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.

Controllable Synthesis and Effects of Porphyrin Copper Nanostructures on Photoelectric Properties

“…Currently, our research on photoelectric materials is mainly focused on the inorganic semiconductor materials, , which are often limited in application due to inefficient light absorption, and so forth. Organic semiconductors have gradually become a research point of special interest and have increasingly fascinated researchers due to their fast light response, low cost, easy processing, and so forth. , In addition, organic materials possess diverse structural compositions and properties, which allow us to design their molecular structure for achieving the desired performance and significantly promote their wide application in the photoelectric field. − Porphyrins are an important class of molecular semiconductors that have been designed into a variety of functional materials for photoelectric conversion, conductive sensing, photolysis of water, , and catalysis , owing to their unique electronic structure and optoelectronic properties. Unfortunately, the short lifetime and radius of Frenkel excitons in porphyrin-based semiconductors are the major impediments for their utilization in the photoelectric process.…”

“…9,10 In addition, organic materials possess diverse structural compositions and properties, which allow us to design their molecular structure for achieving the desired performance and significantly promote their wide application in the photoelectric field. 11−13 Porphyrins are an important class of molecular semiconductors that have been designed into a variety of functional materials for photoelectric conversion, 14 conductive sensing, 15 photolysis of water, 16,17 and catalysis 18,19 owing to their unique electronic structure and optoelectronic properties. Unfortunately, the short lifetime and radius of Frenkel excitons in porphyrin-based semiconductors are the major impediments for their utilization in the photoelectric process.…”

Applying SAXS to study the structuring of Fe3O4 magnetic nanoparticles in colloidal suspensions

“…In microscopy techniques, the sample is diluted and dropped in a sample-holder and dried to evaporate the liquid matrix, inducing particle aggregation in a different way than that expected in concentrated suspensions. A better alternative could be Cryo-TEM, in which the sample is quickly frozen using liquid nitrogen, keeping the MNP structuring [5], nevertheless, as with TEM, the sample must be diluted, diminishing the influence of the distancedependent interactions among particles [6][7][8].…”

Analyses of natural frequency and electromechanical behavior of flexoelectric cylindrical nanoshells under modified couple stress theory

“…Piezoelectric materials in nano-scale also reveal size effects (Zhai et al., 2017). In order to incorporate the electro-mechanical behavior for piezoelectric nanostructures, Wang et al.…”