Effect of pH on the Hydrothermal Synthesis of BN Nanocrystals

Boron nitride (BN) has been synthesized using hydrothermal synthesis method. The experimental results showed that the pH value of the reaction solution has an important effect on the yield and phases of BN samples. As the pH value decreased, the content of cBN increased and the yield improved. The increase in cBN content is resulted from the conversion of oBN into cBN under hydrothermal condition, and the growth of cBN nanocrystals may due to the decrease in the reaction speed, thus the crystalline perfection of BN improved when the pH value decreased.     

Study on the Formation of Urea or Salt Induced Vesicles in Built-system Surfactant

The spontaneous formation of vesicles in the aqueous of cationic surfactant phosphate (PTA) and anionic surfactant sodium dodecyl sulfate (SDS) at certain mixing ratios have obtained^1. The addition of urea or Nal will expand the range of spontaneous vesicle formation. The fact is demonstrated by negative-staining transmission electron microscope(TEM) and dynamic light scattering(DLS) methods. The phenomenon especially in the part of urea is reported by us at first. Mechanism of urea/Nal-induced vesicles formation is discussed from the viewpoint of the molecular geometry packing parameter f, conformation and interaction.     

Chromatographic Characterization of Molecularly Imprinted Microspheres Synthesized by Aqueous Microsuspension Polymerization：Influences of pH,Kinds and Concentration of Buffer on Capacity Factors

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｍｏｌｅｃｕｌａｒｌｙｉｍｐｒｉｎｔｅｄｐｏｌｙｍｅｒｓ (ＭＩＰｓ)ｃａｎａｆ ｆｏｒｄｓｐｅｃｉｆｉｃｒｅｃｏｇｎｉｔｉｏｎｏｆｉｍｐｒｉｎｔｍｏｌｅｃｕｌｅｓａｎｄｍｏｄｅｒ ａｔｅｒｅｃｏｇｎｉｔｉｏｎｏｆｔｈｅｓｔｒｕｃｔｕｒａｌｌｙｒｅｌａｔｅｄｃｏｍｐｏｕｎｄｓ .Ｔｈｅｙｃａｎｂｅｕｓｅｄａｓａｎａｔｔｒａｃｔｉｖｅａｌｔｅｒｎａｔｉｖｅｏｒｃｏｍｐｌｅ ｍｅｎｔｔｏｎａｔｕｒａｌａｎｔｉｂｏｄｉｅｓａｎｄｒｅｃｅｐｔｏｒｓ .1 5ＭＩＰｓｈａｖｅｓｏｍｅａｄ…     

Effect of pH on the Rheology of Al-Mg Mixed Metal Hydroxide——Montmorilonite Aqueous Suspension

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The Effect of Solution pH Value on the Morphology of Ceria–Yttria Co Stabilized Zirconia Particles Prepared Using the Polymerizable Complex Method

Ceria–yttria co stabilized zirconia (CYSZ) was synthesized from solutions through the polymerizable complex method. The only difference in the preparation of the CYSZ samples was the pH of the starting solution, which was set at 1, 7 and 12, respectively. Transmission electron microscopy and scanning electron microscopy analysis revealed that the sample with the pH value of 1 had good homogeneity, low agglomeration, and a quasi-spherical shape with the particle size of 41 nm, while by increasing the pH up to 7 and 12, the particles became more disordered and no more in the range of nano sized materials (≤100 nm). Fourier transform infrared spectroscopy was employed to evaluate the bonding characteristics of the obtained gels at different pH values. thermogravimetric analysis, together with differential thermal analysis, was used to study the differences in the properties of dried gels with temperature. Crystallographic structure of the final product was also studied using X-ray diffraction.     

Effect of pH on the Rheology of A1-Mg M iteed Meta1 Hydroxide——Montmorillonite Aqueous Suspension

The effects of the pHs of Mtsuspension(pH_Mt),AMH sol(pH_A)and mixedsuspension(pH_mix)on the rheology of mixed su sp en sion w ere studied.The mixed suspension consisted of the alum in ium magnesium mixed metal hydroxide(AM H) colloidal prt icles which possessed permanent positive charges and the Na-montmorillon ite(M t)particles which po ssessed permanent nega tive charges.The results showed that the pHs did not affect the Bingham yield poin t(YP)of the mixed suspen sionsin the various pHs(i.e.,pH_Mt,pH_A and pH_mix)range of 8—10 almost. When the pH values were above 10 the YPs increased ma rked ly w ith increa sing pH_Mt and pH_mix,but decreased sharply with increasing pH_A.The mechanisms of the effect of pH on the rheology of mixed suspensions were also investigated.     

Studies of Self-assembled Monolayers Formed by Imidazoline on Iron Surface by SEM and SECM

Self-assembled monolayers (SAMs) formed from organic substances can improve the inhibition of metal corrosion, because uniform and closely packed films formed on the metal surface providing an insulating layer1, 2. SAMs on the iron surface are studied so far because iron is one active metal which is easily corroded in the air. In this paper, SECM and SEM have successfully been applied in the study of SAMs inhibition corrosion for iron. SECM has been used to study the electrochemically a…     

紫精硫醇自组膜与烷基硫醇自交换的电化学研究

近年发展起来的自组膜（SAM）［‘］，是组织有序、定向、密集、完好的单分子层，在分子水平上达到控制电极界面微结构的要求．特别是含电活性基团的硫酸自组膜，为电化学研究提供了一个重要的实验体系，借此可探测电极表面上分子微结构和宏观电化学响应之间的关系．文献中报导     

新型偶氮苯硫醇衍生物自组装膜的制备与结构表征

Self Assembled Monolayers(SAMs) of a series of mercapto contained azobenzene derivatives with the structure of CnH2n+1AzoO(CH 2)mSH (where n =4,6,8,10,12; with m =3,5 respectively) were prepared and characterized. Wettability measurement of water on the SAMs demonstrates that molecular packing density in the monolayers increases while the alkyl chain in the molecules is lengthened. Both the n and m values have similar contribution to the wetting property of SAMs. The RA IR spectra reveal that the alkyl chains in the SAMs tilt away dramatically from the surface normal direction with the increase in their length. However, the orientation of azobenzene moiety is found to be influenced slightly by the alkyl chain length, which is due to the tenderness of the molecule.     

溶剂对自组装单分子膜电化学行为的影响

用循环伏安法、交流阻抗分析和STM研究了溶剂对自组装单分子膜电化学行为的影响.讨论了以丙酮、二甲基亚砜、乙醇、二甲基甲酰胺和水为溶剂制备的4-羟基-6-甲基-2-巯基嘧啶(HMMP)自组装单分子膜对抗坏血酸(AA)、多巴胺(DA)的电化学行为.结果表明,不同溶剂下制备的单分子膜对AA和DA的催化氧化表现出截然不同的行为;交流阻抗分析定量得出HMMP(丙酮)/Au电极与HMMP(二甲基亚砜)/Au电极的交换电流密度分别为1.14μA/cm²和2.04μA/cm²,电极表面覆盖度分别为93.2%和96.2%,STM图象显示出以丙酮和二甲基亚砜为溶剂制备的单分子膜具有不同的致密性和有序性.     

分子动力学模拟多巴在自组装膜上的黏附性

为了更好地理解贻贝在表面的黏附机理,实现水下胶黏,采用分子动力学方法研究了多巴在自组装膜上的黏附性:采用伞形取样和加权柱状图分析方法计算了多巴在不同自组装膜表面的黏附自由能,使用拉伸分子动力学模拟研究了多巴在不同自组装膜表面上黏附后的脱附力.结果表明,多巴在带负电的羧基自组装膜上的黏附能比在带正电的氨基自组装膜上的大,多巴更容易黏附到带负电表面;多巴在带电表面的黏附能比未带电表面的黏附能更强,表明在带电表面黏附更稳定.进一步分析了多巴在不同表面的取向分布,发现多巴与不同表面相互作用的方式不同:与疏水表面主要通过苯环相互作用;与亲水表面主要通过羟基相互作用;与负电表面主要通过氨基相互作用;与正电表面主要通过羧基相互作用.通过模拟比较了多巴在不同自组装膜上的脱附力,发现多巴在带电表面的脱附力比在未带电表面的大,与黏附能的趋势一致.对比4种非带电表面的脱附力,发现多巴在疏水性甲基自组装膜表面的脱附力最大,黏附更稳定,随着表面疏水性的增加,脱附力增大,黏附稳定性增强.本工作可为研发新型水下胶黏剂提供理论指导.     

基于纳米金自组装膜固定辣根过氧化物酶的生物传感研究

将辣根过氧化物酶(HRP)通过纳米技术和自组装技术固定于电极表面,制得了酶修饰电极.纳米金与HRP形成了静电复合物并高效地保持了HRP的生物活性,以对苯二酚作为电子媒介体,差示脉冲伏安法(DPV)研究生物酶电极测定H2O2的线性范围为5.0×10-6～1.0×10-3 mol/L,检测限为2.5×10-6 mol/L,线性方程为△I=0.34765+4.05553CH2O2(mM).酶电极的表观米氏常数(K(app))为0.0675 mmol/L.实验同时证明该生物酶电极具有良好的稳定性和使用寿命.     

偶氮苯自组装单分子膜中长程电子转移机理

利用自组装技术在金电极表面构造了具有不同前端健长度偶氮苯功能化的单分子膜体系：Au／S（CH2）nNHCO-N＝N-OCH2CH3（n＝2，3，4，6）．研究结果表明，仍氮苯到金电极的表现电子转移速率随它们之间的距离长度的增加而呈指数性的下降趋势．基于Marcus电子隧穿理论，得到了此自组装膜体系的长程电子隧穿系数ρ＝（1．35±0．2）／CH2在和可逆电活性分子自组装膜体系及理论计算相比较的基础上，从偶氮苯分子自组装膜结构与电子转移过程的关系角度对这一结果进行了分析和说明．     

环境标准中pH值限值的合理性探讨

鉴于在不同的温度下水(或溶液)的pH值会有所不同,对环境标准中不规定pH值限值的温度条件是否合理进行了论证。通过分析各环境标准的特点、各环境标准中pH值参数的控制目的,结合各环境标准指定的监测方法的技术内容,得出以下结论:《海水水质标准》、《地表水环境质量标准》、《污水综合排放标准》和《土壤环境质量标准》中pH值限值不规定温度条件是合理、可操作的;《危险废物鉴别标准腐蚀性鉴别》pH值限值应该规定温度条件;对于《地下水质量标准》,有待于进一步实验验证温度对pH值的影响程度。     

席夫碱自组装单分子膜的电化学行为

利用自组装技术将席夫碱硫醇衍生物在金表面形成自组装单分子膜,并初步研究了此自组装单分子膜的电化学行为,发现该席夫碱分子在0.1 mol•L－1的KCl溶液中具有电化学不可逆氧化还原行为，且随着自组装时间的增加表观电极反应速率常数值显著减小,最后减小为0,并对此进行了解释.