development of visible-to-ultraviolet upconversion phosphors for light-activated antimicrobial ...

227 Pages·2013·5.9 MB·English

DEVELOPMENT OF VISIBLE-TO-ULTRAVIOLET
UPCONVERSION PHOSPHORS
FOR LIGHT-ACTIVATED ANTIMICROBIAL TECHNOLOGY

A Dissertation
Presented to
The Academic Faculty

By

Ezra Lucas Hoyt Cates

In Partial Fulfillment
Of the Requirements for the Degree
Doctor of Philosophy in Environmental Engineering

Georgia Institute of Technology

May, 2013
DEVELOPMENT OF VISIBLE-TO-ULTRAVIOLET
UPCONVERSION PHOSPHORS
FOR LIGHT-ACTIVATED ANTIMICROBIAL TECHNOLOGY

Approved by:

Dr. Jaehong Kim, Advisor Dr. Seung Soon Jang
School of Civil and Environmental School of Materials Science and
Engineering Engineering
Georgia Institute of Technology Georgia Institute of Technology

Dr. Ching-hua Huang Dr. Angus P. Wilkinson
School of Civil and Environmental School of Chemistry and Biochemistry
Engineering Georgia Institute of Technology
Georgia Institute of Technology

Dr. John C. Crittenden Date Approved: March 13, 2013
School of Civil and Environmental
Engineering
Georgia Institute of Technology
To my parents, who gave me everything
ACKNOWLEDGEMENTS

My achievements in graduate school would not have been possible without the
outstanding hard work, advice, encouragement, and emotional support of my advisor, Dr.
Jaehong Kim. His dedication to his students, research, teaching, family, and desire to
help others is humbling, and I could ask for no greater role model. I feel extremely
lucky to have worked in his lab and spent the last five years in such a supportive
environment where I could grow as a scientist and as a human being. (And thanks for all
the dinners, karaoke, and for finding me a wife).
I wish to thank the members of my committee – Dr. Ching-hua Huang, Dr. John
Crittenden, Dr. Seung Soon Jang, and Dr. Angus Wilkinson – for volunteering to provide
me with guidance on numerous occasions, despite their chaotic schedules. I am
especially indebted to Dr. Wilkinson who donated so much of his time to helping me with
experiments and discussing ideas, despite the lack of any real obligation to do so, aside
from a genuine love of science. He is a truly gifted lecturer whose teachings made it
possible for me to succeed in this research.
I would like to express my sincere appreciation to Dr. Guangxuan Zhu for
working tirelessly to keep things in the Daniel Laboratory working smoothly, and for
keeping everyone safe. I hope I always have someone of his caliber working close by.
Also, thanks to Jenny Eaton for her consistent work and dependability as a critical
support beam for our entire department.
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Special thanks to everyone else who assisted with my research: Dr. Min Cho for
training me and making my the first publication possible; Dr. Felix Castellano and Fan
Deng at Bowling Green State University for welcoming me into your lab and helping me
acquire data; and everyone in the Kim group for all their calming presence and good
times in the office.
I am forever grateful to Stephanie, my coworker and soon-to-be wife, for filling
both my home life and work life with joy. She has helped me with countless experiments
and worked to expand this research into new areas while providing unending support and
affirmation.
Finally and foremost, I thank my parents for their sacrifice and hard work, which
has enabled me to make it this far.

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CONTENTS

ACKNOWLEDGEMENTS……………………………….……………………………iii
LIST OF TABLES…………………………………………………………….……..….ix
LIST OF FIGURES……………………………………………………………..………x
ABBREVIATIONS……………………………………………………………….……xiv
SUMMARY…………………………………………………………………...……….xvii
CHAPTER 1: INTRODUCTION………………………..…………………………….1
1.1. Statement of Problem………………………………….…………………………1
1.2. Research Objectives…………………………………… ………….……………. 4
CHAPTER 2: BACKGROUND………………………………………………….…….7
2.1. Existing Antimicrobial Surface Technologies………………………….…….…7
2.2. Microbial Inactivation by UVC Radiation and Advantages of UC-AMS..… 11
2.3. Upconversion Photoluminescence………………………………………….…. 15
2.3.1. Upconversion Mechanisms in Lanthanide-doped Phosphors…………. .. 15
2.3.2. History and Applications……………………………………………...….19
2.3.3. Phosphor Design Considerations……………………………….………..23
2.3.4. Organic Upconversion Systems……………….……………….……… ..25
2.4. Literature Review: Application of Upconversion Conversion Materials to
Energy and Environmental Technology……..……………………….……….31
2.4.1. Introduction………………………………………………………………31
2.4.2. Enhancing Spectral Response in Solar Cells……………………….…….33
2.4.3. Enhancing Spectral Response of Photocatalysts…….……………..…….38
2.4.4. Challenges……………………………………………………………..….44
2.5. Literature Review: Optical Properties of Praseodymium…….....…...………48
2.5.1. Background on Visible-to-UVC Upconversion……..……………………48
2.5.2 Phosphor Design Considerations………….……………………………..50
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2.6. Acknowledgements………………………………………………………..……54
CHAPTER 3: DEVELOPMENT OF PHOTOLUMINESCENCE SPECTROSCOPY
SYSTEM FOR VISIBLE-TO-UVC UPCONVERSION………………………………..……55
3.1. Introduction…………..……………………………………………….…………55
3.2. Excitation Sources………………………………………………………………57
3.3 Optics and Sample Holder…………………………..………………….………58
3.4 Detection System…………………………………………………………………59
CHAPTER 4: UPCONVERSION ANTIMICROBIAL SURFACES PROOF-OF-
CONCEPT: SURFACE DEVELOPMENT AND MICROBIAL STUDIES……………61
4.1. Introduction………… ………………………………………….………….……61
4.2. Experimental Section……………………...……………………………….……62
4.2.1. Materials………………………….………………………………….……62
4.2.2. Powder Phosphor Synthesis………………………………………….…...63
4.2.3. Coating Procedure…………………………………………………..……64
4.2.4. Characterization…………………………………………………….…….64
4.2.5. Biofilm Growth and Imaging…………...……………………………..….65
4.2.6. Surface Inactivation………………………………………………………66
4.3. Results and Discussion………………………………………………..….......…68
4.3.1. Phosphor Development…………..………………………………………68
4.3.2. Biofilm Inhibition………………………………………………………...75
4.3.3. Surface Inactivation………………………………………………………78
4.4. Acknowledgements…………………………………….……………….....……81
CHAPTER 5: DELINEATING MECHANISMS OF UPCONVERSION
ENHANCEMENT BY Li+ CODOPING IN Y SiO :Pr3+ ………………………...82
2 5
5.1. Introduction………………………………………………………….…………82
5.2. Experimental Section………………………………………………….…….…85
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5.2.1. Syntheses…………………………………………………………..……85
5.2.2. Analyses…………………………………………………………………86
5.3. Results and Discussion……………………………………………………..…..86
5.3.1. Upconversion Emission………………………………………………….86
5.3.2. Crystal Structure and Morphology……………………….………………89
5.3.3. Delineation of Enhancement Mechanisms………………………………96
5.4. Conclusion………………………………………………………….………..…105
5.5. Acknowledgements…………………………………………………..……...…105
CHAPTER 6: UPCONVERSION UNDER POLYCHROMATIC
EXCITATION……………………………………………………………………….106
6.1. Introduction…………………………….……………………………..………106
6.2. Experimental Section………………………………………………….………109
6.3. Results and Discussion………………………………………………..….……111
6.4. Conclusion……………………………………….………………………..……121
6.5. Acknowledgements………………………………………………………..……122
CHAPTER 7: LOW-PHONON ENERGY HOST CRYSTALS: RARE EARTH
OXYFLUORIDES…………………………………………………………………….123
7.1. Introduction…………………………………………………………………….123
7.1.1 Backgound……………………………………………………………….123
7.1.2 Structural Properties of Rare Earth Oxyfluorides………………..………128
7.2. Experimental section…………………………………………………..………131
7.2.1. Syntheses………………………………………………………………..131
7.2.2. Characterization…………………………………………………………132
7.3. Results and discussion……………………………………….…………….…..133
7.3.1. Solid State Reaction Behavior………………………………………..…133
7.3.2. Luminescence…………………………………………………………...137
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7.3.3. Crystal Structure………………………………………………………..144
7.4. Conclusion……………………………………………….…………………….146
CHAPTER 8: PREDICTING THE EFFECT OF MATERIAL AND
ENVIRONMENTAL PARAMETERS ON ESTIMATED ANTIMICROBIAL
EFFICACY………………………………………………………………….….….….147
8.1. Introduction……………………………………………………….……………147
8.2. Methods………………………………………………………………….……...151
8.2.1. Model Development……………………………………………………..151
8.2.4. Pr3+ Efficiency Calibration and Model Use……………………….…….155
8.3. Results and Discussion…………………………………………………..…….157
CHAPTER 9: SUMMARY, OUTLOOK, AND FUTURE WORK……………….161
9.1. Summary of Results……………………………………………………………161
9.2. Outlook………...…………………………………………………………...…..164
9.3. Future Work……………………………………………………………………166
APPENDIX A: PHOTOLUMINESCENCE SPECTROSCOPY SYSTEM
COMPONENTS………………...……………………………………………………..168
APPENDIX B: REFINED CRYSTALLOGRAPHIC PARAMETERS OF
PHOSPHORS………………..………………………………………….……………..172
REFERENCES……...…………………………………………………………………174

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LIST OF TABLES

Table 1. Studies reporting estimated absolute external optical conversion efficiencies of
upconversion phosphors.................................................................................................... 28

Table 2. Advantages (+) and disadvantages (-) of inorganic lanthanide-doped UC
phosphors versus organic TTA UC systems. ................................................................... 30

Table 3. Results of recent studies reporting UC-enhanced solar cells under low power
excitation sources. ............................................................................................................ 37

Table 4. Effects of various codopants on the crystal structure (polymorph) of Y SiO :Pr3+
2 5
annealed at 1000 ºC. ........................................................................................................ 94

Table 5. Properties of crystals and Pr3+ as dopants in each respective host. ................. 127

Table 6. Results of preliminary Lu O F :Pr3+ ceramic syntheses. ........................... 140
x x-1 x+2

Table 7. Parameters affecting the performance of upconversion antimicrobial
surfaces........................................................................................................................... 149

Table 8. Predicted exposure time required for 90% inactivation of E. coli .................. 158

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