UV Intensity Research Articles

Fabricating a photochromic benzonitrile Schiff base into a low-cost reusable paper-based wearable sensor for naked-eye dosimetry of UV radiations

We report in this study a photochromic benzonitrile Schiff base, (E)-4-((2-hydroxy-4-methoxybenzylidene)amino)benzonitrile (HMBAB). The molecular design, synthesis, aggregation-induced emission (AIE) as well as the quantum chemical calculations were outlined. In particular, HMBAB would undergo a reversible tautomerism in response to UV exposure, exhibiting remarkable changes in both absorption and emission: the compound shows yellow color and green-yellow luminescence; after UV exposure, the changes into orange-red while the luminescence is dramatically quenched, accompanied by a large bathochromic-shift. In addition, the photochromic state can be fully recovered via thermal treatment. Such reversible dual-channel photochromism was investigated using UV–vis reflectance spectroscopy and colorimeter, wherein a gradient change with time and a high fatigue resistance in cycle use was recorded. The photochromism is quantified by well-established RGB and Lab color space, in which the color change can be accurately analyzed by the chromatic aberration (ΔE*Lab). Sensitivity test gives a two-stage linear relation between ΔE*Lab and UV intensity, by which a limit of detection (LOD) as low as 67 μW/cm2 is obtained. HMBAB was further fabricated into a paper-based wearable sensor, capable of being integrated into a chest card or a bracelet. It exhibits various degrees of color change in different sunlight environments, which can be readily observed by naked eyes, providing an early warning for high-dose UV radiations.

The Photodissociation and Ionization Fronts in M17-SW Localized with FIFI-LS on Board SOFIA

To understand star formation rates, studying feedback mechanisms that regulate star formation is necessary. The radiation emitted by nascent massive stars play a significant role in feedback by photodissociating and ionizing their parental molecular clouds. To gain a detailed picture of the physical processes, we mapped the photodissociation region (PDR) M17-SW in several fine-structure and high-J CO lines with FIFI-LS, the far-infrared imaging spectrometer aboard SOFIA. An analysis of the CO and [O i]146 μm line intensities, combined with the far-infrared intensity, allows us to create a density and UV intensity map using a one-dimensional model. The density map reveals a sudden change in the gas density crossing the PDR. The strengths and limits of the model and the locations of the ionization and photodissociation front of the edge-on PDR are discussed.

Broad-wave reflection mechanism of polymer-stabilised cholesteric phase liquid crystals doped with natural polymeric nanofibers

ABSTRACT In this study, polymer-stabilised cholesterol-based liquid crystal (PSCLC) films with broadband reflection were prepared using monolayer gelatin nanofiber films as carriers loaded with photoinitiators. To obtain the maximum inhomogeneous distribution of the pitch, a series of studies were conducted on the concentration, temperature, time and UV intensity of the polymerised monomer. By screening different experimental conditions, the optimal conditions for broadening the reflectance band were obtained, and the reflectance band was widened from 240 to 440 nm. The morphology of the nanofibers was observed by SEM, and the effect of doping of the fibre film on the liquid crystals (LCs) weave was characterised by POM. The reflectance wavelength was measured mainly by a UV-vis spectrophotometer. The prepared cholesteric phase LC films with broadband reflection properties have potential applications in brightening films, intelligent windows, infrared shielding devices, laser protective coatings, etc.

Solvothermal Synthesis of LaF3:Ce Nanoparticles for Use in Medicine: Luminescence, Morphology and Surface Properties

A series of LaF3:Ce3+ phosphors for application in photodynamic therapy are synthesized using a one-stage solvothermal synthesis. The synthesis conditions; type and quantity of stabilizer; concentration of activator providing the maximum intensity of UV- and X-ray-excited luminescence; lowest size; and highest colloidal stability of the phosphor nanoparticles are found. As a result of this study, the following parameters are determined using cerium content 5% mol. ethanol as the reaction medium for the solvothermal synthesis and polyvinylpyrrolidone as the stabilizer at an optimized amount.

Broadband reflection induced by chiral dopant-loaded mesoporous polystyrene-divinylbenzene microspheres via diffusion in polymer stabilised cholesteric liquid crystals

ABSTRACT A new method to construct polymer stabilised cholesteric liquid crystal (PSCLC) films with broadband reflection in the near infrared region (NIR) has been proposed which utilises the chiral dopant-loaded mesoporous polystyrene-divinylbenzene (PS-DVB) microspheres. The diffusion time, UV intensity and temperature during polymerisation were investigated to control the diffusion of chiral dopant and the polymerisation process which could affect the non-uniform pitch distribution and thus the reflection bandwidth. The optimised reflection bandwidth was broadened from 300 nm to 860 nm. Potential application fields of broadband reflective films include smart windows for the control of the solar-light irradiation, and military infrared shielding devices.

Photocatalytic discoloration of methylene blue by TiO2 P25 under UV light using ISO 10678 standard as a guide

• TiO 2 is the most used semiconductor for photomineralization of organic compounds. • Discoloration of a dye is the most used technique for photocatalytic performance. • ISO 10678:2010 standard was used e for testing the performance of powdered P25 TiO 2 . • Time of exposure, dye concentration and intensity of the UV light were analyzed. • UV intensity was the only factor statistically significant for photocatalysis. In heterogeneous photocatalysis, TiO 2 is the most used semiconductor for mineralization of organic compounds. The most used technique to determine the photocatalytic performance of semiconductors is the discoloration of an organic dye. However, there is no consensus on the procedure for dye discoloration. In this work, the ISO 10678:2010 standard, applied for catalytic surfaces, was used as a guide for testing the performance of the TiO 2 (P25) for the discoloration of methylene blue under UV light. The time of exposure, dye concentration and intensity of the UV light were the parameters of the study. As a result, the UV intensity was the only factor affecting the photocatalysis.

Materials and Device Design for Epidermal UV Sensors with Real‐Time, Skin‐Color Specific, and Naked‐Eye Quasi‐Quantitative Monitoring Capabilities

AbstractUltraviolet radiations (UVR) sensors provide quantitative and continuous measurement of UV‐induced dermal damage. The challenge though is to develop a sensor that simultaneously offers high sensitivity and rapid response to UVR, as well as compatibility to human skin and skin color specificity. In this paper, an epidermal UV sensor that uses new sets of material and device design strategies to deliver accurate UV intensity measurements is presented. The developed sensor provides real‐time and reversible detection performance (color change and recovery) in less than 30 s. By combining the UV photochromic and absorptive materials, a variety of personalized UV epidermal stickers can be developed to achieve naked‐eye quasi‐quantitative monitoring of UV exposure while simultaneously meeting the specific needs of different skin types. Experimental demonstrations validate the high applicability of these wearable UV sensors for managing the impact of UVR in the daily life.

Transport Mediating Core-Shell Photocatalyst Architecture for Selective Alkane Oxidation.

The high activation barrier of the C-H bond in methane, combined with the high propensity of methanol and other liquid oxygenates toward overoxidation to CO2, have historically posed significant scientific and industrial challenges to the selective and direct conversion of methane to energy-dense fuels and chemical feedstocks. Here, we report a unique core-shell nanostructured photocatalyst, silica encapsulated TiO2 decorated with AuPd nanoparticles (TiO2@SiO2-AuPd), that prevents methanol overoxidation on its surface and possesses high selectivity and yield of oxygenates even at high UV intensity. This room-temperature approach achieves high selectivity for oxygenates (94.5%) with a total oxygenate yield of 15.4 mmol/gcat·h at 9.65 bar total pressure of CH4 and O2. The working principles of this core-shell photocatalyst were also systematically investigated. This design concept was further demonstrated to be generalizable for the selective oxidation of other alkanes.

MONITORING SUMMER SOLAR ULTRAVIOLET (UV) RADIATION ON THE GROUND LEVEL OVER ARDABIL-SAREIN, NW IRAN

Abstract. The UV radiation level at the Earth’s surface is generally affected by several factors such as time, geographic location, and climate. The first observations of solar UV radiation ever made in NW Iran, obtained in June 2019 are reported in this work. The analysis of hourly values of UV irradiances measured in the study area reveals significant diurnal variation during daylight hours, with lower values in the morning and afternoon and higher around noon. Mean hourly UV (A+B) ranged from 2755 to 10434 µW/cm2 with an average value being about 7960 µW/cm2. Mean hourly UV (C) ranged from 40 to 91 µW/cm2 with an average value being about 76 µW/cm2. The results of a short but intense measurement campaign in Ardabil-Sarein indicate the trends for geographical latitude, longitude, and altitude from surface UV measurements. The UV intensity is associated with geographical longitude (r2= 0.15 for UV (A+B); r2= 0.13 for UV (C)). Furthermore, UV intensity varies with the local latitude in the study area. There is a strong linear relationship between average UV and altitude and a trend of rising UV with increasing altitude is obtained. A decrease in UV radiation with increasing solar zenith (°) was observed. However, the correlation between UV radiation and solar azimuth (°) was not significant. Understanding the factors influencing near-surface UV radiation through systematic ground-based UV will help determine whether long-term changes occur as a result of changes in cloud cover or climate change, and how specific it means to identifying the causes.

Efficient metformin transformation in sulfite/UV process co-present with oxygen

UV/sulfite process without oxygen has been extensively explored and used for the degradation of many micro-pollutants. In the present work, a UV/sulfite process in the presence of oxygen was applied to degrade a widely used pharmaceutical compound, metformin (MET). The results showed that the oxygen-involved UV/sulfite process could efficiently degrade MET. At an initial concentration of 2.5 mg/L, 86.0% of MET was removed from the contaminated water within 180 min irradiation at a sulfite dosage of 10 mM, solution pH of 9, and UV intensity of 4,092 μW/cm2. In addition, sulfate radical (SO4•-), hydroxide radical (•OH), hydrogen atom (•H), and hydrated electron (eaq−) were found to be the dominant active species contributing to MET removal in the studied process through scavenging experiments. The increase in UV intensity, sulfite dosage, solution pH, and reaction temperature enhanced MET degradation in the investigated process to a certain extent, whereas the introduction of bicarbonate and fulvic acid slightly suppressed MET degradation. Finally, the degradation products of MET were identified. The oxygen-involved UV/sulfite process exhibited a remarkable denitrification capacity (>80%) in MET. The findings of this study may offer a novel approach for treating emerging contaminants.

Fabrication of self-assembled core-sheath microfibers via formulation of alginate-based bioinks

Core-sheath microfibrous structures are widely used in various tissue engineering applications and drug delivery systems. However, the fabrication of the various core-sheath structures using a 3D printing process supplemented with a coaxial nozzle has been challenging due to the center positioning of the core nozzle enclosed in the bigger shell nozzle. In this work, we developed a new 3D printing process using an alginate-based bioink (a mixture of photo-crosslinkable hydrogel and alginate) and its in situ crosslinking process within a single glass nozzle of the 3D printer. By manipulating the alginate weight fraction, UV intensity, flow rate, and nozzle moving speed, we could fabricate various self-assembled core-sheath structures (straight, wavy, and crimped microfibers in the core region of the structure) in which the photocrosslinked hydrogel resided in the core, and alginate was positioned in the sheath region, like a virtual coaxial nozzle.

Ultra-Violet (UV): A Good Bacterial Sterilizer?

Introduction: The aim of this study was to improve the DISTER-UV and to perform microbiological quality control at the biomedical laboratory of the West African Polytechnic University from January 2022 to November 2022. Methodology: During this eleven-month prospective study, we set up a quality control device (QCD). For microbiological quality control, we performed different cultures of bacteria with different bacteriological and morphological characteristics at T0 (no sterilization) and at T30 (after 30 minutes of sterilization under DISTER-UV). Results: After the realization, the DCQ attached to the DISTER-UV1 allows to display of the UV wavelength present in the light box. This device also displays and alerts when the UV intensity emitted by the lamps is below 250 nm. During microbiological quality control, the cultures carried out at T30 and incubated for 24 hours did not reveal any bacterial colonies. This shows the bactericidal character of DISTER-UV-2. Conclusion: The improvement and the microbiological quality control allowed us to switch from DISTER-UV1 (without sensor) to DISTER-UV-2 (with sensor or DCQ). The biological control allowed us to affirm that the DISTER-UV-2 is bactericidal.

Flight and ground demonstration of reproducibility and stability of photoelectric properties for passive charge management using LEDs

Charges as small as 1 pC degrade the performance of high precision inertial reference instruments when accumulated on their test masses (TMs). Non-contact charge management systems are required for the most sensitive of these instruments, with the TMs free-floating, and their charges compensated by photoelectrons in a feedback loop with a TM charge measurement. Three space missions have successfully demonstrated this technique: the Relativity Mission, Gravity Probe-B launched in 2004, the LISA Pathfinder launched in 2015, and the UV-LED mission launched on SaudiSat 4 in 2014; with the first two using the 254 nm Hg discharge line and the last one a set of 255 nm UV-LEDs. UV-LEDs represent a significant improvement over the discharge sources, in terms of reliability, lifetime, switching speeds, power consumption, weight, and volume. Charge management techniques that eliminate the charge measurement and feedback systems, referred henceforth as passive, reduce the complexities and disturbance effects introduced by these systems, and are thus the subject of active research and development work. Passive charge management (PCM) depends critically on the stability and reproducibility of the photoemission properties of a given system. In support of this work, we present comprehensive flight characterization data for a suite of 16 UV-LEDs in various configurations and 255 ± 1 nm center wavelength. Flight data was acquired between December 2014 and December 2015 with the UV-LED instrument flown on SaudiSat 4. We back up our results with ground-based measurements performed in configurations comparable to the flight one between 4 September 2020, and 8 October 2020. All results confirm the excellent reliability of the UV-LEDs in the space environment, are fully consistent with the findings of ground studies, and support the approach of using LEDs for PCM. We find that the equilibrium potential of the TM, under illumination by the 255 nm LEDs, is independent of the UV intensity and reproduceable to about ≅±6 mV, or ±6 fC pF−1, over periods of up to six months. The value of the equilibrium potential is dependent on the geometry of the electric field between the TM and its enclosure, and thus on the exact configuration of the PCM instrument.

Near-UV Pulsations in the Aurora Region Measured by Orbital Telescope TUS during High-Intensity and Long-Duration Continuous AE Activity

Tracking Ultraviolet Set-up (TUS) on board the Lomonosov satellite measured the UV intensity pulsations in the auroral region. Sixty-four events with pulsations were registered during two measurement periods from 26 December 2016–10 January 2017 and 8–15 November 2017. During both periods, a high-intensity, long-duration, continuous auroral activity (HILDCAA) was detected. Simultaneous measurements in LEO by Lomonosov (DEPRON detector) and Meteor-M2 satellites show the enhanced fluxes of the trapped and precipitated energetic electrons in the region of the Earth’s outer radiation belt during these periods. We found that most of the UV-events correspond to energetic electron (E > 100 keV) precipitation. One can suggest that particles of these and higher energies cause a pulsating emission relatively deep in the atmosphere.

Silver Nanoparticle Synthesis via Photochemical Reduction with Sodium Citrate

The aim of this paper is to provide a simple and efficient photoassisted approach to synthesize silver nanoparticles, and to elucidate the role of the key factors (synthesis parameters, such as the concentration of TSC, irradiation time, and UV intensity) that play a major role in the photochemical synthesis of silver nanoparticles using TSC, both as a reducing and stabilizing agent. Concomitantly, we aim to provide an easy way to evaluate the particle size based on Mie theory. One of the key advantages of this method is that the synthesis can be "activated" whenever or wherever silver nanoparticles are needed, by premixing the reactants and irradiating the final solution with UV radiation. UV irradiance was determined by using Keitz's theory. This argument has been verified by premixing the reagents and deposited them in an enclosed space (away from sunlight) at 25 °C, then checking them for three days. Nothing happened, unless the sample was directly irradiated by UV light. Further, obtained materials were monitored for 390 days and characterized using scanning electron microscopy, UV-VIS, and transmission electron microscopy.

Printing of Nano‐ to Chip‐Scale Structures for Flexible Hybrid Electronics

AbstractFlexible hybrid electronics (FHE) offers potential for fast computation and communication needed in applications such as human–machine interfaces, electronic skin, etc. FHE typically comprises devices that can vary from nano‐ to chip scale, and their integration using a common process is often challenging. Herein, a printed electronics route is presented to integrate the ultrathin chips (chip‐scale) and nanowires (NWs)‐based electronic layers (nanoscale) on the same substrate. The fabrication process is categorized into three stages: i) direct transfer printing of ultrathin chips (UTCs), ii) contact printing of nanoscale structures, and iii) metal printing using the direct ink write (DIW) method to define electrodes/interconnects. The UTC printing process is carefully optimized by studying the performance of transistors present on them. Electrical data collected from 14 transistors located on 3 different chips show negligible variation in performance after they are transfer printed—thus confirming the efficacy of the printing technique. The superior grade quality of ZnO‐NWs‐based electronic layers printed on the same substrate is also demonstrated by constructing UV photodetectors using DIW printing. The photodetectors show high responsivity (≈2 × 107 A W−1) and specific detectivity (≈5 × 1015 Jones) at a low UV intensity of 0.5 µW cm−2.

Developing a UV dosing strategy for UV/chlorine process towards the trade-off between pharmaceuticals and personal care products degradation and disinfection by-products formation

In addition to UV wavelength and pH, UV irradiation intensity and fluence also play crucial roles in the UV/chlorine treatment of drinking water. This work aimed to develop a novel UV irradiation strategy to achieve a trade-off between pharmaceuticals and personal care products (PPCPs) degradation and disinfection by-products (DBPs) formation during UV/chlorine water treatment under a specific chlorine dose. Under high UV irradiation intensity at the same UV fluence, the faster chlorine photolysis produced higher steady-state concentrations of •Cl and •OH species but abated cumulative exposures of free available chlorine (CTFAC = ∫0t[Cl2]dt). As a result, the degradation rate of PPCPs was accelerated, but the removal percentage of some PPCPs decreased. Meanwhile, the degradation of the chromophores of dissolved organic matters (DOM) declined by 23.3%–24.8% under the higher UV irradiation intensity. Reducing CTFAC values (50.7%–57.6%) by high UV irradiation intensity could mitigate the formation of haloacetic acids, trihalomethanes and absorbable organic halogens (13.9%–14.9%), which addressed the key role of active chlorine in the formation of DBPs in the UV/chlorine process. DBPs were mainly generated from the interactions of DOM with reactive chlorine. The Vibrio fischeri data further indicated that increasing UV intensity reduced acute toxicity regardless of UV wavelength or water pH. For the same UV fluence dose, the high UV irradiation intensity can effectively control the trade-off between oxidation efficiency and DBPs formation during UV/chlorine treatment.

Degradation of Carbamazepine by HF-Free-Synthesized MIL-101(Cr)@Anatase TiO2 Composite under UV-A Irradiation: Degradation Mechanism, Wastewater Matrix Effect, and Degradation Pathway

TiO2 has been hampered by drawbacks such as rapid photoelectron and hole recombination and a wide energy band gap of 3.2 eV. In this study, MIL-101(Cr)@TiO2 was synthesised without any mineraliser (HF) as part of material modification approach to overcome those pitfalls. The composite was well characterized by XRD, FT-IR, TEM, XPS, BET, TGA, and Raman spectroscopy. Under optimal synthesis conditions, the 9.17% MIL-101(Cr)@TiO2 composite exhibited 99.9% CBZ degradation after 60 min under UV-A irradiation. This can be attributed to the delayed recombination of photo-generated h+ and e− and a reduced band gap energy of 2.9 eV. A Type II heterojunction structure was proposed for the composite using the Mulligan function of electronegativity with the calculated Ecb and Evb. Besides, trapping experiments and ESR spectroscopy confirmed O2•− as the main ROS for CBZ degradation. The effects of the operating parameters such as pH, UV intensity, composite dosage, and initial pollutant concentration were also evaluated. The scavenging effects of inorganic and organic constituents of pharmaceutical wastewater on the process were also evaluated, with HCO3−, CO32−, and THF having more significant inhibition on the overall CBZ degradation. The degradation pathways of CBZ were also proposed based on detected intermediates with the aid of LC/MS/MS. The composite illustrated reusability and stability without considerable loss in the degradation performance after repeated runs. This work builds on the development of more effective photocatalysts and provides a glimpse into applications for similar MOF heterojunction photocatalysts.

Characterization of the Efficiency of Photo-Catalytic Ultrafiltation PES Membrane Modified with Tungsten Oxide in the Removal of Tinzaparin Sodium

One of the polymeric membranes' main limitations is their susceptibility to fouling, lowering the membrane's performance with time. Therefore, incorporating nanomaterials in polymer matrices has attracted great attention in wastewater treatment applications. It's a promising approach for enhancing membrane hydrophilicity and performance. Herein, ultrafiltration nanocomposite membranes were synthesized by applying the phase inversion method through immobilizing (0.1-0.4 wt.%) tungsten oxide (WO2.89) nanoparticles in a polyether sulfone (PES) matrix. Membrane's anti-fouling performance was evaluated against tinzaparin sodium. The data showed that the pure water flux improved with increasing nanoparticle loading, reaching its optimum value of 54.9 kg/m2 h at 0.4 wt.% WO2.89 nanoparticles compared to the neat membrane's 30.42 kg/m2 h. The results also demonstrated that the rejection efficiency and flux recovery ratio (FRR) against tinzaparin sodium was enhanced, by 44.89% and 12.69%, respectively, for the membranes modified with 0.4wt.% WO2.89 nanoparticles loading compared to the neat PES membrane. The data also showed that after exposing the nanocomposite membranes to UV light irradiation (λ=365 nm) and intensity (1200mW/cm2) for 1h, a further enhancement by 8.34% in FRR as compared to the membranes with the same percentage of nanoparticles loading without irradiation. It is concluded that the photocatalytic activity of WO2.89 nanoparticles in the decomposition of organic molecules on/close to the membrane surface was the impact that caused this improvement in membrane anti-fouling property

Sunlight Parameters Influence the Survival and Decline of Salmonella and Escherichia coli in Water

The effect of variations in temperature, UV radiation, and sunlight intensity on Escherichia coli, E. coli O157:H7, Salmonella Newport, and antibiotic resistant (ABR) variants of E. coli O157:H7 and Salmonella Newport exposed to sunlight was evaluated. Bacterial strains suspended in sterile deionized water at a concentration of 8 log CFU/mL were exposed to sunlight on three different days for 180 min; control treatments were stored in the dark. The mean temperature of 30.08 and 26.57°C on day 1 and day 3, respectively, was significantly different (P < 0.05). The UV intensity was significantly different on all 3 days, and sunlight intensity significantly differed on day 3 (P < 0.05). Bacterial population decline positively correlated with temperature, sunlight, and UV intensity. Differences in bacterial population declines differed among species, ABR profile, and day of exposure (P < 0.05). On day 1 and day 2, the populations of E. coli dropped below the limit of detection (1 log CFU/mL), whereas the percentage of live cells was 67 and 6.6%, respectively. The artificial neural network model developed to predict bacterial survival under different environmental conditions suggested that Salmonella cells were more resistant than E. coli cells. The ABR strains had significantly higher numbers of viable cells after sunlight exposure (P < 0.05). Sunlight-exposed cells resuscitated in tryptic soy broth varied in maximum population density and maximum specific growth rate based on bacterial species and presence of ABR. Morphological changes such as viable but nonculturable state transition and filament formation were detected in subpopulations of sunlight-exposed bacteria. Daily fluctuations in UV and sunlight intensity can result in significant variations in bacterial decline and recovery.