Persistent Luminescence-Based Competitive Enzyme Biosensor for Ultrasensitive and Selective Detection of β-Hexachlorocyclohexane

β-Hexachlorocyclohexane (β-HCH), a highly stable and persistent residue from pesticide use, poses significant risks to the environment and human health, so its sensitive and specific detection is of critical importance for accurate risk assessment. Conventional optical methods are often compromised by autofluorescence and matrix interferences. Here, we report a highly sensitive and selective persistent luminescence-based competitive enzyme biosensor for the detection of β-HCH. A key innovation is the design of a carboxylated HaloTag ligand grafted onto amino-functionalized persistent luminescence nanoparticles, Mn 2+ -doped Zn 2 GeO 4, a conjugate (ZGOM@L) to serve as both the optical reporter and a competing substrate for the dehalogenase LinB. In this competitive assay, the presence of β-HCH preferentially consumes the LinB activity, sparing ZGOM@L for covalent conjugation with the immobilized HaloTag protein. This results in an increasing persistent luminescence proportional to the β-HCH concentration, inherently eliminating matrix-derived optical interference. The proposed method gives a detection limit of 0.02 ng mL –1 along with quantitative recoveries (88.0% to 105.3%) in vegetable samples. This work provides a robust, autofluorescence-free sensing platform and a generalizable strategy for monitoring trace haloalkanes in complex samples.