Au/Ag核-壳结构纳米粒子的制备及其SERS效应

随着大量有关表面增强拉曼散射 (SERS)的实验和理论研究的开展 ,金属纳米粒子作为一类重要的 SERS增强介质 ,已引起了人们浓厚的研究兴趣 [1] .而 Au和 Ag作为最常用的活性基底物质 ,更是研究的热点 [2 ,3 ] .最近 ,美国印第安那大学的 Nie等 [4 ] 在单个银纳米粒子上 ,观察到高达 1 0 14 ～ 1 0 15的SERS因子 .同时 ,他们的另外一项工作表明银纳米粒子的形状和大小对 SERS活性有很大影响 [5] .但是 ,由于 Ag溶胶制备的重复性较差 ,且粒度分布不均匀 ,通过控制银颗粒大小而调控 SERS活性是相当困难的[6] .与 Ag相比 ,Au在可见光…     

光催化还原制备Au/Ag核壳结构纳米粒子及其修饰电极的电催化性能

以Keggin结构硅钨杂多酸H4SiW12O40(SiW12)为光催化还原剂,通过光化学还原法制备Au/Ag核壳结构纳米粒子. 透射电子显微镜分析显示,所得纳米粒子粒径为30～40 nm,呈均匀分散的球形颗粒,该制备方法的特点是可以较好的避免单金属纳米粒子的形成. 将Au/Ag核壳纳米粒子修饰到具有PVP膜的玻碳电极表面,得到SiW12-(Au/Ag)-PVP多层膜修饰电极. 该修饰电极在0.5 mol/L H2SO4介质中具有良好的电化学响应,在0～-0.75 V电位范围内,出现了3对归属于SiW12的氧化还原峰,且电极性能稳定,灵敏度高. 对H2O2的电催化还原性能明显优于单金属Ag纳米粒子修饰电极,说明Au核的存在可以很好的改善Ag的电催化性能,Au和Ag之间存在相互协同催化作用.     

SiO2 /Au核壳结构纳米粒子的制备及表征

通过以金纳米粒子为表面晶种和壳生长的方法制备了金纳米壳包覆二氧化硅的复合纳米粒子。采用TEM 和UV-Vis对复合粒子进行了表征和研究，结果表明所得到的复合粒子粒径均匀、金纳米壳光滑完整，且壳厚度可通过反应物的用量来控制。当核半径与壳厚度之比在4到13之间变化时,复合粒子的光学共振峰在可见光区到近红外光区范围内可发生大于500 nm波长的移动。     

SiO2/PE/ Bi2S3核壳结构纳米颗粒的合成与性能(英)

以多层电解质作为微型反应器，制备了SiO₂/ Polyelectrolyte(PE) / Bi₂S₃核壳纳米粒子。XRD结果表明Bi₂S₃颗粒属于正交晶系。由透射电镜和场发射扫描电镜照片可知，在直径为640 nm左右的SiO₂表面覆盖了厚度35 nm的Bi₂S₃壳层。红外光谱分析结果表明硅烷网络在结构上发生了变化(SiO₂表面的硅烷醇键沉积在Bi₂S₃的表面)。SiO₂核和SiO₂ / PE / Bi₂S₃的紫外-可见吸收光谱显示在900 nm存在典型吸收边。     

Au和SiO2多壳结构的制备和表征

利用自组装技术和胶体还原化学, 制备出金纳米壳Au@SiO₂以及SiO₂包裹的金纳米壳SiO₂@Au@SiO₂; 去除SiO₂@Au@SiO₂颗粒中的金壳层, 获得含有可移动SiO₂核的空心壳H-SiO₂@M-SiO₂. 结果显示: SiO₂@Au@SiO₂复合颗粒表面光滑, 并保留了金壳的近红外吸收特性; 通过改变复合颗粒外层SiO₂厚度, 可以调节其等离激元共振峰的位置; 王水可以有效地去除SiO₂@Au@SiO₂中的金壳, 相应的等离激元共振峰消失.     

Au和SiO2多壳结构的制备和表征

利用自组装技术和胶体还原化学, 制备出金纳米壳Au@SiO₂以及SiO₂包裹的金纳米壳SiO₂@Au@SiO₂; 去除SiO₂@Au@SiO₂颗粒中的金壳层, 获得含有可移动SiO₂核的空心壳H-SiO₂@M-SiO₂. 结果显示: SiO₂@Au@SiO₂复合颗粒表面光滑, 并保留了金壳的近红外吸收特性; 通过改变复合颗粒外层SiO₂厚度, 可以调节其等离激元共振峰的位置; 王水可以有效地去除SiO₂@Au@SiO₂中的金壳, 相应的等离激元共振峰消失.     

核/壳型CdTe@SiO2荧光纳米复合粒子的制备与表征

利用反相微乳法, 以巯基乙酸修饰的水溶性CdTe量子点为核, 包覆SiO₂, 制备得到核壳型CdTe@SiO₂荧光纳米复合粒子. 用紫外-可见(UV-vis)分光光度计, 荧光(PL)分光光度计, 红外(FT-IR)光谱仪, 透射电子显微镜(TEM)等分析测试手段, 对得到的荧光纳米复合粒子的性能进行表征, 结果表明: 得到的CdTe@SiO₂纳米复合粒子是核壳型结构, 由SiO₂壳层包覆多个量子点, 其大小均匀, 水溶性好, 有效地提高了量子点的稳定性, 大大增强了其抗光漂白性能, 为该材料的进一步生物应用打下了良好的基础.     

CdS/MS(M=Ag,Pb,Cu,Zn)半导体纳米复合结构的制备

利用金属硫化物在水溶液中溶度积的差异和通过水热及超声波等辅助方式,利用离子置换法与共沉淀法,对CdS纳米棒上金属离子(Cd²⁺)的部分置换而对纳米微粒进行侵蚀或包覆,形成镶嵌式点缀结构或完全包覆层的异质核-壳结构CdS/MS(M=Ag⁺,Cu²⁺,Pb²⁺,Zn²⁺)。使用XRD和TEM对所得样品进行了表征。     

M/Al2O3-CeO2（M=Pt-Ru，Ru，Pt）催化剂在甲胺催化湿式氧化中的活性与选择性

采用浸渍法制备了M/Al₂O₃-CeO₂（M=Pt-Ru,Ru,Pt）催化剂,并将其用于甲胺的催化湿式氧化反应（CWAO）.结果表明,Pt-Ru/Al₂O₃-CeO₂具有最佳活性和选择性.运用程序升温还原、X射线光电子能谱、X射线衍射、透射电子显微镜、N₂吸附和CO化学吸附等技术对催化剂的物化性质进行了表征.Pt组分的引入可有效提高双金属催化剂活性组分的分散度,从而明显提高了其催化性能.升降温过程中总有机碳（TOC）转化率与N₂选择性迟滞效应表明,甲胺CWAO遵循化学吸附-脱附机理.     

Synthesis and characterization of new sulfide aggregates of the type [{Pt2(μ3-S)2(P-P)2}M(C6F5)2] (M=Ni, Pd, Pt; P-P=2PPh3, 2PMe2Ph, dppf)

The reaction of [Pt₂(μ-S)₂(P-P)₂] (P-P=2PPh₃, 2PMe₂Ph, dppf) [dppf=1,1^′-bis(diphenylphosphino)ferrocene] with cis-[M(C₆F₅)₂(PhCN)₂] (M=Ni, Pd) or cis-[Pt(C₆F₅)₂(THF)₂] (THF=tetrahydrofuran) afforded sulfide aggregates of the type [{Pt₂(μ₃-S)₂(P-P)₂}M(C₆F₅)₂] (M=Ni, Pd, Pt). X-ray crystal analysis revealed that [{Pt₂(μ₃-S)₂(dppf)₂}Pd(C₆F₅)₂], [{Pt₂(μ₃-S)₂(PPh₃)₂}Ni(C₆F₅)₂], [{Pt₂(μ₃-S)₂(PPh₃)₂}Pd(C₆F₅)₂] and [{Pt₂(μ₃-S)₂(PMe₂Ph)₂}Pt(C₆F₅)₂] have triangular M₃S₂ core structures capped on both sides by μ₃-sulfido ligands. The structural features of these polymetallic complexes are described. Some of them display short metal-metal contacts.     

Bis(trifluoromethyltellurato(0))metallates(I) of copper, silver and gold, [M(TeCF3)2] (M = Cu, Ag, Au)

Ligand exchange reactions of [NMe₄]TeCF₃ and CuBr, Ag[BF₄] and AuCl have been studied in molar ratios of 2:1. While evidence is found for [Cu(TeCF₃)₂]⁻ moieties by ¹⁹F-NMR spectroscopic and mass spectrometric means, [NMe₄][Ag(TeCF₃)₂] and [NMe₄][Au(TeCF₃)₂] were isolated. After cation exchange, the latter compounds were fully characterised as the [PNP] salts ([PNP] = bis(triphenylphosphoranylidene)ammonium). The single crystal structure of [PNP][Au(TeCF₃)₂] has been elucidated by XRD measurements (P2₁/a; a = 1765.6(1), b = 1126.0(1), c = 2055.2(1) pm; β = 111.98(1)°; Z = 4).     

Synthesis and physico-chemical characterization of Au/TiO2 nanostructures formed by novel “cold” and “hot” nanosoldering of Au and TiO2 nanoparticles dispersed in water

A novel approach to synthesize Au/TiO₂ nanostructures with interesting optical properties is presented and discussed. It is based on the nanoparticle “cold” or “hot” nanosoldering occurring when two water suspensions of Au and TiO₂ nanoparticles are merely mixed at room temperature or laser irradiated after mixing.Thanks to the high fraction and mutual reactivity of surface species, immediately after the mixing process, the encounters between Au and TiO₂ nanoparticles in liquid phase are enough for “cold” nanosoldering of gold nanoparticles onto TiO₂ nanoparticles to occur. The optical characterizations show that this fast process (timescale less than 1 min) is followed by a slower process, attributable to some change of the Au nanoparticles. This latter process is significantly accelerated by the 532 nm laser light illumination. The structural and optical properties of “cold” and “hot” nanosoldered Au-TiO₂ nanoparticles were investigated by TEM, UV-vis and fluorescence spectroscopies.Interesting optical limiting response was detected at laser fluences above 0.8 J/cm². The nature of the nonlinear effect was investigated by the Z-scan technique, determining both the nonlinear absorption coefficient and the refraction index. Such interesting non-linear optical properties are worth to be tailored for specific applications.     

Synthesis and characterization of monodisperse spherical SiO2@RE2O3 (RE=rare earth elements) and SiO2@Gd2O3:Ln (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles with core-shell structure

Spherical SiO₂ particles have been coated with rare earth oxide layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO₂@RE₂O₃ (RE=rare earth elements) and SiO₂@Gd₂O₃:Ln³⁺ (Ln=Eu, Tb, Dy, Sm, Er, Ho) particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence spectra as well as lifetimes were used to characterize the resulting SiO₂@RE₂O₃ (RE=rare earth elements) and SiO₂@Gd₂O₃:Ln³⁺ (Eu³⁺, Tb³⁺, Dy³⁺, Sm³⁺, Er³⁺, Ho³⁺) samples. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 380 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (40 nm for two deposition cycles). Under the excitation of ultraviolet, the Ln³⁺ ion mainly shows its characteristic emissions in the core-shell particles from Gd₂O₃:Ln³⁺ (Eu³⁺, Tb³⁺, Sm³⁺, Dy³⁺, Er³⁺, Ho³⁺) shells.     

Synthesis and structures of heterobimetallic Ir2M (M=Pd, Pt) sulfido clusters and their catalytic activity for regioselective addition of alcohols to internal 1-aryl-1-alkynes

The heterobimetallic trinuclear sulfido clusters [(Cp*Ir)₂(μ₃-S)₂MCl₂] (M=Pd (3), Pt (4); Cp*=η⁵-C₅Me₅) were synthesized from the dinuclear hydrogensulfido complex [Cp*IrCl(μ-SH)₂IrCp*Cl] (2) and [MCl₂(COD)] (COD=cycloocta-1,5-diene), while the reaction of 2 with [Pd(PPh₃)₄] afforded the cationic trinuclear cluster [(Cp*Ir)₂(μ₃-S)₂PdCl(PPh₃)]Cl (5). Clusters 3 and 4 reacted with PPh₃ to give a series of mono and dicationic clusters including 5, while the dicationic clusters [(Cp*Ir)₂(μ₃-S)₂M(dppe)][BPh₄]₂ (M=Pd (9), Pt (10); DPPE=Ph₂PCH₂CH₂PPh₂) were obtained by the reaction with dppe followed by anion metathesis. The molecular structures of 5·CH₂Cl₂, 9·CH₃COCH₃, and 10·CH₃COCH₃ were determined by X-ray crystallography. Clusters 3 and 4 were found to catalyze the addition of alcohols to alkynes to give the corresponding acetals. Internal 1-aryl-1-alkynes were transformed by cluster 3 into the corresponding 2,2-dialkoxy-1-arylalkanes with high regioselectivity up to 99:1, while cluster 4 was a much less regioselective catalyst.     

Unusual stabilization of cationic “M(η-allyl) (M = Pt, Pd) units by a dianionic cis-{Pt(C6F5)2(CCSiMe3)2} fragment

Chloride abstraction from [{M(η³ --- C₃H₅)Cl}_n] (M = Pt, n = 4 or M = Pd, n = 2) by (NBu₄)₂[cis-Pt(C₆F₅)₂(CCSiMe₃)₂] (1) gives rise to novel homo- and hetero-dinuclear zwitterionic derivatives (NBu₄) [{cis-Pt(C₆F₅)₂(CCSiMe₃)₂}M(η³-C₃H₅)] (M = Pt 2; M = Pd 3) which are formed by a M(η³-allyl)⁺ unit attached to both alkynyl ligands of the {cis-Pt(C₆F₅)₂(CCSiMe₃)₂}²⁻ fragment. The structure of 3 has been established by X-ray diffraction.     

Catalytic properties of LnSrCoO4 (Ln = La, Sm) in the oxidation of CO and C3H8

Perovskite-like LnSrCoO₄(Ln=La, Sm) mixed oxides of K₂NiF₄ structure were synthesized by the polyglycol gel method and used successfully for CO and C₃H₈ oxidation for the first time. The structure was characterized by means of XRD, TEM, BET, O₂-TPD and CO₂-TPD, respectively. An oxidation mechanism over LnSrCoO₄is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis,characterization and antimicrobial studies of mixed ligand silver(I) complexes of thioureas and triphenylphosphine; crystal structure of {[Ag(PPh3)(thiourea)(NO3)]2·[Ag(PPh3)(thiourea)]2(NO3)2}

Mixed ligand silver(I) complexes of triphenylphosphine and thioureas (thiourea (Tu), N-methylthiourea (Metu), N,N′-dimethylthiourea (Dmtu) and N,N′-diethylthiourea (Detu)) with the general formulae, [(Ph₃P)₂Ag(thione)]NO₃ and [(Ph₃P)Ag(thione)₂]NO₃, have been prepared and characterized by elemental analysis, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic methods. The crystal structure of one of them has been determined by X-ray crystallography. The spectral data of the complexes are consistent with sulfur coordination of the thiones to silver(I). The single crystal X-ray structure of complex 1, {[Ag(PPh₃)(thiourea)(NO₃)]₂·[Ag(PPh₃)(thiourea)]₂(NO₃)₂}, shows that the complex consists of two independent centrosymmetric binuclear units, each having the silver atoms coordinated to one PPh₃ and two bridging thiourea molecules. In one of the independent units the silver atom is additionally bound to a nitrate ion, leading to a tetrahedral geometry, while in the other unit the silver atom adopts a trigonal planar environment. Antimicrobial activities of the complexes were evaluated by their minimum inhibitory concentration and the results showed that the complexes show a wide range of activity against two gram-negative bacteria (Escherichiacoli, Pseudomonasaeruginosa) and molds (Aspergillusniger, Penicilliumcitrinum), while the activities were poor against yeasts (Candidaalbicans, Saccharomycescerevisiae). However, the title complex did not show activity against any tested microorganism.     

Selektive Darstellung zweifach diorganophosphido-verbrückter Metallatetrahedrane [Re2(MPR3)2(μ-PR2)2(CO)6] mit Re2M2-Metallgerüst (M = Au,Ag)

Selective Preparation of Twofold Diorganophosphido-bridged Metallatetrahedranes [Re₂(MPR₃)₂(μ-PR₂)₂(CO)₆] with Re₂M₂ Metal Core (M = Au, Ag) The reaction of the in situ prepared salt Li[Re₂(AuPR)(μ-PR₂)(CO)₇Cl] (R = R′ = Cy ( 1 a ), R = Cy, R′ = Ph ( 1 b ), R = Ph, R′ = Cy ( 1 c ), R = Ph, R′ = Et ( 1 d ), R = Ph, R′ = Ph ( 1 e )) with one equivalent HPR in methanolic solution at room temperature yields the neutral cluster complexes [Re₂(AuPR)(μ-PR₂)(CO)₇(ax-HPR) (R = R′ = R″ = Cy ( 2 a ), Ph ( 2 b ), R = R′ = Cy, R″ = Et ( 2 c ), R = Cy, R′ = R″ = Ph ( 2 d ), R = Cy, R′ = Ph, R″ = Et ( 2 e ), R = R″ = Ph, R′ = Et ( 2 f ), R = Ph, R′ = Cy, R″ = Et (2 g)). Photochemically induced these complexes react in the presence of the organic base DBU in THF solution to give the doubly phosphido bridged anions Li[Re₂(AuPR)(μ-PR₂)(μ-PR)(CO)₆], which were characterized as salts PPh₄[Re₂(AuPR)(μ-PR₂)(μ-PR)(CO)₆] (R = R′ = R″ = Ph ( 3 a ), R = R′ = Ph, R″ = Cy ( 3 b ), R = Ph, R′ = Cy, R″ = Et ( 3 c ), R = R″ = Ph, R′ = Et ( 3 d )). These precursor complexes 3 then react with one equivalent of ClMPR (M = Au, Ag) to doubly phosphido bridged metallatetrahedranes [Re₂(MPR₃)₂(μ-PR₂)(μ-PR)(CO)₆] (M = Au, R = R′ = R″ = Ph ( 4 a ), M = Au, R′ = Et, R = R″ = Ph ( 4 b ), M = Au, R = R′ = Ph, R″ = Cy ( 4 c ), M = Au, R = Cy, R′ = Ph, R″ = Et ( 4 d ), M = Ag, R = R′ = R″ = Ph ( 4 e )). All isolated cluster complexes were characterized and identified by the following analytical methods: NMR- (¹H, ³¹P) and ν(CO) IR-spectroscopy and, additionally, complexes 2 b , 4 a and 4 e by X-ray structure analysis.