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«by SONAL SINGH Dr. AARON CATLEDGE, CHAIR Dr. DERRICK R. DEAN Dr. JOSEPH G. HARRISON Dr. EUGENIA KHARLAMPIEVA Dr. YOGESH K. VOHRA A DISSERTATION ...»

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INVESTIGATION OF NANODIAMONDS WITH SI-V DEFECT CENTERS FOR

APPLICATIONS IN FLUORESCENCE-BASED SENSING AND DRUG DELIVERY

by

SONAL SINGH

Dr. AARON CATLEDGE, CHAIR

Dr. DERRICK R. DEAN

Dr. JOSEPH G. HARRISON

Dr. EUGENIA KHARLAMPIEVA

Dr. YOGESH K. VOHRA

A DISSERTATION

Submitted to the graduate faculty of The University of Alabama at Birmingham, in partial fulfillment of the requirements for the degree of Doctor of Philosophy

BIRMINGHAM, ALABAMA

2013

INVESTIGATION OF NANODIAMONDS WITH SI-V DEFECT CENTERS FOR

APPLICATIONS IN FLUORESCENCE-BASED SENSING AND DRUG DELIVERY

SONAL SINGH

DEPARTMENT OF PHYSICS

ABSTRACT

Fluorescent Nanodiamond (FND) offers a promising platform for many therapeutic applications involving drug and gene delivery, optical agents for bioimaging and labeling, and molecular detection. This is due to the potential to incorporate photostable luminescent vacancy-related defects into sub-10 nm diamond crystals which are biologically compatible and easy to functionalize. Moreover, the development of future nanoscale devices and arrays based on nanodiamonds (NDs) will require precise spatial control. Hence, the direct placement and manipulation (control of size, shape and chemical functionality) of brightly fluorescent sub-10 nm NDs offers potential for highly localized /specific imaging and sensing, while also providing the potential for controlled therapeutic dosing and release rate.

As the size of NDs gets smaller (with a corresponding reduced number of defect centers), the ability to maintain a high fluorescent yield is extremely important, especially biomedical imaging and detection. One focus of this dissertation is to develop fluorescent ND as a near ideal luminescent center for biomedical applications by incorporation of silicon vacancy (Si-V) defect centers as a viable alternative to nitrogen-vacancy (NV) defects using microwave plasma chemical vapor deposition (MPCVD). Using this ii technique, we aim to create discrete, clinically relevant sub-10 nm size NDs exhibiting bright fluorescence in the far-red emission spectrum. The resulting narrow-band room temperature photoluminescence is intense, and readily observed even for weakly agglomerated sub-10 nm size diamond. This is in contrast to the well-studied nitrogen- vacancy center in diamond which has luminescence properties that are strongly dependent on particle size, with low probability for incorporation of centers in sub-10 nm crystals and that suffer from low brightness in this size regime. The potential for further enhancement of the room temperature luminescence intensity from Si-V centers in nanodiamonds of averaged size 255 nm is demonstrated through controlled nitrogen codoping by adding varying amounts of N2 in a H2+CH4 feedgas mixture during CVD treatment. The strong dependence of Si-V luminescence intensity on nitrogen co-doping is described in terms of an associated evolution in diamond morphology and quality along with the expected influence of nitrogen on the energy of the defects in the diamond bandgap. At low levels, isolated substitutional nitrogen in {100} growth sectors is believed to act as a donor to increase the population of optically active (Si-V)- at the expense of optically inactive Si-V defects, thus increasing the observed luminescence from this center. At higher levels, clustered nitrogen leads to deterioration of diamond quality with twinning and increased surface roughness primarily on {111} faces, leading to a quenching of the Si-V luminescence.

To further improve the applicability of FNDs, the scanning probe based “Dip Pen” nano-lithography” (DPN) technique was used to determine the feasibility to directly place functionalized/ fluorescent NDs onto SiO2 surface, with the ultra-high resolution

–  –  –

influence that various parameters (such as temperature, relative humidity, dwell time etc.) have on the DPN printing process. We determined that the precision patterning of nanodiamonds was made possible by DPN using electrostatically driven transfer of nanodiamond from “inked” cantilevers to a hydrophilic SiO2 substrate. The potential to incorporate photostable Si-V luminescent defect centers into precisely patterned nanoscale diamond particles was realized by subsequent chemical vapor deposition treatment. The results obtained in this research represent a significant step towards resolving extended intracellular biological processes (which require precise spatial control as well as a photostable luminescent center). In addition, our results point the way toward better control of therapeutic dosage and release in targeted drug delivery as well as enhanced molecular detection and standardization.

We anticipate that the intense and photostable far-red luminescence (~738 nm) observed from Si-V defect centers incorporated into spatially arranged nanodiamonds will address the current limitations associated with nanoparticle agglomeration, photobleaching of conventional fluorophores, toxicity and photoblinking of quantum dots, and interference from cell autofluorescence in biological tissues. Potential applications include molecular sensing, single-particle tracking, and nano-manufacturing of hybrid devices containing precisely placed drug-laden ND for slow-release kinetics.





Keywords: fluorescent nanodiamond (FND), scanning probe lithography, Raman mapping, atomic force microscopy, room temperature photoluminescence, biosensingarray, silicon vacancy (Si-V) defect centers, nitrogen vacancy (NV) defect centers,

–  –  –

I dedicate my dissertation to loving memory of my mother, Malati Singh who believed in the pursuit of academic excellence and its significance for me. I dedicate my doctoral thesis with a special feeling of gratitude to my loving and supportive father, Shyam Narayan Singh, my elder brother Ravi Singh and, my sister in law Rekha Singh for their continual encouragement, support and affection at every step of my life.

–  –  –

I would like to take this opportunity to express and extend my sincere gratitude to many individuals for their kind support in the completion of my doctoral work. First and foremost, I would like to thank my advisor, Dr. Aaron Catledge who was abundantly helpful and offered invaluable assistance, support, guidance, motivation and encouragement throughout this work. It is my pleasure to work with Dr. Catledge who has always been extremely generous with his valuable time and suggestion during my graduate study. I would like to thank my doctoral dissertation advisory committee, Dr.

Yogesh K. Vohra, Dr. Joseph G. Harrison, Dr. Eugenia Kharlampieva, and Dr. Derrick Dean for their valuable time, helpful insights and assistance.

I thank to Dr. Vinoy Thomas for his useful and friendly discussions and SEM measurements, Dr. Harrison for his support and guidelines in the development of a computational framework for my research work and valuable discussions throughout my graduate study, Dr. Mary Ellen Zvanut for her help in EPR measurements and supportive guidance, Dr. Veronika Kozlovskaya for dynamic light scattering measurements, Jeff Montgomery for his help in Raman/Photoluminescence spectroscopy instrument, Mr.

Jerry Swell of the physics department machine shop for his assistance in the modification and building experimental equipment, Mr. Mark Case and Amanda in the physics office for their help in financial/academic matters during my research. I would like to thank Dr.

Vohra for his constant support and suggestions during my graduate study at UAB.

My thanks and appreciations also go to many former/current graduate students,

–  –  –

Ashish Kumar, Harsh Patel, Carrie Schindler, Leigh Booth, Sunil Karna, Yujiao Zou, Parimal Bapat, Oleksandra Zavgorodnya. I am thankful to my wonderful friend Pramesh Singh who has consistently helped me keep perspective, supported and encouraged me throughout the process.

I have no words to express my thanks and deep appreciation to my family. I would like to express my heartfelt gratitude to my beloved parents, my family for their affection and patience, sacrifices, going beyond the norms by sending me abroad for study, their continual support and encouragement.

–  –  –

DEDICATION

ACKNOWLEDGEMENTS

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

CHAPTER-1

INTRODUCTION

1.1 Background and Motivation

1.1.1 The Need for a Perfectly Photostable Biocompatible Luminescent Center for Extended Time Dependent in vivo and/or in vitro Studies

1.1.2 Fabrication of Miniature Devices based on Fluorescent Nanodiamonds with Precise Spatial Control

1.2 Intellectual Merit and Significance

1.2.1 Perfectly Photostable Far-Red Luminescence of Si-V defect center as a viable alternative to NV defects in the clinically-relevant sub-10nm discrete nanodiamonds

1.2.2 Precision Patterned Fluorescent Nanodiamonds using Scanning Probe “Dip-Pen” NanoLithography

1.3 Dissertation Objectives

1.4 Dissertation Overview

viii CHAPTER-2

Literature Review: Diamond Properties and Biomedical Applications

2.1 Diamond

2.2 Properties of Diamond Relevant to Biomedical Application

2.3 Nanodiamond in Biomedical Applications

CHAPTER-3

METHODOLOGY

3.1 Diamond Synthesis and Fabrication Methods

3.1.1 Diamond Synthesis by Microwave Plasma Chemical Vapor Deposition

3.1.2 Precision Pattering of Nanodiamonds using Scanning Probe “Dip-Pen” Nanolithography........37

3.2 Diamond Characterization Techniques

3.2.1 Raman Spectroscopy

3.2.2 Fluorescence Spectroscopy/Microscopy

3.2.3 Atomic Force Microscopy

CHAPTER-4

Incorporation of Si-V Defect Centers in Discrete Diamond Crystals

4.1 Strong Narrow-Band Luminescence from Silicon-Vacancy Color Centers in Spatially Localized Sub-10 nm Nanodiamond

4.1.1 Introduction

4.1.2 Synthesis of Si-V in sub-10nm using MPCVD

4.1.3 Morphological Characterization using Tapping Mode AFM

–  –  –

4.1.5 Room temperature photoluminescence (PL) spectroscopy

4.1.6 Conclusions

4.2 Silicon Vacancy Defect Center Photoluminescence Enhancement in Nanodiamond Particles by Controlled Nitrogen Doping

4.2.1 Introduction

4.2.2 Incorporation of Si-V Defect Center in discrete Nanodiamond Crystals and Nitrogen Co-Doping

4.2.3 Dispersion and Morphology of Nanodiamond Crystals onto Silicon Substrate using Scanning Electron Microscopy

4.2.4 Tapping Mode Atomic Force Microscopy to Investigate the Morphological Evolution with Nitrogen doping

4.2.5 Raman Spectroscopy Analysis

4.2.6 Room temperature photoluminescence

4.2.7 Effect of Nitrogen co-doping

4.2.8 Conclusions

CHAPTER-5

Precision-Patterned Nanodiamonds with Enhanced Far-Red Luminescence............... 98

5.1 Introduction

5.2 Synthesis and Fabrication of Spatially Controlled ND-Array using DPN Technique and Incorporation of Si-V Defect Centers in ND-Array

5.2.1 Raw Materials, Stable Nanodiamond “Ink” Preparation and Study of the Ink Properties.......100 5.2.2 Fabrication of Nanodiamond-Array using Dip-Pen Nanolithography

–  –  –

5.3.1 Raman Spectroscopy Analysis

5.3.2 Room temperature photoluminescence spectroscopy and epi-fluorescence microscopy......112 5.3.3 Tapping Mode AFM: Effect of Dwell Time and Relative Humidity

5.4 Conclusions

CHAPTER-6

Conclusions and Future Perspectives

6.1 Conclusions

6.2 Future Perspectives

6.2.1 Encapsulation of Fluorescent Nanodiamonds in Molecularly Printed Polymer for FRET based Biosensors

6.2.2 Computational Framework to Study the Effect of Nitrogen Co-Doping on Si-V luminescence Enhancement in Diamond

6.2.3 Investigation of Si-V and NV Vacancy Defect Centers in Diamond Lattice using EPR...............126 References

–  –  –

Table-1: Universally accepted classification of diamond based on the optical properties.

In fact, every diamond is different in some way. Some diamonds have been shown to consist of more than one type, for example a complex interweaving of Type I and Type II.

Table-2: Assignments for Raman peaks commonly observed in CVD diamond films............... 42 Table-3: Different applications of Raman technique.

Table-4: An incorrect choice of tip for the required resolution can lead to image artifacts and blurred image.

–  –  –

Figure-1: Schematic illustration of FRET based sensing scheme in precision-patterned fluorescent nanodiamond-array upon analyte binding.

Figure-2: The conventional unit cell of diamond, where a0 is the cubic lattice parameter and d is the C-C bond length. The five darker spheres highlight the tetrahedral structure of diamond.

Figure-3: (a) Crystallographic model of the NV center in diamond, consisting of substitutional nitrogen (in red) adjacent to a vacancy (V). (b) Room-temperature PL spectrum showing the ZPL of the neutral (575 nm) and the negatively charged (637 nm) NV center with pronounced and wide phonon side bands at the lower energy side of each ZPL.

Figure-4: (a) The crystallographic model of the Si-V center in diamond, consisting of an interstitial Si atom at the center of two vacancies. (b) Strong narrow zero-phonon line at 738 nm is accompanied by a weak phonon side-band at 757 nm.

Figure-5: Component of a typical microwave plasma CVD system.

Figure-6: Schematic of the DPN process in which a molecule coated single AFM tip deposits ink via a water meniscus onto a substrate.

Figure-7: General Raman spectrum of gem-quality diamond excited at room temperature at a wavelength of 228.9 nm. The first-, second- and third-order Raman peaks are shown[90,91].



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