Background-free sensing platform for on-site detection of carbamate pesticide through upconversion nanoparticles-based hydrogel suit.

On-site monitoring of carbamate pesticide in complex matrix remians as a challenge in terms of the real-time control of food safety and supervision of environmental quality. Herein, we fabricated robust upconversion nanoparticles (UCNPS)/polydopamine (PDA)-based hydrogel portable suit that precisely quantified carbaryl in complex tea samples with smartphone detector. UCNPS/PDA nanoprobe was developed by polymerization of dopamine monomers on the surface of NaErF ₄ : 0.5% Tm ³⁺ @NaYF ₄ through electrostatic interaction, leading to efficient red luminescence quenching of UCNPS under near-infrared excitation, which circumvented autofluorescence and background interference in complicated environment. Such a luminescence quenching could be suppressed by thiocholine that was produced by acetylcholinesterase-mediated catalytic reaction, thus enabling carbaryl bioassay by inhibiting the activity of enzyme. Bestowed with the feasibility analysis of fluorescent output, portable platform was designed by integrating UCNPS-embedded sodium alginate hydrogel with 3D-printed smartphone device for quantitatively on-site monitoring of carbaryl in the range of 0.5-200 ng mL ^-1 in tea sample, accompanied by a detection limit of 0.5 ng mL ^-1 . Owing to specific UCNPS signatures and hydrogel immobilization, this modular platform displayed sensitive response, portability and anti-interference capability in complex matrix analysis, thus holding great potential in point-of-care application.
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