Abstract Crystallographically anisotropic two-dimensional (2D) molybdenum disulfide (MoS 2 ) with vertically aligned (VA) layers is attractive for electrochemical sensing owing to its surface-enriched dangling bonds coupled with extremely large mechanical deformability. In this study, we explored VA-2D MoS 2 layers integrated on cellulose nanofibers (CNFs) for detecting various volatile organic compound gases. Sensor devices employing VA-2D MoS 2 /CNFs exhibited excellent sensitivities for the tested gases of ethanol, methanol, ammonia, and acetone; e.g. a high response rate up to 83.39% for 100 ppm ethanol, significantly outperforming previously reported sensors employing horizontally aligned 2D MoS 2 layers. Furthermore, VA-2D MoS 2 /CNFs were identified to be completely dissolvable in buffer solutions such as phosphate-buffered saline solution and baking soda buffer solution without releasing toxic chemicals. This unusual combination of high sensitivity and excellent biodegradability inherent to VA-2D MoS 2 /CNFs offers unprecedented opportunities for exploring mechanically reconfigurable sensor technologies with bio-compatible transient characteristics.
more »
« less
Mechanically rollable photodetectors enabled by centimetre-scale 2D MoS 2 layer/TOCN composites
Two-dimensional (2D) molybdenum disulfide (MoS 2 ) layers are suitable for visible-to-near infrared photodetection owing to their tunable optical bandgaps. Also, their superior mechanical deformability enabled by an extremely small thickness and van der Waals (vdW) assembly allows them to be structured into unconventional physical forms, unattainable with any other materials. Herein, we demonstrate a new type of 2D MoS 2 layer-based rollable photodetector that can be mechanically reconfigured while maintaining excellent geometry-invariant photo-responsiveness. Large-area (>a few cm 2 ) 2D MoS 2 layers grown by chemical vapor deposition (CVD) were integrated on transparent and flexible substrates composed of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TOCNs) by a direct solution casting method. These composite materials in three-dimensionally rollable forms exhibited a large set of intriguing photo-responsiveness, well preserving intrinsic opto-electrical characteristics of the integrated 2D MoS 2 layers; i.e. , light intensity-dependent photocurrents insensitive to illumination angles as well as highly tunable photocurrents varying with the rolling number of 2D MoS 2 layers, which were impossible to achieve with conventional photodetectors. This study provides a new design principle for converting 2D materials to three-dimensional (3D) objects of tailored functionalities and structures, significantly broadening their potential and versatility in futuristic devices.
more »
« less
- Award ID(s):
- 1728309
- PAR ID:
- 10274628
- Date Published:
- Journal Name:
- Nanoscale Advances
- Volume:
- 3
- Issue:
- 11
- ISSN:
- 2516-0230
- Page Range / eLocation ID:
- 3028 to 3034
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)2D PtTe 2 layers, a relatively new class of 2D crystals, have unique band structure and remarkably high electrical conductivity promising for emergent opto-electronics. This intrinsic superiority can be further leveraged toward practical device applications by merging them with mature 3D semiconductors, which has remained largely unexplored. Herein, we explored 2D/3D heterojunction devices by directly growing large-area (>cm 2 ) 2D PtTe 2 layers on Si wafers using a low-temperature CVD method and unveiled their superior opto-electrical characteristics. The devices exhibited excellent Schottky transport characteristics essential for high-performance photovoltaics and photodetection, i.e. , well-balanced combination of high photodetectivity (>10 13 Jones), small photo-responsiveness time (∼1 μs), high current rectification ratio (>10 5 ), and water super-hydrophobicity driven photovoltaic improvement (>300%). These performances were identified to be superior to those of previously explored 2D/3D or 2D layer-based devices with much smaller junction areas, and their underlying principles were confirmed by DFT calculations.more » « less
-
Abstract The phase transitions of two-dimensional (2D) materials are key to the operation of many devices with applications including energy storage and low power electronics. Nanoscale confinement in the form of reduced thickness can modulate the phase transitions of 2D materials both in their thermodynamics and kinetics. Here, using in situ Raman spectroscopy we demonstrate that reducing the thickness of MoS 2 below five layers slows the kinetics of the phase transition from 2H- to 1T′-MoS 2 induced by the electrochemical intercalation of lithium. We observe that the growth rate of 1T′ domains is suppressed in thin MoS 2 supported by SiO 2 , and attribute this growth suppression to increased interfacial effects as the thickness is reduced below 5 nm. The suppressed kinetics can be reversed by placing MoS 2 on a 2D hexagonal boron nitride ( h BN) support, which readily facilitates the release of strain induced by the phase transition. Additionally, we show that the irreversible conversion of intercalated 1T′-MoS 2 into Li 2 S and Mo is also thickness-dependent and the stability of 1T′-MoS 2 is significantly increased below five layers, requiring a much higher applied electrochemical potential to break down 1T′-MoS 2 into Li 2 S and Mo nanoclusters.more » « less
-
Molybdenum disulfide (MoS 2 ) may be a promising alternative for lithium ion batteries (LIBs) because it offers a unique layered crystal structure with a large and tunable distance between layers. This enables the anticipated excellent rate and cycling stability because they can promote the reversible lithium ion intercalation and de-intercalation without huge volume change which consequently prevents the pulverization of active materials during repeated charge and discharge processes. Herein, we prepared hierarchical MoS 2 –carbon (MoS 2 –C) microspheres via a continuous and scalable ultrasonic nebulization assisted route. The structure, composition, and electrochemical properties are investigated in detail. The MoS 2 –C microspheres consist of few-layer MoS 2 nanosheets bridged by carbon, which separates the exfoliated MoS 2 layers and prevents their aggregation and restacking, thus leading to improved kinetic, enhanced conductivity and structural integrity. The novel architecture offers additional merits such as overall large size and high packing density, which promotes their practical applications. The MoS 2 –C microspheres have been demonstrated with excellent electrochemical performances in terms of low resistance, high capacity even at large current density, stable cycling performance, etc. The electrodes exhibited 800 mA h g −1 at 1000 mA g −1 over 170 cycles. At a higher current density of 3200 mA g −1 , a capacity of 730 mA h g −1 can be also maintained. The MoS 2 –C microspheres are practically applicable not only because of the continuous and large scale synthesis via the current strategy, but also the possess a robust and integrated architecture which ensures the excellent electrochemical properties.more » « less
-
more » « less
Abstract Biomorph actuators composed of two layers with asymmetric thermal expansion properties are widely explored owing to their high mechanical adaptability. Electrothermal nanomaterials are employed as the Joule heating components in them for controlled thermal expansion, while their large integration thickness often limits resulting actuation performances. This study reports high‐performance ultrathin soft biomorph actuators enabled by near atom‐thickness 2D platinum ditelluride (PtTe2) layers—a new class of emergent metallic 2D transition metal dichalcogenides. The actuators employ wafer‐scale 2D PtTe2layers sandwiched in between two polymer films of largely mismatched thermal expansion coefficients, which are electrically biased to generate Joule heating. This electrical‐to‐thermal conversion causes the asymmetric expansion of the polymers achieving outstanding actuation motions; i.e., large bending curvature, fast responsiveness, as well as high reversibility and endurance, which surpass the performances of previously explored graphene‐based actuators with much smaller dimensions. Furthermore, the 2D PtTe2layers‐enabled actuators are demonstrated to function as soft grippers in lifting and relocating heavier objects, implying the great potential of near atom‐thickness materials in biomimetic devices.
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D0NA01053G
