Study on the anodic reaction of Ni in an alkaline solution by transient pH detection based on scanning electrochemical microscopy (SECM)

The anodic reaction of Ni in an alkaline solution was studied by the tip–substrate voltammetry mode of scanning electrochemical microscopy (SECM) and cyclic voltammetry (CV). A platinum microdisc electrode was selected as the tip electrode, which functioned as a pH sensor with transient response capability. The pH value of the solution near the Ni electrode surface varied while the Ni substrate oxidation reaction occurred, and the pH variation could be detected by the tip faradic current. The cyclic voltammogram results showed that two types of hydroxides: i.e. α‐Ni(OH)₂ and β‐Ni(OH)₂ were formed during Ni oxidation in the lower potential region. In the proceedings of α‐Ni(OH)₂ → γ‐NiOOH and β‐Ni(OH)₂ → β‐NiOOH, the process of OH^? concentration decrease in the solution was ahead and behind of electron transfer in the solid phase, respectively. These results indicate that the OH^? adsorption process occurs as an elementary step in the former reaction and the H⁺ diffusion process from the inner to the outer layer of the solid phase occurs as a subsequent step in the latter reaction. The results also revealed that the oxide film on the Ni surface has a two‐layer structure. The real potential of the oxygen evolution reaction (OER) on the Ni surface with different cycles is also analyzed in the paper. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and characterization of Cu,Ni and Zn binding capability of some amino- and imidazole hydroxamic acids: Effects of substitution of side chain amino-N for imidazole-N or hydroxamic-N-H for -N-CH3 on metal complexation

Solution equilibrium studies on Cu(II)-, Ni(II)- and Zn(II)-N-Me-β-Alaninehydroxamic acid (N-Me-β-Alaha), -N-Me-α-alaninehydroxamic acid (N-Me-α-Alaha), -Imidazole-4-carbohydroxamic acid (Im-4-Cha), -N-Me-imidazole-4-carbohydroxamic acid (N-Me-Im-4-Cha) and -Imidazole-4-acetohydroxamic acid (Im-4-Aha) systems have been performed by pH-potentiometry, UV–Vis spectrophotometry, EPR, CD, ESI-MS and ¹H NMR methods. According to the results: (i) the amino-N atoms are more basic in N-Me-α-Alaha and N-Me-β-Alaha than the hydroxamate function, but the trend is just the opposite between the imidazole-N(3) and hydroxamate. (ii) The metal ion anchor is always the hydroxamate part in the amino acid derivatives, while it is always the imidazole-N(3) in the studied imidazolehydroxamic acids. (iii) The three studied N-Me derivatives do not form metallacrowns. Only hydroxamate type chelate is formed with N-Me-β-Alaha, but with N-Me-α-Alaha a new type of coordination mode (via amino-N and hydroxamate-O) also exists. N-Me-Im-4-Cha also forms a dinuclear complex, [M₂L₃], with Cu(II) and Ni(II) (but not with Zn(II)). In this complex, one of the three ligands might bridge the two metal ions (five-membered hydroxamate-(O,O) plus five-membered (N_im, O_carb) bridging bis-chelating mode), while each of the additional two ligands binds to one metal. (iv) The two studied N–H derivatives, having dissociable proton on the hydroxamic-N, are able to form metallacrown species. A pentanuclear complex, [M₅L₄H₋₄], is exclusively formed above pH 4 between Cu(II) and Im-4-Aha. Interestingly, this 12-metallacrown-4 type complex, although together with various mononuclear binding isomers, appears also with Ni(II) and Zn(II). Unfortunately, the complexes of Im-4-Cha are not soluble in water at physiological pH at all.     

5-[2-(对苯偶氮苯氧基)丁氧基]苯基-10,15,20-三[(对甲氧基苯基)]卟啉及其金属配合物的合成

以5-[2-(4-溴丁氧基)苯基]-10,15,20-三(对甲氧基苯基)卟啉和对羟基偶氮苯为原料,经取代反应合成新化合物5-[2-(对苯偶氮苯氧基)丁氧基]苯基-10,15,20-三[(对甲氧基苯基)]卟啉(2),2经配位反应合成了金属铜,锌配合物(2a)和(2b),其结构经UV-Vis,1H NMR,IR和元素分析表征。     

ICP–AES法测定铬镍不锈钢中锰、铬、镍、硅、磷、铜、钼的含量

建立电感耦合等离子体原子发射光谱(ICP–AES)法测定铬镍不锈钢中锰、铬、镍、硅、磷、铜、钼7种元素含量的方法。试样用盐酸与硝酸混合酸溶液溶解,采用溶解国家标准样品的方法制备校准曲线溶液,确定了元素最佳分析谱线。各元素的含量在其测试范围内与原子发射强度呈良好的线性关系,线性相关系数不小于0.999,7种元素的检出限在0.000 3%~0.003 0%之间。该方法应用于铬镍不锈钢标准样品的测定,测定值与认定值相符,测定值的相对标准偏差在0.12%~1.15%之间(n=8)。应用于铬镍不锈钢样品测定时,加标回收率在90%~110%之间。该方法操作简便、迅速,可满足日常铬镍不锈钢中多元素含量的检测需要。     

聚吡咯/尼龙6纳米纤维膜对Pb2+固相萃取的吸附效能研究

以电纺尼龙6纳米纤维膜为基底,原位氧化聚合制得聚吡咯/尼龙6纳米纤维膜(PPy/Nylon 6-NFsM).通过静态和动态吸附实验考察PPy/Nylon 6-NFsM对Pb2+的吸附行为,探究其作为固相萃取介质富集水中痕量Pb2+的可行性.结果表明:298 K,pH=10时,PPy/Nylon 6-NFsM对Pb2+的静态饱和吸附量达542 mg/g;吸附动力学和吸附等温线分别符合准二级动力学模型和Freundlich模型;优化了PPy/Nylon 6-NF-sM的固相萃取条件,采用火焰原子吸收光谱法检测实际水样中的Pb2+,检出限为1.2 μg/L(信噪比为3计),10 μg/L加标水平加标回收率为95.3％ ～ 100.4％,相对标准偏差(RSD)为1.6％(n=3),可实现实际水样中痕量Pb2+的准确、灵敏的检测.     

Co~Ⅱ(salen~*)存在下的氯丁二烯自由基聚合

研究了N,N'-双(3,5-二叔丁基水杨醛)-1,2-环己二胺钴(Ⅱ)[Co~Ⅱ(salen~*)]存在下氯丁二烯(CP)的自由基聚合,考察了不同溶剂、引发剂用量及配体对聚合反应的影响.结果表明,随着引发剂用量的增加,聚合反应的诱导期缩短,以[ABVN]0/[Co~Ⅱ(salen~*)]0=3/1配比投料,聚合反应表现出较好的可控聚合特征.在苯、甲苯、四氢呋喃(THF)和乙酸乙酯(EA)4种溶剂中按照[CP]_0/[Co~Ⅱ(salen~*)]0/[ABVN]0=400/1/3的配比投料,在苯中的可控聚合程度最好:在低转化率(40%以下)实测聚合物分子量(Mn,GPC)与理论值(Mn,th)吻合,且分子量随转化率增加呈线性增长.研究了THF、三乙胺(NEt3)、吡啶(Py)及水等不同配体对聚合反应的影响,发现在添加THF时,低转化率(40%以下)下Mn,GPC与Mn,th相符,分子量分布(PDI)相对较窄.     

Assessment of silver(I) complexes of salicylaldehyde derivatives—histidine Schiff base as novel α-glucosidase inhibitors

In this study, a novel class of histidine Schiff base silver (I) complexes derived from salicylaldehyde, 1a-9a, was found to be an effective inhibitor of α-glucosidase. The results of this study showed that the newly synthesized complexes inhibited α-glucosidase through noncompetitive mechanisms; the IC₅₀ values were ranging from 0.00431 μmol L^-1 to 0.492 μmol L^-1. The structure-activity relationship was established as well. These results demonstrated that compound 7a, 5-nitro salicylaldehyde Schiff base silver complex, is the most promising α-glucosidase inhibitor with the lowest IC₅₀ value, which could be exploited as a drug candidate to alleviate postprandial hyperglycemia in the treatment of type Ⅱ diabetes mellitus. This research provided a catalyst-free, simple, and environmentally benign reaction to synthesize compounds using mechanochemistry.     

Properties and Extraction for [Ni(NH3)6]2+ of ATPS-a Formed by Aqueous Cationic–Anionic Surfactant Mixtures

The properties and extraction for [Ni(NH₃)₆]²⁺ of anionic aqueous two-phase systems (ATPS-a) that formed in mixtures of cetyltrimethylammonium bromide (CTAB) and excess sodium dodecyl sulfate (SDS) aqueous solutions were investigated. The results showed that the properties and extraction effects were strongly affected by the surfactant concentration, the temperature of system, and the mole fraction of surfactants. The increase of temperature induces narrower phase region and larger phase volume ratio. In addition, [Ni(NH₃)₆]²⁺ was extracted into the surfactant-rich phase with higher distribution coefficient when the liquid crystal had the birefringent properties. Moreover, the distribution coefficient can be improved through reducing the concentration of surfactant from 0.15 to 0.05 mol · L^?1 or increasing mole fraction of CTAB from 21.9% to 23.1%. The results showed that ATPS of cationic–anionic surfactants was efficient for [Ni(NH₃)₆]²⁺ extraction with distribution coefficients of 13.5 when the total surfactant concentration was 0.05 mol · L^?1, mole fraction of CTAB was 21%, and temperature was 34°C.     

铈镧比对CexNi0.5La0.5-xO系催化剂甘油氧化蒸汽重整制氢性能的影响

利用共沉淀法制备了CeO₂和La₂O₃复合载体的Ce_xNi_0.5La_0.5-xOO(CeNiLaO)系催化剂,在固定床反应器中考察其甘油氧化蒸汽重整制氢(OSRG)性能,并采用X射线衍射(XRD)、程序升温还原(H₂-TPR)、激光拉曼光谱(Raman)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等手段对催化剂进行表征分析。结果表明：La₂O₃能够有效地分散Ni颗粒,减弱Ni颗粒在反应过程中的烧结,CeO₂提供的晶格氧能够消除催化剂表面的积碳,同时La会部分进入Ce的晶格取代部分Ce⁴⁺造成晶格畸变,提高表面的氧空穴数。La₂O₃和CeO₂的共同作用有利于减弱Ni因为烧结和积碳引起的失活。在不同Ce/La摩尔比的催化剂中,Ce_0.4Ni_0.5La_0.1O表现出最好的催化活性,并且该催化剂在长达210 h的稳定性测试中,甘油的转化率都在95%以上,气相产物中的氢气浓度达50%。     

Adsorption of Nin (n=1 -4) clusters on perfect and O-defective CuAl2O4 surfaces: A DFT study

The adsorption energies for single Ni atom on CuAl₂O₄(100) and (110) surfaces are 5.30 and 4.08 eV, respectively. The growth and aggregation of Ni can be effectively inhibited on the perfect CuAl₂O₄(100) surface. The adsorption of Ni on the spinel surface is accompanied by charge transfer. The interaction of Ni with CuAl₂O₄ surface is stronger than with the γ-Al₂O₃(110) surface.