Short-wavelength UV Research Articles

Photoreactions of the C2H4-SO2 Complex in a Low-Temperature Matrix Investigated by Infrared Spectroscopy and Density Functional Theory Calculations.

Ethylene and sulfur dioxide molecules were co-deposited on a CsI window at cryogenic temperature, and the photoproducts upon UV irradiation were observed using Fourier transform infrared (FTIR) spectroscopy. The products were found to be UV wavelength-dependent; at shorter wavelengths (λ = 266 nm) one strong peak was observed while more than three peaks were identified at longer UV wavelengths (λ = 300 nm). Spectral features changed seamlessly along with UV wavelength. Density functional theory (DFT) calculations were carried out for potential products, and spectral matches between observations and calculations seemed satisfactory, assuming a cyclic molecule (oxathietane 2-oxide) as the main photoproduct at longer UV wavelengths. On the other hand, the spectra of photoproducts at shorter UV wavelengths were reproduced by assuming the decomposition products of an intermediate, from the supplementary experiments using deuterated samples. Plausible photoreaction schemes were presented to account for the observed photoproducts.

High performance Au/mix-phase MgZnO/Ga-doped ZnO/In heterojunction solar-blind UV detector with small work voltage

High performance UVC (220 nm–280 nm) detectors with low work voltage is key problem in wide application of UVC optoelectronic device. Here, Au/MgZnO/Ga-doped ZnO/In heterojunction detector is made with both high UVC sensitivity mix-phase MgZnO and high carrier density Ga-doped ZnO conductive layers. The heterostructure detector possess relative high response(0.36A/W)at 254 nm deep UV light without bias voltage. The avalanche breakdown phenomenon within the heterojunction detector, introduced high deep UV response (1390.3 A/W at 3.3 μW/cm2 230 nm) of the Au/MgZnO/Ga-doped ZnO/In heterojunction detector under 5 V bias voltage. The high response of Au/MgZnO/Ga-doped ZnO/In heterojunction detector under low work voltage, is not only much higher than MSM structure MgZnO detector under bias voltage over 25 V, but also higher than reported deep UV detector under small bias voltage. In addition, because of different internal breakdown mechanism, the peak response position of the Au/MgZnO/Ga-doped ZnO/In heterojunction detector is located at shorter wavelength position compared with MSM structure MgZnO detector. Therefore, Au/MgZnO/Ga-doped ZnO/In heterojunction detector is an ideal device structure in low voltage driven detector with relative high response at short wavelength UV light.

Photochromic YHO darkening: Local or non-local mechanism?

Photochromic yttrium oxyhydride (YHO) shows a very attractive color-neutral darkening upon photoactivation. However, the exact defect or state responsible for the visible light absorption or the mechanism for its creation is not fully understood. This makes it challenging to optimize and modify the material. In this work, we have investigated the relationship between photon absorption and darkening profile into a YHO film. The extinction coefficient k(λ) is obtained from spectroscopic ellipsometry, and the expected photon absorption profile is calculated. This is then compared to transmittance data during photodarkening by short-wavelength UV (254 nm). Our results show that the darkening is not homogeneous through the film, showing that photon absorption and darkening are positionally correlated, yet we show that the darkening stretches further into the film than the calculated photon absorption. A homogeneously darkened sample cannot always be assumed when assessing optical transmittance, absorbance, and ellipsometry data.

Photodynamic therapy with NIR-II probes: review on state-of-the-art tools and strategies.

In 2022 10% of the world's population was aged 65+, and by 2100 this segment is expected to hit 25%. These demographic changes place considerable pressure over healthcare systems worldwide, which results in an urgent need for accurate, inexpensive and non-invasive ways to treat cancers, a family of diseases correlated with age. Among the therapeutic tools that gained important attention in this context, photodynamic therapies (PDT), which use photosensitizers to produce cytotoxic substances for selectively destroying tumor cells and tissues under light irradiation, profile as important players for next-generation nanomedicine. However, the development of clinical applications is progressing at slow pace, due to still pending bottlenecks, such as the limited tissue penetration of the excitation light, and insufficient targeting performance of the therapeutic probes to fully avoid damage to normal cells and tissues. The penetration depth of long-wavelength near infrared (NIR) light is significantly higher than that of short-wavelength UV and visible light, and thus NIR light in the second window (NIR-II) is acknowledged as the preferred phototherapeutic means for eliminating deep-seated tumors, given the higher maximum permissible exposure, reduced phototoxicity and low autofluorescence, among others. Upon collective multidisciplinary efforts of experts in materials science, medicine and biology, multifunctional NIR-II inorganic or organic photosensitizers have been widely developed. This review overviews the current state-of-the art on NIR-II-activated photosensitizers and their applications for the treatment of deep tumors. We also place focus on recent efforts that combine NIR-II activated PDT with other complementary therapeutic routes such as photothermal therapy, chemotherapy, immunotherapy, starvation, and gas therapies. Finally, we discuss still pending challenges and problems of PDT and provide a series of perspectives that we find useful for further extending the state-of-the art on NIR-II-triggered PDT.

Two Short-Wave UV Antimony(III) Sulfates Exhibiting Large Birefringence.

In the present work, we have successfully obtained two new UV antimony-based sulfates, NH4Sb(SO4)2 and Ca2Sb2O(SO4)4, by a conventional hydrothermal method. Interestingly, both compounds share similar structural building blocks, such as SbO4 seesaws and SO4 tetrahedra, yet they endow discrepant birefringence values measured at 546 nm with values of 0.150 and 0.114, respectively, owing to the different distortions of the SbO4 groups with SCALP electrons. Moreover, both compounds display large band gaps (4.32 and 4.43 eV, respectively), so they can be used as short-wavelength UV birefringent materials. Moreover, NH4Sb(SO4)2 is a noncentrosymmetric compound, showing a frequency doubling effect of 0.2 × KDP. Detailed structural analyses and calculations confirm the source of superior optical performance and the reasons for the different birefringence of the two compounds. This work provides ideas for the following discovery of antimony-based optical materials with excellent properties.

Fabrication, properties, and photodetector of β-(AlxGa1-x)2O3/GaN heteroepitaxial films grown by MOCVD

In this paper, β-(AlxGa1-x)2O3 heteroepitaxial films with different Al content were successfully prepared on p-GaN substrates by MOCVD method. When the “x” values are in a range of 0–0.38, the (AlxGa1-x)2O3 grown on p-GaN is an epitaxial film, maintaining the lattice structure of β-Ga2O3, and presenting an adjustable bandgap of 5.0–5.93 eV. When x = 0.45, the film is amorphous, and present a low bandgap of ∼5.73 eV due to the band tail formed by a large number of defects. φ scanning, HRTEM and SAED results showed that the prepared film was a six-fold domain structure and had an epitaxial relationship with the substrate of β-(AlxGa1-x)2O3 (2‾01) || GaN (0001) with β-(AlxGa1-x)2O3 [102] || GaN <1-100>. The photodetector (PD) based on β-(AlxGa1-x)2O3/GaN p-n junction presents high photoresponsivity (0.045 A/W) at 218 nm. The wavelength is far lower than the optimal responsive wavelength (254 nm) of β-Ga2O3 in previous reports, meaning that β-(AlxGa1-x)2O3 can be used to fabricate shorter wavelength UV photodetector.

Stability of monomeric indigo in the electronic ground state: An experimental matrix isolation infrared and theoretical study

Monomers of indigo were investigated using experimental (matrix-isolation) and theoretical methods. For the first time, the infrared spectrum of indigo molecules isolated in low-temperature Ar matrices was recorded and subjected to a detailed theoretical analysis. An excellent agreement between the experimental spectrum of indigo monomers and the spectrum theoretically predicted for the highly-symmetric (C2h) most stable dioxo form of the compound allowed a very reliable assignment of the observed infrared absorption bands. Matrix-isolated monomers of indigo were exposed to UV–vis radiation of different wavelengths. The conducted experiments demonstrated that molecules of indigo do not undergo any structural changes, even under irradiation with short-wavelength UV (λ > 200 nm) light. Theoretical calculations concerning the stability of photoproducts that could be potentially generated from indigo were conducted. The calculations carried out for the species generated by hydrogen-atom transfer from N1′ to O atom attached to the opposite ring revealed that both the oxo-hydroxy and dihydroxy tautomers of indigo should be unstable in the ground electronic state. The calculations carried out for the C2H tautomer (which may be generated by a hydrogen atom shift from N1′ to C2 of the opposite ring) led to optimization of the structure that is potentially stable, but very much distorted from planarity.

Toward Large Second-Harmonic Generation and Deep-UV Transparency in Strongly Electropositive Transition Metal Sulfates

The development of deep-ultraviolet (DUV)/solar-blind UV nonlinear optical (NLO) crystals simultaneously possessing wide UV transparency, strong second-harmonic generation (SHG) response, and suitable birefringence is a major challenge in advanced laser technology. We herein propose a "cation compensation" strategy for strong optical nonlinearity in inorganic solids that is exemplified by the introduction of strongly electropositive transition metals (TMs). Following this strategy, the first d0 TM UV-transparent NLO sulfates, MF2(SO4) (M = Zr (ZFSO), Hf (HFSO)), have been synthesized. Short UV cutoff edges of 206 nm and below 190 nm are observed for bulk ZFSO and HFSO crystals, respectively, together with the strongest powder SHG responses (3.2 × (ZFSO) and 2.5 × KDP (HFSO)) for solar-blind UV/DUV NLO sulfates, as well as suitable birefringence. This work provides a new and efficient approach to the development of urgently needed high-performance NLO materials for applications in the short-wavelength UV region.

HILIC-UV determination of lysine and chloride counterions in active pharmaceutical ingredients

A rapid, robust, and routinely applicable HILIC based HPLC-UV assay was developed for the quantitative determination of the L-Lysine content of Atorvastatin lysine active substance. During the method validation it turned out that with UV detection at 200 nm, the method is also capable for the direct determination of chloride ions. To the best of our knowledge, the phenomenon of chloride determination by short wavelength UV detection had only been once highlighted earlier in the literature. A wide range of the potential applications are demonstrated as well as the validation of the method as a routinely usable assay for residual chloride determination is also given.

Are Blue-Cut Lenses Safe for Children? Potential Effects on Eye Length and Refractive Disorders

Blue-blocking lenses, including both spectacles and intraocular lenses, are designed to selectively reduce the intensity of short-wavelength visible light and UV radiation using a chromophore. Unlike standard spectacle lenses, which only offer varying degrees of UV protection, blue-blocking lenses provide additional benefits such as enhancing visual performance, reducing eye fatigue from digital screens, protecting the retina from phototoxicity, and minimizing disruption of the circadian rhythm caused by blue light-emitting devices used in the evening. Research has shown that the length of the eye tends to increase over time, especially during the first 10 months of life, indicating the importance of this period in eye development. The Purkinje shift is a phenomenon where the eye becomes more sensitive to blue light in the dark, and it is a normal physiological process. However, there is concern that prolonged use of blue-cut lenses in children may affect the development of eye length and contribute to an increase in refractive eye disorders.

Safety Is in the Air: Ultraviolet light to clean the air typically has to be positioned away from people. Devices using shorter UV wavelengths could change this.

Safety Is in the Air: Ultraviolet light to clean the air typically has to be positioned away from people. Devices using shorter UV wavelengths could change this.

The Effects of Freeze-Thaw and UVC Radiation on Microbial Survivability in a Selected Mars-like Environment.

The purpose of this study was to determine survivability of Escherichia coli, Deinococcus radiodurans and Paraburkholderia fungorum under Mars-simulated conditions for freeze-thawing (−80 °C to +30 °C) and UV exposure alone and in combination. E. coli ATCC 25922, D. radiodurans and P. fungorum remained viable following 20 successive freeze-thaw cycles, exhibiting viabilities of 2.3%, 96% and 72.6%, respectively. E. coli ATCC 9079 was non-recoverable by cycle 9. When exposed to UV irradiation, cells withstood doses of 870 J/m2 (E. coli ATCC 25922), 200 J/m2 (E. coli ATCC 9079), 50,760 J/m2 (D. radiodurans) and 44,415 J/m2 (P. fungorum). Data suggests P. fungorum is highly UV-resistant. Combined freeze-thawing with UV irradiation showed freezing increased UV resistance in E. coli ATCC 25922, E. coli DSM 9079 and D. radiodurans by 6-fold, 30-fold and 1.2-fold, respectively. Conversely, freezing caused P. fungorum to exhibit a 1.75-fold increase in UV susceptibility. Strain-dependent experimentation demonstrated that freezing increases UV resistance and prolongs survival. These findings suggest that exposure to short wavelength UV rays (254 nm) and temperature cycles resembling the daily fluctuating conditions on Mars do not significantly affect survival of D. radiodurans, P. fungorum and E. coli ATCC 25922 following 20 days of exposure.

Understanding photolysis of CH3ONO2 with on-the-fly nonadiabatic dynamics simulation at the ADC(2) level

The nonadiabatic dynamics of methyl nitrate (CH3ONO2) is studied with the on-the-fly trajectory surface hopping dynamics at the ADC(2) level. The results confirmed the existence of the ultrafast nonadiabatic decay to the electronic ground state. When the dynamics starts from S1 and S2, the photoproducts are CH3O+NO2, consistent with previous results obtained from the experimental studies and theoretical dynamics simulations at more accurate XMS-CASPT2 level. The photolysis products are CH3O+NO2 at the ADC(2) level when the dynamics starts from S3, while different photolysis products were obtained in previous experimental and theoretical works. These results demonstrate that the ADC(2) method may still be useful for treating the photolysis mechanism of CH3ONO2 at the long-wavelength UV excitation, while great caution should be paid due to its inaccurate performance in the description of the photolysis dynamics at the short-wavelength UV excitation. This gives valuable information to access the accuracy when other alkyl nitrates are treated at the ADC(2) level.

Uric Acid as a Photosensitizer in the Reaction of Deoxyribonucleosides with UV Light of Wavelength Longer than 300 nm: Identification of Products from 2'-Deoxycytidine.

DNA reacts directly with UV light with a wavelength shorter than 300 nm. Although ground surface sunlight includes little of this short-wavelength UV light due to its almost complete absorption by the atmosphere, sunlight is the primary cause of skin cancer. Photosensitization by endogenous substances must therefore be involved in skin cancer development mechanisms. Uric acid is the final metabolic product of purines in humans, and is present at relatively high concentrations in cells and fluids. When a neutral mixed solution of 2'-deoxycytidine, 2'-deoxyguanosine, thymidine, and 2'-deoxyadenosine was irradiated with UV light with a wavelength longer than 300 nm in the presence of uric acid, all the nucleosides were consumed in a uric acid dose-dependent manner. These reactions were inhibited by the addition of radical scavengers, ethanol and sodium azide. Two products from 2'-deoxycytidine were isolated and identified as N4-hydroxy-2'-deoxycytidine and N4,5-cyclic amide-2'-deoxycytidine, formed by cycloaddition of an amide group from uric acid. A 15N-labeled uric acid, uric acid-1,3-15N2, having two 14N and two 15N atoms per molecule, produced N4,5-cyclic amide-2'-deoxycytidine containing both 14N and 15N atoms from uric acid-1,3-15N2. Singlet oxygen, hydroxyl radical, peroxynitrous acid, hypochlorous acid, and hypobromous acid generated neither N4-hydroxy-2'-deoxycytidine nor N4,5-cyclic amide-2'-deoxycytidine in the presence of uric acid. These results indicate that uric acid is a photosensitizer for the reaction of nucleosides by UV light with a wavelength longer than 300 nm, and that an unidentified radical derived from uric acid with a delocalized unpaired electron may be generated.

BiPO4:Ln3+ (Ln = Eu, Tb, Eu/Tb) nanorods: Room-temperature synthesis, reaction mechanism, and color-tunable emission

Ln3+ (LnEu, Tb, Eu/Tb) doping hexagonal BiPO4 nanorods were synthesized by a room-temperature co-precipitation method using ethylene glycol as solvent. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), thermal gravimetric (TG), and photoluminescence spectroscopy (PL) were utilized to investigate the structure, morphology, surface chemistry, and fluorescence performance of the obtained phosphors, respectively. The results showed that hexagonal phase of BiPO4 formed at room temperature, which consisted almost entirely of nanorods with an average diameter of 70 nm and an average length of 292 nm. The chemical reactions mechanism was well elucidated. Under short-wavelength UV light excitation, the as-obtained BiPO4:Eu3+ and BiPO4:Tb3+ samples exhibited strong orange-red and green emissions, respectively. Moreover, the photoluminescence color could be tuned from red, orange, yellow, and green-yellow, to green by simply adjusting the relative doping concentrations of Tb3+ and Eu3+ ions. The room-temperature synthesis reported in the present study could be extended to prepare other rare-earth doped inorganic luminescent materials.

High UV Transmission Glass Carriers for Advanced Packaging

Abstract Glass carrier wafers are used in many temporary bonding and debonding applications such as wafer thinning and fan-out wafer level packaging. For light-based debonding, a UV light source is often chosen for one or more of the following reasons: limiting light penetration into the sensitive die area; providing uniform light beam energy distribution; minimizing heat problems; maximizing overall process throughput. Corning has recently developed high UV transmission glass carrier wafers in response to market demand. In this paper, we will discuss the benefits of using such glass wafers for 308nm excimer laser debonding as well as a shorter wavelength UV lamp debonding cases.

Use of an ultraviolet light-activated persulfate process to degrade humic substances: effects of wavelength and persulfate dose.

Natural organic matter (NOM), commonly found in surface and ground waters, form disinfection by-products in drinking water. Generally, advanced oxidation processes (AOPs) featuring hydrogen peroxide are used to treat water; however, sulfate radical recently has been used to treat recalcitrant organics, because it is associated with a higher oxidation potential and more effective removal than hydroxyl radicals. Hence, in this research, we evaluated persulfate oxidation efficiency in terms of reductions in humic substance levels and investigated the degradation mechanism. The results showed that ultraviolet-activated persulfate effectively treated humic substances compared with hydrogen peroxide and direct irradiation. Treatment was dose and wavelength dependent; higher persulfate concentrations or shorter UV wavelengths were more effective for treating humic substances as high concentration sulfate radicals were created. The degradation mechanism was similar to that of hydrogen peroxide. Aromatic and chromophore components were more susceptible to degradation than were lower molecular weight components, being initially decomposed into the latter, reducing UV254 absorbance and the SUVA254. Lower molecular weight materials were eventually degraded to end products: NPOC levels fell. And we also treated the inflow of a drinking water treatment plant with persulfate, and humic substances were effectively removed.

Formation of Carbon Quantum Dots via Hydrothermal Carbonization: Investigate the Effect of Precursors

Carbon quantum dots (CQDs) are nanomaterials with a particle size range of 2 to 10 nm. CQDs have a wide range of applications such as medical diagnostics, bio-imaging, biosensors, coatings, solar cells, and photocatalysis. Although the effect of various experimental parameters, such as the synthesis method, reaction time, etc., have been investigated, the effect of different feedstocks on CQDs has not been studied yet. In this study, CQDs were synthesized from hydroxymethylfurfural, furfural, and microcrystalline cellulose via hydrothermal carbonization at 220 °C for 30 min of residence time. The produced CQDs showed green luminescence behavior under the short-wavelength UV light. Furthermore, the optical properties of CQDs were investigated using ultraviolet-visible spectroscopy and emission spectrophotometer, while the morphology and chemical bonds of CQDs were investigated using transmission electron microscopy and Fourier-transform infrared spectroscopy, respectively. Results showed that all CQDs produced from various precursors have absorption and emission properties but these optical properties are highly dependent on the type of precursor. For instance, the mean particle sizes were 6.36 ± 0.54, 5.35 ± 0.56, and 3.94 ± 0.60 nm for the synthesized CQDs from microcrystalline cellulose, hydroxymethylfurfural, and furfural, respectively, which appeared to have similar trends in emission intensities. In addition, the synthesized CQDs experienced different functionality (e.g., C=O, O-H, C-O) resulting in different absorption behavior.

Atomic layer deposition of TbF3 thin films

Lanthanide fluoride thin films have gained interest as materials for various optical applications, including electroluminescent displays and mid-IR lasers. However, the number of atomic layer deposition (ALD) processes for lanthanide fluorides has remained low. In this work, we present an ALD process for TbF3 using tris(2,2,6,6-tetramethyl-3,5-heptanedionato)terbium and TiF4 as precursors. The films were grown at 175–350 °C. The process yields weakly crystalline films at the lowest deposition temperature, whereas strongly crystalline, orthorhombic TbF3 films are obtained at higher temperatures. The films deposited at 275–350 °C are exceptionally pure, with low contents of C, O, and H, and the content of titanium is below the detection limit (&amp;lt;0.1 at. %) of time-of-flight elastic recoil detection analysis (ToF-ERDA). Due to the lack of titanium impurities, the films show high transmittance down to short UV wavelengths.

Ultrasensitive Optical Label-Free Biosensing and Fluorescent Measurements using UV Surface Plasmons in Gold Nanolayers Launched with the Support of a Specially Designed Photonic Crystal

Recently, we used Photonic Crystal (PC) - supported surface plasmons (SP) propagating along thin Pd, Co (in red spectral range) and Au (in blue, 405 nm) nanolayers for ultrasensitive gas sensing (Pd, Au) and magnetoplasmonic researches (Co). In all these cases, without the exploitation of a specially designed PC, the propagation length of the plasmons is just of the order of the wavelength hence there would be no reason to speak about SP at all. Here we experimentally show that the same concept is applicable even in UV spectral range at 375 nm despite the extremely non-favorable conditions of SP excitation at bulk gold - dielectric interface: the real part of the dielectric permittivity of gold at this wavelength is minus 1.5, and its imaginary part 5.6. Nevertheless, the use of a specially designed PC, containing seven pairs of transparent Ta2O5/SiO2 layers plus an additional Ta2O5 and 8 nm-thick gold layer, enabled us to attain the angular width of the surface plasmon excitation around 0.250 and thus the UV SP propagation length of tens of microns. This same structure can be used in quite usual fashion as an ultrasensitive optical label-free biosensor. Besides, the short UV wavelength exploited enables also to use it for excitation of fluorescence for very broad class of studied compounds. The perspectives of the application of this approach to deeper UV, at 280 nm, will be discussed. Such structures will enable direct label-free excitation and measurement of fluorescence from many proteins and DNA/RNA molecules/complexes.