Comparative analysis of response modes for gold nanoparticle biosensor based on localized surface plasmon resonance

The theoretical comparison of possible response measurement techniques for a biosensor based on localized surface plasmon resonance (LSPR) in spherical Au nanoparticle was made. The methods for measuring LSPR response considered differed in the treatment of the change of light extinction spectrum along the wavelength and extinction coordinate axes upon the formation of dense biomolecular monolayer on the surface of the sensitive element. In addition, the transformation of the extinction LSPR band with increase of the nanoparticle radius from 5 to 125 nm was investigated towards the optimization of LSPR response for dipolar and quadmpolar LSPR extinction peaks. A novel method for the measurement of wavelength shift H-top(+) was introduced and top demonstrated to be more effective for estimation of the LSPR biosensor response as compared to commonly measured extinction peak shift Delta lambda(max). These techniques were proved to produce maximal LSPR response when large-size Au nanoparticle (with a radius of 125 nm) was used as a sensitive element of biosensor. The preferable mode of extinction difference measurement turned out to be V-right, which is carried out at a wavelength of the extreme extinction spectrum derivative on a right slope of the LSPR peak. For this method, optimal nanoparticle radii were found to be about 40 nm for the dipolar LSPR peak and near 100-105 nm for the quadrupolar one.