Alcohol induced surface charging of colloidal quantum dots for controllable electrophoretic deposition processing

In this work, we report an alcohol-induced surface charging route of colloidal QDs to achieve controllable electrophoretic deposition processing. By adding a fixed amounts of alcohols into a preformed quantum dots solution in non-polar solvents, the colloidal quantum dots can be positively charged, and then deposited on negative electrode under applied electric field. The surface charging of PbSe quantum dots was investigated by zeta potential, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and discrete Fourier transform calculations. It was found that the zeta potential of oleate acid capped PbSe QDs increases from +1.6 mV to +13.4 mV with the amount of alcohol solvent increasing. The alcohol-induced zeta potential increasing can be explained to the electron cloud shift of active hydrogen mediated by intermolecular hydrogen bonds between carboxy acid and alcohol. Considering the influence of surface charging of quantum dots on their dispersibility, we describe the microscopic mechanism of alcohol-induced electrophoretic deposition processing. Furthermore, we developed a size-selective separation protocol by controlling alcohol-induced electrophoretic deposition processing.