具有双亲特性的水相哑铃型SiO2纳米粒子的制备

以纳米SiO2水溶胶为原料,3?氨丙基三乙氧基硅烷(APTES)和3?氯丙基三乙氧基硅烷(CPTES)为改性剂,在水基环境下分别对SiO2纳米粒子进行改性,得到了具有亲水特性的APTES改性SiO2粒子和具有亲油特性的CPTES改性SiO2粒子水溶胶。2种粒子按不同比例混合,利用接枝在SiO2粒子表面氨基和氯丙基的取代反应,使得2种具有亲水/亲油特性的改性SiO2纳米粒子偶联,制备了粒径为40~50 nm的哑铃型SiO2纳米粒子。并通过透射电镜(TEM)、傅里叶变换红外光谱(FT?IR)、X射线光电子能谱(XPS)以及动态光散射(DLS)等方法对其进行了系统表征。结果表明,2种粒子成功偶联形成了具有哑铃型结构的水相SiO2纳米粒子,该粒子两面具有不同的亲水性,粒径近似等于APTES改性SiO2粒子和CPTES改性SiO2粒子的粒径之和。     

CuO/SiO2制备过程中吸附质相间分配比的调控及其对粒径影响的研究

吸附相反应过程中, 吸附层是反应的场所, 吸附质在吸附层和本体溶液中的分配对吸附层中的反应和粒子的形成、生长过程有重大影响. 通过定义相间分配比的概念, 研究了不同吸附质种类、不同温度和水量条件下吸附质相间分配比的变化规律. 采用XRD和TEM等手段考察了不同条件下制备所得样品的粒子大小、形貌等, 并与相间分配比的变化趋势相比较, 得到了相间分配比对粒径的调控规律. 研究发现不同吸附质在相间分配比上存在的差异导致了晶粒粒径的变化, Cu(OAc)₂的相间分配比大于NaOH的相间分配比, 因此以Cu(OAc)₂为吸附质制备得到的CuO粒子较小. 同时在常温(0～40 ℃)和低水量条件下时, 相间分配比的变化也是导致粒径变化的主要因素, 温度升高和水量增加均导致相间分配比变大进而导致粒径变小.     

In-Cu/SiO2催化剂用于醋酸甲酯加氢反应制乙醇

工业上常用玉米生产乙醇,从而造成粮食和燃料的选择两难局面.随着页岩气研究的不断深入以及全球可观的煤炭存量,用醋酸甲酯加氢制乙醇已引起广泛关注.铜基催化剂对酯加氢生成醇有高的转化率和选择性,其中铜铬催化剂性能较高,但铬对人体和环境的潜在危害限制了其广泛应用.Cu/SiO2催化剂价格低廉,环境友好,但其稳定性较差,容易失活不利于工业上应用.因此人们对Cu/SiO2催化剂进行改性.本文采用氨蒸法制备了一系列掺杂不同量氧化铟(In2O3)的Cu催化剂(In-Cu/SiO2).采用X射线衍射(XRD)、氮气吸脱附、氢气程序升温脱附(H2-TPD)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)以及电感耦合等离子体发射光谱(ICP-OES)等手段对催化剂进行了表征,同时评价了催化剂的活性和稳定性.结果发现,In2O3的改性提高了Cu/SiO2催化剂在醋酸甲酯加氢制乙醇反应中的活性和稳定性; 其中当添加1%In2O3时,醋酸甲酯转化率从83.7%提高至97.8% (反应温度523 K,反应压力3 MPa,氢酯摩尔比15,液时空速2 h?1),且对液时空速的变化耐受性比较强.当液时空速大于3 h?1时,随着液时空速的增加,Cu/SiO2催化剂的活性和选择性急剧下降,而1In-Cu/SiO2催化剂变化相对较小.TEM和XRD结果表明,适量In2O3的掺入改善了Cu/SiO2催化剂活性组分的分散性,铜粒径变小;FT-IR和N2O化学吸附结果显示,In2O3的加入使得页硅酸铜含量增加,从而有效地抑制了催化剂还原过程中铜的聚合,因此催化剂性能提高.XPS结果表明,表面Cu0和Cu+活性位点之间的协同作用有助于改善催化剂性能.Cu/SiO2和1In-Cu/SiO2催化剂100 h的稳定性测试发现,Cu/SiO2催化剂的失活主要是由于活性组分颗粒尺寸聚集变大和表面Cu0和Cu+分布的破坏所致; 而1In-Cu/SiO2催化剂物化性质几乎保持不变,表明适量的In2O3可稳定Cu/SiO2催化剂,延长其使用寿命.由此推断,In2O3可能作为一种隔离剂以抑制铜纳米粒子的热迁移和聚集,从而有效地提高Cu/SiO2催化剂活性和稳定性.     

吸附相反应技术制备Ag纳米粒子的反应机理

利用吸附相反应技术在SiO2表面制备Ag粒子, 研究了温度变化对载体表面NaOH的吸附、生成Ag的反应过程以及产物Ag粒子形貌的影响. NaOH的吸附率测定结果表明, 吸附平衡时间随着温度升高而增加. 温度升高加快了NaOH与Si—O—Si的反应, 使得NaOH的平衡吸附率不随吸附层的破坏而减少. 采用实时在线UV-Vis光谱研究了Ag粒子的生成过程, 发现温度超过40 ℃时, 反应体系中Ag出现的时间、Ag粒子的浓度和粒径分布范围都发生较大变化. 样品的TEM和XRD分析也表明, 当体系温度超过40 ℃时SiO2表面Ag粒子出现了团聚, 其晶粒粒径也出现了突变. 温度升高导致表面吸附层破坏, 使得Ag的生成场所从吸附层转移到SiO2表面, 最终导致Ag的反应机理和粒子形貌的变化.     

(Au，Ag，Cu)/SiO2二元合金分散复合薄膜非线性光吸收的Mie理论模拟

用修正的Mie理论,模拟计算分析了(Ag,Cu)/SiO2、(Au,Cu)/SiO2、(Ag,Au)/SiO2合金纳米颗粒分散体系的理论吸收光谱。研究发现当二元金属纳米颗粒以合金形式存在时,在一个波段处出现SPR吸收峰,峰位与合金组元的相对含量相关。模拟出的理论吸收光谱与实验结果一致。     

反应物的相间分配对吸附相技术制备纳米CuO过程的影响

以SiO2表面的富水吸附层为纳米反应器制备CuO纳米粒子. 不同水量下的吸附量测定、溶剂置换和反应后吸附对比实验结果表明, SiO2表面存在吸附水层, 并且该吸附水层是反应的主要场所. 根据吸附数据, 认为Cu2+在体系中具有三区域浓度分布特点, 体系中水浓度和氢氧化钠浓度的增加均会使得Cu2+向吸附层区域迁移. XRD分析结果表明, 反应温度的升高和NaOH浓度的增大有利于生成更小的CuO晶粒, 其中温度的升高使吸附层厚度减小, 限制了晶粒生长; NaOH浓度的增大则会增大层内溶质过饱和度, 导致晶核形成速率加快.     

改性海藻酸钠活化SiO2纳米粒子稳定载药Pickering乳液及释药性

以胆固醇疏水改性两亲性海藻酸钠衍生物表面,活化SiO2纳米粒子,再制得负载氯氟氰菊酯的O/W型Pickering乳液.通过傅里叶变换红外光谱(FTIR),氢核磁共振波谱(1H NMR)、荧光光谱、动态光散射、光学显微镜和释药实验分别对海藻酸钠衍生物和Pickering乳液的性能进行了表征.结果表明,胆固醇基接枝到了海藻酸钠分子链上,改性后的海藻酸钠临界聚集浓度由1.26 mg/L降为0.28 mg/L,表现出了良好的两亲性.将海藻酸钠衍生物(CSAD)和表面活性剂十六烷基三甲基溴化铵(CTAB)吸附于SiO2纳米粒子表面,得到活化SiO2纳米粒子,其Zeta电位分别为-30.7和16.4 mV,粒径分别增大到583.3和438.4 nm.由CSAD活化SiO2粒子制备的乳液释药速率更缓慢.CSAD的交联作用使吸附于油水界面的活化SiO2粒子形成了比较稳定的网络结构或界面膜.     

对称性降低的SiO2/Ag核壳结构纳米粒子的制备及表面增强拉曼活性研究

采用湿化学还原法在自组装的单层阵列二氧化硅纳米粒子表面沉积银膜制备了SiO2核/Ag帽复合纳米结构。通过透射电镜(TEM)、扫描电镜(SEM)、X射线衍射(XRD)和紫外-可见分光光度计(UV/Vis)研究和表征了该复合纳米结构的表面形貌、结构及光学性质。所制备的复合纳米粒子表面粗糙,其表面呈现无数纳米级谷粒状结构,SiO2内核粒径为350nm的银纳米帽的表面等离子共振吸收的2个共振峰分别位于382和689nm处。以亚甲基蓝作为探测分子研究了SiO2粒径为350和450nm的SiO2/Ag帽状复合纳米粒子的表面增强拉曼散射(SERS)活性,增强因子分别为3.6×109和3.9×109。结果表明,湿化学还原法制备的SiO2核/Ag帽复合纳米结构是很好的拉曼活性基底。     

纳米SiO_2粒子表面静电吸附引发剂的活性研究

引发剂2,2′-偶氮二(2-脒基丙烷)二氢氯化物(AIBA)可通过静电作用而高效稳定地吸附到在弱碱性水相中均匀稳定分散的纳米SiO2粒子表面.对这些吸附引发剂的热分解行为、在纳米SiO2粒子表面原位引发甲基丙烯酸甲酯(MMA)乳液聚合的动力学和纳米SiO2粒子表面的聚合锚固情况进行了研究.发现非吸附和吸附引发剂的热分解活化能分别为148.5kJ/mol和124.5kJ/mol,70℃时半衰期分别为12.6h和5.2h,说明在相同状态下静电吸附引发剂具有比非吸附引发剂更高的活性,因而在原位乳液聚合中表现出比常规乳液聚合更短的诱导期和更高的聚合速率.更关键的是,具有较高活性的吸附引发剂高效稳定地吸附在SiO2粒子表面,可以使聚合反应总是优先发生于纳米SiO2粒子表面,从而可以更好地促进单体在纳米SiO2粒子表面的锚固,最终有效提高无机/有机相间的复合程度.     

SiO2@P（MMA/BA/3FMA）复合纳米粒子的制备及膜性能

通过溶胶-凝胶法与半连续种子乳液聚合法相结合,以正硅酸乙酯(TEOS)制备的纳米SiO2为核,以甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)和甲基丙烯酸三氟乙酯(3FMA)的共聚物P(MMA/BA/3FMA)为壳,合成了SiO2@P(MMA/BA/3FMA)核-壳结构纳米复合粒子.为防止纳米SiO2的团聚,提高其与共聚物的结合力,用乙烯基三甲氧基硅烷(VTMS)对纳米SiO2进行改性.通过红外光谱、透射电子显微镜、动态激光散射粒度仪、静态接触角测试仪、X射线光电子能谱分析和热重分析等表征了乳液结构及膜性能.结果表明,获得的复合纳米粒子呈现粒径分布为40～50 nm的核-壳结构球型颗粒.由于含氟官能团的迁移使得氟元素在膜-空气界面富集,有效降低了膜的表面自由能.当3FMA质量分数达到25%时,膜表面自由能达到最低值(23.13 mN/m).随着3FMA含量的增加,共聚物初始热分解温度由350℃提高到390℃.     

Preparation and characterization of CuO/SiO2 and NiO/SiO2 with bimodal pore structure by sol-gel method

CuO/SiO₂ and NiO/SiO₂ with bimodal pore structure were prepared by sol-gel reactions of Tetra-methoxysilane (TMOS) and the respective metal nitrate in the presence of poly (ethylene oxide) (PEO) with an average molecular weight of 10 000 and the catalyst of acetic acid. In this process, the interconnected macroporous morphology was formed when transitional structures of spinodal decomposition were frozen by the sol-gel transition of silica. The addition of copper and nickel into the silica-PEO system had a negligible effect on the morphology formation. In gel formation, it was found that NiO crystalline sizes in the samples increased with decreasing Si/Ni molar ratio. It was considered that PEO interacted with both silica and nickel cations. In the CuO/SiO₂ with the presence of PEO_, CuO crystalline sizes were larger than those of NiO/SiO_2. It was considered that there was no obvious interaction between the Cu cation and PEO, most of the copper ions in wet silica gel were present in the outer solution. They easily aggregated as copper salts in the drying process of wet gel and decomposed into CuO particles in heating. While in the CuO/SiO₂ with the absence of PEO, the Cu was selectively entrapped as small particles in the gel skeleton due to the interaction between Cu aqua complex and silica gel network.     

Synthesis of Ag/SiO2 nanocomposite material by adsorption phase nanoreactor technique

Ag/SiO₂ nanocomposite was synthesized in a nanoreactor formed by adsorption layer on silica surface. Ag nanoparticles were prepared by the reduction of Ag ion with ethanol at alkaline condition. By using TEM and XRD, the effects of NaOH concentration, water and temperature on the appearance and grain size of Ag particles were analyzed, respectively. The adsorption curve of NaOH was measured by electrical conductivity meter. The experiment result revealed that Ag grain size decreased while increasing NaOH concentration or while increasing water in our system. Ag grain size increased with the increase of temperature. And Ag aggregated seriously when temperature is up to 60 °C. Finally, after exploring the optimum conditions of reaction, we successfully obtained the well-distributed Ag nanoparticles on surface of silica, and average grain size of Ag nanoparticles reached 5 nm.     

Sol-Gel Synthesis of Metal Nanoclusters-Silica Composite Films

In a program on the development of metal nanoclusters in sol-gel derived thin films, attempts were made to synthesize pure and mixed metal clusters, control the cluster size and increase the volume fract f the clusters. Thus, Ag, Cu and Ag-Cu nanoclusters were prepared in silica films using dip- and spin-coating techniques. The annealing of Ag/SiO₂ films in different atmospheres (air, argon and 5% H₂-95% N₂ gas) caused modifications of Ag nanoclusters resulting in changes in their surface plasmon resonance (SPR) peak positions. The Cu and Ag-Cu codoped films were annealed in reducing atmosphere (5% H₂-95% N₂ gas). In order to prepare Cu nanoclusters of different sizes, the concentrations of Cu in Cu/SiO₂ composite films were varied from 8 to 30 mol% and annealed at 800°C for different times for growth. The size of the Cu nanoclusters was measured from the half band width of Cu SPR peak (appearing within 570–557 nm range) and X-ray diffraction. In this way Cu-nanoclusters of size ranges from about 3.5 to 10 nm (average diameters) were prepared . The Ag-Cu nanocluster-containing silica films show the existence of both Ag and Cu SPR peaks with some blue shifting in comparison with to their pure analogues depending on the Ag:Cu ratio.     

Preparation of Cu/SiO2 Catalyst by Solution Exchange of Wet Silica Gel

Structural formation process of Ni/SiO₂ and Cu/SiO₂ catalysts prepared by solution exchange of wet silica gel was investigated. Microstructures of Cu/SiO₂ and Ni/SiO₂ were quite different from each other. In the case of Cu/SiO₂, Cu particles with diameter of ca. 3–5 nm dispersed homogeneously at less Cu content, and the particle size of Cu as well as pore size of silica gel support increased with increasing Cu content. In the Ni/SiO₂, the Ni particles with diameter of ca. 6–10 nm gathered densely to form aggregates in silica matrix resulting in sea-island structure, whereas the size of Ni particle slightly increased with increasing Ni content. The difference in the structure of the metal-silica composites is probably caused by the difference in interaction between silica gel network and metal ions during drying and heating processes.     

Influence of copper species on silver grain size in Ag–CuO–SiO2 ternary nanocomposites

The influence of Cu species on Ag grain size in Ag–CuO–SiO₂ ternary nanocomposites prepared by adsorbed-layer nanoreactor technique (ALRT)was investigated. Ag and CuO nanoparticles were synthesized on the silica surface one after the other, then the grain size of Ag was determined by X-ray diffraction. Ag grains became smaller with increase in amount of Cu, whether Cu species was fed before or after Ag species, implying that the grain growth of Ag was inhibited by the appearance of Cu(OH)₂ in both feeding sequences. Furthermore, after taken away the effect of alkaline concentration on Ag grain size, the inhibition effects of two feeding sequences become more similar.     

三维有序大孔杂化SiO2的制备、表征及应用

本研究将有机-无机杂化功能材料与有序大孔材料独特的有序开孔结构相结合,在制备的三维有序大孔二氧化硅（3DOM SiO₂）孔壁上可控接枝带有功能基团的聚合物链段,制备3DOM杂化材料。采用表面引发原子转移自由基（SI-ATRP）接枝技术在3DOM SiO₂孔壁上可控接枝聚甲基丙烯酸缩水甘油酯（PGMA）链段,讨论了接枝条件对接枝量及接枝链段分子量的影响,并利用FT-IR、SEM、TGA、GPC等对接枝过程进行了表征。PGMA接枝链段上环氧基团可进一步与亲核试剂（二乙醇胺,浓硫酸和二乙烯三胺）发生开环反应,得到一系列带有不同官能团的具有较高接枝密度的功能杂化多孔材料,同时,利用该种材料对水中的水杨酸进行了吸附实验,吸附结果表明经二乙烯三胺开环后得到的功能化多孔材料对水杨酸具有很高的吸附量。本研究对于发展新型杂化多孔材料提供了新的方法。     

CuO/Ti0.5Zr0.5O2催化剂对NO+CO反应的催化作用

环境治理是当今社会面临的一大主要问题。目前,城市空气污染日趋严重,特别是工厂和汽车排放的大量未燃烧的烃类、CO、NOx是主要的空气污染物。其中,氮氧化物(NOx)排放状况尤其严重,它的排放会给环境和人们生活带来严重危害,因此,如何有效地消除NOx已成为目前环境保护中一个非常     

CrOx/SiO2催化剂上丙烷在CO2气氛中脱氢反应的研究

采用XRD、UV-vis DRS、ESR和微分吸附量热等技术,考察了铬担载量分别为2.5、5和10wt%的CrO_x/SiO₂催化剂的结构、表面性质和氧化还原性能。结果表明,催化剂表面上存在多种Cr的氧化态和聚集形式。随着Cr担载量从2.5wt%到10wt%的逐渐增大,催化剂表面占主导地位的Cr物种由CrO₃单体转为多聚CrO₃和Cr₂O₃晶相。在CO₂气氛中催化剂对丙烷转化率和丙烯选择性的大小顺序为2.5wt%CrO_x/SiO₂>5wt%CrO_x/SiO₂>10wt%CrO_x/SiO₂,反应过程中的原位ESR和UV-visDRS测定结果表明,催化剂表面的反应活性中心为Cr⁵⁺,Cr⁵⁺可由催化剂预处理过程中Cr³⁺的氧化及丙烷反应过程中CrO₃单体的还原产生,在反应中CO₂可使Cr³⁺重新氧化为Cr⁵⁺.     

Co或Ni促进的Cu/SiO2-Al2O3催化剂上丙三醇和苯胺气相合成3-甲基吲哚

对丙三醇和苯胺在Co或Ni促进的Cu/SiO2-Al2O3催化剂上气相合成3-甲基吲哚进行了研究.采用N2吸附、氢气程序升温还原(H2-TPR)、电感耦合等离子体(ICP)发射光谱、X射线衍射(XRD)、透射电子显微镜(TEM)、氨程序升温脱附(NH3-TPD)及热重(TG)分析等技术对催化剂进行了表征.结果表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂改善了催化剂的催化性能,钴比镍更加有效.在催化剂Cu-Co/SiO2-Al2O3和Cu-Ni/SiO2-Al2O3上,反应第3 h,3-甲基吲哚收率分别达到47%和45%,而且催化剂经过6次再生收率仍能达到44%和42%.各种表征表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂能增强铜和载体之间的相互作用,其结果不仅促进了铜粒子在载体表面的分散度,而且有效减少了反应过程中铜组分的流失.另外,加入钴或镍助剂还能减少催化剂的中强酸中心数,从而提高3-甲基吲哚的选择性,并且抑制积炭的形成.此外,钴助剂还能增加催化剂的弱酸中心数,促进3-甲基吲哚的生成.提出了金属铜与弱酸中心共同促进3-甲基吲哚合成的催化反应机理.     

Studies on Acrylic Emulsion Polymerization Containing Hydrophilic Hydroxyl Monomer in the Presence of Nano‐SiO2 Particles

Emulsion polymerization with nano‐scale SiO₂ particles as seeds composed of methyl methacrylate (MMA), butyl acrylate (BA), hydroxyethyl methacrylate (HEMA), and acrylic acid (AA) was studied from varying reaction temperatures, level of SiO₂ particle, HEMA, and emulsifier. The morphology of the emulsion particle was examined with a transmission electron microscope (TEM). The results showed that the addition of nano‐SiO₂ particles decreased the coagulum greatly when its level was lower than 7%. The coagulum also decreased with the increasing of temperature from 65°C to 75°C. The level of HEMA and emulsifier had little influence on the coagulum in the presence of nano‐SiO₂. The particle size of the emulsion increased with the increase of level of nano‐SiO₂ and HEMA. Part of the emulsion particles connected together due to the existence of HEMA, and yet some of the nano‐SiO₂ particles were not covered with polymer.