electrochemiluminescence system by nitrogen-doped carbon quantum dots

Here, we show that nitrogen-doped carbon quantum dots (NCQDs) strongly inhibits the anodic electrochemiluminescence (ECL) signal of a tris(4,4 '-dicarboxylic acid-2,2 '-bipyridyl) ruthenium(II) (Ru(dcbpy)32+)/ tripropylamine (TPA) aqueous system. To determine the ECL-quenching mechanism, we used photoluminescence spectroscopy, UV-Visible absorption spectroscopy and dynamic simulation technology. Quenching of the ECL signal of Ru(dcbpy)32+/TPA by NCQDs was predominantly attributed to the interaction between Ru(dcbpy)32+ and NCQDs rather than that between TPA and NCQDs. Specifically, when Ru(dcbpy)32+ and NCQDs were in aqueous solution together, the carboxyl (-COOH) groups of Ru(dcbpy)32+ were in contact with oxygen- and nitrogencontaining groups on the surface of NCQDs and formed intermolecular hydrogen bonds. This process involved energy transfer from the excited-state Ru(dcbpy)32+ to the intermolecular hydrogen bonds, thus resulting in a decrease in the Ru(dcbpy)32+ ECL signal. On this basis, a quenching-type ECL sensor for the quantification of NCQDs was fabricated. The sensor had a wide linear range and an estimated detection limit of 0.0012 mg mL-1, as well as excellent stability and selectivity. Satisfactory recoveries of 97.0-99.5% were obtained using the ECL sensor to quantify NCQDs in tap water. NCQDs could potentially be used as a quenching probe of Ru(dcbpy)32+ to construct various biosensors with widespread applications in the sensing field.

Automated summary

This study demonstrates that nitrogen-doped carbon quantum dots can effectively inhibit the anodic electrochemiluminescence signal of a ruthenium complex, leading to the development of a quenching-type sensor for detecting these quantum dots with satisfactory recoveries in tap water. The interaction mechanism between the ruthenium complex and the quantum dots involves energy transfer and intermolecular hydrogen bonds, indicating potential applications in biosensors for various sensing fields.