Synthesis, Characterization and Conductivity of α-Keggin-type Nanoparticles, Co(en)3PMo12O40·8H2O with Optical Activity

Polyoxometallates Co(en)3PMo12O40·8H2O( ,-)[abbreviated as PMo12-Co( ,-)], nanoparticles were synthesized by the chemical precipitation reaction at room temperature for the first time. They were characterized by means of elemental analyses, IR spectrometry and X-ray diffraction. The images of scanning electron microscopy(SEM) and the results of calculation by using the Scherrer equation for the line widths of the XRD patterns were used to estimate the average particle size of the powder products, which was 40 nm. The results show that the nanoparticle size was affected by starting materials′ concentrations. The particles had a small size and a narrow distribution, when the concentrations of H3PMo12O40·24H2O and Co(en)3I3·H2O were around 1.7×10-4 and 1.0×10-3 mol/L, respectively. When the concentration was increased, there was no significant increase in the particle size, but more polydisperse Co(en)3(PMo12O40)( , -) were obtained. In poly(ethylene glycol)(PEG) with an average molecular weight(MW) of 600 g/mol and containing LiClO4[n(O)/n(Li)=100∶1] as the supporting electrolyte, the conductivity of the composite system increases upon the addition of PMo12-Co( or -) nanoparticles, which was measured by the a.c. impedance technique. The interactions among PEG, LiClO4, PMo12, and Co can be used to explain that the PMo12-Co( or -) nanoparticles could promote the conductivity of the PEG-LiClO4-PMo12-Co system.