Eun-Ah You

Polarization-dependent multipolar plasmon resonances in anisotropic multiscale au particles

This paper reports the fabrication and characterization of three-dimensional (3D) multiscale Au particles with different aspect ratios. Increasing the length of the particles resulted in excitation of a longitudinal mode and two different transverse modes having different multipolar orders. The multipolar orders increased for both longitudinal and transverse modes as the aspect ratio increased. Finite-difference time-domain calculations revealed that the structural asymmetry of the 3D anisotropic particles were the reason for the two distinct transverse plasmon resonances. When the 3D structural change occurred at the ends of the multiscale particle, however, the optical response showed two resonances in the longitudinal direction and only a single resonance in the transverse direction.

Size control of arsenic trioxide nanocrystals grown in nanowells

This paper describes a new strategy to generate nanocrystalline drugs through the precipitation of drug molecules in attoliter nanowells. We controlled the size of arsenic trioxide (ATO) nanocrystals by simply changing the concentration of ATO solution in the nanowells; particles with sizes ranging from 55 to 175 nm were formed. This approach only requires the drugs to be soluble in a solvent and thus can be broadly applicable to produce other drugs in nanocrystalline form.

Transparent, self-cleaning and waterproof surfaces with tunable micro/nano dual-scale structures.

The rational design and facile fabrication of optically transparent, superhydrophobic surfaces can advance their versatile applications, including optoelectronic devices. For the easily accessible and scalable preparation of transparent, superhydrophobic surfaces, various coating methods using a solution-process have been developed. However, obtaining highly transparent, non-wetting surfaces with excellent properties is challenging due to the difficulty in controlling surface roughness. Here, we report on a novel approach to control the surface roughness by fabricating tailorable micro/nano dual-scale surface structures via solution-processed nanoparticle coating. The surface roughness was able to be controlled by micro/nano dual-scale structures that can be manipulated by varying the mixture ratio of two different sizes of Al2O3 nanoparticles. The controllable micro/nano dual-scale structures were optimized to achieve the superior surface properties in both hydrophobicity and transparency, exhibiting a high water contact angle (>160°), low sliding angle (<2°) and high transmittance (>90%). These characteristics allowed an excellent transparency and self-cleaning capability as well as a superior waterproof ability even under applied voltage. Furthermore, we demonstrated the versatile applicability of the developed surface-coating method to a wide range of substrates including glass, paper, fabrics, and even flexible plastics.

Multifunctional Hybrid Multilayer Gate Dielectrics with Tunable Surface Energy for Ultralow-Power Organic and Amorphous Oxide Thin-Film Transistors

For large-area, printable, and flexible electronic applications using advanced semiconductors, novel dielectric materials with excellent capacitance, insulating property, thermal stability, and mechanical flexibility need to be developed to achieve high-performance, ultralow-voltage operation of thin-film transistors (TFTs). In this work, we first report on the facile fabrication of multifunctional hybrid multilayer gate dielectrics with tunable surface energy via a low-temperature solution-process to produce ultralow-voltage organic and amorphous oxide TFTs. The hybrid multilayer dielectric materials are constructed by iteratively stacking bifunctional phosphonic acid-based self-assembled monolayers combined with ultrathin high-k oxide layers. The nanoscopic thickness-controllable hybrid dielectrics exhibit the superior capacitance (up to 970 nF/cm2), insulating property (leakage current densities <10-7 A/cm2), and thermal stability (up to 300 °C) as well as smooth surfaces (root-mean-square roughness <0.35 nm). In addition, the surface energy of the hybrid multilayer dielectrics are easily changed by switching between mono- and bifunctional phosphonic acid-based self-assembled monolayers for compatible fabrication with both organic and amorphous oxide semiconductors. Consequently, the hybrid multilayer dielectrics integrated into TFTs reveal their excellent dielectric functions to achieve high-performance, ultralow-voltage operation (< ± 2 V) for both organic and amorphous oxide TFTs. Because of the easily tunable surface energy, the multifunctional hybrid multilayer dielectrics can also be adapted for various organic and inorganic semiconductors, and metal gates in other device configurations, thus allowing diverse advanced electronic applications including ultralow-power and large-area electronic devices.

Rationally Designed, Multifunctional Self-Assembled Nanoparticles for Covalently Networked, Flexible and Self-Healable Superhydrophobic Composite Films

For constructing bioinspired functional films with various superhydrophobic functions, including self-cleaning, anticorrosion, antibioadhesion, and oil-water separation, hydrophobic nanomaterials have been widely used as crucial structural components. In general, hydrophobic nanomaterials, however, cannot form strong chemical bond networks in organic-inorganic hybrid composite films because of the absence of chemically compatible binding components. Herein, we report the rationally designed, multifunctional self-assembled nanoparticles with tunable functionalities of covalent cross-linking and hydrophobicity for constructing three-dimensionally interconnected superhydrophobic composite films via a facile solution-based fabrication at room temperature. The multifunctional self-assembled nanoparticles allow the systematic control of functionalities of composite films, as well as the stable formation of covalently linked superhydrophobic composite films with excellent flexibility (bending radii of 6.5 and 3.0 mm, 1000 cycles) and self-healing ability (water contact angle > 150°, ≥10 cycles). The presented strategy can be a versatile and effective route to generating other advanced functional films with covalently interconnected composite networks.