十二烷基苯磺酸钠改性膨润土修饰碳糊电极对铅离子的测定研究

用十二烷基苯磺酸钠改性膨润土,并通过红外光谱(IR)及X射线衍射(XRD)对其进行表征。以改性膨润土作为化学修饰剂制成修饰碳糊电极,利用三电极体系循环伏安法,在BR缓冲溶液中测定铅离子(Pb~(2+))的电化学行为。结果表明:用十二烷基苯磺酸钠改性膨润土作为修饰剂提高了碳糊电极的电化学性能,使其对Pb~(2+)的电化学响应和选择性均得到提高。在改性膨润土质量分数为6%,以pH=2.4的BR缓冲溶液为底液的最佳检测条件下,Pb~(2+)响应电流与Pb~(2+)浓度(在0.120μmol/L范围内)呈良好的线性关系,相关系数为0.99492,检出限为6.531×10-8 mol/L。连续测定15d,电极表现出良好的稳定性。在最佳条件下,采用标准加入法对模拟水样中的Pb~(2+)进行测定,Pb~(2+)回收率在96.90%~103.75%之间。     

石墨烯修饰碳糊电极循环伏安法测定铜离子

用石墨烯修饰碳糊电极,采用循环伏安法在BR缓冲溶液中测定Cu2+的电化学行为。研究了不同条件对Cu2+电化学测定的影响。实验表明,石墨与石墨烯比例为8∶1,pH=3.5,扫描速度为100mV/s进行循环伏安法测定时,在0.136V左右处出现一个峰形较好的特征吸收峰;峰电压与Cu2+浓度在5×10-8~1×10-4 mol/L范围内呈良好的线性关系,相关系数为0.9905,检出限为5.572×10-8 mol/L;连续测定两周,电极表现出较好的稳定性。     

基于氧化铜/碳基复合材料电化学传感器检测亚硝酸根

为改善氧化铜(CuO)传感器的灵敏度,以氮苯基甘氨酸(NAN)、氧化石墨烯(GO)为原材料,在磷酸缓冲液支持的电解质溶液中,通过电化学聚合法在玻碳电极上制备出碳基复合材料(rGO/NPAN),并以其为支撑材料,采用循环伏安法将氧化铜与之复合最终形成氧化铜/石墨烯/N取代羧基聚苯胺(CuO/rGO/NPAN)电化学传感器。N取代羧基聚苯胺的强吸附性、及石墨烯的大比表面积、高导电性有利于氧化铜的均匀分布。利用扫描电镜(SEM)对CuO/rGO/NPAN传感器的形貌进行表征,讨论了pH值、扫描速率等因素对电化学活性和电催化活性的影响,采用循环伏安发、计时电位法、交流阻抗法对该传感器的电化学性能进行研究,并对其电化学机理进行探讨。结果表明,该修饰电极具有低的检测电位、高的电化学响应及良好的稳定性,检测亚硝酸根的浓度范围为(0.5×10-6)～(7.4×10-3)mol/L与(7.4×10-3)～(22.9×10-3)mol/L。灵敏度为32.317μA/(mmol·L),检测下限低至0.15μmol/L(S/N=3)。将此传感器用于实际应用,回收率在99.9%～112%之间。     

铁氰化铈/还原石墨烯纳米材料的制备及其对水合肼的电化学检测

通过电沉积的方法,在玻碳电极表面上沉积铁氰化铈/石墨烯(Ce HCF/RGO)纳米复合材料。用扫描电子显微镜(SEM)对其形貌进行表征,发现其粒径大小均一。用循环伏安法(CV)研究水合肼在不同电极的电化学行为。结果表明,与RGO修饰电极(RGO/GCE)和铁氰化铈修饰电极(Ce HCF/GCE)相比,铁氰化铈/石墨烯复合物修饰电极对水合肼具有更好的电催化氧化性能。在一定条件下,它对水合肼响应的线性范围为2.87×10~(-7)~8.56×10~(-4)mol/L,检出限为8.5×10~(-8)mol/L。可用于水合肼的电化学传感检测。     

咖啡酸在溴代十六烷基吡啶修饰碳糊电极上的电化学行为研究

制作了溴代十六烷基吡啶修饰碳糊电极,研究了咖啡酸在该修饰碳糊电极上的电化学行为。在0.1mol.L-1的HAc-NaAc缓冲溶液(PH=3.0)中,咖啡酸在峰电位为0.44V(vs.SCE)左右出现一灵敏的氧化峰,通过选择和优化各项参数,建立了一种直接测定咖啡酸的电分析方法。该方法的线性范围为1.55×10-5~4.16×10-7mol.L-1,检出限为2.0×10-8mol.L-1(富集min)。该修饰电极制作简单,稳定性、重现性良好,可用于药物中咖啡酸含量的则定。     

新型石墨烯-聚苯胺-银基电极复合材料的制备及性能研究

目的设计一个低成本条件下成熟高效制备石墨烯-聚苯胺-银基复合电极材料的工艺路线。方法研究石墨烯的制备工艺以及石墨烯与聚苯胺、银粒子的复合效果,将石墨烯与苯胺、银粒子通过原位聚合的方法制得石墨烯-聚苯胺-银复合材料。利用扫描电子显微镜(SEM)、傅里叶变换-红外光谱(FT-IR)、X射线衍射(XRD)、循环伏安法(CV)和恒电流充放电法(GCD)对石墨烯和石墨烯-聚苯胺-银复合材料的形貌、结构和电化学性能进行分析研究。结果 SEM、FT-IR、XRD等测试表明,聚苯胺类衍生物、石墨烯以及银粒子在整个复合材料中共存。结论 CV和GCD的测试结果表明复合材料有优良的电化学性能,比电容最高可达到293 F/g。     

碳化硅修饰碳糊电极测定汞离子

制备了碳化硅修饰碳糊电极,利用循环伏安法,采用三电极体系测定汞离子的电化学行为。结果表明,以100mV/s的扫描速度测定pH值为2.33的BR缓冲溶液中的Hg2+时,在0.575V左右出现一个特征吸收峰,峰电压与Hg2+浓度在1.0×10-7~1.0×10-4 mol/L范围内可呈良好的线性关系,相关系数为0.9971,检出限为3.7×10-8 mol/L,连续测定2周,电极表现出较好的稳定性。     

氨基-β-环糊精-石墨烯-二茂铁修饰电极对多巴胺的电化学行为研究

利用制备的氨基-β-环糊精-石墨烯-二茂铁(β-CD-NH2/GNs/Fc)复合膜修饰电极,研究了多巴胺(DA)的电化学行为。结果表明,该复合膜修饰电极在pH值=7.00的磷酸盐缓冲溶液(PBS)中对DA有良好的电催化性能,DA的氧化峰电流在0.1～100μmol/L浓度范围内呈良好的线性关系,检出限为8.5×10-8mol/L。结果表明该修饰电极具有较高的检测灵敏度,可用于实际样品的检测。     

石墨烯/银纳米颗粒复合材料的制备及其对双氧水的电化学检测

以氧化石墨烯(GO)和硝酸银为原材料,聚乙烯吡咯烷酮(PVP)为还原剂和稳定剂,通过水热法制备出还原氧化石墨烯/银纳米颗粒(rGO/AgNPs)复合材料。采用透射电子显微镜(TEM)、X射线衍射(XRD)及紫外-可见分光光度计(UV-Vis)对rGO/AgNPs复合材料的形貌、组成和结构进行表征。同时,将rGO/AgNPs复合材料修饰到玻碳电极表面制备出过氧化氢(H_2O_2)电化学传感器,通过循环伏安法(CV)和计时安培响应法(i-t)对传感器进行电化学性能测试。实验结果表明:制备的rGO/AgNPs传感器具有较好的电化学性能,其对H_2O_2检测的灵敏度为340.6μA·(mmol/L)~(-1)·cm~(-2),响应时间为3s,最低检测极限为7.5μmol/L(S/N=3),线性检测范围为20~4950μmol/L(线性相关系数为R=0.9973)。     

掺氮石墨烯的溶剂热制备及对抗坏血酸氧化的电催化性能

以Hummers方法制备的氧化石墨烯为前驱体,在乙二胺和水的混合溶剂热条件下(150℃,8h)合成了掺氮石墨烯(NG)。通过XRD、FT-IR、XPS和电化学阻抗谱研究了掺氮石墨烯的结构和电化学性能。结果表明,通过溶剂热反应在石墨烯表面引入C—N,N—H等含氮基团。乙二胺不仅能对氧化石墨烯进行部分还原,而且还能对其进行掺氮功能修饰。电化学阻抗谱研究表明,掺氮石墨烯(NG)的电子转移阻抗明显小于相同条件下水热还原制备的石墨烯,说明功能修饰石墨烯大大改善了电子转移速率。将掺氮石墨烯修饰电极应用于对抗坏血酸的电化学检测,检出限达1.0×10-5~2.8×10-2 mol/L,最低检测限(3σ/slope)为1.7×10-7 mol/L。     

Fe+注入增强Ti6Al4V表面喷丸强化层的生物摩擦学性能

为改善Ti6Al4V表面喷丸强化层的生物摩擦学性能,把不同参数Fe~+注入到直径4mm喷丸的强化层中。用Nano IndenterⅡ型纳米显微力学探针测定试样改性层的纳米硬度,在MRTR多功能摩擦磨损试验机上以ZrO_2球/改性层为摩擦副进行人工唾液和透明质酸钠溶液润滑下的生物摩擦学试验,使用S-3000N扫描电子显微镜分析改性层组织形貌和生物摩擦学试验后的磨痕形貌。结果表明:Fe~+注入Ti6Al4V表面喷丸强化层的形成相为Fe2Ti。随着注入能量和剂量增加,Fe_2Ti含量从3.7%增至4.7%;Fe~+注入改性层的纳米硬度从8.46GPa增至10.29GPa,都远高于单一喷丸强化层的5.59GPa;在人工唾液和透明质酸钠溶液润滑下的摩擦因数分别从0.53降至0.38和从0.49降至0.28,都低于单一喷丸强化层的0.62和0.59,磨损呈现不同程度的减轻。Fe~+注入能显著提高Ti6Al4V表面单一喷丸强化层的减摩抗磨性能。     

三维网络多孔陶瓷/金属复合材料的研究新进展

三维网络多孔陶瓷/金属双(共)连续相复合材料(C⁴材料)具有各向同性和正向加合性质,在摩擦器件和制动元件、电子封装材料及散热器件、航空航天器件、光学仪表材料、运动器械等领域具有广阔的应用前景。本文较为详细地介绍了C⁴材料的各种制备技术,并对比了它们的优缺点,在此基础上,重点阐述了本课题组提出的原位反应无压浸渗新工艺和最新研究进展,并对C⁴材料的未来发展趋势进行了展望。     

Calibration of Electret-Based Integral Radon Monitors Using NIST Polyethylene-Encapsulated 226Ra/222Rn Emanation (PERE) Standards

The recently developed ²²²Rn emanation standards that are based on polyethylene-encapsulated ²²⁶Ra solutions were employed for a first field-measurement application test to demonstrate their efficacy in calibrating passive integral radon monitors. The performance of the capsules was evaluated with respect to the calibration needs of electret ionization chambers (E-PERM^®, Rad Elec Inc.). The encapsulated standards emanate well-characterized and known quantities of ²²²Rn, and were used in two different-sized, relatively-small, accumulation vessels (about 3.6 L and 10 L) which also contained the deployed electret monitors under test. Calculated integral ²²²Rn activities from the capsules over various accumulation times were compared to the averaged electret responses. Evaluations were made with four encapsulated standards ranging in ²²⁶Ra activity from approximately 15 Bq to 540 Bq (with ²²²Rn emanation fractions of 0.888); over accumulation times from 1 d to 33 d; and with four different types of E-PERM detectors that were independently calibrated. The ratio of the electret chamber response E_Rn to the integral ²²²Rn activity I_Rn was constant (within statistical variations) over the variables of the specific capsule used, the accumulation volume, accumulation time, and detector type. The results clearly demonstrated the practicality and suitability of the encapsulated standards for providing a simple and readily-available calibration for those measurement applications. However, the mean ratio E_Rn/I_Rn was approximately 0.91, suggesting a possible systematic bias in the extant E-PERM calibrations. This 9 % systematic difference was verified by an independent test of the E-PERM calibration based on measurements with the NIST radon-in-water standard generator.     

Al-B4C复合材料中子吸收性能研究

利用蒙特卡罗方法和~(252)Cf中子源研究了在准直热中子入射束下,15%~30%(质量分数)碳化硼含量的Al-B_4C复合材料的中子吸收系数和宏观截面。结果表明,Al-B_4C复合材料的中子吸收系数随碳化硼含量增加而增大,相同碳化硼含量的材料其中子吸收系数随厚度的增加按指数规律变化;~(252)Cf中子源测试得到的中子吸收系数比0.0253eV单能热中子计算得到的吸收系数低0.5%~4.3%;Al-B_4C复合材料的宏观截面随着碳化硼含量的增加呈线性递增的关系,而且理想热中子0.0253eV下的递增率(0.97925cm~(-1)/%)大于~(252)Cf中子源构建0~1eV中子下的递增率(0.58537cm~(-1)/%)。     

Ce3+掺杂钛酸钡纳米管薄膜的制备与性能

以阳极氧化制备的TiO_2纳米管薄膜为模版,通过水热法制备了Ba_(1-x)Ce_xTiO_3(0≤x≤0.08)纳米管薄膜,研究了Ba_(1-x)Ce_xTiO_3的结构、表面形貌及其电性能。采用X射线衍射仪表征其晶体结构,采用扫描电子显微镜和透射电子显微镜观察其表面及断口形貌,采用宽频介电阻抗谱仪测试其介电性能。结果表明,在较为温和的条件下用水热法成功制备出立方相结构的Ba_(1-x)Ce_xTiO_3纳米管薄膜,纳米管孔径在80~95nm之间;将制备的Ba_(1-x)Ce_xTiO_3经退火后生成多晶的Ba1-xCexTiO3纳米管薄膜,且样品的管外径尺寸在90~100nm之间,管壁的厚度为25~30nm,介电常数在1kHz下最高可达472,介电损耗为0.41。     

Fast d-f emission in Ce, Pr and Nd activated RbCl

In the search for new scintillator materials, Ce³⁺ doped chlorides are a promising class of materials, combining a high efficiency and fast response time. Even shorter response times may be achieved by replacing Ce³⁺ by Pr³⁺ or Nd³⁺ as the lifetime of the d-f emission is substantially shorter for these ions. Here we report on the luminescence properties of Ce³⁺, Pr³⁺ and Nd³⁺ in RbCl and investigate the potential as a scintillator material. Under UV excitation Ce³⁺ shows d-f emission between 325 and 425 nm. The emission originates from multiple (differently charge compensated) Ce³⁺ sites. The luminescence lifetime varies with wavelength and is ∼40 ns for the longer wavelength emission. For RbCl:Pr³⁺ three d-f emission band are observed between 250 and 350 nm which can be assigned to transitions from the lowest energy fd state to different ³H_J (J = 4-6) states within the 4f² configuration of Pr³⁺. The decay time is ∼17 ns. For the Nd³⁺ activated sample a weak emission band around 220 nm is observed only at 8 K which may be due to d-f emission. The very short lifetime (4 ns) is faster than the radiative lifetime, indicating that the d-f emission is quenched by relaxation to lower lying 4f³ states or by the process of photoionization. Under VUV excitation at wavelengths below 175 nm (the bandgap of RbCl) the d-f emission is very weak for Ce³⁺, Pr³⁺ and Nd³⁺ doped RbCl and the emission spectra are dominated by defect related emission. This indicates that energy transfer from the host lattice to the fd states is inefficient which prevents application as a scintillator material.     

Laser-induced time-resolved luminescence of orange kyanite Al2SiO5

Manganese is a very important microelement performing a large number of biological functions in human body. We have detected by spectroscopic measurements manganese in mineral kyanite. In this paper we present laser-induced time-resolved luminescence and optical absorbance spectra of orange, Mn containing kyanite. It was proven the orange color is caused by Mn³⁺. Several luminescence lines and bands were found and ascribed to Mn⁴⁺ and Mn³⁺, emission centers. The spectroscopic technique can be utilized for detection of small amounts of manganese in minerals.     

New National Air-Kerma-Strength Standards for 125I and 103Pd Brachytherapy Seeds

The new U.S. measurement standard for the air-kerma strength from low-energy photon-emitting brachytherapy seed sources is formally described in detail. This instrument-based standard was implemented on 1 January 1999, with its salient features and the implications of differences with the previous standard given only through a series of informal communications. The Wide-Angle Free-Air Chamber (WAFAC) is specially designed to realize air kerma from a single-seed source emitting photons with energies up to about 40 keV, and is now used to measure the wide variety of seeds used in prostate-cancer therapy that has appeared in the last few years. For the two ¹²⁵I seed models that have been subject to both the old and new standards, the new standard reduces the air-kerma strength by 10.3 %. This change is mainly due to the removal of the influence on the measurement of the Ti K x rays produced in the source encapsulation, a component with no clinical significance.     

ICARE Radon Calibration Device

An aerodynamic calibration device called ICARE is briefly described. ICARE is currently being used at the Nuclear Research Center of Saclay in France for the certification of instruments employed in measurement of artificial radioactive particulate airborne contamination. ICARE is essentially a blower. Aerosols calibrated in size and labelled with ¹³⁷Cs or ²³⁹Pu are injected in the mainstream of the blower upstream of the test section.To extend ICARE’s field of application to the case of instruments employed in measurement of ²²²Rn and of its decay products, a new line of injection has been designed and is under construction, in the frame of a contract financed by the European Community Commission. The main effort is presently oriented to-ward the development of a reliable ²²²Rn source, based on a solid deposit of ²²⁶Ra on organic fibers, and of a reference method for the measurement of ²²²Rn activity per unit volume of air. This reference is based on a modified version of standard containers being used in the French reference method for calibrated measurements of ¹³³Xe and ⁸⁵Kr by gamma spectroscopy.     

Special Report on Standards for Radioactivity: Report on the 1989 Meeting of the Radionuclide Measurements Section of the Consultative Committee on Standards for the Measurement of Ionizing Radiations

This report describes the activities discussed at the 10th meeting of Section II of the Consultative Committee on Standards for the Measurement of Ionizing Radiations (Comité Consultatif pour les Etalons de Mesure des Rayonnements Ionisants, CCEMRI) held in May 1989 at Sèvres (France). Topics included present and future international comparisons of activity measurements, the status and possible extension of the International reference system for activity measurements of gamma-ray emitting nuclides, reports from other working groups, accomplishments at the International Bureau of Weights and Measures (Bureau International des Poids et Mesures, BIPM), and progress at member laboratories.