Absence Of Illumination Research Articles

Dual-Functional Cs3Bi2Br9 for stable all-solid-state photo-rechargeable batteries

In light of the immense potential solid-state photo-rechargeable batteries hold in the efficient utilization of renewable solar energy, there is a rapidly growing demand for materials that possess both energy harvesting and storage capabilities. In this study, a solid-state photo-rechargeable battery has been designed based on the FTO(Fluorine-doped SnO2 transparent conductive glass)/TiO2/Cs3Bi2Br9/Pt/FTO system, which achieves dual functions of photoelectric conversion and energy storage. The inorganic bismuth-based material employed in these batteries exhibits commendable cyclic stability. Under photo-rechargeable conditions, a single cell can maintain an open-circuit voltage as high as 0.45 V in the absence of illumination. By connecting multiple cells in series, we succeed in powering an LED (Light-emitting diode) continuously for 1 min without light exposure. The findings of this research open new avenues for the design and development of novel materials that could enable highly efficient solid-state photo-rechargeable batteries.

Sedimentation and photophoretic levitation of aerosol clusters in the free molecular regime

Sedimentation of fractal aerosol clusters in rarefied gas medium in the dark and under external illumination similar to sunlight is studied in a numerical experiment taking into account orientation effects, depending on fractal dimension varying within a broad range. The calculation of forces and their moments, including friction forces and photophoretic forces, was carried out on the basis of approximation of free molecular gas kinetic regime and previously developed Monte-Carlo algorithms. Calculation involved 10000 clusters, each of them containing 160 primary spherical particles and efficiently absorbing sunlight and IR radiation, similarly to the particles of soot aggregates.The velocity of multi-particle cluster settling in the absence of illumination, when particle temperatures are equal to the temperature of the gaseous environment, is a distinct function of fractal dimension and is rather close to the velocity of settling of single spherical particles. The settling velocity approximation depending on fractal dimension has been obtained.Illumination brings dramatic changes into sedimentation pattern. The range of cluster sedimentation rate variations broadens substantially, which is a manifestation of gravito-photophoretic effect, so that some clusters even start to levitate. The proportion of levitating clusters is essentially dependent on fractal dimension. For soot-like clusters under irradiation similar to sunlight and pressure equal to atmospheric at the altitude of 30 km, the proportion of levitating aggregates is approximately 7%, which is in good agreement with the experimental data. In the dark and under irradiation, the aggregates rotate, and their trajectories are shaped as spirals.In the context of photophoretic phenomena, a result of principle has been obtained: under irradiation with sunlight, gravito-photophoretic levitation of aerosol soot-like aggregates composed of identical primary particles is possible at a pressure corresponding to the stratospheric altitudes. This result points to the possibility of substantial influence of gravito-photophoretic effect on transport and localization of soot aerosol in the Earth’s stratosphere and mesosphere.

Characterization and Calibration of a Photodiode Based Pyranometer for Solar Energy Applications

<p>In the domain of solar science, a pyranometer assumes a pivotal position, functioning as an indispensable tool for appraising solar irradiance across the abbreviated wavelengths of the solar spectrum, spanning from 300 to 3000 nanometers. Conventional pyranometers typically employ intricate and labour intensive thermopiles. These devices rely on arrays of thermocouples interconnected either serially or in parallel and necessitate rare earth minerals for efficient operation. In this investigation, we advocate for an innovative methodology employing photodetectors, specifically photodiodes and phototransistors, to surmount the limitations linked with traditional pyranometers. Photodiodes, commonly utilized for this purpose, proffer numerous benefits, including accelerated response times, customizable spectral range selection, and cost-effectiveness. Nonetheless, they cannot entirely supplant thermopiles owing to impediments such as the generation of dark current in the absence of illumination, temperature-dependent functionalities, and saturation at elevated irradiance levels. To counteract these constraints, we have devised a pioneering design of a photodiode-based pyranometer that incorporates a data acquisition system and correction mechanism. This innovative approach furnishes a feasible resolution for autonomous solar radiation measurement, furnishing enhanced precision and dependability.</p>

Green synthesis of Co3O4 nanoparticles using spent coffee: Application in catalytic and photocatalytic dye degradation

Clean water is vital for societal progress, however, the pollution caused by dyes presents a significant global challenge. Dye-contaminated industrial effluent overwhelms wastewater treatment facilities, causing harm to water bodies and ecosystems. This study demonstrates the synthesis of Co3O4 nanoparticles using spent coffee extract as a bioreducing agent and its application in dye degradation. The structural and optical properties of nanostructures were confirmed using X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and UV–vis spectroscopy. The Co3O4-activated peroxymonosulfate (PMS) system exhibited exceptional catalytic efficiency by attaining a degradation rate of 89.27 % for Tartrazine dye within a 30-minute timeframe, even in the absence of illumination. When exposed to simulated visible light, the degradation kinetic rate increased by 37.60 %, highlighting the excellent photocatalytic activity of Co3O4 nanoparticles. Furthermore, leveraging natural sunlight led to a notable Tartrazine degradation rate of 97.11 %, signifying a substantial 45.41 % enhancement in reaction efficiency when contrasted with the conventional Co3O4/PMS system. Lastly, the Co3O4 nanoparticles illustrated remarkable degradation of synthetic industrial dye effluents (Tartrazine, Methyl Orange, and Remazol Brilliant Red), reaching up to 92.77 % removal, indicating its potential for use in real-world scenarios.

Rational design and easy fabrication of transparent photothermal/hygroscopic composite coatings with long-lasting antifogging performance under sunlight activation.

Hygroscopic polymers are good candidates for antifogging coatings, but their long-term effectiveness is limited by the equilibrium between water absorption and expansion. As an efficient and environmentally friendly solution, photothermal materials are being introduced into the field of antifogging. However, there is a need for enhancement in the spectral characteristics of most photothermal materials within the visible light region. In addition, photothermal antifogging coatings often exhibit a delay in heating response, which hinders their ability to promptly evaporate condensed water droplets in the absence of illumination or during initial illumination. Here, a bilayer structure design of photothermal nanomaterials/hygroscopic polymers is proposed to achieve long-term antifogging under sunlight activation. Ensuring the rapid absorption of condensed water droplets on the coating surface, while simultaneously achieving efficient photothermal conversion for a swift temperature increase over the entire coating, is key to this approach, which will not only suppress early fogging but also lead to an exponential decrease of the nucleation rate of droplets. During this process, a dynamic equilibrium is gradually established between the condensation and evaporation of fog droplets, leading to long-term antifogging properties. The light transmittance of the composite coatings reaches as high as ca. 75% in the visible light region, making them well suited for a diverse range of transparent substrate and device applications. A clear field of view can be maintained for at least 6 h under 1 sun illumination above 65 °C hot steam. The antifogging/defogging performance is effectively demonstrated even under challenging non-ideal natural conditions, such as low solar irradiation during dusk or when placed indoors behind windows.

High-performance UV photodetector based on nickel oxide loaded with low amount of nitrogen and boron co-doped reduced graphene oxide for bias-switchable photoconductance

In this work, we report a low cost and straightforward chemical synthesis of nickel oxide nanoparticles decorated with low amount of nitrogen and boron co-doped reduced GO for a high-performance UV photodetector. For the first time, NiO/NB-rGO nanomaterial was synthesized following the co-precipitation method and subsequently annealed at 400 °C. The nanomaterial was characterized with several techniques such as SEM, TEM, XRD, and Raman spectroscopy. In addition, the device was subjected to electrical characterizations to determine their responsivity, detectivity, and temporal responses both in the absence of illumination (dark conditions) and under UV illumination of 375 nm. In particular, the studied I-V curve was performed to evaluate the coexistence of positive and negative photoconductivity in our device. The results revealed a better photoresponse of NiO/NB-rGO device to UV light, which showed high responsivity (800 A/W), large detectivity (9.4 ×1011 Jones), and fast rise/fall time (1.38/2.17 s) at reverse bias. Consequently, the Schottky contact of NiO/NB-rGO allowed to switch between carriers’ conduction, which displayed both positive and negative photoconductance at reverse and forward bias.

Voltammetric Measurement of Rates and Energetics for Surface Methoxylation of Si(100) in Methanol with Dissolved Electron Acceptors Using Si Ultramicroelectrodes.

The steady-state voltammetric responses of n-type Si(100) semiconductor ultramicroelectrodes (SUMEs) immersed in air- and water-free methanolic electrolytes have been measured. The response characteristics of these SUMEs in the absence of illumination were modeled and understood through a framework that describes the distribution of the applied potential across the semiconductor/electrolyte contact using four discrete regions: the semiconductor space charge, surface, Helmholtz, and diffuse layers. The latter region was described by the full Gouy-Chapman model. This framework afforded insight on how relevant parameters such as the semiconductor band edge potentials, the reorganization energies for charge transfer, the standard potential of redox species in solution, the density and energy of surface state populations, and the presence of an insulating (tunneling) layer individually and collectively dictate the observable current-potential responses. With this information, the methoxylation of Si surfaces was evaluated by analysis of the change in voltammetric responses during the course of prolonged immersion in methanol. The electrochemical data were consistent with a surface methoxylation mechanism that depended on the standard potential of redox species dissolved in solution. Estimates of the enthalpies of adsorption as well as the potential-dependent rate constant for surface methoxylation were obtained. Collectively, these measurements supported the contention that the rates of Si surface reactions can be systematically tuned by exposure to dissolved outer-sphere electron acceptors. Moreover, the data represent the quantitative utility of voltammetry with SUMEs for the measurement of semiconductor/liquid contacts.

The specificity of photoluminescence n-CdS/p-CdTe in semiconductor heterostructures

The low-temperature (4.2 K) near-band-edge photoluminescence spectrum of a thin fine-grained (h, dcr≤1μm) polycrystalline CdTe layer in an n-CdS/p-CdTe film heterostructure subjected to frontal excitation by an Ar+ laser with an intensity of ~44 W/cm2 consists of a dominant intrinsic (e-h) emission band with a half-width ΔA=10-12 meV and a blue shift ΔEr » 25 meV of the red edge with respect to Eg, its LO+nLA phonon replica (ΔB»40 meV) with a weak doublet structure, and a wide (ΔD»100 meV) surface-interface luminescence band peaking at a frequency ħω»1.49 eV. Rear-side illumination of the photoresistive CdS layer in the intrinsic absorption range with an intensity Lill ≈ 5.102 lx almost completely destroys the e-hband and all related luminescence lines, which are replaced with an asymmetric polariton emission doublet having an exciton resonance frequency ħω»1.59 eV(Δex» 25 meV) and a wide line of shallow donor–acceptor pairs (ΔDAP»40 meV) at a frequency of ħω»1.54 eV, whose maximum intensity is almost two orders of magnitude lower than that of the A line in the absence of illumination.

Elucidating the Roles of Local and Nonlocal Rate Enhancement Mechanisms in Plasmonic Catalysis.

Plasmonic metal nanoparticles (e.g., Ag, Au, and Cu) constitute a class of materials that interact with light via the excitation of localized surface plasmon resonance (LSPR). Numerous studies have reported substantial enhancements in the rates of chemical reactions on illuminated plasmonic nanoparticle catalysts compared to corresponding systems in the absence of illumination. There are two mechanisms that have been proposed to explain the LSPR-induced chemical reactivity. One mechanism assumes a local plasmon-induced hot charge-carrier-mediated activation of the reactants, while the other assumes an LSPR-induced equilibrium heating of the catalyst, which leads to energy transfer to and chemical reaction of the adsorbed reactants. In this contribution, we developed a setup amenable to accurate in situ catalyst temperature and kinetic reaction rate measurements. We employed this setup to study the LSPR-induced rate enhancement in a case study of the CO oxidation reaction on plasmonic, monometallic Ag nanoparticle catalysts supported on α-Al2O3. We explored various Ag loadings and clustering levels. Our data show that the equilibrium heating of the catalyst cannot fully explain the illumination-induced plasmonic rate enhancements. This is the case even for high loading and clustering of Ag nanoparticles, where the equilibrium heating significantly increases. Based on the analysis, we propose that local effects, related to the plasmon-induced activation of adsorbates (reactants) via electronic excitation of the reactant or photothermal heating of the reactants that is highly localized to the individual nanoparticles, play a critical role in driving LSPR-induced chemical reactions.

Environmentally Safe Photodynamic Control of Aedes aegypti Using Sunlight-Activated Synthetic Curcumin: Photodegradation, Aquatic Ecotoxicity, and Field Trial.

This study reports curcumin as an efficient photolarvicide against Aedes aegypti larvae under natural light illumination. Larval mortality and pupal formation were monitored daily for 21 days under simulated field conditions. In a sucrose-containing formulation, a lethal time 50 () of 3 days was found using curcumin at 4.6 mg L−1. This formulation promoted no larval toxicity in the absence of illumination, and sucrose alone did not induce larval phototoxicity. The photodegradation byproducts (intermediates) of curcumin were determined and the photodegradation mechanisms proposed. Intermediates with m/z 194, 278, and 370 were found and characterized using LC-MS. The ecotoxicity of the byproducts on non-target organisms (Daphnia, fish, and green algae) indicates that the intermediates do not exhibit any destructive potential for aquatic organisms. The results of photodegradation and ecotoxicity suggest that curcumin is environmentally safe for non-target organisms and, therefore, can be considered for population control of Ae. aegypti.

Reprint of: Photoperoxidation in Isolated Chloroplasts I. Kinetics and Stoichiometry of Fatty Acid Peroxidation

A photo-induced cyclic peroxidation in isolated chloroplasts is described. In an osmotic buffered medium, chloroplasts upon illumination produce malondialdehyde (MDA)—a decomposition product of tri-unsaturated fatty acid hydroperoxides—bleach endogenous chlorophyll, and consume oxygen. These processes show (a) no reaction in the absence of illumination; (b) an initial lag phase upon illumination of 10-20 minutes duration; (c) a linear phase in which the rate is proportional to the square root of the light intensity; (d) cessation of reaction occurring within 3 minutes after illumination ceases; and (e) a termination phase after several hours of illumination. The kinetics of the above processes fit a cyclic peroxidation equation with velocity coefficients near those for chemical peroxidation.The stoichiometry of MDA/O2 = 0.02, and O2/Chlbleached = 6.9 correlates well with MDA production efficiency in other biological systems and with the molar ratio of unsaturated fatty acids to chlorophyll. The energies of activation for the lag and linear phases are 17 and 0 kcal/mole, respectively, the same as that for autoxidation. During the linear phase of oxygen uptake the dependence upon temperature and O2 concentration indicates that during the reaction, oxygen tension at the site of peroxidation is 100-fold lower than in the aqueous phase.It is concluded that isolated chloroplasts upon illumination can undergo a cyclic peroxidation initiated by the light absorbed by chlorophyll. Photoperoxidation results in a destruction of the chlorophyll and tri-unsaturated fatty acids of the chloroplast membranes.

Voltage controlled bio-organic inverse phototransistor.

Thin films of poly-d-lysine act as polar organic and are also light sensitive. The capacitance-voltage, current-voltage, and transistor behavior were studied to gauge the photoresponse of possible poly-d-lysine thin film devices both with and without methylene blue as an additive. Transistors fabricated from poly-d-lysine act as inverse phototransistors, i.e., the on-state current is greatest in the absence of illumination. The poly-d-lysine thin film capacitance and the transistor current decrease with illumination, both with and without methylene blue as an additive. This suggests that the unbinding of photo exciton is significantly hindered in this system which is supported by the significant charge carrier lifetime for poly-d-lysine films both with and without methylene blue. For the majority carrier, the transistor geometry appears to depend on the gate voltage; in other words, the majority carrier depends on the polarization of the poly-d-lysine films, both with and without methylene blue as an additive.

May the dark be with roots: a perspective on how root illumination may bias invitro research on plant-environment interactions.

Roots anchor plants to the soil, providing them with nutrients and water while creating a defence network and facilitating beneficial interactions with a multitude of living organisms and climatological conditions. To facilitate morphological and molecular studies, root research has been conducted using invitro systems. However, under natural conditions, roots grow in the dark, mainly in the absence of illumination, except for the relatively low illumination of the upper soil surface, and this has been largely ignored. Here, we discuss the results found over the last decade on how experimental exposure of roots to light may bias root development and responses through the alteration of hormonal signalling, cytoskeleton organization, reactive oxygen species or the accumulation of flavonoids, among other factors. Illumination alters the uptake of nutrients or water, and also affects the response of the roots to abiotic stresses and root interactions with the microbiota. Furthermore, we review invitro systems created to maintain roots in darkness, and provide a comparative analysis of root transcriptomes obtained with these devices. Finally, we identify other experimental variables that should be considered to better mimic soil conditions, whose improvement would benefit studies using invitro cultivation or enclosed ecosystems.

Catalytic open-circuit passivation by thin metal oxide films of p-Si anodes in aqueous alkaline electrolytes

Ni and NiOx-based protective thin films catalyze the oxidation of Si in the presence of O2 in strongly alkaline KOH(aq) even in the absence of illumination.

Distance and Potential Dependence of Charge Transport Through the Reaction Center of Individual Photosynthetic Complexes

AbstractCharge separation and transport through the reaction center of photosystem I (PSI) is an essential part of the photosynthetic electron transport chain. A strategy is developed to immobilize and orient PSI complexes on gold electrodes allowing to probe the complex's electron acceptor side, the chlorophyll special pair P700. Electrochemical scanning tunneling microscopy (ECSTM) imaging and current–distance spectroscopy of single protein complex shows lateral size in agreement with its known dimensions, and a PSI apparent height that depends on the probe potential revealing a gating effect in protein conductance. In current–distance spectroscopy, it is observed that the distance‐decay constant of the current between PSI and the ECSTM probe depends on the sample and probe electrode potentials. The longest charge exchange distance (lowest distance‐decay constant β) is observed at sample potential 0 mV/SSC (SSC: reference electrode silver/silver chloride) and probe potential 400 mV/SSC. These potentials correspond to hole injection into an electronic state that is available in the absence of illumination. It is proposed that a pair of tryptophan residues located at the interface between P700 and the solution and known to support the hydrophobic recognition of the PSI redox partner plastocyanin, may have an additional role as hole exchange mediator in charge transport through PSI.

Light-assisted synthesis of copper/cuprous oxide reinforced nanoporous silicon microspheres with boosted anode performance for lithium-ion batteries

Silicon is generally accepted as an outstanding anode material to promote the use of high-capacity lithium-ion batteries (LIBs). Herein, novel Cu/Cu2O reinforced nanoporous silicon microspheres are successfully constructed by a simple photodeposition-galvanic replacement method. The reduction reactions driven by photogenerated electrons and galvanic replacement jointly promote the in-situ deposition of Cu/Cu2O on porous silicon microspheres. Compared with the as-constructed anode materials in the absence of illumination, the composites obtained with the light irradiation display better electrochemical performance. The ratio of Si and Cu in the final products can be effectively adjusted by modulating the concentration of Cu2+ in the reaction solutions. Benefiting from the enhanced structure stability and excellent electronic conductivity, the final optimized product exhibits superior Li-storage performance, delivering a reversible capacity of 1240.1 mAh g−1 after 200 cycles at a high current of 1 A g−1. It is worth mentioning that the as-constructed light-assisted method provides an efficient and universal pathway to tailor and synthesize other superior Si based anode materials.

The Effect of Visible Light on Cell Envelope Subproteome during Vibrio harveyi Survival at 20 °C in Seawater.

A number of Vibrio spp. belong to the well-studied model organisms used to understand the strategies developed by marine bacteria to cope with adverse conditions (starvation, suboptimal temperature, solar radiation, etc.) in their natural environments. Temperature and nutrient availability are considered to be the key factors that influence Vibrio harveyi physiology, morphology, and persistence in aquatic systems. In contrast to the well-studied effects of temperature and starvation on Vibrio survival, little is known about the impact of visible light able to cause photooxidative stress. Here we employ V. harveyi ATCC 14126T as a model organism to analyze and compare the survival patterns and changes in the protein composition of its cell envelope during the long-term permanence of this bacterium in seawater microcosm at 20 °C in the presence and absence of illumination with visible light. We found that V. harveyi exposure to visible light reduces cell culturability likely inducing the entry into the Viable but Non Culturable state (VBNC), whereas populations maintained in darkness remained culturable for at least 21 days. Despite these differences, the starved cells in both populations underwent morphological changes by reducing their size. Moreover, further proteomic analysis revealed a number of changes in the composition of cell envelope potentially accountable for the different adaptation pattern manifested in the absence and presence of visible light.

In situ NMR Investigation of the Photoresponse of Perovskite Crystal

Summary Hybrid perovskites are outstanding candidates for use in optoelectronic devices. Nonetheless, hybrid perovskites present numerous fundamental issues that are not yet fully understood. This study seeks to address this problem by reporting on the occurrence of ultraslow dynamic orientation changes in the methylammonium (MA) cations and the corresponding changes in the inorganic lattice of MAPbI3 perovskite crystals occurring over a time scale of 100 s under continuous illumination based on in situ single-crystal 2H nuclear magnetic resonance and in situ X-ray diffraction results. The demonstrated ultraslow dynamic changes in MAPbI3 are far slower than elementary molecular motions typically having time scales of femtoseconds and picoseconds and have never been reported previously. The ultraslow dynamic changes have been correlated with the reduction of band gap and the increase of absorption coefficient of MAPbI3, providing the molecular origins of the stabilization process in the photoresponse of the MAPbI3 device.

Characterization of microwave photoswitch integrating Metal-Semiconductor-Metal photodetector

An experimental study implemented to present the results of the characterization of microwave photoswitches to recognize the behavior of the microwave signals under laser light of 0.85 μm wavelength. These photoswitches consist of a coplanar line integrating a Schottky contact Metal-Semiconductor-Metal (MSM) photodetectors in the central line growth on GaAs Not Intentionally Doped (N.I.D). Those MSM photodetectors have a single electrode of different finger spacings (D) ranging from 0.2 μm to 1 μm and different finger widths (L) ranging from 0.2 μm to 5 μm. The characterizations of our optoelectronic devices made in the absence of illumination allowed us good isolation equal to −40 dB and under illumination insertion losses equal to −12.7 dB at 20 GHz. The obtained results are quite satisfying, have permitted to deduce the On/Off ratios and allowed to see the influence of the geometrical parameters on the transmission and reflection coefficients.

Luminescent solar concentrators based on melt-spun polymer optical fibers

Luminescent solar concentrators (LSCs) collect incoming sunlight and direct it to a smaller-area photovoltaic cell. In the presented work, form factor and illumination angle-dependent performance of LSCs consisting of bi-component melt-spun fibers is demonstrated. Three thermoplastic polymers act as dispersing host material for the luminescent dye Lumogen Red 305 (LR305). Molecular dynamics simulations provide numerical access to Hildebrand solubility parameters, which are an estimate for the mixing compatibility of dye with polymer matrix. Actual emission intensity measurements from material samples are compared to Monte Carlo ray tracing simulations. Some samples show an increased absorption, which led to the hypothesis that there exist optically passive dye aggregates if the dispersion is not optimal. The best-performing polymer/dye pair is identified and used to melt-spin fibers. Geometrically defined bundles of LSC fibers are studied in a scenario of white light illumination and variation of illumination-angle. This experiment simulates a theoretical daily course-of-sun illumination in absence of atmospheric effects. We report optical conversion efficiencies of the prepared LSCs between 2% and 15%, depending on illumination angle and bundle geometry.