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Nanoparticle (NP) clusters are attractive for many applications, but controllable and regioselective assembly of clusters remains challenging. This communication reports a strategy to precisely assemble Ag nanoplates (NP-As) and Au nanospheres (NP-Bs) grafted with copolymer ligands into defined ABx clusters with controlled coordination number (x) and orientation of the NPs. The directional bonding of shaped NPs relies on the stoichiometric reaction of complementary reactive groups on copolymer ligands. The x value of NP clusters can be tuned from 1 to 4 by varying the number ratio of reactive groups on single NP-Bs to NP-As. The regioselective bonding of nanospheres to the edge or face of a central nanoplate is governed by the steric hindrance of copolymeric ligands on the nanoplate. The clusters exhibit distinctive plasmonic properties that are dependent on the bonding modes of NPs. This study paves a route to fabricating nanostructures with high precision and complexity for applications in plasmonics, catalysis, and sensing.

Shape complementarity is of paramount importance in molecular recognition, but has rarely been adopted in the self-assembly of colloidal particles, especially in the case of nanoparticles of different shapes. Here, we demonstrated a simple, yet powerful strategy for fabricating gold nanoring-based heterogeneous nanostructures (AuNR-HNs) with well-defined geometries and high yield. The assembly of various geometries of AuNR-HNs is modulated by the shape complementarity of plasmonic nanorings and nanospheres. We also present experimental evidence of dark quadrupolar ring mode excitation in AuNR-HNs through single-particle optical measurements. Our strategy will be beneficial in the study of nanoparticle assembly, photonic element interaction, and the development of plasmon-based optical devices.

Patchy colloidal nanoparticles are important for a broad range of applications, especially as building blocks for complex and functional structural materials, but the controllable generation of chemical patches on as-synthesized nanoparticles remains a challenge. This article describes a robust strategy for the scalable synthesis of high-quality patchy nanoparticles in high yield and solid content. A simple thermal treatment of a mixture of gold nanoparticles and thiol-terminated block-random copolymers in selected solvents produced a variety of patchy nanoparticles with a controlled morphology and number of polymeric patches (e.g., beanlike patch, one patch, two patches, three patches, multiple patches, and open-configuration patch). We show in experiments and simulations that the dynamic detachment/attachment of copolymers and the exchange of copolymers between the nanoparticle surface and free micelles in the solution-which are dictated by the architecture of copolymers-govern the formation of polymeric patches. This work not only offers an effective approach to patchy nanoparticles but also provides new insights into the phase behaviors of copolymers on nanoscale surfaces.

Nanoparticle self-assembly has emerged as an indispensable tool in designing structured materials with a wide range of applications, but quantitatively predicting the assembly process and structures still remains challenging. Drawing inspiration from the toolbox of molecular reactions and behaviors is of utmost importance in further advancement of principles and theories for assembling nanoparticles at a length scale orders of magnitude larger. Here we represent a general paradigm for the predictive self-assembly of binary inorganic nanoparticles into linear nanostructures in periodic sequence by expanding the horizon of alternating copolymerization at the molecular level to nanoscale colloidal systems. Nanoparticles grafted with reactive block copolymers are viewed as nanoscale monomers ("nanomers"), and the rapid dimerization of co-nanomers into molecular dipole-like dimers, resembling the preferential formation of dimeric intermediates or charge-transfer complexes from co-monomers in molecular copolymerization, is crucial to the organization of co-nanomers in alternating sequence. We also demonstrate that the classic kinetics and statistics of polycondensation of molecular alternating copolymers (e.g., Nylon-66) can be utilized to quantitatively predict the copolymerization process of nanomers.

This article describes the fabrication of nanosized magneto-vesicles (MVs) comprising tunable layers of densely packed superparamagnetic iron oxide nanoparticles (SPIONs) in membranes via cooperative assembly of polymer-tethered SPIONs and free poly(styrene)- b-poly(acrylic acid) (PS- b-PAA). The membrane thickness of MVs could be well controlled from 9.8 to 93.2 nm by varying the weight ratio of PS- b-PAA to SPIONs. The increase in membrane thickness was accompanied by the transition from monolayer MVs, to double-layered MVs and to multilayered MVs (MuMVs). This can be attributed to the variation in the hydrophobic/hydrophilic balance of polymer-grafted SPIONs upon the insertion and binding of PS- b-PAA onto the surface of nanoparticles. Therapeutic agents can be efficiently encapsulated in the hollow cavity of MVs and the release of payload can be tuned by varying the membrane thickness of nanovesicles. Due to the high packing density of SPIONs, the MuMVs showed the highest magnetization and transverse relaxivity rate ( r

Soft materials undergoing shape transformations in response to changes in ambient environment have potential applications in tissue engineering, robotics and biosensing. Generally, stimulus-responsive materials acquire two stable shapes corresponding to the "on" and "off" states of the external trigger. Here, we report a simple, yet versatile approach to induce multiple shape transformations of a planar hydrogel sheet, each triggered by a particular, well-defined external stimulus. The approach is based on the integration of small-scale multiple polymer components with distinct compositions in the composite gel sheet. In response to different stimuli, the structural components undergo differential swelling or shrinkage, which creates internal stresses within the composite hydrogel sheet and transforms its shape in a specific manner.

Metallic nanotubes represent a class of hollow nanostructures with unique catalytic properties. However, the wet-chemical synthesis of metallic nanotubes remains a substantial challenge, especially for those with dimensions below 50 nm. This communication describes a simultaneous alloying-etching strategy for the synthesis of Pt nanotubes with open ends by selective etching Au core from coaxial Au/Pt nanorods. This approach can be extended for the preparation of Pt nanorings when Saturn-like Au core/Pt shell nanoparticles are used. The diameter and wall thickness of both nanotubes and nanorings can be readily controlled in the range of 14–37 nm and 2–32 nm, respectively. We further demonstrated that the nanotubes with ultrathin side walls showed superior catalytic performance in oxygen reduction reaction.

Controllable self-assembly of nanoscale building blocks into larger specific structures provides an effective route for the fabrication of new materials with unique optical, electronic, and magnetic properties. The ability of nanoparticles (NPs) to self-assemble like molecules is opening new research frontiers in nanoscience and nanotechnology. We present a new class of amphiphilic "colloidal molecules" (ACMs) composed of inorganic NPs tethered with amphiphilic linear block copolymers (BCPs). Driven by the conformational changes of tethered BCP chains, such ACMs can self-assemble into well-defined vesicular and tubular nanostructures comprising a monolayer shell of hexagonally packed NPs in selective solvents. The morphologies and geometries of these assemblies can be controlled by the size of NPs and molecular weight of BCPs. Our approach also allows us to control the interparticle distance, thus fine-tuning the plasmonic properties of the assemblies of metal NPs. This strategy provides a general means to design new building blocks for assembling novel functional materials and devices.

The design and assembly of novel colloidal particles are of both academic and technological interest. We developed a wet-chemical route to synthesize monodisperse bent rigid silica rods by controlled perturbation of emulsion-templated growth. The bending angle of the rods can be tuned in a range of 0–50° by varying the strength of perturbation in the reaction temperature or pH in the course of rod growth. The length of each arm of the bent rods can be individually controlled by adjusting the reaction time. For the first time we demonstrated that the bent silica rods resemble banana-shaped liquid-crystal molecules and assemble into ordered structures with a typical smectic B2 phase. The bent silica rods could serve as a visualizable mesoscopic model for exploiting the phase behaviors of bent molecules which represent a typical class of liquid-crystal molecules.

We report a microfluidic approach to generating capsules of biopolymer hydrogels. Droplets of an aqueous solution of a biopolymer were emulsified in an organic phase comprising a cross-linking agent. Polymer gelation was achieved in situ (on a microfluidic chip) by diffusion-controlled ionic cross-linking of the biopolymer, following the transfer of the cross-linking agent from the continuous phase to the droplets. Gelation was quenched by collecting particles in a large pool of cross-linking agent-free liquid. The structure of microgels (from capsules to gradient microgels to particles with a uniform structure) was controlled by varying the time of residence of droplets on the microfluidic chip and the concentration of the cross-linking agent in the continuous phase. We demonstrated the encapsulation of a controlled number of polystyrene beads in the microgel capsules. The described approach was applied to the preparation of capsules of several polysaccharides such as alginate, kappa-carrageenan, and carboxymethylcellulose.

We report a novel approach to continuous and scalable production of core-shell droplets and polymer capsules in microfluidic devices. The described method is also useful in the synthesis of polymer particles with nonspherical shapes. We used capillary instability-driven break-up of a liquid jet formed by two immiscible fluids. Precise control of emulsification of each liquid allowed for the production of highly monodisperse core-shell droplets with a predetermined diameter of cores and thickness of shells. We also achieved control over the number of cores per droplet and the location of cores in the droplet. We carried out fast throughput photopolymerization of the monomeric shells and obtained polymer particles with various shapes and morphologies, including spheres, truncated spheres and, hemispheres, and single and multicore capsules.

Although an analogy has been drawn between them, organic molecular amphiphiles (MAMs) and inorganic nanoparticle (NP) amphiphiles (NPAMs) are significantly different in dimension, geometry, and composition as well as their assembly behavior. Their concurrent assembly can synergetically combine the inherent properties of both building blocks, thus leading to new hybrid materials with increasing complexity and functionality. Here we present a new strategy to fabricate hybrid vesicles with well-defined shape, morphology, and surface pattern by coassembling MAMs of block copolymers (BCPs) and NPAMs comprising inorganic NPs tethered with amphiphilic BCPs. The assembly of binary mixtures generated unique hybrid Janus-like vesicles with different shapes, patchy vesicles, and heterogeneous vesicles. Our experimental and computational studies indicate that the different nanostructures arise from the delicate interplay between the dimension mismatch of the two types of amphiphiles, the entanglement of polymer chains, and the mobility of NPAMs. In addition, the entropic attraction between NPAMs plays a dominant role in controlling the lateral phase separation of the two types of amphiphiles in the membranes. The ability to utilize multiple distinct amphiphiles to construct discrete assemblies represents a promising step in the self-assembly of structurally complex functional materials.

Amphiphilic plasmonic micelle-like nanoparticles (APMNs) composed of gold nanoparticles (AuNPs) and amphiphilic block copolymers (BCPs) structurally resemble polymer micelles with well-defined architectures and chemistry. The APMNs can be potentially considered as a prototype for modeling a higher-level self-assembly of micelles. The understanding of such secondary self-assembly is of particular importance for the bottom-up design of new hierarchical nanostructures. This article describes the self-assembly, modeling, and applications of APMN assemblies in selective solvents. In a mixture of water/tetrahydrofuran, APMNs assembled into various superstructures, including unimolecular micelles, clusters with controlled number of APMNs, and vesicles, depending on the lengths of polymer tethers and the sizes of AuNP cores. The delicate interplay of entropy and enthalpy contributions to the overall free energy associated with the assembly process, which is strongly dependent on the spherical architecture of APMNs, yields an assembly diagram that is different from the assembly of linear BCPs. Our experimental and computational studies suggested that the morphologies of assemblies were largely determined by the deformability of the effective nanoparticles (that is, nanoparticles together with tethered chains as a whole). The assemblies of APMNs resulted in strong absorption in near-infrared range due to the remarkable plasmonic coupling of Au cores, thus facilitating their biomedical applications in bioimaging and photothermal therapy of cancer.

Asymmetric multicomponent nanoparticles (AMNPs) offer new opportunities for new-generation materials with improved or new synergetic properties not found in their individual components. There is, however, an urgent need for a synthetic strategy capable of preparing hybrid AMNPs with fine-tuned structural and compositional complexities. Herein, we report a new paradigm for the controllable synthesis of polymer/metal AMNPs with well-controlled size, shape, composition, and morphology by utilizing interfacial polymerization. The hybrid AMNPs display a new level of structural–architectural sophistication, such as controlled domain size and the number of each component of AMNPs. The approach is simple, versatile, cost-effective, and scalable for synthesizing large quantities of AMNPs. Our method may pave a new route to the design and synthesis of advanced breeds of building blocks for functional materials and devices.

We report a versatile “inside-out” microfluidic approach to producing monodisperse particle-stabilized emulsions, as well as supracolloidal polymer microspheres. This approach addresses the challenges faced in conventional strategies for the preparation of Pickering emulsions, that is, an insufficient control of droplet dimensions and an excess of particles in the continuous media. The proposed method minimizes waste of particles, due to their introduction in the droplet phase, rather than in the continuous medium; allows control over the coverage of droplets with particles by manipulating the concentration of particles or the flow rates of the liquids; and provides a route for an easier analysis of the dynamics of formation and buckling of Pickering emulsions.

We report a predefined self-organization of gold nanorods (NRs) end-terminated with multiple polymer arms ("pom-poms") in higher-order structures. The assembly of polymer-tethered NRs was controlled by changing the structure of the polymer pom-poms. We show that the variation in the molecular weight of the polymer molecules and their relative location with respect to the long side of the NRs resulted in two competing association modes of the nanorods, that is, their side-by-side and end-to-end assembly, and produced bundles, chains, rings, and bundled chains of the NRs. The superposition of the two variables controlling the organization of NRs allowed us to create a map showing the variation in the longitudinal plasmonic bands of the NRs achieved by their self-assembly.