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Samaha AC, Doumani J, Kritzell TE, Xu H, Baydin A, Ajayan PM, Tahchi ME, Kono J. Graphene Terahertz Devices for Sensing and Communication. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2401151. [PMID: 39087386 DOI: 10.1002/smll.202401151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 04/24/2024] [Indexed: 08/02/2024]
Abstract
Graphene-based terahertz (THz) devices have emerged as promising platforms for a variety of applications, leveraging graphene's unique optoelectronic properties. This review explores recent advancements in utilizing graphene in THz technology, focusing on two main aspects: THz molecular sensing and THz wave modulation. In molecular sensing, the environment-sensitive THz transmission and emission properties of graphene are utilized for enabling molecular adsorption detection and biomolecular sensing. This capability holds significant potential, from the detection of pesticides to DNA at high sensitivity and selectivity. In THz wave modulation, crucial for next-generation wireless communication systems, graphene demonstrates remarkable potential in absorption modulation when gated. Novel device structures, spectroscopic systems, and metasurface architectures have enabled enhanced absorption and wave modulation. Furthermore, techniques such as spatial phase modulation and polarization manipulation have been explored. From sensing to communication, graphene-based THz devices present a wide array of opportunities for future research and development. Finally, advancements in sensing techniques not only enhance biomolecular analysis but also contribute to optimizing graphene's properties for communication by enabling efficient modulation of electromagnetic waves. Conversely, developments in communication strategies inform and enhance sensing capabilities, establishing a mutually beneficial relationship.
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Affiliation(s)
- Anna-Christina Samaha
- Laboratory of Biomaterials and Intelligent Materials, Department of Physics, Faculty of Sciences 2, Lebanese University, Jdeidet, 90656, Lebanon
| | - Jacques Doumani
- Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Applied Physics Graduate Program, Smalley-Curl Institute, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - T Elijah Kritzell
- Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Applied Physics Graduate Program, Smalley-Curl Institute, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - Hongjing Xu
- Department of Physics and Astronomy, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - Andrey Baydin
- Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Smalley-Curl Institute, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - Pulickel M Ajayan
- Smalley-Curl Institute, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Department of Materials Science and NanoEngineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
| | - Mario El Tahchi
- Laboratory of Biomaterials and Intelligent Materials, Department of Physics, Faculty of Sciences 2, Lebanese University, Jdeidet, 90656, Lebanon
| | - Junichiro Kono
- Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Department of Physics and Astronomy, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Smalley-Curl Institute, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Department of Materials Science and NanoEngineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
- Carbon Hub, Rice University, 6100 Main Street, Houston, TX 77005, USA
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Jiang L, Kong KV, He S, Yong K. Plasmonic Biosensing with Nano‐Engineered Van der Waals Interfaces. Chempluschem 2022; 87:e202200221. [DOI: 10.1002/cplu.202200221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 09/27/2022] [Indexed: 11/06/2022]
Affiliation(s)
- Li Jiang
- School of Electrical and Electronic Engineering Nanyang Technological University 639798 Singapore Singapore
- State Key Laboratory of Modern Optical Instrumentation Centre for Optical and Electromagnetics Research JORCEP (Sino-Swedish Joint Research Center of Photonics) Zhejiang University Hangzhou 310058 P. R. China
- CINTRA CNRS/NTU/THALES, UMI 3288 Research Techno Plaza 50 Nanyang Drive Border X Block 637553 Singapore Singapore
| | - Kien Voon Kong
- Department of Chemistry National Taiwan University Taipei City Taiwan 10617
| | - Sailing He
- State Key Laboratory of Modern Optical Instrumentation Centre for Optical and Electromagnetics Research JORCEP (Sino-Swedish Joint Research Center of Photonics) Zhejiang University Hangzhou 310058 P. R. China
| | - Ken‐Tye Yong
- School of Biomedical Engineering The University of Sydney Sydney New South Wales 2006 Australia
- The University of Sydney Nano Institute The University of Sydney Sydney New South Wales 2006 Australia
- The Biophotonics and MechanoBioengineering Lab The University of Sydney Sydney New South Wales 2006 Australia
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3
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Singlet Fission, Polaron Generation and Intersystem Crossing in Hexaphenyl Film. Molecules 2022; 27:molecules27165067. [PMID: 36014308 PMCID: PMC9412266 DOI: 10.3390/molecules27165067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/04/2022] [Accepted: 08/07/2022] [Indexed: 11/17/2022] Open
Abstract
The ultrafast dynamics of triplet excitons and polarons in hexaphenyl film was investigated by time-resolved fluorescence and femtosecond transient absorption techniques under various excitation photon energies. Two distinct pathways of triplet formation were clearly observed. Long-lived triplet states are populated within 4.5 ps via singlet fission-intersystem crossing, while the short-lived triplet states (1.5 ns) are generated via singlet fission from vibrational electronic states. In the meantime, polarons were formed from hot excitons on a timescale of <30 fs and recombined in ultrafast lifetime (0.37 ps). In addition, the characterization of hexaphenyl film suggests the morphologies of crystal and aggregate to wide applications in organic electronic devices. The present study provides a universally applicable film fabrication in hexaphenyl system towards future singlet fission-based solar cells.
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Wu T, Ni W, Gurzadyan GG, Sun L. Singlet fission from upper excited singlet states and polaron formation in rubrene film. RSC Adv 2021; 11:4639-4645. [PMID: 35424413 PMCID: PMC8694490 DOI: 10.1039/d0ra10780h] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 01/14/2021] [Indexed: 11/21/2022] Open
Abstract
Femtosecond fluorescence up-conversion and transient absorption pump-probe setups are applied to study the relaxation dynamics of the lower and upper excited singlet electronic states in easy-to-make rubrene films. Upon 250 nm (4.96 eV) excitation, singlet fission was observed directly from S2 state bypassing S1 state within 30 fs i.e. breaking the classical Kasha rule. From the transient absorption measurements, polaron formation was also detected on the same time scale. Both singlet fission and polaron formation are accelerated from upper excited states compared with S1 state. Our work shows that rubrene films with low degree of crystallinity could display efficient singlet fission, notably in the case of excitation to upper lying electronic states. This can strongly expand the applications of rubrene in organic electronics. Moreover, our results will provide a new direction for synthesizing novel materials with optimized excited state properties for organic photovoltaic applications.
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Affiliation(s)
- Tong Wu
- State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, Dalian University of Technology 116024 Dalian China
| | - Wenjun Ni
- State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, Dalian University of Technology 116024 Dalian China
| | - Gagik G Gurzadyan
- State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, Dalian University of Technology 116024 Dalian China
| | - Licheng Sun
- State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, Dalian University of Technology 116024 Dalian China
- Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology 10044 Stockholm Sweden
- Center of Artificial Photosynthesis for Solar Fuels, School of Science, Westlake University 310024 Hangzhou China
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Prakash G, Srivastava RK, Gupta SN, Sood AK. Plasmon-induced efficient hot carrier generation in graphene on gold ultrathin film with periodic array of holes: Ultrafast pump-probe spectroscopy. J Chem Phys 2019; 151:234712. [PMID: 31864269 DOI: 10.1063/1.5117882] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Using ultrafast pump-probe reflectivity with a 3.1 eV pump and coherent white light probe (1.1-2.6 eV), we show that graphene on gold nanostructures exhibits a strong coupling to the plasmonic resonances of the ordered lattice hole array, thus injecting a high density of hot carriers in graphene through plasmons. The system being studied is single-layer graphene on an ultrathin film of gold with periodic arrangements of holes showing anomalous transmission. A comparison is made with gold film with and without hole array. By selectively probing transient carrier dynamics in the spectral regions corresponding to plasmonic resonances, we show efficient plasmon induced hot carrier generation in graphene. We also show that due to high electromagnetic field intensities at the edge of the submicron holes, fast decay time (10-100 fs), and short decay length (1 nm) of plasmons, a highly confined density of hot carriers (very close to the edge of the holes) is generated by Landau damping of plasmons within the holey gold film. A contribution to transient decay dynamics due to the diffusion of the initial nonuniform distribution of hot carriers away from the hole edges is observed. Our results are important for future applications of novel hot carrier device concepts where hot carriers with tunable energy can be generated in different graphene regions connected seamlessly.
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Affiliation(s)
- Gyan Prakash
- Department of Physics, Indian Institute of Science, Bangalore 560 012, India
| | | | | | - A K Sood
- Department of Physics, Indian Institute of Science, Bangalore 560 012, India
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Yao J, Zhao X, Yan XQ, Kong XT, Gao C, Chen XD, Chen Y, Liu ZB, Tian JG. Making transient optical reflection of graphene polarization dependent. OPTICS EXPRESS 2015; 23:24177-24188. [PMID: 26406624 DOI: 10.1364/oe.23.024177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The polarization dependence of transient optical reflection, induced by nonequilibrium carriers isotropically distributed in momentum space, of graphene on substrate is experimentally and theoretically investigated. It is found that this transient optical reflection could be made greatly polarization dependent by using oblique incidence for light, and the characteristic of this polarization dependence could be flexibly altered with incident angle and incident direction (from graphene to substrate, or from substrate to graphene). Our results suggest that through polarization of incident beam is an efficient way of manipulating graphene transient optical reflection.
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Ulstrup S, Johannsen JC, Crepaldi A, Cilento F, Zacchigna M, Cacho C, Chapman RT, Springate E, Fromm F, Raidel C, Seyller T, Parmigiani F, Grioni M, Hofmann P. Ultrafast electron dynamics in epitaxial graphene investigated with time- and angle-resolved photoemission spectroscopy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:164206. [PMID: 25835249 DOI: 10.1088/0953-8984/27/16/164206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In order to exploit the intriguing optical properties of graphene it is essential to gain a better understanding of the light-matter interaction in the material on ultrashort timescales. Exciting the Dirac fermions with intense ultrafast laser pulses triggers a series of processes involving interactions between electrons, phonons and impurities. Here we study these interactions in epitaxial graphene supported on silicon carbide (semiconducting) and iridium (metallic) substrates using ultrafast time- and angle-resolved photoemission spectroscopy (TR-ARPES) based on high harmonic generation. For the semiconducting substrate we reveal a complex hot carrier dynamics that manifests itself in an elevated electronic temperature and an increase in linewidth of the π band. By analyzing these effects we are able to disentangle electron relaxation channels in graphene. On the metal substrate this hot carrier dynamics is found to be severely perturbed by the presence of the metal, and we find that the electronic system is much harder to heat up than on the semiconductor due to screening of the laser field by the metal.
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Affiliation(s)
- Søren Ulstrup
- Department of Physics and Astronomy, Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Nordre Ringgade 1, 8000 Aarhus C, Denmark
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8
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Ma L, Hu P, Kloc C, Sun H, Michel-Beyerle ME, Gurzadyan GG. Ultrafast spectroscopic characterization of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and its radical anion (TCNQ−). Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.06.029] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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9
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Roberts AT, Binder R, Kwong NH, Golla D, Cormode D, LeRoy BJ, Everitt HO, Sandhu A. Optical characterization of electron-phonon interactions at the saddle point in graphene. PHYSICAL REVIEW LETTERS 2014; 112:187401. [PMID: 24856720 DOI: 10.1103/physrevlett.112.187401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Indexed: 06/03/2023]
Abstract
The role of many-body interactions is experimentally and theoretically investigated near the saddle point absorption peak of graphene. The time and energy-resolved differential optical transmission measurements reveal the dominant role played by electron-acoustic phonon coupling in band structure renormalization. Using a Born approximation for electron-phonon coupling and experimental estimates of the dynamic lattice temperature, we compute the differential transmission line shape. Comparing the numerical and experimental line shapes, we deduce the effective acoustic deformation potential to be Deff(ac)≃5 eV. This value is in accord with recent theoretical predictions but differs from those extracted using electrical transport measurements.
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Affiliation(s)
- Adam T Roberts
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA and U.S. Army Aviation and Missile Research, Development, and Engineering Center, Redstone Arsenal, Alabama 35898, USA
| | - Rolf Binder
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA and Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
| | - Nai H Kwong
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA
| | - Dheeraj Golla
- Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
| | - Daniel Cormode
- Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
| | - Brian J LeRoy
- Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
| | - Henry O Everitt
- U.S. Army Aviation and Missile Research, Development, and Engineering Center, Redstone Arsenal, Alabama 35898, USA
| | - Arvinder Sandhu
- College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA and Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
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10
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Enhanced hot-carrier luminescence in multilayer reduced graphene oxide nanospheres. Sci Rep 2014; 3:2315. [PMID: 23897010 PMCID: PMC3727062 DOI: 10.1038/srep02315] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 07/15/2013] [Indexed: 11/08/2022] Open
Abstract
We report a method to promote photoluminescence emission in graphene materials by enhancing carrier scattering instead of directly modifying band structure in multilayer reduced graphene oxide (rGO) nanospheres. We intentionally curl graphene layers to form nanospheres by reducing graphene oxide with spherical polymer templates to manipulate the carrier scattering. These nanospheres produce hot-carrier luminescence with more than ten-fold improvement of emission efficiency as compared to planar nanosheets. With increasing excitation power, hot-carrier luminescence from nanospheres exhibits abnormal spectral redshift with dynamic feature associated to the strengthened electron-phonon coupling. These experimental results can be well understood by considering the screened Coulomb interactions. With increasing carrier density, the reduced screening effect promotes carrier scattering which enhances hot-carrier emission from such multilayer rGO nanospheres. This carrier-scattering scenario is further confirmed by pump-probe measurements.
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11
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Ma L, Galstyan G, Zhang K, Kloc C, Sun H, Soci C, Michel-Beyerle ME, Gurzadyan GG. Two-photon-induced singlet fission in rubrene single crystal. J Chem Phys 2013; 138:184508. [PMID: 23676057 DOI: 10.1063/1.4804398] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The two-photon-induced singlet fission was observed in rubrene single crystal and studied by use of femtosecond pump-probe spectroscopy. The location of two-photon excited states was obtained from the nondegenerate two-photon absorption (TPA) spectrum. Time evolution of the two-photon-induced transient absorption spectra reveals the direct singlet fission from the two-photon excited states. The TPA absorption coefficient of rubrene single crystal is 52 cm∕GW at 740 nm, as obtained from Z-scan measurements. Quantum chemical calculations based on time-dependent density functional theory support our experimental data.
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Affiliation(s)
- Lin Ma
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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12
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Zhang Q, Zheng H, Geng Z, Jiang S, Ge J, Fan K, Duan S, Chen Y, Wang X, Luo Y. The Realistic Domain Structure of As-Synthesized Graphene Oxide from Ultrafast Spectroscopy. J Am Chem Soc 2013; 135:12468-74. [DOI: 10.1021/ja407110r] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
| | | | | | | | | | | | - Sai Duan
- Department of Theoretical Chemistry
and Biology, School of Biotechnology, Royal Institute of Technology, AlbaNova, S-106 91 Stockholm, Sweden
| | | | | | - Yi Luo
- Department of Theoretical Chemistry
and Biology, School of Biotechnology, Royal Institute of Technology, AlbaNova, S-106 91 Stockholm, Sweden
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13
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Ultrafast collinear scattering and carrier multiplication in graphene. Nat Commun 2013; 4:1987. [PMID: 23770933 DOI: 10.1038/ncomms2987] [Citation(s) in RCA: 392] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 05/08/2013] [Indexed: 12/24/2022] Open
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Murphy S, Huang L. Transient absorption microscopy studies of energy relaxation in graphene oxide thin film. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:144203. [PMID: 23478941 DOI: 10.1088/0953-8984/25/14/144203] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Spatial mapping of energy relaxation in graphene oxide (GO) thin films has been imaged using transient absorption microscopy (TAM). Correlated AFM images allow us to accurately determine the thickness of the GO films. In contrast to previous studies, correlated TAM-AFM allows determination of the effect of interactions of GO with the substrate and between stacked GO layers on the relaxation dynamics. Our results show that energy relaxation in GO flakes has little dependence on the substrate, number of stacked layers, and excitation intensity. This is in direct contrast to pristine graphene, where these factors have great consequences in energy relaxation. This suggests intrinsic factors rather than extrinsic ones dominate the excited state dynamics of GO films.
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Affiliation(s)
- Sean Murphy
- Radiation Laboratory and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
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15
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Koyama T, Ito Y, Yoshida K, Tsuji M, Ago H, Kishida H, Nakamura A. Near-Infrared photoluminescence in the femtosecond time region in monolayer graphene on SiO₂. ACS NANO 2013; 7:2335-2343. [PMID: 23461396 DOI: 10.1021/nn305558r] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigate the dynamical properties of photoexcited carriers in a single monolayer of graphene at room temperature in air using femtosecond time-resolved luminescence spectroscopy. The luminescence kinetics are observed in the near-infrared region of 0.7-1.4 eV and analyzed based on the two-temperature model describing the cooling of thermalized carriers via the carrier-optical phonon interaction. The observed luminescence in the range 0.7-0.9 eV is well reproduced by the model. In the range 1.0-1.4 eV, however, the luminescence, which decays in ∼300 fs, cannot be reproduced by this model. These results indicate that the carrier system is not completely thermalized in ∼300 fs. We also show the importance of the carrier-doping effect induced by the substrate and surrounding environment in the carrier cooling dynamics and the predominance of optical phonons over acoustic phonons in the carrier-phonon interactions even at a temperature of ∼400 K.
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Affiliation(s)
- Takeshi Koyama
- Department of Applied Physics, Graduate School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan.
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16
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Wang R, Wang Y, Xu C, Sun J, Gao L. Facile one-step hydrazine-assisted solvothermal synthesis of nitrogen-doped reduced graphene oxide: reduction effect and mechanisms. RSC Adv 2013. [DOI: 10.1039/c2ra21825a] [Citation(s) in RCA: 114] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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17
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Brida D, Manzoni C, Cerullo G, Tomadin A, Polini M, Nair R, Geim A, Novoselov K, Milana S, Lombardo A, Ferrari AC. Ultrafast Non-Thermal Electron Dynamics in Single Layer Graphene. EPJ WEB OF CONFERENCES 2013. [DOI: 10.1051/epjconf/20134104025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Shang J, Ma L, Li J, Ai W, Yu T, Gurzadyan GG. The origin of fluorescence from graphene oxide. Sci Rep 2012; 2:792. [PMID: 23145316 PMCID: PMC3494035 DOI: 10.1038/srep00792] [Citation(s) in RCA: 282] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 10/10/2012] [Indexed: 12/18/2022] Open
Abstract
Time-resolved fluorescence measurements of graphene oxide in water show multiexponential decay kinetics ranging from 1 ps to 2 ns. Electron-hole recombination from the bottom of the conduction band and nearby localized states to wide-range valance band is suggested as origin of the fluorescence. Excitation wavelength dependence of the fluorescence was caused by relative intensity changes of few emission species. By introducing the molecular orbital concept, the dominant fluorescence was found to originate from the electronic transitions among/between the non-oxidized carbon regions and the boundary of oxidized carbon atom regions, where all three kinds of functionalized groups C-O, C = O and O = C-OH were participating. In the visible spectral range, the ultrafast fluorescence of graphene oxide was observed for the first time.
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Affiliation(s)
- Jingzhi Shang
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Lin Ma
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
| | - Jiewei Li
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
- Key Laboratory for Organic Electronics & Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210046, China
| | - Wei Ai
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
- Key Laboratory for Organic Electronics & Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, Nanjing 210046, China
| | - Ting Yu
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
- Department of Physics, Faculty of Science, National University of Singapore, Singapore 117542
- Graphene Research Centre, National University of Singapore, 2 Science Drive 3, Singapore 117542
| | - Gagik G. Gurzadyan
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
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19
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Excitation of surface electromagnetic waves in a graphene-based Bragg grating. Sci Rep 2012; 2:737. [PMID: 23071901 PMCID: PMC3471096 DOI: 10.1038/srep00737] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 09/25/2012] [Indexed: 11/27/2022] Open
Abstract
Here, we report the fabrication of a graphene-based Bragg grating (one-dimensional photonic crystal) and experimentally demonstrate the excitation of surface electromagnetic waves in the periodic structure using prism coupling technique. Surface electromagnetic waves are non-radiative electromagnetic modes that appear on the surface of semi-infinite 1D photonic crystal. In order to fabricate the graphene-based Bragg grating, alternating layers of high (graphene) and low (PMMA) refractive index materials have been used. The reflectivity plot shows a deepest, narrow dip after total internal reflection angle corresponds to the surface electromagnetic mode propagating at the Bragg grating/air boundary. The proposed graphene based Bragg grating can find a variety of potential surface electromagnetic wave applications such as sensors, fluorescence emission enhancement, modulators, etc.
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Ma L, Zhang K, Kloc C, Sun H, Michel-Beyerle ME, Gurzadyan GG. Singlet fission in rubrene single crystal: direct observation by femtosecond pump-probe spectroscopy. Phys Chem Chem Phys 2012; 14:8307-12. [PMID: 22510785 DOI: 10.1039/c2cp40449d] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The excited state dynamics of rubrene in solution and in the single crystal were studied by femtosecond pump-probe spectroscopy under various excitation conditions. Singlet fission was demonstrated to play a predominant role in the excited state relaxation of the rubrene crystal in contrast to rubrene in solution. Upon 500 nm excitation, triplet excitons form on the picosecond time scale via fission from the lowest excited singlet state. Upon 250 nm excitation, fission from upper excited singlet states is observed within 200 fs.
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Affiliation(s)
- Lin Ma
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
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