Direct visual evidence for the chemical mechanism of surface‐enhanced resonance Raman scattering via charge transfer

Sun, Mengtao; Li, Shasha; Chen, Maodu; Xu, Hongqi

doi:10.1002/jrs.2093

Cited by 84 publications

(80 citation statements)

References 54 publications

(34 reference statements)

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“…Another reason (that the SERS peak intensity of the ∼1584 cm −1 band of 4-MBA adsorbed on the metal pellets decreases when the pressure is varied from 100 to 500 kgf cm −2 ) may be from the tunneling charge transfer (TCT) between particles, [42 -44] since the excitation of particle plasmon emission by tunneling electrons could decrease the enhancement of SERS when the gap among the particles was decreased to below 1 nm. With charge difference density, [45] the phenomenon of TCT has been clearly visualized in metal-molecule-metal junctions when the gap is below 1 nm. [42] When the applied pressure is large enough, the particles will be flattened and connected to each other (the distance of gaps is 0 nm), and the number of effective gaps will decrease, which will also decrease the lightning rod effect and decrease the intensity of SERS spectroscopy.…”

Section: Resultsmentioning

confidence: 98%

Adjustment and control of SERS activity of metal substrates by pressure

Xia

Jia

Liu

et al. 2009

J Raman Spectroscopy

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Metal pellets of silver and copper for surface-enhanced Raman scattering (SERS) spectroscopy were prepared by compression with different pressures. It was found that the SERS activity of the pellet could be controlled by pressure. Enhanced Raman scattering properties of the metal pellets in the presence of adsorbed 4-mercaptobenzoic acid (4-MBA) with excitation at 632.8 or 514 nm could be obtained by choosing proper pressure of pellatization. The SERS peak intensity of the band at ∼1584 cm −1 of 4-MBA adsorbed on the metal pellets varies as a function of applied pressure, and which is about 1.2-32 times greater than when it is adsorbed on silver and copper particles. The calculated results of three-dimensional finite-difference time-domain method (3D-FDTD) are in good agreement with the experimental data. Moreover, no spurious peaks appear in the SERS spectra of the samples because no other chemicals are involved in the simple preparation process of the metal pellets, which will facilitate its use as an SERS-active substrate for analytical purposes. In summary, SERS-active metal pellets can be produced simply and cost effectively by the method reported here, and this method is expected to be utilized in the development of SERS-based analytical devices.

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Section: Resultsmentioning

confidence: 98%

Adjustment and control of SERS activity of metal substrates by pressure

Xia

Jia

Liu

et al. 2009

J Raman Spectroscopy

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“…The effects of SERS are generally divided into types, which are chemical enhancements and physical enhancements, respectively. The mechanism involves the excitation of the SP and chemical enhancement is associated with charge transfer, also known as charge transfer resonance Raman [29,164,165]. When the incident light illuminates the metal surface, metal nanostructures have the ability to compress light into a small volume between two nanoparticles, and the EM field strength of the region is greatly enhanced to produce a hotspot (see Figure 9) [167,168].…”

Section: Sersmentioning

confidence: 99%

Exciton-plasmon coupling interactions: from principle to applications

et al. 2017

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Abstract:The interaction of exciton-plasmon coupling and the conversion of exciton-plasmon-photon have been widely investigated experimentally and theoretically. In this review, we introduce the exciton-plasmon interaction from basic principle to applications. There are two kinds of exciton-plasmon coupling, which demonstrate different optical properties. The strong exciton-plasmon coupling results in two new mixed states of light and matter separated energetically by a Rabi splitting that exhibits a characteristic anticrossing behavior of the exciton-LSP energy tuning. Compared to strong coupling, such as surface-enhanced Raman scattering, surface plasmon (SP)-enhanced absorption, enhanced fluorescence, or fluorescence quenching, there is no perturbation between wave functions; the interaction here is called the weak coupling. SP resonance (SPR) arises from the collective oscillation induced by the electromagnetic field of light and can be used for investigating the interaction between light and matter beyond the diffraction limit. The study on the interaction between SPR and exaction has drawn wide attention since its discovery not only due to its contribution in deepening and broadening the understanding of SPR but also its contribution to its application in light-emitting diodes, solar cells, low threshold laser, biomedical detection, quantum information processing, and so on.

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“…[13,14] Intracluster excitation and CT excitation are direct evidence for the EM mechanism and the chemical mechanism, respectively.…”

Section: Introductionmentioning

confidence: 98%

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

Sun¹,

Xu²

2009

ChemPhysChem

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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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Direct visual evidence for the chemical mechanism of surface‐enhanced resonance Raman scattering via charge transfer

Cited by 84 publications

References 54 publications

Adjustment and control of SERS activity of metal substrates by pressure

Adjustment and control of SERS activity of metal substrates by pressure

Exciton-plasmon coupling interactions: from principle to applications

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

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