Microwave-assisted one-pot synthesis of carbon dots for highly sensitive and selective detection of selenite

Herein, a label-free, sensitive, and selective fluorescence method for the detection of trace selenite (Se(IV)) in water sample by carbon dots (CDs) was reported. The fluorescence CDs probe was simply and rapidly synthesized within 4 min by microwave-assisted pyrolysis of citric acid and 3,3′-diaminobenzidine (DAB), with a relatively uniform size of approximately 2.6 nm. The fluorescence emission of as-prepared CDs was 450 nm upon the excitation of 400 nm with a quantum yield of about 8% against quinine sulfate as reference standard, which can be quenched by the addition of selenite. Benefit from the strong surface chelating reaction between DAB and Se(IV), the proposed sensor owned the advantage of high sensitivity (limit of detection = 0.5 ng/mL), wide linear range (1–100 ng/mL range, relative standard deviation: 3.8%), and excellent selectivity in the presence of various ions, even other forms of selenium, including selenate (Se(VI)), Selenomethionine (SeMet), and L-Selenocystine (SeCys) etc. Preliminary study on fluorescence quenching mechanism studied. The sensor was successfully exemplified for real water samples and exhibits comparative performance.