Emission intensity of terbium(III) bound to benzene-carboxylic acid derivatives

The emission intensity of Tb³⁺ bound to phenol, catechol, resorcinol, benzoic acid, pyridine, nicotonic acid, phthalic acid, salicylic acid, and picolinic acid has been studied. Relative intensities of Tb³⁺ emission indicate that formation of a chelate ring is necessary to observe enhancement of the emission relative to that of Tb³⁺ alone in aqueous solution. The pH dependence of Tb³⁺ emission when bound to phthalic, salicylic, and picolinic acids were examined in detail and evidence was found which indicated that the geometry of the Tb³⁺ ion undergoes several changes as the solution pH is raised. The emission intensities and pH dependences are also found to depend on the ratio of ligand to metal, and this observation support the presence of polynuclear lanthanide complexes existing in solution.     

Studies on Trace Labelling of Bromsulphalein (BSP) with Radioiodine

Two methods have been studied for high specific activity trace iodination of Bromsulphalein (BSP) with radioiodine (¹³¹I). In the first method, BSP in aqueous solution is reacted with iodine and an oxidising agent – hydrogen peroxide or chloramine T. In the second method, iodination is carried out by electrolytically liberated iodine. The electrolytic method gives labelled BSP free from any labelled degradation products. The stability of ¹³¹I-labelled BSP in aqueous solution has been studied. The product has been found to remain more stable in aqueous solutions at a slightly acid pH (4…6.5) than in dilute alkaline solutions (pH 7…9.5).     

硫化锌法原子吸收间接测定谷氨酸络合反应的机理研究

通过编程计算谷氨酸和锌离子的各种存在形式随pH值变化的拟合分布图,研究了在硫化锌法原子吸收间接测定谷氨酸时的pH对原子吸收响应的影响及络合反应的机理。指出在最佳条件pH9.0测定条件下,谷氨酸的pH响应峰是由于谷氨酸和锌离子的两种不同存在形态的变化所引起的。谷氨酸是以负一价离子状态与Zn(OH)_2形成了可溶性络合离子[OO—C—CH—(NH_3~ )—CH_2—CH_2—COO]Zn(OH)_2。理论计算与实验数据能很好地吻合,确定了硫化锌法原子吸收间接测定谷氨酸时的络合物反应机理及络合物的组成结构。     

吡啶羧酸在银电极表面随电极电位变化的表面增强拉曼光谱研究(英文)

本文通过表面增强拉曼散射研究了三种不同构型的吡啶羧酸—皮考酸、异烟酸和烟酸在粗糙银电极表面上的吸附形态随电极电位的变化关系。大量的表面结构信息可从丰富的表面拉曼信号及其随电极电位相应的变化而获得。分析表明在电极电位负移过程中皮考酸分子一直采取通过羧基和苯环上的N原子侧立吸附在银电极表面,与之不同的是,异烟酸分子和烟酸分子在表面的吸附状态都随电位改变发生了变化,我们对此进行了分析和解释     

Study of the deterioration of sandstone due to acid rain and humid SO2 gas

The aim of this work was to study the deterioration of various kinds of sandstone due to acid rain and SO₂ gas. The samples were taken from three quarries in Poland and one sample was from a tomb about 100 years old. To elucidate the mechanism of stone deterioration, simple experiments were performed. The sandstone samples were immersed for several weeks in SO₂ aqueous solution of pH ≈ 4. Similar experiments were performed using SO₂ aqueous solution of pH ≈ 1.5. The concentrations of Ca, Mg and Fe leached from the sandstone samples were measured with TXRF. An additional experiment was carried out with the use of radioactive ³⁵SO₂. The samples were exposed to both ³⁵SO₂ aqueous solution and to ³⁵SO₂ gas. The autoradiograms obtained from the sample cross‐sections indicated that sulfur penetrated to the interior parts of sandstone samples, especially from SO₂ gas. Copyright © 2004 John Wiley & Sons, Ltd.     

Origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid

We report on the investigation of the origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid.The oxide to nitride removal selectivity of the ceria slurry with picolinic acid is as high as 76.6 in the chemical mechanical polishing.By using zeta potential analyzer,particle size analyzer,horizon profilometer,thermogravimetric analysis and Fourier transform infrared spectroscopy,the pre-and the post-polished wafer surfaces as well as the pre-and the post-used ceria-based slurries are compared.Possible mechanism of high oxide to nitride selectivity with using ceria-based slurry with picolinic acid is discussed.     

石英矿物表面反应性的EPR谱学研究

采用顺磁共振谱（ＥＰＲ）方法对不同ｐＨ值条件下石英表面与Ｃｕ＾２＋离子反应的机理进行研究。当溶液的ｐＨ值在２至１１之间地,石英表面Ｃｕ＾２＋离子的吸附覆盖率相应地由０至１０．３２％变化;同时,其ＥＰＲ谱的线形、线宽及ｇ因子值也发生了特征的变化。研究表明,随着石英表面Ｃｕ＾２＋离子的吸附覆盖率的不断升高,表面反应产物的结合形态相应地出现单核化合物、多核化合物直至表面沉淀。     

利用纳秒激光闪光光解技术研究噻吨酮光化学动力学的pH值效应

最近一种对pH值敏感的噻吨酮衍生物荧光探针被报道. 因此,揭示其pH值效应的根本原因能够为将来设计新型荧光探针提供重要的参考. 本文利用纳秒激光闪光光解技术研究了噻吨酮分子本身光化学性质对pH值的依赖性,观测了噻吨酮以及噻吨酮与二苯胺构成的二元体系的瞬态吸收光谱和相应动力学变化. 除了已知的³TX^3*特征吸收峰外,对光谱中其它主要吸收峰(417、518、673和780 nm)进行了归属,证实了光照条件下噻吨酮与二苯胺之间的多步反应机制. 其中,在强酸(pH=3.0)条件下,噻吨酮和质子化的噻吨酮(TXH⁺)存在动态平衡,并且高的质子浓度促进了³TX^3*的主要衰减通道由电子转移变为质子亲和过程,所得到的初级产物³TXH^+*和TX^·-将经历不同的次级过程反应. 在较宽的pH范围内(从5.0到13.0),总反应机理和反应速率都没有显著的变化.     

pH-dependent color change of colloidal dispersions of gold nanoclusters: Effect of stabilizer

Gold nanoclusters protected by 3-mercaptopropionic acid (MPA-Au nanoclusters) were prepared by citrate-reduction of hydrogen tetrachloroaurate(III) in the presence of sodium 3-mercaptopropionate. Color of the dispersions of MPA-Au nanoclusters changed from red to purple by addition of hydrochloric acid and returned from purple to red by addition of an aqueous sodium hydroxide solution. This reversible response can be attributed to synchronized changes between dispersion and ordering of MPA-Au nanoclusters, determined by transmission electron microscopy. Gold nanoclusters protected by poly(acrylic acid) (PAA-Au nanoclusters) were prepared by UV irradiation of an aqueous solution of hydrogen tetrachloroaurate(III) in the presence of poly(sodium acrylate). The pH-dependent spectral change observed for MPA-Au was not observed for PAA-Au. UV-Vis absorption spectra of colloidal dispersions of PAA-Au nanoclusters after addition of hydrochloric acid and an aqueous sodium hydroxide solution were in good agreement with each other, suggesting the stability of PAA-Au nanoclusters to pH change. Received 18 October 2000 and Received in final form 10 April 2002     

离子液体双水相体系-紫外分光光度法测定恶喹酸

建立了由亲水性离子液体溴化1-乙基-3-丁基咪唑[Emim]Br和K2HPO4形成的双水相体系对恶喹酸的紫外分光光度测定方法。优化了[Emim]Br和K2HPO4成相的条件,研究了萃取恶喹酸的最佳体系。采用混合液体（pH=7.0磷酸盐缓冲液,15%三氯醋酸水溶液）提取样品,离子液体双水相体系的富集。回收率为97.6%—98.7%,相对标准偏差为2.4%—15.3%。该检测猪恶喹酸残留具有干扰小、速度快、灵敏度高等优点。     

吡嗪-2-羧酸在γ-改性磷酸锆中的插层组装及发光性能

采用直接沉淀法制备了层状框架γ-磷酸锆（γ-ZrP）及改性磷酸锆（γ-DDZrP）,通过插层化学法将吡嗪-2-羧酸生色团与改性磷酸锆进行杂化组装。X射线衍射结果显示,γ-DDZrP的层间距（3.70 nm）远远大于γ-ZrP（1.11 nm）,这有利于吡嗪-2-羧酸生色团的插入。组装后层状框架的层间距由3.70 nm减小为3.33~3.29 nm。 荧光光谱表明,最大发射峰位置发生了明显蓝移,由溶液中的373 nm蓝移至悬浮液的366 nm。研究发现,吡嗪-2-羧酸在水溶液中的荧光强度很低,但形成插层组装后,悬浮液的荧光强度有了很大程度的提高,当浓度为15 μmol/L时,荧光强度增大了6倍。这说明γ-DDZrP能够改善吡嗪-2-羧酸的荧光性能,有利于其在分子识别和荧光探针等领域的应用。     

Synthesis and Investigation of Double Stimuli-Responsive Behavior of N-Isopropylacrylamide and Maleic Acid Copolymer in Solutions

Poly(N-isopropylacrylamide-co-maleic acid) [poly(NIPAAm-co-MA)] linear copolymer with comonomer molar ratio NIPAAm:MA = 94:6 was synthesized by free-radical copolymerization. The molar mass, M_sD = 28,000 Da, of poly(NIPAAm-co-MA) was determined using hydrodynamic methods. The self-assembly of poly(NIPAAm-co-MA) in aqueous solution at a concentration of 0.015 g cm^?3 within the pH interval from 1.8 to 10.6 and the temperature interval from 22 to 60°C was investigated by static and dynamic light scattering. The copolymer showed a double temperature and pH responsiveness. Three types of particles, namely, macromolecules (or unimers), micellar-like structures, and loose aggregates existed in the poly(NIPAAm-co-MA) aqueous solutions. The fraction of dissolved entities and the hydrodynamic radii of the micellar-like structures and loose aggregates depended considerably on temperature and pH. The temperature of the phase separation and the width of the phase separation interval increased with pH. An influence of pH on kinetic processes in poly(NIPAAm-co-MA) solutions was observed.     

Influence of pH on the dielectric properties of egg-white lysozyme in aqueous solution

The dielectric dispersions of 5% aqueous solutions of egg-white lysozyme have been investigated at three different pH of 3.5, 7.0 and 11.0 respectively. The experiments were performed over a frequency range 0.1 – 50 MHz and at a uniform temperature of 20°C. The dielectric data were fitted to the Debye and Cole-Cole structural equations and the fitted parameters have been presented. Results showed that the dielectric properties of the lysozyme molecules were influenced by changes in pH, and these have been discussed in the light of known aggregation characteristics of the protein in aqueous solution.     

Ultrasound stimulus effect on hydrogen bonding in networked alumina and polyacrylic acid slurry

The influence of ultrasound (US) on the viscosity of aqueous slurry composing polyacrylic acid (PAA) and alumina was studied. For exposure to an aqueous slurry solution, US waves emitted at three different frequencies of 28, 45, and 100 kHz were used. Results show that the stimulus effect of US on viscosity change was a breakage of the hydrogen bonding networks of alumina and PAA in the slurry solution. That decrease in viscosity was enhanced strongly by US exposure as the output power was increased from 175 to 300 W. In addition, a lower US frequency was effective for slurry viscosity reduction. The reduced viscosity of the slurry also depended on the solution pH. After US was stopped, the viscosity increased gradually and recovered to its original value within about 15 min. The stimulus effect on the viscosity change was cycled by US.     

Aqueous lanthanide shift reagents. 10. Proton and carbon-13 studies of the interaction of the aquoions with amino acids

A detailed NMR study of the interaction between the trivalent lanthanide ions and amino acids in aqueous solution is presented. The pH dependence indicates that complex formation occurs with the ionized carboxyl group of the amphiionic form of the amino acid. The useful pH range for studying lanthanide-amino acid interactions is between 4 and 7. Measurements of complex formation at constant pH show that the lanthanide ion behaves as a domain containing two equivalent and independent coordination sites for amino acids. The complex dissociation constant varies little between the beginning (Pr) and the end (Yb) of the series. Lanthanide-induced shifts in the proton and carbon-13 resonances of sarcosine, as well as the previously published relaxation rate increments, demonstrate that along the lanthanide series the complexes are isostructural with respect to the amino acid ligands and the hyperfine coupling constants are invariant. Structural details of the complexes are elucidated from an interpretation of these data. The sarcosine ligand is in the folded (cis) conformation about the NC_α bond.     

Synthesis and Property of Butyl Methacrylate-Butyl Acrylate-Acrylic Acid Terpolymer With Absorptive Capacity

Butyl methacrylate-butyl acrylate-acrylic acid terpolymer was synthesized by suspension polymerization with benzoyl peroxide as an initiator and poly(vinyl alcohol) as a dispersing agent to absorb organic liquids, and then the terpolymer was modified to absorb distilled water, NaCl aqueous solution, and toxic metal ions by swelling in isopropyl alcohol and hydrolysis in sodium hydroxide aqueous solution. The morphology changes during the liquid absorption process were observed via a polarizing light microscope. The thermostabilities of the original and modified terpolymers were tested in a thermogravimetric analyzer. The test results indicated that the unmodified terpolymer could absorb a certain amount of toluene, trichloroethylene or tetrachloroethylene to become a swollen system, and its remaining (residual) ratio was more than 75% after absorbing the organic liquids for 24 h. The modified terpolymer not only had a marked capacity to absorb distilled water and NaCl aqueous solution, but also showed a significant absorption of toxic metal ions; e.g., its saturated absorbency of Cu²⁺ could reach 421.0 mg/g. The morphology changes demonstrated that the modified terpolymer could be swollen in distilled water, forming a gel-like structure. The results obtained from thermogravimetric analysis revealed that the thermal stability of the modified terpolymer was better than that of the unmodified terpolymer.     

Malonic acid-assisted synthesis of LiNi0.8Co0.2O2 cathode active material for lithium-ion batteries

Polycrystalline LiNi_0.8Co_0.2O₂ was synthesized by a solution route with malonic acid as the complexing agent. The effects of temperature, duration of heat treatment, pH of the precursor solution, and the nature of the solvent employed on the performance characteristics of the product were studied. It was observed that a 12-hour 800 °C heat treatment protocol was necessary to obtain products with optimal electrochemical characteristics. Furthermore, an excess lithium stoichiometry of 1.05 was found to be detrimental to the performance of the cathode material. The beneficial effect of ethanol as a solvent over water on the product characteristics is explained by the presence of solvent molecules in the coordination sphere of the cations. A pH of 7, at which malonic acid is complexed completely with the cations without interference from other nucleophiles, was found to be ideal for the synthesis of the cathode active material from aqueous solutions. With ethanol as the medium, the product formed by a 12-h calcination at 800 °C yielded a first-cycle capacity of 173 mAh/g and a tenth-cycle capacity of 169 mAh/g.     

柔性ITO衬底电化学沉积制备Cu/Cu2O薄膜

研究了使用电化学沉积法于碱性条件下在柔性ITO衬底上制备Cu/Cu₂O薄膜的方法。循环伏安曲线表明Cu₂O与Cu的阴极峰分别位于-500 mV(vs Ag/AgCl)和-800 mV(vs Ag/AgCl)附近。利用循环伏安法考察了生长温度和电解液pH值等对Cu₂O与Cu阴极峰电位的影响,阴极峰随生长温度的升高以及pH值的降低而略向阳极移动,沉积电流也随之相应增大。与弱酸性条件相比,上述两个阴极峰随pH值升高而移动的程度明显减小,这可能与碱性条件下C₃H₆O电离程度增大以及C₃H₆O根作为配体的过量程度有关。通过X射线衍射光谱和扫描电子显微镜的表征证实,在所研究的生长温度区间和pH值内可利用电化学沉积法在柔性ITO衬底上制备Cu/Cu₂O纳米混晶薄膜。在相同的生长温度和pH条件下,电化学沉积电位对样品表面形貌和晶体性质具有较大影响。     

2-对二甲氨基苯基-5-氟-6-吗啉苯并咪唑的合成及其光谱学性质研究

合成了一种新的取代苯并咪唑化合物 ,2 对二甲氨基苯基 5 氟 6 吗啉苯并咪唑 ,采用紫外 可见光谱、荧光光谱及荧光寿命等方法探讨了溶液pH值对该化合物吸收光谱的影响及其与 β 环糊精的作用。结果表明 ,pH >7 0时 ,该化合物在溶液中主要以中性分子状态存在 ,当 3 8相似文献   

新生MnO2对酸性媒介黑T的吸附

以化学法合成的新生MnO2为吸附剂，对水中酸性媒介黑T（染料之一）进行了吸附脱色研究，并探讨了影响吸附的因素。结果表明，酸性媒介黑T的脱色率达95%。且PH是影响染料脱色的主要因素。