Essentials in Nanoscience and Nanotechnology
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Preface xiii
Acknowledgments xv
About the Authors xvii
1 Introduction 1
1.1 Definitions of Nanoscience and Nanotechnologies 1
1.2 Uniqueness of the Nanoscale 3
1.3 Nanoscience in Nature 4
1.3.1 Naturally Occurring Nanomaterials 7
1.3.2 Nanoscience in Action in Biological World 8
1.4 Historical Perspective 10
1.5 Nanomaterials 13
1.5.1 Nanoparticles 16
1.5.2 Nanowires and Nanotubes 17
1.5.3 Nanolayers/Nanocoatings 17
1.5.4 Nanoporous Materials 17
1.6 Strategies for Synthesis of Nanomaterials 18
1.7 Properties of Nanomaterials 18
1.8 Significance of Nanoscience 19
1.9 Commercial Applications 20
1.9.1 Food Industry 22
1.9.2 Cosmetics 22
1.9.3 Textile 22
1.9.4 Medicine 22
1.9.5 Electrical and Electronic Goods 23
1.10 Potential Health Hazards and Environmental Risks 24
1.11 Futuristic Outlook 25
Review Questions 26
References 27
2 Nanomaterials: General Synthetic Approaches 29
2.1 Introduction 29
2.2 Top-Down Approach 30
2.2.1 Mechanical Milling 31
2.2.2 Mechanochemical Processing (MCP) 32
2.2.3 Electro-Explosion 33
2.2.4 Sputtering 34
2.2.5 Etching 34
2.2.6 Laser Ablation 36
2.2.7 Lithography 37
2.2.8 Aerosol-Based Techniques 43
2.2.9 Electrospinning 47
2.3 Bottom-Up Approaches 49
2.3.1 Chemical Vapor Deposition 49
2.3.2 Chemical Vapor Condensation (CVC) 54
2.3.3 Plasma Arcing 55
2.3.4 Wet Chemical Methods 55
2.3.5 Hydrothermal/Solvothermal 60
2.3.6 Reverse Micelle Method 60
2.3.7 Sol-Gel Method 61
2.3.8 Sonochemical Method 64
2.3.9 Biomimetic Approaches 66
2.3.10 Molecular Self-Assembly 70
2.3.11 Langmuir-Blodgett (LB) Film Formation 71
2.3.12 Stabilization and Functionalization of Nanoparticles 72
Review Questions 73
References 74
3 Characterization Tools for Nanomaterials 77
3.1 Introduction 77
3.2 Imaging Through Electron Microscopy 79
3.2.1 Scanning Electron Microscope (SEM) 85
3.2.2 Transmission Electron Microscope (TEM) 91
3.3 Scanning Probe Microscopy (SPM) 97
3.3.1 Scanning Tunneling Microscope (STM) 97
3.3.2 Atomic Force Microscope (AFM) 102
3.4 Characterization Through Spectroscopy 107
3.4.1 UV-Visible Plasmon Absorption and Emission 108
3.4.2 Vibrational Spectroscopies: FTIR and Raman Spectroscopy 109
3.4.3 Raman Spectroscopy Based Imaging 116
3.4.4 X-Ray Photoelectron Spectroscopy (XPS) 119
3.4.5 Auger Electron Spectroscopy 126
3.4.6 Secondary Ion Mass Spectrometry (SIMS) 130
3.5 Scattering Techniques 133
3.5.1 X-Ray Diffraction Methods 134
3.5.2 Dynamic Light Scattering (DLS) 140
3.5.3 Zeta Potential Analysis 142
Review Questions 145
References 146
4 Nanomaterials 149
4.1 Introduction 149
4.2 Inorganic Nanomaterials 150
4.2.1 Metals and Alloys 150
4.2.2 Metal Oxides of Transition and Non-transition Elements 156
4.2.3 Non-oxide Inorganic Nanomaterials 161
4.3 Organic Nanomaterials 161
4.3.1 Polymeric Nanoparticles 161
4.3.2 Polymeric Nanofilms 162
4.3.3 Nanocellulose 162
4.3.4 Biodegradable Polymer Nanoparticles 165
4.3.5 Dendrimers 165
4.4 Biological Nanomaterials 166
4.4.1 Categories 167
4.4.2 Potential Applications 169
4.5 Nanoporous Materials 170
4.6 Quantum Dots 173
4.7 Nanoclusters 175
4.8 Nanomaterials in Different Configurations 178
4.8.1 Nanofibers 179
4.8.2 Nanowires 179
4.8.3 Nanotubes 180
4.8.4 Nanobelts 183
4.8.5 Nanorods 184
Review Questions 185
References 186
5 Carbon-Based Nanomaterials 189
5.1 General Introduction 189
5.1.1 Carbon Nanomaterials: Synthetic Carbon Allotropes (SCAs) 190
5.2 Fullerene 192
5.2.1 Properties of Fullerene 193
5.2.2 Application Potentials of Fullerene 195
5.3 Carbon Nanotubes (CNTs) 196
5.3.1 Classification of CNTs 196
5.3.2 Synthesis of CNTs 198
5.3.3 Functionalization of CNTs 203
5.3.4 Purification of CNTs 205
5.3.5 Special Properties of Carbon Nanotubes 207
5.3.6 Applications 208
5.4 Graphene 208
5.4.1 Electronic Structure of Graphene 210
5.4.2 Unique Properties of Graphene 211
5.4.3 Synthesis 212
5.4.4 Characterization of Graphene 219
5.4.5 Applications 221
5.5 Carbon Nano-Onions 222
5.6 Carbon Nanofibers 224
5.7 Carbon Black 225
5.7.1 Crystallinity 227
5.7.2 Homogeneity and Uniformity 227
5.8 Nanodiamond 227
5.8.1 Synthesis of Nanodiamond 228
5.8.2 Properties 230
5.8.3 Applications 232
Review Questions 233
References 234
6 Self-Assembled and Supramolecular Nanomaterials 237
6.1 Introduction: Self-Assembly 237
6.1.1 Supramolecular Chemistry 238
6.2 Historical Perspective of Supramolecular and Self-Assembled Structures 239
6.3 Fundamental Aspects of Supramolecular Chemistry 240
6.3.1 Molecular Self-Assembly 241
6.3.2 Molecular Recognition and Complexation 242
6.3.3 Mechanically Interlocked Molecular Architectures 242
6.3.4 Supramolecular Organic Frameworks (SOFs) 242
6.3.5 Biomimetic 243
6.3.6 Imprinting 243
6.3.7 Molecular Machines 243
6.4 Self-Assembly Via Non-Covalent Interaction 244
6.4.1 Long-Range Forces in Self-Assembly 244
6.4.2 Short-Range Forces in Self-Assembly 247
6.4.3 Self-Assembly in Soft Materials 250
6.4.4 Advantages of Self-Assembly 251
6.4.5 Challenges in Self-Assembly 252
6.5 Synthetic Strategies for Molecular Self-Assembly 252
6.5.1 Physiosorption (Patterned Organic Monolayers) 253
6.5.2 Chemisorption 254
6.5.3 Metal Ion-Ligand Interactions 254
6.6 Biological Self-Assembly 255
6.7 Templated (Non-Molecular) Self-Assembly 256
6.7.1 Self-Assembly Through Capillary Interactions 257
6.7.2 Self Assembly Through Lego Chemistry 258
6.8 Self-Assembled Supramolecular Nanostructures 260
6.8.1 Inorganic Colloidal Systems 261
6.8.2 Liquid-Crystalline Structures 262
6.8.3 Self-Assembled Structured Nano-Objects in Unusual Shapes 263
6.9 Self-Folding Nanostructures 263
6.10 Applications 264
6.10.1 Supramolecular Chemistry 264
6.10.2 Self-Assembled Nanomaterials 265
6.10.3 Nanomotors 266
Review Questions 267
References 268
7 Nanocomposites 271
7.1 Introduction 271
7.1.1 Man-Made Ancient Composites 272
7.1.2 Modern Examples of Composites 273
7.1.3 Nanocomposites 273
7.1.4 Structure and Composition of Nanocomposites 274
7.1.5 Properties of Composite Materials 276
7.1.6 Classification of Nanocomposites 277
7.2 Ceramic-Matrix Nanocomposites 279
7.2.1 Structural Ceramic Nanocomposites 279
7.2.2 Functional Ceramic Nanocomposites 283
7.3 Metal-Matrix Nanocomposites 284
7.3.1 Metal-Ceramic Nanocomposites 285
7.3.2 Carbon Nanotubes-Metal Matrix Composites 286
7.4 Polymer-Matrix Nanocomposites 289
7.4.1 Polymer-Inorganic Nanocomposites (PINCs) 291
7.4.2 Polymer-Clay Nanocomposites (PCNs) 299
7.4.3 Polymer-Carbon Nanocomposites 306
7.4.4 Polymer-Polysaccharide Nanocomposites 310
7.5 Nanocoatings 313
7.5.1 Functional Nanocoating 314
7.5.2 Smart (Responsive) Nanocoatings 321
Review Questions 322
References 323
8 Unique Properties 326
8.1 Introduction 326
8.2 Size Effects 327
8.2.1 Quantum Confinement 328
8.2.2 The Density of States (DOS) 330
8.2.3 High Surface Area 332
8.3 Physical Properties 334
8.3.1 Thermal Properties 335
8.3.2 Optical Properties 336
8.3.3 Electronic Properties 341
8.3.4 Electrical Properties 342
8.3.5 Magnetic Properties 346
8.3.6 Mechanical Properties 352
8.4 Chemical Properties at Nanoscale 353
8.4.1 Bonding 353
8.4.2 Surface Properties 354
8.4.3 Catalysis 354
8.4.4 Detection 355
8.5 The Concept of Pseudo-Atoms 356
Review Questions 356
References 358
9 Applications of Nanotechnology 361
9.1 Introduction 361
9.2 Medicine and Healthcare 363
9.2.1 Diagnosis 363
9.3 Drug Development and Drug Delivery System 368
9.3.1 Drug Design and Screening 368
9.3.2 Advanced Drug Delivery Systems 369
9.3.3 Targeted Drug Delivery 371
9.3.4 Remotely Triggered Delivery Systems 372
9.3.5 Therapy 372
9.3.6 Tissue and Biomaterial Engineering 373
9.4 Information and Computer Technologies 374
9.4.1 Integrated Circuits 375
9.4.2 Data Storage 376
9.4.3 Displays 378
9.5 Nanoelectromechanical Systems (NEMS) 380
9.6 Nanotechnologies in Tags 381
9.7 Nanotechnology for Environmental Issues 382
9.7.1 Water Purification and Remediation 383
9.7.2 Nanotechnology for Air Pollution Control 384
9.8 Energy 385
9.8.1 Photovoltaic Technologies for Solar-Energy Harvesting 386
9.8.2 Artificial Photosynthesis: Production of Solar Fuel 391
9.8.3 Thermoelectric Energy 392
9.8.4 Piezoelectric Nanomaterials 394
9.8.5 Hydrogen Generation and Storage 394
9.8.6 Batteries 397
9.9 Nanotechnology in Enhancing the Fuel Efficiency 401
9.10 Chemical and Biosensors Using Nanomaterials (NMs) 401
9.10.1 Artificial Nose as Chemical/Biosensor 402
9.11 Nanotechnology in Agro Forestry 403
9.11.1 Precision Farming 403
9.11.2 Smart Delivery Systems 404
9.12 Defense Applications 404
9.12.1 Light Military Platforms 405
9.12.2 Nanotechnology for Camouflage/Stealth 405
9.12.3 Affordable Energy 407
9.12.4 Deadly Weapons 407
9.13 Nanotechnology in Space 408
9.13.1 Space Flight and Nanotechnology: Applications Under Development 408
9.14 Consumer Goods 409
9.14.1 Nanotextiles 409
9.14.2 Self-Cleaning 410
9.14.3 Antimicrobial Coatings on Textiles and Other Products 411
9.14.4 Cosmetics 412
9.15 Sport Goods 413
Review Questions 416
References 417
10 Toxicity and Environmental Issues 419
10.1 Introduction 419
10.1.1 Toxicity of Nanoparticles 421
10.2 Sources of Nanoparticles and Their Health Effects 422
10.2.1 Natural Sources of Nanoparticles 422
10.2.2 Anthropogenic Nanomaterials 426
10.3 Toxicology of Engineered Nanoparticles 431
10.3.1 Respiratory Tract Uptake and Clearance 431
10.3.2 Cellular Interaction with Nanoparticles 434
10.3.3 Nervous System Uptake of Nanoparticles 437
10.3.4 Nanoparticles Translocation to the Lymphatic Systems 438
10.3.5 Nanoparticles Translocation to the Circulatory System 438
10.3.6 Liver Spleen Kidneys Uptake of Nanoparticles 441
10.3.7 Gastrointestinal Tract Uptake and Clearance of Nanoparticles 441
10.3.8 Dermal Uptake of Nanoparticles 443
10.3.9 Nanoparticles Uptake via Injection 444
10.3.10 Nanoparticles Generation by Implants 444
10.4 Positive Health Effects of Nanoparticles 445
10.4.1 Nanoparticles as Antioxidants 445
10.4.2 Antimicrobial Activity 445
10.5 Environmental Sustainability 445
10.6 Safe Working with Nanomaterials 447
10.6.1 Safe Laboratory Practices in Handling Nanomaterials 448
10.6.2 Exposure Monitoring 449
10.7 Nanomaterial Waste Management 449
10.8 Gaps in Knowledge about Health Effects of Engineered Nanoparticles 451
10.9 Government Standards and Materials Safety Data Sheets 452
10.9.1 Control Banding 453
10.9.2 Hierarchy of Controls 453
10.9.3 Engineering Controls 453
10.9.4 Administrative Controls 454
10.9.5 Personal Protective Equipment 455
10.10 Risk Management 455
Review Questions 458
References 458
Index 463
Chapter 1
Introduction
1.1 Definitions of Nanoscience and Nanotechnologies
- Nanoscience is a new discipline concerned with the unique properties associated with nanomaterials, which are assemblies of atoms or molecules on a nanoscale. Nanoscience is actually the study of objects/particles and its phenomena at a very small scale, ranging roughly from 1 to 100 nm. "Nano" refers to a scale of size in the metric system. It is used in scientific units to denote one-billionth of the base unit, approximately 100,000 times smaller than the diameter of a human hair. A nanometer is 10-9 m (1 nm = 10-9 m), a dimension in the world of atoms and molecules (the size of H atom is 0.24 nm and, for instance, 10 hydrogen atoms lined up measure about 1 nm). Nanoparticles are those particles that contain from 100 to 10,000 atoms. Thus, the particles in size roughly ranging from 1 to 100 nm are the building block of nanomaterials.
- Nanomaterials: These materials are created from blocks of nanoparticles, and thus they can be defined as a set of substances where at least one dimension is approximately less than 100 nm. However, organizations in some areas such as environment, health, and consumer protection favor a larger size range from 0.3 to 300 nm to define nanomaterials. This larger size range allows more research and a better understanding of all nanomaterials and also allows to know whether any particular nanomaterial shows concerns for human health or not and in what size range. Nanocarbons such as fullerenes, carbon nanotubes, and graphene are excellent examples of nanomaterials. A comparison of the size of nanomaterials with some natural and biological species is illustrated in Figure 1.1.
- Nano-object: Material confined in one, two, or three dimensions at the nanoscale. This includes nanoparticles (all three dimensions in the nanoscale), nanofibers (two dimensions in the nanoscale), and nanoplates (one dimension in the nanoscale). Nanofibers are further divided into nanotubes (hollow nanofiber), nanorods (solid nanofiber), and nanowire (electrically conducting or semiconducting nanofiber). However, the term nano-object is not very popular.
- Particle: It is a minute piece of matter with defined physical boundaries. A particle can move as a unit. This general particle definition applies to nano-objects.
- Nanoparticle: It is a nano-object with all three external dimensions in the nanoscale. Nanoparticles can have amorphous or crystalline form and their surfaces can act as carriers for liquid droplets or gases.
- Nanoparticulate matter: It refers to a collection of nanoparticles, emphasizing their collective behavior.
- Agglomerate: It is a group of particles held together by weak forces such as van der Waals forces, some electrostatic forces, and surface tension. It should be noted that agglomerate will usually retain a high surface-to-volume ratio.
- Aggregate: It is a group of particles held together by strong forces such as those associated with covalent or metallic bonds. It should be noted that an aggregate may retain a high surface-to-volume ratio.
- Nanotechnology is the construction and use of functional structures designed from atomic or molecular scale with at least one characteristic dimension measured in nanometers. Their size allows them to exhibit novel and significantly improved physical, chemical, and biological properties, phenomena, and processes because of their size. Thus, nanotechnology can be defined as research and development that involves measuring and manipulating matter at the atomic, molecular, and supramolecular levels at scales measured in approximately 1-100 nm in at least one dimension.
Figure 1.1 Size comparisons of objects, nanomaterials, and biomolecules.
When characteristic structural features are intermediate between isolated atoms and bulk materials in the range of approximately 1-100 nm, the objects often display physical attributes substantially different from those displayed by either atoms or bulk materials. The term "nanotechnology" is by and large used as a reference for both nanoscience and nanotechnology especially in the public domain. We should distinguish between nanoscience and nanotechnology. Nanoscience is a convergence of physics, chemistry, materials science, and biology, which deals with the manipulation and characterization of matter on length scales between the molecular and the micron size. Nanotechnology is an emerging engineering discipline that applies methods from nanoscience to create products.
1.2 Uniqueness of the Nanoscale
At nanoscale, the laws of physics operate in an unfamiliar way because of two important reasons: high surface-to-volume ratio and quantum effect. The key reason for nano-sized regime being special is the dramatic increase in the surface-to-volume ratio. When the size of building blocks gets smaller, the surface area of the material increases by six orders of magnitude, as illustrated in Figure 1.2, while the volume remaining the same. For example, dissecting a 1 m3 of any material into 1 nm particles increases the total combined surface area from 6 to 60,000,000 m2, approximately 10 million times larger [1]. Nanomaterials have a wider range of applications such as catalysts, cleanup, and capture of pollution and any other application where chemical reactivity is important such as medicine. This effect occurs at all length scales, but what makes it unique at the nanoscale is that the properties of the material become strongly dependent on the surface of the material since the amount of surface is now at the same level as the amount of bulk. In fact, in some cases such as fullerenes or single-walled nanotubes, the material is entirely the surface.
Figure 1.2 Exponential increases in surface area for cubes ranging from meter to nanosize.
Another important attribute of nanoscale materials is the fact that it is possible for the quantum mechanical properties of matter to dominate over bulk properties. One example of this is in the change in the optical properties, for example, in the photoemission, of many semiconductor materials as they "go nano." Figure 1.3 illustrates how, a material whose optical properties may be considered uninteresting, simply by changing its size to the nanoscale one can control the color of the material [2]. This effect is due to quantum confinement.
Figure 1.3 Change in optical properties of a semiconductor ranging from bulk to nanosize. Courtesy of Grossman, MIT, USA.
Important consequence of each of these properties is that they offer completely new methods of tuning the properties of materials and devices. Nanotechnology can provide unprecedented understanding about materials and devices and is likely to impact many fields. By using structure at nanoscale as a tunable physical variable, we can greatly expand the range of performance of existing chemicals and materials. Nanoscience and nanotechnology are broad and interdisciplinary areas of research and development activity that have been growing explosively worldwide in the past two decades. Nanoscience has the potential for revolutionizing the methods in which materials and products are created and the range and nature of functionalities that can be accessed; nanotechnology already has a significant commercial impact that will increase exponentially in future.
1.3 Nanoscience in Nature
Nanostructures are plentiful in nature. In the universe, nanoparticles are distributed widely and are considered to be the building blocks in planet formation processes. Indeed, several natural structures including proteins and the DNA diameter of around 2.5 nm, viruses (10-60 nm), and bacteria (30 nm to 10 µm) fit the above definition of nonmaterial, while others are of mineral or environmental origin. For example, these include the fine fraction of desert sand, oil fumes, smog, fumes originating from volcanic activity or from forest fires, and certain atmospheric dusts. Biological systems have built up inorganic-organic nanocomposite structures to improve the mechanical properties or to improve the optical, magnetic, and chemical sensing in living species. As an example, nacre (mother-of-pearl) from the mollusk shell is a biologically formed lamellar ceramic, which exhibits structural robustness despite the brittle nature of its constituents. These systems have evolved and been optimized by evolution over millions of years into sophisticated and complex structures. In natural systems, the bottom-up approach starting from molecules and involving self-organization concepts has been highly successful in building larger structural and functional components. Functional systems are characterized by complex sensing, self-repair, information transmission and storage, and other functions all based on molecular building blocks. Examples of these complex structures for structural purposes are teeth, such as shark teeth, which consist of a composite of biomineralized fluorapatite and organic compounds. These structures result in the unique combination of hardness, fracture toughness, and sharpness. The evolution has worked on much smaller scales too, producing finely honed nanostructures, parts less than a millionth of a meter across, or smaller than 1/20th of the width of a human hair help animals climb, slither, camouflage, flirt, and thrive. Figure 1.4a shows an electron microscopic image of a sensory patch in amphibian ears,...
