调控Ru的电子态以促进乙烯在酸中高选择性电氧化合成乙二醇

乙二醇(EG)是一种重要的化工产品,由于在化学品制造行业的广泛应用而备受关注.然而,目前工业上制备乙二醇主要采用乙烯作为原料,经过环氧化和水解两步反应,这一过程不仅需要高温高压,还需使用成本高的氧化剂(如H_(2)O_(2)),这违背了绿色化学的原则.因此,电催化阳极氧化作为一种新兴的合成策略,正逐渐受到研究者的青睐.该技术仅通过电子转移并利用水作为氧源,就能够高效合成高附加值含氧化学品.特别是,阳极氧化反应可与阴极还原反应(例如氢析出反应)相耦合,实现能量的高效利用.尽管电催化阳极氧化具有诸多优势,但目前在乙烯电氧化合成乙二醇过程中,其选择性仍然较低,这导致后续的纯化过程变得复杂且成本高昂.因此,开发高选择性的电氧化合成乙二醇技术,成为了一项迫切且极具挑战性的任务.本文提出了一种Ir和Ru合金化策略,以提高乙烯电氧化制备乙二醇的选择性和耐久性.研究结果表明,当Ir和Ru的原子比达到适当的比例(即Ir_(0.54)Ru_(0.46))时,所制备的IrRu合金表现出近100%的乙二醇选择性,远远优于Ru NPs对照组样品(43.8%).此外,在1.475 V的电压下,Ir_(0.54)Ru_(0.46)催化生成乙二醇产率达到了60.62 mmolgRu^(-1) h^(-1),是Ru NPs上最高产率(21.75 mmolgRu^(-1) h^(-1))的2.8倍.在耐久性测试中,Ir_(0.54)Ru_(0.46)能够稳定催化生成乙二醇超过12 h,其生成速率为6μmol L^(-1) h^(-1).相比之下,对照组样品Ru NPs在电解反应3 h后已失去活性.能量损失谱分析显示,Ir_(0.54)Ru_(0.46)在电解2 h后形成了稳定的表面富Ir核壳结构IrRu@Ir,这是催化剂稳定性提升的关键.先进光谱研究进一步揭示,Ir的引入导致了电子由Ru位点向Ir流动,使Ru位点带正电荷,从而减弱了OH的吸附.OH脱附实验结果表明,随着Ir/Ru原子比的增加,OH更容易从Ru位点脱附,这促进了OH与乙烯的偶联反应.自由基淬灭和氘代同位素标记实验结果表明,在IrRu催化剂上,乙烯到乙二醇的转化并非级联反应,而是直接的表面催化反应,其中OH的转移是决速步骤.X射线光电子能谱分析显示,随着合金中Ir比例的增加,合金d带中心下移,这有利于关键中间体(*OH等)的转移.原位红外光谱表明,乙烯分子在Ru位点上通过Pauling型吸附构型被活化.值得注意的是,仅检测到*CH_(2)CH_(2)OH中间体,而未检测到其他氧基团(如羰基),这表明在反应过程中没有发生过氧化现象.密度泛函理论计算进一步证实,与Ir合金化不仅加速了OH的转移,还优化了反应途径,使乙二醇的选择性达到100%.综上,本文设计了不同Ir/Ru原子比的IrRu合金催化剂,通过有效调控活性位点Ru的电子结构,优化了OH的结合能,使乙烯可以100%选择性高效转化为乙二醇,这为开发高选择性电催化剂用于乙二醇电合成提供了新思路.

Implementation and Insights on Science Inquiry Activities in Kindergartens Under the Concept of STEM Education

The STEM education philosophy spans across disciplines such as science,technology,engineering,and mathematics.In the context of thematic activities in kindergartens,teachers can utilize the STEM education philosophy to cultivate children’s innovative thinking qualities and practical operation skills,helping them develop a scientific inquiry spirit and skills.This paper takes the development of science inquiry activities in kindergartens as a path,exploring the significance and implementation paths of applying the STEM education philosophy in such activities.

Diagnostic Value of Dual-Energy CT in Differentiating Malignant and Benign Thyroid Nodules: A Systematic Review and Meta-Analysis

Objectives: To evaluate the diagnostic performance of the quantitative iodine parameters, including Iodine Concentration (IC), Normalized Iodine Concentration (NIC), and λHU, in distinguishing malignant and benign thyroid nodules. Methods: Relevant studies were searched from Web of Science, PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure database and other complementary sources from inception to May 20, 2020. Study selection, data extraction, quality assessment, and data analyses were performed following the Cochrane standards and the PRISMA-DTA guideline. Results: Eight studies were included (595 patients with 737 thyroid nodules). The pooled sensitivity, specificity and summary diagnostic odds ratio of IC were 79% (95% CI: 69% - 86%), 76% (95% CI: 65% - 84%) and 11 (95% CI: 5 - 27) respectively;those of NIC were 78% (95% CI: 70% - 85%), 80% (95% CI: 74% - 85%) and 15 (95% CI: 9 - 24) respectively;those of λHU were 80% (95% CI: 71% - 87%), 77% (95% CI: 70% - 83%) and 14 (95% CI: 8 - 24) respectively. Conclusion: DECT can be a potential evaluation tool for thyroid nodules. The NIC may be the most sensitive iodine parameter and could be comparable between different DECT machines in thyroid nodule assessment.

A New Hesitant Fuzzy Multiple Attribute Decision Making Method with Unknown Weight Information

In this paper, we focus on a new approach based on new generalized hesitant fuzzy hybrid weighted aggregation operators, in which the evaluation information provided by decision makers is expressed in hesitant fuzzy elements (HFEs) and the information about attribute weights and aggregation-associated vector is unknown. More explicitly, some new generalized hesitant fuzzy hybrid weighted aggregation operators are proposed, such as the new generalized hesitant fuzzy hybrid weighted averaging (NGHFHWA) operator and the new generalized hesitant fuzzy hybrid weighted geometric (NGHFHWG) operator. Some desirable properties and the relationships between them are discussed. Then, a new algorithm for hesitant fuzzy multi-attribute decision making (HF-MADM) problems with unknown weight information is introduced. Further, a practical example is used to illustrate the detailed implementation process of the proposed approach. A sensitivity analysis of the decision results is analyzed with different parameters. Finally, comparative studies are given to verify the advantages of our method.

Complex-frequency waves:beat loss and win sensitivity

Recent experiments have demonstrated that synthesized complex-frequency waves can impart a virtual gain to molecule sensing systems,which can effectively restore information lost due to intrinsic molecular damping.The enhancement notably amplifies the signal of trace molecular vibrational fingerprints,thereby substantially improving the upper limit of sensitivity.

Chiral AuCu heterostructures with site-specific geometric control and tailored plasmonic chirality

Rational design and construction of chiral-achiral hybrid structures are of great importance to realize the multifunctional complex chiral structures toward emerging technological applications. However, significant challenges remain due to the lack of fine control over the heterostructure. Here, we have developed a general bottom-up synthetic strategy for the site-selective growth of Cu nanodomains on intrinsically chiral Au nanocrystals. Chiral AuCu heterostructures with three distinct architectures were achieved by controlling the overgrowth of Cu nanodomains in a site-specific manner. The geometry-dependent plasmonic chirality of the heterostructures was demonstrated experimentally by circular dichroism spectroscopy and theoretically through finite-difference time-domain simulations. The site-specific geometric control of chiral AuCu heterostructures was also extended to employ anisotropic chiral Au nanoplates and nanorods as the building blocks. By virtue of the galvanic replacement reactions between metal ions and Cu atoms, chiral heterostructures with increasing architectural complexity and compositional diversity can be further achieved. The current work not only opens up a promising strategy to synthesize complex chiral hybrid nanostructures but also provides an important knowledge framework that guides the rational design of multifunctional chiral hybrid nanostructures toward chiroptical applications.

Versatile Recyclable Kevlar Nanofibrous Aerogels Enabled by Destabilizing Dynamic Balance Strategy

Aerogels are of great interest in diverse fields including thermal insulation,environmental protection,liquid separation,electromagnetic shielding,etc.However,the development of renewable and recyclable aerogels,especially synthetic pol-ymer-based ones,remains an enormous challenge,which seriously hinders the practical application of aerogels.Herein,utilizing Kevlar nanofibers(KNFs)as representative synthetic polymer building blocks,a destabilizing dynamic balance(DDB)strategy is proposed to fabricate recyclable aerogels with high reprocessing consistency.More specifically,aprotic esters(e.g.,di-tert-butyl decarbonate,DiBoc)and alkalis(e.g.,potassium tert-butoxide,t-BuOK)are introduced to trigger the destabilizing dynamic balance between deprotonation–protonation of KNFs,resulting in a reversible sol–gel transition.Meanwhile,the duration of sol–gel transition(i.e.,gelation)time,adjustable from 10^(–2)to 10^(3)min,is compatible with versatile processing methods,such as static mould casting,dynamic wet spinning,dynamic blade coating and dynamic 3D printing.These unique advantages enable the fabrication of various KNF aerogel products(i.e.,continuous fibers,continuous films,large-sized monoliths and 3D-printed articles)with low density(33–165 mg/cm3),high compressive modulus(up to 52 MPa),high specific surface area(360–404 m^(2)/g)and low thermal conductivity(0.027–0.050 W/m·K).Notably,these properties are comparable or superior to that of previously reported KNF aerogels and far superior to that of recyclable aerogels.Compared with direct fabrication from raw materials,the DDB strategy reduces the cost by 50.5%and 82.5%when products are made from recycled aerogels and wet gels,respectively.Such cost reduction further increases with the number of recycling cycles,which is calculated as$275 per kilogram KNF aerogel with 5 cycles.This work develops extraordinary KNF aerogels those can be recycled and reused,as well as provides a strategy that can be applied to design more recyclable aerogels.

Spin-decoupled meta-coupler empowered multiplexing and multifunction of guided wave radiation

Employing couplers to convert guided waves into free-space modes and flexibly control their wavefront is one of the key technologies in chip-integrated displays and communications.Traditional couplers are mainly composed of gratings,which have limitations in footprint,bandwidth,as well as controllability.Though the resonant/geometric metasurface newly emerges as a promising interface for bridging guided waves with free-space ones,it either relies on complex optimizations of multiple parameters,or is subject to the locked phase response of opposite spins,both of which hinder the functional diversity and practical multiplexing capability.Here,we propose and experimentally demonstrate an alternative with a spin-decoupled meta-coupler,simultaneously integrating triple functions of guided wave radiation,polarization demultiplexing,and dual-channel wavefront manipulation into a single device.By endowing polarization-dependent functionalities into a pure geometric metasurface,the out-coupled left-handed and right-handed circular polarization guided waves intelligently identify the predesigned phase modulation and reconstruct desired wavefronts,like bifocal focusing and holography multiplexing,with a polarization extinction ratio over 13.4 dB in experiments.We envision that the robust,broadband,and multifunctional meta-coupler could pave a way for the development of versatile multiplexed waveguide-based devices.

Boosting hydrogen peroxide production via establishment and reconstruction of single-metal sites in covalent organic frameworks

Covalent organic frameworks(COFs)have been well developed in electrocatalytic systems owing to their controllable skeletons,porosities,and functions.However,the catalytic process in COFs remains underexplored,hindering an in-depth understanding of the catalytic mechanism.In this work,uniform Pt-N_(1)O_(1)Cl_(4)sites chelated via C-N and C=O bonds along the one-dimensional and open channels of TP-TTA-COF were established.Different from conventional single-metal sites constructed for the near-free platinum for hydrogen evolution,the as-constructed PtCl-COF showed 2e−oxygen reduction for H_(2)O_(2)production.We tracked the dynamic evolution process of atomic Pt sites in which Pt-N_(1)O_(1)Cl_(4)was transformed into Pt-N_(1)O_(1)(OH)_(2)using in situ X-ray adsorption.The theoretical calculations revealed that the strong Pt-support interaction in Pt-N_(1)O_(1)(OH)_(2)facilitated*OOH formation and thus led to higher selectivity and activity for the oxygen reduction reaction in the 2e−pathway.This work can expand the applications of COFs through the regulation of their local electronic states for the manipulation of the metal center.

1个DYNC2H1基因变异导致的短肋多指综合征Ⅲ型家系的遗传学分析

本文报道1个连续3次妊娠早孕期超声均提示胎儿四肢短小家系的遗传学分析。取第2次妊娠引产胎儿组织行染色体核型分析及全外显子组测序,结果提示DYNC2H1基因存在EX64-EX83 Del及c.8190G>T杂合变异。实时荧光定量聚合酶链反应及Sanger测序验证2个变异分别遗传自表型正常的父亲和母亲,前者为疑似致病性变异,后者为临床意义未明变异。综合病史及变异基因特点,高度怀疑胎儿为常染色体隐性遗传的复合杂合变异导致的短肋多指综合征Ⅲ型。第3次妊娠胎儿引产后采用实时荧光定量聚合酶链反应和Sanger测序进行验证,结果与第2次妊娠胎儿一致。由于第2、3次妊娠胎儿表型相似,提示DYNC2H1基因EX64-EX83 Del及c.8190G>T杂合变异可能是该家系短肋多指综合征Ⅲ型的致病变异。

Broadband achromatic metalens in terahertz regime

Achromatic focusing is essential for broadband operation, which has recently been realised from visible to infrared wavelengths using a metasurface. Similarly, multi-terahertz functional devices can be encoded in a desired metasurface phase profile. However, metalenses suffer from larger chromatic aberrations because of the intrinsic dispersion of each unit element. Here, we propose an achromatic metalens with C-shaped unit elements working from 0.3 to 0.8 THz with a bandwidth of approximately 91% over the centre frequency. The designed metalens possesses a high working efficiency of more than 68% at the peak and a relatively high numerical aperture of 0.385. We further demonstrate the robustness of our Cshaped metalens, considering lateral shape deformations and deviations in the etching depth. Our metalens design opens an avenue for future applications of terahertz meta-devices in spectroscopy, time-offlight tomography and hyperspectral imaging systems.

Floquet spectrum and optical behaviors in dynamic Su–Schrieffer–Heeger modeled waveguide array

Floquet topological insulators(FTIs) have been used to study the topological features of a dynamic quantum system within the band structure. However, it is difficult to directly observe the dynamic modulation of band structures in FTIs. Here, we implement the dynamic Su–Schrieffer–Heeger model in periodically curved waveguides to explore new behaviors in FTIs using light field evolutions. Changing the driving frequency produces near-field evolutions of light in the high-frequency curved waveguide array that are equivalent to the behaviors in straight arrays. Furthermore, at modest driving frequencies,the field evolutions in the system show boundary propagation, which are related to topological edge modes. Finally, we believe curved waveguides enable profound possibilities for the further development of Floquet engineering in periodically driven systems, which ranges from condensed matter physics to photonics.