Gold nanoparticle-based cascade reaction-triggered fluorogenicity for highly selective nitrite ion detection in forensic samples

Nitrite ions are important markers in gunshot residue (GSR) analysis. A highly sensitive and selective sensor that precisely identifies nitrite ions still needs to be developed. This work therefore proposed a new approach for nitrite ion detection based on the oxidative etching of cetyltrimethyl ammonium bromide-stabilized gold nanoparticles (CTAB@AuNPs) by nitrite ions to generate gold ions (Au3+), which can catalyze the decomposition of hydrogen peroxide and further react with fluorogenic substrates (o-phenylenediamine: OPD) to yield efficient fluorescent species (2,3-diaminophenazine; DAP). The concentration of nitrite ions can be indirectly determined by tracing the fluorescence intensity of the generated DAP. The degrees of fluorescence enhancement increased linearly with increasing nitrite ion concentration in the concentration range of 0-60 & micro;M, with a minimum limit of detection (LOD) of 0.07 & micro;M. More importantly, only nitrite ions can cause this fluorescence enhancement, while other tested anions showed no significant effect. Compared with the reference method, the proposed sensor can be applied for the detection of nitrite ions in GSR with satisfactory results.