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Synthesis of Ultrathin Few-Layer 2D Nanoplates of Halide Perovskite Cs <sub/>3</sub> Bi <sub/>2</sub> I <sub/>9</sub> and Single-Nanoplate Super-Resolved Fluorescence Microscopy
摘要： The discovery of new two-dimensional (2D) perovskite halides has created sensation recently because of their structural diversity and intriguing optical properties. The toxicity of Pb-based perovskite halides led to the development of Pb-free halides. Herein, we have demonstrated a one-pot solution-based synthesis of 2D ultrathin (～1.78 nm) few-layer (2?4 layers) nanoplates (300?600 nm lateral dimension), nanosheets (0.6?1.5 μm), and nanocrystals of layered Cs3Bi2I9 by varying the reaction temperature from 110 to 180 °C. We have established a mechanistic pathway for the variation of morphology of Cs3Bi2I9 with temperature in the presence of organic capping ligands. Further, we have synthesized the bulk powder of Cs3Bi2I9 by mechanochemical synthesis and liquid-assisted grinding and crystalline ingot by vacuum-sealed tube melting. 2D nanoplates and bulk Cs3Bi2I9 demonstrate optical absorption edge along with excitonic transition. Photoluminescence properties of individual nanoplates were studied by super-resolution ?uorescence imaging, which indicated the blinking behavior down to the level of an individual Cs3Bi2I9 nanoplate along with its emission at the far-red region and high photostability.
关键词： ultrathin nanoplates,super-resolution ?uorescence imaging,two-dimensional (2D) perovskite halides,Pb-free halides,Cs3Bi2I9
更新于2025-09-09 09:28:46
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Manipulating the Ferroelectric Domain States and Structural Distortion in Epitaxial BiFeO3 Ultrathin Films via Bi Nonstoichiometry
摘要： Exploring and manipulating the domain configurations in ferroelectric thin films are of critical importance for the design and fabrication of ferroelectric heterostructures with novel functional performance. In this study, BiFeO3 (BFO) ultrathin films with various Bi/Fe ratios from Bi-excess to Bi-deficient have been grown on (La0.7Sr0.3)MnO3 (LSMO) covered SrTiO3 substrates by laser molecular beam epitaxy system. Atomic force microscopy and piezoresponse force microscopy measurements show that both the surface morphology and ferroelectric polarization of the films are relevant to the Bi nonstoichiometry. More significantly, the Bi-excess thin films show upward (from substrate to film surface) uniform ferroelectric polarization, while a Bi-deficient thin film exhibits downward uniform polarization, which means the as-grown polarization of the BFO thin films can be controlled by changing Bi contents. Atomic-scale structural and chemical characterizations and second harmonic generation measurements reveal that two different kinds of structural distortion and interface atomic configuration in the BFO/LSMO heterostructures can be induced by the change of Bi nonstoichiometry, leading to the two opposite as-grown ferroelectric polarizations. It has also been revealed that the band gap of the BFO thin films can be modulated via Bi nonstoichiometry. These results demonstrate that Bi nonstoichiometry plays a key role on the ferroelectric domain states and physical properties of BFO thin films, and also open a new avenue to manipulate the structure and ferroelectric domain states in BFO thin films.
关键词： BiFeO3 ultrathin films,interface atomic configuration,ferroelectric domain states,Bi nonstoichiometry,structural distortion
更新于2025-09-09 09:28:46
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Ultrathin Bi4O5Br2 nanosheets for selective photocatalytic CO2 conversion into CO
摘要： The ultrathin two-dimensional materials with the unique catalytic performance attract extensive interests of researchers. In this paper, ultrathin Bi4O5Br2 nanosheet (Bi4O5Br2-UN) is synthesized through precursor method by controlling the mole ratio of Bi(NO3)3·5H2O and cetyltrimethyl ammonium bromide. The ultrathin structure of Bi4O5Br2-UN was con?rmed by X-ray di?raction, atomic force miscroscopy and high-resolution transmission electron microscopy. UV–vis light irradiation, Bi4O5Br2-UN display excellent selective photocatalytic activity for CO2 conversion, which also was proved by isotope experiment. After 2 h reaction, the CO generation over Bi4O5Br2-UN reached 63.13 μmol g?1, which is about 2.3 times higher than that of bulk Bi4O5Br2 (27.56 μmol g?1). Additionally, the CO selectivity of Bi4O5Br2-UN is more than 99.5% in the whole catalytic process. The enhanced CO2 adsorption, suitable band position and improved charge separation induce the outstanding photocatalytic performance of Bi4O5Br2-UN. The photocatalytic mechanism of CO2 conversion with Bi4O5Br2-UN was analyzed by the in situ Fourier transform infrared spectrometry (FT-IR).
关键词： Bi4O5Br2,CO2 conversion,Photocatalysis,Selectivity,Ultrathin
更新于2025-09-09 09:28:46
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Oxygen Vacancy-Rich Ultrathin Sulfur-Doped Bismuth Oxybromide Nanosheet as a Highly Efficient Visible-Light Responsive Photocatalyst for Environmental Remediation
摘要： Designing ultrathin two-dimensional (2D) defective materials and metal-free doped materials as photocatalysts both have received enormous attentions in the field of environmental remediation due to their great potential for removing colorless contaminants. However, whether the synergism of defects and metal-free doping exists and the corresponding oxidative mechanism is unclear, which retard further developments of high performance catalysts. Here, a novel oxygen vacancy (OV)-rich ultrathin sulfur-doped BiOBr nanosheet (BB-xS) was synthesized through a facile one-step solvothermal method. Under visible light irradiation, the optimal BB-5S sample exhibited 98% degradation efficiency of 4-chlorophenol (4-CP) within 120min, which was 4.9 and 18.0 times greater than that of pristine ultrathin BiOBr and oxygen vacancy-poor sulfur-doped BiOBr, respectively. Also, this excellent photoactivity could extend to other colorless organic contaminants, such as bisphenol analogues and sulfonamides, verifying the universal applicability of BB-xS. Based on experimental results and density functional theory (DFT) calculations, it was manifested that a sub-band was generated via the synergistic effect of oxygen vacancies and sulfur doping, and it greatly enhanced the visible-light absorption capability and suppressed the photoinduced charge recombination, which would be beneficial to improve the photocatalytic activity. Additionally, the corresponding photocatalytic degradation pathway of 4-CP was also proposed. This work can provide a new protocol for the design and construction of highly active photocatalysts toward environmental remediation.
关键词： photocatalytic degradation,Ultrathin two-dimensional nanosheets,sulfur-doped,oxygen vacancy,colorless organic contaminants
更新于2025-09-09 09:28:46
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Ultrathin tungsten bronze nanowires with efficient photo-to-thermal conversion behavior
摘要： In this work, we describe a simple one-step solvothermal method to synthesize ultrathin quaternary tungsten bronze nanowires (QTBNWs). In addition, a series of alkali metal-doped QTBNWs can be prepared by simply changing the type of starting alkali carbonate and tungstate. The as-synthesized QTBNWs exhibits strong near-infrared (NIR) rays absorption, high visible light transmission and excellent photo-to-thermal conversion behavior, which are superior to those of tungsten bronze nanorods and ternary TBNWs. And its excellent photothermal performance should be attributed to great localized surface plasmon resonances (SPR).
关键词： solvothermal method,photo-to-thermal conversion,near-infrared absorption,ultrathin tungsten bronze nanowires,surface plasmon resonances
更新于2025-09-09 09:28:46
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Wafer-sized ultrathin gallium and indium nitride nanosheets through the ammonolysis of liquid metal derived oxides
摘要： We report the synthesis of centimeter sized ultrathin GaN and InN. The synthesis relies on the ammonolysis of liquid metal derived two-dimensional (2D) oxide sheets that were squeeze-transferred onto desired substrates. Wurtzite GaN nanosheets featured typical thicknesses of 1.3 nm, an optical bandgap of 3.5 eV and a carrier mobility of 21.5 cm2V-1s-1, while the InN featured a thickness of 2.0 nm. The deposited nanosheets were highly crystalline, grew along the (001) direction and featured a thickness of only three unit cells. The method provides a scalable approach for the integration of 2D morphologies of industrially important semiconductors into emerging electronics and optical devices.
关键词： ultrathin indium nitride,ultrathin gallium nitride,ammonolysis,two-dimensional materials,liquid metal derived oxides
更新于2025-09-04 15:30:14
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Interface Potentials, Intrinsic Defects, and Passivation Mechanisms in Al 2 O 3 , HfO 2 , and TiO 2 Ultrathin Films
摘要： For the tailoring of interface properties in terms of providing active centers for surface reactions, surface passivation, or the adjustment of surface potentials, ultrathin metal oxide surface coatings are of importance. In this contribution we report about the applicability of Al2O3, HfO2, and TiO2 ultrathin films prepared by atomic layer deposition (ALD) regarding the aforementioned items. We have selected these metal oxides because of their wide field of applications. HfO2 is the main competitor for the replacement of SiO2 in microelectronic devices.1,2 Al2O3 ALD films are applied for passivation schemes in silicon-based3 and more recently perovskite solar cells.4 TiO2 is, for example, attractive for resistive switching devices5 and as active or passive layer in energy conversion applications such as solar cells6 or water splitting devices,7,8 to name a few. Here, the use of the ALD technique brings advantages such as: (i) precise thickness control to optimize the trade-off between light absorption (in a range of depletion layer) and charge separation (thinner thickness),7 (ii) high conformity to coat complex structures accompanied by increased light absorption,7 and (iii) capability to control the band-gap narrowing by doping with W7 or N9,10 and hence allow visible light absorption.
关键词： Al2O3,HfO2,TiO2,ultrathin films,interface potentials,intrinsic defects,passivation mechanisms,atomic layer deposition
更新于2025-09-04 15:30:14
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MOFs-derived ultrathin holey Co3O4 nanosheets for enhanced visible light CO2 reduction
摘要： Reducing carbon dioxide (CO2) to various value-added chemical products by photocatalysis could effectively alleviate the serious problems of global warming and energy shortages. Currently, most commonly prepared photocatalysts present poor performance under visible light irradiation. In this study, we adopted a facile, scalable and controllable approach to prepare ultrathin two-dimensional (2D) porous Co3O4 catalysts (Co3O4-NS) by air calcining of the ultrathin metal-organic framework (MOFs) nanosheet templates to validly reduce CO2 with a Ru-based photosensitizer under visible light irradiation. Benefitting from the structural nature of MOFs precursors, the calcined Co3O4-NS inherit the morphology of 2D and well-developed porosity, which support the transport of electrons, enhance the adsorption of CO2 molecules, and render abundant catalytic sites for CO2 activation. As a result, the CO generation rate is approximately 4.52 μmol·h-1 with selectivity of 70.1%, which is superior to the Co3O4 bulk catalysts (Co3O4-BK). Additionally, density functional theory (DFT) calculations reveal that the model of Co3O4 monolayer has stronger CO2 adsorption energy than that of the Co3O4 bulk, which is beneficial for the CO2-to-CO conversion. This MOF-engaged strategy provides new insight into the controlled synthesis of advanced ultrathin holey nanosheets to improve the efficiency of photocatalytic CO2 reduction.
关键词： ultrathin nanosheets,Co3O4,photocatalysis,MOFs derived,CO2 reduction
更新于2025-09-04 15:30:14
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Xenos peckii vision inspires an ultrathin digital camera
摘要： Increased demand for compact devices leads to rapid development of miniaturized digital cameras. However, conventional camera modules contain multiple lenses along the optical axis to compensate for optical aberrations that introduce technical challenges in reducing the total thickness of the camera module. Here, we report an ultrathin digital camera inspired by the vision principle of Xenos peckii, an endoparasite of paper wasps. The male Xenos peckii has an unusual visual system that exhibits distinct benefits for high resolution and high sensitivity, unlike the compound eyes found in most insects and some crustaceans. The biologically inspired camera features a sandwiched configuration of concave microprisms, microlenses, and pinhole arrays on a flat image sensor. The camera shows a field-of-view (FOV) of 68 degrees with a diameter of 3.4 mm and a total track length of 1.4 mm. The biologically inspired camera offers a new opportunity for developing ultrathin cameras in medical, industrial, and military fields.
关键词： ultrathin digital camera,microlenses,biological inspiration,microprisms,Xenos peckii,pinhole arrays
更新于2025-09-04 15:30:14
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Hybridization of an unoccupied molecular orbital with an image potential state at a lead phthalocyanine/graphite interface
摘要： The interaction of a molecular orbital with a surface state is important to understand the spatial distribution of the wave function at the molecule/substrate interface. In this study, we focus on hybridization of an unoccupied state of lead phthalocyanine (PbPc) with the image potential state (IPS) on a graphite surface. The hybridization modifies the energy-momentum dispersions of the IPS on PbPc films as observed by angle-resolved two-photon photoemission. On the PbPc 1 monolayer film, the IPS band forms a band gap and back-folding appears at the first Brillouin zone boundary due to the periodic potential by the adsorbate lattice. The modification of the dispersion is accompanied by the intensity enhancement of the IPS. We attributed the origin of the modified dispersion and intensity enhancement to a hybridization of the IPS with a molecule-derived unoccupied level. From the photon energy-dependent measurement on multilayer films, we have found the diffuse unoccupied molecular level in the vicinity of the IPS. The tail part of the IPS wave function in the substrate is enhanced by the hybridization with the unoccupied state, and thus strengthens the transition from the occupied substrate band to the hybridized IPS.
关键词： organic ultrathin films,image potential states,two-photon photoemission spectroscopy,unoccupied states,hybridization
更新于2025-09-04 15:30:14