Juneui Jung

Bio: Juneui Jung is an academic researcher from Yonsei University. The author has contributed to research in topics: Surface roughness & Biosensor. The author has an hindex of 2, co-authored 4 publications receiving 60 citations.

ZnO nanowire-based glucose biosensors with different coupling agents

Abstract: ZnO-nanowire-based glucose biosensors were fabricated by immobilizing glucose oxidase (GOx) onto a linker attached to ZnO nanowires. Different coupling agents were used, namely (3-aminopropyl)trimethoxysilane (APTMS), (3-aminopropyl)triethoxysilane (APTES), and (3-aminopropyl)methyldiethoxysilane (APS), to increase the affinity of GOx binding to ZnO nanowires. The amount of GOx immobilized on the ZnO nanowires, the performance, sensitivity, and Michaelis–Menten constant of each biosensor, and the electron transfer resistance through the biosensor were all measured in order to investigate the effect of the coupling agent on the ZnO nanowire-based biosensor. Among the different biosensors, the APS-treated biosensor had the highest sensitivity (17.72 μA cm−2 mM−1) and the lowest Michaelis–Menten constant (1.37 mM). Since APS-treated ZnO nanowires showed the largest number of C N groups and the lowest electron transfer resistance through the biosensor, we concluded that these properties were the key factors in the performance of APS-treated glucose biosensors.

Effects of ZnO nanowire synthesis parameters on the photovoltaic performance of dye-sensitized solar cells

Abstract: Determination of the effects of ZnO nanowires on the efficiency of ZnO nanowire-based dye-sensitized solar cells (DSSCs) is important. In this study, we determined the effects of different OH - precursors, concentrations, the ratio of zinc nitrate to hexamethylene tetramine (HMT), and the hydrothermal synthesis temperature on the physical, crystal, and optical properties of ZnO nanowires and investigated the performance of the resulting DSSCs. We observed that ZnO nanowires synthesized using an equimolar ratio of HMT to zinc nitrate yielded a DSSC with high incident photon-to-current efficiency (IPCE), cell efficiency, short circuit current density (J sc ), and fill factor (FF), and low ZnO–dye–electrolyte interface resistance due to an increased amount of dye and a decreased density of defects. Furthermore, ZnO nanowires made using optimal concentrations and ratios of zinc nitrate to HMT had a high surface area and low defect density. All the photovoltaic performance parameters of DSSCs assessed such as IPCE, cell efficiency, J sc , open circuit potential (V oc ), and FF increased with synthesis temperature, which was related to a decrease in the resistance at the ZnO–dye–electrolyte interface. We attributed these results to an increased amount of dye facilitated by a large nanowire surface area and fast electron transfer because of the improved crystalline structure of the ZnO nanowires and their low defect density. By optimizing the ZnO nanowires, we increased DSSC efficiency to 0.26% using ZnO nanowires synthesized with 25 mM of both zinc nitrate and HMT at 90 °C, while only a 0.02% increase in efficiency was obtained when NH 4 OH was used as OH − precursor.

Behavior of Ru surfaces after ozonated water treatment

Abstract: In order for the development of cleaning technology of extreme ultra violet lithography photomask, the behavior of Ru surfaces after treatment with ozonated deionized water (DIO 3 ) solution was studied using Ru and ruthenium oxide particles and 2 nm-thick Ru capping layers. No significant changes in crystalline structures or chemical states of the Ru surfaces, nor any similarities with the structures or states of ruthenium oxide, were observed after DIO 3 treatment. Oxidation of ruthenium to form RuO 2 or RuO 3 was not observed. Adsorption of H 2 O molecules on the Ru layer increased the surface roughness, but the desorption of H 2 O molecules recovered it. Local chemisorption of H 2 O molecules on the Ru surface may be the reason why rougher Ru surfaces were observed after DIO 3 cleaning.

Effect of post-etch cleaning on Ru-capped extreme ultraviolet lithography photomask

Abstract: Ru-capped extreme ultraviolet lithography photomasks require cleaning after patterning of the absorber layer. In this study, it was confirmed that, during Cl 2 dry etching to remove the absorber layer, RuCl 3 was formed on the Ru capping layer surface, and the surface roughness thereby deteriorated. Therefore, the changes in RuCl 3 formation and surface roughness with various cleaning processes were investigated. Among the treatments used, i . e ., sulfuric peroxide mixture, an ammonia peroxide mixture or ozonated water (DIO 3 ), DIO 3 exhibited the most effective Cl removal efficiency and surface roughness recovery. DIO 3 treatment successfully reduced the Cl-terminated Ru surface to its original state and decreased the surface roughness to the pre-Cl 2 -etched Ru value.

Immobilization of antibodies and enzymes on 3-aminopropyltriethoxysilane-functionalized bioanalytical platforms for biosensors and diagnostics.

Abstract: 3‐Aminopropyltriethoxysilane-Functionalized Bioanalytical Platforms for Biosensors and Diagnostics Sandeep Kumar Vashist,*,†,‡ Edmond Lam, Sabahudin Hrapovic, Keith B. Male, and John H. T. Luong †HSG-IMIT Institut für Mikround Informationstechnik, Georges-Koehler-Allee 103, 79110 Freiburg, Germany ‡Laboratory for MEMS Applications, Department of Microsystems Engineering IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg, Germany National Research Council Canada, Montreal, Quebec H4P 2R2, Canada Innovative Chromatography Group, Irish Separation Science Cluster (ISSC), Department of Chemistry and Analytical, Biological Chemistry Research Facility (ABCRF), University College Cork, Cork, Ireland

Effects of Hexamethylenetetramine on the Nucleation and Radial Growth of ZnO Nanowires by Chemical Bath Deposition

Abstract: The growth of ZnO nanowires by chemical bath deposition (CBD) is of great potential for their integration into nanoscale devices. However, the effects of the chemical precursors in solution are still under debate, such as the role of hexamethylenetetramine (HMTA). In order to tackle this issue, these effects are thoroughly disentangled from the effects of the structural morphology of the ZnO seed layer and investigated through a large number of nonequimolar CBDs over a broad range of chemical precursor concentrations and ratios. The analysis is further supported by thermodynamic simulations yielding theoretical solubility plots and speciation diagrams of Zn(II) species. It is shown that the ZnO deposited volume and, to some extent, the length of ZnO nanowires are directly related to the supersaturation in solution, which strongly depends on the chemical precursor concentration and pH. A slight excess of HMTA with respect to zinc nitrate is required to reach the largest axial growth rate of ZnO nanowires. ...

Fabrication and Characterization of Glucose Biosensors by Using Hydrothermally Grown ZnO Nanorods

Abstract: Highly oriented ZnO nanorod (NR) arrays were fabricated on a seeded substrate through a hydrothermal route. The prepared ZnO nanorods were used as an amperometric enzyme electrode, in which glucose oxidase (GOx) was immobilised through physical adsorption. The modified electrode was designated as Nafion/GOx/ZnO NRs/ITO. The morphology and structural properties of the fabricated ZnO nanorods were analysed using field-emission scanning electron microscope and X-ray diffractometer. The electrochemical properties of the fabricated biosensor were studied by cyclic voltammetry and amperometry. Electrolyte pH, electrolyte temperature and enzyme concentration used for immobilisation were the examined parameters influencing enzyme activity and biosensor performance. The immobilised enzyme electrode showed good GOx retention activity. The amount of electroactive GOx was 7.82 × 10−8 mol/cm2, which was relatively higher than previously reported values. The Nafion/GOx/ZnO NRs/ITO electrode also displayed a linear response to glucose ranging from 0.05 mM to 1 mM, with a sensitivity of 48.75 µA/mM and a low Michaelis–Menten constant of 0.34 mM. Thus, the modified electrode can be used as a highly sensitive third-generation glucose biosensor with high resistance against interfering species, such as ascorbic acid, uric acid and L-cysteine. The applicability of the modified electrode was tested using human blood samples. Results were comparable with those obtained using a standard glucometer, indicating the excellent performance of the modified electrode.

ZnO nanostructures in enzyme biosensors

Abstract: Biosensing has developed tremendously since it was demonstrated by Leland C. Clark Jr. in 1962. ZnO nanomaterials are attractive candidates for fabricating biosensors, because of their diverse range of nanostructures, high electron mobility, chemical stability, electrochemical activity, high isoelectric points which promote enzyme adsorption, biocompatibility, and piezoelectric properties. This review covers ZnO nanostructures applied in enzyme biosensors, in the light of electrochemical transduction and field effect transduction. Different assembly processes and immobilization methods have been used to load enzymes into various ZnO nanostructures, providing enzymes with favorable micro-environments and enhancing their sensing performance. We briefly describe recent trends in ZnO syntheses, and the analytical performance of the fabricated biosensors, summarize the advantages of using ZnO nanostructures in biosensors, and conclude with future challenges and prospects.

Research and Development Aspects on Chemical Preparation Techniques of Photoanodes for Dye Sensitized Solar Cells

Abstract: The importance of dye sensitized solar cells (DSSCs) as a low-cost and environmentally friendly photovoltaic (PV) technology has prompted many researchers to improve its efficiency and durability. The realization of these goals is impossible without taking into account the importance of the materials in DSSCs, so the focus on the preparation/deposition methods is essential. These methods can be either chemical or physical. In this study, the chemical applied methods that utilize chemical reaction to synthesize and deposit the materials are covered and categorized according to their gas phase and liquid phase precursors. Film processing techniques that can be used to enhance the materials' properties postpreparation are also included for further evaluation in this study. However, there is a variety of consideration, and certain criteria must be taken into account when selecting a specific deposition method, due to the fact that the fabrication conditions vary and are unoptimized.