Switching off the SERS signal for highly sensitive and homogeneous detection of glucose by attenuating the electric field of the tips

The advances in surface-enhanced Raman scattering (SERS) have resulted in significant improvements for sensing glucose, achieving a highly detecting sensitivity of the order of μM. Highly sensitive glucose detection, however, is still a challenge due to extremely small Raman scattering cross section of glucose molecules and weak interaction between the molecules and the metal nanoparticles. Here, we designed a novel homogeneous SERS-based nanoplatform composing of the SERS tags and glucose oxidase in aqueous solution for a highly sensitive glucose detection. Adding glucose caused enzymatic oxidation reaction to etch the tip electric field (E) of silver nanotriangle. Thus, the decreased intensity of E was greatly amplified by the change of SERS signal (E⁴ dependent), which resulted in an excellent glucose detection limit of 0.4 nM was firstly achieved. Furthermore, the nonlinear relationship between the decreased SERS intensity and the glucose concentrations was reasonably revealed based on theoretical calculations and deeply understanding of the enhancement mechanism, which is very useful in improving the sensitivity and accuracy of trace glucose detection. The as-prepared nanoplatform showed good sensitivity and high selectivity only through observing the SERS intensity change, which is potential for highly sensitive and practical glucose detection for clinical trace analyses.