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Direct exposure of non-equilibrium atmospheric pressure plasma confers simultaneous oxidative and ultraviolet modifications in biomolecules
摘要： Thermal plasmas and lasers are used in medicine to cut and ablate tissues and for coagulation. Non-equilibrium atmospheric pressure plasma (NEAPP) is a recently developed, non-thermal technique with possible biomedical applications. Although NEAPP reportedly generates reactive oxygen/nitrogen species, electrons, positive ions, and ultraviolet radiation, little research has been done into the use of this technique for conventional free radical biology. Recently, we developed a NEAPP device with high electron density. Electron spin resonance spin-trapping revealed ?OH as a major product. To obtain evidence of NEAPP-induced oxidative modifications in biomolecules and standardize them, we evaluated lipid peroxidation and DNA modifications in various in vitro and ex vivo experiments. Conjugated dienes increased after exposure to linoleic and α-linolenic acids. An increase in 2-thiobarbituric acid-reactive substances was also observed after exposure to phosphatidylcholine, liposomes or liver homogenate. Direct exposure to rat liver in saline produced immunohistochemical evidence of 4-hydroxy-2-nonenal- and acrolein-modified proteins. Exposure to plasmid DNA induced dose-dependent single/double strand breaks and increased the amounts of 8-hydroxy-2'-deoxyguanosine and cyclobutane pyrimidine dimers. These results indicate that oxidative biomolecular damage by NEAPP is dose-dependent and thus can be controlled in a site-specific manner. Simultaneous oxidative and UV-specific DNA damage may be useful in cancer treatment.
关键词： 8-OHdG,HNE-modified protein,non-equilibrium atmospheric pressure plasma,electron spin resonance spin-trapping,UV
更新于2025-09-23 15:22:29
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Single-photon emission from single-electron transport in a SAW-driven lateral light-emitting diode
摘要： The long-distance quantum transfer between electron-spin qubits in semiconductors is important for realising large-scale quantum computing circuits. Electron-spin to photon-polarisation conversion is a promising technology for achieving free-space or fibre-coupled quantum transfer. In this work, using only regular lithography techniques on a conventional 15 nm GaAs quantum well, we demonstrate acoustically-driven generation of single photons from single electrons, without the need for a self-assembled quantum dot. In this device, a single electron is carried in a potential minimum of a surface acoustic wave (SAW) and is transported to a region of holes to form an exciton. The exciton then decays and creates a single optical photon within 100 ps. This SAW-driven electroluminescence, without optimisation, yields photon antibunching with g(2)(0) = 0.39 ± 0.05 in the single-electron limit (g(2)(0) = 0.63 ± 0.03 in the raw histogram). Our work marks the first step towards electron-to-photon (spin-to-polarisation) qubit conversion for scaleable quantum computing architectures.
关键词： quantum computing,GaAs quantum well,electron-spin qubits,surface acoustic wave,single-photon emission
更新于2025-09-23 15:19:57
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Geminate recombination in organic photovoltaic blend PCDTBT/PC <sub/>71</sub> BM studied by out-of-phase electron spin echo spectroscopy
摘要： The key process in organic solar cell operation is charge separation under light illumination. Due to the low dielectric constant of organic materials, the Coulomb attraction energy within the interfacial charge-transfer state (CTS) is larger than the thermal energy. Understanding the mechanism of charge separation at the organic donor/acceptor interface still remains a challenge and requires knowledge of the CTS temporal evolution. To address this problem, the CTS in the benchmark photovoltaic blend PCDTBT/PC71BM was studied by the out-of-phase Electron Spin Echo (ESE). The protocol for determining the CTS geminate recombination rate for certain electron-hole distances was developed. Simulating the out-of-phase ESE trace for the CTS in the PCDTBT/PC71BM blend allows precise determination of the electron-hole distance distribution function and its evolution with the increase in the delay after the laser flash. Distances of charge separation up to 6 nm were detected upon thermalization at a temperature of 20 K. Assuming the exponential decay of the recombination rate, the attenuation factor β = 0.08 ??1 is estimated for the PCDTBT/PC71BM blend. Such a low attenuation factor is probably caused by a high degree of hole delocalization along the PCDTBT chain.
关键词： PCDTBT/PC71BM blend,electron spin echo,geminate recombination,organic solar cells,charge transfer state
更新于2025-09-23 15:19:57
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Spin-Controlled Charge Recombination Pathways across the Inorganic/Organic Interface
摘要： Charge transfer and recombination across the inorganic/organic interface in nanocrystal or quantum dot (QD)-molecule hybrid materials has been extensively studied. Principles of controlling charge transfer and recombination via energetics and electronic coupling have been established. However, the use of electron spin to control transfer and recombination pathways in such systems remains relatively underexplored. Here we use CdS QD-alizarin (AZ) as a model system to demonstrate this principle. Using time-resolved spectroscopy, we found that the charge separated states (QD--AZ+) created by selectively exciting AZ molecules mostly recombined to regenerate ground state complexes, whereas the apparently “same” charge separated states created by exciting QDs recombined to produce AZ molecular triplet states. Such a difference can be traced to the distinct spin configurations between excited QDs (QD*, with an ill-defined spin) and AZ (1AZ*, spin singlet) and the asymmetric electron and hole spin-flip rates in II-VI group QDs. The transferability of such a principle was confirmed by similar observations obtained for CdS QD-tetracene complexes. Opening an avenue of controlling charge transfer and recombination pathways via electron spin is potentially important for applications such as artificial photosynthesis.
关键词： CdS QD-alizarin,artificial photosynthesis,quantum dot,inorganic/organic interface,triplet states,electron spin,recombination,time-resolved spectroscopy,Charge transfer
更新于2025-09-23 15:19:57
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Rays via Single-Shot Laser-Electron Interaction
摘要： Generation of circularly polarized (CP) and linearly polarized (LP) γ rays via the single-shot interaction of an ultraintense laser pulse with a spin-polarized counterpropagating ultrarelativistic electron beam has been investigated in nonlinear Compton scattering in the quantum radiation-dominated regime. For the process simulation, a Monte Carlo method is developed which employs the electron-spin-resolved probabilities for polarized photon emissions. We show efficient ways for the transfer of the electron polarization to the high-energy photon polarization. In particular, multi-GeV CP (LP) γ rays with polarization of up to about 95% can be generated by a longitudinally (transversely) spin-polarized electron beam, with a photon flux meeting the requirements of recent proposals for the vacuum birefringence measurement in ultrastrong laser fields. Such high-energy, high-brilliance, high-polarization γ rays are also beneficial for other applications in high-energy physics, and laboratory astrophysics.
关键词： nonlinear Compton scattering,electron-spin-resolved probabilities,high-energy physics,Monte Carlo method,circularly polarized γ rays,vacuum birefringence,quantum radiation-dominated regime,laboratory astrophysics,linearly polarized γ rays
更新于2025-09-23 15:19:57
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Formation of lipid bilayers on the pore walls of macroporous silicon
摘要： Electron paramagnetic resonance (EPR) spectroscopy was used to study the pore filling of macroporous silicon with lipid vesicles (liposomes), added with a spin label. Different EPR spectra were obtained with the magnetic field parallel and perpendicular to the macroporous silicon sample surface. These spectra could be well simulated with an admixture of the isotropic spectrum of liposomes, plus a simulated spectrum corresponding to a cylindrical distribution of lipid bilayers. This means that a portion of the liposomes were disrupted, and supported lipid bilayers were formed covering the inner surface of the pores. Diverse protocols can be explored in order to optimize the lipid covering of the pore walls, and to achieve an adequate lipid hydration. This system can be used as a platform to study lipid phase transitions in a confined environment, and to characterize membrane proteins.
关键词： Liposomes,Electron paramagnetic resonance/electron spin resonance,Supported lipid bilayers,Porous silicon,Spin labels
更新于2025-09-19 17:15:36
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Analysis of the charge transfer and separation in electrically doped organic semiconductors by electron spin resonance spectroscopy
摘要： We investigated the charge generation mechanism of electrically doped organic semiconductors (OSs) by electron spin resonance (ESR) analysis. ESR spectroscopy was used to successfully evaluate the radical density of p-doped OSs to estimate the charge transfer efficiency (CTE) of various doped systems. The results showed that the CTE is efficient close to 100% if the dopant molecules are homogenously dispersed and the energy difference (?E) between the highest occupied molecular orbital (HOMO) level of the host molecule and lowest unoccupied molecular orbital (LUMO) level of the p-dopant is large. The charge separation efficiency to form free carriers from the radicals is rather low (less than 12% in this study) and is a dominant factor controlling the charge generation efficiency (CGE). An organic dopant molybdenum tris[1,2-bis(trifluoromethyl)ethane-1,2-dithiolene] turns out to be an efficient dopant with the CGE of 9.7% due to high CTE originating from homogenous dispersion of the organic p-dopants and low LUMO level, i.e., large ?E.
关键词： charge generation efficiency,p-dopant,charge transfer,electron spin resonance spectroscopy,Organic semiconductors,charge separation
更新于2025-09-19 17:15:36
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Temperature dependence of inter-dot electron-spin transfer among laterally coupled excited states in high-density InGaAs quantum dots
摘要： The temperature dependence of interdot spin-transfer dynamics at laterally coupled excited states (ESs) in high-density InGaAs quantum dots (QDs) was studied using spin- and time-resolved photoluminescence spectroscopy. At low temperatures below 100 K, temporary suppression of electron-spin polarization decay due to selective relaxation of minority spins from emissive ESs to lower-energy states in neighboring QDs was observed. In the temperature range from 20 K to 140 K, thermal activation of electron spins from lower-energy QD states to higher-energy states via interdot transfer prevents the aforementioned selective relaxation of minority spins, leading to a faster decay of electron-spin polarization during light emission. At high temperatures above 140 K, reinjection of depolarized electron spins from barriers after thermal escape from QD ESs accelerates the further decay of the electron-spin polarization, wherein the electron spins can be activated via ladderlike interdot transfer. These findings indicate that the suppression of reinjection of electron spins from barriers in a high-density QD system is crucial for maintaining high electron-spin polarization during light emission at high temperatures.
关键词： electron-spin polarization,InGaAs quantum dots,interdot spin-transfer dynamics,spin- and time-resolved photoluminescence spectroscopy,temperature dependence
更新于2025-09-19 17:13:59
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Coherence of a Driven Electron Spin Qubit Actively Decoupled from Quasistatic Noise
摘要： The coherence of electron spin qubits in semiconductor quantum dots suffers mostly from low-frequency noise. During the past decade, efforts have been devoted to mitigate such noise by material engineering, leading to substantial enhancement of the spin dephasing time for an idling qubit. However, the role of the environmental noise during spin manipulation, which determines the control fidelity, is less understood. We demonstrate an electron spin qubit whose coherence in the driven evolution is limited by high-frequency charge noise rather than the quasistatic noise inherent to any semiconductor device. We employ a feedback-control technique to actively suppress the latter, demonstrating a π-flip gate fidelity as high as 99.04 (cid:1) 0.23% in a gallium arsenide quantum dot. We show that the driven-evolution coherence is limited by the longitudinal noise at the Rabi frequency, whose spectrum resembles the 1=f noise observed in isotopically purified silicon qubits.
关键词： gallium arsenide quantum dot,low-frequency noise,Rabi frequency,1=f noise,semiconductor quantum dots,π-flip gate fidelity,isotopically purified silicon qubits,feedback-control technique,high-frequency charge noise,electron spin qubits
更新于2025-09-19 17:13:59
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Oxygen vacancy induced ferromagnetism in ball milled Zn0.97Ni0.03O: Confirmation through electron spin resonance
摘要： Among the semiconducting materials, ZnO is a versatile multifunctional candidate with a direct band gap of 3.37 eV at 300 K and large excitonic binding energy of 60 meV which can be useful for spintronics device applications. ZnO has high solubility for transition metals. The transition metals which have been used for DMS, Ni is the most efficient doping element to improve the electrical, magnetic properties of ZnO. Ni doped ZnO would be a good candidate to achieve ferromagnetic property with a high curie temperature i.e. above the room temperature. In this study, Zn1?xNixO (x = 0.03) powder sample was successfully synthesized by a ball milling technique. The X-ray diffraction analysis confirms the polycrystalline, hexagonal wurzite structure for 3% Ni doped ZnO nanoparticles. The substitution of Ni in the ZnO matrix has been confirmed by micro-Raman analysis with the observation of E2 (High) vibrational mode at 437 cm?1 which refers to the strongest mode of vibration in wurtzite crystal structure. A broadened peak observed at 570 cm?1 informs about the presence of clusters of oxygen vacancies. VSM measurement of the sample shows the ferromagnetic hysteresis loop at room temperature with saturation moment of 9 × 10?5 emu/g. The calculated ‘g’ value of 1.95 from electron spin resonance spectrum suggests that the observed ferromagnetism is due to the oxygen vacancy.
关键词： Diluted magnetic semiconductor,Electron spin resonance,Defects,Ferromagnetism,ZnO,Nanoparticles
更新于2025-09-19 17:13:59