SOLID STATE, TRANSPARENT, CADMIUM SULFIDE-POLYMER NANOCOMPOSITES By NIKHIL K. KOTHURKAR A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2004 Copyright 2004 by Nikhil K. Kothurkar .`. nih }anen s†z< pivÇimh iv*te, tTSvy< yaegs<isÏ> kalenaTmin ivNdit. Verily, there is nothing in the world more purifying than knowledge. He who prepares his mind through dedicated efforts is sure to find it within. —Bhagavad Gita IV 38 . mm AaTmSvêpay gurve smipRtimdm!. This dissertation is dedicated to my Guru, who is the Indwelling Spirit of all. ACKNOWLEDGMENTS I would like to thank my doctoral adviser and guide, Dr. Anthony B. Brennan for being the wonderful adviser he has been. He inculcated the value for independent thinking and creativity in me from the beginning. I am glad that he gave me the freedom to choose and pursue my research objectives and guidance when needed. In my opinion he has been the perfect combination of freedom and guidance. I would also like to thank my supervisory committee for their time and efforts. Dr. Paul Holloway has been a constant source of inspiration and encouragement to me and I owe him a big thank you. I also appreciate Dr. Douglas for the very informative and useful discussions that I had with him. I thank Dr. Ronald Baney, who has been very kind and understanding in agreeing to substitute on my supervisory committee at a short notice. I thank Dr. Joseph Simmons whose advice, help and encouragement were invaluable during the initial stages of my research. I thank my friends and colleagues from the Brennan Research Group, Clayton Bohn, Dr. Brian Hatcher, Dr. Adam Feinberg, Leslie Wilson, Michelle Carman, Jim Schumacher, Kiran Karve, Thomas Estes, Dr. Charles Seegert, Licheng Zhao, Kenneth Williams and Wade Wilkerson, who have been very cooperative, understanding and helping. I thank, Drs. Jeanne Macdonald, and Jeremy Mehlem who trained me on several instruments and introduced me to graduate research. My thanks to Sherly Jules, who helped me carry out some experiments important for my research. Jennifer Wrighton deserves a special mention for being the best secretary I have met. It is no wonder that iv her understanding, resourcefulness and consideration for everyone, has made her the favorite of everyone who interacts with her. All my thanks and best wishes for her. I owe thanks to the Major Analytical Instrumentation Center for the training and use of their equipment and to Matt Olzta and Dr. Kerry Siebein for their patience and efforts in doing TEM on my samples. I thank Dr. Eric Van Stryland, Dr. David J. Hagan, Joel Hales, Miheala Balu and William Shensky of the Center for Research in Optics and Lasers, University of Central Florida for providing their advice, expertise and equipment for the nonlinear optical measurements. My special thanks to Dr. Jill Verlander Reed at the Electron Microscopy Core, Health Science Center, University of Florida, for providing training and use of the transmission electron microscope (TEM). I also thank Melissa Ann-Lewis, Wencui Zheng, Debbie Akin, for their painstaking efforts in microtoming my samples for TEM I would like to mention my family including my parents, Kishore and Jayshree Kothurkar, my sister, Shirin Navlani and my grandparents, Professor V. K. Kothurkar and Indu Kothurkar. Without their efforts and sacrifices, I would not have been able to pursue my graduate studies here. Murali Rangarajan and Sheshadri Thiruvenkadam have been more than brothers to me as the entire Maitri family has been more than a family to me. I thank them from the bottom of my heart. My wife, Devi has had to go through a lot of hardships and difficulties during the course of my graduate studies. I cannot fully make it up to her but I thank her for being ever so supportive, understanding and just being herself. My daughter Arsha has taught me a lot of patience and given me a sense of responsibility, which has helped me tremendously during my studies. v Lastly I thank and salute to Swami Adhyatma Chaitanya, who is my Guru and best friend. He has been a glorious source of wisdom and inspiration for me throughout my studies. What he has given me transcends all that health, wealth and human relations can give. vi TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................................................................................. iv LIST OF TABLES............................................................................................................. xi LIST OF FIGURES ......................................................................................................... xiii ABSTRACT..................................................................................................................... xvi CHAPTER 1 INTRODUCTION ........................................................................................................1 Introduction...................................................................................................................1 Applications..................................................................................................................2 Optical Limiting ....................................................................................................3 Semiconductor-Polymer Nanocomposite Solar Cells ...........................................4 General Requirements of Nanocomposites for Device Applications...........................5 Specific Aims................................................................................................................6 2 BACKGROUND ..........................................................................................................7 Review of Various Efforts to Synthesize Metal Chalcogenide- Polymer Nanocomposites.......................................................................................................7 Quantum Size Effects in the Absorption Spectra of Semiconductor Nanoparticles ..10 Summary.....................................................................................................................16 3 CADMIUM SULFIDE-POLYSULFONE NANOCOMPOSITES............................17 Introduction.................................................................................................................17 Criteria for Selection of Materials.......................................................................19 Materials and Methods ...............................................................................................20 Sulfonation of Polysulfone..................................................................................20 Synthesis of CdS-PSF Nanocomposites..............................................................21 Phenolated CdS-PSF nanocomposites—Method I (PhCdS-PSF-I) .............22 Phenolated CdS-PSF nanocomposites—Method II (PhCdS-PSF-II)...........23 Amine-capped CdS-SPSF nanocomposites—Method I (AmCdS-SPSF-I) .24 Amine-capped CdS-SPSF nanocomposites—Method II (AmCdS-SPSF-II)25 Fluorothiophenol-capped CdS SPSF nanocomposites (FPhCdS-SPSF)......27 vii Uncapped CdS-PSF nanocomposites (UCdS-PSF)......................................28 Characterization...................................................................................................29 Results and Discussions..............................................................................................30 Optical Properties ................................................................................................35 Scanning Electron Microscopy (SEM) ........................................................36 Transmission Electron Microscopy (TEM)..................................................38 Conclusions.................................................................................................................39 4 CDS-EPOXY NANOCOMPOSITES ........................................................................41 Introduction.................................................................................................................41 Materials and Methods ...............................................................................................43 Synthesis..............................................................................................................43 Characterization...................................................................................................47 Results and Discussion ...............................................................................................49 Optical Images.....................................................................................................49 UV-Visible Spectroscopy....................................................................................50 Fourier Transform Infrared Spectroscopy (FTIR)...............................................55 X-Ray Diffraction................................................................................................57 Transmission Electron Microscopy.....................................................................61 Two Photon Absorption Spectrum (TPA)...........................................................64 Thermogravimetric/Differential Thermal Analysis (TG/DTA) ..........................65 Conclusions.................................................................................................................65 5 AGGREGATION CONTROL IN CDS-EPOXY NANOCOMPOSITES .................68 Introduction.................................................................................................................68