A facile completely 'green' size tunable synthesis of maltose-reduced silver nanoparticles without the use of any accelerator.

A simple, straightforward, cost effective and environmentally benign method for the synthesis of highly stable and small sized silver nanoparticles (Ag-NPs) with narrow size distribution without the use of an accelerator is reported. Silver nitrate, gelatin and maltose, a non-toxic disaccharide sugar were used as silver precursor, stabiliser and reducing agent. By varying the precursor concentration and reaction time, we monitored the temporal evolution of the optical and structural properties of the as-synthesised Ag-NPs. The as-synthesised Ag-NPs were characterised using UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The absorption maxima of the surface plasmon resonance (SPR) were blue-shifted as the reaction time increased indicating decrease in particle size. The TEM images showed that, the particles are small, well dispersed and spherical in shape. The smallest particles with an average particle diameter of 3.76±1.00 nm and 4.09±1.83 nm were obtained at 24h for the 1.0M and 0.5M silver ion precursor solution concentration respectively. The smaller particles produced were attributed to the higher concentration of the reducing saccharides in the reaction system, which in turn increases the formation of stable silver ions in the reaction system. The HRTEM images confirmed the crystalline nature of the material while the FTIR confirmed the stabilisation of the Ag-NPs by the gelatin.