This study was conducted to select target fish species as baseline research for accumulation analysis of major hazardous chemicals entering the aquatic ecosystem in Korea and to analyze the impact on fish community. The test bed was selected from a sewage treatment plant, which could directly confirm the impact of the inflow of harmful chemicals, and the Geum River estuary where harmful chemicals introduced into the water system were concentrated. A multivariable metric model was developed to select target candidate fish species for hazardous chemical analysis. Details consisted of seven metrics: (1) commercially useful metric, (2) top-carnivorous species metric, (3) pollution fish indicator metric, (4) tolerance fish metric, (5) common abundant metric, (6) sampling availability (collectability) metric, and (7) widely distributed fish metric. Based on seven metric models for candidate fish species, eight species were selected as target candidates. The co-occurring dominant fish with target candidates was tolerant (50%), indicating that the highest abundance of tolerant species could be used as a water pollution indicator. A multi-metric fish-based model analysis for aquatic ecosystem health evaluation showed that the ecosystem health was diagnosed as “bad conditions”. Physicochemical water quality variables also influenced fish feeding and tolerance guild in the testbed. Eight water quality parameters appeared high at the T1 site, indicating a large impact of discharging water from the sewage treatment plant. T2 site showed massive algal bloom, with chlorophyll concentration about 15 times higher compared to the reference site.

Copper nanoparticles (CuNPs) are considered of great importance due to their high catalytic and antimicrobial activities. This study focuses on the preparation and characterization of CuNPs, and on their antibacterial/antifungal activities. A copper salt (copper sulfate pentahydrate) as precursor, starch as stabilizing agent, and ascorbic acid as reducing agent were used to fabricate CuNPs. The resulting product was characterized via different techniques such as X-ray diffractrometry (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and Scanning electron microscopy (SEM) to confirm its characteristic properties. Employing the Scherrer formula, the mean crystallite sizes of copper (Cu) and cuprous oxide (Cu2O) nanocrystals were found to be 29.21 and 25.33 nm, respectively, as measured from the main X-ray diffraction peaks. The functional groups present in the resulting CuNPs were confirmed by FTIR. In addition, the engineered CuNPs showed antibacterial and antifungal activity against tested pathogenic bacterial and fungal strains.

Surface plasmon resonance is the resonant oscillation of conduction electrons at the interface between negative and positive permittivity material stimulated by incident light. In particular, when light transmits through the metallic microhole structures, it shows an increased intensity of light. Thus, it is used to increase the efficiency of devices such as LEDs, solar cells, and sensors. There are various methods to make micro-hole structures. In this experiment, micro holes are formed using a wet chemical etching method, which is inexpensive and can be mass processed. The shape of the holes depends on crystal facets, temperature, the concentration of the etchant solution, and etching time. We select a GaAs(100) single crystal wafer in this experiment and satisfactory results are obtained under the ratio of etchant solution with H2SO4:H2O2:H2O = 1:5:5. The morphology of micro holes according to the temperature and time is observed using field emission - scanning electron microscopy (FE-SEM). The etching mechanism at the corners and sidewalls is explained through the configuration of atoms.

An effective cleaning method for Ni removal in Ni-induced lateral crystallization(Ni-MILC) poly-Si TFTs and their electrical properties are investigated. The HCN cleaning method is effective for removal of Ni on the crystallized Si surface, while the nitric acid treatment results decrease by almost two orders of magnitude in the Ni concentration due to effective removal of diffused Ni mainly in the poly-Si grain boundary regions. Using the HCN cleaning method after the nitric acid treatment, re-adsorbed Ni on the Si surfaces is effectively removed by the formation of Ni-cyanide complexions. After the cleaning process, important electrical properties are improved, e.g., the leakage current density from 9.43 × 10−12 to 3.43 × 10−12 A and the subthreshold swing values from 1.37 to 0.67 mV/dec.

Phosphorus (P) is a limited, essential, and irreplaceable nutrient for the biological activity of all the living organisms. Sewage sludge ash (SSA) is one of the most important secondary P resources due to its high P content. The SSA has been intensively investigated to recover P by wet chemicals (acid or alkali). Even though H2SO4 was mainly used to extract P because of its low cost and accessibility, the formation of CaSO4 (gypsum) hinders its use. Heavy metals in the SSA also cause a significant problem in P recovery since fertilizer needs to meet government standards for human health. Therefore, P recovery process with selective heavy metal removal needs to be developed. In this paper some of the most advanced P recovery processes have been introduced and discussed their technical characteristics. The results showed that further research is needed to identify the chemical mechanisms of P transformation in the recovery process and to increase P recovery efficiency and the yields.

In this study, Fe-Ni bimetallic catalyst supported on kaolin is prepared by a wet impregnation method. The effects of mass of kaolin support, pre-calcination time, pre-calcination temperature and stirring speed on catalyst yields are examined. Then, the optimal supported Fe-Ni catalyst is utilised to produce multi-walled carbon nanotubes (MWCNTs) using catalytic chemical vapour deposition (CCVD) method. The catalysts and MWCNTs prepared using the optimal conditions are characterized using high resolution transmission electron microscope (HRTEM), high-resolution scanning electron microscope (HRSEM), electron diffraction spectrometer (EDS), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), and X-ray diffraction (XRD). The XRD/EDS patterns of the prepared catalyst confirm the formation of a purely crystalline ternary oxide (NiFe2O4). The statistical analysis of the variance demonstrates that the combined effects of the reaction temperature and acetylene flow rate predominantly influenced the MWCNT yield. The N2 adsorption (BET) and TGA analyses reveal high surface areas and thermally stable MWCNTs. The HRTEM/HRSEM micrographs confirm the formation of tangled MWCNTs with a particle size of less than 62 nm. The XRD patterns of the MWCNTs reveal the formation of a typical graphitized carbon. This study establishes the production of MWCNTs from a bi-metallic catalyst supported on kaolin.

Copper nanoparticles attract much attention as substitutes of noble metals such as silver and can help reduce the manufacturing cost of electronic products due to their lower cost and good conductivity. In the present work, the chemical reduction is examined to optimize the synthesis of nano-sized copper particles from copper sulfate. Sodium borohydride and ascorbic acid are used as reducing and antioxidant agents, respectively. Polyethylene glycol (PEG) is used as a size-control and capping agent. An appropriate dose of PEG inhibits the abnormal growth of copper nanoparticles, maintaining chemical stability. The addition of ascorbic acid prevents the oxidation of nanoparticles during synthesis and storage. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) are used to investigate the size of the synthesized nanoparticles and the coordination between copper nanoparticles and PEG. For chemical reduction, copper nanoparticles less than 100 nm in size without oxidized layers are successfully obtained by the present method.

Cobalt coated tungsten carbide-cobalt composite powder has been prepared through wet chemical reductionmethod. The cobalt sulfate solution was converted to the cobalt chloride then the cobalt hydroxide. The tungsten carbidepowders were added in to the cobalt hydroxide, the cobalt hydroxide was reduced and coated over tungsten carbidepowder using hypo-phosphorous acid. Both the cobalt and the tungsten carbide phase peaks were evident in the tungstencarbide-cobalt composite powder by X-ray diffraction. The average particle size measured via scanning electron micro-scope, particle size analysis was around 380 nm and the thickness of coated cobalt was determined to be 30~40 nm bytransmission electron microscopy.

Synthesis of RGO (reduced graphene oxide)-CdS composite material was performed through CBD (chemical bath deposition) method in which graphene oxide served as the support and Cadmium Sulfate Hydrate as the starting material. Graphene-based semiconductor photocatalysts have attracted extensive attention due to their usefulness for environmental and energy applications. The band gap (2.4 eV) of CdS corresponds well with the spectrum of sunlight because the crystalline phase, size, morphology, specic surface area and defects, etc., of CdS can affect its photocatalytic activity. The specific surface structure (morphology) of the photocatalyst can be effective for the suppression of recombination between photogenerated electrons and holes. Graphene (GN) has unique properties such as a high value of Young's modulus, large theoretical specific surface area, excellent thermal conductivity, high mobility of charge carriers, and good optical transmittance. These excellent properties make GN an ideal building block in nanocomposites. It can act as an excellent electron-acceptor/transport material. Therefore, the morphology, structural characterization and crystal structure were observed using various analytical tools, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. From this analysis, it is shown that CdS particles were well dispersed uniformly in the RGO sheet. Furthermore, the photocatalytic property of the resulting RGO-CdS composite is also discussed in relation to environmental applications such as the photocatalytic degradation of pollutants. It was found that the prepared RGO-CdS nanocomposites exhibited enhanced photocatalytic activity as compared with that of CdS nanoparticles. Therefore, better efficiency of photodegradation was found for water purification applications using RGO-CdS composite.