Liquid Phase Plasma Process Research Articles

Gold nanoparticles with natural polymer synthesized by plasma–liquid interactions: Size-control, characterization and colorimetric detection of melamine based on the size effect of gold nanoparticles

This work reports the synthesis of size-controlled gold nanoparticles as AuNP colloids in aqueous solutions with capping natural polymer matrices – the sodium salt of carboxymethyl cellulose, using a liquid-phase plasma process. The effects of the solution plasma process discharge time, concentrations of gold(III) chloride trihydrate precursor (0.06–2.5 mmol/L) and correlations of the precursor/CMC ratios on the characteristics on the synthesized Au NPs, including size distribution and optical absorption properties, were investigated. The average size (20–90 nm) and form (spherical, hexagonal and triangular) of the AuNPs can be change depending on the initial concentration of Au3+ and the ratios of precursor/CMC on the process synthesis. Gold nanoparticles were used to study a straightforward colorimetric detection of melamine. Melamine caused the AuNPs to agglomerate in aqueous solution, changing their visible color from red to blue. The prepared AuNPs can be used for the detection of melamine with a low LOD and an extremely wide linear range (0.005–0.21 μM.).

Decomposition of the antibiotic sulfamethoxazole by the liquid-phase plasma process enhanced by peroxymonosulfate

In this study, sulfamethoxazole (SMZ) was successfully degraded using the liquid phase plasma (LPP) method, a new advanced oxidation process (AOPs). The effects of LPP process variables and side reactions on SMZ decomposition reactions were evaluated, and optimal LPP process conditions were determined based on these data. To increase the efficiency of the SMZ decomposition reaction, peroxymonosulfate (PMS) was added to the LPP reaction. The optimal addition amount was derived by tracking the change in the amount of oxidation radicals produced according to the addition of PMS. By analyzing the reaction intermediates generated in the SMZ decomposition reaction, the decomposition pathway of SMZ by the LPP method was proposed.

Removal of oxytetracycline from water by liquid-phase plasma process with an iron precipitated TiO2 photocatalyst

This study developed a new water treatment method using liquid-phase plasma (LPP) process that can decompose oxytetracycline (OTC) remaining in the aquatic environment. Relatedly, the OTC causes damage to the human body and cannot be removed by traditional water treatment methods. The study also prepared Fe/TiO2 photocatalyst responding to visible light using the LPP process. In particular, the OTC decomposition efficiency of the LPP process improved by more than 10% with the use of the Fe/TiO2 photocatalyst as compared to that of the one with the use of bare TiO2 photocatalyst. Further, the optimal LPP process parameters and Fe/TiO2 photocatalyst amount in the LPP process for OTC decomposition were established in the study. Finally, the degradation pathway of the OTC in the LPP process was found based on the five intermediates of the LPP reaction that were detected by the liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analysis. In particular, the decomposition pathway was estimated to be involving the mineralization of the OTC through demethylation, deamination, dehydration, and ring cleavage.

Diclofenac degradation properties of a La-doped visible light-responsive TiO2 photocatalyst

Diclofenac (DCF), which is detected in the aquatic environment, can act as a harmful factor to the ecosystem and human health, but it is difficult to remove it with existing water treatment methods. DCF can be removed using the TiO2 photocatalysis process, and in this study, a method for removing it using visible light was sought. A visible-light reactive TiO2 photocatalyst doped with lanthanum (La) was synthesized using an LPP (Liquid Phase Plasma) process, and the photocatalytic activity was investigated by decomposing diclofenac. La was doped uniformly into the TiO2 powder, and the content of doped La increased with increasing concentration of the initial precursor. The La dopant was in the form of La2O3, and the bandgap and photoluminescence intensity decreased with increasing amount of doped La. In the photolysis experiment using a UV light source, the La-doped TiO2 photocatalysts (LDTPs) showed slightly higher activity than the bare TiO2, but the photocatalyst activity of the LDTPs under the visible light irradiation was superior. In the degradation experiment of DCF by LDTP, four major by-product intermediates were detected. Moreover, it was estimated that degradation proceeded through two pathways: hydroxylation and ring closure.

Recent applications of the liquid phase plasma process

In this paper, the principle and application of plasma are briefly described, and in particular, the principle and practical application for plasma generated in liquid are introduced. Also, the research results of water treatment, synthesis of metal nanoparticle, synthesis of visible light-responsive photocatalyst, synthesis of energy material, and hydrogen gas production, which were tested using liquid phase plasma, are introduced. Various water pollutants were treated and hydrogen gas was produced using the strong chemical oxidizing species and ultraviolet rays in the plasma field generated in the reactant aqueous solution during the liquid phase plasma (LPP) process. The effects of plasma discharge conditions, dissolved oxygen concentration, pH value, photocatalytic behavior, as well as the properties of organic solutions on the LPP reaction were investigated experimentally and reported. Based on these previous studies, metal nanoparticles were synthesized using hydrogen atom radicals as well as the numerous electrons in the plasma field generated during the LPP process. Additionally, these studies indicate that visible light-responsive photocatalysts can be obtained when metal nanoparticles are precipitated in TiO2. They also provide evidence that metal nanoparticles can be precipitated in various carbon materials for application as electrodes in secondary batteries and supercapacitors. Therefore, the LPP process has been successfully applied in various fields given that it can be easily and conveniently used, and presently it is being applied in several new fields and many possibilities for its future application are expected.

Fabrication of Molybdenum Oxide/Activated Carbon Using Liquid Phase Plasma Reaction and Its Electrochemical Performance.

In this study, molybdenum oxide/carbon nanocomposites (MOCNCs) were prepared by precipitating molybdenum oxide nanoparticles on activated carbon powder using liquid phase plasma process. The molybdenum oxide nanoparticles were impregnated on the AC surface and the amount impregnated was dependent on the concentration of the molybdenum precursor. MoO₃ nanoparticles were predominantly precipitated and their size was about 20-80 nm. The specific capacitance of MOCNCs was increased with increasing the amount of molybdenum nanoparticles. Moreover, the resistances of MOCNCs were reduced than that of bare AC.

Assessing the photocatalytic activity of europium doped TiO2 using liquid phase plasma process on acetylsalicylic acid

In this study, europium (Eu) was precipitated in TiO2 powder using liquid phase plasma (LPP) process to prepare a photocatalyst with higher activity, even in the visible light range. Eu was uniformly deposited on the surface of TiO2 by the LPP method. It was observed that the amount of Eu precipitated on the TiO2 surface increased with increasing precursor concentration. XPS and EDS analysis showed that Eu was precipitated as europium oxide. The precipitation of Eu shifted the position of the Raman peak to a higher wavelength; with higher Eu content, the band gap energy decreased. Particularly, the photocatalytic efficiency of the Eu doped TiO2 photocatalyst (EDTP) in the visible light source was much higher than that of bare TiO2, and with higher Eu content, the photocatalytic activity was improved. Acetylsalicylic acid was attacked by HO∙ produced on the EDTP’s surface and assumed to be finally mineralized to H2O and CO2via two decomposition pathways, namely, decarboxylation and deacetylation.

액상 플라즈마 공정을 이용한 니켈-코발트 산화물 나노입자/활성탄 복합체 제조와 응용

액상 플라즈마 공정을 이용한 니켈-코발트 산화물 나노입자/활성탄 복합체 제조와 응용

Fabrication of Yb-doped TiO2 using liquid phase plasma process and its photocatalytic degradation activity of naproxen

Photocatalysts responding to visible light were prepared by doping ytterbium (Yb) to TiO2 powder by LPP method. Yb2O3 nanoparticles were uniformly precipitated on the surface of TiO2 powder, and when the precursor concentration was increased, the precipitated Yb2O3 nanoparticles increased. The precipitated Yb element lowered the band gap energy of Yb-doped TiO2 photocatalyst (YTP) by 0.07 to 0.14 eV compared to bare TiO2. YTPs degraded naproxen (NPX) better than bare TiO2, especially under blue LED light (maximum wavelength 470 nm), and YTP containing higher Yb elements showed higher decomposition activity. NPX was decomposed into CO2 and H2O by decarboxylation and demethylation by hydroxyl radicals generated from TiO2 photocatalysts, suggesting a degradation pathway based on the three intermediates detected by LC/MS analysis.

Rapid decomposition of chloroform by a liquid phase plasma reaction with titanium dioxide and hydrogen peroxide

• Chloroform in aqueous solution was successfully degraded by liquid phase plasma reaction. • The operation parameters of power supply played an important role in the chloroform degradation reaction. • Degradation rate of chloroform is proportional to an increase in operation parameter. • Addition of titanium dioxide or hydrogen peroxide to liquid phase plasma reaction improved the degradation of chloroform. • When titanium dioxide and hydrogen peroxide used simultaneously, the synergetic effect was observed. The degradation of chloroform in a liquid phase plasma (LPP) reactor was examined according to the operating parameters and other influencing factors. The operating parameters included the applied voltage, frequency, and pulse width. The effects of titanium dioxide, hydrogen peroxide, and their combination on the degradation of chloroform were evaluated in terms of the influencing factors. Increasing the operating parameters up to the maximum allowed in the LPP process made chloroform decompose much faster than that of the minimum. On the other hand, increasing either the titanium dioxide or hydrogen peroxide concentrations in the reactant solution did not always destroy the chloroform efficiently compared to degradation without their loading. Although the impact of titanium dioxide was slightly higher than that of hydrogen peroxide, the synergistic effect between them enhanced the breakdown of chloroform further. Overall, both the operating parameters and influencing factors should be determined carefully to maximize the decomposition efficiency in the given treatment system, particularly for processes involving the LPP reaction.

Synthesis of Au Nanoparticles in Natural Matrices by Liquid-Phase Plasma: Effects on Cytotoxic Activity against Normal and Cancer Cell Lines

Wrapping of gold nanoparticles (AuNPs) with a biocompatible matrix, to gain AuNP colloids, is a general strategy to synthesize the AuNPs for biomedical purposes. This work reports the synthesis of AuNP colloids in the aqueous solution of several natural matrices using a liquid-phase plasma process. Two classes of natural substances used are sugars (including: glucose, fructose, and sucrose) and biopolymers (including: carboxymethyl cellulose, sodium alginate, and gelatin). All are negatively charged water-soluble substances that are claimed to be sources of energy for cells to grow and have a high potential to be compatible with them. The study has emerged since one question arises: “Do these matrices also promote the growth of cancer cells?” The synthesis is performed by generating plasma across a pair of electrodes immersed in an aqueous solution of a natural matrix containing a gold precursor (HAuCl4·3H2O). Two concentrations of the matrices (0.5 and 1.0% w/v) are used, and the plasma treatment times a...

Assessment of photocatalytic performance of Fe/N-TiO2 photocatalysts prepared by liquid phase plasma process

Abstract To improve the photocatalytic performance of TiO2 photocatalysts, a new method, liquid phase plasma (LPP) method, was used to introduce nitrogen and iron oxide. Interstitial or substitutional nitrogen and Fe3+ iron nanoparticles were impregnated on the surface of TiO2 by LPP reaction without additional chemical reduction agent and the amount of iron of modified TiO2 photocatalysts was affected by the amount of initial precursor. The adsorption edge of modified TiO2 photocatalysts was shifted to the visible region in proportion to the amount of nitrogen and iron oxide, and the band gap energy was decreased, and the photocatalytic activity was confirmed by PL and EPR analysis. The photocatalytic activities of modified TiO2 photocatalysts were measured under UV and blue LED lamps and compared with pure TiO2 powder (P-25). The modified TiO2 exhibited better photocatalytic degradation performance than pure TiO2 under blue LED light conditions, but exhibited low degradation activity under UV LED light conditions. Through GC–MS analysis, it was found that the methylene blue was finally decomposed into an inorganic substance through intermediates such as benzene sulfonic acid and phenol by OH radicals. From these results, we found that the modified TiO2 photocatalysts can be easily prepared using the LPP method and can be used in the visible region.

Heterogeneous photocatalytic degradation and hydrogen evolution from ethanolamine nuclear wastewater by a liquid phase plasma process

Ethanolamine in a wastewater which is released from nuclear power plant was decomposed using a plasma discharged into the solution directly. Ni-TiO2 supported on mesoporous materials were employed as a photocatalyst. The photocatalytic reaction using the liquid phase plasma led to a degradation of ethanolamine with hydrogen evolution, simultaneously. The ethanolamine in the wastewater was degraded over 90% on the photocatalytic decomposition reaction by irradiation of liquid phase plasma. The rate of hydrogen evolution increased significantly with Ni incorporation on TiO2 because the bandgap was reduced with Ni incorporation on TiO2. Incorporating Ni on TiO2 nanocrystallites brought out an improvement of the ethanolamine degradation with hydrogen generation. The rate of hydrogen evolution in the ethanolamine-containing aqueous solution was increased in comparison with that in pure water. Additional hydrogen evolution by the photodecomposition of ethanolamine was attributed to the increasing H2 production.

Photocatalytic hydrogen production with purification of wastewater from nuclear power plant under irradiation of liquid phase plasma

Liquid phase plasma process was applied in production of hydrogen and purification of wastewater. Ethanolamine released from a nuclear power plant was degraded by photocatalytic decomposition using the liquid phase plasma with perovskite photocatalysts. Eu-doped CaTiO3 and Eu-doped SrAl2O4 perovskites were compared with that of commercial TiO2 photocatalyst. The photocatalytic decomposition of ethanolamine-contained water induced the degradation of ethanolamine and H2 evolution, simultaneously. The degradation of ethanolamine and H2 evolution were elevated on Eu-doped CaTiO3 perovskite which having less bandgap energy. The rate of H2 evolution in the ethanolamine-containing water was higher than that in pure water, which was attributed to the additional H2 evolution by the photo-decomposition of ethanolamine in water.

Preparation and Characterization of Bimetallic Fe-Ni Oxide Nanoparticles Using Liquid Phase Plasma Process.

The Fe-Ni oxide bimetallic nanoparticles (FNOBNPs) were synthesized in the liquid phase plasma (LPP) method employed an iron chloride and nickel chloride as metal precursors. The sphericalshaped FNOBNPs were synthesized by the LPP process and, the size of particles was growing along with the progression of LPP reaction. The synthesized FNOBNPs were comprised of Fe₃O₄ and NiO. Iron had a higher reduction potential than nickel and resulted in higher iron composition in the synthesized FNOBNPs. The control of molar ratio of metal precursors in initial reactant solution was found that it could be employed as a means to control the composition of the elements in FNOBNP.

Facile Synthesis of Chromium Oxide on Activated Carbon Electrodes for Electrochemical Capacitor Application.

Chromium oxide/carbon nanocomposites (COCNC) were synthesized by using a liquid phase plasma process, and the electrical properties of the supercapacitor electrode were investigated. Spherical chromium oxide (Cr₂O₃) nanoparticles with the size of 100-150 nm were dispersed uniformly on activated carbon powder surface. The quantity of chromium oxide nanoparticle precipitate increased with increasing LPP reaction time and the specific capacitance of COCNC increased with increasing LPP reaction time.

Enhanced Electrochemical Performance of Carbon Nanotube with Nitrogen and Iron Using Liquid Phase Plasma Process for Supercapacitor Applications.

Nitrogen-doped carbon nanotubes (NCNTs) and iron oxide particles precipitated on nitrogen-doped carbon nanotubes (IONCNTs) were fabricated by a liquid phase plasma (LPP) process for applications to anode materials in supercapacitors. The nitrogen element and amorphous iron oxide nanoparticles were evenly disseminated on the pristine multiwall carbon nanotubes (MWCNTs). The electrochemical performance of the NCNTs and IONCNTs were investigated and compared with those of pristine MWCNTs. The IONCNTs exhibited superior electrochemical performance to pristine MWCNTs and NCNTs. The specific capacitance of the as-fabricated composites increased as the content of nitrogen and iron oxide particles increased. In addition, the charge transfer resistance of the composites was reduced with introducing nitrogen and iron oxide.

Degradation of dimethyl phthalate using a liquid phase plasma process with TiO2 photocatalysts

The liquid phase plasma (LPP) method with a TiO2 photocatalyst and hydrogen peroxide was used to decompose dimethyl phthalate (DMP). As the applied voltage, pulse width, and frequency were increased, the rate of decomposition was increased and the decomposition rate was 63% for 180 min under plasma optimum conditions. The addition of TiO2 photocatalyst and hydrogen peroxide increased the DMP decomposition reaction rate, but an excess cause a decrease in decomposition rate due to a decrease in conductivity, blocking of ultraviolet light, and scavenger effect. When the TiO2 photocatalyst and hydrogen peroxide were used together, the decomposition reaction rate of DMP was greatly improved by using LPP single process alone. Also, when all the processes were used at the same time, the decomposition reaction rate was improved to about 2.8 times. DMP undergoes bond cleavage and ultimately decomposes into CO2 and H2O via dimethyl 4-hydroxyphthalate and methyl salicylates due to hydroxyl radicals and various active species generated by the LPP reaction.

Facile preparation of tungsten oxide doped TiO2 photocatalysts using liquid phase plasma process for enhanced degradation of diethyl phthalate

In a present study, tungsten oxide was employed to improve the removal efficiency of the parent compound diethyl phthalate as well as to reduce the band gap energy of the original photocatalyst titanium dioxide. The modified photocatalyst was prepared by depositing tungsten oxide onto titanium dioxide through the liquid phase plasma. The decomposition of the parent compound was examined by varying the loading of tungsten oxide in the photocatalyst surface under different light sources, UV and blue light sources. Results showed that the band gap energy in the modified photocatalyst was lower than that of the original photocatalyst, which was attributed to increased loading of tungsten oxide in the modified photocatalyst surface resulted from an increase in the initial precursor concentrations. Tungsten doped in the photocatalyst surface existed in the form of the WO3, which led to a decrease in the specific surface area for the modified photocatalyst. The degradation performance of the parent compound increased in response to an increase in the amount of tungsten oxide under blue light, but decreased with increasing the loading of tungsten oxide under UV light. Two intermediates observed during the photocatalytic degradation appeared to be involved in the proposed degradation pathway.

Development of hydrogen production by liquid phase plasma process of water with Ni[sbnd]TiO2/carbon nanotube photocatalysts

Hydrogen evolution by water photocatalysis using liquid phase plasma system was disserted over metal-loaded TiO2 photocatalysts. Carbon nanotube was applied as a support for the metal-loaded TiO2 nanocrystallites. Photocatalytic activities of the photocatalysts were estimated for hydrogen production from water. Hydrogen was produced from the photodecomposition of water by liquid phase plasma irradiation. The rate of hydrogen evolution was improved by the metal loading on the TiO2 surface. TiO2 nanocrystallites were incorporated above 40 wt% onto the carbon nanotube support. The carbon nanotubes could be applied as a useful photocatalytic support for the fixation of TiO2. Hydrogen evolution was enhanced by the Ni loading on the TiO2 nanocrystallites supported on the carbon nanotube. Hydrogen evolution was increased apparently with addition of the alcohols which contributes as a kind of sacrificial reagent promoting the photocatalysis.