Effect of substituent carboxylic group on the self-assembly of cadmium coordination polymers: Syntheses,topological analyses and photoluminescence properties

Two coordination polymers, formulated as {[Cd(1,4-BDC)(ppene)]·CH₃CN}_n (1) and [Cd(H₂O)(1,2,4-HBTC)(ppene)_0.5]_n (2) have been synthesized through the solvothermal reactions between Cd(NO₃)₂·4H₂O and 4-pyr-poly-2-ene (ppene) in the presence of 1,4-benzenedicarboxylic acid (1,4-H₂BDC) or its derivative 1,2,4-benzenetricarboxylic acid (1,2,4-H₃BTC). These two compounds were structurally characterized by infrared spectroscopy, elemental analysis, single crystal X-ray diffraction and powder X-ray diffraction. Compound 1 exhibits a three-dimensional two-fold interpenetrating 4¹²6³-pcu network. The coordination network of 2 shows a three-dimensional (4,5)-connected framework with rare (4⁴6²)(4⁴6⁶) tcs topology. Owing to the linkage of hydrogen bonding interactions between protonated carboxylic groups, 2 further displays a three-dimensional (5,5)-connected supramolecular network with an unprecedented Schläfli symbol (4⁸6²)(4⁶6⁴). Thermal stability and photoluminescence properties of 1 and 2 were also investigated.     

Selective removal of heavy metal ions from aqueous solutions with surface functionalized silica nanoparticles by different functional groups

The industrial silica fume pretreated by nitric acid at 80 °C was re-used in this work. Then, the obtained silica nanoparticles were surface functionalized by silane coupling agents, such as（3-Mercaptopropyl） triethoxysilane（MPTES） and（3-Amincpropyl） trithoxysilane（APTES）. Some further modifications were studied by chloroaceetyl choride and 1,8-Diaminoaphalene for amino modified silica. The surface functionalized silica nanoparticles were characterized by Fourier transform infrared（FI-IR） and X-ray photoelectron spectroscopy（XPS）. The prepared adsorbent of surface functionalized silica nanoparticles with differential function groups were investigated in the selective adsorption about Pb2＋, Cu2＋, Hg2＋, Cd2＋ and Zn2＋ions in aqueous solutions. The results show that the（3-Mercaptopropyl） triethoxysilane functionalized silica nanoparticles（SiO2-MPTES） play an important role in the selective adsorption of Cu2＋ and Hg2＋, the（3-Amincpropyl） trithoxysilane（APTES） functionalized silica nanoparticles（SiO2-APTES） exhibited maximum removal efficiency towards Pb2＋ and Hg2＋, the 1,8-Diaminoaphalene functionalized silica nanoparticles was excellent for removal of Hg2＋ at room temperature, respectively.     

纳米技术在功能性食品中应用

近年来,纳米技术在功能性食品中应用正处快速发展阶段,其作为高新技术在功能性食品领域应用研究得到越来越多关注;纳米技术不仅可用于功能性食品生产和加工,也可提高生物活性、吸收率、稳定性、降低毒性。该文重点介绍纳米技术在功能性食品中应用。     

气相色谱-质谱法测定奶粉中香兰素的不确定度评估

目的采用气相色谱-质谱法对奶粉中香兰素含量的不确定度评估。方法建立不确定度评估的数学模型,通过对不确定度的各主要分量进行分析计算,得出合成不确定度以及扩展不确定度。结果当香兰素的测定结果为57.1 mg/kg时,其扩展不确定度为4.4 mg/kg,k=2。结论采用气相色谱-质谱法测定奶粉中香兰素含量,其不确定度的主要来源为样品的回收率和最小二乘法拟合的标准曲线,该评估模型为检测奶粉中香兰素的不确定度评估提供了参考依据。     

食品中无机元素分析方法研究进展

食品中所含的无机元素,对人体的营养健康和摄入安全有至关重要的作用,研究和分析食品中的无机元素,有利于评价食品的营养价值,规避有毒有害食品;了解食品被污染的情况和程度,以便查清和控制污染源;也有利于指导营养强化食品的生产和开发及食品加工工艺的改进和食品质量的提高。因此,在食品生产过程都需要对无机元素含量进行监控和检测。本文综述了目前国内外食品中无机元素分析的主要方法及其特点和质量控制水平,既包含了传统的化学法、物理法,也涵盖了近些年才兴起的纳米技术法、生物技术法等,并列举了这些分析检测方法在近年来的实际应用,阐明了食品中无机元素分析方法的研究发展趋势,旨在为食品中无机元素分析检测研究者和从业者提供一定参考。     

微波技术在食品加工与检测中应用

微波技术在现代高新技术领域具有重要地位,具有快速、节能、清洁等优点;目前微波技术发展很快、涉及面也很广,在食品加工和检测方面得到广泛应用.该文介绍微波技术在食品加工和检测中研究与应用进展.     

晒青茶、普洱茶(生茶)紧压茶实物样研制及其品质特征分析

根据普洱茶(生茶)拼配规则及各普洱茶生产企业的产品质量生产情况,为进一步推动普洱茶(生茶)实物标准样的科学制备,规范普洱茶原料及普洱茶(生茶)产品,揭示影响云南大叶种晒青茶滋味品质的物质基础,并探讨影响因素间的相互作用。以临沧、普洱、大理、西双版纳的春、夏、秋三个季节的云南大叶种晒青茶为原料：(1)通过筛选可拼配单样、小样试拼及排序、大样拼堆及评定等程序,严格通过品质水平均匀性、稳定性检验,制备出二套实物标准样：晒青茶实物标准样、普洱茶(生茶)实物标准样。(2)通过理化分析及感官审评,通径分析表明,茶多酚与氨基酸、黄酮是影响晒青茶滋味品质的主要因素,其中,黄酮对晒青茶的滋味品质直接作用最明显,茶多酚通过其余变量对晒青茶滋味品质的间接作用综合影响最大。本研究不仅为普洱茶的质量标准信息化研究、茶饮料开发等方面提供分析方法参考,更为促进普洱茶的高质量、绿色化、品牌化发展提供科学依据。     

Effect of Yb3+ concentration on the green-yellow upconversion emission of SrGe4O9:Er3+ phosphors

This work presents the structural, morphological and luminescent, properties of SrGe₄O₉ (SGO):Er³⁺,Yb³⁺ phosphors. These phosphors were synthesized by simple combustion synthesis and subsequently annealed at 1100 °C. The XRD patterns revealed that all the SGO samples doped with Yb³⁺ concentrations from 2 to 10 at.% presented a trigonal pure phase (the Er³⁺ concentration was fixed to 1 at.%). The morphology of the SGO samples was analyzed by scanning electron microscopy and found that they are formed by microparticles with irregular shapes and average sizes in the range of 0.2 μm–3 μm. The luminescence measurements of the SGO:Er³⁺,Yb³⁺ samples showed the presence of two main emission bands at 551 nm (green) and at 662 nm (red) under excitation at 980 nm, which are associated to Er³⁺ transitions. For Yb concentration of 2 and 3 at.% the green band dominated, but the red band became more intense for Yb concentrations above 5 at.%. As result, the CIE coordinate changed from the green to the yellow region. The increase for the Yb content from 2 to 10 at.% also enhanced of the NIR emission of Er³⁺ ≈5 times and the maximum upconversion emission was observed for 8% of Yb concentration. Further, the surface of the SGO samples was analyzed by the FTIR technique in order to find OH groups which are common luminescent quenching centers, but these groups were not detected on the samples. Since the SGO samples presented tunable emission, absence of OH groups on their surface and stable crystalline structure for high Yb dopant concentrations, they could be good candidates as phosphors for solid state lighting or displays applications.     

A pair of novel helical Zn(II) enantiomers constructed from l- and d-threonine Schiff bases: Synthesis,crystal structures and properties

Two novel homochiral helical Zn(II) coordination polymers, {[Zn₂(nap-l-thr)₂(H₂O)₂]·H₂O}_n (1) and {[Zn₂(nap-d-thr)₂(H₂O)₂]·H₂O}_n (2) (H₂nap-l-thr = N-(2-hydroxy-1-naphthylmethylidene)-l-threonine, H₂nap-d-thr = N-(2-hydroxy-1-naphthylmethylidene)-d-threonine) have been successfully synthesized and characterized by elemental analysis, IR, UV–visible and single-crystal X-ray diffraction. It is interesting to note that both complexes are a pair of enantiomers: 1 exhibits 1D right-handed helical chain of [Zn-COO⁻]_∞ and 2 is 1D left-handed helical chain of [Zn-COO⁻]_∞. There are various hydrogen bonds between the adjacent helical chains which result in a 2D homochiral supramolecular layer structure. Notably, under similar synthetic procedure by using the NO₃⁻, CH₃COO⁻, Cl⁻ salts of Zn^2 + ion as a starting reagent, and identical compounds were obtained. In addition, the chiral nature of complexes 1 and 2 are confirmed by the results of circular dichroism (CD) spectra measurements. Thermal stability and luminescence properties were also investigated.     

气质联用仪测定汽油中含氧化合物、苯和甲苯的含量

利用选择离子法（SIM）对汽油中含氧化合物、苯和甲苯进行定量分析,可以简化分析步骤,缩短分析时间,有效消除汽油中复杂成分对目标组分分析结果的影响,提高了分析结果的准确性。15种组分标准曲线的线性相关系数均大于0.998 8,最低检测限为2~5 μg•g^-1,回收率为90%~103%,保留时间相对标准偏差小于0.5%,峰面积相对标准偏差小于11.05%。