Efficient Nanophotocatalysts Research Articles

TiO2/ZnWO3 with improved photocatalytic performance in the preparation of chromeno[4,3-b]chromenes, as cardiovascular drugs

Chromeno[4,3-b]chromenes have shown potential as effective drugs against cardiovascular diseases, primarily due to their diverse biological activities, including anti-inflammatory and antioxidant properties. This study was conducted on a new heterojunction nanocomposite TiO2/ZnWO3 consisting of titanium dioxide (TiO2) and zinc tungstate (ZnWO3) with enhanced photocatalytic capability. TiO2/ZnWO3 nanophotocatalyst is characterized by FT-IR, XRD, DRS, SEM, and EDX and performed as an efficient nanophotocatalyst in the synthesis of chromeno[4,3-b]chromene derivatives. The research focused on the intricate interplay of the components, aiming to optimize the catalytic reactions under green-light irradiation. Through this investigation, insights were gained into the mechanistic pathways and the potential for improved yields in the formation of the desired chromene. TiO2 has the ability to absorb light and produce electrons and holes when exposed to the direct light; but to increase its photocatalytic activity, an additional component ZnWO3 is combined. Effect of photocatalyst amount, reaction time, temperature, and solvent as well as reusability of the nanocomposite are investigated. The research focused on the intricate interplay of the components, aiming to optimize the catalytic reactions under green-light irradiation. Through this investigation, insights were gained into the mechanistic pathways and the potential for improved yields in the formation of the desired chromene. TiO2 has the ability to absorb light and produce electrons and holes when exposed to the direct light; but to increase its photocatalytic activity, an additional component ZnWO3 is combined. Effect of photocatalyst amount, reaction time, temperature, and solvent as well as reusability of the nanocomposite are investigated.

Green-route synthesis and ab-initio studies of a highly efficient nano photocatalyst:Ce/zinc-oxide nanopetals

In the present work, Zinc-oxide nanostructures and Ce/Zinc-oxide nanopetals were synthesized by a new environmentally friendly green synthesis method using the Withania coagulans plant. Cerium nitrate Ce(NO3)3 and zinc nitrate Zn(NO3)2 were used as precursors. The prepared nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet spectroscopy (UV–vis). Crystal planes (100), (002), (101), (102), (110), (103), (200), (112) and (201) at 2θ 31.75°, 34.35°, 36.2°, 47.55°, 56.6°, 62.75°, 66.3°, 67.9°, and 69.09° respectively confirmed the hexagonal wurtzite crystal structure of Zinc-oxide. Angular shifts for Ce1% doped Zinc-oxide and Ce3% doped Zinc-oxide nanopetal nanostructures were observed in the (100) and (101) planes of the crystal. More specifically, using Scherrer's equation, the crystallite sizes of Zinc-oxide, Ce1% doped Zinc-oxide nanopetals, Ce3% doped Zinc-oxide nanopetals, and Ce5% doped Zinc-oxide nanopetals were 16.48 ± 02 nm, 17.8 ± 2 nm, 18.8 ± 2 nm, and 18.87 ± 2 nm, respectively. The pure Zinc-oxide grain had the appearance of a nanoflower. On the other hand, the nanopetal structure of Ce5% doped Zinc-oxide nanopetals had oval-shaped nanopetal morphology. The absorption peaks were observed at 373, 376.4, 377, and 378 nm for Zinc-oxide, Ce1% doped Zinc-oxide nanopetals, Ce3% doped Zinc-oxide nanopetals, and Ce5% doped Zinc-oxide nanopetals, respectively, which results in a progressive redshift. The gap energies of Zinc-oxide, Ce1% doped Zinc-oxide nanopetals, Ce3% doped Zinc-oxide nanopetals, and Ce5% doped Zinc-oxide nanopetals were 2.796, 2.645, 2.534, and 2.448 eV, respectively. Photodegradation under visible light (>400 nm) indicates the high efficiency of the photocatalyst based on Ce5% doped Zinc-oxide nanopetals. DFT calculations, structural changes, charge analysis, and electronic band structures were carried out to confirm the experiment.

Rational engineering and fabrication of efficient nanophotocatalysts based on ZnO-SrO-CdS for pharmaceutical pollutants based wastewater degradation

Cleaner production processes in conjunction with sustainability is the main requirement for clean and cost-effective industrial process. Moreover, the rapid growth of the world population in conjunction with limited sources of drinking water anticipated water crisis in many countries. Herein, indirect Z-scheme ZnO-3%SrO-2CdS photocatalyst was fabricated for the first time via thermal treatment and well identified by XRD, FT-IR, SEM, EDX and, XPS, meanwhile, the optical properties were evaluated using DRS, PL, and EPR analyses. The photocatalytic activity of noble metal free ZnO-3%SrO-2CdS was investigated in the photodegradation of six antibiotics, namely tetracycline, doxycycline, ofloxacin, amoxicillin, cephalexin, and sulfamethoxazole. Furthermore, kinetic study, pH, initial concentration, dosage, mass ratio, photoreactor type and different water source parameters have been investigated. Results demonstrated a high removal efficiency of tetracycline by ZnO-3%SrO-2CdS of 98.8% within 120 min at pH 7 and dosage 10 mg. This high efficiency could be attributed to SrO channels that facilitate charge migration process and conserve electrons/holes with high redox power for reactive oxygen species production. Besides, the hydroponics study to examine the phytotoxicity of treated tetracycline solution reflected the effectiveness of the treating process since T. foenum-graecum seeds were germinated successfully in the treated tetracycline solution.

Enhanced Photocatalytic Degradation of the Antidepressant Sertraline in Aqueous Solutions by Zinc Oxide Nanoparticles

Antidepressants are one of the main pollutants in the aquatic environment. They are being widely studied due to their widespread use, possible health effects, and partial removal from wastewater treatment plants by conventional methods. Photocatalysis is an effective and ecologically beneficial method in wastewater treatment. In the present study, the photocatalytic degradation of sertraline hydrochloride (SERT) in water using nano-sized zinc oxide (ZnO-NPs) was investigated. The ZnO-NPs were synthesized from zinc gluconate as a precursor by the sol–gel method. The crystal structure, morphology, surface charge, and textural properties were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analyses, transmission electron microscopy, Fourier-transform infrared spectroscopy, zeta potential, and N2 adsorption–desorption measurements. The removal of SERT in water was explored by different processes: H2O2/UV, ZnO-NPs/H2O2/UV, and ZnO-NPs/UV. Our results indicate that the combination of both UV illumination and the ZnO-NP as a catalyst was necessary for the efficient degradation of the drug. Nearly complete removal of SERT (98.7%) was achieved in 30 min with the ZnO-NPs/UV process at room temperature. The photodegradation of SERT follows first-order kinetics with a rate constant of 0.0678 min−1. The results reveal that SERT degradation with ZnO-NPs/UV is pH-dependent, as the maximum drug removal was achieved at pH 11. Initial drug concentration, catalyst dose, and hydrogen peroxide concentration were also crucial in the removal of SERT. Our findings indicate that the high specific surface area and porous structure of ZnO-NP enhance its photocatalytic performance toward photodegradation of SERT, i.e., ZnO-NP is an efficient nanophotocatalyst for the degradation of SERT under UV irradiation.

Fabrication of ruthenium doped Ag@TiO2 core-shell nanophotocatalyst for the efficient reduction of nitrophenols

In the present study, a novel Ag@Ru/TiO2 core–shell nanophotocatalyst with silver metal cores and ruthenium-doped TiO2 semiconductor shells has been fabricated via an impregnation method and was characterized by XRD, Raman spectroscopy, XPS, UV–vis DRS, STEM, EDX, photoluminescence (PL) spectroscopy, FTIR, and BET analysis. In Ag@Ru/TiO2, the Ag NPs core serves as electron traps to prevent the electron-hole pairs recombination, and Ru doping significantly increases the absorption of visible light of the TiO2. The photocatalytic efficiency of Ag@Ru/TiO2 was assessed by the reduction of 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP), and 2,4,6-trinitrophenol (2,4,6-TNP) in presence of visible light. Ag@Ru/TiO2 demonstrated superior photocatalytic performance and attained 100% photocatalytic reduction of 4-NP in 2 min, 2,4-DNP in 3 min, and 2,4,6-TNP in 4 min to their corresponding aminophenols, which was almost 58 and 2.35 times higher than TiO2 and Ag@TiO2. Different experimental parameters including the NaH4 concentration, and the catalyst quantity were also explored. The order of reduction rate constant has been found to be: 4-NP (2.33 min−1) > 2,4-DNP (1.99 min−1) > 2,4,6-TNP (1.4 min−1). Reusability studies revealed the high stability and excellent photocatalytic efficiency of Ag@Ru/TiO2. This novel and highly efficient nanophotocatalyst is a good material for photoreduction of aromatic nitro compounds.

Visible active narrow/narrow band gap CuO/Cu2SnS3 nanoheterostructures as efficient nanophotocatalysts.

Binary metal oxide/ternary metal sulphide based nanoheterostructures, such as CuO/Cu2SnS3, were prepared via a modified hydrothermal route. The prepared nanoheterostructures were characterized using scanning electron microscopy, x-ray powder diffractometer, XPS, ultraviolet-visible spectroscopy, isoelectric point, and Brunauer-Emmett-Teller techniques. The XPS results revealed the successful incorporation of Cu+/Cu2+ with different ratios. The prepared heterostructures were tested as solar active photocatalysts for Methylene Blue (MB) photodegradation. The CuO/Cu2SnS3 (20% Cu2SnS3/80% CuO) photocatalytic results exhibited a high photodegradation efficiency (90%) after 60min. In addition, the photonic efficiency values (ζ) were calculated to be 15.9%, 44%, and 61.4% for CuO, Cu2SnS3, and CuO/Cu2SnS3 nanoheterostructures, respectively. In addition, the reactive oxidative species were detected by the trapping experiments to get a clear insight about the photocatalytic reactivity factors. Total organic carbon (TOC) was conducted to confirm the safe photodegradation of MB dye without the formation of colorless hazardous (95.5% TOC removal). Based on the electronic band structure, the mechanism of photodegradation was investigated. The currently investigated heterostructure system is narrow/narrow bandgap, which fulfills the two contradictory conditions in terms of high solar photocatalytic activity and overcomes the rapid recombination process.

Aluminium Doped Cerium Oxide as an Efficient Nanophotocatalyst for the Elimination of Rhodamine B Dye Present in Water

The photodegradation efficiency of rhodamine B (RhB) dye present in water using aluminium-doped CeO2 (Ce1-xAlxO2-δ; x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) nanoparticles was studied in this work. The synthesis of nanoparticles was done by simple wet chemical precipitation route. The photochemical characteristics of Al doped CeO2 was studied by UV-visible (UV) and photoluminescence (PL) techniques. The photocatalytic removal of RhB dye was studied using the above nanomaterials as photocatalysts and the degradation efficiency was optimized by varying the pH and the concentration of dye solution under UV light. Among the samples studied, 0.02 g of sample with the composition of Ce0.50Al0.50O2-δ exhibited a higher photocatalytic degradation efficiency of 70.94% against RhB dye having concentration of 0.05 g/L at the pH of 11 under UV irradiation for 60 min at room temperature.

Origanum vulgare manganese ferrite nanocomposite: An advanced multifunctional hybrid material for dye remediation

The purpose of the study was to fabricate sustainable and cost-effective material for the thorough cleansing of polluted water. In this context, an economical, phytogenic and multifunctional Origanum vulgare plant-based nanocomposite material, MnFe2O4/OV, was prepared via one-pot synthetic technique. The synthesized nanocomposite with a band gap of 2.02 eV behaved as an efficient nano-photocatalyst for the degradation of both cationic (crystal violet) and anionic (congo red) dyes under direct sunlight irradiation. The material also inhibited the growth of E. coli and S. aureus bacteria and simultaneously adsorbed both cationic and anionic dyes from water through adsorption. A variety of techniques have been used to characterize the nanocomposite, including X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). Additionally, the kinetics of photodegradation of the aforementioned organic dyes has also been investigated. The MnFe2O4/OV exhibited excellent photocatalytic performance, leading to 43% and 72% degradation within 3 h at rate constants of 2.0 × 10−3 min−1 and 6.0 × 10−3 min−1 for crystal violet and congo red, respectively. The crystal violet and congo red were used to testify to the composite's potential for adsorption under the influence of several process variables, including initial solution pH, contact time, temperature, initial dye concentration, and amount of MnFe2O4/OV. The Langmuir maximum adsorption capacity Qmax as in the range 14.06–14.59 mgg−1 for crystal violet and 34.45–23.93 mgg−1 for congo red at pH 7 within 90 min contact time in the temperature range of 30–50 °C. The phenomenon of adsorption was found feasible and endothermic at all the investigated temperatures. Also, E. coli and S. Aureus bacteria have shown growth suppression activity when exposed to MnFe2O4/OV.As a result, the synthesized nanocomposite, MnFe2O4/OV, proved to be an antimicrobial, multifunctional novel nanocomposite, which is in high demand, and could serve as an affordable, and sustainable material for comprehensive water filtration.

Biosynthesized CuO as a Green and Efficient Nanophotocatalyst in the Solvent-Free Synthesis of Some Chromeno[4, 3-b]Chromenes. Studying anti- Gastric Cancer Activity

Gastric cancer is a foremost one among many regular carcinoma cases globally and most of the enhanced treatments could not significantly decrease the mortality range of this cancer. The current work is planned to develop a new rote for the synthesis of a nanophotocatalyst and substituted chromenones that are effective drugs against gastric cancer. Thus, CuO as a new heterogeneous green nanophotocatalyst is biosynthesized from Cressa leaf extract and the prepared nanophotocatalyst is applied in the synthesis of chromenones under air by the mediation of a green color LED in a solventless condition. In addition, in order to obtain the optimum synthesis conditions for the photocatalytic process, a Central Composite Design (CCD) is also applied, which predicted the optimal temperature of 33.8 °C, reaction time of 69 min, and catalyst amount of 5.9 mg. Fortunately, these findings fitted well with the experimentally attained optimal conditions. Furthermore, reusability and stability tests guarantee acceptable reproducibility of the protocol. It is found that the photocatalytic reaction mainly occurs through a radical-based mechanism involving •O2 -, OH•, and h+. The significant features of this study invole the photocatalytic nature of the protocol with the irradiation of a commercially cheap LED, simple and inexpensive photocatalyst, low temperature, high yield, solvent-free, facile work-up, wide scope, and proper atom economy. At the final part of this report, the in-vitro cellular cytotoxicity of CuO nanoparticles and 3-nitro-substituted chromene is examined on KATO-III human gastric cell line with MTT assay. The reduction in cell viability confirmed cytotoxicity of these materials against the performed cancer cell line.

Biosynthesis of silver nanoparticles by Cyperus pangorei and its potential in structural, optical and catalytic dye degradation

The development of effective photocatalyst through green and eco-friendly approach has become a great concern for the light-induced degradation of organic pollutant dyes. This article reports a simple, cost-effective, and a benign environmental biosynthesis of Ag nanoparticles (NPs) using Cyperus pangorei, a plant extract with three different concentrations of AgNO3 in aqueous media. The synthesized silver nanoparticles were performed ultraviolet–visible spectroscopy (UV–Vis), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), photoluminescence (PL), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The surface plasmon resonance (SPR) peak at 437 nm in UV–Vis spectroscopy confirmed the reduction of Ag+ ions into Ag nanoparticles. FTIR spectra revealed that plant extract could reduce/stabilize/capping to form Ag nanoparticles, and strong PL emission spectra tend to exhibit higher photocatalytic activity. The structural information is derived from XRD and TEM, which can exhibit the FCC structure and polydisperse with the spherical shape. EDX addresses the presence of Ag constitute. XPS confirmed the Ag nanoparticles in characteristic silver peaks, plant extract derivatives, and their oxidative states’ binding energy. The photocatalytic activity of Ag nanoparticles against dye Rhodamine B (Rh-B) under ultraviolet irradiation with periodic interval and pseudo-first-order kinetics were also studied. The obtained results show that the synthesized Ag nanoparticles can degrade dye (Rh-B) up to 86% within 2 h of irradiation time. Furthermore, the present study suggests that the biosynthesized Ag nanoparticles could be potential photocatalysts against various industrial dyes as well as C. pangorei; plant extract can be usto modify and develop more efficient nano-photocatalyst for other application.

ZnO nanorods/sulfophenylporphyrin nanocomposites facilely embedded with special copper for improved photocatalytic hydrogen evolution

Novel and efficient copper-implanted ZnO nanorod/5,10,15,20-tetrakis(4-sulfophenyl)porphyrin composite photocatalysts (ZnO NR-Cu-TSPP) were facilely fabricated. The assembly mechanism was investigated and showed that the TSPP was anchored onto the ZnO NR-Cu through dual interaction, hydrogen bond and coordination interaction. Importantly, the ZnO NR-Cu-TSPP nanocomposite exhibited high photocatalytic activity on account of extended light absorption and greatly enhanced charge separation at the heterointerface. The photocatalytic mechanism revealed that, with the small sized Cu as interfacial linker, not only the interaction between ZnO NR and TSPP was strengthened, but also more active sites for photocatalytic H2 evolution were produced. Furthermore, by the introduction of a certain amount of TSPP, the photocatalytic activity of the nanocomposite can be significantly enhanced, which is higher than those controlled porphyrins with other substituents. Moreover, the composite showed a superior stability according to the cycling tests. This work provides a new idea for fabricating high efficient nano photocatalysts for hydrogen production.

Photocatalytic degradation of methyl orange dye under UV irradiation in the presence of synthesized PVP capped pure and gadolinium doped ZnO nanoparticles

The present study focuses on the development of efficient nanophotocatalysts (pure and Gadolinium doped Zinc oxide) for the degradation of methyl orange dye in polluted water. Chemical co-precipitation technique was employed for the synthesis of target compounds using zinc acetate and gadolinium nitrate as metal precursors. The synthesized nanoparticles were characterized by various spectroscopic techniques namely X-ray diffraction, Fourier Transform infra red spectroscopy, Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The synthesized pure and Gadolinium doped Zinc oxide nanoparticles were used as photocatalysts for the degradation of methyl orange dye under ultra-violet light irradiation. Doping of ZnO nanoparticles with Gadolinium has greatly increased its catalytic efficiency.

LED-activated immobilized Fe-Ce-N tri-doped TiO2 nanocatalyst on glass bed for photocatalytic degradation organic dye from aqueous solutions

Abstract The aim of this study was to evaluate the photocatalytic process efficiency of titanium dioxide (TiO2) nanoparticles doped with nitrogen (N), iron (Fe), and cerium (Ce) stabilized on a glass bed for the removal of organic dye from an aqueous medium in the presence of visible light. Synthesis of nanocatalysts was performed by sol–gel method. SEM, XRD, FTIR, DLS, AFM, and Zeta-potential analyses were used to identify and describe the properties of synthesized nanocatalysts. The effect of operating parameters, including pH, initial dye concentration, light intensity, contact time, and nanoparticle type on the removal efficiency was explored in a series of photocatalytic experiments. The results showed that doping TiO2 with N, Fe, and Ce resulted nanoparticles with different sizes and increased the photocatalytic activity as well as the surface charge of TiO2 nanoparticles. The Fe-N-Ce-TiO2 was found as the most efficient nanophotocatalyst among synthesized nanoparticles under both visible light and darkness. The experimental results showed that the removal of dyes in acidic pH was higher than that in neutral and alkaline pH. The complete removal of Direct Blue 15 dye under LED radiation could be achieved in optimal conditions of pH = 5.7, current intensity of 0.68 A (1000 lux), initial concentration of 25 mg/L, nanoparticle dose of 10 mg/cm 2 and 60 min of contact time. Findings of this study clearly demonstrated that the nanocatalytic process of Fe-Ce-N tri-doped TiO2 was highly effective in oxidizing dye pollutants in the visible light range, and the it could be very suitable for areas rich in sunlight for the oxidation of dye contaminants.

Foliar-mediated Ag:ZnO nanophotocatalysts: green synthesis, characterization, pollutants degradation, and in vitro biocidal activity

AbstractA green, biomimetic, and one-pot synthesis of silver-doped zinc oxide (ZnO:Ag) nanoparticles via hydrothermal route utilizingPrunus cerasiferaleaf extract has been reported for the first time. Synthetic route involved optimization for leaf extract. Doped nanoparticles were characterized for crystalline, optical, compositional, and morphological makeup via X-ray diffraction (XRD), ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy. Direct energy bandgap was calculated through Tauc plot. The incorporation of Ag+into Zn2+sites within ZnO crystal was obtained using leaf extract as a reducing agent. Ag inculcated positional modifications in ZnO structure confirmed via XRD-shifted peaks. Ag:ZnO nanoparticles were found to be an efficient nanophotocatalyst against bromocresol green and bromophenol blue (R2=0.83 and 0.95, respectively) in direct solar irradiance. Degradation efficiencies up to 86% and 95% in less than 15min were achieved. Furthermore, the synthesized doped nanoparticles expressed highly active to active zones of inhibition against nine microbes of pathogenic nature toward human and crops. Doped nanoparticles inhibitory activity was found to exceed standard antibiotic drugs ampicillin and amphotericin B in a standard Kirby-Bauer disc diffusion assay. Creditable photocatalytic and antimicrobial activities of synthesized doped nanoparticles signify their prospects in commercialization into nanophotocatalyst and bactericidal/fungicidal agent at industrial scale.

Nano-TiO2-P25-SO3H as a new and robust photo-catalyst: The acceleration effect of selective oxidation of aromatic alcohols to aldehydes under blue LED irradiation

Nano photo-catalyst ‘TiO2-P25-SO3H’ has been synthesized for the first time as a covalently grafted solid acid and used for the oxidation of different aromatic alcohols to the corresponding carbonyl compounds under visible light irradiation (blue LED, λ > 420 nm). This new and efficient nano photo-catalyst has selectively converted primary aromatic alcohols to the corresponding aldehydes in the presence of nitrobenzene as available industrial oxidant with excellent yields. This new powerful nano photo-catalyst provides a green and mild approach for photo-oxidation of alcohols.

Zeolitic imidazolate framework-7: Novel ammonia atmosphere-assisted synthesis, thermal and chemical durability, phase reversibility and potential as highly efficient nanophotocatalyst

This is the first representation of novel sodalite zeolitic imidazolate framework-7 (ZIF-7) which has been made in ethanolic solution at room temperature via an ammonia atmosphere. High thermal stability up to 400 °C is representative of great persistence which has been proved by XRD and TG data. Chemical durability of the as-made ZIF-7 especially at boiled DMF exhibited by XRD patterns can present it as an interesting material without structural alteration after treatment in such harsh condition. Reversible phase transformation of ZIF-7 was totally checked by immersing in ethanol and DMF indicated that the framework can maintain its structural flexibility under heat and solvent treatment. Moreover, the “gate-opening” phenomenon performed by CO2 adsorption–desorption reveals structural breathing effect of ZIF-7 framework that makes it as potential material in CO2 adsorption/separation. In the end, the sacrificial metal-doped (Mn2+, Ni2+, Cu2+, Cd2+ and Ag+) ZIF-7 precursors were applied for preparation of their corresponded metal-doped ZnO as the heterogeneous catalyst to degrade Rhodamine-B (RhB) dye in water under UV-irradiation (up to 99% within 90 min by 0.5% Ag-ZnO (S15)). The recyclability experiment after 5 runs for the optimized catalyst demonstrated that the metal-doped ZnO can be operated consecutively without remarkable decreasing in its activity. These observations exhibit the excellent and beneficial properties of metal-doped ZnO can be as heterogeneous photocatalyst for the removal of organic contaminants in water.

Evaluation of an ultrasonic-assisted mechanical stirring technique for the synthesis of an efficient nano-photocatalyst

Photocatalysis has emerged as an efficient technique for the removal of contaminants from wastewater. In this work, conventional mechanical stirring was compared with ultrasonic-assisted mechanical stirring for the synthesis of an efficient nano-photocatalyst (Al2O3)1−x(ZnO) x Fe2O3. The photocatalytic activity of (Al2O3)1−x(ZnO) x Fe2O3 synthesized by both techniques was compared for the degradation of methyl orange dye (MO) under visible light irradiation. Important process parameters were optimized during the study and the results indicated that the photocatalyst synthesized by ultrasonic-assisted mechanical stirring was more efficient with 93.5% photocatalytic activity for the degradation of MO dye than that synthesized by using a simple mechanical stirring technique which resulted in photocatalytic activity of 83.7%. (Al2O3)0.75(ZnO)0.25Fe2O3 nano-photocatalysts synthesized by both methods were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, dynamic light scattering and BET surface area analysis. The results indicated that the particle size of the (Al2O3)0.75(ZnO)0.25Fe2O3 catalyst synthesized by ultrasonic-assisted mechanical stirring was significantly smaller and the surface area larger than the particles prepared by the conventional mechanical stirring method. A cyclic study evaluated the reusability of the photocatalyst and found minimal loss in degradation efficiency after seven cycles. The optimal photocatalyst produced in this study can degrade higher concentrations of MO with a higher efficiency using a lower or similar catalyst dose compared to other materials published in the literature.

Synthesis of ZnO/Bi-doped porous LaFeO3 nanocomposites as highly efficient nano-photocatalysts dependent on the enhanced utilization of visible-light-excited electrons

ZnO coupled Bi-doped porous LaFeO3 nanocomposites have successfully been fabricated via a wet-chemical method. It is confirmed that Bi3+ enters into the crystal lattice of PLFO and substitute La3+, while the ZnO with diameter of ∼15 nm is coupled to the Bi-doped PLFO. It is shown that the amount-optimized 5Zn/7Bi-PLFO nanocomposite exhibits greatly improved visible-light activities for 2,4-dichlorophenol (2,4-DCP) degradation and CO2 conversion, compared to the unmodified PLFO with rather high photoactivity due to its large specific surface area. Based on the measurements of valence band XPS spectra, steady-state surface photovoltage spectra, transient-state surface photovoltage responses, photoelectrochemical I–V curves, fluorescence spectra related to produced OH amount and photocurrent action spectra, it is clearly demonstrated that the significantly improved visible-light activities are attributed to the enhanced utilization of visible-light-excited high-level-energy electrons (HLEEs) by coupling with nanocrystalline ZnO to introduce a new energy platform for accepting electrons and to the extended visible-light absorption by doping Bi3+ to create surface states. Interestingly, it is proved that under UV–vis irradiation, the amount-optimized nanocomposite exhibit much higher photoactivity for 2,4-DCP degradation compared to the commercially available P25 TiO2. Moreover, it is confirmed by means of radical trapping experiments that the dominant radicals to decompose 2,4-DCP on PLFO could be modulated by doping Bi3+ and coupling ZnO. Furthermore, the possible decomposition pathways, respectively related to the OH and O2−, of 2,4-DCP over the amount-optimized Bi-doped PLFO and ZnO coupled Bi-doped PLFO samples are proposed by means of the liquid chromatography tandem mass spectrometry analysis of the intermediates, especially with the used isotopic D2O.

Improving photoelectrochemical reduction of Cr(VI) ions by building α-Fe2O3/TiO2 electrode.

Photoelectrochemical process is an environmentally friendly technology and has a wide application in the control of environmental pollutants. Efficient nanophotocatalysts responsive to visible light are still highly attractive. In this work, α-Fe2O3/TiO2 were grown on fluorine doped tin oxide (FTO) substrates by hydrothermal method for photoelectrochemical reduction of Cr(VI). Compared with the separate α-Fe2O3 and TiO2 electrodes, the composite α-Fe2O3/TiO2 electrodes show higher photocurrent density. Under visible light irradiation, 100% removal efficiency of Cr(VI) was obtained after 40min treatment. The composite α-Fe2O3/TiO2 electrodes showed an enhanced absorbance in visible light region and had good stability to photoelectrochemical reduction of Cr(VI). The role of hole scavengers (citric acid and oxalic acid) and pH values was systematically investigated. This novel intensification approach provides new insight on the application of photoelectrochemical reduction in environmental remediation.

Synthesis of nano SnO2-coupled mesoporous molecular sieve titanium phosphate as a recyclable photocatalyst for efficient decomposition of 2,4-dichlorophenol

It is essential to develop a cheap, recyclable, and efficient photocatalyst to help degrade pollutants contaminating the environment. Herein, mesoporous molecular sieve titanium phosphate (MMS-TiP) was used as an efficient nano-photocatalyst to degrade 2,4-dichlorophenol (2,4-DCP) and to oxidize CO. The catalyst was successfully synthesized by a simple and convenient hydrothermal method in the presence of a tri-block copolymer surfactant. Exceptional photoactivity of the optimized MMS-TiP mainly depends on its porous structure, with a large surface area by means of O2 temperature-programmed desorption curves and fluorescence spectra related to the amounts of produced hydroxyl radical. Interestingly, the photocatalytic activity of the prepared MMS-TiP could be greatly improved by coupling with nanocrystalline SnO2. This is likely due to the increase in the lifetime and separation of photogenerated charges by transferring electrons to SnO2 and was observed by steady-state surface photovoltage spectra and time-resolved surface photovoltage responses. The SnO2-coupled MMS-TiP exhibits better photocatalytic performance for 2,4-DCP degradation and better self-settlement than those of the commercial catalyst P25 TiO2. Moreover, it was confirmed by radical-trapping experiments that ·O2–is the main activated species for the photocatalytic degradation of 2,4-DCP, and is photogenerated by electron transfer from MMS-TiP to SnO2. Furthermore, the main intermediates in the degradation of 2,4-DCP, like parachlorophenol superoxide and 1,2-benzenediol superoxide radicals, were detected, and a possible decomposition pathway related to ·O2–attack is proposed. These experimental results provide new strategies for developing a recyclable molecular sievebased nano-photocatalyst with high photocatalytic activity for environmental remediation.