Comparative study of sol-gel-hydrothermal and sol-gel synthesis of titania-silica composite nanoparticles

Titania-silica composite nanoparticles were prepared by sol-gel-hydrothermal and sol-gel routes, respectively, and their physico-chemical and photocatalytic properties were compared. The results of XRD, TEM and BET surface areas showed that sol-gel-hydrothermal route led to anatase titania-silica composite nanoparticles with large specific surface area, but the sol-gel route tended to form mixture of anatase and rutile. The composite nanoparticles prepared by sol-gel-hydrothermal route had better thermal stability against phase transformation from anatase to rutile, agglomeration and particle growth than those prepared by sol-gel route. On the basis of XRD, FT-IR, XPS and ²⁹Si MAS-NMR, a strong interaction was found between SiO₂ and TiO₂, and Ti-O-Si bonds formed during both the two routes. But more Ti-O-Si bonds formed in the composite nanoparticles prepared by sol-gel-hydrothermal route than those prepared by sol-gel route. As a result, the titania-silica composite nanoparticles prepared by sol-gel-hydrothermal route exhibited higher photocatalytic activity in decomposition of methylene blue than that prepared by sol-gel route, and it had excellent photocatalytic activity even after calcined at 1000 °C.     

A practical, enantioselective synthetic route to a key precursor to the tetracycline antibiotics

A practical, enantioselective synthetic route to a key precursor to the tetracycline antibiotics is reported. The route proceeds in nine steps (21% yield) from the commercial substance methyl 3-hydroxy-5-isoxazolecarboxylate. Key steps in the route involve enantioselective addition of divinylzinc to 3-benzyloxy-5-isoxazolecarboxaldehyde and an endo-selective intramolecular furan Diels-Alder cycloaddition reaction. The route described has provided more than 40 g of chromatographically pure 1 with 93% ee.     

Linear total synthetic routes to beta-D-C-(1,6)-linked oligoglucoses and oligogalactoses up to pentaoses by iterative Wittig olefination assembly

Two complementary routes, A and B, have been followed for the stepwise iterative assembly of beta-D-(1,6)-glucopyranose and galactopyranose residues through methylene bridges. In route A the building block was constituted by 2,3,4-tri-O-benzyl-6-O-tert-butyldiphenylsilyl (O-TBDPS) beta-linked galactosylmethylenephosphorane, while in route B the building block was a beta-linked formyl C-glycopyranoside with a similar orthogonal protection of hydroxy groups. In route A each cycle consisted of the reaction of the phosphorane building block with a sugar residue bearing a formyl group at the C-5 carbon atom (coupling) and transformation of the O-TBDPS-protected primary alcohol into the formyl group (arming). Accordingly, route A is defined as the aldehyde route. On the other hand, each cycle in route B involved the coupling of the sugar aldehyde building block with a substrate bearing a phosphorus ylide at C-6 and introduction of the phosphonium group in the arming step as a precursor of the ylide functionality. Accordingly, route B is defined as the ylide route. The efficiency of route A proved to be seriously hampered by the 1,2-elimination of BnOH under the basic reaction conditions of the Wittig olefination, giving rise to the formation of substantial amounts of enopyranose. On the other hand, the ylide route B proved to be more efficient since very good yields (70-93%) of the isolated Wittig products were obtained throughout four consecutive cycles. Individual olefins and polyolefins obtained by routes A and B using gluco and galacto substrates were reduced and debenzylated in one pot by H(2)/Pd(OH)(2) to give the corresponding beta-D-C-(1,6)-linked oligosaccharides up to the pentaose stage. The latter compounds were fully characterized by high-field NMR spectroscopy (500 MHz).     

奥斯米韦合成进展

在综述神经氨酸酶抑制剂发展现状的基础上, 重点介绍了奥斯米韦的合成研究进展: 以(−)-奎尼酸、(−)-莽草酸、D-甘露糖和由苯及其衍生物为原料合成奥斯米韦的方法; 烯类化合物经Diels-Alder 反应合成奥斯米韦的方法.     

A convenient new and efficient commercial synthetic route for dasatinib (Sprycel®)

A new and efficient synthetic route for dual-Src/Abl kinase inhibitor dasatinib (Sprycel®), an anticancer drug, is described. This commercially viable process yields dasatinib monohydrate free of potential impurities with consistent yield of 68% in route A and 61% in route B with HPLC purity >99.80% over four stages.     

Measurement of cosmic radiation dose to air crew connecting for a typical polar route flight

In order to compare cosmic radiation dose for air crew including pilot and flight attendant between polar route flight and non-polar route flight, a typical polar flight route that is from Beijing to New York was selected and compared with non-polar route. Optically stimulated luminescence dosimeter and track etch detector CR-39 were worn as personal dosimeters to measure the cosmic radiation dose to air crew. The mean annual effective dose for air crew from polar route and non-polar route was (5.79 ± 0.92) mSv/year and (2.14 ± 0.64) mSv/year, respectively. The effective dose per 1,000 flight hours for air crew was (3.10 ± 0.27) mSv/1,000 h and (2.21 ± 0.46) mSv/1,000 h, respectively. The result is analyzed by using SPSS 15.0 statistical software. There was significant difference between the two groups for both mean annual effective dose (t = 30.25, P < 0.05) and the effective dose per 1,000 flight hours (t = 7.60, P < 0.05). The dose to pilot was higher than that of flight attendant for both polar route and non-polar route, and there was significant difference between them, for polar route (t = 7.96, P < 0.05), for non-polar route (t = 4.70, P < 0.05). The effective dose from cosmic radiation to air crew of polar route was higher than that of non-polar route, however, it did not exceed 20 mSv/year, which is the limit on cosmic radiation exposure set by many countries in the world.     

Synthesis of Stimuli-responsive Nanoparticles by Solution Polymerization

In this study, stimuli-responsive nanoparticles were prepared by solution polymerization. Two synthesis routes are proposed to synthesize the particles, the monomer route and the polymer/monomer route. For the monomer route, pH and thermal sensitive nanoparticles were synthesized from acrylic acid and N-isopropylacrylamide. For the polymer/monomer route, the pH sensitive nanoparticles were synthesized from chitosan and acrylic acid. The effect of reaction time, initiator concentration and agitation rate on the particle size and the size distribution were investigated. The stimuli-responsive nanoparticles could be directly blended with other polymers to prepare stimuli-responsive functional membranes.     

Self-assembled monolayer and multilayer films of the nanocluster [HxPMo12O40 subsetH4Mo72Fe30(O2CMe)15O254(H2O)68] on gold

Films of the molybdenum-iron nanocluster [H x PMo 12O 40 subsetH 4Mo 72Fe 30(O 2CMe) 15O 254(H2O) 68] (FeMoC) were generated on gold via the self-assembly technique using two divergent routes. The first route entails the self-assembly of unfunctionalized FeMoC onto a preprepared carboxyl-terminated SAM on gold. The second route involves the preparation of thiol-terminated functionalized FeMoC clusters, which are then allowed to self-assemble onto bare gold surfaces. Monolayer films of FeMoC clusters are attained via both routes, with the second route requiring shorter immersion times (2 days) than the first route (6 days). Multilayer films of FeMoC are formed via the second route for immersion times longer than 2 days. Characterization of these films using optical ellipsometry, X-ray photoelectron spectroscopy, and atomic force microscopy confirm the self-assembly of the clusters on the surfaces.     

A comparative study of microstructural development in the sol–gel derived alumina–mullite nanocomposites using colloidal silica and tetraethyl orthosilicate

This paper compares the microstructure development of two alumina–15 vol% mullite composites during the sintering. The nanopowders of alumina–mullite composite were synthesized by the sol–gel method using aluminum chloride hexahydrate and two different silicon sources (colloidal silica in route 1 and tetraethyl orthosilicate in route 2). The alumina–mullite composites were prepared by pressing and sintering of the nanopowders. Although the intergranular mullites were observed in both routes, there were mullite particles in route 2 formed inside the alumina grains (intragranular mullite). Formation of the intragranular mullite is attributed to the drop in silica solubility, which occurs during the transition from metastable alumina to stable alumina. Compared to route 1, the relative density and the average grain size were increased and accelerated by route 2. The two-stage sintering is not useful for the mullite decomposition.     

Tuning rheochaos by temperature in wormlike micelles

We investigate the critical role played by the mean micellar length during the route to rheochaos for wormlike micellar gels of surfactant cetyltrimethylammonium tosylate in the presence of salt sodium chloride that show coupling of flow to concentration fluctuations. To this end, we have carried out stress/shear rate relaxation experiments at a fixed shear rate/stress but at different temperatures to take the sample through the route to rheochaos. We see the type-II intermittency route to rheochaos in stress relaxation measurements and the type-III intermittency route to rheochaos in shear rate relaxation measurements. We have also carried out linear rheology measurements at different temperatures to estimate the mean micellar length (-)L, the reptation time tau(rep), and the breaking time tau(break). It is shown that (-)L changes by approximately 58%, as the sample goes through the route to rheochaos.     

Total syntheses of bupleurynol and its analog

An efficient route to the natural products bupleurynol and its analog (RB-2), isolated from Bupleuri Radix, was established based on versatile intermediate (15). In this synthetic route, Sonogashira and Cadiot-Chodkiewicz coupling as well as Julia-Kocienski olefination are utilized as key steps. The highly efficient synthetic route provides opportunities to explore the biological behavior of bupleurynol and RB-2.     

氢氧混合体系下Ag／TS－1催化剂上丙烯的高效环氧化反应

 在氢氧混合体系中，沉积-沉淀法制备的Ag/TS-1催化剂对丙烯环氧化反应具有高的催化活性和选择性。本文主要考察了载体TS-1的硅钛比和反应温度对催化剂性能的影响。结果表明：当载体TS-1硅钛比为64，反应温度150℃时，2wt%Ag/TS-1催化剂表现出优异的催化性能，丙烯转化率和环氧丙烷选择性可分别达1.37%和93.51%。     

间叔丁基苯乙醚的合成研究

通过两条路线合成了生产新型农药乙螨唑的关键中间体间叔丁基苯乙醚。其一以叔丁基苯为原料,通过溴代、硝化、还原(脱卤素)、重氮化和乙醚化反应得到目标化合物;另一采用对氨基叔丁基苯为原料,通过乙酰化、溴代、脱乙酰化、重氮化去氨基和乙醚化反应得到目标化合物。两条路线的总收率都较高,分别为45%和63%。所得产品中未检测到异构体对叔丁基苯乙醚,质量好,纯度高。其中路线一原料便宜,操作简单,更适合进一步工业化放大生产。合成路线中的有机中间体和目标化合物的化学结构通过MS和NMR进行确证。     

六方相NaYF4:Yb/Er纳米晶制备方法研究进展

综述了六方相NaYF4:Yb/Er纳米晶的制备方法,着重总结了三氟乙酸盐热分解法、共沉淀法、碳酸盐热分解法、离子热法、水热法及两步法的研究进展,并就其发展前景进行了展望.     

Self-catalytic solution for single-crystal nanowire and nanotube growth

Vast majority of nanowires is grown by the chemical vapor deposition (CVD), molecular beam epitaxy (MBE), metal-organic CVD (MOCVD), or the laser ablation method via the vapor-liquid-solid (VLS) route. Others are grown via the oxide-assisted route. In this investigation a self-catalytic synthesis route based on VLS formalism and suitable for the CVD, MBE, MOCVD, or the laser ablation method has been described. Various issues pertaining to growth kinetics, nanowire alignment, diameter distribution, and nanotube formation have been addressed. The strength of the self-catalytic route has been highlighted. As this route does not make use of foreign element catalytic agents to mediate the synthesis, it suffers from difficulties. Attempts have been made to elucidate means to overcome these difficulties. Attempts have also been made to explain the means to separate the nanowires thus produced from the substrate/scaffold, and to control their physicochemical characteristics.     

介孔金属氧化物/复合物的合成方法

介孔金属氧化物及其复合物由于其特有的组成与结构, 在催化、传感、光、电、磁等领域有着广泛的应用, 是近年来国内外跨学科领域研究的热点。本文对近几年来介孔金属氧化物及其复合物的合成方法进行了归纳总结, 其合成途径大致可以分为软模板法、硬模板法及纳米晶粒组装法。     

A stereoselective synthesis of digitoxin and digitoxigen mono- and bisdigitoxoside from digitoxigenin via a palladium-catalyzed glycosylation

A convergent and stereocontrolled route to trisaccharide natural product digitoxin has been developed. The route is amenable to the preparation of both the digitoxigen mono- and bisdigitoxoside. This route featured the iterative application of the palladium-catalyzed glycosylation reaction, reductive 1,3-transposition, diastereoselective dihydroxylation, and regioselective protection. The natural product digitoxin was fashioned in 15 steps starting from digitoxigenin 2 and pyranone 8a or 18 steps from achiral acylfuran.     

A Facile Route to Metal Nitride Clusterfullerenes by Using Guanidinium Salts: A Selective Organic Solid as the Nitrogen Source

Using guanidinium salts 1 and 2 as the new nitrogen sources, metal nitride clusterfullerenes (NCFs) based on a variety of metals (Dy, Sc, Y, Gd, Lu, and mixed metals Sc/Dy, Sc/Gd, Sc/Lu, and Lu/Ce) have been synthesized based on a new “selective organic solid” (SOS) route. The synthesis of Dy‐NCFs by using Dy/ 1 was studied in detail, and the optimum molar ratio of 1 /Dy/C has been determined to be 2.5:1:10. For several representative metals such as Sc, Y, Gd, Dy, and Sc/Dy, we quantitatively compared the yield of M₃N@C₈₀ synthesized by the SOS route with the reported “reactive gas atmosphere” route, thereby indicating that the yield of M₃N@C₈₀ by using 1 could be comparable to that obtained by the reactive gas atmosphere route. Three other nitrogen sources ( 3 – 5 ) were also studied for comparison, which were mixed with Dy metal but did not result in the formation of Dy‐NCF. A possible reaction scheme for the solid‐state reaction of 1 , metal, and graphite is proposed. The SOS route appears to be a general route for the synthesis of NCFs that promises both high selectivity of NCFs and high reproducibility of the fullerene yield. Another advantages of the SOS route compared to the reported “trimetallic nitride template” (TNT) process and the reactive gas atmosphere route is that no additional heating pretreatment is needed, thus simplifying the procedure and being much more facile.     

Development of a scalable synthetic route towards a 2,2,6-trisubstituted chiral morpholine via stereoselective hydroalkoxylation

A scalable synthetic route towards a chiral 2,2,6-trisubstituted chiral morpholine, which is a known opioid antagonist, was developed. The synthetic route involves incorporating an aryl group via Suzuki-Miyaura coupling and stereoselective hydroalkoxylation catalyzed by trifluoromethanesulfonic acid. Late stage incorporation of both the aryl and N-alkyl groups make this route suitable for further SAR studies on this molecule.     

Structural effects of dopants and polymerization methodologies on the solid‐state ordering and morphology of polyaniline

The solid‐state three‐dimensional ordering of polyaniline–dopant complexes was investigated with four structurally different sulfonic acid dopants. The doped materials were produced in three different ways: polyaniline emeraldine base doped with sulfonic acid (aqueous route), in situ polymerization at the organic–water solvent interface (interfacial route), and in situ polymerization in organic and aqueous solvent mixtures (bilayer route). p‐Toluenesulfonic acid (PTSA), 5‐sulfosalicilic acid (SSA), camphorsulfonic acid (CSA), and dodecylbenzene sulfonic acid (DBSA) were employed as dopants. The conductivity of the aqueous‐route samples showed 10 and 100 times higher conductivity than the interfacial and bilayer routes, respectively. WXRD studies suggested that the crystallinity of the doped samples was dependent on both the structure of the dopants and the polymerization techniques. DBSA increases the polyaniline interplanar distance and produced highly crystalline materials via the aqueous and bilayer routes but failed with the interfacial route because of poor solubility in water. CSA, PTSA, and SSA produced highly crystalline samples by the interfacial route but failed with the aqueous (except for CSA) and bilayer routes. SEM analysis revealed that the doped materials of the interfacial route had excellent continuous morphology and uniform submicrometer‐size particle distributions in comparison with those of the aqueous and bilayer routes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1321–1331, 2005