Mesocrystals and Nonclassical Crystallization

Through both explanation and discussion, this title presents a complete review into mesocrystals, and accurately describes this relatively new study of established materials. This book also provides an introduction to other areas of crystallisation including self-assembly, classical crystallisation and colloidal crystals.

Key features:

• Description of crystals as well as their formation processes and ways to modify them.
• Examines new ways towards the design of new materials and aids comprehension of the building principles of biominerals.
• Helps to explain many unusual observations made in the study of crystallisation.

Written by the professionals in this subject ‘Mesocrystals: New Self-Assembled Structures’ outlines the future potential of this topic within a variety of disciplines including engineering science, physics and chemistry, making it a versatile and valuable text.

Preface ix

1 Mesocrystals and Nonclassical Crystallization 1

1.1 Introduction 1

References 6

2 Physico-Chemical Principles of Crystallization 7

2.1 Classical Crystallization 7

2.2 Definition of a Crystal and Crystal Growth 9

2.3 Nucleation Theories 15

2.3.1 Classical Nucleation Theory 15

2.3.2 Experimental Tests of Nucleation Theories 19

2.4 Some Points towards a More Realistic View of Supersaturation and Crystallization 19

2.4.1 Concentration Fluctuations and ‘Spinodal Crystallization’ 19

2.4.2 Reduction of Supersaturation by the Formation of Clusters and Amorphous Intermediates 21

2.5 Thermodynamic and Kinetic Crystallization Pathways 22

2.6 Polymorph Control 25

2.7 Crystal Morphology and the Role of Additives and Selective Adsorption 28

2.7.1 Crystal Morphology 30

2.7.2 What Determines Adsorption of an Additive? 36

2.8 Properties of Single Crystals and Polycrystals 39

2.8.1 Electrical Polarization 39

2.8.2 Light Refraction and Birefringence 43

2.8.3 Mechanical Properties 44

References 47

3 Examples of Crystals Challenging the Classical Textbook Mechanism 51

3.1 Some Biomineral Examples 51

3.1.1 Elongated Magnetite Nanocrystals in Magnetotactic Bacteria 52

3.1.2 Calcite with Complex Form and Single Crystal Behavior in Foraminifera 53

3.1.3 Calcite with Complex Form and Single Crystal Behavior in Sea Urchin Spines 56

3.1.4 Calcite Single Crystals with Complex Form in Coccoliths 57

3.1.5 Morphological Complexity Develops with Time 58

3.2 From Biology to Biomimetics: In Vitro Mineralization Examples 59

3.3 Biomorphs 68

3.4 Other Synthetic Examples 69

References 71

4 Nonclassical Crystallization 73

4.1 Amorphous Precursors 75

4.2 Liquid Precursors 78

4.3 Oriented Attachment 83

4.4 Mesocrystals 96

References 98

5 Self-Assembly and Self-Organization 103

References 106

6 Colloidal Crystals with Spherical Units: Opals and Colloidal Nanocrystals 107

References 111

7 Mesocrystal Systems 113

7.1 Mesocrystals and Their Properties 113

7.2 Early Reports on Mesocrystals 114

7.3 One-Dimensional Mesocrystals 117

7.4 Two-Dimensional Mesocrystals 118

7.5 Mesocrystals in Biomineralization 122

7.6 Mesocrystals in Gels 129

7.7 Mesocrystals Formed without Additives 135

7.8 Mesocrystals Formed with Simple Ion Additives 138

7.9 Mesocrystals Formed with Polymer Additives 142

7.10 Mesocrystals in Nonaqueous Systems 152

7.11 Mesocrystals Formed via Solid-State Reactions 157

7.11.1 Solid Matrices for Mesocrystal Formation 157

7.11.2 Topotactic Reactions 159

7.12 Liquid Crystals, Tactoids, Somatoids, and Schiller Layers 163

References 173

8 Mechanisms of Mesocrystal Formation 179

8.1 Principal Mechanisms Leading to Mesocrystals 179

8.2 Conditions for Mesocrystal Formation 186

8.3 Alignment by Colloidal Forces, Capillarity and Other Short-Ranged Physical Fields 190

8.3.1 Alignment by Capillary Forces 190

8.3.2 Alignment by Hydrophobic Forces and Interface Energies 192

8.3.3 Alignment by Minimization of the Interfacial Energy 192

8.3.4 Alignment by Additive Coding of Nanoparticles 194

8.3.5 Alignment by a Mechanical Stress Field 196

8.4 The Role of Magnetic Fields 198

8.5 The Role of Dipole and Polarization Forces 204

8.5.1 Polarization Forces 204

8.6 The Role of External Electric Fields 219

8.7 Self-Similar Assembly and Shape Constraints 222

8.8 Shaping of Mesocrystals 226

8.9 Mesocrystals as Intermediates in Single Crystal Formation 228

References 233

9 Analysis of Mesocrystals 237

9.1 Nucleation and Growth of Primary Nanoparticles 238

9.2 Rapid Aggregation and Formation of Randomly Oriented Aggregates 239

9.3 Mesocrystal Formation 239

9.4 Fusion of the Mesocrystal to a Single Crystal/Ripening and Ion-Mediated Recrystallization Towards an Outer Single Crystalline Shell 240

9.5 Analytical Techniques for Mesocrystals 241

References 244

10 Tuning of Properties 247

References 249

11 A Unifying Crystallization Mechanism 251

References 255

12 Analogy between Oriented Attachment or Hierarchically Structured Crystals and Polymers 257

12.1 Analogy between Oriented Attachment and Polymerization 259

12.2 Structural Levels in Hierarchically Structured Crystals and

Biopolymers 263

References 264

13 Summary and Outlook 265

13.1 Summary 265

13.2 Outlook 267

References 270

Index 271

Helmut Cöelfen and Markus Antonietti are the authors of Mesocrystals and Nonclassical Crystallization, published by Wiley. Crystallization is certainly among the most studied processes n science and also of great practical importance. Not only does it create beautiful objects of esthetic value, but the properties of many solid bodies and materials depend on their crystal structure, the crystal shape, and their mutual texture. Over many years, a classical picture of crystallization has been established that describes crystallization as a layer-wise deposition of atoms/ions/molecules on the surfaces of a crystal nucleus. However, it is well known that this classical model does not apply for many "real-life" crystallization processes. Thus, the comprehensive treatment of classical and nonclassical crystallization in this book will help catalyze progress in the field since it identifies mechanisms on the basis of their typical features and by using suitable analytical techniques.

The book gives an introduction to self-assembly, classical crystallization, colloidal crystals, and mesocrystals. The principles of crystallization are described with examples, and nonclassical crystallization, self-assembly, and colloidal crystals are then discussed. This is followed by an exploration of mesocrystal systems, their formation, analysis, and properties. A unifying crystallization scenario combining classical and nonclassical crystallization is then presented, and the analogy between hierarchically structured crystals and biopolymers is made. Finally there is an overview of what might be possible in the future with an "extended crystallization toolbox".

This book is essential reading for scientists involved in crystallization, materials science, self-assembly, colloid science, nanosciences, biomineralization, and graduate students of material science. it is also invaluable for dealing with highly complex crystal systems.