Palladium oxide-decorated mesoporous silica on graphene oxide nanosheets as a heterogeneous catalyst for the synthesis of ß-substituted indole derivatives.

In this work, an efficient and facile strategy has been adopted for the stepwise synthesis of the RGO-MSiO2/PdO hybrid nanomaterial (HY-NM). Herein, a hybrid nanostructure of mesoporous silica over graphene oxide (GO) sheets has been developed followed by immobilizing palladium oxide nanoparticles (PdO NPs), and then it has been utilized for catalyzing a multicomponent reaction (MCR). To authenticate the successful synthesis of the HY-NM and successive immobilization of PdO NPs, various physicochemical characterization techniques were utilized such as SEM, EDAX, HR-TEM, HR-XRD, TGA, BET, FT-IR, and XPS analysis. The activity of the HY-NM has been determined by performing the catalyst-mediated synthesis of ß-substituted indole derivatives (yield 90-98%). The excellent catalytic activity of the prepared HY-NM could be observed due to its high surface area and large porosity, which facilitates the penetration and interaction of reactant molecules with the catalytic active species. This protocol eliminates the requirement of further purification after the isolation of the product from the reaction mixture. The ease of handling, recyclability of the catalyst, and simple work-up procedure are the main features of this protocol. The synthesized HY-NM could be recycled for multiple catalytic cycles making it a very effective heterogeneous catalyst.

Ru x Pd y Alloy Nanoparticles Uniformly Anchored on Reduced Graphene Oxide Nanosheets (Ru x Pd y @rGO): A Recyclable Catalyst.

In this work, Ru x Pd y alloy nanoparticles were uniformly decorated on a two-dimensional reduced graphene oxide (rGO) sheet by an in situ chemical co-reduction process. The resulting products were characterized by various physiochemical techniques such as X-ray diffraction, Raman spectroscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic absorption spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Further, the synthesized Ru x Pd y @rGO nanocomposites have been employed as a heterogeneous catalyst for three different catalytic reactions: (1) dehydrogenation of aqueous ammonia borane (AB); (2) hydrogenation of aromatic nitro compounds using ammonia borane as the hydrogen source, and (3) for the synthesis of aromatic azo derivatives. The present work illustrates the sustainable anchoring of metal nanoparticles over the surface of rGO nanosheets, which could be used for multifarious catalytic reactions.

The Role of Imidazolium-Based Surface-Active Ionic Liquid to Restrain the Excited-State Intramolecular H-Atom Transfer Dynamics of Medicinal Pigment Curcumin: A Theoretical and Experimental Approach.

The naturally occurring polyphenolic compound curcumin has shown various medicinal and therapeutic effects. However, there are various challenges associated with curcumin, which limits its biomedical applications, such as its high degradation rate and low aqueous solubility at neutral and alkaline pH. In the present study, efforts have been directed towards trying to resolve such issues by encapsulating curcumin inside the micelles formed by imidazolium-based surface-active ionic liquid (SAIL). The shape and size of the micelles formed by the SAIL have been characterized by using DLS analysis as well as TEM measurements. The photo-physics of curcumin in the presence of ionic liquid (IL) and also with the addition of salt (NaCl) has been explored by using different optical spectroscopic tools. The time-dependent absorption studies have shown that there is relatively higher suppression in the degradation rate of curcumin after encapsulation by the imidazolium-based SAIL in an aqueous medium. The TCSPC studies have revealed that there is deactivation in the nonradiative intramolecular hydrogen transfer process of curcumin in the presence of IL micelles as well as with the addition of salt. Furthermore, the time-dependent fluorescence anisotropy measurement has been carried out to figure out the location of curcumin inside the micellar system. In order to correlate all experimental findings, density functional theory (DFT) and classical molecular dynamics (MD) simulations at neutral pH media have been performed. It has been found that the van der Waals force of interactions plays a major role in the stabilization of curcumin in the micelles rather than the coulombic forces. It also has been observed that the van der Waals interactions remain unaffected in the presence of salt. However, as revealed by the MD simulation results, the micelles are found to be more compact in size after the addition of salt. The RMSD results show that the micelles formed by the SAIL achieve greater stability after a particular time constraint. Our results have divulged that the SAIL could act as a promising drug delivery system.

Nitrogen-Rich and Porous Graphitic Carbon Nitride Nanosheet-Immobilized Palladium Nanoparticles as Highly Active and Recyclable Catalysts for the Reduction of Nitro Compounds and Degradation of Organic Dyes.

In the present study, we have successfully synthesized nitrogen-rich graphitic carbon nitride (g-C3N4) nanosheets by a simple direct thermal polymerization approach. The synthesized g-C3N4 nanosheets were exfoliated using HCl to make their surface a few nanometers thick. The ultrathin surface was achieved by simply mixing g-C3N4 in 3 M HCl. After that, palladium nanoparticles were uniformly immobilized on the surface of g-C3N4. The synthesized materials were characterized by various physiochemical techniques such as X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Information about morphology and size was obtained through transmission electron microscopy and scanning electron microscopy. The Brunauer-Emmett-Teller surface area, pore volume, and pore diameter were determined using nitrogen adsorption-desorption measurements. The prepared material (Pd/g-C3N4) was utilized as an efficient catalyst for the reduction of hazardous nitroarenes and degradation of organic dyes. The catalyst could be easily recovered through centrifugation and then could be reused multiple times for the further catalytic cycles with a little loss in its catalytic activity. The work presented here illustrates the sustainable anchoring of metal nanoparticles over the surface of nitrogen-rich g-C3N4 nanosheets and could be utilized for different types of catalytic reactions.

Synthesis of dendritic fibrous nanosilica over a cubic core (cSiO2@DFNS) with catalytically efficient silver nanoparticles for reduction of nitroarenes and degradation of organic dyes.

In this study, dendritic fibrous core-shell silica particles having cubic morphology with uniform and vertical nanochannels have been successfully synthesised. The synthesized dendritic fibrous nanosilica over a cubic core (cSiO2@DFNS) have been characterized by using various techniques, such as powder X-ray diffraction, TEM, FE-SEM, TGA EDS, FT-IR and N2 adsorption-desorption experiments. The prepared DFNS particles demonstrated a very high surface area and pore diameter. Amine groups were functionalized on the fibres of cSiO2@DFNS and after that silver nanoparticles could be successfully immobilized on amine functionalized cubic silica particles. Due to the presence of a high surface area and a uniform pore diameter, the silver nanoparticle loaded cSiO2@DFNS could be successfully employed as an efficient and recoverable catalyst for reduction of toxic aromatic nitro compounds and degradation of organic dyes. Higher catalytic activity of the prepared material could be attributed to its fibrous morphology which could facilitate proper interactions of the reactants molecules with the silver nanoparticles.