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Zinc oxide is a promising material for the creation of various types of sensors, in particular UV detectors. In this work, arrays of ordered nanorods were grown by chemical vapor deposition. The effect of environmental humidity on the sensing properties of zinc oxide nanorod arrays was investigated, and a prototype UV sensor using indium as an ohmic contact was developed. UV photoresponses were measured for the samples stored in dry and wet atmospheres. The increase in sensitivity and response of the ZnO nanorod arrays was observed after prolonged exposure to a wet atmosphere. A model was proposed to explain this effect. This is due to the formation of hydroxyl groups on the surface of zinc oxide nanorods, which is confirmed by FTIR spectroscopy data. For the first time, it has been shown that after storage in a wet atmosphere, the sensory properties of the structure remain stable regardless of the ambient humidity. [ABSTRACT FROM AUTHOR]

In this paper, the relaxation isomerization properties of a spiropyran-doped poly(methyl methacrylate) (PMMA) UV light-responsive dynamic material are presented. The polar liquid (acetonitrile) and solid (PMMA matrix) medium may contain two merocyanine isoforms of the selected spiropyran. A complex equilibrium of the colored and colorless spiropyran isoforms resulted in specific transformations of the absorption spectra during the relaxation process. Bands at 522 nm and 580 nm characterized the absorption of the fabricated dynamic material in the ground (non-activated) state in the visible range. The presence of colored and colorless isoforms of spiropyran incorporated into the PMMA matrix using Raman spectroscopy was revealed. The photosensitive polymer samples were irradiated with a UV LED (365 nm and 390 nm) under various temperatures (0–30 °C). Spectral changes within the relaxation process demonstrated their complex dynamics. Surprisingly, the photodegradation of the dynamic material was estimated at about 25% (using 390 nm) and 7% (using 365 nm) after eight photoswitch cycles for one isoform, and no fatigue after an additional one (using 390 nm) was discovered. The presented light-responsive material is of interest for UV sensors and new hybrid material design. [ABSTRACT FROM AUTHOR]

Zinc oxide nanopowder was synthesized by the coprecipitation method. FT-IR and EDS analyses were performed to qualitatively determine the composition of the nanopowder. FE-SEM images revealed the morphology of the nanopowder formed by clusters of nanoparticles. An XRD analysis confirmed the wurtzite structure with a crystallite size of ~21.2 nm. UV–Vis measurements were performed to determine the ZnO bandgap (~3.05 eV) using the Tauc plot method in the absorbance spectra. The ZnO nanopowder and two comb-like metal contacts were confined and compacted between two polymeric layers by a low-temperature thermal lamination method, resulting in a flexible Polymer/ZnO/Metal/ZnO/Polymer structure. Part of each comb-like metal was kept uncovered by a polymeric layer in order to be used for electrical characterization. I-V measurements of the flexible structure were performed in the dark and under UV illumination, showing the capacity to detect UV radiation and its potential application as a visible-blind UV sensor. A facile and low-cost flexible optoelectronic device is presented, avoiding using high-vacuum or high-temperature technology. This new and novel approach to developing optoelectronic devices proposes using powder materials as semiconducting active regions instead of thin films; this could eliminate the cracking and delamination problems of flexible devices based on thin film technology. [ABSTRACT FROM AUTHOR]

With the presence of triethanolamine (TEOA) and N,N-Dimethylformamide (DMF) as organic functional reagents, ZnSn(OH) 6 precursors composed of hollow-sphere particles were synthesized by co-precipitation method. Microstructure characterization shows that the crystallization growth of ZnSn(OH) 6 precursor can be affected by DMF, and that its particle size and average grain size are changed with the mass ratio (x) of DMF to TEOA. Each ZnSnO 3 sample (ZSO- x) from its ZnSn(OH) 6 counterpart (ZSOH- x) is amorphous structure due to the generation of oxygen vacancy defects. When x is 0.75, the resulting ZSO-0.75 sample has a higher photo-to-dark-current ratio (10,976 at 3 V) than other samples under 365 nm illumination. Further comparison indicates that although ZSO-0.75 sample has more oxygen vacancies than ZSO-0 sample, the dark current of the former is less than that of the latter at the same voltage, which may be related to the formation of tight-binding excitons and homostructures based on the thermal excitation of oxygen vacancies. [ABSTRACT FROM AUTHOR]

This paper contains the design of active optical lenses used for the detection of arc flashing emissions. The phenomenon of an arc flashing emission and its characteristics were contemplated. Methods of preventing these emissions in electric power systems were discussed as well. The article also includes a comparison of commercially available detectors. An analysis of the material properties of fluorescent optical fiber UV-VIS-detecting sensors constitutes a major part of the paper. The main purpose of the work was to make an active lens using photoluminescent materials, which can convert ultraviolet radiation into visible light. As part of the work, active lenses with materials such as Poly(methyl 2-methylpropenoate) (PMMA) and phosphate glass doped with lanthanides, such as terbium (Tb3+) and europium (Eu3+) ions, were analyzed. These lenses were used to make optical sensors, which were supported by commercially available sensors in their construction. [ABSTRACT FROM AUTHOR]

Zinc oxide is a promising material for the creation of various types of sensors, in particular UV detectors. In this work, arrays of ordered nanorods were grown by chemical vapor deposition. The effect of environmental humidity on the sensing properties of zinc oxide nanorod arrays was investigated, and a prototype UV sensor using indium as an ohmic contact was developed. UV photoresponses were measured for the samples stored in dry and wet atmospheres. The increase in sensitivity and response of the ZnO nanorod arrays was observed after prolonged exposure to a wet atmosphere. A model was proposed to explain this effect. This is due to the formation of hydroxyl groups on the surface of zinc oxide nanorods, which is confirmed by FTIR spectroscopy data. For the first time, it has been shown that after storage in a wet atmosphere, the sensory properties of the structure remain stable regardless of the ambient humidity.

Zinc oxide nanopowder was synthesized by the coprecipitation method. FT-IR and EDS analyses were performed to qualitatively determine the composition of the nanopowder. FE-SEM images revealed the morphology of the nanopowder formed by clusters of nanoparticles. An XRD analysis confirmed the wurtzite structure with a crystallite size of ~21.2 nm. UV–Vis measurements were performed to determine the ZnO bandgap (~3.05 eV) using the Tauc plot method in the absorbance spectra. The ZnO nanopowder and two comb-like metal contacts were confined and compacted between two polymeric layers by a low-temperature thermal lamination method, resulting in a flexible Polymer/ZnO/Metal/ZnO/Polymer structure. Part of each comb-like metal was kept uncovered by a polymeric layer in order to be used for electrical characterization. I-V measurements of the flexible structure were performed in the dark and under UV illumination, showing the capacity to detect UV radiation and its potential application as a visible-blind UV sensor. A facile and low-cost flexible optoelectronic device is presented, avoiding using high-vacuum or high-temperature technology. This new and novel approach to developing optoelectronic devices proposes using powder materials as semiconducting active regions instead of thin films; this could eliminate the cracking and delamination problems of flexible devices based on thin film technology.

Modern high-performance photodetector research is driven by the need to simultaneously improve multiple parameters, but also fit the decreasing size of electronics and maintain low production price. Here, we demonstrated how our synthesized ZnO tetrapod (ZnO-T) nanostructure was deposited on electrodes with variating gap by four coating methods including drop casting, microdrop casting, spray coating and slot-die coating with the same thickness. Optimizing the inter-electrode gap and coating method the record IUV/IDark ratio per unit area value of 8.73 × 106 was obtained. The fastest rise time 0.78 s and fastest decay time 0.94 s were obtained by slot-die coated sensors. High photoresponse of ZnO-Ts, the inter-electrode gap size influences formation of ZnO-T microstructure during coating process and morphology influence on photoresponse was explained. We demonstrate that even with the same optimized ZnO-T nanostructures photoresponse can be improved by 2 orders of magnitude. Our work shows the importance of coating morphology and inter-electrode gap optimization.

Nanocomposites formed by aluminum-doped zinc oxide nanoparticles (AZO–NP) and multiwall carbon nanotubes (CNT) are proposed here as a promising material for UV light sensing applications, with the great advantage of operating in air, at room temperature, and at low voltage. Nanocomposite layers were prepared with different AZO:CNT weight ratios by a simple methodology at room temperature. They were characterized by means of UV–Vis spectroscopy, scanning and transmission electron microscopies (SEM and TEM), and X-ray photoelectron spectroscopy (XPS). The interaction between the two nanomaterials was demonstrated by comparing the properties of the nanocomposite with the ones shown by the AZO–NPs. Dense AZO–CNT nanocomposite layers were deposited between two metal electrodes on a SiO2/Si substrate, and the electrical properties were investigated in dark condition and under UV light irradiation. The electrical response to the UV light was a sudden current increase that reduced when the light was switched off. Several UV on/off cycles were performed, showing good repeatability and stability of the response. The mechanisms involved in the electrical response are discussed and compared to the ones previously reported for ZnO–CNT nanocomposites. [ABSTRACT FROM AUTHOR]

In order to ensure the health and welfare of livestock, there has been an emphasis on precision farming of ruminant animals. Monitoring the life index of ruminant animals is of importance for intelligent farming. Here, a wearable sensor for monitoring ultraviolet (UV) radiation is demonstrated to understand the effect of primary and secondary photosensitization on dairy animals. Thin films of wide bandgap semiconductor zinc oxide (ZnO) comprising multilevel of nanostructures from microparticles (MP) to nanoparticles (NP), and tetrapod (T–ZnO), were prepared as the UV sensing active materials. The sensitivity was evaluated by exposing the films to various radiation sources, i.e., 365 nm (UV A), 302 nm (UV B), and 254 nm (UV C), and measuring the electrical resistance change. T–ZnO is found to exhibit higher sensitivity and stable response (on/off) upon exposure to UV A and UV B radiation, which is attributed to their higher surface area, aspect ratio, porosity, and interconnective networks inducing a high density of chemical interaction sites and consequently improved photocurrent generation. A wearable sensor using T–ZnO is packaged and attached to a collar for dynamic monitoring of UV response on ruminant animals (e.g., sheep in this study). The excellent performance of T–ZnO wearable sensors for ruminant animals also holds the potential for a wider range of applications such as residential buildings and public spaces. [ABSTRACT FROM AUTHOR]

This work reports on a new TBO–Pluronic F–127 three-dimensional (3D) gel dosimeter for UV light dose distribution measurements. The optimal gel composition was found to be 60 µM Toluidine Blue O (TBO), which acts as a UV-sensitive compound; 5% w/w hydrogen peroxide (H2O2), which is necessary for initiation of TBO photodegradation and 25% w/w poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F–127), which forms a physical gel matrix. The dosimeter becomes discoloured when exposed to UV radiation and a discolouration is the more intense, the higher the absorbed dose is. The samples after irradiation with UVA, UVB and UVC radiation were measured using UV-Vis spectrophotometry to obtain the basic dose–response characteristic of the dosimeter, including dose sensitivity, linear and dynamic dose range, threshold dose, stability over time and dose–response for fractioned and non-fractioned doses. Additionally, the TBO–Pluronic F–127 gel dosimeter was investigated for spatial stability and the ability to measure the dose distribution of UV radiation. The results obtained indicate that the TBO–Pluronic F–127 dosimeter is a promising UV sensor and 2D/3D UV dosimeter. [ABSTRACT FROM AUTHOR]

This paper contains the design of active optical lenses used for the detection of arc flashing emissions. The phenomenon of an arc flashing emission and its characteristics were contemplated. Methods of preventing these emissions in electric power systems were discussed as well. The article also includes a comparison of commercially available detectors. An analysis of the material properties of fluorescent optical fiber UV-VIS-detecting sensors constitutes a major part of the paper. The main purpose of the work was to make an active lens using photoluminescent materials, which can convert ultraviolet radiation into visible light. As part of the work, active lenses with materials such as Poly(methyl 2-methylpropenoate) (PMMA) and phosphate glass doped with lanthanides, such as terbium (Tb3+) and europium (Eu3+) ions, were analyzed. These lenses were used to make optical sensors, which were supported by commercially available sensors in their construction.

Nanocomposites formed by aluminum-doped zinc oxide nanoparticles (AZO–NP) and multiwall carbon nanotubes (CNT) are proposed here as a promising material for UV light sensing applications, with the great advantage of operating in air, at room temperature, and at low voltage. Nanocomposite layers were prepared with different AZO:CNT weight ratios by a simple methodology at room temperature. They were characterized by means of UV–Vis spectroscopy, scanning and transmission electron microscopies (SEM and TEM), and X-ray photoelectron spectroscopy (XPS). The interaction between the two nanomaterials was demonstrated by comparing the properties of the nanocomposite with the ones shown by the AZO–NPs. Dense AZO–CNT nanocomposite layers were deposited between two metal electrodes on a SiO2/Si substrate, and the electrical properties were investigated in dark condition and under UV light irradiation. The electrical response to the UV light was a sudden current increase that reduced when the light was switched off. Several UV on/off cycles were performed, showing good repeatability and stability of the response. The mechanisms involved in the electrical response are discussed and compared to the ones previously reported for ZnO–CNT nanocomposites.

We report studies of multifunctional, nanostructured diamond composites that were fabricated using chemical vapor deposition (CVD) techniques. Grain sizes from micrometer, to submicron, nano, and ultrananocrystalline diamond (UNCD) were controlled by varying CH4, hydrogen, and argon gas concentrations during the syntheses. Scanning electron microscopy (SEM) and Raman scattering spectroscopy were used to investigate the morphologies, composites, and crystallinities of the films. Four multifunctional sensor prototypes were designed, fabricated, and tested, based on the four diamond materials of different grain sizes. The responses of the four prototypes to either pollution gas or UV light illumination were systematically investigated at different operating temperatures. Experimental data indicated the obtained UNCD composite from the low-cost simple CVD fabrication technique appeared to have very good sensitivities when exposed to low concentrations of H2 or NH3 gas with a decent response and fast recovery time. Furthermore, highly induced photocurrents from both microdiamond- and UNCD-based prototypes to deep UV illumination were also demonstrated, with responsivities up to 2750 mA/W and 550 mA/W at 250 nm wavelength, respectively. Overall, the fabricated UNCD prototypes displayed a good balance in performance for multifunctional sensor applications in terms of responsivity, stability, and repeatability.

In order to ensure the health and welfare of livestock, there has been an emphasis on precision farming of ruminant animals. Monitoring the life index of ruminant animals is of importance for intelligent farming. Here, a wearable sensor for monitoring ultraviolet (UV) radiation is demonstrated to understand the effect of primary and secondary photosensitization on dairy animals. Thin films of wide bandgap semiconductor zinc oxide (ZnO) comprising multilevel of nanostructures from microparticles (MP) to nanoparticles (NP), and tetrapod (T–ZnO), were prepared as the UV sensing active materials. The sensitivity was evaluated by exposing the films to various radiation sources, i.e., 365 nm (UV A), 302 nm (UV B), and 254 nm (UV C), and measuring the electrical resistance change. T–ZnO is found to exhibit higher sensitivity and stable response (on/off) upon exposure to UV A and UV B radiation, which is attributed to their higher surface area, aspect ratio, porosity, and interconnective networks inducing a high density of chemical interaction sites and consequently improved photocurrent generation. A wearable sensor using T–ZnO is packaged and attached to a collar for dynamic monitoring of UV response on ruminant animals (e.g., sheep in this study). The excellent performance of T–ZnO wearable sensors for ruminant animals also holds the potential for a wider range of applications such as residential buildings and public spaces.

Calcium-doped zinc oxide (CaZnO) and magnesium-doped zinc oxide (MgZnO) nanostructures were synthesized by a chemical bath deposition method. X-ray diffraction results revealed c-axis plane dominance for the ZnO and MgZnO samples, and a-axis plane dominance for the CaZnO samples. Scanning electron microscopy results showed well-aligned nanorods for the ZnO and MgZnO nanostructures. However, flower- and cotton-type surface was found for the Ca-doped samples. Energy-dispersive spectroscopy results confirmed the calcium and magnesium dopants. Band gap values of 3.20 eV and 3.34 eV were revealed for higher doping concentrations of calcium and magnesium, respectively. The super-hydrophobic state was observed for the 5% Mg-doped ZnO sample, with a water contact angle of 152°. However, a hydrophobic state was observed for the 5% Ca-doped ZnO sample, with a water contact angle of 90°. The super-hydrophilic state was detected for all samples by the induction of ultraviolet light. Better contact angle reduction rates with values of 0.022 and 0.023 were estimated for the calcium-doped nanostructure. The contact angle recovery time was also evaluated, and values of 35 h and 40 h were achieved for Ca- and Mg-doped samples, respectively. The ultraviolet sensing performance was evaluated for all the samples, and the best photo-response was obtained for the 5% Mg-doped ZnO sample. [ABSTRACT FROM AUTHOR]

The main area of research all around the world during this pandemic is finding a cure for COVID-19 disease. The pandemic has put up immense pressure on doctors and other medical personnel to work diligently. Their main aim is to treat all patients with utmost care as well as carry out research to find out a vaccine and cure. So, a definite protocol is to be developed which ensures safety for all. COVID-19 creates a chain and spreads to all people within a proximity circle. This is approximately estimated to be around 6 feet and that too for a very prolonged period. This spread is effected when an infected person either coughs, sneezes or even if he simply talks. Saliva droplets due to the above mentioned actions are forcibly launched into air, which can now easily land on other people nearby. The splattered droplets can be unknowingly inhaled into the lungs from where the infection originates. A recent survey indicates that all people who are infected do not necessarily display the symptoms. These persons now act as active carriers ands play a predominant role in spreading the virus. This proposed model is designed in such a way that it is very compact and its primary feature is to give an automatic announcement to the user, whenever the user is out in public areas. The proposed contact tracer is an intelligent system that is mainly designed around an Arduino Uno processor that forms the primary component. The Arduino Uno processor is readily and easily compatible with both a Bluetooth as well as a zigbee module that play major roles in detection. ZigBee module used to transfer the persons numbers to nearby people, Bluetooth module will send that received number to mobile number and buzzer will hoot when we go near to anyone so we will maintain social distance as well. There are many ways to educate the people but maintaining the app and hardware is the combination to give the very fast accurate information to people, here we are proposing the new technique to trace the covid19 patients very quickly and they can view the positive cases around his current location. [ABSTRACT FROM AUTHOR]

This work reports on a new TBO–Pluronic F–127 three-dimensional (3D) gel dosimeter for UV light dose distribution measurements. The optimal gel composition was found to be 60 µM Toluidine Blue O (TBO), which acts as a UV-sensitive compound; 5% w/w hydrogen peroxide (H2O2), which is necessary for initiation of TBO photodegradation and 25% w/w poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F–127), which forms a physical gel matrix. The dosimeter becomes discoloured when exposed to UV radiation and a discolouration is the more intense, the higher the absorbed dose is. The samples after irradiation with UVA, UVB and UVC radiation were measured using UV-Vis spectrophotometry to obtain the basic dose–response characteristic of the dosimeter, including dose sensitivity, linear and dynamic dose range, threshold dose, stability over time and dose–response for fractioned and non-fractioned doses. Additionally, the TBO–Pluronic F–127 gel dosimeter was investigated for spatial stability and the ability to measure the dose distribution of UV radiation. The results obtained indicate that the TBO–Pluronic F–127 dosimeter is a promising UV sensor and 2D/3D UV dosimeter.

In chromatographic separation, the simulated moving bed (SMB) has been recognized as an important and the cleanest technology. Basically, the SMB is constructed of several columns in series, and can be operated continuously with a fixed switching time. Owing to the adsorption of different substances by the adsorbent, the concentration of the separated substance flowing in the columns changes with time. The success of chromatographic separation will be determined by the time change, substance flow rate, and other possible influencing factors. Therefore, if the concentration of the flowing substance in SMB columns can be sensed immediately, then the accurate control of the SMB can be executed. In this paper, the prediction of substance concentration in SMB chromatographic separation by using an ultraviolet (UV) sensor and a neural network (NN) is presented. In this study, a UV sensor was used to monitor the concentration of the substance, and the NN model was used to predict the substance concentration in real time. The predicted concentration can be used for the real-time control of the moving bed. From the research results shown, it is found that the real-time prediction of substance concentration by the NN based on the sensed UV light intensity can indeed reach a very high accuracy. This result is very promising for the future development of an SMB automatic control mechanism. [ABSTRACT FROM AUTHOR]

The possibility of creating resonant ultraviolet (UV) sensors based on the structure of ZnO nanorods/La3Ga5SiO14 microbalance (LCM) has been investigated. The principle of sensor operation is based on the desorption of oxygen from the surface of ZnO nanorods upon irradiation with UV light and an increase in the concentration of charge carriers that leads to an increase in the capacitance of the structure of ZnO nanorods/LCM. It has been shown that UV radiation intensity affects the resonance oscillation frequency of the LCM sensor. After the end of irradiation, the reverse process of oxygen adsorption on the surface of ZnO nanorods occurs, and the resonance frequency of the sensor oscillations returns to the initial value.

The aim of this study is to investigate the influences of annealing temperature on initial device characteristics and their correlations with ultraviolet (UV) radiation sensitivity of n-type zinc oxide/p-silicon (n-ZnO/p-Si) heterojunction photodiodes. Evolutions on the crystalline structure, surface morphology, ideality factor, barrier potential, interface state density, and donor concentration were systematically analyzed during the initial device characterizations before testing the UV sensitivities of the photonic devices. The results demonstrate that the sensitivity of each n-ZnO/p-Si photodiode annealed at various temperatures was linearly correlated with different UV illumination intensities. The devices annealed at 750 ° C and 550 ° C exhibit more sensitive performance than devices annealed at 150 ° C and 350 ° C owing to lower dark currents and good oxide quality. However, the presence of an interfacial suboxide or silicate oxide layer significantly decreased the responsivity of the photodiodes annealed at 750 ° C. The maximum responsivity value was 126 mA/W for the photodiode annealed at 550 ° C. It can be concluded that the photodiode annealed at 550 ° C exhibits promising performance for UV sensing applications. [ABSTRACT FROM AUTHOR]

A р-ZnTe/n-CdSe heterojunction was used for making polycrystalline ZnTe-based UV sensors. The heteropair components have the same crystal structure and close lattice parameters. ZnTe and CdSe were grown using thermal evaporation and quasi-closed space condensation. A transparent current collecting electrode for the surface-barrier structure of р-ZnTe/n-CdSe heterojunction was made of degenerate p-Cu1.8S. Surface relief of ZnTe grown on different substrates was studied with scanning atomic force microscopy. The energy band offset diagrams of heterojunction are built and photosensitivity spectra are presented.

Hitherto, most research has primarily focused on improving the UV sensor efficiency via surface treatments and by stimulating the ZnO nanorod (ZNR) surface Schottky barriers. However, to the best of our knowledge, no study has yet probed the intrinsic crystal defect generation and its effects on UV sensor efficiency. In this study, we undertake this task by fabricating an intrinsic defect-prone hydrothermally grown ZNRs (S1), Ga-doped ZNRs (S2), and defect-free microwave-assisted grown ZNRs (S3). The defect states were recognized by studying X-ray diffraction and photoluminescence characteristics. The large number of crystal defects in S1 and S2 had two pronged disadvantages. (1) Most of the UV light was absorbed by the defect traps and the e−h pair generation was compromised. (2) Mobility was directly affected by the carrier−carrier scattering and phonon scattering processes. Hence, the overall UV sensor efficiency was compromised based on the defect-induced mobility-response model. Considering the facts, defect-free S3 exhibited the best UV sensor performance with the highest on/off ratio, the least impulse response time, the highest recombination time, and highest gain-induced responsivity to 368 nm UV light, which was desired of an efficient passive metal oxide-based UV sensor. Our results were compared with the recently published results.

Uniformity in mass-fabrication of nanostructured device is important for its practical application. In this paper, we developed a step-corner growth mode to on-chip fabricate uniform oblique-bridged ZnO nanowire UV sensor. By strictly controlling the microelectronic processing including photolithography and magnetron sputtering procedures during the seed layer deposition and electrode fabrication, ZnO NW array could nucleate at the upper step-corner of the seed layer due to the high catalytic activities at the surface steps and kinks, and then grow in a distribution of circular sector to form an oblique bridging configuration, which guaranteed the device performance and uniformity at the same time. For the within-chip uniformity, in a 4 × 4 sensor array that randomly chosen under the 365 nm UV light of 2.5 mW/cm 2 and at the bias voltage of 1 V, the light-to-dark current ratio all kept in the level of 10 6 with the average value of 1.84 × 10 6 . There were 75% of them in the range of 1.1 × 10 6 ~ 3 × 10 6 . The detectivity all kept in the level of 10 15 Jones with the average value of 3.53 × 10 15 Jones. There were 75% of them in the range of 2 × 10 15 ~4 × 10 15 Jones. For the chip-to-chip uniformity, in 12 packaged devices that randomly chosen from three fabrication lots, the light-to-dark current ratio all kept in the level of 10 6 with the average value of 2.70 × 10 6 . There were 75% of them in the range of 1 × 10 6 ~ 3 × 10 6 . The detectivity all kept in the level of 10 15 Jones with average value of 3.69 × 10 15 Jones. There were 75% of them in the range of 1 × 10 15 ~ 4 × 10 15 Jones. The uniformity would deteriorate if the step height of seed layer was short, because NW would nucleate at the lower corner of the step and difficult to form the oblique bridge. Fabrication uniformity was also influenced by the step exposure degree, the compactness of the seed layer and the flatness of the substrate. [ABSTRACT FROM AUTHOR]

In the article a novel construction of a side-detecting luminescent optical fiber for an UV sensor application has been presented. In the fiber, structure phosphate glass doped with 0.5 mol% Tb3+ ions was used as a UV sensitive core/ribbon. The luminescence spectrum of glass and the optical fiber was measured under UV excitation using a deuterium lamp. It was found that large energy gap between upper (metastable) and lower (ground) levels of terbium ions incorporated in phosphate matrix leads to the effective emission at wavelengths of 489, 543, 586 and 621 nm, which correspond to 5D4 → 7FJ, (J = 3, 4, 5, 6) transitions respectively. Phosphate glass doped with optimal (the strongest VIS emission) concentration of Tb3+ (0.5 mol%) was used as the active core/ribbon in the construction of UV side-detecting optical fiber.

This article reports that it is possible to make multifunctional sensing devices with ZnO infiltrated polymers while the sensing interactions could occur throughout the polymer. As such, we find that infiltrated devices with SU-8 polymer can result in highly sensitive UV sensors. Mesh dielectric core devices were found to make sensitive gas sensors with a better than 5 ppm sensitivity for formaldehyde and NO2. A new type of p-n junction device is further demonstrated that is sensitive to UV illumination, thus making it an enhanced UV sensor. Sensing devices relying on volume interactions, such as light absorption, can significantly benefit from the infiltrated polymer. In contrast, devices that rely on surface interactions, such as gas sensors, do not gain performance in any significant way with or without the infiltrated polymer.

In this work, physical properties of neodymium tin oxide pyrochlore ceramics prepared by solid state reaction technique are investigated by means of X-ray diffraction, scanning electron microscopy, ultraviolet-visible light (UV-Vis) spectrophotometry and temperature dependent electrical resistivity measurements. The pyrochlore is observed to have a cubic FCC crystal lattice with lattice parameter of 10.578 A° . The planes of the cubic cell are best oriented in the [2 2 2] direction. From the X-ray, the UV-Vis spectrophotometry and the electrical resistivity data analysis, the grain size, strain, dislocation density, optical and thermal energy band gaps, localized energy band tail states and resistivity activation energies are determined and discussed. The pyrochlore is observed to have an optical energy band gap of ~3.40 eV. This value corresponds to 365 nm UV light spectra which nominates the neodymium tin oxide pyrochlore ceramics for the use as UV sensors. [ABSTRACT FROM AUTHOR]

A zero-power, low-cost ultraviolet (UV)-C colorimetric sensor is demonstrated using a gallium oxide and reduced graphene oxide (rGO) hybrid via photoelectrochemical reactions. A wide bandgap semiconductor (WBS) such as gallium oxide with an energy bandgap of 4.9 eV generates electron-hole pairs (EHPs) when exposed under a mercury lamp emitting 254 nm. While the conventional UVC sensors employing WBS convert the generated EHPs into an electrical signal via a solid-state junction device (SSD), our newly proposed UVC sensory system works by converting EHPs into an electrochemical reaction. The electrochemical reaction causes the degradation of a cationic thiazine redox dye, methylene blue (MB) and thereby spontaneously changes its color. As more rGO was hybridized with the gallium oxide, MB degradation was effectively expedited. Thus, the level of MB degradation under UVC can be evaluated as a UVC indicator. Unlike conventional SSD-based UVC sensors, our responsive colorimetric sensor can be applied where needed inexpensively and zero power. [ABSTRACT FROM AUTHOR]

We introduce an integration concept between a bioinspired optoelectronic integrated circuit (OEIC) and a field-programmable gate array (FPGA) to realize a single-chip smart ultraviolet (UV) imaging sensor. The bioinspired OEIC stacks the Pt/n-Al0.49Ga0.51N backside-illuminated (BSI) Schottky barrier diode (SBD) photodiode array onto the complementary metal oxide semiconductor (CMOS) edge detection circuits (EDCs). The EDC mimics the outer vertebrate retina that has the purpose of reducing the digital analysis information by extracting the edge from the detected object before being processed by the FPGA, and thus decreasing the power consumption. The binary images produced by the bioinspired OEIC are analyzed in the FPGA using a histogram projection circuit to generate information about the location, size, moving speed, moving direction, and spreading status of the detected object, which is the UV radiation coming from the hydrogen flames. In this study, an EDC chip of 1 × 16 pixels was fabricated and integrated with the FPGA using wires. We evaluated the speed calculation performance of the system with a moving object in the range of 1.7-2,049 pixels/s. [ABSTRACT FROM AUTHOR]

In this paper two simple and low-cost fiberoptic sensors for detection of UV radiation are presented. A U-shaped sensor covered with an UV marker for UV radiation detection and a fiber-optic sensor with one end covered with powder from a mercury lamp are produced and described in details. Both sensors are made of large-core PMMA plastic optical fibers. As UV sources, a solar simulator and four different UV lamps are used. The light spectrum on the fiber output is measured by using an USB spectrometer. Dependence of output light intensity on the distance of end-type sensor with powder from a mercury lamp from UV lamp is investigated as well. On the output of the sensor covered with powder from a mercury lamp are obtained peaks of fluorescent emission at approximately 616 nm and 620 nm wavelengths.

In this paper, synthesis and results of the low temperature sensing of carbon monoxide (CO) gas and room temperature UV sensors using one dimensional (1-D) ZnO nanostructures are presented. Comb-like structures, belts and rods, and needle-shaped nanobelts were synthesized by varying synthesis temperature using a vapor transport method. Needle-like ZnO nanobelts are unique as, according to our knowledge, there is no evidence of such morphology in previous literature. The structural, morphological and optical characterization was carried out using X-ray diffraction, scanning electron microscopy and diffused reflectance spectroscopy techniques. It was observed that the sensing response of comb-like structures for UV light was greater as compared to the other grown structures. Comb-like structure based gas sensors successfully detect CO at 75 °C while other structures did not show any response.

Abstract The phenomenon of persistent photoconductivity is elusive and has not been addressed to an extent to attract attention both in micro and nanoscale devices due to unavailability of clear material systems and device configurations capable of providing comprehensive information. In this work, we have employed a nanostructured (nanowire diameter 30–65 nm and 5 μm in length) ZnO-based metal–semiconductor–metal photoconductor device in order to study the origin of persistent photoconductivity. The current–voltage measurements were carried with and without UV illumination under different oxygen levels. The photoresponse measurements indicated a persistent conductivity trend for depleted oxygen conditions. The persistent conductivity phenomenon is explained on the theoretical model that proposes the change of a neutral anion vacancy to a charged state.

AbstractThe ZnO nanostructures consisting of micro spheres in a network of nano wires were synthesized by direct vapor phase method. X-ray Photoelectron Spectroscopy measurements were carried out to understand the chemical nature of the sample. ZnO nanostructures exhibited band edge luminescence at 383 nm. The nanostructure based ZnO thin films were used to fabricate UV sensors. The photoresponse measurements were carried out and the responsivity was measured to be 50 mA W−1. The rise and decay time measurements were also measured.

Aim: To develop a novel plasmonic nanosensing technique to monitor the exposure levels of UV light for sunlight disease prevention. Methods: Anisotropic gold nanoparticles were grown inside a UV photoresponsive fluid, which was previously exposed to UV radiation from different sources. The morphology and optical properties of the obtained nanoparticles were monitored by spectroscopy and microscopy. Results: The morphological and optical properties of the nanoparticles were dependent on the UV dose. The UV exposure levels were accurately correlated to the UV minimal doses to produce erythema to different skin types. Conclusion: This plasmonic nanosensing technique can be employed as novel sunlight-indexing tool for monitoring the dangerous level of skin exposure. [ABSTRACT FROM AUTHOR]

A p-ZnTe/n-CdSe heterojunction was used for making polycrystalline ZnTebased UV sensors. The heteropair components have the same crystal structure and close lattice parameters. ZnTe and CdSe were grown using thermal evaporation and quasiclosed space condensation. A transparent current collecting electrode for the surfacebarrier structure of p-ZnTe/n-CdSe heterojunction was made of degenerate p-Cu1.8S. Surface relief of ZnTe grown on different substrates was studied with scanning atomic force microscopy. The energy band offset diagrams of heterojunction are built and photosensitivity spectra are presented. [ABSTRACT FROM AUTHOR]

We characterize a single titanium (Ti) transition edge sensor (TES) designed for in situ detection of individual \He2^{\ast} excimers. We find a critical temperature of 420 mK, an electrothermal time constant of \sim\!\! 3\ \mu\s, and a total energy resolution of 1.5 eV. We observe the detector response to short laser pulses and present a successful analysis strategy for extracting direct-TES-hit pulses from a much larger background (due to substrate hits). We also present the response of a similar Ti TES with a built-in aperture designed to eliminate substrate background; this device has an energy resolution of better than 1.5 eV and a much reduced substrate signal. We discuss near-term plans for coupling multiple such TESs together with a shared aluminum (Al) absorber, increasing the \He2^{\ast} collection area to millimeter scales. [ABSTRACT FROM PUBLISHER]

Unintentional arc faults due to damaged power line cords and loose connections can cause serious fires; thus, they are a safety hazard in residential areas. Therefore, arc fault circuit interrupters are being increasingly used in homes to protect against arcs that may cause fires. In this paper, we analyzed the ignition characteristics of series arcs on the basis of load current. Furthermore, we recommended suitable arc clearing times through characteristics analysis in the Korean residential electric environment. We determined the arc clearing time via the carbonized path arc clearing time test using an ultraviolet signal detecting system according to the test method of the UL 1699 standard. In the experiments, heat-resistant indoor PVC insulated (HIV) wires, which is a type of residential electrical wire, were used as the wire specimens. [ABSTRACT FROM AUTHOR]