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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]

Excessive exposure to sunlight's ultraviolet (UV) radiation causes adverse effects such as premature aging, sunburn, and skin cancers. Monitoring daily exposure to sunlight is essential to avoid developing health risks. Colorimetric UV sensors change color as a function of UV exposure, provide onsite information about the level of exposure, and can act as a personal wearable device to assist in making informed decisions on sunlight exposure. These sensors utilize radiation-induced reactions on a dye to produce a color change. Here, BiOCl based UV sensor is reported for monitoring UV exposure where a white-to-black color transformation is induced due to the creation of oxygen vacancies in BiOCl. This color transformation is not quantifiable in bulk BiOCl; hence BiOCl was purposely dispersed on filter paper to form petal-like nanostructures that help quantify the color change. Four different dye molecules, 6-carboxyfluorescein, 5-carboxyfluorescein, rhodamine-B, and Prussian blue were evaluated, where 6-carboxyfluorescein gave the best color contrast. The sensor responds to UVA, UVB, and UVC and with proper UV filters can be made selective for specific UV radiations. This unique colorimetric UV sensor can help manage personal UV exposure and reduce the risk of sun exposure ailments. [ABSTRACT FROM AUTHOR]

Ultraviolet radiations (UVR) sensors provide quantitative and continuous measurement of UV‐induced dermal damage. The challenge though is to develop a sensor that simultaneously offers high sensitivity and rapid response to UVR, as well as compatibility to human skin and skin color specificity. In this paper, an epidermal UV sensor that uses new sets of material and device design strategies to deliver accurate UV intensity measurements is presented. The developed sensor provides real‐time and reversible detection performance (color change and recovery) in less than 30 s. By combining the UV photochromic and absorptive materials, a variety of personalized UV epidermal stickers can be developed to achieve naked‐eye quasi‐quantitative monitoring of UV exposure while simultaneously meeting the specific needs of different skin types. Experimental demonstrations validate the high applicability of these wearable UV sensors for managing the impact of UVR in the daily life. [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]

UV sensors possess high importance for modern electronics such as environmental monitoring, health diagnostics, and optoelectronic devices. Thus UV-sensing-materials with high stability has drawn significant interest for next generation UV sensors. Herein, a simple synthesis method of SbPS 4 has been proposed. Then the SbPS 4 crystals are effectively delaminated by micromechanical exfoliation into a few-nanometer-scale nanowires, which is the first demonstration of the material's possibility of exfoliation down to one-molecular-layer thickness. Weak van der Waals (vdW) interaction within the crystal lattice can be easily overcome. The exfoliated SbPS 4 nanowires showed one-dimensional tube structure, and the work function of SbPS 4 showed strong thickness dependence and was confirmed through Scanning Kelvin probe microscopy. The bandgap of 2.54 eV of SbPS 4 , showed great sensitivity to UV lights, depicting SbPS 4 as a promising future UV sensing material for future optoelectronic application. [Display omitted] • Synthesis of one-dimensional van der Waals material SbPS 4 with a tubular molecular structure • Single chain exfoliation of SbPS 4 and its thickness-dependency of work function • Optical property of SbPS 4 as UV-detecting material [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]

An excellent flexible nanocomposites films, which consists of flower-like ZnO and conducting polymer (poly (3,4ethelyenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) on flexible transparent plastic sheets were prepared and reported its unusual negative UV photoresponse, that is increasing resistance in nanocomposite under UV illumination. Nanocomposite (NC) films with varying ZnO loading are used to study the UV photoresponse. Negative photoresponse decreases after a critical concentration of ZnO in NC. Different ZnO concentration NC films were prepared using a simple drop-casting method on flexible transparent plastic sheets. Well-arranged flower-like structured ZnO were prepared by a wet chemical method. A structural investigation based on X-ray diffraction pattern shows the small variations in structural parameters such as lattice constant, crystalline size, microstrain, and dislocation density when ZnO mix with polymer. UV spectroscopy reveals the bandgap variation due to increasing ZnO loading in NC. The photoluminescence study of ZnO gives a broad emission ranging from 485 to 630 nm under an excitation wavelength of 330 nm. Raman spectroscopic and FT-IR studies were also done to know the vibrational properties of prepared samples. Thermogravimetric analysis of prepared NC shows the thermal stability of NC increases with increasing ZnO concentration in NC. Photoresponsivity of NC films was studied by varying ZnO concentration in NC towards UV radiation. Negative photoresponse is changing with ZnO concentration in fixed PEDOT:PSS concentration. [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]

Blind and disabled people suffer a loT to reach their destination, and there are many dangerous risks that disabled people must face. To avoid the inconvenience while walking, a smart electronic walking stick was proposed. This paper proposes a low-cost walking stick based on the latest technology, and a new implementation is intended to effectively interface with the blind. Basically, an ultrasonic sensor is implemented in a walking stick to detect obstacles in front of the blind or handicapped. If there is any obstacle, it will warn the blind person to avoid that obstacle and alert them in the form of a voice announcement. Every day in different ways to ensure people's flexible and safe movement. In this technology-driven world where people strive to live independently, this paper provides an inexpensive 3D ultrasonic stick for the blind to gain personal independence so the disabled can move from one place to another easily and safely. A portable stick is being designed and developed that detects the obstacles in the path of the blind using ultrasonic sensors. The voice alert is activated when any obstacle is detected. In addition, the flash drive is equipped with a system of Short Message Service (SMS) messages. The SMS system is used by the blind to send SMS messages to the numbers stored in the microcontroller in case of an emergency. This system has been successfully programmed with a voice announcement. Computer simulations are performed to evaluate system performance using Proteus software. [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]

This study explores the physical properties and electrical characteristics of a regioregular poly 3-hexylthiophene (rr-P3HT) semiconductor blended with the polymer insulator polystyrene. Given the high operating voltage required by conventional P3HT transistors, we employed a hybrid dielectric layer, combining plasma-reacted metal oxide with a polymer pre-layer (AlO x /PMMA and HfO x /PMMA), to reduce the operating voltage of P3HT transistors. As a result, an operating voltage lower than −5 V for the blended sample was achieved. The structural, morphological, and electrical properties of the prepared blended sample were investigated using XRD, AFM, XPS, UV–Visible spectroscopy, Raman spectroscopy, and I–V characteristics. The blended sample exhibits improved crystalline ordering and an extended effective conjugation length, accompanied by an increased formation of dendritic P3HT fibrils that enhance UV absorption. PS captures generated electrons, effectively delaying their recombination with generated holes in P3HT. This leads to heightened UV responsivity in P3HT/PS transistors. The key discovery of this study is the ultra-low power consumption UV sensing device. The blended sample, illuminated with a UV intensity of 550 μW/cm2, exhibited the highest sensitivity of 194.5, nearly 60 times higher than that of pristine P3HT. Consequently, our investigated device shows promise for applications in visible-blind sunlight or environmental monitoring systems, given its ultra-high-power efficiency. we employed a hybrid dielectric layer, combining plasma-reacted metal oxide with a polymer pre-layer (AlO x /PMMA and HfO x /PMMA), to reduce the operating voltage of P3HT transistors. The blended sample exhibits improved crystalline ordering and an extended effective conjugation length, accompanied by an increased formation of dendritic P3HT fibrils that enhance UV absorption. PS effectively captures generated electrons, delaying their recombination with generated holes in P3HT. This leads to heightened UV responsivity in P3HT/PS transistors. The key discovery of this study is the ultra-low power consumption UV sensing device. The blended sample, illuminated with a UV intensity of 550 μW/cm2, exhibited the highest sensitivity of 194.5, nearly 60 times higher than that of pristine P3HT. [Display omitted] • High performance and low-driving voltage P3HT/PS transistors are realized. • A hybrid plasma-reacted AlO x /HfO x with PMMA are involved in gate insulator fabrication. • The blend P3HT/PS films are comprehensive studied. • An ultra-high power efficiency UV sensor is made. [ABSTRACT FROM AUTHOR]

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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.

An ultraviolet (UV) sensor consisting of a zinc oxide (ZnO) nanofiber sensing membrane and a quartz crystal microbalance (QCM) was fabricated. ZnO nanofibers were prepared by electrospinning and calcination. The morphology and structure of the nanofiber sensing membrane were characterized by scanning electron microscopy and X-ray diffraction. The QCM sensor based on ZnO nanofibers was found to be sensitive to 254-nm UV light in nitrogen, oxygen and air atmospheres. When the QCM sensor was placed under UV irradiation, the resonant frequency difference rapidly decreased. When the light was removed, the frequency difference recovered until reaching 0 Hz. The stability and repeatability of the proposed ZnO nanofiber-based QCM sensor were demonstrated, and the sensing mechanism was briefly discussed. [ABSTRACT FROM AUTHOR]

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]

Zinc oxide (ZnO) has been widely investigated as an important ultraviolet (UV) sensing material in view of its wide band gap (~3.4 eV). However, the fabrication of continuous thin films of ZnO generally requires complex, time-consuming, and expensive processes, such as sputtering and atomic layer deposition. Herein, we demonstrate a bilayer film consisting of a conducting polymer and ZnO nanoparticles sequentially deposited using a simple, rapid, and inexpensive two-step spin-coating process. In this approach, it is not necessary to have a continuous ZnO nanoparticle film as the active layer, because the conducting polymer deposited under the ZnO nanoparticles acts as a conductive and continuous supporting layer for the particles. Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) is used as the auxiliary layer to promote the efficient transport of photo-carriers generated from ZnO nanoparticles under UV light. As a result, under UV light (365 nm), photocurrents obtained from a ZnO/PEDOT: PSS bilayer film are significantly higher (∼20 times) than that from a ZnO layer for a given voltage bias. The photoelectric performance can be further tuned by controlling the speed of spin-coating in the deposition of ZnO nanoparticles. The stability and photo response (rise and decay time) of the ZnO/PEDOT: PSS bilayer film under the repeated on-off condition are also reported. [ABSTRACT FROM AUTHOR]

This paper presents an improvement of the acoustoelectric effect by sensitivity and response of ultraviolet (UV) sensors by changing the argon/oxygen ratio. The acoustoelectric sensor is a delay-line type with a center frequency of 240.2625 MHz and fabricated on a piezoelectric substrate. Aluminum thin films were deposited as interdigitated transducers and patterned, and the ZnO thin film was deposited as a UV sensing layer by controlling the ratio of argon and oxygen with an RF magnetron sputtering. By increasing the oxygen partial pressure during ZnO deposition, the photoconductivity increased by 6.5 times, thereby increasing the frequency change related to the sensitivity of the sensor. The sensitivity to UV light was 110.4 Hz cm2/μW under an argon/oxygen ratio of 6:4, which is an increase of 5.1 times from 21.76 Hz cm2/μW obtained under a ratio of 10:2. In addition, the response and recovery times were improved by 2.85 times and 3.02 times, respectively. Image 1 • An improvement of the sensitivity and response of the acoustoelectric UV sensor by changing the argon–oxygen ratio was demonstrated. • The ZnO thin film was deposited as a UV sensing layer by controlling the ratio of argon and oxygen. • By increasing the oxygen partial pressure during ZnO deposition, the photoconductivity increased. • The sensitivity to UV light was 110.4 Hz·cm2/μW under an argon–oxygen ratio of 6:4. [ABSTRACT FROM AUTHOR]

Fabrication temperature is an important factor affecting the manufacturability of electronic devices, especially for the bottom-up self-assembled nano-device. In this study, we used a lateral-bridged zinc oxide (ZnO) nanowire array UV sensor as a model to investigate the influence of temperature on device performance over the entire manufacturing process, from sensor fabrication to packaging. We found that annealing of the SiO2 substrate would make ZnO seed layer on top of it more compact and uniform, and hence improve the lateral orientation and uniformity of ZnO nanowires grown from the seed layer. With the annealed substrate, the light-to-dark current ratio increased by two orders of magnitude. On the contrary, annealing the ZnO seed layer would deteriorate the light-to-dark current ratio of the sensor, because annealing caused most of the grains in the seed layer to become vertically aligned, which in turn affected the lateral growth of ZnO nanowire arrays. During the packaging process, the surface structure of ZnO nanowires would change if the chip welded at a temperature of 230°C for 2 min, resulting in a decrease of light-to-dark current ratio by three orders of magnitude. [ABSTRACT FROM AUTHOR]

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Sensitivity of flexible surface acoustic wave (SAW) sensors to ultraviolet (UV) light is enhanced by the application of ZnO micro- and nanostructured networks as sensing layers. In this study, the influence of three-dimensional (3D) tetrapodal ZnO microstructured networks (T-ZnO MNs) spin coated onto Al foil/ZnO piezoelectric film SAW devices on the sensor performance under a stimulus of UV-light irradiation and the influence of relative humidity was investigated. The UV-light sensitivity is increased from −3.03 × 10–6 to −5.25 × 10–6 cm2 mW–1 with the application of 3D T-ZnO MNs. Likewise, the humidity sensitivity is enhanced by a factor of 2.9 at 90% relative humidity, which is explained by the porous structure of T-ZnO MNs. In addition, the measured sensitivity to the UV-light intensity is demonstrated to be significantly modified under bent conditions because the surface of the ZnO piezoelectric film is relatively denser in the case of bending. This study also demonstrates that the sensing performance of the respiratory characteristics is increased by nearly a factor of 1.7 under bent conditions after utilization of the T-ZnO MNs, showing its capability for breath and respiration monitoring applications. [ABSTRACT FROM AUTHOR]

This work presents an optical sensor for ultraviolet radiation (UV) detection, based on the combined effects of Lossy Mode Resonance (LMR) in the mid infrared (MIR) spectral region and the photoisomerization of a polymeric dye coating. LMR was obtained by means of a sputtered SnO 2 thin film on a tetrafluoroethylene-perfluoro (or alkoxy Vinyl Ether, PFA) substrate, along with a photo sensitive coating based on poly R-478. Obtained devices shown response and recovery times of 12 and 43 s, respectively, for an UV excitation of 71 mW at 365 nm. Sensitivity as a function of the excitation wavelength was studied with the highest value of 26 nm/mW obtained at 280 nm. For this excitation wavelength, the limit of detection (LoD) obtained was 0.024 mW. Four different excitation wavelengths were used to cover all UV regions (280, 310, 365 and 395 nm). All measurements were performed at room temperature and humidity (25 °C ± 1 °C and 13% R.H. ± 2% R.H. respectively). As far as we know, it is the first time that the LMR effect has been recognized in combination with a photoisomerization process. [Display omitted] • The photoisomerization and the birefringence of the R-478 polymer coating are activated with UV radiation. • LMR effect combined with polymeric photoisomerization achieve a highly sensitive optical sensor for UV detection. • The Refractive Index of the poly R-478 coating decrease selectively under UV radiation. • Poly R-478 has a reversible photoisomerization activated with UV. [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.

In this study, the effects of thermal annealing on RF-coated GZO thin films on n-Si and PET substrates at room temperature at 200 W RF power were investigated systematically. Deposited film on the n-Si substrate was annealed at range of 100 - 600°C for 1 hour in air at atmospheric pressure with CTA. UV-Vis measurements of flexible films prepared at 100 and 200°C were evaluated due to the deterioration of the PET substrate form at 300°C temperature. The energy band gaps of the films were found as 3.10 and 3.30 eV, respectively. It was revealed from the XRD results that GZO films grown on Si have c-oriented hexagonal wurtzite structure. UV sensor fabrication was performed from the flexible GZO film annealed at 200°C with the highest band gap energy. The UV-light sensitivity of the produced sensor was determined by I-V measurements in light (γ= 365 nm) and dark conditions. Photo-sensitivity of the flexible sensor was found to be 8.07 at 2V. [ABSTRACT FROM AUTHOR]

The potential of finely-structured zinc oxide (ZnO) coatings developed via solution precursor plasma spraying (SPPS) as CO 2 gas and UV light sensor was explored in this work. The coatings were deposited on stainless steel substrates using aqueous solutions of zinc nitrate and zinc acetate as precursors. The coatings' microstructures were studied in relation to the solution precursors used. Relatively porous coatings were obtained when using acetate as starting precursor compared to the coatings from the nitrate precursor. This was attributed to the different chemical routes of ZnO formation for each precursor droplet upon contact with plasma jet. Phase analysis confirmed the formation of polycrystalline ZnO having wurtzite structure from both precursors. The sprayed ZnO coatings showed good sensitivity and recovery towards UV light. Moreover, the coatings were sensitive towards carbon dioxide (CO 2) analyte gas but did not show any good recovery which was attributed to the microstructure of the coatings. These results showed the feasibility of SPPS process for the fabrication of finely-structured ZnO coatings as sensors of CO 2 gas and UV light. • (1) Polycrystalline ZnO coatings were developed via SPPS process using different starting solution precursors • (2) Microstructures were influenced by solution precursors used due to different chemical routes of ZnO formation in plasma jet • (3) Relatively porous coatings were obtained when using acetate as compared to using the nitrate one • (4) ZnO coatings showed good sensitivity towards CO 2 gas but do not show any good recovery • (5) ZnO coatings had good response and recovery when exposed to UV light [ABSTRACT FROM AUTHOR]

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]

Abstract In this work, we have developed a new modeling tools based on physical, mathematical and numerical models for the analysis of UV-photodetectors based on ZnO NRs/PPV-C6 hybrid heterojunctions. The photoelectrical equivalent circuit parameters are the series resistance (R s), the shunt resistance (R p), the reverse current density (J 0), the ideality factor (n) and the photocurrent density (J ph). A combined physical-mathematical-numerical approach based on the modified Schockley model, the Lambert W function and the optimized method of the Root Mean Square error (RMSE) was applied to analyze the different devices performances. The results demonstrate that the incorporation of PPV-C6 polymer to the ZnO NRs structure leads to significant amelioration in the interface and increase of both the J ph and responsivity with a decrease of the R s. This kind of hybrid heterojunction based UV light sensor is promising for future low cost and high performance optoelectronic devices development. [ABSTRACT FROM AUTHOR]

Abstract In this work, monolithically integrated wavelength-selective 4H-SiC UV-sensor arrays were manufactured using two photolithography masks and only one implantation sequence demonstrating the potential of the advanced 4H-SiC process technology for the first time. The process technology is described in detail for the fabrication of a 2 × 2 wavelength-sensitive UV-sensor array including two variants with different thicknesses of the p-emitter. The maximum spectral responsivity is 92 mA/W for a wavelength of 300 nm and the devices with a thick p-emitter and 162 mA/W for a wavelength of 290 nm and devices with the thin p-emitter. The corresponding values of the external quantum efficiency are 38%, and 69%, respectively. Furthermore, another UV-sensor characteristic is found evaluating the current difference between both types with a maximum spectral responsivity of 80.2 mA/W at a wavelength of 270 nm. [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.

Highlights • Ultraviolet-light-driven photoresponse of Graphene/MoS 2 based FET is investigated. • The increment in photocurrent of FET is observed by increasing V ds. • The enhancement in photoresponsivity is observed in Graphene/MoS 2 heterostructure. • Detectivity and external quantum efficiency of device were also enhanced. Abstract Two dimensional materials such as graphene and transition metal dichalcogenides (TMDC) have gained profound research interest as novel optical material owing to their remarkable optical and electrical properties. The formation of atomically controlled van der Waals (vdW) heterostructured architectures facilitates comprehending innovative photosensing and optoelectronic devices exhibiting unique properties than conventional counterparts. We have demonstrated the use of MoS 2 /graphene heterostructured field effect transistor (FET) for photosensing applications. For different drain to source voltages (V ds), the effect of DUV irradiations is studied, revealing an increased photoresponse. Optical performance of FET is studied by evaluating photoresponsivity (R λ), detectivity (D∗) and external quantum efficiency (EQE). Optical response with R λ and D∗ approaching 3.34 × 103 AW−1 and 1.004 × 1012 jones, respectively is obtained. This approach of creating TMDCs/graphene based heterostructured devices provide new insights for development of high performance photosensors for next generation optical and sensing applications. [ABSTRACT FROM AUTHOR]

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 this work, ZnO nanowires (ZnO NWs) and urchin-like ZnO nanowires (U-ZnO NWs) based on self-assembled ordered polystyrene sphere (PS) were successfully prepared by combining atomic layer deposition (ALD) and electrochemical deposition (ECD) processes to build UV photosensors. The photo-response of the prepared samples was investigated and compared. The growth of the nanowires on self-assembled, ordered PS introduces a significant modification on the morphology, crystal orientation and grain size of U-ZnO NWs compared to randomly, vertically aligned ZnO NWs, and therefore improves the photo-response of U-ZnO NWs. The photocurrent may be produced by either a surface or bulk-related process. For ZnO NW-based photosensors, the photocurrent was monitored by a surface related process, whereas, it was mainly governed by a bulk related process for U-ZnO NWs, resulting in a higher and faster photo-response. The study of the rise and decay time constants for both materials showed that these parameters were strikingly sensitive to the optical properties. [ABSTRACT FROM AUTHOR]

GaN-based metal–insulator–semiconductor–insulator-metal (MISIM) photodiodes using three kinds of high-k dielectrics (Al2O3, HfO2, and ZrO2 were fabricated, and their electrical, photo response, and noise properties were characterized. The GaN MISIM photodiode using ZrO2 showed the lowest dark current density of 5.43 \times 10^-9 A/cm2 at 10 V bias and the highest UV-visible rejection ratio of 257 at 1 V bias. No Fowler-Nordheim tunneling phenomenon was observed in the diode under UV illumination. The noise spectral density and the trap-time-constant of the device using ZrO2 were 9.79 \times 10^-31~\textA^2 /Hz for $f = 10$ Hz at 1 V and 335~\mu \text{s} , respectively, which were lowest compared with the other two samples. ZrO2 was identified as the better GaN, the passivation material among the three dielectrics. [ABSTRACT FROM PUBLISHER]