Musa paradisiaca L. peel extract-bioinspired anisotropic nano-silver with the multipurpose of hydrogenation eco-catalyst and antimicrobial resistance.

In an effort to pursue a green synthesis approach, the biosynthesis of nano-silver (nAg) using plant extracts has garnered significant attention, particularly for its antimicrobial resistance and medical applications, which have been the focus of numerous studies. However, there remains a gap in surface catalytic studies, especially regarding the hydrogenation of 4-nitrophenol. While some studies have addressed catalytic kinetics, thermodynamic aspects have been largely overlooked, leaving the catalytic mechanisms of biosynthesized nAg unclear. In this context, the present work offers a straightforward, eco-friendly, and efficient protocol to obtain nano-silver inspired by Musa paradisiaca L. peel extract. This nAg serves multiple purposes, including antimicrobial resistance and as an eco-catalyst for hydrogenation. Predominantly consisting of zero-valent silver with anisotropic polyhedral shapes, mainly decahedra with an edge length of 50 nm, this nAg demonstrated effective antimicrobial action against both S. aureus and E. coli bacteria. More importantly, both kinetic and thermodynamic studies on the hydrogenation of 4-nitrophenol to 4-aminophenol catalyzed by this bio-inspired nAg revealed that the rate-limiting step is not diffusion-limited. Instead, the adsorbed hydrogen and 4-nitrophenolate react together via electron transfer on the surface of the nAg. The activation energy of 26.24 kJ mol-1 indicates a highly efficient eco-catalyst for such hydrogenation processes.

Thiol-Surface-Engineered Cellulose Nanocrystals in Favor of Copper Ion Uptake.

Cellulose, the most abundant natural polymer on earth, has recently gained attention for a large spectrum of applications. At a nanoscale, nanocelluloses (mainly involving cellulose nanocrystals or cellulose nanofibrils) possess many predominant features, such as highly thermal and mechanical stability, renewability, biodegradability and non-toxicity. More importantly, the surface modification of such nanocelluloses can be efficiently obtained based on the native surface hydroxyl groups, acting as metal ions chelators. Taking into account this fact, in the present work, the sequential process involving chemical hydrolysis of cellulose and autocatalytic esterification using thioglycolic acid was performed to obtain thiol-functionalized cellulose nanocrystals. The change in chemical compositions was attributed to thiol-functionalized groups and explored via the degree of substitution using a back titration method, X-ray powder diffraction, Fourier-transform infrared spectroscopy and thermogravimetric analysis. Cellulose nanocrystals were spherical in shape and ca. 50 nm in diameter as observed via transmission electron microscopy. The adsorption behavior of such a nanomaterial toward divalent copper ions from an aqueous solution was also assessed via isotherm and kinetic studies, elucidating a chemisorption mechanism (ion exchange, metal chelation and electrostatic force) and processing its operational parameters. In contrast to an inactive configure of unmodified cellulose, the maximum adsorption capacity of thiol-functionalized cellulose nanocrystals toward divalent copper ions from an aqueous solution was 4.244 mg g-1 at a pH of 5 and at room temperature.