Changes In Electrical Properties Research Articles

Tunable insulator-metal transition in epitaxial VO2 thin films via strain and defect engineering.

The Metal to Insulator Transition (MIT) in materials, particularly vanadium dioxide (VO2), has garnered significant research interest due to its potential applications in smart windows, memristors, transistors, sensors, and optical switches. The transition from an insulating, monoclinic phase to a conducting, tetragonal phase involves changes in optical and electrical properties, opening avenues in adaptive radiative coolers, optical memories, photodetectors, and optical switches. VO2 exhibits MIT close to 68 °C, thereby requiring tuneable transition temperatures (T c) in VO2 thin films for practical device applications. In this work, we explore the role of strain and defect engineering in tuning the MIT temperature in epitaxial VO2 thin films deposited on c-cut sapphire using Pulsed Laser Deposition (PLD). The study involves tuning the metal-to-insulator transition (MIT) by varying growth parameters, mainly temperature and oxygen partial pressure. Strain engineering along the b-axis helped tune the transition temperature from 65 °C to 82 °C with the out-of-plane b-strain varying from -0.71% to -0.44%. Comprehensive structural and property analyses, including X-ray diffraction (XRD), Reciprocal Space Mapping (RSM), X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy, and resistivity-temperature (R-T) measurements, were performed to correlate structural properties with T c. Additionally, density functional theory (DFT) calculations were performed using Quantum Espresso within the generalized gradient approximation of the revised Perdew-Burke-Ernzerhof (PBEsol) functional to provide theoretical validity to the experimentally obtained results. Our study provides critical insights into the interplay between strain and oxygen vacancies and their effect on the physical properties of VO2 thin films with DFT calculations supporting the experimental findings.

Study of electronic and magnetic properties of Mn-doped KNbO3: A first-principles approach

Changes in the electronic structure of Mn-doped KNbO3 have been studied by first-principles calculations, using the projector-augmented-wave method, within the generalized gradient approximation with on-site Hubbard-U potential (GGA + U), for the exchange-correlation potential. In our study, we analyze different Mn-dopant concentrations, namely 2.5, 5, and 10 %, with Mn entering Nb, K or both sites. Our results show that all doped structures acquire a ferromagnetic character. When Mn enters in Nb or K sites, the structures acquire a metallic character and when Mn enters in both Nb and K, the structures conserve a semiconductor character. The site-decomposed partial density of states shows that the metallic character comes from an up-shift in energy of O-p orbitals when Mn enters Nb sites and a down-shift energy when Mn enters K sites. Furthermore, when Mn enters in both Nb and K sites, a combination of the former cases takes place, resulting a structure with a semiconductor character. Analyzing the formal oxidation states of component atoms allows us to explain changes in electrical and magnetic properties.

Role of chloride on the instability of blue emitting mixed-halide perovskites

Although perovskite light-emitting diodes (PeLEDs) have seen unprecedented development in device efficiency over the past decade, they suffer significantly from poor operational stability. This is especially true for blue PeLEDs, whose operational lifetime remains orders of magnitude behind their green and red counterparts. Here, we systematically investigate this efficiency-stability discrepancy in a series of green- to blue-emitting PeLEDs based on mixed Br/Cl-perovskites. We find that chloride incorporation, while having only a limited impact on efficiency, detrimentally affects device stability even in small amounts. Device lifetime drops exponentially with increasing Cl-content, accompanied by an increased rate of change in electrical properties during operation. We ascribe this phenomenon to an increased mobility of halogen ions in the mixed-halide lattice due to an increased chemically and structurally disordered landscape with reduced migration barriers. Our results indicate that the stability enhancement for PeLEDs might require different strategies from those used for improving efficiency.Graphical

Changes in Microstructure, Mechanical and Electrical Properties with Progress of Cold Wire-Drawing for AA1070

Commercial AA1070 alloy for electrical wire is severely deformed by the drawing process when a rod with a diameter of 2 mm is greatly reduced to 0.4 mm by multi-pass. Changes in the microstructure, mechanical properties, and electrical properties of the Al alloy during the wire-drawing process were investigated in detail. The as-drawn Al wires showed a deformation structure in which the grains are greatly elongated in the drawing direction, even though recovery and/or partial recrystallization occurred more actively in the specimens which had more than 84% in reduction of cross-sectional area (<i>R<sub>A</sub></i>). In addition, the fraction of high angle grain boundaries tended to increase with the increase of <i>R<sub>A</sub></i>. For all drawn specimens, the fiber texture of the {110}<111> and {112}<111> components was mainly developed, and their maximum intensity tended to increase with increasing <i>R<sub>A</sub></i>. Recrystallization texture of (001)[100] and (110)[001] began to appear at an <i>R<sub>A</sub></i> higher than 84%. The hardness tended to increase with increasing <i>R<sub>A</sub></i> due to work hardening. In particular, increasing <i>R<sub>A</sub></i> to 84% resulted in a great rise in hardness, accompanied by a distinct non-uniformity in hardness in the thickness direction. However, the average hardness hardly changed at <i>R<sub>A</sub></i> above 84%, even when <i>R<sub>A</sub></i> was increased to 96%. The strength also tended to increase stepwise as <i>R<sub>A</sub></i> increased, very similar to the change in hardness. The specimen with an <i>R<sub>A</sub></i> of 93% showed the highest tensile strength of 192 MPa, 2.8 times higher than that of the specimen before drawing. The electric conductivity did not decrease significantly, even with extreme increases in <i>R<sub>A</sub></i>, and remained at an average value of 61.6 %IACS.

Effect of CNT on the Physical and Electrical Properties of CNT/UHMWPE Nanocomposite Sensor

Nano Composites Polymer represents a class of multifunctional sensors that can effectively respond to changes in electrical properties when subjected to external forces acting on their physical characteristics. The research aims to develop nanocomposite polymer sensors that can respond well and be easily molded. The experimental process involved mixing Ultra-high-molecular-weight polyethylene (UHMWPE) with 1%, 4%, and 7wt% of carbon nanotubes (CNT) using the hot pressing method, leading to remarkable improvements in the electrical and mechanical properties of the composite polymers. The distribution patterns of CNT at different weight ratios showed that 4 wt% exhibited a more desirable and uniform distribution. However, at 1 wt%, the amount of CNT was insufficient, resulting in scattering and disconnection. On the other hand, at 7 wt%, the CNT distribution appeared to be densely bundled in some areas, leading to detrimental effects on the mechanical and electrical properties, as well as the electrical percolation threshold of the composites. Regarding the mechanical properties test, significant improvements were found at 4 wt% for the tensile strength, but when the filler content exceeded 4 wt%, there was a reduction in the tensile strength of the CNT/UHMWPE composites. Additionally, the change in electrical resistance based on the physical characteristics was examined by varying the percentage of CNT added to UHMWPE through compression and bending tests. The compression tests were conducted using weights ranging from 0 to 10 kg, and the bending tests were performed with angles from 0° to 40° degrees. In terms of the test results, however, with 4% and 7% wt% CNT filler, the electrical resistance values could be successfully measured by a multimeter. The electrical percolation threshold was found to be very good at 4 wt%. For the compression testing results, the resistance values ranged from approximately 27.329 to 32.389 KΩ for the 4 wt% filler and from 0.504 to 0.552 KΩ for the 7 wt% filler. As for the bending testing, the resistance values ranged from approximately 4.019 to 4.044 KΩ for the 4 wt% filler and from 0.427 to 0.432 KΩ for the 7 wt% filler.

BOOSTING THE MICROWAVE ABSORPTION PROPERTIES USING GRAPHENE FUNCTIONALIZED WITH MG-MN-ZN-BI FERRITES

Graphene (Gr) composites with Mg0.5Mn0.375Zn0.125Bi0.05Fe1.95O4 (MMZB nano ferrites), (Gr= 0%, 1%, 2%, 3%, 4%) were synthesized by using the sol gel auto combustion method. XRD, FTIR and Uv-Vis confirmed the significant improvement in structural, vibrational and optical properties of MMZB ferrites\Gr composites with fusion of Gr. The lattice parameter ‘a’ varies with increasing Gr concertation. From the FT-IR spectra the absorption bands observed in the range of 541-563 cm-1 and 421-461 cm-1 are attributed to the fusion of Gr in MMZB Ferrite/Gr Composites. The d.c resistivity of ferrite samples increased as the temperature increased in ferromagnetic region up to curie temperature, after that its decreased. However, increase in resistivity was observed with increasing Gr concentration except at Gr = 3%. The values of optical band gap were found to decreased from 4.45 to 3.50 eV with increasing Gr content. It has been observed that both the dielectric constant and loss factor decreased with the increase of frequency. The minimum dielectric loss was observed for Gr =4 %. The values of saturation magnetization and microwave frequency decreases with fusion of Gr. A remarkable change in microstructures, electrical and magnetic properties was observed with fusion of Gr. Due to these promising properties these materials may be used for microwave frequency devices.

Toward improved PVDF-BaTiO3 composite dielectrics: mechanical activation of the filler versus filler content

Barium titanate (BT) perovskite particles were surface modified by means of mechanical treatment and used as inorganic component in polyvinylidene fluoride (PVDF) based composites. The changes in electrical properties of the composite films with increasing in filler content were followed by dielectric spectroscopy, breakdown strength and D-E measurements. A comparison of the properties of the composites prepared with untreated and mechanically activated particles revealed that there is a significant difference in their performances at low filler concentrations (<20 wt%). Introduction of the surface modified ceramic particles into PVDF matrix led to an increase of the dielectric constant without affecting significantly the electrical breakdown strength. In contrast, when as received BT particles were used a filler, both dielectric constants and breakdown strengths of the composite films were lower than the corresponding values observed for the pure PVDF. At higher concentrations, however, the influence of pre-treatment of the filler on the effective electrical properties becomes less significant. The obtained results were discussed in terms of the pronounced crystallization of polar β and γ crystal phases of PVDF in the presence of surface modified BT fillers, which is confirmed by Raman spectroscopy.

Cellular excitability and ns-pulsed electric fields: Potential involvement of lipid oxidation in the action potential activation

Recent studies showed that nanosecond pulsed electric fields (nsPEFs) can activate voltage-gated ion channels (VGICs) and trigger action potentials (APs) in excitable cells. Under physiological conditions, VGICs’ activation takes place on time scales of the order 10–100 µs. These time scales are considerably longer than the applied pulse duration, thus activation of VGICs by nsPEFs remains puzzling and there is no clear consensus on the mechanisms involved. Here we propose that changes in local electrical properties of the cell membrane due to lipid oxidation might be implicated in AP activation. We first use MD simulations of model lipid bilayers with increasing concentration of primary and secondary lipid oxidation products and demonstrate that oxidation not only increases the bilayer conductance, but also the bilayer capacitance. Equipped with MD-based characterization of electrical properties of oxidized bilayers, we then resort to AP modelling at the cell level with Hodgkin-Huxley-type models. We confirm that a local change in membrane properties, particularly the increase in membrane conductance, due to formation of oxidized membrane lesions can be high enough to trigger an AP, even when no external stimulus is applied. However, excessive accumulation of oxidized lesions (or other conductive defects) can lead to altered cell excitability.

Change of Electrical and Transport Properties of Nickel Oxide by Carrier Concentration and Temperature through First-Principle Calculations

Nickel is typically used as one of the main components in electrical contact devices or connectors. Nickel oxide (NiO) is usually formed on the surfaces of electrodes and can negatively impact system performance by introducing electrical contact resistance. The thermal, electrical, and transport properties of NiO, as a Mott insulator or a p-type semiconductor, can be altered by operating and environmental conditions such as temperature and stress/strain by contact. In this study, we investigate the fundamental material properties of NiO through the first-principle calculations. First, we obtain and compare the lattice parameter, magnetic moment, and electronic structure for NiO via the WIEN2K simulations with four different potentials (i.e., GGA, GGA + U, LSDA, and LSDA + U). Then, using the WIEN2K simulation results with LSDA + U potential that produces a highly accurate bandgap for NiO, we calculate the electrical conductivity and electrical part of the thermal conductivity of nickel and NiO as a function of temperature and carrier concentration through the BoltzTraP simulations. Systematic simulation results revealed that the electrical conductivity relative to the relaxation time for NiO increases with the carrier concentration, while it shows a slightly decreasing trend with temperature under a fixed carrier concentration. By contrast, the electrical part of the thermal conductivity shows an increasing trend considering carrier concentration and temperature.

Real-Time Nitrate Ion Monitoring with Poly(3,4-ethylenedioxythiophene) (PEDOT) Materials.

Nitrate (NO3) pollution in groundwater, caused by various factors both natural and synthetic, contributes to the decline of human health and well-being. Current techniques used for nitrate detection include spectroscopic, electrochemical, chromatography, and capillary electrophoresis. It is highly desired to develop a simple cost-effective alternative to these complex methods for nitrate detection. Therefore, a real-time poly (3,4-ethylenedioxythiophene) (PEDOT)-based sensor for nitrate ion detection via electrical property change is introduced in this study. Vapor phase polymerization (VPP) is used to create a polymer thin film. Variations in specific parameters during the process are tested and compared to develop new insights into PEDOT sensitivity towards nitrate ions. Through this study, the optimal fabrication parameters that produce a sensor with the highest sensitivity toward nitrate ions are determined. With the optimized parameters, the electrical resistance response of the sensor to 1000 ppm nitrate solution is 41.79%. Furthermore, the sensors can detect nitrate ranging from 1 ppm to 1000 ppm. The proposed sensor demonstrates excellent potential to detect the overabundance of nitrate ions in aqueous solutions in real time.

Multi-modal sensing with integrated machine learning to differentiate specific leukocytes targeted by electrically sensitive hybrid particles

The growing need for personalized, accurate, and non-invasive diagnostic technology has resulted in significant advancements, from pushing current mechanistic limitations to innovative modality developments across various disease-related biomarkers. However, there still lacks clinical solutions for analyzing multiple biomarkers simultaneously, limiting prognosis for patients suffering with complicated diseases or comorbidities. Here, we conceived, fabricated, and validated a multifrequency impedance cytometry apparatus with novel frequency-sensitive barcoded metal oxide Janus particles (MOJPs) as cell-receptor targeting agents. These microparticles are modulated by a metal oxide semi-coating which exhibit electrical property changes in a multifrequency electric field and are functionalized to target CD11b and CD66b membrane proteins on neutrophils. A multi-modal system utilizing supervised machine learning and simultaneous high-speed video microscopy classifies immune-specific surface receptors targeted by MOJPs as they form neutrophil-MOJP conjugates, based on multivariate multifrequency electrical recordings. High precision and sensitivity were determined based on the type of MOJPs conjugated with cells (>90% accuracy between neutrophil-MOJP conjugates versus cells alone). Remarkably, the design could differentiate the number of MOJPs conjugated per cell within the same MOJP class (>80% accuracy); which also improved comparing electrical responses across different MOJP types (>75% accuracy) as well. Such trends were consistent in individual blood samples and comparing consolidated data across multiple samples, demonstrating design robustness. The configuration may further expand to include more MOJP types targeting critical biomarker receptors in one sample and increase the modality’s multiplexing potential.

Abrasion-resistant, transparent, conductive In2O3@SiO2 films

External smart wearable films requires that films have good transparency, electrical conductivity, wear resistance and corrosion resistance, but the research on some issues have not been discussed anywhere. The composite In2O3@SiO2 functional films intended for smart wearable devices were synthesised via closed-field unbalanced magnetron sputtering from a powder target. This study investigated the impact of the Si:In atomic ratio in the target on the films' transparency, conductivity, resistance to sweat corrosion, and wear resistance, while elucidating the underpinning mechanisms. Results revealed that the film roughness declined from 4.41 to 1.5 nm with increasing Si:In ratio, and the preferred orientations observed in the pure In2O3 film were lost upon the incorporation of SiO2 particles. The films maintained a visible-region transmittance of 82–85%. However, the band gaps and sheet resistances increased from 3.78 to 4.3 eV and 52–2740 Ω·sq−1, respectively. The In2O3@SiO2 film with 10 at. % SiO2 demonstrated relative structural integrity, and minimal changes in optical and electric properties after acid treatment. Films with 15 at. % SiO2, both with and without exposure exhibited pitting and peeling, with changes in transmittance and sheet resistance of 14.44% and 13.08%, respectively. The alkali-treated films displayed minimal changes. The pure In2O3 film failed after 30 h of vibration. After 48 h of vibratory wear, the In2O3@SiO2 films' transmittance decreased to approximately 72%, and sheet resistances increased to 2.5 KΩ for 10 at. % SiO2 and 23 KΩ for 15 at. % SiO2. The evenly dispersed SiO2 nanodots of the In2O3@SiO2 film with 10 at. % SiO2 showed superior overall properties, including transparency, conductivity, sweat corrosion resistance, and wear resistance, attributed to the ‘maze effect’ obstructing corrosion pathways and the ‘mosaic pattern’ enhancing the abrasive properties.

Electromechanical Characterization of Commercial Conductive Yarns for E-Textiles

With the development of smart and multi-functional textiles, conductive yarns are widely used in textiles. Conductive yarns can be incorporated into fabrics with traditional textile techniques, such as weaving, knitting and sewing. The electromechanical properties of conductive yarns are very different from conventional yarns, and they also affect the processability during end-product manufacturing processes. However, systematic evaluation of the electromechanical properties of commercial conductive yarns is still elusive. Different conductive materials and production methods for making conductive yarns lead to diverse electromechanical properties. In this work, three types of conductive yarn with different conductive materials and yarn structures were selected for electromechanical characterization. A total of 15 different yarns were analyzed. In addition, the change of resistance with strain was tested to simulate and predict the possible changes in electrical properties of the yarn during weaving, knitting, sewing and other end uses. It was found that Metal-based yarns have good electrical properties but poor mechanical properties. The mechanical properties of Metal-coated yarns are similar to conventional yarns, but their electrical properties are relatively poor. The data shown in this research is instructive for the subsequent processing (weaving, knitting, sewing, etc.) of yarns.

Speculation of salinity and heterogeneity for some dry and saturated sandstone rocks

Salinity and conductivity are related because dissolved ions increase both salinity and conductivity. The variation of heterogeneity can significantly affect the electrical properties of materials. The main change in electrical properties is related to the conductor concentration, but this change does not increase monotonically with the concentration due to heterogeneity. Sandstone samples were gathered parallel to the layer direction and perpendicular to it. Electrical parameters were obtained at room temperature at rates ranging from 42 Hz to 5 MHz for distinct salinities. Heterogeneity is carried out by deformation of the grain shapes and changes in the components and compositions of the material. Loading pressure will cause grain deflection (anisotropy), and electrical properties change as a consequence. Samples were measured in parallel and perpendicular layers of precipitation (for anisotropy and isotropy measurements) and at different salinities. When a layer is heterogeneous, the electrical characteristics change in both perpendicular directions. The effect of electrical characteristics increases as salinity concentration is increased.

Control of electrical properties of Ti3C2Tx mediated by facile alkalization

The surface functional groups of MXenes make the material group special and play a critical role in determining their electrical properties. In this work, Ti3C2Tx MXene's surface functional groups were adjusted by a facile alkalization method, using NaOH and KOH. The alkalization was effective even at very low alkaline concentrations below 0.1 M. It was disclosed that the interlayer spacing became wider and the crystal quality was improved after alkalization. Molecular characterizations showed a clear transition from F-rich terminations to OH/O-rich terminations as a consequence of alkalization. Hall measurements, which can trace multiple electrical parameters elaborately, were utilized to examine the electrical property change induced by alkalization. An abrupt rise of sheet resistance and a sharp drop of carrier concentration were simultaneously observed for a MXene alkalized with a very low alkali concentration. Temperature-dependent Hall measurements and UV–Vis absorption tests revealed that the alkalized MXene did not behave like a semiconductor. Such electrical property change was explained in relation to the modulation of surface functional groups. The results of this work demonstrate that the electrical properties of Ti3C2Tx MXene can be widely tuned within a metal domain by a simple alkalization method, offering a practical property control technique for the expanded application of MXenes.

In-situ microstructure monitoring during tempering of quenched AISI4340 steels using a high temperature electromagnetic sensor

AISI 4340 steels are used in applications where high strength and toughness are required, for example, in power transmission gears and shafts, aircraft landing gear and other structural components. The required mechanical properties are achieved by hot rolling and quenching and tempering (Q&amp;T) heat treatment. For optimum process efficiency and quality control, it is desirable to monitor the microstructural development during tempering in situ, as the microstructure is directly linked to the mechanical properties. Electromagnetic (EM) sensors have been shown to be sensitive to steel microstructural changes due to the associated changes in magnetic and electrical properties. This study reports on using a high-temperature laboratory EM sensor that operates inside a furnace to assess microstructural changes that occur during tempering at 250°C for AISI4340 steel samples. The sensor operates at low magnetic field and low frequency where the signal is affected by changes in magnetic permeability due to microstructural changes. The microstructure and hardness have been characterised to correlate to the measured EM sensor signal. The results have shown that the EM sensor signal is affected by temperature and microstructural changes on the slow heating to the tempering temperature and then is sensitive to the continuing microstructure changes that occur during the isothermal hold. The results show the potential for in-situ EM sensor monitoring during heat treatment.

Computational Prediction of Stacking Mode in Conductive Two-Dimensional Metal-Organic Frameworks: An Exploration of Chemical and Electrical Property Changes.

Conductive two-dimensional metal-organic frameworks (2D MOFs) have attracted interest as they induce strong charge delocalization and improve charge carrier mobility and concentration. However, characterizing their stacking mode depends on expensive and time-consuming experimental measurements. Here, we construct a potential energy surface (PES) map database for 36 2D MOFs using density functional theory (DFT) for the experimentally synthesized and non-synthesized 2D MOFs to predict their stacking mode. The DFT PES results successfully predict the experimentally synthesized stacking mode with an accuracy of 92.9% and explain the coexistence mechanism of dual stacking modes in a single compound. Furthermore, we analyze the chemical (i.e., host-guest interaction) and electrical (i.e., electronic structure) property changes affected by stacking mode. The DFT results show that the host-guest interaction can be enhanced by the transition from AA to AB stacking, taking H2S gas as a case study. The electronic band structure calculation confirms that as AB stacking displacement increases, the in-plane charge transport pathway is reduced while the out-of-plane charge transport pathway is maintained or even increased. These results indicate that there is a trade-off between chemical and electrical properties in accordance with the stacking mode.

Microstructure, Magnetic and Electrical Transport Properties of Sol-Gel Synthesized La&lt;sub&gt;0.7&lt;/sub&gt;Sr&lt;sub&gt;0.2&lt;/sub&gt;Ca&lt;sub&gt;0.1&lt;/sub&gt;MnO&lt;sub&gt;3&lt;/sub&gt;:TiO&lt;sub&gt;2&lt;/sub&gt; Composite

Electrical transport in materials have been studied extensively due to its great potential in spintronic technology. The introduction of the secondary phase into the manganite matrix can modify the electrical properties, subsequently improving the low-field magnetic resistance (LFMR). In this work, we study the change in electrical properties at different temperatures of polycrystalline (1-x)La0.7Sr0.2Ca0.1MnO3/xTiO2 (LT) composites where x = 0, 0.05 and 0.1. Polycrystalline La0.7Sr0.2Ca0.1MnO3 (LSCMO) was synthesized by sol-gel method, calcined at 700 °C, and pre-sintered at 800 °C for 6 h before adding TiO2. TiO2 as filler was mixed with LSCMO by wet mixing and stirring for about 30 min until a homogeneous compound was formed. Composite LT was then inserted to oven up to 100 °C for 2h to remove the moisture, compacted at 10 MPa, and sintered at 1200°C for 12 h. All samples in the LSCMO phase have a rhombohedral crystal structure with space group R3c. The crystal structure parameters were studied using Rietveld refinement through GSAS II software. The sample was characterized by SEM to represent the morphology of the sample. As the TiO2 content increased, the magnetization decreased, as observed by VSM analysis at room temperature. The electrical transport properties of pure LSCMO and LT were characterized by cryogenic from 195K to 260 K. The resistivity of LT10 is too high compared to that of LT5 and as the temperature increases, the resistivity in this range will decrease. For 200 K, the resistivity of LSCMO, LT5 and LT10 are 3.09 x 10-2 ohm.cm, 4.40 x 103 ohm.cm and 4.77 x 104 ohm.cm respectively.

Temperature cycling effect on structural, optical and electrical properties of nanostructured sodium titanates

Sodium titanates represent a promising alternative for the construction of anodes for sodium-ion batteries. To study the electrical response of nanostructured sodium titanate samples under plausible temperature conditions, we evaluate the electrical impedance in the range of temperatures from −30 ∘C to 50 ∘C, and the effect of consecutive temperature cycling. Strong changes in electrical properties are observed during the first temperature cycle, followed by a stabilization in the consecutive cycles. This behavior is reversible when the sample is exposed to external conditions and room temperature for less than an hour. Probably a structural and surface water removal and a surface water reabsorption occur, affecting the charge carriers and with it the impedance. Structurally, no differences are detected before and after the cycles, nor when evaluating only the vacuum process. However, when the optical properties are evaluated we find non-reversible changes after the temperature cycles. The optical behavior after the temperature cycling becomes uniform, the same type of electronic defects become predominant and similar direct and indirect band gap values are obtained, regardless of the starting synthesis condition. These results have significant implications for potential technological applications of these materials.

Effects of pulse repetition rate in static electrochemotherapy models

Electroporation alters cell membrane structure and tissue electrical properties by short and intense pulsed electric fields (PEF). Static mathematical models are often used to explain the change in electrical properties of tissues caused by electroporation. Electric pulse repetition rate may play an important role, as tissue dielectric dispersion, electroporation dynamics, and Joule heating may affect the electrical properties. In this work, we investigate the effects on the magnitude of the electric current when the repetition rate of the standard electrochemotherapy protocol is increased. Liver, oral mucosa, and muscle tissues were studied. Ex vivo animal experiments show that the magnitude of the electric current increases when the repetition rate is changed from 1 Hz to 5 kHz (10.8% for liver, 5.8% for oral mucosa, and 4.7% for muscle). Although a correction factor could reduce the error to less than 1%, dynamic models seem to be necessary to analyze different protocol signatures. Authors should be aware that static models and experimental results can only be compared if they use exactly the same PEF signature. The repetition rate is a key information to consider in the pretreatment computer study because the current at 1 Hz PEF differs from a 5 kHz PEF.