UV Part Research Articles

Spectral diagnostics of an optical discharge propagating along a hollow-core optical fibre

The results of spectral diagnostics of an optical discharge (OD) plasma propagating through a hollow-core revolver fibre under the action of repetitively pulsed laser radiation are presented. The revolver fibre is made of silica glass, with a diameter of the hollow core being 20 μm. The peak values of the laser radiation intensity reach 1012 W cm−2at an average Nd : YAG laser power of about 2 W. The time-averaged spectrum of the OD plasma in the visible range has the form of a continuum and is close to the blackbody spectrum with a temperature of 13.3 – 17 kK. The form of the spectrum does not depend on the gas filling of the fibre core (air or argon). In the UV part of the spectrum, lines of neutral silicon are observed, which are indicative of the partial evaporation of the reflecting cladding of the fibre.

Shuffle algebra realization of quantum affine superalgebra [formula omitted

Inspired by [12], we give shuffle algebra realization of positive part of quantum affine superalgebra Uv(Dˆ(2,1;θ)) associated to any simple root systems. We also determine the shuffle algebra associated to slˆ(2|1) with odd root system when v is a primitive root of unity of even order, generalizing results in [4].

Analyzing the synthesis of various inorganic nanoparticles and their role in UV-shielding

In recent days we have been using many devices equipped with LED in one or other way, as display or light sources. These sources have large contribution of UV emission in their total emission of light. This adds the amount of UV radiations and its effect which we have already faced during the exposure of sun. To protect not only the human body, skin and eyesight, but also some essential surfaces of exteriors, plastic roof, we need some protecting film/materials that can absorb UV part from light radiation. Already aware of the harm that UV-A and UV-B rays from sun cause to the biotic components of the ecosystem, researchers and scientists have started seriously working in developing some films using polymer nanocomposites or nanomaterials which have improved tranceparancy, flexibility, durability features. Mainly concentrating on UV shielding applications, the article talks about various nanoparticles prominently used in the said purpose, namely CeO2, TiO2, ZnO, MnO2 and graphene oxide. Along with their respective synthesis methods, particle size, band gap, other experimental results have been highlighted. Green synthesis of ZnO nanoparticles with the assistance of fungus and bacteria also finds mention which is significant in reducing our dependence on chemicals. Hexagon shaped pristine and Al doped ZnO nanodisks (NDs) with exposed ± [0001] polar facets successfully synthesized with absolute ethanol: water system as dual solvent mixture show exceptionally good absorbance of 99% in UV range upto 390 nm. It also emphasizes upon the importance of the synergistic effect of the incorporated nanoparticles & the matrix material used and the conversion of cellulose acetate matrix into cellulose acetate naphthoate in order to enhance its service life in the commercial anti-UV applications.

The structural and optical band gap energy evaluation of nano TiO2 powders by diffuse reflectance spectroscopy prepared via combustion method

Nanocrystalline TiO2 powders with different optical band gap have been successfully prepared using solution combustion method starting directly from titanium metal. The emphasis is placed on the role of fuel urea on the variations of optical band gap which is obtained from DRS data in the range of 190–1100 nm. The samples were characterized with XRD, FTIR, FESEM, and DRS. It is shown that the powders calcined at 800 ℃ are predominantly anatase and minor rutile according to XRD results where the crystallite size ranges from 13.2 nm to 22 nm. The size of powders can affect the photo catalytic activity of TiO2 where the surface/ volume ratio determines the available sites for electrons to migrate. The micronized aggregated powders composed of sub-particles in the order of less than 100 nm have no preferred morphology based-on FESEM images. FTIR analysis satisfactorily matched with the standard data. The results of diffuse reflectance spectroscopy (DRS) accompanied with mathematical calculations extracted the values of optical direct band gap of TiO2 powders in the range of 3.53 to 3.6 eV which is in the border of UV and Vis part of electromagnetic radiation. Overall, optical band gap and crystallite size can be controlled by fuel in combustion method.

Transparent regenerated cellulose bionanocomposite film reinforced by exfoliated montmorillonite with polyhedral oligomeric silsesquioxane bearing amino groups

ABSTRACT Here, transparent films were prepared from regenerated cellulose. Microcrystalline cellulose was solubilized in N,N-dimethylacetamide with lithium chloride. Exchange of organic solvent for water resulted in the gelation of solution. Transparent hydrogel served then for stable film preparation. No cellulose chemical modification and cross-linking was applied. To reinforce films, 5 wt% montmorillonite was added. Both pristine and modified clay was used. Modification was provided through intercalation by synthesized polyhedral oligomeric silsesquioxane (POSS) bearing eight amino groups. Examination of films with modified montmorillonite revealed its exfoliation for clay nanoparticles and POSS in the course of their preparation. In that case, a significant increase of tensile strength and elongation at break was observed, while a notable decrease of transparency for the UV part of the sun spectrum was also observed, which is important for the UV protection by cellulosic materials.

Harvesting the lost photon by plasmonic enhanced hematite-upconversion nanocomposite for water splitting.

Converting solar energy to chemical energy in the form of hydrogen via water splitting is one of the promising strategies to solve the global energy crisis. Hematite, a traditional semiconducting oxide photoelectrode, can only absorb UV and visible parts of the solar spectrum, losing 40% infrared energy. In this paper, we report a novel plasmonic enhanced water splitting photoanode based on hematite-lanthanide upconversion nanocomposites to harvest lost photons below the bandgap of hematite. NaYF4:Er, Yb upconversion nanoparticles can upconvert photons from 980 nm to 510 nm-570 nm within the bandgap of hematite. More importantly, a gold nanodisk array with a plasmonic peak centered ∼1000 nm can further boost the photocurrent by 93-fold. It is demonstrated that the excitation process of lanthanide upconversion nanoparticles can be significantly enhanced by plasmonic nanostructures and can thus improve the water oxidation activity via plasmonic enhanced upconversion and hot electron injection, respectively. This new promising strategy will pave the way for plasmonic enhanced lost photon harvesting for applications in solar energy conversion.

Plumage coloration and morphometrics of the Little Owl Athene noctua in the Western Palearctic

The Little Owl is a species with a wide range in the Palearctic. Thirteen subspecies have been described based on small coloration or size differences. Recently, genetic studies in the western portion of the European range have shown the presence of some well distinct clades. We examined the variation in structural size and coloration of Western Palearctic birds, with particular attention to the pattern of light and dark pigmentation on the tail, and we checked for the presence of UV reflection through reflectance spectroscopy. We did not find clear-cut differences in size or plumage between the currently accepted subspecies, nor between individuals pertaining to the different genetic clade areas. There is a trend for individuals from the western genetic clade (Iberia, France, England and central Europe) to have longer tarsus with smaller wings, while individuals from the eastern generic clade (Balkans) have an opposite pattern. Italian birds are intermediate. The tail of Balkan birds has a wider dark pigmentation, with reduced light spots. Little owl feathers do not show reflectance in the UV part of the spectrum. We found a very large variation of morphological and color patterns between individuals collected in the same geographical area. Currently, the arrangement of individuals to any Little owls' subspecies on morphological data appears to be a very difficult task.

Biofortification with selenium and iodine changes morphological properties of Brassica oleracea L. var. gongylodes) and increases their contents in tubers

Kohlrabi (Brassica oleracea L. var. gongylodes L.) was biofortified with selenium (Se), as selenite and selenate, and iodine (I), as iodide and iodate, and their combinations through foliar spraying, to study absorption of these elements by the plants, separately and in combination. The effects on selected physiological and morphological traits and optical characteristics were monitored. Treatments with Se positively affected total chlorophylls and carotenoids, and leaf stomata dimensions. Addition of I decreased total chlorophylls and increased anthocyanins. In reflectance spectra of the leaves, specific colour regions differed significantly due to the different treatments. Reflectance in the UV correlated positively with Se and I contents of the leaves, which indicated lower demand for production of phenolic compounds. Differences in reflectance in UV part of the spectra could be a consequence of changes in the cuticle. The Se and I levels increased markedly in leaves and tubers, without loss of biomass or yield. Se had antagonistic effects on accumulation of I in leaves. The similar levels of Se and I in the leaves and tubers suggest that the transport of both elements in these plants occurs from the leaves to the tubers through the phloem. According to the Se and I contents in the kohlrabi tubers, biofortification with both elements simultaneously is feasible for human nutrition.

Super alkali (OLi3) doped boron nitride with enhanced nonlinear optical behavior

In this study, density functional theory is used to examine the electronic and nonlinear optical properties of a narrative class boron nitride (B[Formula: see text]N[Formula: see text]) doped with super alkali OLi3. From the computational investigations, these complexes are highly stable and superalkali prefer a cubic position of the nanocage energetically to be chemisorbed. When superalkali doped on B[Formula: see text]N[Formula: see text], a significant decrease in the HOMO–LUMO energy gap was observed and this shifted the B[Formula: see text]N[Formula: see text] nanocage from insulator to n-type semiconductor. The HOMO–LUMO energy gap of pure B[Formula: see text]N[Formula: see text] was 6.84[Formula: see text]eV and when superalkali (OLi3) is doped on it, the HOMO–LUMO energy gap was changed in the range of 3.94–0.42[Formula: see text]eV. BNM2b showed a HOMO–LUMO energy gap of 3.94[Formula: see text]eV, while BNM4a showed a minimum HOMO–LUMO energy gap (0.42[Formula: see text]eV). Further, these systems showed a remarkable large first hyperpolarizability ([Formula: see text]) in the range of 626.72–75,757[Formula: see text]au and 1045–12,6261[Formula: see text]au. When the charge was shifted from superalkali to the nanocage, a small change in transition energies has occurred and consequently, hyperpolarizability ([Formula: see text]) values increased significantly. The vertical ionization energy of pure B[Formula: see text]N[Formula: see text] is 7.71[Formula: see text]eV, as superalkali is doped on it showed a significant change in VIE in BNM2b that indicated the highest VIE of about 6.47[Formula: see text]eV and BNM4a indicated lowest VIE 2.51[Formula: see text]eV. The TD-DFT investigations described that complexes illustrated greater transparency in the UV part which involves apart from greater NLO response for practical applications in the area of activity of optoelectronics.

Basics of Photocatalysis and Different Strategy for Enhancing the Photocatalytic Efficiency

This review reports on the basic mechanism of photocatalysis and different ways of enhancing the photocatalytic efficiency. It further examines enhancement of the photocatalytic property using the different combinations of semiconductor oxides (TiO2, ZnO, stratified WO3/TiO2, WO3/ZnO). TiO2, ZnO semiconductors have been widely used from the recent few decades in the photocatalytic degradation process, but the main drawback of these materials is able to utilize the UV part of the solar spectrum. So many researchers tried to utilize a major portion of the solar spectrum using different strategies such as doping, applying external bias, stratified films, etc. The main aim of this review is providing different strategies for enhancing the photocatalytic efficiency.

Optical, acoustic and thermal performance assessment of semi-transparent amorphous silicon PV glazing systems

In this research, a unique PV glazing technology, thermally resistive PV glazing (TRPVG), is introduced, and its thermal, optical and acoustic performance parameters are experimentally investigated. In the previous works, multifunctional benefits of TRPVG as a novel building element such as high thermal resistance, promising electricity generation potential, self-cleaning and competitive cost are addressed. Within the scope of the present research, absorption of UVC and UVA part of incoming sunlight, control of visible light transmittance and solar thermal radiation, reduction of different noise levels, and temperature difference across the PV glazing are comprehensively analysed. The tests are conducted in April 2019 for a specific sample (TRPVG-Ar16) in which a 16 mm thick argon is utilised as inert gas behind a-Si PV cells for thermal resistance, and a novel low-e coated thermally resistive glass is reinforced at the rear. The results reveal that TRPVG-Ar16 is a very good thermal insulator at first glance. The average temperature difference between front and back surfaces is determined to be 16.59 oC, which is promising and a strong function of incoming solar radiation. The average solar radiation is measured to be 527.6 W/m2 during the test period, and the aforesaid value behind the PV glazing is found to be 41.6 W/m2. A similar tendency is observed for the visible light transmittance. Average light intensity measurements from the front and back of TRPVG-Ar16 are reported to be 622.3 and 75.4 Lux, respectively. UVC and UVA measurements reveal that the novel TRPVG-Ar16 technology is capable of blocking 100% of UV part of incoming sunlight, which needs to be noted. The tests carried out for various noise levels also demonstrate that TRPVG-Ar16 is a promising noise absorber. Outside the simulation environment, the noise level is measured to be 84.3 dBA while it is 56.5 dBA for the indoor, which corresponds to about 33% reduction in dBA value.

Gravitational wave spectrometry with a Hong–Ou–Mandel interferometer in space

The possibility to use a Hong–Ou–Mandel (HOM) interferometer to carry out gravitational waves detection and spectrometry is investigated. The noise budget of the instrument is evaluated. The basic experimental requirements are calculated. It is shown that the power and wavelength of the heralded photon source, together with the angular accuracy of the measurement of the photon polarization rotation, form the main constraints to determine the type of gravitational waves sources, which would be the target of HOM gravitational wave spectrometers. The currently available pW power heralded photon sources, with typical heralded photon frequencies in the order of 1014 Hz (visible—UV part of the optical spectrum) are totally unsuitable, in terms of required detection time for any of the GW sources, which are presently targeted by ground and space based GW detectors. The operation of the HOM interferometer as a GW spectrometer is illustrated with a numerical model that uses the gravitational wave strain data recorded by LIGO on 14 September 2015 (GW150914 event). Assuming an angular accuracy of rad for the measurement of photons polarization rotation, these measurements could only be carried out with HOM interferometer’s arm lengths of the order of 10.000 km (only achievable in space, if we do not use optical cavities), and by using heralded photon sources of about 1 W power, producing heralded photons with wavelengths in the radio-wave band of the electromagnetic spectrum, 10 MHz. Although the technology to produce this type of heralded photon sources is currently not available, a brief discussion of the possible implementation of a large arm HOM interferometer in space is introduced.

A low-cost hyperspectral scanner for natural imaging and the study of animal colour vision above and under water

Hyperspectral imaging is a widely used technology for industrial and scientific purposes, but the high cost and large size of commercial setups have made them impractical for most basic research. Here, we designed and implemented a fully open source and low-cost hyperspectral scanner based on a commercial spectrometer coupled to custom optical, mechanical and electronic components. We demonstrate our scanner’s utility for natural imaging in both terrestrial and underwater environments. Our design provides sub-nm spectral resolution between 350–950 nm, including the UV part of the light spectrum which has been mostly absent from commercial solutions and previous natural imaging studies. By comparing the full light spectra from natural scenes to the spectral sensitivity of animals, we show how our system can be used to identify subtle variations in chromatic details detectable by different species. In addition, we have created an open access database for hyperspectral datasets collected from natural scenes in the UK and India. Together with comprehensive online build- and use-instructions, our setup provides an inexpensive and customisable solution to gather and share hyperspectral imaging data.

Stratospheric aerosol characteristics from space-borne observations: extinction coefficient and Ångström exponent

Abstract. Stratospheric aerosols are of a great importance to the scientific community, predominantly because of their role in climate, but also because accurate knowledge of aerosol characteristics is relevant for trace gas retrievals from remote-sensing instruments. There are several data sets published which provide aerosol extinction coefficients in the stratosphere. However, for the instruments measuring in the limb-viewing geometry, the use of this parameter is associated with uncertainties resulting from the need to assume an aerosol particle size distribution (PSD) within the retrieval process. These uncertainties can be mitigated if PSD information is retrieved. While occultation instruments provide more accurate information on the aerosol extinction coefficient, in this study, it was shown that limb instruments are more sensitive to the smaller particles in the visible–near-infrared spectral range. However, the sensitivity of occultation instruments improves if the UV part of the wavelength spectrum is considered. A data set containing PSD information was recently retrieved from SCIAMACHY limb measurements and provides two parameters of the unimodal lognormal PSD for the SCIAMACHY operational period (2002–2012). In this study, the data set is expanded by aerosol extinction coefficients and Ångström exponents calculated from the retrieved PSD parameters. Parameter errors for the recalculated Ångström exponents and aerosol extinction coefficients are assessed using synthetic retrievals. For the extinction coefficient the resulting parameter error is within ±25 %, and for the Ångström exponent, it is better than 10 %. The SCIAMACHY aerosol extinction coefficients recalculated from PSD parameters are compared to those from SAGE II. The differences between the instruments vary from 0 % to 25 % depending on the wavelength. Ångström exponent comparison with SAGE II shows differences between 10 % at 31 km and 40 % at 18 km. Comparisons with SAGE II, however, suffer from the low number of collocated profiles. Furthermore, the Ångström exponents obtained from the limb-viewing instrument OSIRIS are used for the comparison. This comparison shows an average difference within 7 %. The time series of these differences do not show signatures of any remarkable events (e.g., volcanic eruptions or biomass burning events). In addition, the temporal behaviour of the Ångström exponent in the tropics is analyzed using the SCIAMACHY data set. It is shown that there is no trivial relation between the Ångström exponent value at a single wavelength pair and the PSD because the same value of Ångström exponent can be obtained from an infinite number of combinations of the PSD parameters.

UV contributions to energy of a static quark-antiquark pair in large-β0 approximation

The total energy of a static quark-antiquark pair Etot(r)=2mpole+VQCD(r) is known to include O(ΛQCD3r2) and O(ΛQCD3/m‾2) renormalon uncertainties in the large-β0 approximation, after canceling O(ΛQCD) renormalons. We compute the (renormalon-free) genuine UV part in terms of the MS‾ mass m‾, extending a recently-proposed method which conforms with OPE. In particular the r-independent part is determined. The result would help understanding the nature of Etot(r) in the context of OPE with renormalon subtraction.

Formation of Highly Conducting Optically Transparent Films with Multigraphene Structure via Carbonization of Polyimide Langmuir–Blodgett Films

Multigraphene films have been for the first time obtained on the surface of quartz glass via carbonization of polyimide Langmuir–Blodgett films. The Raman spectra of the films show bands G and D and a broad band at 2300–3200 cm–1, which are characteristic of graphite-like films. The transmission electron microscopy demonstrated that the films are constituted by “stacks” of layers spaced by 0.36 nm. The surface resistance of the 5-nm-thick films was 1.2 ± 0.2 kΩ, and the transmittance was 87% at λ = 550 nm. The transmittance was 97% in the IR part of the spectrum and 70–80% in the UV part.

Features of diazo dye photodecomposition in aqueous solutions containing zinc, aluminum and erbium salts

Subject of research.The features of diazo dye Chicago Sky Blue 6B photodecomposition in aqueous solutions containing the salts of zinc, aluminum and erbium were studied. The paper presents the research of effect of the type and concentration of salts of these metals on the spectral properties of solutions and kinetic dependencies of the decomposition processes of a diazo dye under the action of UV radiation from DRT-240 high-pressure mercury lamp. Method. The methodology of the studies consisted in the sequential measurement of the absorption spectra of the solutions on a Perkin-Elmer Labda 650 spectrophotometer in the UV and visible parts of the spectrum after UV irradiation of various durations and analysis of the observed spectral changes. Main results. Based on the research carried out, it was shown that the absorption spectrum of the dye changes in the presence of metal salts in solutions and an additional maximum appears on the characteristic broad and intense absorption band of the dye in the visible part of the spectrum (λ = 540–680 nm). That fact suggests the behavior of dye molecular structuring. When metal salts are introduced into the solution, the mechanism of its decomposition under the action of UV radiation also changes significantly. In the presence of metal salts, along with a decrease in the intensity of the absorption band of the dye in the visible part of the spectrum, its substantial shift to the shortwave region is also observed. Studies of the dye decomposition kinetics under UV irradiation showed that the rate of the dye photodegradation sharply increases in the presence of metal nitrates in solutions. The introduction of zinc nitrate into the solution has particularly strong effect on the dye photodegradation in an aqueous solution. Practical relivance.The experimental results obtained can be used in the development of photochemical processes for the purification of water from organic pollutants.

Optically Active Upconverting Nanoparticles with Induced Circularly Polarized Luminescence and Enantioselectively Triggered Photopolymerization.

In this work, lanthanide-doped upconversion nanoparticles (UCNPs) showing upconverted circularly polarized luminescence were demonstrated in an organic-inorganic co-assembled system. Achiral UCNPs (NaYF4:Yb/Er or NaYF4:Yb/Tm) can be encapsulated into chiral helical nanotubes through the procedure of co-gelation. These co-gel systems display intense upconverted circularly polarized luminescence (UC-CPL) ranging from ultraviolet (UV, 300 nm) to near-infrared (NIR, 850 nm) wavelength. In addition, the UV part of UC-CPL can be used to initiate the enantioselective polymerization of diacetylene.

Tuning solar absorption spectra via carbon quantum dots/VAE composite layer and efficiency enhancement for crystalline Si solar module

AbstractIn this work, fluorescent carbon quantum dots (CQDs) composite transparent film with blue emission was prepared via hydrothermal fabrication, mixing with vinyl acetate‐ethylene (VAE) emulsion, coated and cross‐linked on the glass in sequence. This CQD/VAE film has good sticking ability and compatibility of sealing ethylene‐vinyl acetate (EVA) material and works well as luminescent downshifting (LDS) materials. Based on these features, we did a set of optical characteristics analysis for CQD/VAE film and inserted a CQD/VAE film between glass and EVA encapsulation in a mini metal wrap through (MWT) solar module. This LDS could convert UV part of solar spectra, which are normally blocked by EVA, into the blue range and improve the light absorption by solar cell. Enhancement in the performance of solar modules was proved, especially the improvement of current of short circuit (Isc), external quantum efficiency (EQE) of the UV wavelength and solar module efficiency. This material provides the chance for prompt application, since it simply solves the dispersion problem of LDS material inside encapsulation and keeps the transparency of sealing polymer materials.

RETRACTED: Significant enhancement of photoactivity in one-dimensional TiO2 nanorods modified by S-, N-, O-doped carbon nanosheets

Abstract Titanium dioxide (TiO2) represents one of the most active photocatalysts among metal oxides for the degradation of pollutants and for solar water splitting to produce hydrogen. The most critical drawbacks hindering its broad practical use are the absorption majorly in the UV part of solar spectrum and slow charge dynamics. Combination of TiO2 with a suitable partner in a hybrid nanostructure can effectively address these drawbacks. Here we report a novel nanocomposite system based on one-dimensional TiO2 nanorods wrapped with a sulfur-, nitrogen-, and oxygen-doped carbon (SNOC) nanosheets. The SNOC nanosheets are synthesized by a cost-effective and facile route using eco-friendly carrageenan as a sulfur, oxygen, and carbon source and urea as a nitrogen source. Silica was used as the templating agent that leads to large surface area materials after its removal at the end of the synthesis. Therefore, the synthesized material exhibits superior photocatalytic performance for decoloring representative Rhodamine B (RhB) under visible light irradiation. SNOC shows the apparent rate constant of 7.6 × 10–3 min–1, which is almost 3 times higher than that of a SNOC material without using silica (2.8 × 10–3 min–1). This performance of doped carbon material can be assigned to the effect of large surface area and effective visible light adsorption. The TiO2 NRs / SNOC nanocomposite was investigated for photoelectrochemical water splitting showing much higher photocurrent densities (0.85 mA cm–2) than pure TiO2 nanorod arrays (0.35 mA cm–2), which was due to significant improvement in the charge transfer dynamics and co-catalytic effect of SNOC. All the materials prepared were evaluated on the basis of physical properties such as crystalline structure, optical absorption, surface topography, and electronic properties.