Imaginary Part Of Dielectric Constant Research Articles

Investigation of Structural, Dielectric, Magnetic and Impedance Spectroscopy of MgO/CuFe2O4 Nanocomposites

This study investigates the properties of (MgO)x/(CuFe2O4)1-x x= 10–50 wt.% nanocomposites (NCPs) prepared by physical mixing of both materials. The crystal structure, phase identification and morphology were analyzed by x-ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The investigation revealed the formation of required phases which are in nanometer dimension (22–54 nm) computed by Debye-Sherrer’s formula. Both the real and imaginary parts of dielectric constant (ε/ & ε//), a.c. conductivity (σac), and impedance were measured in the frequency range of 1kHz to 2MHz by LCR meter. The ε/ and ε// revealed a decreasing trend with frequency, while MgO weight fractions in NCPs enhance the permittivity values. The real and imaginary parts of impedance (Z/ & Z//) demonstrate a decreasing trend with frequency which is ascribed to increase in σac. The complex impedance spectroscopy (CIS) analysis shows semicircular arcs at higher frequency, which are due to electrical transport properties of conducting grains. The effect of MgO contents on magnetic properties were analyzed by measuring M-H loops at room temperature through vibrating sample magnetometer (VSM). Both the saturation magnetization (Ms) and coercivity (Hc) values show a decreasing profile with MgO fractions, which are due to increase in nonmagnetic contents and decrease in surface anisotropy respectively.

Molybdenum Based Manganese Oxides as Optoelectronic Nanomaterials: Synthesis, Structural & Optical Characterization

AbstractThis work reports the synthesis of molybdenum based manganese oxide nanomaterials named as (CH1‐CH5) via a facile hydrothermal approach. Nanomaterials were characterized through Powder XRD, SEM, BET, UV‐Vis, Photoluminescence, and FTIR analysis. Structural characterization revealed triclinic crystal structure of nanomaterials having particle sizes in the range of 23.08–52.7 nm with very low levels of microstrain levels (<0.05) and dislocation densities. Surface areas were found to be in the range of 42.37–52.32 m2/g with mesoporous structures and solid bar and cross surface morphology. Optical band gaps (Eg) calculated from absorption data was found to be in the range of 4.65–4.75 eV for direct transitions whereas 4.60–4.74 eV for indirect transitions. The Eg calculated from emission data was found to be in the range of 2.42–2.67 eV. Absorption edge broadening was investigated by urbach energy (EU) calculated to be in the range of 1.23–1.51 eV whereas fermi energy (Ef) were obtained as 4.66–4.72 eV. Refractive index (n) was calculated to be in the range of 0.13–0.21 whereas high values obtained for real and imaginary parts of dielectric constants (ϵ) indicating polarization relaxation in synthesized materials. The calculated structural and optical characteristics indicates that these materials can be potential candidates for optoelectronic and catalytic applications.

Comprehensive study of Cesium-Tantalum Oxide for electronic, optical and thermoelectric properties under the effect of pressure for energy applications

The perovskites are important class of materials which are utilized for memory as well as spintronic devices. The thermoelectric response calculations for some perovskite oxides are also reported but their attributes under pressure had not really been touched. This study covers the repercussions of pressure on structure, electronic dispersions, optical constants and transport parameters of CsTaO3 perovskite oxides in cubic phase by employing semi-classical Boltzmann theory. The CsTaO3 was previously reported dynamically stable through optimization of energy against volume and phonon properties at ambient pressure conditions, having wide (direct) energy gap of 2.90 eV. This gap is decreasing with increasing pressure and behaves like the interesting diluted magnetic semiconductors. The comprehensive insights of the imaginary part of dielectric constant is predicting it’s utility in optoelectronic devices and sensors. The different transport parameters are computed in the temperature range 50 K to 1200 K with 50 K step size and pressure 0–100 GPa with 10 GPa step. The calculated power factor value and optical parameter proving CsTaO3 as a latent material for energy application.

Effect of substrate type on the physical properties of thermally evaporated CdS thin films for CdTe/CdS solar cells applications

Cadmium Sulfide (CdS) thin films were grown on crystal quartz as a nonconductive substrate, and Indium tin oxide (ITO) and Fluorine doped tin oxide (FTO) as transparent conducting oxide (TCO) films. The thin films with the thickness of 100 nm were fabricated at 150 °C under the pressure of 2 × 10−5 mbar using the thermal evaporation method. The x-ray diffraction (XRD) results showed that all grown CdS films had cubic crystal structures with the preferred orientation (111) and a crystallite size between 11.72 nm and 14.84 nm. Raman spectra also revealed an increase in peak intensity and shift toward single-crystal mode in the films grown on TCOs. The homogeneous and uniform surfaces of CdS films were shown in scanning electron microscopy (SEM) images. The optical parameters of the deposited CdS thin films such as absorption, transmission, refractive index, extinction coefficient, and real and imaginary parts of dielectric constant, were improved. The energy band gap of the films was decreased from 2.45 eV for the CdS/quartz film to 2.36 eV for the CdS/FTO one. The key electrical parameters of the deposited films on TCO, such as conductivity, mobility and carrier concentration, as calculated by the Hall effect measurement system, were enhanced too. High efficient heterojunction cadmium telluride (CdTe)-based solar cells with the experimentally grown CdS films were designed by SCAPS-1D simulator. The efficiency of the designed cells with CdS/quartz, CdS/ITO, and CdS/FTO layers was obtained to be 19.40%, 21.23%; and 21.16%, respectively. The impact of the CdTe absorber layer thickness and device temperature on the photovoltaic parameters of the simulated cells was then investigated. The optimized cell was obtained for an Au/CdTe/CdS/ITO structure with the efficiency of 22.80% by employing a 3 μm thickness of the CdTe layer at a device temperature of 300 K.

Study on the Electronic Structure and Optical Properties of (K, Rb, Cs, Fr) Doped CoSi Based on the First Principle

In this paper, the band structure, density of States and optical properties of CoSi, K, Rb, Cs and Fr doped CoSi are calculated by first principles. It is found that the bottom and top of the conduction band pass through the Fermi level before and after doping, showing metal properties. The static permittivity of undoped CoSi, K, Rb, Cs and Fr doping is 28.9,154,168,110,105 respectively, which indicates that the static permittivity is improved after doping the refractive index of doped K, Rb, Cs and Fr increases compared with that of undoped CoSi. After doping, the maximum imaginary part of dielectric constant is 18.4; 608; 56; 32.9; 31 respectively.CoSi, K-CoSi, Rb-CoSi, Cs-CoSi and Fr-Cosi have strong absorption of light in the far ultraviolet region, and the maximum absorption coefficients are 3.83, 3.69, 3.37, 3.34 and 3.33 respectively. The maximum reflection peak of undoped CoSi is 0.807, that of K-doped system is 0.774, that of Rb-doped system is 0.713, that of Cs-doped system is 0.731, and that of Fr-doped system is 0.758. It can be seen that the reflectivity of doped CoSi decreases, and the reflectivity of Rb-doped system is the smallest Compared with the undoped system, the photoconductivity of the doped system moves to the high energy region, resulting in a blue shift.

Study of the Optical properties for CdS before and after irradiated by CO2 laser for different exposure times

Cadmium sulphide (CdS) thin films were deposited on glass substrates using thermal vacuum evaporation technique at pressure (10-6) Torr at room temperature then samples irradiated by CO2 laser of power (1 watt) and wave length (10.6) μm at distance 10 cm from the source during different exposure times (3, 5, 10, 15) sec. The absorbance spectra was recorded using UV-visible spectrophotometer .Optical properties such as transmission , reflection ,absorption coefficient (α), optical band gap (Eg), extinction coefficient (K), refractive index (n), and complex dielectric constants (er&ei) were evaluated from absorbance spectra. The results shows that the laser irradiation cause increased in reflectance R, absorption coefficient a, the extinction coefficient K, the refractive index n and the real part and imaginary part of dielectric constant while irradiation cause decrease in the transmittance T and the value of the energy gap Eg.

Electronic and optical properties of double perovskites Ba[formula omitted]Sr[formula omitted]BiSbO[formula omitted] (x = 0, 1)

The electronic and optical properties of ordered double perovskites Ba2BiSbO6 and BaSrBiSbO6 have been studied using density functional theory within the generalized gradient approximation. The electronic structure calculation shows these materials to be semiconducting with an indirect band gap of 1.68 eV for Ba2BiSbO6 and 1.67 eV for BaSrBiSbO6 with spin–orbit coupling taken into account. With hybrid-functionals, the band gap rises to an insulating domain for both materials. In the density of states and band structure around the valence band maximum and conduction band minimum, the main contributions are from O−2p, Bi−6s, Bi−6p, and Sb−5s states. From optical calculations, the optical band gap obtained from the imaginary part of dielectric constants agrees fairly with the electronic band gap. Both Ba2BiSbO6 and BaSrBiSbO6 are found to be optically active in ultraviolet as well as visible regions of the incident photon energies. The noted optical response indicates these materials as possible candidates for opto-electronic devices.

Impact of ZnO Nanoparticle on the Structural and Optical Properties of Poly(vinyl alcohol) Film

Using the cast technique thin films of poly (vinyl alcohol) (PVA) containing varying amounts of Zinc Oxide ZnO nanoparticles (0.001, 0.002, 0.003, 0.004 and 0.005) g were formed. Physical properties excluded structural; (X-Ray Diffraction) (XRD), Fourier Transform Infrared (FT-IR) spectroscopy and UV-Visible spectroscopy. XRD results showed the amorphous structure of PVA film and Hexagonal crystalline structure of ZnONPs, PVA/ZnO nanocomposite appears as pattern of PVA films so the peaks of ZnO don't appear in it. FTIR spectra reveled ZnONPs doesn't have any influence on polymer structure. The effects of the ZnONPs on optical characteristics of PVA like the absorption spectrum, transmission spectrum, energy band gap, absorption coefficient, extinction coefficient, refractive index, real and imaginary parts of dielectric constant has been studied using UV-Vis spectroscopy. This study demonstrates that increasing the number of ZnONPs has an effect on all of these parameters.

EFFECT OF ERBIUM DOPING ON PHYSICAL PROPERTIES OF LaFeO3


 
 
 Multiferroic La1-xErxFeO3 (x= 0, 0.2, 0.4, 0.6, 0.8 and 1) successfully synthesized using auto combustion sol-gel citrate method. The crystalline structure examined by X-ray Diffraction (XRD) analysis is orthorhombic. Infrared (IR) active phonons for Erbium substitution in La1-xErxFeO3 studied at room temperature in frequency range 30-1000 cm-1 via Fourier transformed infrared (FTIR) spectroscopy. The experimental reflectivity spectra has been fitted using Lorentz oscillator model and obtain the parameter like damping factor, optical frequency as well as oscillator strength. Real and imaginary part of dielectric constant, optical conductivity, loss function and energy band gap in addition to transverse and longitudinal optical frequency modes have been calculated by these parameters. The frequency shift has been observed with doping concentration of Erbium in LaFeO3. Optical conductivity spectra are of semiconducting type. La1-xErxFeO3 is further characterized by UV- visible spectroscopy and electrical resistivity measurements. The optical spectrum of UV-Visible phenomena exhibits typical semiconductor behaviour. Investigation shows there is a drop in activation energy of samples if doped element Er increases. The electrical resistivity trend shows semiconducting behaviour of the sample which exhibit p-type polaronic conduction.
 
 

Preparation and Optical Studies on PAN: NaI based Gel Polymer Electrolytes

Sodium iodide (NaI) doped polymer polyacrylonitrile (PAN) based gel polymer electrolytes were synthesized with different compositions by solution cast technique. Optical characterizations were performed by UV-visible absorption spectroscopy in the wavelength range of 200-800 nm. Optical transmission, optical absorption, energy bandgap, real and imaginary parts of dielectric constants were studied on the prepared samples. Optical absorption, absorption coefficient, refractive index and extinction coefficient achieved high values for 70% PAN:30% NaI whereas some properties like transmittance and dielectric constant for imaginary parts have achieved minimum values for the same concentration.

Synthesis and characterization of copper zinc iron sulphide (CZFS) thin films

In an aqueous bath, quaternary thin films (TFs) of copper zinc iron sulphide (CZFS) were deposited on glass (soda-lime) substrates. The present study aimed to analyse the effect of deposition periods on the properties of the prepared CZFS TFs using Chemical bath deposition (CBD). The precursor and films were examined by Fourier Transform Infrared (FTIR) spectroscopy to check for the chemical formation present. Rutherford backscattering spectroscopy (RBS) was used to determine the elemental compositions and stoichiometry of the deposited films. The optical characteristics were observed by a UV-Vis Spectrophotometer and a four-point probe (FPP) for the electrical properties. The optical characterization revealed a direct transition band-gap energy that decreased from 1.96 to 1.50 eV with an increase in deposition period. The optical constants were studied with respect to the wavelength within the range of 300–900 nm. The films exhibited high resistive properties with a conductivity that varied with an increase in deposition period. The effect of deposition periods on the optical properties of refractive index, extinction coefficient, and real and imaginary parts of dielectric constants has been reported. All these parameters were found to increase with deposition period except for the film deposited for 18 h (C3). These results confirm that the aqueous deposited CZFS films can be tuned for various optoelectronic applications.

Correlated Sample-Based Prior in Bayesian Inversion Framework for Microwave Tomography

When using the statistical inversion framework in microwave tomography (MWT), generally, the real and imaginary parts of the unknown dielectric constant are treated as uncorrelated and independent random variables. Thereby, in the maximum <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a posteriori</i> estimates, the two recovered variables may show different structural changes inside the imaging domain. In this work, a correlated sample-based prior model is presented to incorporate the correlation of the real part with the imaginary part of the dielectric constant in the statistical inversion framework. The method is used to estimate the inhomogeneous moisture distribution (as dielectric constant) in a large cross section of polymer foam. The targeted application of MWT is in industrial drying to derive intelligent control methods based on tomographic inputs for selective heating purposes. One of the features of the proposed method shows how to integrate lab-based dielectric characterization, often available in MWT application cases, in the prior modeling. The method is validated with numerical and experimental MWT data for the considered moisture distributions.

SmFeO3@(x)polyaniline composites with porous structure for efficient microwave-absorbing application

SmFeO3@(x)Polyaniline(PA) composites were successfully synthesized by sol–gel self-propagating combustion and in-situ oxidation polymerization. Different contents of PA had distinct effects on the electromagnetic parameters of SmFeO3@(x)PA composites. The addition of PA not only increased the values of real and imaginary parts of dielectric constant, but also adjusted the impedance matching of SmFeO3@(x)PA composites. The effects of 50 wt%, 70 wt%, 90 wt% PA contents on the microwave-absorption properties of SmFeO3@(x)PA composites were also investigated and discussed. Due to the porous structure of dielectric-magnetic-type SmFeO3@(x)PA composites and the formation of heterogeneous interfaces, the multiple reflection and scattering of electromagnetic-wave in the composites were conducive to enhance the microwave attenuation. In all samples, SmFeO3@(70 wt%)PA composites had the strongest absorption capacity, RLmin was −31.3 dB at 6.61 GHz. The work show that the porous structure of SmFeO3@(x)PA was the key to realize the high microwave-absorption performances.

Influence of Al dopant on structural and optical parameters of AgInSe2 thin film

Chalcopyrite thin films ternary Silver Indium Diselenide AgInSe2 (AIS) pure and Aluminum Al doped with ratio 0.03 was prepared using thermal evaporation with a vacuum of 7*10-6 torr on glass with (400) nm thickness for study the structural and optical properties. X-ray diffraction was used to show the inflance of Al ratio dopant on structural properties. X-ray diffraction show that thin films AIS pure, Al doped at RT and annealing at 573 K are polycrystalline with tetragonal structure with preferential orientation (112). raise the crystallinity degree. AFM used to study the effect of Al on surfaces roughness and Grain Size Optical properties such as the optical band gap, absorption coefficient, Extinction coefficient, refractive index, real and imaginary part of dielectric constant were calculated to inspect the influence of the Aluminum on the optical Parameters of AIS thin film. UV/Visible measure show the lowering in energy gap to 1.35 eV for AgInSe2: Al at 573 K this energy gap making these samples suitable for photovoltaic application.

Annealing temperature effect on structural and optoelectronic properties of γ-In2Se3 thin films towards highly stable photodetector applications

Metal chalcogenide-based photodetectors have been studied extensively in recent years. However, the dark current, detective spectral ranges, responsivities, and response time are still unsatisfactory. Also, the major challenge for photodetector material is the deposition of large-scale material, a high-quality film with high reliability and low variability. In this work, we have synthesized Indium selenide (γ-In2Se3) thin films using the RF magnetron sputtering technique. We have thoroughly investigated the effect of annealing temperature on structural, optical, morphological, and photo-sensing properties of the synthesized thin films. Low angle XRD confirms the formation of hexagonal γ-In2Se3 films. The crystallite size increases from 56 nm to 64 nm with an increase in annealing temperature. Raman spectroscopy and XPS techniques confirm the γ phase of indium selenide. FE-SEM analysis revealed that the synthesized films are compact and uniform. Also, they are free from holes and cracks, which is necessary for semiconductor applications. The agglomeration of particles is observed with an increase in annealing temperature. The EDS spectra revealed that synthesized γ-In2Se3 films have ideal stoichiometry with In:Se ratio of 2:3. The UV–visible spectroscopy analysis showed a slight decrease in bandgap from 2.0 eV to 1.93 eV with an increase in annealing temperature. Other optical properties, such as absorption coefficient (α), extinction coefficient (k), the real and imaginary part of dielectric constant, optical conductivity, etc., of synthesized γ-In2Se3 films critically depend on the annealing temperature. Finally, the synthesized γ-In2Se3 thin films were used to fabricate photodetectors on ITO-coated interdigital electrodes. All γ-In2Se3 photodetector shows good stability and repeatability under dark and illumination conditions. The rise and decay time decrease with increase in annealing temperature. Photodetector with γ-In2Se3 thin film annealed at 300 °C exhibited excellent photoresponsivity (1.12 mA/ W) and stable photoswitching behavior. A fast rise (0.22 s) and decay time (2.85 s) were observed for the prepared photodetector. Our work demonstrates that γ-In2Se3 photodetector can be a promising material for photodetection applications.

Optical and electrochemical properties of pure and Ti-doped CdO nanoparticles for device applications

Cadmium oxide (CdO) is one among the transparent conducting oxides which is famous for its various applications in optoelectronics, gas sensors, and electrochemical sensors, etc. The present work therefore reports the synthesis and structural, optical, and electrochemical properties of pure CdO and Ti doped CdO nanoparticles which were synthesized using simple sol–gel method. The structural analysis of the prepared samples was done by using x-ray diffraction (XRD) technique. The XRD peaks revealed the existence of crystalline structure of the samples. The average crystallite sizes of the samples were calculated by considering the intense peaks observed in the XRD spectrum and they were found to be 59.45 nm and 55.25 nm for pure CdO and Ti doped CdO nanoparticles respectively. The absorption and transmission spectra of synthesized nanoparticles were recorded in the UV–VIS-NIR region. Using the absorption and transmission spectra, the optical band gap of pure CdO and Ti doped CdO were estimated as 2.14 eV and 2.99 eV respectively, using Tauc plot method. The Urbach energies were calculated, and they were found to be 1059 meV and 679 meV for the pure and Ti doped CdO nanoparticles. The optical conductivity, real and imaginary part of dielectric constant, dielectric loss tangent were also investigated using UV–VIS-NIR spectral data for the possible application in opto-electronic devices. The electrochemical performance of the samples was investigated using cyclic voltammetry (CV) technique. The specific capacitance and diffusion coefficients were calculated using the recorded cyclic voltammogram. The results of CV data showed that the maximum specific capacitance was occurred to be 390F/g at the rate 25 mV/s and 219F/g at the rate 50 mV/s for the pure and Ti-doped CdO nanomaterials respectively. The outcome of the present study provided an useful information for the possibilities of these materials in the device applications.

Iron oxide (Fe2O3) synthesized via solution-combustion technique with varying fuel-to-oxidizer ratio: FT-IR, XRD, optical and dielectric characterization

This study addresses the effect of fuel-to-oxidizer ratio (∅ =1.47, 1.57, 1.67, 1.77 and 1.87) on the structural, optical and dielectric properties of iron oxide nanoparticles synthesized through solution-combustion technique with glycine as the fuel. The synthesized samples were characterized using scanning electron microscopy, energy dispersive X-ray (EDX) spectroscopy, Fourier transform-infrared spectroscopy (FT-IR), ultraviolet–visible (UV-VIS) diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRPD) with Rietveld refinement, thermogravimetric analysis (TGA) and frequency-dependent dielectric analysis. Electron micrographs show no change in morphology with respect to ∅. The EDX results revealed the existence of Fe and O. FT-IR confirmed the metal-oxygen (M − O) functional groups of iron oxides typically present near ∼ 570 and ∼ 520 cm−1. The synthesized samples showed typical reflectance spectrum of iron oxides during UV–Vis DRS analysis, where the maximum optical band gap of 1.80 eV was displayed by Fe2O3 with ∅ = 1.67. The diffraction peaks were indexed with two phases: α-Fe2O3 and γ-Fe2O3. It was observed that the γ-phase decreased as ∅ increased. Rietveld refinement showed that ∅ = 1.47 had γ-phase as the majority (96.46 wt%), while ∅ = 1.87 had α-phase as the majority (79.90 wt%). The average crystallite size of α-phase was found to be 44.72 nm, while that of the γ-phase was 27.53 nm. The real and imaginary parts of dielectric constant, dielectric tangent loss, electric modulus, impedance and ac conductivity with respect to varying frequency were studied. All the parameters display typical trends shown by Fe-based ceramics agreeing to the Maxwell-Wagner type of interfacial polarization. The modulus studies revealed that the samples show non-Debye type relaxations and it can be concluded that these materials are well suited for high-frequency applications.

Improving the Structural, Optical and Photovoltaic Properties of Sb- and Bi- Co-Doped MAPbBr3 Perovskite Solar Cell

We prepared 1% Bi- and (0, 0.5%, 1% and 1.5%) Sb- co-doped MAPbBr3 films by a sol-gel spin coating technique. For the first time, the detailed structural properties including grain size, dislocation line density, d-spacing, lattice parameters, and volume of co-doped MAPbBr3 films have been investigated. XRD confirmed the cubic structure of MAPbBr3 with high crystallinity and co-doping of Bi and Sb. The 1% Bi and 1% Sb co-doping have a surprising effect in MAPbBr3 structures, such as large grain size (59.5 nm), d-space value (6.23 Å), small dislocation line dislocation (2.79 × 1018 m−2), and small lattice parameters (a = b = c = 6.3 Å) and volume of unit cell. The detailed optical properties, including energy band gap (Eg), refractive index (n), extinction coefficient (k) and dielectric constant (Ɛ), which are very important for optoelectronics applications, were investigated by UV-Vis spectroscopy. The film of 1% Bi and 1% Sb co-doped MAPbBr3 showed good optical response including small Eg, high n, low value of k, high real and low imaginary parts of dielectric constant, making it good for solar cell applications. Solar cells were fabricated from these films. The cell fabricated with pure MAPbBr3 has Jsc of 8.72 mA cm−2, FF of 0.66, Voc of 1.29 V, and η of 7.5%. All the parameters increased by co-doping of Bi and Sb in MAPbBr3 film. The cell fabricated with 1% Bi and 1% Sb co-doped MAPbBr3 film had high current density (12.12 mA-cm−2), open circuit voltage (Voc), fill factor (0.73), and high efficiency (11.6%). This efficiency was 65% larger than a pure MAPbBr3-based solar cell.

Influence of Thermal Annealing to Material Properties of TiO2, ZnO, and TiO2/ZnO Bilayer Films by Sol-Gel Method

This study reported on the material properties of TiO2, ZnO, and TiO2/ZnO bilayer thin films fabricated by sol-gel spin coating technique after annealing. ZnO thin films were prepared by dissolving zinc acetate dehydrated into a solvent of ethanol and diethanolamine (DEA) was later added. Meanwhile, for TiO2 films, titanium tetraisopropoxide (TTIP) was dissolved into ethanol and an acetate acid was added. Afterwards all film samples were annealed at different temperatures in the range of 400 – 600 oC for 60 minutes. For TiO2/ZnO bilayer thin films, the structural properties showed that after annealing at 600 oC, the X-RD peak intensity was more pronounced compared to at 400 and 500 oC. This indicated that the amorphous phase of the films decreased after annealing at 600 oC. Furthermore, the crystallite sizes of the films increase as the annealing temperature increased to 600 oC, while the strain reduces at this temperature. In the case of (UV-Vis) spectroscopy, it was seen that after annealing the transmittance value of the TiO2/ZnO bilayer increase. The band gap energy of the films consists of low and high energy. The low energy which is around 3.30 eV refers to the transitions of valenceconduction band in ZnO films and high energy was around 3.60 eV corresponding to the impurity transitions. In addition, the refractive index (n), the extinction coefficient (k), and the real and imaginary part of dielectric constant were determined from the transmittance and absorbance spectra results. Based on the SEM results indicate that there was no cluster in the surface of TiO2/ZnO bilayer thin films.

Dual electroactive AgM (M=Ru, Pt) NPs for double electroanalysis of HER2 and EpCAM

Parallel multiple detections of tumor markers is of significant for the efficient and accurate early monitoring of related cancers. Electrochemical aptasensors possess excellent selectivity and sensitive quantitative detection while maintaining multiple detection ability. The study of high and different electrochemical beacons is urgent to achieve multiple-level parallel detection. In this work, electroactive AgRu NPs and AgPt NPs were explored to exhibit electrooxidation peaks at 0.8 V and − 0.7 V, respectively. Plasmonic AgRu NPs and AgPt NPs harvested light energy and exhibited amplified electrooxidation activity under local surface plasmon resonance (LSPR) excitation. Plasmon-enhanced electrooxidation principle was proposed for AgM (M=Ru, Pt) NPs owing to the distinct imaginary part of dielectric constants between Ag and platinum group metals (PGM). The strong and non-interference electrooxidation peaks at 0.8 V and − 0.7 V enabled AgRu NPs and AgPt NPs to be different electroactive beacons for the sensitive and reliable quantitative dual detection of human epidermal growth factor receptor-2 (HER2) and epithelial cell adhesion molecule (EpCAM). The LODs were 0.3 pg mL−1 (7.5 amol mL−1) for EpCAM and 0.6 pg mL−1 (3.2 amol mL−1) for HER2. The proposed plasmon-promoted electrooxidation principle provides a novel route for the design of multiple electroactive plasmonic metal-PGM composite electrochemical beacons for simultaneous electroanalysis applications.