Subnanometer clusters exhibit unique properties not observed at the bulk or nanometer scale. Many applications, however, require clusters to be monodisperse in size and composition. While substantial progress has been made empirically on producing specific-sized gold clusters using different ligands, the mechanisms of cluster formation remain insufficiently understood. Using high mass-resolution electrospray ionization mass spectrometry, we characterized the formation of cationic triphenylphosphine-ligated gold clusters [Au_x(PPh₃)_y^z+] in solution. Our data provides evidence that small hydrogen-containing intermediate “building blocks” (i.e., Au₂(PPh₃)₂H⁺, Au₄(PPh₃)₄H⁺, and Au₇(PPh₃)₇H₅²⁺) are responsible for the growth of larger gold clusters (i.e., Au₆(PPh₃)₆²⁺ and Au₈(PPh₃)₇²⁺) over several hours. In addition, intermediate degradation and cluster growth are shown to be dependent on irradiation of the reacting solution with light. Specifically, the rate of growth of large clusters is demonstrated to scale with the intensity of light exposure. Complementary theoretical calculations were also performed that provide molecular-level insight into the nature of the bonding between the hydrogens and gold atoms in the intermediate Au-phosphine clusters. Collectively, our joint experimental and theoretical findings advance the understanding of the factors at play in the size-selective synthesis of ligated gold clusters in solution.

中文翻译：

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光暴露促进中间体降解和磷化氢键金簇的生长。

亚纳米团簇表现出独特的性质，在体积或纳米尺度上没有观察到。然而，许多应用要求簇在尺寸和组成上是单分散的。尽管在使用不同的配体生产特定尺寸的金簇上，在经验上已取得实质性进展，但对簇形成的机理仍知之甚少。使用高质量的电喷雾电离质谱，我们表征了溶液中阳离子三苯基膦连接的金簇[Au _x（PPh ₃）_y ^{z +} ]的形成。我们的数据提供了证据表明，小中间“积木”含氢（即，金₂（PPH ₃）₂ ħ ⁺，AU ₄（PPH ₃）₄ ħ ⁺和Au ₇（PPH ₃）₇ ħ ₅ ²⁺）负责较大金簇的生长（即，金₆（PPH ₃）₆ ²⁺和Au ₈（PPh ₃）₇ ²⁺）几个小时。另外，显示出中间降解和簇生长取决于光照射反应溶液。具体而言，证明了大簇的生长速率与曝光强度成比例。还进行了补充的理论计算，从而提供了分子级的洞察力，了解了中间金膦簇中氢与金原子之间的键合性质。总而言之，我们的联合实验和理论研究结果使人们对溶液中结扎的金团簇的尺寸选择性合成中起作用的因素有了更深入的了解。