层状复合金属氢氧化物-聚丙烯酸钠水分散体系的双絮凝现象及机理探讨

研究了聚丙烯酸钠(PAAS)对镁铝型层状复合金属氢氧化物(MgAl-LDH)的胶体水分散体系稳定性的影响. 利用总有机碳(TOC)分析技术测定了PAAS在LDH颗粒上的吸附量, 并利用ζ电位表征了LDH颗粒的电性质. 实验结果表明, 在质量分数为1%的LDH水分散体系中加入0.006~2.400 mmol/L PAAS, 随着PAAS浓度的增加, LDH-PAAS混合体系出现了絮凝-分散-再絮凝变化. 同时, 随着PAAS浓度的增加, PAAS在LDH颗粒上的吸附导致颗粒ζ电位由正减至0, 并进一步负向增加, 颗粒间静电斥力先减小后增加, 因此体系先絮凝再分散. 随着LDH颗粒负电性的进一步增强, 未吸附的PAAS引发颗粒间产生的空缺引力成为体系再次絮凝的主要原因. 对吸附PAAS的LDH颗粒的红外光谱分析表明, PAAS主要通过-COO-与LDH的相互作用而吸附在颗粒上.     

荧光法快速检测有机磷农药残留总量

在pH4.60的B-R缓冲溶液中,中性红(NR)与一定浓度的十二烷基苯磺酸钠(SDBS)发生荧光增强反应,在该体系中加入有机磷农药后,在激发波长560 nm,发射波长604 nm处体系的荧光强度明显降低,且降低程度与有机磷农药的加入量呈良好的线性关系,其线性范围和检出限分别为0.024~0.40 mg/L,0.014 mg/L。据此建立了测定有机磷农药残留总量的新方法。方法已用于面粉和土壤中有机磷农药残留总量的检测,回收率在92.0%~100.5%之间,RSD在1.1~1.9%之间。     

流动注射化学发光抑制法测定阿魏酸钠

提出了Fe2+-H2O2-亚甲基蓝化学发光新体系并用于阿魏酸钠的测定。实验发现,在酸性介质中,Fe2+-H2O2体系可与亚甲基蓝反应产生极强的化学发光,阿魏酸钠对此化学发光具有显著的抑制作用。据此,结合流动注射技术,建立了阿魏酸钠化学发光分析新方法。研究了影响化学发光强度的因素,化学发光信号的降低值(ΔI)与阿魏酸钠浓度在4.5×10-6～4.5×10-5mol/L范围内呈良好的线性关系,方法的检出限为7.0×10-7mol/L。对4.8×10-6mol/L的阿魏酸钠进行了11次平行测定,其RSD=0.8%,该法已用于片剂中阿魏酸钠含量的测定。     

A New Example of the Structure Type A2[{Z2R4}X9]: Synthesis and Crystal Structure of Na2[{(ON)Ce4}Cl9]

First single crystals of Na₂[{(ON)Ce₄}Cl₉] were obtained during synthesis attempts for the cerium nitride chloride Ce₂NCl₃(= {N₂Ce₄}Cl₆). With a molar ratio of 8:10:3 for Ce, CeCl₃ and NaN₃ along with an excess of the flux NaCl, the mixture obviously contained a small amount of CeOCl that led to the formation of quinary Na₂[{(ON)Ce₄}Cl₉]. It crystallizes in the monoclinic space group P2₁/m(no. 11) with two formula units in the unit cell with dimensions of a = 813.21(6) pm, b = 1146.13(9) pm, c = 942.86(7) pm and β = 107.504(5) °. As the dominating structural feature {ZCe₄}^9.5+ tetrahedra are fused through trans‐oriented edges to generate chains (Z = ¹/₂ O + ¹/₂ N) just as in the structurally isotypic compounds A₂[{Z₂R₄}X₉] (A = Na, K; R = Pr, Nd, Gd; X = Cl, Br; Z = O, O/N).     

Two Coordination Polymers Constructed from Pillared M–O (M = Na+ or Ba2+) Subunits with 3‐Formyl‐4‐hydroxybenzenesulfonic Acid as Ligand

Two new coordination polymers, [Na(H₂L)(H₂O)₂]_n ( 1 ) and [Ba(H₂L)₂(H₂O)]_n ( 2 ) (H₃L = 3‐formyl‐4‐hydroxybenzenesulfonic acid) were synthesized and structurally characterized. The H₂L^– ligand shows three different bridging modes, μ₃ in 1 , μ₃ and μ₄ in 2 . Compound 1 presents a 2D pillared structure, whereas 2 forms a 3D framework. Both 1 and 2 show blue luminescence at 380 nm in aqueous solution, however, their solid state emissions are at 406 and 446 nm, respectively.     

Synthesis and Crystal Structure of the Palladium(IV) Polyoxomolybdate,K0.75Na3.75[PdMo6O24H3.5]·17H2O

The first example of a heteropolyoxomolybdate containing palladium(IV) was isolated and characterized by X‐ray crystallography. The palladium(IV) hexamolybdate, K_0.75Na_3.75[PdMo₆O₂₄H_3.5]·17H₂O, was isolated from an aqueous solution at pH 4.5 in the space group P\bar{1} , a 10.790(2), b 12.244(3), c 14.086(3) Å, α 113.77(1), β 90.41(1),γ 107.86(1)°, and the structure was determined using X‐ray diffraction methods, refining to a residual of 0.0301 for 5334 reflections. A formal “[PdMo₆O₂₄H₃]^5–” subunit exhibits the basic Anderson structure, with two [PdMo₆O₂₄H₃]^5– cluster anions in the structure bridged by a hydrogen atom (formally an H⁺) situated on a center of symmetry to give a “[Pd₂Mo₁₂O₄₈H₇]^9–” dimeric anion. The palladium(IV) atom occupies a slightly distorted octahedral environment, with Pd–O distances ranging from 1.968 to 2.009 Å.     

Improved synthesis of P(3HB-co-3HV-co-3HHx) terpolymers by mutant Cupriavidus necator using the PHA synthase gene of Chromobacterium sp. USM2 with high affinity towards 3HV

Unlike polyhydroxyalkanoates (PHAs) copolymers, the controlled and efficient synthesis of PHA terpolymers from triglycerides and fatty acids are yet to be established. This study demonstrates the production of P(3HB-co-3HV-co-3HHx) terpolymer with a wide range of 3HV monomer compositions from mixtures of crude palm kernel oil and 3HV precursors using a mutant Cupriavidus necator PHB⁻4 transformant harboring the PHA synthase gene (phaC) of a locally isolated Chromobacterium sp. USM2. The PHA synthase of Chromobacterium has an unusually high affinity towards 3HV monomer. P(3HB-co-3HV-co-3HHx) terpolymers with 3HV monomer composition ranging from 2 to 91 mol% were produced. Generation of 3HHx monomers was affected by the concentration and feeding time of 3HV precursor. P(3HB-co-24 mol% 3HV-co-7 mol% 3HHx) exhibited mechanical properties similar to that of common low-density polyethylene. P(3HB-co-3HV-co-3HHx) terpolymers with a wide range of 3HV molar fraction had been successfully synthesized by adding lower concentrations of 3HV precursors and using a PHA synthase with high affinity towards 3HV monomer.     

Synthesis of epoxy and aziridino malonyl peptidomimetics

Short malonyl dehydro peptides have been epoxidized using H₂O₂/Na₂WO₄ dihydrate. The obtained diastereomeric epoxides were separated by HPLC and successfully tested in the ring opening reaction with N-Boc l-cysteine methyl ester, to indicate their electrophilic behavior. Moreover, by a simple two-step reaction, the epoxy malonyl peptides can be converted into the corresponding aziridino malonyl peptides.     

Water-promoted unprecedented chemoselective nucleophilic substitution reactions of 1,4-quinones with oxygen nucleophiles in aqueous micelles

Unique nucleophilic substitution and addition reactions of nitrogen and sulfur nucleophiles with 1,4-quinones in aqueous suspension with amines and thiols have recently been demonstrated by us.² However, the reactivity of oxygen nucleophiles toward nucleophilic substitution compared to nitrogen and sulfur nucleophiles ‘on water’ is not facile. An unprecedented economical, green methodology approach using ordinary laundry detergent (LD; washing powder, 0.5 mol %, reusable)/SDS as surfactant ‘in water’ for nucleophilic substitution by oxygen nucleophiles in 1,4-quinones in excellent yields has been demonstrated.