Star-shaped Gold nanoparticles
Immagina STARGOLD are star-shaped gold nanoparticles with dimensions ranging from 40 to 150 nm (Figure 1) and with unique optical properties.
Figure 1. Left: Transmission and Inset: False color scanning electron microscopy image of STARGOLD nanoparticles. Right: Image of STARGOLD solution in water.
The absorption spectra of spherical and STARGOLD gold colloids appear very different revealing a pronounced absorption at 530 nm for the spherical nanoparticles. On the contrary, the absorption maximum of the STARGOLD is 615 nm. (Figure 2).
Figure 2. Normalized UV–vis absorption spectra of 60 nm spherical gold nanoparticles (red line) and STARGOLD nanoparticles (blue line). Inset: SEM images of spherical and STARGOLD nanoparticles.
The localized plasmon can be exploited in order to enhance the Raman spectrum of a molecule placed near the nanoparticles. The effect of the particular morphology of the STARGOLD surface on the SERS efficiency was investigated by using Rhodamine 6G (Rh6G) molecules (Figure 3). Remarkably, the STARGOLD showed a higher (around one order of magnitude) Raman enhancement relative to that observed for the spherical nanoparticles of the same diameter.
Figure 3. Normalized Raman spectra of Rh6G adsorbed on STARGOLD and Au NP.
For their possible use in biological applications, a further stabilization of the nanoparticles may be obtained by conjugation with various polymers containing functional groups. STARGOLD can be easy functionalized by thiol-terminated polyethylenglycol. The high scattering of the branched gold nanoparticles was exploited for STARGOLD localization in cells by laser scanning confocal microscopy analysis without the need of fluorescent probes (Figure 4).
Figure 4. Laser scanning confocal microscopy analysis of A549 cancer cell line incubated with STARGOLD–PEG sample. Green (WGA-AlexaFluor 488 fluorescence), Red (STARGOLD–PEG).
SELECTED REFERENCE: L. Minati, F. Benetti, A. Chiappini, G. Speranza One-step synthesis of star-shaped gold nanoparticles Colloids and Surfaces A: Physicochemical and Engineering Aspects 441, 623-628
Near Infraded absorbing STARGOLD GREEN.
Immagina STARGOLD GREEN are 70 nm gold nanostar with a pronunced absorption in the NIR.
Figure 5. Left: UV–vis absorption spectra of STARGOLD GREEN nanoparticles. Right: Image of STARGOLD GREEN solution in water.
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