柠檬酸钠辅助光化学合成Cu_2-_xSe纳米晶

近年来,纳米颗粒由于具有许多独特的物理、化学性能而引起人们的高度重视[1].硒化铜纳米晶也因其组成多样性且能广泛应用于太阳能电池,超离子导体等领域而成为学术界的研究热点之一.

Nanoscale architecture of ceria-based model catalysts: Pt-Co nanostructures on well-ordered CeO_(2)(111) thin films

We have prepared and characterized atomically well-defined model systems for ceria-supported Pt-Co core-shell catalysts. Pt@Co and Co@Pt core-shell nanostructures were grown on well-ordered CeO2(111) films on Cu(111) by physical vapour deposition of Pt and Co metals in ultrahigh vacuum and investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy. The deposition of Co onto CeO2(111) yields CoCeO2(111) solid solution at low Co coverage(0.5 ML), followed by the growth of metallic Co nanoparticles at higher Co coverages. Both Pt@Co and Co@Pt model structures are stable against sintering in the temperature range between 300 and 500 K. After annealing at 500 K, the Pt@Co nanostructure contains nearly pure Co-shell while the Pt-shell in the Co@Pt is partially covered by metallic Co. Above 550 K, the re-ordering in the near surface regions yields a subsurface Pt-Co alloy and Pt-rich shells in both Pt@Co and Co@Pt nanostructures. In the case of Co@Pt nanoparticles, the chemical ordering in the near surface region depends on the initial thickness of the deposited Pt-shell. Annealing of the Co@Pt nanostructures in the presence of O2 triggers the decomposition of Pt-Co alloy along with the oxidation of Co, regardless of the thickness of the initial Pt-shell. Progressive oxidation of Co coupled with adsorbate-induced Co segregation leads to the formation of thick CoO layers on the surfaces of the supported Co@Pt nanostructures. This process is accompanied by the disintegration of the CeO2(111) film and encapsulation of oxidized Co@Pt nanostructures by CeO2 upon annealing in O2 above 550 K. Notably, during oxidation and reduction cycles with O2 and H2 at different temperatures, the changes in the structure and chemical composition of supported Co@Pt nanostructures were driven mainly by oxidation while reduction treatments had little effect regardless of the initial thickness of the Pt-shell.

Optical closure of parameterized bio-optical relationships

An optical closure study on bio-optical relationships was carried out using radiative transfer model matrix operator method developed by Freie Universitat Berlin. As a case study, the optical closure of bio-optical relationships empirically parameterized with in situ data for the East China Sea was examined. Remote-sensing reflectance （Rrs） was computed from the inherent optical properties predicted by these biooptical relationships and compared with published in situ data. It was found that the simulated Rrs was overestimated for turbid water. To achieve optical closure, bio-optical relationships for absorption and scattering coefficients for suspended particulate matter were adjusted. Furthermore, the results show that the Fournier and Forand phase functions obtained from the adjusted relationships perform better than the Petzold phase function. Therefore, before bio-optical relationships are used for a local sea area, the optical closure should be examined.

Solar Photochemical Pre-Treatment for Sulphurous Ground Water Purification Process

The sulfurous water deposit exploitation in volcanic, swamp, or wetland regions, represents an alternative option for potable water supply in cities and communities around the world. However, before its consumption, it must be treated by the application of physicochemical or biological methods with the ability to separate high contents in sulfates, hydrogen sulphite and sulphides which have laxative, allergic and toxic properties in humans. Conventional methods require the supply of chemical compounds or the adequate control of different parameters such as pH, temperature, etc., and the constant maintenance within their reactors. For these reasons, the systems could have elevated operating costs and require additional steps to enable the treatment of its separated products and the final disposal of its residual waste generated. In this research, compound parabolic collectors are implemented for the use of solar energy radiation, UV-B type, in Solar Advanced Oxidation Processes in H2O2/O3/UVsolar homogeneous phase. Its application during the pre-treatment of four sulfur water wells from the region of Puebla, Mexico, demonstrated its ability to transform their sulfur compounds in sulfates of easy removal by a later stage of reverse osmosis, in an approximately 15 min treatment time process.

Effect of atmospheric aerosol on surface ozone variation over the Pearl River Delta region

Our analysis of the surface aerosol and ultraviolet （UV） measurements in Pearl River Delta （PRD） region shows that the surface UV radiation is reduced by more than 50% due to high aerosol concentrations. This has important impacts on urban ecosystem and photochemistry, especially on ozone photochemical production over the region. The quantitative effect of aerosols on surface ozone is evaluated by analyzing surface observations （including ozone, ultraviolet radiation, aerosol radiative parameters） and by using radiative and chemical models. A case study shows that the aerosol concentrations and UV radiation are significantly correlated with ozone concentrations. The correlation coefficient between the aerosol optical depth （AOD） and the PM10 mass concentration is very high, with a maximum of 0.98, and the AOD and UV radiation/ozone is anti- correlated, with a correlation coefficient of-0.90. The analysis suggests that ozone productivity is significantly decreased due to the reduction of UV radiation. The noon-time ozone maximum is considerably depressed when AOD is 0.6, and is further decreased when AOD is up to 1.2 due to the reduction of ozone photochemical productivity. Because the occurring probability of aerosol optical depth for AOD550m≥0.6 and AOD340mm ≥1.0 is 47, and 55% respectively during the dry season （October, November, December, January）, this heavy aerosol condition explains the low ozone maximum that often occurs in the dry season over the Guangzhou region. The analysis also suggests that the value of single scattering albedo （SSA） is very sensitive to the aerosol radiative effect when the radiative and chemical models are applied, implying that the value of SSA needs to be carefully studied when the models are used in calculating ozone production.

Terahertz band simulations using two different radiative transfer models

A high-resolution dual-band terahertz(THz) radiometer was designed to measure vertical distributions of chemical elements in the middle atmosphere of the Tibetan Plateau. A forward simulation, which always should be conducted firstly for the development of a matching retrieval algorithm, has not been done before. We use two radiative transfer models, ARTS and AM, to simulate the water vapor, ozone and carbon monoxide spectra on the plateau based on the spectral design of the THz radiometer. The emission line characteristics of the three gases in this spectral band are identified. Reasons for the differences in the spectral simulations between the two models are analyzed for individual gases. The impact of several different spectral parameter settings on the simulations are evaluated through a series of sensitivity experiments. This study suggests that the ARTS is more suitable for the development of the THz radiometer retrieval algorithm. An optimal parameter setting of the ARTS for the three elements are given.