In-plane Resonance Research Articles

Epitaxial Fe/Rh bilayers for efficient spin-to-charge conversion

To address the spin pumping in the conventional ferromagnetic/“normal” metal systems, we fabricated 6 nm Fe/1–15 nm Rh epitaxial bilayers and determined the g-factor, magnetic anisotropy, and magnetization damping by combining both 0–40 GHz CPW-based frequency-dependent and cavity-based 9.56 GHz in-plane angular-dependent ferromagnetic resonance measurements at room temperature. Auger electron spectroscopy and low-energy electron diffraction show that Rh grows epitaxially on Fe. The epitaxial bilayers exhibit a high spin mixing conductance gmix↑↓=(2.9±0.2)×1019 m−2 and a spin diffusion length in Rhodium λsd=9.0±1.3 nm. This makes Rh comparable to Pt and Pd in terms of spin pumping and spin transport efficiency at room temperature.

Synthesis, Characterization, Acute Dermal Toxicity, Anti-inflammatory, and Wound Healing Potential of Biogenic Silver Nanoparticles in Balb C Mice.

The current study aimed to develop an economic plant-based therapeutic agent to improve the treatment strategies for diseases at the nano-scale. In the current research, silver nanoparticles were synthesized using Trillium govanianum aqueous extract. Characterizations were done using UV-visible spectrophotometer, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. In vivo biological activities such as acute dermal toxicity, wound healing, and anti-inflammatory were done on Balb C mice. Absorbance at 295 nm corresponds to the out-of-plane quadrupole Plasmonresonance while at 350 nm corresponds to in-plane dipole resonance. SEM images showed the morphology of TGAgNPs is not exactly spherical while XRD analysis shows that highly crystalline TGAgNPs with an average size of 27.94 nm. The FTIR spectrum represents sharp peaks of aldehyde, amide I, aromatic rings, and polysaccharides. The microscopic assessment did not find any epidermal and dermal layer abnormalities in Blab C mice when exposed to TGAgNPs during acute dermal toxicity. Results revealed that 1000 mg/kg is not a lethal dose. In the wound healing activity, no mortality and no abnormal signs were observed when petroleum jelly, nitrofuranose, TGaqu, and TGAgNPs-based ointments were applied. Enhanced epithelization was recorded in TGaqu and TGAgNPs treated mice (p≤0.001). The wound contraction percentage was higher in nitrofuranose-treated mice (74%) followed by TGAgNPs (71%), and TGaqu (69%) compared to vehicle-treated and open-wounded mice. The paw edema model proved the potential use of TGAgNPs and TGaqu as anti-inflammatory agents. Hence, the results proved that both TGaqu and TGAgNPs are not toxic and possessed strong anti-inflammatory and wound-healing effects due to the presence of phytochemical constituents and could be used in various drug production as a therapeutic agent.

Seedless synthesis of Au nanoplates with tunable plasmonic peaks

Au nanoplates with tunable in-plane dipolar localized surface plasmon resonance peaks in a broad range from the visible to near-infrared region were obtained in high yield using a seedless wet chemical growth method after purification. Cetyltrimethylammonium chloride was used as a surfactant, while hydrogen peroxide and sodium borohydride were used as the weak and strong reducing agents, respectively. The edge length and in-plane dipolar localized surface plasmon resonance peak of the Au nanoplates could be adjusted by varying the amounts of hydrogen peroxide and sodium borohydride. The Au nanoplates were further used as the saturable absorber to generate pulsed laser output in a passively Q-switched solid-state laser at approximately 2 µm. Our study offers a new method for obtaining Au nanoplates with tunable plasmonic peaks over a broad range.

External and internal resonances of thin-walled curved beams under three-directional moving harmonic loads

This paper deals with the internal and external resonances of simply supported curved beams subjected to three-directional harmonic moving loads. Firstly, based on the differential transformation methods and the Glerkin methods, the analytical solutions are newly proposed for vertical, torsional, radial and axial response of thin-walled curved beams under three-directional harmonic moving loads. Then, in the proposed analytical solutions, this study attains the conditions for the external resonance for in-plane and out-of-plane vibrations by letting the denominator of the proposed analytical solutions equal to zero. Besides, the semi-analytical solution for the internal resonance of curved beams is first proposed in this paper by the coincidence of both two mentioned-above resonant frequencies of beams. The internal resonance will occur when the beam is designed with the critical length for the given cross-section. The derived condition for the internal resonance can offer a basis for structural design to avoid the resonant appearance. All the analytical solutions are in good agreement with the results addressed in existing literature and numerical ones obtained from the finite element method (FEM). The results reveal that the corresponding motion of curved beams diverges, reaching a maximum value during the duration of the harmonic moving loads, when in the external resonance. Moreover, under the internal resonance condition, the curved beams are in repetitive transition between the out-of-plane mode and the in-plane mode without any external energy input. Additionally, in this scenario, the excitation frequency can coincide with the two resonance frequencies of beams resulting in simultaneous occurrences of out-of-plane and in-plane resonances on curved beams. The aim of this study highlights the potential resonant appearances on beams and provide reference in the design phase to avoid the internal resonance appearance and ensure the safety of structures.

Greatly Improved the Tunable Amplitude of Ferromagnetism Based on Interface Effect of Flexible Pt/YIG Heterojunctions.

Flexible quantum spin electronic devices based on ferromagnetic insulators have attracted wide attention due to their outstanding advantages of low-power dissipation and noncontact sensing. However, ferromagnetic insulators, such as monocrystalline yttrium iron garnet (Y3Fe5O12, YIG), hve weak stress effects with a small magnetostrictive coefficient (λ110, 10 ppm), making it difficult to achieve a large magnetic tunable amplitude. In this paper, large-scale (with a diameter of 40 mm), flexible Pt/YIG heterojunctions were obtained by double-cavity magnetron sputtering technology, indicating typical soft magnetism and good bending fatigue characteristics. Here, the 3 nm thickness of the Pt layer triggers an obvious magnetic proximity effect, in which the in-plane ferromagnetic resonance field is decreased by 70 Oe compared to flexible Cu/YIG heterojunctions. Meanwhile, it shows a wide tunable amplitude of 110 Oe under the flexible bending stresses, which is induced by the sensitive interface effect of Pt (3 nm)/YIG heterojunctions. The saturation magnetization of Pt/YIG heterojunctions is negatively correlated with Pt thickness rather than the relative stability of Cu/YIG heterojunctions, depending on the magnetic proximity effect. It brings greater application possibilities for flexible stress-sensitive magnetic oxides in spin logic electronic devices.

Ferromagnetic resonators synthesized by metal-organic decomposition epitaxy

Metal-organic decomposition epitaxy is an economical wet-chemical approach suitable to synthesize high-quality low-spin-damping films for resonator and oscillator applications. This work reports the temperature dependence of ferromagnetic resonances and associated structural and magnetic quantities of yttrium iron garnet nanofilms that coincide with single-crystal values. Despite imperfections originating from wet-chemical deposition and spin coating, the quality factor for out-of-plane and in-plane resonances approaches 600 and 1000, respectively, at room temperature and 40 GHz. These values increase with temperature and are 100 times larger than those offered by commercial devices based on complementary metal-oxide semiconductor voltage-controlled oscillators at comparable production costs.

Nonlinear vibration of pinned FGP-GPLRC arches under a transverse harmonic excitation: A theoretical study

The non-linear in-plane primary resonance of functionally graded porous (FGP) sinusoidal arches made of graphene platelet reinforced composites (GPLRC) subjected a transverse harmonic excitation is investigated in this paper. To eliminate the coupling of inner forces and facilitate the derivation, the neutral plane-based equations of motion are established considering the force and bending moment equilibrium conditions. By utilizing an incremental harmonic balance (IHB) technique, the frequency response features, dynamic time history, and limit cycle under primary resonance and 1/2 super-harmonic resonance are determined. FE analysis is conducted to verify the accuracy of the presented results. To further examine the computational efficiency of IHB procedure, a fourth order Runge–Kutta method is used to determine the structural responses as a counterpart. Comprehensive parametric studies are then carried out, particular focus is paid to the cases of material compositions, geometric properties, and dynamic parameters on the frequency response characteristics. It is found that the increasing porosity coefficient significantly exacerbates the left-inclined softening behaviors of the frequency response curves. On the contrary, the left-inclined effect continues to weaken as the GPL weight fraction gradually grows.

Quasi-guided modes resulting from the band folding effect in a photonic crystal slab for enhanced interactions of matters with free-space radiations.

We elucidate that guided modes supported by a regular photonic crystal slab structure composed of a square lattice of air holes in a silicon slab will transition into quasi-guided (leaky) modes when the radius of every second column of air holes is changed slightly. This intentional geometric perturbation will lead to a doubling of the period in one direction and the corresponding shrinkage of the first Brillouin zone. Because of the translational symmetry in the k-space, leaky waves inheriting the spatial dispersion of the original guided modes, which do not interact with external radiation, will appear with the dispersion curves above the light cone. Our results show that ultrahigh Q-factor resonances with large operating bandwidth can be achieved. Interestingly, the perturbation in only one direction of the photonic lattice will lead to an in-plane wave number-dependent resonance characteristic in both directions. Our numerical results demonstrate a local enhancement of the electric field magnitude by the order of 102, which is even more significant than those in most plasmonic structures. These quasi-guided modes with superior properties will provide a new platform for efficient light-matter interactions.

A theoretical and experimental study on in-plane parametric resonance of laminated composite circular arches under a vertical base excitation

For the first time, analytical solutions for the in-plane dynamic instability of laminated composite circular arches under a vertical base excitation are developed and experimentally verified in this paper. Hamilton principle is used to derive the governing equation of motion of the laminated arch from which the principal instability region corresponding to parameter resonance can be determined. An experimental system is designed and set up to verify the developed solutions and investigate the dynamic performance of laminated arches. Comprehensive analytical and experimental results are presented, with a particular focus on the effects of rise-to-span ratio and stacking sequence on the dynamic instability region of the laminated arch. It is found that dynamic instability region mainly occurs when the excitation frequency is nearly twice the fundamental frequency. For an arch with a lower rise-to-span ratio, both the critical excitation frequency and the width of its dynamic instability region increase significantly. Under the same excitation amplitude, the dynamic instability region of an angle-ply laminated arch becomes wider as the ply-angle increases. Results also show that the critical excitation frequency is highly sensitive to the stacking sequence and quickly grows as the zero-degree ply is placed further away from the midplane.

Passive silicon on-chip optic accelerometer for low frequency vibration detection.

In this article, a fiber optic accelerometer based on a Fabry-Perot interferometer is presented and prepared by micromachining on a silicon substrate. The inertial sensing structure of the accelerometer is built by a center block mass and four folded springs with a high thickness-to-width ratio, providing an in-plane resonance vibration. The miniature-sized sensor has large flexibility in structural design and its acceleration response can be predicted by theoretical estimation and finite element simulation. Experimental results show that the proposed sensor's sensitivity is over 161 rad/g in frequency range of 1 to 63 Hz. It also achieved a low average noise level of 67.4 ng/Hz1/2 on the working band. The sensor's transverse crosstalk is less than 1.38%, proving its potential ability in low frequency vibration detection applications.

Plasmon Coupling and Efficient Charge Transfer in Rough-Surfaced Au Nanotriangles/MXene Hybrids as an Ultrasensitive Surface-Enhanced Raman Scattering Platform.

The rational design of Raman substrate materials with prominent electromagnetic enhancement and charge transfer is quite important for surface-enhanced Raman scattering (SERS). Herein, an efficient SERS substrate based on two-dimensional ultrathin Ti3C2T x MXene and rough-surfaced Au nanotriangles (NTs) was successfully prepared for efficient detection of organic molecules due to the synthetic effect of an optimized electromagnetic field and charge transfer. Uniform Au NTs with tunable surface roughness were controllably prepared by selectively depositing of Au on the smooth Au NTs. Due to the large surface area, tunable plasmon resonance, and abundant hotspots on the planar surface, the modified Au NTs showed much better SERS performance than initial Au NTs. By combination of the rough-surfaced Au NTs with MXene, the Ti3C2T x /Au NT hybrids exhibited much better SERS performance than initial Au NTs and Au NTs with a rough surface. The detection limit is down to 10-12 M, and the analytical enhancement factors reach 3.6 × 109 (at 1174 cm-1) on detecting crystal violet excited at 785 nm. This is because the strong plasmon coupling between the in-plane resonance of Au NTs and transversal plasmon resonance of Ti3C2T x MXene around 785 nm can generate an intense interfacial electromagnetic field for amplifying SERS signals. Additionally, the efficient charge transfer between Au NTs, MXene, and molecules also plays an important role in enhancing the SERS performance. This work presents a new insight to develop high-performance SERS substrates based on plasmon.

Thickness-scaling phonon resonance: A systematic study of hexagonal boron nitride from monolayers to bulk crystals

Phonons are important lattice vibrations that affect the thermal, electronic, and optical properties of materials. In this work, we studied infrared phonon resonance in a prototype van der Waals (vdW) material—hexagonal boron nitride (hBN)—with the thickness ranging from monolayers to bulk, especially on ultra-thin crystals with atomic layers smaller than 20. Our combined experimental and modeling results show a systematic increase in the intensity of in-plane phonon resonance at the increasing number of layers in hBN, with a sensitivity down to one atomic layer. While the thickness-dependence of the phonon resonance reveals the antenna nature of our nanoscope, the linear thickness-scaling of the phonon polariton wavelength indicates the preservation of electromagnetic hyperbolicity in ultra-thin hBN layers. Our conclusions should be generic for fundamental resonances in vdW materials and heterostructures where the number of constituent layers can be conveniently controlled. The thickness-dependent phonon resonance and phonon polaritons revealed in our work also suggest vdW engineering opportunities for desired thermal and nanophotonic functionalities.

Etching-dependent SERS activity of Ag triangular nanoplates: From decrease to increase

Bimetallic silver/gold nanostructures with high chemical stability and numerous “hot spots” have received much attention in surface-enhanced Raman scattering (SERS) application. In this work, silver/gold nanoplates were synthesized using a facile etching method based on silver triangular nanoplates (Ag TNPs) template. In the synthetic process, the morphology changes of the Ag/Au nanoplates clearly demonstrate the etching evolves with the increased dosage of HAuCl4 solution. At the etching continued, the in-plane dipole resonance peak of the etched Ag TNPs exhibited a non-monotonic response: first red-shift and then blue-shift. What's more interesting is that the SERS activity of the etched Ag TNPs was sharply reduced at first, then gradually increased to a certain intensity, and maintained stability subsequently. The observed etching-dependent SERS activity was different with previous reports and the possible reason was discussed. The increased SERS activity of etched Ag TNPs was even higher than that of pure Ag TNPs when using the big Ag TNPs as the template. It is expected that the etching formed Ag/Au nanoplates are ideal candidates in applications related to SERS sensing.

Annealing enhanced ferromagnetic resonance of thickness-dependent FeGa films

We report the influence of different annealing temperatures on the magnetic property of FeGa thin films. The measurement was done for the film thickness from 42 to 420 nm. Our results show that the annealing temperature affects not only the microstructure but also the ferromagnetic resonance signal of the film. Annealing of a FeGa film improves the in-plane remanence ratio and reduces the in-plane ferromagnetic resonance linewidth by a factor of five. This annealing treatment promotes film texture and releases compressive stresses in the film. Our results demonstrate that the structural control via annealing is viable. The necessary magnetic softness of the FeGa film for microwave applications can be achieved.

Plasmonic excitations in nanorings: Thickness dependent unusual coupling effects

Plasmonic coupling in both metallic and graphene nanostructures, is of particular interest for fundamental physics and potential applications. Here, we study plasmonic coupling in gold nanorings possessing different vertical thickness, by using three-dimensional finite element method as implemented in COMSOL MULTIPHYSICS. As well known, the coupling between inner and outer edges will result in mode splitting, namely, a symmetric (lower frequency) mode and an antisymmetric (higher frequency) mode; and a larger coupling corresponds to a larger mode shifting, e.g. with a blueshift for the antisymmetric mode and a redshift for the symmetric mode. However, in very thin gold nanorings, we find as increasing the ratio of inner radius to outer radius (equivalently increasing the coupling), the antisymmetric mode exhibits a redshift at first and then a blueshift, which is consistent with that in graphene nanorings of zero thickness. We show this unusual coupling effect depends on the thickness and size of nanorings, and is more significant in nanorings of smaller thickness and size. Our work is a nature extension of recent plasmonic studies, and offers an alternative way to tune in-plane plasmonic resonances by the vertical dimension.

Localization of Laterally Confined Modes in a 2D Semiconductor Microcavity

Monolayer semiconductor embedded planar microcavities are becoming a promising light-matter interacting system to uncover a wealth of photonic, excitonic, and polaritonic physics at the two-dimensional (2D) limit. In these 2D semiconductor microcavities employing the longitudinal Fabry-Perot resonance, major attention has been paid to the coupling of excitons with vertically confined cavity photons; by contrast, the lateral confinement effect on exciton-photon interactions is still elusive. Here we observe the localized distribution of laterally confined modes with discrete energies in a 2D semiconductor embedded microcavity. Monolayer tungsten disulfides with equilateral triangular geometries but varied edge lengths are selected as the active media incorporated into a dielectric planar microcavity. With the shortening of the edge length, photoluminescence mappings of active regions present spatially localized emission patterns, which are attributed to the presence of in-plane triangular waveguiding resonance caused by total internal reflection at the one-dimensional closed boundary between the monolayer semiconductor and its surrounding cavity material. Unlike the conventional quantum confinement effect of native excitons appearing at the nanometer scale, the mode emission at the active-medium center exhibits apparent size-dependent features at the micrometer scale due to the optical confinement effect correlated with its photonic nature. By reducing the area of active media, single-mode dominant emission is achieved together with its nondispersive energy and improved directionality. Our work highlights the crucial role of lateral mode control in monolayer semiconductor embedded planar microcavities and encourages the investigation of the quantum billiard problem in 2D semiconductors.

Synthesis of silver nanoparticles using bio valorization coffee waste extract: photocatalytic flow-rate performance, antibacterial activity, and electrochemical investigation.

It is well known that biogenic synthesis, as compared to other processes, has proven to be highly effective in the fabrication of silver nanoparticles (AgNPs). Thus, our current study focused on synthesizing AgNPs using coffee waste extract (CWE). CWE contains many compounds identified by HPLC, which reduce, cap, and stabilize AgNPs in its solution. The as-synthesized AgNPs were produced with a monodispersed small size around 20 nm and exhibited in-plane dipole plasmon resonances of hexagonal nanoplates. AgNPs were characterized by both physical and spectroscopic methods, which confirmed their nanoscale dimensions with a hexagonal shape. The as-prepared AgNPs (12 mg) enabled the photodegradation of phenol compounds (20 mL) with a removal efficiency of ~ 94.6% in a short time in the presence of citric acid. Additionally, the second promising application of AgNPs was the tendency to remove the hazard 2,4 dinitroaniline (2,4 DNA) with a percent more than 97% while using only 7 mg of AgNPs. Moreover, the green synthesized AgNPs are superior in inhibiting bacterial growth and killing most infected microbes such as B. subtilis, P. aeruginosa, S. aureus, and E. coli. The electrochemical characteristics of the AgNPs were evaluated using a three-electrode system. The calculated specific capacitance was 280 F g−1 at 0.56 A g−1. Furthermore, after 1000 cycles at 2.2 A g−1, the AgNPs electrode demonstrates an excellent cycling stability behavior with 94.8% capacitance retention. Based on the previous promising results, it can be concluded that CWE is an environmentally benign extract to prepare AgNPs with low cost, saving and easily used for many great domains in photocatalytic, phenol compound removals, and production of functional nanodevices.

Electromechanical response of laterally clamped piezoelectric wafers: Absence of in-plane mechanical resonances in the electromechanical impedance spectrum

We discuss the electromechanical response characteristics of laterally clamped piezoelectric wafers. The impedance spectra (both magnitude and phase) obtained from finite element simulations of uniformly polarized free and clamped circular and square wafers are first presented. It is observed that the magnitude and phase of the impedance spectrum for free piezoelectric wafers shows all the in-plane extensional modes as electromechanical resonances, while that for a clamped wafer does not show any of them. However, it is also shown that the spectrum corresponding to the out-of-plane displacement on the surface of the wafer actually shows the in-plane resonances for both free and clamped wafers. In other words, it is found that the clamped wafer shows in-plane mechanical resonances but these do not appear in the electromechanical impedance spectrum. This observation is then generalized and explained using an analytical model for thin piezoelectric wafers of arbitrary shape. In particular, it is shown that the impedance spectrum of laterally clamped piezoelectric wafers of any arbitrary shape do not show in-plane extensional modes as electromechanical resonances. Moreover, the impedance spectrum of a laterally clamped wafer is shown to depend only on its area and thickness but not its shape. The above findings are relevant to measurement techniques that rely explicitly on the characteristics of the impedance spectrum observed for a piezoelectric wafer. In addition, the absence of resonances resulting from lateral clamping allows for broadband operation of piezoelectric wafers as sensors and actuators for applications such as ultrasonic range finding, underwater acoustics and acoustic imaging.

Carboxymethyl chitosan/graphene oxide/silver nanotriangles nanohybrid as the sensing materials for the enhancement of ammonia localized surface plasmon resonance sensor

This work reports the application of silver nanotriangles (AgNT) incorporated with chitosan/graphene oxide (Chit/GO) and carboxymethyl chitosan/graphene oxide (CMChit/GO) for the enhancement of ammonium localized surface plasmon resonance (SPR) sensor. The ammonium is detected through the hydrogen bonding between the hydroxyl functional group on the sensing material surface with ammonium. AgNT was successfully synthesized via the direct chemical reduction method. The appearance of three peaks in UV–visible analysis, 334, 486 and 677 nm corresponded to the out of plane quadrupole resonance, anisotropic nanoparticles, and in-plane dipole resonance formations, respectively. The morphology analysis by FESEM exhibits that the AgNT has a diameter of 45.16 nm. Zeta analysis depicts the average size distribution and surface potential of AgNT with 16.53 d.nm and −34.5 mV, respectively. Meanwhile, Chit/GO derivatives were synthesized via the solution mixing method. The AFM analysis resulted in the surface roughness for Chit/GO and CMChit/GO with 28.65 nm and 20.43, respectively, due to the abundance of electronegative groups on their surface, which provides more active sites for ammonium attachment. Chit/GO and CMChit/GO were incorporated with AgNT before the sensor performance analysis. In localized SPR sensing, Chit/GO/AgNT and CMChit/GO/AgNT exhibit the sensitivity of 0.39 and 2.41 nm ppm−1, respectively.

Dielectric nanocavity-coupled surface lattice resonances for high-efficiency plasmonic sensing

Surface lattice resonances (SLRs) arising in metal nanostructure arrays have shown tremendous application prospects in the field of plasmonic biosensing. However, these SLRs still suffer from poor optical properties, such as broad linewidth or weak resonance intensity that is especially excited under normal incidence and asymmetric environments, which hinder further practical applications. Herein, we theoretically propose an effective strategy to tailor the SLRs performance of metal nanostructure arrays by introducing a dielectric nanocavity. Originating from the strong interference between the in-plane lattice resonance mode and plasmonic gap cavity modes, the dielectric nanocavity-mediated gold nanostructure arrays exhibit both narrow spectral features with a linewidth of ∼8.2 nm and strong resonance intensity with absorbance amplitude exceeding 95%, even though under normal incidence and asymmetric environment excitation. The simulation results then show that the sensitivity and the figure of merit can reach up to 527.5 nm RIU−1 and 64.3, respectively, as for plasmonic refractive index sensing. This work not only paves the way toward the achievement of effective control of in-plane SLRs, but also provides a potentially attractive candidate for the development of high-efficiency plasmonic sensors.