气体团簇离子束装置的设计及其在表面平坦化、自组装纳米结构中的应用

根据超声膨胀原理,n(10-10^4)个气体原子可以绝热冷却后凝聚在一起形成团簇,经过离化后,形成带一个电荷量的团簇离子,比如Arn^+.当团簇离子与固体材料相互作用时,由于平均每个原子携带的能量(~eV)较低,仅作用于材料浅表面区域,因此,气体团簇离子束是材料表面改性的优良选择.本文介绍了一台由武汉大学加速器实验室自主研制的气体团簇离子束装置,包括整体构造、工作原理及实验应用.中性团簇束由金属锥形喷嘴(F=65-135μm,q=14°)形成,平均尺寸为3000 atoms/cluster,经离化后,其离子束流达到了50μA.Ar团簇离子因其反应活性较低,本文运用Ar团簇离子(平均尺寸为1000 atoms/cluster)进行了平坦化和自组装纳米结构的研究.单晶硅片经Ar团簇离子束处理后,均方根粗糙度由初始的1.92 nm降低到0.5 nm,同时观察到了束流的清洁效应.利用Ar团簇离子束的倾斜(30°-60°)轰击,在宽大平坦的单晶ZnO基片上形成了纳米波纹,而在ZnO纳米棒表面则形成了有序的纳米台阶,同时,利用二维功率谱密度函数分析了纳米结构在基片上的表面形貌和特征分布,并计算了纳米波纹的尺寸和数量.     

Thermochemical study of [Sm(C7H5O3)2·(C4H6NO2S)]·2H2O

The product from reaction of samarium chloride hexahydrate with salicylic acid and Thioproline, [Sm(C₇H₅O₃)₂·(C₄H₆NO₂S)]·2H₂O, was synthesized and characterized by IR, elemental analysis, molar conductance, and thermogravimetric analysis. The standard molar enthalpies of solution of [SmCl₃·6H₂O(s)], [2C₇H₆O₃(s)], [C₄H₇NO₂S(s)] and [Sm(C₇H₅O₃)₂·(C₄H₇NO₂S)·H₂O(s)] in a mixed solvent of absolute ethyl alcohol, dimethyl sulfoxide(DMSO) and 3 mol L^?1 HCl were determined by calorimetry to be Δ_s H _m ^Φ [SmCl₃ δ6H₂O (s), 298.15 K]= ?46.68±0.15 kJ mol^?1 Δ_s H _m ^Φ [2C₇H₆O₃ (s), 298.15 K]= 25.19±0.02 kJ mol^?1, Δ_s H _m ^Φ [C₄H₇NO₂S (s), 298.15 K]=16.20±0.17 kJ mol^?1 and Δ_s H _m ^Φ [Sm(C₇H₅O₃)₂·(C₄H₆NO₂S)]·2H₂O (s), 298.15 K]= ?81.24±0.67 kJ mol^?1. The enthalpy change of the reaction (1) $$ SmCl_3 \cdot 6H_2 O(s) + 2C_7 H_6 O_3 (s) + C_4 H_7 NO_2 S(s) = Sm(C_7 H_5 O_3 )_2 \cdot (C_4 H_6 NO_2 S) \cdot 2H_2 O(s) + 3HCl(g) + 4H_2 O(1) $$ was determined to be Δ_s H _m ^Φ =123.45±0.71 kJ mol^?1. From date in the literature, through Hess’ law, the standard molar enthalpy of formation of Sm(C₇H₅O₃)₂(C₄H₆NO₂S)δ2H₂O(s) was estimated to be Δ_s H _m ^Φ [Sm(C₇H₅O₃)₂·(C₄H₆NO₂S)]·2H₂O(s), 298.15 K]= ?2912.03±3.10 kJ mol^?1.     

Comparison of polysaccharides from two species of Ganoderma

Ganoderma lucidum and Ganoderma sinense, known as Lingzhi in Chinese, are commonly used Chinese medicines with excellent beneficial health effects. Triterpenes and polysaccharides are usually considered as their main active components. However, the content of triterpenes differs significantly between the two species of Ganoderma. To date, a careful comparison of polysaccharides from the two species of Ganoderma has not been performed. In this study, polysaccharides from fruiting bodies of two species of Lingzhi collected from different regions of China were analyzed and compared based on HPSEC-ELSD and HPSEC-MALLS-RI analyses, as well as enzymatic digestion and HPTLC of acid hydrolysates. The results indicated that both the HPSEC-ELSD profiles and the molecular weights of the polysaccharides were similar. Enzymatic digestion showed that polysaccharides from all samples of Lingzhi could be hydrolyzed by pectinase and dextranase. HPTLC profiles of their TFA hydrolysates colored with different reagents and their monosaccharides composition were also similar.     

荧光和UV-Vis光谱法研究DL-天冬氨酸-Ag的反应

用UV-Vis、荧光光谱和电泳等方法研究了DL-天冬氨酸(Asp)同银(Ⅰ)离子的相互作用及介质的pH、Asp浓度等条件对天冬氨酸同银(Ⅰ)离子作用的影响.天冬氨酸-银体系在235.2nm和493nm左右有最大吸收;在281.7nm激发波长下天冬氨酸产生荧光(发射波长为333.8nm),当Asp同银离子发生反应后,出现了荧光猝灭现象.天冬氨酸-银体系带负电荷,双电层的电动电位为-1.81×10-4V.     

粗晶材料晶粒散射波的实验鉴别

在利用超声波束对粗晶材料样品或工件进行检测时，接收回波中，除伤波、底波外，还存在晶粒散射波及其它干扰杂波。本文对晶粒散射波主要特征：晶粒散射波随传播时间出现的最大值位置；晶粒散射波最早到达时间；以及传播过程中晶粒散射波的频谱特性进行了实验验证。其中，用脉冲频谱合成方法，计算了双探买发．收复合声场声轴上声压分布，据此对最大值的出现位置给予了物理解释。并用短时傅立叶变换分析了声波传播过程中晶粒散射波的频谱特性。获得了一些有用结果。     

In2O3敏化ZnO纳米棒阵列的性能及其光电催化活性

以掺氟SnO₂ (FTO)导电玻璃为基底, 采用水热法制备了ZnO纳米棒阵列. 通过In(NO₃)₃水溶液水洗的方法, 合成了In₂O₃敏化ZnO纳米棒阵列光催化剂. 采用场发射扫描电子显微镜(FESEM), X射线能谱(EDX), X射线衍射(XRD)及紫外-可见漫反射光谱(UV-Vis DRS)对样品的形貌、结构、组成、晶相等进行一系列的表征. 以罗丹明B (RhB)为目标降解物, 探究了In₂O₃敏化ZnO 纳米棒阵列光电催化活性. 采用场诱导表面光伏技术(FISPV)研究了不同含量的In₂O₃敏化ZnO纳米棒阵列在光照射下的光生电荷行为. 结合电化学工作站检测不同样品的光电流, 随着In₂O₃敏化量的改变, 光电流和开路电压也随之改变. 并探讨了In₂O₃敏化ZnO纳米棒阵列光生电荷行为与光电催化活性之间的关系. 结果表明, 适量In₂O₃敏化的ZnO光催化剂在可见光下2 h内对罗丹明B的降解效率达到95%, 是单纯ZnO纳米棒阵列的2.4倍.     

Capping polymer-enhanced electrocatalytic activity on Pt nanoparticles: a combined electrochemical and in situ IR spectroelectrochemical study

Unexpected yet highly remarkable and intriguing observations of the polymer-enhanced electro-catalytic activity of the Pt nanoparticles for electro-oxidations of both methanol and formic acid were reported. In situ FTIR investigation suggests strongly that the observed activity enhancements are highly likely due to the PVP-induced additional reaction pathways. These observations may open up a new paradigm of research in which the protecting/stabilizing organic ligands can now be incorporated as an advantageous part and/or a finer catalytic activity tuner of a nanocatalytic system.     

Growth rate for beta-expansions

Let β > 1 and let m > β be an integer. Each \({x\in I_\beta:=[0,\frac{m-1}{\beta-1}]}\) can be represented in the form

$$x=\sum_{k=1}^\infty \epsilon_k\beta^{-k},$$

where \({\epsilon_k\in\{0,1,\ldots,m-1\}}\) for all k (a β-expansion of x). It is known that a.e. \({x\in I_\beta}\) has a continuum of distinct β-expansions. In this paper we prove that if β is a Pisot number, then for a.e. x this continuum has one and the same growth rate. We also link this rate to the Lebesgue-generic local dimension for the Bernoulli convolution parametrized by β. When \({\beta < \frac{1+\sqrt5}2}\), we show that the set of β-expansions grows exponentially for every internal x.

     

Growth rate for beta-expansions

Let β > 1 and let m > β be an integer. Each x ? I_b:=[0,\fracm-1b-1]{x\in I_\beta:=[0,\frac{m-1}{\beta-1}]} can be represented in the form

Novel electrochemical sensor based on functionalized graphene for simultaneous determination of adenine and guanine in DNA

A nano-material carboxylic acid functionalized graphene (graphene-COOH) was prepared and used to construct a novel biosensor for the simultaneous detection of adenine and guanine. The direct electrooxidation behaviors of adenine and guanine on the graphene-COOH modified glassy carbon electrode (graphene-COOH/GCE) were carefully investigated by cyclic voltammetry and differential pulse voltammetry. The results indicated that both adenine and guanine showed the increase of the oxidation peak currents with the negative shift of the oxidation peak potentials in contrast to that on the bare glassy carbon electrode. The electrochemical parameters of adenine and guanine on the graphene-COOH/GCE were calculated and a simple and reliable electroanalytical method was developed for the detection of adenine and guanine, respectively. The modified electrode exhibited good behaviors in the simultaneous detection of adenine and guanine with the peak separation as 0.334V. The detection limit for individual determination of guanine and adenine was 5.0×10(-8)M and 2.5×10(-8)M (S/N=3), respectively. Furthermore, the measurements of thermally denatured single-stranded DNA were carried out and the value of (G+C)/(A+T) of single-stranded DNA was calculated as 0.80. The biosensor exhibited some advantages, such as simplicity, rapidity, high sensitivity, good reproducibility and long-term stability.