Fine tune localized surface plasmon resonance for chemical and biological sensors

Metallic nanoparticles usually exhibit localized surface plasmon resonance (LSPR) due to the collective oscillation of electrons upon light excitation. Different applications require specific LSPR wavelengths and absorbance spectra. The ability to engineer the nanostructure and to tune the location of the LSPR wavelength is very important for the sensing applications. We present a simple but versatile fabrication technique, the oblique angle deposition, to tune the LSPR wavelength of Ag thin films. Oblique angle deposition was used to produce silver nanoparticle films with nominal thickness from 5 nm to 100nm and two deposition angles, 0° and 85°. With increasing thickness, the LSPR wavelength is blue shifted. At the large deposition angle, the LSPR wavelength is blue shifted by 3nm on average with every 5nm thickness increment. The stability of the Ag LSPR substrate under liquid environment has been studied, and a surface passivation method is proposed. Those substrates are capable of detection 10-10 M NeutrAvidin.