Detection Of Ultraviolet Radiation Research Articles

Giant photoresponse in p-type sodium-doped ZnO films

The detection of ultraviolet radiation is currently a topic that deserves the attention of society. This research shows that the addition of sodium (Na) to ZnO thin films enhances the generation and collection of photogenerated carriers at room temperature, making ZnO:Na a promising candidate for photosensors. This effect is particularly pronounced at 10 % Na-concentration, with a photoresponse around 104, suggesting a decrease in the role of deep traps. Additionally, as a defect engineering approach, annealing in different controlled atmospheres shows that the N2 atmosphere provides a markedly faster photoresponse. By introducing Na atoms into the ZnO crystal lattice, charge compensation levels are formed, inducing the p-type conductivity in some ranges of temperature, particularly at 300 K. Annealing in controlled atmospheres also influences both the transition from n-type to p-type conductivity and light-stimulated phenomena.

Spectrally-Selective and High-Resolution Visualization Detection of UVR Based on Efficient Photo-Oxidation

Ultraviolet radiation (UVR) is like a double-edged sword, which has dual significance to human life and health. Current UV sensors struggle to accurately discriminate and quantify UVA, B, and C simultaneously. Additionally, common colorimetric sensors have low visualization resolution. Herein, we constructed a ratiometric fluorescent UVR sensing strategy with spectrally-selective, accuracy, significant color change, and adjustable sensitivity based on the photo-induced fluorescence quenching properties of carbon dots (CDs) and the photosensitization of protoporphyrin IX (PPIX). For daily UVR monitoring, a portable fluorescence reader is developed, which can simultaneously detect dose and intensity. Unlike conventional radiometers, it can sensitively and rapidly discriminate and quantify UVA, B, and C in complex light sources at a lower cost (< 100 $). To ensure the safety of UVR use, wearable fluorescent film sensors (< 0.5 $/piece) we developed for real-time visual monitoring of the cumulative dose of UVA/B during UV phototherapy. Considering individuals with color vision deficiency, we propose a strategy to transform “color analysis” into “count analysis” through creative design, making quantification easier. CDs-PPIX composite offers great potential for UVR detection in our daily lives due to its excellent performance.

High-speed performance self-powered short wave ultraviolet radiation detectors based on κ(ε)-Ga2O3

High-speed solar-blind short wavelength ultraviolet radiation detectors based on κ(ε)-Ga2O3 layers with Pt contacts were demonstrated and their properties were studied in detail. The κ(ε)-Ga2O3 layers were deposited by the halide vapor phase epitaxy on patterned GaN templates with sapphire substrates. The spectral dependencies of the photoelectric properties of structures were analyzed in the wavelength interval 200–370 nm. The maximum photo to dark current ratio, responsivity, detectivity and external quantum efficiency of structures were determined as: 180.86 arb. un., 3.57 A/W, 1.78 × 1012 Hz0.5∙cm∙W−1 and 2193.6%, respectively, at a wavelength of 200 nm and an applied voltage of 1 V. The enhancement of the photoresponse was caused by the decrease in the Schottky barrier at the Pt/κ(ε)−Ga2O3 interface under ultraviolet exposure. The detectors demonstrated could functionalize in self-powered mode due to built-in electric field at the Pt/κ(ε)-Ga2O3 interface. The responsivity and external quantum efficiency of the structures at a wavelength of 254 nm and zero applied voltage were 0.9 mA/W and 0.46%, respectively. The rise and decay times in self-powered mode did not exceed 100 ms.

Highly sensitive self-powered solar-blind ultraviolet photodetectors based on n-Zn1-xFexO/p-Si heterojunctions

The pristine and iron-doped ZnO thin films were fabricated on p-type silicon and glass substrates using the radio-frequency magnetron sputter deposition technique. The structural, morphological, and electrical properties of the deposited thin films were analyzed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), and I-V characteristics. XRD analysis revealed the preferential growth of ZnO along the c-axis, with lattice parameter (c) values of 5.216, 5.234, and 5.241 Å for the pristine ZnO, Zn0.97Fe0.03O, and Zn0.95Fe0.05O thin films, respectively. The crystallite sizes were measured to be 13.2 nm, 16.2 nm, and 18.3 nm for the respective films. The elemental analysis of the deposited films was done under X-ray photoelectron spectroscopy (XPS), which revealed the concentrations of iron Zn0.97Fe0.03O, and Zn0.95Fe0.05O thin films were 2.93 at% and 5.14 at%, respectively. Raman spectroscopy confirmed the presence of the hexagonal wurtzite structural form in the deposited films. The I-V characteristics of the deposited films confirmed the formation of a heterojunction between the film and the silicon substrate. Furthermore, the constructed heterojunction devices were evaluated for their ability to detect ultraviolet (UV) radiations of wavelengths 365 nm and 254 nm. The devices exhibited response and recovery times of less than 1 s. The detectivity values were found to be 0.321 ×1011, 1.051 ×1011, and 2.992 ×1011 Jones for the ZnO/p-Si, Zn0.97Fe0.03O/p-Si, and Zn0.95Fe0.05O/p-Si devices, respectively, under a fixed illumination intensity of 0.812 mW/cm2 for a UVA source with a wavelength of 365 nm. These results confirm the excellent photodetection ability of the constructed devices. The mechanism of UV radiation detection by the devices has also been extensively discussed.

LUMINESCENT DETERMINATION OF EUROPIUM AND CERIUM IN THE JOINT PRESENCE IN SOLUTIONS – MELTS OF EQUIMOLAR MIXTURES NaCl–KCl

Europium and Cerium belong to lanthanides of variable valency and have similar chemical properties. Luminescent method was proposed for the analytical determination of Eu(III) and Ce(III) with the simultaneous presence in the sample of [EuF3–CeF3 (1:1)]–[NaCl–KCl] (2:8), which is a promising material for detecting UV-solar radiation. Determination of Eu(III) was carried out by the method of sensitized 4f-4f luminescence in a complex with nalidixic acid at an emission wavelength of 613 nm, λex =351 nm. During complexation, a standard ratio of Stark components to Europium is observed in the luminescence spectra, in contrast to the spectrum of the sample solution without the reagent. This fact indicates that the formation of complexes not only increases the intensity of Eu(III) luminescence, but also reduces the effect of Cerium present in the solution. To determine Ce(III), its own luminescence caused by 5d-4f electronic transitions was used at an emission wavelength of 351 nm, λex =263 nm. The presence of Europium ions in the solution does not affect the nature of the luminescence excitation spectra and Ce(III) luminescence spectra. For the quantitative determination of these lanthanides, the additive method was used, which allows to level the mutual influence of ions, as well as the influence of Ce(IV) on the determination of Ce(III). It was found that the content of Eu(III) in the melt is 2.44–2.53% weight, which is in good agreement with the data obtained earlier when studying the EuF3 – [NaCl–KCl](1:9) system. Compared to EuF3, the solubility of CeF3 ((0.028–0.032)% weight) is significantly lower than that predicted by previous thermodynamic calculations. The obtained data allow us to conclude that the solubility of fluoride systems containing Eu in the NaCl–KCl melt is almost the same, and the presence of Ce(III) does not significantly affect the EuF3 dissolution process, and therefore does not affect the properties of the systems [EuF3 – CeF3] – [NaCl–KCl] as detectors of ultraviolet solar radiation.

Probing the tunable optical properties of highly luminescent functionalized graphene quantum dots as downconverters for superior detection of ultraviolet radiation

Detection and utilization of ultraviolet (UV) radiation are of paramount importance as commonly used Si photodetectors and photovoltaic cells suffer from poor UV response. Herein, we demonstrate the applications of graphene quantum dots (GQDs) as downconverters to sensitize Si photodiodes for extended and enhanced UV detection down to 300 nm and facilitating distinct visible response to UV wavelength-specific excitation. Stable blue (B-) and orange-red (R-) emitting nitrogen functionalized GQDs, synthesized by cost-effective solvothermal method, exhibit high photoluminescence (PL) quantum yield (57–62%), strong UV absorption, and large Stokes shift (130–250 nm). A scalable threefold improvement in UV response (330 nm) with a relative enhancement factor of 200% is recorded from a Si photodetector externally sensitized with visible-blind B-GQDs. The engineered combination of B- and R-GQDs in a tandem fashion exhibits distinct visible emission and facilitates bare-eye recognition of UV sub-bands. The present study provides a new pathway of UV detection with or without integrated devices by employing thin layers of solution-processed GQDs.

Influence of White Light on the Photoelectric Characteristics of UV Detectors Based on β-Ga2O3

In this report, we consider the effect of radiation with a radiation energy below the β-Ga2O3 band-gap on the photoelectric characteristics of ultraviolet (UV) radiation detectors based on gallium oxide thin films. The gallium oxide film was deposited by the radio frequency magnetron sputtering. Interdigital Ti/V electrodes were formed with an inter electrode distance d = 30 μm. The structures exhibit high value of photocurrent under irradiation with wavelength of λ = 254 nm and intensity of 780 μW/cm2. The detectors exhibit persistent photoconductivity after exposure to UV radiation. The presence of persistent conductivity is explained by the high concentration of traps in the Ga2O3 film and their recharging under UV irradiation. Radiation with an energy quantum below the the β-Ga2O3 band-gap changes the charge state of trap centers in a gallium oxide film. This effect leads to an increase in photocurrent under UV exposure and increases the stability of detectors.

Study of the Sensor Properties of Ordered ZnO Nanorod Arrays for the Detection of UV Radiation

Zinc oxide is one of the most promising materials used to create devices in the ultraviolet (UV) range. In this article, we study the sensor properties of ordered ZnO nanorod arrays grown by chemical vapor deposition. The possibility of their use as an indicator of UV radiation to control the dose of UV radiation, both from natural and artificial light sources, is assessed. The X-ray diffraction, Raman spectroscopy (RS), and cathodoluminescence (CL) data demonstrate the high quality of nanorods. Based on the ZnO nanorod array, a sensor prototype was fabricated based on the change in ZnO conductivity under the UV irradiation. A compari-son of the response of such a sensor with the readings of a UV radiometer showed a high correlation.

Long persistent luminescence and photostimulated luminescence in Y3GaO6:Pr3+ phosphor

Long persistent luminescence (LPL) phosphors have a wide range of potential applications, including multi-color anticounterfeiting and long-term continuous detection of short-wavelength ultra-violet (UV) radiation. However, developing a stable carrier container that can provide ultra-long carrier storage for activators and visible multi-color LPL is a challenging task. In this work, we presented a series of Pr3+-doped Y3GaO6 (YGO) LPL phosphors that take full advantage of the synergistic relationship between the host lattice, emitters, and carrier traps. The host provides a suitable lattice site for rare-earth Pr3+ and offers a broad band gap of 5.69 eV to hold traps with depths ranging from 1.01 to 2.17 eV. We observed LPL that was visible to the naked eye for 6 h after excitation, and strong thermoluminescence (TL) spectra could be detected after the phosphor was placed in darkness for 20 days at room temperature. Additionally, we observed photostimulated luminescence under 980 nm and 808 nm laser irradiation with a power density of 5 W cm-2, indicating that low-energy excitation not only leads to LPL but also accelerates the elimination of previously stored carriers. After investigating the crystal structure and possible defects generated in the materials, we proposed a mechanism for LPL. Our findings demonstrate the potential of Pr3+-doped YGO LPL phosphors for a range of applications, such as multi-color anticounterfeiting and long-term continuous detection of short-wavelength UV radiation.

Perspectives on MOVPE-grown (100) β-Ga2O3 thin films and its Al-alloy for power electronics application

Beta gallium oxide (β-Ga2O3) is a promising ultra-wide bandgap semiconductor with attractive physical properties for next-generation high-power devices, radio frequency electronics, and solar-blind ultraviolet radiation detectors. Here, we present an overview and perspective on the development of MOVPE-grown (100) β-Ga2O3 thin films and its role in supplementing high-power electronics. We review the development path of the growth process on (100) β-Ga2O3 thin films with a discussion regarding the solved and remaining challenges. The structural defect formation mechanism, substrate treatment strategies, and different growth windows are analyzed to optimize the grown film to fulfill the requirements for device fabrication. Toward industrial applications, MOVPE-grown β-Ga2O3 thin films are evaluated in two aspects: thick layers with smooth surface roughness and the electrical properties in terms of high carrier mobility and low doping concentration. Based on the reviewed results, we propose strategies in substrate preparation treatments and supportive tools such as the machine learning approaches for future growth process optimization and envision the rising interest of the β-Ga2O3-related alloy, β-(AlxGa1−x)2O3.

Study of UV interactions on PMMA based ZnCuInS/ZnS quantum dot films

Scintillator materials are used to transform radiation into light. In recent years scintillator materials of small dimensions in nano-scale or quantum dots are investigated, since they exhibit increased efficiency in optical photon production. In addition, polymethyl-methacrylate (PMMA) is an easy to shape material that can be used in the form of a PMMA/scintillator compound for the detection of ultraviolet radiation. Methods: In this paper, a PMMA/[ZnCuInS/ZnS] compound is theoretically examined, via an analytical model, in terms of its optical photon output efficiency, under UV excitation. Results: Assuming exponential attenuation of the radiation in the PMMA/QD detectors, the UV attenuation coefficients were found as 0.008 cm-1, 0.036 cm-1, 0.093 cm-1 and 0.156 cm-1 for QD concentrations in the PMMA/[ZnCuInS/ZnS] compound of 25, 100, 150 and 250 mg/ml respectively. The detector thickness was not found to affect the light output efficiency significantly. Conclusions: The model predicted that the highest efficiency could be obtained by a 310 mg/ml concentration PMMA/[ZnCuInS/ZnS] thin film sample.

Low-Cost Naked-Eye UVB and UVC Dosimetry Based on 3,3',5,5'-Tetramethylbenzidine.

Ultraviolet radiation (UVR) is both useful to human beings and can cause irreversible harm of varying degrees (UVA, UVB, and UVC). Especially, in areas with excessive sunlight, the appearance of UVB results in an increased risk of skin cancer. On the other hand, UV lamps (254 nm, UVC) are widely used in disinfection (air, water, and factory food) and hospital sterilization; the leakage of UVC is thus sometimes inevitable, which may cause fatal injuries to the related staff. Therefore, low-cost UV dosimetry-based personal protective equipment (PPE) and industrial monitoring devices are of great importance. Here, for the first time, we found that 3,3',5,5'-tetramethylbenzidine (TMB) could be rapidly oxidized upon UVB and UVC irradiation in a dose-dependent manner, in which TMB acts as a self-photosensitizer. Since TMB is a typical and widely used chromogenic substrate in enzyme-linked immunosorbent assay (ELISA), it is well-commercialized with low cost and vast availability worldwide, which permitted the development of low-cost naked-eye UVB and UVC dosimetry. A wearable bracelet mounted with TMB-loaded paper was developed for successful indication of whether the UVB exposure in the sunlight exceeded the minimum erythema dose (MED). In addition, we also developed a clock dial equipped with a TMB solution for unattended detection of UVC leakage from UVC disinfection lamps. The UVB- and UVC-selective coloration and low cost of TMB offered remarkable potential in facile detection of UVR in our daily life.

Intelligent sensitivity analysis framework based on machine learning for spacecraft thermal design

The variance-based method of global sensitivity analysis (GSA) has been widely applied in spacecraft thermal design, which is typically calculated using Monte Carlo estimations. However, such estimations require a large number of samples to ensure sufficient accuracy, which makes GSA expensive to perform when modeling is difficult. Moreover, multimodal or highly skewed output distributions may result in the use of variance as an uncertain agent that generates contradictory results. Therefore, an intelligent density-based GSA framework based on machine learning and multi-fidelity metamodels called IDGSA-3M is proposed. An intelligent batch processing system based on a real-time data interaction between MATLAB and NX/TMG was designed that uses many cheap low-fidelity sample points to reduce the cost of model evaluation while using a small number of expensive high-fidelity sample points to maintain high accuracy, thus achieving trade-offs between high accuracy and low computational cost. A radial basis function (RBF) neural network based on an improved mind evolutionary algorithm was applied to approximate the multi-fidelity metamodel of a spacecraft thermophysical model calculated using a batch processing system, which had a computational speed that was 1000+ times faster than that of the traditional thermophysical model and a high computational accuracy of 99%+. The output distributions of the RBF were then characterized by its cumulative distribution functions to obtain density-based sensitivity indices. Both the theoretical and experimental results of GSA for the thermal design parameters of the extreme ultraviolet radiation detector on the space-based Lyman-Alpha Solar Telescope, developed in China, demonstrated that the convergence rate of IDGSA-3M can be improved up to 10-fold for a fixed convergence level in comparison with two other GSA methods, thereby verifying its superiority.

A prospective, real‐world, clinical pharmacokinetic study to inform lacosamide dosing in critically ill patients undergoing continuous venovenous haemofiltration (PADRE‐02)

Although the use of continuous renal replacement therapy (CRRT) has increased, limited dosing information exists on the effect of CRRT on antiepileptic drug pharmacokinetics. The objectives of this practice-based study are to evaluate the pharmacokinetics of lacosamide and recommend individualized dosing recommendations in critically ill patients receiving continuous venovenous haemofiltration (CVVH). Seven patients receiving lacosamide and CVVH in a neurocritical care unit were enrolled. Pre-filter, post-filter and ultrafiltrate samples were obtained at baseline, right after the completion of the infusion, and up to six additional sampling time points post-administration. Patient-specific flow rates and clinical measures were also collected simultaneously at the time of sampling. Plasma concentrations were measured using a validated high-performance liquid chromatography with ultraviolet radiation detection (HPLC-UV) bioanalytical method. Non-compartmental analysis was utilized to characterize the pharmacokinetics of lacosamide. The observed mean sieving coefficient for lacosamide was 0.80 ± 0.10, suggesting high removal of lacosamide. Concentrations measured in six out of seven patients were observed to be outside the therapeutic range (5-12 mg/L). The estimated average volume of distribution was found to be similar to healthy patients (0.58 L/kg). The mean bias and precision of the estimated total clearance was -2.53% and 14.9%, respectively. Simulations of various doses suggest that effluent flow rate-based dosing regimens could be used to individualize lacosamide therapeutics. CVVH clearance contributed a major fraction of the total lacosamide clearance in neurocritically ill patients. Given that drug clearance increases with higher effluent flow rates, lacosamide dosing regimens should be increased to match exposures observed in patients with normal renal function.

Temperature Dependence of the Sensitivity of Silicon Photomultipliers in the Regime of Single-Photon Detection of Ultraviolet Radiation

Temperature Dependence of the Sensitivity of Silicon Photomultipliers in the Regime of Single-Photon Detection of Ultraviolet Radiation

A Self-Powered Wearable Ultraviolet Radiation Detector Integrated with Wireless Devices Based on T-ZnO/PVDF Composite Fabric

Research on wearable devices has promoted the development of real-time ultraviolet intensity monitoring technology. This paper proposes a self-powered wearable ultraviolet radiation detector based on T-ZnO nanowires/PVDF composite fabric. The soft fabric base allows the device to attach to various muscles of the human body. Due to the piezoelectric and photoelectric properties, the devices can transform mechanical energy into electrical energy. The output closely relates to the ultraviolet intensity. Therefore, this kind of stable, flexible, and micro device can output piezoelectric voltage as both an energy source and a sensing signal on human bodies. Experiments have proved that the wearable ultraviolet detector has high sensing stability and can work on the skin. The self-powered feature allows it to integrate with wireless transmission equipment, which can upload the ultraviolet intensity data collected by the self-powered wearable ultraviolet radiation detector to the Big Data Cloud. This system will contribute to the formation of the Internet of Things.

Titanium dioxide thin films as vacuum ultraviolet photoconductive detectors with enhanced photoconductivity by gamma-ray irradiation

We show that titanium dioxide (TiO2) thin films can be used as photoconductive detectors of vacuum ultraviolet (VUV) radiation, with further improvement in performance after recovery from gamma ray irradiation. An initial decrease in photocurrent was observed after irradiation with 3.4 kilo gray gamma rays as oxygen vacancies and trivalent titanium ion states are formed as confirmed by optical and photoluminescence spectroscopies showing a red-shift in the transmission edge, narrowing of the optical band gap, and appearance of a broad absorption band in the 392-528 nm wavelength range. Subsequent recovery of these defects increased the photoconductivity beyond what was displayed by the pristine detector. After recovering, the photosensitivity of the detector increased by a factor of about 8 and 124 compared to its photosensitivity before and immediately after irradiation, respectively. As the applications of VUV light continue to grow and development of light sources progress, there is increased demand for detectors in this short wavelength region. Our results demonstrate the potential of TiO2 thin films as VUV detectors including the use of gamma ray irradiation as post-fabrication treatment for improved photoconductivity.

Ultraviolet radiation detector based on artificial periclase nanocrystals (MgO)

Ultraviolet radiation detector based on artificial periclase nanocrystals (MgO)

Electrochemical synthesis of hydroxyl group-functionalized PProDOT/ZnO for an ultraviolet photodetector.

Ultraviolet (UV) detectors based on zinc oxide (ZnO) nanorods (NRs) are ideal materials for UV radiation detection. However, owing to the surface effect of ZnO NRs, their speed of photoresponse and photosensitivity need to be improved. In this study, a UV photodetector was fabricated via electrochemical coating of poly(3,4-propylenedioxythiophene) grafted with functional groups (–OH) on a hydrothermally grown ZnO NRs. For comparison, poly(3,4-propylenedioxythiophene)/ZnO composites were synthesized using the same method. The structure of the composite film was characterized by Fourier transform infrared spectroscopy (FT-IR), UV-visible spectroscopy (UV-vis), X-ray diffraction (XRD), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The effect of the polymer structure on the UV sensing ability of ZnO NRs was evaluated by fabricating a UV detector with a composite material. The structural results indicated that the PProDOT-type conductive polymer and ZnO composites were successfully synthesized. The UV photodetection results showed that the presence of functional groups (–OH) in polymer chains could enhance the responsivity of the material. The response time of the ZnO/PProDOT–OH composite was 15 s shorter than that of the ZnO/PProDOT composite. A rise in photocurrent induced an increase from 2.5 A W−1 to 34.75 A W−1 in the UV photoresponsivity of the ZnO/PProDOT–OH composite, compared with that of the pure ZnO NRs. The external quantum efficiency and detectivity significantly improved, the increases of which were attributed to the coupling of the polymer and ZnO NRs.

Stimulation of Photoactive Absorption of Sunlight in Thin Layers of Silicon Structures by Metal Nanoparticles

This study is devoted to analysis by the method of modeling photoelectric processes of charge transfer in thin silicon structures with a p–n junction containing nanoparticles of various metals, their sizes, and volume distribution.The absorption and current–voltage (I–V) characteristics of thin-film silicon solar cells, which contain the metal nanoparticles localized on the surface dielectric antireflecting coating, in the emitter and base with high and low doping degree, and on the interfaces of these layers, are defined. As a basic method for research, the Sentaurus TCAD is chosen, which includes the Structure Device Editor, Sentaurus Device, Sentaurus Visual, and Sentaurus Workbench packages with wide capabilities for modelling silicon solar cells with a flat p–n junction. The absorption and I–V characteristics of photoelectric converters, containing metal nanoparticles in various thin layers of the structure, are determined by analyzing the computational results and discussing the physical nature of observable processes. The recommendations are offered for creating thin-film silicon plasmonic p–n junction solar cells with optimized sizes of metal nanoparticles, their distribution, and, hence, with improved efficiency of photoelectric conversion of energy. The expediency of creation of ultraviolet radiation detectors on the basis of thin-film silicon structures with metal nanoparticles is shown. The absorption and I–V characteristics of photoelectric converters, containing metal nanoparticles in thin layers of the dielectric coating, emitter, and base with high and low doping degrees and also on interfaces of these layers are compared. The most effective absorption of the solar spectrum in the region of the emitter up to the metallurgical border of the p–n junction and the best efficiency of photoelectric energy conversion of silicon solar cells are revealed. The optimum sizes of metals nanoparticles, regularities of their distribution, and depths of occurrence of the p–n junction for thin layers of crystalline silicon are defined. The recommendations for creation of third-generation thin-film silicon plasmonic solar cells and high-sensitivity photovoltaic detectors of ultra-violet radiation are developed.