UV Part Research Articles

Hexa-(2-ethylhexyl)-hexa-peri-hexabenzocoronene as archetypal model compound of asphaltenes and MAONs

Hexa(ethylhexyl)-hexa-(peri)-hexabenzocoronene (HEH-HBC) was selected as model compound of asphaltenes. In fact, in the “island” model the asphaltenes are described with a relatively large aromatic core surrounded by aliphatic chains attached to the edges of the core. In their turn the asphaltenes are considered model compounds of MAONs (Mixed Aromatic-aliphatic Organic Nanoparticles), the possible carriers of the Unidentified Infrared Bands (UIBs), i.e. a set of certain infrared features found in very different astrophysical objects. The differential scanning calorimetric analysis (DSC) shows that HEH-HBC displays a discotic liquid crystal behavior, similar to that observed also in a selected authentic petroleum asphaltene sample. The electronic absorption spectrum of HEH-HBC was recorded for the first time in hydrocarbon solvents fully transparent in the UV, permitting to observe the UV part of HEH-HBC and to compare it with that of unsubstituted HBC. The FT-IR spectrum of HEH-HBC was recorded not only at room temperature but also at higher resolution at the liquid nitrogen temperature. The molar extinction coefficients and integrated molar absorptivity of the main bands were also estimated. The results are briefly discussed from an astrochemical perspective.

Extended aerosol and surface characterization from S5P/TROPOMI with GRASP algorithm. Part II: Global validation and Intercomparison

This paper is the second part of companion papers describing the development of GRASP approach for aerosol and surface retrieval from Sentinel-5P/TROPOMI. Here we focus on the S5P/TROPOMI GRASP aerosol and surface products global validation and systematic intercomparison with other products from independent instruments and algorithms. Specifically, we have validated the S5P/TROPOMI GRASP, Suomi-NPP/VIIRS DB and MODIS/TERRA DT + DB aerosol products with the ground-based AERONET referenced measurements using the same methodology and intercompare the validation results. In addition, the global pixel-to-pixel intercomparisons of the aerosol products (AOD, fine/coarse mode AOD and SSA) are performed over different surfaces, i.e., ocean and land surface with different NDVIs. Besides, we compared the S5P/TROPOMI GRASP, MODIS MCD43 surface BRDF/albedo as well as OMI, GOME-2 and SCIAMACHY Lambertian-Equivalent Reflectivity (LER) albedo climatology developed by Royal Netherlands Meteorological Institute (KNMI) with the surface reference dataset generated based on the synergetic retrieval of AERONET and S5P/TROPOMI measurements. Finally, the intercomparisons of the surface BRDF and albedo datasets were performed globally at the UV, VIS, NIR and SWIR parts of the spectrum. Overall, generally good agreement was observed between independent aerosol and surface datasets with a high percentage of pixels satisfying the Optimal and Target requirements. We would emphasize two advantages for TROPOMI/GRASP aerosol and surface products: (i) it provides spectral AOD together with detailed aerosol properties, such as fine/coarse mode AOD, spectral AAOD and SSA at UV, VIS, NIR and SWIR wavelengths, which are important for constraining aerosol environmental and climate effects; (ii) the TROPOMI/GRASP aerosol and surface products are globally retrieved simultaneously in a fully consistent manner.

(Invited) Tuning the Optoelectronic Properties of Inorganic and Carbon-Based Quantum Dots for Highly Efficient Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) are an old class of devices based on semitransparent windows, in which luminophores are embedded in a transparent matrix.[1] The luminophores can absorb and re-emit solar light and are able to generate electric power by collecting the re-emitted light at the borders of the slab. In the past, lab-to-fab transition of such devices was impeded by intrinsic limitations of the luminophores in terms of low quantum yield, strong resorption due to small Stokes shift, low optical and photoconversion efficiency of the final device. In the last years, a renaissance of such devices has been driven by the development of new 0-dimensional nanostructures, with tunable optical properties, which can guarantee good performance of LSCs.[2,3] Specifically, high quantum yield can be obtained; resorption losses can be limited by modulating the Stokes shift; final color of the window can be tuned by tuning light absorption properties; UV and IR parts of solar spectrum can be exploited without affecting window transparency. We will give examples of different 0-dimensional systems, which have been developed toward high efficiency LSCs, among which inorganic quantum dots and carbon dots.[4,5] Several strategies will be illustrated to tune the optoelectronic properties of the luminophores, including doping, core-shell structuring, and surface treatments.

Degradation of Orange G, Acid Blue 161, and Brillant Green Dyes Using UV Light-Activated GA-TiO2-Cd Composite.

In this study, photocatalysts with high photocatalytic activity performance are synthesized by synthesizing graphene aerogel-supported, cadmium-doped TiO2 composites by hydrothermal method for the effective degradation of organic dyes in wastewater. Here, GA-TiO2-Cd is investigated as a photocatalyst for the degradation of toxic dyes named Orange G, Acid Blue 161, and Brilliant Green in the UV part of the light spectrum. As a result of the experiments, it is observed that the effective decomposition of organic dyes is due to graphene aerogel (GA) and cadmium-doped TiO2 nanoparticles. The results show that for 20 ppm solutions of Orange G, Acid Blue 161, and Brilliant Green, dyes are removed at approximately 81.075%, 84.15%, and 95.18% in 120 min. The morphology and elemental analysis of the synthesized composites are determined using SEM-EDS, crystal structure analysis by XRD, chemical bond analysis by FTIR, optical properties by UV-Vis-NIR spectrophotometry, and thermal resistance by TGA analysis.

Wavelength-dependent direct and indirect photochemical transformations of organic pollutants

Sunlight-induced photochemical transformations greatly affect the persistence of organic pollutants in natural environment. Whereas sunlight intensity is well-known to affect pollutant phototransformation rates, the reliance of pollutant phototransformation kinetics on sunlight spectrum remains poorly understood, which may greatly vary under different spatial-temporal, water matrix, and climatic conditions. Here, we systematically assessed the wavelength-dependent direct and indirect phototransformations of 12 organic pollutants. Their phototransformation rates dramatically decreased with light wavelength increasing from 375 to 632 nm, with direct photolysis displaying higher wavelength-dependence than indirect photolysis. Remarkably, UV light dominated both direct (90.4–99.5 %) and indirect (64.6–98.7 %) photochemical transformations of all investigated organic pollutants, despite its minor portion in sunlight spectrum (e.g., 6.5 % on March 20 at the equator). Based on wavelength-dependent rate constant spectrum, the predicted phototransformation rate of chloramphenicol (4.5 ± 0.7 × 10−4 s−1) agreed well with the observed rate under outdoor sunlight irradiation (4.3 ± 0.0 × 10−4 s−1), and there is no significant difference between the predicted rate and the observed rate (p-value = 0.132). Moreover, rate constant and quantum yield coefficient (QYC) spectrum could be applied for facilely investigate the influence of spectral changes on the phototransformation of pollutants under varying spatial-temporal (e.g., season, latitude) and climatic conditions (e.g., cloud cover). Our study highlights the wavelength-dependence of both direct and indirect phototransformation of pollutants, and the UV part of natural sunlight plays a decisive role in the phototransformation of pollutants.

Использование смартфона в твердофазно-флуориметрическом определении некоторых полипептидных антибиотиков в лекарственных препаратах

The analysis of semi-products at different stages of production and finished medicinal products is an integral part of an effective quality assurance system for pharmaceutical production. The traditional methods used in the pharmaceutical field, such as capillary electrophoresis, gas and liquid chromatography, are quite versatile and effective. However, they are distinguished by the high cost of instrumentation and component materials, the need to use high-purity solvents, the lack of mobility and the possibility of in situ studies. Such shortcomings can be overcome by using the digital colorimetry method. Its significant popularization has been facilitated by the development of portable and personal electronic devices, among which the smartphone can be distinguished. The aim of the work was to develop a fast and simple method for the determination of a number of polypeptide antibiotics in drugs by digital colorimetry using a smartphone as a color recording device. To implement the solid phase fluorimetric determination of polypeptide antibiotics, HPTLC plates based on silica gel with an aluminum substrate were used as a matrix. Under these conditions, the fluorescence of actinomycin D, virginiamycin M1, virginiamycin S1, and novobiocin was observed when exposed to monochromatic radiation in the UV part of the spectrum (365 nm). The measurement of fluorescence intensity on the surface of the matrices was carried out using a smartphone. Calibration characteristics were constructed for the determination of polypeptide antibiotics in the concentration range of 32–500 μg/mL. The method for assessing the quality of finished drugs was tested on commercial products “Piostacin”, “Cosmegen”, “Dactinomycin” purchased in retail chains. The relative standard deviation of the analysis results does not exceed 0.05. The duration of the analysis was 10–15 min. Based on the results of the studies, the paper presents a method for determining some antibiotics of the polypeptide series by the intrinsic fluorescence of deposited solutions on a solid substrate during treatment with monochromatic UV radiation. The experimental delivery conditions used allow the analysis of drugs based on actinomycin D, virginiamycin M1, virginiamycin S1, and novobiocin.

A critical evaluation of decadal solar cycle imprints in the MiKlip historical ensemble simulations

Abstract. Studies concerning solar–terrestrial connections over the last decades claim to have found evidence that the quasi-decadal solar cycle can have an influence on the dynamics in the middle atmosphere in the Northern Hemisphere (NH) during the winter season. It has been argued that feedbacks between the intensity of the UV part of the solar spectrum and low-latitude stratospheric ozone may produce anomalies in meridional temperature gradients which have the potential to alter the zonal-mean flow in middle to high latitudes. Interactions between the zonal wind and planetary waves can lead to a downward propagation of the anomalies, produced in the middle atmosphere, down to the troposphere. More recently, it has been proposed that top-down-initiated decadal solar signals might modulate surface climate and synchronize the North Atlantic Oscillation. A realistic representation of the solar cycle in climate models was suggested to significantly enhance decadal prediction skill. These conclusions have been debated controversial since then due to the lack of realistic decadal prediction model setups and more extensive analysis. In this paper we aim for an objective and improved evaluation of possible solar imprints from the middle atmosphere to the surface and with that from head to toe. Thus, we analyze model output from historical ensemble simulations conducted with the state-of-the-art Max Planck Institute for Meteorology Earth System Model in high-resolution configuration (MPI-ESM-HR). The target of these simulations was to isolate the most crucial model physics to foster basic research on decadal climate prediction and to develop an operational ensemble decadal prediction system within the “Mittelfristige Klimaprognose” (MiKlip) framework. Based on correlations and multiple linear regression analysis we show that the MPI-ESM-HR simulates a realistic, statistically significant and robust shortwave heating rate and temperature response at the tropical stratopause, in good agreement with existing studies. However, the dynamical response to this initial radiative signal in the NH during the boreal winter season is weak. We find a slight strengthening of the polar vortex in midwinter during solar maximum conditions in the ensemble mean, which is consistent with the so-called “top-down” mechanism. The individual ensemble members, however, show a large spread in the dynamical response with opposite signs in response to the solar cycle, which might be a result of the large overall internal variability compensating for rather small solar imprints. We also analyze the possible surface responses to the 11-year solar cycle and review the proposed synchronization between the solar forcing and the North Atlantic Oscillation. We find that the simulated westerly wind anomalies in the lower troposphere, as well as the anomalies in the mean sea level pressure, are most likely independent from the timing of the solar signal in the middle atmosphere and the alleged top-down influences. The pattern rather reflects the decadal internal variability in the troposphere, mimicking positive and negative phases of the Arctic and North Atlantic oscillations throughout the year sporadically, which is then assigned to the solar predictor time series without any plausible physical connection and sound solar contribution. Finally, by applying lead–lag correlations, we find that the proposed synchronization between the solar cycle and the decadal component of the North Atlantic Oscillation might rather be a statistical artifact, affected for example by the internal decadal variability in the ocean, than a plausible physical connection between the UV solar forcing and quasi-decadal variations in the troposphere.

Metal–semiconductor–metal detectors ZnS/GaP for the ultraviolet and visible part of the spectrum with electrically tunable spectral photosensitivity

High-quality ZnS epitaxial layers grown on GaP semiconductor substrates by MOCVD method. Photodetectors of the visible and UV parts of the spectrum based on new interdigitated Schottky barrier metal–semiconductor–metal (MSM) contacts to semiconductor structure ZnS/GaP. The detectors exhibit low dark current values. The dependence of the characteristics of the spectral response of detectors on voltage has been established offsets. It was found that the long-wavelength response boundary of ZnS/GaP MSM detectors can shift from 355 to 450 nm when the bias voltage changes from 10 to 30 V. At the maximum photosensitivity wavelength of 450 nm, the ampere-watt sensitivity of the detector was 0.3 A/W at a bias voltage of 60 V, and the quantum efficiency was 82%.

Photodetectors based on chemical vapor deposition or liquid processed multi-wall carbon nanotubes

Carbon nanotubes (CNTs) have attracted great interest for applications due to their unique mechanical, electronic and optoelectronic properties. The advantages of the multiple wall carbon nanotubes for optoelectronic devices like photodetectors and photodiodes are the large effective photo-collector surface as well as the possibility to tune the band gap and absorbance by controlling the growth parameters. In this work, we demonstrate two types of hybrid Multi-Wall CNTs/Si3N4/n-Si photodetectors based on ordered (produced with Chemical Vapor Deposition – CVD) and solution processed MWCNTs and evaluate their performance in UV and visual spectrum (275 nm, 655 nm). Device parameters were obtained by comparison of I–V characteristics to Schottky barrier models and C–V characteristics to standard MIS capacitor models. The role of silicon nitride layer was also examined by comparing devices with different nitride layer thickness. Focusing on the UV part of the spectrum, the solution processed device was photosensitive in the voltage range 3V–6V giving its best performance (External Quantum Efficiency - E.Q.E. 85%@275 nm) at 5V and illumination of 5 μW. The CVD processed device showed lower EQE for the same bias voltage range. Both devices showed a low performance in optical part of the spectrum compared to the corresponding one in the UV part of the spectrum. The mean optical responsivity values obtained at the UV part of the spectrum in both cases indicate that the Visible light blind MWCNT/Si3N4/n-Si system have a potential use in UV photodetector applications. In particular, solution processed devices may pave the way for cheap production of UV sensor systems.

Enhancement of Luminescence of PET Films after Swift Heavy Ion Irradiation

The novelty of the study is that the ordering that occurs in a PET film under the action of SHI irradiation manifests itself as an increase in the integral intensity of intrinsic luminescence. The Urbach behaviour of the red shift of the absorption edge is used as a baseline for further analysis of experimental optical transmission spectra of PET films irradiated by swift heavy ions (SHI) previously published by the authors. Negative deviations of the experimental spectra from the Urbach baseline in the visible and UV parts of the spectrum are attributed to enhanced by SHI irradiation intrinsic luminescence. The observed dependence of the integral intensity of luminescence of irradiated PET films on the SHI fluence and ion charge provides further confirmation of the presence of SHI-induced ordering of the molecular structure in SHI latent tracks.

The neglected influence of zinc oxide light‐soaking on stability measurements of inverted organic solar cells

AbstractAlthough zinc oxide (ZnO) is one of the most commonly used materials for electron transport layers in organic solar cells (OSCs), it also comes with disadvantages such as the so‐called light‐soaking issues, i.e., its need for exposure to UV light to reach its full potential in OSCs. Here, the impact of ZnO light‐soaking issues on stability measurements of OSCs is investigated. It is found that in the absence of UV light a reversible degradation occurs, which is independent of the used active layer material and accelerates at higher temperatures but can be undone with a short UV exposure. This reversible aging is attributed to the re‐adsorption of oxygen, which for manufacturing reasons is trapped at the interface of ZnO, even in an oxygen‐free environment. This oxygen can be removed with a UV pretreatment of the ZnO but at the expense of device efficiency and production that has to take place in an oxygen‐free environment. This study establishes that stability measurements of ZnO‐containing OSCs must be performed exclusively with a light source including a UV part since the usage of a simple white light source – as often reported in the literature – can lead to erroneous results.

Doped Graphene Quantum Dots UV-vis Absorption Spectrum: A High-Throughput TDDFT Study.

We report on time-dependent density functional theory calculations of the excited states of 63 different graphene quantum dots (GQDs) in square shape with side lengths of 1, 1.5, and 2 nm. We investigate the systematics and trends in the UV-vis absorption spectra of these GQDs, which are doped with elements B, N, O, S, and P at dopant percentages of 1.5%, 3%, 5%, and 7%. The results show how the peaks in the UV and visible parts of the spectrum as well as the total absorption evolve in the chemical parameter space along the coordinates of size, dopant type, and dopant percentage. The absorption spectra calculated here can be used to obtain particular GQD mixture proportions that would yield a desired absorption profile such as flat absorption across the whole visible spectrum or one that is locally peaked around a chosen wavelength.

Effect of the crystal structure on the optical properties and Ag sensitization of Tb3+/Yb3+ ions in silica-zirconia glasses and glass-ceramics

The role of the material structure in the energy transfer between Ag and Tb3+/Yb3+ ions is studied in silica-soda-zirconia sol-gel glasses and glass-ceramics. The preparation of Tb3+ and Yb3+ doped silica-soda-zirconia layers was carried out by sol-gel and dip-coating, followed by thermal annealing. The precipitation of zirconia nanocrystals was obtained by controlling the annealing temperature: from a full amorphous glass at 700 °C into a glass-ceramic at 1000 °C. A different crystalline structure of zirconia nanocrystals, tetragonal or cubic, was controlled by the rare-earth doping and investigated in relation to the Tb3+/Yb3+ optical properties. Moreover, Ag codoping was introduced by ion-exchange, obtaining a significant photoluminescence enhancement, both in the intensity and in the broadness of the excitation band, covering the whole UV region and part of the violet-blue region. Ag-sensitized Tb3+/Yb3+ doped silica-soda-zirconia glass-ceramics were attested to be potential candidates for energy-related applications, such as spectral conversion layers for solar cells, lasers and light-emitting devices (LEDs) in the visible and NIR spectral regions.

Multipurpose Solar Photoelectrochemical Hybrid Multilayer Films Based on Porphyrin and Preyssler Type Polyoxometalates for Solar Cell and Ag Nanomaterial Synthesis

Multilayer films with electrostatic interaction between Preyssler,s Polyanions (NH4)14[NaP5W30O110]14- .31H2O and tetracationic free base porphyrin [H2TN+(Me)3PyP]4+ have been alternately deposited on quartz and ITO substrates. and characterized by UV-visible absorption spectroscopy to follow the successive deposition of multilayer film. Solution phase interaction of both components revealed the stiochiometric ratio of the electrostatic complex formed . The morphology and composition of films were studied by atomic force microscopy and X-ray photoelectron spectroscopy (XPS ) .While permeability to cations in aqueous media and redox behavior were studied by cyclic voltametry . The solar photoctalytic activity of hybrid films is identified by TEM images obtained after heterogeneous aqueous photoreduction of Ag2SO4(aq) and KAuCl4 (aq) to yield diversified nanostructures . The study is first and initial report on preyssler type polyanions and porphyrin based heterogenous photocatalysis that provide a green, solar and multiple applications for precious metal recovery as nanoparticle ,sustainable wastewater purification and solar photocurrent generation.Polyoxometalates (POMs) are metal−oxygen framework of early metal elements in their highest oxidation state , able to undergo reversible, stepwise, multielectron-transfer reactions, which are the basis for many catalytic processes[1].These polyanions clusters exhibit applications in catalysis, medicine, materials science [2]. They offer effective photocatalytic properties in oxidation and reduction processes. On photolysis, the high oxidizing ability of excited POMs can lead to the degradation of a variety of organic compounds such as pollutants, leading to a process for water purification [3]. In the presence of a sacrificial electron donor , their photolysis lead to the formation of reduced POMs which can in turn reduce metallic ions. It could be a good alternative for precious metals recovery or synthesis of metal nanoparticles. [4,5]. However, polyoxometalates absorb in the uv part of spectrum, thus they require UV excitation, which cease its large-scale environmental application. One of obvious strategy is to couple it with some chromophore group which can be sensitized by visible light. Metal porphyrins are attractive components in materials because of their appealing chemical and photochemical properties: high stability, intense visible absorption bands, long-lived excited states, and tunability by chemical derivatization [2]. Figure 1.1 R.H.S. Representation of the porphyrin used 5, 10, 15, 20-Tetrakis (4-trimethylammoniophenyl) porphyrin tetra(p-toluenesulfonate), namely [H2TN+(Me)3PyP]4+) used with the Preyssler type (NH4)14[NaP5W30O110]14- .31H2O . L.H.S. UV-visible record on quartz and ITO shows layer by layer absorbance. Formation of Multilayer Films :H2TN+(Me)3PyP4+] / [(NH4)14[NaP5W30O110]14- .31H2O ] The alternate deposition of positively charged porphyrin, H2TN+(Me)3PyP4+, and negatively charged [NaP5W30O110]14-on slides of quartz and Indium tin Oxide (ITO) lectrodes by layer-by-layer were performed.

Synthesis, experimental and theoretical characterization of a new copolymer bearing pyrrole and anthracene units

The present work represents an experimental and theoretical investigation of a new copolymer having Anthracene and Pyrrole units named poly [anthracene-polypyrrole] and noted poly[ANT-PPy]. The synthesized material was obtained by oxidative polymerization of anthracene and pyrrole monomers using the ferric chloride (FeCl3) as an oxidant agent. Prepared material was experimentally characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), and thermogravimetric analysis measurements (ATD/TGA). The FTIR analysis confirmed the formation of a new backbone incorporating a unit of pyrrole associated to anthracene group. The XRD and SEM analyses showed that the poly[ANT-PPy] material exhibited an ordered phase of low crystalline. Based on optical absorption analysis, the obtained material absorbs essentially in the UV part with a shoulder absorption band in the visible part centered at 410 nm. Thermal analysis (ATD/TGA) showed that the obtained material had excellent thermal properties compared to that of unmodified one. Besides, electronic and structural properties of synthesized copolymer were examined through a computational approach using Density Functional Theory (DFT) method. The experimental optical band gap was found to be 2.76 eV while theoretically calculated value was 3.37 eV. The synthesized material showed promising properties that would favorite future exploration and applications.

High photocatalytic efficiency of α-Fe2O3 - ZnO composite using solar energy for methylene blue degradation

The present report illustrates the photocatalytic degradation of methylene blue dye under solar energy through α-Fe2O3 - ZnO composite synthesized by adopting a facile and simple chemical method. Various characterization techniques particularly X-ray diffraction (XRD), Transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR), etc., have been employed to characterize the as-synthesized composite. The XRD reveals the successful formation of the as-synthesized sample. The TEM studies illustrate the agglomeration of particles with sizes in the range of ∼10–60 nm. HRTEM micrograph indemnifies the formation of lattice fringes pertaining to inter-planner spacing∼ 0.149 nm and ∼0.138 nm corresponding to (214) reflection plane of hematite and (112) reflection plane of ZnO, respectively. The as-synthesized α-Fe2O3 – ZnO composite shows double absorption edges which correspond to the bandgap of α-Fe2O3 (2.2 eV) and ZnO (3.2 eV). Furthermore, α-Fe2O3 - ZnO composite shows a remarkable enhanced degradation capacity than bare hematite nanoparticles and zinc oxide nanoparticles, and α-Fe2O3 – ZnO (1:2) composite demonstrates the best degradation performance among all the variants. Moreover, it clearly suggests that the UV part of solar light plays a vital role in the catalytic degradation of methylene blue whereas the visible part of light remains unresponsive.

Upwelling Irradiance below Sea Ice—PAR Intensities and Spectral Distributions

Upwelling and downwelling spectral (320–920 nm) distributions and photosynthetic active radiation (PAR) intensities were measured below a first-year land-fast sea ice in a western Greenland fjord with and without a snow cover. Time-series of surface upwelling PAR, downwelling PAR, and under-ice PAR were also obtained. Spectral distributions of upwelling and downwelling irradiances were similar except for reduced intensities in the UV, the red, and NIR parts of the spectrum when the ice was snow-covered. Upwelling PAR amounted to about 10% of downwelling intensities, giving 5.1 µmol photons m−2 s−1 at the bottom of the ice with a snow cover and 8.2 µmol photons m−2 s−1 without. PAR partitioning analyses showed that the upwelling was related to scattering by suspended particles in the water column. A snow melt increased under-ice daily maximum downwelling PAR from 50 to 180 µmol photons m−2 s−1 and overall under-ice PAR of 55 and 198 µmol photons m−2 s−1 with 10% upwelling. It is concluded that upwelling PAR below sea ice might be an important factor regarding sea ice algae photophysiology and performance with a 10% higher PAR; specifically when PAR > Ek the light saturation point of the sea ice algae.

Synthesis, spectroscopic, electrochemical and photophysical properties of high band gap polymers for potential applications in semi-transparent solar cells

BackgroundThe design of new polymers able to filter the electromagnetic spectrum and absorb distinctly in the UV and high-energy part of visible spectrum is crucial for the development of semi-transparent solar cells. Herein, we report on the synthesis and spectroscopic, electrochemical, and photophysical characteristics of three new polymers, namely (i) Poly(triamterene-co-terephthalate), (ii) Poly[triamterene-co- 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-p,p′-disulfonamide], and (iii) Poly(5-hydroxyindole-2-carboxylate) that might show promise as materials for semi-transparent solar cells.ResultsThe energy band gap, refractive index, dielectric constant, and optical conductivity of the electron donor polymer, poly(triamterene-co-terephthalate), were determined to be 2.92 eV, 1.56, 2.44 and 2.43 × 104 S cm−1, respectively. The synthesized electron acceptor polymers showed a relatively high refractive index, dielectric constant, and optical conductivity. The presence of a direct allowed transition was confirmed between intermolecular energy bands of the polymers.ConclusionsThe polymers showed relatively high energy gap and deep HOMO levels, making them strong absorbers of photons in the UV region and high energy part of the visible region. The synthesized donor and acceptors performed well relative to P3HT and fullerenes due to the close match of the HOMO and LUMO levels. With further development, the polymers could be viable for use as the active layers of semi-transparent solar cells.

Is color data from citizen science photographs reliable for biodiversity research?

Color research continuously demands better methods and larger sample sizes. Citizen science (CS) projects are producing an ever‐growing geo‐ and time‐referenced set of photographs of organisms. These datasets have the potential to make a huge contribution to color research, but the reliability of these data need to be tested before widespread implementation.We compared the difference between color extracted from CS photographs with that of color extracted from controlled lighting conditions (i.e., the current gold standard in spectrometry) for both birds and plants. First, we tested the ability of CS photographs to quantify interspecific variability by assessing > 9,000 CS photographs of 537 Australian bird species with controlled museum spectrometry data. Second, we tested the ability of CS photographs to quantify intraspecific variability by measuring petal color data for two plant species using seven methods/sources with varying levels of control.For interspecific questions, we found that by averaging out variability through a large sample size, CS photographs capture a large proportion of across species variation in plumage color within the visual part of the spectrum (R2 = 0.68–0.71 for RGB space and 0.72–0.77 for CIE‐LAB space). Between 12 and 14 photographs per species are necessary to achieve this averaging effect for interspecific studies. Unsurprisingly, the CS photographs taken with commercial cameras failed to capture information in the UV part of the spectrum. For intraspecific questions, decreasing levels of control increase the color variation but averaging larger sample sizes can partially mitigate this, aside from particular issues related to saturation and irregularities in light capture.CS photographs offer a very large sample size across space and time which offers statistical power for many color research questions. This study shows that CS photographs contain data that lines up closely with controlled measurements within the visual spectrum if the sample size is large enough, highlighting the potential of CS photographs for both interspecific and intraspecific ecological or biological questions. With regard to analyzing color in CS photographs, we suggest, as a starting point, to measure multiple random points within the ROI of each photograph for both patterned and unpatterned patches and approach the recommended sample size of 12–14 photographs per species for interspecific studies. Overall, this study provides groundwork in analyzing the reliability of a novel method, which can propel the field of studying color forward.

Ellipsometry Study of Hexagonal Boron Nitride Using Synchrotron Radiation: Transparency Window in the Far‐UVC

The linear optical response of the ultrawide bandgap h‐BN is investigated by spectroscopic ellipsometry. The ordinary dielectric function of h‐BN is determined up to 25 eV on a high‐quality single‐crystal platelet. The direct bandgap and the high‐energy transitions are characterized with the aid of ab initio self‐consistent GW calculations and the optical properties are calculated using the Bethe–Salpeter equation. The dispersion of the ordinary refractive index in the visible and UV part of the spectrum below the bandgap is in excellent agreement with previous transmission experiments. A sharp excitonic peak at 6.1 eV associated with the direct bandgap dominates the absorption spectrum, and a second peak is observed at 6.8 eV. At higher energies, a strong absorption peak emerges at 15 eV associated with higher σ → σ* transitions. As a consequence of the unique electronic band structure of h‐BN, a transparency window is observed in the far‐UV region between 7 and 13 eV, where the light penetration depth reaches a value of 38 nm, as opposed to the value of 0.8 nm at the absorption peak of the fundamental bandgap.