Coenzyme based synthesis of silver nanocrystals

In this work we have carried out systematic studies to identify the critical role of a coenzyme (β-NADPH) to synthesize silver nanoparticle. Interestingly, both roles of reducing and stabilizing agents are played by β-NADPH. Nanoparticles obtained by this route exhibit a good crystallinity, a narrow size distribution and excellent stability in aqueous solution. The most advantageous points of this single-step environmentally friendly approach are that it takes place at nearly room temperature (20 °C), overcomes many limitations encountered in other biological methods (such as the restricted concentration of AgNO3, maintenance and manipulation of microorganisms, preparing extracts and contamination from residual reactants), bypasses the use of surfactants or capping agents and does not necessitate pH adjustment. The nano-Ag were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), zeta potential, UV–vis, and energy-dispersive X-ray spectroscopy (EDX). DLS, TEM and XRD measurements showed the formation of nano-Ag with an average diameter of 20.77 ± 0.67 nm. XRD studies confirmed the nanocrystalline nature of the silver particles. Zeta potential measurements revealed that the particles are surrounded with negatively charged groups (−41 ± 5 mV) making them stable in an aqueous medium. The EDX spectrum of the silver nanoparticles confirmed the presence of elemental silver signal in high percentage. In addition to the easy and ecofriendly method of synthesis, β-NADPH can be regenerated by enzymatic means through glucose 6-phosphate dehydrogenase, potentially making the synthesis more cost effective.

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► Nano-Ag were synthesized using NADPH as reducing and stabilizing agent.
► Reaction was conducted at room temperature in aqueous solution.
► Stable concentrated aqueous dispersions of silver nanoparticles of narrow size distribution were synthesized.
► β-NADPH was regenerated by glucose-6-phosphate dehydrogenase to utilize again for the synthesis of the nano-Ag.