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Cooperative interactions among CTA^＋, Br^-and Ag^＋ during seeded growth of gold nanorods

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Nano Research 2017年第6期10卷 2146-2155页

作者： Yong Xu Lei Chen Xingchen Ye Xuchun Wang Jiaqi Yu Yang Zhao Muhan Cao Zhouhui Xia Baoquan Sun Qiao Zhang Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices Institute of Functional Nano and Soft Materials (FUNSOM) Soochow University Suzhou 215123 China Department of Chemistry University of California Berkeley Berkeley CA 94720 USA

We have carried out a comprehensive study on the formation mechanism of Au nanorods （AuNRs） in binary surfactant mixtures composed of quaternary ammonium halide and sodium oleate （NaOL）. We identify the cetyltrimethyl ammonium （CTA）-Br-Ag^＋ complex as the key ingredient in directing the anisotropic growth of AuNRs. Based on the improved understanding of the cooperative interactions among CTA^＋, Br^- and Ag^＋, we further demonstrate that AgBr, which is readily solubilized by the cetyltrimethyl ammonium bromide （CTAB） or cetyltrimethyl ammonium chloride （CTAC） micelles, can be employed as the combined source of Ag^＋ and Br^- for the preparation of AuNRs. The growth of high-quality AuNRs can be completed within 15 min under extremely low bromide content （0.1 mM）.

关键词： gold nanorods anisotropic nanostructure surface plasmon resonance seeded growth cetyltrimethyl ammoniumbromide (CTAB)

Vertical Bridgman seeded growth of Cd_(1-x)Zn_xTe Crystals

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Rare Metals 1994年第2期13卷 126-129页

作者：侯清润陈纪安赵乐敏张新敏 North China Research Inst of Electro-optics Beijing China

The method of vertical Bridgman seeded growth of *** crystals was studied. This method ispromising in obtaining large size single crystals and improving the crystal structure. However, some prob-lems such as seeded growth failurc exist at present.(111)-oriented Cd_(0.96)Zn_(0.04)Te single crystal substrateswith size greater than 15×15 mm￣2 arc obtained. The FWHM ranges from 18 to 66 *** and theresistivity is greater than 10￣6 obmem.

关键词： seeded growth Vertical Bridgman method CdZnTe

Combining the Curvature and Ligand Effects for Regioselective growth on Au Nano-bipyramids

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Precision Chemistry 2023年第2期1卷 94-99页

作者： Tingting Jiang Jianpeng Zong Yuhua Feng Hongyu Chen Institute of Advanced Synthesis School of Chemistry and Molecular EngineeringNanjing Tech UniversityNanjing 211816 Jiangsu ProvinceChina

We demonstrate the regioselective growth of Au on Au nanobipyramids,either with etching of the tips,uniform coating except the tips,or forming a single island on the axial tip or an island on the equatorial ***,the regioselectivity not only arises from the local curvature,as suggested by the recent literature,but also critically depends on the extent of ligand coverage on the seed *** is important to consider the competitive growth together with the curvature−ligand interplay:when there are insufficient ligands,they bind preferentially to the sharp tip for high surface energy,so that the remaining growth materials are diverted elsewhere;when the bipyramid is fully covered by ligands,the growth then selectively occurs at the tips because of the larger gaps among the ligands *** results demonstrate the great potentials in the rational design and synthesis when constructing sophisticated hybrid structures for functional nanomaterials.

关键词： Curvature effect Ligand effect Regioselective growth seeded growth Ligand coverage

Ag^＋-assisted heterogeneous growth of concave Pd@Au nanocubes for surface enhanced Raman scattering （SERS）

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Nano Research 2017年第10期10卷 3509-3521页

作者： Bo Jiang Li Xu Wei Chen Chao Zou Yun Yang Yunzhi Fu Shaoming Huang College of Materials and Chemical Engineering Hainan University Haikou 570228 China Nanomaterials and Chemistry Key Laboratory Wenzhou University Wenzhou 325027 China

AgNO3 is often used in the preparation of Au nanostructures since Ag-based substances （AgBS） can selectively be adsorbed on Au（100） and significantly modulate the growth of Au nanocrystals. High-index-faceted Au nanostructures have demonstrated excellent performance in catalysis and surface enhanced Raman scattering （SERS）, thus attracting the interest of many researchers in the past several decades. Herein, high-index-faceted Pd@Au concave nanocubes （CNCs） were prepared using AgBS as growth-directing agents in the heterogeneous growth of Au on Pd nanocubes （NCs）. During the growth of Pd@Au CNCs, Au atoms are initially deposited on the Pd{100} facets leading to the formation of thin Au shells, and then AgBS are quickly adsorbed on the formed Au（100）, favoring the growth along 〈111〉 and the formation of Pd@Au CNCs. Transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, energy dispersive spectroscopy （EDS）, high angle annular dark field （HAADF）, and scanning transmission electron microscopy EDS （STEM- EDS） were used to systematically investigate the growth of Pd@Au CNCs. We also demonstrated that the high-index-faceted Pd@Au CNCs exhibited excellent SERS performances.

关键词： heterogeneous growth nanocube concave seeded growth

Nucleation and growth Mechanisms for Pd-Pt Bimetallic Nanodendrites and Their Electrocatalytic Properties

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Nano Research 2010年第2期3卷 69-80页

作者： Byungkwon Lim Majiong Jiang Taekyung Yu Pedro H.C.Camargo Younan Xia Department of Biomedical Engineering Washington UniversitySt.LouisMissouri 63130USA Department of Chemistry Washington UniversitySt.LouisMissouri 63130USA

In a seed-mediated synthesis, nanocrystal growth is often described by assuming the absence of homogeneous nucleation in the solution. Here we provide new insights into the nucleation and growth mechanisms underlying the formation of bimetallic nanodendrites that are characterized by a dense array of Pt branches anchored to a Pd nanocrystal core. These nanostructures can be easily prepared by a one-step, seeded growth method that involves the reduction of K2PtCl4 by L-ascorbic acid in the presence of 9-nm truncated octahedral Pd seeds in an aqueous solution. Transmission electron microscopy (TEM) and high-resolution TEM analyses revealed that both homogeneous and heterogeneous nucleation of Pt occurred at the very early stages of the synthesis and the Pt branches grew through oriented attachment of small Pt particles that had been formed via homogeneous nucleation. These new findings contradict the generally accepted mechanism for seeded growth that only involves heterogeneous nucleation and simple growth via atomic addition. We have also investigated the electrocatalytic properties of the Pd-Pt nanodendrites for the oxygen reduction and formic acid oxidation reactions by conducting a comparative study with foam-like Pt nanostructures prepared in the absence of Pd seeds under otherwise identical conditions.

关键词： Palladium platinum seeded growth oxygen reduction formic acid oxidation