UV absorption properties of ceria-modified compositions within the fluorite-type solid solution CeO2-Y6WO12

A new fluorite-type solid solution domain has been evidenced in the system (1−x) CeO₂−x/7 Y₆WO₁₂□₂ using the amorphous citrate route. All the studied phases (0?x?1) crystallize in a cubic-type symmetry. Diffuse reflectance spectra reveal a strong optical absorption between 380 and 400 nm. All substituted compositions spectral selectivities are estimated suitable for application as inorganic UV absorbers. The non linear variation observed in the optical gap values between Y₆WO₁₂ and CeO₂ is attributed to the presence of the cerium 4f-block band. Additionally, Time Resolved Microwave Conductivity (TRMC) experiment and phenol photodegradation analyses carried out on the Ce_0.81Y_0.16W_0.03O_1.95□_0.05 (x=0.19) composition do not indicate any photocalatytic activity for this material.     

Determination of Metal Ions by High Performance Liquid Chromatography

The mixture of metal ions [Bi(III), Fe(III), Fe(II), Cu(II), Zn(II), Ni(II), Co(II), Pb(II), Cd(II), Mn(II)] were separated in the bonded-phase strong cation exchange column (Vydac-401 SA) and monitored at 540 nm after a postcolumn reaction with 4-(2-pyridylazo)-resorcinol (PAR). Citrate, tartrate, lactate and α-hydroxyisobutyrate buffer were used as eluent and it has been found that the elution order of some metal ions were changed with different eluents. The detection limits and the calibration curves of metal ions were also studied.     

Aqueous Synthesis of Water-Soluble Citrate-Modified Cadmium Selenide/Cadmium Sulfide/Zinc Sulfide Quantum Dots

Water-soluble cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots were synthesized in aqueous solution using trisodium citrate as modifier. The crystal structure, morphology, component, and spectral properties of cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots were characterized by X-ray power diffraction, transmission electron microscope, energy dispersive X-ray analysis, infrared spectrum, ultraviolet–visible absorption spectrum, and fluorescence spectrum. The results show that the spherical citrate-modified cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots with diameter around 3.6 nm belong to the cubic zinc blende structure. The citrate-modified cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots show a narrow, symmetric, and strong fluorescence emission spectrum band with narrow full width at half maximum of 53 nm, and the fluorescence quantum yield can reach up to 37.3%. The high-quality citrate-modified cadmium selenide/cadmium sulfide/zinc sulfide core/shell/shell quantum dots with good fluorescence properties have potential for application in biological fluorescence analysis.     

一步可控合成二氧化硅纳米管和空心球

通过简单的溶胶凝胶法在相同体系中可控合成了新颖有序的二氧化硅纳米管和空心球,对制备二氧化硅纳米管的多种反应条件进行了系统研究。发现反应时间、溶液中水和乙醇比例、搅拌和滴加速度对形成管状结构都有着重要影响。同时,纳米管的形成机理研究表明,在醇水混合溶液中柠檬酸三铵晶体为细柱状形貌,其作为重要的结构导向剂为二氧化硅胶晶附着提供模板,从而形成管状结构,二氧化硅空心球也显示了相似的形成过程。     

The effect of triethyl citrate on the dispersibility and water vapor sorption behavior of polylactic acid/zeolite composites

The aim of this study was to investigate the water vapor adsorption behavior and mechanical properties of poly (lactic acid) (PLA)/zeolite (5, 10, or 15 phr) composites prepared with triethyl citrate (TEC; 20 phr) via a melting process. TEC was used to improve the flexibility of the PLA and the dispersibility of the zeolite in TEC-zeolite suspensions that were ultra-sonicated. It was found that zeolite was uniformly dispersed in the PLA matrix, and the interfacial adhesion between the PLA matrix and zeolite was enhanced by TEC. In addition, the tensile strengths and Young's modulus of the composites improved with increasing zeolite content. The PLA/zeolite composites prepared with TEC had increased water vapor permeability and contact angles compared to neat PLA and standard PLA/zeolite due to the presence of TEC. In particular, TEC accelerated the hydrolysis of the PLA surface in a high humidity environment, resulting in an improvement in water vapor sorption capacity. At the same zeolite content of 15 phr, the equilibrium moisture content (EMC) values of PLA/zeolite films prepared with TEC increased by up to 39.25 mg/g whereas those prepared without TEC only increased by up to 24.33 mg/g. The results suggest the possibility of applying PLA/zeolite films prepared with TEC as a flexible active packaging material.     

低浓度部分水解聚丙烯酰胺/柠檬酸铝交联体系剪切稳定性研究

采用粘度法、核孔膜过滤和动态光散射(DLS)法,研究了高分子量低浓度的部分水解聚丙烯酰胺(HPAM)与柠檬酸铝(AlCit)反应所形成的交联体系的剪切稳定性和HPAM剪切降解后与AlCit反应所形成的体系的封堵性能及降解机理.研究结果表明,低浓度的HPAM与AlCit反应所形成的交联聚合物体系随剪切速率增加,其对1.2μm的核孔膜的封堵能力降低.HPAM稀溶液剪切降解后再与AlCit反应,低剪切速率对其封堵性能影响较小,而高剪切速率会使得其封堵性能大大降低.HPAM/AlCit交联体系和HPAM剪切降解后形成的交联体系的封堵性能下降的原因是HPAM/AlCit交联体系中交联聚合物线团(LPC)尺寸和HPAM中高分子线团的尺寸变小.     

Preparation of heterogeneous catalysts

The preparation of heterogeneous catalysts has been for many years a dynamic field of sub-nanotechnology and remains so nowadays. The approach to preparation must be examined in function of the specific demands concerning (i) activity and (ii) selectivity, that both depend on the arrangement of atoms at a scale smaller than 0.02 nm. Adequate access of reactants to the surface must be provided. Most catalysts are used in the form of pellets or cylinders obtained by pressing, extrusion or other techniques. This implies a control of texture at dimension scales extending from a fraction of a nanometer to several millimetres (and sometimes more). A third demand (iii) is resistance to ageing. In particular, stability at relatively high temperatures is necessary.The strategy adopted in the majority of cases is to start from a material that is homogeneous in composition at the Angström scale, generally a liquid or a solid of complex composition, frequently amorphous. A general objective is to locate the different constituting atoms at precise positions. The main difficulty is to transform the starting precursor into a highly porous solid without segregation of different elements that would produce tiny parts with different properties.The specific approach to catalyst preparation is based on the general concepts used for controlling the reactivity of solids. Typical methods of general use will be examined. Chemical bonds of practically any kind can retain the elements constituting the future catalyst at the position they have in the precursor. The so-called ‘citrate process’ and its variants are of wide application. More elaborate approaches start from molecules or polymers associating the necessary elements.     

高效液相色谱法测定枸橼酸他莫昔芬片的含量

An RP-HPLC method for the quantitative determination of contents of tamoxifeni citrate tablets was devel-oped.The operating conditions are as follows:CN column,250mm×4.6mm;mobile phase:mixture of methanol-water-glacial acetic acid-sodium heptyl sulfonate(340:160:1: 0.5);internal standard,trimethoprim;detectionwaveiength,254nm;and flow rate,0.6mL/min,Coefficient of variaion was1.1%,This method is simple and re-liable.     

光度法测定枸橼酸西地那非及尿中西地那非的含量

枸橼酸西地那非(Sildenafil citrate)商品名为万艾可(Viagra),是治疗男性性功能障碍药。目前测定西地那非含量的方法主要是HPLC,操作繁琐,仪器昂贵。本文在pH2．5-4．7的酸性介质中,发现乙基曙红(EE)与西地那非(SD)反应后,生成红色离子缔合物,其最大显色波长和最大褪色波长分别为550nm和520nm,表观摩尔吸光     

改性层状双氢氧化物对铜离子(Ⅱ)和双酚A的协同吸附

采用离子交换法制备了十二烷基苯磺酸根(DBS^-)和柠檬酸根(Cit^3-)复合改性层状双氢氧化物(LDHs),简写为DBS-Cit-LDHs。 利用粉末X射线衍射分析、红外光谱分析、比表面积测定以及元素分析等技术手段对样品进行了表征。 结果表明,DBS^-和Cit^3-已柱撑进入LDHs层间。 研究了DBS-Cit-LDHs对水中重金属离子Cu²⁺和有机污染物双酚A(BPA)的协同吸附性能。 吸附实验结果表明,DBS-Cit-LDHs能同时高效去除Cu²⁺和BPA;对Cu²⁺的强吸附能力缘于DBS-Cit-LDHs层间Cit^3-与Cu²⁺形成了稳定配合物;对BPA的强吸附能力缘于分配作用,且吸附能力与样品比表面积无关。 DBS-Cit-LDHs对Cu²⁺的吸附动力学和热力学分别符合准二级动力学方程和Freundlich等温式;对BPA的吸附分别符合准一级动力学方程和Linear等温式。 二者吸附过程的ΔG^o和ΔH^o均为负值,表明吸附为自发放热过程。