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Theoretical Characterization of Optical Processes in Modecular Complexes
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
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.
Keyword [en]
one-photon absorption, two-photon absorption, surface-enhanced Raman scattering
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-4629ISBN: 978-91-7178-857-3 (print)OAI: oai:DiVA.org:kth-4629DiVA: diva2:13151
Public defence
2008-02-25, FA32, Roslagstullsbacken 21, AlbaNova University Center, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100823Available from: 2008-02-05 Created: 2008-02-05 Last updated: 2010-08-23Bibliographically approved
List of papers
1. Origin of the Q-band splitting in the absorption spectra of aluminum phthalocyanine chloride
Open this publication in new window or tab >>Origin of the Q-band splitting in the absorption spectra of aluminum phthalocyanine chloride
2007 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 438, no 1-3, 36-40 p.Article in journal (Refereed) Published
Abstract [en]

The Q-band of aluminum phthalocyanine chloride (AlPcCl) shows experimentally distinct splitting in the aqueous solution. Time-dependent density functional theory calculations with inclusion of polarizable continuum model have been performed to reveal the origin of this splitting. It is found that the spectral splitting caused by the formation of dimers and interaction with two water molecules are much smaller than what was predicted by previous semi-empirical study. Our calculations indicate that the experimentally observed large Q-band splitting can be explained by considering the geometrical distortions that are associated with changes of bonds between carbon and nitrogen atoms.

Keyword
Carbon; Chemical bonds; Dimers; Molecular dynamics; Nitrogen; Quantum theory; Spectrum analysis; Aluminum phthalocyanine chloride; Nitrogen atoms; Q-band splitting; Water molecules; Aluminum compounds
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-6974 (URN)10.1016/j.cplett.2007.02.048 (DOI)000245776300007 ()2-s2.0-84962429310 (Scopus ID)
Note
QC 20100820Available from: 2007-04-16 Created: 2007-04-16 Last updated: 2017-12-14Bibliographically approved
2. Aggregation effects on two-photon absorption spectra of octupolar molecules
Open this publication in new window or tab >>Aggregation effects on two-photon absorption spectra of octupolar molecules
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2007 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, no 2, 026101- p.Article in journal (Refereed) Published
Abstract [en]

Aggregation effects on two-photon absorption cross sections of an octupolar molecule, 1,3,5-triamino-2,4,6-trinitrobenzene, have been examined by means of density functional theory calculations in combination with molecular dynamic simulations. It is shown that this octupolar molecule becomes polar in solution and forms aggregates due to the presence of hydrogen bonding between molecules, which can induce a strong redshift of the charge-transfer state and significantly alter the TPA cross section.

Keyword
Absorption spectra; Agglomeration; Charge transfer; Computer simulation; Density functional theory; Hydrogen bonds; Molecular dynamics; Photons; Cross sections; Octupolar molecules; Redshift; Nitrogen compounds
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-7956 (URN)10.1063/1.2751190 (DOI)000248020000038 ()2-s2.0-34547152716 (Scopus ID)
Note
QC 20100820Available from: 2008-02-05 Created: 2008-02-05 Last updated: 2017-12-14Bibliographically approved
3. Two-photon absorption of hydrogen-bonded octupolar molecule clusters
Open this publication in new window or tab >>Two-photon absorption of hydrogen-bonded octupolar molecule clusters
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2008 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 112, no 14, 4387-4392 p.Article in journal (Refereed) Published
Abstract [en]

Charge-transfer octupolar molecules can form clusters in solution through intermolecular hydrogen bonds. In the present work we explore the role of such clustering on two-photon absorption (TPA) spectra assuming 1,3,5-triamino-2,4,6- trinitrobenzene (TATB) as a model system. Using density functional quadratic response theory we examine different cluster structures of TATB dimers, trimers, and tetramers taken from snapshots of molecular dynamics simulations. In comparison with the TPA spectrum of a monomer, significant red shifts of charge-transfer states are predicted for all chosen clusters, which mainly is the result of the distortion of the structures induced by the aggregation. The TPA spectra for dimers and trimers show strong conformation dependence, whereas they turn out to be more stable for tetramers. Enhancements of TPA absorption have also been found for clusters containing less distorted molecules connected by hydrogen bonds.

Keyword
Absorption; Astrophysics; Binding sites; Density functional theory; Dimers; Dynamics; Hydrogen; Light absorption; Luminescence of organic solids; Molecular dynamics; Molecules; Monomers; Multiphoton processes; Oligomers; Optical materials; Photons; Quantum chemistry; American Chemical Society (ACS); Charge transfer state (CTS); charge transfers; cluster structures; Density-functional (DF); Distorted molecules; Distortion (deformation); form clusters; Intermolecular hydrogen bonds; model systems; Molecular dynamics simulations (MDS); molecule clusters; octupolar molecules; Quadratic response (QR); red shifting; Tetramers; TPA spectra; Trinitrobenzene; Two-photon absorption (TPA) spectra; Two-photon-absorption (TPA)
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-7957 (URN)10.1021/jp712118w (DOI)000254659900033 ()2-s2.0-46449138465 (Scopus ID)
Note
QC 20100823. Uppdaterad från accepted till published (20100823). Tidigare titel: Two-photon absorption of hydrogen bonded octupolar molecular clustersAvailable from: 2008-02-05 Created: 2008-02-05 Last updated: 2017-12-14Bibliographically approved
4. Hyperpolarizabilities of end-capped triply branched dendrimers: a theoretical study
Open this publication in new window or tab >>Hyperpolarizabilities of end-capped triply branched dendrimers: a theoretical study
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(English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690Article in journal (Other academic) Submitted
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-7958 (URN)
Note
QS 20120328Available from: 2008-02-05 Created: 2008-02-05 Last updated: 2017-12-14Bibliographically approved
5. Stabilizing single-molecular Raman spectrum of a nonbonding molecule on Ag nanoparticles
Open this publication in new window or tab >>Stabilizing single-molecular Raman spectrum of a nonbonding molecule on Ag nanoparticles
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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.

Keyword
urface-enhanced raman, spectroscopy, scattering
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-7959 (URN)10.1039/b819402e (DOI)000263849800007 ()2-s2.0-61849169677 (Scopus ID)
Note
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: 2017-12-14Bibliographically approved
6. Raman spectra of a single perylene molecule on silver clusters
Open this publication in new window or tab >>Raman spectra of a single perylene molecule on silver clusters
(English)Manuscript (Other academic)
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-7960 (URN)
Note
QC 20100823Available from: 2008-02-05 Created: 2008-02-05 Last updated: 2010-08-23Bibliographically approved
7. An efficient first-principle approach for electronic structures calculations of nanomaterials
Open this publication in new window or tab >>An efficient first-principle approach for electronic structures calculations of nanomaterials
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2008 (English)In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 29, no 3, 434-444 p.Article in journal (Refereed) Published
Abstract [en]

An efficient parallel implementation has been realized for a recently proposed central insertion scheme (Jiang, Liu, Lu, Luo. J Chem Phys 2006,124,214711; J Chem Phys 2006,125, 149902) that allows to calculate electronic structures of nanomaterials at various density functional theory levels. It has adopted the sparse-matrix format for Fock/Kohn-Sham and overlap matrices, as well as a combination of implicitly restarted Arnoldi methods (IRAM) and spectral transformation for computing selected eigenvalues/eigenvectors. A systematic error analysis and control for the proposed method has been provided based on a strict mathematical basis. The efficiency and applicability of the new implementation have been demonstrated by calculations of electronic structures of two different nanomaterials consisting of one hundred thousand electrons.

Keyword
nanomaterials; density functional theory; electronic structures; carbon nanotubes; diamondoids
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-6984 (URN)10.1002/jcc.20799 (DOI)000252864500011 ()2-s2.0-38349153574 (Scopus ID)
Note
QC 20100726Available from: 2007-04-17 Created: 2007-04-17 Last updated: 2017-12-14Bibliographically approved

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