(102c) Organic Nanoparticle Deposition in Organosilane Nano-Arrays

The ability to make nano-arrays enables high-throughput screening and nanofluidics. This paper describes a method to generate octadecyltrichlorosilane (OTS) nano-arrays on oxidized silicon wafers for nanoconfining small organic molecules. Particle lithography was carried out on 300 and 900 nm polystyrene particle array templates by chemical vapor deposition of OTS, which reacted with the substrate in the water menisci to form a ring pattern. We discovered reaction conditions that favor bulk polymerization resulting in ~14 nm thick rings for the 900 nm particles and ~9 nm thick rings for the 300 nm particles, both of which exceed the OTS monolayer thickness of 2.6 nm. It is estimated that a 1×1 cm² wafer (900 nm particles) contains more than 100 million ordered “nano-flasks” with volume ~3×10^-10 nL. The nano-array pattern is stable against common organic solvents thus allowing repeated use in solution crystallization screening experiments. Several hydrophobic compounds including docosane and aspirin were deposited on the nano-array pattern for the study of nanoconfinement effect on molecular crystallization. The conditions for preferential deposition of the compounds insider the “nano-flasks” will be discussed. The resultant organic nanoparticle arrays on the nanopattern were characterized by AFM and field-emission SEM.