A versatile colloidal photonic crystal assisted SERS template for the detection of pesticides, explosives, and dyes

Abstract We report the systematic investigation of detecting diverse hazardous analyte molecules, including explosives, pesticides, and dyes, using cost-effective thin colloidal photonic crystal (CPhC)- based surface-enhanced Raman spectroscopic (SERS) templates. A CPhC template combined with plasmonic nanoparticles (NPs) was used to effectively detect various molecules by utilizing the local electric field enhancement mechanism of the photonic crystals (PhCs). The excitation wavelength within the PhC stop band enhances the local E-field. Polystyrene (PS) colloidal PhC templates are coated with gold NPs (AuNPs) to make SERS active. The FESEM images depicted the morphology of uniformly distributed AuNPs on the PhC surface. The efficiency and reproducibility of the PhC-AuNPs template are initially studied using crystal violet (CV) dye as the probe molecule. Subsequently, the investigations were extended to include the detection of a textile dye molecule, Nile blue (NB), a pesticide (thiram), and two significant explosive molecules—trinitrotoluene (TNT) and picric acid (PA). Furthermore, we demonstrate the versatility of the CPhC-AuNP templates in SERS-based trace analytes detection. The calculated limit of detection (LOD) of the molecules CV, NB, thiram, TNT, and PA are 98 nM, 282 pM, 2.5 µ M, 58 µ M, and 67 µ M, respectively, clearly indicating the sensitivity of the template in detecting different molecules. A qualitative understanding of the local electric field (E-field) enhancement in the CPhC-AuNP template is obtained through finite element method simulations implementation of COMSOL Multiphysics-Wave Optics module.