Highly ordered nanoparticle monolayer deposition on substrate using ester bond reaction

Abstract

Nanoparticle monolayer on the substrate has unique properties than individual nanoparticle for collective effect from the highly ordered structure. Up to now, there were many methods proposed, solvent interface deposition or DNA mediated deposition, to form gold nanoparticle monolayer on the substrate. Recently, stability (solvent, pH level, and temperature) have been issued for expanding the scope of nanoparticle monolayer on the substrate. In this thesis, the ester bond was suggested to synthesize a highly stable gold nanoparticle monolayer on the substrate. Monodisperse 8.8nm diameter size spherical gold nanoparticle was functionalized as carboxylic acid and counter functional group (alkyl chloride) ligand attached to the gold-coated wafer. TBAF, a weak base, was used as a catalyst to form ester bond between carboxylic acid-functionalized 8.8 nm gold nanoparticle and alkyl chloride functionalized gold-coated wafer. From the Small-angle X-ray scattering measurement and scanning electron microscope, gold nanoparticle monolayer formed a hexagonally packed structure based on hydrophobic interaction and esterification. To best our knowledge, this is the first report for the gold nanoparticle monolayer deposition using esterification. The covalent bond between molecules could be expected to give high solvent stability on gold nanoparticle monolayer. So that, solvent stability (DMF, Ethanol, THF, Toluene) and high-temperature stability test was operated by SAXS measurement. In summary, a highly ordered gold nanoparticle monolayer was deposited on the functionalized substrate by esterification between functionalized gold nanoparticle and substrate. Cause of highly stable covalent bonds, gold nanoparticle monolayer has high stability and it would have a high potential for catalyst, electrode, and sensor.