Electrochemical and Spectroscopic Characterization of Surface Sol−Gel Processes

Abstract

3-Mercaptopropyl)trimethoxysilane (MTS) forms a unique film on a platinum substrate by self-assembly and sol-gel cross-linking. The gelating and drying states of the self-assembled MTS sol-gel films were probed by use of electrochemical and spectroscopic methods. The thiol moiety was the only active group within the sol-gel network. Gold nanoparticles were employed to detect the availability of the thiol group and their interaction further indicated the physicochemical states of the sol-gel inner structure. It was found that the thiol groups in the open porous MTS aerogel matrix were accessible to the gold nanoparticles while thiol groups in the compact MTS xerogel network were not accessible to the gold nanoparticles. The characteristics of the sol-gel matrix change with time because of its own irreversible gelating and drying process. The present work provides direct evidence of gold nanoparticle binding with thiol groups within the sol-gel structures and explains the different permeability of "aerogel" and "xerogel" films of MTS on the basis of electrochemical and spectroscopic results. Two endogenous species, hydrogen peroxide and ascorbic acid, were used to test the permeability of the self-assembled sol-gel film in different states. The MTS xerogel film on the platinum electrode was extremely selective against ascorbic acid while maintaining high sensitivity to hydrogen peroxide in contrast to the relatively high permeability of ascorbic acid in the MTS aerogel film. This study showed the potential of the MTS sol-gel film as a nanoporous material in biosensor development.

Characterisation of gold electrodes modified with methyltrimethoxysilane and (3-mercaptopropyl) trimethoxysilane sol–gel processed films

“…Additionally, the presence of SH group in the MPS gel is verified by the S-H stretching band observed at 2555 cm À1 [37,40]. The S-H band indicates that only a fraction of thiol groups reacts with Au and the polymer is composed of Si-O-Si network with OH and C 3 H 6 SH functional groups.…”

“…This was achieved by sol-gel processing of methyltrimethoxysilane (MTMOS) on gold surface premodified with 3-mercaptopropyltrimethoxysilane (MPS). Although, the self assembly of the latter compound on Au [34][35][36], Ag [36] or Pt surface [37] or its application for three dimensional film preparation on gold [38,39] or platinum [40] was already reported according to our knowledge it was not previously used for anchoring silicate film based on other precursor.…”

Synthesis and biomedical applications of aerogels: Possibilities and challenges

“…High overall porosity, good accessibility of pores, high active surface area and possibility to maintain a variety of materials make silica aerogels a potential matrix for the design of biological sensor [197] [245,246]. Ayers et al [196] in their pioneering work, utilized photoluminescence silica-based aerogel as an active element Power et al [65] reported biosensor based on wetted mesoporous silica aerogels, which can be integrated as a scaffold for immobilization and growth of bacteria with a special biological function of their porosity for detection and collection of aerosol viral particles.…”

Ultrasensitive electrochemical immunosensors for clinical immunoassay using gold nanoparticle coated multi-walled carbon nanotubes as labels and horseradish peroxidase as an enhancer

“…(3-Mercaptopropyl) trimethoxysilane (MPTS) is known to form a 3-D structure and is full of thiol tail groups from the hydrolysis process. 23 The thiol group has a strong affinity to Au through the cleavage of the S-H bonds. 24 Because of these thiol groups distributed throughout the network, the colloidal gold nanoparticles can be conveniently self-assembled on the thiol groups which present both inside and on the surface of the network.…”