Due to their extraordinary properties, boron nitride nanosheets (BNNSs) have great promise for many applications. However, the difficulty of their efficient preparation and their poor dispersibility in liquids are the current factors that limit this. A simple yet efficient sugar‐assisted mechanochemical exfoliation (SAMCE) method is developed here to simultaneously achieve their exfoliation and functionalization. This method has a high actual exfoliation yield of 87.3%, and the resultant BNNSs are covalently grafted with sugar (sucrose) molecules, and are well dispersed in both water and organic liquids. A new mechanical force–induced exfoliation and chemical grafting mechanism is proposed based on experimental and density functional theory investigations. Thanks to the good dispersibility of the nanosheets, flexible and transparent BNNS/poly(vinyl alcohol) (PVA) composite films with multifunctionality is fabricated. Compared to pure PVA films, the composite films have a remarkably improved tensile strength and thermal dissipation capability. Noteworthy, they are flame retardant and can effectively block light from the deep blue to the UV region. This SAMCE production method has proven to be highly efficient, green, low cost, and scalable, and is extended to the exfoliation and functionalization of other two‐dimensional (2D) materials including MoS2, WS2, and graphite.
Among two-dimensional (2D) transition-metal dichalcogenides (TMDCs), platinum diselenide (PtSe 2 ) stands in a distinct place due to its fancy transition from type-II Dirac semimetal to semiconductor with a thickness variation from bulk to monolayer (1 ML) and the related versatile applications especially in mid-infrared detectors. However, achieving atomically thin PtSe 2 is still a challenging issue. Herein, we have designed a facile chemical vapor deposition (CVD) method to achieve the synthesis of atomically thin 1T-PtSe 2 on an electrode material of Au foil. Thanks to the high crystalline quality, we have confirmed the complete transition from semimetal to semiconductor from trilayer (3 ML) to 1 ML 1T-PtSe 2 . More importantly, we have found that such atomically thin 1T-PtSe 2 can serve as perfect electrocatalysts, featured with a record high hydrogen evolution reaction (HER) efficiency (comparable to traditional Pt catalyst). Our work is helpful toward the large-scale synthesis, exotic physical property exploration, and intriguing application development of atomically thin TMDCs.
2D metallic TaS is acting as an ideal platform for exploring fundamental physical issues (superconductivity, charge-density wave, etc.) and for engineering novel applications in energy-related fields. The batch synthesis of high-quality TaS nanosheets with a specific phase is crucial for such issues. Herein, the successful synthesis of novel vertically oriented 1T-TaS nanosheets on nanoporous gold substrates is reported, via a facile chemical vapor deposition route. By virtue of the abundant edge sites and excellent electrical transport property, such vertical 1T-TaS is employed as high-efficiency electrocatalysts in the hydrogen evolution reaction, featured with rather low Tafel slopes ≈67-82 mV dec and an ultrahigh exchange current density ≈67.61 µA cm . The influence of phase states of 1T- and 2H-TaS on the catalytic activity is also discussed with the combination of density functional theory calculations. This work hereby provides fundamental insights into the controllable syntheses and electrocatalytic applications of vertical 1T-TaS nanosheets achieved through the substrate engineering.
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