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

A novel class of fiber-optic evanescent-wave sensor, which is simple to construct and easy to use, is presented and analyzed. This fiber-optic sensor is 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 colloids change with the different refractive index of the environment near the surface of gold colloids. The sensor response of gold colloids increases linearly with solvents of increasing refractive index. When the colloidal gold surface was modified with a dinitrophenyl compound (DNP), experimental results show that the signal increase linearly with increasing concentration of the analyte, and the detection limit of the sensor for anti-DNP is 1.4 × 10−7 g/mL or 9.5 × 10−10 M.