A versatile low-cost experimental set-up and adjoining measurement protocol for continuous temperature dependent electrical measurements in the temperature range of 100 K – 500 K is described. The ...set-up can perform continuous measurements of DC and AC electrical properties of a sample under test (SUT) as a function of its temperature in the mentioned temperature range without any artefacts. The SUT can be in the form of film, or, powders pressed into pellets. The set-up comprises of automatic data acquisition system equipped with LabVIEW programme for real time data acquisition during measurements. The errors involved in the measurements using the set-up have been calculated by measuring the temperature dependent resistance of standard Pt100 RTD temperature sensor and from temperature response of dielectric constant of standard polycrystalline BaTiO3. The high measurement accuracy of the present set-up in artefact-free AC and DC electrical measurements has been demonstrated by measuring the temperature response of the electrical properties of standard polycrystalline BaTiO3, standard polycrystalline SnO2 and nano polycrystalline SnO2 samples.
•A low-cost set-up for continuous temperature dependent electrical measurements in range 100 K – 500 K has been developed.•The adjoining measurement protocol has also been discussed.•The sample-under-test (SUT) can be either in the form of pellet or a film.•The heating or cooling rate of SUT in the set-up do not affect the intrinsic nature of its measured electrical properties.•The error in measured DC electrical resistance is ≈ ± 0.7%, which is much lower than the earlier reports.
•Microflow system based on cotton thread as the solution channel and screen-printed electrode as detector.•New voltammetric procedure for estriol determination in pharmaceutical ...formulations.•Development of electroanalytical thread-device of low cost and easy preparation.•Excellent analytical performance: low limit of detection, high sensitivity and stability of the proposed system.
Microflow systems are powerful analytical tools that explore similar principles of typical flow injection analysis driven to in a microfluidic device. Generally, microfluidic devices can promote a low consumption of reagents and samples, high speed of analysis and possibility of portability. Several advances have been reached applying a simple and low cost device based on cotton thread as microfluidic channel where the transportation of solutions is based on capillary force helped by gravity. In the present work, we have demonstrated the versatility of thread-based electroanalytical devices (μTED) constructed using a cotton thread as the solution channel and screen-printed electrodes (SPE) surface modified with carbon nanotubes (CNT) as electrochemical detectors for the amperometric determination of estriol hormone in pharmaceutical samples. The parameters involved in the amperometric detection and microflow system were studied and optimized, using the best experimental conditions (flow rate of 0.50μLs−1, 10mm of analytical path, 2.0μL of volume of injection and potential of detection of 0.75V) a linear response was observed for concentration range (LDR) of 1.0 to 1000μmolL−1 with limits of detection (LOD) and quantification (LOQ) of 0.53μmolL−1 and 1.77μmolL−1, respectively, and frequency of injection of 32 per hour. The proposed methodology was applied for determination of estriol in commercial samples and results were compared with those provided by spectrophotometric method (official methodology). The obtained results are in agreement at a 95% of confidence level.
Engineering semiconductor devices requires an understanding of charge carrier mobility. Typically, mobilities are estimated using Hall effect and electrical resistivity meausrements, which are are ...routinely performed at room temperature and below, in materials with mobilities greater than 1 cm2 V‐1 s‐1. With the availability of combined Seebeck coefficient and electrical resistivity measurement systems, it is now easy to measure the weighted mobility (electron mobility weighted by the density of electronic states). A simple method to calculate the weighted mobility from Seebeck coefficient and electrical resistivity measurements is introduced, which gives good results at room temperature and above, and for mobilities as low as 10−3 cm2 V‐1 s‐1,
μw=331cm2Vs(mΩ cmρ) (T300 K)−3/2 exp |S|kB/e−21+exp−5(|S|kB/e−1) +3π2|S|kB/e1+exp5(|S|kB/e−1) Here, μw is the weighted mobility, ρ is the electrical resistivity measured in mΩ cm, T is the absolute temperature in K, S is the Seebeck coefficient, and kB/e = 86.3 µV K–1. Weighted mobility analysis can elucidate the electronic structure and scattering mechanisms in materials and is particularly helpful in understanding and optimizing thermoelectric systems.
The weighted mobility, easily computed from measurements of the Seebeck coefficient and electrical resistivity, is an accurate measure of the charge carrier mobility and effective mass. It is even more sensitive than measurements of the Hall effect for revealing electron transport mechanisms in complex materials ranging from metals, semiconductors, and conducting polymers.
A novel non-enzymatic H2O2 sensor was fabricated by electrodepositing 5–16nm AuNPs onto porous GaN electrode. The AuNPs/porous GaN sensor exhibited good sensitivity, repeatability and long-term ...stability towards H2O2 detection.
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•A novel non-enzymatic H2O2 sensor was fabricated by electrodepositing 5–16nm AuNPs onto porous GaN electrode.•As far as I know, this is the first time to report porous GaN based electrochemical H2O2 biosensor.•Our work focuses on the design of simply prepared and good practicability H2O2 biosensor. There is no doubt that our work has wider societal impact.
Here we report the electrodeposition of gold nanoparticles (AuNPs) onto porous GaN electrode obtained by photoelectrochemical etching planar GaN to fabricate a non-enzymatic hydrogen peroxide (H2O2) sensor. SEM images revealed porous GaN has uniformly high-porosity structure and the diameter of AuNPs is 5–16nm. The AuNPs/porous GaN electrode exhibited good electrocatalytic activity toward the reduction of H2O2 and performed as amperometric sensor for the detection of H2O2. The AuNPs/porous GaN electrode showed linear amperometric responses for H2O2 in the concentration range from 10 to 100μM with the sensitivity of 281.5μAmM−1. The limit of detection (LOD) is 2μM with a signal-to-noise ratio of 3. In addition, the AuNPs/porous GaN electrode exhibited good repeatability, reproducibility, selectivity and long-term stability for H2O2 detection, in the meanwhile, AuNPs showed excellent adhesive capacity to the porous GaN electrode, which was tested by continually sonicating the AuNPs/porous GaN electrode for 3h. Above results demonstrated this simply prepared H2O2 sensor has good practicability and is promising to measure the analyte in practical applications.
In this article, ternary oxide NiO-CdO-ZnO nanocomposite along with pure NiO, CdO and ZnO were prepared by the homogeneous co-precipitation method. The XRD pattern confirmed the formation of ...nanocomposite with NiO (cubic)–CdO (cubic)–ZnO (hexagonal). The volume fractions were 38% NiO, 6% CdO and 56% ZnO phase in nanocomposite determined by direct comparison method. Crystallite size and lattice strain were calculated using Scherrer plot, Williamson-Hall and Size-Strain plot methods. The UV–vis was used to study optical properties such as bandgap (Eg), refractive index (n), extinction coefficient (k), optical conductivity (σopt) and dielectric constants (εr, εi). FTIR and Raman analyses have confirmed the successful formation of NiO-CdO-ZnO nanocomposite. The current-voltage measurements revealed that nanocomposite has high electrical response. SEM images shown that nanocomposite has roughly spherical morphology and EDX described that Zn has higher concentration than Ni and Cd. PL spectra of nanocomposite demonstrated the emission bands associated with new energy levels induced by defects. The photocatalytic activity of grown nanocomposite against rhodamine B (RhB) and methylene blue (MB) dyes under sunlight revealed high degradation efficiency 99% for RhB and 98% for MB in 60 and 90 min illumination respectively, indicated that grown nanocomposite is a propitious sunlight-driven photocatalyst to eliminate organic toxins.
The aim of this article is to detect electron traps in AlInN/GaN transistors operating at room temperature by combining pulsed electrical measurement with photoionization techniques to rapidly assess ...their activation energies and time constants. In addition, this technique can also reveal the presence of electron traps that cannot be observed by using pulsed measurements alone. Thus, two electron traps were identified including a deep level whose origin could be related to dislocations in the GaN buffer existing in the devices. At the same time, this study has shown that the time constants of these electron traps are inferior to 400 ns and that the electrical behavior of the components is also degraded by the presence of surface states with a time constant of 4 <inline-formula> <tex-math notation="LaTeX">\mu</tex-math> </inline-formula>s. Moreover, these two traps are at the origin of the gate lag effects observed during the pulsed electrical characterization of the AlInN/GaN high electron mobility transistors (HEMTs). Likewise, a negative output conductance induced by a trapping effect has been put forward.
A facile strategy has been developed to fabricate silver nanoparticles (Ag NPs) through an electrochemical method with the assistance of metformin functionalized MWCNT (Ag@MH/MWCNT nanocomposite). ...Investigations by field emission scanning electron microscopy (FESEM) confirmed that the prepared nanocomposite have a porous structure that is constructed by interconnecting functionalized MWCNT framework. Electrochemical studies show that the nanocomposite exhibits high stability and excellent activity for electrocatalytic oxidation of glucose in alkaline solutions, which allows the Ag@MH/MWCNT to be used in enzyme-free amperometric sensors for glucose determination. It was confirmed that the Ag@MH/MWCNT based glucose biosensor presents wide response window for glucose concentrations of 1.0nM–350μM, short amperometric response time (4s), low detection limit of 0.0003μM (S/N=3), high sensitivity as well as good selectivity.
Electrical detection methodologies are likely to underpin the progressive drive towards miniaturised, sensitive and portable biomarker detection protocols. In being easily integrated within standard ...electronic microfabrication formats, and developing capability in microfluidics, the facile multiplexed detection of a range of proteins in a small analytical volume becomes entirely feasible with something costing just a few thousand pounds and benchtop or handheld in scale. In this review, we focus on recent important advances in label free assays of protein using a number of electrical methods, including those based on electrochemical impedance spectroscopy (EIS), amperometry/voltammetry, potentiometry, conductometry and field-effect methods. We introduce their mechanistic features and examples of application and sensitivity. The current state of the art, real world applications and challenges are outlined.
The aim of this article is to show that it is possible to rapidly estimate the activation energies of electron traps in AlInN/GaN transistors operating at room temperature by combining pulsed ...electrical measurements with photoionization techniques using infrared illumination. This technique avoids the time‐consuming task of performing electrical measurements at different temperatures to determine the activation energies of the electron traps using Arrhenius laws. Thus, a deep level at 1.3 eV is detected and attributed to the presence of carbon in GaN buffer of the component. Moreover, we have highlighted that the trapping effect can be screened when the transistors are biased with a high drain‐source voltage during pulsed measurements.
It is possible to rapidly estimate the activation energies of electron traps in AlInN/GaN transistors operating at room temperature by combining pulsed electrical measurements with photoionization techniques using red and infrared illumination. Deep levels at 1.3 and 20 eV are detected and attributed to the presence of carbon and dislocations in GaN buffer of the component.
A nanocomposite containing α-Fe2O3 nanoparticles entangled with reduced graphene oxide nanosheets have been synthesized via simple hydrothermal and ultra-sonication method. It is observed that ...graphene nanosheets enhanced the electrical conductivity and electrochemical activity of α-Fe2O3 nanoparticles. The superior electrical conductivity of α- Fe2O3/rGO nanocomposite was confirmed by two probe current-voltage (I-V) measurements. The enhanced electrochemical activity of α- Fe2O3/rGO nanocomposite was confirmed by electrochemical impedance spectroscopy measurements and cyclic voltammetry experiments. It is observed that as-prepared α- Fe2O3/rGO nanocomposite has superior charge-transfer resistance and higher specific capacitance than bare α-Fe2O3 nanoparticles. Moreover, nanocomposite retained 75% of the initial capacitance after 1000 cycles. Due to tremendous electrochemical performance, the α- Fe2O3/rGO nanocomposite have potential applications in energy storage devices.
•A novel α- Fe2O3/rGO nanocomposite was synthesized.•The novel α-Fe2O3/rGO nanocomposite exhibited high conductivity and high capacitance.•The α- Fe2O3/rGO nanocomposite show potential for next-generation energy storage devices.
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