Functional Organic and Hybrid Nanostructured Materials E-Book
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- Herausgeber: Wiley-VCH Verlag GmbH & Co. KGaA
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
The first book to explore the potential of tunable functionalities in organic and hybrid nanostructured materials in a unified manner.
The highly experienced editor and a team of leading experts review the promising and enabling aspects of this exciting materials class, covering the design, synthesis and/or fabrication, properties and applications. The broad topical scope includes organic polymers, liquid crystals, gels, stimuli-responsive surfaces, hybrid membranes, metallic, semiconducting and carbon nanomaterials, thermoelectric materials, metal-organic frameworks, luminescent and photochromic materials, and chiral and self-healing materials.
For materials scientists, nanotechnologists as well as organic, inorganic, solid state and polymer chemists.
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Seitenzahl: 1168
Veröffentlichungsjahr: 2018
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Table of Contents
Cover
Title Page
Copyright
Preface
Chapter 1: Controllable Self-Assembly of One-Dimensional Nanocrystals
1.1 Introduction
1.2 Assembly Strategies
1.3 Properties and Applications
1.4 Perspectives and Challenges
References
Chapter 2: Self-Assembled Graphene Nanostructures and Their Applications
2.1 Introduction
2.2 State-of-the-Art Self-Assembly Strategies of Graphene Nanostructures
2.3 Applications of Self-Assembled Graphene Nanostructures
2.4 Outlook
References
Chapter 3: Photochromic Organic and Hybrid Self-Organized Nanostructured Materials: From Design to Applications
3.1 Introduction
3.2 Photochromic Organic and Hybrid Nanoparticles
3.3 Photochromic Carbon-Based Nanomaterials
3.4 Photochromic Chiral Liquid-Crystalline Nanostructured Materials
3.5 Summary and Perspective
Acknowledgments
References
Chapter 4: Photoresponsive Host–Guest Nanostructured Supramolecular Systems
4.1 Introduction
4.2 Photoresponsive Supramolecular Polymers and Their Assemblies
4.3 Photoresponsive Host–Guest Systems Immobilized on Surfaces
4.4 Conclusions and Prospects
Acknowledgments
Abbreviations
References
Chapter 5: π-Electronic Ion-Pairing Assemblies Providing Nanostructured Materials
5.1 Introduction
5.2 Nanostructures Based on Self-Assembling π-Electronic Charged Species
5.3 Ionic Liquid Crystals Based on π-Electronic Charged Species
5.4 Assemblies Based on Genuine π-Electronic Ions
5.5 Ion-Pairing Assemblies Based on π-Electronic Anion-Responsive Molecules
5.6 Conclusion
References
Chapter 6: Stimuli-Responsive Nanostructured Surfaces for Biomedical Applications
6.1 Introduction
6.2 Thin-Film Formation by Assembly on Surfaces
6.3 Lithographic Techniques
6.4 Electrically Driven Nanostructured Responsive Surfaces
6.5 Photodriven Nanostructured Responsive Surfaces
6.6 Thermo-Driven Nanostructured Responsive Surfaces
6.7 Chemically Controlled Nanostructured Surfaces
6.8 Concluding Remarks and Perspectives
References
Chapter 7: Stimuli-Directed Self-Organized One-Dimensional Organic Semiconducting Nanostructures for Optoelectronic Applications
7.1 Introduction to Discotic Liquid Crystals
7.2 Application of Columnar Phases in Organic Electronics
7.3 Alignment of Col LC Phases through Different Stimuli
7.4 Conclusions and Perspective
References
Chapter 8: Stimuli-Directed Helical Axis Switching in Chiral Liquid Crystal Nanostructures
8.1 Introduction
8.2 Self-Organized Chiral Nematic LCs
8.3 Field-Induced Helical Axis Switching: Dielectric/Magnetic Torque and Flexoelectric Effect
8.4 Optically Driven Helical Axis Switching
8.5 Confinement Mediated Helical Axis Change
8.6 Helical Axis Switching in CLC Polymer Composites
8.7 Summary and Outlook
References
Chapter 9: Electrically Driven Self-Organized Chiral Liquid-Crystalline Nanostructures: Organic Molecular Photonic Crystal with Tunable Bandgap
9.1 Introduction
9.2 Self-Assembled Photonic Crystals
9.3 Electric-Field-Induced, Self-Assembled, Tunable Photonic Crystals
9.4 Conclusions
Acknowledgments
References
Chapter 10: Nanostructured Organic–Inorganic Hybrid Membranes for High-Temperature Proton Exchange Membrane Fuel Cells
10.1 Introduction
10.2 Nanostructured Nafion-Based Hybrid Membranes
10.3 Hydrocarbon Polymer-Based Hybrid Membranes
10.4 Nanostructured PBI-Based Hybrid Membranes
10.5 Alternative PA-Doped Hybrid Membranes
10.6 Conclusions and Outlook
Acknowledgment
References
Chapter 11: Two-Dimensional Organic and Hybrid Porous Frameworks as Novel Electronic Material Systems: Electronic Properties and Advanced Energy Conversion Functions
11.1 Introduction
11.2 Electronic Function Control in Two-Dimensional Organic and Hybrid Porous Frameworks
11.3 Electronic Functions in 2D Organic Frameworks and Applications
11.4 Electronic Functions in Two-Dimensional Hybrid Porous Frameworks and Applications
11.5 Concluding Remarks
Acknowledgments
References
Chapter 12: Organic/Inorganic Hybrid Nanostructured Materials for Thermoelectric Energy Conversion
12.1 Introduction
12.2 Organic/Inorganic Thermoelectric Nanostructured Materials
12.3 Surface-Transfer Doping of Organic/Inorganic Thermoelectric Nanocomposites
12.4 Outlook
Abbreviations
References
Chapter 13: Hybrid Organic–Nitride Semiconductor Nanostructures for Biosensor Applications
13.1 Introduction
13.2 AlGaN/GaN Functionality and Active Region
13.3 Device Fabrication
13.4 Au-Linking and Thiol Group Employment
13.5 Oxidation of Nitride Surfaces in Preparation for Functionalization
13.6 Silanization of Oxidized Nitride Surfaces
13.7 DNA Immobilization and Hybridization
13.8 Biotin–Streptavidin
13.9 ImmunoFETs
13.10 Summary and Outlook
References
Chapter 14: Polymer–Nanomaterial Composites for Optoacoustic Conversion
14.1 Introduction
14.2 Optoacoustic Conversion in Nanomaterials
14.3 Polymer–Nanomaterial Composite for Optoacoustic Conversion
14.4 Applications of Optoacoustic Conversion in Nanocomposites
14.5 Outlook and Future Direction
References
Chapter 15: Functional Nanostructured Conjugated Polymers
15.1 Introduction
15.2 DiLCPAs with Blue and Green LPL
15.3 Lyotropic N* diLCPAs with Green CPL
15.4 Dynamic Switching of CPL by Selective Reflection through a Thermotropic N*-LC
15.5 Liquid-Crystallinity-Enforced Chirality Transfer from Chiral MonoLCPA to Achiral LCPPE
15.6 Conclusions and Outlook
Acknowledgments
References
Chapter 16: Nanostructured Self-Organized Heliconical Nematic Liquid Crystals: Twist-Bend Nematic Phase
16.1 Introduction
16.2 Characterization of Ntb Phase
16.3 Ntb Phase in Different Classes of Liquid Crystal Compounds
16.4 Ntb Phase in Mixtures
16.5 Heliconical Cholesteric Phase
16.6 Summary and Outlook
References
Index
End User License Agreement
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Guide
Cover
Table of Contents
Preface
Begin Reading
List of Illustrations
Chapter 1: Controllable Self-Assembly of One-Dimensional Nanocrystals
Figure 1.1 Assembly of Au NRs on a patterned solid substrate. (a) Scheme of capillary assembly of Au NRs onto substrates with geometrical patterns. (b) SEM images of Au NRs patterns by topographically templated capillary assembly. Scale bar: 250 nm.
Figure 1.2 Schematic illustration of Au NRs assembled in an end-to-end or a side-by-side manner within cylindrically confined nanodomains of BCPs.
Figure 1.3 Scheme of assembling CdSe NRs using a patterned template generated by phase separation of BCPs on the substrate. (a) Floating template on an aqueous solution of PEO-capped CdSe NRs. (b) PEO-capped CdSe NRs within the channels and on the surface of PS template. (c) CdSe NRs isolated in channels after rinsing the template.
Figure 1.4 (a) Scheme of experimental setup for electric-field-assisted assembly of CdSe NRs. (b) TEM image of the “self-corralling” of CdSe NRs in PMMA. Scale bar: 100 nm.
Figure 1.5 (a) SEM image of ribbons of magnetic Janus rods. Scale bar, 5 µm. (b) Deformation modes of ribbon: images accompanied by schematic illustrations. Scale bar: 2 µm. (c) End-on view of a ribbon accompanied by schematic illustrations. Scale bar: 2 µm. (d-1) Single ring forms from linear ribbon through a C-shaped intermediate. (d-2) Two ring forms from a linear ribbon through the S-shaped intermediate. (d-3) Three rings formed from a linear ribbon. Scale bar: 4 µm. (e-1–e-7) Deformation of ring to form a ribbon in response to a small field. Scale bar: 2 µm.
Figure 1.6 (a,b) Scheme of flow assembly to form (a) a parallel NW array and (b) a multiple crossed NWs array using fluidic channel. (c) SEM image of parallel arrays of indium phosphide NWs. (d) SEM image of crossed arrays of indium phosphide NW. Scale bar: 2 µm.
Figure 1.7 (a,b) TEM images of linear binary assemblies of (a) Au NS and (b) Au NRs with Au NWs. (c,d) SEM images of (c) Au NSs and (d) Au NRs embedded in Au NW bundles. Scale bar: 200 nm.
Figure 1.8 (a,b) LB NW assembly process at the (a) initial and (b) final compression stage. (c,d) SEM images of Ag NWs monolayer at different magnifications.
Figure 1.9 (a) SEM mages of vertically oriented CdS NRs with progressive zoom from left to right. (b) Ninety-six percent vertical alignment of CdS NRs on a device scale (1 cm
2
).
Figure 1.10 (a) Schematic illustration of the formation of superparticles form CdSe/CdS NRs. (b–p) TEM images of superparticles made from NRs of length 28 nm and width 6.7 nm.
Figure 1.11 Self-assembly of polymer-tethered Au NRs in selective solvents. (a–e) SEM images of self-assembled Au NR structures: rings (a) and chains (b) formed in dimethyl formamide (DMF)/water mixture at water content of 6 and 20 wt%, respectively; side-to-side bundles of NRs (c) and NSs (d) formed on tetrahydrofuran (THF)/water mixture at 6 and 20 wt%, respectively; bundled NR chains obtained in DMF/THF/water mixture at the weight ratio of liquids 42.5 : 42.5 : 10.
Figure 1.12 (a) Curved surface of spherical particles (left) cannot support an equal number of idealized oligonucleotide interactions without DNA deformation as flat surfaces of anisotropic nanostructures (middle and right). (b,c) TEM images of (a) hexagonal 3D layer of Au NRs and (c) 1D lamellar assemblies of Au triangular nanoprisms by DNA directed assembly. The inset shows the scheme of the NC array.
Figure 1.13 (a) Exciton theory picture of the essence of coupled longitudinal plasmon excitation in dimers of NRs. (b,c) Simulated (b) longitudinal and (c) transverse plasmon extinction efficiency spectra of Au NRs (length of 80 nm and width of 20 nm) assembled in a side-by-side orientation as a function of the inter-nanorod center-to-center distance.
Figure 1.14 PL spectra of laterally and vertically aligned and disordered CdSe/CdS core–shell NRs with an aspect ratio of 10. The insets show the corresponding images of the laser backscattering and confocal setup and TEM images of the respective regions.
Chapter 2: Self-Assembled Graphene Nanostructures and Their Applications
Figure 2.1 Langmuir–Blodgett assembly of GO single layers. (a–d) SEM images showing the collected GO monolayers on a silicon wafer at different regions of the isotherm. The packing density was continuously tuned: (a) dilute monolayer of isolated flat sheets, (b) monolayer of close-packed GO, (c) overpacked monolayer with sheets folded at interconnecting edges, and (d) overpacked monolayer with folded and partially overlapped sheets interlocking with each other. (e) Isothermal surface pressure vs. area plot showing the corresponding regions a–d at which the monolayers were collected. Scale bars in a–d represent 20 µm.
Figure 2.2 Schematic illustration of the generation of graphene thin films using an electrostatic layer-by-layer (LbL) assembly between oppositely charged graphene nanosheets and subsequent thermal treatment.
Figure 2.3 Morphology and structure of GO paper. (a–d) Digital camera images of GO paper: (a) 1 mm thick; (b) folded, 5-mm-thick semitransparent film; (c) folded, 25-mm-thick strip; (d) strip after fracture from tensile loading. (e) Side-view SEM images of a 10-mm-thick sample.
Figure 2.4 (a) Photographs of a 2 mg mL
−1
homogeneous GO aqueous dispersion before and after hydrothermal reduction. (b) Photographs of a strong graphene hydrogel allowing easy handling and weight support. (c,d) Scanning electron microscopy (SEM) images with different magnifications of the graphene hydrogel's interior microstructures.
Figure 2.5 (a) Polarized optical microscopy image of GO LCs with volume fractions of 0.76%. (b) A long GO fiber wound on a Teflon drum with a diameter of 2 cm. (c) SEM image of a knotted GO fiber. (d) A Chinese character pattern knitted in the cotton network (white) using two graphene fibers (black).
Figure 2.6 (a) Schematic of the synthesis of carbon hybrid microfibres. The inset shows the optical image of the wet fiber. (b–d) SEM images of the full view, outer surface, and fracture end area of the rGO fiber. (e–g) SEM images of the cross-section of a CNT–rGO fiber. The square area in (e) is shown expanded in (f).
Figure 2.7 (a) Schematic diagram for the green synthesis of graphene–CNT hybrid aerogels. SEM images of the resulting graphene–MWCNT (b,c) and graphene–c-MWCNT (d, c) hybrid aerogels.
Figure 2.8 Schematics showing the fabrication of (a) macroporous PSS-G/PVA) monoliths using ice-segregation-induced self-assembly and (b) hollow PSS-G microspheres with colloidal templating method. SEM images of (c) longitudinal sections and (e) cross-sections of a PSS-G/PVA freeze-dried monolith. (d) SEM images of PSS-G-coated PAH-functionalized polystyrene beads (PS/PAH/PSS-G). The inset shows the curled edge of adsorbed PSS-G sheet. (f) SEM images of aggregated film of PAH/PSS-G hollow microsphere. The inset in f shows a single hollow microsphere. Scale bar: c,e = 10 µm; d = 500 nm; f = 1 µm.
Figure 2.9 Schematic illustration of the fabrication of the 3D porous electrocatalyst 3DGN/CoAl-NS.
Figure 2.10 (a) Schematic illustration of the fabrication procedure of rGO–PW multilayer films. (b) Optical images of a (PAH/GO/PAH/PW)
6
multilayer film prepared on flexible PET substrate after 6 h of UV photoreduction. (c) Cross-section of the photodetector device. (d) Photocurrent response of the photodetector versus time with chopped irradiation at a bias voltage of 10 V.
Chapter 3: Photochromic Organic and Hybrid Self-Organized Nanostructured Materials: From Design to Applications
Figure 3.1 Photochromism of (a) azobenzene, (b) dithienylcyclopentene, and (c) spiropyran.
Figure 3.2 Effect of the spacer length on the relative yield of azobenzene isomerization on the surface of gold nanoparticles. The relative yield, Φ
sltn
/Φ
NP
, has been defined as the ratio of the azobenzene isomerization quantum yield in solution and on the nanoparticle surface.
Figure 3.3 (a) Schematic representation of the reversible trapping of polar molecules during light-induced self-assembly of photoresponsive nanoparticles. (b) Electron micrographs (at different magnifications) of colloidal crystals prepared by exposing 6-nm gold nanoparticles to ultraviolet light (scale bar in the inset, 200 nm). (c) Schematic representation of how the reversible formation of confined spaces can accelerate a chemical reaction.
Figure 3.4 Light-controlled self-assembly of non-photoresponsive nanoparticles. (a) Light-induced disassembly of MUA (11-mercaptoundecanoic acid)-coated nanoparticles in methanol. The particles spontaneously reassemble in the dark.
Figure 3.5 Photoinduced fluorescence modulation in QDs functionalized with well-defined monolayers of SP switches. (a) Structural transformation and visual changes accompanying UV and visible light irradiation. (b) Modulation of fluorescence intensity with alternating UV and visible light irradiation.
Figure 3.6 The surfaces of QDs are coated by amphiphilic comb polymers with pendant photochromic moieties. Fluorescent Alexa 647 dye was adsorbed via hydrophobic interactions between the aliphatic chains with the lipophilic ligands on the QD surface. The luminescence of the QD is modulated by the photoconversion of the photochromic component while the Alexa647 acts as the internal fluorescence standard.
Figure 3.7 Schematic diagram of the light-stimulated operation of Azo-MSNs. Azo-MSNs were made by co-condensing azo linkers inside the cylindrical pores of MSNs. Exciting Azo-MSNs at a wavelength where both isomers absorb promotes continual large-amplitude isomerization motion.
Figure 3.8 Two approaches to the operation and function of the “azobenzene-modified MCM-41 carrying nanovalves.” Py-β-CD or β-CD threads onto the
trans
-azobenzene stalks to seal the nanopores. Upon UV irradiation (351 nm), the isomerization of
trans
- to
cis-
azobenzene units leads to the dissociation of Py-β-CD or β-CD rings from the stalks, thus opening the gates to the nanopores and releasing the cargo.
Figure 3.9 (a) Molecular bridges between the ends of an individual SWNT electrode. (b) Switching between conjugated and nonconjugated molecular structures.
Figure 3.10 Reaction scheme for photochemical charging and thermal activation of energy release in Azo-SWCNTs.
Figure 3.11 (a) Schematic representation of the aggregation and dispersion of spiropyran-modified MWNTs in response to light and their influence on the activity of HRP. (b) The reversible change between the spiro form (SP, yellow) and the ring-opened merocyanine form (MC, purple) by exposure to UV or visible light.
Figure 3.12 (a) Structures and space-filling models of
trans
- and
cis
-azobenzene. (b) Schematic representation of a graphene–azobenzene junction.
Figure 3.13 Reduced graphene oxide/hyaluronic acid-spiropyran (rGO/HA-SP) used for
in vivo
fluorescence imaging. (a) Schematic illustration of rGO/HA-SP as fluorescent probe. (b)
In vivo
fluorescence images of rGO/HA-SP in mice after tail vein injection.
Figure 3.14 (a) Molecular structure of a photochromic chiral switch. (b) Schematic description of reversible tuning of self-organized helical superstructures with chiral switch and UCNPs upon irradiation with an NIR laser at different power densities. (c, d) Reflection colors of the CLCs with 3 wt% chiral molecular switch 4 and 1.5 wt% UCNPs in a 10-µm-thick planar cell at room temperature, taken from a polarized reflective mode microscope (c) upon irradiation with 980-nm NIR laser at high power density and followed by (d) irradiation with 980-nm NIR laser at low power density.
Figure 3.15 (a) Schematic description on the structure of the (core–multishell nanotransducers (UCNPs)) and the reversible switching process of the thermally irreversible chiral switch (
S
,
S
)
-8
triggered by NIR light of different wavelengths. Note that 808-nm NIR light drives the open form to its closed form, whereas the reverse process occurs under 980-nm NIR irradiation. (b) Schematic mechanism of wavelength-selective NIR-light-triggered reversible handedness inversion of the self-organized helical superstructure incorporated with chiral diarylethene switch and core–multishell nanotransducers.
Figure 3.16 (a) Typical textures and (b) Kossel diagrams of BPs doped with 0.07 wt% M-GNRs in 10 mm-thick cells with planar alignment upon cooling, where the typical diagrams indicate phase transitions from isotropic to BP II followed by BP II to BP I transition. (c) Schematic illustration of the NIR-light tunable self-organized soft photonic superstructures. The yellow dots represent the cross section of GNRs in the BP matrices.
Figure 3.17 (a) Optically tunable omnidirectional laser in the 3D cholesteric liquid-crystalline microshells.
Chapter 4: Photoresponsive Host–Guest Nanostructured Supramolecular Systems
Scheme 4.1 Cartoon representation of the reversible self-assembly/disassembly of a host–guest system.
Figure 4.1 Formation of linear and net-like supramolecular polymers from the triple-functional molecules and their photoinduced sol–gel transformation.
Figure 4.3 (a) Schematic representation of the formation of a linear supramolecular polymer and (b) its reversible conversion with supramolecular network.
Figure 4.3 (a) Schematic presentation of phototriggered supramolecular polymerization. (b) Chemical structures of molecules
4
and
5
.
Figure 4.4 (a) Supramolecular nanotructured polymer based on host–guest interaction between BSC4 and a pseudo[3]rotaxane. (b) SEM and cryo-TEM images of
SP*
and irradiated
SP*
.
Figure 4.5 A facile photocontrollable, reversible disassembly/reassembly process of a polypseudorotaxane (PPR)-based hydrogel.
Figure 4.6 (a) Chemical structures of AAPs
1–3
. Schematic representation of AAP- and CD-based supramolecular systems including (b) CDV and (c) CDAuNP.
Figure 4.7 (a, b) Chemical structures of polymeric gels with the photoresponsive properties. (c) Photographs of photoresponsive dry-type xerogel actuators under irradiation of UV light.
Figure 4.8 (a) Chemical structures of the CB[8] and guest molecules. (b) Schematic presentation of a cross-linked supramolecular polymer.
Figure 4.9 (a) Formation and response of the dual-stimuli respone supramolecular polymers. (b) Supramolecular sol–gel transformation and its dual-mode response to heat.
Figure 4.10 Preparation of the supramolecular, noncovalent linear polymer (NCP) and net-like polymer (NNP) by host–guest interactions between coumarin derivatives
10
(a) and
11
(b) and γ-CD, respectively, and the photoswitching between noncovalent polymers and their corresponding covalent polymers.
Figure 4.11 Photoresponsive supramolecular hydrogel based on host–guest interaction between a deoxycholic acid-modified β-CD and an azobenzene-branched poly(acrylic acid) copolymer.
Figure 4.12 (a) Chemical structures of the polymers. (b) Schematic presentation and photographs of the reversible sol–gel transition. (c) Schematic presentation of red-light-induced protein release.
Figure 4.13 (a) Chemical structure of the copolymers
17
and
18
. (b) Three-component host–guest complex obtained using a bottom-up hierarchical assembly strategy.
Figure 4.14 (a) Layer-by-layer self-assembly of polyelectrolytes. (b) CB[8]-containing multilayer films. (c) Reversible binding and release of a guest molecule in photoresponsive films. (d) Chemical structures of host/guest molecules.
Figure 4.15 Two types of noncovalently cross-linked branched supramolecular polymers.
Figure 4.16 A rapidly self-healing supramolecular hydrogel.
Figure 4.17 Photocontrolled ternary complex for DNA capture or release.
Figure 4.18 (a) Reversible aggregation of BPs. (b) Light-responsive host–guest recognition between CD and azobenzene that triggers the aggregation.
Figure 4.19 (a) Chemical structures of host and guest molecules. (b) Schematic presentation of the dual-responsive self-assembly and disassembly of the supramolecular nanostructured amphiphile.
Figure 4.20 Fluorescence photomodulation of supramolecular self-assemblies formed by sulfonatocalixarenes and tetraphenylethenes.
Figure 4.21 Chemical structures of
30
,
31
and schematic representation of the photoresponsive self-assembly.
Figure 4.22 Dual-responsive controlled supramolecular vesicle for calcein molecule release.
Figure 4.23 Scheme of a photoswitchable supramolecular catalysis based on Au-surface-grafted host–guest complex between a β-CD dimer and an azobenzene derivative.
Figure 4.24 (a) Chemical structures of host and guest molecules. (b) Photoreversible inclusion of
trans
-
36
in α-CD-coated AuNPs. (c) Light-responsive phase transfer between the water and toluene phases.
Figure 4.25 Photoresponsive aggregation and dispersion of β-CD-functionalized silica nanoparticles (β-CD-NPs) with a linear monoditopic azobenzene linker.
Figure 4.26 (a) Hybrid vesicle MNP-CDV based on CD. (b) Azobenzene-containing photoresponsive guest molecule
38
as a cross-linker.
Figure 4.27 (a) Stepwise formation of a ternary complex and its assembly and disassembly upon irradiation. (b) Formation of HRC and its light-induced disassembly.
Figure 4.28 Schematic presentation of the dual-mode controlled self-assembly of TiO
2
NPs through CB[8]-enhanced radical cation dimerization interaction.
Chapter 5: π-Electronic Ion-Pairing Assemblies Providing Nanostructured Materials
Figure 5.1 Three representative modes of π-electronic ion pairs: (a) a pair of electronically neutral π-electronic systems possessing a charged part(s) and its corresponding counterion(s); (b) a pair of charged π-electronic systems; and (c) π-electronic receptor–ion complex and its counterion(s).
Figure 5.2 Conceptual diagram of the assembling modes comprising π-electronic charged species.
Figure 5.3 (a) Amphiphilic HBC
1
. (b)(i) TEM image of the nanofibers of
1
obtained from a DMSO–ethanol solution, (ii) SEM image of the nanofibers of
1
obtained from an aqueous solution, and (iii) TEM image of the nanofibers of
1
from an aqueous solution in a hexane-saturated chamber.
Figure 5.4 (a) Amphiphilic Pt
II
complexes
2–5
possessing different alkyl substituents. (b) TEM images (negatively stained) of (i)
2
, (ii)
3
, (iii)
4
, and (iv)
5
from aqueous solutions. (c)(i) An assembling mode in sheet structures and (ii) an assembling mode in fiber structures.
Figure 5.5 (a) Schematic structure, (b) confocal fluorescence microscopy, and (c) assembling mode of phosphonium ion pair
6
.
Figure 5.6 (a) BNAX salt with bromide
7
, obtained from the drop-casting of a MeOH solution (5 × 10
−4
M).
Figure 5.7 (a)(i) Ionic porphyrins
15
and
16
(X, X´ = Cl
−
, OH
−
, H
2
O) and (ii) TEM image of the nanotubes obtained from an aqueous solution (pH 2) of
15
·
16
.
Figure 5.8 (a)(i) PQP
+
salts
19
and
20
, (ii) nanofibers of
19
in MeOH (10
−1
M), (iii) nanotubes of
20
in MeOH (10
−1
M), and the assembling modes of (iv)
19
, and (v)
20
.
Figure 5.9 (a) Imidazolium-based ion pairs
23
and
24
. (b) Ammonium-based ion pairs
25–27
. (c) Phosphonium-based ion pairs
28–30
. (d) Imidazolium-appended triphenylene ion pairs
31–33
. (e) Pyridinium tripodal ion pairs
34–36
. (f) Azobenzene-modified sulfonate with ammonium cations
37
and
38
.
Figure 5.10 (a) π-Electronic sulfonates
39–41
, along with (b) ammonium
42–48
and imidazolium
49–51
cations for ion-pairing assemblies.
Figure 5.11 (a)(i) Ion pairs of dodecyl-substituted BNAX
52
and
53
and (ii) schematic representation of aggregation mode of
53
. (b)(i) Ion pairs of PQP cation with alkyl-substituted sulfonates
54
and
55
, (ii) polarized optical microscopy (POM) image, and (iii) 2D WAXS of
55
at 30 °C.
Figure 5.12 (a) Ion pairs of PCCp
−
with various alkylammonium cations
56–59.
(b) (i,ii) Single-crystal X-ray structure of
57
as the representative packing modes and the stacking mode of a space-filling model, viewed from the side as indicated by the arrow in (i) (dark gray and gray represent PCCp
−
and BuMe
3
N
+
, respectively). (c) (i) POM and (ii) synchrotron XRD of
59
at 70 °C upon first cooling.
Figure 5.13 (a)(i) PMCp
−
-based π-electronic ion pairs
60
and
61
and (ii) π-electronic ion pair PCCp
−
·Ch
+
62
. (b)(i) A representative packing mode of the single-crystal X-ray structure of
62
, as the top view of one layer, and (ii,iii) the space-filling model, viewed from the side as indicated by the arrows in (i) (magenta and cyan represent PCCp
−
and Ch
+
, respectively).
Figure 5.14 (a) Chemical structure and TBAOH-assisted deprotonation of dipyrrolylnitrophenol
63
. (b) Single-crystal X-ray structures of (i)
63
−
·TBA
+
and (ii)
63
−
·15-crown-5·Na
+
as side views represented by space-filling models (magenta and cyan parts represent
63
−
and corresponding cationic species, respectively).
Figure 5.15 Chemical structure and TBAOH-assisted deprotonation of BF
2
complexes of
meso
-hydroxy dipyrrolyldiketones
64
and
65
.
Figure 5.16 (a) Schematic representation of the formation of a receptor–anion complex as a planar anion. (b)(i) Triazole-based macrocycle
66
, (ii) triazole-based acyclic anion-responsive π-electronic molecule
67
, and (iii) solid-state packing diagram of
67
·Cl
−
-TBA
+
.
Figure 5.17 (a) Pyrrole-based anion-responsive molecule
68
and the corresponding anion-binding mode. (b) Representative derivatives
69–79
.
Figure 5.18 Top and side-packing views from single-crystal X-ray analysis of (a)
69
·Cl
−
-TPA
+
, (b)
73
·Cl
−
-TPA
+
, (c)
76
·Cl
−
-TBA
+
, (d)
69
·Cl
−
-TATA
+
, (e)
73
·Cl
−
-TATA
+
, and (f)
76
·Cl
−
-TATA
+
.
Figure 5.19 (a) AFM image in the tapping mode of
70
, taken from the octane gel (10 mg mL
−1
) (inset: photograph of the gel under UV
365 nm
light). (b) SEM image at 20 °C (inset: photograph of the gel under UV
365 nm
light). (c)(i) XRD pattern at 25 °C and (ii) a proposed assembled model of the xerogel of
70
·Cl
−
-TATA
+
derived from octane.
Figure 5.20 (i) POM images and (ii) XRD patterns and proposed assembled models of (a)
71
·Cl
−
-TATA
+
at (i) 70 °C and (ii) 101 °C, (b)
74
·Cl
−
-TATA
+
at (i) 150 °C and (ii) 101 °C, (c)
70
·Cl
−
-TATA
+
at (i) 50 °C and (ii) 101 °C, and (d)
77
·Cl
−
-TBA
+
at (i,ii) 62 °C upon cooling from Iso.
Figure 5.21 (a) Dications
80
2+
and
81
2+
and positively charged receptor–Cl
−
complexes. (b) POM texture, and (c) synchrotron XRD pattern of
70
·Cl
−
-
81
2+
·Cl
−
at 115 °C upon cooling from Iso.
Figure 5.22 (a)(i) Modified cations
82
+
–
84
+
, (ii) POM texture of
69
·Cl
−
-
83
+
at 125 °C (second heating), and (iii) synchrotron XRD pattern of
69
·Cl
−
-
83
+
at 90 °C (second heating). (b)(i) Modified anions
85
−
–
87
−
, (ii) POM texture of
70
·
85
−
-TBA
+
at 80.5 °C upon cooling from Iso, and (iii) synchrotron XRD pattern of
69
·
85
−
-TBA
+
in the solid state at room temperature.
Chapter 6: Stimuli-Responsive Nanostructured Surfaces for Biomedical Applications
Figure 6.1 (a) Cartoon representation of the molecular structure of a SAM and their representation (b) in a low-density SAM, (c) multicomponent SAM, and (d) when employed for orthogonal functionalization of a substrate exposing two different materials at its surface.
Figure 6.2 (a) Layer-by-layer assembly of thin films using different assembly approaches.
Figure 6.3 Scheme representing the main lithographic techniques used to create stimuli-responsive nanostructured surfaces.
Figure 6.4 Scheme representing micropatterned surface for controlling cell detachment. (a) Cross-sectional view of the ITO electrodes functionalized with RGD peptide, showing cell detachment from one of the electrodes upon applying a negative potential. (b) Top view of the ITO electrodes, showing contact pads for potentiostat connection.
Figure 6.5 Scheme illustrating two different approaches, using either (a) a charged backbone [54] or (b) charged neighbor molecules, to electrically control the exposure and concealment of RGD, and thus promote or inhibit cell adhesion [55].
Figure 6.6 (a) Schematic illustration of a multilayer film on a gold electrode. (b) Schematic diagram of a DNA nanodevice, where the OFF state reversibly changes to the ON state in the presence of complementary DNA, resulting in the generation of fluorescence (F representing a fluorophore and Q representing a quencher).
Figure 6.7 Schematic representation of reversible change of pore size and drug release rate in an electrically responsive nanoporous membrane.
Figure 6.8 (a) Schematic representation of a photoresponsive surface, showing an azide-terminated SAM that allows covalent immobilization, via click chemistry, of a linker containing a photocleavable nitrobenzyl group and additional immobilization of a bioactive molecule exhibiting an amide group. (b) Schematic representation of selective detachment of bioactive molecules by localized exposure to light.
Figure 6.9 (a) Schematic representation of a photoresponsive surface formed of mixed monolayers of PEG and c(RGDfK)-azobenzene [82]. (b) Structure of c(RGDfK)-azobenzene immobilized on a glass substrate.
Figure 6.10 Schematic representation of a reversible light-responsive surface, which employs host–guest chemistry to promote the release of cells. HeLa cells cultured on the substrate are detached when
trans
-azobenzene is transformed to
cis
-azobenzene upon UV irradiation.
Figure 6.11 Schematic representation of reversible photoisomerization of covalent frameworks (COFs), based on polycondensation of diboronic acid (ABBA).
Figure 6.12 Schematic representation of reversible guest release in the BTB-NG host
–
guest system, triggered by a thermal stimulus. NG, the guest species, is released when BTB switches from a compact (closed) structure to a low-density (open) structure at the HOPG interface.
Figure 6.13 Illustration of a nanopatterned PNIPAM surface, which switches from a state where a biomolecule attached to the surface is exposed to a state where the biomolecule is hidden. It occurs as a result of changes in temperature that induces conformational changes of the PNIPAM brushes.
Figure 6.14 Schematic representation of a thermoresponsive surface, showing attachment of bacteria followed by biocidal exposure and further release of killed bacteria from the surface.
Figure 6.15 Illustration of a thermoresponsive surface containing RGD cell-adhesive peptides for interaction with cells.
Figure 6.16 (a) Schematic representation of the interaction between an antibody and an antigen on a thermoresponsive bioelectrode. The system switches reversibly in response to temperature changes from an OFF state, where access of the antigen to the immobilized antibody is denied, to an ON state, where access is accepted. (b) Impedance values at distinct temperatures.
Figure 6.17 Illustration of a reversible switchable surface in which immobilized bioactive ligands are accessible or not to cells due to the interaction of complementary zipper molecules.
Figure 6.18 Schematic representation of a surface functionalization strategy, starting from PHEMA-
g
-PBA, followed by introduction of RGD-PGAPMA, which in turn is reversibly removed from the matrix when glucose or fructose is added due to a specific molecule-exchange process. This functionalized surface then allows reversible cell adhesion, triggered by the addition of glucose or fructose.
Figure 6.19 Illustration of (a) a responsive surface composed of SiN arrays coated with polyAAPBA and transmission electron microscopy image showing the thickness of polyAAPBA and SiN. (b) Reversible switching between cell capture and release upon changes in pH and glucose concentration, on the same surface.
Figure 6.20 Illustration of (a) reversible binding between aptamer and thrombin in response to a change in pH and (b) reversible volume change in the pH-responsive hydrogel P(AAc-
co
-AAM). (c) Capture and release system in a biphasic microfluidic chamber, showing binding of target molecules to the aptamers attached to polymeric fins at pH 7.2 and release of target molecules to the bottom layer upon pH change to 3.2.
Figure 6.21 Illustration of (a) the pH-responsive polymer PEG-PAA-
g
-CD assembly on azobenzene-based SAM via host
–
guest interactions between azobenzenes and cyclodextrins. (b) Reversible surface switching from a state where adsorption of protein cytochrome c occurs to a state where the protein is released in response to structural changes of PAA chains induced by pH variation.
Figure 6.22 Illustration of a pH-responsive surface based on SiN arrays and PMAA polymer. It shows infiltration of lysosymes at acidic pH, attachment of bacteria at neutral pH, and release of killed bacteria at basic pH, when the polymer chains are in fully extended state.
Chapter 7: Stimuli-Directed Self-Organized One-Dimensional Organic Semiconducting Nanostructures for Optoelectronic Applications
Figure 7.1 (a) General template of a DLC. (b) Commonly used cores for p-type DLCs. (c) Commonly used cores for n-type DLCs.
Figure 7.2 (a) Schematics of discotic nematic (
N
D
) phase. (b) Columnar nematic (
N
C
) phase. (c) Nematic lateral (
N
L
) phase.
Figure 7.3 (a) Schematics of columnar hexagonal (Col
h
) phase. (b) Square columnar (Col
sq
) phase. (c) Columnar rectangular (Col
r
) phase. (d) Columnar oblique (Col
ob
) phase. (e) Columnar plastic (Col
p
) phase. (f) Columnar helical (H) phase. (g) Columnar lamellar (Col
L
) phase.
Figure 7.4 (a) Schematic showing the device structure of organic heterojunction solar cell. (b) The corresponding energy-level diagram showing charge separation and transport.
Figure 7.7 Schematic representations of (a) homeotropic alignment and (b) homogeneous (planar) alignment of discotic columnar phase.
Figure 7.5 Schematic diagram of an OLED device. Electrons introduced at the metal electrode (cathode) recombine with holes introduced at the ITO electrode (anode) to emit light.
Figure 7.6 Schematic of OFET device configurations. (a) Top-contact device, with source and drain electrodes deposited onto the organic semiconducting layer. (b) Bottom-contact device, with organic semiconductor deposited onto prefabricated source and drain electrodes.
Figure 7.8 POM images of compound
2
in a sandwiched cell on slow cooling (1 °C min
−1
) from the isotropic phase (a) with crossed polarizers and (b) with parallel polarizers. The broken lines in (b) indicate the growth directions of the dendritic structures, and the arrows in (a) indicate linear defects in the homeotropic alignment.
Figure 7.9 Molecular structures of DLCs
1–10
.
Figure 7.10 Schematic representations and POM images of the fluorinated porphyrin
10d
in a cell at 220 °C. (a) Homeotropic alignment before shearing. (b) Homogeneous alignment after shearing. Arrow shows the shearing direction.
Figure 7.11 Molecular structures of DLCs 11 to 18.
Figure 7.12 (a) Schematic structure of the two compounds
13
(where only one of the two regioisomers is sketched) and
14
. Contact preparation of the sample in the isotropic state shows their low degree of miscibility. Observation performed by bright field microscopy. (b) X-ray diffraction pattern of the homeotropically oriented bilayer in the geometry of an open, supported thin film. The two sixfold symmetries are the signature of the “face-on” (homeotropic) alignment of the two Col
h
phases. Experiment was performed in transmission with the X-ray beam normal to the plane of the substrate (scale bar indicates 2 nm
−1
).
Figure 7.13 (a) Schematic diagram showing the planar alignment of the DLC columns with respect to the oriented PTFE layers.
Figure 7.14 (a) Molecular structure of polymeric
o
-phenylene octamer
19
. (b) OM and POM (inset) images of hexaoctyloxy triphenylene on a glass substrate spin-coated with polymer
19
.
Figure 7.15 Schematic illustration of the deposition of DLCs onto a substrate with the “edge-on” arrangement using the Langmuir–Blodgett technique.
Figure 7.16 Molecular structures of amphiphilic DLCs
20–28
.
Figure 7.17 (a) Schematic showing the adsorption of three cores of hexaalkyl thiotriphenylene (
31
) on a Au(111) surface in “face-on” orientation. (b) Three molecules of the hexaakyloxytriphenylene thiol derivative
25a
adsorbed on a Au(111) surface in “edge-on” orientation. (The alkyl substituents were omitted in this schematic drawing. For the binding of the sulfur atoms, no specific positions on the gold lattice were chosen.) (c) AFM image of a SAM of thiol
25a
imaged on Au(111) in ethanol.
Figure 7.18 (a) Schematic representation of the DLC (
25b
)-functionalized gold nanorods (DLC-GNRs). (b) and (c) Schematic of the hexahexyloxy triphenylene doped with 1 wt% DLC-GNRs (3D and top 2D view) showing potential packing inefficiencies around a single-DLC-capped GNR that are potentially compensated as evidenced by XRD. (d) Transmission electron microscopy images of the DLC-GNRs dried on TEM grids from dispersion in toluene.
Figure 7.19 (a) Schematic showing the lithographically controlled wetting (LCW) applied on isotropic phase. (b) OM images in the bright field of the stamp. (c) POM images of the patterned Pc film.
Figure 7.20 Molecular structures of DLCs
29–42
.
Figure 7.21 (a) A schematic showing the creation of enlongated droplets of DLC. The droplets are created by dewetting from adjacent hydrophobic stripes onto hydrophilic stripes; (b) Tapping mode AFM image of dewetted DLC
29
, at room temperature, aligned on a patterned organosilane surface. The patterning pitch was 20 µm. Note the difference in horizontal and vertical scales on the 3D image; Dewetted DLC
29
on patterned organosilane surfaces with a patterning period of 25 µm: (c,d) the orientation is ±45° to the polarizers, and (e,f) with the compensator in place. The dark gray line indicates the orientation of the slow axis of the compensator. The color difference indicates that the slow axis of the DLC lies parallel to the stripe direction.
Figure 7.22 (a) Procedure of stamp-printing for the preparation of silane molecular monolayer on a substrate: (i) immersion of PDMS stamp in OTS solution for 30 s; (ii) drying the stamp; (iii) pressing the PDMS stamp onto peroxidized substrate; (iv) silanization and then cleaning and drying the substrate. (b) Photograph of the layer of compound
38
in a cell constructed using substrates whose surfaces were preoxidized and then partially coated with OTS monolayer (on the left-hand side of the sample in the picture). The sample was placed between crossed polarizers and kept at 100 °C.
Figure 7.23 AFM images of Pc
12
film (a) before and (b, c) after the electromigration process; (d) High-resolution AFM image of the film in (c); (e–g) Schematic drawing of the migration of Pc molecules at a temperature about 460K, molecular fluidity in these schematic layers is lower in the proximity of the substrate and higher at the top; (h) dewetted film at room temperature. The color scale in the schematic drawing represents the fluidity of molecules, viz. dark gray: low, light gray: high.
Figure 7.24 Fabrication process of homeotropically aligned thin films of Pc derivative. The last step serves only to demonstrate the function of the sacrificial layer. (Reprinted with permission from [103]. Copyright 2009 American Chemical Society)
Figure 7.25 SEM images of released, aligned columnar wires with diameters of (a) 400 nm and (b) 60 nm. (Reprinted with permission from [104]. Copyright 2005 American Chemical Society)
Figure 7.26 (a) Schematic showing the spontaneous self-assembly of HBC
40
from the isotropic state to Col phase within a 2-mm-thick capillary on cooling (a and d). (b) 2D WAXS pattern of the isotropic phase and (c) after controlled cooling down to room temperature.
Figure 7.27 (a) Schematic illustration of the zone casting technique. (b) Optical microscopy image taken in reflection mode for a zone-cast HBC
9c
layer on a silicon substrate. (c) Large-area image from HRTEM of a zone-cast HBC
9c
layer displaying homogeneous film formation with single columnar features lying in the zone-casting direction. (d) Filtered inverse-FFT (IFFT) image showing the intermolecular periodicity within the columns.
Figure 7.28 (a) Schematic illustration of the zone casting technique; (b) An optical microscopy image taken in reflection mode for a zone-cast HBC 9c layer on a silicon substrate; (c) Large-area image from HRTEM of a zone-cast HBC 9c layer displaying homogeneous film formation with single columnar features lying in the zone-casting direction; (d) Filtered inverse-FFT (IFFT) image showing the intermolecular periodicity within the columns. (Reprinted with permission from [112]. Copyright 2005 John Wiley & Sons.)
Figure 7.29 (a) Schematic illustration of the zone crystallization technique used for the alignment of DLCs; (b) 2D-WAXS, POM, and AFM of the aligned film of compound 40; the arrow indicates the moving direction of the sample (Reprinted with permission from [116]. Copyright 2004 American Chemical Society.)
Figure 7.30 Setup for the dipping experiment of HBC 41(a); at the deposition zone, a meniscus is formed at which the material crystallized onto the moving support (b); 2D WAXS pattern of the oriented HBC 41 film (arrow indicates an artifact); POM of the nucleation site, at which the structures begin to grow in the moving direction of the support (c); POM of the interior of the film revealing a uniaxial orientation of the microfibers (d).(Reprinted with permission from [117]. Copyright 2005 American Chemical Society).
Figure 7.31 (a) Schematic diagrams of solvent vapor annealing (SVA): a previously spincoated or drop-cast film is exposed to a solvent saturated atmosphere to enable molecular reorganization on the surface. (b) solvent induced precipitation (SIP): precipitation of fibers from solution, either by adding a small amount of solution to a vial containing a non-solvent, or by multiple additions over several hours of a small amount of non-solvent to a vial containing the solution (Compound 49) Topographical AFM images of an HDTT spin-coated film on SiOx: (c) as prepared film and (d) after SVA treatment. z-Scale: (c) 50 nm and (d) 150 nm. The fibres produced by fast and slow SIP showed some notable differences, the most obvious being their different sizes: fast SIP fibres, seen in (e) AFM and (f) optical microscopy, were considerably shorter than slow SIP fibres, as seen in (g) AFM and (h) optical microscopy. All samples prepared on SiOx, vertical scale of (g) is 1000 nm and (h) 1500 nm. (Reprinted with permission from [118]. Copyright 2011 Royal Society of Chemistry).
Figure 7.32 Molecular structures of DLCs
43–50
.
Figure 7.33 Concept of the uniaxial alignment using a rotating magnetic field
H
. The schematics of columnar domain distributions (a) in the absence of an applied magnetic field, (b) in the presence of an applied static magnetic field, and (c) in the presence of a rotating magnetic field are described. The DLC used in this study is
45
.
Figure 7.34 (a) Setup of the apparatus for electric field alignment of HBC (
9b
) molecules. (b) AFM phase images of field-force oriented HBC (
9b
) films on a glass substrate. (c) Transmission electron micrograph of an oriented HBC (
9b
) film replica. (d) Schematic representation of HBC (
9b
) molecules creating lamellar structures.
Figure 7.35 POM images of (a) corannulene
46
at 140 °C and (b) triphenylene
47
at 110 °C. (The dashed lines represent the borders of
E
-field operating and nonoperating parts.) A sandwich-type glass cell composed of patterned ITO electrodes with a gap of 5 mm, at which an
E
-field (10–50 Vpp mm
−1
) was site-selectively applied to a part of each sample, located between the ITO electrodes, from a vertical direction relative to the substrate.
Figure 7.36 Schematic representations of alignment change of triphenylene
30
(a) on linearly polarized infrared irradiation and (b) circularly polarized infrared irradiation.
Figure 7.37 (a) Schematic diagram of the soft-landing setup used. (b) The two different types of phases observed in (a).
Figure 7.38 (a) Large-scale STM image (140 × 140 nm
2
,
U
t
= 0.20 V,
I
t
= 71 pA) of a triphenylene
35
self-assembled monolayer at the
n
-tetradecane/Au(111) interface. In the α-domains, molecular rows are perpendicular to the Au step edge (AB, lower left corner) and form an angle close to 30º with molecular rows of β-domains. (b) High-resolution STM image of an R-domain (17 × 17 nm
2
,
U
t
= 0.26 V,
I
t
= 96 pA), revealing the triangular shape of the triphenylene aromatic cores and the alkyl-chains positions. Molecular rows R
1
and R
2
associate through triphenylene
35
pairs (or dimers) as delimited by the white ellipse. Possible model for the packing of triphenylene
35
on Au(111). A triphenylene
35
dimer is identified by an ellipse. (c) Inside each dimer, triphenylene
35
molecules are in an antiparallel position.
Chapter 8: Stimuli-Directed Helical Axis Switching in Chiral Liquid Crystal Nanostructures
Figure 8.1 (a) Schematic representation of a CLC helicoidal arrangement. The black arrow represents the helical axis orientation. Each cylinder represents the local orientation of the director. (b,c) Polarizing microscopy image and schematic drawing of the planar texture. (d,e) Focal-conic texture. (f,g) The lying aligned texture. Note that in each picture the red arrow represents the local orientation of the helical axis, and the drawings (c, e, and g) represent a tiny region of the cell.
Figure 8.2 CLC structure at zero field (a) and with field, where a wrinkled state is induced by electric field. In the zero-field state, light is reflected following Bragg's law. In the wrinkled state, light suffers total internal reflection (depending on the inclination of the helical axis) and therefore does not reach the observer's eye. (b) Field on and off zones for intermediate fields.
Figure 8.3 (a) Cell representation of the flexoelectric-based display and the mechanism behind the flexoelectric phenomenon in CLCs.
Figure 8.4 Helix axis control for diffraction grating. (a) DM texture in a CLC sample. (b) SEM image of a PSLC in the aligned fingerprint texture.
Figure 8.5 Controlling helical axis locally by light. (a) Example of dubbed triple-twist torons. (b) Light intensity of the LG beams with charge 2 in the
x–y
and
x–z
planes. (c) CLC generated 3D patterns of T3s and an array of them used to form the letters “CU.”
Figure 8.6 (a) Periodic patterns in CLCs doped with a photoactive material for three different layer thicknesses.
Figure 8.7 (a) Molecular structure of the motor. (b) Fingerprint texture of the thin film. (c) Glass rod rotating as the helical axis is continuously rotated under UV illumination. (d) Atomic force microscopy image showing the surface structure of the CLC.
Figure 8.8 (a) Spiral pattern caused by UV illumination with Gaussian profile of the non-photochromic and azobenzene-based chiral compound based CLC. (b) Same as in (a) but under visible light.
Figure 8.9 Schematic representation of the 3D helical axis switching under UV and visible light.
Figure 8.10 Photomicrographs of the CLC cell under visible light irradiation showing the several states the helical axis is switched.
Figure 8.11 (a) Blue shift in the reflected color as the annealing time increases. (b) AFM, optical microscopy, SEM, and TEM images of the polygonal texture. In the TEM image, the tilting of the helical axis is very pronounced.
Figure 8.12 (a
–
k) Different CLC droplets at different times under a thermal gradient. Panels (d
–
g) show the droplets with helical axis parallel to the thermal gradient while (h
–
k) show the droplets with helical axis perpendicular to the gradient.
Figure 8.13 (a, b) Array of CLC droplets presenting directed and interface mediated cross-communication. (Panels (a) and (b) Noh
et al
. 2014 [122].
Figure 8.14 (a, b) Colloidal particles at the interface of CLC and oil: (a) shows the transmission image between crossed polarizers of the particles and the layer deformation; (b) shows the fluorescent confocal image.
Figure 8.15 Active LC elastomer with gold nanocrystals. (a
–
d) Optical microphotographs between crossed polarizers (a and c) and with the insertion of a retardation plate (b and d). (e
–
f) Complicated change in the CLC arrangement mediated by morphology modification of the elastomer, bending layers, and changing the helical axis direction.
Figure 8.16 (a, b) Proposed mechanism of helical poylacetylene alignment in CLCs.
Figure 8.17 (a, b) Confocal microscopy images of the flat and fingerprint surfaces. (c, d) The corresponding surface profiles. (e) 3D protrusions with aligned helical axis and (f) its surface profile.
Figure 8.18 (a) Left handed and (b) right handed helicoid elastomers at a 384 K. (c) A spiral ribbon at same temperature. (d
–
f) Simulated results of the system represented in (a
–
c).
Chapter 9: Electrically Driven Self-Organized Chiral Liquid-Crystalline Nanostructures: Organic Molecular Photonic Crystal with Tunable Bandgap
Figure 9.1 Comparison of electronic and photonic crystals.
Figure 9.2 Simple examples of one-, two-, and three-dimensional photonic crystals. The different colors represent materials with different dielectric constants.
Figure 9.3 Energy dispersion relations for a free electron and an electron in a (1D) solid, and for a free photon and a photon in a photonic crystal.
Figure 9.4 Photonic band structure of a layered dielectric system with period
a
. (a) The dark and light layers correspond to high and low refractive indices;
k
1
,
k
2
are two standing wave modes, usually known as air mode and dielectric mode, respectively. (b) Dipersion curve showing the corresponding energies of these two modes (
k
1
,
k
2
), and a PBG (horizontal green bar) exits between these two modes.
Figure 9.5 Molecular organization in a nematic liquid crystal phase.
Figure 9.6 Molecular organization in (a) nematic phase, (b) smectic A phase, and (c) smectic C phase.
Figure 9.7 Schematic explanation of the appearance of a photonic bandgap in the right-handed spiral periodic structure.
Figure 9.8 (A) (Left) Setup used for the growth of thin-film opals. The substrate is placed in a dispersion at an angle of 30°. The domains form in the direction parallel to the surface, and the thickness is defined perpendicular to the sample. (Right) Optical microscope image of a typical opal. The growth direction, the top, and the bottom are indicated. (B-a) SEM images of polystyrene opal film (B-b) and SiO
2
inverse opal film prepared from polystyrene spheres with a diameter of 260 nm. (C) Reflection spectra of an inverse opal film with diameter of 260 nm (black line), after infiltration with the LC mixture (brown line). (D) Variation in reflected intensity with change in voltage.
Figure 9.9 (Left) Cell configurations and pitch dilation during the application of an external electric field to the wavelength shifter. (Right) Reflection spectra and polarizing optical microscope images of the visible shifter at different voltages.
Figure 9.10 Electrically tunable, polymer-stabilized CLC (a) showing the transmitted spectra (intensity vs wavelength), tuned over a range of 400 nm in a CLC made of a negative dielectric liquid crystal during application of a 0–140 V DC field.
Figure 9.11 Selective light reflection. (a) Typical reflection spectra of a cell for different amplitudes of the electric field, shown underneath the spectra in volts per micrometer (V µm
–1
) units. (b) Electric field dependencies of the wavelength and bandwidth of the selective reflection peak.
Figure 9.12 Electric-field-induced textures in a cholesteric mixture. Polarizing optical microscope textures of field-induced (a) unwound nematic; (b–g) heliconical states with reflected (b) blue, (c) green, (d) orange, and (e) red colors, (f,g) two IR-reflective states; (h) fingerprint state. The root-mean-squared (rms) amplitude of the electric field is indicated on the figures.
Figure 9.13 (a) Micrographs from a polarizing optical microscope in the transmission mode of the CLC mixture inside an electro-optic cell under an external electric field, producing a continuous blue shift from the central wavelength
λ
c
1
= 720 nm to
λ
c
2
= 570 nm. (b) Experimental results showing the tuning range Δ
λ
= 150 nm (in 30 s) of the reflected intensity for the CLC mixture of central
λ
c
= 720 nm inside the 4-µm cell. (c) Threshold field dependence on tuning and the three different thresholds corresponding to three different substrate thicknesses – blue: 1.5 mm, red: 500 µm, and green: 100 µm. In all cases, Δ
λ
≅150 nm (in 30 s). (d) Tuning range (Δ
λ
, nm) dependence on chiral dopant concentration (wt%). (e) Central wavelengths (
λ
c
).
Chapter 10: Nanostructured Organic–Inorganic Hybrid Membranes for High-Temperature Proton Exchange Membrane Fuel Cells
Figure 10.1 Operating principle of a PEMFC.
Figure 10.2 The temperature windows where appropriate materials are missing.
Figure 10.3 Proton transport in different membrane configurations. (a) Proton transport in Nafion membrane. (b) Proton transport in polymer/nanoparticle composite membranes.
Figure 10.4 (a) Cross-sectional SEM image of a 20% polymer/clay composite membrane. (b) EDX images of silicon elemental mapping through the cross section of the composite membrane.
Figure 10.5 (a) Scheme for the synthesis of Nafion-SiO
2
nanoparticles by the self-assembly method. The inset shows the TEM image of the as-synthesized Nafion-SiO
2
nanoparticles. (b) Limiting oxidation current densities for H
2
crossover through Nafion 212, conventional, and self-assembled Nafion/SiO
2
membranes under accelerated wet/dry RH cycling tests at 90 °C. Arrows indicate the pores/voids formed.
Figure 10.6 AFM images of Nafion-based nanocomposite membranes at fully hydrated conditions: (a) Pristine Nafion 115 membrane, (b) NTP (2.1 wt%), (c) NTP (5.4 wt%), and (d) NTP (9.7 wt%).
Figure 10.7 (a) Water uptake and proton conductivity measurements of the CPS/Si membranes as a function of silica content. (b) Polarization curves for the membranes at 120 °C, 30% RH.
Figure 10.8 Synthesis and structure of silane-cross-linked CSiSPIBI membranes.
Figure 10.9 Porous PBI and hybrid porous PBI film formation procedures by leaching out the porogen with ethanol.
Figure 10.10 Durability of PA/PBI membranes with various loadings of the PWA-
meso
-silica filler. The current load is 0.2 A cm
−2
at a H
2
/O
2
system, and the test temperature is 200 °C and 0% RH.
Figure 10.11 (A) Scheme of the fabrication of PWA-NH
2
-HMS. (B) HAADF STEM image of the PWA-NH
2
-HMS particle with the corresponding element mapping of (C) W, and (D) Si. (E) Peak power density of the PES-PVP composite membrane cells with various loading of the PWA-NH
2
-HMS filler. (F) Stability of the composite membrane cells at 200 °C. (a) 10% PWA-NH
2
-HMS; (b) 5% PWA-NH
2
-HMS; (c) 15% PWA-NH
2
-HMS; (d) 10% NH
2
-HMS; (e) pristine PES-PVP composite membrane (unpublished results).
Chapter 11: Two-Dimensional Organic and Hybrid Porous Frameworks as Novel Electronic Material Systems: Electronic Properties and Advanced Energy Conversion Functions
Figure 11.1 Schematic illustration of the development of PCPs/MOFs. There are several classifications in the state of the art of PCPs/MOFs.
Figure 11.2 Schematic illustration of a series of COFs. A wide variety of COF structures can be designed.
Figure 11.3 Finding of new functions in 2D organic and hybrid frameworks. (a) Topologically nontrivial phases and (b) electronic structure control in PCPs/MOFs and COFs, ushering in a new dawn for these material systems.
Figure 11.4 Electronic structure of honeycomb lattice systems and several unique features of graphene as a model atomically thin 2D material. (a) (Left) Lattice structure of graphene and (right) the corresponding Brillouin zone. The Dirac cones are located at the
K
and
K'
points. (b) Energy dispersion in the honeycomb lattice showing a zoom-in of energy band close to a Dirac point. (c) Cyclotron mass of charge carriers in graphene as a function of their concentration
n
. Positive and negative
n
correspond to electrons and holes, respectively. (d) Quantum Hall effect of graphene.
Figure 11.5 A variety of crystal structures of CNFs. (a) Graphitic carbon nitride. (b) Covalent triazine-based frameworks. (c) Triazine-based graphitic carbon nitride.
Figure 11.6 (a) Structures of CTF-1 and CTF-TCPB. Black and blue balls show carbon and nitrogen atoms, respectively. (b, c) Theoretically calculated densities of states (DOS) of (b) CTF-1 and (c) CTF-TCPB. The experimentally obtained DOS of CTFs were compared with theoretically calculated values and showed good agreement.
Figure 11.7 Fe-based materials as a model for electronic structure vs. electrochemical property. (a) Change of crystal structure leads to change of electronic structure; this modification is reflected in the character of bonds. (b) Metal (M) and ligand (X) bonds are key for the tuning of bond character, that is, ionic or covalent. (c) Example for different electrochemical properties as the result of different electronic (i.e., crystal) structures.
Figure 11.8 Schematic of the relation between electrochemical reactions and the electronic structure.
Figure 11.9 (a) Energy storage principle of rechargeable battery system using CTF-1 and (b) its Ragone plots compared with electrochemical capacitors (ECs), other battery systems, and fuel cells. (c) Cycling performance of CTF-1 electrode in sodium battery system.
Figure 11.10
g
-C
3
N
4
as a photocatalyst for hydrogen production under visible light. (a)
g
-C
3
N
4
constructed from melem units. (b) Ultraviolet–visible diffuse reflectance spectrum of
g
-C
3
N
4
. Inset: Photograph of the photocatalyst. (c) Time course of H
2
production from water containing 10 vol.% triethanolamine as an electron donor under visible light (of wavelength longer than 420 nm) by (i) unmodified
g
-C
3
N
4
and (ii) 3.0 wt% Pt-deposited
g
-C
3
N
4
. The reaction was continued for 72 h, with evacuation of every 24 h (dashed line). (d) Time courses of O
2
production from water containing 0.01 M silver nitrate as an electron acceptor under visible light (of wavelength longer than 420 nm) by 3.0 wt% RuO
2
-loaded
g
-C
3
N
4
.
Figure 11.11 2D porous corrugated framework/metal heterojunction strategy for efficient electrode process. (a) Schematic illustration of the heterojunction. (b) HER activity obtained by linear sweep voltammetry. (c) Tafel slopes of Pt, 2D C
3
N
4
/Au heterojunction, and Au. (d) Efficient ORR pathway emerged by the heterojunction.
Figure 11.12 2D hybrid frameworks. (a) Schematic illustration of a planar nickel bis(dithiolene) framework and (b,c) its physical characterization by using AFM and STM. Close-up of the hexagonal pattern shown in the white square in (d). The upper-right and lower-left insets are the fast Fourier transform (FFT) of the STM image and the FFT-filtered image in (e). (f) Conductivity measurement for this framework. (g) Ni
3
(HITP)
2
system, which is another hybrid system showing a high conductivity.
Figure 11.13 Theoretical prediction of topologically nontrivial phases in 2D hybrid porous frameworks I. (a) Crystal structure of a planar nickel bis(dithiolene) complexes used for theoretical calculations, (b) its band structure, and (c) the zoom-in kagome bands around two spin-orbit coupling (SOC) gaps. The semi-infinite edge states for the (d) spin-up and (e) spin-down components, respectively.
Figure 11.14 Theoretical prediction of topologically nontrivial phases in 2D hybrid porous frameworks II. (a) Band structure was compared by using single orbital tight-binding (TB) model and density-functional theory (DFT) calculations for the flat (I) and Dirac (II and III) bands. (b) Same comparison for the quantized spin Hall conductance in the energy window of the two SOC gaps. (c) Spin Berry curvatures in the reciprocal space for flat (column I) and Dirac bands (column II and III). The dashed lines mark the first Brillouin zone.
Figure 11.15 Theoretical prediction of topologically nontrivial phases in 2D hybrid porous frameworks III. (a) Crystal structure of
trans
-Au
3
(THTAP)
2
(THTAP = trihydroxytriaminophenalenyl), (b) its band structure, and (c) zoom-in of (b) around the Fermi energy. (d) Zoom-in of the band structure calculated with spin–orbit coupling. (e) Band structure for a ribbon of
trans
-Au-THTAP. The black solid lines represent the bulk states, and the red (blue) dashed lines represent topological edge states along the bottom (top) edge.
Chapter 12: Organic/Inorganic Hybrid Nanostructured Materials for Thermoelectric Energy Conversion
Figure 12.1 Thermoelectric module showing the direction of charge flow on both cooling and power generation.
Figure 12.2 Various TE materials used in thermoelectric research and development.
Figure 12.3 Evolution of the maximum
ZT
over time.
Figure 12.4 Figure of merit (
ZT
) of the state-of-the-art commercial TE bulk materials without nanostructering.
Figure 12.5 Thomson Reuters Web of Science publication report for the topic “organic thermoelectric” from 2000 to 2015.
Figure 12.6 Formation of TE nanocomposites from inorganic–organic materials.
Figure 12.7 Electrical conductivity and Seebeck coefficient of PEDOT composite pellets with different PbTe contents.
Figure 12.8 (a) Electrical conductivity and (b) power factor (
PF
) of PEDOT:PSS/expanded graphite composites.
Figure 12.9 (a) Electrical conductivity (indicated by red circles)/thermopower (indicated by blue squares) and (b) thermal conductivities of CNT/PVAc composites at room temperature when the CNT concentrations are 0, 0.5, 1, 2, 3, 4, 5, 10, and 20 wt%, respectively.
Figure 12.10 Schematic of the CNT/PVAc nanocomposites. The CNTs form a three-dimensional network along the surfaces of the spherical PVAc particles.
Figure 12.13 (a) SEM image of the PANI-coated CNT array (side view). (b) TEM image of individual CNTs coated with a PANI layer. (c) Seebeck coefficient versus temperature for CNT/PANI nanocomposites made from CNT arrays, compared with those of uncoated CNT arrays and PANI.
Figure 12.11 (a) Thermopower and (b) electrical conductivity of the CNT/PANI network composites with different mass percents of 3D CNT network at 373 K. (c) SEM image of the CNT/PANI composites.
Figure 12.12 PEDOT:PSS/CNT nanocomposites. (a) Scanning electron micrographs of cold-fractured cross sections along the out-of-plane direction for a composites with 40 wt% CNT, 40 wt% PEDOT:PSS, and 20 wt% PVAc. Scale bar: 2 µm. (b) Carbon nanotubes coated by PEDOT:PSS particles, forming CNT/PEDOT:PSS/CNT junctions in the composites.
Figure 12.14 Comparison of (a) thermal conductivity, (b) Seebeck coefficient, and (c) the dimensionless Figure of merit (
ZT
) of pure Bi
2
Te
3
, CNT/Bi
2
Te
3
composite, and CNT/Bi
2
(Se,Te)
3
composite as a function of temperature.
Figure 12.15 Electric conductivities,
S
,(relative to neat P3OT of 0% Ag,
S
0
) of P3OT/Ag nanocomposites versus Ag concentrations (mass%).
Figure 12.16 Schematic band diagrams of an organic–inorganic (molecule-silicon here for example) interface showing surface transfer doping. CB and VB are the conduction bands and valence bands, respectively. E
F
is Fermi level. HOMO and LUMO are the highest occupied molecular orbital and the lowest unoccupied molecular orbital, respectively. Here we just use the molecule to demonstrate the idea of surface transfer doping. Polymers are also popular as organic dopants.
