Anatase Research Articles

A multi-omics approach reveals differences in toxicity and mechanisms in rice (Oryza sativa L.) exposed to anatase or rutile TiO2 nanoparticles

Titanium dioxide nanoparticles (TiO2 NPs) have been widely used in agriculture, which increased the risk to soil-plant systems. Studies have demonstrated that TiO2 NPs can induce phytotoxicity. However, the toxicity mechanisms, particularly under the stress of TiO2 NPs with different crystalline forms, remain inadequately reported. In this study, we combined transcriptomics and metabolomics to analyze the toxicity mechanisms in rice (Oryza sativa L.) under the stress of anatase (AT) or rutile (RT) TiO2 NPs (50 mg/kg, 40 days). The length (decreased by 1.1-fold, p = 0.021) and malondialdehyde concentration (decreased by 1.4-fold, p = 0.0027) of rice shoots was significantly reduced after AT exposure, while no significant changes were observed following RT exposure. Antioxidant enzyme activities were significantly altered both in the AT and RT groups, indicating TiO2 NPs induced rice oxidative damage (with changes of 1.1 to 1.4-fold, p < 0.05). Additionally, compared to the control, AT exposure altered 3247 differentially expressed genes (DEGs) and 56 significantly differentially metabolites in rice (collectively involved in pyrimidine metabolism, TCA cycle, fatty acid metabolism, and amino acid metabolism). After RT exposure, 2814 DEGs and 55 significantly differentially metabolites were identified, which were collectively involved in fatty acid metabolism and amino acid metabolism. Our results indicated that AT exposure led to more pronounced changes in biological responses related to oxidative stress and had more negative effects on rice growth compared to RT exposure. These findings provide new insights into the phytotoxic mechanisms of TiO2 NPs with different crystalline forms. Based on the observed adverse effects, the study emphasizes that any form of TiO2 NPs should be used with caution in rice ecosystems. This study is the first to demonstrate that AT is more toxic than RT in paddy ecosystems, providing crucial insights into the differential impacts and toxic mechanisms of TiO2 NPs with different crystalline forms. These findings suggest prioritizing the use of RT when TiO2 NPs are necessary in agricultural development to minimize toxicity risks.

Mutual influence of cupric cations and several anions in anatase and rutile TiO2 photocatalysis.

Copper ions in aqueous solution are known to promote organic oxidation in semiconductor photocatalysis, but the counter anions seem to be important as well. In this work, the performance of Cu(ClO4)2 in presence of several anions in sodium forms (F-, Cl-, ClO4-, NO3-, and SO42-) has been examined. Phenol oxidation in aqueous solution (pH 4) under UV light was used as model reaction and TiO2 in the forms of anatase (AT) and rutile (RT) as photocatalysts. On the addition of 0.1-5mM Cu2+, the reactions on AT and RT all increased. On the addition of 1mM anions, reactions on AT increased by F-and SO42-, but reactions on RT all decreased. In presence of 3mM Cu2+, however, reactions on AT and RT all decreased by 1mM anions except NO3-. Such anion effects were also observed for H2 production on AT and RT in presence of Cu2+ and 10% methanol. A possible mechanism for the positive and negative anion effects is discussed. This work indicates that the formation of a Cu(II)/Cu(I) complex with anions weakens the positive effect of copper ions on organic oxidation in TiO2 photocatalysis.

Synergistic effect of biomass-derived carbon and conducting polymer coatings on the supercapacitive energy storage performance of TiO2

Abstract The application of anatase titanium dioxide (TiO2), which is an abundant and cost effective resource, in supercapacitors has been restricted due to its poor electronic conductivity and limited mechanical stability. A biomass-derived carbon was coated on anatase TiO2 nanoparticles via practical and green hydrothermal carbonization in order to overcome these limitations. Hierarchically porous carbon provided a capacitive double layer for charge storage and the TiO2/C nanocomposite exhibited a specific capacitance of 61 F × g-1 (0.25 A × g-1, 0 to 1 V vs. Ag/AgCl, 1 M H2SO4 aqueous electrolyte). The TiO2/C/PEDOT:PSS nanocomposite with enhanced specific capacitance and rate capability (189 F × g-1 at 0.25 A × g-1, 161 F × g-1 at 0.5 A × g-1, 123 F × g-1 at 1 A × g-1, 91 F × g-1 at 2 A × g-1) was obtained by the application of an electrochemically active PEDOT:PSS layer. The prominent electrochemical and mechanical stability of the ternary nanocomposite was demonstrated by its ability to retain 98 % of its initial capacitance after 1500 cycles of charge-discharge at a high current rate (3 A × g-1). The synergistic use of sustainable organic and inorganic components with environmentally friendly and practical methods yields extremely promising electrochemical performances for supercapacitor applications. The TiO2/C/PEDOT:PSS nanocomposite presented in this work delivered an electrochemical performance comparable to its published counterparts which are obtained by more sophisticated or hazardous methods and with expensive components.

Optimization of Solar-Photocatalytic Degradation of Polychlorinated Biphenyls using Photocatalyst (Nd/Pd/TiO2 ) by Taguchi Technique and Detection by Solid Phase Nano Extraction

Nd/Pd/TiO2 photocatalyst has been synthesized in the presence of Hydroxyl Propyl Cellulose by a sol-gel method with Titanium tetra isopropoxide as titanium precursor. Photocatalyst size and structure properties of the nano-catalyst have been determined by X-ray diffraction. It has contained the anatase phase in advance. The surface area is measured by the Brunauer, Emmett, and Teller(BET) method. The presence of Ti, Nd, and Pd in the nanostructure has been confirmed by EDX, equipped tool with SEM. Photocatalytic degradation of PCB-28 under solar light has been investigated by the Taguchi method with five factors such as the amount of HPC(gg-1sol), the percentage of Pd(%), the percentage of Nd(%), calcination temperature(°C) and calcination time(h). Under optimal conditions such as, 0.003 of HPC (gg-1sol), 0.2 percentage of Pd(%), 0.2 percentage of Nd(%), 700°C of the calcination temperature and 5hours for the calcination time, the best desorption result monitored by Solid-phase nano extraction technique(SPNE) method before degradation process. By GC-ECD, complete degradation of PCBs observed after solar irradiation in 12min, and no PCBs chromatogram observed after this time.

Impact of silver ions doping and calcination on the physicochemical characteristics of TiO2 nanoparticles with photocatalytic and regeneration potential

Visible light driven Ag+ doped TiO2 photocatalysts were successfully prepared with modified low cost liquid impregnation (LI) method yielding up to 95 % product. The native and newly synthesized photocatalysts were calcined at various temperatures and characterized using diffused reflectance spectroscopy (UV/Vis-DRS), XRD, XPS, TEM, EDX, XRF and pHPZC analyses. The XRD results for all samples revealed that the anatase phase was dominant at all calcination temperatures. The Ag+ doping reduced the band gap energy to 2.88 eV, which significantly enhanced the photocatalytic efficiency towards Methylene Blue (MB) under compact fluorescent light. The photocatalytic efficacy of the nano-catalysts was also tested using a binary solution containing a model dye (MB) and Cd2+ under ordinary compact fluorescent light. The presence of competitive ions i.e. Cd2+ increased the MB degradation up to 4 folds under the ambient conditions whereby the maximum amount of MB adsorbed by nano-catalysts reached to 46 mg/g. The high temperature combustion method was found more effective for the regeneration of TiO2 photocatalysts compared to the chemically regeneration. The reusable character of the regenerated samples posed a significant impact of the current work to be applied in wastewater treatment in bulk.

Photocatalytic Degradation of Phenol in Aqueous Solutions Using TiO2/SiO2 Composite

Photocatalytic degradation of phenol in aqueous solutions was investigated using TiO2/SiO2 composites with different Ti/Si molar ratios (95/5(75/25) and calcined at 500 (C. The synthesized composites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption-desorption isotherms. Their photocatalytic activities for phenol degradation were evaluated in a batch reactor under simulated visible light using a special 26 W compact lamp. The results showed that all synthesized composites consist of pure anatase phase with high crystallinity and exhibit high photocatalytic activities for phenol degradation. At the initial concentration 10 ppm phenol and catalyst dose 0.10 g/L, the highest photocatalytic activity for phenol degradation was observed with the synthesized TS05 composite (Ti/Si molar ratio of 95/5), resulting in 53.5 % phenol degradation yield after 4 h. The corresponding phenol degradation yields using the synthesized composites TS15 (Ti/Si molar ratio of 85/15) was ~ 40.0 % and TS25 ((Ti/Si molar ratio of 75/25) was ~ 36.0 %. The TS05 composite could be a promising photocatalyst for the removal and degradation of organic pollutants.

Sol-Gel Fabricated Tio₂ Coating on Titanium Surface Promoted In Vitro Osteoblasts Differentiation.

Titanium has been used for biomedical devices due to its excellent biocompatibility, which is based partly on its 2-8 nm thick titanium oxide layer. However, the relatively poor surface hardness, wear resistance and metal release of these layers may cause some problems in clinical application. In this study, titanium surfaces were modified using a TiO₂ sol-gel coating, in order to improve surface properties and osteoblast function. No significant difference in surface roughness was observed between titanium and TiO₂ sol-gel discs. The surface of TiO₂ sol-gel discs possessed more wettability than titanium discs. The X-ray diffraction results showed amorphous TiO₂ phase on titanium discs, whereas TiO₂ sol-gel surfaces presented TiO₂ rutile and anatase phase. After 4 hours, the number of osteoblasts seeded on TiO₂ surface was significantly higher than those on titanium discs. The mRNA expression of bone sialoprotein and osteocalcin were also higher on day 5 and 7, respectively. Enzyme-linked immunosorbent assay(ELISA) analysis confirmed the increase of osteocalcin protein synthesis in osteoblasts grown on the TiO₂ sol-gel surface. Alizarin red-S staining showed higher amount of calcium deposition from osteoblasts cultured on TiO₂ surface than those on titanium discs at day 20. In conclusion, TiO₂ sol-gel coated-titanium could enhance osteoblasts differentiation and promote mineralization, indicating its potential in improving osseointegration for clinical application.

The Effect of Crystalline Phase on the Simultaneous Degradation of Phenol and Reduction of Chromium (VI) Using UV/TiO 2 Photocatalysis

Chromium (IV) contamination in industrial wastewater has been on the rise due to increased anthropogenic activities. Similarly, typical industrial wastewater contains high levels of phenol as a result of the direct disposal on phenol into industrial effluent or as degradation products from phenolic compounds. Both these contaminants have adverse effects to human health and the environment and it is therefore necessary to develop technologies to remove them in a sustainable manner. Photocatalysis using TiO2 catalyst activated by UV light is one such technology as it can either oxidize and mineralize organic pollutants or reduce heavy metals contaminants into a noble form. Degussa P25 TiO2 is normally used in photocatalysis due its ability to reduce electron-hole recombination. It has been theorized that the addition of organic compounds as hole scavengers during the photocatalytic reduction of Cr(VI) aids in the reduction efficiency. This study investigated the use of anatase-form TiO2 on the reduction of Cr(VI) in the presence of phenol and compared the results to similar work carried out by our group out Degussa P25 as catalyst. The anatase was shown to be an effective catalyst in the reduction of Cr(VI) with as much as 32 % reduction occurring at neutral pH with no phenol present. Adjusting the solution pH to 3 increased the percentage reduction to 40.7 % whilst addition of 100 ppm of phenol at pH 3 resulted in a 52.3 % Cr(VI) reduction. Comparison of the results obtained for anatase and Degussa P25 TiO2 at the same pH revealed approximately the same Cr(VI) reduction efficiencies with the Degussa P25 having a slight edge. This suggests that the nature of the crystal phase of the two TiO2 investigated does not significantly influence the reduction efficiency of Cr(VI) in the presence of phenol.

Synthesis and applications of TiO 2 -based multi-shelled hollow structures

Hierarchical micro-/nano-structured hollow materials, especially multi-shelled hollow structured materials have drawn wide attention recently benefiting from large specific surface area, low density and stable structure. As active electrode materials for lithium-ion batteries, multi-shelled hollow structures show several advantages including: (1) The nanoparticles with large specific surface area can contact well with the electrolyte improving the conductivity; (2) the composed nanoparticles with reduced size can shorten the lithium-ion diffusion pathways enhancing the high rate performance; (3) the stable hollow micro-structures can buffer the volumetric expansion/contraction during the discharge/charge processes sustaining cyclic capacity. As photoanode materials for dye-sensitized solar cells (DSSCs) or for photocatalysts, multi-shelled hollow structures can reflect and scatter light for multiple times increasing the light capture thus enhancing the performance. The large specific surface can also adsorb more dyes or harmful organic pollutants to be degraded. TiO2 is a promising semiconductor used in many fields. As anode materials for lithium-ion batteries, first, the volumetric change during the lithium insertion/extraction processes is small, which is beneficial for stable structure and better cyclic stability. Second, the cut-off potential is relatively high, hence no unstable solid electrolyte interface (SEI) film will be formed during the discharge process, which leads to high safety. Third, the high rate performance of TiO2 is good, which is suitable for high power applications. By using multi-shelled hollow structured TiO2, the buffer function of hollow structures further maintains more stable structure thus better cyclic performance. On the other hand, the suitable band gap, high stability towards acid or base, and environment friendliness make it popular for DSSCs and photocatalysis. The multiple light reflecting/scattering function can further enhance the performance of TiO2. Up to date, there are more and more work on design and investigation of TiO2-based multi-shelled hollow structures. However, more precise synthesis and control of TiO2-based multi-shelled hollow structures is still challenging. In order to better control the synthesis, we need to learn more from previous work. In this review, we have summarized recent progress on the synthesis and applications of TiO2-based multi-shelled hollow structures. Firstly, since the crystal structure affects the properties greatly, we have introduced basic information of the main TiO2 polymorphs including anatase, rutile, TiO2(B) and brookite phases. Secondly, we have summarized the methods to synthesize TiO2-based multi-shelled hollow structures. Hard template, soft template and template-free methods are usually used, among which hard template method is more popular. Especially, sequential templating approach (STA) is more simple and effective to control the shell number, shell thickness, space between the shells and the shell composition. Although the traditional layer-by-layer hard template method is complex, it is effective to synthesize TiO2-based multi-shelled hollow structures with different compositional inner and outer shells. Thirdly, the applications of TiO2-based multi-shelled hollow structures in the lithium-ion batteries, DSSCs and photocatalysis fields have been summarized. Finally, the summary and outlook is provided. Up to date, researchers have made great achievements on the synthesis methods. However, more precise control on not only the shell structures but also the composition of shells is still highly desirable. Heterogeneous structures sometimes show special or improved properties. It may be a hotspot to design and fulfill the synthesis of multi-shelled hollow structures with heterogeneous compositions, which will be a big challenge. However, opportunity comes together with challenge. We believe the development of precise control on multi-shelled hollow structured materials will bring more opportunities for material field in future.

Study on Photocatalytic Cement Concrete for the Degradation of Textile Dyes

This process is developed in the way that low level usage of chemical such as Titanium-di-oxide and urea along with the cement concrete structure for the photocatalytic activity under sunlight. When the cement concrete structure is introduced the sustainability of the process is increased so the efficient use of the reactant is achieved. From this study we obtained that the photocatalytic way of separation of waste ions can increase the purification process. The feed water is the waste from the common effluent plant with high in BOD and COD content. Two crystalline forms of TiO 2 , viz. anatase and rutile were tested for their photocatalytic activity. The extent of photocatalytic degradation was found to increase with increasing TiO 2 concentration up to 2 g/L TiO 2 , 5 g/L urea above which degradation remained practically constant. Textile waste degradation was enhanced at acidic conditions and in the addition of hydrogen peroxide. For the assessment of catalyst activity on repeated use, experiments were performed; after thrice successive uses, TiO 2 had sufficiently retained its photocatalytic activity and to perform the kinetic studies.

Fabrication of SWCNTs ModifiedTiO 2 Nanocomposite towards Enhanced Photocatalytic Carbon Dioxide Reduction to Fuels under Visible Light

In this study, fabrication of single wall carbon nanotubes modified titanium dioxide (SWCNTs/TiO2) composite catalyst for selective and enhanced photocatalytic CO2 reduction to fuels has been investigated. The samples were synthesized by a modified one-pot sol-gel method and were characterized by X-ray diffraction (XRD), Scanning Electrons Microscopy (SEM) and Photoluminescence (PL) Spectroscopy. The pure anatase phase with reduced crystal size and hindered charges recombination was obtained by modifying TiO2 with SWCNTs. The performance of newly developed nano-catalyst was investigated for photo-induced CO2-hydrogen reduction under visible light irradiations. The products detected were CO, CH4 and CH3OH with appreciable amounts of C2-C3 hydrocarbons. The yield of CO as the main product over 5 wt% SWCNTs/TiO2 was 1,220 µmole g-cat.-1 h-1, a 5.35 times more than the pure TiO2 NPs. Similarly, yield of methanol of 23.4 µmole g-cat.-1 h-1 was detected, 6.5 folds the amount produced over the pure TiO2 NPs. The SWCNTs found to be efficient to enhance TiO2 activity due to its ability to capture visible light irradiations with proficient charges separations over the TiO2 surface. The higher interaction between SWCNTs/TiO2, efficient adsorption-desorption and hindered charges recombination rate promoted the photoactivity and products selectivity. The reaction mechanism to understand the role of SWCNTs in TiO2 for CO2-hydrogen conversion is also deliberated.

Study of Structural, Thermic, µ-Raman and Optic Transformation of PVA/TiO2 Polymeric Membranes

Composites (1-x)PVA/xTiO2 (0,025≤x≤0,250) were prepared from aqueous solution. The influence of TiO2 ceramic fillers on polymer matrix was characterized by: X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA), micro-Raman scattering, UV-visible absorption (UV-vis) and scanning electronic microscopy (SEM). Raman and XRD results showed the amorphous and monoclinic phases for PVA and anatase phase for TiO2. SEM micrographs showed spread TiO2 fillers in PVA polymeric matrix forming aggregates. DSC and TGA thermograms show phase transitions with temperature, glass transition temperature (Tg) and thermal stability of polymeric matrix. The band gap energy (Eg) related to TiO2 (anatase) has been calculated from UV-visible measures, showing a strong absorption at near-UV region due to ceramic fillers.

Compact TiO2/Anatase TiO2 Single-Crystalline Nanoparticle Electron-Transport Bilayer for Efficient Planar Perovskite Solar Cells

Electron-transport layer (ETL)/perovskite interface modification plays a key task for producing efficient planar perovskite solar cells (PSCs). In this study, interfacial modification of compact TiO2 using novel, one-step hydrothermally synthesized single-crystalline anatase (AT) titania nanoparticles (TiO2 NPs) (average diameter = 6–10 nm) was applied as an ETL bilayer to enhance the efficient charge generation and extraction and eliminate the electron–hole recombination ratio. We report here an easy approach for enhancing the performance of planar PSCs by introducing a compact TiO2/AT TiO2 NPs bilayer through spray pyrolysis (SP) deposition and spin-coating (SC) techniques, respectively. The enhanced performance of the devices with an SP-TiO2/SC-AT TiO2 NPs bilayer facilitated more efficient electron transport, charge extraction, and low interfacial recombination. Ultimately, the best device had a 17.05% power conversion efficiency resulting from the significant decrease in J–V hysteresis, presenting al...

Tio2 supported on brick waste as low cost photocatalyst for dye photodegradation

Photocatalysis is one of the most important technology for treating water pollutants effectively. The method is better compared to adsorption method in that photocatalysis gives advance destroying organic contaminants and has better reusability. In other side, textile industry including Batik’s industry is a potential source of wastewater contaminated with dyes which can cause serious environmental problems. For photocatalysis purposes, TiO2 is the popular material. In order to enhance both economic and photocatalytic activity of TiO2, supporting TiO2 into solid material is interesting effort. In this research, brick waste was chosen as low cost and effective support for TiO2. TiO2 supporting onto brick waste by impregnation method was carried out. The composite of TiO2/Brick waste (TiO2/BW) was conducted by dispersing titanium tetraisopropoxide as TiO2 precursor followed by calcination. Characterization of TiO2/BW was performed by XRD analysis, Diffuse Reflectance UV-Vis and FTIR analysis. For photocatalytic activity, experiments on photocatalysis and photooxidation of rhodamine B solution were examined. Prepared Ti-BW exhibits the formation of TiO2 in mixed anatase and rutile phases as presented by XRD pattern. From the DRUV-Vis analysis, it is found that the band gap energy of composite material lays in UV-Visible region. TiO2/BW showed high photoactivity as represented by faster degradation rate of rhodamine B over photooxidation and photocatalysis compared to adsorption method. From the data simulation, it is revealed that rhodamine B degradation over photocatalysis mechanism follow pseudo-first order while over photooxidation the kinetic obey pseudo-second order.

Enhanced Photocatalytic degradation of methyl orange using Ag-doped TiO2 photocatalyst

In the present study, Ag-doped Titanium dioxide (Ag-TiO2 ) photocatalyst was prepared by wet impregnation method. The effect of dopant concentration, incubation temperature and incubation time on the photocatalytic degradation of Methyl Orange (MO) in aqueous suspension under Ultra Violet (UV) light irradiation were studied systematically. The synthesized photocatalyst was characterized using XRD and SEM-EDX mapping. The characterization results confirmed that Ag was successfully doped into TiO2 with anatase phase structure. The Ag-TiO2 photocatalyst exhibited the highest dye removal of 85% efficiency with 5 wt.% dopant concentration when the incubation temperature and time were 70�C and 8 h, respectively. The kinetic study revealed that photocatalytic reaction follows Langmuir Hinshelwood (L-H) Model and pseudo-first order law with the highest regression coefficient of 0.992. Ag-TiO2 was found to be an efficient photocatalyst showing enhanced photocatalytic activity for MO decolorization under UV irradiation.

Elaboration and Enhanced Activity of the Mixed Oxide Zr x Ti 1 - x O 2 Nano-photocatalyst

The photocatalysis activity of mixed nanocomposite ZrxTi1-xO2 catalyst was studied. The catalysts with x=0, 0.1 and 0.2 were prepared via sol-gel method in a reactor with rapid micromixing using titanium tetra- isopropoxide and zirconium tetra-propoxide precursors and n-propanol solvent. The colloids were coated on cleaned borosilicate beads and treated at temperatures in the range between 400 and 600 °C to achieve crystalline anatase phase. The prepared materials were characterized by ICP-OES, BET, TDA and optical absorption measurements. The photocatalytic experiments were carried out in a continuous-flow fixed bed reactor on the gaseous ethylene decomposing. The photocatalytic activity of the prepared material was depended on the elemental compositions and calcination temperature. The enhanced activity, 50% higher compared to pure anatase TiO2, was obtained in the material containing 10 mol% Zr and thermally treated at 500 °C.

Synthesis and characterization of carbon doped TiO2 photocatalysts supported on stainless steel mesh by sol-gel method

This study synthesized pure anatase carbon doped TiO₂ photocatalysts supported on a stainless steel mesh using a sol-gel solution of 8% polyacrylonitrile (PAN)/dimethylformamide (DMF)/TiCl₄. The influence of the pyrolysis temperature and holding time on the morphological characteristics, particle sizes and surface area of the prepared catalyst was investigated. The prepared catalysts were characterized by several analytical methods: high resolution scanning electron microscopy (HRSEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). The XRD patterns showed that the supported TiO₂ nanocrystals are typically anatase, polycrystalline and body-centered tetragonal in structure. The EDS and XPS results complemented one another and confirmed the presence of carbon species in or on the TiO₂ layer, and the XPS data suggested the substitution of titanium in TiO₂ by carbon. Instead of using calcination, PAN pyrolysis was used to control the carbon content, and the mesoporosity was tailored by the applied temperature. The supported TiO₂ nanocrystals prepared by pyrolysis at 300, 350, and 400oC for 3 h on a stainless steel mesh were actual supported carbon doped TiO₂ nanocrystals. Thus, PAN/DMF/TiCl₄ offers a facile, robust sol-gel related route for preparing supported carbon doped TiO₂ nanocomposites.

Fabrication of Dye Sensitized Solar Cell and Efficiency Enhancement by Using N719 and Z907 Dyes Mixture

This study aims to investigate the effect of N719 and Z907 dyes mixture (1:1 v/v ratio) on the DSSCs fabricated successfully using a simple procedure without the need for any complicated facilities. The XRD analysis of the TiO2 layer confirmed that it has a polycrystalline structure belonging to anatase phase with crystallite size of 12.4 nm. UV-Vis spectroscopy was used to characterize the absorbance spectra of the TiO2 layer, N719 dye, Z907 dye, dyes mixture and the fabricated DSSCs as well. The absorption spectra in the wavelength range of (350-750) nm show that the DSSC fabricated with dyes mixture has higher absorption compared to the other two cells. The dyes mixture performs better than the individual dyes due to the broadening of its UV-Vis spectrum in the blue region. The energy gap of the TiO2 layer estimated by Tauc’s plot was 3.12 eV. The SEM micrograph of the TiO2 layer shows that the layer has a spongy shape with reduction in the number of open pores making easy for dye adsorption and electron transport. The average roughness, root mean square roughness and grain size of the TiO2 layer estimated from the AFM micrograph and the granularity cumulative distribution chart were about 0.356 nm, 0.423 nm and 82.48 nm respectively. Solar cells with efficiency as high as 2.287% have been achieved using the dyes mixture as sensitizer which represents an enhancement of ~ 70% and ~ 106% compared to the DSSCs efficiencies prepared by N719 and Z907 dyes respectively.

Study of the photocatalytic and antibacterial activity of tio2 powder synthesized by microwave-assisted sol-gel method

TiO2 powder was prepared by microwave-assisted sol-gel method. The powder was refluxed at 180 W for 1, 2 and 3 h and dried at 180 W for 1 h by a conventional microwave oven. Several analytical techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface area measurement (BET) were employed to characterize the synthesized powder. Photocatalytic activity of the powder was examined via the degradation of methylene blue (MB) solution under UV irradiation for a certain time. The efficiency of antibacterial activity was evaluated by the inactivation of Staphylococcus aureus (S. aureus). The results showed that only anatase TiO2 was observed and the as-prepared powder exhibited the agglomeration of spherical nanoparticles with crystallite sizes of 20.7, 13.8 and 9.3 nm when the refluxed time was 1, 2 and 3 h, respectively. The highest efficiency for the photocatalytic and antibacterial activities was 66.68 and 91.67%, respectively, belonging to those powders using the reflux time of 3 h.

Electronic structure of (Cu+N) co-doped anatase TiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; at the surfaces of (001) and (101): A first-principle study

采用基于密度泛函理论的第一性原理方法研究了3d过渡元素Cu掺杂及(Cu+N)共掺杂于锐钛矿相TiO 2 (001)面和(101)面的电子性质, 给出了不同掺杂形式形成能、能带结构、态密度及电荷分布的变化, 得出了(Cu+N)共掺杂时最稳定的结构. 通过计算Cu表层吸附、表层和次表层替位掺杂以及晶体间隙掺杂的形成能, 发现Cu掺杂更易发生在TiO 2 (001)面的空穴位, 此时N偏向于在水平方向上的O位发生替位掺杂. 计算结果表明(Cu+N)共掺杂后Cu-3d与O-2p, N-2p及Ti-3d轨道上的电子发生p-d杂化效应, 引发O-2p, N-2p态发生劈裂使得价带范围扩大, Ti-3d态下移且发生劈裂形成新的导带底, 并且禁带中产生了新的电子态, 禁带宽度减小, 同时(Cu+N)施主受主杂质对的出现可以有效防止电子空穴对的复合, 提高了TiO 2 的光催化活性.