Investigation of the effect of amine and thiol as functional groups on gold Nanobipyramids properties

Abstract

Metal nanoparticles are increasingly popular due to their unique properties, such as their vast surface area, tiny size, strong reactivity in live cells, and high-temperature stability. Gold nanoparticles, as one of the metal nanoparticle types, are frequently utilized in biosensor applications because of their adjustable Localized Surface Plasmon Resonance (LSPR) characteristics, less cytotoxic nature, and increased sensitivity to changes in the surrounding medium. The anisotropic metal nanoparticle of gold nanobipyramids (GNBPs) provides for higher Refractive Index Sensitivity (RIS) and Figure of Merit (FOM) value than others, allowing for higher sensitivity. This work lies in the comprehensive investigation of GNBPs functionalized with amine and thiol groups over varying shorter time durations (0.5 – 12 h) through the immediate change in optical, structural, morphological, electrical surfaces, and molecular properties. The findings show amine groups enable the red-shifted spectrum, whereas thiol groups impact the blue-shifted spectrum. By employing amine groups, it is able to produce side peaks in the XRD pattern made up of amine atoms. The use of thiol groups, meanwhile, has an impact on the growth increase in the (111) direction. Then, the highest surface density is obtained in 3 h, 59.78 % for amine-functionalized GNBPs (a-GNBPs) and 75.49 % for thiol-functionalized GNBPs (t-GNBPs). Next, a-GNBPs generate the highest angle slope compared to t-GNBPs, i.e., 140.422⁰. In addition, for the electrical surface effect, amine functionalization increases the zeta potential value from 0.3 to 2.5 mV, indicating the inhibition of nanoparticle agglomeration. On the other hand, thiol functionalization affects the decreasing of zeta potential value from 0.3 to -0.5 mV, allowing for nanoparticle agglomeration. Subsequent FTIR characterization analysis obtained shifts in the wave numbers, with the -OH bond exhibiting changes within the range of 3306.75 – 3269.95 cm-1, C=-CH bond providing for 2138.48 – 2136.56 cm-1 range, and the C = O bond showing alterations between 1637.59 – 1637.33 cm-1 following amine and thiol functionalization. Extended observation reveals that both a-GNBPs and t-GNBPs exhibit significant signal responses in glucose detection applications utilizing LSPR-based sensors, suggesting the feasibility of functionalizing GNBPs with amine and thiol groups for potential biosensor development.