A novel ratiometric fluorescent nanosensor based-on UiO-66-NH capped carbon dots for nitrite determination.

Nitrite is a commonly used food preservative and a water contaminant that has garnered significant attention due to its harmful effects on human health. Developing a simple and sensitive method for determining nitrite levels is crucial for safeguarding public health. In this paper, we present a novel ratiometric fluorescent nanosensor (CDs@UiO-66-NH), created by combining orange-red-emitting CDs with blue-emitting UiO-66-NH. This ratiometric probe detects nitrite ions (NO) based on the diazotization reaction between the amino group in UiO-66-NH and the target NO, where the blue emission of UiO-66-NH is quenched but the orange-red emission of CDs remains stable. The probe demonstrated a detection range of 0.5-20 μM with a limit of detection (LOD) of 0.157 μM for NO. Due to the probe's distinct color changes in response to NO, RGB values can be easily read using a smartphone, enabling ultrasensitive visual detection of NO with an LOD of 0.76 μM. This sensor was successfully applied to detect NO in environmental water samples. Finally, a smartphone-based RGB reading method using CDs@UiO-66-NH for visual quantitative detection of NO was proposed, broadening the application of CDs@UiO-66-NH in environmental protection.