化学•材料最新文献

{"title":"Synaptic Properties of an Interfacial Memristor Based on a Ga₂O₃/Nb:SrTiO₃ Heterojunction.","authors":"Youhong Wang, Wei Hu, Kaijin Kang, Caili Dong, Xiaosheng Tang","doi":"10.1021/acs.jpclett.4c02548","DOIUrl":"10.1021/acs.jpclett.4c02548","url":null,"abstract":"<p><p>Memristors have been extensively studied for tremendous potential for future neuromorphic computing hardware applications because of their ability to imitate biological synaptic processes. Herein, we report an interfacial memristor based on a Ga₂O₃/Nb:SrTiO₃ heterojunction that shows stable bipolar resistive switching behavior, long retention time, and high switching ratio. The conductance of the Au/Ga₂O₃/Nb:SrTiO₃/In memristor can be gradually modulated under the voltage sweep mode as well as positive and negative pulse voltage stimulations, respectively, thus realizing the long-term potentiation/depression characteristics of the simulated biological synapse. A neural network based on the prepared memristor was built to recognize the handwritten picture data set with a recognition accuracy of 92.78% by using the NeuroSimV3.0 platform. Our work indicates that the Ga₂O₃/Nb:SrTiO₃ heterojunction memristor has significant potential in a neuromorphic computing system.</p>","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142542933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Insights into Chemical Bonding Modes and Heat Transport at the Molecular Level.","authors":"Shintaro Fujii, Yoshiaki Shoji, Yuma Masuda, Takanori Fukushima, Tomoaki Nishino","doi":"10.1021/acs.jpclett.4c02325","DOIUrl":"10.1021/acs.jpclett.4c02325","url":null,"abstract":"<p><p>Despite the demand for nanoscale thermal management technologies of material surfaces and interfaces using organic molecules, heat transport properties at the single molecular level remain elusive due to the experimental difficulty of measuring temperature at the nanoscopic scale. Here we show how chemical bonding modes can affect the heat transport properties of single molecules. We focused on four molecular systems: benzylthiol linked to another phenyl group by either a triple (compound <b>1</b>), double (<b>3</b>), or amide (<b>4</b>) bond and a common linear alkanethiol (<b>2</b>), all of which are nearly identical in molecular length. We prepared binary self-assembled monolayers (SAMs) using <b>1</b> as a common reference in combination with <b>2</b>-<b>4</b> and investigated their relative heat transport properties using scanning thermal microscopy (SThM). Two-dimensional temperature mapping of the binary SAMs showed that C≡C and C=C bonds provide more effective pathways for heat transport compared to C-C bonds. Since the amide molecule has resonance structures with C=N double bond character, we expected that its heat transport properties would be comparable to those of the thiols containing triple or double bonds. However, the heat transport properties of this molecule prevailed over the others, most likely due to the formation of additional heat transport pathways caused by intermolecular hydrogen bonding. These findings may provide important guidelines for the design of organic materials for nanoscale thermal management.</p>","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142556673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular Modeling of Glycosylated Catalytic Domain of Human Carbonic Anhydrase IX.","authors":"Ritwika Dey, Srabani Taraphder","doi":"10.1021/acs.jpcb.4c03514","DOIUrl":"10.1021/acs.jpcb.4c03514","url":null,"abstract":"<p><p>Glycans exhibit significant structural diversity due to the flexibility of glycosidic bonds linking their constituent monosaccharides and the formation of numerous hydrogen bonds. The present work searches a simulated ensemble of glycan chain conformations attached to the catalytic domain of N-glycosylated human carbonic anhydrase IX (HCA IX-c) to identify conformations pointed away or back-folded toward the protein surface guided by different amino acid residues. A series of classical molecular dynamics (MD) simulation studies for a total of 30 μs followed by accelerated MD simulations for a total of 2 μs have been performed using two different force fields to capture varying degrees of fluctuations of both glycan chain and HCA IX. From the underlying free energy profile and kinetics derived using hidden Markov state model, several stable glycan orientations are identified that extend away from the protein surface and convert among each other with rate constants of the order 10⁷-10¹⁰ _S^-1. Most importantly, we have identified a <i>rare</i> glycan conformation which reaches close to a catalytically important amino acid residue, Glu-106. We further enlist the protein residues that couple such less frequent event of the glycan chain back-folding toward the surface of the protein.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142563542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Slope of the Delocalization Function Is Proportional to Analytical Hardness.","authors":"Bin Wang, Paul Geerlings, Farnaz Heidar-Zadeh, Paul W Ayers, Frank De Proft","doi":"10.1021/acs.jpclett.4c02263","DOIUrl":"10.1021/acs.jpclett.4c02263","url":null,"abstract":"<p><p>Conceptual Density Functional Theory (CDFT) has been extended beyond its traditional role in elucidating chemical reactivity to the development of density functional theory methods, e.g., the investigation of the delocalization error. This delocalization error causes the dependence of the energy on the number of electrons (<i>N</i>) to deviate from its exact piecewise linear behavior, an error which is the basis of many well-known limitations of commonly used density-functional approximations (DFAs). Following our previous work on the analytical hardness η^± for pure functionals, we extend its application to hybrid and range-separated functionals. A comparison is made between the analytical hardness and the slope of the delocalization function introduced by Hait and Head-Gordon. Our results show that there is a linear relationship between its slope and the analytical hardness. An approximate scheme is presented to construct the energy vs <i>N</i> curve without fractional occupation number calculations. The extension to densities is discussed.</p>","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142566368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular Dynamics and Self-Assembly in Double Hydrophilic Block and Random Copolymers.","authors":"Achilleas Pipertzis, Angeliki Chroni, Stergios Pispas, Jan Swenson","doi":"10.1021/acs.jpcb.4c05398","DOIUrl":"10.1021/acs.jpcb.4c05398","url":null,"abstract":"<p><p>We investigate the self-assembly and dynamics of double hydrophilic block copolymers (DHBCs) composed of densely grafted poly[oligo(ethylene glycol) methacrylate] (POEGMA) and poly(vinyl benzyl trimethylammonium chloride) (PVBTMAC) parent blocks by means of calorimetry, small- and wide-angle X-ray scattering (SAXS/WAXS), and dielectric spectroscopy. A weak segregation strength is evident from X-ray measurements, implying a disordered state and reflecting the inherent miscibility between the host homopolymers. The presence of intermixed POEGMA/PVBTMAC nanodomains results in homogeneous molecular dynamics, as evidenced through isothermal dielectric and temperature-modulated DSC measurements. The intermixed process undergoes a glass transition at a temperature approximately 40 K higher than the vitrification of bulk POEGMA segments, and it shifts to an even higher temperature by increasing the content of the hard block. At temperatures below the intermixed glass transition temperature, the confined POEGMA segments between the glassy intermixed regions contribute to a segmental process featuring (i) reduced glass transition temperature (<i>T</i>_g), (ii) reduced dielectric strength, (iii) broader distribution of relaxation times, and (iv) reduced fragility compared to the POEGMA homopolymer. We also observe two glass transition temperatures of dry PVBTMAC, which we attribute to the backbone and side chain segmental relaxation. To the best of our knowledge, this is the first time in the literature that these glass transitions of dry PVBTMAC have been reported. Finally, this study shows that excellent mixing of the two homopolymers is obtained, and this implies that different properties of this copolymer system can be tailored by adjusting the concentration of each homopolymer.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142575457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unusual and Persistent Free Radical Intermediate Production from 2-Pyridyl Ketones via UV Irradiation: A Direct ESR Study.","authors":"Lin-Na Xie, Chun-Hua Huang, Dan Xu, Zhen-Huan Li, Li Qin, Bo Shao, Li Mao, Jie Shao, Zhi-Sheng Liu, Jing Chen, Zhi-Guo Sheng, Zhi-Hui Zhang, Ben-Zhan Zhu","doi":"10.1021/acs.jpclett.4c02657","DOIUrl":"10.1021/acs.jpclett.4c02657","url":null,"abstract":"<p><p>Aryl ketones are often used as photosensitizers and photoinitiators. Free radical intermediates have been suggested, but not confirmed, to be generated after photoirradiation. Here we found, unexpectedly, that a persistent radical was produced from di-2-pyridyl ketone after UV irradiation, which was detected by the direct ESR method. Interestingly, the persistent radical was very sensitive to oxygen and the pH of the reaction medium. A similar persistent radical was also observed from phenyl-2-pyridyl ketone, but not from 3-benzoylpyridine, 4-benzoylpyridine, and benzophenone, suggesting that the presence of a carbonyl group connected to the <i>ortho</i>-position of the pyridine ring is critical for such radical production. By complementary applications of ESR, HPLC, and ESI-Q-TOF-MS, the possible chemical structures of the persistent radical and final product were identified, and the possible underlying reaction mechanism was proposed. This represents the first report on UV-induced persistent radical generation from 2-pyridyl ketones, which should be of great significance for future studies.</p>","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142581037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tailoring Superatomic Stability with Transition Metals in Silicon Cages: Shrinking to M@Si15 (M = Re, Os, Ir)","authors":"Takumi Ichikawa, Kazuya Terasaka, Ayaka Sasaki, Atsushi Nakajima","doi":"10.1021/acs.jpclett.4c02797","DOIUrl":"https://doi.org/10.1021/acs.jpclett.4c02797","url":null,"abstract":"The design of materials with intriguing electronic properties is crucial for advancing nanoscale technologies, where precise control over atomic structure and electronic behavior is essential. Metal-encapsulating silicon cage superatoms (SAs) provide a new paradigm for molecular-scale material design, allowing fine-tuning of both structure and electronic characteristics. The formation of superatoms mimicking halogens, noble gases, and alkali metals has been well-studied, particularly with M@Si₁₆, where early transition metals from groups 3 to 5 stabilize within a Si₁₆ cage, achieving a 68-electron configuration. For late transition metals with excess electrons, a Si₁₅ cage offers enhanced stability by fulfilling the 68-electron rule with one fewer Si atom. This research synthesizes Si₁₅ cage-SAs with rhenium (Re) from group 7 and iridium (Ir) from group 9 on <i>p</i>-type and <i>n</i>-type organic substrates. The stability of Re@Si₁₅ and Ir@Si₁₅ is evaluated via oxidative reactivity with X-ray photoelectron spectroscopy and theoretical calculations, including osmium (Os) from group 8. Re@Si₁₅^–, Os@Si₁₅⁰, and Ir@Si₁₅⁺ exhibit superatomic behaviors similar to halogens, noble gases, and alkali metals due to the 68-electron shell closure. Among them, Re@Si₁₅^– on <i>p</i>-type organic substrates shows superior electronic and geometric properties. These findings advance our understanding of M@Si_<i>n</i> systems for transition metals, addressing longstanding questions about their properties at <i>n</i> = 15 and 16.","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":null,"pages":null},"PeriodicalIF":6.475,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610038","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cu-Catalyzed Multicomponent Reaction of Arylhydrazines with β-Ketoesters and TBN: One-Pot Access to N2-Aryl 1,2,3-Triazole-1-Oxides","authors":"Mohammad Mujahid, Vijay Vara, Usman Arshad, Rama Krishna Gamidi, M. Muthukrishnan","doi":"10.1021/acs.joc.4c00298","DOIUrl":"https://doi.org/10.1021/acs.joc.4c00298","url":null,"abstract":"We report a copper-catalyzed one-pot, multicomponent strategy for the convenient synthesis of <i>N</i>²-aryl 1,2,3-triazole-1-oxides using arylhydrazines, β-ketoesters, and <i>tert</i>-butyl nitrite. This mild and simple reaction proceeds in an atom-economic manner with broad substrate scope, affording a variety of <i>N</i>²-aryl 1,2,3-triazole-1-oxide derivatives. Other salient features of the reaction are good functional group tolerance, scalability, and product diversification.","PeriodicalId":57,"journal":{"name":"The Journal of Organic Chemistry","volume":null,"pages":null},"PeriodicalIF":4.354,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Solvent-Controlled Rh(III)-Catalyzed Mono- and Dual Functionalization of Quinolyl Aldoximes with Diazo Compounds","authors":"Peng Zhang, Shan Xu, ShihaoZhi Wang, Xue-jing Zhang, Ming Yan","doi":"10.1021/acs.joc.4c01896","DOIUrl":"https://doi.org/10.1021/acs.joc.4c01896","url":null,"abstract":"A solvent-controlled Rh(III)-catalyzed mono- and dual-C–H bond activation/carbene migratory insertion with diazo compounds as a single coupling partner was demonstrated. The reaction proceeded under mild conditions, yielding products in good to excellent yields. These results are significant for the development of the domino multiple functionalization of C(sp²)–H bonds via a carbenoid insertion approach.","PeriodicalId":57,"journal":{"name":"The Journal of Organic Chemistry","volume":null,"pages":null},"PeriodicalIF":4.354,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"What Is the Protonation State of Proteins in Crystals? Insights from Constant pH Molecular Dynamics Simulations.","authors":"Noora Aho, Gerrit Groenhof, Pavel Buslaev","doi":"10.1021/acs.jpcb.4c05947","DOIUrl":"10.1021/acs.jpcb.4c05947","url":null,"abstract":"<p><p>X-ray crystallography is an important technique to determine the positions of atoms in a protein crystal. However, because the native environment in which proteins function, is not a crystal, but a solution, it is not a priori clear if the crystal structure represents the functional form of the protein. Because the protein structure and function often depend critically on the pH, the question arises whether proton affinities are affected by crystallization. X-ray diffraction usually does not reveal protons, which makes it difficult to experimentally measure p<i>K</i>_a shifts in crystals. Here, we investigate whether this challenge can be addressed by performing in silico titration with constant pH molecular dynamics (MD) simulations. We compare the computed p<i>K</i>_a values of proteins between solution and crystal environment and analyze these differences in the context of molecular interactions. For the proteins considered in this work, p<i>K</i>_a shifts were mostly found for residues at the crystal interfaces, where the environment is more apolar in the crystal than in water. Although convergence was an obstacle, our simulations suggest that in principle it is possible to apply constant pH MD to protein crystals routinely and assess the effect of crystallization on protein function more systematically than with standard MD simulations. We also highlight technical challenges that need to be addressed to make MD simulations of crystals more reliable.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142542927","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}