(nm) A

282 Pages·2007·3.37 MB·English

A BUILDING BLOCK APPROACH TOWARDS NOVEL NONLINEAR OPTICAL
MATERIALS

by

Ajit Bhaskar

A dissertation submitted in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
(Macromolecular Science and Engineering)
in The University of Michigan
2007

Doctoral Committee:

Professor Theodore Goodson III, Chair
Professor Frank E. Filisko
Professor Richard E. Robertson
Professor Robert Zand
Dedication, Determination,

and Inspiration.
The three most important things needed for a PhD and these are where I got them from.
© Ajit Bhaskar
2007
Dedication

I dedicate this dissertation to my parents for their unwavering support and
encouragement.
ii
Acknowledgements

First of all, I would like to express my sincere gratitude to my advisor Professor
Goodson. Not only did he introduce me to the fascinating world of ultrafast spectroscopy
but also provided me with an extremely healthy and synergistic working environment.
His constant motivation and encouragement enabled me to raise everyday and look
forward going to work with a smile on my face. I also consider him as a mentor and I
would look up to him as a role model if I choose to become a faculty member in the
future.
I would like to thank the members on my dissertation committee Professor Frank
Filisko, Professor Richard Robertson and Professor Robert Zand for their valuable
discussions and suggestions.
I would also like to thank Professor Goodson’s group members, particularly Dr
Ramakrishna Guda, Dr Oleg Varnavski, Dr Ying Wang and Dr Xingzhong Yan for
patiently teaching me the details of various spectroscopic tools in our lab. I would like to
thank the other postdoctoral scholars and graduate students of Professor Goodson’s group
who have also been an integral part of making the lab a fun place to work.
Undergraduate and high school students like Unique Luna and Adam Ross have
provided me with the opportunity to mentor and impart my knowledge to them. I would
like to thank them for the opportunity.
My work would not be possible without the synthetic capabilities of Professor
Robert Twieg at Kent State University, Professor Michael Haley at The University of
Oregon, Professor Peter Bauerle at The University of Ulm, Professor Masahiko Iyoda at
Tokyo Metropolitan University and Professor Kazuya Ogawa at Nara Institute of Science
iii
and Technology. I would like to sincerely thank them for providing me with the
opportunity to apply my skills and knowledge on their materials.
I would also like to thank the Macromolecular Science and Engineering program,
particularly Nonna Hamilton and the Macro graduate students for making my stay in Ann
Arbor an extremely pleasant and memorable one.
Last, but never least, I would like to thank my family for their invaluable support.
Without them, I wouldn’t be where I am today.

iv
Table of Contents

Dedication...........................................................................................................................ii
Acknowledgements............................................................................................................iii
List of Figures....................................................................................................................ix
List of Tables..................................................................................................................xvii
Abstract..........................................................................................................................xviii
Chapter 1 Introduction and Background.............................................................................1
1.1. Nonlinear Optics and Nonlinear Optical Materials............................................1
1.2. Two-Photon Absorption......................................................................................5
1.2.1. Background.................................................................................................6
1.2.2. Theoretical Considerations.......................................................................16
1.2.3. Excitations in Conjugated Aggregates......................................................20
1.2.4. Structure-Function Relationships for Developing Organic Materials for
TPA 23
1.3. Overview of Subsequent Chapters....................................................................29
1.4. References.........................................................................................................33
Chapter 2 Experimental Techniques.................................................................................39
2.1. Lasers: The Choice of Light Source for Studying NLO Processes..................39
2.1.1. Properties of Laser Light..........................................................................40
2.2. Generation of Fast Pulses..................................................................................41
2.3. Experimental Methods for Determination of TPA Cross Sections...................47
2.3.1. Two-Photon Excited Fluorescence Method..............................................48
2.3.2. Nonlinear Transmission (NLT).................................................................50
2.3.3. Z-Scan.......................................................................................................51
2.3.4. Non-Degenerate Pump Probe Method13...................................................53
2.4. Techniques for Investigating Excited State and Fluorescence Dynamics........54
2.4.1. Fluorescence Lifetime Measurements......................................................54
v
2.4.2. Ultrafast Transient Absorption Spectroscopy...........................................57
2.4.3. Fluorescence Upconversion......................................................................62
2.5. Reference..........................................................................................................67
Chapter 3 Rigid, Symmetric, Two-Dimensional Graphidyne Networks..........................69
3.1. Introduction.......................................................................................................69
3.2. Experimental.....................................................................................................71
3.2.1. Optical Absorption and Emission Measurements.....................................72
3.2.2. Fluorescence Quantum Yield Measurements...........................................72
3.2.3. Two Photon Absorption Cross Section Measurements............................74
3.2.4. Transient Absorption Measurements........................................................74
3.3. Results and Discussion.....................................................................................75
3.3.1. Optical Absorption and Steady State Fluorescence Measurements..........75
3.3.2. TPA Cross Section Measurements............................................................78
3.3.3. Ultrafast Transient Absorption Measurements.........................................93
3.4. Conclusions.....................................................................................................100
3.5. References.......................................................................................................102
Chapter 4 Investigation of Two-Photon Absorption Properties in Branched Architectures
........................................................................................................................................104
4.1. Overview.........................................................................................................104
4.2. Structure-Property Relationships in Novel Alkene and Alkyne Branched
Chromophores.............................................................................................................105
4.2.1. Background.............................................................................................105
4.2.2. Experimental Details...............................................................................108
4.2.3. Results and Discussion...........................................................................112
4.2.4. Factors Influencing TPA Cross Sections and Rationale.........................122
4.3. Ultrafast Excited State Relaxation Dynamics of a Branched Donor-π-Acceptor
Chromophore: Evidence of Charge Delocalized State...............................................125
4.3.1. Background.............................................................................................125
4.3.2. Experimental...........................................................................................127
4.3.3. Results and Discussion...........................................................................129
vi
4.4. Oligothiophene Dendrimers as Novel Materials for Nonlinear Optical
Applications................................................................................................................140
4.4.1. Introduction.............................................................................................140
4.4.2. Experimental...........................................................................................143
4.4.3. Results and Discussion...........................................................................145
4.5. Conclusions.....................................................................................................152
4.6. References.......................................................................................................155
Chapter 5 Investigation of Enhancement of Two-Photon Absorption Cross Section in
Macrocyclic Thiophenes.................................................................................................164
5.1. Introduction.....................................................................................................164
5.2. Two-Photon Absorption Behavior of Macrocycles Containing Short Thiophene
and Alkyne Segments.................................................................................................166
5.2.1. Background.............................................................................................166
5.2.2. Experimental Details...............................................................................169
5.2.3. Results and Discussion...........................................................................171
5.3. TPA Enhancement in Thiophene Macrocycles Consisting of Alternating
Thiophene and Alkyne Segments...............................................................................186
5.3.1. Background.............................................................................................186
5.3.2. Experimental Details...............................................................................188
5.3.3. Results and Discussion...........................................................................189
5.4. Conclusions.....................................................................................................195
5.5. References.......................................................................................................198
Chapter 6 Nonlinear Optical Properties of Giant Porphyrin Macrocycles.....................201
6.1. Introduction.....................................................................................................201
6.2. Experimental Section......................................................................................204
6.2.1. Materials.................................................................................................204
6.2.2. Steady State Measurements....................................................................205
6.2.3. Two-Photon Absorption Measurements.................................................207
6.2.4. Ultrafast Transient Absorption Measurements.......................................208
6.3. Results and Discussion...................................................................................208
6.3.1. Steady State Measurements....................................................................208
vii
6.3.2. Two Photon Absorption Measurements..................................................210
6.3.3. Ultrafast Transient Absorption...............................................................211
6.4. Conclusions.....................................................................................................213
6.5. Reference........................................................................................................215
Chapter 7 Zinc Ion Sensing via Enhancement of Two-Photon Excited Fluorescence...220
7.1. Introduction.....................................................................................................220
7.2. Experimental...................................................................................................221
7.2.1. Synthesis of Chromophores....................................................................221
7.2.2. Steady state measurements.....................................................................222
7.2.3. Two-Photon Absorption Cross Section measurements...........................222
7.2.4. Ultrafast Transient Absorption Measurements.......................................223
7.3. Results and Discussion...................................................................................223
7.3.1. Steady Stateand TPA measurements.....................................................223
7.3.2. Transient Absorption Measurements......................................................238
7.4. Conclusions.....................................................................................................251
7.5. Reference........................................................................................................253
Chapter 8 Overall Summary and Outlook......................................................................255
8.1. Summary.........................................................................................................255
8.2. Outlook...........................................................................................................259

viii