Electron Impedance Spectroscopy Research Articles

Preparation and characterization of polypyrrole/organophilic montmorillonite nanofibers obtained by electrospinning

We performed an aqueous in situ polymerization of pyrrole in presence of modified montmorillonite particles to obtain a polypyrrole/organophilic montmorillonite clay (PPy/MMTO) nanocomposite with an intercalated structure. The natural clay was previously modified to become organophilic. The PPy/MMTO was mixed to PVA to prepare nanofibers through electrospinning methods. The different nanocomposites were characterized through Fourier transform infrared spectroscopy and UV–Vis spectroscopy, X-ray diffraction, scanning electron microscopy and impedance spectroscopy. We confirmed the clay organophilization by observing the (001) plane displacement from 6,1° to 5,5° and the presence of absorption bands in 2924 cm−1, 2853 cm−1 and 1479 cm−1, by XRD and FTIR analyses, respectively. We observed that the conductivity of the final PVA/PPy-MMTO nanofibers increased upon exposure to ammonia vapors, confirming that this hybrid material exhibits promising properties for use as active elements in gas sensors.

An injection molding method to prepare chitosan-zinc composite material for novel biodegradable flexible implant devices

ABSTRACTNovel biodegradable flexible implant materials require precise fabrication and novel design on top of the biocompatibility and biodegradability. By injection modeling technic, the thin and well-designed circuits can be precisely manufactured. Therefore, it emerged as an attractive method toward the research of advanced implant. In this study, a simple two-step method, natural precipitation and galvanization, was introduced to prepare a chitosan-zinc composite for conducting circuit and electrodes fabrications. The chitosan–zinc composite is biocompatible and biodegradable. The unique bond between chitosan and zinc solves the conventional unstable connection problem and secures the structural stability of our products. To optimize this processing, the effect of composition and galvanization time on viscosity and ohm resistance were investigated. The high structural stability, good shear-thinning characteristics, and fine high pass signal transferring ability were verified by viscosity test, scanning electronic microscopy (SEM) and electronic impedance spectroscopy (EIS), separately.

Behaviour of charge carriers in thermally reduced graphene oxide: Magnetism and ambipolar transport

We report a research study on reduced graphene oxide conducted with electron paramagnetic resonance and impedance spectroscopy techniques. Coupling of the two experimental methods allowed us to obtain detailed information on the charge carrier transport in the graphene material and make an attempt at explaining the peculiar behaviour of para- and ferromagnetic properties of the studied system. Two scattering processes characterized by different dynamics were found. An ambipolar-like character of the charge transport was observed with transition between holes and electrons driven by the bias voltage, temperature, and adsorption. Electron paramagnetic resonance spectra showed a typical signal from localized centers as well as weak ferromagnetism. The latter correlates with the change of carriers' polarity. This indicates that ferromagnetic coupling between the localized states in graphene is related to the type of charge carriers. Such behavior points to the similarity of reduced graphene oxide to the dilute (ferro)magnetic semiconductors.

Microalgae degradation follow up by voltammetric electronic tongue, impedance spectroscopy and NMR spectroscopy

Microalgae play a fundamental role in aquatic primary production and the food chain. They are a recognized source of fatty acids and fatty acid-based lipids of potential interest in the preparation of functional health products, biofuels and renewable chemicals. The exploitation of this bioresource requires a fine monitoring of each production stage. The aim of this work is the microalgae degradation follow up after the concentration stage at the end of the production process by voltammetric electronic tongue, impedance spectroscopy and 1H NMR spectroscopy. Microalgae samples were allowed to progress along time (from 1 to 23 days). At scheduled selected times, voltammetry, impedance spectroscopy and 1H NMR measurements were performed. Multivariate analysis was carried out on these data by PLSR. A model calculated in a training set was then applied to a set of validation to predict the time of evolution. For the three techniques good results in prediction for the validation set were obtained (R2/RMSEP of 0.961/1.51, 0.956/1.67 and 0.969/1.25 respectively for impedance, voltammetry and NMR spectroscopy). The three techniques were sensitive to the evolution of the microalgae samples. The detection of metabolical changes in the 1H NMR spectra is also included. This proof of concept could be the basis for future development of rapid and robust strategies for quality control on microalgae production plants.

Iron/zinc doped 8 mol% yttria stabilized zirconia electrolytes for the green fuel cell technology: A comparative study of thermal analysis, crystalline structure, microstructure, mechanical and electrochemical properties

Abstract Pristine and Fe/Zn doped 8 mol% yttria stabilized zirconia (8YSZ) were prepared by ball milling technique for potential application in the green fuel cell technology. The series consisted of (8YSZ)0.97(Fe2O3)x(ZnO)3-x, where x indicates 0.5, 1.0, 1.5, 2.0 and 2.5 mol% Fe or Zn alternatively. A number of analytical techniques were used to characterize 8YSZ included X-ray diffraction, scanning electron microscopy, impedance spectroscopy, dilatometer, and hardness test. The analytical results indicated a decrease in the densification in the doped 8YSZ as the activation energy for densification decreased from 1087 kJ/mol in the pristine 8YSZ sample to 264 kJ/mol in the doped 8YSZ. The optimum doped 8YSZ was recognised with 2.0 mol% Fe and 1.0 mol% of Zn exhibit the highest percentage of the cubic phase approaching 62.4 wt%, while the shortest lattice parameter of 0.5132 nm and crystallite size equivalent to 26.34 nm. This composition also indicated pore-free morphology, the highest densification up to ∼94%, the greatest hardness value (above 740 MPa), while improve total conductivity about 7.398 × 10−6 S/cm at 300 °C. The results provide new insights on the effect of mixed dopants as ceramic composite as well as on the fuel cell technology.

Metal-Doping of La5.4MoO11.1 Proton Conductors: Impact on the Structure and Electrical Properties.

La5.4MoO11.1 proton conductors with different metal doping (Ca2+, Sr2+, Ba2+, Ti4+, Zr4+, and Nb5+) have been prepared and structurally and electrically characterized. Different polymorphs are stabilized depending on the doping and cooling rate used during the synthesis process. The most interesting results are obtained for Nb-doping, La5.4Mo1- xNb xO11.1- x/2, where single compounds are obtained in the compositional range 0 ≤ x ≤ 0.2. These materials are fully characterized by structural techniques such as X-ray and neutron powder diffraction and transmission electron microscopy, which independently confirm the changes of polymorphism. Scanning electron microscopy and impedance spectroscopy measurements in dry/wet gases (N2, O2, and 5% H2-Ar) showed an enhancement of the sinterability and electrical properties of the materials after Nb-doping. Conductivity measurements under very reducing conditions revealed that these materials are mixed ionic-electronic conductors, making them potential candidates for hydrogen separation membranes.

Polarization and Ni content effects on structural properties, electrical conductivity, complex impedance and dielectric constant of Co-Mg-ferrites

Pechini sol-gel technique was used to prepare Mg0.6-xNixCo0.4Fe2O4 (x = 0 , 0.2, 0.4 and 0.6)-ferrite materials. Then, X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy techniques are used to investigate the structural, morphological, electrical and dielectric properties. The X-ray diffraction patterns show that the prepared samples have a single phase. The SEM micrograph shows that the particle has an unchanging grain size distribution. Electrical measurements show that the DC conductivity is sensitive to temperature. Then, it is well noticed that the Mott and Davis law is governed by the small polaron hopping model. Also, impedance measurements show that the real part of impedance is extensively reduced when applying a voltage bias of $ V_{p}=10$ V. Such behavior can be related to the reduction of the available density of trapped charge. The results of Nyquist fitting are coherent with the electrical measurements according to which the sample with the highest DC conductivity possesses the lowest grain boundary resistance. Dielectric measurements confirm that the thermal evolution of the dielectric constant of the samples containing intermediary amounts of Ni (x = 0.2 and x = 0.4 is classical and show that the dielectric transition temperature is affected by polarization.

Graphene quantum dots decorated TiO2 mesoporous film as an efficient electron transport layer for high-performance perovskite solar cells

In mesoscopic perovskite solar cells, the electron transport layer plays an important role in charge extraction and determines the charge-transport property to attain a superior photovoltaic performance. Herein, we report a low-cost, solution-based deposition procedure of decorating graphene quantum dots on the surface of mesoporous TiO2 film, expecting that a more effective electron-transport channel can be formed for the enhancement of solar cell performance, finally, an impressive power conversion efficiency of 20.45% is achieved in the resulting optimized perovskite solar cell. Furthermore, the results of various spectroscopic characterizations including electronic impedance spectroscopy, steady-state and time-resolved photoluminescence spectrum elucidate that the introduction of GQDs on the surface of mesoporous TiO2 film not only enhance the electron extraction but also facilitate the charge transportation at interface between the perovskite and electron transport layer.

Facile hydrothermal assisted synthesis of time dependent Cu2S thin films for efficient photoelectrochemical application

In present investigation, we have successfully synthesized nanocrystalline Cu2S thin films at different deposition time via single step hydrothermal route. The synthesized Cu2S thin films characterized for their optostructural, morphological, compositional and photoelecrochemical properties as function of deposition time. Thickness of deposited Cu2S thin films increases with increase in deposition time. The optical studies revealed that band gap of Cu2S thin films decrease with increase in deposition time. Structural study confirm that Cu2S thin films are nanocrystalline in nature with pure hexagonal crystal structure. Crystallite size were increases with increase in deposition time. Raman spectrum shows the presence of sharp band at 472 cm−1 confirms the formation of pure phase hexagonal Cu2S thin film. Scanning electron microscopy micrographs of Cu2S thin films demonstrate that significant change in surface morphology. The high resolution transmission electron microscopy and selected area emission diffraction study indicate that nanocrystalline Cu2S thin films formation. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy show the presence of elements and preferred valence state with stoichiometric composition of the Cu2S thin films. electron impedance spectroscopy reveals that charge transfer resistance (Rct) decreases with increase in deposition time. From J–V measurements, it was found that, Cu2S thin films shows maximum conversion efficiency is 0.27% for film after deposition of 6 h.

Na2O doped CeO2 and their structural, optical, conducting and dielectric properties

In the present study, Na2O doped CeO2 has been prepared by solid state reaction method. The prepared samples are characterized by X-ray diffraction (XRD), UV–Visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscope (SEM) and Impedance spectroscopy. The optical band gap of all the samples lies in the semiconducting range i.e. 3.04–3.25 eV. The highest optical band gap is observed for 5 mol% Na2O doped CeO2. The SEM images show a non-uniform distribution of particles with an average particle size of ∼3.15 μm for all the samples. The lowest dielectric constant is observed to be ∼11 at 100 °C and 100 Hz for 10 mol% doped CeO2 which is lower than the undoped CeO2. The conductivity of the samples lies in the range of 10−7 S/cm at 700 °C.

Microstructure–conductivity relationship of Na3Zr2(SiO4)2(PO4) ceramics

AbstractThe ionic conductivity of solid electrolytes is dependent on synthesis and processing conditions, ie, powder properties, shaping parameters, sintering time (ts), and sintering temperature (Ts). In this study, Na3Zr2(SiO4)2(PO4) was sintered at 1200 and 1250°C for 0‐10 hours and its microstructure and electrical performance were investigated by means of scanning electron microscopy and impedance spectroscopy. After sintering under all conditions, the sodium super‐ionic conductor‐type structure was formed along with ZrO2 as a secondary phase. The microstructure investigation revealed a bimodal particle size distribution and grain growth at both Ts. The density of samples increased from 60% at 1200°C for 0 hours to 93% at 1250°C for 10 hours. The ionic conductivity of the samples increased with ts due to densification and grain growth, ranging from 0.13 to 0.71 mS/cm, respectively. The corresponding equivalent circuit fitting for the impedance spectra revealed that grain boundary resistance is the prime factor contributing to the changing conductivity after sintering. The activation energy of the bulk conductivity (Ea,bulk) remained almost constant (0.26 eV) whereas the activation energy of the total conductivity (Ea) exhibited a decreasing trend from 0.37 to 0.30 eV for the samples with ts = 0 and 10 hours, respectively—both sintered at 1250°C. In this study, the control of the grain boundaries improved the electrical conductivity by a factor of 6.

Synthesis and Characterisation of AWO4 (A = Mg, Zn) Tungstate Ceramics

The AWO4 (A = Mg, Zn) tungstate ceramics have been prepared using conventional solid-state route and characterised. Samples were analysed X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy (IS). Phase-pure ZnWO4 and MgWO4 were successfully obtained at temperatures 1000°C for 24 and 12 hours, respectively, where both compounds had a wolframite-like structure monoclinic, space group P2/c (13). Preliminary results of electrical properties of ZnWO4 indicated that ZnWO4 is a dielectric insulator with permittivity, εr ∼ 20 at room temperature. The inhomogeneous electrical properties of ZnWO4 is observed where the grain boundary and bulk contributions effects were seen at temperature excess of 100°C.

The electrical conductivity and photocatalytic activity of ultrafine iron hydroxide/oxide systems

The ultrafine iron hydroxide/oxide systems are fabricated by a hydrothermal approach, using iron nitrate and citric acid as precursors. The phase composition, crystal and magnetic microstructures, morphology, conductivity, and optical properties are characterized by X-ray diffraction, scanning electron microscope, impedance spectroscopy, Mössbauer spectroscopy, and UV-VIS spectroscopy. The mechanisms of phase transformation of amorphous ultrafine γ-FeOOH→ nanocomposite γ-Fe2O3/α-Fe2O3 in the temperature interval 150–350оС are established. The photocatalytic activity of samples was estimated by the degradation of methylene blue and formaldehyde under UV or visible light in an aqueous solution. The results indicate that the photocatalytic degradation activities of amorphous γ-FeOOH and nanocomposite γ-Fe2O3/α-Fe2O3 are higher than that of phase pure γ-Fe2O3. The photocatalytic property of samples is related to their conductivity and band gap. This implies that a synergistic effect exists between the conductivity and the photocatalytic activity in the ultrafine iron hydroxide/oxide systems. In addition, it can be attributed to the active heterogeneous Fenton process for γ -FeOOH and the microstructure of γ-Fe2O3/α-Fe2O3, which is probably caused by a successful combination of electronic structures of the phases of magnetite and hematite.

Synthesis and Characterization of Novel Polypyrrole/Cerium Oxide Nanocomposite Sensor for the Voltammetric Quantification of Flupirtine Maleate

The highly conducting and novel Polypyrrole/Cerium Oxide (Ppyl/CeO2) nanocomposite material was synthesized and characterized by various spectral (FTIR, XRD, SEM) and electrochemical methods (voltammetry) along with electron impedance spectroscopy (EIS). The spectral data as shown in figure 1 clearly describes the successful synthesis of the Ppyl/CeO2 nanocomposite material. The Ppyl/CeO2 nanocomposite was used to modify the glassy carbon electrode (GCE) for the fabrication of Ppyl/CeO2/GCE nanocomposite sensor. The electrochemical characterization of the Ppyl/CeO2/GCE along with its other modified forms viz CeO2/GCE, Ppyl/GCE including bare GCE confirms the successful fabrication of the nanocomposite sensor. The surface area, heterogeneous electron transfer (HET) rate constant (k0 eff), and charge transfer resistance of the fabricated sensor were also determined by cyclic voltammetry (CV) and EIS respectively. The fabricated sensor was further optimized to carry out the voltammetric quantification of the Flupirtine Maleate (FPM). The sensor under optimized experimental conditions exhibits a linear relationship over a concentration range of 100 ng mL−1 to 500 ng mL−1 with the correlation coefficient (r2) of 0.9940 for the oxidation of FPM. The limit of detection (LOD) and limit of quantification (LOQ) calculated from calibration curve was found to be 26.76 ng mL−1 and 89.20 ng mL-1 respectively. The results thus clearly demonstrated that the newly fabricated voltammetric nanocomposite sensor possesses an ultra sensitivity for the oxidation of FPM. Figure 1

Niobium and zinc doped titanium-tin-oxide solid-solution ceramics: Synthesis, structure and electrical characterization

This paper describes the processing, microstructure, optical and electrical properties of the nanocrystalline (NC) niobium and zinc doped titanium-tin-oxide (TTO:NZ) based ceramics. Variety of techniques was employed (X-ray diffraction, scanning electron microscopy, energy dispersive, Raman and impedance spectroscopy) in the characterization of the obtained TTO:NZ, which confirmed the formation of NC solid-solution matrix with Ti0.8Sn0.2O2 composition. A specific highly dense (approximately 97% of the theoretical density was reached) varistor like microstructure (matrix metal-oxide grains surrounded by the grain-boundary regions) and accordingly resembling electrical properties (breakdown electric field of approximately 130 V/mm and nonlinearity coefficient of α ≈ 6.5) were achieved through double cation doping and elected condition of the mechanochemical solid-state synthesis. Impedance response analysis of TTO:NZ ceramics by means of an equivalent electrical circuit based on the brick-layer model for polycrystalline materials revealed the presence of two temperature dependent electrical relaxation phenomena of the non-Debye type as well as the negative temperature coefficient of resistance behavior.

Facile Deposition of Nb2O5 Thin Film as an Electron-Transporting Layer for Highly Efficient Perovskite Solar Cells

In a typical high-performance perovskite solar cell (PSC), the electron-transporting layer (ETL) plays a critical role in facilitating the transportation of the photogenerated carriers from perovskite to electrode. In the present work, the solution-processed Nb2O5 film is successfully prepared to serve as an alternative for replacing the overwhelmingly dominated TiO2 ETL with a facile deposition approach. By adjusting the spin-coating process of the precursor solution, the best power conversion efficiency of 19.2% is achieved in the Nb2O5-based planar PSC when the thickness of C–Nb2O5 ETL is about 100 nm. The characterization including ultraviolet photoelectron spectroscopy, electronic impedance spectroscopy, and photoluminescence spectrum results elucidate that the impressive photovoltaic performances can be attributed to the proper Nb2O5 ETL conductive band, the lower charge recombination rate, the more efficient extraction, and transportation of the photogenerated carriers from the perovskite absorber.

The Li+ conducting composite based on LiTi2(PO4)3 and Li3BO3 glass

The LiTi2(PO4)3 based composites containing amorphous Li3BO3 were formed and investigated by means of X–ray diffractometry, thermogravimetry, scanning electron microscopy, impedance spectroscopy and density methods. The study shows that when a polycrystalline LiTi2(PO4)3 material is sintered with Li3BO3 glass, the resultant ceramics exhibit very high total ion conductivity. The maximum conductivity of 1.43 × 10−4 S cm−1 at 30 °C was achieved for the LTP–0.3LBO material sintered at 900 °C compared to 5.15 × 10−8 S cm−1 of the ceramic LiTi2(PO4)3.

Roll-to-Roll Slot-Die-Printed Polymer Solar Cells by Self-Assembly.

Extremely simplified one-step roll-to-roll slot-die-printed flexible indium tin oxide (ITO)-free polymer solar cells (PSCs) are demonstrated based on the ternary blends of electron-donor polymer thieno[3,4- b]thiophene/benzodithiophene, electron-acceptor fullerene [6,6]-phenyl-C71-butyric acid methyl ester, and electron-extracting polymer poly[(9,9-bis(3'-( N, N-dimethylamino)propyl)-2,7-fluorene)- alt-2,7-(9,9-dioctylfluorene)] (PFN) at room temperature (RT) in ambient air. The flexible ITO-free PSC exhibits a comparable power conversion efficiency (PCE) with the device employing complicated two-step slot-die printing (5.29% vs 5.41%), which indicates that PFN molecules can migrate from the ternary nanocomposite toward the Ag cathode via vertical self-assembly during the one-step slot-die printing process in air. To confirm the migration of PFN, the morphology and elemental analysis as well as charge transport of different active layers are investigated by the in situ transient film drying process, transmission electron microscopy, atomic force microscopy, contact angle and surface energy, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy, transient photovoltage and transient photocurrent, and laser-beam-induced current. Moreover, the good air and mechanical stability of the flexible device with a decent PCE achieved in 1 cm2 PSCs at RT in air suggests the feasibility of energy-saving and time-saving one-step slot-die printing to large-scale roll-to-roll manufacture in the future.

Molybdenum disulfide-based modifier for electrochemical detection of 4-nitrophenol

We report the synthesis, characterization, and electrochemical sensing application of molybdenum disulfide (MoS2) nanoparticles. The MoS2 nanoparticles have been prepared by the gas-solid reaction method, and they have been characterized using different techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis, photoluminescence, FTIR, Raman, and impedance spectroscopy. The electrocatalytic activity of MoS2 nanoparticles towards the reduction of 4-nitrophenol (4-NP) has been studied using cyclic voltammetry. The experimental parameters such as the effect of scan rate and pH have been optimized for the electrochemical detection of 4-NP. The linear relationship between the peak current and the concentration of 4-nitrophenol was found to be in the range of 4 × 10−6 M to 2 × 10−8 M with an impressive detection limit of 10 nM. The performance of MoS2-modified glassy carbon electrode towards 4-NP detection shows good stability, reproducibility with the recovery percentage of ~ 95%. The obtained results clearly indicate the potential application of MoS2 nanoparticles for the selective and sensitive electrochemical detection of 4-NP.

The lithium-ion-conducting ceramic composite based on LiTi2(PO4)3 with addition of LiF

The ceramic composites formed in the system LiTi2(PO4)3–LiF were studied by means of X-ray diffractometry, thermogravimetry, scanning electron microscopy, impedance spectroscopy, and density methods. Introduction of the foreign phase into the polycrystalline LiTi2(PO4)3-based material resulted in significant reduction of grain boundary resistance. However, a slight decrease of the conductivity could be observed when higher contents of lithium fluoride additive were present in the composite. The maximum total conductivity of ca. 3.08 × 10−5 S cm−1 was obtained for lithium titanium phosphate (LTP)–0.1LiF sample sintered at 1073 K in comparison to 5.15 × 10−8 S cm−1 for the pure ceramic LTP. The most dense material was obtained after sintering at 1073 K.