Pulsed UV Light Research Articles

The effects of sub-monolayer laser etching on the chemical and electrical properties of the (100) diamond surface

Tailoring the surface chemistry of diamond is critical to a range of applications from quantum science to electronics. It has been recently shown that dosing the diamond surface with pulsed UV light at fluences below the ablation threshold provides a practical method for precision etching of the surface. Here, we track the evolution of the surface chemistry and its electrical properties as a function of dose using x-ray surface analysis, Hall and resistance measurements. It is found that the surface properties evolve rapidly, even for doses that correspond to removal of less than 5% of the top carbon monolayer and fluences less than 1 J/cm2. As well altering XPS-measured surface populations, sub-monolayer etch doses lower the valence band by up to 0.2 eV, and produce a permanent increase in the conductivity of the hydrogen terminated surface by up to 7 times. Similar enhancements in conductivity are obtained for doses that remove up to 1600 ML. The results provide guidance for manipulating diamond surface chemistry by UV laser etching and introduce a promising method for enhancing the performance of diamond devices such as field-effect transistors.

Computational Fluid Dynamics Analysis and Biodosimetry-Based Microbial Validation for Continuous-Flow Pulsed UV Light Reactors for Processing of Model Liquid Foods

Computational Fluid Dynamics Analysis and Biodosimetry-Based Microbial Validation for Continuous-Flow Pulsed UV Light Reactors for Processing of Model Liquid Foods

Aspects of quercetin stability and its liposomal enhancement in yellow onion skin extracts

Quercetin is a flavonoid that occurs in many types of fruit and vegetables and is stable for no longer than 4.5 h in the investigated pH range (6.0–8.0), even at 4 °C in the dark. At higher temperatures, the degradation/oxidation process is much faster. Simple but effective proliposomal encapsulation was used to protect the quercetin from environmental conditions such as pH. With this approach, 65 to 90% of pure quercetin and quercetin-rich onion extract was kept after >60 days under conditions that favoured its oxidation (pH 7.4). In addition, the encapsulated quercetin decreases the lipid peroxidation induced by pulsed UV light by >50%. At a mass ratio of 1:100 quercetin to lipids (w/w), the liposomes remained intact in solutions for six months. Quercetin in lipid bilayers simultaneously protects the unsaturated lipids from peroxidation.

First operation of a multi-channel Q-Pix prototype: measuring transverse electron diffusion in a gas time projection chamber

We report measurements of the transverse diffusion of electrons in P-10 gas (90% Ar, 10% CH4) in a laboratory-scale time projection chamber (TPC) utilizing a novel pixelated signal capture and digitization technique known as Q-Pix. The Q-Pix method incorporates a precision switched integrating transimpedance amplifier whose output is compared to a threshold voltage. Upon reaching the threshold, a comparator sends a 'reset' signal, initiating a discharge of the integrating capacitor. The time difference between successive resets is inversely proportional to the average current at the pixel in that time interval, and the number of resets is directly proportional to the total collected charge. We developed a 16-channel Q-Pix prototype fabricated from commercial off-the-shelf components and coupled them to 16 concentric annular anode electrodes to measure the spatial extent of the electron swarm that reaches the anode after drifting through the uniform field of the TPC. The swarm is produced at a gold photocathode using pulsed UV light. The measured transverse diffusion agrees with simulations in PyBoltz across a range of operating pressures (200–1500 Torr). These results demonstrate that a Q-Pix readout can successfully reconstruct the ionization topology in a TPC.

Novel method to study saturation of silicon photomultiplier in scintillation detector

Signal saturation in the Silicon PhotoMultiplier (SiPM) often causes a serious problem in using a detector equipped with SiPMs for scintillator readout. Conventionally, SiPM signal saturation is measured through direct injection of visible light pulses to the SiPM. However, the method works poorly with the scintillation detector because the effects of the time constant of the emission of scintillation light are not included. Here, we present a novel method to measure the precise degree of SiPM signal saturation in scintillation detectors. The key difference from the conventional method is to use UV light pulses, as opposed to visible light ones, to inject and excite scintillation light in the detector. It allows us to directly measure the degree of saturation in situ taking into account all the major effects in the detector, such as the time constant of the scintillation emission. We also develop a new model for SiPM signal saturation and validate it with the measured degree of saturation with the above-mentioned new method.

Effect of pulsed ultraviolet light on the degree of antigenicity and hydrolysis in cow's milk proteins

AbstractIn order to reduce the quantity of allergens that are causing harm to consumer, it is imperative that the proteins found in cow's milk undergo controlled hydrolysis. Investigated were the effects of different pulsed UV light fluences (0.1–10 J/cm2) on samples of commercial cow's milk proteins (CCMP: casein (CN), α‐lactalbumin (α‐LA), and β‐lactoglobulin (β‐LG)) and reconstituted cow's milk proteins (RCMP). The degree of hydrolysis (DH) and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) profiles in RCMP and CCMP, as well as the degree of antigenicity in RCMP, were assessed for this purpose. The DH increased in CCMP and RCMP samples at the highest fluence applied. SDS PAGE profiles showed a decrease in the intensity of the bands of the CCMP samples for fluences of 5 and 10 J/cm2; however, this was not the case for α‐LA. Finally, the degrees of antigenicity measured with Elisa assay in CN and β‐LG were reduced by 24% and 47%, respectively, at a fluence of 10 J/cm2. Therefore, this nonthermal technology could be an alternative to conventional treatments to reduce the allergenic potential of cow's milk proteins; however, future clinical trials to confirm an anti‐allergenic effect on consumer are needed.Practical ApplicationsPulsed UV light is a nonthermal technology of great relevance in the dairy industry. The aim of this article was to generate knowledge of the effect of pulsed UV light on allergenic dairy proteins. Therefore, this article aimed to demonstrate that pulsed UV light can be a novelty compared with conventional methods of inactivation of commercial and reconstituted dairy allergenic proteins.

Optoelectronic Synapse Based on 2D Electron Gas in Stoichiometry-Controlled Oxide Heterostructures.

Emulating synaptic functionalities in optoelectronic devices is significant in developing artificial visual-perception systems and neuromorphic photonic computing. Persistent photoconductivity (PPC) in metal oxides provides a facile way to realize the optoelectronic synaptic devices, but the PPC performance is often limited due to the oxygen vacancy defects that release excess conduction electrons without external stimuli. Herein, a high-performance optoelectronic synapse based on the stoichiometry-controlled LaAlO3/SrTiO3 (LAO/STO) heterostructure is developed. By increasing La/Al ratio up to 1.057:1, the PPC is effectively enhanced but suppressed the background conductivity at the LAO/STO interface, achieving strong synaptic behaviors. The spectral noise analyses reveal that the synaptic behaviors are attributed to the cation-related point defects and their charge compensation mechanism near the LAO/STO interface. The short-term and long-term plasticity is demonstrated, including the paired-pulse facilitation, in the La-rich LAO/STO device upon exposure to UV light pulses. As proof of concepts, two essential synaptic functionalities, the pulse-number-dependent plasticity and the self-noise cancellation, are emulated using the 5×5 array of La-rich LAO/STO synapses. Beyond the typical oxygen deficiency control, the results show how harnessing the cation stoichiometry can be used to design oxide heterostructures for advanced optoelectronic synapses and neuromorphic applications.

Non-thermal processing of watermelon and red grape juices in thin-profile continuous-flow pulsed UV light reactors: Effect on microbiological safety and nutritional value

Herein, we report successful non-thermal pasteurization of fruit juices (watermelon and red grape juices) in a flow-through pulsed light (PL) reactor. Impact of PL reactor configuration (annular/coiled tube), product flow rates (14–75 L/h) and pulse frequency (1–5 Hz) on the inactivation of Escherichia coli ATCC 29055, Listeria innocua ATCC 33090, and Clostridium sporogenes ATCC 7955 in red grape (pH = 3.37) and watermelon juice (pH = 5.02), and changes in quality and nutritional parameters, was explored. >5 and > 7 log10 microbial reductions were achieved in annular and coiled reactor respectively, demonstrating PL's potential in juice pasteurization. Watermelon juice exhibited higher microbial inactivation, while E. coli was found to be most susceptible. The inactivation kinetics using three different models were compared wherein ‘log-linear plus tail model’ showed the best fit. During PL processing, there were minor changes in pH and colour of both juices, whereas nutritional parameters (total anthocyanins, total phenolics, antioxidant capacity, vitamin C, trans-resveratrol, and lycopene content) decreased significantly (p < 0.05) by up to 39.1%, 62.2%, 53.8%, ∼70%, 82%, and 46.8%, respectively, yet at levels lower than conventional thermal pasteurization. These results shall inspire commercialization of PL based fruit beverage pasteurization systems.

Roll-to-roll gravure printed large-area flexible carbon nanotube synaptic photogating transistor arrays for image recognitions

The development of novel large-area flexible optoelectronic synaptic devices is of great interest for visual neuromorphic computing. In this paper, we have successfully manufactured 33 × 34 flexible carbon nanotube synaptic photogating transistor arrays via the roll-to-roll gravure printing technology using the mixture of photosensitive rhodamine 6G and poly(vinylidene fluoride-co-hexa-fluoropropylene) as the composite dielectric layer. The resulting thin-film transistor devices exhibit excellent electrical properties with high Ion/Ioff (>105), the maximum carrier mobility (10.71 cm2V−1s−1) and low operating voltage (−1.5 V∼ 0.5 V), and excellent optoelectronic synaptic properties, which are capable of performing not only the excitatory postsynaptic current and paired pulse facilitation but also complex biological synaptic functions such as optical writing and electrical erasure, dynamic learning and forgetting processes, and Pavlov's dog experiment. Significantly, the ultralow energy consumption per light spike event as low as 0.03 fJ can be achieved under the pulse UV light illumination. Moreover, according to the trend that the LTP/LTD curve conforms to the concave function, we successfully embed the specific update rules of our synaptic devices into the generative adversarial network (GAN) that can generate high-quality (7680 × 4096 pixels) images, which is impossible for the human eye to distinguish the difference between the original labels and real labels.

Decoupling the Conflicting Roles of Photoactivation and Boosting Chemiresistor Response by Pulsed UV Light Modulation.

UV photoactivation has been widely employed to trigger the response of semiconductor chemiresistors at room temperature (RT). Generally, continuous UV (CU) irradiation is applied, and an apparent maximal response could be obtained via optimizing UV intensity. However, owing to the conflicting roles of (UV) photoactivation in the gas response process, we do not think the potential of photoactivation has been fully explored. Herein, a pulsed UV light modulation (PULM) photoactivation protocol has been proposed. Pulsed UV-on facilitates the generation of surface reactive oxygen species and refreshes the surface of chemiresistors, while pulsed UV-off avoids the side effects of UV-induced desorption of the target gas and the decline of base resistance. PULM enables decoupling those conflicting roles of CU photoactivation, resulting in a drastic boost of response to trace (20 ppb) NO2 from 1.9 (CU) to 131.1 (PULM UV-off), and a decline of limit of detection from 2.6 ppb (CU) to 0.8 ppb (PULM) for a ZnO chemiresistor. This work highlights that PULM allows full exploitation of the potential of nanomaterials for sensitively detecting trace (ppb-level) toxic gas molecules and opens a new opportunity for designing highly sensitive, low-power consumed RT chemiresistors for ambient air quality monitoring.

Controlled Production of Carnosic Acid and Carnosol in Cell Suspensions of Lepechinia meyenii Treated with Different Elicitors and Biosynthetic Precursors.

Lepechinia meyenii is a medicinal plant specialized in the biosynthesis of different types of antioxidants including the diterpenes carnosic (CA) acid and carnosol (CS). Herein we present the results of plant tissue culture approaches performed in this medicinal plant with particular emphasis on the generation and evaluation of a cell suspension system for CA and CS production. The effect of sucrose concentration, temperature, pH, and UV-light exposure was explored. In addition, diverse concentrations of microbial elicitors (salicylic acid, pyocyanin, Glucanex, and chitin), simulators of abiotic elicitors (polyethylene glycol and NaCl), and biosynthetic precursors (mevalonolactone, geranylgeraniol, and miltiradiene/abietatriene) were evaluated on batch cultures for 20 days. Miltiradiene/abietatriene obtainment was achieved through a metabolic engineering approach using a recombinant strain of Saccharomyces cerevisiae. Our results suggested that the maximum accumulation (Accmax ) of CA and CS was mainly conferred to stimuli associated with oxidative stress such as UV-light exposure (Accmax , 6.2 mg L-1 ) polyethylene glycol (Accmax , 6.5 mg L-1 ) NaCl (Accmax , 5.9 mg L-1 ) which simulated drought and saline stress, respectively. Nevertheless the bacterial elicitor pyocyanin was also effective to increase the production of both diterpenes (Accmax , 6.4 mg L-1 ). Outstandingly, the incorporation of upstream biosynthetic precursors such as geranylgeraniol and miltiradiene/abietatriene, generated the best results with Accmax of 8.6 and 16.7 mg L-1 , respectively. Optimized batch cultures containing 100 mg L-1 geranylgeraniol, 50 mg L-1 miltiradiene/abietatriene (95 : 5 %) and 5 g L-1 polyethylene glycol treated with 6 min UV light pulse during 30 days resulted in Accmax of 26.7 mg L-1 for CA and 17.3 mg L-1 for CS on days 18-24. This strategy allowed to increase seven folds the amounts of CA and CS in comparison with batch cultures without elicitation (Accmax , 4.3 mg L-1 ).

Measurement of stray electric fields in a capacitive inertial sensor using contactless test-mass charge modulation

We present a new technique for measuring the stray electric field in precision space inertial sensors by modulating the electric charge of a free-falling test mass and measuring the resulting coherent Coulomb force. The free charge of the test mass is controlled by ultraviolet photoemission using a pulsed light source synchronized with an oscillating potential capacitively induced on the test mass. We can modulate the test mass charge sinusoidally at an arbitrarily chosen frequency by varying the phase of the UV light pulses relative to the induced test mass potential at the appropriate rate. This technique allows us to optimize the precision of the measurement by choosing a modulation frequency that is within the most sensitive band of the sensor. We present an experimental validation of this approach using an inertial sensor integrated with a torsion pendulum, measuring the equivalent stray potential of the sensor with milliVolt precision in ${10}^{4}\text{ }\text{ }\mathrm{s}$. We discuss the applicability of this technique for the upcoming Laser Interferometer Space Antenna (LISA) gravitational-wave observatory.

Visualization of Hydrogen Penetration Generated in an Atmospheric Corrosion and a Crevice Corrosion

Hydrogen could form in the corrosion reaction and sometimes causes hydrogen-related deterioration of steel. Spatial distribution of hydrogen penetration in steels has been observed using a photocurrent mapping method. In this method, hydrogen penetrated from the backside of the steel sheet formed by the cathodic polarization or corrosion reaction causes an enhancement of photocurrent intensity under the photo-irradiation to the passive film in the anodic biased condition. This photocurrent enhancement may be provided by the photo-generated holes that oxidize hydrogen atoms efficiently on the passive film surface. This work conducted hydrogen penetration mapping using a photo-charge mapping method newly developed for rapid mapping measurement. In this method, a polarization current during single UV-light pulse irradiation was integrated to obtain the charge Q a, and then a charge Q b during the irradiation was subtracted to obtain a photo-charge Q PC = Q a-Q b for a single pulse. This process was performed by the electronics circuit controlled by the computer. Combination of pulse system and X-Y galvano-mirror-scanning device for a light beam emitted from pulse UV (405 nm, 0.2 W) pulse laser, rapid photocharge mapping was achieved, e.g., 24 s for 40 x 40 = 1600 pixel map. In the experiments, a Devanathan-type cell composed of a top cell of a humidity control room and a bottom electrochemical cell was constructed. A UV laser beam was induced to the bottom cell via a quartz window to scan the bottom iron surface. Fig. 1 shows an example of the time-transition of photocharge maps measured for an iron sheet. In the experiment, a droplet of NaCl solution was put on the surface, and the humidity of the top cell was changed to wet/dry/wet conditions. In the figure, a droplet grew with absorbing moisture at 48 ks, rust expanded and precipitated in the droplet at 131 ks, dried to form rust at 668 ks, and soaked again at 534 ks. In this process, penetration of hydrogen was observed at the bottom face. Initially, hydrogen appeared only at the center of the droplet and then expanded to the lateral direction by increasing the photocharge. Fig. 1. Time-transition of top images of an iron sheet (0.1 mmt) with a single NaCl solution droplet and photocharge maps measured for the bottom side of the iron sheet polarized at 0.7 V vs. Ag/AgCl in pH8.4 borate solution. Figure 1

Pulsed UV Integrated Infrared Dryer System for Orthosiphon Stamineus Herb.

The drying system is an important part for food and herbs preservation. Therefore, an effective drying system are needed to ensure the increase the shelf life of the food and herb without degrade its good nutrient and bioactive compound. In this study, Orthosiphon stamineus herb was used to dry using an Infrared dryer and combination of Pulsed UV light treatment + Infrared drying. Infrared drying involves transferring heat by radiation from a hot source to a lower-temperature substance that has to be heated or dried, meanwhile the pulsed UV light is a non-thermal treatment. The temperature of the heated element determines the peak wavelength of the radiation. The objective of this study is to design an infrared dryer system and analyze the quality of the dried herb. The Orthosiphon Stamineus have been dried using a 200W Infrared dryer system at 60°C. Total phenolic compounds and antioxidant capacity were determined using the Folin-Ciocalteu method and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity assay measured using a UV/VIS Spectrophotometer. A moisture analyzer was used to look at the changes in moisture content, and a colorimeter was used to look at the colour changes. The result showed that drying Orthosiphon stamineus by using an Infrared dryer and combination of Pulsed UV light treatment + Infrared drying under 60°C has significantly affected the herbal leaves quality in terms of moisture content, colour properties, Antioxidant capacity, and Total phenolic content.

Solid-Ionic Memory in a van der Waals Heterostructure.

Defect states dominate the performance of low-dimensional nanoelectronics, which deteriorate the serviceability of devices in most cases. But in recent years, some intriguing functionalities are discovered by defect engineering. In this work, we demonstrate a bifunctional memory device of a MoS2/BiFeO3/SrTiO3 van der Waals heterostructure, which can be programmed and erased by solely one kind of external stimuli (light or electrical-gate pulse) via engineering of oxygen-vacancy-based solid-ionic gating. The device shows multibit electrical memory capability (>22 bits) with a large linearly tunable dynamic range of 7.1 × 106 (137 dB). Furthermore, the device can be programmed by green- and red-light illuminations and then erased by UV light pulses. Besides, the photoresponse under red-light illumination reaches a high photoresponsivity (6.7 × 104 A/W) and photodetectivity (2.12 × 1013 Jones). These results highlighted solid-ionic memory for building up multifunctional electronic and optoelectronic devices.

Intense pulsed UV light treatment to design functional optical films from perhydropolysilazane: an alternative to conventional heat treatment processes

Intense pulsed UV light treatment to design functional optical films from perhydropolysilazane: an alternative to conventional heat treatment processes

Monitoring the Response of Multiple Signal Network Components to Acute Chemo-Optogenetic Perturbations in Living Cells.

Cells process information via signal networks that typically involve multiple components which are interconnected by feedback loops. The combination of acute optogenetic perturbations and microscopy‐based fluorescent response readouts enables the direct investigation of causal links in such networks. However, due to overlaps in spectra of photosensitive and fluorescent proteins, current approaches that combine these methods are limited. Here, we present an improved chemo‐optogenetic approach that is based on switch‐like perturbations induced by a single, local pulse of UV light. We show that this approach can be combined with parallel monitoring of multiple fluorescent readouts to directly uncover relations between signal network components. We present the application of this technique to directly investigate feedback‐controlled regulation in the cell contraction signal network that includes GEF‐H1, Rho and Myosin, and functional interactions of this network with tumor relevant RhoA G17 mutants.

The Effects of Pulsed UV Light Implementation on the Preservation Duration of Şavak Cheese Made from Raw Milk

This study aimed to investigate the effect of pulsed UV light on the the preservation of the Şavak cheese. In this study, the samples of Savak cheese (average 2 cm) that were produced from raw milk were exposed to two-sided pulsed UV light. The microbial analysis (enterobacteria, psychrophilic aerob, lactic acid, sulphate reducing bacteria, S.aureus and yeast-fungus) and chemical analysis (acidity, pH and the number of thiobarbituric acid) of şavak cheese were performed during storage time (25 days) at 4°C. According to the results, spoilage was observed in the control group after ten days, Group 1 was the best in terms of microbiological quality. When experimental samples were compared to the control group, no statistically differences were observed in terms of TBA, acidity, and pH value.

Pulsed UV Light Irradiation Processing of Black Tea Infusions: Effect on Color, Phenolic Content, and Antioxidant Capacity

Pulsed UV Light Irradiation Processing of Black Tea Infusions: Effect on Color, Phenolic Content, and Antioxidant Capacity

N,N'-Bis(3-methylphenyl)-N,N'-dyphenylbenzidine Based Distributed Feedback Lasers with Holographically Fabricated Polymeric Resonators.

The molecule N,N′-bis(3-methylphenyl)-N,N′-dyphenylbenzidine (TPD) has been widely used in optoelectronic applications, mainly for its hole-transporting properties, but also for its capability to emit blue light and amplified spontaneous emission, which is important for the development of organic lasers. Here, we report deep-blue-emitting distributed feedback (DFB) lasers based on TPD dispersed in polystyrene (PS), as active media, and dichromated gelatin layers with holographically engraved relief gratings, as laser resonators. The effect of the device architecture (with the resonator located below or on top of the active layer) is investigated with a dye (TPD) that can be doped into PS at higher rates (up to 60 wt%), than with previously used dyes (<5 wt%). This has enabled changing the index contrast between film and resonator, which has an important effect on the laser performance. With regards to thresholds, both architectures behave similarly for TPD concentrations above 20 wt%, while for lower concentrations, top-layer resonator devices show lower values (around half). Remarkably, the operational durability of top-layer resonator devices is larger (in a factor of around 2), independently of the TPD concentration. This is a consequence of the protection offered by the resonator against dye photo-oxidation when the device is illuminated with pulsed UV light.