| 1. |
- Sun, Mengtao, et al.
(författare)
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Direct visual evidence for the chemical mechanism of surface-enhanced resonance Raman scattering via charge transfer
- 2009
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 40:2, s. 137-143
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Tidskriftsartikel (refereegranskat)abstract
- We describe the chemical and electromagnetic enhancements of surface-enhanced resonance Raman scattering (SERRS) for the pyridine molecule absorbed on silver clusters, in which different incident wavelength regions are dominated by different enhancement mechanisms. Through visualization we theoretically investigate the charge transfer (CT) between the molecule and the metal cluster, and the charge redistribution (CR) within the metal on the electronic intracluster collective oscillation excitation (EICOE). The CT between the metal and the molecule in the molecule-metal complex is considered as an evidence for chemical enhancement to SERRS. CR within the metal on EICOE is considered as an evidence for the electromagnetic enhancement by collective plasmons. For the incident wavelength from 300 to 1000 nm, the visualized method of charge difference density can classify the different wavelength regions for chemical and electromagnetic enhancement, which are consistent with the formal fragmented experimental studies. Copyright (C) 2008 John Wiley & Sons, Ltd.
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| 2. |
- Sun, Mengtao, et al.
(författare)
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Direct Visualization of the Chemical Mechanism in SERRS of 4-Aminothiophenol/Metal Complexes and Metal/4-Aminothiophenol/Metal Junctions
- 2009
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 10:2, s. 392-399
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Tidskriftsartikel (refereegranskat)abstract
- We theoretically investigate the mechanism of chemical enhancement of surface-enhanced resonance Roman scattering (SERRS) of para-aminothiophenol (PATP)/metal complexes and metal/PATP/metal junctions. The method of charge difference density is used to visualize intracluster excitation and charge transfer (CT) between PATP and metal during the process of resonant electronic transitions. It is found that the selective enhancement of the b(2) mode in SERRS spectra result not only from Albrecht's A term (the Frank-Condon term), but also from the Herzberg-Teller term (Albrecht's B mechanism) via resonant CT For the metal/PATP/metal junctions, the calculated results reveal that the Roman spectrum is of SERRS nature and the nontotally symmetric b(2) mode is strongly enhanced at the incident wavelength of 1064 nm when Au and Ag nanoparticles are the first and second layer, respectively, and the dominant enhancement mechanism is the Herzberg-Teller term in chemical enhancement via tunneling charge transfer (intervalence electron transfer from the Ag cluster to the Au cluster). When the first and second layers were inverted (i.e. the Ag and Au nanoparticles are the first and second layers, respectively), the Roman spectrum at on incident wavelength of 1064 nm is due to normal Roman scattering, and the nontotally symmetric b(2) mode is not strongly enhanced. Our theoretical results not only support the experimental findings, but also provide a clear physical interpretation.
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| 3. |
- Wei, H., et al.
(författare)
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Cascaded logic gates in nanophotonic plasmon networks
- 2011
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 2:1, s. art.no. 387-
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Tidskriftsartikel (refereegranskat)abstract
- Optical computing has been pursued for decades as a potential strategy for advancing beyond the fundamental performance limitations of semiconductor-based electronic devices, but feasible on-chip integrated logic units and cascade devices have not been reported. Here we demonstrate that a plasmonic binary NOR gate, a 'universal logic gate', can be realized through cascaded OR and NOT gates in four-terminal plasmonic nanowire networks. This finding provides a path for the development of novel nanophotonic on-chip processor architectures for future optical computing technologies.
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| 4. |
- Anttu, Nicklas, et al.
(författare)
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Drastically increased absorption in vertical semiconductor nanowire arrays: A non-absorbing dielectric shell makes the difference
- 2012
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Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 5:12, s. 863-874
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Tidskriftsartikel (refereegranskat)abstract
- Enhanced absorption of especially long wavelength light is needed to enable the full potential of semiconductor nanowire (NW) arrays for optoelectronic applications. We show both experimentally and theoretically that a transparent dielectric shell (Al2O3 coating) can drastically improve the absorption of light in InAs NW arrays. With an appropriate thickness of the Al2O3 shell, we achieve four times stronger absorption in the NWs compared to uncoated NWs and twice as good absorption as when the dielectric completely fills the space between the NWs. We provide detailed theoretical analysis from a combination of full electrodynamic modeling and intuitive electrostatic approximations. This reveals how the incident light penetrates better into the absorbing NW core with increasing thickness of the dielectric shell until a resonant shell thickness is reached. We provide a simple description of how to reach this strongly absorbing resonance condition, making our results easy to apply for a broad wavelength range and a multifold of semiconductor and dielectric coating material combinations.
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| 5. |
- Anttu, Nicklas, et al.
(författare)
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Excitations of surface plasmon polaritons in double layer metal grating structures
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:9
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Tidskriftsartikel (refereegranskat)abstract
- We study the light scattering properties of double layer gratings (DLGs) made from Au on SiO2 substrates. It is found that surface plasmon polaritons (SPPs) can be excited in the DLGs for a separation of up to 150 nm between the two Au grating layers and the collective reflectance spectra exhibit a strong resonant peak and a closely lying dip as a result of the surface plasmon polariton excitations. It is also found that the angle-resolved specular reflectance spectra show a dip-peak pair structure, while the angle-resolved reflectance spectra of higher diffracted orders show a complementary peak-dip pair structure. Finally, operation of the DLGs for efficient wavelength demultiplexing is proposed and discussed in light of these results. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3690947]
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| 6. |
- Balmes, Olivier, et al.
(författare)
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Homogeneous surface-enhanced Raman scattering observed from self-assembled gold nanoparticle films deposited from the liquid-liquid interface
- 2005
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Ingår i: Vibrational Spectroscopy. - : Elsevier BV. - 0924-2031. ; 37:2, s. 189-193
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Tidskriftsartikel (refereegranskat)abstract
- The self-assembled gold nanoparticle film deposited from the liquid-liquid interface has been fabricated, and homogeneous surfaceenhanced Raman scattering (SERS) of R6G molecules on the film has been observed. The SERS enhancement factor of the film is estimated to be in the range 10(8)-10(10). Occasionally, there are some sudden jumps in the Raman signal, where the signal is increased a few times. Such jumps are probably caused by single-molecule SERS in some extremely "hot" sites. (c) 2004 Elsevier B.V. All rights reserved.
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| 7. |
- Chen, Jianing, et al.
(författare)
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Probing Strain in Bent Semiconductor Nanowires with Raman Spectroscopy.
- 2010
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:4, s. 1280-1286
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Tidskriftsartikel (refereegranskat)abstract
- We present a noninvasive optical method to determine the local strain in individual semiconductor nanowires. InP nanowires were intentionally bent with an atomic force microscope and variations in the optical phonon frequency along the wires were mapped using Raman spectroscopy. Sections of the nanowires with a high curvature showed significantly broadened phonon lines. These observations together with deformation potential theory show that compressive and tensile strain inside the nanowires is the physical origin of the observed phonon energy variations.
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| 8. |
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| 9. |
- Chen, Jianing, et al.
(författare)
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Tip-enhanced Raman scattering of p-thiocresol molecules on individual gold nanoparticles
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:9
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of tip-enhanced Raman scattering on Au aerosol nanoparticles deposited on gold films. Under the tunneling current state, the Au tip and the Au aerosol nanoparticle form a narrow cavity, where large electromagnetic field enhancements are created to enhance Raman scattering enormously. Colorless p-thiocresol molecules are used as probe molecules. The estimated Raman enhancement is about nine orders of magnitude for the tip/particle configuration.
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| 10. |
- Cong, Feng-Zi, et al.
(författare)
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A facile synthesis of branched silver nanowire structures and its applications in surface-enhanced Raman scattering
- 2012
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Ingår i: Frontiers of Physics. - : Springer Science and Business Media LLC. - 2095-0462 .- 2095-0470. ; 7:5, s. 521-526
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Tidskriftsartikel (refereegranskat)abstract
- We report a facile method of preparing novel branched silver nanowire structures such as Y-shaped, K-shaped and other multi-branched nanowires. These branched nanostructures are synthesized by reducing silver nitrate (AgNO3) in polyethylene glycol (PEG) with polyvinglpyrrolidone (PVP) as capping agent. Statistical data indicate that for the "y" typed branched nanowire, the branches grow out from the side of the trunk nanowire in a preferential orientation with an angle of 55A degrees between the branch and the trunk. Transmission electron microscopy (TEM) studies indicate that the defects on silver nanowires could support the growth of branched nanowires. Conditions such as the molar ratio of PVP/AgNO3, the reaction temperature, and the degree of polymerization of reducing agent and PVP play important roles in determining the yield of the silver branches. Due to the rough surface, these branched nanostructures can be used as efficient substrates for surface-enhanced Raman scattering applications.
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