Ultrasmall Hollow Gold–Silver Nanoshells with Extinctions Strongly Red-Shifted to the Near-Infrared

Abstract

Hollow gold-silver nanoshells having systematically varying sizes between 40 and 100 nm were prepared. These particles consist of a hollow spherical silver shell surrounded by a thin gold layer. By varying the volume of the gold stock solution added to suspensions of small silver-core templates, we tailored the hollow gold-silver nanoshells to possess strong tunable optical extinctions that range from the visible to the near-IR spectral regions, with extinctions routinely centered at ∼950 nm. The size and morphology of these core/shell nanoparticles were characterized by dynamic light scattering (DLS), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). Separately, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used for measuring their elemental composition; UV-vis spectroscopy was used to evaluate their optical properties. Given their relatively small size compared to other nanoparticles that absorb strongly at near IR wavelengths, these easy-to-synthesize particles should find use in applications that require ultrasmall nanoparticles with extinctions comfortably beyond visible wavelengths (e.g., medicinal therapies, diagnostic imaging, nanofluidics, and display technologies).

Novel core–shell structured Paclitaxel-loaded PLGA@Ag–Au nanoparticles

“…Using a replacement reaction [7], the formation of Ag-Au nanoshells was achieved by adding the K-gold solution to PLGA@Ag nanocolloids. Fig.…”

“…As the Au 0 continued to deposit onto the exterior of Ag NPs, Au nanoshells began to form. As the reaction proceeded, a porous bimetallic Ag-Au nanoshell was produced on each PLGA NP [7]. A UV-vis absorption spectrum of PLGA@Ag-Au NPs is shown as Fig.…”

“…Sun et al developed hollow Ag-Au nanoshells based on Ag nanoparticles, upon the addition of Au 3 þ [6].The plasmon band of the shell depended on its thickness and had a large effect on the efficiency of generating SERS signals. The SPR absorption of Ag-Au nanoshells was tunable from the visible to the near-infrared spectral regions, enabling the nanoshells to be photothermal energy converters which can be used in photothermal cancer therapy and photothermally triggered drug release [7]. On the other hand, Ag-Au bimetallic nanostructures are good candidates as SERS media [8].…”

Controllable Cobalt Oxide/Au Hierarchically Nanostructured Electrode for Nonenzymatic Glucose Sensing

“…Briefly, noble metal nanoparticles, exhibiting NIR absorption in the appropriate size regime (20-100 nm) for biological applications, are modified with either an antibody or ligand specific to an antigen or receptor, on the surface of a tumor cell [38,53,190]. NIR absorbing particles are preferred since it is well known that blood and tissue are most readily penetrated by light in this wavelength region [191][192][193]. The bioconjugated nanoparticles are then introduced, either in vitro or in vivo, and allowed to incubate or circulate and bind to the tumor site.…”

“…Typically penetration in the range of 1-20 mm is sufficient for the ablation of cancer cells that are near the surface of the skin [160,191,193,204]. However, it has been reported that depths of 50-80 mm have been achieved [186,205].…”