Phase transition in confined Se nanoclusters

Raman scattering is an inelastic process, in which we can obtain information about material lattice vibration frequencies. If the wavelength of the excitation laser is within the electronic spectrum of the material, the intensity of some Raman-active vibrations will increase enormously. This resonant Raman effect can be quite useful to explore the electron-phonon coupling in the substance. In this article, we report the investigations on the electron-phonon coupling effect in Se nanoclusters using resonant Raman technique. Up to 1 0 different laser lines are used in the experiment. The Raman intensity strongly depends on the energy of the laser lines used for excitation. The one-phonon symmetric modes for Se single helix and Se8 rings are enhanced in the vicinity of their absorption bands. Detailed analysis shows that the Raman intensity in the high frequency range 450 -550 cm1 is a sum of individual second-order Raman scattering intensities for the confined Se species. These two-phonon Raman shifts occur at twice the frequency shift of the first-order Raman lines, and their intensities are also enhanced when the excitation laser energy matches an electronic transition in Se nanoclusters.

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“…[5][6][7]. Raman scattering experiments were performed at ambient condition using a back scattering geometry.…”

Section: Methodsmentioning

confidence: 99%

<title>Resonant Raman technique-a powerful tool for exploring electron-phonon coupling in Se nanoclusters</title>

Zhai

Tang

et al. 2006

SPIE Proceedings

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“…Selenium (Se) is frequently encountered as a guest material in the design of both clusters and isolated one-dimensional (1D) nano-structures in microporous crystals of zeolites and related crystals. [1][2][3][4][5][6][7][8] When Se is loaded into zeolites the differences in electronic properties and structure are obvious and are caused by its confinement within the nano-space of the zeolites. [9][10][11][12][13][14] A number of research groups have attempted to elucidate the structure using various analytical methods, but the disordered structure of Se atoms in the microporous crystals has made the analysis and interpretation difficult.…”

Section: Introductionmentioning

confidence: 99%

The selective adsorption of tellurium in the aluminosilicate regions of AFI- and MOR-type microporous crystals

Kodaira

Ikeda

2014

Dalton Trans.

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Attempts have been made to load tellurium (Te) atoms into the one-dimensional nano-channels of microporous crystals of aluminophosphate AlPO4-5 and of aluminosilicate mordenites of the Na(+) form (Na-MOR) and the H(+)-form (H-MOR) at 673 K. The density of the atoms adsorbed was in the sequence 0 ∼ AlPO4-5 ≪ H-MOR < Na-MOR. AlPO4-5 provides a shallow potential of periodical charge fluctuation for Te atoms, from the alternate ordering of Al and P atoms through O atoms. Mordenite offers a sufficiently strong potential for Te adsorption, but the magnitude varies with the type of cation. Dipoles between framework AlO2(-) anion sites and their Na(+) counter-ions in Na-MOR provide a stronger potential than the Brønsted acid points in H-MOR. The adsorption of Te atoms in the silico-aluminophosphate SAPO-5 was between that of AlPO4-5 and H-MOR, leading us to suspect that Te atoms are selectively adsorbed in the aluminosilicate regions accompanying the Brønsted acid points distributed in the major aluminophosphate network. The aluminosilicate regions in SAPO-5 are below 500 nm in size and are distributed throughout a single crystal.

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Nanocomposite Materials: Semiconductors in Zeolites

Goldbach

Saboungi

2005

Encyclopedia of Inorganic Chemistry

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Encapsulation in zeolites holds considerable promise for organizing semiconductor quantum dots and quantum wires into ordered two‐ and three‐dimensional arrays that can be used in a variety of applications. While the use of such materials has been limited until now by a number of practical difficulties, considerable progress has been made in the last few years in surmounting these obstacles. This article reviews recent progress in the field, particularly with regard to stabilization of the nanocomposites against moisture, modulation of their properties by appropriate cation substitution, and preparation of materials in the form of thin films that can exhibit strong nonlinear optical activity. Finally, the article discusses the present perspectives for the field and outlines some research directions that must be pursued for these materials to achieve their full range of potential applications.

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Phase transition in confined Se nanoclusters

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Cited by 7 publications

References 20 publications

<title>Resonant Raman technique-a powerful tool for exploring electron-phonon coupling in Se nanoclusters</title>

<title>Resonant Raman technique-a powerful tool for exploring electron-phonon coupling in Se nanoclusters</title>

The selective adsorption of tellurium in the aluminosilicate regions of AFI- and MOR-type microporous crystals

Nanocomposite Materials: Semiconductors in Zeolites

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