AVS 56th International Symposium & Exhibition
    Nanometer-scale Science and Technology Tuesday Sessions
       Session NS-TuP

Paper NS-TuP13
Photo-patterning of Nitrophenyl-Terminated Self-Assembled Monolayers by using Localized Surface Plasmon

Tuesday, November 10, 2009, 6:00 pm, Room Hall 3

Session: Nanometer-scale Science and Technology Poster Session
Presenter: S. Uenishi, Kyoto University, Japan
Authors: S. Uenishi, Kyoto University, Japan
T. Ichii, Kyoto University, Japan
K. Murase, Kyoto University, Japan
H. Sugimura, Kyoto University, Japan
Correspondent: Click to Email
Patterning of self-assembled monolayers (SAMs) has attracted much attention owing to its potential applications to various microdevices fabrication processes. In particular, photochemical micropatterning of SAMs is of special interest, since it can be adopted into photolithography which has been the most successful microprocessing technology with high productivities. Recently, photoinduced reduction of nitrophenyl-terminated SAMs on silver surfaces has been reported [1], where nitrophenyl groups were converted to phenylamine groups by visible light irradiation. This must be prominently useful technique in the field of biotechnology and photochemistry, because some biomolecules and nanoobjects of noble metals can be adsorbed on amino-terminated surfaces. However, visible light irradiation is difficult to be applied to nanoscale patterning owing to diffraction limit. This can be overcome by using localized surface plasmon with nanoobjects of noble metals. Electromagnetic field relative to the surface plasmon is localized in a few tens of nanometer, which is independent of light wavelength. In this study, we demonstrated photoinduced reduction from nitrophenyl groups to phenylamine groups by using direct light irradiation and localized surface plasmon.

First, 4-nitrobenzenthiol (NBT) SAMs were irradiated with visible light through photomask. The SAMs were formed on gold substrates by immersing the substrate in ethanol solution of NBT (1 mM) at room temperature for 24 hours. Photochemical changes were detected as surface potential shift using Kelvin-probe force microscopy. The surface potential of the irradiated regions was positively shifted by approximately 10 mV. This potential change suggests some photochemical changes induced by the light irradiation on the SAM. Water contact angle measurement and X-ray photoelectron spectroscopy (XPS) were also applied to the SAMs which are irradiated with the light through plain glass plate in these cases. Water contact angle increased from about 45 degrees to about 50 degrees after visible light irradiation. Proof of the photoinduced reduction was not detected by the XPS measurement probably because X-ray irradiation also promoted reduction of the nitrophenyl groups. These results suggest some changes induced on the surfaces by the light irradiation.

[1] M. Naoki, S. Takahiro, O. Masatoshi and U. Isamu, Chemistry Letters, 24, 145 (1994).