자기조립 방법을 이용한 할로이사이트 나노튜브의 표면개질

Abstract

Surface modification of halloysite nanotubes (HNTs) were carried out using self-assembled monolayer (SAMs) and layer-by-layer (LbL) deposition techniques. Inner and outer surfaces of HNT can be modified by the adsorption of organic molecules with phosphoric acid and silane functional groups. Octadecyltrimethoxysilane (ODTMS), octadecylphosporic acid (ODPA) and (3-aminopropyl)triethoxysilane SAMs-modified HNTs were investigated by Fourier transform infrared spectrometer, Transmission electron microscopy, and Brunauer Emmett Teller surface area analysis. The FTIR spectra of CH2 vibration at 2918 cm-1 and 2850 cm-1 shows HNTs modified with ODPA and ODTMS from their long alkyl chain. LbL self-assembly is one of the powerful methods for fabricating multilayer thin films on inorganic substrates. In this study, dopamine-modified hyaluronic acid (HA_Dopa) and polyethylenimine (PEI) multilayer was built on the surface of silicon-based substrates such as Si wafer, quartz and HNT outer surface. LbL method is based on the successive adsorption of polyanions and polycations via electrostatic interactions and hydrogen bonding. Hyaluronic acid (HA) is a natural polyanions that plays essential role in initiating of the biological reactions. Dopamine contains the catechol functional group, which forms strong interaction with a variety of substrates via covalent or noncovalent bonds. With this advantage, it is possible to produce biocompatible multilayer films using LbL technique. Multilayer films consisting of PEI and HA_Dopa were utilized as bio-inspired heavy metal sensitive films. The formation of multilayer films of conjugate HA_Dopa and PEI can produce surfaces with distinct properties, when compared with the conventional HA and PEI. The surface morphology and formation of HA_Dopa and PEI multilayer films by the LbL technique were investigated by means of atomic force microscopy and UV/Visible spectroscopy. It was demonstrated that the palladium ions are effectively captured in these multilayer films, and it was confirmed by the UV/Visible spectroscopy. The captured palladium ions on HNT are reduced by reducing agent, resulting in the formation of metallic palladium nanoparticles. Result from x-ray diffraction analysis, a weak peak is observed at 40.1°, corresponding to (111) diffraction of palladium. Those results indicate that palladium salts (Pd(II)) have been reduced to metallic Pd(0), which is embedded HNT as nanoparticles.