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Artificial photosynthesis holds immense promise for sustainable clean energy harvesting, with recent strides in material engineering with the earth abundant elements enabling efficient utilization of the visible solar spectrum for photoelectrochemical catalytic water splitting. Here, we have investigated the impact of substitutional Cu doping at all three cation sites in Ba2YNbO6 (BYN) using density functional theory calculations at the Heyd-Scuseria-Ernzerhof-06 level. One of the key findings is that the defect formation energy follows the hierarchy Nb > Ba > Y. The presence of an oxygen vacancy (OV) enhances the co-solubility of Cu substitution of Nb, particularly when placed outside the CuO6 unit, while it has a contrary effect for Y substitution. Cu replacement reduces the bandgap as Nb > Y ≫ Ba vis-à-vis pure BYN, while extending it into the visible part of the solar spectrum for Nb and Y replacement cases, albeit with OV causing a slight blue shift to them, without reducing the oxidation state of Cu due to strong charge-delocalization. Cu doping at Y and Nb sites retains the direct band transition character of BYN, a feature removed by OV. While all the bare Cu doped systems exhibit formation of a weak electron polaron, the placement of OV tends to annihilate this except for the system comprising first nearest neighbor placement of an OV relative to the Cu substitution at an Nb site. Notably, Cu doping at the Nb site significantly enhances optical activity, particularly ∼2.0–2.5 eV, resulting in promising candidates for photoelectrochemical catalysts. [ABSTRACT FROM AUTHOR]

In recent years, the exploration of solar absorbers has grown in favor due to the scarcity of energy. Here, we propose an absorber with an array of a circular ring surrounding disk (RSD) for solar energy capture. The novel structure keeps above 93.5% absorption with an average absorption of 96.95% in wavelengths from 300 to 4000 nm. Meanwhile, the proposed absorber is advantageous in that the structure is generalizable to other metals and dielectric materials. Furthermore, the data results show that the absorber has polarization-independent properties as well as maintaining >90% absorption in the considered wavelength range up to an incidence angle of 52° and >95% absorption at large process tolerances. Finally, the excellent absorption under the AM1.5 solar spectrum demonstrates the RSD absorber's ability to capture solar energy. These results show the potential of the absorber for applications in electromagnetic invisibility cloaking, thermal emitters, and solar energy capture and conversion. [ABSTRACT FROM AUTHOR]

In this study, low-cost laser marker ablation of vanadium-coated glass was adopted to prepare self-cleaning, anti-reflective, and anti-fog micro-nano structures on its surface. The surface had a hierarchical micro-nano structure composed of a quasi-periodic microstructure and ∼100 nm-sized worm-like clusters interspersed with dispersed nanoparticles. The solar spectrum (AM 1.5) weighted average transmission of treated glass was enhanced by 3.87% over control glass in the wavelength range of 400–1100 nm. Importantly, the water contact angle of the laser-treated samples achieved and maintained 0° for a duration of 25 days, and the laser-treated samples achieved and maintained excellent anti-fog performance for 150 days. The antifog performance degraded substantially afterward, though was still noticeable compared to the reference even after 428 days of storage in the laboratory. Furthermore, co-achievement of exceptional self-cleaning anti-fog performance and broadband transmission enhancement through laser treatment of glass has rarely been previously reported. [ABSTRACT FROM AUTHOR]

Taking into account the electron-rich and visible light response of thiophene, first-principles calculations have been carried out to explore the photocatalytic activity of donor–acceptor polymers incorporating thiophene and boron. Honeycomb-kagome boron–thiophene (BTP) polymers with varying numbers of thiophene units and fixed B center atoms are direct bandgap semiconductors with tunable bandgaps ranging from 2.41 to 1.88 eV and show high absorption coefficients under the ultraviolet and visible regions of the solar spectrum. Fine-tuning the band edges of the BTP polymer is efficiently achieved by adjusting the pore size through the manipulation of thiophene units between the B centers. This manipulation, achieved without excessive chemical functionalization, facilitates the generation of an appropriate quantity of photoexcited electrons and/or holes to straddle the redox potential of the water. Our study demonstrates that two units between B centers of thiophene in BTP polymers enable overall photocatalytic water splitting, whereas BTP polymers with larger pores solely promote photocatalytic hydrogen reduction. Moreover, the thermodynamics of hydrogen and oxygen reduction reactions either proceed spontaneously or need small additional external biases. Our findings provide the rationale for designing metal-free and single-material polymer photocatalysts based on thiophene, specifically for achieving efficient overall water splitting. [ABSTRACT FROM AUTHOR]

VO2-based thermochromic coatings have gained much attention in temperature-adaptive smart windows, and constructing multilayer film structures is the main way to obtain high thermochromic performances. Based on the self-developed objective-orientated automatic optimization code, the present research realized customized designs of thermochromic multilayer coatings composed of VO2, TiO2, and SiO2 from the objectives of visible luminance (Tlum) and solar light modulation (ΔTsol). The TiO2/VO2/s, VO2/TiO2/s, TiO2/VO2/TiO2/s, and SiO2/TiO2/VO2/TiO2/s (s denotes substrate) multilayer film systems were then prepared by magnetron sputtering and vacuum controllable heating, with their structures, insulator-metallic transition, and thermochromic properties being carefully studied. The result showed that the best trade-off between high Tlum and high ΔTsol was achieved for these film assemblies, and solar light modulation was mainly limited at the near-IR wavelength region of the solar spectrum, with the difference between cool- and hot-state Tlum being greatly reduced. In the case of the four-layer SiO2/TiO2/VO2/TiO2/s, very high average Tlum (60%) and high ΔTsol (14%) were obtained. A 100 × 100 mm2 of the SiO2/TiO2/VO2/TiO2/s was also prepared, and it showed an obvious temperature adjustment, and the service life can last for 14 years under normal weather conditions. Not limited to the prepared multilayer film systems, the methodology used here is also suitable for the fast development of other multilayer film systems. [ABSTRACT FROM AUTHOR]

The generation of hydrogen fuel, and wastewater treatment according to solar-driven catalysis possesses considerable prospective for establishing a carbon-neutral and ecologically sound power infrastructure. Driven by this problem, we suggest in this study, adopting a simple impregnation method, a customized association of CoAl-LDH and graphitic carbon nitride (CN), a visible light active narrow and wide band gap semiconductors. Several characterization approaches were implemented to understand the CoAl-LDH@g-C 3 N 4 (CACN) composites' physiochemical and optical features. The CACN hetero structural forms exhibited significantly improved solar light-induced photocatalytic H 2 generation and dye pollutants decomposition in contrast with pristine materials. The most effective catalyst 5 wt% CoAl-LDH@g-C 3 N 4 (5-CACN) generated the highest hydrogen (∼430.7 μmolg−1h−1), which is 11.9-fold H 2 production efficiency compared with CN and depicted significant Brilliant black dye removal efficacy via photocatalytic degradation (up to ∼79%). This was primarily ascribed to the development of the Type-II CACN heterojunctions, which promoted the separation of charges and expanded the abundance of surface-active sites while absorbing the visible spectrum of solar light. To examine the photocatalytic proficiency for H 2 production and dye pollutant removal over CoAl-LDH@g-C 3 N 4 heterojunction nanocomposites synthesized via a facile impregnation approach and plausible schematic photocatalytic mechanism for H 2 production and Brilliant black dye pollutant removal under visible photons illumination. [Display omitted] • A facile single-step hydrothermal method was employed to synthesize the CoAl-LDH nanotextures. • Type-II heterojunction CoAl-LDH@g-C 3 N 4 composites were prepared via a simple impregnation approach. • Type-II heterojunction CoAl-LDH@g-C 3 N 4 composites display an enhanced H 2 production during sunlight illumination. • Type-II heterojunction CoAl-LDH@g-C 3 N 4 depicts a significantly superior photocatalytic degradation of Brilliant Black dye in a water sample. • Plausible mechanism of Type-II heterojunction CoAl-LDH@g-C 3 N 4 for H 2 production and photocatalytic degradation of Brilliant Black dye. [ABSTRACT FROM AUTHOR]

The anomalous cosmic rays have been studied for about fifty years. Through theoretical and numerical models, we can learn how and where they are originating. When Voyager 1 and 2 spacecraft observed the solar wind termination shock, the main efforts were focused on try to explain the source spectrum and the acceleration mechanism. Nevertheless, there is another feature of the spectrum that need a better understanding, and it is related with the peak intensity in the energy spectrum, that occurred at different energies in consecutive solar minima. Qualitatively, it can be explained in terms of drifts and its relation with the acceleration process. In the past some works have been partially successful to explain the observations. In this paper we do another effort to explain the shift in the peak intensity of anomalous cosmic ray energy spectrum. We use a numerical model which includes diffusive shock acceleration, and the effects of the heliosheath. The present work analyzes the role played by different factors in the energy shift of the peak intensity between two successive minima, in particular the location of the region of observations with respect to the shock, the heliospheric distance, the effects of turbulence on the reduction of weak scattering drifts, as well as a possible latitudinal dependence in the ion injection on the shock. [ABSTRACT FROM AUTHOR]

The study examined the photo-stability of the thermal control coating (TCC), a class of "Optical Solar Reflectors", used in spacecrafts. This TCC is achieved by applying a layer of dielectric ceramic paste (DCP) onto the substrate using a printer (PCB printing). The DCP was prepared from filler (ground Al 2 O 3 ceramic) and solvent with thickener (terpineol with ethylcellulose). The coating obtained by high-temperature firing (T = 850 оC, 2 h) has high reflectivity in the solar range of the spectrum (0.2–2.5 μm) with the solar absorptance (α s) of DCP equal to 0.143. It has high adhesion and photo-stability that exceeds photo-stability parameters of ZnO, TiO 2 , BaSO 4 , and CaSiO 3 pigments. The developed coating can be recommended not only as a TCC for spacecrafts, but also as a protective or dielectric layer in manufacturing of printed circuit boards in various fields of technology, where increased resistance to solar radiation or its ultraviolet region is required. [ABSTRACT FROM AUTHOR]

The practical application of solar energy harvesting urgently calls for the facile preparation of high‐performance ultrablack surfaces with broadband and omnidirectional light absorption performance; however, some roadblocks still need to meet these requirements simultaneously. Herein, cone‐array ultrablack (CAUB) surfaces are prepared by combining feasible template replication and blade coating techniques. The elaborate micro‐sized cone structure and high absorptive materials (polydimethylsiloxane@carbon black, PDMS@CB) offer the CAUB extremely high, broadband, and omnidirectional light absorption over the solar spectrum with an average absorbance of 99.35%. Under one sun irradiation, the CAUB can efficiently absorb solar energy, reaching a surface temperature as high as 75 °C. A solar‐thermal‐electric generator (STEG) made from the CAUB film demonstrates real‐time solar‐heat‐electric conversion, achieving a high output power density of 330 µW cm−2. The CAUB film possesses excellent water repellency, flexibility, chemical solvent resistance, and potential for large‐scale production, satisfying the application requirements of solar energy harvesting and utilization. [ABSTRACT FROM AUTHOR]

Utilization of the near‐infrared (NIR) light in the solar spectrum is critical for efficiency improvement of photocatalytic H2 evolution. However, common semiconductors have low response to the NIR light and narrow bandgap semiconductors have inappropriate redox potentials. Here, the study presents a new dual‐functional up‐conversion strategy in one sensitizer for promoting photocatalytic hydrogen production reactions by converting NIR light to visible light and high‐energy electrons simultaneously, via photon‐photon conversion and photo‐electronic process, respectively. Using WO3:Yb,Er as the sensitizer and Zn0.5Cd0.5S as the hydrogen evolution reaction catalyst, a photocatalytic hydrogen release rate of 24.3 mmol g−1 h−1 under simulated solar‐light has been achieved without using any co‐catalyst. After loading Ni2P as a co‐catalyst, the photocatalytic hydrogen production performance can be further improved to 41.3 mmol g−1 h−1 at 10 °C and 93.3 mmol g−1 h−1 under non‐temperature‐controlled conditions, exceeding most photocatalysts. This work offers a new strategy to improve the NIR light utilization of the solar‐light for promoting photocatalytic hydrogen generation through synergistic photo‐optical, photo‐electronic, and photo‐thermal effects. [ABSTRACT FROM AUTHOR]

Effects of the extreme-ultraviolet (EUV) late phase of solar flares on the ionosphere were rarely studied. Here we simulated such effects on the ionospheric electron density using an ionosphere−thermosphere coupled model driven by the realistic solar spectrum observed during the X1.8 flare on 2012 October 23. Global total electron content (TEC) observations and simulations showed that the dayside ionospheric TEC during the EUV late phase increased more than that of the flare's main phase. We examined the performance of the model for flares with EUV late phase. The results showed that the F-region electron density enhancement and recovery did not vary in the same pace as the temporal variations of the EUV late phase, and the presence of the EUV late phase prolonged the recovery of electron density by ∼9 hr. We also found that the enhancement in electron density was mainly determined by the chemical production, while the recovery of electron density was primarily controlled by the electric field transport effects. This study enhanced understanding of the intricate physical and photochemical processes governing Earth's space environment and similar planetary systems during solar flare events with EUV late phase. [ABSTRACT FROM AUTHOR]

CuInSe2 (CISe) is a semiconductor compound used in photovoltaic applications. There are many ways to synthesize CISe, and the different synthesis methods result in CISe compounds with very different properties. The photoelectric conversion efficiency of a single-junction solar cell is predicted by Shockley and Queisser to be as high as 32%; however, the prediction only considers the semiconductor's bandgap value and the incident solar spectrum. In this study, a nearly cubic CISe supercell is constructed, and the influence of defects under different chemical potentials on the properties, especially the photovoltaic properties, is examined. The results show that p-type CISe is favorable in the stable chemical potential region when defect features are accounted for, but it has a photoelectric conversion efficiency of approximately 15%. The densities of the defects are calculated for the first time, revealing that the deep-level CuIn defect with a high density could be the limiting factor for efficiency. Notably, there is a narrow chemical potential range that allows a high carrier density and relatively low defect density. The efficiency of p-type CISe can reach 22.77% within this chemical potential with a deep-level defect density, n0, and p0 carrier densities of 1.119 × 1016, 1.295 × 102, and 9.827 × 1017 cm− 3, respectively. These findings help clarify defect-induced efficiency loss, which is crucial for improving the large-scale low-cost fabrication of high-efficiency solar cells with intrinsically high defect densities. [ABSTRACT FROM AUTHOR]

Industrial wastewater poses a serious threat to human health and the environment. The rising demand for an easy, efficient, environment‐friendly, and cost‐effective method for wastewater treatment has paved the way for the photocatalytic degradation of wastewater. Organic dyes, which comprise a major portion of organic pollutants in industrial wastewater, are highly toxic and carcinogenic. The hydrothermal method, being economical, easily available, and environmentally friendly, is used to prepare the time‐varying KBiFe2O5 samples. KBiFe2O5 is a lead‐free (nonhazardous), low‐bandgap brownmillerite‐structured crystalline material that can use a wide range of solar spectrum. Their phase purity is also confirmed by powder X‐ray diffraction (XRD), UV–Vis diffuse reflectance spectrophotometer (UV–Vis DRS) is done to confirm the bandgap value and Fourier transform infrared (FTIR) spectroscopy is performed to identify the chemical bonds in the material. Degrading textile organic effluent methylene blue (MB) dye under visible light and comparing its photodegradation performance are conducted to investigate the synthesized samples' photocatalytic properties. The photocatalytic activity is relatively enhanced by adding H2O2 in a precise amount. So, the synthesized samples effectively demonstrate photocatalytic behavior, which has been used for wastewater remediation purposes. [ABSTRACT FROM AUTHOR]

Uvsq-Sat NG is a French 6U CubeSat (10 × 20 × 30 cm) of the International Satellite Program in Research and Education (INSPIRE) designed primarily for observing greenhouse gases (GHG) such as CO2 and CH4, measuring the Earth's radiation budget (ERB), and monitoring solar spectral irradiance (SSI) at the top-of-atmosphere (TOA). It epitomizes an advancement in CubeSat technology, showcasing its enhanced capabilities for comprehensive Earth observation. Scheduled for launch in 2025, the satellite carries a compact and miniaturized near-infrared (NIR) spectrometer capable of performing observations in both nadir and solar directions within the wavelength range of 1100 to 2000 nm, with a spectral resolution of 7 nm and a 0.15° field of view. This study outlines the preflight calibration process of the Uvsq-Sat NG NIR spectrometer (UNIS), with a focus on the spectral response function and the absolute calibration of the instrument. The absolute scale of the UNIS spectrometer was accurately calibrated with a quartz-halogen lamp featuring a coiled-coil tungsten filament, certified by the National Institute of Standards and Technology (NIST) as a standard of spectral irradiance. Furthermore, this study details the ground-based measurements of direct SSI through atmospheric NIR windows conducted with the UNIS spectrometer. The measurements were obtained at the Pommier site (45.54°N, 0.83°W) in Charentes–Maritimes (France) on 9 May 2024. The objective of these measurements was to verify the absolute calibration of the UNIS spectrometer conducted in the laboratory and to provide an extraterrestrial solar spectrum using the Langley-plot technique. By extrapolating the data to AirMass Zero (AM0), we obtained high-precision results that show excellent agreement with SOLAR-HRS and TSIS-1 HSRS solar spectra. At 1.6 μm, the SSI was determined to be 238.59 ± 3.39 mW.m−2.nm−1 (k = 2). These results demonstrate the accuracy and reliability of the UNIS spectrometer for both SSI observations and GHG measurements, providing a solid foundation for future orbital data collection and analysis. [ABSTRACT FROM AUTHOR]

Studies of the impact of biomass burning and the emissions of trace gases from biomass burning, especially using long-term observations, are scarce in China. We utilize solar absorption spectra obtained via ground-based high-resolution Fourier transform infrared (FTIR) spectroscopy to retrieve the atmospheric total columns and vertical profiles of carbon monoxide (CO), formaldehyde (H2CO), and hydrogen cyanide (HCN) in Hefei, China. Seasonal and interannual variability in the three gases from 2016 to 2022 are analyzed. Atmospheric CO shows significant seasonal variations, peaking during spring and winter, and declining during summer, with a seasonal amplitude of 8.07 × 1017 molecules cm−2 and a seasonal variability of 29.35%. H2CO and HCN have similar seasonal patterns to each other, with high concentrations in summer and low concentrations in winter. The seasonal amplitude of H2CO and HCN are 1.89 × 1016 molecules cm−2 and 2.32 × 1015 molecules cm−2, respectively, with a seasonal variability of 133.07% and 34.69%, respectively. The means of the annual variation rate for CO, H2CO, and HCN are (−2.67 ± 2.88)% yr−1, (2.52 ± 12.48)% yr−1 and (−3.48 ± 7.26)% yr−1, respectively. To assess the influence of biomass burning on the variations in column concentrations of the three gases, the correlation between CO, H2CO, and HCN was analyzed. The months during which the monthly correlation coefficient between CO and H2CO with HCN exceeds 0.8, and the fire radiative power (FRP) observed by satellites is larger than its monthly average are regarded as a biomass-burning occurrence in Anhui province. Additionally, the enhancement ratios of ΔH2CO/ΔCO and ΔHCN/ΔCO were calculated for the periods impacted by the biomass burning. Finally, backward trajectory cluster analysis and the potential source contribution function (PSCF) calculation identified the air mass transport pathways and the potential source areas at the Hefei site. [ABSTRACT FROM AUTHOR]

This study aimed to explore the Doppler shift at different wavelengths in the IRIS solar spectrum and analyze the evolution and statistical properties of longitudinal oscillations with damping in chromosphere and transition region bright points (BPs). Understanding the damping mechanism and statistical properties of oscillations in BPs is crucial for gaining insights into the dynamics and energy transport within the solar atmosphere.This study explores the Doppler shift at different wavelengths in the solar spectrum of the Interface Region Imaging Spectrograph (IRIS) and implements a comprehensive consideration of Doppler velocity oscillations in the IRIS channels. This comprehensive consideration reveals a propagating periodic perturbation in a large number of chromosphere and transition region (TR) bright points (BPs). To the best of our knowledge, this is the first investigation of the longitudinal oscillations with damping in BPs using comprehensive consideration of the Doppler velocity at various wavelengths. The phenomena of attenuation in the red and blue Doppler shifts of the solar wavelength range were seen several times during the experiments. We utilized deep learning techniques to examine the statistical properties of damping in network and internetwork BPs, as well as active, quiet areas, and coronal hole areas. Our results revealed varying damping rates across different regions, with 80% of network BPs exhibiting damping in quiet areas and 72% in coronal hole areas. In active areas, the figure approached 33%. For internetwork BPs, the values were 65%, 54%, and 63% for quiet areas, coronal hole areas, and active regions, respectively. The damping rate in active regions is twice as high at Internetwork's BPs. The damping components in this study were computed, and the findings show that the damping at all points is underdamped. The observed damping process suggests the propagation and leaking of energetic waves out of TR bright points, potentially contributing to the energy transport from the bright magnetic footpoints to the upper chromosphere, transition region, and corona. [ABSTRACT FROM AUTHOR]

Increasing climate‐related extreme weather events and conflicts hinder safe water sanitation for vulnerable populations. In developing areas, centralized water systems are impractical due to high costs and poor infrastructure. Thus, technologies utilizing renewable energy like solar and mechanical energy for water treatment hold promise. It is critical to develop photocatalysts and piezoelectric/triboelectric catalysts that capture solar energy as well as mechanical energy to generate disinfectants to maximize energy utilization. The latest advancements in principles, materials, and processes utilizing solar and mechanical energy for water disinfection are highlighted in this review. First, we elucidate both direct and indirect mechanisms of sunlight‐mediated water disinfection, discuss the evolution of photocatalysts from simple UV absorption to visible‐light utilization, and even near‐infrared light exploitation to enhance solar spectrum utilization efficiency. Furthermore, we delve into the fundamental principles of piezoelectricity and triboelectricity relying on mechanical energy conversion as well as summarize the development of piezo/triboelectric catalysts from being driven by high‐frequency energy to utilizing low‐frequency mechanical energy from the environment. Finally, challenges and directions for efficient systems are outlined to inspire rational design strategies and accelerate the production of superior catalytic systems applicable across a broad range. [ABSTRACT FROM AUTHOR]

Personal thermal regulation through passive radiative cooling is an effective strategy to achieve sustainable development. Although recent advances have introduced various cooling textile designs, the extensive use of materials unsuitable for common textiles, alongside coating or compositing technologies, not only compromises the wearability and safety of these textiles but also impacts green sustainability. Herein, it is shown that wool is a promising natural material for transferring mid‐infrared human body radiation, but the high absorption in the solar spectrum prohibits wool from achieving satisfactory daytime radiative cooling. Thus the natural wool impregnates zinc ions into the protein chains to form a zinc‐ion woolen (wool‐Zn) fabric. The wool‐Zn fabric can provide humans with a cooling sensation both indoors and daytime outdoors, showing a temperature reduction of 2 °C on human skin indoors and a reduction of 7 °C on artificial skin under direct sunlight, respectively, when covered by wool‐Zn fabrics compared to when covered with cotton. Moreover, the wool‐Zn fabric shows desirable antibacterial properties and durability against washing and abrasion, while maintaining desirable wearability. As a result, the wool‐Zn fabric shows great potential for commercial application in personal thermoregulation and provides an effective avenue toward sustainable energy and environment. [ABSTRACT FROM AUTHOR]

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Developing efficient photocatalysts with low cost, high performance, and high selectivity is essential and imperative for CO 2 conversion and utilization, yet it remains a big challenge. Herein, a novel Ce-doped TiO 2 aerogel with oxygen vacancy anchored on the oriented carbonaceous (Ce–TiO 2 @CS) is synthesized by the sol-gel technique, combined with the freeze casting, supercritical drying technique, and heat treatment processes. The Ce–TiO 2 @CS aerogel has a typical aerogel-like structure, with the Ce–TiO 2 aerogel anchored on the oriented porous carbon, rendering a large BET-specific surface area of 124 m2/g, which leads to enhanced photocatalytic activity. The Ce-doping into the pristine TiO 2 results in impurity levels within the band gap, which extends the light response range to the visible light region. In addition, the rapid combination of electrons and holes is prevented via the two-phase microstructures and rapid transfer rate of electrons within the oriented porous carbon. The yields of CH 4 and CO are as high as 9.45 μmol h−1 g−1 and 42.26 μmol h−1 g−1, respectively, which are 28.6 and 2.46 times higher than those of pristine TiO 2 aerogel under simulated solar spectrum conditions without any sacrificial agents or co-catalysts, The density functional theory (DFT) calculation shows that larger C–O bonds of CO 2 molecule and more negative adsorption energy have occurred on the Ce–TiO 2 @CS aerogel, indicating that the CO 2 activation has been enhanced, which greatly improves the CO 2 photoreduction activity. This work may guide the designing of aerogel-based photocatalysts for CO 2 photocatalytic reduction. [ABSTRACT FROM AUTHOR]

This study presents an approach for fabricating super hydrophilic self-cleaning anti-fog micro-nano structures on silicon-coated glass utilizing a laser marking machine. The surface features a periodic microstructure interspersed with irregular nanoparticles, which contribute to its durable superhydrophilicity, maintaining a 0° contact angle for up to one year—the longest duration recorded to date. Moreover, it sustained its anti-fogging and self-cleaning abilities for 467 days, establishing the lengthiest duration for maintaining a 0° contact angle and retaining anti-fogging performance without visible deterioration. The sample also retained excellent anti-fogging and self-cleaning properties even after 43 days of outdoor exposure. Such remarkable performance was attributed not only to surface chemistry and roughness but also to the presence of dense, uniform, and minimally varying microstructures. The unique structure also enhanced the solar spectrum (AM 1.5) weighted average transmission by 3.84 % over control glass in the wavelength range of 400–1100 nm. It holds promising potential for use in automotive rearview mirrors, windows, and solar cells. [ABSTRACT FROM AUTHOR]

Water remediation has become a hot subject of study due to textile, pharmaceutical, and agricultural discharge to the water bodies. Photocatalysis with photocatalyst having favorable structure, reduced charge carrier recombination and ability to harness UV–Visible spectrum has emerged as efficient way to completely mineralize the persistent organic pollutants (POPs) (Sharma et al. in J Environ Chem Eng 9(5):105812, 2021; Chawla et al. in Coord Chem Rev 491:215246, 2023). In this research, we reported the synthesis of SnO2/Fe2O3/MoS2 ternary composite. The motive of the composite formation is to harvest the entire solar spectrum with prolonged electron–hole recombination. The band gap has reduced from 3.46 to 2.30 eV with the formation of SnO2/Fe2O3/MoS2 ternary composite. The ternary composite exhibited an excellent photocatalytic activity of 95% against Congo red after 80 min at a rate constant of 0.018 min−1. Moreover, the composite showed a photocatalytic activity of 85% and 93% against diclofenac sodium and pendimethalin at a rate constant of 0.017 min−1 and 0.02 min−1 respectively. Through trapping experiments, we determined that hydroxyl radicals scavenging had reduced the photocatalytic degradation of Congo red, diclofenac sodium and pendimethalin to 25%, 22%, and 15% respectively. Beyond its exceptional photocatalytic degradation capabilities, the SnO2/Fe2O3/MoS2 ternary composite also ushered in new possibilities for utilizing wide band gap materials reinforced with visible light active materials along with 2-D materials. [ABSTRACT FROM AUTHOR]

At high frequencies beyond the acoustic cut-off, a peak-like structure is visible in the solar power spectrum. Known as the pseudo-modes, their frequencies have been shown to vary in anti-phase with solar magnetic activity. In this work, we determined temporal variations in these frequencies across the solar disc, with the aim of identifying any potential latitudinal dependence of pseudo-mode frequency shifts. We utilised nearly 22 years of spatially resolved GONG data for all azimuthal orders, m , for harmonic degrees 0 ≤ l ≤ 200 , and determined shifts using the resampled periodogram method. Periodogram realisations were created from overlapping, successive 216 day-long segments in time, and cropped to 5600 – 6800 μHz. Cross-correlation functions were then repeatedly generated between these realisations to identify any variation in frequency and the uncertainty. We categorised each mode by its latitudinal sensitivity and used this categorisation to produce average frequency shifts for different latitude bands (15∘ and 5∘ in size) which were compared to magnetic proxies, the F 10.7 index and GONG synoptic maps. Morphological differences in the pseudo-mode shifts between different latitudes were found, which were most pronounced during the rise to solar maximum where shifts reach their minimum values. At all latitudes, shift behaviour was strongly in anti-correlation with the activity proxy. Additionally, periodicities shorter than the 11-year cycle were observed. Wavelet analysis was used to identify a periodicity of four years at all latitudes. [ABSTRACT FROM AUTHOR]

A solvent‐free sulfur‐bridge‐eosin‐Y (SBE‐Y) polymeric framework photocatalyst was prepared for the first time through an in situ thermal polymerization route using elemental sulfur (S8) as a bridge. The addition of a sulfur bridge to the polymeric framework structure resulted in an allowance of the harvesting range of eosin‐Y (E‐Y) for solar light. This shows that a wider range of solar light can be used by the bridge material's photocatalytic reactions. In this context, supercharged solar spectrum: enhancing light absorption and hole oxidation with sulfur bridges. This suggests that the excited electrons and holes through solar light can contribute to oxidation–reduction reactions more potently. As a result, the photocatalyst‐enzyme attached artificial photosynthesis system developed using SBE‐Y as a photocatalyst performs exceptionally well, resulting in high 1,4‐NADH regeneration (86.81%), followed by its utilization in the exclusive production of formic acid (210.01 μmol) from CO2 and synthesis of fine chemicals with 99.9% conversion yields. The creation of more effective photocatalytic materials for environmental clean‐up and other applications that depend on the solar light‐driven absorption spectrum of inorganic and organic molecules could be one of the practical ramifications of this research. [ABSTRACT FROM AUTHOR]

As one of the most intriguing absorbers for environmentally friendly and low cost thin-film photovoltaic materials, Cu(In,Ga)Se2 (CIGS)-based solar cells with high device conversion efficiency, high stability, tunable bandgap, and high optical absorption coefficients have attracted widespread attention. As we know, the last record efficiency of 23.35% for CIGS solar cell devices maintained close to four years to be broken. The main obstacle for this stagnation is ascribed to the narrow band gap of CIGS absorber layer. Simultaneously, the highly efficient CIGS solar cells exceed 22% with the absorber bandgap energy (Eg) below 1.2 eV, it is lower than that of the global optimum lies of 1.34 eV. Therefore, widening the absorber layer bandgap to match the solar spectrum can be meaningful for the further efficiency improvement. However, the wide-gap CIGS solar cell encounters the current pronounced limitation is the large VOC deficit, which is related to the inappropriate heterogeneous junction interface of CdS/CIGS (cliff-like structure). Excitingly, with silver (Ag) alloying, the wider band gap of CIGS can keep the heterojunction interface always in a spike-like structure and optimize the heterojunction structure of the buffer layer/absorber layer. Simultaneously, with the introducing of Ag, the current record efficiency of CIGS has arrived to 23.6% in 2024. The aim in here is to evaluate recent advances with Ag to widening the bandgap of the absorber layer to match the solar spectrum along with several emerging prospective superiorities, including: (i) suppressing the lattice disorder, (ii) ameliorating crystallization properties, (iii) controlling heterojunction interfaces, (iv) tailoring band gap gradient, and surface modification with alkali elements. [ABSTRACT FROM AUTHOR]

Photovoltaic technology has become one of the major renewable ways to generate electric power. However, the mismatch between the incident solar spectrum and photo-electric response efficiency of solar cells severely constrains their performance. Hence, spectral modification technologies, e.g., up-conversion (UC), down-conversion (DC), and luminescent down-shifting (LDS) technologies have been applied widely in the photovoltaic field to reform the incident spectrum to match the best response band possible. In this paper, we review the latest developments of the three technologies above in terms of material selection, optical characteristics, and photovoltaic performance. It is found that the three most popular materials for conversion are NaYF4: Er3+, Yb3+, and Yb3+. The excitation bands for the three technologies are 800–1550 nm, 250–488 nm, and 250–488 nm, respectively, while the emission bands are 523–669 nm, 520–1031 nm, and 490–1010 nm, respectively. Furthermore, issues hindering the development of spectral modification technologies are pointed out, e.g., low absorption efficiency, poor quantum conversion efficiency, and hurdles in commercialization. Finally, suggestions and solutions to address the above-mentioned issues are provided. [ABSTRACT FROM AUTHOR]

Highly solar light-absorbing poly(vinyl alcohol) (PVA) nanocomposite films have garnered wide attention in fields such as flexible optoelectronics, solar energy harvesting, and photothermal therapy. However, fabricating PVA nanocomposite films with a broad spectrum of solar absorption using cost-effective and non-toxic nanofillers remains challenging. Herein, nanocomposite films of PVA incorporating various concentrations of mixed-phase 2D MoSe2 nanosheets (i.e., a combination of the 2H and 1T phase) were prepared using a solution casting technique. Scanning electron microscopy (SEM) shows homogenous dispersion of MoSe2 nanosheets in the PVA matrix even at higher concentrations, while atomic force microscopy (AFM) reveals increasing surface roughness with increasing MoSe2 content, reaching a plateau after 20 wt%. With the increase in the concentration of MoSe2, the nanocomposite films exhibit interesting light absorption characteristics reaching their highest absorption (average 94.9%) at 40 wt% MoSe2. The incorporated mixed-phase MoSe2 nanosheets induce a significant change in the energy levels of the PVA matrix, which is reflected in the reduced optical band gap energy (2.63 eV) at 40 wt% MoSe2 against pure PVA (5.28 eV). The excellent light absorption of PVA nanocomposite films across the entire range from 250 nm to 2500 nm is attributed to the thin 2D structure of MoSe2 and the presence of its mixed phase. [ABSTRACT FROM AUTHOR]

This article delves into the domain of low bandgap perovskite solar cells, driven by the quest for enhanced device performance and expanded access to various solar energy spectra. The study systematically explores the materials, device design, and optimization strategies pertinent to low bandgap perovskite solar cells. The initial section focuses on the current status of low bandgap perovskite materials, scrutinizing approaches to enhance bandgap, stability, and charge transport. Novel materials such as mixed-halide perovskites, double perovskites, and perovskite quantum dots are examined to improve efficiency and broaden the spectral utilization. The investigation culminates in a comprehensive exploration of diverse device topologies aimed at enhancing the performance of low bandgap perovskite solar cells. This encompasses discussions on electron and hole transport materials, interfacial engineering techniques, various device designs, tandem configurations, and their respective merits and limitations. Additionally, the research scrutinizes methodologies to enhance the performance of low-bandgap perovskite solar cells, with a specific focus on light management, charge extraction, and mitigating recombination losses. The incorporation of passivation layers and interfacial modifications is discussed as a strategy for bolstering device stability and mitigating deterioration through interface engineering. [ABSTRACT FROM AUTHOR]

Background: From new results presented in the literature we discuss the hypothesis, presented in an our previous work, that the ultrafast periodic spectral modulations at f S = 0.607 ± 0.08 THz found in the spectra of 236 stars of the Sloan Digital Sky Survey (SDSS) were due to oscillations induced by dark matter (DM) cores in their centers that behave as oscillating boson stars. Two other frequencies were found by Borra in the redshift-corrected SDSS galactic spectra, f 1 , G = 9.71 − 0.19 + 0.20 THz and f 2 , G = 9.17 − 0.16 + 0.18 THz; the latter was then shown by Hippke to be a spurious frequency introduced by the data analysis procedure. Results: Within the experimental errors, the frequency f 1 , G is the beating of the two frequencies, the spurious one, f 2 , G and f S that was also independently detected in a real solar spectrum, but not in the Kurucz's artificial solar spectrum by Hippke, suggesting that f S could actually be a real frequency. Independent SETI observations by Isaacson et al., taken at different epochs, of four of these 236 stars could not confirm with high confidence—without completely excluding—the presence of f S in their power spectra and with the same power initially observed. Instead, the radio SETI deep-learning analysis with artificial intelligence (AI) gave an indirect confirmation of the presence of f S through the detection of a narrowband Doppler drifting of the observed radio signals in two stars, over a sample of 7 with a high S/N. These two stars belong to the set of the 236 SDSS stars. Numerical simulations confirm that this drifting can be due to frequency and phase modulation in time of the observed frequencies (1.3–1.7 GHz) with f S . Conclusions: Assuming the DM hypothesis, the upper mass limit of the axion-like DM particle is m a ≃ 2.4 × 10 3 μ eV , in agreement with the results from the gamma ray burst GRB221009A, laser interferometry experiments, suggesting new physics with additional axion-like particle fields for the muon g-2 anomaly. [ABSTRACT FROM AUTHOR]

Photocatalysis based on titanium dioxide (TiO2) has become a promising method to remediate industrial and municipal effluents in an environmentally friendly manner. However, the efficiency of TiO2 is hampered by problems such as rapid electron–hole recombination and limited solar spectrum absorption. Furthermore, the sensitization of TiO2 through heterojunctions with other materials has gained attention. Vanadium, specifically in the form of ammonium vanadate ((NH4)2V3O8), has shown promise as a photocatalyst due to its ability to effectively absorb visible light. However, its use in photocatalysis remains limited. Herein, we present a novel synthesis method to produce lamellar (NH4)2V3O8 as a sensitizer in a supramolecular hybrid photocatalyst of TiO2–stearic acid (SA), contributing to a deeper understanding of its structural and magnetic characteristics, expanding the range of visible light absorption, and improving the efficiency of photogenerated electron–hole separation. Materials, such as TiO2–SA and (NH4)2V3O8, were synthesized and characterized. EPR studies of (NH4)2V3O8 demonstrated their orientation-dependent magnetic properties and, from measurements of the angular variation of g-values, suggest that the VO2+ complexes are in axially distorted octahedral sites. The photocatalytic results indicate that the 2D/2D heterojunction layered TiO2/vanadate at a ratio (1:0.050) removed 100% of the methylene blue, used as a model contaminant in this study. The study of the degradation mechanism of methylene blue emphasizes the role of reactive species such as hydroxyl radicals (•OH) and superoxide ions (O2•−). These species are crucial for breaking down contaminant molecules, leading to their degradation. The band alignment between ammonium vanadate ((NH4)2V3O8) and TiO2–SA, shows effective separation and charge transfer processes at their interface. Furthermore, the study confirms the chemical stability and recyclability of the TiO2–SA/(NH4)2V3O8 photocatalyst, demonstrated that it could be used for multiple photocatalytic cycles without a significant loss of activity. This stability, combined with its ability to degrade organic pollutants under solar irradiation, means that the TiO2–SA/(NH4)2V3O8 photocatalyst is a promising candidate for practical environmental remediation applications. [ABSTRACT FROM AUTHOR]

Recent improvements in advanced technology for toxic chemical remediation have involved the application of titanium oxide nanoparticles as a photocatalyst. However, the large energy bandgap associated with titanium oxide nanoparticles (3.0–3.20 eV) is a limitation for their application as a photocatalyst within the solar spectrum. Various structural modification methods have led to significant reductions in the energy bandgap but not without their disadvantages, such as electron recombination. In the current investigation, biochar was made from the leaves of an invasive plant (Acacia saligna) and subsequently applied as a support in the synthesis of titanium oxide nanoparticles. The characterization of biochar-supported titanium oxide nanoparticles was performed using scanning electron microscopy, Fourier transformer infrared, X-ray diffraction, and Brunauer–Emmett–Teller analyses. The results showed that the titanium oxide was successfully immobilized on the biochar's external surface. The synthesized biochar-supported titanium oxide nanoparticles exhibited the phenomenon of small hysteresis, which represents the typical type IV isotherm attributed to mesoporous materials with low porosity. Meanwhile, X-ray diffraction analysis revealed the presence of a mixture of rutile and anatase crystalline phase titanium oxide. The synthesis of biochar-supported titanium oxide nanoparticles was highly efficient in the degradation of Orange II Sodium dye under solar irradiation. Moreover, 83.5% degradation was achieved when the biochar-supported titanium oxide nanoparticles were used as photocatalysts in comparison with the reference titanium oxide, which only achieved 20% degradation. [ABSTRACT FROM AUTHOR]

• Recent researches on various types of photocatalysts and heterojunctions have been outlined. • Recent researches on wastewater treatment by photocatalysis have been summarized. • Investigated photocatalysts for air purification have been summarized. • The application of photocatalysis for conversion including CO 2 reduction and H 2 evolution have been summarized. In the quest for effective solutions to address Environ. Pollut. and meet the escalating energy demands, heterojunction photocatalysts have emerged as a captivating and versatile technology. These photocatalysts have garnered significant interest due to their wide-ranging applications, including wastewater treatment, air purification, CO 2 capture, and hydrogen generation via water splitting. This technique harnesses the power of semiconductors, which are activated under light illumination, providing the necessary energy for catalytic reactions. With visible light constituting a substantial portion (46%) of the solar spectrum, the development of visible-light-driven semiconductors has become imperative. Heterojunction photocatalysts offer a promising strategy to overcome the limitations associated with activating semiconductors under visible light. In this comprehensive review, we present the recent advancements in the field of photocatalytic degradation of contaminants across diverse media, as well as the remarkable progress made in renewable energy production. Moreover, we delve into the crucial role played by various operating parameters in influencing the photocatalytic performance of heterojunction systems. Finally, we address emerging challenges and propose novel perspectives to provide valuable insights for future advancements in this dynamic research domain. By unraveling the potential of heterojunction photocatalysts, this review contributes to the broader understanding of their applications and paves the way for exciting avenues of exploration and innovation. [Display omitted] [ABSTRACT FROM AUTHOR]

In the period December 12, 2022, to February 28, 2023, we performed a series of UBVRI observations of 65 asteroids, including 50 primitive-type objects, which could be observed near perihelion at that time, and calculated their approximated reflectance spectra. The observations were aimed at searching for spectral signs of sublimation-driven dust activity in the asteroids and formation of a transient dust exosphere, which are caused by the presence of Н2О ice in their interior and the highest subsolar temperature. Based on the analysis of the accuracy and shape of approximated reflectance spectra of the primitive-type asteroids, a set of which was conventionally restricted by the geometric albedo value not exceeding 0.10, we found sublimation-driven dust activity in asteroids 164 Eva, 360 Carlova, and 750 Oskar by distinct short-term variations in the reflectance of these asteroids in the U band. During one of the nights, similar spectral changes and sublimation-driven dust activity related to them were detected in asteroid 629 Bernardina; the geometric albedo of this asteroid is somewhat higher (0.14 or 0.19), which may be indicative of a heterogeneous composition of its material and, apparently, a local outcropping of water ice on its surface. Moreover, in three asteroids of a high-temperature type, 757 Portlandia, 1121 Natascha, and 1687 Glarona, noticeable variations were detected in the entire spectral range; they may be connected with ejection of submicron dust particles from the surface by some other mechanisms. To substantiate and interpret the results of observations, we numerically modeled the reflectance spectra of conditional asteroids of taxonomic types C and S (with low- and high-temperature mineralogy, respectively), which are enveloped by an optically thin dust exosphere containing aggregate or homogeneous submicron particles of different composition. On the basis of this modeling, we introduce a quantitative criterion to identify a weak sublimation-driven dust activity in primitive-type asteroids in the visible range. [ABSTRACT FROM AUTHOR]

The impedance spectra of perovskite solar cells frequently exhibit multiple features that are typically modelled by complex equivalent circuits. This approach can lead to the inclusion of circuit elements without a sensible physical interpretation and create confusion where different circuits are adopted to describe similar cells. Spectra showing two distinct features have already been well explained by a drift‐diffusion model incorporating a single mobile ionic species but spectra with three features have yet to receive the same treatment and have even been dismissed as anomalous. This omission is rectified here by showing that a third (mid‐frequency) impedance feature is a natural consequence of the drift‐diffusion model in certain scenarios. Our comprehensive framework explains the shapes of all previously published spectra, which are classified into six generic types, each named for an animal resembling the Nyquist plot, and approximate solutions to the drift‐diffusion equations are obtained in order to illustrate the specific conditions required for each of these types of spectra to be observed. Importantly, it is shown that the shape of each Nyquist plot can be linked to specific processes occurring within a cell, allowing useful information to be extracted by a visual examination of the impedance spectra. [ABSTRACT FROM AUTHOR]

Lead-based perovskite solar cells (PSCs) typically initiate photogeneration at wavelengths around 800 nm, resulting in substantial spectral energy loss in the near-infrared (NIR) region. Enhancing light absorption beyond 800 nm into the NIR spectrum can significantly increase photocurrent generation and overall PSC efficiency. This study introduces a straightforward method to incorporate NIR-absorbing aluminum-doped zinc oxide (AZO) into the perovskite material as absorbers. This integration aims to extend the photoresponse range of PSCs and enhance their efficiency. The modified solar cells demonstrate NIR photocurrent generation with a measured photocurrent of 18.755 mA/cm2, surpassing the perovskite active layer's contribution of 16.772 mA/cm2. Consequently, PSCs with AZO nanoparticles achieve an efficiency of 13.9% up from 9.92%, which is a significant increase in the operational stability under continuous one-sun illumination. The results also suggested that AZO-doped PSC was 2.33% more efficient as compared to rGO-based PSC at similar doping concentration. These findings underscore the potential of directly incorporating a wide bandgap oxide semiconductor into perovskite active layers, thereby extending light absorption in the NIR region for higher efficiency, addressing surface trap issues, and developing highly efficient and stable PSCs. This innovation could also enhance the durability and performance of flexible and wearable solar technologies. [ABSTRACT FROM AUTHOR]

The reverse bias stability is a key concern for the commercialization and reliability of halide perovskite photovoltaics. Here, the robustness of perovskite‐silicon tandem solar cells to reverse bias electrical degradation down to −40 V is investigated. The two‐terminal tandem configuration, with the perovskite coupled to silicon, can improve the solar cell resistance to severe negative voltages when the tandem device is properly designed. While perovskite cells typically exhibit early reverse bias breakdown voltages, the serial connection with silicon cells with large shunt resistances and high voltage breakdown limits their negative polarization and prevent the passage of large current densities when reverse biased. The importance of careful optical design is illustrated, with bottom‐limited conditions required to prevent the perovskite top cell from exploring its own breakdown. This aspect is of great importance in the case of partial shading events when the solar spectrum is richer in the IR components than the standard AM1.5G. Notably, 100% of efficiency retained after polarization at −40 V in different stressing conditions is observed. The results presented suggest that standard industrial bypass diode schemes may be compatible with silicon/perovskite tandem photovoltaics and provide new guidelines for the standardization of the stressing protocols. [ABSTRACT FROM AUTHOR]

The aim of this study is to quantify the impact of the effect of long-term solar cycle variations in solar irradiance on the accuracy and temporal stability of ToA reflectance values from Enhanced Thematic Mapper Plus (ETM+/L7) sensor images. We used 1382 ETM+ scenes corresponding to five Pseudo-Invariant Calibration Sites (PICS), obtained between 2003 and 2020. Solar irradiance data from the Spectral Irradiance Monitor (SIM/SORCE) were used to calculate daily values of mean exoatmospheric solar irradiance (ESUN), implemented in the radiometric correction of ToA reflectance. Enhanced temporal stability coefficients and variance tests were calculated to evaluate the stability of the time series obtained. The results indicate that the use of daily SIM/SORCE solar spectra has a significant impact (alpha <0.001) on radiometric correction and the accuracy of ToA reflectance values. In radiometric calibration, the percentage of top of atmosphere temporal stability that can be recovered based on 5 Sahara PICS ETM+/L7 scenes can exceed 0.75%, 0.50%, 0.39%, 0.45%, 0.30% and 0.25% in the blue, green, red, NIR, SWIR-1 and SWIR-2 spectral bands, respectively, and is not considered statistically significant (alpha >0.05). We concluded that considering the effects of solar cycles during the radiometric calibration of multispectral sensors contributes to improving the long-term stability of ToA reflectance products. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) has emerged as a clean and versatile energy carrier to power a carbon‐neutral economy for the post‐fossil era. Hydrogen generation from low‐cost and renewable biomass by virtually inexhaustible solar energy presents an innovative strategy to process organic solid waste, combat the energy crisis, and achieve carbon neutrality. Herein, the progress and breakthroughs in solar‐powered H2 production from biomass are reviewed. The basic principles of solar‐driven H2 generation from biomass are first introduced for a better understanding of the reaction mechanism. Next, the merits and shortcomings of various semiconductors and cocatalysts are summarized, and the strategies for addressing the related issues are also elaborated. Then, various bio‐based feedstocks for solar‐driven H2 production are reviewed with an emphasis on the effect of photocatalysts and catalytic systems on performance. Of note, the concurrent generation of value‐added chemicals from biomass reforming is emphasized as well. Meanwhile, the emerging photo‐thermal coupling strategy that shows a grand prospect for maximally utilizing the entire solar energy spectrum is also discussed. Further, the direct utilization of hydrogen from biomass as a green reductant for producing value‐added chemicals via organic reactions is also highlighted. Finally, the challenges and perspectives of photoreforming biomass toward hydrogen are envisioned. [ABSTRACT FROM AUTHOR]

Agarose/micrometer titanium dioxide (TiO2) beads were essayed to test the photocatalytic capacity of two of the most widely prescribed drugs worldwide: paracetamol and ibuprofen. Although the initial tests demonstrated promising degradation rates for both drugs, the presence of turbidity, due to TiO2 leakage, during the photocatalytic essays induced to improve the stability of the photocatalytic composites. Among the different strategies adopted to strengthen such materials, crosslinking with citric acid and the use of alternative gelling agents: gellan, agargel™, and agar were chosen. Composites obtained by merging both strategies were characterized and employed to degrade both drugs under a simulated light that mimics the solar spectrum (indoor). Considering the superior degradation rates obtained when agar and agarose were used to shape the titanium oxide particles (up to 70–75% of drug destruction), such composites were subjected to a more realistic experiment (outdoor): solar illumination, tap water, and higher volumes, that should facilitate its ulterior scale up as a real wastewater depollution procedure. Degradation rates between 80 and 90% are attained under such conditions for both drugs. [ABSTRACT FROM AUTHOR]

Abstract—Based on the data of several spaced magnetic stations, the spectrum of geomagnetic variations is studied in the range of periods from two to 40 years. Special attention is paid to spectral features in the supposed range of action of intraterrestrial processes that cause geomagnetic jerks. It is shown that the detected spectral peak in the vicinity of the period of 6.5 years aligns with the previously revealed recurrence pattern of jerks with a period of three to four years; however, this peak is absent in the spectrum of solar activity. The possible wave mechanisms of the occurrence of jerks and their 6-year quasi-periodicity caused by known types of magnetohydrodynamic waves in the liquid core of the Earth, are considered, and it is shown that they are not sufficiently convincing in reproducing observations of jerks. [ABSTRACT FROM AUTHOR]

The hyperfine transition of atomic hydrogen at a wavelength of about 21 cm is an essential tool for studies of interstellar gas. It has been argued that also fine-structure transitions of hydrogen could be detected in astronomical sources. Our aim is to detect the fine-structure transition 2 2 P 3 / 2 − 2 2 S 1 / 2 of hydrogen at ∼10 GHz in the radio spectrum of the Sun, with a spectral resolution which enables a detailed study of the line profile. The Sun was observed with the 13.7 m radio telescope at the Metsähovi Radio Observatory, in Finland. We detect emission from two of the three hyperfine components of the transition. The width of the components is ∼15 MHz, much less than the expected natural line width of ∼100 MHz (broadened solely by the uncertainty principle). At red-shifted Doppler velocities, the lines show enhanced emission and possibly self-absorption. If the absorption happens at the chromosphere, our observations challenge the traditional view that chromospheric temperature increases gradually towards higher altitudes. Our unconventional results have to be confirmed by further observations. This transition would be the only known spectral line in the Sun at radio frequencies. [ABSTRACT FROM AUTHOR]

The Sun is a major source of energy for the planetary system in our solar system. The solar output shows variations in timescales from a few days (Bartel's 27-day solar rotation cycle) to several years (the 11-year solar cycle and longer timescales). This variability can be seen in the magnetic field, particle flux, and electromagnetic radiation flux behavior. Several indicators, such as the sunspot number and the Mg II index, have been used as solar activity proxies. Further, direct measurements in radio at centimeter wavelengths have been conducted since 1947 (the F10.7 index). This work uses multiscale techniques to study the relations between these solar indexes and their long-term variations through multiscale techniques. The monthly averages of these indexes from 1979 to 2022 are analyzed using wavelet scalogram, global wavelet spectrum, wavelet cross-correlation, and wavelet entropy techniques. As a result, some nonlinear multiscale aspects in the long-term variations of these solar indexes are identified. The major scales at which these indexes vary are found to be, in order of decreasing energy: sunspots (130.1, 253.9, 11.7, 5.0, and 2.0 months); F10.7 (130.1, 253.9, 39.1, 10.9, 9.9, and 5.4 months), and Mg II (132.9, 39.0, and 10.3 months). Thus, all three indexes present the nearly 11-year solar cycle period as the strongest signal. The three indexes are correlated with a coefficient higher than 0.85 and vary in phase for scales near the 11-year solar cycle, with slight and large deviations from it for longer and shorter scales, respectively. The wavelet entropy analysis shows that the F10.7 and sunspot number values are comparable, while Mg II entropy values are much lower. The entropy also indicates that the minimum values for all the indexes occur close to the solar minimum. However, after the last solar maximum in 2014, the entropy increased even in the declining phase of the cycle, during the 2015 – 2020. [ABSTRACT FROM AUTHOR]

HXI on ASO-S and STIX onboard Solar Orbiter are the first simultaneously operating solar hard X-ray imaging spectrometers. ASO-S's low Earth orbit and Solar Orbiter's periodic displacement from the Sun–Earth line enables multi-viewpoint solar hard X-ray spectroscopic imaging analysis for the first time. Here, we demonstrate the potential of this new capability by reporting the first results of 3D triangulation of hard X-ray sources in the SOL2023-12-31T21:55 X5 flare. HXI and STIX observed the flare near the east limb with an observer separation angle of 18°. We triangulated the brightest regions within each source, which enabled us to characterise the large-scale hard X-ray geometry of the flare. The footpoints were found to be in the chromosphere within uncertainty, as expected, while the thermal looptop source was centred at an altitude of 15.1 ± 1 Mm. Given the footpoint separation, this implies a more elongated magnetic-loop structure than predicted by a semi-circular model. These results show the strong diagnostic power of joint HXI and STIX observations for understanding the 3D geometry of solar flares. We conclude by discussing the next steps required to fully exploit their potential. [ABSTRACT FROM AUTHOR]

When analyzing a narrowband signal, the Hilbert transform is often used, which makes it possible to describe the process through slowly changing functions: the envelope (amplitude) and, weakly dependent on time, the characteristic signal frequency—the "instantaneous" frequency. Based on the smoothness of these characteristics, one can evaluate the process and compare it at different periods. This approach was used to analyze the spectral components of a series of average monthly Wolf numbers. This description of the main and second harmonics, supplemented by the properties of the long-period component, gives a fairly complete picture of the entire series of monthly averages. The work examines the correspondence of the characteristics of reliable data, with this approach, to the accepted description in terms of the parameters of cycles (maximum of the cycle, duration of the cycle, and its growth branches) and constructs an "envelope" of the maxima of the cycles. The time dynamics of the instantaneous frequencies of the fundamental and second harmonics of the entire series are also presented, and significant differences in their behavior are noted in the intervals corresponding to the reconstructed and reliable parts. [ABSTRACT FROM AUTHOR]

The Sun's history is still a subject of interest to modern astrophysics. Observationally constrained rates of Coronal Mass Ejections (CMEs) of young solar analogues are still lacking, as those require dedicated monitoring. We present medium-resolution optical spectroscopic monitoring of a small sample of bright and prominent solar analogues over a period of 3 yr using the 0.5-m telescope at observatory Lustbühel Graz (OLG) of the University of Graz, Austria. The aim is the detection of flares and CMEs from those spectra. In more than 1700 h of spectroscopic monitoring, we found signatures of four flares and one filament eruption on EK Dra which has been reported in previous literature, but we complementarily extended the data to cover the latter phase. The other stars did not reveal detectable signatures of activity. For these non-detections, we derive upper limits of occurrence rates of very massive CMEs, which are detectable with our observational setup, ranging from 0.1 to 2.2 d−1, but these may be even smaller than the given rates considering observational biases. Furthermore, we investigate the detectability of flares/CMEs in OLG spectra by utilizing solar 2D Hα spectra from Mees Solar Observatory. We find that solar-sized events are not detectable within our observations. By scaling up the size of the solar event, we show that with a fractional active region area of 18 per cent in residual spectra and 24 per cent in equivalent width time series derived from the same residuals that solar events are detectable if they had hypothetically occurred on HN Peg. [ABSTRACT FROM AUTHOR]

Solar energy, as a clean and renewable energy source, holds significant promise for addressing water shortages. Utilizing solar energy for water evaporation is seen as an effective solution in this regard. While many existing interfacial photothermal water evaporation systems rely on nanoparticles or graphene as photothermal or support materials, this study introduced polydopamine (PDA) as a photothermal material due to its environmental friendliness and excellent photon absorption characteristics that closely match the solar spectrum. Polystyrene (PS) was also introduced as a support material for its porous structure and density similar to water, enabling it to float on water. The resulting PS-PDA composite porous structure solar evaporator exhibited a photothermal conversion efficiency comparable to nanoparticles (over 75%), yet with lower production costs and minimal environmental impact. This innovative approach offers a scalable solution for water-scarce regions, providing a cost-effective and efficient means to address water scarcity. The use of PDA and PS in this context highlights the potential for utilizing common materials in novel ways to meet pressing environmental challenges. [ABSTRACT FROM AUTHOR]

Computational analysis of triple absorber‐based solar cell structure is undertaken. This solar cell device configuration allows better utilization of the incident solar spectrum. Three different absorbers with a band gap in the range 1–1.5 eV are sandwiched between high‐doped p+ and n+ regions in descending order of electron affinity to form an energy‐matched multiple absorber device. A comprehensive analysis of key device parameters influencing performance, including band gap, conduction band alignment, interfacial defects, and thickness, is presented. The optimized triple absorber device shows beyond Shockley–Queisser limit (SQ limit) performance under the constraint of passivated interfaces with defect density below 1013 cm−2. Wide spectrum coverage leads to high short circuit current and an efficiency of 40.3%, which is higher than the SQ limit for single band gap solar cell. [ABSTRACT FROM AUTHOR]

Focusing on the imperative requirement for materials possessing both high solar reflectivity and low cost, by utilizing the finite difference time domain method, the relationship between the fiber diameters and the solar reflectivity of TiO2 nanofiber membranes was simulated. The results indicate that, at a TiO2 nanofiber diameter of 300 nm, the material demonstrates optimal broadband scattering capabilities, yielding an integrated scattering coefficient of 2.462 within the solar spectrum; the solar reflectivity demonstrates a direct correlation with the thickness of the fiber film, and the membrane material exhibits exceptional sunlight reflection performance while the thickness of the fiber film surpasses 150 μm. By manipulating the electrospinning process parameters and duration of spinning, TiO2 nanofiber membranes with varying fiber diameters and thicknesses were meticulously crafted. The solar reflectance test findings of the membrane material reveal that when the mean diameter of the fabricated TiO2 nanofibers is 293.2 nm and the thickness of the membrane is 155 μm, the membrane material exhibits a substantial solar reflectivity of 94.50%. [ABSTRACT FROM AUTHOR]