Non-instrumental and ultrasensitive detection of Acetamiprid residue based on Tyndall effect of silver nanoparticles

Pesticide detection is of great significance in the fields of food safety and environmental monitoring. Herein, an unprecedented and facile non-instrumental detection strategy for pesticide residues was developed based on the Tyndall effect. The silver nanoparticles (Ag NPs) protected by specifically designed DNA aptamer were applied as the signal producer, and their different aggregation state induced by the addition of pesticide target were sensitively observed and evaluated through the Tyndall effect with the aid of merely a laser pointer. Combining with the pesticide target, the DNA chain folded up to certain conformation which rendered the Ag NPs a more dispersed and stable state, leading to weaker scattering and thus the weaker Tyndall effect. Taking advantage of this phenomenon, a relationship between pesticide concentration and intensity of Tyndall effect was established. Experimental results showed that the concentration of pesticide target, taking acetamiprid as representative, has a good linear relationship with gray value of Tyndall effect in the range of 3.4 × 10−9 ∼ 1.03 × 10−6 mol/L, with the detection limit of 1.2 nmol/L under optimum conditions selected through the orthogonal design. Furthermore, the satisfying results of anti-interference and recovery assay manifested the admirable practicality of this approach for real samples. Getting rid of complicated detection processes and expensive instruments, our strategy might open up a promising prospect for on-site and household detection of contamination with simple operation, low cost, and high sensitivity.