RESUMEN
Sulfate-modified Ag2CO3 was successfully synthesized via a simple precipitation method. Its visible light photocatalytic performance against the removal of Orange G was found to be significantly enhanced in comparison with the one of pure Ag2CO3. While SO42--Ag2CO3 ensured a removal efficiency of 100% of OG within 30 min, the unmodified Ag2CO3 exhibited a degradation threshold at hardly 60%. Likewise, the degradation rate constant in the presence of SO42--Ag2CO3 photocatalyst was assessed to be twice that determined upon the involvement of pristine Ag2CO3. Furthermore, Total Organic Carbon (TOC) measurements evidenced the occurrence of a quasi-total mineralization of the dye pollutant upon the use of SO42--Ag2CO3 photocatalyst. Scavenger experiments highlighted the dominant role of photo-induced h+ along with ËO3- ozonide radicals in the OG photocatalytic oxidation mechanism. Reuse cycles revealed that the modification by SO42- is a promising route to improve the stability of silver carbonate against photocorrosion. All these improvements could be ascribed to electronic transfer from the upper SO42- HOMO to the lower Ag2CO3 conduction band.
RESUMEN
Structural properties of SiO(x)C(y)-Ag nanocomposite thin films prepared by a dual process PVD-PECVD in the same reactor have been investigated. The experimental results have demonstrated the influence of a PECVD process carried out at room temperature for the growth of a dielectric matrix on the size and the distribution density of Ag nanoparticles (NPs) deposited beforehand by magnetron sputtering. The plasma during the growth of the encapsulation SiO(x)C(y) layer caused a diffusion of silver from NPs through the SiO(x)C(y) matrix associated with a decrease in the average size of nanoparticles and an increase of their distribution density. Silver diffusion is blocked at a barrier interface to form a buried layer of individual Ag NPs which, for instance, can find plasmonic applications. Silver also diffuses toward the outer surface inducing antibacterial properties. In both cases initial Ag NPs act as reservoirs for multifunctional properties of advanced nanostructured films.
RESUMEN
We present optical and morphological characterizations performed on thermochromic V2O5 coatings. V2O5 coatings were obtained by oxidation of as-deposited VOx films. Comparisons were made among coatings oxidized at various temperatures. Photographic evidence is also shown to provide the reader a clear visual description of the color change that occurs during thermochromic process. Detailed study and analysis regarding this data can be found in Kumar et al. (2017, in press) [1,2].
RESUMEN
Although di-vanadium pentoxide (V2O5) has been a candidate of extensive research for over half a century, its intrinsic thermochromism has not been reported so far. Films of V2O5 grown on silicon, glass, and metal substrates by metal organic chemical vapor deposition in this study exhibit a thermally induced perceptible color change from bright yellow to deep orange. Temperature-dependent UV-vis spectroscopy and X-ray diffraction allow the correlation between the reversible continuous red shift of the absorption and the anisotropic thermal expansion along the (001) direction, that is, perpendicular to the sheets constituting the layered structure. Furthermore, the possibility of tuning the thermochromic behavior was demonstrated via a chemical doping with chromium.
RESUMEN
As a strongly correlated metal oxide, VO2 inspires several highly technological applications. The challenging reliable wafer-scale synthesis of high quality polycrystalline VO2 coatings is demonstrated on 4" Si taking advantage of the oxidative sintering of chemically vapor deposited VO2 films. This approach results in films with a semiconductor-metal transition (SMT) quality approaching that of the epitaxial counterpart. SMT occurs with an abrupt electrical resistivity change exceeding three orders of magnitude with a narrow hysteresis width. Spatially resolved infrared and Raman analyses evidence the self-assembly of VO2 disordered metamaterial, compresing monoclinic (M1 and M2) and rutile (R) domains, at the transition temperature region. The M2 mediation of the M1-R transition is spatially confined and related to the localized strain-stabilization of the M2 phase. The presence of the M2 phase is supposed to play a role as a minor semiconducting phase far above the SMT temperature. In terms of application, we show that the VO2 disordered self-assembly of M and R phases is highly stable and can be thermally triggered with high precision using short heating or cooling pulses with adjusted strengths. Such a control enables an accurate and tunable thermal control of the electrical switching.