We report, for the first time, a technique to synthesize free-standing, one-atom thick 2D gold crystals (namely, goldene) and self-assembled 2D periodic arrays of goldene. High-resolution transmission electron microscopy (HRTEM) imaging of goldene revealed herringbone and honeycomb lattices, which are primarily gold surface features due to its reconstruction. Imaging of these surface-only features by a nonsurface characterization technique such as HRTEM is an unequivocal proof of the absence of three-dimensionality in goldene. Atomic force microscopy confirmed 1–2 Å thickness of goldene. High-resolution X-ray photoelectron spectroscopy (HR-XPS), selective area electron diffraction, and energy-dispersive X-ray spectroscopy confirmed the chemical identity of goldene. We discovered the phenomenon of electric field-induced self-assembly of goldene supracrystals with a herringbone structure and developed an electric field printing (e-print) technique for goldene arrays. Goldene showed a semiconductor response with a knee voltage of ∼3.2 V, and I/V spectroscopy revealed periodic room temperature Coulomb blockade oscillations. These observations are consistent with the theoretical calculations reported in the literature predicting enhanced Coulombic interactions between gold valence electrons and the nucleus in stable 2D gold. Goldene exhibited multiple, intense, and well-resolved optical absorption peaks and several fine bands across the UV–vis region, and we calculated its optical band gap to be 3.59 eV. Magnetic force microscopy measurements of goldene periodic arrays showed a ∼5 mV peak amplitude confirming its ferromagnetism. Optical and magnetic properties of goldene are consistent with those reported in the literature for 2D planar gold clusters with less than 12 atoms.

中文翻译：

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自组装单原子层金晶体的合成-Goldene

我们首次报告了一种合成独立的单原子厚二维金晶体（即 goldene）和自组装二维周期性 goldene 阵列的技术。goldene 的高分辨率透射电子显微镜 (HRTEM) 成像揭示了人字形和蜂窝状晶格，由于其重建，它们主要是金表面特征。通过 HRTEM 等非表面表征技术对这些仅表面特征进行成像是 goldene 中不存在三维性的明确证据。原子力显微镜证实了 1–2 Å 的金色厚度。高分辨率 X 射线光电子能谱 (HR-XPS)、选择性区域电子衍射和能量色散 X 射线光谱证实了黄金的化学特性。我们发现了具有人字形结构的 goldene 超晶的电场诱导自组装现象，并开发了一种用于 goldene 阵列的电场印刷（e-print）技术。Goldene 显示出半导体响应，拐点电压约为 3.2 V，并且I / V谱显示周期性室温库仑阻塞振荡。这些观察结果与文献中报告的理论计算一致，预测金价电子与稳定二维金中的原子核之间的库仑相互作用增强。Goldene 在紫外-可见光区域显示出多个强烈且分辨率良好的光学吸收峰和几个精细的波段，我们计算出其光学带隙为 3.59 eV。黄金周期性阵列的磁力显微镜测量显示~5 mV 的峰值振幅证实了其铁磁性。goldene 的光学和磁学性质与文献中报道的少于 12 个原子的二维平面金团簇的性质一致。