Synthesis and characterization of metal nanoparticles templated chitosan-SiO2 catalyst for the reduction of nitrophenols and dyes

Copper(II) oxide nanoparticles coated cellulose sponge-an effective heterogeneous catalyst for the reduction of toxic organic dyes

Discharge of unprocessed coloured waste water from industries gives rise to water contamination. In the current work, we propose the application of CuO nanoparticles supported on cellulose kitchen wipe sponge as a heterogeneous catalyst for the reductive decolourization of various toxic cationic and anionic dye molecules. The catalytic activity of the CuO nanoparticles under normal light for reduction has been examined in which sunlight irradiation is not necessitated. The CuO nanoparticles were synthesized by a simple wet chemical method and characterized using High Resolution Transmission Electron Microscope (HRTEM), SEM, EDX, XRD, XPS and TGA analyses. In the presence of CuO@CS catalyst and sodium borohydride, decolourization reaction of dyes such as acid red, acid green, methylene blue, rhodamine B and solochrome black-T was carried out. The catalytic reduction behaves as a pseudo-first-order reaction and is found to be superior in comparison with other reported catalysts in terms of reaction velocity. The reduction reaction can be further accelerated by increasing the reaction temperature. The developed catalyst drives the reduction faster on exposing the reaction mixture to sunlight confirming the usage of the catalyst at normal light and sunlight conditions. The catalyst retains 100% efficiency even after 5 cycles and remains suitable even for further use. Thus, a low-cost heterogeneous catalyst has been successfully developed and employed to decolourize various dye molecules in short duration with good recyclability and therefore can be used as the potential candidate in environmental remediation.

Utilization of chitosan/Ag bionanocomposites as eco-friendly photocatalytic reactor for Bactericidal effect and heavy metals removal

Chitosan is a nontoxic, eco-friendly, and biocompatible natural polymer which could be used in an extensive range of applications for example in the areas of membranes, biomedicine, hydrogels, wastewater treatment, food packaging. Moreover, chitosan based nanomaterials had high sorption capacities, chelating activities, stability, and versatility, that would be potentially applied as green reactants in various scientific and engineering applications. The current study involved the preparation of silver nanoparticles incorporated into chitosan thin films and used for various purposes including photo-oxidation of organic pollutants, heavy metal removal (Cd, Pb, Cr, and Fe) and antibacterial activity. The fabricated chitosan/silver (CS/Ag) bionanocomposites thin films were characterized by the ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and Fourier transforms infrared (FT-IR) spectroscopy. Furthermore, the prepared CS/Ag bionanocomposites had revealed good photodegradation rate, heavy metals removal and antimicrobial activity against gram-negative bacteria like E. coli, and gram-positive bacteria like G. bacillus, with increasing the loading of different concentrations of chitosan and silver nanoparticles incorporated into the prepared bionanocomposite thin films. Consequently, the prepared CS/Ag bionanocomposites are considered good candidates for wastewater treatment through photo-oxidation of organic pollutants, heavy metal removal as well as respectable antibacterial materials.

Bimetallic Nanoparticles Anchored on Core-Shell Support as an Easily Recoverable and Reusable Catalytic System for Efficient Nitroarene Reduction

We report an easily recoverable and reusable versatile magnetic catalyst (Fe3O4@CS_AgNi, where CS = chitosan) for organic reduction reactions. The catalytic system is prepared by dispersing AgNi bimetallic nanoparticles on the magnetite core-shell (Fe3O4@CS). The as-synthesized catalyst has been characterized by spectroscopic techniques, such as IR, UV-vis, and X-ray photoelectron spectroscopy (XPS), and analytical tools, such as thermogravimetric analysis, powder X-ray diffraction, Brunauer-Emmett-Teller adsorption, FEG-scanning electron microscopy, high-resolution transmission electron microscopy (HR-TEM), inductively coupled plasma-atomic emission spectroscopy, and magnetic measurements. HR-TEM studies indicate the core-shell structure of Fe3O4@CS and confirm the presence of AgNi nanoparticles on the surface of Fe3O4@CS spheres. IR spectral and XPS studies lend evidence for the occurrence of a strong chemical interaction between the amino groups of CS and AgNi nanoparticles. The nano-catalyst Fe3O4@CS_AgNi rapidly reduces p-nitrophenol to p-aminophenol using NaBH4 as the reductant within a few minutes under ambient conditions (as monitored by UV-visible spectroscopy). The utility of this catalytic system has also been extended to the reduction of other nitroarenes. A strong interaction between Fe3O4@CS and AgNi nanoparticles impedes the leaching of AgNi nanoparticles from the core-shell support, leading to excellent reusability of the catalyst.

Microbial synthesis of Pd-Pt alloy nanoparticles using Shewanella oneidensis MR-1 with enhanced catalytic activity for nitrophenol and azo dyes reduction

Bimetallic nanoparticles (NPs) often exhibit improved catalytic performance due to the electronic and spatial structure changes. Herein, a novel green biosynthesis method for Pd-Pt alloy NPs using Shewanella oneidensis MR-1 was proposed. The morphology, size and crystal structure of Pd-Pt alloy NPs were studied by a suite of characterization techniques. Results showed Pd-Pt alloy NPs were successfully synthesized inside and outside the cell. The biosynthesized Pd-Pt alloy NPs were polycrystalline and face-centered-cubic structure with the particle size ranged from 3-40 nm. Furthermore, the catalytic experiment demonstrated that the Pd-Pt alloy NPs exhibited the highest performance for the catalytic reduction of nitrophenol and azo dyes compared with the as-synthesized Pd and Pt monometallic NPs. This enlarged catalytic activity resulted from the synergistic effect of Pd and Pt element. Thereby, this paper provided a simple biosynthesis method for producing bimetallic alloy nanocatalyst with superior activity for contaminant degradation.

MnCo2O4+x nanowire arrays grown on carbon sponge: improved electrochemical and catalytic performances

MnCo₂O_4+x nanowire arrays with improved electrochemical and catalytic performances were successfully grown on carbon sponge via a hydrothermal–pyrolysis route.