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

In this work, we report alcohol induced surface charging of colloidal quantum dots for controllable electrophoretic deposition processing. By adding a fixed amount of alcohol into a preformed quantum dots solution in non-polar solvents, 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. Based on the results, Zeta potential of oleate acid capped PbSe quantum dots increases from +1.6 to +13.4 mV as the amount of alcohol solvent increases. The alcohol induced Zeta potential increase can be explained by the electron cloud shift of active hydrogen mediated by intermolecular hydrogen bonds between carboxylic 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.