bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphological Varied and Scalable MoS2 for Electrochemical Energy Storage Devices
Authors: Patel Mumukshu D. , Cha Eunho , Choudhary Nitin , Kang Chiwon , Choi Wonbong 
Published: February 2020

A versatile non-graphene 2D material (MoS2) has recently attracted great research attention owing to their novel structure-property relation for high performance energy storage devices. The unique hexagonal layered family of transition metal dichalcogenides (TMDs-MX2) composed of X-M-X layers; are stacked together by van der Waals bonding. Different fabrication methods including mechanical/chemical exfoliation, chemical vapor deposition, co-evaporation, and hydrothermal reactions have been employed to fabricate different thickness of MoS2. However, there is continuous pursuit to explore various novel methods for uniform and large-scale synthesis of MoS2 on different substrate. Here in, we present two different applications of MoS2for electrochemical energy storage devices:
Firstly, MoS2 nanomaterials are very efficient supercapacitor electrode due to its sheet like structure providing high surface area for double layer charge storage and exhibits multiple oxidation states for pseudo capacitive charge transfer due to intercalation of H+ and Li+ into MoS2 structure. We have synthesized large scale and flexible MoS2 electrodes just by using direct magnetron sputtering technique. The novel three-dimensional (3D) porous structure of the MoS2 on copper film exhibits an excellent capacitance of 330 F /cm3 along with a high volumetric power and energy density of 40–80 W/cm3 and 1.6–2.4 mWh/cm3, respectively. Additionally, it shows excellent cycling stability upto 5000 cycles with capacitance retention of 97%.
Secondly,a unique binder-free electrode of 3-dimensional carbon nanotubes (3D CNTs) coated by MoS2 has been fabricated by a chemical vapor deposition (CVD) and direct magnetron sputtering method. The unique vertically oriented nanoflakes of MoS2 are strongly bonded on 3D CNTs with diameter of 50-100nm. The 3D geometry for the accommodation of active material (MoS2) provides high surface area with active electrochemical sites, enhances ion diffusivity, and compensates volumetric expansion of MoS2. The electrochemical performance of the binder-free 3D CNTs-MoS2 electrode shows very high areal capacity of ~1.65mAh/cm2 with an areal density (of MoS2) of ~0.35mg/cm2 at 0.5C rate; it also shows capacity retention of ~82% after 50 cycles. The unique architecture of 3D CNTs-MoS2 is suggestive to be a promising anode for next generation Li-ion batteries with high capacity and long cycle life.

References:

(a) N. Choudhary+, M. Patel+ (+ First Authors), Y.H. Ho, N.B. Dahotre, W.Lee, J.Y. Hwang, W.Choi, Directly deposited MoS2 thin film electrodes for high performance supercapacitors, J. Mater. Chem. A 3 (2015) 24049-24054
(b) M.D. Patel, E. cha, N. Choudhary, C. Kang, W. Lee, J. Hwang, W. Choi, Vertically oriented MoS2 nanoflakes coated on 3D carbon nanotubes for next generation Li-ion batteries, Nanotechnology 27 (2016) 495401-495410
Modulation of the Electrostatic and Quantum Capacitances of Few Layered Graphenes through Plasma Processing
Authors: Bandaru Prabhakar R , Narayanan Rajaram , Yamada Hidenori , Rao Apparao M. , Podila Ramakrishna , Karakaya Mehmet 
Published: February 2020

A comprehensive understanding of the characteristics of graphene, with regard to its unique electrical and structural attributes, would be incomplete unless the inevitable presence of defects have been considered. While such imperfections may limit the realization of theoretically predicted characteristics, they may also be vital for uncovering new fundamental phenomena and related applications. Here we show that the charged defect generation, through argon ion based plasma processing, in few layer graphene (FLG) could be integral to the substantial enhancement of the electrical capacitance, and be of potential use in electrochemical (EC) energy storage. By combining EC characterization techniques with detailed Raman spectroscopic analysis, we elucidate the contributions of plasma-induced defects to electrostatic and quantum capacitance.
We then show that charged defect generation, through argon ion based plasma processing, in FLG could substantially enhance the electrical capacitance, and could be used for electrochemical energy storage. Detailed consideration of the constituent space charge and quantum capacitances were used to delineate a new length scale, correlated to electrically active defects contributing to the capacitance, and which was found to be smaller than a structural correlation length determined through Raman spectroscopy. The study offers insights into an industrially viable method (i.e., plasma processing) for modifying and enhancing the energy density of graphene-based electrochemical capacitors.
Metallic Phase MoS2-Graphene Composite for High Performance Coin Cells Supercapacitors
Authors: Aynalem Andinet Ejigu , Dryfe Robert AW , Kinloch Ian A 
Published: February 2020

Molybdenum disulphide exhibits two possible crystal states, the naturally occurring semiconducting phase (2H-MoS2), and the non-naturally occurring metallic state (1T-MoS2) which can be prepared by intercalation chemistry.1 The metallic 1T phase has a conductivity up to 107 times higher than the 2H phase.2 Consequently, metallic phase MoS2 nanosheets are very attractive for a number of electrochemical applications including supercapacitor electrodes and catalysts for hydrogen evolution.2
,
3 For example, Acerce et al. recently demonstrated that the gravimetric capacitance of chemically exfoliated 1T-MoS2 was 20 times higher than the gravimetric capacitance of the 2H-MoS2.2

In this work, we compare the capacitive behaviour of 1T-MoS2, 2H-MoS2, graphene and 1T-MoS2/graphene composite using symmetrical coin cell architecture. The electrodes were prepared by filtering a known volume of the respective dispersion over pre-weighed polyvinylidene fluoride membrane using syringe pump dispenser. The gravimetric capacitance of 1T-MoS2 was over 100 F g-1 in aqueous solution which is higher than the gravimetric capacitance obtained using 2H-MoS2 or graphene electrodes. The capacitance performance of 1T-MoS2 was further enhanced by making a composite electrode with highly conducting graphene. A volumetric capacitance of over 560 F cm-3 in an aqueous solution and 250 F cm-3 in a non-aqueous solution were achieved using these composite electrodes. The composite electrode displayed capacity retention of over 90 % after 5,000 cycles. The enhanced capacitance in the composite material was probably due to a synergistic effect between 1T-MoS2 and graphene where graphene enhances the overall conductivity of the composite whilst also reducing the re-aggregation of the sheets.
1. M. A. Py and R. R. Haering, Can. J. Phys., 1983, 61, 76-84.
2. M. Acerce, D. Voiry and M. Chhowalla, Nat. Nanotechnol., 2015, 10, 313-318.
3. M. A. Lukowski, A. S. Daniel, F. Meng, A. Forticaux, L. S. Li and S. Jin, J. Am. Chem. Soc., 2013, 135, 10274-10277.
Investigating Properties of Graphene Oxide As a Drug Delivery/Imaging Platform
Authors: Sizemore Elizabeth , Hasan Md Tanvir , Culp Marais , Naumov Anton V 
Published: February 2020

Graphene and its derivatives are novel materials with a number of unique properties that can be applied in electronics, sensing and biotechnology. Particularly, graphene oxide (GO) is an exceptional system that, unlike graphene, can be chemically mass-produced at low cost and possesses physical properties that are critical for biomedical applications. GO exhibits pH-dependent fluorescence emission in the visible/near-infrared, providing a possibility of molecular imaging and pH-sensing. It is also water soluble and has a substantial platform for functionalization, which allows for the delivery of multiple therapeutics, or the attachment of different sensing moieties. Some of these properties can be adjusted by the means of chemical/physical processing to fit the desired therapeutic delivery or sensing approaches. We utilize and modify these properties to yield a multifunctional delivery/imaging/sensing platform geared toward the analysis of cancer therapeutics delivery in vitro. In our work GO serves as a drug transport agent when paired with cancer therapeutic drugs and as a molecular marker for imaging the delivery pathways. The optimal emission and excitation of the graphene oxide flakes are selected to maximize the imaging modality in the spectrally-confined region and reduce the effects of biological autofluorescence. We also modify GO physical properties via controlled oxidation to maximize the emission and reduce the cytotoxicity to low/negligible levels: we report over 90% cell viability with GO concentration levels of 15 ug/mL based on the MTT assay in HEK-293 cells. GO emission in healthy (HEK-293) and cancer (HeLa) cells is quantified for a variety of pH environments, as well as flake sizes, to identify the ideal conditions for cellular internalization and pH-sensing of acidic cancerous environments. In addition, in-vitro fluorescence microscopy analysis provide quantitative assessment of the drug delivery and preferential targeting for cancer versus healthy cells. The results of this work suggest GO as an innovative and effective multifunctional platform for cancer therapeutics.
Heterostructures Beyond Van Der Waals
Authors: Perez Emilio M 
Published: February 2020

One of the most attractive areas of research in Nanoscience is the combination of 2D materials through van der Waals forces heterostructures.1 Here, we present strategies beyond dispersion forces to interface 0D-2D and 2D-2D materials.
We will show examples of 0D-2D heterostructures connected through covalent and noncovalent chemistry. In the first example, we will show a method to functionalize graphene covalently with exquisite (>98%) atomic selectivity.2 In the second example, we will show that the photoresponse of MoS2 photodetectors can be enhanced by simple and reversible supramolecular functionalization with organic dyes.3 Finally, we will also the unique example of franckeite, a naturally occuring van der Waals heterostructure that can be thinned down to very few layers, both mechanically and through liquid-phase exfoliation.4

References:
(1) Novoselov, K. S.; Mishchenko, A.; Carvalho, A.; Castro Neto, A. H. Science
2016, 353, DOI: 10.1126/science.aac9439
(2) Navarro, J. J.; Leret, S.; Calleja, F.; Stradi, D.; Black, A.; Bernardo-Gavito, R.; Garnica, M.; Granados, D.; Vazquez de Parga, A. L.; Pérez, E. M.; Miranda, R. Nano Lett.
2016, 16, 355.
(3) Molina-Mendoza, A. J.; Vaquero-Garzon, L.; Leret, S.; de Juan-Fernandez, L.; Pérez, E. M.; Castellanos-Gomez, A. Chem. Commun.
2016, 52, 14365.
(4) Molina-Mendoza, A. J.; Giovanelli, E.; Paz, W. S.; Nino, M. A.; Island, J. O.; Evangeli, C.; Aballe, L.; Foerster, M.; Van der Zant, H. S. J.; Rubio-Bollinger, G.; Agrait, N.; Palacios, J. J.; Perez, E. M.; Castellanos-Gomez, A. 2016, arXiv:1606.06651 (final version accepted in Nature Comms.)
A Wafer-Scale Bernal Stacked Bilayer Graphene Film Obtained on a Cu(0.5 %at Ni) Foil Using Atmpspheric Pressure Vapour Deposition
Authors: Manyala Ncholu , Madito Jack 
Published: February 2020

Graphene has attracted wide interest due to its promising potential applications in electronics and photonics. However, many of these applications are restricted by zero band gap of graphene. Nonetheless, a considerable band gap of up to 250 meV can be opened up in Bernal (AB) stacked bilayer graphene by applying a perpendicular electric field between the two superimposed layers. Hence, graphene synthesis has been focused on growing high-quality and large-area AB-stacked bilayer graphene. Chemical vapour deposition (CVD) is a favourable synthesis technique for graphene since it can grow high-quality and large-area or wafer-scale graphene, which is important for electronic devices. In addition, atmospheric-pressure CVD is technologically more accessible for graphene growth. The metallic substrate like Cu which mostly used for CVD grown graphene is found to be favouring to grow monolayer graphene because of limitation of C arbsorption in Cu, while Cu substrate engineered with Ni is found to grow multilayer graphene because of significant arbsorption of C in Ni and hence if it well controlled it can grow AB stacked graphene.
In this study we focuse on the AP-CVD synthesis and characterization of high-quality and wafer-scale (scale of an entire foil) AB-stacked bilayer graphene film obtained on a dilute Cu(0.61 at% Ni) foil and compared the growth to the results of AP-CVD growth under identical conditions on pure Cu foil. Atomic force microscopy (AFM) average step height analysis showed thickness of bilayer graphene, scanning electron microscopy (SEM) micrographs showed uniform and continuous graphene layers and the Raman optical microscopy images and spectroscopy data supported by selected area electron diffraction (SAED) data showed high-quality and continuous (wafer-scale) AB-stacked bilayer graphene for graphene film obtained on a dilute Cu(0.5 at% Ni) foil.
In Situ variable-Temperature Scanning Tunneling Microscopy Studies of 2D Graphene and Hexagonal Boron Nitride (hBN) Layer Growth Kinetic
Authors: Kodambaka Suneel 
Published: February 2020

The rich physical phenomena and properties associated with two-dimensional (2D) graphene layers have led to a surge in research efforts focused on synthesis, characterization, and, even large-scale production of a variety of 2D crystals. In the newly emergent class of 2D layered materials (and devices), some of the highly exciting developments are a result of leveraging the properties of individual layers via stacking of dissimilar 2D materials held together by van der Waals (vdW) forces. Such vdW-layers exhibit new properties (e.g., valleytronics) and are ideal for ultrathin flexible devices.
Graphene is semi-metallic, while its insulating 2D layered analog is hexagonal boron nitride (hBN). Graphene and hBN are isostructural and nearly lattice matched. Composite, lateral, and vertical heterostructures of graphene and hBN layers are expected to exhibit new physical phenomena and properties: tunable bandgap, magnetism, unique electronic and thermal transport properties, robust half-metallic behavior without applied electric fields, and more. Access to such new properties and hence novel applications, hinge on the ability to assemble the 2D materials in desired architecture. This requires fundamental understanding of the mechanisms governing the formation of epitaxial stacks of desired stacking sequences and layer thicknesses, atomically-abrupt graphene-hBN interfaces and domain widths within a single atomic layer, and desired composition within a 2D sheet. As a first step toward this goal, we investigated the chemical vapor deposition (CVD) kinetics of monolayer graphene and hBN on Pd(111) using ultra-high vacuum (UHV) variable-temperature scanning tunneling microscopy (VT-STM).
In this talk, we present in situ VT-STM observations of graphene growth using ethylene and hBN growth using borazine on Pd(111) as a function of substrate temperature, borazine flux, and deposition time. We observe the formation of monolayer graphene islands bounded by Pd surface steps. Using scanning tunneling spectroscopy (STS) measurements along with density functional theory (DFT) calculations, we show that graphene/Pd(111) exhibits a bandgap due to the strong interaction between graphene and the Pd substrate. During the CVD of borazine, we observe the nucleation and growth of chemisorbed borazine islands on Pd(111). Using STS, we determined the effect of hBN domain orientation with respect to Pd(111) on its bandgap. From the STM experiments, we identified the growth parameters critical to the formation of single-domain hBN layers on Pd(111). Our studies, which provide new insights into the growth of graphene and hBN monolayers, are useful in developing recipes for the growth of heterostructures of desired architecture.
(Invited) Black Phosphorus Field Effect Transistors: Passivation By Oxidation, and the Role of Anisotropy in Magnetotransport
Authors: Szkopek Thomas , Gervais Guillaume , Peruzzini Maurizio , Heun Stefan 
Published: February 2020

Black phosphorus (bP) is an elemental allotrope with an anisotropic layered crystal structure consisting of a puckered honeycomb lattice that can be mechanically exfoliated down to atomic layer thickness. bP is the most thermodynamically stable allotrope of phosphorus but is nonetheless subject to photo-­oxidation in the presence of water, oxygen and visible light with a reaction rate that increases as bP layer thickness decreases [1]. In the first part of my talk, I will describe our experiments showing how oxidation can be used for passivation of black phosphorus field effect transistors. In the second part of my talk, I will describe magnetotransport measurements of black phosphorus transistors and their relation to the anisotropy of the bP crystal lattice.
Motivated by the experimental observation that reactive ion etching produces a phosphorus oxide / black phosphorus interface that does not inhibit photo-luminescence yield [2], we have fabricated bP field effect transistors with an encapsulating phosphorus oxide layer that acts as a passivation layer. X-ray photoemission spectroscopy (XPS) reveals the oxide layer to have a P205 stoichiometry. Air stable, top gated bP field effect transistors with room temperature field effect mobilities exceeding 100 cm2/Vs are demonstrated using a gate oxide formed by reactive ion etching and subsequent atomic layer deposition of aluminum oxide.
We have also investigated the magnetotransport properties of black phosphorus at modest fields. Weak localization was observed in a black phosphorus field-effect transistor 65 nm thick [3]. The weak localization behavior was found to be in excellent agreement with the Hikami-Larkin-Nagaoka [4] model for fields up to 1 T, from which characteristic scattering lengths could be inferred. The temperature dependence of the phase coherence length L

ϕ

was investigated, and above 1 K, it was found to decrease weaker than the L

ϕ ~ T

−1/2 dependence characteristic of electron-electron scattering in the presence of elastic scattering in two dimensions. Rather, the observed power law was found to be close to that observed previously in quasi-one-dimensional systems such as metallic nanowires [5] and carbon nanotubes [6]. The potential role of strong in-plane anisotropy resulting from a puckered honyecomb structure on localization will be discussed.
[1] A. Favron et al., Nat. Mater. 14, 826 (2015).
[2] J. Pei et al., Nat. Comm. 7, 10450 (2016).
[3] N. Hemsworth et al., Phys. Rev. B 94, 245404 (2016).
[4] S. Hikami et al., Prog. Theor. Phys. 63, 707 (1980).
[5] D. Natelson et al., Phys. Rev. Lett. 86, 1821 (2001).
[6] J. Appenzeller et al., Phys. Rev. B 64, 121404(R) (2001).
Thickness Dependence of Graphene-Hexagonal Boron Nitride-Graphene Based 2D Capacitor
Authors: Stehle Yijing , Vlassiouk Ivan , Polyzos Georgios , Smirnov Sergie , Datskos Panos 
Published: February 2020

In this paper, a nanoscale dielectric capacitor was fabricated through wet transfer of CVD growth hexagonal boron nitride hBN as dielectric materials between monolayer graphene electrodes. The specific capacitance, power, and energy the capacitor with different hBN layer number were evaluated through cyclic voltammetry test. Different to traditional capacitor, whose capacitance decrease with dielectric layer distance once electrode is set, the capacitance of graphene-hBN-graphene based nanocapacitor increase with layer number before the thickness goes above 3nm at low scan rate (<50mv/s) due to the strong influence of interface quantum capacitance. The thickness-dependent stacked hBN thin film’ effective permittivity between graphene electrode was analyzed by impedance spectroscopy. we experimentally reveal that the permittivity of hBN thin film first increase then decrease with it layer number increase, which is also observed in other layered structure dielectric materials. The fabricated capacitor also shows promising transparency and flexibility.
(Invited) Plasmonic Enhancement of Single- and Multi-Electron Transfer Reactions on Modified Electrodes
Authors: Ikeda Katsuyoshi 
Published: February 2020

In a photo-energy conversion system, the efficiency of photon capture is one of key issues that determine the overall efficiency. Metal nanostructures are recently drawing attention due to their unique optical properties, which are known as localized surface plasmon resonance (LSPR). Since metal nanostructures can confine incoming photon energy into the nanoscale region through excitation of LSPR, they are expected to function as optical nano-antennas. Indeed, various optical processes such as Raman scattering or fluorescence can gain intensity from LSPR. Such plasmonic enhancement is theoretically well explained and various applications have been demonstrated. On the other hand, plasmonic enhancement of photochemical reactions is still under discussion because the efficiency of photochemical reactions is influenced by many factors. Moreover, kinetics of photochemical reactions may be much slower than the lifetime of LSPR; plasmonic effect is not straightforward in this case. We have reported that photo-induced uphill single-electron transfer reaction can be enhanced by forming plsmonic nano-antennas on top of porphyrin-linked molecular monolayers at an Au electrode. In this talk, plasmonic enhancement of multi-electron transfer reactions will also be discussed, which are governed by more complicated and slower kinetics.
Fig. local field enhancement near an Au nanoparticle deposited on molecular monolayer on an Au substrate

Figure 1