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Daniel Ricard

Bio: Daniel Ricard is an academic researcher from École Polytechnique. The author has contributed to research in topics: Quantum dot & Kerr effect. The author has an hindex of 20, co-authored 46 publications receiving 4137 citations. Previous affiliations of Daniel Ricard include Centre national de la recherche scientifique.

Papers
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TL;DR: In this article, the energy levels for the electron and the hole are calculated with the spherical confinement, the nonparabolicity of the conduction band, and the valence band degeneracy taken into account.
Abstract: CdSe is used as a prototype to show the implications of valence-band degeneracy for the optical properties of strongly quantum-confined nanocrystals. Absorption spectra and photoluminescence spectra obtained under intermediate and strong pulsed excitation show the presence of new structures. The energy levels for the electron and the hole are calculated with the spherical confinement, the nonparabolicity of the conduction band, and the valence band degeneracy taken into account. The oscillator strengths of the dipole-allowed transitions are also calculated. This model is found to be in good agreement with the experimental observations, which originate mainly from the quantization of the energy spectrum of holes with due account given to valence-band degeneracy.

681 citations

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TL;DR: In this paper, the authors considered theoretically the various mechanisms contributing to the Kerr nonlinearity in small gold particles, including conduction electron intraband contribution, saturation of direct interband transitions and the change in dielectric constant due to hot photoexcited electrons.
Abstract: We first consider theoretically the various mechanisms contributing to the Kerr nonlinearity in small gold particles. The major ones are the conduction electron intraband contribution, the saturation of direct interband transitions and the change in dielectric constant due to hot photoexcited electrons. We present experimental results obtained using optical phase conjugation in gold-doped glasses. By varying several parameters, we were able to ascertain the origin of the nonlinear response: the main contributions are the hotelectron and the interband contributions. All experimental results, including saturation behaviour, are fully understood.

529 citations

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TL;DR: It is shown that the optical phase-conjugated reflectivity from silver and gold colloids is enhanced by several orders of magnitude and this enhancement is traced to the nonlinearities of the electrons in the metal particles and the value of their optical Kerr-effect coefficient is extracted.
Abstract: We show that the optical phase-conjugated reflectivity from silver and gold colloids is enhanced by several orders of magnitude. The reflectivity on resonance is comparable with that of CS(2) for metal-particle volume concentration of a few parts in 10(6). We trace this enhancement to the nonlinearities of the electrons in the metal particles and extract the value of their optical Kerr-effect coefficient.

527 citations

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TL;DR: It is shown that the coupling strength is size independent when the typical dimensions of the electron charge distribution scale as the sphere radius, and the existence of surface modes is shown.
Abstract: We study electron-phonon coupling in the case of Fr\"ohlich or polar interaction, with special emphasis on the size dependence of the coupling strength for semiconductor nanospheres exhibiting quantum confinement of the carriers. We first derive the expression of the vibrational LO (longitudinal optic) and SO (surface optic) eigenfunctions for a sphere in the continuum approximation. After having quantized the vibrational eigenmodes, we give the electron-phonon interaction Hamiltonian. Using a model electronic charge distribution, we then show that the coupling strength is size independent when the typical dimensions of the electron charge distribution scale as the sphere radius. These theoretical considerations are then compared with experimental results obtained using resonant Raman scattering by CdSe-doped glasses with particles of various sizes. The experiments confirm the size independence of the coupling strength and also show the existence of surface modes.

452 citations

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TL;DR: In this paper, the authors have observed a darkening effect and the formation of permanent volume gratings in CdSSe semiconductor-doped glasses, both phenomena being certainly due to the same photochemical mechanism.
Abstract: We have observed a darkening effect and the formation of permanent volume gratings in CdSSe semiconductor-doped glasses, both phenomena being certainly due to the same photochemical mechanism. This allowed us to reconcile contradictory results concerning the speed of their nonlinear response. We also studied the frequency dependence of χ(3) below the gap and the intensity dependence of the reflectivity of these phase-conjugate mirrors. Our results can be interpreted in terms of the band-filling model with Boltzmann statistics. Finally, frequency- and time-resolved luminescence measurements helped us to interpret various results.

335 citations


Cited by
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Journal ArticleDOI
TL;DR: A review of gold nanoparticles can be found in this article, where the most stable metal nanoparticles, called gold colloids (AuNPs), have been used for catalysis and biology applications.
Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

11,752 citations

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TL;DR: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties are equally important.
Abstract: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

6,852 citations

Journal ArticleDOI
TL;DR: In this paper, a synthesis of highly luminescent (CdSe)ZnS composite quantum dots with CdSe cores ranging in diameter from 23 to 55 A was reported.
Abstract: We report a synthesis of highly luminescent (CdSe)ZnS composite quantum dots with CdSe cores ranging in diameter from 23 to 55 A. The narrow photoluminescence (fwhm ≤ 40 nm) from these composite dots spans most of the visible spectrum from blue through red with quantum yields of 30−50% at room temperature. We characterize these materials using a range of optical and structural techniques. Optical absorption and photoluminescence spectroscopies probe the effect of ZnS passivation on the electronic structure of the dots. We use a combination of wavelength dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, small and wide angle X-ray scattering, and transmission electron microscopy to analyze the composite dots and determine their chemical composition, average size, size distribution, shape, and internal structure. Using a simple effective mass theory, we model the energy shift for the first excited state for (CdSe)ZnS and (CdSe)CdS dots with varying shell thickness. Finally, we characterize the...

4,293 citations

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TL;DR: The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology.
Abstract: The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology. A good example of the synergism between scientific discovery and technological development is the electronics industry, where discoveries of new semiconducting materials resulted in the evolution from vacuum tubes to diodes and transistors, and eventually to miniature chips. The progression of this technology led to the development * To whom correspondence should be addressed. B.L.C.: (504) 2801385 (phone); (504) 280-3185 (fax); bcushing@uno.edu (e-mail). C.J.O.: (504)280-6846(phone);(504)280-3185(fax);coconnor@uno.edu (e-mail). 3893 Chem. Rev. 2004, 104, 3893−3946

2,621 citations

Journal ArticleDOI
TL;DR: This paper presents a meta-analysis of four-Wave Mixing and its applications in nanofiltration, which shows clear trends in high-performance liquid chromatography and also investigates the role of nano-magnifying lens technology in this process.
Abstract: 12.2.2. Four-Wave Mixing (FWM) 4849 12.2.3. Dye Aggregation 4850 12.2.4. Optoelectronic Nanodevices 4850 12.3. Sensor 4851 12.3.1. Chemical Sensor 4851 12.3.2. Biological Sensor 4851 12.4. Catalysis 4852 13. Conclusion and Perspectives 4852 14. Abbreviations 4853 15. Acknowledgements 4854 16. References 4854 * Corresponding author E-mail: tpal@chem.iitkgp.ernet.in. † Raidighi College. § Indian Institute of Technology. 4797 Chem. Rev. 2007, 107, 4797−4862

2,414 citations