Particle lithography was applied to successfully to create complex heterostructures at the nanoscale. Experiments with atomic force microscopy demonstrate capabilities to reproducibly generate surface platforms with spatial selectivity for the attachment of multicomponent nanopillars. Images of the main steps of the surface reactions were captured <i>ex situ</i> with AFM to reveal changes in the growth and morphology of the nanopillars. A protocol was developed to confine and pattern the growth of porphyrins to specific sites of designed nanopillars of 4-chloromethylphenyltrichlorosilane (CMPS). Steps of immersion particle lithography were developed to selectively passivate a surface of Si(111) with octadecyltrichlorosilane (OTS) to prepare a test platform of nanoholes. The exposed sites within the nanoholes were used direct and confine the surface assembly of CMPS nanopillars. Silica mesospheres were used as a surface mask to prepare nanoholes within a passivated OTS matrix. Areas surrounding the CMPS nanopillars were passivated with the methyl-terminated organosilane to prevent nonspecific binding of CMPS. After OTS nanopores were generated and subsequently characterized via AFM, the samples were immersed in a solution of CMPS prepared with toluene. By controlling the concentration, solvent, temperature and time, nanopillars of defined height and morphology were generated within the exposed nanoholes. The CMPS nanopillars were characterized with tapping-mode AFM. The samples were then refluxed in a porphyrin solution to facilitate the attachment of porphyrins. The attachment of porphyrins to CMPS nanopillars was evaluated by measuring changes in the height and width of nanopillars. Through each step of the surface reactions, the surrounding OTS matrix revealed minimal nonspecific adsorption. An increase in the average height of nanopillars was observed after addition of the porphyrin, which corresponds to multilayers of porphyrin macrocycles being attached. Porphyrins have practical applications in dye-sensitized solar cells, flat screen displays and as commercial dyes.

Localization of porphyrins to spatially confined sites of self-polymerized 4-(chloromethyl)phenyltrichlorosilane studied with atomic force microscopy

251st National Meeting (2016)

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