• Bulletin of the Korean Chemical Society
• /
• v.31 no.11
• /
• pp.3407-3410
• /
• 2010

• Journal of the Korean Electrochemical Society
• /
• v.15 no.2
• /
• pp.83-89
• /
• 2012

We investigate the electrocatalytic activities for oxygen reduction at nanoporous gold (NPG) surfaces fabricated by selective dissolution of Ag from electrodeposited Ag-Au layers on electrode surfaces. The structure of NPG was controlled by changing the concentration ratios of precursor metal complexes during the electrodeposition of Ag-Au layers and the corresponding surface morphology and surface area was examined. NPG structures with Ag/Au ratio of 2.0 exhibited the highest electrocatalytic activity for oxygen reduction, where the nanoporous structure plays a key role, but the surface area does not affect on the electrocatalytic activity. The mechanism of electroreduction of oxygen was investigated by rotating disk electrode techniques. In acidic media, oxygen was first reduced to hydrogen peroxide followed by further reduction to water through 2-step 4-electron mechanism, whereas the oxygen was reduced directly to water by 4-electron mechanism in basic media.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.354.1-354.1
• /
• 2016

Nanoporous gold (NPG) is a very promising material in various fields such as sensor, actuator, and catalysis because of its high surface to volume ratio and conducting nature. In this study, we fabricated a NPG based amperometric sensor on a glass substrate by means of co-sputtering of Au and Si. During the sputtering process, we found the optimum conditions for heat treatment to reduce the residual stress and to improve adhesion between NPG films and the glass substrate. Subsequently, Si was selectively etched from Au-Si alloy by KOH solution, which forms nanoporous structures. Scanning electron microscopy (SEM) and auger electron spectroscopy (AES) were used to estimate the structure of NPG films and their composition. By employing appropriate heat treatments, we could make very stable NPG films. We tested the performance of NPG sensor with aniline molecules, which shows high sensitivity for sensing low concentration of aniline.

• Journal of the Korean Electrochemical Society
• /
• v.13 no.4
• /
• pp.251-255
• /
• 2010

We report on the electrocatalytic reduction of hydrogen peroxide at nanoporous gold (NPG) surfaces. Various NPG surfaces with different surface structure were prepared by changing the conditions of electrodeposition for Ag-Au layers such as the concentration ratios of $KAu(CN)_2$ over $KAg(CN)_2$ and deposition charges. The effects of different electrochemical conditions on the electrocatalysis of $H_2O_2$ reduction were investigated. The NPG surfaces exhibited sensitive amperometric responses for $H_2O_2$ reduction, from which calibration plots with higher sensitivity than a bare Au surface were obtained.

• Journal of the Korean Chemical Society
• /
• v.63 no.1
• /
• pp.45-50
• /
• 2019

Because arsenic (As) is a chemical substance toxic to humans, there have been extensive investigations on the development of As detection methods. In this study, the electrochemical determination of As on nanoporous gold (NPG) electrodes was investigated using anodic stripping voltammetry. The electrochemical surface area of the NPG electrodes was controlled by changing the reaction times during the anodization of Au for NPG preparation, and its effect on the electrochemical behavior during As detection was examined. The detection efficiency of the NPG electrodes improved as the roughness factor of the NPG electrodes increased up to around 100. A further increase in the surface area of the NPG electrodes resulted in a decrease of the detection efficiency due to high background current levels. The most efficient As detection efficiency was obtained on the NPG electrodes prepared with an anodization time of 50 s. The effects of the detection parameters and of the Cu interference in As detection were investigated and the NPG electrode was compared to flat Au electrodes.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.353.1-353.1
• /
• 2016

다공성 물질은 동공의 크기에 따라 미세동공(Micropore), 메조동공(Mesopore), 거대동공(Macropore)으로 나누어 분류한다. 다공성 재료의 장점은 높은 비표면적으로써, 촉매, 센서, 연료전지 전극, 에너지 저장장치 등으로의 이용 가능성을 보여주는 연구가 활발히 보고되고 있다. 종래의 연구는 두 가지 이상의 원소로 구성된 박막을 제작한 후 전기화학적 분해법, 선택적 용해법 등 습식공정을 통해 다공성 구조체를 제작하였다. 하지만 본 연구에서는 Au, Ag 타겟과 $CH_4$ gas를 이용해 ICP-assisted reactive magnetron sputtering 장비를 활용하여 450 nm 두께의 Au-C, Ag-C 박막을 제작하였다. 이후 연속적으로 RF 250 W를 ICP antenna 에 인가하여 $O_2$ plasma dealloying 공정을 통해 탄소(Carbon) 만을 선택적으로 제거함으로써, 건식 공정만으로 Si wafer ($10{\times}10mm^2$) 기판 위에 250 ~ 300 nm 두께의 다공성 Au, Ag 박막을 제작하였다. SEM (Scanning Electron Microscopy)를 활용하여 표면, 단면 형상을 관찰해 다공성 구조를 확인하였으며, AES (Auger Electron Spectroscopy)를 통해 plasma dealloying 전 후 박막의 조성변화를 관찰하였다. 따라서 plasma dealloying 공정으로 제작된 다공성 Au, Ag 박막은 기존의 습식 공정 대비 청결하고 신속한 공정이 가능하며 높은 재현성을 통해 위의 적용분야에 보다 쉽게 사용될 수 있을 것으로 기대된다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2008.02a
• /
• pp.144-144
• /
• 2008

• Journal of the Korean Chemical Society
• /
• v.60 no.5
• /
• pp.310-316
• /
• 2016

Oxidation-reduction cycling (ORC) procedures are widely used for cleaning nanoparticle surfaces when investigating their electrocatalytic activities. In this work, the effect of ORC on the surface structures and electrocatalytic oxygen reduction activity of Au electrodes is analyzed. Different structural changes and variations in electrocatalysis are observed depending on the initial structure of the Au electrodes, such as flat bulk, nanoporous, nanoplate, or dendritic Au. In particular, dendritic Au structures lost their sharp-edge morphology during the ORC process, resulting in a significant decrease in its electrocatalytic oxygen reduction activity. The results shown in this paper provide an insight into the pretreatment of nanoparticle-based electrodes during investigation of their electrocatalytic activities.

• Applied Chemistry for Engineering
• /
• v.22 no.5
• /
• pp.575-578
• /
• 2011

We fabricated a novel simple and rapid method of three dimensional nanoporous gold thin film (NPGF) onto a Au substrate using electrochemical deposition method. The NPGF-modified electrode analysis by scanning electron microscope and reveals the formation of nanopores, approximately 30~50 nm in diameter. differential pulse voltammetry was measured for the determination of ${\gamma}$-aminobutiric acid in the concentration range of ($10{\sim}100{\mu}M$ using a NPGF. The high sensitivity feature of NPGF is expected to be applied for real sample biosensor applications.

• Journal of the Korean Institute of Gas
• /
• v.12 no.2
• /
• pp.32-37
• /
• 2008

For a development of U-safety system, liquid/gas-sensors that are easy to carry and install in any place are needed. Therefore, in this work, we prepared porous gold using a templating method with nanoporous alumina, and it was used as sensing materials and electrode. The resulting materials showed high purity macroporous structure with $200{\sim}300\;nm$ of window-pore and $4.8\;m^2/g$ of surface area. Because porous gold had good electric conductivity, convenience to measure the change of electric resistivity and good reproducibility, it could be used as potential sensing materials. As a proof-of-concept test, the detection test for mercury ion was carried out.