Ti ³⁺ state in metal doped TiO ₂ based on lattice distortion that encouraged the formation of oxygen vacancy defects.

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.

Localized surface plasmon resonance (LSPR) properties of metallic nanostructures, such as gold, are very sensitive to the dielectric environment of the material, which can simply be adjusted by changing its shape and size through modification of the synthesizing process. Thus, these unique properties are very promising, particularly for the detection of various types of chemicals, for example boric acid which is a non-permitted preservative employed in food preparations. For the sensing material, gold (Au) nanoplates with a variety of shapes, i.e., triangular, hexagonal, truncated pentagon and flat rod, were prepared using a seed-mediated growth method. The yield of Au nanoplates was estimated to be ca. 63% over all areas of the sensing material. The nanoplates produced two absorption bands, i.e., the transverse surface plasmon resonance (t-SPR) and the longitudinal surface plasmon resonance (l-SPR) at 545 nm and 710 nm, respectively. In the sensing study, these two bands were used to examine the response of gold nanoplates to the presence of boric acid in an aqueous environment. In a typical process, when the sample is immersed into an aqueous solution containing boric acid, these two bands may change their intensity and peak centers as a result of the interaction between the boric acid and the gold nanoplates. The changes in the intensities and peak positions of t-SPR and l-SPR linearly correlated with the change in the boric acid concentration in the solution.