Longitudinal Plasma Resonance Shifts in Gold Nanoparticle Aggregates

Norman, Thaddeus J.; Grant, Christian D.; Magana, Donny; Anderson, Roger W.; Zhang, Jin Z.; Cao, D.; Bridges, F.; Li, Jun; Buuren, T. van

doi:10.1117/12.451216

Cited by 10 publications

(15 citation statements)

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“…Cationic surfactant caused aggregation by neutralizing the negative charge on the surface. Previous studies suggested that once the particles were aggregated, hard agglomerates formed and the particles became fused together, similar to what is revealed in Figure . − Recent small-angle X-ray scattering data on gold particles produced by reduction of HAuCl 4 with Na 2 S also show clear evidence of aggregates …”

Section: Discussionsupporting

confidence: 78%

Near Infrared Optical Absorption of Gold Nanoparticle Aggregates

Norman¹,

Grant²,

Magana³

et al. 2002

J. Phys. Chem. B

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257

258

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The reduction of HAuCl 4 by Na 2 S has been reported to produce gold nanoparticles with an optical absorption in the near-infrared along with its characteristic absorption in the visible. The optical resonances in the visible are due to the gold surface plasma, which are a function of the geometry of the particles. The near-infrared absorption had been attributed to the formation of Au 2 S/Au core/shell structures. In this report we present new electronic absorption, electron microscopy, and X-ray absorption data in several systems to show that the near-infrared absorption does not involve core/shell structures. We further suggest that the near-infrared adsorption is most likely the result of the formation of aggregates of gold nanoparticles. The identification of the origin of the near-infrared resonance is critical in understanding the optical properties of metal nanoparticle systems.

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Section: Discussionsupporting

confidence: 78%

Near Infrared Optical Absorption of Gold Nanoparticle Aggregates

Norman¹,

Grant²,

Magana³

et al. 2002

J. Phys. Chem. B

Self Cite

257

258

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“…Spherical gold particles will show only the transverse plasmon band due to their totally symmetric geometry. ,, Throughout the reaction, aggregates, not spherical particles, are formed as evidenced by the growth of the EPB indicating strong interparticle interactions. Previous work has shown that particle−particle separation is small, bound together by sulfur species on the nanoparticle surface. , Although similar absorption characteristics are observed in core/shell and nanorod structures, it was shown previously that the spectral characteristics here are due to strong particle−particle interation. ,,, Interparticle distance is an important factor for SERS studies due to its direct correlation to electromagnetic enhancement. Xu et al have reported that for two 90 nm nanoparticles, decreasing the spacing from 5.5 to 1 nm increases the theoretical enhancement by 4 orders of magnitude .…”

Section: Resultssupporting

confidence: 63%

Unique Gold Nanoparticle Aggregates as a Highly Active Surface-Enhanced Raman Scattering Substrate

et al. 2004

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A unique gold nanoparticle aggregate (GNA) system has been shown to be an excellent substrate for surface-enhanced Raman scattering (SERS) applications. Rhodamine 6G (R6G), a common molecule used for testing SERS activity on silver, but generally difficult to detect on gold substrates, has been found to readily bind to the GNA and exhibit strong SERS activity due to the unique surface chemistry afforded by sulfur species on the surface. This GNA system has yielded a large SERS enhancement of 107−109 in bulk solution for R6G, on par with or greater than any previously reported gold SERS substrate. SERS activity has also been successfully demonstrated for several biological molecules including adenine, l-cysteine, l-lysine, and l-histidine for the first time on a gold SERS substrate, showing the potential of this GNA as a convenient and powerful SERS substrate for biomolecular detection. In addition, the SERS spectrum of R6G on single aggregates has been measured. We have shown that the special surface properties of the GNA, in conjunction with strong near-IR absorption, make it useful for SERS analysis of a wide variety of molecules.

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“…The in situ study of the HAuCl 4 -Na 2 S reaction monitored by SAXS and UV-VIS simultaneously hint at a link between fractal structure and the position of the longitudinal plasma resonance. As demonstrated here and by others [16,23,24], the position of the longitudinal plasma resonance blue shifts as the HAuCl 4 -Na 2 S reaction progresses (Fig. 1b).…”

Section: Resultssupporting

confidence: 58%

“…In our previous work it was demonstrated that the reaction of HAuCl 4 with Na 2 S lead to the formation of aggregates of gold nanoparticles and not Au 2 S/Au core/shell structures [13,16]. It was noticed that the EPR blue shifts during the reaction in the first few hours.…”

Section: Introductionmentioning

confidence: 96%