Yonsei Advanced Science Institute

[Evolutionary Nanomaterials & Nanodevices] Integrating Aerogel into van der Waals Crystals for a High-Strength Thermal Insulator
Achieving low thermal conductivity and high mechanical strength presents a material design challenge due to intrinsic trade-offs, such as the aerogel"s porosity, impeding applications in construction, industry, and aerospace. This study presents a composite that incorporates a silica aerogel within a thermally expanded 2D layered vermiculite matrix. This design overcomes limitations imposed by van der Waals bonding lengths, typically less than 10 A, which hinder aerogel integration with van der Waals crystals. Our method employs a thermal spark reaction to expand the vermiculite interlayer space, allowing aerogel incorporation. This maintains aerogel"s intrinsic low thermal conductivity of 29.6 mW m–1 K–1, while enhancing its Young"s modulus to 66.0 MPa─a more than 103-fold increase over pure aerogel. The innovative embedding of aerogels within van der Waals crystals marks a significant advancement in high-strength insulation technology, paving the way for development in demanding environments that require thermal management without compromising structural integrity.

Jan 9, 2025

[Evolutionary Nanomaterials & Nanodevices] Molecular Drillers for 2 nm Resolution Nanochannel Perforation of 2D Nanoplates
Perpendicular nanochannel creation of two-dimensional (2D) nanostructures requires highly controlled anisotropic drilling processes of the entire structure via void formation. However, chemical approaches for the creation of porosity and defects of 2D nanostructures have been challenging due to the strong basal plane chemical stability and the use of harsh reactants, tending to give randomly corroded 2D structures. In this study, we introduce Lewis acid–base conjugates (LABCs) as molecular drillers with attenuated chemical reactivity which results in the well-defined perpendicular nanochannel formation of 2D TiS2 nanoplates. With the treatment of LABCs, tris(trimethylsilyl)pnictogens (TMS3P or TMS3As), high resolution perforation of TiS2 nanoplates was achieved while maintaining their initial shape and structures. Such perforated TiS2 nanoplates are tunable in their channel diameter between 4 and 10 nm with 2 nm resolution. With their increased surface area and enhanced adsorption of Li2Sx, perforated TiS2 nanoplates served as a diffusion barrier of lithium–sulfur (Li–S) cells, leading to a 2.5-fold improvement in cell performance compared to pristine TiS2 nanoplates. Our molecular design concept for attenuated reactivity of LABCs is simple and could serve as a new approach for chemical drilling processes of 2D metal chalcogenides.

Jan 6, 2025

[Evolutionary Nanomaterials & Nanodevices] Photocatalytic Dehalogenation of Aryl Halides Mediated by the Flexible Metal–Organic Framework MIL-53(Cr)
The catalytic potential of flexible metal–organic frameworks (MOFs) remains underexplored, particularly in liquid-phase reactions. This study employs MIL-53(Cr), a prototypical 'breathing' MOF capable of structural adaptation via pore size modulation, as a photocatalyst for the dehalogenation of aryl halides. Powder X-ray diffraction and Pair Distribution Function analyses reveal that organic solvents influence pore opening, while substrates and products dynamically adjust the framework configuration during catalysis. This structural flexibility enables precise tuning of photocatalytic efficiency via solvent-mediated control of the pore aperture. The results demonstrate that the dynamic behavior of MIL-53(Cr) facilitates enhanced catalytic activity and selectivity, advancing the application of flexible MOFs as tunable, enzyme-mimicking catalysts. These findings pave the way for the rational design of next-generation flexible photocatalysts.

Jan 2, 2025

[Evolutionary Nanomaterials & Nanodevices] Enantioselective Electrochemical L-Phenylalanine Sensor Based on Molecularly Imprinted Polymer Embedded with Redox Probes
Phenylketonuria (PKU) patients require rapid and decentralized monitoring of their phenylalanine (Phe) level to manage high levels of L-phenylalanine (L-Phe). However, affinity-based detection of L-Phe is still challenging due to its small size compared to traditional receptors as well as the necessity of enantiomeric selectivity against D-Phe. In this study, nanoscale electrochemistry was utilized for affinity-based enantioselective detection of L-Phe by utilizing the electrochemical signal of redox probes within artificial receptors upon selective binding. We prepared a molecularly imprinted polymer composite (MIPC) for L-Phe with nanoscale thickness through electrochemical copolymerization of redox-active methylene blue (MB) and β-cyclodextrin (β-CD), achieving self-reporting detection of L-Phe with high enantioselectivity. Using the differential pulse voltammetry (DPV), the MIPC-based enantioselective sensor can detect L-Phe in the range of 1.00 × 10?8 M–1.00 × 10?4 M with a detection limit of 6.83 × 10?9 M (S/N = 3). Additionally, the MIPC-based L-Phe sensor demonstrated the ability to perform repetitive L-Phe measurements after a simple regeneration step. The detection of L-Phe in human serum was conducted with the present sensor, and the results were validated using enzyme-linked immunosorbent assay (ELISA) analysis. The present nanoscale MIPC-based L-Phe sensor offers excellent chiral selectivity and reusability in human serum samples, paving the way for advancements in enantioselective point-of-care diagnostics.

Jan 2, 2025

[Nanobio Interface] Low-Power Scalable Multilayer Optoelectronic Neural Networks Enabled with Incoherent Light
Optical approaches have made great strides towards the goal of high-speed, energy-efficient computing necessary for modern deep learning and AI applications. Read-in and read-out of data, however, limit the overall performance of existing approaches. This study introduces a multilayer optoelectronic computing framework that alternates between optical and optoelectronic layers to implement matrix-vector multiplications and rectified linear functions, respectively. Our framework is designed for real-time, parallelized operations, leveraging 2D arrays of LEDs and photodetectors connected via independent analog electronics. We experimentally demonstrate this approach using a system with a three-layer network with two hidden layers and operate it to recognize images from the MNIST database with a recognition accuracy of 92% and classify classes from a nonlinear spiral data with 86% accuracy. By implementing multiple layers of a deep neural network simultaneously, our approach significantly reduces the number of read-ins and read-outs required and paves the way for scalable optical accelerators requiring ultra low energy.

Dec 18, 2024

[Evolutionary Nanomaterials & Nanodevices] Li-Ion Transport in Two-Dimensional Nanofluidic Membranes
The growing demand for lithium, driven by its critical role in lithium-ion batteries (LIBs) and other applications, has intensified the need for efficient extraction methods from aqua-based resources such as seawater. Among various approaches, 2D channel membranes have emerged as promising candidates due to their tunable ion selectivity and scalability. While significant progress has been made in achieving high Li+/Mg2+ selectivity, enhancing Li+ ion selectivity over Na+ ion, the dominant monovalent cation in seawater, remains a challenge due to their similar properties. This review provides a comprehensive analysis of the fundamental mechanisms underlying Li+ selectivity in 2D channel membranes, focusing on the dehydration and diffusion processes that dictate ion transport. Inspired by the principles of biological ion channels, we identify key factors—channel size, surface charge, and binding sites—that influence energy barriers and shape the interplay between dehydration and diffusion. We highlight recent progress in leveraging these factors to enhance Li+/Na+ selectivity and address the challenges posed by counteracting effects in ion transport. While substantial advancements have been made, the lack of comprehensive principles guiding the interplay of these variables across permeation steps represents a key obstacle to optimizing Li+/Na+ selectivity. Nonetheless, with their inherent chemical stability and fabrication scalability, 2D channel membranes offer significant potential for lithium extraction if these challenges can be addressed. This review provides insights into the current state of 2D channel membrane technologies and outlines future directions for achieving enhanced Li+ ion selectivity, particularly in seawater applications.

Dec 12, 2024