Zn/Al layered double hydroxide and carboxymethyl cellulose composite beads as support for the catalytic gold nanoparticles and their applications in the reduction of nitroarenes.

Until now, many efficient catalysts have been reported that are used for the reduction of nitroarenes. However, a catalyst reusability is a challenge that is often faced in practical environment. In this report, we designed a hydrogel composite (CMC-LDH), which act as support and making it possible to address this challenge. In this research work, zinc/aluminum based layered double hydroxides (Zn/Al LDH) have been assembled with carboxymethyl cellulose (CMC) to prepare CMC/LDH hydrogel beads. The CMC/LDH hydrogel beads were prepared by the ionotropic gelation method. For CMC/LDH/Au preparation, the already prepared CMC/LDH beads were kept in gold ion (Au3+) solution, and their subsequent reduction with sodium borohydride (NaBH4). For the characterization of the prepared samples different instrumental techniques, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy, and scanning electron microscopy (SEM) were adopted. For the catalytic evaluation of CMC/LDH/Au, it was utilized as a catalyst in 4-NP and 4-NA reduction reactions. The continuity of the reaction was monitored by a UV-visible spectrophotometer. Rate constant (kapp) of 0.48474 min-1 and 0.7486 min-1 were obtained for 4-NP and 4-NA reduction, respectively. The hydrogel beads were recycled and reused for up to five successive cycles without significantly changing their catalytic efficiency.

Efficient fabrication, antibacterial and catalytic performance of Ag-NiO loaded bacterial cellulose paper.

This study reports the synthesis of bacterial cellulose (BC) hydrogel sheets and their utilization as a support for silver­nickel oxide nanocomposites (Ag/NiO). A two-step facile hydrothermal method was employed for the preparation of Ag/NiO, followed by impregnation into BC hydrogel sheets. A 20% Ag/NiO composition was revealed by dry weight analysis. The stability of nanocomposites-Hydrogel was confirmed by Ag+ and Ni2+ ion release study. The catalytic activity of the BC-Ag/NiO was evaluated against chemical reduction of congo red, methyl orange and methylene blue. The reduction reaction followed pseudo first order kinetics and kapp values of 0.1147 min-1, 0.1323 min-1 and 0.12989 min-1 were obtained for CR, MO, and MB dyes, respectively. The BC-Ag/NiO catalyst could be easily recovered and re-used in another reaction without centrifugation. The synthesized nanocomposites hydrogel was also tested for its antibacterial activity against Gram-negative bacteria, Escherichia coli (E.coli) and Gram-positive bacteria, Staphylococcus aureus (S.aureus).

Catalytic potential of cobalt oxide and agar nanocomposite hydrogel for the chemical reduction of organic pollutants.

In this study, cobalt oxide nanoparticles (Co3O4 NPs) were synthesized by precipitation method from cobalt sulphate solution with basic pH, followed by calcination. The ex-situ synthesized Co3O4 NPs were mixed with hot agar (AG) aqueous solution. The preparation of AG- Co3O4 nanocomposite hydrogel was carried out by self-association method promoted by thermal denaturation. The quenching of hot suspension from 80 °C to room temperature resulted in the formation of AG-Co3O4 nanocomposite hydrogel. The as-synthesized AG-Co3O4 was characterized by FTIR, XRD and SEM techniques. In order to test the catalytic activity, AG-Co3O4 was used as a heterogeneous catalyst for the reduction of methylene blue (MB), congo red (CR) and 4-nitrophenol (4-NP). The excellent performance of the AG-Co3O4 was shown by the reaction rate constant (kapp) values of 0.3623, 0.2114 and 0.2893 for MB, 4-NP and CR, respectively. All these results were obtained with R2 above 94 and utilization of an AG-Co3O4 catalyst. Furthermore, the catalytic reduction was studied with varying dye concentration and catalyst dose. This study showed that AG-Co3O4 catalyst has high potential for remediation of environmental pollutants in wastewaters.