Wavelength Of Visible Light Research Articles

The piezoelectric properties of transparent 0.75Pb(Mg1/3Nb2/3)O3-0.25PbTiO3:Pr3+ ceramics

The enhancement of both transparency and piezoelectric properties in transparent ferroelectric ceramics is a challenge. In this work, we prepared transparent 0.75Pb(Mg1/3Nb2/3)O3-0.25PbTiO3:xPr3+ ceramics by oxygen atmosphere sintering together with hot pressing sintering. When x = 1.5 mol%, a transparency of 68% @ 900 nm (close to the theoretical value ~71%) was achieved, and the piezoelectric properties increased to twice as much as those in undoped ceramics (x = 0). The small average domain size (below 200 nm) that far below the visible light wavelength was believed to benefit light transmittance. Meanwhile, the minute amount of tetragonal component induced by Pr3+ irons, was supposed to be responsible for the improved piezoelectric properties. These merits make Pr3+-doped 0.75PMN-0.25PT transparent ceramics promising functional materials for transparent piezoelectric devices.

Transparent Polyisocyanurate-Polyurethane-Based Aerogels: Key Aspects on the Synthesis and Their Porous Structures

The effect of the catalyst concentration on the synthesis and textural properties of polyisocyanurate-polyurethane aerogels is analyzed. The use of different catalyst amounts allows obtaining low-density aerogels (0.10–0.16 g/cm3) with high porosities (85–91%). Their porous structures were analyzed by scanning electron microscopy and nitrogen adsorption–desorption isotherm. A noticeable decrease in the size of the scattering centers, particles and pores, was achieved when reducing the catalyst amount. In some samples, the small size of these features, much smaller than the wavelength of visible light, causes a bare light dispersion, leading to the first transparent polyisocyanurate-polyurethane aerogels. Light transmittance measurements at 532 nm have been made showing high values (ca. 76% for 1 mm thick samples) for the formulations with the smallest particle and pore sizes. These aerogels presenting optical transparency have many potential applications such as solar collectors, glazing systems for insulating windows, and sensors, among others.

Monte Carlo simulations of photodynamic therapy in human blood model.

This study aims to simulate a therapeutic plan for a normal human blood model under various patho-physiological conditions, such as the development of leukemia/blood diseases, by means of Monte Carlo multilayered simulation. The photosensitizing compound selectively accumulates in the target cells. A superficial treatment of a blood sample was performed at different ratios of oxygen saturation ([Formula: see text]) under the concentration ([Formula: see text] = 30µM) effect of merocyanine 540 (MC540) in the blood irradiation. This was done under the application of visible light of wavelength ~ [Formula: see text] at an exposure time ~ 60s. The dose of photodynamic therapy (PDT) was evaluated for the biological damage, leading to necrosis and blood damage during the treatment. In addition, the effect of PDT treatment response in the blood is related to hemoglobin oxygen saturation, resulting in an excellent relationship between the changes caused by the treatment in the blood at a peculiar oxygen saturation rate (for the highest response: [Formula: see text] 50%) and a light dose (LD) of 3.83 [Formula: see text] above the minimal toxicity of normal tissues. The photodynamic dose is related to the depth of necrosis and the time of treatment for the achievement of the LD delivery at the PDT of blood.

Generation of wavelength-tunable optical vortices using an off-axis spiral phase mirror

Wavelength-tunable optical vortices with a topological charge equal to l=1 of orbital angular momentum (OAM) were experimentally realized using a single off-axis spiral phase mirror (OSPM) with lasers of various visible-light wavelengths. Using an OSPM designed for 561 nm and an incidence angle of 45°, circular doughnut-shaped l=1 optical vortices were obtained at 561, 473, and 660 nm by rotating the OSPM to modify the laser incidence angle. Wavelength-tunable l=1 optical vortices were obtained at the respective incidence angles of 45°, 53.4°, and 33.7°, because the effective geometrical thickness of the OSPM, which determines the order of OAM, was identical at each wavelength. This flexible OSPM which operates over a wide wavelength range will provide continuously wavelength-tunable optical vortices for applications in the fields of advanced optics and photonics in which optical vortices with wide wavelength tunability are in demand.

Computational Study of Novel Semiconducting Sc2CT2 (T = F, Cl, Br) MXenes for Visible-Light Photocatalytic Water Splitting

Seeking candidate photocatalysts for photocatalytic water splitting, via visible light, is of great interest and importance. In this study, we have comprehensively explored the crystal structures, electronic properties, and optical absorbance of two-dimensional (2D) Sc2CT2 (T = F, Cl, Br) MXenes and their corresponding photocatalytic water splitting, under the visible-light region, by first-principles calculations. Herein, we have proposed that 2D Sc2CT2 MXenes can be fabricated from their layered bulk compounds, alternatively to the traditional chemical etching method. Creatively, we proposed Sc2CT2 (T = F, Br) as new materials; the band edge alignments of Sc2CF2 can be tuned to meet the water redox potentials at pH = 8.0. It is highlighted that Sc2CF2 shows outstanding optical spectra harvested under visible-light wavelength regions, and efficient separation of photo-induced electrons and holes in different zones. These present results provide eloquent evidence and open a new door on the photocatalysis applications of such novel semiconducting MXenes.

Photonic Bandgap in Achiral Liquid Crystals-A Twist on a Twist.

Achiral mesogenic molecules are shown to be able to spontaneously assemble into liquid crystalline smectic phases having either simple or double-helical structures. At the transition between these phases, the double-helical structure unwinds. As a consequence, in some temperature range, the pitch of the helix becomes comparable to the wavelength of visible light and the selective reflection of light in the visible range is observed. The photonic bandgap phenomenon is reported for achiral liquid crystals.

Retention and deformation of the blue phases in liquid crystalline elastomers

The blue phases are observed in highly chiral liquid crystalline compositions that nascently organize into a three-dimensional, crystalline nanostructure. The periodicity of the unit cell lattice spacing is on the order of the wavelength of visible light and accordingly, the blue phases exhibit a selective reflection as a photonic crystal. Here, we detail the synthesis of liquid crystalline elastomers that retain blue phase I, blue phase II, and blue phase III. The mechanical properties and optical reconfiguration via deformation of retained blue phases are contrasted to the cholesteric phase in fully solid elastomers with glass transition temperatures below room temperature. Mechanical deformation and chemical swelling of the lightly crosslinked polymer networks induces lattice asymmetry in the blue phase evident in the tuning of the selective reflection. The lattice periodicity of the blue phase elastomer is minimally affected by temperature. The oblique lattice planes of the blue phase tilt and red-shift in response to mechanical deformation. The retention of the blue phases in fully solid, elastomeric films could enable functional implementations in photonics, sensing, and energy applications.

Transparent nanocomposites with enhanced performances from poly(propylene carbonate) and silica

AbstractIn this study, silica nanoparticles with a refractive index matching PPC and a diameter smaller than the visible light wavelength were chosen to prepare enhanced PPC/silica nanocomposites by a simple melt compounding method. The result exhibited all the nanocomposites possessed excellent transparency (about 90%), even in the nanocomposite with a silica content of 10 wt%. For PPC/silica nanocomposites, the percolation threshold was determined to be 7.5 wt% based on the dynamic rheological behavior and percolation theory. Moreover, the overall performance of the PPC‐based nanocomposite with a silica content of 7.5% is the best. The optimal nanocomposite showed a Young's modulus of 3792 MPa, a yield strength of 46.5 MPa, a storage modulus of 3812 MPa and a highest temperature at maximum weight‐loss rate (Tmax, 309°C). These characteristics are very important for potential commodity applications of PPC.

Design of a waveguide eye-tracking system operating in near-infrared with holographic optical elements

Recent research in augmented reality (AR) eyewear has prompted interest in using volume holographic optical elements for this application. However, many sensing operations in AR systems require the use of wavelengths in the near-infrared (NIR) (750 to 900 nm). These wavelengths typically exceed the sensitivity range of available commercial holographic recording materials (450 to 650 nm), which complicates the design of optical elements with power since significant aberrations result when the reconstruction wavelength differs from the construction wavelength. Several methodologies for designing a waveguide hologram imaging system in NIR are reviewed and evaluated. The design approach presented in our work integrates the most effective practices such as fabrication point source location optimization and aberration analysis to realize effective holographic waveguide couplers formed with visible wavelength light and reconstructed in the NIR. The technique is demonstrated by designing and fabricating an input waveguide hologram in conjunction with a multiplexed output coupling hologram. The resulting input/output waveguide holograms can achieve an image resolution of (∼3 lp / mm) with a 0.6-mm-thick glass substrate that has a refractive index of 1.8.

Controlling Antibacterial Activity Exclusively with Visible Light: Introducing a Tetra‐ortho‐Chloro‐Azobenzene Amino Acid

The introduction of a novel tetra‐ortho‐chloroazobenzene amino acid (CEBA) has enabled photoswitching of the antimicrobial activity of tyrocidine A analogues by using exclusively visible light, granting spatiotemporal control under benign conditions. Compounds bearing this photoswitchable amino acid become active upon irradiation with red light, but quickly turn‐off upon exposure to other visible light wavelengths. Critically, sunlight quickly triggers isomerisation of the red light‐activated compounds into their original trans form, offering an ideal platform for self‐deactivation upon release into the environment. Linear analogues of tyrocidine A were found to provide the best photocontrol of their antimicrobial activity, leading to compounds active against Acinetobacter baumannii upon isomerisation. Exploration of their N‐ and C‐termini has provided insights into key elements of their structure and has allowed obtaining new antimicrobials displaying excellent strain selectivity and photocontrol.

Room temperature NO2 sensing properties of ZnO1-α coating prepared by hydrogen reduction method

NO2 emission is currently one of the important factors threatening the quality of life of residents. Preparing ZnO-based gas sensors to monitor the concentration of NO2 has attracted growing attention. This article reports a method for preparing ZnO1-α by hydrogen heat treatment. The ZnO coating prepared by the spin coating method is directly placed in a reduced atmosphere with 3% hydrogen for heat treatment to produce a self-doped ZnO1-α coating with oxygen vacancies, which can effectively narrow the bandgap. The article studied the influence of heat treatment time and visible light wavelength on sensing properties. The results show that under the conditions of room temperature and blue light irradiation, the coating heat-treated in a reduced atmosphere for 1 h showed the best gas-sensing properties to 1 ppm NO2 with a response of 7.0. The outstanding selectivity of ZnO1-α coating has been displayed.

Laser Light Trapping Phenomenon in a 3D Radiotherapy Polymer Gel Dosimeter.

This paper aims to explain the phenomenon of laser light trapping (LLT) in a 3D polymer gel dosimeter. A VIC-T polymer gel dosimeter containing 17% N-vinylpyrrolidone, 8% N,N′-methylenebisacrylamide, 12% tert-butyl alcohol, 5% gelatine, 0.02% hydroquinone and 14 mM tetrakis(hydroxymethyl)phosphonium chloride was used in this study. It was exposed to green laser light with a wavelength of 532 nm. A film was recorded during the exposure. After exposure, Raman spectroscopy was used to study the reactions taking place inside the dosimeter. The obtained results were used to explain what the LLT phenomenon is, what are the consequences for the dosimeter in which such a phenomenon occurs, and what dosimeter components play an important role in the occurrence of LLT. In addition, the conditions under which 3D polymer gel dosimeters can be measured using optical computed tomography at short wavelengths of visible laser light are indicated.

Of mice, light, and eyeball length

Neurodevelopment The incidence of myopia continues to increase, fueling hypotheses that link society's increasingly indoor lifestyle to nearsightedness. Indeed, violet light, with the shortest wavelengths of visible light (360 to 400 nm), protects against the development of myopia in the mouse, chicken, and human. Jiang et al. have found a link with circadian rhythm, showing that violet light delivered to mice (which are nocturnal) in the evening is protective against induced myopia. The protective effect depends on neuropsin, which is required for photoentrainment of mouse retinal circadian clocks. Neuropsin is expressed in retinal ganglion cells, which support the development of the vascular choroid layer that nourishes the retina. A robust choroid normalizes eyeball shape. The authors hypothesize that equivalent timing of violet light exposure for humans might be dawn. Maybe the early bird gets the worm because it can actually see it? Proc. Natl. Acad. Sci. U.S.A. 118 , e2018840118 (2021).

Application Of Ba0.5Sr0.5TiO3 (Bst) Film Doped With RuO2 (0%, 2%, 4% and 6%) On A Rice-Stalk Cutting Robot Model Based On A Line Follower With Hc-05 Bluetooth Control

Ba0.5Sr0.5TiO3 (BST) film doped with RuO2 with varying concentrations (0%, 2%, 4%, and 6%) on a p-type (100) silicon substrate has been successfully grown using the Chemical Solution Deposition (CSD) method and spin coating at a rotational speed of 3000 rpm for 30 seconds. The film on the substrate was then heated at 850 oC for 15 hours. BST film+RuO2 variations were characterized for their sensitivity as a light sensor. BST film+RuO2 variations were tested with a varied light source and reflective surface colors. Thin films have a range at the visible light wavelength, so LED lights were used as the light source in the present study. The light source selected was the blue LED because it had a high contrast in differentiating between dark and light-colored surfaces. Various electronic circuits assisted sensitivity characterization with the aim to produce a sensor that is highly sensitive to light. The response of BST film+ RuO2 variations differed according to the RuO2 doping concentration. BST film doped with RuO2 6% had a very good response to changes in light, so this film was applied as the line detector sensor in the line follower-based rice-stalk cutter model with an HC-05 Bluetooth control. Before being integrated with the microcontroller, the output voltage of the BST film was strengthened using an op-amp circuit so that the microcontroller could read the output voltage of the BST film.

Design and Optimization of the Antireflective Coating Properties of Silicon Solar Cells by Using Response Surface Methodology

The design and optimization of a nanostructured antireflective coatings for Si solar cells were performed by using response surface methodology (RSM). RSM was employed to investigate the effect on the overall optical performance of silicon solar cells coated with three different nanoparticle materials of titanium dioxide, aluminum oxide, and zinc oxide nanostructures. Central composite design was used for the optimization of the reflectance process and to study the main effects and interactions between the three process variables: nanomaterial type, the radius of nanoparticles, and wavelength of visible light. In this theoretical study, COMSOL Multiphysics was utilized to design the structures by using the wave optics module. The optical properties of the solar cell’s substrate and the three different nanomaterial types were studied. The results indicated that ZnO nanoparticles were the best antireflective coating candidate for Si, as the ZnO nanoparticles produced the lowest reflection values among the three nanomaterial types. The study reveals that the optimum conditions to reach minimum surface reflections for silicon solar cell were established by using ZnO nanoparticles with a radius of ~38 nm. On average, the reflectance reached ~5.5% along the visible spectral range, and approximately zero reflectance in the 550–600 nm range.

Photoluminescence Properties of Copolyimides Containing Naphthalene Core and Analysis of Excitation Energy Transfer between the Dianhydride Moieties

The photoluminescence (PL) properties of semi-aromatic polyimide (PI) films and their model compounds (MCs) prepared from dianhydrides having a rigid naphthalene core were analyzed. The PMMA-dispersed MC and copolymerized PI (CoPI) films derived from 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTDA) exhibited long-lived phosphorescence owing to the suppression of molecular motion by the rigidity of a naphthalene core. Additionally, the PMMA-dispersed MC and the CoPI films derived from 1,5-dibromo derivative of NTDA (DBrNT) exhibited room-temperature phosphorescence due to the enhancement of spin-orbit coupling by bromine atoms. The photophysical processes of the CoPI films prepared from NTDA/DBrNT and 4,4'-oxydiphtalic dianhydride (ODPA) in which the latter absorption band is located at a shorter wavelength than the former were analyzed. After UV irradiation, efficient excitation energy transfer occurs from the ODPA to NTDA/DBrNT moieties, and only the emission from the latter moieties was observed. These results demonstrate that the CoPI films derived from two dianhydrides absorbing different UV wavelengths can be used as spectral conversion films that convert a wide range of UV-light into longer wavelength visible light.

Advances in engineering perovskite oxides for photochemical and photoelectrochemical water splitting

Solar-driven water splitting is an efficient process for converting solar energy into chemical energy. In this process, semiconductor materials are excited by solar energy to generate free electrons to participate in the water-splitting reaction. Among these semiconductor materials, inorganic perovskite oxides have a spatial structure that is easy to control and thereby lead to different energy band structures and photocatalytic properties. More importantly, perovskite oxides can be compounded with other organic/inorganic materials to promote charge separation and improve apparent quantum yield. However, the low solar-to-hydrogen conversion efficiency has not yet reached the requirements of practical applications. In this review, the fundamental principles of solar-driven water splitting based on perovskite materials are introduced according to the most recently published results. In addition, the innovative modification techniques for water splitting based on perovskite oxides have been summarized, focusing on the following methods: element doping, homo/heterojunction formation, Z-scheme, plasmon effect, dye sensitization, carbon enhancement, and surface modifications. Note that the applications in the visible light wavelength range have been described, with emphasis among all these modification materials. Furthermore, the recent water-splitting reaction systems for practical applications are briefly discussed. As a summary, we outline the challenges and potential utilization associated with visible light–driven water splitting based on perovskite oxides for future commercial applications. This review describes various modification methods to improve photochemical performance of perovskite oxides as well as illustrates the potential to employ perovskite oxides as a key material for the practical application of water splitting.

Development of the Calibration System and Characterization of the Avalanche Photodiode for Scintillation Detection

Branches of physics and application technologies have widely utilized avalanche photodiodes (APDs) by coupling of scintillators with advantages of multiplication process and effective photosensitivity in a wide range of visible light wavelength. In addition, to meet the requirements for the purpose of each experiment, various types of APDs have been developed. The calibration system and characteristics of APD were constructed and studied by comparing several calibration methods. Electronics calibration is presented with charge injection and quantum efficiency (QE)-calibrated photodiode. By utilizing visible light-emitting diodes (LEDs) and with conventional electronic characteristics and a scintillation crystal with <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> Na radioactive source, the APD gain was measured. Furthermore, the following were measured from the calibration method: QE, excess noise factor, and noise level. In this article, we compare our test results with one another, which are provided in the datasheet presented by the manufacturer, and discuss the possibility of standardizing the characterization of APDs by this calibration system.

Spectro-Photo-Electrochemical Study of Selected Flavine Derivatives for Application in Photocatalysis

The photocatalysis of chemical reactions in organic chemistry by the light of visible wavelengths has undergone great development in recent years, however many challenges remain. The effort to create reducing agent with power of alkali metals using light from the visible region of the spectrum remains unattained. Alkali metals are still used in some organic reactions as reducing agents despite the known risks and formation of undesirable by-products.Flavin derivatives, which are the subject of this work, have the potential to accomplish these challenges. By the reduction and subsequent excitation by the visible light, flavine derivatives create long-lived excited states which behaves as extremely strong reduction agents (reduction potential comparable to sodium). These properties could be used to perform a number of hardly realizable reactions. Because it is a matter of redox processes and properties and the electron transfer, the electrochemical approach to this issue is very suitable. Most of published works deal with the use of flavines as oxidizing agents and by them catalyzed transformations. However, these substances have the potential to act as extreme reducing agents, which has not yet received such attention as their oxidizing abilities. It is therefore desirable to investigate their photo-reduction capabilities and their use in the field of organic synthesis.The aim of this work is to study selected flavine derivatives using electrochemical and spectroscopic methods and use gained knowledge to generate extremely strong reducing agents in situ and then perform model reactions. Combining electrochemical reduction and photochemical excitation with subsequent chemical reaction in one reaction cell would significantly save time, amount of solvents and the overall cost of performing these otherwise hardly realizable reactions.At first, selected flavine derivatives were characterized by cyclic voltammetry (using different materials of electrodes) and DC-polarography. The first reduction step of isoalloxazine and alloxazine derivatives is diffusion controlled and reversible with potential of -0,8 V (vs. SCE) for isoalloxazine and -1,3 V (vs. SCE) for alloxazine (both in acetonitrile). In the second stage of this work measured reduction potentials are used in potentiostatic electrolyses of flavine derivatives with aryl halides in one photo-electrochemical reaction cell. The cell is irradiated by visible light (450 nm) during the electrolysis. The combination of applied potential and visible light irradiation in one moment leads to electro-photocatalytic dehalogenation creating aryl radical. Afterwards, the products of model reactions are studied by spectroscopic methods like UV/VIS and NMR spectroscopy and correlated with quantum chemical calculations.Derivatives of isoalloxazine, alloxazine and 5-deazaflavin have been selected as model substances, whose excited states may have the potential to reduce aryl halides forming an aryl radical, which may be directly used in organic synthesis. All experiments were performed in the non-aqueous solvent (acetonitrile) without the presence of oxygen.Acknowledgement:The financial support of the grant 19-22806S (Czech Science Foundation - GAČR) and the institutional support RVO: 61388955 are highly appreciated. The authors are grateful to Prof. R. Cibulka for introduction to this problem and for valuable discussion. Figure 1

Synthesis scaly Ag-TiO2 loaded fly ash magnetic bead particles for treatment of xanthate wastewater

It is a challenging problem which Titanium dioxide (TiO 2 ) has low utilization of visible light and difficult recovery. In this work, the Ag-TiO 2 -FAMB photocatalyst was prepared by the sol-gel method, with Ag as the dopant and Fly Ash Magnetic Bead (FAMB) as the carrier to improve its photocatalytic performance and recovery rate. The samples prepared were characterized by XRD, SEM, EDS, VSM, UV–vis diffuse reflection. The effects of the amount of photocatalyst, initial pH value and concentration of xanthate, and the intensity of light on the degradation of xanthate were investigated. Free radical quenching test, full-spectrum ultraviolet scanning, and ion test are used to explore the potential mechanism of xanthate degradation. The test results show that the synthesized Ag-TiO 2 is scaly and uniformly supported on the surface of FAMB and its response of the photocatalyst to visible light shifts to 475 nm. When the photocatalyst concentration is 3.0 mg/L, the initial pH value is 5.0, the initial concentration of xanthate is 10.0 mg/L and the light intensity is 250 W, the degradation rate of xanthate reaches 98.5% after 30 h of light. The photocatalyst recovered by the external magnetic field was reused 5 times, and the degradation rate of xanthate remained above 83.8%. Superoxide radical (·O 2 - ) is the main active species for photocatalytic degradation of xanthate, and xanthate peroxide (ROCSSO - ) is an intermediate product, which is finally degraded into CO 2 , SO 4 2- , H 2 O. • FAMB as a carrier for preparing photocatalytic materials. • The new type Ag-TiO 2 -FAMB uses visible light wavelength to extend to 475 nm. • The new type Ag-TiO 2 -FAMB can be magnetically recycled and reused.