Unified Methodology for Fabrication and Quantification of Gold Nanorods, Gold Core Silver Shell Nanocuboids, and Their Polymer Nanocomposites (original) (raw)
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Langmuir, 2014
A novel, solution-based method is presented to prepare bifunctional gold nanorods (B-NRs), assemble B-NRs end-to-end in various solvents, and disperse linked B-NRs in a polymer matrix. The B-NRs have poly(ethylene glycol) grafted along its long axis and cysteine adsorbed to its ends. By controlling cysteine coverage, bifunctional ligands or polymer can be end-grafted to the AuNRs. Here, two dithiol ligands (C6DT and C9DT) are used to link the B-NRs in organic solvents. With increasing incubation time, the nanorod chain length increases linearly as the longitudinal surface plasmon resonance shifts toward lower adsorption wavelengths (i.e., red shift). Analogous to step-growth polymerization, the polydispersity in chain length also increases. Upon adding poly(ethylene glycol) or poly(methyl methacrylate) to chloroform solution with linked B-NR, the nanorod chains are shown to retain end-to-end linking upon spin-casting into PEO or PMMA films. Using quartz crystal microbalance with dissipation (QCM-D), the mechanism of nanorod linking is investigated on planar gold surfaces. At submonolayer coverage of cysteine, C6DT molecules can insert between cysteines and reach an areal density of 3.4 molecules per nm 2 . To mimic the linking of Au NRs, this planar surface is exposed to cysteine-coated Au nanoparticles, which graft at 7 NPs per μm 2 . This solution-based method to prepare, assemble, and disperse Au nanorods is applicable to other nanorod systems (e.g., CdSe) and presents a new strategy to assemble anisotropic particles in organic solvents and polymer coatings.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2006
Simple methods of preparing silver and gold nanoshells on the surfaces of monodispersed polystyrene microspheres of different sizes as well as of silver nanoshells on free-standing gold nanoparticles are presented. The plasmon resonance absorption spectra of these materials are presented and compared to predictions of extended Mie scattering theory. Both silver and gold nanoshells were grown on polystyrene microspheres with diameters ranging from 188 to 543 nm. The commercially available, initially carboxylate-terminated polystyrene spheres were reacted with 2aminoethanethiol hydrochloride (AET) to yield thiol-terminated microspheres to which gold nanoparticles were then attached. Reduction of silver nitrate or gold hydroxide onto these gold-decorated microspheres resulted in increasing coverage of silver or gold on the polystyrene core. The nanoshells were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and UV-vis spectroscopy. By varying the core size of the polystyrene particles and the amount of metal (silver or gold) reduced onto them, the surface plasmon resonance of the nanoshell could be tuned across the visible and the near-infrared regions of the electromagnetic spectrum. Necklace-like chain aggregate structures of gold core-silver shell nanoparticles were formed by reducing silver nitrate onto free citrate-gold nanoparticles. The plasmon resonance absorption of these nanoparticles could also be systematically tuned across the visible spectrum.
Langmuir, 2007
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Nanotechnologies in Russia, 2009
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