NH3R++NHR2(R=H,CH3)体系质子传递反应的从头算研究

用从头计算法在HF/6-31G^*基组水平上研究了NH₄⁺+NH₃→NH₃+NH₄⁺,NH₄⁺+NH₂CH₃→NH₃+NH₃CH₃⁺,NH₄⁺+NH(CH₃)₂→NH₃+NH₂(CH₃)₂⁺以及NH₃CH₃⁺+NH₂CH₃→NH₂CH₃+NH₃CH₃⁺等4个体系的质子传递反应的机理.结果表明:(1)上述质子传递反应均具有双阱型的势能面,质子沿N(1)、N(2)连线直接传递;(2)质子受体分子中的甲基对质子传递起促进作用,而质子给体离子中的甲基则阻碍质子的传递。     

拉曼光谱法研究Na+, Mg2+//SO42-, Cl-, H2O四元体系中SO42-离子缔合结构特征及其变化规律

复杂水盐体系存在稳态和介稳固液相平衡以及复杂的成盐规律。为了解固液平衡状态下液相的结构特征,本文采用拉曼光谱技术并结合高斯-洛伦兹去卷积分峰拟合程序对Na⁺, Mg²⁺//SO₄^2-, Cl^-, H₂O四元体系及其二元和三元子体系中ν₁-SO₄^2-的离子缔合结构特征进行了分析。研究结果表明:SO₄^2-在Na₂SO₄-H₂O体系存在自由态SO₄^2-和SO₄^2-离子簇两种结构,在MgSO₄-H₂O, MgSO₄-MgCl₂-H₂O及Na⁺, Mg²⁺//SO₄^2-, Cl^-, H₂O等含镁体系中,还有Mg²⁺-H₂O-SO₄^2-和Mg²⁺-OSO₃^2-两种缔合结构。在二元和三元体系中ν₁-SO₄^2-的离子缔合结构以自由态SO₄^2-为主,随着SO₄^2-离子总浓度的变化,上述四种结构所占比例会发生规律性变化。Na⁺, Mg²⁺//SO₄^2-, Cl^-, H₂O四元体系在NaCl减少及等温蒸发过程中,自由态SO₄^2-结构比例逐步降低, Mg²⁺和SO₄^2-相结合形成Mg²⁺-H₂O-SO₄^2-或Mg²⁺-OSO₃^2-结构的机会增多,在复盐区还会形成SO₄^2-离子簇结构。由此判断溶液结构的适应性变化是导致介稳现象的重要原因。进一步的相关分析表明:SO₄^2-的浓度和耶涅克指数J与ν₁-SO₄^2-峰的峰强度和峰面积存在正相关关系, Mg²⁺浓度是影响ν₁-SO₄^2-峰中四种缔合结构的比例发生变化的主要因素。     

(Na+、K+、Mg2+),(Cl-、SO42-),H2O五元系统介稳平衡的研究

本文报道(Na⁺、K⁺、Mg²⁺),(Cl^-、SO₄^2-),H₂O五元系统介稳平衡实验的数据。并作出25℃的(Na⁺、K⁺、Mg²⁺),(Cl^-、SO₄^2-),H₂O五元介稳平衡相图。包括八个均为氯化钠所饱和的结晶区域即:氯化钾、钾钠芒硝(3K₂SO₄·MgSO₄)、软钾镁矾(MgSO₄·K₂SO₄·6H₂O)、硫酸钠、白钠镁矾(MgSO₄·Na₂SO₄·4H₂O)、七水硫酸镁、光卤石和水氯镁石(MgCl₂·6H₂O)。(Na⁺、K⁺、Mg²⁺),(Cl^-、SO₄^2-),H₂O五元系统介稳平衡相图研究的成功证明在复杂的多组元系统中存在介稳平衡。和Van't Hoff的该五元系统稳定平衡相图比较有较大的差别:钾镁矾(MgSO₄·K₂SO₄·4H₂O)、钾盐镁矾(KCl·MgSO₄·3H₂O)及硫酸镁的低水化合物结晶区域消失了;钾钠芒硝、白钠镁矾结晶区域缩小;氯化钾、七水硫酸镁、光卤石结晶区域增大,特别是软钾镁矾结晶区域约增大20倍,这对于制取硫酸型钾盐具有重要意义。在所制作的五元系统介稳相图中,由于钾镁矾和钾盐镁矾结晶区域消逝,因而硫酸镁与氯化钾结晶区直接连接,在蒸发海水时,有可能直接析出氯化钾。根据所作的五元系统介稳相图,提出了自盐湖析出的芒硝和光卤石、氯化钠直接加工为硫酸型钾盐的原则流程。     

改性氧化石墨烯去除重金属离子的分子动力学模拟

通过硅烷化反应在氧化石墨烯(Graphene oxide, GO) 表面嫁接螯合官能团N-(三甲氧基硅丙烷)乙二胺三酸(EDTA-Si), 得到改性氧化石墨烯(GO-EDTA), 采用分子动力学模拟在分子水平上研究了Pb²⁺在GO-EDTA 表面的动态吸附分布、 构象及动力学性质, 比较了Pb²⁺和单价Na⁺离子在氧化石墨烯上的吸附行为, 模拟了GO-EDTA与Ca²⁺相互作用, 与Pb²⁺的吸附行为进行了对比. 模拟结果表明, Pb²⁺和Na⁺的吸附位点是GO-EDTA 体系中的羧基, 而非氧化石墨烯表面的羟基; Pb²⁺和 Na⁺ 与羧基的吸附构象不同, 前者吸附构象以摩尔比2:1为主, 即两个羧基对一个Pb²⁺离子, 而后者更多倾向于摩尔比1:1的吸附模式, 即一个羧基对一个Na⁺离子; Pb²⁺离子相对于Ca²⁺和Na⁺离子, 形成的COO^--Pb²⁺离子对构象越过的能垒最低, 但是破坏该离子对构象时能垒较高, 表明Pb²⁺离子在氧化石墨烯膜上表现出良好的吸附性.     

多反应离子的质子转移反应质谱

在无放射性辉光放电离子源内, 采用不同试剂气体进行放电, 为质子转移反应质谱(PTR-MS)新增了强度在10⁵ cps量级的3种反应离子NH₄⁺, NO⁺和O₂⁺, 纯度大于95%; 测试了这3种反应离子的离子-分子反应特征. 采用H₃O⁺, NH₄⁺, NO⁺和O₂⁺等4种反应离子对同分异构体丙醛/丙酮进行检测发现, H₃O⁺和NH₄⁺均不能区分的丙醛/丙酮可采用NO⁺或O₂⁺进行区分. 结果表明, 增加反应离子不仅使PTR-MS的可检测有机物范围不再局限于质子亲和势(PA)大于H₂O的有机物, 还提高了PTR-MS区分同分异构体的能力.     

离子水化过程的核磁共振研究——二-(2-乙基己基)膦酸-长链醇-煤油-水体系

本文利用无水皂化萃取剂加水生成微乳状液研究离子水化的新方法,研究了酸性膦酸酯D₂EHPA(碱金属盐)-ROH-煤油-水体系中,通过对水质子化学位移变化的规律来研究碱金属的水合作用,所得结果与环烷酸体系相似。当[M⁺]/[H₂O]从100/1向1/100变化时,可以看到配位水的化学位移比缔合水(即正常液体水)向低场移动近2ppm,这比通常在浓盐水溶液中观察到的差值提高了一个数量级。当[M⁺]/[H₂O]大于100/1时,配位水的化学位移随阳离子不同而趋于不同的极限值,其顺序为NH₄⁺(6.76)>Li⁺(6.60)>Na⁺(5.96)>K⁺(5.40)。 从不同体系NMR图峰形和半高宽度Δv_1/2的变化,可以观察到阴离子的结构和组成对离子的水化作用有较大的影响。有关阴离子水合情况的研究工作正在进行中。     

生物铵转运蛋白对NH3/NH4+作用机理研究

铵转运蛋白广泛存在于细菌、真菌、植物以及动物等各种生命体中。生物铵转运蛋白对NH₃/NH₄⁺的传输作用已被广泛研究,然而,对于通过铵转运蛋白疏水性孔腔的物种是带电荷的NH₄⁺离子还是电中性的NH₃分子,仍存在很大争议。本文综述了近年来生物铵转运蛋白对NH₃/NH₄⁺作用机理的研究进展,主要包括NH₃或NH₄⁺的传输及NH₃和H⁺共传输等机理。     

基于铂修饰丝网印刷电极检测土壤中铵态氮的电化学传感器

土壤中铵态氮(NH₄⁺)含量的现场检测对于提高氮肥的利用率、减少环境污染,从而实现精准农业具有重要意义.针对目前土壤检测方法存在的周期长、成本高及时效性差等问题,本文基于铂粒子对NH₄⁺具有特异性电催化响应,通过在丝网印刷电极(SPE)表面电沉积铂颗粒,制备了一种电化学传感器.采用碳酸盐排除土壤中未知离子的干扰,结合土壤铵态氮快速提取装置,实现了对土壤中铵态氮的现场快速检测.该传感器对NH₄⁺检测的线性范围为0.1～5 mmol/L(R²=0.997),检出限为13μmol/L(S/N=3),检测时间约5 min;并且对土壤中NH₄⁺具有良好的选择性和稳定性,可应用于实际土壤样品中NH₄⁺的快速检测.相比于传统的检测方法,该方法无需大型仪器、操作便捷、检测速度快,可望为土壤中铵态氮的快速检测提供新方法,为精准农业提供重要的数据支持.     

乙二胺杂化锗酸锌纳米带的绿色合成及其对铀酰离子的吸附与检测

该文采用水热法合成了一种新型乙二胺杂化的锗酸锌纳米带(NH₂-Zn₂GeO₄ NRs),并用于铀酰离子(UO₂²⁺)的检测和吸附。利用透射电子显微镜(TEM)、傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)、X射线衍射(XRD)、紫外-可见吸收光谱(UV-Vis)以及荧光光谱等对纳米带的结构及其光学特性进行了表征。结果表明NH₂-Zn₂GeO₄ NRs表面含有大量的—Ge—O—H和—NH₂基团,为UO₂²⁺的检测和吸附提供了丰富的结合位点。此外NH₂-Zn₂GeO₄ NRs可高效、高选择性地吸附和检测UO₂²⁺,其对UO₂²⁺的吸附符合Langmuir等温模型,最大吸附量为190 mg...     

SCR脱硝催化剂对烟气中零价汞的氧化效率研究

采用模拟实验方法,在氧化气氛工况和SCR(选择性催化还原法)工况下,对比研究新鲜的和运行40 000 h的SCR催化剂对零价汞(Hg⁰)的氧化效率,并结合N₂吸/脱附、SEM-EDS、FT-IR、离子色谱法等手段对催化剂的组成及结构进行了表征。结果表明,在氧化气氛工况下(一定的HCl和O₂浓度),40 000 h催化剂对零价汞的氧化效率比新鲜催化剂低5%~20%,但是,在SCR工况(氧化气氛下加入NH₃和NO)下,氧化效率仅下降5%~10%。运行40 000 h催化剂出现表面颗粒的团聚现像,而且比表面积、活性物质V及V⁵⁺=O基团的含量均相对下降;然而,运行40 000 h催化剂的水溶性离子含量(特别是Na⁺、K⁺、NH₄⁺、SO₄^2-)要高于新鲜催化剂。这些因素都会影响催化剂表面活性位和内部孔道结构,从而影响到催化剂对于烟气中Hg⁰的氧化效率。     

Unimolecular artificial transmembrane channel with terminal dihydrogen phosphate groups showing transport selectivity for ammonium

A new artificial transmembrane channel molecule bearing dihydrogen phosphate groups has been synthesized.The terminal dihydrogen phosphate groups enable the channel to be highly negatively charged at both ends of the channel structures.The artificial channel could incorporate into the lipid bilayer efficiently under low concentration.The channel displays high NH4+/K+selectivity due to the electrostatic interaction and hydrogen bonding between NH4+and the terminal dihydrogen phosphate groups.     

氧化石墨阳离子交换容量测定过程中结构的变化

氧化石墨(GO)结构层上的碳羟基(―C―OH)和边缘羧基(―COOH)在水介质中发生质子化反应解离出的H+具有阳离子可交换性。实验采用甲醛缩合法测量了GO的阳离子交换容量(CEC),用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和X射线光电子能谱(XPS)分析测试手段对GO阳离子交换过程中间产物的结构变化进行了分析。结果表明,GO的CEC高达541.48 mmol/100 g。NH_4~+和Ca~(2+)交换后的GO,保持稳定的层状结构,c轴方向层间距分别增大了0.1499和0.2905 nm。NH_4+和Ca~(2+)主要以层间可交换阳离子形式存在于层间域中,并与水分子形成可交换水化阳离子层,部分以[NH_4(H_2O)_6]+和[Ca(H_2O)_6]_2+的形式存在于结构层的边缘附近,共同平衡结构层水解产生的负电荷。     

Vibrational dependence of the NH3 (v2)+NO and NO(v)+NH3 charge transfer cross sections

A tandem quadrupole mass spectrometer is used to study the charge transfer reactions NH₃⁺ + NO and NO⁺ + NH₃ over a collision energy range 1.5–13 eV. The vibrational state of the reagent ions is selected by resonance-enhanced multiphoton ionization. For the 0.9 eV exothermic process NH₃⁺ + NO → NH₃ + NO⁺ excitation of the v₂ umbrella bending mode (v₂ = 0–12) causes no marked change in the charge transfer cross section, while in the reverse process NO⁺ + NH₃ → NO + NH₃⁺ excitation of the NO⁺ vibration (v = 0–6) strongly enhanced the charge transfer cross section.     

Ion chromatography of organic-rich natural waters from peatlands II. Na, NH4, K, Mg and Ca

Organic rich natural waters from peat bogs in continental (Switzerland) and maritime (Shetland Islands, Scotland) environments were analysed for Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺ using ion chromatography. These cations were determined simultaneously in surface and pore water samples from the continental bogs using a 250-μl injection loop in an isocratic separation. Using this loop, detection limits of the order of 1 ng/g were achieved. An organics-removal cartridge (Dionex OnGuard P) was used to remove humic materials. Analyses of deionized water filtered through these cartridges showed acceptably low blank values (e.g., ca. 5 ng/g) and appeared to have no significant effect on the measured cation concentration. For the maritime bog waters, the low concentrations of NH₄⁺ (ca. 1 μg/g) compared with Na⁺ (ca. 100 μg/g) required improved peak separation. This was accomplished using a gradient separation beginning with 40 mM HCl—1 mM , -2,3-diaminopropionic acid monochloride (DAP) and switching to 40 mM HCl-12 mM DAP after 2 min. Using a 25 μl injection loop, Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺ were determined simultaneously in less than 25 min. In this instance, even with Na⁺/NH₄⁺ > 100, there was no interference from Na⁺ in the determination of NH₄⁺ (baseline separated).     

Molecular recognition of sulfonatocalixarene with organic cations at the self-assembled interface: a thermodynamic investigation

A microcalorimetric study on molecular recognition of p-sulfonatocalix[4]arene derivatives at selfassembled interface in comparison with in bulk water was performed,inspired by the dramatic change in physicochemical characteristics from bulk water to interface.A total of six cationic molecules were screened as model guests,including ammonium(NH_4~+),guanidinium(Gdm~+).N,N'-dimethyl-1,4-diazabicyclo[2.2.2]octane(DMDABCO~(2+)),tropylium(Tpm~+),N-methyl pyridinium(N-mPY*) and methyl viologen(MV~(2+)).The complexation with NH_4~+.Gdm~+ and DMDABCO2* is pronouncedly enhanced when the recognition process moved from bulk water to interface,whereas the complexation stabilities with Tpm~+,N-mPY~+ and MV2* increase slightly or even decrease to some extent.A more interesting phenomenon arises from the NH_4~+/Gdm~+ pair that the thermodynamic origin at interface differs definitely from each other although with similar association constants.The results were discussed in terms of differential driving forces,electrostatic,hydrogen bond as well as π-stacking interactions,originating from the unique physicochemical features of interfaces,mainly the polarity and dielectric constant.     

阳离子交换型聚合物AQ薄膜修饰碳纤维电极及伏安行为

本文成功地制备了Eastman-AQ-55D聚合物修饰碳纤维电极,用循环伏安法探讨了一些实验参数的影响,并对Ru(NH₃)₆³⁺、甲基紫精进行了分析,结果表明,AQ-55D修饰的微电极稳定性好,修饰方法简单,灵敏度和选择性都有一定的提高,Ru(NH₃)₆³⁺、甲基紫精的峰电流与浓度在1.2×10^-6～1.2×10^-5mol/L、1.7×10^-6～1.4×10^-5mol/L范围内呈线性关系,其相关系数分别为0.999、0.998.利用此电极测定了几种离子在膜中的扩散系数.     

Thermal dissociation of the protein homodimer ecotin in the gas phase

The influence of charge on the thermal dissociation of gaseous, protonated, homodimeric, protein ecotin ions produced by nanoflow electrospray ionization (nanoES) was investigated using the blackbody infrared radiative dissociation technique. Dissociation of the protonated dimer, (E₂ + nH)ⁿ⁺ E₂ⁿ⁺ where n = 14–17, into pairs of monomer ions is the dominant reaction at temperatures from 126 to 175 °C. The monomer pair corresponding to the most symmetric charge distribution is preferred, although 50–60% of the monomer product ions correspond to an asymmetric partitioning of charge. The relative abundance of the different monomer ion pairs produced from E₂¹⁴⁺, E₂¹⁵⁺, and E₂¹⁶⁺ depends on reaction time, with the more symmetric charge distribution pair dominating at longer times. The relative yield of monomer ions observed late in the reaction is independent of temperature indicating that proton transfer between the monomers does not occur during dissociation and that the different monomer ion pairs are formed from dimer ions which differ in the distribution of charge between the monomers. For E₂¹⁷⁺, the yield of monomer ions is independent of reaction time but does exhibit slight temperature dependence, with higher temperatures favoring the monomers corresponding to most symmetric charge distribution. The charge distribution in the E₂¹⁵⁺ and E₂¹⁶⁺ dimer ions influences the dissociation kinetics, with the more asymmetric distribution resulting in greater reactivity. In contrast, the charge distribution has no measurable effect on the dissociation kinetics and energetics of the E₂¹⁷⁺ dimer.     

8-羟基喹啉合十钒酸盐的研究(Ⅲ)——锂、钾、铵盐的合成、鉴定与性质

在合成与研究钠盐的基础上^[1,2],我们又合成了锂、钾和铵盐,通过元素分析、分子量测定、质谱分析、X射线衍射、紫外和红外吸收光谱分析和热重分析确定了新化合物的组成与化学式并推测了化合物的结构式。     

SO_4~(2-)功能化处理对Fe_2O_3催化剂上氨选择性催化还原NO_x性能的促进机理研究

采用沉淀法制备了Fe(OH)_3和Fe_2O_3。通过硫酸化处理得到SO_4~(2-)/Fe(OH)_3和SO_4~(2-)/Fe_2O_3两种催化剂,并将其应用于氨选择性催化还原NO_x(NH_3-SCR)反应,研究了SO_4~(2-)功能化处理对Fe_2O_3催化剂上NH_3-SCR脱硝性能的促进机理。结果表明,与纯的Fe_2O_3相比,硫酸化处理得到的催化剂上SCR活性得到显著提升;其中,SO_4~(2-)/Fe(OH)_3表现出更加优异的催化性能,在250-450℃时NO_x转化率高于80%,且具有优异的稳定性和抗H_2O+SO_2性能。XRD、Raman、TG、FT-IR、H_2-TPR、NH_3-TPD和in situ DRIFTS等表征结果显示,硫酸功能化处理能抑制Fe_2O_3的晶粒生长,同时SO_4~(2-)与Fe~(3+)结合形成硫酸盐复合物,提高了催化剂表面酸性位点的数量和酸强度,抑制了Fe_2O_3上的氨氧化反应,从而提高了其脱硝催化性能。