Nanopatterned and Nanoparticle-Modified Electrodes E-Book
151,99 €
Mehr erfahren.
- Herausgeber: Wiley-VCH Verlag GmbH & Co. KGaA
- Kategorie: Wissenschaft und neue Technologien
- Serie: Advances in Electrochemical Sciences and Engineering
- Sprache: Englisch
Volume XVII in the "Advances in Electrochemical Science and Engineering" series, this monograph covers progress in this rapidly developing field with a particular emphasis on important applications, including spectroscopy, medicinal chemistry and analytical chemistry.
As such it covers nanopatterned and nanoparticle-modified electrodes for analytical detection, surface spectroscopy, electrocatalysis and a fundamental understanding of the relation between the electrode structure and its function.
Written by a group of international experts, this is a valuable resource for researchers working in such fields as electrochemistry, materials science, spectroscopy, analytical and medicinal chemistry.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 867
Veröffentlichungsjahr: 2017
Ähnliche
Table of Contents
Cover
Title Page
Copyright
List of Contributors
Series Preface
Preface
Chapter 1: Surface Electrochemistry with Pt Single-Crystal Electrodes
1.1 Introduction
1.2 Concepts of Surface Crystallography
1.3 Preparation of Single-Crystal and Well-Oriented Surfaces
1.4 Understanding the Voltammetry of Platinum
1.5 Potential of Zero Charge of Platinum Single Crystals
1.6 The Laser-Induced Temperature Jump Method and the Potential of Maximum Entropy
1.7 Electrocatalytic Studies with Single-Crystal Electrodes
1.8 Concluding Remarks
Acknowledgments
References
Chapter 2: Electrochemically Shape-Controlled Nanoparticles
2.1 Introduction
2.2 Metal Nanoparticles of High-Index Facets and High Surface Energy
2.3 Metallic Alloy Nanoparticles of High-Index Facets and High Surface Energy
2.4 Metal Nanoparticles of Low-Index Facets
2.5 Nanoparticles of Metal Oxides and Chalcogenides
2.6 Summary and Perspectives
Acknowledgment
References
Chapter 3: Direct Growth of One-, Two-, and Three-Dimensional Nanostructured Materials at Electrode Surfaces
3.1 Introduction
3.2 Growth of 1D Nanomaterials
3.3 Nanowires
3.4 Nanorods
3.5 Nanotubes
3.6 Direct Growth of Two-Dimensional Nanomaterials
3.7 Growth of Three-Dimensional Nanomaterials
3.8 Summary
Acknowledgments
References
Chapter 4: One-Dimensional Pt Nanostructures for Polymer Electrolyte Membrane Fuel Cells
4.1 Introduction
4.2 Shape-Controlled Synthesis of 1D Pt Nanostructures
4.3 1D Pt-Based Nanostructures as Electrocatalysts for PEM Fuel Cells
4.4 Conclusions and Outlook
References
Chapter 5: Investigations of Capping Agent Adsorption for Metal Nanoparticle Stabilization and the Formation of Anisotropic Gold Nanocrystals
5.1 Introduction and Scope
5.2 The Multifunctional Role of Nanoparticle Capping Agents
5.3 Controlled Growth of Anisotropic Nanoparticle
5.4 Measuring Capping Agent Adsorption
5.5 Experimental Techniques
5.6 Citrate-Stabilized Nanoparticles
5.7 Quaternary Ammonium Surfactants as Capping Agents
5.8 Pyridine Derivative Capping Agents
5.9 Conclusions and Perspectives
Acknowledgments
References
Chapter 6: Intercalation of Ions into Nanotubes for Energy Storage – A Theoretical Study
6.1 Introduction
6.2 Ionization in Nanotubes
6.3 Electrostatic Interactions
6.4 Details of the Investigated Systems
6.5 Ionic Charges
6.6 Effect of Ion Insertion on the Band Structure
6.7 Screening of the Coulomb Potential
6.8 Energetics of Ion Insertion
6.9 Capacity of a Narrow Nanotube in Contact with an Ionic Liquid
6.10 Other Literature
6.11 Outlook
Acknowledgments
References
Chapter 7: Surface Spectroscopy of Nanomaterials for Detection of Diseases
7.1 An Introduction to Plasmonics
7.2 An Overview of Plasmonic Techniques
7.3 Plasmonic Spectroelectrochemistry
7.4 Plasmonic Biosensing for the Detection of Diseases
7.5 Outlook and Perspectives
References
Chapter 8: Raman Spectroscopy at Nanocavity-Patterned Electrodes
8.1 Introduction
8.2 Fabrication Methods
8.3 Plasmonics
8.4 Raman Spectroscopy
8.5 Surface-Enhanced Raman Spectroscopy
8.6 SERS on Nanohole Arrays
8.7 SERS at Sphere Segment Void (SSV) Surfaces
8.8 Some Applications in Electrochemical SERS
8.9 Other Surface-Enhanced Phenomena
8.10 Conclusions
Acknowledgment
References
Chapter 9: Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) of Electrode Surfaces
9.1 Introduction
9.2 Advantages of Isolated Mode over Contact Mode
9.3 3D-FDTD Simulations
9.4 Synthesis of SHINs
9.5 Characterization of SHINs
9.6 Applications of SHINERS in Electrochemistry
9.7 Summary and Outlook
Acknowledgments
References
Chapter 10: Plasmonics-Based Electrochemical Current and Impedance Imaging
10.1 Introduction
10.2 Principle of Plasmonics-Based Electrochemical Current Microscopy (PECM)
10.3 Principle of Plasmonics-Based Electrochemical Impedance Microscopy (PEIM)
10.4 Imaging Local Electrochemical Current by PECM
10.5 Imaging the Electrocatalytic Activity of Single Nanoparticles
10.6 Mapping Local Quantum Capacitance of Graphene with PEIM
10.7 Conclusions
References
Index
End User License Agreement
Pages
xi
xii
xiii
xiv
xv
xvii
xix
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
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
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
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
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
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
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
403
404
405
406
407
408
409
Guide
Cover
Table of Contents
Preface
Begin Reading
List of Illustrations
Chapter 1: Surface Electrochemistry with Pt Single-Crystal Electrodes
Figure 1.1 2D representation of the process of cutting a crystal through a plane, resulting on a stepped surface.
Figure 1.2 Illustration showing the definition of Miller indices of a surface as three integer numbers proportional to the reciprocal of the intercepts of the plane defining the surface with the three crystallographic axes.
Figure 1.3 Schematic diagrams illustrating the procedure for obtaining the stereographic projection of the faces of a crystal. (a) 3D representation showing the reference sphere and the projection for a general pole with three coordinates
x
,
y
,
z
. (b) Side view and projection of a pole with
x
= 0.
Figure 1.4 (a) Stereographic projection of the main poles for a cubic crystal. The (001) axis has been oriented perpendicular to the plane of the paper. (b) Enlargement of the crystal model, showing the crystallographic axis. The crystal has been slightly tilted to show the (100), (110), and (010) faces, which would be otherwise perpendicular to the paper. (c) Stereographic triangle containing a representative subset of surfaces. All other surfaces can be obtained from those in the triangle by symmetry operations.
Figure 1.5 Atomic structure of basal planes for an fcc crystal.
Figure 1.6 Hard sphere model of stepped surfaces for an fcc crystal: (A) tilted view; (B) side view, showing interlaying spacing; and (C) top view, showing dimensions of the unit cell, projected on the plane of the terrace. (a) (775) = 7(111) × (111); (b) (433) = 7(111) × (100); and (c) (13 1 1) = 7(100) × (111).
Figure 1.7 Hard sphere model of two kinked surfaces, (643), with same distribution of terrace, steps, and kinks but with different chirality. The Cahn–Ingold–Prelog rule is illustrated in the figure.
Figure 1.8 Orientation of the crystal and necessary rotations for the preparation of any stepped surface in the zones and .
Figure 1.9 Orientation of the crystal and necessary rotations for the preparation of the surface with Miller indices (421).
Figure 1.10 Cyclic voltammograms for the three Pt basal planes in (a) 0.5 M H
2
SO
4
and (b) 0.1 M HClO
4
. (A) Pt(111); (B) Pt(100), and (C) Pt(110). Scan rate: 50 mV s
−1
.
Figure 1.11 Cyclic voltammograms for Pt stepped surfaces in the zone, Pt(S)-[(
n
− 1)(111) × (110)], with Miller indices Pt(
n n n
− 2). (a) 0.1 M HClO
4
and (b) 0.1 M H
2
SO
4
. Scan rate: 50 mV s
−1
.
Figure 1.12 Counting the atoms on the (775) surface. (a) Atoms whose center lies inside the unit cell should be counted. The atoms in corner of the unit cell should be counted as ¼ each one. The atom marked with a light gray “1” is the step atom. (b) Decomposition of the unit cell into terrace and step contributions.
Figure 1.13 Comparison of voltammetric charges (symbols) and charges from the hard sphere model (lines) for Pt(S)[
n
(111) × (111)] stepped surfaces. (i) Terrace charge considering (111) step. (ii) Terrace charge considering (110) step. (iii) Step charge.
Figure 1.14 Cyclic voltammograms for stepped surfaces in the zone, Pt(S)-[
n
(111) × (100)], with Miller indices Pt(
n
+ 1
n
− 1
n
− 1). (a) 0.1 M HClO
4
and (b) 0.5 M H
2
SO
4
. Scan rate: 50 mV s
−1
.
Figure 1.15 Cyclic voltammograms in 0.1 M H
2
SO
4
for stepped surfaces in the zone, Pt(S)-[
n
(100) × (111)], with Miller indices Pt(2
n
− 1 1 1). Scan rate: 50 mV s
−1
. Arrows indicate the increase of the step density.
Figure 1.16 Description of different voltammetric peaks to different ensemble of atoms for (100) × (111) stepped surfaces.
Figure 1.17 Cartoon illustrating the concept of free and total charge on ideally nonpolarizable interphases involving adsorption equilibrium.
Figure 1.18 Illustration of the procedure for the determination of the charge versus potential curve from the combination of CO charge displacement and the integration of the voltammogram for Pt(111) in 0.1 M HClO
4
. (a) Cyclic voltammogram 50 mV s
−1
. (b) Uncorrected charges obtained neglecting the residual charge on the CO-covered surface. (c) Charges corrected considering = 1 V. (d) Free charge extrapolated considering constant value of the double-layer differential capacity. The circle represents the opposite of the displaced charge at 0.1 V RHE.
Figure 1.19 Comparison of surface excesses of bromide (solid line), chloride (dashed line), and sulfate (dotted line) in 0.1 M HClO
4
with 10
−3
M of the anion. Hydrogen and OH surface excesses in 0.1 M HClO
4
are also included for comparison.
Figure 1.20 Laser-induced potential transients for Pt(111) at
E
= 0.15 V in (0.1 −
x
) M KClO
4
+
x
M HClO
4
, where
x
equals (a) 0.1, (b) 10
−2
, (c) 10
−3
, and (d) 10
−4
.
Figure 1.21 Laser-induced potential transients for the Pt(111) electrode in 0.1 M KClO
4
+ 10
−3
M HClO
4
at different potentials as indicated. (The Pd/H
2
reference electrode is shifted 50 mV with respect to the RHE).
Figure 1.22 Values of (a) pme's, uncorrected (open symbols) and corrected (filled symbols) from the thermodiffusion potential, and (b) pztc's for Pt(111), Pt(100), and Pt(110) electrodes in (0.1 −
x
) M KClO
4
+
x
M HClO
4
solutions. Lines are drawn to indicate the tendencies of pztc values, and they are reproduced in the left Figure in order to facilitate the comparison with pme values.
Figure 1.23 Linear sweep voltammograms for oxygen reduction on selected Pt-stepped electrodes in the in 0.5 M H
2
SO
4
. Scan rate: 50 mV s
−1
. Rotation rate: 1600 rpm.
Figure 1.24 Plot of (a)
j
0
for the zone and (b)
E
1/2
for the zone for ORR as a function of the angle and step density, respectively, in 0.5 M H
2
SO
4
(close symbols) and 0.1 M HClO
4
(open symbols) (a) Maciá 2004 [146]; b) Kuzume 2007 [142]. Reproduced with permission of Elsevier).
Chapter 2: Electrochemically Shape-Controlled Nanoparticles
Figure 2.1 Variation of surface energy of different {
hkl
} facets and corresponding fcc metals (Au, Pd, Pt, Rh) polyhedral shapes.
Figure 2.2 (a,b) Illustrations of the two-step and one-step square-wave potential method for the preparation of {
hk
0} high-index faceted NPs, respectively. (c–f) SEM images of THH Pt, Pd, and Rh NPs and concave cubic Pt NPs, respectively. The insets show the corresponding high-magnification SEM images and atomic models of {
hk
0} high-index planes. (g,h) Transient current density curves of formic acid oxidation (at 0.25 V, vs SCE) and ethanol oxidation (at 0.30 V, vs SCE), respectively, on the Pt THH, Pt nanospheres, and Pt/C catalyst. (i) Cyclic voltammograms of THH Pd NPs and commercial Pd black catalyst in 0.1 M ethanol + 0.1 M NaOH (scan rate: 10 mV s
−1
). (j) LSVs of THH Rh NPs and commercial Rh black catalyst in 1.0 M ethanol + 1.0 M NaOH solution (scan rate: 50 mV s
−1
).
Figure 2.3 (a,b) SEM images of TPH Pd NPs, and the inset shows the corresponding geometrical TPH model. (c,d) SEM images of TPH Pt NPs, and the inset shows the corresponding geometrical TPH model; (e,f) SAED pattern, TEM image of an individual TPH Pt NP along the [110] direction; (g) HRTEM image of the area in the white box in Figure 2.3d; and (h–j) cyclic voltammograms of the electrooxidation of CO, formic acid, and methanol on TPH Pt NPs and commercial Pt/C: (h) CO stripping curves in 0.5 M H
2
SO
4
, (f) 0.25 M formic acid + 0.1 M HClO
4
solution, and (g) 1 M methanol + 0.1 M HClO
4
solution; scan rate: 50 mV s
−1
.
Figure 2.4 (a,b) SEM images of TIH Pt NPs, and the inset shows the corresponding geometrical model. (c) TEM image taken along the [011] direction, and the insets shows the corresponding SAED pattern and model of TIH Pt NPs. (d) HRTEM image of the area in the white box in Figure 2.4c. (e) Atomic models of the Pt{771} plane. (f) Cyclic voltammograms (50 mV s
−1
) and (g) chronoamperometric curves (0.45 V, vs SCE) of ethanol oxidation on TIH Pt NPs and the commercial Pt black catalyst in 0.1 M ethanol + 0.1 M HClO
4
solution [47].
Figure 2.5 SEM images of concave HOH Pd (a), concave HOH Pt (b), convex HOH Pt (c), and concave DTH Pd (d) NPs, respectively. The insets show the high-magnification SEM images and the corresponding geometrical models.
Figure 2.6 (a) Shape evolution of Pt NPs from THH to TPH via HOH by increasing the
E
U
or
E
L
of the square-wave potential. (b) Illustration of multiple effects of square-wave potential on the surface structures of Pt NPs. (c–g) SEM images of Pd NPs synthesized in DES at different
E
U
: (c) −0.05, (d) 0, (e) 0.025, (f) 0.05, and (g) 0.10 V, respectively. (h) Illustration of shape evolution of polyhedral Pd NPs by adjusting
E
U
.
Figure 2.7 (A–C) Illustrations of TNTAs with as-deposited Pd NPs after heavy ECMF and after heavy and mild ECFM, respectively; (a–c) the corresponding SEM image. (D) TEM image of the Pd-loaded TNTA electrode after heavy and mild ECMF. (E) Pd nanoparticles found in the electrolyte after heavy and mild ECMF. (F,H) HRTEM images of the TNTA-supported Pd nanoparticles and (G,I) atomic models with face assignment along the [110] direction. Cyclic voltammograms of TNTAs with deposited Pd recorded in (J) 0.1 M HClO
4
and (K) 2 M KOH with 10 wt% ethanol. Scan rate: 50 mV s
−1
. Curve 1: TNTA-Pd as deposited. Curve 2: TNTA-Pd after heavy ECMF. Curve 3: TNTA-Pd after heavy and mild ECMF.
Figure 2.8 (a) SEM image of THH Pd–Pt NPs. (b) TEM image of a THH Pd
0.90
Pt
0.10
NP recorded along the [001] crystal zone. (c) SAED pattern. (d) Atomic model of Pt(10 3 0) plane. (e) STEM image and EDS elemental mapping of Pd and Pt in a THH Pd
0.90
Pt
0.10
NP. (f) Current potential curves of THH Pd–Pt NPs, Pd THH, and commercial Pd black recorded in 0.25 M formic acid + 0.25 M HClO
4
(scan rate: 50 mV s
−1
). (g) Comparison of oxidation current density at the peak (
j
P
) and at 0 V (
j
@0V
).
Figure 2.9 (a) SEM image of THH Pt–Rh NPs. TEM image (b) and SAED pattern (c) of a THH Pt–Rh NP recorded along the [001] crystal zone. (d) Atomic model of the {830} facet. (e) STEM image and EDS elemental mapping of Pt and Rh in a THH Pt–Rh NP. (f) SEM image of TPH Pt–Rh NPs. TEM image (g) and SAED pattern (h) of a TPH Pt–Rh NP recorded along the [001] crystal zone. (i) Atomic model of the {311} facet. (j) STEM image and EDS elemental mapping of Pt and Rh in a THH Pt–Rh NP. (k) Cyclic voltammograms of Pt–Rh THH, Pt–Rh TPH, Pt THH, Pt TPH, and commercial Pt/C catalysts recorded in 0.1 M ethanol + 0.1 M HClO
4
, scan rate: 50 mV s
−1
.
Figure 2.10 SEM images of concave nanocubes with different Ni contents: (a) 22%, (b) 31%, and (c) 47%. (d) HRTEM image of a concave FeNi nanocube with 47% Ni content and (e) SAED pattern from the [001] axis, with red circles marking the fcc spots in a bcc pattern. (f) Schematic diagram illustrating a plausible mechanism for the formation of high-index facets of a concave nanocube. (g) SEM images of typical nanocubes (47% Ni) with increasing deposition time from 3 to 20 s. (h–j) SEM images of FeNi nanocages obtained after one, two, and three CV cycles in a 10 mM PBS solution at pH = 3 and a scan rate of 50 mV s
−1
. (k) CVs of concave nanocubes (with zero etching cycles) and the aforementioned concave nanocages in 5 mM 4-aminophenol in PBS (pH = 7). The inset shows the corresponding current densities measured at 0.45 V (Ag/AgCl) for concave nanocubes after different numbers of CV cycles.
Figure 2.11 SEM images of Fe NPs and the corresponding models. Shape transformation of Fe NPs from (a–e) RD and (f–j) TB to a series of 18-facet polyhedral shapes and finally to cubic, respectively. (k)
j–E
curves for Fe NPs with different shapes recorded on nano-Fe/GC electrodes in 0.01 M NaNO
2
+ 0.2 M NaOH (scan rate: 1 mV s
−1
). (l) Relationship between electrocatalytic activity of the Fe NPs, represented by
j
measured at −1.188 V in (k), and the ratio of active surface atoms.
Figure 2.12 SEM images of Cu NPs: (a) deposited at −0.4 V (Ag/AgCl); (b) deposited at potential between −0.6 and −0.8 V (Ag/AgCl), scan rate: 0.50 mV s
−1
; and (c,d) deposited at −0.25 and −0.15 V (vs SCE), respectively.
Figure 2.13 SEM images of Pt NPs synthesized by square-wave potential: (a) cubes, (b) truncated cubes, and (c) octahedrons.
Figure 2.14 SEM of cuprous oxide crystals electrodeposited at different synthetic conditions, showing the effects of surfactants (a), pH (b), additives (c), current densities (d), and precursor concentrations (e) [119] on tuning shape of crystals.
Figure 2.15 The shape evolution of PbS crystals with decreasing PbCl
2
concentration at a constant deposition current of 0.2 mA and with deposition time of 75 s: (a) 0.027 g, (b) 0.025 g, (c) 0.022 g, (d) 0.020 g, (e) 0.018 g, (f) 0.016 g, (g) 0.014 g, (h) 0.012 g, and (i) 0.010 g, respectively.
Chapter 3: Direct Growth of One-, Two-, and Three-Dimensional Nanostructured Materials at Electrode Surfaces
Figure 3.1 (a) Low- and (b) high-magnification SEM images of the sample synthesized in 2.5 M NaOH at 150 °C for 15 h. (c) TEM and (d) HRTEM and SAED (inset) of Na
2
Ti
6
O
13
nanowires. (e) HRTEM image and SAED (inset) of the as-synthesized samples after acid treatment. (f) XRD of H
2
Ti
3
O
7
nanowire arrays annealed for 5 h at 450, 600, and 750 °C. HRTEM and SAED (inset) results of the samples synthesized from H
2
Ti
3
O
7
nanowire arrays annealed at 450 °C for 5 h (g) and at 750 °C for 5 h (h).
Figure 3.2 Scheme of all phase conversions from Na
2
Ti
6
O
13
to H
2
Ti
3
O
7
by an ion-exchange process and of transformation from H
2
Ti
3
O
7
to anatase and rutile at high temperatures by annealing and the ideal crystal structure of these materials: (a) Na
2
Ti
6
O
13
, (b) H
2
Ti
3
O
7
, (c) anatase, and (d) rutile.
Figure 3.3 A schematic illustration of the procedures used for the fabrication of nanostructures: (a) pure Al plate; (b) Al/PAA membrane; (c) PAA/Al/PAA sandwich; and (d) PAA(Zn)/Al/PAA(Co) sandwich.
Figure 3.4 (a) AFM image of PAA, (b) SEM images of the Zn nanowire arrays embedded into the PAA film on one side of the PAA/Al/PAA sandwich, and (c) SEM image of Co nanowire arrays filled on the other side of the PAA/Al/PAA of the sandwich.
Figure 3.5 (a) Top view of SEM image of the TiO
2
nanowires grown on the Ti substrate. (b) TEM image of an individual TiO
2
nanowire, inset: SAED pattern of the formed TiO
2
nanowire. (c) Cross-sectional SEM image of carbon-coated TiO
2
nanowire. (d) EDS spectrum of fabricated carbon-modified TiO
2
nanowires, inset: STEM image of single carbon-coated TiO
2
nanowire. (e) Chronoamperometric response of the carbon-modified TiO
2
nanowire electrode after GOx immobilization in O
2
-saturated PBS at pH 7.4 upon injection of different concentrations of glucose. (f) Corresponding calibration curve.
Figure 3.6 SEM images of the TiO
2
samples prepared by oxidizing Ti using (a) O
2
, (b) HCOOH, (c) H
2
O, (d) CH
3
CH
2
OH, (e) CH
3
CHO, and (f) CH
3
COCH
3
as oxygen sources at 850 °C for 1.5 h.
Figure 3.7 Scheme (I) illustrates the possible growth of titanium oxide occurring at the oxide/gas interface, inside the oxide film, and/or at the oxide/metal interface. Scheme (II) shows the growth processes of (a) polycrystalline films, (b) microcrystalline fibers, and (c) well-aligned nanorod arrays from different oxygen sources.
Figure 3.8 (a) and (b) Low- and high-magnification SEM images of TiO
2
nanotubes respectively. (c) SEM image of nanoporous TiO
2
. (d) Mechanism of TiO
2
nanotube growth.
Figure 3.9 (a) SEM image, (b) EDS, and (c) XRD of the as-prepared Au nanoparticle-decorated TiO
2
nanotube electrode. (d) Amperometric current responses of the Ti/TiO
2
NT/Au electrode as the result of the successive addition of Cr(VI) at the electrode potential of 0.28 V in a 0.1 M HCl solution. The inset is the enlarged amperometric responses of the low Cr(VI) concentration area (marked by a black rectangle).
Figure 3.10 SEM images of (a) WO
3
– 30 min, (b) WO
3
– 1 h, (c) WO
3
– 2 h, and (d) WO
3
– 3 h.
Figure 3.11 (a–d) Images of the electrode depicting the alteration of the electrode during the electrochemical reduction treatment. The electrode was 1 × 1 cm. (e) SEM image of the electrode illustrating WO
3
nanospheres following electrochemical treatment.
Figure 3.12 SEM images of WO
3
(a) and WO
3
–Pt (b). (c) Comparison of the CVs of the WO
3
electrode prior to and following the deposition of the Pt nanoparticles. (d) Kinetic curves of the degradation of RhB on WO
3
–Pt bifunctional electrode at various applied conditions.
Figure 3.13 FE-SEM images obtained for rGO (a) and Au nanoparticle/rGO (b). XPS spectra of the C 1 s region for GO (c) and Au 4f (d) region for the Au–rGO nanocomposite.
Figure 3.14 Morphology of the as-synthesized Pt-containing nanostructures. SEM images shown with the normalized Pt:Pb atomic ratio determined by quantitative EDS analysis: (a) 95 : 5 and (b) 50 : 50. SEM image of (c) Pt:Bi (95 : 5) and (d) Pt:Bi (70 : 30).
Figure 3.15 SEM images of the samples prepared by using 1 mM HF at 100 °C for different times: (a) 120 min, (b) 180 min, (c) 240 min, and (d) 600 min.
Figure 3.16 SEM images: (a) low magnification, (b) individual flower-like structure of the as-prepared Sn nanoflowers, (c) low magnification, and (d) typical flower-like morphology of SnO
2
formed by the RGTO process.
Chapter 4: One-Dimensional Pt Nanostructures for Polymer Electrolyte Membrane Fuel Cells
Figure 4.1 Selective possible shapes of platinum nanoparticles (a,b) without defects and bounded by (a) one group and (b) two groups of facets and (c–f) with different numbers of defects. The notation (
m
,
n
) represents the number of defects
m
and different facets
n
in crystals.
Figure 4.2 (a) Schematic illustration of preparation process of Pt nanowires using PAM template. FE-SEM images of (b) top view of porous alumina template and (c) side view and (d) top view of as-prepared Pt nanowire arrays prepared by electrochemical deposition. The diameter of Pt nanowire: ∼90 nm.
Figure 4.3 (a,b) Schematic illustration of preparation process of Pt nanowires using PAM template via an electroless deposition method (left panel). SEM (c,d) and TEM (e) images of Pt nanowires with 40 nm in diameter.
Figure 4.4 (a) Schematic illustration of preparation process of Pt nanowires using soft CTAB template and (b, c) TEM images of the as-synthesized Pt nanowire networks.
Figure 4.5 (A) Schematic detailing all of the major steps and conditions for controlling the reduction kinetics of a Pt(IV) precursor by ethylene glycol (EG) and the corresponding morphologies observed for the Pt nanostructures: (a) spheres, (b) stars, (c,d) multiple pods, and (e) rods on aggregates of Pt nanoparticles. (B) (a) SEM images of the hierarchically structured Pt agglomerates. The inset: enlarged SEM image of Pt nanorods. (b) Cross-sectional TEM image of a microtomed sample. The inset: enlarged TEM image of the boxed region indicating aligned Pt nanorods. (c) TEM image and ED pattern of Pt nanowires. (d) HRTEM image of the tip of an individual Pt nanowire. (e) SEM images of Pt nanowires formed on the surface of Pt agglomerates. The inset shows an enlarged image of Pt nanowires. (f) TEM image and (inset) ED pattern of Pt multipods.
Figure 4.6 (a,b) SEM images of Pt nanoflowers composed of nanowires. (c) TEM image of a Pt nanowires. (d) HRTEM image of the tip of an individual Pt nanowires, indicating it to be a single crystal, with its growth direction along the ⟨111⟩ axis.
Figure 4.7 SEM images of Pt nanowires grown on various supports. (a,b) Carbon fibers of carbon paper (Sun 2008 [75]. Reproduced with permission of John Wiley & Sons.). (c) Carbon black spheres (Sun 2008 [10]. Reproduced with permission of John Wiley & Sons.). (d) Carbon nanotubes (Sun 2007 [76]. Reproduced with permission of American Chemical Society.). (e) Sn@CNT nanocables. (Sun 2010 [77]. Reproduced with permission of John Wiley & Sons.)
Figure 4.8 TEM images of pristine N-doped CNTs before (a) and after (b) the growth of ultrathin Pt nanowires. TEM (c) and HRTEM (d) images of Pt nanowires grown on N-CNT.
Figure 4.9 (a) FESEM, (b) TEM, and (c, d) HRTEM images of Pt NW assemblies. The inset in (a) shows an optical photo of a Pt NW membrane, 2 cm in diameter, fabricated by a simple casting process. The insets in (b–d) show the corresponding high-magnification images. One inset in (c) displays the SAED pattern. The mismatch of Pt nanowires is indicated by the white circle in (c). The surface atomic arrangements of nanowires are also shown in the insets of (c) and (d), which indicate the existence of step structures on the surface of Pt nanowires. The double arrows in (c) and (d) indicate the ⟨111⟩ growth direction of Pt nanowires.
Figure 4.10 (A) Setup of electrospinning apparatus for fabrication of nanowires. (B) The morphology of electrospun PVP/H
2
PtCl
6
composite wire at ultra combination of PVP/H
2
PtCl
6
. They are (a) 33.1 mg ml
−1
PVP, 10.6 mg ml
−1
H
2
PtCl
6
, (b) 33.1 mg ml
−1
PVP, 2.6 mg ml
−1
H
2
PtCl
6
, (c) 9.9 mg ml
−1
PVP, 10.6 mg ml
−1
H
2
PtCl
6
, and (d) 9.9 mg ml
−1
PVP, 2.6 mg ml
−1
H
2
PtCl
6
.
Figure 4.11 (a) SEM cross-sectional image of the Pt nanocolumns perfectly perpendicular to the substrate surface. (b) SEM top view showing the homogeneous growth of the Pt nanocolumns on the substrate, which was completely covered. (c) SEM magnification of the Pt nanocolumn tip, consisting of four triangular {111} facet faces. (d) TEM cross-sectional image of Pt nanocolumns, showing that Pt tips are sharp and 20 nm wide. (e) High-resolution TEM image of the nanocolumn tip, indicating that the four triangular top faces possess a lattice space of 0.227 nm, related to the
d
111
space of cubic Pt, as modeled in the inset.
Figure 4.12 (a) A schematic of physical templating. (b) SEM images of Pt nanotubes that were prepared by coating for 18 h, followed by dissolution of Se wires in hydrazine monohydrate. (c) TEM image and electron diffraction pattern of the same sample. (d) TEM image of another sample where the coating only proceeded for 30 min. A segment of the Se core had been removed
in situ
via continuous exposure to the electron beam. (e) TEM image of a third sample where the coating lasted for 3 days. The sample was briefly sonicated to expose the Se core by partially removing the Pt sheath. The inset shows an electron diffraction pattern taken from the exposed Se core, indicating that no structural change was involved for the template during Pt coating.
Figure 4.13 (a) The schematic setup (cross section) to achieve porous AAO template and deposition of Pt nanotubes.
Figure 4.14 (A) Schematic of the fabrication procedure of Pt nanotube arrays on Al. (B) SEM images of Pt nanotubules in porous alumina films after deposition for (a–c) 3 min and (d) 7 min. The images show different angles of the Pt nanotubules: (a) top view, (b,c) vertical sections, and (d) transverse section.
Figure 4.15 (A). Schematic illustration of fabrication of Pt DNT by means of electrodeposition using AAO template. The light and dark gray lines are Pt and Pd, respectively. (B) (a) TEM image of a Pt DNT. (b) EDS line scanning spectra show ⓐ outer and ⓑ inner wall at a side view of the Pt DNT. The blue and red lines are Pt and Pd, respectively. (c) TEM image of the FIB-prepared cross section through the Pt DNTs. The insets of each panel show the high-resolution TEM images of the red boxes corresponding to (a) and (c), respectively.
Figure 4.16 (a) Experimental setup to prepare Pt nanotubes by PC template in a U tube. (b,c) SEM images of isolated Pt nanotubes.
Figure 4.17 (a) Structural diagram of C
12
EO
9
and Tween 60 molecules. (b) TEM image of Pt nanotube obtained by reducing Pt precursory mixed-surfactant LC phases with hydrazine.
Figure 4.18 (A) Schematic view of the preparative procedure for mesoporous Pt nanorods and nanotubes. (B) SEM images of (a,b) mesoporous Pt nanorods and (c,d) mesoporous Pt nanotubes. Panels (b) and (d) are highly magnified images of (a) and (c), respectively.
Figure 4.19 (A) Schematic of the fabrication procedure of Pt nanotube arrays via Ag nanowire template. (B) (a) SEM image of AgNWs. (b) TEM image and electron diffraction pattern (inset) of AgNWs. (c) SEM image of PtNTs. (d) TEM image and electron diffraction pattern (inset) of PtNTs.
Figure 4.20 (a) HRTEM image of PtNTs. (b) Selected area diffraction pattern of PtNTs.
Figure 4.21 (A) Schematic illustration of the formation mechanism of PtNTs. (B) (a) TEM image of the Te nanowires used as templates. (b) TEM image of PtNTs. Inset of (b) shows HRTEM image of PtNTs.
Figure 4.22 TEM images of Pt nanocrystals with a branched morphology: (a) highly branched multipods prepared using the polyol process in the presence of a trace amount of Fe
III
species under the protection of N
2
after initial exposure to air for 11.5 h. (Chen 2005 [33]. Reproduced with permission of John Wiley & Sons.). (b) Star-like Pt nanoparticles prepared with the addition of Pt tetrahedrons as seeds. (Mahmoud 2008 [139]. Reproduced with permission of American Chemical Society.) (c) Tripods. (Maksimuk 2006 [35]. Reproduced with permission of Royal Society of Chemistry.). (d) Hyperbranched multipods by applying adsorptive organic molecules as capping agents. (Sun 2002 [38]. Reproduced with permission of American Chemical Society.)
Figure 4.23 Reaction pathways of (a) oxygen reduction (ORR), (b) hydrogen oxidation (HOR), (c) methanol oxidation (MOR), and (d) formic acid oxidation reactions (FAOR). (Peng 2009 [4]. Reproduced with permission of Elsevier.)
Figure 4.24 (a) Comparison study of the loss of electrochemical Pt surface area (ECSA) of Pt/C (E-TEK), platinum black (PtB; E-TEK), and PtNT catalysts with a number of CV cycles in Ar-purged 0.5 M H
2
SO
4
solution at 60 °C (0–1.3 V vs RHE, sweep rate 50 mV s
−1
). (b) Polarization curves of Pt/C, PtB, PtNTs, and PdPtNTs for ORR performed in O
2
-saturated 0.5 M H
2
SO
4
solution at room temperature (1600 rpm, sweep rate 5 mV s
−1
). Inset: mass activity (top) and specific activity (bottom) for the four catalysts at 0.85 V. (Chen 2007 [12]. Reproduced with permission of John Wiley & Sons.). (c) Loss of ECSA for PtNTs and Pt/C as a function of cycles of durability testing. ECSAs were calculated by hydrogen adsorption charges every 6000 cycles during the 30 000 cycles between 0.6 and 1.1 V versus RHE. (d) Polarization curves for oxygen reduction at 20 mVs
−1
, 1600 rpm for porous PtNTs, Pt/C, and BP-Pt in an oxygen-saturated 0.1 M HClO
4
electrolyte. Inset: mass activity (top) and specific activity (bottom) of porous PtNTs, Pt/C, and BP-Pt at 0.9 V versus RHE.
Figure 4.25 (A) Loss of electrochemical surface area (ECSA) of Pt/C (E-TEK), star-like PtNW/C, and supportless PtNW catalysts as a function of cycling numbers in O
2
-purged 0.5 M H
2
SO
4
solution at room temperature (0.6–1.2 V vs RHE, sweep rate 50 mV s
−1
). (B) Polarization curves for ORR of Pt/C (E-TEK) and star-like PtNW/C catalysts in O
2
saturated 0.5 M H
2
SO
4
solution at room temperature (1600 rpm, sweep rate 10 mV s
−1
). Inset: mass and specific activity at 0.9 V (vs RHE) for the two catalysts. (C) Schematic of morphology changes that occur in Pt during accelerated electrochemical cycling. (a) Pt NPs/C (E-TEK); (b) Pt NWs/C; and (c) supportless Pt NWs
Figure 4.26 (a) CVs for MOR on Pt NW-19h grown on TiO
2
nanowires and Pt/C. The CVs were recorded at a scan rate of 50 mV s
−1
and a mixture of 0.5 M MeOH and 0.5 M H
2
SO
4
. (b) Chronoamperometry curves recorded at 0.85 V for various samples.
Figure 4.27 (A) Cyclic voltammograms for methanol oxidation (1 M methanol in 0.5 M H
2
SO
4
). Trace (a), before growth of Pt NWs trace (b), after growth of Pt NWs; and trace (c), ETEK commercial catalyst of Pt nanoparticle on carbon black. (B) CVs of (a) PtNW-CNT@SnNW electrode and (b) of a standard 30 wt% Pt/C electrode in the presence of CO in 0.5 M H
2
SO
4
aqueous solution at room temperature. Potential scan rate: 50 mV s
−1
.
Figure 4.28 (a) CVs and (b) ECSAs for the Pt NRs (black), Pt SNTs (red), and Pt DNTs (blue) with the same length (about 2.4 µm) in 0.5 M H
2
SO
4
solution at a scan rate of 50 mV s
−1
. (c) Anodic CO oxidation reaction (50 mV s
−1
in 0.5 M H
2
SO
4
solution) for different catalysts, showing only the oxidative CO removal region. (d) CVs for electro-oxidation of 0.1 M methanol in 0.5 M H
2
SO
4
at a scan rate of 20 mV s
−1
. (e) Comparison of specific activity (black) and mass activity (red) calculated from high MOR currents of (d). (f) Chronoamperometric
i–t
curves of methanol oxidation reaction on Pt NR, Pt SNT, and Pt DNT catalysts in N
2
-saturated 0.1 M MeOH and 0.5 M H
2
SO
4
at a constant potential (0.4 V vs Ag/AgCl). (g) Schematic illustration of Pt DNTs double-walled porous structure.
Figure 4.29 Cyclic voltammetric response (a) and comparison of the transient current density curves (b) of Pt/C-multipod, Pt/C-disk, Pt/C-hexagon, and Pt/C toward formic acid oxidation.
Figure 4.30 Comparison of the electrocatalytic activity of Pt-Y/C, Pt-NW/C, and Pt/C. (a) Transient current density curves and (b) potential-dependent steady-state current density of formic acid oxidation.
Chapter 5: Investigations of Capping Agent Adsorption for Metal Nanoparticle Stabilization and the Formation of Anisotropic Gold Nanocrystals
Figure 5.1 (a) Back Laue X-ray diffraction setup for orienting single crystals, (b) X-ray diffraction pattern for Au(111), and (c) schematic of hanging meniscus configuration for electrochemical studies.
Figure 5.2 Electrochemical characterization of Au(111) single crystal using (a) cyclic voltammetry in 50 mM KClO
4
(20 mV s
−1
scan rate) and (b) differential capacitance in 50 mM KClO
4
(25 Hz, 5 mV rms ac perturbation superimposed on a 5 mV s
−1
potential sweep).
Figure 5.3 Cyclic voltammetry curves of Au(111) in 0.001 M HClO
4
/0.050 M KClO
4
(pH 3, solid curve) and in 0.10 M HClO
4
(pH 1, dotted curve) with a formal citric acid concentration of 7.8 × 10
−4
M; scan rate 20 mV s
−1
.
Figure 5.4 Gibbs excess Γ plotted versus the electrode potential,
E
, for Au(111) in 0.001 M HClO
4
/0.050 M KClO
4
, pH 3 and 0.1 M HClO
4
, pH 1 solutions. Each curve corresponds to different formal citric acid concentrations in the bulk of solution.
Figure 5.5 Outer Helmholtz potential
φ
2
plotted versus the electrode potential for Au(111) in 0.001 M HClO
4
/0.005 M KClO
4,
pH 3 and in 0.1 M HClO
4
, pH 1. Solid horizontal line represents the maximum
ζ
potential observed for citrate-stabilized Au nanoparticles.
Figure 5.6 (a) CVs (20 mV s
−1
) in 0.10 M NaF supporting electrolyte (black dotted line) in the presence of 1.0 mM OTATf (solid line) for (a) Au(111) [73] and (b) Au(100).
Figure 5.7 (a) Gibbs surface excesses versus electrode charge density at the Au(111)/0.1 M NaF interface for 1.0 mM OTA
+
in the absence of NaBr () and 1.0 mM OTA
+
in the presence of 1.0 mM Br
−
(•). The adsorption isotherm for 1.0 mM bromide co-adsorption in the presence of 1.0 mM OTATf is also plotted using the right-hand ordinate (). (b) Gibbs surface excesses versus electrode charge density at the Au(100)/0.1 M NaF interface for 1.0 mM OTA
+
in the presence of 1.0 mM NaBr () and 1.0 mM Br
−
in the presence of 1.0 mM OTA
+
(•).
Figure 5.8 Adsorption isotherms for 1.0 mM OTA
+
adsorption in the presence of 1.0 mM NaBr on the Au(111) () and Au(100) () electrode surfaces as a function of surface charge density. Inset shows the corresponding adsorption isotherms for 1.0 mM Br
−
adsorption in the presence of 1.0 mM OTATf.
Figure 5.9 Schematic representation of the phase transfer of quaternary ammonium bromide-stabilized nanoparticles from toluene to water using DMAP as well as the proposed resonance structure of adsorbed DMAP.
Figure 5.10 Differential capacity curves for polycrystalline gold in 50 mM KClO
4
supporting electrolyte (dark gray lines) in the presence of 0.1 mM formal concentration DMAP (light gray lines) as a function of pH. (a) pH = 11, (b) pH = 4.5, and (c) pH = 2.0. (d) It shows the state II coverage of DMAP, as determined using Equation 5.23, as a function of electrolyte pH.
Figure 5.11 Charge density versus electrode potential curves for polycrystalline gold in 50 mM KClO
4
supporting electrolyte (dotted trace) and the formal DMAP concentrations between 0.01 and 0.10 mM (lines with symbols and symbols) in (a) pH = 9.7 and (b) pH = 4.5 electrolyte.
Figure 5.12 Gibbs surface excesses as a function of electrode potential and formal DMAP concentrations in 50 mM KClO
4
pH adjusted to (a) pH 9.7 and (b) pH 4.5. The insets show pictures of Au-DMAP nanoparticles in aqueous media of corresponding pH.
Figure 5.13 Subtractively normalized SEIRAS data for 0.1 mM DMAP as a function of potential in pH (a) 10 and (b) 4.5 electrolyte (50 mM KClO
4
). The reference potential was −0.8 V versus Ag/AgCl. The * denotes bands appearing due to the desorption of DMAPH
+
electrostatically bound to the gold electrode at the reference potential.
Figure 5.14 Cartoon description of the adsorption orientation and speciation of DMAP adsorbed on polycrystalline gold as a function of pH and the electrical state of the gold surface.
Figure 5.15 UV–visible extinction spectra of aqueous dispersions of DMAP-stabilized gold nanoparticles in the absence (dark gray lines) and presence of 5 mM electrolyte (light gray lines). Electrolyte was NaF (a–c) and NaCl (d–f) pH adjusted to 9.5 (a,d), pH 7.5 (b,e), and pH 5.5 (c,f). TEM images of nanoparticles in the corresponding electrolytes are shown in the insets.
Figure 5.16 Gibbs surface excess plotted as a function of electrode potential for DMAP (open squares) and chloride (closed circles) on polycrystalline gold at pH 7.5 for an equal formal concentration of DMAP and sodium chloride (0.25 mM). Inset shows a plot of the Gibbs surface excess of DMAP(H
+
) species versus the Gibbs surface excess of chloride. A schematic of halide-induced aggregation is shown below the isotherm plots.
Figure 5.17 Positive-going differential capacity traces of 0.1 mM (formal concentration) DMAP in 50 mM KClO
4
electrolyte pH adjusted to (a) 9.7 and (b) 4.5. Solid lines are for Au(111), dashed lines are for Au(100), and dotted lines are Au(poly).
Figure 5.18 (a) Color of colloidal gold dispersions resulting from the addition of NaBH
4
to HAuCl
4
–DMAP mixtures and (b) UV–vis–NIR optical spectra of the dispersions. The time between mixing the Au
III
precursor with DMAP and the addition of NaBH
4
(
τ
) is indicated.
Figure 5.19 Transmission electron micrographs of Au nanocrystals formed from the NaBH
4
reduction of HAuCl
4
–DMAP mixtures as a function of
τ
. (a)
τ
= 0 min, (b)
τ
= 0.5 min, (c)
τ
= 1 min, (d)
τ
= 3 min, (e)
τ
= 5 min, and (f)
τ
= 10 min.
Figure 5.20 Open-circuit potential measurements during the evolution of gold nanocrystals. The working electrode compartment of the cell initially contained 4 ml of 0.1 M DMAP and 100 µl of 0.01 M HAuCl
4
that had been allowed to react for a controlled amount of time,
τ
. The origin of the time axis corresponds to the moment that NaBH
4
was added to the cell. The shaded region defines the potential range where DMAP is preferentially adsorbed on Au{100} and Au(poly) facets. As the lines are labeled in the plot it is not necessary to also label them in the caption.
Figure 5.21 (a) Integrated peak areas (left ordinate) for adsorbed MOP vibrational peaks at 1300 cm
−1
(), 1500 cm
−1
(•), and 1615 cm
−1
() obtained using SEIRAS and the differential capacitance curves (right ordinate) for the supporting electrolyte in the absence (
—
) and presence (
−
) of 0.1 mM MOP (formal concentration) in pH 7 electrolyte. Panel (b) provides the equivalent data in pH 4.5 electrolyte.
Figure 5.22 Results of the numeric differentiation of charge density versus potential curves for 4-methoxypyridine (dark gray line) and 4-dimethylaminopyridine (light gray line) adsorbed on Au(111) in 50 mM KClO
4
with the pH adjusted to the p
K
a
of the corresponding protonated pyridine derivative.
Figure 5.23 Gibbs free energies of adsorption as a function of potential for MOP () and DMAP (•) for the vertical state of adsorption at pH = p
K
a
.
Figure 5.24 Optical spectrum and transmission electron micrograph (inset) of Au nanocrystals formed from the NaBH
4
reduction of KAuCl
4
in the presence of 0.1 M MOP.
Chapter 6: Intercalation of Ions into Nanotubes for Energy Storage – A Theoretical Study
Figure 6.1 The universal dimensionless function that describes the image interactions; .
Figure 6.2 Examples of lithium ions inside of gold nanotubes (b) and carbon rings (a) investigated. The redlines on the right represent the unit cell.
Figure 6.6 Screened Coulomb potential along the axis of the tube as a function of the distance from the ion.
Figure 6.9 Screened Coulomb potential along the axis of a (8,0)CNT and a (6,3)CNT; the ion sits at the origin at the center of the tube.
Figure 6.3 Charge difference plots for a chlorine atom and a sodium atom in a (10,0) . Red(blue) indicates an excess of negative (positive) charge.
Figure 6.4 Densities of states for a Na atom and a Br atom placed inside a (10,0)CNT.
Figure 6.5 Bandstructure of the (8,0)CNT near the Fermi level, both in the presence and in the absence of ion insertion; the energy zero is at the Fermi level.
Figure 6.7 Screened Coulomb potential along the axis of (10,0)CNT as a function of the distance from the ion. The vertical dotted line indicates the end of the ring.
Figure 6.8 Screened Coulomb potential along the axis of the tube as a function of the distance for a (8,8)AuNT and a (10,0)CNT as obtained by DFT and the corresponding curves obtained by fitting the data to Equation refclas in order to obtain the effective image radius.
Figure 6.9 Screened Coulomb potential along the axis of a (8,0)CNT and a (6,3)CNT; the
ion sits at the origin at the center of the tube.
Figure 6.10 Examples for the energies of ions in nanotubes obtained by DFT as a function of position. The coordinate is along the axis of the cylinder. In order to obtain a two-dimensional plot, we have chosen for each value of and the coordinate where the energy is lowest and plotted the corresponding energy as a function of and . Because of the symmetry, only a sector is displayed. The energy scales are in electron volts.
Figure 6.11 Insertion energy of halide ions in various carbon nanotubes.
Figure 6.12 Insertion energy of alkali ions in various carbon nanotubes. Values marked with an asterisk refer to adsorption sites off the axis.
Figure 6.13 Two views of a chlorine atom adsorbed in (8,8)AuNT. Note the deformation of the gold lattice.
Figure 6.14 Interfacial capacity as a function of the charge density (a) and of the average interionic distance (b).
Chapter 7: Surface Spectroscopy of Nanomaterials for Detection of Diseases
Figure 7.1 (a) Schematic of the working principle of an SPR instrument; a light beam impinges on the glass–metal interface, which enters resonance with the SP, shown as the SP field. (b) Schematic representation of the excitation of a localized surface plasmon in LSPR experiments where light enters resonance with the free electrons (gray shade) of the metallic nanoparticles. The electron cloud oscillates in resonance with the electric field of the light. (c) Graphical depiction of the MEF effect on nanoparticles. The excitation laser (in green) irradiates a nanoparticle and enters resonance with the SP, causing a shift in the emitted fluorescence (shown in red). (d) Graphical depiction of the SERS effect, where the excitation laser (in green) also enters resonance with the SP of the nanoparticle. The inelastically scattered photons are represented as a Raman spectrum (black).
Figure 7.2 UV-Vis spectrum of 30 nm Au nanoparticles.
Figure 7.3 Electromagnetic field enhancement contours between two silver nanoparticle dimers separated by a 2 nm gap for varying excitation wavelengths.
Figure 7.4 (a) Jablonski diagram for metal-enhanced fluorescence, where an additional excitation pathway with the plasmon (
E
m
) increases the excitation rate and an additional fluorescence pathway mediated with the plasmon (Γ
m
) contributes to the increase in fluorescence.
E
and Γ represent the normal excitation and radiative emission pathways, respectively, while
k
NR
includes all nonradiative relaxation processes. (b) Influence of the distance on MEF-dependent parameters. The electric field (
E
-field) from the plasmon decays exponentially from the surface, decreasing the
E
m
contribution for fluorophores located farther from the surface. The free space intensity increases with distance due to the reduction of the quenching mechanism from the metal surface. The overall fluorescence intensity (labeled “MEF”) increases with distance to attain a maximum corresponding to the ideal distance to locate a fluorophore, which constitutes a compromise between minimal quenching and
E
-field enhancement.
Figure 7.5 (a) Principles of SPCE in a classical SPR instrument. The excitation laser illuminates the fluorophore (the SPR light source can also serve to excite the fluorophore), which emits via the surface plasmon at the glass–metal interface and at an angle set from the material of the glass and the emission wavelength (see Equation 7.3). (b) Graphical representation of the concept of anisotropic fluorescence emission on nanoparticles. The (green) laser irradiates the nanoparticle and excites the fluorophore and the plasmon. Fluorescence is emitted (red glow) anisotropically by the nanoparticle.
Figure 7.6 (a) Photograph of a Au prism for classical SPR, (b) scanning electron microscopy (SEM) image of nanohole arrays, and (c) transmission electron microscopy (TEM) image of Au nanoparticles.
Figure 7.7 Working principle of electrochemical melting as has been applied to the detection of DNA mutations responsible for cystic fibrosis. As the applied potential is increased, the dehybridization of the DNA causes the SERS intercalator to move out with the field of enhancement, thus reducing the intensity observed.
Figure 7.8 (a) Working principle of ESPR for the detection of pathogenic DNA using nanoswitches. In the presence of the target DNA, the electrochemical component moves out with the range of the electrode, causing a change in the surface plasmons as well at the potential output. (b) Schematic of the instrumentation involved in the analysis including both SPR and electrochemical components.
Chapter 8: Raman Spectroscopy at Nanocavity-Patterned Electrodes
Figure 8.1 SEM images of Au nanohole arrays fabricated by e-beam lithography.
Figure 8.2 SEM images of 3D plasmonic cavity nanosensors composed of a nanohole array membrane with coregistered nanocone array. (a) A 230 nm thick Au nanohole array membrane with 500 nm periodicity and 87 nm hole radius fabricated on a Pyrex substrate with a single 250 nm deep cavity. (b) Magnified image shown in (a) representing the dimensions of the truncated Au nanocones with an apex radius of 44 nm, a base radius of 87 nm, and a height of 150 nm.
Figure 8.3 (a) A master with nanopillar arrays is fabricated via EBL using a negative tone resist, which can be used to make gold quasi-3D nanostructure arrays on a PDMS stamp via soft lithography followed by metallization or to make gold 2D nanohole arrays on a silicon substrate by lift-off nanopillars from the master. (b) SEM images of a gold 2D nanohole array on a silicon substrate fabricated via the lift-off nanopillars using a PDMS stamp. (c) SEM image of gold quasi-3D nanostructure array on PDMS cast from an Ma-N 2403 master with nanopillars that have a diameter of 400 nm, pitch of 500 nm, and height of 300 nm fabricated via EBL.
Figure 8.4 SEM images of a nanohole arrays fabricated by focused ion beam milling. (a) A copper nanohole array with 133 nm holes. (Anema 2008 [10]. Reproduced with permission of American Chemical Society.) (b) A gold nanohole array with 100 nm holes.
Figure 8.5 SEM images of Au nanomesh films with different numbers of layers and pore sizes. Average pore sizes are (a,d,g) 69 ± 2 nm, (b,e,h) 50 ± 2 nm, and (c,f,i) 41 ± 1 nm. Inset in (a) indicates the side view of the nanomesh, and the scale bar is 100 nm.
Figure 8.6 (a–d) Schematic illustration of the procedure for fabricating a silver nanobowl array. (e) SEM images of the nanobowls.
Figure 8.7 Scanning electron micrographs of a silver nanohole array fabricated by nanosphere lithography with reactive ion etching and metal evaporation.
Figure 8.8 (a) AFM image of a nanohole array with a periodicity of 450 nm with a diameter of 195 ± 19 nm. (b) SEM image of a nanohole array demonstrating the (
i
,
j
) nomenclature and the irregular edges of each nanohole.
Figure 8.9 (a) SEM image of silver hierarchical bowl-like array film fabricated using 5 µm polystyrene sphere monolayer template infiltrated with silver by thermal decomposition of silver acetate. (Adapted from Li 2007 [36]. Reproduced with permission of American Chemical Society.) (b) SEM images of macroporous platinum with ∼320 nm diameter voids fabricated by electroless deposition through a colloidal silica template. Bottom left insets show FFTs, and upper right inset shows interconnecting pores and the rough surface of the sample.
Figure 8.10 SEM image of a gold sphere segment void (SSV) structure. Note the smooth electroplated metal walls and top surface. The rough circular areas at the bottom of each cavity are the evaporated gold substrate.
Figure 8.11 In (a), an array of seven rows of spheres is guided by a 3.7 µm wide stripe. This excessive width allows for a natural triangular distortion of the array which increases the sphere density. In (b), an array of eight rows of spheres is guided by a 3.9 µm wide stripe. The dimensional match results in a perfectly guided sphere array. Similarly, in (c), an array of eight rows of spheres is guided by a 4.2 µm wide stripe resulting in a distorted array. In (d), an array of nine rows of spheres is guided by a 4.3 µm wide stripe, resulting in perfect guidance. Note that in (d), the sphere self-assembly is expanded to the SiO
2
region indicating that the sphere deposition process is not always selective. SEM image of self-assembled inverse sphere Ni arrays guided by (e) 1.3 µm Si/SiO
2
and (f) 2.6 µm stripes. The uniform black area is SiO
2
while the honeycomb-like white structure is the surface of the Ni. The holes in the array correspond to the spherical Ni cavities with the Si bottom appearing black at the centers.
Figure 8.12 Combined electromagnetic wave and surface charge character of a surface plasmon.
Figure 8.13 Energy-level diagram for plasmon hybridization in a metal nanoshell by combination of the plasmons for a sphere and a cavity. The two nanoshell plasmons are symmetrically and antisymmetrically coupled and have energies given by Equation 8.4.
Figure 8.14 (a) Orthogonal reflectivity mapping of the array. The dashed lines are deduced from the phase-matching equation, indicating (−1,0) Au/air surface plasmon polaritons are excited. Inset: the SEM image of the array. (b) The corresponding reflectivity spectra extracted from the mapping at different incident angles. The dashed lines are the best fits by using coupled mode theory.
Figure 8.15 Graphical images of a sphere segment void (SSV) structure for different normalized thicknesses. For thickness below around 0.4 of the sphere diameter, there is a continuous top surface punctuated by a hexagonal array of sphere segment cavities. Between around 0.4 and 0.6 of the sphere diameter, this top surface is broken up by the “windows” that occur where the spheres touch in the template. Above around 0.6, the continuous top surface reforms.
Figure 8.16 (a) Schematic of surface and localized plasmons on nanostructured gold surfaces. Inset shows definition of normalized thickness
t
. (b) Typical dispersion of a Bragg plasmon; black lines indicate theoretical dispersion modeled using the Bragg scattering equation. (c) Mie plasmon dispersion; dashed black lines indicate guide to eye. Color scale in both images is dark gray for 0% plasmon absorption to white for 80% of incident light coupled into the plasmon mode.
Figure 8.17 Spatial intensity distributions at increasing thickness, with (right) field profiles from Mie theory. Vertical position of the maximum optical field for the
1
P
+
and
0
P modes with increasing normalized thickness (
t
) indicated by black arrows. Field orientations for rim (black) and void (gray) modes indicated by arrows.
Figure 8.18 The SERS process. (1) The impinging laser light,
ω
0
, excites plasmons at the metal surface; (2) these plasmons convey optical energy into the molecule; (3) the molecule undergoes Raman scattering taking up a vibrational quantum of energy (
ω
0
−
ω
sc
), Stokes scattering; (4) a plasmon at longer wavelength is produced; and (5) this plasmon decays away into an emitted photon,
ω
sc
, which is detected in the spectrometer.
Figure 8.20 (a) Experimental and computational (FDTD) transmission spectra for a hexagonal nanohole array with a periodicity of 400 nm and a circular hole shape. (Inset) The direction of (1,0) and (1,1) resonances. (b) Experimental spectra measured at nine different locations on a nanohole array substrate. (c) Time-averaged intensity map of the plasmonic field (
z
-component of the electric field) at
λ
= 422 and 672 nm. The FDTD result confirms the wavelength of the transmission peak at each interface. (d) A top-down view of the electric field intensity at the air/silver interface at
λ
= 422 nm.
Figure 8.21 (A) Experimental (a) and calculated (b) 600 nm SSV position-resolved absorption maps are integrated over a range of incident angles from 0° to 30° for direct comparison with SERS measurements taken on a microscope. The peak SERS signal for laser wavelengths of 633, 785, and 1064 nm is overlaid on each plot. The bright areas indicate absorption. Dashed lines are incident laser wavelength, and solid lines are for the 1571 cm
−1
Raman peak of benzenethiol at their absolute wavelengths red-shifted from the laser. The size of the circles is proportional to the intensity of the SERS peak and is relative to each other only for each respective laser excitation. (B) Fields of identified modes. The maximum E-field enhancement for the
1
P
+
mode is 60 while for the
1
P
−
mode it is about three times weaker. (C) SEM showing experimentally realized structure and (D) schematic of the tip mode.
Figure 8.22 SERS spectra recorded on a 600 nm diameter silver SSV substrate with a normalized thickness,
t
, of 0.7 after soaking in an ethanolic 10 mM benzenethiol solution for different times. The times in seconds are indicated for each spectrum. After the specified time, the substrate was washed with ethanol and dried under a stream of nitrogen. Spectra recorded with a 633 nm laser at 3 mW laser power with a single scan of 10 s. The spectra are NOT offset from each other. Inset: extracted peak height of the 1572 cm
−1
benzenethiol peak (squares) and the absolute intensity of the background at 2750 cm
−1
(circles).
Figure 8.23 (a) SPR calibration spectra of gold microhole arrays measured in air (RI = 1.0) and sucrose solution of RI = 1.3337, 1.3484, 1.3588, 1.3715, 1.3817, and 1.3942. The plasmon band shifts to longer wavelength with increasing refractive index. (b) Calibration curves of SPR sensors with sucrose solutions comparing the result for the nanohole array with an array of nanotriangles and a flat film. The calibration curve represents the average response from three independent samples.
Chapter 9: Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) of Electrode Surfaces
Figure 9.1 The working modes of SERS, TERS, and SHINERS: the bare gold NP contact mode (a), the TERS noncontact mode (b), and the SHINERS shell-isolated mode (c).
Figure 9.2 Schematic illustrations of four different experiments. (a) Contact with the chemical environment. (b) Electrical contact with the surface. (c) Contact with probe molecules. (d) NP isolation by an inert shell. (e) SERS and SHINERS spectra showing CO adsorption on a Pt(111) electrode in 0.1 M HClO
4
solution saturated with CO gas.
Figure 9.3 A 3D-FDTD simulation reveals the distribution of the optical electric field surrounding a 2 × 2 array of 55 nm Au@4 nm SiO
2
SHINs on a perfectly smooth gold surface. The shell-to-shell distance is 4 nm. Side view (a) and top view (b); the direction of incidence (a) and the polarization (b) of the 633 nm laser are also shown. (c) SHINERS spectra of Py adsorbed on a smooth Au surface modified by 55 nm Au@SiO
2
NPs with different silica shell thicknesses. (d) The shell thickness dependence of the integrated SHINERS intensity of Py (squares) and the corresponding 3D-FDTD calculation result (triangles).
Figure 9.4 General overview of SHINs synthesis.
Figure 9.5 HRTEM images of various SHINs. Au@SiO
2
NPs with a 55 nm spherical core (a), a 120 nm spherical core (b), a nanocube core (c), a nanorod core (d), a shell-isolated nanoparticle with a Ag core (e), and a 55 nm Au@SiO
2
NP with 20 nm silica shell (f). Also shown are SHINs with a gold core and a shell of SiO
2
(g), Al
2
O
3
(h), MnO
2
(i), and Ag
2
S (j).
Figure 9.6 SHINERS spectra of pyridine using SHINs with pinholes (a) and without pinholes (b) on a Si wafer, without pinholes on a Au(111) single-crystal electrode (c), and without pinholes on a smooth silver electrode (d). Pyridine readily adsorbs on gold and silver, but not on Si or silica.
Figure 9.7 CVs of Au(111)-(1 × 1) single-crystal bead electrodes unmodified (black lines) and modified (solid gray lines) with Au@SiO
2
NPs. The dotted gray traces were recorded with “as-prepared” NPs, while the solid gray lines represent data obtained with HER-SHINERS NPs. The voltammograms in the double-layer region are displayed with a magnification factor of 30. Solution: 0.1 M (a) H
2
SO
4
and (b) HClO
4
. Scan rate: 10 mV s
−1
.
Figure 9.8 (a) CVs obtained from Au(111), Au(100), and Au(110) electrodes in 1 mM pyridine + 0.1 M NaClO
4
using a Pt coil auxiliary electrode and a Ag/AgCl reference electrode. (b) SHINERS spectra of pyridine on Au(111) in the potential range −0.8 to 0.4 V. The dependence of Raman frequency (c) and normalized Raman intensity (d) on applied potential for the
ν
1
mode (data points connected by straight lines) are compared with surface concentration isotherms (bold curves).
Figure 9.9 (a) SHINERS spectra of pyridine adsorbed on Pt(111), Pt(100), and Pt(110) at 0.0 V. Solution: 10 mM pyridine + 0.1 M NaClO
4
. (b) SHINERS spectra of pyridine on Pt(110) at different applied potentials.
Figure 9.10 (A) Potential-dependent SHINERS spectra from Cu(100), Cu(111), and polycrystalline Cu in 0.75 mM BTA, 0.1 M H
2
SO
4
for the anodic sweep (a), (c), (e), and (g) and the cathodic sweep (b), (d), (f), and (h). Spectra are offset for clarity. Arrows indicate scan direction. Potential-dependent ratio of peak intensities for 1190/1140 cm
−1
bands for Cu(100) (i), Cu(111) (j), Cu(poly) (k), and roughened Cu(poly) (l) in 0.75 mM BTA, 0.1 M H
2
SO
4
. (B) Potential-dependent ratio of peak intensities for 1190/1140 cm
−1
bands for Cu(100) (a), Cu(111) (b), Cu(poly) (c), and roughened Cu(poly) (d) in 0.75 mM BTA, 0.1 M H
2
SO
4
.
Figure 9.11 (A) Potential-dependent Raman spectra of BMIBF
6
on Au(111) covered with Au@SiO
2
NPs. (B) Proposed interfacial structure of Au single-crystal electrode/imidazolium-based ionic liquid at different potential regions.
Figure 9.12 (a)
In situ
electrochemical SHINERS spectra of electrooxidation at Au(111), Au(100), and Au(110) electrode surfaces in 0.1 M NaClO
4
(pH ∼9). (b) Normalized SHINERS intensities of the stretching mode of AuO and the bending mode of AuOH at different potentials. CV of Au(111) electrode in 0.1 M NaClO
4
is presented (pH ∼9, scan rate is 2 mV s
−1
).
Figure 9.13 (a) SERS spectra of the Au/SHINs electrode immersed in a 0.1 M Na
2
S
2
O
3
electrolyte (pH = 10.0) between 5 and 10 h. (b) The normalized integrated band intensity as a function of immersion time,
I
D
t
, of the [Au(S
2
O
3
)
2
]
3−
complex at 382 cm
−1
, adsorbed sulfide at 316 cm
−1
, and polymeric sulfur at 460 cm
−1
.
Chapter 10: Plasmonics-Based Electrochemical Current and Impedance Imaging
Figure 10.1 Equivalent circuits used for modeling surface impedance. (a) Randles equivalent circuit, (b) two-component model with a resistor and capacitor in parallel, and (c) two-component model with a resistor and capacitor in series.
Figure 10.3 PECM images of fingerprint pattern. (a) Schematic illustration of PECM. (b) Cyclic voltammograms measured by the conventional EC method (red line) and by PECM technique (open circles) of a bare gold electrode. Note that for a close comparison between the two approaches, the cycle voltammogram from the PECM technique is averaged over the entire electrode surface. The electrolyte is 0.25 M phosphate buffer containing 10 mM Ru(NH
3
)
6
3+
, and the potential sweep rate is 0.1 V s
−1
