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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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Haloalkanes and aromatic hydrocarbons sensing using Langmuir–Blodgett thin film of pillar[5]arene-biphenylcarboxylic acid
摘要： Here, a pillar[5]arene derivative including biphenylcarboxylic acid groups was designed for obtaining a macrocycle with an ideal cavity for volatile organic compounds. The pillar[5]arene-biphenylcarboxylic acid (P5-BPCA) based Langmuir-Blodgett (LB) thin films were produced onto 50 nm thick gold-coated glass and 3.5 MHz quartz crystal substrates to form a thin film chemical sensor element. Surface plasmon resonance (SPR) and Quartz crystal microbalance (QCM) techniques were employed to characterize all the P5-BPCA LB thin film layers. The mass of LB film layer loaded onto a quartz crystal and the resonance frequency shifts per layer were determined to be 711.71 ng per layer (2.68 ng mm?2) and 48.24 Hz per layer, respectively. The P5-BPCA LB thin film sensor element was exposed to various haloalkane and aromatic hydrocarbon vapors. The sensitivities of the P5-BPCA LB film sensor were determined between 1.776 and 3.976 Hz ppm-1. Sensitivity with detection limits were obtained between 0.754 and 1.689 ppm against organic vapors. The results showed that P5-BPCA LB thin film was highly selective with a large response to chloromethane vapor.
关键词： Quartz Crystal Microbalance,Pillararene,Langmuir-Blodgett,Volatile Organic Compounds,Swelling,Surface Plasmon Resonance
更新于2025-09-23 15:23:52
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Direct Imaging of Surface Plasmon-Driven Hot Electron Flux on the Au Nanoprism/TiO <sub/>2</sub>
摘要： Direct measurement of hot electron flux from a plasmonic Schottky nanodiode is important for obtaining fundamental insights explaining the mechanism for electronic excitation on a surface. Here, we report the measurement of photo-induced hot electrons on a triangular Au nanoprism on TiO2 under incident light with photoconductive atomic force microscopy (pc-AFM), which is direct proof of the intrinsic relation between hot electrons and localized surface plasmon resonance. We find that the local photocurrent measured on the boundary of the Au nanoprism is higher than that inside the Au nanoprism, indicating that field confinement at the boundary of the Au nanoprism acts as a hot spot, leading to the enhancement of hot electron flow at the boundary. Under incident illumination with a wavelength near the absorption peak (645 nm) of a single Au nanoprism, localized surface plasmon resonance resulted in the generation of a higher photo-induced hot electron flow for the Au nanoprism/TiO2, compared with that at a wavelength of 532 nm. We show that the application of a reverse bias results in a higher photocurrent for the Au nanoprism/TiO2, which is associated with a lowering of the Schottky barrier height caused by the image force. These nanoscale measurements of hot electron flux with pc-AFM indicate efficient photon energy transfer mediated by surface plasmons in hot electron-based energy conversion.
关键词： hot electron,Photoconductive atomic force microscopy,localized surface plasmon resonance,Schottky diode,field confinement,Au nanoprism
更新于2025-09-23 15:23:52
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Refractive Index Sensor Based on a Gradient Grating Period Guided-Mode Resonance
摘要： In this study, we introduce a novel refractive index sensor based on gradient grating period guided-mode resonance (GGP-GMR). Rather than a constant grating period, as in typical GMR, GGP-GMR comprises a grating period varying in increments of 2 nm. For grating variation from 386 to 392 nm, a detection range of 0.109 RIU with a bulk sensitivity of 1433.7 μm/RIU and theoretical and experimental detection limits of 5.58 × 10?3 and 10?2 RIU, respectively, can be achieved. Several tactics that can be readily adopted are suggested to improve the limit of detection by an order to 10?4 RIU, sufficient for detecting many clinically relevant biomarkers. The readout system requires a narrow band of light and a simple charge-coupled device combined with the compact design of the GGP-GMR sensor, which eases the miniaturization of the system for handheld devices as well as its integration with smartphones.
关键词： Bandstop filter,guided-mode resonance,subwavelength nanostructure.
更新于2025-09-23 15:22:29
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Narrowband and Full-Angle Refractive Index Sensor Based on a Planar Multilayer Structure
摘要： This work reports a design of a narrowband and full-angle refractive index sensor based on Tamm plasmon resonance (TPR) by introducing a distributed Bragg reflector (DBR) integrated with a non-adjacent metal layer. The analyte flows into the cavity comprising of the DBR and the non-adjacent metal layer. Simulated results show that the incident light can be strongly confined in the specially designed cavity. The sharp reflection dip within the forbidden band of the isolated DBR indicates the excitation of Tamm mode, and the spectral characteristics were monitored upon exposure to various analytes with different refractive indices. The optimally designed system shows the sensitivity (S) and full width at half-maximum (FWHM) can be up to 860 nm/RIU (refractive index unit) and ~2.2 nm with a figure of merit (FOM) of 391. Furthermore, the highly-sensitive characteristic can be sustained in a wide angle range of 0° to almost 90° under both TM- and TE-polarized lights.
关键词： sensitivity,refractive index sensor,Tamm plasmon resonance,figure of merit
更新于2025-09-23 15:22:29
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Direct exposure of non-equilibrium atmospheric pressure plasma confers simultaneous oxidative and ultraviolet modifications in biomolecules
摘要： Thermal plasmas and lasers are used in medicine to cut and ablate tissues and for coagulation. Non-equilibrium atmospheric pressure plasma (NEAPP) is a recently developed, non-thermal technique with possible biomedical applications. Although NEAPP reportedly generates reactive oxygen/nitrogen species, electrons, positive ions, and ultraviolet radiation, little research has been done into the use of this technique for conventional free radical biology. Recently, we developed a NEAPP device with high electron density. Electron spin resonance spin-trapping revealed ?OH as a major product. To obtain evidence of NEAPP-induced oxidative modifications in biomolecules and standardize them, we evaluated lipid peroxidation and DNA modifications in various in vitro and ex vivo experiments. Conjugated dienes increased after exposure to linoleic and α-linolenic acids. An increase in 2-thiobarbituric acid-reactive substances was also observed after exposure to phosphatidylcholine, liposomes or liver homogenate. Direct exposure to rat liver in saline produced immunohistochemical evidence of 4-hydroxy-2-nonenal- and acrolein-modified proteins. Exposure to plasmid DNA induced dose-dependent single/double strand breaks and increased the amounts of 8-hydroxy-2'-deoxyguanosine and cyclobutane pyrimidine dimers. These results indicate that oxidative biomolecular damage by NEAPP is dose-dependent and thus can be controlled in a site-specific manner. Simultaneous oxidative and UV-specific DNA damage may be useful in cancer treatment.
关键词： 8-OHdG,HNE-modified protein,non-equilibrium atmospheric pressure plasma,electron spin resonance spin-trapping,UV
更新于2025-09-23 15:22:29
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Reflective SPR Sensor for Simultaneous Measurement of Nitrate Concentration and Temperature
摘要： In this paper, a reflective fiber optic sensor based on surface plasmon resonance (SPR) was proposed to measure nitrate concentration and temperature simultaneously. The sensor adopted reflective structure, and used gold film as metal film for exciting SPR. Then, Cu-nanoparticles/carbon nanotubes composite film was used as sensitive material to measure nitrate concentration, and it was coated on the surface of the gold film by the dip coating method. Finally, polydimethylsiloxane was coated on part of the sensing probe to produce two independent resonance dips in the output spectrum. When the nitrate concentration and temperature changed, the two resonance dips would all move, but with different sensitivities. By monitoring the wavelength shifts of the two dips, the nitrate concentration and temperature could be measured simultaneously with using the dual-wavelength matrix method. Experimental results demonstrated that the measurement sensitivity of the nitrate concentration could reach 3.25 nm/lg[M], and the temperature measurement sensitivity was ?2.02 nm/°C. Moreover, the sensor had high-mechanical strength and was easy to package, which could be applied to remote measurement field.
关键词： reflective surface plasmon resonance (SPR),optical fiber sensor,Nitrate concentration,simultaneous measurement,temperature
更新于2025-09-23 15:22:29
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Application of FRA to Improve the Design and Maintenance of Wireless Power Transfer Systems
摘要： Frequency response analysis (FRA) plays an important role in the assessment of the mechanical integrity and hence, reliability of high-voltage power transformers. Wireless power transfer (WPT) system introduced by Tesla a 100 years ago based on Faraday’s law of electromagnetic induction is similar to a conventional power transformer. Therefore, the reliability of a large WPT system can also be evaluated using FRA measurement. When the WPT system is constructed, the electrical components and the desired transfer distance need to be ascertained accurately. Furthermore, the structure of the winding and the electrical characteristic of the components in WPT systems may vary due to aging or fault events. FRA measurement can examine the discrepancy between the WPT system parameters and the reference fingerprint data to provide cost-effective condition monitoring-based maintenance scheme for the WPT systems. This paper presents a detailed circuit analysis of a two-coil inductively coupled WPT model in different compensating topologies to accomplish efficient energy transfer. Then, FRA measurement is used to detect the variation in the amplitude and the phase angle of the developed circuit input impedance in a wide frequency range. In addition, displacements due to the placement of ferrite material and the variation of the transfer distance between the transmitter and receiver units are investigated through practical measurements.
关键词： RLC resonance,inductive power transfer (IPT),Frequency response analysis (FRA),wireless power transfer (WPT)
更新于2025-09-23 15:22:29
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The Dependence of Resonance Frequency to Landing Angle in Reciprocal Scattering Phenomena of the Waves From an Elliptical Plasma Dielectric Antenna
摘要： Scattering of an electromagnetic plane wave in transverse electric mode which is obliquely incident to an elliptical plasma antenna with a dielectric rod is comprehensively investigated. The field solutions of the incident, transmitted, and the scattered waves will be derived in terms of Mathieu and modified Mathieu functions. Using asymptotic expansions of Mathieu functions, the scattering cross section per unit length is obtained. It will be shown that in such an elliptical plasma antenna, the backscattering cross section depends on the incident angle and the bistatic scattering cross section varies with scattering angle significantly. Such effects are not seen in antennas with circular cross section due to the circular symmetry in them. The validation of the presented formulations and numerical computation will be examined with the circular case that is an asymptotic well-known case. The graphs of backscattering cross section, scattering pattern, and their corresponding to the polarized charge densities are presented. The dependence of the backscattering cross section and the scattering pattern upon the density and geometrical dimension of the plasma and dielectric are investigated. In addition, it will be shown that the resonance frequencies, under which the plasma antenna response will be maximum, essentially depend on the incident angle of the incident wave.
关键词： dielectric rod,resonance frequency,polarized charge density,Backscattering cross section,scattering pattern,elliptical plasma antenna
更新于2025-09-23 15:22:29
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Investigation of a low cost tapered plastic fiber optic biosensor based on manipulation of colloidal gold nanoparticles
摘要： We demonstrate a low cost Tapered Fiber Optic Biosensor (TFOBS) based on manipulation of colloidal gold nanoparticle in the evanescent field of tapered fiber. The sensor consists of a biconical tapered plastic optical fiber with colloidal gold nanoparticles coated on the tapered region. The strength of evanescent field absorption as a function of gold nanoparticle size is evaluated using Finite Difference Time Domain simulation. Simulation results suggest that in order to achieve maximum absorption in visible range of wavelength, the size of the gold nanoparticle should be in the range 3-4 nm. Gold nanoparticle of desired size is then synthesized and coated on the tapered region to fabricate a TFOBS. It is found experimentally that coating of gold nanoparticles enhances the fraction of light coming out to the cladding surface. This is explained as a consequence of local surface plasmonic resonance. The TFOBS is then tested for its sensing application to detect Bovine Serum Albumin. Level of detection of the proposed sensor is calculated and is found as 0.326gm/dL.As normal albumin level in healthy human blood serum is between 3.5 to 5.5gm/dL, the proposed TFOBS can be used as a low cost accurate albumin sensor.
关键词： Tapered Fiber Optic Sensor,Local Surface Plasmon Resonance,Manipulation of nanoparticle
更新于2025-09-23 15:22:29