A5030207185- 2D Materials and Applications
- Graphene research and applications
- MXene and MAX Phase Materials
- Carbon Nanotubes in Composites
- Perovskite Materials and Applications
- Chalcogenide Semiconductor Thin Films
- Supercapacitor Materials and Fabrication
- Graphene and Nanomaterials Applications
- Molecular Junctions and Nanostructures
- Catalytic Processes in Materials Science
- Advancements in Battery Materials
- Electrocatalysts for Energy Conversion
- Advanced Photocatalysis Techniques
- Gas Sensing Nanomaterials and Sensors
- Advanced Thermoelectric Materials and Devices
- Advanced Condensed Matter Physics
- Boron and Carbon Nanomaterials Research
- Electrospun Nanofibers in Biomedical Applications
- ZnO doping and properties
- Diamond and Carbon-based Materials Research
- Quantum Dots Synthesis And Properties
- Organic and Molecular Conductors Research
- Advanced Fiber Laser Technologies
- Catalysis and Hydrodesulfurization Studies
- Plasmonic and Surface Plasmon Research
Binghamton University
2020-2024
Charles University
2024
Pennsylvania State University
2012-2021
Park University
2020
Shinshu University
2005-2013
Center for NanoScience
2009-2010
Rice University
2010
Institute for Scientific and Technological Research
2006-2009
Arizona State University
2005-2006
Universidad Nacional Autónoma de México
2006
Individual monolayers of metal dichalcogenides are atomically thin two-dimensional crystals with attractive physical properties different from those their bulk counterparts. Here we describe the direct synthesis WS2 triangular morphologies and strong room-temperature photoluminescence (PL). The Raman response as well luminescence a function number S–W–S layers is also reported. PL weakens increasing due to transition band gap in monolayer indirect multilayers. edges exhibit signals...
The Raman scattering of single- and few-layered WS2 is studied as a function the number S-W-S layers excitation wavelength in visible range (488, 514 647 nm). For three wavelengths used this study, frequency A1g(Γ) phonon mode monotonically decreases with layers. single-layer WS2, 514.5 nm laser generates second-order resonance involving longitudinal acoustic (LA(M)). This results from coupling between electronic band structure lattice vibrations. First-principles calculations were to...
Graphene is a two-dimensional network in which sp(2)-hybridized carbon atoms are arranged two different triangular sub-lattices (A and B). By incorporating nitrogen into graphene, its physico-chemical properties could be significantly altered depending on the doping configuration within sub-lattices. Here, we describe synthesis of large-area, highly-crystalline monolayer N-doped graphene (NG) sheets via atmospheric-pressure chemical vapor deposition, yielding unique N-doping site composed...
Abstract Few‐layered films of WS 2 , synthesized by chemical vapor deposition on quartz, are successfully used as light sensors. The film samples structurally characterized Raman spectroscopy, atomic force microscopy, scanning electron and high‐resolution transmission microscopy. produced consist few layered sheets possessing up to 10 layers. UV–visible absorbance spectra reveals absorption peaks at energies 1.95 2.33 eV, consistent with the A B excitons characteristic . Current–voltage ( I...
The isolation of few-layered transition metal dichalcogenides has mainly been performed by mechanical and chemical exfoliation with very low yields. In this account, a controlled thermal reduction-sulfurization method is used to synthesize large-area (~1 cm(2)) WS2 sheets thicknesses ranging from monolayers few layers. During synthesis, WOx thin films are first deposited on Si/SiO2 substrates, which then sulfurized (under vacuum) at high temperatures (750-950 °C). An efficient route transfer...
It is a challenge to fabricate graphene bulk materials with properties arising from the nature of individual sheets, and which assemble into monolithic three-dimensional structures. Here we report scalable self-assembly randomly oriented sheets additive-free, essentially homogenous sponge that provide combination both cork-like rubber-like properties. These sponges, densities similar air, display Poisson's ratios in all directions are near-zero largely strain-independent during reversible...
Ternary two-dimensional dichalcogenide alloys exhibit compositionally modulated electronic structure, and hence, control of dopant concentration within each individual layer these compounds provides a powerful tool to efficiently modify their physical chemical properties. The main challenge arises when quantifying locating the atoms in order better understand fine-tune desired Here we report synthesis molybdenum disulfide substitutionally doped with broad range selenium concentrations,...
Although the main Raman features of semiconducting transition metal dichalcogenides are well known for monolayer and bulk, there important differences exhibited by few layered systems which have not been fully addressed. WSe2 samples were synthesized ab-initio calculations carried out. We calculated phonon dispersions Raman-active modes in systems: WSe2, MoSe2, WS2 MoS2 ranging from monolayers to five-layers bulk. First, we confirmed that as number layers increase, E′, E″ E2g shift lower...
In this report, we compare the toxicological effects between pure carbon multiwalled nanotubes (MWNTs) and N-doped (CNx) nanotubes. Different doses of tubes were administered in various ways to mice: nasal, oral, intratracheal, intraperitoneal. We have found that when MWNTs injected into mice's trachea, mice could die by dyspnea depending on doses. However, CNx never caused death any mouse. always far more tolerated compared MWNTs. Extremely high concentrations administrated directly trachea...
We report the use of transition metal nanoparticles (Ni or Co) to longitudinally cut open multiwalled carbon nanotubes in order create graphitic nanoribbons. The process consists catalytic hydrogenation carbon, which particles sp2 hybridized atoms along that results liberation hydrocarbon species. Observations reveal presence unzipped were by nanoparticles. also partially nanotubes, have been predicted novel magnetoresistance properties.1 nanoribbons produced are typically 15−40 nm wide and...
We investigate Second Harmonic Generation (SHG) in monolayer WS₂ both deposited on a SiO₂/Si substrate or suspended using transmission electron microscopy grids. find unusually large second order nonlinear susceptibility, with an estimated value of d(eff) ~ 4.5 nm/V nearly three orders magnitude larger than other common crystals. In to quantitatively characterize the susceptibility two-dimensional (2D) materials, we have developed formalism model SHG based Green's function 2D sheet source....
Defects play a significant role in tailoring the optical properties of two-dimensional materials. Optical signatures defect-bound excitons are important tools to probe defective regions and thus interrogate quality as-grown semiconducting monolayer We have performed systematic study using photoluminescence (PL) spectroscopy combined with atomically resolved scanning electron microscopy first-principles calculations. Spatially PL at low temperatures revealed bound that were present only on...
Resonant Raman spectroscopy (RRS) is a very useful tool to study physical properties of materials since it provides information about excitons and their coupling with phonons. We present in this work RRS samples WSe2 one, two, three layers (1L, 2L, 3L), as well bulk 2H-WSe2, using up 20 different laser lines covering the visible range. The first- second-order features exhibit resonant behavior, agreement double (and triple) resonance mechanism(s). From energy dependence intensities (Raman...
We report the fabrication of a photosensor based on as-grown single crystal monolayers MoS2 synthesized by chemical vapor deposition (CVD). The measurements were performed using Au/Ti leads in two terminal configuration CVD-grown SiO2/Si substrate. device was operated air at room temperature low bias voltages ranging from −2 V to 2 and its sensing capabilities tested for different excitation wavelengths (514.5 nm 488 nm). responsivity reached 1.1 mA W−1 when excited with 514.5 laser 1.5 V....
The recent interest and excitement in graphene has also opened up a pandora's box of other two-dimensional (2D) materials material combinations which are now beginning to come the fore. One family these emerging 2D is transition metal dichalcogenides (TMDs). So far there very limited understanding on wetting behavior "monolayer" TMD materials. In this study, we synthesized large-area, continuous monolayer tungsten disulfide (WS2) molybdenum (MoS2) films SiO2/Si substrates by thermal...
Significance The gas-sensing performance of graphene could be remarkably enhanced by incorporating dopants into its lattice based on theoretical calculations. However, to date, experimental progress boron-doped (BG) is still very scarce. Here, we achieved the controlled growth large-area, high-crystallinity BG sheets and shed light their electronic features associated with boron at atomic scale. As a proof-of-concept, it demonstrated that doping in lead much sensitivity when detecting toxic...
N-doped graphene can be used as a substrate for different molecules to effectively enhance their Raman scattering signal.
Graphene oxide (GO) has recently become an attractive building block for fabricating graphene-based functional materials. GO films and fibers have been prepared mainly by vacuum filtration wet spinning. These materials exhibit relatively high Young's moduli but low toughness a tendency to tear or break. Here, we report alternative method, using bar coating drying of water/GO dispersions, preparing large-area thin (e.g., 800-1200 cm(2) larger) with outstanding mechanical behavior excellent...
Doping lies at the heart of modern semiconductor technologies. Therefore, for two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs), significance controlled doping is no exception. Recent studies have indicated that, by substitutionally 2D TMDs with a judicious selection dopants, their electrical, optical, magnetic, and catalytic properties can be effectively tuned, endowing them great potential various practical applications. Herein, inspired sol-gel process, we report...
Large-area (∼cm2) films of vertical heterostructures formed by alternating graphene and transition-metal dichalcogenide (TMD) alloys are obtained wet chemical routes followed a thermal treatment at low temperature. In particular, we synthesized stacked WxMo1-xS2 alloy phases that were used as hydrogen evolution catalysts. We observed Tafel slope 38.7 mV dec-1 96 onset potential (at current density 10 mA cm-2) when the heterostructure was annealed 300 °C. These results indicate W0.4Mo0.6S2...
We describe the synthesis of novel monocrystalline FeCo nanowires encapsulated inside multiwalled carbon nanotubes (MWNTs). These exhibit homogeneous Fe and Co concentrations do not contain an external oxide layer due to presence insulating nanotube layers. The method involves aerosol thermolysis toluene-ferrocene-cobaltocene solutions in inert atmospheres. materials have been carefully characterized using state-of-the-art high-resolution transmission electron microscopy (HRTEM),...
Cutting graphene by a catalytic hydrogenation process can generate pieces with smooth edges of atomic precision and well-defined shapes. Controlled cutting creating step oxidation or plasma etching is demonstrated. A combination cutting, transfer, lithography shown to allow the fabrication isolated devices specific edge shape control. Detailed facts importance specialist readers are published as "Supporting Information". Such documents peer-reviewed, but not copy-edited typeset. They made...