Search

Your search keyword '"Berner, Nina C."' showing total 100 results
Start Over Author "Berner, Nina C."
100 results on '"Berner, Nina C."'

1. High-performance hybrid electronic devices from layered PtSe2 films grown at low temperature

Author

Yim, Chanyoung, Lee, Kangho, McEvoy, Niall, Brien, Maria O, Riazimehr, Sarah, Berner, Nina C., Cullen, Conor P., Kotakoski, Jani, Meyer, Jannik C., Lemme, Max C., and Duesberg, Georg S.

Subjects
Condensed Matter - Materials Science
Abstract

Layered two-dimensional (2D) materials display great potential for a range of applications, particularly in electronics. We report the large-scale synthesis of thin films of platinum diselenide (PtSe2), a thus far scarcely investigated transition metal dichalcogenide. Importantly, the synthesis by thermal assisted conversion is performed at 400 {\deg}C, representing a breakthrough for the direct integration of this novel material with silicon (Si) technology. Besides the thorough characterization of this new 2D material, we demonstrate its promise for applications in high-performance gas sensing with extremely short response and recovery times observed due to the 2D nature of the films. Furthermore, we realized vertically-stacked heterostructures of PtSe2 on Si which act as both photodiodes and photovoltaic cells. Thus this study establishes PtSe2 as a potential candidate for next-generation sensors and (opto-)electronic devices, using fabrication protocols compatible with established Si technologies.

Published
2016
Full Text
View/download PDF

2. Raman Characterization of Platinum Diselenide Thin Films

Author

O'Brien, Maria, McEvoy, Niall, Motta, Carlo, Zheng, Jian-Yao, Berner, Nina C., Kotakoski, Jani, Elibol, Kenan, Pennycook, Timothy J., Meyer, Jannik C., Yim, Chanyoung, Abid, Mohamed, Hallam, Toby, Donegan, John F., Sanvito, Stefano, and Duesberg, Georg S.

Subjects
Condensed Matter - Materials Science
Abstract

Platinum diselenide (PtSe2) is a newly discovered 2D material which is of great interest for applications in electronics and catalysis. PtSe2 films were synthesized by thermally-assisted selenization of predeposited platinum films and scanning transmission electron microscopy revealed the crystal structure of these films to be 1T. Raman scattering of these films was studied as a function of film thickness, laser wavelength and laser polarization. Eg and A1g Raman active modes were identified using polarization measurements in the Raman setup. These modes were found to display a clear position and intensity dependence with film thickness, for multiple excitation wavelengths, and their peak positions agree with simulated phonon dispersion curves for PtSe2. These results highlight the practicality of using Raman spectroscopy as a prime characterization technique for newly-synthesized 2D materials.

Published
2015
Full Text
View/download PDF

3. Understanding and optimising the packing density of perylene bisimide layers on CVD-grown graphene

Author

Berner, Nina C., Winters, Sinéad, Backes, Claudia, Yim, Chanyoung, Dümbgen, Kim C., Kaminska, Izabela, Mackowski, Sebastian, Cafolla, Attilio A., Hirsch, Andreas, and Duesberg, Georg S.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

The non-covalent functionalisation of graphene is an attractive strategy to alter the surface chemistry of graphene without damaging its superior electrical and mechanical properties. Using the facile method of aqueous-phase functionalisation on large-scale CVD-grown graphene, we investigated the formation of different packing densities in self-assembled monolayers (SAMs) of perylene bisimide derivatives and related this to the amount of substrate contamination. We were able to directly observe wet-chemically deposited SAMs in scanning tunnelling microscopy (STM) on transferred CVD graphene and revealed that the densely packed perylene ad-layers adsorb with the conjugated {\pi}-system of the core perpendicular to the graphene substrate. This elucidation of the non-covalent functionalisation of graphene has major implications on controlling its surface chemistry and opens new pathways for adaptable functionalisation in ambient conditions and on the large scale., Comment: 27 pages (including SI), 10 figures

Published
2015
Full Text
View/download PDF

4. Intermolecular dehalogenation reactions on passivated germanium(001)

Author

Berner, Nina C., Sergeeva, Yulia N., Sergeeva, Natalia N., Senge, Mathias O., Cafolla, Attilio A., and McGovern, Ignatius T.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

We present results of experiments to reproduce the bottom-up formation of covalently bonded molecular nanostructures from single molecular building blocks, previously demonstrated on various coinage metal surfaces, on a technologically more relevant semiconductor surface: Ge(001). Chlorine was established as the most stable passivation agent for this surface, successfully enabling diffusion of the organic molecular building blocks. Subsequent thermal activation of the intermolecular dehalogenation reactions on this surface resulted in the desired covalently connected molecules, however showing poor network quality when compared to those formed on noble metal substrates., Comment: 17 pages, 5 figures (including TOC graphic)

Published
2015

5. Direct Observationof DegenerateTwo-Photon Absorption and Its Saturation in WS2 and MoS2 Monolayer and Few-Layer Films

Author

Zhang, Saifeng, Dong, Ningning, McEvoy, Niall, O'Brien, Maria, Winters, Sinéad, Berner, Nina C., Yim, Chanyoung, Li, Yuanxin, Zhang, Xiaoyan, Chen, Zhanghai, Zhang, Long, Duesberg, Georg S., and Wang, Jun

Subjects
Physics - Optics, Condensed Matter - Materials Science
Abstract

The optical nonlinearity of WS2, MoS2 monolayer and few-layer films was investigated using the Z-scan technique with femtosecond pulses from the visible to the near infrared. The dependence of nonlinear absorption of the WS2 and MoS2 films on layer number and excitation wavelength was studied systematically. WS2 with 1~3 layers exhibits a giant two-photon absorption (TPA) coefficient. Saturation of TPA for WS2 with 1~3 layers and MoS2 with 25~27 layers was observed. The giant nonlinearity of WS2 and MoS2 is attributed to two dimensional confinement, a giant exciton effect and the band edge resonance of TPA.

Published
2015
Full Text
View/download PDF

6. Liquid exfoliation of solvent-stabilised black phosphorus: applications beyond electronics

Author

Hanlon, Damien, Backes, Claudia, Doherty, Evie, Cucinotta, Clotilde S., Berner, Nina C., Boland, Conor, Lee, Kangho, Lynch, Peter, Gholamvand, Zahra, Harvey, Andrew, Zhang, Saifeng, Wang, Kangpeng, Moynihan, Glenn, Pokle, Anuj, Ramasse, Quentin M., McEvoy, Niall, Blau, Werner J., Wang, Jun, Sanvito, Stefano, ORegan, David D., Duesberg, Georg S., Nicolosi, Valeria, and Coleman, Jonathan N.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Few layer black phosphorus is a new two-dimensional material which is of great interest for applications, mainly in electronics. However, its lack of stability severely limits our ability to synthesise and process this material. Here we demonstrate that high-quality, few-layer black phosphorus nanosheets can be produced in large quantities by liquid phase exfoliation in the solvent N-cyclohexyl-2-pyrrolidone (CHP). We can control nanosheet dimensions and have developed metrics to estimate both nanosheet size and thickness spectroscopically. When exfoliated in CHP, the nanosheets are remarkably stable unless water is intentionally introduced. Computational studies show the degradation to occur by reaction with water molecules only at the nanosheet edge, leading to the removal of phosphorus atoms and the formation of phosphine and phosphorous acid. We demonstrate that liquid exfoliated black phosphorus nanosheets are potentially useful in a range of applications from optical switches to gas sensors to fillers for composite reinforcement., Comment: 6 figures

Published
2015
Full Text
View/download PDF

14. Enabling Flexible Heterostructures for Li‐Ion Battery Anodes Based on Nanotube and Liquid‐Phase Exfoliated 2D Gallium Chalcogenide Nanosheet Colloidal Solutions

Author

Zhang, Chuanfang (John), primary, Park, Sang‐Hoon, additional, Ronan, Oskar, additional, Harvey, Andrew, additional, Seral‐Ascaso, Andrés, additional, Lin, Zifeng, additional, McEvoy, Niall, additional, Boland, Conor S., additional, Berner, Nina C., additional, Duesberg, Georg S., additional, Rozier, Patrick, additional, Coleman, Jonathan N., additional, and Nicolosi, Valeria, additional

Published
2017
Full Text
View/download PDF

17. Raman characterization of platinum diselenide thin films

Author

O’Brien, Maria, primary, McEvoy, Niall, additional, Motta, Carlo, additional, Zheng, Jian-Yao, additional, Berner, Nina C, additional, Kotakoski, Jani, additional, Elibol, Kenan, additional, Pennycook, Timothy J, additional, Meyer, Jannik C, additional, Yim, Chanyoung, additional, Abid, Mohamed, additional, Hallam, Toby, additional, Donegan, John F, additional, Sanvito, Stefano, additional, and Duesberg, Georg S, additional

Published
2016
Full Text
View/download PDF

20. A Commercial Conducting Polymer as Both Binder and Conductive Additive for Silicon Nanoparticle-Based Lithium-Ion Battery Negative Electrodes

Author

Higgins, Thomas M., primary, Park, Sang-Hoon, additional, King, Paul J., additional, Zhang, Chuanfang (John), additional, McEvoy, Niall, additional, Berner, Nina C., additional, Daly, Dermot, additional, Shmeliov, Aleksey, additional, Khan, Umar, additional, Duesberg, Georg, additional, Nicolosi, Valeria, additional, and Coleman, Jonathan N., additional

Published
2016
Full Text
View/download PDF

21. Comparison of liquid exfoliated transition metal dichalcogenides reveals MoSe2to be the most effective hydrogen evolution catalyst

Author

Gholamvand, Zahra, primary, McAteer, David, additional, Backes, Claudia, additional, McEvoy, Niall, additional, Harvey, Andrew, additional, Berner, Nina C., additional, Hanlon, Damien, additional, Bradley, Conor, additional, Godwin, Ian, additional, Rovetta, Aurlie, additional, Lyons, Michael E. G., additional, Duesberg, Georg S., additional, and Coleman, Jonathan N., additional

Published
2016
Full Text
View/download PDF

23. Production of Ni(OH)2nanosheets by liquid phase exfoliation: from optical properties to electrochemical applications

Author

Harvey, Andrew, primary, He, Xiaoyun, additional, Godwin, Ian J., additional, Backes, Claudia, additional, McAteer, David, additional, Berner, Nina C., additional, McEvoy, Niall, additional, Ferguson, Auren, additional, Shmeliov, Aleksey, additional, Lyons, Michael E. G., additional, Nicolosi, Valeria, additional, Duesberg, Georg S., additional, Donegan, John F., additional, and Coleman, Jonathan N., additional

Published
2016
Full Text
View/download PDF

24. Liquid exfoliation of solvent-stabilized few-layer black phosphorus for applications beyond electronics

Author

Hanlon, Damien, primary, Backes, Claudia, additional, Doherty, Evie, additional, Cucinotta, Clotilde S., additional, Berner, Nina C., additional, Boland, Conor, additional, Lee, Kangho, additional, Harvey, Andrew, additional, Lynch, Peter, additional, Gholamvand, Zahra, additional, Zhang, Saifeng, additional, Wang, Kangpeng, additional, Moynihan, Glenn, additional, Pokle, Anuj, additional, Ramasse, Quentin M., additional, McEvoy, Niall, additional, Blau, Werner J., additional, Wang, Jun, additional, Abellan, Gonzalo, additional, Hauke, Frank, additional, Hirsch, Andreas, additional, Sanvito, Stefano, additional, O’Regan, David D., additional, Duesberg, Georg S., additional, Nicolosi, Valeria, additional, and Coleman, Jonathan N., additional

Published
2015
Full Text
View/download PDF

26. Direct Observation of Degenerate Two-Photon Absorption and Its Saturation in WS2 and MoS2 Monolayer and Few-Layer Films

Author

Zhang, Saifeng, primary, Dong, Ningning, additional, McEvoy, Niall, additional, O’Brien, Maria, additional, Winters, Sinéad, additional, Berner, Nina C., additional, Yim, Chanyoung, additional, Li, Yuanxin, additional, Zhang, Xiaoyan, additional, Chen, Zhanghai, additional, Zhang, Long, additional, Duesberg, Georg S., additional, and Wang, Jun, additional

Published
2015
Full Text
View/download PDF

27. Basal-Plane Functionalization of Chemically Exfoliated Molybdenum Disulfide by Diazonium Salts

Author

Knirsch, Kathrin C., primary, Berner, Nina C., additional, Nerl, Hannah C., additional, Cucinotta, Clotilde S., additional, Gholamvand, Zahra, additional, McEvoy, Niall, additional, Wang, Zhenxing, additional, Abramovic, Irena, additional, Vecera, Philipp, additional, Halik, Marcus, additional, Sanvito, Stefano, additional, Duesberg, Georg S., additional, Nicolosi, Valeria, additional, Hauke, Frank, additional, Hirsch, Andreas, additional, Coleman, Jonathan N., additional, and Backes, Claudia, additional

Published
2015
Full Text
View/download PDF

28. Preparation of Gallium Sulfide Nanosheets by Liquid Exfoliation and Their Application As Hydrogen Evolution Catalysts

Author

Harvey, Andrew, primary, Backes, Claudia, additional, Gholamvand, Zahra, additional, Hanlon, Damien, additional, McAteer, David, additional, Nerl, Hannah C., additional, McGuire, Eva, additional, Seral-Ascaso, Andrés, additional, Ramasse, Quentin M., additional, McEvoy, Niall, additional, Winters, Sinéad, additional, Berner, Nina C., additional, McCloskey, David, additional, Donegan, John F., additional, Duesberg, Georg S., additional, Nicolosi, Valeria, additional, and Coleman, Jonathan N., additional

Published
2015
Full Text
View/download PDF

36. Edge and confinement effects allow in situ measurement of size and thickness of liquid-exfoliated nanosheets

Author

Backes, Claudia, primary, Smith, Ronan J., additional, McEvoy, Niall, additional, Berner, Nina C., additional, McCloskey, David, additional, Nerl, Hannah C., additional, O’Neill, Arlene, additional, King, Paul J., additional, Higgins, Tom, additional, Hanlon, Damien, additional, Scheuschner, Nils, additional, Maultzsch, Janina, additional, Houben, Lothar, additional, Duesberg, Georg S., additional, Donegan, John F., additional, Nicolosi, Valeria, additional, and Coleman, Jonathan N., additional

Published
2014
Full Text
View/download PDF

39. Production of Ni(OH)2 nanosheets by liquid phase exfoliation: from optical properties to electrochemical applications.

Author

Harvey, Andrew, He, Xiaoyun, Godwin, Ian J., Backes, Claudia, McAteer, David, Berner, Nina C., McEvoy, Niall, Ferguson, Auren, Shmeliov, Aleksey, Lyons, Michael E. G., Nicolosi, Valeria, Duesberg, Georg S., Donegan, John F., and Coleman, Jonathan N.

Abstract

Here we demonstrate that liquid phase exfoliation can be used to convert layered crystals of nickel hydroxide into Ni(OH)2 nanosheets in relatively large quantities and without the need for ion intercalation. While other procedures require harsh synthesis conditions and multiple reaction steps, this method involves ultrasonication of commercially available powders in aqueous surfactant solutions and so is relatively mild and potentially scalable. Such mild exfoliation is possible because the surface energy of Ni(OH)2, as measured by inverse gas chromatography, is relatively low at ∼70 mJ m−2, similar to other layered materials. TEM, AFM, XPS and Raman spectroscopy show the exfoliated nanosheets to be relatively thin (mean ∼10 monolayers thick) and of good quality. Size selection by liquid cascade centrifugation allowed the production of samples with mean nanosheet lengths ranging from 55 to 195 nm. Optical measurements on dispersions showed the optical absorption coefficient spectra to be relatively invariant with nanosheet size while the scattering coefficient spectra varied strongly with size. The resultant size-dependence allows the extinction spectra to be used to estimate nanosheet size as well as concentration. We used the exfoliated nanosheets to prepare thin film electrodes for use in supercapacitors and as oxygen evolution catalysts. While the resultant capacitance was reasonably high at ∼1200 F cm−3 (20 mV s−1), the catalytic performance was exceptional with currents of 10 mA cm−2 observed at overpotentials as low as 297 mV, close to the state of the art. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

40. Functionalization of Two-Dimensional MoS2: On the Reaction Between MoS2 and Organic Thiols.

Author

Chen, Xin, Berner, Nina C., Backes, Claudia, Duesberg, Georg S., and McDonald, Aidan R.

Subjects
*THIOLS, *TRANSITION metals, *CYSTEINE, *OXIDATION, *DISULFIDES
Abstract

Two-dimensional layered transition metal dichalcogenides (TMDs) have attracted great interest owing to their unique properties and a wide array of potential applications. However, due to their inert nature, pristine TMDs are very challenging to functionalize. We demonstrate a general route to functionalize exfoliated 2H-MoS2 with cysteine. Critically, MoS2 was found to be facilitating the oxidation of the thiol cysteine to the disulfide cystine during functionalization. The resulting cystine was physisorbed on MoS2 rather than coordinated as a thiol (cysteine) filling S-vacancies in the 2H-MoS2 surface, as originally conceived. These observations were found to be true for other organic thiols and indeed other TMDs. Our findings suggest that functionalization of two-dimensional MoS2 using organic thiols may not yield covalently or datively tethered functionalities, rather, in this instance, they yield physisorbed disulfides that are easily removed. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

42. A New 2H-2H′/1T Cophase in Polycrystalline MoS2and MoSe2Thin Films

Author

Naz, Mehwish, Hallam, Toby, Berner, Nina C., McEvoy, Niall, Gatensby, Riley, McManus, John B., Akhter, Zareen, and Duesberg, Georg S.

Abstract

We report on 2H-2H′/1T phase conversion of MoS2and MoSe2polycrystalline films grown by thermally assisted conversion. The structural conversion of the transition metal dichalcogenides was successfully carried out by organolithium treatment on chip. As a result we obtained a new 2H-2H′/1T cophase system of the TMDs thin films which was verified by Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The conversion was successfully carried out on selected areas yielding a lateral heterostructure between the pristine 2H phase and the 2H′/1T cophase regions. Scanning electron microscopy and atomic force microscopy revealed changes in the surface morphology and work function of the cophase system in comparison to the pristine films, with a surprisingly sharp lateral interface region.

Published
2016
Full Text
View/download PDF

43. High-Performance Hybrid Electronic Devices from Layered PtSe2Films Grown at Low Temperature

Author

Yim, Chanyoung, Lee, Kangho, McEvoy, Niall, O’Brien, Maria, Riazimehr, Sarah, Berner, Nina C., Cullen, Conor P., Kotakoski, Jani, Meyer, Jannik C., Lemme, Max C., and Duesberg, Georg S.

Abstract

Layered two-dimensional (2D) materials display great potential for a range of applications, particularly in electronics. We report the large-scale synthesis of thin films of platinum diselenide (PtSe2), a thus far scarcely investigated transition metal dichalcogenide. Importantly, the synthesis by thermally assisted conversion is performed at 400 °C, representing a breakthrough for the direct integration of this material with silicon (Si) technology. Besides the thorough characterization of this 2D material, we demonstrate its promise for applications in high-performance gas sensing with extremely short response and recovery times observed due to the 2D nature of the films. Furthermore, we realized vertically stacked heterostructures of PtSe2on Si which act as both photodiodes and photovoltaic cells. Thus, this study establishes PtSe2as a potential candidate for next-generation sensors and (opto-)electronic devices, using fabrication protocols compatible with established Si technologies.

Published
2016
Full Text
View/download PDF

44. Functionalization of Liquid-Exfoliated Two-Dimensional 2H-MoS2.

Author

Backes, Claudia, Berner, Nina C., Xin Chen, Lafargue, Paul, LaPlace, Pierre, Freeley, Mark, Duesberg, Georg S., Coleman, Jonathan N., and McDonald, Aidan R.

Subjects
*TRANSITION metals, *OPTOELECTRONICS, *FOURIER transform infrared spectroscopy, *THERMOGRAVIMETRY, *SOLVENTS
Abstract

Layered two-dimensional (2D) inorganic transition-metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS2. We found that the reaction of liquid-exfoliated 2D MoS2, with M(OAc)2 salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS2-M(OAc)2 materials. Importantly, this method furnished the 2H-polytype of MoS2 which is a semiconductor. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT-IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS2 surface sulfur atoms to the M(OAc)2 salt. Interestingly, functionalization of 2H-MoS2 allows for its dispersion/processing in more conventional laboratory solvents. [ABSTRACT FROM AUTHOR]

Published
2015
Full Text
View/download PDF

45. Functionalization of Liquid-Exfoliated Two-Dimensional 2H-MoS2.

Author

Backes, Claudia, Berner, Nina C., Xin Chen, Lafargue, Paul, LaPlace, Pierre, Freeley, Mark, Duesberg, Georg S., Coleman, Jonathan N., and McDonald, Aidan R.

Subjects
*CHEMICAL reactions, *X-ray photoelectron spectroscopy, *SEMICONDUCTORS, *FOURIER transform spectroscopy, *THERMOGRAVIMETRY
Abstract

Layered two-dimensional (2D) inorganic transition-metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS2. We found that the reaction of liquid-exfoliated 2D MoS2, with M(OAc)2 salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS2–M(OAc)2 materials. Importantly, this method furnished the 2H-polytype of MoS2 which is a semiconductor. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT–IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS2 surface sulfur atoms to the M(OAc)2 salt. Interestingly, functionalization of 2H-MoS2 allows for its dispersion/processing in more conventional laboratory solvents. [ABSTRACT FROM AUTHOR]

Published
2015
Full Text
View/download PDF

46. Functionalization of Liquid-Exfoliated Two-Dimensional 2H-MoS2.

Author

Backes, Claudia, Berner, Nina C., Xin Chen, Lafargue, Paul, LaPlace, Pierre, Freeley, Mark, Duesberg, Georg S., Coleman, Jonathan N., and McDonald, Aidan R.

Subjects
TRANSITION metals, OPTOELECTRONICS, FOURIER transform infrared spectroscopy, THERMOGRAVIMETRY, SOLVENTS
Abstract

Layered two-dimensional (2D) inorganic transition-metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS2. We found that the reaction of liquid-exfoliated 2D MoS2, with M(OAc)2 salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS2-M(OAc)2 materials. Importantly, this method furnished the 2H-polytype of MoS2 which is a semiconductor. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT-IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS2 surface sulfur atoms to the M(OAc)2 salt. Interestingly, functionalization of 2H-MoS2 allows for its dispersion/processing in more conventional laboratory solvents. [ABSTRACT FROM AUTHOR]

Published
2015
Full Text
View/download PDF

47. Functionalization of Liquid-Exfoliated Two-Dimensional 2H-MoS2.

Author

Backes, Claudia, Berner, Nina C., Xin Chen, Lafargue, Paul, LaPlace, Pierre, Freeley, Mark, Duesberg, Georg S., Coleman, Jonathan N., and McDonald, Aidan R.

Subjects
CHEMICAL reactions, X-ray photoelectron spectroscopy, SEMICONDUCTORS, FOURIER transform spectroscopy, THERMOGRAVIMETRY
Abstract

Layered two-dimensional (2D) inorganic transition-metal dichalchogenides (TMDs) have attracted great interest as a result of their potential application in optoelectronics, catalysis, and medicine. However, methods to functionalize and process such 2D TMDs remain scarce. We have established a facile route towards functionalized layered MoS2. We found that the reaction of liquid-exfoliated 2D MoS2, with M(OAc)2 salts (M=Ni, Cu, Zn; OAc=acetate) yielded functionalized MoS2–M(OAc)2 materials. Importantly, this method furnished the 2H-polytype of MoS2 which is a semiconductor. X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT–IR), and thermogravimetric analysis (TGA) provide strong evidence for the coordination of MoS2 surface sulfur atoms to the M(OAc)2 salt. Interestingly, functionalization of 2H-MoS2 allows for its dispersion/processing in more conventional laboratory solvents. [ABSTRACT FROM AUTHOR]

Published
2015
Full Text
View/download PDF

48. Direct Observation of Degenerate Two-Photon Absorption and Its Saturation in WS2and MoS2Monolayer and Few-Layer Films

Author

Zhang, Saifeng, Dong, Ningning, McEvoy, Niall, O’Brien, Maria, Winters, Sinéad, Berner, Nina C., Yim, Chanyoung, Li, Yuanxin, Zhang, Xiaoyan, Chen, Zhanghai, Zhang, Long, Duesberg, Georg S., and Wang, Jun

Abstract

The optical nonlinearity of WS2and MoS2monolayer and few-layer films was investigated using the Z-scan technique with femtosecond pulses from the visible to the near-infrared range. The nonlinear absorption of few- and multilayer WS2and MoS2films and their dependences on excitation wavelength were studied. WS2films with 1–3 layers exhibited a giant two-photon absorption (TPA) coefficient as high as (1.0 ± 0.8) × 104cm/GW. TPA saturation was observed for the WS2film with 1–3 layers and for the MoS2film with 25–27 layers. The giant nonlinearity of WS2and MoS2films is attributed to a two-dimensional confinement, a giant exciton effect, and the band edge resonance of TPA.

Published
2015
Full Text
View/download PDF

49. Liquid exfoliation of solvent-stabilized few-layer black phosphorus for applications beyond electronics.

Author

Hanlon, Damien, Backes, Claudia, Doherty, Evie, Cucinotta, Clotilde S., Berner, Nina C., Boland, Conor, Lee, Kangho, Harvey, Andrew, Lynch, Peter, Gholamvand, Zahra, Zhang, Saifeng, Wang, Kangpeng, Moynihan, Glenn, Pokle, Anuj, Ramasse, Quentin M., McEvoy, Niall, Blau, Werner J., Wang, Jun, Abellan, Gonzalo, and Hauke, Frank

Subjects
PHOSPHORUS, CHEMICAL peel, PHOTOLUMINESCENCE, ELECTRONICS, NONMETALS
Abstract

Few-layer black phosphorus (BP) is a new two-dimensional material which is of great interest for applications, mainly in electronics. However, its lack of environmental stability severely limits its synthesis and processing. Here we demonstrate that high-quality, few-layer BP nanosheets, with controllable size and observable photoluminescence, can be produced in large quantities by liquid phase exfoliation under ambient conditions in solvents such as N-cyclohexyl-2-pyrrolidone (CHP). Nanosheets are surprisingly stable in CHP, probably due to the solvation shell protecting the nanosheets from reacting with water or oxygen. Experiments, supported by simulations, show reactions to occur only at the nanosheet edge, with the rate and extent of the reaction dependent on the water/oxygen content. We demonstrate that liquid-exfoliated BP nanosheets are potentially useful in a range of applications from ultrafast saturable absorbers to gas sensors to fillers for composite reinforcement. [ABSTRACT FROM AUTHOR]

Published
2015
Full Text
View/download PDF

50. A New 2H-2H'/1T Cophase in Polycrystalline MoS 2 and MoSe 2 Thin Films.

Author

Naz M, Hallam T, Berner NC, McEvoy N, Gatensby R, McManus JB, Akhter Z, and Duesberg GS

Abstract

We report on 2H-2H'/1T phase conversion of MoS 2 and MoSe 2 polycrystalline films grown by thermally assisted conversion. The structural conversion of the transition metal dichalcogenides was successfully carried out by organolithium treatment on chip. As a result we obtained a new 2H-2H'/1T cophase system of the TMDs thin films which was verified by Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The conversion was successfully carried out on selected areas yielding a lateral heterostructure between the pristine 2H phase and the 2H'/1T cophase regions. Scanning electron microscopy and atomic force microscopy revealed changes in the surface morphology and work function of the cophase system in comparison to the pristine films, with a surprisingly sharp lateral interface region.

Published
2016
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results