| Summary: | Using citric acid (CA) and ethylenediamine (EDA) as precursors, stable nitrogen-doped carbon dots (CD) nanosols were prepared by microwave procedure and characterized in detail. It was found that CD<sub>N</sub>s catalyze ethanol (Et)-HAuCl<sub>4</sub> to generate gold nanoparticles (AuNPs), which have strong surface plasmon resonance, Rayleigh scattering, (RRS) and a surface plasmon resonance (SPR) absorption (Abs) effect at 370 nm and 575 nm, respectively. Compled the new catalytic amplification indicator reaction with the specific As<sup>3+</sup> aptamer reaction, a new RRS/Abs dual-mode aptamer sensor for the assay of trace As<sup>3+</sup> was developed, based on the RRS/Abs signals increasing linearly with As<sup>3+</sup> increasing in the ranges of 5–250 nmol/L and 50−250 nmol/L, whose detection limits were 0.8 nmol/L and 3.4 nmol/L As<sup>3+</sup>, respectively. This analytical method has the advantages of high selectivity, simplicity, and rapidity, and it has been successfully applied to the detection of practical samples.
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