Heterostuctures of 4-(chloromethyl)phenyltrichlorosilane and 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine prepared on Si(111) using particle lithography: Nanoscale characterization of the main steps of nanopatterning

Abstract

Nanostructures of 4-(chloromethyl)phenyltrichlorosilane (CMPS) were used as a foundation to attach and grow heterostructures of porphyrins and organosilanes. A protocol was developed with particle lithography using steps of immersion in organosilane solutions to selectively passivate the surface of Si(111) with octadecyltrichlorosilane (OTS). A methyl-terminated matrix was chosen to direct the growth of CMPS nanostructures to fill the uncovered sites of Si(111) to enable spatial confinement of the surface reaction. Silica spheres with a diameter of 500 nm were used as a surface mask to prepare nanoscopic holes within the OTS matrix film. Next, the samples were immersed in solutions of CMPS dissolved in toluene or bicyclohexane. Nanostructures of CMPS formed within the nanoholes, to furnish spatially selective sites for binding porphyrins. The samples were then characterized with AFM to evaluate the height and morphology of the CMPS nanostructures that had formed within the nanoholes of OTS. The samples were then refluxed in a porphyrin solution for selective binding to produce heterostructures. The attachment of porphyrins was evidenced by increases in the height and width of the CMPS nanopatterns. The measurements of size indicate that multiple layers of porphyrins were added. Through each step of the surface reaction the surrounding matrix of OTS showed minimal areas of nonspecific adsorption. The AFM studies provide insight into the mechanism of the self-polymerization of CMPS as a platform for constructing porphyrin heterostructures.

Surface Coupling of Octaethylporphyrin with Silicon Tetrachloride

“…Nanoholes within a film of methyl-terminated OTS was used to furnish nanoscopic containers for depositing Si-porphyrin. In previous studies, we have successfully used OTS as a generic matrix with colloidal lithography to pattern 4-(chloromethyl)phenyl trichlorosilane, 86 polymers, 57 proteins, 61,87 rare-earth oxide nanoparticles, 88 as well as free-base and metallated porphyrins. 89 Methyl-terminated decyltrichlorosilane was used as a resist for patterning OTS by Brownfield et al 79 Patterns of n -docosane, aspirin, and clarithromycin were produced within a matrix of OTS, as reported by Wang et al 80 Beyond colloidal lithography, matrices of OTS have also been used with other nanolithography approaches for patterning organic films to attach carbon nanotubes, 90 metal wires, 91 nanoparticles, 92,93 and proteins.…”