微波法一步制备新型荧光碳量子点及光学性能研究

首次以中药材贝母为碳源,采用微波法一步合成新型荧光碳量子点。通过原料用量、微波功率和反应时间优化,获得了制备荧光碳量子点的最佳实验条件。同时通过透射电镜和X射线光电子能谱仪对荧光碳量子点进行了形貌及结构表征,通过荧光光谱和紫外-可见吸收光谱对荧光碳量子点进行了光学性能研究。结果表明:原料用量2g,微波功率800W,反应时间8min为合成荧光碳量子点最佳反应条件,制备得到的荧光碳量子点平均粒径5nm,最大激发波长310nm,最大荧光发射波长位于400nm处,最大紫外吸收波长280nm。     

生物质碳量子点的简便合成及对Hg~(2+)荧光传感研究

将厌氧条件处理的牛粪作为碳源通过水热法合成了蓝色荧光发射的碳量子点。该量子点在水中稳定性和分散性良好,具有激发波长依赖的荧光发射现象,从430nm红移至560nm。在中性水溶液中,汞离子(Hg~(2+))对碳量子点的荧光发射干扰明显。随着Hg~(2+)体积的增加,450nm处的荧光强度逐渐减弱,两者呈现出较好的线性关系。对定性定量检测环境中的Hg~(2+)具有重要的意义。     

碳量子点：不同发光行为原因分析及其性能（英文）

以柠檬酸铵为原料采用一步水热法,通过改变反应温度合成出了两种分别具有激发波长独立和激发波长依赖荧光的碳量子点。通过考察两类碳量子点的物理、化学性质以及光学性能,可以推断碳点的结构与荧光发射之间的关系,最终研究碳量子点产生不同发光行为的原因。结果发现升高合成温度可以在碳量子点中引入更多的氧、氮杂原子,增加了结构缺陷(杂原子的化学态)的总量,并调变了各类化学态含量比。正是由于两种碳量子点的结构缺陷含量比例的不同,导致了碳量子点发光行为不同。合成温度高的碳量子点所含的各类结构缺陷含量比例较为均衡使得其呈现激发波长依赖性荧光;合成温度低的碳量子所含结构缺陷总量不高且主要以某种形式(如C=O)存在,是其拥有激发独立发光行为的主要原因。同时由于合成温度高的碳量子点所含的含氮基团的增加,使得碳量子点拥有更强的荧光发射。进一步考察还发现其具有非常优良的稳定性,因此可以预期有很好的应用前景。     

以甘蔗渣为基质的碳量子点的制备及表征

以甘蔗渣为基质制备碳量子点,先将甘蔗渣高温碳化得到黑色固体,再利用化学氧化法制备碳量子点。通过高分辨率透射电子显微镜、傅里叶变换红外光谱仪、荧光光谱仪以及紫外-可见分光光度计对制备的碳量子点的形貌、表面官能团及荧光特征进行了表征。结果表明:碳量子点颗粒直径在10～20nm之间,晶格为0.30nm;碳量子点表面含有一定量的羟基等含氧基团;在激发波长300nm处有较强的荧光发射峰。通过检测不同储存时间的碳量子点的荧光强度发现,储存120d碳量子点荧光强度仍能保持80.07%。     

樟子松基碳量子点的制备工艺优化

目的 将樟子松木材包装废弃物转化为荧光碳量子点,为实现废弃樟子松木材包装的高值化综合利用探索一条新途径。方法 以60目樟子松木材包装废弃物为碳量子点前驱体,分别以硫酸和乙二胺为硫和氮掺杂剂,在温度为200 ℃、时间为10 h的水热条件下合成樟子松基碳量子点。采用紫外可见光分光光度计、荧光分光光度计、透射电子显微镜、傅里叶红外光谱仪和X射线光电子能谱仪等表征手段,研究原材料配比对所制备樟子松基碳量子点物理结构、化学结构和光学性质的影响,并以碳量子点的荧光量子产率为评价指标,优化樟子松基碳量子点的制备工艺。结果 所得硫氮掺杂碳量子点呈规则球形,其平均粒径及粒径分布分别为4.30 nm和2.01~6.63 nm;当原材料配比为m(樟子松木粉)∶m(硫酸)∶m(乙二胺)=1∶1∶1时,合成的掺杂碳量子点的荧光最强、荧光量子产率最高。当樟子松木粉、去离子水、硫酸和乙二胺的质量比为1.250∶50∶1.250∶1.250时,掺杂碳量子点的荧光量子产率比未掺杂碳量子点的高约80倍。结论 将樟子松木材包装废弃物转化为荧光碳量子点,是实现废弃樟子松木材包装的高值化综合利用的新途径。     

一种具有室温磷光的碳量子点基复合材料

碳量子点的荧光性能已被广泛研究,但很少有人关注碳量子点的磷光现象和机理。通过静电自组装法将带负电荷的碳量子点作为发光中心和核心先后吸引活性Ba~(2+)和活性SO_4~(2-),使碳量子点固定在所生成的BaSO_4基质中,形成一种新型的同时具有优异室温磷光和荧光的碳量子点基复合材料(记作CQDs@BaSO4)。该材料在激发波长为365nm下显示出的长磷光寿命为281ms,平均寿命为251ms,并且在水和酸碱溶液中都具有稳定的室温磷光发射现象。同时研究了磷光现象的机理,该材料室温磷光归因于碳量子点表面的其表面所含芳香羰基化合物的三重态和BaSO_4分子有效的刚化这些芳香族羰基基团,从而抑制非辐射钝化途径产生室温磷光。基于该材料磷光性能的优点,成功将其制成防伪印泥材料,探讨其在磷光防伪上的应用。     

氨基功能化荧光碳量子点的制备及对铜离子的检测

以柠檬酸作为碳源,聚乙烯亚胺(BPEI)作为修饰剂,经一步水热合成法,制备出一种具有高荧光强度的氨基功能化碳量子点(BPEI-CQDs)。所合成的荧光碳量子点在365 nm紫外光照射下呈现出明亮的蓝色荧光。通过透射电镜(TEM)观察发现,BPEI-CQDs在水中分散均匀,没有明显团聚现象,其平均粒径约为6.5 nm。拉曼光谱表明,修饰后的碳量子点表面缺陷程度增大。Cu~(2+)可与BPEI-CQDs表面的氨基结合形成铜胺络合物,进而导致碳量子点的荧光猝灭。在0~1μmol/L Cu~(2+)浓度范围内,BPEICQDs的荧光强度与Cu~(2+)浓度呈现出良好的线性关系,检测限可达8.7 nmol/L。     

一步法合成特异性pH响应碳量子点及其发光机理研究

本研究利用溶剂热反应, 以柠檬酸为碳源, 甲酰胺和水为混合溶剂, 一步合成氮掺杂碳量子点。研究表明, 所制备的氮掺杂碳量子点具有良好的水溶性和明亮的蓝光发射, 以及典型的依赖于激发光的荧光发射特性。特别的是, 该碳量子点显示出不同于普通碳量子点的、独特的pH响应行为, 除了具有传统的荧光强度随着pH变化的响应行为外, 还表现出在碱性条件下, 产生新的不依赖于激发光的红光发射的性能。通过系统研究碳量子点在不同碱性环境和不同羟基含量溶液中的荧光特性, 结合拉曼光谱、红外、XPS等表征, 分析其化学组成与表面态分子, 探讨了其发光机制, 证实这种特异性pH响应行为是由于在强碱性环境中含有的大量氢氧根结合在碳量子点表面, 从而改变碳量子点的表面状态, 形成新的稳定的发光中心。最后, 通过细胞毒性实验及细胞成像分析表明, 所获得的碳量子点具有低细胞毒性, 并可作为荧光探针应用于细胞成像, 显示其在生物成像领域的潜在应用价值。     

基于生物质烟灰的碳量子点的制备及性能

分别以河北沧州和山东日照的民居烟道灰为原料,通过酸回流法成功制备了具有良好水溶性和稳定性的碳量子点。高分辨透射电子显微镜观察表明碳量子点为球形颗粒,内核尺寸小于1 nm;傅里叶变换红外光谱仪和X-射线光电子能谱仪研究表明碳量子点表面含有羧基、羟基等有机官能团;拉曼光谱和X-射线衍射测量表明碳量子点结晶性差,内部含有大量缺陷;荧光光谱测量结果表明碳量子点发射黄色荧光,波长大于500 nm且具有较高的荧光量子产率,最高可达3. 83%。结果表明,民居烟道灰有望成为碳量子点制备的新型廉价原料,所获得的黄光发射碳量子点在生物成像等领域具有广阔的应用前景。     

掺氮荧光碳量子点的制备及性能研究

以柠檬酸为碳源、对氨基苯甲酸为氮源，通过一步水热法制备了氮掺杂荧光碳量子点(N-CQDs),采用透射电子显微镜、傅里叶变换红外光谱仪、稳态瞬态荧光磷光光谱仪对其形貌、结构和光谱进行表征，研究了反应温度、反应时间、酸碱度对N-CQDs荧光性能的影响。结果表明：N-CQDs呈球形，具有良好的分散性；N-CQDs的荧光强度较碳量子点增强约17倍，N-CQDs最佳激发波长为404nm,最佳发射波长为480nm,说明氮的掺杂有助于碳量子点荧光强度的增强；反应温度为180℃、反应时间为6h,酸碱度为中性时，N-CQDs荧光强度最强。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.