Nanoscale functionalization and site-specific assembly of colloids by particle lithography

Numerous studies have demonstrated the bottom-up assembly of complex structures such as colloidal crystals, close-packed aggregates, and even rings and tetramers. In this paper we produce a simple localized and nanoscale charge distribution on the surfaces of individual colloidal microspheres using our technique of "particle lithography". In this technique parts of the microspheres are masked off, while polyelectrolytes (or other molecules) cover the remaining portions of the microspheres. The effectiveness of this process is demonstrated by the accurate and reproducible production of colloidal heterodoublets composed of oppositely charged microspheres. These "colloidal molecules" have the potential for significantly higher information content than previous attempts in the literature. The particle lithography technique is advantageous because it is not limited by the resolution of photolithography or by functionalizing chemistries, and the technique opens the door for complex site-specific functionalization of particles.