UV Wavelengths Research Articles

Closing gaps to our origins

This article reproduces the contents of the White Paper entitled by the same name submitted to the call issued by the European Space Agency soliciting ideas from the scientific community for the science themes that should be covered during the Voyage 2050 planning cycle. This contribution focus in the investigation of the emergence of life and the role that astronomy has to play in it. Three fundamental areas of activity are identified: [1] measuring the chemical enrichment of the Universe, [2] investigating planet formation and searching for exoplanets with signatures of life and, [3] determining the abundance of amino acids and the chemical routes to amino acid and protein growth in astronomical bodies. This proposal deals with the first two. The building blocks of life in the Universe began as primordial gas processed in stars and mixed at galactic scales. The mechanisms responsible for this development are not well-understood and have changed over the intervening 13 billion years. To follow the evolution of matter over cosmic time, it is necessary to study the strongest (resonance) transitions of the most abundant species in the Universe. Most of them are in the ultraviolet (UV; 950 Å - 3000 Å ) spectral range that is unobservable from the ground; the “missing” metals problem cannot be addressed without this access. Habitable planets grow in protostellar discs under ultraviolet irradiation, a by-product of the accretion process that drives the physical and chemical evolution of discs and young planetary systems. The electronic transitions of the most abundant molecules are pumped by this UV field that is the main oxidizing agent in the disc chemistry and provides unique diagnostics of the planet-forming environment that cannot be accessed from the ground. Knowledge of the variability of the UV radiation field is required for the astrochemical modelling of protoplanetary discs, to understand the formation of planetary atmospheres and the photochemistry of the precursors of life. Earth’s atmosphere is in constant interaction with the interplanetary medium and the solar UV radiation field. The exosphere of the Earth extends up to 35 planetary radii providing an amazing wealth of information on our planet’s winds and the atmospheric compounds. To access to it in other planetary systems, observation of the UV resonance transitions is required. The investigation for the emergence of life calls for the development of large astronomical facilities, including instrumentation in optical and UV wavelengths. In this contribution, the need to develop a large observatory in the optical and in the UV is revealed, in order to complete the scientific goals to investigate the origin of life, inaccessible through other frequencies in the electromagnetic spectrum.

Star-dust geometry main determinant of dust attenuation in galaxies

ABSTRACT Analysing a large representative sample of local galaxies (8707), we find that the variation in the shape of their dust attenuation curves is driven primarily by their structure, i.e. distribution of stars (and dust) within them. The attenuation curve for spheroid dominated galaxies, as compared to the disc-dominated ones, is nearly twice as steep. Both structural types cover distinct ranges of attenuation slope values. Similar findings are reflected in the case of star-forming and passive galaxies. Spheroids and passive galaxies witness minimal attenuation in the optical compared to UV wavelengths, underlining the lack of dusty birth-clouds that define complex star-dust geometry. The distinction in the attenuation properties of spheroids and discs is maintained in each stellar mass range, emphasising that structure is the primal cause of variation. However, within a structural group, the attenuation curve becomes shallower with both the increase in total stellar mass and optical depth of the galaxy. Overall, with the extinction curve fixed to be the same for all galaxies, the star-dust geometry emerges to be the prime determinant of the variation in their attenuation properties.

Degradation of 1-naphthylamine by a UV enhanced Fe2+/peroxymonosulfate system: A novel pH-dependent activation pathway

This study demonstrated an Advanced Oxidation Process (AOPs) by the activation of Peroxymonosulfate (PMS) through Fe2+ and UV for the degradation of 1-naphthylamine (1-NA). A series of processes including Fe2+/PMS, Fe2+/UV, PMS/UV, Fe2+/PMS/UV and direct photolysis by UV-A, UV-B, UV-C were examined. Comparatively, the Fe2+/PMS/UV process was highlighted to have the most remarkable degradation efficiency with 100% 1-NA removal within 20 min. The total organic carbon (TOC) removal can achieve 83.5% (mineralization rate = 0.08 g TOC/min) by 1.5 h under higher Fe2+/PMS dosage. The superior performance was ascribed to the activation of PMS into exclusive sulfate radicals (SO4•–) and hydroxyl radicals (•OH). The optimal Fe2+/PMS ratio, pH level, and UV wavelength were determined to be [Fe2+: PMS]0 = 1: 2, wavelength = 254 nm, pH = 2.98. This process was observed to be a pH dependent process. A rise of degradation efficiency was observed once the pH was adjusted to above the pKa of 1-NA and was rationalized by the NaOH activation of PMS. Pigments were observed in different conditions and were justified by spectrophotometric analysis. By proposing GC/MS and LC/MS analysis, lawsone and juglone were identified as the major product. The oxidation reaction initiated by SO4•– and •OH has contributed a dominant role in the process, nevertheless, the redox cycle introduced by Fe2+/Fe3+ can contribute the reduction of diol to quinone intermediates, which can accelerate the degradation ultimately.

Multi-angle comparison of UV/chlorine, UV/monochloramine, and UV/chlorine dioxide processes for water treatment and reuse

Advanced oxidation processes (AOPs) have been increasingly studied and practiced for micropollutant abatement in drinking water treatment and potable water reuse. This study conducted the multi-angle comparison of the UV/chlorine, UV/monochloramine (UV/NH2Cl), and UV/chlorine dioxide (UV/ClO2) AOPs with respect to reactive species generation, micropollutant degradation, byproduct formation, and toxicity change. The concentrations of radicals (HO·, Cl·, and ClO·) generated in the three AOPs followed the order of UV/chlorine > UV/NH2Cl > UV/ClO2 at an oxidant dose of 70 μM, an irradiation wavelength of 254 nm, and a pH of 7.5. The concentration of ozone generated in the UV/ClO2 AOP was higher than that in the UV/chlorine AOP, while ozone was not generated in the UV/NH2Cl AOP. The effects of pH (pH 6.0, 7.5, and 9.0) and UV wavelength (254 nm, 285 nm, and 300 nm) on the three AOPs were evaluated and compared. Using the radical and ozone concentrations determined in this study, the pseudo-first-order degradation rate constants of 24 micropollutants by the three AOPs were predicted and compared. When the three AOPs were used to treat the water containing the same concentration of natural organic matter, the formation of total organic chlorine (TOCl) and the organic byproduct-associated toxicity followed the same order of UV/chlorine > UV/NH2Cl > UV/ClO2. On the contrary, the inorganic byproduct-associated toxicity followed the order of UV/ClO2 > UV/chlorine > UV/NH2Cl, due to the high concentrations of chlorite and chlorate formed in the UV/ClO2 AOP. Findings in this study offer fundamental information useful for the selection and operation of AOPs for micropollutant abatement in drinking water treatment and potable water reuse.

Engineering 2D semiconductors of PbI2@NdI2 and NdI2@CuI with respect of photovoltaic and solar cell applications

In this study, given the high capability and potential of PbI2, CuI halide semiconductors and NdI2 in new technologies, PbI2@NdI2 and NdI2@CuI nanostructures were introduced and their electro-optical properties were investigated by density functional theory calculations. The results showed that the morphology of PbI2@NdI2 and NdI2@CuI appropriate for stable synthesize and strength structures. Both compounds have the majority carrier densities of hole and the charge carriers density of PbI2@NdI2 was higher than that of NdI2@CuI. Investigation calculation on optical properties showed that the optical behavior of the two structures is favorable at UV and IR wavelengths. However, light absorption of NdI2@CuI in the visible region is higher than PbI2@NdI2 and in the UV region is less than PbI2@NdI2. Also, the optical gap of PbI2@NdI2 and NdI2@CuI was calculated at 2 eV and 1.3 eV, respectively. The static dielectric constant of PbI2@NdI2 and NdI2@CuI were obtained at 1.05 and 0.95, respectively. Therefore, calculation studies show that PbI2@NdI2 and NdI2@CuI nanostructures can improve the efficiency of photovoltaic solar cells by increasing the absorption of the solar spectrum. Also, PbI2@NdI2 has lower structural losses at different wavelengths and can be a good combination for making high power laser filters.

A systematic study of Surface Plasmon Enhanced Electric Field in Nanoparticle Dimers for UV Plasmonics

AbstractSurface plasmon mediated electric field enhancement in the dimer arrangement of Al, Ag and, Au nanoparticles using multipole spectral expansion (MSE) approach has been studied. MSE method has flexibility and simplicity in extending the approach to treat an arbitrary arrangement of nanoparticles by solving corresponding general eigenvalue problem. The field enhancement behavior of Al, Ag, and Au nanoparticle dimers has been investigated, covering UV–VIS spectral range. The role of embedding medium, particle–particle separation, and the metal type were studied. The resonance wavelength showed the red shift with increasing the dielectric constant of the ingrained material. The red shift with increasing particle size and the dielectric constant of embedded or ingrained medium has been studied. This study was used to design plasmonic nanoparticle dimer with resonant optical response at crucial wavelengths in UV–VIS spectral region.

Epidemiology of Panton Valentine Leukocidin in clinical Staphylococcus aureus isolates - A prospective study at a tertiary care centre in North India

BackgroundStaphylococcus aureus is a cause of wide range of infections. The pathogenicity of Staphylococcus aureus is related to a number of virulence factors. Panton-Valentine Leukocidin (PVL), a cytolysin that has the ability of leukocyte destruction and tissue necrosis is one such virulence factor determining the pathogenicity of Staphylococcus aureus infections. This study aims to know the distribution of pvl gene in various clinical specimens and associate pvl gene with antimicrobial resistance in Staphylococcus aureus, particularly MRSA. MethodsConsecutive clinical samples including pus, blood, respiratory samples and body fluids received in laboratory, during the study period, which gave growth of Staphylococcus aureus were included in the study. Further antibiotic sensitivity testing was done using CLSI guidelines. Detection of pvl gene was done by extraction of DNA using boiling method followed by conventional PCR. The amplified DNA was analysed by 264 nm wavelength UV transillumination via Gel Electrophoresis. ResultsOut of 258 Staphylococcus aureus pvl gene was detected in 24.03%(62/258, p < 0.05). The distribution of PVL in Staphylococcus aureus isolates among various clinical samples was 29.9% in pus samples, 12% blood culture samples, 26.4% in respiratory samples. Only 1 of 5 body fluid Staphylococcus aureus isolate detected PVL. Out of 62 pvl gene positive isolates 79% of were MRSA and 20.9% were Methicillin sensitive. ConclusionAssociation with pvl gene was significantly higher in skin and soft tissue infection but it also detected in blood stream infection and pneumonia, which indicate association of pvl gene with invasive infection.

Photocurable Printed Piezocapacitive Pressure Sensor Based on an Acrylic Resin Modified with Polyaniline and Lignin

AbstractThe design of suitable materials for the manufacture of pressure sensors with high sensitivity and flexibility in wearable electronics is still a challenge. In this study, a flexible and portable pressure sensor is developed based on a photopolymeric formulation of polyaniline (PANI)/Lignin/acrylate. The amount of photoinitiator and the presence of lignin within the filler are investigated to obtain the best printability and capacitive response. Low PANI contents drastically increase the dielectric constant and 4 wt% photoinitiator improves the signal and sensitivity. A sensitivity of 0.012 kPa–1 is achieved in a linear range (0–10 kPa) with only 3.5 wt% PANI. Lignin improves both the dispersion of the filler within the matrix and the printability of the resin, due to lower absorptivity at the UV wavelength of the 3D printer. Thus, the PANI‐Lignin filler is selected for the fabrication of a piezocapacitive prototype transducer. The pressure transducer demonstrate its practical application by responding to a human footfall and transmitting its corresponding electrical signal. This study shows the enhanced properties of lignin modified PANI acrylate composites. Based on lignin, an abundant natural waste, a sustainable photocurable cost‐effective polymer is proposed for the fabrication of printable, wearable electronics.

Fabric phase sorpitive extraction and passive sampling of ultraviolet filters from natural waters using a zirconium metal organic framework-cotton composite

In this work, we introduce the use of MOFs immobilized on cotton fabrics as a sorbent phase for the fabric phase sorptive extraction and passive sampling of non-polar organic compounds from water samples. A water-stable, Zr4+-based MOF (UiO-66(Zr)-NH2) was irreversibly immobilized on polydopamine decorated cotton through a step-wise synthetic procedure that maximized the amount of MOF immobilized on the fabric surface. In this manner it was possible to combine the permeability and the large contact surface area of the host cotton substrate with the high specific surface area and sorption capacity of the MOF. The MOF@cotton composite was used as a new sorbent phase for the fabric phase sorptive extraction of UV filters, as model organic compounds, not only under static (i.e. stirring assisted) but also in dynamic, flow-through extraction mode (i.e. as a solid phase extraction sorbent phase), producing satisfactory analytical results in terms of linearity of calibration curves (10–250 µg L−1), precision (<11%), detection limits <10 µg L−1 (using a single wavelength UV detector) and recoveries (86 - 119%) from various natural water samples. As a passive sampling sorbent phase, the MOF@cotton composite could linearly accumulate UV filters over time period of 35 days with sampling rates from 0.026 to 0.352 L d−1, which are comparable to other passive sampling sorbent phases.

Work‐Function‐Tunable MXenes Electrodes to Optimize p‐CsCu2I3/n‐Ca2Nb3‐xTaxO10 Junction Photodetectors for Image Sensing and Logic Electronics

AbstractTunable work function has a high profile for the MXene‐based optoelectronic devices, and surface modification provides the huge potential to shift its Fermi level and modulate the work function. In this work, the window of MXene's work function is engineered from 4.55 to 5.25 eV by surface modification with LiF, Se, and polyethylenimine ethoxylated (PEIE). The vertical p‐CsCu2I3/n‐Ca2Nb3‐xTaxO10 junction photodetectors are constructed on the basis of the above surface‐modified MXenes, which changes the Schottky barrier between n‐Ca2Nb3‐xTaxO10 and the electrodes. In particular, the rectification effect is significantly enhanced by utilizing PEIE‐decorated MXene electrodes, resulting in a high rectification ratio of 16 136 and improved UV responsivity of 81.3 A W–1. Such high‐performance devices based on MXenes electrodes are compatible with the standard clean room fabrication process, realizing large‐scale flexible UV detectors that maintain 80% of the original current after 5000 times bending. Meanwhile, a photodetector array stimulated with UV of different wavelengths is constructed to reveal its potential for image sensing. Finally, functional “AND” and “OR” optoelectronic logic gates are developed for UV communication using Au/CsCu2I3/Ca2Nb3‐xTaxO10/MXene–PEIE photodetectors, enriching the application of MXene‐based optoelectronic devices. This work on tuning MXene work function via surface modification demonstrates that MXene is a promising candidate for future optoelectronics.

Influence of nitrate/nitrite on the degradation and transformation of triclosan in the UV based disinfection

This study investigated the influence of nitrate/nitrite on the degradation and transformation pathway of triclosan (TCS) in UV, UV/peracetic acid (PAA) and UV/HClO processes. The results indicated that the function of nitrate/nitrite significantly depended on the UV source and wavelength, especially nitrate. Generally, the presence of nitrate decreased the direct photo-degradation of TCS in the UV based disinfection. In the LED-UV and LED-UV/HClO processes, the presence of nitrate improved the radical oxidation, and transformation pathway of TCS was varied accordingly. However, nitrate more played a role of photo-competitor in the UV/PAA process, and the reactive nitrogen species (RNS) was difficult to participant in the degradation of TCS due to low redox potential. Compared to nitrate, the presence of nitrite decreased the degradation of TCS in three different UV based disinfection processes. Under UV irradiation, nitrite primarily acted as an irradiation competitor and radical scavenger. Thus, the indirect photo-degradation of TCS was reduced. Noticeably, nitrate/nitrite were the improtant precersors of nitrogenous products in the UV base disinfection. Many new nitrogenous products were identified. But RNS preferentially reacted with the intermediates by –NO2 addition compared to directly reacted with TCS.

A hot and luminous source at the site of the fast transient AT2018cow at 2–3 yr after its explosion

ABSTRACT We report the discovery of a luminous late-time source at the position of the fast blue optical transient AT2018cow on images taken by the Hubble Space Telescope at 714 d and 1136 d after its explosion. This source is detected at both UV and optical wavelengths and has prominent Hα emission. It has a very stable brightness between the two epochs and a very blue spectral energy distribution consistent with fλ $\propto \, \lambda ^{-4.1 \pm 0.1}$, i.e. the Rayleigh–Jeans tail of a hot blackbody with a very high temperature of log(T/K) &amp;gt; 4.7 and luminosity of log(L/L⊙) &amp;gt; 7.0. This late-time source is unlikely to be an unrelated object in chance alignment, or due to a light echo of AT2018cow. Other possible scenarios also have some difficulties in explaining this late-time source, including companion star(s), star cluster, the survived progenitor star, interaction with circumstellar medium, magnetar, or delayed accretion in a tidal disruption event. Long-term and multi-wavelength monitoring will help to resolve its nature and finally reveal the origin of the ‘Cow’.

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.

Cover Feature: Photoionization, Structures, and Energetics of Na‐Doped Formic Acid–Water Clusters (ChemPhysChem 5/2022)

The Cover Feature shows the natural difference orbital profiles of the first electronic excited states in the UV wavelength range of Na⋅⋅⋅HCOOH⋅⋅⋅(H2O)n clusters. The existence of these Rydberg–type electronic transitions could explain the cluster ionization at laser energy lower than their vertical ionization potential, enabling the correct data interpretation on acid-water cluster formation. More information can be found in the Research Article by Tonia M. Di Palma and co-workers.

Rare-earth-doped electrospun scheelite CaWO4 nanofibers with excitation-dependent photoluminescence and high-linearity cathodoluminescence for ratiometric UV wavelength and radiation sensors

Scheelite structured AWO4 compounds (A = Ba, Ca, Pb and Sr) are efficient hosts for rare-earth dopants. In this work, high-aspect-ratio AWO4 (A = Ba, Ca, Pb and Sr) nanofibers, doped with 5 mol.% Tb and 5 mol.% Eu on A site, were synthesized using a sol-gel electrospinning technique, and their performances as a ratiometric sensor for the detection of UV light wavelength were comparatively studied. High-resolution electron microscopy reveals the presence of nanosized grains composing the nanofibers. The AWO4:5Tb-5Eu nanofibers exhibit strong characteristic photoluminescence (PL) and cathodoluminescence (CL) emission from both Tb3+ and Eu3+ ions. In the case of CaWO4 lattice, the emission intensity ratio of Tb3+/Eu3+ is found to show a linear relationship with the excitation wavelength in the tested range of 240–330 nm, with efficient energy transfer from host lattice to rare-earth ions. However, a similar result is not observed in other scheelite structured BaWO4, PbWO4, and SrWO4 nanofibers. The unique PL emission characteristics of CaWO4:5Tb-5Eu under different UV excitation wavelengths are due to its unique excitation band. This study reveals a potential new application of CaWO4:5Tb-5Eu as a fluorescent probe for UV wavelength detection. Additionally, the CL intensities from CaWO4:5Tb-5Eu nanofibers exhibit highly linear dependences on the applied voltage and current without saturation, which can be utilized for radiation detection.

Light-induced high-efficient cellular production of immune functional extracellular vesicles.

Extracellular vesicle (EV)‐based therapies and vaccines are emerging. However, employment at the scale for population‐based dose development is always a huge bottleneck. In order to overcome such a roadblock, we introduce a simple and straightforward approach for promoting cellular production of dendritic cell derived EVs (DEVs) by leveraging phototherapy based light induction. Under the optimization of light wavelengths, intensities, and exposure times, we achieved more than 13‐fold enhancement in DEV production rate, while maintaining good integral quality and immune function from produced EVs. The LED light at 365 nm is optimal to reliably trigger enhanced cellular production of EVs no matter cell line types. Our observation and other reported studies support longer near UV wavelength does not impair cell growth. We conducted a series of investigations in terms of size, zeta potential, morphology, immune surface markers and cytokines, biocompatibility, cellular uptake behaviour, and immune‐modulation ability on eliciting cellular responses in vitro. We also validated the biodistribution, immunogenicity, and administration safety using light‐promoted DEVs in mice models from both male and female genders. Overall data supports that light promoted DEVs are highly immune functional with great biocompatibility for serving as good therapeutic platforms. The in vivo animal study also demonstrated light‐promoted DEVs are as well tolerated as native DEVs, with no safety concerns. Taken together, the data supports that light promoted DEVs are in excellent quality, high biocompatibility, in vivo tolerant, and viable for serving as an ideal therapeutic platform in scalable production.

Deep UV transparent conductive oxide thin films realized through degenerately doped wide-bandgap gallium oxide

Deep UV transparent thin films have recently attracted considerable attention owing to their potential in UV and organic-based optoelectronics. Here, we report the achievement of a deep UV transparent and highly conductive thin film based on Si-doped Ga2O3 (SGO) with high conductivity of 2500 S/cm. The SGO thin films exhibit high transparency over a wide spectrum ranging from visible light to deep UV wavelength and, meanwhile, have a very low work-function of approximately 3.2 eV. A combination of photoemission spectroscopy and theoretical studies reveals that the delocalized conduction band derived from Ga 4s orbitals is responsible for the Ga2O3 films’ high conductivity. Furthermore, Si is shown to act as an efficient shallow donor, yielding high mobility up to approximately 60 cm2/Vs. The superior optoelectronic properties of SGO films make it a promising material for use as electrodes in high-power electronics and deep UV and organic-based optoelectronic devices.

Multiple Bioactivities of Manihot esculenta Leaves: UV Filter, Anti-Oxidation, Anti-Melanogenesis, Collagen Synthesis Enhancement, and Anti-Adipogenesis.

The cassava root is an important global agro-industrial crop that yields cassava leaf as a left-over co-product of interest for further development as a sustainable resource of health and cosmeceutical active compounds. This work aimed to investigate the cosmeceutical potential and chemical composition of an ethanolic cassava leaf extract (BM). rutin, apigenin, and kaempferol were found to be major constituents via HPLC-DAD UV analysis. Interestingly, the multiple beneficial bioactivities of BM for cosmeceutical applications were manifested in a dose-dependent manner, including anti-oxidation in a 2,2-diphenyl-1-picrylhydrazyl assay, anti-melanogenesis in B16 melanoma cells, collagen synthesis enhancement in human fibroblasts, and anti-adipogenesis in 3T3-L1 adipocytes. Furthermore, the potential of the collagen synthesis enhancement of BM and rutin was significant when compared to ascorbic acid. Additionally, a UV filter property comparable to BEMT with characteristics of board spectral absorption and constant high absorptivity throughout all UV wavelength ranges was exhibited by UV-visible spectrophotometric analysis. In conclusion, the cassava leaf was found to be a potential natural cosmeceutical active agent with multiple cosmeceutical-related bioactivities with respect to a substantial composition of bioactive flavonols. These obtained data will support and encourage the further study and development of cassava leaves as potential economic and sustainable sources of bioactive agents for health and cosmeceutical applications.

A Study of Wave Confinement and Optical Force in Polydimethlysiloxane-Arylazopyrazole Composite for Photonic Applications.

A refractive index of dielectrics was modified by several methods and was known to have direct influence on optical forces in nanophotonic structures. The present contribution shows that isomerization of photoswitching molecules can be used to regulate refractive index of dielectrics in-situ. In particular, spectroscopic study of a polydimethylsiloxane–arylazopyrazole (PDMS–AAP) composite revealed that refractive index of the composite shifts from 2.0 to 1.65 in trans and cis states, respectively, of the embedded AAP. Based on this, a proposition is made for a waveguide structure, in which external UV/Vis source reversibly regulates the conformation of the PDMS–AAP core. Computational study is performed using Maxwell’s equations on buried waveguide structure. The simulation, implemented in PYTHON, sequentially utilizes empirical refractive indices of the composite in the isomeric states in lieu of regulation by a source. The simulation revealed highly confined wave propagations for injected signals of 340 and 450 nm wavelengths. It is observed that the cis state suppresses higher order mode when propagating UV wavelength but allows it for visible light. This modal tuning demonstrated that single mode can be selectively excited with appropriate waveguide dimensions. Further impact of the tuning is seen in the optical force between waveguide pair where the forces shift between attractive and repulsive in relation to the isomeric state of the PDMS–AAP core. These effects which stem from the adjustment of refractive index by photoisomerization suggests that in-situ regulation of index is achievable by successful integration of photoswitching molecules in host materials, and the current PDMS–AAP composites investigated in this study can potentially enhance nanophotonic and opto-mechanical platforms.

Effective UV wavelength range for increasing aflatoxins reduction and decreasing oil deterioration in contaminated peanuts

Many studies have demonstrated that UV radiation can degrade aflatoxins (AF) in contaminated foods. However, the effective wavelength ranges for AF decomposition and their impacts on the quality of foods have not been elucidated. This study investigated the AF reduction and oil quality change in peanuts subjected to three types of 17 W low-pressure (LP) UV lamps covering UV-A (Max. emission: 365 nm), UV-B (Max. emission: 310 nm), and UV-C (Max. emission: 254 nm) ranges and a 2000 W medium-pressure UV lamp covering from UV-A to UV-C. We used peeled-kernels for this study since the peanut skin represented an ability to protect AF from being degraded by UV. LP UV-A lamp treatment has shown the highest AF reduction in artificially spiked peeled-kernels and no detectable oil deterioration. With the same delivered UV dosage as LP lamp, MP lamp has shown the same level of AF reduction as LP UV-A lamp did, indicating such treatment was energy inefficient. Treating Aspergillus nomius inobulated peeled-kernels by two LP UV-A lamps (2.76 mW/cm2) for 1.0 h reduced 40% of AF if the kernels were milled into 1 mm-diameter particle, implying that exposing the interior part of kernels to UV radiation is necessary for an AF decontamination process. In the oil deterioration test, we found that UV-C strongly induced the oil oxidation of peanuts. Accordingly, we concluded that UV-A is the effective wavelength range to degrade AF as well as maintain the oil quality in foods allowing UV radiation to well penetrate the sample, such as liquid foods with low turbidity or solid foods in the particle form. These results also justify the use of solar radiation as an AF decontamination method, rendering this method to be employed in in areas that lack infrastructure.