181,99 €
Mehr erfahren.
- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Serie: The ECS Series of Texts and Monographs
- Sprache: Englisch
A comprehensive guide to an explosively popular and transformative technology
Nanotechnology has revolutionized the manipulation of matter at the molecular level, with extraordinary consequences for a huge range of technological and scientific fields. Metallic, magnetic and carbon-based nanomaterials have been at the forefront of this revolution, with their impact felt especially strongly in biomedical industries. The future of drug delivery, imaging, diagnostics, and more will be transformed by nanotechnology and its ever-growing applications.
Metallic, Magnetic and Carbon-Based Nanomaterials offers a comprehensive introduction to these materials and their recent developments. Beginning with the foundational concepts of nanotechnology, its characterization, and its methods, the book moves through major categories of nanotechnology in turn. Detailed discussion of applications and future areas of research rounds out an indispensable volume.
Metallic, Magnetic and Carbon-Based Nanomaterials readers will also find:
- Fully up-to-date data on major nanotechnology synthesis techniques
- Detailed discussion of nanotechnologies including quantum dots, magnetic nanoparticles, graphene, and many more
- Analysis of applications including tumor biology investigation, in vivo animal imaging, and others
Metallic, Magnetic and Carbon-Based Nanomaterials is ideal for graduate students in pharmaceutical sciences, biomedical engineering, and materials sciences. It is also a useful reference book for researchers working in the areas of biomedical engineering and nanomaterials synthesis, as well as those working in toxicology, especially nanotoxicology.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 1244
Veröffentlichungsjahr: 2024
Ähnliche
Table of Contents
Cover
Table of Contents
Title Page
Copyright
About the Authors
Preface
1 Nanomaterials
1.1 Nanoscience and Nanotechnology: An Outline of Terms and Concepts
1.2 Special Effects of Nanosystems
1.3 Aspects of Synthesis of Nanomaterials
1.4 Synthesis and Characterization of Gold Nanoparticles
1.5 Synthesis and Characterization of Silver Nanoparticle
1.6 Synthesis of Magnetic Nanoparticles
1.7 Synthesis of Classical Quantum Dots
1.8 Synthesis of Carbon-Based Nanomaterials
1.9 Conclusion and Future Perspective
References
2 Gold and Silver Nanoparticles for Biomedical Applications
2.1 Biomedical Applications of Gold Nanoparticles
2.2 Biomedical Applications of Silver Nanoparticles
2.3 Toxicity of Gold and Silver Nanoparticles
2.4 Conclusion and Future Perspectives
References
3 Biomedical Applications of Iron-Oxide-based Magnetic Nanoparticles
3.1 Biomedical Applications of MNPs
3.2 Toxicity of MNPs to Biological Systems
3.3 Conclusion and Future Perspectives
References
4 Biomedical Application of Quantum Dots
4.1 Biomedical Applications of QDs
4.2 Toxicity of Quantum Dots
4.3 Conclusion and Future Outlook
References
5 Biomedical Applications of Carbon-Based Nanomaterials
5.1 Introduction
5.2 Classification of Carbon Nanotubes (CNTs)
5.3 Biofunctionalization/Biomodification of Carbon Nanotubes (CNTs)
5.4 Biomedical Applications of CNTs
5.5 Biomedical Applications of Graphene
5.6 Discussion on Toxicity of CNMs
5.7 Conclusion and Future Outlook
References
6 Biomedical Applications of Silica-Based Nanomaterials and Polymeric Nanomaterials
6.1 Biomedical Applications of Silica Nanoparticles
6.2 Biomedical Applications of Polymeric Nanoparticles
6.3 Toxicity Studies
6.4 Conclusions and Future Scope
References
7 Nanotechnology-Based Biomedical Products, Devices, and Applications
7.1 Nanotechnology-Based Treatments for Heart Disease
7.2 Nanotechnology for the Treatments for Diabetes
7.3 Nanotechnology for Kidney Disease Treatments
7.4 Nanotechnology-Based Wound Dressings for Accelerated Wound Healing
7.5 Nanotechnology in Cancer Treatment
7.6 Conclusion and Future Perspectives
References
Index
End User License Agreement
List of Tables
Chapter 3
Table 3.1 Summary of the studies on both coated and uncoated magnetic nanopa...
Chapter 4
Table 4.1 A comparison of the typical optical characteristics of green-emitt...
Chapter 5
Table 5.1 Examples of biosensing applications.
Chapter 6
Table 6.1 Summary of the applications of SNPs as nanocarriers and biomodulat...
List of Illustrations
Chapter 1
Figure 1.1 Variation of bandgap energy with size of (a) metals and (b) semic...
Figure 1.2 Various methods used for the synthesis of nanoparticles.
Figure 1.3 (A) Illustration of a comparison between the (a) direct and inver...
Figure 1.4 (A) Transmission electron microscope images of gold nanoparticles...
Figure 1.5 (A) Schematic representation of Newkome-type stabilized Au NPs. (...
Figure 1.6 (A) Depiction of pH-dependent RCE Au NPs when exposed to UV irrad...
Figure 1.7 (A) Displays (a) transmission electron microscopy (TEM) images of...
Figure 1.8 (A) Illustrates the progression of gold nanoparticle formation wi...
Figure 1.9 (A) Scanning electron microscopy (SEM) images depict silver nanop...
Figure 1.10 (A) By prolonging the polyol reaction for a specific duration, i...
Figure 1.11 (A) UV-visible spectra of Ag nanoparticle colloids generated thr...
Figure 1.12 (A) Transmission electron microscopy images of silver nanostruct...
Figure 1.13 (a) UV–visible spectrum of Ag nanocrystals produced through the ...
Figure 1.14 (A) Displays scanning electron microscopy (SEM) visuals of the F...
Figure 1.15 Illustrates core materials of representative quantum dots (QDs),...
Figure 1.16 (A) Illustrates the process of synthesizing near-infrared (NIR) ...
Figure 1.17 (A) Shows (a) UV-visible absorption and photoluminescence (PL) s...
Figure 1.18 (A) Presents a transmission electron micrograph of a carbon nano...
Figure 1.19 (A) Displays chosen TEM illustrations of flakes produced through...
Figure 1.20 Illustrates schematic diagrams of (a) thermal CVD and (b) plasma...
Chapter 2
Figure 2.1 (A) Illustration depicting GC-coated (GC-AuNPs) and MMP peptide p...
Figure 2.2 (A) Displays representative transmission electron microscopy pict...
Figure 2.3 Illustrates the induction of apoptosis in rabbit articular chondr...
Figure 2.4 (A) Presents (a) the absorption spectra of AuNPs-mAb, comparing t...
Figure 2.5 (A) Displays near-infrared (NIR) transmission images of mice befo...
Figure 2.6 Electron energy loss spectroscopy (EFTEM) images depicting
E. col
...
Figure 2.7 (A) Displays representative outcomes illustrating the antibacteri...
Figure 2.8 (A) Showcases the characterization of MOS-PS-AgNPs through transm...
Figure 2.9 (A) Illustrates the impact of the surface characteristics of AuNR...
Chapter 3
Figure 3.1 (A) Depicts the in vitro assessment of peptide-coated USPIONs. Th...
Figure 3.2 (A) Depicts the following: (a) In vivo near-infrared fluorescence...
Figure 3.3 (A) Outline of the Core−Shell Synthesis Scheme, while (B) demonst...
Figure 3.4 (A): Magnetism-engineered iron oxide (MEIO) nanoparticles and eff...
Figure 3.5 Illustrates the effectiveness of in vitro gene silencing on DU145...
Figure 3.6 (A) Presents images obtained through transmission electron micros...
Chapter 4
Figure 4.1 (a) Variation in photoluminescence (PL) color based on size.(...
Figure 4.2 The fluorescence intensity over time of silanized nanocrystals an...
Figure 4.3 (a) The three-dimensional path of a single IgE-FcεRI labeled with...
Figure 4.4 In vivo imaging in a nude mouse model 24 hours post intravenous Q...
Figure 4.5 (a) Illustration and experimental outcomes depicting the transfec...
Figure 4.6 Representative images of mixed neuronal glial cultures. In Subfig...
Figure 4.7 The outcomes of STORM imaging on BKQD-treated neuronal cultures. ...
Figure 4.8 The outcomes of STORM imaging for neuronal cultures treated with ...
Figure 4.9 Showcase images of cell membranes, both fixed and live, that were...
Figure 4.10 Showcase fixed and live cell membranes that underwent indirect l...
Figure 4.11 QD labeling of Sigmar1 in heart tissues of adult mice. (a,b) Rep...
Chapter 5
Figure 5.1 Schematic models of (a) graphene and (b) graphene oxide.
Figure 5.2 Types of carbon nanotubes: (a) SWCNT, (b) DWCNT, (c) MWCNT, (d) c...
Figure 5.3 Methods for chemical functionalization of carbon nanotubes: (a) o...
Figure 5.4 Representative of hybrid approach where an NHS-functionalized pyr...
Figure 5.5 Key methods for chemical modification of biomolecules bearing ami...
Figure 5.6 (a) Atomic force microscopy (AFM) image of the GQDs; (b) fluoresc...
Figure 5.7 (A) Diagram illustrating the synthesis of GO-PEI-DNA complexes th...
Figure 5.8 Graphene promotes osteogenic differentiation. (a) Visual depictio...
Figure 5.9 Utilizing GO with PEI coverage for co-delivery of cis-platin and ...
Figure 5.10 Schematic representation of the synthesis and cellular uptake of...
Figure 5.11 (a) The molecular composition of nanographene, coated with polyg...
Figure 5.12 Thiol-maleimide-functionalized reduced graphene oxide (rGO) inco...
Figure 5.13 The collective tissue engineering applications of graphene and g...
Figure 5.14 The PLGO/GO/HA matrices were employed as scaffolds to promote ce...
Figure 5.15 (a) Graphene oxide (GO) is used to enhance the fluorescence imag...
Figure 5.16 Effective two-photon fluorescent markers for imaging cellular st...
Figure 5.17 (a) Procedure for synthesizing alkyne-PEG. (b) Diagram depicting...
Figure 5.18 (a) The biochemical reaction illustrates glucose sensing utilizi...
Chapter 6
Figure 6.1 Disulfide bond-incorporated DMONs-PEI enhance mRNA transfection i...
Figure 6.2 Enhancing cancer chemo-immunotherapy synergistically with immune ...
Figure 6.3 Nanochelators induce both antiangiogenesis and obstruction of tum...
Figure 6.4 Drug delivery systems employing magnetic nanoparticles based on s...
Figure 6.5 A drug delivery system based on mesoporous silica nanoparticles (...
Figure 6.6 (a) The concept of bonding swollen polymer networks together usin...
Figure 6.7 (Top) Illustration depicting the process of biofilm formation in ...
Figure 6.8 The illustration presents three methods for imparting antifouling...
Figure 6.9 This figure illustrates injectable hydrogel composite materials i...
Figure 6.10 Instances of antibacterial prosthetic materials produced through...
Figure 6.11 A schematic depicting the advantages provided by polymeric nanop...
Figure 6.12 The cytotoxicity, represented by the half-maximum effective dose...
Chapter 7
Figure 7.1 (A) Schematic illustrations of the electrochemiluminescence (ECL)...
Figure 7.2 (A) Diagrams depicting the formation and delivery of the AT1-PEG-...
Figure 7.3 (A) In vitro targeting of cardiac cells. (a) Targeting of cardiac...
Figure 7.4 (A) Silica nanoparticle characterization and interaction with hum...
Figure 7.5 Assessment of the temporal impact, metabolism, and cellular chara...
Figure 7.6 Suppression of hypoxia-induced VEGF expression by PEDF34-NP in AR...
Figure 7.7 Suppression of ischemia-induced retinal neovascularization by PED...
Figure 7.8 (A) Illustration outlining the systematic procedure for the const...
Figure 7.9 Analysis of KTP-NPs properties. (a) Examination of KTP-NPs dimens...
Figure 7.10 KTP-NPs’ intrarenal location and cell-type specificity. (a). KTP...
Figure 7.11 Illustration of the complicated immunotherapy pathway for cancer...
Figure 7.12 Image-guided surgical suites for nano-oncology: present and futu...
Guide
Cover
Table of Contents
Title Page
Copyright
About the Authors
Preface
Begin Reading
Index
End User License Agreement
Pages
ii
iii
iv
ix
xi
xii
1
2
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
50
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
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
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
168
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
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
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
270
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
300
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
346
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
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
447
448
449
450
451
452
453
454
455
456
457
458
459
460
THE ELECTROCHEMICAL SOCIETY SERIES
ECS - The Electrochemical Society
65 South Main Street
Pennington, NJ 08534-2839
http://www.electrochem.org
A complete list of the titles in this series appears at the end of this volume.
Metallic, Magnetic and Carbon-Based Nanomaterials
Synthesis and Biomedical Applications
Ajit Khosla
School of Advanced Materials and Nanotechnology, Xidian University, Xian
Shaanxi, China
Irshad A. Wani
Department of Chemistry, Govt. Degree College Anantnag, Anantnag, University of Kashmir
Jammu and Kashmir, India
Mohammad N. Lone
Department of Chemistry, Central University of Kashmir, Ganderbal
Jammu and Kashmir, India
Copyright © 2025 by John Wiley & Sons, Inc. All rights reserved, including rights for text and data mining and training of artificial technologies or similar technologies.
Published by John Wiley & Sons, Inc., Hoboken, New Jersey.Published simultaneously in Canada.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission.
Trademarks: Wiley and the Wiley logo are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates in the United States and other countries and may not be used without written permission. All other trademarks are the property of their respective owners. John Wiley & Sons, Inc. is not associated with any product or vendor mentioned in this book.
Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com.
Library of Congress Cataloging-in-Publication Data Applied for:
Hardback ISBN: 9781119870654
Cover Design: WileyCover Image: © ARTUR PLAWGO/SCIENCE PHOTO LIBRARY/Getty Images
About the Authors
Ajit Khosla, PhD, is a distinguished professor; he is a fellow of the Royal Society of Chemistry (UK); fellow of the Electrochemical Society (USA), School of Advanced Materials and Nanotechnology, Xidian University, China (https://amn.xidian.edu.cn/); founding editor-in-chief in ECS Sensors Plus; editor in The Electrochemical Society journals (JES and JSS). He is one of top 2% scientists listed by Elsevier and Stanford University.
Irshad A. Wani, PhD, is currently serving as an Assistant Professor in Chemistry at Postgraduate Department of Chemistry, Govt. Postgraduate Degree College Anantnag, University of Kashmir, India. He has earlier served as Lecturer in Chemistry from 2010–2017 in J&K School Education Department. Since 2017, Dr. Wani has been teaching Chemistry at Undergraduate & Postgraduate level in various college of J&K Higher Education Department. Dr. Wani has more than fourteen years of teaching experience. Dr. Irshad A. Wani did his masters in chemistry in the year 2007 & Ph.D. in Nanochemistry in the year 2012 from Jamia Millia Islamia, New Delhi, India. He has received various prestigious awards notably ICTSGS Services Award (2021) conferred by SPAST foundation & B N Kailoo Memorial ISCAS Medal (2009) conferred by ISCAS, India etc. He has a good track record of publications & has published research papers in various esteemed international journals. He is a co-editor of some edited books & has also authored several book chapters. Dr. Wani has served as a Topical Editor of S-Cube: Sustainable Solutions and Society (SPAST) Journal. He is serving as a peer reviewer of various international journals. Dr. Wani is also a life member of various prestigious scientific societies. His current research interests include Green Synthesis of Inorganic nanoparticles, Inorganic-Organic Hybrid Nanoparticles, Conjugation of nanoparticles with various significant molecules for biomedical, therapeutic & sensing applications.
Dr. Mohammad N. Lone, PhD, is working as an Assistant Professor of Chemistry in the School of Life Sciences, Central University of Kashmir. Dr. Nadeem received his M.Sc. in Chemistry from Jamia Millia Islamia (Central University) New Delhi in 2012. For his Ph.D. he worked with Prof. Imran Ali in the same university with focus on development of anticancer heterocycles and chiral drugs. During his Ph.D., Dr. Nadeem was awarded Basic Scientific Research Meritorious Juniour and Senior Research Fellowships by University Grants Commission, New Delhi. He has research interests in heterocyclic synthesis, nano formulations, metallodrugs and anticancer studies. Dr. Nadeem has authored and co-authored more than nineteen research publications (original research papers, reviews, book chapters, books and conference papers) of national and international repute.
Preface
Nanotechnology, situated at the convergence of physics, chemistry, biology, and engineering, represents an unparalleled domain in scientific exploration, offering unprecedented avenues for precise manipulation of matter at atomic and molecular scales. This intricate manipulation has led to the development of materials with unique properties, notably metallic, magnetic, and carbon-based nanomaterials, which have found myriad applications, particularly within biomedicine.
The book Metallic, Magnetic, and Carbon-Based Nanomaterials: Synthesis and Biomedical Applications serves as a comprehensive compendium of cutting-edge research and collaborative interdisciplinary efforts aimed at understanding the synthesis, characterization, and biomedical utility of these extraordinary materials. Authored by experts in the field, the book aims to present the forefront of nanomaterial science while offering practical insights into their deployment in biomedicine.
Chapter 1 serves as a foundational exploration of nanomaterial synthesis methods and characterization techniques. From the intricacies of top-down and bottom-up approaches to the synthesis and characterization of gold, silver, magnetic ferrite, and carbon-based nanoparticles, this chapter lays the groundwork for understanding the structural and physicochemical properties that underpin their biomedical functionalities.
In Chapter 2, delves into the multifaceted biomedical applications of gold and silver nanoparticles. These noble metal nanoparticles exhibit extraordinary optical and physicochemical properties that render them indispensable in bioimaging, biosensing, drug delivery, and antimicrobial therapies. Yet, a comprehensive understanding of their toxicity profiles is essential to mitigate potential adverse effects and ensure their safe integration into clinical practice.
Chapter 3 delves into the biomedical applications of magnetic nanoparticles, particularly ferrites. From their role as MRI contrast agents to enabling targeted drug delivery and magnetic hyperthermia, magnetic nanomaterials offer unprecedented opportunities for diagnostic and therapeutic innovation. However, unraveling the intricacies of their toxicity is paramount for their successful translation from the bench to the bedside.
Chapter 4 explores the biomedical applications of quantum dots, semiconductor nanocrystals endowed with tunable optical properties. These quantum wonders hold immense potential for bioimaging, cell tracking, pathogen detection, and tumor biology investigations. Nonetheless, comprehensive studies on their toxicity are imperative to ensure their safe and effective utilization in clinical diagnostics and therapeutics.
In Chapter 5, delves into the biomedical applications of carbon-based nanomaterials, including carbon nanotubes and graphene. With their exceptional mechanical, electrical, and biocompatible properties, carbon-based nanomaterials offer unprecedented opportunities for controlled drug delivery, medical nanorobotics, tissue engineering, and biosensing. However, rigorous assessment of their toxicity profiles is essential for their seamless integration into biomedical applications.
Chapter 6 explores the biomedical applications of silica-based and polymeric nanoparticles, elucidating their roles as versatile drug carriers, imaging agents, antibacterial treatments, and vaccine adjuvants. Understanding the intricacies of their toxicity profiles is paramount for harnessing their full potential in addressing pressing biomedical challenges and improving patient outcomes.
Finally, Chapter 7 paints a visionary picture of nanotechnology-based treatments, devices, and applications across various medical domains, including cardiovascular health, diabetes management, wound healing, antibacterial treatments, and cancer therapy. Nanotechnology offers a transformative paradigm for personalized medicine and precision healthcare, ushering in an era of unprecedented therapeutic efficacy and patient-centric care.
In conclusion, Metallic, Magnetic, and Carbon-Based Nanomaterials: Synthesis and Biomedical Applications stands as a testament to the collective ingenuity and interdisciplinary collaboration driving the field of nanotechnology forward. May this book inspire future generations of researchers, innovators, and clinicians to continue pushing the boundaries of scientific discovery and biomedical advancement.
January 2025
Ajit Khosla, Ph.D
School of Advanced Materials and NanotechnologyXidian University, Xian, Shaanxi, China
Irshad A. Wani, Ph.D
Department of Chemistry, Govt. Degree College Anantnag,Anantnag, University of Kashmir, Jammu and Kashmir, India
Mohammad N. Lone, Ph.D
Department of Chemistry, Central University of Kashmir,Ganderbal, Jammu and Kashmir, India
1NanomaterialsSynthesis Methods and Characterization Techniques
Ajit Khosla1, Irshad A. Wani2, and Mohammad N. Lone3
1School of Advanced Materials and Nanotechnology, Xidian University, Xian, Shaanxi, China
2Department of Chemistry, Govt. Degree College Anantnag, Anantnag, University of Kashmir, Jammu and Kashmir, India
3Department of Chemistry, Central University of Kashmir, Ganderbal, Jammu and Kashmir, India
1.1 Nanoscience and Nanotechnology: An Outline of Terms and Concepts
The definition of nanotechnology remains a central concern in the scientific community, prompting questions about its precise scope and boundaries. Nanotechnology generally pertains to the study and manipulation of materials and phenomena at the nanoscale, typically below 100 nm, where size-dependent quantum mechanical effects become prominent [1]. While this range captures the essence of nanotechnology and its unique properties, some experts caution against strictly adhering to the 100 nm boundary, as certain devices and materials in the pharmaceutical domain may be excluded [2].
An additional crucial aspect in defining nanotechnology is to consider whether the materials involved are natural, synthetic, or manufactured [3]. Naturally occurring biomolecules in living cells often exist at the nanoscale, which could redefine disciplines like biochemistry and molecular biology as integral parts of nanotechnology.
The following definition of nanotechnology is provided by the U.S. National Nanotechnology Initiative (NNI) [3]: “The understanding & control of matter at dimensions between approximately 1 & 100 nanometers, where unique phenomena enable novel nanotechnology applications.” Other noteworthy definitions of nanotechnology encompass its broad scope and applications [2]. For example, it can be described as “The design, characterization, production, and utilization of structures, devices, and systems attained through deliberate manipulation of size and shape at the nanometer scale (atomic, molecular, and macromolecular scale) that demonstrate at least one unique or enhanced characteristic or property.” Nanotechnology can also be viewed as “Developing objects and surfaces with unique functionalities stemming directly from nanoscale dimensions and/or arrangement.” These unique properties may manifest in mechanical, electrical, or photochemical attributes not observed in bulk materials.
The term “nanotechnology” originates from the ancient Greek word “ννoς” and the Latin word “nanus,” both meaning “dwarf” or “very small.” Within the International System of Units (SI), “nano” represents a reduction factor of 10–9 times, indicating manipulation of matter at a scale one billionth of a meter (10–9 m) [4].
Nanotechnology represents more of an engineering approach than a standalone science, drawing extensively from fields such as biology, physics, chemistry, and materials science [5]. Its potential impact on these sciences is expected to be transformative. The term “nanotechnology” was initially coined by Eric Drexler in his publication “Engines of Creation” (1986). It refers to the manipulation of individual atoms and molecules to create structures characterized by exact atomic specifications [6]. It is observed that the concept of nanotechnology has its roots in physicist Richard Feynman’s seminal lecture from 1959, titled “There’s Plenty of Room at the Bottom” [7, 8]. In 1974, Norio Taniguichi of Tokyo Science University coined the term “nanotechnology” in reference to semiconductor processes involving control on the order of nanometers, which continues to serve as the foundational statement [9]: “Nanotechnology primarily involves the manipulation of materials through processes such as separation, consolidation, and deformation at the level of individual atoms or molecules.” Nanoscience encompasses the examination of phenomena and the control of materials at atomic, molecular, and macromolecular levels, where properties exhibit notable deviations from those observed at larger scales. Nanotechnologies, on the other hand, entail the design, characterization, manufacturing, and utilization of structures, devices, and systems through precise control of shape and size at the nanometer scale [10].
Nanotechnology pertains to the manipulation and study of materials and phenomena at the nanoscale, corresponding to one-billionth of a meter or one-millionth of a millimeter [1, 4]. The nanoscale, defined by the order of magnitude 10−9 in the metric system, encompasses volumes, weights, and units of time. To illustrate, a nanometer bears a similar relation to a meter as the diameter of a hazelnut does to the diameter of the Earth. For instance, a water molecule spans approximately 0.3 nm, a single gold atom’s diameter is about a third of a nanometer, a red blood cell is roughly 7000 nm wide, and a sheet of paper is about 100,000 nm thick.
At the nanoscale, materials exhibit unique physical, chemical, and biological properties at the nanoscale often exhibit substantial disparities from their bulk counterparts and individual atoms or molecules [11]. These distinctive properties have captured scientific interest due to the emergence of unusual phenomena and behaviors in nanomaterials. The term “nanoparticle” derives from “nanos” (Greek for dwarf) and “particulum” (Latin for a particle) [12]. In the context of nanotechnology, “nano” predominantly refers to particle length. Nanoparticles encompass objects ranging from 1 to several hundred nanometers in size [12–14]. On the other hand, nanocrystals represent crystalline clusters consisting of a few hundred to a few thousand atoms typically possess dimensions within the nanoscale range. Their properties are influenced primarily by their surfaces rather than their bulk volumes due to their small size. Nanoparticles can be composed of materials, including metals, metal oxides, micelles, biomolecules, and synthetic polymers [15]. The quality of colloidal inorganic nanocrystals depends on factors such as their crystalline nature, narrow size distribution, unique shape, and dispersion stability. “Nanocluster” refers to small aggregates of atoms and molecules with diameters typically in the nanoscale, ranging from a few units to several thousand [16]. Although there is not a strict demarcation between clusters and nanoparticles, the behavior of nanoparticles is significantly influenced by their nanometer dimensions. As such, characterizing nanoparticles involves investigating size, shape, surface charge, and porosity to comprehend and predict their behavior.
Nanoscience and nanotechnology are not entirely novel concepts. For instance, polymers composed of nanoscale monomers have been studied by chemists for over two decades [17]. However, recent advancements in fabrication tools have allowed direct probing and examination of atoms and molecules with great precision, further advancing nanoscience and nanotechnology [18]. Incorporating nanomaterials into bulk materials can drastically alter their properties, resulting in materials with enhanced strength and unique characteristics due to quantum confinement effects and increased surface area-to-volume ratios at the nanoscale.
In summary, nanotechnology explores and manipulates materials and phenomena at the nanoscale, where distinctive properties emerge. Nanoparticles and nanoclusters play vital roles in this domain, offering unique attributes with potential applications across various fields, promising transformative advancements in science and technology.
1.1.1 Nanomaterials: Properties and Classification
Nanomaterials are materials wherein 50% or more of the constituent particles possess external dimensions falling within the size range of 1–100 nm [19]. Determining whether a material qualifies as a nanomaterial can be done through specific conditions, one of which is the volume-specific surface area (VSSA) or surface area-to-volume ratio. A VSSA greater than 60 m2/cm3 serves as a reliable indicator of nanomaterials; however, certain nanomaterials, such as metal nanoparticles, may have a VSSA below this threshold. Thus, the VSSA criterion confirms nanomaterial classification but is not applicable in the reverse direction [20].
Nanoparticles boast significantly larger surface areas per unit mass compared to larger particles [21, 22]. To illustrate the impact of particle size on surface area, let us consider an American Silver Eagle coin weighing 31 g and possessing a total surface area of approximately 3000 mm2. If this coin were to be subdivided into spherical nanoparticles of, for instance, 10 nm size, the total surface area of all the resulting nanoparticles would amount to around 7000 m2. This remarkable increase in surface area is equivalent to nearly the size of a soccer field. In essence, the total surface area of all nanoparticles with a size of 10 nm is over two million times greater than the surface area of the silver dollar coin.
As materials are reduced to the nanoscale, quantum effects and surface phenomena begin to exert significant dominance over their properties [23]. When approaching the lower end of the nanoscale, various characteristics of the material, such as optical, electrical, and magnetic behavior, undergo alterations. These effects are particularly pronounced in materials like QDs and quantum well lasers, which find applications in optoelectronics. For crystalline solids and other materials, diminishing their size to the nano range results in a substantial increase in interfacial area. This phenomenon profoundly impacts both the mechanical and electrical properties of these solids [24]. For instance, in materials like metals, the boundaries between grains play a vital role in slowing down or arresting the propagation of defects under stress, thereby providing strength to the material. When the grain size is reduced to the nanoscale, the interfacial area within the material significantly rises, leading to a remarkable enhancement in strength. This is precisely why nanocrystalline materials exhibit much greater strength compared to their bulk counterparts. An exemplary illustration of this phenomenon is nanocrystalline nickel, which demonstrates a strength comparable to that of hardened steel.
Two key factors that markedly differentiate nanomaterials from conventional materials are the enhanced relative surface area and the manifestation of quantum effects [25, 26]. These factors have the potential to modify or enhance properties like strength, reactivity, and electrical characteristics. A key characteristic that makes nanoparticles intriguing from a technical perspective is their surface-to-volume ratio, which grows as their particle diameter decreases. Consequently, nanoparticles consist of a few to several thousand atoms, with a considerable portion of these atoms located on the particle surface. As the particle size diminishes, a higher proportion of atoms occupies the surface in comparison to the interior. For instance, in a 30 nm particle, 5% of its atoms are on the surface, whereas a 10 nm particle has 20% of approximately 30,000 atoms positioned on its surface. This trend continues, with a 5 nm particle containing 40% of approximately 4000 atoms on its surface, and a 1 nm diameter particle having almost all 30 atoms on the surface. The surface atoms, distinct from those inside the material, possess unsaturated bonds, which contribute to the heightened reactivity of the particle surface.
Nanomaterials showcase heightened reactivity, serving as a cornerstone for their diverse range of applications [27]. Precise manipulation of particle size enables the creation of a new generation of exceptionally selective catalysts, capable of expediting specific chemical processes and generating targeted products from raw materials [28]. The increased reactivity of nanomaterials also accounts for their lower melting point, facilitating the reduction of firing temperatures in ceramics through the incorporation of nanoparticulate raw materials. Moreover, these composite materials exhibit minimized shrinkage during the hardening process, making them highly valuable for dental prosthetics. Nanoporous materials, with their expansive pore-specific surface area, find utility in efficient substance filtration, offering an ideal platform for the deposition of filtered substances [29]. These materials also function as potent catalytic agents and promoters of adsorption due to their heightened reactivity [30]. Additionally, nanomaterials possess remarkable optical attributes, such as transparency, absorption, luminescence, and scattering, opening up new possibilities for their utilization.
Given that nanoparticles possess sizes well below the visible light wavelength range (380–780 nm), they have a propensity to absorb light of specific wavelengths [14, 31]. Understanding this light absorption by nanoparticles requires a quantum mechanics-level comprehension. Semiconductor nanoparticles, commonly known as QDs, offer a means to tailor fluorescence wavelength [32]. These optical properties make nanoparticles particularly intriguing candidates for applications in optoelectronics, medical diagnostics, and cosmetics [33, 34]. Furthermore, magnetic materials in the nanometer range can be magnetized as permanent magnets in one direction only [35]. As a result, magnetic nanoparticles (MNPs) contribute to increased storage capacity in magnetic data storage devices. Additionally, the magnetic characteristics of nanomaterials display a relatively low sensitivity to temperature fluctuations.
Nanomaterials are categorized based on the number of dimensions that fall within the nanoscale range (<100 nm) [36, 37]. These classifications are as follows:
Zero-dimensional (0D) nanomaterials
. These materials have all three dimensions measured within the nanoscale, and none of the dimensions exceed 100 nm. 0D nanomaterials are commonly known as nanoparticles and include examples such as metal nanoparticles and QDs.
One-dimensional (1D) nanomaterials
. This category comprises materials in which one of the three dimensions extends beyond the nanoscale, while the other two dimensions are confined within the nanorange. Examples of 1D nanomaterials include nanotubes, nanorods, and nanowires.
Two-dimensional (2D) nanomaterials
. In this type, two dimensions are outside the nanoscale range, while the material is limited to the nanorange in the third dimension. Such nanomaterials exhibit plate-like shapes, and notable examples include graphene, nanofilms, nanolayers, and nanocoatings.
Three-dimensional (3D) nanomaterials
. These materials are not confined to the nanoscale in any dimension. The 3D nanomaterials category encompasses bulk powders, bundles of nanowires and nanotubes, as well as multi nanolayers.
1.1.2 Forms of Nanoparticles
Nanoparticles can exhibit diverse chemical compositions, encompassing inorganic materials like metals, metal oxides, and semiconductor materials, as well as organic materials such as carbon-based compounds, including fullerenes and carbon nanotubes [27]. Engineered or synthetic nanoparticles can be categorized into specific types based on their distinct chemical and physical attributes.
Carbon-based nanoparticles can be synthesized in various forms, such as spherical nanoparticles like fullerenes or cylindrical nanotubes like carbon nanotubes [38]. Carbon black, an industrially produced soot, is a precisely defined material, purposefully synthesized under controlled conditions with a carbon content exceeding 96%. On the other hand, soot resulting from chimney and diesel combustion contains organic and inorganic contaminations to varying degrees, making them less well-defined combustion by-products of hydrocarbons or coal.
Metal nanoparticles are submicron-scale entities composed of pure metals like gold, platinum, silver, titanium, zinc, cerium, iron, and thallium. They find extensive applications, particularly in catalysis and the biomedical field [39].
Metal oxide-based nanoparticles are formed from metal oxides like zinc oxide (ZnO) or titanium dioxide (TiO2) [40]. Certain oxide nanoparticles are widely used in consumer goods, such as paints, cosmetics, and varnish [41, 42]. Others, such as aluminum oxide (Al2O3) and Zircon (ZrO2) nanopowders, are employed in technical ceramics components to enhance hardness and breaking strength [43, 44].
Semiconductor nanoparticles originate from diverse compounds [45]. Depending on the elements they are derived from and their placement in the periodic table, they are classified as II–VI, III–V, or IV–VI semiconductors [46]. For instance, silicon and germanium fall under group IV, while GaN, GaP, GaAs, InP, and InAs are categorized as III–V semiconductors. II–VI semiconductors include ZnO, ZnS, CdS, CdSe, and CdTe. These semiconductor nanocrystals, with their distinctive optical properties, find applications in laboratory and medical diagnostics.
Composites, wherein the matrix is often composed of polymers, offer a remarkable approach to combine the unique characteristics of nanoparticles with those of the composite matrix.
1.2 Special Effects of Nanosystems
Nanosystems, often involving structures and materials at the nanometer scale, exhibit an array of exceptional and unique effects that transcend the boundaries of conventional science and engineering. These special effects manifest in various ways, influencing the behavior of materials, biological systems, and devices.
1.2.1 Quantum Confinement Effect
Inorganic nanosystems refer to chemical entities composed solely of inorganic materials. They demonstrate novel behaviors stemming from quantum size effects and the presence of significant surface areas and interfaces at the nanoscale, leading to unique phenomena. Indeed, individual molecules showcase characteristics governed by quantum mechanical principles, whereas the chemical and physical attributes of bulk materials adhere to quantum mechanics laws. Nanosystems exhibit electronic, electrochemical, photochemical, magnetic, optical, mechanical, or catalytic properties that deviate notably not only from individual molecular units but also from macroscopic systems.
Quantum-size effects manifest in nanosized entities due to their overall dimensions being on the same scale as the characteristic wavelength for fundamental excitations in materials [47, 48]. These excitations, which encompass the wavelengths of electrons, photons, and similar particles, transport energy quanta within materials, thereby dictating the dynamics of their transmission and transformation from one state to another. Yet, when the size of structures aligns with the order of magnitude of these characteristic wave functions, the transmission and behavior of quanta undergo significant perturbation. Consequently, quantum mechanical selection rules, typically imperceptible on a larger scale, become apparent. Take metals as an example; their conventional “metallic” attributes, such as conductivity, diminish as their size decreases as the number of atoms comprising the sample significantly reduces. In fact, the electronic conduction band of a metal transitions from continuous levels in bulk infinite materials to discrete states as size diminishes, leading to a rise in bandgap energy (Figure 1.1a).
Figure 1.1 Variation of bandgap energy with size of (a) metals and (b) semiconductors. (c) Illustrations of plasmon oscillations in a spherical object, demonstrating the movement of the conduction electron charge distribution concerning the atomic nuclei.
Source: (a, b) Reproduced with permission from Sumanth Kumar et al. [49]/Elsevier, (c) Unser et al. [50]/MDPI/CC BY 4.0.
Likewise, QDs possess electronic characteristics that fall between those of bulk semiconductors and isolated molecules [31]. Their optoelectronic attributes are influenced by their dimensions and shapes, and these attributes change depending on these factors. For instance, when QDs are stimulated by a photon with energy represented as hν (where ν signifies the frequency of the incoming photon), larger QDs, typically around 5–6 nm in size, emit light in the orange or red wavelength range [49]. Smaller QDs emit shorter wavelengths, falling within the blue or green spectrum. Consequently, one can intentionally adjust these features by modifying the size and shape of the QDs to attain the desired results. Figure 1.1b provides a visual representation of how the bandgap of QDs changes with varying sizes. These QDs can be produced from single-element materials like silicon or germanium, or from compound semiconductors such as CdSe, PbSe, CdTe, and PbS [51–56]. Sometimes, QDs are referred to as “artificial atoms” since they exhibit discrete electronic states, akin to what is observed in atoms and molecules.
1.2.2 Concept of Surface Plasmon Resonance (SPR)
“How light interacts with matter” has been a subject of inquiry, notably pursued by Michael Faraday in his investigation of metal colloids. Faraday’s pioneering work revealed that even when metal particles are substantially smaller than the wavelength of light, they exhibit substantial light scattering and absorption, resulting in vivid colors, even in dilute solutions [57, 58]. Notably, Faraday’s exploration led to the understanding that the collective oscillation of conduction electrons within metal particles is accountable for the scattering and absorption of light at specific frequencies, giving rise to distinct colors, particularly in the cases of silver and gold. This occurrence, now known as SPR, derives its name from the polarization of surface charges generated by collective electron oscillations (surface) and the analogy to electron oscillations in gaseous plasma (plasmon) [59].
Localized surface plasmons (LSPs) refer to charge density oscillations constrained within metallic nanoparticles, often referred to as metal clusters, and metallic nanostructures (Figure 1.1c) [59]. The excitation of LSPs by an incident electric field, at wavelengths corresponding to resonance, results in robust light scattering, the emergence of intense surface plasmon (SP) absorption bands, and an augmentation of local electromagnetic fields. The frequency (absorption maxima or color) and intensity of these SP absorption bands are intrinsic to the material type, typically gold, silver, or platinum, and are remarkably sensitive to factors like size, size distribution, shape of nanostructures, and the surrounding environment [50]. These specific characteristics have spurred considerable interest in LSPs, leading to the development of a wide array of LSP-based sensors and devices.
The striking red color observed in aqueous colloidal gold dispersions is a direct manifestation of localized SPR. Throughout history, colloidal gold has intrigued many, having been used to provide color in medieval cathedral windows and believed, until the eighteenth century, to possess life-prolonging and rejuvenating properties when ingested as aurum potabilis [60, 61]. In contemporary times, colloidal gold has witnessed exponential growth in its utilization as a biological label, marker, and stain in various microscopic applications [62]. More recently, metallic nanoparticles and nanostructures have found successful use as molecular recognition elements and amplifiers in sensors and biosensors, as well as integral components in nanoscale optical devices [63–65]. Notably, surface plasmons are distributed unevenly around nonspherical metallic nanoparticles and nanostructures, resulting in shape-dependent LSPR absorption spectra [66]. For instance, in metallic nanorods, the plasmon resonance splits into low and high-energy absorption bands, with the high-energy band corresponding to electron oscillations perpendicular to the major axis and the low-energy band arising from electron oscillations along the major axis. This separation becomes more pronounced with increasing aspect ratio of the nanorods [67–69]. Triangular particles exhibit multiple plasmon resonances, including a longitudinal (bulk) plasmon mode and a highly localized enhancement at their sharp tips [70, 71].
Mie theory has been extended to cylindrical and needle-like nanoparticles, and optical properties, including absorption, extinction, and scattering efficiencies, have been calculated using discrete dipole approximations for metallic nanoparticles with arbitrary shapes [72–74]. The analysis of scattering spectra from differently shaped individual nanoparticles (e.g., spherical, rod-like, triangular, pentagonal, and tetrahedral) of silver, gold, and nickel through total internal reflection spectroscopy has obviated the necessity for producing highly monodisperse nanoparticle populations in specific shapes and provided valuable insights into the correlations between shape, environment, and spectra.
It is worth noting that Mie theory is only applicable to noninteracting nanoparticles that are well separated in their solid state or present at low concentrations in dispersions. For interacting particles, the plasmon resonance red-shifts, followed by the emergence of a lower-energy absorption band, similar to the longitudinal absorption band observed in nanorods. Two main types of interactions occur between arrayed metallic nanoparticles: near-field coupling, which involves particles in close proximity, and far-field dipolar interactions [75]. Dipolar interactions are electrodynamic in nature, with dipole fields from a plasmon oscillation in one particle inducing surface plasmon oscillation in adjacent particles [76].
1.3 Aspects of Synthesis of Nanomaterials
Atoms and molecules serve as the fundamental constituents of all matter, shaping its properties and interactions. Understanding how these basic units assemble is crucial for comprehending material behavior. Precise control over synthetic pathways becomes imperative in crafting nanoscale building blocks of varied sizes and shapes, which in turn can facilitate the development of advanced devices and technologies with enhanced capabilities. To achieve this, two complementary approaches are pursued: a top-down strategy focusing on miniaturizing existing components and materials, and a bottom-up approach involving the construction of increasingly intricate molecular structures at the atomic or molecular level [77]. These divergent methods underscore the organizational complexity of nanosystems, situated at the intersection between molecular entities and bulk materials (Figure 1.2). Richard Feynman famously advocated for the top-down approach in his seminal 1959 lecture, emphasizing the ample opportunities for exploration at the nanoscale [79]. This method excels in achieving structures with long-range order and bridging connections with the macroscopic world. Conversely, Jean-Marie Lehn championed the bottom-up approach, recognizing the vast potential at the nanoscale and the ability to establish short-range order through assembly [80]. Integrating these two techniques promises to offer the most comprehensive toolkit for nanofabrication, theoretically enabling a wide array of possibilities.
1.3.1 Top-Down Approach
The top-down approach utilizes techniques such as machining, templating, or lithography to achieve miniaturization. Typically, this method starts with patterns created at larger scales, often in the microscale, which are then scaled down to the nanoscale [81]. An important advantage of this strategy is that components are both patterned and constructed in situ, obviating the need for additional assembly steps.
Various nanostructures can be crafted through methods like electronic, ionic, or X-ray lithography [27, 82]. Initially, a quantum well, characterized by two finite dimensions, is fashioned, followed by the creation of a quantum wire with one finite dimension. Ultimately, a quantum dot, a zero-dimensional structure with all dimensions in the nanoscale, is produced. While current short-wavelength optical lithography techniques can achieve dimensions of at least 100 nm, which traditionally mark the nanoscale threshold, efforts are ongoing to develop extreme ultraviolet and X-ray sources to extend lithographic printing capabilities to dimensions ranging from 10–100 nm. However, challenges persist, particularly related to beam focalization. Furthermore, scanning beam techniques like electron-beam lithography can generate patterns down to approximately 20 nm, with even smaller features attainable using scanning probes for depositing or removing thin layers.
Mechanical printing techniques usually start with the creation of a high-resolution master “stamp” using lithographic methods, as previously described [83]. This stamp, or its copies, is then used to transfer the pattern onto a surface. Finally, the thin layer of masking material under the stamped regions is removed. These nanoscale printing methods provide several benefits, including the capability to work with various materials on curved surfaces.
Figure 1.2 Various methods used for the synthesis of nanoparticles.
Source: Bloch et al. [78]/Frontiers Media S.A./CC BY 4.0.
These techniques are generally expensive and involve complex manufacturing processes. Despite their success at the microscale, top-down methods encounter difficulties when working at nanoscale dimensions. Moreover, they often yield two-dimensional structures, limiting the production of arbitrary three-dimensional objects due to their reliance on layer-by-layer patterning. Notably, the progress of top-down methodology has been mainly propelled by disciplines like materials engineering and physics, with limited input from inorganic chemists in leveraging these approaches.
1.3.2 Bottom-Up Approach
Bottom-up techniques in nanofabrication involve the step-by-step accumulation of atoms or clusters, utilizing either chemical or physical forces at the nanoscale to guide the assembly of basic units into more extensive structures [77]. Typically, this method entails the chemical synthesis of nanoscale materials within colloidal or supramolecular setups, often undergoing phase changes like sonochemical surface deposition or solid-phase precipitation from solutions. These strategies draw inspiration from biological systems, where chemical interactions drive the formation of diverse vital structures. Researchers seek to emulate nature’s ability to produce precise atom clusters, enabling their spontaneous arrangement into sophisticated configurations. Obtaining the desired shape and size requires meticulous control over the material’s nucleation and growth. This synthesis method is particularly captivating for chemists. Bottom-up approaches, which initiate from individual atoms and molecules, resonate deeply with the principles of chemistry and molecular biology. Given that a significant portion of chemistry already revolves around manipulating nanoscale entities or coordinating the self-assembly of molecules into more extensive structures, this methodology offers a natural progression for exploration and innovation. Bottom-up techniques present numerous advantages. They offer a wide range of preparation methods, facilitating meticulous control over scale dimensions, including at the atomic or molecular level. Moreover, they typically incur lower costs compared to top-down approaches [13, 14, 84–86]. Nonetheless, despite these benefits, realizing preprogrammed self-assembly of arbitrarily large systems with complexities similar to those observed in natural systems remains a formidable hurdle.
Preparation of nanomaterials can be classified into physical and chemical methods. The physical methods are based on subdivision of bulk metals, including pulverization or mechanical crushing of bulk metal, arc discharge between metal electrodes, etc. Metal nanoparticles thus produced are usually large in size and have a wide size distribution [46]. Several physical methods have been reported for the synthesis of nanosized particles. These include vapor condensation methods, spray pyrolysis, mechanical deformation, thermochemical decomposition of metal–organic precursors in flame reactor, and other aerosol processes named after the energy sources applied to provide the high temperature during gas-particle conversion [47, 48]. The chemical methods are grounded on the concept of reduction of metal ions or decomposition of precursors to form atoms, followed by aggregation of the atoms. Nanoparticles prepared by chemical methods usually have a narrow size distribution [46]. Increasing interest in chemical synthesis of nanoparticles is clearly indicated by the number of reports and reviews on this subject [49, 51–55]. However, it is notable that some methods can be considered as either chemical or physical routes depending on the media, precursors, and operating conditions such as milling.
The formation of metal nanoparticles by chemical methods can be carried out by reduction of metal ions with chemical reductants or decomposition of metal precursors with extra energy. The chemical reductants involve molecular hydrogen, alcohol, hydrazine (HA), NaBH4, LiAlH4, citrate, etc. Energy provided from the outside involves photoenergy (ultraviolet and visible light), γ-ray, electricity, thermal energy (heat), nonchemical energy, etc. In order to produce metal nanoparticles with a narrow size distribution, agents stabilizing colloidal dispersion of metal nanoparticles are of vital importance [46]. Various methods of the nanoparticle’s synthesis can be classified based on the process media, including vapor, liquid, and solid-state processing routes, and combined method, such as vapor–solid–liquid approach [53].
Many of the properties associated with nanoparticles are directly related to the relatively higher energetic state of atoms and molecules at a surface when compared with those in the bulk. In many cases, the production of nanoparticles involves techniques to hinder the natural course of thermodynamics through the manipulation of kinetics. In other cases, it is possible to hinder the natural growth of phases through the use of dilution or via protection of surfaces using surface-active agents or by coating and encapsulation of nanoparticles in a glassy media such as those used for instance in the case of polymers [56].
1.4 Synthesis and Characterization of Gold Nanoparticles
The synthesis and characterization of Au NPs stand as an intriguing and essential domain within the realm of nanotechnology and materials science. Gold nanoparticles, celebrated for their distinct size-dependent properties, have been widely applied across diverse fields such as electronics, medicine, catalysis, and environmental science. This research endeavor involves the controlled creation of gold nanoparticles, often on a nanometer scale, and the subsequent detailed examination of their physical, chemical, and optical properties. Understanding how to synthesize these nanoparticles and precisely characterize their attributes is fundamental to harnessing their potential in various technological advancements and innovations. In this paper, we delve into the intricacies of synthesizing and characterizing gold nanoparticles, shedding light on their diverse applications and the remarkable insights they offer into the nanoscale world of materials. Numerous methodologies have been employed for the fabrication of gold nanoparticles, encompassing techniques such as chemical, electrochemical, thermal, and sonochemical pathways. Synthesis of Au NPs by employing these methods is discussed below.
1.4.1 Chemical Methods of Synthesis
Synthesis of Au NPs by chemical reduction technique involves two steps. The primary step involves reducing the gold salt through the utilization of reducing agents like borohydrides, HA, amino boranes, hydroxyl amine, formaldehyde, and hydrogen peroxide and organic reducing molecules such as citric acid, oxalic acid, polyols, sugars, and acetylene. Electron-rich molecules such as metal sandwich complexes have also been used for the reduction of gold salts to produce Au NPs. The second step involves the stabilization of the synthesized Au NPs by various stabilizers such as trisodium citrate, sulfur-containing ligands such as thiolates, oxygen-based ligands, phosphorus-based ligands, nitrogen-based ligands including heterocyclic compounds, polymers, surfactants, dendrimers, etc. One of the well-known techniques for fabricating Au NPs was designed by Turkevisch in 1951 [57]. Turkevisch method involves the conventional chemical route by reducing gold salt (HAuCl4) in aqueous sodium citrate solution. It involves adding sodium citrate to the boiling HAuCl4 solution under vigorous stirring. Wine red Au NP solution is produced within few minutes of stirring with Au NP size of around 20 nm. Polte et al. [87] studied the mechanistic details of the Au NP formation using classical Turkevisch method. The study analyzed various aspects of Au NP formation, including their size, shape, and growth mechanisms, employing techniques such as SEM, HRTEM, UV-vis spectra, XANES, and SAXS. The findings and their interpretation are as follows. The nanoparticles produced in the study closely matched values reported in the literature for similar syntheses. The particles were predominantly spherical and nearly uniform in size, with a polydispersity of around 12% and a mean radius of 7.6 nm. The UV-vis spectra showed an absorbance maximum in the range of 520–550 nm, which is typical for the plasmon resonance of gold nanoparticles. During the synthesis, the peak maximum shifted slightly from about 540 nm to approximately 523 nm, indicating changes in particle size. The curve depicting the intensity at each peak position versus time demonstrated the typical time-dependent behavior, with a slow initial intensity increase followed by more rapid growth. However, the growth mechanism based on UV data remained controversial. Evolution of XANES spectra revealed an initially slow reduction process, followed by a significant decrease in Au(III) content after approximately 50 minutes, coinciding with the rapid escalation in the intensity of the Au NPs plasmon resonance detected via UV-Vis studies. The data suggested that a considerable portion of Au(III) species was being converted into metallic Au(0). SAXS analysis provided information on particle growth during the synthesis. The data indicated different phases of GNP formation. Initially, there was rapid nucleation, resulting in small particles with a mean radius of 2 nm and high polydispersity. Subsequently, particles grew by coalescence, followed by further growth through a diffusion-limited process. The final phase showed a rapid growth in particle size, accompanied by the near-complete consumption of Au(III) species. The study varied reaction temperature and the concentration of the gold precursor. Higher temperatures and increased precursor concentrations led to significantly faster Au NP formation, suggesting that the reduction of Au(III) is an activated chemical process with a reaction order greater than one. The experiments proposed a sequential process of Au NP formation that did not fully align with previously proposed mechanisms. It revealed rapid nucleation, followed by coalescence and further precursor reduction contributing to particle growth. These findings challenged the classical theory of self-nucleation and highlighted the importance of coalescence processes in obtaining monodisperse GNPs. Varying the concentration of sodium borohydride produced the Au NPs of various morphologies such as nanospheres, nanowires, nanorods, and nanotriangles [88]. Frens in 1973 modified the Turkevisch method to produce Au NPs in size from 15 to 150 nm by changing the ratio of reducing agent and gold salt [89]. Several research teams have modified the Turkevich and Frens method to synthesize citrate-stabilized Au NPs with diverse sizes and diameters. For example, it was demonstrated by Kimling et al. that smaller-sized Au NPs are produced at higher concentration of citrate whereas lower concentration of citrate produced large-sized Au NPs by aggregation of small Au NPs [90]. Kumar et al. [91] investigated the mechanism behind the Turkevich–Frens method, illustrating the formation process of dicarboxy acetone (DCA) through the citrate oxidation, followed by the reduction of gold salt to Au atoms, which then assemble to form gold nanoparticles (Au NPs). The dicarboxyl acetone produced serves as a stabilizing agent, distinct from the role of citrate itself. Turkevisch method was further modified by various research groups to study the effect of varying the pH [92–95], reaction temperature, citrate concentration [96], and gold salt concentration [97] on Au NP shape, size distribution, and other characteristic properties. Utilizing ascorbic acid as a reducing agent in chemical reduction and an aqueous surfactant, cetyltrimethylammonium bromide (CTAB) as a shape director also resulted in the production of anisotropic Au NPs. The size and characteristics of gold nanoparticles (Au NPs) were found to be significantly affected by the alteration in the sequence of reagent addition. In a study by Jiménez et al. [98] the order of reagent addition was modified keeping factors such as the SC : Au ratio (13.6), temperature (100 °C), final volume (150 mL), and total reaction time (5 minutes) constant. The two methods were employed: (i) direct synthesis (SC was added to a hot HAuCl4 solution) and (ii) inverse synthesis (HAuCl4 solution was added to a boiling sodium citrate solution). A blue shift in the SPR peak, from 527.5 nm (direct synthesis) to 518 nm (inverse synthesis), indicating smaller Au NPs in the inverse method, was revealed by UV-vis spectra (Figure 1.3A). This shift was corroborated by TEM analysis (Figure 1.3B), which demonstrated a decrease in mean particle size and an improved size distribution, from 36.6 ± 6.8 nm (SD ∼ 18%) for direct synthesis to 9.0 ± 1.2 nm (SD ∼ 13%) for inverse synthesis. The same trend was observed for a lower SC : HAuCl4 ratio (6.8), where a blue shift in the SPR peak from 522 nm (direct) to 519 nm (inverse) was observed, accompanied by a decrease in the absorbance maximum. Once again, TEM analysis confirmed a reduction in Au NP size and polydispersity, from 17.8 ± 2.5 nm (SD ∼ 14%) for direct synthesis to 14.9 ± 1.5 nm (SD ∼ 10%) for inverse synthesis. The addition of DCA to the reducing mixture had a notable impact on Au NP size and reaction rate. With a fixed SC : HAuCl4 ratio (13.6), changing the SC : DCA ratios in the reducing mixture influenced reaction kinetics. A decrease in SPR peak from 523 to 519 nm was observed when increasing DCA content from 100 : 0 to 90 : 10 (SC : DCA), but it returned to 523 nm at a 50 : 50 ratio (Figure 1.3C). TEM analysis confirmed a correlation between SC : DCA ratio, final Au NP size, and monodispersity (
