DPV Study on Platinum Core-Shell Nanoclusters

Nanoparticles whose properties depend on their size are, in purely scientific terms, fascinating. Large (>4 nm) metal ones have properties like those of bulk metals, whereas small ones exhibitmolecule-like properties such as HOMO-LUMO gaps. In between, one finds quantized capacitors. Size dependent electrochemical behavior of nanoclusters has been investigated by voltammetry at nanoscale. Due to the high sensitivity of differential pulse voltammetry (DPV) todetect very small faradaic current, this technique is considered as a method of choice in this research. In this regime of nanoparticle voltammetry, the MPCs behave as quantum capacitors. It means that the MPCs behave as multivalent redox species during charge transfer at nanoscale asthe injection of charge to the cores is quantized. Because the quantized charging currents of the clusters are diffusion controlled, their voltammetric behavior is proportional with their size. CV/DPV electrochemical characterization of fractionated nanoclusters approves observation of Quantized Double Layer (QDL) phenomena which is detected as a fingerprint on the size of aspreparednanoclusters. Long-term stability of nanoclusters has been checked after even one year at room temperature. Chemically synthesized platinum nanocluster is fractionated in a dispersantand then the solid phase repeatedly separated. Voltammetry behaviour of finalized dispersionseriously can be attributed to the size of generated nanoclusters. Quantized capacitance charging of Pt nanoclusters so called Monolayer Protected Clusters (MPC) has been frequently observedwhich confirms the nanometric size of as-prepared nanoclusters. The equally spaced peaks in CV and DPV arise from successive, quantized (single-electron) capacitative charging of ensembles of individual cluster cores (i.e., electrochemical ensemble Coulomb staircase charging). The final application of this ultrafine grained nanostructured material is in catalysis, energy storage and conversion.

کلیدواژه ها:

Monolayer Protected Clusters (MPC) ، Electrochemical Quantized Charging