不同环境下聚合物表面酸碱性的变化

应用测接触角并辅以XPS分析,研究了一种共聚物(MMA-Co-4Vp)在各种表面成型条件下及介质环境中的表面酸碱性变化,探索了其变化规律及导致变化的原因。     

DrugFET的研究（Ⅳ）.硅钨酸—麻黄碱FET的研制与应用

将离子敏感场效应晶体管与药物敏感膜相结合研制成一种对盐酸麻黄碱有良好响应的药物敏感场效应晶体管传感器。     

纸张保存的化学

讨论了纸张保存过程中的某些化学问题,对纸张的酸性、酸性来源和纤维系酸催化水解以及影响纸张变质的其它因素进行了分析,评述了近年来在纸张脱酸、脱色和利用新的浆内施胶剂等方面研究取得的一些成果。     

ZSM-5分子筛酸位分布及其甲醇制烯烃催化性能的定向管理与调控

ZSM-5分子筛在甲醇制烯烃(MTO)过程中的催化性能和反应机理与其孔道中酸位点分布位置紧密相关. 本文证明在水热合成过程中加入适量的钠离子(Na⁺)可以增加ZSM-5分子筛交叉腔酸位点比例; 从而促进高级甲基苯的生成并加速芳烃循环, 有利于乙烯生成. 相反, 在合成过程中不添加钠离子, 所制备的ZSM-5分子筛直孔道和正弦孔道酸位点比例明显提高, 有利于促进烯烃循环并提高丙烯和C₃₊烯烃选择性.     

基于混酸回流制备碳点的中和过程

Carbon dots (C dots) are relatively novel carbon nanomaterials that have attracted significant interest due to their unique photoluminescence, good biocompatibility, and stability. The preparation methods of C dots was usually summarized into "top-down" and "bottom-up", and mixed acid reflux is a top-down strategy that can be used to synthesize C dots, during which neutralization is a necessary step that can significantly influence the properties and potential applications of the final product. Previously, this research area mainly focused on tuning the properties of C dots by changing the starting materials and/or varying the reaction conditions; the influence of the reagents used during neutralization has been largely ignored. As the previously reported C dots prepared by mixed acid reflux were obtained from different starting materials under varied conditions, a meaningful comparison is difficult. Herein, yellow-emitting C dots were prepared by mixed acid-refluxing a carbon-rich material derived from fullerene carbon soot. For the same batch of as-prepared C dots, the influences of four reagents, i.e., NaOH, Na₂CO₃, K₂CO₃, and NH₃·H₂O, during neutralization on the structures and photoluminescence of the resulting C dots were investigated in detail. The results of thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy clearly showed that the reagent used during neutralization can affect the degree of dissociation of the acidic functional groups on the C dots. This is further supported by examination of the C dot/surfactant mixtures where subtle changes in the phase behavior were observed. Structural changes of the C dots cause variations in their surface states, ultimately altering the optical characteristics, including UV-vis absorption and fluorescence. Among the treated C dots, the sample prepared with Na₂CO₃ showed the strongest emission under the same excitation wavelength, while that prepared with NH₃·H₂O exhibited a distinct red shift (~8 nm) in the emission curve. The results presented herein provide clear evidence that neutralization reagent selection is important for optimizing the properties of the resulting C dots obtained by mixed acid reflux. In addition, the photoluminescence of the C dots can be influenced by their counterions, providing a novel method for tuning the properties of C dots while explaining their behavior in saline solutions. In short, the basicity of the neutralizing reagent and the type of counterions affect the structure of the C dots surface, which brings different performances. This work reminds researchers that it is necessary to use the type of neutralizing reagent as an experimental condition when preparing C dots in the future.     

Synergistic effect of dealumination and ceria impregnation to the catalytic properties of MOR zeolite

MOR zeolite has been extensively employed as a catalyst in industries. However, high Brønsted acidity in MOR leads to rapid deactivation due to coke deposition on the pore mouths; thus, the surface acidity of MOR needs to be moderated. Herein, we report a modification of MOR chemical composition via acid treatment and deposition of ceria nanoparticles using a wet impregnation method. The acid treatment successfully increases the Si/Al ratio of MOR from 8.39 to 11.58 and reduces the total acid site concentration of MOR from 990 μmol/g to 752 μmol/g. The acidity of MOR is decreased when the Si/Al ratio is increased since the quantity of Brønsted acid sites is proportional to the number of Al framework. In addition, the acid treatment also improves the external surface area of MOR. Furthermore, ceria particles were successfully deposited on the MOR surface using wet impregnation method. The ceria content of parent MOR sample is lower compared to that of preceded by the acid treatment, which may be attributed to the formation of more terminal silanol groups. Finally, catalytic test on Friedel–Crafts alkylation of toluene with benzyl alcohol shows that the synergy between dealumination and the impregnation of ceria significantly improves the activity of MOR zeolite.     

对电极材料对非贵金属电催化剂耐久性评价的影响

质子交换膜燃料电池(PEMFCs)环境友好,具有高的能量转换效率,已受到了广泛的关注.目前,铂基电催化剂广泛使用在 PEMFCs中,但铂的储量有限,活性低,耐久性差,成本高,急需开发高性能的非贵金属电催化剂替代铂基电催化剂.非贵金属电催化剂的电化学表征基本上都沿用了铂基电催化剂的评价体系和方法,不一定适用于非贵金属电催化剂的表征.
　　本文选用铂和石墨为对电极考察其对非贵金属电催化剂在酸性电解质中耐久性测试的影响.当使用铂对电极时,商业 Pt/C电催化剂的氧还原(ORR)活性随着耐久性测试圈数的增加而降低,而非贵金属电催化剂的氧还原活性在耐久性测试过程中的变化规律与商业 Pt/C不同,呈现先降低,后升高的规律.耐久性测试前后的透射电镜(TEM)分析表明非贵金属电催化剂经过耐久性测试后,在电催化剂表面生长了铂纳米颗粒.高分辨透射电镜(HRTEM)和能量色散 X射线光谱(EDX)进一步证明以铂为对电极的三电极体系,在进行非贵金属电催化剂耐久性测试的过程中,非贵金属电催化剂表面生长了铂纳米颗粒,使得非贵金属电催化剂的 ORR活性在耐久性测试后得到显著提高.耐久性测试前后,非贵金属电催化剂氧还原过程的电子转移数由3.7变为4.0,再次证明了耐久性测试过程中铂颗粒的生成.在三电极电化学体系中,当工作电极发生阴极反应时,对电极为阳极反应,反之亦然,即在工作电极上发生的任何电化学过程,都会在对电极上完成相反的电化学过程.在循环电位扫描过程中,当铂对电极的电压高于1.0 V (vs RHE)时,开始发生铂的溶解现象,并且当电压高于1.2 V (vs RHE)时,铂的溶解量会急剧增加,部分溶解的铂会扩散到工作电极附近,并在工作电极的非贵金属电催化剂表面发生沉积作用.随着扫描圈数的增加,沉积的铂纳米颗粒的数量增加,颗粒变大,从而使非贵金属电催化剂的表观 ORR活性显著提高.该现象使得非贵金属电催化剂在酸性电解质中无法表现出其真实的耐久性.当选用石墨棒为对电极材料时,非贵金属电催化剂在酸性电解质中的 ORR活性不会受到对电极材料的影响.
　　通过考察对电极材料对非贵金属电催化剂在酸性电解质中耐久性能的影响,可以得出结论,即对非贵金属电催化剂在酸性电解质中的耐久性测试中,不宜使用铂对电极,应该使用石墨为对电极材料,以防止对电极材料干扰耐久性测试.     

Estimation of acidity constants,ionic mobilities and charges of antimicrobial peptides by capillary electrophoresis

Capillary electrophoresis (CE) was employed for the determination of thermodynamic acidity constants (pK_a) and actual ionic mobilities of polycationic antimicrobial peptides (AMPs). The effective electrophoretic mobilities of AMPs were measured by CE in a series of the background electrolytes within a wide pH range (2.00–12.25), at constant ionic strength (25 mM) and ambient temperature, using polybrene coated fused silica capillaries to suppress sorption of cationic AMPs to the capillary wall. Eventually, Haarhoff–Van der Linde peak fitting function was used for the determination of correct migration times of some AMPs peaks that were distorted by electromigration dispersion. The measured effective mobilities were corrected to 25°C. Mixed acidity constants, , and actual ionic mobilities, m_i, of AMPs were determined by the nonlinear regression analysis of pH dependence of their effective mobilities. The values were recalculated to thermodynamic pK_as using the Debye–Hückel theory. Thermodynamic pK_a of imidazolium group of histidine residues was found to be in the range 3.72–4.98, pK_a of α‐NH₃⁺ group was in the range 6.14–6.93, and pK_a of ε‐NH₃⁺ group of lysine spanned the interval 7.26–9.84, depending on the particular amino acid sequence of the AMPs. Actual ionic mobilities of AMPs with positive charges from one to six elementary units achieved values (9.8 – 36.5) × 10^?9 m²V^?1s^?1.     

酸水解-离子色谱法测定精四氯化钛中三氯乙酰氯

建立了酸水解-离子色谱法测定精四氯化钛中痕量三氯乙酰氯(CCl3COCl)的方法.四氯化钛样品与2 mol/L HCl按体积比1∶4水解平衡后,采用氢氧化物共沉淀法去除溶液中Ti4+,V5+和Fe3+等金属离子,用Ag2O沉淀法降低水解溶液中Cl-浓度,水解溶液通过H型阳离子交换柱和水系滤膜,离子色谱法测定溶液中三氯乙酸(TCAA),据TCAA与CCl3COCl摩尔量守恒计算样品中CCl3COCl含量.结果表明,共沉淀溶液pH值在9.0～10.0范围内,可将目标金属离子基本去除完全;加入Ag2O降低溶液Cl-浓度后,溶液中Cl-,NO3-和SO42-的浓度对水解溶液中TCAA的色谱法峰无影响.本方法对精四氯化钛样品中CCl3COCl的定量限为1.20 μg/g,低于俄罗斯精四氯化钛中CCl3COCl允许限值(5μg/g);方法加标回收率在84.1％ ～87.3％之间,共沉淀时溶液pH值的轻微变化对回收率无明显影响,分析结果稳定可靠;方法用于5个平行样品中CCl3COCl含量测定(45.6,37.9,40.8,38.9和43.5 μg/g),相对标准偏差7.7％,方法精密度较好.方法满足精四氯化钛中CCl3COCl质量控制要求.     

Mn(Ⅱ)/Mn(Ⅲ)电对在硫酸溶液中氧化还原行为

采用循环伏安法对Mn(Ⅱ)/Mn(Ⅲ)电对在硫酸溶液中铂电极上的氧化还原与Mn(Ⅱ)浓度、酸浓度、扫描速率、温度以及对流因素的函数关系进行了研究.结果发现,Mn(Ⅱ)在铂电极上Mn(Ⅱ)的氧化及Mn(Ⅲ)的还原均受扩散控制；升高温度和磁搅拌均能增加Mn(Ⅱ)氧化为Mn(Ⅲ)的速率；增加酸浓度和Mn(Ⅱ)浓度有利于增加Mn(Ⅲ)的稳定性,减少Mn(Ⅲ)的歧化和水解.