U-Shaped Fiber Based-Long Range Surface Plasmon Resonance Sensor for Sensitive Hg 2+ Detection

An U-shaped fiber long range surface plasmon resonance (LRSPR) sensor is proposed to detect trace Hg2+in water system. The U-shaped fiber is bend and coated with 100 nm MgF2and 50 nm Au film, the U-shaped fiber LRSPR senor could combine the advantage of high sensitivity and low full width of half maximum (FWHM) by the optimization of the fiber bending radius (BR) and MgF2thickness. With the functionalization of single-stranded DNA (ssDNA) on the Au layer by covalent bond, the Hg2+could be selectively detected by the thymine (T) base pairs, which would form stable T-Hg-T structure by the folding of ssDNA and cause the change in surface refractive index (RI). The detection range of Hg2+is 50 nM-5 mM, and the limit of detection (LOD) reaches at 60 nM. The selectivity and stability are proved to be good and the recovery from the spiked tap water is also tested. The good performance and wide range of the proposed sensor indicates high potential for future Hg2+sensor development and multiple using scenarios.