Precise Dimerization of Hollow Fullerene Compartments

Paddle-like self-stirring nanoreactors with multi-chambered mesoporous branches for enhanced dual-dynamic cascade reactions

Developing artificial nanomaterial systems that can convert external stimuli to achieve nanoscale self-sustainable motion (for example, self-rotation), and simultaneously integrate and deploy the spatial localization of multiple active sites to unravel the intraparticle diffusion patterns of molecules, is of great importance for green synthetic chemistry. Here we show a paddle-like self-stirring mesoporous silica nanoreactor system with separated chambers and controllable proximity of active sites. The nanoreactors are designed by encapsulating magnetic Fe3O4 (~20 nm) in the first chamber, and meantime, Au and Pd nanocrystals are spatially isolated in different domains. Such a nanoreactor generates nanoscale rotation under the rotating magnetic fields and exhibits an order of magnitude activity enhancement in the cascade synthesis of 5,6-dimethylphenanthridinium (96.4% selectivity) compared with conventional macro-stirring. Meanwhile, we quantitatively uncovered the rotation-induced enhancement in sequential and reverse transfer of reactive intermediates, consequently revealing the relevance of self-rotation and proximity effects in controlling the catalytic performance.

Liquid Active Surface Growth: Explaining the Symmetry Breaking in Liquid Nanoparticles

In our previous studies of metal nanoparticle growth, we have come to realize that the dynamic interplay between ligand passivation and metal deposition, as opposed to static facet control, is responsible for focused growth at a few active sites. In this work, we show that the same underlying principle could be applied to a very different system and explain the abnormal growth modes of liquid nanoparticles. In such a liquid active surface growth (LASG), the interplay between droplet expansion and simultaneous silica shell encapsulation gives rise to an active site of growth, which eventually becomes the long necks of nanobottles. For this synthetic control, the imbalance of the said interplay is the critical factor, as demonstrated by carefully designed control experiments. Thus, LASG provides a coherent mechanism that encompasses a wide range of liquid-derived nanostructures, including hollow nanospheres, asymmetric teardrops, and hollow nanobottles with an opening. By adapting nanosynthesis techniques from the solid to liquid realm, we believe that LASG would provide deeper insights and more sophisticated synthetic controls.

3D Nanofabrication via Directed Material Assembly: Mechanism, Method, and Future

Fabrication of complex three-dimensional (3D) structures at nanoscale is the core of nanotechnology, as it enables the creation of various micro-/nano-devices such as micro-robots, metamaterials, sensors, photonic devices, etc. Among most 3D nanofabrication strategies, the guided material assembly, an efficient bottom-up approach capable of directly constructing designed structures from precise integration of material building blocks, possesses compelling advantages in diverse material compatibility, sufficient driving forces, facile processing steps, and nanoscale resolution. In this review, we focus on assembly-based fabrication methods capable of creating complex 3D nanostructures (instead of periodic or 2.5D-only structures). Recent advances are classified based on the different assembly mechanisms, i.e., assembly driven by chemical reactions, physical interactions, and the synergy of multiple microscopic interactions. The design principles of representative fabrication strategies with an emphasis on their respective advantages, e.g., structural design flexibility, material compatibility, resolution, or applications are analyzed. In the summary and outlook, existing challenges, as well as possible paths to solutions for future development are reviewed. We believe that with recent advances in assembly-based nanofabrication strategies, 3D nanofabrication has achieved tremendous progress in resolution, material generality, and manufacturing cost, for it to make a greater impact in the near future.

Lipid-inspired biomimicking morphosynthesis of a series of complex concave silica architectures

The lipid-inspired biosilicification process enables the creation of a series of concave silica nanoarchitectures in the complex shapes of nanobowls, nanodishes, nanoboats, and nanoloops. The reaction at a pH of 8 initially allows the formation of thin and elastic circular gel nanosheets that can undergo inducible stretching and folding, which subsequently evolves into nanodish and nanobowl through a potential global buckling process. The adjustment of the pH to 9 and 4 enables the production of more complex morphogens of nanoboat and nanoloop, respectively. These unique silica nanoarchitectures may have a wide scope of potential application from nanoreactors in heterogenous catalysis to drug delivery systems and optical materials.

Molecular Engineering of Colloidal Atoms

Creation of architectures with exquisite hierarchies actuates the germination of revolutionized functions and applications across a wide range of fields. Hierarchical self-assembly of colloidal particles holds the promise for materialized realization of structural programing and customizing. This review outlines the general approaches to organize atom-like micro- and nanoparticles into prescribed colloidal analogs of molecules by exploiting diverse interparticle driving motifs involving confining templates, interactive surface ligands, and flexible shape/surface anisotropy. Furthermore, the self-regulated/adaptive co-assembly of simple unvarnished building blocks is discussed to inspire new designs of colloidal assembly strategies.

Inorganic-organic coprecipitation: spontaneous formation of enclosed and porous silica compartments with enriched biopolymers

We show that it is possible to spontaneously form all-enclosed compartments with microporous shells and enriched biopolymers via simple coprecipitation of silica and biopolymers. The reaction involves mild conditions and tolerates the random mixing of multiple reagents. Such a synthetic advance points to a new direction for resolving the chicken-egg dilemma of how the early life forms were hosted: without a physical barrier it would be difficult to maintain organized reactions, but without organized reactions, it would be difficult to create a cell membrane. In our synthesis, the divalent cation Ca²⁺ plays a critical role in the co-precipitation and in creating hollow compartments after simple dilution with water. The precursor of silica, poly(silicic acid), is a negatively charged, cross-linked polymer. It could be co-precipitated with negatively charged biopolymers such as DNA and proteins, whereas the remaining silica precursor forms a conformal and microporous shell on the surface of the initial precipitate. After etching, the biopolymers are retained inside the hollow compartments. The fact that multiple favorable conditions are easily brought together in enclosed compartments opens new possibilities in theorizing the host of early life forms.

Three-dimensional nanofabrication via ultrafast laser patterning and kinetically regulated material assembly

A major challenge in nanotechnology is the fabrication of complex three-dimensional (3D) structures with desired materials. We present a strategy for fabricating arbitrary 3D nanostructures with a library of materials including metals, metal alloys, 2D materials, oxides, diamond, upconversion materials, semiconductors, polymers, biomaterials, molecular crystals, and inks. Specifically, hydrogels patterned by femtosecond light sheets are used as templates that allow for direct assembly of materials to form designed nanostructures. By fine-tuning the exposure strategy and features of the patterned gel, 2D and 3D structures of 20- to 200-nm resolution are realized. We fabricated nanodevices, including encrypted optical storage and microelectrodes, to demonstrate their designed functionality and precision. These results show that our method provides a systematic solution for nanofabrication across different classes of materials and opens up further possibilities for the design of sophisticated nanodevices.

Supramolecular Engineering of Crystalline Fullerene Micro-/Nano-Architectures

Fullerenes are a molecular form of carbon allotrope and bear certain solubility, which allow the supramolecular assembly of fullerene molecules-also together with other complementary compound classes-via solution-based wet processes. By well-programmed organizing these building blocks and precisely modulating over the assembly process, supramolecularly assembled fullerene micro-/nano-architectures (FMNAs) are obtained. These FMNAs exhibit remarkably enhanced functions as well as tunable morphologies and dimensions at different size scales, leading to their applications in diverse fields. In this review, both traditional and newly developed assembly strategies are reviewed, with an emphasis on the morphological evolution mechanism of FMNAs. The discussion is then focused on how to precisely regulate the dimensions and morphologies to generate functional FMNAs through solvent engineering, co-crystallization, surfactant incorporation, or post-fabrication treatment. In addition to C₆₀ -based FMNAs, this review particularly focuses on recently fabricated FMNAs comprising higher fullerenes (e.g., C₇₀ ) and metallofullerenes. Meanwhile, an overview of the property modulation is presented and multidisciplinary applications of FMNAs in various fields are summarized, including sensors, optoelectronics, biomedicines, and energy. At the end, the prospects for future research, application opportunities, and challenges associated with FMNAs are proposed.

Remodeling nanodroplets into hierarchical mesoporous silica nanoreactors with multiple chambers

Multi-chambered architectures have attracted much attention due to the ability to establish multifunctional partitions in different chambers, but manipulating the chamber numbers and coupling multi-functionality within the multi-chambered mesoporous nanoparticle remains a challenge. Herein, we propose a nanodroplet remodeling strategy for the synthesis of hierarchical multi-chambered mesoporous silica nanoparticles with tunable architectures. Typically, the dual-chambered nanoparticles with a high surface area of ~469 m² g⁻¹ present two interconnected cavities like a calabash. Furthermore, based on this nanodroplet remodeling strategy, multiple species (magnetic, catalytic, optic, etc.) can be separately anchored in different chamber without obvious mutual-crosstalk. We design a dual-chambered mesoporous nanoreactors with spatial isolation of Au and Pd active-sites for the cascade synthesis of 2-phenylindole from 1-nitro-2-(phenylethynyl)benzene. Due to the efficient mass transfer of reactants and intermediates in the dual-chambered structure, the selectivity of the target product reaches to ~76.5%, far exceeding that of single-chambered nanoreactors (~41.3%).

Multi-chambered structures have attracted great attention due to their ability to create multifunctional partitions in different chambers. Here, the authors prepared mesoporous silica nanoreactors with hierarchical chambers for catalytic cascades.

Preparation of asymmetric particles by controlling the phase separation of seeded emulsion polymerization with ethanol/water mixture

Alcohols are discovered for the first time to tune the morphology of poly(vinyl benzyl chloride)-poly(3-methacryloxypropyltrimethoxysilane) (PVBC-PMPS) composite particles through seeded emulsion polymerization within the alcohol/water mixture. Here, monodispersed linear PVBC particles was synthesized through the dispersion polymerization and employed as the seeds. The as-obtained PVBC-PMPS composite particles could be dramatically tuned from core-shell structures to snowman-like particles, to dumbbell-shaped particles, to inverse snowman-like particles when the ethanol content in reaction mixtures is only adjusted within a narrow range. The morphology of fresh PMPS bulges was observed after removing the linear PVBC seeds with N,N'-dimethyl formamide, and their formation mechanism was studied by monitoring the free radical polymerization and sol-gel process of 3-methacryloxypropyltrimethoxysilane. It has been confirmed that the sol-gel kinetics were the main factor on the particles' morphology. In addition, morphologies of PVBC-PMPS particles were also varied by the MPS feeding amount, types of the co-solvent and pH values of alcohol/water mixtures.

From flat to deep concave: an unusual mode of facet control

Au particles with rhombic dodecahedron outlines and deep cavities are obtained by epitaxial growth from a triangular nanoplate. An unusual "wrapping" growth that combines ligand-promoted facet-selective growth and site-specific deposition is proposed. Such a templateless growth not only allows the extreme defect-tolerance, but also broadens the synthetic control at the nanoscale.

Soft Patch Interface-Oriented Superassembly of Complex Hollow Nanoarchitectures for Smart Dual-Responsive Nanospacecrafts

Meticulous surface patterning of nanoparticles with anisotropic patches as analogs of functional groups offers fascinating potential in many fields, particularly in controllable materials assembly. However, patchy colloids generally evolve into high-symmetry solid structures, mainly because the assembly interactions arise between patches via patch-to-patch recognition. Here, we report an assembly concept, that is, a soft patch, which enables selective and directional fusion of liquid droplets for producing highly asymmetrical hollow nanospacecrafts. Our approach enables precise control of hollow nanoparticle diameters by manipulating droplet fusion regions. By controlling the patch number, more orientations are accessible to droplet fusion, allowing for increased degrees of complexity of hollow self-assemblies. The versatility and curvature-selective growth of this strategy are demonstrated on three nonspherical nanoparticles, enabling the creation of highly asymmetric nanospacecrafts. By patterning Au-core Ag-shell nanorods, the nanospacecraft can be programmed in response to either H₂O₂ or near-infrared light, exhibiting dual-mode response behavior with a 208% increase in the diffusion coefficient in both modes compared with other nanoscale low-asymmetry active materials. Overall, these findings are a significant step toward designing new patch interactions for materials self-assembly for creating complex hollow colloids and functional nanodevices that are otherwise inaccessible.

Fullerene superlattices containing charge transfer complexes for an improved nonlinear optical performance

To improve the nonlinear optical (NLO) properties of fullerene C₆₀, chemical modifications are normally needed to construct a donor-π-acceptor (D-π-A) system, which requires tedious and time-consuming synthesis procedures. In addition, the conjugated structure of C₆₀ will inevitably be destroyed, which is disadvantageous for other applications. Here, we use solvent-based nanoarchitectonics to obtain highly ordered, three-dimensional (3D) C₆₀ supramolecular structures. For this purpose, a liquid-liquid interfacial precipitation (LLIP) method was employed using quinoline as the good solvent. Hollow polyhedra (HPH) and multilayer flowers (MFs) were obtained when methanol and ethanol were selected as the poor solvents, respectively. While quinoline failed to enter the HPH, it was found to be successfully intercalated with the MFs, which induced a transition of the C₆₀ organization from a pristine face-centered-cubic (fcc) phase to a hexagonal close packed (hcp) lattice. When embedded in a poly(methyl methacrylate) (PMMA) matrix, the HPH and MFs both show reverse saturable absorption (RSA) and optical limiting (OL) properties. The MFs-based film showed a third-order nonlinear absorption coefficient (β) of 1.25 × 10⁵ cm·GW^-1 and an optical limiting threshold (F_ol) of 0.00625 J·cm^-2. Comparatively, the HPH-based film exhibited a lower β value of 9.80 × 10⁴ cm GW^-1 and a higher F_ol value of 0.00834 J cm^-2. The better NLO performance of the MFs was mainly ascribed to the formation of the charge transfer complexes between quinoline and C₆₀, proven by UV-vis and electrochemical measurements. The fine tuning of the NLO properties of C₆₀ without chemical modification provides new opportunities for C₆₀ to be applied in nonlinear optics.

Spiral self-assembly of lamellar micelles into multi-shelled hollow nanospheres with unique chiral architecture

Functional carbon nanospheres are exceptionally useful, yet controllable synthesis of them with well-defined porosity and complex multi-shelled nanostructure remains challenging. Here, we report a lamellar micelle spiral self-assembly strategy to synthesize multi-shelled mesoporous carbon nanospheres with unique chirality. This synthesis features the introduction of shearing flow to drive the spiral self-assembly, which is different from conventional chiral templating methods. Furthermore, a continuous adjustment in the amphipathicity of surfactants can cause the packing parameter changes, namely, micellar structure transformations, resulting in diverse pore structures from single-porous, to radial orientated, to flower-like, and to multi-shelled configurations. The self-supported spiral architecture of these multi-shelled carbon nanospheres, in combination with their high surface area (~530 m² g⁻¹), abundant nitrogen content (~6.2 weight %), and plentiful mesopores (~2.5 nm), affords them excellent electrochemical performance for potassium-ion storage. This simple but powerful micelle-directed self-assembly strategy offers inspiration for future nanostructure design of functional materials.

Self-regulated co-assembly of soft and hard nanoparticles

Controlled self-assembly of colloidal particles into predetermined organization facilitates the bottom-up manufacture of artificial materials with designated hierarchies and synergistically integrated functionalities. However, it remains a major challenge to assemble individual nanoparticles with minimal building instructions in a programmable fashion due to the lack of directional interactions. Here, we develop a general paradigm for controlled co-assembly of soft block copolymer micelles and simple unvarnished hard nanoparticles through variable noncovalent interactions, including hydrogen bonding and coordination interactions. Upon association, the hairy micelle corona binds with the hard nanoparticles with a specific valence depending exactly on their relative size and feeding ratio. This permits the integration of block copolymer micelles with a diverse array of hard nanoparticles with tunable chemistry into multidimensional colloidal molecules and polymers. Secondary co-assembly of the resulting colloidal molecules further leads to the formation of more complex hierarchical colloidal superstructures. Notably, such colloidal assembly is processible on surface either through initiating the alternating co-assembly from a micelle immobilized on a substrate or directly grafting a colloidal oligomer onto the micellar anchor.

Colloidal self-assembly enables bottom-up manufacture of materials with designed hierarchies and functions. Here the authors develop a facile method to construct multidimensional colloidal architectures via the association of soft block copolymer micelles with simple unvarnished hard nanoparticles.

Ligand-Mediated Spatially Controllable Superassembly of Asymmetric Hollow Nanotadpoles with Fine-Tunable Cavity as Smart H2O2-Sensitive Nanoswimmers

Ligand-mediated interface control has been broadly applied as a powerful tool in constructing sophisticated nanocomposites. However, the resultant morphologies are usually limited to solid structures. Now, a facile spatially controllable ligand-mediated superassembly strategy is explored to construct monodispersed, asymmetric, hollow, open Au-silica (SiO₂) nanotadpoles (AHOASTs). By manipulating the spatial density of ligands, the degree of diffusion of silica can be precisely modulated; thus the diameters of the cavity can be continuously tuned. Due to their highly anisotropic, hollow, open morphologies, we construct a multicompartment nanocontainer with enzymes held and isolated inside the cavity. Furthermore, the resulting enzyme-AHOASTs are used as biocompatible smart H₂O₂-sensitive nanoswimmers and demonstrate a higher diffusion coefficient than other nanoscaled swimmers. We believe that this strategy is critical not only in designing sophisticated hollow nanosystem but also in providing great opportunities for applications in nanomaterial assembly, catalysis, sensors, and nanoreactors.

Low lattice thermal conductivity of a 5-8-peanut-shaped carbon nanotube

5-8-defects are well-known in graphene and other 2D carbon structures, but not well-studied in one dimensional (1D) carbon materials. Here, we design a peanut-shaped carbon nanotube by assembling the 5-8-cage composed of carbon 5- and 8-membered rings, named 5-8-PSNT. Using first-principles calculations and molecular dynamics simulations, we find that 5-8-PSNT is not only thermally and dynamically stable, but also metallic. Moreover, its lattice thermal conductivity is only 95.87 W m-1 K-1, which is less than one tenth of the value of (6, 6) carbon nanotube that has a radius similar to that of 5-8-PSNT. A further analysis of the phonon properties reveals that the low lattice thermal conductivity of 5-8-PSNT arises from its low phonon group velocity, short relaxation time, large lattice vibrational mismatch and strong anharmonicity. These findings further suggest that a pentagon and an octagon as structural units can effectively modulate the properties of carbon materials.