Rapid Detection of Chlorothalonil Fungicide Using Anisotropic Gold Nanoparticles Plasmonic Sensor

Anisotropic gold nanoparticles (AuNPs) are well-known for their remarkable optical properties, particularly their dual-band surface plasmon resonance (SPR) behaviour. In this study, we harnessed these unique features to develop a rapid fungicide detection system. The sensing approach relies on monitoring changes in the intensity and position of the SPR peaks, with the absorbance spectrum serving as the primary detection signal. Upon light exposure, the sensor could detect chlorothalonil in at least three seconds. Notably, chlorothalonil alone does not produce significant SPR peaks; however, when combined with AuNPs, two distinct SPR bands emerge, corresponding to the transverse (t-SPR) and longitudinal (l-SPR) resonance modes. As chlorothalonil concentration increases, the absorbance intensity of the AuNPs also rises, likely due to an increase in refractive index around the nanoparticles. Stability assessments revealed minimal variation in SPR peak values, which were consistently recorded at 1.30 ± 0.00001 and 1.18 ± 0.00001 a.u. over a 600-second period. In repeatability tests, the sensor demonstrated dependable performance across six measurement cycles, with the signal reliably returning to baseline after each medium change. The AuNPs exhibited a fast optical response, reaching maximum spectral shifts within 30 seconds. These findings underscore the potential of anisotropic AuNPs as an effective platform for rapid, consistent, and sensitive detection of fungicides.