S-doped TiO2 Nanoparticles Research Articles

Heterostructured S-TiO2/g-C3N4 Photocatalysts with High Visible Light Photocatalytic Activity

Novel heterojunctions associating graphitic carbon nitride g-C3N4 and S-doped TiO2 nanoparticles were successfully designed and prepared via a hydrothermal method and used for photocatalytic degradations. The loading in S-TiO2 nanoparticles on g-C3N4 was varied (5, 10 and 20 wt%), and the photocatalysts were characterized by XRD, FT-IR, solid-state UV-visible diffuse reflectance, photoluminescence, XPS, TEM and SEM. The S-TiO2 (5%)/g-C3N4 catalyst exhibits the highest activity for the photocatalytic degradation of the methylene blue (MB) dye under visible light irradiation. The high photocatalytic performance originates from the enhanced separation and transfer of photogenerated charge carriers. The S-TiO2 (5%)/g-C3N4 photocatalyst is stable and can be reused five times without a sharp drop in activity, indicating its high potential for wastewater remediation.

Enhanced antibacterial activity of visible light activated sulfur-doped TiO2 nanoparticles against Vibrio cholerae

Pure and S-doped TiO2 nanoparticles were synthesized using a facile hydrothermal technique and the influence of sulfur doping on the structural and optical properties of TiO2 are highlighted. The focus of this work is to develop a photocatalyst having enhanced antibacterial activity against Gram negative bacteria. The crystallinity and phase composition of the synthesized nanoparticles were confirmed using X-ray diffraction (XRD) technique which showed that nanoparticles have anatase TiO2 structure which is in good agreement with the Raman studies. In addition, with S-doping crystallite size varied between 17.84 and 33.25 nm. The presence of S in the TiO2 matrix was confirmed by the elemental composition analysis carried out through EDAX measurements. FTIR spectra also revealed a band at 1068.01 cm−1, which is found to be associated with the Ti–O–S bond. UV-Vis measurements showed that the bandgap energy is, in general, decreased with the introduction of S in the TiO2 lattice. TiO2 doped with 40% S content (F-4) showed 71% bacterial growth reduction at concentration of 0.01 μg/mL. The safety of the synthesized nanoparticles was tested in vitro on hepatocellular carcinoma (Huh-7) human cell lines, which suggested that these particles are safe for the treatment of drinking water against Vibrio cholera.

Visible light responsive S-Doped TiO2 nanoparticles: synthesis, characterization and photocatalytic degradation of pollutants

Visible light responsive S-Doped TiO2 nanoparticles: synthesis, characterization and photocatalytic degradation of pollutants

Nanosized S-Doped TiO<sub>2</sub> with Effective Visible-Light Degradation of BTEX from Wood-Based Panels

S-doped TiO2 nanoparticles were fabricated by hydrothermal process and post-calcination, and their morphology, crystalline phase and chemical composition were characterized with transmission electron microscopy, powder X-ray diffraction and selected area electron diffraction. The results showed that S was successfully doped into the TiO2. We investigated the photocatalytic reactions in a simulated environment in tandem with thermal desorption-gas chromatography-mass spectrometry determinations. The catalytic activity of S-doped TiO2 was evaluated by monitoring the photodegradation of BTEX from wood-based panels, and 95% degradation rate in 75 min demonstrated efficient visible-light catalytic performance.

Novel green synthesis of S-doped TiO2 nanoparticles using Malva parviflora plant extract and their photocatalytic, antimicrobial and antioxidant activities under sunlight illumination

Visible-light-responsible S-doped TiO2(GST) nanoparticles (NPs) are synthesized via sol-gel process, and an aqueous extract of Malva parviflora (MP) plant is used as the green and versatile medium with excellent reducing and capping properties to facilitate the S-doping and crystal growth of anatase. Compared with the counterpart (CST) derived from the conventional organic solvent. GST show a smaller average particle size (20.3 vs. 29.5 nm) with a larger surface area (135 vs 95 m2/g), together with the more significant red shift to longer wavelength in the visible light region. XPS analysis shows Ti4+ cations are substituted by S6+ ions into the lattice structure of TiO2 for both samples. The photodynamics of CST and GST catalysts are examined by electron paramagnetic resonance (EPR) spectroscopy, which shows the surface Ti3+ sites can be oxidized easily by the surface adsorbed O2 molecules, forming O2− radicals. Their photocatalytic activities (PCA) are evaluated by degrading methyl orange (MO) dye under the visible light irradiation. GST exhibit higher PCA in MO bleaching and chemical oxygen demand (COD) reduction. In addition, antimicrobial and antioxidant assays of CST and GST NPs also show that the irradiated NPs samples show higher antibacterial activities. GST NPs have a higher antibacterial activity than CST NPs against all tested bacteria and the minimum inhibitory concentration (MIC) is optimized to 25 μg/mL. The in-vitro antioxidant activity evaluated by the radical cation de-colorization test using 1,1-diphenyl-2-picrylhydrazyl (DPPH) further demonstrates that GST NPs give a better antioxidant activity.

TiO2 modified orthocortical and paracortical cells having enhanced photocatalytic degradation and photoreduction properties

In this study, cortical cells resultant from wool fibers were loaded with TiO2 nanoparticles in a hydrothermal process and were then engineered as organic-nonorganic hybrid composite photocatalysts for both photodegradation of organic dyes and photoreduction of heavy metal ions. The microstructure and photocatalytic properties of TiO2 modified cortical cells (i.e. both orthocortical and paracortical cells) were systematically characterized using a series of analytical techniques including FESEM, TEM, element analysis, Mott–Schottky curve, BET specific surface area, Zeta potentials, as well as XRD, FTIR, XPS, DRS, PL, UPS, EDS and ESR spectra. Their photocatalytic performance and trapping experiments of the TiO2 modified cortical cells were measured in the photodegradation of methylene blue (MB) dye and Congo Red (CR) dye as well as the photoreduction of Cr(VI) ions under visible light irradiation. It was found that anatase TiO2 nanoparticles were chemically grafted on the surface of the two cortical cells via O–Ti4+/O–Ti3+ bonds, and that TiO2 nanoparticles were formed inside the orthocortical cells in the hydrothermal process. The TiO2 modified orthocortical and paracortical cells possessed much higher photocatalytic efficiency than the commercially available TiO2 nanoparticle powder, Degussa P25, in the photodegradation of cationic MB dye and photoreduction of Cr(VI) ions, while their photocatalytic efficiency in the photodegradation of anionic CR dye is smaller because of their greater negative Zeta potentials and photogenerated holes as the main reactive radical species. In comparison with the TiO2 modified paracortical cells, the higher photocatalytic efficiency of the TiO2 modified orthocortical cells was demonstrated in the photodegradation of MB dye solution and this might be due to both the S-doped TiO2 nanoparticles infiltrated into the naturally hydrophilic orthocortical cells and the primary reactive radical species of photogenerated holes being trapped in the cells.

Visible light response and superior dispersed S-doped TiO2 nanoparticles synthesized via ionic liquid

Visible light response and superior dispersed S6+-doped TiO2 nanoparticle catalysts (S-TiO2) were prepared via ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate. The phenol was used for the evaluation of the S-TiO2 photocatalytic activity. S-TiO2 was characterized by XPS, UV–vis DRS, FE-SEM, TEM, XRD, TG/DSC, FTIR, and BET. The results showed that S-TiO2 with appropriate S doping prepared via ionic liquid had smaller particle size, better dispersion, higher activity, and higher surface area (SBET) than that prepared in water. Cationic S6+ incorporation into TiO2 lattice substitutes for Ti4+ lattice site, generates Ti–O–S bonds in TiO2, and leads to the formation of donor defect levels in band gap, so that the photocatalytic sensitization of TiO2 has been extended to visible light region. The optimal content in S doping for the better photocatalytic performance can optimize electrical properties of the intrinsic n-type TiO2 by adding the adequate amount of donor defect of STi2+ for considering the lifetime of the photo-induced charge pairs.

Full visible-light absorption of TiO2 nanotubes induced by anionic S22− doping and their greatly enhanced photocatalytic hydrogen production abilities

TiO2, as a benchmark photocatalyst for hydrogen production through water splitting, has a relatively large band gap (3.2eV for anatase and 3.0eV for rutile) requiring UV light (290–400nm) for electronic excitations from the valence band to the conduction band, hence utilizing only a small part of the solar spectrum. The construction of new electronic band gap, especially in the visible region (400–800nm), is of great importance for improving TiO2 optical and photocatalytic properties. In this work, though it is deem metastable and can induce a broad visible-light adsorption in previous literatures, anionic S22− has been successfully introduced into TiO2 nanotubes, which is different from the previous works about S-doped TiO2 that contain only cationic S4+ and S6+. Resultantly, the S22− doped TiO2 nanotubes exhibit a full visible-light absorption (from 400 to 800nm) and a greatly enhanced photocatalytic H2-production rate under visible-light irradiation (9610μmolh−1g−1, about 13.7 and 37 times of other cationic and anion S-doped TiO2 nanoparticles, respectively, almost highest in all the results reported previously in literatures of TiO2 doped with non-metal elements).

New Method to Synthesize S-Doped TiO2 with Stable and Highly Efficient Photocatalytic Performance under Indoor Sunlight Irradiation

In this paper, we report a new, low-cost, and facile solvothermal approach to synthesize visible-light-active S-doped TiO2 (S-TiO2) by using dimethyl sulfoxide (DMSO) as both the S source and the solvent. Energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) solidly confirmed the presence of S element in the final product. The as-prepared S-TiO2 nanoparticles exhibited excellent and long-term stable photocatalytic performance for the degradation of organic pollutants under visible and indoor sunlight illumination. The catalyst still maintained high photoactivity even after several months of exposure to the indoor sunlight irradiation. This result suggests a new approach to achieve stable and highly efficient solar light driven photocatalysts for water purification.

A facile route to synthesis of S-doped TiO2 nanoparticles for photocatalytic activity

There is always a market for cost effective methods of pollution degradation and one of the best areas to keep costs down is through synthesis techniques. This paper provides a simple technique to synthesise porous TiO2 nanoparticles with increased surface area through a scaffold template technique. Their photocatalytic activity is enhanced by incorporating sulphur as a dopant and were validated by analysing the degradation of malachite green (MG). The materials were doped at a molar ratio of 100:1 (Ti:S) and calcined at different temperatures to adjust the anatase/rutile content. Detailed characterisation of the materials was undertaken using XRD, BET, XPS, TEM and FTIR. The nanoparticles displayed a microporous structure and had an increased surface area of 115m2g−1 which was reduced by doping and temperature induced phase transformation. Photocatalytic testing showed that the doped materials calcined at 700°C preformed the best in. It was observed that 20mgl−1 of MG was decomposed in 30min using a 40W UV bulb at pH 9 and the results surpassed those achieved by the commercial catalyst P25 which was also tested for comparison.

An in vivo study on the photo-enhanced toxicities of S-doped TiO2 nanoparticles to zebrafish embryos (Danio rerio) in terms of malformation, mortality, rheotaxis dysfunction, and DNA damage

The role of light on the acute toxicities of S-doped and Sigma TiO2 nanoparticles in zebrafish was studied. Metrics included mortality for both, and rheotaxis dysfunction and DNA damage for S-doped only. It was found that the acute toxicity of S-TiO2 nanoparticles was enhanced by simulated sunlight (SSL) irradiation (96-h LC50 of 116.56 ppm) and exceeded that of Sigma TiO2, which was essentially non-toxic. Behavioral disorder, in terms of rheotaxis, was significantly increased by treatment with S-TiO2 nanoparticles under SSL irradiation. In order to further understand its toxicity mechanism, we investigated hair cells in neuromasts of the posterior lateral line (PLL) using DASPEI staining. Significant hair cell damage was observed in the treated larvae. The Comet assay was employed to investigate the DNA damage, which might be responsible for the loss of hair cells. Production of the superoxide anion (), a major ROS generated by TiO2 nanoparticles, was assayed and used to postulate causative factors to account for these damages. Oxidative effects were most severe in the liver, heart, intestine, pancreatic duct, and pancreatic islet – results consistent with our earlier findings in the investigation of embryonic malformation. TEM micrographs, used to further investigate the fate of S-TiO2 nanoparticles at the cellular level, suggested receptor-mediated autophagy and vacuolization. Our findings validate the benefit of using the transparent zebrafish embryo as an in vivo model for evaluating photo-induced nanotoxicity. These results highlight the importance of conducting a systematic risk assessment in connection with the use of doped TiO2 nanoparticles in aquatic ecosystems.

A Comparison of TiO<SUB>2</SUB> Nanoparticles and Nanotubes for Catalytic Gas Phase Destruction of H<SUB>2</SUB>S Gas at High Temperatures

Reduction of H2S gas over Sulphur doped TiO2 nanoparticles and TiO2 nanotubes was studied in this work. Fixed bed catalytic system was used for the catalytic reduction of H2S gas at a high temperature of 450 degrees C under laboratory conditions. 99.97% reduction was achieved using S-doped TiO2. 2.89% Sulphur was adsorbed on S-doped TiO2 nanoparticles in the form of Ti(SO4)2, while 95.6% reduction was achieved in case of TiO2 nanotubes and the sulphur adsorption was 2.67%. The XRD, SEM, and EDX techniques were carried out to characterize the nanoparticles and nanotubes, while gas reduction analysis was carried out using GC-MS for gas samples.

Optical investigation on sulfur-doping effects in titanium dioxide nanoparticles

The sulfur-doping (S-doping) effects in TiO2 nanoparticles are investigated by means of Raman spectroscopy and UV–Vis spectroscopy with different S-doping levels (10 and 50%). Raman spectra indicate that the rutile and anatase phases dominate for the low S-doped (10%) and high S-doped (50%) TiO2 nanoparticles, respectively. The variation of phase with different S-doping levels has been ascribed to the different S-doping processes into TiO2 nanoparticles. In addition, an extra absorption band is observed in both the S-doped TiO2 nanoparticles. With increasing S-doping level from 10 to 50%, the extra absorption band shows a blue-shift from 470 to 445 nm, which may be ascribed to the variation of phase from rutile to anatase for TiO2.

Development of metal cation compound-loaded S-doped TiO2 photocatalysts having a rutile phase under visible light

We have synthesized S (S4+)-doped TiO2 photocatalysts having a rutile phase. Rutile S-doped TiO2 photocatalysts loaded with metal ion compounds (Fe3+, Rh3+, Cu2+, Co3+, Ni2+, Cr3+) have also been prepared (S-doped TiO2-Mn+). The metal ions were adsorbed on the surfaces of S-doped TiO2 nanoparticles by impregnation methods (IM) or photodeposition methods (PH). The photocatalytic activities of S-doped TiO2 for oxidation of acetaldehyde in gas phase were drastically improved after adsorbing treatment of metal ions under a wide range of incident light wavelengths. Under photoirradiation at wavelengths longer than 350 or 420 nm, S-doped TiO2-Cu2+ (PH) shows the highest level of activity among the metal ions. S-doped TiO2-Fe3+ (IM) shows the highest level of activity for oxidation of acetaldehyde in gas phase compared to the activity levels of S-doped TiO2 with loading of other metal ions such as Rh3+, Cu2+ Co3+, Ni2+, and Cr3+ under a wide range of incident light wavelengths. The optimum amount of metal ion compound nanoparticles adsorbed on S-doped TiO2 was 0.1 wt%. In order to elucidate the role of metal ions adsorbed on the surface of S-doped TiO2, we measured the double beam photoacoustic spectra (DB-PA). The amount of Ti3+ generated as a result of the reaction between Ti4+ and photoexcited electrons was analyzed by this spectroscopy. The relationship between the reaction rate of photocatalytic oxidation of acetaldehyde on S-doped TiO2 adsorbed with metal ions and the charge separation between photoexcited electrons and holes is discussed.