Controlled Synthesis of 2D Palladium Diselenide for Sensitive Photodetector Applications

2018-11-17T22:32:13+00:00November 17th, 2018|Categories: Publications|Tags: |

This study reports on the wafer‐area synthesis of high‐quality 2D PdSe2 layer through a simple selenization method. Both experimental analysis and theoretical simulation reveal that the PdSe2 film exhibits a gradual transition from a semiconductor (monolayer) to semimetal (bulk). Further combination of PdSe2 with Si leads to a fast and sensitive broadband photodiode, with a high responsivity and specific detectivity. Abstract Palladium diselenide (PdSe2), a thus far scarcely studied group‐10 transition metal dichalcogenide has exhibited promising potential in future optoelectronic and electronic devices due to unique structures and electrical properties. Here, the controllable synthesis of wafer‐scale and homogeneous 2D PdSe2 film is reported by a simple selenization approach. By choosing different thickness of precursor Pd layer, 2D PdSe2 with thickness of 1.2–20 nm can be readily synthesized. Interestingly, with the increase in thickness, obvious redshift in wavenumber is revealed by Raman spectroscopy. Moreover, in accordance with density functional theory (DFT) calculation, optical absorption and ultraviolet photoemission spectroscopy (UPS) analyses confirm that the PdSe2 exhibits an evolution from a semiconductor (monolayer) to semimetal (bulk). Further combination of the PdSe2 layer with Si leads to a highly sensitive, fast, and broadband photodetector with a high responsivity (300.2 mA W−1) and specific detectivity (≈1013 Jones). By decorating the device with black phosphorus quantum dots, the device performance can be further optimized. These results suggest the as‐selenized PdSe2 is a promising material for optoelectronic application.

Published in: "Advanced Functional Materials".

Graphene‐Based Actuator with Integrated‐Sensing Function

2018-11-17T22:32:10+00:00November 17th, 2018|Categories: Publications|Tags: , |

A graphene‐based actuator with integrated‐sensing function is developed. It realizes real‐time measurements of the shape deformation of the actuator. A smart gripper based on the actuator demonstrates perfect integration of actuating and sensing functions. It can not only grasp and release an object, but also sense every actuation state of the actuator. Abstract Flexible actuators have important applications in artificial muscles, robotics, optical devices, and so on. However, most of the conventional actuators have only actuation function, lacking in real‐time sensing signal feedbacks. Here, to break the limitation and add functionality in conventional actuators, a graphene‐based actuator with integrated‐sensing function is reported, which avoids the dependence on image post‐processing for actuation detection and realizes real‐time measurement of the shape‐deformation amplitudes of the actuator. The actuator is able to show a large bending actuation (curvature of 1.1 cm−1) based on a dual‐mode actuation mechanism when it is driven by near infrared light. Meanwhile, the relative resistance change of the actuator is −17.5%. The sensing function is attributed to piezoresistivity and thermoresistivity of the reduced graphene oxide and paper composite. This actuator can be used as a strain sensor to monitor human motions. A smart gripper based on the actuators demonstrates perfect integration of the actuating and sensing functions, which can not only grasp and release an object, but also sense every actuation state of the actuator. The developed integrated‐sensing actuator is hopeful to open new application fields in soft robotics, artificial muscles, flexible wearable devices, and other integrated‐multifunctional devices.

Published in: "Advanced Functional Materials".

Graphene Sheets: Planar Alignment of Graphene Sheets by a Rotating Magnetic Field for Full Exploitation of Graphene as a 2D Material (Adv. Funct. Mater. 46/2018)

2018-11-17T22:32:06+00:00November 17th, 2018|Categories: Publications|Tags: |

An aligned graphene assembly amplifies the anisotropic properties of individual sheets, creating in a strong dark/bright contrast in the all‐graphene Panda display. Zhiming M. Wang, Jiming Bao, and co‐workers report in article number 1805255, that such alignment can be achieved with a pair of rotating magnets in an arbitrary direction and space, which opens the opportunity of transfering graphene’s superior properties to a macroscopic graphene assembly.

Published in: "Advanced Functional Materials".

Laser‐Induced Graphene Strain Sensors Produced by Ultraviolet Irradiation of Polyimide

2018-11-17T22:32:05+00:00November 17th, 2018|Categories: Publications|Tags: |

Laser‐induced graphene is obtained by irradiation of polyimide by an ultraviolet laser instead of the typical infrared source, with a fourfold decrease in the penetration depth and doubled spatial resolution. Electromechanical strain sensors are patterned in substrates with different thicknesses and their performance is measured. A low‐cost arterial pulse wave monitor is built, exploring the higher sensitivity of thinner substrates. Abstract Laser‐induced graphene (LIG) can be obtained by irradiation of a polymer by a laser source. The present work demonstrates that it is possible to obtain this kind of material using an ultraviolet laser instead of the typical infrared source. Using this approach, a fourfold decrease in the penetration depth (5 µm) is achieved, while the spatial resolution is doubled. Electromechanical strain LIG sensors are patterned in polyimide substrates with different thicknesses and their performance to strain, bending, and force inputs is measured. A low‐cost arterial pulse wave monitor is built, exploring the high force sensitivity of the sensors produced on the thinner substrates.

Published in: "Advanced Functional Materials".

Humidity‐Controlled Ultralow Power Layer‐by‐Layer Thinning, Nanopatterning and Bandgap Engineering of MoTe2

2018-11-17T22:32:03+00:00November 17th, 2018|Categories: Publications|Tags: |

A precision, laser‐assisted, humidity‐controlled, layer‐by‐layer thinning method in 2D MoTe2 films is presented. Field effect transistors fabricated from thinned layers exhibit an order of magnitude increase in on/off current, enhanced field‐effect mobility, and the fastest photoresponse for (visible) MoTe2 photodetectors reported to date. Localized band gap engineering is also performed, with sub‐200 nm spatial resolution, via the creation of lateral homojunctions. Abstract A highly effective laser thinning method is demonstrated to accurately control the thickness of MoTe2 layers. By utilizing the humidity present in the ambient atmosphere, multilayered MoTe2 films can be uniformly thinned all the way down to monolayer with layer‐by‐layer precision using an ultralow laser power density of 0.2 mW µm−2. Localized bandgap engineering is also performed in MoTe2, by creating regions with different bandgaps on the same film, enabling the formation of lateral homojunctions with sub‐200 nm spatial resolution. Field‐effect transistors fabricated from these thinned layers exhibit significantly improved electrical properties with an order of magnitude increase in on/off current ratios, along with enhancements in on‐current and field‐effect mobility values. Thinned devices also exhibit the fastest photoresponse (45 µs) for an MoTe2‐based visible photodetector reported to date, along with a high photoresponsivity. A highly sensitive monolayer MoTe2 photodetector is also reported. These results demonstrate the efficiency of the presented thinning approach in producing high‐quality MoTe2 films for electronic and optoelectronic applications.

Published in: "Advanced Functional Materials".

Exfoliated Layered Manganese Trichalcogenide Phosphite (MnPX3, X = S, Se) as Electrocatalytic van der Waals Materials for Hydrogen Evolution

2018-11-17T22:32:00+00:00November 17th, 2018|Categories: Publications|Tags: |

Metal phosphorus chalcogenides (MPX 3) have reclaim ample interest as 2D layered materials, due to favorable performances in energy storage and conversion. Herein, MnPX 3 (X = S, Se) are synthetized and submitted to shear force exfoliation. Exfoliated MnPSe3 has the lowest onset potential and best stability for hydrogen evolution. Such materials show a great promise for future in a hydrogen‐based economy. Abstract Layered metal trichalcogen phosphites, also entitled as metal phosphorus chalcogenides (MPX 3), have regained abundant interest, not only due to their magnetic properties, but also due to promising performances in energy storage and conversion. Herein, two different layered manganese trichalcogen phosphites, MnPX3 (X = S, Se), are synthetized and submitted to shear force exfoliation. Structural and morphological characterization point to the fact that exfoliated MPX 3 (exf‐MnPX 3) undergo mainly a downsizing process, alongside with delamination. Layered exf‐MnPSe3 has the lowest onset potential for hydrogen evolution reaction (HER) in both media. In acidic media, a comparative improvement of 350 mV is observed for exf‐MnPSe3 relative to the bulk MnPSe3. The materials stability as electrocatalysts is also tested for HER in a wide pH range, in which exf‐MnPSe3 has a good stability after 100 cycles. The improved performance of exf‐MnPSe3 can be correlated with the lower relative abundance of Mn and P oxides detected in the Mn 2p and P 2p core levels. Such materials show a great promise for future in a hydrogen‐based economy.

Published in: "Advanced Functional Materials".

Direct CVD Growth of Graphene on Traditional Glass: Methods and Mechanisms

2018-11-17T02:35:38+00:00November 17th, 2018|Categories: Publications|Tags: |

A summary of the chemical vapor deposition (CVD) growth techniques of graphene on traditional glass as well as the growth mechanisms is provided. Direct thermal CVD growth, molten‐bed CVD growth, metal‐catalyst‐assisted growth, and plasma‐enhanced growth are covered. Emphasis is laid on the strategy of growth corresponding to the different natures of glass substrates. Abstract Chemical vapor deposition (CVD) on catalytic metal surfaces is considered to be the most effective way to obtain large‐area, high‐quality graphene films. For practical applications, a transfer process from metal catalysts to target substrates (e.g., poly(ethylene terephthalate) (PET), glass, and SiO2/Si) is unavoidable and severely degrades the quality of graphene. In particular, the direct growth of graphene on glass can avoid the tedious transfer process and endow traditional glass with prominent electrical and thermal conductivities. Such a combination of graphene and glass creates a new type of glass, the so‐called “super graphene glass,” which has attracted great interest from the viewpoints of both fundamental research and daily‐life applications. In the last few years, great progress has been achieved in pursuit of this goal. Here, these growth methods as well as the specific growth mechanisms of graphene on glass surfaces are summarized. The typical techniques developed include direct thermal CVD growth, molten‐bed CVD growth, metal‐catalyst‐assisted growth, and plasma‐enhanced growth. Emphasis is placed on the strategy of growth corresponding to the different natures of glass substrates. A comprehensive understanding of graphene growth on nonmetal glass substrates and the latest status of “super graphene glass” production are provided.

Published in: "Advanced Materials".

Rollable, Stretchable, and Reconfigurable Graphene Hygroelectric Generators

2018-11-17T02:35:36+00:00November 17th, 2018|Categories: Publications|Tags: |

Rollable, stretchable, and 3D space‐deformable graphene‐based hygroelectric generators are developed by a laser processing strategy, which exhibit excellent electricity‐generation ability without any significant performance loss despite being deformed arbitrarily, and are promising as power supply for applications in complicated conditions. Abstract Moisture‐triggered electricity generation has attracted much attention because of the effective utilization of the water‐molecule diffusion process widely existing in atmosphere. However, the monotonous and rigid structures of previously developed generators have heavily restricted their applications in complex and highly deformable working conditions. Herein, by a rational configuration design with a versatile laser processing strategy, graphene‐based hygroelectric generators (GHEGs) of sophisticated architectures with diversified functions such as rollable, stretchable, and even multidimensional transformation are achieved for the first time. More importantly, a wide range of 3D deformable generators that can automatically assemble and transform from planar geometries into spacial architectures are also successfully fabricated, including cubic boxes, pyramids, Miura‐ori, and footballs. These GHEGs demonstrate excellent electricity‐generation performance in curling and elongating states. The generated voltages are easily up to 1.5 V under humidity variation in atmosphere, powering a variety of commercial electronic components. These deformable GHEGs can be applied on complicated surfaces, human bodies, and many more beyond those demonstrated in this work.

Published in: "Advanced Materials".

Exfoliated Layered Manganese Trichalcogenide Phosphite (MnPX3, X = S, Se) as Electrocatalytic van der Waals Materials for Hydrogen Evolution

2018-11-17T02:32:30+00:00November 17th, 2018|Categories: Publications|Tags: |

Metal phosphorus chalcogenides (MPX 3) have reclaim ample interest as 2D layered materials, due to favorable performances in energy storage and conversion. Herein, MnPX 3 (X = S, Se) are synthetized and submitted to shear force exfoliation. Exfoliated MnPSe3 has the lowest onset potential and best stability for hydrogen evolution. Such materials show a great promise for future in a hydrogen‐based economy. Abstract Layered metal trichalcogen phosphites, also entitled as metal phosphorus chalcogenides (MPX 3), have regained abundant interest, not only due to their magnetic properties, but also due to promising performances in energy storage and conversion. Herein, two different layered manganese trichalcogen phosphites, MnPX3 (X = S, Se), are synthetized and submitted to shear force exfoliation. Structural and morphological characterization point to the fact that exfoliated MPX 3 (exf‐MnPX 3) undergo mainly a downsizing process, alongside with delamination. Layered exf‐MnPSe3 has the lowest onset potential for hydrogen evolution reaction (HER) in both media. In acidic media, a comparative improvement of 350 mV is observed for exf‐MnPSe3 relative to the bulk MnPSe3. The materials stability as electrocatalysts is also tested for HER in a wide pH range, in which exf‐MnPSe3 has a good stability after 100 cycles. The improved performance of exf‐MnPSe3 can be correlated with the lower relative abundance of Mn and P oxides detected in the Mn 2p and P 2p core levels. Such materials show a great promise for future in a hydrogen‐based economy.

Published in: "Advanced Functional Materials".

Realization of flat band with possible nontrivial topology in electronic Kagome lattice

2018-11-16T22:36:24+00:00November 16th, 2018|Categories: Publications|Tags: |

The energy dispersion of fermions or bosons vanishes in momentum space if destructive quantum interference occurs in a frustrated Kagome lattice with only nearest-neighbor hopping. A discrete flat band (FB) without any dispersion is consequently formed, promising the emergence of fractional quantum Hall states at high temperatures. Here, we report

Published in: "Science Advances".

2D proximate quantum spin liquid state in atomic-thin α -RuCl 3

2018-11-16T14:33:54+00:00November 16th, 2018|Categories: Publications|

Two-dimensional (2D) atomic crystals have made major inroads into condensed-matter physics and give rise to fascinating phenomena due to quantum confinement. Here we report the first Raman scattering study on phonon-magnetic scattering coupling, proximate quantum spin liquid ground state and collective fractionalized excitations in exfoliated α -RuCl 3 atomic layers. Our results uncover that 2D α -RuCl 3 could harbour the unusual magnetic continuum, serving as a hallmark of the 2D proximate quantum spin liquid state and frustrated magnetic interactions. More importantly, our work demonstrates that the unusual magnetic scattering, as compared with bulk, is more obvious in 2D α -RuCl 3 , indicating that the frustrated magnetic interactions are enhanced strongly. Such unusual enhancement of frustrated magnetic interactions may be responsible for the gigantic phonon-magnetic scattering coupling of 2D α -RuCl 3 and play a…

Published in: "2DMaterials".

Synergistic effect of functionalized graphene oxide and carbon nanotube hybrids on mechanical properties of epoxy composites

2018-11-16T14:32:37+00:00November 16th, 2018|Categories: Publications|Tags: , |

RSC Adv., 2018, 8,38689-38700DOI: 10.1039/C8RA08312F, Paper Open Access &nbsp This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.Zehao Qi, Yefa Tan, Zhongwei Zhang, Li Gao, Cuiping Zhang, Jin TianThe 3D structure hybrids obtained by combining CNT and epoxy functionalized GO

Published in: "RSC Advances".

Inorganic molecule (O2, NO) adsorption on nitrogen- and phosphorus-doped MoS2 monolayer using first principle calculations

2018-11-16T14:32:35+00:00November 16th, 2018|Categories: Publications|Tags: |

RSC Adv., 2018, 8,38656-38666DOI: 10.1039/C8RA07638C, Paper Open Access &nbsp This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.Hafiz Ghulam Abbas, Tekalign Terfa Debela, Sajjad Hussain, Iftikhar HussainWe performed a systematic study of the adsorption behaviors of O2 and NO gas

Published in: "RSC Advances".

Coulomb scattering mechanism transition in 2D layered MoTe 2 : effect of high- κ passivation and Schottky barrier height

2018-11-16T12:35:23+00:00November 16th, 2018|Categories: Publications|Tags: |

Clean interface and low contact resistance are crucial requirements in two-dimensional (2D) materials to preserve their intrinsic carrier mobility. However, atomically thin 2D materials are sensitive to undesired Coulomb scatterers such as surface/interface adsorbates, metal-to-semiconductor Schottky barrier (SB), and ionic charges in the gate oxides, which often limits the understanding of the charge scattering mechanism in 2D electronic systems. Here, we present the effects of hafnium dioxide (HfO 2 ) high- κ passivation and SB height on the low-frequency (LF) noise characteristics of multilayer molybdenum ditelluride (MoTe 2 ) transistors. The passivated HfO 2 passivation layer significantly suppresses the surface reaction and enhances dielectric screening effect, resulting in an excess electron n -doping, zero hysteresis, and substantial improvement in carrier mobility. After the high- κ HfO 2 passivation, the obtained …

Published in: "Nanotechnology".

Growth of two-dimensional materials on hexagonal boron nitride ( h -BN)

2018-11-16T12:35:22+00:00November 16th, 2018|Categories: Publications|Tags: , |

With its atomically smooth surface yet no dangling bond, chemical inertness and high temperature sustainability, the insulating hexagonal boron nitride ( h -BN) can be an ideal substrate for two-dimensional (2D) material growth and device measurement. In this review, research progress on the chemical growth of 2D materials on h -BN has been summarized, such as chemical vapor deposition and molecular beam epitaxy of graphene and various transition metal dichalcogenides. Further, stacking of the as-grown 2D materials relative to h -BN, thermal expansion matching between the deposited materials and h -BN, electrical property of 2D materials on h -BN have been discussed in detail.

Published in: "Nanotechnology".

Ultrafine MnO2 nanowires grown on RGO-coated carbon cloth as a binder-free and flexible supercapacitor electrode with high performance

2018-11-16T12:33:28+00:00November 16th, 2018|Categories: Publications|Tags: , , |

RSC Adv., 2018, 8,38631-38640DOI: 10.1039/C8RA05890C, Paper Open Access &nbsp This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence.Zhihui Xu, Shishuai Sun, Wen Cui, Dan Yu, Jiachun DengReduced graphene oxide coated carbon cloth has been used as a substrate for the

Published in: "RSC Advances".

Phosphorus‐Mediated MoS2 Nanowires as a High‐Performance Electrode Material for Quasi‐Solid‐State Sodium‐Ion Intercalation Supercapacitors

2018-11-16T04:38:32+00:00November 16th, 2018|Categories: Publications|Tags: , |

We propose an efficient P‐anion doping strategy to enhance the electrochemical performance of the MoS2 nanowires by increasing the number of electrochemically active sites, improving the electrical conductivity, and decreasing the energy barrier of Na+ ion diffusion. The P‐doped MoS2 delivers remarkable specific capacitance and rate capability. This study highlights the dominating role of P dopants in electrode materials for supercapacitors. Abstract Molybdenum disulfide (MoS2) is a promising electrode material for electrochemical energy storage owing to its high theoretical specific capacity and fascinating 2D layered structure. However, its sluggish kinetics for ionic diffusion and charge transfer limits its practical applications. Here, a promising strategy is reported for enhancing the Na+‐ion charge storage kinetics of MoS2 for supercapacitors. In this strategy, electrical conductivity is enhanced and the diffusion barrier of Na+ ion is lowered by a facile phosphorus‐doping treatment. Density functional theory results reveal that the lowest energy barrier of dilute Na‐vacancy diffusion on P‐doped MoS2 (0.11 eV) is considerably lower than that on pure MoS2 (0.19 eV), thereby signifying a prominent rate performance at high Na intercalation stages upon P‐doping. Moreover, the Na‐vacancy diffusion coefficient of the P‐doped MoS2 at room temperatures can be enhanced substantially by approximately two orders of magnitude (10−6–10−4 cm2 s−1) compared with pure MoS2. Finally, the quasi‐solid‐state asymmetrical supercapacitor assembled with P‐doped MoS2 and MnO2, as the positive and negative electrode materials, respectively, exhibits an ultrahigh energy density of 67.4 W h kg−1 at 850 W kg−1 and excellent cycling stability with 93.4% capacitance

Published in: "Small".

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