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1. The development of 2D materials for electrochemical energy applications: A mechanistic approach

   https://doi.org/10.1063/1.5085187  

   Hynek, David_J; Pondick, Joshua_V; Cha, Judy_J (March 2019, APL Materials)

   Energy production and storage is one of the foremost challenges of the 21st century. Rising energy demands coupled with increasing materials scarcity have motivated the search for new materials for energy technology development. Nanomaterials are an excellent class of materials to drive this innovation due to their emergent properties at the nanoscale. In recent years, two dimensional (2D) layered materials have shown promise in a variety of energy related applications due to van der Waals interlayer bonding, large surface area, and the ability to engineer material properties through heterostructure formation. Despite notable results, their development has largely followed a guess and check approach. To realize the full potential of 2D materials, more efforts must be made towards achieving a mechanistic understanding of the processes that make these 2D systems promising. In this perspective, we bring attention to a series of techniques used to probe fundamental energy related processes in 2D materials, focusing on electrochemical catalysis and energy storage. We highlight studies that have advanced development due to mechanistic insights they uncovered. In doing so, we hope to provide a pathway for advancing our mechanistic understanding of 2D energy materials for further research. 

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2. Dynamic magnetic field alignment and polarized emission of semiconductor nanoplatelets in a liquid crystal polymer

   https://doi.org/10.1038/s41467-022-30200-2  

   Kim, Dahin; Ndaya, Dennis; Bosire, Reuben; Masese, Francis K.; Li, Weixingyue; Thompson, Sarah M.; Kagan, Cherie R.; Murray, Christopher B.; Kasi, Rajeswari M.; Osuji, Chinedum O. (May 2022, Nature Communications)

   Abstract Reconfigurable arrays of 2D nanomaterials are essential for the realization of switchable and intelligent material systems. Using liquid crystals (LCs) as a medium represents a promising approach, in principle, to enable such control. In practice, however, this approach is hampered by the difficulty of achieving stable dispersions of nanomaterials. Here, we report on good dispersions of pristine CdSe nanoplatelets (NPLs) in LCs, and reversible, rapid control of their alignment and associated anisotropic photoluminescence, using a magnetic field. We reveal that dispersion stability is greatly enhanced using polymeric, rather than small molecule, LCs and is considerably greater in the smectic phases of the resulting systems relative to the nematic phases. Aligned composites exhibit highly polarized emission that is readily manipulated by field-realignment. Such dynamic alignment of optically-active 2D nanomaterials may enable the development of programmable materials for photonic applications and the methodology can guide designs for anisotropic nanomaterial composites for a broad set of related nanomaterials. 

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3. Progress in Electronic, Energy, Biomedical and Environmental Applications of Boron Nitride and MoS2 Nanostructures

   https://doi.org/10.3390/mi15030349  

   Uddin, Join; Dubey, Raksha; Balasubramaniam, Vinaayak Sivam; Kabel, Jeff; Khare, Vedika; Salimi, Zohreh; Sharma, Sambhawana; Zhang, Dongyan; Yap, Yoke Khin (March 2024, Micromachines)

   In this review, we examine recent progress using boron nitride (BN) and molybdenum disulfide (MoS2) nanostructures for electronic, energy, biomedical, and environmental applications. The scope of coverage includes zero-, one-, and two-dimensional nanostructures such as BN nanosheets, BN nanotubes, BN quantum dots, MoS2 nanosheets, and MoS2 quantum dots. These materials have sizable bandgaps, differentiating them from other metallic nanostructures or small-bandgap materials. We observed two interesting trends: (1) an increase in applications that use heterogeneous materials by combining BN and MoS2 nanostructures with other nanomaterials, and (2) strong research interest in environmental applications. Last, we encourage researchers to study how to remove nanomaterials from air, soil, and water contaminated with nanomaterials. As nanotechnology proceeds into various applications, environmental contamination is inevitable and must be addressed. Otherwise, nanomaterials will go into our food chain much like microplastics. 

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4. Functional two-dimensional high-entropy materials

   https://doi.org/10.1038/s43246-023-00341-y  

   Nemani, Srinivasa Kartik; Torkamanzadeh, Mohammad; Wyatt, Brian C.; Presser, Volker; Anasori, Babak (February 2023, Communications Materials)

   Abstract Multiple principal element or high-entropy materials have recently been studied in the two-dimensional (2D) materials phase space. These promising classes of materials combine the unique behavior of solid-solution and entropy-stabilized systems with high aspect ratios and atomically thin characteristics of 2D materials. The current experimental space of these materials includes 2D transition metal oxides, carbides/carbonitrides/nitrides (MXenes), dichalcogenides, and hydrotalcites. However, high-entropy 2D materials have the potential to expand into other types, such as 2D metal-organic frameworks, 2D transition metal carbo-chalcogenides, and 2D transition metal borides (MBenes). Here, we discuss the entropy stabilization from bulk to 2D systems, the effects of disordered multi-valent elements on lattice distortion and local electronic structures and elucidate how these local changes influence the catalytic and electrochemical behavior of these 2D high-entropy materials. We also provide a perspective on 2D high-entropy materials research and its challenges and discuss the importance of this emerging field of nanomaterials in designing tunable compositions with unique electronic structures for energy, catalytic, electronic, and structural applications. 

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5. Two-dimensional halide perovskites featuring semiconducting organic building blocks

   https://doi.org/10.1039/d0qm00233j  

   Gao, Yao; Wei, Zitang; Hsu, Sheng-Ning; Boudouris, Bryan W.; Dou, Letian (January 2020, Materials Chemistry Frontiers)

   Two-dimensional (2D) organic–inorganic hybrid halide perovskites exhibit unique properties, such as long charge carrier lifetimes, high photoluminescence quantum efficiencies, and great tolerance to defects. Over the last several decades tremendous progress has occurred in the development of 2D layered halide perovskite semiconductor materials and devices. Chemical functionalization of 2D halide perovskites is an effective approach for tuning their electronic properties. A large amount of effort has been made in compositional engineering of the cations and anions in the perovskite lattice. However, few efforts have incorporated rationally designed semiconducting organic moieties into these systems to alter the overall chemical and optoelectronic properties of 2D perovskites. In fact, incorporation of large conjugated organic groups in the spatially confined inorganic perovskite matrix was found to be challenging, and this synthetic challenge hinders a deeper understanding of the materials’ structure–property relationships. Recently, exciting progress has been made regarding the molecular design, optical characterization, and device fabrication of novel 2D halide perovskite materials that incorporate functional organic semiconducting building blocks. In this article, we provide a timely review regarding this recent progress. Moreover, we discuss successes and current challenges regarding the synthesis, characterization, and device applications of such hybrid materials and provide a perspective on the true future promise of these advanced nanomaterials. 

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