Electrochemical behaviour of layer-by-layer constructed of silver nanoparticles and Dawson-type polyoxometalates

Dawson-type polyoxometalate (POM), [(n-C3H7)4N]4S2W18O62 [S2W18], was co-assembled with silver nanoparticles (AgNps) into a multilayer film on the surface of a glassy carbon electrode by using a layer-by-layer approach. The systematic growth of the multilayer film was monitored by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The [S2W18]- AgNps multilayers exhibited excellent redox activity and good stability towards multiple redox cycling and thin layer behaviour up to 100 mV/s. CV of the multilayer film showed two redox peaks corresponding to the W units present in the POM structure. The slope values of the pH plot suggesting ca. 0.2 and 0.6 protons were related to processes I (one electron transfer) and II (two electron transfer), respectively. The multilayers were found to be highly conductive due to the presence of the nanoparticles as inferred by EIS and resulting charge transfer resistance values obtained for the layers.