Graphene oxide-based dual-color thin-film fluorescent nanolabels for enhanced immunochromatographic detection of pesticides.

Background: The excessive use of pesticide pollutants in agricultural production seriously threatens food safety. Traditional detection techniques are difficult to meet the detection requirements due to the complex sample pretreatment and high detection costs. The immunochromatography method (ICA) is simple to operate and fast, and is suitable for on-site rapid detection. However, existing technologies still need to improve in terms of accuracy and sensitivity. Therefore, developing a new type of ICA technology with high sensitivity and specificity is an urgent task to meet the demand for on-site rapid detection.

Results: This study introduces an advanced Dual-Color Gradient Fluorescent Immunochromatographic (DCG-FIC) system powered by graphene oxide-quantum dot nanolabels (G-TQD). By ingeniously engineering two-dimensional GO as a versatile nanoplatform, we developed dual-color fluorescent nanolabels that significantly enhances the sensitivity and specificity of small-molecule contaminant detection. Our DCG-FIC approach demonstrates substantial improvements in detection performance, achieving femtogram-level detection limits of 0.611 pg/mL for imidacloprid (IMI) and 2.16 pg/mL for azoxystrobin (AZO)-a notable 46-fold enhancement over conventional gold nanoparticle methods. The innovative thin-film nanostructure improves signal amplification and uniformity while reducing material consumption. With a rapid 15-min detection protocol, spiked recovery rates of 85.13-105.14 %, and relative standard deviations below 8.45 %, this method offers a promising solution for multiplex pesticide residue screening in economic crops.

Significance: This research innovatively developed a red-green dual fluorescence labeling system, combined with an intelligent reading device to achieve signal amplification, and was able to simultaneously complete high-precision detection of two target substances on a single detection line. This research provides a valuable framework for advancing biosensing platforms, integrating nanotechnology, fluorescence engineering, and immunoassay methodologies to support agricultural food safety and public health.