Seedless, Surfactantless, High-Yield Synthesis of Branched Gold Nanocrystals in HEPES Buffer Solution

Abstract

In this work, three-dimensional branched gold nanocrystals were produced at high yield by reacting an aqueous solution of chloroauric acid with a Good's buffer, HEPES, at room temperature. This particular method of preparation was scalable to gram-quantity. The branched nanocrystals containing one to eight tips were stable at room temperature and could be stored as a powder after freeze-drying. They were, however, unstable at higher temperatures and transformed into spherical particles upon boiling. The formation of the branched gold nanocrystals was kinetically controlled, as shown by the dependence of shapes on temperature and precursor salt concentration. The growth of branched gold nanocrystals in the HEPES buffer was monitored by microscopic and spectroscopic techniques, allowing the detection of several key intermediates in the growth process. Piperazine in HEPES molecule was identified as the principal moiety responsible for forming highly branched Au nanocrystals in the HEPES buffer.

Microwave-assisted synthesis of anisotropic gold nanocrystals in polymer matrix and their catalytic activities

“…These special properties have been applied in various fields ranging from microelectronics to biomedical science. [8] Au nanoparticles with interesting morphologies have been synthesised through various methods, such as chemical, [9][10][11][12] electrochemical, [13] sonochemical, [14] green synthesis, [15,16] conventional polyol process, [17,18] and spraypyrolysis method, [19] g-irradiation route, [20] ultraviolet irradiation, [21] template approach, [22][23][24][25] etc. Growth of nanostructures having different morphologies can result in the modification of its physical properties and improvement in performance characteristics.…”

Gold nanostars for efficient in vitro and in vivo real-time SERS detection and drug delivery via plasmonic-tunable Raman/FTIR imaging

“…HEPES buffers (3-[4-(2-hydroxyethyl)piperazine-1-yl]propane-1-sulphonic acid) have been used commonly used in cell culture and work as a functional reducing agent to directly change the shape of spherical gold nanoparticles to star shape. 29 Using this method we were able to produce three-dimensional branched gold nanostars and drug-nanostars.…”

Chemically Exfoliated MoS2 as Near‐Infrared Photothermal Agents

“…[5] These shapes serve as local plasmon antennas for NIR absorbance, but they are encumbered by complicated syntheses. More importantly, because of the non-equilibrium morphologies, anisotropic gold nanostructures inevitably tend to evolve into spheres upon heating.…”

“…More importantly, because of the non-equilibrium morphologies, anisotropic gold nanostructures inevitably tend to evolve into spheres upon heating. [5] Consequently, researchers have begun to investigate the NIR photothermal properties of graphene derivatives such as graphene oxide (GO) [6] and reduced graphene oxide (rGO). [7] The exceptional surface-area-to-mass ratio of these two-dimensional (2D) materials makes them promising photothermal candidates that can be loaded with high cargo concentrations.…”