An intermolecular hydrogen-bond-induced quench-type Ru(dcbpy)32+/TPA 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 nitrogen-containing 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.