The elastic and vibrational properties of a material, bulk or planar waveguide, are studied by BriUouin and Raman spectroscopy to follow the process of nanocrystals growth in glass-ceramics. The nanoparticles cause th...The elastic and vibrational properties of a material, bulk or planar waveguide, are studied by BriUouin and Raman spectroscopy to follow the process of nanocrystals growth in glass-ceramics. The nanoparticles cause the appearance, in the low frequency Raman spectrum, of characteristic peaks, whose position depends on the size of the crystals. At the same time, sharp crystal peaks, due to optical phonons, appear in the Raman spectra, allowing the determination of the nucleated phase, and a frequency shift of the BriUouin peaks is observed.展开更多
We consider a two-dimensional(2D)trapped ion model in which two laser beams drive the corresponding vibrational motions and are carrier resonant with the two-level of the ion.Due to the coherent superposition of two s...We consider a two-dimensional(2D)trapped ion model in which two laser beams drive the corresponding vibrational motions and are carrier resonant with the two-level of the ion.Due to the coherent superposition of two sub-Rabi oscillations involved in the bimodal vibrations,the Rabi frequency degeneration and offset may occur in this model.This provides a possibility to generate the pair coherent state in the 2D trapped ion.展开更多
We have comparatively studied the addition of Cr and V in titania.Cr and V content were changed by means of insets placed in the Ti target.Structural,compositional and electrical analyses of different series of thin f...We have comparatively studied the addition of Cr and V in titania.Cr and V content were changed by means of insets placed in the Ti target.Structural,compositional and electrical analyses of different series of thin films,made by XRF, XRD,are presented.Electrical characterization not only showed that Cr doped layers were very sensitive to ethanol within a useful range for applications,but also allowed to verify that the electrical behaviour is dependent on the structure of film. Finally,the Cr and V concentrations that gives the best results in terms of sensing performances has been determined and a correlation between structural and electrical measurement has been evidenced.展开更多
Here we examine the findings obtained for disaccharide/water mixtures near glass transition that involves cooperative relaxation features on kinetic by viscosity and on thermodynamic behaviour by neutron scattering. T...Here we examine the findings obtained for disaccharide/water mixtures near glass transition that involves cooperative relaxation features on kinetic by viscosity and on thermodynamic behaviour by neutron scattering. Then to address cooperative phenomena that mitigate the Debye-Waller behaviour we invoke Adam-Gibbs’ idea of a cooperative rearranging region. Neutron results suggest that the excess mean square displacement behaves as free volume and is closely connected to an elementary step of the structural relaxation. Then viscosity data evidence a breakdown of the Einstein-Debye relation, decoupling attributed to the intermolecular cooperativity.展开更多
This contribution reports on application of low-wavenumber Raman scattering on acoustical vibrational modes of nanoparticles.Theoretical background as well as the experimental results in determination of oxide and sem...This contribution reports on application of low-wavenumber Raman scattering on acoustical vibrational modes of nanoparticles.Theoretical background as well as the experimental results in determination of oxide and semiconductor particle size distribution will be presented.展开更多
With the growing interest in the applications of gold nanoparticles in biotechnology and their physiological effects, possible toxicity of gold nanoparticles is becoming an increasingly important issue. A large number...With the growing interest in the applications of gold nanoparticles in biotechnology and their physiological effects, possible toxicity of gold nanoparticles is becoming an increasingly important issue. A large number of studies carried out over the past few years under a variety of experimental conditions and following different protocols have produced conflicting results, leading to divergent views about the actual safety of gold nanoparticles in human applications. This work is intended to provide an overview of the most recent experimental results and thereby summarize current state-of-the-art. Rather than presenting a comprehensive review of the available literature in this field, which would be impractically broad, we have selected representative examples of both in vivo and in vitro studies, which clearly demonstrate the need for urgent and rigorous standardization of experimental protocols. Despite their significant potential, the safety of gold nanoparticles is highly controversial at this time, and important concerns have been raised that need to be properly addressed. Factors such as shape, size, surface charge, coating, and surface functionalization are expected to influence the interactions of particles with biological systems to a different extent, resulting in different outcomes and influencing the potential of gold nanoparticles for biomedical applications. Moreover, despite continuous attempts to establish a correlation between structure of the particles and their interactions with biological systems, we are still far from elucidating the toxicological profile of gold nanoparticles in an indisputable manner. This review is intended to contribute towards this goal, offering a number of suggestions on how to achieve the systematization of data on the most relevant physico-chemical parameters, which govern and control the toxicity of ~old nanot^articles at cellular and whole-organism levels.展开更多
The single-wall carbon nanotubes (SWCNs) were discovered in '93 [1] and are made of pure carbon atoms just like a single sheet of graphite wrapped around a cylindrical axis. The same material with slight variation...The single-wall carbon nanotubes (SWCNs) were discovered in '93 [1] and are made of pure carbon atoms just like a single sheet of graphite wrapped around a cylindrical axis. The same material with slight variations in the geometrical arrangement yields different electronic properties, which could range from metallic to semiconducting behavior. They have fascinating chemical, mechanical and electrical properties which result remarkably different from those of any other carbon-based materials and which suggest enormous potential application in many technological areas, as catalysis, energy and gas storage, electron emitters, sensors,fast acting switches, molecular electronics, etc. [2-6]. In this contest it is very important to know and to control the electronical and chemical characteristics of the SWCNs.……展开更多
基金The present work has been funded partly with the financial supportof MIUR-FIRB RBNE012N3X, MIUR PRIN, PAT FAPVU 2004-2006.
文摘The elastic and vibrational properties of a material, bulk or planar waveguide, are studied by BriUouin and Raman spectroscopy to follow the process of nanocrystals growth in glass-ceramics. The nanoparticles cause the appearance, in the low frequency Raman spectrum, of characteristic peaks, whose position depends on the size of the crystals. At the same time, sharp crystal peaks, due to optical phonons, appear in the Raman spectra, allowing the determination of the nucleated phase, and a frequency shift of the BriUouin peaks is observed.
基金Supported by the National Natural Science Foundation of China under Grant Nos.19774013 and 10074008Palermo University,Italy.
文摘We consider a two-dimensional(2D)trapped ion model in which two laser beams drive the corresponding vibrational motions and are carrier resonant with the two-level of the ion.Due to the coherent superposition of two sub-Rabi oscillations involved in the bimodal vibrations,the Rabi frequency degeneration and offset may occur in this model.This provides a possibility to generate the pair coherent state in the 2D trapped ion.
文摘We have comparatively studied the addition of Cr and V in titania.Cr and V content were changed by means of insets placed in the Ti target.Structural,compositional and electrical analyses of different series of thin films,made by XRF, XRD,are presented.Electrical characterization not only showed that Cr doped layers were very sensitive to ethanol within a useful range for applications,but also allowed to verify that the electrical behaviour is dependent on the structure of film. Finally,the Cr and V concentrations that gives the best results in terms of sensing performances has been determined and a correlation between structural and electrical measurement has been evidenced.
文摘Here we examine the findings obtained for disaccharide/water mixtures near glass transition that involves cooperative relaxation features on kinetic by viscosity and on thermodynamic behaviour by neutron scattering. Then to address cooperative phenomena that mitigate the Debye-Waller behaviour we invoke Adam-Gibbs’ idea of a cooperative rearranging region. Neutron results suggest that the excess mean square displacement behaves as free volume and is closely connected to an elementary step of the structural relaxation. Then viscosity data evidence a breakdown of the Einstein-Debye relation, decoupling attributed to the intermolecular cooperativity.
文摘This contribution reports on application of low-wavenumber Raman scattering on acoustical vibrational modes of nanoparticles.Theoretical background as well as the experimental results in determination of oxide and semiconductor particle size distribution will be presented.
文摘With the growing interest in the applications of gold nanoparticles in biotechnology and their physiological effects, possible toxicity of gold nanoparticles is becoming an increasingly important issue. A large number of studies carried out over the past few years under a variety of experimental conditions and following different protocols have produced conflicting results, leading to divergent views about the actual safety of gold nanoparticles in human applications. This work is intended to provide an overview of the most recent experimental results and thereby summarize current state-of-the-art. Rather than presenting a comprehensive review of the available literature in this field, which would be impractically broad, we have selected representative examples of both in vivo and in vitro studies, which clearly demonstrate the need for urgent and rigorous standardization of experimental protocols. Despite their significant potential, the safety of gold nanoparticles is highly controversial at this time, and important concerns have been raised that need to be properly addressed. Factors such as shape, size, surface charge, coating, and surface functionalization are expected to influence the interactions of particles with biological systems to a different extent, resulting in different outcomes and influencing the potential of gold nanoparticles for biomedical applications. Moreover, despite continuous attempts to establish a correlation between structure of the particles and their interactions with biological systems, we are still far from elucidating the toxicological profile of gold nanoparticles in an indisputable manner. This review is intended to contribute towards this goal, offering a number of suggestions on how to achieve the systematization of data on the most relevant physico-chemical parameters, which govern and control the toxicity of ~old nanot^articles at cellular and whole-organism levels.
基金Wu Z.Y. acknowledges the financial support provided by the Major-Research (90206032)and the Outst6anding Youth scholars Fund (10125523) of the National Natural Science Foundation of China.
文摘The single-wall carbon nanotubes (SWCNs) were discovered in '93 [1] and are made of pure carbon atoms just like a single sheet of graphite wrapped around a cylindrical axis. The same material with slight variations in the geometrical arrangement yields different electronic properties, which could range from metallic to semiconducting behavior. They have fascinating chemical, mechanical and electrical properties which result remarkably different from those of any other carbon-based materials and which suggest enormous potential application in many technological areas, as catalysis, energy and gas storage, electron emitters, sensors,fast acting switches, molecular electronics, etc. [2-6]. In this contest it is very important to know and to control the electronical and chemical characteristics of the SWCNs.……
