Novel Size-Tunable and Straightforward Ultra-Small Nanoparticle Synthesis in a Varying Concentration Range of Glycerol as a Green Reducing Solvent.

Despite all the possibilities available so far for the synthesis of nanoparticles (NPs), synthesizing ultra-small (<10 nm) monodispersed particles is still demanding. Getting a particular size with a straightforward method is a trial-and-error approach. To explore this prospective, in the current study, we have introduced a protocol which offers a varying concentration range of glycerol to successfully generate the NPs of repeatable and consistent particle size in each synthesis, thus giving an alternative from lengthy tentative preparations and/or testing protocols. Since synthesizing controlled sized nanoparticles in aqueous medium is somewhat difficult as the balance of particle growth and nucleation is challenging to control, herein, we used a polyol method with glycerol both as a solvent medium as well as reducing species for silver nitrate, as an example model ion source, to execute the nanoparticle synthesis. In order to maintain the stability of the synthesized NPs, polyvinylpyrolidone (PVP) was added as a stabilizer. The synthesis, monodispersity, and stability were confirmed using techniques such as UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), and X-ray powder diffraction (XRD), while morphological analysis and ultra-small size validation were conducted using TEM, SEM, and AFM. Interestingly, in the various concentrations of glycerol solution used (10-100%), we have observed a tunable linear size range to obtain ultra-small nanoparticles (<10 nm) up to 60% glycerol, while further increasing the glycerol component increased the size approximately to ∼160 nm, providing tunable properties in this synthesis procedure. Hence, this study provides a distinct possibility to obtain ultra-small nanoparticles with a tunable size feature for further applications in numerous fields.