Accounts of materials research最新文献

{"title":"Supramolecular-Based One-Pot Separation of Highly Pure Adsorbent-Free Semiconducting Single-Walled Carbon Nanotubes and Machine Learning-Based Nanotube Solubilization","authors":"Naotoshi Nakashima*,&nbsp;Yoshiyuki Nonoguchi and Aleksandar Staykov,&nbsp;","doi":"10.1021/accountsmr.4c0011310.1021/accountsmr.4c00113","DOIUrl":"https://doi.org/10.1021/accountsmr.4c00113https://doi.org/10.1021/accountsmr.4c00113","url":null,"abstract":"<p >Carbon nanotubes are classified into single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes and multiwalled carbon nanotubes. Among these, SWNTs have remarkable electronic, mechanical, optical, chemical and thermal properties, which are derived from their one-dimensional extended π-conjugated structures, and thus, they demonstrate a high potential toward the development of the next-generation nanoelectronics, (nano)bio, and energy and environmental materials and devices. As-produced SWNTs are a mixture of semiconducting (sem-) and metallic (met-)-SWNTs; thus, chirality sorting is highly important. So far various methods have been presented for such a separation including (i) use of chemical adsorbents such as polyfluorenes (PFOs) and their analogues and (ii) physical methods including surfactant-aided density gradient ultracentrifugation (DGU), gel chromatography techniques, and the surfactant-aided aqueous two-phase extraction method. However, such methods are not simple, and the removal of the wrapped adsorbents on the SWNTs is very difficult. Thus, the development of a method to remove the adsorbent from the sorted SWNTs is highly important to obtain adsorbent-free pure sem-SWNTs.</p><p >In this Account, we provide a summary of a one-pot highly efficient sem-SWNT sorting using a solubilizer and removal of the wrapped solubilizer/adsorbent from the surfaces of the sorted tubes to provide highly pure adsorbent-free sem-SWNTs, in which the design and synthesis of adsorbents that selectively sorts sem-SWNTs from as-produced SWNTs, a mixture of sem-SWNTs and met-SWNTs, with easy removal property by a suitable method are described. In particular, we demonstrate a solubilizer-free sem-SWNT sorting based on supramolecular chemistry. The development of easy/simple and an efficient adsorbent-free sem-SWNT sorting method is highly important for proper fundamental use and application of SWNTs in industry. In addition, we describe computer simulations for selective sem-SWNT sorting based on a DFT method; in particular, we summarize our density functional theory (DFT) approach for helical wrapping of flavin molecules on the (8,6)-SWNT, leading to successful SWNT chirality separation. Finally, the introduction of a machine learning approach for SWNT solubilization is summarized.</p>","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"5 8","pages":"958–970 958–970"},"PeriodicalIF":14.0,"publicationDate":"2024-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142039346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rational Control of Packing Arrangements in Organic Semiconducting Materials toward High-Performance Optoelectronics","authors":"Junfeng Guo, Chunfeng Shi, Yonggang Zhen, Wenping Hu","doi":"10.1021/accountsmr.4c00054","DOIUrl":"https://doi.org/10.1021/accountsmr.4c00054","url":null,"abstract":"Organic semiconducting materials have sparked a great deal of interest because of their structural versatility, lightweight, mechanical flexibility, as well as low temperature and large area fabrication, opening up possibilities for the development of next-generation electronic devices. Packing arrangements of organic semiconducting materials influence significantly the optoelectronic performance by alteration of electronic couplings, band structures, and exciton behaviors. The packing structures of small-molecule organic semiconductors can be typically classified into herringbone, slipped, and brickwork motifs. The preferred packing arrangement depends on the steric hindrance driven by the molecular structure and the weight of contribution of each interaction term, which are closely associated with the unpredictable and uncontrollable process of crystal nucleation and growth, involving lots of multiple variables such as the weak and subtle intramolecular or intermolecular interactions in organic materials. Therefore, it remains a long-standing challenge to tailor precisely the packing arrangements for high-performance or multifunctional organic semiconducting materials. In addition, the in-depth relationship between packing arrangements and optoelectronic properties is far from clear, preventing the development of high-performance organic optoelectronic materials.","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141732742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rational Control of Packing Arrangements in Organic Semiconducting Materials toward High-Performance Optoelectronics","authors":"Junfeng Guo,&nbsp;Chunfeng Shi,&nbsp;Yonggang Zhen* and Wenping Hu,&nbsp;","doi":"10.1021/accountsmr.4c0005410.1021/accountsmr.4c00054","DOIUrl":"https://doi.org/10.1021/accountsmr.4c00054https://doi.org/10.1021/accountsmr.4c00054","url":null,"abstract":"&lt;p &gt;Organic semiconducting materials have sparked a great deal of interest because of their structural versatility, lightweight, mechanical flexibility, as well as low temperature and large area fabrication, opening up possibilities for the development of next-generation electronic devices. Packing arrangements of organic semiconducting materials influence significantly the optoelectronic performance by alteration of electronic couplings, band structures, and exciton behaviors. The packing structures of small-molecule organic semiconductors can be typically classified into herringbone, slipped, and brickwork motifs. The preferred packing arrangement depends on the steric hindrance driven by the molecular structure and the weight of contribution of each interaction term, which are closely associated with the unpredictable and uncontrollable process of crystal nucleation and growth, involving lots of multiple variables such as the weak and subtle intramolecular or intermolecular interactions in organic materials. Therefore, it remains a long-standing challenge to tailor precisely the packing arrangements for high-performance or multifunctional organic semiconducting materials. In addition, the in-depth relationship between packing arrangements and optoelectronic properties is far from clear, preventing the development of high-performance organic optoelectronic materials.&lt;/p&gt;&lt;p &gt;Herein, we summarize our recent progress on the control of packing arrangements of organic semiconducting materials toward high-performance optoelectronics, shedding light on the structure–property relationship. First, we discuss the functionalization at the conjugated backbone of molecular materials to enhance carbon/hydrogen (C/H) ratios, constructing more dense herringbone or slipped packing structures with superior carrier mobilities. Next, we present the regulation of packing arrangements of organic semiconductors based on the same molecular structures, namely, control of the crystal polymorph. There is a very small energy gap between the highest occupied molecular orbital (HOMO) and HOMO–1 for C6-DBTDT; thus, the electronic couplings between (HOMO–1)s or along different directions have significant impacts on the charge transport behaviors. Finally, we demonstrate the role of the second component in the packing arrangements of organic optoelectronic materials. By nonstoichiometric ratio molecular doping, we have tailored the packing modes from traditional herringbone packing to face-to-face columnar stack with sufficient delocalization of radicals, showing acid-responsive high conductivity for one-dimensional (1D) organic nanomaterials. By stoichiometric ratio cocrystal engineering, we have achieved halogen-bonded or hydrogen-bonded cocrystal materials with different packing motifs or modification proportions. Short intermolecular contacts in a segregated-stack material give rise to larger radiative decay selectivity, accounting for an enhanced amplified spontaneous emi","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"5 8","pages":"907–919 907–919"},"PeriodicalIF":14.0,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142039480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Engineering Functional Particles to Modulate T Cell Responses","authors":"Yudong Li, Shukun Li, Jari F. Scheerstra, Tania Patiño, Jan C. M. van Hest, Loai K. E. A. Abdelmohsen","doi":"10.1021/accountsmr.4c00105","DOIUrl":"https://doi.org/10.1021/accountsmr.4c00105","url":null,"abstract":"T cells play a critical role in adaptive immune responses. They work with other immune cells such as B cells to protect our bodies when the first line of defense, the innate immune system, is overcome by certain infectious diseases or cancers. Studying and regulating the responses of T cells, such as activation, proliferation, and differentiation, helps us understand not only their behavior <i>in vivo</i> but also their translation and application in the field of immunotherapy, such as adoptive T cell therapy and immune checkpoint therapy, the situations in which T cells cannot fight cancer alone and require external engineering regulation to help them. Nano- to micrometer-sized particulate biomaterials have achieved great progress in the assistance of T cell-based immunomodulation. For example, various types of microparticles decorated with T cell recognition and activation signals to mimic native antigen-presenting cells have shown successful <i>ex vivo</i> expansion of primary T cells and have been approved for clinical use in adoptive T cell therapy. Functional particles can also serve as vehicles for transporting cargos including small molecule drugs, cytokines, and antibodies. Especially for cargos with limited bioavailability and high repeat-dose toxicity, systemic administration in their free form is difficult. By using particle-assisted systems, the delivery can be tailored on demand, of which targeting and controlled release are two typical examples, ultimately aiding in the regulation of T cell responses. Furthermore, when T cells become overactive and behave in ways that contradict our expectations, such as attacking our own cells or innocuous foreign molecules, this can lead to a breakdown of immune tolerance. In such cases, particles to help reprogram those overactive T cells or suppress their activity are appreciated <i>in vivo</i>. The urgent need to introduce immune stimulation into the treatment of cancers, infectious diseases, and autoimmune diseases has driven recent advances in the engineering of functional particulate biomaterials that regulate T cell responses. In this Account, we will first cover a brief overview of the process of T cell-based immunomodulation from principle to development. It then outlines critical points in the design of functional particle platforms, including materials, size, morphology, surface engineering, and delivery of cargos, to modulate the features of T cells, and introduces selected work from our and other research groups with a focus on three major therapeutic applications: adoptive T cell therapy, immune checkpoint therapy, and immune tolerance restoration. Current challenges and future opportunities are also discussed.","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Engineering Functional Particles to Modulate T Cell Responses","authors":"Yudong Li,&nbsp;Shukun Li,&nbsp;Jari F. Scheerstra,&nbsp;Tania Patiño,&nbsp;Jan C. M. van Hest* and Loai K. E. A. Abdelmohsen*,&nbsp;","doi":"10.1021/accountsmr.4c0010510.1021/accountsmr.4c00105","DOIUrl":"https://doi.org/10.1021/accountsmr.4c00105https://doi.org/10.1021/accountsmr.4c00105","url":null,"abstract":"<p >T cells play a critical role in adaptive immune responses. They work with other immune cells such as B cells to protect our bodies when the first line of defense, the innate immune system, is overcome by certain infectious diseases or cancers. Studying and regulating the responses of T cells, such as activation, proliferation, and differentiation, helps us understand not only their behavior <i>in vivo</i> but also their translation and application in the field of immunotherapy, such as adoptive T cell therapy and immune checkpoint therapy, the situations in which T cells cannot fight cancer alone and require external engineering regulation to help them. Nano- to micrometer-sized particulate biomaterials have achieved great progress in the assistance of T cell-based immunomodulation. For example, various types of microparticles decorated with T cell recognition and activation signals to mimic native antigen-presenting cells have shown successful <i>ex vivo</i> expansion of primary T cells and have been approved for clinical use in adoptive T cell therapy. Functional particles can also serve as vehicles for transporting cargos including small molecule drugs, cytokines, and antibodies. Especially for cargos with limited bioavailability and high repeat-dose toxicity, systemic administration in their free form is difficult. By using particle-assisted systems, the delivery can be tailored on demand, of which targeting and controlled release are two typical examples, ultimately aiding in the regulation of T cell responses. Furthermore, when T cells become overactive and behave in ways that contradict our expectations, such as attacking our own cells or innocuous foreign molecules, this can lead to a breakdown of immune tolerance. In such cases, particles to help reprogram those overactive T cells or suppress their activity are appreciated <i>in vivo</i>. The urgent need to introduce immune stimulation into the treatment of cancers, infectious diseases, and autoimmune diseases has driven recent advances in the engineering of functional particulate biomaterials that regulate T cell responses. In this Account, we will first cover a brief overview of the process of T cell-based immunomodulation from principle to development. It then outlines critical points in the design of functional particle platforms, including materials, size, morphology, surface engineering, and delivery of cargos, to modulate the features of T cells, and introduces selected work from our and other research groups with a focus on three major therapeutic applications: adoptive T cell therapy, immune checkpoint therapy, and immune tolerance restoration. Current challenges and future opportunities are also discussed.</p>","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"5 9","pages":"1048–1058 1048–1058"},"PeriodicalIF":14.0,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/accountsmr.4c00105","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Single-Molecule Functional Chips: Unveiling the Full Potential of Molecular Electronics and Optoelectronics","authors":"Heng Zhang,&nbsp;Junhao Li,&nbsp;Chen Yang* and Xuefeng Guo*,&nbsp;","doi":"10.1021/accountsmr.4c0012510.1021/accountsmr.4c00125","DOIUrl":"https://doi.org/10.1021/accountsmr.4c00125https://doi.org/10.1021/accountsmr.4c00125","url":null,"abstract":"&lt;p &gt;An ideal methodology for miniaturizing the physical size, enhancing the operational frequency, and building the multifunctional capability of functional chips is to use opto- or electroactive single molecules as their central elements; such devices are generally termed single-molecule electronics and optoelectronics. The exploration of the electronic and optoelectronic properties of materials at the single-molecule level also allows the complete elucidation of the correlation between molecular structure and function, which in turn aids technological advances that can help to address the challenge raised by Moore’s Law. In this Account, we present our ongoing investigative pursuits in the realm of single-molecule electronics and optoelectronics, with a particular emphasis on studies using graphene-molecule-graphene single-molecule junctions as the primary framework. To date, we have established a diverse range of single-molecule multifunctional devices, including photoswitches, field-effect transistors, rectifiers, light-emitting diodes, spin electronic devices, memristors, and molecular wires. These types of devices possess stable graphene electrodes and robust covalent molecule-electrode interfaces.&lt;/p&gt;&lt;p &gt;The main focuses of this account are our proposed molecular/interface engineering strategy including interface design using particular linkers, spacers, insulation, and functional centers and our device engineering strategy that covers the design of the device structure and electrode materials. These strategies adequately consider the coupling between functional centers and their external environment, thus affording the ability to evaluate and manipulate the intrinsic behaviors of target molecules. Specifically, a covalent molecule-electrode interface enables high device stability at a high bias voltage. Three nonconjugated methylene groups are inserted at the electrode-molecule interface to prevent the quenching of the excited state of the central molecule (e.g., diarylethene) by the graphene electrode, thereby achieving robust and reversible photoswitches. Cyclodextrins are introduced as insulating groups around molecular bridges to weaken the coupling of the bridges with the environment, which increases the quantum yield of light-emitting diodes. Additional reactive sites are introduced on the sides of the molecular bridges, providing the ability to add new functional centers. We show that using materials with a high dielectric constant as the dielectric layer enables efficient electrical manipulations of single-molecule electronics and optoelectronics by the gate voltage. We reveal that the use of ferromagnetic metal electrodes in single-molecule electronics and optoelectronics can meet the requirements for spin injection. In particular, the two-dimensional structure of graphene electrodes that can be tailored by etching enables high-density integration of molecules, paving the way for future logical manipulation and real-time communic","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"5 8","pages":"971–986 971–986"},"PeriodicalIF":14.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142039478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Single-Molecule Functional Chips: Unveiling the Full Potential of Molecular Electronics and Optoelectronics","authors":"Heng Zhang, Junhao Li, Chen Yang, Xuefeng Guo","doi":"10.1021/accountsmr.4c00125","DOIUrl":"https://doi.org/10.1021/accountsmr.4c00125","url":null,"abstract":"An ideal methodology for miniaturizing the physical size, enhancing the operational frequency, and building the multifunctional capability of functional chips is to use opto- or electroactive single molecules as their central elements; such devices are generally termed single-molecule electronics and optoelectronics. The exploration of the electronic and optoelectronic properties of materials at the single-molecule level also allows the complete elucidation of the correlation between molecular structure and function, which in turn aids technological advances that can help to address the challenge raised by Moore’s Law. In this Account, we present our ongoing investigative pursuits in the realm of single-molecule electronics and optoelectronics, with a particular emphasis on studies using graphene-molecule-graphene single-molecule junctions as the primary framework. To date, we have established a diverse range of single-molecule multifunctional devices, including photoswitches, field-effect transistors, rectifiers, light-emitting diodes, spin electronic devices, memristors, and molecular wires. These types of devices possess stable graphene electrodes and robust covalent molecule-electrode interfaces.","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141631722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Colloidal Nanocrystals: A Promising Semiconductor Platform for Photon/Exciton Manipulation","authors":"Xing Lin,&nbsp;Zikang Ye,&nbsp;Zhiyuan Cao,&nbsp;Haiyan Qin and Xiaogang Peng*,&nbsp;","doi":"10.1021/accountsmr.3c0028610.1021/accountsmr.3c00286","DOIUrl":"https://doi.org/10.1021/accountsmr.3c00286https://doi.org/10.1021/accountsmr.3c00286","url":null,"abstract":"&lt;p &gt;The invention of single-crystalline semiconductors and related devices allows us to manipulate electrons (or holes) as free charge carriers with ease. Photons and electrons are two types of fundamental particles for electromagnetic interaction, and optical/optoelectronic devices are thus likely as important as semiconductor electronic devices. Photons themselves have negligible direct interactions with each other, and manipulating photons─controlling their color purity and color accuracy, phase coherency and polarity, conversion from/to other forms of energy, etc.─is primarily achieved through their interactions with matter. Different from dealing with a single type of quasiparticle (electrons or holes) in a specific spatial region for electron manipulation, either absorbing or emitting a photon by matter, always involves a colocalized electron–hole pair as the transient state. In this sense, the key for manipulating photons is manipulating electron–hole pairs that are often called excitons. Similar to the corresponding bulk semiconductor, the binding energy is insufficient to stably bond a Wannier–Mott exciton in a typical semiconductor nanocrystal. However, two dynamic quasiparticles (electron and hole) are spatially confined within a nanocrystal by the energy barriers provided by the surrounding ligands/solvents, leading to formation of a special type of exciton, i.e., dynamic exciton.&lt;/p&gt;&lt;p &gt;We will begin this account by comparing dynamic excitons in a nanocrystal with two commonly encountered electron–hole states, namely, free carriers (completely unbounded electron and hole) in conventional semiconductors and Frenkel exciton in organic semiconductors. This reveals challenges faced by the current workhorse of optoelectronic devices mostly based on conventional semiconductors and highlight the unique advantages of colloidal nanocrystals as a semiconductor platform for photon/exciton manipulation. Colloidal semiconductor nanocrystals are synthesized and processed in solution, an indispensable advantage not only in terms of economic/environmental cost but also for exciton manipulation.&lt;/p&gt;&lt;p &gt;Solution chemistry coupled with dynamic excitons offer special means for exciton/photon manipulation. Specifically, properties of a dynamic exciton can be synthetically tuned by varying the size/shape/composition/ligands of the nanocrystals to match properties of the involved photons. Namely, these include precisely accurate recombination energy for color accuracy, engineered exciton–phonon coupling for color purity, orientation of anisotropic transition dipole for polarized photon emission, continuous absorption with tunable absorption onset, designed spatial localization of two quasiparticles through monolayer-accurate epitaxial shell growth, largely adjustable energies of top (bottom) of valence (conduction) band for charge transfer in optoelectronics and photochemistry, exciton radiative decay and Auger nonradiative decay lifetimes tunable in the m","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"5 8","pages":"884–895 884–895"},"PeriodicalIF":14.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142039476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Colloidal Nanocrystals: A Promising Semiconductor Platform for Photon/Exciton Manipulation","authors":"Xing Lin, Zikang Ye, Zhiyuan Cao, Haiyan Qin, Xiaogang Peng","doi":"10.1021/accountsmr.3c00286","DOIUrl":"https://doi.org/10.1021/accountsmr.3c00286","url":null,"abstract":"The invention of single-crystalline semiconductors and related devices allows us to manipulate electrons (or holes) as free charge carriers with ease. Photons and electrons are two types of fundamental particles for electromagnetic interaction, and optical/optoelectronic devices are thus likely as important as semiconductor electronic devices. Photons themselves have negligible direct interactions with each other, and manipulating photons─controlling their color purity and color accuracy, phase coherency and polarity, conversion from/to other forms of energy, etc.─is primarily achieved through their interactions with matter. Different from dealing with a single type of quasiparticle (electrons or holes) in a specific spatial region for electron manipulation, either absorbing or emitting a photon by matter, always involves a colocalized electron–hole pair as the transient state. In this sense, the key for manipulating photons is manipulating electron–hole pairs that are often called excitons. Similar to the corresponding bulk semiconductor, the binding energy is insufficient to stably bond a Wannier–Mott exciton in a typical semiconductor nanocrystal. However, two dynamic quasiparticles (electron and hole) are spatially confined within a nanocrystal by the energy barriers provided by the surrounding ligands/solvents, leading to formation of a special type of exciton, i.e., dynamic exciton.","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141625220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tailoring Stepped Layered Titanates for Sodium-Ion Battery Applications","authors":"Wei Yin, Juhyeon Ahn, Gözde Barim, Judith Alvarado, Marca M. Doeff","doi":"10.1021/accountsmr.4c00080","DOIUrl":"https://doi.org/10.1021/accountsmr.4c00080","url":null,"abstract":"Concerns about sustainability and supply chain issues associated with lithium-ion batteries (LIBs) have led researchers and companies around the world to investigate alternative technologies. Of all the so-called “beyond LIBs”, sodium-ion batteries (NIBs) are in the most advanced stage of development, and are being considered for grid storage applications as well as moderate-range electric vehicles. While graphite is the most commonly used anode material for LIBs, hard carbons are used in NIBs because sodium insertion into graphite does not occur to a useful extent. Other possibilities, based on cost and availability arguments, are titanates, which are generally denser than disordered carbons, meaning more material can be packed into a given volume, leading potentially to greater energy density. We have researched stepped layered titanates for use as anode materials, focusing on two types of structures. The first is “sodium nonatitanate” or NNT, with the composition NaTi₃O₆(OH)·2H₂O having six Ti⁴⁺O₆ octahedra joined together in steps to form layers with sodium ions and water in-between. The lepidocrocite-type titanate structure, contains zigzag layers (or steps one Ti⁴⁺O₆ unit across). These exist in a wide range of compositions, and contain large exchangeable cations between the layers. An unusual feature of both NNT and the lepidocrocite titanates is the very low potentials (0.3–0.5 V vs Na⁺/Na) at which they insert sodium. This makes them particularly attractive for anode applications. Another interesting feature is the ability to tailor the electrochemical properties by various modifications, such as heat-treatment to remove water and change the structure, introduction of vacancies, ion-exchange, surface modifications, and carbon coating or graphene wrapping, all of which alter the electrochemical properties. Finally, heterostructuring (interleaving titanate layers with carbon) results in new materials with different redox properties. For all the titanates, the first cycle Coulombic efficiency (C.E.) is very sensitive to the binder used in the electrode fabrication and the electrolyte used. Because sodium insertion occurs at such a low potential, some electrolyte and binder are irreversibly reduced during the first cycle to form a protective solid electrolyte interphase (SEI). In a full cell, it is important to maximize the C.E. because all the cyclable sodium must come from the cathode, so cells must be overbuilt to compensate for these losses. Proper selection of binder and electrolyte results in improved cycling performance and minimal first cycle losses. Finally, examples of full cells containing some of the materials under discussion are provided.","PeriodicalId":72040,"journal":{"name":"Accounts of materials research","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141625150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}