Solution Plasma Process Research Articles

Li–air battery and ORR activity of nanocarbons produced with good synthesis rate by solution plasma process

Nanocarbons were successfully synthesized from benzene (BZ), nitro-benzene (BZ-NO2) and aniline (BZ-NH2) by solution plasma process (SPP).

N-Doped few-layer graphene encapsulated Pt-based bimetallic nanoparticles via solution plasma as an efficient oxygen catalyst for the oxygen reduction reaction

A superior durability of N-doped few-layer graphene shell for Pt-based bimetallic core protection by solution plasma process.

Investigation on the role of the free radicals and the controlled degradation of chitosan under solution plasma process based on radical scavengers

This study investigated the role of various active species (OH, O, and H2O2) under solution plasma process (SPP) degradation based on the influence of different radical scavengers on the degradation effect and ESR spectra. The structures of oligochitosan with different radical scavengers were characterized by FT-IR, 1H NMR, and XRD analysis. The results indicated that OH, O, and H2O2 played important roles in SPP degradation. The degradation effect of the O was even higher than that of the OH. The physical effects (e.g. UV light and shockwaves) of SPP method or Fenton's reaction might contribute to the degradation treatment. Furthermore, the different scavengers could adjust the degradation effect of the corresponding free radicals. FT-IR, 1H NMR, and XRD analysis revealed that the primary chemical structure of chitosan was not changed by the scavengers. This study found that the controlled degradation by addition of a radical scavenger is feasible. Therefore, this study provided a straightforward analysis of the role of the free radicals and the controlled degradation of chitosan under SPP treatment, which will be beneficial to further develop SPP techniques for chitosan degradation.

Study on size control of TiO2 nanoparticles synthesized using solution plasma process

The research was conducted to study the size control of TiO2 nanoparticles synthesised. The TiO2 nanoparticles was formed using the solution plasma process. This method is an electrolysis of water-based experiment. When compared to other methods, the solution plasma method offers both a shorter synthesis time as well as a simple setup. Researches conducted on nanomaterials have proven that these materials tend to have varying properties when compared to bulk metals. With this, being able to vary the sizes of the TiO2 nanoparticles meant being able to study its possible future applications. One being using these nanoparticles for the fabrication of solar cells. Varying the sizes of these nanoparticles could bring a difference in the reactivity which can help enhance the performance of the solar cells. In order to vary the sizes of the nanoparticles, the concentration of the electrolyte was varied. During the research, it was found that the sizes of the TiO2 nanoparticles decreases with the increase in the concentration of the electrolyte.

Synthesis and Size Control of Aluminum Nanoparticles using Solution Plasma Process

This research was conducted to investigate the various control techniques to vary the size of aluminum nanoparticles through solution plasma process, specifically the submerged glow-discharge plasma process. Aluminum nanoparticles have received many attention due to their unique combustion, resistance and superhydrophobic properties. A lab-scale based submerged glow-discharge setup has been constructed to produce the nanoparticles. Different concentration of potassium carbonate electrolyte (0.1M – 0.5M) and cathode submerged length (50 mm – 100mm) were used in this study. The results were viewed and analyzed using scanning electron microscopy. As the major results showed that the diameter size distribution ranges from 80nm to 2µm. Higher concentrations have shown to produce smaller nanoparticles due to the overlapping of electron beams on the cathode surface. Also, shorter cathode submerged lengths have resulted in larger-sized nanoparticles.

Structural and magnetic properties of highly Fe-doped ZnO nanoparticles synthesized by one-step solution plasma process

Among many preparation methods for the synthesis of Fe-doped ZnO nanoparticles which have been widely investigated due to versatile properties and potential applications in optoelectronics, photovoltaics, and spintronic devices, solution-based methods such as sol-gel, hydrothermal, and precipitation processes usually consume many reagents and involve numerous steps. In this study, we report a one-step synthesis of highly Fe-doped ZnO nanoparticles (NPs) by a solution plasma process (SPP) using FeCl2 and FeCl3 as precursors without any addition of chemicals. Breakdown of water bubbles caused by plasma discharge led to the formation of hydroxyl radicals, which reacted with the dissolved Zn2+ ions producing Zn(OH)2 that was indeed converted to ZnO through thermal dehydration. Meanwhile, Fe ions were incorporated into the host ZnO lattice during the synthesis process. Fe-doping levels in Zn1-xFexO NPs are easily controllable by changing the Fe precursor concentration and plasma discharging time. We achieved a high doping content (x = 0.14–0.46) within 30 min, which is difficult to achieve using traditional solution-based synthesis approaches. All the Fe-doped NPs exhibit ferromagnetic behavior, but the magnitude is strongly dependent on the Fe content and doping ratio of Fe2+ to Fe3+ ions, which are explained by the dominance and competition between the ferromagnetic and antiferromagnetic exchange interactions through the presence of mixed Fe2+ and Fe3+ ions. The observed optimal ratio of Fe2+ to Fe3+ for maximizing the magnetization is approximately 3:7. It is noteworthy that the magnetization of Fe-doped ZnO NPs can be simply controlled by manipulating the Fe content and composition of Fe2+ and Fe3+ ions achieved through the SPP. This result provides a platform for studying fundamental magnetic properties of TM-doped semiconductors for potential spintronic applications. Thus, the SPP has great potential as an alternative strategy for the synthesis of highly Fe-doped ZnO NPs, which can be expanded to the synthesis of other doped metal-oxide nanostructures for a broad range of research applications.

Effects of a Dielectric Barrier Discharge (DBD) on Characteristics of Polyaniline Nanoparticles Synthesized by a Solution Plasma Process with an Ar Gas Bubble Channel

The quality of polyaniline nanoparticles (PANI NPs) synthesized in plasma polymerization depends on the discharge characteristics of a solution plasma process (SPP). In this paper, the low temperature dielectric barrier discharge (DBD) is introduced to minimize the destruction of aniline molecules induced by the direct current (DC) spark discharge. By adopting the new electrode structure coupled with a gas channel, a low temperature DBD is successfully implemented in a SPP, for the first time, thus inducing an effective interaction between the Ar plasma and aniline monomer. We examine the effects of a low temperature DBD on characteristics of polyaniline nanoparticles synthesized by a SPP with an Ar gas bubble channel. As a result, both carbonization of aniline monomer and erosion of the electrode are significantly reduced, which is confirmed by analyses of the synthesized PANI NPs.

Novel synthesis of highly phosphorus-doped carbon as an ultrahigh-rate anode for sodium ion batteries

Carbonaceous materials are the most promising anode materials in electrochemical energy storage systems. However, poor electrochemical performance is a major obstacle to their practical use. Here, P-doped carbon balls (PCBs) are synthesized through a simple novel method, the solution plasma process (SPP), which is different from the conventional synthesis method, and used as an anode material in sodium ion batteries (SIBs). The PCBs synthesized by this approach show a high P content of about 4 at%. Meanwhile, P doping and disordered amorphous structures of PCBs provide abundant active sites and capacitive-dominant Na+ adsorption behavior, while large amounts of meso- and macropores shorten the Na+ diffusion distance, accelerating ion transport. The PCB anode material provides a high initial coulombic efficiency of about 75% and a high reversible capacity of 340 mAh g−1 at a current density of 1 A g−1. Even at an ultrahigh current density of 100 A g−1, an outstanding rate performance of 130 mA g−1 and reversible capacity of 83 mAh g−1 after 40,000 cycles provide excellent cycling stability. This synthesis strategy not only provides a very efficient approach to heteroatom doping but will also be a great impetus for the practical use of SIBs.

Enhanced Solar Photothermal Catalysis over Solution Plasma Activated TiO2.

Colored wide‐bandgap semiconductor oxides with abundant mid‐gap states have long been regarded as promising visible light responsive photocatalysts. However, their catalytic activities are hampered by charge recombination at deep level defects, which constitutes the critical challenge to practical applications of these oxide photocatalysts. To address the challenge, a strategy is proposed here that includes creating shallow‐level defects above the deep‐level defects and thermal activating the migration of trapped electrons out of the deep‐level defects via these shallow defects. A simple and scalable solution plasma processing (SPP) technique is developed to process the presynthesized yellow TiO2 with numerous oxygen vacancies (Ov), which incorporates hydrogen dopants into the TiO2 lattice and creates shallow‐level defects above deep level of Ov, meanwhile retaining the original visible absorption of the colored TiO2. At elevated temperature, the SPP‐treated TiO2 exhibits a 300 times higher conversion rate for CO2 reduction under solar light irradiation and a 7.5 times higher removal rate of acetaldehyde under UV light irradiation, suggesting the effectiveness of the proposed strategy to enhance the photoactivity of colored wide‐bandgap oxides for energy and environmental applications.

Bactericidal Silver Nanoparticles by Atmospheric Pressure Solution Plasma Processing.

Silver nanoparticles have applications in plasmonics, medicine, catalysis and electronics. We report a simple, cost-effective, facile and reproducible technique to synthesise silver nanoparticles via plasma-induced non-equilibrium liquid chemistry with the absence of a chemical reducing agent. Silver nanoparticles with tuneable sizes from 5.4 to 17.8 nm are synthesised and characterised using Transmission Electron Microscopy (TEM) and other analytic techniques. A mechanism for silver nanoparticle formation is also proposed. The antibacterial activity of the silver nanoparticles was investigated with gram-positive and gram-negative bacteria. The inhibition of both bacteria types was observed. This is a promising alternative method for the instant synthesis of silver nanoparticles, instead of the conventional chemical reduction route, for numerous applications.

In situ synthesis of copper nanoparticles encapsulated by nitrogen-doped graphene at room temperature via solution plasma.

Metal–carbon core–shell nanostructures have gained research interest due to their better performances in not only stability but also other properties, such as catalytic, optical, and electrical properties. However, they are limited by complicated synthesis approaches. Therefore, the development of a simple method for the synthesis of metal–carbon core–shell nanostructures is of great significance. In this work, a novel Cu–core encapsulated by a N-doped few-layer graphene shell was successfully synthesized in a one-pot in-liquid plasma discharge, so-called solution plasma (SP), to our knowledge for the first time. The synthesis was conducted at room temperature and atmospheric pressure by using a pair of copper electrodes submerged in a DMF solution as the precursor. The core–shell structure of the obtained products was confirmed by HR-TEM, while further insight information was explained from the results of XRD, Raman, and XPS measurements. The obtained Cu-core encapsulated by the N-doped few-layer graphene shell demonstrated relatively high stability in acid media, compared to the commercial bare Cu particles. Moreover, the stability was found to depend on the thickness of the N-doped few-layer graphene shell which can be tuned by adjusting the SP operating conditions.

Bottom-up synthesis of nitrogen-doped nanocarbons by a combination of metal catalysis and a solution plasma process.

We aimed to develop the bottom-up synthesis of nanocarbons with specific functions from molecules without any leaving group, halogen atom and boronic acid, by employing a metal catalyst under solution plasma irradiation. Pyridine was used as a source of carbon. In the presence of a Pd catalyst, the plasma treatment enabled the synthesis of N-doped carbons with a pyridinic configuration, which worked as an active catalytic site for the oxygen reduction reaction.

Retraction: Honeycomb-like Co-B amorphous alloy catalysts assembled by a solution plasma process show enhanced catalytic hydrolysis activity for hydrogen generation.

Retraction of ‘Honeycomb-like Co–B amorphous alloy catalysts assembled by a solution plasma process show enhanced catalytic hydrolysis activity for hydrogen generation’ by Dong Ge Tong et al., RSC Adv., 2012, 2, 2369–2376.

Hydrogen production from a solution plasma process of bio-oil

This study examined the possibility of hydrogen production using a solution plasma process (SPP). The reactants were lignin model compounds and actual lignin oil. The highest amount of hydrogen was generated in SPP using m-cresol. The total amount of gas generated by the plasma reaction for 20 min using 23 g of m-cresol was 1.69 L, which comprised of 65.51% hydrogen and 29.85% CO. Furthermore, a maximum of 1.91 L of hydrogen was generated by a reaction between pyrolysis oil and ethanol with a weight ratio of 1:1. The presence of carbon black, a reaction byproduct, was measured by Fourier transform infrared spectroscopy, which revealed molybdenum trioxide peaks. It was confirmed that molybdenum used as an electrode was doped on carbon.

Nitriding an Oxygen-Doped Nanocarbonaceous Sorbent Synthesized via Solution Plasma Process for Improving CO2 Adsorption Capacity.

The synthesis of carbon nanoparticles (Cn) and oxygen-doped nanocarbon (OCn) was successfully done through a one-step synthesis by the solution plasma process (SPP). The Cn and OCn were nitrogen-doped by nitridation under an ammonia atmosphere at 800 °C for 2 h to yield NCn and NOCn, respectively, for carbon dioxide (CO2) adsorption. The NOCn exhibited the highest specific surface area (~570 m2 g−1) and highest CO2 adsorption capacity (1.63 mmol g−1 at 25 °C) among the synthesized samples. The primary nitrogen species on the surface of NOCn were pyridinic-N and pyrrolic-N. The synergistic effect of microporosity and nitrogen functionality on the NOCn surface played an essential role in CO2 adsorption enhancement. From the thermodynamic viewpoint, the CO2 adsorption on NOCn was physisorption, exothermic, and spontaneous. The NOCn showed a more negative enthalpy of adsorption, indicating its stronger interaction for CO2 on the surface, and hence, the higher adsorption capacity. The CO2 adsorption on NOCn over the whole pressure range at 25–55 °C best fitted the Toth model, suggesting monolayer adsorption on the heterogeneous surface. In addition, NOCn expressed a higher selective CO2 adsorption than Cn and so was a good candidate for multicycle adsorption.

Possible application of gold thin films formed from surfactant free gold nano-particle dispersed in aqueous solutions to surface-enhanced Raman scattering spectroscopy

Detailed procedure to form gold (Au) thin films from surfactant free Au nano-particle dispersed aqueous solution prepared by solution plasma processing was investigated for surface-enhanced Raman scattering (SERS) spectroscopy measurement. The averaged diameter, thickness, and the weight of each Au thin film in our experimental conditions from 40 mL of 1% Au dispersed aqueous solution, were evaluated to be around 2.4 mm, 4.6 μm and 0.4 mg, respectively. SERS spectra of dye molecule (crystal violet: CV) adsorbed on Au thin film and silver (Ag) substrate were successfully measured upon excitation at 532 nm of solid type laser and 632.8 nm of He-Ne laser, respectively. These SERS spectra of CV adsorbed both on Au and Ag surfaces were coincided with each other, and the intensity from Au surface was unexpectedly much stronger as compared to those from Ag surface. The possible application of Au thin film for SERS platform on solid/liquid interfaces was demonstrated by observation of SERS spectra from p-nitrothiophenol (PNTP) adsorbed on Au thin film/aqueous solution interface.

In situ solution plasma synthesis of silver nanoparticles supported on nitrogen-doped carbons with enhanced oxygen reduction activity

Silver nanoparticles supported on nitrogen-doped carbons (Ag/NC) were in situ synthesized by a solution plasma process. In the solution plasma, Ag nanoparticles were produced via the sputtering of Ag electrode, while the NC supports were simultaneously synthesized from 2-cyanopyridine (C6H4N2). The results of the characterization show that Ag nanoparticles had good crystallinity and the NC supports possessed an amorphous structure. The oxygen reduction reaction (ORR) catalyzed on Ag/NC proceeded via the co-existence of two and four-electron pathways in alkaline solution, with the four-electron pathway being found to be more dominant. An enhanced ORR activity of Ag/NC was attributed to the synergistic effect of Ag nanoparticles and NC supports. Moreover, Ag/NC exhibited long-term durability and high resistance to methanol oxidation in comparison with the commercial Pt/C catalyst.

Synthesis of Biocompatible Cellulose-Coated Nanoceria with pH-Dependent Antioxidant Property.

Recent developments in nanomedicine have validated nanoceria as an antioxidant of therapeutic potential. However, its clinical application is far too limited in view of its poor stability in vivo and the use of hazardous solvents during its synthesis. There is a pertinent need for development of improved strategies for nanoceria to work better, especially by complexation with a matrix to improve upon its antioxidant property without toxicity. In the present study, cellulose has been used as a matrix of nanobiocomposite in which nanoceria are embedded, adopting solution plasma process (SPP). This resulted in cellulose-nanoceria(C/nanoceria) biocomposite by plasma reactions for 15 min using cellulose powder and Ce(NO3)2. Three-dimensional scaffold of the C/nanoceria biocomposite was prepared by lyophilization. The biocomposite was characterized adopting UV-vis spectroscopy, FTIR, FESEM equipped with EDS, and HRTEM analysis. The cubical nanoceria, in the size range 3.2-32 nm, were successfully internalized in the cellulose nanomatrix without agglomeration and exhibited excellent antioxidant property in pH-dependent manner. The nanobiocomposite is not cytotoxic to HeLa cell at a concentration as high as >1 mg.mL-1 as revealed in the cytotoxicity assay. Thus, we describe for the first time synthesis of C/nanoceria, in a manner that is green and sustainable, which has potential in external clinical applications as an effective antioxidative green material for scavenging reactive oxygen species.

Assessing the Efficiency of Sodium Ferrate Production by Solution Plasma Process

Application of sodium ferrate (Na2FeO4) is considered as the environmental friendly and cost-effective method for oxidation, coagulation and disinfection processes of water and wastewater treatment. Even though many methods of Na2FeO4 production have been proposed, they are still a challenge for the production of large Na2FeO4 quantity. This study aims to verify the optimum operating conditions of Na2FeO4 production by solution plasma process (SPP) of using both anode and cathode made of low-carbon steel placed in electrolyte solution with a distance of 3 cm. The results showed that the efficiency of Na2FeO4 production by SPP that does not obey Faraday’s law is higher than that by conventional electrochemical process. The optimum operating conditions of SPP were verified in 16 M NaOH solution at 30 °C and imposed by 35 V of the voltage while the maximum concentration and the average particle size of the Na2FeO4 production as high as 14.7 mM and 35 nm, respectively, were verified. The maximum current efficiency of 512% and the minimum energy consumption of 6 kWh/kg were verified for the formation of Na2FeO4 during 2 h due to an increased activity of OH− ions. A new approach of large Na2FeO4 production has been proposed to support the development of advanced technologies in water and wastewater treatment.

Enhanced degradation of methylene blue by a solution plasma process catalyzed by incidentally co-generated copper nanoparticles.

This study presents a catalytic organic pollution treatment using the solution plasma process (SPP) with incidentally co-generated copper (Cu) nanoparticles via Cu electrode erosion. Methylene blue (MB) was used as a model organic contaminant. The treatment time was from 0 to 60 minutes at the plasma frequencies of 15 and 30 kHz. The treatment efficacy using the Cu electrode was compared with that of the tungsten (W) electrode. The high erosion-resistant W electrode provided no W nanoparticles, while the low erosion-resistant Cu electrode yielded incidental nanoparticles (10-20 nm), hypothesized to catalyze the MB degradation during the SPP. The percentage of MB degradation and the hydrogen peroxide (H2O2) generation were determined by an ultraviolet-visible spectrophotometer. The results showed that, after the SPP by the Cu electrode for 60 minutes, the MB was degraded up to 96%. Using the Cu electrode at a high plasma frequency strongly accelerated the Cu nanoparticle generation and MB treatment, although the amount of H2O2 generated during the SPP using the Cu electrode was less than that of the W electrode. The Cu nanoparticles were hypothesized to enhance MB degradation via both homogeneous (release of dissolved Cu ions) and heterogeneous (on the surface of the particles) catalytic processes.