Controlling the Optical Properties of Gold Nanorods in One-Pot Syntheses

Abstract

We present the characterization of the CTAB-oleate controlled synthesis of gold nanorods (AuNRs). Concentrations of key compounds in the synthetic system were varied in the presence of oleate, including HCl, borohydride, silver nitrate, and ascorbic acid. The longitudinal surface plasmon resonance peak was sensitive to changes in all concentrations. Reducing the concentration of Ag ions below 66 μM led to slower reaction kinetics and incomplete Au reduction. Variation of the ascorbic acid concentration revealed that oleate is responsible for around 44% of reduction of Au 3+ to Au + before nucleation in these experiments. Increasing the oleate concentration significantly slows the growth kinetics and leads to much longer synthesis times of above 12 h for reaction completion. These observations will enable the design of better methods of synthesizing of AuNRs using binary surfactants.

NIR/pH Dual-Responsive DOX-Loaded AuNRs@S-β-CD Nanocomposite for Highly Effective Chemo-photothermal Synergistic Therapy against Lung Cancer Cells

“…Gold nanoparticles (AuNPs) such as gold nanorods, nanospheres, nanocubes, nanoshells, nanocages, nanostars, etc. with high optical absorption in the near-infrared (NIR) region have attracted much attention for cancer photothermal therapy. − NIR light allows for greater depth penetration with minimal absorption, and scattering through tissue, than do shorter wavelengths in the visible region.…”

Controlled synthesis of monodisperse gold nanorods with a small diameter of around 10 nm and largest plasmon wavelength of 1200 nm

“…21,29,30,32,44,47 Without addition of silver ions, there was only one extinction peak at 540 nm, indicating that no AuNR was formed because of the absence of LSPR wavelength. 18 The TEM images shown in Fig. 2a confirm that the product synthesized under this condition is composed of non-rod-shaped nanoparticles including spheres, cubes, and other irregular shapes.…”

“…Based on these results, it is clear that: first, a broadening of FWHM before 0.5 mL of silver ion shown in the extinction spectrum that reflects an enlargement of distribution discrepancy of the aspect ratio is caused by a quick increase in the rod's length and a decrease in diameter with already a small value. 18,23,51 Second, in the range of 0.5-0.8 mL, a relatively fixed AuNR length is displayed accompanied by a slow decrease in diameter, so that both the increase in aspect ratio and enhancement in size uniformity of AuNRs are acquired and shown as a red-shift and a FWHM decrease of the LSPR. Third, beyond 0.8 mL of silver ions, a reverse trend of diameter and length changes is displayed, resulting in a blue-shift of LSPR and further a decrement of FWHM as smaller length and larger diameter acquired.…”

“…Via the introduction of different additives to vary the reducibility of AA, the spectral and geometrical properties of the acquired AuNR can be improved obviously. [15][16][17][18] Among them, hydrochloride acid is the most commonly used. The increase in hydrogen ion concentration via the addition of hydrochloride acid can weaken the reducibility of AA, which will remarkably facilitate the formation of AuNRs.…”

Precise Tailoring of Mesoporous Silica-Coated Gold Nanorods for Laser Ignition at 1064 nm

“…Notwithstanding it has been generally pointed out that silver nitrate usually functions as a morphology director in the anisotropic growth of Au nanostructures, − a well-fitted linear correlation between the LSPR peak and the concentration of silver nitrate somehow failed to be established. ,,− The underlying mechanisms for the robust linear correlation fitted in this study were further investigated. One of the explanations is that the reduced type of reagents (without HCl) involved in the growth solution makes the synthetic system clear and simple, which decreases the interaction and synergy between different reagents (Table S1, Supporting information).…”