Temperature-Derived Purification of Gold Nano-Bipyramids for Colorimetric Detection of Tannic Acid

Abstract

Gold nanostructures have attracted broad attention. Among various nanostructures, gold nanobipyramids have shown great potential in sensing, biomedicine, environmental protection, chemical catalysis, and optics due to their unique physical and optical properties and ease of chemical functionalization. Compared with other plasmonic nanostructures, gold nanobipyramids possess narrow optical resonances, stronger plasmonic local field enhancement, and size-and shape-dependent surface plasmon resonance. However, the synthesis and purification of homogeneous gold nanobipyramids are very challenging. The gold nanobipyramids synthesized via the commonly used seed-mediated growth method have low yields and are often coproduced with spherical nanoparticles. In this study, we reported a temperature-derived purification method for the isolation of gold bipyramids. In the presence of salt, by altering the temperature of the solution, large gold bipyramids can be separated from small spherical nanoparticles. As a result, a yield of as high as 97% gold nanobipyramids can be achieved through a single round of purification, and correspondingly, the ratio between the longitudinal surface plasmon resonance (LSPR) and transverse SPR intensity significantly increases to as high as 6.7. The purified gold nanobipyramids can be used as a colorimetric probe in the detection of tannic acid with a detection limit of 0.86 μM and a linear detection range from 1.25 to 37.5 μM.

Application of Anisotropic Gold Nanomaterials in Plasmonic Sensors for Detection of Glyphosate

“…The UV-Vis spectra of figure 1a range shows the absorption peak of t-SPR occurs within the wavelength range of 550-600 nm, and around the wavelength of 700-900 nm for the l-SPR absorption peak. This results of t-SPR and l-SPR AuNBP peaks formed are the same as previous studies [11][12]. In this research, as the growth time increases, the absorption of both t-SPR and l-SPR peaks also increases.…”

Gold Nanobipyramids as Plasmonic Sensor for Insecticide Detection in Lettuce

“…AuNBPs have been utilized in prior studies as LSPR sensors for the detection of glyphosate [12,16], as well as for colorimetric [17] and IgG sensing applications [18]. The findings of this investigation align with the previous work which also observed the presence of pyramidal shapes [19].…”

Quantifying Shape Transition in Anisotropic Plasmonic Nanoparticles through Geometric Inversion. Application to Gold Bipyramids

“…Anisotropic plasmonic nanoparticles stand out in finely tuning their localized surface plasmon resonance (LSPR) and creating strong electric fields by precisely adjusting the nanoparticle aspect ratio, particularly the length-to-width ratio, surpassing the impact of size variations in isotropic nanoparticles. − While gold (Au) nanorods remain the most versatile and consolidated type of anisotropic nanoparticles, − Au bipyramids (AuBPs) become an optimal alternative due to a superior number of physical properties and applications across plasmon resonance, ,− electric field enhancement, ,,− thermal stability, coupling processes, − sensing capabilities, − photocatalysis, , acoustic characteristics, and nonlinear optics. − Tuning the shape and size of plasmonic nanoparticles under optical excitation can initiate/elicit chemical transformations near/on their surfaces . These processes leverage the enhanced localized electric fields associated with plasmon excitation (by photothermal effect and/or hot carriers generation), presenting possibilities to drive reduction or oxidation reactions. − Also, AuBPs are particularly appealing for bottom-up fabrication, offering a wide range of structural diversity in two-dimensional (2D) systems and three-dimensional (3D) supercrystals .…”