SYNTHESIS OF NEW NANOCRYSTAL MATERIALS by Yasser Hassan Abd El-Fattah Hassan A ...

265 Pages·2016·10.54 MB·English

SYNTHESIS OF NEW NANOCRYSTAL MATERIALS
by
Yasser Hassan Abd El-Fattah Hassan
A thesis submitted in conformity with the requirements
for the degree of Doctor of Philosophy
Department of Chemical Engineering and Applied Chemistry
University of Toronto
© Copyright by Yasser Hassan 2016
Synthesis of New Nanocrystal Materials
Yasser Hassan
Doctor of Philosophy
Department of Chemical Engineering and Applied Chemistry
University of Toronto
2016

Abstract
Colloidal
semiconductor nanocrystals (NCs) have sparked great excitement in the scientific
community in last two decades. NCs are useful for both fundamental research and technical
applications in various fields owing to their size and shape-dependent properties and their
potentially inexpensive and excellent chemical processability. These NCs are versatile
fluorescence probes with unique optical properties, including tunable luminescence, high
extinction coefficient, broad absorption with narrow photoluminescence, and photobleaching
resistance. In the past few years, a lot of attention has been given to nanotechnology based on using
these materials as building blocks to design light harvesting assemblies. For instant, the pioneering
applications of NCs are light-emitting diodes, lasers, and photovoltaic devices.
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Synthesis
of the colloidal stable semiconductor NCs using the wet method of the pyrolysis of
organometallic and chalcogenide precursors, known as hot-injection approach, is the chart-topping
preparation method in term of high quality and monodisperse sized NCs. The advancement in the
synthesis of these artificial materials is the core step toward their applications in a broad range of
technologies.
This
dissertation focuses on exploring various innovative and novel synthetic methods of
different types of colloidal nanocrystals, both inorganic semiconductors NCs, also known as
quantum dots (QDs), and organic-inorganic metal halide-perovskite materials, known as
perovskites. The work presented in this thesis focuses on pursuing fundamental understanding of
the synthesis, material properties, photophysics, and spectroscopy of these nanostructured
semiconductor materials.
This
thesis contains 6 chapters and conclusions. Chapters 13 focus on introducing theories and
background of the materials being synthesized in the thesis. Chapter 4 demonstrates our synthesis
of colloidal linker–free TiO /CdSe NRs heterostructures with CdSe QDs grown in the presence of
2
TiO NRs using seeded–growth type colloidal injection approach. Chapter 5 explores a novel
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approach of directly synthesized CdSe NCs with electroactive ligands. The last Chapter focuses
on a new class of perovskites. I describe my discovery of a (bottom-up) simple method to
synthesize colloidally stable methyl ammonium lead halide perovskite nanocrystals seeded from
high quality PbX NCs with a pre-targeted size. This chapter reports advances in preparation of
2
both these materials (PbX , and lead halide perovskite NCs).
2
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Dedication
To My Parents and My Stepmother
To My Wife Marwa H. Ibrahim
To My Brothers and Sisters
To My Beautiful Kids
To My Teachers
To My Family
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To Every knowledge seeker:
Al-Khatib al-Baghdadi stated in his book “The History of the
City of Peace: The History of Baghdad” that:
Imam Al-Juwayni (died 1085) wrote to one of his students said
Imam Al-Shafi‘i wrote a rhyme of poetry:
نايبب اهليصفت نع كئبنأس ةتسب لاإ ملعلا لانت نل يخأ
نامز لوطو ذاتسأ نيقلتو ةبرغو راقتفاو صرحو ءاكذ
“Oh my brother you will never become a scholar until you
complete the six pillars of THE REQUISITES OF
KNOWLEDGE:
A QUICK MIND, ZEAL FOR LEARNING, POVERTY,
FOREIGN LAND, A PROFESSOR'S INSPIRATION, AND OF
LIFE A LONG SPAN.”
End of Quote!

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Acknowledgments
I would like to thank a number of individuals, without their unique insights and wisdom, I would
have struggled to find the motivation, enthusiasm, inspiration, support, and guidance to complete
this work.
First of all, I wish to express my deepest gratitude to my advisors, Professor Gregory D. Scholes
and Professor Mitch Winnik for their inspiration, continued encouragement, priceless suggestions,
and support while working in Toronto. Their mentorship has helped me become a better scientific
writer, strategic planner and critical thinker about science. I would like to express my profound
appreciation to my advisor Professor Scholes who graciously welcomed my visit to his lab
20092010 and then provided me with the incredible opportunity to complete my Ph.D. at the
University of Toronto. There is no doubt without his continued encouragement, invaluable
suggestions, invaluable mentorship, exceptional support and keen insights, patient guidance, I
would not have made it to this stage of success. Greg became more of a mentor and friend than a
professor. Moreover, the work environment in Professor Scholes’ lab was a fantastic experience.
Additionally, I would like to thank Professor Tim Bender and Professor Dwight Seferos for being
members in my committee and for all of their help and kind suggestions related to my research. I
am indebted to Professor Bender to be a friend and mentor. Thanks Tim! This is highly appreciated.
I would like to thank Professor Zheng-Hong Lu and Professor Peng Zhang for their willingness to
spend time reading this thesis and be part of my departmental examination.
I would also like to thank and to express deep appreciation to my coworkers who assisted me on
these research projects. I am so thankful to my colleagues and friends at the university, especially
the ones in the Scholes and Winnik groups. They were all exceptional people. All of their support
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and encouragements helped me significantly toward the completion of my studies at the University
of Toronto. The following is a list of all my former and current coworkers and colleagues who
helped me carry out the different research projects at the University of Toronto. I was fortunate to
work within this environment. In particular I would like to thank my friend and colleague Ahmed
Abdelrahman for working on the documents, renting an apartment, and his countless support
during my the past seven years. Thanks Ahmed. I feel you are one part of the family. I would to
thank Dr. Anna Lee and Dr. Gerald Guerin for their advice and support. I thank my current and
former fellow labmates from Scholes group. I would like to thank Dr. Haizheng Zhong and Yaser
Khan for all their insightful comments and help provided in the beginning of my work in Scholes’
lab. I would like to thank my friend Dr. Mahmoud Dawood (University of Zagazig) for helping in
reproducing Figures 2.12, 3.1 and 3.2.
An acknowledgement with a very special thanks goes out and deeply appreciation to Dr. Ryan
Pensack, Dr. Yoichi Kobayashi, Dr. Yin Song, and Dr. Elsa Cassette. Without whose
encouragement and technical support, I would not have finished up my Chapters 5 and 6 of this
thesis.
Special thanks for Dr. Ryan Pensack (the Boss) for being a fantastic mentor, always helping and
being the greatest friend. Boss, I am so indebted for having you during my PhD!!
I must also acknowledge my collaborators: (a) Professor Clemens Burda and his student Chi-Hung
Chuang for their insightful comments and help provided for transient absorption measurements
done for the colloid linker-free TiO /CdSe Nanorods synthesis project which presented in Chapter
2
4. (b) Professor Datong Song and his student Trevor Janes for their insightful comments and
involvement in the “Direct Synthesis of CdSe Nanocrystals with Electro-active Ligands” project
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found in Chapter 5 of this thesis. (c) Professor Axel Guenther and his students Milad Abolhasani,
Parnian Saberi for their collaborations.
I gratefully acknowledge the funding sources that funded my Ph.D. work. First I thank the Egyptian
Ministry of Higher Education for funding my visit to U of T in 20092010 and the Natural Sciences
and Engineering Research Council of Canada (NSERC) for funding my PhD work. This financial
support has enabled me to focus on my professional and scientific development. It is my hope that
our efforts in this thesis can add to a better quality of life throughout the world.
I would like to thank my entire family and long-time friends for their love, support and
encouragement. I would like to express profound gratitude and deeply appreciation to my parents
and all siblings from whom I got unconditional love and inspiration that shaped my actions and
morals.
Last and not least, I am greatly indebted to of my beautiful wife, Marwa Hamza Ibrahim. None of
this could have happened without her patience and sacrifices. I am thankful for her endless love
and encouragement. Marwa, you are always there cheering me up, supporting me spiritually
throughout my good times and bad times of our life. I thank my lovely kids. You are a blessing in
my life. Thanks God!!
To you all, without you this thesis would not have been possible. I thank you.

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Table of Contents
Abstract…………………………………………………………………………………………..ii
Acknowledgments ........................................................................................................................ vi
Table of Contents ......................................................................................................................... ix
List of Tables .............................................................................................................................. xiv
List of Figures .............................................................................................................................. xv
List of Abbreviations ............................................................................................................... xxvi
List of Mathematical Terms .................................................................................................. xxviii
List of Materials ....................................................................................................................... xxix
Chapter 1: Introduction .............................................................................................................. 1
1.1 Motivation and Background: The Global Energy Demand ................................................ 1
1.2 Fossil Fuels and Climate Change ........................................................................................ 3
1.3 Renewable Energy Resources ............................................................................................. 4
1.4 Development of Material Architectures for Solar Energy .................................................. 6
1.5 Thesis Goal ......................................................................................................................... 8
1.6 References ........................................................................................................................... 9
Chapter 2: Semiconductors: Review and Theory.................................................................... 10
2.1 Semiconductor Conductivity ............................................................................................ 10
2.2 The interaction of Light with Semiconductors ................................................................. 11
2.3 Semiconductor Crystal Structures ..................................................................................... 12
2.3.1 The Bravais Lattice ........................................................................................................... 13
2.3.2 The Atom Positions and Crystal Structure ........................................................................ 15
2.3.3 Coordination Number ....................................................................................................... 16
2.3.4 Miller Indices .................................................................................................................... 17
2.3.5 Interplanar Spacing ........................................................................................................... 19
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2.4 Popular Types of Semiconductor Crystal Structures ........................................................ 20
2.4.1 Wurtzite Crystal Structure ................................................................................................ 20
2.4.2 Zinc Blende Crystal Structure ........................................................................................... 22
2.4.3 Perovskite Crystal Structure ............................................................................................. 23
2.5 The Crystal Structure and Physical Properties of the Material ......................................... 25
2.6 Crystal Structure and Origin of the Band Gap .................................................................. 26
2.6.1 Drude-Lorentz model-Free Electron Theory .................................................................... 26
2.6.2 Braggs’ Diffraction ........................................................................................................... 28
2.6.3 Kronig-Penney Model (Periodically Repeated Potential Well) ........................................ 30
2.7 Exciton in Semiconductors ............................................................................................... 34
2.7.1 Frenkel Exciton ................................................................................................................. 34
2.7.2 Wannier-Mott exciton ....................................................................................................... 36
2.8 Different types of Perovskite materials and Their Applications ....................................... 40
2.8.1 Inorganic Perovskite Materials ......................................................................................... 40
2.8.2 Organic-Inorganic Metal Halide-Perovskite Materials ..................................................... 41
2.9 References ......................................................................................................................... 45
Chapter 3 Semiconductor Nanocrystals: An Overview ........................................................... 48
3.1 Quantum Confinement: Definition ................................................................................... 48
3.2 Major Milestones toward Nanocrystals ............................................................................ 49
3.2.1 The Idea of Small Scale .................................................................................................... 49
3.2.2 Nanometer-Thick Foils Called Quantum Wells (2D Structures) ...................................... 50
3.2.3 From 2D QW Heterostructures to 1D and to 0D Structures ............................................. 51
3.2.4 Colloidal Quantum Dots-Wet Chemistry .......................................................................... 53
3.3 Discovery of Organometallic Synthesis of QDs: .............................................................. 54
The Hot-injection Approach .................................................................................................... 54
3.3.1 Progress in Nanocrystals Synthesis Using Hot-injection Approach ................................. 56
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