The shape- and structure-directing ability of capping agents, namely, acetic acid (AA) and folic acid (FA), has been analyzed in the synthesis of hollow plasmonic nanostructures via the nanoscale Kirkendall effect. FA was found to possess both shape-directing and structure-directing abilities when spherical solid Ag2O nanoparticles were transformed into hollow silver nanocubes (HAgNCs). In contrast, AA acted only as a structure-directing agent in the transformation from solid Ag2O nanospheres to hollow Ag nanospheres (HAgNSs). FA capping leads to enhanced plasmon tunability range from 535 to 640 nm in the hollow silver nanostructures. The size and shape of nanostructures were analyzed by high-resolution transmission electron microscopy (HRTEM). HRTEM revealed that the outer diameter of AA-capped HAgNSs is 50 ± 10 nm while edge-length for FA-capped HAgNCs is 100 ± 15 nm. The diameter of inner void space was found to be 30 ± 5 and 43 ± 5 nm for HAgNSs and HAgNCs, respectively. The phase purity of the hollow nanostructures was confirmed by X-ray diffraction and energy dispersive X-ray measurements. Due to unique structural and plasmonic features, FA-capped HAgNCs are well-suited for biomedical applications.

中文翻译：

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空心银纳米结构：封端剂在调整形状、结构和等离子体特性中的作用

已经通过纳米级柯肯达尔效应在中空等离子体纳米结构的合成中分析了封端剂，即乙酸 (AA) 和叶酸 (FA) 的形状和结构导向能力。当球形固体Ag时，FA被发现具有形状导向和结构导向能力2O 纳米颗粒被转化为空心银纳米立方体（HAgNCs）。相比之下，AA 仅在固体 Ag 的转变中充当结构导向剂2O 纳米球到空心银纳米球（HAgNS）。FA 封端导致中空银纳米结构中 535 至 640 nm 的等离子体可调谐范围增强。通过高分辨率透射电子显微镜（HRTEM）分析纳米结构的尺寸和形状。HRTEM 显示，AA 封端的 HAgNS 的外径为 50 ± 10 nm，而 FA 封端的 HAgNC 的边长为 100 ± 15 nm。HAgNS 和 HAgNCs 的内部空隙空间直径分别为 30 ± 5 和 43 ± 5 nm。通过 X 射线衍射和能量色散 X 射线测量证实了中空纳米结构的相纯度。由于独特的结构和等离子体特征，FA 封端的 HAgNC 非常适合生物医学应用。