A nano-crystalline Hf(iv) MOF for precise fluorometric recognition of carcinogenic nicotine and herbicide benfluralin: characterization, real-life application and mechanistic investigation

Abstract

Nicotine (NIC), an extensively consumed neuroteratogenic alkaloid with addictive properties, and benfluralin, a broadly used herbicide, are both potent toxic organic pollutants with several serious health impacts. Extensive exposure to NIC and benfluralin in the environment poses a noxious effect on both flora and fauna. Moreover, precise detection and monitoring of NIC and benfluralin in complex environmental samples are indeed challenging. Therefore, in this work, we have strategically synthesized a robust nano-crystalline Hf-based luminescent metal–organic framework (MOF), 1′, for fluorescence-based aqueous phase turn-on (31-fold) detection of NIC, in addition to turn-off-based (89.6%) recognition of benfluralin in MeOH medium. Fluorogenic detection of NIC and benfluralin was carried out with higher selectivity, with exceptionally low limit of detection (LOD) values of 160.8 nM and 82.4 nM, respectively. The notably high K_SV value of 4.03 × 10³ M⁻¹ observed for benfluralin indicates its strong quenching efficiency. Moreover, the extended investigation was conducted using probe 1′ for quantitative detection and monitoring of NIC in biofluids, real wastewater specimens and tobacco leaf extracts. The reusability of probe 1′ for the targeted detection of NIC and benfluralin was evaluated up to three consecutive cycles to confirm its stability and sustainable performance. Additionally, the biocompatibility of 1′ and its in vivo NIC recognition capability were extensively studied in live MDAMB-231 breast cancer cells through cell imaging. Furthermore, 1′ powder was cast in a biocompatible, cost-effective 1′@chitosan@paper composite strip for instantaneous detection of NIC and benfluralin through a visible change in fluorescence response. Additionally, a detailed mechanistic investigation was performed to validate a plausible mechanistic pathway for the observed optical response of 1′ in the presence of both NIC and benfluralin. This work offers a new approach to precisely monitor and reduce the release of toxic NIC and benfluralin, thereby contributing to safeguarding public health and the environment.