Anatase Crystallite Size Research Articles

Regulation of synthesis pH value and post-treatment of ZSM-5 for improving adsorption and photocatalytic properties of TiO2/ZSM-5 composites

TiO2/ZSM-5 composites with enhanced adsorption and photocatalytic properties were synthesized via regulation of synthesis pH value and post (acid/alkali) treatment of ZSM-5. The influences of synthesis pH values and post-treatment of ZSM-5 on microstructure, adsorption and photocatalytic properties of the composites were investigated. The methyl orange was used to assess the adsorption and photocatalytic properties of the samples. The results showed that the synthesis pH values and acid/alkali treatment had significant influences on the microstructure, adsorption and photocatalytic properties of TiO2/ZSM-5 composites. The composites synthesized at pH 7 had a relatively higher TiO2 content, smaller anatase crystallite size, greater specific surface area, the most effective separation of photogenerated electron-hole pairs, the fastest interfacial charge transfer, and therefore exhibited excellent adsorption and photocatalytic properties. Acid treatment could significantly increase the specific surface area, Si/Al ratio of ZSM-5, the separation efficiency of photogenerated electron-hole pairs, and amount of produced active free radicals •O2– and •OH. The TiO2/acid-treated ZSM-5 exhibited excellent photodegradation with 99.3 % methyl orange in 150 min, which is higher than that of the TiO2/ZSM-5 and TiO2/alkali-treated ZSM-5.

Effect of Silver Doping on the Microstructure and Photocatalytic Performance of Ag-TiO2 Coatings on Unglazed Ceramic

TiO2 coating photocatalytic activity is limited to short-wavelength ultraviolet (UV) irradiation. To extend its potential to the visible range, doping with semiconductors such as silver (Ag) has been proposed. The optimal amount of Ag incorporation is still under investigation. High Ag concentrations can decrease surface charge, causing agglomeration of Ag species and reduction to Ag° particles on the TiO2 surface. On the other hand, lower Ag concentrations lead to the formation of AgO, Ag2O and Ag°. In this study, Ag-TiO2 coatings were deposited on unglazed ceramic tiles using the dip coating method, with silver contents of 2.5, 5 and 7.5 mol %. The effects of Ag content on the crystalline phase, crystal size, elemental distribution, morphology and cross-sectional surface were analysed. The coatings were heat-treated at 500 °C and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM). Photocatalytic performance was evaluated through the degradation of methylene blue under both UV and visible light irradiation. XRD analyses revealed the presence of anatase, rutile, Ag2O and metallic Ag in all samples. The degree of crystallinity and anatase crystallite size increased with higher Ag content. Surface morphology showed visible cracks and a dense surface at 2.5 and 5 mol % Ag, while the 7.5 mol % Ag coating exhibited a wavy surface. Energy-dispersive X-ray spectroscopy (EDS) on the surface and cross-sectional layers confirmed the presence of Ti, O and metallic Ag particles. The Ag-TiO2 coating with 2.5 mol % Ag demonstrated better photocatalytic activity under UV light irradiation, while the 7.5 mol % Ag coating exhibited the highest photocatalytic activity under visible light irradiation.

Influence of heterogeneous inclusions on the process of formation, structural transformations, and growth of TiO2 nanocrystals

The processes of formation and growth of titanium dioxide nanocrystals with a certain structure, the phase transition of anatase to rutile in the presence of a heterogeneous inclusions during thermal and hydrothermal treatment are investigated in this work. Preformed TiO2 nanoparticles with anatase and rutile structure having different morphology were used as heterogeneous inclusions at the precipitation stage. It was shown that heterogeneous inclusions with this composition and structure could not be considered either as geometrical limitations preventing crystallization or as crystallization nuclei at the stage of titanium dioxide formation. A decrease in the temperature of the anatase-rutile structural transformation by 200 °C and a reduction in the average size of anatase crystallites in the presence of inclusions of the rutile modification in the initial material under hydrothermal conditions and during heat treatment were demonstrated. A conclusion was made about the effect of the size of anatase nanoparticles on their stability. The dependence of the morphological, dimensional, and surface characteristics of the resulting titanium dioxide nanoparticles on the parameters of hydrothermal synthesis and heat treatment, and the presence of inclusions in the reaction system is estimated.

An emerging expanse: Novel and eco-friendly-biogenic synthesis of E. cardamomum-wrapped TiO2 nanoparticles for environmental and biological applications

The present research is targeted at E. cardamomum-derived TiO2-photocatalyst synthesis, reporting for the first time. The structural properties observed from the XRD pattern reveal that EC:TiO2 has an anatase phase and crystallite size is assessed by Debye-Scherrer's method (3.56 nm), WH-method (3.30 nm), and Modified-Debye-Scherrer's method (3.27 nm). An optical study by the UV–Vis spectrum shows strong absorption at 313 nm, and the corresponding band gap value is 3.28 eV. The topographical and morphological properties revealed by SEM and HRTEM images, elucidate the formation of multi-shaped particles of nano-size. Further, the phytochemicals on the EC:TiO2 NPs' surface are confirmed by the FTIR spectrum. The photocatalytic activity is well studied under UV light towards Congo Red dye, along with an effect of the dose of catalyst. EC:TiO2 (20 mg) has exhibited high photocatalytic efficiency up to 97% for 150 min of exposure due to the morphological, structural, and optical properties. CR degradation reaction exhibits pseudo-first-order kinetics, displaying a rate constant value of 0.01320 min−1. Reusability investigations reveal that after four photocatalysis cycles, EC:TiO2 has an effective efficiency of >85%. Additionally, EC:TiO2 NPs have been assessed for antibacterial activity and show potential against two bacterial species (S. aureus and P. aeruginosa). Therefore, these research outcomes from the eco-friendly and low-cost synthesis, are promising for the use of EC:TiO2 as a talented photocatalyst towards the removal of crystal violet dye as well as an antibacterial agent against bacterial pathogens.

Titania nanoparticles for photocatalytic degradation of ethanol under simulated solar light.

TiO2 nanoparticles were synthesized by laser pyrolysis from TiCl4 vapor in air in the presence of ethylene as sensitizer at different working pressures (250-850 mbar) with and without further calcination at 450 °C. The obtained powders were analyzed by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy. Also, specific surface area and photoluminescence with optical absorbance were evaluated. By varying the synthesis parameters (especially the working pressure), different TiO2 nanopowders were obtained, whose photodegradation properties were tested compared to a commercial Degussa P25 sample. Two series of samples were obtained. Series "a" includes thermally treated TiO2 nanoparticles (to remove impurities) that have different proportions of the anatase phase (41.12-90.74%) mixed with rutile and small crystallite sizes of 11-22 nm. Series "b" series represents nanoparticles with high purity, which did not require thermal treatment after synthesis (ca. 1 atom % of impurities). These nanoparticles show an increased anatase phase content (77.33-87.42%) and crystallite sizes of 23-45 nm. The TEM images showed that in both series small crystallites form spheroidal nanoparticles with dimensions of 40-80 nm, whose number increases with increasing the working pressure. The photocatalytic properties have been investigated regarding the photodegradation of ethanol vapors in Ar with 0.3% O2 using P25 powder as reference under simulated solar light. During the irradiation H2 gas production has been detected for the samples from series "b", whereas the CO2 evolution was observed for all samples from series "a".

Synthesis and Characterization of SiO2/TiO2 as Photocatalyst on Methylene Blue Degradation

The paper presents a modification of titanium dioxide with fumed silica. The SiO2/TiO2 photocatalysts were obtained by the sol-gel method and then were calcined under an argon atmosphere. Various SiO2 weights (2–17.2 wt.%) were used in the materials’ preparation stage. The obtained samples were characterized using advanced analytical methods, such as FT-IR/DRS infrared spectroscopy, X-ray diffraction, SEM scanning electron microscopy, and UV-Vis/DRS spectroscopy. The BET specific surface area and zeta potential of samples were also measured. Based on the obtained results, it was observed that the modification of titanium dioxide with SiO2 effectively inhibited the increase in crystallite size of anatase and brookite during calcination and the decrease in specific surface area values. Moreover, the presence of SiO2 in the nanomaterials contributed to the increase in the size of specific surface area and the change in band gap energy values. The photocatalytic activity was determined based on the decomposition of methylene blue under UV irradiation. Thermal modification in an inert gas atmosphere significantly increased the dye removal rate. It should be noted that all the obtained SiO2/TiO2 photocatalysts showed higher activity compared to the starting TiO2. It was also found that the photocatalytic activity increased along with the increase in SiO2 content in the sample (up to 14.3 wt.% of SiO2). The highest activity was recorded for SiO2(11.1%)/TiO2_400 and SiO2(14.3%)/TiO2_400 samples.

Microstructural view of anatase to rutile phase transformation examined by in-situ high-temperature X-ray powder diffraction

The phase transformation of commercial TiO2 was investigated carefully by in-situ high-temperature X-ray powder diffraction. The diffractograms between 25 ​°C and 800 ​°C were employed to determine the composition, unit cell parameters, and microstructure. The phase transition initiated slowly at 400 ​°C due to the seeding effect of pre-existing rutile and accelerated above 600 ​°C. The unit cell volume of anatase exhibits a third-degree polynomial distribution similar to c-direction, where the volume increased before and decreased during the phase transition. In contrast, a and b unit cell parameters increased with temperature, following a second-degree polynomial distribution. The unit cell parameters and volume of rutile increased continually with temperature following a third-degree polynomial distribution. A slight difference in expansion rates before and during phase transformation reflects the formation and amalgamation of newly materialized rutile with pre-existing one. Both lattice strain and crystallite size of anatase increased before and decreased during the phase transition. The vigorous lattice vibration of the dominant anatase lattice is likely responsible for minor changes in the crystallite shape of pre-existing rutile, resulting in a nominal size decrease before phase transition. The materialization of newly formed rutile occurred under decreased lattice strain and increased crystallite size.

Light-assisted synthesis of Au/TiO2 nanoparticles for H2 production by photocatalytic water splitting

A series of Au/TiO2 photocatalysts was synthesized via the light assistance through the photo-deposition for H2 production by photocatalytic water splitting using ethanol as the hole scavenger. Effect of solution pH in the range of 3.2–10.0 on the morphology and photocatalytic activity for H2 production of the obtained Au/TiO2 photocatalysts was explored. It was found that all Au/TiO2 photocatalysts prepared in different solution pH exhibited comparable anatase fraction (∼0.84–0.85) and crystallite size of TiO2 (21–22 nm), but showed different quantity of deposited Au nanoparticles (NPs) and other properties, particularly the particle size of the Au NPs. Among all prepared Au/TiO2 photocatalysts, the Au/TiO2 (10.0) photocatalyst exhibited the highest photocatalytic activity for H2 production, owning to its high metallic state and small size of Au NPs. Via this photocatalyst, the maximum H2 production of 296 μmol (∼360 μmol/g⋅h) was gained at 240 min using the 30 vol% ethanol as the hole scavenger at the photocatalyst loading of 1.33 g/L under the UV light intensity of 0.24 mW/cm2 with the quantum efficiency of 61.2% at 254 nm. The loss of the photocatalytic activity of around 20% was observed after the 5th use.

Structural changes of TiO2 as a result of CNTs incorporation

The subject of this research work was to analyze the structural and morphological changes of TiO2 as a result of incorporation of CNTs and interpret the underlying principles for the observed interactions. Hybrid TiO2/CNTs nanostructures were prepared by simplified sol-gel method followed by monitoring the thermally-induced alterations occurring up to 400 ºC. The effects of different type of CNTs (activated MWCNTs and as prepared SWCNTs) as well as the variation of the content of MWCNTs in association with the metal-dopant (Pt or Co) influencing the structural parameters of TiO2 was monitored. Addition of CNTs and metallic phase causes reduction of TiO2 (anatase) crystallite size. The applied instrumental techniques such as XRPD, Raman spectroscopy and thermal (TG, DTA and DTG) analysis points out on achieved interaction between TiO2 and incorporated CNTs. Morphological changes, observed from the SEM micrographs, revealed better inter-locking of the TiO2 matrix with SWCNTs than with MWCNTs. Formation of a more structurally disordered and non-stoichiometric anatase phase seemed to be a preferred choice for the obtained TiO2-CNT-metalic phase nanocomposites for further utilization in sensor-design products.

PHOTOCATALYTIC ACTIVITY OF MESOPOROUS TiO2 (ANATAS) IN THE REACTION OF HYDROGEN RELEASE FROM AQUEOUS-ETHANOLIC MIXTURE

Samples of mesoporous nanocrystalline titanium dioxide (anatase with a crystallite size of about 10 nm) were obtained by a modified sol-gel method in the presence of a template of dibenzo-18-crown-6 and small additives of surfactant (dodecylmethylethylammonium bromide) or ions of lanthanum (III) in butyl alcohol in combination with hydrothermal treatment at 175 °C for 24 hours followed by calcination in air at 500 °C for 4 hours. The photocatalytic activity of the obtained TiO2 samples was investigated in a model reaction of the photocatalytic release of H2 from an aqueous-ethanol mixture. It was found that in all cases the use of hydrothermal treatment significantly increases the photoactivity of the obtained sample, which in some cases is more than 3-4 times higher than the corresponding characteristic for commercial photocatalyst Evonik P25. The key effect of hydrothermal treatment on the increase of photoactivity of the samples is probably the consequence of a drastic increase in the treated samples of pore volume and diameter, as well as a decrease in the size of anatase crystallites. These changes (along with a significant increase in the specific surface area) are greater for samples obtained in the presence of La3+ ions. It is shown that samples of TiO2 microspheres obtained at the same concentrations of reagents in the reaction mixture show slightly higher photocatalytic activity than the corresponding lanthanum-stabilized samples of mesoporous TiO2 powders (micrometer-scale particles are not formed in the presence of lanthanum (III) ions). However, with an increasing concentration of reagents in the reaction mixture, the photocatalytic activity has the sample containing lanthanum. Probably, this can be explained by the high textural characteristics of the TiO2 sample in combination with the peculiarities of its morphology - the formation of secondary nanoparticles of agglomerated formations and the influence of La3+ ions. It is worth noting that the photocatalytic activity of TiO2 samples prepared in the presence of La3+ ions reduces as their specific surface area decreases.

Brookite vs. rutile vs. anatase: What`s behind their various photocatalytic activities?

The results of investigating the morphological, optical and electronic properties of three synthesized TiO2 polymorphs (anatase (A and A2), brookite (B and B2) and rutile (R)) show that the origin of their different catalytic efficiency in the heterogeneous photocatalytic process lies in the depths of the charge carrier traps. The presence of shallow electron traps in brookite extends the number and “lifetime” of generated holes, so brookite is a good choice as a photocatalyst in such heterogeneous photocatalytic systems where these two variables are the reaction limiting factors. Low generation and high recombination rate of charge carriers in rutile are the consequence of too deep electron traps, therefore the generated electrons are not able to participate in reactive oxygen species generation reactions on the catalyst surface. The longer “lifetime” of charge carriers generated in anatase is due to the fact that anatase belongs to the indirect band gap semiconductors. It was further revealed that the increase of the anatase crystallite size (from 10 to 20 nm) can compensate the negative effect of decreasing specific surface area (from 129.5 to 65.0 m2/g) on the photocatalytic activity of anatase. The negative effect of decreasing specific surface area was very well expressed in the case of brookite, where the photocatalytic activity dropped with decreasing specific surface area (from 17.2 to 3.0 m2/g) while keeping constant brookite crystallite size (≈ 80 nm). Heterogeneous photocatalytic experiments with the model pollutant bisphenol A show that the deposition of bisphenol A degradation products on the catalyst surface can have a detrimental effect on photocatalytic activity of low specific surface area TiO2 polymorphs. The specifics (electronic properties, geometry of particles and photocatalytic activity of each TiO2 polymorph) of the investigated heterogeneous photocatalytic system for reactive oxygen species generation are the reason that the “synergistic effect” between the anatase and rutile phase when used as a physical mixture, regardless of the ratio between them, was not expressed. The anatase phase was shadowed by small and abundant rutile nanoparticles with low photocatalytic activity, which acted also as a harvester of UV-light due to a wider UV-light absorption range. We can conclude that the less studied TiO2 polymorph brookite is worthy of investigation, as the results of the present study show that the photocatalytic activity of brookite with the adequate specific surface area is comparable to the photocatalytic activity of the widely investigated anatase TiO2. In addition, it can be concluded that in the physical mixtures of different TiO2 polymorphs, the use of TiO2 particles of close diameters is of crucial importance to achieve a “synergistic” photocatalytic effect triggered by particle collisions.

Size-strain line-broadening analysis of anatase/brookite (TiO2)-based nanocomposites with carbon (C): XRPD and Raman spectroscopic analysis.

A size-strain line-broadening analysis of the XRPD patterns and Raman spectra for two anatase/brookite (TiO2)-based nanocomposites with carbon (C) was carried out and the results compared with those of a similar sample free of carbon. The crystal structures and microstructures of anatase and brookite, as well as their relative abundance ratio, have been refined from XRPD data by the Rietveld method (the low amount of carbon is neglected). The XRPD size-strain analysis resulted in reliable structure and microstructure results for both anatase and brookite. The experimental Raman spectra of all the samples in the region 100-200 cm-1 are dominated by a strong feature primarily composed of the most intense modes of anatase (Eg) and brookite (A1g). The anatase crystallite sizes of 14-17 nm, estimated by XRPD, suggest the application of the phonon confinement model (PCM) for the analysis of the anatase Eg mode, whereas the relatively large brookite crystallite size (27-29 nm) does not imply the use of the PCM for the brookite A1g mode. Superposition of the anatase Eg mode profile, calculated by the PCM, and the Lorentzian shape of the brookite A1g mode provide an appropriate simulation of the change in the dominant Raman feature in the spectra of TiO2-based nanocomposites with carbon. Raman spectra measured in the high-frequency range (1000-2000 cm-1) provide information on carbon in the investigated nanocomposite materials. The results from field-emission scanning electron microscope (SEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and nitrogen physisorption measurements support the XRPD and Raman results.

Micro-mesoporous TiO2/SiO2 nanocomposites: Sol-gel synthesis, characterization, and enhanced photodegradation of quinoline

Micro-mesoporous TiO2/SiO2 nanocomposite powders have been successfully synthesized by the sol-gel process with different TiO2/SiO2 molar ratios and were applied in the UV-photodegradation of quinoline (λ = 254 nm). The structural, morphological, and textural characterization of the powders showed a homogeneous distribution of TiO2 nanoparticles within a porous amorphous SiO2 matrix. Due to the micro-mesoporous character of the materials, their textural characteristics were evaluated by the N2 adsorption method, by comparing BET, DR, Langmuir, and DFT theories. Si60Ti40 powders (60%SiO2/40%TiO2) presented the highest specific surface area (SSA) obtained from BET (SSA = 363 m2g-1), DR (SSA = 482 m2g-1), and Langmuir (SSA = 492 m2g-1) due to the adequate particle size of TiO2 and its high dispersion in the porous matrix. A higher degradation of quinoline in the presence of H2O2 (66%) was achieved using Si80Ti20 powders (80%SiO2/20%TiO2), as compared to pure sol-gel TiO2 powders, (51%) under the same reaction conditions (1 UVC lamp - 250W, t = 180 min). The better performance of the Si80Ti20 nanocomposite could be attributed to the small TiO2 anatase crystallite size (<5.7 nm), high dispersion of these crystallites in the SiO2 matrix, great specific surface area (DR SSA = 342 m2 g−1), and the formation of Ti–O–Si bond, which is associated with new catalytic sites in TiO2/SiO2 composite.

Peroxy titanium complex derived Fe-doped TiO2 Nanoparticles: Synthesis, properties and antibacterial activity

The synthesis of Fe3+-TiO2 nanoparticles (NPs) derived from peroxytitanium complex carried out using hydrothermal method. Pure TiO2 and Fe3+ doped TiO2 powders were characterized to study their structural, compositional, morphological and optical properties. The X-ray diffraction patterns shows crystalline pure anatase TiO2 and crystallite size decreases from 10.17 to 8.25 nm with addition of Fe3+ ion. FE-SEM micrographs reveal well diffused aggregates with nanograin morphology. The efficiency of antibacterial activity against E. coli was studied under different physicochemical parameters. The antibacterial activity varies with concentration of Fe3+ in TiO2 matrix against E. coli bacteria. The antibacterial activity was increased with increasing Fe3+ content in TiO2 NPs and the highest antibacterial activity was observed for 2.15 wt.% Fe3+-TiO2.

Light induced catalytic and electrochemical enhancement in metal nanoparticles crafted one dimensional TiO2 nanotubes

One-dimensional nanostructures of titanium dioxide (TiO2) pay tremendous attention to photocatalysis. In this context, we present the consequence of bimetallic nanoparticles (Zn-Pd) on electrochemical and photocatalytic properties of TiO2 nanotubes (TiNTs). Bimetallic nanoparticles of Zn-Pd are crafted on TiNTs by photodeposition process at room temperature. The presence of bimetallic nanoparticles (MNPs) decreases the ability of the recollection of the electron-hole pairs and modifies structure of TiNTs. Crafting of Zn-Pd on TiNTs modify the structure of ZnPd-TiNTs as evident by scanning electron microscopy (SEM). The results showed that nanoparticles of Zn-Pd are crafted uniformly over TiNTs. The detailed analysis of TiNTs and ZnPd-TiNTs are investigated via X-ray diffraction (XRD) and raman spectroscopy. Observations reveals intensity of plane increases after crafting of Zn-Pd, showing increased anatase phase crystallinity and crystallite size. In addition, the change in the peak position of ZnPd-TiNTs is due to the crafting of Zn-Pd over TiO2, resulting in a change in the TiO2 structure. The changed structure of TiNT extensively changes the catalytic properties of the hybrids of ZnPd-TiNTs that have been further corroborated by photocatalytic applications. The photocatalytic behavior of ZnPd-TiNT hybrids is found to be significantly higher than TiNTs. The enhancement in photocatalytic activity of ZnPd-TiNTs hybrids is owing to the better charge separation.

Hierarchical TiO2 Nanoflower Photocatalysts with Remarkable Activity for Aqueous Methylene Blue Photo-Oxidation.

This study systematically evaluates the performance of a series of TiO2 nanoflower (TNF) photocatalysts for aqueous methylene blue photo-oxidation under UV irradiation. TNF nanoflowers were synthesized from Ti(IV) butoxide by a hydrothermal method and then calcined at different temperatures (T = 400–800 °C) for specific periods of time (t = 1–5 h). By varying the calcination conditions, TNF-T-t photocatalysts with diverse physicochemical properties and anatase/rutile ratios were obtained. Many of the TNF-T-1 photocatalysts demonstrated remarkable activity for aqueous methylene blue photo-oxidation at pH 6 under UV excitation (365 nm), with activities following the order TNF-700-1 > TNF-600-1 > TNF-500-1 > TNF-400-1 ∼ P25 TiO2 ≫ TNF-800-1. The activity of the TNF-700-1 photocatalyst (99% anatase, 1% rutile) was 2.3 times that of P25 TiO2 at pH 6 and 14.4 times that of P25 TiO2 at pH 4. Prolonged calcination of the TNFs at 700 °C proved detrimental to dye degradation performance due to excessive rutile formation, which reduced the photocatalyst surface area and suppressed OH• generation. The outstanding activities of TNF-700-1 and TNF-600-1 are attributed to their hierarchical nanoflower morphology which benefitted UV absorption, a near-ideal anatase crystallite size for efficient charge separation, and their unusually low isoelectric point (IEP = 4.3–4.5).

Post-harvest treatment of carbendazim in Chinese chives using TiO2 nanofiber photocatalysis with different anatase/rutile ratios

Carbendazim residues in Chinese chives were treated by photocatalysis using the following three electrospun TiO2 nanofibers: TTiP/PVP, TTiP/PVAc, and TBOT/PVP. The as-spun fibers were calcined at 500–650 °C to achieve anatase/rutile (A/R) ratios of 100:0, 80:20, 70:30, 50:50, and 30:70. The obtained anatase crystallite sizes were in the range of 13.9–28.1 nm, while the rutile crystallite sizes were 21.1–30.6 nm. The experiments were conducted in glass reactors. These were filled with water and each type of the fiber and irradiated from above by black light lamps for 5 min. Then, 50 g of the samples of Chinese chives was immersed for 5, 15, 30, and 60 min. Carbendazim in the chives was extracted using the matrix solid-phase dispersion (MSPD) method and analyzed using UHPLC. The ˙OH formation from each fiber type was investigated using the coumarin fluorescent probe method. An A/R ratio of 70:30 yielded the highest ˙OH formation, as well as the greatest carbendazim degradation. Rutile plays a crucial role in inhibition of electron-hole recombination and ˙O2− stabilization. The degradation efficiencies for carbendazim from TTiP/PVP, TTiP/PVAc, and TBOT/PVP fibers after a 60-min treatment were 98.6–99.5%, 91.2–97.1%, and 99.5–99.9%, respectively. The TTiP/PVP and TBOT/PVP fibers produced levels of retained carbendazim in the chives that were within EU maximum residue limits of 0.1 mg/kg. The thermal stability of the TTiP/PVAc fiber limited ˙OH formation and carbendazim degradation.

Influence of annealing temperature of ZnS-coated TiO2 films on the performance of dye-sensitized solar cells

This work deals with ZnS-coated TiO2 films prepared via liquid phase deposition and immersion techniques and then applied as photoanode of dye-sensitized solar cells. The samples underwent annealing treatment at various annealing temperatures. The morphology of TiO2 is nanograss and covered by agglomerate and hexagonal ZnS layer. The anatase crystallite size, absorption peak wavelength and optical reflectance increase with annealing temperature. However, the energy gap decreases with the temperature. The device utilizing the sample annealed at 400 °C performed the highest η of 0.24 % due to this device owns the lowest leak current and the longest carrier lifetime.

Electrospun Ag-TiO2 Nanofibers for Photocatalytic Glucose Conversion to High-Value Chemicals.

TiO2 nanofibers were fabricated by combination of sol–gel and electrospinning techniques. Ag-doped TiO2 nanofibers with different Ag contents were prepared by two different methods (in situ electrospinning or wetness impregnation of Ag on TiO2 nanofibers) and heat treated at 500 °C for 2 h under an air or N2 atmosphere. The obtained catalysts were characterized by field emission scanning electron microscopy, X-ray diffraction, photoluminescence, and N2 adsorption analyzed by the Brunauer–Emmett–Teller (BET) method. Photocatalytic glucose conversions with electrospun TiO2 and Ag-doped TiO2 nanofibers for production of high-value products were carried out. From different doping methods, the results indicated that 1 wt % Ag-TiO2 nanofibers prepared by an in situ method with calcination under N2 achieved the highest glucose conversion (85.49%). From several Ag loading contents (i.e., 0, 1, 2, and 4 wt %) in Ag-doped TiO2 nanofibers, the nanofibers exhibited different glucose conversions [in order of 2 wt % (99.65%) > 1 wt % (85.49%) > 4 wt % (77.72%) > 0 wt % (29.64%)]. Arabinose, xylitol, gluconic acid, and formic acid were found as the high-value chemicals with the photocatalytic reaction of TiO2 and Ag-doped TiO2 nanofibers under UVA irradiation. Product yields of each converted chemicals from different photocatalysts from different Ag loading contents showed relatively same trends with the glucose conversion. From all results, it can be concluded that the good characteristics of 2 wt % Ag-TiO2 nanofibers such as the smallest anatase crystallite size (8.25 nm) and the highest specific surface area (SBET = 53.69 m2/g) promoted the highest photocatalytic activity. Additionally, TiO2 and Ag-doped TiO2 nanofibers exhibited higher photocatalytic performance for glucose conversion than commercial TiO2 (P25) and synthesized TiO2 nanoparticles. Finally, Ag-doped TiO2 nanofibers showed recycling ability with high photocatalytic glucose conversion after four-time use.

Photoelectrocatalytic Degradation of C.I. Basic Blue 9 under UV Light Using Silver-Doped Titanium Dioxide Nanotubes

Titanium dioxide is a widely-investigated semiconductor photocatalyst due to its wide availability and low cost. Although it has been successfully used in the photocatalytic treatment of various organics in wastewater, it remains a challenge to modify its structure to achieve enhanced catalytic properties at a wider light spectrum. Doping with transition metals was seen to narrow its optical band gap yet synthesis routes have been largely limited to the use of high-end equipment. Herein we demonstrate the use of a simpler one-pot approach to synthesize nanoporous arrays of silver-doped titanium dioxide nanotubes (Ag-TiNTs) by double anodization of titanium sheets. The synthesized Ag-TiNTs have an average inner diameter of 58.68 nm and a wall thickness of 16.46 nm. ATR-FTIR spectroscopy revealed its characteristic peaks attributed to O-Ti-O bonds. Silver doping increased the lattice volume and crystallite size of anatase with a corresponding decrease in the degree of crystallinity due to the introduction of impurity Ag atoms in its tetragonal structure. Silver was homogeneously distributed across the nanotube surface at an average loading of 1.41 at. %. The synthesized Ag-TiNTs were shown to have a superior photoelectrocatalytic activity in degrading C.I. Basic Blue 9 under UV illumination with a pseudo-first-order kinetic rate of 1.0253 x 10-2 min-1. Most importantly, the Ag-TiNTs are photoelectrocatalytically-active even at a low Ag loading.