Photocatalytic degradation effect of malachite green and catalytic hydrogenation by UV–illuminated CeO 2 /CdO multilayered nanoplatelet arrays: Investigation of antifungal and antimicrobial activities

Controllable Synthesis of Zn-Doped α-Fe2O3 Nanowires for H2S Sensing

One-dimensional Zn-doped α-Fe₂O₃ nanowires have been controllably synthesized by using the pure pyrite as the source of Fe element through a two-step synthesis route, including the preparation of Fe source solution by a leaching process and the thermal conversion of the precursor solution into α-Fe₂O₃ nanowires by the hydrothermal and calcination process. The microstructure, morphology, and surface composition of the obtained products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was found that the formation process of α-Fe₂O₃ is significantly influenced by the introduction of Zn²⁺. The gas sensing measurements indicated that the sensor based on 1% Zn-doped α-Fe₂O₃ nanowires showed excellent H₂S sensing properties at the optimum operating temperature of 175 °C. Notably, the sensor showed a low H₂S detection limit of 50 ppb with a sensor response of 1.5. Such high-performance sensing would be ascribed to the one-dimensional structure and high specific surface area of the prepared 1% Zn-doped α-Fe₂O₃ nanowires, which can not only provide a large number of surface active sites for the adsorption and reaction of the oxygen and H₂S molecules, but also facilitate the diffusion of the gas molecules towards the entire sensing materials.

Sonophotocatalytic treatment of rhodamine B using visible-light-driven CeO2/Ag2CrO4 composite in a batch mode based on ribbon-like CeO2 nanofibers via electrospinning

CeO₂/Ag₂CrO₄ composite photocatalyst was successfully fabricated using electrospinning and calcination and chemical precipitation method based on CeO₂ ribbon-like fibers and characterized by field-emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS) and Fourier-transform infrared spectroscopy (FT-IR). The as-obtained CeO₂/Ag₂CrO₄ composite used photocatalytic performance in the sonophotodegradation of rhodamine B in aqueous solution under visible-light (LED) irradiation. DRS analysis illustrates that CeO₂/Ag₂CrO₄ composite exhibited enhanced absorption in the visible region-attributed CeO₂ nanofibers_. The effect of four effective parameters including initial concentration of rhodamine B (RhB), photocatalyst dosage, pH, and irradiation time was studied and optimized using central composite design. The kinetic studies confirmed ability of pseudo first-order reaction based on the Langmuir-Hinshelwood model for fitting empirical data, while its rate constant (k_obs), L-H rate constants (k_r), and L-H adsorption constants (K_A) were 0.0449 min^-1, 11.66 mg L^-1 min^-1 and 1.09E-3 mg L^-1, respectively. The enhanced photocatalytic activity could be ascribed to the ultrasound field and formation of a heterojunction system among CeO₂ and Ag₂CrO₄, which lead to a better mass transfer and higher efficiency of charge electron-hole separation, respectively.

Ultrathin CdS shell-sensitized hollow S-doped CeO2 spheres for efficient visible-light photocatalysis

By virtue of the systematic effects of S-doping on CeO₂ and the ultrathin shell structure of CdS, the CeO_2−xS_x@CdS nanocomposite exhibits excellent photocatalytic activity under visible-light illumination for both H₂ evolution (rate up to 1147.2 μmol g⁻¹ h⁻¹) and RhB degradation (efficiency reached 99.8%) as compared to CeO₂, CeO_2−xS_x, and CdS.

In situ growth of copper(ii) phthalocyanine-sensitized electrospun CeO2/Bi2MoO6 nanofibers: a highly efficient photoelectrocatalyst towards degradation of tetracycline

Copper(ii) phthalocyanine-sensitized electrospun CeO₂/Bi₂MoO₆ nanofibers (TNCuPc/CeO₂/Bi₂MoO₆ nanofibers) were fabricated and applied as an efficient novel photocatalyst with enhanced photoelectrocatalytic activity.

Heterogeneous photocatalysis and its potential applications in water and wastewater treatment: a review

There has been a considerable amount of research in the development of sustainable water treatment techniques capable of improving the quality of water. Unavailability of drinkable water is a crucial issue especially in regions where conventional drinking water treatment systems fail to eradicate aquatic pathogens, toxic metal ions and industrial waste. The research and development in this area have given rise to a new class of processes called advanced oxidation processes, particularly in the form of heterogeneous photocatalysis, which converts photon energy into chemical energy. Advances in nanotechnology have improved the ability to develop and specifically tailor the properties of photocatalytic materials used in this area. This paper discusses many of those photocatalytic nanomaterials, both metal-based and metal-free, which have been studied for water and waste water purification and treatment in recent years. It also discusses the design and performance of the recently studied photocatalytic reactors, along with the recent advancements in the visible-light photocatalysis. Additionally, the effects of the fundamental parameters such as temperature, pH, catalyst-loading and reaction time have also been reviewed. Moreover, different techniques that can increase the photocatalytic efficiency as well as recyclability have been systematically presented, followed by a discussion on the photocatalytic treatment of actual wastewater samples and the future challenges associated with it.

Green synthesis of SnO2 quantum dots using Parkia speciosa Hassk pods extract for the evaluation of anti-oxidant and photocatalytic properties

In the present study, microwave heating method was established for the biosynthesis of SnO₂ Quantum dots (QDs) using Parkia speciosa Hassk pods extract. The as-synthesized quantum dots have been characterized by various techniques such as UV, XRD, EDX, TEM, HRTEM, SAED and FTIR spectroscopy. The biosynthesized SnO₂ QDs was employed for the first time as an efficient photocatalyst for the degradation of a food dye, acid yellow 23 dye from aqueous phase under the UV₂₅₄ light. Various parameters, such as the effect of catalyst dose, the initial concentration of acid yellow 23 dye (AY23), pH of the solution and irradiation time on the photodegradation process are also studied for efficient and better use of the synthesized SnO₂ QDs as a catalyst. The biosynthesized SnO₂ QDs exhibited excellent photocatalytic performances with degradation efficiency 98% on the degradation of an aqueous solution of AY23 of concentration 5 mg/L with a catalyst dose of 20 mg under UV₂₅₄ light within 24 min. The synthesized SnO₂ QDs can be reused up to 5 cycles of photodegradation experiment without losing its stability and efficiency. The biosynthesized SnO₂ QDs also shows a fair activity in the scavenging of 2,2-diphenyl-1-picrylhydrazyl free radical with the IC₅₀ value of 312.6 ± 0.025 μg/mL.

Surfactant-assisted synthesis of ceria-titania-rich mesoporous silica materials and their catalytic activity towards photodegradation of organic dyes

Ceria-titania doped highly ordered hexagonal and cubic mesoporous silica composite samples with varying amounts of Ce and Ti have been synthesized using hexadecyltrimethylammonium bromide (CTAB) surfactant as a template under basic conditions in the presence of ammonia. The removal of the template resulted in the formation of mesoporous composites doped with Ce and Ti, which were thoroughly characterized via small-angle X-ray scattering (SAXS), wide-angle X-ray diffraction (WAXRD), N₂ adsorption, scanning and transmission electron microscopy analysis with energy-dispersive spectrometry mapping (SEM-TEM-EDS), inductively coupled plasma atomic emission spectrophotometry (ICP-AES), and ultraviolet-visible diffuse reflectance spectrometry (UV-visible). The electronic states of Ti and Ce species present on the surface of silica were also investigated by X-ray photoelectron spectroscopy (XPS). The catalytic activity of these Ti-modified ceria-silica samples for the photodecomposition of rhodamine B under visible-light irradiation was investigated. The results revealed that a sample with a higher Ti content, as well as equal amounts of Ce and Ti, displayed higher catalytic activity for the photodegradation of the organic dye rhodamine B.

Co-doped TiO2 nanostructures as a strong antibacterial agent and self-cleaning cover: Synthesis, characterization and investigation of photocatalytic activity under UV irradiation

The aim of this work was synthesis and investigation of various properties of Co-doped titanium dioxide nanostructures. However, dopant has no effect on XRD pattern of the host but it can influence on the various characteristics of host such as optical and electrical properties. The results of optical properties showed that absorption energy of TiO₂ decreases in presence of cobalt as dopant. Red-shift in absorption spectrum that may be due to the excitation of 3d electrons of Co ions to the conduction band of TiO₂ can be considered as a strong evidence to confirm the presence of Co as dopant in TiO₂ lattice. Photocatalytic activity of products was examined by degradation of three dyes including: Acid Red 1 (A.R.1.), Reactive Blue 21 (R.A.21.) and Acid Blue 74 (A.B.74.) under UV irradiation and antibacterial activity of this product was tested by inhibition of the growth of three bacteria: Pseudomonas aeruginosa, S. aureus and E. coli. High percent of dye degradation and decreasing the contact angle of surfaces in the presence of this product as a cover confirm that Co-doped TiO₂ can be used as a self-cleaning cover on various surfaces. The antibacterial activity is another property of this product as an antibacterial agent.

Bioreduction potentials of dried root of Zingiber officinale for a simple green synthesis of silver nanoparticles: Antibacterial studies

Green synthesis of silver nanoparticles (Ag NPs) using an extract of dried Zingiber officinale (ginger) root as a reducing and capping agent in the presence of microwave irradiation was herein reported for the first time. The formation of symmetrical spheres is confirmed from the UV-Visible spectrum of Ag NPs. Fourier transform infra-red spectroscopy confirms the formation of the Ag NPs. X-ray diffraction analysis was utilized to calculate the crystallite size of Ag NPs and the value was found to be 10nm. High-resolution transmission electron microscopy and high-resolution scanning electron microscopy were used to investigate the morphology and size of the synthesized samples. The sphere like morphology is confirmed from the images. The purity and crystallinity of Ag NPs is confirmed by energy-dispersive X-Ray analysis and selected area electron diffraction respectively. The electrochemical behavior of the synthesized Ag NPs was assessed by cyclic voltammetry (CV) and shows the redox peaks in the potential range of -1.1 to +1.1V. Agar diffusion method is used to examine the antibacterial activity of Ag NPs. For this purpose, two gram positive and two gram negative bacteria were studied. This single step approach was found to be simple, short time, cost-effective, reproducible, and eco-friendly.

Ce3+-ion, Surface Oxygen Vacancy, and Visible Light-induced Photocatalytic Dye Degradation and Photocapacitive Performance of CeO2-Graphene Nanostructures

Cerium oxide nanoparticles (CeO₂ NPs) were fabricated and grown on graphene sheets using a facile, low cost hydrothermal approach and subsequently characterized using different standard characterization techniques. X-ray photoelectron spectroscopy and electron paramagnetic resonance revealed the changes in surface states, composition, changes in Ce⁴⁺ to Ce³⁺ ratio, and other defects. Transmission electron microscopy (TEM) and high resolution TEM revealed that the fabricated CeO₂ NPs to be spherical with particle size of ~10–12 nm. Combination of defects in CeO₂ NPs with optimal amount of two-dimensional graphene sheets had a significant effect on the properties of the resulting hybrid CeO₂-Graphene nanostructures, such as improved optical, photocatalytic, and photocapacitive performance. The excellent photocatalytic degradation performances were examined by monitoring their ability to degrade Congo red ~94.5% and methylene blue dye ~98% under visible light irradiation. The photoelectrode performance had a maximum photocapacitance of 177.54 Fg⁻¹ and exhibited regular capacitive behavior. Therefore, the Ce³⁺-ion, surface-oxygen-vacancies, and defects-induced behavior can be attributed to the suppression of the recombination of photo-generated electron–hole pairs due to the rapid charge transfer between the CeO₂ NPs and graphene sheets. These findings will have a profound effect on the use of CeO₂-Graphene nanostructures for future energy and environment-related applications.

Elucidation of photocatalysis, photoluminescence and antibacterial studies of ZnO thin films by spin coating method

The ZnO thin films have been prepared by spin coating followed by annealing at different temperatures like 300°C, 350°C, 400°C, 450°C, 500°C & 550°C and ZnO nanoparticles have been used for photocatalytic and antibacterial applications. The morphological investigation and phase analysis of synthesized thin films well characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Photoluminescence (PL), Transmission Electron Microscopy (TEM) and Raman studies. The luminescence peaks detected in the noticeable region between 350nm to 550nm for all synthesized nanosamples are associated to the existence of defects of oxygen sites. The luminescence emission bands are observed at 487nm (blue emission), and 530nm (green emission) at the RT. It is observed that there are no modification positions of PL peaks in all ZnO nanoparticles. In the current attempt, the synthesized ZnO particles have been used photocatalytic and antibacterial applications. The antibacterial activity of characterized samples was regulated using different concentrations of synthesized ZnO particles (100μg/ml, 200μg/ml, 300μg/ml, 400μg/ml, 500μg/ml and 600μg/ml) against gram positive and gram negative bacteria (S. pnemoniae, S. aureus, E. coli and E. hermannii) using agar well diffusion assay. The increase in concentration, decrease in zone of inhibition. The prepared ZnO morphologies showed photocatalytic activity under the sunlight enhancing the degradation rate of Rhodamine-B (RhB), which is one of the common water pollutant released by textile and paper industries.