Pineapple Peel-Derived Ascorbic Acid-Assisted Green Synthesis of Fluorescent Silicon Nanoparticles for Dual-Mode Monitoring of Nitenpyram

The widespread occurrence of neonicotinoid insecticides, particularly nitenpyram (Nite), in aquatic environments has created an urgent demand for rapid, sensitive, and sustainable monitoring technologies. Herein, we developed a dual-mode sensing platform based on fluorescent silicon nanoparticles (P-SiNPs) synthesized through a facile one-step room-temperature method using pineapple peel waste-derived ascorbic acid (AA) as a renewable reducing agent and 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (AEEA) as the silicon precursor. The AA content in pineapple peel extract was quantified by iodometric titration, confirming its effectiveness as a biomass-derived reductant for green SiNPs synthesis. The resulting P-SiNPs exhibited strong green fluorescence, excellent aqueous stability, and enabled sensitive Nite detection through complementary fluorometric and colorimetric responses. Increasing Nite concentrations induced progressive fluorescence quenching of P-SiNPs accompanied by enhanced UV-vis absorption signals, allowing quantitative analysis using three independent optical outputs. The developed sensor achieved detection limits of 0.028 μM and 0.0018 μM for fluorometric and colorimetric detection, respectively, demonstrating high sensitivity for trace-level Nite monitoring. Mechanistic investigations indicated that Nite-induced fluorescence quenching involves a substantial static contribution, probably associated with surface interaction and modulation of the emissive states of P-SiNPs. Furthermore, the sensor showed excellent selectivity against structurally related pesticides and common interferents, with satisfactory recoveries of 95.7–104.3% in real environmental water samples. This work provides a sustainable circular chemistry strategy for converting agricultural waste into functional fluorescent nanomaterials and establishes an efficient platform for monitoring hazardous neonicotinoid contaminants in aquatic ecosystems.