Study on electrophoretic deposition of size-controlled quinacridone nanoparticles

We have prepared quinacridone (QA) colloids with various particle sizes (25-120 nm) and different crystalline phases by nanosecond laser ablation of its microcrystalline powder dispersed in water and fabricated the prepared colloidal particles into homogeneous films on an indium-tin-oxide electrode by an electrophoretic deposition (EPD) method. The nanoparticle-assembled films consist of closely packed nanoparticles and many nanosized pores. We evaluated the porous nature of the film by scanning electron microscopy observation and by measuring the film thickness dependence of the absorption. It was found that the film morphology is sensitive to the applied bias, and the optimum bias for the QA colloid was determined to be about 10 V/cm. We also demonstrated that organic thin films with different grain sizes and crystalline phases can be fabricated arbitrarily by combining the EPD method with nanoparticle preparation by laser ablation.