gamma-Cyclodextrin capped silver and gold nanoparticles as colorimetric and Raman sensor for detecting traces of pesticide "Chlorpyrifos" in fruits and vegetables

Organophosphorous compounds are extensively used in agriculture as pesticides, which impose great threat to the safety of environment, food and public health. These demands for the development of reliable pesticide detection platform. In this study, noble metal nanoprobes, gamma-CD-Ag and gamma-CD-Au were developed using a facile one-step green synthetic approach using gamma-cyclodextrin (gamma-CD) that serves as a platform for colorimetric and Raman sensing of the pesticide, chlorpyrifos (CPP). The noble metal nanoparticles (NPs), owing to their unique optical properties are capable of undergoing colorimetric changes based on variations in their surroundings. The intensity variation of the Raman bands, viz. 417 (1328) and 411 (773) cm(-1) as a function of CPP concentration was used to quantify the sensitivity of the gamma-CD-Ag and gamma-CD-Au nanoprobes. The colorimetric changes as well as enhancement in the Raman bands of CPP resulted due to the interaction of the metal particles with CPP, primarily through the amine and phosphorothioate functional groups. The applicability of the nanoprobe was tested in apple and tomato. The gamma-CD-Ag and gamma-CD-Au nanoprobes showed excellent colorimetric and Raman response towards the pesticide. The detection limit was found to be 1 ppb and 10 ppb for the nanoprobes, in aqueous solution and apple/tomato, respectively. The methodology developed for pesticide detection is cost-effective and shows relatively fast colorimetric and Raman response. This study thus, provides new insight towards the development of novel nanoprobes for prospective applications in environmental monitoring.