Longitudinal Plasmon Resonance of Gold Nanorods for Glucose Sensing

Gold nanorods are known for their unique surface plasmon resonance, a weak transverse band and a strong longitudinal band. In this study the strong longitudinal band was harnessed to detect glucose concentrations. First, cetyltrimethylammonium bromide (CTAB) stabilized gold nanorods modified by having negatively charged dextran sulfate form a coat electrostatically around the positively charged CTAB bilayer. The decorated gold nanorods were able to form clusters in the presence of concanavalin A (ConA), and thereby revealing apparent red shift of longitudinal plasmon band when compared to the band of original gold nanorods. The shift was found proportional to ConA concentrations. The cluster of ConA treated gold nanorods were demonstrated by the TEM micrographs. When ConA treated gold nanorods were mixed with glucose containing solution, the peak of longitudinal plasmon band shifts back towards original peak of the gold nanorods coated with dextran sulfate. The peak back shifting of longitudinal plasmon band is strongly affected by the concentration of glucose, therefore making the ConA associated gold nanorods a potential sensor system.