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Exfoliation behavior of van der Waals strings: case study of Bi <sub/>2</sub> S <sub/>3</sub>
摘要： The family of crystals constituting covalently bound strings, held together by van der Waals forces, can be exfoliated into smaller entities, similar to crystals made of van der Waals sheets. Depending on the anisotropy of such crystals, and the spacing between their strings in each direction, van der Waals sheets or ribbons can be obtained after the exfoliation process. In this work, we demonstrate that ultra-thin nanoribbons of bismuth sulfide (Bi2S3) can be synthesized via a high power sonication process. The thickness and width of these ribbons are governed by the van der Waals spacings around the strings within the parent crystal. The lengths of the nanoribbons are initially limited by the dimensions of the starting bulk particles. Interestingly, these nanoribbons change stoichiometry, composition and are elongated when the duration of agitation increases, due to Ostwald ripening. An application of the exfoliated van der Waals strings is presented for optical biosensing using photoluminescence of Bi2S3 nanoribbons, reaching detection limits of less than 10 nM L-1 in response to bovine serum albumin. The concept of exfoliating van der Waals strings could be extended to a large class of crystals for creating bodies ranging from sheets to strings, with optoelectronic properties different from that of their bulk counterparts.
关键词： bio-sensing,photo luminescence,van der Waals strings,bismuth sulfide,liquid phase exfoliation,Bi2S3,Ostwald ripening
更新于2025-09-10 09:29:36
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A universal method for large-yield and high-concentration exfoliation of two-dimensional hexagonal boron nitride nanosheets
摘要： Hexagonal boron nitride (hBN) is an ultra-wide bandgap insulating material, which possesses a graphite-like layered structure, and the two-dimensional (2D) hexagonal boron nitride nanosheets (hBNNS), exfoliated from the bulk hBN, have promising applications in electronic packaging and high-power devices, due to the high thermal conductivity, excellent thermal/chemical stability as well as the ultra-wide band gap. However, the exfoliation of hBNNS is still a challenge with respect to high cost, time consuming, and low yield. Herein, a facile hydrothermal exfoliation method was proposed for the first time to exfoliate the hBNNS in a large yield and high concentration. In the optimized hydrothermal conditions, the lithium ion (Li+) intercalation, isopropanol (IPA) solvent, and the strong stirring could give rise to a large exfoliation yield up to (cid:1)55% and a high concentration (cid:1)4.13 mg/mL. In addition, the exfoliated hBNNS could enhance the methyl orange (MO) photodegradation efficiency of TiO2 from 91% to 96.4 %. Most importantly, this hydrothermal exfoliation method could be a universal approach for the exfoliation of 2D materials.
关键词： Hydrothermal exfoliation,Nanosheets,2D materials,Hexagonal boron nitride,Solubility parameters theory,Universal approach
更新于2025-09-10 09:29:36
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Increased yield of MoS <sub/>2</sub> monolayer exfoliation through the bimetallic corrosion of aluminum
摘要： In this paper, we propose a corrosion assisted exfoliation method as an improvement to the traditional tape exfoliation to obtain transition-metal dichalcogenide monolayers. Our method primarily relies on the electrochemical potential difference between transition metals and aluminum. The assistance of bubbles resulting from the bimetallic corrosion increases the yield of the exfoliation process for monolayers by 30-fold while boosting the probability of obtaining isolated monolayers. We use Raman measurements and a statistical comparison of the improved method with tape exfoliation to lay the evidence for our findings.
关键词： transition-metal dichalcogenides,MoS2,bimetallic corrosion,monolayer exfoliation,aluminum
更新于2025-09-10 09:29:36
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Construction of acetaldehyde-modified g-C3N4 ultrathin nanosheets via ethylene glycol-assisted liquid exfoliation for selective fluorescence sensing of Ag+
摘要： We successfully prepared acetaldehyde-modified g-C3N4 ultrathin nanosheets (ACNNSs) by a simple ethylene glycol-assisted liquid exfoliation method. The introduction of acetaldehyde regulated the surface energy of g-C3N4 to better match with that of water, which improved the exfoliation efficiency. Moreover, the acetaldehyde introduces defects into the g-C3N4 structure, which can act as excitation energy traps and cause considerable variation in the fluorescence emission. Benefiting from the stable photoluminescence (PL) emission, good water solubility and biocompatibility, the obtained ACNNSs showed a selective fluorescent response to Ag+ both in aqueous solution and living cells. The strong absorption and intimate contact with Ag+, and its appropriate redox potential of ACNNSs contributed to this excellent fluorescent response. A simple and environmental friendly approach was proposed to simultaneously achieve modification and exfoliation of g-C3N4 in aqueous solution. These findings might lead to wider applications of carbon-based nanomaterials as active materials for fluorescence detection in the environment.
关键词： Graphitic carbon nitride nanosheets,Living-cell imaging,Glycol-assisted exfoliation,Fluorescent sensor,Acetaldehyde-modified,Ag+
更新于2025-09-10 09:29:36
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Polyphenol-Assisted Exfoliation of Transition Metal Dichalcogenides into Nanosheets as Photothermal Nanocarriers for Enhanced Antibiofilm Activity
摘要： Transition metal dichalcogenides (TMDs) nanosheets have evoked enormous research enthusiasm and have shown increased potentials in biomedical field. However, a great challenge lies in high-throughput, large-scale and eco-friendly preparation of TMDs nanosheets dispersions with high quality. Herein, we report a universal polyphenol-assisted strategy to facilely exfoliate various TMDs into monolayer or few-layer nanosheets. By optimizing the exfoliation condition of molybdenum disulfide (MoS2), the yield and concentration of as-exfoliated nanosheets is up to 60.5% and 1.21 mg/mL, respectively. This is the most efficient aqueous exfoliation method at present and is versatile for the choices of polyphenols and TMDs nanomaterials. The as-exfoliated MoS2 nanosheets possess superior biomedical stability as nanocarriers to load antibiotic drug. They show high photothermal conversion effect and thus induce a synergetic effect of chemotherapy and photothermal therapy to harvest enhanced antibiofilm activity under near-infrared (NIR) light. All these results offer an appealing strategy toward the synthesis and application of ultrathin TMDs nanosheets, with great implications for their development.
关键词： monolayer nanosheets,aqueous exfoliation,photothermal nanocarrier,transition metal dichalcogenides (TMDs),antibiofilm activity
更新于2025-09-10 09:29:36
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Direct Exfoliation of Natural SiO2-Containing Molybdenite in Isopropanol: A Cost Efficient Solution for Large-Scale Production of MoS2 Nanosheetes
摘要： The cost-effective exfoliation of layered materials such as transition metal dichalcogenides into mono- or few- layers is of significant interest for various applications. This paper reports the preparation of few-layered MoS2 from natural SiO2-containing molybdenite by exfoliation in isopropanol (IPA) under mild ultrasonic conditions. One- to six-layer MoS2 nanosheets with dimensions in the range of 50-200 nm are obtained. By contrast, MoS2 quantum dots along with nanosheets are produced using N-methyl-pyrrolidone (NMP) and an aqueous solution of poly (ethylene glycol)-block-poly (propylene glycol)-block-poly (ethylene glycol) (P123) as exfoliation solutions. Compared with molybdenite, commercial bulk MoS2 cannot be exfoliated to nanosheets under the same experimental conditions. In the exfoliation process of the mineral, SiO2 associated in molybdenite plays the role of similar superfine ball milling, which significantly enhances the exfoliation efficiency. This work demonstrates that isopropanol can be used to exfoliate natural molybdenite under mild conditions to produce nanosheets, which facilitates the preparation of highly concentrated MoS2 dispersions or MoS2 in powder form due to the volatility of the solvent. Such exfoliated MoS2 nanosheets exhibit excellent photoconductivity under visible light. Hence, the direct mild exfoliation method of unrefined natural molybdenite provides a solution for low-cost and convenient production of few-layered MoS2 which is appealing for industrial applications.
关键词： MoS2 nanosheet,liquid exfoliation,SiO2,photoelectric properties,natural molybdenite
更新于2025-09-10 09:29:36
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Isolation of Nb2Se9 Molecular Chain from Bulk One-Dimensional Crystal by Liquid Exfoliation
摘要： The optimum solvent for Nb2Se9 dispersion, which is a new type of one dimensional (1D) material, is investigated. Among several solvents (16 solvents in total), strong dispersion was observed in benzyl alcohol, isopropyl alcohol, isobutyl alcohol, and diacetone alcohol, which have medium dielectric constants in the range of 10 to 30 and surface tension in the range of 25 to 35 mJ m?2. 1D Nb2Se9 chains, whose size is less than 10 nm, are well dispersed and it is possible to disperse mono-chains of 1 nm or less in a specific dispersion region. The 1D unit chain with dangling bond free surface and high volume to area ratio is expected to be used in applications that utilize the surface of the material. Such dispersion is an important first step towards various potential applications and is an indispensable scientific goal for the practical applications of Nb2Se9.
关键词： Nb2Se9,1D materials,liquid exfoliation,solvent dispersion
更新于2025-09-09 09:28:46
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Quantifying the Exfoliation Ease Level of 2D Materials via Mechanical Anisotropy
摘要： The isolation of 2D materials from mother bulks into nanoscale is of vital importance for fulfilling their applications in many technological fields. Among known methods, mechanical exfoliation is one of the most widely utilized ways due to its simplicity. For a given 2D material, both its inter-layer and intra-layer bonding strengths need to be taken into accounted for understanding the exfoliation process as the former dominates the ease level for cleaving adjacent molecular layers while the later regulates the ability for resisting cracking. In this regard, strong intra-layer but weak inter-layer bonding interactions respectively lead to large and thin nanosheets, hence facile exfoliation (and vice versa). As the bonding forces can be directly reflected through elastic properties of materials, here we propose to use the ratio between the in-plane and out-of-plane elastic modulus (E) as a universal index, AIn/Out (= EIn-plane/EOut-of-plane), to quantify the ease level of a 2D material’s mechanical exfoliation. Such ratios, which can be facilely obtained from routine computational and mechanical experiments, could provide useful information for estimating suitable exfoliation methods of 2D materials.
关键词： nanosheets,elastic modulus,2D materials,mechanical exfoliation,mechanical anisotropy
更新于2025-09-09 09:28:46
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High-Yield and Damage-free Exfoliation of Layered Graphdiyne in Aqueous Phase
摘要： The two-dimensional carbon material graphdiyne (GDY) holds great promise as a semiconductor and porous material, however, exfoliation of bulk GDY into single- or few-layered GDY in the aqueous phase remains a challenge. We report an efficient method for the damage-free exfoliation of bulk GDY into single- or few-layered GDY with high yield in an aqueous solution of inorganic salts (e.g., Li2SiF6). This was confirmed by spherical-aberration-corrected scanning transmission electron microscopy, scanning/transmission electron microscopy, atomic force microscopy, Fourier transform infrared/Raman spectroscopy, X-ray photoelectron spectroscopy. The method gives high exfoliation efficiency (75 wt %) without creating additional structural defects or oxides in the exfoliated GDY. Theoretical calculations suggest that non-covalent adsorption of the anion, diffusion of the cation, and subsequent repulsive forces between adjacent flakes are the main driving force for the efficient exfoliation.
关键词： non-covalent adsorption,carbon materials,graphdiyne,surface chemistry,liquid-phase exfoliation
更新于2025-09-09 09:28:46
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(111)Si thin layers detachment by stress-induced spallation
摘要： In this work, results of controlled detachment of (111) silicon by stress induced spalling (SIS) process, which is based on a gluing on a metallic stressor layer by an epoxy adhesive on top of a silicon substrate, are presented. It is shown that silicon foils mainly (1x1) cm2 with different thicknesses (~50-170 μm) can be successfully detached using different materials (steel, copper, aluminum, nickel and titanium) as stressor layers with thicknesses ~50-500 μm. Such detachment can be realized by dipping of a stressor/glue/silicon wafer based structure into liquid nitrogen. As a result, Si foils with different thicknesses from ~50 μm to ~170 μm can be detached. An analytical and numerical approaches based on principles of linear elastic fracture mechanics is developed and they are shown that such approaches can predict general trends and conditions for the detachment of silicon foils with desired thicknesses using a stressor layer. Raman spectroscopy analysis of the residual stresses in detached silicon foils shows, that tensile stresses (up to - 36MPa) as well as higher value compressive stresses (up to ~444 MPa) are present in such foils. Moreover, optical and scanning electron microscopy (SEM) measurements show that surface of the detached foils exhibits some periodic lines originated by stresses.
关键词： Exfoliation of silicon,Thermal stress,Raman spectroscopy,Kerf-free,photovoltaics (PV)
更新于2025-09-09 09:28:46