The discovery of graphene has triggered great interest in two‐dimensional (2D) nanomaterials for scientists in chemistry, physics, materials science, and related areas. In the family of newly ...developed 2D nanostructured materials, 2D soft nanomaterials, including graphene, BxCyNz nanosheets, 2D polymers, covalent organic frameworks (COFs), and 2D supramolecular organic nanostructures, possess great advantages in light‐weight, structural control and flexibility, diversity of fabrication approaches, and so on. These merits offer 2D soft nanomaterials a wide range of potential applications, such as in optoelectronics, membranes, energy storage and conversion, catalysis, sensing, biotechnology, etc. This review article provides an overview of the development of 2D soft nanomaterials, with special highlights on the basic concepts, molecular design principles, and primary synthesis approaches in the context.
Two‐dimensional (2D) soft nanomaterials are reviewed, including graphene, BxCyNz nanosheets, 2D polymers, covalent organic frameworks, and 2D supramolecular organic nanostructures, etc. The basic concepts, molecular design principles, and primary synthesis approaches developed for 2D soft nanomaterials in the past five years are introduced.
The development of nanodevices currently requires the formation of morphologically controlled or highly ordered arrays of metal, semiconducting, or magnetic nanoparticles. In this context, polymer ...self-assembly provides a powerful bottom-up approach for constructing these materials. The self-assembly of block copolymers (BCPs) in solution is a facile and popular method for the preparation of aggregates of controllable morphologies, including spherical micelles, cylindrical micelles, vesicles (or polymersomes), thin films, and other complex structures that range from zero to three dimensions. Researchers can generally control the morphology of the aggregates by varying copolymer composition or environmental parameters, including the copolymer concentration, the common solvent, the content of the precipitant, or the presence of additives such as ions, among others. For example, as the content of the hydrophilic block in amphiphilic copolymers decreases, the aggregates formed from the copolymers can change from spherical micelles to cylindrical micelles and to vesicles. The aggregates of various morphologies provide excellent templates for the organization of the nanoparticles. The presence of various domains, such as cores, interfaces, and coronas, in BCP aggregates allows for selective localization of nanoparticles in different regions, which may critically affect the resulting properties and applications of the nanoparticles. For example, the incorporation of quantum dots (QDs) into micelle cores solves many problems encountered in the utilization of QDs in biological environments, including enhancement of water solubility, aggregation prevention, increases in circulation or retention time, and toxicity clearance. Simultaneously it preserves the unique optical performance of QDs compared with those of organic fluorophores, such as size-tunable light emission, improved signal brightness, resistance against photobleaching, and simultaneous excitation of multiple fluorescence colors. Therefore, many studies have focused on the selective localization of nanoparticles in BCP aggregates. This Account describes the selective localization of preformed spherical nanoparticles in different domains of BCP aggregates of controllable morphologies in solution, including spherical micelles, cylindrical micelles, and vesicles. These structures offer many potential applications in biotechnology, biomedicine, catalysis, etc. We also introduce other types of control, including interparticle spacing, particle number density, or aggregate size control. We highlight examples in which the surface coating, volume fraction, or size of the particles was tailored to precisely control incorporation. These examples build on the thermodynamic considerations of particle–polymer interactions, such as hydrophobic interactions, hydrogen bonding, electrostatic interactions, and ligand replacement, among others.
The controlled incorporation of preformed gold nanoparticles (AuNPs) into only the central portion of polystyrene190-block-poly(acrylic acid)20 (PS190-b-PAA20) block copolymer rods and micelles is ...described in this note. The strategy involves the formation of the rods or micelles in solution in the presence of AuNPs coated with PS270-b-PAA15 diblock copolymer. Statistical analysis shows that about 80% of the AuNPs are incorporated into the central ca. 4 vol % portion of the rods. The method does not require the block copolymers to bind, solvate, or otherwise interact during preparation with the ions of the metal involved, nor does it involve postassembly chemical reactions within the aggregates, and is thus suitable for a wide range of particles and block copolymer systems.
This paper reports facile synthesis of nitrogen‐doped mesoporous carbon nanospheres (MCNSs) with average diameters of around 300 nm and well‐controlled pore sizes ranging from 8 to 38 nm, by ...employing polystyrene‐b‐poly(ethylene oxide) (PS‐b‐PEO) diblocks with different PS block lengths as the soft templates and dopamine as the carbon‐rich precursor. For the first time, a linear equation is achieved for the quantitative control of the average pore size of MCNSs by simply adjusting a block length of diblock copolymer. The resultant MCNSs possess high surface areas of up to 450 m2 g−1 and nitrogen doping contents of up to ≈3 wt%. As electrode materials of supercapacitors, the MCNSs exhibit excellent electrochemical performance with high specific capacitances of up to 350 F g−1 at 0.1 A g−1, superior rate capability, and cycling stability. Interestingly, the specific capacitance of the MCNSs reduces linearly with increasing pore size, whereas the normalized capacitance by specific surface area remains invariable. This represents a new spectrum of the relationship between electrochemical capacitance and pore size (>5 nm) for porous carbons, which makes a complement to the existing spectra focusing on pore diameters of <5 nm.
A simple linear equation for the quantitative control of the average pore size of mesoporous carbon nanospheres by simply adjusting a block length of diblock copolymer, and also affords a new spectrum of the relationship between electrochemical capacitance and pore size for porous carbons.
Titania has received considerable attention as a promising anode material of Li-ion battery (LIB). Controlling the structure and morphology of titania nanostructures is crucial to govern their ...performance. Herein, we report a mesoporous titania scaffold with a bicontinuous shifted double diamond (SDD) structure for anode material of LIB. The titania scaffold was synthesized by the cooperative self-assembly of a block copolymer poly(ethylene oxide)-
block
-polystyrene template and titanium diisopropoxide bis(acetylacetonate) as the inorganic precursor in a mixture solvent of tetrahydrofuran and HCl/water. The structure shows tetragonal symmetry (space group
I
4
1
/amd
) comprising two sets of diamond networks adjoining each other with the unit cell parameter of
a
= 90 nm and
c
= 127 nm, which affords the porous titania a specific surface area (SSA) of 42 m
2
·g
−1
with a mean pore diameter of 38 nm. Serving as an anode material of LIB, the bicontinuous titania scaffold exhibits a high specific capacity of 254 mAh·g
−1
at the current density of 1 A·g
−1
and an alluring self-improving feature upon charge/discharge over 1,000 cycles. This study overcomes the difficulty in building up ordered bicontinuous functional materials and demonstrates their potential in energy storage application.
Despite the availability of numerous two‐dimensional (2D) materials with structural ordering at the atomic or molecular level, direct construction of mesoscale‐ordered superstructures within a 2D ...monolayer remains an enormous challenge. Here, we report the synergic manipulation of two types of assemblies in different dimensions to achieve 2D conducting polymer nanosheets with structural ordering at the mesoscale. The supramolecular assemblies of amphipathic perfluorinated carboxylic acids and block co‐polymers serve as 2D interfaces and meso‐inducing moieties, respectively, which guide the polymerization of aniline into 2D, free‐standing mesoporous conducting polymer nanosheets. Grazing‐incidence small‐angle X‐ray scattering combined with various microscopy demonstrates that the resulting mesoscale‐ordered nanosheets have hexagonal lattice with d‐spacing of about 30 nm, customizable pore sizes of 7–18 nm and thicknesses of 13–45 nm, and high surface area. Such template‐directed assembly produces polyaniline nanosheets with enhanced π–π stacking interactions, thereby resulting in anisotropic and record‐high electrical conductivity of approximately 41 S cm−1 for the pristine polyaniline nanosheet based film and approximately 188 S cm−1 for the hydrochloric acid‐doped counterpart. Our moldable approach creates a new family of mesoscale‐ordered structures as well as opens avenues to the programmed assembly of multifunctional materials.
Ultrathin conducting polymer nanosheets were achieved by synergistically manipulating the self‐assembly of perfluorocarboxylic acids and polystyrene‐b‐poly(ethylene oxide) diblock copolymers. The nanosheets feature mesoscale‐ordered hexagonal pore arrays, tunable morphologies and pore sizes, large specific surface area as well as anisotropic and record‐high electrical conductivity.
Self-assembly of block copolymers Mai, Yiyong; Eisenberg, Adi
Chemical Society reviews,
2012-Sep-21, Letnik:
41, Številka:
18
Journal Article
Recenzirano
Block copolymer (BCP) self-assembly has attracted considerable attention for many decades because it can yield ordered structures in a wide range of morphologies, including spheres, cylinders, ...bicontinuous structures, lamellae, vesicles, and many other complex or hierarchical assemblies. These aggregates provide potential or practical applications in many fields. The present tutorial review introduces the primary principles of BCP self-assembly in bulk and in solution, by describing experiments, theories, accessible morphologies and morphological transitions, factors affecting the morphology, thermodynamics and kinetics, among others. As one specific example at a more advanced level, BCP vesicles (polymersomes) and their potential applications are discussed in some detail.
Graphene nanoribbons (GNRs) with atomically precise width and edge structures are a promising class of nanomaterials for optoelectronics, thanks to their semiconducting nature and high mobility of ...charge carriers. Understanding the fundamental static optical properties and ultrafast dynamics of charge carrier generation in GNRs is essential for optoelectronic applications. Combining THz spectroscopy and theoretical calculations, we report a strong exciton effect with binding energy up to ∼700 meV in liquid-phase-dispersed GNRs with a width of 1.7 nm and an optical band gap of ∼1.6 eV, illustrating the intrinsically strong Coulomb interactions between photogenerated electrons and holes. By tracking the exciton dynamics, we reveal an ultrafast formation of excitons in GNRs with a long lifetime over 100 ps. Our results not only reveal fundamental aspects of excitons in GNRs (strong binding energy and ultrafast exciton formation etc.) but also highlight promising properties of GNRs for optoelectronic devices.
Covalent organic frameworks （COFs） were nano-coated onto single-walled carbon nanotubes （SWCNTs） by in situ polymerization of TpPa-COFs together with SWCNTs under solvotherma conditions. At the ...molecular level, the COF/SWCNT interface can be efficiently controlled. Thus, the TpPa-COF-SWCNTs nano-hybrid wire, which combines the excellent conductivity of SWCNTs and the high porosity and good redox activity of TpPa-COFs, was employed as active electrode materials for supercapacitors. The strategy reported in this work can give guidance for the design of other similar COF-based electrodes, and hold a great potential in energy storages
Structurally well-defined graphene nanoribbons (GNRs) have attracted great interest as next-generation semiconductor materials. The functionalization of GNRs with polymeric side chains, which can ...widely broaden GNR-related studies on physiochemical properties and potential applications, has remained unexplored. Here, we demonstrate the bottom-up solution synthesis of defect-free GNRs grafted with flexible poly(ethylene oxide) (PEO) chains. The GNR backbones possess an armchair edge structure with a width of 1.0–1.7 nm and mean lengths of 15–60 nm, enabling near-infrared absorption and a low bandgap of 1.3 eV. Remarkably, the PEO grafting renders the GNRs superb dispersibility in common organic solvents, with a record concentration of ∼1 mg mL–1 (for GNR backbone) that is much higher than that (<0.01 mg mL–1) of reported GNRs. Moreover, the PEO-functionalized GNRs can be readily dispersed in water, accompanying with supramolecular helical nanowire formation. Scanning probe microscopy reveals raft-like self-assembled monolayers of uniform GNRs on graphite substrates. Thin-film-based field-effect transistors (FETs) of the GNRs exhibit a high carrier mobility of ∼0.3 cm2 V–1 s–1, manifesting promising application of the polymer-functionalized GNRs in electronic devices.
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