Florida State University, Department of Chemistry and Biochemistry, 95 Chieftan Way, Tallahassee, FL 32306, USA.
Phys Chem Chem Phys. 2018 May 9;20(18):12992-13007. doi: 10.1039/c7cp08682b.
We detail the characterization of atomically precise, luminescent silver and gold bimetallic nanoclusters (Ag and AgAuNCs) grown in the presence of bidentate lipoic acid (LA, the oxidized form) and dihydrolipoic acid (DHLA, the reduced form) ligands. We found that while doping AuNCs with Ag or Cu precursors using up to a 50% molar fraction (during growth) did not lead to any photoluminescence enhancement, doping of AgNCs with Au resulted in a six-fold enhancement of the PL emission compared to undoped AgNCs. The effect of doping is also reflected in the optical absorption and PL excitation spectra of the gold-doped NCs (AgAuNCs), where a clear blue shift in the absorbance features with respect to the pure AgNCs has been measured. Mass spectrometry measurements using ESI-MS showed that the AgNCs and Au-doped AgNCs had the compositions Ag29(DHLA)12 and Ag28Au(DHLA)12, respectively. The bimetallic nature of the AgAuNC cores was further supported by X-ray Photoelectron Spectroscopy (XPS) measurements. Data showed that the binding energies of the Ag and Au atoms measured from the nanoclusters were shifted with respect to those of the Ag and Au metals. Furthermore, the change in the Ag binding energy was affected by the presence of Au atoms. DOSY-NMR measurements performed on both sets of nanoclusters yielded no change in the hydrodynamic radius measured for either set of NCs when capped with the same ligands.
我们详细描述了在双齿硫辛酸（LA，氧化形式）和二氢硫辛酸（DHLA，还原形式）配体存在下生长的原子精确、发光的银和金双金属纳米团簇（Ag 和 AgAuNCs）的特性。我们发现，尽管使用高达 50%摩尔分数（在生长过程中）的 Ag 或 Cu 前体掺杂 AuNCs 不会导致任何光致发光增强，但 Au 掺杂 AgNCs 会导致与未掺杂 AgNCs 相比，PL 发射增强六倍。掺杂的效果也反映在金掺杂 NCs（AgAuNCs）的光吸收和 PL 激发光谱中，其中已经测量到相对于纯 AgNCs 的吸收特征明显蓝移。使用 ESI-MS 的质谱测量表明，AgNCs 和 Au 掺杂的 AgNCs 的组成为 Ag29(DHLA)12 和 Ag28Au(DHLA)12，分别。AgAuNC 核的双金属性质还得到了 X 射线光电子能谱（XPS）测量的支持。数据表明，从纳米团簇中测量的 Ag 和 Au 原子的结合能相对于 Ag 和 Au 金属的结合能发生了位移。此外，Ag 结合能的变化受到 Au 原子的存在的影响。对两组纳米团簇进行的 DOSY-NMR 测量表明，当用相同的配体封端时，两组 NCs 的流体力学半径均未发生变化。
