高活性方形氧化铅与可视化电解槽协同促进电催化臭氧生产

臭氧是一种环境友好型氧化剂,可直接用于消毒、杀菌和废水处理,对于维护和促进公共卫生安全至关重要.由于臭氧容易分解,不利于储存,因此需要现制即用.目前臭氧生成技术主要包括:电晕放电法和电催化臭氧生产(EOP)技术.相较于电晕放电法,EOP是一种本质安全的臭氧生产技术.然而,该工艺相较于电晕放电技术电能消耗量大,为了使其更具商业可行性,有必要开发高活性且低成本的电催化剂.此外,合理的电解槽设计对于实现高效EOP过程也至关重要.然而,目前研究主要集中在提高EOP催化剂活性方面,对电解槽的结构设计优化的关注较少.本文通过开发高效电催化剂进而将其应用于结构优化后的电解槽中,实现了更加高效的EOP过程.本文采用水热方法成功制备了一种具有较高EOP活性的方形氧化铅(PbO_(x)-CTAB-120)电催化剂.在标准三电极测试系统中,电流密度为50 mA cm^(-2)的测试条件下,法拉第效率(FE)可达20.7%,与商用β-PbO_(2)(17.1%)相比提高了21.1%.此外,设计了具有平行流场的可视化EOP电解槽,该可视化电解槽在传质和传热方面具有明显优势,有利于实现更加高效的EOP过程.将催化剂PbO_(x)-CTAB-120组装至可视化电解槽中,在1.0 A cm^(-2)的测试电流密度下,电解液为超纯水,该体系气态臭氧产量可以达到588 mg h^(-1)g^(-1)catalyst,比能量消耗(PEOP)为56 Wh g^(-1)gaseous ozone.体系臭氧产量约为商用β-PbO_(2)在传统电解槽中产量的2倍,并且PEOP降低率超过62%.原位18O同位素标记差分电化学质谱和密度泛函理论计算结果表明,PbO_(x)-CTAB-120电催化剂在EOP过程中遵循晶格氧机理路径,晶格氧迁移产生的氧空位能有效稳定OOH^(*)和O_(2)^(*)反应中间体,因此有利于催化剂在EOP过程中保持较好的反应活性和稳定性.同时,还利用先进的高速摄像可视化工具和计算流体力学(CFD)仿真模拟研究了平行流场EOP电解槽的运行过程和高效传质传热的原理.CFD模拟结果表明,与传统流场模型相比,平行流场对应的出口气泡停留时间更长,说明平行流场更有利于产物气泡从出口逸出,即气泡容易快速扩散,与实验结果一致.因此,PbO_(x)-CTAB-120电催化剂与新型可视化电解槽相结合,有助于在超纯水中实现较好的气态臭氧产率和较低比能耗.此外,二者的结合充分发挥了电催化剂的EOP活性和电解槽的传质特性所带来的优势,实现了反应性和传输性的协同增强,从而极大促进了原位有机污染物降解效率.综上所述,本文在制备高效阳极催化剂的基础上,同时利用优化电解槽结构实现了提升臭氧产率和降低过程能耗,为高活性电催化剂与优化的电解槽耦合以实现高效EOP过程及其有效应用提供参考.

氧官能团MXenes用于电催化合成氨的理论筛选

电催化合成氨技术以绿色可再生的电能为驱动力,通过在室温条件下改变外加电压来克服速控步能垒,被认为是一种取代哈伯工艺的潜在选择.然而,该技术存在法拉第效率较低、氨气产率不高等问题.因此,设计高效的电合成氨催化剂是目前亟待解决的关键问题.氧官能团的二维过渡金属碳化物和氮化物(MXenes)由于具有独特的几何结构、高导电性和表面易调变等特点,在全水解、碳转化、氧还原或固氮等电催化过程中应用十分广泛.其中,表面氧官能团不饱和覆盖的MXenes材料的电催化合成氨性能较好,这是因为适量的氧空位能够调节活性中心的电荷分布,从而优化关键中间体的结合强度;同时,氧空位的存在为反应提供了足够的活性位点.然而,氧官能团MXenes家族庞大,种类众多,如何从中筛选出合适的合成氨电催化剂尚且缺乏理论指导.本文设计了一系列氧官能团的二维过渡金属碳化物和氮化物(MXenes)作为合成氨电催化剂,并通过密度泛函理论从稳定性、选择性和活性角度出发提出了一套较完善的筛选流程.以纯MXenes表面覆盖17/18氧官能团所需的极限电位来判断氧官能团MXenes的稳定性.通过对催化剂上氮气分子和氢原子的吸附行为进行比较来证明其选择性.通过比较潜在热力学决速步的吉布斯自由能(包括G_(N2-NNH),G_(NH-NH_(2))和G_(NH_(2)-NH3))快速获得反应所需的极限电位,可以快速筛选出最佳催化剂.在此基础上,通过吉布斯自由能计算,完整分析了Nb_(3)C_(2)O_(x)上电催化合成氨的反应机理并利用催化性能来验证筛选的准确性.计算结果表明,Nb_(3)C_(2)O_(x)催化剂上的热力学决速步为*NH_(2)加氢,吉布斯自由能仅上升了0.45 eV,与筛选结果一致.此外,结合套索算法,回归了氧官能团MXenes电催化合成氨性能Gx的表达式,探寻了催化活性来源.同时,由吸附能组成的描述符被证明是描述热力学决速步吉布斯自由能的重要变量.

Experimental study on preparation of nanoparticle-surfactant nanofluids and their effects on coal surface wettability

To improve the efficiency of coal seam water injection,the influence of nanofluids on coal surface wettability was studied based on the nano drag reduction and injection enhancement technology in the field of tertiary oil recovery.The composition optimization and performance evaluation of nanofluids with nano-silica and sodium lauryl sulfate as the main components were carried out,and the effects of the nanofluid with the optimal ratio on coal wettability were studied through spontaneous upward imbibition experiments.The results show that the composite nanofluid has a lower surface tension,and the lowest value of the interfacial tension is 15.79 m N/m.Therefore,the composite nanofluid can enhance the wettability of coal.However,its effects on coal samples with different metamorphic degrees is different,that is,low rank coal is the largest,middle rank coal is the second,and high rank coal is the least.In addition,a functional relationship between time and imbibition height is found for pulverized coal with different particle sizes.When the particle size of pulverized coal is 60–80 mesh,the wettability of nanofluid to coal is best.The findings in this paper provide a new perspective for improving the water injection efficiency for coal seams with low permeability.

Micromechanics of substrate-supported thin films

The mechanical properties of metallic thin films deposited on a substrate play a crucial role in the performance of micro/nano-electromechanical systems(MEMS/NEMS)and flexible electronics. This article reviews ongoing study on the mechanics of substrate-supported thin films, with emphasis on the experimental characterization techniques,such as the rule of mixture and X-ray tensile testing. In particular, the determination of interfacial adhesion energy, film deformation, elastic properties and Bauschinger effect are discussed.

A first-principles study of reaction mechanism over carbon decorated oxygen-deficient TiO_(2) supported Pd catalyst in direct synthesis of H_(2)O_(2)

The choice of support is one of the most significant components in the direct synthesis of H_(2)O_(2).Aiming to improvement of activity and selectivity of H_(2)O_(2) on Pd/TiO_(2) surface,we systematically investigated the important elementary steps on Pd/TiO_(2)-Vo@C,Pd/TiO_(2)-Vo,Pd/TiO_(2)-2 Vo,Pd/TiO_(2),and Pd/C using the first-principles calculations.The Bader charge analysis and charge density difference of O_(2) adsorption elucidate the relationship between the electronic distribution and chemisorption energy.The effective barrier analysis further enables to quantitatively estimate the reactivity of H_(2)O_(2) and H2O.We demonstrate unambiguously that the selectivity of H2O formation is boosted as the oxygen vacancy concentration raised.Moreover,the introduction of C into a TiO_(2) with appropriate oxygen vacancies can slightly reduce the effective barrier for H_(2)O_(2) formation and increase the effective barrier for H2O formation leading to a higher activity and selectivity of H_(2)O_(2) formation.Our finding suggests that carbon-doped oxygen vacancy TiO_(2) supported Pd is potential alternative catalyst compared with the Pd/TiO_(2).

Carrier fringe method of moire interferometry for tiny strain measurements in micro-field

In this paper, we demonstrate a new optical method for tiny strain measurements based on the principle of carrier fringes of moire interferometry. A cross-line grating with frequency of 1200 lp/mm is replicated on the specimen surface, and the strain can be deduced from the changes in carrier fringes before and after the deformation of an object. Four coherent laser beams are used to obtain the carrier fringe patterns of field U and V. Both theoretical analysis and numerical simulation indicate that the ideal accuracy of strain can be controlled within a range of ±1με. Case study of a plane extension experiment shows that the measurement accuracy of strain can be controlled within the range of ±10με. The average strain values of every row of field U and every column of field V can be obtained by using this method, and approximated strain of every pixel in the whole-field can be further acquired, and thus it is possible to measure tiny strains occurred in a micro-field. The technology in this paper can provide comprehensive information for analyzing related mechanical content in the field of MEMS.

Elastic property determination of nanostructured W/Cu multilayer films on a flexible substrate

An experimental method for a single layer is extended to determine the elastic properties of nanostructured W/C u multilayers on a flexible substrate.The strain difference between the W/Cu-polyimide-W/Cu composite and the uncoated substrate,measured by dual digital image correlation,allows us to extract the effective Young's modulus of W/Cu multilayers(20 periods)equaling 216±13 GPa.Finite element method is then performed,which agrees well with the experiment and classical rule of mixture(ROM)theory demonstrating that the extension to multilayers is effective and reliable.The numerical analysis also interestingly shows that the strain difference is linearly related to the thickness ratio(W/Cu),periods and sublayer thickness,respectively.In contrast to ROM theory,this approach could potentially be used for the evaluation of properties and design of emerging/unknown functional multilayers,whether or not they are crystalline or amorphous.

Comparative Experiment on Different Pepper Varieties in Solar Greenhouse in Lhasa Area

In order to screen the pepper varieties suitable for planting in the solar greenhouse in Lhasa, variety comparison test was conducted to the continuous cropping of pepper in solar greenhouse. The results showed that Qianlv Tianshi F_1, Oriental Changlong F_1 and Qujiao 1 F_1 had higher yields than the control, and significantly lower root incidence rates than the control. Therefore, the 3 varieties were suitable fro planting in Lhasa.

Analysis on diffusion-induced stress for multi-layer spherical core-shell electrodes in Li-ion batteries

Silicon-based carbon composites are believed as promising anodes in the near future due to their outstanding specific capacity and relatively lower volume effect compared to pure silicon anodes.Herein,a multilayer spherical core-shell(M-SCS)electrode with a graphite framework prepared with Si@O-MCMB/C nanoparticles is developed,which aims to realize chemically/mechanically stability during the lithiation/delithiation process with high specific capacity.An electrochemical-/mechanical-coupling model for the M-SCS structure is established with various chemical/mechanical boundary conditions.The simulation of finite difference method(FDM)has been conducted based on the proposed coupling model,by which the diffusion-induced stress along both the radial and the circumferential directions is determined.Moreover,factors that influence the diffusion-induced stress of the M-SCS structure have been discussed and analyzed in detail.

NIR-switchable local hydrogen generation by tandem bimetallic MOFs nanocomposites for enhanced chemodynamic therapy

The inadequate quantity of hydrogen peroxide(H_(2)O_(2))in cancer cells promptly results in the constrained success of chemodynamic therapy(CDT).Significant efforts made throughout the years;nevertheless,researchers are still facing the great challenge of designing a CDT agent and securing H_(2)O_(2) supply within the tumor cell.In this study,taking advantage of H_(2)O_(2) level maintenance mechanism in cancer cells,a nanozyme-based bimetallic metal-organic frameworks(MOFs)tandem reactor is fabricated to elevate intracellular H_(2)O_(2) levels,thereby enhancing CDT.In addition,under nearinfrared excitation,the upconversion nanoparticles(UCNPs)loaded into the MOFs can perform photocatalysis and generate hydrogen,which increases cellular susceptibility to radicals induced from H_(2)O_(2),inhibits cancer cell energy,causes DNA damages and induces tumor cell apoptosis,thus improving CDT therapeutic efficacy synergistically.The proposed nanozyme-based bimetallic MOFs-mediated CDT and UCNPs-mediated hydrogen therapy act as combined therapy with high efficacy and low toxicity.

Biomedical applications of magnetosomes: State of the art and perspectives

Magnetosomes, synthesized by magnetotactic bacteria (MTB), have been used in nano- and biotechnological applications, owing to their unique properties such as superparamagnetism, uniform size distribution, excellent bioavailability, and easily modifiable functional groups. In this review, we first discuss the mechanisms of magnetosome formation and describe various modification methods. Subsequently, we focus on presenting the biomedical advancements of bacterial magnetosomes in biomedical imaging, drug delivery, anticancer therapy, biosensor. Finally, we discuss future applications and challenges. This review summarizes the application of magnetosomes in the biomedical field, highlighting the latest advancements and exploring the future development of magnetosomes.

自修复水凝胶材料的设计合成及生物医学应用

水凝胶柔软且有弹性,含水量高,其结构、性能与生物组织相似,生物相容性和生物安全性好.因此,被广泛应用于组织工程、药物输送、创伤敷料等领域,具有非常广阔的应用前景.自修复材料模仿生物体损伤自愈原理,自行发现损伤和裂纹并通过一定机理自修复愈合,是近年来水凝胶领域的研究热点和难点.本文综述了近10年来具有代表性的自修复物理水凝胶和自修复化学水凝胶等新型高分子水凝胶方面的重要研究进展,总结了其设计与合成的基本原理和方法,介绍了几种典型的水凝胶自修复机制,阐述了基于静电作用、疏水作用、氢键作用、主客体作用等物理作用,以及基于酰腙键、亚胺键、二硫键等可逆化学键作用的自修复水凝胶的应激自修复原理和特性.在此基础上,分析讨论了自修复水凝胶作为潜在生物材料仍需解决的关键科学问题,并对本领域的发展趋势进行了展望.

基于纳米材料的肿瘤声动力治疗研究进展

声动力治疗(sonodynamic therapy, SDT)因其组织穿透性强、精度高、毒副作用小等优点在抗肿瘤领域显示出广阔的应用前景. SDT主要依靠超声波激活聚集在肿瘤部位的声敏剂以产生抗肿瘤效应.然而,传统声敏剂固有的水溶性差、血液循环能力弱、靶向性低等缺点较大程度上限制了SDT的应用.以纳米材料为基础的新型纳米声敏剂可以有效克服这些弊端,在SDT中表现出独特的优势.本文首先对SDT的可能作用机制,包括超声空化效应、活性氧效应、肿瘤微环境调控效应等进行了综述;其次重点介绍了近年来纳米材料在声动力治疗肿瘤中的相关应用进展,包括聚合物、脂质体、无机纳米材料等传统声敏剂载体用于SDT疗效的增强,以及本身具有声敏效应的金属基、硅基、碳基等纳米材料用于SDT新治疗策略的研究;最后对SDT的发展前景进行展望,并提出确认SDT的作用机制和开发新型高效的纳米声敏剂将是其未来的研究重点.

铜掺杂生物活性玻璃的生物医学应用

生物活性玻璃作为一种既能与骨组织键合又能与软组织连接的活性材料,可通过降解过程实现对活性离子的控制释放,在临床生物医学方面得到长足发展.本文综述了近年来合成的铜掺杂生物活性玻璃的基本特征,并对相关生物医学应用研究进展进行介绍,对研究中存在的问题和面临的挑战进行深入剖析.其中,基本特征内容包括结构及分类,具体细分为45S5型、1393型、70S型和1393 B3型等;生物医学应用进展内容涵盖抗菌、抗癌、骨/软骨修复再生及血管生成.

Basic research on machinery fault diagnostics： Past, present, and future trends

Machinery fault diagnosis has progressed over the past decades with the evolution of machineries in terms of complexity and scale. High-value machineries require condition monitoring and fault diagnosis to guarantee their designed functions and performance throughout their lifetime. Research on machinery Fault diagnostics has grown rapidly in recent years. This paper attempts to summarize and review the recent R＆D trends in the basic research field of machinery fault diagnosis in terms of four main aspects： Fault mechanism, sensor technique and signal acquisition, signal processing, and intelligent diagnostics. The review discusses the special contributions of Chinese scholars to machinery fault diagnostics. On the basis of the review of basic theory of machinery fault diagnosis and its practical applications in engineering, the paper concludes with a brief discussion on the future trends and challenges in machinery fault diagnosis.

Supercritical fluid-assisted controllable fabrication of open and highly interconnected porous scaffolds for bone tissue engineering

Recently tremendous progress has been evidenced by the advancements in developing innovative three-dimensional(3 D)scaffolds using various techniques for addressing the autogenous grafting of bone. In this work, we demonstrated the fabrication of porous polycaprolactone(PCL) scaffolds for osteogenic differentiation based on supercritical fluid-assisted hybrid processes of phase inversion and foaming. This eco-friendly process resulted in the highly porous biomimetic scaffolds with open and interconnected architectures. Initially, a 2^3 factorial experiment was designed for investigating the relative significance of various processing parameters and achieving better control over the porosity as well as the compressive mechanical properties of the scaffold. Then, single factor experiment was carried out to understand the effects of various processing parameters on the morphology of scaffolds. On the other hand, we encapsulated a growth factor, i.e., bone morphogenic protein-2(BMP-2), as a model protein in these porous scaffolds for evaluating their osteogenic differentiation. In vitro investigations of growth factor loaded PCL scaffolds using bone marrow stromal cells(BMSCs) have shown that these growth factor-encumbered scaffolds were capable of differentiating the cells over the control experiments. Furthermore, the osteogenic differentiation was confirmed by measuring the cell proliferation, and alkaline phosphatase(ALP) activity, which were significantly higher demonstrating the active bone growth. Together, these results have suggested that the fabrication of growth factor-loaded porous scaffolds prepared by the eco-friendly hybrid processing efficiently promoted the osteogenic differentiation and may have a significant potential in bone tissue engineering.

The Structural and Chemical Reactivity of Lattice Oxygens on β-PbO_(2 ) EOP Electrocatalysts

The oxygen evolution reaction(OER)and electrochemical ozone production(EOP)attracted considerable attention due to their wide applications in electrocatalysis,but the detailed reaction mechanism of product formation as well as the voltage effect on O_(2)/O_(3)formation still remains unclear.In this work,density functional theory calculations were used to systematically investigate the possible reaction mechanisms of OER and EOP on the PbO_(2)(110)surface,with the possible reaction network involving surface lattice oxygen atoms(LOM)proposed.The results show that the LOM-2 reaction pathway involving two surface lattice oxygen atoms(Olatt)and one oxygen atom from H_(2)O was the most thermodynamically reactive.Different potential determining step(PDS)was obtained depending on the multiple reaction pathway,and the results show that the facile diffusion of Olattwould proceed the LOM pathway and promote the formation of surface oxygen vacancies(O_(vac1)/O_(vac2)).Furthermore,O_(vac1)/O_(vac2)formation on the surface would trigger further reactions of H_(2)O adsorption and splitting,which refilled the oxygen vacancy and ensured the considerable stability of the PbO_(2)(110)surface.Multiple H_(2)O dissociation pathways were proposed on PbO_(2)(110)with oxygen vacancy sites:the acid-base interaction mechanism and the vacancy fulfilling mechanism.

3D bioprinting of conductive hydrogel for enhanced myogenic differentiation

Recently,hydrogels have gained enormous interest in three-dimensional(3D)bioprinting toward developing functional substitutes for tissue remolding.However,it is highly challenging to transmit electrical signals to cells due to the limited electrical conductivity of the bioprinted hydrogels.Herein,we demonstrate the 3D bioprinting-assisted fabrication of a conductive hydrogel scaffold based on poly-3,4-ethylene dioxythiophene(PEDOT)nanoparticles(NPs)deposited in gelatin methacryloyl(GelMA)for enhanced myogenic differentiation of mouse myoblasts(C2C12 cells).Initially,PEDOT NPs are dispersed in the hydrogel uniformly to enhance the conductive property of the hydrogel scaffold.Notably,the incorporated PEDOT NPs showed minimal influence on the printing ability of GelMA.Then,C2C12 cells are successfully encapsulated within GelMA/PEDOT conductive hydrogels using 3D extrusion bioprinting.Furthermore,the proliferation,migration and differentiation efficacies of C2C12 cells in the highly conductive GelMA/PEDOT composite scaffolds are demonstrated using various in vitro investigations of live/dead staining,F-actin staining,desmin and myogenin immunofluorescence staining.Finally,the effects of electrical signals on the stimulation of the scaffolds are investigated toward the myogenic differentiation of C2C12 cells and the formation of myotubes in vitro.Collectively,our findings demonstrate that the fabrication of the conductive hydrogels provides a feasible approach for the encapsulation of cells and the regeneration of the muscle tissue.