Improved Sensitivity and Selectivity of Direct Localized Surface Plasmon Resonance Sensor Using Gold Nanobipyramids for Glyphosate Detection

Direct localized surface plasmon resonance (LSPR) sensor using anisotropic gold nanoparticles with bipyramidal structure namely as gold nanobipyramids (GNBPs) has been proposed. The high curvature at the tips of GNBPs enhanced LSPR effect owing to electron-rich sites thus improved sensor performance. In this study, we demonstrated that GNBPs-based LSPR sensor is sensitive and can detect the presence of glyphosate as low as 0.1 % (w/w). Our experimental studies show that the GNBPs-based LSPR sensor exhibits improved sensitivity compared to the gold bone nanorods (GBNRs) and gold nanorods (GNRs)-based LSPR sensor. For t-SPR band, the GNBPs provided sensitivity factor as high as 4.76 and 5.17 times larger than the sensitivity factor of GBNRs and GNRs, while for l-SPR band, the sensitivity factor of GNBPs are 2.87 times larger than GBNRs and 1.57 times larger than GNRs. The selectivity of GNBPs-based LSPR sensor was evaluated by comparing its response to four different analytes and the response of LSPR sensor towards glyphosate is much higher than the responses towards chlorpyrifos, acetic acid and acetone. Hence, it is confirmed that GNBPs-based LSPR sensor has a good selectivity towards glyphosate. In addition, the proposed sensor system shows a good stability and repeatability for a period of 600 seconds and during five cycling tests, respectively.