Growth time dependency on the formation of gold nanobipyramids for efficient detection towards chlorpyrifos-based LSPR sensor

The structure of gold nanobipyramids (GNBPs) is very promising for specific Localized Surface Plasmon Resonance (LSPR) properties, and thus potentially to be used in various applications, especially in sensing. This work reported growth time dependency on the formation of GNBPs for application in LSPR sensors for chlorpyrifos detection. The study on the growth time found that GNBPs formation at the initial stage is dominated by elongation direction and its optimum growth time is 2 h. The optimum GNBPs with 106.32 ± 2.50 in length, 42.17 ± 0.82 in width and an aspect ratio of 2.55 ± 0.08 were implemented as a sensing material for direct and rapid localized surface plasmon resonance (LSPR) sensors to detect chlorpyrifos. The mechanism is based on the change in spectrum intensity and wavelength shift between GNBPs when tested in deionized water and chlorpyrifos solution. The change arises from molecular interaction between the targeted analyte and the sensing material and effectively changes the dielectric features of the medium. The presence of chlorpyrifos in the 1 – 100 mg/mL concentration range has been successfully detected. The proposed sensor offers better sensitivity as high as 1.22 times for transverse LSPR mode and 2.04 for longitudinal LSPR mode than the LSPR sensor based on gold nanosphericals. Moreover, the sensor stability and repeatability response showed a reliable performance for determining chlorpyrifos. Furthermore, this sensor also shows high selectivity towards chlorpyrifos compared to other organophosphate and organochlorine pesticides such as malathion, chlorothalonil, and triclopyr-butotyl.