed to prepare high quality nano-anatase TiO2 in solution form making the fabrication process simple and straightforward. Then, the resulted solutions (TiO2 and GO) are effortlessly drop casted and reduced on SU8 two channels waveguide and extensively examined against several humid conditions. Investigating the sensitivity and performance (response time) of the device, reveals a great linearity in a wide range of RH (35% to 98%) and a variation of more than 30 dB in transmitted optical power with a response time of only ~0.7 sec. The effect of coating concentration and UV treatment are studied on the performance and repeatability of the sensor and the attributed mechanisms explained. In addition, we report that using the current approach, devices with high sensitivity and very low response time of only 0.3 sec can be fabricated. Also, the proposed device was comprehensively compared with other state of the art proposed sensors in the literature and the results were promising. Since high sensitivity ~0.47dB/%RH and high dynamic performances were demonstrated, this sensor is a proper choice for biomedical applications.

Ultra-Sensitive Humidity Sensor Based on Optical Properties of Graphene Oxide and Nano-Anatase TiO2

PubMed Central

Ghadiry, Mahdiar; Gholami, Mehrdad; Lai, C. K.; Ahmad, Harith; Chong, W. Y.

2016-01-01

Generally, in a waveguide-based humidity sensors, increasing the relative humidity (RH) causes the cladding refractive index (RI) to increase due to cladding water absorption. However, if graphene oxide (GO) is used, a reverse phenomenon is seen due to a gap increase in graphene layers. In this paper, this interesting property is applied in order to fabricate differential humidity sensor using the difference between RI of reduced GO (rGO) and nano-anatase TiO2 in a chip. First, a new approach is proposed to prepare high quality nano-anatase TiO2 in solution form making the fabrication process simple and straightforward. Then, the resulted solutions (TiO2 and GO) are effortlessly drop casted and reduced on SU8 two channels waveguide and extensively examined against several humid conditions. Investigating the sensitivity and performance (response time) of the device, reveals a great linearity in a wide range of RH (35% to 98%) and a variation of more than 30 dB in transmitted optical power with a response time of only ~0.7 sec. The effect of coating concentration and UV treatment are studied on the performance and repeatability of the sensor and the attributed mechanisms explained. In addition, we report that using the current approach, devices with high sensitivity and very low response time of only 0.3 sec can be fabricated. Also, the proposed device was comprehensively compared with other state of the art proposed sensors in the literature and the results were promising. Since high sensitivity ~0.47dB/%RH and high dynamic performances were demonstrated, this sensor is a proper choice for biomedical applications. PMID:27101247

Charge transfer between biogenic jarosite derived Fe3+and TiO2 enhances visible light photocatalytic activity of TiO2.

PubMed

Chowdhury, Mahabubur; Shoko, Sipiwe; Cummings, Fransciuos; Fester, Veruscha; Ojumu, Tunde Victor

2017-04-01

In this work, we have shown that mining waste derived Fe 3+ can be used to enhance the photocatalytic activity of TiO 2 . This will allow us to harness a waste product from the mines, and utilize it to enhance TiO 2 photocatalytic waste water treatment efficiency. An organic linker mediated route was utilized to create a composite of TiO 2 and biogenic jarosite. Evidence of FeOTi bonding in the TiO 2 /jarosite composite was apparent from the FTIR, EFTEM, EELS and ELNEFS analysis. The as prepared material showed enhanced photocatalytic activity compared to pristine TiO 2 , biogenic jarosite and mechanically mixed sample of jarosite and TiO 2 under both simulated and natural solar irradiation. The prepared material can reduce the electrical energy consumption by 4 times compared to pristine P25 for degradation of organic pollutant in water. The material also showed good recyclability. Results obtained from sedimentation experiments showed that the larger sized jarosite material provided the surface to TiO 2 nanoparticles, which increases the settling rate of the materials. This allowed simple and efficient recovery of the catalyst from the reaction system after completion of photocatalysis. Enhanced photocatalytic activity of the composite material was due to effective charge transfer between TiO 2 and jarosite derived Fe 3+ as was shown from the EELS and ELNEFS. Generation of OH was supported by photoluminesence (PL) experiments. Copyright © 2016. Published by Elsevier B.V.

Evaluation of natural organic matter changes from Lake Hohloh by three-dimensional excitation-emission matrix fluorescence spectroscopy during TiO(2)/UV process.

PubMed

Valencia, Sergio; Marín, Juan M; Restrepo, Gloria; Frimmel, Fritz H

2014-03-15

This study shows the changes of natural organic matter (NOM) from Lake Hohloh, (Black Forest, Germany) during heterogeneous photocatalysis with TiO2 (TiO2/UV). The effect of pH on the adsorption of NOM onto TiO2 in the dark and TiO2/UV degradation of NOM was followed using three-dimensional excitation-emission matrix (EEM) fluorescence. At pH values between 4 and 9, the NOM was adsorbed onto TiO2 in the dark with a greater decrease in the fluorescence intensity and in the spectral shapes, especially under acidic pH conditions. However, at pH = 10 there was not adsorption on NOM which led to a negligible changes the fluorescence intensity. A significant high linear correlation was observed between the DOC adsorption onto TiO2 and the maximum fluorescence intensity. Additionally, the NOM adsorption onto TiO2 and its TiO2/UV degradation shifted the fluorescence maxima toward shorter wavelengths in the EEM contour plots, with a decrease in aromaticity. These changes were accompanied by a substantial decrease in the organically bound halogens adsorbable on activated carbon (AOXFP) and the trihalomethane formation potential (THMFP). Thus, the decrease in maximum fluorescence intensity can be used as an indicator of AOXFP and TTHMFP removal efficiency. Therefore, fluorescence spectroscopy is a robust analytical technique for evaluate TiO2/UV removal of NOM. Copyright © 2013 Elsevier Ltd. All rights reserved.

Rapid synthesis of rutile TiO2 nano-flowers by dealloying Cu60Ti30Y10 metallic glasses

NASA Astrophysics Data System (ADS)

Wang, Ning; Pan, Ye; Wu, Shikai; Zhang, Enming; Dai, Weiji

2018-01-01

The 3D nanostructure rutile TiO2 photocatalyst was rapidly synthesized by dealloying method using Cu60Ti30Y10 amorphous ribbons as precursors. The preparation period was kept down to just 3 h, which is much shorter than those of the samples by dealloying Cu60Ti30Al10, Cu70Ti30 and Cu60Ti30Sn10. The synthesized sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). XRD and XPS reveal the successful synthesis of rutile TiO2. The SEM and TEM images show that the synthesized rutile TiO2 nano-material presents homogeneous distributed 3D nanoflowers structure, which is composed of large quantities of fine rice-like nanorods (40-150 nm in diameter and 100-250 nm in length). BET specific surface areas of the samples were investigated by N2 adsorption-desorption isotherms, the fabricated rutile TiO2 exhibits very high specific surface area (194.08 m2/g). The photocatalytic activities of the samples were evaluated by degrading rhodamine B (RhB) dye (10 mg/L) under the irradiation of both simulated visible light (λ > 420 nm) and ultraviolet (UV) light (λ = 365 nm). The results show that the photocatalytic activity of rutile TiO2 prepared by dealloying Cu60Ti30Y10 amorphous ribbons is higher than those of commercial rutile and the sample synthesized by dealloying Cu70Ti30 precursors. The advantages of both short preparation period and superior photocatalytic activity suggest that Cu60Ti30Y10 metallic glasses are really a kind of perfect titanium source for rapidly fabricating high efficient TiO2 nano-materials. In addition, the influence of chemical composition of the amorphous precursors on preparation period of the rutile TiO2 nano-material was investigated from the point of view of standard electrode potentials.

Catalytic destruction of PCDD/Fs over vanadium oxide-based catalysts.

PubMed

Yu, Ming-Feng; Lin, Xiao-Qing; Li, Xiao-Dong; Yan, Mi; Prabowo, Bayu; Li, Wen-Wei; Chen, Tong; Yan, Jian-Hua

2016-08-01

Vanadium oxide-based catalysts were developed for the destruction of vapour phase PCDD/Fs (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans). A vapour phase PCDD/Fs generating system was designed to supply stable PCDD/Fs steam with initial concentration of 3.2 ng I-TEQ Nm(-3). Two kinds of titania (nano-TiO2 and conventional TiO2) and alumina were used as catalyst supports. For vanadium-based catalysts supported on nano-TiO2, catalyst activity is enhanced with operating temperature increasing from 160 to 300 °C and then reduces with temperature rising further to 350 °C. It is mainly due to the fact that high volatility of organic compounds at 350 °C suppresses adsorption of PCDD/Fs on catalysts surface and then further inhibits the reaction between catalyst and PCDD/Fs. The optimum loading of vanadium on nano-TiO2 support is 5 wt.% where vanadium oxide presents highly dispersed amorphous state according to the Raman spectra and XRD patterns. Excessive vanadium will block the pore space and form microcrystalline V2O5 on the support surface. At the vanadium loading of 5 wt.%, nano-TiO2-supported catalyst performs best on PCDD/Fs destruction compared to Al2O3 and conventional TiO2. Chemical states of vanadium in the fresh, used and reoxidized VOx(5 %)/TiO2 catalysts at different operating temperature are also analysed by XPS.

Hybrid TiO2 -Ruthenium Nano-photosensitizer Synergistically Produces Reactive Oxygen Species in both Hypoxic and Normoxic Conditions.

PubMed

Gilson, Rebecca C; Black, Kvar C L; Lane, Daniel D; Achilefu, Samuel

2017-08-28

Photodynamic therapy (PDT) is widely used to treat diverse diseases, but its dependence on oxygen to produce cytotoxic reactive oxygen species (ROS) diminishes the therapeutic effect in a hypoxic environment, such as solid tumors. Herein, we developed a ROS-producing hybrid nanoparticle-based photosensitizer capable of maintaining high levels of ROS under both normoxic and hypoxic conditions. Conjugation of a ruthenium complex (N3) to a TiO 2 nanoparticle afforded TiO 2 -N3. Upon exposure of TiO 2 -N3 to light, the N3 injected electrons into TiO 2 to produce three- and four-fold more hydroxyl radicals and hydrogen peroxide, respectively, than TiO 2 at 160 mmHg. TiO 2 -N3 maintained three-fold higher hydroxyl radicals than TiO 2 under hypoxic conditions via N3-facilitated electron-hole reduction of adsorbed water molecules. The incorporation of N3 transformed TiO 2 from a dual type I and II PDT agent to a predominantly type I photosensitizer, irrespective of the oxygen content. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of TiCl4 precursor in hydrothermal synthesis of TiO2 nanostructures

NASA Astrophysics Data System (ADS)

Kartikay, Purnendu; Nemala, Siva Sankar; Mallick, Sudhanshu

2017-05-01

Rutile TiO2 films were deposited on the FTO substrate by the hydrothermal process using TTIP and TiCl4 as the titania precursor. Our study manifestly exhibits the influence of TiCl4 precursor on the hydrothermal growth of the TiO2 structure. The morphology of prepared film varies from nano-cauliflower to nano-flower to nano-parallelepiped rod-like structure with the addition of TiCl4 as the precursor. When TiCl4 is introduced in the precursor HCl corresponding to four times of the Ti4+ concentration is generated as a by-product during the reaction, these additional HCl promotes the etching of the nanostructure enabling the nanostructure to unfurl. We conclude that the tailoring of the nanostructure can be performed by addition of TiCl4 in the precursor

Report: Discussion on the development of nano Ag/TiO2 coating bracket and its antibacterial property and biocompatibility in orthodontic treatment.

PubMed

Zhang, Ronghe; Zhang, Weiwei; Bai, Xueyan; Song, Xiaotong; Wang, Chunyan; Gao, Xinxin; Tian, Xubiao; Liu, Fengzhen

2015-03-01

This paper aims to explore the antibacterial property of nano Ag/TiO2 coating bracket for the common bacteria in oral cavity, and discuss its biocompatibility. Micro morphology in the surface of nano Ag/TiO2 coating bracket was detected by scanning electron microscope (SEM), and surface roughness of ordinary mental bracket, nano TiO2 coating bracket and nano Ag/TiO2 coating bracket were measured. First, antibacterial property of nano Ag/TiO2 coating bracket on the common bacteria in oral cavity was studied by sticking membrane method. Secondly, bonding strength of nano TiO2 coating and nano Ag/TiO2 coating bracket in groups were detected by scratching test. The result showed that, the synthetic nano Ag/TiO2 coating was nanogranular films with rigorous organizational structure, presenting as smooth and clean surface, and antibacterial rate of nano Ag/TiO2 coating for the common bacteria in oral cavity for 20 min was more than 79% in the dark. All the findings suggested that, nano Ag/TiO2 coating bracket not only has antibacterial effect but also has good biocompatibility, therefore, it can satisfy the clinical request of orthodontic treatment.

Solar photocatalysis for treatment of Acid Yellow-17 (AY-17) dye contaminated water using Ag@TiO2 core-shell structured nanoparticles.

PubMed

Khanna, Ankita; Shetty K, Vidya

2013-08-01

Wastewater released from textile industries causes water pollution, and it needs to be treated before discharge to the environment by cost effective technologies. Solar photocatalysis is a promising technology for the treatment of dye wastewater. The Ag@TiO2 nanoparticles comprising of Ag core and TiO2 shell (Ag@TiO2) have unique photocatalytic property of inhibition of electron-hole recombination and visible light absorption, which makes it a promising photocatalyst for use in solar photocatalysis and with higher photocatalytic rate. Therefore, in the present work, the Ag@TiO2 nanoparticles synthesized by one pot method with postcalcination step has been used for the degradation of Acid Yellow-17 (AY-17) dye under solar light irradiation. The Ag@TiO2 nanoparticles were characterized using thermogravimetric-differential thermal analysis, X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray analysis. The catalyst has been found to be very effective in solar photocatalysis of AY-17, as compared to other catalysts. The effects of pH, catalyst loading, initial dye concentration, and oxidants on photocatalysis were also studied. The optimized parameters for degradation of AY-17 using Ag@TiO2 were found to be pH 3, dye/catalyst ratio of 1:10 (g/g), and 2 g/L of (NH4)2S2O8 as oxidant. Efficient decolorization and mineralization of AY-17 was achieved. The kinetics of color, total organic carbon, and chemical oxygen demand removal followed the Langmuir-Hinshelwood model. Ag@TiO2 catalyst can be reused thrice without much decline in efficiency. The catalyst exhibited its potential as economic photocatalyst for treatment of dye wastewater.

The Application of Nano-TiO2 Photo Semiconductors in Agriculture

NASA Astrophysics Data System (ADS)

Wang, Yan; Sun, Changjiao; Zhao, Xiang; Cui, Bo; Zeng, Zhanghua; Wang, Anqi; Liu, Guoqiang; Cui, Haixin

2016-11-01

Nanometer-sized titanium dioxide (TiO2) is an environmentally friendly optical semiconductor material. It has wide application value in many fields due to its excellent structural, optical, and chemical properties. The photocatalytic process of nano-TiO2 converts light energy into electrical or chemical energy under mild conditions. In recent years, the study and application of nano-TiO2 in the agricultural sector has gradually attracted attention. The nano-TiO2 applications of degrading pesticides, plant germination and growth, crop disease control, water purification, pesticide residue detection, etc. are good prospects. This review describes all of these applications and the research status and development, including the underlying principles, features, comprehensive applications, functional modification, and potential future directions, for TiO2 in agriculture.

Visible Light Driven Benzyl Alcohol Dehydrogenation in a Dye-Sensitized Photoelectrosynthesis Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Wenjing; Vannucci, Aaron K.; Farnum, Byron H.

2014-06-27

Light-driven dehydrogenation of benzyl alcohol (BnOH) to benzaldehyde and hydrogen has been shown to occur in a dye-sensitized photoelectrosynthesis cell (DSPEC). In the DSPEC, the photoanode consists of mesoporous films of TiO2 nanoparticles or of core/shell nanoparticles with tin-doped In2O3 nanoparticle (nanoITO) cores and thin layers of TiO2 deposited by atomic layer deposition (nanoITO/TiO2). Metal oxide surfaces were coderivatized with both a ruthenium polypyridyl chromophore in excess and an oxidation catalyst. Chromophore excitation and electron injection were followed by cross-surface electron-transfer activation of the catalyst to RuIV=O2+, which then oxidizes benzyl alcohol to benzaldehyde. The injected electrons are transferred tomore » a Pt electrode for H2 production. The nanoITO/TiO2 core/shell structure causes a decrease of up to 2 orders of magnitude in back electron-transfer rate compared to TiO2. At the optimized shell thickness, sustained absorbed photon to current efficiency of 3.7% was achieved for BnOH dehydrogenation, an enhancement of ~10 compared to TiO2.« less

Novel high potential visible-light-active photocatalyst of CNT/Mo, S-codoped TiO2 hetero-nanostructure

NASA Astrophysics Data System (ADS)

Hamadanian, M.; Shamshiri, M.; Jabbari, V.

2014-10-01

The current study deals with synthesize of novel nanophotocatalysts of CNT/Mo,S-codoped TiO2 by reacting between titanium isopropoxide (Ti(OC3H7)4) and CNT in aqueous ammonia and subsequent calcining of hydrolysis of the products. The prepared catalysts were characterized by N2 adsorption-desorption measurements, XRD, SEM, TEM, EDX, FT-IR, and UV-vis DRS spectroscopy. SEM and TEM images exhibited uniform coverage of CNT with anatase TiO2 nanoclusters. It was also demonstrated that the presence of S and Mo within the TiO2 acts as electrons traps and prevents the charge recombination and also enables the TiO2 photocatalyst to be active in visible-light region. Moreover, the CNT/Mo,S-doped TiO2 nanohybrids has been proven to has a excellent photocatalytic performance in photodecomposition of Congored (CR), at which the rate of decomposition reaches 100% in only 20 and 30 min under UV and visible-light irradiation, respectively. The enhanced photocatalytic activity was ascribed to the synergetic effects of excellent electrical property of CNT and metal-non-metal codoping. Finally, which to best of our knowledge is done for the first time, we have demonstrated that Mo- and S-doped TiO2 decorated over CNT, or CNT/Mo,S-codoped TiO2, may have high potential applications in photocatalysis and environmental protection with superior catalytic activity under visible-light illumination.

Photocatalytic activity of self-assembled porous TiO2 nano-columns array fabricated by oblique angle sputter deposition

NASA Astrophysics Data System (ADS)

Shi, Pengjun; Li, Xibo; Zhang, Qiuju; Yi, Zao; Luo, Jiangshan

2018-04-01

A well-separated and oriented TiO2 nano-columns arrays with porous structure were fabricated by the oblique angle sputter deposition technique and subsequently annealing at 450 °C in Ar/O2 mixed atmosphere. The deposited substrate was firstly modified by a template of self-assembled close-packed arrays of 500 nm-diameter silica (SiO2) spheres. Scanning electronic microscopic (SEM) images show that the porous columnar nanostructure is formed as a result of the geometric shadowing effect and surface diffusion of the adatoms in oblique angle deposition (OAD). X-ray diffraction (XRD) measurements reveal that the physically OAD film with annealing treatment are generally mixed phase of rutile and anatase TiO2 polymorphic forms. The morphology induced absorbance and band gap tuning by different substrates was demonstrated by the UV–vis spectroscopy. The well-separated one-dimensional (1D) nano-columns array with specific large porous surface area is beneficial for charge separation in photocatalytic degradation. Compared with compact thin film, such self-assembled porous TiO2 nano-columns array fabricated by oblique angle sputter deposition performed an enhanced visible light induced photocatalytic activity by decomposing methyl orange (MO) solution. The well-designed periodic array-structured porous TiO2 films by using modified patterned substrates has been demonstrated significantly increased absorption edge in the UV-visible light region with a narrower optical band gap, which are expected to be favorable for application in photovoltaic, lithium-ion insertion and photocatalytic, etc.

Titanium dioxide nanostructure synthesized by sol-gel for organic solar cells using natural dyes extracted from black and red sticky rice

NASA Astrophysics Data System (ADS)

Ramelan, A. H.; Harjana, H.; Sakti, L. S.

2012-06-01

Nanocrystalline semiconductor metal oxides have achieved a great importance in our industrial world today. They may be defined as metal oxides with crystal size between 1 and 100 nm. TiO2 nanosize particles have attracted significant interest of materials scientists and physicists due to their special properties and have attained a great importance in several technological applications such as photocatalysis, sensors, solar cells and memory devices. TiO2 nanoparticles can be produced by a variety of techniques ranging from simple chemical to mechanical to vacuum methods, including many variants of physical and chemical vapour deposition techniques. In the present research work we report the synthesis of TiO2 nanoparticles by Sol-Gel technique. The characterization of particles was carried out by XRD and XRF techniques. The importance and applications of these nanoparticles for solar cells are also discussed in this work.

The synergetic effect of UV rays on the decomposition of xylene in dielectric barrier discharge plasma and photocatalyst process

NASA Astrophysics Data System (ADS)

Li, Wenjuan; Gu, Zhenyu; Teng, Fuhua; Lu, Jianhai; Dong, Shibi; Miao, Xiaoping; Wu, Zhongbiao

2018-06-01

The degradation of xylene in the dielectric barrier discharge plasma and photocatalyst process was studied, focusing on the synergetic effect of UV rays from plasma process and external UV lamps on the decomposition of xylene. The results showed that xylene could be decomposed by the discharge process in plasma system, whereas the UV rays from plasma process was very weak. After adding TiO2, the removal efficiency of xylene and energy yield in plasma process were enhanced since energetic particles activated the catalysis of TiO2. The removal efficiency of xylene and energy field in plasma and photocatalyst process combined with external UV lamps were further enhanced attributed to the degradation effect of plasma, the catalysis of TiO2 activated by plasma, the photolysis of UV rays and the photocatalysis of photocatalyst. The synergetic effect of UV rays from external UV lamps was obvious.

Using Nanomaterials to Solve Environmental Problems: Advancing the Science and Engineering of Photocatalysis

NASA Astrophysics Data System (ADS)

Brame, Jonathon Andrew

Photocatalysis is a process by which materials can transfer light energy into chemical energy in the form of reactive oxygen species (ROS), which can then oxidize chemical and biological contaminants in water. Whereas photocatalysis offers the potential to treat many recalcitrant priority pollutants in a cost-effective manner, it has yet to become a viable, wide-spread treatment option due to implementation barriers that include limitations in treatment efficiency and relatively high costs of some photocatalytic material. This thesis seeks to increase the applicability and understanding of nanomaterial-enhanced photocatalytic oxidation processes to help overcome these barriers. Increased photocatalytic efficiency can be accomplished through informed choice of ROS-producing materials. For example, hydroxyl radicals are shown to be much more susceptible to hindrance by natural organic matter (NOM), phosphate and wastewater treatment plant effluent than 1O 2, which is only slightly inhibited by NOM and not by phosphate or wastewater effluent. Additionally, a novel crystallization mechanism for photocatalytic TiO2 nanotubes enabled photo-production of multiple ROS types. This "cocktail" of reactive oxygen species contributed to increased efficiency. Novel applications for nanotechnology-enhanced photocatalysis were demonstrated at the lab scale. These include (1) photocatalytic pre-treatment of weathered oil from the 2010 Gulf oil spill, which increased soluble organic carbon content (indicative of increased bioavailability) by 60% and enhanced subsequent biodegradation by 37%; and (2) a water disinfection case study in rural Swaziland, which produced a prototype fluidized bed photoreactor capable of removing 99.9% of bacteria and viruses in <60 seconds. These projects show both a variety of applications for photocatalysis, and ways to increase its efficiency and effectiveness. To achieve wide-spread implementation, however, the price of photocatalysis must be reduced. Extensive reuse of treatment materials (>60 cycles), and utilization of less-purified starting materials (>90% cost reduction) highlight possible ways to reduce the cost of nanomaterial photocatalysis. By reducing financial implementation barriers, defining niches where photocatalysis can be superiorly effective, engineering reactor systems that enable real-world testing of this technology, and increasing understanding of photocatalytic inhibition mechanisms, photocatalysis can become a tool to help solve global water challenges.

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. Copyright © 2015 Elsevier B.V. All rights reserved.

Synthesis and characterization of Cu-Zn/TiO2 for the photocatalytic conversion of CO2 to methane.

PubMed

Rana, Adeem Ghaffar; Ahmad, Waqar; Al-Matar, Ali; Shawabkeh, Reyad; Aslam, Zaheer

2017-05-01

Different Cu-Zn/TiO 2 catalysts were synthesized by using the wet impregnation method. The prepared catalysts were used for the conversion of CO 2 into methane by photocatalysis. Various characterization techniques were used to observe the surface morphology, crystalline phase, Brunauer-Emmett-Teller (BET) surface area, presence of impregnated Cu and Zn, and functional group. Scanning electron microscope analysis showed spherical morphology, and slight agglomeration of catalyst particles was observed. BET analysis revealed that the surface area of the catalyst was decreased from 10 to 8.5 m 2 /g after impregnation of Cu and Zn over TiO 2 support. Synergetic effect of Cu and Zn over TiO 2 support (Cu 2.6 /TiO 2 , Zn 0.5 /TiO 2 and Cu 2.6 -Zn 0.5 /TiO 2 ) and the effects of Cu loading (0, 1.8, 2.1, 2.6 and 2.9 wt%) were also investigated at different feed molar ratios of H 2 /CO 2 (2:1 and 4:1). The Cu 2.6 -Zn 0.5 /TiO 2 catalyst showed a maximum conversion of 14.3% at a feed molar ratio of 4. The addition of Zn over the catalyst surface increased the conversion of CO 2 from 10% to 14.3% which might be due to synergy of Cu and Zn over TiO 2 support.

Enhanced photocatalytic degradation of dyes under sunlight using biocompatible TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Bharati, B.; Sonkar, A. K.; Singh, N.; Dash, D.; Rath, Chandana

2017-08-01

As TiO2 is one of the most popular photocatalysts, we have studied here the photocatalytic degradation of the most common dyestuffs like rhodamine B (RhB), congo red (CR) and methylene blue (MB), which mainly come from the textile and photographic industries using nanoparticles of TiO2. Nanoparticles of TiO2 synthesized through a simple and cost effective sol-gel technique crystallizes in the anatase phase, showing a band gap less than that of bulk value. Particles consisting of coherently scattered domains of size 33 nm are found to be agglomerated and polycrystalline in nature. While the degradation rates of MB, CR and RhB after irradiating with a renewable source of energy, i.e. sunlight, show 100% degradation, TiO2 irradiated with UV light of 4.8 eV shows a much slower degradation rate. To use the waste water after photocatalysis, we examine further the biocompatibile nature of the TiO2 nanoparticles by platelet interaction activity, hemolysis effect and MTT assay. It is worth mentioning here that TiO2 nanoparticles are found to be highly hemocompatible, show no platelet aggregation, and the level of intracellular ROS in human platelets does not show significant change in ROS level. We conclude that TiO2 nanoparticles constitute an excellent photocatalyst and biocompatible material, and that after photocatalytic degradation of dye effluents obtained from textile industries, purified water can be used in agriculture and domestic sectors.

Efficient solar light-driven degradation of Congo red with novel Cu-loaded Fe3O4@TiO2 nanoparticles.

PubMed

Arora, Priya; Fermah, Alisha; Rajput, Jaspreet Kaur; Singh, Harminder; Badhan, Jigyasa

2017-08-01

In this work, Cu-loaded Fe 3 O 4 @TiO 2 core shell nanoparticles were prepared in a single pot by coating of TiO 2 on Fe 3 O 4 nanoparticles followed by Cu loading. X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), thermogravimetric analysis (TGA), Brunauer-Emmett- Teller (BET), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), and valence band X-ray photoelectron spectroscopy (VB XPS) techniques were used for characterization of as prepared nanoparticles. Synergism between copper and titania was evaluated by studying the solar light-driven photodegradation of Congo red dye solution in the presence of Fe 3 O 4 @TiO 2 nanoparticles on one side and Cu-loaded Fe 3 O 4 @TiO 2 nanoparticles on the other side. The latter performed better than the former catalyst, indicating the enhanced activity of copper-loaded catalyst. Further photodegradation was studied by three means, i.e., under ultraviolet (UV), refluxing, and solar radiations. Cu-loaded Fe 3 O 4 @TiO 2 enhanced the degradation efficiency of Congo red dye. Thus, Cu act possibly by reducing the band gap of TiO 2 and widening the optical response of semiconductor, as a result of which solar light could be used to carry out photocatalysis. Graphical abstract Photodegradation of congo red over Cu-loaded Fe 3 O 4 @TiO 2 nanoparticles.

The preparation, surface structure, zeta potential, surface charge density and photocatalytic activity of TiO2 nanostructures of different shapes

NASA Astrophysics Data System (ADS)

Grover, Inderpreet Singh; Singh, Satnam; Pal, Bonamali

2013-09-01

Titania based nanocatalysts such as sodium titanates of different morphology having superior surface properties are getting wide importance in photocatalysis research. Despite having sodium (Na) contents and its high temperature synthesis (that generally deteriorate the photoreactivity), these Na-titanates often exhibit better photoactivity than P25-TiO2 catalyst. Hence, this work demonstrated the influence of crystal structure, BET surface area, surface charge, zeta potential (ζ) and metal loading on the photocatalytic activity of as-prepared sodium titanate nanotube (TNT) and titania nanorod (TNR). Straw like hollow orthorhombic-TNT (Na2Ti2O5·H2O) particles (W = 9-12 nm and L = 82-115 nm) and rice like pure anatase-TNR particles (W = 8-13 nm and L = 81-134 nm) are obtained by the hydrothermal treatment of P25-TiO2 with NaOH, which in fact, altered the net surface charge of TNT and TNR particles. The observed ζ = -2.82 (P25-TiO2), -13.5 (TNT) and -22.5 mV (TNR) are significantly altered by the Ag and Cu deposition. It has been found here that TNT displayed best photocatalytic activity for the imidacloprid insecticide (C9H10ClN5O2) degradation to CO2 formation under UV irradiation because of its largest surface area 176 m2 g-1 among the catalysts studied.

The photovoltaic efficiency of the fabrication of copolymer P3HT:PCBM on different thickness nano-anatase titania as solar cell

NASA Astrophysics Data System (ADS)

Lazim, Haidar Gazy; Ajeel, Khalid I.; Badran, Hussain A.

2015-06-01

Organic solar cells based on (3-hexylthiophene):[6,6]-phenyl C61-butyric acid methylester (P3HT:PCBM) bulk heterojunction (BHJ) with an inverted structure have been fabricated using nano-anatase crystalline titanium dioxide (TiO2) as their electron transport layer, which was prepared on the indium tin oxide coated glass (ITO-glass), silicon wafer and glass substrates by sol-gel method at different spin speed by using spin-coating (1000, 2000 and 3000 rpm) for nano-thin film 58, 75 and 90 nm respectively. The effect of thickness on the surface morphology and optical properties of TiO2 layer were investigated by atomic force microscopy (AFM), X-ray diffraction and UV-visible spectrophotometer. The optical band gap of the films has been found to be in the range 3.63-3.96 eV for allowed direct transition and to be in the range 3.23-3.69 eV for forbidden direct transition to the different TiO2 thickness. The samples were examined to feature current and voltages darkness and light extraction efficiency of the solar cell where they were getting the highest open-circuit voltage, Voc, and power conversion efficiency were 0.66% and 0.39% fabricated with 90 nm respectively.

Effects of exposure to nano and bulk sized TiO2 and CuO in Lemna minor.

PubMed

Dolenc Koce, Jasna

2017-10-01

Nanoparticles of TiO 2 and CuO are among most commonly used nanoparticles, and elevated concentrations of them are expected to be found in all environments, including aquatic. A standard growth inhibition test ISO/CD 20079 was used to determine the toxicity of nano sized and larger micro sized (bulk) particles in the concentrations of 0.1, 1, 10, 100 and 1000 μM CuO and TiO 2 on common duckweed (Lemna minor L.). Both nano and bulk CuO particles caused changes in the structure and function of treated plants. The number of fronds and colonies decreased by as much as 78%, the length of roots and fronds decreased by 99% and 14%, respectively. Furthermore, photochemical efficiency was reduced by up to 35%, and the activities of antioxidative enzymes guaiacol peroxidase, ascorbate peroxidase and glutathione reductase increased by more than 240%. The altered physiological state of the CuO exposed plants was also reflected in the elevated occurrence of necrosis and bleaching in the duckweed colonies. Nano sized particles of CuO proved more phytotoxic than bulk particles, and the effects of both studied CuO sizes were concentration dependent. On the other hand, both bulk and nano sized particles of TiO 2 caused no severe phytotoxic effects, there was no concentration dependence and they could be considered as non-harmful to common duckweed. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Inverse kinetic solvent isotope effect in TiO2 photocatalytic dehalogenation of non-adsorbable aromatic halides: a proton-induced pathway.

PubMed

Chang, Wei; Sun, Chunyan; Pang, Xibin; Sheng, Hua; Li, Yue; Ji, Hongwei; Song, Wenjing; Chen, Chuncheng; Ma, Wanhong; Zhao, Jincai

2015-02-09

An efficient redox reaction between organic substrates in solution and photoinduced h(+) vb /e(-) cb on the surface of photocatalysts requires the substrates or solvent to be adsorbed onto the surface, and is consequentially marked by a normal kinetic solvent isotope effect (KSIE ≥ 1). Reported herein is a universal inverse KSIE (0.6-0.8 at 298 K) for the reductive dehalogenation of aromatic halides which cannot adsorb onto TiO2 in a [D0 ]methanol/[D4 ]methanol solution. Combined with in situ ATR-FTIR spectroscopy investigations, a previously unknown pathway for the transformation of these aromatic halides in TiO2 photocatalysis was identified: a proton adduct intermediate, induced by released H(+) /D(+) from solvent oxidation, accompanies a change in hybridization from sp(2) to sp(3) at a carbon atom of the aromatic halides. The protonation event leads these aromatic halides to adsorb onto the TiO2 surface and an ET reaction to form dehalogenated products follows. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

Characterization, Degradation, and Reaction Pathways of Indoor Toluene over Visible-light-driven S, Zn Co-doped TiO2

NASA Astrophysics Data System (ADS)

Chu, H.; Lin, Y. H.; Lin, C. Y.

2017-01-01

Sulfur and Zinc co-doped TiO2 prepared by a sol-gel method to degrade toluene under a fluorescent lamp was investigated. The results indicate that S,Zn co-doped TiO2 photocatalysts are mainly nano-size with an anatase phase structure. The degradation reactions of toluene were performed under various operation conditions. The results show that the toluene conversion increases with increasing toluene concentration and decreasing relative humidity. Based on the results of activity test, S0.05Zn0.001/TiO2 was chosen for further studies. The main oxidation products of toluene photodegradation are CO2, H2O, benzyl alcohol, acetone, butadiene and acetic acid. Two possible mechanisms have been developed for photodegradation of toluene in a dry and a humid environment.

Application of concrete surfaces as novel substrate for immobilization of TiO2 nano powder in photocatalytic treatment of phenolic water.

PubMed

Delnavaz, Mohammad; Ayati, Bita; Ganjidoust, Hossein; Sanjabi, Sohrab

2015-01-01

In this study, concrete application as a substrate for TiO2 nano powder immobilization in heterogeneous photocatalytic process was evaluated. TiO2 immobilization on the pervious concrete surface was done by different procedures containing slurry method (SM), cement mixed method (CMM) and different concrete sealer formulations. Irradiation of TiO2 was prepared by UV-A and UV-C lamps. Phenolic wastewater was selected as a pollutant and efficiency of the process was determined in various operation conditions including influent phenol concentration, pH, TiO2 concentration, immobilization method and UV lamp intensity. The removal efficiency of photocatalytic process in 4 h irradiation time and phenol concentration ranges of 25-500 mg/L was more than 80 %. Intermediates were identified by GC/Mass and spectrophotometric analysis. According to the results, photocatalytic reactions followed the pseudo-first-order kinetics and can effectively treate phenol under optimal conditions.

Atomic layer deposition of nano-TiO2 thin films with enhanced biocompatibility and antimicrobial activity for orthopedic implants

PubMed Central

Liu, Luting; Bhatia, Ritwik; Webster, Thomas J

2017-01-01

Titanium (Ti) and its alloys have been extensively used as implant materials in orthopedic applications. Nevertheless, implants may fail due to a lack of osseointegration and/or infection. The aim of this in vitro study was to endow an implant surface with favorable biological properties by the dual modification of surface chemistry and nanostructured topography. The application of a nanostructured titanium dioxide (TiO2) coating on Ti-based implants has been proposed as a potential way to enhance tissue-implant interactions while inhibiting bacterial colonization simultaneously due to its chemical stability, biocompatibility, and antimicrobial properties. In this paper, temperature-controlled atomic layer deposition (ALD) was introduced for the first time to provide unique nanostructured TiO2 coatings on Ti substrates. The effect of nano-TiO2 coatings with different morphology and structure on human osteoblast and fibroblast functions and bacterial activities was investigated. In vitro results indicated that the TiO2 coating stimulated osteoblast adhesion and proliferation while suppressing fibroblast adhesion and proliferation compared to uncoated materials. In addition, the introduction of nano-TiO2 coatings was shown to inhibit gram-positive bacteria (Staphylococcus aureus), gram-negative bacteria (Escherichia coli), and antibiotic-resistant bacteria (methicillin-resistant Staphylococcus aureus), all without resorting to the use of antibiotics. Our results suggest that the increase in nanoscale roughness and greater surface hydrophilicity (surface energy) together could contribute to increased protein adsorption selectively, which may affect the cellular and bacterial activities. It was found that ALD-grown TiO2-coated samples with a moderate surface energy at 38.79 mJ/m2 showed relatively promising antibacterial properties and desirable cellular functions. The ALD technique provides a novel and effective strategy to produce TiO2 coatings with delicate control of surface nanotopography and surface energy to enhance the interfacial biocompatibility and mitigate bacterial infection, and could potentially be used for improving numerous orthopedic implants. PMID:29263665

Photocatalysis applications of some hybrid polymeric composites incorporating TiO2 nanoparticles and their combinations with SiO2/Fe2O3

PubMed Central

Buruiana, Tinca; Melinte, Violeta; Buruiana, Emil C

2017-01-01

Polymer nanocomposites containing titanium oxide nanoparticles (TiO2 NPs) combined with other inorganic components (Si–O–Si or/and γ-Fe2O3) were prepared by the dispersion of premade NPs (nanocrystalline TiO2, TiO2/SiO2, TiO2/Fe2O3, TiO2/SiO2/Fe2O3) within a photopolymerizable urethane dimethacrylate (polytetrahydrofuran-urethane dimethacrylate, PTHF-UDMA). The physicochemical characterization of nanoparticles and hybrid polymeric composites with 10 wt % NPs (S1–S4) was realized through XRD, TEM and FTIR analyses. The mean size (10–30 nm) and the crystallinity of the NPs varied as a function of the inorganic constituent. The catalytic activity of these hybrid films was tested for the photodegradation of phenol, hydroquinone and dopamine in aqueous solution under UV or visible-light irradiation. The best results were obtained for the films with TiO2/Fe2O3 or TiO2/SiO2/Fe2O3 NPs. The degradation of the mentioned model pollutants varied between 71% and 100% (after 250 min of irradiation) depending on the composition of the hybrid film tested and the light applied (UV–visible light). Also, it was established that such hybrid films can be reused at least for five cycles, without losing too much of the photocatalytic efficiency (ca. 7%). These findings could have implications in the development of new nanocatalysts. PMID:28243566

Study on the enhanced adsorption properties of lysozyme on polyacrylic acid modified TiO2 nano-adsorbents

NASA Astrophysics Data System (ADS)

Liu, Yufeng; Jin, Zu; Meng, Hao; Zhang, Xia

2018-01-01

The adsorption and immobilization of enzymes onto solid carriers has been focused on due to their many advantages, such as improved stability against a thermal or organic solvent and a good cycle usability. TiO2 nanoparticles is one of excellent nano-adsorbents owing to its excellent biocompatibility, non-inflammatory, and abundant surface hydroxyl groups, which are convenient to be combined with various functional groups. In this paper polyacrylic acid (PAA) modified TiO2 nanoparticles were synthesized through an in situ light-induced polymerization of acrylic acid on the surface of TiO2 nanoparticles. The structure and surface physicochemical properties of the PAA/TiO2 nanoparticles were characterized by TEM, XRD, FT-IR, Zeta potential measurements and TG-DSC. The experimental results showed that the isoelectric point of PAA/TiO2 significantly reduced to 1.82 compared with that of pure TiO2 nanoparticles (6.08). In the adsorption tests of lysozyme (Lyz), the PAA/TiO2 nanoparticles displayed enhanced adsorption activity compared with pristine TiO2. The maximum adsorption capacity of PAA/TiO2 for Lyz was 225.9 mg g-1 under the optimum conditions where the initial concentration of Lyz was 300 mg ml-1, the addition amount of PAA/TiO2 was 6.4 mg, the adsorption time was 30 min and the pH value was 7.0. The sodium dodecyl sulfate (SDS, 0.5%) presented the best efficiency (76.86%) in the removal of adsorbed Lyz, and the PAA/TiO2 nanoparticles showed excellent adsorption stability based on five cyclic adsorption-desorption tests. The fitting calculation results of the adsorption isotherm and the thermodynamics indicated the adsorption was an exothermic, entropy increasing, spontaneous and monomolecular layer adsorption process.

Effect of dye extracting solvents and sensitization time on photovoltaic performance of natural dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Hossain, Md. Khalid; Pervez, M. Firoz; Mia, M. N. H.; Mortuza, A. A.; Rahaman, M. S.; Karim, M. R.; Islam, Jahid M. M.; Ahmed, Farid; Khan, Mubarak A.

In this study, natural dye sensitizer based solar cells were successfully fabricated and photovoltaic performance was measured. Sensitizer (turmeric) sources, dye extraction process, and photoanode sensitization time of the fabricated cells were analyzed and optimized. Dry turmeric, verdant turmeric, and powder turmeric were used as dye sources. Five distinct types of solvents were used for extraction of natural dye from turmeric. Dyes were characterized by UV-Vis spectrophotometric analysis. The extracted turmeric dye was used as a sensitizer in the dye sensitized solar cell's (DSSC) photoanode assembly. Nano-crystalline TiO2 was used as a film coating semiconductor material of the photoanode. TiO2 films on ITO glass substrate were prepared by simple doctor blade technique. The influence of the different parameters VOC, JSC, power density, FF, and η% on the photovoltaic characteristics of DSSCs was analyzed. The best energy conversion performance was obtained for 2 h adsorption time of dye on TiO2 nano-porous surface with ethanol extracted dye from dry turmeric.

Preparation, stabilization and characterization of TiO(2) on thin polyethylene films (LDPE). Photocatalytic applications.

PubMed

Zhiyong, Yu; Mielczarski, E; Mielczarski, J; Laub, D; Buffat, Ph; Klehm, U; Albers, P; Lee, K; Kulik, A; Kiwi-Minsker, L; Renken, A; Kiwi, J

2007-02-01

An innovative way to fix preformed nanocrystalline TiO(2) on low-density polyethylene film (LDPE-TiO(2)) is presented. The LDPE-TiO(2) film was able to mediate the complete photodiscoloration of Orange II using about seven times less catalyst than a TiO(2) suspension and proceeded with a photonic efficiency of approximately 0.02. The catalyst shows photostability over long operational periods during the photodiscoloration of the azo dye Orange II. The LDPE-TiO(2) catalyst leads to full dye discoloration under simulated solar light but only to a 30% TOC reduction since long-lived intermediates generated in solution seem to preclude full mineralization of the dye. Physical insight is provided into the mechanism of stabilization of the LDPE-TiO(2) composite during the photocatalytic process by X-ray photoelectron spectroscopy (XPS). The adherence of TiO(2) on LDPE is investigated by electron microscopy (EM) and atomic force microscopy (AFM). The thickness of the TiO(2) film is seen to vary between 1.25 and 1.69 microm for an unused LDPE-TiO(2) film and between 1.31 and 1.50 microm for a sample irradiated 10h during Orange II discoloration pointing out to a higher compactness of the TiO(2) film after the photocatalysis.

Entomotoxicity Assay of Silica, Zinc Oxide, Titanium Dioxide, Aluminium Oxide Nanoparticles on Lipaphis pseudobrassicae

NASA Astrophysics Data System (ADS)

Debnath, Nitai; Das, Sumistha; Brahmachary, R. L.; Chandra, Ramesh; Sudan, Sandeep; Goswami, Arunava

2010-10-01

High volume uses of conventional pesticides end up contaminating ground water and soil with highly toxic pesticide residues. Nano-pesticides and nano-encapsulated pesticides are expected to reduce the volume of application and slow down the fast release kinetics. Nature inspired Diatomaceous Earth (DE) were used to design and fabricate a variety of 15-50 nm size range hydrophilic, hydrophobic and lipophilic SiO2, ZnO, TiO2 (anatase and rutile) and Al2O3 (α and γ) nanoparticles (Nanocides). Mustard aphid (Lipaphis pseudobrassicae) causes devastations on oil producing mustard crops every year in Asia. Due to several distinct adaptations present in insects, tools of Genetics, Plant breeding, Biochemistry and Transgenic technology have not been so far effective. Nano Al2O3 and amorphous nano SiO2 were found to be highly effective and nano TiO2 was moderately effective against L. pseudobrassicae. But nano Al2O3 has deleterious effects on plant growth, whereas non crystalline nano SiO2 has no such adverse effect on plants. Here we present the first report showing that nanocides, especially nano SiO2 can be effectively used to control insect pests.

Synthesis of silver-titanium dioxide nanocomposites for antimicrobial applications

NASA Astrophysics Data System (ADS)

Yang, X. H.; Fu, H. T.; Wang, X. C.; Yang, J. L.; Jiang, X. C.; Yu, A. B.

2014-08-01

Silver-titanium dioxide (Ag-TiO2) nanostructures have attracted increasing attention because of unique functional properties and potential applications in many areas such as photocatalysis, antibacterial, and self-cleaning coatings. In this study, Ag@TiO2 core-shell nanostructures and Ag-decorated TiO2 particles (TiO2@Ag) (the size of these two nanoparticles is ranging from 200-300 nm) have been synthesized by a developed facile but efficient method. These two types of hybrid nanostructures, characterized by various advanced techniques (TEM, XRD, BET and others), exhibit unique functional properties particularly in antibacterial toward Gram negative Escherichia coli, as a case study. Specifically: (i) the TiO2@Ag nanoparticles are superior in bacterial growth inhibition in standard culture conditions (37 °C incubator) to the Ag@TiO2 core-shell ones, in which silver may dominate the antibacterial performance; (ii) while after UV irradiation treatment, the Ag@TiO2 core-shell nanoparticles exhibit better performance in killing grown bacteria than the TiO2@Ag ones, probably because of the Ag cores facilitating charge separation for TiO2, and thus produce more hydroxyl radicals on the surface of the TiO2 particles; and (iii) without UV irradiation, both TiO2@Ag and Ag@TiO2 nanostructures show poor capabilities in killing mature bacteria. These findings would be useful for designing hybrid metal oxide nanocomposites with desirable functionalities in bioapplications in terms of sterilization, deodorization, and water purification.

He+ ion irradiation response of Fe–TiO2 multilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderoglu, O.; Zhou, M. J.; Zhang, J.

2013-04-01

The accumulation of radiation-induced defect clusters and He bubble formation in He+ ion irradiated nanocrystalline TiO2 and Fe–TiO2 multilayer thin films were investigated using transmission electron microscopy (TEM). Prior to ion irradiation it was found that the crystallinity of TiO2 layers depends on the individual layer thickness: While all TiO2 layers are amorphous at 5 nm individual layer thickness, at 100 nm they are crystalline with a rutile polymorph. After He+ irradiation up to ~6 dpa at room temperature, amorphization of TiO2 layers was not observed in both nanocrystalline TiO2 single layers and Fe–TiO2 multilayers. The suppression of radiation-induced amorphizationmore » in TiO2 is interpreted in terms of a high density of defect sinks in these nano-composites in the form of Fe–TiO2 interphase boundaries and columnar grains within each layer with nano-scale intercolumnar porosity. In addition, a high concentration of He is believed to be trapped at these interfaces in the form of sub-nanometer-scale clusters retarding the formation of relatively larger He bubbles that can be resolved in TEM.« less

Minimization of methabenzthiazuron residues in leaching water using amended soils and photocatalytic treatment with TiO2 and ZnO.

PubMed

Fenoll, José; Flores, Pilar; Hellín, Pilar; Hernández, Joaquín; Navarro, Simon

2014-04-01

In the present work, potential groundwater pollution by methabenzthiazuron (MTBU) and the effect of three different amendments (composted sheep manure, composted pine bark and spent coffee grounds) on its mobility were investigated under laboratory conditions. The efficiency of ZnO and TiO2 suspensions in the photocatalytic degradation of MTBU in leaching water was also investigated. The relative and cumulative breakthrough curves were obtained from disturbed soil columns. The presence and/or addition of organic matter drastically reduced the movement of the herbicide. On other hand, photocatalytic experiments showed that the addition of ZnO and TiO2 strongly enhances the degradation rate of this herbicide compared with the results of photolytic experiments under artificial light. ZnO appeared to be more effective in MTBU oxidation than TiO2. The results obtained point to the interest of using organic wastes and heterogeneous photocatalysis for reducing the pollution of groundwater by pesticide drainage. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Generating Color from Polydisperse, Near Micron-Sized TiO2 Particles.

PubMed

Alam, Al-Mahmnur; Baek, Kyungnae; Son, Jieun; Pei, Yi-Rong; Kim, Dong Ha; Choy, Jin-Ho; Hyun, Jerome K

2017-07-19

Single particle Mie calculations of near micron-sized TiO 2 particles predict strong light scattering dominating the visible range that would give rise to a white appearance. We demonstrate that a polydisperse collection of these "white" particles can result in the generation of visible colors through ensemble scattering. The weighted averaging of the scattering over the particle size distribution modifies the sharp, multiple, high order scattering modes from individual particles into broad variations in the collective extinction. These extinction variations are apparent as visible colors for particles suspended in organic solvent at low concentration, or for a monolayer of particles supported on a transparent substrate viewed in front of a white light source. We further exploit the color variations on optical sensitivity to the surrounding environment to promote micron-sized TiO 2 particles as stable and robust agents for detecting the optical index of homogeneous media with high contrast sensitivities. Such distribution-modulated scattering properties provide TiO 2 particles an intriguing opportunity to impart color and optical sensitivity to their widespread electronic and chemical platforms such as antibacterial windows, catalysis, photocatalysis, optical sensors, and photovoltaics.

Facile synthesis of bird's nest-like TiO2 microstructure with exposed (001) facets for photocatalytic degradation of methylene blue

NASA Astrophysics Data System (ADS)

Zhang, Guozhong; Zhang, Shuqu; Wang, Longlu; Liu, Ran; Zeng, Yunxiong; Xia, Xinnian; Liu, Yutang; Luo, Shenglian

2017-01-01

The scrupulous design of hierarchical structure and highly active crystal facets exposure is essential for the creation of photocatalytic system. However, it is still a big challenge for scrupulous design of TiO2 architectures. In this paper, bird's nest-like anatase TiO2 microstructure with exposed highly active (001) surface has been successfully synthesized by a facile one-step solvothermal method. Methylene blue (MB) is chosen as a model pollutant to evaluate photocatalytic activity of as-obtained TiO2 samples. The results show that the photocatalytic activity of the bird's nest-like sample is more excellent than P25 in the degradation of MB due to high specific surface area and highly active (001) crystal facets exposure when tested under simulated solar light. Besides, it can be readily separated from the photocatalytic system by sedimentation after photocatalytic reaction, which is a significant advantage against conventional powder photocatalyst. The bird's nest-like microspheres with novel structure may have potential application in photocatalysis and other fields.

Effects of titanium dioxide nanoparticles derived from consumer products on the marine diatom Thalassiosira pseudonana

EPA Science Inventory

Increased manufacture of TiO2 nano-products has caused concern about the potential toxicity of these products to the environment and in public health. Identification and confirmation of the presence of TiO2 nanoparticles derived from consumer products as opposed to industrial TiO...

A novel synthesis method for TiO2 particles with magnetic Fe3O4 cores.

PubMed

Dong, Qi; Zhang, Keqiang; An, Yi

2014-01-01

TiO2@(AC/Fe3O4) (AC is activated carbon) was prepared by using AC and Fe3O4 as joint support. The morphological features, crystal structure, and magnetism of the final product were characterized. The results indicate that TiO2 particles formed on the surface of AC and Fe3O4; the sizes of TiO2 and Fe3O4 were 0.5 and 0.7 μm respectively, and that of AC fell within a wide range. The highly crystalline cubic structures of the TiO2 particles was in accord with the standard X-ray diffractometry spectrum of magnetite and anatase. The maximum saturation magnetization of TiO2@(AC/Fe3O4) was 75 emu g(-1), which was enough to support magnetic recovery. The rate of methylene blue (MB) removal photocatalyzed by TiO2@(AC/Fe3O4) was higher by 50% than that achieved with AC/Fe3O4 photocatalysis, and similar to that achieved with TiO2@AC. The removal rate (kobs) decreased drastically from 1.77 × 10(-2) to 9.36 × 10(-3)min(-1) when the initial concentration of MB solution increased from 2.0 to 5.0 mg L(-1). The kobs value increased from 9.41 × 10(-3) to 1.34 × 10(-2)min(-1) with increasing photocatalyst dosage from 0.2 to 1.0 g, then slightly decreased to 1.33 × 10(-2)min(-1) at 2.0 g dosage.

Development of solar-driven electrochemical and photocatalytic water treatment system using a boron-doped diamond electrode and TiO2 photocatalyst.

PubMed

Ochiai, Tsuyoshi; Nakata, Kazuya; Murakami, Taketoshi; Fujishima, Akira; Yao, Yanyan; Tryk, Donald A; Kubota, Yoshinobu

2010-02-01

A high-performance, environmentally friendly water treatment system was developed. The system consists mainly of an electrochemical and a photocatalytic oxidation unit, with a boron-doped diamond (BDD) electrode and TiO(2) photocatalyst, respectively. All electric power for the mechanical systems and the electrolysis was able to be provided by photovoltaic cells. Thus, this system is totally driven by solar energy. The treatment ability of the electrolysis and photocatalysis units was investigated by phenol degradation kinetics. An observed rate constant of 5.1 x 10(-3)dm(3)cm(-2)h(-1) was calculated by pseudo-first-order kinetic analysis for the electrolysis, and a Langmuir-Hinshelwood rate constant of 5.6 microM(-1)min(-1) was calculated by kinetic analysis of the photocatalysis. According to previous reports, these values are sufficient for the mineralization of phenol. In a treatment test of river water samples, large amounts of chemical and biological contaminants were totally wet-incinerated by the system. This system could provide 12L/day of drinking water from the Tama River using only solar energy. Therefore, this system may be useful for supplying drinking water during a disaster. (c) 2009 Elsevier Ltd. All rights reserved.

Photolytic and photocatalytic degradation of quinclorac in ultrapure and paddy field water: identification of transformation products and pathways.

PubMed

Pareja, Lucía; Pérez-Parada, Andrés; Agüera, Ana; Cesio, Verónica; Heinzen, Horacio; Fernández-Alba, Amadeo R

2012-05-01

Quinclorac (QNC) is an effective but rather persistent herbicide commonly used in rice production. This herbicide presents a mean persistence in the environment so its residues are considered of environmental relevance. However, few studies have been conducted to investigate its environmental behavior and degradation. In the present work, direct photolysis and TiO(2) photocatalysis of the target compound in ultrapure and paddy field water were investigated. After 10h photolysis in ultrapure water, the concentration of QNC declined 26% and 54% at 250 and 700 W m(-2), respectively. However, the amount of quinclorac in paddy field water remained almost constant under the same irradiation conditions. QNC dissipated completely after 40 min of TiO(2) photocatalysis in ultrapure water, whereas 130 min were necessary to degrade 98% of the initial concentration in paddy field water. Possible QNC photolytic and photocatalytic degradation pathways are proposed after structure elucidation of the main transformation products, through liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry and exact mass measurements. Pyridine ring hydroxylation at C-9 followed by ring opening and/or oxidative dechlorination were the key steps of QNC degradation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Standalone anion- and co-doped titanium dioxide nanotubes for photocatalytic and photoelectrochemical solar-to-fuel conversion.

PubMed

Ding, Yuchen; Nagpal, Prashant

2016-10-14

Several strategies are currently being investigated for conversion of incident sunlight into renewable sources of energy, and photocatalytic or photoelectrochemical production of solar fuels can provide an important alternative. Titanium dioxide (TiO 2 ) has been heavily investigated as a material of choice due to its excellent optoelectronic properties and stability, and anion-doping proposed as a pathway to improve light absorption as well as improving the efficiency of oxygen production. While several studies have used morphological tuning, elemental doping, and surface engineering in TiO 2 to extend its absorption, there is a need to optimize simultaneously charge transport and improve interfacial chemical reaction kinetics. Here we show anion-doped (nitrogen, carbon) standalone TiO 2 nanotube membranes that absorb visible light for the water-splitting reaction, using both wireless (photocatalysis) and wired (photoelectrochemical) solar-to-fuel conversion (STFC) cells. Using simulated solar radiation, we show generation of hydrogen as a solar fuel using visible light photocatalysis. Furthermore, using a model we elucidate detailed photophysics and photoelectrochemical properties of these nanotubes, and explain the kinetics of photogenerated charge carriers following light absorption. We show that while visible light induces a superlinear photoresponse for catalytic reduction and may benefit from higher incident light intensity, ultraviolet light shows a linear photoresponse and saturation with higher light flux due to trapping of photogenerated charges (mainly electrons). These results can have important implications for design of other metal-oxide membranes for solar fuel generation, and appropriate design of dopants and induced energy levels in these photocatalysts.

A weak-light-responsive TiO2/g-C3N4 composite film: photocatalytic activity under low-intensity light irradiation.

PubMed

Wang, Peifang; Guo, Xiang; Rao, Lei; Wang, Chao; Guo, Yong; Zhang, Lixin

2018-05-10

A TiO 2 /g-C 3 N 4 composite photocatalytic film was prepared by in situ synthesis method and its photocatalytic capability under weak-visible-light condition was studied. The co-precursor with different ratio of melamine and TiO 2 sol-gel precursor were treated using ultrasonic mixing, physical deposition, and co-sintering method to form the smooth, white-yellow, and compact TiO 2 /g-C 3 N 4 composite films. The prepared TiO 2 /g-C 3 N 4 materials were characterized by SEM, TEM, EDS, XRD, BET, VBXPS, and UV-vis diffuse reflectance spectra. The results of composite showed that TiO 2 and g-C 3 N 4 have close interfacial connections which are favorable to charge transfer between these two semiconductors with suitable band structure, g-C 3 N 4 retard the anatase-to-rutile phase transition of TiO 2 significantly, the specific surface area were increased with g-C 3 N 4 ratio raised. Under weak-light irradiation, composite films photocatalytic experiments exhibited RhB removal efficiency approaching 90% after three recycles. Powders suspension degradation experiments revealed the removal efficiency of TiO 2 /g-C 3 N 4 (90.8%) was higher than pure TiO 2 (52.1%) and slightly lower than pure g-C 3 N 4 (96.6%). By control experiment, the enhanced photocatalysis is ascribed to the combination of TiO 2 and g-C 3 N 4 , which not only produced thin films with greater stability but also formed heterojunctions that can be favorable to charge transfer between these two semiconductors with suitable band structure. This study presents the potential application of photocatalytic film in the wastewater treatment under weak-light situation.

Degradation of trichloroethylene by photocatalysis in an internally circulating slurry bubble column reactor.

PubMed

Jeon, Jin Hee; Kim, Sang Done; Lim, Tak Hyoung; Lee, Dong Hyun

2005-08-01

The effects of initial trichloroethylene (TCE) concentration, recirculating liquid flow rate and gas velocity on photodegradation of TCE have been determined in an internally circulating slurry bubble column reactor (0.15m-ID x 0.85 m-high). Titanium dioxide (TiO2) powder was employed as a photocatalyst and the optimum loading of TiO2 in the present system is found to be approximately 0.2 wt%. The stripping fraction of TCE by air flow increases but photodegradation fraction of TCE decreases with increasing the initial TCE concentration, recirculating liquid flow rate and gas velocity. The average removal efficiency of TCE is found to be approximately 97% in an internally circulating slurry bubble column reactor.

Visible-Light-Responsive Catalyst Development for Volatile Organic Carbon Remediation Project

NASA Technical Reports Server (NTRS)

Zeitlin, Nancy; Hintze, Paul E.; Coutts, Janelle

2015-01-01

Photocatalysis is a process in which light energy is used to 'activate' oxidation/reduction reactions. Unmodified titanium dioxide (TiO2), a common photocatalyst, requires high-energy UV light for activation due to its large band gap (3.2 eV). Modification of TiO2 can reduce this band gap, leading to visible-light-responsive (VLR) photocatalysts. These catalysts can utilize solar and/or visible wavelength LED lamps as an activation source, replacing mercury-containing UV lamps, to create a "greener," more energy-efficient means for air and water revitalization. Recently, KSC developed several VLR catalysts that, on preliminary evaluation, possessed high catalytic activity within the visible spectrum; these samples out-performed existing commercial VLR catalysts.

Energy efficiency for the removal of non-polar pollutants during ultraviolet irradiation, visible light photocatalysis and ozonation of a wastewater effluent.

PubMed

Santiago-Morales, Javier; Gómez, María José; Herrera-López, Sonia; Fernández-Alba, Amadeo R; García-Calvo, Eloy; Rosal, Roberto

2013-10-01

This study aims to assess the removal of a set of non-polar pollutants in biologically treated wastewater using ozonation, ultraviolet (UV 254 nm low pressure mercury lamp) and visible light (Xe-arc lamp) irradiation as well as visible light photocatalysis using Ce-doped TiO2. The compounds tracked include UV filters, synthetic musks, herbicides, insecticides, antiseptics and polyaromatic hydrocarbons. Raw wastewater and treated samples were analyzed using stir-bar sorptive extraction coupled with comprehensive two-dimensional gas chromatography (SBSE-CG × GC-TOF-MS). Ozone treatment could remove most pollutants with a global efficiency of over 95% for 209 μM ozone dosage. UV irradiation reduced the total concentration of the sixteen pollutants tested by an average of 63% with high removal of the sunscreen 2-ethylhexyl trans-4-methoxycinnamate (EHMC), the synthetic musk 7-acetyl-1,1,3,4,4,6-hexamethyltetrahydronaphthalene (tonalide, AHTN) and several herbicides. Visible light Ce-TiO2 photocatalysis reached ~70% overall removal with particularly high efficiency for synthetic musks. In terms of power usage efficiency expressed as nmol kJ(-1), the results showed that ozonation was by far the most efficient process, ten-fold over Xe/Ce-TiO2 visible light photocatalysis, the latter being in turn considerably more efficient than UV irradiation. In all cases the efficiency decreased along the treatments due to the lower reaction rate at lower pollutant concentration. The use of photocatalysis greatly improved the efficiency of visible light irradiation. The collector area per order decreased from 9.14 ± 5.11 m(2) m(-3) order(-1) for visible light irradiation to 0.16 ± 0.03 m(2) m(-3) order(-1) for Ce-TiO2 photocatalysis. The toxicity of treated wastewater was assessed using the green alga Pseudokirchneriella subcapitata. Ozonation reduced the toxicity of treated wastewater, while UV irradiation and visible light photocatalysis limited by 20-25% the algal growth due to the accumulation of reaction by-products. Three transformation products were identified and tracked along the treatments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Assessment of the effectiveness of combined adsorption and photocatalysis for removal of the herbicide isoproturon

NASA Astrophysics Data System (ADS)

Dávila-Jiménez, Martín M.; Elizalde-González, María P.; García-Díaz, Esmeralda; Santes-Aquino, Alba M.

2016-02-01

The aim of this research was to decompose isoproturon and adsorb its photoproducts by developing a carbon material from a juice industry waste. Carbon-TiO2 hybrid materials were obtained by impregnating carbonized guava seeds with TiO2 gels prepared from TiOSO4ṡxH2O and NH4OH using glycerol as a binder and thermally treating the materials at 500 °C. Raman studies confirmed the anatase phase of TiO2. SEM images showed isolated TiO2 agglomerates firmly attached to the carbon surface. The adsorption behavior of isoproturon on guava carbon was studied and yielded S-type adsorption isotherms. The photocatalytic activities of the prepared hybrid materials were monitored to study the kinetics and elimination process both of the herbicide and its photoproducts. The reaction was monitored by UV-Vis spectrophotometry, LC-DAD and LC-MS, enabling identification of some intermediate species. Among the photoproducts produced by carbon-TiO2 hybrid materials, amino-isopropylphenol was detected.

Electrochemical characterization of nano-sized Pd-based catalysts as cathode materials in direct methanol fuel cells.

PubMed

Choi, M; Han, C; Kim, I T; An, J C; Lee, J J; Lee, H K; Shim, J

2011-01-01

To improve the catalytic activity of palladium (Pd) as a cathode catalyst in direct methanol fuel cells (DMFCs), we prepared palladium-titanium oxide (Pd-TiO2) catalysts which the Pd and TiO2 nanoparticles were simultaneously impregnated on carbon. We selected Pd and TiO2 as catalytic materials because of their electrochemical stability in acid solution. The crystal structure and the loading amount of Pd and TiO2 on carbon were characterized by X-ray diffraction (XRD) and energy dispersive X-ray microanalysis (EDX). The electrochemical characterization of Pd-TiO2/C catalysts for the oxygen reduction reaction was carried out in half and single cell systems. The catalytic activities of the Pd-TiO2 catalysts were strongly influenced by the TiO2 content. In the single cell test, the Pd-TiO2 catalysts showed very comparable performance to the Pt catalyst.

UV-responsive nano-sponge for oil absorption and desorption

PubMed Central

Kim, Do Hyun; Jung, Min Chan; Cho, So-Hye; Kim, Sang Hoon; Kim, Ho-Young; Lee, Heon Ju; Oh, Kyu Hwan; Moon, Myoung-Woon

2015-01-01

Controlled surface wettability for oil has been intensively studied to remove industrial oil waste or oil spill pollution from seas or rivers. In particular, external stimuli-induced special wetting materials, such as photo-responsive TiO2, have attracted considerable attention for oil-water separation. In this study, a novel method is reported to fabricate a nano-sponge which is composed of hydrophobic hydrocarbon and hydrophilic TiO2 nanoparticles for oil absorption or desorption that are responsive to UV irradiation. The hydrocarbon in the nano-sponge could selectively absorb oil from water, whereas the absorbed oil is released into the water by TiO2 in response to UV irradiation. The nano-sponge functionalized porous polydimethylsiloxane released more than 98% of the absorbed crude oil with UV irradiation and air-bubbling. It could be continuously reused while maintaining a high absorption capacity and desorption efficiency without incurring secondary air or water pollution. This smart oil absorption/desorption methodology with excellent selectivity and recyclability with almost perfect removal of absorbed oil can be applied for oil-water separation, oil spill cleanup and reuse of spilled oil. PMID:26260470

Dispersions of geometric TiO2 nanomaterials and their toxicity to RPMI 2650 nasal epithelial cells

NASA Astrophysics Data System (ADS)

Tilly, Trevor B.; Kerr, Lei L.; Braydich-Stolle, Laura K.; Schlager, John J.; Hussain, Saber M.

2014-11-01

Titanium dioxide (TiO2) based nanofilaments—nanotube, nanowire, nanorod—have gained interest for industrial, electrical, and as of recent, medical applications due to their superior performance over TiO2 nanoparticles. Safety assessment of these nanomaterials is critical to protect workers, patients, and bystanders as these technologies become widely implemented. Additionally, TiO2 based nanofilaments can easily be inhaled by humans and their high aspect ratio, much like asbestos fibers, may make them toxic in the respiratory system. The tendency of TiO2 nanofilaments to aggregate makes evaluating their nanotoxicity difficult and the results controversial, because incomplete dispersion results in larger particle sizes that are no longer in the nano dimensional size range. TiO2 nanofilaments are aggregated and difficult to disperse homogeneously in solution by conventional methods, such as sonication and vortexing. In this study, a microfluidic device was utilized to produce stable, homogeneous dosing solutions necessary for in vitro toxicity evaluation by eliminating any toxicity caused by aggregated TiO2 nanomaterials. The toxicity results could then be directly correlated to the TiO2 nanostructure itself. The toxicity of four TiO2 nanogeometries—nanotube, nanowire, nanorod, and nanoparticle—were assessed in RPMI 2650 human nasal epithelial cells at representative day, week, and month in vitro exposure dosages of 10, 50, 100 μg/ml, respectively. All TiO2 based nanomaterials dispersed by the microfluidic method were nontoxic to RPMI 2650 cells at the concentrations tested, whereas higher concentrations of 100 μg/ml of nanowires and nanotubes dispersed by sonication reduced viability up to 27 %, indicating that in vitro toxicity results may be controlled by the dispersion of dosing solutions.

Voltammetric sensor for buzepide methiodide determination based on TiO2 nanoparticle-modified carbon paste electrode.

PubMed

Kalanur, Shankara S; Seetharamappa, Jaldappagari; Prashanth, S N

2010-07-01

In this work, we have prepared nano-material modified carbon paste electrode (CPE) for the sensing of an antidepressant, buzepide methiodide (BZP) by incorporating TiO2 nanoparticles in carbon paste matrix. Electrochemical studies indicated that the TiO2 nanoparticles efficiently increased the electron transfer kinetics between drug and the electrode. Compared with the nonmodified CPE, the TiO2-modified CPE greatly enhances the oxidation signal of BZP with negative shift in peak potential. Based on this, we have proposed a sensitive, rapid and convenient electrochemical method for the determination of BZP. Under the optimized conditions, the oxidation peak current of BZP is found to be proportional to its concentration in the range of 5 x 10(-8) to 5 x 10(-5)M with a detection limit of 8.2 x 10(-9)M. Finally, this sensing method was successfully applied for the determination of BZP in human blood serum and urine samples with good recoveries. 2010 Elsevier B.V. All rights reserved.

Enhancement of photocatalytic degradation of furfural and acetophenone in water media using nano-TiO2-SiO2 deposited on cementitious materials.

PubMed

Soltan, Sahar; Jafari, Hoda; Afshar, Shahrara; Zabihi, Omid

2016-10-01

In the present study, silicon dioxide (SiO 2 ) nanoparticles were loaded to titanium dioxide (TiO 2 ) nano-particles by sol-gel method to make a high porosity photocatalyst nano-hybrid. These photocatalysts were synthesized using titanium tetrachloride and tetraethyl orthosilicate as titanium and silicon sources, respectively, and characterized by X-ray powder diffraction (XRD) and scanning electron microscope methods. Subsequently, the optimizations of the component and operation conditions were investigated. Then, nano-sized TiO 2 and TiO 2 -SiO 2 were supported on concrete bricks by the dip coating process. The photocatalytic activity of nano photocatalysts under UV irradiation was examined by studying the decomposition of aqueous solutions of furfural and acetophenone (10 mg/L) as model of organic pollutants to CO 2 and H 2 O at room temperature. A decrease in the concentration of these pollutants was assayed by using UV-visible absorption, gas chromatography technique, and chemical oxygen demand. The removal of these pollutants from water using the concrete-supported photocatalysts under UV irradiation was performed with a greater efficiency, which does not require an additional separation stage to recover the catalyst. Therefore, it would be applicable to use in industrial wastewater treatment at room temperature and atmospheric pressure within the optimized pH range.

Method for simultaneous imaging of endogenous low molecular weight metabolites in mouse brain using TiO2 nanoparticles in nanoparticle-assisted laser desorption/ionization-imaging mass spectrometry.

PubMed

Shrivas, Kamlesh; Hayasaka, Takahiro; Sugiura, Yuki; Setou, Mitsutoshi

2011-10-01

We report the detection of a group of endogenous low molecular weight metabolites (LMWM) in mouse brain (80-500 Da) using TiO(2) nanoparticles (NPs) in nanoparticle-assisted laser desorption/ionization-imaging mass spectrometry (Nano-PALDI-IMS) without any washing and separation step prior to MS analysis. The identification of metabolites using TiO(2) NPs was compared with a conventional organic matrix 2,5-dihydroxybenzoic acid (DHB) where signals of 179 molecules were specific to TiO(2) NPs, 4 were specific to DHB, and 21 were common to both TiO(2) NPs and DHB. The use of TiO(2) NPs enabled the detection of a higher number of LMWM as compared to DHB and gold NPs as a matrix. This approach is a simple, inexpensive, washing, and separation free for imaging and identification of LMWM in mouse brain. We believe that the biochemical information from distinct regions of the brain using a Nano-PALDI-IMS will be helpful in elucidating the imbalances linked with diseases in biomedical samples.

Effects of Structural Properties of Electrospun TiO2 Nano-fiber Meshes on their Osteogenic Potential

PubMed Central

Wang, Xiaokun; Gittens, Rolando A.; Song, Rosemary; Tannenbaum, Rina; Olivares-Navarrete, Rene; Schwartz, Zvi; Chen, Haifeng; Boyan, Barbara D.

2011-01-01

Ideal outcomes in the field of tissue engineering and regenerative medicine involve biomaterials that can enhance cell differentiation and production of local factors for natural tissue regeneration without the use of systemic drugs. Biomaterials typically used in tissue engineering applications include polymeric scaffolds that mimic the 3-D structural environment of the native tissue, but these are often functionalized with proteins or small peptides to improve their biological performance. For bone applications, titanium (Ti) implants, or more appropriately the titania (TiO2) passive oxide layer formed on their surface, have been shown to enhance osteoblast differentiation in vitro and to promote osseointegration in vivo. In this study we evaluated the effect on osteoblast differentiation of pure TiO2 nano-fiber meshes with different surface micro-roughness and nano-fiber diameters, prepared by the electrospinning method. MG63 cells were seeded on TiO2 meshes, and cell number, differentiation markers and local factor production were analyzed. The results showed that cells grew throughout the entire surfaces and with similar morphology in all groups. Cell number was sensitive to surface micro-roughness, whereas cell differentiation and local factor production was regulated by both surface roughness and nano-fiber diameter. These results indicate that scaffold structural cues alone can be used to drive cell differentiation and create an osteogenic environment without the use of exogenous factors. PMID:22075122

Design of a highly sensitive ethanol sensor using a nano-coaxial p-Co3O4/n-TiO2 heterojunction synthesized at low temperature.

PubMed

Liang, Y Q; Cui, Z D; Zhu, S L; Li, Z Y; Yang, X J; Chen, Y J; Ma, J M

2013-11-21

In this paper, we describe the design, fabrication and gas-sensing tests of nano-coaxial p-Co3O4/n-TiO2 heterojunction. Specifically, uniform TiO2 nanotubular arrays have been assembled by anodization and used as templates for generation of the Co3O4 one-dimensional nanorods. The structure morphology and composition of as-prepared products have been characterized by SEM, XRD, TEM, and XPS. A possible growth mechanism governing the formation of such nano-coaxial heterojunctions is proposed. The TiO2 nanotube sensor shows a normal n-type response to reducing ethanol gas, whereas TiO2-Co3O4 exhibits p-type response with excellent sensing performances. This conversion of sensing behavior can be explained by the formation of p-n heterojunction structures. A possible sensing mechanism is also illustrated, which can provide theoretical guidance for the further development of advanced gas-sensitive materials with p-n heterojunction.

Carbon and nitrogen co-doped bowl-like Au/TiO2 nanostructures with tunable size for enhanced visible-light-driven photocatalysis

NASA Astrophysics Data System (ADS)

Li, Yayuan; Cao, Shubo; Zhang, Ang; Zhang, Chen; Qu, Ting; Zhao, Yongbin; Chen, Aihua

2018-07-01

It is of great importance to extend the UV response of anatase TiO2 into the visible light range for the practical applications. Here, a facile rout to carbon and nitrogen co-doped, Au loaded bowl-like TiO2 nanostructures with tunable size are proposed by using self-assembled polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) spherical micelles as templates. Amphiphilic PS-b-P4VP self-assembles to form PS@P4VP core-shell spherical micelles with P4VP as the out layer in an evaporable mixed solvents of ethanol/tetrahydrofuran (THF). The size of uniform PS@P4VP spherical micelles can be precisely tuned in the range of a few nm to several hundred nm by controlling the molecular composition of the BCPs. Bowl-like TiO2 nanostructures with a replicate size loaded with highly dispersed Au nanoparticles (NPs) of ∼5 nm in diameter are fabricated from these spherical micelles because of strong complex ability of pyridine groups. PS-b-P4VP provides carbon and nitrogen sources to dope the resulting samples simultaneously. The special carbon and nitrogen co-doped bowl-like Au/TiO2 nanostructures exhibit much higher photocatalytic activity in the photodegradation of rhodamine B (RhB) compared to Au/P25 under visible light irradiation. Furthermore, the photocatalytic activity is significantly influenced by the BCP molecular composition due to different surface area and loading capacity of the resulting samples. This study provides a facile way to synthesize multi-element doped hollow or bowl-like nanoparticles with tunable size in the nanometer range which have potential application at photocatalysis, oxygen reduction reaction, etc.

Up-conversion nanoparticles sensitized inverse opal photonic crystals enable efficient water purification under NIR irradiation

NASA Astrophysics Data System (ADS)

Zhang, Yuanyuan; Wang, Lili; Ma, Xiumei; Ren, Junfeng; Sun, Qinxing; Shi, Yongsheng; Li, Lin; Shi, Jinsheng

2018-03-01

A novel porous monolayer inverse opal (IO) structure was prepared by a simple sol-gel method combined with a self-assembly PS photonic crystal (PC) as template. By prolonging deposition time of PS spheres, three-dimensional multilayer TiO2 IOPC was also fabricated. Up-conversion nanoparticles (UCNPs) were selected to sensitize TiO2 IOPCs. Photocatalytic activity of as-prepared materials was investigated by disinfection of bacteria and organic pollutant degradation. Under NIR light irradiation, a large improvement in bacterial inactivation and photodegradation efficiency could be seen for NYF/TiO2 composites in comparison with other samples. As for monolayer NYF/TiO2, water disinfection of 100% inactivation of bacteria is realized within 11 h and kinetic constant of RhB degradation is 0.133 h-1, which is about 10 times higher than that of pure TiO2 IOPCs. Reasons of enhanced photocatalytic activity were systematically investigated and a possible mechanism for NIR-driven photocatalysis was reasonably proposed.

Atomically engineered epitaxial anatase TiO 2 metal-semiconductor field-effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Brian S. Y.; Minohara, Makoto; Hikita, Yasuyuki

Here, anatase TiO 2 is a promising material for a vast array of electronic, energy, and environmental applications, including photocatalysis, photovoltaics, and sensors. A key requirement for these applications is the ability to modulate its electrical properties without dominant dopant scattering and while maintaining high carrier mobility. Here, we demonstrate the room temperature field-effect modulation of the conducting epitaxial interface between anatase TiO 2 and LaAlO 3 (001), which arises for LaO-terminated LaAlO 3, while the AlO 2-terminated interface is insulating. This approach, together with the metal-semiconductor field-effect transistor geometry, naturally bypasses the gate/channel interface traps, resulting in a highmore » field-effect mobility μ FE of 3.14 cm 2 (V s) –1 approaching 98% of the corresponding Hall mobility μ Hall. Accordingly, the channel conductivity is modulated over 6 orders of magnitude over a gate voltage range of ~4 V.« less

Mechanism of phenol photodegradation in the presence of pure and modified-TiO2: A review.

PubMed

Grabowska, Ewelina; Reszczyńska, Joanna; Zaleska, Adriana

2012-11-01

In recent years, the application of heterogeneous photocatalytic water purification processes has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible-light spectrum. By far, titania has played a much larger role in this scenario compared to other semiconductor photocatalysts due to its costly effectiveness, inert nature and photostability. A substantial amount of research has focused on the enhancement of TiO(2) photocatalysis by modification with metal, non-metal and ion doping. This paper aims to review and summarize the recent works on the titanium dioxide (TiO(2)) photocatalytic oxidation of phenol and discusses various mechanisms of phenol photodegradation (indicating the intermediates products) and formation of OH radicals. Phenol degradation pathway in both systems, TiO(2)/UV and doped-TiO(2)/Vis, are described. Copyright © 2012 Elsevier Ltd. All rights reserved.

Atomically engineered epitaxial anatase TiO 2 metal-semiconductor field-effect transistors

DOE PAGES

Kim, Brian S. Y.; Minohara, Makoto; Hikita, Yasuyuki; ...

2018-03-26

Here, anatase TiO 2 is a promising material for a vast array of electronic, energy, and environmental applications, including photocatalysis, photovoltaics, and sensors. A key requirement for these applications is the ability to modulate its electrical properties without dominant dopant scattering and while maintaining high carrier mobility. Here, we demonstrate the room temperature field-effect modulation of the conducting epitaxial interface between anatase TiO 2 and LaAlO 3 (001), which arises for LaO-terminated LaAlO 3, while the AlO 2-terminated interface is insulating. This approach, together with the metal-semiconductor field-effect transistor geometry, naturally bypasses the gate/channel interface traps, resulting in a highmore » field-effect mobility μ FE of 3.14 cm 2 (V s) –1 approaching 98% of the corresponding Hall mobility μ Hall. Accordingly, the channel conductivity is modulated over 6 orders of magnitude over a gate voltage range of ~4 V.« less

Low temperature RF plasma nitriding of self-organized TiO2 nanotubes for effective bandgap reduction

NASA Astrophysics Data System (ADS)

Bonelli, Thiago Scremin; Pereyra, Inés

2018-06-01

Titanium dioxide is a widely studied semiconductor material found in many nanostructured forms, presenting very interesting properties for several applications, particularly photocatalysis. TiO2 nanotubes have a high surface-to-volume ratio and functional electronic properties for light harvesting. Despite these manifold advantages, TiO2 photocatalytic activity is limited to UV radiation due to its large band gap. In this work, TiO2 nanotubes produced by electrochemical anodization were submitted to plasma nitriding processes in a PECVD reactor. The plasma parameters were evaluated to find the best conditions for gap reduction, in order to increase their photocatalytic activity. The pressure and RF power density were varied from 0.66 to 2.66 mbar and 0.22 to 3.51 W/cm2 respectively. The best gap reduction, to 2.80 eV, was achieved using a pressure of 1.33 mbar and 1.75 W/cm2 RF power at 320 °C, during a 2-h process. This leads to a 14% reduction in the band gap value and an increase of 25.3% in methylene blue reduction, doubling the range of solar photons absorption from 5 to 10% of the solar spectrum.

Effects of titanium nanotubes on the osseointegration, cell differentiation, mineralisation and antibacterial properties of orthopaedic implant surfaces.

PubMed

Su, E P; Justin, D F; Pratt, C R; Sarin, V K; Nguyen, V S; Oh, S; Jin, S

2018-01-01

The development and pre-clinical evaluation of nano-texturised, biomimetic, surfaces of titanium (Ti) implants treated with titanium dioxide (TiO 2 ) nanotube arrays is reviewed. In vitro and in vivo evaluations show that TiO 2 nanotubes on Ti surfaces positively affect the osseointegration, cell differentiation, mineralisation, and anti-microbial properties. This surface treatment can be superimposed onto existing macro and micro porous Ti implants creating a surface texture that also interacts with cells at the nano level. Histology and mechanical pull-out testing of specimens in rabbits indicate that TiO 2 nanotubes improves bone bonding nine-fold (p = 0.008). The rate of mineralisation associated with TiO 2 nanotube surfaces is about three times that of non-treated Ti surfaces. In addition to improved osseointegration properties, TiO 2 nanotubes reduce the initial adhesion and colonisation of Staphylococcus epidermidis Collectively, the properties of Ti implant surfaces enhanced with TiO 2 nanotubes show great promise. Cite this article: Bone Joint J 2018;100-B(1 Supple A):9-16. ©2018 The British Editorial Society of Bone & Joint Surgery.

Influence of energy band alignment in mixed crystalline TiO2 nanotube arrays: good for photocatalysis, bad for electron transfer

NASA Astrophysics Data System (ADS)

Mohammadpour, Raheleh

2017-12-01

Despite the wide application ranges of TiO2, the precise explanation of the charge transport dynamic through a mixed crystal phase of this semiconductor has remained elusive. Here, in this research, mixed-phase TiO2 nanotube arrays (TNTAs) consisting of anatase and 0-15% rutile phases has been formed through various annealing processes and employed as a photoelectrode of a photovoltaic cell. Wide ranges of optoelectronic experiments have been employed to explore the band alignment position, as well as the depth and density of trap states in TNTAs. Short circuit potential, as well as open circuit potential measurements specified that the band alignment of more than 0.2 eV exists between the anatase and rutile phase Fermi levels, with a higher electron affinity for anatase; this can result in a potential barrier in crystallite interfaces and the deterioration of electron mobility through mixed phase structures. Moreover, a higher density of shallow localized trap states below the conduction band with more depth (133 meV in anatase to 247 meV in 15% rutile phase) and also deep oxygen vacancy traps have been explored upon introducing the rutile phase. Based on our results, employing TiO2 nanotubes as just the electron transport medium in mixed crystalline phases can deteriorate the charge transport mechanism, however, in photocatalytic applications when both electrons and holes are present, a robust charge separation in crystalline anatase/rutile interphases will result in better performances.

Sonosynthesis of nano TiO2 on wool using titanium isopropoxide or butoxide in acidic media producing multifunctional fabric.

PubMed

Behzadnia, Amir; Montazer, Majid; Rashidi, Abousaeid; Rad, Mahnaz Mahmoudi

2014-09-01

This study presents a novel idea to prepare nanocrystalline structure of TiO2 under ambient pressure at 60-65 °C using in situ sonochemical synthesis by hydrolysis of either titanium isopropoxide or titanium butoxide in an acidic aqueous solution. The nano titanium dioxide coated wool fabrics possess significant antibacterial/antifungal activity and self-cleaning property by discoloring Methylene blue stain under sunlight irradiation. This process has no negative effect on cytotoxicity and tensile strength of the sonotreated fabric even reduces alkaline solubility and photoyellowing and improves hydrophilicity. More titanium isopropoxide or titanium butoxide as a precursor led to higher photocatalytic activities of the treated fabrics. Also introducing more ethanol improved the adsorption of TiO2 on the wool fabric surface leading to enhanced photocatalytic activity. EDS and XRD patterns, SEM images, X-ray mapping confirmed the presence of nano TiO2 particles on the fabric surface. The role of both solvent and precursor concentrations on the various properties of the fabric was investigated and the optimized conditions were obtained using response surface methodology. Copyright © 2014 Elsevier B.V. All rights reserved.

Virus inactivation by silver doped titanium dioxide nanoparticles for drinking water treatment.

PubMed

Liga, Michael V; Bryant, Erika L; Colvin, Vicki L; Li, Qilin

2011-01-01

Photocatalytic inactivation of viruses and other microorganisms is a promising technology that has been increasingly utilized in recent years. In this study, photocatalytic silver doped titanium dioxide nanoparticles (nAg/TiO(2)) were investigated for their capability of inactivating Bacteriophage MS2 in aqueous media. Nano-sized Ag deposits were formed on two commercial TiO(2) nanopowders using a photochemical reduction method. The MS2 inactivation kinetics of nAg/TiO(2) was compared to the base TiO(2) material and silver ions leached from the catalyst. The inactivation rate of MS2 was enhanced by more than 5 fold depending on the base TiO(2) material, and the inactivation efficiency increased with increasing silver content. The increased production of hydroxyl free radicals was found to be responsible for the enhanced viral inactivation. Copyright © 2010 Elsevier Ltd. All rights reserved.

Biocompatibility of Mg Ion Doped Hydroxyapatite Films on Ti-6Al-4V Surface by Electrochemical Deposition.

PubMed

Lee, Kang; Choe, Han-Cheol

2016-02-01

In this study, we prepared magnesium (Mg) doped nano-phase hydroxyapatite (HAp) films on the TiO2 nano-network surface using electrochemical deposition method. Ti-6Al-4V ELI surface was anodized in 5 M NaOH solution at 0.3 A for 10 min. Nano-network TiO2 surface were formed by these anodization steps which acted as templates and anchorage for growth of the Mg doped HAp during subsequent pulsed electrochemical deposition process at 85 degrees C. The phase and morphologies of HAp deposits were influenced by the Mg ion concentration.

Fabrication of predominantly Mn4+ -doped TiO2 nanoparticles under equilibrium conditions and their application as visible-light photocatalyts.

PubMed

Wang, Lijie; Fan, Jiajie; Cao, Zetan; Zheng, Yichao; Yao, Zhiqiang; Shao, Guosheng; Hu, Junhua

2014-07-01

The chemical state of a transition-metal dopant in TiO(2) can intrinsically determine the performance of the doped material in applications such as photocatalysis and photovoltaics. In this study, manganese-doped TiO2 is fabricated by a near-equilibrium process, in which the TiO(2) precursor powder precipitates from a hydrothermally obtained transparent mother solution. The doping level and subsequent thermal treatment influence the morphology and crystallization of the TiO(2) samples. FTIR spectroscopy and X-ray photoelectron spectroscopy analyses indicate that the manganese dopant is substitutionally incorporated by replacing Ti(4+) cations. The absorption band edge can be gradually shifted to 1.8 eV by increasing the nominal manganese content to 10 at %. Manganese atoms doped into the titanium lattice are associated with the dominant 4+ valence oxidation state, which introduces two curved, intermediate bands within the band gap and results in a significant enhancement in photoabsorption and the quantity of photogenerated hydroxyl radicals. Additionally, the high photocatalytic performance of manganese-doped TiO(2) is also attributed to the low oxygen content, owing to the equilibrium fabrication conditions. This work provides an important strategy to control the chemical and defect states of dopants by using an equilibrium fabrication process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TiO2 as a photocatalyst for control of the aquatic invasive alga, Cladophora, under natural and artificial light

USGS Publications Warehouse

Peller, J.R.; Whitman, R.L.; Griffith, S.; Harris, P.; Peller, C.; Scalzitti, J.

2007-01-01

Cladophora, a nuisance and invasive, filamentous algae (Chlorophyta), massively accumulates along the shores of the lower Great Lakes each summer causing great economic damage and compromising recreational opportunity and perhaps public health. In vitro experiments showed that Cladophora samples were physically and biologically degraded when subjected to TiO2-mediated photocatalysis. For the most successful photocatalytic process, TiO2 was immobilized on a glass surface and used in combination with either sunlight or artificial UV light. The loss of vital algal pigments was monitored using UV–vis spectrophotometry, and cell structural changes were determined by microscopic observation. Cladophora, in the presence of TiO2-covered glass beads, experienced a loss of chloroplast pigments after 2 h of UV lamp light irradiation. In a separate experiment, sunlight exposure over 4 days (∼24 h) resulted in the complete oxidative degradation of the green chloroplast pigments, verified by the UV spectra of the algal extracts. These results suggest that TiO2, mobilized on sunlit silicates may be useful in controlling growth and survival of this alga in the Great Lakes, thus mitigating many of the economic, aesthetic ecological impacts of this invasive alga.

Comparison of Infectious Agents Susceptibility to Photocatalytic Effects of Nanosized Titanium and Zinc Oxides: A Practical Approach

NASA Astrophysics Data System (ADS)

Bogdan, Janusz; Zarzyńska, Joanna; Pławińska-Czarnak, Joanna

2015-08-01

Nanotechnology contributes towards a more effective eradication of pathogens that have emerged in hospitals, veterinary clinics, and food processing plants and that are resistant to traditional drugs or disinfectants. Since new methods of pathogens eradication must be invented and implemented, nanotechnology seems to have become the response to that acute need. A remarkable achievement in this field of science was the creation of self-disinfecting surfaces that base on advanced oxidation processes (AOPs). Thus, the phenomenon of photocatalysis was practically applied. Among the AOPs that have been most studied in respect of their ability to eradicate viruses, prions, bacteria, yeasts, and molds, there are the processes of TiO2/UV and ZnO/UV. Titanium dioxide (TiO2) and zinc oxide (ZnO) act as photocatalysts, after they have been powdered to nanoparticles. Ultraviolet (UV) radiation is an agent that determines their excitation. Methods using photocatalytic properties of nanosized TiO2 and ZnO prove to be highly efficient in inactivation of infectious agents. Therefore, they are being applied on a growing scale. AOP-based disinfection is regarded as a very promising tool that might help overcome problems in food hygiene and public health protection. The susceptibility of infectious agents to photocatalylic processes can be generally arranged in the following order: viruses > prions > Gram-negative bacteria > Gram-positive bacteria > yeasts > molds.

Synergistic Effects of Nano-Sized Titanium Dioxide and Zinc on the Photosynthetic Capacity and Survival of Anabaena sp.

PubMed Central

Tang, Yulin; Li, Shuyan; Qiao, Junlian; Wang, Hongtao; Li, Lei

2013-01-01

Anabaena sp. was used to examine the toxicity of exposure to a nano-TiO2 suspension, Zn2+ solution, and mixtures of nano-TiO2 and Zn2+ suspensions. Typical chlorophyll fluorescence parameters, including effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse-amplitude modulated fluorometer. Nano-TiO2 particles exhibited no significant toxicity at concentrations lower than 10.0 mg/L. The 96 h concentration for the 50% maximal effect (EC50) of Zn2+ alone to Anabaena sp. was 0.38 ± 0.004 mg/L. The presence of nano-TiO2 at low concentrations (<1.0 mg/L) significantly enhanced the toxicity of Zn2+ and consequently reduced the EC50 value to 0.29 ± 0.003 mg/L. However, the toxicity of the Zn2+/TiO2 system decreased with increasing nano-TiO2 concentration because of the substantial adsorption of Zn2+ by nano-TiO2. The toxicity curve of the Zn2+/TiO2 system as a function of incremental nano-TiO2 concentrations was parabolic. The toxicity significantly increased at the initial stage, reached its maximum, and then decreased with increasing nano-TiO2 concentration. Hydrodynamic sizes, concentration of nano-TiO2 and Zn2+ loaded nano-TiO2 were the main parameters for synergistic toxicity. PMID:23852017

Modulation of physiological responses with TiO2 nano-particle in Azolla pinnata R.Br. under 2,4-D toxicity.

PubMed

De, Arnab Kumar; Ghosh, Arijit; Debnath, Subhas Chandra; Sarkar, Bipul; Saha, Indraneel; Adak, Malay Kumar

2018-06-05

The present work is emphasised with the herbicidal tolerance of Azolla pinnata R.Br. and its modulation with TiO 2 nano-particle. Both carbohydrate and nitrogen metabolism were effected with 2,4-D as herbicide and in few cases TiO 2 -NP had recovered few detrimental effects. From the nutrient status in Azolla it recorded the recovery of nitrogen as well as potassium by TiO 2 -NP but not in case of phosphorus. However, a conversion of nitrate to ammonium was more induced by TiO 2 -NP under herbicidal toxicity. Similar results were obtained for inter-conversion of amino acid-nitrate pool, but no changes with glutamine synthase activity with TiO 2 -NP. Initially, the effects of 2,4-D was monitored with changes of chlorophyll content but had not been recovered with nanoparticle. Photosynthetic reserves expressed as both total and reducing sugar were insensitive to TiO 2 -NP interference but activity of soluble and wall bound invertase was in reverse trend as compared to control. The 2,4-D mediated changes of redox and its oxidative stress was ameliorated in plants with over expressed ADH activity. As a whole the Azolla bio system with TiO 2 supplementation may be useful in sustenance against 2,4-D toxicity through recovery of nitrogen metabolism. Thus, Azolla-TiO 2 -NP bio system would be realised to monitor the herbicidal toxicity in soil and its possible bioremediation.

Enhancing antimicrobial activity of TiO2/Ti by torularhodin bioinspired surface modification.

PubMed

Ungureanu, Camelia; Dumitriu, Cristina; Popescu, Simona; Enculescu, Monica; Tofan, Vlad; Popescu, Marian; Pirvu, Cristian

2016-02-01

Implant-associated infections are a major cause of morbidity and mortality. This study was performed using titanium samples coated by anodization with a titanium dioxide (TiO2) shielded nanotube layer. TiO2/Ti surface was modified by simple immersion in torularhodin solution and by using a mussel-inspired method based on polydopamine as bio adhesive for torularhodin immobilization. SEM analysis revealed tubular microstructures of torularhodin and the PDA ability to function as a catchy anchor between torularhodin and TiO2 surface. Corrosion resistance was associated with TiO2 barrier oxide layer and nano-organized oxide layer and the torularhodin surface modification does not bring significant changes in resistance of the oxide layer. Our results demonstrated that the torularhodin modified TiO2/Ti surface could effectively prevent adhesion and proliferation of Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, and Pseudomonas aeruginosa. The new modified titanium surface showed good biocompatibility and well-behaved haemocompatibility. This biomaterial with enhanced antimicrobial activity holds great potential for future biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Phototoxicity of Nano Titanium Dioxides in HaCaT Keratinocytes – Generation of Reactive Oxygen Species and Cell Damage

PubMed Central

Yin, Jun-Jie; Liu, Jun; Ehrenshaft, Marilyn; Roberts, Joan E.; Fu, Peter P.; Mason, Ronald P.; Zhao, Baozhong

2012-01-01

Nano-sized titanium dioxide (TiO2) is among the top five widely used nanomaterials for various applications. In this study, we determine the phototoxicity of TiO2 nanoparticles (nano-TiO2) with different molecular sizes and crystal forms (anatase and rutile) in human skin keratinocytes under UVA irradiation. Our results show that all nano-TiO2 particles caused phototoxicity, as determined by the MTS assay and by cell membrane damage measured by the lactate dehydrogenase (LDH) assay, both of which were UVA dose- and nano-TiO2 dose- dependent. The smaller the particle size of nano-TiO2 the higher the cell damage. The rutile form of nano-TiO2 showed less phototoxicity than anatase nano-TiO2. The level of photocytotoxicity and cell membrane damage is mainly dependent on the level of reactive oxygen species (ROS) production. Using polyunsaturated lipids in plasma membranes and human serum albumin as model targets, and employing electron spin resonance (ESR) oximetry and immuno-spin trapping as unique probing methods, we demonstrated that UVA irradiation of nano-TiO2 can induce significant cell damage, mediated by lipid and protein peroxidation. These overall results suggest that nano-TiO2 is phototoxic to human skin keratinocytes, and that this phototoxicity is mediated by ROS generated during UVA irradiation. PMID:22705594

TiO2-Nanofillers Effects on Some Properties of Highly- Impact Resin Using Different Processing Techniques.

PubMed

Aziz, Hawraa Khalid

2018-01-01

The criteria of conventional curing of polymethyl methacrylate do not match the standard properties of the denture base materials. This research was conducted to investigate the addition of TiO 2 nano practical on impact strength, thermal conductivity and color stability of acrylic resin cured by microwave in comparison to the conventional cured of heat-polymerized acrylic resin. 120 specimens made of high impact acrylic resin were divided into two main groups according to the type of curing (water bath, microwave), then each group was subdivided into two groups according to the addition of 3% TiO 2 nano-fillers and control group (without the addition of TiO 2 0%). Each group was subdivided according to the type of test into 3 groups with 10 specimens for each group. Data were statistically analyzed using Student t-test to detect the significant differences between tested and control groups at significance level ( P <0.05). According to curing type methods, the results showed that there was a significant decrease in impact strength of microwaved cured resin, but there was no significant difference in the thermal conductivity and color stability of resin. In addition, by using nanofiller, there was a significant increase in the impact strength and color stability with the addition of 3% TiO 2 nanofillers, but no significant difference was found in the thermal conductivity of the acrylic resin. The microwave curing of acrylic resin had no change in the color stability and thermal conductivity in comparison to the water bath, but the impact strength was decreased. The addition of 3% TiO 2 improved the impact and the color stability, but the thermal conductivity did not change.

Removal of pharmaceutically active compounds from synthetic and real aqueous mixtures and simultaneous disinfection by supported TiO2/UV-A, H2O2/UV-A, and TiO2/H2O2/UV-A processes.

PubMed

Bosio, Morgana; Satyro, Suéllen; Bassin, João Paulo; Saggioro, Enrico; Dezotti, Márcia

2018-05-01

Pharmaceutically active compounds are carried into aquatic bodies along with domestic sewage, industrial and agricultural wastewater discharges. Psychotropic drugs, which can be toxic to the biota, have been detected in natural waters in different parts of the world. Conventional water treatments, such as activated sludge, do not properly remove these recalcitrant substances, so the development of processes able to eliminate these compounds becomes very important. Advanced oxidation processes are considered clean technologies, capable of achieving high rates of organic compounds degradation, and can be an efficient alternative to conventional treatments. In this study, the degradation of alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine was evaluated through TiO 2 /UV-A, H 2 O 2 /UV-A, and TiO 2 /H 2 O 2 /UV-A, using sunlight and artificial irradiation. While using TiO 2 in suspension, best results were found at [TiO 2 ] = 0.1 g L -1 . H 2 O 2 /UV-A displayed better results under acidic conditions, achieving from 60 to 80% of removal. When WWTP was used, degradation decreased around 50% for both processes, TiO 2 /UV-A and H 2 O 2 /UV-A, indicating a strong matrix effect. The combination of both processes was shown to be an adequate approach, since removal increased up to 90%. H 2 O 2 /UV-A was used for disinfecting the aqueous matrices, while mineralization was obtained by TiO 2 -photocatalysis.

Heterogeneous photocatalytic degradation of toluene in static environment employing thin films of nitrogen-doped nano-titanium dioxide

NASA Astrophysics Data System (ADS)

Kannangara, Yasun Y.; Wijesena, Ruchira; Rajapakse, R. M. G.; de Silva, K. M. Nalin

2018-04-01

Photocatalytic semiconductor thin films have the ability to degrade volatile organic compounds (VOCs) causing numerous health problems. The group of VOCs called "BTEX" is abundant in houses and indoor of automobiles. Anatase phase of TiO2 has a band gap of 3.2 eV and UV radiation is required for photogeneration of electrons and holes in TiO2 particles. This band gap can be decreased significantly when TiO2 is doped with nitrogen (N-TiO2). Dopants like Pd, Cd, and Ag are hazardous to human health but N-doped TiO2 can be used in indoor pollutant remediation. In this research, N-doped TiO2 nano-powder was prepared and characterized using various analytical techniques. N-TiO2 was made in sol-gel method and triethylamine (N(CH2CH3)3) was used as the N-precursor. Modified quartz cell was used to measure the photocatalytic degradation of toluene. N-doped TiO2 nano-powder was illuminated with visible light (xenon lamp 200 W, λ = 330-800 nm, intensity = 1 Sun) to cause the degradation of VOCs present in static air. Photocatalyst was coated on a thin glass plate, using the doctor-blade method, was inserted into a quartz cell containing 2.00 µL of toluene and 35 min was allowed for evaporation/condensation equilibrium and then illuminated for 2 h. Remarkably, the highest value of efficiency 85% was observed in the 1 μm thick N-TiO2 thin film. The kinetics of photocatalytic degradation of toluene by N-TiO2 and P25-TiO2 has been compared. Surface topology was studied by varying the thickness of the N-TiO2 thin films. The surface nanostructures were analysed and studied with atomic force microscopy with various thin film thicknesses.

Optical properties of titanium-di-oxide (TiO2) prepared by hydrothermal method

NASA Astrophysics Data System (ADS)

Rahman, Kazi Hasibur; Biswas, Sayari; Kar, Asit Kumar

2018-05-01

Research on titanate and its derived TiO2 nanostructures with large specific surface area have received great attention due to their enhanced efficiency in photocatalysis, DSSC etc. Here, in this communication TiO2 powder has been prepared by hydrothermal method at 180 °C. In this work we have shown the changes in optical properties of the powder with two different sintering temperatures ‒ 500 °C and 800 °C. The as prepared powder was also studied. FESEM images show spherical particles for the as prepared samples which look more like agglomeration after sintering. Band gaps of the prepared samples were calculated from UV-Vis spectroscopy which lies in the range 2.85 eV ‒ 3.13 eV. The photoluminescence (PL) spectra of the prepared samples were recorded at room temperature in the range of 300‒700 nm. It shows two distinct peaks at 412 nm and 425 nm.

Assessment of the roles of reactive oxygen species in the UV and visible light photocatalytic degradation of cyanotoxins and water taste and odor compounds using C-TiO2.

PubMed

Fotiou, Theodora; Triantis, Theodoros M; Kaloudis, Triantafyllos; O'Shea, Kevin E; Dionysiou, Dionysios D; Hiskia, Anastasia

2016-03-01

Visible light (VIS) photocatalysis has large potential as a sustainable water treatment process, however the reaction pathways and degradation processes of organic pollutants are not yet clearly defined. The presence of cyanobacteria cause water quality problems since several genera can produce potent cyanotoxins, harmful to human health. In addition, cyanobacteria produce taste and odor compounds, which pose serious aesthetic problems in drinking water. Although photocatalytic degradation of cyanotoxins and taste and odor compounds have been reported under UV-A light in the presence of TiO2, limited studies have been reported on their degradation pathways by VIS photocatalysis of these problematic compounds. The main objectives of this work were to study the VIS photocatalytic degradation process, define the reactive oxygen species (ROS) involved and elucidate the reaction mechanisms. We report carbon doped TiO2 (C-TiO2) under VIS leads to the slow degradation of cyanotoxins, microcystin-LR (MC-LR) and cylindrospermopsin (CYN), while taste and odor compounds, geosmin and 2-methylisoborneol, were not appreciably degraded. Further studies were carried-out employing several specific radical scavengers (potassium bromide, isopropyl alcohol, sodium azide, superoxide dismutase and catalase) and probes (coumarin) to assess the role of different ROS (hydroxyl radical OH, singlet oxygen (1)O2, superoxide radical anion [Formula: see text] ) in the degradation processes. Reaction pathways of MC-LR and CYN were defined through identification and monitoring of intermediates using liquid chromatography tandem mass spectrometry (LC-MS/MS) for VIS in comparison with UV-A photocatalytic treatment. The effects of scavengers and probes on the degradation process under VIS, as well as the differences in product distributions under VIS and UV-A, suggested that the main species in VIS photocatalysis is [Formula: see text] , with OH and (1)O2 playing minor roles in the degradation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Photoproducts of carminic acid formed by a composite from Manihot dulcis waste.

PubMed

Antonio-Cisneros, Cynthia M; Dávila-Jiménez, Martín M; Elizalde-González, María P; García-Díaz, Esmeralda

2015-04-15

Carbon-TiO2 composites were obtained from carbonised Manihot dulcis waste and TiO2 using glycerol as an additive and thermally treating the composites at 800 °C. Furthermore, carbon was obtained from manihot to study the adsorption, desorption and photocatalysis of carminic acid on these materials. Carminic acid, a natural dye extracted from cochineal insects, is a pollutant produced by the food industry and handicrafts. Its photocatalysis was observed under different atmospheres, and kinetic curves were measured by both UV-Vis and HPLC for comparison, yielding interesting differences. The composite was capable of decomposing approximately 50% of the carminic acid under various conditions. The reaction was monitored by UV-Vis spectroscopy and LC-ESI-(Qq)-TOF-MS-DAD, enabling the identification of some intermediate species. The deleterious compound anthracene-9,10-dione was detected both in N2 and air atmospheres. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fabrication of polymeric nano-batteries array using anodic aluminum oxide templates.

PubMed

Zhao, Qiang; Cui, Xiaoli; Chen, Ling; Liu, Ling; Sun, Zhenkun; Jiang, Zhiyu

2009-02-01

Rechargeable nano-batteries were fabricated in the array pores of anodic aluminum oxide (AAO) template, combining template method and electrochemical method. The battery consisted of electropolymerized PPy electrode, porous TiO2 separator, and chemically polymerized PAn electrode was fabricated in the array pores of two-step anodizing aluminum oxide (AAO) membrane, based on three-step assembling method. It performs typical electrochemical battery behavior with good charge-discharge ability, and presents a capacity of 25 nAs. AFM results show the hexagonal array of nano-batteries' top side. The nano-battery may be a promising device for the development of Micro-Electro-Mechanical Systems (MEMS), and Nano-Electro-Mechanical Systems (NEMS).

Photocatalysis and the origin of life: synthesis of nucleoside bases from formamide on TiO2(001) single surfaces.

PubMed

Senanayake, S D; Idriss, H

2006-01-31

We report the conversion of a large fraction of formamide (NH(2)CHO) to high-molecular-weight compounds attributed to nucleoside bases on the surface of a TiO(2) (001) single crystal in ultra-high vacuum conditions. If true, we present previously unreported evidence for making biologically relevant molecules from a C1 compound on any single crystal surface in high vacuum and in dry conditions. An UV light of 3.2 eV was necessary to make the reaction. This UV light excites the semiconductor surface but not directly the adsorbed formamide molecules or the reaction products. There thus is no need to use high energy in the form of photons or electrical discharge to make the carbon-carbon and carbon-nitrogen bonds necessary for life. Consequently, the reaction products may accumulate with time and may not be subject to decomposition by the excitation source. The formation of these molecules, by surface reaction of formamide, is proof that some minerals in the form of oxide semiconductors are active materials for making high-molecular-weight organic molecules that may have acted as precursors for biological compounds required for life in the universe.

Application of solar AOPs and ozonation for elimination of micropollutants in municipal wastewater treatment plant effluents.

PubMed

Prieto-Rodríguez, L; Oller, I; Klamerth, N; Agüera, A; Rodríguez, E M; Malato, S

2013-03-15

Conventional municipal wastewater treatment plants are not able to entirely degrade some organic pollutants that end up in the environment. Within this group of contaminants, Emerging Contaminants are mostly unregulated compounds that may be candidates for future regulation. In this work, different advanced technologies: solar heterogeneous photocatalysis with TiO(2), solar photo-Fenton and ozonation, are studied as tertiary treatments for the remediation of micropollutants present in real municipal wastewater treatment plants effluents at pilot plant scale. Contaminants elimination was followed by Liquid Chromatography/Quadrupole ion trap Mass Spectrometry analysis after a pre-concentration 100:1 by automatic solid phase extraction. 66 target micropollutants were identified and quantified. 16 of those contaminants at initial concentrations over 1000 ng L(-1), made up over 88% of the initial total effluent pollutant load. The order of micropollutants elimination efficiency under the experimental conditions evaluated was solar photo-Fenton > ozonation > solar heterogeneous photocatalysis with TiO(2). Toxicity analyses by Vibrio fischeri and respirometric tests showed no significant changes in the effluent toxicity after the three tertiary treatments application. Solar photo-Fenton and ozonation treatments were also compared from an economical point of view. Copyright © 2012 Elsevier Ltd. All rights reserved.

The photovoltaic efficiency of the fabrication of copolymer P3HT:PCBM on different thickness nano-anatase titania as solar cell.

PubMed

Lazim, Haidar Gazy; Ajeel, Khalid I; Badran, Hussain A

2015-06-15

Organic solar cells based on (3-hexylthiophene):[6,6]-phenyl C61-butyric acid methylester (P3HT:PCBM) bulk heterojunction (BHJ) with an inverted structure have been fabricated using nano-anatase crystalline titanium dioxide (TiO2) as their electron transport layer, which was prepared on the indium tin oxide coated glass (ITO-glass), silicon wafer and glass substrates by sol-gel method at different spin speed by using spin-coating (1000, 2000 and 3,000 rpm) for nano-thin film 58, 75 and 90 nm respectively. The effect of thickness on the surface morphology and optical properties of TiO2 layer were investigated by atomic force microscopy (AFM), X-ray diffraction and UV-visible spectrophotometer. The optical band gap of the films has been found to be in the range 3.63-3.96 eV for allowed direct transition and to be in the range 3.23-3.69 eV for forbidden direct transition to the different TiO2 thickness. The samples were examined to feature current and voltages darkness and light extraction efficiency of the solar cell where they were getting the highest open-circuit voltage, Voc, and power conversion efficiency were 0.66% and 0.39% fabricated with 90 nm respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of different TiO2 blocking films on the photovoltaic performance of perovskite solar cells

NASA Astrophysics Data System (ADS)

Zhang, Chenxi; Luo, Yudan; Chen, Xiaohong; Ou-Yang, Wei; Chen, Yiwei; Sun, Zhuo; Huang, Sumei

2016-12-01

Organolead trihalide perovskite materials have been successfully used as light absorbers in efficient photovoltaic (PV) cells. Cell structures based on mesoscopic metal oxides and planar heterojunctions have already demonstrated very impressive and brisk advances, holding great potential to grow into a mature PV technology. High power conversion efficiency (PCE) values have been obtained from the mesoscopic configuration in which a few hundred nano-meter thick mesoporous scaffold (e.g. TiO2 or Al2O3) infiltrated by perovskite absorber was sandwiched between the electron and hole transport layers. A uniform and compact hole-blocking layer is necessary for high efficient perovskite-based thin film solar cells. In this study, we investigated the characteristics of TiO2 compact layer using various methods and its effects on the PV performance of perovskite solar cells. TiO2 compact layer was prepared by a sol-gel method based on titanium isopropoxide and HCl, spin-coating of titanium diisopropoxide bis (acetylacetonate), screen-printing of Dyesol's bocking layer titania paste, and a chemical bath deposition (CBD) technique via hydrolysis of TiCl4, respectively. The morphological and micro-structural properties of the formed compact TiO2 layers were characterized by scanning electronic microscopy and X-ray diffraction. The analyses of devices performance characteristics showed that surface morphologies of TiO2 compact films played a critical role in affecting the efficiencies. The nanocrystalline TiO2 film deposited via the CBD route acts as the most efficient hole-blocking layer and achieves the best performance in perovskite solar cells. The CBD-based TiO2 compact and dense layer offers a small series resistance and a large recombination resistance inside the device, and makes it possible to achieve a high power conversion efficiency of 12.80%.

The regulation of TiO2 nanoparticles on the expression of light-harvesting complex II and photosynthesis of chloroplasts of Arabidopsis thaliana.

PubMed

Ze, Yuguan; Liu, Chao; Wang, Ling; Hong, Mengmeng; Hong, Fashui

2011-11-01

Recent studies demonstrated that titanium dioxide nanoparticles (TiO2 NPs) could significantly promote photosynthesis and plant growth, but its mechanism is still unclear. In this article, we studied the mechanism of light absorption and transfer of chloroplasts of Arabidopsis thaliana caused by TiO2 NPs treated. The results showed that TiO2 NPs could induce significant increases of light-harvesting complex II (LHCII) b gene expression and LHCII II content on the thylakoid membrane in A. thaliana, and the increases in LHCII were higher than the non-nano TiO2 (bulk-TiO2) treatment. Meanwhile, spectroscopy assays indicated that TiO2 NPs obviously increased the absorption peak intensity of the chloroplast in red and blue region, the fluorescence quantum yield near 680 nm, the excitation peak intensity near 440 and 480 nm and/or near 650 and 680 nm of the chloroplast. TiO2 NPs treatment could reduce F480/F440 ratio and increase F650/F680 ratio and accelerate the rate of whole chain electron transport and oxygen evolution of the chloroplast. However, the photosynthesis improvement of the non-nanoTiO2 treatment was far less effective than TiO2 NPs treatment. Taken together, TiO2 NPs could promote the light absorption of chloroplast, regulate the distribution of light energy from PS I to PS II by increasing LHCII and accelerate the transformation from light energy to electronic energy, water photolysis, and oxygen evolution.

Investigation of TiO2 based Mixed-metal Oxide Catalysts for the Production of Hydrogen

NASA Astrophysics Data System (ADS)

Luo, Si

Abstract of the Dissertation. Investigation of TiO2 based Mixed-metal Oxide Catalysts for the Production of Hydrogen. by. Si Luo. Doctor of Philosophy. in. Chemistry. Stony Brook University. 2017. The environmental impacts of fossil fuel consumption and the resulting global warming have attracted increasing attention to technologies and fuels that are both sustainable and renewable in the 21st century. To date, hydrogen has been proposed as an encouraging candidate of the next generation of chemical fuels, which meets all demands for carbon free and efficient chemistries that could be produced from a variety of sources. However, despite tremendous efforts, there is a clear need to develop new catalysts for the production of hydrogen through catalytic processes that are sustainable, such as in the photocatalytic splitting of water (PCS: H2O → H2 + 0.5O2) and the water-gas shift process (WGS: CO + H2O → H2 + CO2). This thesis is primarily motivated by this challenge and has focused on the photochemical and thermal production of H2 by the employment of novel TiO2 based catalysts. TiO2 is one of the most widely studied photocatalysts in all history, due to its relatively high activity, robust stability, safety and low cost. In this thesis, several TiO2-based mixed metal oxide nano catalysts (CeOx-TiO2, Ru-TiO2, Ga-TiO2) have been synthesized with carefully controlled morphology/structure and with inclusion of co-catalysts (Pt). These novel materials were comprehensively characterized to better understand their morphology, crystal structure, and electronic properties in an attempt to unravel phenomena responsible for high catalytic performance for the production of H2 from H2O. We have discovered the importance of low-dimensional metal oxide and interfacial stabilized nano-scaled mixed metal oxides for H2 production, while learning how best to tune such structure to optimize both thermal and photochemical conversion. Optimized structure and/or composition have been identified for TiO2 modified in different ways by another metal oxide (CeOx) or with dopants (Ga, Ru). In addition, we have also studied the water gas shift reaction on several TiO2 supported catalysts, where similar concepts can be applied. Advanced In situ characterization enabled the investigation of the catalyst structure, surface chemical intermediates and active species under reaction conditions. The influence of metal-oxide, oxide-oxide interactions has been further revealed for both the water-gas shift and the photocatalytic splitting of water.

New large solar photocatalytic plant: set-up and preliminary results.

PubMed

Malato, S; Blanco, J; Vidal, A; Fernández, P; Cáceres, J; Trincado, P; Oliveira, J C; Vincent, M

2002-04-01

A European industrial consortium called SOLARDETOX has been created as the result of an EC-DGXII BRITE-EURAM-III-financed project on solar photocatalytic detoxification of water. The project objective was to develop a simple, efficient and commercially competitive water-treatment technology, based on compound parabolic collectors (CPCs) solar collectors and TiO2 photocatalysis, to make possible easy design and installation. The design, set-up and preliminary results of the main project deliverable, the first European industrial solar detoxification treatment plant, is presented. This plant has been designed for the batch treatment of 2 m3 of water with a 100 m2 collector-aperture area and aqueous aerated suspensions of polycrystalline TiO2 irradiated by sunlight. Fully automatic control reduces operation and maintenance manpower. Plant behaviour has been compared (using dichloroacetic acid and cyanide at 50 mg l(-1) initial concentration as model compounds) with the small CPC pilot plants installed at the Plataforma Solar de Almería several years ago. The first results with high-content cyanide (1 g l(-1)) waste water are presented and plant treatment capacity is calculated.

Anti-flammable vinyl ester resin nano-composite with nano-titania

NASA Astrophysics Data System (ADS)

Das, Rajib

Anti-flammable material is a common expectation for any industry and household applications to protect the material from fire accident. Polymer composites also play a significant role in preparing anti flammable materials. Vinyl ester resins (VERs) are thermosetting resins that have excellent mechanical and thermal properties of epoxy resins and Nanotitania is an inexpensive, nontoxic and biocompatible inorganic material. In this paper to investigate the flame retardency of polymer nanocomposites VER is used as polymer matrix and TiO2 is used as inorganic nanofiller.3-[2-(2-aminoethylamino) ethylamino]propyl-trimethoxysilane (TATMS), a kind of silane is used as a coupling agent to functionalize the surface of nanoTiO2 to improve its flame retardency by adding Si and N2 group. TGA test and FTIR test have been performed and different peaks for Si and N2 in the modified nanofiller and weight loss of fabricated nanofiller confirmed that fabrication method was successful. After that, nanocomposite sample of VERs reinforced with nano TiO2 prepared and the effects of different loadings on mechanical and flame retardant properties are investigated after and before the modification of nanofillers. From tensile test result it is found that up to 5% loading of modified nanofiller the tensile strength is 62 MPa that is almost as same as pure VER and the tensile strength of unmodified nanofiller based PNC is 68 MPa which is not significant improvement in its mechanical property. From MCC test of flame retardancy it is found that the normalized heat release capacity of modified nanofiller based nanocomposite is decreased by 27.7% than unmodified nanofiller based PNC that is 9.8%. Also the normalized total heat release of modified nanofiller based PNC is 21.4% than unmodified PNC that is 12.4%.

Titanium Dioxide Coating Prepared by Use of a Suspension-Solution Plasma-Spray Process

NASA Astrophysics Data System (ADS)

Du, Lingzhong; Coyle, Thomas W.; Chien, Ken; Pershin, Larry; Li, Tiegang; Golozar, Mehdi

2015-08-01

Titanium dioxide coatings were prepared from titanium isopropoxide solution containing nano TiO2 particles by use of a plasma-spray process. The effects of stand-off distance on coating composition and microstructure were investigated and compared with those for pure solution precursor and a water-based suspension of TiO2. The results showed that the anatase content of the coating increased with increasing stand-off distance and the rate of deposition decreased with increasing spray distance. Anatase nanoparticles in solution were incorporated into the coatings without phase transformation whereas most of the TiO2 in the precursor solution was transformed into rutile. The microstructure of preserved anatase particles bound by rutile improved the efficiency of deposition of the coating. The amount of anatase phase can be adjusted by variation of the ratio of solution to added anatase TiO2 nanoparticles.

A three-dimensional carbon nano-network for high performance lithium ion batteries

DOE PAGES

Tian, Miao; Wang, Wei; Liu, Yang; ...

2014-11-20

Three-dimensional (3D) network structure has been envisioned as a superior architecture for lithium ion battery (LIB) electrodes, which enhances both ion and electron transport to significantly improve battery performance. Herein, a 3D carbon nano-network is fabricated through chemical vapor deposition of carbon on a scalably manufactured 3D porous anodic alumina (PAA) template. As a demonstration on the applicability of 3D carbon nano-network for LIB electrodes, the low conductivity active material, TiO 2, is then uniformly coated on the 3D carbon nano-network using atomic layer deposition. High power performance is demonstrated in the 3D C/TiO 2 electrodes, where the parallel tubesmore » and gaps in the 3D carbon nano-network facilitates fast Li ion transport. A large areal capacity of ~0.37 mAh·cm –2 is achieved due to the large TiO 2 mass loading in the 60 µm-thick 3D C/TiO 2 electrodes. At a test rate of C/5, the 3D C/TiO 2 electrode with 18 nm-thick TiO 2 delivers a high gravimetric capacity of ~240 mAh g –1, calculated with the mass of the whole electrode. A long cycle life of over 1000 cycles with a capacity retention of 91% is demonstrated at 1C. In this study, the effects of the electrical conductivity of carbon nano-network, ion diffusion, and the electrolyte permeability on the rate performance of these 3D C/TiO 2 electrodes are systematically studied.« less

Food grade titanium dioxide disrupts intestinal brush border microvilli in vitro independent of sedimentation.

PubMed

Faust, James J; Doudrick, Kyle; Yang, Yu; Westerhoff, Paul; Capco, David G

2014-06-01

Bulk- and nano-scale titanium dioxide (TiO2) has found use in human food products for controlling color, texture, and moisture. Once ingested, and because of their small size, nano-scale TiO2 can interact with a number of epithelia that line the human gastrointestinal tract. One such epithelium responsible for nutrient absorption is the small intestine, whose constituent cells contain microvilli to increase the total surface area of the gut. Using a combination of scanning and transmission electron microscopy it was found that food grade TiO2 (E171 food additive coded) included ∼25% of the TiO2 as nanoparticles (NPs; <100 nm), and disrupted the normal organization of the microvilli as a consequence of TiO2 sedimentation. It was found that TiO2 isolated from the candy coating of chewing gum and a commercially available TiO2 food grade additive samples were of the anatase crystal structure. Exposure to food grade TiO2 additives, containing nanoparticles, at the lowest concentration tested within this experimental paradigm to date at 350 ng/mL (i.e., 100 ng/cm(2) cell surface area) resulted in disruption of the brush border. Through the use of two independent techniques to remove the effects of gravity, and subsequent TiO2 sedimentation, it was found that disruption of the microvilli was independent of sedimentation. These data indicate that food grade TiO2 exposure resulted in the loss of microvilli from the Caco-2BBe1 cell system due to a biological response, and not simply a physical artifact of in vitro exposure.

Investigation of energy band alignments and interfacial properties of rutile NMO2/TiO2 (NM = Ru, Rh, Os, and Ir) by first-principles calculations.

PubMed

Yang, Chen; Zhao, Zong-Yan

2017-11-08

In the field of photocatalysis, constructing hetero-structures is an efficient strategy to improve quantum efficiency. However, a lattice mismatch often induces unfavorable interfacial states that can act as recombination centers for photo-generated electron-hole pairs. If the hetero-structure's components have the same crystal structure, this disadvantage can be easily avoided. Conversely, in the process of loading a noble metal co-catalyst onto the TiO 2 surface, a transition layer of noble metal oxides is often formed between the TiO 2 layer and the noble metal layer. In this article, interfacial properties of hetero-structures composed of a noble metal dioxide and TiO 2 with a rutile crystal structure have been systematically investigated using first-principles calculations. In particular, the Schottky barrier height, band bending, and energy band alignments are studied to provide evidence for practical applications. In all cases, no interfacial states exist in the forbidden band of TiO 2 , and the interfacial formation energy is very small. A strong internal electric field generated by interfacial electron transfer leads to an efficient separation of photo-generated carriers and band bending. Because of the differences in the atomic properties of the components, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures demonstrate band dividing, while RhO 2 /TiO 2 and IrO 2 /TiO 2 hetero-structures have a pseudo-gap near the Fermi energy level. Furthermore, NMO 2 /TiO 2 hetero-structures show upward band bending. Conversely, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures present a relatively strong infrared light absorption, while RhO 2 /TiO 2 and IrO 2 /TiO 2 hetero-structures show an obvious absorption edge in the visible light region. Overall, considering all aspects of their properties, RuO 2 /TiO 2 and OsO 2 /TiO 2 hetero-structures are more suitable than others for improving the photocatalytic performance of TiO 2 . These findings will provide useful information for understanding the role and effects of a noble metal dioxide as a transition layer between a noble metal co-catalyst and a TiO 2 photocatalyst.

Characterization of an LED based photoreactor to degrade 4-chlorophenol in an aqueous medium using coumarin (C-343) sensitized TiO2.

PubMed

Ghosh, Jyoti P; Langford, Cooper H; Achari, Gopal

2008-10-16

A detailed performance evaluation of a simple high intensity LED based photoreactor exploiting a narrow wavelength range of the LED to match the spectrum of a dye in a photocatalysis system is reported. A dye sensitized (coumarin-343, lambda max = 446 nm) TiO 2 photocatalyst was used for the degradation of 4-chlorophenol (4-CP) in an aqueous medium using the 436 nm LED based photoreactor. The LED reactor performed competitively with a conventional multilamp reactor and sunlight in the degradation of 4-CP. Light intensities entering the reaction vessel were measured by conventional ferrioxalate actinometry. The results can be fitted by approximate first order kinetic behavior in this system. Hydroxyl radicals were detected by spin trapping EPR, and effects of OH radical quenchers on kinetics suggest that the reaction is initiated by these radicals or their equivalents. LEDs operating at competitive intensities offer a number of advantages to the photochemist or the environmental engineer via long life, efficient current to light conversion, narrow bandwidth, forward directed output, and direct current power for remote operation. Matching light source spectrum to chromophore is a key.

Photocatalytic properties of P25-doped TiO2 composite film synthesized via sol-gel method on cement substrate.

PubMed

Guo, Xiang; Rao, Lei; Wang, Peifang; Wang, Chao; Ao, Yanhui; Jiang, Tao; Wang, Wanzhong

2018-04-01

TiO 2 films have received increasing attention for the removal of organic pollutants via photocatalysis. To develop a simple and effective method for improving the photodegradation efficiency of pollutants in surface water, we herein examined the preparation of a P25-TiO 2 composite film on a cement substrate via a sol-gel method. In this case, Rhodamine B (RhB) was employed as the target organic pollutant. The self-generated TiO 2 film and the P25-TiO 2 composite film were characterized by X-ray diffraction (XRD), N 2 adsorption/desorption measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS). The photodegradation efficiencies of the two films were studied by RhB removal in water under UV (ultraviolet) irradiation. Over 4day exposure, the P25-TiO 2 composite film exhibited higher photocatalytic performance than the self-generated TiO 2 film. The photodegradation rate indicated that the efficiency of the P25-TiO 2 composite film was enhanced by the addition of the rutile phase Degussa P25 powder. As such, cooperation between the anatase TiO 2 and rutile P25 nanoparticles was beneficial for separation of the photo-induced electrons and holes. In addition, the influence of P25 doping on the P25-TiO 2 composite films was evaluated. We found that up to a certain saturation point, increased doping enhanced the photodegradation ability of the composite film. Thus, we herein demonstrated that the doping of P25 powders is a simple but effective strategy to prepare a P25-TiO 2 composite film on a cement substrate, and the resulting film exhibits excellent removal efficiency in the degradation of organic pollutants. Copyright © 2017. Published by Elsevier B.V.

Synthesis and characterization of ZnO:TiO2 nano composites thin films deposited on glass substrate by sol-gel spray coating technique

NASA Astrophysics Data System (ADS)

Sutanto, Heri; Nurhasanah, Iis; Hidayanto, Eko; Wibowo, Singgih; Hadiyanto

2015-12-01

In this work, (ZnO)x:(TiO2)1-x nano composites thin films, with x = 1, 0.75, 0.5, 0.25, and 0, have been prepared by sol-gel spray coating technique onto glass substrate. Pure TiO2 and ZnO thin films were synthesized from titanium isopropoxide-based and zinc acetate-based precursor solutions, respectively, whereas the composite films were obtained from the mixture of these solutions at the specific % vol ratios. The properties and performance of nano composite ZnO, TiO2 and ZnO:TiO2 thin films at different composition have been investigated. Ultraviolet - Visible (UV-Vis) Spectrophotometer and Scanning Electron Microscopy (SEM) were employed in order to get morphology and transmittance of thin films. Testing the ability of photocatalytic activity of obtained films was conducted on photodegradation of methylene blue (MB) dye and organic pollutants of wastewater under a 30 watt UV light irradiation, then testing BOD, COD and TPC were conducted. Using the Tauc model, the band-gap energy decreased from 3.12 eV to 3.02 eV for the sample with x = 1 and 0, respectively. This decrease occured along with the replacement of percentage of ZnO by TiO2 on the films. This decrease also reduced the minimum energy that required for electron excitation. Obtained thin films had nanoscale roughness level with range 3.64 to 17.30 nm. The film with x= 0 has the biggest removal percentage on BOD, COD and TPC mesurements with percentage 54.82%, 62.73% and 99.88%, respectively.

Thin film nano-photocatalyts with low band gap energy for gas phase degradation of p-xylene: TiO2 doped Cr, UiO66-NH2 and LaBO3 (B  =  Fe, Mn, and Co)

NASA Astrophysics Data System (ADS)

Loc Luu, Cam; Thuy Van Nguyen, Thi; Nguyen, Tri; Nguyen, Phung Anh; Hoang, Tien Cuong; Ha, Cam Anh

2018-03-01

By dip-coating technique the thin films of nano-photocatalysts TiO2, Cr-doped TiO2, LaBO3 perovskites (B  =  Fe, Mn, and Co) prepared by sol-gel method, and UiO66-NH2 prepared by a solvothermal were obtained and employed for gas phase degradation of p-xylene. Physicochemical characteristics of the catalysts were examined by the methods of BET, SEM, TEM, XRD, FT-IR, TGA, Raman and UV-vis spectroscopies. The thickness of film was determined by a Veeco-American Dektek 6M instrument. The activity of catalysts was evaluated in deep photooxidation of p-xylene in a microflow reactor at room temperature with the radiation sources of a UV (λ  =  365 nm) and LED lamps (λ  =  400-510 nm). The obtained results showed that TiO2 and TiO2 doped Cr thin films was featured by an anatase phase with nanoparticles of 10-100 nm. Doping TiO2 with 0.1%mol Cr2O3 led to reduce band gap energy from 3.01 down to 1.99 eV and extend the spectrum of photon absorption to the visible region (λ  =  622 nm). LaBO3 perovkite thin films were also featured by a crystal phase with average particle nanosize of 8-40 nm, a BET surface area of 17.6-32.7 m2 g-1 and band gap energy of 1.87-2.20 eV. UiO66-NH2 was obtained in the ball shape of 100-200 nm, a BET surface area of 576 m2 g-1 and a band gap energy of 2.83 eV. The low band gap energy nano-photocatalysts based on Cr-doped TiO2 and LaBO3 perovskites exhibited highly stable and active for photo-degradation of p-xylene in the gas phase under radiation of UV-vis light. Perovskite LaFeO3 and Cr-TiO2 thin films were the best photocatalysts with a decomposition yield being reached up to 1.70 g p-xylene/g cat.

A new preparation of doped photocatalytic TiO2 anatase nanoparticles: a preliminary study for the removal of pollutants in confined museum areas

NASA Astrophysics Data System (ADS)

Greco, Enrico; Ciliberto, Enrico; Cirino, Antonio M. E.; Capitani, Donatella; Di Tullio, Valeria

2016-05-01

The use of nanotechnology in conservation is a relatively new concept. Usually, classical cleanup methods take into account the use of other chemicals: On the one hand they help the environment destroying pollutants, but on the other hand they often become new pollutants. Among the new oxidation methods called advanced oxidation processes, heterogeneous photocatalysis has appeared an emerging technology with several economic and environmental advantages. A new sol-gel method of synthesis of TiO2 anatase is reported in this work using lithium and cobalt (II) salts. The activation energy of the doped photocatalyst was analyzed by solid-state UV-Vis spectrophotometer. The mobility of Li ions on TiO2 NPs surface was studied by 7Li MAS NMR spectroscopy. Use of doped nanotitania is suggested from authors for the removal of pollutants in confined areas containing goods that must be preserved from decomposition and aging phenomena.

Preconcentration and speciation of ultra-trace Se (IV) and Se (VI) in environmental water samples with nano-sized TiO2 colloid and determination by HG-AFS.

PubMed

Fu, Jiaqi; Zhang, Xu; Qian, Shahua; Zhang, Lin

2012-05-30

A united method for speciation analysis of Se (IV) and Se (VI) in environmental water samples was developed using nano-sized TiO(2) colloid as adsorbent and hydride generation atomic fluorescence spectrometry (HG-AFS) as determination means. When the pH values of bulk solution were between 6.0 and 7.0, successful adsorption onto 1 mL nano-sized TiO(2) colloid (0.2%) was achieved for more than 97.0% of Se (IV) while Se (VI) barely got adsorbed. Therefore, the method made it possible to preconcentrate and determine Se (IV) and Se (VI) separately. The precipitated TiO(2) with concentrated selenium was directly converted to colloid without desorption. Selenium in the resulting colloid was then determined by HG-AFS. The detection limits (3σ) and relative standard deviations (R.S.D) of this method were 24 ng/L and 42 ng/L, 7.8% (n=6) and 7.0% (n=6) for Se (IV) and Se (VI), respectively. This simple, sensitive, and united method was successfully applied to the separation and speciation of ultra-trace Se (IV) and Se (VI) in environmental water samples. Copyright © 2012 Elsevier B.V. All rights reserved.

Comparison of photocatalysis and photolysis of malathion, isomalathion, malaoxon, and commercial malathion--products and toxicity studies.

PubMed

Bavcon Kralj, M; Cernigoj, U; Franko, M; Trebse, P

2007-11-01

Malathion, one of the most widely applied insecticides, is still used in agriculture. There are many studies regarding its degradation under different experimental conditions, but few deal with its transformation products, i.e. malaoxon and isomalathion. Thus, malathion, malaoxon, isomalathion, and Radotion (one of its over 6000 commercial forms) were studied in terms of their degradation kinetics, identification of their transformation products, their toxicity, and their degree of mineralization, during UV photolysis (lambda = 254 nm) and TiO(2) photocatalysis (lambda = 355 nm). The degradation kinetics was similar for all four starting materials. More than 75% of theoretically expected sulfur in PS and P-S groups was oxidized after 240 min of photolysis and photocatalysis. On the other hand, less than 30% of stoichiometrically predicted amounts of phosphate was detected in the photolytic experiments, but more than 80% of expected phosphate was detected after photocatalytic treatment of all four organophosphorous materials. Several transformation products were identified by mass spectra of representative gas chromatographic peaks. Oxidation and isomerization were found as the main reactions of butenedioc acid diethyl esters and their analogs. The formation of malaoxon, isomalathion or trimethyl phosphate esters correlated well with the induced toxicity (inhibition of acetylcholinesterase), which was observed in photocatalysis of malathion and Radotion, and in photolysis of malaoxon and Radotion.

Visible light photoactivity of Polypropylene coated Nano-TiO2 for dyes degradation in water

PubMed Central

Giovannetti, R.; Amato, C. A. D’; Zannotti, M.; Rommozzi, E.; Gunnella, R.; Minicucci, M.; Di Cicco, A.

2015-01-01

The use of Polypropylene as support material for nano-TiO2 photocatalyst in the photodegradation of Alizarin Red S in water solutions under the action of visible light was investigated. The optimization of TiO2 pastes preparation using two commercial TiO2, Aeroxide P-25 and Anatase, was performed and a green low-cost dip-coating procedure was developed. Scanning electron microscopy, Atomic Force Microscopy and X-Ray Diffraction analysis were used in order to obtain morphological and structural information of as-prepared TiO2 on support material. Equilibrium and kinetics aspects in the adsorption and successive photodegradation of Alizarin Red S, as reference dye, are described using polypropylene-TiO2 films in the Visible/TiO2/water reactor showing efficient dyes degradation. PMID:26627118

Intensification of electrochemiluminescence of luminol on TiO2 supported Au atomic cluster nano-hybrid modified electrode.

PubMed

Yu, Zhimin; Wei, Xiuhua; Yan, Jilin; Tu, Yifeng

2012-04-21

With TiO(2) nanoparticles as carrier, a supported nano-material of Au atomic cluster/TiO(2) nano-hybrid was synthesized. It was then modified onto the surface of indium tin oxide (ITO) by Nafion to act as a working electrode for exciting the electrochemiluminescence (ECL) of luminol. The properties of the nano-hybrid and the modified electrode were characterized by XRD, XPS, electronic microscopy, electrochemistry and spectroscopy. The experimental results demonstrated that the modification of this nano-hybrid onto the ITO electrode efficiently intensified the ECL of luminol. It was also revealed that the ECL intensity of luminol on this modified electrode showed very sensitive responses to oxygen and hydrogen peroxide. The detection limits for dissolved oxygen and hydrogen peroxide were 2 μg L(-1) and 5.5 × 10(-12) M, respectively. Besides the discussion of the intensifying mechanism of this nano-hybrid for ECL of luminol, the developed method was also applied for monitoring dissolved oxygen and evaluating the scavenging efficiency of reactive oxygen species of the Ganoderma lucidum spore.

Development of Electrodeposited Zn/nano-TiO2 Composite Coatings with Enhanced Corrosion Performance

NASA Astrophysics Data System (ADS)

Benea, L.; Dănăilă, E.

2017-06-01

Pure zinc coatings have been found ineffective when are used in aggressive environments such as those which contain chlorides or industrial pollutants [1]. In this paper, Zn/nano-TiO2 composite coatings with various contents of TiO2 nanoparticles (diameter size of 10 nm) were prepared on low-carbon steel by electro-codeposition technique. The deposition was carried out at different cathodic potentials ranging from -1600 mV to -2100 mV for different deposition times between 5-15 min. Pure Zn coatings were also produced under the same experimental conditions for comparison. Present work aims to investigate the effects of selected electrodeposition parameters (cathodic potential, TiO2 nanoparticle concentration in the plating bath and electrodeposition time) on the corrosion behavior of electrodeposited Zn/nano-TiO2 composite obtained. The corrosion experiments were performed in natural seawater, using electrochemical methods such as open circuit potential, potentiodynamic polarization and linear polarization resistance. The results showed that the inclusion of TiO2 nanoparticles into zinc matrix lead to an improved corrosion resistance comparatively with pure zinc coatings obtained under similar conditions.

Synthesis of hybrid cellulose nanocomposite bonded with dopamine SiO2/TiO2 and its antimicrobial activity

NASA Astrophysics Data System (ADS)

Ramesh, Sivalingam; Kim, Gwang-Hoon; Kim, Jaehwan; Kim, Joo-Hyung

2015-04-01

Organic-inorganic hybrid material based cellulose was synthesized by the sol-gel approach. The explosion of activity in this area in the past decade has made tremendous progress in industry or academic both fundamental understanding of sol-gel process and applications of new functionalized hybrid materials. In this present research work, we focused on cellulose-dopamine functionalized SiO2/TiO2 hybrid nanocomposite by sol-gel process. The cellulose-dopamine hybrid nanocomposite was synthesized via γ-aminopropyltriethoxysilane (γ-APTES) coupling agent by in-situ sol-gel process. The chemical structure of cellulose-amine functionalized dopamine bonding to cellulose structure with covalent cross linking hybrids was confirmed by FTIR spectral analysis. The morphological analysis of cellulose-dopamine nanoSiO2/TiO2 hybrid nanocomposite materials was characterized by XRD, SEM and TEM. From this different analysis results indicate that the optical transparency, thermal stability, control morphology of cellulose-dopamine-SiO2/TiO2 hybrid nanocomposite. Furthermore cellulose-dopamine-SiO2/TiO2 hybrid nanocomposite was tested against pathogenic bacteria for antimicrobial activity.

New Photocatalysis for Effective Degradation of Organic Pollutants in Water

NASA Astrophysics Data System (ADS)

Zarei Chaleshtori, M.; Saupe, G. B.; Masoud, S.

2009-12-01

The presence of harmful compounds in water supplies and in the discharge of wastewater from chemical industries, power plants, and agricultural sources is a topic of global concern. The processes and technologies available at the present time for the treatment of polluted water are varied that include traditional water treatment processes such as biological, thermal and chemical treatment. All these water treatment processes, have limitations of their own and none is cost effective. Advanced oxidation processes have been proposed as an alternative for the treatment of this kind of wastewater. Heterogeneous photocatalysis has recently emerged as an efficient method for purifying water. TiO2 has generally been demonstrated to be the most active semiconductor material for decontamination water. One significant factor is the cost of separation TiO2, which is generally a powder having a very small particle size from the water after treatment by either sedimentation or ultrafiltration. The new photocatalyst, HTiNbO5, has been tested to determine whether its photocatalytic efficiency is good enough for use in photocatalytic water purification since it has high surface area and relatively large particle size. The larger particle sizes of the porous materials facilitate catalyst removal from a solution, after purification has taken place. It can be separated from water easily than TiO2, a significant technical improvement that might eliminate the tedious final filtration necessary with a slurry. These materials are characterized and tested as water decontamination photocatalysts. The new catalyst exhibited excellent catalytic activity, but with a strong pH dependence on the photo efficiency. These results suggest that elimination of the ion exchange character of the catalyst may greatly improve its performance at various pHs. This new research proposes to study the effects of a topotactic dehydration reaction on these new porous material catalysts.

Eosin-Y sensitized core-shell TiO2-ZnO nano-structured photoanodes for dye-sensitized solar cell applications.

PubMed

Manikandan, V S; Palai, Akshaya K; Mohanty, Smita; Nayak, Sanjay K

2018-06-01

In the current investigation, TiO 2 and TiO 2 -ZnO (core-shell) spherical nanoparticles were synthesized by simple combined hydrolysis and refluxing method. A TiO 2 core nanomaterial on the shell material of ZnO was synthesized by utilizing variable ratios of ZnO. The structural characterization of TiO 2 -ZnO core/shell nanoparticles were done by XRD analysis. The spherical structured morphology of the TiO 2 -ZnO has been confirmed through field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) studies. The UV-visible spectra of TiO 2 -ZnO nanostructures were also compared with the pristine TiO 2 to investigate the shift of wavelength. The TiO 2 -ZnO core/shell nanoparticles at the interface efficiently collect the photogenarated electrons from ZnO and also ZnO act a barrier for reduced charge recombination of electrolyte and dye-nanoparticles interface. This combination improved the light absorption which induced the charge transfer ability and dye loading capacity of core-shell nanoparticles. An enhancement in the short circuit current (J sc ) from 1.67 mA/cm 2 to 2.1 mA/cm 2 has been observed for TiO 2 -ZnObased photoanode (with platinum free counter electrode), promises an improvement in the energy conversion efficiency by 57% in comparison with that of the DSSCs based on the pristine TiO 2 . Henceforth, TiO 2 -ZnO photoelectrode in ZnO will effectively act as barrier at the interface of TiO 2 -ZnO and TiO 2 , ensuring the potential for DSSC application. Copyright © 2018 Elsevier B.V. All rights reserved.

From nanocorals to nanorods to nanoflowers nanoarchitecture for efficient dye-sensitized solar cells at relatively low film thickness: All Hydrothermal Process

NASA Astrophysics Data System (ADS)

Mali, Sawanta S.; Betty, Chirayath A.; Bhosale, Popatrao N.; Patil, Pramod S.; Hong, Chang Kook

2014-06-01

Simple and low temperature hydrothermal process is employed to synthesize exotic nanostructures of TiO2. The nanostructures are obtained merely by changing the nature of the precursors and processing parameters. The chloride and isopropoxide salts of titanium are used to grow high quality thin films comprising anatase nanocorals, rutile nanorods and rutile nanoflowers respectively. A novel route of addition of room temperature ionic liquid (RTIL) is used to synthesize hitherto unexplored nano-morphologies. The Bronsted Acidic Ionic Liquid [BAIL] 0.01 M, 1: 3-ethoxycarbonylethyl-1-methyl-imidazolium chloride [CMIM][HSO4] RTIL directed growth of TiO2 flowers with bunch of aligned nanorods are obtained. The structural, optical and morphological properties of hydrothermally grown TiO2 samples are studied with the different characterization techniques. The influence of these exotic nano-morphologies on the performance of dye sensitized solar cells (DSSCs) is investigated in detail. It is found that [CMIM][HSO4] can facilitate the formation of novel nanoflower morphology with uniform, dense, and collectively aligned in regular petal like oriented TiO2 nanorods and hence improves the dye adsorption and the photovoltaic performance of DSSCs, typically in short-circuit photocurrent and power conversion efficiency. A best power conversion efficiency of 6.63% has been achieved on a DSSC based on nanoflowers (TNF) film obtained from a [CMIM][HSO4] solution.

Highly Visible Light Responsive, Narrow Band gap TiO2 Nanoparticles Modified by Elemental Red Phosphorus for Photocatalysis and Photoelectrochemical Applications

PubMed Central

Ansari, Sajid Ali; Cho, Moo Hwan

2016-01-01

This paper reports that the introduction of elemental red phosphorus (RP) into TiO2 can shift the light absorption ability from the UV to the visible region, and confirmed that the optimal RP loading and milling time can effectively improve the visible light driven-photocatalytic activity of TiO2. The resulting RP-TiO2 nanohybrids were characterized systematically by a range of techniques and the photocatalytic ability of the RP-TiO2 photocatalysts was assessed further by the photodegradation of a model Rhodamine B pollutant under visible light irradiation. The results suggest that the RP-TiO2 has superior photodegradation ability for model contaminant decomposition compared to other well-known photocatalysts, such as TiO2 and other reference materials. Furthermore, as a photoelectrode, electrochemical impedance spectroscopy, differential pulse voltammetry, and linear scan voltammetry were also performed in the dark and under visible light irradiation. These photoelectrochemical performances of RP-TiO2 under visible light irradiation revealed more efficient photoexcited electron-hole separation and rapid charge transfer than under the dark condition, and thus improved photocatalytic activity. These findings show that the use of earth abundant and inexpensive red phosphorus instead of expensive plasmonic metals for inducing visible light responsive characteristics in TiO2 is an effective strategy for the efficient energy conversion of visible light. PMID:27146098

Photocatalytic Nanocomposites for the Protection of European Architectural Heritage

PubMed Central

Roveri, Marco; Goidanich, Sara; Toniolo, Lucia

2018-01-01

In the field of stone protection, the introduction of inorganic nanoparticles, such as TiO2, ZnO, and Ag in polymeric blends can enhance the protective action of pristine treatments, as well as confer additional properties (photocatalytic, antifouling, and antibacterial). In the framework of the “Nano-Cathedral” European project, nanostructured photocatalytic protective treatments were formulated by using different TiO2 nanoparticles, solvents, and silane/siloxane systems in the blends. The results about the characterization and application of two promising nano-TiO2 based products applied on Apuan marble and Ajarte limestone are here reported, aiming at investigating the complex system “treatment/stone-substrate”. The nanocomposites show better performances when compared to a commercial reference siloxane based protective treatment, resulting in different performances once applied on different carbonatic substrates, with very low and high open porosity, confirming the necessity of correlating precisely the characteristics of the stone material to those of the protective formulations. In particular, the TiO2 photocatalytic behavior is strictly linked to the amount of available nanoparticles and to the active surface area. The alkyl silane oligomers of the water-based formulation have a good penetration into the microstructure of Ajarte limestone, whereas the solvent-based and small size monomeric formulation shows better results for Apuan marble, granting a good coverage of the pores. The encouraging results obtained so far in lab will be confirmed by monitoring tests aiming at assessing the effectiveness of the treatments applied in pilot sites of historical Gothic Cathedrals. PMID:29301338

Revealing the Double-Edged Sword Role of Graphene on Boosted Charge Transfer versus Active Site Control in TiO2 Nanotube Arrays@RGO/MoS2 Heterostructure.

PubMed

Quan, Quan; Xie, Shunji; Weng, Bo; Wang, Ye; Xu, Yi-Jun

2018-05-01

Charge separation/transfer is generally believed to be the most key factor affecting the efficiency of photocatalysis, which however will be counteracted if not taking the active site engineering into account for a specific photoredox reaction. Here, a 3D heterostructure composite is designed consisting of MoS 2 nanoplatelets decorated on reduced graphene oxide-wrapped TiO 2 nanotube arrays (TNTAs@RGO/MoS 2 ). Such a cascade configuration renders a directional migration of charge carriers and controlled immobilization of active sites, thereby showing much higher photoactivity for water splitting to H 2 than binary TNTAs@RGO and TNTAs/MoS 2 . The photoactivity comparison and mechanistic analysis reveal the double-edged sword role of RGO on boosted charge separation/transfer versus active site control in this composite system. The as-observed inconsistency between boosted charge transfer and lowered photoactivity over TNTAs@RGO is attributed to the decrease of active sites for H 2 evolution, which is significantly different from the previous reports in literature. The findings of the intrinsic relationship of balanced benefits from charge separation/transfer and active site control could promote the rational optimization of photocatalyst design by cooperatively manipulating charge flow and active site control, thereby improving the efficiency of photocatalysis for target photoredox processes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of humic acids on the aggregation and sorption of nano-TiO2.

PubMed

Li, Yanjie; Yang, Chen; Guo, Xuetao; Dang, Zhi; Li, Xiaoqin; Zhang, Qian

2015-01-01

In this study, humic acids (HAs) from three sources, peat, sediment and straw, used to coat nano-TiO2 were investigated. The results indicated that HAs isolated from peat were aromatic-rich, whereas those isolated from sediment and straw were aliphatic-rich. The nano-TiO2 sedimentation experiments indicated that the presence of aromatic-rich HAs was more capable of stabilizing nano-TiO2 particles than was the presence of aliphatic-rich HAs. This result is because the deionized phenolic groups in the HAs were preferentially adsorbed on the nano-TiO2 surfaces, which generated a higher charge density on the nano-TiO2 surfaces and caused stronger repulsive forces among particles. Furthermore, the aromatic-rich TiO2-HA complexes exhibited a greater sorption capacity than the aliphatic-rich TiO2-HAs complexes and nonlinear phenanthrene sorption because of their higher affinity and the condensed state of aromatic fractions. Note that natural organic matters, such as humic acids, in aquatic environments can not only increase the stability of nanoparticles but can also influence the mobility of hydrophobic organic compounds (HOCs). Copyright © 2014. Published by Elsevier Ltd.

Solar physical vapor deposition preparation and microstructural characterization of TiO2 based nanophases for dye-sensitized solar cell applications.

PubMed

Negrea, Denis; Ducu, Catalin; Moga, Sorin; Malinovschi, Viorel; Monty, Claude J A; Vasile, Bogdan; Dorobantu, Dorel; Enachescu, Marian

2012-11-01

Titanium dioxide exists in three crystalline phases: anatase, rutile and brookite. Although rutile is thermodynamically more stable, anatase is considered as the most favorable phase for photocatalysis and solar energy conversion. Recent studies have shown a significant improvement of light harvesting and overall solar conversion efficiency of anatase nanoparticles in dye-sensitized solar cells (DSSCs) when using a mixture of anatase and rutile phases (10-15% rutile). TiO2 nanopowders have been prepared by a solar physical vapor deposition process (SPVD). This method has been developed in Odeillo-Font Romeu France using "heliotron" solar reactors working under concentrated sunlight in 2 kW solar furnaces. By controlling reactor's atmosphere type (air/argon) and gas pressure, several types of anatase/rutile nanophases have been obtained with slightly different microstructural properties and morphological characteristics. X-ray diffraction analyses (XRD) were performed on precursor and on the SPVD obtained nanopowders. Information concerning their phase composition and coherence diffraction domain (crystallites size and strain) was obtained. Nanopowders morphology has been studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Gas-generated thermal oxidation of a coordination cluster for an anion-doped mesoporous metal oxide.

PubMed

Hirai, Kenji; Isobe, Shigehito; Sada, Kazuki

2015-12-18

Central in material design of metal oxides is the increase of surface area and control of intrinsic electronic and optical properties, because of potential applications for energy storage, photocatalysis and photovoltaics. Here, we disclose a facile method, inspired by geochemical process, which gives rise to mesoporous anion-doped metal oxides. As a model system, we demonstrate that simple calcination of a multinuclear coordination cluster results in synchronic chemical reactions: thermal oxidation of Ti8O10(4-aminobenzoate)12 and generation of gases including amino-group fragments. The gas generation during the thermal oxidation of Ti8O10(4-aminobenzoate)12 creates mesoporosity in TiO2. Concurrently, nitrogen atoms contained in the gases are doped into TiO2, thus leading to the formation of mesoporous N-doped TiO2. The mesoporous N-doped TiO2 can be easily synthesized by calcination of the multinuclear coordination cluster, but shows better photocatalytic activity than the one prepared by a conventional sol-gel method. Owing to an intrinsic designability of coordination compounds, this facile synthetic will be applicable to a wide range of metal oxides and anion dopants.

Comparison of different wastewater treatments for removal of selected endocrine-disruptors from paper mill wastewaters.

PubMed

Balabanič, Damjan; Hermosilla, Daphne; Merayo, Noemí; Klemenčič, Aleksandra Krivograd; Blanco, Angeles

2012-01-01

There is increasing concern about chemical pollutants that have the ability to mimic hormones, the so-called endocrine-disrupting compounds (EDCs). One of the main reasons for concern is the possible effect of EDCs on human health. EDCs may be released into the environment in different ways, and one of the most significant sources is industrial wastewater. The main objective of this research was to evaluate the treatment performance of different wastewater treatment procedures (biological treatment, filtration, advanced oxidation processes) for the reduction of chemical oxygen demand and seven selected EDCs (dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate, bisphenol A and nonylphenol) from wastewaters from a mill producing 100 % recycled paper. Two pilot plants were running in parallel and the following treatments were compared: (i) anaerobic biological treatment followed by aerobic biological treatment, ultrafiltration and reverse osmosis (RO), and (ii) anaerobic biological treatment followed by membrane bioreactor and RO. Moreover, at lab-scale, four different advanced oxidation processes (Fenton reaction, photo-Fenton reaction, photocatalysis with TiO(2), and ozonation) were applied. The results indicated that the concentrations of selected EDCs from paper mill wastewaters were effectively reduced (100 %) by both combinations of pilot plants and photo-Fenton oxidation (98 %), while Fenton process, photocatalysis with TiO(2) and ozonation were less effective (70 % to 90 %, respectively).

Influence of calcinated and non calcinated nanobioglass particles on hardness and bioactivity of sol-gel-derived TiO2-SiO2 nano composite coatings on stainless steel substrates.

PubMed

Dadash, Mohammad Saleh; Karbasi, Saeed; Esfahani, Mojtaba Nasr; Ebrahimi, Mohammad Reza; Vali, Hojatollah

2011-04-01

Thick films of calcinated and non calcinated nanobioglass (NBG)-titania composite coatings were prepared on stainless steel substrates by alkoxide sol-gel process. Dip-coating method was used for the films preparation. The morphology, structure and composition of the nano composite films were evaluated using environmental scanning electron microscope, X-ray diffraction and Fourier transform infrared spectroscope. The SEM investigation results showed that prepared thick NBG-titania films are smooth and free of macrocracking, fracture or flaking. The grain size of these films was uniform and nano scale (50-60 nm) which confirmed with TEM. Also FTIR confirmed the presence of Si-O-Si bands on the calcinated NBG-titania films. The hardness of the prepared films (TiO(2)-calcinated NBG and TiO(2)-Non calcinated NBG) was compared by using micro hardness test method. The results verified that the presence of calcinated NBG particles in NBG-titania composite enhanced gradually the mechanical data of the prepared films. The in vitro bioactivity of these films was discussed based on the analysis of the variations of Ca and P concentrations in the simulated body fluid (SBF) and their surface morphologies against immersion time. Surface morphology and Si-O-Si bands were found to be of great importance with respect to the bioactivity of the studied films. The results showed that calcinated NBG-titania films have better bioactivity than non calcinated NBG-titania films.

Effect of TiO2 photocatalytic preservation on quality of kiwifruit during shelf life

NASA Astrophysics Data System (ADS)

Hou, Chengjie; Jiang, Yong; Qi, Shasha; Zhang, Changfeng; Guo, Fengjun

2018-04-01

In order to study the effect of titanium dioxide photocatalysis technology on the quality of kiwifruit during shelf life, the texture properties of kiwifruit during shelf life were measured by simulating the effect of cross-ripening among fruits and vegetables under the mixed environment of different fruits and vegetables. The results showed that the kiwifruit after photocatalytic preservation maintained a more mature state in the middle and preliminary stage of shelf life, chewiness is better than the control group and the blank group, compared with the over-ripen control group and low-maturity blank group, experimental group has the best commodity value. Therefore, using nanometer photocatalytic preservation can effectively reduce the ripening effect of kiwifruit in the mixed environment, control the after-ripening of kiwifruit, and meanwhile maintain the commodity value of the kiwifruit during the shelf life.iO2, Photocatalysis, Kiwifruit, Shelf-life.

3D Bi2S3/TiO2 cross-linked heterostructure: An efficient strategy to improve charge transport and separation for high photoelectrochemical performance

NASA Astrophysics Data System (ADS)

Han, Minmin; Jia, Junhong

2016-10-01

A novel 3D cross-linked heterostructure of TiO2 nanorods connecting with each other via ultrathin Bi2S3 nanosheets is constructed by a facile and effective strategy. The growth mechanism has been investigated and proposed based on the evolution of microstructure by changing the reaction parameters. Benefiting from the unique cross-linked heterostructure, the as-prepared Bi2S3 nanosheets modified TiO2 nanorods arrays could achieve a high energy conversion efficiency of 3.29% which is the highest value to date for Bi2S3-only sensitized solar cells as the reported highest value is 2.23% and other reported values are less than 1%. Furthermore, the photoelectrochemical studies clearly reveal that the novel cross-linked heterostructure exhibits much better activity than 0D nanoparticles decorated TiO2 nanorods under visible light irradiation, which may be primarily ascribed to the efficient electron transfer from 2D ultrathin Bi2S3 nanosheets to 1D TiO2 nanorod arrays. The promising results in this work confirm the advantages of cross-linked heterostructure and also undoubtedly offer an attractive synthesis strategy to fabricate other nanorod-based hierarchical architecture as well as nano-devices for solar energy conversion.

Effect of annealing on the structural and optical properties of TiO2 powder prepared by sol-gel route

NASA Astrophysics Data System (ADS)

Halder, Nilanjan; Misra, Kamakhya Prakash

2016-05-01

Using titanium isopropoxide as the precursor, Titanium dioxide (TiO2) powder was synthesized via sol-gel method, a promising low temperature route for preparing nanosized metal oxide semiconductors with good homogeneity at low cost. The as-prepared nano powder was thermally treated in air at 550, 650, 750, 900 and 1100°C for 1hr after drying at room temperature and used for further characterization. X-ray diffraction measurements showed that the annealing treatment has a strong impact on the crystal phase of TiO2 samples. The crystallite size as calculated from Debye Scherer formula lies in the range 29-69 nm and is found to increase with increase in annealing temperature. Photoluminescence studies exhibit an improvement in the optical efficiency of the samples with post synthesis heat treatment. Annealing at temperature above 900°C results in a degradation of the structural and optical quality of the TiO2 nano powder samples.

Removal of reactive blue 19 dye by sono, photo and sonophotocatalytic oxidation using visible light.

PubMed

Khan, Muhammad Abdul Nasir; Siddique, Maria; Wahid, Fazli; Khan, Romana

2015-09-01

An efficient sonophotocatalytic degradation of reactive blue 19 (RB 19) dye was successfully carried out using sulfur-doped TiO2 (S-TiO2) nanoparticles. The effect of various treatment processes that is sonolysis, photolysis, catalysis, sonocatalysis, photocatalysis, and sonophotocatalysis were investigated for RB 19 removal. S-TiO2 were synthesized in 1, 3 and 5 wt.% of sulfur by sol-gel process and characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX), UV-Visible diffuse reflectance spectra (DRS). The results confirm anatase phase of TiO2, porous agglomerate structure, and a red shift in the absorbance spectra of S-TiO2. The dye degradation was studied by using UV-Vis spectrophotometer at λ max=594 nm. The reaction parameters such as pH, catalyst dosage, initial dye concentration, ultrasonic power and effect of sulfur doping in different weight percent were studied to find out the optimum degradation conditions. Optimum conditions were found as: S-TiO2=5 wt.%, catalyst (S-TiO2 5 wt.%)=50mg, RB 19 solution concentration=20 mg L(-1), pH=3, ultrasound power=100 and operating temperature=25°C. The response of 5 wt.% S-TiO2 was found better than 1 and 3 wt.% S-TiO2 and other forms TiO2. The sonophotocatalysis process was superior to other methods. During this process the ultrasound cavitation and photocatalysis water splitting takes place which leads to the generation of OH. As reveled by the GCMS results the reactive blue 19 (20 mg L(-1)) was degraded to 90% within 120 min. The S-TiO2 sonophotocatalysis system was studied for the first time for dye degradation and was found practicable, efficient and cost effective for the degradation of complex and resistant dyes such as RB19. Copyright © 2015. Published by Elsevier B.V.

Fabrication of hierarchically porous TiO2 nanofibers by microemulsion electrospinning and their application as anode material for lithium-ion batteries.

PubMed

Zhang, Jin; Cai, Yibing; Hou, Xuebin; Song, Xiaofei; Lv, Pengfei; Zhou, Huimin; Wei, Qufu

2017-01-01

Titanium dioxide (TiO 2 ) nanofibers have been widely applied in various fields including photocatalysis, energy storage and solar cells due to the advantages of low cost, high abundance and nontoxicity. However, the low conductivity of ions and bulk electrons hinder its rapid development in lithium-ion batteries (LIB). In order to improve the electrochemical performances of TiO 2 nanomaterials as anode for LIB, hierarchically porous TiO 2 nanofibers with different tetrabutyl titanate (TBT)/paraffin oil ratios were prepared as anode for LIB via a versatile single-nozzle microemulsion electrospinning (ME-ES) method followed by calcining. The experimental results indicated that TiO 2 nanofibers with the higher TBT/paraffin oil ratio demonstrated more axially aligned channels and a larger specific surface area. Furthermore, they presented superior lithium-ion storage properties in terms of specific capacity, rate capability and cycling performance compared with solid TiO 2 nanofibers for LIB. The initial discharge and charge capacity of porous TiO 2 nanofibers with a TBT/paraffin oil ratio of 2.25 reached up to 634.72 and 390.42 mAh·g -1 , thus resulting in a coulombic efficiency of 61.51%; and the discharge capacity maintained 264.56 mAh·g -1 after 100 cycles, which was much higher than that of solid TiO 2 nanofibers. TiO 2 nanofibers with TBT/paraffin oil ratio of 2.25 still obtained a high reversible capacity of 204.53 mAh·g -1 when current density returned back to 40 mA·g -1 after 60 cycles at increasing stepwise current density from 40 mA·g -1 to 800 mA·g -1 . Herein, hierarchically porous TiO 2 nanofibers have the potential to be applied as anode for lithium-ion batteries in practical applications.

Comparison of TiO2 nanoparticle and graphene-TiO2 nanoparticle composite phototoxicity to Daphnia magna and Oryzias latipes

EPA Science Inventory

With a dramatic rise in complexity, needs of nanotoxicology research go beyond simple forms of nanomaterials. This study compared the phototoxicity of nano-TiO2and graphene-TiO2 nanocomposite (GNP). GNP was synthesized based on a hydrothermal method, which simultaneously performe...

Design of a plasmonic micromotor for enhanced photo-remediation of polluted anaerobic stagnant waters.

PubMed

Zhang, Zhijun; Zhao, Andong; Wang, Faming; Ren, Jinsong; Qu, Xiaogang

2016-04-25

A motor plasmonic photocatalyst (MPP) is developed to promote photocatalysis in an anaerobic stagnant environment. The MPP is fabricated through the newly developed nano/micromotor fabrication method: template-assisted aqueous phase synthesis. With the help of H2O2 (fuel), the solar photocatalytic efficiency of the MPP can be enhanced more than 110 times.

The highly efficient photocatalytic and light harvesting property of Ag-TiO2 with negative nano-holes structure inspired from cicada wings.

PubMed

Zada, Imran; Zhang, Wang; Zheng, Wangshu; Zhu, Yuying; Zhang, Zhijian; Zhang, Jianzhong; Imtiaz, Muhammad; Abbas, Waseem; Zhang, Di

2017-12-08

The negative replica of biomorphic TiO 2 with nano-holes structure has been effectively fabricated directly from nano-nipple arrays structure of cicada wings by using a simple, low-cost and highly effective sol-gel ultrasonic method. The nano-holes array structure was well maintained after calcination in air at 500 °C. The Ag nanoparticles (10 nm-25 nm) were homogeneously decorated on the surface and to the side wall of nano-holes structure. It was observed that the biomorphic Ag-TiO 2 showed remarkable photocatalytic activity by degradation of methyl blue (MB) under UV-vis light irradiation. The biomorphic Ag-TiO 2 with nano-holes structure showed superior photocatalytic activity compared to the biomorphic TiO 2 and commercial Degussa P25. This high-performance photocatalytic activity of the biomorphic Ag-TiO 2 may be attributed to the nano-holes structure, localized surface plasmon resonance (LSPR) property of the Ag nanoparticles, and enhanced electron-hole separation. Moreover, the biomorphic Ag-TiO 2 showed more absorption capability in the visible wavelength range. This work provides a new insight to design such a structure which may lead to a range of novel applications.

Photocatalysis of gaseous trichloroethylene (TCE) over TiO2: the effect of oxygen and relative humidity on the generation of dichloroacetyl chloride (DCAC) and phosgene.

PubMed

Ou, Hsin-Hung; Lo, Shang-Lien

2007-07-19

Batch photocatalytic degradation of 80+/-2.5 ppm V trichloroethylene (TCE) was conducted to investigate the effect of the oxygen and relative humidity (RH) on the formation of the dichloroacetyl chloride (DCAC) and phosgene. Based on the simultaneous ordinary differential equations (ODEs), the reaction rate constants of TCE ((2.31+/-0.28) approximately (9.41+/-0.63)x10(-2) min(-1)) are generally larger than that of DCAC ((0.94+/-1.25) approximately (9.35+/-1.71)x10(-3) min(-1)) by approximate one order. The phenomenon indicates the degradation potential of TCE is superior to that of DCAC. DCAC appreciably delivers the same degradation behavior with TCE that means there exists an optimum RH and oxygen concentration for photocatalysis of TCE and DCAC. At the time the peak yield of DCAC appears, the conversion ratio based on the carbon atom from TCE to DCAC is within the range of 30-83% suggesting that the DCAC generation is significantly attributed to TCE degradation. Regarding the phosgene formation, the increasing oxygen amount leads to the inhibitory effect on the phosgene yield which fall within the range of 5-15%. The formation mechanism of phosgene was also inferred that the Cl atoms attacking the C-C bond of DCAC results to the generation of phosgene rather than directly from the TCE destruction.

Adsorption-photodegradation of humic acid in water by using ZnO coupled TiO2/bamboo charcoal under visible light irradiation.

PubMed

Wang, Xuejiang; Wu, Zhen; Wang, Yin; Wang, Wei; Wang, Xin; Bu, Yunjie; Zhao, Jianfu

2013-11-15

ZnO coupled TiO2/bamboo charcoal (ZnO-TiO2/BC) was prepared using the sol-gel method combined with microwave irradiation. The ZnO-TiO2/BC and TiO2/BC were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N2 adsorption (BET), and UV-vis diffuse reflectance spectroscopy (UV-vis-DRS). The ZnO dopant promoted the transformation of anatase TiO2 to rutile phase, and a significant red shift of absorption edge was brought out due to the interfacial coupling effect between ZnO and TiO2 particles. The BET specific surface area and total pore volume decreased with ZnO doping, indicating that some micropores were blocked. SEM studies indicated that ZnO was almost uniformly deposited on the surface of the ZnO-TiO2/BC. The adsorption and photocatalytic degradation experiments showed that the photo-degrade efficiency for Zno-TiO2/BC was higher than that of TiO2/BC, and for both composites, the removal efficiency of HA increased as pH decreased from 10.0 to 2.0. The degradation of HA by ZnO-TiO2/BC and TiO2/BC fitted well with the Langmuir-Hinshelwood kinetics model, and HA degradation was achieved through a synergistic mechanism of adsorption and photocatalysis. ZnO-TiO2/BC could be used as an effective and alternative photocatalyst for the treatment of water contaminated by organic pollutants. Copyright © 2013 Elsevier B.V. All rights reserved.

A facile preparation of TiO2/ACF with Csbnd Ti bond and abundant hydroxyls and its enhanced photocatalytic activity for formaldehyde removal

NASA Astrophysics Data System (ADS)

Liu, R. F.; Li, W. B.; Peng, A. Y.

2018-01-01

The quantum yields and efficiency(ACF) was prepared via a modified deposition-precipitation method to facilitate its photon absorption and of photogenerated charge carriers have been the major issues for photocatalysis on titania catalyst. The TiO2/ACF catalyst with anatase TiO2 uniformly dispersed on activated carbon fibers electron transfer, thus improve the quantum yields and efficiency of the photogenerated electrons and holes. XPS analysis on the catalyst demonstrates the existence of Ti3+ and Ti2+ species, Csbnd Ti bond and abundant hydroxyls, which are also proved by UV-vis DRS and TG-DSC analysis. It is believed that the acid environment in preparation plays an essential role in the formation of Csbnd Ti bond and surface hydroxyls, which can be tuned by changing hydrothermal synthesis time. The Csbnd Ti bond can improve the electron transfer in the catalyst and the substantial surface hydroxyls lead to high absorption for UV lines and enhanced adsorption of water and formaldehyde, resulting in more active OH free radicals and the outstanding photocatalytic activity of TiO2/ACF, which is much higher than the titania powder for photocatalytic removal of low concentration formaldehyde. The essential role of surface hydroxyls for photocatalytic activity was confirmed surpassing that of chemical bond between carbon and titanium in TiO2-carbon composite for the first time.

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.

Use of photovoltaic detector for photocatalytic activity estimation

NASA Astrophysics Data System (ADS)

Das, Susanta Kumar; Satapathy, Pravakar; Rao, P. Sai Shruti; Sabar, Bilu; Panda, Rudrashish; Khatua, Lizina

2018-05-01

Photocatalysis is a very important process and have numerous applications. Generally, to estimate the photocatalytic activity of newly grown material, its reaction rate constant w.r.t to some standard commercial TiO2 nanoparticles like Degussa P25 is evaluated. Here a photovoltaic detector in conjunction with laser is used to determine this rate constant. This method is tested using Zinc Orthotitanate (Zn2TiO4) nanoparticles prepared by solid state reaction and it is found that its reaction rate constant is six times higher than that of P25. The value is found to be close to the value found by a conventional system. Our proposed system is much more cost-effective than the conventional one and has the potential to do real time monitoring of the photocatalytic activity.

The reduced bioavailability of copper by nano-TiO₂ attenuates the toxicity to Microcystis aeruginosa.

PubMed

Chen, Jinyuan; Qian, Yi; Li, Herong; Cheng, Yanhong; Zhao, Meirong

2015-08-01

Nano-TiO2 is a widely applied nanoparticle (NPs) and co-exists with other pollutants such as heavy metals in aquatic environments. However, minimal knowledge is available concerning the ecological risk of these mixtures. Our study reported that at no toxic effect concentrations of TiO2 nanoparticles (5 mg/L), the toxicity of Cu ions to the algae Microcystis aeruginosa was significantly attenuated by TiO2 nanoparticles. Specifically, the concentration of photosynthetic pigments (i.e., concentration of Chla) increased 37% when comparing only Cu ions treated and the nano-TiO2-Cu co-incubation. The levels of phycocyanin (PC), allophycocyanin (APC), phycoerythrin (PE), and phycobiliprotein (PBPs) were also recovered at levels ranging from 23 to 35% after 72 h. For oxidative indexes, the decreased activities of the superoxide dismutase (SOD), peroxidase (POD) content, and malondialdehyde (MDA) with the existence of nano-TiO2 displayed a lower level compared to Cu ions treatment only at 24 and 48 h. This toxicity attenuation can be confirmed by subcellular structures because the impairment to cellular membranes and organelles reduced with the presence of nano-TiO2. The potential mechanisms of the antagonism between the nano-TiO2 and Cu ions can be partially attributed to the sorption of copper onto TiO2 nanoparticles, which fitted the Freundlich isotherm (coefficient = 0.967). The decreased bioavailability of Cu ions protected algae cells from being attacked by free Cu ions. Given the abundance of released nanoparticles and unique physicochemical property of nanoparticles, our results elucidated the ecosafety of nanoparticles and co-substrates in aquatic systems.

Photocatalytic degradation of NO/NO2 gas injected into a 10-m3 experimental chamber.

PubMed

Hot, Julie; Martinez, T; Wayser, B; Ringot, E; Bertron, A

2017-05-01

This paper investigates a new test method to assess the photocatalytic activity of plasterboards coated with a TiO 2 dispersion under real-world conditions. The degradation of nitrogen oxides NO x (NO and NO 2 ) is studied and the photocatalytic efficiency under UV illumination is evaluated in a 10-m 3 room after a constant gas injection. Two ultrafine TiO 2 dispersions are used: 0.85% TiO 2 and 5% TiO 2 , and three types of gas are tested: an NO/NO 2 mixture (8/8 mol-ppm), NO (45 mol-ppm) and NO 2 (45 mol-ppm). The test method presented here is midway between laboratory and real-scale procedures and allows better control of the experimental parameters than a real field experiment. Testing a mixture of NO and NO 2 is a way to get closer to real-world conditions as air is polluted by various gases. This study focuses on the degradation of NO and NO 2 under UV illumination when two types of TiO 2 dispersions are used and highlights the difference in behaviour between these two molecules in terms of photocatalytic degradation. The results show that photocatalytic activity does not appear to be efficient to degrade NO 2 molecules. Another mechanism seems to be responsible for the reduction of the concentration of NO 2 , namely adsorption. Encouraging results are obtained with NO molecules, which can be degraded by photocatalysis. The degradation observed is even greater with the more concentrated TiO 2 dispersion.

A Brown Mesoporous TiO2-x /MCF Composite with an Extremely High Quantum Yield of Solar Energy Photocatalysis for H2 Evolution.

PubMed

Xing, Mingyang; Zhang, Jinlong; Qiu, Bocheng; Tian, Baozhu; Anpo, Masakazu; Che, Michel

2015-04-24

A brown mesoporous TiO2-x /MCF composite with a high fluorine dopant concentration (8.01 at%) is synthesized by a vacuum activation method. It exhibits an excellent solar absorption and a record-breaking quantum yield (Φ = 46%) and a high photon-hydrogen energy conversion efficiency (η = 34%,) for solar photocatalytic H2 production, which are all higher than that of the black hydrogen-doped TiO2 (Φ = 35%, η = 24%). The MCFs serve to improve the adsorption of F atoms onto the TiO2 /MCF composite surface, which after the formation of oxygen vacancies by vacuum activation, facilitate the abundant substitution of these vacancies with F atoms. The decrease of recombination sites induced by high-concentration F doping and the synergistic effect between lattice Ti(3+)-F and surface Ti(3+)-F are responsible for the enhanced lifetime of electrons, the observed excellent absorption of solar light, and the photocatalytic production of H2 for these catalysts. The as-prepared F-doped composite is an ideal solar light-driven photocatalyst with great potential for applications ranging from the remediation of environmental pollution to the harnessing of solar energy for H2 production. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TiO2 effect on crystallization mechanism and physical properties of nano glass-ceramics of MgO-Al2O3-SiO2 glass system.

PubMed

Jo, Sinae; Kang, Seunggu

2013-05-01

The effect of TiO2 on the degree of crystallization, thermal properties and microstructure for MgO-Al2O3-SiO2 glass-ceramics system containing 0-13 wt% TiO2 and 0-1.5 wt% B2O3 in which the cordierite is the main phase was studied. Using Kissinger and Augis-Bennett equations, the activation energy, 510 kJ/mol and Avrami constant, 1.8 were calculated showing the surface-oriented crystallization would be preferred. The alpha-cordierite phase was generated in the glass-ceramics of containing TiO2 of 0-5.6 wt%. However, for the glass-ceramics of TiO2 content above 7 wt%, an alpha-cordierite disappeared and micro-cordierite phase was formed. The glass-ceramics of no TiO2 added had spherical crystals of few tens nanometer size spread in the matrix. As TiO2 content increased up to 5.6 wt%, a lump of dendrite was formed. In the glass-ceramics containing TiO2 7-13 wt%, in which the main phase is micro-cordierite, the dendrite crystal disappeared and a few hundred nanometer sized crystal particles hold tightly each other were generated. The thermal conductivity of glass-ceramics of both a-cordierite and micro-cordierite base decreased with TiO2 contend added. The thermal conductivity of glass-ceramics of 1.5 wt% TiO2 added was 3.4 W/mK which is 36% higher than that of glass-ceramics of no TiO2 added. The sintering temperature for 1.5 wt% TiO2 glass-ceramics was 965 degrees C which could be concluded as to apply to LTCC process for LED packaging.

Understanding the effect of surface/bulk defects on the photocatalytic activity of TiO2: anatase versus rutile.

PubMed

Yan, Junqing; Wu, Guangjun; Guan, Naijia; Li, Landong; Li, Zhuoxin; Cao, Xingzhong

2013-07-14

The sole effect of surface/bulk defects of TiO2 samples on their photocatalytic activity was investigated. Nano-sized anatase and rutile TiO2 were prepared by hydrothermal method and their surface/bulk defects were adjusted simply by calcination at different temperatures, i.e. 400-700 °C. High temperature calcinations induced the growth of crystalline sizes and a decrease in the surface areas, while the crystalline phase and the exposed facets were kept unchanged during calcination, as indicated by the characterization results from XRD, Raman, nitrogen adsorption-desorption, TEM and UV-Vis spectra. The existence of surface/bulk defects in calcined TiO2 samples was confirmed by photoluminescence and XPS spectra, and the surface/bulk defect ratio was quantitatively analyzed according to positron annihilation results. The photocatalytic activity of calcined TiO2 samples was evaluated in the photocatalytic reforming of methanol and the photocatalytic oxidation of α-phenethyl alcohol. Based on the characterization and catalytic results, a direct correlation between the surface specific photocatalytic activity and the surface/bulk defect density ratio could be drawn for both anatase TiO2 and rutile TiO2. The surface defects of TiO2, i.e. oxygen vacancy clusters, could promote the separation of electron-hole pairs under irradiation, and therefore, enhance the activity during photocatalytic reaction.

Facile decoration of TiO2 nanoparticles on graphene for solar degradation of organic dye

NASA Astrophysics Data System (ADS)

Salem, Shiva; Salem, Amin; Rezaei, Mostafa

2016-11-01

The reduced graphene oxide is interesting material for the synthesis of TiO2-based photocatalyst. In the present investigation, blackberry fruit, which contains high levels of anthocyanins and other phenolic compounds, was employed as a reducing agent mainly due to its high antioxidant capacity. The nano-crystalline TiO2 was decorated on different amounts of graphene oxide with sol-gel method and then the photocatalytic activity for degradation of cationic dye was evaluated by UV spectroscopy to achieve the optimum content of graphene oxide. The decoration of anatase nanoparticles on prepared reduced graphene oxide was investigated by X-ray diffraction, scanning and transmission electron microscopy techniques. The new composite gives significantly higher activity when is compared to the compositions fabricated by graphene oxide. The compact layer provides a large TiO2-graphene contact area and reduces the electron recombination. The decoration of TiO2 nanoparticles, 5-10 nm, on the graphene oxide reduced by blackberry juice further improves the dye removal. The results imply that the nanoparticle decoration is the key strategy to increase the degradation capacity.

Low temperature synthesis of polyaniline-crystalline TiO2-halloysite composite nanotubes with enhanced visible light photocatalytic activity.

PubMed

Li, Cuiping; Wang, Jie; Guo, Hong; Ding, Shujiang

2015-11-15

A series of one-dimensional polyaniline-crystalline TiO2-halloysite composite nanotubes with different mass ratio of polyaniline to TiO2 are facilely prepared by employing the low-temperature synthesis of crystalline TiO2 on halloysite nanotubes. The halloysite nanotubes can adsorb TiO2/polyaniline precursors and induce TiO2 nanocrystals/polyaniline to grow on the support in situ simultaneously. By simply adjusting the acidity of reaction system, PANI-crystalline TiO2-HA composite nanotubes composed of anatase, a mixed phase TiO2 and different PANI redox state are obtained. The XRD and UV-vis results show that the surface polyaniline sensitization has no effect on the crystalline structure of halloysite and TiO2 and the light response of TiO2 is extended to visible-light regions. Photocatalysis test results reveal the photocatalytic activity will be affected by the pH value and the volume ratio of ANI to TTIP. The highest photocatalytic activity is achieved with the composite photocatalysts prepared at pH 0.5 and 1% volume ratio of ANI and TTIP owing to the sensitizing effect of polyaniline and the charge transfer from the photoexcited PANI sensitizer to TiO2. Moreover, the PANI-TiO2-HA composite nanotubes synthesized by one-step at pH 0.5 with 1% volume ratio of ANI to TTIP exhibit higher visible light photocatalytic activity than those synthesized by the two-step. Heterogeneous PANI-TiO2-HA composite nanotubes prepared at pH 0.5 exhibit a higher degradation activity than that prepared at pH 1.5. The redoped experiment proves that the PANI redox state plays the main contribution to the enhanced visible light catalytic degradation efficiency of PANI-TiO2-HA prepared at pH 0.5. Furthermore, the heterogeneous PANI-crystalline TiO2-HA nanotubes have good photocatalytic stability and can be reused four times with only gradual loss of activity under visible light irradiation. Copyright © 2015 Elsevier Inc. All rights reserved.

Nano-titanium dioxide modulates the dermal sensitization potency of DNCB

PubMed Central

2012-01-01

We determined the ability of a model nanoparticle (NP) (titanium dioxide, TiO2) to modulate sensitization induced by a known potent dermal sensitizer (dinitrochlorobenzene) using a variant of the local lymph node assay called lymph node proliferation assay. BALB/c mice received sub-cutaneous injections of vehicle (2.5 mM sodium citrate), TiO2 NPs (0.004, 0.04 or 0.4 mg/ml) or pigment particles (0.04 mg/ml) both stabilized in sodium citrate buffer at the base of each ear (2x50μl), before receiving dermal applications (on both ears) of 2,4-Dinitrochlorobenzene (DNCB) (2x25μl of 0.1%) or its vehicle (acetone olive oil – AOO (4:1)) on days 0, 1 and 2. On day 5, the stimulation index (SI) was calculated as a ratio of 3HTdR incorporation in lymphocytes from DNBC-treated mice and AOO-treated controls. In a second experiment the EC3-value for DNCB (0 to 0.1%) was assessed in the absence or presence of 0.04 mg/ml TiO2. In a third experiment, the lymphocyte subpopulations and the cytokine secretion profile were analyzed after TiO2 (0.04 mg/ml) and DNCB (0.1%) treatment. Injection of NPs in AOO-treated control mice did not have any effect on lymph node (LN) proliferation. DNCB sensitization resulted in LN proliferation, which was further increased by injection of TiO2 NPs before DNCB sensitization. The EC3 of DNCB, with prior injection of vehicle control was 0.041%, while injection with TiO2 decreased the EC3 of DNCB to 0.015%. TiO2 NPs pre-treatment did not alter the lymphocyte subpopulations, but significantly increased the level of IL-4 and decreased IL-10 production in DNCB treated animals. In conclusion, our study demonstrates that administration of nano-TiO2 increases the dermal sensitization potency of DNCB, by augmenting a Th2 response, showing the immunomodulatory abilities of NPs. PMID:22621278

Effect of TiO2 nano fillers on the electrical conductivity of PSAN/TiO2 polymer nanocomposites

NASA Astrophysics Data System (ADS)

Ningaraju, S.; Munirathnamma, L. M.; Kumar, K. V. Aneesh; Ravikumar, H. B.

2016-05-01

The microstructural characterization of Polystyrene co-acrylonitrile and Titanium dioxide (PSAN/TiO2) nanocomposites has been performed by Positron Annihilation Lifetime Spectroscopy. The decrease of positron lifetime parameters viz. o-Ps lifetime (τ3) and free volume size (Vf) up to 0.6 wt% of TiO2 is attributed to the filling of free volume holes by TiO2 nanoparticles. The increased free volume size (Vf) after 0.6 wt% of TiO2 indicates the formation of interface due to TiO2 nanoclusters. The variation of electrical conductivity at the lower and higher concentration of TiO2 in (PSAN/TiO2) nanocomposites is attributed to the blocking effect and space charge effect respectively.

Positron annihilation lifetime study of Nafion/titanium dioxide nano-composite membranes

NASA Astrophysics Data System (ADS)

Lei, M.; Wang, Y. J.; Liang, C.; Huang, K.; Ye, C. X.; Wang, W. J.; Jin, S. F.; Zhang, R.; Fan, D. Y.; Yang, H. J.; Wang, Y. G.

2014-01-01

Positron annihilation lifetime (PAL) technique is applied for investigation of size and number density of free volumes in Nafion/TiO2-nanoparticles composite membrane. The proton transporting ability is correlated with the properties of free volume inside the membrane. It is revealed that composite membrane with 5 wt% of TiO2 nano-fillers exhibits good electrochemical performance under reduced humidity and it can be saturated with water at relative humidity of 50%, under which ionic clusters and proton transporting channels are formed, indicating that composite membranes with 5 wt% of TiO2 nano-fillers are effective electrolyte for fuel cells operated at reduced humidification levels. The results suggest that PAL can be a powerful tool for elucidating the relationship between microstructure and ion transport in polymer electrolyte membranes.

Characteristics of phase-change materials containing oxide nano-additives for thermal storage.

PubMed

Teng, Tun-Ping; Yu, Chao-Chieh

2012-11-06

In this study, the authors report the production of nanocomposite-enhanced phase-change materials (NEPCMs) using the direct-synthesis method by mixing paraffin with alumina (Al2O3), titania (TiO2), silica (SiO2), and zinc oxide (ZnO) as the experimental samples. Al2O3, TiO2, SiO2, and ZnO were dispersed into three concentrations of 1.0, 2.0, and 3.0 wt.%. Through heat conduction and differential scanning calorimeter experiments to evaluate the effects of varying concentrations of the nano-additives on the heat conduction performance and thermal storage characteristics of NEPCMs, their feasibility for use in thermal storage was determined. The experimental results demonstrate that TiO2 is more effective than the other additives in enhancing both the heat conduction and thermal storage performance of paraffin for most of the experimental parameters. Furthermore, TiO2 reduces the melting onset temperature and increases the solidification onset temperature of paraffin. This allows the phase-change heat to be applicable to a wider temperature range, and the highest decreased ratio of phase-change heat is only 0.46%, compared to that of paraffin. Therefore, this study demonstrates that TiO2, added to paraffin to form NEPCMs, has significant potential for enhancing the thermal storage characteristics of paraffin.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Miao; Wang, Wei; Liu, Yang

Three-dimensional (3D) network structure has been envisioned as a superior architecture for lithium ion battery (LIB) electrodes, which enhances both ion and electron transport to significantly improve battery performance. Herein, a 3D carbon nano-network is fabricated through chemical vapor deposition of carbon on a scalably manufactured 3D porous anodic alumina (PAA) template. As a demonstration on the applicability of 3D carbon nano-network for LIB electrodes, the low conductivity active material, TiO 2, is then uniformly coated on the 3D carbon nano-network using atomic layer deposition. High power performance is demonstrated in the 3D C/TiO 2 electrodes, where the parallel tubesmore » and gaps in the 3D carbon nano-network facilitates fast Li ion transport. A large areal capacity of ~0.37 mAh·cm –2 is achieved due to the large TiO 2 mass loading in the 60 µm-thick 3D C/TiO 2 electrodes. At a test rate of C/5, the 3D C/TiO 2 electrode with 18 nm-thick TiO 2 delivers a high gravimetric capacity of ~240 mAh g –1, calculated with the mass of the whole electrode. A long cycle life of over 1000 cycles with a capacity retention of 91% is demonstrated at 1C. In this study, the effects of the electrical conductivity of carbon nano-network, ion diffusion, and the electrolyte permeability on the rate performance of these 3D C/TiO 2 electrodes are systematically studied.« less

Phototoxicity of TiO2 nanoparticles to a freshwater benthic amphipod: are benthic systems at risk?

EPA Science Inventory

This study investigated phototoxicity of TiO2 nanoparticles (nano-TiO2) to a freshwater benthic amphipod (Hyalella azteca) using 48-h and 96-h bioassays. Thorough monitoring of particle interactions with exposure media (Lake Superior water, LSW) and the surface of organisms was p...

Phototoxicity of TiO2 Nanoparticles to Two Aquatic Species: Daphnia magna and Zebrafish (Danio rerio) Embryo

EPA Science Inventory

Ecotoxicological studies on TiO2 nanoparticles (nano-TiO2) are expanding rapidly due to their widespread use in both industrial and consumer products. However, few studies have focused on their potential phototoxicity related to the photocatalytic property of the material. In thi...

Studies on Nano-Engineered TiO2 Photo Catalyst for Effective Degradation of Dye

NASA Astrophysics Data System (ADS)

Sowmya, S. R.; Madhu, G. M.; Hashir, Mohammed

2018-02-01

All Heterogeneous photo catalysis employing efficient photo-catalyst is the advanced dye degradation technology for the purification of textile effluent. The present work focuses on Congo red dye degradation employing synthesized Ag doped TiO2 nanoparticles as photocatalyst which is characterized using SEM, XRD and FTIR. Studies are conducted to study the effect of various parameters such as initial dye concentration, catalyst loading and pH of solution. Ag Doped TiO2 photocatalyst improve the efficacy of TiO2 by reducing high band gap and electron hole recombination of TiO2. The reaction kinetics is analyzed and the process is found to follow pseudo first order kinetics.

Comparative study of photocatalytic oxidation on the degradation of formaldehyde and fuzzy mathematics evaluation of filters

NASA Astrophysics Data System (ADS)

Yu, Huili; Zhang, Jieting

2012-04-01

In this study, formaldehyde, one of the major volatile organic compounds, is chosen as the target pollutant. The polytetrafluoroethylene (PTFE) filter, a low cost and commonly used material in industry, is employed as the substrate for nano TiO2 photocatalyst coating at room temperature, which has been scarcely used compared to ceramics or glass beads. Furthermore, a specific experimental set-up that is similar to actual air purification system is developed for the testing. The degradation mechanisms of photolysis reaction, adsorption and photocatalytic oxidation reaction on volatile organic compounds are present respectively. The influences of three aspects mentioned above are compared by a serial of experimental data. The high efficiency of volatile organic compounds on the degradation of formaldehyde is assured. Furthermore, the purification characteristics of three kinds of activated carbon filters and PTFE filter with nano TiO2 are evaluated with the method of fuzzy mathematics. In the end, the result shows that the filter with nano TiO2 has the optimal comprehensive performances.

Comparative study of photocatalytic oxidation on the degradation of formaldehyde and fuzzy mathematics evaluation of filters

NASA Astrophysics Data System (ADS)

Yu, Huili; Zhang, Jieting

2011-11-01

In this study, formaldehyde, one of the major volatile organic compounds, is chosen as the target pollutant. The polytetrafluoroethylene (PTFE) filter, a low cost and commonly used material in industry, is employed as the substrate for nano TiO2 photocatalyst coating at room temperature, which has been scarcely used compared to ceramics or glass beads. Furthermore, a specific experimental set-up that is similar to actual air purification system is developed for the testing. The degradation mechanisms of photolysis reaction, adsorption and photocatalytic oxidation reaction on volatile organic compounds are present respectively. The influences of three aspects mentioned above are compared by a serial of experimental data. The high efficiency of volatile organic compounds on the degradation of formaldehyde is assured. Furthermore, the purification characteristics of three kinds of activated carbon filters and PTFE filter with nano TiO2 are evaluated with the method of fuzzy mathematics. In the end, the result shows that the filter with nano TiO2 has the optimal comprehensive performances.

Solar photo-Fenton using peroxymonosulfate for organic micropollutants removal from domestic wastewater: comparison with heterogeneous TiO₂ photocatalysis.

PubMed

Ahmed, Moussa Mahdi; Brienza, Monica; Goetz, Vincent; Chiron, Serge

2014-12-01

This work aims at decontaminating biologically treated domestic wastewater effluents from organic micropollutants by sulfate radical based (SO4(-)) homogeneous photo-Fenton involving peroxymonosulfate as an oxidant, ferrous iron (Fe(II)) as a catalyst and simulated solar irradiation as a light source. This oxidative system was evaluated by using several probe compounds belonging to pesticides (bifenthrin, mesotrione and clothianidin) and pharmaceuticals (diclofenac, sulfamethoxazole and carbamazepine) classes and its kinetic efficiency was compared to that to the well known UV-Vis/TiO2 heterogeneous photocatalysis. Except for carbamazepine, apparent kinetic rate constants were always 10 times higher in PMS/Fe(II)/UV-Vis than in TiO2/UV-Vis system and more than 70% of total organic carbon abatement was reached in less than one hour treatment. Hydroxyl radical (OH) and SO4(-) reactivity was investigated using mesotrione as a probe compound through by-products identification by liquid chromatography-high resolution-mass spectrometry and transformation pathways elucidation. In addition to two OH based transformation pathways, a specific SO4(-) transformation pathway which first involved degradation through one electron transfer oxidation processes followed by decarboxylation were probably responsible for mesotrione degradation kinetic improvement upon UV-Vis/PMS/Fe(II) system in comparison to UVVis/TiO2 system. Copyright © 2014 Elsevier Ltd. All rights reserved.

Fabrication of Eu-TiO2 NCs functionalized cotton textile as a multifunctional photocatalyst for dye pollutants degradation

NASA Astrophysics Data System (ADS)

Caschera, Daniela; Federici, Fulvio; de Caro, Tilde; Cortese, Barbara; Calandra, Pietro; Mezzi, Alessio; Lo Nigro, Raffaella; Toro, Roberta G.

2018-01-01

A modified one step and cost-effective chemical green route has been used to synthesize oleate-capped TiO2 anatase nanocrystals (NCs) doped with different amounts of europium, with high yields and without high-temperature post-calcination processes. Europium doping endowed TiO2 NCs with an intense red luminescence associated with the 5D0 → 7F2 transition of the electronic structure of Eu3+ and was responsible for both the morphological change of the NCs structure (from nanorods to spherical nanoparticles) and the blue shift in the absorption edge respect to the undoped TiO2 NCs. Furthermore, photocatalytic experiments revealed that a low-content (0.5 mol%) Eu3+ doped TiO2 NCs showed the best ability as photocatalyst for the degradation of methylene blue (MB) under both UV and visible light irradiation, even if all the Eu3+ doped oleate-capped TiO2 NCs were more effective under visible light. Moreover, taking advantage of their photocatalytic activity, the 0.5% Eu3+ doped oleate-capped TiO2 photocatalysts has been employed on cotton fabrics. Our results highlighted that functionalization of cotton textile with Eu3+ doped oleate-capped TiO2 NCs imparted new functionalities, such as a high photocatalytic activity toward MB degradation under visible light. In addition, it determined also the change in the wetting behaviour of cotton that switches to a superhydrophobic nature. The obtained fabric also showed stable and robust superhydrophobicity against strong acid and alkaline environments. Multifunctional materials having simultaneously luminescence, superhydrophobicity and visible light photocatalysis are expected to be very useful in many technological applications.

"A bridge over troubled gaps": up-conversion driven photocatalysis for hydrogen generation and pollutant degradation by near-infrared excitation.

PubMed

Acosta-Mora, P; Domen, K; Hisatomi, T; Lyu, H; Méndez-Ramos, J; Ruiz-Morales, J C; Khaidukov, N M

2018-02-15

Spectral up-conversion (UC) has been attracting growing interest for the effective harvesting of the near-infrared (NIR) part of sunlight for photocatalytic hydrogen production and environmental purification. We present evidence of NIR-to-UV-VIS photon conversion for degradation of organic dyes and hydrogen and oxygen evolution via water-splitting by TiO 2 and Rh-Cr oxide-loaded SrTiO 3 :Al photocatalysts, respectively.

Photodegradation of pharmaceuticals and personal care products in water treatment using carbonaceous-TiO2 composites: A critical review of recent literature.

PubMed

Awfa, Dion; Ateia, Mohamed; Fujii, Manabu; Johnson, Matthew S; Yoshimura, Chihiro

2018-05-23

The high concentrations of pharmaceuticals and personal care products (PPCP) that found in water in many locations are of concern. Among the available water treatment methods, heterogeneous photocatalysis using TiO 2 is an emerging and viable technology to overcome the occurrence of PPCP in natural and waste water. The combination of carbonaceous materials (e.g., activated carbon, carbon nanotubes and graphene nanosheets) with TiO 2 , a recent development, gives significantly improved performance. In this article, we present a critical review of the development and fabrication of carbonaceous-TiO 2 and its application to PPCP removal including its influence on water chemistry, and the relevant operational parameters. Finally, we present an analysis of current priorities in the ongoing research and development of carbonaceous-TiO 2 for the photodegradation of PPCP. Copyright © 2018 Elsevier Ltd. All rights reserved.

Absolute band structure determination on naturally occurring rutile with complex chemistry: Implications for mineral photocatalysis on both Earth and Mars

NASA Astrophysics Data System (ADS)

Li, Yan; Xu, Xiaoming; Li, Yanzhang; Ding, Cong; Wu, Jing; Lu, Anhuai; Ding, Hongrui; Qin, Shan; Wang, Changqiu

2018-05-01

Rutile is the most common and stable form of TiO2 that ubiquitously existing on Earth and other terrestrial planets like Mars. Semiconducting mineral such as rutile-based photoredox reactions have been considered to play important roles in geological times. However, due to the inherent complexity in chemistry, the precision determination on band structure of natural rutile and the theoretical explanation on its solar-driven photochemistry have been hardly seen yet. Considering the multiple minor and trace elements in natural rutile, we firstly obtained the single-crystal crystallography, mineralogical composition and defects characteristic of the rutile sample by using both powder and single crystal X-ray diffraction, electron microprobe analysis and X-ray photoelectron spectroscopy. Then, the band gap was accurately determined by synchrotron-based O K-edge X-ray absorption and emission spectra, which was firstly applied to natural rutile due to its robustness on compositions and defects. The absolute band edges of the rutile sample was calculated by considering the electronegativity of the atoms, band gap and point of zero charge. Besides, after detecting the defect energy levels by photoluminescence spectra, we drew the schematic band structure of natural rutile. The band gap (2.7 eV) of natural rutile was narrower than that of synthetic rutile (3.0 eV), and the conduction and valence band edges of natural rutile at pH = pHPZC were determined to be -0.04 V and 2.66 V (vs. NHE), respectively. The defect energy levels located at nearly the middle position of the forbidden band. Further, we used theoretical calculations to verify the isomorphous substitution of Fe and V for Ti gave rise to the distortion of TiO6 octahedron and created vacancy defects in natural rutile. Based on density functional theory, the narrowed band gap was interpreted to the contribution of Fe-3d and V-3d orbits, and the defect energy state was formed by hybridization of O-2p and Fe/V/Ti-3d orbits in the forbidden band. Therefore, excitons can be created under visible light. The conduction band electrons and valence band holes enabled the photoreduction of CO2 to organic molecules (e.g., acetic acid and CH4) and photooxidative generation of oxidants (e.g., radOH, O2 and ClO4-) via rutile photocatalysis, respectively. This study underlies the capability of natural semiconducting minerals in solar energy utilization and the implications of their photocatalysis in both the origin of primitive life on Earth and formation of modern environments on Mars.

Photo-oxidation of cork manufacturing wastewater.

PubMed

Silva, Carla A; Madeira, Luis M; Boaventura, Rui A; Costa, Carlos A

2004-04-01

Several photo-activated processes have been investigated for oxidation of a cork manufacturing wastewater. A comparative activity study is made between different homogeneous (H2O2/UV-Vis and H2O2/Fe2+/UV-Vis) and heterogeneous (TiO2/UV-Vis and TiO2/H2O2/UV-Vis) systems, with degradation performances being evaluated in terms of total organic carbon (TOC) removal. Results obtained in a batch photo-reactor show that photo-catalysis with TiO2 is not suitable for this kind of wastewater while the H2O2/UV-Vis oxidation process, for which the effect of some operating conditions was investigated, allows to remove 39% of TOC after 4 h of operation (for C(H2O2)=0.59 M, pH=10 and T=35 degrees C). The combined photo-activated process, i.e., using both TiO2 and H2O2, yields an overall TOC decrease of 46% (for C(TiO2)=1.0 gl(-1)). The photo-Fenton process proved to be the most efficient, proceeds at a much higher oxidation rate and allows to achieve 66% mineralization in just 10 min of reaction time (for C(H2O2)=0.31 M, T=30 degrees C, Fe2+:H2O2=0.12 (mol) and pH=3.2).

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. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating

NASA Astrophysics Data System (ADS)

Hang, Tian; Chen, Hui-Jiuan; Xiao, Shuai; Yang, Chengduan; Chen, Meiwan; Tao, Jun; Shieh, Han-ping; Yang, Bo-ru; Liu, Chuan; Xie, Xi

2017-12-01

Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials.

TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating

PubMed Central

Hang, Tian; Chen, Hui-Jiuan; Xiao, Shuai; Yang, Chengduan; Chen, Meiwan; Tao, Jun; Shieh, Han-ping; Yang, Bo-ru; Liu, Chuan

2017-01-01

Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials. PMID:29308265

Increased visible-light photocatalytic activity of TiO2 via band gap manipulation

NASA Astrophysics Data System (ADS)

Pennington, Ashley Marie

Hydrogen gas is a clean burning fuel that has potential applications in stationary and mobile power generation and energy storage, but is commercially produced from non-renewable fossil natural gas. Using renewable biomass as the hydrocarbon feed instead could provide sustainable and carbon-neutral hydrogen. We focus on photocatalytic oxidation and reforming of methanol over modified titanium dioxide (TiO2) nanoparticles to produce hydrogen gas. Methanol is used as a model for biomass sugars. By using a photocatalyst, we aim to circumvent the high energy cost of carrying out endothermic reactions at commercial scale. TiO2 is a semiconductor metal oxide of particular interest in photocatalysis due to its photoactivity under ultraviolet illumination and its stability under catalytic reaction conditions. However, TiO2 primarily absorbs ultraviolet light, with little absorption of visible light. While an effective band gap for absorbance of photons from visible light is 1.7 eV, TiO2 polymorphs rutile and anatase, have band gaps of 3.03 eV and 3.20 eV respectively, which indicate ultraviolet light. As most of incident solar radiation is visible light, we hypothesize that decreasing the band gap of TiO2 will increase the efficiency of TiO2 as a visible-light active photocatalyst. We propose to modify the band gap of TiO2 by manipulating the catalyst structure and composition via metal nanoparticle deposition and heteroatom doping in order to more efficiently utilize solar radiation. Of the metal-modified Degussa P25 TiO2 samples (P25), the copper and nickel modified samples, 1%Cu/P25 and 1%Ni/P25 yielded the lowest band gap of 3.05 eV each. A difference of 0.22 eV from the unmodified P25. Under visible light illumination 1%Ni/P25 and 1%Pt/P25 had the highest conversion of methanol of 9.9% and 9.6%, respectively.

[Spectral studies on nano-sized titania photocatalysts prepared by different drying methods].

PubMed

Ye, Zhao; Zhang, Han-hui; Pan, Hai-bo; Pan, Hong-qing

2002-12-01

Nano-sized TiO2 photocatalysts were prepared by drying the ethanol gel of titanium tetrabutoxide through natural state, supercritical ethanol, supercritical carbon dioxide drying methods and characterized by XRD, FTIR spectroscopy, FT-Raman spectroscopy and fluorescent spectroscopy, respectively. We regard degradation of rhodamine B by photocatalyst as a model reaction, and compare photocatalytic activities of samples obtained. The experimental results show that different drying methods have strong effect on crystal structure, energy band structure, optical adsorption property, surface quality and photocatalytic activity, TiO2 photocatalyst prepared by supercritical carbon dioxide drying method has superior photocatalytic activity.

Removing volatile organic compounds in cooking fume by nano-sized TiO2 photocatalytic reaction combined with ozone oxidation technique.

PubMed

Li, Yu-Hua; Cheng, Su-Wen; Yuan, Chung-Shin; Lai, Tzu-Fan; Hung, Chung-Hsuang

2018-06-05

Chinese cooking fume is one of the sources of volatile organic compounds (VOCs) in the air. An innovative control technology combining photocatalytic degradation and ozone oxidation (UV/TiO 2 +O 3 ) was developed to decompose VOCs in the cooking fume. Fiberglass filter (FGF) coated with TiO 2 was prepared by an impregnation procedure. A continuous-flow reaction system was self-designed by combining photocatalysis with advanced ozone oxidation technique. By passing the simulated cooking fume through the FGF, the VOC decomposition efficiency in the cooking fume could be increased by about 10%. The decomposition efficiency of VOCs in the cooking fume increased and then decreased with the inlet VOC concentration. A maximum VOC decomposition efficiency of 64% was obtained at 100 ppm. Similar trend was observed for reaction temperature with the VOC decomposition efficiencies ranging from 64 to 68%. Moreover, inlet ozone concentration had a positive effect on the decomposition of VOCs in the cooking fume for inlet ozone≤1000 ppm and leveled off for inlet ozone>1000 ppm. 34% of VOC decomposition efficiency was achieved solely by ozone oxidation with or without near-UV irradiation. A maximum of 75% and 94% VOC decomposition efficiency could be achieved by O 3 +UV/TiO 2 and UV/TiO 2 +O 3 techniques, respectively. The maximum decomposition efficiencies of VOCs decreased to 79% for using UV/TiO 2 +O 3 technique with adding water in the oil fume. Comparing the chromatographical species of VOCs in the oil fume before and after the decomposition of VOCs by using UV/TiO 2 +O 3 technique, we found that both TVOC and VOC species in the oil fume were effectively decomposed. Copyright © 2018 Elsevier Ltd. All rights reserved.

Photocatalytic degradation of dimethoate in Bok choy using cerium-doped nano titanium dioxide.

PubMed

Liu, Xiangying; Li, Yu; Zhou, Xuguo; Luo, Kun; Hu, Lifeng; Liu, Kailin; Bai, Lianyang

2018-01-01

Dimethoate, a systemic insecticide, has been used extensively in vegetable production. Insecticide residues in treated vegetables, however, pose a potential risk to consumers. Photocatalytic degradation is a new alternative to managing pesticide residues. In this study, the degradation of dimethoate in Bok choy was investigated under the field conditions using cerium-doped nano titanium dioxide (TiO2/Ce) hydrosol as a photocatalyst. The results show that TiO2/Ce hydrosol can accelerate the degradation of dimethoate in Bok choy. Specifically, the application of TiO2/Ce hydrosol significantly increased the reactive oxygen species (ROS) contents in the treated Bok choy, which speeds up the degradation of dimethoate. Ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS) analysis detected three major degradation products, including omethoate, O,O,S-trimethyl thiophosphorothioate, and 1,2-Bis (acetyl-N-methyl-) methane disulfide. Two potential photodegradation pathways have been proposed based on the intermediate products. To understand the relationship between photodegradation and the molecular structure of target insecticides, we investigated the bond length, Mulliken atomic charge and frontier electron density of dimethoate using ab initio quantum analysis. These results suggest the P = S, P-S and S-C of dimethoate are the initiation sites for the photocatalytic reaction in Bok choy, which is consistent with our empirical data.

Toxicological aspects of photocatalytic degradation of selected xenobiotics with nano-sized Mn-doped TiO2.

PubMed

Ozmen, Murat; Güngördü, Abbas; Erdemoglu, Sema; Ozmen, Nesrin; Asilturk, Meltem

2015-08-01

The toxic effects of two selected xenobiotics, bisphenol A (BPA) and atrazine (ATZ), were evaluated after photocatalytic degradation using nano-sized, Mn-doped TiO2. Undoped and Mn-doped TiO2 nanoparticles were synthesized. The samples were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), UV-vis-diffuse reflectance spectra (DRS), X-ray fluorescence spectroscopy (XRF), and BET surface area. The photocatalytic efficiency of the undoped and Mn-doped TiO2 was evaluated for BPA and ATZ. The toxicity of the synthesized photocatalysts and photocatalytic by-products of BPA and ATZ was determined using frog embryos and tadpoles, zebrafish embryos, and bioluminescent bacteria. Possible toxic effects were also evaluated using selected enzyme biomarkers. The results showed that Mn-doped TiO2 nanoparticles did not cause significant lethality in Xenopus laevis embryos and tadpoles, but nonfiltered samples caused lethality in zebrafish. Furthermore, Mn-doping of TiO2 increased the photocatalytic degradation capability of nanoparticles, and it successfully degraded BPA and AZT, but degradation of AZT caused an increase of the lethal effects on both tadpoles and fish embryos. Degradation of BPA caused a significant reduction of lethal effects, especially after 2-4h of degradation. However, biochemical assays showed that both Mn-doped TiO2 and the degradation by-products caused a significant change of selected biomarkers on X. laevis tadpoles; thus, the ecological risks of Mn-doped TiO2 should be considered due to nanomaterial applications and for spilled nanoparticles in an aquatic ecosystem. Also, the risk of nanoparticles should be considered using indicator reference biochemical markers to verify the environmental health impacts. Copyright © 2015 Elsevier B.V. All rights reserved.

An external template-free route to uniform semiconducting hollow mesospheres and their use in photocatalysis

NASA Astrophysics Data System (ADS)

Yang, Di; Wang, Mengye; Zou, Bin; Zhang, Gu Ling; Lin, Zhiqun

2015-07-01

Solid amorphous TiO2 mesospheres were synthesized by controlled hydrolysis of Ti-containing precursors. Subsequently, solid TiO2 mesospheres were exploited as scaffolds and subjected to a one-step external template-free hydrothermal treatment, yielding intriguing hollow anatase TiO2 mesospheres. The synthetic protocol was optimized by investigating the effect of buffer reagents and fluoride ions on the formation of hollow TiO2 spheres. The diameter of hollow mesospheres, ranging from 308 to 760 nm, can be readily tailored by varying the precursor concentration. The average thickness of a shell composed of TiO2 nanocrystals was approximately 40 nm with a mean crystal size of 12.4-20.0 nm. Such hollow TiO2 mesospheres possessed a large surface area and were employed in photocatalytic degradation of methylene blue under UV irradiation. Interestingly, the synthetic conditions were found to exert a significant influence on the photocatalytic ability of hollow TiO2 mesospheres. The correlation between the degradation ability of hollow TiO2 mesospheres and the precursor concentration as well as the hydrothermal time was scrutinized. The optimal photocatalytic performance of hollow TiO2 mesospheres was identified.Solid amorphous TiO2 mesospheres were synthesized by controlled hydrolysis of Ti-containing precursors. Subsequently, solid TiO2 mesospheres were exploited as scaffolds and subjected to a one-step external template-free hydrothermal treatment, yielding intriguing hollow anatase TiO2 mesospheres. The synthetic protocol was optimized by investigating the effect of buffer reagents and fluoride ions on the formation of hollow TiO2 spheres. The diameter of hollow mesospheres, ranging from 308 to 760 nm, can be readily tailored by varying the precursor concentration. The average thickness of a shell composed of TiO2 nanocrystals was approximately 40 nm with a mean crystal size of 12.4-20.0 nm. Such hollow TiO2 mesospheres possessed a large surface area and were employed in photocatalytic degradation of methylene blue under UV irradiation. Interestingly, the synthetic conditions were found to exert a significant influence on the photocatalytic ability of hollow TiO2 mesospheres. The correlation between the degradation ability of hollow TiO2 mesospheres and the precursor concentration as well as the hydrothermal time was scrutinized. The optimal photocatalytic performance of hollow TiO2 mesospheres was identified. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02685g

Synthesis, characterization and multifunctional properties of plasmonic Ag-TiO2 nanocomposites

NASA Astrophysics Data System (ADS)

Prakash, Jai; Kumar, Promod; Harris, R. A.; Swart, Chantel; Neethling, J. H.; Janse van Vuuren, A.; Swart, H. C.

2016-09-01

We report on the synthesis of multifunctional Ag-TiO2 nanocomposites and their optical, physio-chemical, surface enhanced Raman scattering (SERS) and antibacterial properties. A series of Ag-TiO2 nanocomposites were synthesized by sol-gel technique and characterized by x-ray diffraction, scanning and transmission electron microscopy, energy-dispersed x-ray analysis, photoluminescence, UV-vis, x-ray photoelectron and Raman spectroscopy and Brunauer-Emmett-Teller method. The Ag nanoparticles (NPs) (7-20 nm) were found to be uniformly distributed around and strongly attached to TiO2 NPs. The novel optical responses of the nanocomposites are due to the strong electric field from the localized surface plasmon (LSP) excitation of the Ag NPs and decreased recombination of photo-induced electrons and holes at Ag-TiO2 interface providing potential materials for photocatalysis. The nanocomposites show enhancement in the SERS signals of methyl orange (MO) molecules with increasing Ag content attributed to the long-range electromagnetic enhancement from the excited LSP of the Ag NPs. To further understand the SERS activity, molecular mechanics and molecular dynamics simulations were used to study the geometries and SERS enhancement of MO adsorbed onto Ag-TiO2 respectively. Simulation results indicate that number of ligands (MO) that adsorb onto the Ag NPs as well as binding energy per ligand increases with increasing NP density and molecule-to-surface orientation is mainly flat resulting in strong bond strength between MO and Ag NP surface and enhanced SERS signals. The antimicrobial activity of the Ag-TiO2 nanocomposites was tested against the bacterium Staphylococcus aureus and enhanced antibacterial effect was observed with increasing Ag content explained by contact killing action mechanism. These results foresee promising applications of the plasmonic metal-semiconductor based nano-biocomposites for both chemical and biological samples.