Mrs Bulletin最新文献

The perovskite heterostructure is a novel semiconducting building block that contains multiple spatially organized functionalities within individual particles. The structurally tunable organic ligands in a two-dimensional (2D) perovskite heterostructure play a central role enhancing the stability and affecting the optical properties. Here, we report the synthesis of ligand-variant 2D perovskite lateral heterostructure nanocrystals, based on the sequential solvent evaporation strategy. The fabricated 2D perovskite heterostructures can tolerate large lattice mismatch in the vertical orientation as much as 16.5 percent. The synthesis strategy can be expanded to various combinations of ligands and halides, yielding a clear interface and tailorable electronic structure. This work presents an important step to further the understanding of the interfacial structure of the 2D perovskite heterostructure and the design of perovskite nanodevices with tailored optoelectronic properties.

The phase-field method enables simulating the spatiotemporal evolution of the coupled physical-order parameters under externally applied fields in a wide range of materials and devices. Leveraging advanced numerical algorithms for solving the nonlinear partial differential equations and scalable parallelization techniques, the phase-field method is becoming a powerful computational tool to model and design devices operating based on multiple-coupled physical processes. This article will highlight examples of applying phase-field simulations to predict new mesoscale physical phenomena and design new-concept magnetomechanical devices by identifying the desirable combination of the composition, size, and geometry of monolithic materials as well as the device structure. A brief outlook of the opportunities and challenges for modeling and designing magnetomechanical devices with phase-field modeling is also provided.

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The phase-field method has been extensively applied to predicting the domain structures and their responses to external fields and understanding experimentally observed domain states under different electromechanical conditions in ferroelectric heterostructures. This article highlights the successful examples of phase-field applications in guiding the design of relaxor ferroelectric ceramics and crystals with record-high piezoelectricity and the discovery of simultaneous high light transparency and piezoelectricity of relaxor ferroelectric crystals for a wide range of biomedical, robotics, and optoelectronics applications.

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Fuel cells are highly efficient electrochemical energy-conversion devices with a wide application potential, spanning from portable power sources to stationary power generation. They are typically categorized according to their operating temperature, for example, low temperature (<100°C), intermediate temperature (450‒800°C) and high temperature (>800°C). Recently, reduced temperature fuel cells operating at 200‒400°C have also received considerable attention for their multiple benefits. A single fuel cell is composed of a porous anode for fuel oxidation, a dense electrolyte for ion transportation, and a porous cathode for oxygen reduction. Due to their different functions and operating environments, each layer of the cell faces unique materials requirements in terms of ionic and electronic conductivity, chemical and mechanical stability, thermal expansion, etc. This article gives a thorough perspective on the challenges and recent advances in anode, electrolyte, and cathode materials for the various types of fuel cells. Emerging fuel cells operating at 200‒400°C are also discussed and commented. Finally, the key areas of need and major opportunities for further research in the field are outlined.

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Emulsions are omnipresent in our everyday life; for example, in food, certain drug and cosmetic formulations, agriculture, and as paints. Moreover, they are frequently used to perform high-throughput screening assays with minimum sample volumes. Key to the successful use of emulsions is a good drop stability. Most frequently, drops are stabilized with surfactants composed of hydrophilic and hydrophobic parts. Appropriate surfactants are often selected based on the ratio of their hydrophilic to the hydrophobic parts, their hydrophilic–lipophilic balance (HLB), which determines their solubility. However, how the HLB value of perfluorinated surfactants influences the emulsion stability remains to be determined. To address this question, we report a benign and cost-effective synthesis of diblock-copolymer surfactants that consist of a perfluorinated block covalently linked to a hydrophilic poly(ethylene glycol) (PEG)-encompassing block. The compositions of the fluorophilic and hydrophilic blocks are very similar to those of commercially available triblock-copolymer surfactants commonly used within the microfluidic community that employs poly(dimethylsiloxane) (PDMS)-based devices. By deliberately tuning the ratio of the hydrophobic to the hydrophilic blocks of our diblock-copolymer surfactants, we obtain HLB values varying between 0.9 and 3.3. We demonstrate that the best emulsion stability is obtained if the molecular weight ratio of the hydrophobic to the hydrophilic blocks is between 5 and 7, corresponding to HLB values between 2.5 and 3.3. Importantly, our cost-effective surfactant displays a similar performance to that of the rather costly commercially available Pico-Surf surfactant. Thereby, this study presents guidelines for a cheap, benign, and targeted synthesis of appropriate perfluorinated surfactants that efficiently stabilize water-in-perfluorinated oil emulsions.

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