A recyclable silver ions-specific surface-enhanced Raman scattering (SERS) sensor

A highly sensitive and recyclable surface-enhanced Raman scattering (SERS) chip sensor is designed for the determination of silver ions . It is based on the specific reversible binding between silver ions and glucose oxidase (GOD). The sensing chip is made by layer-by-layer assembling GOD on a metal nanoparticle-assembled, SERS-active chip with a positive charged polyelectrolyte as a linker. Iso-alloxazine, a chromophore in flavin adenine dinucleotide (FAD) in GOD, coordinates with silver ions, which causes significant variation in SERS spectra of GOD. The reaction shows high sensitivity and selectivity for silver ions with the detection limit of 1.0×10 −10   M. Most significantly, the bonded Ag(I) in GOD can be reduced to Ag(0) by sodium borohydride and the GOD structure can be recovered then. Thus, the chip sensor is recyclable. Merits of using GOD as a novel SERS probe toward Ag + are embodied in not only a simplified sensor structure based on its dual role of Ag + accepter and SERS signal reporter, but also a nontoxic label to biological systems, indicating that it is promising for tracing Ag + in vivo.