Broadband UV Research Articles

Multicolor luminescence and high efficient optical thermometric performance of Eu3+ and Sm3+ in self-activated Na2LuMg2V3O12 garnet

To develop efficient luminescence and optical thermometry materials for color display and non-contact temperature measurement, novel RE3+ (RE = Eu, Sm) doped self-activated Na2LuMg2V3O12 phosphors were prepared by a typical solid-state reaction method. Their crystal structure, morphology, multi-color luminescence and temperature sensing properties were elaborately investigated. Under UV light excitation, an intense and broad green-yellow emission band from VO43– group is observed in the Na2LuMg2V3O12 matrix, indicating its potential application in solid state lighting. After the incorporation of Eu3+ and Sm3+ ions, efficient energy transfer (ET) from VO43– group to Eu3+/Sm3+ ions occurs and the emission color of the samples can be readily tuned among different color ranges. Besides, based on the change of luminescence intensity and lifetimes of VO43– group in Na2LuMg2V3O12:Eu3+ and Na2LuMg2V3O12:Sm3+, the ET efficiency was analyzed and the mechanism is illustrated. Finally, large discrepancy between the thermal stability of VO43– group and Eu3+/Sm3+ ions are observed in the temperature-dependent emission spectra of Na2LuMg2V3O12:Eu3+ and Na2LuMg2V3O12:Sm3+. By taking advantage of the luminescence intensity ratio (LIR) between VO43– group and Eu3+/Sm3+ ions in Na2LuMg2V3O12:0.01Eu3+ and Na2LuMg2V3O12:0.07Sm3+, two new types of optical thermometry mediums were designed and their basic temperature sensing parameters were calculated.

Hollow-Core Fiber for Single-Mode, Low Loss Transmission of Broadband UV Light

Hollow-Core Fiber for Single-Mode, Low Loss Transmission of Broadband UV Light

A MEMS Thermopile With Al Decorated Nanoforests Capable of Broadband UV Detection

A MEMS Thermopile With Al Decorated Nanoforests Capable of Broadband UV Detection

Latent fingerprint imaging using irradiated novel mixed metal oxides (MXOY, M=Ba, Zn, Al, Ce) nanophosphor.

Latent fingerprint developed at the site of crime is considered as crucial physical evidence in forensic investigation. The mixed metal oxides (MXOY, M=Ba, Zn, Al, Ce) nanophosphor was synthesised by irradiating the precursor solution with 60Co gamma radiation followed by solution combustion method. The structural, morphological, optical characteristics and fingerprint imaging were studied using X-ray diffraction (XRD), scanning electron microscopy, UV-visible spectroscopy and powder dusting method, respectively. The XRD results revealed that the average crystallite size is found to be 30nm with the estimated bandgap of 3.18eV. The broadband UV exited luminescence of the phosphors was observed at λMax=330nm. The PL spectrum shows three emission bands at 432, 444 and 460nm that corresponds to blue regions, suggesting that the synthesised nanophosphor is a potential luminous material for latent fingerprinting and luminescent devices.

Individual quantification of ozone and reactive nitrogen species in mixtures by broadband UV–visible absorption spectra deconvolution

Ozone (O3), nitrogen oxides (NO x ), and reactive nitrogen species (RNS) play critical roles in atmospheric-pressure plasma applications. Although it is crucial to individually quantify these species to understand atmospheric-pressure plasmas and increase their effectiveness, the lack of reliable and cost-effective diagnostics makes this difficult for many researchers. To address this problem, we introduce a new deconvolution method of broadband ultraviolet–visible absorption spectra for the simultaneous measurement of eight species—O3, NO, NO2, NO3, N2O4, N2O5, HONO, and HNO3. Processing of broadband spectra enables deconvolution of similar cross-section profiles and measurement of high densities exceeding the instrumental limit. Novel correction processes enable accurate analysis despite incomplete cross-section data and utilize a priori chemical knowledge to ensure theoretically reasonable results. Two case studies test the efficacy of the method: NO2 and N2O4 equilibria, and reactive species produced by a surface dielectric barrier discharge. With an analysis time of 15–20 ms per spectrum, the measured densities agree well with other theoretical and experimental results, and detection limits on the order of ppmv were achieved with a short path length of 15 cm. This spectral analysis method will facilitate the real-time monitoring of O3, NO x , and RNS in many scientific research and industrial applications of atmospheric pressure plasmas.

In situ O2-releasing quantum dot composites with enhanced radical scavenging behaviour, biosafety, and broadband UV shielding applications

Understanding the defect-driven photophysics-surface chemistry interplay at the nanoscale further augments new design considerations for active ingredients used in sun-protection, emphasizing affordability, safety, and multi-functionality. Accelerating it, our study unravelled broad-spectrum UV attenuation (250 nm–400 nm) and long-lasting photostability (>5 h) exhibited by in-house fabricated β-cyclodextrin functionalized, oxygen vacancy (VO●) engineered-CeO2(x)/ZnO(1-x) quantum dot composites (Em-C(x)Z(1-x)). A conceptually different strategy was pursued, involving artificially engineering surface VO● defects to modulate the band structure and enhance the molar absorptivity through photogenerated electron-hole separation. Unlike conventional inorganic UV blockers, these QD composites harnessed surface VO● for a self-cascading antioxidant effect, scavenging 62.8 % ●OH radicals. Results indicated that autocatalytic endogenous O2 generation from H2O2 scavenging, accelerated by Ce3+/Ce4+ couple, begets anti-photoaging and sunburn alleviation. Em-C(x)Z(1-x) demonstrated synergistic suppression of oxidative stress development and remarkable cell viability (≥90 %) even under UV irradiation. These underlying principles can be extended to prevent and treat other ROS-induced skin ailments. Incorporating Em-C0.3Z0.7 in commercial sunscreens unveiled a substantial enhancement in overall sun protection and antioxidative efficacy. Thus, it is envisioned that Em-C(x)Z(1-x) holds promise for developing safe, efficacious, and economical sunscreens.

Conformational Analysis of Trifluoroacetyl Triflate, CF3C(O)OSO2CF3: Experimental Vibrational and DFT Investigation

The conformations of trifluoroacetyl triflate, CF3C(O)OSO2CF3, were investigated through experimental vibrational methods (gas-phase FTIR, liquid-phase Raman, and Ar matrix FTIR spectroscopy) and density functional theory (DFT) calculations. A potential energy surface was computed using the B3P86/6-31+g(d) approximation as a function of the dihedral angles τ1 = CC−OS and τ2 = CO−SC. The surface reveals three minima, which were further optimized using the B3LYP method with various basis sets (6-31++G(d), 6-311++G(d), tzvp, and cc-pvtz). The global minimum corresponds to a syn–anti conformer (the C=O double-bound syn with respect the O−S single bond and the C−O single bond anti with respect to S−C single bond). The other two minima represent enantiomeric syn–gauche forms. The Ar matrix FTIR spectrum exhibited clear evidence of the presence of two conformers. Furthermore, the randomization process observed following broadband UV–visible irradiation facilitated the identification of the IR absorption of each conformer. Based on the Ar matrix FTIR experiments, the vapour phase of trifluoroacetyl triflate at room temperature was composed of approximately 60–70% of the syn–anti conformer and 30–40% of the syn–gauche form.

Kinetics of the Gas-Phase Reactions of syn- and anti-CH3CHOO Criegee Intermediate Conformers with SO2 as a Function of Temperature and Pressure.

Kinetics of reactions between SO2 and CH3CHOO Criegee intermediate conformers have been measured at temperatures between 242 and 353 K and pressures between 10 and 600 Torr using laser flash photolysis of CH3CHI2/O2/N2/SO2 gas mixtures coupled with time-resolved broadband UV absorption spectroscopy. The kinetics of syn-CH3CHOO + SO2 are pressure-dependent and exhibit a negative temperature dependence, with the observed pressure dependence reconciling apparent discrepancies between previous measurements performed at ∼298 K. Results indicate a rate coefficient of (4.80 ± 0.46) × 10-11 cm3 s-1 for the reaction of syn-CH3CHOO with SO2 at 298 K and 760 Torr. In contrast to the behavior of the syn-conformer, the kinetics of anti-CH3CHOO + SO2 display no significant dependence on temperature or pressure over the ranges investigated, with a mean rate coefficient of (1.18 ± 0.21) × 10-10 cm3 s-1 over all conditions studied in this work. Results indicate that the reaction of syn-CH3CHOO with SO2 competes with unimolecular decomposition and reaction with water vapor in areas with high SO2 concentration and low humidity, particularly at lower temperatures.

Significance of melanin distribution in the epidermis for the protective effect against UV light

Melanin, the most abundant skin chromophore, is produced by melanocytes and is one of the key components responsible for mediating the skin’s response to ultraviolet radiation (UVR). Because of its antioxidant, radical scavenging, and broadband UV absorbing properties, melanin reduces the penetration of UVR into the nuclei of keratinocytes. Despite its long-established photoprotective role, there is evidence that melanin may also induce oxidative DNA damage in keratinocytes after UV exposure and therefore be involved in the development of melanoma. The present work aimed at evaluating the dependence of UV-induced DNA damage on melanin content and distribution, using reconstructed human epidermis (RHE) models. Tanned and light RHE were irradiated with a 233 nm UV-C LED source at 60 mJ/cm2 and a UV lamp at 3 mJ/cm2. Higher UV-mediated free radicals and DNA damage were detected in tanned RHE with significantly higher melanin content than in light RHE. The melanin distribution in the individual models can explain the lack of photoprotection. Fluorescence lifetime-based analysis and Fontana–Masson staining revealed a non-homogeneous distribution and absence of perinuclear melanin in the tanned RHE compared to the in vivo situation in humans. Extracellularly dispersed epidermal melanin interferes with photoprotection of the keratinocytes.

Multi-wavelength and broadband AlGaN-based LED for versatile and artificial UV light source

This study focuses on modeling and analyzing a multi-wavelength (MW) ultraviolet light-emitting diode (UV LED) equipped with grading transition layers, which holds potential as a versatile and artificial UV light source. Commencing with the exploration of simple dual and triple-wavelength UV LEDs, we delve into the device mechanism, including the role of the grading transition layer and the control of emission intensity ratios. The grading transition layer connects modules with different emission wavelengths, effectively enhancing hole injection by diminishing the effective hole barrier and providing three-dimensional hole gas (3DHG). Besides, the emission intensity ratio of different modules is modulated through electron overflow, which is finely and coarsely controlled respectively by altering the quantum well number and the Al composition of electron controlling layers (ECLs). Modulating the ECL composition and quantum well number has good unilaterality facilitated by using grading transition layers, promoting a lower overall design complexity. Band diagrams, current dynamics, and carrier concentration distribution are analyzed to uncover various device mechanisms. After investigating dual-wavelength and triple-wavelength LEDs, a broadband UV LED is designed and demonstrated through the numerical method. The LED incorporates five emission modules, and each module has a similar emission intensity, contributing to a near 100 nm width UV spectrum. We expect this work lays the foundation for MW and broadband UV LED designs, fostering advancements in the AlGaN-based UV LED community.

Topological Insulator TlBiSe2/GaN Vertical Heterojunction Diode for High Responsive Broadband UV to Near-Infrared Photodetector

Topological Insulator TlBiSe2/GaN Vertical Heterojunction Diode for High Responsive Broadband UV to Near-Infrared Photodetector

Cerium dioxide nanoparticles modulate the oxidative metabolism of neutrophils upon blood irradiation with a pulsed broadband UV source

Cerium dioxide nanoparticles modulate the oxidative metabolism of neutrophils upon blood irradiation with a pulsed broadband UV source

Phenylpropiolic acid isolated in cryogenic nitrogen and xenon matrices: NIR and UV-induced study.

Phenylpropiolic acid (C6H5C≡CCOOH, PPA) isolated in nitrogen and xenon cryogenic matrices was studied by infrared spectroscopy. The experimental studies were complemented by a series of quantum chemical calculations carried out at the density functional theory (B3LYP) and MP2 levels of theory (with different basis sets). The calculations predicted the existence of two planar PPA conformers, differing in the arrangement of the carboxylic group. The higher-energy trans-PPA conformer has a negligible population in the gas phase at room temperature and was prepared in situ in the N2 cryomatrix through vibrationally-induced rotamerization of the lower-energy cis-PPA conformer, achieved using selective narrowband infrared excitation of the OH stretching coordinate of the latter species. Broadband UV (λ > 235nm) irradiation of matrix-isolated cis-PPA was also undertaken, leading to the observation of cis-PPA → trans-PPA isomerization. No other UV-induced photoreactions were observed. The in situ generated trans-PPA conformer was found to decay back to cis-PPA in the dark by tunneling, and its lifetimes under different experimental conditions were determined. The assignment of the infrared spectra of both conformers is presented, considerably extending the vibrational information available on this molecule.

Multifunctional carbon dots reinforced gelatin-based coating film for strawberry preservation

The development of safe, non-toxic, multifunctional nano preserved materials with excellent performance has become a hot research topic. Multifunctional Sophora Japonica extract (95% rutin)-derived carbon dots (R-CDs) were prepared by hydrothermal method. The π-π conjugation structure of R-CDs enabled them UV broadband absorption properties. The excellent antioxidant properties of R-CDs were attributed to the presence of the sp2 carbon in core and a large number of hydroxyl groups at the edges, and their degradation rate of potassium permanganate and scavenging activity of superoxide anion radical were better than that of ascorbic acid. The presence of CO bond may be the site for the generation of reactive oxygen species (ROS) and thus they could kill Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis) and Listeria monocytogenes (L. monocytogenes) at a concentration of 2 mg/mL and inhibited the growth of fungi (Botrytis cinerea). Then R-CDs were uniformly dispersed in gelatin-based solution, and the as-prepared films had smooth surface, good hydrophilicity, strong mechanical properties and good biocompatibility. With the increase of R-CDs addition, the tensile strength increased and then decreased, and the elongation at break rose to 358%. The film inherited the broadband UV absorption, antioxidant and antibacterial properties of R-CDs. The storage period of strawberries was prolonged after coating. The variety and abundance of microorganisms on the surface of strawberries was reduced and the growth of harmful bacteria was inhibited. This work provides more possibilities for the application of nanomaterials in fruit preservation.

Estimation of Inactivation time for the SARS-CoV-2 virus from the UV biometer in South Korea.

The coronavirus disease 2019 (COVID-19) is a result of the infection by "severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and has caused various social and economic effects over the globe. As the SARS-CoV-2 is effectively inactivated by the exposure to the UV-B radiation (shorter than 315nm), the exposure time for inactivation of the SARS-CoV-2 was estimated using the broadband UV observation instrument over 11 observation sites in South Korea. For the limitation of the UV biometer, which has limited spectral information, the coefficient for conversion from the erythemal UV (EUV) to the radiation for virus inactivation was adopted before estimating the inactivation time. The inactivation time of SARS-CoV-2 is significantly dependent on seasonal and diurnal variations due to the temporal variations of surface incident UV irradiance. The inactivation times in summer and winter were around 10 and 50min, respectively. The inactivation time was unidentified during winter afternoons due to the weak spectral UV solar radiation in winter. As the estimation of inactivation time using broadband observation includes the uncertainty due to the conversion coefficient and the error due to the solar irradiance, the sensitivity analysis of the inactivation time estimation was also conducted by changing the UV irradiance.

Influences of Mn2+/Eu3+ dopants on the microstructures and optical properties of glass-embedded CsPbBr3 quantum dots

All inorganic CsPbX3 (X = Cl, Br, I) perovskite quantum dots (PQDs) exhibit excellent photoelectric properties, such as high photoluminescence quantum yield, exceptional defect tolerance, and a long carrier diffusion length. However, their poor stability limits their applications. In this study, CsPbBr3 PQDs were precipitated in a phosphate glass matrix by a melt quenching method. The influences of Mn2+ and Eu3+ dopants on the microstructure and optical properties of CsPbBr3 PQDs glass were investigated in detail. The DSC and XRD results reveal that Mn2+/Eu3+ can act as a nucleating agent to promote the precipitation of CsPbBr3 PQDs in the glass matrix and optimize its microstructure. Simultaneously, PL spectra shows that appropriate Mn2+/Eu3+ doping concentration can enhance the optical performance of CsPbBr3 PQDs glass. The luminescence intensity increases by 46.9% and 44.3%, respectively, with the additions of these dopants. Finally, Mn2+ and Eu3+ single-doped CsPbBr3 PQDs glass is proved to have excellent broadband UV spectral response characteristics, indicating its potential application for photoelectric detection.

Broadband UV Supercontinuum Generation by Three-Color Ionizing Laser Pulses

We theoretically investigated the properties of the ultraviolet secondary radiation generated under the action of three-color ionizing pulses obtained from parametric light generators. We show that the combination components in the spectrum of electron currents generated under the action of such three-color pulses can form a strictly exponentially decreasing sequence. For moderately short pump pulse durations (30 fs at 800 nm main field) with the use of this effect, it is possible to generate a smooth broadband supercontinuum in the 800–100 nm range.

High-sensitivity IR to UV broadband ellipsometry and transmission characterization of high-purity glasses

Glasses are widely used as transparent substrates in thin-film and optical applications, but also as window materials in devices and operando cells. Determining the dielectric properties of the glass over a wide spectral range is often the crucial first step for the subsequent quantitative spectroscopic analysis, design and application of layer stacks and complex sample systems. Reflection-based ellipsometry—the method of choice for this task—is challenging for thick transparent substrates because of backside reflections that influence the optical response. Here, we extend the methodological treatment of backside reflections in ellipsometry by accounting for the spatial overlap—and its dependence on incidence angle, thickness and refractive index—between the light beams’ cross-sections and the detector aperture. We thereby demonstrate the incorporation of backside reflections in high-sensitivity multi-instrument, multi-angle ellipsometry and transmission for both measurement and quantitative modeling of glasses. Consolidating data from three instruments, we determine the dielectric function of two high-purity fused silica (Suprasil1) and quartz (Herasil102) glasses from the deep-ultraviolet to the mid-infrared (200–25000nm), with a sensitivity to absorption features as small as 10–7. Our non-destructive approach obviates the need for sample modifications like backside roughening, thus laying the foundation for future detailed ellipsometry studies on lower-purity glasses such as soda–lime- and borosilicate-based substrates for thin-film applications.

UV photoreaction pathways of acetylacetaldehyde trapped in cryogenic matrices.

The broadband UV photochemistry kinetics of acetylacetaldehyde, the hybrid form between malonaldehyde and acetylacetone (the two other most simple molecules exhibiting an intramolecular proton transfer), trapped in four cryogenic matrices, neon, nitrogen, argon, and xenon, has been followed by FTIR and UV spectroscopy. After deposition, only the two chelated forms are observed while they isomerize upon UV irradiation toward nonchelated species. From previous UV irradiation effects, we have already identified several nonchelated isomers, capable, in turn, of isomerizing and fragmenting; even fragmentation seems to be most unlikely due to cryogenic cages confinement. Based on these findings, we have attempted an approach to understand the reaction path of electronic relaxation. Indeed, we have demonstrated, in previous studies, that in the case of malonaldehyde, this electronic relaxation pathway proceeds through singlet states while it proceeds through triplet ones in the case of acetylacetone. We observed CO and CO2 formations when photochemistry is almost observed among nonchelated forms, i.e., when the parent molecule is almost totally consumed. In order to identify a triplet state transition, we have tried to observe a "heavy atom effect" by increasing the weight of the matrix gas, from Ne to Xe, and to quench the T1 state by doping the matrices with O2. It appears that, as in the case of acetylacetone, it is the nonchelated forms that fragment. It also appears that these fragmentations certainly take place in the T1 triplet state and originate in an Π* ← n transition.

A Bioinspired Skin UV Filter with Broadband UV Protection, Photostability, and Resistance to Oxidative Damage.

In recent years, sunscreens' adverse impacts on the environment and biology have gained wide attention. The improvement of sunscreen safety has become one of the major priorities in skin photoprotection research. It is an effective strategy to develop bionic photoprotective materials by simulating the photoprotective mechanism existing in nature. Inspired by the photoprotective mechanisms of skin and plant leaves, the bionic photoprotective material CS-SA-PDA nanosheet was developed using the free radical grafting method and Michael addition, with natural melanin analogue polydopamine (PDA) nanoparticles and plant sunscreen molecular sinapic acid (SA) as sun protection factors and natural polymer chitosan (CS) as the connecting arm. The results show that CS-SA-PDA can effectively shield UVB and UVA due to the possible synergistic effect between PDA and SA. The introduction of polymer CS significantly improved the photostability of SA and reduced the skin permeability of PDA nanoparticles. The CS-SA-PDA nanosheet can also effectively scavenge photoinduced free radicals. Furthermore, in vivo toxicity and anti-UV evaluations confirm that CS-SA-PDA has no skin irritation and is excellent against skin photodamage, which makes it an ideal skin photoprotective material.