Nyquist Plots Research Articles

Electromechanical properties of multi-reinforced self-sensing cement-based mortar with MWCNTs, CFs, and PPs

This experimental research examines the electromechanical properties of hybrid cement-mortar composites strengthened with different amounts of multi-walled carbon nanotubes (MWCNTs), carbon fibers (CFs), and polypropylene microfibers (PPs). The experimental program included optimal mechanical improvement at the nano and micro levels. The optimum micro-composite mortar derives from the finest mechanical response of the CFs and PPs micro-modified specimens in terms of flexural and compressive strength. Further, the electrical response of the mortars with the improved mechanical response was examined. The improved mechanical and electromechanical response of the optimum amounts of the two scales indicates the hybrid mortar with exceptional performance. This optimum amount in micro-scale in synergy with the optimum amount of MWCNTs constituted the hybrid-reinforced cement-based mortar. The optimized nano-, micro-, and hybrid-reinforced mortars were examined for their electrical properties in terms of electrical conductivity, impedance, and piezo-resistivity. These measurements in combination with the Nyquist plots of the resistance-reactance specified the sensing ability of the cementitious self-sensor. Results indicated that the optimum reinforcement in the nanoscale is 0.2 wt% MWCNT and in microscale 0.5% wt.% CFs exhibited improvement in flexural strength, compressive strength, and flexural toughness. The optimum nano- and micro-reinforced cement-based mortars presented much higher conductivity of about 867% and 633%, and lower impedance of about 89.4% and 86%, respectively, compared to the reference specimen, and a one-order-of-magnitude compared to the other contents. The excellence of the hybrid combination of 0.2 wt% MWCNΤs and 0.5% wt.% CFs occur with even more improved flexural strength of about 27%, flexural toughness of about 1607%, conductivity of 2617% more than the reference mortar, and lower impedance of about 96%, compared to the reference specimen. The piezoresistive response of the tested cement-mortar composites denotes the enhanced strain-sensing ability of the examined multi-reinforced mortars, highlighting the superiority of the hybrid one.

The Impact of Phase-Locked Loop (PLL) Architecture on Sub-Synchronous Control Interactions (SSCI) for Direct-Driven Permanent Magnet Synchronous Generator (PMSG)-Based Type 4 Wind Farms

Electric vehicles (EVs) are a promising solution to reduce carbon dioxide (CO2) emissions, but this reduction depends on the fraction of renewable sources used to generate electricity. Wind energy is thus a vital candidate and has experienced a remarkable surge recently, establishing itself as a leading renewable power source worldwide. The research on Direct-Driven Permanent Magnet Synchronous Generator (PMSG)-based type 4 wind farms has indicated that the Phase-locked Loop (PLL) bandwidth significantly impacts Sub-Synchronous Resonance (SSR). However, the influence of PLL architecture on SSR remains unexplored and warrants investigation. Therefore, this paper investigates PLL architectural variations in PLL Loop Filter (LF) to understand their impact on SSR in type 4 wind farms. Specifically, an in-depth analysis of the Notch Filter (NF)-based enhanced PLL is conducted using eigenvalue analysis of the admittance model of a PMSG-based type 4 wind farm. The findings demonstrate that the NF-based enhanced PLL exhibits superior performance and improved passivity in the sub-synchronous frequency range, limiting the risk of SSR below 20 Hz. Additionally, Nyquist plots are employed to assess the impact on system stability resulting in increased stability margins. In the future, it is recommended to further investigate and optimize the PLL to mitigate SSR in wind farms.

Y2O3 electrodeposited TiO2 nanotube arrays as photoanode for enhanced photoelectrochemical water splitting

Y2O3 deposited TiO2 nanotubes (Y-TNTs) are investigated as photoanodes for efficient photoelectrochemical water splitting. Y2O3 is electrodeposited on TiO2 nanotubes for 5–15 min. The physicochemical and optical properties of Y-TNTs reveal that Y2O3 anchored on the TNTs enhances the visible light absorption. The Y-TNTs show good photocurrent response compared to pristine TNTs. Y2O3 deposition for 10 min on TNTs produces highest photocurrent of 609 μA cm−2 at 1.23 VRHE. Presence of Y2O3 increases the lifetime of the charge carriers as revealed by the Nyquist plot analysis and Mott-Schottky analysis. Y-TNTs-10 min sample shows 2.75 times higher photoconversion efficiency compared to pristine TNTs. Computational analysis shows that Y–TiO2 has negative free energy of adsorption for OER intermediates as compared to bare TiO2 which has positive values. The rare earth metal electrodeposition on TiO2 nanotubes is another approach to improve the photoelectrochemical water splitting activity without distorting the nanotube structure.

Capacitance characterization of graphene/n-Si Schottky junction solar cell with MOS capacitor

Abstract We have demonstrated a simple and accurate method for characterizing the capacitance of Graphene/n-Si Schottky junction solar cells (GSSCs) which embed the metal-oxide-semiconductor (MOS) capacitor. We measured two types of GSSCs, one with thermal annealing treatments (w-a) and one without (wo-a). It was found that the wo-a GSSC exhibits a two-step feature in the phase versus forward bias voltage relationship, which may be attributed to the presence of polymethyl methacrylate residues. By considering the capacitance of the MOS capacitor (Cmos) and its standard deviation, we successfully obtained the capacitance of the Schottky junction (CSch), and evaluated meaningful built-in potentials (Schottky barrier heights) which are 0.51 V (0.78 eV) and 0.47 V (0.75 eV) for the w-a and wo-a GSSCs, respectively, by the Mott–Schottky analysis. We also briefly discuss the relationship between CSch and the Nyquist and Bode plots, finding that the RC time constant decreases due to the subtraction of Cmos.

Impedance Response Influenced by Variability in the Random Distribution of Physical Properties of Coated Materials in Two-Dimensional Space

Heterogeneous physical characteristics of a system featuring a single-layer film on a metallic surface have been explored via its impedance response. The Nyquist plot showed a distorted semicircle, indicative of the system’s unique distribution characteristics. Utilizing a copula-based probability method, a two-dimensional deterministic impedance model was successfully integrated, accounting for spatial physical properties such as permittivity and electrical conductivity. This strategy enabled in-depth exploration and mechanistic quantification of a broad spectrum of properties. A quantitative understanding of impedance signal alterations, characterized by normally or log-normally correlated variables, was achieved through the variation in aspect ratio and characteristic frequency of the impedance spectra. Log-normally distributed electrical properties provided a superior representation of the distorted impedance spectra. As coefficient of variation (CV) values fluctuated, the aspect ratio and characteristic frequency showed heightened sensitivity to log-normal permittivity compared to log-normal electrical conductivity. Notably, a marked positive linear correlation between electrical properties resulted in an impedance response that approximated perfect semicircular spectra. The variability in the electrical properties’ distribution was demonstrated by considering the correlation coefficient between electrical conductivity and the z-direction position. The highest aspect ratio of the impedance spectra was observed when the electrical conductivity was randomly distributed across the z-direction space.

Improving Pure Titanium's Biological and Mechanical Characteristics through ECAP and Micro-Arc Oxidation Processes.

Pure titanium is limited to be used in biomedical applications due to its lower mechanical strength compared to its alloy counterpart. To enhance its properties and improve medical implants feasibility, advancements in titanium processing technologies are necessary. One such technique is equal-channel angular pressing (ECAP) for its severe plastic deformation (SPD). This study aims to surface modify commercially pure titanium using micro-arc oxidation (MAO) or plasma electrolytic oxidation (PEO) technologies, and mineral solutions containing Ca and P. The composition, metallography, and shape of the changed surface were characterized using X-ray diffraction (XRD), digital optical microscopy (OM), and scanning electron microscope (SEM), respectively. A microhardness test is conducted to assess each sample's mechanical strength. The weight % of Ca and P in the coating was determined using energy dispersive spectroscopy (EDS), and the corrosion resistance was evaluated through potentiodynamic measurement. The behavior of human dental pulp cell and periodontal cell behavior was also studied through a biomedical experiment over a period of 1-, 3-, and 7-days using culture medium, and the cell death and viability can be inferred with the help of enzyme-linked immunosorbent assay (ELISA) since it can detect proteins or biomarkers secreted by cells undergoing apoptosis or necrosis. This study shows that the mechanical grain refinement method and surface modification might improve the mechanical and biomechanical properties of commercially pure (CP) titanium. According to the results of the corrosion loss measurements, 2PassMAO had the lowest corrosion rate, which is determined to be 0.495 mmpy. The electrode potentials for the 1-pass and 2-pass coated samples are 1.44 V and 1.47 V, respectively. This suggests that the coating is highly effective in reducing the corrosion rate of the metallic CP Ti sample. Changes in the grain size and the presence of a high number of grain boundaries have a significant impact on the corrosion resistance of CP Ti. For ECAPED and surface-modified titanium samples in a 3.6% NaCl electrolyte solution, electrochemical impedance spectroscopy (EIS) properties are similar to Nyquist and Bode plot fitting. In light of ISO 10993-5 guidelines for assessing in vitro cytotoxicity, this study contributes valuable insights into pulp and periodontal cell behavior, focusing specifically on material cytotoxicity, a critical factor determined by a 30% decrease in cell viability.

Synthesis of ternary GNP-CNT-ZrO2 nanocomposite as a high-performance anode for lithium-ion batteries

The modulation of electrical charge transport in electrodes through mesoscale structural design is crucial in developing high-performance lithium-ion batteries (LIBs). In this study, three nanocomposites were fabricated by incorporating ZrO2 nanoparticles into carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and GNP-CNT structures. The synthesizing was a simple hydrothermal method followed by annealing to prepare CNT-ZrO2 (C-Z), GNP-ZrO2 (G-Z), and GNP-CNT-ZrO2 (G-C-Z) materials for a three-dimensional highly efficient anode for LIBs. The electrochemical performance was evaluated using cyclic voltammetry (CV), which demonstrated excellent reversibility for the G-C-Z material. A study on the rate performance confirmed reversible discharge capacity of 512, 274, 248, 206, and 175 mAh/g at 0.2, 1, 5, 15, and 20 A/g, respectively, for the G-C-Z anode, which demonstrated the highest reversibility among the synthesized anodes. Even after 500 cycles at a current density of 5 A/g, this electrode maintained its specific capacity and electrochemical cycling reversibility at almost 98.5%. The lower capacity of C-Z and G-Z structures was attributed to the aggregation of constituents. The Nyquist plots after 500 cycles demonstrated the lowest charge transfer resistance (Rct) of 52.19 Ω and the highest value of Li-ion diffusion coefficient (DLi+) for the G-C-Z anode, ensuring excellent long-life electron conductivity.

Pd Nanoparticle-Decorated Novel Ternary Bi2O2CO3-Bi2MoO6-CuO Heterojunction for Enhanced Photo-electrocatalytic Ethanol Oxidation.

Recently, photo-electrooxidation of fuel using a noble metal-semiconductor junction has been one of the most promising approaches in fuel cell systems. Herein, we report the development of a Pd-supported Bi2MoO6-Bi2O2CO3-CuO novel ternary heterojunction for ethanol oxidation in alkali in the presence and absence of visible light. Various spectroscopic and microscopic characterization techniques confirm strong coupling between palladium nanoparticles and Bi2MoO6-Bi2O2CO3-CuO ternary heterojunction supports. The photo-electrocatalytic efficacy of the synthesized catalysts was inspected by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The CV study reveals that the forward peak current density (in mA mg-1 of Pd) of the synthesized quaternary heterojunction was about 1482.5, which is 2.4, 4, and 4.6 times higher than that of Pd/CuO (608.3), Pd/Bi2MoO6-Bi2O2CO3 (368.3), and similarly synthesized Pd catalyst (321.5) under visible light radiation. The best heterojunction catalyst shows 2.21-fold higher peak current density in visible light compared to that in dark. CA study reveals that after operation for 6000 s, the current density of the quaternary electrode is 1.5 and 3.4 times greater than that of Pd/CuO and Pd/C catalysts, respectively. The greater photocurrent response, lower photoluminescence (PL) emission intensity, and smaller semicircle arc in the Nyquist plot of the quaternary catalyst demonstrate the efficient segregation and higher charge transfer conductance of photogenerated charges to facilitate the photo-electrooxidation process of ethanol. The stability test shows that the quaternary catalyst loses only 9.8 and 7.7% of its maximum current density after 500 cycles of CV operation in the dark and light, respectively, indicating that light energy is more beneficial in establishing high stability. The dramatic enhancement of the photo-electrocatalytic activity of the quaternary electrode is owing to the lower band gap, high ECSA, enhanced charge separation of photogenerated carriers (e--h+), and all cocatalytic support of Bi2MoO6, Bi2O2CO3, and CuO in Pd/ Bi2MoO6-Bi2O2CO3-CuO under visible light radiation. The morphology and structure of the used quaternary catalyst are tested using FESEM and PXRD. Finally, ex situ FTIR spectroscopy and HPLC techniques help understand the ethanol electrooxidation reaction mechanism.

Ternary Heterostructures Based on BaTiO3/MoO3/Ag for Highly Efficient and Reusable Photocatalytic Applications

AbstractThis work shows the fabrication of an efficient ternary heterostructure photocatalyst by integrating ferroelectric BaTiO3 (BTO) as the bottom layer, semiconductor MoO3 as the middle layer and plasmonic silver nanoparticles (Ag NPs) as the top layer, respectively. The BaTiO3/MoO3/Ag (BMA) heterostructure exhibits a higher photodegradation and photocatalytic efficiency of 100% for rhodamine B (RhB) dye under a UV–Visible light illumination of 60 min when compared with its binary heterostructure counterparts BaTiO3/Ag (BA) and MoO3/Ag (MA). The increased photocatalytic activity in BMA heterostructure is attributed to its enhanced interfacial electric field due to the electric double layer formation at BTO‐MoO3 and MoO3‐Ag interfaces. The higher blueshift in the surface plasmon resonance (SPR) peak observed for the BMA heterostructure clearly indicates an increased electron transfer toward the top Ag NPs layer under optical illumination. The higher resistive switching (RS) ratio, the increased difference in voltage minima, and the improved photocurrent generation, as evident from the I–V characteristics, illustrate the enhanced charge carrier generation and separation in BMA heterostructure. A smaller arc radius observed for the Nyquist plot of BMA heterostructure clearly showcases its increased interfacial charge transfer (CT). The CT mechanism and reusability of the BMA heterostructure are also studied.

Carbon-based electrode materials with ion exchange membranes for enhanced membrane capacitive deionization

Potable clean water is in high demand for human life. Numerous technologies like reverse osmosis, flash distillation and electrodialysis are employed and explored to overcome the scarcity of potable water. Last decade has witnessed great attraction of researchers towards membrane capacitive deionization (MCDI) as an alternative technology for water desalination. MCDI holds ability to compete with benchmark desalination techniques as it involves adsorption of ions by porous carbon material on application of low voltage (<1.4 V). Ions are desorbed back into the stream on reversing the potential hence, regenerating the electrodes. Addition of ion exchange membranes enhances the desalination efficiency by reducing the effect of co-ions, which is not possible in traditional capacitive deionization (CDI). Present study aims to synthesize and explore the best fit carbon-based material for MCDI. SPEEK and QPPO polymers were used for CEM and AEM preparation over the porous carbon materials respectively. SEM, XRD and Raman spectroscopy were used to investigate the structural information about carbon materials. Nyquist plots were obtained to analyze diffusive behavior and formation of electrolyte double layer (EDL) on electrode-electrolyte interface. Capacitive behavior of the electrodes was analyzed through cyclic voltammetry (CV) and Galvanostatic charge discharge (GCD). Water desalination performance of membrane coated carbon materials was observed through batch-mode MCDI set-up. Important CDI parameters like salt adsorption capacity (SAC) and specific capacitance were also calculated to evaluate performance of the prepared MCDI electrodes. Among all four synthesized materials, CMGO (carbon spheres modified graphene oxide) reports highest SAC value i.e. 22.5 mg g−1 which suggest CMGO as a promising material for large scale MCDI application.

Conducting polymer encrusted Cu/Mn-MOF-CNDs: A facile synthesis, characterization and its hydrogen evolution activity in alkaline media and seawater

The Composites of polyaniline-bimetallic metal-organic framework with carbon nanodots (PANI/bi-MOF@CNDs) were fabricated by chemically oxidising aniline monomer for the hydrogen evolution process (HER). In this investigation, the composite structure, topography, and characteristics were analysed. The Fourier transform infrared spectroscopy analyses found evidence of electrostatic interaction between the CNDs@MOF and the backbone of the PANI matrix. Investigations using scanning electron microscopy and transmission electron microscopy showed that the CNDs@MOF exhibited uneven crystals with an additional enveloping PANI material. In an alkaline medium, the produced PANI composite (PANI/bi-MOF@CNDs) electrocatalyst showed a small overpotential and significant Tafel slope (110 mV and 180 mV/dec at 10 mA/cm2), as well as the RCT value of about 12.26 Ω, determined from Nyquist plot. PANI composite structural characteristics and electrical conductivity have also resulted in a faster rate of electron charge transfer and more accessible surface edge active sites. In addition, the catalyst is stable for 48 h at the specified operating conditions, and no further buffered electrolytes are required. As a result of the enhanced electrochemical performance, a strategic approach for the development of low-priced electrocatalysts for power conversion has been discovered.

Some diazepinone analogs as corrosion inhibitors for carbon steel in a hydrochloric acid medium: An integrated theoretical and practical study

Corrosion is not just an undesirable phenomenon but a global economic challenge. With the help of current state-of-the-art research facilities, this work proposes the inhibition activity of two diazepinone analogs, namely 4-Phenyl-5a, 6, 7, 8, 9,9a-hexahydro-1 H-1,5-benzodiazepin- 2(5 H)-one (POBD) and 7-phenyl-1,4-diazepin-5-one (PTDZ) for carbon steel (CS) corrosion in 1 M hydrochloric acid using chemical and electrochemical corrosion analysis, especially electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), surface analysis (SEM & UV-vis), and modeling techniques. Results showed that chemical structure and concentration had an impact on the diazepinone analogs capacity to inhibit. POBD and PTDZ functioned in mixed mode, according to PDP data. Due to the inhibitor molecules' adsorption on the CS surface, the Nyquist plots showed that when the concentration of POBD and PTDZ was raised, polarization resistance increased and double-layer capacitance decreased. The POBD and PTDZ were adsorbed on the metal surface, which followed the Langmuir adsorption isotherm model. The proposed mixed-type adsorption of the examined diazepinone compounds on the CS surface was based on thermodynamic adsorption and activation characteristics. The steel was shown to be shielded from acidic ions by an adsorbed layer of inhibitor molecules by surface examination via scanning electron microscopy (SEM). The interactions between diazepam and the CS surface have been clarified and linked using MDS and DFT.

Crossover to the negative dielectric constant in La3+ and Dy3+ doped Co-Zn spinel nanoferrites

The paper is focused on a comprehensive study of cation distribution and impedance spectroscopy analysis of pristine and rare earth ions (La3+ and Dy3+) doped Co0.7Zn0.3Fe2O4 ferrite nanocrystals. The samples have a single phase spinel cubic structure of space group Fd3̅m with a in the range of 0.8400−0.8408 nm as confirmed by Rietveld refinement analysis of the X-ray diffraction (XRD) data. The cation distribution property of these compositions has been thoroughly studied using the data of XRD as well as Raman spectra. It is predicted that Co2+ and Zn2+ ions prefer to occupy both the sites, tetrahedral A and octahedral B, but rare earth ions have a strong preference for B-site. The non-uniform, agglomerated grains of these samples have been observed using the field emission scanning electron microscope. Up to a particular temperature, the samples have shown a positive dielectric constant, but above that, an unusual result of negative dielectric constant is observed; the Nyquist plots and other related parameters change their features in this crossover region. The doped samples have shown higher dielectric constant and lower loss as compared to the parent sample in the frequency range of 104–106 Hz and temperature interval of 25−300 °C. The variation of dielectric modulus confirms the non-Debye type relaxor behavior of the samples. Our reported results would facilitate applications of these materials for a wide range of microwave devices.

Defect controlled diffusion of lithium ions in Mn doped V2O5 for potential applications as cathode material

With a motivation to unravel the effect of cation (Mn) doping-induced modifications in structure, charge transfer resistance, and Li-ion diffusion in V2O5 a systematic study using X-ray diffraction (XRD), Raman Spectroscopy and electrochemical impedance spectroscopy (EIS) has been employed using three electrodes configuration. Structural investigations using XRD suggest the selective diffusion of Mn ion towards the c-axis at a low doping percentage. Raman spectroscopy suggests the shift in 994 cm-1 modes which substantiates the uniaxial diffusion of Mn ions. Nyquist plots show that interfacial charge transfer resistance is highest for the lowest doping i.e., 1% Mn-doped V2O5 and exhibits the lowest diffusion coefficient as compared to other doped V2O5 samples. Specific capacitance calculated from cyclic voltammetry is found to be highest for the 4% Mn-doped V2O5 sample. Moreover, diffusion of Lithium ions improves with an increase in doping concentration due to higher concentration of defects as evident from Δd/d and Nelson–Riley factor (NRF) for pure V2O5 and Mn-doped V2O5.

Ag2S-Ag2O-Ag/poly-2-aminobenzene-1-thiol Nanocomposite as a Promising Two-Electrode Symmetric Supercapacitor: Tested in Acidic and Basic Mediums.

A Ag2S-Ag2O-Ag/poly-2-aminobenzene-1-thiol (P2ABT) nanocomposite was prepared using the photopolymerization reaction using AgNO3 as an oxidant. The size of the nanocomposite was about 40 nm, in which the morphology was confirmed using TEM and SEM analyses. The functional groups of Ag2S-Ag2O-Ag/P2ABT were confirmed using FTIR; also, XRD confirmed the inorganic Ag2S, Ag, and Ag2O formation. This nanocomposite has great performance in supercapacitor applications, with it tested in acidic (1.0 M HCl) and basic mediums (1.0 M NaOH). This pseudo-capacitor has great performance that appeared through the charge time in an acid medium in comparison to the basic medium with values of 118 s and 103 s, correspondingly. The cyclic voltammetry (CV) analysis further confirmed the excellent performance of the supercapacitor material, as indicated by the large area under the cyclic curve. The specific capacitance (CS) and energy density (E) values (at 0.3 A/g) were 92.5 and 44.4 F/g and 5.0 and 2.52 W·h·Kg-1 in the acidic and basic mediums, correspondingly. The charge transfer was studied through a Nyquist plot, and the produced Rs values were 4.9 and 6.2 Ω, respectively. Building on these findings, our objective is to make a significant contribution to the progress of supercapacitor technology through a prototype design soon.

Investigation of the corrosion behavior of 6082 aluminum alloy in deicing salt

AbstractThe corrosion behavior of 6082 aluminum alloy in deicing salt was investigated by electrochemical impedance spectra combined with an X‐ray diffractometer, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscope. The experiment results showed that the corrosion tendency of 6082 aluminum alloy in deicing salt strongly depends on its different matrix and grain boundary precipitates, which also show the characteristics of transformation during the corrosion process. The Nyquist plot exhibits the characteristics of double capacitive resistance arcs, and the capacitive resistance arcs were affected by corrosion characteristics and corrosion products on aluminum alloy surface. The nucleation and development of pitting and the formation of a passive film were closely related to the Si phase in the 6082 aluminum alloy.

Robust one-pot solvothermal incorporation of InVO4 with polymeric-C3N4 nanosheets with improved charge carrier separation and transfer: A highly efficient and stable photocatalyst for solar fuel (H2) generation

Polymeric-C3N4 is a photocatalyst with desirable properties for efficient solar fuel (H2) generation. However, p- C3N4 exhibits a low H2 evolution rate. Herein, InVO4 is successfully incorporated on the surface of p- C3N4 nanosheets via a one-pot solvothermal method to generate solar fuel (H2) effectively. The optical gap energy of p- C3N4 was red-shifted to 2.23 eV after incorporating InVO4. A small arc radius of the Nyquist plot and substantial quenching of PL was observed when InVO4 was added to p- C3N4. The optimized catalyst loading (15 wt%) shows a maximum H2 production activity of 8980 µmol/g/h. This outstanding performance is a nearly 56-fold enhancement in comparison with bare p-C3N4. Furthermore, the STH conversion efficiency of 1.87% is achieved with the optimized photocatalysts, which is higher than many g- C3N4 - based photocatalysts. Moreover, the H2 generation activity achieved in the present work is higher than the reported one using the same InVO4-g- C3N4 photocatalysts.

VEGF Detection via Impedance Spectroscopy on Surface Functionalized Interdigitated Biosensor.

Vascular endothelial growth factor (VEGF), a clinically important biomarker, often plays a key role in angiogenesis, would healing, tumor growth, lung development, and in retinal diseases. Hence, detecting and quantifying VEGF is deemed medically important in clinical diagnosis for many diseases. In this report, a simple yet highly cost-effective platform was proposed for VEGF protein detection using commercially available interdigitated sensors that are surface modified to present DNA optimally for VEGF capture. The dielectric characteristics between the fingers of the sensor were modulated by the negatively charged aptamer-VEGF capture, and the impedance was estimated using an impedance analyzer. Impedance-spectra tests were compared among pristine unmodified surfaces, functionalized monolayer surfaces, and aptamer-grafted surfaces in order to evaluate the efficacy of VEGF detection. From our results, the sensitivity experiments as conducted showed the ability of the interdigitated sensor to detect VEGF at a low concentration of 5 pM (200 pg/mL). The specificity of the functionalized sensor in detecting VEGF was further examined by comparing the impedance to platelet-derived growth factor, and the results confirm the specificity of the sensor. Finally, the Nyquist plot of impedance spectra was also presented to help data visualization and the overall performance of the device was found to be a highly suitable template for a smart biosensor for the detection of VEGF.

Coprecipitation Methodology Synthesis of Cobalt-Oxide Nanomaterials Influenced by pH Conditions: Opportunities in Optoelectronic Applications

The cobalt oxide (Co3O4) nanomaterials were prepared by coprecipitation synthesis technique by maintaining the pH of the mother solution at 7, 8, and 9. The prepared nanomaterials were subjected to structural and optical characterizations, and the results were examined. The optical absorption spectral studies reveal that the two absorption bands indicate ligand–metal coordination. The photoluminescence spectra contain emission peak at 488 and 745 nm due to size and shape of the synthesized materials. The magnetic nature of the samples was identified from the hysteresis loop traced by vibrating sample magnetometry (VSM). The Fourier transform infrared (FT-IR) spectrum of Co3O4 nanomaterials reveals two sharp bands absorbed in 584 and 666 cm-1. This ascribes to the Co-O and O-Co-O stretching, respectively. As the pH of the solution varied from 7 to 10, the SEM image authenticates the transformation of Co3O4 nanomaterials morphology from spherical to cubic to agglomerated shape. From the UV-Vis spectra, two absorption bands around 473 nm and 762 nm are observed for the materials prepared at pH 7 and 8. But at pH 9, these two peaks were shifted towards higher wavelengths 515 nm and 777 nm. The observed ferromagnetic nature of Co3O4 nanomaterials clearly show the role of surface spins and surface morphology on the magnetic properties of Co3O4 nanomaterials. The cyclic voltammetry (CV) curves show the rectangular type of voltammogram. This is an indication of good charge propagation with the electrodes. The Nyquist plots of Co3O4 nanomaterials have a semicircle in the high frequency region and a vertical line in the low frequency region. The results suggest that Co3O4 is found to be a promising material for the fabrication of light-emitting diodes, solar cells, and optoelectronic devices.

Revealing the photophysics of N719 dye based dye-sensitized solar cell

Dye-sensitized solar cell (DSSC) has demonstrated promising photovoltaic performance with several photo-sensitizers. N719 dye, is a popular sensitizer used in DSSC due to its ability to absorb light in the visible region and its unique characteristics such as ultrafast electron injection and stable anchoring to the TiO2 surface. However, many of its intriguing optoelectronic properties and charge carrier relaxation at low frequency are contested. Here impedance and modulus spectroscopy were employed to extensively explore the charge carrier dynamics under both light-off and illumination conditions, and it was found that there is a significant change observed in the low-frequency regime in both cases. The fabricated N719 dye based DSSC exhibit the highest JSC of 10.89 mA/cm2, a highest VOC of 0.672 V, a fill-factor of 0.65 and photoconversion efficiency of 4.81%. The Nyquist plot of N719 DSSC under light-off and illumination conditions demonstrates that at higher frequency, a small arc is observed, and at a lower value, a large arc is observed. Moreover, the Nyquist plots exhibit depressed semicircles due to deviation from ideal Debye relaxation nature. The dielectric relaxation is found to follow the interfacial polarization of Maxwell-Wagner type probably attributed to the grain boundary effects. Furthermore, the comparative analysis of modulus and impedance spectra at low frequency reveals the localized carrier relaxation in this N719 DSSC which has been correlated with conductivity hopping process.