Nano-Ag on vanadium dioxide. II. Thermal tuning of surface plasmon resonance

Thermal tuning of the localized surface plasmon resonance (LSPR) of Ag nanoparticles on a thermochromic thin film of VO2 was studied experimentally. The tuning is strongly temperature dependent and thermally reversible. The LSPR wavelength lambda(SPR) shifts to the blue with increasing temperature from 30 to 80 degrees C, and shifts back to the red as temperature decreases. A smart tuning is achievable on condition that the temperature is controlled in a stepwise manner. The tunable wavelength range depends on the particle size or the mass thickness of the metal nanoparticle film. Further, the tunability was found to be enhanced significantly when a layer of TiO2 was introduced to overcoat the Ag nanoparticles, yielding a marked sensitivity factor Delta lambda(SPR)/Delta n, of as large as 480 nm per refractive index unit (n) at the semiconductor phase of VO2.

Investigation of Interfacial Tensions for Carbon Dioxide Aqueous Solutions by Perturbed-Chain Statistical Associating Fluid Theory Combined with Density-Gradient Theory

The perturbed-chain statistical associating fluid theory and density-gradient theory are used to construct an equation of state (EOS) applicable for the phase behaviors of carbon dioxide aqueous solutions. With the molecular parameters and influence parameters respectively regressed from bulk properties and surface tensions of pure fluids as input, both the bulk and interfacial properties of carbon dioxide aqueous solutions are satisfactorily correlated by adjusting the binary interaction parameter (k(ij)). Our results show that the constructed EOS is able to describe the interfacial properties of carbon dioxide aqueous solutions in a wide temperature range, and illustrate the influences of temperature, pressure, and densities in each phase on the interfacial properties.

Replacement of methane from quartz sand-bearing hydrate with carbon dioxide-in-water emulsion

The replacement of CH4 from its hydrate in quartz sand with 90:10, 70:30, and 50:50 (W-CO2:W-H2O) carbon dioxide-in-water (C/W) emulsions and liquid CO2 has been performed in a cell with size of empty set 36 x 200 mm. The above emulsions were formed in a new emulsifier, in which the temperature and pressure were 285.2 K and 30 MPa, respectively, and the emulsions were stable for 7-12 h. The results of replacing showed that 13.1-27.1%, 14.1-25.5%, and 14.6-24.3% of CH4 had been displaced from its hydrate with the above emulsions after 24-96 It of replacement, corresponding to about 1.5 times the CH4 replaced with high-pressure liquid CO2. The results also showed that the replacement rate of CH4 with the above emulsions and liquid CO2 decreased from 0.543, 0.587, 0.608, and 0.348 1/h to 0.083, 0.077, 0.069, and 0.063 1/h with the replacement time increased from 24 to 96 h. It has been indicated by this study that the use of CO2 emulsions is advantageous compared to the use of liquid CO2 in replacing CH4 from its hydrate.

Determination of appropriate condition on replacing methane from hydrate with carbon dioxide

This paper is intended to determine the appropriate conditions for replacing CH4 from NGH with CO2. By analyzing the hydration equilibrium graphs and geotherms, the HSZs of NGH and CO2 hydrate, both in permafrost and under deep sea, were determined. Based on the above analysis and experimental results, it is found that to replace CH4 from NGH with gaseous CO2, the appropriate experimental condition should be in the area surrounded by four curves: the geotherm, (H-V)(CO2), (L-V)(CO2) and (H-V)(CH4), and to replace CH4 from NGH with liquid CO2, the condition should be in the area surrounded by three curves: (L-V)(CO2), (H-L)(CO2) and (H-V)CH4. For conditions in other areas, either CO2 can not form a hydrate or CH4 can release little from its hydrate, which are not desirable results.

Hydrate dissociation conditions for gas mixtures containing carbon dioxide, hydrogen, hydrogen sulfide, nitrogen, and hydrocarbons using SAFT

A new method, a molecular thermodynamic model based on statistical mechanics, is employed to predict the hydrate dissociation conditions for binary gas mixtures with carbon dioxide, hydrogen, hydrogen sulfide, nitrogen, and hydrocarbons in the presence of aqueous solutions. The statistical associating fluid theory (SAFT) equation of state is employed to characterize the vapor and liquid phases and the statistical model of van der Waals and Platteeuw for the hydrate phase. The predictions of the proposed model were found to be in satisfactory to excellent agreement with the experimental data.

THE STUDY OF MICROSTRUCTURE IN IRON-DOPED AND SULFUR-DOPED INP CRYSTALS BY MEANS OF HREM AND COMPUTER-SIMULATION

The microstructures in iron- and sulphur-doped InP crystals were studied using both electron microscopy and electron diffraction. A modulated structure has been found in S-doped InP crystal, where the commensurate modulations corresponded to periodicities of 0.68 nm and 0.7 nm in real space and were related to the reflections of the cubic lattice in [111] and [113BAR] directions; they were indexed as q111* = 1/2(a* + b* + c*) and q113BAR* = 1/4(-a* - b* + 3c*), respectively. Single atomic layers of iron precipitate were observed, with preferred orientations along which precipitates are formed. Simulated calculations by means of the dynamical theory of electron diffraction using models for the precipitate structure were in good agreement with our experimental results. The relation between the modulated structure and the precipitates is also discussed.

Sulfur forming an isoelectronic center in zinc telluride thin films

ZnTe1-xSx epitaxial layers grown on GaAs by molecular-beam epitaxy were studied by photoluminescence (PL) as a function of temperatures, excitation powers, and hydrostatic pressures. A sulfur-related emission peak, labeled as P-2, is identified as a deep-level emission by hydrostatic-pressure PL measurement. This indicates that sulfur atoms form isoelectronic centers in a ZnTe matrix. The results qualitatively agree with the theoretical prediction and show experimental evidence of isoelectronic S in ZnTe. A model is proposed to explain the emission mechanisms in the ZnTe1-xSx system with small x values.