Abstract
We report herein a one-step synthesis of gold nanoparticles (Au NPs) of various shapes such as triangles, hexagons, and semispheres, using 5-hydroxyindoleacetic acid (5-HIAA) as the reducing agent in the presence of potassium bromide (KBr). Anisotropic Au NPs have received ever-increasing attention in various areas of research due to their unique physical and chemical properties. Numerous synthetic methods involving either top-down or bottom-up approaches have been developed to synthesize Au NPs with deliberately varied shapes, sizes, and configurations; however, the production of templateless, seedless, and surfactant-free singular-shaped anisotropic Au NPs remains a significant challenge. The concentrations of hydrogen tetrachloroaurate (HAuCl4), 5-HIAA, and KBr, as well as the reaction temperature, were found to influence the resulting product morphology. A detailed characterization of the resulting Au NPs was performed using ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy. The as-prepared Au NPs exhibited excellent surface-enhanced Raman scattering (SERS) properties, which make them very attractive for the development of SERS-based chemical and biological sensors.
Highlights
Raman spectroscopy, based on molecular vibrational transitions, has long been regarded as a valuable tool for the identification and quantification of chemical and biological species [1, 2]
While it is well known that signals in normal Raman spectroscopy are extremely weak, great progress has been made since the discovery of surface-enhanced Raman scattering (SERS) [3,4,5]
The solutions were mixed on a stir plate set at approximately 300 rpm for 30 minutes under ambient conditions
Summary
Raman spectroscopy, based on molecular vibrational transitions, has long been regarded as a valuable tool for the identification and quantification of chemical and biological species [1, 2]. While it is well known that signals in normal Raman spectroscopy are extremely weak, great progress has been made since the discovery of surface-enhanced Raman scattering (SERS) [3,4,5]. The surface chemistry of gold is quite versatile, as it can be manipulated into a variety of sizes and shapes [6,7,8,9,10]. If it is possible to match the plasmon absorption wavelength of Au NPs with the excitation wavelength of the laser, resonance Raman, yet another boost to the Raman signal, is possible. Being able to manipulate the size and shape of a gold nanoparticle would allow for simple and easy modifications to analytical devices that utilize SERS technology that would greatly improve sensitivity and selectivity
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