Colloidal Dispersions of Gold Rods:  Synthesis and Optical Properties

Abstract

Colloidal dispersions of rod-shaped gold particles are obtained by electrodeposition of gold in the nanopores of anodized alumina attached to a conductive support followed by dissolution of the alumina and release of the rods from the support. Coagulation is prevented by steric repulsion due to adsorption of poly-(vinylpyrrolidone) on the gold surface. The synthesis method presented is suitable for the preparation of dispersions of nearly monodisperse colloidal gold rods with adjustable aspect ratio L/d in the range 1.8 < L/d < 49. The length, L, is tuned between 39 and 729 nm, and the diameter, d, is between 12 and 22 nm. The absorbance spectra of randomly oriented colloidal gold rods display a transverse and a longitudinal resonance contribution. With increasing aspect ratio, the transverse resonance shows a small shift to shorter wavelengths, while the longitudinal resonance shifts into the near-infrared regime. The positions of the absorbance maxima agree with the predictions of the Gans theory.

Comparison of Plasmonic Sensing between Polymer- and Silica-coated Gold Nanorods

“…4 In addition, the SPL band is superior for analytical application in biomaterials, such as in-vivo imaging of biotissues, 5 since it appears in the near-infrared region whose light has high permeability to biomaterials. 6 Due to the recent progress on the preparation methods of AuNRs, such as electrochemical method, 7 template method, 8 seed-mediated method, 9 photochemical methods, 10 and the combination of chemical reduction method and photoirradiation method, 11,12 studies on the optical and analytical applications of AuNRs have been growing year to year. However, the problem of the dispersibility of AuNRs still restricts expansions of the utilization of AuNRs.…”

Uniform Gold Nanorod Arrays from Polyethylenimine-Coated Alumina Templates

“…27,28,29 Several earlier studies have shown that Au nanorods with controlled aspect ratios can be prepared within AAO membranes primed with Ag. 30,31,32,33,34 Nanoporous AAO films should thus be ideal templates for preparing Au nanorod arrays with uniform height and 2D smectic order, but to the best of our knowledge this subject has not been adequately addressed, aside from some interesting examples of amphiphilic metalpolymer nanorods assembling into micelle-like monolayers. 35 The paucity of work in this area may be related to the challenges of establishing homogeneous growth conditions within each nanopore, which can be perturbed by poor or variable ohmic contact with the cathode.…”

Microwave green synthesis of PVP-stabilised gold nanoparticles and their adsorption behaviour for methyl orange

“…AC shows peaks at 2 ¼ 24. 4 . The crystallinity of AC was apparently lower than that of the PVP-supported AuNPs-coated AC.…”

“…The free electrons give rise to a surface plasmon absorption band that depends on both the particle size and chemical surrounding. Right now, the shape-controlled synthesis of nanoparticles has been achieved to regulate the particle growth either by using geometric templates [4], or by using some additive, such as polymers [5] or inorganic anions [6]. Accurate controls of size, composition, morphology and stability and the use of environmentfriendly procedures are highly desirable for the synthesis of nanoparticles.…”