Resonance Detection Research Articles

Detection of electron paramagnetic resonance of two electron spins using a single NV center in diamond

An interacting spin system is an excellent testbed for fundamental quantum physics and applications in quantum sensing and quantum simulation. For these investigations, detailed information on the interactions, e.g., the number of spins and their interaction strengths, is often required. In this study, we present the identification and characterization of a single nitrogen vacancy (NV) center coupled to two electron spins. In the experiment, we first identify a well-isolated single NV center and characterize its spin decoherence time. Then, we perform NV-detected electron paramagnetic resonance (EPR) spectroscopy to detect surrounding electron spins. From the analysis of the NV-EPR signal, we precisely determine the number of detected spins and their interaction strengths. Moreover, the spectral analysis indicates that the candidates of the detected spins are diamond surface spins. This study demonstrates a promising approach for the identification and characterization of an interacting spin system for realizing entangled sensing using electron spin as quantum reporters.

Integrated sensor chip of a resonant cavity light emitter and photon detector for wearable optical medicine

This work presents an integrated chip of a resonant cavity light emitter and photon detector (RCLEPD) to address the requirements of wearable optical medical devices for compact size, high efficiency, and interference resistance sensors. The optical radiation pattern and light extraction efficiency of the resonant cavity light emitting diode (RCLED) as well as the optical absorption spectrum of the resonant cavity enhanced photon detector (RCEPD) are theoretically simulated. Additionally, the wavelength selectivity of the RCEPD absorption spectrum is analyzed. Material epitaxial growth of RCLEPD was performed using metal-organic chemical vapor deposition (MOCVD), and an integrated sensing chip with an area of 2 × 2 mm2 was fabricated. Experimental results demonstrate that RCLED achieves a maximum external quantum efficiency of 10.206%, consistent with the simulation results, while maintaining a peak wavelength at 677.5 nm within a current range of 0-20 mA. Furthermore, the RCEPD exhibits a peak response wavelength at 678 nm, matching that of the RCLED. Utilizing RCLEPD as the sensor, photoplethysmography (PPG) signals are collected from the human wrist under different RCLED driving currents resulting in an average period of 977 ms which aligns with a human pulse frequency of 61 beats/min. With further processing techniques applied to PPG signals, RCLEPD is expected to be used as a sensor in wearable blood pressure and glucose monitoring devices.

Sensing force gradients with cavity optomechanics while evading backaction

We study force-gradient sensing with a coherently driven mechanical resonator and phase-sensitive detection of motion through the two-tone backaction evading measurement of cavity optomechanics. The response of the optomechanical system, solved by numerical integration of the classical equations of motion, shows an extended region which is monotonic to changes in force gradient. We use Floquet theory to model the fluctuations, which rise only slightly above that of the usual backaction evading measurement in the presence of the mechanical drive. The monotonic response and minimal backaction are advantageous for applications such as atomic force microscopy. Published by the American Physical Society 2024

Cumulative damage characteristics of rock samples under cyclic low energy inclined plane impact

The ore pass wall in underground mines is often damaged by the impact and wear caused by unloaded ores. Studying the mechanisms of rock damage and failure under different impact angles can provide technical insights for the design and maintenance of the ore passes. This study employed an inclined impact experimental device along with a drop hammer loading test machine to perform cyclic low-energy impact tests on sandstone samples at five different inclined plane angles. The porosity of the rock samples was measured using a nuclear magnetic resonance (NMR) detection system, which provided data on porosity, T2 spectrum distribution, and NMR images of the samples after different numbers of impacts at different slope angles. The results indicate that: (1) Under cyclic inclined plane impact loading, an increase in the inclination angle, leads to reduced damage to the rock sample. The rock sample impacted at a 45° inclined plane exhibited the most severe damage. Rock samples with large inclination angles are more prone to experience rupture fractures at the tip of the inclined plane, primarily due to shear-tensile failure. The porosity changes dramatically at initially slope angles, resulting in greater damage. (2) As the number of impacts increases, the porosity of the samples first decreases, then increases, and subsequently decreases again. This progression corresponds to the closure of large pores following the first impact, followed by the expansion of micropores into macropores after 5 impacts, ultimately leading to gradual degradation of the samples until failure. (3) As the number of impacts increases, new cracks form within the rock sample and small cracks expand. Despite an increase in the number of micropores, the macropores still exert a significant influence on the rock samples, with the macropore spectrum area accounting for over 95%.

Study on photocatalytic degradation and antibacterial properties of conjugated microporous polymers/TiO2 composite membranes

Conjugated microporous polymers (CMPs) are widely used in the field of photocatalysis due to their unique conjugated structures and various synthesis methods. Herein, we report the design and synthesis of conjugated microporous polymers hollow spheres (CMPs-HS) superhydrophilic modified by acetylcysteine (CMPs-HS-S) and compounded with the inorganic semiconductor material titanium dioxide (CMPs-HS-S/TiO2) for efficient photocatalytic degradation. To facilitate recycling, the composite membrane material was prepared by combining the materials mentioned above with PVDF membrane. The composite membrane materials had good hydrophilic and photocatalytic properties. Under visible light, the degradation rate of tetracycline (TC) (10 mg/L 180 min) reached 90 %, and the bactericidal rates for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 89 % and 99.99 %, respectively. The efficient photocatalytic performance of the composite membranes could be attributed to the hollow sphere structure of CMPs and the role of TiO2 as a photogenic electron transfer platform. Additionally, the hydrophilicity of the membrane also helped to accelerate the occurrence of photocatalytic reactions. After electron paramagnetic resonance (EPR) detection, h+, 1O2 and O2− were proved to be important reactive substances, which played a major role in degradation. These studies reflect the versatility of CMPs-based photocatalysts and provide a new idea for the future development of CMPs-based photocatalysts.

Detection of electron spin resonance of a single nitrogen-vacancy center in diamond using the excited-state lifetime

Detection of electron spin resonance of a single nitrogen-vacancy center in diamond using the excited-state lifetime

Iron–molybdenum bimetals incorporated montmorillonite-based catalytic ceramic membrane for heterogenous Fenton reaction towards the degradation of micropollutants in water

This study developed an innovative material approach that integrated Fenton catalysis with membrane filtration in a single system using iron–molybdenum bimetal oxides (FeMoO) incorporated montmorillonite (MMT)-based ceramic membrane (FeMoMMTCM) to achieve continuous Fenton reaction for water purification. The embedded bimetallic FeMoO catalyst created abundant active Fe(II) sites on the external and internal surfaces of the ceramic membrane (CM) for H2O2 activation. Using naproxen (NPX) as a model micropollutant in water, the FeMoMMTCM/H2O2 system achieved a 98.6 % removal of NPX (10 mg/L) within a filtration period of 3.4 min through the membrane, in comparison to a 17.5 % removal by FeMoMMTCM filtration with no H2O2 dosing and a 21.1 % removal by the FeMoO-less MMTCM/H2O2 system. The catalytic membrane demonstrated its high NPX removal efficiency over multiple cycles, retaining its effectiveness even in the presence of co-existing ions and organic matter in the water matrix. Furthermore, the FeMoMMTCM/H2O2 system was able to remove nearly 70 % of residual organic pollutants from the actual secondary wastewater effluent. The quenching tests and electro-paramagnetic resonance (EPR) detection confirmed the generation of hydroxyl (OH) and superoxide (O2−) radicals from H2O2. The excellent catalytic performance can be attributed to the Fe-Mo bimetallic catalyst, in which the active Mo(VI)/Mo(IV) cycle can facilitate the Fe(II)/Fe(III) cycle for continuous Fenton reaction. The cost analysis indicates that the low-cost MMT and its low sintering temperature for ceramics would greatly decrease the cost of MMTCM (243.1 US$/m2 vs. 541.5 US$/m2 of alumina-based CM). Overall, the research presents a technical strategy for the fabrication of highly cost-effective catalytic membranes with Fenton reaction for removing micropollutants from water.

Near-infrared light enhanced oxygen vacancies on metal organic frameworks through photothermal effect for peroxydisulfate activation to remove organic pollutants

Peroxydisulfate (PDS)-based advanced oxidation processes (AOPs) are a promising strategy for addressing the challenges of contamination in aqueous environment. Taking advantage of solar energy based photocatalysis showed great potential on PDS activation for pollution control. However, the limited usage of near-infrared (NIR) region by photocatalysts restricted the realization of using full sunlight energy. Herein, zeolitic imidazolate frameworks derived materials (ZNC) with oxygen vacancies (VO) are designed and obtained, which can efficiently activate PDS under NIR light due to the photothermal effect, exhibiting superior carbamazepine (CBZ) degradation performance (84 % of CBZ within 60 min). Further quenching tests and electron paramagnetic resonance detection demonstrate that the photothermal effect can enhance the concentration of oxygen vacancies on the surface and facilitate charge separation of ZNC, which effectively activate PDS to generate O2−, 1O2, and h+, thus significantly enhancing the photocatalytic degradation of CBZ. Additionally, combining the results of intermediates analysis and DFT calculation, a systematic CBZ degradation pathway by two tracks is proposed. Moreover, the overall potential risks of CBZ are expected to be weakened in the ZNC/PDS/NIR process through photothermal catalytic degradation. Thus, a new strategy is provided for optimizing the use of solar energy to boost PDS activation for water purification.

An Ultrasensitive Molecular Detector for Direct Sensing of Spin Currents at Room Temperature.

The experimental analysis of pure spin currents at interfaces is one major goal in the field of magnonics and spintronics. Complementary to the established Spin-Hall effect using the spin-to-charge conversion in heavy metals for information processing, we present a novel approach based on spin pumping detection by an interfacial, resonantly excited molecular paramagnet adsorbed to the surface of the spin current generating magnet. Here, we show that the sensitivity of this electron paramagnetic resonance (EPR) detector can be enhanced by orders of magnitude through intramolecular transfer of spin polarization at room temperature. Our proof-of-principle sample consists of octahedral-shaped ferrimagnetic Fe3O4 nanoparticles covered by oleic acid (OA) which has two paramagnetic centers, S1 and S2. S1 arises from the chemisorption of OA and is located directly at the interface to Fe3O4. S2 originates from radical formation at the center of the molecule close to the double bond of oleic acid and is not influenced by chemisorption. Using ferromagnetic resonance (FMR) excitation of the Fe3O4 nanoparticles to pump spins into S1, a population inversion of the spin-split levels of S2 is formed, vastly enhancing the detection sensitivity on the atomic scale.

X-Band Single Chip Integrated Pulsed Electron Spin Resonance Microsystem.

We report on the design and characterization of a single chip integrated pulsed electron spin resonance detector operating at 9.1 GHz. The microsystem consists of an excitation microcoil, a detection microcoil, a low noise microwave preamplifier, a mixer, and an intermediate frequency (IF) amplifier. The chip area is about 0.7 mm2. To exemplify its possible applications, we report the results of single pulse, Rabi nutation, Hahn echo, two echoes, Carr-Purcell, and inversion recovery echo experiments performed on 0.02 and 0.05 nL samples of α, γ-bisdiphenylene-β-phenylallyl (BDPA) and 1% BDPA in polystyrene (BDPA:PS) at room temperature. The measured spin sensitivity is about 8 × 107 spins/Hz1/2 on a sensitive volume of about 0.1 nL. The microsystem power consumption is less than 100 mW, the radio frequency (RF) input bandwidth is 8.8 to 9.8 GHz, the IF output bandwidth is DC to 350 MHz, and the deadtime is less than 30 ns.

Large-enhancement nanoscale dynamic nuclear polarization near a silicon nanowire surface.

Dynamic nuclear polarization (DNP) has revolutionized the field of nuclear magnetic resonance spectroscopy, expanding its reach and capabilities to investigate diverse materials, biomolecules, and complex dynamic processes. Bringing high-efficiency DNP to the nanometer scale would open exciting avenues for studying nanoscale nuclear spin ensembles, such as single biomolecules, virus particles, and condensed matter systems. Combining pulsed DNP with nanoscale force-detected magnetic resonance measurements, we demonstrated a 100-fold enhancement in the Boltzmann polarization of proton spins in nanoscale sugar droplets at 6 kelvin and 0.33 tesla. Crucially, this enhancement corresponds to a factor of 200 reduction in the averaging time compared to measurements that rely on the detection of statistical fluctuations in nanoscale nuclear spin ensembles. These results substantially advance the capabilities of force-detected magnetic resonance detection as a practical tool for nanoscale imaging.

Resonant switching current detector based on underdamped Josephson junctions

Current-biased Josephson junctions can act as detectors of electromagnetic radiation. At optimal conditions, their sensitivity is limited by fluctuations causing stochastic switching from the superconducting to the resistive state. This work provides a quantitative description of a stochastic switching current detector, based on an underdamped Josephson junction. It is shown that activation of a Josephson plasma resonance can greatly enhance the detector responsivity in proportion to the quality factor of the junction. The ways of tuning the detector for achieving optimal operation are discussed. For realistic parameters of Nb/AlOx/Nb tunnel junctions, the sensitivity and noise-equivalent power (NEP) can reach values of S≃5×1012 (V/W) and NEP≃2×10−23 (WHz−1/2), respectively. These outstanding characteristics facilitate both bolometric and single-photon detection in microwave and terahertz ranges. Published by the American Physical Society 2024

Electrical Detection of Acoustic Antiferromagnetic Resonance in Compensated Synthetic Antiferromagnets.

Compensated synthetic antiferromagnets (SAFs) stand out as promising candidates to explore various spintronic applications, benefitting from high precession frequency and negligible stray field. High-frequency antiferromagnetic resonance in SAFs, especially the optic mode (OM), is highly desired to attain fast operation speed in antiferromagnetic spintronic devices. SAFs exhibit ferromagnetic configurations above saturation field; however in that case, the intensity of OM is theoretically zero and hard to be detected in well-established microwave resonance experiments. To expose the hidden OM, the exchange symmetry between magnetic layers must be broken, inevitably introducing remanent magnetization. Here, we experimentally demonstrate a feasible method to break the symmetry via surface acoustic waves with the maintenance of compensated SAF structure. By introducing an out-of-plane strain gradient inside the Ir-mediated SAFs, we successfully reveal the hidden OM. Remarkably, the OM intensity can be effectively modulated by controlling strain gradients in SAFs with different thicknesses, confirmed by finite-element simulations. Our findings provide a feasible scheme for detecting the concealed OM, which would trigger future discoveries in magnon-phonon coupling and hybrid quasiparticle systems.

Crown ethers: Small organic molecules unexpectedly hidden in nuclear magnetic resonance

The new class of ten macrocyclic compounds, lactic acid derived crown ethers, was designed and synthesized. They mainly composed of lactic acid and benzene or iodobenzene skeletons, and the introduction of iodine on the benzene ring was crucial to the formation of more regular crown ether conformation, starting from the diacid precursor. They possessed stable and larger cavities than classical macrocycles such as cyclodextrins. These crown ethers were discovered hiding function onto small molecules such as ethyl lactate, methanol, ethanol, aniline and phenol in nuclear magnetic resonance detection.

Highly sensitive terahertz polarization biosensor utilizing chiral metasurface

In order to achieve a highly sensitive biosensor with a simple structure, we propose a chiral metasurface polarization sensor. Using immunological surface plasmon resonance (SPR) detection, the antigen or antibody is fixed as a probe on the SPR metasurface to detect the corresponding antibody or antigen. Through the change of the refractive index of the analyte on the surface facial mask, the terahertz signal changes, and finally the sensing detection of avian influenza virus can be achieved. The designed metasurface adopts a hollow split sector chiral structure to generate chiral surface current, which can convert linearly polarized incident waves as elliptical polarized waves. The structure achieves the high sensitivity of 401 deg/RIU at frequency of 0.8 THz, and the avian influenza virus (H1N1, H5N2 and H9N2) with the same real part of the refractive index can also be distinguished. Influenza viruses belong to the family Orthomyxoviridae of RNA viruses, divided into three types: A, B, and C. In this article, avian influenza viruses belong to type A influenza viruses. It can clearly identify different Avian Influenza Viruses by the two polarization characteristic parameters of the reflection spectrum PEA (Polarization Ellipse Angle) and PRA (Polarization Rotation Angle). This method has a significant application prospect in the fields of biomedicine and food industries.

Controlling 229Th isomeric state population in a VUV transparent crystal

The radioisotope thorium-229 (229Th) is renowned for its extraordinarily low-energy, long-lived nuclear first-excited state. This isomeric state can be excited by vacuum ultraviolet (VUV) lasers and 229Th has been proposed as a reference transition for ultra-precise nuclear clocks. To assess the feasibility and performance of the nuclear clock concept, time-controlled excitation and depopulation of the 229Th isomer are imperative. Here we report the population of the 229Th isomeric state through resonant X-ray pumping and detection of the radiative decay in a VUV transparent 229Th-doped CaF2 crystal. The decay half-life is measured to 447(25) s, with a transition wavelength of 148.18(42) nm and a radiative decay fraction consistent with unity. Furthermore, we report a new “X-ray quenching” effect which allows to de-populate the isomer on demand and effectively reduce the half-life. Such controlled quenching can be used to significantly speed up the interrogation cycle in future nuclear clock schemes.

Quantum gravity signatures in gravitational wave detectors placed inside a harmonic trap potential

In this work, we consider a general gravitational wave detector of gravitational waves interacting with an incoming gravitational wave carrying plus polarization only placed inside a harmonic trap. This model can be well acquainted with the description of a resonant detector of gravitational waves as well. The well-known detector-gravitational wave interaction scenario uses the method of a semiclassical approach where the detector is treated quantum mechanically but the gravitational wave is considered at a classical level. In our analysis, we use a discrete mode decomposition of the gravitational wave perturbation which results in a Hamiltonian involving the position and momentum operators corresponding to the gravitational wave and the harmonic oscillator. We have then calculated the transition probability for the harmonic oscillator-gravitational wave tensor product state for going from an initial state to some unknown final state. Using the energy flux relation of the gravitational waves, we observe that if we consider the total energy as a combination of the number of gravitons in the initial state of the detector then the transition probability for the resonant absorption case scenario takes the analytical form which is exactly similar to the semiclassical absorption case. In the case of the emission scenario, we observe a spontaneous emission of a single graviton which was completely absent in the semiclassical analog of this model. This therefore gives a direct signature of linearized quantum gravity. Published by the American Physical Society 2024

Distributed estimation cascade second-order tri-stable stochastic resonance method for random noise suppression in continuous-wave mud pulse telemetry

The extraction of high-quality useful signals in downhole environments has perennially posed a technical challenge for continuous wave mud pulse transmission systems. Traditional denoising methods, such as adaptive filtering and wavelet transform, inevitably compromise the integrity of the original signal's useful components while removing noise. Different from the traditional denoising methods, stochastic resonance (SR) is capable of transferring the energy of noise to the signal, thereby accomplishing the objective of noise suppression. In this paper, based on the second-order tri-stable stochastic resonance detection method combined with the estimation of distribution algorithm (EDA), a distributed estimation cascade second-order tri-stable stochastic resonance (EDA- CSTSR) detection method is proposed for the first time. By constructing 5 groups of simulation signals with different signal-to-noise ratios (SNRs), the denoising performance of distributed estimation CSTSR, Langevin SR, and Duffing SR is analyzed in detail. The results show that compared with Langevin SR and Duffing SR, the EDA-CSTSR can increase the SNR of the input simulation signal by at least 17 dB and significantly increase the amplitude of the useful pulse signal. Moreover, the EDA-CSTSR is applied to process actual data obtained from a drilling site, enabling the recognition of weak signals amidst strong background noise, which highlights the method's excellent practical application value and underscores its potential for further enhancement.

Influence of water vapor concentration on photoacoustic spectroscopy‐based characteristic gas analysis of transformer faults

AbstractThe water vapor in the ambient air affects the accuracy of the photoacoustic (PA) dissolved gas analysis system for transformer health monitoring. A laser PA system was evaluated by dry and humidified standard gases to study the influence of water vapor concentration on PA gas detection. Theoretical analysis was conducted on the effect of gas molecule relaxation on PA signal detection. A high‐frequency resonant PA cell and a low‐frequency nonresonant PA cell were used to detect acetylene (C2H2) and carbon monoxide (CO), respectively. The experimental results show that the PA signal of humidified CO is about 12 times higher than PA signal of dry gas for the resonant PA detection system, respectively. In addition, as the frequency is increased from 30 to 980 Hz, the PA signals of humidified and dry CO attenuate by 1.5 and 6.9 times, respectively.

Enhanced Degradation of Micropollutants in a Peracetic Acid/Mn(II) System with EDDS: An Investigation of the Role of Mn Species.

Extensive research has been conducted on the utilization of a metal-based catalyst to activate peracetic acid (PAA) for the degradation of micropollutants (MPs) in water. Mn(II) is a commonly employed catalyst for homogeneous advanced oxidation processes (AOPs), but its catalytic performance with PAA is poor. This study showed that the environmentally friendly chelator ethylenediamine-N,N'-disuccinic acid (EDDS) could greatly facilitate the activation of Mn(II) in PAA for complete atrazine (ATZ) degradation. In this process, the EDDS enhanced the catalytic activity of manganese (Mn) and prevented disproportionation of transient Mn species, thus facilitating the decay of PAA and mineralization of ATZ. By employing electron spin resonance detection, quenching and probe tests, and 18O isotope-tracing experiments, the significance of high-valent Mn-oxo species (Mn(V)) in the Mn(II)-EDDS/PAA system was revealed. In particular, the involvement of the Mn(III) species was essential for the formation of Mn(V). Mn(III) species, along with singlet oxygen (1O2) and acetyl(per)oxyl radicals (CH3C(O)O•/CH3C(O)OO•), also contributed partially to ATZ degradation. Mass spectrometry and density functional theory methods were used to study the transformation pathway and mechanism of ATZ. The toxicity assessment of the oxidative products indicated that the toxicity of ATZ decreased after the degradation reaction. Moreover, the system exhibited excellent interference resistance toward various anions and humid acid (HA), and it could selectively degrade multiple MPs.