# Polyethyleneimine-Doped Carbon Quantum Dots as a Highly Sensitive Fluorescent Probe for HClO Sensing in Live Cell Imaging

## TL;DR

Researchers created fluorescent carbon dots that can detect hypochlorous acid in live cells and real-world samples with high sensitivity and selectivity.

## Contribution

A new fluorescent probe using nitrogen-doped carbon quantum dots for highly sensitive and selective HClO detection in live cell imaging.

## Key findings

- The N-CQDs showed a detection limit as low as 0.17 μmol/L for HClO with a linear range of 0–40 μmol/L.
- The probe exhibited high selectivity and anti-interference capability against various common species.
- The probe was successfully applied to detect HClO in river water, beer, and live cells.

## Abstract

In this work, we synthesized blue-fluorescent nitrogen-doped carbon quantum dots (N-CQDs) via a facile, economical, and environmentally friendly one-pot synthesis, using citric acid as the carbon source and polyethyleneimine (PEI) as the nitrogen dopant. The as-prepared N-CQDs exhibited uniform size distribution, with an average diameter of approximately 3 nm and a quantum yield of up to 23.6%. Based on the mechanism of HClO-triggered static fluorescence quenching and oxidation of surface amine groups on the N-CQDs, we established a quantitative detection platform for hypochlorous acid (HClO). The proposed method demonstrated a linear response over the concentration range of 0–40 μmol/L, with a detection limit as low as 0.17 μmol/L. It also featured a rapid response time (within 2 min), high selectivity, and strong anti-interference capability against various common species, including Cl−, H2O2, NO2−, NO3−, TBHP, TBO•, Br−, I−, S2−, F−, O2− and HO•. Furthermore, the probe was successfully applied to detect HClO in real-world samples such as river water and beer. Owing to its outstanding photostability and low toxicity, it proved highly effective for monitoring intracellular HClO in living cells.