Critical Concentrations and Role of Ascorbic Acid (Vitamin C) in
the Crystallization of Gold Nanorods within Hexadecyltrimethyl
Ammonium Bromide (CTAB)/Tetraoctyl Ammonium Bromide
(TOAB) Micelles
Oscar R. Miranda
Norman R. Dollahon
Temer S. Ahmadi
10.1021/cg060455l.s001
https://acs.figshare.com/articles/journal_contribution/Critical_Concentrations_and_Role_of_Ascorbic_Acid_Vitamin_C_in_the_Crystallization_of_Gold_Nanorods_within_Hexadecyltrimethyl_Ammonium_Bromide_CTAB_Tetraoctyl_Ammonium_Bromide_TOAB_Micelles/3043378
Growth of gold nanorods is investigated in the presence of ascorbic acid in an aqueous mixed micelle solution of
hexadecyltrimethyl ammonium bromide (CTAB) and tetraoctyl ammonium bromide (TOAB) through photochemical reduction of
HAuCl<sub>4</sub>·3H<sub>2</sub>O using 300 nm Hg lamps. The role of the ascorbic acid concentration, [H<sub>2</sub>A], in the formation of gold nanorods was
studied using UV−vis absorption and transmission electron microscopy. Gold nanorods were produced only if [H<sub>2</sub>A]/[Au<sup>3+</sup>] ≥ 0.75
in the reaction cell. For 0.75 < [H<sub>2</sub>A]/[Au<sup>3+</sup>] < 6.2, the aspect ratio of nanorods increased as [H<sub>2</sub>A] increased. For [H<sub>2</sub>A]/[Au<sup>3+</sup>]
> 6.2, the aspect ratio decreased, and shorter nanorods formed as [H<sub>2</sub>A] increased. These results are indicative of a lower and upper
limit in the concentrations of ascorbic acid and its conjugate base (ascorbate anion) for the formation of gold nanorods. The roles
of ascorbic acid and ascorbate ions are discussed, and these observations support the existence of soft templates formed by CTAB/TOAB micelles where Au nanorods grow. Evidence for parallel nucleation and growth processes is also presented.
2006-12-06 00:00:00
tetraoctyl ammonium bromide
CTAB
gold nanorods
TOAB
UV
ascorbic acid
H 2A
Hexadecyltrimethyl Ammonium Bromide
transmission electron microscopy
hexadecyltrimethyl ammonium bromide
300 nm Hg lamps
ascorbic acid concentration
aspect ratio