Width Of Resonance Peak Research Articles

Resonant tunneling properties of laser dressed hyperbolic Pöschl-Teller double barrier potential

We examine the resonant tunneling properties of the laser-dressed hyperbolic Pöschl-Teller double quantum barrier structure. We use the non-equilibrium Green's function method to investigate structure parameters and electric field bias on the transmission properties of the system. The transmission probabilities and resonance energy levels are significantly influenced by the well widths and barrier heights. The barrier height increases, resonance energy levels shift toward higher values, and the resonance peak width narrows, leading to sharper and more selective tunneling behavior. Our results show that increasing the electric field bias leads to a decrease in the transmission probability at the first resonance peak, but this effect is not as strong for the subsequent peaks. Moreover, we find that changes in the laser field's parameter and structure parameters allow for fine control over the electronic spectra, allowing for modifications like red or blue shifts based on particular needs. The significance of comprehending the interaction among structural factors, external fields, and transmission qualities in quantum barrier structures is highlighted by our research, providing valuable information for the development and enhancement of electronic and optoelectronic systems with customized functionality. Our findings show the laser field has a considerable impact on resonant tunneling properties, opening the door to new device applications.

Influence of relativistic effects on photoionization process of hydrogen-like ions in plasma environment

In this study, the photoionization cross sections of C<sup>5+</sup>, Al<sup>12+</sup>, and W<sup>73+</sup> ions in a Debye plasma environment are calculated in the dipole approximation. The main emphasis is placed on investigating the influence of relativistic effects on shape resonances, Cooper minima, and virtual state effects. The relativistic effects lead to fine-structure splittings, allowing the appearance of double-shape resonance peaks in the total cross-section. Because the width and energy position of resonance peak are affected by the near critical screening length, the increase of nuclear charge Z leads to the significant differences in the size, width, and position of the double-shape resonance peak. The energy position of Cooper minimum in the photoelectrons is related to the critical screening length corresponding to the final continuum state. Unlike the deeper minima observed in the total photoionization cross-sections for C<sup>5+</sup> and Al<sup>12+</sup> ions, for the higher nuclear charge of W<sup>73+</sup> ions, the significant fine-structure splitting arising from relativistic effects results in substantial differences in the positions of the Cooper minima in the partial cross-sections. Therefore, when superimposed on the total cross section, these minima appear shallower. The W<sup>73+</sup> ion has a higher nuclear charge, and the screening length related to the virtual state effect is completely different from that of C<sup>5+</sup> ion and Al<sup>12+</sup> ion. Moreover, for the same screening length, there is a significant difference in the virtual state enhancement amplitude between C<sup>5+</sup> ion and Al<sup>12+</sup> ion in the low energy region .

Properties of hydrated poly(2-methoxyethyl acrylate) observed by 13C-nuclear magnetic resonance spectroscopy

It is well-known that poly(2-methoxyethyl acrylate) (PMEA) exhibits excellent blood compatibility and various investigations have examined the underlying mechanism of this compatibility in terms of the water structure in PMEA and/or inherent PMEA properties. However, information regarding the dynamic properties of the PMEA remains limited. This study was performed to clarify the effect of water molecules on the structure and dynamic properties of hydrated PMEA by comparing dry PMEA using temperature-variable 13C nuclear magnetic resonance spectroscopy (13C-NMR) with a solution probe at 15 –45 °C. Hydration changed the chemical shift values of the four carbons in the PMEA side chain (−COOCH2 CH2OCH3). Investigations of spin-lattice relaxation times and resonance peak widths showed that hydration increased PMEA mobility and the side chain mobility markedly changed at approximately 30 °C, especially in dry PMEA.

SPR Sensor Based on a Tapered Optical Fiber with a Low Refractive Index Liquid Crystal Cladding and Bimetallic Ag-Au Layers.

This paper presents a study of the influence of bimetallic layer covers of a tapered optical fiber surrounded by a low refractive index liquid crystal on the properties of light propagation in the taper structure. This research follows previous works on the effect of monometallic thin films (Au and Ag). In this case, the total thicknesses of the bimetallic layers were h = 10 nm, and the participation of gold and silver was equal. The films were deposited on one side of the tapered waist area. The liquid crystal cells were controlled with a voltage U from 0 to 200 V, with and without amplitude modulation at a frequency of fmod = 5 Hz. For the purposes of this research, spectral characteristics were obtained for a wavelength λ ranging from 550 to 1200 nm. Measurements were carried out at room temperature for three types of rubbed layers orientation—orthogonal, parallel, and twist in relation to the fiber axis. Obtained resonant peaks were compared with the previous results regarding the resonant wavelength, peak width, SNR, and maximum absorption. In the presented paper, the novelty is mainly focused on the materials used and their time stability, as well as corresponding changes in the technological parameters used.

High spectral and spatial resolution MRI of prostate cancer: a pilot study.

High spectral and spatial resolution (HiSS) MRI is a spectroscopic imaging method focusing on water and fat resonances that has good diagnostic utility in breast imaging. The purpose of this work was to assess the feasibility and potential utility of HiSS MRI for the diagnosis of prostate cancer. HiSS MRI was acquired at 3 T from six patients who underwent prostatectomy, yielding a train of 127 phase-coherent gradient echo (GRE) images. In the temporal domain, changes in voxel intensity were analyzed and linear (R) and quadratic (R1, R2) quantifiers of signal logarithm decay were calculated. In the spectral domain, three signal scaling-independent parameters were calculated: water resonance peak width (PW), relative peak asymmetry (PRA), and relative peak distortion from ideal Lorentzian shape (PRD). Seven cancer and five normal tissue regions of interest were identified in correlation with pathology and compared. HiSS-derived quantifiers, except R2, showed high reproducibility (coefficients of variation, 5%-14%). Spectral domain quantifiers performed better than temporal domain quantifiers, with receiver operator characteristic areas under the curve ranging from of 0.83 to 0.91. For temporal domain parameters, the range was 0.74 to 0.91. Low absolute values of the coefficients of correlation between monoexponential decay markers (R, PW) and resonance shape markers (PRA, PRD) were observed (range, 0.23-0.38). The feasibility and potential diagnostic utility of HiSS MRI in the prostate at 3 T without an endorectal coil was confirmed. Weak correlation between well-performing markers indicates that complementary information could be leveraged to further improve diagnostic accuracy.

Определение коэффициентов затухания по измеренным частотным характеристикам обмоток силовых трансформаторов. Ч. 2. Анализ результатов измерений

In the first part of the article, based on the results of theoretical studies performed for a simplified transformer winding equivalent scheme, it was shown that the damping factors can be estimated from the width of the resonant peaks of the frequency responses of the module and the reactive component of the voltage at the midpoint of the equivalent scheme, as well as the active component of the input admittance and neutral current of the considered resonant scheme. In this part of the article, the practical possibility of applying the obtained theoretical relations between the damping factors and the width of resonant peaks in relation to the frequency responses of power transformer windings is considered. The results of calculations of the damping factors at the two power transformers made by using the fitting of the free component of transient voltage and by determining the width of the resonance peaks of the active component of winding neutral current and the voltage transfer function, corresponding to intermediate points of the winding. It is shown that the evaluation of the values of the winding damping factors can be performed as a byproduct of transformer condition assessment by frequency response analysis (FRA).

Direct Printing of Micropatterned Plasmonic Substrates of Size‐Controlled Gold Nanoparticles by Precision Photoreduction

AbstractAlthough the extraordinary optical property of gold nanoparticles (AuNPs) has been known for a long time, the anticipated applications of AuNPs in plasmonically enhanced substrates and photonic microdevices are still under development. In this paper, a method for the direct printing of micrometer‐scale patterns of size‐controlled AuNPs is presented for plasmonic substrates and microsensor development. Using in‐house digital ultraviolet lithography, a precision photoreduction technology is developed for light‐controlled growth of AuNPs to create micrometer‐scale micropatterns on a titanium dioxide photocatalytic layer. The titanium dioxide thin layer not only enables a photocatalytic reduction process for high‐precision printing of size‐controlled AuNPs in an additive manner, but also introduces a Fano resonance that can sharpen spectral width of localized surface plasmon resonance peak and increase its peak‐to‐valley value. This printing technology can be used to cost‐effectively fabricate size‐scalable micropatterned plasmonic substrates of size‐controlled AuNPs and thus offers new opportunities to develop various types of miniature plasmonic devices ranging from plasmonic biochemical sensors to plasmonically enhanced photothermal and photovoltaic microdevices.

Evaluation Damping Performance for Hydrostatic Bearing Film by Damping Ratio Scaling

This paper investigates how to evaluate the damping ratio in practical measurement for hydrostatic bearing which possesses overdamped damping. The traditional methods such as decayed response, band width of resonant peak, transient response of step excitation and hysteresis circle cannot be utilized for get over overdamped behavior. Because the fundamental mode of worktable supported by hydrostatic bearing is overdamped, high modes must be blended into or influenced by this mode. This paper uses the dimensionless frequency responses with damping ratio as parameter of single DOF mass-damper-spring model to generate a scale to evaluate the damping ratio of the fundamental mode from the experimental measurement of impact response. Using this scaling method, this paper has investigated the influences the operation and design parameters of pressure compensations in hydrostatic bearing on the damping performance.

Sharp selective scattering of red, green, and blue light achieved via gain material's loss compensation.

Frequency-selective scattering of light can be achieved by metallic nanoparticle's localized surface plasmon resonance (LSPR). And this property may find an application in a transparent projection screen: ideally, specially designed metallic nanoparticles dispersed in a transparent matrix only selectively scatter red, green and blue light and transmit the visible light of other colors. However, optical absorption and surface dispersion of a metallic nanoparticle, whose size is comparable or smaller than mean free path of electrons in the constituent material, degenerate the desired performance by broadening the resonance peak width (i.e., decreasing frequency-selectivity) and decreasing light scattering intensity. In this work, it is shown that the problem can be solved by introducing gain material. Numerical simulations are performed on nanostructures based on silver (Ag), gold (Au) or aluminum (Al) with or without gain material, to examine the effect of gain material and to search for suitable structures for sharp selective scattering of red, green and blue light. And it is found that introducing gain material greatly improves performance of the structures based on Ag or Au except the structures based on Al. The most suitable structures for sharp selective scattering of red, green and blue light are, respectively, found to be the core-shell structures of silica/Au (core/shell), silica/Ag and Ag/silica, all with gain material.

SiO2-doping Films Effects on Optical Properties of Optical Fiber Surface Plasmon Resonance Hydrogen Sensor

SiO2-doping WO3 films were obtained by magnetron sputtering. Experiments indicated more obvious optical phenomenon with SiO2-doping films. Different thickness of the SiO2 film was discussed for better optical properties, according to the resonance peak width, the resonance depth and the sensitivity. This work can provide theory support for the design of optical fiber surface plasmon resonance hydrogen sensor.

Determination of Fluid Density and Viscosity by Analyzing Flexural Wave Propagations on the Vibrating Micro-Cantilever.

The determination of fluid density and viscosity using most cantilever-based sensors is based on changes in resonant frequency and peak width. Here, we present a wave propagation analysis using piezoelectrically excited micro-cantilevers under distributed fluid loading. The standing wave shapes of microscale-thickness cantilevers partially immersed in liquids (water, 25% glycerol, and acetone), and nanoscale-thickness microfabricated cantilevers fully immersed in gases (air at three different pressures, carbon dioxide, and nitrogen) were investigated to identify the effects of fluid-structure interactions to thus determine the fluid properties. This measurement method was validated by comparing with the known fluid properties, which agreed well with the measurements. The relative differences for the liquids were less than 4.8% for the densities and 3.1% for the viscosities, and those for the gases were less than 6.7% for the densities and 7.3% for the viscosities, showing better agreements in liquids than in gases.

Possible observation of Griffith phase over large temperature range in plasma sintered La0.67Ca0.33MnO3

We report on the possible observation of Griffith phase in a wide range of temperature (>272–378K) in the 2.5min plasma sintered La0.67Ca0.33MnO3 (LCMO) as deduced from careful electron spin resonance studies. This is 106K higher than the paramagnetic to ferromagnetic transition (Curie transition ∼272K) temperature. The indication of Griffith phase in such a wide range is not reported earlier by any group. We purposefully prepared LCMO samples by plasma sintering technique so as to create a disordered structure by rapid quenching which we believe, is the prime reason for the observation of Griffith Phase above the Curie transition temperature. The inverse susceptibility curve represents the existence of ferromagnetic cluster in paramagnetic region. The large resonance peak width (40–60mT) within the temperature range 330–378K confirms the sample magnetically inhomogeneity which is also established from our electron probe microstructure analysis (EPMA). EPMA establishes the presence of higher percentage of Mn3+ cluster in comparison to Mn4+. This is the reason for which Griffith state is enhanced largely to a higher range of temperature.

(Allen J. Bard Award in Electrochemical Science Address) Electroanalytical Techniques Coupled with in-Situ Structural Characterization of Electrodes in Devices for Energy Storage and Conversion

Inspired by the seminal work of A. J. Bard in electroanalytical chemistry during more than half of a century, we are trying to apply novel electroanalytical tools in conjunction with in-situ spectro-electrochemical techniques for the study of the most reactive electrochemical systems, related to energy storage and conversion. A variety of electroanalytical methods are widely used in advanced batteries and super-capacitors research for screening and optimization of electrode materials including their characteristic electrochemical windows, onset potentials of ions insertion and extraction, formation of protective surface-solution interphases etc. These parameters affect the electrodes stability, capacity retention, cycling efficiency and rate capability. Electroanalytical methods have their own intrinsic accessible time windows and different amplitude of electric perturbation (potential or current). Among these methods electrochemical impedance spectroscopy (EIS) has the widest time window from ca. 10-5 to 103 s and small potential amplitude which enables the probing the kinetics of a large variety of processes accompanying electrochemical insertion of Li , Na and Mg ions into battery electrodes separating them by the characteristic time constants of these processes. In contrast, cyclic voltammetry (CV) effectively probes kinetic steps in the long time window (from 102 to 105 s) close to either quasi-equilibrium intercalation or intercalation process in the form of first-order phase transition. CV is a large-amplitude technique, and attempts to apply it for a shorter time domain, e.g. corresponding to characteristic solid-state diffusion time constants inevitably results in lack of their resolution with respect to electrode potential (or intercalation level). The niche between EIS and CV is effectively bridged by intermittent titration techniques (PITT, GITT) ensuring highly resolved separation between the different sequential phase transitions in the long time domain, and potential-resolved chemical diffusion coefficients of intercalated ions. [1] The area-averaged responses of battery electrodes obtained by electroanalytical techniques depend on the local chemical or porous electrode structure: very often this information is required for correct interpretation of the electrochemical characteristics (e.g. chemical diffusion coefficients).Recent progress in electroanalytical methods adapted for application in LIB , NIB and Mg batteries research relates to development of non-gravimetric EQCM-D (electrochemical quartz-crystal microbalance with dissipation monitoring) techniques , which in contrast to classical EQCM, tracks not only resonant frequency change DF/n (n is overtone order) but also dissipation of the oscillation energy (or equivalently, resonance peak width change, DW/n). Tracking complex frequency change, DF*/n = DF/n + iDW/n, for rigid porous battery electrodes as a function of the penetration depth of transverse oscillation wave in the electrolyte solution, d (dependent on the overtone order and liquid’s density and viscosity) over multiple harmonics ,allows the characterization of the complex electric and mechanical properties of thin electrode coatings in electrolyte solutions (using the most relevant materials for advanced rechargeable batteries and super-capacitors) under applied potential. Intercalation-induced changes of dimensional and porous electrodes’ structure can be quantified in terms of hydrodynamic admittance models by fitting well developed models for momentum transfer to the experimental RQCM-D data retrieving structural parameters in way similar to fitting experimental EIS data (e.g. Nyquist plots) by equivalent electrical circuit analogs. Validation of the extracted parameters for their internal consistency and comparison with the results from complimentary other in-situ techniques (e.g. scanning probe microscopes) is required. The methodology of hydrodynamic spectroscopy of porous solids and composite electrodes that we develop in recent years is inexpensive, noninvasive and highly useful in a broad spectrum of applications including deeper insights into the dynamic build-up and subsequent development of solid-electrolyte interfaces in Li and Na battery electrodes and stresses-volume changes-stability interrelation of ion intercalation electrodes.[3] References [1] M.D. Levi and D. Aurbach, Electrochim. Acta 45 (1999) 167-185. [2] N. Shpigel, M.D. Levi, S. Sigalov, O. Girshevitz, D. Aurbach, L. Daikhin, P. Pikma, M. Marandi, A. Janes, E. Lust, N. Jackel, V. Presser, Nat. Mater. 15 (2016) 570-575.[3] S. Sigalov, N. Shpigel, M. D. Levi, M. Feldberg, L. Daikhin, D. Aurbach, Anal. Chem. 88, (2016) 10151–10157.

Contact resonances of U-shaped atomic force microscope probes

Recent approaches used to characterize the elastic or viscoelastic properties of materials with nanoscale resolution have focused on the contact resonances of atomic force microscope (CR-AFM) probes. The experiments for these CR-AFM methods involve measurement of several contact resonances from which the resonant frequency and peak width are found. The contact resonance values are then compared with the noncontact values in order for the sample properties to be evaluated. The data analysis requires vibration models associated with the probe during contact in order for the beam response to be deconvolved from the measured spectra. To date, the majority of CR-AFM research has used rectangular probes that have a relatively simple vibration response. Recently, U-shaped AFM probes have created much interest because they allow local sample heating. However, the vibration response of these probes is much more complex such that CR-AFM is still in its infancy. In this article, a simplified analytical model of U-shaped probes is evaluated for contact resonance applications relative to a more complex finite element (FE) computational model. The tip-sample contact is modeled using three orthogonal Kelvin-Voigt elements such that the resonant frequency and peak width of each mode are functions of the contact conditions. For the purely elastic case, the frequency results of the simple model are within 8% of the FE model for the lowest six modes over a wide range of contact stiffness values. Results for the viscoelastic contact problem for which the quality factor of the lowest six modes is compared show agreement to within 13%. These results suggest that this simple model can be used effectively to evaluate CR-AFM experimental results during AFM scanning such that quantitative mapping of viscoelastic properties may be possible using U-shaped probes.

Effect of Synthesis Techniques on Crystallization and Optical Properties of Ag-Cu Bimetallic Nanoparticles

Silver (Ag)-copper (Cu) bimetallic nanoparticles (NPs) were synthesized by the reduction of silver nitrate and copper (II) acetate monohydrate using ethylene glycol in a microwave (MW) heating system with controlled reaction times ranging from 5 min to 30 min. The molar ratio Ag/Cu was varied from 1:1 to 1:3. The effect of reaction conditions on the bimetallic NPs structures and compositions were characterized by x-ray photoelectron spectroscopy, x-ray diffraction and transmission electron microscopy. The average particle size was approximately 150 nm. The surface plasmon resonance (SPR) of Ag-Cu bimetallic NPs was investigated by monitoring the SPR band peak behavior via UV/Vis spectrophotometry. The resonance peak positions and peak widths varied due to the different structures of the bimetallic NPs created under the synthesis conditions. In the MW heating method, the reduction of Cu was increased and Cu was inhomogeneously deposited over the Ag cores. As the composition of Cu becoming higher in the Ag-Cu bimetallic NPs, the absorption between 400 nm to 600 nm was greatly enhanced.

(Invited) The Use of Eqcm-D for in-Situ Characterization of Dimensional Changes in Cycled Battery Electrodes

Ions adsorption/desorption in nanoporous carbon electrodes and, especially, Li-ion insertion/extraction to/from typical battery electrodes are accompanied by significant volume changes, which complicates enormously gravimetric analysis by EQCM of the ionic fluxes involved in these processes. [1, 2] Gravimetric analysis by EQCM is based on the use of the classical Sauerbrey’s equation, which transforms ions insertion-induced resonance frequency changes into mass (or ions population) changes. Such an approach implies that additional mass onto quartz-crystal coating is of pure inertial origin, so that the dissipation factor of the oscillating crystal, and hence the related resonance width, remain constant. Figure 1 shows a drastic increase in the resonance width accompanying frequency change during Li-ion extraction from a thin LiFePO4 electrode. A finite difference of about 20% exists between the experimentally measured frequency shift and that calculated from the Sauerbrey’s equation (based on the electrochemical data that enable calculations of mass changes). As has been recently reported, [3] measuring frequency differences together with the changes in the resonance peak width can provide input parameters of the hydrodynamic admittance models of composite battery electrodes. With such information it is possible to obtain important potential-dependent structural parameters of the composite electrodes, namely, effective thickness of the porous active mass and its permeability (linked to porosity). This new approach to characterization of composite battery materials has been recently developed in collaboration with researchers from Tel-Aviv University [1,2], and was applied successfully to describe dynamics of Li ion batteries electrodes [3] and to understand the capacitive paradox of Ti3C2 MXene phase electrodes [4] in collaboration with research teams at the Leibnitz Institute (Germany) and Drexel University (USA), respectively. The method is based on the fact that intercalation-induced changes in geometric structural parameters of electrodes, modify their hydrodynamic interactions of with the electrolyte solutions. These are nicely recorded by EQCM-D and analyzed in terms of suitable admittance models. Until recently, we applied this approach to composite electrodes containing only rigid binders (such as PVdF in contact with aqueous solutions). Herein we are going to extend the EQCM-D based methodology for structural characterization of composite electrodes containing viscoelastic polymeric binders, developing thus a non-invasive in-situ dynamic monitoring of elastic properties of composite battery electrodes (using EQCM-D) [5]. This unique method can be adjusted for the characterization of viscoelastic behavior of polymeric binders during long-term cycling of composite electrodes used in all kinds of batteries. References (1) Levi, M.D; Sigalov S.; Aurbach, D.; Daikhin, L. J. Phys. Chem. C 2013, 117, 14876−14889. (2) Daikhin, L.; Levi, M.D.; Sigalov, S.; Salitra, G.; Aurbach, D. Anal. Chem., 2011, 83, 9614–9621. (3) Levi, M.D; Sigalov S.; Salitra, G.; Elazari, R.; Aurbach, D.; Daikhin, L.; Presser, V. J. Phys. Chem. C 2013, 117, 1247−1256. (4) Levi, M. D.; Lukatskaya , M. R.; Sigalov, S.; Beidaghi, M.; Shpigel, N.; Daikhin, L.; Aurbach, D.; Barsoum, M. W.; Gogotsi, Y.;. Adv. Energy Mater. 2015, 1400815. (5) Shpigel, N.; Levi, M.D; Sigalov, S.; Girshevitz,O.; Aurbach, D.; Daikhin, L.; Jäckel, N.;] Presser, V. Angew. Chemie, 2015 (accepted) DOI: 10.1002/anie.201501787. Figure 1

SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

Nanostructured Au and Ag thin films were obtained by nanosecond pulsed laser ablation in presence of a controlled Ar atmosphere. Keeping constant other deposition parameters such as target-to-substrate distance, incidence angle, laser wavelength and laser fluence, the film morphology, revealed by SEM, ranges from isolated NPs to island structures and sensibly depends on gas pressure (10–100 Pa) and on the laser pulse number (500–3 × 10 $$^{4}$$ ). The control of these two parameters allows tailoring the morphology and correspondingly the optical properties of the films. The position and width of the surface plasmon resonance peak, in fact, can be varied with continuity. The films showed remarkable surface-enhanced Raman activity (SERS) that depends on the adopted deposition conditions. Raman maps were acquired on micrometer-sized areas of both silver and gold substrates selected among those with the strongest SERS activity. Organic dyes of interest in cultural heritage studies (alizarin, purpurin) have been also considered for bench marking the substrates produced in this work. Also the ability to detect the presence of biomolecules was tested using lysozyme in a label free configuration.

Numerical study of anomalous TE-polarized light scattering by metallic nanowires using realistic data

We report the result of a numerical study of surface plasmon induced anomalous behaviors in TE light scattering by single silver and gold nanowires of radius a. Going beyond the restricted case of nondissipative and nondispersive scatterers often reported previously, the current numerical calculation is performed directly on the basis of Mie's general formula, adopting the refractive index data of Johnson and Christy. Our result does not show the appearance of well resolved and multipole resonances in Q sca plotted against q(= 2πa/λ), for certain wire radii. It does show however, the growing contributions of the higher order modes as a increases. A series of closely-placed but well separated resonance curves nevertheless show up for varying wire radii within the range of small q, exhibiting systematic changes indicative of the size effects on the scattered waves. The further deduced Q sca (λ) spectra display the distinct resonance curves for different wire radii showing peculiar mix of monotonous and nonmonotonous variations of the resonance peak and spectral width with increasing a, as a result of complicated competitions among the growing contributions of the higher order modes. Finally, while the silver and gold scatterers appear to exhibit qualitatively similar behaviors, they differ largely in details due to the significantly different indices of refraction and dispersive properties.

Electrochemical quartz crystal admittance studies of ion adsorption on nanoporous composite carbon electrodes in aprotic solutions

This paper describes the application of Electrochemical Quartz Crystal Admittance (EQCA) methodology to the tracking of ion adsorption on composite electrode coatings consisting of highly porous activated carbon particles and polyvinylidene difluoride (PVdF) binder rigidly attached to quartz crystal surfaces. Solutions of LiBF4 and (C2H5)4NBF4 in propylene carbonate (PC) were used in this study. At small charge densities, the effect of frequency change is nearly of gravimetric nature. We propose a new method to determine the mass contribution to the resonance frequency shift due to adsorption of ions and accompanying solvent molecules, revealing different ion/solvent population ratios for Li+, (C2H5)4 N+ and BF4 − ions correlated to the ion solvation ability. The EQCA model applied describes the change in the frequency and in resonance peak width in terms of dimensional changes of large carbon particles (bumps) and of pseudo-uniform layers of smaller particles mixed with PVdF. The type of oscillation energy dissipation in composite carbon electrodes with PVdF binder strongly depends on non-uniform potential-induced deformations of electrode particles, and this suggests a strong effect of solvent nature on the mechanical properties of polymeric binders. EQCA may provide important information on the role of polymeric binders during cycling of composite electrodes both for supercapacitors and for Li-ion batteries electrodes.

Integration of large-area metallic nanohole arrays with multimode optical fibers for surface plasmon resonance sensing

Here, we report an implementation of enhanced surface plasmon resonance sensing on optical fibers through integration of large-area metallic nanohole arrays on the endfaces of multimode optical fibers by a template transfer method. The Au nanohole array integrated optical fiber sensors show a high refractive index sensitivity 559 nm per refractive index unit, narrow resonant peak width less than 10 nm in aqueous solution, and consistent optical responses with peak position variation less than 0.5 nm for various core diameters of optical fibers at same dielectric conditions. These specifications demonstrates that the nanohole array based optical fibers can serve as a high-performance, portable and lensless plasmonic platform with superior robustness and accessibility for surface plasmon resonance sensing.