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Doping heterometal atoms into ligand-protected gold superatom nanoclusters (Au n NCs) is proposed to further diversify their geometrical and electronic structures and enhance their photoluminescence properties, which is attributed to the mixing and effects between atoms. However, the fundamental principles that govern the optoelectronic properties of the doped Au n NCs remain elusive. Herein, we systematically explored two prototypical 8-electron Au n ( n = 11 and 13) NCs with and without Ir dopant atoms using comprehensive ab initio calculations and real-time nonadiabatic molecular dynamics simulations. These doped Au n NCs maintain their parent geometrical structures and 8-electron superatomic configuration (1S 2 1P 6 ). Strong core-shell (Ir-Au n ) electronic coupling significantly expands the energy gap, resulting in a weak nonadiabatic coupling matrix element, which in turn increases the carrier lifetime. This increase is mainly governed by the low-frequency vibration mode. We uncovered the relationship between electronic structures, electron-vibration, and carrier dynamics for these doped Au n NCs. These calculated results provide crucial insights for the atomically precise design of metal NCs with superior optoelectronic properties.

We have synthesized single crystals of a highly stable Ag 8 nanocluster protected by six ligands of diphenyl-2-phosphinic pyridine (DPPY) plus six ligands of phenylacetylene (PhCC). This Ag 8 (DPPY) 6 (PhCC) 6 cluster bears a triangular superatomic Ag 8 core, with the vertex and edge Ag atoms (quasi-triangle Ag 6 ) being protected by both P and N bidentate coordination of the six DPPY ligands; meanwhile, the six PhCC ligands via μ 3 -C coordination form coordination on the two central Ag atoms capped on both sides of the triangle facet. Apart from the well-organized coordination of the two ligands pertaining to the balanced interactions with the Ag 8 core, this Ag 8 nanocluster exhibits superatomic stability with two delocalized valence electrons (1S 2 ||1P 0 ), assuming that the six PhCC ligands fix 6 localized electrons from the Ag atoms. Interestingly, the Ag 8 (DPPY) 6 (PhCC) 6 NCs display temperature-dependent dual emissions at 330 and 535 nm under deep ultraviolet excitation. TD-DFT calculations reproduced the experimental spectrum, shedding light on the nature of excitation states and metal-ligand interactions in such a superatomic metal cluster.

Layered magnetic materials have recently received tremendous attention due to an attractive combination of functional properties suitable for nanoelectronics and spintronic applications. Enhancing the air stability of the material is a prerequisite for long-term durability of devices. However, the oxidation mechanism of layered magnetic materials is yet to be revealed. Herein we explore the oxidation behavior of monolayer and multilayer Fe n GeTe 2 ( n = 3, 4, 5) and Cr 2 Ge 2 Te 6 using first-principles calculations. The results show that these monolayer systems are prone to be oxidized in ambient air. With increasing thickness, however, multilayer Fe n GeTe 2 exhibits distinct oxidation behavior from its monolayer counterparts, originating from its unexpected strong interlayer coupling characterized by wavefunction overlapping of adjacent Te atoms between Fe n GeTe 2 layers. Moreover, O 2 adsorption does not severely deteriorate the magnetism of layered Fe n GeTe 2 and Cr 2 Ge 2 Te 6 . Given the fact that oxidation properties can be altered by interlayer coupling, our work opens a paradigm for obtaining oxidation-resistant layered materials.

We examine the atomic structure of chemical vapour deposition grown multilayer WS2 pyramids using aberration corrected annular dark field scanning transmission electron microscopy coupled with an in situ heating holder. The stacking orders and specific types of defects after partial degradation by S and W atomic loss at high temperature are resolved layer-by-layer. Our study of an individual WS2 pyramid with at least six layers, reveals a mixed 2H and 3R polytype stacking. Etching occurred both top and bottom of the WS2 pyramid, which aids in determining the exact vertical layer stacking configurations in the thicker regions. We provide an extensive catalogue of the contrast profiles associated with defects in WS2 as a function of layer number and stacking type, as imaged using ADF-STEM. These results provide extensive details about the identification of a wide range of defects in S2 layers, and the unique ADF-STEM contrast patterns that arise from complex multilayer stacking.

Hydrogenation of carbon dioxide (CO2) is among the most promising approaches for reclaiming the major greenhouse gases to produce fuels and chemicals. Developing catalysts composed of natural abundant, economical and eco-friendly elements is critical for the industrialization of this technology. Silicon satisfies all these requirements but lacks activity. Using first-principles calculations, we show for the first time that the two-dimensional phase of silicon, i.e., mono- and few-layer silicene supported by a Ag(111) substrate, exhibits superior catalytic activity for CO2 hydrogenation, with selectivity being intrinsically controlled by the number of layers. The supported silicene monolayer as a catalyst leads to the formation of carbon monoxide, formic acid and formaldehyde, while the formation of methanol and methane is favored on bilayer silicene on the Ag substrate. The key parameters governing activity and selectivity are the densities and energy levels of surface dangling bond states, which in turn are mediated by the substrate coupling and covalent interaction between silicene layers. These theoretical results elucidate the fundamental principles for tailoring the catalytic properties of non-metal materials by controlling the number of layers and manipulating the surface states and will advance the development of silicon-based catalysts for renewable energy technologies.

When secondary domains nucleate and grow on the surface of monolayer MoS2, they can extend across grain boundaries in the underlying monolayer MoS2 and form overlapping sections. We present an atomic level study of overlapping antiphase grain boundaries (GBs) in MoS2 monolayer-bilayers using aberration-corrected annular dark field scanning transmission electron microscopy. In particular we focus on the antiphase GB within a monolayer and track its propagation through an overlapping bilayer domain. We show that this leads to an atomically sharp interface between 2H and 3R interlayer stacking in the bilayer region. We have studied the micro-nanoscale "meandering" of the antiphase GB in MoS2, which shows a directional dependence on the density of 4 and 8 member ring defects, as well as sharp turning angles 90°-100° that are mediated by a special 8-member ring defect. Density functional theory has been used to explore the overlapping interlayer stacking around the antiphase GBs, confirming our experimental findings. These results show that overlapping secondary bilayer MoS2 domains cause atomic structure modification to underlying anti-phase GB sites to accommodate the van der Waals interactions.