• Clean Technology
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• v.27 no.4
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• pp.291-296
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• 2021

Recently, there has been increasing demand for advancing photocatalytic techniques that are capable of the efficient removal of organic pollutants in water. TiO₂, a representative photocatalytic material, has been commonly used as an effective photocatalyst, but it is rather expensive and an alternative is required that will fulfill the requirements of both high performing photocatalytic activities and cost-effectiveness. In this work, ZnO, which is more cost effective than TiO₂, was synthesized by using a microreactor-assisted nanomaterials (MAN) process. The process enabled a continuous production of ZnO nanoparticles (NPs) with a flower-like structure with high uniformity. In order to resolve the limited light absorption of ZnO arising from its large band gap, Ag NPs were uniformly decorated on the flower-like ZnO surface by using the MAN process. The plasmonic effect of Ag NPs led to a broadening of the absorption range toward visible wavelengths. Ag NPs also helped inhibit the electron-hole recombination by drawing electrons generated from the light absorption of the flower-like ZnO NPs. As a result, the Ag-ZnO nanocomposites showed improved photocatalytic activities compared with the flower-like ZnO NPs. The photocatalytic activities were evaluated through the degradation of methylene blue (MB) solution. Scanning electron microscopy (SEM), x-ray diffraction (XRD), and energy-dispersive x-ray spectroscopy (EDS) confirmed the successful synthesis of Ag-ZnO nanocomposites with high uniformity. Ag-ZnO nanocomposites synthesized via the MAN process offer the potential for cost-effective and scalable production of next-generation photocatalytic materials.

• Applied Chemistry for Engineering
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• v.32 no.6
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• pp.684-689
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• 2021

In this paper, we develop a cost effective and disposable voltammetric sensing platform involving screen-printed carbon electrode (SPCE) modified with the nanocomposites composed of multi-walled carbon nanotubes, polyelectrolyte, and tyrosinase for bisphenol A. This is known as an endocrine disruptor which is also related to chronic diseases such as obesity, diabetes, cardiovascular and female reproductive diseases, precocious puberty, and infertility. A negatively charged oxidized multi-walled carbon nanotubes (MWCNTs) wrapped with a positively charged polyelectrolyte, e.g., polydiallyldimethylammonium, was first wrapped with a negatively charged tyrosinae layer via electrostatic interaction and assembled onto oxygen plasma treated SPCE. The nanocomposite modified SPCE was then immersed into different concentrations of bisphenol A for a given time where the tyrosinase reacted with OH group in the bisphenol A to produce the product, 4,4'-isopropylidenebis(1,2-benzoquinone). Cyclic and differential pulse voltammetries at the potential of -0.08 V vs. Ag/AgCl was employed and peak current changes responsible to the reduction of 4,4'-isopropylidenebis(1,2-benzoquinone) were measured which linearly increased with respect to the bisphenol A concentration. In addition, the SPCE based sensor showed excellent selectivity toward an interferent agent, bisphenol S, which has a very similar structure. Finally, the sensor was applied to the analysis of bisphenol A present in an environmental sample solution prepared in our laboratory.

• Journal of the Speleological Society of Korea
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• no.63
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• pp.1-8
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• 2004

The non-magnetic materials with non-conductive showing high structure dispersity were developed on the base of natural quartz and lava-scoria which was collected from Je-ju island in Korea, and treated by methane-chemical technology those were obtained novel properties of magnetization through the analyzing. Depending on the processing conditions and subsequent applications the materials produced by strong methane-chemical reaction (MCR) in alcohol solution showed concurrently magnetic, dielectric and electrical properties. The obtained magnetic-electrical powders classified by aggregate complex of their features as segnetomagnetics, containing a dielectric material as a carrying nucleus, particularly the quartz on that surface one or more layers of different compounds were synthesized having thickness up to 10～50 nm and showing magnetic, electrical and other properties. It was confirmed in magnetizing process that powders of quartz and lava-scoria produced by MCR were better oil adsorbent as of oleophilic and floating matter on water surface although their specific gravities are comparably more than 1 in quartz or less than unity, as that of water, in lava-scoira. Therefore, it will be Possible and very useful to remove low density and light gravity oil spillage in difficult recovery from sea and inland water contamination spread on water surface, by marine accident and ship sinking accident occurring frequently in recent years, by way of magnetic adsorbent conveyer system in continuous, if it could be built up the mass Production system of water-floating magnetizable oleophilic adsorbent materials with use of iow cost and good Qualify lava-scoria spread on volcano district in Je-ju island. And, there will also be urgent advent of necessity with strong possibility to develop useful applications of various magnetic functional materials include oleophilic adsorbent for removal of sea oil-contaminants and maritime pollutants, and other kinds of various utilities in industrial applications and practical uses of novel functional materials in the fields of environments and health care applications with in deep expectation.