Deep-ultraviolet (DUV, wavelength λ < 200 nm) nonlinear optical (NLO) crystal is the core component of frequency conversion to generate DUV laser, which plays an important role in cutting-edge laser ...technology and fundamental science. Significant progress has been made in both experimental exploration and theoretical design in the field of DUV NLO crystals over the past three decades. In-depth insight into "structure-property correlations", in particular, allows for rigorous and precise identification of DUV NLO crystals. In this article, we reviewed the current experimental and theoretical research progress while elucidating the core concepts and stringent criteria of qualified DUV phase-matched second-harmonic generation crystals. We also discussed the development of the DUV NLO "structure-property correlations" from first principles and how it has sparked interest in related materials, as well as future directions for obtaining potential DUV NLO crystals.
Defining the metabolic strategies used by wheat to tolerate and recover from drought events will be important for ensuring yield stability in the future, but studies addressing this critical research ...topic are limited. To this end, the current study quantified the physiological, biochemical, and agronomic responses of a drought tolerant and drought sensitive cultivar to periods of water deficit and recovery. Drought stress caused a reversible decline in leaf water relations, membrane stability, and photosynthetic activity, leading to increased reactive oxygen species (ROS) generation, lipid peroxidation and membrane injury. Plants exhibited osmotic adjustment through the accumulation of soluble sugars, proline, and free amino acids and increased enzymatic and non-enzymatic antioxidant activities. After re-watering, leaf water potential, membrane stability, photosynthetic processes, ROS generation, anti-oxidative activities, lipid peroxidation, and osmotic potential completely recovered for moderately stressed plants and did not fully recover in severely stressed plants. Higher photosynthetic rates during drought and rapid recovery after re-watering produced less-pronounced yield declines in the tolerant cultivar than the sensitive cultivar. These results suggested that the plant's ability to maintain functions during drought and to rapidly recover after re-watering during vegetative periods are important for determining final productivity in wheat.
Hybrid metamaterials that exhibit reconfigurable responses under external stimulus, such as electric fields and light radiation, have only recently been demonstrated by combining active media with ...patterned metallic structures. Nevertheless, hybrid terahertz (THz) metamaterials whose spectral performance can be dynamically tuned over a large scale remain rare. Compared with most active media (for instance, silicon) that provide limited activity, vanadium dioxide (VO
), which exhibits an insulator-to-metal transition, has been recently explored to facilitate dynamically tunable metamaterials. More importantly, the phase transition yields a three orders of magnitude increase in THz electrical conductivity, which suggests the potential for creating VO
based hybrid resonators that operate at THz frequencies. Here, we show that an integration of VO
structures and conventional metallic resonating components can enable a class of highly tunable THz metamaterials. Considering the widely studied phase-transition dynamics in VO
, the proposed hybrid metamaterials are capable of offering ultrafast modulation of THz radiation.
We demonstrate enormously strong chiral effects from a photonic metamaterial consisting of an array of dual-layer twisted-arcs with a total thickness of ∼λ/6. Experimental results reveal a circular ...dichroism of ∼0.35 in the absolute value and a maximum polarization rotation of ∼305°/λ in a near-infrared wavelength region. A transmission of greater than 50% is achieved at the frequency where the polarization rotation peaks. Retrieved parameters from measured quantities further indicate an actual optical activity of 76° per λ and a difference of 0.42 in the indices of refraction for the two circularly polarized waves of opposite handedness.
Despite the exotic material properties that have been demonstrated to date, practical examples of versatile metamaterials remain exceedingly rare. The concept of metadevices has been proposed in the ...context of hybrid metamaterial composites: systems in which active materials are introduced to advance tunability, switchability and nonlinearity. In contrast to the successful hybridizations seen at lower frequencies, there has been limited exploration into plasmonic and photonic nanostructures due to the lack of available optical materials with non-trivial activity, together with difficulties in regulating responses to external forces in an integrated manner. Here, by presenting a series of proof-of-concept studies on electrically triggered functionalities, we demonstrate a vanadium dioxide integrated photonic metamaterial as a transformative platform for multifunctional control. The proposed hybrid metamaterial integrated with transition materials represents a major step forward by providing a universal approach to creating self-sufficient and highly versatile nanophotonic systems.
Solar‐energy‐driven CO2 conversion into value‐added chemical fuels holds great potential in renewable energy generation. However, the rapid recombination of charge carriers and deficient reactive ...sites, as two major obstacles, severely hampers the photocatalytic CO2 reduction activity. Herein, a desirable surface halogenation strategy to address the aforementioned concerns over a Sillén‐related layer‐structured photocatalyst Bi2O2(OH)(NO3) (BON) is demonstrated. The surface halogen ions that are anchored on the Bi atoms by replacing surface hydroxyls on the one hand facilitate the local charge separation, and, on the other hand, activate the hydroxyls that profoundly boost the adsorption of CO2 molecules and protons and facilitate the CO2 conversion process, as evidenced by experimental and theoretical results collectively. Among the three series of BON‐X (X = Cl, Br, and I) catalysts, BON‐Br shows the most substantially enhanced CO production rate (8.12 µmol g−1 h−1) without any sacrificial agents or cocatalysts, ≈73 times higher than that of pristine Bi2O2(OH)(NO3), also exceeding that of the state‐of‐the‐art photocatalysts reported to date. This work presents a surface polarization protocol for engineering charge behavior and reactive sites to promote photocatalysis, which shows great promise to the future design of high‐performance materials for clean energy production.
Surface‐halogenation‐induced atomic site activation and local charge separation of layered Bi2O2(OH)(NO3) is presented. Br−‐modified Bi2O2(OH)(NO3) shows the most prominent CO2 activation activity with a CO production rate of 8.12 µmol g−1 h−1, which is 73 times higher than that of bulk Bi2O2(OH)(NO3), exceeding that of most previously reported state‐of‐the‐art photocatalysts.
Through the combination of Bi3+ and a large negative charge ion (BO3)3–, two novel Bi-based borate photocatalysts Bi4B2O9 and Bi2O2BO2(OH) with layered structure have been successfully developed. For ...the first time, the borates were investigated as photocatalysts. They were synthesized by solid-state reaction and hydrothermal method, respectively, and further characterized by XRD, SEM, TEM, HRTEM, and DRS. Bi4B2O9 and Bi2O2BO2(OH) possess direct and indirect transition optical band gaps of 3.02 and 2.85 eV, respectively. Density functional calculations revealed that the valence band (VB) and conduction band (CB) of both borates were composed of hybridized states of the O 2p and Bi 6p or 6s orbitals, and a large dispersion was observed in the energy band of Bi2O2BO2(OH). The photodecomposition experiments demonstrated that Bi4B2O9 and Bi2O2BO2(OH) can be used as effective photocatalysts under simulated solar irradiation, and Bi2O2BO2(OH) exhibits the high photocatalytic activity, which is 2.5 and 3.2 times compared with that of P25 and Bi2O2CO3, respectively. Moreover, the photocurrent conversion further confirmed that Bi4B2O9 and Bi2O2BO2(OH) were potential photofunctional materials. The layered structure with (Bi2O2)2+ layer, hybridized and dispersion energy band, and large negative charge of (BO3)3– ion should be responsible for the high photocatalytic activity of Bi2O2BO2(OH).
In vivo vagus nerve stimulation holds great promise in regulating food intake for obesity treatment. Here we present an implanted vagus nerve stimulation system that is battery-free and spontaneously ...responsive to stomach movement. The vagus nerve stimulation system comprises a flexible and biocompatible nanogenerator that is attached on the surface of stomach. It generates biphasic electric pulses in responsive to the peristalsis of stomach. The electric signals generated by this device can stimulate the vagal afferent fibers to reduce food intake and achieve weight control. This strategy is successfully demonstrated on rat models. Within 100 days, the average body weight is controlled at 350 g, 38% less than the control groups. This work correlates nerve stimulation with targeted organ functionality through a smart, self-responsive system, and demonstrated highly effective weight control. This work also provides a concept in therapeutic technology using artificial nerve signal generated from coordinated body activities.
In this study, a series of coumarin derivatives were designed and synthesized, their structures were characterized using nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS) ...testing methods. In the pharmacological experiment, two behavior-monitoring methods, the forced swim test (FST) and the tail suspension test (TST), were used to determine the antidepressant activity of coumarin derivatives. Compounds that showed potential activity were analyzed for their effects on 5-hydroxytryptamine (5-HT) levels in the brains of mice. Molecular docking experiments to simulate the possible interaction of these compounds with the 5-HT1A receptor was also be predicted. The results of the pharmacological experiments showed that most coumarin derivatives exhibited significant antidepressant activity. Among these compounds, 7-(2-(4-(4-fluorobenzyl)piperazin-1-yl)-2-oxoethoxy)-2H-chromen-2-one (6i) showed the highest antidepressant activity. The results of the measurement of 5-HT levels in the brains of mice indicate that the antidepressant activity of coumarin derivatives may be mediated by elevated 5-HT levels. The results of molecular docking demonstrated that compound 6i had a significant interaction with amino acids around the active site of the 5-HT1A receptor in the homology model. The physicochemical and pharmacokinetic properties of the target compounds were also predicted using Discovery Studio (DS) 2020 and Chemdraw 14.0.
In this paper, we investigated the corrosion behavior of the AlCoCrFeNi2.1 eutectic high-entropy alloy in 3.5 wt% NaCl solution and 3.5 wt% NaCl + 0.01 mol/L NaHSO3 solution at different temperatures ...by electrochemical testing, XPS and SEM/EDS. The findings indicate that the AlCoCrFeNi2.1 eutectic high-entropy alloy can be passivated in 3.5 wt% NaCl solution at different temperatures, with the passive film dominated by metal oxides. The component proportions in the passive film change with temperature, with pitting corrosion occurring at the phase rich in Al-Ni as the primary form of corrosion. However, it cannot be passivated in 3.5 wt% NaCl + 0.01 mol/L NaHSO3 solution at any temperatures. Additionally, the surface of the corrosion product film mainly consists of metal hydroxide on the surface, while the proportion of components in the corrosion product film varies with temperature. Furthermore, the corrosion is caused by the dissolution of the Al-Ni-rich phase. The AlCoCrFeNi2.1 eutectic high-entropy alloy does not demonstrate adequate anti-corrosion property in Cl--containing acid Solution.
•AlCoCrFeNi2.1 cannot be passivated in the acid test solution.•The impact of temperature on corrosion is more obvious in the acid test solution.
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