Kangkyun Baek

Synthetic Ion Channel Based on Metal–Organic Polyhedra†

A root crop washer has a rotatable washing drum which is partially immersed in a water trough, and a stone separator mounted before an inlet of the drum. A loading hopper is provided for delivering a root crop to the stone separator. An elevator is mounted at an outlet of the washing drum for discharge of cleaned produce from an outlet of the washing drum. Rotating paddles within the stone separator impart a swirling motion about a vertical axis to water in the stone separator. The root crop is supported by the water and moved around an inner sidewall of the stone separator between an inlet and an outlet of the stone separator. At the same time unwanted heavier material such as stones and clay falls downwardly through the stone separator for discharge through a waste outlet at a bottom of the stone separator.

Unconventional U-shaped conformation of a bolaamphiphile embedded in a synthetic host

The X-ray crystal structure of 1,12-dodecane diammonium (C(12)DA(2+)) encapsulated in cucurbit[8]uril reveals an unconventional U-shaped conformation of C(12)DA(2+), which is attributed to the favorable host-guest interactions to overcome the charge-charge repulsion of the two ammonium groups in close proximity and high internal strain.

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.

Self-assembled, covalently linked, hollow phthalocyanine nanospheres

A rational design and synthesis of covalently linked Pc nanospheres with a very thin shell and hollow interior, composed of approximately 12 000 Pc units on average, was demonstrated through thiol–ene “click” chemistry without using any templates or emulsifiers. The ZnPc nanospheres allow post-synthetic modification to improve their dispersibility in aqueous solution without altering the morphology of the nanospheres or the properties of ZnPc cores. More importantly, the ZnPc nanospheres showed higher singlet oxygen generation efficiency and in vitro phototoxicity than monomeric Pc molecules, suggesting that ZnPc nanospheres are potentially useful as a PS for PDT. We anticipate that the ZnPc nanospheres would allow other post-synthetic modifications such as the introduction of targeting ligands to deliver the nanospheres to specific target sites and perform a dual chemo- and photodynamic therapy by the encapsulation of therapeutic agents. The easy synthesis of a hollow spherical framework with a high Pc content, coupled with facile post-synthetic modification may allow Pc nanospheres to be a versatile platform for a diverse range of medical and non-medical applications.

A Multifunctional Subphthalocyanine Nanosphere for Targeting, Labeling, and Killing of Antibiotic‐Resistant Bacteria

Developing a material that can combat antibiotic-resistant bacteria, a major global health threat, is an urgent requirement. To tackle this challenge, we synthesized a multifunctional subphthalocyanine (SubPc) polymer nanosphere that has the ability to target, label, and photoinactivate antibiotic-resistant bacteria in a single treatment with more than 99 % efficiency, even with a dose as low as 4.2 J cm(-2) and a loading concentration of 10 nM. The positively charged nanosphere shell composed of covalently linked SubPc units can increase the local concentration of photosensitizers at therapeutic sites. The nanosphere shows superior performance compared to corresponding monomers presumably because of their enhanced water dispersibility, higher efficiency of singlet-oxygen generation, and phototoxicity. In addition, this material is useful in fluorescence labeling of living cells and shows promise in photoacoustic imaging of bacteria in vivo.

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. In addition, their size can be tuned by controlling the initial monomer concentrations, an observation that is supported by a theoretical analysis. These hollow microrings can encapsulate guest molecules in the intratoroidal nanospace, and their peripheries can act as templates for circular arrays of metal nanoparticles.

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. Moreover, reversible morphological transformations between these structures can be achieved by simple solvent exchanges. This work is a novel approach for the formation of robust nano/microstructured materials that dynamically respond to environmental stimuli.