A novel 1,8-naphthalimide-based fluorescent probe for selective and portable detection of Hg2 + in environmental and food samples

Abstract

As a heavy metal ion, Hg²⁺ represents a serious environmental and health threat due to its neurotoxicity and bioaccumulation potential, highlighting the urgent need for effective detection techniques. Traditional detection methods, though accurate, are often impractical for on-site applications. To address this challenge, we designed and synthesized a novel fluorescent probe, NX601, based on a 1,8-naphthalimide fluorophore modified with branched-chain carboxyl hydrophilic groups and an N₄O recognition moiety. NX601 exhibits a selective "turn-on" fluorescence response to Hg²⁺ via suppression of the photoinduced electron transfer (PET) process, enabling rapid and sensitive detection in aqueous media. With a low limit of detection of 18.95 nM and a rapid response of less than 5 s, the probe demonstrated exceptional selectivity and reliability, even in the presence of interfering metal ions. Furthermore, portable detection tools, including test paper, cotton swabs, spray bottle and a smartphone-integrated platform, were developed for real-time, on-site Hg²⁺ detection. The smartphone-based approach demonstrated excellent agreement with inductively coupled plasma (ICP) analysis, highlighting its potential for environmental monitoring and food safety applications. This study not only presents a highly effective fluorescent probe for Hg²⁺ detection but also bridges the gap between laboratory research and real-world applications.