无模板剂条件下ZSM-5与丝光沸石之间的可控转晶

采用预晶化液添加法,即将高温(190oC)预晶化液添加到低温(150oC)晶化母液中合成沸石分子筛,考察了高温预晶化液的Na2O:SiO2比、预晶化时间以及低温晶化母液的Na2O:SiO2比对ZSM-5与丝光沸石之间转晶的影响,并采用X射线衍射和扫描电子显微镜对合成的产物进行了表征.研究发现,通过调节整体合成液的Na2O:SiO2比可有效控制ZSM-5沸石与丝光沸石之间的转晶.当整体合成液的组成为xNa2O:100SiO2:2.5Al2O3:12SO42?:4000H2O时,Na2O:SiO2=0.18是ZSM-5沸石和丝光沸石的一个分界线.通过调节母液的Na含量,使Na2O:SiO2>0.18时,高温预晶化过程中产生MFI结构的晶体在低温晶化时可向丝光沸石发生转晶;当Na2O:SiO2≤0.18时,具有MFI和丝光沸石结构共生的晶体在低温晶化时向MFI结构的ZSM-5沸石发生转晶.ZSM-5与丝光沸石之间转晶的前提条件是高温预晶化所形成晶体的结晶度不能太高(≤30%).另外,整体合成液中Na2O含量对生成晶体的形貌也有影响.     

含氟复合模板剂体系对Hβ沸石酸性的影响

 采用XRD,NH3-TPD,FT-IR和MAS NMR等表征技术和甲醇脱水探针反应研究了含氟复合模板剂体系对Hβ沸石酸性的影响. 与单四乙基溴化铵模板剂体系相比,含氟复合模板剂中的氟离子使铝更易于进入β沸石骨架,提高了沸石的总酸量、B酸/L酸比及强酸/弱酸比,使沸石表现出强的B酸酸性.     

ZSM—35,ZSM—5及丝光沸石中模板分子TMEDA质子化的研究

用＾１３Ｃ魔角固体核磁共振及化学分析研究处在高硅沸石ＺＳＭ－３５、ＺＳＭ－５及丝光沸石孔道中模板分子四甲基乙撑二胺（ＴＭＥＤＡ）的质子化。＾１３Ｃ核磁共振谱中δ＝３４～３７ｐｐｍ的共振峰可归属于单端质子化的模板分子。它们有序地分布在上述沸石的主孔道中。质子告近－ＣＨ３基团，远离－Ｃ２Ｈ４－基团。     

模板分子TMEDA成CF—3及ZSM—39沸石笼中的位置及其与骨…

用ＸＲＤ、ＦＴＩＲ、ＴＧ－ＤＴＡ、＾１３Ｃ魔角固体核磁共振表征用四甲基乙基二胺（ＴＭＥＤＡ）为结构异向剂合成的高硅沸石ＣＦ－３及ＺＳＭ－３９．ＴＭＥＤＡ不同基团的＾１３Ｃ化学位移，共振峰相对强度在交叉极化（ＣＰ）及高功率去偶（ＨＰＤＥＣ）核磁共振谱中的变化，揭示出模板分子在尺寸不同的沸石笼中的位置、运动状态及其与骨架的相互作用。在ＺＳＭ－３９沸石中的ＴＭＥＤＡ分子，它的－Ｃ２Ｈ４－基团＾１３Ｃ共振     

纳米氧化锌及负载沸石的抗菌性能研究

霉变是引起饲料变质的主要因素.目前已知污染饲料的产毒霉菌约100多种,可产生200多种霉菌毒素,其中,黄曲霉菌产生的有毒代谢物黄曲霉毒素（AFT）已成为世界很多地区的主要问题.实践证明,最有效的办法之一是在饲料中添加防霉物质即防霉剂.丙酸盐对于霉菌、酵母菌及细菌具有广泛的抗菌作用,尤其是对黄曲霉等抑制作用比山梨酸钾和苯甲酸钠盐都要强得多,生产成本又较低.因此,早在五、六十年代就已被大多数发达国家作为最重要、最广泛的食品防腐剂使用.但是丙酸受热损失大,不适合制粒,挥发快,防霉持续期比较短,易受钙盐中和而造成活力损失.丙酸腐蚀性强,有刺激性气味,也影响饲料适口性,而且饲料需要在一定的酸性条件下才能发挥防霉的功效[1].由此可见,丙酸类防霉剂有着很多的缺陷,亟待更替.     

层叠层技术组装纳米沸石--沸石涂饰纤维和沸石空心纤维

以纳米沸石为基元构件,通过层(layer-by-layer)组装技术在碳纤维模板上成功制备了纳米沸石涂饰纤维(zeolitecoatedfibers),焙烧除去碳纤维模板后,制微了完整的沸石空心纤维(hollowzeolitefibers),并系统研究了它们的制备条件和材料结构。发现纳米沸石胶体溶液的pH值是制备沸石涂饰纤维和空心沸石纤维的关键因素,其它条件,诸如吸附液的离子强度,每层吸附后的干燥以及每次干燥前是否用PDDA溶液预浸泡,对纤维的完美性也有影响。通过改变吸附纳米沸石的类型和层数可能调变沸石层的组成和厚度,而交替吸附不同的纳米沸石可能制备复合沸石涂饰纤维及复合空心沸石纤维。     

纤维素模板可控制备功能纳米材料的研究进展

作为自然界中最丰富的天然高分子材料,纤维素具备无毒无害、可再生、价格低廉和多层次空间结构等优点,被广泛应用在纺织、化学、可降解材料等领域。其中,纤维素特有的分子排列和多层次的空间结构,使其被广泛用作生物模板,进行可控制备功能纳米材料,纳米材料可以实现最大程度地复制出纤维素模板的纳米结构。本文综述了应用纤维素为模板,可控制备多种功能纳米材料（氧化物纳米材料、金属纳米材料、无机非金属复合纳米材料和其他无机纳米材料等）的最新进展,并展望了以纤维素模板可控制备功能纳米材料的未来研究方向。     

纳米沸石合成的影响因素

对影响纳米沸石合成的因素进行了综述.在合成体系中,通过加分散剂、分散介质、矿化剂、导向剂、晶种,减少碱金属离子,改善工艺条件等途径,可减小沸石的粒径,制备出粒径为纳米级的沸石.     

模板剂在沸石合成过程中的作用机理研究

通过分子模拟途径,对有机模板剂分子与沸石骨架间非成键互作用的能学分析 ,论证不同链长的双季铵盐[(CH3)3N(CH2)nN(CH3)3]2Br-在四种沸石（ZSM-50、ZSM-12、NU-87[HTK]和ZSM-23）合成中所起的模板作用。认为这种模板作用可用非成键互作用能定量表达;在一定程度上解释了Moini等人固定胶凝条件、实验考察以双季铵盐系列作为模板剂的合成结果。     

THF-FER沸石的系列研究—Ⅱ．模板剂分子THF的位置

用^13C HPDEC MAS NMR与热分析方法表征了在四氢呋喃（THF）-Na2O-SiO2- Al2O3-H2O体系中水热合成的高硅Na-THF-FER沸石、酸交换后的H-THF-FER沸石以及 吸附于Na-FER和H-FER沸石中的THF。结果证明,模板剂分子THF位于Na-THF-FER沸 石骨架的FER笼内,平衡骨架阳离子Na^+主要存在于十元环孔道;而吸附子FER沸石 中的THF仅处于十元环孔道中,合成样品中THF的化学位移与液态THF相比,向低场 移动,谱线明显变宽,表明THF分子与FER笼之间存在很强的相互作用。     

Diffusing wave spectroscopy investigations of acid milk gels containing pectin

The influence of the polysaccharide pectin on the gelation of acidified milk is studied in concentrated, undiluted, quiescent systems, primarily using diffusing wave spectroscopy. For pectins with a low degree of methylesterification (DM), interactions with milk-serum calcium yielded precipitated polysaccharide aggregates, even without acidification, that subsequently did not interact with casein micelles. However, high DM fine structures do not interact significantly with serum-calcium and absorb onto casein micelles as the pH is reduced below 5. A limited surface coverage of high DM pectin facilitates efficient bridging which enhances the rate of micelle aggregation and subsequent gelation and produces a clear signature in the shape of the measured MSD. The work highlights the fact that the behaviour of pectin in milk systems depends not only on the interaction of different polymeric fine structures with casein micelles, but also to a large extent on the interactions with calcium.     

Controllable synthesis and catalysis application of hierarchical PS/Au core-shell nanocomposites

Polystyrene (PS)/gold (Au) core-shell nanocomposites with tunable size, high stability, and excellent catalytic activity have been synthesized by a facile method that combines the ionic self-assembly with the in situ reduction. The composition and stoichiometry, as well as its morphology and optical properties of these nanocomposites have been examined and verified by various characterization techniques. The size and the coverage of gold nanoparticles (NPs) can be simply tailored by changing the amount of 3-aminopropyltrimethoxysilane (APTES), the functionalization time, the protonation time, and the amount of chloroauric acid (HAuCl₄). The continuous red shifts of the localized surface plasmon resonance absorption of the Au NPs on the PS spheres are observed. Importantly, the obtained Au NPs with controllable and uniform size on the surfaces of amino-functionalized PS spheres exhibit excellent size-dependent catalytic properties for the reduction of 4-nitrophenol (4-NP) by NaBH₄.     

Controllable synthesis and micelles preparation of tri-block copolymers from 2,2-dimethyl-trimethylene carbonate and ethylene glycol

Amphiphilic triblock copolymer of poly(2,2-dimethyl-trimethylene carbonate)–poly(ethylene glycol)–poly(2,2-dimethyl trimethylene carbonate) (PDTC–PEG–PDTC) was synthesized by dihydroxyl capped PEG with molecular weight of 1,000, 4,000, and 6,000 in the presence of rare earth tris(2,6-di-tert-butyl-4-methylphenolate)s. The rare earth phenolates/PEG system could prepare triblock copolymer with predictable molecular weights with narrow molecular weight distribution. The polymers were characterized by nuclear magnetic resonance spectroscopy, gel permeation chromotography, and differential scanning calorimetry to confirm the structure. The micelles formed from the amphiphilic triblock copolymer were determined by fluorescence spectrophotometer and dynamic light scattering. The critical micelle concentrations fell in the range of 1.67∼5.25 mg/L. Transmission electron microscopy pictures showed that the micelles possess spherical morphology, and the diameters of micelles in number averaged scale ranged from 20–70 nm. The micelles formed from triblock amphiphilic copolymers were explored as carrier for indomethacin (IND), and they could enhance IND solubility in water dramatically.     

Controllable design of Zn-Ni-P on g-C3N4 for efficient photocatalytic hydrogen production

Synthesizing a stable and efficient photocatalyst has been the most important research goal up to now. Owing to the dominant performance of g-C₃N₄ (graphitized carbonitride), an ordered assemble of a composite photocatalyst, Zn-Ni-P@g-C₃N₄, was successfully designed and controllably prepared for highly efficient photocatalytic H₂ evolution. The electron transport routes were successfully adjusted and the H₂ evolution was greatly improved. The maximum amount of H₂ evolved reached about 531.2 μmol for 5 h over Zn-Ni-P@g-C₃N₄ photocatalyst with a molar ratio of Zn to Ni of 1:3 under illumination of 5 W LED white light (wavelength 420 nm). The H₂ evolution rate was 54.7 times higher than that over pure g-C₃N₄. Moreover, no obvious reduction in the photocatalytic activity was observed even after 4 cycles of H₂ production for 5 h. This synergistically increased effect was confirmed through the results of characterizations such as XRD, TEM, SEM, XPS, N₂ adsorption, UV-vis DRS, transient photocurrent, FT-IR, transient fluorescence, and Mott-Schottky studies. These studies showed that the Zn-Ni-P nanoparticles modified on g-C₃N₄ provide more active sites and improve the efficiency of photogenerated charge separation. In addition, the possible mechanism of photocatalytic H₂ production is proposed.     

可控合成具有氧化还原分区的Au-TiO2纳米哑铃光催化剂（英文）

太阳能因其环保清洁和来源丰富的特性被认为是最理想的资源之一.而光催化水分解是将太阳能转化为化学能的众多转换技术中,使用最广泛的策略之一.但H2和O2的逆反应显著降低了光催化水分解的效率,并且在实际应用中需要高昂的气体分离成本.因此,找到一种既可实现光催化有效水分解,同时抑制逆反应的策略具有十分重要的意义.到目前为止,为了实现光生电荷的有效分离,构建一维(1D)异质纳米结构光催化剂,被认为是抑制逆反应最有效的策略之一.其中哑铃状纳米结构,如Au-SiO2,Au-Fe3O4,Cu1.94S-CuS,Au-PbS(PbSe),Cu-Ag,Ag-Fe3O4,在促进光生电荷有效分离方面具有很大优势.但关于上述哑铃状纳米结构材料合成条件相对复杂,生长机理尚不清楚.对此,我们通过一种简便的合成策略制备了Au纳米棒/TiO2纳米哑铃结构光催化剂(Au NRs/TiO2 NDs).TiO2纳米颗粒(NP)仅包裹在Au NRs的两端.由于其独特的结构,可以实现电子空穴的定向分离,并减少它们在光照射下的复合,从而显著地提高电荷分离效率.同时,形成了氧化和还原反应的空间分离区域,从而有效地抑制了逆反应.通过SEM,XRD,和UV-Vis研究了可控合成哑铃状结构形态的关键因素.发现反应温度和酸度对Au NRs末端TiO2的包裹量有显著影响.基于此,我们提出了Au NRs/TiO2 NDs结构光催化剂的合成机理.并且通过改变加入的NaHCO3含量精准调节TiO2在Au NRs两端的包覆量,从而逐步提高Au NRs/TiO2 NDs光催化剂的产氢活性.在不断优化条件下,H2产率可达60264μmol/g/h,大约是报道的Au/TiO2光催化剂6倍.而电化学测试结果显示,在UV光照射下,Au NRs末端TiO2的包裹量越大,光电流相应越大.进一步证明光生电子定向从TiO2注入到Au NRs中,发生还原反应,而空穴留在TiO2上,发生氧化反应,从而实现氧化还原反应的分区.     

Controllable synthesis and characterization of ammonium polyphosphate with crystalline form V by phosphoric acid process

Ammonium polyphosphate (APP) with crystalline form V (APP-V) was synthesized by heating a mixture of 85% food-grade phosphoric acid and melamine under dry ammonia atmosphere. Effects such as raw material ratios, charging methods, dehydration temperature, condensation temperature and condensation time were investigated. Its water solubility was tested, its XRD and FTIR were characterized and compared with those of industrial APP-I and APP-II. Results showed that the prepared APP-V was insoluble in water, its XRD spectrum was the same as APP-V in literature. The molecular structures of the prepared APP-V and APP-I/APP-II were speculated and discussed in detail.     

可控交联聚醚醚酮的合成与热性能研究

聚醚醚酮因其优异的综合性能 (耐热性、耐水解、耐辐射等 )在许多领域得到应用 [1～ 4 ] .但聚醚醚酮的玻璃化转变温度 ( Tg)较低 ( 4 2 6K) ,导致其使用温度较低 (在 5 1 3K以下 ) .为进一步提高聚芳醚酮类材料的使用温度 ,人们在聚醚醚酮主链中引入刚性结构 ,通过提高聚芳醚酮的刚性度来提高聚芳醚酮的熔点 ( Tm)及 Tg,从而提高材料的使用温度 [5,6 ] .文献 [7]中聚芳醚酮的 Tm 已经高达 741 K,但此材料很难加工成型 .通常热塑性材料具有优异的加工性能 ,但使用温度较低 .热固性材料的使用温度较高 ,但在加工固定尺寸形状铸件时存在困…     

Controllable fabrication of metal-confined carbon nanotubes from the self-templated conversion of supramolecular gel nanofibers

Nanostructured supramolecular gels with self-assembled fibrillar networks are promising candidates for fabricating advanced functional materials for energy-related applications. Several fundamental challenges, including poor structural stability and monotonous fibrous morphology, greatly hinder their practical applications. To the best of our knowledge, supramolecular gel-derived carbon nanotubes (CNTs) have not been reported in the literature. Herein, we present a unique strategy for controllable fabrication of metal-confined carbon nanotubes (M/CNT) from the self-templated conversion of guanosine-based supramolecular gel (GSMG) nanofibers. Benefitting from the high tunability of GSMGs, it was demonstrated that the introduction of metal source (Ni and Fe) to improve the stability of the material and simply changing the KOH concentrations in the precursor materials, the structure of GSMG nanofibers derived active materials was controllably tuned from metal-constrained solid carbon nanofiber to hollow M/CNT. The optimized NiFe/B, N-CNT showed a superior oxygen evolution reaction catalytic activity with a low overpotential of 355 mV at a current density of 10 mA cm^?2. By taking advantage of the unique structural features of supramolecular gels, this strategy provides a simple and effective synthetic route for functional CNT.     

分子识别在纳米材料组装中的应用

分子识别应用于纳米材料组装中的研究正受到人们的广泛关注,并逐渐成为超分子化学研究领域中的一个热点。本文对近年来利用分子识别实现纳米材料的组装及可控组装的研究工作进行了综述,并对该领域的研究前景进行了展望。     

Effects of Oxygen Limitation on Xylose Fermentation, Intracellular Metabolites, and Key Enzymes of Neurospora crassa AS3.1602

The effects of oxygen limitation on xylose fermentation of Neurospora crassa AS3.1602 were studied using batch cultures. The maximum yield of ethanol was 0.34 g/g at oxygen transfer rate (OTR) of 8.4 mmol/L·h. The maximum yield of xylitol was 0.33 g/g at OTR of 5.1 mmol/L·h. Oxygen limitation greatly affected mycelia growth and xylitol and ethanol productions. The specific growth rate (μ) decreased 82% from 0.045 to 0.008 h⁻¹ when OTR changed from 12.6 to 8.4 mmol/L·h. Intracellular metabolites of the pentose phosphate pathway, glycolysis, and tricarboxylic acid cycle were determined at various OTRs. Concentrations of most intracellular metabolites decreased with the increase in oxygen limitation. Intracellular enzyme activities of xylose reductase, xylitol dehydrogenase, and xylulokinase, the first three enzymes in xylose metabolic pathway, decreased with the increase in oxygen limitation, resulting in the decreased xylose uptake rate. Under all tested conditions, transaldolase and transketolase activities always maintained at low levels, indicating a great control on xylose metabolism. The enzyme of glucose-6-phosphate dehydrogenase played a major role in NADPH regeneration, and its activity decreased remarkably with the increase in oxygen limitation.