Colorimetric sensing using nanomaterials is widely studied, yet its application to nanoplastic detection remains underdeveloped. In this study, a non-destructive colorimetric method was developed to detect polypropylene nanoplastic (nano-PP) by inhibiting salt-induced aggregation of gold nanoparticles (AuNP). The method utilizes the electrostatic and steric stabilization effects of nano-PP to prevent aggregation triggered by NaCl (0.05–0.10 M), resulting in a quantifiable change in the localized surface plasmon resonance (LSPR) at 520 nm. Without nano-PP, rapid AuNP aggregation caused a red-to-gray color transition and LSPR signal loss. In contrast, increasing nano-PP concentrations effectively restored dispersion and recovered the 520 nm peak. Zeta potential analysis revealed a shift in nano-PP surface charge from –45.97 mV to + 39.27 mV, enabling electrostatic interaction with negatively charged AuNP. Control experiments using stabilizing agent or toluene alone failed to inhibit aggregation, confirming that stabilization occurred specifically in the presence of nano-PP. The detection limit ranged from 0.15 to 1.26 mL (9.95–51.08 mg/L), depending on NaCl concentration, with full detection achieved in 1 min. This technique offers a rapid, sensitive, and cost-effective alternative to conventional spectroscopic methods and establishes a foundation for extending colorimetric sensing to other nanoplastics in aqueous environments.

中文翻译：

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新型比色法通过抑制金纳米颗粒的盐诱导聚集检测聚丙烯纳米塑料

纳米材料的光度传感研究广泛，但其应用于纳米塑料检测仍处于发展阶段。在本研究中，开发了一种非破坏性光度法，通过抑制金纳米粒子（AuNP）的盐诱导聚集来检测聚丙烯纳米塑料（nano-PP）。该方法利用 nano-PP 的静电和立体稳定化效应，防止由 NaCl（0.05-0.10 M）引起的聚集，导致 520 nm 处的局域表面等离子体共振（LSPR）发生可量化的变化。没有 nano-PP 时，AuNP 的快速聚集导致红到灰的颜色转变和 LSPR 信号丢失。相比之下，增加 nano-PP 浓度有效地恢复了分散性并恢复了 520 nm 峰。Zeta 电位分析显示，nano-PP 表面电荷从-45.97 mV 转移到+ 39.27 mV，使其能够与带负电的 AuNP 发生静电相互作用。使用稳定剂或仅使用甲苯的控制实验未能抑制聚集，证实了稳定作用仅在 nano-PP 存在时发生。 检测限从 0.15 到 1.26 毫升（9.95-51.08 毫克/升）不等，取决于 NaCl 浓度，1 分钟内即可实现完全检测。这项技术为快速、灵敏且经济的替代传统光谱方法提供了可能，并为将比色传感扩展到水环境中其他纳米塑料奠定了基础。