UV Applications Research Articles

Panoramic analysis of 2D dirubidium telluride monolayer benchmarking the DFT approach

Through the DFT computations, the structural, vibrational, electronic, elastic, optical and thermal (thermoelectric, thermodynamic) properties of the two-dimensional Rb2Te monolayer are briefly contemplated. The Perdew-Bruke-Ernzerhof (PBE) form of generalized gradient approximation (GGA) functional in WIEN2k was deployed for the analysis of all these material properties. The trigonally crystallizing monolayer with an indirect band gap of 1.72 eV may be an upright single-layer that suffices distinct applications. ‘No negative’ phonon bands confirm the dynamical stability of the monolayer. The Rb2Te monolayer has large indirect band gap than Rb2S and Rb2Se. It exhibits mechanical stability with positive elastic constants satisfying the Born-Huang criterion for two-dimensional materials. The absorption coefficient spanning largely in the ultra-violet range makes the monolayer a congruous material for UV applications. Also, the thermoelectric figure of merit for p-type Rb2Te single-layer at room temperature is high (0.67) compared to the analogous series of compounds, that makes the monolayer a viable one for thermoelectric flexibility and experimental synthesis. The monolayer has high hole effective mass and D ratio. The obtained results aids in revealing the outstanding properties and excellent stability of the monolayer. Based on these findings the Rb2Te monolayer paves the way for promising applications in the fields of photovoltaics, thermoelectrics and UV-based applications.

Comprehensive analysis of Nd0.5Ba0.5CoO3 cobaltite: Unveiling electrical, optical and magnetic characteristics for optoelectronic applications

In this study, we successfully synthesized the perovskite cobaltite Nd0.5Ba0.5CoO3 (NBCO) using the sol-gel method and thoroughly characterized its optical and magnetic properties. Optical measurements, using UV absorption, the Tauc model, and diffuse reflectance spectroscopy (DRS), revealed multiple direct bandgap energies, with the most significant values being 5.23 eV (Tauc method), 5.1 eV (DRS), and 4.9 eV (reflectance). The high bandgap energies highlight NBCO's suitability for UV and optoelectronic applications. The refractive index varied between 2.48 and 3.55, while the Urbach energy was measured at 2.32 eV, indicating a moderate level of localized disorder. Magnetic characterization demonstrated a ferromagnetic-to-paramagnetic transition at 125 K, with strong molecular field effects influencing the exchange interactions. The dielectric analysis revealed an exceptionally low loss factor (tan δ ≈ 0.0012), underscoring NBCO's potential for efficient energy storage and electronic applications. These results show that NBCO offers a unique combination of high optical bandgaps, strong magnetic properties, and low dielectric loss, making it a promising candidate for advanced optoelectronic and magnetic devices.

Efficacy of UVC-LED radiation in bacterial, viral, and protozoan inactivation: an assessment of the influence of exposure doses and water quality

Ultraviolet light-emitting diodes (UV-LEDs) have demonstrated the ability to inactivate microorganisms in water, offering an environmentally safer alternative to the conventional mercury lamp, in UV applications. While several studies have explored the microbiological effect of UVC-LEDs (200nm-280nm), limited information exists regarding their effects on waters with critical qualities. These critical qualities encompass bacteria, viruses, and protozoa – drinking water quality indicators defined by the World Health Organization for small water systems. For the first time, this work reports on the Escherichia coli, PhiX-174, MS2, and Cryptosporidium oocysts inactivation using a bench-scale UVC-LED (280 nm) water disinfection system. UV doses at a wavelength of 280 nm (UV280) of up to 143.4 mJ/cm2 were delivered under two quality-critical water conditions: filtered water (UV transmittance at 280 nm – UVT280 90.2 %) and WHO challenge water (UVT 15.7 %). Results revealed microbiological reductions dependent on exposure time and UVT. For UV280 dose of 16.1 mJ/cm2, 2.93-3.70 log E. coli reductions were observed in UVT 90.2 % and 15.7 %, 3.49-4.21 log for PhiX-174, 0.63-0.78 log for MS2, and 0.02-0.04 log for Cryptosporidium oocysts. Significantly higher UV280 doses of 143.4 mJ/cm2 led to reductions of 3.94-5.35 log for MS2 and 0.42-0.46 log for Cryptosporidium oocysts. Statistical analysis revealed that the sensitivity among the organisms to UV280 exposure was E. coli = PhiX-174 > MS2 >> Cryptosporidium oocysts. Although experiments with WHO challenge water posed greater challenges for achieving 1 log reduction compared to filtered water, this difference only proved statistically significant for PhiX-174 and MS2 reductions. Overall, UVC-LED technology demonstrated notable efficacy in microbiological inactivation, achieving significant reductions based on WHO scheme of evaluation for POU technologies in both bacteria and viruses even in critical-quality waters. The findings emphasize the potential for extending the application of UVC-LED as a viable solution for household water treatment.

The Effect of UV-A / UV-B Radiation on Quality Changes of Harvested Curly Lettuce During the Storage

This study investigated the effects of UV-A and UV-B radiation on curly lettuce quality. Results focused on colour, total phenolic content, antioxidant activity, and ascorbic acid. The findings revealed that the highest phenolic content (46.1 mg GAE/100 g FL) had been observed in lettuce samples treated with high dose UV-B on the 7th day. The lowest phenolic content (13.7 mg GAE/100 g FL) was recorded in those treated with low dose UV-B on the same day of storage. Data showed an increase of 29.7% in antioxidant activity and 53.7% in total phenolic content after 7 days of storage in samples treated with high dose UV-B. High dose UV-A radiation was found to be the most effective in maintaining and enhancing the ascorbic acid content of the lettuce. UV applications did not cause yellowing in the stored lettuce leaves. Further research on different doses and optimization is recommended.

3D-Printed Smartwatch Fabricated via Vat Photopolymerization for UV and Temperature Sensing Applications.

Ultraviolet (UV) exposure overdose can cause health issues such as skin burns or other skin damage. In this work, a UV and temperature sensor smartwatch is developed, utilizing a multimaterial 3D printing approach via a vat photopolymerization-digital light processing technique. Photochromic (PC) pigments with different UV sensitivities, UVA (315-400 nm) and UVB (315-280 nm), were utilized to cover a wider range of UV exposure and were mixed in transparent resin, whereas the smartwatch was printed with controlled thickness gradients. A multifunctional sensor was next fabricated by adding a thermochromic (TC) material to PC, which is capable of sensing UV and temperature change. Colorimetric measurements assisted by a smartphone-based application provided instantaneous as well as cumulative UV exposure from sunlight. The mechanical properties of the device were also measured to determine its durability. The prototype of the wearable watch was prepared by fixing the 3D-printed dial to a commercially available silicon wristband suitable for all age groups. The 3D-printed watch is water-resistant and easily removable, allowing for its utilization in multiple outdoor activities. Thus, the developed wearable UV sensor alerts the user to the extent of their UV exposure, which can help protect them against overexposure.

Regulating the microscopic structure of solutions to synthesize centimeter-sized low-dimensional CsmSbnClm+3n perovskite single crystals for visible-blind ultraviolet photodetectors

Centimeter-sized CsmSbnClm+3n single crystals were prepared by using DMSO and hydrochloric acid. The α-Cs3Sb2Cl9 photodetector exhibits excellent wavelength selectivity and fast response speed, demonstrating its great potential in UV applications.

Physical properties of magnesium fluoride: FPLAPW Approach

ABSTRACT MgF2 is a compound that is transparent to the full spectrum from UV to IR and is a good candidate for UV applications. Structural, optical, electronic and elastic properties of MgF2 compounds in the three phases in which our materials may crystallize have been studied using the linearized full potential self-consistent plane wave (FLAPW) method with Wu-Cohen generalized gradient approximation (WC-GGA) and modified Becke–Johnson potentials. The most remarkable is the similarity between the properties of the three phases at all levels (gaps, optical constants). A comparison of our outcomes with the literature indicates great agreement.

A 0D lead-free Nickel halide-based perovskite exhibiting greenish light emission and high color rendering index

In this paper, a novel low-dimensional Ni(II)-based hybrid perovskite compound [(C3H7)4N]Ni2Cl6 endowed with interesting solid-state light-emission properties has been investigated using thermal (TGA-DSC), Hirshfeld surfaces, FT-Infrared spectroscopy, optical and photoluminescence measurements. The structure packing consists of 0D framework ascribed as a layered arrangement of organic and dimeric [Ni2Cl6]1− groups perpendicular to the crystallographic c axis and stabilized by means of weak intermolecular bonds yielding a 3D framework. The UV-visible investigation reveals a direct optical gap energy of value 3.72 eV, confirming the semi-conducting nature of the elaborated material. The photoluminescence properties reveals a greenish broad-band emission caused by self-trapped excitonic states (STESs) as well as the remarquable the inorganic tetrahedron distortion in the 0D crystal dimensionality. Such bright light emission yields to good luminescence properties with a very high CRI value of 96, CIE color coordinates of (0.32; 0.35), and a CCT value of 5722 K and. The Stokes shift between excitation wavelengths (325, 345, 375, 395 nm) and their corresponding emission bands (450, 460, 472, 480 nm) are discussed. The current findings could be used for the development of environment-friendly hybrid perovskites for UV and solar cell applications.

Stability of doped and undoped ScNbO4 compound: Insight from first principle calculations

The quest for potential applications for a newly synthesized material is pragmatic and essential for building new devices. Doping it with rare-earth ions is one way to tune and approve its properties. We present a density functional calculation on the pristine and doped ScNbO4 compounds in this paper. In this context, we used the charged point defect procedure within the projector augmented wave method. The result of the phonon dispersion plot shows that ScNbO4 is dynamically stable in the monoclinic wolframite-type structure. According to the electronic calculations, ScNbO4 has a wide band gap, which favors a variety of UV and other optical applications, including the luminescence effect. To analyze the capability of the title compound as a host of doped rare-earth ions, a number of ions were evaluated by checking the site and growth conditions. Furthermore, the application of the Freysoldt methodology showed that the charge transition level in the doped ScNbO4 material has a stable valence band maximum under rich and poor Yb growing conditions. The analysis of the result shows that the p-type structure is more favorable to growth, paving the way for LED applications.

A Broad Spectral Photodetector Using Organic Bisindolo Quinoxaline on ZnO Nanorods

Inorganic/organic hybrids of ZnO nanorods (NRs)/bisindolo quinoxaline (BIQ) were fabricated for broadband photosensing applications. Multiple material characterizations revealed the BIQ was self-assembled in a regular form of rod-like domain and an irregular form of amorphous aggregation that were distributed on the ZnO NRs. Optical measurements showed that BIQ can absorb visible light with a wavelength up to 630 nm and effectively generate photoelectrons. Moreover, clustering of BIQ can be observed via the 3D optical microscopy. ZnO/BIQ hybrids were promising for future UV and visible light environmental monitoring applications.

Mechanical, optoelectronic and thermoelectric properties of the transition metal oxide perovskites YScO3 and LaScO3: First principle calculation

In this paper, we report a density functional theory (DFT) calculation study based on the full potential linear augmented plane wave (FP-LAPW) to discuss the mechanical stability as well as the optoelectronic and thermoelectric properties of two proposed orthorhombic transition metal oxide perovskites, namely, YScO3 and LaScO3. We found that our proposed perovskites are mechanically stable and elastically anisotropic materials. Also, they present promising thermal barrier coating (TBC) due to their high mechanical parameters. The topology of the band structure is of a wide energy gap insulator character for our compounds. We tested several functionals to recover the observed band gaps; especially the Eg band gap of LaScO3 has been a challenging problem with conventional exchange-correlation (XC) functionals used in the DFT calculations. Thus, the Yukawa-screened hybrid XC YS-PBE0 successfully gives Eg = 5.78 eV which is in good agreement with the experimental value of 5.8 eV. With DF-PT (perturbation theory) taking into account the lattice vibration, we found that our compounds have a high dielectric constant. We also calculated the main optical properties and found that both compounds have a large optical Eg, very small reflectivity, and could absorb light in the UV region and therefore, making them promising host materials for UV applications and ideal for optoelectronic devices.

Electromagnetic wave representation as a superposition of the quantized vector potential field of single photons

Without stating postulates or advancing any hypothesis, we show that a physical representation for the photon results directly from Maxwell’s theory once the vector potential amplitude is normalized at a single photon level. Electromagnetic waves are composed of a superposition of single photon states with circular polarizations, each extended over a wavelength and occupying a specific quantization volume. This representation is valid at any frequency and consequently can be applied for the modeling of advanced devices ranging from X-Rays and UV applications to fiber optics, microwave antennas and radio waves emitters.

Optical Properties and Moisture Stability of HfO2 Thin Films Prepared by Ion Assisted Deposition for UV Applications

In this study the progress in the realization of environmentally stable, high phase thickness, long-pass edge filters for UV applications is reported. These filters are characterized by extremely sharp transitions from full transmittance to deep blocking. Such filters are manufactured via physical vapor deposition of Hafnia (HfO2). Filters with highest phase thickness exhibit the steepest edge slopes. In this work we produce two types of filters, the first one manufactured using Ion Assisted Deposition (IAD), and the second one prepared by Physical Vapor Deposition (PVD) technique. When comparing the results for moisture stability of edge filters produced by IAD and PVD, it is found that the filters produced with ion assist exhibit wet-dry shifts in edge wavelength location less than 0.05%.

Homogenization and reduction of the roughness of polished sapphire surfaces via inert gas plasma post-processing

In this paper, we report on the post-processing of classically precision polished sapphire surfaces by means of a dielectric barrier discharge plasma at atmospheric pressure. Here, the lateral distribution of roughness values over the surface was significantly reduced, leading to a higher lateral homogeneity. This effect is shown by a decrease in the standard deviation of the roughness values measured at different positions over the sample surface where an overall plasma-induced reduction by a factor of 8.7 was achieved. Moreover, the residual roughness was notably decreased by a mean factor of up to 2.9 to merely a few angstrom. The obtained results are of high interest for the enhancement of large-scale optical components made of sapphire, especially for UV or laser applications. This is finally visualized by the comparison of the total integrated scatter values calculated for untreated and post-processed surfaces.

Sterilization studies of hydrogel nanocomposites designed for possible biomedical applications before in vivo research

This study emphasized the importance of hydrogel-based therapy in repairing cartilage tissue and discussed the nanoscopic requirements for the physical sterilization of hydrogels, which are repairable, biochemically compatible with cartilage structure, and shape memory under mechanical effects.The nanostructured and the shape memory hydrogel composites, previously designed, synthesized, and nano-structurally characterized by our group, were used as material in the present study. Samples are including poly(N,N-dimethylacrylamide) (poly (DMAA) chains, n-octadecyl acrylate (C18A) segments and with/without lauryl methacrylate (LM).The study consists of four main sections in which physical sterilization processes (with electromagnetic waves from low energy (UV) to high energy (X-ray and Gamma-ray) are applied, structural changes are determined at microscopic and nanoscopic scale, and biofilm formations in the mentioned hydrogel materials are evaluated.The present study investigated these hydrogels' potential as artificial cartilage or cartilage tissue scaffolds. To initiate in vivo studies, it was aimed to determine the most appropriate physical sterilization method.In the result of the study, the most convenient hydrogel sample for surgical (in vivo) research, the useful physical sterilization methods, and the ability to resist biofilm formation was determined for the sample of N:3, [DMMA/C18A/LM, (70/30/0.0) l (Pre stretching ratio) = 1.8]. UV applications were also determined as the most generally suitable sterilization method for these hydrogels. As the pre-stretching ratio increases, the emergence of more compact and globular nano formations in hydrogel structures also affects the bioactive properties. It was also shown that, with the help of the usage of energetic electromagnetic waves for sterilizations, the new 3D nano aggregation morphologies might be created in the hydrogel structures.

Stability, elastic and electronic properties of the CsSrI3 halid perovskite

Due to the importance of halide perovskite in many applications, namely optical and electronic ones, it is a challenging task to determine the precise stable studied structure for a given overall use. In view of this point, we present in this work, for the first time, theoretical calculations carried out by means of the full-potential linearized augmented plane wave (FP−LAPW) method on the CsSrI3compound. Deep analysis of energetic and dynamical investigations shows that this compound adopts an orthorhombic Cmcm structure. Meanwhile, both bonding and mechanical properties reveal a strong ionic/anisotropic behavior of the studied materials. This trend drastically influences electronic properties, giving rise to a wide band gap energy of 4 eV. The analysis of band structure and effective mass predicts favorable properties for UV applications.

Development of a Low-Cost Device for Measuring Ultraviolet Solar Radiation

Accurate measurements of solar ultraviolet radiation are needed for air quality monitoring, especially to understand the formation and photolysis of tropospheric ozone near the ground. It is interesting to investigate whether this demand could be met using recently developed low-cost UV sensors and new communication technologies. Despite the promising possibilities, their use is still scarce and their potential applications have not yet been thoroughly explored. This study aims to use low-cost sensors to develop devices that accurately measure solar ultraviolet radiation. The de vices should be low-cost, small, portable, and have low power consumption and IoT connectivity. For this purpose, three popular low-cost commercial sensors ML8511, UVM30A and VEML6075 are selected and implemented in several prototypes. The sensors are analyzed in terms of their spectral response, leveling, angular response and comparison with reference data. For that aim, experimental measurements are performed at the radiometric station of the Physics Department of the University of Extremadura in Badajoz, Spain. Results indicate that sensors of the same model might have different calibrations. The leveling and the angular response measurements indicate a strong azimuth dependence for the ML8511 and, especially, VEML6075 sensors, while the UVM30A sensor shows a much weaker dependence, probably due to the use of a circular diffuser. The angular response is identified as the main issue of the sensors, notably limiting their accuracy and preventing a widespread use. With the knowledge gained, a final version with LoRa communication and optimized power consumption is developed. The strength of the LoRa connection is measured at different locations on the University Campus using Receiver Signal Strength Indication. It ranges from -27 dB near the gateway to -122 dB at the farthest location on the Campus. The optimization of the power consumption allows 14 days of autonomy if operating only during daylight hours. The study illustrates the suitability of low-cost sensors for UV applications, provided that a good angular response of the sensors is ensured. It contributes to a wider use of these sensors for the measurement of air quality variables by identifying those characteristics that need to be improved by manufacturers to meet the standards.

UVC, UVB and UVA susceptibility of Phi6 and its suitability as a SARS-CoV-2 surrogate.

For SARS-CoV-2 disinfection systems or applications that are based on UVC, UVB or UVA irradiation, it would be desirable to have a SARS-CoV-2 surrogate for tests and development, which does not require a laboratory with a high biosafety level. The bacteriophage Phi 6, an enveloped RNA virus like coronaviruses, is an obvious candidate for such a surrogate. In this study, UVC, UVB and UVA log-reduction doses for Phi6 are determined by plaque assay. Log-reduction doses for SARS-CoV-2 are retrieved from a literature research. Because of a high variability of the published results, median log-reduction doses are determined for defined spectral ranges and compared to Phi6 data in the same intervals. The measured Phi6 log-reduction doses for UVC (254 nm), UVB (311 nm) and UVA (365 nm) are 31.7, 980 and 14 684 mJ/cm2, respectively. The determined median log-reduction doses for SARS-CoV-2 are much lower, only about 1.7 mJ/cm2 within the spectral interval 251–270 nm. Therefore, Phi6 can be photoinactivated by all UV wavelengths but it is much less UV sensitive compared to SARS-CoV-2 in all UV spectral ranges. Thus, Phi6 is no convincing SARS-CoV-2 surrogate in UV applications.

Growth design for high quality AlxGa(1−x)N layer with high AlN-fraction on Si (1 1 1) substrate by MOCVD

The constraints on increasing the AlN content in active AlGaN device layers on Si substrates for AlGaN-channel HEMTs and UV applications are explored. The essential qualifications an AlGaN semiconductor material must satisfy to be used as functional device are crack free films, a surface roughness of <1 nm, dislocation densities approaching that of GaN (∼109 cm2) and a reasonable thickness of around 1 μm; each one of the material specifications demand a growth condition that is mostly unfavourable to achieve the other one. To meet these diversified requirements thorough optimisation of growth conditions is carried out. As a result, compositions containing up to 30% AlN-fraction have been achieved. This has been accomplished by understanding the role of growth temperature and buffer design on stress, defect and surface evolution in the AlGaN epilayers. Our studies show that higher AlN-fraction containing epilayers are achievable if stress relaxation during its growth is minimised while simultaneously keeping the growth front smooth under the given growth condition. Such a growth condition can be successfully exploited if the dislocation density at the beginning of epilayer growth is lowered. A smooth heterointerface between Al0.13Ga0.87N and Al0.37Ga0.63N has been realized and formation of 2DEG at this this interface has been confirmed through C-V measurements.

The impact of bacterial cell aggregation on UV inactivation kinetics

Reconditioning of food processing water streams for reuse is an increasingly common water management practice in the food industry and UV disinfection is often employed as part of the water treatment. Several factors may impact the effect of UV radiation. Here, we aim to assess the impact of cell aggregation on UV inactivation kinetics and investigate if UV exposure induces aggregation. Three strains, isolated from food processing water reuse lines (Raoultella ornithinolytica, Pseudomonas brenneri, Rothia mucilaginosa) and both an aggregating and a non-aggregating strain of Staphylococcus aureus were exposed to UVC light at 255 nm using UV LED equipment. Total Viable Count and phase-contrast microscopy, coupled with image analysis, were used to compare the UV inactivation kinetics with the average particle size for a range of UV doses. Tailing effect, seen as a strong reduction in inactivation rate, was observed for all strains at higher UV doses (industrial strains ≥ 50 or 120 mJ/cm2, S. aureus strains ≥ 40 or 60 mJ/cm2). The naturally aggregating strains were more UV tolerant, both within and between species. When aggregates of S. aureus were broken, UV tolerance decreased. For the processing water isolates, the lowest applied UV dose (25 mJ/cm2) significantly increased the average particle size. Application of higher UV doses obtained with longer exposure times did not further increase the particle size compared with untreated samples. For the S. aureus strains, however, no consistent change in average particle size was observed due to UV. Our results demonstrate that aggregating strains have a higher degree of protection and that UV radiation induces aggregation in some, but not all bacteria. A better understanding of the mechanisms governing microbial aggregation and survival during UV treatment could help to improve UV applications and predictions of microbial inactivation.