Development of Tetrapod Zinc Oxide-Based UV Sensor for Precision Livestock Farming and Productivity (original) (raw)
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Zinc oxide tetrapod synthesis and application for UV sensors
Materials Physics and Mechanics, 2012
Zinc oxide tetrapods (ZnO-Ts) were synthesized by air oxidation of zinc vapor. For stable production of the ZnO-Ts at the furnace temperatures of 900 °C, the lowest evaporator temperature was found to be 480 °C. Aerosol measurements showed that the fraction of naturally charged particles decreased with evaporator temperature from 89 % at 480 o C to 43 % at 420 o C. Various UV sensors were prepared to study the response and reset times and the On/Off ratio as a function of the ZnO-T concentrations, interelectrode distance and air humidity conditions. The presence of humid air was found to increase the conductivity of the ZnO-T sensors and to lower the response and reset times as well as On/Off ratio to 98, 96 and 88 %, respectively.
Surface Modified Zinc Oxide Nanoparticles as Smart UV Sensors
Journal of Electronic Materials, 2019
The present paper examines the synthesis of ZnO nanoparticles and their surface modification via the microwave assisted sonochemical method along with its successful application in designing a smart UV sensor. The structure of the prepared samples was investigated using XRD, XPS and its respective crystallinity studies. The photoluminescence spectroscopy identified an increase in the green emission intensity due to surface modification which is attributed to the density of oxygen vacancies. The variation in the dielectric constant and dielectric loss values with surface modification is clearly substantiated. As a case study, it was observed a smart UV sensor fabricated using this surface modified ZnO response and decay time that are 14 s and 16 s, respectively. Also, the possibility of surface modification in tuning the sensing responses has been investigated in detail.
Synthesis of ZnO tetrapods for flexible and transparent UV sensors
Nanotechnology, 2012
ZnO tetrapods (ZnO-Ts) were synthesized in a vertical flow reactor by gas phase oxidation of Zn vapor in an air atmosphere. The morphology of the product was varied from nearly spherical nanoparticles to ZnO-Ts, together with the partial pressure of Zn and reaction temperature. MgO introduced during synthesis, increased the band gap, the optical transparency in the visible range, and also changed the ZnO-T structure. Fabricated flexible transparent UV sensors showed a 45-fold current increase under UV irradiation with an intensity of 30 µW cm −2 at a wavelength of 365 nm and response time of 0.9 s.
The Strategy to Control the Morphology of ZnO Nanostructure UV Sensor
IOP Conference Series: Materials Science and Engineering, 2015
The larger surface-area-to-volume ratio compared with their bulk counterpart, Nanomaterials based electronic devices are the subject of keen interest, probably because of cost effective nature and fast sensing capabilities. Moreover the control morphology at specific area of electrodes is a challenging task. Therefore in the current research article the ZnO thin film and ZnO nanorods were selectively deposited by low cost sol-gel and hydrothermal growth process at the selective area of microgap electrodes spacing and further electrically tested for ultraviolet (UV) sensing application. On exposure to ultraviolet (UV) light the current gains, response/recovery times, repeatability, of the fabricated sensors displayed the promising application for UV light detection. The surface morphologies structural, optical and electrical properties of the as synthesized nanostructures ZnO were characterized using SEM, XRD, and source meter respectively.
Sensors and Actuators A: Physical, 2020
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Development of highly sensitive UV sensor using morphology tuned ZnO nanostructures
Applied Physics A, 2014
We report synthesis, electrical, optical, and UV sensing properties of morphology tuned one-dimensional ZnO nanostructures. Morphology tuning was achieved by varying the temperature using very simple vapor transport method. The structural, morphological, and compositional properties of the samples were investigated by powder X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and energy dispersive analysis of X-rays spectroscopy. Photoluminescence and diffused reflectance spectroscopy were used to optically characterize films. The structural and morphological features revealed demonstrated that the synthesized nanostructures were high-density crystalline nanowires, nanorods, and nanobelts. Synthesized nanostructures were employed in UV sensing applications. The photosensors exhibit a current response range from 5 to 217 lA for UV light (365 nm) at room temperature. The sensor showed a relatively fast temporal response (0.25-35 s) and baseline recovery time (1-12 s) when irradiated with UV light. Response measurements showed that such a sensor is suitable for use as an optical switch. Recently, one-dimensional ZnO nanowires, nanobelts, and nanorods have shown potential as next-generation UV sensors as well as self-powered photodetectors [5, 15, 16]. UV sensors are highly desirable in many fields such as environmental studies, space communications, medical, and communication equipment [17, 18]. ZnO nanostructures are potential candidate for UV sensors due to their high surface to volume and ON/OFF current ratios [2], fast
Evaluation of zinc oxide nano-microtetrapods for biomolecule sensing applications
Micro+Nano Materials, Devices, and Systems, 2015
Zinc oxide (ZnO) is a well-known II-VI semiconductor material that has gained renewed interest in the past decade due to the developments of growth technologies and the availability of high-quality ZnO bulk single crystals. Owing to a wide direct band gap (3.37 eV), large exciton binding energy (60 meV), and high electron mobility (440 cm 2 V-1 s-1), ZnO has been used for applications including actuators, optoelectronics, and sensors. ZnO nanoparticles can be synthesized in a broad variety of morphologies, such as nanotetrapods, nanotubes, and nanowires. Among these nanostructures, the tetrapods have attracted significant attention due to their unique morphology consisting of four legs connected together in a tetrahedral symmetry. Recently, it has been reported that nano-microstructured ZnO tetrapods (ZnO-Ts) can be synthesized by flame transport synthesis (FTS) in a rapid and up-scalable approach. Compared to conventional ZnO nanoparticles, the nanomicrostructured ZnO-Ts can reduce cellular uptake, while still exhibiting specific nanomaterial properties due to the nanoscale tips. Moreover, the anisotropic ZnO-Ts have the advantages of multiple electron transfer paths, chemical stability, and biocompatibility, which make the ZnO-Ts promising candidates for biomolecule sensing applications. This work herein reports a systematical study on the structural, optical and electrochemical properties of the ZnO-Ts, which were synthesized by FTS using precursor Zn microparticles. The morphology of the ZnO-Ts was confirmed by scanning electron microscopy (SEM) as joint structures of four single crystalline legs, of which the diameter of each leg is 0.7-2.2 μm in average from the tip to the stem. The ZnO-Ts were dispersed in glucose solutions to study the photoluminescence as well as photocatalytic activity in a mimicked biological environment. The photoluminescence (PL) intensity in the ultraviolet (UV) region decreased with linear dependence on the glucose concentration up to 4 mM. The ZnO-Ts were also attached with glucose oxidase (GOx) and over coated with Nafion ® to form the active media for electrochemical glucose sensing. The active layers were confirmed by Fourier transform infrared spectroscopy (FT-IR). Furthermore, the current response of the active layers to glucose was studied by cyclic voltammetry (CV) in various glucose concentration conditions. Stable current response to glucose was detected with linear dependence on the glucose concentration up to 12 mM, which confirms the potential of ZnO-Ts for biomolecule sensing applications.
Vacuum, 2019
Rapid detection and fast response of nanoelectronic devices based on semiconducting oxides is nowadays a modern and stringent subject of research. Device performances depend mainly on the morphologies of the metal oxide nanostructures. In the scope of this work, the influence of the structural morphology of three-dimensional (3-D) ZnO nano-and microstructured networks on the room temperature UV detection properties is studied in detail. We show that the formation of multiple potential barriers between the nanostructures, as well as the diameter of the nanostructures, which is in the same order of magnitude as the Debye length, strongly influence the UV sensing properties. Consequently, 3-D ZnO networks consisting of interconnected ultra-long wire-like tips (up to 10 μm) and with small wire diameters of 50-150 nm, demonstrated the highest UV sensing performances (UV response ratio of ∼3100 at 5 V applied bias voltage). Furthermore, we demonstrate the possibility of substantially increasing the UV sensing performances of individual ZnO nanowire (NW) (diameter of ∼50 nm) by surface functionalization with carbon nanotubes (CNTs), showing high response ratio (∼60-50 mW/cm 2), as well as fast response (∼1 s) and recovery (∼1 s) times. The obtained results thus provide a platform with respect to the next generation of portable UV radiation detectors based on semiconducting oxide networks.
Rapid Fabrication Technique for Interpenetrated ZnO Nanotetrapod Networks for Fast UV Sensors
Recent developments on the synthesis of networked nanostruc-tures have added new amplitudes for designing multifunc-tional devices, including sensors and UV photodetectors. The importance of UV detectors is growing because of the demand for wide range of environmental, military, industrial, fl ame sensing, water sterilization, and early missile plume detection applications. [ 1 ] With their high performances, but own drawbacks , Si-, GaN-or III–V-compound-based UV detectors are available on the market. Although the Si-based photo-devices are known for quick responses compared with ZnO-based UV detectors, they exhibit severe limitations, such as poor selectivity towards visible and infrared (IR) light, which demands complex fi lters, ultra-high vacuum condition, and high voltage. [ 2 ] By contrast, for ZnO-based UV detectors, these types of limitations are easily ruled out because of their wide and direct band-gaps and ability to operate in harsh environmental conditions. In this work, we demonstrate two novel fl ame transport synthesis (FTS) methods, namely, burner fl ame transport synthesis (B-FTS) and crucible fl ame transport synthesis (C-FTS) for fabrication of the ZnO nano-microstructure-based UV photodetec-tors. The FTS approach utilizes Zn microparticles in contrast to many conventional fl ame synthesis methods that are based on precursor gases. Both of the techniques allow facile and cost-effective growth of ZnO nano-microstructures, bridging the 2–10 μ m size gaps between two Au contacts on pre-patterned chips. High crystalline qualities of the fabricated nano-micro-structures grown by rapid B-FTS and C-FTS approaches were confi rmed by XRD and Raman studies. The SEM investigations revealed interpenetrating nanojunctions between the bridging ZnO nano-microstructures grown on the gaps between two Au contacts. The B-FTS approach exhibits the unique feature of ultra-rapid growth of ZnO nanotetrapods within few milliseconds and simultaneously in situ bridging electrical contacts. These bridging nanotetrapods were directly integrated on a chip and demonstrated signifi cantly improved performances as a UV photodetector. Comparison of the UV photodetectors performances built from interpenetrating ZnO nano-microstruc-tures fabricated by B-FTS and C-FTS techniques are presented. Fastest response/recovery time constant (≈32 ms) under 365 nm UV light irradiation of B-FTS-made photodetectors (on/off ratio ≈4.5 × 10 3 at 2.4 V) is reported. Different type of nanojunctions formed between neighbor nanowires or nanotet-rapods (with 'arm' thickness <50 nm) could be the reason for such improved characteristics. The role of nanojunctions in fast UV photodetectors from networked ZnO nanowires and nano-tetrapods is discussed. On the basis of the rapid B-FTS fabrication process and fast UV photodetection capabilities, such networked ZnO nanotetrapods can be potential candidates for various nanosensor applications. Metal oxide nanostructures, such as nanorods, nano wires, and nanotetrapods, have gained a lot of research interest for multifunctional device applications owing to their electrical , optical, and mechanical properties. [ 3–6 ] With wide direct bandgap (3.37 eV) and large exciton binding energy (≈60 meV) at room temperature, ZnO nanostructures are one of the most investigated materials for different nanotechnological