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Molecular polarization bridging physical and chemical enhancements in surface enhanced Raman scattering
KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.ORCID-id: 0000-0002-3282-0711
KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.ORCID-id: 0000-0003-0007-0394
2011 (engelsk)Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, nr 41, s. 11438-11440Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We present a practical method which demonstrates how the physical and chemical enhancements in SERS for a molecule adsorbed on metal junctions are conceptually coupled through the polarization of the molecule and its surroundings. Calculations with the state-of-the-art density functional reveal that the coupling factor considered in the present work can be as large as 10(6), such that it is indeed important for certain vibrational modes.

sted, utgiver, år, opplag, sider
2011. Vol. 47, nr 41, s. 11438-11440
Emneord [en]
sers spectra, silver, metal, spectroscopy, modes, gold
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-46869DOI: 10.1039/c1cc14962hISI: 000295696300012Scopus ID: 2-s2.0-80053947493OAI: oai:DiVA.org:kth-46869DiVA, id: diva2:454296
Forskningsfinansiär
Swedish Research Council
Merknad
QC 20111107Tilgjengelig fra: 2011-11-07 Laget: 2011-11-07 Sist oppdatert: 2017-12-08bibliografisk kontrollert
Inngår i avhandling
1. Geometrical and Electronic Structures at Molecule-Metal Interfaces from Theoretical Modeling
Åpne denne publikasjonen i ny fane eller vindu >>Geometrical and Electronic Structures at Molecule-Metal Interfaces from Theoretical Modeling
2012 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In this thesis, we focus on theoretical investigations on metal interfaces where many heterogeneous chemical reactions take place. Surface-enhanced Raman scattering (SERS) spectroscopy and the modern electrochemical methods are important in-situ techniques that have been widely employed for a variety of applications. Theoretical simulations have become an indispensable tool to infer the molecular details of interfacial structures that are not directly accessible from experimental measurements. In this context, we have proposed several new theoretical models for both SERS and interfacial electrochemistry, which allow us to provide molecular-level understanding of the interfacial structures under the realistic experimental conditions.

 

The first part of the thesis has addressed the basic theory of SERS that offers the vibrational structure of the interfacial molecules. It is well known that the huge enhancement of Raman intensity in this technique can be attributed to two independent factors, namely the physical and chemical enhancements. The former is resulted from the enhanced electromagnetic field induced by the plasmonic excitations, while the latter comes from the changing of interaction between the molecule and the surface. The interplay between these two enhancement factors, which has long been an issue of debate, is revealed in this thesis. They are coupled through molecular polarizability. A practical computational approach is proposed and used to demonstrate the importance of the coupling on different molecular systems. It is found that for certain systems the coupling factor can be as large as 106. This finding is of great importance towards a comprehensive understanding of the SERS mechanisms and a quantitative prediction of the enhancement factor.

 

The other part of the thesis is devoted to the theory of interfacial electrochemistry, in particular the effects of water solution. A novel protocol that combines classical molecular dynamics (MD) and the first principles density functional theory (DFT) calculations is proposed to address the statistical behavior of interfacial properties. Special attention has been paid to the work function of Pt(111) surface and CO adsorption energy on Pt(111) surface in aqueous solution. It has been found that in this case the work function of Pt surface illustrates a surprisingly broad distribution under the room temperature, sheds new light on the understanding of reaction activity of the surface. The proposed protocol is able to provide results in very good agreement with experiments and should be applied routinely in future studies.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2012. s. xii, 67
Serie
Trita-BIO-Report, ISSN 1654-2312 ; 2012:14
Emneord
SERS, Electrochemistry, DFT, MD
HSV kategori
Forskningsprogram
SRA - Energi
Identifikatorer
urn:nbn:se:kth:diva-94120 (URN)978-91-7501-372-5 (ISBN)
Disputas
2012-06-07, FB54, Albanova University Center, Roslagstullsbacken 21, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Forskningsfinansiär
StandUp
Merknad

QC 20120515

Tilgjengelig fra: 2012-05-15 Laget: 2012-05-07 Sist oppdatert: 2013-04-18bibliografisk kontrollert

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