Chemically Modified Carbon Nanotubes for Commercial Applications E-Book
151,99 €
Mehr erfahren.
- Herausgeber: Wiley-VCH GmbH
- Kategorie: Fachliteratur
- Sprache: Englisch
Chemically Modified Carbon Nanotubes for Commercial Applications
Discover the go-to handbook for developers and application-oriented researchers who use carbon nanotubes in real products
Carbon nanotubes have held much interest for researchers since their discovery in 1991. Due to their low mass density, large aspect ratio, and unique physical, chemical, and electronic properties, they provide a fertile ground for innovation in nanoscale applications. The development of chemical modifications that can enhance the poor dispersion of carbon nanotubes in solvents and improve interactions with other materials have enabled extensive industrial applications in a variety of fields.
As the chemistry of carbon nanotubes and their functionalization becomes better understood, Chemically Modified Carbon Nanotubes for Commercial Applications presents the most recent developments of chemically modified carbon nanotubes and emphasizes the broad appeal for commercial purposes along many avenues of interest. The book reviews their already realized and prospective applications in fields such as electronics, photonics, separation science, food packaging, environmental monitoring and protecting, sensing technology, and biomedicine. By focusing on their commercialization prospects, this resource offers a unique approach to a significant and cutting-edge discipline.
In Chemically Modified Carbon Nanotubes for Commercial Applications readers will also find:
- Case studies that emphasize the information presented in each chapter
- Each chapter includes important websites and suggested reading materials
- Discussion of current applications of the relevant methodologies in every chapter
- A look at future perspectives in each application area to highlight the scope for next steps within the industry
Chemically Modified Carbon Nanotubes for Commercial Applications is a valuable reference for material scientists, chemists (especially those focused on environmental concerns), and chemical and materials engineering scientists working in R&D and academia who want to learn more about chemically modified carbon nanotubes for various scalable commercial applications. It is also a useful resource for a broad audience: anyone interested in the fields of nanomaterials, nanoadsorbents, nanomedicine, bioinspired nanomaterials, nanotechnology, nanodevices, nanocomposites, biomedical application of nanomaterials, nano-engineering, and high energy applications.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 958
Veröffentlichungsjahr: 2022
Ähnliche
Table of Contents
Cover
Title Page
Copyright
Preface
About the Editors
Part I: Chemically Modified Carbon Nanotubes: Overview, Commercialization, and Economic Aspects
1 A Detailed Study on Carbon Nanotubes: Properties, Synthesis, and Characterization
1.1 Introduction
1.2 Evolution of Carbon: Graphite to CNTs
1.3 Conclusion
Declaration of Competing Interest
Companies Dealing with Chemically Modified CNTs
Acknowledgments
References
2 Surface Modification Strategies for the Carbon Nanotubes
2.1 Introduction
2.2 Classification of Carbon Nanotubes and Their Fabrication
2.3 Purification of CNTs
2.4 Surface Modification of CNTs
2.5 Characterization of CNTs
2.6 Conclusion
References
3 Latest Developments in Commercial Scale Fabrications for Chemically Modified Carbon Nanotubes
Abbreviations
3.1 Introduction
3.2 Industrial Scale Fabrication Strategies
3.3 CVD on the Basis of Reactor Wall Temperature
3.4 Arc-Discharge
3.5 Laser Vaporization
3.6 Other Synthesis Methods
3.7 Applications
3.8 Future Scope
3.9 Conclusion
Conflict of Interest
Other Sources
Acknowledgments
References
4 Economical Uses of Chemically Modified Carbon Nanotubes
4.1 Introduction
4.2 Properties of Carbon Nanotubes
4.3 Synthesis of Carbon Nanotubes
4.4 Functionalization of Carbon Nanotubes
4.5 Characterization/Analysis of Functionalized Carbon Nanotubes
4.6 Economy of Carbon Nanotubes
4.7 Economic Importance of Carbon Nanotubes
4.8 Hydrogen Fuel Cells
4.9 Water Splitting
4.10 Dye-Sensitized Solar Cells
4.11 Quantum Dot Solar Cells
4.12 Silicon-Based Solar Cells
4.13 Thermoelectric Fabrics
4.14 Cost of Carbon Nanotubes
4.15 Globalization of Carbon Nanotubes
4.16 Conclusion
References
Part II: Chemically Modified Carbon Nanotubes: Energy and Environment Applications
5 Chemically Modified Carbon Nanotubes in Energy Production and Storage
Abbreviations
5.1 Introduction
5.2 Production of Carbon Nanotubes
5.3 History of Energy Storage Devices and Materials
5.4 Carbon Nanotubes for Energy Storage
5.5 Present and Future of Carbon Nanotubes
5.6 Commercial-Scale Application of Chemically Modified CNTs for Energy Storage
5.7 Companies Produced CNTs for the Application of Chemically Modified Carbon Nanotubes for Energy Storage
References
6 Chemically Modified Carbon Nanotubes for Pollutants Adsorption
6.1 Introduction
6.2 Chemically Modified CNTs
6.3 Chemically Modified CNTs for Adsorptive Removal of Pollutants
6.4 Influencing Factors
6.5 Adsorption Mechanisms of Chemically Modified CNTs
6.6 Modified CNT-Based Materials Toward Commercialization
6.7 Conclusion and Future Perspectives
Acknowledgments
References
7 Chemically Modified Carbon Nanotubes in Removal of Textiles Effluents
7.1 Introduction
7.2 History of Removal of Textiles Effluents
7.3 Chemically Modified Carbon Nanotubes
7.4 Dyes Removal Techniques
7.5 Adsorption
7.6 Carbon-Based Nanoadsorbents
7.7 Carbon Nanotubes
7.8 Carbon Nanotubes as an Adsorption of Dye Molecules
7.9 Industrial Application of Synthetic Dyes
7.10 Conclusion
Acknowledgment
References
8 Chemically Modified Carbon Nanotubes in Membrane Separation
8.1 Introduction
8.2 Carbon Nanotubes (CNTs) Overview
8.3 Method of Synthesis of Carbon Nanotube (CNT)
8.4 Fabrication Methods of CNTs
8.5 Functionalization of CNTs
8.6 Chemically Modified Derivatization of CNTs
8.7 Polymer Grafting
8.8 Carbon Nanotubes Enhanced with Nanoparticles
8.9 Advantages of CNTs
8.10 Challenges in CNTs
8.11 Applications of CNTs as Membrane Separation
8.12 Commercial-Scale of Chemically Modified CNTs in Membrane Separation
8.13 Future Insights
8.14 Conclusion
References
9 Chemically Modified Carbon Nanotubes for Water Purification System
Abbreviations
9.1 Introduction
9.2 History of Water Purification Methods
9.3 Carbon Nanotubes CNTs Types
9.4 Vital of Modification of CNTs
9.5 Surface Modified CNTs for Water Purification
9.6 Polymer/CNTs Grafting for Water Purification
9.7 Bulk Modified CNTs for Water Purification
9.8 Important of Carbon Nanotubes for Water Purification
9.9 Conclusions and Future Research Directions
9.10 Commercial Application of Chemically Modified CNTs in Water Purification
9.11 Companies Produced CNTs for the Application of Chemically Modified Carbon Nanotubes for Water Purification System
References
Part III: Chemically Modified Carbon Nanotubes: Electronic and Electrical Applications
10 Chemically Modified Carbon Nanotubes for Electronics and Photonic Applications
10.1 Introduction
10.2 Chemical Modifications of CNTs
10.3 Chemically Modified CNTs in Electronics
10.4 Chemically Modified CNTs in Photonics
10.5 Summary and Future Scope
References
11 Chemically Modified Carbon Nanotubes for Electrochemical Sensors
11.1 Introduction
11.2 Functionalization of Carbon Nanotubes Toward Sensors
11.3 Electrochemical Sensing Applications of CNTs
11.4 Summary and Outlook
References
12 Chemically Modified Carbon Nanotubes for Lab on Chip Devices
Abbreviations
12.1 Introduction
12.2 Allotropes of Carbon
12.3 Carbon Nanotube Used in Solar Cells
12.4 Carbon Nanotube Used in Optical Sensors
12.5 Carbon Nanotube Used in Light-Emitting Diodes
12.6 Carbon Nanotube Used in Electronic Device Fabrication
12.7 Carbon Nanotube Used in Lithium-Ion Batteries (LIBs)
12.8 Carbon Nanotube Used in Chip Cooling
12.9 Carbon Nanotube Used in Photovoltaic Devices
12.10 Carbon Nanotube Used in Nonvolatile Random Access Memory
12.11 Carbon Nanotube Used in Potential Device
12.12 Carbon Nanotube Used in On-Chip Inductor
12.13 Carbon Nanotube Used in Electronic Device
12.14 Carbon Nanotube Used in Quantum CNFETs
12.15 Carbon Nanotube Used in Schottky-Barrier Ballistic CNFETs
12.16 Carbon Nanotube Used in Chemical Sensors and Biosensors
12.17 Carbon Nanotube Used in Field Emission of Electrons
12.18 Carbon Nanotube Used in Supercapacitor Devices with Enhanced Electrochemical Performance
12.19 Carbon Nanotube Used in Flip-Chip High Power Amplifiers
12.20 Carbon Nanotube Used in Transistor Device Application
12.21 Carbon Nanotube Used in Supercapacitors and Batteries
12.22 Future Scope
12.23 Conclusion
Acknowledgments
References
Part IV: Chemically Modified Carbon Nanotubes: Biomedical Applications
13 Chemically Modified Carbon Nanotubes in Cancer Therapy
13.1 Introduction
13.2 Carbon Nanotubes as Novel Nanocarriers
13.3 The Need for Chemical Modification and Its Importance
13.4 Chemically Modified Approaches of Carbon Nanotubes
13.5 Chemically Modified Carbon Nanotubes as a Nanocarrier for Cancer Delivery System
13.6 Limitations and Challenges of Chemically Modified CNTs
13.7 Conclusion and Future Perspective
References
Note
14 Chemically Modified Carbon Nanotubes in Drug Delivery
14.1 Introduction
14.2 Antibacterial
14.3 Antifungal
14.4 Anticancer
14.5 Others
14.6 Conclusions and Future Perspectives
Acknowledgments
References
15 Chemically Modified Carbon Nanotubes in Tissue Engineering
15.1 Introduction
15.2 Applications of Modified Carbon Nanotubes in Tissue Engineering
15.3 Conclusion and Future Outlook
Few Websites Related to CNTs Engineering
References
16 Applications of Chemically Modified Carbon Nanotubes for Tissue Engineering
16.1 Introduction
16.2 Biochemical Modifications for Tissue Engineering
16.3 Tissue Engineering Applications of Carbon Nanotubes
16.4 Challenges and Future Perspectives
References
Part V: Chemically Modified Carbon Nanotubes: Construction Applications
17 Chemically Modified Carbon Nanotubes in Cement and Concrete Field
17.1 Introduction
17.2 CNT Dispersion in Cement-Based Materials: Methodologies
17.3 Improvement of Concrete Properties by Addition of CNTs
17.4 Improvement in the Hydration Reaction
17.5 Improvement in Mechanical Properties and Relevant Mechanisms
17.6 Enhanced Durability
17.7 Improvements in Electrical and Thermal Conductivity
17.8 Improvements in Corrosion Resistance Properties of Cement/Concrete
17.9 Potential Structural Applications of CNTs Reinforced Cement-Based Materials
17.10 Challenges
17.11 Conclusions and Future Scope
References
Part VI: Chemically Modified Carbon Nanotubes: Emerging Applications
18 Chemically Modified Carbon Nanotubes in 3D and 4D Printing
18.1 Introduction
18.2 Method for the Carbon Nanotubes (CNTs) Modification
18.3 Chemically Modified CNT for 3D Printing
18.4 Application of Chemically Modified CNTs for 3D Printing
18.5 Modified CNTs for 4D Printing Technique
18.6 Boundaries for 3D/4D Printings and Prospects
18.7 Conclusions
References
Questions
19 Chemically Modified Carbon Nanotubes for Tribology Applications
19.1 Introduction
19.2 Tribological Phenomena – Principle, Mechanism, and Application
19.3 Contemporary Research on Carbon Nanomaterials for Tribological Application
19.4 Improvement of Tribological Behaviors of Bulk CNT Materials
19.5 Recent Advances in Hybrid CNT Materials in Tribological Application
19.6 High-Temperature Tribology of CNTs
19.7 Biotribology of CNTs
19.8 Modified CNTs for Commercial-Scale Tribology Applications
19.9 Other Nanomaterials for Tribological Applications
19.10 Summary and Outlook
Acknowledgments
References
20 Chemically Modified Carbon Nanotubes for Corrosion Protection
20.1 Introduction
20.2 Modification Approaches
20.3 Commercial-Scale Application
20.4 Summary
References
21 Chemically Modified Carbon Nanotubes and Sustainability
Abbreviations
21.1 Introduction
21.2 Chemically Modified Carbon Nanotubes
21.3 Future Scope
21.4 Conclusion
Author's Contributions
Conflict of Interest
Other Sources
Acknowledgments
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Various parameters for SWNTs.
Chapter 2
Table 2.1 Analytical methods for CNTs and their relevance.
Chapter 6
Table 6.1 Examples of chemically modified CNT-based adsorbents and their dye...
Table 6.2 Reported results of adsorptive removal of metal ions by using modi...
Chapter 7
Table 7.1 Applications of synthetic dyes in the service and industrial secto...
Chapter 8
Table 8.1 Toxicity characteristics of several kinds of CNTs were compared in...
Chapter 11
Table 11.1 Typical comparison among covalent and noncovalent functionalizati...
Table 11.2 CNT-based electrochemical sensors for the determination of differ...
Table 11.3 Reported CNTs-based electrochemical sensors toward sensing applic...
Chapter 12
Table 12.1 TCI ratings of patents with a high priority.
Table 12.2 List of various organizations and their applications in manufactu...
Table 12.3 Solid-state lasers with SWCNT-SAs.
Table 12.4 Various Sn/graphene-based binary electrodes.
Chapter 13
Table 13.1 Clinical trials for chemically modified CNTs in the treatment of ...
Table 13.2 Patents related to the chemically modified CNTs.
Chapter 14
Table 14.1 Drug functionalized CNTs for biomedical applications.
Chapter 15
Table 15.1 Scaffolds and implants made of carbon nanotubes for use in bone t...
Chapter 20
Table 20.1 A quick review of the investigated oxidized/silanized CNTs and th...
List of Illustrations
Chapter 1
Figure 1.1 Figure (a) and (b) show the schematic diagram for SWNTs and MWNTs...
Figure 1.2 Figure shows the UV–vis–NIR analysis for various SWNTs samples. F...
Figure 1.3 Figure shows the various defects involved in CNTs. Figure (a) sho...
Figure 1.4 Functionalization types of CNTs: (a) chemical side wall functiona...
Figure 1.5 Figure (a–c) show the schematic diagram of arc-discharge, laser a...
Figure 1.6 Schematic diagram of various stages of V–L–S growth mechanism. Fi...
Figure 1.7 Figure (a) shows the FE-SEM image of CNTs growing on the Al
2
O
3
su...
Figure 1.8 Figure shows the SEM monographs for as-grown CNTs with taking tem...
Figure 1.9 Figure (a) shows the phenomenon for Raman Scattering. Plot of fig...
Figure 1.10 Figure (a) shows the Raman spectra of SWNTs. Figure (b) shows th...
Chapter 2
Figure 2.1 Classification of carbon nanotubes.
Figure 2.2 Covalent and non-covalent methods of functionalization.
Figure 2.3 Approaches for the functionalization of CNTs via covalent reactio...
Figure 2.4 Schematic illustration of functionalization, conjugation, and dru...
Figure 2.5
In vivo
consequences of intervention of mentioned formulations. (...
Figure 2.6 Cell viability after treatment with (i) filled bar: CS_MWCNT. (ii...
Figure 2.7 The internalization of MWCNT-PEG-Ap. (A) Flow cytometry evaluatio...
Chapter 3
Scheme 3.1 Five year development on fabrication for chemically modified carb...
Figure 3.1 Flow chart of different CVD categories.
Figure 3.2 High-pressure CVD reactor cross section for SWCNT synthesis.
Figure 3.3 Experimental set up (schematic) for methane CVD synthesis of SWNT...
Figure 3.4 Schematic representation of an arc-discharge apparatus.
Figure 3.5 Schematic representation of a laser vaporization apparatus.
Chapter 4
Figure 4.1 Best utilization of functionalized carbon nanotubes in different ...
Figure 4.2 Block diagram of fuel cell based on carbon nanotubes.
Figure 4.3 Pictorial presentation of solar water splitting.
Chapter 5
Figure 5.1 A diagram of CNT in energy production and storage [27].
Figure 5.2 The effect of flaws on Li insertion in SWCNT (5, 5) Red balls rep...
Figure 5.3 A flexible SC is depicted in this diagram.
Figure 5.4 The preparation method, as well as the energy storage and release...
Chapter 6
Figure 6.1 Available wastewater treatment techniques for the removal of diff...
Figure 6.2 Development of chemically modified CNT-based adsorbents for the r...
Figure 6.3 Molecular structure of some organic moieties used for surface med...
Figure 6.4 Molecular structure of pharmaceutical products, which was adsorbe...
Figure 6.5 Illustration represents the parameters that affect the adsorption...
Chapter 7
Figure 7.1 Schematic for reducing carbon substrates with hypophosphorous aci...
Figure 7.2 Two electrons and two protons from the anthraquinone/anthrahydroq...
Figure 7.3 A chemical process that involves thermal oxidation of nanotubes f...
Figure 7.4 Different forms of carbon nanotubes (a) single-walled carbon nano...
Figure 7.5 The possible mechanism of CNT in adsorption and photocatalysis.
Chapter 8
Figure 8.1 Comparison of water stress by country: 2040 and 2019 (Wikipedia s...
Figure 8.2 Chemically modified carbon nanotubes advancement in past 20 years...
Figure 8.3 Classification of carbon nanotubes (CNTs).
Figure 8.4 Different method of synthesis of carbon nanotubes (CNTs).
Figure 8.5 The fragrant diazonium electrolytic reduction salt is depicted in...
Figure 8.6 Carbon alteration by amine oxidation is depicted schematically.
Figure 8.7 MWCNTs poly-diphenylamine sensor modification. (a) Amine function...
Figure 8.8 Applications of carbon nanotubes (CNTs) as membrane separation.
Figure 8.9 Growth of chemically modified carbon nanotubes (CNTs).
Chapter 9
Figure 9.1 Diverse classes of environmental applications of functionalized C...
Figure 9.2 Surface functionalization of CNTs through different routes.
Figure 9.3 Mechanism of water passing through the four types of carbon nanot...
Figure 9.4 A mechanism of functionalization of Al
2
O
3
/MWCNTs to remove Cd
+2
...
Chapter 10
Figure 10.1 Market forecast for various CNT-based electronic and photonic pr...
Figure 10.2 Schematic of different chemical modification techniques of CNTs....
Figure 10.3 (a) XPS (deconvoluted) spectra of pristine, chemically modified,...
Figure 10.4 (a) Chemical addition of functional groups by one step free radi...
Figure 10.5 (a) Illustration showing B, N doping, and densification of CNTs;...
Figure 10.6 Schematic diagram showing different electronic and photonic appl...
Figure 10.7 (a) Representation of fabrication and implementation of liquid-g...
Figure 10.8 (a) Schematic figure showing fabrication of Au-Gr/GCNT-PET (Au-g...
Figure 10.9 (a) Dye (three diazonium compounds: AA-N
+
, NR-N
2
+
, and C...
Chapter 11
Figure 11.1 Graphical illustration for the construction of MWCNT-electrochem...
Figure 11.2 (a) Oxidation, (b) photochemical, and (c) electrochemical modifi...
Figure 11.3 Possible illustration displaying the fabrication process of the ...
Figure 11.4 (a) Amperometric analyses of the fabricated biosensors, (b) the ...
Figure 11.5 Overall illustration for construction of covalently linked DNA-C...
Chapter 12
Figure 12.1 Crystallographic structure of the carbon allotropes.
Figure 12.2 Classification of CNTs.
Figure 12.3 Graph depicting the number of scientific research publications d...
Chapter 13
Figure 13.1 The recent development of chemically modified carbon nanotubes i...
Figure 13.2 Overview of functionalization of carbon nanotubes using differen...
Figure 13.3 Schematic representation of cellular internalization of carbon n...
Figure 13.4 Different strategies using functionalized CNTs for the treatment...
Figure 13.5 (a) Schematic representation of functionalization of SWCNTs with...
Figure 13.6 Chemically modified CNTs as a nanocarrier in various cancer deli...
Chapter 14
Figure 14.1 TEM images of derivative
4
/MWCNT composites.
Figure 14.2 (a) Neat (COCl)
2
;Pht-N(CH
2
CH
2
O)
2
-CH
2
CH
2
-NH
2
, dry THF, reflux; (b...
Figure 14.3 TEM images of (a) pristine SCWNTs (0.5 μm), (b) SWCNT-COOH (0.5 ...
Chapter 15
Figure 15.1 A schematic illustration of recent advancements made in the fiel...
Figure 15.2 Spreading of MC3T3-E1 cells on IP-CHA and CNTp scaffolds. Cells ...
Figure 15.3 The fundamental components of a GIC and the interaction with a t...
Chapter 16
Figure 16.1 (a) Schematic representation of carbon nanotubes (CNTs) and thei...
Figure 16.2 Recent studies on the polymer-based modification in combination ...
Figure 16.3 The multifunctional hydrogel for wound healing applications. An ...
Figure 16.4 Recent studies on the nanoparticle-based modification in combina...
Figure 16.5
In vivo
study of polycaprolactone-MWCNTs 3D-printed scaffold imp...
Figure 16.6 Modified-CNT-coated 3D-printed scaffolds for bone tissue regener...
Figure 16.7 Modified-CNT scaffolds for neural tissue regeneration: (a, i) ef...
Figure 16.8 Modified-CNT-coated 3D-printed scaffolds for neural tissue regen...
Figure 16.9 Modified-CNT scaffolds for cardiovascular tissue regeneration: (...
Figure 16.10 Modified-CNT-coated 3D-printed scaffolds for vascular tissue re...
Chapter 17
Figure 17.1 TG/DTG curves of plain cement and GNP-cement composite at the ag...
Figure 17.2 The chloride diffusion coefficient of UHSC with different conten...
Figure 17.3 Mechanical properties of UHSC containing MWCNTs. (a) Compressive...
Figure 17.4 MIP analysis of pore size distribution.
Figure 17.5 Typical FE-SEM images of samples after 28 days of curing: (a and...
Figure 17.6 Average electrical surface resistivity of MWCNTs-mortar samples....
Figure 17.7 Corrosion current for the two mortar groups against time of expo...
Figure 17.8 Gravimetric and electrochemical mass loss (mg) vs. time, of the ...
Figure 17.9 Effect of adding CNTs to corrosion rates of steel in concrete....
Figure 17.10 Changes in (a) corrosion potential (
E
corr
) and (b) corrosion ra...
Figure 17.11 Illustration of self-sensing concrete pavement for traffic flow...
Chapter 18
Figure 18.1 shows a diagram showing 1D, 2D, 3D, and 4D printing.
Figure 18.2 Types of 3D printing techniques.
Figure 18.3 A schematic of the extruder and a photo of a twin extruder assem...
Figure 18.4 A typical view of stereolithography 3D printing technique of For...
Figure 18.5 A schematic representation of SLA's operation.
Figure 18.6 A digital light processing printer depicted as a diagram.
Figure 18.7 Number of publications related to 3D/4D printing from 2013 to 20...
Figure 18.8 (a) CNT network-oriented at random in SEM micrograph. SWCNTs (b)...
Figure 18.9 Modification of MWCNTs-polydiphenylamine with amine functionaliz...
Figure 18.10 3D printers (a) Ender (Model 23525). (b) Dolomite (Model 410163...
Figure 18.11 Preparation of nanocomposite filaments and 3D printing. (a) Dig...
Figure 18.12 3D printing of carbon nanotube-based MSCs schematic illustratio...
Figure 18.13 A representation of a list of stimuli and the properties and fu...
Figure 18.14 Shape memory nanocomposites printed in 3D and 4D (a) PLMC cross...
Chapter 19
Figure 19.1 Statistical data on carbon nanomaterial-related tribology topics...
Figure 19.2 Snapshots of the composites in the middle and final states of th...
Figure 19.3 (a) Location of dog cartilage sample extraction (b) attachment f...
Figure 19.4 Summary of inorganic nanomaterials investigated for tribological...
Chapter 20
Figure 20.1 The effect of CNTs with different levels of oxidation on the str...
Figure 20.2 Protection mechanism in the CNT-containing epoxy zinc-rich coati...
Figure 20.3 The synthesis scheme of PANI- grafted CNTs (i) and possible inte...
Figure 20.4 The detailed synthesis scheme of O-MWCNT-PANI-Zn nanostructures....
Figure 20.5 The synthesis scheme of m-MWCNTs.
Figure 20.6 Schematic procedure to prepare CeO
2
-PDACNTs.
Chapter 21
Scheme 21.1 Flow chart depicting CNT modification.
Figure 21.1 Different functionalization methods of CNTs.
Figure 21.2 Schematic presentation of functionalization of CNTs.
Figure 21.3 SWCNT functionalized with pyrene-based molecular tether, 1-pyren...
Figure 21.4 Amine groups on a protein react with the attached succinimidyl e...
Guide
Cover
Title Page
Copyright
Preface
About the Editors
Table of Contents
Begin Reading
Index
End User License Agreement
Pages
iii
iv
xvii
xviii
xix
xx
1
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
95
96
97
98
99
100
101
102
103
104
105
106
107
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
397
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
419
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
491
492
493
494
495
496
497
498
499
500
501
502
503
505
506
507
508
509
510
511
512
513
514
515
516
517
Chemically Modified Carbon Nanotubes for Commercial Applications
Edited by Jeenat Aslam, Chaudhery Mustansar Hussain, and Ruby Aslam
Editors
Dr. Jeenat AslamTaibah UniversityCollege of ScienceDepartment of ChemistryYanbu 30799Al-Madina, Saudi Arabia
Prof. Chaudhery Mustansar HussainNew Jersey Institute of Technology (NJIT)Department of Chemistry and Environmental SciencesNewarkNew Jersey 07102USA
Dr. Ruby AslamAligarh Muslim UniversityDepartment of Applied Chemistry202002 AligarhIndia
Cover Image: © Maciej Frolow/Photographer's Choice RF/Getty Images
All books published by WILEY-VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.
Library of Congress Card No.: applied for
British Library Cataloguing-in-Publication DataA catalogue record for this book is available from the British Library.
Bibliographic information published by the Deutsche NationalbibliothekThe Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.
© 2023 WILEY-VCH GmbH, Boschstr. 69469 Weinheim, Germany
All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.
Print ISBN: 978-3-527-35072-8ePDF ISBN: 978-3-527-83881-3ePub ISBN: 978-3-527-83880-6oBook ISBN: 978-3-527-83879-0
Preface
Carbon nanotubes, 1D allotropes of carbon, have fascinated significant research interest since their innovation in 1991 due to their low mass density, large aspect ratio, and unique physical, chemical, and electronic properties that offer exciting possibilities for nanoscale applications. Chemically modified treatments can improve carbon nanotubes' poor dispersion in solvents and their interactions with other materials, thereby increasing their industrial applications. Chemically modified carbon nanotubes are relatively flexible and interact with cell membranes and penetrate different biological tissues. This book covers a broad range of topics related to carbon nanotubes, from synthesis to chemical modification to commercial applications. In general, this book summarizes the recent progress and developments in commercial applications of chemically modified carbon nanotubes at both experimental and theoretical model scales.
To capture the inclusive portrait of commercial applications of chemically modified carbon nanotubes and to offer readers a logical and eloquent design of the topic and concentrated up-to-date references, the book is divided into six parts, with each part comprising several chapters. Part 1 explores the overview, commercialization, and economic aspects of chemically modified carbon nanotubes. Topics covered in Chapters 1–4 include the overview and fundamentals of chemically modified carbon nanotubes, surface modification strategies for carbon nanotubes, and latest developments in commercial-scale fabrications for chemically modified carbon nanotubes and their economic aspects. Part 2 discusses the energy and environmental applications of chemically modified carbon nanotubes. Topics covered in Chapters 5–9 are chemically modified carbon nanotubes in energy production and storage, pollutant adsorption, removal of textile effluents, membrane separation, and water purification systems. Part 3 debates electronics and electrical applications of chemically modified carbon nanotubes. Topics covered in Chapters 10–12 include chemically modified carbon nanotubes for electronics and photonic applications, electrochemical sensors, and lab-on-a-chip devices. Part 4 talks about biomedical applications of chemically modified carbon nanotubes. Topics covered in Chapters 13–16 are chemically modified carbon nanotubes in cancer therapy, drug delivery, tissue engineering, and tissue engineering. Part 5 describes the construction applications of chemically modified carbon nanotubes. The topic covered in Chapter 17 is chemically modified carbon nanotubes in cement and concrete field. Lastly, Part 6 discovers the emerging applications of chemically modified carbon nanotubes. Topics covered in Chapters 18–21 are chemically modified carbon nanotubes in 3D and 4D printing, tribology applications, corrosion protection and chemically modified carbon nanotubes and their sustainability.
The aim of this book is to deliver the recent advancements in chemically modified carbon nanotubes for commercial applications arena. This book is intended for a very wide-ranging audience working in the fields of advanced materials science, chemistry, chemical engineering and technology, etc. This book will be an invaluable reference source for the libraries in universities and industrial institutions, government and independent institutes, individual research groups, and scientists. Overall, this book is planned to be a useful source for advanced undergraduates, graduate students, researchers, and scientists who are looking for chemically modified carbon nanotubes for commercial applications to meet modern research demands. The editors and contributors of all chapters are well-known researchers, scientists, and experts from academia and industry. On behalf of Wiley, we are very much pleased to thank the contributors of all chapters for their exceptional and wholehearted efforts in the making of this book. Invaluable thanks to Dr. Martin Preuss (Associate Publisher, Academic Publishing), Miss Daniela Bez (Managing Editor), and the Editorial Team at Wiley for their wholehearted support and help during this project. In the end, all appreciation to Wiley for publishing the book.
Dr. Jeenat Aslam
Department of Chemistry, College of Science
Taibah University, Yanbu-30799
Al-Madina, Saudi Arabia
Prof. Chaudhery Mustansar Hussain
Department of Chemistry and
Environmental Science
New Jersey Institute of Technology
Newark, N J 07102, USA
Dr. Ruby Aslam
Department of Applied Chemistry
Aligarh Muslim University
Aligarh, India
About the Editors
Jeenat Aslam, PhD, is currently working as an associate professor at the Department of Chemistry, College of Science, Taibah University, Yanbu, Al-Madina, Saudi Arabia. She obtained her PhD in surface science/chemistry at the Aligarh Muslim University, Aligarh, India. Her research is mainly focused on the materials and corrosion, nanotechnology, and surface chemistry. Dr. Jeenat has published several research and review articles in peer-reviewed international journals of ACS, Wiley, Elsevier, Springer, Taylor & Francis, and Bentham Science. She has authored and edited many books and has contributed to twenty-seven book chapters.
Chaudhery Mustansar Hussain, PhD, is an adjunct professor and director of laboratories in the Department of Chemistry and Environmental Science at New Jersey Institute of Technology (NJIT), Newark, New Jersey, United States. His research is focused on the applications of nanotechnology and advanced materials, environmental management, analytical chemistry, smart materials and technologies, and other various industries. Dr. Hussain is the author of numerous papers in peer-reviewed journals as well as a prolific author and editor of around 100 books, including scientific monographs and handbooks in his research areas. He has published with Elsevier, American Chemical Society, Royal Society of Chemistry, Springer, Wiley, and CRC Press.
Ruby Aslam, PhD, is currently a research associate fellow under CSIR-HRDG, New Delhi, in the Department of Applied Chemistry, Aligarh Muslim University, Aligarh, India. She received her MSc, MPhil, and PhD degrees from the same university. She has authored/coauthored several research papers in international peer-reviewed journals of wide readership, including critical reviews and book chapters.
Part IChemically Modified Carbon Nanotubes: Overview, Commercialization, and Economic Aspects
1A Detailed Study on Carbon Nanotubes: Properties, Synthesis, and Characterization
Nishant Tripathi1, Prachi Sharma1,2, Vladimir Pavelyev1, Anastasiia Rymzhina1, and Prabhash Mishra1,3,4
1Nanoengineering Department, Samara National Research University, 34, Moskovskoye Shosse, Samara, 443086, Russia
2Department of Electrical, Electronics and Communication Engineering, GITAM School of Technology, Bengaluru Campus, GITAM (Deemed to be University) NH 207, Nagadenehalli, Doddaballapura, Karnataka 561203, India
3Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, Jamia Nagar, New Delhi, 110025, India
4Center for Photonics & 2D Materials, Moscow Institute of Physics and Technology (MIPT), Dolgoprudny 141700, Russia
1.1 Introduction
The present chapter deals with the evolution of carbon allotropes, especially with carbon nanotubes (CNTs). CNTs are one of the most important nanomaterials of the carbon family. The invention of CNTs brought a real revolution in the field of nanoscience and nanotechnology. The astonishing properties of CNTs make them a suitable material for the development of applications in electronics, optoelectronics, medical, and in many other fields. Worldwide researchers are doing aggressive work on CNTs-based gas sensors, optical detectors, heat detectors, humidity sensors, transistors, nanoelectronics devices, and display applications [1, 2]. It has been observed that different types of applications based on CNTs require different types of CNTs. For example, sensors, especially for gas and optical applications, required horizontal aligned/network type of CNTs while field emission devices required vertically aligned CNTs. So, it has become very important to grow CNTs with selective structure and orientation [3]. Generally, CNTs can be grown by chemical vapor deposition (CVD), arc discharge, and laser ablation technique but among all the techniques CVD is the most preferable due to its capability to grow CNTs with selective properties. In general, the growth process of CNTs by using CVD system, a catalyst film deposited substrate is loaded into the chamber of CVD system, and then the chamber is heated around 800 °C in presence of a carrier gas; at 800 °C along with carrier gas, a hydrocarbon gas is supplied in CVD chamber for CNTs growth. CVD has lots of parameters to tune to decide CNTs' structural quality as well as morphology. The major parameters are the type of catalyst, catalyst deposition technique, catalyst engineering, growth temperature, growth duration as well as the type of carrier and hydrocarbon gas [3–5].
After synthesis of CNTs, its analysis became an important task. To analyze CNTs, researchers utilized various nanomaterial characterization tools such as scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), Raman spectroscopy, and X-ray diffraction (XRD). SEM and AFM are useful for analyzing morphology of CNTs while TEM, Raman spectroscopy, and XRD are useful for the characterization of structural quality of CNTs.
All of the discussions mentioned motivated us to write a present book chapter. The chapter deals with evolution of Carbon from graphite, diamond, graphene to CNTs. It covers in detail various structures of CNTs, defects in CNTs, and their applications. It also covers the various synthesis and characterization techniques of CNTs. Finally, we made a broad discussion on the synthesis of selective CNTs.
1.2 Evolution of Carbon: Graphite to CNTs
The fundamental constituent or the building block of CNTs is Carbon. This group IV element of the periodic table is well known for its incredible ability to form crystalline solids and a variety of other compounds. It is placed in sixth position in the periodic table. Two out of its six electrons lie in 1s orbital, remaining electrons form sp3, sp2, or sp hybrid orbital. These four valence electrons constitute allotropes of Carbon such as CNT, diamond, graphite, graphene, and fullerenes [6]. It is an important fact that existing electronic bonds are very poor in the outer two orbitals as compared to the first orbital. Due to the weaker attraction of outer shell electrons than inner shell electrons, outer orbital electrons participate in electron hybridization. Small energy gradient between outer two orbitals (i.e. 2s and 2p) aids the overlapping of orbital wave functions favoring electron hybridization. There are three accessible mixing of atomic orbitals in carbon atoms making hybrid orbitals typically referred to as sp, sp2, and sp3 hybridization. In sp hybridization, one 2s and one 2p electrons participate in mixing (forming σ-bonds) and leaving two 2p electrons free of mixing (π-bonds). sp2 hybridization involves the mixing of one's orbital electron and two 2p electrons. In sp3 hybridization, all outer shell electrons of carbon atoms take part in mixing. The orbitals are focused on corners of a tetrahedron restricted to carbon atoms. According to hybridization, a carbon atom makes bonds with minimum one to maximum of four partners to produce compounds. Structural quality of carbon-based compounds and allotropes also depend on type of hybridization. For spl hybridization, (l + 1) σ bonds take charge to form generally one-dimensional local structure.
The linear chain compound of carbon i.e. “Carbyne” is an example of sp hybridization. sp2 hybridization leads to the formation of two-dimensional structures such as graphene. 3D-structures such as diamond are formed by sp3 hybridization. It is also noticed that in sp and sp2 mixing one or two p orbital does not involve hybridization, instead showing their presence in the form π-bonds. Depending on orbital mixing carbon has many allotropes and among these amorphous carbon, diamond, graphite, graphene, and CNTs have received a great amount of attention [7]. These allotropes of carbon exhibit a part or completely different properties in nature. For their commendable and extraordinary multidimensional properties be it CNTs, graphene or diamond, and others, allotropes of carbon have become a hot cake for research investigations.
1.2.1 Graphite
The word graphite is taken from a Greek word “graphein” i.e. “write.” Pencil, which is an attractive and widely used tool for writing and drawing, is made from it. It was invented by Debye et al. in 1917 [8]. Graphite is a combined structure of layers. Each layer is called Graphene [9]. In graphite structure, carbon atoms are situated in hexagonal fashion on the XY plane [10]. The distance between carbon atoms in a single layer of graphite is 0.142 nm. The separation distance between layers of graphite is approximately 0.335 nm [11].
The graphene layers are held together by weak van der Waals forces to form solid structure graphite. Each carbon atom is situated on edge of hexagon having three σ-bond in sp2 hybridization form in which three valence electrons participate in hybridization and one valence electron exists in pz orbital creating two-dimensional electron gas in the form of π-bond or cloud. It is spread all over on individual XY planes of graphite. Due to the mobility of said electron gas, graphite shows electrical conductivity. It is more reactive than diamond. The separation distance between the nearest two carbon atoms on an individual layer of graphite is around 0.142 nm that is approximately equal to band order of 1.5 and two times larger than the aromatic carbon atom's covalent radius. The separation gap among the nearest two layers of graphite is approximately two times of van der Waals radius. The weak van der Waals interaction within layers of graphite causes the layers of graphite to easily move along the XY plane. Generally, two types of graphite are found in nature abundantly: a stable form that is hexagonal or α-graphite and rhombohedral or β-graphite. β-graphite is more abundant in nature than α-graphite. By heat treatment, β-graphite can be changed into α-graphite. Other than these two, a few more types of graphite are found in nature. Sometimes, due to some disorder in stacking, no more attraction exists between layers and hence individual layers of graphene or graphite randomly turn around the z-axis and move in the XY plane resulting in a turbostratic structure.
1.2.2 Diamond
Diamond is an allotrope of carbon with sp3 hybridization. Every carbon atom in diamond is bonded to four nearest carbon atoms. Each diamond cell has a tetrahedron structure with a bond length of 154.45 pm. Mainly, two types of structures of diamond are found: cubic and hexagonal. Cubic structure is more available than hexagonal [12, 13]. Hexagonal-shaped diamonds are very precious and rare to find. It was first found in 1967 in a meteorite. Still, there is a possible way to synthesize artificially hexagonal type diamond from graphite by heat treatment of graphite under high pressure with ambient temperature along the vertical axis. Some other structures are also found in which nitrogen molecules are mixed with carbon atoms. Some noticed nitrogen-contained diamonds are Ia, Ib, IIa, and IIb. If nitrogen contamination is like platelets then it is Ia structure of C3N composition. In Ib type nitrogen, molecules are homogeneously spread all over the structure. And, if the diamond structure has null nitrogen then it is called IIa. The last structure has a very small probability of being in nature. The last type, i.e. IIb, is a semiconducting diamond. In that case, nitrogen is completely absent. Instead of nitrogen, IIb type of the diamond structure has some contamination of aluminum. In a normal diamond unit cell, eight atoms exist having face-centered cubic packing. The lattice constant of diamond lattice is 356.68 pm [14–18]. Another noticeable point about diamond's structure is that it's packed in a sphalerite kind instead of dense packing. Its structure is a penetration of two faces. Its centered cubic lattice can be moved along unit cell space diagonal. Another thing is that if diamond is heated with specific conditions, i.e. 3750 °C temperature and 1840 psi pressure, it is converted to graphite. It is also possible to make a hexagonal structure like its cubic type structure from tetrahedrons of carbon with different configurations. In the specified configuration, the cell is made from four carbon atoms with lattice parameters a0 = 252 pm and c = 412 pm [15].
1.2.3 Graphene
As described in Section 1.2.1, if a single layer of graphite is peeled-off from the bulk material, then it is called graphene. It is a single planar structure containing covalent bonded carbon atoms [19] thus also known as planar allotrope of carbon. Buckyballs, nanotubes, and graphite are allotropes of graphene. If graphene is folded in a shape of sphere then it becomes the buckyball or if rolled along any of its axes then it takes the form of a nanotube. Stacked layers of graphene through its XY plane are graphite. Therefore, graphene may be called a generator of three allotropes of carbon. Thus it is vital to study the properties of graphene to understand the properties of CNTs and the other two allotropes. The 2s, 2px, and 2py electrons interact in hybridized fashion giving graphene its characteristics such as physical and electrical ones [19].
sp2 hybridization results in the formation of very stable covalent bonds (σ-bonds) on graphene surface which is the reason for graphene and CNTs being the strongest material with superior mechanical properties among other materials known. Not hybridized atomic 2pz orbital forms π-bonds normal to XY plane due to the electron gas delocalization. These π-bonds provide graphene with distinctive electronic properties [20]. Structurally, graphene has two types of lattice arrangements: direct and reciprocal lattice.
1.2.3.1 Direct Lattice
The honeycomb structure of direct lattice graphene can be explained by ball and stick model. In the ball and stick model, carbon atoms are denoted by ball and sticks represent σ-bonds. σ-bonds of graphene have a bond length around 1.42 Å. Such type of lattice may be considered as a Bravais lattice. The Bravais lattice basis is 2 given as two π electrons per unit cell and depicts enhanced electronic properties of graphene [21]. The primitive unit cell of mentioned honeycomb lattice may be taken as an equilateral parallelogram. The parallelogram side length is as following:
The vectors of primitive unit cell are as following:
where the vector |a1| = |a2| = a describes the separation distance between two nearest carbon atoms.
with |R1| = |R2| = |R3| = length of σ-bond.
1.2.3.2 The Reciprocal Lattice
The rotated lattice with an angle of 90° with reference to the direct lattice is called a reciprocal lattice of graphene [17]. Similar to the direct lattice, the reciprocal lattice also has carbon atoms arranged in a honeycomb structure. The vectors of said lattice are given below:
where .
1.2.4 Carbon Nanotubes
The history of Carbon tubular structures start after the invention of electron microscopes in 1950 [22]. In 1952, a hollow tube of carbon was invented by a Russian researcher, Radushkevich and Lukyanovich, however, the article did not gather much attention being published in a local language [23]. Baker et al. again investigated related structure in 1972 [24]. In 1976, Oberlain et al. described single cylinder hubs in a graphite structure of carbon fibers [25]. Finally, in 1991 Sumio Iijima, an electron microscopist, discovered the cylindrical structure of carbon while analyzing fullerenes, another allotrope of carbon [26]. His discovery caught the attention of worldwide researchers in the field of nanotechnology. Almost two years later, the same group of researchers achieved another milestone in the field of nanotechnology with the invention of single wall carbon nanotubes (SWNTs). CNT is one of the essential allotropes of graphene and is formed when a graphene sheet is rolled into a seamless hollow tube. Practically, it is impossible to roll a graphene sheet into a cylindrical structure because of its ultra-small dimensions. It is only said to understand the structure of CNTs. Generally, diameter of CNTs lies between 0.5 and 5 nm thus termed as nanotubes. The length of CNTs, however, falls from a few mm to several cm [7]. CNTs are also called tubical fullerenes. Generally, CNTs are found in two structures: (i) SWNTs (see Figure 1.1a) and (ii) multi wall carbon nanotubes (MWCNTs) (see Figure 1.1b). If single graphene sheet is rolled to make CNTs then it is called SWNTs and if more than one graphene sheet is concentrically rolled in the “Russian dolls model” then the tubes are called MWNTs. SWNTs are discussed below followed by an introduction about the MWNTs.
1.2.4.1 SWNTs: Types and Structure
Based on structure, SWNTs are divided in three categories:
Zigzag
Armchair
Chiral
Figure 1.1 Figure (a) and (b) show the schematic diagram for SWNTs and MWNTs, respectively. Figure (c) shows the honeycomb structure of carbon atoms; (d) shows different types of CNTs structure.
Source: Ahmad Aqel et al. [27]/with permission of Elsevier.
The types of SWNTs depend on the type of rolling of graphene sheets, which are the basis of the CNTs tubular structure. It is possible to calculate the chirality (helicity) as well as the diameter of SWNTs from a vector, called the chiral vector Ch. It is defined as
where n, m = 1, 2, 3, … with notation as (n, m).
The diameter of SWNTs according to the said model is calculated by the following equation:
where b has the value of 0.142 nm, which represents the carbon–carbon bond length. It is observed that the diameter of CNTs strongly depends on its chirality. A CNT having (5,5) chirality tends to have a smaller diameter than a CNT with (10,10) chirality. The steps for calculating chirality are as mentioned below [27, 28]:
Plot the tube axes. The tube axes are the nanotubes edges. If the tube axes join with each other in the form of a cylinder then it becomes nanotubes (see
Figure 1.1
c).
Mark a point A along the tube axis where the tube axis interacts with carbon atoms.
Draw the armchair line (thin green line) by finding any point along the tube axis that travels across each hexagon, separating them into two equal halves.
Take point B on the second tube axis at the intersection of the tube axis and carbon atoms. It should be the nearest intersection point from the armchair line.
Draw a line AB representing the chiral vector
C
h
. The chiral vector is equivalent to the CNTs circumference.
Angle
θ
between the armchair line and chiral vector decides the types of SWNTs.
If the armchair line and chiral vector overlap each other, i.e. when
θ
= 0° (
n
=
m
)
, then the resulting SWNTs are called the armchair SWNTs (see
Figure 1.1
d).
If the said wrapping angle is
θ
= 30° (
m
= 0)
, then zigzag nanotubes are formed (see
Figure 1.1
d).
If the wrapping angle
θ
is between
0°
and
30°
, then the fabricated SWNTs are called chiral.
Among all types of CNTs, chiral type CNTs have the superior place. Because chirality is an elemental theory to investigate different configured CNTs and their relative electronic band structures. Therefore, it is important to understand the concept and its application to identify CNTs structure. Table 1.1 shows parameters and their relative equations for CNTs.
Table 1.1 Various parameters for SWNTs.
S. no.
Symbol
Name
Chiral CNT
Armchair CNTs
Zigzag CNTs
1.
C
h
Chiral vector
C
h
=
na
1
+
ma
2
= (
n
,
m
)
C
h
= (
n
,
m
)
C
h
= (
n
,0)
2.
C
h
Length of chiral vector
C
h
=
an
3.
d
t
Diameter
4.
Θ
Chiral angle
θ
= 30°
θ
= 0°
5.
N
Number of hexagons/cells
N
= 2
n
N
= 2
n
1.2.4.2 Chirality
The word chirality comes from the Greek language that means HAND. It is used to represent reflection symmetry between an object and its mirror image. In general, a chiral object is anti-symmetric to its mirror image. For example, if we take the mirror image of our left hand and try to superimpose it on our left hand, it does not accurately superimpose, indicating that hands are chiral objects. Similarly, CNTs that are superimposed to their mirror image are called achiral CNTs. Zigzag and armchair CNTs are examples of achiral CNTs.
1.2.4.3 Electronic Properties of CNTs
Electronic properties of CNTs provide great opportunities in nano-electronic research applications. Ultra-small dimensions and ultra-symmetric structures create remarkable quantum effects and electronic properties of nanotubes. Due to the circumferential confinement effect on tubes, SWNTs and MWNTs [28–33] show the quality of a quantum wire. Experimental investigations have proved that MWNTs and the rope of SWNTs behaved like a parallel assembly of single SWNTs. The electronic conductance for said assembly is given by
where, the calculated value of the quantized conductance Go is 12.9 kΩ−1. Another parameter used in the equation, i.e. M is the measurement of exact conducting channels, and its exact value for an ideal defect-free SWNT is 2. The value of M is determined by the intrinsic properties of nanotubes, coupling between tubes impurities, defects in the structure of tubes, interaction with the substrate, and on contacts made for electronic connections. Therefore, the experimental value of conductance is less than the quantized value [34].
Many research groups reported about graphite's resistivity. It depends strongly on the quantity of graphite taken for analysis. The best quality graphite has the resistivity around 0.4 μΩm at room temperature [35]. In the case of CNTs, the MWNTs, as well as the rope of SWNTs, have much higher resistivity than the best quality graphite. It is also reported that the resistivity of the nanotubes mentioned above decreases with temperature. These results were found due to a random orientation of nanotubes on the substrate. The same measurements were made for purified CNTs aligned between four electrodes and were found to be much less than 0.4 μΩm [34, 36]. In defect-free nanotubes, π electrons are more distributed as compared to graphite. It happens due to σ–π re-hybridization. These conditions made graphene more conductive as compared to graphite [34]. Therefore, CNTs are called 1-D conductors.
1.2.4.4 Optical Properties of CNTs
Defect-free SWNTs have a direct band gap. They also have a well-defined structure of the sub band. Such type of structure is considered ideal for optical applications. Optical spectra of SWNTs may be obtained by resonant Raman spectroscopy [35] and by fluorescence spectroscopy [36, 37]. An optical spectrum obtained for grouped SWNTs, as well as for graphite under compression, is shown in Figure 1.2. Three important peaks that are found in SWNTs are invisible in graphite and attributed to symmetric transitions between the lowest sub-bands in semiconducting (A and B) and metallic (C) tubes. Generally, it is found that grown CNTs area a mixture of semiconducting and metallic tubes. In CNTs, the measured peak position and intensity of optical spectra provide information about the electronic structure or tube chirality or (D, Θ). Thus, for a detailed composition investigation of CNTs, optical spectra become indispensable. To understand the optical properties of CNTs, it is necessary to understand their band structure and density of states (DOS), which is already discussed in the electronic dispersion Section 1.2.4.3.
The optical transportation is only possible when electrons or holes are triggered from a lower energy level to a higher energy level. The energy required for optical transactions is donated by Epq. There are two selection rules that are defined for that. First, if p − q = 0, it is defined for inter-band transitions. It is symmetric to the Fermi energy of the polarized light along the tube axis. Second, it requires light that is normal to the tube axis. However, it does not appear in optical spectra. It happens due to very weak transitions [37].
Figure 1.2 Figure shows the UV–vis–NIR analysis for various SWNTs samples. Figure (a) shows the absorbance spectra of SWNTs as well as of colloidal graphite. Figure (b) shows plots of the density of states for semiconducting and metallic CNTs.
Source: Hagen and Hertel [37]/with permission of American Chemical Society.
1.2.4.5 Chemical Properties of CNTs
Due to ultra-small dimensions and ultra-large specific area with σ–π re-hybridization, CNTs are highly sensitive to chemicals and environmental interactions. It is important to study the chemical properties of CNTs such as opening, wetting, filling, adsorption, charge transfer, doping, and intercalation for application purposes.
Opening It is reported by several research groups that the ends of CNTs are more reactive than their complete structure. CNTs' ends have metallic catalyst particles with a large curvature on their open end. Therefore, many approaches have been focused on opening CNTs ends such as treatment with acids, plasma treatment, etc. [38, 39].
Wetting and Filling CNTs are hydrophobic in nature. Mostly aqueous solvents are unable to wet CNTs. However, some organic elements, HNO3, S, Cs, Rb, and Se as well as some oxides Bi2O2 are able to wet CNTs, if they are pressurized with capillary pressure. Using this technique, some other nonwetting elements may also be injected into CNTs. The capillary pressure for nanotubes is proportional to [40].
Adsorption and Charge Transfer It is expected that CNTs have enhanced molecular adsorption as well as charge transfer. Researchers have reported that CNTs show very good adsorption and charge transfer from oxygen to CNTs at room temperature. The localized sites on CNTs where pores exist, interstitials in tube bundles, the surface of CNTs as well as a groove between two attached CNTs are the perfect places for charge transfer and adsorption. In fact, the mentioned sites show the capability of CNTs for adsorption and charge transfer.
The CNTs property discussed above is successfully used in NO2, C6H5NO2, C6H6, NH3 as well as in CH4 sensing. When these molecules interact with CNTs, a change in CNTs resistance is observed. It is possible to design electronic device for sensing application on that principle [41, 42].
Chemical Doping, Intercalation, and Modification The discussed adsorption method may be used for noncovalent bonding doping of CNTs to make p-type as well as n-type CNTs to enhance their electronic conductivity. Intercalation of alkali metals is also used to enhance electronic conductivity. Researchers reported on behalf of the experimental evidence that alkali metals diffuse into inter tube space or defects that exist in CNTs, and hence enhance the CNTs charge transfer ability. To enhance the electrochemical capacity of CNTs, CNTs itself can be used as electrodes. In CNT-based electronic devices for energy production or harvesting, the flow of electrons is generated by reduction and oxidation reactions occurring at the electrodes [43–47].
1.2.4.6 Defects in CNTs
Defects, being a deterministic factor for the physical and chemical properties of a nanomaterial, are considered significant. Although nanomaterials like CNTs are perfect and have unique electrical and mechanical properties which change due to presence of certain defects such as vacancies, heptagon–pentagon pairs type transformations, doping, and interstitials, edges and adatoms (see Figure 1.3) [49], resulting CNTs can be used for further applications, such as sensing, hydrogen storage, and drug delivery systems.
Structural Defects Structural defects in CNTs arise due to their topology distortion caused by the introduction of pentagonal, heptagonal, and octagonal rings into the hexagonal carbon network, affecting nanotubes electrical properties resulting in a conical structure with sharp tips due to the presence of a pentagonal ring at the nanotubes peaks (as shown in Figure 1.3a,b). Also, different vertex angles are obtained by a pentagon insertion into a hexagonal carbon graphitic structure leading to 30° bend dictating that pentagon and hexagon are separated maximally that is they are placed opposite to each other (as shown in Figure 1.3c) and 0° bend is obtained when both structures are combined. Thereby, we can conclude that the vertex angles can indicate the count of hexagon–pentagon pairs present in the CNTs.
A spiral CNT (as shown in Figure 1.3d) is an out-of-plane structure obtained by introducing pentagonal and heptagonal rings in a perfect graphitic sheet and then rolling it with a rotation angle. Atoroidal CNT (as shown Figure 1.3e) is an in-plane structure obtained by connecting CNTs of various diameters by inserting pentagons and hexagons [50].
Bond Rotation Thrower stone wales (TSW) type defects produced by bond rotation in the nanotube are due to 90° rotation of CC bond in a hexagonal network such as in fullerenes, resulting in a translation of two heptagons and pentagons (as shown in Figure 1.3f) [48–51]. Unlike the conical-end structure formed in structural defects, this TSW type defect does not result in large curvature deviations of the nanotube. TSW type defects cause a plasticity failure at elevated temperatures and can alter the chirality of CNTs. Further elongation of the tube at the defect location can lead to the nanotube collapse. Its significance lies in the innovation of nanoelectronic devices [52].
Doping-Induced Defects In order to increase the conductivity of a CNT, dopant atoms can be inserted (see Figure 1.3g) in the carbon lattice. Another method consists of the functionalization of nanotubes, which makes it suitable for biochemical and gas sensing purposes. The boron (p-type dopant) and nitrogen (n-type dopant) atoms in the internal CNT structure are used to sense carbon monoxide and water molecules. The boron (B) atom doping is carried out by arc discharge method using BN-rich as an anode and the nitrogen (N) atom doping is carried out by ferrocene-melamine mixture pyrolysis at high temperatures [53]. As a result of doping, both nanotubes become metallic in nature with no band-gap in comparison with the undoped lattice structure. Other atoms used for doping purposes are P, S, and Si in addition to B and N atoms; all of them alter the reactivity of the nanotube, enhancing the binding energy of the sensing molecule with the doped species [54–57].
Figure 1.3
