Tandem-biocatalysis reactors constructed by topological evolution of CaCO particles into hollow metal hydroxide spheres.

Despite remarkable advances in the design and synthesis of hollow inorganic spheres (HISs), the harsh synthetic conditions have precluded the applications of HISs to biochemical and biological fields. Herein we report a biocompatible strategy for synthesizing metal hydroxide HISs (MH-HISs) by simply mixing CaCO particles with metal ions in water. The ion-exchange reaction between Ca and metal ions leads to the structural and chemical evolution from solid CaCO particles to hollow MH-HISs via core-shell and yolk-shell structures, while enabling the encapsulation of enzymes to the shells without loss of catalytic activities.

A Natural Virucidal and Microbicidal Spray Based on Polyphenol-Iron Sols.

Numerous disinfection methods have been developed to reduce the transmission of infectious diseases that threaten human health. However, it still remains elusively challenging to develop eco-friendly and cost-effective methods that deactivate a wide range of pathogens, from viruses to bacteria and fungi, without doing any harm to humans or the environment. Herein we report a natural spraying protocol, based on a water-dispersible supramolecular sol of nature-derived tannic acid (TA) and Fe, which is easy-to-use and low-cost.

Vortex-assisted, nanoarchitectonic manipulation of microparticles with flavonoid-Fe complex in biphasic water-oil systems.

Coordination-driven self-assembly of metal-ligand complexes is a powerful nanoarchitectonic tool for particle engineering, but its usability is limited when using two immiscible coating components. This paper reports that simple vortexing of a biphasic system of Fe ions in water and flavonoids in oil forms nanoshells on individual particles, thereby enabling the utilization of water-insoluble ligands as coating materials. Mechanistic studies suggest that the biphasic mass-transfer equilibrium of flavonoid-Fe species controls the shell formation, with the oil phase acting as a reservoir of coating precursors for continuous coating.

Enzyme-Mediated Kinetic Control of Fe-Tannic Acid Complexation for Interface Engineering.

Supramolecular self-assembly of Fe and tannic acid (TA) has received great attention in the fields of materials science and interface engineering because of its exceptional surface coating properties. Although advances in coating strategies often suggest that kinetics in the generation of interface-active Fe-TA species is deeply involved in the film formation, there is no acceptable elucidation for the coating process. In this work, we developed the enzyme-mediated kinetic control of Fe oxidation to Fe in a Fe-TA complex in the iron-gall-ink-revisited coating method.

Reversed Anionic Hofmeister Effect in Metal-Phenolic-Based Film Formation.

Although metal-phenolic species have emerged as one of the versatile material-independent-coating materials, providing attractive tools for interface engineering, mechanistic understanding of their film formation and growth still remains largely unexplored. Especially, the anions have been overlooked despite their high concentration in the coating solution. Considering that the anions are critical in the reactivity of metal-organic complex and the formation and/or property of functional materials, we investigated the anionic effects on the characteristics of film formation, such as film thickness and properties, in the Fe-tannic acid coating.

Ascorbic acid-mediated reductive disassembly of Fe-tannic acid shells in degradable single-cell nanoencapsulation.

Rapid degradation of Fe-tannic acid films is achieved under mild conditions via ascorbic acid-mediated Fe reduction, which overcomes the problems in the disassembly of a metal-organic complex including slow reaction rates and reaction incompatibility with living cells. The strategy of reductive disassembly is applied to degradable single-cell nanoencapsulation, providing an advanced tool for tightly controlling and manipulating the cell-material interface.

Engineering of Nebulized Metal-Phenolic Capsules for Controlled Pulmonary Deposition.

Particle-based pulmonary delivery has great potential for delivering inhalable therapeutics for local or systemic applications. The design of particles with enhanced aerodynamic properties can improve lung distribution and deposition, and hence the efficacy of encapsulated inhaled drugs. This study describes the nanoengineering and nebulization of metal-phenolic capsules as pulmonary carriers of small molecule drugs and macromolecular drugs in lung cell lines, a human lung model, and mice.

Ricocheting Droplets Moving on Super-Repellent Surfaces.

Droplet bouncing on repellent solid surfaces (e.g., the lotus leaf effect) is a common phenomenon that has aroused interest in various fields.

Modular Assembly of Host-Guest Metal-Phenolic Networks Using Macrocyclic Building Blocks.

The manipulation of interfacial properties has broad implications for the development of high-performance coatings. Metal-phenolic networks (MPNs) are an emerging class of responsive, adherent materials. Herein, host-guest chemistry is integrated with MPNs to modulate their surface chemistry and interfacial properties.

Tuning the Mechanical Behavior of Metal-Phenolic Networks through Building Block Composition.

Metal-phenolic networks (MPNs) are an emerging class of functional metal-organic materials with a high degree of modularity in terms of the choice of metal ion, phenolic ligand, and assembly method. Although various applications, including drug delivery, imaging, and catalysis, have been studied with MPNs, in the form of films and capsules, the influence of metals and organic building blocks on their mechanical properties is poorly understood. Herein, we demonstrate that the mechanical properties of MPNs can be tuned through choice of the metal ion and/or phenolic ligand.

Spray Assembly of Metal-Phenolic Networks: Formation, Growth, and Applications.

Hybrid conformal coatings, such as metal-phenolic networks (MPNs) that are constructed from the coordination-driven assembly of natural phenolic ligands, are of interest in areas including biomedicine, separations, and energy. To date, most MPN coatings have been prepared by immersing substrates in solutions containing the phenolic ligands and metal ions, which is a suitable method for coating small or flexible objects. In contrast, more industrially relevant methods for coating and patterning large substrates, such as spray assembly, have been explored to a lesser extent toward the fabrication of MPNs, particularly regarding the effect of process variables on MPN growth.

Self-Assembled Metal-Phenolic Networks on Emulsions as Low-Fouling and pH-Responsive Particles.

Interfacial self-assembly is a powerful organizational force for fabricating functional nanomaterials, including nanocarriers, for imaging and drug delivery. Herein, the interfacial self-assembly of pH-responsive metal-phenolic networks (MPNs) on the liquid-liquid interface of oil-in-water emulsions is reported. Oleic acid emulsions of 100-250 nm in diameter are generated by ultrasonication, to which poly(ethylene glycol) (PEG)-based polyphenolic ligands are assembled with simultaneous crosslinking by metal ions, thus forming an interfacial MPN.

Smart SERS Hot Spots: Single Molecules Can Be Positioned in a Plasmonic Nanojunction Using Host-Guest Chemistry.

Single-molecule surface-enhanced Raman spectroscopy (SERS) offers new opportunities for exploring the complex chemical and biological processes that cannot be easily probed using ensemble techniques. However, the ability to place the single molecule of interest reliably within a hot spot, to enable its analysis at the single-molecule level, remains challenging. Here we describe a novel strategy for locating and securing a single target analyte in a SERS hot spot at a plasmonic nanojunction.

Synthesis of Metal Nanoparticles in Metal-Phenolic Networks: Catalytic and Antimicrobial Applications of Coated Textiles.

The synthesis of metal nanoparticle (NP)-coated textiles (nanotextiles) is achieved by a dipping process in water without toxic chemicals or complicated synthetic procedures. By taking advantage of the unique nature of tannic acid, metal-phenolic network-coated textiles serve as reducing and stabilizing sites for the generation of metal nanoparticles of controllable size. The textiles can be decorated with various metal nanoparticles, including palladium, silver, or gold, and exhibit properties derived from the presence of the metal nanoparticles, for example, catalytic activity in water (>96% over five cycles using palladium nanoparticles) and antibacterial activity against Gram-negative bacteria (inhibition of Escherichia coli using silver nanoparticles) that outperforms a commercial bandage.

Covalent Self-Assembly and One-Step Photocrosslinking of Tyrosine-Rich Oligopeptides to Form Diverse Nanostructures.

We present covalently self-assembled peptide hollow nanocapsule and peptide lamella. These biomimetic dityrosine peptide nanostructures are synthesized by one-step photopolymerization of a tyrosine-rich short peptide without the aid of a template. This simple approach offers direct synthesis of fluorescent peptide nanocages and free-standing thin films.

Hydrolytic Transformation of Microporous Metal-Organic Frameworks to Hierarchical Micro- and Mesoporous MOFs.

A new approach to the synthesis of hierarchical micro- and mesoporous MOFs from microporous MOFs involves a simple hydrolytic post-synthetic procedure. As a proof of concept, a new microporous MOF, POST-66(Y), was synthesized and its transformation into a hierarchical micro- and mesoporous MOF by water treatment was studied. This method produced mesopores in the range of 3 to 20 nm in the MOF while maintaining the original microporous structure, at least in part.

Reversible morphological transformation between polymer nanocapsules and thin films through dynamic covalent self-assembly.

A facile method has been developed for synthesizing polymer nanocapsules and thin films using multiple in-plane stitching of monomers by the formation of reversible disulfide linkages. Owing to the reversibility of the disulfide linkages, the nanostructured materials readily transform their structures in response to environmental changes at room temperature. For example, in reducing environments, the polymer nanocapsules release loaded cargo molecules.

Highly stable, water-dispersible metal-nanoparticle-decorated polymer nanocapsules and their catalytic applications.

A facile synthesis of highly stable, water-dispersible metal-nanoparticle-decorated polymer nanocapsules (M@CB-PNs: M=Pd, Au, and Pt) was achieved by a simple two-step process employing a polymer nanocapsule (CB-PN) made of cucurbit[6]uril (CB[6]) and metal salts. The CB-PN serves as a versatile platform where various metal nanoparticles with a controlled size can be introduced on the surface and stabilized to prepare new water-dispersible nanostructures useful for many applications. The Pd nanoparticles on CB-PN exhibit high stability and dispersibility in water as well as excellent catalytic activity and recyclability in carbon-carbon and carbon-nitrogen bond-forming reactions in aqueous medium suggesting potential applications as a green catalyst.

Hollow nanotubular toroidal polymer microrings.

Despite the remarkable progress made in the self-assembly of nano- and microscale architectures with well-defined sizes and shapes, a self-organization-based synthesis of hollow toroids has, so far, proved to be elusive. Here, we report the synthesis of polymer microrings made from rectangular, flat and rigid-core monomers with anisotropically predisposed alkene groups, which are crosslinked with each other by dithiol linkers using thiol-ene photopolymerization. The resulting hollow toroidal structures are shape-persistent and mechanically robust in solution.

Free-standing, single-monomer-thick two-dimensional polymers through covalent self-assembly in solution.

The design and synthesis of two-dimensional (2D) polymers is a challenging task, hitherto achieved in solution only through the aid of a solid surface "template" or preorganization of the building blocks in a 2D confined space. We present a novel approach for synthesizing free-standing, covalently bonded, single-monomer-thick 2D polymers in solution without any preorganization of building blocks on solid surfaces or interfaces by employing shape-directed covalent self-assembly of rigid, disk-shaped building blocks having laterally predisposed reactive groups on their periphery. We demonstrate our strategy through a thiol-ene "click" reaction between (allyloxy)12CB[6], a cucurbit[6]uril (CB[6]) derivative with 12 laterally predisposed reactive alkene groups, and 1,2-ethanedithiol to synthesize a robust and readily transferable 2D polymer.

A new three-way supramolecular switch based on redox-controlled interconversion of hetero- and homo-guest-pair inclusion inside a host molecule.

A novel three-way supramolecular switch based on the interconversion of hetero-guest-pair (D-A) and homo-guest-pair (D(2) or A(2)) inclusion inside cucurbit[8]uril is reported, which can be selectively controlled by chemical or electrochemical stimuli.