Diverse chiral assemblies of nanoparticles directed by achiral block copolymers via nanochannel confinement

Single-molecule resolution of the conformation of polymers and dendrimers with solid-state nanopores

Polymers and dendrimers are macromolecules, possessing unique and intriguing characteristics, that are widely applied in self-assembled functional materials, green catalysis, drug delivery and sensing devices. Traditional approaches for the structural characterization of polymers and dendrimers involve DLS, GPC, NMR, IR and TG, which provide their physiochemical features and ensemble information, whereas their unimolecular conformation and dispersion also are key features allowing to understand their transporting profile in confined ionic nanochannels. This work demonstrates the nanopore approach for the determination of charged homopolymers, neutral block copolymer and dendrimers under distinct bias potentials and pH conditions. The nanopore translocation properties reveal that the dispersion and transporting of PEI is pH-dependent, and its capture rate is much lower than that of PAA. The neutral block copolymer with longest molecular chain threads through with longest blockage duration, its highest capture rate was achieved in 0.5 M KCl at pH 5 with slow diffusion and high temporal resolution. The two generations of neutral dendrimers could also translocate under bias potentials, probably due to the ions adsorption on the dendrimers and driven by Brownian force. The TEG-81 with larger molecular size translocates with longer residence time and higher blockage ratio, as expected. Both of the dendrimers exhibit a higher blockage ratio at pH 7.4 than either acidic or alkalic condition, indicating a larger stretched conformation adopted under neutral condition. This work presents the analysis of unimolecular charged and neutral polymers and dendrimers, which will be insightful in understanding the self-assembly motion and transfer of synthetic macromolecules in confined space. It also provides a good indication for deciphering the macromolecule-nanopore interplay under electrophoretic condition.

Single-molecule resolution of macromolecules with nanopore devices

Nanopore-based electrical detection technology holds single-molecule resolution and combines the advantages of high sensitivity, high throughput, rapid analysis, and label-free detection. It is widely applied in the determination of organic and biological macromolecules, small molecules, and nanomaterials, as well as in nucleic acid and protein sequencing. There are a wide variety of organic polymers and biopolymers, and their chemical structures, and conformation in solution directly affect their ensemble properties. Currently, there is limited approach available for the analysis of single-molecule conformation and self-assembled topologies of polymers, dendrimers and biopolymers. Nanopore single-molecule platform offers unique advantages over other sensing technologies, particularly in molecular size differentiation of macromolecules and complex conformation analysis. In this review, the classification of nanopore devices, including solid-state nanopores (SSNs), biological nanopores, and hybrid nanopores is introduced. The recent developments and applications of nanopore devices are summarized, with a focus on the applications of nanopore platform in the resolution of the structures of synthetic polymer, including dendritic, star-shaped, block copolymers, as well as biopolymers, including polysaccharides, nucleic acids and proteins. The future prospects of nanopore sensing technique are ultimately discussed.

Seeded RAFT Polymerization-Induced Self-assembly: Recent Advances and Future Opportunities

Over the past decade, polymerization-induced self-assembly (PISA) has fully proved its versatility for scale-up production of block copolymer nanoparticles with tunable sizes and morphologies; yet, there are still some limitations. Recently, seeded PISA approaches combing PISA with heterogeneous seeded polymerizations have been greatly explored and are expected to overcome the limitations of traditional PISA. In this review, recent advances in seeded PISA that have expanded new horizons for PISA are highlighted including i) general considerations for seeded PISA (e.g., kinetics, the preparation of seeds, the selection of monomers), ii) morphological evolution induced by seeded PISA (e.g., from corona-shell-core nanoparticles to vesicles, vesicles-to-toroid, disassembly of vesicles into nanospheres), and iii) various well-defined nanoparticles with hierarchical and sophisticated morphologies (e.g., multicompartment micelles, porous vesicles, framboidal vesicles, AXn -type colloidal molecules). Finally, new insights into seeded PISA and future perspectives are proposed.

Enhanced dielectric permittivity of hierarchically double-gyroid nanocomposites via macromolecular engineering of block copolymers

It is a challenging task to realize the periodically bicontinuous gyroid nanostructures of flexible nanocomposites with high loading of functionalized nanoparticles, which could exhibit high dielectric permittivity for energy storage and electronic devices. Herein, with the aid of the concept of macromolecular engineering, we propose novel nanocomposites, composed of A'(A''B)_n miktoarm star copolymers and nanoparticles, to obtain a double-gyroid structure through self-consistent field theory coupled with density functional theory. By tailoring the architecture of this copolymer, a large window of the double-gyroid phase extending to a high loading concentration of nanoparticles is achieved, leading to a hierarchical structure of a percolation network of nanoparticles within the gyroid channels. Furthermore, the finite difference quasielectrostatic method is integrated to reveal an enhanced dielectric permittivity of the structured nanocomposites by increasing the loading concentration of nanoparticles. The simultaneous achievement of an ordered double-gyroid phase and high loading nanoparticles represents a crucial step toward the realization of fully three-dimensional network-like metamaterials via a rational molecular design of nanocomposites.

1D Colloidal chains: recent progress from formation to emergent properties and applications

Integrating nanoscale building blocks of low dimensionality (0D; i.e., spheres) into higher dimensional structures endows them and their corresponding materials with emergent properties non-existent or only weakly existent in the individual building blocks. Constructing 1D chains, 2D arrays and 3D superlattices using nanoparticles and colloids therefore continues to be one of the grand goals in colloid and nanomaterial science. Amongst these higher order structures, 1D colloidal chains are of particular interest, as they possess unique anisotropic properties. In recent years, the most relevant advances in 1D colloidal chain research have been made in novel synthetic methodologies and applications. In this review, we first address a comprehensive description of the research progress concerning various synthetic strategies developed to construct 1D colloidal chains. Following this, we highlight the amplified and emergent properties of the resulting materials, originating from the assembly of the individual building blocks and their collective behavior, and discuss relevant applications in advanced materials. In the discussion of synthetic strategies, properties, and applications, particular attention will be paid to overarching concepts, fresh trends, and potential areas of future research. We believe that this comprehensive review will be a driver to guide the interdisciplinary field of 1D colloidal chains, where nanomaterial synthesis, self-assembly, physical property studies, and material applications meet, to a higher level, and open up new research opportunities at the interface of classical disciplines.

Hierarchically Chiral Nanostructures Self-Assembled from Nanoparticle Tethered Block Copolymers

Chiral nanostructures of nanoparticle assemblies have attracted tremendous interest for their fascinating functional properties. Herein, through theoretical simulations, we show that nanoparticle tethered block copolymers can self-assemble into hierarchically chiral nanostructures. Two-fold helices are formed in the hierarchically chiral nanostructures: the diblock copolymers form helical supercylinders while the nanoparticles arrange into chiral assemblies wrapped around the helical supercylinders. The hierarchically chiral nanostructures can be formed in a large parameter window. Circular dichroism calculations demonstrate that the coexistence of polymeric helices and chiral nanoparticle assemblies improves the chiroptical activity. These findings can provide guidelines for designing hierarchically ordered chiral nanostructures with advanced functional properties. This article is protected by copyright. All rights reserved.

Template-assisted self-assembly of achiral plasmonic nanoparticles into chiral structures

The acquisition of strong chiroptical activity has revolutionized the field of plasmonics, granting access to novel light-matter interactions and revitalizing research on both the synthesis and application of nanostructures. Among the different mechanisms for the origin of chiroptical properties in colloidal plasmonic systems, the self-assembly of achiral nanoparticles into optically active materials offers a versatile route to control the structure-optical activity relationships of nanostructures, while simplifying the engineering of their chiral geometries. Such unconventional materials include helical structures with a precisely defined morphology, as well as large scale, deformable substrates that can leverage the potential of periodic patterns. Some promising templates with helical structural motifs like liquid crystal phases or confined block co-polymers still need efficient strategies to direct preferential handedness, whereas other templates such as silica nanohelices can be grown in an enantiomeric form. Both types of chiral structures are reviewed herein as platforms for chiral sensing: patterned substrates can readily incorporate analytes, while helical assemblies can form around structures of interest, like amyloid protein aggregates. Looking ahead, current knowledge and precedents point toward the incorporation of semiconductor emitters into plasmonic systems with chiral effects, which can lead to plasmonic-excitonic effects and the generation of circularly polarized photoluminescence.

Nanophotonic Approaches for Chirality Sensing

Chiral nanophotonic materials are promising candidates for biosensing applications because they focus light into nanometer dimensions, increasing their sensitivity to the molecular signatures of their surroundings. Recent advances in nanomaterial-enhanced chirality sensing provide detection limits as low as attomolar concentrations (10^-18 M) for biomolecules and are relevant to the pharmaceutical industry, forensic drug testing, and medical applications that require high sensitivity. Here, we review the development of chiral nanomaterials and their application for detecting biomolecules, supramolecular structures, and other environmental stimuli. We discuss superchiral near-field generation in both dielectric and plasmonic metamaterials that are composed of chiral or achiral nanostructure arrays. These materials are also applicable for enhancing chiroptical signals from biomolecules. We review the plasmon-coupled circular dichroism mechanism observed for plasmonic nanoparticles and discuss how hotspot-enhanced plasmon-coupled circular dichroism applies to biosensing. We then review single-particle spectroscopic methods for achieving the ultimate goal of single-molecule chirality sensing. Finally, we discuss future outlooks of nanophotonic chiral systems.

Self-Assembled Open Porous Nanoparticle Superstructures

Imparting porosity to inorganic nanoparticle assemblies to build up self-assembled open porous nanoparticle superstructures represents one of the most challenging issues and will reshape the property and application scope of traditional inorganic nanoparticle solids. Herein, we discovered how to engineer open pores into diverse ordered nanoparticle superstructures via their inclusion-induced assembly within 1D nanotubes, akin to the molecular host-guest complexation. The open porous structure of self-assembled composites is generated from nonclose-packing of nanoparticles in 1D confined space. Tuning the size ratios of the tube-to-nanoparticle enables the structural modulation of these porous nanoparticle superstructures, with symmetries such as C₁, zigzag, C₂, C₄, and C₅. Moreover, when the internal surface of the nanotubes is blocked by molecular additives, the nanoparticles would switch their assembly pathway and self-assemble on the external surface of the nanotubes without the formation of porous nanoparticle assemblies. We also show that the open porous nanoparticle superstructures can be ideal candidate for catalysis with accelerated reaction rates.

Structural transformations of growing thin colloidal crystals in confined space via convective assembly

The structural evolution of growing thin colloidal crystals in a confined space via the convective assembly technique has been investigated. The thin colloidal crystals were grown in a wedge-shaped cell, where the height of the cell increased with increased crystal growth. Triangle and square patterns, denoted as [111]- and [100]-oriented grains, respectively, were formed alternately as the height of the cell increased. The structural transformation was associated with an increase in the number of layers when the n-layer [100]-oriented grains changed to n + 1-layer [111]-oriented grains. Between the different grain structures, a stripe pattern was observed, which was a transitional region, where particle configuration gradually changed. The structural transformation occurred through the continuous change of particle configuration rather than through the abrupt formation of a grain boundary. The interval of the strip pattern lengthened as the number of layers increased, which is understood to be the structure with the highest packing density. The findings of the study give a better insight into convective assembly in a confined space, and also contribute to the greater structural control of colloidal crystals, useful for a number of applications.

POSS-based starlike hybrid helical poly(phenyl isocyanide)s: their synthesis, self-assembly, and enantioselective crystallization ability

Well-defined starlike hybrid helical poly(phenyl isocyanide)s with POSS cores were designed and synthesized, and their self-assembly behaviour and enantioselective crystallization ability were investigated.

Self-Assembly of Polymer Grafted Nanoparticles within Spherically Confined Diblock Copolymers

Geometric confinement plays an important role in the generation of interesting microstructures on account of structural frustration and confinement-induced entropy loss. In the present study, self-consistent field calculations have been performed to examine the self-assembly behavior of a mixture of diblock copolymers and polymer grafted nanoparticles within a spherical confinement. The analysis is aimed at obtaining the equilibrium distribution of nanoparticles with a high degree of order. The ordered mesophases of diblock copolymers provide useful templates to achieve ordering of nanoparticles in a selective domain. Self-assembly of nanoparticles within frustrated diblock copolymers is found to be very different from the bulk. A rich variety of equilibrium morphologies are observed depending on the degree of confinement and the extent of particle loading. In addition, the role of particle size and selectivity along with the length and the number of polymer chains grafted onto the surface of nanoparticles are analyzed to understand the self-assembly behavior. The specific interest is to obtain the chiral structures out of achiral block copolymers subjected to spherical confinement. The realization of various captivating microstructures, such as chiral ordering of nanoparticles, is highly essential to produce advanced nanomaterials with superior physical properties.

2D Chiral Stripe Nanopatterns Self-Assembled from Rod-Coil Block Copolymers on Microstripes

Chiral nanoarchitectures usually possess unique and intriguing properties. However, the construction of 2D chiral nanopatterns through polymer self-assembly is a challenge. Reported herein is the formation of chiral stripe nanopatterns through surface self-assembly of polypeptide-based rod-coil block copolymers on microstripes. The nanostripes align oblique to the boundary of the microstripes, resulting in the chirality of the nanopatterns. The chirality of the nanopatterns is closely related to the width of the microstripes, i.e., a narrower width results in higher chirality. Besides, the chiral sense of the nanopatterns can be regulated by the chirality of the polypeptide blocks. This work demonstrates the transmission of chirality from polymer to nanoarchitecture on a confined surface, which can guide the preparation of nanopatterns with tuned chiral features.

Stereospecific interactions between chiral inorganic nanomaterials and biological systems

Chirality is ubiquitous in nature and plays mysterious and essential roles in maintaining key biological and physiological processes.