球形SnO2 纳米微粒的合成及形成机理分析

以SnCl4·5H2 O为主要原料 ,用溶剂热技术在油酸体系中成功地合成了球形SnO2 纳米微粒 ,在无水乙醇体系中合成了菱形的SnO2 纳米微粒 .通过X射线粉末衍射 (XRD) ,选区电子衍射 (SAED)和透射电镜 (TEM )对两种产物进行了表征 ,并对两种产物的形成机理进行了分析 .透射电镜 (TEM)结果表明 :在油酸体系中得到了平均尺寸约为 3.5nm的球形SnO2 纳米微粒 ,此微粒趋向于特殊高的比表面积 ,适合于作气敏探测器材料方面的应用     

The first entry to pyrrolo[2,3-c]quinoline-2,4(3aH,5H)-diones

Wittig olefination of 3-aminoquinoline-2,4(1H,3H)-diones 1 with ethyl (triphenylphosphoranylidene)acetate (Ph₃PCHCO₂Et) afforded (E)-3-amino-4-ethoxycarbonylmethylene-1,2,3,4-tetrahydro-2-quinolones (E)-2 and pyrrolo[2,3-c]quinoline-2,4(3aH,5H)-diones 3. An alternative approach for the synthesis of 3 via 3-bromoacetamidoquinoline-2,4(1H,3H)-diones 7, their corresponding triphenylphosphonium salts 8, and ylides A that undergo intramolecular Wittig reaction, was investigated. Under the applied reaction conditions, the phosphonium salts 8 and ylides A are so unstable that they partly decompose to 3-acetamidoquinoline-2,4(1H,3H)-diones 9 during the synthesis of 3.     

Degradation of electrospun SF/P(LLA-CL) blended nanofibrous scaffolds in vitro

Nanofibrous scaffolds of silk fibroin (SF) and poly(l-lactic acid-co-?-caprolactone) (P(LLA-CL)) blends fabricated via electrospinning possessed good mechanical property and biocompatibility, as demonstrated by a previous study in vitro. However, the degradation behavior of the scaffolds, which may significantly influence tissue repair and regeneration, needs further exploration. In this study, in vitro degradation of pure SF, P(LLA-CL) and SF/P(LLA-CL) blended nanofibrous scaffolds were performed in phosphate-buffered saline (PBS, pH 7.4 ± 0.1) at 37 °C for 6 months. A series of analyses and characterizations (including morphologic changes, loss weight, pH changes of PBS solutions, DSC, XRD and FTIR-ATR) were conducted to the nanofibrous scaffolds after degradation and the results showed that the pure SF nanofibrous scaffolds were not completely degradable in PBS while pure P(LLA-CL) nanofibrous scaffolds had the fastest degradation rate. Moreover, the addition of SF reduced the degradation rate of P(LLA-CL) in SF/P(LLA-CL) blended nanofibrous scaffolds. This was probably caused by the intermolecular interactions between SF and P(LLA-CL), which hindered the movement of P(LLA-CL) molecular chains.     

Nanostructure of montmorillonite barrier layers: A new insight into the mechanism of flammability reduction in polymer nanocomposites

This study describes the mechanism of flammability reduction in flame-retarded polymer matrix organo-montmorillonite reinforced nanocomposites. Morphologies of untested polymer nanocomposites and char residues formed by combustion in the mass loss calorimeter are characterized by XRD and TEM techniques. It is postulated that a combination of well-dispersed montmorillonite platelets and flame retardants in the polymer matrix provides nano-structured char formation. Initial montmorillonite dispersion in flame-retarded nanocomposites is found to be a major controlling factor on formed char nanostructures. An initially intercalated structure is invariantly converted to complete montmorillonite collapse whereas an initially exfoliated structure transforms to nano-structured chars demonstrating retained exfoliation or a new state of intercalation via incomplete collapse of montmorillonite layers. It is proposed that nano-structured char formation is the effective mechanism of flammability reduction, i.e. reduction in rate of heat release during combustion, in flame-retarded polymer nanocomposites.     

磁性AgBr/Ag3PO4/ZnFe2O4复合催化剂的制备及光催化性能

水热法结合原位沉淀法成功制备新型磁性溴化银/磷酸银/铁酸锌(AgBr/Ag₃PO₄/ZnFe₂O₄)复合催化剂,并通过X射线衍射、能量色散X射线、场发射扫描电子显微镜、透射电子显微镜和紫外-可见漫反射光谱对其晶相结构、组成、形貌及吸光性能进行了表征。在可见光照射下,所制备的AgBr/Ag₃PO₄/ZnFe₂O₄复合催化剂光催化降解罗丹明B (RhB)的活性优于Ag3PO4/ZnFe₂O₄、AgBr/ZnFe₂O₄和P25 TiO₂。在酸性和碱性溶液中,AgBr/Ag₃PO₄/ZnFe₂O₄光催化剂呈现出优良光催化性能。在AgBr/Ag₃PO₄/ZnFe₂O₄体系中,光催化降解RhB的速率随着反应体系温度的升高而增大,由阿伦尼乌斯方程计算获得反应体系活化能为31.9 kJ·mol^-1。AgBr/Ag₃PO₄/ZnFe₂O₄复合材料优异的可见光催化活性归因于光生电荷的有效分离,所产生的超氧自由基和空穴是RhB降解的主要活性物种。     

甲磺酸帕珠沙星的热分解机理及动力学

采用热重(TG)和差示扫描量热(DSC)法测定了甲磺酸帕珠沙星(PZFX)在氮气氛和空气氛中的热分解过程,测定了PZFX及其在热分解过程中不同阶段残余物的红外光谱,运用量子化学GAMESS软件计算了PZFX分子的键级,推断了PZFX的热分解机理.结果表明PZFX的热分解过程的起始步骤是甲磺酸的分解.采用Ozawa方法计...     

Microbial desulfurization of waste latex rubber with Alicyclobacillus sp.

A microbe with desulfurizing capability, Alicyclobacillus sp., was selected to recycle waste latex rubber (WLR). The growth characteristics of the microorganism and the technical conditions in the co-culture desulfurization process were studied. The desulfurization effect of Alicyclobacillus sp. on the WLR was characterized, and the mechanism for the microbial desulfurization of WLR was tentatively explored. The results showed that adding 5% (w/v) WLR into medium had little effect on the growth of Alicyclobacillus sp. The surfactant polysorbate 80 (Tween 80) had a toxic effect on Alicyclobacillus sp., but the growth of the microbe was vigorous if the proper technique was used: the mixing of WLR with Tween 80, followed by the addition of the mixture into the culture media. With the increase of desulfurization time, the swelling value of desulfurizated waste latex rubber (DWLR) increased, but the crosslink density decreased. After co-culture desulfurization for 8–10 days, a DWLR with good desulfurization effect was obtained. The mechanical properties of natural rubber (NR)/DWLR composite improved significantly over those of NR/WLR composite. XPS and FTIR results revealed that Alicyclobacillus sp. could break the crosslinked sulfur bonds and oxidize them to sulfones groups. The increase of O element content on the surface of DWLR was confirmed by water contact angle measurements. The relationship between the crosslink density and sol fraction of DWLR with different desulfurization times agreed with the Horikx equation, an indication that the microorganisms could break the crosslinked sulfur bonds on the surface of WLR, but leaving the main chains intact.     

A DFT study of the Huisgen 1,3-dipolar cycloaddition between hindered thiocarbonyl ylides and tetracyanoethylene

The mechanism for the 1,3-dipolar cycloaddition between the hindered thiocarbonyl ylide 1 and tetracyanoethylene 2 has been studied at the B3LYP/6-31G^∗ level. Formation of the [3+2] cycloadduct 4 takes place through a stepwise mechanism that is initiated by the nucleophilic attack of the thiocarbonyl ylide 1 to the ethylene derivative 2 to give a zwitterionic intermediate IN. The subsequent cyclization of IN yields a seven-membered cyclic ketene imine 6, which equilibrates with the thermodynamically more stable [3+2] cycloadduct 4. The computed free energies are in agreement with the experimental outcomes.     

Formation of α-Mn2O3 nanorods via a hydrothermal-assisted cleavage-decomposition mechanism

A hydrothermal cleavage-decomposition mechanism was used to synthesize single-crystal α-Mn₂O₃ nanorods at 160 °C for 16 h using KMnO₄ as manganese source and CTAB as reducing regent. The as-synthesized products were characterized by powder X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and infrared spectrum. The results indicate that the reaction temperature is a crucial factor for the formation of α-Mn₂O₃ nanorods. These nanorods exhibit single-crystal nature, and have an average diameter of 36 nm and lengths of up to 1 μm. Based on our experimental results, a hydrothermal cleavage-decomposition mechanism has been proposed on the formation of α-Mn₂O₃ nanorods.     

甲壳素和壳聚糖的接枝共聚改性

天然高分子甲壳素、壳聚糖由于分子链上大量存在的反应性官能团 ,易于通过自由基引发与乙烯基单体接枝共聚 ,也可与其它高分子链偶合制得接枝共聚物。通过接枝共聚改性 ,可以赋予甲壳素和壳聚糖以某些新的性能 ,扩大了其应用范围。本文对甲壳素、壳聚糖的接枝共聚改性反应进展、机理以及产物的性能等进行了介绍