Surfactantless photochemical growth of Ag nanostructures on GaN epitaxial films with controlled morphologies and their application for SERS
Surfactantless photochemical growth of Ag nanostructures on GaN epitaxial films with controlled morphologies and their application for SERS
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DOI：
10.1039/c1jm13928b
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发表时间：
2012-01
影响因子：
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通讯作者：
Ruijun Wang;Duo Liu;Zhiyuan Zuo;Qian Yu;Zhaobin Feng;Hong Liu;Xiangang Xu
中科院分区：
文献类型：
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作者：
Ruijun Wang;Duo Liu;Zhiyuan Zuo;Qian Yu;Zhaobin Feng;Hong Liu;Xiangang Xu
通过一种方便、快速、无表面活性剂的光化学方法，在GaN外延膜上合成了形貌可控的银纳米结构。在n型氮化镓上，在AgNO3水溶液中进行短时间（30 s ~ 5 min）光化学反应，获得了均匀的高密度球形银纳米颗粒。降低AgNO3浓度得到支链银纳米结构。氮化镓衬底上的银纳米粒子表现出一种fabry - perot型表面等离子体共振（SPR）。在p型氮化镓上，通过改变AgNO3溶液的浓度，可以得到立方体、截断立方体、长方体、截断八面体和八面体等形状明确的银纳米晶体（nc）。我们认为多面体Ag纳米结构的形成是由氮化镓表面的成核和生长分离引起的。表面状态和载流子浓度在生长过程中都起着重要的作用。这种无表面活性剂的光化学方法是通用的，可以在室温下很容易地合成银纳米结构，这可以推广到在GaN或其他宽禁带半导体（如sic）上合成其他贵金属纳米结构，如au、Pt和Pd。所得的Ag/GaN杂化体系具有作为表面增强拉曼散射（SERS）分析的固体衬底的潜力。
Ag nanostructures with controlled morphologies have been synthesized on GaN epitaxial films through a convenient, fast, and surfactantless photochemical method. On n-type GaN, uniform spheroidic Ag nanoparticles (NPs) of high density were obtained after photochemical reaction for a short time (30 s to 5 min) in AgNO3 aqueous solution. Reducing AgNO3 concentration yielded branched Ag nanostructures. The Ag NPs on the GaN substrates exhibit a Fabry–Perot-type surface plasmon resonance (SPR). On p-type GaN, Ag nanocrystals (NCs) with well-defined shapes ranging from cubes, truncated cubes, cuboctahedra, truncated octahedra, and octahedra were obtained through varying the concentration of AgNO3 solution. We propose that the formation of polyhedral Ag NCs is induced by the separation of the nucleation and growth processes by the GaN surface. Both surface states and carrier concentration are considered to play substantial roles during the growth process. This surfactantless photochemical method is general and enables the facile synthesis of Ag nanostructures at room temperature, which may be extended for the synthesis of other noble metal nanostructures, e.g.Au, Pt, and Pd, on GaN or other wide bandgap semiconductors, e.g.SiC. The obtained Ag/GaN hybrid systems show potential application as solid substrates for surface enhanced Raman scattering (SERS) analysis.