Self-Assembled Organic-Inorganic Nanostructures

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1 Self-Assembled Organic-Inorganic Nanostructures Optics and Dynamics edited by Eduard Zenkevich Christian von Borczyskowski

2 Self-Assembled Organic-Inorganic Nanostructures

4 Self-Assembled Organic-Inorganic Nanostructures Optics and Dynamics editors Preben Maegaard Anna Krenz Wolfgang Palz edited by Eduard Zenkevich Christian von Borczyskowski The Rise of Modern Wind Energy Wind Power for the World

5 Published by Pan Stanford Publishing Pte. Ltd. Penthouse Level, Suntec Tower 3 8 Temasek Boulevard Singapore editorial@panstanford.com Web: British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Self-Assembled Organic-Inorganic Nanostructures: Optics and Dynamics Copyright 2016 Pan Stanford Publishing Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. ISBN (Hardcover) ISBN (ebook) Printed in the USA

6 For Tamara and Sabine

8 Contents Preface Acknowledgments xv xix 1. Structural and Energetic Dynamics in Quantum Dot Dye Nanoassemblies 1 Eduard Zenkevich and Christian von Borczyskowski 1.1 Introduction QD Surface Properties and Interface Phenomena Formation Strategies for QD Dye Nanoassemblies Verification of QD Photoluminescence Quenching in QD Dye Nanoassemblies Self-Assembly of Semiconductor Quantum Dots and Functionalized Dye Molecules Interacting Subunits and Self-Assembly Approach Nanoassemblies Based on Quantum Dots and Porphyrin Molecules Comparative titration experiments and nanoassembly formation Conditions for nanoassembly formation Quantitative studies of QD PL quenching and porphyrin fluorescence sensitization in QD porphyrin nanoassemblies Nanoassemblies Based on QDs and Perylene Diimide Molecules 45

9 viii Contents Nanoassembly formation and manifestation of surface-related and temperature effects Role of the Solvent Polarity in Competition between FRET and Non-FRET Quenching Processes for QD PL in Nanoassemblies Single Nanoassembly Quantum Dot Blinking Statistics in QD Porphyrin Nanoassemblies PL Quenching, Geometry of Nanoassemblies and Conformational Stability of PDI Molecules on QD Surfaces Time Dependent Fluctuations of FRET in Single QD Dye Nanoassemblies Quantitative Analysis of Non-Radiative Relaxation Pathways for Quantum Dots in Nanoassemblies QD PL Quenching via Foerster Resonant Energy Transfer in QD Dye Nanoassemblies Size-Dependent Non-FRET QD PL Quenching in QD Dye Nanoassemblies Competition of FRET and Non-FRET Processes Tuning Quantum Dot Electronic States and Exciton Relaxation Dynamics by One Attached Dye Molecule Conclusions Interrelation of Assembly Formation and Ligand Depletion in Colloidal Quantum Dots 149 Danny Kowerko 2.1 Introduction Experimental Methods Bulk Fluorimetry of QDS, PBI Molecules and QD-PBI Assemblies Single-Molecule Spectroscopy Data Analysis 154

10 Contents ix Software and Gauss-Fit Based Analysis Extracting PL Decay Rates and Electronic States from PL Lifetime Intensity Distributions Monoexponential PL lifetime distributions Multi-exponential PL lifetime distributions Surface-Chemistry of Quantum Dots Studied at the Ensemble and Single-Molecule Level Ensemble Spectroscopy of CdSe/ZnS Quantum Dots Ligand depletion and spectral heterogeneity revealed by spectroscopy of diluted CdSe/ZnS QDs Non-FRET type PL quenching and spectral blue shifts of CdSe/ZnS QD-dye assemblies PL lifetime analysis of diluted CdSe/ZnS QDs Single-Molecule and Single-Particle Spectroscopy PL lifetime intensity relations of single quantum dots Correlation of intensity and spectral fluctuations indicates the quantum confined Stark effect Photo-oxidation of single CdSe/ZnS QDs investigated by time-resolved single-molecule spectroscopy Non-FRET PL quenching in single QD-dye assemblies Comparison of Surface-Related Photophysical Phenomena of Ensemble and Single-Particle Experiments Conclusion 193

11 x Contents 3. Fluorescence Quenching of Semiconductor Quantum Dots by Multiple Dye Molecules 201 Thomas Blaudeck 3.1 Introduction Theory of Acceptor Redistribution in Heteroaggregates Fluorescence Quenching Evaluation of Photoluminescence Quenching Experiments and Modified Stern Volmer Formalism Derivation of the Photoluminescence Quantum Yield of a Donor in Presence of Multiple Acceptors Case Study: A Donor with Quasi-Infinite Numberof Binding Sites Case Study: A Donor with a Finite Number of Binding Sites Application of the Redistribution Model to Experiments Conclusion Static and Dynamic Quenching of Quantum Dot Photoluminescence by Organic Semiconductors and Dye Molecules 215 Ines Trenkmann, Thomas Blaudeck, and Christian von Borczyskowski 4.1 Introduction Experimental Results and Discussion Decrease of Photoluminescence with Observation Time Stern Volmer Formalism for Photoluminescence Quenching Photoluminescence Intensity as a Function of TPD Concentration 223

12 Contents xi Photoluminescence Decay Time as a Function of TPD Concentration Deconvolution of Static and Dynamic PL Quenching Ligand-Replacement Model for PL Quenching Static and Dynamic PL Quenching by Functionalized Porphyrin Molecules Conclusion Selected Applications of QDs and QD-Based Nanoassemblies 245 Eduard Zenkevich and Christian von Borczyskowski 5.1 Introduction A Brief Overview of the Early History of QDs Applications Semiconductor Nanostructures for Solar Cells and Photovoltaics Singlet Oxygen Generation and Biomedical Aspects for Semiconductor Quantum Dots and Their Bioconjugates Quantum Dot-Based Nanoassemblies in Sensing, Imaging, and Diagnostics Super-Resolution Microscopy with Quantum Dots Conclusions Nanolithography and Decoration of Generated Nanostructures by Dye Molecules 295 Harald Graaf and Thomas Baumgärtel 6.1 Introduction Silicon Oxide Nanostructures on Alkyl-Terminated Silicon Surfaces Attachment of CdSe-Nanocrystals on Alkyl-Terminated Silicon 303

13 xii Contents 6.4 Attachment of Charged Dye Molecules Attachment of Rhodamine 6G and Cresyl Violet to the LAO Oxide Structure Attachment of a Spermine-Functionalized Perylene Diimide Derivative to the LAO Oxide Optical emission at room temperature Optical emission at low temperature Fluorescence life time investigations Covalent Attachment of FITC Conclusion Identification of Heterogeneous Surface Properties via Fluorescent Probes 353 Daniela Täuber and Christian von Borczyskowski 7.1 Introduction Impact of Chemical Inhomogeneities of SiO 2 Surfaces Optical Decoration of Silanol Groups Influence of Surface Inhomogeneities on Diffusion Dynamics in Ultrathin Liquid Films Decorating Charged Si Nanoparticles with Charge-Sensitive Dye Molecules Conclusion Selective Surface Binding of Dye Molecules on Hybrid Humidity Sensors 371 Ines Trenkmann 8.1 Introduction Experimental Results 375

14 Contents xiii Analysis of the As-Prepared Hybrid Structures Analysis of Rhodamine-Functionalized Hybrid Structures Discussion 382 Index 385

16 Preface The current state and perspectives in sciences are strongly linked to the development of novel complex materials as well as to the availability of sophisticated state-of-the-art experimental tools that enable the investigation and manipulation of the objects at various levels of organization, including single nanoobjects and biological sub-structures. The combination of organic and inorganic materials promises to make use of advantages of both types of materials, e.g., downsizing inorganic materials to the nanoscale (as is typical for state-of-the-art devices) and, e.g., nearly unlimited synthesis of functional organic compounds (even mimicking biologically relevant entities). Of special interest are those organic/inorganic entities that are formed due to self-assembly offering chemically specific and versatile formation routes according to the concepts of supramolecular chemistry. Due to the high functionality of such self-assembled nanostructures, applications are readily envisaged or already realized in nanosensorics, bio-medical applications, and photovoltaics. Recent advancements in nanotechnology permit to produce a variety of functional colloidal semiconductor quantum dots (QDs) and QD-based nanomaterials with unique optical and physicochemical properties which are principally different from those of bulk materials of the same composition. Science and technology of QDs and QD-based nanomaterials have to deal with (on every length scale, from the molecular to the macro) surface and interfacial phenomena that can be tuned by varying the surface and interfacial energy and by changing the specific chemical interactions with organic compounds attached to such surfaces and interfaces. It means that namely the surface chemistry related to organic/ inorganic interactions plays the principal role in the formation of optical properties of QDs and QD-based nanomaterials as well as may be considered as gateway to their possible applications in optoelectronic devices and nanosensors and as optical labels and drug carriers in biomedicine.

17 xvi Preface An alternative approach to inorganic/organic self-assembled structures on the nanoscale is to scale down inorganic substrates via nanolithography resulting in functionalized nanostructures or to even make use of inherent chemical heterogeneities of an inorganic surface. Again, in both cases appropriate organic molecules self-assemble on such artificial or natural nanostructures. In a recent Monograph, Tuning Semiconducting and Metallic Quantum Dots: Spectroscopy and Dynamics, we described the optical properties and photophysics of quantum dots concentrating on interfaces/surfaces and the perspectives of tuning the energies of electronic states and related dynamics. Basically, the present book provides a comprehensive description of the morphology and main physico-chemical properties of QD dye self-assembled nanostructures and natural or lithographically generated surface inhomogeneities (with focus on results, including even some unpublished ones, obtained in our groups within the past decade, as well as some applications in the field of nanotechnology. It crosses disciplines to examine essential nanoassembly principles of inorganic nanostructures with organic molecules, excited state dynamics in nanoobjects, theoretical models, and methodologies. We show that upon nanoassembly formation, photochemical processes occurring at the interface between inorganic nanostructures and functionalized organic molecules and/or bio-objects are complex and may yield new and unexplored phenomena. Additionally, we discuss what parameters may control the photochemical and optical properties of such structures upon attachment of functionalized moieties and how such attachment onto the respective surface proceeds. Especially, we describe a solid base for the application of QD dye based nanoassemblies in various fields of nanotechnology and biomedicine. Organized into eight chapters, the book begins with Chapter 1, titled Structural and Energetic Dynamics in Quantum Dot Dye Nanoassemblies, which describes the results of basic research concerning formation principles and energetic dynamics in heterogeneous organic-inorganic QD dye nanoassemblies, based on CdSe QDs and various dye molecules. Using a combination of ensemble (steady-state and time-resolved technique in a temperature range K) and single-molecule spectroscopy

18 Preface xvii of QDs and nanoassemblies, we show that single functionalized dye molecules act as extremely sensitive probes for studying the complex interface physics and exciton relaxation processes in QDs. Our findings discussed here and in Chapters 2 (Interrelation of Assembly Formation and Ligand Depletion in Colloidal Quantum Dots), 3 (Fluorescence Quenching of Semiconductor Quantum Dots by Multiple Dye Molecules), and 4 (Static and Dynamic Quenching of Quantum Dot Photoluminescence by Organic Semiconductors and Dye Molecules) show that surface-mediated processes dictate the probability of several of the most interesting and potentially useful photophysical phenomena observed for colloidal QDs. In fact, Förster resonance energy transfer (FRET), charge transfer, and non- FRET processes are the main reasons for QD photoluminescence quenching in QD dye nanoassemblies. We have succeeded to quantitatively clarify that the major part of the observed QD photoluminescence quenching in QD dye nanoassemblies, namely non-fret processes, can be understood, on one hand, in terms of electron tunneling beyond the CdSe core under conditions of quantum confinement and, on the other hand, by the influence of ligand dynamics. Such a comparative approach is presented in this book for the first time. Chapter 5, titled Selected Applications of QDs and QD-Based Nanoassemblies, lists a brief history of QD applications as well as representative selected examples of how QDs and QD-based nanomaterials can be applied in photovoltaics, sensing, biomedicine and sub-diffraction imaging (the last one together with single molecule detection was awarded by the 2014 Nobel Prize in Chemistry). Chapters 6 (Nanolithography and Decoration of Generated Nanostructures by Dye Molecules), 7 (Identification of Heterogeneous Surface Properties via Fluorescent Probes), and 8 (Selective Surface Binding of Dye Molecules on Hybrid Humidity Sensors) are devoted to the description of the interaction of dye molecules with lithographically generated or natural surface inhomogeneities with dye molecules. The bibliography at the end of each chapter contains numerous leading papers, recent reviews, and books in which the readers will find specific references relevant to their subjects of interest.

19 xviii Preface Concluding, this book links interdisciplinary fundamental research (including lithography, surface chemistry, photochemistry of semiconductor QDs, and QD dye nanoassembly formation), and selected perspectives for applications of QD dye nanoassemblies and other organic/inorganic nanostructures. It offers an overview for graduate students, academics, researchers, and industry professionals, and anyone interested in this interdisciplinary field of nanomaterials. Eduard Zenkevich Minsk, Belarus Christian von Borczyskowski Chemnitz, Germany September 2016

Hydrophobic and Superhydrophobic Organic-Inorganic Nanohybrids. Chang-Sik Ha Saravanan Nagappan

Hydrophobic and Superhydrophobic Organic-Inorganic Nanohybrids Chang-Sik Ha Saravanan Nagappan Hydrophobic and Superhydrophobic Organic-Inorganic Nanohybrids Hydrophobic and Superhydrophobic Organic-Inorganic