A resonance cavity antenna (RCA) has been explored employing nontransparent solid metal sheet as superstrate which, to the best of our knowledge, is reported for the first time. The proposed configuration is much advantageous in terms of design, simplicity, structural stability, fabrication, and cost without compromising in gain, efficiency, and bandwidth. A probe-fed dielectric resonator antenna (DRA) with ε r =10 has been used as the primary radiator. Proposed RCA bearing overall size 1.1λ×1.1λ×0.6λ promises for large impedance bandwidth (23%) with considerably high gain (11.8 to 12.2 dBi). The superstrate size is relatively compact compared to its semi-transparent versions, investigated earlier. Present design has been experimentally validated indicating as much as 12 dBi peak gain with more than 96.5% efficiency.
The present study concerns development of an efficient alcohol sensor by controlling the stoichiometry, length, and wall thickness of electrochemically grown TiO2 nanotube array for its use as the sensing layer. Judicious variation of H2O content (0, 2, 10 and 100% by volume) in the mixed electrolyte comprising ethylene glycol and NH4F resulted into the desired variation of stoichiometry. The sensor study was performed within the temperature range of 27 to 250 °C for detecting the alcohols in the concentration range of 10-1000 ppm. The nanotubes grown with the electrolyte containing 2 vol % H2O offered the maximum response magnitude. For this stoichiometry, variation of corresponding length (1.25-2.4 μm) and wall thickness (19.8-9 nm) of the nanotubes was achieved by varying the anodization time (4-16 h) and temperatures (42-87 °C), respectively. While the variation of length influenced the sensing parameters insignificantly, the best response magnitude was achieved for ∼13 nm wall thickness. The underlying sensing mechanism was correlated with the experimental findings on the basis of structural parameters of the nanotubes.
Nanotechnology has acquired an immense recognition in cancer theranostics. Considerable progress has been made in the development of targeted drug delivery system for potent delivery of anticancer drugs to tumor-specific sites. Recently, multifunctional nanomaterials have been explored and used as nanovehicles to carry drug molecules with enhanced therapeutic efficacy. In this present work, graphene oxide quantum dot (GOQD) was conjugated with folic acid functionalized chitosan (FA-CH) to develop a nanocargo (FA-CH-GOQD) for drug delivery in cancer therapy. The synthesized nanomaterials were characterized using Fourier transform infrared spectroscopy, ultraviolet−visible spectroscopy, scanning electron microscopy, transmission electron microscopy, and dynamic light scattering. Photoluminescence spectroscopy was also employed to characterize the formation of GOQD. To validate the efficacy of FA-CH-GOQD as nanocarriers, doxorubicin (DOX) drug was chosen for encapsulation. The in vitro release pattern of DOX was examined in various pH ranges. The drug release rate in a tumor cell microenvironment at pH 5.5 was found higher than that under a physiological range of pH 6.5 and 7.4. An MTT assay was performed to understand the cytotoxic behavior of GOQD and FA-CH-GOQD/DOX. Cytomorphological micrographs of the A549 cell exhibited the various morphological arrangements subject to apoptosis of the cell. Cellular uptake studies manifested that FA-CH-GOQD could specifically transport DOX within a cancerous cell. Further anticancer efficacy of this nanomaterial was corroborated in a breast cancer cell line and demonstrated through 4′,6-diamidino-2-phenylindole dihydrochloride staining micrographs.
In this paper, we report on the development of a highly sensitive, relatively low-temperature ethanol sensor based on sol-gel derived p-TiO 2 thin film. The p-type anatase TiO 2 thin film was deposited by sol-gel technique on a thermally oxidized <100> p-Si (resistivity 5 cm) substrate. Anatase TiO 2 phase with <101> nanocrystallinity was confirmed with an average particle size of ∼11 nm from X-ray diffraction and field emission scanning electron microscopic study. Ethanol sensor study, in the resistive mode, was carried out at a relatively low operating temperature range (75°C-175°C) for sensing low concentrations of ethanol in air (5-100 ppm). Response magnitude of ∼146% was observed at 150°C toward 100-ppm ethanol (in air) with corresponding response time and recovery time of 39 and 15 s, respectively. The sensor showed appreciably highresponse magnitude (129%) even at low ethanol concentration (5 ppm) with acceptable response and recovery time (54 and 22 s, respectively) at the same operating temperature (150°C). At a particular temperature, for all the ethanol concentrations, sensor showed minimal base line resistance drift, thereby offering highly repeatable and stable sensing performance. Ethanol selectivity study against other volatile organic compounds, such as methanol, acetone, and 2-butanone, was also investigated and was found to be quite promising. Ethanol sensing mechanism for such p-type TiO 2 has also been discussed in the light of corresponding oxygen vacancy model. Index Terms-p-TiO 2 , ethanol sensing, high response, relatively low operating temperature, low concentrations, repeatibility, selectivity.
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