Evaluation on La2O3 garlanded ceria heterostructured binary metal oxide nanoplates for UV/ visible light induced removal of organic dye from urban wastewater

Ball Milling of La2O3 Tailors the Crystal Structure, Reactive Oxygen Species, and Free Radical and Non-Free Radical Photocatalytic Pathways

Non-free radical photocatalysis with metal oxide catalysts is an important advanced oxidation process that enables the removal of various emerging environmental pollutants, such as tetracycline. Here, four hexagonal La2O3 photocatalysts with different densities of oxygen vacancy and crystalline features are synthesized and then further treated by ball milling. Ball milling of these La2O3 photocatalysts is found to increase the amount of oxygen vacancies on their surfaces and thereby the amount of 1O2 species produced by them. The photocatalytic degradation of TC by these La2O3 photocatalysts depends on the oxygen vacancies present on them. Furthermore, the ones with a strong (101) diffraction peak remove tetracycline from water systems largely with 1O2 and •OH species, whereas those with a weak (101) diffraction peak do so mainly via 1O2 and direct electron transfer (DET) process. Their overall catalytic properties are also studied by density functional theory calculations. Moreover, the organic products produced from tetracycline by La2O3 photocatalysts containing a strong (101) diffraction peak are found to be less toxic than those produced by La2O3 photocatalysts containing a weak (101) diffraction peak. This study also provides convincing evidence that the structures of La2O3 determine the species that is produced by it and that end up mediating photocatalytic reaction pathways (i.e., free radical versus non-free radical) to degrade an emerging environment pollutant.

Enhanced Industrial Dye Degradation and Antibacterial Activity Supported by the Molecular Docking Study of Yttrium and Carbon Sphere-Doped Lanthanum Oxide Nanostructures

As the population grows, the scientific community remains focused on researching new materials, methods, and devices to ensure the availability of safe drinking water. The main aim of this research was to decrease the recombination rate of the charge carriers of La2O3 and enhance the catalytic and antimicrobial activity by employing Y/Cs- doped La2O3, respectively. In the current study, different concentrations of yttrium (Y) and a fixed amount of carbon spheres (Cs) doped into lanthanum oxide (La2O3) nanostructures (NSs) were synthesized by the coprecipitation technique. Cs are used as a cocatalyst as they have a high surface area and small size attributed to increased active sites and decreased recombination rate. Moreover, Y was further incorporated as it activates the generation of reactive oxygen species in the inhibition zone, enhancing the antibacterial activity and reducing the emission intensity. Advanced techniques were utilized to determine the structural properties, optical emission and absorption, elemental composition, and d-spacing of the synthesized samples. The reported ternary catalyst works efficiently, improving the catalytic activity and bactericidal potential. Moreover, in silico molecular docking studies, Cs-doped La2O3 and Y/Cs-doped La2O3 nanostructures toward DNA gyrase Escherichia coli showed good efficacy for antibacterial activity.

Efficient Dye Degradation and Antibacterial Activity of Carbon Dots/Chitosan-Doped La2O3 Nanorods: In Silico Molecular Docking Analysis

This work demonstrates the degradation of toxic RhB (rhodamine B) dye from polluted water in various pH environments. It assesses the antibacterial action of CDs (carbon dots)/CS (chitosan)-doped La₂O₃ (lanthanum oxide) NRs (nanorods). CS and CDs have been introduced as dopants to modify the characteristics of La₂O₃ to achieve efficient outcomes. The influence of doping on the structural, morphological, optical, and elemental properties of synthesized La₂O₃ NRs was investigated through a number of analytical techniques. The structural analysis of XRD revealed a hexagonal phase. The rod-like structure of pure La₂O₃ and reduction in the size of NRs upon doping were exhibited by TEM micrographs. From UV-vis spectroscopy, increased absorption upon doping and introduction of redshift that led to reduced bandgap energy were observed. The FTIR spectra indicate the presence of functional groups of pure and integrated samples. The catalytic activity of specimens in basic medium toward dye showed excellent results (94.57%). The inhibition zone of diameter 4.15 mm was evaluated by 6 mL of CDs/CS-doped La₂O₃ NRs against Escherichia coli once the surface area increased by dopants. In silico experiments were performed for enoyl-[acyl-carrier-protein] reductase (FabI) and DNA gyrase enzymes to assess the potency of CS-doped La₂O₃ and CDs/CS-doped La₂O₃ as their inhibitors and to justify their possible mechanism of action.

Enhanced UV-Irradiated Photocatalytic Degradation of Malachite Green by Porous WO3 Decorated on 2D Graphene Sheet

High efficient and environment friendly one-pot in situ microwave irradiation method was implemented towards the preparation of porous reduced graphene oxide/WO₃ (rGOW) nanocomposites for the first time. Here, 3D porous WO₃ nanoparticles were evenly decorated on 2D rGO sheets. The crystal phase purity and the functional group characterizations of the as-synthesized nanomaterials were examined by powder XRD and Raman spectral analyses. The morphological studies from the SEM, TEM, and BET measurements clearly revealed the highly porous nature of nano-sized WO₃ and its distribution on the surface of rigid 2D graphene sheet. The UV along with visible light-driven degradation mechanism of malachite green (MG) dye in the rGOW nanocomposites was well illustrated with the schematic diagram and discussed in detail through the kinetics of the degradation process upon calculating the rate constant and half-life time. The rGO/WO₃ photocatalyst delivered high MG degradation efficiency of 97% under UV irradiation.

Synthesis of CeO2-Fe2O3 Mixed Oxides for Low-Temperature Carbon Monoxide Oxidation

In this study, the CeO2-Fe2O3 mixed oxide catalysts have been prepared by combustion method using gel-created tartaric acid. The ability of effective carbon monoxide (CO) oxidation to carbon dioxide (CO2) by CeO2-Fe2O3 catalyst under low-temperature conditions was also demonstrated. The calcined CeO2-Fe2O3 material has a porous honeycomb structure and good gaseous absorption-desorption ability. The solid solution of CeO2-Fe2O3 mixed oxides was formed by the substitution of Fe+3 ions at some Ce4+ ion sites within the CeO2 crystal lattice. The results also showed that the calcination temperature and the molar ratio of Ce3+ ions to Fe3+ ions (CF) affected the formation of the structural phase and the catalytic efficiency. The catalytic properties of the CeO2-Fe2O3 mixed oxide were good at the CF ratio of 1 : 1, the average crystal size was near 70 nm, and the specific surface area was about 20.22 m2.g-1. The full conversion of CO into CO2 has been accomplished at a relatively low temperature of 270 °C under insufficient O2 conditions.

Ag doped Sn3O4 nanostructure and immobilized on hyperbranched polypyrrole for visible light sensitized photocatalytic, antibacterial agent and microbial detection process

Ag doped Sn₃O₄ Nanostructure and immobilized on hyperbranched polypyrrole is investigated in this project. The product was synthesized by the hydrothermal synthesis method. The surface and structural characteristics of the product was studied by different instrumental analysis. The fabricated nanocomposites was utilized as a nano photocatalyst in the removal of methylene blue dye. The crystallography results depicts the triclinic phase of Sn₃O₄ with the crystallite size 36.3 nm. The band gap of the Ag-Sn₃O₄/hyperbranched polypyrrole was found 1.50 eV from kubelka-munk measurements. The specific surface area was increased in the presence of the hyperbranched polypyrrole as compared to Ag-Sn₃O₄ samples. The photo-catalytic activity of composites was found 100.0% degradation of CR in 30 min under visible light irradiation. The catalytic kinetic was followed from the first kinetic model. Moreover, the Ag/Sn₃O₄/hyperbranched polypyrrole was applied as a bactericidal agent against Streptococcus pneumoniae, and Pseudomonas aeruginosa bacteria. Determination of Streptococcus pyogenes as a pathogenic bacteria was investigated by using aptamer/Ag/Sn₃O₄/hyperbranched polypyrrole in peroxidase activity. The detection limit of S. pyogenes was 71.0 CFU/mL by using the nano-aptamer.

Green synthesis of single phase hausmannite Mn3O4 nanoparticles via Aspalathus linearis natural extract

Abstract

Nowadays, green synthesis of nanoparticles using plant precursors has been extensively studied. However, less attention has been given to Mn3O4. This contribution validates the synthesis of single-phase Hausmannite Mn3O4 nanoparticles by a green approach without using any standard acid/base compounds, surfactants, and organic/inorganic dissolving agents. The chemical chelation of the Mn precursor was performed via bioactive compounds of the Aspalathus Linearis’ extract, an African indigenous plant. Annealing at 400 °C for ~ 1 h was required to crystallize the small amorphous nanoparticles with an initial bimodal size distribution peaking at $$\left\langle {\phi_{1} } \right\rangle$$ ϕ 1  ~ 4.21 nm and $$\left\langle {\phi_{2} } \right\rangle$$ ϕ 2  ~ 8.51 nm respectively. Such annealing lead to increase in the diameter of the nanoparticles from 17 to 28 nm.The morphological, structural, vibrational, surface, and photoluminescence properties of the single-phase Hausmannite nanoparticles were comprehensively investigated by High Resolution Transmission Electron Microscopy(HRTEM),Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD), Raman and X-rays Photoelectron Spectroscopy (XPS), spectroscopy as well as room temperature photoluminescence. Structural and morphological investigations revealed the formation of quasi-spherical nanoparticles having a single phase Hausmannite Mn3O4 crystal structure. XPS results also validated the XRD results about the formation of Hausmannite Mn3O4 nanoparticles. Raman investigations allowed a crystal-clear distinction between the Mn3O4 nature of the nanoparticles from the potential γ -Mn2O3 phase as both phases belong to the same space group and both assume tetragonally-distorted cubic lattices of nearly similar dimensions. The optical studies of the single phase Hausmannite crystalline nanoparticles exhibited a broad photoluminescence in the spectral range of 300–700 nm, which is ideal for emission devices.

Graphic abstract

Synthesis and Characterization of CeO2/CuO Nanocomposites for Photocatalytic Degradation of Methylene Blue in Visible Light

Removal of hazardous organic dyes from polluted water bodies requires the introduction of strong adsorbents and photocatalysts to industrial wastewaters. Herein, photocatalytic CeO2 nanoparticles and CeO2/CuO nanocomposite were synthesized following a co-precipitation method for low cost elution of methylene blue (MB) from water. The crystallinity and surface structure of the as-prepared materials have been analyzed using characterization techniques including X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), ultra-violet visible spectroscopy (UV–Vis), and Fourier-transform infrared spectroscopy (FTIR). The average particle size of both the nano scaled samples were approximately 20–30 nm. The photocatalytic properties of CeO2/CuO were investigated under visible light against methylene blue (MB). The results showed 91% photodegradation of MB organic pollutant in 3 h as monitored by UV–Vis spectroscopy. Absorbance peaks appeared at around 670 nm corresponding to degradation of MB. Such output displayed the effectiveness of Ce nanocomposites for environmental benefits. Hence, CeO2/CuO nanocomposite could be useful for treatment of industrial wastewaters by removing hazardous MB dye.

Optical properties of biosynthesized nanoscaled Eu2O3 for red luminescence applications

This contribution reports on the optical properties of biosynthesised Eu₂O₃ nanoparticles bioengineered for the first time by a green and cost effective method using aqueous fruit extracts of Hyphaene thebaica as an effective chelating and capping agent. The morphological, structural, and optical properties of the samples annealed at 500°C were confirmed by using a high-resolution transmission electron microscope (HR-TEM), x-ray diffraction analysis (XRD), UV-Vis spectrocopy, and photoluminescence spectrometer. The XRD results confirmed the characteristic body-centered cubic (bcc) structure of Eu₂O₃ nanoparticles with an average size of 20 nm. HR-TEM revealed square type morphology with an average size of ∼6nm. Electron dispersion energy dispersive x-ray spectroscopy spectrum confirmed the elemental single phase nature of pure Eu₂O₃. Furthuremore, the Fourier transformed infrared spectroscopy revealed the intrinsic characteristic peaks of Eu-O bond stretching vibrations. UV-Vis reflectance proved that Eu₂O₃ absorbs in a wide range of the solar spectrum from the VUV-UV region with a bandgap of 5.1 eV. The luminescence properties of such cubic structures were characterized by an intense red emission centered at 614 nm. It was observed that the biosynthesized Eu₂O₃ nanoparticles exhibit an efficient red-luminescence and hence a potential material as red phosphor.

NaxWO3 + TiO2 nanocomposites as plasmonic photocatalysts for the degradation of organic dyes

The combination of plasmonic metal nanostructures with semiconductor photocatalysts can improve their photocatalytic efficiency by increasing light absorption and aiding in charge separation. Metallic Na x WO3 has been shown to be strongly plasmonic and offers a readily synthesized and low-cost replacement for the noble metals which are conventionally used in plasmonic photocatalysts. In this work, a range of Na x WO3 + TiO2 nanocomposites were fabricated. Composites containing both semiconducting (x < 0.25) and metallic (x > 0.25) Na x WO3 were prepared. The degradation of rhodamine 6G (R6G) under visible and near infrared (NIR) light illumination was observed only when Na x WO3 and TiO2 were both present in the composite. Photocatalytic activity was generally higher in metallic samples than in semiconducting ones, but the sample with the highest activity had a mixture of both. This suggests that a combination of interband transitions and plasmonics-enhanced processes can be used together to catalyse reactions.

Green synthesis of zinc ferrite nanoparticles for photocatalysis of methylene blue

In this study, zinc ferrite nanoparticles (ZF-NPs) were synthesized using aqueous seed extract of Piper nigrum as a bio-reducing and stabilizing agent. FTIR, SEM, FE-SEM, XRD, and TGA have been used for characterizing ZF-NPs. The results showed that Piper nigrum stabilized ZF-NPs have high purity and size range of 60-80 nm. The performance of the ZF-NPs has been investigated by photocatalytic reduction of methylene blue (MB) in the presence of sunlight. The factors responsible for affecting the degradation values of the reaction were also explored for developing a better understanding of the phenomenon.