Upconversion luminescence nanosensor for quantitative detection of nitrite and sparfloxacin based on IFE mechanism of azo quencher

On the basis of inner filter effect (IFE) mechanism, a convenient “off-on” upconversion luminescence (UCL) nanosensor for nitrite (NO 2 − ) and sparfloxacin (SPX) detection was constructed. This nanosensor used upconversion nanoparticles (UCNPs) as luminescent probes and p-aminobenzoic acid (PABA) and N-(1-naphthyl) ethylenediamine hydrochloride (NEDC) as specific recognition elements. Under acidic condition, NO 2 − can react with PABA to generate diazo compounds, which further react with NEDC to generate azo compound 1 (AZO1), and SPX can compete with PABA to bind NO 2 − to generate azo compound 2 (AZO2). Due to the significant overlap between the UCL emission spectrum of UCNPs at 545 nm and the UV–Vis absorption spectrum of AZO1, the resulting IFE effect effectively quenches UCL. Therefore, the attenuation based on UCL intensity can achieve the detection of NO 2 − , while UCL recovery can realize the detection of SPX. The linear range for NO 2 − detection is 0.05–10 μM with a limit of detection (LOD) of 0.0459 μM, while the linear range for SPX detection is 0.05–0.75 μM with a LOD of 0.0193 μM. The proposed nanosensor with “One-stone-two-birds” strategy provides a new approach for fast detection of NO 2 − and SPX.