Hye Young Koo

Facile Fabrication of Core-in-Shell Particles by the Slow Removal of the Core and Its Use in the Encapsulation of Metal Nanoparticles

Core-in-shell particles with controllable core size have been fabricated from core-shell particles by means of the controlled core-dissolution method. These cores in inorganic shells were employed as scaffolds for the synthesis of metal nanoparticles. After dissolution of the cores, metal nanoparticles embedded in cores were encapsulated into the interior of shell, without any damage or change. This article describes a very simple method for deriving core-in-shell particles with controllable core size and encapsulation of nanoparticles into the interior of shell.

Synthesis of raspberry-like particles using polyelectrolyte multilayer-coated particles

The formation of raspberry particles from polyelectrolyte multilayer-modified particles is described. This synthesis represents a new use for polyelectrolyte multilayers as nanoscale-thick reaction vessels for the immobilization and reaction of inorganic reagents. The dissolution of Au nanoparticles inside PEM layers that are capped with a SiO2 layer leads to the hydrolysis and subsequent redeposition of SiO2 nanoparticles. The size of these particles is in the 200 nm range and their loading can be controlled by adding various amounts of Au nanoparticles to the PEMs.

Direct Growth of Optically Stable Gold Nanorods onto Polyelectrolyte Multilayered Capsules

Layer-by-layer (LbL) self-assembled polyelectrolyte multilayer (PEM) capsules are of scientific and technological interest for use as microand nanosized reactors, optical materials, and building components for nanoengineering owing to their controllable permeability and ease of surface functionalization. Shell of these capsules can be readily functionalized with various ions, functional molecules, and inorganic nanoparticles through electrostatic interaction. In particular, PEM capsules doped with gold nanoparticles (AuNPs) are attractive for many optical, biomedical applications benefited from strong plasmon resonance of AuNPs that can act as absorption antennas. For this reason, many efforts have been devoted to the preparation of PEM capsules functionalized with AuNPs. For example, Gittins and co-workers have prepared AuNP-doped PEM capsules by infiltration of the preformed AuNPs onto the PEM-coated colloidal template and subsequent removal of the cores, which allows the release of the encapsulated material on demand upon irradiation with laser light. In another study, AuNPdoped PEM capsules were used for enhanced Raman imaging and optical spectra. In our previous work, AuNPs were directly grown inside the PEM shells through electrostatic binding of Au precursor onto a PEM and subsequent chemical reduction. Recently, interest in gold nanorods (AuNRs) has increased due to their optical response in the visible and near-infrared

A remote-controlled generation of gold@polydopamine (core@shell) nanoparticles via physical-chemical stimuli of polydopamine/gold composites.

We present the synthesis of polydopamine particle-gold composites (PdopP-Au) and unique release of Au@Pdop core@shell nanoparticles (NPs) from the PdopP-Au upon external stimuli. The PdopP-Au was prepared by controlled synthesis of AuNPs on the Pdop particles. Upon near infrared (NIR) irradiation or NaBH4 treatment on the PdopP-Au, the synthesized AuNPs within the PdopPs could be burst-released as a form of Au@Pdop NPs. The PdopP-Au composite showed outstanding photothermal conversion ability under NIR irradiation due to the ultrahigh loading of the AuNPs within the PdopPs, leading to a remote-controlled explosion of the PdopP-Au and rapid formation of numerous Au@Pdop NPs. The release of the Au@Pdop NPs could be instantly stopped or re-started by off or reboot of NIR, respectively. The structure of the released Au@Pdop NPs is suitable for a catalyst or adsorbent, thus we demonstrated that the PdopP-Au composite exhibited excellent and sustained performances for environmental remediation due to its capability of the continuous production of fresh catalysts or adsorbents during the reuse.

Surface Design of Separators for Oil/Water Separation with High Separation Capacity and Mechanical Stability

A convection heat treatment that can replace existing chemical oxidation methods was developed for the preparation of hierarchically oxidized Cu meshes with various surface morphologies, representing a very simple and green route that does not involve toxic chemicals. Three types of Cu meshes [bumpy-like (BL) and short and long needle-like (NL) structures] exhibited similar separation efficiencies of 95-99% over 20 separation cycles, as indicated by their similar water contact angles (WCAs; 147-150°). However, these Cu meshes exhibited different flux behaviors. Excessively rough and excessively smooth surfaces of the Cu mesh resulted in increased resistance to flow and to a decrease of the penetration of oil. A surface with intermediate smoothness, such as the BL-Cu mesh, was necessary for high flux over a broad range of oil viscosities. Furthermore, a less rough surface was more suitable for the separation of highly viscous oil. Computational fluid dynamics (CFD) simulations were carried out to support our experimental results. The BL-Cu meshes also showed outstanding mechanical stability because of their low resistance to the flow of fluids.

Synthesis of Binary Complex Colloidal Particles by Using Polyelectrolyte Multilayer-Coated Particles as Templates

We report a feasible fabrication of binary complex particles based on polyelectrolyte multilayer-coated particles (PEMPs). Binary complex particles were synthesized by combination of large organic and small inorganic nanoparticles. The PEMPs were prepared by alternating adsorption of two kinds of polyelectrolytes with opposite charges onto colloidal particles. In this structure, polyelectrolytes act as a matrix to bind precursor for metal nanoparticles. Following reduction and hydrolysis of the PEMPs could generate bimetallic complexes onto PEMPs. We found that size and composition of the bimetallic complexes depend on the amount of gold precursor added to the suspension of the PEMPs.