Structural phase transition and negative thermal expansion in Cu1.8Zn0.2V2–x P x O7 solid solutions

Negative thermal expansion (NTE) is exhibited over the entire x range for Cu1.8Zn0.2V2–xPxO7. In particular, dilatometric measurements using epoxy resin matrix composites containing the spray-dried powder demonstrated that the thermal expansion suppressive capability was almost unchanged for x≤0.1. With increasing x, the x-ray diffraction peak position moves systematically, but some peaks are extremely broad and/or asymmetric, suggesting disorder in the internal structure. The crystallographic analysis confirmed NTE enhancement by microstructural effects at least for x=0.2. Preliminary measurements suggest higher resistivity and lower dielectric constant than that of pure vanadate, which is suitable for application to electronic devices.

CTAB Reverse Micelles as Catalysts for the Oxidation of Ascorbic Acid by K3[Fe(CN)6]

The oxidation of ascorbic acid by K3[Fe(CN)6] was studied in reverse micellar systems composed of CTAB (Cetyltrimethylammonium bromide), and it was found the observed first order (k1(aq) = 5.2×10−5 s−1, k1(rev) = 61.4×10−4 s−1) rate constant in reverse micellar medium is around forty times higher compared to aqueous medium under identical conditions. The rate enhancement (k2(aq) = 0.9×10−5 mole−1.dm3.sec−1, k2(rev) = 1.75×10−3 mole−1.dm3.sec−1) is attributed to the large concentration effect and lower dielectric constant in the reverse micelles. The rate of the reaction increases with increase in W = {[H2O]/[surfactant]} which is explained in terms of ionic strength of the water pool. The effect of surfactant concentration on rate was explained on the basis of Berezin pseudo phase model. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

In-band RCS reduction antennas using an EBG surface

The paper has proposed a multilayer, polarization rotation featured, low radar cross-section (RCS) antenna using electromagnetic band-gap (EBG)-based frequency selective surface (FSS) at 8.25 GHz. Cross-shaped EBG unit cells offer zero reflection phase and −25 dB reflection magnitude at 8.25 GHz. The FSS layer consists of eight cross-shaped EBG unit cells sandwiched between two substrates to offer high absorptivity at the desired band. The circular patch antenna resonating at 8.25 GHz is placed on the top substrate having a lower dielectric constant. Four circular-shaped patches are etched at the four corners of the top layer and are coupled with two feed lines which are aligned 90° to each other at the bottom layer and interconnected diagonally to achieve polarization rotation. The proposed antenna offers a gain of 6.72 dB and an in-band RCS of −21.4 dBsm. Incident energy is backscattered into eight directions separated by angle ϕ = 45°. The proposed antenna has the RCS reduction band of 7.7–9.4 GHz. It offers normalized polarization rotation ratio more than 0.8 within the −40° to 40° angular region at the frequency band 8–8.5 GHz. The measured result using the fabricated prototype agrees well with the simulated one.

Investigation and Design of Dual Gate Dielectrically Modulated Junction less TFET for Biomolecule Recognition

This paperwork includes a tunnelling transistor with dual gate and employing the use of dielectric modulation (DG-DM-JL-TFET) based structure. In order to recognize the biomolecule like protein, biotin, uricase etc a nano cavity is presented above the tunnelling. Charge plasma technique is used to form the drain and source regions into the substrate. High work function creates a hole in source and similarly a lower work function will create an electron in drain. The “N” region is etched into the substrate using hafnium electrode with a work function of 3.9 eV. Si02 of 0.5nm thickness is inserted between electrode of source. The “P+” region is etched on intrinsic silicon substrate using Platinum electrode having a work function of 5.93 eV. The device structure proposed in this paper shows results for sensitivity for charged and neutral biological molecules. The sensitivity of the biological molecules having higher dielectric constant is greater than those biological molecules possessing lower dielectric constant.

The Localized Enhancement of Surface Plasmon Standing Waves Interacting With Single Nanoparticles

Real-time, high-sensitivity, and label-free detection to single nanoparticles has been achieved via visualizing the interaction between surface plasmon polaritons (SPPs) and nanoparticles, which is widely applied to chemistry and biology. In this work, aiming to enhance the detection sensitivity to nanoparticles, we explore the interaction of SPP standing waves with single nanoparticles. Compared with SPPs, the inhomogeneous fields of SPP standing waves modulate charge distributions around the particle and excite different electric dipole modes that tailor localized enhancements. For nanoparticles situating at electric antinodes of SPP standing waves, a vertical electric dipole is excited and high-density charges are stimulated around nanoparticle-film nanocavities, leading to further increased localized enhancement. The localized enhancement experiences more increase with smaller particle size, lower dielectric constant of surrounding medium, and lower particle refractive index. Via tailoring the localized enhancement by SPP standing waves, the sensitivity of SPP microscopy can be improved, which would broaden its applications on nanotechnology, biomedicine, and environmental monitoring.

Role of Electrospinning Parameters on Poly(Lactic-co-Glycolic Acid) and Poly(Caprolactone-co-Glycolic acid) Membranes

Poly(lactic-co-glycolic acid) (PLGA) and poly(caprolactone-co-glycolic acid) (PCLGA) solutions were electrospun into membranes with tailored fiber diameter of 1.8 μm. This particular fiber diameter was tuned depending on the used co-polymer by adjusting the electrospinning parameters that mainly influence the fiber diameter. The greatest setting of the fiber diameter was achieved by varying the polymer solution parameters (polymer concentration, solvents and solvents ratio). PLGA was adequately electrospun with 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), whereas PCLGA required a polar solvent (such as chloroform) with a lower dielectric constant. Moreover, due to the amorphous morphology of PCLGA, pyridine as salt had to be added to the starting solution to increase its conductivity and make it electrospinnable. Indeed, the electrospinning of this co-polymer presents notable difficulties due to its amorphous structure. Interestingly, PCLGA, having a higher glycolic acid molar fraction than commonly electrospun co-polymers (caprolactone:glycolic acid ratio of 45:55 instead of 90:10), could be successfully electrospun, which has not been reported to date. To an accurate setting of fiber diameter, the voltage and the distance from needle to collector were varied. Finally, the study of the surface tension, conductivity and viscosity of the polymer solutions allowed to correlate these particular characteristics of the solutions with the electrospinning variables so that prior knowledge of them enables predicting the required processing conditions.

Design and Performance Investigation of Symmetrical Dual Gate Doping-less TFET for Biomolecule Recognition

This manuscript presents a dielectric modulated doping-less dual metal Gate Tunnel Field Effect Transistor (DL-DMG-TFET) sensor. In which a nano-cavity is presented above the tunnelling point to recognize the bio-molecule like amino acids (AAs), protein, and so on the proposed P+ and N+ sections are invented relying on the electrode's work-function on silicon body. The impacts of metal work regulation, cavity length and thickness variety are investigated for improving band-to-band tunnelling probability at the source-channel intersection. The proposed structure shows perceptible affectability results for neutral and charged biomolecules. The sensitivity of the higher dielectric constant bio-molecules are higher as compared to bio-molecule having lower dielectric constant; the drain current sensitivity of the Gelatin (k=12) is assessed as which is 13% and 35% higher than the affectability of Keratin (k=10) and Bacteriophage T7 (k=5) separately at the nano-cavity length of 30 nm.

Structural Design of Wearable Miniaturized Textile Antenna

Worldwide demand of wearable devices is arduous. In field of movable technology ‘hands-free’ status is requirement of persistent communication. With this regards, extensive research has been carried out on wearable technologies. Antennas made of fully fabric material are natural choice. This work presents performance comparison of between classical micro-strip antenna, fabric antenna with metal patch and fully fabric antenna. The fabric antennas show better gain and return loss but are larger in size owing to lower dielectric constant of fabric material. The fabric antennas being conceptually similar to the traditional micro-strip antennas, almost all the micro-strip design techniques could be seamlessly applicable to them. This work further presents an innovative technique of introducing an edge slot in the radiating patch and achieves a reasonable size reduction. This edge slot wearable antenna has been fabricated and the results are compared well with simulated results.

Effect of Doping on the Electrical Characteristics of ZnSe

The effect of sulfur, iron, and chromium doping on the electrical characteristics of ZnSe single crystals was studied. The crystals, grown by the physical vapor transport method (PVT) at NASA Marshall Space Flight Center, were characterized by measuring electrical resistivity, capacitance, and dielectric constant using LCR meter. The morphology was studied by scanning electron microscopy to determine the crystallinity and micro defects. The measured resistivity and dielectric constant showed tunability as the function of frequency in the range of 100 Hz to 100,000 Hz, indicating the suitability of doped material for tuning devices. Besides, for the range from 50 mV to 1000mV, there was no difference in values for the studied frequency range, indicating no degradation or breakdown in the material. All doped ZnSe crystals with sulfur, iron, and chromium showed a similar trend as the function of frequency. Cr-ZnSe showed very high resistivity and lower dielectric constant compared to S-ZnSe and Fe-ZnSe crystals.