Visible-Light Active and Magnetically Recyclable Nanocomposites for the Degradation of Organic Dye.
ABSTRACT: Recyclable visible-light photocatalyst Fe₃O₄@TiO₂ with core-shell structure was prepared by a simple synthetic strategy using solvothermal crystallization of titanium precursor on preformed Fe₃O₄ nanopartiles. The photo-degradation reaction of neutral red aqueous solution was tested to evaluate the visible-light photocatalytic activity of the as prepared Fe₃O₄@TiO₂ nanoparticles, which show excellent photocatalytic activity compared with commercial P25 catalyst. Moreover, the Fe₃O₄@TiO₂ nanocomposites can be easily separated from the reaction mixture, and maintain favorable photocatalytic activity after five cycles. The high visible light absorption of the Fe₃O₄@TiO₂ nanocomposites may originate from the absence of electronic heterojunction, excellently dispersity and the high specific surface area of the as-synthesized Fe₃O₄@TiO₂ samples.
Project description:Using ilmenite as a raw material, iron was converted into Fe?O? magnetic fluid, which further was combined with titanium filtrate by a solvothermal method. Finally Fe?O?/TiO? nanocomposites with the uniform size of 100-200 nm were prepared. This approach uses rich, inexpensive ilmenite as a titanium and iron source, which effectively reduces the production cost. The crystal structure, chemical properties and morphologies of the products were characterized by SEM, TEM, XRD, FTIR, BET, UV-Vis, XPS and VSM. The novel photocatalyst composed of face-centered cubic Fe?O? and body-centered tetragonal anatase-TiO? exhibits a spherical shape with porous structures, superparamagnetic behavior and strong absorption in the visible light range. Using the degradation reaction of Rhodamine B (RhB) to evaluate the photocatalytic performance, the results suggest that Fe?O?/TiO? nanocomposites exhibit excellent photocatalytic activities and stability under visible light and solar light. Moreover, the magnetic titania nanocomposites displayed good magnetic response and were recoverable over several cycles. Based on the trapping experiments, the main active species in the photocatalytic reaction were confirmed and the possible photocatalytic mechanism of RhB with magnetic titania was proposed. The enhanced photocatalytic activity and stability, combined with excellent magnetic recoverability, make the prepared nanocomposite a potential candidate in wastewater purification.
Project description:Visible-lightdriven C-TiO<sub>2</sub> nanocomposites were prepared via a simple calcination and acid etching process. The C-TiO<sub>2</sub> nanocomposites were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and high-resolution TEM. The results showed that TiO<sub>2</sub> nanoparticles were combined with a porous carbon layer through surface C-O groups, which facilitates the strong interface interaction. The interface combination of nano-TiO<sub>2</sub> and carbon material increases the specific surface area of nano-TiO<sub>2</sub>, widens the range of light response, and improves the efficiency of light-induced electron migration. The visible-light photocatalytic activity of the prepared photocatalyst was evaluated by the decomposition of tetracycline aqueous solution. Compared with that of pure TiO<sub>2</sub>, the photocatalytic activity of C-TiO<sub>2</sub> nanocomposites was significantly improved. Furthermore, a possible photocatalytic mechanism was also tentatively proposed. This work can promote the development of active photocatalysts under solar light for the photodegradation of environmental pollutants.
Project description:Two series of Fe<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> samples were prepared via impregnation and photodeposition methods. The effect of preparation method on the properties and performance of Fe<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> for photocatalytic degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under UV light irradiation was examined. The Fe<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> nanocomposites prepared by impregnation showed lower activity than the unmodified TiO<sub>2</sub>, mainly due to lower specific surface area caused by heat treatment. On the other hand, the Fe<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> nanocomposites prepared by photodeposition showed higher photocatalytic activity than the unmodified TiO<sub>2</sub>. Three times higher photocatalytic activity was obtained on the best photocatalyst, Fe<sub>2</sub>O<sub>3</sub>(0.5)/TiO<sub>2</sub>. The improved activity of TiO<sub>2</sub> after photodeposition of Fe<sub>2</sub>O<sub>3</sub> was contributed to the formation of a heterojunction between the Fe<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub> nanoparticles that improved charge transfer and suppressed electron-hole recombination. A further investigation on the role of the active species on Fe<sub>2</sub>O<sub>3</sub>/TiO<sub>2</sub> confirmed that the crucial active species were both holes and superoxide radicals. The Fe<sub>2</sub>O<sub>3</sub>(0.5)/TiO<sub>2</sub> sample also showed good stability and reusability, suggesting its potential for water purification applications.
Project description:A convenient route was developed for the selective preparation of two stable nanocomposites, Ti<sup>3+</sup>/TiO<sub>2</sub>/CNT (labeled as TTOC-1 and TTOC-3) and Ti<sup>3+</sup>/TiO<sub>2</sub>/carbon layer (labeled as TTOC-2), from the same precursor by varying the amount of single-walled carbon nanotubes used in the synthesis. TiO<sub>2</sub> is an effective photocatalyst; however, its wide bandgap limits its usefulness to the UV region. As a solution to this problem, our prepared nanocomposites exhibit a small bandgap and wide visible-light (VL) absorption because of the introduction of carbonaceous species and Ti<sup>3+</sup> vacancies. The photocatalytic efficiency of the nanocomposites was examined via the degradation of methylene blue dye under VL. Excellent photocatalytic activity of 83%, 98%, and 93% was observed for TTOC-1, TTOC-2, and TTOC-3 nanocomposites within 25 min. In addition, the photocatalytic degradation efficiency of TTOC-2 toward methyl orange, phenol, rhodamine B, and congo red was 28%, 69%, 71%, and 91%, respectively, under similar experimental conditions after 25 min. Higher reusability and structural integrity of the as-synthesized photocatalyst were confirmed within five consecutive runs by photocatalytic test and X-ray diffraction analysis, respectively. The resulting nanocomposites provide new insights into the development of VL-active and stable photocatalysts with high efficiencies.
Project description:The use of the surface plasmon resonance (SPR) effect of plasmonic metal nanocomposites to promote photocarrier generation is a strongly emerging field for improving the catalytic performance under visible-light irradiation. In this study, a novel plasmonic photocatalyst, AuPt/N⁻TiO₂, was prepared via a photo-deposition⁻calcination technique. The Au nanoparticles (NPs) were used herein to harvest visible-light energy via the SPR effect, and Pt NPs were employed as a cocatalyst for trapping the energetic electrons from the semiconductor, leading to a high solar-energy conversion efficiency. The Au₂Pt₂/N⁻TiO₂ catalyst, herein with the irradiation wavelength in the range 460⁻800 nm, exhibited a reaction rate ~24 times greater than that of TiO₂, and the apparent quantum yield at 500 nm reached 5.86%, indicative of the successful functionalization of N⁻TiO₂ by the integration of Au plasmonic NPs and the Pt cocatalyst. Also, we investigated the effects of two parameters, light source intensity and wavelength, in photocatalytic reactions. It is indicated that the as-prepared AuPt/N⁻TiO₂ photocatalyst can cause selective oxidation of benzyl alcohol under visible-light irradiation with a markedly enhanced selectivity and yield.
Project description:Our research was focused on the evaluation of the photocatalytic and antimicrobial properties, as well as biocompatibility of cotton fabrics coated with fresh and reused dispersions of nanoscaled TiO₂-1% Fe-N particles prepared by the hydrothermal method and post-annealed at 400 °C. The powders were characterized by X-ray diffraction (XRD), Mössbauer spectroscopy and X-ray photoelectron spectroscopy. The textiles coated with doped TiO₂ were characterized by scanning electron microscopy and energy dispersive X-ray analyses, and their photocatalytic effect by trichromatic coordinates of the materials stained with methylene blue and coffee and exposed to UV, visible and solar light. The resulting doped TiO₂ consists of a mixture of prevailing anatase phase and a small amount (~15%-20%) of brookite, containing Fe3+ and nitrogen. By reusing dispersions of TiO₂-1% Fe-N, high amounts of photocatalysts were deposited on the fabrics, and the photocatalytic activity was improved, especially under visible light. The treated fabrics exhibited specific antimicrobial features, which were dependent on their composition, microbial strain and incubation time. The in vitro biocompatibility evaluation on CCD-1070Sk dermal fibroblasts confirmed the absence of cytotoxicity after short-term exposure. These results highlight the potential of TiO₂-1% Fe-N nanoparticles for further use in the development of innovative self-cleaning and antimicrobial photocatalytic cotton textiles. However, further studies are required in order to assess the long-term skin exposure effects and the possible particle release due to wearing.
Project description:In this manuscript, "Get two mangoes with one stone" strategy was used to study the electrochemical detection and photocatalytic mineralization of furaltadone (FLT) drug using Cu/Ni/TiO<sub>2</sub>/MWCNTs nanocomposites for the first time. The bi-functional nanocomposites were synthesized through a hydrothermal synthesis technique. The successfully synthesized nanocomposites were analyzed by various analytical techniques. The Cu/Ni/TiO<sub>2</sub>/MWCNTs nanocomposites decorated screen-printed carbon electrode (SPCE) exhibit a good electrocatalytic ability towards detection of FLT. Moreover, the electrocatalytic detection of FLT based on the nanocomposites decorated SPCE have high stability, lower detection limit, and excellent sensitivity of 0.0949 μM and 1.9288 μA μM<sup>-1</sup> cm<sup>-2</sup>, respectively. In addition, the nanocomposites decorated SPCE electrodes performed in real samples, such as river water and tap water, the satisfactory results were observed. As UV-Visible spectroscopy revealed that the Cu/Ni/TiO<sub>2</sub>/MWCNTs nanocomposites had an excellent photocatalytic ability for degradation of FLT drug. The higher degradation efficiency of 75% was achieved within 45 min under irradiation of visible light. In addition, after the degradation process various intermediates are produced which is confirmed by GC-MS analysis. The excellent photocatalytic ability was improved to the dopant ions and restrictions of electron-hole pair.
Project description:Noble metal nanoparticles (NMNPs) enhanced TiO<sub>2</sub> response and extended its activity under visible light. Photocatalytic activity of TiO<sub>2</sub> modified with noble metal nanoparticles strongly depends on the physicochemical properties of NMNPs. Among others, the differences in the size of NMNPs seems to be one of the most important factors. In this view, the effect of the metal's nanoparticles size, type and amount on TiO<sub>2</sub> photocatalytic and biocidal activity was investigated. TiO<sub>2</sub> modified with mono- and bimetallic nanoparticles of Pt, Cu and Ag were prepared using chemical and thermal reduction methods. Obtained nanocomposites were characterized using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and diffuse-reflectance spectroscopy (DR/UV-Vis) techniques. The photocatalytic activity was examined in 2-propanol oxidation and hydrogen generation processes. The mechanism of modified TiO<sub>2</sub> excitation was evaluated in action spectrum measurements during phenol oxidation. A possibility of using less energy-consuming light sources as a set of light-emitting diodes (LEDs) selected based on action spectrum results was examined. It was found that the differences in NMNPs size were the result of the reduction method. Moreover, coupling with a second metal strongly affected and differentiated the photocatalytic and biocidal activity of the obtained TiO<sub>2</sub>-based photocatalysts.
Project description:TiO? nanoparticles are immobilized on chlorella cells using the hydrothermal method. The morphology, structure, and the visible-light-driven photocatalytic activity of the prepared chlorella/TiO? composite are investigated by various methods. The chlorella/TiO? 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 TiO? 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.
Project description:To photo-catalytically degrade RhB dye using solar irradiation, CeO<sub>2</sub> doped TiO<sub>2</sub> nanocomposites were synthesized hydrothermally at 700 °C for 9 hrs. All emission spectra showed a prominent band centered at 442 nm that was attributed to oxygen related defects in the CeO<sub>2</sub>-TiO<sub>2</sub> nanocrystals. Two sharp absorption bands at 1418 cm<sup>-1</sup> and 3323 cm<sup>-1</sup> were attributed to the deformation and stretching vibration, and bending vibration of the OH group of water physisorbed to TiO<sub>2</sub>, respectively. The photocatalytic activities of Ce-TiO<sub>2</sub> nanocrystals were investigated through the degradation of RhB under UV and UV+ visible light over a period of 8 hrs. After 8 hrs, the most intense absorption peak at 579 nm disappeared under the highest photocatalytic activity and 99.89% of RhB degraded under solar irradiation. Visible light-activated TiO<sub>2</sub> could be prepared from metal-ion incorporation, reduction of TiO<sub>2</sub>, non-metal doping or sensitizing of TiO<sub>2</sub> using dyes. Studying the antibacterial activity of Ce-TiO<sub>2</sub> nanocrystals against E. coli revealed significant activity when 10 μg was used, suggesting that it can be used as an antibacterial agent. Its effectiveness is likely related to its strong oxidation activity and superhydrophilicity. This study also discusses the mechanism of heterogeneous photocatalysis in the presence of TiO<sub>2</sub>.