Light Absorption Coefficient Research Articles

Time‐Resolved Measurements of PM2.5 Chemical Composition and Brown Carbon Absorption in Nanjing, East China: Diurnal Variations and Organic Tracer‐Based PMF Analysis

AbstractTo understand diurnal variations in PM2.5 composition and aerosol extract absorption, PM2.5 samples were collected at intervals of 2 hr from 8:00 to 20:00 and 6 hr from 20:00 to 8:00 (the next day) in northern Nanjing, China, during the winter and summer of 2019–2020 and analyzed for bulk components, organic tracers, and light absorption of water and methanol extracts—a proxy measure of brown carbon (BrC). Diurnal patterns of measured species reflected the influences of primary emissions and atmospheric processes. Light absorption coefficients of water (Abs365,w) and methanol extracts (Abs365,m) at 365 nm shared a similar diurnal profile peaking at 18:00–20:00, generally following changes in biomass burning tracers. However, Abs365,w, Abs365,m, and their normalizations to organic aerosols increased at 14:00–16:00, earlier than that of levoglucosan in the late afternoon, which was attributed to secondarily formed BrC. The methanol extracts showed a less drastic decrease in light absorption at night than the water extracts and elevated absorption efficiency during 2:00–8:00. This is due to the fact that the water‐insoluble OC has a longer lifetime and stronger light absorption than the water‐soluble OC. According to the source apportionment results solved by positive matrix factorization (PMF), biomass burning and secondary formation were the major BrC sources in northern Nanjing, with an average total relative contribution of about 90%. Compared to previous studies, diurnal source cycles were added to the PMF simulations in this work by using time‐resolved speciation data, which avoided misclassification of BrC sources.

Influence of transition metal substitution on Cs2AgBiBr6/M3C2 (M = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) interfaces: First-principles and experimental studies

In this study, we have constructed and characterized Cs2AgBiBr6/M3C2 (M = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) heterostructures, utilizing a combination of density functional theory (DFT) and experimental studies. We constructed eighteen different Cs2AgBiBr6/M3C2 heterojunctions by considering the two different terminal types of Cs2AgBiBr6 as well as the nine different terminal types on the side of various early transition metal carbides. The results indicate that AgBiBr3/M3C2 heterostructures possess superior interfacial properties compared to Cs2BiBr3/M3C2 heterostructures, displaying a smaller interfacial distance, higher binding energy, and better charge transfer ability. Among the AgBiBr3/M3C2 heterostructures, AgBiBr3/Ti3C2 and AgBiBr3/Zr3C2 showed the best binding energy and charge transfer ability. Additionally, all the constructed heterostructures exhibited improved light absorption coefficient, broadened visible light absorption range, and reduced effective mass of the charge carriers. Finally, to validate the experimental synthesis feasibility of the theoretical models, we synthesized Cs2AgBiBr6/Ti3C2 composite materials, and scanning electron microscopy (SEM) images confirmed the presence of a composite structure consisting of Cs2AgBiBr6/Ti3C2. These results provide valuable theoretical guidance for developing high-performance Cs2AgBiBr6/M3C2 heterostructures in optoelectronic perovskite devices.

The synergistic regulation effect on the structure and electronic properties of graphene by methane plasma, Stone-Wales defect and equibiaxial strain

The synergistic regulation effects on the structure and electronic properties of graphene by methane plasma, Stone-Wales defect and equibiaxial strain has been investigated. It is found that the graphene containing Stone-Wales defect (SWG77) has metallicity, when surface adsorbing a CH3+ion, CH3+@SWG77 is a semiconductor with 0.339 eV indirect band gap. The stress-strain curve results indicate that adsorbing different plasma fragments in methane may influence to varying degrees on the ultimate strain of the SWG77 system. The hole mobility has an enhanced tendency as the tensile strain increases for the CH3+@SWG77 system. In addition, the hole mobilities seem to reach saturation when applied equibiaxial strain increase to 2 % or larger. Applying equibiaxial strain on the system substrate, the band gaps of CH3+@ SWG77 and 2CH3+@ SWG77 systems are almost unaffected. In addition, the concentration of CH3+ ion has a certain effect on the light absorption coefficient, reflectivity, and energy loss of the SWG77 system in the visible light region (1.62 eV–3.11 eV) and ultraviolet regions (3.11 eV–5.50 eV). Therefore, defect graphene with appropriate carrier mobility and band gap may be designed by adjusting the equiaxial strain and methyl concentration, which provides useful theoretical support for the development of optical electrical multifunctional electronic devices based on graphene, and is conducive to promoting the application of graphene materials in the field of band gap engineering.

Atmospheric humic-like substances (HULIS) in Chongqing, Southwest China: Abundance, light absorption properties, and potential sources

Atmospheric humic-like substances (HULIS) have a great impact on radiative forcing and atmospheric oxidative capacity due to their efficient light absorption properties. Knowledge on atmospheric HULIS abundance and light absorption properties in southwest China is still very limited. In this study, a total of 81 daily samples of fine particulate matter (PM2.5) were collected at two sites in Chongqing during four one-month periods in 2015, each of which representing a typical season. Mass concentrations of HULIS in term of carbon (HULIS-C) were measured by a total organic carbon analyzer, while mass absorption efficiency at 365 nm (MAE365) and absorption Ångström exponent (AAE) were estimated from light absorption of HULIS that was recorded by UV–visible spectrophotometry. The annual mean concentration of HULIS-C was around 3.4 ± 1.6 μg m−3, while the annual mean values of MAE365 and AAE were approximately 2.7 ± 0.7 m2 g−1C and 4.0 ± 0.2, respectively. Seasonal variations were significant for MAE365 but negligible for AAE at both sites. A direct comparison of MAE365 of HULIS in this study with the median MAE365 values from different sources in laboratory studies indicated that crop residues burning and/or wood burning were the primary sources of light-absorbing HULIS, as is also supported by the strong correlation between the light absorption coefficient at 365 nm (Abs365) and K+ (r > 0.85, p < 0.01) throughout the year. Furthermore, the good correlation between Abs365 and secondary organic carbon implied secondary sources also contributed to light-absorbing HULIS (e.g., nitrated aromatic compounds production), as evidenced by the good correlation between Abs365 and NO3− and NH4+. The contribution of primary and secondary sources to light-absorbing HULIS was quantified using a machine learning algorithm, which showed >65% contribution from primary sources during the cold season, but only 35% during the warm seasons.

Spatial-Temporal Regularities of Hydrooptical Characteristics of the Ob River

Field studies conducted in spring (March 26 — April 9, 2022) and summer (June 5-16, 2022) in the Ob River mouth region at the three hydromorphological stations „Kazym-Mys“, „Azovy“, and „Salemal“ (YaNAO) to obtain new data on the hydrooptical characteristics of water in the Lower Ob river. Also, the trophic status and ecological state of the Lower Ob river region were assessed. The greatly varying light attenuation coefficient ε(λ) was calculated at the four characteristic wavelengths of 430, 450, 550, and 670 nm, respectively. It ranges from 9.3 m-1 to 22.1 m-1 during the winter low water (freeze-up) period and from 7.3 m-1 to 33.0 m-1 during the open water (high water) period. The calculated relative spectral contributions of major optically active components of water (pure water, suspension, yellow substance, chlorophyll) to ε(λ) suggest that suspension and yellow substance make up the maximal contribution at different horizons. Additionally, the calculated coefficient of light absorption by yellow substance кys(λ) varies within the ranges from 5.5 m-1 to 9.9 m-1 (spring) and from 3.1 m-1 to 17.0 m-1 (summer), respectively. The relative transparency was measured using the Secchi disc. The concentrations of yellow substance and major photosynthetic pigments — chlorophylls a, b, c, and carotenoids — were estimated alongside. The obtained results could be useful for environmental monitoring and predicting the dynamics of aquatic ecosystems in the region under climate change and increased anthropogenic pressure caused by the use of natural resources.

Synthesis and Optimization of Cs2B'B″X6 Double Perovskite for Efficient and Sustainable Solar Cells.

Hybrid perovskite materials with high light absorption coefficients, long diffusion lengths, and high mobility have attracted much attention, but their commercial development has been seriously hindered by two major problems: instability and lead toxicity. This has led to lead-free halide double perovskite becoming a prominent competitor in the photovoltaic field. For lead-free double perovskites, Pb2+ can be heterovalent, substituted by non-toxic metal cations as a double perovskite structure, which promotes the flexibility of the composition. However, the four component elements and low solubility in the solvent result in synthesis difficulties and phase impurity problems. And material phase purity and film quality are closely related to the number of defects, which can limit the photoelectric performance of solar cells. Therefore, based on this point, we summarize the synthesis methods of Cs2B'B″X6 double perovskite crystals and thin films. Moreover, in the application of solar cells, the existing research mainly focuses on the formation process of thin films, band gap adjustment, and surface engineering to improve the quality of films and optimize the performance of devices. Finally, we propose that Cs2B'B″X6 lead-free perovskites offer a promising pathway toward developing highly efficient and stable perovskite solar cells.

Impact of 2020 COVID-19 lockdowns on particulate air pollution across Europe

Abstract. To fight against the first wave of coronavirus disease 2019 (COVID-19) in 2020, lockdown measures were implemented in most European countries. These lockdowns had well-documented effects on human mobility. We assessed the impact of the lockdown implementation and relaxation on air pollution by comparing daily particulate matter (PM), nitrogen dioxide (NO2) and ozone (O3) concentrations, as well as particle number size distributions (PNSDs) and particle light absorption coefficient in situ measurement data, with values that would have been expected if no COVID-19 epidemic had occurred at 28 sites across Europe for the period 17 February–31 May 2020. Expected PM, NO2 and O3 concentrations were calculated from the 2020 Copernicus Atmosphere Monitoring Service (CAMS) ensemble forecasts, combined with 2019 CAMS ensemble forecasts and measurement data. On average, lockdown implementations did not lead to a decrease in PM2.5 mass concentrations at urban sites, while relaxations resulted in a +26 ± 21 % rebound. The impacts of lockdown implementation and relaxation on NO2 concentrations were more consistent (−29 ± 17 and +31 ± 30 %, respectively). The implementation of the lockdown measures also induced statistically significant increases in O3 concentrations at half of all sites (+13 % on average). An enhanced oxidising capacity of the atmosphere could have boosted the production of secondary aerosol at those places. By comparison with 2017–2019 measurement data, a significant change in the relative contributions of wood and fossil fuel burning to the concentration of black carbon during the lockdown was detected at 7 out of 14 sites. The contribution of particles smaller than 70 nm to the total number of particles significantly also changed at most of the urban sites, with a mean decrease of −7 ± 5 % coinciding with the lockdown implementation. Our study shows that the response of PM2.5 and PM10 mass concentrations to lockdown measures was not systematic at various sites across Europe for multiple reasons, the relationship between road traffic intensity and particulate air pollution being more complex than expected.

Theoretical study on photocatalytic hydrogen generation performance of two-dimensional GaN/ReS2 heterostructure

One effective way to solve energy crises and environmental problems is to find efficient photocatalysts to decompose water and produce hydrogen. In this work, the electronic structure and optical properties of GaN/ReS2 van der Waals heterostructure were studied by first-principles calculations. The findings demonstrate that the GaN/ReS2 heterostructure is an indirect band gap semiconductor with a band gap of 1.901 eV, exhibiting stability and type II band alignment characteristics. This ensures the spatial separation of photoexcited electron-hole pairs. At the heterostructure interface, a minor built-in electric field extends from the charge depletion layer of GaN to the charge accumulation layer of ReS2. Moreover, the heterostructure's visible light absorption coefficient is significantly enhanced compared to a single two-dimensional material. These calculations suggest that the GaN/ReS2 heterostructure holds potential as a photocatalytic material, offering theoretical guidance for future experimental research.

Direct band-gap iodide double perovskite solar cell materials by doping strategy: First-principles predictions

As alternatives to lead-based halide perovskite materials, the lead-free halide double-perovskite materials have many advantages but often show wide indirect band gaps and exceed the optimum band-gap range of 0.9–1.6 eV. Based on first-principles calculations, we scan a serial of halide double-perovskites Cs2B′B''X6 (B′ = Li, Na, K; B'' = In, Bi; X = Cl, Br, I) and find that most of Cs2B′B''X6 double-perovskite materials have direct band gaps but larger than 1.6 eV, while the direct band gaps of Cs2LiInI6 and Cs2NaInI6 are smaller than 0.9 eV. We modulate the electronic structure of Cs2B′InI6 (B′ = Li, Na, K) by an ionic doping strategy through substituting partial In ions with Bi ions and discover more halide double-perovskite solar cell materials with suitable band gap. By exploring the stability, electronic structures and optical properties of the doped double-perovskite Cs2B′In1-xBixI6 (B′ = Li, Na, K, x = 0.25 and 0.75), we discover the Cs2B′In0.75Bi0.25I6 (B′ = Li, Na and K) DP materials show direct band gaps within the optimal band-gap range of 0.90 − 1.60 eV for promising solar-cell materials. Meanwhile, the doped Cs2B′In1-xBixI6 DP materials show good carrier mobility as high as 103 cm2S−1V−1. Moreover, the predicted new materials exhibit excellent light absorption coefficients of 106 cm−1 in the visible light range. These new lead-free inorganic DP materials may offer great promise as candidates for highly efficient solar absorber materials for photovoltaic applications.

Light Absorption by Optically Active Components in the Arctic Region (August 2020) and the Possibility of Application to Satellite Products for Water Quality Assessment

In August 2020, during the 80th cruise of the R/V “Akademik Mstislav Keldysh”, the chlorophyll a concentration (Chl-a) and spectral coefficients of light absorption by phytoplankton pigments, non-algal particles (NAP) and colored dissolved organic matter (CDOM) were measured in the Norwegian Sea, the Barents Sea and the adjacent area of the Arctic Ocean. It was shown that the spatial distribution of the three light-absorbing components in the explored Arctic region was non-homogenous. It was revealed that CDOM contributed largely to the total non-water light absorption (atot(λ) = aph(λ) + aNAP(λ) + aCDOM(λ)) in the blue spectral range in the Arctic Ocean and the Barents Sea. The fraction of NAP in the total non-water absorption was low (less than 20%). The depth of the euphotic zone depended on atot(λ) in the surface water layer, which was described by a power equation. The Arctic Ocean, the Norwegian Sea and the Barents Sea did not differ in the Chl-a-specific light absorption coefficients of phytoplankton. In the blue maximum of phytoplankton absorption spectra, Chl-a-specific light absorption coefficients of phytoplankton in the upper mixed layer (UML) were higher than those below the UML. Relationships between phytoplankton absorption coefficients and Chl-a were derived by least squares fitting to power functions for the whole visible domain with a 1 nm interval. The OCI, OC3 and GIOP algorithms were validated using a database of co-located results (day-to-day) of in situ measurements (n = 63) and the ocean color scanner data: the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra (EOS AM) and Aqua (EOS PM) satellites, the Visible and Infrared Imager/Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (S-NPP) and JPSS-1 satellites (also known as NOAA-20), and the Ocean and the Land Color Imager (OLCI) onboard the Sentinel-3A and Sentinel-3B satellites. The comparison showed that despite the technological progress in optical scanners and the algorithms refinement, the considered standard products (chlor_a, chl_ocx, aph_443, adg_443) carried little information about inherent optical properties in Arctic waters. Based on the statistic metrics (Bias, MdAD, MAE and RMSE), it was concluded that refinement of the algorithm for retrieval of water bio-optical properties based on remote sensing data was required for the Arctic region.

Ab Initio Investigation for Solar Technology on the Optical and Electronic Properties of Double Perovskites Cs2AgBiX6(X=Cl, Br, I)

In the present paper, the first principal computations have been made to explore the optical and electronic characteristics of Cs2AgBiX6 (X=Cl, Br, I) double perovskite. To determine the energy of the band gap, we have used the GGA potentials. The values found for I, Cl, and Br are 0.815 eV, 1.417 eV, and 1.836 eV, respectively. According to our numerical simulation, the Cs2AgBiX6 (X=Cl, Br, I) have an important light absorption coefficient, exceeding a value of 104 cm−1 which makes it a viable absorbing material for Solar Systems. Other optical properties such as refractive index and dielectric function were also computed in this work. We have found ε re = 7.72, ε re = 5.22, and ε re = 4.12 for I, Cl, and Br respectively. About the equivalent static refractive indices values of Cs2AgBiX6 (X=Cl, Br, I), we have found n 0 = 2.77, n 0 = 2.28, and n 0 = 2.03 for I, Br, and Cl respectively. Also, we have used SCAPS software to simulate solar cells made of Cs2AgBiX6 (X=Cl, Br, I). The efficiency, fill factor and other parameters have been computed. Our results are 1.52 V, 1.08 V, 0.54 V, and 16.56 mA∕cm2, 28.65 mA cm−2, and 50.25 mA cm−2 in Voc and Jsc for and respectively. The efficiency computed are 22.85%, 27.46%, and 22.46% for and respectively. These estimated results demonstrate the potential of Cs2AgBiX6(X=Cl, Br, I) as a potentially useful substance in solar cells.

Electronic and optical characteristics of Silicane/GeAs van der Waals heterostructures: Effects of external electric field and biaxial strain: A first-principles study

The van der Waals heterostructure offers unusual physical properties to design novel structures for efficient optoelectronic applications. To enhance the low mobility of monolayer SiH and broaden the light absorption coefficient and range of monolayer SiH, a lattice-matched SiH/GeAs vdWh has been constructed. At the same time, the basic electronic and optical properties were investigated by first-principles calculations. The SiH/GeAs vdWh with six different structural configurations were compared, and the most stable configuration model H2 has a type-II band alignment with an indirect bandgap semiconductor value of 1.54 eV. It is associated with a strong charge transfer. Moreover, SiH/GeAs vdWh possesses anisotropic transport properties with high electron mobility along the y-direction. Interestingly, both external electric field and biaxial strain can adjust band offsets and bandgaps values. After applying vertical electric fields, The SiH/GeAs vdWh has a mutual transformation from type-I (symmetric) to type-II(staggered) to type-III(broken) band alignment, and metal-semiconductor phase transitions occurred at −0.35 and 0.15 V/Å. Besides, it's found that band alignment transition from type-II to type-I emerged under the in-plane biaxial strain of 2% and transformed indirect into direct bandgap. More importantly, tensile biaxial strain can enhance the visible-light absorption while sustaining type-II band alignment, which is favorable for photocatalysis of visible light. Our results indicate that the SiH/GeAs vdWh's moderate bandgap, excellent transport properties and optical performance may have potential applications in the field of nanoelectronic and optoelectronic devices.

Translucent multi-layered zirconia: Sandblasting effect on optical and mechanical properties.

The aim of this study was to evaluate the influence of the sandblasting treatment on the microstructure, optical and mechanical properties of multi-layered translucent zirconia. Samples of yttria-stabilized zirconia were prepared by stratifying four layers (L1, L2, L3 and L4) of ML-type KATANA multi-layered monolithic discs, whose surfaces were then sandblasted with alumina particles (110µm and 0.2MPa) in order to evaluate its effect on the presence of different crystalline phases as well as on the optical and mechanical properties of each of the four layers. The optical characterization was carried out by measuring the reflectance spectrum and colorimetric parameters by UV-Vis spectrophotometric analysis and the transmittance curves were indirectly obtained using the Kubelka-Munk model (KM). Microstructural, structural, mechanical and roughness characterizations were also performed using SEM, XRD, biaxial flexural strength B3B, and light interferometry, respectively RESULTS: According to the KM model there are different degrees of translucency between the upper and lower layers of the monolithic discs, but there was no influence of the Al2O3-sandblasting treatment on this optical property. The disk pigmentation causes greater absorption of light below 600nm, decreasing the transmittance rate to values below 25% in this region of the spectrum. The yellowing index presented higher values for inner disk layers L3 and L4, in agreement with the highest values of the light absorption coefficient K observed for these layers. The roughness of the samples did not change significantly with the surface treatment performed and the sandblasting did not result in new crystalline phases. SEM analysis showed the presence of different grain sizes in all layers analyzed, being related to the co-occurring presence of cubic (c-ZrO2) and tetragonal (t-ZrO2) phases in similar contents (∼ 50wt%). The Weibull statistical analysis, in turn, showed an increase in the Weibull characteristic stress value (σ0) for most layers subjected to sandblasting, except for the second layer (central region of the disk). It was also verified an increase in the value of the structural reliability of the material (m), referring to the samples of the central region of the disc (L2 and L3 layers) after sandblasting. The pigmentation in the disk causes a decrease of the transmittance rate to values well below 25% in the region of the spectrum 400-600nm and the inner layers (L3 and L4) have even lower transmittance than the outer layers in this spectrum range. Although the CR index indicates variation related to the Al2O3-sandblasting treatment, the transmittance spectra of KM model show that the sandblasting did not cause a significant change in the transmittance rate of the four analyzed layers. Also, there is no significant difference in the light scattering of the different layers of the disc, either before or after Al2O3-sandblasting treatment.

Electrodeposited CZTS loaded titania nanotubes for photocatalytic water splitting

Copper Zinc Tin Sulphide (Cu2ZnSnS4 (CZTS)) is a promising semiconductor material with optimum direct band gap of 1.4-1.6 eV, large light absorption coefficient (> 104 cm-1) and p-type electrical conductivity. In addition, its earth abundant and non-toxic elemental constituents make it a good candidate to replace the CdTe and CIGS absorber layers used in thin film solar cells. Also, it has properties that make it useful as a buffer layer that helps to reduce the effective band gap of TiO2 when used as an anode for photocatalytic splitting of water. We prepared titania nano tube (TNT) arrays by anodization of titanium foil. Raman spectrum of TNT confirmed the presence of pure anatase phase of TiO2. Field emission scanning electron microscopy images were obtained to analyse the surface morphology of TNT. CZTS sensitized titania nano tube arrays were then prepared by the electrodeposition of CZTS thin films over TNT arrays. FESEM images of the CZTS sensitized titania nano tube arrays showed that the electrodeposited CZTS layer had a fibrous structure. A photo electro chemical (PEC) cell was set up with CZTS sensitized titania nanotubes as anode. An anodic current density of 0.19 mA/cm2 was shown by the PEC cell when the anode was irradiated with blue light of wavelength 430 nm at power 50 mW/cm2. The incident photon to current conversion efficiency was 1.1 %.

Numerical investigation on improving photoacoustic imaging contrast based on temperature difference effect in biological tissues

Exploiting the variances in light absorption among different components of biological tissues and utilizing the light absorption coefficient as an imaging contrast, photoacoustic imaging achieves remarkable imaging resolution. Within the laser wavelength range commonly employed in photoacoustic imaging, biological tissue components like hemoglobin and melanin exhibit higher light absorption coefficients compared to other components. Consequently, these components generate stronger photoacoustic signals during the imaging process. However, this heightened signal strength obscures components of biological tissues with low light absorption coefficients, making it challenging to clearly visualize them in the resulting images. To address this limitation and enhance the visibility of low absorption coefficient components against a background of intense photoacoustic signals produced by high absorption coefficient components, we propose a method that utilizes low-intensity unfocused ultrasound to induce the temperature difference (TD) effect in biological tissues during photoacoustic imaging. By analyzing the disparities between the photoacoustic signals collected before and after introducing the TD effect, we establish a novel imaging parameter that improves the imaging contrast. To validate the feasibility and effectiveness of inducing photoacoustic effects in biological tissues, we conducted simulations using the finite element method, which yielded positive results. Subsequent simulations of photoacoustic imaging incorporating the TD effect demonstrated enhanced visualization of components with low light absorption coefficients in biological tissue. The method proposed in this paper is expected to provide a research idea for improving the photoacoustic imaging contrast of biological tissues.

Emission of water soluble brown carbon from different combustion sources: optical properties and functional group characterisation

Brown carbon (BrC) has a large impact on the Earth’s radiative balance. This study examined BrC’s optical characteristics, chemical functional groups, and total organic carbon (TOC) in deposited particulate matter from combustion of biomass, fossil fuels, and mosquito coil. A UV–vis spectrophotometer was used to assess BrC’s optical properties, a TOC analyzer was used to quantify TOC, and attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR) was used to identify functional group. The light absorption properties (absorption coefficient (babs-BrC), mass absorption efficiency (MAE365), absorption angstrom exponent (AAE), and refractive index (kabs-BrC)) were determined. Among biomasses, wheat straw exhibited the greatest value of babs-BrC (27.26 × 103 ± 4.09 × 103 Mm−1) whereas maize straw had the lowest value of babs-BrC (7.38 × 103 ± 1.11 × 103 Mm−1). A higher light absorption coefficient at 365 nm suggested that chromophores contributed more to the process. AAE followed this sequence - mosquito coil (5.46 ± 0.82) > biomass (5.13 ± 1.45) > fossil fuels (2.85 ± 0.32). The highest value of MAE365 (0.99 ± 0.15 m2 gC−1) and kabs-BrC (0.028 ± 0.004) was obtained in wheat straw, whereas the lowest value of MAE365 (0.07 ± 0.011 m2 gC−1) and kabs-BrC (0.002) was identified in octane. Biomasses samples showed a strong peak at ∼850, ∼1368, ∼1370, ∼1306, and near 1640 cm−1, indicating that the major component of BrC was organic nitrate R-ONO2 which is responsible to increase the light absorption properties. It also contains complex heterocyclic aromatic ring compounds, carbonyl group (C=O), and nitrogen-containing groups such as −NO 2, C≡N. The projected substantial contribution of BrC to overall light absorption is one illustration of the probable climatic effect of biomasses and fossil fuel burning in Southeast Asian region.

Recent Advances in the Synthesis and Application of Vacancy-Ordered Halide Double Perovskite Materials for Solar Cells: A Promising Alternative to Lead-Based Perovskites.

Lead-based halide perovskite materials are being developed as efficient light-absorbing materials for use in perovskite solar cells (PSCs). PSCs have shown remarkable progress in power conversion efficiency, increasing from 3.80% to more than 25% within a decade, showcasing their potential as a promising renewable energy technology. Although PSCs have many benefits, including a high light absorption coefficient, the ability to tune band gap, and a long charge diffusion length, the poor stability and the toxicity of lead represent a significant disadvantage for commercialization. To address this issue, research has focused on developing stable and nontoxic halide perovskites for use in solar cells. A potential substitute is halide double perovskites (HDPs), particularly vacancy-ordered HDPs, as they offer greater promise because they can be processed using a solution-based method. This review provides a structural analysis of HDPs, the various synthesis methods for vacancy-ordered HDPs, and their impact on material properties. Recent advances in vacancy-ordered HDPs are also discussed, including their role in active and transport layers of solar cells. Furthermore, valuable insights for developing high-performance vacancy-ordered HDP solar cells are reported from the detailed information presented in recent simulation studies. Finally, the potential of vacancy-ordered HDPs as a substitute for lead-based perovskites is outlined. Overall, the ability to tune optical and electronic properties and the high stability and nontoxicity of HDPs have positioned them as a promising candidate for use in photovoltaic applications.

Gamma‐ray irradiation effect on microstructure and physical performances of porous silica

AbstractIn this paper, the gamma irradiation effect on the microstructure and physical performances of porous silica, including mechanical, thermal, and optical performances, are systematically investigated by using molecular dynamics and density‐functional theory‐based methods. The study of bond angle distribution, pair distribution function, coordination number distribution, and average ring size distribution show that, after gamma‐ray irradiation, the microstructure of porous silica is obviously modified. The tight packing of SiO2 tetrahedrons in the porous silica network is broken by gamma‐ray irradiation. Defects of three‐coordinated Si and non‐bridging oxygen are induced by gamma‐ray irradiation. Moreover, we find that the defects concentrations rapidly grow as gamma‐ray dose increases. The mechanical, thermal, and optical performances of porous silica are all seriously degenerated by gamma‐ray irradiation. Our results show that, for mechanical performance, Young's modulus, Bulk modulus, and Shear modulus first decrease and then keep stable as gamma‐ray dose increases, but the change of Poisson's ratio is slight. For thermal performance, the thermal conductivity decreases exponentially as gamma‐ray dose increases. For optical performance, light absorption coefficients increase exponentially and light transmittance drops as gamma‐ray dose increases in the working range (photon energy range around 3.5 eV) of inertial confinement fusion. Present work is expected to be valuable for studying the degradation mechanism of silicate materials under gamma radiation and developing gamma‐ray irradiation protection technology.

Water brownness regulates the bioavailability of a fluoroquinolone antibiotic: UV-absorbance as a predictor of ciprofloxacin ecotoxicity

Dissolved organic carbon (DOC) is a powerful regulator of the ecotoxicity of ciprofloxacin (CIP), a widely applied fluoroquinolone antibiotic. In this study, we investigated the impact of DOC from a variety of sources on CIP bioavailability, using a cyanobacteria growth inhibition test with Microcystis aeruginosa. We analyzed the impact from two perspectives: (1) DOC concentration, and (2) water brownness, defined in this work as the light absorbance of DOC solutions. The toxicity tests were conducted with (1) unprocessed freshwater DOC in the naturally occurring state, (2) DOC extracted from a freshwater stream (Schwarzbach stream, Küchelscheid, Belgium), and (3) the commercial DOC product Suwannee River organic matter. Across all DOC sources investigated, a strong negative correlation was observed between CIP ecotoxicity and light absorbance at four wavelengths across the ultraviolet–visible range (e.g., A350), whereas CIP ecotoxicity correlated poorly with the DOC concentration. In addition, the interactions between CIP and DOC were modelled as a CIP-DOC binding process to allow the quantification of the inhibitory effects of DOC on CIP toxicity via binding constants (Kd,CIPx, with x being the ionic charge + or +/−, L g−1). Processed DOC sources showed higher binding potency than most of the unprocessed DOC sources, suggesting that toxicity tests employing only processed DOC potentially overestimates the impact of DOC in natural environments. Nonetheless, the light absorption coefficient (i.e., ε350) appeared a reliable predictor of the Kd,CIP+/− (and thus of the potential of the DOC source to reduce ecotoxicity of CIP) of both processed and unprocessed DOC. The relationship can be further incorporated into model simulations to estimate CIP bioavailability in dynamic environments. It is concluded that the brownness of water is a better predictor of the impact of DOC on CIP bioavailability than the DOC concentration itself.

Differences between one- and two-photon excited circularly polarized light emission processes in cholesteric liquid-crystalline semiconductors

Recently, cholesteric liquid-crystalline (CLC)-semiconductors have been studied for the purpose of realizing circularly polarized light (CPL) emission by electrical pumping. In this study, we investigated the one- and two-photon excited CPL emission properties of glassy CLC film of oligo (p-phenylenevinylene) derivatives. In the case of one-photon excitation, the CPL emission spectra were significantly different between the forward and backward configurations of the detector to the excitation light. This is because spontaneous emission occurred near the sample surface due to the large absorption coefficient for the excitation light. In contrast, in the case of two-photon excitation, the CPL emission spectra in the forward and backward configurations were almost identical. This is because the absorption coefficient for two-photon excitation was smaller than that for one-photon excitation, and spontaneous emission occurred over the entire sample. This result indicates that two-photon excitation is a useful optical pumping method for spectral analysis in CLC-semiconductors.