Reference UVC LED Source

A compact reference UVC source based on commercially available LED has been developed. The article presents the design and results of the study of the optical characteristics of the radiation of the reference UVC LED source. The source provides a power density of radiation up to 400 μW/cm2 on area of 3×3 mm with inhomogeneity of 1.5 %.The emission band of a source with a maximum of 265 nm is predominantly 97 % in the UV-C spectrum region, and a small part of it is inUV-B and UV-A regions, 2.7 % and 0.3 %, respectively. The use of ComboSource for laser diodes allowed to precisionally stabilize the injection current and temperature of the LED. It is shown that overheating of the active region of the selected UV LED is only 10°C - 25°C at the recommended injection currents due to the peculiarities of its design. This results in a low degradation rate of the UV LED. Possible ways to improve the characteristics of the reference UVCsource are discussed.

Comparative study of the electronic structure and optical properties of the Heusler alloys Co2MGa and Co2MAl (M = Fe and Ni)

The electronic structure and optical properties of the Heusler alloys Co2NiGa, Co2NiAl, Co2FeGa, and Co2FeAl are reported and compared in this work. In the Fe-based alloys, Co2FeGa and Co2FeAl, the electronic structure is found to have 100% spin polarization with the indirect energy gap in the [Formula: see text]-[Formula: see text] direction, whereas in Co2NiGa and Co2NiAl, the density of states is metallic in both spin projections with spin polarization of 55% (Co2NiGa) and 37% (Co2NiAl). Total and Co partial magnetic moments of all Heusler alloys for the optimized lattice parameters were found in a good agreement with previous calculations and experimental data. The frequency dependence of the real and imaginary parts of the complex dielectric constant for the Heusler alloys is studied in the spectrum region of 0.08–5 eV. The research results are discussed based on the performed calculations of the electronic structure. It was found that the character of variations of the spectral parameters of the alloys is typical for media with the metallic conductivity. In the IR region, the mechanism of the intraband acceleration of electrons by the light wave field dominates. The significant changes in the optical spectrum, magnetic moment, spin polarization and electronic structure were revealed in Co2MGa and Co2MAl for different M atoms which motivate further investigations of the Co-based Heusler alloys as promising materials for spintronics.

Efficiency Enhancement in Dye Sensitized Solar Cell Using 1D Photonic Crystal

1D SiO2/TiO2 photonic crystal based ZnO-Pt DSSC with N719 dye is theoretically designed. The optical properties of theoretically designed DSSC such as transmittivity, Absorptivity and reflectivity are calculated using transfer matrix method in order to calculate numerically the key parameters like open circuit voltage (VOC), Photo current density (Jph) of the DSSC. It is found that the desired integrated system may enable to maximize the absorption in the selective spectrum region (400-900nm) and hence the maximum efficiency achieved is 4.5 % for a 1D SiO2/TiO2 photonic crystal layers with two number of periods.

Construction of PtSe2/Ge heterostructure-based short-wavelength infrared photodetectors array for image sensing and optical communication applications

In this work, we present the construction of a multilayered PtSe2/Ge heterostructure-based photodetectors array comprising 1×10 device units operating in the short-wavelength infrared (SWIR) spectrum region. The as-fabricated heterostructures show...

Hyperspectral longwave infrared reflectance spectra of naturally dried algae, anthropogenic plastics, sands and shells

Remote sensing of litter is foreseen to become an important source of additional information relevant to scientific awareness about plastic pollution. Here, we document directional hemispherical reflectance measurements of anthropogenic and natural materials gathered along the shorelines of the Chiloé Archipelago, Chile. These spectral observations were completed in a Chilean laboratory using a state-of-the-art hyperspectral HyLogger-3™ thermal infrared (TIR) spectrometer starting from the medium-wave infrared spectrum (6 µm) and going to the longwave infrared (14.5 µm) spectrum at 0.025 µm intervals. The samples we investigated included sands, shells, algae, nautical ropes, Styrofoam®, gunny sacks and several fragments of plastic-based items. The apparent visible colours of these samples included shades of black, blue, brown, green, orange, white and yellow. We grouped the samples using robust statistical approaches (derivatives, peak-seeking technique) and visual analyses of the derived hyperspectral reflectances. In each group we derived an average or TIR end-member signal and determined diagnostic wavebands. Most of the diagnostic wavebands picked were found to be inside the atmospheric window of the TIR spectrum region. Furthermore, this laboratory reference dataset and findings might become useful in related field observations using similar thermal infrared technologies, especially in identifying anomalies resulting from environmental and meteorological perturbations. Validation and verification of proposed diagnostic wavebands would be part of a continuing effort to advance TIR remote sensing knowledge as well as support robust detection algorithm development to potentially distinguish plastics in litter throughout the natural environments. Data are available in open-access form via the online repository PANGAEA, database of the World Data Center for Marine Environmental Sciences: https://doi.org/10.1594/PANGAEA.919536 (Acuña-Ruz and Mattar, 2020).

Hyperspectral longwave infrared reflectance spectra of dry anthropogenic plastics and natural materials

Remote sensing of litter is foreseen to be an important source of additional information relevant to scientific awareness about plastic pollution. Here, we document directional hemispherical reflectance measurements of anthropogenic and natural materials gathered along the shorelines of Chiloé Archipelago, Chile. These spectral observations were completed in a laboratory using a state-of-the-art hyperspectral HyLogger-3™ spectrometer in the thermal infrared (TIR) region; medium wave infrared (6000 nm) to long wave infrared (14 500 nm) spectrum at 25 nm intervals. The samples we investigated included sands, shells, algae, nautical ropes, Styrofoam®, gunny sacks and several fragments of plastic based items. The visible colours of these samples included shades of black, blue, brown, green, orange, white and yellow. We grouped the samples using robust statistical approaches (derivatives, peak seeking technique) and visual analyses of the derived hyperspectral reflectances. In each group we derived the average or TIR end-member signal as well as deduced diagnostic wavebands. Most of the diagnostic wavebands picked were found to be inside the atmospheric window of the TIR spectrum region. Furthermore, this laboratory reference dataset and findings might become useful in related field observations using similar thermal infrared technologies, especially in identifying anomalies resulting from environmental and meteorological perturbations. Validation and verification of proposed diagnostic wavebands would be part of a continuing effort to advance TIR remote sensing knowledge as well as assist robust detection algorithm development to potentially distinguish plastics in litter throughout the natural environments. Data is available in open-access via the online repository PANGAEA database of the World Data Centre for Marine Environmental Sciences https://doi.pangaea.de/10.1594/PANGAEA.919536 (Acuña-Ruz and Mattar B., 2020).

Rapid inactivation of SARS-CoV-2 with LED irradiation of visible spectrum wavelenghts

The COVID-19 pandemic has caused a global health crisis. The difficulty to control the viral spread due to the absence of vaccines and prophylactics measures has raised concerns about prevention and control of SARS-CoV-2. Therefore, it becomes more and more crucial the reduction of environmental risk factors through viral inactivation of aerosols and fomites. Photodynamic inactivation of microorganisms by light energy emitted in the visible spectrum region (VIS), not harmful for mammalian cells and safe for humans, has recently been described. A LED-device emitting a special combination of frequencies in the visible light spectrum was tested on SARS-CoV-2 infected cell surnatant dilutions in order to evaluate the antiviral efficacy. This preliminary in vitro study showed for the first time the ability to inactivate SARS-CoV-2 through LED irradiation of visible spectrum wavelengths. If further and more extensive studies will confirm these data, the usage of this LED could potentially have a big impact on the sanitization of virtually all human environments.