▎ 摘　　要

We report a highly sensitive label-free chemical sensor for the detection of heavy metal ions. The sensor was derived from a micro-tapered long-period fiber grating (MTLPFG) functionalized by graphene oxide and poly dopamine modified graphene oxide, respectively. Because of the combination of chemical bonding and optical tweezer effect, the materials were deposited on the MTLPFG fiber grating surface. The morphology and elemental composition of the nanocomposites were characterized by scanning electron microscope, Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Herein, we demonstrate a high sensitivity MTLPFG detection of cobalt ions in a large concentration range from 1 ppb to 10(7) ppb. The highest sensitivity of 2.4 x 10(-3) dB.ppb(-1) at the PDA concentrations of 0.05 g.L-1 was obtained by MTLPFG functionalized with PDA-GO (PDA-GO-MTLPFG). The result was significantly higher than GO-deposited MTLPFG (GO-MTLPFG). The proposed PDA-GO-MTLPFG demonstrates superior application value in chemical sensing fields.