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Anomalous shape evolution of Ag2O2 nanocrystals modulated by surface adsorbates during electron beam etching
摘要： An understanding of nanocrystal shape evolution is significant for the design, synthesis and applications of nanocrystals with surface-enhanced properties such as catalysis or plasmonics. Surface adsorbates that are selectively attached to certain facets may strongly affect the atomic pathways of nanocrystal shape development. However, it is a great challenge to directly observe such dynamic processes in situ with high spatial resolution. Here, we report the anomalous shape evolution of Ag2O2 nanocrystals modulated by the surface adsorbates of Ag clusters during electron beam etching, which is revealed through in situ transmission electron microscopy (TEM). In contrast to the Ag2O2 nanocrystals without adsorbates, which display the near-equilibrium shape throughout the etching process, Ag2O2 nanocrystals with Ag surface adsorbates show distinct facet development during etching by electron beam irradiation. Three stages of shape changes are observed: a sphere-to-a cube transformation, side etching of a cuboid, and bottom etching underneath the surface adsorbates. We find that the Ag adsorbates modify the Ag2O2 nanocrystal surface configuration by selectively capping the junction between two neighboring facets. They prevent the edge atoms from being etched away and block the diffusion path of surface atoms. Our findings provide critical insights into the modulatory function of surface adsorbates on shape control of nanocrystals.
关键词： surface adsorbates,Ag2O2 nanocrystal,shape evolution,In situ TEM,electron beam etching
更新于2025-09-23 15:23:52
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Effective shape-controlled synthesis of gallium selenide nanosheets by vapor phase deposition
摘要： The controlled synthesis of large and uniform gallium selenide (GaSe) crystals is crucial for its various applications based on the attractive properties of this emerging material. In this work, vapor phase growth of high-quality monolayer GaSe nanosheets with multiple shape and size is achieved by tuning the Ga/GaSe ratio in the precursor. A theoretical model based on density functional theory calculations and kinetic Wulff construction theory describe the observed shape evolution of the GaSe nanosheets. Results show that the Ga/Se ratio plays a critical role in the evolution of the domain shape and size. Moreover, the as-grown GaSe nanosheets show improved performance with photoresponse time less than 0.7 ms and responsibility up to 3,000 A/W. This study presents a previously unexplored strategy for the controlled growth of two-dimensional (2D) GaSe nanosheets for promising applications in next-generation optoelectronics.
关键词： shape-evolution,gallium selenide,photodetector,growth dynamics,controllable growth
更新于2025-09-23 15:19:57
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Self-assembled shape evolution of the domain wall and formation of nanodomain wall traces induced by multiple IR laser pulse irradiation in lithium niobate
摘要： The formation of the domain structure in congruent lithium niobate crystals by multiple pulse irradiation using an infrared laser was studied experimentally. The qualitative change of the domain wall shape with an increase of the pulse number was revealed. The chains of isolated nanodomains representing the domain wall traces appeared after each laser pulse irradiation in the samples with an irradiated polar surface covered by an indium–tin oxide layer. This effect allowed extraction of the detailed information about the evolution of the domain wall shape. The domain kinetics under the action of the pyroelectric field has been considered. The mechanism of the self-assembled shape evolution of the moving domain wall as a result of the local wall accelerations and retardations caused by the shape fluctuations (bumps and valleys) was proposed. The experimentally observed formation of the quasi-regular comb-like domain structures with randomly distributed bumps and valleys was confirmed by computer simulation. The discovered effects allowed us to create the stable random and quasi-regular domain structures and open the way for further development of the domain engineering methods.
关键词： pyroelectric field,infrared laser,nanodomains,domain wall shape evolution,lithium niobate,domain structure
更新于2025-09-23 15:19:57
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Curtailing the Overpotential of Lia??CO2 Batteries with Shapea??Controlled Cu2O as Cathode: Effect of Illuminating the Cathode
摘要： Li-air batteries are circumscribed to lab-scale research due to the uninterrupted formation of discharge products. In the case of Li–CO2 batteries, the increase in overpotential due to Li2CO3 formation results in cell death. In this study, we have synthesized Cu2O crystals having three different types of shapes, i.e., cubic, octahedral, and rhombic, to compare the catalytic activity toward CO2 reactions. The full-cycle and long-term stability test reveals that rhombohedral Cu2O facilitates Li2CO3 decomposition more efficiently than that of cubic and octahedral Cu2O. We have extended the cycle to dig into the photocatalytic activeness of the rhombic Cu2O by illuminating the cell. The repeated cycles to 1 h show maximum overpotential of 1.5 V, which is 0.5 V less than that of the cell without illumination. A postmortem analysis of the cell after dividing the cycles into segments demonstrates interesting results on the role of light and Cu2O during the cell cycle.
关键词： Li-CO2 batteries,Shape evolution,Cu2O cathode catalyst,Illumination effect,Charge overpotential
更新于2025-09-16 10:30:52