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<sup>125</sup> Te nuclear magnetic resonance and impedance spectroscopy study of topological insulator Bi <sub/>2</sub> Te <sub/>3</sub> nanoparticles mixed with insulating Al <sub/>2</sub> O <sub/>3</sub> nanoparticles
摘要： We have studied topological insulator Bi2Te3 nanoparticles mixed with insulating Al2O3 nanoparticles by means of 125Te nuclear magnetic resonance (NMR) and impedance spectroscopy. Our 125Te NMR lineshape measurements revealed the Knight shift of a satellite peak that increased with the mixing ratio of the Al2O3 nanoparticles, indicating that the mixing increases the surface-to-volume ratio of the Bi2Te3 nanoparticles. It is also shown that the impedance spectroscopy can be employed as a simple and effective means of distinguishing the surface electrical properties of the topological insulators in general.
关键词： surface electrical properties,topological insulator Bi2Te3 nanoparticles,125Te nuclear magnetic resonance,impedance spectroscopy
更新于2025-09-23 15:23:52
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Effect of Nb-doping on the structural and electrical properties of Ba0.97La0.02Ti1-xNb4x/5O3 ceramics at room temperature synthesized by molten-salt method
摘要： We, herein, report on the structural and electrical properties of Ba0,97La0.02Ti1-xNb4x/5O3 ceramics prepared by the molten-salt method. The XRD patterns of the samples at room temperature showed a single perovskite phase having a tetragonal structure with a P4/mmm space group. The electrical properties were studied by complex impedance spectroscopy in the frequency range (1–107Hz) at room temperature. The real and imaginary parts of impedance decreased with increasing Nb concentration. The complex impedance plot exhibited a single impedance semicircle for each compound, identified over the high and medium frequencies followed by a linear section, at low frequency, is explained by Warburg’s element. The study of the normalization curves of impedance and electrical modulus showed a mismatch of both peaks, which suggests the presence of short-range motion of charge carriers. The electrical conductivity decreased with increasing niobium amount and the experimental data were fitted using Jonscher’s universal power law. The exponent n is slightly superior to 1, indicating that the hopping occurs between neighboring sites.
关键词： molten-salt,conductivity,Ba0.97La0.02Ti1-xNb4x/5O3,EIS spectrum,impedance spectroscopy,Warburg element
更新于2025-09-23 15:22:29
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Properties of Porous Silicon Precipitated with Nickel for Gas Sensors
摘要： The preparation and properties of modified porous silicon is discussed and a proposal of a sensitive layer for a gas detector is presented. The modification is done by precipitation and electrochemical deposition of nickel. The morphology of sample surfaces is examined by atomic force microscopy and scanning electron microscopy (SEM). SEM-coupled energy dispersive spectroscopy is used to analyse the chemical composition of the samples. Magnetic response is measured with a SQUID magnetometer. Electrochemical impedance spectroscopy is used to study the sensitivity of the samples to isopropanol vapour in the presence of alternating electric current. A series of samples prepared with a higher anodic current density show higher sensitivity to isopropanol vapours in comparison to a lower anodic current.
关键词： Electrochemical Impedance Spectroscopy,Porous Silicon,Gas Sensors,SQUID,Electroless Nickel Deposition,Atomic Force Microscopy
更新于2025-09-23 15:22:29
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Impedance Spectroscopy: A Versatile Technique to Understand Solution-Processed Optoelectronic Devices
摘要： Solution-processed optoelectronic devices based on conjugated polymers, colloidal quantum dots (CQDs), halide perovskites, and so on are now emerging as a new-generation semiconductor technology which prevails its conventional counterparts in terms of low fabrication cost, ease of scalable manufacturing, and abundant material designability. However, the solution-processed thin films obtained through spin-coating, spray, inkjet printing, and doctor blading usually suffer from low film quality and a high defect density especially at the interfaces of different functional layers. Currently, the most significant subject is to address the non-ideal interfaces for achieving improved performance of the devices. Impedance spectroscopy (IS) is a universal technique that can help to examine the charge behavior at the interfaces in an electrochemical or solid-state multilayered device. Owing to its ability to elucidate the charge transfer, charge transport, and accumulation within the interfaces of electrochemical or multilayered devices with minimal effects to the devices themselves, the use of IS has increased vividly in the last decades. This review provides the basic principles of IS and its applications on solution-processed optoelectronic devices.
关键词： optoelectronic devices,metal halide perovskites,quantum dots,impedance spectroscopy,solution processing
更新于2025-09-23 15:22:29
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Effect of pH Values on the Structural, Optical and Electrical Properties of SnO2 Nanostructures
摘要： In the present work, we have synthesized the SnO2 nanostructures via precipitation method under optimal conditions at different pH values (3, 7 and 11) and studied the effect of different pH values on the structural, optical and electrical properties. The prepared samples are characterized by XRD, FESEM, TEM, PL, UV–Visible, FTIR spectroscopy and EIS measurements. XRD analysis reveals the tetragonal crystal structure for the prepared SnO2 nanostructures. TEM images show that the morphology of SnO2 nanostructures changed from spherical to hexagonal as pH values increased from 3 to 11. The deconvoluted PL spectra show various defects present in the synthesized samples that act as luminescent centers. The absorption spectra revealed that the maximum optical band-gap is obtained for SnO2 nanostructures synthesized using acidic solutions. The FTIR spectrum verifies the presence of stretching vibration mode of O-Sn-O bond and, stretching and bending bonds of O-H bonds in the prepared samples. A detailed exploration on frequency and temperature dependent impedance properties of SnO2 nanostructures has been done with the change in pH values.
关键词： Impedance spectroscopy,SnO2,PL,TEM,pH values,Nanostructures,FESEM
更新于2025-09-23 15:21:21
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Exploiting lateral current flow due to doped layers in semiconductor devices having crossbar electrodes
摘要： Organic electronic devices such as light-emitting diodes, solar cells or rectifying diodes normally have a sandwich layer architecture stacked between the electrodes in a crossbar layout. Often however, the side effects of operating the devices in such an arrangement are either ignored or give rise to misinterpretations regarding the device performance or layer quality. For the sake of simplicity, device currents are typically assumed to exclusively flow in the direction vertical to the substrate, even though the conductivity of doped organic layers is high and gives rise to significant lateral current flows. Here, we study the vertical and lateral charge up along the n-doped and the p-doped layers as well as the resulting capacitance increase of charging the intrinsic layer outside the active area. We observe that controlling such lateral charging by structuring the doped layers can reduce the leakage current dramatically. We employ impedance spectroscopy to investigate the lateral charging responsibility for the capacitance increase at low frequencies. Modeling of the devices by a distributed RC circuit model yields information about the thickness, the conductivity, and the corresponding activation energy of both, the n-doped and the p-doped layers, simultaneously. We demonstrate that the capacitive effects from lateral charging can easily be misinterpreted as trap states in capacitance frequency characteristics. However, correct analysis with the proposed model actually yields rich and detailed post-fabrication information which can be utilized in device failure and degradation tests. Moreover, our results will aid the design and characterization of new electronic devices where lateral charge flow is part of the device concept.
关键词： Parasitic current,Leakage current,Impedance spectroscopy,Crossbar electrodes,Lateral current flow,Organic light-emitting diode,Capacitance,Organic solar cell,Structuring
更新于2025-09-23 15:21:21
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Fluorinating ??a??Extended Molecular Acceptors Yields Highly Connected Crystal Structures and Low Reorganization Energies for Efficient Solar Cells
摘要： The synthesis and characterization of new semiconducting materials is essential for developing high-efficiency organic solar cells. Here, the synthesis, physiochemical properties, thin film morphology, and photovoltaic response of ITN-F4 and ITzN-F4, the first indacenodithienothiophene nonfullerene acceptors that combine π-extension and fluorination, are reported. The neat acceptors and bulk-heterojunction blend films with fluorinated donor polymer poly{[4,8-bis[5-(2-ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b′]-dithiophene-2,6-diyl]-alt-[2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]]} (PBDB-TF, also known as PM6) are investigated using a battery of techniques, including single crystal X-ray diffraction, fs transient absorption spectroscopy (fsTA), photovoltaic response, space-charge-limited current transport, impedance spectroscopy, grazing incidence wide angle X-ray scattering, and density functional theory level computation. ITN-F4 and ITzN-F4 are found to provide power conversion efficiencies greater and internal reorganization energies less than their non-π-extended and non-fluorinated counterparts when paired with PBDB-TF. Additionally, ITN-F4 and ITzN-F4 exhibit favorable bulk-heterojunction relevant single crystal packing architectures. fsTA reveals that both ITN-F4 and ITzN-F4 undergo ultrafast hole transfer (<300 fs) in films with PBDB-TF, despite excimer state formation in both the neat and blend films. Taken together and in comparison to related structures, these results demonstrate that combined fluorination and π-extension synergistically promote crystallographic π-face-to-face packing, increase crystallinity, reduce internal reorganization energies, increase interplanar π–π electronic coupling, and increase power conversion efficiency.
关键词： impedance spectroscopy,organic solar cells,crystal structures,femtosecond transient absorption spectroscopy,computational chemistry
更新于2025-09-23 15:21:01
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Enhanced stability and efficiency in inverted perovskite solar cells through graphene doping of PEDOT:PSS hole transport layer
摘要： Poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) plays a relevant role in the device performance as hole extraction layer (HTL) of inverted perovskite solar cells. Here, we show a simple low-temperature spin coating method for obtaining homogenous graphene-doped thin films of PEDOT:PSS with improved electrical conductivity without decreasing optical transmittance. Moreover, the crystallinity and stability in ambient conditions of the perovskite grown on it are enhanced. The hydrophobic character of graphene probably blocks undesirable reactions hampering degradation. By impedance spectroscopy it is demonstrated better charge extraction and reduction of recombination mechanisms at the doped-HTL/perovskite interface, resulting in improved photovoltaic parameters of the solar cell and greater stability at room operation conditions thus providing a simple and cost-effective method of preparing solar cells based on hybrid perovskites.
关键词： perovskite solar cell,PEDOT:PSS,doping,graphene,hole transport layer,impedance spectroscopy
更新于2025-09-23 15:21:01
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Laser-Induced Graphene Electrochemical Immunosensors for Rapid and Label-Free Monitoring of <i>Salmonella enterica</i> in Chicken Broth
摘要： Food-borne illnesses are a growing concern for the food industry and consumers, with millions of cases reported every year. Consequently, there is a critical need to develop rapid, sensitive, and inexpensive techniques for pathogen detection in order to mitigate this problem. However, current pathogen detection strategies mainly include time-consuming laboratory methods and highly trained personnel. Electrochemical biosensors offer a rapid, low-cost alternative to laboratory techniques, but the electrodes used in these biosensors require expensive nanomaterials to increase their sensitivity, such as noble metals (e.g., platinum, gold) or carbon nanomaterials (e.g., carbon nanotubes, or graphene). Herein, we report the fabrication of a highly sensitive and label-free laser-induced graphene (LIG) electrode that is subsequently functionalized with antibodies to electrochemically quantify the food-borne pathogen Salmonella enterica serovar Typhimurium. The LIG electrodes were produced by laser induction on the polyimide film in ambient conditions and, hence, circumvent the need for high-temperature, vacuum environment, and metal seed catalysts commonly associated with graphene-based electrodes fabricated via chemical vapor deposition processes. After functionalization with Salmonella antibodies, the LIG biosensors were able to detect live Salmonella in chicken broth across a wide linear range (25 to 105 CFU mL?1) and with a low detection limit (13 ± 7 CFU mL?1; n = 3, mean ± standard deviation). These results were acquired with an average response time of 22 min without the need for sample preconcentration or redox labeling techniques. Moreover, these LIG immunosensors displayed high selectivity as demonstrated by nonsignificant response to other bacteria strains. These results demonstrate how LIG-based electrodes can be used for electrochemical immunosensing in general and, more specifically, could be used as a viable option for rapid and low-cost pathogen detection in food processing facilities before contaminated foods reach the consumer.
关键词： biosensor,foodborne pathogens,graphene,food safety,Salmonella Typhimurium,electrochemical impedance spectroscopy
更新于2025-09-23 15:21:01
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Enhanced efficiency in dye-sensitized solar cell by localized surface plasmon resonance effect of gold nanoparticles
摘要： Strong localized surface plasmon resonance (LSPR) ˉeld, which is generated from gold nanoparticles, may enhance photons absorption of dyes in dye-sensitized solar cells (DSSCs), resulting in the improvement of their power conversion e±ciency (PCE). In this paper, we report the incorporation of oleylamine capped gold nanoparticles (AuOA NPs) into the N-719 dye layer in DSSCs. The cells were prepared by varying the weight percentage of AuOA NPs with respect to the dye weight in dye solutions. The dye solutions containing 1.44 wt.%, 1.92 wt.% and 2.4 wt.% of AuOA NPs exhibited an enhancement in their absorption spectra in the UV-Visible range, which may be the result of the excitation of localized SPR. The J (cid:1) V characteristics of those DSSCs show an enhancement in their photocurrent along with their PCE, from 4.18% to 5.14% for the cells made from the dye solutions without AuOA and with addition of 2.4 wt.% of AuOA, respectively. This improvement is due to the enhancement of light absorption and hence charge carrier generation by the Plasmonic wave generated by AuOA NPs through the LSPR phenomenon.
关键词： gold nanoparticles,impedance spectroscopy,localized surface plasmon resonance,J (cid:1) V characteristics,Dye-sensitized solar cells
更新于2025-09-23 15:21:01