• Journal of the Korean institute of surface engineering
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• v.48 no.4
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• pp.158-162
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• 2015

To substitute indium tin oxide (ITO), many substituents have been studied such as metal nanowires, carbon based materials, 2D materials, and conducting polymers. These materials are not good enough to apply to an electrode because theses exhibit relatively high resistance. So metal grids are required as an additionalelectrode to improve the conductivities of substituents. The metal grids were printed by electrohydrodynamic printing system using Ag nanoparticle based ink. The Ag grids showed high uniformity and the line width was about $10{\mu}m$. The Ag nanoparticles are surrounded by dispersants such as unimolecular and polymer to prevent aggregation between Ag nanoparticles. The dispersants lead to low conductivity of Ag grids. Thus, the sintering process of Ag nanoparticles is strongly recommended to remove dispersants and connect each nanoparticles. For sintering process, the interface and microstructure of the Ag grid were controlled in 1.0 torr Ar atmosphere at aound $400^{\circ}C$ of temperature. From the sintering process, the uniformity of the Ag grid was improved and the defects on the Ag grids were reduced. As a result, the resistivity of Ag grid was greatly reduced up to $5.03({\pm}0.10){\times}10^{-6}{\Omega}{\cdot}cm$. The metal grids embedded substrates containing low pressure Ar sintered Ag grids showed 90.4% of transmittance in visible range with $0.43{\Omega}/{\square}$ of sheet resistance.

• Journal of Microbiology and Biotechnology
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• v.29 no.11
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• pp.1841-1851
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• 2019

Garcinol, a well-known medicinal phytochemical, was extracted and isolated from the dried fruit rinds of Garcinia quaesita Pierre. In this study, garcinol has successfully used to reduce silver ions to silver in order to synthesize garcinol-capped silver nanoparticles (G-AgNPs). The formation and the structure of G-AgNPs were confirmed by UV-visible spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The antimicrobial activity of garcinol and G-AgNPs were investigated by well diffusion assays, broth micro-dilution assays and time-kill kinetics studies against five microbial species, including Staphylococcus aureus (ATCC 25923), Pseudomonas aeruginosa (ATCC 27853), Escherichia coli (ATCC 25922), Candida albicans (ATCC 10231) and clinically isolated methicillin-resistant Staphylococcus aureus (MRSA). The formation of G-AgNPs is a promising novel approach to enhancing the biological activeness of silver nanoparticles, and to increase the water solubility of garcinol which creates a broad range of therapeutic applications.

• Journal of Sensor Science and Technology
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• v.23 no.6
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• pp.397-401
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• 2014

This paper describes the fabrication and characteristics of $C_2H_2$ gas sensor based on Ag-doped hierarchical ZnO nanostructures. In this work, a pure hierarchical ZnO structure was prepared using a simple hydrothermal method, and Ag nanoparticles doped the hierarchical ZnO structure were uniformly synthesized through photochemical route. The synthesized samples were characterized by SEM, TEM, EDS, XRD and PL spectra. Average size of prepared ZnO structures was around $2{\sim}3{\mu}m$ and showed highly uniform. The average size of Ag nanoparticles was 70 nm. The gas sensing properties of as-prepared products were investigated using resistivity-type gas sensors. 5 at% Ag-doped ZnO based sensors exhibited good performances for $C_2H_2$ gas in comparison with the un-doped one. The sensor based on Ag-doped hierarchical ZnO structures had linear response property from 5~1000 ppm of $C_2H_2$ concentration at working temperature of $200^{\circ}C$. The response values with 100 ppm $C_2H_2$ at $200^{\circ}C$ were 10% and 75% for pure and 5 at% Ag-doped hierarchical ZnO nanostructures, respectively. Moreover, the device showed excellent selectivity towards to $C_2H_2$ gas at optimal working temperature of $200^{\circ}C$.

• Journal of IKEEE
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• v.20 no.2
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• pp.177-180
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• 2016

The effect of varying thickness of Ag/Ti metal bilayer and annealing time have investigated for controlling self-organized nanoparticles (NPs) on 4H-SiC substrate. In addition, Glass and Si substrate which have different surface energy from SiC were fabricated for analyzing interaction of agglomeration. The results of FE-SEM indicated the different formation behaviors of NPs in various ranges of fabrication condition. The surface energy was measured by using a Contact Angle Analyzer. The formation of network-like NPs was observed on Glass and 4H-SiC, respectively, whereas it was not the case on Si substrates. It has been found that the size of NPs increases with decreasing surface energy, due to particle size-dependent hydrophilic properties of substrates. The different formation behavior was explained by using Young's equation for the contact angles between the metal and different substrates.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1391-1396
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• 2013

The photocontrolled reduction of silver nitrate to silver (Ag) nanoparticles on honeycomb-patterned poly(N-vinylcarbazole) (PVK)-cellulose triacetate (CTA) composite thin films was studied. The composites were prepared via the oxidative polymerization of N-vinylcarbazole with ferric chloride using different CTA concentrations. A honeycomb-patterned film was fabricated by casting the composite solution under humid conditions. Ag particles with a homogeneous distribution were produced by the composite film in a moderate CTA concentration, whereas aggregated Ag was obtained from the pure PVK film.

• Rapid Communication in Photoscience
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• v.2 no.3
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• pp.79-81
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• 2013

A novel method of fabricating polythiophene-gold nanoparticle composite film electrodes for photoelectric conversion is demonstrated. The method includes electrodeposition of gold and electropolymerization of 2,2'-bithiophene onto an indium-tin-oxide (ITO) electrode. First, electrodeposition of gold onto the ITO electrode was carried out with various repetition times of pulsed applied potential (0.25 s at -2.0 V vs. Ag/AgCl) in an aqueous solution of $HAuCl_4$. Significant progress of the number density of deposited gold nanoparticles was confirmed from scanning electron micrographs, from 4 (1 time) to 25% (15 times). Next, electropolymerization of 2,2'-bithiophene onto the above ITO electrode was performed under controlled charge condition (+1.4 V vs. Ag wire, 15 $mC/cm^2$). Structural characterization of as-fabricated films were carried out by spectroscopic and electron micrographic methods. Photocurrent responses from the sample film electrodes were investigated in the presence of electron acceptors (methyl viologen and oxygen). Photocurrent intensities increased with increasing the density of deposited gold nanoparticles up to ~10%, and tended to decrease above it. It suggests that the surplus gold nanoparticles exhibit quenching effects rather than enhancement effects based on localized electric fields induced by surface plasmon resonance of the deposited gold nanoparticles.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.6
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• pp.250-255
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• 2006

The synthesis and characterization of silver colloidal nanoparticles by chemical reduction of silver ions in aqueous $AgNO_3$ using sodium borohydride $(NaBH_4)$ as the reducing agent are described. The experimental conditions for aggregation and paricle size of nanosilver particles in water is investigated in terms of concentration of $NaBH_4$, reaction temperature, dropping rate of $AgNO_3$ and concentration of laponite. Stable nanosilver sol is obtained at three molar ratio of $NaBH_4/AgNO_3$ in conditions of without laponite. The size of nanosilver particles is increased as the reaction temperature is increased. The large size of nanosilver sol is obseved as the dropping rate of $AgNO_3$ is increased due to the aggregation of initial high local concentration of nanosilver particles. Stable nanosilver sol at high temperature $(>\;100^{\circ}C)$ can be prepared when laponite is used as protective colloid.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.53-53
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• 2010

The development of synthetic pathway to produce a highly yield nanoparticles is an important aspect of industrial technology. Herein, we report a simple, rapid approach to synthesize organic-soluble Cu and Ag nanoparticles in colloidal method for the application in a conductive pattern using inkjet printing. The silver nanoparticles have been synthesized in highly concentrated organic phase. The Cu nanoparticles have been synthesized by the reducing of the copper oxide materials using acid molecules in high concentrated organic phase. Their sintering and electric conductivity properties were investigated by melting process between $200^{\circ}C$ and $250^{\circ}C$ for application to printed electronics.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.611-616
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• 2016

In this study, we synthesized $Ag_2Se$ nanoparticles (NPs) in an aqueous solution and investigated the thermoelectric characteristics of $Ag_2Se$ NPs thin films on plastic substrates. Regardless of thermal annealing treatment, all the $Ag_2Se$ NPs thin films show the negative Seebeck coefficients, indicating the n-type characteristics. As the annealing temperature increases, the electric conductivity increases while the Seebeck coefficient decreases. The electric conductivity of the thin film annealed at $180^{\circ}C$ is larger by $10^6$ times, compared with the as-prepared thin film, And the maximum power density for the thin film annealed at $180^{\circ}C$ is calculated to be $44{\mu}W/cm^2$.

• The korean journal of orthodontics
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• v.53 no.1
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• pp.16-25
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• 2023

Objective: We aimed to evaluate the cell viability and antimicrobial effects of orthodontic bands coated with silver or zinc oxide nanoparticles (nano-Ag and nano-ZnO, respectively). Methods: In this experimental study, 30 orthodontic bands were divided into three groups (n = 10 each): control (uncoated band), Ag (silver-coated band), and ZnO (zinc oxide-coated band). The electrostatic spray-assisted vapor deposition method was used to coat orthodontic bands with nano-Ag or nano-ZnO. The biofilm inhibition test was used to assess the antimicrobial effectiveness of nano-Ag and nano-ZnO against Streptococcus mutans, Lactobacillus acidophilus, and Candida albicans. Biocompatibility tests were conducted using the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay. The groups were compared using oneway analysis of variance with a post-hoc test. Results: The Ag group showed a significantly higher reduction in the number of L. acidophilus, C. albicans, and S. mutans colonies than the ZnO group (p = 0.015, 0.003, and 0.005, respectively). Compared with the control group, the Ag group showed a 2-log₁₀ reduction in all the microorganisms' replication ability, but only S. mutants showed a 2-log₁₀ reduction in replication ability in the ZnO group. The lowest mean cell viability was observed in the Ag group, but the difference between the groups was insignificant (p > 0.05). Conclusions: Coating orthodontic bands with nano-ZnO or nano-Ag induced antimicrobial effects against oral pathogens. Among the nanoparticles, nano-Ag showed the best antimicrobial activity and nano-ZnO showed the highest biocompatibility.