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Table of contents
Introduction
Chapter I. Colloidal semiconductor nanocrystals – Physics and chemistry of Quantum Dots
I.1. Introduction
I.1.1. Description
I.1.2. Crystallinity
I.1.3. Historical background
I.2. Electronic properties of Quantum Dots
I.2.1. Bulk material
I.2.2. Quantum confinement theory
I.2.2.1. Different confinement regimes
I.2.2.2. Particle-in-a-sphere model
I.2.2.3. Optimization of the model
I.2.3. First excited state : 1Se – 1S3/2
I.2.3.1. Degeneracy of first excited state
I.2.3.2. Dark and bright excitons
I.3. Optical properties of Quantum Dots
I.3.1. On an ensemble of Quantum Dots
I.3.1.1. Absorption
I.3.1.2. Fluorescence Emission
I.3.2. On a single Quantum Dot
I.3.2.1. Creation of an exciton and thermal relaxation of charge carriers
I.3.2.2. Exciton recombination and lifetime
I.3.2.3. Auger recombination
I.3.2.4. Quantum yield
I.4. Synthesis of colloidal semiconductor nanocrystals
I.4.1. Nucleation-growth – LaMer theory
I.4.2. Ostwald ripening
I.4.3. Mechanistic approach
I.4.4. Core/shell system
I.4.4.1. Advantages of a core/shell system
I.4.4.2. Different types of core/shell structures
I.4.4.3. Band-gap engineering
I.4.5. Synthesis methods
I.4.5.1. Synthesis of the cores – with precursor injection
I.4.5.2. Synthesis of the cores – one pot
I.4.5.3. Synthesis of the shell – SILAR
I.4.5.4. Synthesis of the shell – dropwise addition
I.5. Blinking of the Quantum Dots emission
I.5.1. The blinking phenomenon
I.5.2. Quantum Dots blinking
I.5.2.1. Characterization of blinking
I.5.2.2. Causes of blinking
I.5.3. Reduction of blinking
I.5.3.1. Addition of molecules
I.5.3.2. Compositions gradient between the core and the shell
I.5.3.3. Thick-shell Quantum Dots
I.6. Two-dimensional systems – Nanoplatelets
I.6.1. Nanoplatelets : atomically flat nanocrystals
I.6.2. Quantum wells & unique optical features
I.7. Conclusion
Chapter II. Synthesis of CdSe/CdS Quantum Dots
II.1. Setup used for the synthesis
II.2. Characterization methods
II.2.1. Absorption
II.2.2. Fluorescence emission
II.2.3. Determination of the Quantum Yield
II.2.4. Excitation (PLE)
II.2.5. Transmission Electron Microscopy
II.2.6. Energy dispersive X-ray spectrometry (EDX)
II.2.7. X-ray Diffraction (XRD)
II.2.8. Magneto-optical measurements
II.3. Synthesis of CdSe cores
II.3.1. Preparation of precursors
II.3.2. Zinc-blende CdSe cores
II.3.2.1. One-pot synthesis
II.3.2.2. Injection synthesis
II.3.3. Wurtzite CdSe cores
II.4. Synthesis of CdSe/CdS Quantum Dots – Dropwise addition
II.4.1. Growth of a thick CdS shell on CdSe one-pot zinc-blende cores (studied in III.2):
II.4.2. Growth of a thick CdS shell on CdSe injection-synthesized zincblende cores:
II.4.3. Growth of a thick CdS shell on CdSe wurtzite cores:
II.4.4. Growth of a composition gradient and thick CdS shell on CdSe wurtzite cores:
II.5. Summary of the Quantum Dots synthesized for the study
II.6. Conclusion
Chapter III. CdSe/CdS Quantum Dots with 100% quantum yield in air, at room temperature
III.1. Setup used for spectroscopic studies
III.1.1. Epifluorescence microscope
III.1.2. Confocal microscope and acquisition setup
III.1.3. Time-resolved acquisitions
III.1.3.1. Photoluminescence trace
III.1.3.2. Photoluminescence decay
III.1.3.3. Photoluminescence intensity autocorrelation
III.1.3.4. Preparation of the sample for single particle studies
III.2. Thick-shell CdSe/CdS Quantum Dots
III.2.1. Zinc-blende CdSe core with a thick CdS shell
III.2.1.1. Optical and Structural characterization
III.2.1.2. Two emissive states at room temperature
III.2.1.3. One grey state under vacuum
III.2.1.4. 100% quantum yield at cryogenic temperature
III.2.1.5. Thermal activation of Auger processes
III.2.2. Other samples
III.2.3. Conclusion
III.3. Bulky-gradient QDs – thick-shell and gradient composition
III.3.1. Optical and Structural characterization
III.3.2. Correlative optical/electron microscopy
III.3.3. 100% quantum yield in air, at room temperature
III.3.3.1. Low excitation regime
III.3.3.2. 100% quantum yield
III.3.3.3. High excitation power
III.3.4. Evolution under vacuum
III.3.5. Quantum yield of the biexciton
III.3.6. White-light emitting Quantum Dots
III.3.7. Lifetime measurements
III.3.8. Evolution at cryogenic temperature
III.3.9. Magneto-optical measurements
III.3.10. Slow recombination dynamics
III.3.11. Amplified spontaneous emission
III.3.12. Conclusion
III.4. Golden-QD – hybrid Quantum Dots/gold nanoshell nanoparticles
III.4.1. Surface plasmons and Purcell effect
III.4.2. Description of Golden-QDs and synthesis
III.4.4. First observations with thin-shell CdSe/CdS QDs
III.4.5. Golden-QDs with thick-shell CdSe/CdS QDs
III.4.6. Effect on blinking behavior
III.4.7. Increased photostability…
III.4.7.1. …with time
III.4.7.2. …with power
III.4.8. Correlative light-electron microscopy
III.4.9. Conclusion
III.5. Conclusion
Chapter IV. Spectroscopic studies of thick-shell CdSe/CdS nanoplatelets
IV.1. Synthesis of nanoplatelets
IV.1.1. Synthesis of CdSe NPLs
IV.1.2. Synthesis of CdSe/CdS core/shell NPLs
IV.2. Optical properties of CdSe nanoplatelets
IV.2.1. Photoluminescence
IV.2.2. Time-resolved photoluminescence
IV.2.3. Blinking behavior
IV.3. Optical properties of CdSe/CdZnS core/shell nanoplatelets synthesized at room temperature
IV.3.1. Photoluminescence
IV.3.2. Time-resolved photoluminescence
IV.3.3. Blinking behavior
IV.4. Optical properties of new generation of core/shell nanoplatelets
IV.5. Conclusion
Chapter V. Quantum Dots as probes for biological imaging
V.1. Fluorescent probes for biology
V.2. Quantum Dots vs organic fluorophores
V.2.1. Photobleaching
V.2.2. Excitation and emission ranges
V.2.3. Lifetime
V.2.4. Functionalization and surface chemistry
V.2.5. Multimodal imaging
V.2.6. Cytotoxicity of Quantum Dots
V.3. Ligand exchange on the surface of Quantum Dots
V.3.1. Necessity of a ligand exchange
V.3.2. Choice of proper ligand
V.4. Targeting of Voltage Dependent Calcium Channels in C.elegans
V.4.1. C.elegans – anatomy and interest
V.4.1.1. A model organism…
V.4.1.2. … widely used in biology
V.4.2. Voltage Dependent Calcium Channels in C.elegans
V.4.2.1. Genetic modification of C. elegans
V.4.2.2. Quantum Dots as bimodal probes for targeting of VDCCs
V.4.2.3. Quantum Dots for biological applications
V.4.3. New polymeric ligand
V.4.4. Preparation of antiGFP-QDs
V.4.4.1. Ligand exchange on the QDs
V.4.4.2. Coupling of anti-GFP antibody to an amino group
V.4.4.3. Coupling of anti-GFP antibody to a carboxylic group
V.4.4.4. Coupling of anti-GFP antibody to a thiol group
V.4.4.5. In vitro evaluation of the coupling specificity of the antiGFP-QDs
V.4.5. Microinjection of antiGFP-QD
V.4.6. High-pressure freezing
V.4.7. Macroscopic targeting in living worms
V.4.8. Nanometer resolution analysis
V.4.9. Conclusion
V.5. DNA nanocage as a functional biocompatible scaffold
V.5.1. DNA nanocage: a versatile scaffold
V.5.2.1. Preparation of Quantum Dots
V.5.2.2. Encapsulation of QDs in the nanocage
V.5.2.3. Verification of encapsulation
V.5.3. Monofunctionalization of DNA icosahedron
V.5.4. Probing the Shiga toxin endocytosis pathway
V.5.5. Conclusion
Conclusion
References
