Suchergebnisse

We investigate the effect of the cross-sectional profile of an array of metallic nanowires on the feasibility of a localized surface plasmon resonance (LSPR) biosensor. Calculations were performed using rigorous coupled-wave analysis with an emphasis on the extinction properties of the LSPR structure. The results indicate that the nanowire structure, particularly that of a T-profile, delivers an extremely linear sensing performance over a wide range of the target refractive index with much enhanced sensitivity. The extinction-based LSPR structure also involves a relatively large dimension and thus is expected to provide a feasible biosensor using current semiconductor technology. ; This work was supported by the Science Research Center and Engineering Research Center program of the Ministry of Science and Technology of the Korea Science and Engineering Foundation (KOSEF) (R11-2000-075- 01001-1). D. Kim acknowledges the support by KOSEF through the National Core Research Center for Nanomedical Technology (R15-2004-024-00000-0) and by the Korea Research Foundation Grant funded by the Korean government (MOEHRD) under KRF-2005-205-D00051.

A localized surface plasmon resonance (LSPR) biosensor using surface relief nanostructures was investigated to evaluate the importance of target localization on the sensitivity enhancement. The LSPR device was modeled as periodic metallic nanowires with a square profile on a gold film and the target as a self-assembled monolayer in buffer solution. The numerical results using rigorous coupled-wave analysis and the finitedifference time domain method demonstrated localized plasmonic fields induced by the surface nanostructure from which the effect of target localization on the sensitivity was quantitatively analyzed. Interestingly, it was found that target localization on nanowire sidewalls improves sensitivity significantly because of strong overlap with localized plasmonic fields. An LSPR structure optimized for a localized target on sidewalls provides sensitivity enhancement per unit target volume by more than 20 times in water ambience. ; This work was supported by the Korea Research Foundation grant funded by the Korean Government Basic Research Promotion Fund (MOEHRD)-(KRF-2008-331- D00229). D. Kim acknowledges support by the Korea Science and Engineering Foundation (KOSEF) through the National Core Research Center for Nanomedical Technology (R15-2004-024-00000-0), KOSEF 2007-8- 1158, and R01-2007-000-20821-0 funded by the Korean Government Ministry of Science and Technology (MOST). Partial support was provided by the "System IC 2010" project of Ministry of Knowledge Economy and by the MEMS Research Center for National Defense funded by the Defense Acquisition Program Administration under 2006-MM-41-5ND0600407. S. M. Jang and S. J. Kim were supported by the KOSEF through the Nano Bioelectronics and Systems Research Center (NBS-ERC) at Seoul National University

S. M. Jang and S. J. Kim thank the support by a grant of the Korea Healthcare technology R&D Project, Ministry for Health, Welfare & Family Affairs, Republic of Korea(A084359) and the support by the Korea Science and Engineering Foundation (KOSEF) through the Nano Bioelectronics and Systems Research Center (NBS-ERC) at Seoul National University. K. M. Byun thanks the support by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD, Basic Research Promotion Fund) (KRF-2008-331-D00229). D. Kim thanks the support by the Korea Science and Engineering Foundation (KOSEF) through National Core Research Center for Nanomedical Technology (R15-2004- 024-00000-0) and KOSEF 2007-8-1158. D. Kim was also supported by "System IC 2010" project of Ministry of Knowledge Economy and by the IT R&D program of MIC/IITA [2007-S001-01, Development of Implantable System Based on Biomedical Signal Processing].

We have experimentally confirmed sensitivity enhancement of a nanowire-based surface plasmon resonance (SPR) sensor structure. Gold nanowires with periods of 200 and 500 nm were fabricated, respectively, by electron-beam and interference lithography on a gold/SF10 substrate. Sensitivity enhancement was measured to be 44% compared with a conventional thin-film-based SPR structure for nanowires of 200 nm period and 31% for 500 nm when evaluated using ethanol at a varied concentration. This result is consistent with numerical data. Surface roughness is responsible for sensitivity reduction by more than 10%. More significant sensitivity improvement can be achieved by inducing strong localized plasmon coupling with finer nanowires ; This work was supported by the Korean Science and Engineering Foundation (KOSEF) through National Core Research Center for Nanomedical Technology (R15-2004-024-00000-0) and by the Korea Research Foundation Grant funded by the Korean Government [Ministry of Education and Human Resources Development (MOEHRD)] under KRF-2005- 205-D00051. K. M. Byun and S. J. Kim acknowledge support by the SRC/ERC program of Ministry of Science and Technology/KOSEF (R11-2000-075- 01001-1).

We have investigated the effect of surface roughness on the sensitivity of conventional and nanowire-based surface plasmon resonance (SPR) biosensors. The theoretical research was conducted using rigorous coupledwave analysis with Gaussian surface profiles of gold films determined by atomic force microscopy. The results suggest that, when surface roughness ranges near 1 nm, the sensitivity of a conventional SPR system is not significantly affected regardless of the correlation length. For a nanowire-based SPR biosensor, however, we have found that the sensitivity degrades substantially with decreasing correlation length. In particular, at a correlation length smaller than 100 nm, a random rough surface may induce destructive coupling between excited localized surface plasmons, which can lead to prominent reduction of sensitivity enhancement. ; This work was supported by the Korea Science and Engineering Foundation (KOSEF) through the National Core Research Center for Nanomedical Technology (R15-2004- 024-00000-0) and also by the Korea Research Foundation (KRF) grant funded by the Korean Government, the Ministry of Education and Human Resources Development (MOEHRD), under KRF-2005-205-D00051. K. M. Byun and S. J. Kim acknowledge support by the Engineering Research Center (ERC) program of the Ministry of Science and Technology (MOST)/KOSEF (R11-2000-075- 01001-1). We appreciate Hyun Seok Lee and Professor Kyung Hwa Yoo for kindly providing assistance for the AFM measurements.