地球化学样品中有机碳的光谱分析

有机碳已成为多目标地球化学调查、土地质量地球化学调查等项目研究的必测指标,对有机碳的准确定量是地球化学调查工作的重要内容,准确测定有机碳含量具有重要意义。然而传统的重量法、容量法流程长、速度慢,已经不能满足大批量及快速测定地球化学样品的要求。采用稀盐酸去除样品中的无机碳,应用高频红外碳硫分析仪对不同类型地球化学样品中有机碳的测定进行了研究,着重从称样量、酸的选择、最佳浓度及用量、助熔剂的选择和最佳加入量进行对比实验,优化出适合分析地球化学样品中有机碳含量的条件,并采用国家一级地球化学标准物质建立校准曲线,建立盐酸预处理-红外吸收光谱法测定地球化学样品中有机碳含量的分析方法。结果表明：陶瓷坩埚经1 200 ℃灼烧处理可以有效降低碳空白,减小对分析结果的影响;选择50.0～70.0 mg称样量,测试准确度高且样品熔融时不易喷溅;0.40～0.60 mL稀盐酸（1+7）除尽样品中的无机碳同时减少有机碳流失损失;0.40～0.50 g纯铁屑和1.50～1.70 g钨粒作为助熔剂,助熔效果稳定;采用国家一级地球化学标准物质建立校准曲线,校准曲线线性良好（R2=0.998 5）。该方法的检出限为69 μg·g-1,测定结果的相对标准偏差（RSD,n=12）均小于8%。经63个不同类型国家一级地球化学标准物质（土壤、岩石、水系沉积物）验证,测定结果与标准值相符。本方法操作简便,检出限低,灵敏度高,结果准确可靠,适用于地球化学样品中有机碳含量的测定。     

β-榄香烯振动光谱的量子化学从头计算

利用G98及GAMESS从头计算程序的RHF／6－31方法,对β－榄香烯的全部振动基频作了计算,并与实测红外光谱做了对比,归属了它们的振动模式,讨论了它们的特征基频,并对理论计算的振动频率进行了标度校正。     

A Novel Fluorescent Probe for ATP Detection Based on Synergetic Effect of Aggregation-induced Emission and Counterion Displacement

In this work,a fluorescent probe(TPEBe-I)was developed for adenosine triphosphate(ATP)detection based on the synergetic effect of aggregation-induced emission and counterion displacement.TPEBe-I gave weak emission in aqueous solution due to the heavy-atom effect of counter iodide ion.However,upon the addition of ATP,the new aggregate complex(TPEBe-ATP)was formed between the cationic unit of TPEBe-I and ATP through electrostatic interactions,which not only restricted the intramolecular motion of luminogen but also eliminated the quenching effect of iodide ion.As a result,the fluorescent light-up detection for ATP was successfully achieved.Moreover,TPEBe-I exhibited high selectivity towards ATP and showed a wide linear detection region towards the logarithm of ATP concentration(5—600μmol/L)with a detection limit of 1.0μmol/L,enabling TPEBe-I as a promising probe for ATP quantitative analysis.     

玻璃中CdSeS纳米晶体的生长及其性能

对掺有镉、硒、硫的玻璃在500—800℃退火2—24h,生长了不同尺寸的CdSxSe1x纳米晶体.用分光光度计和光致发光光谱(PL)分析了纳米晶体的性能.退火温度低于550℃,纳米晶体处于成核阶段,600—625℃处于正常扩散生长阶段,700—800℃处于竞争生长阶段;而650℃处于两种生长阶段之间.虽然650℃下生长的纳米晶体的尺寸分布比较窄,但纳米晶体的尺寸随退火时间的延长几乎不变,在该温度改变退火时间很难改变纳米晶体的平均尺寸.在所有样品中出现了深能级缺陷,在650℃退火时间小于4h或大于16h有利 关键词： 纳米晶体 生长机理 深能级缺陷     

Beam dynamics studies on BEPC-Ⅱstorage rings at the commissioning stage

During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider(BEPC Ⅱ),which started on Nov.12,2006 and Oct.24,2007,respectively,we got the luminosity one tenth of its design value,provided beams to synchrotron radiation users for about 4 months,and studied beam dynamics as well.In this paper,some beam dynamics studies on the storage rings and their preliminary results are given.     

Pretilt study of double‐layer alignment film (DLAF)

A novel double‐layer alignment film (DLAF) was developed to obtain greater control of the alignment characteristics of the liquid crystal director. The DLAF consists of a thin fluorinated polymer layer on the top of a rubbed non‐fluorinated, non‐branched polyimide layer (PI 2555). Two types of fluorinated polymer with different chemical structures and wetting behaviour on PI 2555 were chosen, to provide either continuous or discontinuous top layers. The continuous top layer DLAF (DLAF‐1) exhibits an abrupt pretilt transition from planar to homeotropic as the top layer thickness increases. The discontinuous top layer DLAF (DLAF‐2) exhibits a gradual transition where the pretilt correlates with the coverage of fluorinated top layer. These two types of transitions fit with de Gennes' local Frederick's transition and Kwok's inhomogeneous alignment theories, respectively. The abrupt pretilt transition system may be promising for chemical/biosensor applications, whereas the gradual transition system is suitable for pretilt control in LCD devices.     

A novel caged-prenylxanthone from Garcinia bracteata

<正>A novel caged-prenylxanthone xanthone,neobractatin(1),was isolated from the twig of Garcinia bracteata.Its structure was elucidated by spectroscopic methods,especially 2D NMR techniques.