Binary clusters: homogeneous alloys and nucleus-shell structures

Sinzig, J.; Radtke, U.; Quinten, Michael; Крейбиг, У.

doi:10.1007/bf01429157

Cited by 86 publications

(70 citation statements)

References 6 publications

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“…18 Optical measurements on ensembles of Ag-Au shell-core colloids in solution also revealed two extinction peaks, indicating independent plasmon excitations in shell and core of the particles. 12,13,16 As in the present work, the Au shell-Ag core particles showed less defined optical extinction spectra compared to the opposite configuration, which again suggests enhanced diffusion of Ag atoms towards the cluster surface. Taking these arguments into consideration, an enrichment of Ag atoms in the Au shell provides a plausible explanation for the reduced wavelength difference between shell and core plasmon peaks observed in this experiment.…”

Section: Optical Properties Of Ag-au Shell-core Clusterssupporting

confidence: 68%

“…10 A strong dependence of the plasmon energy on the composition has earlier been observed for ensembles of Ag-Au alloy clusters embedded in photosensitive glass. 12,13 The extinction spectra were also characterized by a single resonance, which monotonously shifted from the Au ͑510 nm͒ to the Ag ͑405 nm͒ position with increasing Ag fraction. Our results on single clusters are in line with this observation, emphasizing that STM-induced light emission is not dominated by the properties of the tip-sample cavity, but reflects the properties of the alloy particle in the tunneling contact.…”

Section: B Optical Properties Of Ag-au Alloy Clustersmentioning

confidence: 99%

“…Mie-plasmon excitations in pure Ag and Au particles are well separated in energy, but converge with an increasing alloying of both materials. [11][12][13] The analysis of Mie plasmons in mixed Ag-Au particles is therefore a sensitive means to characterize the alloying process.…”

Section: Introductionmentioning

confidence: 99%

“…Due to their perfect miscibility and distinct optical properties, they represent a model system to obtain a principle understanding of the alloy formation in small particles. Mixed Ag-Au colloids have been prepared in aqueous solution, 11,[14][15][16][17][18] and solid matrices, such as glass, 12,13 silica, 19 and alumina. 20 Optical absorption and extinction spectroscopy was employed to analyze the cluster ensembles.…”

Section: Introductionmentioning

confidence: 99%

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Photon Emission Spectroscopy of Single Oxide-Supported Ag-Au Alloy Clusters

Benten¹,

Nilius²,

Ernst³

et al. 2005

Phys. Rev. B

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The alloying of Ag and Au has been investigated on the level of individual clusters by analyzing the light emission excited by electron injection from an STM tip. Different Ag-Au alloy and shell-core clusters have been prepared at room temperature on a thin Al 2 O 3 film on NiAl͑110͒ by simultaneous and successive deposition of both noble metals. For simultaneous deposition, one Mie-plasmon resonance has been detected with a wavelength position shifting from the pure Au to the Ag value with increasing Ag content. The results are in agreement with calculations based on Mie theory indicating a complete mixing of both materials. For successive deposition, two Mie resonances have been observed, attributed to plasmon excitations in the shell and core of the clusters. Comparing these results to model calculations, a considerable intermixing of the core and shell materials is concluded, which is especially strong in Au shell-Ag core clusters.

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Section: Optical Properties Of Ag-au Shell-core Clusterssupporting

confidence: 68%

Section: B Optical Properties Of Ag-au Alloy Clustersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Photon Emission Spectroscopy of Single Oxide-Supported Ag-Au Alloy Clusters

Benten¹,

Nilius²,

Ernst³

et al. 2005

Phys. Rev. B

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“…Alloy clusters with diameters between 9 and 15 nm were obtained in photosensitive glasses. 8,26 The disadvantage of this preparation method is, however, the fact that an increasing silver content also results in larger particles. Liz-Marzan et al 27 used inorganic fibers in aqueous solution for the stabilization of gold-silver particles with diameters of 2 to 3 nm after the simultaneous reduction of gold and silver salts by sodium borohydride.…”

Section: Introductionmentioning

confidence: 99%

Alloy Formation of Gold−Silver Nanoparticles and the Dependence of the Plasmon Absorption on Their Composition

1999

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Gold-silver alloy nanoparticles with varying mole fractions are prepared in aqueous solution by the coreduction of chlorauric acid HAuCl 4 and silver nitrate AgNO 3 with sodium citrate. As the optical absorption spectra of their solutions show only one plasmon absorption it is concluded that mixing of gold and silver leads to a homogeneous formation of alloy nanoparticles. The maximum of the plasmon band blue-shifts linearly with increasing silver content. This fact cannot be explained by a simple linear combination of the dielectric constants of gold and silver within the Mie theory. On the other hand, the extinction coefficient is found to decrease exponentially rather than linearly with increasing gold mole fraction x Au . Furthermore, the size distribution of the alloy nanoparticles is examined using transmission electron microscopy (TEM). Highresolution TEM (HRTEM) also confirms the formation of homogeneous gold-silver alloy nanocrystals. IntroductionThe intense research in the field of nanoparticles by chemists, physicists, and materials scientists is motivated by the search for new materials in order to further miniaturize electronic devices as well as by the fundamental question of how molecular electronic properties evolve with increasing size in this intermediate region between molecular and solid-state physics. [1][2][3][4][5][6][7] Possible future applications include the areas of ultrafast data communication and optical data storage. [4][5][6] Semiconductor nanoparticles are also used in building solar cells 7 and metal nanoparticles are very important as catalysts because of their high surface-to-volume ratios. 4 Metal nanoparticles have mainly been studied because of their unique optical properties as especially nanoparticles of the alkali metals and the noble metals copper, silver, and gold have a broad absorption band in the visible region of the electromagnetic spectrum. [8][9][10][11][12][13][14][15] Solutions of these metal nanoparticles show a very intense color, which is absent for the bulk material as well as for the atoms. Their origin is attributed to the collective oscillation of the free conduction electrons induced by an interacting electromagnetic field. These resonances are also denoted as surface plasmons.Mie 16 was the first to explain this phenomenon by applying classical electrodynamics to spherical particles and solving Maxwell's equations for the appropriate boundary conditions. The total extinction cross section composed of absorption and scattering is given as a summation over all electric and magnetic multipole oscillations. The Mie theory has the advantage of being conceptually simple and has found wide applicability in explaining experimental results. 8,9,14,15 However, all of the material properties are represented by a complex dielectric function of the absorbing metal nanoparticles thus obscuring somehow the underlying microscopic events, such as the possible decay mechanisms of the coherent motion of the free electrons.

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Absorption and Reflection of Infrared Radiation by Ultrathin Films

Tolstoy¹,

Чернышова²,

Skryshevsky³

2003

Handbook of Infrared Spectroscopy of Ultrathin Films

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The primary characteristics that one identifies from infrared (IR) spectra of ultrathin films for further analysis are the resonance frequencies, oscillator strengths (extinction coefficients), and damping (bandwidths), related to different kinds of vibrational, translational, and frustrated rotational motion inside the thin-film material [1][2][3][4][5][6][7]. However, the microscopic processes inside or at the surface of a film (motion of atoms and electrons) give rise to the frequency dependence (the dispersion) not only of the extinction coefficient but also of the refractive index of the film. As a result, a real IR spectrum of an ultrathin film is, as a rule, distorted by so-called optical effects. Specifically, the spectrum strongly depends upon the conditions of the measurement, the film thickness, and the optical parameters of the surroundings and substrate impeding extraction of physically meaningful information from the spectrum. Thus after introduction of the nomenclature accepted in optical spectroscopy and a brief discussion of the physical mechanisms responsible for absorption by solids on a qualitative level, this introductory chapter will concentrate on the basic macroscopic or phenomenological theory of the optical response of an ultrathin film immobilized on a surface or at an interface.The theoretical analysis of the IR spectra of ultrathin films on various substrates and at interfaces will involve two assumptions: (1) the problem is linear and (2) the system under investigation is macroscopic; that is, one can use the macroscopic Maxwell formulas containing the local permittivity. The first assumption is valid only for weak fields. The second assumption means that the volume considered for averaging, a (the volume in which the local permittivity is formed), is lower than the parameter of inhomogeneity of the medium, d (e.g., the effective thickness of the film, the size of islands, or an effective dimension of polariton), a < d. In this case, the response of the medium to the external electromagnetic field is essentially the response of a continuum. The 1

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Binary clusters: homogeneous alloys and nucleus-shell structures

Cited by 86 publications

References 6 publications

Photon Emission Spectroscopy of Single Oxide-Supported Ag-Au Alloy Clusters

Photon Emission Spectroscopy of Single Oxide-Supported Ag-Au Alloy Clusters

Alloy Formation of Gold−Silver Nanoparticles and the Dependence of the Plasmon Absorption on Their Composition

Absorption and Reflection of Infrared Radiation by Ultrathin Films

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