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Abdullah Alharbi, Darren Armstrong, Somayah Alharbi, Davood Shahrjerdi
Physically unclonable cryptographic primitives are promising for securing the rapidly growing number of electronic devices. Here, we introduce a new class of physically unclonable primitives from layered molybdenum disulfide (MoS2) by leveraging the natural randomness of their island growth during chemical vapor deposition (CVD). We synthesize a MoS2 monolayer film covered with speckles of multilayer islands, where the growth process is engineered for an optimal speckle density. Using the Clark-Evans test, we confirm that the distribution of islands on the film exhibits complete spatial randomness, hence indicating the growth of multilayer speckles is a spatial Poisson process...
November 16, 2017: ACS Nano
Pan Li, Kai Yuan, Der-Yuh Lin, Xiaolong Xu, Yilun Wang, Yi Wan, Haoran Yu, Kun Zhang, Yu Ye, Lun Dai
The construction of the mixed-dimensional van der Waals (vdW) heterostructures with two-dimensional (2D) and one-dimensional (1D) materials can advantageously integrate their respective dimensional properties to produce new device functionalities and/or enhance device performance. In this case, a single semiconductor nanowire (NW) can function as an optical cavity and a gain medium, while the atomically thin 2D material does not strongly absorb the NW's light emission or disturb the optical propagation mode...
November 16, 2017: Nanoscale
Parmeshwar Prasad, Nishta Arora, A K Naik
Parametric amplification is widely used in diverse areas from optics to electronic circuits to enhance low level signals by varying relevant system parameters. Parametric amplification has also been performed in several micro-nano resonators including nano-electromechanical system (NEMS) resonators based on a two-dimensional (2D) material. Here, we report the enhancement of mechanical response in a MoS2 drum resonator using degenerate parametric amplification. We use parametric pumping to modulate the spring constant of the MoS2 resonator and achieve a 10 dB amplitude gain...
November 16, 2017: Nanoscale
Hua Yu, Mengzhou Liao, Wenjuan Zhao, Guodong Liu, X J Zhou, Zheng Wei, Xiaozhi Xu, Kaihui Liu, Zonghai Hu, Ke Deng, Shuyun Zhou, Jin-An Shi, Lin Gu, Cheng Shen, Tingting Zhang, Luojun Du, Li Xie, Jianqi Zhu, Wei Chen, Rong Yang, Dongxia Shi, Guangyu Zhang
Large scale epitaxial growth and transfer of monolayer MoS2 has attracted great attention in recent years. Here, we report the wafer-scale epitaxial growth of highly oriented continuous and uniform monolayer MoS2 films on single-crystalline sapphire wafers by chemical vapor deposition (CVD) method. The epitaxial film is of high quality and stiched by many 0°, 60° domains and 60°-domain boundaries. Moreover, such wafer-scale monolayer MoS2 films can be transferred and stacked by a simple stamp-transfer process and the substrate is reusable for subsequent growth...
November 15, 2017: ACS Nano
Weijia Li, Zhaoyong Lin, Guowei Yang
Semiconductor photocatalysis for hydrogen production is a promising route to address current energy demands. It is still a great challenge to spatially separate photogenerated electrons and holes in bulk photocatalysts because of the long carrier transport pathway from the bulk to the surface. 2D heterostructured photocatalysts with the type II band alignment can not only shorten the carrier transport pathway, but also create an electric field at the interface to suppress the carrier recombination. However, ultrathin and intimate-contact 2D heterostructured photocatalysts have rarely been achieved so far...
November 15, 2017: Nanoscale
Wen Wen, Junhao Lin, Kazu Suenaga, Yuzheng Guo, Yiming Zhu, Hung-Pin Hsu, Liming Xie
Band structure engineering of two-dimensional (2D) metal dichalcogenides (TMDs) is crucial for their light-matter interaction and optoelectronic applications. Alloying of different metal or chalcogen elements with different stoichiometries in TMDs provides a versatile and efficient approach for modulating the electronic structure and properties of 2D materials. In 2D alloys, quantification of spatial distribution and local coordination of atoms facilitates the establishment of the structure-property relationship at the atomic scale...
November 15, 2017: Nanoscale
Lili Hu, Xinyan Shan, Yanling Wu, Jimin Zhao, Xinghua Lu
The recently discovered novel properties of two dimensional materials largely rely on the layer-critical variation in their electronic structure and lattice symmetry. Achieving layer-by-layer precision patterning is thus crucial for junction fabrications and device engineering, which hitherto poses an unprecedented challenge. Here we demonstrate laser thinning and patterning with layer-by-layer precision in a two dimensional (2D) quantum material MoS2. Monolayer, bilayer and trilayer of MoS2 films are produced with precise vertical and lateral control, which removes the extruding barrier for fabricating novel three dimensional (3D) devices composed of diverse layers and patterns...
November 14, 2017: Scientific Reports
Javad Hassanzadeh, Alireza Khataee
Developing a novel non-enzyme mimetic in biosensors is of great significance. Here, a synergetic peroxidase-like activity was disclosed for mixed MoS2 quantum dots (MoS2 QDs) and graphene quantum dots (GQDs). The high catalytic effect of this mixture was studied on the chemiluminescence system. It was observed that the simultaneous presence of MoS2 QDs and GQDs had a powerful enhancing effect on the chemiluminescence (CL) emission of rhodamine B (RB)-H2O2 reaction. MoS2 QDs and GQDs mixture (prepared with a ratio of 3:2) showed a superior catalytic activity when compared to each of the constituents...
February 1, 2018: Talanta
Zengqiang Gao, Yueyun Li, Xiaobo Zhang, Jinhui Feng, Ling Kong, Ping Wang, Zhiwei Chen, Yunhui Dong, Qin Wei
A sensitive sandwich-type electrochemical immunosensor for the detection of hepatitis B e antigen (HBeAg) was successfully developed based on the gold@palladium nanoparticles (Au@Pd NPs) loaded by molybdenum disulfide functionalized multiwalled carbon nanotubes (Au@Pd/MoS2@MWCNTs). The resultant nanocomposites not only possessed high specific surface area and good biocompatibility, but also exhibited excellent electro-catalytical property. Au NPs functionalized porous graphene oxide (p-GO@Au) were used as sensing platforms and primary antibodies carriers, which can accelerate the electron transfer and improve the load capacity of primary antibodies (Ab1), improving the sensitivity of the immunosensor...
November 9, 2017: Biosensors & Bioelectronics
Bartlomiej Graczykowski, Marianna Sledzinska, Marcel Placidi, David Saleta Reig, Maciej Kasprzak, Francesc Alzina, Clivia Marfa Sotomayor Torres
The performance gain oriented nano-structurisation has opened a new pathway for tuning mechanical features of solid matter vital for application and maintained performance. Simultaneously, the mechanical evaluation has been pushed down to dimensions way below one micrometre. To date, the most standard technique to study the mechanical properties of suspended 2D materials is based on nano-indentation experiments. In this work, by means of micro-Brillouin light scattering we determine the mechanical properties, i...
November 14, 2017: Nano Letters
Yan Wang, Chang-Hyun Kim, Youngdong Yoo, James E Johns, C Daniel Frisbie
The ability to improve and to modulate the heterogeneous charge transfer kinetics of two dimensional (2D) semiconductors, such as MoS2, is a major challenge for electrochemical and photoelectrochemical applications of these materials. Here we report a continuous and reversible physical method for modulating the heterogeneous charge transfer kinetics at a monolayer MoS2 working electrode supported on a SiO2/p-Si substrate. The heavily doped p-Si substrate serves as a back gate electrode; application of a gate voltage (VBG) to p-Si tunes the electron occupation in the MoS2 conduction band and shifts the conduction band edge position relative to redox species dissolved in electrolyte in contact with the front side of the MoS2...
November 14, 2017: Nano Letters
Shengxue Yang, Minghui Wu, Bin Wang, Li-Dong Zhao, Li Huang, Chengbao Jiang, Su-Huai Wei
Van der Waals heterojunctions formed by stacking various two-dimensional (2D) materials have a series of attractive physical properties, thus offering an ideal platform for versatile electronic and optoelectronic applications. Here, we report few-layer SnSe/MoS2 van der Waals heterojunctions and study their electrical and optoelectronic characteristics. The new heterojunctions present excellent electrical transport characteristics with a distinct rectification effect and a high current on/off ratio (~ 1 × 105)...
November 14, 2017: ACS Applied Materials & Interfaces
Yeonsig Nam, Daeheum Cho, Jin Yong Lee
Electrical control of magnetic exchange coupling interactions is central to designing magnetic materials. In this study, we performed density functional theory calculations to investigate the magnetic spin configuration, magnetic moment, and magnetic coupling strength of zigzag MoS2 nanoribbons (zMoS2NRs) with different edge passivation, that is, pristine (Pristine), hydrogen termination (H-tem), sulfur termination (S-term), and sulfhydryl termination (SH-term). Further, we investigated the influence of an external electric field (FExt) on the magnetic properties...
November 14, 2017: Physical Chemistry Chemical Physics: PCCP
Szymon J Zelewski, Robert Kudrawiec
Photoacoustic (PA) and modulated reflectance (MR) spectroscopy have been applied to study the indirect and direct band gap for van der Waals (vdW) crystals: dichalcogenides (MoS2, MoSe2, MoTe2, HfS2, HfSe2, WS2, WSe2, ReS2, ReSe2, SnS2 and SnSe2) and monochalcogenides (GaS, GaSe, InSe, GeS, and GeSe). It is shown that the indirect band gap can be determined by PA technique while the direct band gap can be probed by MR spectroscopy which is not sensitive to indirect optical transitions. By measuring PA and MR spectra for a given compound and comparing them with each other it is easy to conclude about the band gap character in the investigated compound and the energy difference between indirect and direct band gap...
November 13, 2017: Scientific Reports
Congpu Mu, Jiefang Song, Bochong Wang, Can Zhang, Jianyong Xiang, Fusheng Wen, Zhongyuan Liu
In this work, hierarchical architecture MoS2/CNT nanohybrids synthesized by hydrothermal method, with different CNT proportions are systematically investigated their microwave absorption. MoS2 nanoflowers are anchored uniformly on the surface of CNT when the proportion of the MoS2/CNT nanohybrids was 10:2, and the reflection loss (RL) can attain -20 dB in the range of 3.4-13.9 GHz with multiple thicknesses from 1.5 mm to 5.0 mm, while an optimal consequence of -46 dB can be reached at 6.6GHz in 2.9 mm. The excellent performance indicates that the MoS2/CNT=10:2 nanohybrids have potential for using as microwave absorbing materials...
November 13, 2017: Nanotechnology
Yating Yang, Wei-Hai Fang, Run Long
Two-dimensional transition metal dichalcogenides (TMDs) heterojunctions are appealing candidates for optoelectronics and photovoltaics. Using time-domain density functional theory combined with nonadiabatic (NA) molecular dynamics, we show that photoexcitation dynamics exhibit a significant difference in the vertical and lateral MoS2/WSe2 heterojunctions arising from the disparity in the donor-acceptor interaction and fundamental band alignment. The obtained electron transfer time scale in the vertical heterojunction shows excellent agreement with experiment...
November 14, 2017: Journal of Physical Chemistry Letters
Mikko Hakala, Rasmus Kronberg, Kari Laasonen
Electrochemical devices for efficient production of hydrogen as energy carrier rely still largely on rare platinum group metal catalysts. Chemically and structurally modified metal dichalcogenide MoS2 is a promising substitute for these critical raw materials at the cathode side where the hydrogen evolution reaction takes place. For precise understanding of structure and hydrogen adsorption characteristics in chemically modified MoS2 nanostructures, we perform comprehensive density functional theory calculations on transition metal (Fe, Co, Ni, Cu) doping at the experimentally relevant MoS2 surfaces at substitutional Mo-sites...
November 10, 2017: Scientific Reports
Li Gao, Qin Li, Zebin Deng, Brendan Brady, Ni Xia, Yang Zhou, Haixia Shi
Molybdenum disulfide (MoS2) has shown highly attractive superiority as a platform for sensing. However, DNA physisorption on the surface of MoS2 was susceptible to nonspecific probe displacement and false-positive signals. To solve these problems, we have developed a novel MoS2-aptamer nanosheet biosensor for detecting thrombin using a covalently linked aptamer to the MoS2 nanosheet. Ten percent Tween 80 was used to prevent thrombin from nonspecific binding and to rapidly form thiol-DNA/gold nanoparticle (AuNP) conjugates...
2017: International Journal of Nanomedicine
Di Wu, Tai Min, Jian Zhou, Chen Li, Guobin Ma, Gaotian Lu, Minggang Xia, Zhengbin Gu
In van der Waals epitaxial growth, the substrate plays a particularly important role in the crystal morphology. Here, we synthesized MoS2 by chemical vapour deposition on silicon carbide (SiC). The obtained MoS2 dendritic crystals show six-fold symmetry, which are different from the conventional triangular shapes on SiO2 substrate and from those with three-fold symmetry on SrTiO3 substrate. Interestingly, these MoS2 dendritic crystals on SiC exhibit an average fractal dimension 1.76, which is slightly larger than the classical Diffusion-limited-Aggregation fractal dimension 1...
November 9, 2017: Scientific Reports
Weiwei Qin, Yuan Li, Yongqiang Teng, Tao Qin
MoS2/reduced graphene oxide composites (MoS2/rGO) were successfully prepared by a designed tris(hydroxymethyl)methyl aminomethane (named THAM)-assisted hydrothermal method, which involves the modification of THAM on the surfaces of graphene oxide via hydrogen bonds and then the adsorption of MoO4(2-) on the decorated surfaces due to the electrostatic attraction. The three-dimensional framework of interconnected rGO nanosheets provides good electronic conductivity and facile strain release during the electrochemical reaction, thus enhancing the overall performance of the MoS2-based electrode...
November 2, 2017: Journal of Colloid and Interface Science
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