铂-金交替修饰的铂核纳米颗粒的制备与表征

通过吸附在铂纳米颗粒表面的氢交替还原氯金酸和氯铂酸,得到了复合型纳米颗粒Pt@Au/Pt,用UV-Vis光谱、TEM和XRD对其进行了表征.     

Pt/Au双金属纳米微粒的催化性能

制备了不同比例的Pt/Au双金属纳米微粒,应用UV-VIS、TEM等手段对其结构进行了表征,并比较了它们对丁醛氢化还原反应的催化活性.     

阳离子聚合物修饰纳米Pt颗粒的合成

纳米Pt;季铵阳离子;合成;阳离子聚合物修饰纳米Pt颗粒的合成     

小尺寸金石墨纳米颗粒的合成与表征

在表面增强拉曼光谱(SERS)的研究领域中,基于局域表面等离子体共振效应的等离子体SERS基底的制备成为过去几十年的研究热点。然而,通常开发的等离子体金属基底具有较差的稳定性和重现性。对于SERS而言,石墨烯类材料具有拉曼化学增强效应,除此之外,还具有分子富集、强的稳定性与荧光猝灭能力等优点,因此基于石墨金属复合纳米材料的SERS基底受到了研究人员的重视。我们利用化学气相沉积(CVD)法制备了小尺寸的金石墨核壳纳米颗粒(Au@G),其粒径约为17 nm。我们通过在Au NP上包覆介孔二氧化硅来控制Au@G的尺寸,同时还研究了包覆二氧化硅过程中,正硅酸乙酯(TEOS)的浓度对于石墨壳层形成的影响。结果表明当TEOS在一定浓度范围内,其浓度的降低有利于得到石墨化程度高的Au@G。进一步利用Au@G对结晶紫分子进行拉曼检测,也表明了Au@G具有较好的拉曼增强效果。这种小尺寸的Au@G在分子检测与细胞成像分析领域中具有广泛的应用潜力。     

水溶性稀土上转换纳米颗粒的合成与表征

以稀土离子、油酸、间氯过氧苯甲酸和mPEG等为原料合成了一种新型水溶性NaLaF4:12%Yb3+,3%Er3+(摩尔分数)稀土上转换纳米颗粒(mPEG-UCNPs)。利用核磁共振谱、红外光谱、原子力显微镜、透射电子显微镜、分子荧光光谱等手段对mPEG-UCNPs的结构进行了表征。结果表明:mPEG-UCNPs粒径较为均一,粒径均在15~25 nm之间;同时,mPEG-UCNPs在510~580 nm和635~700 nm有较好的上转换荧光性质。     

异质哑铃型纳米颗粒合成中的关键因素(英文)

哑铃型纳米颗粒由一种包含强相互作用的异质结构成,它两端是不同物质的纳米颗粒.这两种不同功能的纳米颗粒紧密相连,形成一种哑铃形的外观.这种结构的纳米颗粒在电子、磁性、光学及催化等方面有着不同于单一组分纳米颗粒的独特性质,因此受到人们广泛关注.哑铃型纳米颗粒的这些独特性质是由两种物质交界面处的电子转移引起的,得益于较强的界面相互作用,两种物质都可以通过界面处的电子转移得到改良,使得这种结构的催化剂在较低温度下催化氧化有机废气时活性很高.以CO氧化反应为例,Au纳米颗粒通常情况下对该反应没有催化活性,但是被负载到金属氧化物上面以后,却表现出了很高的催化活性.这正是氧化物载体与Au纳米颗粒之间电子传输的结果.通常在核壳结构中,核心物质以及两种物质的交界面都被外壳所包裹,而哑铃型结构当中的两种物质的功能面以及它们之间活泼的交界面均可以充分地暴露在反应物中,从而极大提升了其催化效果.这种独特的结构优势也在疾病诊断与治疗中的多功能探针上得到了广泛应用.由于哑铃型结构的两种物质的纳米颗粒相对位置是固定的,当用作催化剂时可以发挥出很好的抗烧结性能,还可使这两种物质更协调地均匀分布.因此哑铃型结构催化剂不仅催化活性更高,而且在较高温度下具有较高的稳定性.哑铃型结构可以看作是独立纳米颗粒与核壳型纳米颗粒之间的一种中间状态,它通常是由一种物质的纳米颗粒在另一种种子颗粒上面经过外延生长得到的.这与核壳结构纳米颗粒的合成很相似,但是必须准确地控制成核过程,使得成核可以各向异性地发生在种子颗粒的某一个晶面上.而在核壳结构的合成中,这一成核过程是均匀分布的.所以在制备哑铃型结构纳米颗粒时,很重要的就是要促进非均质成核,同时抑制均相成核.由于哑铃型纳米颗粒的特殊结构,在制备时想要准确控制上述成核条件是非常困难的,所以到目前为止,仅有很少种类的物质可以被制成哑铃型结构,比如Au(Ag,Pt,Pd)-Fe3O4(Co3O4),Au-PbS(PbSe),FePt-CdS和Cu-Ag等,这些物质中大多数都是由贵金属纳米颗粒和磁性纳米粒子组成的.哑铃型纳米颗粒由于受限于物质种类,它在催化氧化方面的应用也被局限在了很少一部分气体上,如CO.而通过其它很多种催化剂已经可以在较低温度(甚至零下数摄氏度)下实现CO催化氧化.因此,哑铃型结构的优势在CO催化氧化中并不能得到很好利用和体现,而用于甲烷等一些在较低温度下更难氧化的气体的催化氧化尚未见报道.这正是由合成多种多样的哑铃型纳米颗粒的巨大困难所致.因此,找到合成哑铃型纳米颗粒的困难所在以及合成过程中的一些重要影响因素非常有意义,这将帮助我们使用更多的物质合成出一些新的哑铃型纳米颗粒,进而利用其高催化活性,使得更多难以氧化的气体在较低温度下被氧化.本文总结了合成哑铃型纳米颗粒时的多种影响因素,并介绍了相关的一些合成方法.种子颗粒的尺寸以及两种颗粒之间的尺寸比例可以影响制备过程中外延生长的可控性,颗粒尺寸以及两种颗粒的尺寸差别越小,反应越容易控制.反应温度和反应时间需要根据反应物的性质进行精确控制才可以得到合适的尺寸以及较好的粒径分布.而两种不同的物质最终能不能形成哑铃型结构则是由很多种因素决定的,比如反应溶剂的极性、两种物质之间的晶格错配度以及反应中所用乳化剂的含量.除此之外,合适的前驱体、氧化还原剂以及操作环境等都可以影响哑铃型纳米颗粒的合成结果     

聚吡咯纳米颗粒的静态法合成及表征

在无模板、无表面活性剂条件下,采用静态化学氧化聚合法合成了高聚合产率(93%)聚吡咯纳米颗粒.以红外光谱、广角X射线衍射、四探针仪、扫描电子电镜和透射电子显微镜对聚吡咯的结构、电性能和形貌进行了表征.并研究了搅拌条件、氧化剂种类、过硫酸铵/吡咯摩尔比、聚合反应温度和反应介质对聚吡咯纳米颗粒的粒径、形貌的影响.结果发现,聚吡咯纳米颗粒的尺寸随聚合反应条件的变化而改变.在静态条件下,以过硫酸铵为氧化剂、过硫酸铵/吡咯摩尔比为0.25,于0℃冰水浴中有利于获得聚吡咯纳米颗粒.透射电子显微镜的结果表明以过硫酸铵/吡咯摩尔比为0.25,于0℃下1.0mol/LHCl水溶液介质中可以聚合得到直径为43nm、颗粒大小均匀的球形聚吡咯纳米颗粒.盐酸掺杂聚吡咯纳米颗粒的室温电导率可达5.5S/cm.     

基于超分子晶体制备超细铂纳米颗粒用于催化加氢硝基苯

由于纳米催化剂的独特催化活性,因而开发稳定的超细纳米催化剂的制备方法引起了广大科研工作者们的关注.然而,复杂的合成过程和结构的不稳定性己经成为纳米催化剂研究和实际应用的瓶颈.本工作通过原位还原氯铂酸和十甲基五元瓜环(Me10CB[5])构筑的超分子晶体材料,成功制备了粒径尺寸约为3.0 nm的超细铂纳米粒子.Me10C...     

银纳米颗粒的制备及表征

用鞣酸还原法制得了PVP保护的Ag纳米颗粒,并通过TEM、XRD、TG、DTA及FT IR对其结构进行了表征.结果表明在所选择的实验条件下制备了粒径小、单分散且化学稳定的Ag PVP纳米颗粒,其粒径约10nm,有良好的水分散性.PVP的加入和银氨络离子的形成对制备出小尺寸纳米银起了重要作用.     

Pt/Cu双金属纳米颗粒的制备及其催化制氢活性

采用化学共还原法合成了聚乙烯吡咯烷酮保护的Pt/Cu双金属纳米颗粒(BNPs),并采用紫外可见吸收光谱、透射电子显微镜、高分辨透射电子显微镜等对所合成的Pt/Cu BNPs进行了表征。研究了化学组成对Pt/Cu BNPs催化Na BH4水解制氢性能的影响。结果表明,所制备的Pt/Cu BNPs平均粒径为1.8~2.3nm,其催化活性远高于单金属Pt和Cu NPs的活性,其中Pt90Cu10BNP的催化活性最高,其在30℃的条件下,催化Na BH4制氢的活性可达6570mol-H2·mol-cat-1·h-1,约为相同粒径的Pt单金属NP的1.6倍。密度泛函理论的计算结果表明,Pt/Cu BNPs优异的催化性能可归因于电荷转移效应,Pt原子与Cu原子之间发生的电子转移使得Pt原子带负电而Cu原子带正电,荷电的Pt和Cu原子成为催化反应的活性中心。     

Pt/Au双金属纳米粒子的制备及表征

Poly (N-vinyl-2-pyrrolidone)-protected Pt/Au bimetallic nanoparticles were obtained by reducing the mixture of HAuCl4 and H2PtCl6 with sodium borohydride. UV-vis spectra, transmission electronic microscopy and X-my diffraction reveal that the prepared bimetallic nanoparticles are of alloy structure.     

ZnO/Ag复合纳米粒子的制备与表征

以乙酸锌为前驱物,乙醇为溶剂,油酸钠为表面修饰剂,采用溶液化学法,在乙醇体系中制得纳米Zn O。然后缓慢加入一定量的硝酸银乙醇溶液,在乙醇的还原作用下将Ag+还原为Ag纳米粒子,制得Zn O/Ag复合纳米粒子。通过紫外-可见吸收光谱(UV-Vis)、荧光光谱(FL)、透射电子显微镜(TEM)和X射线衍射(XRD)等方法对所制备的氧化锌-银复合纳米粒子样品进行表征。结果表明,所合成的Zn O/Ag复合纳米粒子为球形,尺寸为20-30nm且粒径分布较窄。Ag纳米粒子附着于Zn O纳米粒子表面,并起到良好的表面修饰作用。对制备Zn O/Ag复合纳米粒子的机理进行了初步探究。     

Preparation and characterization of hexagonal close-packed Ni nanoparticles

Hexagonal close-packed Ni nanoparticles were synthesized using a heat-treating technique with the precursors prepared by the sol-gel method. The synthesis condition, structure, and morphology of the samples were characterized and analysed by thermogravimetric analysis (TG), differential thermal analysis (DTA), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results indicate that the hexagonal close packed Ni nanoparticles were synthesized at a heat-treating temperature of 300°C. The cell constants are calculated at a = 0.2652 nm and c = 0.4334 nm. The average grain size of the hexagonal close-packed Ni particles evaluated by Scherrer equation is about 12 nm. The phase transformation from a hexagonal close-packed Ni to a face-centered cubic Ni structure occurred when the heat-treating temperature was increased. __________ Translated from Chemical Journal of Chinese Universities, 2007, 28(7): 1232–1234 [译自: 高等学校化学学报]     

Oxygen dissociation on palladium and gold core/shell nanoparticles

Oxygen dissociation reaction on gold, palladium, and gold‐palladium core/shell nanoparticles was investigated with plane wave basis set, density functional theory. Bader population analysis of charge and electron distribution was employed to understand the change of catalytic activity as a function of the nanopaticle composition. The nanoparticles’ electronic properties were investigated and the degree of core/shell charge polarization was estimated for each composition. It was found that surface polarization plays an important role in the catalysis of the initial step of electrophile reactions such as oxygen dissociation. We have investigated the O₂ adsorption energy on each nanoparticle and the activation barrier for the oxygen dissociation reaction as a function of the nanoparticle structure. Furthermore, we have investigated the influence of surface geometry, that is., surface bond lengths on the catalytic activity. We have compared the electronic and the geometry effects on the oxygen activation and dissociation. Our design rules for core/shell nanoparticles offer an effective method for control of the surface catalytic activity. Palladium and gold are often used as catalysts in synthetic chemistry. First‐principles calculations elucidate the mechanisms that control the surface reactivity of gold, palladium, and gold‐palladium core shell nanoparticles in oxygen dissociation reactions. Oxygen dissociation is promoted on the gold surface of gold/palladium core‐shell nanoparticles by favorable electron transfer from the core to the shell. Such core‐shell electronic effects can be used for fine‐tuning the nanoparticles catalytic activity.     

Preparation, characterization, and controlled release of novel nanoparticles based on MMA/beta-CD copolymers

A series of random copolymers with different beta-cyclodextrin contents were synthesized by radical copolymerization of MMA with a monovinyl beta-CD monomer. The copolymers were characterized with IR spectroscopy, elemental analysis, DSC, and TGA. Based on these copolymers, their nanoparticles were prepared by using DMF, water, and acetone as solvents. Aqueous dispersions of the nanoparticles were further obtained by dialysis against water. Zetasizer Nano-ZS dynamic light scattering and transmission electron microscopy were employed to characterize the nanoparticles. Using camptothecin as a model drug molecule, the encapsulation efficiency and release behavior of the nanoparticles were investigated.     

Preparation and application of polystyrene‐grafted ZnO nanoparticles

The precursor of ZnO was prepared by precipitation and ZnO nanoparticles were obtained by calcination afterwards. Poly(styrene) (PSt) was grafted onto the ZnO nanoparticles in a non‐aqueous suspension to reduce the aggregation among nanoparticles and to improve the compatibility between nanoparticles and the organic matter. The obtained samples were characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT‐IR), zeta potential measurement, lipophilic degree (LD) test, photocatalytic experiments, sedimentation test, and contact angle measurement. The LD of composite particles after a high‐temperature treatment was stable. The photoluminescence of PSt‐grafted ZnO nanoparticles was observed by naked eyes and was recorded using a digital camera. The ZnO nanoparticles were used to reinforce poly(vinylidene fluoride) (PVDF) films and the mechanical and electric properties of the films were also measured. Copyright © 2007 John Wiley & Sons, Ltd.     

银/铂双金属中空纳米颗粒的制备及光学性质研究

通过以Ag纳米颗粒为模板的置换和沉积反应,制备了Ag/Pt双金属复合纳米颗粒.用透射电子显微镜(TEM)对颗粒的形貌、尺寸和结构进行了表征,发现复合颗粒具有中空结构.紫外可见吸收光谱(UV-Vis)研究表明,Ag/Pt双金属中空复合纳米颗粒具有单峰的表面等离子共振吸收特征,随着反应溶液中氯铂酸和硝酸银摩尔比的增加,吸收峰先红移后蓝移.表面增强拉曼光谱实验结果表明,Ag/Pt双金属复合纳米颗粒对吡啶分子具有较好的增强效果.     

各向异性金纳米粒子的制备及其在催化中的应用

尽管有关金纳米粒子催化的研究工作很多,但其中大多数都是采用传统的浸渍法将金盐负载到载体上、共沉淀或沉积-沉淀法制得负载的纳米粒子,但这些方法并未吸收最新的纳米技术。最近,金催化剂的研究者开发了在胶态悬浮液中制取金属纳米粒子,然后进行固载,从而使得单金属和双金属催化剂的催化活性和形貌控制取得较大进展。另一方面,最近十年出现了金纳米粒子合成的高级控制技术,得到了许多各向异性的金纳米粒子,且很容易制得新的形貌,可以控制纳米粒子的表面原子配位数和光学特性(可调的等离子体带),这些都与催化密切相关。这些形貌包括纳米棒、纳米星、纳米花、树枝状纳米结构或多面体纳米粒子等。除了高度关注各向异性金纳米粒子的最新开发的制备方法和性质,本综述也清楚地总结了这些纳米粒子独特的催化性能,以及通过提供更高催化性能的金催化剂、控制暴露的活性位,以及热、电和光催化的鲁棒性和可调性,从而给多相催化领域带来令人惊奇的潜在变革。     

Local structural characterization of Au/Pt bimetallic nanoparticles

In this study, we examined the amount-dependent change in morphology for a series of Au/Pt bimetallic nanoparticles synthesized using chemical reduction. The Au/Pt molar ratio was varied from 1/1 to 1/4 to synthesize Pt shell layers with different thicknesses. We have obtained that these bimetallic nanoparticles can form flower-like nanoparticles. Moreover, an extended X-ray absorption fine structure (EXAFS) analysis was used to demonstrate the structure of Au/Pt bimetallic nanoparticles. The EXAFS results confirmed the formation of a core–shell structure and inter-diffusion between Au and Pt atoms. The composition of the shell layer was found to be Pt-enriched Au/Pt alloy.     

Hydrogenation Size-Selective Pt/Hollow Beta Catalysts

The aim of the present work is to synthesize a zeolite-based catalyst with a hollow morphology and highly dispersed metal nanoparticles (NPs) encapsulated inside the zeolite micropores. For this purpose, we have studied a treatment using tetraalkylammonium (TAA) bromides for the selective removal of a large Pt particle from the outer surface of a hollow Beta zeolite. TEM analysis reveals that we succeeded in the synthesis of a hollow beta zeolite single crystal with encapsulated particles, with a high dispersion of 50–60 %. The molecular-sieve-type mechanism of the obtained catalysts was evaluated in the model reaction of toluene and mesitylene catalytic hydrogenation. Thanks to the high dispersion. a 10-fold activity enhancement has been obtained with respect to hollow beta zeolites with encapsulated NPs recently described in the literature.