Kyoungja Woo

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Quantum dots (QDs) are novel tools with multiple biological and medical applications because of their superior photoemission and photostability characteristics. However, leaching of toxic metals from QDs is of great concern. Therefore, for the successful application of QDs in bioscience, it is essential to understand their biological fate and toxicity. We(More)
Silver nanoparticles (AgNPs) are considered to be a potentially useful tool for controlling various pathogens. However, there are concerns about the release of AgNPs into environmental media, as they may generate adverse human health and ecological effects. In this study, we developed and evaluated a novel micrometer-sized magnetic hybrid colloid (MHC)(More)
Herein, we report highly bright multicolor-emitting β-Na(Y,Gd)F₄:Ce,Tb,Eu/β-NaYF₄ nanoparticles (NPs) with precise color tunability. First, highly bright sub-20 nm β-Na(Y,Gd)F₄:Ce,Tb,Eu NPs were synthesized via a heating-up method. By controlling the ratio of Eu(3+) to Tb(3+), we generated green, yellow-green, greenish yellow, yellow, orange, reddish(More)
A pathway for achieving intense green light emitting LiGdF4:Yb,Er upconversion nanophosphors (UCNPs) via Y(3+) doping is demonstrated. It was revealed that Y(3+) doping initiated the formation of a tetragonal phase and affected the particle size. Single tetragonal-phase LiGd0.4Y0.4F4:Yb(18%),Er(2%) (LGY0.4F:Yb,Er) UCNPs exhibited strong upconversion (UC)(More)
We report the systematic control of the morphology of β-NaYF4:Yb,Er/Tm upconversion nanophosphors (UCNPs) from large spheres (37.9 nm) to rods (length = 60.1 nm, width = 21.5 nm) and from rods to hexagonal prisms (length = 48.8 nm, width = 44.0 nm) or small spheres (14.0 nm) by the use of a surfactant, an additive, and lanthanide doping. Increasing the(More)
The major challenges in practically utilising the immense potential benefits of nanomaterials are controlling aggregation, recycling the nanomaterials, and fabricating well-defined nanoparticulate materials using innovative methods. We present a novel innovative synthetic strategy for core-shell bimetallic nanoparticles that are well-defined, ligand-free,(More)
Blue (<480 nm) emitting Cd-free quantum dots (QDs) are in great demand for various applications. However, their synthesis has been challenging. Here we present blue emitting InP/ZnS core/shell QDs with a band edge emission of 475 nm and a full width at half maximum of 39 nm (215 meV) from their quantum confined states. The drastic temperature drop(More)
We present colloidal silica microspheres encapsulating a homogeneous quantum dot layer at radial equidistance from the centre by utilizing electrostatic interaction between surface-engineered silica microspheres and QDs. The microspheres show dramatically enhanced optical absorption and emission with an appropriate silica shell thickness.
Although the quantum efficiencies of quantum dots (QDs) are approaching unity through advances in the synthesis of QD materials, their luminescence efficiencies after mixing with resin and thermal curing for white light-emitting diodes (LEDs) are seriously lowered because of aggregation and oxidation of QDs and poor adhesion of QDs to the resin. To overcome(More)
This paper describes a pH-responsive multilayer film composed of two layered components, namely poly(allylamine hydrochloride) (PAH) and a copolymer of acrylic acid and [1,3]oxazine-modified acrylate (POA). The oxazine ring is an acidochromic chromophore and opens to form either cationic 3H-indolium or anionic hemiaminal in a pH-dependent manner. This(More)