Herein, we report the preparation of positively charged and stable gold nanoparticles (AuNPs) using a strong polycation, polydiallyldimethylammonium chloride (PDADMAC), as a stabilizing agent, for the colorimetric detection of a typical organophosphorus pesticide, chlorpyrifos (CPF). As deduced from zeta potentials, beside strong interaction of sulfur atom in CPF molecule with AuNPs, the hydrophobic interaction of CPF with PDADMAC outer shell significantly enhanced the sensitivity of the method, with an ultralow detection limit down to 2.28 ppb, which satisfies stringent requirement for maximum residue limit allowed by the United State Environmental Protection Agency (EPA) in agricultural products. In the presence of CPF, the PDADMAC-AuNP solution gave a linear increase of maximum absorption wavelength with CPF concentrations. Under the optimum conditions of pH 5, incubation time 25 min, and 3 × 10⁻³ M Na₂SO₄, this method achieved a wide linear range from 2.5 × 10⁻⁸ to 10⁻⁶ M, a low limit of detection (LOD) of 6.5 × 10⁻⁹ M (2.28 ppb), and high precision (RSD < 5%). High selectivity for CPF over other pesticides is also demonstrated. The developed sensor can be applied to detect CPF in various real samples such as vegetables or environmental water samples.

在此，我们报告了使用强聚阳离子聚二烯丙基二甲基氯化铵 (PDADMAC) 作为稳定剂制备带正电荷且稳定的金纳米粒子 (AuNP)，用于比色检测典型的有机磷农药毒死蜱 (CPF)。从 zeta 电位推导出，除了 CPF 分子中的硫原子与 AuNPs 的强相互作用外，CPF 与 PDADMAC 外壳的疏水相互作用显着提高了该方法的灵敏度，检测限低至 2.28 ppb，满足严格的要求美国环境保护署（EPA）在农产品中允许的最大残留限量。在 CPF 存在下，PDADMAC-AuNP 溶液的最大吸收波长随 CPF 浓度呈线性增加。⁻³  M Na ₂ SO _{4 ，该方法实现了从2.5 × 10} ⁻⁸到10 ⁻⁶ M的宽线性范围、6.5 × 10 ⁻⁹ M (2.28 ppb) 的低检测限(LOD) 和高精度(RSD < 5%)。还证明了 CPF 相对于其他农药的高选择性。开发的传感器可用于检测蔬菜或环境水样等各种真实样品中的CPF。