Micromixer: An Effective Tool for the Production of Sub-Nanosized Noble Metal Particles

Abstract

This paper demonstrates the functionality of a simple and convenient microfluidic method in synthesizing a series of poly(vinylpyrrolidone) (PVP) stabilized nanoparticles (NPs) of various novel metals (Pt, Pd, Ru, Rh, Ag, and Au) with an average diameter of [Formula: see text]2 nm. In this method, the use of microfluidic mixture provided a homogenous mixing of the metal precursors and reducing agent nearly at the molecular level, that yield monodispersed sub-nanosize NPs. Core diameters of the produced NPs determined by transmission electron microscopy (TEM), were [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text][Formula: see text]nm for Pt, Pd, Ru, Rh, Ag and Au NPs, respectively. Of them, Pt NPs were detailed characterized. The obtained Pt NPs were found to have fcc crystal structure with 1.2 nm crystalline size which is very similar to the corresponding TEM result. The efficiency of the synthesis of NPs by micromixer was compared with batch/NaBH4 reduction method for the Pt NPs. It was found that in batch method the as-prepared NPs decreased the reducing ability of NaBH4 by catalytic degradation. In contrast, the micromixer could separate the produced metal NPs from the reaction system soon after the formation of NPs and enables feeding the fresh NaBH4 solution throughout the synthesis. Fourier Transform Infrared (FTIR) spectrometry measurements of adsorbed [Formula: see text]CO molecules on Pt NPs showed that the NPs surface were negatively charged with a high population of edge and vertices atoms.