A hybrid of carbon dots with 4-chloro-7-nitro-2,1,3-benzoxadiazole for selective detection of p-phenylenediamine

Abstract

The nucleophilic substitution reaction between 4-chloro-7-nitro-2,1,3-benzoxadiazole (NBD-Cl) and –NH₂ groups on amino-functionalized carbon dots (CDs) produces a novel carbon dot-based hybrid, CDs@NBD for short. In addition to the characteristic fluorescence emission of carbon dots at λ_ex/λ_em = 360/443 nm, the CDs@NBD hybrid gives rise to new photoluminescence at λ_ex/λ_em = 460/544 nm, which is significantly quenched by p-phenylenediamine (PPD) via static quenching. This provides a novel sensing approach for fluorometric detection of PPD with CDs@NBD as a probe. A linear calibration graph is obtained within two concentration ranges of 0.1–1.0 μmol L⁻¹ and 1.0–10.0 μmol L⁻¹, along with a detection limit of 56 nmol L⁻¹ and a RSD of <3% (at 1.0 μmol L⁻¹). The common coexisting species in environmental and biological sample matrices cause no obvious interferences on the detection of PPD. The colour change of the CDs@NBD hybrid solution with the variation in PPD concentration also facilitates visual detection of PPD, which further demonstrates promising applications in environmental and biological sample analysis.