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Influence of gold nanolayer coating on the continuous-wave laser ablation of a pure aluminum surface: Evaluations of structural and optical features
摘要： In this paper, formation of uniform and large-area micro/nanostructures on pure aluminum surfaces using a continuous-wave laser irradiation is presented. Gold nanolayer coating was utilized as a confinement layer for controlling the possible hydrodynamic phenomena in a molten area. Dependency of the laser-induced morphology on the thickness of a gold coating was investigated in this regard. Scanning electron microscopy, energy dispersive spectroscopy, grazing test of the X-ray diffraction, and optical absorption/reflection spectroscopy in UV/visible/IR ranges were employed to characterize the samples. Results showed that the formation of uniform structures of average sizes of 50 nm-5μm on aluminum surface was possible following the irradiation of a continuous-wave CO2 laser, delivering 130 W beam power. Alterations of the surface morphology brought about an increase in specific absorption peaks at the UV region and the appearance of an absorption peak in the visible range. In addition, these structure-covered surfaces provided interesting reflection behaviors in different spectral areas, which can clearly reflect their high potential to be used as selective solar absorbers. The results of this investigation indicated that optical characteristics such as absorption and emission coefficients as well as ξ factor were 0.98, 0.13, and 7.53, respectively. It can therefore be concluded that this process can be considered an efficient and fast technique to fabricate selective solar absorbers.
关键词： Nanostructures,Aluminum,Selective solar absorber,Sputtering,Nanolayer,Continuous-wave CO2 laser,Gold,Black carbon
更新于2025-09-23 15:22:29
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A novel single-cavity three-wavelength photoacoustic spectrometer for atmospheric aerosol research
摘要： The spectral light-absorbing behavior of carbonaceous aerosols varies depending on the chemical composition and structure of the particles. A new single-cavity three-wavelength photoacoustic spectrometer was developed and characterized for measuring absorption coefficients at three wavelengths across the visible spectral range. In laboratory studies, several types of soot with different organic content were generated by a diffusion flame burner and were investigated for changes in mass-specific absorption cross section (MAC) values, absorption and scattering ?ngstr?m exponents (αabs and αsca), and single scattering albedo (ω). By increasing the organic carbonaceous (OC) content of the aerosol from 50 to 90 % of the total carbonaceous mass, for 660 nm nearly no change of MAC was found with increasing OC content. In contrast, for 532 nm a significant increase, and for 445 nm a strong increase of MAC was found with increasing OC content of the aerosol. Depending on the OC content, the ?ngstr?m exponents of absorption and scattering as well as the single scattering albedo increased. These laboratory results were compared to a field study at a traffic-dominated urban site, which was also influenced by residential wood combustion. For this site a daily average value of αabs(445–660) of 1.9 was found.
关键词： light absorption,carbonaceous aerosols,organic carbon,photoacoustic spectrometer,black carbon,single scattering albedo,?ngstr?m exponents
更新于2025-09-23 15:19:57
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Light absorption by organic aerosol emissions rivals that of black carbon from residential biomass fuels in South Asia
摘要： Solid biomass fuel-based residential cookstoves are the largest source of aerosol emissions in the Indian subcontinent. For assessing radiative forcing due to this pollutant source, laboratory-generated cookstove performance datasets are currently used, which have established black carbon (BC) as the dominant atmospheric warming aerosol species. We report findings on the strong near-ultraviolet wavelength absorption characteristics of emitted organic carbon (OC) aerosol from household stove combustion of nationally-representative biomass fuels. OC emission from cookstoves have been conventionally parameterized in emission inventory and regional climate models to be non-light-absorbing in the visible solar spectra. We conclude that light-absorbing OC contributes roughly as much as BC to total absorption cross-sections, thereby enhancing the associated positive forcing estimates. Our findings underscore the importance of including light-absorbing OC within the subcontinent’s air quality and climate impact assessment frameworks.
关键词： South Asia,black carbon,radiative forcing,biomass fuels,organic carbon,light absorption,cookstoves,aerosol emissions
更新于2025-09-19 17:13:59
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Quantification of source specific black carbon scavenging using an aethalometer and a disdrometer
摘要： Aerosol black carbon (BC) is the second strongest contributor to global warming, after CO2, and it is linked to many adverse health effects. A sampling campaign of 15 months was carried out in León (Spain) in order to evaluate the scavenging of BC with an ensemble aethalometer-disdrometer. The aethalometer provides the concentration of equivalent black carbon (eBC), and the disdrometer, the raindrop size distribution. A total of seventy-five rain events were studied and in 73% of them there was an effective (eBCinitial > eBCfinal) scavenging, with a mean decrease of 48 ± 37% in long rain events (>8 h) and 39 ± 38% in short rain events. The scavenging of BC is strongly related to its source. Thus, the scavenging coefficient (SC) mean value of the BC from fossil fuel (eBCff) for short and long rain events was 5.1 10-5 and 1.3 10-5 s-1, respectively. For the BC from biomass burning (eBCbb), the SC values were 1.6 10-4 and 2.8 10-5 s-1 in short and long events, respectively. There was a significant positive correlation between the SC and the number of drops with diameters between 0.375 and 2.5 mm. Rain scavenging of eBC was analyzed depending on the air mass origin obtaining an effective scavenging for air masses from Atlantic, Arctic and Africa. A linear model (R2=0.72) was built to estimate the ?eBC values with variables from an aethalometer, a disdrometer and a weather station: eBC concentration before rain, swept volume and precipitation accumulated. A Kolmogorov-Smirnov statistical test confirmed the goodness of fit of the model to the measured data.
关键词： BC scavenging estimation model,rainfall,scavenging coefficient,Black carbon,raindrop diameter,wet deposition
更新于2025-09-10 09:29:36
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Electrospray-Surface Enhanced Raman Spectroscopy (ES-SERS) for probing surface chemical compositions of atmospherically relevant particles
摘要： We present electrospray-surface enhanced Raman spectroscopy (ES-SERS) as a new approach to measuring the surface chemical compositions of atmospherically relevant particles. The surface-sensitive SERS is realized by electrospraying Ag nanoparticle aerosols over analyte particles. Spectral features at v(SO42-), v(C-H) and v(O-H) modes were observed from the normal Raman and SERS measurements of laboratory-generated supermicron particles of ammonium sulfate (AS), AS mixed with succinic acid (AS/SA) and AS mixed with sucrose (AS/sucrose). SERS measurements showed strong interaction (or chemisorption) between Ag nanoparticles and surface aqueous sulfate [SO42-] with [SO42-]AS/sucrose > [SO42-]AS/SA > [SO42-]AS. Enhanced spectra of the solid AS and AS/SA particles revealed the formation of surface-adsorbed water on their surfaces at 60% relative humidity. These observations of surface aqueous sulfate and adsorbed water demonstrate a possible role of surface-adsorbed water in facilitating the dissolution of sulfate from the bulk phase into its water layer(s). Submicron ambient aerosol particles collected in Hong Kong exhibited non-enhanced features of black carbon and enhanced features of sulfate and organic matter (carbonyl group), indicating an enrichment of sulfate and organic matter on the particle surface.
关键词： Electrospray-Surface Enhanced Raman Spectroscopy,succinic acid,atmospherically relevant particles,surface chemical compositions,ES-SERS,sucrose,Ag nanoparticles,surface-adsorbed water,organic matter,ammonium sulfate,black carbon
更新于2025-09-09 09:28:46