Search Results (646)

The tension in the relationship between water and energy seriously restricts the harmonious coexistence between man and the ecological environment. The solar-powered interface evaporation technology emerging in recent years has shown good application prospects in high-salt wastewater treatment for achieving the zero-discharge treatment of wastewater. In this review, advanced solar-driven interfacial evaporation is primarily focused on its mechanisms, photothermal materials optimization, and the structure of solar evaporators for salt removal. The high wide-spectrum solar absorption rate of photothermal materials determines the total energy that can be utilized in the evaporation system. The light-to-heat conversion capacity of photothermal materials directly affects the efficiency and performance of solar interface evaporators. We highlight the microstructures enabled by the nanophotonic designs of photothermal material-based solar absorbers, which can achieve highly efficient light harvesting across the entire solar irradiance spectral range with weighted solar absorptivity. Finally, based on current research, existing problems, and future development directions for high-salt wastewater evaporation research are proposed. The review provides insights into the effective treatment of high-salt wastewater. Full article

Background/Objectives: This study reports the synthesis of TiO₂ nanoparticles, their functionalization with folic acid (FA), and the subsequent loading with zinc phthalocyanine (ZnPc) to develop photosensitizers for photodynamic therapy (PDT) targeting glioma cells. Methods: TiO₂, TiO₂-FA, and TiO₂-FA-ZnPc nanoparticles were synthesized via a sol–gel process involving the hydrolysis and condensation of titanium (IV) isopropoxide. FA and ZnPc were incorporated in vitro during the synthesis. The resulting materials were characterized by transmission and scanning electron microscopy (TEM and SEM), X-ray diffraction (XRD), Raman and UV–Vis spectroscopy, thermogravimetric analysis (TGA), and nitrogen adsorption–desorption measurements. Reactive oxygen species (ROS) generation was evaluated in vitro using the 1,3-diphenylisobenzofuran (DPBF) probe. A 40 ppm solution of each TiO₂ system was irradiated with UV light, and the degradation of DPBF was monitored. Biological assays were conducted to assess the viability of human glioblastoma cells (LN18 and U251) incubated with the TiO₂-based materials, with and without UV exposure. Human fibroblast cells (BJ) were used to evaluate biocompatibility. Results: All TiO₂-based materials retained key characteristics, including high surface area (~600–700 m²/g), mesoporous structure (pore diameter ~4–5 nm), mixed anatase–amorphous morphology, and a bandgap of approximately 3.46 eV. The UV–Vis spectrum of TiO₂-FA-ZnPc displayed additional absorption bands in the visible region (600–700 nm), consistent with ZnPc incorporation. Upon UV irradiation, the DPBF absorbance at 410 nm decreased over time, indicating ROS generation and resulting in complete degradation within 10 min (TiO₂), 12 min (TiO₂-FA), and 14 min (TiO₂-FA-ZnPc). BJ cells exhibited good biocompatibility at all concentrations. LN18 and U251 cells showed no cytotoxicity below 100 μg/mL unless exposed to UV light. Conclusions: The synthesized TiO₂-based systems demonstrate good biocompatibility and significant phototoxicity under UV irradiation, highlighting their strong potential for application in photodynamic therapy. Full article

We investigated a metasurface broadband absorber composed entirely of iron and featuring a simple bilayer structure: a metallic iron substrate topped with an iron nanodisk-patterned layer. This absorber structure achieved over 90% absorption across the visible spectrum, with an average absorption of 97%. The designed metasurface structure had an aspect ratio of less than 1, which facilitated high-quality sample fabrication. In contrast to precious or rare metals typically utilized in visible broadband metasurface absorbers, this absorber offers a significant cost advantage. Furthermore, it exhibits polarization insensitivity and maintains a stable performance under oblique incidence over a wide angular range, making it suitable for practical applications. Additionally, the high melting point and favorable thermal conductivity of iron satisfy the requirements for solar harvesting and photothermal conversion devices. Therefore, this paper presents a highly efficient, low-cost, easy-to-fabricate, and operationally stable solution that is amenable to large-scale deployment in solar energy-harvesting devices. Full article

Polyethylene glycol (PEG) is among the most intensively researched and applied polymers, exhibiting a very wide range of industrial, pharmaceutical, and biomedical applications. The strongest and most highly diagnostic absorbance in the FTIR spectrum of PEG and of PEG-containing polyurethanes, is the ether C-O-C stretching absorbance, which consistently appears as a triple-peak absorbance in a semicrystalline state. Surprisingly, this phenomenon has very seldom been mentioned or elaborated, and no direct structural diagnostic FTIR assignment has been determined for each component of the triple-peak. The present research conclusively demonstrates that the left-side and right-side components of the triple-peak are assigned to the chain-fold regions and the extended-chain regions of the crystallized chains, respectively, while the strong-wide central component is assigned to the randomly oriented chains in the amorphous phase of the semicrystalline PEG. The present demonstration was facilitated via the synthesis of a highly oriented fibrillar polyurethane block-copolymer, exclusively containing extended-chain-crystallized PEG soft-segments, obtained through dense hard-segment crosslinking under vigorous unidirectional shear-stress continuously applied during the synthesis. The present research results enable us to directly relate the FTIR spectra of PEG and block copolymers synthesized thereof, to their crystallization mechanisms and chain conformations, thus facilitating the development of improved industrial processing methods. Full article

PSR B1259-63/LS 2883 is a well-studied gamma-ray binary hosting a pulsar in a 3.4-year eccentric orbit around a Be-type star. Its non-thermal emission spans from radio to TeV energies, exhibiting a significant increase near the periastron passage. This paper is dedicated to the analysis of INTEGRAL observations of the system following its last periastron passage in June 2024. We aim to study the spectral evolution of this gamma-ray binary in the soft (0.3–10 keV) and hard (30–300 keV) X-ray energy bands. We performed a joint analysis of the data taken by INTEGRAL/ISGRI in July–August 2024 and quasi-simultaneous Swift/XRT observations. The spectrum of the system in the 0.3–300 keV band is well described by an absorbed power law with a photon index of $\Gamma =1.42\pm 0.03$. We place constraints on potential spectral curvature, limiting the break energy $E_{\mathrm{b}}>30$ keV for $\Delta \Gamma >0.3$ and cutoff energy $E_{\mathrm{cutoff}}>150$ keV at a 95% confidence level. For one-zone leptonic emission models, these values correspond to electron distribution spectral parameters of $E_{\mathrm{b},\mathrm{e}}>0.8$ TeV and $E_{\mathrm{cutoff},\mathrm{e}}>1.7$ TeV, consistent with previous constraints derived by H.E.S.S. Full article

The aim of this study was to determine the connection between oscillations in operating pressure values and the appearance of various irregularities on machined surfaces. Such oscillations are a consequence of the high water pressure generated during abrasive water jet machining. Oscillations in the operating pressure values are periodic, namely due to the cyclic operation of the intensifier and the physical characteristics of water. One of the most common means of reducing this phenomenon is installing an attenuator in the hydraulic system or a phased intensifier system. The main hypothesis of this study was that the topography of a machined surface is directly influenced by the inability of the pressure accumulator to fully absorb water pressure oscillations. In this study, we monitored changes in hydraulic oil pressure values at the intensifier entrance and their connection with irregularities on the machined surface—such as waviness—when cutting aluminum AlMg3 of different thicknesses. Experimental research was conducted in order to establish this connection. Aluminum AlMg3 of different thicknesses—from 6 mm to 12 mm—was cut with different traverse speeds while hydraulic oil pressure values were monitored. The pressure signals thus obtained were analyzed by applying the fast Fourier transform (FFT) algorithm. We identified a single-sided pressure signal amplitude spectrum. The frequency axis can be transformed by multiplying inverse frequency data with traverse speed; in this way, a single-sided amplitude spectrum can be obtained, examined against the period in which striations are expected to appear (in millimeters). In the lower zone of the analyzed samples, striations are observed at intervals determined by the dominant hydraulic oil pressure harmonics, which are transferred to the operating pressure. In other words, we demonstrate how the machined surface topography is directly induced by water jet pressure frequency characteristics. Full article

Melanin-like nanoparticles (NPs) exhibit a remarkable ability to absorb light across a wide range of wavelengths, from the ultraviolet (UV) to the near-infrared (NIR) spectrum. This characteristic enables them to serve as effective photothermal agents (PTAs). Upon irradiation, especially within the NIR window, a region where biological tissues are highly transparent, these NPs efficiently convert light energy into heat. This phenomenon, known as the photothermal effect, leads to localized temperature increases. The resulting heat can be strategically employed to induce selective cell death in photothermal therapy (PTT) or to enhance the release of therapeutic agents directly from the NPs. The inherent versatility of melanin-like NPs, stemming from their synthesis methods and the presence of various functional groups, allows for straightforward loading with drugs or other bioactive molecules. Consequently, they are attractive tools for photothermally activated release. This review paper thoroughly examines and critically discusses the latest applications of melanin-like NPs in photothermally controlled release. We dedicate a specific section to general mechanisms and approaches, and this paper concludes with an analysis of critical challenges and prospective future developments. Full article

The shortage of freshwater resources has become the core bottleneck of global sustainable development. Traditional freshwater harvesting technologies are restricted by geographical conditions and environmental limitations, making them increasingly difficult to satisfy the growing water demand. In this study, based on the synergistic coupling mechanism of photothermal conversion and radiative cooling, a solar auto-tracking assisted selective solar absorber and radiative cooling all-weather freshwater harvesting device was innovatively developed. The prepared selective solar absorber achieved a high absorptivity of 0.91 in the solar spectrum (0.3–2.5 μm) and maintained a low emissivity of 0.12 in the mid-infrared range (2.5–20 μm), significantly enhancing the photothermal conversion efficiency. The radiative cooling film demonstrated an average cooling effect of 7.62 °C during typical daytime hours (12:00–13:00) and 7.03 °C at night (22:00–23:00), providing a stable low-temperature environment for water vapor condensation. The experimental results showed that the experimental group equipped with the solar auto-tracking system collected 0.79 kg m⁻² of freshwater in 24 h, representing a 23.4% increase compared to the control group without the solar auto-tracking system. By combining theoretical analysis with experimental validation, this study presents technical and economic advantages for emergency water and island freshwater supply, offering an innovative solution to mitigate the global freshwater crisis. Full article

An ancient repertoire of ultraviolet (UV)-absorbing pigments which survive today in the phylogenetically oldest extant photosynthetic organisms, the cyanobacteria, point to a direction in evolutionary adaptation of the pigments and their associated biota; from largely UV-C absorbing pigments in the Archean to pigments covering ever more of the longer wavelength UV and visible regions in the Phanerozoic. Since photoprotection is not dependent on absorption, such a scenario could imply selection of photon dissipation rather than photoprotection over the evolutionary history of life, consistent with the thermodynamic dissipation theory of the origin and evolution of life which suggests that the most important hallmark of biological evolution has been the covering of Earth’s surface with organic pigment molecules and water to absorb and dissipate ever more completely the prevailing surface solar spectrum. In this article we compare a set of photophysical, photochemical, biosynthetic, and other inherent properties of the two dominant classes of cyanobacterial UV-absorbing pigments, the mycosporine-like amino acids (MAAs) and scytonemins. We show that the many anomalies and paradoxes related to these biological pigments, for example, their exudation into the environment, spectral coverage of the entire high-energy part of surface solar spectrum, their little or null photoprotective effect, their origination at UV-C wavelengths and then spreading to cover the prevailing Earth surface solar spectrum, can be better understood once photodissipation, and not photosynthesis or photoprotection, is considered as being the important variable optimized by nature. Full article

A novel, environmentally friendly cloud point extraction (CPE) method based on 4-nitrocatechol (H₂L) was developed in this study to spectrophotometrically determine trace vanadium. This method utilizes a mixed micelle-mediated system comprising a cationic surfactant (cetylpyridinium chloride, CPC) and a nonionic surfactant (Triton X-114). In contrast to conventional CPE, the present approach does not employ centrifugation to separate the two phases. The distinguishing characteristic of the extracted species, (CP⁺)[V^VOL₂], is its ability to absorb light across the entire visible spectrum. The measurement at 670 nm, where the complex displays a local maximum, is advantageous for two primary reasons. Firstly, the blank exhibits virtually no absorption, a property that engenders stable and reproducible results. Secondly, selectivity is high because almost all other metal complexes have absorption bands at shorter wavelengths. The proposed method has the following characteristics: a linear range of 2–305 ng mL⁻¹, a limit of detection of 0.6 ng mL⁻¹, a molar absorptivity coefficient of 1.22 × 10⁵ M⁻¹ cm⁻¹, a Sandell sensitivity of 0.42 ng cm⁻², and a blue applicability grade index (BAGI) of 67.5. Its efficacy was demonstrated in the analysis of mineral water, a spent vanadium-containing catalyst, and a dietary supplement. Full article

Plastic waste and pollution is growing rapidly worldwide and most plastics end up in landfill or are incinerated because high-quality recycling is not possible. Plastic-type identification with a low-cost, handheld spectral approach could help in parts of the world where high-end spectral imaging systems on conveyor belts cannot be implemented. Here, we investigate how two fundamentally different handheld infrared spectral devices can identify plastic types by benchmarking the same analysis against a high-resolution bench-top spectral approach. We used the handheld Plastic Scanner, which measures a discrete infrared spectrum using LED illumination at different wavelengths, and the SpectraPod, which has an integrated photonics chip which has varying responsivity in different channels in the near-infrared. We employ machine learning using SVM, XGBoost, Random Forest and Gaussian Naïve Bayes models on a full dataset of plastic samples of PET, HDPE, PVC, LDPE, PP and PS, with samples of varying shape, color and opacity, as measured with three different experimental approaches. The high-resolution spectral approach can obtain an accuracy (mean ± standard deviation) of (0.97 ± 0.01), whereas we obtain (0.93 ± 0.01) for the SpectraPod and (0.70 ± 0.03) for the Plastic Scanner. Differences of reflectance at subsequent wavelengths prove to be the most important features in the plastic-type classification model when using high-resolution spectroscopy, which is not possible with the other two devices. Lower accuracy for the handheld devices is caused by their limitations, as the spectral range of both devices is limited—up to 1600 nm for the SpectraPod, while the Plastic Scanner has limited sensitivity to reflectance at wavelengths of 1100 and 1350 nm, where certain plastic types show characteristic absorbance bands. We suggest that combining selective sensitivity channels (as in the SpectraPod) and illuminating the sample with varying LEDs (as with the Plastic Scanner) could increase the accuracy in plastic-type identification with a handheld device. Full article

Using optical spectroscopy methods including absorption in the UV-VIS, FTIR, Raman, and fluorescence, the spectra of 25 different Baltic amber samples were measured, and the ability of each method to distinguish between thermally modified and naturally aged material was analyzed. The natural ambers studied are characterized by a wide range of spectral properties: the position of the transmission edge in the UV-VIS spectra, the absorbance ratios of the C-H and C=O groups in the IR spectra, a difference of approximately 20% in the fluorescence intensity level, and differences in the band ratios in the C=C and C-H bonds in the Raman spectrum. Spectral studies were carried out on samples of natural and thermally modified amber at temperatures of 100, 150, and 200 °C for 2–8 h. Drastic changes occur at temperatures above 150 °C: the color changes to dark brown, the UV-VIS transmission edge shifts, the absorbance of the C=O group increases, the absorbance intensity of the C=C bond decreases, and fluorescence disappears. In some special cases, fluorescence methods allow for the unambiguous distinction of amber from different geographical regions (e.g., Baltic and Dominican). Spectroscopic methods can distinguish natural amber from thermally modified amber only for large changes in the spectrum at temperatures of 150–200; for smaller changes, the differences between individual samples of natural amber may be greater than in the case of thermal modification. Full article

Photothermal conversion is a pivotal energy transformation mechanism in solar energy systems. Achieving high-efficiency and broadband photothermal conversion within the solar radiation spectrum holds strategic significance in driving the innovative development of renewable energy technologies. In this study, a transmission matrix method was employed to design an interference-type solar selective absorber based on multilayer Cr-SiO₂ planar films, successfully achieving an average absorption of 94% throughout the entire solar spectral range. Further analysis indicates that this newly designed absorber shows excellent absorption performance even at a relatively large incident angle (up to 60°). Additionally, the newly designed absorber demonstrates lower polarization sensitivity, enabling efficient operation under complicated incident conditions. With its simple fabrication process and ease of preparation, the proposed absorber holds substantial potential for applications in photothermal conversion fields such as solar thermal collectors. Full article

To extend the spectral utilisation of In₂S₃, an In₂S₃/C₃N₄ nanocomposite was prepared. The effects of different sulphur sources, electrodes, and bias voltages on the optoelectronic performance were examined. Photoelectric properties in response to light sources with wavelengths of 405, 532, 650, 780, 808, 980, and 1064 nm were investigated using Au electrodes and the carbon electrodes with 5B pencil drawings. This study shows that the aggregation states of the In₂S₃/C₃N₄ nanocomposite possess photocurrent switching responses in the broadband region of the light spectrum. Combining two types of partially visible light-absorbing material extends utilisation to the near-infrared region. Impurities or defects embody an electron-donating effect. Since the energy levels of defects or impurities with an electron-donating effect are close to the conduction band, low-energy lights (especially NIR) can be utilised. The non-equilibrium carrier concentration (photogenerated electrons) of the nanocomposites increases significantly under NIR photoexcitation conditions. Thus, photoconductive behaviour is manifested. A good photoelectric signal was still measured when zero bias was applied. This demonstrates self-powered photoelectric response characteristics. Different sulphur sources significantly affect the photoelectric performance, suggesting that they create different defects that affect charge transport and base current noise. It is believed that interfacial interactions in the In₂S₃/C₃N₄ nanocomposite create a built-in electric field that enhances the separation and transfer of electrons and holes produced by light stimulation. The presence of the built-in electric field also leads to energy band bending, which facilitates the utilisation of the light with longer wavelengths. This study provides a reference for multidisciplinary applications. Full article

Transition metal dichalcogenide (TMD) materials have demonstrated promising potential for applications in photodetection due to their tunable bandgaps, high carrier mobility, and strong light absorption capabilities. However, limited by their intrinsic bandgaps, TMDs are unable to efficiently absorb photons with energies below the bandgap, resulting in a significant attenuation of photoresponse in spectral regions beyond the bandgap. This inherently restricts their broadband photodetection performance. By introducing metasurface structures consisting of subwavelength optical elements, localized plasmon resonance effects can be exploited to overcome this absorption limitation, significantly enhancing the light absorption of TMD films. Additionally, the heterogeneous integration process between the metasurface and two-dimensional materials offers low-temperature compatibility advantages, effectively avoiding the limitations imposed by high-temperature doping processes in traditional semiconductor devices. Here, we systematically investigate metasurface-enhanced two-dimensional MoSe₂ photodetectors, demonstrating broadband responsivity extension into the mid-infrared spectrum via precise control of metasurface structural dimensions. The optimized device possesses a wide spectrum response ranging from 808 nm to 10 μm, and the responsivity (R) and specific detection rate (D*) under 4 μm illumination achieve 7.1 mA/W and 1.12 × 10⁸ Jones, respectively. Distinct metasurface configurations exhibit varying impacts on optical absorption characteristics and detection spectral ranges, providing experimental foundations for optimizing high-performance photodetectors. This work establishes a practical pathway for developing broadband optoelectronic devices through nanophotonic structure engineering. Full article