Zinc-ion Batteris (ZIBs) are recently being considered as energy storage devices due to their high specific capacity and high safety, and the abundance of zinc sources. Especially, ZIBs can overcome the drawbacks of conventional lithium ion batteris (LIBs), such as cost and safety issues. However, in spite of their advantages, the cathode materials under development are required to improve performance of ZIBs, because the capacity and cycling stability of ZIBs are mainly influenced by the cathode materials. To design optimized cathode materials for high performance ZIBs, a novel manganese oxide (MnO2) coated graphite sheet is suggested herein with improved zinc-ion diffusion capability thanks to the uniformly decorated MnO2 on the graphite sheet surface. Especially, to optimize MnO2 on the graphite sheet surface, amounts of percursors are regulated. The optimized MnO2 coated graphite sheet shows a superior zinc-ion diffusion ability and good electrochemical performance, including high specific capacity of 330.8 mAh g−1 at current density of 0.1 A g−1, high-rate performance with 109.4 mAh g−1 at a current density of 2.0 A g−1, and remarkable cycling stability (82.2 % after 200 cycles at a current density of 1.0 A g−1). The excellent electrochemical performance is due to the uniformly decorated MnO2 on the graphite sheet surface, which leads to excellent zinc-ion diffusion ability. Thus, our study can provide a promising strategy for high performance next-generation ZIBs in the near future.

Dynamic behavior of piezoelectric ZnO nanowires is investigated using finite element analyses (FEA) on FE models constructed based on previous experimental observations in which nanowires having aspect ratios of 1:2. 1:31, and 1:57 are obtained during a hydrothermal process. Modal analyses predict that nanowires will vibrate in lateral bending, uniaxial elongation/contraction, and twisting (torsion), respectively, for the three ratios. The natural frequency for each vibration mode varies depending on the aspect ratio, while the frequencies are in a range of 7.233 MHz to 3.393 GHz. Subsequent transient response analysis predicts that the nanowires will behave quasi-statically within the load frequency range below 10 MHz, implying that the ZnO nanowires have application potentials as structural members of electromechanical systems including nano piezoelectric generators and piezoelectric dynamic strain sensors. When an electric pulse signal is simulated, it is predicted that the nanowires will deform in accordance with the electric signal. Once the electric signal is removed, the nanowires exhibit a specific resonance-like vibration, with the frequency synchronized to the signal frequency. These predictions indicate that the nanowires have additional application potential as piezoelectric actuators and resonators.

Using lanthanum zinc oxide (LZO) film with the ion-beam irradiation, uniform and homogeneous liquid crystal (LC) alignment was achieved. To fabricate the LZO thin film on glass substrate, solution process was conducted as a deposition method. Cross-polarized optical microscopy (POM) and the crystal rotation method reveal the state of LC alignment on the ion-beam irradiated LZO film. Between orthogonally placed polarizers, POM image showed constant black color with regular transmittance. Furthermore, collected incidence angle versus transmittance curve from the crystal rotation method revealed that the LC molecules on the ion-beam irradiated LZO film were aligned homogeneously. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were conducted to reveal the relationship between the ion-beam irradiation and the LC alignment. The ion-beam irradiation changed the LZO film surface to rougher than before by etching effect. Numerical roughness values from AFM analysis supported this phenomenon specifically. XPS analysis showed the chemical composition change due to the ion-beam irradiation by investigation of O 1s, La 3d and Zn 2p spectra. The ion-beam irradiation induced the breakage of chemical bonds in the LZO film surface and this occurred surface chemical anisotropic characteristics for uniform LC alignment.

Synthesizing one-dimensional nanostructures of oxide semiconductors is a promising approach to fabricate highefficiency photoelectrodes for hydrogen production from photoelectrochemical (PEC) water splitting. In this work, vertically aligned zinc oxide (ZnO) nanorod arrays are successfully synthesized on fluorine-doped-tin-oxide (FTO) coated glass substrate via seed-mediated hydrothermal synthesis method with the use of a ZnO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Zn metal thin film. The structural, optical and PEC properties of the ZnO nanorod arrays synthesized at varying levels of Zn sputtering power are examined to reveal that the optimum ZnO nanorod array can be obtained at a sputtering power of 20W. The photocurrent density and the optimal photocurrent conversion efficiency obtained for the optimum ZnO nanorod array photoanode are 0.13 mA/cm2 and 0.49 %, respectively, at a potential of 0.85 V vs. RHE. These results provide a promising avenue to fabricating earth-abundant ZnO-based photoanodes for PEC water oxidation using facile hydrothermal synthesis.

The ion-beam irradiated lanthanum zinc oxide (LZO) films were conducted as liquid crystal (LC) alignment layer to achieve uniform and homogeneous alignment of LC molecules. Polarized optical microscopy and the pre-tilt angle measurements revealed the alignment characteristics of LC molecules on the LZO film surface. Physical characteristics of the LZO film surface were analyzed by field emission scanning electron microscope and atomic force microscopy. The strong ion-beam irradiation on the LZO film changed surface rougher than before and induced physical anisotropic characteristics. Chemical composition of the LZO film was investigated by X-ray photoelectron spectroscopy and it was revealed that the ion-beam irradiation induced the breakage of the metal-oxide bonds. Due to this, anisotropic dipole moment which related with van der Waals force between LC molecules and alignment layer was induced. Because of this, LC molecules were anchored to the LZO film surface to achieve uniform LC alignment. Collecting the capacitance-voltage curve, residual DC of the LC cell with the LZO films was measured and it was verified that the LC cell with the LZO film had a nearly zero residual DC. Therefore, the ion-beam irradiated LZO film is an efficient method as an LC alignment layer

We report on the fabrication and characterization of an oxide photoanode with a zinc oxide (ZnO) nanorod array embedded in cuprous oxide (Cu2O) thin film, namely a ZnO/Cu2O oxide p-n heterostructure photoanode, for enhanced efficiency of visible light driven photoelectrochemical (PEC) water splitting. A vertically oriented n-type ZnO nanorod array is first prepared on an indium-tin-oxide-coated glass substrate via a seed-mediated hydrothermal synthesis method and then a p-type Cu2O thin film is directly electrodeposited onto the vertically oriented ZnO nanorod array to form an oxide p-n heterostructure. The introduction of Cu2O layer produces a noticeable enhancement in the visible light absorption. From the observed PEC current density versus voltage (J-V) behavior under visible light illumination, the photoconversion efficiency of this ZnO/Cu2O p-n heterostructure photoanode is found to reach 0.39 %, which is seven times that of a pristine ZnO nanorod photoanode. In particular, a significant PEC performance is observed even at an applied bias of 0 V vs Hg/Hg2Cl2, which makes the device self-powered. The observed improvement in the PEC performance is attributed to some synergistic effect of the pn bilayer heterostructure on the formation of a built-in potential including the light absorption and separation processes of photoinduced charge carriers, which provides a new avenue for preparing efficient photoanodes for PEC water splitting.

A heterogeneous photocatalytic system is attracting much interest for water and air purification because of its reusability and economical advantage. Electrospun nanofibers are also receiving immense attention for efficient photocatalysts due to their ultra-high specific surface areas and aspect ratios. In this study, ZnO nanofibers with average diameters of 71, 151 and 168 nm are successfully synthesized by facile electrospinning and a subsequent calcination process at 500 ℃ for 3 h. Their crystal structures, morphology features and optical properties are systematically characterized by X-ray diffraction, scanning electron microscopy, UV-Vis and photoluminescence spectroscopies. The photocatalytic activities of the ZnO nanofibers are evaluated by the photodegradation of a rhodamine B aqueous solution. The results reveal that the diameter of the nanofiber, controlled by changing the polymer content in the precursor solution, plays an important role in the photocatalytic activities of the synthesized ZnO nanofibers.

Finite element analyses are carried out to understand the piezoelectric behaviors of ZnO nanowires. Three different types of ZnO nanowires, with aspect ratios of 1:2. 1:31, and 1:57, are analyzed for uniaxial compression, pure bending, and buckling. Under the uniaxial compression with a strain of 1.0 × 10−4 as the reference state, it is predicted that all three types of nanowires develop the same magnitude of the piezoelectric fields, which suggests that longer nanowires exhibit higher piezoelectric potential. However, this prediction is not in agreement with the experimental results previously reported in the literature. Such discrepancy is understood when the piezoelectric behaviors under bending and buckling are considered. When only the strain field due to bending is present in bending or buckling, the antisymmetric nature of the through-thickness stain distribution indicates that two piezoelectric fields, the same in magnitude and opposite in sign, develop along the thickness direction, which cancels each other out, resulting in a zero net piezoelectric field. Once additional strain contribution due to axial deformation is superposed on the bending, such field cancelling is compensated for due to the axial component of the piezoelectric field. Such numerical predictions seem to explain the reported experimental results while providing a guideline for the design of nanowire-based piezoelectric devices.

산화아연 나노입자는 식품산업에서 항균 식품포장재, 항균 식품첨가물 및 아연보충제로 사용되고 있다. 식품산업에서 나노물질 사용이 증가 됨에 따라 식품성분과의 상호작용 가능성이 제기되고 있는데, 이 같은 상호작용은 나노물질의 독성 및 체내 흡수에 영향을 줄 수 있다. 따라서 산화아연 나노입자와 식품성분과의 상호작용에 대해 규명하고자 본 연구에서는 아연강화성분으로 산화아연이 첨가될 수 있는 탈지분유를 사용하였으며, 탈지분유의 주된 구성성분인 카제인과 유당을 사용하여 비교 연구를 수행하였다. 산화아연 나노입자와 탈지분유의 상호작용에 의한 물리화학적 특성변화는 수분상 입자크기와 표면전하 변화를 측정하여 확인하였고, 단백질과 상호작용은 형광 쇠기 감쇠 정도로, 그리고 유당과 상호작용은 HPLC를 이용하여 정량분석 하였다. 또한 탈지분유, 카제인 및 유당 존재 하 산화아연 나노입자의 세포독성 및 세포 내 유입양상, 3D 인체 장관 모델을 통한 수송 기작을 확인하였다. 그 결과, 산화아연 나노입자의 상호작용 정도는 탈지분유 혼합성분으로 존재 시 더 많이 일어나는 것으로 확인되었으나, 이 같은 상호작용은 세포독성, 세포 내 유입 및 장내 수송 기작에는 영향을 미치지 않는 것으로 나타났다. 본 연구결과는 산화아연 나노입자가 식품성분에 따라 상호작용 정도가 달라질 수 있음을 규명함으로써, 향후 나노물질과 식품성분 상호작용에 따른 잠재적 독성을 예측하는 데에 유용하게 활용될 수 있을 것으로 보인다.

산화아연 나노물질(나노 ZnO)은 식품산업에서 식품포장재, 식품첨가물 및 아연 보충제 등과 같이 다양한 분야에 사용되고 있으나 생체 내 단백질과의 상호작용 및 그에 따른 독성연구는 미진한 실정이다. 나노물질은 체내에서 생체단백질과의 흡착에 의한 나노-단백질 코로나를 형성할 수 있는데, 이 같은 현상은 나노물질의 흡수, 조직분포 및 독성에 영향을 미칠 수 있을 것이다. 본 연구에서는 입자크기(나노 vs 벌크)에 따른 산화아연의 체내 단백질과 상호작용을 생체모사용액(위액, 장액, 혈장) 및 ex vivo 조직추출액을 이용하여 연구하였다. 그 결과, 모든 생체모사조건에서 나노 ZnO의 표면전하는 벌크 ZnO와 유의적으로 다르게 변화하는 것이 관찰되었고, 혈액모사조건에서 단백질과 상호작용 정도가 더 큰 것으로 확인되었다. 반면, 입자크기에 따른 용해도 및 장관 상피세포 흡수기작의 차이는 나타나지 않았다. 프로테오믹스 분석 결과, 입자크기에 관계없이 알부민, 피브리노겐 및 피브로넥틴이 ZnO-단백질 코로나 형성에 주로 관여하는 혈장단백질로 확인되었으나, 벌크 ZnO 대비 나노 ZnO와의 상호작용 정도가 더 큰 것으로 나타났다. 본 연구결과는 식품용 ZnO의 입자 크기에 따라 체내 단백질과의 상호작용 정도가 달라질 수 있음을 규명함으로써, 향후 나노물질과 생체 내 단백질의 상호작용에 따른 잠재적 독성을 예측하는데 중요한 자료로 활용될 수 있을 것이다.