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A Nanostructured Gold/Graphene Microfluidic Device for Direct and Plasmonic-Assisted Impedimetric Detection of Bacteria
摘要： Hierarchical 3D gold nano-micro islands (NMIs) are favourably structured for direct and probe-free capture of bacteria in optical and electrochemical sensors. Moreover, their unique plasmonic properties make them a suitable candidate for plasmonic-assisted electrochemical sensors, yet the charge transfer needs to be improved. In the present study, we propose a novel plasmonic-assisted electrochemical impedimetric detection platform based on hybrid structures of 3D gold NMIs and graphene (Gr) nanosheets for probe-free capture and label-free detection of bacteria. The inclusion of Gr nanosheets significantly improves the charge transfer, addressing the central issue of using 3D gold NMIs. Notably, the 3D gold NMIs/Gr detection platform successfully distinguishes between various types of bacteria including Escherichia coli (E. coli) K12, Pseudomonas putida (P. putida) and Staphylococcus epidermidis (S. epidermidis) when electrochemical impedance spectroscopy is applied under visible light. We show that distinguishable and label-free impedimetric detection is due to dissimilar electron charge transfer caused by various sizes, morphologies, and compositions of the cells. In addition, the finite-difference time-domain (FDTD) simulation of the electric field indicates the intensity of charge distribution at the edge of the NMI structures. Furthermore, the wettability studies demonstrated that contact angle is a characteristic feature of each type of captured bacteria on the 3D gold NMIs, which strongly depends on the shape, morphology, and size of the cells. Ultimately, exposing the platform to various dilutions of the three bacteria strains, revealed the ability to detect dilutions as low as ~20 CFU/mL in a wide linear range of detection of 2(cid:3)101-105, 2(cid:3)101-104 and 1(cid:3)102-1(cid:3)105 CFU/mL for E. coli, P. putida, and S. epidermidis, respectively. The proposed hybrid structure of 3D gold NMIs and Gr combined by novel plasmonic and conventional impedance spectroscopy techniques open interesting avenues in ultrasensitive label-free detection of bacteria with low cost and high stability.
关键词： Label-free bacteria detection,Hierarchical gold nano-micro islands,Surface properties,Impedance spectroscopy,plasmonic-assisted electrochemical detection platform
更新于2025-09-23 15:19:57
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Impedimetric detection of Banana bunchy top virus using CdSe quantum dots for signal amplification
摘要： Banana bunchy top virus is considered to be the most economically destructive pathogens of banana that causes severe economic loss in banana plantations worldwide, including India. In this present study we have developed an improved electrochemical ELISA for detection of Banana bunchy top virus (BBTV). For enhanced and accurate detection we have used cadmium selenide (CdSe) quantum dots (QDs) as signal amplifiers. Experiments in this study were performed using primary antibody raised from recombinant coat protein of BBTV. CdSe QDs could significantly amplify the electrical signals in this assay and make the method appropriate for lab use. The result of electrical conduction showed the difference of impedance between the healthy and diseased sample of the order of ~ 100 Ω. The electrochemical ELISA could detect the virus in plant sap up to dilution of 1:25 as compared to 1:10 of conventional ELISA.
关键词： Faradic impedance spectroscopy,Cadmium selenide quantum dots (CdSe QDs),Banana bunchy top virus
更新于2025-09-23 15:19:57
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Electrochemical Immunosensor for Human IgE Using Ferrocene Self-Assembled Monolayers Modified ITO Electrode
摘要： The immunoglobulin E (IgE) level in serum is an important factor in the examination of allergy. Ferrocene (Fc)-modified self-assembled monolayers (SAMs) were placed on an indium tin oxide (ITO) electrode as a sensing layer for the detection of human IgE. The Fc moiety in the SAMs facilitated the electron transfer through the organic SAMs layer and electrocatalytic signal amplification. The electrochemical measurement was accomplished after the sandwich type immobilization of the receptor antibody, target human IgE, and enzyme conjugated secondary antibody. The enzyme product, p-aminophenol, was quantitatively analyzed by redox cycling via Fc. In addition, the electrochemical impedance spectroscopy (EIS) was investigated for the detection of IgE. The limit of detection (LOD), limit of quantification (LOQ), and dynamic range of the electrochemical sensor were 3 IU/mL, 10 IU/mL, and from 10 IU/mL to 100 IU/mL, respectively.
关键词： electrocatalytic reaction,indium tin oxide (ITO),human immunoglobulin E,electrochemical impedance spectroscopy,ferrocene
更新于2025-09-23 15:19:57
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How Reproducible are Electrochemical Impedance Spectroscopic Data for Dye-Sensitized Solar Cells?
摘要： Dye-sensitized solar cell (DSC) technology has been broadly investigated over the past few decades. The sandwich-type structure of the DSC makes the manufacturing undemanding under laboratory conditions but results in the need for reproducible measurements for acceptable DSC characterization. Electrochemical impedance spectroscopy (EIS) offers the possibility to study complex electronic systems and is commonly used for solar cells. There is a tendency in the literature to present impedance data only for one representative device. At the same time, as current density–voltage plots illustrate, measurements can vary within one set of DSCs with identical components. We present multiple DSC impedance measurements on “identical” devices prepared using two different dyes and present a statistical analysis regarding the reproducibility.
关键词： dye,statistical analysis,dye-sensitized solar cells,electrochemical impedance spectroscopy
更新于2025-09-23 15:19:57
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Dielectric Response of ZnTea??Ti/Al Schottky Junctions with CdTe Quantum Dots Studied by Impedance Spectroscopy
摘要： The electrical properties of ZnTe–Ti/Al Schottky junctions were investigated by the impedance spectroscopy (IS) method. Current-voltage (I-V) and capacitance-voltage (C-V) measurements were also performed. The studied samples were the CdTe quantum dot structures embedded in ZnTe matrix and a reference ZnTe sample without quantum dots. C-V characteristics confirmed the presence of quantum dots (QDs) in the structures. Electric modulus and impedance data were analyzed. IS studies proved that long-range conductivity governs the relaxation processes in the junctions. For both samples, the data were fitted with a simple RC circuit composed of a depletion layer capacitance in parallel with bulk resistance and a series resistance of contacts. The activation energy of the relaxation process observed for the reference sample obtained from the Arrhenius plot of the resistance, imaginary impedance, and electric modulus equals 0.4 eV at zero bias. For the quantum dot sample, the value of activation energy determined with the help of the same methods equals 0.2 eV. In conclusion, it was assumed that the relaxation processes for the reference sample are attributed to the trap present in ZnTe host material, whereas those observed for the QD structure are assigned to the deep level associated with defects located close to the QDs created during their growth.
关键词： quantum dots,defects,impedance spectroscopy,CdTe,ZnTe
更新于2025-09-23 15:19:57
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A Comparative Study via Photophysical and Electrical Characterizations on The Interfacial and Bulk Exciplex-Forming Systems for Efficient Organic Light-Emitting Diodes
摘要： An efficient organic light-emitting diode (OLED) based on BCzPh:CN-T2T exciplex as emitting layer (EML) has been fabricated by exploiting the charge balance and favorable molecular orientations. To further understand the details of the exciplex-forming mechanism, time-resolved photoluminescence (TRPL), capacitance-voltage (CV), impedance spectroscopy (IS), and transient electroluminescence (EL) measurements were used to probe the photophysical and electrical characteristics of EL devices incorporating interfacial- (BCzPh/CN-T2T) and bulk- (BCzPh:CN-T2T) exciplex as emitting layer. The interfacial- and bulk-exciplex devices reveal maximum external quantum efficiency (EQE) of 7.7% and 26.4%, respectively. The reason for different device performance was rationalized by comparing the amount of charge density accumulated at the EML’s interface responsible to exciplex emission. In addition, the TRPL measurement monitored from short to long wavelength was used to explore the harvest of non-radiative triplet back to singlet via reverse intersystem crossing as well as to examine the efficiency of delayed fluorescence. The bulk-exciplex system showed a distinct delayed fluorescence as compared to that of the interfacial one, which was also corroborated by the observation in the transient EL. The result indicates that bulk-exciplex can reduce the accumulated charge in EML rapidly, resulting in the improvement of EL efficiency. This assumption was further verified by the CV and IS measurements. Our results reveal that the accumulated charge density as well as the bulk resistance of the bulk-exciplex device are much lower as compared to those of the interfacial counterpart device.
关键词： transient photoluminescence,impedance spectroscopy,Interfacial exciplex,transient electroluminescence,bulk exciplex
更新于2025-09-23 15:19:57
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AIP Conference Proceedings [Author(s) PROCEEDINGS OF THE 3RD INTERNATIONAL SYMPOSIUM ON CURRENT PROGRESS IN MATHEMATICS AND SCIENCES 2017 (ISCPMS2017) - Bali, Indonesia (26–27 July 2017)] - Room temperature electrical behaviour of La0.9Sr0.1Fe1-xMoxO3 (x = 0.1, 0.2, 0.3) perovskite material
摘要： The synthesis and electrical properties of La0.9Sr0.1Fe1-xMoxO3 (LSFMO) (x = 0.1, 0.2, 0.3) perovskite materials have been studied. The samples were synthesized by sol-gel and sintering method. The structural properties were investigated by X-ray Diffraction (XRD) and X-ray Fluorescence (XRF). XRD characterization results in orthorhombic crystal structure (space group Pnma) for all samples and the crystallite sizes in the range of 40 - 60 nm. XRF result shows the atomics ration and mass ration is suitable for stoichiometric of La0.9Sr0.1Fe1-xMoxO3. The electrical behavior of LSFMO at room temperature was measured by impedance spectroscopy method using RLC meter. Impedance data were represented in the Nyquist plot. The impedance absolute values of LSFMO increase from increasing to Mo-doped. Finally, from the dielectric studies, it is observed that the dielectric constant (ε’) decreases and dielectric loss (tan δ) increases with an increase of Mo-doped.
关键词： impedance spectroscopy,dielectric,La0.9Sr0.1Fe1-xMoxO3
更新于2025-09-19 17:15:36
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Electrochemical Impedance Characterization of Cell Growth on Reduced Graphene Oxide–Gold Nanoparticles Electrodeposited on Indium Tin Oxide Electrodes
摘要： The improved binding ability of graphene–nanoparticle composites to proteins or molecules can be utilized to develop new cell-based assays. In this study, we fabricated reduced graphene oxide–gold nanoparticles (rGO-AuNP) electrodeposited onto a transparent indium tin oxide (ITO) electrode and investigated the feasibility of the electrochemical impedance monitoring of cell growth. The electrodeposition of rGO–AuNP on the ITO was optically and electrochemically characterized in comparison to bare, rGO-, and AuNP-deposited electrodes. The cell growth on the rGO–AuNP/ITO electrode was analyzed via electrochemical impedance measurement together with the microscopic observation of HEK293 cells transfected with a green fluorescent protein expression vector. The results showed that rGO–AuNP was biocompatible and induced an increase in cell adherence to the electrode when compared to the bare, AuNP-, or rGO-deposited ITO electrode. At 54 h cultivation, the average and standard deviation of the saturated normalized impedance magnitude of the rGO–AuNP/ITO electrode was 3.44 ± 0.16, while the value of the bare, AuNP-, and rGO-deposited ITO electrode was 2.48 ± 0.15, 2.61 ± 0.18, and 3.01 ± 0.25, respectively. The higher saturated value of the cell impedance indicates that the impedimetric cell-based assay has a broader measurement range. Thus, the rGO–AuNP/ITO electrode can be utilized for label-free and real-time impedimetric cell-based assays with wider dynamic range.
关键词： gold nanoparticle,graphene oxide,electrochemical impedance spectroscopy,cell-based assay,electrodeposition
更新于2025-09-19 17:15:36
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Flash Sintering Samaria-Doped Ceria–Carbon Nanotube Composites
摘要： Composite ceramic green pellets were prepared by attrition milling a mixture of (CeO2)0.8(Sm2O3)0.2 (samaria-doped ceria, SDC) ceramic powder and carbon nanotubes (CNTs), followed by uniaxial and isostatic pressing. The pellets were sintered inside a dilatometer by applying AC electric fields at 850 °C and limiting the electric current to 1 A, achieving 20.2% final shrinkage. The SDC samples reached 13.3% shrinkage under the same conditions. Higher average grain sizes were measured in specimens flash sintered with CNTs. Impedance spectroscopy analyses show that the specimens flash sintered with addition of CNTs have higher electrical conductivity. Higher delivered Joule heating at the interfaces due to the presence of the electronic conductors (CNTs) are proposed as the main reason for that improvement of the electrical behavior.
关键词： flash sintering,solid electrolytes,carbon nanotubes,impedance spectroscopy,samaria-doped ceria
更新于2025-09-19 17:15:36
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Photosensitizing Dye: Its Voltammetric Behavior and Determination in Cosmetics
摘要： We developed a method that uses electrochemical impedance spectroscopy (EIS) to choose an electrode to determine photosensitizing dye No. 201 (quaternium-73), a thiazolium derivative, in cosmetics. The method is based on nanoparticle metal oxide (tin, cerium, cobalt, iron, and nickel)-modified carbon paste electrodes. Using differential pulse voltammetry (DPV), we found that the electrocatalytic property of tin oxide was better than that of the other metal oxides tested. When the proposed method was used to determine photosensitizing dye No. 201 in commercial cosmetics, the results were comparable to those obtained using high-performance liquid chromatography with ultraviolet detection.
关键词： cosmetics,Nanoparticle metal oxide-modified carbon-paste electrodes,photosensitizing dye,electrochemical impedance spectroscopy
更新于2025-09-19 17:15:36