UV Sensor Research Articles

Structural modification of ZnO nanorod array through Fe-doping: Ramification on UV and humidity sensing properties

Iron (Fe)-doped zinc oxide (ZnO) nanotip arrays (FZO) were prepared using low temperature sol–gel immersion method. The X-ray diffraction analysis reveals that the crystallite size reduces from 30.7 to 28.3 nm after doped with Fe. Besides, it is perceived that the lattice strain metamorphoses from tensile to compressive strain after doping with value of -0.23%. Field emission scanning electron microscopy images show that the Fe doping induced a significant modification to the ZnO structure; transforming the structure from rod-like to tip-like structure. The current–voltage measurement results indicate that the FZO film has good electrical properties with resistance value of 12.34 MΩ. The FZO is also capable of performing well as UV and humidity sensors. This study points out that FZO films are suitable for multifunctional uses particularly for UV and humidity sensing.

The fabrication of zinc oxide nanorods and nanowires by solgel immersion methods

The zinc oxide (ZnO) nanorods (NRs) (4 hours) and nanowires (NWs) (12 and 24 hours) were synthesized on the magnesium ZnO (MgZnO) seed layer by using sol-gel immersion method. The ZnO NRs and NWs were characterized by FESEM, XRD, UV-Vis and four-point probe measurement. The FESEM images showed uniform, dense and vertically aligned structure. The smallest diameter observed in ZnO NWs (24 hours) in the range ∼ 47.6-99.2 nm. The XRD spectra also presented the c-axis growth of ZnO NRs and NWs. The ZnO NWs (24 hours) demonstrated higher transmittance and electrical conductivity of ∼77.8% and 2.6 × 10−1 S cm−1 as compared to ZnO NRs of 66.7% and 1.1 ×10−2 S cm−1, respectively. Therefore, the ZnO NWs (24 hours) showed a good structure to be applied in solar cells and UV sensor applications.

Nano Molecular Motor of Azo Antibiotics on Edge-Carboxylated Graphene: A UV and Visible-Switchable Sensors

In this work, halogenated azobenzene and alpha cyclodexterin (αCD) are simulated as an axle and a wheel respectively, while the edge carboxylated graphene sheet (ECG) is a stopper. Azobenzene onto αCD and combination with ECG can be used such a non-covalent system for photo-isomer-controlled machine. It has been exhibited a new system of molecular motor which works like a hinge motion, and has introduced as light-driven molecular hinges. The αCD ring in the system can be reversibly switched through irradiation of wide range of UV and visible lights. Various sensors can be simulated to predict a model for applying the drug delivery of those antibiotics which cannot be used through straight injection.

Multifunctional Screen-Printed TiO2 Nanoparticles Tuned by Laser Irradiation for a Flexible and Scalable UV Detector and Room-Temperature Ethanol Sensor.

Recently, multifunctional devices printed on flexible substrates, with multisensing capability, have found new demand in practical fields of application, such as wearable electronics, soft robotics, interactive interfaces, and electronic skin design, revealing the vital importance of precise control of the fundamental properties of metal oxide nanomaterials. In this paper, a novel low-cost and scalable processing strategy is proposed to fabricate all-printed multisensing devices with UV- and gas-sensing capabilities. This undertaken approach is based on the hierarchical combination of the screen-printing process and laser irradiation post-treatment. The screen-printing is used for the patterning of silver interdigitated electrodes and the active layer based on anatase TiO2 nanoparticles, whereas the laser processing is utilized to fine-tune the UV and ethanol-sensing properties of the active layer. Different characterization techniques demonstrate that the laser fluence can be adjusted to optimize the morphology of the TiO2 film by increasing the contribution from volume porosity, to improve its electrical properties and enhance its UV photoresponse and ethanol-sensing characteristics at room temperature. Furthermore, results of the UV and ethanol-sensing investigation show that the optimized UV and ethanol sensors have good repeatability, relatively fast response/recovery times, and excellent mechanical flexibility.

Indium Gallium Oxide Thin Film Transistor for Two-Stage UV Sensor Application

In this work, indium gallium oxide (IGO) thin film transistor (TFT) was fabricated by radio-frequency (RF) sputtering. The transmittance of the TFT shows larger than 80% cross the visible light region. As a wide bandgap and high transparency semiconducting material, IGO is a potential candidate for UV-detection applications. Measured in the dark, the IGO TFT exhibits a threshold voltage of 0.9 V, mobility of 2.66 cm2/Vs, on-off ratio of 1.21 × 106, subthreshold swing of 0.41 V/dec. The TFT was then employed to detect UV light and the sensing properties are investigated. The IGO phototransistor has a high responsivity of 5.012 A/W and a rejection ratio of 1.65 × 105. The above results reveal that IGO phototransistor is a brilliant multi-functional device, which can serve as either a switch component or a UV sensor.

Синтез нанонитей оксида индия-цинка и исследование их чувствительности к ультрафиолетовому излучению

Indium-zinc oxide (IZO) nanofibers are synthesized on Si-SiO2 substrates by the electrospinning method. The nanofibers’ dimensions, morphology, crystalline structure, and composition are studied by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray analysis, and X-ray diffraction. The results of studying the electrical properties of nanofibers, as well as their sensitivity to UV radiation depending on the In to Zn concentration ratio, are presented. It is shown that the highest sensitivity to UV is observed at the indium content of about 50 atomic %. The photocurrent increment in this case, with respect to the dark current, is more than 4 orders of magnitude. The response and recovery times are 60 and 500 s, respectively. The results obtained suggest that IZO nanofibers can find application as UV sensors with improved characteristics.

Rutile TiO2 nanowire arrays interconnected with ZnO nanosheets for high performance electrochemical UV sensors

Hierarchical nanostructures consisting of TiO2 nanowire arrays and ZnO nanosheets were prepared and investigated as active materials in photoelectrochemical UV sensors.

Кинетика фототока УФ-сенсора на основе нанонитей индий-цинк оксида

The paper presents an analysis of the experiments on current rise and fall kinetics under the influence of hard ultraviolet radiation on the indium-zinc oxide fibrous layer obtained by electrospinning. It is shown that the photocurrent increase rate can be varied by the radiation intensity, and its decrease – by the oxygen partial pressure on the nanofibers’ surface. The proposed UV sensor with a layer of nanoscale fibers possesses a higher response rate as compared to that of homogeneous film structures due to the significantly larger area of the active surface, where the centers of oxygen adsorption are concentrated.

Uncertainties of SO 2 Vertical Column Density Retrieval from Ground-based Hyper-spectral UV Sensor Based on Direct Sun Measurement Geometry

Uncertainties of SO 2 Vertical Column Density Retrieval from Ground-based Hyper-spectral UV Sensor Based on Direct Sun Measurement Geometry

Photoresponses of Gallium Zinc Tin Oxide Thin-Film Transistors Fabricated by Cosputtering Method

In this article, gallium zinc tin oxide (GaZTO) thin-film transistor (TFT) was deposited by radio-frequency cosputtering. High transmittance in the visible light region and wide energy bandgap of GaZTO thin film were ascertained by UVVisNIR spectrophotometer. GaZTO TFT exhibited a threshold voltage of 2.98V, mobility of 3.86 cm2Vs, onoff ratio of 1.5 106, and subthreshold swing of 0.392Vdecade. The TFT was employed to detect UV light, and the optoelectrical properties were investigated in detail. The UV-visible rejection ratio of GaZTO TFT under illumination was 9.8 105. The results revealed that GaZTO phototransistor is versatile and able to serve as a UV sensor.

Seasonal Deposition and Lifting of Dust on Mars as Observed by the Curiosity Rover

In situ measurements by the Curiosity rover provide a unique opportunity for studying the effects of dust on assets placed at the surface of Mars. Here we use in situ measurements of solar UV radiation to quantify the seasonal and interannual variability of dust accumulation on the sensor on the rover deck. We show that the amount of dust accumulated on the sensor follows a seasonal cycle, with net dust removal during the perihelion season until Ls ~ 300°, and net dust deposition until the end of the aphelion season (Ls ~ 300°–180°). We use independent in situ measurements of atmospheric opacity and pressure perturbations in combination with numerical modeling, showing that daytime convective vortices and nighttime winds are likely responsible for the seasonal dust cleaning, with the role of nighttime wind being more important in Martian Year (MY) 32 than in MY 33 and that of daytime convective vortices being more important in MY 33 than in MY 32. The fact that the UV sensor is cleaner in MY 33 than in MY 32 indicates that natural cleaning events make solar energy an excellent candidate to power extended (multiannual) Mars missions at similar latitudes as the Curiosity rover.

Laser-induced electrodes towards low-cost flexible UV ZnO sensors

Flexible electronics is a branch of electric fabrication that allows for increasingly ergonomic devices. However, its production still requires multi-step, expensive, and time-consuming processes. Laser-direct writing (LDW) is a clean and low-cost alternative technique for producing electrodes on flexible substrates with high resolution, without the need of masks or direct contact with the device. Laser-induced graphene (LIG), a particular type of LDW, is a technique in which, by the irradiation of polyimide (PI) and polyetherimide (PEI) films with a pulsed CO2 infrared laser, a photothermal reaction occurs which leads to the formation of stacked graphene structures. LIG thus emerges as a rising substitute to produce graphene-based devices. This work consists of the development and optimization of flexible UV sensors with zinc oxide nanostructures as the active layer for photodetection, PI or PEI as the substrates, and the respective LIG as electrodes. The nanostructures with higher area-volume ratio, synthesized through a microwave-assisted hydrothermal method, were selected and deposited by drop-casting onto electrodes that in turn were optimized to enhance electrical properties by varying the laser parameters. The assembled sensors were able to successfully detect UV radiation with a responsivity of 92 and 2 nA W−1 for 1 V bias for the PI and PEI substrates, respectively. In addition, the PI sensor has shown to be capable of working under strain and to be stable after several hours of constant cyclic operation.

Wearable UV Sensor Based on Carbon Nanotube-Coated Cotton Thread.

A fabric-compatible UV sensor is presented using a cellulose-based thread coated with single-wall carbon nanotube ink. Two-terminal resistive responses of the thread were measured upon exposure to UV, and the effects of intensity, wavelength, and on/off cycling were studied. The sensor was tested in the field under direct sunlight, demonstrating practical usability for a wearable/flexible UV sensor system. The results here confirm the potential for an inexpensive wearable sensor in contrast to the conventional rigid and bulky solid-state detectors.

The onboard software of the EUSO‐SPB pathfinder experiment

SummaryIn this paper, the flight software architecture of the EUSO‐SPB mission is described. The JEM‐EUSO program aims at developing an advanced large space‐borne UV telescope designed to detect ultra high energy cosmic rays. In this framework, the EUSO‐SPB experiment is the third pathfinder mission of the JEM‐EUSO program, the second that has been launched on a stratospheric balloon to test the technological readiness of the detectors and to carry out some preliminary scientific observations. The EUSO‐SPB software has a modular structure conceived to control all the instruments and the ancillary subsystems, to acquire data, and to manage data transfer to ground. System programming in C and C++ languages and Bash scripts have been used to implement and run the modules. The software runs on the data processor, an onboard computer that communicates with several payload blocks, the UV sensor, and the synchronization and time tagging board. The control software module controls all the subsystems, provides communication to ground through the NASA telemetry or the Internet, runs the acquisition control and download software, and manages the execution of the acquisition software. The acquisition software module directly operates the subsystems for the data acquisition activity. The acquisition control and download software module runs the acquisition software upon request of the control software and transfers scientific data to ground. The software system performed as expected during the flight on April 2017.

Flexible lateral-bridged ZnO nanowire UV sensor for focal-plane image sensor application

We report a large-format flexible UV image-sensing array consisting of 32 × 32 sensors based on lateral-bridged ZnO nanowires (NWs). Systematic investigations for the array have shown that 100% of the sensors showed a response with high uniformity (the nonuniformity of photocurrent was 44%) and high average light–dark current ratio (∼1.1 × 105), average responsivity (∼923 A/W), and average detectivity (∼2.5 × 1014 Jones). The pixel size is 60 × 125 µm2 and pixel pitch is 150 µm. The array also exhibited excellent flexibility and electrical stability under the bending state. The results indicate that the sensor array offers exacting possibilities for fabricating flexible UV focal-plane image sensors.

Skin color-specific and spectrally-selective naked-eye dosimetry of UVA, B and C radiations

Spectrally–selective monitoring of ultraviolet radiations (UVR) is of paramount importance across diverse fields, including effective monitoring of excessive solar exposure. Current UV sensors cannot differentiate between UVA, B, and C, each of which has a remarkably different impact on human health. Here we show spectrally selective colorimetric monitoring of UVR by developing a photoelectrochromic ink that consists of a multi-redox polyoxometalate and an e− donor. We combine this ink with simple components such as filter paper and transparency sheets to fabricate low-cost sensors that provide naked-eye monitoring of UVR, even at low doses typically encountered during solar exposure. Importantly, the diverse UV tolerance of different skin colors demands personalized sensors. In this spirit, we demonstrate the customized design of robust real-time solar UV dosimeters to meet the specific need of different skin phototypes. These spectrally–selective UV sensors offer remarkable potential in managing the impact of UVR in our day-to-day life.

Growth and characterization of ammonium nickel-copper sulfate hexahydrate: A new crystal of Tutton's salt family for the application in solar-blind technology

We have obtained the mixed crystals ammonium nickel-copper sulfate hexahydrate compounds which exhibits 98% transmittance in the ultraviolet region, a promising material for UV light filters and UV sensors for solar-blind technology. These crystals belong to the family of Tutton's salt having empirical formula (NH4)2NixCu(1-x) (SO4)2.6H2O and they were synthesized by employing growth from the slow evaporation of aqueous solution technique. The crystallographic parameters, three-dimensional Hirshfeld surface analysis and the calculation of two-dimensional fingerprint plots of the sample crystal (NH4)2Cu(SO4)2.6H2O were determined with the help of single crystal X-Ray diffraction. The X-ray powder diffraction of the pulverized samples were carried out at ambient temperature, 200 °C and 350 °C with the purpose to observe the change in the crystalline structure when subjected to higher temperatures. The thermal analysis of the samples was conducted in the temperature range 30–900 °C with the help of thermogravimetric analysis (TGA), which provides the information about the thermal stability and decomposition process during the heat treatment. Some of our sample crystals demonstrated high dehydration temperature up to 108 °C and they can be considered as an excellent candidate for UV light filters for high temperature applications. The direct and indirect band gaps of the samples were determined from UV–Vis spectra with the help of Tauc's equation. The overtones and combinations of fundamental vibrations of the functional groups our sample crystals were investigated by utilizing near-infrared spectroscopy in the wavelength range 830–2500 nm.

UV sensor based on polyurethane foam

Ultraviolet light (UV) present in solar radiation has an important effect on the health of human skin. For that reason, we developed a disposable and easy-to-manufacture UV light sensor based on surface color change of a polyurethane (PU) film and examined its performance against radiation received from a lamp or from the sun. The chemical modification after UV exposition and the consequent color variation from light yellow to brown in PU sensor were studied by using RGB image analysis and a reflectance prototype containing an Arduino board. It was found that the photochemical modification of PU films increases absorption of visible radiation in the blue spectrum range. Furthermore, PU surface was more sensitive to UV (<390) than that found in visible light when exposed to sunlight, which was associated with the presence of a chromophore in the material modified. In addition, it was found that the extract obtained from irradiated PU showed its maximum absorption at 309 nm. Hence, the use of this economical light radiation sensor seems to be a very promising tool to determine exposure to UV light from the solar spectrum.

Ultra-sensitive UV and H2S dual functional sensors based on porous In2O3 nanoparticles operated at room temperature

A dual functional sensor for detecting both UV light and H2S gas was fabricated using the hexagonal phase porous In2O3 nanoparticles, which were prepared using the hydrothermal and calcination process. The porous In2O3 nanoparticles with large surface areas and pore volumes could provide plenty of active sites to produce much active oxygen species, which were beneficial for the UV light and H2S gas sensing reactions, thus resulting in a good sensing performance. At room temperature, the dual functional sensor based on porous In2O3 nanoparticles exhibited ultra-high responses for sensing both UV light (with a wavelength of 365 nm) and H2S gas. As a UV sensor, its response was 12886.0 for a UV power intensity of 1.287 mW/cm2 and its detection limit was 0.013 mW/cm2. As a H2S gas sensor, the sensor exhibited an ultra-high response (26268.5–1 ppm H2S) and a very low detection limit (1 ppb of H2S), and it also have excellent selectivity, reversibility and stability.

Hydrothermal synthesis of nanomoss Nb2O5 films and their ultraviolet photodetection performance

Hydrothermal process is one of the most suitable and highly controlled synthesis methods for engineering or tailoring the nanostructures of metal oxide. In the present work, etching agent assisted hydrothermal process was employed to synthesis nanostructured Nb2O5. Nanomoss Nb2O5 films were successfully synthesized on niobium foil in the ammonia fluoride based solution with concentration of 0.5 and 1.65 M at 95 °C for 24 h. Material analysis of the nanomoss Nb2O5 was carried out by field emission scanning electron microscopy, atomic force microscopy, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy analysis and Ultraviolet–visible spectroscopy. The XRD characterization revealed that the nanomoss Nb2O5 only become crystalline after annealing for 60 min at 440 °C. That annealing condition also contributes to the growth of hump structure on the nanomoss films. Furthermore, it was observed that the films produce low reflectance properties in the range of 2.73–26.0% at UV wavelengths, which make them a potential candidate in UV sensor applications. To fabricate the UV sensor, platinum (Pt) electrode was deposited as a contact pad. Based on the UV characterization, the UV sensor based on nanomoss Nb2O5 films exhibited good photosensitivity of 2.0 and response time in the range of 51.4–76.8 s when exposed under turn on/off of UV light (365 nm, 750 µW/cm2) at a bias voltage of 10 V.