Study On The Biosensor Based On Local Surface Plasmon Resonance (LSPR) Of Gold Nanoparticles

Local surface plasmon resonance (LSPR) of noble metallic nanoparticles is related to the size, appearance, distance, refractive index and so on. It can be used in biosensor area due to their advantages of label-free, high sensitivity, real-time and rapid detection.In this paper, we developed a synthetic method to controllable prepare metallic nano-particles by electrolyzing hydrogen tetrachloroaurate (HAuCl4). Gold nanospheres for average diameter in the range of 25-95 nm were directly deposited onto the indium tin oxide (ITO) glass surface by cyclic voltammetric method. The GNPs on ITO substrate were characterized by means of scanning electron microscopy (SEM) and UV-vis spectroscopy. The three different sizes of gold nanospheres for average diameter of 30, 50, 95 nm were used to investigate the changes of localized surface plasmon resonance (LSPR) properties due to small changes in the refractive index (RI) of the surrounding medium close to the particle surface. Results demonstrated that the sensitivity of refractive index sensor increased as gold nanoparticles became larger. The sensitivity of the 30 nm gold nanosphere was 74nm/RIU. The sensitivity of the 50nm gold nanosphere was 103nm/RIU, and the sensitivity of the 95nm gold nanosphere reached 133nm/RIU. We choose two types of system, one is Streptavidin/Biotin System, the other is m-IgG/goat anti-m-IgG System. Because of the special reaction, we can detect the red shift by UV-vis spectroscopy achieving the high sensitivity sensor. This part proves that LSPR of gold nanosphere is related to the sizes of gold nanospheres.On the other hand, we electrochemical deposited gold nanoclusters onto ITO surface. The gold nanocluster GNPs on ITO substrate were characterized by means of SEM and UV-vis spectroscopy. Then the gold nanoclusters were used to investigate the response of different organic solvents and showed a sensitivity of 158nm/RIU, which is higher than nanospheres. We also choose the two types of system. Because of the special reaction, we can detect the red shift by UV-vis spectroscopy achieving the high sensitivity sensor. This part proves that LSPR is related to the appearance of gold nanoparicles.