Ultrasonication-assisted synthesis of transition metal carbide of MXene: an efficient and promising material for photocatalytic organic dyes degradation of rhodamine B and methylene blue in wastewater.

Water pollutants of non-biodegradable toxic aromatic dye including Methylene blue (MB) and Rhodamine (RhB) are extremely carcinogenic thiazines used in various industries such as leather industry, paper industry, and the dyeing industry. The presence of dyes in wastewater causes severe threats to human health that are responsible for various harmful chronic or acute diseases and also shows an adverse impact on the environment as it reduces transparency and is harmful to water microorganisms. To overcome severe issues, many traditional techniques have been used to remove toxic pollutants, but these methods are insufficient to remove chemically stable dyes that remain in the treated wastewater. However, the photocatalytic degradation process is an efficient approach to degrade the dye up to the maximum extent with improved efficiency. Therefore, in this work, a new class of two-dimensional (2D) transition metal carbide of Titanium Carbide (Ti3C2Tx) MXene material was used for the organic dyes degradation such as MB and RhB using a photocatalytic process. A layered structure of hexagonal lattice symmetry of Ti3C2Tx MXene was successfully synthesized from the Titanium Aluminum Carbide of Ti3AlC2 bulk phase using an exfoliation process. Further, the XRD spectrum confirms the transformation of bulk MAX phase having (002) plane at 9.2° to Ti3C2Tx MXene of (002) plane at 8.88° confirms the successful removal of Al layer from MAX phase. A smooth, transparent, thin sheet-like morphology of Ti3C2Tx nanosheet size were found to be in the range of 70 to 150 nm evaluated from TEM images. Also, no holes or damages in the thin sheets were found after the treatment with strong hydrofluoric acid confirms the formation Ti3C2Tx layered sheets. The synthesized Ti3C2Tx MXene possesses excellent photocatalytic activity for the degradation of dyes MB, RhB, and mixtures of MB and RhB dyes. MB dye degraded with a degradation percentage efficiency of 99.32% in 30 min, while RhB dye was degraded upto 98.9% in 30 min. Also, experiments were conducted for degradation of mixture of MB and RhB dyes by UV light, and the degradation percentage efficiency were found to be 98.9% and 99.75% for mixture of MB and RhB dye in 45 min, respectively. Moreover, reaction rate constant (k) was determined for each dye of MB, RhB, and mixtures of MB and RhB and was found to be 0.0215 min-1 and 0.0058 min-1, and for mixtures, it was 0.0020 min-1 and 0.009 min-1, respectively.

Synergistic effect in the structural, optical, and electrical properties of harnessing NiFe2O4/CuO nanocomposite for enhanced environmental remediation.

This study presents the synthesis and characterization of composite material comprised of NiFe2O4 and CuO. The preparation of this composites involves a facile and cost-effective co-precipitation method, followed by heat treatment. The aim of this study is to explore the potential of this composite material for various catalytic applications. The synthesized NiFe2O4/CuO composites were extensively characterized using various analytical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), impedance analyzer, UV-Visible spectroscopy (UV-Vis.), Brunner-Emmett-Teller (BET), and X-ray photoelectron spectroscopy (XPS). These characterizations revealed the successful formation of a nanocomposite material with a well-defined structure and identified the oxygen vacancies/defects in the samples which might result in enhanced photocatalytic efficiency. Photocatalytic activity of 0.5NiFe2O4/0.5CuO composite showed degradation of methylene blue dye by 96.15% in 120 min. This work is not only to understand the photocatalytic mechanism but also to develop effective catalysts for the degradation of harmful organic pollutants.

Remediation of recalcitrant pollutants in water solution using visible light responsive cerium-doped tungsten trioxide nanoparticles.

In order to attain a solar energy-driven photocatalyst for wastewater remediation, cerium-doped WO3 (W1-xCexO3 with x = 0, 0.02, 0.04, 0.06, and 0.08) nanoparticles have been synthesized via a chemical co-precipitation technique. X-ray diffraction (XRD) analysis confirmed that W1-xCexO3 nanoparticles retained their monoclinic structure even after doping. The presence of the vast number of defects produced in the WO3 lattice was corroborated by Raman spectroscopy. Scanning electron microscopy confirmed the spherical shape of the nanoparticles with particle size range 50-76 nm. The optical band gap of W1-xCexO3 nanoparticles decreases from 3.07 to 2.36 eV with an increase in x, as confirmed by UV-Vis spectroscopy. Photoluminescence (PL) spectroscopy confirmed that the minimum rate of recombination was observed for W1-xCexO3 with x = 0.04. Degradation efficiency was explored for methyl violet (MV) and rhodamine-B (Rh-B) with 0.01 g of photocatalyst in a photoreactor chamber having a 200-W xenon lamp as a visible source of light. The results showed that the maximum photo-decolorization towards MV (94%) and rhodamine-B (79.4%) was observed in x = 0.04 sample in just 90 min because of its least recombination rate, highest adsorption capacity, and optimum band edge positions. Intriguingly, it has been observed that the modification with cerium in WO3 nanoparticles enhances the photocatalytic activity by narrowing the band gap and by efficaciously lowering the recombination rate due to electron entrapment by defects produced in the lattice.

Facile synthesis of carbon dots via pyrolysis and their application in photocatalytic degradation of rhodamine B (RhB).

Carbon Quantum dot (CQDs) is one of the newest materials in carbon-based nanomaterials. It is pertinent to study the synthesis and the application of these carbon dots. Here we have studied the effect of precursor on the optical, morphological, and photocatalytic properties of CQDs. We have synthesized CQDs using pyrolysis method using the precursors citric acid, urea, polyethyleneimine. We have synthesized two samples: CQD-S1; synthesized using urea and polyethyleneimine, and CQD-S2; synthesized using citric acid and polyethyleneimine. In optical properties study two distinct peaks have been obtained at 243 nm and 345 nm for CQD-S1, and at 265 nm and 335 nm for CQD-S2. In fluorescence study, the maximum emission was found at excitation wavelength of 340 nm for CQD-S1 and at excitation wavelength of 350 nm for CQD-S2. In morphological studies, Transmission Electron Microscope (TEM) revealed particle size of sample CQD-S1 and CQD-S2 were 1.91 nm and 1.61 nm, respectively. EDX confirmed the elemental composition in both samples. The rhodamine B (RhB) dye degradation percentages in dark and under visible and UV light were found to 6, 13, and 98.4% respectively for CQD-S1. Similarly, dye degradation for CQD-S2 were 7, 11, and 99.63%, respectively. Effective degradation of photocatalysis performed under UV-light within 100 min using mineralization process.

Visible Light Assisted Enhanced Photocatalytic Performance of ZnO/NiO Nanocomposites Prepared by Chemical Co-Precipitation Method.

A series of Ni1-xZnxO (x═0.1 to 0.4) nanocomposites is synthesized by facile chemical coprecipitation method. The structural analysis is carried out using X-ray diffraction (XRD) graph which reveals both cubic (NiO) and hexagonal (ZnO) phases. Chemical bonding, morphology, elemental composition and optical properties of prepared nanocomposites are investigated by Fourier Transform Infrared (FTIR) Spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), and UV-Vis spectroscopy respectively. FESEM micrographs show the formation of nanorods at higher concentration of zinc content. Introducing higher amount of Zn, optical band gap of composites is considerably reduced. Furthermore, solutions of Rose Bengal (RB) and Methylene Blue (MB) dyes are used to investigate the photocatalytic ability of synthesized samples in the presence of sunlight. It was found that the percentage degradation of dye concentration increases with irradiation time and also with the increase in concentration of zinc in prepared samples.