Real Part Of Impedance Research Articles

Investigation of Electrical and Dielectrically Properties of a Novel Structure of PANI-PPy--GO-MWCNTs Composite/MnO2/Fe3O4/n-Si Structure

We investigated here the electrical properties of the novel structure of PANI-PPy-GO-MWCNTs composite/MnO2/Fe3O4/n-Si. This structure has not been addressed in literature before, the manufacture of this novel structure is carried out using a simple technique. So, we introduce here a novel structure with a simple method of manufacture. The imaginary part of modulus M″ has two behaviors, the first behavior at high and low frequency and the second behavior at mid frequency, so the M″ gives two contrarian behaviors, The M″ is a strong function of frequency and we can change the behavior of M″ by change of frequencies. The Col—Col diagram of modulus has ideal figures at some voltages including two semicircles of grains and grain boundaries. The imaginary part of impedance Z″ vs frequency creates peaks, the peaks shift toward the low frequencies. The novel here the Z″ has positive and negative values, despite the Z″ should have negative values only. The real part of impedance Z″ keeps on without change at high frequencies and splits for all temperatures at low and mid frequencies. Some electrical properties such as barrier height ɸb,Wd the width of the depletion layer, Nss the density of states, and acceptor carrier concentration Na were obtained by C—V2. All these parameters were strong functions of frequency.

High-Frequency Electrochemical Impedance Spectroscopy for Detecting Li Deposition Toward Assessing Thermal Stability in LiBs

Li deposition decreases the thermal stability of Li-ion batteries (LiBs), reducing safety. We have developed High-Frequency Electrochemical Impedance Spectroscopy (HF-EIS) to detect Li deposition from the high-frequency real part impedance in the MHz range. The evaluation of the relationship between the onset temperature of thermal runaway and the change in high-frequency impedance demonstrated that HF-EIS is capable of quantitatively evaluating the safety associated with Li deposition. The HF-EIS can be a diagnostic tool for safety quantification and can contribute to the development of battery materials by reducing the cost of destructive testing.

Dielectric behavior and impedance spectroscopy of Niobium substituted Lanthanum based orthovanadates at high temperatures

We present the detailed study of the temperature dependent dielectric properties, impedance spectroscopy and electrical conductivity of LaV1−xNbxO4 (x=0–1) samples prepared by the solid-state reaction method. The dielectric constant (ϵr′) increases (decreases) with increase in the temperature (frequency); while, the magnitude of ϵr′ remains almost invariant (order of 104 at 100 Hz and 600 °C) with x. The single phase x=0 (monoclinic-monazite, P21/n) and x=1 (monoclinic fergusonite, I2/a) samples show the lower values of loss factor [tanδ= (4–8)] as compared to the x=0–0.8 samples [tanδ= (12–18)] having mixed tetragonal and monoclinic phases, which indicates the strong correlation between the crystal structure and the dielectric properties. The real part of impedance (Z′) decreases with both temperature and frequency, and the observed weak relaxation remains almost unaltered with x. The imaginary part of impedance (Z′′) shows strong relaxation peaks shifting towards higher temperatures with frequency, which is attributed to the effect of grains, grain boundaries, and electrodes in the samples. The activation energy of the relaxation process is estimated to be 0.8–1.0 eV for the x=0–0.6 samples, and ≈1.4 eV for the x=0.8; whereas the x=1 sample shows two values (≈0.5 eV and ≈1.0 eV) in the higher and lower temperature range, respectively. Further, the change in total conductivity with the angular frequency, which found to be in the range of 10−3 to 10−5 S/m, is fitted using the Jonsher power law. The analysis suggests the overlapping large polaron tunneling (OLPT) model for all the samples, whereas the x = 1 sample exhibit a transition near 480 °C and at higher temperatures it shows non-overlapping small polaron tunneling (NSPT) and quantum mechanical tunneling (QMT). This transition is corroborated by the tangent loss curves and may be associated with the change in structure.

Remaining useful life prediction of lithium-ion batteries via an EIS based deep learning approach

Reliable life prediction technology is of great significance in ensuring a safe and efficient lifetime of lithium batteries. However, the traditional health factors such as battery capacity are the effects of battery aging rather than the direct causes, which cannot directly reflect the internal degradation mechanism information of the battery, and the prediction accuracy is easily affected by the working environment of the battery. Electrochemical impedance spectroscopy (EIS) data can more directly reflect the internal mechanism information of the battery, which includes a wealth of battery aging information. In order to deeply investigate the mapping relationship between impedance spectrum and remaining useful life (RUL) of lithium batteries, EIS method is employed to obtain the impedance and phase of lithium batteries under different health states and temperatures, as well as explore the visualization and quantification of impedance frequency response of lithium battery. Furthermore, the mapping relationship between RUL and the lithium battery impedance is investigated in a full impedance spectrum at different temperatures. It is found that, as lithium battery aging, its negative imaginary parts impedance increases significantly, especially in the middle of the frequency band, and has no significant dependence on temperature. While the real part impedance shows an obvious dependence on temperature. Therefore, it is found that the negative imaginary parts impedance of impedance spectrum has a well-fit characterization ability for RUL of a lithium battery. In this paper, a fusion neural network model of Conv1d-SAM (one-dimensional convolutional neural network-self-attention mechanism) was established with negative imaginary part impedance as input factor to predict battery RUL. The predicted results show that Conv1d-SAM has improved accuracy and stability in RUL prediction, and the mean absolute error function of the proposed model is increased by 72% compared with the latest published method.

Longitudinal parameters measurement at BEPC II storage rings

A new upgrade to BEPC II has been deployed to improve the luminosity and maximum energy. After the upgrade, the maximum beam energy will reach to 2.8 GeV, and the optimized luminosity at 2.35 GeV will be tripled through squeezing the bunch length and the vertical beta function at the interaction point β y *. Therefore, one more RF cavity will be added to each ring to increase the RF voltage to 3.3 MV. In order to study the feasibility of this upgrade and the longitudinal beam characteristics after the upgrade, some beam-based experiments were carried out at the electron and positron rings of BEPC II. Bunch length and its variation with RF gap voltage are measured, shows that it can be squeezed by approximately 30% at 3.3 MV compared to the normal 1.65 MV operation voltage. Bunch synchronous phases at different RF voltages are also obtained by fitting the variation of bunch centroid with RF voltage at low current. The longitudinal broadband coupling impedance is measured with streak camera, real part impedance is obtained from synchronous phase shift with current, and the imaginary part from bunch lengthening with current. Energy loss per turn at 2.474 GeV is 363.2 ± 14.5 keV by measuring synchrotron tune varies with RF voltages.

A Self-Packaged SISL Low-Power Rectifier Based on a High-Impedance Line for C-Band Applications

In this letter, a self-packaged substrate-integrated suspended line (SISL) rectifier is proposed. The rectifier consists of a quarter-wavelength high-impedance transmission line, a diode, a tuning inductor, and a dc pass filter. The lower the power is, the lower the rectifying efficiency is. At a low input power level, the diode impedance real part is almost zero. A tuning inductor is introduced to form a parallel resonator to enhance the diode voltage. A quarter-wavelength high-impedance line is presented to match the rectifying diode to the source. In addition, due to the self-packaging characteristics and air cavity of SISLs, the radiation loss and dielectric loss of the proposed rectifier are reduced. A rectifier was designed, fabricated, and measured at 5.8 GHz. The radio frequency (RF)-dc conversion efficiency reaches 3.5% at −30 dBm, which is close to its theoretical estimated efficiency at 5.8 GHz. This ultralow power rectifier may be used in energy harvesting at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula> -band.

Structural, conductivity and dielectric studies of pure and KCL doped polymer electrolyte films

Using the solution cast method, poly (vinyl alcohol) complexed with KCl was used to make solid polymer electrolyte films. XRD was used to look at the structure of these films. The outcomes of the Powder × - ray diffraction show that the composite films had more noncrystalline phases of PVA matrix. An AC impedance spectroscopy suggested that the ionic conductivity mainly arisen from grain effect. Conductivity of pure PVA is found to be of the order of 10-8 S/cm. With the addition of 20 wt% of KCl, the conductivity is dropped to the order of 10-10 S/cm, and then increased with the addition of KCl. The increase in conductivity with dopant type is based on the ionic character of the dopant. Real part of Impedance (Z') and imaginary part of impedance (Z“) of pure PVA and various composite films with 20 wt% of KCl, additives with different weight ratios were measured as a function of frequency. Dielectric permittivity and dielectric loss of all PVA with KCl 20 wt% of Polymer films investigated as a function of frequency at a room temperature is studied.Different electrochemical applications can be developed using these kinds of solid electrolytes.

Response Characteristics of Contactless Impedance Detection (CID) Sensor on Slug Flow in Small Channels: The Investigation on Slug Separation Distance.

In recent years, CID sensors have displayed great development potential in parameter measurement of gas-liquid two-phase flow in small channels. However, the fundamental/mechanism research on the response characteristics of CID sensors is relatively insufficient. This work focuses on the investigation of the influence of separation distance between slugs on the impedance (real part, imaginary part and amplitude) response characteristics of slug flow in small channels. Experiments were carried out with the CID sensors in four small channels with inner pipe diameters of 1.96 mm, 2.48 mm, 3.02 mm and 3.54 mm, respectively. The experimental results show that for a CID sensor, the slug separation distance has significant influence on the impedance response characteristics. There is a critical value of slug separation distance. When the slug separation distance is larger than the critical value, the impedance response characteristics of each slug can be considered independent of each other, i.e., there is no interaction between the slugs. When the slug separation distance is less than the critical value, the impedance response characteristics show obvious interaction between the slugs. It is indicated that the ratios of the critical values to the pipe inner diameters are approximate 100.

A Detection Method for Crop Fungal Spores Based on Microfluidic Separation Enrichment and AC Impedance Characteristics.

The timely monitoring of airborne crop fungal spores is important for maintaining food security. In this study, a method based on microfluidic separation and enrichment and AC impedance characteristics was proposed to detect spores of fungal pathogens that cause diseases on crops. Firstly, a microfluidic chip with tertiary structure was designed for the direct separation and enrichment of Ustilaginoidea virens spores, Magnaporthe grisea spores, and Aspergillus niger spores from the air. Then, the impedance characteristics of fungal spores were measured by impedance analyzer in the enrichment area of a microfluidic chip. The impedance characteristics of fungal spores were analyzed, and four impedance characteristics were extracted: absolute value of impedance (abs), real part of impedance (real), imaginary part of impedance (imag), and impedance phase (phase). Finally, based on the impedance characteristics of extracted fungal spores, K-proximity (KNN), random forest (RF), and support vector machine (SVM) classification models were established to classify the three fungal spores. The results showed that the microfluidic chip designed in this study could well collect the spores of three fungal diseases, and the collection rate was up to 97. The average accuracy of KNN model, RF model, and SVM model for the detection of three disease spores was 93.33, 96.44 and 97.78, respectively. The F1-Score of KNN model, RF model, and SVM model was 90, 94.65, and 96.18, respectively. The accuracy, precision, recall, and F1-Score of the SVM model were all the highest, at 97.78, 96.67, 96.69, and 96.18, respectively. Therefore, the detection method of crop fungal spores based on microfluidic separation, enrichment, and impedance characteristics proposed in this study can be used for the detection of airborne crop fungal spores, providing a basis for the subsequent detection of crop fungal spores.

Room temperature ferromagnetism and dielectric enhancement in nanocomposites ZnO doped with iron

Pure and iron with different concentrations (0.2, 1, 5, 10, 15, 20, 25, 30, 35 and 40 Mol. %) doped zinc oxide, symbolic as Zn: (0.2, 1, 5, 10, 15, 20, 25, 30, 35 and 40 Fe Mol. %) were synthesized using the self-modified sol–gel technique in powder form. Structural and morphological properties of the samples were studied comparatively by (XRD), (XPS), (FESEM), and (HRTEM), which revealed that the used samples adapted the hexagonal wurtzite structure. Some structural parameters such as strain, crystalline size, and dislocation density, were calculated to have accurate investigation giving rise to the nanostructure phase. The Laser-based Raman micro-spectroscopy presents the homogenous distribution of the iron oxide. The sensing performance of the samples toward the effect of increasing the temperature (from 25 to 150 °C) on the dielectric high-frequency range between 1 MHz up and 1 GHz was investigated with the help of a network impedance analyser (KEYSIGHT-E4991B). The mentioned increase in temperature record ε′ increases values while, it decreases by increasing the frequency, indicating a Debye-type dielectric dispersion. Compared to pure zinc oxide, an enhancement in both (σac) and the impedance real part Z′ was observed in the nanocomposite Z0.2F sample at higher dielectric temperature up to 130 °C. In contrast to pure ZnO, the area of the hysteresis loop against iron concentration for the doped samples increases with an increase in iron concentration. This behavior enhances ferromagnetism in Fe-doped ZnO nanostructure material.

Exploring the influence of ionic liquid and temperature on the dielectric properties and microwave absorption of SWCNT based PVDF/PANI blend nanocomposites

This study reveals the electromagnetic shielding effectiveness (EMISE) and dielectric relaxation phenomena of single walled carbon nanotube (SWCNT) based poly (vinylidene fluoride) (PVDF)/poly aniline (PANI) blend nanocomposites. An imidazolium base salt which is a liquid at room temperature is introduced in the polymer blend for improved dispersion of SWCNT phase. The extent of dispersion of SWCNT phase at the interface and the improved dispersion in the ionic liquid (IL) incorporated systems are investigated with High resolution transmission electron microscopy (HRTEM). The qualitative morphology and interaction between the different phases are correlated the obtained dielectric and EMISE outcomes. Analysis of various properties of the fabricated nanocomposite systems like, AC conductivity (σac), impedance (real and imaginary part), dielectric permittivity (ε′) have been done in the frequency range of 1–106 Hz of the applied external electric field. Introduction of IL to the composite systems affects the dielectric properties which is also analysed and the observed significant high value of ε′ is a result of effortless polarization at the interface of SWCNT and PANI phase. Microwave absorption efficiency of the SWCNT incorporated composite systems are explored in X-band range of frequencies (8–12 GHz) and high absorbance with low transmittance as well as low reflectance of microwave is noticed for the developed PVDF/PANI/SWCNT nanocomposites. The absorbance is predominantly increased with increasing the SWCNT loading level.

Swallowing Events Recognition Method Based on Complex Impedance Pharyngography and Nyquist Plots

Early screening is of great significance to reduce the incidence of dysphagia, and accurate recognition of swallowing events (SEs) becomes an inevitable step during the screening and treatment of dysphagia. Impedance pharyngography (IPG) has been developed as a promising noninvasive SE detection method in the last 20 years, but the conventional IPG technique can only measure impedance amplitude and misses the equally important phase information. To further improve the analysis capability of the IPG technique, this article proposes a new complex IPG (CIPG) detection method, which can dynamically extract the complex impedance (impedance amplitude and phase) information during the swallowing process. First, the CIPG measurement principle based on integer-period digital lock-in amplifier (IP-DLIA) is proposed, and an FPGA-based CIPG system is built. Then, an intelligent algorithm for SE recognition is designed in which the Nyquist plots (impedance real part versus imaginary part) are adopted as 2-D-image inputs of the residual nets convolutional neural network (CNN) algorithm. Finally, an SE recognition experiment is performed, in which different SEs, including dry swallowing, drinking water, drinking yogurt, eating bread, and coughing, are recorded using the CIPG system. The results show that the overall SE recognition accuracy reaches 97.8%, which is much higher than those based on the traditional IPG method or other sensors. This study demonstrates the effectiveness and superiority of the proposed CIPG technology and the intelligent SE recognition algorithm and lays theoretical and technical foundations on further developing an early screening method for dysphagia based on CIPG.

Synthesis and performance of aluminous cements containing zirconium and strontium as alternatives to the calcium aluminate cements designed for the production of high performance refractories

Composite cements belonging to the CaO–Al2O3–ZrO2 (C-A-Z) and CaO–SrO–Al2O3–ZrO2 (C–Sr-A-Z) systems were evaluated as alternatives to calcium aluminate cements (CACs) for use in the refractory castables technology. The mineralogical phases in the as-synthesized C-A-Z and C–Sr-A-Z clinkers confirmed by XRD and SEM-EDS were CaAl2O4, Ca7ZrAl6O18 and CaZrO3 or (Ca,Sr)Al2O4, (Ca,Sr)Al4O7 and (Ca,Sr)ZrO3, respectively. The present work aimed at developing novel Zr-containing cements with excellent mechanical performance, i.e. modulus of rupture and cold crushing strength. Both hydration behavior of the C-A-Z, C–Sr-A-Z, CAC and their hydration products, were studied with isothermal calorimetry, XRD, SEM-EDS and NMR. Impedance camera instrument was firstly successfully applied for time-resolved electrochemical impedance spectroscopy measurements under nonstationary conditions and record the time-dependent evolution of the Nyquist plots for hydrating cement pastes. A sharp increase in the real part of impedance Z’ versus hydration time were corresponded to the second exothermic peak detected on the calorimetry curves.

Frequency regulation in alternating current transportation properties for electron correlated rare-earth nickelates heterostructures

Although the rare-earth nickelate (ReNiO3) based heterostructures exhibit promising applications in logical devices based on the metal to insulator transition property that regulates abruptly their direct current transportations, their alternating current (ac) properties have not been fully studied. Herein, we demonstrate the frequency manipulation in the ac properties of various SmNiO3-based heterostructures as grown by pulsed laser deposition including SmNiO3/SrRuO3/SrTiO3, SmNiO3/SrRuO3/LaAlO3, and SmNiO3/SrRuO3/quartz. The activation energies as calculated from the dielectric relaxation process of the SmNiO3 heterostructure from the ac aspect are in consistence with the ones obtained from their direct current (dc) conduction. Assisted by the complex impedance equivalent circuit fitting, we further distinguished the dominance in carrier transportations associated with the intrinsic SmNiO3 crystal (SmNiO3/SrRuO3/SrTiO3), interfacial defects (SmNiO3/SrRuO3/LaAlO3), or grain boundaries (SmNiO3/SrRuO3/quartz). Owing to the strong Coulomb interaction between the electron carrier and NiO6 octahedron within the electron correlated insulating phase of SmNiO3, the temperature dependence in their real part impedance cross-linked at characteristic ranges of temperature and frequency. As a result, their electronic transportations gradually transit from the negative temperature coefficient resistance thermistor toward delta-tendency via elevating the input ac-frequency. This functionality is expected to enrich potential applications of SmNiO3-based correlated electronic devices in temperature sensing and control.

Modulation of dielectric and magnetic ordering of DyFeO3 system with Fe-site doping

In this attempt, dysprosium orthoferrite (DyFeO3) system is explored to investigate dielectric and magnetic ordering by modulating ferrites structure using Ni and Co-dopants in place of Fe. X-ray diffraction (XRD) study confirms the formation of single-phase materials; dopants effect on modifications of atomic-scale structural parameters like lattice parameters, Fe–O bond angles, and O–Fe–O bridging angles are extracted from Rietveld refinement. Microstructural features of sintered pellet of DFO system exhibits compacted sample having grain size around 100 nm. Frequency and temperature- dependent dielectric studies depict systematic decrease of dielectric constant and loss with temperature for almost all systems. Moreover, it is found that dielectric constant and loss increases by doping; for Co and Co-Ni co-dopants the effect is maximum. Temperature profile of dielectric constant of DFO system is found to exhibit relaxor behavior. A real part of impedance as a function of frequency indicates the values of Z′ coincides with high frequency, indicates reduction of barrier potentials at high frequency due to increase in AC-conductivity. Low-frequency resistance of doped systems is lower than DFO, except Co-doped DFO. Impedance loss spectra reveal relaxation behavior of the system, which is influenced by dopants. Relaxation frequency of Ni-doped and Ni-Co codoped DFO is found shifting toward higher frequency side than DFO and DCFO systems; indicate charge relaxation is faster in DNFO and DNCFO than DFO and DCFO systems. However, activation energy of charge relaxation is found lowest for DCFO system. Same trends are revealed from Modulus spectra. Conductivity mechanisms are revealed from a combined plot of M′′(f) and –Z′′(f) as a function of frequency and corresponding relaxation process. The results conclude that conductivity in DFO and Ni-doped DFO system is dominated by delocalized motion of charge carriers, while DCFO and DNCFO systems are due long-range motion. Magnetic hysteresis (M-H) curve shows the presence of a canted antiferromagnetic ordering matrix within weak Ferromagnetic components. Coercivity of doped DFO is greated than pure DFO.

Effect of aging, temperature, and ambient gases on the complex impedance of As2Te13Ge8S3 glassy films

The work is focused on the application of the impedance spectroscopy method to provide evidence and study the effects of aging, temperature, and gas adsorption in chalcogenide-based thin films. The experiments are carried out with thin films of glassy quaternary composition As2Te13Ge8S3 in a wide frequency range at different temperatures under different environmental conditions, in particular, either dry or wet air or their mixtures with NO2 or CO2. It is found that aging has a significant effect on the impedance spectra of Pt–As2Te13Ge8S3–Pt functional structures, which make evidence for the presence of substantial spatial and compositional disordering. This effect can be stabilized by the post-preparation annealing of the sample. The effect of temperature on impedance spectra consists in a variation in the both real and imaginary parts of impedance that appear to be extremely sensitive to adsorptive processes. Adsorption of nitrogen dioxide results in a significant frequency-dependent decrease in the impedance parameters, which is attributed to an effective “strong” chemisorption process due to the interaction of "odd" electrons of NO2 molecules with lone pair electrons of chalcogen atoms. The effect of water vapors leads only to an increase in the real part of impedance, while the imaginary part abruptly decreases; this fact is attributed to a “weak” form of chemisorption. The effect of carbon dioxide on the impedance spectra is attributed to the physical adsorption of CO2 molecules. This effect is weak; however, it is reversible and clearly observed even at room temperature.

Synthesis of a Novel Nanoparticle BaCoO2.6 through Sol‐Gel Method and Elucidation of Its Structure and Electrical Properties

The physical properties of cobalt oxide with varied oxidation states, and coordination numbers, in the transition series, have numerous applications. The present study explores the physical properties of BaCoO2.6 nanoparticles synthesized through the sol‐gel method. The X‐ray diffraction figure exhibits a 25 nm crystallite size hexagonal phase. The observational data shows the reduction in the real part of impedance (Z’), dielectric constant (ξ’), dielectric loss (ξ”), and a raise in ac conductivity of mixed type of conduction with an elevation in frequency analyzed through impedance spectroscopy. The conductivity due to grain and grain boundaries is shown foremost in the complex impedance analysis. The plot of ∆V/∆T (Seebeck coefficient) in the low‐temperature range indicates p‐type behavior and the metal‐insulator transition in the as‐synthesized sample. The sample characteristics suggest applications in optical and switching devices. The Seebeck coefficient is the generation of potential difference when subjected to temperature difference. Thermoelectric materials are associated with the concept of high electrical conductivity like crystals and low thermal conductivity to that of glass. Nanothermoelectric materials can decrease further the thermal conductivity through phonon scattering. Electrical characterization suggests the presence of both NTCR and PTCR behavior in the sample, and hence, it explores the application in thermistor/resistance temperature detector’s (RTD) and low dielectric constant and loss to electro‐optical and higher conversion efficiency to storage devices. Additionally, impedance spectroscopy helps in the study of electrochemical systems and solid‐state devices wherein the transition of metal‐insulator is an add‐on to the research.

(Invited) Impedimetric Detection of Histamine Using PEDOT:PSS-Based Organic Electrochemical Sensor for Precision Animal Agriculture

Introduction As human world population is expected to reach 9.8 billion by the year 2050 [1], the consumption of animal products is also expected to increase by a large margin, including dairy and meat. Therefore, improving the feed nutrients convergence to final products in a sustainable way is highly needed. One approach is diagnosing animal diseases in early stage with the use of biosensors, which can monitor various biomarkers, chemical molecules, present inside rumen. This will allow improvement in animal diet, with subsequent increase of energy convergence from diet to animal protein [2].Our group is currently developing a set of technologies to accomplishing such early diagnosis. One of the components is a miniature robotic agent, termed RUMENS (Rumen Understanding through Millipede-Engineered Navigation and Sensing), an active sensing platform hosting an array of commercial and purpose-built sensors [3]. Histamine is a biomarker present inside rumen, of which high levels are closely linked to subacute ruminal acidosis (SARA). SARA is a common disease in high-producing lactating cows, leading to decrease in production of animal proteins [4]. Here, we report on an electrochemical impedimetric histamine sensor. Method Polymeric semiconductor poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, or PEDOT:PSS, (Clevios PH 1000) was purchased from Heraeus (Holding GmbH Hanau, Germany). Histamine, ethylene glycol (EG), isopropyl alcohol (IPA), 3-glycidoxypropyltrimethoxysilane (GOPS), dodecylbenzenesulfonic acid solution (DBSA), acetone, and phosphate-buffered saline powder (pH=7.4) were all purchased from Sigma Aldrich (St. Louis, MO, USA). All chemicals were used without any purification. PEDOT:PSS solution was prepared by mixing 95 Vt.% PEDOT:PSS aqueous suspension with 1 Vt.% of GOPS, 3.98 Vt.% of EG, and 0.02 Vt.% DBSA. The electrolytes were histamine dissolved in phosphate buffer saline (PBS, pH=7.4). The glass substrates were cleaned by sonicating in DI water, IPA, and acetone. Cr and Au were thermally evaporated (Lesker, Nano 36) on clean substrates, with a thicknesses of 4 nm and 30 nm, respectively. Subsequently, a plasma processing in high mode for 3 minutes was carried out, using reactive ion etching (Glow Research) to activate the substrate surface. Next, PEDOT:PSS film was spin cast at 2000 rpm for 60 seconds, followed by annealing at 140 °C for 70 minutes in air, resulting in a thickness of 150 nm. Finally, PEDOT:PSS was patterned using dry plasma etching through a shadow mask.An impedance measurement was carried out to test the impedance with different histamine concentrations (from 0.1 µM to 1 mM). 3 μL electrolyte was dropped on the PEDOT:PSS layer (at the right-top of Figure1). Devices were cleaned by immersion in DI water for 10 min between measurements to remove remaining histamine. Results and Conclusions As shown in Figure 1, the real part (Z’) of impedance was increasing with the increased histamine concentration: at lower frequencies, the increase in Z’ was monotonically correlated with the concentration (right side of the graph), which did not hold at higher frequencies (left side of the graph). More specifically, we can find that from the left-top inset, the real part of the impedance has a significant positive relationship with the histamine concentration, with R2 as high as 0.95. Since PEDOT:PSS is a ionic semiconductor, which means the ions could diffuse into PEDOT and PSS moieties. The active aliphatic amino group on the ethylamine part in histamine is protonated in neutral electrolyte. Thus, histamine plays the role of cations, which can reversibly penetrate into PEDOT:PSS layer then block the holes transport by a dedoping process. Consequently, the diamine will be oxidized, while the partially doped PEDOT segment will be reduced to the dedoped state. Higher histamine concentration represents higher degree of dedoping process. Therefore, the conductivity of PEDOT:PSS will decrease, leading to increase in impedance [5].

Design and Characterization of (140–220) GHz Frequency Compensated Power Detector

This article presents the design and characterization of a real-time frequency-compensated power detector (PD), based on NMOS transistor, integrated in SiGe 55-nm BiCMOS technology from STMicroelectronics, and dedicated to on-chip power detection in the G-band frequencies. An innovative simple circuit (named attenuator) is designed in order to compensate the variation of the voltage sensitivity value with frequency, which is established by exhibiting lower attenuation (smaller real part impedance) at higher frequencies. As a result, the measured sensitivity value is compensated with a small variation (1800 V/W±10%) over the frequency band (140-220) GHz. To the best of the authors' knowledge, this detector is the first design which proposes a real-time frequency compensation at such high- and large-frequency bands. The attenuator was also designed to exhibit an inductive impedance (in the G-band) in order to compensate the capacitive effect of the NMOS, which helps to use smaller NMOS size and, therefore, obtain a higher sensitivity value. Compared to recent works, our detector exhibits a performance belong the current state-of-the-art with a very low noise equivalent power (NEP) value 4.56 pW/ √Hz and a relatively high voltage sensitivity value.

One‐step preparation of poly(NIPAM‐pyrrole) electroconductive composite hydrogel and its dielectric properties

AbstractConductive polymers and hydrogels are two of the hot prospect polymer types that are used for new stimuli responsive materials. In this study, one‐step preparation of electroconductive composite hydrogels containing polypyrrole (PPy) and N‐isopropylacrylamide (NIPAM) using free radical polymerization technique was achieved with N,N‐methylenebisacrylamide as a crosslinker and ammonium peroxy disulphate (APS) as initiator, in mixture of water/isopropyl alcohol. The equilibrium swelling degree of the poly(NIPAM)‐pyrrole) electroconductive composite hydrogel was 9.88 g of H2O/g dry polymer. According to TGA results, the thermal stability of the prepared composite poly(NIPAM‐PPy) conductive hydrogel (700°C) hydrogel is higher than that of pure poly(NIPAM) hydrogel (600°C). Furthermore, prepared samples were characterized by FTIR, and SEM analyzes. Later, the samples were pressured into pellets so that electrical impedance spectroscopy (EIS) measurements were taken between 10 and 10 MHz at room temperature. The dielectric constant value of composite poly(NIPAM‐PPy) hydrogel at 10 Hz is almost 10 times higher than that of poly(NIPAM) hydrogel. Both samples' real and imaginary parts of dielectric constant decreased with increased frequency. Samples exhibited non‐Debye relaxation since experimental data fit into dielectric model of Havriliak‐Negami. Moreover, low frequency data yielded d.c. conductivity of the pure and composite samples as 3.74 × 10−11 and 1.02 × 10−8 S/cm, respectively. Real part of impedance at low frequencies also points out ~103 times lower resistance values at 10 Hz for composite poly(NIPAM‐PPy) hydrogel. Therefore, EIS results support that electroconductive composite hydrogel fabrication was achieved using free radical polymerization technique.