Light-absorbing Surface Research Articles

A system for efficient and sustainable cogeneration of water and electricity: Temperature difference induced by photothermal conversion and evaporative cooling

Solar energy, with its sustainable properties, has garnered considerable attention for its potential to produce green electricity and clean water. This paper proposes a multistage energy transfer co-generation system (MWCNTs-covered thermoelectric module with aerogel and cooler, AC-CTEM) combining power generation and evaporative cooling. On the light-absorbing surface, the hot side of a thermoelectric module is covered with a hydrophobic coating made of PDMS and MWCNT. The cold side transfers heat to the evaporation zone using a heat sink. Aerogel evaporators are cross-linked with chitosan and polyurethane, which reduces the enthalpy of evaporation and facilitates efficient interfacial evaporation to remove heat and return it to refrigeration. Additionally, with the addition of Fresnel lenses and wind energy to the enhancement device, the system achieved an evaporation rate of 3.445 kg m−2 h−1 and an open-circuit voltage of 201.12 mV under 1 kW m−2 solar irradiation. The AC-CTEM system also demonstrated long-term stability and effectiveness in treating various types of non-potable water. Furthermore, we demonstrated the practical utility of the system by successfully cultivating grass seeds and powering electronic equipment. The AC-CTEM system exemplifies a practical energy-saving approach for the development of highly efficient co-generation systems.

Photoreduction of carbon dioxide into methane and ethylene using TiO2 inverse opal-derived PCN-222(M)

Solar-driven photocatalytic CO2 reduction has significant potential to address the energy crisis and mitigate greenhouse gas emissions by producing valuable organic compounds. Narrow bandgap materials enhance photon absorption within the visible light spectrum, thereby improving exciton generation. Both the inverse opal (IOT) and the porphyrin-based MOF (PCN-222) exhibit biomimetic design concepts. The IOT has a highly ordered porous structure that increases the light-absorbing surface area, facilitating efficient light harvesting. Conversely, the PCN-222 structure, which is modelled on biological porphyrin molecules, has a highly ordered pore structure and abundant active centers. Under hydrothermal conditions, PCN-222 self-assembles on the IOT surface to form a P(Cu, Fe, Zn)/IOT heterostructure. The tight interface of this heterostructure promotes rapid electron-hole separation and transport. In addition, the slow-light effect is exploited to increase the light absorption efficiency, thus improving the overall photocatalytic reaction efficiency and stability. In this study, the morphology, structure and photoelectric properties of P(Cu, Fe, Zn)/IOT heterostructures are investigated, revealing enhanced photocatalytic efficiency. The P(Fe)/IOT composite demonstrated outstanding CO2 conversion rates under simulated sunlight, yielding carbon monoxide (62 %), methane (0.11 %), and ethylene (0.09 %). The Z-scheme charge transfer mechanism significantly enhances photocatalytic performance by improving the efficiency of carrier separation and transfer, thereby increasing the overall photocatalytic reaction efficiency. This advance offers significant benefits for environmental and renewable energy remediation. The study provides key insights and recommendations for enhancing the efficiency of Z-scheme photocatalytic systems in future research and development.

All-Optical Rapid Formation, Transport, and Sustenance of a Sessile Droplet in a Two-Dimensional Slit with Few-Micrometer Separation.

We present a sessile droplet manipulation platform that enables the formation and transport of a droplet on a light-absorbing surface via local laser-beam irradiation. The mechanism relies on solutocapillary Marangoni flow arising from a concentration gradient in a binary mixture liquid. Because the mixture is strongly confined in a two-dimensional slit with a spacing of a few micrometers, the wetting film is stably sustained, enabling the rapid formation, deformation, and transport of a sessile droplet. In addition, to sustain the droplet in the absence of laser irradiation, we developed a method to bridge the droplet between the top and bottom walls of the slit. The bridge is stably sustained because of the hydrophilicity of the slit wall. Splitting and merging of the droplet bridges are also demonstrated.

Plants exposed to titanium dioxide nanoparticles acquired contrasting photosynthetic and morphological strategies depending on the growing light intensity: a case study in radish

Due to the photocatalytic property of titanium dioxide (TiO2), its application may be dependent on the growing light environment. In this study, radish plants were cultivated under four light intensities (75, 150, 300, and 600 μmol m−2 s−1 photosynthetic photon flux density, PPFD), and were weekly sprayed (three times in total) with TiO2 nanoparticles at different concentrations (0, 50, and 100 μmol L−1). Based on the obtained results, plants used two contrasting strategies depending on the growing PPFD. In the first strategy, as a result of exposure to high PPFD, plants limited their leaf area and send the biomass towards the underground parts to limit light-absorbing surface area, which was confirmed by thicker leaves (lower specific leaf area). TiO2 further improved the allocation of biomass to the underground parts when plants were exposed to higher PPFDs. In the second strategy, plants dissipated the absorbed light energy into the heat (NPQ) to protect the photosynthetic apparatus from high energy input due to carbohydrate and carotenoid accumulation as a result of exposure to higher PPFDs or TiO2 concentrations. TiO2 nanoparticle application up-regulated photosynthetic functionality under low, while down-regulated it under high PPFD. The best light use efficiency was noted at 300 m−2 s−1 PPFD, while TiO2 nanoparticle spray stimulated light use efficiency at 75 m−2 s−1 PPFD. In conclusion, TiO2 nanoparticle spray promotes plant growth and productivity, and this response is magnified as cultivation light intensity becomes limited.

Engineering salt-rejecting solar evaporator from naturally hierarchical tree root for sufficient clean water production

Solar desalination has been recognized as one of the most promising technologies for solving current freshwater scarcity. However, enhancement of the photothermal conversion efficiency and prohibiting salt crystallization on the top light-absorbing surface are the two major critical challenges for developing highly-efficient and stable solar evaporators. Here, we have discovered that tree roots, often as processing waste when utilizing woods, can serve as a high-efficient solar evaporation device for continuous desalination. The naturally occurring hierarchical structure of tree roots possesses multilevel longitudinal channels from micrometer to millimeter-scale and interconnected porous microstructures, which allows excellent water transport and multidirectional salt exchange, exhibiting a superior anti-salt-accumulation capability even in 21% brine. Together with a mountain-shaped hydrophobic absorber surface obtained from the in situ synthesized Fe3O4 nanoparticles, the designed tree root-based solar evaporator demonstrates an evaporation rate of 1.64 kg m−2 h−1 and ultra-high conversion efficiency of 96% at 1 solar irradiation, rendering it as one of the best performing wood-based solar evaporators. Furthermore, such a high-efficacy, techno-economic and long-term stable seawater desalination platform provided by the architectures of multi-level channel-array in tree root will inspire material scientists and engineers to tailor structurally similar materials from building blocks of broader selections.

Photoreceptor Discs: Built Like Ectosomes.

The light-sensitive outer segment organelle of the vertebrate photoreceptor cell is a modified cilium filled with hundreds of flattened 'disc' membranes that provide vast light-absorbing surfaces. The outer segment is constantly renewed with new discs added at its base every day. This continuous process is essential for photoreceptor viability. In this review, we describe recent breakthroughs in the understanding of disc morphogenesis, with a focus on the molecular mechanisms responsible for initiating disc formation from the ciliary membrane. We highlight the discoveries that this mechanism evolved from an innate ciliary process of releasing small extracellular vesicles, or ectosomes, and that both disc formation and ectosome release rely on the actin cytoskeleton.

Ag/polypyrrole co-modified poly(ionic liquid)s hydrogels as efficient solar generators for desalination

Solar steam generation is one of the most promising technologies to utilize solar energy, which is applied to extract fresh water from seawater or contaminated water. However, solar vapour generation is usually restricted to the underutilization of solar energy or depends on complicated light-harvesting adjuncts. Here, a novel hierarchically double-layered evaporation device was demonstrated based on poly(ionic liquid)s hydrogel with the upper surface co-modified by polypyrrole (PPy) and silver particles (named as Ag/PPy-PMBA-BrILs). The evaporation system exhibits a cooperative interaction of the double-layer with efficient light-absorbing and water transportation, leading to a high evaporation rate of 1.37 kg m−2 h−1 with a photothermal conversion efficiency of 88.7% under 1 sun illumination. The high evaporation rate is mainly due to the synergistic light absorption of polypyrrole and silver particles as well as the excellent water transfer capability of poly(ionic liquid)s hydrogel. Moreover, the hydrogel-based evaporation device also exhibits excellent salt-resistant performance for solar desilination in artificial sea water. The high-efficiency poly(ionic liquid)s hydrogel based solar steam generator with co-modified light-absorbing surface may open new opportunities for the future design and fabrication of high-performanced solar steam generator for practical applications.

Detachment of particles from surfaces by thermocapillary flows induced by a moving laser beam

The thermocapillary flows produced by heating with the moving laser beam in a thin liquid layer on a light-absorbing solid surface have recently been recognized to be effective for the removal of particulate impurities from the surface. We performed the comparative analysis of adhesion and thermocapillary removal forces acting on particles attached to the solid surface. A simplified hydrodynamic model was used to evaluate the velocity field of the thermocapillary flow in the liquid layer covering particles. Hydrodynamic forces such as the drag force, the lifting force induced by the shear flow far away from the receding contact line and the maximal lifting force caused by the transversal velocity in the layer near the receding contact line were identified as the cleaning forces, which are determined by the temperature gradient along the surface. It was found out that the lifting force is not enough to overcome the adhesion force and detach particles from the solid surface. The drag and the maximal lifting forces were shown to be responsible for removal of particles by using the proposed method. A reasonable qualitative agreement between experimental results and the quantitative force analysis was observed.

CFD Modeling of Operating Processes of a Solar Air Heater in ANSYS Fluent

Rapid development of the technologies of use of renewable energy sources in the recent decade has opened up prospects for satisfying our society′s ever growing needs for fuel and power resources. In the present work, the author has shown results of investigation into the thermal and aerodynamic characteristics of a solar air heater. A computer model whose adequacy has been confirmed using experimental data was developed in the ANSYS Fluent software product. It has been determined that for the end of calendar autumn, the operating efficiency of the solar air heater is the highest at the angle of inclination of the absorption surface to the earth α = 60°. The dependence of the value of heating of air in the solar heater during daylight hours has been determined in the physical and computer experiment; it has been established that for the city of Samara (GMT + 4) the maximum air heating is observed in the interval between 13.00 and 14.00. The influence of transverse ribs on the heat exchange between the light-absorbing surface and the air has been shown. A curvilinear shape of the temperature contour is formed in the immediate vicinity of the ribs due to the formation of vortices and reverse-current zones.

Watching Three-Dimensional Movements of Single Membrane Proteins in Lipid Bilayers.

It is challenging to assess protein-membrane interactions because of the lack of appropriate tools to detect position changes of single proteins in the ∼4 nm range of biological membranes. We developed an assay recently, termed surface-induced fluorescence attenuation (SIFA). It is able to track both vertical and lateral dynamic motion of singly labeled membrane proteins in supported lipid bilayers. Similar to the FRET (fluorescence resonance energy transfer) principle, SIFA takes advantage of the energy transfer from a fluorophore to a light-absorbing surface to determine the distance at 2-8 nm away from the surface. By labeling a protein with a proper fluorophore and using graphene oxide as a two-dimensional quencher, we showed that SIFA is capable of monitoring three-dimensional movements of the fluorophore-labeled protein not only inside but also above the lipid bilayer atop the graphene oxide. Our data show that SIFA is a well-suited method to study the interplay between proteins and membranes.

ANSYS Fluent CFD Modeling of Solar Air-Heater Thermoaerodynamics

Numerical modeling of thermal and aerodynamic processes taking place in a solar air heater with light-absorbing L-shaped fins is performed. The study is carried out by means of an ANSYS Fluent Solver with an integrated solar calculator for the city of Samara, Russia. The influence of the design (the step between the fins) and technological variables (the Reynolds number) on heat-exchange processes and flow aerodynamics was established during the CFD analysis. Pictorial contours are determined for the velocity distribution, pressure, and other characteristics of the airflow in the solar air-heater box. Thermoaerodynamic characteristics and effective values of technological parameters for the effective use of a solar air heater are studied. The maximum thermoaerodynamic characteristic for the solar air heater with a finned lightabsorbing surface is 1.91 for Re = 1500, and the minimum test fin pitch is 30 mm.

Infrared Spectroscopy of Ultrablack Films Based on Electrodeposited Ni–P Alloys

Introduction. Black coatings with low refl ection coeffi cients for visible and near-IR electromagnetic radiation are widely used to produce optical devices for reducing the scattered light background and in laser-radiation power meters as operating light-absorbing surfaces [1]. It was shown [2] that surfaces formed by chemical etching of chemically deposited Ni–P coatings with P contents of 3–10 at% were some of the blackest. It was established that the low refl ection coeffi cients of such coatings were due to a combination of the surface morphology produced by etching and the formation of a thin light-absorbing surface layer [3, 4]. The black color of the layer was explained by higher nickel oxides and hydroxides in it. However, the role of P in the formation of the black coating was not found. The P must be present in the coating because Ni coatings without P do not form black surfaces during etching in various acids. IR spectroscopy can be used to obtain information about the presence of oxidized P species. The goal of the present work was to study the chemistry of ultrablack fi lms prepared by chemical etching of electrodeposited Ni–P coatings in an oxidizing medium. Experimental. Ni–P coatings of thickness 30 �� m were prepared by electrochemical deposition by the published

Optical Properties of Nanocrystal Interfaces in Compressed MgO Nanopowders

The optical properties and charge trapping phenomena observed on oxide nanocrystal ensembles can be strongly influenced by the presence of nanocrystal interfaces. MgO powders represent a convenient system to study these effects due to the well-defined shape and controllable size distributions of MgO nanocrystals. The spectroscopic properties of nanocrystal interfaces are investigated by monitoring the dependence of absorption characteristics on the concentration of the interfaces in the nanopowders. The presence of interfaces is found to affect the absorption spectra of nanopowders more significantly than changing the size of the constituent nanocrystals and, thus, leading to the variation of the relative abundance of light-absorbing surface structures. We find a strong absorption band in the 4.0−5.5 eV energy range, which was previously attributed to surface features of individual nanocrystals, such as corners and edges. These findings are supported by complementary first-principles calculations. The possibility to directly address such interfaces by tuning the energy of excitation may provide new means for functionalization and chemical activation of nanostructures and can help improve performance and reliability for many nanopowder applications.

Temperature field and heat flows through transparent covers of flat-plate solar collector housing

Analytical expressions to calculate the temperature field and heat flows through transparent covers of flat-plate solar collector housings are proposed, taking into account the exponential distribution of the power of the internal source through its thickness, which is formed as a result of partial absorption and conversion to heat of the transmitted total (direct and diffuse) solar radiation incident on its front surface and the diffuse solar radiation incident on its back surface and reflected by the light-absorbing surface of the collector heat-exchange panel.

Heat power capacity of the internal source in light-transparent coatings of planar solar collectors

The results are presented of numerical determination of the heat power capacity of the internal source in light-transparent coatings of planar solar collectors; the power results from partial absorption of the transit total (direct and diffuse) solar radiation and its transfer into heat, as well as from the diffuse solar radiation reflected from the light-absorbing surface of the heat exchange collector panel, are presented.

Fluorescence Lifetime Correlation Spectroscopy Combined with Lifetime Tuning: New Perspectives in Supported Phospholipid Bilayer Research

A new concept based on fluorescence lifetime correlation spectroscopy (FLCS) is presented allowing the simultaneous determination of diffusion coefficients of identical molecules located in different environments. The difference in fluorescence lifetimes, which is the main prerequisite for FLCS, is reached by locating one population of the dye close to a light-absorbing surface. Since such surfaces quench fluorescence, the fluorescence lifetime of chromophores located close to these surfaces can be tuned in a specific manner. This approach has been demonstrated for a BODIPY-tail-labeled lipid in supported phospholipid bilayers (SPBs) as well as in phospholipid multilayers adsorbed onto solid supports. In particular, the effect of the solid support type on the fluorescence lifetime as well as its dependence on the BODIPY-support distance has been characterized and verified by theoretical considerations based on precise determination of refractive indices of the used supports. While the fluorescence lifetime of BODIPY dye is 5.6 ns in small unilamellar vesicles (SUVs) composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dioleoyl-sn-glycero-3-[phospho-L-serine] (DOPS), the lifetime is 1.8 ns in DOPC/DOPS SPBs adsorbed onto ITO-covered glass or 3.0 ns in a DOPC/DOPS monolayer adsorbed onto seven 1,2-dipalmitoyl-sn-glycero-3-phosphate (DPPA) layers on oxidized silicon. Using these particular systems, we demonstrated that FLCS enables one to characterize simultaneously two-dimensional lipid diffusion in the planar lipid layers and three-dimensional vesicle diffusion in bulk above the lipid layers using single dye labeling. The autocorrelation functions obtained by this new approach do agree with those obtained by standard FCS on isolated SPBs or vesicles. Possible applications of this virtual two-channel measurement using single dye labeling as well as one detection channel are discussed.

Infrared and Raman spectroscopy of particle-beam induced damage of silicon carbide

The damaging of 6H-SiC by ion implantation (Ar +, 320 keV) leads to the formation of a light-absorbing surface layer with a thickness of about 0.4 μm and a dielectric function which indicates a disordering of the crystal structure. Raman spectra show the existence of amorphous carbon, silicon and silicon carbide. Ion bombardment with 1.4 MeV He + ions generates a 3 μm thick surface layer with small lattice distortions and light-absorbing centers and a 0.4 μm thick interface layer with a larger refractive index.

A physiological analysis of the responses of the lettuce variety ‘Rapide’ and its hybrid with ‘Hamadan’ to day-length and light intensity

The lettuce variety viz. Rapide and the hybrid Rapide x Hamadan were grown in climate rooms at a temperature of 20°C and two day-lengths (16 and 8 hours) each combined with three light intensity levels and at a day-length of 12 hours with one light intensity level. The more rapid growth of Rapide x Hamadan as compared with Rapide was caused by the formation of a larger light-absorbing surface per gramme of leaf fresh weight. No difference occurred with respect to the photosynthetic system. Both varieties were using the light energy more efficiently when grown under long-day conditions than when grown in short days.

Metabolic changes associated with pigmentary effector activity and pituitary removal in Xenopus lævis —I. Respiratory exchange

There are various indications of connection between the pituitary gland and basal metabolism; between the pituitary gland and ovarian activity; and between ovarian activity and calcium metabolism. Progress in the study of the relationship of the pituitary to metabolism had been held back by the technical difficulties of mammalian hypophysectomy. By a method described by Hogben, the removal of the pituitary gland as a whole or of the anterior lobe alone can be performed without great difficulty and with great rapidity in adult Amphibia. The animals survive the operation indefinitely. The same author has shown that the posterior lobe of the pituitary gland plays a predominent rôle in controlling colour change, and latterly, in collaboration with Slome, has given strong indications that the anaterior lobe of the gland also plays a part in determining the pigmentary effector activity of the South African clawed toad, Xenopus lævis (Daudin). These circumstances have suggested the advisability of parallel investigation of the effects of the total or partial removal of the pituitary gland and the influence of normal agencies affecting colour change (and thereby pituitary activity) upon the metabolism of this species. The present communication is connected with two issues:— 1. Total respiratory exchange in air. 2. Dermal oxygen consumption in water. The conditions affecting colour response, and the time relations of colour response, etc., in Xenopus lævis , have been recorded thoroughly (Slome and Hogben). These authors have shown that photic stimuli are the predominant natural agencies, the condition for pallor being that the field of vision is occupied by a light-scattering surface, and the condition for darkening that the field of vision is occupied by a light-absorbing surface. Eyeless animals are intermediate in hue but the condition of eyeless animals or animals kept in the dark has been shown to be physiologically different from intermediat animals in a stage of transition from the white background to the black blackground response and vice versa . This conclusion, based on an analysis of the time curve, receives some confirmation from the data hereafter recorded.