UV Photocatalytic Activity Research Articles

PREFACE INTERNATIONAL SYMPOSIUM ON ADVANCES IN HYDROPROCESSING OF OIL FRACTION (ISAHOF 2017)

The photocatalytic capabilities of La2O3 incorporated in CeO2 for the removal of Pb(II) ions in water are reported in this work. La2O3–modified CeO2 particles are prepared by a solid-state reaction method at calcination temperature of 1000 °C and 1400 °C. The x-ray diffraction result demonstrates a solid solution Ce0.9La0.1O1.95 phase coexisting with the CeO2 matrix phase (Ce0.9La0.1O1.95–CeO2) obtained at a calcination of 1400 °C, while the mixed La2O3/La(OH)3–CeO2 phase is obtained at 1000 °C. The UV-photocatalytic activity for Pb(II) ion removal of the La2O3–modified CeO2 particles is significantly higher than that of pure CeO2. Ce0.9La0.1O1.95–CeO2 particles show stronger visible light absorption capacity and higher ability of photoelectrodeposition for the Pb(II) ion removal than the mixed La2O3/La(OH)3–CeO2 particles and pure CeO2. The high photocatalytic activity is supported by a strong photoluminescence signal from the Ce0.9La0.1O1.95–CeO2 particles, suggesting a high efficiency of photogenerated charge separation. A formation of p-type Ce0.9La0.1O1.95 and n-type CeO2 heterojunctions in Ce0.9La0.1O1.95–CeO2 particles also promote photogenerated charge transfer and efficiency restraining recombination of the charges.

A synergetic effect of ytterbium-doping and ammoniation on enhancing UV and visible photocatalytic activities of TiO2

A synergetic effect of rare earth (Yb) ion doping and ammoniation on the enhancements of both ultraviolet and visible photocatalytic activities of TiO2 is reported. It is found that ammoniation can dope both nitrogen and hydrogen ions for bandgap narrowing and dangling bond passivation, respectively. Meanwhile, the Yb-doping results in the formation of defective bands that are close to the conduction band minimum, and have strong electron capture abilities to prevent recombination of photogenerated electrons and holes. The synergism of the two effects of Yb doping and ammoniation leads to a significant enhancement of both ultraviolet and visible photocatalysis.

Influence of carbon content on photocatalytic performance of C@ZnO hollow nanospheres

Mesoporous C@ZnO hollow spheres were successfully synthesized through a carbon-sphere template combined hydrothermal method. The photocatalytic activities of the samples to rhodamine B (RhB) were investigated, and the sample of 3 wt% carbon has the best photocatalytic activity to RhB. The excellent photocatalytic performance could come from both enhanced photogenerated electron–hole pair separation, and the larger specific surface area induced by mesoporous hollow nanostructure. The photocatalytic performance sensitively depends upon content of amorphous carbon. Too much or too little carbon content decreases sample performance. The changes in performance according to carbon content are probably a result of the competing mechanism: the increasing rate of separation efficiency of photogenerated carriers and the decreasing contact area of ZnO with RhB according to the carbon content. This work would help us to better understand the important roles of carbon content in the fabricated nano-heterojunctions and also provide us with a feasible route to improve UV photocatalytic activities of ZnO and other metal oxides greatly.

Influence of Au content on photocatalytic performance of C@ZnO@Au hollow nanospheres

Mesoporous C@ZnO@Au hollow spheres were synthesized through a stepwise method. The photocatalytic activities of the samples to RhB under UV irradiation were investigated. The sample with a 1/1000 mol ratio of Au/ZnO was found to have the best photocatalytic activity, which is far better than P25. The improved performance could come from the larger specific area induced by mesoporous hollow nanostructure, enhanced light absorption, or improved photogenerated electron-hole pair separation. Sample performance is a function of Au content. Too much or too little Au content decreases sample performance. The changes in performance according to Au content are a result of various competing mechanisms. This work serves to help us to better understand the important roles of Au content in the fabricated nano-heterojunction catalysts and also provide us with a feasible route to improve UV photocatalytic activities of ZnO and other metal oxides.

Photoelectrodeposition effect of lanthanum oxide-modified ceria particles on the removal of lead (II) ions from water

The photocatalytic capabilities of La2O3 incorporated in CeO2 for the removal of Pb(II) ions in water are reported in this work. La2O3–modified CeO2 particles are prepared by a solid-state reaction method at calcination temperature of 1000°C and 1400°C. The x-ray diffraction result demonstrates a solid solution Ce0.9La0.1O1.95 phase coexisting with the CeO2 matrix phase (Ce0.9La0.1O1.95–CeO2) obtained at a calcination of 1400°C, while the mixed La2O3/La(OH)3–CeO2 phase is obtained at 1000°C. The UV-photocatalytic activity for Pb(II) ion removal of the La2O3–modified CeO2 particles is significantly higher than that of pure CeO2. Ce0.9La0.1O1.95–CeO2 particles show stronger visible light absorption capacity and higher ability of photoelectrodeposition for the Pb(II) ion removal than the mixed La2O3/La(OH)3–CeO2 particles and pure CeO2. The high photocatalytic activity is supported by a strong photoluminescence signal from the Ce0.9La0.1O1.95–CeO2 particles, suggesting a high efficiency of photogenerated charge separation. A formation of p-type Ce0.9La0.1O1.95 and n-type CeO2 heterojunctions in Ce0.9La0.1O1.95–CeO2 particles also promote photogenerated charge transfer and efficiency restraining recombination of the charges.

Efficient antibacterial nanosponges based on ZnO nanoparticles and doxycycline

Bacterial soft rot is responsible for the loss of about 25% of worldwide production in vegetables and fruits. Efforts have been made to develop an effective nanosponge with the capacity to load and release antibacterial drugs to protect plants. Based on the potential of the ZnO nanoparticles (ZnO–NPs) to achieve this goal, this study synthesized NP via the sol-gel and hydrothermal methods by controlling native defects, such as oxygen vacancies, using thermal treatments and reduced atmospheres. To characterize the ZnO NPs, X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), optical spectroscopy, electron paramagnetic resonance (EPR), Zeta Potential measurements and surface area with the Brunauer–Emmett–Teller (BET) method were used. The photophysical and photochemical properties via spin trapping method aligned with EPR using UVA light showed a greater formation of electron-hole pairs and hydroxyl radicals for the reduced ZnO NPs when compared with the oxidized ones. Additionally, we found that reduced ZnO-NPs have high effectively against Escherichia coli, Erwinia carotovora and Pantoea sp. bacteria using the photocatalytic effect in the UV range. Moreover, ZnO-NPs loaded with DOX release profile enables the release of DOX within 46days, where 25% was released during the first 10h followed by a second delivery phase with an interesting short-term efficacy (<1day) against E. carotovora and Pantoea sp. Bacteria. For the first time, it was demonstrated that ZnO-NPs and ZnO-NPs loaded with DOX have efficient UV photocatalytic activities against bacterial soft rot infections.

Modified graphitic carbon nitride prepared via a copolymerization route for superior photocatalytic activity

Molecular doping strategy has been applied for regulating the electronic band structure of graphitic carbon nitride (g-C3N4). By incorporating the electron-withdrawing impurity group of N,N′,N″-s-triazine-2,4,6-triyl-tri-p-aminobenzoic acid (H3TATAB) into the network of g-C3N4, a series of H3TATAB-doped g-C3N4 (TABCN) photocatalysts were synthesized via thermal copolymerization at 550 °C for 4 h. H3TATAB doping shifts the VB of TABCN from 1.78 eV (pristine g-C3N4) to a low position (2.07 eV for TCBCN0.8), which enhances the oxidation ability of the VB hole for producing hydroxyl radicals in aqueous solution, and, therefore, the UV photocatalytic activity of TABCN0.8 is estimated to be about twice as high as that of g-C3N4 for the degradation of AO7. Further, doping the H3TATAB impurity group into the g-C3N4 network induces plenty of defect levels below the CB of g-C3N4, which gives a significant absorbance enhancement in the visible region. As a result, the visible light photocatalytic activity of TABCN0.8 is 7.5 times higher than that of g-C3N4 for the degradation of AO7. This work may provide guidance on designing an efficient g-C3N4 polymer photocatalyst with desirable electronic structure.

White light emitting magnesium aluminate nanophosphor: Near ultra violet excited photoluminescence, photometric characteristics and its UV photocatalytic activity

MgAl2O4:Dy3+ (1–11 mol %) nanophosphors (NPs) were synthesized using single step, self ignited solution combustion route at very low temperature and the final product was well characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence techniques. The bandgap energy (Eg) was estimated using diffuse reflection data and the values were found to be in the range 5.40–6.10 eV. Characteristic emission peaks of Dy3+ ions were recorded between 480 and 680 nm and are ascribed to transitions from 4F9/2 to 6Hj (j=5/2, 13/2 and 11/2) respectively due to 4f-4f transitions of Dy3+ ions upon 354 nm excitation and show good quantum efficiency of ∼66%. The photometric studies revealed that the prepared samples were quite useful for the fabrication of white light emitting diodes. Electrochemical Impedance Spectroscopy (EIS) measurements were performed and found that the reversibility of the electrode reaction, increases the double layer capacitance of the electrode due to reduction in the charge transfer resistance. The synthesized sample exhibited excellent photocatalytic activity towards the degradation of AR-88 dye under UV light. It opens a new window to use this simple method to synthesize multifunctional MgAl2O4 based materials in the area of photocatalysis, display applications as well as for energy storage devices.

Achieving UV and visible-light photocatalytic activity enhancement of AgI/BiOIO3 heterostructure: Decomposition for diverse industrial contaminants and high mineralization ability

Heterostructure photocatalyst fabrication is of great significance for promoting the photoreactivity and solar-energy utilization efficiencies. In this work, AgI/BiOIO3 heterostructure photocatalysts are synthesized by a facile in-situ crystallization of AgI on BiOIO3. The photocatalytic performance is first surveyed by decomposition of model dye methyl orange (MO) separately with illumination of UV light and visible-light (λ>420nm). It indicates that AgI/BiOIO3 shows highly improved photocatalytic activity regardless of the light source, which should be attributed to the matchable band energy levels between AgI and BiOIO3, benefiting the efficient charge separation. Notably, AgI/BiOIO3 shows a universal photocatalytic activity for treating diverse antibiotics and phenols, including tetracycline hydrochloride, chlortetracycline hydrochloride, 2,4-dichlorophenol (2,4-DCP), phenol and bisphenol A (BPA), and the strong mineralization ability of AgI/BiOIO3 was also demonstrated. Additionally, the different mechanisms under UV and visible light irradiation are investigated in detail. This work provides a new reference for design and manipulation of high-performance nonselective heterostructure photocatalyst for environmental purification.

Preparation of spindle-like BiPO4 and its photocatalytic performance

ABSTRACT(Ionic Liquid-BiPO4) IL-BiPO4 was synthesized by sonochemical process at 70C using 1-methylimidazolium dehydrogenate phosphate ([Hmim] H2PO4) and Bi(NO3)3.5H2O as raw material. A simple synthesized method of BiPO4 was carried out with IL at moderate condition. Moreover, the ionic liquid (IL) is environmentally friendly. The IL are synthesized using 1-methylimidazolium and H2PO4 as raw materials. The IL also is a surface agent showing excellent performances such as low viscosity, high dispersion and good structure-direction. Moreover, IL can be reused. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), surface area analysis (BET), and diffuse reflectance spectroscopy. The XRD results show an increase in peak intensity for IL-BiPO4, and diffusive reflectance spectra reveal that there is a red shift in the optical absorption, which indicates a decrease in the band gap in IL-BiPO4. BET analytic results show that IL-BiPO4 is three times as large special surface as Na-BiPO4. Spindlelike IL-BiPO4 and rod-like Na-BiPO4 were observed by SEM and TEM. The IL-BiPO4 exhibits excellent UV photocatalytic activity and degradation for methyl blue solution compared with Na-BiPO4.

Characterization and Photocatalytic Activity of SmMnO&lt;sub&gt;3&lt;/sub&gt; Prepared by Sol-Gel Process

Using samarium (III) nitrate hexahydrate, manganese nitrate and citric acid as main raw materials, the SmMnO3 gel was prepared by sol-gel process. The gel was kept at 100 °C for 24 h to get the xerogel. Then, the xerogel was respectively calcined in muffle furnace at 600 °C, 700 °C, 800 °C and 900 °C. The structure and morphology of samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier Transform Infrared (FT-IR) spectroscopy. The UV photocatalytic activities of SmMnO3 were investigated by methyl orange which was used as simulated sewage. The results show that the pure SmMnO3 can be obtained through calcination between 700 °C and 800 °C, and the SmMnO3 have an average particle size of 80 nm. The SmMnO3 samples calcined at 700 °C and 800 °C show high photocatalytic activity for decomposition of methyl orange under UV-light irradiation. The SmMnO3 samples are consistent with first-order kinetics for the degradation of methyl orange. And the apparent rate constants are respectively k700 =0.01206 min-1and k800=0.01088 min-1.

Sol–gel synthesis of TiO2 from TiOSO4: characterization and UV photocatalytic activity for the degradation of 4-chlorophenol

Nanosized titanium dioxide (TiO2) powders were prepared by an aqueous sol–gel method using an inorganic titanium precursor, titanium oxysulfate (TiOSO4). The synthesized powders were characterized by XRD, N2 sorption analysis, SEM, TEM, FTIR and UV-vis DRS spectroscopy. The important synthesis parameters such as precursor concentration, precipitating pH value, peptization temperature, aging time and temperature, heating rate and time and calcination temperature were systematically investigated for their effect on the physicochemical and photocatalytic properties of TiO2. XRD analysis revealed that powders prepared at precipitating pH value ranges from 5 to 9, calcined at 300–600 °C were composed of anatase and brookite. UV-vis DRS analysis showed that the variation in band gap for composite mixture is related to the fraction of brookite and rutile phase. Using low precursor concentration (0.1 and 0.2 M) the final material was composed of anatase–brookite composite mixture, in contrast, at high precursor concentration (0.4 M), pure anatase TiO2 was formed. An increase in aging time beyond 24 h favors the phase transformation of brookite into anatase and increase in peptization temperature from 40 to 70 °C shows a great influence on crystal structure, leading to enhanced crystallization rate with the formation of pure anatase phase. The synthesized powders activity was tested in the degradation of an aqueous solution of 4-chlorophenol (4-CP) under UV light. The TiO2 powder prepared at pH 6 and calcined at 300 °C showed the highest activity, which is attributed to powder composite nature (anatase–brookite; 81–19 wt.%), relative high specific area (157.0 m2 g−1), high crystallinity and degree of hydroxyl groups and moderate band gap. In addition, in terms of reusability, recyclability and chemical stability, the developed photocatalyst showed very encouraging results.

α-Bi2O3 nanorods: synthesis, characterization and UV-photocatalytic activity

In this study, Monoclinic bismuth oxide nanorods (α-Bi2O3 NRs) were successfully synthesized by a simple one-step hydrothermal route using (water: ethanol) (1:1) as a mixed solvents at optimum conditions. The Bi2O3 nano-powder was characterized in detail by different techniques in terms of their structural, morphological, compositional, optical and photocatalytic properties. X-ray diffraction (XRD) analysis indicated that the as-synthesized Bi2O3 NRs exhibited high purity with monoclinic structure (α-Bi2O3) and good crystallinity. The Transmission electron microscope (TEM), Energy dispersive x-ray spectroscopy (EDXS) and Field Emission scanning electron microscope (FE-SEM) analysis clearly confirmed the high purity and the nanorod morphology of the as-synthesized Bi2O3 sample. The optical band gap of α-Bi2O3 NRs was estimated using the UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) analysis according to the Kubelka–Munk theory. The optical band gap of α-Bi2O3 NRs was found to be 3.55 eV for an indirect allowed transition and 3.63 eV for a direct allowed transition. The Fourier transfer infrared spectroscopy (FTIR) was employed to check the structure as well as to evaluate the phonon vibration modes corresponding to Bi2O3. Photocatalytic activity of α-Bi2O3 NRs was investigated using UV source lamp. The as-synthesized α-Bi2O3 NRs photocatalyst exhibited better performance for degradation and decolorization of Methylene blue (MB) under ultraviolet (UV) irradiation. MB was completely photodegraded after 210 min under UV irradiation using α-Bi2O3 NRs as photocatalyst.

Photon-induced interfacial charge transfer mechanism of porous silicon/TiO 2 nanoparticles for photoelectrochemical performance

Abstract Highly ordered porous silicon array (PSA) films were fabricated by anodic oxidation of p-type silicon wafer. Using the methods of magnetron sputtering and thermal annealing, dispersed TiO 2 nanoparticles (NPs) were decorated onto the top of PSA films. Steady-state photoluminescence (PL) spectra and nanosecond time-resolved transient photoluminescence (NTRT-PL) spectra of as-fabricated nano-composites were studied under light irradiation with wavelengths of 266 nm and 400 nm, respectively. A distinct blue-shift in the NTRT-PL spectra is observed owing to the presence of Si 3+ and Ti 3+ cations, which is further confirmed by X-ray photoelectron spectroscopy (XPS). Such a phenomenon could be well explained by considering the competition mechanism between the photo-generated charge separation process and recombination associated with oxygen vacancy (OV). Our present research demonstrates a novel approach to investigate charge separation and transport in a dual-band gap photoelectrochemical (PEC) system. Following this scheme, UV and visible-light photocatalytic activities of TiO 2 /PSA heterojunction composites were evaluated through photodegradation of methyl orange (MO) in aqueous solution. Our current work is expected to provide a simple strategy for synthesising composite photocatalysts, with the hope that optimal sunlight harvesting would be achieved.

A practical pathway for the preparation of Fe2O3 decorated TiO2 photocatalyst with enhanced visible-light photoactivity

Shifting the ultra-violet of titania to visible light driven photocatalysis can be realized by coupling with metallic or non-metallic elements. However, time-consuming multi-step process and significant loss of UV photocatalytic activity of such TiO2-based photocatalysts severely hinder their practical applications. In this work, we explore the idea of creating a practical method for the preparation of Fe2O3 decorated TiO2 (TiO2/Fe2O3) photocatalyst with controlled visible-light photoactivity. This method only involves the calcination of the mixture (commercial P25 powders and magnetic Fe3O4 nanoparticles) prepared by a mechanical process. The morphology and properties of TiO2/Fe2O3 composites were characterized by Transmission electron microscope, X-ray diffraction, UV–vis spectroscopy, and X-ray photoelectron spectroscopy. Results confirm the fusion of TiO2 and Fe2O3, which promotes photo-generated electrons/holes migration and separation. Because of the strong synergistic effect, the as-synthesized TiO2/Fe2O3 composites manifest an enhanced visible-light photocatalytic activity. Especially, the TiO2/Fe2O3 photocatalyst is very easy to be constructed via an one-step protocol that efficiently overcomes the time-consuming multi-step processes used in existed strategies for the preparation of Fe2O3/TiO2 photocatalysts, providing a new insight into the practical application of TiO2/Fe2O3 visible light photocatalyst.

Correction: 3D Au-decorated Bi2MoO6 nanosheet/TiO2 nanotube array heterostructure with enhanced UV and visible-light photocatalytic activity

Correction for ‘3D Au-decorated Bi2MoO6 nanosheet/TiO2 nanotube array heterostructure with enhanced UV and visible-light photocatalytic activity’ by Jingsheng Cai et al., J. Mater. Chem. A, 2017, DOI: 10.1039/c7ta02077e.

3D Au-decorated BiMoO6 nanosheet/TiO2 nanotube array heterostructure with enhanced UV and visible-light photocatalytic activity

To develop an efficient visible-light-driven photocatalyst electrode for environmental remediation, a novel ternary nanocomposite of an Au-decorated Bi2MoO6 nanosheet/TiO2 nanotube array (NTA) heterojunction was successfully fabricated for the first time via a facile solvothermal method combined with mussel-inspired functional modification of electrochemical polymerization of dopamine.

Chemical Assembly of Titania P25 on MoO3 Nanobelts with Enhanced UV and Visible Photocatalytic Activities

Chemical Assembly of Titania P25 on MoO₃ Nanobelts with Enhanced UV and Visible Photocatalytic Activities

High UV-photocatalytic activity of ZnO and Ag/ZnO synthesized by a facile method

ZnO nanoparticles have been successfully synthesized by a facile precipitation procedure by mixing aqueous solutions of Zn(II) acetate and dissolved Na2CO3 at pH ca. 7.0 without template addition. We have investigated the effect of annealing temperature in the final surface and structural properties. Photocatalytic studies were performed using two selected substrates, Methyl Orange and Phenol, both as single model substrates and in mixtures of them.It has been stated that calcination treatments lead to a significant improvement in the photocatalytic properties of the studied samples, even better than TiO2(P25). As expected, the addition of Ag+ during the photocatalytic degradation of MO increases the reaction rate of the degradation of MO, giving a resultant Ag/ZnO photocatalyst which, after recovery, can be reused at least 18 times for the MO degradation tests, being even more photoactive than ZnO.

Bifunctional bridging linker-assisted synthesis and characterization of TiO2/Au nanocomposites

Using a simple organic bifunctional bridging linker, titanium dioxide (TiO2) nanoparticles were coupled with the Au nanoparticles to form TiO2/Au nanocomposites with a variety of Au loadings. This organic bifunctional linker, meso-2,3-dimercaptosuccinic acid, contains two types of functional groups: (i) the carboxyl group, which enables binding to the TiO2, and (ii) the thiol group, which enables binding to the Au. In addition, the organic bifunctional linker acts as a stabilizing agent to prevent the agglomeration and growth of the Au particles, resulting in the formation of highly dispersed Au nanoparticles. To form the TiO2/Au nanocomposites in a simple way, we deliberately applied a synthetic method that simultaneously ensures: (i) the capping of the Au nanoparticles and (ii) the binding of different amounts of Au to the TiO2. The TiO2/Au nanocomposites formed with this method show enhanced UV and Vis photocatalytic activities when compared to the pure TiO2 nanopowders.