Protocols were developed for nanopatterning porphyrins i.e. nanorods and nanodots on Au(111) using immersion particle lithography. Porphyrins with and without a central metal ion, 5,10,15,20-tetraphenyl-21H,23H-porphine (TPP) and 5,10,15,20-tetraphenyl-21H,23H-porphine cobalt(II) (TPC) were patterned as surface test platforms for conductive probe-atomic force microscopy (CP-AFM). A film of silica mesospheres was used as a surface mask to prepare patterns of nanopores within an alkanethiol matrix film. When the surface mask of mesospheres was rinsed away, a periodic arrangement of nanopores is produced. The uncovered circular areas within the nanopores are exposed gold substrate. The nanopores within a methyl-terminated alkanethiol matrix were filled by immersing the sample in a solution of porphyrins. By controlling the concentration and immersion interval, nanorods or nanodots of porphyrins were generated. Individual nanostructures of porphyrins were spatially isolated into well-defined, nanoscale arrangements directed by a template film of the thiol monolayer prepared with particle lithography. Regular geometries with defined spacing can be reproducibly generated for surface test platforms on Au(111). Surface structures of porphyrin nanorods and nanodots exhibited differences in dimensions at the nanoscale, which enabled size-dependent measurements of conductive properties. The conductivity along the horizontal direction of the nanorods was evaluated using CP-AFM. Changes in conductivity were measured along the long axis of nanorods. The TPP nanorods exhibited conductive behavior of a rectifier. The TPC nanorods exhibited profiles that are typical of a semi-conductor. The conductivity in the z-direction was measured for test platforms of porphyrin nanodots formed by TPC or TPP, exhibiting semi-conductive I-V curves. Wire-like conductive I-V curves were detected with cobalt-coordinated TPC nanodots. The applicability of particle lithography will be demonstrated for preparing surface platforms for the measurement of conductive properties at the nanoscale. Fundamental knowledge of the conductivity of porphyrins at the nanoscale is applicable for the manufacture and testing of molecular devices.

Size-dependent measurements with spatially confined nanoclusters of porphyrins using conductive probe atomic force microscopy

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.