Pub Date : 2023-12-17DOI: 10.1088/2053-1583/ad1675
K. V. Kumar, Aminul Islam, P. S. Kiran, Niranjan Pandit, Rahul Kumar, Satish Indupuri, A. Keshri
Here, we exfoliated high-quality turbostratic graphene with a clean interface at a high production rate (10 g/h) directly from graphite using an industrial-friendly technique i.e., plasma spraying, catching note of its growing global interest. The reduction of the (002) X-ray diffraction peak and the transparent scanning electron microscope (SEM) image are used to characterize the exfoliation. The thickness of exfoliated graphene layers is measured using an atomic force microscope (AFM). Turbostratic nature (twist) in graphene is identified based on the appearance of three Raman combination bands (TS1, TS2, and TS3) between 1800 cm-1 and 2300 cm-1. The twist between the layers is precisely measured using selected area electron diffraction (SAED), and the turbostratic nature is confirmed by observing a moiré pattern utilizing a high-resolution transmission electron microscope (HR-TEM). The produced turbostratic graphene exhibited large variability in twist angles (2⁰-30⁰) with a visible moiré pattern. The high crystalline quality and clean interface between single layers of graphene were confirmed by the moiré pattern and SAED. Later, we demonstrated the mechanism underlying the twist in our exfoliated graphene, which could open the way for the production of high-quality turbostratic graphene with clean interfaces.
{"title":"Exfoliation of graphite to turbostratic graphene","authors":"K. V. Kumar, Aminul Islam, P. S. Kiran, Niranjan Pandit, Rahul Kumar, Satish Indupuri, A. Keshri","doi":"10.1088/2053-1583/ad1675","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1675","url":null,"abstract":"\u0000 Here, we exfoliated high-quality turbostratic graphene with a clean interface at a high production rate (10 g/h) directly from graphite using an industrial-friendly technique i.e., plasma spraying, catching note of its growing global interest. The reduction of the (002) X-ray diffraction peak and the transparent scanning electron microscope (SEM) image are used to characterize the exfoliation. The thickness of exfoliated graphene layers is measured using an atomic force microscope (AFM). Turbostratic nature (twist) in graphene is identified based on the appearance of three Raman combination bands (TS1, TS2, and TS3) between 1800 cm-1 and 2300 cm-1. The twist between the layers is precisely measured using selected area electron diffraction (SAED), and the turbostratic nature is confirmed by observing a moiré pattern utilizing a high-resolution transmission electron microscope (HR-TEM). The produced turbostratic graphene exhibited large variability in twist angles (2⁰-30⁰) with a visible moiré pattern. The high crystalline quality and clean interface between single layers of graphene were confirmed by the moiré pattern and SAED. Later, we demonstrated the mechanism underlying the twist in our exfoliated graphene, which could open the way for the production of high-quality turbostratic graphene with clean interfaces.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"20 4","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138965758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-15DOI: 10.1088/2053-1583/ad1313
Srdjan Stavrić, Paolo Barone, Silvia Picozzi
Bilayer CrI3 attracted much attention due to stacking-induced switching between the layered ferromagnetic and antiferromagnetic order. This discovery brought under the spotlight the interlayer Cr–Cr exchange interaction, which despite being much weaker than the intralayer exchange, plays an important role in shaping the magnetic properties of bilayer CrI3. In this work we delve into the anisotropic part of the interlayer exchange with the aim to separate the contributions from the Dzyaloshinskii–Moriya (DMI) and the Kitaev interactions (KI). We leverage the density functional theory calculations with spin Hamiltonian modeling and develop an energy mapping procedure to assess these anisotropic interactions with μeV accuracy. After inspecting the rhombohedral and monoclinic stacking sequences of bilayer CrI3, we reveal a considerable DMI and a weak interlayer KI between the sublattices of a monoclinic bilayer. We explain the dependence of DMI and KI on the interlayer distance, stacking sequence, and the spin–orbit coupling strength, and we suggest the dominant superexchange processes at play. In addition, we demonstrate that the single-ion anisotropy in bilayer CrI3 is highly stacking-dependent, increasing by 50% from monoclinic to rhombohedral bilayer. Remarkably, our findings prove that iodines are highly efficient in mediating the DMI across the van der Waals gap, much owing to spatially extended 5p orbitals which feature strong spin–orbit coupling. Our study gives promise that the interlayer chiral control of spin textures, demonstrated in thin metallic films where the DMI is with a much longer range, can be achieved with similar efficiency in semiconducting two-dimensional van der Waals magnets.
{"title":"Delving into the anisotropic interlayer exchange in bilayer CrI3","authors":"Srdjan Stavrić, Paolo Barone, Silvia Picozzi","doi":"10.1088/2053-1583/ad1313","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1313","url":null,"abstract":"Bilayer CrI<sub>3</sub> attracted much attention due to stacking-induced switching between the layered ferromagnetic and antiferromagnetic order. This discovery brought under the spotlight the interlayer Cr–Cr exchange interaction, which despite being much weaker than the intralayer exchange, plays an important role in shaping the magnetic properties of bilayer CrI<sub>3</sub>. In this work we delve into the anisotropic part of the interlayer exchange with the aim to separate the contributions from the Dzyaloshinskii–Moriya (DMI) and the Kitaev interactions (KI). We leverage the density functional theory calculations with spin Hamiltonian modeling and develop an energy mapping procedure to assess these anisotropic interactions with <inline-formula>\u0000<tex-math><?CDATA $mumathrm{eV}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi>μ</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">e</mml:mi><mml:mi mathvariant=\"normal\">V</mml:mi></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"tdmad1313ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> accuracy. After inspecting the rhombohedral and monoclinic stacking sequences of bilayer CrI<sub>3</sub>, we reveal a considerable DMI and a weak interlayer KI between the sublattices of a monoclinic bilayer. We explain the dependence of DMI and KI on the interlayer distance, stacking sequence, and the spin–orbit coupling strength, and we suggest the dominant superexchange processes at play. In addition, we demonstrate that the single-ion anisotropy in bilayer CrI<sub>3</sub> is highly stacking-dependent, increasing by 50% from monoclinic to rhombohedral bilayer. Remarkably, our findings prove that iodines are highly efficient in mediating the DMI across the van der Waals gap, much owing to spatially extended 5<italic toggle=\"yes\">p</italic> orbitals which feature strong spin–orbit coupling. Our study gives promise that the interlayer chiral control of spin textures, demonstrated in thin metallic films where the DMI is with a much longer range, can be achieved with similar efficiency in semiconducting two-dimensional van der Waals magnets.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"33 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138686980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-12DOI: 10.1088/2053-1583/ad10b9
Preeti Lata Mahapatra, Caique Campos de Oliveira, Gelu Costin, Suman Sarkar, Pedro A S Autreto, Chandra Sekhar Tiwary
Silicon dioxide’s potential for having magnetic properties is fascinating, as combining its electronic capabilities with magnetic response seems promising for spintronics. In this work, the mechanisms that drive the change from diamagnetic behavior in pure silicates like SiO2 to paramagnetic behavior in transition metal-doped silicates like Rhodonite silicate (CaMn3Mn(Si5O15)) are explored. This naturally occurring Rhodonite (R)-silicate was thinned down while retaining its magnetic properties by liquid-phase scalable exfoliation. Exfoliating R-silicate into the two-dimensional (2D) structure by LPE increases magnetic coercivity, and the internal resistance to demagnetization (ΔHc) up to ∼23.95 Oe compared to 7.08 Oe for its bulk phase. DFT spin-polarized calculations corroborate those findings and explain that the origin of the magnetic moment comes mainly from the Mn in the doped 2D silicate due to the asymmetrical components of the Mn d and Si p states in the valence band. This result is further illustrated by the spin component differential charge densities showing that Mn and Si atoms display a residual up spin charge. Rhodonite’s unusual magnetic behavior has considerable potential for spintronics, data storage, and sensing technologies. Understanding the complex relationships between the structural, magnetic, and electronic properties of silicates is essential for developing new materials and composites as well as for driving future research.
二氧化硅具有磁性能的潜力令人着迷，因为将其电子功能与磁性响应相结合似乎很有希望用于自旋电子学。在这项研究中，我们探索了从纯硅酸盐（如二氧化硅）中的二磁行为到掺杂过渡金属的硅酸盐（如红柱石硅酸盐（CaMn3Mn(Si5O15)）中的顺磁性行为的转变机制。通过液相可扩展剥离，这种天然存在的红柱石（R）硅酸盐在保持其磁性能的同时被减薄。通过 LPE 将 R 硅酸盐剥离成二维（2D）结构可提高磁矫顽力和退磁内阻（ΔHc），最高可达 ∼23.95 Oe，而其体相仅为 7.08 Oe。DFT 自旋极化计算证实了这些发现，并解释了磁矩的来源主要来自掺杂二维硅酸盐中的锰，这是因为价带中的锰 d 态和硅 p 态存在不对称成分。自旋分量差电荷密度进一步说明了这一结果，表明锰原子和硅原子显示出残余的上自旋电荷。红柱石不寻常的磁性行为在自旋电子学、数据存储和传感技术方面具有相当大的潜力。了解硅酸盐的结构、磁性和电子特性之间的复杂关系对于开发新材料和复合材料以及推动未来研究至关重要。
{"title":"Paramagnetic two-dimensional silicon-oxide from natural silicates","authors":"Preeti Lata Mahapatra, Caique Campos de Oliveira, Gelu Costin, Suman Sarkar, Pedro A S Autreto, Chandra Sekhar Tiwary","doi":"10.1088/2053-1583/ad10b9","DOIUrl":"https://doi.org/10.1088/2053-1583/ad10b9","url":null,"abstract":"Silicon dioxide’s potential for having magnetic properties is fascinating, as combining its electronic capabilities with magnetic response seems promising for spintronics. In this work, the mechanisms that drive the change from diamagnetic behavior in pure silicates like SiO<sub>2</sub> to paramagnetic behavior in transition metal-doped silicates like Rhodonite silicate (CaMn<sub>3</sub>Mn(Si<sub>5</sub>O<sub>15</sub>)) are explored. This naturally occurring Rhodonite (R)-silicate was thinned down while retaining its magnetic properties by liquid-phase scalable exfoliation. Exfoliating R-silicate into the two-dimensional (2D) structure by LPE increases magnetic coercivity, and the internal resistance to demagnetization (ΔHc) up to ∼23.95 Oe compared to 7.08 Oe for its bulk phase. DFT spin-polarized calculations corroborate those findings and explain that the origin of the magnetic moment comes mainly from the Mn in the doped 2D silicate due to the asymmetrical components of the Mn d and Si p states in the valence band. This result is further illustrated by the spin component differential charge densities showing that Mn and Si atoms display a residual up spin charge. Rhodonite’s unusual magnetic behavior has considerable potential for spintronics, data storage, and sensing technologies. Understanding the complex relationships between the structural, magnetic, and electronic properties of silicates is essential for developing new materials and composites as well as for driving future research.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"54 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138687446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-11DOI: 10.1088/2053-1583/ad10bb
Sabin Gautam, Joseph McBride, William R Scougale, Piumi I Samarawickrama, Danilo De Camargo Branco, Peilin Yang, ZhuangEn Fu, Wenyong Wang, Jinke Tang, Gary J Cheng, John Ackerman, TeYu Chien, Brian M Leonard, Jifa Tian
The investigation of exotic properties in two-dimensional (2D) topological superconductors has garnered increasing attention in condensed matter physics, particularly for applications in topological qubits. Despite this interest, a reliable way of fabricating topological Josephson junctions (JJs) utilizing topological superconductors has yet to be demonstrated. Controllable structural phase transition presents a unique approach to achieving topological JJs in atomically thin 2D topological superconductors. In this work, we report the pioneering demonstration of a structural phase transition from the superconducting to the semiconducting phase in the 2D topological superconductor 2M-WS2. We reveal that the metastable 2M phase of WS2 remains stable in ambient conditions but transitions to the 2H phase when subjected to temperatures above 150 °C. We further locally induced the 2H phase within 2M-WS2 nanolayers using laser irradiation. Notably, the 2H phase region exhibits a hexagonal shape, and scanning tunneling microscopy uncovers an atomically sharp crystal structural transition between the 2H and 2M phase regions. Moreover, the 2M to 2H phase transition can be induced at the nanometer scale by a 200 kV electron beam. The electrical transport measurements further confirmed the superconductivity of the pristine 2M-WS2 and the semiconducting behavior of the laser-irradiated 2M-WS2. Our results establish a novel approach for controllable topological phase change in 2D topological superconductors, significantly impacting the development of atomically scaled planar topological JJs.
{"title":"Controllable superconducting to semiconducting phase transition in topological superconductor 2M-WS2","authors":"Sabin Gautam, Joseph McBride, William R Scougale, Piumi I Samarawickrama, Danilo De Camargo Branco, Peilin Yang, ZhuangEn Fu, Wenyong Wang, Jinke Tang, Gary J Cheng, John Ackerman, TeYu Chien, Brian M Leonard, Jifa Tian","doi":"10.1088/2053-1583/ad10bb","DOIUrl":"https://doi.org/10.1088/2053-1583/ad10bb","url":null,"abstract":"The investigation of exotic properties in two-dimensional (2D) topological superconductors has garnered increasing attention in condensed matter physics, particularly for applications in topological qubits. Despite this interest, a reliable way of fabricating topological Josephson junctions (JJs) utilizing topological superconductors has yet to be demonstrated. Controllable structural phase transition presents a unique approach to achieving topological JJs in atomically thin 2D topological superconductors. In this work, we report the pioneering demonstration of a structural phase transition from the superconducting to the semiconducting phase in the 2D topological superconductor 2M-WS<sub>2</sub>. We reveal that the metastable 2M phase of WS<sub>2</sub> remains stable in ambient conditions but transitions to the 2H phase when subjected to temperatures above 150 °C. We further locally induced the 2H phase within 2M-WS<sub>2</sub> nanolayers using laser irradiation. Notably, the 2H phase region exhibits a hexagonal shape, and scanning tunneling microscopy uncovers an atomically sharp crystal structural transition between the 2H and 2M phase regions. Moreover, the 2M to 2H phase transition can be induced at the nanometer scale by a 200 kV electron beam. The electrical transport measurements further confirmed the superconductivity of the pristine 2M-WS<sub>2</sub> and the semiconducting behavior of the laser-irradiated 2M-WS<sub>2</sub>. Our results establish a novel approach for controllable topological phase change in 2D topological superconductors, significantly impacting the development of atomically scaled planar topological JJs.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"21 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138686722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-08DOI: 10.1088/2053-1583/ad10ba
Urvesh Patil, Nuala M Caffrey
Liquid phase exfoliation is the most promising method for the low-cost, scalable production of two-dimensional nanosheets from their bulk counterparts. Extensive exfoliation occurs in most solvents due to the huge amount of energy introduced by sonication or shear mixing. However, the subsequent dispersion is not always stable, with extensive reaggregation occurring in some solvents. Identifying the optimal solvent for a particular layered material is difficult and requires a fundamental understanding of the mechanism involved in maintaining a stable dispersion. Here, we use molecular dynamics calculations to show that when graphene is immersed in a solvent, distinct solvation layers are formed irrespective of the choice of solvent and their formation is energetically favourable for all considered solvents. However, energetic considerations such as these do not explain the experimental solvent-dependence of the dispersion concentration. Instead, we find that solvents with high diffusion coefficients parallel to the graphene layer result in the lowest experimental concentration of graphene in solution. This can be explained by the enhanced ease of reaggregation in these solvents. Solvents with smaller diffusion coefficients result in higher experimental graphene concentrations as reaggregation is prevented. In the low diffusion limit, however, this relationship breaks down. We suggest that here the concentration of graphene in solution depends primarily on the separation efficiency of the initial exfoliation step. Based on this, we predict that the concentration of exfoliated graphene in solvents such as benzaldehyde and quinoline, which have low diffusion constants, can be increased dramatically by careful tuning of the experimental sonication parameters.
{"title":"The role of solvent interfacial structural ordering in maintaining stable graphene dispersions","authors":"Urvesh Patil, Nuala M Caffrey","doi":"10.1088/2053-1583/ad10ba","DOIUrl":"https://doi.org/10.1088/2053-1583/ad10ba","url":null,"abstract":"Liquid phase exfoliation is the most promising method for the low-cost, scalable production of two-dimensional nanosheets from their bulk counterparts. Extensive exfoliation occurs in most solvents due to the huge amount of energy introduced by sonication or shear mixing. However, the subsequent dispersion is not always stable, with extensive reaggregation occurring in some solvents. Identifying the optimal solvent for a particular layered material is difficult and requires a fundamental understanding of the mechanism involved in maintaining a stable dispersion. Here, we use molecular dynamics calculations to show that when graphene is immersed in a solvent, distinct solvation layers are formed irrespective of the choice of solvent and their formation is energetically favourable for all considered solvents. However, energetic considerations such as these do not explain the experimental solvent-dependence of the dispersion concentration. Instead, we find that solvents with high diffusion coefficients parallel to the graphene layer result in the lowest experimental concentration of graphene in solution. This can be explained by the enhanced ease of reaggregation in these solvents. Solvents with smaller diffusion coefficients result in higher experimental graphene concentrations as reaggregation is prevented. In the low diffusion limit, however, this relationship breaks down. We suggest that here the concentration of graphene in solution depends primarily on the separation efficiency of the initial exfoliation step. Based on this, we predict that the concentration of exfoliated graphene in solvents such as benzaldehyde and quinoline, which have low diffusion constants, can be increased dramatically by careful tuning of the experimental sonication parameters.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"22 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138687384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-05DOI: 10.1088/2053-1583/ad1251
Derrick Butler, Chinmay S. Sankhe, Pouya Soltan Khamsi, Esther W. Gomez, Aida Ebrahimi
Nitric oxide plays an important role in cardiovascular function, immune response, and intercellular signaling. However, due to its short lifetime, real-time detection of nitric oxide is challenging. Herein, an electrochemical sensor based on fibronectin-modified, solution-processed graphene ink for nitric oxide detection is developed using a facile fabrication method involving spin-coating and hot-plate annealing. The sensor is first electrochemically characterized with a nitric oxide donor, spermine NONOate, exhibiting a dynamic range of 10 – 1000 μM. The fibronectin-functionalized graphene supports the attachment and growth of MDA-MB-231 breast cancer cells, as confirmed by optical microscopy. Extracellular nitric oxide production is stimulated using the amino acid L-arginine. Nitric oxide production results in morphological changes to the adhered cells, which are reversible upon the addition of the nitric oxide synthase antagonist Nω-nitro-L-arginine methyl ester (L-NAME). The production of nitric oxide is also confirmed using real-time amperometric measurements with the fibronectin-functionalized graphene sensors. While this work focuses on nitric oxide detection, this potentially scalable platform could be extended to other cell types with envisioned applications including the high-throughput evaluation of therapeutics and biocompatible coatings.
一氧化氮在心血管功能、免疫反应和细胞间信号传导中起重要作用。然而，由于其寿命短，实时检测一氧化氮是具有挑战性的。本文采用旋转涂层和热板退火的简易制造方法，开发了一种基于纤维连接蛋白修饰的溶液处理石墨烯墨水的电化学传感器，用于一氧化氮检测。该传感器首先用一氧化氮供体精胺NONOate进行了电化学表征，其动态范围为10 - 1000 μM。光学显微镜证实，纤维连接蛋白功能化的石墨烯支持MDA-MB-231乳腺癌细胞的附着和生长。细胞外一氧化氮的产生是由氨基酸l -精氨酸刺激的。一氧化氮的产生导致粘附细胞的形态变化，这种变化在加入一氧化氮合酶拮抗剂n ω-硝基- l -精氨酸甲酯(L-NAME)后是可逆的。利用纤维连接蛋白功能化石墨烯传感器的实时安培测量也证实了一氧化氮的产生。虽然这项工作的重点是一氧化氮检测，但这个潜在的可扩展平台可以扩展到其他细胞类型，包括治疗药物和生物相容性涂层的高通量评估。
{"title":"Solution-processed graphene films for electrochemical monitoring of extracellular nitric oxide released by breast cancer cells","authors":"Derrick Butler, Chinmay S. Sankhe, Pouya Soltan Khamsi, Esther W. Gomez, Aida Ebrahimi","doi":"10.1088/2053-1583/ad1251","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1251","url":null,"abstract":"\u0000 Nitric oxide plays an important role in cardiovascular function, immune response, and intercellular signaling. However, due to its short lifetime, real-time detection of nitric oxide is challenging. Herein, an electrochemical sensor based on fibronectin-modified, solution-processed graphene ink for nitric oxide detection is developed using a facile fabrication method involving spin-coating and hot-plate annealing. The sensor is first electrochemically characterized with a nitric oxide donor, spermine NONOate, exhibiting a dynamic range of 10 – 1000 μM. The fibronectin-functionalized graphene supports the attachment and growth of MDA-MB-231 breast cancer cells, as confirmed by optical microscopy. Extracellular nitric oxide production is stimulated using the amino acid L-arginine. Nitric oxide production results in morphological changes to the adhered cells, which are reversible upon the addition of the nitric oxide synthase antagonist Nω-nitro-L-arginine methyl ester (L-NAME). The production of nitric oxide is also confirmed using real-time amperometric measurements with the fibronectin-functionalized graphene sensors. While this work focuses on nitric oxide detection, this potentially scalable platform could be extended to other cell types with envisioned applications including the high-throughput evaluation of therapeutics and biocompatible coatings.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"40 5","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138600801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The recent growth of two-dimensional (2D) layered crystals of MoSi<sub>2</sub>N<sub>4</sub> and WSi<sub>2</sub>N<sub>4</sub> has sparked significant interest due to their outstanding properties and potential applications. This development has paved the way for a new and large family of 2D materials with a general formula of <italic toggle="yes">MA</italic> <sub>2</sub> <italic toggle="yes">Z</italic> <sub>4</sub>. In this regard, motivated by this exciting family, we propose two structural phases (<italic toggle="yes">1T</italic>- and <italic toggle="yes">1H</italic>-) of <italic toggle="yes">M</italic>Si<sub>2</sub>N<sub>4</sub> (<italic toggle="yes">M</italic> = Ge, Sn, and Pb) monolayers and investigate their structural, vibrational, mechanical, electronic and optical properties by using first-principles methods. The two phases have similar cohesive energies, while the <italic toggle="yes">1T</italic> structures are found to be more energetically favorable than their <italic toggle="yes">1H</italic> counterparts. The analysis of phonon spectra and <italic toggle="yes">ab initio</italic> molecular dynamics simulations indicate that all the suggested monolayers, except for <italic toggle="yes">1H</italic>-GeSi<sub>2</sub>N<sub>4</sub>, are dynamically and thermally stable even at elevated temperatures. The elastic stability and mechanical properties of the proposed crystals are examined by calculating their elastic constants (<italic toggle="yes">C</italic> <sub> <italic toggle="yes">ij</italic> </sub>), in-plane stiffness (<inline-formula> <tex-math><?CDATA $Y_{textrm{2D}}$?></tex-math> <mml:math overflow="scroll"><mml:msub><mml:mi>Y</mml:mi><mml:mrow><mml:mrow><mml:mtext>2D</mml:mtext></mml:mrow></mml:mrow></mml:msub></mml:math> <inline-graphic xlink:href="tdmad0f2bieqn1.gif" xlink:type="simple"></inline-graphic> </inline-formula>), Poisson’s ratio (<italic toggle="yes">ν</italic>), and ultimate tensile strain (UTS). Remarkably, the considered systems exhibit prominent mechanical features such as substantial in-plane stiffness and high UTS. The calculated electronic band structures reveal that both the <italic toggle="yes">1T</italic>- and <italic toggle="yes">1H</italic>-<italic toggle="yes">M</italic>Si<sub>2</sub>N<sub>4</sub> nanosheets are wide-band-gap semiconductors and their energy band gaps span from visible to ultraviolet region of the optical spectrum, suitable for high-performance nanoelectronic device applications. Lastly, the analysis of optical properties shows that the designed systems have isotropic optical spectra, and depending on the type of the system, robust absorption of ultraviolet and visible light (particularly in <italic toggle="yes">1H</italic>-PbSi<sub>2</sub>N<sub>4</sub> monolayer) is predicted. Our study not only introduces new members to the family of 2D <italic toggle="yes">MA</italic> <sub>2</sub> <italic toggle="yes">Z</italic> <sub>4</sub> crystals but also unveils their intriguing physical properties and s
{"title":"Two-dimensional MSi2N4 (M = Ge, Sn, and Pb) monolayers: promising new materials for optoelectronic applications","authors":"Mirali Jahangirzadeh Varjovi, Soheil Ershadrad, Biplab Sanyal, Sergio Tosoni","doi":"10.1088/2053-1583/ad0f2b","DOIUrl":"https://doi.org/10.1088/2053-1583/ad0f2b","url":null,"abstract":"The recent growth of two-dimensional (2D) layered crystals of MoSi<sub>2</sub>N<sub>4</sub> and WSi<sub>2</sub>N<sub>4</sub> has sparked significant interest due to their outstanding properties and potential applications. This development has paved the way for a new and large family of 2D materials with a general formula of <italic toggle=\"yes\">MA</italic>\u0000<sub>2</sub>\u0000<italic toggle=\"yes\">Z</italic>\u0000<sub>4</sub>. In this regard, motivated by this exciting family, we propose two structural phases (<italic toggle=\"yes\">1T</italic>- and <italic toggle=\"yes\">1H</italic>-) of <italic toggle=\"yes\">M</italic>Si<sub>2</sub>N<sub>4</sub> (<italic toggle=\"yes\">M</italic> = Ge, Sn, and Pb) monolayers and investigate their structural, vibrational, mechanical, electronic and optical properties by using first-principles methods. The two phases have similar cohesive energies, while the <italic toggle=\"yes\">1T</italic> structures are found to be more energetically favorable than their <italic toggle=\"yes\">1H</italic> counterparts. The analysis of phonon spectra and <italic toggle=\"yes\">ab initio</italic> molecular dynamics simulations indicate that all the suggested monolayers, except for <italic toggle=\"yes\">1H</italic>-GeSi<sub>2</sub>N<sub>4</sub>, are dynamically and thermally stable even at elevated temperatures. The elastic stability and mechanical properties of the proposed crystals are examined by calculating their elastic constants (<italic toggle=\"yes\">C</italic>\u0000<sub>\u0000<italic toggle=\"yes\">ij</italic>\u0000</sub>), in-plane stiffness (<inline-formula>\u0000<tex-math><?CDATA $Y_{textrm{2D}}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msub><mml:mi>Y</mml:mi><mml:mrow><mml:mrow><mml:mtext>2D</mml:mtext></mml:mrow></mml:mrow></mml:msub></mml:math>\u0000<inline-graphic xlink:href=\"tdmad0f2bieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>), Poisson’s ratio (<italic toggle=\"yes\">ν</italic>), and ultimate tensile strain (UTS). Remarkably, the considered systems exhibit prominent mechanical features such as substantial in-plane stiffness and high UTS. The calculated electronic band structures reveal that both the <italic toggle=\"yes\">1T</italic>- and <italic toggle=\"yes\">1H</italic>-<italic toggle=\"yes\">M</italic>Si<sub>2</sub>N<sub>4</sub> nanosheets are wide-band-gap semiconductors and their energy band gaps span from visible to ultraviolet region of the optical spectrum, suitable for high-performance nanoelectronic device applications. Lastly, the analysis of optical properties shows that the designed systems have isotropic optical spectra, and depending on the type of the system, robust absorption of ultraviolet and visible light (particularly in <italic toggle=\"yes\">1H</italic>-PbSi<sub>2</sub>N<sub>4</sub> monolayer) is predicted. Our study not only introduces new members to the family of 2D <italic toggle=\"yes\">MA</italic>\u0000<sub>2</sub>\u0000<italic toggle=\"yes\">Z</italic>\u0000<sub>4</sub> crystals but also unveils their intriguing physical properties and s","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"9 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138686727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-05DOI: 10.1088/2053-1583/ad0f2a
Victor Nuñez, Sergio Bravo, J D Correa, Leonor Chico, M Pacheco
We investigate a pentagonal monolayer of palladium diselenide, a stable two-dimensional system, as a material realization of a crystalline phase with nontrivial topological electronic properties. We find that its electronic structure involves an atomic obstructed insulator related to higher-order topology, which is a consequence of the selenium-selenium bond dimerization along with inversion and time-reversal symmetry). By means of first-principles calculations and the analysis of symmetry indicators and topological invariants, we also characterize the electronic corner states associated with the atomic obstruction and compute the corresponding corner charge for a finite geometry, which is found to be not quantized but still inversion-protected. Applying tensile strain to the finite geometry we verify the robustness of the corner states and also achieve a strain-controlled variation of the corner charge magnitude.
{"title":"Higher-order obstructed atomic insulator phase inpentagonal monolayer PdSe2","authors":"Victor Nuñez, Sergio Bravo, J D Correa, Leonor Chico, M Pacheco","doi":"10.1088/2053-1583/ad0f2a","DOIUrl":"https://doi.org/10.1088/2053-1583/ad0f2a","url":null,"abstract":"We investigate a pentagonal monolayer of palladium diselenide, a stable two-dimensional system, as a material realization of a crystalline phase with nontrivial topological electronic properties. We find that its electronic structure involves an atomic obstructed insulator related to higher-order topology, which is a consequence of the selenium-selenium bond dimerization along with inversion and time-reversal symmetry). By means of first-principles calculations and the analysis of symmetry indicators and topological invariants, we also characterize the electronic corner states associated with the atomic obstruction and compute the corresponding corner charge for a finite geometry, which is found to be not quantized but still inversion-protected. Applying tensile strain to the finite geometry we verify the robustness of the corner states and also achieve a strain-controlled variation of the corner charge magnitude.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"9 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138686648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-04DOI: 10.1088/2053-1583/ad0f2c
Rui Wang, Libo Du, Yang Liu, Yueliang Gu, Xiaolong Li, Yuehui Li
Photocatalytic reduction of carbon dioxide (CO2) has been expected to be an effective way to reduce carbon emissions. Designing photocatalytic materials with long-term effectiveness is the key of photocatalytic technology. In this work, CoO nanoparticles loaded on the surface of reduced graphene oxide (rGO) membranes on silicon substrate were in-situ fabricated by one-step method. The resulting materials can convert CO2 into carbon monoxide (CO) up to 70 h at a steady rate of ∼185 ± 30 µmol g−1 h−1 with a selectivity of nearly 100%. This material system contained rich oxygen vacancies and generated new oxygen vacancies during the photocatalytic process. Oxygen vacancies mediate the interactions with excitons: (i) promoting the dissociation of free excitons; (ii) leading to form bound excitons under the coupling effect with phonons, inhibiting the recombination of photogenerated electrons and holes as well as enhancing the long-term effectiveness of photocatalytic CO2 reduction. We hope this work can provide valuable insights for the design and optimization of photocatalytic materials.
{"title":"Oxygen vacancy in CoO/reduced graphene oxide composite for enhancing long-term effectiveness of photocatalytic CO2 reduction via mediating exciton","authors":"Rui Wang, Libo Du, Yang Liu, Yueliang Gu, Xiaolong Li, Yuehui Li","doi":"10.1088/2053-1583/ad0f2c","DOIUrl":"https://doi.org/10.1088/2053-1583/ad0f2c","url":null,"abstract":"Photocatalytic reduction of carbon dioxide (CO<sub>2</sub>) has been expected to be an effective way to reduce carbon emissions. Designing photocatalytic materials with long-term effectiveness is the key of photocatalytic technology. In this work, CoO nanoparticles loaded on the surface of reduced graphene oxide (rGO) membranes on silicon substrate were <italic toggle=\"yes\">in-situ</italic> fabricated by one-step method. The resulting materials can convert CO<sub>2</sub> into carbon monoxide (CO) up to 70 h at a steady rate of ∼185 ± 30 <italic toggle=\"yes\">µ</italic>mol g<sup>−1</sup> h<sup>−1</sup> with a selectivity of nearly 100%. This material system contained rich oxygen vacancies and generated new oxygen vacancies during the photocatalytic process. Oxygen vacancies mediate the interactions with excitons: (i) promoting the dissociation of free excitons; (ii) leading to form bound excitons under the coupling effect with phonons, inhibiting the recombination of photogenerated electrons and holes as well as enhancing the long-term effectiveness of photocatalytic CO<sub>2</sub> reduction. We hope this work can provide valuable insights for the design and optimization of photocatalytic materials.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"197 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138686725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-30DOI: 10.1088/2053-1583/ad0f29
Xuzhou Sun, Ke Yang, Yuqiang Fang, Hua Wu, Fuqiang Huang
Layered ferromagnetic (FM) materials are significant for nano-spintronic devices, however, low transition temperature and air instability remain major challenges for layered FM compounds. Herein, we have synthesized layered crystals CrIr2Sn10 with FM transition below 315 K. The ratio of the magnetization between in-plane and out-of-plane is 41. Moreover, the magnetism of CrIr2Sn10 is derived from the highly spin-polarized Cr atoms. CrIr2Sn10 will be a promising platform for 2D magnetism and spintronic devices.
层状铁磁（FM）材料对纳米自旋电子器件具有重要意义，然而，低转变温度和空气不稳定性仍然是层状 FM 化合物面临的主要挑战。在此，我们合成了层状晶体 CrIr2Sn10，其调频转变温度低于 315 K。此外，CrIr2Sn10 的磁性来自高度自旋极化的铬原子。CrIr2Sn10 将成为二维磁性和自旋电子器件的一个前景广阔的平台。
{"title":"Above-room-temperature ferromagnetism in a layered CrIr2Sn10 crystal","authors":"Xuzhou Sun, Ke Yang, Yuqiang Fang, Hua Wu, Fuqiang Huang","doi":"10.1088/2053-1583/ad0f29","DOIUrl":"https://doi.org/10.1088/2053-1583/ad0f29","url":null,"abstract":"Layered ferromagnetic (FM) materials are significant for nano-spintronic devices, however, low transition temperature and air instability remain major challenges for layered FM compounds. Herein, we have synthesized layered crystals CrIr<sub>2</sub>Sn<sub>10</sub> with FM transition below 315 K. The ratio of the magnetization between in-plane and out-of-plane is 41. Moreover, the magnetism of CrIr<sub>2</sub>Sn<sub>10</sub> is derived from the highly spin-polarized Cr atoms. CrIr<sub>2</sub>Sn<sub>10</sub> will be a promising platform for 2D magnetism and spintronic devices.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"7 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138686643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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