Superhydrophobic Materials: Overcoming The Water Vulnerability Of Electronic Devices: A Highly Water‐Resistant ZnO Nanodevice With Multifunctionality (Adv. Mater. 38/2011)

Lee, Seunghyup,Kim, Wooseok,Yong, Kijung WILEY‐VCH Verlag 2011 ADVANCED MATERIALS Vol.23 No.38

<P>Water‐resistant electronic devices are developed based on superhydrophobic nanostructures. A ZnO resistive switching device is tested as a model system. As reported on page 4398 by Kijung Yong and co‐workers, the application of superhydrophobic nanostructures on device surfaces efficiently blocks the direct contact of water with electronic components and the devices work even when water is poured on the surface of the device. </P>

Evaluation of pathogen inactivation on sliced cheese induced by encapsulated atmospheric pressure dielectric barrier discharge plasma

Yong, Hae In,Kim, Hyun-Joo,Park, Sanghoo,Alahakoon, Amali U.,Kim, Kijung,Choe, Wonho,Jo, Cheorun Elsevier 2015 FOOD MICROBIOLOGY Vol.46 No.-

<P><B>Abstract</B></P> <P>Pathogen inactivation induced by atmospheric pressure dielectric barrier discharge (DBD) (250 W, 15 kHz, air discharge) produced in a rectangular plastic container and the effect of post-treatment storage time on inactivation were evaluated using agar plates and cheese slices. When agar plates were treated with plasma, populations of <I>Escherichia coli</I>, <I>Salmonella</I> Typhimurium, and <I>Listeria monocytogenes</I> showed 3.57, 6.69, and 6.53 decimal reductions at 60 s, 45 s, and 7 min, respectively. When the pathogens tested were inoculated on cheese slices, 2.67, 3.10, and 1.65 decimal reductions were achieved at the same respective treatment times. The post-treatment storage duration following plasma treatment potently affected further reduction in pathogen populations. Therefore, the newly developed encapsulated DBD-plasma system for use in a container can be applied to improve the safety of sliced cheese, and increasing post-treatment storage time can greatly enhance the system's pathogen-inactivation efficiency.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Encapsulated atmospheric pressure dielectric barrier discharge plasma was developed. </LI> <LI> The plasma treatment inactivated pathogens on agar and cheese. </LI> <LI> Post-treatment duration following plasma increased the inactivation further. </LI> <LI> The plasma system can be applied for improvement of food safety. </LI> </UL> </P>

Interfacial Properties of Hf-silicate∕Si and Hf-silicate∕Al[sub 2]O[sub 3]∕Si Deposited by Atomic Layer Chemical Vapor Deposition

Kim, Jaehyun,Yong, Kijung The Electrochemical Society 2005 Journal of the Electrochemical Society Vol.152 No.10

A novel composite hierarchical hollow structure: one-pot synthesis and magnetic properties of W₁₈O₄₉–WO₂ hollow nanourchins

Jeon, Seongho,Yong, Kijung The Royal Society of Chemistry 2009 Chemical communications Vol.2009 No.45

<p>A novel composite hierarchical hollow structure is reported. The as-prepared products consist of discrete WO<SUB>2</SUB> hollow core spheres with W<SUB>18</SUB>O<SUB>49</SUB> nanorod shells (“hollow urchins”). The products showed unusual magnetic behavior.</p> <P>Graphic Abstract</P><P>A new type of composite hierarchical structure was synthesized using a one-pot solution-phase route. The as-prepared products consist of WO<SUB>2</SUB> hollow core spheres with W<SUB>18</SUB>O<SUB>49</SUB> nanorod shells (“hollow urchins”). <img src='http://pubs.rsc.org/ej/CC/2009/b916234h/b916234h-ga.gif'> </P>

Physical and electrical characterizations of ultrathin Si-rich Hf-silicate film and Hf-silicate/SiO2 bilayer deposited by atomic layer chemical vapor deposition

Kim, Jaehyun,Yong, Kijung American Institute of Physics 2006 JOURNAL OF APPLIED PHYSICS - Vol.100 No.4

Synthesis and characterization of tungsten oxide nanorods from chemical vapor deposition-grown tungsten film by low-temperature thermal annealing

Jeon, Seongho,Yong, Kijung Cambridge University Press (Materials Research Soc 2008 Journal of materials research Vol.23 No.5

<P>A simple thermal annealing was performed to prepare tungsten oxide nanorods directly from tungsten (W) film. The W film was deposited on Si(100) substrate by chemical vapor deposition (CVD) at 450 °C using W(CO)6. A high density of tungsten oxide nanorods was produced by heating of the W film at 600-700 °C. The morphology, structure, composition, and chemical binding states of the prepared nanorods were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) analysis. XRD and TEM results showed that the grown nanorods were single-crystalline W18O49. According to XPS analysis, the W18O49 nanorods contained ∼55.69% W<SUP>6+</SUP>, ∼32.28% W<SUP>5+</SUP>, and ∼12.03% W<SUP>4+</SUP>. The growth mechanism based on thermodynamics is discussed for the growth of tungsten oxide nanorods from W film.</P>

Surface chemistry controlled superhydrophobic stability of W₁₈O₄₉ nanowire arrays submerged underwater

Lee, Junghan,Yong, Kijung The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.38

<P>Superhydrophobic surfaces with quasi-aligned W<SUB>18</SUB>O<SUB>49</SUB> nanowire (NW) arrays were fabricated using a simple thermal evaporation and surface chemistry modification method. The fabricated superhydrophobic W<SUB>18</SUB>O<SUB>49</SUB> NW surface has shown reliable stability in submerged underwater conditions, exhibiting silvery surfaces caused by total reflection between the water layer and air pockets. The stability of superhydrophobicity in underwater conditions decreased exponentially as the hydrostatic pressure applied to the substrates increased. In addition, variations in stability were investigated according to changes in the surface energy of W<SUB>18</SUB>O<SUB>49</SUB> NW arrays. As surface energy decreased, the underwater stability of the superhydrophobic surface increased sharply. Based on these results, the models explaining tendencies of superhydrophobic stability underwater resulting from hydrostatic pressure and surface energy were designed. This study on fabrication and modeling of underwater superhydrophobic stability will help in designing highly stable superhydrophobic surfaces and broadening fields of superhydrophobic applications.</P> <P>Graphic Abstract</P><P>Superhydrophobic surfaces with quasi-aligned W<SUB>18</SUB>O<SUB>49</SUB> nanowire (NW) arrays were fabricated using a simple thermal evaporation and surface chemistry modification method. Underwater stability of W<SUB>18</SUB>O<SUB>49</SUB> NW arrays was analyzed and the models explaining tendencies of superhydrophobic stability underwater were designed. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm34307j'> </P>

Mechanism Study of ZnO Nanorod-Bundle Sensors for H₂S Gas Sensing

Kim, Jaehyun,Yong, Kijung American Chemical Society 2011 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.115 No.15

<P>This work reports the H<SUB>2</SUB>S gas-sensing properties of ZnO nanorod bundles and an investigation of their gas sensing mechanism. A one-dimensional ZnO nanostructure was synthesized using the hydrothermal method; scanning electron microscopy (SEM); and X-ray diffraction (XRD) spectra confirmed that the structures were crystalline ZnO of hexagonal structure. A furnace-type gas sensing system was used to characterize the nanorod bundles’ sensing properties in air containing dilute H<SUB>2</SUB>S gas (50 ppm) at sensing temperatures <I>T</I><SUB>s</SUB> ≤ 500 °C. The response of ZnO nanorod-bundle sensors to H<SUB>2</SUB>S gas increased with <I>T</I><SUB>s</SUB>; this trend may be due to chemical reaction of nanorods with gas molecules. X-ray photoelectron spectroscopy results indicated that the sensing mechanism of the ZnO nanorod-bundle sensor was explained by both the well-known surface reaction between H<SUB>2</SUB>S and adsorbed oxygen on ZnO, and the formation of zinc−sulfur bonding in ZnO nanorods, which becomes a dominant sensing mechanism at high <I>T</I><SUB>s</SUB> above 300 °C.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-15/jp110129f/production/images/medium/jp-2010-10129f_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp110129f'>ACS Electronic Supporting Info</A></P>

Highly efficient visible light photocatalysis of novel CuS/ZnO heterostructure nanowire arrays

Lee, Mikyung,Yong, Kijung IOP Pub 2012 Nanotechnology Vol.23 No.19

<P>Here, a facile approach for the fabrication of CuS nanoparticle (NP)/ZnO nanowire (NW) heterostructures on a mesh substrate through a simple two-step solution method is demonstrated. Successive ionic layer adsorption and reaction (SILAR) was employed to uniformly deposit CuS NPs on the hydrothermally grown ZnO NW array. The synthesized CuS/ZnO heterostructure NWs exhibited superior photocatalytic activity under visible light compared to bare ZnO NWs. This strong photocatalytic activity under visible light is due to the interfacial charge transfer (IFCT) from the valence band of the ZnO NW to the CuS NP, which reduces CuS to Cu<SUB>2</SUB>S. After repeated cycles of photodecolorization of Acid Orange 7 (AO7), the photocatalytic behavior of CuS/ZnO heterostructure NWs exhibited no significant loss of activity. Furthermore, our CuS/ZnO NWs/mesh photocatalyst floats in solution via partial superhydrophobic modification of the NWs.</P>

ZnO-Based Nanostructuring Strategy Using an Optimized Solution Process in CuInS₂ Superstrate Photovoltaics

Lee, Dongwook,Yong, Kijung American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.15

<P>Nanostructuring strategies have received significant attention recently in the context of thin-film solar cell design. Superstrate-type CuInS<SUB>2</SUB> (CIS) thin-film solar cells based on hydrothermally grown ZnO nanorod (NR) arrays have been prepared through dimensional optimization and comparative parametric characterization to yield a highly efficient device configuration. Solution-processed transparent ZnO nanostructures covered with a uniform CdS buffer layer were prepared using liquid processing methods to achieve efficient light harvesting and transport of photogenerated charge carriers. Molecular precursor solutions containing metal and chalcogen precursors of CIS light absorbers yielded interpenetrated radial p–n junctions across nanostructured CdS/ZnO NR arrays. The performances of solar cells could be improved by experimentally optimizing device configurations across certain experimental parameters, such as the CIS annealing temperature, the buffer-layer thickness, or the NR length, all of which affect charge conduction and charge recombination kinetics. The interfacial charge-transfer properties and recombination characteristics were investigated by observing the dark current, electrochemical impedance, and open-circuit voltage (<I>V</I><SUB>oc</SUB>) decay. Impedance data were fit to a proposed equivalent circuit model consisting of resistor–capacitor (ZnO/CdS) and resistor–constant phase element (CPE) (CdS/CIS) components as a means for characterizing the interfacial properties. Recombination at the p–n interface increased in samples comprising a thin buffer layer and long NRs. A 250 °C process temperature and optimal CdS deposition and ZnO NR growth times yielded the best efficiency, 6.8%. Our results suggest that solution-processed superstrate structures prepared using nanostructuring approaches could provide highly efficient low-cost photovoltaic devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-15/jp4127607/production/images/medium/jp-2013-127607_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp4127607'>ACS Electronic Supporting Info</A></P>