• 한국가시화정보학회지
• /
• 제15권2호
• /
• pp.16-20
• /
• 2017

A coffee-ring effect is from capillary flow by different evaporation rate across the droplet. The capillary flow tends particles to accumulate at the edges of the droplet and makes the ring-shaped stain pattern. These coffee-ring formation and suppression of coffee-ring have been a critical role in printing and coating technologies. In this study, we present the experimental study on coffee-ring effect of silver nanowire inside the evaporating sessile droplet. Size and concentration effect of nanowires at coffee-ring effect has been investigated. From the coffee-ring, we observed the regimes of connected rings and disconnected ones and measure the resistivity of single ring pattern with different nanowire length.

• 반도체디스플레이기술학회지
• /
• 제16권3호
• /
• pp.31-35
• /
• 2017

We have fabricated flexible and stretchable pressure sensors using silver nanowires (AgNWs) and analyzed their electric responses. AgNWs are spray coated directly onto uncured polydimethylsiloxane (PDMS) such that AgNWs penetrate into the uncured PDMS, enhancing the adhesion properties of AgNWs. However, the single-layered AgNW sensor exhibits unstable electric response and low pressure sensitivity. To tackle it, we have coated a conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) onto the AgNW layer. Such a hybrid bilayer sensor ensures a stable electric response because the over-coating layer of PEDOT:PSS effectively suppresses the protrusion of AgNWs from PDMS during release. To enhance the sensitivity further, we have also fabricated a stacked bilayer AgNW sensor. However, its electric response varies depending sensitively on the initial overlap pressure.

• 환경생물
• /
• 제34권3호
• /
• pp.183-192
• /
• 2016

지금까지 개발된 나노물질 중 은나노물질은 일상 생활제품에 가장 많이 활용된 나노물질 중 하나로 알려져 있고 다양한 경로를 통해 환경에 유입되어 환경 및 인체에 부정적인 영향을 미칠 수 있는 것으로 알려져 있다. 화학물질과 달리 나노물질은 물리화학적 특성에 따라 동일 나노물질이더라도 그 유해성이 다르다고 알려져 있지만 기존 연구들은 다양한 특성을 동일 시험조건에서 평가하기 보다는 하나의 특성에 대해 독성을 보고하는 수준에 그치고 있다. 따라서 기존 연구들의 서로 다른 시험생물, 시험조건, 나노물질 특성 등을 고려할 때 나노물질의 물리화학적 특성에 따른 독성의 체계적인 비교평가가 어려운 한계가 존재한다. 본 연구는 은나노물질의 다양한 물리화학적 특징에 따라 수생생물에 미치는 독성영향을 평가하고자 한다. 대표적인 3종 (어류, 물벼룩, 조류)의 수생생물에 대한 은나노물질의 입자상 크기 (50, 100, 150 nm), 형태 (입자형, 선형), 코팅물질 종류 (PVP, citrate)에 따라 생태독성평가를 진행하였다. 연구결과, 나노 물질의 크기가 작을수록 그리고 입자상 형태보다 선형에서 독성이 비교적 높게 나타났다. 특히 선형 은나노의 경우, 길이에 비례하여 그리고 입자에 비해 비교적 높은 독성을 나타냈다. 반면, 은나노의 코팅물질 종류는 대상 수생생물에 따라 독성의 영향이 다르게 평가되었다. 본 연구는 은나노물질의 다양한 물리화학적 특성에 기인한 독성을 동일한 시험 조건, 시험생물에서 체계적으로 비교 평가하였다는 점에서 의의가 있으며 본 연구결과는 은나노물질의 환경 및 인체 위해성평가 자료로서 활용될 수 있을 뿐 아니라 보다 안전한 은나노물질 소재개발을 위한 과학적 자료로서 활용될 수 있을 것으로 사료된다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.379.1-379.1
• /
• 2016

Recently, new types of wearable devices such as textile electronics are considered as the next generation wearable electronics. To realize the textile electronics, conductive fibers are required to supply the power and for signal processing. Conventionally, silver nanowires (Ag NWs) have been attracted as one of the conductive additives in the fibers, however, using the Ag NWs may lead to high production cost since it is a noble metal. Many researches have been done to replace the Ag NWs into a cheaper materials such as copper nanowires (Cu NWs). Here, we synthesized ultra-long Cu NWs for a conductive filler material in conductive fibers, taking advantages of their structural features. To investigate the effect of capping agents on the aspect ratio of the synthesized Cu NWs, we used various capping agents such as hexadecylamine, butylamine, ethylenedilamine and oleylamine in the Cu NW synthesis. In this research, the effects of capping agents on the structure and the synthesis of Cu NWs are presented.

• 한국가시화정보학회지
• /
• 제15권2호
• /
• pp.41-47
• /
• 2017

Microring/nanoring structure has high applicability for nano-antenna and biosensor thanks to its superior optical characteristics. Although coiling nanowires manufactured using immiscible emulsion droplets have an advantage in mass production, this process also forms nanowire bundles. In this study, we solved the nanowire bundle problem by size-selective sorting of the emulsion droplets in a pinched flow fractionation microchannel. Utilizing silver nanowires and immiscible emsulsion droplets, we investigated the correlation between the size of ring droplets and bundle droplet. We visualized the sorting process for glass particles and microring-containing emulsion droplets. Droplets were sorted based on their size, and the ratio of bundle droplets in solution decreased. This droplet-sorting strategy has potential to help the printing and coating process for manufacturing of ring structure patterns and developing of functional materials.

• Transactions on Electrical and Electronic Materials
• /
• 제16권4호
• /
• pp.212-220
• /
• 2015

We investigated nanotextured Si solar cells using the silver-assisted chemical etching process. The nanotexturing process is very sensitive to the concentration of chemical etching solution. The high concentration process results in a nanowire formation for the nanosurfaces and causes severe surface damage to the top region of the micropyramids. These nanowires show excellent light absorption in photoreflectance spectra and radiative light emission in photoluminescence spectra. However, the low concentration process forms a nano-roughened surface and provides high minority carrier lifetimes. The nano-roughened surfaces of the samples show the improved electrical cell properties of quantum efficiency, conversion efficiency, and cell fill factor due to the reduction in the formation of the over-doped dead layer.

• Journal of Electrochemical Science and Technology
• /
• 제2권3호
• /
• pp.157-162
• /
• 2011

We report a simple route for synthesizing multi-dimensional structured silicon anode materials from commercially available bulk silicon powders via metal-assisted chemical etching process. In the first step, silver catalyst was deposited onto the surface of bulk silicon via a galvanic displacement reaction. Next, the silver-decorated silicon particles were chemically etched in a mixture of hydrofluoric acid and hydrogen peroxide to make multi-dimensional silicon consisting of one-dimensional silicon nanowires and micro-scale silicon cores. As-synthesized silicon particles were coated with a carbon via thermal decomposition of acetylene gas. The carbon-coated multi-dimensional silicon anodes exhibited excellent electrochemical properties, including a high specific capacity (1800 mAh/g), a stable cycling retention (cycling retention of 89% after 20 cycles), and a high rate capability (71% at 3 C rate, compared to 0.1 C rate). This process is a simple and mass-productive (yield of 40-50%), thus opens up an effective route to make a high-performance silicon anode materials for lithiumion batteries.

• 반도체디스플레이기술학회지
• /
• 제17권2호
• /
• pp.1-5
• /
• 2018

Elastic resistive pressure sensor is fabricated by a direct spray coating of silver nanowires (AgNWs) on uncured polydimethylsiloxane (PDMS) and an additional coating of a conductive polymer, poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS). To improve the sensitive and stability, we have fabricated sandwich-structured AgNW/polymer sensor where two AgNW/polymer-coated PDMS films are laminated with the conducting surfaces contacted by pressure lamination. It shows a resistance decrease upon loading due to the formation of dense network of AgNWs. It is demonstrated that the sandwich-structured AgNW/polymer sensor exhibits very high sensitivity ($2.59kPa^{-1}$) and gauge factor (37.8) in the low pressure regime. It can also detect a subtle placement and removal of a weight as low as 3.4 mg, the corresponding pressure of which is about 5.4 Pa. It is shown that the protrusion of AgNWs from PDMS is suppressed substantially by the over-coated PEDOT:PSS layer, thereby reducing hysteresis and rendering the sensor more stable.

• 반도체디스플레이기술학회지
• /
• 제19권4호
• /
• pp.6-10
• /
• 2020

The silver nanowires (AgNWs) were synthesized by the conventional polyol process, which revealed 25 ㎛ and 30 nm of average length and diameter, respectively. The synthesized AgNWs were applied to the CdSe/CdZnS quantum dot (QD) based transparent light-emitting device (LED). The device using a randomly networked AgNWs electrode had some problems such as the high threshold voltage (for operating the device) due to the random pores from the networked AgNWs. As a method of improvement, a composite electrode was formed by overlaying the ZnO:Ga on the AgNWs network. The device used the composite electrode revealed a low threshold voltage (4.4 Vth) and high current density compared to the AgNWs only electrode device. The brightness and current density of the device using composite electrode were 55.57 cd/㎡ and 41.54 mA/㎠ at the operating voltage of 12.8 V, respectively, while the brightness and current density of the device using (single) AgNWs only were 1.71 cd/㎡ and 2.05 mA/㎠ at the same operating voltage. The transmittance of the device revealed 65 % in a range of visible light. Besides the reliability of the devices was confirmed that the device using the composite electrode revealed 2 times longer lifetime than that of the AgNWs only electrode device.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.467.2-467.2
• /
• 2014

유기태양전지는 친환경 에너지 소스로써 저가 대량 생산이 가능하고 특히 유연한 기판에 적용이 가능하여 많은 관심을 받고 있다. 그럼에도 불구하고 기존에 사용되는 indium tin oxide (ITO)의 사용으로 인한 유연성 부족으로 대체되는 투명전극의 개발이 요구되어지고 있다. 이로 인해 carbon nanotubes, graphene, thin metals, metal grids, and conducting polymers 등이 연구되고 있으며, 이중 Silver nanowires (Ag NWs)를 이용한 방식도 많은 관심과 함께 전기광학적 특성에 대한 연구가 진행되고 있다. 하지만 유기전자소자에 사용되기에는 몇 가지 문제점이 발생하는데 이를 해결하기 위한 노력이 다양하게 이루어지고 있다. 특히 다양한 물질의 혼합을 통해 개선하고자 하는 노력이 증가하고 있는데 적층구조의 전도성필름 형성을 통해 ITO-free OPVs에서 Ag nanowire를 transparent conductive electrodes로 활용하였다. Ag NWs층과 PEDOT:PSS layer의 복합화를 통해 저가의 ITO-free OPVs용 transparent anodes가 가능해졌다.