Surface modification of 2- and 3-dimensional substrates

Abstract

Surface modification of substrates has been widely implemented in various areas including materials sciences, nanotechnology, and biotechnology. In particular, encapsulation of individual nanoparticles, surface modification for nanoparticles, has gained great attention as a method for both stabilizing nanoparticles and tailoring surface properties of nanoparticles. Especially, the encapsulation of nanoparticles with silica shells is advantageous for bioconjugation and applications to (nano)biotechnology. In chapter 1 and 2, we reported a method for constructing gold nanoparticle (AuNP)/silica core/shell hybrid structures by biomimetic silicification of silicic acids. The procedure in chapter 1 consisted of surface-initiated, atom transfer radical polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) from AuNPs and biomimetic polycondensation of silicic acids by using poly(DMAEMA) as a synthetic counterpart of silaffins that were found in diatoms. The resulting AuNP/silica hybrids were characterized by Fourier-transform infrared spectroscopy, energy dispersive X-ray spectroscopy, UV-vis spectroscopy and transmission electron microscopy. In addition, the immobilization of biological ligands onto the hybrids was investigated for potential applications to biotechnology. As a model ligand, biotin was attached onto the AuNP/silica hybrids through substitution reaction and Michael addition reaction, and the attachment was confirmed by fluorescence microscopy after complexation with fluorescein-conjugated streptavidin. In chapter 2, we formed ultrathin (~1.5 nm) silica shell-coated nanomaterials by using self-assembled monolayers as organic templates for silicification. The procedure consisted of simple two steps: immobilization of a thiol-terminated imidazolium ion onto AuNPs and biomimetic polycondensation of silicic acids. The resulting AuNP/silica hybrids were characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, and U...