Synthesis of Hybrid Colloidal Nanoparticles for a Generic Approach to 3D Electrostatic Directed Assembly: Application to Anti-Counterfeiting

Abstract Hypothesis: The capability of making 3D directed assembly of colloidal nanoparticles on surfaces, instead of 2D one, is of major interest to generate, tailor, and enhance their original functionalities. The nanoxerography technique, i.e. electrostatic trapping of nanoparticles on charged patterns, showed such 3D assembly potentialities but is presently restricted to polarizable nanoparticles with a diameter superior to 20 nm. Hence, it should be possible to exploit a generic approach based on hybrid systems using larger nanoparticles as cargos to anchor smaller ones. Experiments: A synthesis of hybrid nanoparticles in a raspberry-like configuration was performed using 50 nm SiO2 nanoparticles and photoluminescent 3-5 nm InP@ZnS (visible emission) or PbS (infrared emission) nanoparticles. Complete topographical and photoluminescent characterizations were carried out on hybrid nanoparticle patterns assembled by nanoxerography and systematically compared to patterns obtained from single photoluminescent nanoparticles. Findings: The synthesis approach was generic. Every hybrid nanoparticle system has led to 3D assemblies with improved photoluminescent signals compared to 2D assemblies. Straightforward applications for anti-counterfeiting were illustrated. The versatility of the proposed concept is expected to be applied to other nanoparticles to make the most of their magnetic, catalytic, optical etc. properties in a wide range of applications, sensors and devices.