New Ag-Doped COF Catalytic Amplification Aptamer Analytical Platform for Trace Small Molecules with the Resonance Rayleigh Scattering Technique

Covalent organic frameworks (COFs) and Ag-doped COFs (AgCOFs) are prepared by the polycondensation procedure and characterized by electron microscopy and molecular spectral techniques. Their catalysis of the Cu2O particle reaction of glucose (GL)–Cu(II) was examined by resonance Rayleigh scattering (RRS), and AgCOFs were found to exhibit the strongest catalysis. The melamine (ML) aptamers (AptML) can attach to the surface of AgCOF and inhibit its catalytic activity. When melamine (ML) is added to this reacting solution, AptML–ML complexes are formed and the Apts are desorbed from the surface of AgCOF. As the concentration of ML increased, the catalytic activity of AgCOF increased and the RRS signal enhanced due to the increase in Cu2O particles. When the ML concentration was in the range of 0.79–13.2 nmol/L, the RRS intensity increased linearly, with a detection limit of 0.72 nmol/L. When the Apts of urea and bisphenol A (BPA) were replaced by the AptML, 66.7–1333 nmol/L urea and 0.33–2.7 nmol/L BPA, respectively, could also be determined, with detection limits of 30.4 nmol/L urea and 0.15 nmol/L BPA. Based on this, a new AgCOF amplification RRS method was established.