Green synthesis and characterization of gold nanoparticles for optical biosensing applications

Abstract The goal of the current study is to show how to use green synthesis to create gold nanoparticles, and present a method to determine the dielectric constant of nanoparticles solutions that are used in optical biosensing applications. Green tea (Camellia sinensis) leaf extract was used as a reducing agent to obtain nanoparticles. The gold nanoparticles were synthesized for different concentrations of green tea, directly impacting the particle's size and refractive index. The experimental data from the absorption spectroscopy of colloidal solutions and the zeta test potential were used to determine the dielectric parameters of the gold nanoparticles. Three theoretical expressions proposed for the electrical permittivity have been used to estimate the measured absorption coefficient. The behavior of the estimated absorption coefficient curves is quite similar to the curves obtained from the UV-Vis spectrophotometry. The absolute error of the peak value of the absorption coefficient is less than 1.5\% in the case of the theoretical expression that most accurately describes the dielectric constant of the colloidal solution of gold nanoparticles.