Fiber optic biochemical sensing using colloidal gold-modified long period fiber grating

We present a novel class of fiber-optic evanescent-wave sensor based on the modification of the grating portion of a long-period fiber grating with self-assembled gold colloids. The transmission spectra and optical properties of gold nanospheres change with the different refractive index of the environment near the surface of gold nanospheres. The sensor response of gold colloids increases linearly with solvents of increasing refractive index. When the colloidal surface was modified with DNP, results show that the signal increase linearly with increasing concentration of the analyte, and the detection limit of the sensor for anti-DNP is 8.43×10^-5 g/mL or 3.8×10^-7 M.