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Stabilizing single-molecular Raman spectrum of a nonbonding molecule on Ag nanoparticles
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).ORCID iD: 0000-0003-0007-0394
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
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2009 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 11, 1342-1344 p.Article in journal (Other academic) Published
Abstract [en]

The applicability of single-molecule surface-enhanced Raman spectroscopy to a nonbonding molecular system is demonstrated on a uniformly assembled colloidal Ag nanoparticle substrate.

Place, publisher, year, edition, pages
2009. no 11, 1342-1344 p.
Keyword [en]
urface-enhanced raman, spectroscopy, scattering
National Category
Theoretical Chemistry
URN: urn:nbn:se:kth:diva-7959DOI: 10.1039/b819402eISI: 000263849800007ScopusID: 2-s2.0-61849169677OAI: diva2:13148
QC 20100823. Updated from submitted to published, QC 20120314. Previous title: Controlling single molecular Raman behavior of a nonbonding molecule on Ag nanoparticlesAvailable from: 2008-02-05 Created: 2008-02-05 Last updated: 2012-03-14Bibliographically approved
In thesis
1. Theoretical Characterization of Optical Processes in Modecular Complexes
Open this publication in new window or tab >>Theoretical Characterization of Optical Processes in Modecular Complexes
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The main theme of this thesis is to study effects of different environments on geometric and electronic structures, as well as optical responses, of molecules using time-(in)dependent density functional theory. Theoretical calculations have been carried out for properties that can be measured by conventional and advanced experimental techniques, including one-photon absorption (OPA), two-photon absorption (TPA), surface-enhanced Raman scattering (SERS) and second order nonlinear optical (NLO) response. The obtained good agreement between the theory and the experiment allows to further extract useful information about inter- and intra-molecular interactions that are not accessible experimentally.

By comparing calculated one-photon absorption spectra of aluminum phthalocyanine chloride (AlPcCl) and AlPcCl -water complexes with the corresponding experiments, detailed information about the interaction between water molecules and AlPcCl, and geometric changes of AlPcCl molecule has been obtained. Effects of aggregation on two-photon absorption spectra of octupolar molecules have been examined. It is shown that the formation of clusters through inter-molecular hydrogen bonding can drastically change profiles of TPA spectra. It has also demonstrated that a well designed molecular aggregate/cluster, dendrimer, can enhance the second order nonlinear optical response of the molecules. In collaboration with experimentalists, a series of end-capped triply branched dendritic chromophores have been characterized, which can lead to large enhancement of the second order NLO property when the dipoles of the three branches in the dendrimers are highly parallelized.

Surface-enhanced Raman scattering has made the detection of single molecules on metal surface become possible. Chemically bonded molecule-metal systems have been extensively studied. We have shown in a joint experimental and theoretical work that stable Raman spectra of a non-bonding molecule, perylene, physically adsorbed on Ag nano-particles can also be observed at low temperature. It is found that the local enhanced field has a tendency to drive molecule toward a gap of two closely lying nano-particles. The trapped molecule can thus provide a stable Raman spectrum with high resolution when its thermal motion is reduced at low temperature.

For the ever growing size of molecular complexes, there is always the need to develop new computational methods. A conceptually simple but computationally efficient method, named as central insertion scheme (CIS), is proposed that allows to calculate electronic structure of quasi-periodic system containing more than 100,000 electrons at density functional theory levels. It enables to monitor the evolution of electronic structure with respect to the size of the system.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 60 p.
one-photon absorption, two-photon absorption, surface-enhanced Raman scattering
National Category
Theoretical Chemistry
urn:nbn:se:kth:diva-4629 (URN)978-91-7178-857-3 (ISBN)
Public defence
2008-02-25, FA32, Roslagstullsbacken 21, AlbaNova University Center, Stockholm, 14:00
QC 20100823Available from: 2008-02-05 Created: 2008-02-05 Last updated: 2010-08-23Bibliographically approved

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Luo, YiLiu, Kai
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