Optical Properties of Noble Metal Clusters as a Function of the Size: Comparison between Experiments and a Semi-Quantal Theory

Cottancin, E.; Celep, G.; Lermé, J.; Pellarin, M.; Huntzinger, Jean-Roch; Vialle, Jean; Broyer, M.

doi:10.1007/s00214-006-0089-1

Cited by 188 publications

(192 citation statements)

References 36 publications

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“…TD-DFT provides a method to take into account the inherent excitation aspect; however, it is numerically very demanding. Many TD-DFT studies have considered only the noble-metal's 6s electrons explicitly, approximating the remaining ionic cores as a smooth charge background in the so-called jellium model, and describing the filled shell of the polarizable 5d electrons by an appropriate dielectric function derived from the optical functions of the bulk material 34,35 . Consequently, these calculations cannot precisely describe the contributions from the 5d band and, in particular, not the strong quantization effects in the 5d bands that alter the properties of the quantum-sized clusters with respect to the bulk metal.…”

Section: Resultsmentioning

confidence: 99%

“…The product gold-hexanethiolate clusters were then extracted from the precipitated material into dichloromethane solution. The as-obtained material contains Au 144 (SR) 60 as a major product, R ¼ C 6 H 13 , but also smaller quantities of lower-mass clusters (Au 25 (SR) 18 , Au 67 (SR) 35 and Au 102 (SR) 44 ) as well as larger ones in the 70-kDa mass range. Smaller clusters were removed from powder samples by extraction into acetone.…”

Section: Methodsmentioning

confidence: 99%

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Information on quantum states pervades the visible spectrum of the ubiquitous Au144(SR)60 gold nanocluster

et al. 2014

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Absorption spectra of very small metal clusters exhibit individual peaks that reflect the discreteness of their localized electronic states. With increasing size, these states develop into bands and the discrete absorption peaks give way to smooth spectra with, at most, a broad localized surface-plasmon resonance band. The widely accepted view over the last decades has been that clusters of more than a few dozen atoms are large enough to have necessarily smooth spectra. Here we show through theory and experiment that for the ubiquitous thiolate cluster compound Au 144 (SR) 60 this view has to be revised: clearly visible individual peaks pervade the full near-IR, VIS and near-UV ranges of low-temperature spectra, conveying information on quantum states in the cluster. The peaks develop well reproducibly with decreasing temperature, thereby highlighting the importance of temperature effects. Calculations using time-dependent density-functional theory indicate the contributions of different parts of the cluster-ligand compound to the spectra.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Information on quantum states pervades the visible spectrum of the ubiquitous Au144(SR)60 gold nanocluster

et al. 2014

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“…16 Classical models fail to describe this behavior and semi-quantal models or full ab initio approaches are required. 17,18 The optical response of small noble metal clusters is impacted by the close proximity of filled d levels. Because of the large s-d separation in Ag atoms, silver clusters are better described by free electron models than gold or copper clusters with a small s-d energy separation.…”

Section: Introductionmentioning

confidence: 99%

“…19,20 Optical absorption spectra of size selected noble metal clusters can be obtained by embedding them in inert gas 21 or in transparent ceramic matrices. 17 Such matrices prevent the clusters from effectively dissociating upon irradiation and allow using commercially available spectrophotometers. Limitations related to size and shape distributions of the matrix embedded particles can be overcome by spatial modulation far-field optical techniques, permitting optical identification of single particles.…”

Section: Introductionmentioning

confidence: 99%

Copper doping of small gold cluster cations: Influence on geometric and electronic structure

Lang

Claes

Cuong

et al. 2011

The Journal of Chemical Physics

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Analytical approach for the excited-state Hessian in time-dependent density functional theory: Formalism, implementation, and performance J. Chem. Phys. 135, 184111 (2011) Stability analysis of multiple nonequilibrium fixed points in self-consistent electron transport calculations J. Chem. Phys. 135, 174111 (2011) Communication: Orbital instabilities and triplet states from time-dependent density functional theory and longrange corrected functionals J. Chem. Phys. 135, 151103 (2011) All-electron time-dependent density functional theory with finite elements: Time-propagation approach J. Chem. Phys. 135, 154104 (2011) Additional information on J. Chem. Phys. The effect of Cu doping on the properties of small gold cluster cations is investigated in a joint experimental and theoretical study. Temperature-dependent Ar tagging of the clusters serves as a structural probe and indicates no significant alteration of the geometry of Au n + (n = 1-16) upon Cu doping. Experimental cluster-argon bond dissociation energies are derived as a function of cluster size from equilibrium mass spectra and are in the 0.10-0.25 eV range. Near-UV and visible light photodissociation spectroscopy is employed in conjunction with time-dependent density functional theory calculations to study the electronic absorption spectra of Au 4-m Cu m + (m = 0, 1, 2) and their Ar complexes in the 2.00−3.30 eV range and to assign their fragmentation pathways. The tetramers Au 4 + , Au 4 + · Ar, Au 3 Cu + , and Au 3 Cu + · Ar exhibit distinct optical absorption features revealing a pronounced shift of electronic excitations to larger photon energies upon substitution of Au by Cu atoms. The calculated electronic excitation spectra and an analysis of the character of the optical transitions provide detailed insight into the composition-dependent evolution of the electronic structure of the clusters.

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“…Observed SPR band positions have been reported to blue-shift or red-shift depending on a variety of features (18,21,(24)(25)(26). Unfortunately, reliable theoretical predictions based on quantum mechanics are very difficult (or even impossible) to obtain at present, and approximate approaches also lead to conflicting predictions (18,21,27,28). Experimentally deducing the correct SPR size-dependence of metal NPs in the 2-20 nm regime requires synthesis of NPs with: (i) very narrow size distributions (<10%) to attenuate heterogeneous broadening, (ii) high uniformity in morphology and surface environment, and (iii) excellent dispersibility to eliminate the influence of aggregation.…”

mentioning

confidence: 99%

Reversing the size-dependence of surface plasmon resonances

Peng

McMahon

Schatz

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

428

436

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The size-dependence of surface plasmon resonances (SPRs) is poorly understood in the small particle limit due to complex physical/chemical effects and uncertainties in experimental samples. In this article, we report an approach for synthesizing an ideal class of colloidal Ag nanoparticles with highly uniform morphologies and narrow size distributions. Optical measurements and theoretical analyses for particle diameters in the d ≈ 2-20 nm range are presented. The SPR absorption band exhibits an exceptional behavior: As size decreases from d ≈ 20 nm it blue-shifts but then turns over near d ≈ 12 nm and strongly red-shifts. A multilayer Mie theory model agrees well with the observations, indicating that lowered electron conductivity in the outermost atomic layer, due to chemical interactions, is the cause of the red-shift. We corroborate this picture by experimentally demonstrating precise chemical control of the SPR peak positions via ligand exchange.T he ability to control surface plasmon resonances (SPRs) in metal nanostructures is critical for achieving advances in many areas, including chemical and biological sensing, imaging, optoelectronics, energy harvesting and conversion, and medicine (1-12). Metal nanoparticles (NPs), particularly those of the noble metals (e.g., Au and Ag) that exhibit strong SPRs, have been the focus of much work (13-17). SPRs have intense and broad optical absorption bands that arise from coherent oscillations of conduction electrons near the NP surfaces. In general, SPRs are influenced by their size, morphology, composition, surface chemistry, and surrounding environment (18,19). However, the size-dependence of SPRs that is important for the aforementioned applications (1-12) is poorly understood in the small particle limit due to complex physical and chemical effects as well as uncertainties in experimental samples. Here, we report an approach for synthesizing an ideal class of colloidal Ag NPs with highly uniform morphologies and narrow size distributions. The SPR absorption band for particles with diameters, d, in the range of 2-20 nm is found to exhibit an exceptional behavior: As size decreases from d ≈ 20 nm it blue-shifts but then turns over near d ≈ 12 nm and strongly red-shifts. We have developed a multilayer Mie theory model and the corresponding calculation results agree well with the observations, indicating that the lowered electron conductivity in the outermost atomic layer, due to chemical interactions, is the cause of the red-shift. We corroborate this picture by experimentally demonstrating precise chemical control of the SPR peak positions via ligand exchange. Such chemical control of the NP surface layer may provide a promising strategy for sensitively probing species strongly adsorbed (or bonded) to the NPs.For metal NPs with d or structural features larger than 20 nm, often a purely continuum-level, classical electrodynamics picture suffices for interpretation or prediction of their optical properties. In this approach the bulk dielectric constants for the vario...

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Optical Properties of Noble Metal Clusters as a Function of the Size: Comparison between Experiments and a Semi-Quantal Theory

Cited by 188 publications

References 36 publications

Information on quantum states pervades the visible spectrum of the ubiquitous Au144(SR)60 gold nanocluster

Information on quantum states pervades the visible spectrum of the ubiquitous Au144(SR)60 gold nanocluster

Copper doping of small gold cluster cations: Influence on geometric and electronic structure

Reversing the size-dependence of surface plasmon resonances

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