Rapid Response and High Selectivity for Reactive Nitrogen Species Based on Carbon Quantum Dots Fluorescent Probes

Reactive nitrogen species (RNS) are vital signaling molecules involved in most physiological and pathological processes. Within RNS, nitric oxide (NO) and its metabolite nitrite (NO 2 − ) have been widely applied in medicinal, food, and environmental fields. However, at present, the methods of detecting RNS by fluorescence quenching through chemical reactions have disadvantages, such as long reaction time and weak anti-interference ability. In response to these existing problems, we have developed a novel fluorescent probe, namely, carbon quantum dots (CDs) that are passivated by benzylamine. The obtained CDs (named B-CDs) possess excellent down- and upconversion properties. In particular, upconversion is used to sensitively and selectively measure NO and NO 2 − under different pH conditions in aqueous media via two different mechanisms (static and dynamic quenching). At pH 7.4, the nanomolar concentration of NO, produced from sodium nitroprusside (SNP) in a concentration-dependent manner, can be rapidly detected with a correlation coefficient ( R 2 ) greater than 0.99. Similarly, the quantitative detection of NO 2 − at pH 1.6 also shows a good linear relationship with a linear range of 0–14 μM, and a limit of detection (LOD) that is as low as 43 nM and 0.65 μM at excitation wavelengths of 800 nm and 375 nm, respectively. Notably, this probe stands out due to its extremely short response time and outstanding selectivity and anti-interference ability against a variety of common interfering substances, while realizing the fast and highly selective and sensitive detection of NO and NO 2 − . Finally, this probe has been successfully applied to the sensing of NO in fetal bovine serum (FBS) samples and NO 2 − in milk and tap water samples. Graphical abstract