# An “On–Off” AIE-Based Lock-and-Key Fluorescent Probe System for Detection of Fentanyl/Norfentanyl

## TL;DR

A new fluorescent probe can detect fentanyl and norfentanyl quickly and accurately, offering a promising tool for on-site drug screening.

## Contribution

A novel 'on–off' fluorescent probe system for fentanyl/norfentanyl detection with high sensitivity and specificity.

## Key findings

- The probe TP-CF3-COOH enables quantitative detection of fentanyl/norfentanyl with low detection limits.
- Fentanyl interaction triggers self-assembly and fluorescence quenching, confirmed by blue-shifted emission.
- The probe is cost-effective, rapid, and suitable for on-site detection of fentanyl and its metabolites.

## Abstract

The misuse of fentanyl poses significant social risks, and accurately and swiftly detecting fentanyl in field settings presents a considerable challenge. Herein, we have designed and synthesized a fluorescent probe TP-CF3-COOH, which is composed of carboxyl- and trifluoromethyl-binding center tetraphenyl butadiene. The unique centrosymmetric configuration of the TP-CF3-COOH probe allows for the construction of a fluorescence “on–off” mechanism recognition platform by spatially matching fentanyl and its metabolite norfentanyl. Importantly, this study reveals that the interaction of fentanyl or norfentanyl with TP-CF3-COOH results in spontaneous self-assembly, generating a three-dimensional complex sphere that is smaller than the two-dimensional sheet fluorescence probe. This self-assembly process results in the quenching of fluorescence. Theoretical calculations demonstrate that this process is accompanied by intermolecular through-space charge transfer during self-assembly, leading to a blue shift in emission wavelength. As a result, the TP-CF3-COOH fluorescent probe enables the quantitative detection of fentanyl/norfentanyl within a range of 1 × 10−2–1 × 103 μg/L, with limits of detection of 2 × 10−4 μg/L and 3 × 10−4 μg/L, respectively. This cost-effective, rapid, and sensitive fluorescent probe holds great potential for the onsite screening and detection of fentanyl and its analogues.