TlCl-CdCl_2-H_2O体系在0°,25°,50°和75°的溶解度

(1)本文报告TlCl-CdCl_2-H_2O体系在0°,25°,50°,75°的溶解度。 (2)体系中存在的固相为CdCl_2·2(1/2)H_2O,TlCl·CdCl_2,TlCl(0°,25°)和CdCl_2·H_2O,TlCl·CdCl_2,TlCl(50°,75°)。 (3)TlCl·CdCl_2为一固液异成分化合物,針狀晶体,比重5.155,遇水即行分解。其存在的濃度范圍極广,在研究的温度范圍內始終存在。     

TiO2/CdS/Ru(bpy)2(NCS)2作为太阳电池光阳极的探讨

将CdS纳米粒子复合成TiO2纳米多孔膜上，用染料Ru(bpy)2(NCS)2对此复合半导体纳米膜电极进行每化，测量了不同CdS复合量的ITO／TiO2/CdS/Ru(bpy)2(NCS)2光阳极组成光电池的能量转换效率，实验证明，ITO／TiO2/CdS/Ru(bpy)2(NCS)2作为太阳电池光阳极的能量转换效率与TiO2/CdS复合半导体中CdS的含量有关，当CdS复合时间为5min的电池的短路电流为5．23A／m^2,开路电压为0．716V，能量转换效率为0．77％。     

CdS/TiO_2复合纳米网的制备及光催化性能研究

采用阳极氧化法和连续离子层吸附方法,制备出高催化活性的CdS/TiO_2复合纳米材料并研究其催化活性。制得的CdS纳米粒子未堵塞管口并均匀地分布在TiO_2纳米网上。相对于未修饰的TiO_2纳米网,CdS/TiO_2复合催化剂大大改善了TiO_2对光的吸收并表现出更高的光催化活性。在光照120min后,CdS/TiO_2复合纳米材料对亚甲基蓝的降解率为98.3%,远高于未修饰的TiO_2纳米网的71.3%。此外,通过光电流实验可知,当沉积CdS圈数为15圈时,CdS/TiO_2复合纳米材料的光电流最强。复合材料表现出比TiO_2更高的光催化活性可能是因为CdS是一个窄带隙的半导体,可增强TiO_2对可见光的吸收以及降低空穴和电子对的复合率。     

纳米TiO_2改性蚕丝丝素蛋白膜的研究

用溶胶凝胶法制备纳米TiO2改性再生蚕丝丝素蛋白膜.该丝素膜机械强度提高,在水中溶失率下降.UV、AFM、SEM测试的结果表明,丝素中纳米TiO2粒径约为80 nm,纳米粒子在丝素膜中分布均匀;XRD、FTIR测试结果表明,纳米TiO2的加入,可使改性丝素膜的结晶结构从SilkⅠ向SilkⅡ转化,其结晶度也随之提高;TGA测试表明改性丝素膜的热转变温度比纯丝素膜有所改变.     

溶胶-凝胶法制备纳米TiO2/丝素复合膜及结构性能研究

用溶胶凝胶法制备不同比例纳米TiO₂改性再生蚕丝丝素蛋白复合膜. UV和AFM测试结果表明, 该丝素膜中纳米TiO₂均匀分散在丝素中, TiO₂粒径约为80 nm; 同时该丝素膜的结构和热性能用FTIR, XRD, EDS, TGA和DTG进行表征. XRD测试结果表明, 随着纳米TiO₂的加入, 复合丝素膜的结晶结构从Silk I向Silk II转化, 但当纳米TiO₂的加入超过一定量时, 又破坏复合丝素膜的结晶结构; FTIR和EDS测试结果表明, TiO₂与丝素形成较好的键合; TGA和DTG测试表明复合丝素膜的热转变温度相比于纯丝素膜有所提高.     

纳米复合材料CdS/TiO2制备与不同模式光催化降解多种染料

采用化学水浴沉淀法再结合溶胶-凝胶和程序升温溶剂热两步法制备了一系列不同比例的CdS/TiO2。通过XRD、XPS、SEM、UV-Vis/DRS等手段对所合成纳米复合材料的组成、结构和形貌等进行了表征。结果表明,该系列CdS/TiO2为锐钛矿TiO2和六方相CdS的混合晶相,其在可见光有较强吸收,并且随着复合材料中TiO2比例的增加,BET值明显增大。另外,所合成CdS/TiO2呈圆球形,颗粒比较均匀。紫外光催化降解甲基橙的实验结果表明,摩尔比为1:4的CdS/TiO2的活性明显高于CdS、P25以及其它不     

溶胶-凝胶法制备纳米TiO2/丝素复合膜及结构性能研究

用溶胶凝胶法制备不同比例纳米TiO₂改性再生蚕丝丝素蛋白复合膜. UV和AFM测试结果表明, 该丝素膜中纳米TiO₂均匀分散在丝素中, TiO₂粒径约为80 nm; 同时该丝素膜的结构和热性能用FTIR, XRD, EDS, TGA和DTG进行表征. XRD测试结果表明, 随着纳米TiO₂的加入, 复合丝素膜的结晶结构从Silk I向Silk II转化, 但当纳米TiO₂的加入超过一定量时, 又破坏复合丝素膜的结晶结构; FTIR和EDS测试结果表明, TiO₂与丝素形成较好的键合; TGA和DTG测试表明复合丝素膜的热转变温度相比于纯丝素膜有所提高.     

黄色硫化镉纳米粒子的共振瑞利散射光谱研究

在高分子聚乙烯醇存在下 ,Cd2 + 与S2 - 反应生成黄色CdS纳米微粒。当CdS浓度小于 5× 1 0 - 4 mol L时 ,它在 4 70nm产生一个最强RRS峰 ,这是由低浓度较小粒径黄色CdS纳米微粒或黄色CdS分子与光源相互作用的结果 ;当CdS浓度大于 7.5× 1 0 - 4 mol L时 ,在 5 2 0nm产生一个最强的特征RRS峰。黄色CdS纳米微粒体系在可见光区无吸收峰。当CdS纳米微粒的浓度在 7.5× 1 0 - 4 ～ 2 .0× 1 0 - 3mol L范围内 ,所得纳米粒子的粒径为 4 3nm。实验表明 :光源发射强度分布和CdS纳米粒子的形成是产生其RRS光谱峰的主要原因     

Involvement of unusual noncovalent interactions in the self-assembly of cucurbit[6]uril with[CdCl4]2- anions

The [CdCl_4]~(2-) anion as a structure inducer has proved to be useful in the construction of cucurbit[n]urilmetal coordination architectures and materials. In order to better understand the role and influence of the structure inducer in Q[n] systems, we report herein the self-assembly of Q[6] solely in the presence of[CdCl_4]~(2-)anions and in the presence of both a linear cationic organic guest and [CdCl_4]~(2-)anions. X-ray diffraction analysis revealed that 1D Q[6] porous channels were formed by the noncovalent interactions between Q[6] and [CdCl_4]~(2-)anions, but the ‘‘honeycomb effect' was not observed in the present study.However, it seems that the ‘‘honeycomb effect' and the self-assembly of Q[6] with [CdCl_4]~(2-)anions can be significantly modified and switched in the presence of a linear cationic dibutylamine guest through some unusual noncovalent interactions.     

伯胺N1923从盐酸溶液中萃取镉(Ⅱ)的机理

伯胺N_(1923)从HCl介质中可以两种机理萃取Cd(Ⅱ),在微酸性溶液中以配位反应萃取Cd(Ⅱ)生成的化合物为(RNH_2)_3CdCl_2;而在酸性溶液中萃取机理为加合反应,萃合物的组成是(RNH_3~+)_3[CdCl_5~(3-)],并计算了两种反应的浓度平衡常数及热力学函数。     

丝素膜上药物渗透量对溶液PH值的响应

蚕丝丝素蛋白膜是一种具有弱碱性和弱酸性的两性荷电膜。因此在丝素膜－水溶液体系中，水溶液ｐＨ值变化会影响丝素膜上溶质的渗透速度和渗透量。丝素膜的等电点ｐＨ≈４．５。丝素膜上药物渗透实验的结果表明：在ｐＨ＝３．０～９．０的范围内，当溶液的ｐＨ＜４．５时，丝素膜带正电，正离子苄三甲氯化铵的渗透系数下降；当溶液的ｐＨ＞４．５时，丝素膜带负电，负离子酚磺酸钠的渗透系数明显下降。中性分子间苯二酚在丝素膜上的透过不受外部溶液ｐＨ值变化的影响。当溶液的ｐＨ＞８或ｐＨ＞４．５时，离子化的药物５－氟尿嘧啶或维生素Ｃ的渗透系数明显变小，这是因为两者分别在ｐＨ＝８（ｐＫａ＝８．０）和ｐＨ＝４．５（ｐＫａ＝４．２５）以上变成带电离子。这表明离子化药物在蚕丝丝素膜上的渗透速度和渗透量对溶液ｐＨ值变化有较好的响应特性。     

丝素蛋白膜上5-氟尿嘧啶的包埋及其释放

讨论了包埋在丝素膜中的５－氟脲嘧啶（５－ＦＵ）的固定状况,在不同ＰＨ值下测定了丝素５－ＦＵ复合膜中药物的释放,实验结果表明：５－ＦＵ均匀地被包埋在丝素膜中,即丝素膜可以作为５－ＦＵ载体,经过比涂层保护,丝素５－ＦＵ复合膜中的５－ＦＵ溶解释放速率变慢,释放时间延长;经涂层的 素５－ＦＵ复合膜在接近丝素蛋白等电点（ＰＨ＝４．５）时,５－ＦＵ在溶液中释放速度较慢,释放时间较长,表明用调节外部溶液ＰＨ值的     

丝素膜修饰电极pH电荷选择效应的研究

研究了丝素膜的带电特性,其等电点在pH4.5附近,利用丝系膜在等电点前后的两性荷电特性和电荷之间的静电作用,研制了丝素膜修饰石墨电极,多巴胺在膜中的表观扩散系数为2.65×10^-7cm^2/s,其电极反应异相电子转移速率常数为8.9×10^-6cm/s,电极用于神经递质类化合物体系的测定中,验证了此修饰电极的pH电荷选择效应。     

光谱法研究pH值对再生桑蚕丝素蛋白在水溶液中结构的影响

通过一系列光谱实验手段研究了再生桑蚕(Bombyx mori)丝素蛋白在水溶液中的构象转变情况. 由于丝素蛋白含有较多带电荷的氨基酸残基, 因此环境pH值对丝素蛋白的结构有着一定的影响: 酸性越强, 丝素蛋白越容易发生从无规线团到β-折叠结构转变; 相对而言, 碱性条件则更有利于丝素蛋白以无规线团结构稳定存在. 特别是当pH在4附近时, 丝素蛋白的无规结构最易发生改变; 而pH为6左右时, 丝素蛋白的结构则较为稳定. 这种变化趋势与沿着成熟蚕腺体中丝素蛋白所处的环境及其状态相当吻合, 由此表明pH值的调节是蚕在生物体中控制其丝素蛋白状态的一个相当重要的手段. 这一结果对人工纺制动物丝条件的调控有着极其重要的现实意义. 同时我们还发现, 在相当宽的pH范围内, 丝素蛋白的二级结构存在着中间体形态, 表明丝素蛋白的变性过程不符合简单的二态机制.     

丝素纳米颗粒的制备及应用于L-天冬酰胺酶的固定化

丝素蛋白纤维溶于高浓度中性盐溴化锂溶液或氯化钙-乙醇-水三元溶剂中, 经过透析和纯化可以制成3种液态丝素. SDS-PAGE分析结果表明, 其分子量分布范围明显不同. 应用能与水混溶的有机溶剂如丙酮等可将这种丝素制成丝素纳米颗粒, 用SEM观察到丝素纳米颗粒粒径分布范围为50~120 nm. 以戊二醛为交联剂, 将治疗急性淋巴性白血病常用酶制剂L-天冬酰胺酶共价结合在丝素纳米颗粒上. 酶活性分析结果表明, 由肽链断裂较少的丝素制备的纳米颗粒更适合于酶的生物结合. 酶动力学研究结果表明, 这种固定化酶活性回收率为44%, 热稳定性较游离酶有明显提高, 最适pH值范围加宽为6.0~8.0, 最适反应温度提高10 ℃; 抗胰蛋白酶水解能力明显增强. 结果表明, 丝素纳米颗粒与丝素蛋白膜一样, 是一种酶固定化的良好载体, 在药物缓释系统方面具有潜在的研究和开发价值.     

Silk fibroin solution properties related to assembly and structure

The impact of physiological factors on silk fibroin solution properties was studied. Specifically, the impact of fibroin concentration, protein purity, cation type and concentration, and pH on aqueous solution viscosity, shear behavior, and surface tension were assessed in the context of silk protein assembly. The results demonstrate that in vitro results could be correlated to in vivo processing events during silk spinning. Rheological properties with reference to the amphiphilic block structure of the protein are described, pH dependency of shear response was quantitatively correlated to the predicted pI values of the fibroin protein, and cooperativity among environmental factors such as pH and salts was identified. Stabilization of silk fibroin solution states by calcium was identified as a mode to control shear sensitivity of the fibroin solution. The cooperativities identified suggest tight control of fibroin aqueous solution rheological properties to gain a window of protection against premature crystallization of the fibroin during processing, assuring safe storage, transport, and finally successful fiber spinning.     

Charge-selective recognition at fibroin-modified electrodes for analytical application

A novel fibroin-modified electrode with charge recognition is reported. The characteristics of silk fibroin membranes have been exploited for analytical applications. The membrane, with an isoelectric point of pH 4.5, was applied to graphite and carbon-fiber electrodes. The modified electrode was negatively charged in solutions of pH>4.5, and so rejected anions and attracted cations. In solutions of pH<4.5 the electrode was positively charged, and so rejected cations and attracted anions. The pH-responsive charge recognition of the modified electrode was investigated for some neurocompounds. A fibroin carbon-fiber electrode was used for in-vivo determination of the concentration of the cationic neurotransmitter dopamine (DA).This revised version replaces the article published online on April 2005.     

pH值对丝素蛋白构象转变的影响

模仿家蚕吐丝过程中伴随丝素蛋白自然脱水的纤维化过程,研究了再生丝素蛋白在各种pH值的磷酸盐缓冲溶液体系中自然干燥脱水成膜后的构象转变.利用激光拉曼散射光谱及其二维相关光谱,定性分析了丝素蛋白酰胺区(1600～1700cm^-1)散射峰的相关组成及结构.在此基础上,利用¹³CCP-MAS固体核磁共振谱对丝素蛋白丙氨酸C_β峰(δ14.5～22)进行了解析拟合.从而确定了体系中与Silk及Silk构象相关的组成含量与pH值的关系.结果表明,pH=5.2的酸性溶液有利于蚕丝丝素蛋白从Silk向Silk构象转变,而中性与碱性溶液(pH=6.9和8.0)则对丝素蛋白的构象转变影响甚小.     

Entrapment of both glucose oxidase and peroxidase in regenerated silk fibroin membrane

Two enzmyes, glucose oxidase and peroxidase, were for the first time simultaneously immobilized in regenerated silk fibroin membrane. The structure and morphology of the regenerated silk fibroin membrane containing both glucose oxidase and peroxidase were investigated with IR spectra and SEM. The bienzymes do not change the structures of the regenerated silk fibroin in the membrane, which has an islands-sea structure. For the first time, an amperometric methylene green mediating sensor for glucose based on co-immobilization of both glucose oxidase and peroxidase in regenerated silk fibroin was constructed. Cyclic voltammetry and amperometry were used to test the suitability of methylene green shuttling electrons between peroxidase and the glassy carbon electrode. The bienzyme-based system offers fast response and high sensitivity of the sensor to glucose. The effects of pH, temperature, and the concentration of the mediator on the response current were evaluated, and the dependence of the Michaelis-Menten constant K(m)(app) on the concentration of the mediator was investigated.     

Entrapment of both glucose oxidase and peroxidase in regenerated silk fibroin membrane

Two enzmyes, glucose oxidase and peroxidase, were for the first time simultaneously immobilized in regenerated silk fibroin membrane. The structure and morphology of the regenerated silk fibroin membrane containing both glucose oxidase and peroxidase were investigated with IR spectra and SEM. The bienzymes do not change the structures of the regenerated silk fibroin in the membrane, which has an islands-sea structure. For the first time, an amperometric methylene green mediating sensor for glucose based on co-immobilization of both glucose oxidase and peroxidase in regenerated silk fibroin was constructed. Cyclic voltammetry and amperometry were used to test the suitability of methylene green shuttling electrons between peroxidase and the glassy carbon electrode. The bienzyme-based system offers fast response and high sensitivity of the sensor to glucose. The effects of pH, temperature, and the concentration of the mediator on the response current were evaluated, and the dependence of the Michaelis-Menten constant K_m^app on the concentration of the mediator was investigated.