title: Distance-Dependent Measurements of the Conductance of Porphyrin Nanorods Studied with Conductive Probe Atomic Force Microscopy.
abstract: Protocols for nanopatterning porphyrins on Au(111) were developed based on immersion particle lithography. Porphyrins with and without a central metal ion, 5,10,15,20-tetraphenyl-21H,23H-porphyrin (TPP) and 5,10,15,20-tetraphenyl-21H,23H-porphyrin cobalt(II) (CoTPP), were selected for study, which spontaneously formed nanorod geometries depending on concentration parameters. The elongated shapes of the nanorods offers an opportunity for successive distance-dependent conductive probe atomic force microscopy (CP-AFM) measurements along the length of the nanorods. To prepare patterns of TPP and CoTPP nanorods, a mask of silica mesospheres was placed on gold substrates to generate nanoholes within an alkanethiol matrix film. The nanoholes prepared by particle lithography with an immersion step were backfilled with porphyrins by a second immersion step. By controlling the concentration and immersion interval, nanorods of porphyrins were generated with one end of the nanostructure attached to gold within a nanohole. The porphyrin nanorods exhibited slight differences in dimensions at the nanoscale to enable size-dependent measurements of conductive properties. The conductivity along the horizontal direction of the nanorods was evaluated with CP-AFM studies. Changes in conductivity were measured along the long axis of TPP and CoTPP nanorods. The TPP nanorods exhibited conductive profiles of an insulating material, and the CoTPP nanorods exhibited profiles of a semiconductor. The experiments demonstrate the applicability of particle lithography for preparing unique and functional surface platforms of porphyrins to measure distance-dependent conductive properties on gold.
authors.affiliation: Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States.
authors.forename: Xianglin
authors.initials: X
authors.lastname: Zhai
authors.affiliation: Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States.
authors.forename: Denzel
authors.initials: D
authors.lastname: Alexander
authors.affiliation: Institute for Micromanufacturing, Chemistry Department, and Physics Department, Louisiana Tech University , Ruston, Louisiana 71272, United States.
authors.forename: Pedro
authors.initials: P
authors.lastname: Derosa
authors.affiliation: Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70803, United States.
authors.forename: Jayne C
authors.identifier: 0000-0003-3446-1780
authors.initials: JC
authors.lastname: Garno
mesh_terms: D006046:Gold / Q000737:chemistry; D018625:Microscopy, Atomic Force; D015394:Molecular Structure; D043942:Nanotubes / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010316:Particle Size; D011166:Porphyrins / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013499:Surface Properties
chemical_list: D009942:Organometallic Compounds; D011166:Porphyrins; D013438:Sulfhydryl Compounds; D006046:Gold; D012822:Silicon Dioxide