Cow urine-based green synthesis of sunlight-responsive ZrO2-Bi2O3 and its application in photocatalysis of 2,4-Dichlorophenoxyactetic acid in aqueous solution – Kinetics, mechanisms and sustainability analysis

WO3 is a widely studied material for electrochromic and photocatalytic applications. In the present study, WO3 nanoparticles with a controlled structure (monoclinic or hexagonal) were obtained by controlled thermal decomposition of hexagonal ammonium tungsten bronze in air at 500 °C and 600 °C, respectively. The formation, morphology, structure and composition of the as-prepared nanoparticles were studied by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX). The photocatalytic activity of the monoclinic and hexagonal WO3 nanoparticles was studied by decomposing methyl orange in aqueous solution under UV light irradiation. In order to study the electrochromic properties of the WO3 nanoparticles, as well to introduce them for self-cleaning photocatalytic surface applications, thin films were prepared from the WO3 particles together with a conductive polymer. For this, PEDOT:PSS was used, which gives excellent opportunities for obtaining transparent and conductive thin films, suitable for both electrochromic and photocatalytic applications. By spin-coating, transparent PEDOT:PSS/WO3 composite thin films were prepared, on which cyclic voltammetry measurements were performed, and the coloring and bleaching states were studied. Our initial results for the PEDOT:PSS/WO3 composite thin films are promising, suggesting that such composites, after further development, might be successfully used in electrochromic devices and photocatalysis.

Low-temperature atomic layer deposition of TiO2 activated by laser annealing: Applications in photocatalysis

Enormous Promotion of Photocatalytic Activity through the Use of Near-Single Layer Covalent Organic Frameworks

This paper reports the results of an investigation into enhancement of the electrochemical oxidation of p-aminophenol (4-AP) in an aqueous solution with a boron-doped diamond (BDD) electrode, assisted by photocatalysis using a zeolite-supported TiO2 (Z-TiO2) catalyst. The BDD electrode was characterised in 0.1 M Na2SO4-supporting electrolyte and the presence of 4-AP by open-circuit potential behaviour (OCP) and cyclic voltammetry (CV). The electrode behaviour was investigated in the dark and following UV irradiation and in the absence/presence of the Z-TiO2 catalyst. The electro-oxidation process was carried out using chronoamperometry (CA) and multiple-pulsed amperometry (MPA) at the selected potential under potentiostatic conditions. The electrochemical degradation process of 4-AP on the BDD electrode was improved by the application of a pulsed potential, which allowed both in-situ electrochemical cleaning of the electrode and indirect oxidation of 4-AP by oxygen evolution. The application of photocatalysis using Z-TiO2 in the 4-AP electrochemical degradation exhibited an enhanced effect when the anodic potential was set at +1.25 V vs. Ag/AgCl in the water stability region, close to the oxygen evolution potential.

Porous TiO2 structures have been of great interest in various photocatalytic applications over the past decade. However, the synthetic methods reported so far in the literature are complex and time consuming. This study presents a simple one-pot fabrication method of hollow porous TiO2 nanospheres using a sol-gel process involving CO2 generation in aqueous solution. The CO2 nanobubbles produced in the reaction act as a template for the crystal growth of TiO2 resulting in highly porous hollow nanospheres. The unique nanocrystal structure with a hollow nanosphere centre surrounded by an outer shell of prickle-like porous nanocrystals was observed. The prepared hollow porous TiO2 nanospheres exhibited excellent adsorption properties as demonstrated by the adsorption measurements and dynamic extraction of methylene blue in aqueous solution. Furthermore, the hollow porous TiO2 nanospheres hydrothermally treated at 180 °C exhibit 3.2 times higher photocatalytic performance in the decomposition of methylene blue than the commercial P25 TiO2. The idea of this work provides a new direction for facile green synthesis routes of various metal oxides with cavities, channels or crevices for various technological applications.

Nanotechnology is a fast-expanding area with a wide range of applications in science, engineering, health, pharmacy, and other fields. Nanoparticles (NPs) are frequently prepared via a variety of physical and chemical processes. Simpler, sustainable, and cost-effective green synthesis technologies have recently been developed. The synthesis of titanium dioxide nanoparticles (TiO2 NPs) in a green/sustainable manner has gotten a lot of interest in the previous quarter. Bioactive components present in organisms such as plants and bacteria facilitate the bio-reduction and capping processes. The biogenic synthesis of TiO2 NPs, as well as the different synthesis methods and mechanistic perspectives, are discussed in this review. A range of natural reducing agents including proteins, enzymes, phytochemicals, and others, are involved in the synthesis of TiO2 NPs. The physics of antibacterial and photocatalysis applications were also thoroughly discussed. Finally, we provide an overview of current research and future concerns in biologically mediated TiO2 nanostructures-based feasible platforms for industrial applications.

Green synthesis of CuO nanoparticles: A promising material for photocatalysis and electrochemical sensor

BackgroundThe aim of this work was to synthesize copper oxide nanoparticles (CuO NPs) utilizing heartwood aqueous extract of Suaeda maritima (L.) Dumort. The synthesis of CuO NPs using green methodology with small size and high stability paved the way to protect the environment by not involving toxic chemicals and environment-friendly methodology for pharmacological and photocatalytic applications. The aqueous areal parts extract of S. maritima (L.) Dumort was used for synthesis, characterization of CuO NPs was studied, and further its antioxidant, antibacterial, and photocatalytic activity for the removal of methylene blue was studied. ResultsThe synthesized CuO NPs shows characteristic UV-visible absorption maximum at 282 nm. The FT-IR spectra shows peak at 3640 cm−1 attributed to hydrogen bonded O-H group of poly phenols, alcohols, and N-H of amide. Strong peak at 1122 cm−1 corresponds to C-OH stretch in phenols and alcohols. Peaks at 1467 cm−1 and 1585 cm−1 corresponds to C=C in aromatic compounds. Strong peak at 1749 cm−1 represents the C=O in aldehydes or in keto compounds. Several strong bonds identified in the range of 1088 to 1225 cm−1 representing C-O-C stretch vibrations. The synthesized particles were circular in shape with rough surface morphology and dispersed as clusters with size of 37 nm with metallic content of 73.8%. The synthesized CuO NPs were proved as potent antibacterial and antioxidant activities. The photocatalytic for the removal of methylene blue in aqueous solution was studied and results proved that the CuO NPs were effectively remove the dye up to 86.91% within less time of 75 min. Hence, the CuO NPs synthesized are high efficiency with less particle size and can be used as antioxidant, antibacterial agent, and also applicable for the removal of hazardous methylene blue dye from effluents and can contribute indirectly to clean up the environment. ConclusionsThe investigation reports the eco-friendly, cost-effective method for synthesizing copper oxide nanoparticles from S. maritima extract with biomedical applications.

Tunable photoluminescent-functionalized carbon quantum dots CQDs@Ln (TFA)3 (Ln = Eu, Tb; TFA: trifluoroacetylacetone) were designed and synthesized by introducing lanthanide complexes into the modified CQDs surface through the carboxyl group. The as-prepared CQDs@Ln (TFA)3 emit strong blue–green light with the peak at 435 nm and simultaneously show the characteristic emission of Ln3+ under irradiation of 365 nm light in aqueous solution. Moreover, these functionalized CQDs exhibit excellent photoluminescence properties. In addition, a white luminescent solution CQDs@Eu/Tb (TFA)3 was obtained by adjusting the ratio of Eu3+/Tb3+ and the excitation wavelengths. Moreover, CQDs@Tb (TFA)3 can be utilized as a fluorescent probe for the sensitive and selective detection of MnO4− without interference from other ions in aqueous solution. These results provide the meaningful data for the multicomponent assembly and the photoluminescent-functionalized materials based on the modified CQDs and lanthanide, which can be expected to have potential application in photocatalytic or sensors.

We have reported the role of annealing temperature Fe3O4/SnO2 nanocomposites as a photocatalyst for remove methylene blue (MB) dye from aqueous solution. However, how to enhanced the degradation performance of Fe3O4/SnO2 nanocomposites is important to its photocatalytic application. Therefore, in this work Fe3O4/SnO2 nanocomposites was combined with two different types of graphene materials (NGP and grahene) to improve the photocatalytic performance for remove methylene blue (MB) dye. Fe3O4/SnO2/NGP and Fe3O4/SnO2/graphene have been successfully synthesized by co-precipitation method. The influence of two types graphene on Fe3O4/SnO2 nanocomposites properties were systematically investigated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Thermal gravimetric analysis (TGA). Degradation of methylene Blue (MB) in aqueous solution was studied in detail under photocatalytic process. Effect of catalyst dosage (0.1-0.4 g/L) and scavengers on dye degradation were carried out to check the efficiency of photocatalyst. The results indicated Fe3O4/SnO2/graphene displayed higher photocatalytic activity than other catalyst. The reusability tests have also been done to ensure the stability of the used photocatalyst.

Extracts of Pelargonium hortorum: A natural and efficient fluid for fast and eco-friendly biosynthesis of CeO2 nanoparticles for antioxidant and photocatalytic applications

Graphitic carbon nitride nanosheets decorated by multiple functional groups (denoted as CN−KNa) were as a multipurpose material, both in photocatalytic applications and as a photo‐induced indicator. The presented g‐C3N4 is fabricated via a facile alkali‐salt‐assisted calcination method. The structural analysis reveals significant changes in the structure of the host CN−KNa nanosheets associated with the existence of multiple functional groups (for example, hydroxy, carbonyl, and cyano groups). Such modifications lead to enhanced light absorption and charge separation, resulting in an efficient photocatalyst not only for solar‐driven hydrogen production but also for primary amine detection in aqueous solution. Thus, the solar light driven photocatalytic hydrogen evolution yield using the synthesized CN−KNa sample is found to be 50.3 μmol h−1, which is approximately 14 times higher than that of bulk g‐C3N4. More importantly, this functional‐group‐decorated CN−KNa facilitated electron transportation between CN−KNa and amine compounds, causing a colour change in the solution mixture, which has been observed for the first time. This novel observation indicates that CN−KNa can be considered a new class of photo‐induced indicator agent to detect primary amine compounds in aqueous solution.

This work reports a green method to produce efficient photocatalytic nanopowders. Titanium dioxide nanoparticles were easily synthetized by an extract of Thymus vulgaris, and then decorated with commercial silver nanoparticles. A detailed morphological, structural, and chemical characterization was performed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) adsorption–desorption of N2, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), Raman spectroscopy, transmission electron microscopy (TEM), and UV–Vis spectroscopy. The synthetized TiO2 nanoparticles showed a mean size of 10–15 nm, and had the anatase crystallographic phase. The photocatalytic efficiency of the TiO2 nanoparticles was demonstrated by the photo-degradation under UV-light irradiation of different pollutants in aqueous solution (methylene blue, diclofenac, and sodium dodecyl sulfate). TiO2 was coupled to Ag nanoparticles with different percentage in weight (from 0.25 to 3%), to investigate an eventual improvement of its photocatalytic efficiency. The best photocatalytic composite among the tested compositions was the one with the lowest Ag percentage (0.25%). Zebrafish embryo toxicity tests ruled out the toxicity of the synthetized nanoparticles. The present results offer a new, green, and easy method to prepare TiO2/Ag nanoparticles with high photocatalytic efficiency. The proposed materials are therefore promising for applications in photocatalysis, especially for wastewater remediation and reuse.

Importance of carbon (prepared from Azadirachta indica) for photo catalytic applications

Controlled synthesis of nitrogen-doped binary and ternary TiO2 nanostructures with enhanced visible-light catalytic activity