Aptamer SERS and RRS determination of trace lead ions using nitrogen-doped carbon dot to catalyze the new nano-gold reaction.

Nitrogen-doped carbon dots (CD) were prepared by microwave hydrothermal method using ammonium citrate (AC) and ethylenediaminetetraacetic acid (EDTA) as precursor. It was characterized by transmission electron microscopy (TEM) and infrared spectroscopy (IR). The CD was found to catalyze the reduction of HAuCl to produce gold nanoparticles (AuNP), among which fructose was an effective reducing agent. Using malachite green (MG) as a molecular probe, the surface enhanced Raman scattering (SERS) intensity at 1617 cm and the resonance Rayleigh scattering (RRS) intensity at 375 nm increased linearly with increasing CD concentration, respectively. The catalytic activity of CD is inhibited because the aptamer (Apt) can be adsorbed on the surface of the catalyst CD. The aptamer (Apt)-Pb reaction and CD-Apt adsorbing reaction were competitive reaction. When there is Pb that binds more tightly to Apt, Apt is desorbed, and the catalytic ability of CD is restored. Accordingly, an Apt-mediated nanocatalytic amplification SERS/RRS platform for quantitative detection of lead ions was constructed. For the SERS method, the linear range was 0.5-120 nmol/L with DL of 0.11 nmol/L. For the RRS method, the Pb concentration was linear in the range of 50-400 nmol/L with the RRS intensity, and the DL was 15.32 nmol/L. The analysis platform uses CD catalyzed nanoreactions to generate AuNP products with SERS activity as a substrate, thus overcoming the shortcomings of Pb without scattering activity, and realizing the possibility of SERS and RRS detection of metal ions. It was used for the determination of Pb in real samples with relative standard deviations were 0.94-2.71 % and recovery was 99.00-103.70 %, respectively. In addition, the mechanism of CD nanoenzyme heterogeneous catalysis of nano-gold reactions was discussed.