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Yujing Ma, Sadhu Kolekar, Horacio Coy Diaz, Johannes Aprojanz, Ilio Miccoli, Christoph Tegenkamp, Matthias Batzill
Twin grain boundaries in MoSe2 are metallic and undergo a metal to insulator Peierls transition at low temperature. Growth of MoSe2 by molecular beam epitaxy results in the spontaneous formation of a high density of these twin grain boundaries, likely as a mechanism to incorporation Se-deficiency in the film. Using scanning tunneling microscopy, we study the grain boundary network that is formed in homoepitaxially grown MoSe2, and for MoSe2 grown heteroepitaxially on MoS2- and HOPG- substrates. No statistically relevant variation of the grain boundary concentration has been found for the different substrates, indicating that the grain boundary formation is substrate independent and depends mainly on the growth conditions...
April 28, 2017: ACS Nano
T L Atallah, J Wang, M Bosch, D Seo, R A Burke, O Moneer, Justin Zhu, M Theibault, L E Brus, J Hone, X-Y Zhu
Defects in monolayer transition-metal dichalcogenides (TMDCs) may lead to unintentional doping, charge-carrier trapping, and nonradiative recombination. These effects impair electronic and optoelectronic technologies. Here we show that charged defects in MoS2 monolayers can be effectively screened when they are in contact with an ionic liquid (IL), leading to an increase in photoluminescence (PL) yield by up to two orders of magnitude. The extent of this PL enhancement by the IL correlates with the brightness of each pretreated sample...
April 28, 2017: Journal of Physical Chemistry Letters
Junyoung Kwon, Jong-Young Lee, Young-Jun Yu, Chul-Ho Lee, Xu Cui, James Hone, Gwan-Hyoung Lee
2D semiconductors, including transition metal dichalcogenides (TMDs), have been widely studied recently. However, the device performance is deteriorated due to the significant contact resistance. The contact resistance of MoS2-metal contacts decreases with the thickness of MoS2. We obtained a Schottky barrier height as low as about 70 meV when MoS2 is trilayer-thick. It is important to find the optimal choice of contact metal and layer thickness of MoS2.
April 27, 2017: Nanoscale
Amirhasan Nourbakhsh, Ahmad Zubair, Sameer Joglekar, Mildred Dresselhaus, Tomás Palacios
Obtaining a subthreshold swing (SS) below the thermionic limit of 60 mV dec(-1) by exploiting the negative-capacitance (NC) effect in ferroelectric (FE) materials is a novel effective technique to allow the reduction of the supply voltage and power consumption in field effect transistors (FETs). At the same time, two-dimensional layered semiconductors, such as molybdenum disulfide (MoS2), have been shown to be promising candidates to replace silicon MOSFETs in sub-5 nm-channel technology nodes. In this paper, we demonstrate NC MoS2 FETs by incorporating a ferroelectric Al-doped HfO2 (Al : HfO2), a technologically compatible material, in the FET gate stack...
April 27, 2017: Nanoscale
Lingdan Kong, Lingxi Xing, Benqing Zhou, Lianfang Du, Xiangyang Shi
Exploitation of novel hybrid nanomaterials for combinational tumor therapy is challenging. In this work, we synthesized dendrimer-modified MoS2 nanoflakes for combinational gene silencing and photothermal therapy (PTT) of cancer cells. Hydrothermally synthesized MoS2 nanoflakes were modified with generation 5 (G5) poly(amidoamine) dendrimers partially functionalized with lipoic acid via disulfide bond. The formed G5-MoS2 nanoflakes display good colloidal stability and superior photothermal conversion efficiency and photothermal stability...
April 25, 2017: ACS Applied Materials & Interfaces
Ryohei Wakatsuki, Yu Saito, Shintaro Hoshino, Yuki M Itahashi, Toshiya Ideue, Motohiko Ezawa, Yoshihiro Iwasa, Naoto Nagaosa
Lack of spatial inversion symmetry in crystals offers a rich variety of physical phenomena, such as ferroelectricity and nonlinear optical effects (for example, second harmonic generation). One such phenomenon is magnetochiral anisotropy, where the electrical resistance depends on the current direction under the external magnetic field. We demonstrate both experimentally and theoretically that this magnetochiral anisotropy is markedly enhanced by orders of magnitude once the materials enter into a superconducting state...
April 2017: Science Advances
Shunsong Tang, Changhui Fu, Longfei Tan, Tianlong Liu, Jingsong Mao, Xiangling Ren, Hongying Su, Dan Long, Qianqian Chai, Zhongbing Huang, Xudong Chen, Jingzhuo Wang, Jun Ren, Xianwei Meng
It is an ambitious target to improve overall Hepatocellular Carcinoma therapeutic effects. Recently, MW ablation has emerged as a powerful thermal ablation technique, affording favorable survival with excellent local tumor control. To achieve better therapeutic effects of MW ablation, MW sensitizers are prepared for enhanced MW ablation to preferentially heat tumor territory. However, it is still not practicable for treatment of the orthotopic transplantation tumor. Herein, biocompatible and degradable methoxy poly(ethylene glycol)-poly(lactic-co-glycolic acid) (mPEG-PLGA) microcapsules with hierarchical structure have been designed for microwave-induced tumor therapy...
April 14, 2017: Biomaterials
Anupam Giri, Heeseung Yang, Kalianan Thiyagarajan, Woosun Jang, Jae Min Myoung, Ranbir Singh, Aloysius Soon, Kilwon Cho, Unyong Jeong
Ultrathin transition metal dichalcogenides (TMDs) have exotic electronic properties. With success in easy synthesis of high quality TMD thin films, the potential applications will become more viable in electronics, optics, energy storage, and catalysis. Synthesis of TMD thin films has been mostly performed in vacuum or by thermolysis. So far, there is no solution phase synthesis to produce large-area thin films directly on target substrates. Here, this paper reports a one-step quick synthesis (within 45-90 s) of TMD thin films (MoS2 , WS2 , MoSe2 , WSe2 , etc...
April 24, 2017: Advanced Materials
Qiusen Han, Xinhuan Wang, Xinghang Jia, Shuangfei Cai, Wei Liang, Yan Qin, Rong Yang, Chen Wang
Single or few-layered MoS2 nanosheets, as a novel class of 2D nanomaterials, have received tremendous attention due to their fantastic physical and chemical properties. Here, we fabricated MoS2-PEG-CpG with a small and uniform size as a multifunctional platform for photothermal enhanced immunotherapy. MoS2 nanosheets were fabricated by chemical exfoliation and further probe sonication. To realize MoS2-based adjuvant delivery, MoS2 nanosheets were functionalized with cytosine-phosphate-guanine (CpG) and polyethylene glycol (PEG) to form MoS2-PEG-CpG nanoconjugates...
April 24, 2017: Nanoscale
Xianhong Wu, Zhiyu Wang, Mengzhou Yu, Luyang Xiu, Jieshan Qiu
The MXenes combining hydrophilic surface, metallic conductivity and rich surface chemistries represent a new family of 2D materials with widespread applications. However, their poor oxygen resistance causes a great loss of electronic properties and surface reactivity, which significantly inhibits the fabrication, the understanding of the chemical nature and full exploitation of the potential of MXene-based materials. Herein we report a facile carbon nanoplating strategy for efficiently stabilizing the MXenes against structural degradation caused by spontaneous oxidation, which provides a material platform for developing MXene-based materials with attractive structure and properties...
April 24, 2017: Advanced Materials
Changdeuck Bae, Thi Anh Ho, Hyunchul Kim, Seonhee Lee, Seulky Lim, Myungjun Kim, Hyunjun Yoo, Josep M Montero-Moreno, Jong Hyeok Park, Hyunjung Shin
We describe the spontaneous formation of composite chalcogenide materials that consist of two-dimensional (2D) materials dispersed in bulk and their unusual charge transport properties for application in hydrogen evolution reactions (HERs). When MoS2 as a representative 2D material is deposited on transition metals (such as Cu) in a controlled manner, the sulfidation reactions also occur with the metal. This process results in remarkably unique structures, that is, bulk layered heterojunctions (BLHJs) of Cu-Mo-S that contain MoS2 flakes inside, which are uniformly dispersed in the Cu2S matrix...
March 2017: Science Advances
Pengpeng Chen, Xiaoyan Liu, Rundong Jin, Wangyan Nie, Yifeng Zhou
A novel environmental friendly dye adsorbent composited of hydroxypropyl cellulose (HPC) and molybdenum disulfide (MoS2) were fabricated, which can be recycled and reused by illumination due to the photo-catalytic properties of MoS2. In order to promote a more homogeneous dispersion of MoS2 nanosheets in HPC, MoS2 was functionalized with HPC chains through esterification. The successful functionalization of MoS2 was confirmed by FTIR, XRD, XPS characterizations. The morphologies of the HPC and HPC-MoS2/HPC hydrogels were compared by SEM...
July 1, 2017: Carbohydrate Polymers
A Stesmans, S Iacovo, D Chiappe, I Radu, C Huyghebaert, S De Gendt, V V Afanas'ev
A low-temperature electron spin resonance study has been carried out on large-area high-purity polycrystalline two-dimensional few monolayer (ML) 2H MoS2 films synthesized by sulfurization of Mo layers, with intent to atomically assess mobility-degrading detrimental point defects. This reveals the presence of a distinct previously unreported anisotropic defect of axial symmetry about the c-axis characterized by g // = 2.00145 and g ⊥ = 2.0027, with corresponding density (spin S = ½) ~3 × 10(12) cm(-2) for a 4 ML thick film...
December 2017: Nanoscale Research Letters
Charlie Tsai, Hong Li, Sangwook Park, Joonsuk Park, Hyun Soo Han, Jens K Nørskov, Xiaolin Zheng, Frank Abild-Pedersen
Recently, sulfur (S)-vacancies created on the basal plane of 2H-molybdenum disulfide (MoS2) using argon plasma exposure exhibited higher intrinsic activity for the electrochemical hydrogen evolution reaction than the edge sites and metallic 1T-phase of MoS2 catalysts. However, a more industrially viable alternative to the argon plasma desulfurization process is needed. In this work, we introduce a scalable route towards generating S-vacancies on the MoS2 basal plane using electrochemical desulfurization. Even though sulfur atoms on the basal plane are known to be stable and inert, we find that they can be electrochemically reduced under accessible applied potentials...
April 21, 2017: Nature Communications
Chang Lu, Zhicheng Huang, Biwu Liu, Yibo Liu, Yibin Ying, Juewen Liu
Attaching DNA to nanomaterials is the basis for DNA-directed assembly, sensing, and drug delivery using such hybrid materials. Poly-cytosine (poly-C) DNA is a high affinity ligand for four types of commonly used nanomaterials, including nanocarbons (graphene oxide and single-walled carbon nanotubes), transition metal dichalcogenides (MoS2 and WS2 ), metal oxides (Fe3 O4 and ZnO), and metal nanoparticles (Au and Ag). Compared to other homo-DNA sequences, poly-C DNA has the highest affinity for the first three types of materials...
April 21, 2017: Angewandte Chemie
Xu-Bing Li, Yu-Ji Gao, Hao-Lin Wu, Yang Wang, Qing Guo, Mao-Yong Huang, Bin Chen, Chen-Ho Tung, Li-Zhu Wu
Due to their enhanced light harvesting, favored interfacial charge transfer and excellent proton reduction activity, hybrid photocatalysts of metallic 1T-MoS2 nanosheets and inorganic-ligand stabilized CdSe/ZnS QDs obtained via a self-assembly approach can produce H2 gas with a rate of ∼155 ± 3.5 μmol h(-1) mg(-1) under visible-light irradiation (λ = 410 nm), the most exceptional performance of solar H2 evolution using MoS2 as a cocatalyst known to date.
April 21, 2017: Chemical Communications: Chem Comm
Zhongying Wang, Yin-Jia Zhang, Muchun Liu, Andrew Peterson, Robert H Hurt
This letter demonstrates a simple method to achieve high-yields of 1H semiconducting MoS2 monolayers in concentrated, colloidally-stable aqueous suspension. The method is based on oxidation suppression during the hydrothermal processing step used for metal-to-semiconductor phase reversion. Accompanying DFT calculations on elementary steps in the MoS2 wet oxidation reaction suggest that a two-site corrosion mechanism is responsible for the observed high reactivity and low stability of 1T metallic MoS2.
April 20, 2017: Nanoscale
Ashish Arora, Jonathan Noky, Matthias Drüppel, Bhakti Jariwala, Thorsten Deilmann, Robert Schneider, Robert Schmidt, Osvaldo Del Pozo-Zamudio, Torsten Stiehm, Arnab Bhattacharya, Peter Krüger, Steffen Michaelis de Vasconcellos, Michael Rohlfing, Rudolf Bratschitsch
Atomically thin materials such as graphene or MoS2 are of high in-plane symmetry. Crystals with reduced symmetry hold the promise for novel optoelectronic devices based on their anisotropy in current flow or light polarization. Here, we present polarization-resolved optical transmission and photoluminescence spectroscopy of excitons in 1T'-ReSe2. On reducing the crystal thickness from bulk to a monolayer, we observe a strong blue shift of the optical band gap from 1.37 to 1.50 eV. The excitons are strongly polarized with dipole vectors along different crystal directions, which persist from bulk down to monolayer thickness...
April 21, 2017: Nano Letters
Fangfang Cao, Enguo Ju, Yan Zhang, Zhenzhen Wang, Chaoqun Liu, Wei Li, Yanyan Huang, Kai Dong, Jinsong Ren, Xiaogang Qu
Silver nanoparticles (AgNPs) have been used as a broad-spectrum antimicrobial agent, whose toxicity originates from the localized release of Ag(+) ions. However, the residual AgNPs core could generate potential risk to humans and waste of noble metals. Herein, we infused the cysteine-modified molybdenum disulfide with minimum Ag(+) ions and coated with a layer of cationic polyelectrolyte to construct an efficient and benign antimicrobial depot. The system exhibited much enhanced broad-spectrum antibacterial activity compared with an equivalent amount of silver nitrate, owing to its increasing accessibility of released Ag(+) to the cell walls of microorganisms...
April 17, 2017: ACS Nano
H-Y He
The transition metal dichagenides and their metallic 1T structure are attracting contemporary attentions for applications in high-performance devices because their peculiar optical and electrical properties. The single and few layers 1T structure is generally obtained by mechanical or chemical exfoliation. This work presents facile one-step synthesis of 2H-1T MoS2:Cu/reduced graphene oxide nanosheets. The experiment results indicated that the MoS2 and MoS2:Cu prepared by simple chemical solution reaction possessed 2H-1T structures...
April 13, 2017: Scientific Reports
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