Nanosensors : Physical, chemical and biological

NANOSENSORS

PHYSICAL, CHEMICAL,

AND BIOLOGICAL

Series in Sensors

Series Editors: Barry Jones and William B. Spillman

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Current Advances in Sensors

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Edited by K. T. V. Grattan and S. H. Khan

in Film Resistive Sensors

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Novel Sensors and Sensing

R. G. Jackson

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SERIES IN SENSORS

A TAY LOR & F RANCI S BOOK

CRC Press is an imprint of the

Taylor & Francis Group, an informa business

Boca Raton London New York

NANOSENSORS

PHYSICAL, CHEMICAL,

AND BIOLOGICAL

Vinod Kumar Khanna

CRC Press

Taylor & Francis Group

6000 Broken Sound Parkway NW, Suite 300

Boca Raton, FL 33487-2742

© 2012 by Taylor & Francis Group, LLC

CRC Press is an imprint of Taylor & Francis Group, an Informa business

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Version Date: 20110518

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Dedicated to the loving memory of my late father

Shri Amarnath Khanna

for nurturing my educational career.

Also dedicated to my mother Shrimati Pushpa Khanna,

my daughter Aloka Khanna, and my wife Amita Khanna

for their affection and support.

vii

Contents

Preface.................................................................................................................... xxi

Acknowledgments.............................................................................................. xxv

Author.................................................................................................................xxvii

1. Introduction to Nanosensors.........................................................................1

1.1 Getting Started with Nanosensors......................................................1

1.2 Natural Sciences.....................................................................................1

1.3 Physics.....................................................................................................2

1.3.1 Definition of Physics.................................................................2

1.3.2 Branches of Physics...................................................................2

1.3.3 Matter: Its States, Materials, and Particles............................2

1.3.4 Molecules, Atoms, and Atomic Structure.............................2

1.3.5 Mechanics..................................................................................4

1.3.6 Heat.............................................................................................6

1.3.7 Sound..........................................................................................6

1.3.8 Light............................................................................................6

1.3.9 Electricity...................................................................................7

1.3.10 Magnetism.................................................................................8

1.3.11 Electromagnetism.....................................................................9

1.3.12 SI System of Units.....................................................................9

1.4 Chemistry.............................................................................................. 10

1.4.1 Definition of Chemistry......................................................... 10

1.4.2 Elements and Compounds.................................................... 10

1.4.3 Organic and Inorganic Compounds.................................... 10

1.4.4 Subdivisions of Chemistry.................................................... 10

1.4.5 Natural and Artificial Elements........................................... 10

1.4.6 Metals, Nonmetals, and Metalloids..................................... 11

1.4.7 Periodic Table of Elements..................................................... 11

1.4.8 Chemical Change and Reaction............................................ 11

1.4.9 Electronic Configuration (Structure) of Elements..............12

1.4.10 Chemical Bond........................................................................12

1.4.11 Oxidation and Reduction....................................................... 13

1.4.12 Acid, Base, and Salt................................................................. 13

1.4.13 Expressing Concentrations of Solutions and Gases........... 13

1.4.14 Hydrocarbons: Saturated and Unsaturated........................ 13

1.4.15 Alkyl and Aryl Groups.......................................................... 14

1.4.16 Alcohols and Phenols............................................................. 14

1.4.17 Carboxylic Acids..................................................................... 14

1.4.18 Aldehydes and Ketones......................................................... 15

viii Contents

1.4.19 Amines and Amino Acids..................................................... 15

1.4.20 Lipids........................................................................................ 15

1.4.21 Carbohydrates......................................................................... 15

1.4.22 Proteins and Enzymes........................................................... 15

1.5 Biology................................................................................................... 16

1.5.1 What Is Biology?..................................................................... 16

1.5.2 Subbranches of Biology.......................................................... 16

1.5.3 Origin and Evolution of Life................................................. 16

1.5.4 The Cell.................................................................................... 16

1.5.5 Differences between Bacteria and Viruses......................... 17

1.5.6 Heredity, Chromosomes, Genes, and Related Terms........ 18

1.6 Semiconductor Electronics................................................................. 18

1.6.1 What Is Semiconductor Electronics?.................................... 18

1.6.2 Energy Bands in Conductors, Semiconductors, and

Insulators................................................................................. 18

1.6.3 Interesting Properties of Semiconductors........................... 19

1.6.4 P–N Junction............................................................................ 21

1.6.5 Bipolar Junction Transistor....................................................23

1.6.6 Metal-Oxide-Semiconductor Field-Effect Transistor......... 24

1.6.7 Analog and Digital Circuits.................................................. 24

1.7 Nanometer and Appreciation of Its Magnitude..............................25

1.8 Nanoscience and Nanotechnology....................................................26

1.9 Nanomaterials and the Unusual Behavior at Nanoscales.............27

1.10 Moving toward Sensors and Transducers: Meaning of

Terms “Sensors” and “Transducers”.................................................30

1.11 Definition of Sensor Parameters and Characteristics..................... 31

1.12 Evolution of Semiconductor-Based Microsensors........................... 32

1.13 From Macrosensor to Microsensor Age and Necessity of

Nanoscale Measurements...................................................................33

1.13.1 A Miniaturized Sensor Can Accomplish Many Tasks

That a Bulky Device Cannot Perform..................................33

1.13.2 The Issue of Power Consumption........................................34

1.13.3 Low Response Times..............................................................35

1.13.4 Multi-Analyte Detection and Multifunctionality..............35

1.13.5 Sensitivity Considerations and Need of

Functionalization....................................................................36

1.13.6 Interfacing with Biomolecules..............................................36

1.13.7 Low Costs.................................................................................36

1.13.8 Possibility of a New Genre of Devices................................. 37

1.14 Definition and Classification of Nanosensors................................. 37

1.15 Physical, Chemical, and Biological Nanosensors............................39

1.16 Some Examples of Nanosensors........................................................ 41

1.16.1 Common Nanosensors........................................................... 41

1.16.2 Carbon Nanotube–Based Nanosensors............................... 41

1.16.3 Nanoscaled Thin Film Sensors............................................. 41

Contents ix

1.16.4 Microcantilever- and Nanocantilever-Enabled

Nanosensors............................................................................42

1.17 Getting Familiar with Analytical and Characterization

Tools: Microscopic Techniques to View Nanomaterials

and Nanosensors..................................................................................42

1.17.1 Scanning Electron Microscope.............................................43

1.17.2 Transmission Electron Microscope......................................44

1.17.3 Scanning Tunneling Microscope..........................................44

1.17.4 Atomic Force Microscope......................................................44

1.18 Spectroscopic Techniques for Analyzing Chemical

Composition of Nanomaterials and Nanosensors..........................46

1.18.1 Infrared Spectroscopy............................................................47

1.18.2 Ultraviolet–Visible Spectroscopy..........................................48

1.18.3 Raman Spectroscopy..............................................................49

1.18.4 Energy Dispersive X-Ray Spectroscopy..............................50

1.18.5 Auger Electron Spectroscopy................................................50

1.18.6 X-Ray Diffraction.................................................................... 51

1.18.7 X-Ray Photoelectron Spectroscopy or Electron

Spectroscopy for Chemical Analysis................................... 51

1.18.8 Secondary Ion Mass Spectrometry...................................... 51

1.19 The Displacement Nanosensor: STM................................................ 52

1.19.1 Principle of Operation............................................................ 52

1.19.2 Transmission Coefficient.......................................................54

1.19.3 Tunneling Current..................................................................60

1.19.4 Measurements with STM.......................................................63

1.19.4.1 Topography..............................................................63

1.19.4.2 Density of States......................................................64

1.19.4.3 Linecut......................................................................65

1.19.4.4 DOS Map..................................................................65

1.20 The Force Nanosensor: AFM..............................................................65

1.20.1 Operating Principle................................................................65

1.20.2 Lennard–Jones Potential and the van der

Waals Forces...........................................................................66

1.20.3 Other Forces and Potentials..................................................71

1.20.4 Force Sensor (Cantilever) and Force Measurement...........71

1.20.5 Static and Dynamic Atomic Force Microscopy..................73

1.20.6 Classification of Modes of Operation of AFM on

the Basis of Contact.................................................................75

1.20.6.1 Contact Mode...........................................................75

1.20.6.2 Noncontact Mode....................................................75

1.20.6.3 Tapping Mode (Intermittent-Contact Mode)....... 76

1.20.7 Frequency-Modulation Atomic Force Microscopy............77

1.20.8 Generic Calculation................................................................79

1.21 Outline and Organization of the Book.............................................80

1.22 Discussion and Conclusions............................................................... 81

x Contents

Review Exercises.............................................................................................82

References........................................................................................................83

2. Materials for Nanosensors...........................................................................85

2.1 Introduction..........................................................................................85

2.2 Nanoparticles or Nanoscale Particles, and Importance of

the Intermediate Regime between Atoms and Molecules,

and Bulk Matter...................................................................................85

2.3 Classification of Nanoparticles on the Basis of Their

Composition and Occurrence............................................................86

2.4 Core/Shell-Structured Nanoparticles...............................................87

2.4.1 Inorganic Core/Shell Nanoparticles....................................88

2.4.2 Organic–Inorganic Hybrid Core/Shell Nanoparticles......89

2.5 Shape Dependence of Properties at Nanoscale...............................89

2.6 Dependence of Properties of Nanoparticles on Particle Size........90

2.7 Surface Energy of a Solid....................................................................90

2.8 Metallic Nanoparticles and Plasmons.............................................. 91

2.8.1 Surface Plasmon Resonance on Bulk Metals......................92

2.8.2 Surface Plasmon Band Phenomenon in Metal

Nanoparticles..........................................................................97

2.9 Optical Properties of Bulk Metals and Metallic

Nanoparticles.......................................................................................98

2.9.1 Light Absorption by Bulk Metals and Metallic

Nanoparticles..........................................................................98

2.9.2 Light Scattering by Nanoparticles...................................... 103

2.10 Parameters Controlling the Position of Surface Plasmon

Band of Nanoparticles....................................................................... 104

2.10.1 Effect of the Surrounding Dielectric Medium.................. 104

2.10.2 Influence of Agglomeration-Preventing Ligands

and Stabilizers....................................................................... 105

2.10.3 Effect of Nanoparticle Size and Shape............................... 106

2.10.4 Compositional Effect............................................................ 106

2.11 Quantum Confinement..................................................................... 106

2.11.1 Quantum Confinement in Metals...................................... 107

2.11.2 Quantum Confinement in Semiconductors...................... 107

2.11.3 Bandgap Energies................................................................. 110

2.11.4 Bandgap Behavior Explanation by Particle-in-a-One￾Dimensional Box Model of Electron Behavior................. 110

2.12 Quantum Dots.................................................................................... 116

2.12.1 Fundamentals........................................................................ 116

2.12.2 Tight-Binding Approach to Optical Bandgap

(Exciton Energy) versus Quantum Dot Size..................... 118

2.12.3 Comparison of Quantum Dots with Organic

Fluorophores..........................................................................122

2.12.4 Types of Quantum Dots Depending on Composition......125

Contents xi

2.12.5 Classification of Quantum Dots Based on Structure.......125

2.12.6 Capping Molecules or Ligands on the Surfaces of

Quantum Dots....................................................................... 127

2.13 Carbon Nanotubes............................................................................. 127

2.13.1 What Are Carbon Nanotubes?............................................ 127

2.13.2 Structure of Graphene.......................................................... 129

2.13.3 Structure of SWCNT............................................................. 130

2.13.4 Mechanical Properties of CNTs.......................................... 132

2.13.5 Electrical, Electronic, and Magnetic

Properties of CNTs............................................................... 133

2.14 Inorganic Nanowires......................................................................... 134

2.15 Nanoporous Materials....................................................................... 134

2.15.1 Nanoporous Silicon.............................................................. 135

2.15.2 Nanoporous Alumina.......................................................... 137

2.15.3 Nano-Grained Thin Films................................................... 137

2.16 Discussion and Conclusions............................................................. 138

Review Exercises........................................................................................... 138

References...................................................................................................... 139

3. Nanosensor Laboratory.............................................................................. 143

3.1 Introduction........................................................................................ 143

3.2 Nanotechnology Division................................................................. 143

3.2.1 Synthesis of Metal Nanoparticles....................................... 143

3.2.1.1 Gold Nanoparticles............................................... 143

3.2.1.2 Silver Nanoparticles.............................................. 145

3.2.1.3 Platinum Nanoparticles....................................... 145

3.2.1.4 Palladium Nanoparticles..................................... 146

3.2.2 Synthesis of Semiconductor Nanoparticles...................... 146

3.2.3 Synthesis of Semiconductor Nanocrystals:

Quantum Dots....................................................................... 147

3.2.3.1 CdSe/ZnS Core/Shell QDs.................................. 148

3.2.3.2 CdSe/CdS Core/Shell QDs.................................. 148

3.2.3.3 PbS and PbS/CdS Core/Shell QDs..................... 149

3.2.4 Synthesis of Metal Oxide Nanoparticles........................... 150

3.2.5 Synthesis of Carbon Nanotubes......................................... 152

3.2.5.1 Arc Discharge Method of CNT Production...... 154

3.2.5.2 Laser Ablation Method of CNT Production...... 154

3.2.5.3 Chemical Vapor Deposition Method of

CNT Production.................................................... 155

3.2.5.4 Difficulties Faced with Carbon Nanotubes....... 156

3.3 Micro- and Nanoelectronics Division............................................. 158

3.3.1 Semiconductor Clean Room................................................ 158

3.3.2 Silicon Single Crystal Growth and Wafer Production..... 159

3.3.3 Molecular Beam Epitaxy...................................................... 160

3.3.4 Mask Making......................................................................... 160

xii Contents

3.3.5 Thermal Oxidation............................................................... 162

3.3.6 Diffusion of Impurities in a Semiconductor..................... 164

3.3.7 Ion Implantation.................................................................... 169

3.3.8 Photolithography.................................................................. 170

3.3.8.1 Physical Limits....................................................... 172

3.3.8.2 Optical Lithography.............................................. 174

3.3.8.3 Electron-Beam Lithography................................. 174

3.3.8.4 X-Ray Lithography................................................ 174

3.3.8.5 Dip-Pen Nanolithography.................................... 174

3.3.8.6 Nanoimprint Lithography................................... 175

3.3.8.7 Nanosphere Lithography..................................... 175

3.3.9 Chemical Vapor Deposition................................................ 176

3.3.10 Wet Chemical Etching and Common Etchants................ 179

3.3.11 Reactive Ion Etching............................................................. 179

3.3.12 Focused Ion Beam Etching and Deposition...................... 180

3.3.13 Metallization.......................................................................... 181

3.3.14 Dicing, Wire Bonding, and Encapsulation........................ 182

3.3.15 IC Downscaling: Special Technologies and Processes...... 183

3.3.15.1 Downscaling Trends............................................. 183

3.3.15.2 SOI-MOSFETs........................................................ 184

3.3.15.3 SIMOX Process....................................................... 185

3.3.15.4 Smart Cut Process................................................. 185

3.3.15.5 Strained Silicon Process....................................... 185

3.3.15.6 Top–Down and Bottom–Up Approaches.......... 186

3.3.15.7 DNA Electronics.................................................... 186

3.3.15.8 Spintronics.............................................................. 187

3.4 MEMS and NEMS Division.............................................................. 188

3.4.1 Surface and Bulk Micromachining.................................... 188

3.4.2 Machining by Wet and Dry Etching Techniques............. 189

3.4.3 Deep Reactive Ion Etching.................................................. 190

3.4.4 Front- and Back-Side Mask Alignment.............................. 193

3.4.5 Multiple Wafer Bonding and Glass–Silicon Bonding...... 193

3.4.6 Wafer Lapping....................................................................... 194

3.4.7 Chemical Mechanical Polishing......................................... 194

3.4.8 Electroplating........................................................................ 195

3.4.9 LIGA Process......................................................................... 195

3.4.10 Micro-Injection Molding...................................................... 196

3.4.11 Hot Embossing and Electroforming.................................. 197

3.4.12 Combination of MEMS/NEMS and CMOS Processes...... 198

3.5 Biochemistry Division....................................................................... 198

3.5.1 Surface Functionalization and Biofunctionalization

of Nanomaterials................................................................... 199

3.5.2 Immobilization of Biological Elements..............................200

3.5.3 Protocols for Attachment of Antibodies on Sensors.......204

Contents xiii

3.5.4 Functionalization of CNTs for Biological Applications......206

3.5.5 Water Solubility of Quantum Dots.....................................206

3.5.6 Low Cytotoxicity Coatings.................................................. 207

3.6 Chemistry Division............................................................................208

3.6.1 Nanoparticle Thin Film Deposition...................................208

3.6.2 Polymer Coatings in Nano Gas Sensors............................208

3.6.3 Metallic Nanoparticle Functionalization of Si

Nanowires for Gas Sensing Applications.........................209

3.7 Nanosensor Characterization Division..........................................209

3.8 Nanosensor Powering, Signal Processing, and

Communication Division.................................................................. 210

3.8.1 Power Unit............................................................................. 210

3.8.1.1 Lithium Nanobatteries......................................... 210

3.8.1.2 Self-Powered Nanogenerators............................. 211

3.8.1.3 Energy Harvesting from the Environment....... 211

3.8.1.4 Synthetic Chemical Batteries Based on

Adenosine Triphosphate...................................... 212

3.8.2 Signal Processing Unit......................................................... 212

3.8.3 Integrated Nanosensor Systems......................................... 212

3.8.4 Wireless Nanosensor Networks......................................... 213

3.9 Discussion and Conclusions............................................................. 214

Review Exercises........................................................................................... 214

References...................................................................................................... 216

4. Mechanical Nanosensors........................................................................... 219

4.1 Introduction........................................................................................ 219

4.2 Nanogram Mass Sensing by Quartz Crystal Microbalance........220

4.3 Attogram (10−18 g) and Zeptogram (10−21 g) Mass Sensing by

MEMS/NEMS Resonators................................................................223

4.3.1 Microcantilever Definitions and Theory...........................225

4.3.1.1 Resonance Frequency Formula...........................233

4.3.1.2 Deflection Formula............................................... 241

4.3.2 Energy Dissipation and Q-Factor of Cantilever............... 243

4.3.3 Noise of Cantilever and Its Mass Detection Limit........... 245

4.3.4 Doubly Clamped and Free–Free Beam Resonators......... 249

4.4 Electron Tunneling Displacement Nanosensor.............................250

4.5 Coulomb Blockade Electrometer–Based Displacement

Nanosensor......................................................................................... 252

4.5.1 Coulomb Blockade Effect..................................................... 252

4.5.2 Comparison with Tunneling Sensors................................255

4.6 Nanometer-Scale Displacement Sensing by

Single-Electron Transistor.................................................................255

4.7 Magnetomotive Displacement Nanosensor...................................258

4.8 Piezoresistive and Piezoelectric Displacement Nanosensors......258

xiv Contents

4.9 Optical Displacement Nanosensor..................................................260

4.10 Femtonewton Force Sensors Using Doubly Clamped

Suspended Carbon Nanotube Resonators..................................... 261

4.11 Suspended CNT Electromechanical Sensors for

Displacement and Force....................................................................264

4.12 Membrane-Based CNT Electromechanical Pressure Sensor.......268

4.13 Tunnel Effect Accelerometer............................................................ 269

4.13.1 Principle of Motion Detection............................................. 269

4.13.2 Construction and Working.................................................. 270

4.13.3 Micromachined Accelerometer...........................................272

4.14 NEMS Accelerometer........................................................................ 274

4.15 Silicon Nanowire Accelerometer..................................................... 275

4.16 CNT Flow Sensor for Ionic Solutions.............................................. 276

4.17 Discussion and Conclusions............................................................. 278

Review Exercises........................................................................................... 281

References......................................................................................................283

5. Thermal Nanosensors................................................................................. 287

5.1 Introduction........................................................................................ 287

5.2 Nanoscale Thermocouple Formed by Tungsten and

Platinum Nanosize Strips.................................................................288

5.3 Resistive Thermal Nanosensor Fabricated by Focused Ion

Beam Chemical Vapor Deposition...................................................289

5.4 “Carbon-Nanowire-on-Diamond” Resistive

Temperature Nanosensor.................................................................290

5.5 Carbon Nanotube Grown on Nickel Film as Resistive

Low-Temperature (10–300K) Nanosensor...................................... 291

5.6 Laterally Grown CNT between Two Microelectrodes as

Resistive Temperature Nanosensor................................................. 292

5.7 Silicon Nanowire Temperature Nanosensors: Resistors

and Diode Structures........................................................................ 295

5.8 Ratiometric Fluorescent Nanoparticles for Temperature

Sensing................................................................................................. 296

5.9 Er3+/Yb3+ Co-Doped Gd2O3 Nano-Phosphor as Temperature

Nanosensor Using Fluorescence Intensity Ratio Technique.......300

5.10 Optical Heating of Yb3+–Er3+ Co-Doped Fluoride

Nanoparticles and Distant Temperature Sensing through

Luminescence.....................................................................................303

5.11 Porphyrin-Containing Copolymer as Thermochromic

Nanosensor.........................................................................................305

5.12 Silicon-Micromachined Scanning Thermal Profiler.....................306

5.13 Superconducting Hot Electron Nanobolometers..........................308

5.14 Thermal Convective Accelerometer Using CNT Sensing

Element................................................................................................ 312

5.15 SWCNT Sensor for Airflow Measurement..................................... 313

Contents xv

5.16 Vacuum Pressure and Flow Velocity Sensors Using

Batch-Processed CNT Wall............................................................... 314

5.17 Nanogap Pirani Gauge...................................................................... 315

5.18 Carbon Nanotube–Polymer Nanocomposite as

Conductivity Response Infrared Nanosensor............................... 317

5.19 Nanocalorimetry................................................................................ 319

5.20 Discussion and Conclusions............................................................. 324

Review Exercises........................................................................................... 328

References...................................................................................................... 329

6. Optical Nanosensors...................................................................................333

6.1 Introduction........................................................................................333

6.2 Noble-Metal Nanoparticles with LSPR and UV–Visible

Spectroscopy....................................................................................... 337

6.3 Nanosensors Based on Surface-Enhanced Raman Scattering......341

6.4 Colloidal SPR Colorimetric Gold Nanoparticle

Spectrophotometric Sensor...............................................................345

6.5 Fiber-Optic Nanosensors..................................................................349

6.5.1 Fabry–Perot Reflectometric Optochemical

Nanosensor Using Optical Fibers and SWCNTs..............349

6.5.2 In-Fiber Nanocavity Sensor................................................. 352

6.5.3 Fiber-Optic Nanosensors for Probing Living Cells.........354

6.6 Nanograting-Based Optical Accelerometer................................... 357

6.7 Fluorescent pH-Sensitive Nanosensors..........................................358

6.7.1 Renewable Glass Nanopipette with Fluorescent

Dye Molecules.......................................................................358

6.7.2 Ratiometric pH Nanosensor................................................359

6.7.3 pH-Sensitive Microcapsules with Nanoparticle

Incorporation in the Walls...................................................360

6.8 Disadvantages of Optical Fiber and Fluorescent

Nanosensors for Living Cell Studies..............................................363

6.9 PEBBLE Nanosensors to Measure the Intracellular

Environment.......................................................................................364

6.10 Quantum Dots as Fluorescent Labels.............................................368

6.11 Quantum Dot FRET-Based Probes.................................................. 375

6.11.1 QD-FRET Protein Sensor..................................................... 378

6.11.2 QD-FRET Protease Sensor................................................... 379

6.11.3 QD-FRET Maltose Sensor.................................................... 379

6.11.4 Sensor for Determining the Dissociation Constant

(Kd) between Rev and RRE.................................................. 382

6.12 Electrochemiluminescent Nanosensors for Remote Detection......383

6.13 Crossed Zinc Oxide Nanorods as Resistive UV Nanosensors....386

6.14 Discussion and Conclusions............................................................. 387

Review Exercises...........................................................................................389

References......................................................................................................390