Preface ....................................................... xix
Acknowledgments ............................................... xxi
List of Symbols ............................................. xxiii
List of Acronyms ............................................. xxxi
1 What are Chemical Sensors? ................................... 1
1.1 Chemical Sensors: Definition and Components ............. 1
1.2 Recognition Methods ..................................... 2
1.2.1 General Aspects .................................. 2
1.2.2 Ion Recognition .................................. 3
1.2.3 Recognition by Affinity Interactions ............. 3
1.2.4 Recognition by Nucleic Acids ..................... 3
1.2.5 Recognition by Enzymes ........................... 4
1.2.6 Recognition by Cells and Tissues of Biological
Origin ........................................... 4
1.2.7 Gas and Vapor Sorption ........................... 4
1.3 Transduction Methods .................................... 4
1.3.1 General Aspects .................................. 4
1.3.2 Thermometric Transduction ........................ 5
1.3.3 Transduction Based on Mechanical Effects ......... 5
1.3.4 Resistive and Capacitive Transduction ............ 5
1.3.5 Electrochemical Transduction ..................... 5
1.3.6 Optical Transduction ............................. 6
1.4 Sensor Configuration and Fabrication .................... 6
1.5 Sensor Calibration ...................................... 7
1.6 Sensor Figures of Merit ................................. 8
1.6.1 Reliability of the Measurement ................... 9
1.6.2 Selectivity and Specificity ..................... 10
1.6.3 Detection and Quantification Capabilities ....... 10
1.6.4 Response Time ................................... 11
1.7 Sensor Arrays .......................................... 11
1.7.1 Quantitative Analysis by Cross-Sensitive
Sensor Arrays ................................... 11
1.7.2 Qualitative Analysis by Cross-Sensitive Sensor
Arrays .......................................... 12
1.7.3 Artificial Neural Network Applications in the
Artificial Nose/Tongue .......................... 13
1.7.4 Outlook ......................................... 14
1.8 Sensors in Flow Analysis Systems ....................... 14
1.9 Applications of Chemical Sensors ....................... 14
1.9.1 Environmental Applications of Chemical Sensors .. 15
1.9.2 Healthcare Applications of Chemical Sensors ..... 15
1.9.3 Application of Chemical Sensors in the Food
Industry, Agriculture and Biotechnology ......... 16
1.9.4 Chemical Sensors in Defense Applications ........ 16
1.10 Literature on Chemical Sensors and Biosensors .......... 17
1.11 Organization of the Text ............................... 17
References ............................................. 19
2 Protein Structure and Properties ............................ 21
2.1 Amino Acids ............................................ 21
2.2 Chemical Structure of Proteins ......................... 22
2.3 Conformation of Protein Macromolecules ................. 22
2.4 Noncovalent Chemical Bonds in Protein Molecules ........ 24
2.5 Recognition Processes Involving Proteins ............... 25
2.6 Outlook ................................................ 26
References ............................................. 27
3 Enzymes and Enzymatic Sensors ............................... 28
3.1 General ................................................ 28
3.2 Enzyme Nomenclature and Classification ................. 29
3.3 Enzyme Components and Cofactors ........................ 30
3.4 Some Enzymes with Relevance to Biosensors .............. 32
3.4.1 Oxidases ........................................ 32
3.4.2 Dehydrogenases .................................. 33
3.4.3 Hydrolases ...................................... 34
3.4.4 Lyases .......................................... 35
3.4.5 Outlook ......................................... 35
3.5 Transduction Methods in Enzymatic Biosensors ........... 36
3.5.1 Transduction Methods ............................ 36
3.5.2 Multienzyme Sensors ............................. 37
3.6 Kinetics of Enzyme Reactions ........................... 38
3.6.1 The Michaelis-Menten Mechanism .................. 38
3.6.2 Other Mechanisms ................................ 40
3.6.3 Expressing the Enzyme Activity .................. 41
3.6.4 pH Effect on Enzyme Reactions ................... 42
3.6.5 Temperature Effect on Enzyme Reactions .......... 43
3.6.6 Outlook ......................................... 43
3.7 Enzyme Inhibition ...................................... 44
3.7.1 Reversible Inhibition ........................... 44
3.7.2 Irreversible Inhibition ......................... 46
3.7.3 Enzymatic Sensors for Inhibitors: Design and
Operation ....................................... 46
3.7.4 Applications of Enzyme-Inhibition Sensors ....... 46
3.8 Concluding Remarks ..................................... 48
References ............................................. 48
4 Mathematical Modeling of Enzymatic Sensors .................. 50
4.1 Introduction ........................................... 50
4.2 The Enzymatic Sensor under External Diffusion
Conditions ............................................. 50
4.2.1 The Physical Model .............................. 50
4.2.2 The Mathematical Model .......................... 51
4.2.3 The Zero-Order Kinetics Case .................... 52
4.2.4 The First-Order Kinetics Case ................... 52
4.2.5 The Dynamic Range and the Limit of Detection
under External Diffusion Conditions ............. 54
4.3 The Enzymatic Sensor under Internal Diffusion Control .. 55
4.3.1 The Steady-State Response ....................... 55
4.3.2 The Transient Regime and the Response Time
under Internal Diffusion Conditions ............. 58
4.4 The General Case ....................................... 60
4.4.1 The Model ....................................... 60
4.4.2 Effect of the Biot Number ....................... 61
4.4.3 Effect of Partition Constants and Diffusion
Coefficients .................................... 63
4.4.4 Experimental Tests for the Kinetic Regime of
an Enzymatic Sensor ............................. 63
4.5 Outlook ................................................ 64
References .................................................. 64
5 Materials and Methods in Chemical-Sensor Manufacturing ...... 66
5.1 Introduction ........................................... 66
5.2 Noncovalent Immobilization at Solid Surfaces ........... 66
5.3 Covalent Conjugation ................................... 68
5.3.1 Zero-Length Crosslinkers ........................ 68
5.3.2 Bifunctional Crosslinkers ....................... 69
5.3.3 Immobilization by Protein Crosslinking .......... 69
5.4 Supports and Support Modification ...................... 70
5.4.1 General Aspects ................................. 70
5.4.2 Natural Polymers ................................ 71
5.4.3 Synthetic Polymers .............................. 72
5.4.4 Coupling to Active Polymers ..................... 72
5.4.5 Coupling to Inactive Polymers ................... 72
5.4.6 Inorganic Supports .............................. 73
5.4.7 Carbon Material Supports ........................ 73
5.4.8 Metal Supports .................................. 75
5.4.9 Semiconductor Supports .......................... 76
5.5 Affinity Reactions ..................................... 77
5.6 Thin Molecular Layers .................................. 78
5.6.1 Self-Assembly of Amphiphilic Compounds .......... 78
5.6.2 Bilayer Lipid Membranes ......................... 79
5.6.3 Alternate Layer-by-Layer Assembly ............... 80
5.7 Sol-Gel Chemistry Methods .............................. 81
5.8 Hydrogels .............................................. 83
5.8.1 Physically Crosslinked Hydrogels ................ 84
5.8.2 Chemically Crosslinked Hydrogels ................ 84
5.8.3 Redox Hydrogels ................................. 84
5.8.4 Responsive Hydrogels ............................ 84
5.9 Conducting Polymers .................................... 86
5.10 Encapsulation .......................................... 88
5.11 Entrapment in Mesoporous Materials ..................... 89
5.12 Polymer Membranes ...................................... 90
5.12.1 Deposition of Polymers onto Solid Surfaces ...... 90
5.12.2 Perm-Selective Membranes ........................ 91
5.13 Microfabrication Methods in Chemical-Sensor
Technology ............................................. 92
5.13.1 Spot Arraying ................................... 92
5.13.2 Thick-Film Technology ........................... 92
5.13.3 Thin-Film Techniques ............................ 94
5.13.4 Soft Lithography ................................ 95
5.13.5 Microcontact Printing of Вiocompounds ........... 95
5.14 Concluding Remarks ..................................... 97
References .................................................. 97
6 Affinity-Based Recognition ................................. 101
6.1 General Principles .................................... 101
6.2 Immunosensors ......................................... 101
6.2.1 Antibodies: Structure and Function ............. 101
6.2.2 Antibody-Antigen Affinity and Avidity .......... 103
6.2.3 Analytical Applications ........................ 103
6.2.4 Label-Free Transduction Methods in
Immunosensors .................................. 104
6.2.5 Label-Based Transduction Methods in
Immunosensors .................................. 104
6.2.6 Enzyme Labels in Immunoassay ................... 105
6.3 Immobilization Methods in Immunosensors ............... 106
6.4 Immunoassay Formats ................................... 106
6.5 Protein and Peptide Microarrays ....................... 109
6.6 Biological Receptors .................................. 110
6.7 Artificial Receptors .................................. 111
6.7.1 Cyclodextrins and Host-Guest Chemistry ......... 111
6.7.2 Calixarenes .................................... 113
6.7.3 Molecularly Imprinted Polymers (MIPs) .......... 113
6.8 Outlook ............................................... 115
References ................................................. 115
7 Nucleic Acids in Chemical Sensors .......................... 118
7.1 Nucleic Acid Structure and Properties ................. 118
7.2 Nucleic Acid Analogs .................................. 121
7.3 Nucleic Acids as Receptors in Recognition Processes ... 122
7.3.1 Hybridization: Polynucleotide Recognition ...... 122
7.3.2 Recognition of Non-Nucleotide Compounds ........ 123
7.3.3 Recognition by Nucleic Acid Aptamers ........... 124
7.4 Immobilization of Nucleic Acids ....................... 126
7.4.1 Adsorption ..................................... 126
7.4.2 Immobilization by Self-Assembly ................ 127
7.4.3 Immobilization by Polymerization ............... 127
7.4.4 Covalent Immobilization on Functionalized
Surfaces ....................................... 128
7.4.5 Coupling by Affinity Reactions ................. 128
7.4.6 Polynucleotides-Nanoparticles Hybrids .......... 129
7.5 Transduction Methods in Nucleic Acids Sensors ......... 129
7.5.1 Label-Free Transduction Methods ................ 129
7.5.2 Label-Based Transduction ....................... 129
7.5.3 DNA Amplification .............................. 130
7.6 DNA Microarrays ....................................... 131
7.7 Outlook ............................................... 132
References ................................................. 133
8 Nanomaterial Applications in Chemical Sensors .............. 135
8.1 Generals .............................................. 135
8.2 Metallic Nanomaterials ................................ 136
8.2.1 Synthesis of Metal Nanoparticles ............... 136
8.2.2 Functionalization of Gold Nanoparticles ........ 137
8.2.3 Applications of Metal Nanoparticles in
Chemical Sensors ............................... 138
8.3 Carbon Nanomaterials .................................. 138
8.3.1 Structure of CNTs .............................. 139
8.3.2 Synthesis of CNTs .............................. 140
8.3.3 Chemical Reactivity and Functionalization ...... 140
8.3.4 CNT Applications in Chemical Sensors ........... 142
8.3.5 Carbon Nanofibers (CNFs) ....................... 142
8.4 Polymer and Inorganic Nanofibers ...................... 144
8.5 Magnetic Micro-and Nanoparticles ...................... 145
8.5.1 Magnetism and Magnetic Materials ............... 145
8.5.2 Magnetic Nanoparticles ......................... 146
8.5.3 Magnetic Biosensors and Biochips ............... 146
8.5.4 Magnetic Nanoparticles as Auxiliary
Components in Biosensors ....................... 148
8.5.5 Outlook ........................................ 148
8.6 Semiconductor Nanomaterials ........................... 149
8.6.1 Synthesis and Functionalization of Quantum
Dots ........................................... 149
8.6.2 Applications of Quantum Dots ................... 151
8.7 Silica Nanoparticles .................................. 151
8.7.1 Synthesis, Properties, and Applications ........ 151
8.8 Dendrimers ............................................ 152
8.8.1 Properties and Applications .................... 152
8.9 Summary ............................................... 153
References ................................................. 153
9 Thermochemical Sensors ..................................... 157
9.1 Temperature Transducers ............................... 157
9.1.1 Resistive Temperature Transducers .............. 157
9.1.2 Thermopiles .................................... 157
9.2 Enzymatic Thermal Sensors ............................. 158
9.2.1 Principles of Thermal Transduction in
Enzymatic Sensors .............................. 158
9.2.2 Thermistor-Based Enzymatic Sensors ............. 159
9.2.3 Thermopile-Based Enzymatic Sensors ............. 160
9.2.4 Multienzyme Thermal Sensors .................... 160
9.2.5 Outlook ........................................ 161
9.3 Thermocatalytic Sensors for Combustible Gases ......... 162
9.3.1 Structure and Functioning Principles ............ 162
References ............................................ 163
10 Potentiometrie Sensors ..................................... 165
10.1 Introduction .......................................... 165
10.2 The Galvanic Cell at Equilibrium ...................... 165
10.2.1 Thermodynamics of Electrolyte Solutions ........ 166
10.2.2 Thermodynamics of the Galvanic Cell ............ 167
10.3 Ion Distribution at the Interface of Two Electrolyte
Solutions ............................................. 170
10.3.1 Charge Distribution at the Junction of Two
Electrolyte Solutions. The Diffusion
Potential ...................................... 170
10.3.2 Ion Distribution at an Aqueous/Semipermeable
Membrane Interface ............................. 172
10.4 Potentiometrie Ion Sensors - General .................. 173
10.4.1 Sensor Configuration and the Response
Function ....................................... 173
10.4.2 Selectivity of Potentiometrie Ion Sensors ...... 175
10.4.3 The Response Range of Potentiometrie Ion
Sensors ........................................ 177
10.4.4 Interferences by Chemical Reactions
Occurring in the Sample ........................ 177
10.4.5 The Response Time of Potentiometrie Ion
Sensors ........................................ 178
10.4.6 Outlook ........................................ 178
10.5 Sparingly Soluble Solid Salts as Membrane Materials ... 178
10.5.1 Membrane Composition ........................... 178
10.5.2 Response Function and Selectivity .............. 179
10.6 Glass Membrane Ion Sensors ............................ 181
10.6.1 Membrane Structure and Properties .............. 181
10.6.2 Response Function and Selectivity .............. 182
10.6.3 Chalcogenide Glass Membranes ................... 183
10.7 Ion Sensors Based on Molecular Receptors. General
Aspects ............................................... 184
10.8 Liquid Ion Exchangers as Ion Receptors ................ 185
10.8.1 Ion Recognition by Liquid Ion Exchangers ....... 185
10.8.2 Charged Receptor Membranes ..................... 185
10.8.3 Response Function and Selectivity .............. 186
10.8.4 Outlook ........................................ 187
10.9 Neutral Ion Receptors (Ionophores) .................... 187
10.9.1 General Principles ............................. 187
10.9.2 Chemistry of Ion Recognition by Neutral
Receptors ...................................... 188
10.9.3 Effect of Bonding Multiplicity, Steric, and
Conformational Factors ......................... 189
10.9.4 Neutral Receptor Ion-Selective Membranes:
Composition, Selectivity and Response
Function ....................................... 190
10.9.5 Neutral Noncyclic Ion Receptors ................ 192
10.9.6 Macrocyclic Cation Receptors ................... 193
10.9.7 Macrocyclic Anion Receptors .................... 194
10.9.8 Neutral Receptors for Organic Ions ............. 194
10.9.9 Porphyrins and Phthalocyanines as Anion
Receptors ...................................... 195
10.9.10 Outlook ....................................... 196
10.10 Molecularly Imprinted Polymers as Ion-Sensing
Materials ............................................. 197
10.11 Conducting Polymers as Ion-Sensing Materials ......... 198
10.12 Solid Contact Potentiometrie Ion Sensors ............. 198
10.13 Miniaturization of Potentiometrie Ion Sensors ........ 199
10.14 Analysis with Potentiometrie Ion Sensors ............. 200
10.15 Recent Advances in Potentiometrie Ion Sensors ........ 201
10.16 Potentiometrie Gas Sensors ........................... 203
10.17 Solid Electrolyte Potentiometrie Gas Sensors ......... 204
10.17.1 General Principles ............................ 204
10.17.2 Solid Electrolyte Potentiometrie Oxygen
Sensors ....................................... 205
10.17.3 Applications of Potentiometrie Oxygen
Sensors ....................................... 206
10.17.4 Types of Solid Electrolyte Potentiometrie
Gas Sensors ................................... 207
10.17.5 Mixed Potential Potentiometrie Gas Sensors .... 208
10.17.6 Outlook ....................................... 209
10.18 Potentiometrie Biocatalytic Sensors .................. 210
10.19 Potentiometrie Affinity Sensors ...................... 211
10.20 Summary .............................................. 212
References ................................................. 213
11 Chemical Sensors Based on Semiconductor Electronic
Devices .................................................... 217
11.1 Electronic Semiconductor Devices ...................... 217
11.1.1 Semiconductor Materials ........................ 217
11.1.2 Band Theory of Semiconductors .................. 218
11.1.3 Metal-Insulator-Semiconductor (MIS)
Capacitors ..................................... 219
11.1.4 Metal-Insulator-Semiconductor Field Effect
Transistors (MISFETs) .......................... 221
11.1.5 Outlook ........................................ 224
11.2 FED Ion Sensors and Their Applications ................ 224
11.2.1 Electrolyte-Insulator-Semiconductor (EIS)
Devices ........................................ 224
11.2.2 FED pH Sensors ................................. 226
11.2.3 pH ISFET-Based Gas Probes ...................... 228
11.2.4 Membrane-Covered ISFETs ........................ 229
11.2.5 Light-Addressable Potentiometrie Sensors
(LAPS) ......................................... 230
11.2.6 Reference Electrodes for ISFET Sensors ......... 231
11.2.7 Enzymatic FET Sensors (EnFETs) ................. 232
11.2.8 Outlook ........................................ 232
11.3 FED Gas Sensors ....................................... 234
11.3.1 FED Hydrogen Sensors ........................... 234
11.3.2 Metal Gate FED Sensors for Other Gases ......... 235
11.3.3 Organic Semiconductors as Gas-Sensing
Materials ...................................... 236
11.3.4 Organic Semiconductors FED Gas Sensors ......... 237
11.3.5 Response Mechanism of FED Gas Sensors .......... 238
11.3.6 Outlook ........................................ 239
11.4 Schottky-Diode-Based Gas Sensors ...................... 240
11.5 Carbon-Nanotube-Based Field-Effect Transistors ........ 242
11.6 Concluding Remarks .................................... 243
References ................................................. 244
12 Resistive Gas Sensors (Chemiresistors) ..................... 246
12.1 Semiconductor Metal Oxide Gas Sensors ................. 246
12.1.1 Introduction ................................... 246
12.1.2 Gas-Response Mechanism ......................... 246
12.1.3 Response to Humidity ........................... 247
12.1.4 Sensor Configuration ........................... 248
12.1.5 Synthesis and Deposition of Metal Oxides ....... 249
12.1.6 Fabrication of Metal-Oxide Chemiresistors ...... 249
12.1.7 Selectivity and Sensitivity .................... 250
12.1.8 Outlook ........................................ 251
12.2 Organic-Material-Based Chemiresistors ................. 252
12.3 Nanomaterial Applications in Resistive Gas Sensors .... 253
12.4 Resistive Gas Sensor Arrays ........................... 254
12.5 Summary ............................................... 255
References ................................................. 256
13 Dynamic Electrochemistry Transduction Methods .............. 258
13.1 Introduction .......................................... 258
13.2 Electrochemical Cells in Amperometric Analysis ........ 258
13.3 The Electrolytic Current and its Analytical
Significance .......................................... 260
13.3.1 Current-Concentration Relationships ............ 260
13.3.2 The Current-Potential Curve: Selecting the
Working Potential .............................. 262
13.3.3 Irreversible Electrochemical Reactions ......... 264
13.3.4 Sign Convention ................................ 265
13.3.5 Geometry of the Diffusion Process .............. 265
13.3.6 Outlook ........................................ 265
13.4 Membrane-Covered Electrodes ........................... 266
13.5 Non-Faradaic Processes ................................ 267
13.5.1 Origin of Non-Faradaic Currents ................ 267
13.5.2 The Electrical Double Layer at the Electrode/
Solution Interface ............................. 268
13.5.3 The Charging Current ........................... 269
13.5.4 Applications of Capacitance Measurement in
Chemical Sensors ............................... 270
13.6 Kinetics of Electrochemical Reactions ................. 270
13.6.1 The Reaction Rate of an Electrochemical
Reaction ....................................... 270
13.6.2 Current-Potential Relationships ................ 272
13.6.3 Mass-Transfer Effect on the Kinetics of
Electrochemical Reactions ...................... 273
13.6.4 Equilibrium Conditions ......................... 274
13.6.5 The Electrochemical Reaction in the Absence
of Mass-Transfer Restrictions .................. 275
13.6.6 Polarizable and Nonpolarizable Electrodes ...... 276
13.6.7 Achieving Steady-State Conditions in
Electrochemical Measurements ................... 277
13.6.8 Outlook ........................................ 278
13.7 Electrochemical Methods ............................... 280
13.7.1 Steady-State Methods ........................... 280
13.7.2 Constant-Potential Chronoamperometry ........... 280
13.7.3 Polarography ................................... 281
13.7.4 Linear-Scan Voltammetry (LSV) and Cyclic
Voltammetry (CV) ................................ 282
13.7.5 Pulse Voltammetry .............................. 285
13.7.6 Square-Wave Voltammetry (SWV) .................. 286
13.7.7 Alternating-Current Voltammetry ................ 287
13.7.8 Chronopotentiometric Methods ................... 288
13.7.9 Electrochemistry at Ultramicroelectrodes ....... 289
13.7.10 Current Amplification by Reactant Recycling ... 291
13.7.11 Scanning Electrochemical Microscopy ........... 292
13.7.12 Outlook ....................................... 293
13.8 Electrode Materials ................................... 294
13.8.1 Carbon Electrodes .............................. 295
13.8.2 Noble-Metal Electrodes ......................... 296
13.8.3 Metal-Oxide Films .............................. 297
13.8.4 Electrode Fabrication .......................... 297
13.8.5 Carbon Nanomaterial Applications in
Electrochemistry ............................... 298
13.8.6 Outlook ........................................ 298
13.9 Catalysis in Electrochemical Reactions ................ 299
13.9.1 Homogeneous Redox Catalysis .................... 299
13.9.2 Homogeneous Mediation in Electrochemical
Enzymatic Reactions ............................ 300
13.9.3 Catalysis by Immobilized Enzymes ............... 301
13.9.4 Heterogeneous Redox Catalysis .................. 302
13.9.5 Surface Activation of Electrochemical
Reactions ...................................... 304
13.9.6 Outlook ........................................ 304
13.10 Amperometric Gas Sensors ............................. 306
13.10.1 The Clark Oxygen Sensor ....................... 306
13.10.2 Nitric Oxide Sensors .......................... 307
13.10.3 Other Types of Amperometric Gas Sensors ....... 308
13.10.4 Galvanic Cell-Type Gas Sensors ................ 309
13.10.5 Solid Electrolyte Amperometric Gas Sensors .... 309
References ............................................ 310
14 Amperometric Enzyme Sensors ................................ 314
14.1 First-Generation Amperometric Enzyme Sensors .......... 314
14.2 Second-Generation Amperometric Enzyme Sensors ......... 316
14.2.1 Principles ..................................... 316
14.2.2 Inorganic Mediators ............................ 317
14.2.3 Organic Mediators .............................. 317
14.2.4 Ferrocene Derivatives as Mediators ............. 319
14.2.5 Electron-Transfer Mediation by Redox Polymers .. 320
14.2.6 Sensing by Organized Molecular Multilayer
Structures "H- ................................. 321
14.3 The Mediator as Analyte ............................... 322
14.4 Conducting Polymers in Amperometric Enzyme Sensors .... 323
14.5 Direct Electron Transfer: 3rd-Generation
Amperometric Enzyme Sensors ........................... 324
14.5.1 Conducting Organic Salt Electrodes ............. 324
14.5.2 Direct Electron Transfer with FAD-Heme
Enzymes ........................................ 325
14.5.3 Achieving Direct Electron Transfer by Means
of Nanomaterials ............................... 326
14.6 NAD/NADH+as Mediator in Biosensors .................... 327
14.7 Summary ............................................... 328
References ............................................ 328
15 Mathematical Modeling of Mediated Amperometric Enzyme
Sensors .................................................... 332
15.1 External Diffusion Conditions ......................... 332
15.1.1 Model Formulation .............................. 332
15.1.2 Sensor Response: Limiting Cases ................ 334
15.1.3 The Dynamic Range and the Limit of Detection ... 336
15.1.4 Other Theoretical Models ....................... 338
15.1.5 Outlook ........................................ 338
15.2 Internal Diffusion Conditions ......................... 339
15.2.1 Model Formulation .............................. 339
15.2.2 Dimensionless Parameters and Variables ......... 340
15.2.3 Limiting Conditions ............................ 342
15.2.4 Solving the Differential Equations. The Case
Diagram ........................................ 343
15.2.5 Kinetic Currents ............................... 343
15.2.6 Diffusion Currents ............................. 343
15.2.7 Outlook ........................................ 345
References ............................................ 345
16 Electrochemical Affinity and Nucleic Acid Sensors .......... 347
16.1 Amperometric Affinity Sensors ......................... 347
16.1.1 Redox Labels in Amperometric Immunosensors ..... 347
16.1.2 Enzyme-Linked Amperometric Immunosensors ....... 347
16.1.3 Separationless Amperometric Immunosensors ...... 349
16.1.4 Nanomaterials Applications in Amperometric
Immunosensors .................................. 350
16.1.5 Imprinted Polymers in Amperometric Affinity
Sensors ........................................ 351
16.1.6 Outlook ........................................ 353
16.2 Electrochemical Nucleic Acid-Based Sensors ............ 354
16.2.1 Electrochemical Reactions of Nucleobases ....... 354
16.2.2 Amperometric Nucleic Acid Sensors Based on
Self-Indicating Hybridization .................. 355
16.2.3 Intercalating Redox Indicators ................. 357
16.2.4 Covalently Bound Redox Indicators in Sandwich
Assays ......................................... 357
16.2.5 CoValently Bound Redox Indicators in
Spatially Resolved Transduction ................ 359
16.2.6 Enzyme Labels in Amperometric Nucleic Acid
Sensors ........................................ 359
16.2.7 Electrochemical DNA Arrays ..................... 361
16.2.8 Nucleic Acids as Recognition Materials for
Non-Nucleotide Compounds ....................... 361
16.2.9 Aptamer Amperometric Sensors ................... 361
16.2.10 Outlook ....................................... 363
References ............................................ 364
17 Electrical-Impedance-Based Sensors ......................... 367
17.1 Electrical Impedance: Terms and Definitions ........... 367
17.2 Electrochemical Impedance Spectrometry ................ 369
17.2.1 Basic Concepts and Definitions ................. 369
17.2.2 Non-Faradaic Processes ......................... 370
17.2.3 Faradaic Processes ............................. 372
17.2.4 Probing the Electrode Surface by
Electrochemical Impedance Spectrometry ......... 373
17.3 Electrochemical Impedance Affinity Sensors ............ 375
17.3.1 Electrochemical Impedance Transduction in
Affinity Sensors ............................... 375
17.3.2 Configuration of Impedimetric Biosensors ....... 376
17.3.3 Capacitive Biosensors .......................... 377
17.3.4 Signal Amplification ........................... 379
17.3.5 Synthetic Receptor-Based Impedimetric Sensors .. 379
17.3.6 Applications of Impedimetric Affinity Sensors .. 380
17.4 Biocatalytic Impedimetric Sensors ..................... 381
17.5 Outlook ............................................... 382
17.6 Nucleic Acid Impedimetric Sensors ..................... 383
17.6.1 Non-Faradaic Impedimetric DNA Sensors .......... 383
17.6.2 Faradaic Impedimetric DNA Sensors .............. 384
17.6.3 Impedimetric Aptasensors ....................... 385
17.7 Conductometric Sensors ................................ 386
17.7.1 Conductivity of Electrolyte Solutions .......... 386
17.7.2 Conductance Measurement ........................ 388
17.7.3 Conductometric Transducers ..................... 389
17.7.4 Conductometric Enzymatic Sensors ............... 389
17.7.5 Conductometric Transduction by Chemoresistive
Materials ...................................... 391
17.7.6 Ion-Channel-Based Conductometric Sensors ....... 394
17.7.7 Outlook ........................................ 394
17.8 Impedimetric Sensors for Gases and Vapors ............. 395
17.8.1 Humidity: Terms and Definitions ................ 395
17.8.2 Resistive Humidity Sensors ..................... 396
17.8.3 Capacitive Humidity Sensors .................... 397
17.8.4 Capacitive Gas Sensors ......................... 399
17.8.5 Integrated Impedimetric Gas Sensors and
Sensor Arrays .................................. 399
17.8.6 Outlook ........................................ 400
References ................................................. 400
18 Optical Sensors - Fundamentals ............................. 404
18.1 Electromagnetic Radiation ............................. 404
18.2 Optical Waveguides in Chemical Sensors ................ 405
18.2.1 Optical Fibers: Structure and Light
Propagation .................................... 406
18.2.2 Passive Fiber Optic Sensor Platforms ........... 407
18.2.3 Active Fiber Optic Sensor Platforms ............ 407
8.2.4 Planar Waveguides ............................. 408
18.2.5 Capillary Waveguides ........................... 409
18.2.6 Outlook ........................................ 409
18.3 Spectrochemical Transduction Methods .................. 409
18.3.1 Light Absorption ............................... 409
18.3.2 Diffuse Reflectance Spectrometry ............... 410
18.3.3 Luminescence ................................... 411
18.3.4 Fluorescence Spectrometry ...................... 412
18.3.5 Steady-State Fluorescence Measurements ......... 413
18.3.6 Time-Resolved Fluorimetry ...................... 414
18.3.7 Fluorescence Quenching ......................... 416
18.3.8 Resonance Energy Transfer ...................... 417
18.3.9 Chemiluminescence and Bioluminescence .......... 417
18.3.10 Electrochemically Generated
Chemiluminescence ............................. 418
18.3.11 Raman Spectrometry ............................ 419
18.3.12 Outlook ....................................... 420
18.4 Transduction Schemes in Spectrochemical Sensors ....... 421
18.4.1 Direct Transduction ............................ 421
18.4.2 Indirect (Competitive-Binding) Transduction .... 423
18.4.3 Outlook ........................................ 424
18.5 Fiber Optic Sensor Arrays ............................. 424
18.6 Label-Free Transduction in Optical Sensors ............ 425
18.6.1 Surface Plasmon Resonance Spectrometry ......... 425
18.6.2 Interferometric Transduction ................... 426
18.6.3 The Resonant Mirror ............................ 428
18.6.4 Resonant Waveguide Grating ..................... 429
18.6.5 Outlook ........................................ 429
18.7 Transduction by Photonic Devices ...................... 430
18.7.1 Optical Microresonators ........................ 430
18.7.2 Photonic Crystals .............................. 431
18.7.3 Outlook ........................................ 433
References ............................................ 433
19 Optical Sensors - Applications ............................. 435
19.1 Optical Sensors Based on Acid-Base Indicators ......... 435
19.1.1 Optical pH Sensors ............................. 435
19.1.2 Optical Sensors for Acidic and Basic Gases ..... 437
19.2 Optical Ion Sensors ................................... 438
19.2.1 Direct Optical Ion Sensors ..................... 438
19.2.2 Indirect Optical Ion Sensors ................... 439
19.3 Optical Oxygen Sensors ................................ 440
19.4 Optical Enzymatic Sensors ............................. 442
19.4.1 Principles and Design .......................... 442
19.4.2 Optical Monitoring of Reactants or Products .... 442
19.4.3 Coenzyme-Based Optical Transduction ............ 443
19.4.4 Outlook ........................................ 443
19.5 Optical Affinity Sensors .............................. 444
19.5.1 Optical Immunosensors .......................... 444
19.5.2 Optical Sensors Based on Biological Receptors .. 445
19.5.3 Outlook ........................................ 446
19.6 Optical DNA Sensors and Arrays ........................ 447
19.6.1 Fluorescence Transduction in Nucleic Acid
Sensors ........................................ 447
19.6.2 Fiber Optic Nucleic Acid Sensors ............... 448
19.6.3 Fiber Optic Nucleic Acid Arrays ................ 450
19.6.4 Optical DNA Microarrays ........................ 451
19.6.5 Outlook ........................................ 451
References ................................................. 452
20 Nanomaterial Applications in Optical Transduction .......... 454
20.1 Semiconductor Nanocrystals (Quantum Dots) ............. 454
20.1.1 Quantum Dots: Structure and Properties ......... 454
20.1.2 Applications of Quantum Dots in Chemical
Sensing ........................................ 456
20.1.3 Outlook ........................................ 461
20.2 Carbon Nanotubes as Optical Labels .................... 462
20.2.1 Light Absorption and Emission by CNTs .......... 462
20.2.2 Raman Scattering by CNTs ....................... 464
20.2.3 CNT Optical Sensors and Arrays ................. 464
20.2.4 Outlook ........................................ 466
20.3 Metal Nanoparticle in Optical Sensing ................. 466
20.3.1 Optical Properties of Metal Nanoparticles ...... 466
20.3.2 Optical Detection Based on Metal
Nanoparticles .................................. 467
20.3.3 Metal Nanoparticles in Optical Sensing ......... 468
20.4 Porous Silicon ........................................ 470
20.5 Luminescent Lanthanide Compound Nanomaterials ......... 471
20.6 Summary ............................................... 471
References ................................................. 471
21 Acoustic-Wave Sensors ...................................... 473
21.1 The Piezoelectric Effect .............................. 473
21.2 The Thickness-Shear Mode Piezoelectric Resonator ...... 474
21.2.1 The Quartz Crystal Microbalance ................ 474
21.2.2 The Unperturbed Resonator ...................... 476
21.2.3 QCM Loading by a Rigid Overlayer. The
Sauerbrey Equation ............................. 477
21.2.4 The QCM in Contact with Liquids ................ 478
21.2.5 The QCM in Contact with a Newtonian Liquid ..... 479
21.2.6 The QCM in Contact with a Viscoelastic Fluid ... 480
21.2.7 Modeling the Loaded TSM Resonator .............. 480
21.2.8 The Quartz Crystal Microbalance with
Dissipation л. Monitoring (QCM-D) .............. 485
21.2.9 Operation of QCM Sensors ....................... 486
21.2.10 Calibration of the QCM ........................ 487
21.2.11 Outlook ....................................... 488
21.3 QCM Gas and Vapor Sensors ............................. 489
21.4 QCM Affinity Sensors .................................. 489
21.4.1 QCM Immunosensor ............................... 490
21.4.2 Amplification in QCM Immunosensors ............. 491
21.4.3 Determination of Small Molecules Using
Natural Receptors .............................. 492
21.4.4 QCM Sensors Based on Molecularly Imprinted
Polymers ....................................... 492
21.4.5 QCM Sensors Based on Small Synthetic
Receptors ...................................... 494
21.4.6 Outlook ........................................ 494
21.5 Hwfeteic Acid Sensors ................................. 495
21.5.1 ftytoridization Sensors ........................ 495
21.5.2 ftezoelecttic Aptasensors ...................... 496
41.5.3 Outlook ........................................ 497
21.6 Surface-Launched Acoustic-Wave Sensors ................ 497
21.6.1 Principles ..................................... 497
21.6.2 The Surface Acoustic Wave ...................... 498
21.6.3 Plate-Mode SLAW Devices ........................ 498
21.6.4 SLAW Gas and Vapor Sensors ..................... 499
21.6.5 Liquid-Phase SLAW Sensing ...................... 501
21.6.6 Outlook ........................................ 502
21.7 Summary ............................................... 503
References ............................................ 504
22 Microcantilever Sensors .................................... 507
22.1 Principles of Microcantilever Transduction ............ 507
22.1.1 The Microcantilever ............................ 507
22.1.2 Static Deformation Transduction ................ 508
22.1.3 Resonance-Mode Transduction .................... 509
22.2 Measurement of Cantilever Deflection .................. 510
22.2.1 Optical Measurement of Cantilever Deflection ... 510
22.2.2 Electrical Measurement of Cantilever
Deflection ..................................... 511
22.3 Functionalization of Microcantilevers ................. 512
22.4 Microcantilever Gas and Vapor Sensors ................. 513
22.5 Microcantilever Affinity Sensors ...................... 513
22.5.1 General Aspects ................................ 513
22.5.2 Microcantilever Protein Sensors ................ 514
22.5.3 Microcantilever Pathogen Sensors ............... 514
22.5.4 Microcantilever Affinity Sensors Based on
Other Recognition Receptors .................... 514
22.6 Enzyme Assay by Microcantilever Sensors ............... 515
22.7 Microcantilever Nucleic Acid Sensors .................. 515
22.8 Outlook ............................................... 516
References ................................................. 516
23 Chemical Sensors Based on Microorganisms, Living Cells
and Tissues ................................................ 518
23.1 Living Material Biosensors'. General Principles ....... 518
23.2 Sensing Strategies in Living-Material-Based Sensors ... 518
23.2.1 Biocatalytic Sensors ........................... 518
23.2.2 External-Stimuli-Based Biosensors .............. 519
23.3 Immobilization of Living Cells and Microorganisms ..... 519
23.4 Electrochemical Microbial Biosensors .................. 520
23.4.1 Amperometric Microbial Biosensors .............. 520
23.4.2 Potentiometrie Microbial Biosensors ............ 522
23.4.3 Conductometric Microbial Sensors ............... 523
23.4.4 Electrical Impedance Transduction .............. 523
23.5 Optical Whole-Cell Sensors ............................ 524
23.5.1 Optical Respiratory Biosensors ................. 524
23.5.2 External-Stimuli-Based Optical Sensors ......... 525
23.5.3 Bioreporters ................................... 526
23.6 Improving the Selectivity of Microorganisms
Biosensors ............................................ 526
23.7 Conclusions ........................................... 527
References ................................................. 528
Index ......................................................... 531
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