Strong nanocatalysis of silver-doped carbon nitride and its application to aptamer SERS and RRS coupled dual-mode detection of ultra-trace K+

A novel nanocatalyst of silver-doped carbon nitride quantum dots (AgCNs) was prepared by microwave procedure, and characterized by electron microscopy, infrared (IR), surface-enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS), fluorescence and absorption techniques. Using the slope procedure to evaluate the nanocatalysis, it was found that AgCNs strongly catalyzed the nanoreaction of glucose (GL) reduction of HAuCl4 to generate gold nanoparticles (AuNP). The produced AuNP had strong SERS activity and RRS effect. With Victoria blue B (VBB) molecular probe, the SERS intensity at 1616 cm-1 increased linearly with concentration of AgCNs nanocatalyst. Similar to the SERS, the RRS intensity at 370nm also increased linearly. Apt could inhibited AgCNs catalytic activity. K+ combined with Apt to form stable G-quadruplexes and release AgCNs that enhanced SERS and RRS signals due to resuming the catalysis. Coupled with two scattering techniques of inelastic scattering SERS and elastic scattering RRS, we developed a dual-mode scattering method for label-free Apt detection of 5-150 nmol/L K+ with a detection limit of 0.92 nmol/L. Furthermore, we have proved the principle of coupled two mode scattering analysis and improving the SERS precision, and proposed a reasonable AgCNs catalytic mechanism.