(186l) Engineering Nanoparticle Array Patterns for the Study of Molecular Crystallization Under Nanoconfinement

Organic-inorganic nanohybrids that combine and sometimes enhance the functionalities of different materials are promising materials for electronic, optical, and biosensing applications. We present methods to fabricate inorganic nanoparticle arrays. We developed a chemical vapor deposition method to make aminopropyltrimethoxysilane (APTMS) nanopatterns based on colloidal particle lithography. Polystyrene particles of size 30, 300, and 900 nm were used to make lithographic masks on silicon wafer substrates. APTMS reacts with silanol groups on the substrate in the colloidal interstitial space. The reaction and the subsequent pattern are sensitive to the amount of water in the interstitial space. We were able to vary the nanopattern from 2-D arrays of nano-holes, to nano-rings, and to nano-dots. The APTMS nanopatterns were further functionalized with 11-mercaptoundecanoic acid (MUA) protected gold nanoparticles (AuNPs). MUA-AuNPs were used to induce nanorod formation of carboxylic acids including eicosanoic acid (C20A). The presence of the nanoparticles strongly perturbs the self-assembled patterns of carboxylic acids on graphite. We hypothesize that the curvature of nanoparticles prevents tangential crystallization and results in narrow rod-shaped crystals. We demonstrate that the nanoparticle-induced nanorod formation can be widely applies beyond the initial MUA-AuNPs/C20A combination to include organic conductors such as tetrathiafulvalene. Organic crystal network generated on the nanoparticle arrays represents a novel approach to connect and further functionalize nanoparticle-based thin film devices.