Synthesis of Dumbbell-Shaped Au−Ag Core−Shell Nanorods by Seed-Mediated Growth under Alkaline Conditions

Abstract

We report a simple synthesis of Au-Ag core-shell nanorods (NRs) under alkaline conditions (pH 8.0-10.0) from silver and ascorbate ions using gold nanorods (GNRs) as the seeds. The silver ions that are reduced by the ascorbate ions become deposited on the surfaces of the GNRs to form differently dumbbell-shaped Au-Ag core-shell NRs and nanoparticles, depending on the pH and the concentration of silver ions. The longitudinal plasmon absorbance bands of the Au-Ag core-shell NRs are stronger and appear at shorter wavelengths than those for the original GNRs. We confirmed the formation of Au-Ag core-shell NRs by both energy-dispersive X-ray spectrometry and inductively coupled plasma mass spectrometry measurements, which indicate that the 109Ag/197Au ratios are 0.046, 0.085, and 0.097 at pH 8.0, 9.0, and 10.0, respectively. The transmission electron microscopy measurements show that the Au-Ag core-shell NRs are monodispersed (>90%).

Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications

“…[184] Silver coating is generally conducted by the reduction of silver nitrate with ascorbic acid at base condition in the presence of gold nanorods and stabilizing agents such as citrate, CTAB, and polyvinylpyrrolindone (PVP). [185,186] Reduction of saturated silver chloride aqueous solution with hydroxyamine oxide could also chemically deposit a silver shell on gold nanorods. [187] The silver thickness can be controlled by tuning the concentration of the silver precursor and the mild reducing agents.…”

Communication: A density functional investigation of structure-property evolution in the tetrakis hexahedral C4Al14 nanocluster

“…The conventional image tends to be that of a (roughly) spherical core-shell ensemble, although alternative shapes are now known to be important, particularly in light of their potential applications in diverse areas such as nanoelectronics and biomedical sensors. [8][9][10][11] In our previous studies on core-shell C n Al 12 species, the n = 4 system has exhibited a unique behaviour. The original Al 12 shell generally preserved its near-icosahedral structure for n = 1 to 3, but, apparently due to an "oversized" carbon core, acquired a tetracapped-cube-like geometry for C 4 Al 12 .…”

Probing Silver Deposition on Single Gold Nanorods by Their Acoustic Vibrations

“…5−8 Typically this deposition process is monitored through shifts of the surface plasmon resonance due to the changes in the shape and composition of the particle. 9,10 However, the plasmon resonance is mostly sensitive to the shape of the particle, whereas the exact dimensions are difficult to obtain from the spectrum (the line width only depends weakly on the particle volume for intermediate particle sizes 11 ). A prime example of this effect is the longitudinal plasmon of a subwavelength gold nanorod, whose frequency strongly depends on the aspect ratio (length/diameter) of the particle but only weakly on its volume.…”