水相合成CdTe量子点及其性能表征

以NaTeO3为碲源,巯基乙酸(TGA)为稳定剂,合成CdTe量子点。研究Cd2+的浓度、Cd2+-TGA前驱体室温静置时间对CdTe量子点荧光光谱、荧光量子效率的影响,并用X射线粉末衍射仪和透射电子显微镜对其结晶性能、结构以及形貌进行表征。实验表明,所制备的CdTe量子点具有闪锌矿结构和球形形貌。且在Cd2+-TGA前驱体室温静置50min后参与回流,Cd2+浓度为0.00067mol/L时,荧光量子效率最高可达48.4%。     

水溶性Cu∶CdTe/CdS核壳量子点的合成、表征及细胞毒性检测

采用水相法合成了Cu掺杂CdTe量子点,并用CdS壳层进行包覆,得到了Cu∶CdTe/CdS核壳结构量子点。采用荧光发射光谱(FL)、紫外可见吸收光谱(UV-Vis)、透射电镜(TEM)以及能谱仪(EDS)等手段对CdTe量子点和Cu∶CdTe/CdS核壳量子点进行了表征。研究了不同Cu掺杂浓度、CdS壳层生长时间以及Cd/硫脲物质的量比对Cu∶CdTe掺杂量子点光学性能的影响,并采用人成骨肉瘤细胞(MG-63细胞)对样品做了细胞毒性分析。研究结果表明:通过掺杂和包壳的步骤,合成的Cu∶CdTe/CdS核壳量子点在CdTe量子点的基础上实现了荧光发射红移,荧光强度提高,以及细胞毒性降低。     

羧基CdSe荧光量子点的制备及其荧光特性研究

以氯化镉、硒粉为前驱体,巯基乙酸(TGA)为稳定剂,制备了羧基CdSe量子点,并研究了其荧光特性与影响因素。结果表明,反应温度、反应时间与反应体系的pH值是影响量子点生长和荧光性能的主要因素。制备羧基CdSe量子点的最优条件为反应温度90℃、pH=11、n(Cd)∶n(Se)=2∶1。制备的羧基CdSe量子点的粒径随反应时间的延长而逐渐增大,量子点荧光稳定性好,荧光强度高,光漂白时间延长。     

圆偏振光诱导CdTe量子点再生长及其对光致发光的影响

实验研究了以3-巯基丙酸为配体合成的水溶性CdTe量子点经过非偏振光与圆偏振光照射处理后, 量子点的再生长变化规律。采用光致发光谱、紫外-可见吸收光谱、透射电子显微镜与X射线衍射等表征手段分析表明: 非偏振光会促进CdTe量子点的光氧化, 导致量子点尺寸缩小, 荧光发光峰位蓝移, 且发光效率降低; 而圆偏振光增强了配体的光氧化, 在量子点表面形成CdS层, 导致量子点尺寸进一步增大, 荧光发光峰红移, 且发光效率提升。进一步讨论了CdTe量子点与配体之间的键合作用, 相关光化学反应机制及其对量子点光致发光性质的影响。     

CdTe量子点的微波合成及其在双光子显微成像中的应用

采用微波辐射加热的方法,以亚碲酸钠(Na2TeO3)作碲源,以谷胱甘肽(GSH)作稳定剂,在水相中合成出高质量的CdTe量子点。所合成量子点的发射波长从515～630nm可调,荧光量子产率(PLQYs)最高达95%。利用X射线粉末衍射(XRD)、高分辨透射电镜(HRTEM)、紫外-可见吸收光谱(UV-Vis)和荧光发射光谱(PL)等技术表征产物的物相结构和光学性质。用双光子激发荧光法研究CdTe量子点的双光子吸收性质。用双光子激发荧光成像技术,以发红光的CdTe量子点作为双光子荧光探针成功标记了人肺腺癌细胞(A549)。     

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。     

2,4-二-N-甲基丙烯酰胺-α-萘酚及其自聚物的合成与荧光性能研究

以α-萘酚与N-羟甲基丙烯酰胺为原料,经Friedel-Crafts反应合成了荧光单体2,4-二-N-甲基丙烯酰胺-α-萘酚并进一步合成其自聚物。考察了催化剂用量、反应温度、原料物质的量比、反应时间对产率的影响。分别用超导核磁共振谱仪和元素分析仪对产物结构进行分析,并对单体与自聚物的荧光性能进行了对比。结果表明,最佳反应条件为:n(α-萘酚)∶n(N-羟甲基丙烯酰胺)=1∶2,V(溶剂)∶V(催化剂)=10∶1,反应温度40℃,反应时间5h。聚合物的荧光强度高于单体的荧光强度。     

反应时间对CaWO_4∶Eu~(3+)纳米晶形貌及发光性能影响

采用溶剂热法,以钨酸钠(Na_2WO_4·2H_2O)和氯化钙(CaCl_2)为原料,在V(醇)∶V(水)=3∶1,十二烷基磺酸钠(SDS)摩尔分数为1%,pH=7,180℃下,制备出了四方晶系结构的球形铕掺杂钨酸钙(CaWO_4∶Eu~(3+))纳米晶。通过X射线衍射(XRD)、扫描电镜(SEM)及荧光光谱(PL)对不同条件下制备出的产物的物相、形貌以及荧光性质进行表征,探讨了反应时间对产物形貌及发光性能的影响。结果表明,在不同反应时间下合成出了不同形貌的CaWO_4∶Eu~(3+)纳米晶。从荧光发射光谱可以看出,反应时间为24h的体系下合成出的球形CaWO_4∶Eu~(3+)纳米晶在393nm激发下于612nm处有强发射峰。由此,反应时间对CaWO_4∶Eu~(3+)纳米晶的物相和形貌及发光性能起到重要作用。     

石墨烯-CdTe量子点复合材料的电化学发光传感器研究

以巯基丁二酸为修饰剂制备了CdTe量子点(CdTe QDs),采用微波辐射法还原氧化石墨且通过加入聚二烯丙基二甲基氯化铵(PDDA)得到带正电荷的石墨烯,并与带负电荷的CdTe QDs通过静电作用结合得到石墨烯-CdTe量子点复合材料(CdTe QDs/RGO-PDDA)复合物。研究了不同取样时间下CdTe QDs的电化学发光性能,并考察了扫描速度、共反应剂浓度和缓冲溶液pH值对CdTe QDs电化学发光强度的影响,通过对CdTe QDs/RGO-PDDA复合物电化学发光的研究,得出石墨烯的加入可以提高CdTe QDs电化学发光的强度和稳定性;最后基于CdTe QDs/RGO-PDDA构建了对Ag~+检测的电化学发光传感器,该传感器具有较强的抗干扰性,并得出线性回归方程为Y=10007.25-172.12X,线性回归系数R~2=0.9861。     

CdS半导体纳米晶的生长及其光谱研究

用玻璃沉淀技术制备了含过饱和CdS的玻璃固溶体,在一定条件下晶化处理使其长出CdS量子点,并采用了X射线衍射、高分辨扫描电镜、光吸收谱和荧光发光光谱等测试手段分析其性能,结果表明经过晶化处理可以在玻璃中长出CdS量子点,尺寸大约为10～25nm,吸收谱中出现明显的红移现象,反映出量子点的量子限域效应,荧光发光图谱中可以看出量子点发光主要由带隙发光和表面缺陷态发光组成,提高热处理温度可以改善晶粒的完整性.     

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.     

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.     

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.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.