Optical Properties and Ultrafast Dynamics of Metallic Nanocrystals

Link, Stephan; El‐Sayed, Mostafa A.

doi:10.1146/annurev.physchem.54.011002.103759

Cited by 1,531 publications

(1,602 citation statements)

References 217 publications

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“…As seen in Figure 5a, C ext for nanospheres increases as the nanosphere size is increased. This trend has been commonly observed in experiments 33,34 and reflects the direct dependence of the nanosphere extinction cross-section on the sphere volume in Figure 4. Tunability of the plasmon resonance maximum in nanoparticles.…”

Section: Resultssupporting

confidence: 81%

“…It is well-known that, by changing the shape of nanoparticles to that of elongated rods, the optical characteristics can be significantly changed. 2,33,34,36,43,73 Gold nanorods possess, in addition to the surface plasmon band around 528 nm seen in gold nanospheres, a band at longer wavelengths due to the plasmon oscillation of electrons along the long axis of the nanorods. 2,33,34,36,43,73 The calculated absorption, scattering, and extinction spectra of the surface plasmon band of gold nanorods have been shown in Figure 3.…”

Section: Resultsmentioning

confidence: 99%

“…1,2,[32][33][34] In addition, Halas and co-workers have shown that the use of composite nanoparticles based on a core-shell morphology (e.g., silica-gold nanoshells) allows optical tunability by variation in the composition. 35 There have been several experimental reports 2,36 on the optical properties of metal nanoparticles, including gold nanospheres, 33,34,[36][37][38][39][40][41][42] nanorods, 33,34,36,43 and nanoprisms, 44 silver nanospheres, 36,37,39,[45][46][47] nanowires, 48 and nanoprisms, [49][50][51][52] copper nanospheres, 37,45,53 aluminum nanospheres, 36 bimetallic nanoparticles, 54,55 composite nanoparticles with a core-shell structure, 35,[56][57][58][59][60] and nanoparticle chains and assemblies. [61][62][63] At the same time, well-established theoretical tools based on the Mie theory 64 and the discrete dipole approximation (DDA) 65 method ...…”

Section: Introductionmentioning

confidence: 99%

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Calculated Absorption and Scattering Properties of Gold Nanoparticles of Different Size, Shape, and Composition: Applications in Biological Imaging and Biomedicine

et al. 2006

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The selection of nanoparticles for achieving efficient contrast for biological and cell imaging applications, as well as for photothermal therapeutic applications, is based on the optical properties of the nanoparticles. We use Mie theory and discrete dipole approximation method to calculate absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles: gold nanospheres, silica-gold nanoshells, and gold nanorods. The calculated spectra clearly reflect the well-known dependence of nanoparticle optical properties viz. the resonance wavelength, the extinction cross-section, and the ratio of scattering to absorption, on the nanoparticle dimensions. A systematic quantitative study of the various trends is presented. By increasing the size of gold nanospheres from 20 to 80 nm, the magnitude of extinction as well as the relative contribution of scattering to the extinction rapidly increases. Gold nanospheres in the size range commonly employed (∼40 nm) show an absorption cross-section 5 orders higher than conventional absorbing dyes, while the magnitude of light scattering by 80-nm gold nanospheres is 5 orders higher than the light emission from strongly fluorescing dyes. The variation in the plasmon wavelength maximum of nanospheres, i.e., from ∼520 to 550 nm, is however too limited to be useful for in vivo applications. Gold nanoshells are found to have optical cross-sections comparable to and even higher than the nanospheres. Additionally, their optical resonances lie favorably in the near-infrared region. The resonance wavelength can be rapidly increased by either increasing the total nanoshell size or increasing the ratio of the core-toshell radius. The total extinction of nanoshells shows a linear dependence on their total size, however, it is independent of the core/shell radius ratio. The relative scattering contribution to the extinction can be rapidly increased by increasing the nanoshell size or decreasing the ratio of the core/shell radius. Gold nanorods show optical cross-sections comparable to nanospheres and nanoshells, however, at much smaller effective size. Their optical resonance can be linearly tuned across the near-infrared region by changing either the effective size or the aspect ratio of the nanorods. The total extinction as well as the relative scattering contribution increases rapidly with the effective size, however, they are independent of the aspect ratio. To compare the effectiveness of nanoparticles of different sizes for real biomedical applications, size-normalized optical cross-sections or per micron coefficients are calculated. Gold nanorods show per micron absorption and scattering coefficients that are an order of magnitude higher than those for nanoshells and nanospheres. While nanorods with a higher aspect ratio along with a smaller effective radius are the best photoabsorbing nanoparticles, the highest scattering contrast for imaging applications is obtained from nanorods of high aspect ratio with a larger effective radi...

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Section: Resultssupporting

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Calculated Absorption and Scattering Properties of Gold Nanoparticles of Different Size, Shape, and Composition: Applications in Biological Imaging and Biomedicine

et al. 2006

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“…When metal nanoparticles are exposed to light on resonance with their absorption wavelength, a collective oscillation of electrons in the conduction band takes place [13,14]. This creates a charge separation with respect to the lattice [2,15].…”

Section: Localized Surface Plasmon Resonance (Lspr) and Mie Theorymentioning

confidence: 99%

“…The confined conduction band electrons in the small particle volume then begin to move in phase with the radiation plane wave excitation, creating a coherent electromagnetic (EM) response which strengthens both the near field energy and the optical extinction associated with the nanoparticle surface [16,17]. The optical extinction, or maximum intensity of the oscillation frequency, is composed of both scattering (elastic and radiative) and absorption (inelastic and non-radiative) efficiencies [14,17]. The coherent oscillatory response of a dipole induced noble metal nanoparticle conduction band electrons on resonance with an incident light at a specific frequency is illustrated schematically in Fig.…”

Section: Localized Surface Plasmon Resonance (Lspr) and Mie Theorymentioning

confidence: 99%

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

2016

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By electrodeposition and galvanic replacement reaction, we developed a facile, time-saving, cost-effective, and environmentally friendly, two-step synthesis route to obtain a controllable cobalt oxide/Au hierarchically nanostructured electrode for glucose sensing. The nanomaterials were characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, energy-dispersive spectrometry, and X-ray photoelectron spectroscopy, meanwhile, the sensing performance was investigated by cyclic voltammetry and amperometric response. The results revealed that this novel electrode exhibited excellent electrocatalytic performance toward glucose oxidation, with a wide double-linear range from 0.2 μM to 20 mM and a low detection limit of 0.1 μM based on a signal-to-noise ratio of 3, which was mainly attributed to the ability of loading a small amount of Au with good electron conductivity on the surface of cobalt oxide nanosheets with large active surface area and synergistic electrocatalytic activity of Au and cobalt oxide toward glucose electrooxidation. This facile, sensitive, and selective glucose sensor is also proven to be suitable for the detection of glucose in human serum.

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Liquid‐Phase Synthesis of Inorganic Nanoparticles

Caruntu

O’Connor

2005

Encyclopedia of Inorganic Chemistry

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In this article we review some of the most representative liquid‐phase synthetic methodologies for the preparation of inorganic nanoparticles. Metallic nanoparticles and alloys have been chosen as a model to discuss the preparation of colloidal nanocrystals and their functionalization with organic molecules. Of a particular interest have been the synthetic methodologies allowing not only the compositional control of the nanoparticles but also the size/shape of the nanoparticles along with their ability to organize into hierarchical architectures suitable for different technological applications.

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Optical Properties and Ultrafast Dynamics of Metallic Nanocrystals

Cited by 1,531 publications

References 217 publications

Calculated Absorption and Scattering Properties of Gold Nanoparticles of Different Size, Shape, and Composition: Applications in Biological Imaging and Biomedicine

Calculated Absorption and Scattering Properties of Gold Nanoparticles of Different Size, Shape, and Composition: Applications in Biological Imaging and Biomedicine

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

Liquid‐Phase Synthesis of Inorganic Nanoparticles

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