Preparation and properties of CdS/Au composite nanorods and hollow Au tubes

1-dimensional (1D) metal-semiconductor nano-scale composite superstructures based on Au nanoparticles and CdS nanorods were prepared.The outer surface of CdS nanorods was modified with mercapto-ethylamine (MEA) in advance.With the aid of MEA,dense and uniform Au nanoparticles were deposited onto the external wall of CdS nanorods through in situ chemical reduction of AuCl4-ions.Those Au nanoparticles induced further electroless deposition and a continuous layer of Au was formed on CdS nanorods.Stable hollow ...     

金/二氧化硅中空核壳纳米球的制备与表征

采用水热反应法和正硅酸乙酯水解法制备出核壳结构的Au/C纳米球颗粒以及夹层结构的Au/C/SiO<,2>纳米球颗粒,在空气中锻烧将Au/C/SiO<,2>夹层结构中的碳层除去,得到内部带有可移动纳米金核、壳层厚度约为20 nM的中空Au/SiO<,2>纳米球颗粒.用透射电子显微镜对所制得的纳米微球的形貌进行表征,并用红...     

纳米CeO2的表面改性及其在水介质中的分散性能

采用阴离子型表面活性剂十二烷基硫酸钠对纳米CeO₂进行表面修饰,考察了表面改性工艺条件对纳米CeO₂在水介质中粒度分布及Zeta电位的影响,确定了适宜的表面改性工艺条件：改性剂质量浓度60g/L、改性温度25℃、改性时间4h、搅拌速率150r/min,pH 9~11。采用TEM、FT-IR、XRD对改性前后的纳米CeO₂颗粒进行了表征,结果表明改性后纳米CeO₂表面包裹了一层改性剂分子,颗粒在水介质中分散性良好,达到了单分散。此外,采用溶液共混法制备聚乙烯醇（PVA）/ CeO₂纳米复合膜材料,利用UV-Vis分光光度计表征了复合膜材料的光学性能,发现纳米复合膜具有良好的紫外屏蔽性能以及高的可见光透过率,在300~400nm的近紫外光区,复合膜的紫外屏蔽率可达97%,添加5%纳米粒子的复合膜在650nm处的可见光透过率比纯PVA膜降低了3%,保证了复合膜的透明度。     

连续还原法制备Au/Fe3O4纳米复合粒子

采用共沉淀法制备20～40nm的Fe₃O₄颗粒。在Fe₃O₄悬浮液中分别利用柠檬酸钠单独作为还原剂、四羟甲基氯化磷（THPC）和抗坏血酸共同作为还原剂还原HAuCl₄,生成10～90nm的Au纳米颗粒,形成Au/Fe₃O₄复合颗粒。通过透射电子显微镜和紫外分光光度计对Au/Fe₃O₄进行表征,研究还原剂种类对Au/Fe₃O₄粒径、形貌和分散性的影响,结果表明：柠檬酸钠为还原剂时,生成Au纳米颗粒的反应主要在Fe₃O₄纳米颗粒表面进行,Au纳米颗粒的负载量随柠檬酸钠用量增加而减少,粒径在28.08～77.71nm之间;THPC和抗坏血酸共同作为还原剂时,先在Fe₃O₄ 纳米颗粒表面生成THPC-Au,加入抗坏血酸后生成Au纳米颗粒,粒径在71.44～153.2nm之间。     

中心掺杂对CNT-C_(60)-CNT分子结电子输运性质影响的第一性原理研究

用第一性原理计算方法研究了在C60中心掺入Si、Li、Au等单原子后对CNT-C60-CNT分子结电子输运性质的影响,包括掺杂前后各体系在不同接触距离下输运性质的变化.计算结果表明:在C60中心,Li原子的存在显著增大了其平衡电导,而Si,Au等原子对体系电子输运性质的影响比较复杂.最后,研究并比较了各体系在非平衡态下的I-V特性.     

电化学沉积Rh制备紫外拉曼活性基底

Rh在紫外激发区间有着较强的表面增加拉曼散射(SERS).用循环伏安法研究了RhCl3溶液中Rh3 在Au电极上的电化学还原行为,用恒电位阶跃法在Au基底上制备了Rh沉积层,并用场发射扫描电子显微镜、能谱及电化学方法对得到的沉积层进行了表征.结果表明,在所选择的电位下用电沉积方法能够在金表面得到均匀的Rh沉积层,该沉积层保持了金属Rh原有的电化学特性.采用电化学方法通过先粗糙Au电极再沉积Rh的策略,可以制备粗糙的Rh表面作为紫外SERS基底.拉曼光谱实验表明,以吡啶为探针分子,该基底具有很好紫外SERS活性.     

阶梯状InGaN量子阱发光二极管的光学特性

利用有效质量理论,研究了传统量子阱结构(样品A)、In_(0.15)Ga_(0.85)N/In_(0.25)Ga_(0.75)N阶梯状量子阱结构(样品B)和In_(0.25)Ga_(0.75)N/In_(0.15)Ga_(0.85)N阶梯状量子阱结构(样品C)发光二极管的光学性质。数值结果表明,在较大的注入电流密度下,样品B具有最大的内量子效率,并且能有效地抑制效率下降效应。其可归因于二方面:一方面,相比样品A和C,样品B在较高跃迁能级具有更大的光学动量矩阵元和电子-空穴费米分布函数之积,从而导致了更大的总辐射复合率;另一方面,由于样品B在导带中具有更大的内部电场,致使电子在阱层中分布在更窄的区域内,降低了电子-空穴交叠,俄歇复合率也被降低了。值得注意的是,样品C在价带中具有较大的内部电场,导致了空穴在阱层中分布在较窄的区域内。尽管如此,由于电子空穴的有效质量不一样,内部电场对电子空穴分布的影响也不同,反而导致了样品C具有更大的电子-空穴交叠,更高的俄歇复合率。此外,通过降低阶梯状量子阱中第一层InGaN层的厚度,样品B的发光效率能进一步提高。     

基于植酸胶束制备纳米金及其SERS特性研究

在溶液中用替换法合成稳定的拉曼信号较强的金纳米粒子,即首先以植酸为稳定剂和控型剂,用柠檬酸三钠还原硝酸银合成银纳米粒子,再利用银纳米粒子还原氯金酸,在水溶液中制备金纳米粒子.采用紫外-可见(UV-Vis)吸收光谱、透射电子显微镜(TEM)、能量散射光谱(EDX)对金纳米粒子的光学性质及形貌结构进行了表征,实验表明合成的金纳米粒子结构均一、分散性好.以罗丹明6G为探针分子,研究了金纳米粒子作为基底的表面增强拉曼光谱(SERS)效应,结果表明:这种金纳米粒子具有SERS信号强、检测限低、稳定性强等优点.     

Au(Cu、Ag)／SiO_2纳米薄膜的制备及其微观结构表征

用多靶磁控溅射技术制备了不同形貌的Au(Ag、Cu)纳米颗粒分散SiO2薄膜。利用透射电镜对Au／SiO2薄膜的微观结构、表面形貌进行了表征。结果表明通过调控金属颗粒的沉积时间和靶材的溅射频率可以制备不同形貌金属颗粒ISi02单层薄膜。单层Au／SiO2薄膜中Au沉积时问为5s时,Au颗粒为圆形,当沉积时间为10s时,Au颗粒连接成网络状结构;单层AgiSi02薄膜中,Ag靶的射频功率为150W时,颗粒形状接近圆形,Ag靶的射频功率为100W时,Ag颗粒几乎密集在一起,形成膜状结构:单层Cudsi02薄膜中Cu的沉积时间为10s时,Cu颗粒形成网络状结构,Cu的沉积时问为20s时,形成的是Cu膜。     

以金纳米粒子为探针研究二价金属离子与脂质双层膜的相互作用

采用一步法制备了二1-联十六烷醇磷酸氢酯(DHP)脂质双层膜保护的金纳米粒子,并以此为探针用紫外-可见吸收光谱法研究了二价金属离子Ca2+和Mg2+与金纳米粒子表面支撑的DHP双层膜之间的相互作用.结果表明,Ca2+和Mg2+能够促使DHP双层膜发生聚集、融合和倒塌,并且Ca2+的作用要强于Mg2+.     

咪唑类离子液体在金纳米粒子表面结构性质的模拟研究

采用分子动力学(Molecular Dynamics,MD)模拟方法,研究了1-丁基-3-甲基咪唑四氟硼酸盐([BMIM][BF₄])离子液体在不同尺寸的金纳米粒子表面的结构性质.计算结果在分子水平上揭示了咪唑类离子液体在Au纳米粒子表面的结构特征与纳米粒子尺寸密切相关.通过分析,发现阳离子中的烷基侧链在小尺寸Au₁₃纳米粒子表面聚集的最多,然而阳离子中的咪唑环则在大尺寸Au₃₀₉纳米粒子表面聚集的最多.同时,取向分布也表明阳离子中的咪唑环倾向于分布在大尺寸Au₃₀₉纳米粒子周围而不是小尺寸Au₁₃纳米粒子.进一步的能量分析表明,阳离子中的烷基侧链与小尺寸的Au₁₃纳米粒子相互作用能要强于阳离子中的咪唑环,而Au₃₀₉纳米粒子则与咪唑环的相互作用能最强.此外,无论是对于小尺寸的Au₁₃纳米粒子还是大尺寸的Au₃₀₉纳米粒子,阴离子的相互作用能都是最小的.这预示着阴离子对于Au纳米粒子表面结构性质是典型的间接作用.     

Ohmic contact properties of p-type surface conductive layer on H-terminated diamond films prepared by DC arc jet CVD

With the advantages of high deposition rate and large deposition area, polycrystalline diamond films prepared by direct current (DC) arc jet chemical vapor deposition (CVD) are considered to be one of the most promising materials for high-frequency and high-power electronic devices. In this paper, high-quality self-standing polycrystalline diamond films with the diameter of 100 mm were prepared by DC arc jet CVD, and then, the p-type surface conductive layer with the sheet carrier density of 1011-1013 cm?2 on the H-terminated diamond film was obtained by micro-wave hydrogen plasma treatment for 40 min. Ti/Au and Au films were deposited on the H-terminated diamond surface as the ohmic contact electrode, respectively, afterwards, they were treated by rapid vacuum annealing at different temperatures. The properties of these two types of ohmic contacts were investigated by measuring the specific contact resistance using the transmission line method (TLM). Due to the formation of Ti-related carbide at high temperature, the specific contact resistance of Ti/Au contact gradually decreases to 9.95 × 10?5 Ω·cm2 as the temperature increases to 820℃. However, when the annealing temperature reaches 850℃, the ohmic contact for Ti/Au is degraded significantly due to the strong diffusion and reaction between Ti and Au. As for the as-deposited Au contact, it shows an ohmic contact. After annealing treatment at 550℃, low specific contact resistance was detected for Au contact, which is derived from the enhancement of interdiffusion between Au and diamond films.     

Surface modifications of Pt-based atomically ordered nanoparticles to improve catalytic performances for oxygen reduction reaction

Bimetallic platinum-cobalt (Pt–Co) nanostructure catalysts represent superior catalytic performances for oxygen reduction reaction (ORR). In a variety of Pt–Co catalyst structures, atomically ordered structure catalysts show excellent catalytic performances in the ORR. In this work, for promoting their catalytic performances, atomically ordered PtCo nanoparticles (PtCo/C) with carbon supported were successfully prepared by an improved impregnation method and annealing. Then, the ordered PtCo/C catalysts have been significantly improved by doped with ultralow amount of Au and Cr transition metal. The physical and electrochemical test results demonstrate the Cr–PtCo/C and Au–PtCo/C catalysts have superior catalytic performances including mass activity and stability compared to commercialized Johnson Matthey (JM) Pt/C, which was the result of the modified electronic properties of Pt surface and atomically ordered structure. The presence of Au and Cr enhances the stability of PtCo/C catalysts. This work represents a simple way to promote the catalytic performances of the atomically ordered catalysts.     

表面增强拉曼光谱研究尼古丁与金属纳米粒子的相互作用

以金、银纳米及Au@Ag、Au-Ag合金复合纳米粒子为基底,研究尼古丁分子的表面增强拉曼光谱,讨论分子在4种纳米粒子表面的作用方式及可能的吸附取向.结果表明,分子在金纳米和Au-Ag合金纳米粒子表面的吸附取向相同——垂直吸附,不同的是与金纳米粒子形成了稳定的N-Au键;由于银纳米粒子和Au@Ag核壳纳米粒子表面均富含大...     

Synthesis of Au–Ag alloy nanoparticles supported on silica gel via galvanic replacement reaction

Synthesis of supported Au-Ag bimetallic has attracted much attention since we found for the first time that Au and Ag had synergistic effect on CO oxidation and preferential CO oxidation in rich hydrogen.In this work,the formation of Au-Ag alloy nanoparticles supported on silica gel by galvanic replacement reaction has been investigated.We applied various characterizations including X-ray diffraction(XRD),transmission electronic microscopy(TEM),ultraviolet-visible spectroscopy(UV-vis),X-ray absorption spectroscopy(XAS) to characterize the formation process of Au-Ag alloy.Although the average particle sizes of the Au-Ag alloy nanoparticles obtained by the galvanic replacement reaction are relatively large comparing with that of loading Au first,the catalytic activity of the catalyst in preferential CO oxidation is almost the same.This result manifested that the particle size effect of Au-Ag nanoparticles was not as tremendous as that of monometallic gold.The formation of Au-Ag alloy made it less sensitive to the particle size.     

镍-磷/金纳米粒子复合化学镀层的研究

在化学镀镍磷溶液中添加金纳米粒子，在基体钢铁上沉积得到镍-磷/金纳米粒子复合镀层. 金纳米粒子在镀液中的浓度为1.0?μmol•L-1. 用扫描电子显微镜，能谱仪，示差扫描热量分析仪，X 射线衍射仪，显微硬度计等仪器对镀层性能进行了分析. 通过EDS分析表明，Ni P镀层中P的质量分数为9.72%，而Ni P/Au镀层中P质量分数为9.29%，金的质量分数为0.93%. 与镍-磷合金镀层相比，纳米复合镀层具有较高的硬度，并且镀层组织致密，孔隙率小，对基体具有更好的保护作用.     

Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation.The dependence of laser fl uence on the surface plasmon characteristics of the nanoparticles was investigated.Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids.The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process.The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones.The surface enhanced Raman scattering activity of the Au,Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules.Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.     

氩气保护条件下碳对AM60镁合金组织性能的影响

在氩气保护精炼条件下研究了煤粉、石墨粉、碳纤维等形态的碳元素对AM60镁合金组织与性能的影响,探讨了C元素对其合金组织的细化机理。研究结果表明,在AM60镁合金中加入少量不同形态的碳元素能有效地改善其显微组织,使AM60镁合金的铸态室温力学性能有了不同程度的提高;当碳以纤维状态加入时,合金室温铸态力学性能的提高幅度最大,其抗拉强度和延伸率分别达到了242.4 MPa和13.2%,分别在原合金的基础上提高了23%和2.5倍。     

Microstructural evolutions of Cu(Ni)/AuSn/Ni joints during reflow

Interfacial reactions of the Ni/AuSn/Ni and Cu/AuSn/Ni joints are experimentally studied at 330℃for various reflow times.The microstructures and mechanical properties of the as-solidified solder joints are examined.The as-solidified solder matrix of Ni/AuSn/Ni presents a typical eutecticξ-(Au,Ni)_5Sn+δ-(Au,Ni)Sn lamellar microstructure after reflow at 330℃for 30 s.After reflow for 60 s,a thin and flat(Ni,Au)_3Sn_2 intermetallic compound(IMC) layer is formed,and some needle-like(Ni,Au)_3Sn_2 phases grow f...     

Surface transfer doping of diamond

The electronic properties of many materials can be controlled by introducing appropriate impurities into the bulk crystal lattice in a process known as doping. In this way, diamond (a well-known insulator) can be transformed into a semiconductor, and recent progress in thin-film diamond synthesis has sparked interest in the potential applications of semiconducting diamond. However, the high dopant activation energies (in excess of 0.36 eV) and the limitation of donor incorporation to (111) growth facets only have hampered the development of diamond-based devices. Here we report a doping mechanism for diamond, using a method that does not require the introduction of foreign atoms into the diamond lattice. Instead, C60 molecules are evaporated onto the hydrogen-terminated diamond surface, where they induce a subsurface hole accumulation and a significant rise in two-dimensional conductivity. Our observations bear a resemblance to the so-called surface conductivity of diamond seen when hydrogenated diamond surfaces are exposed to air, and support an electrochemical model in which the reduction of hydrated protons in an aqueous surface layer gives rise to a hole accumulation layer. We expect that transfer doping by C60 will open a broad vista of possible semiconductor applications for diamond.