合成高产率的Au21(SR)15纳米簇

近年来，精确原子个数的金纳米簇因其在催化、生物医药、传感等领域具有潜在应用而备受关注。本研究中使用金刚烷硫醇(HS-Adam)作为配体制备了Au₂₃(S-Adam)₁₆纳米簇。在室温条件下，通过HS-Adam刻蚀Au₂₃(S-Adam)₁₆纳米簇，得到了纯度较高的Au₂₁(S-Adam)₁₅，其转换率可达20% (根据金原子计算)。并通过紫外可见吸收光谱(UV-Vis)，电喷雾(ESI)和基质辅助激光解析飞行时间(MALDI)质谱以及热重分析(TGA)对合成的金纳米簇进行表征。

Synthesis of High Yield Au21(SR)15 Nanoclusters

In recent years, Au nanoclusters have attracted much attention as new nanomaterials, which contain several to two hundred Au atoms and are protected by ligands. The structures and properties of Au nanoclusters are usually sensitive to the particle size due to quantum confinement effect. Au nanoclusters have been applied to different fields, such as optical properties, catalysis, and biology. There are two common methods for the synthesis of atomically precise Au nanoclusters: "size focusing" and "ligand exchange". Although a series of Au nanocluster have been obtained via "size focusing" and "ligand exchange", obtaining high yield of such Au nanoclusters is a challenge. Au₂₁(S-Adam)₁₅ was previously synthesized via etching Au₁₈ nanoclusters with excess thiols, and its crystal structure was determined by X-ray diffraction crystallography; however, the yield of Au nanoclusters was low. In this study, we prepared Au₂₁(S-Adam)₁₅ in high yield via conversion of Au₂₃(S-Adam)₁₆ to Au₂₁(S-Adam)₁₅. Firstly, Au₂₃(S-Adam)₁₆ nanoclusters were synthesized using adamantanethiols(HS-Adam) as the protecting ligand and HAuCl₄ as the gold resource in ethyl acetate solvent. Au₂₃(S-Adam)₁₆ were further etched with excess thiols at room temperature. After reacting for 30 min, highly pure Au₂₁(S-Adam)₁₅, with high yield of ~20% based on HAuCl₄ precursor, were successfully prepared. Au₂₃(S-Adam)₁₆ and Au₂₁(S-Adam)₁₅ were characterized by electrospray ionization (ESI), UV-Vis absorption spectroscopy, matrix-assisted laser desorption ionization (MALDI) mass spectrometry, and thermogravimetric analysis (TGA). ESI-MS and UV-Vis spectra confirm the high purity of the Au₂₃(S-Adam)₁₆. After conversion, UV-Vis spectra show the absorption peaks of Au₂₁(S-Adam)₁₅ at 700, 540, 435 and 380 nm. The MALDI-MS of Au₂₁(S-Adam)₁₅ shows several peaks at 6502, 6471, 6106, 5411, and 5048, assigned to Au₂₁(S-Adam)₁₄S, Au₂₁(S-Adam)₁₄, Au₂₀(S-Adam)₁₃, Au₁₉(S-Adam)₁₀, and Au₁₈(S-Adam)₉, respectively. The fragments of Au nanoclusters were produced by the strong laser intensity, which easily removes carbon tails from HS-Adam. Thermogravimetric analysis (TGA) was also performed to check the purity of Au₂₁(S-Adam)₁₅ nanoclusters. The TGA curve shows a weight loss of 42% (expected value, 38%). UV-Vis absorption spectroscopy was performed to track the conversion of Au₂₃(S-Adam)₁₆ to Au₂₁(S-Adam)₁₅. It was found that Au₂₃(S-Adam)₁₆ can convert to Au₂₁(S-Adam)₁₅ with a conversion efficiency of up to 97%, using excess thiols at room temperature within 30 min. In general, we successfully synthesized highly pure Au₂₁(S-Adam)₁₅ nanoclusters, with high yield of ∼20% based on HAuCl₄, by etching Au₂₃(S-Adam)₁₆ with excess thiols at room temperature.