4 research outputs found

    Vacuum gauge from ultrathin MoS2 transistor

    Full text link
    We fabricate monolayer MoS2 field effect transistors and study their electric characteristics from 10^-6 Torr to atmospheric air pressure. We show that the threshold voltage of the transistor increases with the growing pressure. Hence, we propose the device as an air pressure sensor, showing that it is particularly suitable as a low power consumption vacuum gauge. The device functions on pressure-dependent O2, N2 and H2O molecule adsorption that affect the n-doping of the MoS2 channel.Comment: 10 pages, 4 figure - conference pape

    Functionalization of two-dimensional transition metal oxides for the sensing applications

    Get PDF

    Hybrid heterostructures and materials based on transition metal dichalcogenides

    Get PDF
    La irrupci贸n de los nanomateriales en la vida moderna es un claro indicador del avance cient铆fico. El dise帽o de materiales a la carta permite establecer un control preciso sobre las propiedades finales de estos. El objetivo principal que ha motivado la presente Tesis es la combinaci贸n y funcionalizaci贸n de l谩minas de MoS2 ultrafinas qu铆micamente exfoliadas (ce-MoS2) con diferentes sistemas de base molecular. La Tesis se divide en los siguientes Cap铆tulos: Cap铆tulo I: En primer lugar, se introducen brevemente los nanomateriales. En segundo lugar, se describen los materiales bidimensionales (2D). A continuaci贸n, se detallan algunos aspectos generales de los dicalcogenuros de metales de transici贸n (TMDCs). Luego, la atenci贸n se dirige al MoS2, el TMDC m谩s estudiado. En este bloque, se ofrece informaci贸n detallada sobre los politipos m谩s conocidos, los principales m茅todos de exfoliaci贸n y la preparaci贸n de materiales de tipo composite (composite) basados en l谩minas de MoS2. Finalmente, se profundiza en la funcionalizaci贸n del MoS2. Cap铆tulo II: Se centra en la preparaci贸n de un composite a partir de la combinaci贸n de l谩minas de ce-MoS2 con precursores de azul de Prusia (PB). La estrategia sint茅tica se basa en el doble rol del ce-MoS2 (como agente reductor y plataforma 2D de nucleaci贸n). Se demuestra que las l谩minas de MoS2 se oxidan completamente como consecuencia de su funcionalizaci贸n con el PB. El composite resultante exhibe un excelente rendimiento como material cat贸dico en bater铆as de iones sodio y potasio (SIBs and KIBs, respectivamente). Finalmente, se explica c贸mo reducir el contenido de 贸xido en el composite final. Cap铆tulo III: Se basa en la preparaci贸n de un nuevo composite a partir de la combinaci贸n de ce MoS2 y cubo molecular diamagn茅tico de Fe y Co. Como consecuencia de la transferencia electr贸nica del ce-MoS2 al cubo diamagn茅tico de partida, el sistema diamagn茅tico se transforma en un compuesto paramagn茅tico. Cap铆tulo IV: Tiene por objetivo la funcionalizaci贸n covalente de ce-MoS2 con un sistema fotocr贸mico (derivado de ditienileteno) tanto en su forma abierta como en la cerrada. Los resultados obtenidos mediante diferentes t茅cnicas de caracterizaci贸n confirman la formaci贸n de nuevos enlaces covalentes (C-S) entre los dos componentes. Adem谩s, parece que la fotoluminiscencia (PL) inherente al sistema fotocr贸mico decae despu茅s de la funcionalizaci贸n, indicando una posible transferencia de carga entre el material 2D y el derivado de ditienileteno. Cap铆tulo V: Trata sobre la formaci贸n de heterostructuras de WS2/MoS2. El m茅todo que se propone consta de 2 partes: i) funcionalizaci贸n de ce-MoS2 con un cl煤ster de tungsteno a trav茅s de interacciones electrost谩ticas, ii) tratamiento t茅rmico del composite resultante a fin de inducir la formaci贸n de nanodominos de WS2 sobre las l谩minas de MoS2. Esta estrategia sint茅tica combina las ventajas de un m茅todo en disoluci贸n (sencillez, escalabilidad y bajo coste) con la formaci贸n de interfases de alta calidad. Adem谩s, como consecuencia del fuerte acoplamiento entre ambos dicalcogenuros, se observa una atenuaci贸n de la PL correspondiente a la heterostructura. Cap铆tulo VI: Recoge las conclusiones principales de la Tesis.The outbreak of nanomaterials is a clear sensor of the scientific advance. The design of nano-sized materials at will permits to tailor the fascinating novel properties resulting from a drastic reduction in dimensionality. In this vein, we have done our particular contribution to the field of the so-called 2D materials. The main goal that has motivated the development of this Thesis is the functionalization and combination of ultrathin MoS2 flakes obtained by chemical exfoliation (abbreviated as ce-MoS2 flakes) with different molecular-based systems. This Thesis is divided into the following blocks: Chapter I: It begins with a brief introduction to nanomaterials. After that, two-dimensional (2D) materials are succinctly described. Subsequently, the family of layered transition metal dichalcogenides (TMDCs) is presented. Next, the focus turns to MoS2, the most studied layered TMDC. In this latter section, we can find detailed information about the most common polytypes, dry and wet exfoliation methods, and composites based on MoS2 layers. Finally, the molecular functionalization of MoS2 is described. Chapter II: It is focused on the preparation of a new MoS2-based composite by combining ce MoS2 flakes and Prussian blue (PB) precursors. The synthetic strategy here described takes profit from negative-charged MoS2 flakes as both reducing agent and 2D platform for the PB nucleation. We show that MoS2 layers are fully oxidized after functionalization. Interestingly, the resultant composite exhibits an excellent performance as cathode material for sodium- and potassium-ion batteries (SIBs and KIBs, respectively). Finally, we give some insights about how to reduce the oxidation extent into our final composite. Chapter III: It aims to the preparation of a novel composite by combining ce-MoS2 flakes and a preformed diamagnetic FeCo molecular cube. We provide evidence to support the idea that the diamagnetic system is transformed into a paramagnetic compound, as a result of the electron transfer from negative-charged MoS2 flakes to the starting FeCo cube. Chapter IV: It talks about the covalent functionalization of ce-MoS2 flakes via the well-known diazonium strategy, starting from a photochromic dithienylethene derivative (in its open- and closed structure forms) bearing two reactive sites. The results obtained from several characterization techniques confirm the formation of new C鈥揝 bonds between both interacting components. Interestingly, it appears that the inherent photoluminescence (PL) of the organic molecule is quenched after functionalization, indicating a possible charge transfer between the 2D material and the attached dithienylethene derivative. Chapter V: It tackles the formation of WS2/MoS2 heterostructures through the thermal treatment of MoS2 layers electrostatically functionalized with W3S4-core clusters. This chemical strategy combines the advantages of a solution approach (simplicity, scalability, and low cost) with the formation of good quality interfaces (usually, reached by more complex physical methods). The PL of both counterparts is significantly quenched, which would confirm an efficient interlayer coupling between them. Chapter VI: It summarizes the main conclusions of this Thesis
    corecore