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SUMMARY: Data integration workflows for multiomics data take many forms across academia and industry. Efforts with limited resources often encountered in academia can easily fall short of data integration best practices for processing and combining high-content imaging, proteomics, metabolomics, and other omics data. We present Phenonaut, a Python software package designed to address the data workflow needs of migration, control, integration, and auditability in the application of literature and proprietary techniques for data source and structure agnostic workflow creation. AVAILABILITY AND IMPLEMENTATION: Source code: https://github.com/CarragherLab/phenonaut, Documentation: https://carragherlab.github.io/phenonaut, PyPI package: https://pypi.org/project/phenonaut/.
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Metabolómica , Multiómica , Proteómica , Programas Informáticos , Flujo de TrabajoRESUMEN
Conducting heterostructures have emerged as a promising strategy to enhance physical properties and unlock the potential application of such materials. Herein, we conduct and investigate the electronic and transport properties of the BSe/Sc2CF2 heterostructure using first-principles calculations. The BSe/Sc2CF2 heterostructure is structurally and thermodynamically stable, indicating that it can be feasible for further experiments. The BSe/Sc2CF2 heterostructure exhibits a semiconducting behavior with an indirect band gap and possesses type-II band alignment. This unique alignment promotes efficient charge separation, making it highly promising for device applications, including solar cells and photodetectors. Furthermore, type-II band alignment in the BSe/Sc2CF2 heterostructure leads to a reduced band gap compared to the individual BSe and Sc2CF2 monolayers, leading to enhanced charge carrier mobility and light absorption. Additionally, the generation of the BSe/Sc2CF2 heterostructure enhances the transport properties of the BSe and Sc2CF2 monolayers. The electric fields and strains can modify the electronic properties, thus expanding the potential application possibilities. Both the electric fields and strains can tune the band gap and lead to the type-II to type-I conversion in the BSe/Sc2CF2 heterostructure. These findings shed light on the versatile nature of the BSe/Sc2CF2 heterostructure and its potential for advanced nanoelectronic and optoelectronic devices.
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van der Waals heterostructures provide a powerful platform for engineering the electronic properties and for exploring exotic physical phenomena of two-dimensional materials. Here, we construct a graphene/BSe heterostructure and examine its electronic characteristics and the tunability of contact types under electric fields. Our results reveal that the graphene/BSe heterostructure is energetically, mechanically, and thermodynamically stable at room temperature. It forms a p-type Schottky contact and exhibits a high carrier mobility, making it a promising candidate for future Schottky field-effect transistors. Furthermore, applying an electric field not only reduces contact barriers but also induces a transition from a p-type to an n-type Schottky contact and from a Schottky to an ohmic contact, offering further potential for the control and manipulation of the heterostructure's electronic properties. Our findings offer a rational basis for the design of energy-efficient and tunable heterostructure devices based on the graphene/BSe heterostructure.
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In this study, we construct new 2D Janus MGeSN2 (M = Ti, Zr, and Hf) monolayers and systematically investigate their electronic band structures under applied biaxial strain. Their crystal lattice and electronic as well as transport properties are also examined based on the first-principles calculations and deformation potential theory. The results show that the MGeSN2 structures have good dynamical and thermal stability, and their elastic constants satisfy the criteria of Born-Huang also indicating the good mechanical stability of these materials for experimental synthesis. Our calculated results indicate that the TiGeSN2 monolayer exhibits indirect-bandgap semiconductor characteristics whereas the ZrGeSN2 and HfGeSN2 monolayers exhibit direct-bandgap semiconductor characteristics. Importantly, the biaxial strain shows significant influences on the electronic energy band structures of the monolayers in the presence of a phase transition from semiconductor to metal, which is an important feature of these materials for their application in electronic devices. All three structures exhibit anisotropic carrier mobility in both x and y transport directions, suggesting their great potential for application in electronic devices.
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Novel Janus materials have attracted broad interest due to the outstanding properties created by their out-of-plane asymmetry, with increasing theoretical exploration and more reports of successful fabrication in recent years. Here, we construct and explore the crystal structures, stabilities, electronic band structures, and transport properties - including carrier mobilities - of two-dimensional Janus MGeSiP4 (M = Ti, Zr, or Hf) monolayers based on density functional theory calculations. From the cohesive energies, elastic constants, and phonon dispersion calculations, the monolayers are confirmed to exhibit structural stability with high feasibility for experimental synthesis. All the structures are indirect band-gap semiconductors with calculated band-gap energies in the range of 0.77 eV to 1.01 eV at the HSE06 (Heyd-Scuseria-Ernzerhof) level. Interestingly, by applying external biaxial strain, a semiconductor to metal phase transition is observed for the three Janus structures. This suggests potential for promising applications in optoelectronic and electromechanical devices. Notably, the MGeSiP4 monolayers show directionally anisotropic carrier mobility with a high electron mobility of up to 2.72 × 103 cm2 V-1 s-1 for the ZrGeSiP4 monolayer, indicating advantages for applications in electronic devices. Hence, the presented results reveal the novel properties of the 2D Janus MGeSiP4 monolayers and demonstrate their great potential applications in nanoelectronic and/or optoelectronic devices. This investigation could stimulate further theoretical and experimental studies on these excellent materials and motivate further explorations of new members of this 2D Janus family.
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Stacking different two-dimensional materials to generate a vertical heterostructure has been considered a promising way to obtain the desired properties and improve device performance. Here, in this work, using first principles calculations, we design a vertical heterostructure by stacking graphene (GR) and silicane (SiH) and investigate the electronic properties and electrical contact in the GR/SiH heterostructure as well as the possibility of tuning these properties under an external electric field and vertical strain. The GR/SiH heterostructure is structurally and mechanically stable at the equilibrium interlayer separation. The GR/SiH heterostructure exhibits a p-type Schottky contact with a small Schottky barrier of 0.43 eV, presenting great tunability of the electrical contact from Schottky to Ohmic contact under different conditions. The external electric field not only leads to a transition from the p-type to n-type Schottky contact but also induces a transformation from a Schottky contact to Ohmic one. Furthermore, changing the interlayer separation can be considered a useful tool to regulate the Schottky barriers and electric contact in the GR/SiH heterostructure, which is prominent for constructing electronic devices. Our findings could provide an effective tool for the design of high-performance nanoelectronic devices based on the GR/SiH heterostructure.
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The C57BL/6.NOD-Aec1Aec2 mouse has been extensively studied to define the underlying cellular and molecular basis for the onset and development of Sjögren's syndrome (SS), a human systemic autoimmune disease characterized clinically as the loss of normal lacrimal and salivary gland functions leading respectively to dry eye and dry mouth pathologies. While an overwhelming majority of SS studies in both humans and rodent models have long focused primarily on pathophysiological events and the potential role of T lymphocytes in these events, recent studies in our murine models have indicated that marginal zone B (MZB) lymphocytes are critical for both development and onset of SS disease. Although migration and function of MZB cells are difficult to study in vivo and in vitro, we have carried out ex vivo investigations that use temporal global RNA transcriptomic analyses to track early cellular and molecular events in these exocrine glands of C57BL/6.NOD-Aec1Aec2 mice. In the present report, genome-wide transcriptome analyses of lacrimal glands indicate that genes and gene-sets temporally upregulated during early onset of disease define the Notch2/NF-kß14 and Type1 interferon signal transduction pathways, as well as identify chemokines, especially Cxcl13, and Rho-GTPases, including DOCK molecules, in the cellular migration of immune cells to the lacrimal glands. We discuss how the current results compare with our recently published salivary gland data obtained from similar studies carried out in our C57BL/6.NOD-Aec1Aec2 mice, pointing out both similarities and differences in the etiopathogeneses underlying the autoimmune response within the two glands. Overall, this study uses the power of transcriptomic analyses to identify temporal molecular bioprocesses activated during the preclinical covert pathogenic stage(s) of SS disease and how these findings may impact future intervention therapies as the disease within the two exocrine glands may not be identical.
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Aparato Lagrimal , Síndrome de Sjögren , Animales , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades/metabolismo , Perfilación de la Expresión Génica/métodos , Aparato Lagrimal/patología , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , ARN/metabolismo , TranscriptomaRESUMEN
The C57BL/6.NOD-Aec1Aec2 mouse model has been extensively studied to define the underlying cellular and molecular bioprocesses critical in the onset of primary Sjögren's Syndrome (pSS), a human systemic autoimmune disease characterized clinically as the loss of lacrimal and salivary gland functions leading to dry eye and dry mouth pathologies. This mouse model, together with several gene knockout mouse models of SS, has indicated that B lymphocytes, especially marginal zone B (MZB) cells, are necessary for development and onset of clinical manifestations despite the fact that destruction of the lacrimal and salivary gland cells involves a classical T cell-mediated autoimmune response. Because migrations and functions of MZB cells are difficult to study in vivo, we have carried out ex vivo investigations that use temporal global RNA transcriptomic analyses to profile autoimmunity as it develops within the salivary glands of C57BL/6.NOD-Aec1Aec2 mice. Temporal profiles indicate the appearance of Notch2-positive cells within the salivary glands of these SS-susceptible mice concomitant with the early-phase appearance of lymphocytic foci (LF). Data presented here identify cellular bioprocesses occurring during early immune cell migrations into the salivary glands and suggest MZB cells are recruited to the exocrine glands by the upregulated Cxcl13 chemokine where they recognize complement (C')-decorated antigens via their sphingosine-1-phosphate (S1P) and B cell (BC) receptors. Based on known MZB cell behavior and mobility, we propose that MZB cells activated in the salivary glands migrate to splenic follicular zones to present antigens to follicular macrophages and dendritic cells that, in turn, promote a subsequent systemic cell-mediated and autoantibody-mediated autoimmune T cell response that targets exocrine gland cells and functions. Overall, this study uses the power of transcriptomic analyses to provide greater insight into several molecular events defining cellular bioprocesses underlying SS that can be modelled and more thoroughly studied at the cellular level.
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Linfocitos B/inmunología , Glándulas Salivales/inmunología , Síndrome de Sjögren/genética , Síndrome de Sjögren/inmunología , Transcriptoma , Animales , Autoanticuerpos/inmunología , Movimiento Celular/inmunología , Quimiocina CXCL13/metabolismo , Modelos Animales de Enfermedad , Perfilación de la Expresión Génica , Lisofosfolípidos/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , Receptor Notch2/metabolismo , Receptores de Antígenos de Linfocitos B/metabolismo , Síndrome de Sjögren/metabolismo , Esfingosina/análogos & derivados , Esfingosina/metabolismo , Receptores de Esfingosina-1-Fosfato/metabolismo , Linfocitos T/inmunologíaRESUMEN
The C57BL/6.NOD-Aec1Aec2 mouse is considered a highly appropriate model of Sjögren's Syndrome (SS), a human systemic autoimmune disease characterized primarily as the loss of lacrimal and salivary gland functions. This mouse model, as well as other mouse models of SS, have shown that B lymphocytes are essential for the development and onset of observed clinical manifestations. More recently, studies carried out in the C57BL/6.IL14α transgenic mouse have indicated that the marginal zone B (MZB) cell population is responsible for development of SS disease, reflecting recent observations that MZB cells are present in the salivary glands of SS patients and most likely initiate the subsequent loss of exocrine functions. Although MZB cells are difficult to study in vivo and in vitro, we have carried out an ex vivo investigation that uses temporal global RNA transcriptomic analyses to profile differentially expressed genes known to be associated with cell migration. Results indicate a temporal upregulation of specific chemokine, chemokine receptor, and Rho-GTPase genes in the salivary glands of C57BL/6.NOD-Aec1Aec2 mice that correlate with the early appearance of periductal lymphocyte infiltrations. Using the power of transcriptomic analyses to better define the genetic profile of lymphocytic emigration into the salivary glands of SS mice, new insights into the underlying mechanisms of SS disease development and onset begin to come into focus, thereby establishing a foundation for further in-depth and novel investigations of the covert and early overt phases of SS disease at the cellular level.
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Glándulas Salivales/inmunología , Síndrome de Sjögren/inmunología , Proteínas de Unión al GTP rho/metabolismo , Animales , Movimiento Celular , Quimiocinas/metabolismo , Linfocitos/fisiología , Ratones Endogámicos C57BL , Ratones Transgénicos , Transducción de Señal , Síndrome de Sjögren/enzimología , Transcriptoma , Proteínas de Unión al GTP rho/genéticaRESUMEN
Sjögren's syndrome (SjS) is a chronic autoimmune disease primarily involving the exocrine glands in which the involvement of the innate immune system is largely uncharacterized. Mer signaling has been found to be protective in several autoimmune diseases but remains unstudied in SjS. Here, we investigated the role of Mer signaling in SjS. Mer knockout (MerKO) mice were examined for SjS disease criteria. SjS-susceptible (SjSS) C57BL/6.NOD-Aec1Aec2 mice were assessed for defective Mer signaling outcomes, soluble Mer (sMer) levels, A disintegrin and metalloprotease 17 (ADAM17) activity, and Rac1 activation. In addition, SjS patient plasma samples were evaluated for sMer levels via ELISA, and sMer levels were correlated to disease manifestations. MerKO mice developed submandibular gland (SMG) lymphocytic infiltrates, SMG apoptotic cells, anti-nuclear autoantibodies (ANA), and reduced saliva flow. Mer signaling outcomes were observed to be diminished in SjSS mice, as evidenced by reduced Rac1 activation in SjSS mice macrophages in response to apoptotic cells and impaired efferocytosis. Increased sMer was also detected in SjSS mouse sera, coinciding with higher ADAM17 activity, the enzyme responsible for cleavage and inactivation of Mer. sMer levels were elevated in patient plasma and positively correlated with focus scores, ocular staining scores, rheumatoid factors, and anti-Ro60 levels. Our data indicate that Mer plays a protective role in SjS, similar to other autoimmune diseases. Furthermore, we suggest a series of events where enhanced ADAM17 activity increases Mer inactivation and depresses Mer signaling, thus removing protection against the loss of self-tolerance and the onset of autoimmune disease in SjSS mice.
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Regulación Enzimológica de la Expresión Génica , Síndrome de Sjögren/inmunología , Síndrome de Sjögren/metabolismo , Tirosina Quinasa c-Mer/genética , Proteína ADAM17/metabolismo , Animales , Anticuerpos Antinucleares/química , Apoptosis , Autoanticuerpos/metabolismo , Autoinmunidad , Modelos Animales de Enfermedad , Femenino , Humanos , Macrófagos/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , Ratones Noqueados , Fenotipo , Saliva/metabolismo , Transducción de Señal , Timocitos/metabolismoRESUMEN
T cells recognize peptides bound to major histocompatibility complex (MHC) class I and class II molecules at the cell surface. This recognition is accomplished by the expression of T cell receptors (TCR) which are required to be diverse and adaptable in order to accommodate the various and vast number of antigens presented on the MHCs. Thus, determining TCR repertoires of effector T cells is necessary to understand the immunological process in responding to cancer progression, infection, and autoimmune development. Furthermore, understanding the TCR repertoires will provide a solid framework to predict and test the antigen which is more critical in autoimmunity. However, it has been a technical challenge to sequence the TCRs and provide a conceptual context in correlation to the vast number of TCR repertoires in the immunological system. The exploding field of single-cell sequencing has changed how the repertoires are being investigated and analyzed. In this review, we focus on the biology of TCRs, TCR signaling and its implication in autoimmunity. We discuss important methods in bulk sequencing of many cells. Lastly, we explore the most pertinent platforms in single-cell sequencing and its application in autoimmunity.
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Receptores de Antígenos de Linfocitos T/genética , Análisis de Secuencia , Análisis de la Célula Individual , Animales , Autoinmunidad/inmunología , Antígenos de Histocompatibilidad Clase I/inmunología , Humanos , Receptores de Antígenos de Linfocitos T/inmunología , Linfocitos T/inmunología , Linfocitos T/metabolismoRESUMEN
Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease that is estimated to affect 35 million people worldwide. Currently, no effective treatments exist for Sjögren's syndrome, and there is a limited understanding of the physiological mechanisms associated with xerostomia and hyposalivation. The present work revealed that aquaporin 5 expression, a water channel critical for salivary gland fluid secretion, is regulated by bone morphogenetic protein 6. Increased expression of this cytokine is strongly associated with the most common symptom of primary Sjögren's syndrome, the loss of salivary gland function. This finding led us to develop a therapy in the treatment of Sjögren's syndrome by increasing the water permeability of the gland to restore saliva flow. Our study demonstrates that the targeted increase of gland permeability not only resulted in the restoration of secretory gland function but also resolved the hallmark salivary gland inflammation and systemic inflammation associated with disease. Secretory function also increased in the lacrimal gland, suggesting this local therapy could treat the systemic symptoms associated with primary Sjögren's syndrome.
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Acuaporina 1/genética , Acuaporina 5/genética , Terapia Genética , Síndrome de Sjögren/terapia , Adulto , Anciano , Animales , Acuaporina 5/metabolismo , Proteína Morfogenética Ósea 6/genética , Proteína Morfogenética Ósea 6/metabolismo , Línea Celular , Permeabilidad de la Membrana Celular , Regulación hacia Abajo , Femenino , Silenciador del Gen , Humanos , Aparato Lagrimal/metabolismo , Masculino , Ratones Endogámicos C57BL , Ratones Endogámicos NOD , Persona de Mediana Edad , Glándulas Salivales/metabolismo , Síndrome de Sjögren/genética , Agua/metabolismo , Adulto JovenRESUMEN
Primary Sjögren's syndrome (pSS) is an autoimmune disease in which the underlying cause has yet to be elucidated. The main objective of this study was to determine the T cell receptor (TCR) repertoires of individual infiltrating T helper (Th)-1 and 17 cells of pSS patients using single-cell analysis. Single-cell analysis of ex-vivo infiltrating T cells demonstrated that pSS patients had higher frequencies of activated Th17 cells. Single-cell TCR sequencing revealed that TCRß variable (TRBV)3-1/joint (J)1-2 (CLFLSMSACVW) and TRBV20-1/J1-1 (SVGSTAIPP*T) were expressed by activated Th1 and Th17 cells in both cohorts. Uniquely, TCRα variable (TRAV)8-2/J5 (VVSDTVLETAGE) was expressed by Th1 cells present only in patients and complementarity-determining region (CDR)3α-specific motif (LSTD*E) present in both Th1/Th17 cells. The study demonstrates that both activated Th1 and Th17 cells of pSS patients showed restricted clonal diversities of which two CDR3 motifs were present in controls and patients, with another two motifs unique to pSS.
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Análisis de la Célula Individual/métodos , Síndrome de Sjögren/inmunología , Células TH1/inmunología , Células Th17/inmunología , Adulto , Anciano , Secuencias de Aminoácidos/genética , Secuencias de Aminoácidos/inmunología , Secuencia de Aminoácidos , Estudios de Cohortes , Femenino , Humanos , Activación de Linfocitos/genética , Activación de Linfocitos/inmunología , Masculino , Persona de Mediana Edad , Receptores de Antígenos de Linfocitos T/genética , Receptores de Antígenos de Linfocitos T/inmunología , Receptores de Antígenos de Linfocitos T/metabolismo , Síndrome de Sjögren/genética , Síndrome de Sjögren/metabolismo , Células TH1/metabolismo , Células Th17/metabolismoRESUMEN
Since the discovery of mouse hybridoma technology by Kohler and Milstein in 1975, significant progress has been made in monoclonal antibody production. Advances in B cell immortalization and phage display technologies have generated a myriad of valuable monoclonal antibodies for diagnosis and treatment. Technological breakthroughs in various fields of 'omics have shed crucial insights into cellular heterogeneity of a biological system in which the functional individuality of a single cell must be considered. Based on this important concept, remarkable discoveries in single-cell analysis have made in identifying and isolating functional B cells that produce beneficial therapeutic monoclonal antibodies. In this review, we will discuss three traditional methods of antibody discovery. Recent technological platforms for single-cell antibody discovery will be reviewed. We will discuss the application of the single-cell analysis in finding therapeutic antibodies for human immunodeficiency virus and emerging Zika arbovirus.
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Anticuerpos Monoclonales/uso terapéutico , Enfermedades Transmisibles/tratamiento farmacológico , Infecciones por VIH/tratamiento farmacológico , Análisis de la Célula Individual/métodos , Infección por el Virus Zika/tratamiento farmacológico , Animales , Descubrimiento de Drogas , VIH/genética , VIH/fisiología , Humanos , Virus Zika/genética , Virus Zika/fisiología , Infección por el Virus Zika/virologíaRESUMEN
For decades, Sjögren's syndrome (SS) and Sjögren's syndrome-like (SS-like) disease in patients and mouse models, respectively, have been intensely investigated in attempts to identify the underlying etiologies, the pathophysiological changes defining disease phenotypes, the nature of the autoimmune responses, and the propensity for developing B cell lymphomas. An emerging question is whether the generation of a multitude of mouse models and the data obtained from their studies is actually important to the understanding of the human disease and potential interventional therapies. In this brief report, we comment on how and why mouse models can stimulate interest in specific lines of research that apparently parallel aspects of human SS. Focusing on two mouse models, NOD and B6·Il14α, we present the possible relevance of mouse models to human SS, highlighting a few selected disease-associated biological processes that have baffled both SS and SS-like investigations for decades.
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Modelos Animales de Enfermedad , Ratones , Síndrome de Sjögren/inmunología , Animales , Autoinmunidad/genética , Autoinmunidad/inmunología , Humanos , Interferones/genética , Interferones/inmunología , Linfoma de Células B/genética , Linfoma de Células B/inmunología , Ratones Transgénicos , Virus ARN/genética , Virus ARN/inmunología , ARN Bicatenario , Síndrome de Sjögren/genética , TranscriptomaRESUMEN
Minimizing the contact barriers at the interface, forming between two different two-dimensional metals and semiconductors, is essential for designing high-performance optoelectronic devices. In this work, we design different types of metal-semiconductor heterostructures by combining 2D metallic MX2 (M = Nb, Hf; X = S, Se) and 2D semiconductor SiH and investigate systematically their electronic properties and contact characteristics using first principles calculations. We find that all the MX2/SiH (M = Nb, Ta; X = S, Se) heterostructures are energetically stable, suggesting that they could potentially be synthesized in the future. Furthermore, the generation of the MX2/SiH metal-semiconductor heterostructures leads to the formation of the Schottky contact with ultra-low Schottky barriers of a few tens of meV. This finding suggests that all the 2D MX2 (M = Nb, Ta; X = S, Se) metals act as effective electrical contact 2D materials to contact with the SiH semiconductor, enabling electronic devices with high charge injection efficiency. Furthermore, the tunneling resistivity of all the MX2/SiH (M = Nb, Ta; X = S, Se) MSHs is low, confirming that they exhibit high electron injection efficiency. Our findings underscore fundamental insights for the design of high-performance multifunctional Schottky devices based on the metal-semiconductor MX2/SiH heterostructures with ultra-low contact barriers and high electron injection efficiency.
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A significant problem in the area of rechargeable alkali ion battery technologies is the exploration of anode materials with overall high specific capacities and superior physical properties. By using first-principles calculations, we have determined that monolayer TiSi2N4 is precisely such a potential anode candidate. Its demonstrated dynamic, thermal, mechanical, and energetic stabilities make it feasible for experimental realization. An important benefit of the electrode conductivity is that the electronic structure reveals that the pristine system experiences a change from a semiconductor to a metal throughout the entire alkali adsorption process. What's more interesting is that monolayer TiSi2N4 can support up to double-sided 3-layer ad-atoms, resulting in extremely high theoretical capacities for Li, Na, Mg, and K of 1004, 854, 492 and 531 mA h g-1 and low average open-circuit voltages of 0.55, 0.25, 0.55, and -1.3 V, respectively. Alkali diffusion on the surface has been demonstrated to occur extremely quickly, with migration energy barriers for Li, Na, Mg, and K as low as 0.25, 0.14, 0.10, and 0.07 eV, respectively. The results reveal that the migration barrier energy is the lowest for Li and Mg from path-2 and Na and K from path-1. Overall, these findings suggest that monolayer TiSi2N4 is a suitable anode candidate for use in high-performance and low-cost metal-ion batteries.
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The auxetic materials have exotic mechanical properties compared to conventional materials, such as higher indentation resistance, more superior sound absorption performance. Although the auxetic behavior has also been observed in two-dimensional (2D) nanomaterials, to date there has not been much research on auxetic materials in the vertical asymmetric Janus 2D layered structures. In this paper, we explore the mechanical, electronic, and transport characteristics of Janus Si2OX (X = S, Se, Te) monolayers by first-principle calculations. Except for the Si2OTe monolayer, both Si2OS and Si2OSe are found to be stable. Most importantly, both Si2OS and Si2OSe monolayers are predicted to be auxetic semiconductors with a large negative Poisson's ratio. The auxetic behavior is clearly observed in the Janus Si2OS monolayer with an extremely large negative Poisson's ratio of -0.234 in the x axis. At the equilibrium state, both Si2OS and Si2OSe materials exhibit indirect semiconducting characteristics and their band gaps can be easily altered by the mechanical strain. More interestingly, the indirect-direct bandgap phase transitions are observed in both Si2OS and Si2OSe monolayers when the biaxial strains are introduced. Further, the studied Janus structures also exhibit remarkably high electron mobility, particularly along the x direction. Our findings demonstrate that Si2OS and Si2OSe monolayers are new auxetic materials with asymmetric structures and show their great promise in electronic and nanomechanical applications.
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The emergence of van der Waals (vdW) heterostructures, which consist of vertically stacked two-dimensional (2D) materials held together by weak vdW interactions, has introduced an innovative avenue for tailoring nanoelectronic devices. In this study, we have theoretically designed a metal/semiconductor heterostructure composed of NbS2 and Janus MoSSe, and conducted a thorough investigation of its electronic properties and the formation of contact barriers through first-principles calculations. The effects of stacking configurations and the influence of external electric fields in enhancing the tunability of the NbS2/Janus MoSSe heterostructure are also explored. Our findings demonstrate that the NbS2/MoSSe heterostructure is not only structurally and thermally stable but also exfoliable, making it a promising candidate for experimental realization. In its ground state, this heterostructure exhibits p-type Schottky contacts characterized by small Schottky barriers and low tunneling barrier resistance, showing its considerable potential for utilization in electronic devices. Additionally, our findings reveal that the electronic properties, contact barriers and contact types of the NbS2/MoSSe heterostructure can be tuned by applying electric fields. A negative electric field leads to a conversion from a p-type Schottky contact to an n-type Schottky contact, whereas a positive electric field gives rise to a transformation from a Schottky into an ohmic contact. These insights offer valuable theoretical guidance for the practical utilization of the NbS2/MoSSe heterostructure in the development of next-generation electronic and optoelectronic devices.
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Two-dimensional (2D) van der Waals (vdW) heterostructures are considered as promising candidates for realizing multifunctional applications, including photodetectors, field effect transistors and solar cells. In this work, we performed first-principles calculations to design a 2D vdW MoTe2/MoS2 heterostructure and investigate its electronic properties, contact types and the impact of an electric field and in-plane biaxial strain. We find that the MoTe2/MoS2 heterostructure is predicted to be structurally, thermally and mechanically stable. It is obvious that the weak vdW interactions are mainly dominated at the interface of the MoTe2/MoS2 heterostructure and thus it can be synthesized in recent experiments by the transfer method or chemical vapor deposition. The construction of the vdW MoTe2/MoS2 heterostructure forms a staggered type II band alignment, effectively separating the electrons and holes at the interface and thereby extending the carrier lifetime. Interestingly, the electronic properties and contact types of the type II vdW MoTe2/MoS2 heterostructure can be tailored under the application of external conditions, including an electric field and in-plane biaxial strain. The semiconductor-semimetal-metal transition and type II-type I conversion can be achieved in the vdW MoTe2/MoS2 heterostructure. Our findings underscore the potential of the vdW MoTe2/MoS2 heterostructure for the design and fabrication of multifunctional applications, including electronics and optoelectronics.