A Nanoscale Optical Biosensor:  The Long Range Distance Dependence of the Localized Surface Plasmon Resonance of Noble Metal Nanoparticles

The elucidation of the long range distance dependence of the localized surface plasmon resonance (LSPR) of surface-confined noble metal nanoparticles is the aim of this work. It was suspected that the linear distance dependence found in CH3(CH2)xSH self-assembled monolayer (SAM) formation was the thin shell limit of a longer range, nonlinear dependence. To verify this, multilayer SAM shells based on the interaction of HOOC(CH2)10SH and Cu2+ were assembled onto surface-confined noble metal nanoparticles and were monitored using UV−visible spectroscopy. Measurement of the LSPR extinction peak shift versus number of layers and adsorbate thickness is nonlinear and has a sensing range that is dependent on the…