Resonance Absorption Effect Research Articles

Ultrafast dynamics and mechanism of structure formation in titanium nitride upon femtosecond laser irradiation for plasmonic enhanced photothermal effect

Femtosecond laser has great potential in controlling the surface structure of titanium nitride (TiN) to promote plasmonic photothermal effect. Studying the mechanism of femtosecond laser irradiation on the surface and inside of the TiN benefits the photothermal microdevices. Ultrafast dynamics of electrons and lattices of TiN films with different thicknesses were first studied through pump-probe technique, which found that the electron density is easier to reach the maximum on the surface than the electrons in deep-layers. High-frequency ripple was formed by tiny nucleation resulted from weak eruption of surface material on the thin TiN film, and low-frequency ripple was emerged through large nucleation of material clusters simultaneously on the thick TiN film. The blue shift and intensity changes of Raman peak on 200 nm TiN film indicate the heterogeneous structure changed from TiN to TiN0.26 after laser processing, and the vacancy occupies causes the lattice vibration weakened. The 200 nm TiN film after processing shows enhanced local surface plasma resonance absorption effect, which induced the reflectivity is reduced by 30 %, and the light and thermal conversion efficiency increased by 80 %. These results proved the promising utilization of TiN in biological and medical applications, energy collection and thermal auxiliary magnetic records.

Design of a Far-Infrared Broadband Metamaterial Absorber with High Absorption and Ultra-Broadband

We designed a metamaterial far-infrared absorber based on an MDM (metal–dielectric–metal) structure. We made a hollow crossed Ti microstructure at the top of the absorber. It is known that the coupling effect of equipartitional exciton resonance and intrinsic absorption at the surface of the depleting material has a strong influence on the absorber. Based on this, we investigated the absorption characteristics of the absorber using the Finite Difference in Time Domain (FDTD) theory. The results show that the absorber absorbed more than 90% of the light within a bandwidth of 12.01 μm. The absorber has an average absorption of 94.08% in the longwave infrared (LWIR) to ultra-longwave infrared (UWIR) bands (10.90–22.91 μm). The polarization insensitivity of the designed absorber is demonstrated by analyzing the absorption spectra of the absorber at different polarization angles. By adjusting the relevant geometric parameters, the absorption spectrum can be independently adjusted. Furthermore, the absorber exhibits good incidence angle insensitivity in both transverse electric (TE) and transverse magnetic (TM) modes. The absorbers are simple and easy to configure for applications such as optical cloaking, infrared heat emitters, and photodetectors. These advantages will greatly benefit the application of absorbers in practice.

Novel synthesis of CuFe2O4/g-C3N4 based on microwave ferromagnetic resonance effect for the thorough removal of TC in mariculture wastewater under natural sunlight

Superior separation of photogenerated carriers holds the key to intensive degradation of tetracycline (TC) in mariculture wastewater under natural sunlight. CuFe2O4/g-C3N4 (CFO/g) was synthesized by secondary microwave co-precipitation (SMCP) based on the ferromagnetic resonance absorption effect. Under the reaction conditions of pH = 6.5, CFO/g = 0.2 g/L, [H2O2] = 1 mM, 99.0 % TC removal was realized in 40 min. Enhanced performance for TC removal in high-salinity environments heavily relied on elevated ionic strength and rapid electron transfer of CFO/g in conjunction with high-salinity interactions. To ecologically remediate mariculture wastewater under natural sunlight, we immobilized powdered CFO/g to a ferrite magnet and devised a continuous flow reaction apparatus, incorporating the controlled injection of hydrogen peroxide (H2O2), to achieve the 100 % TC removal and simultaneously undertake the pretreatment of other contaminants (∼70 %). Ultimately, a safety assessment demonstrated that the degradation of mariculture wastewater by the CFO/g photo-Fenton system is a reliable and efficient technology, and the growth of clownfish remained unimpaired. SMCP successfully accelerated the conversion of high-valent metal ions to low-valent ones and eased the activation barriers of H2O2, enabling various active species to execute their respective roles productively. Innovative application of microwave resonance to enhance the magnetic properties of CFO/g and to support the equilibrium conversion of elemental valence states in high-salinity environments from real wastewater.

Trifunctional Fe3O4@MIP nanocatalytic probe-gold nanosol SERS quantitative analysis of ultratrace dinotefuran

A new trifunctional magnetic nanosurface imprinted polymer (MMIP) nanoprobe (Fe3O4@MIP) were rapidly prepared by microwave digestion procedure, and the nanoprobe was characterized in details. It was found that the nanoprobe not only could specifically recognize dinotefuran (DNT), but also could catalyze the HAuCl4-pyruvate indication reaction to produce gold nanoparticles (AuNPs). The generated AuNPs have strong surface enhanced Raman scattering (SERS) effect using VB4r as molecular probes, resonant Rayleigh scattering (RRS) and surface plasmon resonance absorption (Abs) effect. After adding DNT, it specifically combined with Fe3O4@MIP to form Fe3O4@MIP-DNT conjugates with weak catalytic activity, and the SERS/RRS/Abs signal decreased linearly. Based on this, a new SERS/RRS/Abs trimode sensing platform was constructed for detection DNT with detection limit of 0.009, 0.01 and 0.35 nmol/L, respectively. Due to the unique magnetic properties of the nanoprobe, DNT could be easily and quickly identified, separated and enriched, the enrichment factor was up to 100 times. As a comparison, we also investigated the catalytic and specific recognition effects of MMIP nanoprobes prepared with different neonicotinoid insecticides template molecules and functional monomers.

Resonant Absorption of Magnetohydrodynamic Body Modes under Photospheric Conditions

Observations reveal that surface and body modes exist in solar pores under photospheric conditions. While the effects of resonant absorption on photospheric surface modes are well established, its effect on body modes is not known yet. In this paper, we investigate resonant absorption for the body modes under photospheric conditions. We numerically solve the dispersion relation induced by thin boundary approximation and obtain the wave dispersion curves and damping rates of three arbitrarily chosen body modes for sausage and kink waves, respectively. The results show that resonant absorption for the body modes is weaker than for the slow surface modes in both cusp and Alfvén continua. The damping behavior of body modes is similar to slow surface modes while the higher body mode has stronger resonant absorption.

Sound absorption performance of micro-perforated plate sandwich structure based on triply periodic minimal surface

The sandwich structure based on Triply periodic minimal surface (TPMS) is a lightweight and high-strength multifunctional composite material that combines the versatility of heat exchange, impact resistance, and energy absorption, and has been widely used in various fields such as aviation and aerospace. However, its sound absorption performance has not meant fully studied. In this paper, a Micro-perforated plate Diamond sandwich structure (MPP-DSS) was designed based on TPMS method, which was composed of aluminum alloy solid panel, aluminum alloy macroscopically ordered porous Diamond structure and aluminum alloy micro-perforated plate. The acoustic absorption performance in low and medium frequency band was studied by impedance tube method. The results show that MPP-DSS has higher absorption coefficient and bandwidth than traditional perforated plate structure with the same structural parameters. Increasing the thickness of micro-perforated plate can improve the sound absorption capacity of MPP-DSS in the low frequency range, but the width of the sound absorption band will be narrowed accordingly. Different from the resonant sound absorption mechanism of the traditional perforated plate structure, the sound absorption mechanism of MPP-DSS is the combined effect of resonant sound absorption and friction loss sound absorption. This study broadens the versatility of the TPMS structure and can serve as a reference for the design of integrated load-bearing and sound-absorbing structures.

Recognition and nanocatalytic amplification of binary MXene carbon dot surface molecularly imprinted nanoprobe for determination of thiamethoxam by molecular spectroscopy

In this experiment, using MXene quantum dot (MQD) as the core and thiamethoxam (TMX) as the template, a dual-functional surface molecularly imprinted polymer nanoprobe (MQD@MIP) for detecting of TMX was synthesized by microwave digestion procedure. And MQD@MIP was characterized in detail. It was found that this nanoprobe had dual function, which not only could specifically recognize TMX, but also could strongly catalyze the new indicator reaction of HAuCl4-maleic acid to produce gold nanoparticles (AuNPs). The AuNPs exhibit strong surface enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS) and surface plasmon resonance absorption (Abs) effect. Based on this, a new SERS/RRS/Abs trimode biosensoring platform was constructed for the determination of TMX, with a linear range of 1.0–150, 1.0–150, and 5.0–125 nmol/L TMX, and detection limit of 0.57 nmo/L, 0.84 nmol/L and 3.5 nmol/L, respectively. As a comparison, we used carbon dots (CDs) as the core to prepare surface molecularly imprinted polymers (CD@MIP) nanoprobe, and investigated the catalytic effect on the nanogold indicator reaction and the specific recognition effect on TMX.

Damping Scenarios of Kink Oscillations of Solar Coronal Loops

The transition from the large-amplitude rapidly-decaying regime of kink oscillations of plasma loops observed in the corona of the Sun to the low-amplitude decayless oscillations is modelled. In this study, the decayless regime is associated with the energy supply from coronal plasma flows, i.e., self-oscillations, or random movements of footpoints of the oscillating loop. The damping is attributed to the linear effect of resonant absorption. We demonstrate that the decay of an impulsively excited kink oscillation to the self-oscillatory stationary amplitude differs from the exponential decay. The damping time is found to depend on the oscillation amplitude to the power of a negative constant whose magnitude is less than unity. In this scenario, a better model for the damping seems to be super-exponential. In the separately considered case of the decayless oscillatory regime supported by a random driver, the oscillation amplitude experiences an exponential decay to the decayless level. Implications of this finding for magnetohydrodynamic seismology of the solar corona based on the effect of resonant absorption are discussed.

Peculiarities of Resonant Absorption of Electromagnetic Signals in Multilayer Bolometric Sensors.

We examine the effect of resonant absorption of electromagnetic signals in a silicon semiconductor plasma layer when the dielectric plate is placed behind it both experimentally and numerically. It is shown that such plate acts as a dielectric resonator and can significantly increase the electromagnetic energy absorption in the semiconductor for certain frequencies determined by the dielectric plate parameters. Numerical modelling of the effect is performed under the conditions of conducted experiment. The numerical results are found to be in qualitative agreement with experimental ones. This study confirms the proposed earlier method of increasing the efficiency of bolometric-type detectors of electromagnetic radiation.

Calibration and field test of mobile lidar for remote sensing of atmospheric methane

Subject of study. Methane concentration in near-the-surface tropospheric sensing paths was investigated under background conditions using a mobile differential absorption lidar. Aim of study. A mobile differential absorption lidar for remote sensing of atmospheric methane in the mid-infrared spectral range was designed, calibrated, and tested in natural field experiments. Method. The designed lidar enables investigation in the atmosphere using the differential absorption method. This method is based on the effect of resonant absorption of laser emission by gases. The emission source of the lidar has two operating wavelengths, one (on-line) in the center of the methane absorption line and the other (off-line) on the wing of the absorption line. The lidar signals obtained at on- and off-line wavelengths enable retrieval of the methane concentration under background conditions. Main results. The designed mobile IR differential absorption lidar for investigation of atmospheric methane is described. The mobile IR emission source of the differential absorption lidar was calibrated in the informative range of methane sensing near 3400 nm. The results of a natural field test of the mobile IR lidar for detection of atmospheric response at the calibrated sensing wavelengths and retrieval of methane background concentrations of approximately 2.0 ppm in horizontal surface atmospheric sensing paths are presented. Practical significance. The technical solutions for the design of the mobile lidar for remote methane sensing proposed in this paper enable formulation of the requirements on its further improvement aiming to increase the measurement range, design a vertical configuration for remote sensing from an aircraft, and use it at arctic latitudes.

Optical properties of plasmonic metal nanoparticles on GaN surface

Effect of the plasmonic resonant absorption in metal nanoparticles formed on the GaN surface on optical properties of samples is studied. Silver and gold nanoparticles are formed by solid-state dewetting on epitaxial GaN grown by molecular beam epitaxy (MBE) on c-sapphire substrate. Theoretical and experimental optical characteristics show the appearance characteristic absorption of the surface plasmon resonance. The results of the work show the possibility of increasing the efficiency of GaN-based optoelectronic devices.

A Simple and Sensitive Nanogold RRS/Abs Dimode Sensor for Trace As3+ Based on Aptamer Controlled Nitrogen Doped Carbon Dot Catalytic Amplification.

Using citric acid (CA) and ethylenediamine (EDA) as precursors, stable nitrogen-doped carbon dots (CD) nanosols were prepared by microwave procedure and characterized in detail. It was found that CDNs catalyze ethanol (Et)-HAuCl4 to generate gold nanoparticles (AuNPs), which have strong surface plasmon resonance, Rayleigh scattering, (RRS) and a surface plasmon resonance (SPR) absorption (Abs) effect at 370 nm and 575 nm, respectively. Compled the new catalytic amplification indicator reaction with the specific As3+ aptamer reaction, a new RRS/Abs dual-mode aptamer sensor for the assay of trace As3+ was developed, based on the RRS/Abs signals increasing linearly with As3+ increasing in the ranges of 5–250 nmol/L and 50−250 nmol/L, whose detection limits were 0.8 nmol/L and 3.4 nmol/L As3+, respectively. This analytical method has the advantages of high selectivity, simplicity, and rapidity, and it has been successfully applied to the detection of practical samples.

Directly electrospinning synthesized Z-scheme heterojunction TiO2@Ag@Cu2O nanofibers with enhanced photocatalytic degradation activity under solar light irradiation

Electrospinning has become a universal and direct method for the preparation of nanofibers with rich porosity and large specific surface area. In this work, the Z-scheme heterojunction TiO2@Ag@Cu2O nanofibers photocatalyst was prepared via electrospinning and showed excellent visible light catalytic degradation performance with the obtained degradation efficiency of methylene blue as high as 99% within two hours. The main active compounds for the photocatalytic degradation of the dye methylene blue were superoxide radical (•O2−) and hydroxyl radicals (•OH) as well as H+. Compared to pure TiO2, following its combination with Cu2O for visible light absorption, the recombination rate of the photogenerated electron-hole pairs was reduced. After Ag doping, due to the strong surface plasmon resonance absorption effect of Ag, a red shift occurs during the pyrolysis process, showing an outstanding contribution to the effective use of sunlight. Electrochemical test results showed that a Z-scheme hybrid structure was formed in the TiO2@Ag@Cu2O nanofibers. The photocurrent density of TiO2@Ag@Cu2O nanofibers was 3.78 times higher than that of TiO2@Cu2O nanofibers and 47.6 times higher than that of TiO2 nanofibers. The Z-scheme heterojunction not only improved the visible light absorption efficiency, but also separated and transferred carriers, effectively preventing the recombination of photogenerated carriers. Therefore, we believe that TiO2@Ag@Cu2O nanofibers photocatalyst advances the development of photocatalysis technology and is promising for use in a broad range of applications in environmental remediation.

Absorption enhancement of ultraviolet detector in plasmonic nanoparticles-decorated GaN/AlGaN nanostructures

In this article, we numerically studied the optical response characteristics of GaN/AlGaN nanowire arrays decorated with metallic nanoparticles. Based on the finite element simulation software COMSOL Multiphysics, we systematically studied the influence of the size and material of nanoparticles, diameter and period ratio (D∕P ratio) and angle of incident light (AOI) on the optical response in the incident light wavelength range of 200–400 nm. Decorated with gold and silver nanoparticles, we discussed the absorption efficiency, electric field distribution and absorption enhancement of plasmonics AlxGa1−xN nanowire arrays (NWAs). The calculation results show that the resonance absorption effect is usually related to the structure and size of the metallic nanoparticles. By optimizing the material and geometric parameters of AlGaN NWs and metal balls with varying Al composition, double-layered AlxGa1−xN nanostructure decorated with Ag NPs – the bottom layer of which consisted of Al0.35Ga0.65N and the top layer of GaN – showed enhanced efficiency. The calculation results from this article will provide a valuable reference for the theoretical and experimental research of plasmonic AlxGa1−xN NWAs photocathode.

The Effect of the Flux Separability Approximation on Multigroup Neutron Transport

The angular dependence of flux-weighted multigroup cross sections is commonly neglected when generating multigroup libraries. The error of this flux separability approximation is typically not isolated from other error sources due to a lack of availability of library generation and corresponding solvers that cannot relax this approximation. These errors can now be isolated and quantified with the availability of a multigroup Monte Carlo transport and multigroup library-generation capability in the OpenMC Monte Carlo transport code. This work will discuss relevant details of the OpenMC implementation, provide an example case useful for detailing the type of errors one can expect from making the flux separability approximation, and end with more realistic problems which show the impact of the approximation and highlight how it can strongly arise from an energy-dependent resonance absorption effect. Since the angle-dependence is intrinsically linked to the energy group structure, these examples also show that relaxing the flux separability approximation with angle-dependent cross sections could be used to reduce either the fine-tuning required to set a multigroup energy structure for a specific reactor type or the number of energy groups required to obtain a desired level of accuracy for a given problem. This trade-off could increase the costs of generating multigroup cross sections, and has the potential to require more memory for storing the multigroup library during the transport calculations, but it can significantly reduce the computational time required since the runtime of a discrete ordinates or method of characteristics neutron transport solver scales roughly linearly with the number of groups.

Design and fabrication of frequency-responsive terahertz transmittance modulator based on vanadium dioxide spherical films

In this paper, a spherical film array structure based on vanadium dioxide (VO2) was designed and fabricated aimed to enhance the frequency response of transmittance in terahertz (THz) band of VO2 films. Vanadium dioxide and vanadium pentoxide composite spherical films were grown on the surface of two-dimensional single layer array of SiO2 sphere by magnetron sputtering and rapid thermal annealing method, and the frequency response of transmittance of spherical films was studied. The THz transmittance modulation depth (MD) of spherical films increased significantly in the 1.5–3 THz range as frequency increased, while MD of planar films only increased slightly throughout the frequency band. We attributed the frequency response of the MD of spherical films to the absorption by electric dipole resonance. The numerical simulations and electric field distributions illustrate that the regulating effect of resonance absorption would increase as the width of spherical gaps increase. When the width of the spherical gaps was 0.05μm, the absorptivity would increase by 120% from 1.5 to 3 THz, showing the possibility of further improving the THz MD of spherical films. This research would provide a good candidate material in the active modulation in terahertz band which broaden a path for dynamic terahertz radiation manipulation devices.

Design and preparation of a VO2-based high-performance metamaterial for smart windows

Vanadium dioxide (VO2) is an ideal material for smart windows, which can initiate an automatic reversible metal-to-insulator transition from tetragonal to monoclinic structure at the transition temperature (Tc) of 68 °C, resulting in a large difference in near-infrared transmittance, but its application is limited by the poor luminous transmittance (Tlum) and low solar modulation ability (ΔTsol). Besides, metamaterials have shown their superiority as one of the strong competitors and candidates according to previous researches. In this paper, a VO2-based metamaterial structure (VO2(ms), where “ms” is an abbreviation for metamaterial structure) uniformly distributed with round holes was introduced to form a VO2(ms)/TiO2/VO2 multilayer structure, which is designed and produced by simulation and polystyrene microsphere-assisted preparation for enhanced performance. The simulation results obtained a considerable Tlum up to 50.4% and an ultra-high ΔTsol of 22.8%; this is due to the introduction of VO2(ms) which causes the multilayer structure to form metal–insulator–metal cavities at high temperatures and produces a resonance absorption effect. Meanwhile, it is found that the spacing of the round holes (D) has a great influence on the performance of the structure; specifically, an increase in D results in a slight decrease in both ΔTsol and Tlum. Moreover, the experimentally prepared sample demonstrated a ΔTsol of 20.4% and a Tlum of 42.6%, slightly lower than simulation because it has a larger spacing D, which is consistent with the analysis. In summary, both simulation and experiment can get ultra-high ΔTsol while guaranteeing a high Tlum. Such enhanced performance will benefit the application for VO2-based smart windows.

Ultratrace Nitroaromatic Vapor Detection via Surface-Enhanced Fluorescence on Carbazole-Terminated Black Silicon.

Detection of nitroaromatic compounds (NACs) is an important applied task for environmental monitoring, medical diagnostics, and forensic analysis. However, detection of NAC vapors is challenging owing to their low vapor pressure and relatively weak sensitivity of the existing detection techniques. Here, we propose a novel concept to design fluorescence (FL) detection platforms based on chemical functionalization of nanotextured dielectric surfaces exhibiting resonant light absorption, trapping, and localization effects. We demonstrate highly-efficient NAC vapor sensor with selective FL-quenching response from monolayers of carbazole moieties covalently bonded to a spiky silicon surface, "black" silicon, produced over the centimeter-scale area using simple reactive ion etching. The sensor is shown to provide unprecedented ppt (10-12) range limits of detection for several NAC vapors. Easy-to-implement scalable fabrication procedure combined with simple and versatile functionalization techniques applicable to all-dielectric surfaces make the suggested concept promising for realization of various gas sensing systems for social and environmental safety applications.

Ultra-rapid microwave sintering employing thermal instability and resonant absorption

Abstract

High-Performance Sample Substrate of Gold Nanoparticle Multilayers for Surface-Assisted Laser Desorption/Ionization Mass Spectrometry.

The development of a sample substrate with superior performance for desorption and ionization of analyte is the key issue to ameliorate the quality of mass spectra for measurements of small molecules in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). Herein, the homogeneous sample substrate of gold nanoparticle multilayers (AuNPs-ML) with hexagonal lattice was successfully prepared by self-assembly technique. With strong surface plasmon resonance absorption and superior photothermal effect, the sample substrate of AuNPs-ML exhibited high signal sensitivity and low background noise for the detection of model analyte of glucose without additional matrixes in SALDI-MS. Furthermore, compared to merchant matrixes of α-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB), the sample substrate of AuNPs-ML was demonstrated to ameliorate the quality of mass spectra, including signal strength, background interference and signal/noise (S/N) ratio. The sucrose and tryptophan were also measured to show the extensive applications of AuNPs-ML sample substrate for the detections of small molecules in SALDI-MS. Most importantly, the remarkable reproducibility of glucose mass spectra with relative signal of 7.3% was obtained by the use of AuNPs-ML sample substrate for SALDI-MS. The homogeneous sample substrate of AuNPs-ML greatly improved the quality of mass spectra because of its strong absorption of laser energy, low specific heat, high heat conductivity and extraordinary homogeneity. We believe that AuNPs-ML could be a practical sample substrate for small molecule detection in SALDI-MS.