电极用纳米Ag2O的电化学性能研究Ⅲ.电极的循环伏安行为

研究了3种具有不同组成的氧化银（Ⅰ）电极在2种不同扫描条件下的循环伏安（CV）行为,发现在较慢扫速（0.5mV/s)条件下,不同组成电极的峰形相差较大。各电极的峰电流值都呈现出明显的差异,即具有合适配比的混配电极展示出良好的循环可逆性能,而纯纳米粒子组成的电极接受电荷的能力明显较强。对于各极峰位的偏移及峰电流的涨消做了对比解析,表明最佳混配电极中的电活性粒子具有合理的分布,电极极化小,活性物质利用率高,因而能够展示出良好的电化学性能。     

鱼明胶介质中AgBr/I纳米粒子的生长与感光性能

本文以鱼明胶为分散介质,采用双注法制备AgBr/I纳米粒子乳剂,控制银盐与卤溶液的注入速率(R),以TEM观测了粒子的生长,据此探讨了该乳剂中AgBr/I纳米粒子平均粒径(d)及分布(±σ)与反应条件的关系.发现在R为1.3 mmol/min^-8 mmol/min范围内,随R增大,d减小,R-d间呈良好的线性关系.除个别外,±σ值变化不明显.对于该纳米粒子乳剂采用二氧化硫脲进行化学敏化,结果表明:适当增加二氧化硫脲的加入量和延长敏化时间,均可有效提高乳剂的感光度,并有助于改善其低照度互易律失效,此外还揭示了曝光光源色温对该乳剂感光性能的影响.     

颗粒内部的碘离子对碘溴化银微晶照相性能的影响

本文研究了用连体四角锥碘化银为晶核制备类似于四面体碘溴化银微晶和用六方角锥碘化银为晶核制备片状碘溴化银微晶的方法,并对两种不同微晶的结构,形态和性能进行了比较和分析.     

苯并三氮唑对硫增感溴化银乳剂的过增感效应

采用在曝光前后用苯并三氮唑溶液对未增感的和硫增感的立方体溴化银乳剂涂层的处理方法,考察了苯并三氮唑在溴化银成像过程的两个阶段:曝光潜影的形成阶段和潜影中心得以放大的显影阶段的作用.有意义地发现苯并三氮唑对硫增感溴化银乳剂有明显的过增感效应.实验结果表明:1)对于未增感的立方体溴化银乳剂涂层,在曝光前吸附了苯并三氮唑后会抑制潜影的形成,但曝光后吸附了苯并三氮唑对显影有十分明显的促进作用;2)对于硫增感的立方体溴化银乳剂涂层,曝光前用苯并三氮唑溶液处理后,产生显著的过增感效应,相对感光度可提高4倍左右,在曝光后用苯并三氮唑溶液处理,随着苯并三氮唑浓度的增加对显影也有一定程度的促进作用;3)对于硫增感的溴化银涂层,先经过388 mV的氧化还原缓冲液处理,再经苯并三氮唑溶液处理过的样片的感光度都要较未经缓冲液处理的提高4倍左右,这说明苯并三氮唑对硫增感乳剂产生的过增感效应只与硫敏化中心内(Ag₂S)_n的存在有关,与(Ag)_m是否存在无关.     

Photocatalytic Effects of Rutile Phase TiO2 Ultrafine Powder with High Specific Surface Area Obtained by a Homogeneous Precipitation Process at Low Temperatures

The photocatalytic characteristics of nanostructured TiO₂ ultrafine powder with rutile phase produced using the homogeneous precipitation process at low temperatures (HPPLT) were compared with those of commercial P-25 TiO₂ powder by flame hydrolysis. The TiO₂ powder by the HPPLT showed much higher photoactivity in the removal rate, showing lower pH values in the solution than the P-25 powder when eliminating metal ions such as Pb and Cu from the aqueous metal-EDTA solutions. This can be inferred as the more rapid photo-oxidation or -reduction of metal ions from the aqueous solution, together with relatively higher efficiencies in the use of an electron-hole pair formed on the surface of the TiO₂ particles under UV light irradiation. Also, in the view of the TiO₂ particle morphology, compared to the well-dispersed spherical P-25 particles, the agglomerated TiO₂ secondary particles by the HPPLT consist of acicular typed primary particles with a thickness in the range of 3–7 nm and the primary particles radialize in all directions, which would be more effective to photocatalytic reactions without the large electron-hole recombination on the surface of the TiO₂ particle under UV light irradiation. It can be, therefore, thought that the higher photoactivity of the rutile TiO₂ powder by the HPPLT in the aqueous solutions results mainly from having a larger surface area by the acicular shaped primary particles with very thin thickness and radialization in all directions.     

喷雾热分解法制备的钛酸钡颗粒内钡钛元素分布

基于氯化钡和二氧化钛具有不同的溶解特性,采用溶剂萃取法分别对喷雾热分解法和喷雾水解反应法制备的钛酸钡前驱体干燥产物颗粒内钡和钛分布进行定性分析,从而间接钛酸钡颗粒内的钡和钛分布情况。实验结果表明,该法可快速而准确地分析组合分析组分偏析情况。     

双黄连粉针剂中黄芩苷的高效毛细管电泳-电导法测定

建立了双黄连粉针剂中黄芩苷含量测定的高效毛细管电泳电导法;以未涂层融硅毛细管(75μm×50cm)为分离柱,Tris-H3BO3为电泳介质(15mmo1/LTris,1.5mmol/LH3BO3),在18kV、pH85的碱性环境下,柱端电导检测双黄连粉针剂中的黄芩苷含量;重点探讨了缓冲溶液的种类、浓度、分离电压、进样时间对检测的影响;该法的线性范围为10～720mg/L,检出限为2.5mg/L;结果表明该法简便、快速、结果准确,适用于含黄芩苷的制剂含量的测定.     

Pseudopolymorphic Clathrate Structures Formed by an Alicyclic Dialcohol Inclusion Host

Dialcohol host 2,7-dimethyltricyclo[4.3.1.0^3,8]undecane-syn-2,syn-7-diol 1 can form either ellipsoidal clathrate or helical tubulate inclusion compounds where only dispersion forces operate between the hosts and guests. The former (tetragonal space group I4₁/acd), built from two interpenetrating sublattices containing both diol enantiomers, encloses the guests in rugby ball-shaped cavities. The latter (trigonal space group P3₁21 or P3₂21), containing only one diol enantiomer, traps the guests within parallel tubes. Which inclusion type is produced is determined by the guest size and shape and, hence, control is possible over these structures. At room temperature, cyclohexane gives the tetragonal structure, but fluorocyclohexane yields the trigonal structure. Chloroform produces both pseudopolymorphs: the tetragonal form at higher and the trigonal form at lower temperatures. Powder and single-crystal structural X-ray data are reported for these clathrate compounds.     

Structure determination from powder diffraction

The review surveys modern methods for the determination of unknown crystal structures of organic and inorganic compounds from powder diffraction data. The main stages of this process, from the preparation of the specimen to a search for the structural motif followed by the Rietveld refinement, are considered. The results obtained on different diffractometers using X-ray, synchrotron, and neutron radiations are demonstrated to be well reproducible. Examples of successful structure solution are cited, which provide evidence that powder diffraction is a reliable tool in establishing structures of a wide range of compounds for which single crystals are unavailable.     

在线性或交联的聚氨酯粒子内原位还原制备纳米银粒子

纳米金属粒子有特异性质 ,可用作高效催化剂、非线性光学材料等 .为防止其聚集 ,不少研究者采用表面活性剂 [1]、配位体 [2 ]和高分子等以阻止纳米金属粒子的聚集 .近年来高分子金属复合纳米粒子引起人们广泛的兴趣 [3～ 9] .文献上大多采用线性或嵌段双亲高分子作纳米金属的分散稳定剂[6 ] 或在高分子粒子表面沉积纳米金属粒子[5] ,也有人采用多孔交联高分子微球的孔洞作为微反应器形成纳米金属粒子[7] .这些方法均不能有效地控制金属粒子的粒径 ,特别难以合成粒径小于 3 0 nm的银粒子 .本文首次报道了在常温处于粘弹态 ,线性或交联的高分…