红外光谱分析丙烯酸树脂包膜尿素膜降解特征

采用傅里叶变换红外光谱吸收(FTIR)方法分析丙烯酸树脂包膜尿素及与生化抑制剂结合的四种肥料在棕壤中膜降解特征,尝试利用红外光谱技术分析丙烯酸树脂膜降解特征,为包膜尿素肥料的应用提供科学依据。分析表明,成膜的化学成分,分子结构和膜组成没有因不同种生化抑制剂的加入而受到影响。膜特征峰出现在3 479～3 195,2 993～2 873,1 741～1 564,1 461～925和850～650cm-1之间,主要是CH3,CH2的—C—H,—OH,C—O,C—C,C—O—C,CO,CC的不对称、对称伸缩振动吸收,峰面随时间变化由平到尖,由宽到窄,吸收强度因化学键量变强弱不一。60d前四种肥料膜红外吸收光谱没有明显区别,膜降解缓慢;而60d后降解速度加快,以120d降解速度最快,310d后四种肥料膜主要分子结构没有实质性改变,膜材料主要成分在棕壤中降解十分缓慢,降解速度并没有明显受到不同生化抑制剂的影响。降解特征可以用红外吸收光谱测定与描述,红外光谱能够描绘膜降解动态,物质化学基团变化,降解速度的差别。     

甲基异丁酮萃取-原子荧光光谱法间接测定碘

在硝酸浓度为0.1mol.L-1介质中,I-和Hg2+能生成稳定的化合物,被甲基异丁酮萃取,原子荧光光谱法测定有机相中的汞,间接得到碘的含量。工作考察了萃取条件以及其他影响因素。在优化的实验条件下,碘的含量在0～12μg.L-1范围内呈良好的线性关系,方法的检出限是0.14μg.L-1,相对标准偏差3.3%,对蛋类样品加标回收率为101.8%～110.4%。     

非共价作用双水相萃取分光光度法测定镧

研究了稀土金属La（Ⅲ）的在聚乙二醇2000（PEG）-硫酸铵[（NH4）₂SO₄]-甲基红（MR）双水相体系中,用甲基红作萃取剂和显色剂的液-液萃取行为。实验表明将DP-La（Ⅲ）配合物从pH 3.5的溶液中萃取到PEG相,其最大吸收波长位于545nm,ε=2.23×10⁵L·mol^-1·cm^-1。La（Ⅲ）的线性范围为0—0.8μg·mL^-1,La（Ⅲ）与MR的配合比为1:2。该方法对共存离子的抗干扰能力较强。     

乙基橙-溴酸钾体系动力学光度法测定痕量甲醛

研究了在稀H2SO4介质中,痕量甲醛催化KBrO3氧化乙基橙褪色反应的适宜条件和影响因素,建立了测定痕量甲醛的动力学光度法。方法采用固定时间法于507 nm波长处测量体系的吸光度,在适宜条件下,ΔA与甲醛质量浓度具有良好的线性关系,方法的线性范围为0~0.24 mg/L,检出限为0.004 mg/L。该方法用于饮料、废水和废气中痕量甲醛的测定,测定结果的相对标准偏差RSD≤3%(n=6),回收率为102%。     

羧甲基纤维素对某些碱性吖啶染料的褪色作用及其分析应用

在近中性至弱碱性介质中,羧甲基纤维素钠(CMC)由于多个羧基离解而以大阴离子状态存在,它能与吖啶黄(AY)或吖啶橙(AO)阳离子借静电引力和疏水作用力而形成离子缔合复合物。此时,溶液的吸收光谱发生变化,染料在紫外和可见区的最大吸收显著降低,最大褪色波长分别位于264nm和434nm附近(AY体系)以及266nm和488nm附近(AO体系);反应有很高的灵敏度,最大摩尔吸光系数分别达7.20×107L(mol·cm)-1(AY体系λ=264nm)和1.13×108L(mol·cm)-1(AO体系λ=488nm);方法有较好的选择性,且简便快速,可用于烟丝中微量CMC的紫外可见分光光度法测定。     

Thermal degradation and flame retardance in copolymers of methyl methacrylate with diethyl(methacryloyloxymethyl)phosphonate

Methyl methacrylate (MMA) has been free radically copolymerized, both in bulk and in solution, with diethyl(methacryloyloxymethyl)phosphonate (DEMMP), to give polymers which are significantly flame retarded when compared with PMMA, as indicated by the results of limiting oxygen index (LOI) measurements, UL 94 tests, and the results of cone calorimetric experiments. The physical and mechanical properties of the copolymers are similar to those of PMMA, except that the bulk copolymers are slightly crosslinked, and are better than those of PMMA flame retarded to a similar extent by some phosphate and phosphonate additives. Examination of the some of the gaseous products of pyrolysis and combustion, and of chars produced on burning, show that flame retardation occurs in the copolymers by both a condensed-phase and a vapour-phase mechanism. The condensed-phase mechanism is shown to involve generation of phosphorus acid species followed by reaction of these with MMA units giving rise to methacrylic acid units. The methacrylic acid units subsequently form anhydride links, which probably impede depolymerization of the remaining MMA sequences, resulting in evolution of less MMA (the major fuel when MMA-based polymers burn). By undergoing decarboxylation, leading to interchain cyclisation and, eventually, to aromaticisation, the anhydride units are probably also the principal precursors to char.     

In situ monitoring of the H concentration change near an electrode surface through electrolysis using slab optical waveguide pH sensor

The H⁺ concentration change was monitored near an electrode surface through an electrolysis using a slab optical waveguide technique. Indium tin oxide transparent electrode modified by porous insulating polymer to which methyl red was covalently immobilized was used as a guiding layer, and the absorbance change of the polymer film was monitored. H⁺ generation at the vicinity of the electrode through the oxidation of ascorbic acid could be monitored by this technique.     

Metal Derivatives of Heterocyclic Thioamides: Synthesis and Crystal Structures of Copper Complexes with 1‐Methyl‐1,3‐imidazoline‐2‐thione and 1,3‐Imidazoline‐2‐thione

Reactions of copper(I) halides (Cl, Br, I) with 1‐methyl‐1, 3‐imidazoline‐2‐thione (mimzSH) in 1 : 2 molar ratio yielded sulfur‐bridged dinuclear [Cu₂X₂(μ‐S‐mimzSH)₂(η¹‐S‐mimzSH)₂] (X = I, 1 , Br, 2 ; Cl, 3 ) complexes. Copper(I) iodide with 1,3‐imidazoline‐2‐thione (imzSH₂) and Ph₃P in 1 : 1 : 1 molar ratio has also formed a sulfur‐bridged dinuclear [Cu₂I₂(μ‐S‐imzSH₂)₂(PPh₃)₂] ( 4 ) complex. The central Cu(μ‐S)₂Cu cores form parallelograms with unequal Cu–S bond distances {2.324(2), 2.454(3) Å} ( 1 ); {2.3118(6), 2.5098(6) Å} ( 2 ); {2.3075(4), 2.5218(4) Å} ( 3 ); {2.3711(8), 2.4473(8) Å} ( 4 ). The Cu···Cu separations, 2.759–2.877Å in complexes 1 – 3 are much shorter than 3.3446Å in complex 4 . The weak intermolecular interactions {H₂CH···S^# ( 2 ); CH···Cl^# ( 3 ); NH···I^# ( 4 )} between dimeric units in complexes 2 – 4 lead to the formation of linear 1D polymers.     

Studies on the Graft Copolymerization of Methyl Acrylate and Ethyl Acrylate onto Corn Starch Using Potassium Persulfate-Sodium Thiosulphatc as Initiation System

Grafting copolymerizations of methyl acrylate(MA) and ethyl acrylate(EA) onto corn starch, respectively, initiated by potassium persulfate-sodium thiosulphate (KPS-STS) redox system, were studied. The structures of poly(MA)-g-starch and poly(EA)-g-starch were characterized by IR, SEM and X-ray diffraction. Experimental results show that KPS-STS is an efficient initiation system for grafting of MA and EA onto corn starch. The maximum percent grafting was obtained at [KPS] of 6.0× 10~3 mol/L, [STS] of 1.8× 10 5 mol/L, [M] of 6. 0× 101 mol/L, S:L=4:100 at 40℃ for 6 h. The reactivity order is MA>EA.     

Catalytic degradation of organic dyes using biosynthesized silver nanoparticles

The green synthesis of metallic nanoparticles paved the way to improve and protect the environment by decreasing the use of toxic chemicals and eliminating biological risks in biomedical applications. Plant mediated synthesis of metal nanoparticles is gaining more importance owing to its simplicity, rapid rate of synthesis of nanoparticles and eco-friendliness. The present article reports an environmentally benign and unexploited method for the synthesis of silver nanocatalysts using Trigonella foenum-graecum seeds, which is a potential source of phytochemicals. The UV–visible absorption spectra of the silver samples exhibited distinct band centered around 400–440 nm. The major phytochemicals present in the seed extract responsible for the formation of silver nanocatalysts are identified using FTIR spectroscopy. The report emphasizes the effect of the size of silver nanoparticles on the degradation rate of hazardous dyes, methyl orange, methylene blue and eosin Y by NaBH₄. The efficiency of silver nanoparticles as a promising candidate for the catalysis of organic dyes by NaBH₄ through the electron transfer process is established in the present study.