Carbon-based nanohybrid films on solid substrates for bioanalytical applications

Abstract

The bioanalytical applications of carbon nanomaterials have attacted much research interest to efficiently solve the existing problems by using their unique properties. For bioanalysis, the surface functionalization is a critical step to detect specific target species without interference from nonspecific adsorption of undesired biomolecules. The surface functionalization of solid substrates by forming self-assembled monolayer was achieved with various thiol and silane compounds and the self-assembled monolayer was successfully applied to preparation of mammalian cell arrays by combination with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Based on the surface functionalization techniques, graphene oxide (GO), an oxidized form of graphene with various oxygen-containing functional groups, was immobilized on the solid substrates because GO possesses important properties such as strong UV optical absorption for laser desorption/ionization mass spectrometry (LDI-MS) and surface enhanced Raman scattering (SERS). First, the GO films were hybridized with multi-walled cabon nanotube (MWCNT) by electrostatic adsorption. The resulting GO/MWCNT double layer films showed excellent performance as LDI-MS analysis platform for analysis of small molecules and mouse brain tissue. In addition, the LDI-MS efficiency was further improved by controlling the structure of GO/MWCNT hybrid films through the layer by layer assembly technique. Second, the GO films were reduced to make graphene analogue and hybridized with gold nanostructures by seedless and seed-mediated growth methods. The seedless growth on reduced GO (RGO) films resulted in growth of gold rods with low density but the gold rod showed high SERS activity compared to spherical gold particles. To increase the density of gold rods, the seed-mediated growth was carried out on pyrene ethylene glycol amine (PEA)-functinoalized RGO films. The seed-mediated growth on PEA-RGO films resulted in dense...