Confinement of Electron Beams by Mesh Arrays in a Relativistic Klystron Amplifier

Wang, Pingshan; Shen, Yu; Fang-Yan, Lei; Luo, Min; Ma, Qiang; Jie, Tan; Gu, Bin-lin

doi:10.7498/aps.47.485

SERS‐BasedRaman Probes

Vo‐Dinh¹,

Stokes²

2001

Handbook of Vibrational Spectroscopy

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The sections in this article are Introduction Different SERS ‐Based Probes Metal Electrodes Metal Colloids Solid SERS Probes Based on Metallic Nanostructures Metal Nanoparticle Island Films Silver‐Coated Nanosphere Probes Metal‐Coated Nanoparticle SERS Probes SERS Probes Based on Metal‐Coated Quartz Posts SERS Probes Based on Chemically and Abrasively Roughened Solid Surfaces SERS Probes Based on Inherently Rough Materials SERS ‐Based Probes Based on Metal Nanoparticle‐Embedded Media SERS Probe Coatings General Organic, Metallic and Dielectric Coatings SAMs Monolayers of Bioreceptors Advanced Sensing Technologies Based on SERS Probes Remote Fiber Optic SERS Monitors and Nanosensors Dual‐Fiber Systems Integrated Single‐Fiber System and Nanosensors Surface‐Enhanced R aman Scattering‐Scanning Near‐Field Optical Microscopy Conclusion Acknowledgments

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Surface‐Enhanced Raman Scattering of p‐Aminothiophenol on a Au(core)/Cu(shell) Nanoparticle Assembly

Cao

¹

,

Diao

²

,

Tong

³

et al. 2005

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Surface-enhanced Raman scattering (SERS) of p-aminothiophenol (PATP) molecules adsorbed onto assemblies of Au(core)/Cu(shell) nanoparticles is reported. We compare it with the SERS spectrum of PATP adsorbed onto gold nanoparticles: both the absolute and relative scattered intensities of various bands in the two spectra are very different. The difference in relative intensity can be ascribed to chemical effects; the chemical enhancement ratio of the two substrates is approximately 3-5. A theoretical analysis based on a charge-transfer model is carried out, which yields a consistent result and shows that the difference in chemical enhancement is mainly due to the state densities and Fermi levels of the substrates. The difference in absolute intensity originates from electromagnetic (EM) enhancement. EM enhancement of Au(core)/Cu(shell) nanoparticles is unlike that of single-component gold or copper SERS-active substrates. The core/shell particle size for optimal enhancement is about 20 nm in the case of a 632.8 nm incident laser (the size ratio of the core and shell layers is about 0.6).

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Direct Visualization of the Chemical Mechanism in SERRS of 4‐Aminothiophenol/Metal Complexes and Metal/4‐Aminothiophenol/Metal Junctions

Sun¹,

Xu²

2009

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Direct visualization of photoinduced tunneling charge transfer (TCT) in an Au(5)/para-aminothiophenol (PATP)/Ag(6) junction in which Au and Ag clusters form the first and second layer, respectively, is provided by the charge difference density (see picture; green and red stand for holes and electrons, respectively). We theoretically investigate the mechanism of chemical enhancement of surface-enhanced resonance Raman 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 Raman 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 Raman spectrum at an incident wavelength of 1064 nm is due to normal Raman 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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Confinement of Electron Beams by Mesh Arrays in a Relativistic Klystron Amplifier

Cited by 6 publications

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SERS‐BasedRaman Probes

SERS‐BasedRaman Probes

Surface‐Enhanced Raman Scattering of p‐Aminothiophenol on a Au(core)/Cu(shell) Nanoparticle Assembly

Direct Visualization of the Chemical Mechanism in SERRS of 4‐Aminothiophenol/Metal Complexes and Metal/4‐Aminothiophenol/Metal Junctions

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