Structure and growth mechanism of self-assembled monolayers of metal protoporphyrins and octacarboxylphthalocyanine on silicon dioxide

Abstract

In this work, we studied the structure and the growth of various conjugated macrocyclic SAMs (two protoporphyrins ZnPP and FePP, and one phthalocyanine ZnPc(COOH) 8 ) on silicon dioxide previously functionalized by aminopropyltrimethoxysilane (APTMS) for covalent grafting of macrocycles on the surface. The samples were characterized by atomic force microscopy (AFM), ellipsometry, contact angle measurements, Fourier transform infrared (FTIR) and UV-visible spectroscopy. A growth model of macrocycle layers in three steps was established from ellipsometry and UV-visible results at various deposition times. Firstly, a fast adsorption of macrocycles occurs on the surface in a disordered way followed by a rearrangement phase. Then, the layers get denser by adsorption of supplementary macrocycles on the surface. Spectroscopic and morphological analyses reveal a specific structure for each deposited macrocycle. The size of the macrocycle core and nature of the metallic atom are shown to be key factors which govern orientation and assembly of macromolecules on the surface. Finally, the essential issue of film stability in an ambient atmosphere has been addressed.

Protoporphyrin IX‐Functionalized AgSiO2 Core–Shell Nanoparticles: Plasmonic Enhancement of Fluorescence and Singlet Oxygen Production

“…The functionalization of the SiO 2 shell with PpIX was achieved by mixing the freshly synthesized AgSiO 2 NPs with PpIX stock solution. The average PpIX payload, determined on the basis of the PpIX removed from the supernatant after sample cleaning, was calculated as between 0.82 and 1.58 PpIX molecules per nm 2 , which is in agreement with values reported in the literature . According to Cherian and Wamser, approximately 0.43 molecules of tetracarboxy‐porphyrin would be supported per surface area unit (nm 2 ) when porphyrin is adsorbed in a flat geometry, while around 1.66 molecules per nm 2 corresponds to the porphyrin adsorption in an upright orientation .…”

Surface Coupling of Octaethylporphyrin with Silicon Tetrachloride

“…By incorporating thiols in peripheral groups of the molecular design, porphyrins can be linked to metal surfaces by chemisorption. − A silicon substrate was functionalized with 3-aminopropyl trimethoxysilane (APTMS) to link 5,10,15,20-tetrakis-(4-aminophenyl)­porphyrin to surface amines using a urea coupling reaction with 1,4-phenylene diisocyanate . Zinc and iron porphyrins were attached to silicon substrates functionalized with APTMS by forming an amide bond between the conjugated macrocycle and surface amino groups that were activated by carboxydiimidazole . The nitrogen of pyridyl moieties was linked to chloro groups of chloromethylphenylsilane to attach tetrapyridyl porphyrin (TPyP) to functionalized Si(100) substrates .…”

“…42 Zinc and iron porphyrins were attached to silicon substrates functionalized with APTMS by forming an amide bond between the conjugated macrocycle and surface amino groups that were activated by carboxydiimidazole. 43 The nitrogen of pyridyl moieties was linked to chloro groups of chloromethyl- phenylsilane to attach tetrapyridyl porphyrin (TPyP) to functionalized Si(100) substrates. 44 Cobalt tetraphenyl porphyrins were functionalized with peripheral groups of amines for binding to gold substrates, as reported by Lokesh et al 45 As a strategy to covalently bind porphyrin to surfaces of Si(100) and quartz substrates, multilayer thin films were prepared with TPyP by coating the surface with [p-(chloromethyl)phenyl] trichlorosilane as a coupling layer and then assembling sequential layers with linkers connected to pyridyl groups of the porphyrin ring.…”

Phthalocyanine Photoregeneration for Low Power Consumption Chemiresistors

“…In either case, the interaction results in a change of resistance (and impedance) that can be correlated with analyte concentration . Regarding the gas-sensing characteristics of Pc films, their morphology also plays a significant role . The most familiar phthalocyanine polymorphs are α, β, χ, and τ.…”

“…19 Regarding the gas-sensing characteristics of Pc films, their morphology also plays a significant role. 20 The most familiar phthalocyanine polymorphs are α, β, χ, and τ. The first two, the α and β forms, are common in phthalocyanine thin films.…”