Search

TiO2 is known for its strong photocatalytic activity for the degradation of organic pollutants. However, the activity is limited to UV light irradiation. Metal-based nanoparticles have been introduced to enhance the absorbance and activity of TiO2 in the visible light region. The localized surface plasmon resonance (LSPR) effect of the metal improved the degradation efficiency in the visible light region. In this study, Ag was introduced into TiO2 nanoparticulate thin films using a simultaneous one-step plasma-enhanced chemical vapor deposition and physical vapor deposition (PECVD-PVD) method. Metal Ag nanoparticles were prepared using a simple gas-phase PVD method. Adding Ag to TiO2 increases the light absorption for longer wavelengths of light irradiation. The existence of Ag was confirmed by the LSPR absorbance peak originating from the Ag nanoparticles. Further analysis of the Ag nanoparticles was also conducted using X-ray photoelectron spectroscopy, which confirmed the stability of Ag metal upon annealing in N2 atmosphere. The functionality of the nanoparticulate thin films was tested for the degradation of rhodamine 6 G under visible light irradiation, revealing an optimum concentration of 0.24 wt% Ag content exhibited the best activity compared to our fabricated pristine TiO2 nanoparticulate thin film and even commercial TiO2 nanoparticles immobilized on a substrate. This paper presents the potential for producing films composed of nanoparticles through a one-step aerosolized process toward broadening the application scope of photocatalysts in the visible light region.

Complete spinal cord injury causes an irreversible disruption in the central nervous system, leading to motor, sensory, and autonomic function loss, and a secondary injury that constitutes a physical barrier preventing tissue repair. Tissue engineering scaffolds are presented as a permissive platform for cell migration and the reconnection of spared tissue. Iodine-doped plasma pyrrole polymer (pPPy-I), a neuroprotective material, was applied to polylactic acid (PLA) fibers and implanted in a rat complete spinal cord transection injury model to evaluate whether the resulting composite implants provided structural and functional recovery, using magnetic resonance (MR) imaging, diffusion tensor imaging and tractography, magnetic resonance spectroscopy, locomotion analysis, histology, and immunofluorescence. In vivo, MR studies evidenced a tissue response to the implant, demonstrating that the fibrillar composite scaffold moderated the structural effects of secondary damage by providing mechanical stability to the lesion core, tissue reconstruction, and significant motor recovery. Histologic analyses demonstrated that the composite scaffold provided a permissive environment for cell attachment and neural tissue guidance over the fibers, reducing cyst formation. These results supply evidence that pPPy-I enhanced the properties of PLA fibrillar scaffolds as a promising treatment for spinal cord injury recovery. [ABSTRACT FROM AUTHOR]

Biological treatments involve the application of metallic material coatings to enhance biocompatibility and properties. In invasive therapies, metallic electrodes are utilized, which are implanted in patients. One of these invasive therapeutic procedures is deep brain stimulation (DBS), an effective therapy for addressing the motor disorders observed in patients with Parkinson's disease (PD). This therapy involves the implantation of electrodes (IEs) into the subthalamic nucleus (STN). However, there is still a need for the optimization of these electrodes. Plasma-synthesized polypyrrole doped with iodine (PPPy/I) has been reported as a biocompatible and anti-inflammatory biomaterial that promotes nervous system regeneration. Given this information, the objective of the present study was to develop and characterize a PPPy/I-coated electrode for implantation into the STN. The characterization results indicate a uniform coating along the electrode, and physical–chemical characterization studies were conducted on the polymer. Subsequently, the IEs, both coated and uncoated with PPPy/I, were implanted into the STN of male rats of the Wistar strain to conduct an electrographic recording (EG-R) study. The results demonstrate that the IE coated with PPPy/I exhibited superior power and frequency signals over time compared to the uncoated IE (p < 0.05). Based on these findings, we conclude that an IE coated with PPPy/I has optimized functional performance, with enhanced integrity and superior signal quality compared to an uncoated IE. Therefore, we consider this a promising technological development that could significantly improve functional outcomes for patients undergoing invasive brain therapies. [ABSTRACT FROM AUTHOR]

Laser ablation in liquids (LAL) is an emerging laser technique for rapidly producing surfactant-free nanoparticles (NPs), which require minimal postprocessing and purification. Current work employing LAL has primarily focused on the generation of metal oxides and NPs composed of a single element. Here, we show that the ablation of hafnium (Hf) foil in different organic liquids allows for the controlled synthesis of HfO2 and HfC in selected ratios, resulting in a synthetic scheme for the rational design of materials relevant for high temperature and plasma applications. Additionally, the physical properties of the organic solvents can dictate the overall NP size distribution; specifically, solvents with low boiling points produce a large dispersity of NPs. This work indicates that the material-formation process is much more complicated than previous studies have indicated and paves the way for a pulsed-laser synthesis methodology that is tunable for desired properties. [ABSTRACT FROM AUTHOR]

Hybrid nanofluids (HNFs) of metallic oxide-based nanoparticles (NPs) have been prepared in different basefluids (BFs) employing the thermal plasma technique. NPs of ZnO–MgO were directly dispersed into pristine coolant, engine oil, distilled water (DW), and coconut oil. Plasma was generated between two identical electrodes applying 8.0 kV at the ambient conditions and proved economically viable in preparing stable HNFs. X-ray Diffractometry (XRD) showed ZnO and MgO NPs possessed hexagonal and cubic crystal structures, respectively. The band gap is calculated through UV-visible spectroscopy. The thermal conductivity (TC) of the HNFs has been measured using a thermal conductivity analyzer based on the transient hot wire method. The band gaps of pristine coolant and its HNFs were obtained to be 3.35 eV and 3.33 eV, respectively. In engine oil and its HNFs, band gaps of 3.16 eV and 3.02 eV have been extracted. There appears to be a slight reduction in band gap for coolant and engine oil-based HNFs. The band gap value of coconut oil-based HNFs was 4.05 eV, which showed a higher value than the pristine coconut oil-based HNFs (3.95 eV). The band gap calculated in the case of DW-based HNFs was 3.79 eV. TC of HNFs with volume concentration of 0.019 % for DW, 0.020 % for coolant, 0.016 % for engine oil, and 0.017 % for coconut oil were tested between 20 and 60 °C. An increase in TC was observed with the rise in temperature of the HNFs. Maximum increment in TC was observed at 60 °C for coolant-based HNFs, which was 19 %, followed by DW (18%), coconut oil (18%), and engine oil (16%), respectively. DW-based HNFs can be used as a coolant and optical filter for optoelectronics devices like photovoltaic cells for better performance. The study underscores precise control of NPs size as pivotal for band gap influence. HNFs hold promise as the next-gen heat transfer fluids (HTFs), revolutionizing thermal conductivity across industries. This research lays a firm foundation for plasma-synthesized HNFs' application in enhanced heat transfer and optoelectronic devices. Coolant-based HNFs excel in thermal conductivity, addressing heat transfer challenges.

In this work, synthesis of WO 3 nanoparticles is reported using a novel, yet simplified microwave-metal discharge approach. The discharge was triggered from the pointed tip of a tungsten electrode, which eventually got vaporized and deposited on the collector substrates surrounding the metallic electrode. The buildup of high electric field at the tip of the tungsten electrode ionized the surrounding air molecules that lead to the discharge formation. X-Ray diffraction revealed monoclinic phase of the synthesized WO 3 nanoparticles. The morphological analysis executed using transmission electron microscopy showed the presence of single crystalline nanoparticles in spherical, rhombic, and rectangular shapes. X-ray photoelectron spectroscopy confirmed the elemental composition and showed formation of stoichiometric WO 3. Thermal stability analysis showed high stability of the nanoparticles below 1200 °C. The nitrogen absorption-desorption studies suggested that the nanoparticles exhibited a mesoporous structure. The antimicrobial susceptibility tests indicated an increased resistance towards Gram-negative bacteria (E. coli) compared to Gram-positive bacteria (S. aureus). [Display omitted] [ABSTRACT FROM AUTHOR]

The steadily high interest in metal oxides, including in the form of fine powders, has led to a rapid increase in their production, the search for new synthetic methods and the expansion of possible applications. CO 2 has proven itself as a cheap and abundant source of mild oxidant, which can potentially be used for oxidation reactions. However, the key problem of CO 2 application is the necessity to break the bonds of the CO 2 molecule that requires a large amount of energy. This work presents a fundamentally new approach for metal oxide synthesis, when applying CO 2 as a gaseous precursor and oxidant, based on application of a pulsed arc discharge plasma of the electroerosion type. The implementation of the proposed method called plasma dynamic synthesis results in obtaining dispersed metal oxides that is demonstrated by the examples of Cu–O, Fe–O, Ti–O and Al–O systems. The influence of the metal-containing plasma type and operation modes on the formation of metal-oxide dispersed materials is studied. The multi-pulse operation mode in the considered system with titanium and aluminum electrodes provides obtaining almost completely oxidized products that is found to depend on the electronegativity of the initial metals. When applying aluminum electrodes, the process not only provides a high productivity of obtaining dispersed materials (up to 15 g per cycle), but also allows the CO 2 conversion rate of up to 14.5%. Moreover, the electroerosion plasma demonstrates the energy efficiency of CO 2 decomposition exceeding other plasma-based methods due to ongoing exothermic reactions of metal oxide formation. The as-synthesized products can be used to obtain bulk ceramic materials that is shown by the example of aluminum oxide powders. The hardness of the obtained ceramic specimens produced by SPS method is found to be ∼22 GPa and correlates with the best samples for aluminum oxides. • Plasma sputtering in CO 2 medium results in forming dispersed metal oxides. • CO 2 conversion rate in multi-pulse operation mode of system with Al electrodes is 14.5%. • Electronegativity of electrode metal affects the oxide formation process and CO 2 conversion rate. • Electroerosive plasma application provides higher energy efficiency of CO 2 conversion. • Obtained Al–O-based dispersed materials can serve as a charge for hard ceramics (22 GPa). [ABSTRACT FROM AUTHOR]

We have studied the structure of tungsten borides prepared from a tungsten-containing mineral concentrate using an experimental microwave arc plasma system. A configuration of such a system has been proposed which includes a microwave generator, indirect plasma source, and reaction chamber. We address some issues pertaining to the positioning of the plasma source on the waveguide chamber and the formation of a microwave plasma flow in the confusor zone, followed by the exit of the flow to the concentrator zone, and describe processes involved in the plasma synthesis of tungsten borides. A process is proposed for the preparation of a mixture based on a multicomponent mineral (scheelite) concentrate from the Russian Far East and results are presented on the physicochemical properties of tungsten borides prepared via local exposure to a high-energy plasma flow with a power density from 10 to 100 kW/cm2. In our experiments, the WB, WB2, W2В, and W2В5 compounds have been obtained. We assess the potential of using plasma technologies for preparing boron- and tungsten-based refractory compounds from scheelite concentrate. [ABSTRACT FROM AUTHOR]

In microwave-plasma synthesis of few-layer graphene from hydrocarbon precursors, the carbon-to-oxygen and the carbon-to-hydrogen ratios are known to influence the product ratio of graphene to amorphous soot-like particles. While the role of oxygenated hydrocarbons and water as oxygen-supplying species has been studied before, in this paper, we compare the effect of carbon dioxide, molecular oxygen, and nitrous oxide mixed with ethylene to systematically change the C/O ratio while keeping the hydrogen supply constant. Ex situ powder analysis, emission spectroscopy, gas chromatography, and simple reaction kinetics simulations are employed to evaluate and describe the synthesis process. Additionally, thermophoretically sampled nanomaterials are collected close after the first particle inception and analyzed ex situ. The results show that molecular oxygen and nitrous oxide increase the graphene fraction with decreasing C/O ratios and pure graphene is reached at 2:1.5. The decrease in C/O ratio results in an overall decrease in solid carbon yield. With carbon dioxide, pure graphene cannot be generated at a C/O ration of 2:1.5, although a similar reduction of the particle yield is observed. Thermophoretic sampling showed that the specific mixture of carbon allotropes is already defined a few cm downstream to the plasma zone. Emission spectroscopy shows that carbon dioxide forms carbon species during its decomposition in the plasma, we hypothesize that these released carbon species might influence the environment for local nucleation of solid carbon. Thus, the C/O ratio and available carbon fraction for growth cannot always be used to tailor the carbon microstructure. Moreover, the source of oxygen atoms also seems to have an effect on the resultant microstructure.

Nanogold is an emerging material for enhancing surface-enhanced Raman scattering (SERS), which enables the detection of hazardous analytes at trace levels. This study presents a simple, single-step plasma synthesis method to control the size and yield of Au nanoparticles by using plasma-liquid redox chemistry. The pin-based argon plasma reduces the Au 3+ precursor in under 5 min, synthesizing Au spherical particles ranging from ∼20 nm at 0.025 mM to ∼90 nm at 1.0 mM, in addition to plate-like particles occurring at concentrations of 0.25-1.0 mM. The enhanced SERS responses correlated with the UV-vis absorption and reflectance profiles, which can be attributed to synergistic plasmonic hotspots created by the sphere-sphere, plate-sphere, and plate-plate nanogold interactions. This nanogold mixture, combined with gold-plated CPU grid pin arrays, facilitated the detection of trace explosives, including aromatic (TNT, TNB, and TNP) and aliphatic (RDX, PETN, and HMX) compounds. We demonstrate that stabler aliphatic analytes, associated with lower vapor pressure (10 -8 -10 -11 atm), exhibit smaller signal fluctuations (RSD ∼ 6-10%) compared to their more volatile (10 -5 atm) aromatic (RSD ∼ 12-17%) counterparts at similar analyte concentrations. The calculated limit of detection (LoD) was found to be ∼2-6 nM and ∼600-900 pM for aromatic and aliphatic explosives, respectively. Finally, we show that the poorer performance of aromatic explosives under the same sensing conditions affects SERS-PCA separation, which can then be improved either by a machine learning approach (PCA with k-NN classification) or by consideration of a specific NO 2 symmetric stretching fingerprint range.

The paper deals with the thermal plasma synthesis of anorthite (CaO·Al2O3·2SiO2). It is shown that the optimum synthesis parameters include 100 A current, 110 V voltage, 14 nL/min gas rate, and 25–30 s exposure time. According to the X-ray diffraction analysis, the initial mixture melting provides the silicate melt formation followed by its cooling and the anorthite phase formation. For the synthesis of the anorthite phase enriched with the calcium-containing CaO·Al2O3·2SiO2·nCaO compound, it is necessary to increase the calcium oxide content up to 38%. For synthesis of the anorthite phase enriched with silicon-containing CaO·Al2O3·2SiO2·nSiO2 compound, the silicon oxide content must be increased up to 67%. Idiomorphism of anorthite acicular crystals is observed. The practical implication of synthesized anorthite is the ceramics production. [ABSTRACT FROM AUTHOR]

The effect of metallic (Fe, Cu, Co, Ni, Ti) and non-metallic additives (Si, B) on the formation of fullerenes from graphite powders was studied in radiofrequency (RF) thermal plasma. The main component of the synthesized fullerene mixtures was C60, but higher fullerenes (C70, C82, and C84) could be detected as well. Fe and Cu additives increased the fullerene content in the soot. In contrast, the fullerene formation decreased in the presence of Ti, Si, and B as compared to the synthesis without additives. However, Ti and B addition enhanced the formation of higher fullerenes. We provide experimental evidence that decreasing the reactor pressure results in a lower yield of fullerene production, in accordance with thermodynamic calculations and numerical simulations published earlier. In the presence of titanium, a significant quantity of TiC was also formed as a by-product. The fullerene mixture synthesized with boron additives showed higher stability during storage in ambient conditions as compared to other samples. [ABSTRACT FROM AUTHOR]

Citrate-capped silver nanoparticles (Ag@Cit NPs) were synthesized by a simple plasma-assisted reduction method. Homogenous colloidal Ag@Cit NPs solutions were produced by treating a A g N O 3 -trisodium citrate-deionized water with an atmospheric-pressure argon plasma jet. The plasma-synthesized Ag@Cit NPs exhibited quasi-spherical shape with an average particle diameter of about 5.9−7.5 nm, and their absorption spectra showed surface plasmon resonance peaks at approximately 406 nm. The amount of Ag@Cit NPs increased in a plasma exposure duration-dependent manner. Plasma synthesis of Ag@Cit NPs was more effective in the 8.5 cm plume jet than in the shorter and longer plume jets. A larger amount of Ag@Cit NPs were produced from the 8.5 cm plume jet with a higher pH and a larger number of aqua electrons, indicating that the synergetic effect between plasma electrons and citrate plays an important role in the plasma synthesis of Ag@Cit NPs. Plasma-assisted citrate reduction facilitates the synthesis of Ag@Cit NPs, and citrate-capped nanoparticles are stabilized in an aqueous solution due to their repulsive force. Next, we demonstrated that plasma-synthesized Ag@Cit NPs exhibited a significant degradation of methylene blue dye. [ABSTRACT FROM AUTHOR]

Titanium dioxide is currently one of the most known promising photocatalysts. However, its use in the visible light range is limited due to its high energy gap. In this work, to solve the mentioned problem, it is proposed to obtain highly defect structures of titanium dioxide by means of a high-energy plasma dynamic synthesis method. It possible to synthesize TiO 2 Titanium dioxide powders with a tunable ratio of rutile and anatase modifications, as well as a particle size distribution were synthesized, by optimizing the synthesis conditions, including the process energy and parameters of the gaseous medium. The formation of shock-wave structures in the pulsed synthesis process results in obtaining fine particles of rutile and anatase with a highly defective crystal structure. The final product was revealed to have an extended working absorption spectrum region and a reduced band gap (2.74 eV). A possibility of photocatalytic applications for the synthesized TiO 2 powder was demonstrated in measurements of photocurrent density with time (j - t) under intermittent visible light irradiation. • TiO 2 with rutile and anatase structures can be synthesized in arc discharge plasma. • The phase composition can be tuned by changing the process energy and oxygen concentration. • The formed shock-wave plasma jet makes it possible to obtain defective TiO 2 structures. • The synthesized defect fine titanium dioxide has a smaller band gap of 2.74 eV. [ABSTRACT FROM AUTHOR]

Recently, cold atmospheric-pressure plasma has been studied extensively as an efficient and green method to synthesize gold nanoparticles (AuNPs). Although the characteristics of the AuNPs, especially their homogeneousness, depend very much on the plasma synthesis parameters, there is a lack of a study involving these parameters systematically. Moreover, most of AuNPs-cold-plasma synthesis reports so far either required organic capping agents or resulted in highly non-uniform AuNPs. In this work, we systematically study the effect of most important synthesis parametersâ€" including distance from the plasma jet to the solution, gas flow rate, plasma frequency, volume and concentration of the precursor, plasma interaction time as well as the effect of the synthesis environment (humidity and temperature)â€"on the uniformity of the AuNPs. Through various characterization measurements, we show that homogeneous and highly stable intrinsic AuNPs with an average size of 45 nm can be obtained with optimized synthesis parameters and in the absence of a stabilizer. The synthesized AuNPs yield advanced optical sensing properties in comparison with commercial AuNPs and can be further applied in developing versatile and high-sensitivity biosensors. [ABSTRACT FROM AUTHOR]

Purpose: Application of plasma glow discharge to copper oxide nanostructure growth is studied. The simplicity of the proposed technique may be beneficial for the development of new plasma reactors for large-scale production of diverse metal oxide nanostructures. Design/methodology/approach: Copper sample was placed on anode of a setup designed to ignite plasma glow discharge. The proposed approach allows eliminating the negative effects of ion bombardment, like sputtering and generation of defects on a surface of the growing nanostructures, but preserves the advantages of thermal growth. The growth process was explained in terms of thermal processes interaction occurring on a surface of the anode with the glow discharge plasma. Findings: Plasma treatment resulted in generation of reach and diverse nanostructures that was confirmed by SEM images. Nanowire-like, flower-like, anemone-like nanostructures and nanodisks composed into the nanoassemblies are observed; the nanostructures are associated with microbabbles on CuO layer. These findings allow concluding about the possible implementation of the proposed method in industry. Research limitations/implications: The main limitation is conditioned by the lack of heat supplied to the anode, and absence of independent control of the heat and ion fluxes; thus, the additional heater should be installed under the anode in order to expand the nomenclature of the nanospecies in the future studies. Practical implications: High-productivity plasma process in copper oxide nanostructures synthesis was confirmed in this research. It may be applied for field emitter and supercapacitor manufacturing. Originality/value: Oxide nanostructure synthesis is conducted by use of a simple and wellknown glow discharge technique in order to expand the production yield and diversity of nanostructure obtained in the processes of thermal growth. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) is a key process in electrochemical water splitting. To lower the cost and environmental impact of this process, it is highly motivated to develop electrocatalysts with low or no content of noble metals. Here, we report on an ingenious synthesis of hybrid PtxNi1–x electrocatalysts in the form of a nanoparticle–nanonetwork structure with very low noble metal content. The structure possesses important features such as good electrical conductivity, high surface area, strong interlinking, and substrate adhesion, which render an excellent HER activity. Specifically, the best performing Pt0.05Ni0.95 sample demonstrates a Tafel slope of 30 mV dec–1 in 0.5 M H2SO4 and an overpotential of 20 mV at a current density of 10 mA cm–2 with high stability. The impressive catalytic performance is further rationalized in a theoretical study, which provides insight into the mechanism on how such small platinum content can allow for close-to-optimal adsorption energies for hydrogen. [ABSTRACT FROM AUTHOR]

Fourier‐transform infrared spectroscopy and proton‐transfer‐reaction–mass spectrometry are used in a complementary way to study gas‐phase processes during decomposition of ethanol in a microwave plasma torch. Decomposition products (C, C2 and simple hydrocarbons) reassemble into higher hydrocarbons and graphene nuclei and further grow into graphene nanosheets (GNS). Depending on microwave power, ethanol flow rate and molecular gas admixture, the material structure changes from amorphous to crystalline. The presence of C2n + 1Hy species was found to be responsible for the formation of defects in the GNS structure. O2 and H2 admixtures change the gas temperature axial profile and consequently modify reaction pathways influencing growth and production rate of GNS. Determination of reaction pathway selectivity enables us to predict whether high‐quality or defective GNS are produced. [ABSTRACT FROM AUTHOR]

The effect of metallic (Fe, Cu, Co, Ni, Ti) and non-metallic additives (Si, B) on the formation of fullerenes from graphite powders was studied in radiofrequency (RF) thermal plasma. The main component of the synthesized fullerene mixtures was C60, but higher fullerenes (C70, C82, and C84) could be detected as well. Fe and Cu additives increased the fullerene content in the soot. In contrast, the fullerene formation decreased in the presence of Ti, Si, and B as compared to the synthesis without additives. However, Ti and B addition enhanced the formation of higher fullerenes. We provide experimental evidence that decreasing the reactor pressure results in a lower yield of fullerene production, in accordance with thermodynamic calculations and numerical simulations published earlier. In the presence of titanium, a significant quantity of TiC was also formed as a by-product. The fullerene mixture synthesized with boron additives showed higher stability during storage in ambient conditions as compared to other samples.

Silicon nanoparticles produced via a plasma-based technique have been sintered into bulk nanostructured samples. These samples have micron-sized crystalline domains and contain well-dispersed oxide nanoinclusions. We have compared the thermoelectric performance of such structure to that of a control sample produced by sintering ball-milled silicon powders. The control sample has lower precipitate density and is composed of nanograins. Despite the stark difference in nanostructure, both samples have comparable thermal conductivity, and the sample with nanoinclusions has higher power factor and ZT. This result confirms that grain size engineering is not the only promising route to achieving improved thermoelectric performance.

The promising fields of gallium oxide application are the production of hybrid cars, electrical equipment of high-power, ultraviolet radiation sensors and uninterruptible power supplies. However, the main factor hindering its massive commercial use is the lack of synthesis technologies, that should be cheap, reproducible, and scalable. In this work we develop a novel plasma-chemical method of Ga2O3 synthesis. The high-purity elemental gallium was used as the precursor, which was delivered by argon flow to the reaction zone, where the interaction with iodide pentoxide took place. RF (40.68 MHz) non-equilibrium plasma discharge at low pressure (0.1 Torr) was employed for the initiation of interactions between precursors. Optical Emission Spectroscopy in tandem with quantum-chemical calculations allowed us to find out the reactive species formed in the plasma discharge. The properties of the solid phase obtained were studied as well. [ABSTRACT FROM AUTHOR]

This study investigates the feasibility of plasma‐supported in‐line functionalization of silicon nanoparticles (NPs) in an atmospheric pressure gas‐phase reactor. The approach utilizes the synthesis of core silicon NPs and their subsequent coating downstream of the particle formation zone. In‐line coating is accomplished with a cylindrical coating nozzle to achieve homogenous mixing of coating precursor vapors with in‐coming NPs. Multiple siloxanes were tested for their coating suitability and their ability towards coating homogeneity. It was found that tetraethyl orthosilicate is favored for thin layers consisting of almost pure silica while hexamethyldisiloxane and octamethylcyclotetrasiloxane (OMCTS) coatings contained reasonable amounts of hydrocarbons. Moreover, OMCTS showed a pronounced tendency towards homogeneous nucleation, thus leading to the additional formation of silica NPs due to homogeneous nucleation. [ABSTRACT FROM AUTHOR]

In atmospheric pressure (AP) plasma polymerization, increasing the effective volume of the plasma medium by expanding the plasma-generating region within the plasma reactor is considered a simple method to create regular and uniform polymer films. Here, we propose a newly designed AP plasma reactor with a cruciform wire electrode that can expand the discharge volume. Based on the plasma vessel configuration, which consists of a wide tube and a substrate stand, two tungsten wires crossed at 90 degrees are used as a common powered electrode in consideration of two-dimensional spatial expansion. In the wire electrode, which is partially covered by a glass capillary, discharge occurs at the boundary where the capillary terminates, so that the discharge region is divided into fourths along the cruciform electrode and the discharge volume can successfully expand. It is confirmed that although a discharge imbalance in the four regions of the AP plasma reactor can adversely affect the uniformity of the polymerized, nanostructured polymer film, rotating the substrate using a turntable can significantly improve the film uniformity. With this AP plasma reactor, nanostructured polythiophene (PTh) films are synthesized and the morphology and chemical properties of the PTh nanostructure, as well as the PTh-film uniformity and electrical properties, are investigated in detail.

Polyethylene glycol-functionalized gold nanoparticles (Au@PEG NPs) were prepared by a simple plasma-assisted method without additional reducing chemicals. After irradiating tetrachloroauric acid (HAuCl4) and polyethylene glycol (PEG) in aqueous medium with an argon plasma jet, the gold precursor transformed into an Au@PEG NP colloid that exhibited surface plasma resonance at 530 nm. When the plasma jet entered the water, additional reactive species were induced through interactions between plasma-generated reactive species and aqueous media. Interaction of the gold precursor with the plasma-activated medium allowed the synthesis of gold nanoparticles (AuNPs) without reductants. The plasma-synthesized Au@PEG NPs had a quasi-spherical shape with an average particle diameter of 32.5 nm. The addition of PEG not only helped to stabilize the AuNPs but also increased the number of AuNPs. Au@PEG NP-loaded paper (AuNP-paper) was able to detect the degradation of rhodamine B, therefore, indicating that AuNP-paper can act as a surface-enhanced Raman scattering platform. Dye degradation by plasma treatment was investigated by optical absorption and Raman spectroscopy. The method proposed for the fabrication of Au@PEG NPs is rapid, low-cost, and environment-friendly and will facilitate the application of plasma-synthesized nanomaterials in sensors.

Selective N moieties in N-doped carbon catalysts were successfully controlled by a room temperature plasma process, where its ORR catalytic activity was found to be related to Lewis Basicity of catalysts. • Tailored 4 types of nitrogen bonding states in N-doped carbon by plasma synthesis. • Correlated the Lewis basicity of N-doped carbon catatlysts to their ORR activities. • Amino-N showed the superior Lewis basicity and ORR activity. The ORR electrocatalytic activity of nitrogen-doped carbon (N-doped carbon) is highly related to the type of nitrogen bondings, which is originated to the charge transfer between carbon and nitrogen. Based on Lewis theory of acid-base reactions, N-doped carbon can be defined as a Lewis base catalyst. The lone pair of electrons on the nitrogen atom mainly contributed to its reactivity, or in other terms, Lewis basicity. Herein, we fabricated selective amino-N, pyrrolic-N, nitrile-N, and oxide-N in N-doped carbon systematically, as well as compared their electrocatalytic activities and Lewis basicities for the first time. Based on the molecular structure of four starting precursors, aniline (C 6 H 5 NH 2), pyrrole (C 4 H 5 N), benzonitrile (C 5 H 7 N), and nitrobenzene (C 6 H 5 NO 2) were successfully formed as selective amino-N, pyrrolic-N, nitrile-N and oxide-N, respectively, via a room temperature plasma synthesis process. From the electrochemical performance, N-doped carbon catalyst with highly selective amino-N demonstrated comparatively higher ORR activity in terms of ORR onset potential and current density. Also, we confirmed the correlation between the ORR activity and Lewis basicity of various N moieties. Based on the electronic structural properties, amino-N with the most superior ORR activity also exhibited the highest basic strength among the studied C N bonding structure. This study provided the relationship among the structural properties, Lewis basicity, and electrocatalytic activity of selective N-doped carbon. [ABSTRACT FROM AUTHOR]

Abstract Thermally conductive composites aimed for dielectric application were achieved by embedding spherical MgSiO 3 -SiO 2 -hBN powders into cyanate ester resin as functional fillers. The MgSiO 3 -SiO 2 -hBN particles were prepared by plasma sythesized process employing talc and hexagonal boron nitride (hBN) as sources. The morphology, phase structure of the MgSiO 3 -SiO 2 -hBN powders were characterized by changing the content of BN. Meanwhile, the thermal and dielectric properties of the composites with different filler loading were investigated. Results show that phase transformation from talc to protoenstatite and critobalite occurred. The thermal conductivity shows a drastic enhancement with the increase of the filler loading. Further contrast analyzed by Bruggeman model shows that the tested values agree well with estimated ones when fillers fraction are less than 15 vol%. However, an obvious deviation for the values of thermal conductivities is thought to arise from the randomly oriented hBN and the formation of the thermal conductive networks in composites. Relatively low dielectric constants and dielectric losses (tanδ) are obtained for all the composites. [ABSTRACT FROM AUTHOR]

A one-step method for plasma synthesis of nitrogen-doped carbon nanomesh is presented. The method involves a molten polymer, which is a source of carbon, and inductively coupled nitrogen plasma, which is a source of highly reactive nitrogen species. The method enables the deposition of the nanocarbon layer at a rate of almost 0.1 µm/s. The deposited nanocarbon is in the form of randomly oriented multilayer graphene nanosheets or nanoflakes with a thickness of several nm and an area of the order of 1000 nm2. The concentration of chemically bonded nitrogen on the surface of the film increases with deposition time and saturates at approximately 15 at.%. Initially, the oxygen concentration is up to approximately 10 at.% but decreases with treatment time and finally saturates at approximately 2 at.%. Nitrogen is bonded in various configurations, including graphitic, pyridinic, and pyrrolic nitrogen.

Substrate and catalyst free gas-phase plasma synthesis of freestanding few-layer graphene (FLG) flakes leads to crumpled FLG structures. In this paper, we elucidate a folding-based mechanism and structure-formation process in accordance with literature on the stability of graphene sheets. Transmission electron microscopy is applied to thermophoretically-sampled FLG at various distances from the plasma zone. Single-layer and few-layer graphene were observed, and a morphology pattern evolution could be discerned. A conceptual model of graphene formation and growth is derived, starting from initial rounded single-layer graphene of a few hundred nanometer in diameter to, eventually, self-folded and strongly crumpled FLG. [Display omitted] • Plasma synthesis and TEM images to study growth of free-standing few-layer graphene. • Experimentally demonstrated how outer shape of graphene flakes form and evolve. • First single-layer free-standing graphene sheets have a rounded shape. • Single-layer graphene sheets crumple/self-fold to form larger crumpled structures. • It seems to exist a maximum diameter for a single unfolded graphene layer (≤370 nm). [ABSTRACT FROM AUTHOR]

The diversity of carbon materials has allowed them to be used for fundamental and applied research to date. The newest modifications of carbon, such as nanodiamonds, graphene, fullerenes, and nanotubes, are of particular interest owing to their outstanding physical and chemical properties, as well as to prospects of their practical application in various fields of industry, from medicine to nanoelectronics. At the same time, one-dimensional forms of carbon, predicted in the 1960s, were underestimated because of imperfection of experimental tools [1-3]. [ABSTRACT FROM AUTHOR]

ABSTRACT: A carbon‐supported cobalt nano‐catalyst (Co/C) synthesized through plasma was tested for Fischer‐Tropsch activity. Catalyst deactivation and activation protocols studied included in situ sample pre‐treatment at 673 K in gas flowing at the rate of 250 cm3 · min−1 in: (a) H2 only, (b) CO only, and (c) CO followed by H2, with each cycle lasting 24 h. The so‐treated catalyst samples were then tested for FTS activity for over 50 h of time‐on‐stream (TOS), at 2.2 MPa pressure and 493 or 518 K temperature in a 3‐phase continuously‐stirred tank slurry reactor (3‐φ‐CSTSR) using squalane (C30H62) as the carrier liquid phase. The feed gas composition of molar H2:CO = 1.7 comprising 50 % H2, 30 % CO, and 10 % CO2 balanced in Ar for mass balance determination, flowing at a gas hourly space velocity (GHSV) of 3360 cm3 · h−1 · g−1 of catalyst. Fresh catalysts and those reduced by CO‐only were completely inactive at 493 K and initial inactivity was attributed to the excessive C matrix formed around the metal nanoparticles during catalyst synthesis. The sample that was reduced by H2 only was the most active, although it showed the fastest declining activity due to cumulative high H2O vapour pressure in the FTS reactor, while the sample pre‐treated in both CO and H2 demonstrated a higher degree of stability with TOS. [ABSTRACT FROM AUTHOR]

Nucleation is a core scientific concept that describes the formation of new phases and materials. While classical nucleation theory is applied across wide-ranging fields, nucleation energy landscapes have never been directly measured at the atomic level, and experiments suggest that nucleation rates often greatly exceed the predictions of classical nucleation theory. Multistep nucleation via metastable states could explain unexpectedly rapid nucleation in many contexts, yet experimental energy landscapes supporting such mechanisms are scarce, particularly at nanoscale dimensions. In this work, we measured the nucleation energy landscape of diamond during chemical vapor deposition, using a series of diamondoid molecules as atomically defined protonuclei. We find that 26-carbon atom clusters, which do not contain a single bulk atom, are postcritical nuclei and measure the nucleation barrier to be more than four orders of magnitude smaller than prior bulk estimations. These data support both classical and nonclassical concepts for multistep nucleation and growth during the gas-phase synthesis of diamond and other semiconductors. More broadly, these measurements provide experimental evidence that agrees with recent conceptual proposals of multistep nucleation pathways with metastable molecular precursors in diverse processes, ranging from cloud formation to protein crystallization, and nanoparticle synthesis. [ABSTRACT FROM AUTHOR]

Silicon nanoparticles produced via a plasma-based technique have been sintered into bulk nanostructured samples. These samples have micron-sized crystalline domains and contain well-dispersed oxide nanoinclusions. We have compared the thermoelectric performance of such structure to that of a control sample produced by sintering ball-milled silicon powders. The control sample has lower precipitate density and is composed of nanograins. Despite the stark difference in nanostructure, both samples have comparable thermal conductivity, and the sample with nanoinclusions has higher power factor and ZT. This result confirms that grain size engineering is not the only promising route to achieving improved thermoelectric performance. [ABSTRACT FROM AUTHOR]

Abstract: Although nitrogen‐doped carbon catalysts are promising candidates for oxygen reduction reactions (ORRs), the role of the nitrogen bonding structure, such as pyridinic‐N, amino‐N, and graphitic‐N, on the ORR activity remains controversial. Furthermore, despite recent progress in tuning the C−N chemical bonding states within the carbon materials by using chemical vapor deposition and post heat treatment, a systematic evaluation of various N moieties remains challenging, owing to the differences in the thermal stabilities of different types of bonds. Herein, we successfully designed a method to tailor pyridinic‐N, amino‐N, and graphitic‐N bonding in N‐doped carbon nanoparticles fabricated through a plasma process combined with post heat treatment. Investigations on the electrochemical performance of the fabricated materials suggested that catalysts with dominant amino‐N exhibited higher current density, where graphitic‐N has a positive effect on the ORR onset potential. This synthetic strategy provides a simple and efficient approach for studying the relationship between the C−N bonding structure and the electrochemical performance of N‐doped carbon catalysts. [ABSTRACT FROM AUTHOR]

Nickel (Ni) nanoparticles have been synthesized from the dissociation of nickelocene (Ni(Cp)2) in an argon‐hydrogen (Ar‐H2) low pressure continuous‐flow non‐thermal plasma. The influence of process parameters on the synthesized Ni nanomaterial structure, size, size‐dispersion, and carbon content has been characterized by EDS and TEM analysis. The role of hydrogen dilution and plasma input power on material throughput is carefully discussed. These data, in combination with the prediction of the electron affinity and ionization potential of Ni(Cp)2 by DFT calculations, supports the hypothesis that the material loss‐mechanism to the reactor walls is due to the inherent ambipolar diffusion present in this synthesis technique. This study suggests that precursors should be screened with care when attempting to produce nanoparticle via a low pressure, continuous flow plasma reactor. [ABSTRACT FROM AUTHOR]

This article reports the synthesis of tungsten nanoparticles predominantly in α-W phase by a single step plasma expansion technique. The oxidation of the metal and contribution from the β-W phase in the nanomaterial samples was observed to decrease with the increase of both the pressure in the sample collection chamber and the plasma power. We had observed production of faceted, lightly sintered particles with up to 300 nm individual sizes during high plasma current/high pressure synthesis conditions, which were measured to have the highest specific surface area of 35 m 2 /g. Condensation of this high temperature material at low saturation ratio and the high collisional regime had led to the synthesis of relatively bigger particle sizes in this experiment. Cauliflower like particle morphologies was observed during low pressure synthesis conditions, which is considered to have formed through spherulitic growth processes. Transmission Electron Microscopy (TEM) micrographs show very small crystallites remaining dispersed in an amorphous moss like the background, which was confirmed to be a mixture of tungsten and its oxides. [ABSTRACT FROM AUTHOR]

The evolution of magnetic phases in multi-phase iron oxide nanoparticles, synthesized via the transferred arc plasma induced gas phase condensation method, was investigated by X-ray diffraction, vibrating sample magnetometry and 57 Fe Mössbauer spectroscopy. The particles are proposed to be consisting of three different iron oxide phases: α-Fe 2 O 3 , γ-Fe 2 O 3 and Fe 3 O 4 . These nanoparticles were exposed to high temperature (∼935 K) under vacuum (10 −3 mbar He pressure), and the thermally induced phase transformations were investigated. The Rietveld refinement of the X-ray diffraction data corroborates the least-squares fitting of the transmission Mössbauer spectra in confirming the presence of Fe 3 O 4 , γ-Fe 2 O 3 and α-Fe 2 O 3 phases before the thermal treatment, while only Fe 3 O 4 and α-Fe 2 O 3 phases exist after thermal treatment. On thermal annealing in vacuum, conversion from γ-Fe 2 O 3 to Fe 3 O 4 and α-Fe 2 O 3 was observed. Interestingly, we have observed a phase transformation occurring in the temperature range ∼498 K–538 K, which is strikingly lower than the phase transformation temperature of γ-Fe 2 O 3 to α-Fe 2 O 3 (573–623 K) in air. Combining the results of Rietveld refinement of X-ray diffraction patterns and Mössbauer spectroscopy, we have attributed this phase transformation to the phase conversion of a metastable “defected and strained” d- Fe 3 O 4 phase, present in the as-prepared sample, to the α-Fe 2 O 3 phase. Stabilization of the phases by controlling the phase transformations during the use of different iron-oxide nanoparticles is the key factor to select them for a particular application. Our investigation provides insight into the effect of temperature and chemical nature of the environment, which are the primary factors governing the phase stability, suitability and longevity of the iron oxide nanomaterials prepared by the gas-phase condensation method for various applications. [ABSTRACT FROM AUTHOR]

We have used high heat flux plasma synthesis process to grow Co those for the morphology, stoichiometry and the local structure as a function of plasma current. We find that the nanoparticles produced by the thermal plasma method have different shapes and size distribution with the plasma current being a key parameter in controlling the formation of composition, morphology and crystalline structure. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements at Co K-edge have revealed formation of metal and metal oxide nanoparticles with the composition mainly depending on the arc current. While low plasma current appears to produce nanoparticles solely of CoO with a small amount of Co metal, the high plasma current tends to produce nanoparticles of CoO and Co 3 O 4 oxides with increased amount of Co metal. The results are consistent with the morphological and structural analysis, showing nanoparticles of different shapes and size depending on the arc current. [ABSTRACT FROM AUTHOR]

From this study, we present results of a nanometric, gold-promoted Fischer-Tropsch synthesis (FTS) catalyst, with carbon support. A ternary 5%Ni-70%Co-25%Fe/C formulation was synthesized using induction suspension plasma spray (SPS) technology; the so-produced formulation was doped with 5%Au through the impregnation method. The catalysts (Au-Ni-Co-Fe/C and Ni-Co-Fe/C) were tested for 24 h in a continuously stirred tank reactor (CSTR) operated at 260 °C, 2-MPa pressure and H/CO molar ratio of 2 using feed gas composition set at 0.6 L/L (60 vol%) H and 0.3 L/L (30 vol%) CO balanced in Ar flowing at gas hourly specific velocity (GHSV) of 3600 cm h g of catalyst. Catalyst performance was benchmarked against comparable plasma-synthesized bimetallic 80%Co-20%Fe/C and ternary 10%Ni-70%Co-20%Fe/C formulations. The bimetallic Co-Fe/C showed (a) catalytic activity of ∼40% CO conversion and (b) selectivity of ∼19% for gasoline fraction (C-C) and 55% towards diesel (C-C). Addition of 10%Ni to the Co-Fe/C improved CO conversion from 40 to 50% with enhanced selectivity for gasoline from 19 to 50%, but the diesel fraction dropped from 55 to 22%. Incorporation of 5%Au in the 5%Ni-Co-Fe/C catalyst led to 60% CO conversion. Yet, when compared to the un-promoted 5%Ni-Co-Fe/C catalyst that showed 90% CO conversion with relatively high selectivity towards the undesired CO (14%) and CH (23%), presence of Au cut HO production by almost half and improved selectivity for gasoline fraction from 38 to 41% and for diesel from 20 to 32%. All tested catalysts' α-values lay between 0.78 and 0.88 in the C region. [ABSTRACT FROM AUTHOR]

We report a versatile route for the preparation of metal phosphides using PH 3 plasma for supercapacitor applications. The high reactivity of plasma allows rapid and low temperature conversion of hydroxides into monometallic, bimetallic, or even more complex nanostructured phosphides. These same phosphides are much more difficult to synthesize by conventional methods. Further, we present a general strategy for significantly enhancing the electrochemical performance of monometallic phosphides by substituting extrinsic metal atoms. Using NiCoP as a demonstration, we show that the Co substitution into Ni 2 P not only effectively alters the electronic structure and improves the intrinsic reactivity and electrical conductivity, but also stabilizes Ni species when used as supercapacitor electrode materials. As a result, the NiCoP nanosheet electrodes achieve high electrochemical activity and good stability in 1 M KOH electrolyte. More importantly, our assembled NiCoP nanoplates//graphene films asymmetric supercapacitor devices can deliver a high energy density of 32.9 Wh kg −1 at a power density of 1301 W kg −1 , along with outstanding cycling performance (83% capacity retention after 5000 cycles at 20 A g −1 ). This activity outperforms most of the NiCo-based materials and renders the NiCoP nanoplates a promising candidate for capacitive storage devices. [ABSTRACT FROM AUTHOR]

In this paper, a novel approach to the synthesis of the carbon nanotubes (CNTs) in reactors operating at atmospheric pressure is presented. Based on the literature and our own research results, the most effective methods of CNT synthesis are investigated. Then, careful selection of reagents for the synthesis process is shown. Thanks to the performed calculations, an optimum composition of gases and the temperature for successful CNT synthesis in the CVD (chemical vapor deposition) process can be chosen. The results, having practical significance, may lead to an improvement of nanomaterials synthesis technology. The study can be used to produce CNTs for electrical and electronic equipment (i.e., supercapacitors or cooling radiators). There is also a possibility of using them in medicine for cancer diagnostics and therapy. [ABSTRACT FROM AUTHOR]

Amorphous carbon nitride (ACN) is a promising semiconductor photocatalyst for photocatalytic H 2 O 2 production. However, its actual activity is hindered by a high recombination rate of photoexcited charge carriers. Herein we report a K-doped ACN (K-ACN) photocatalyst synthesized via Ar plasma treatment to the modified melamine and KCl powder mixture at a moderate temperature. The as-synthesized K-ACN exhibits significantly enhanced photocatalytic properties for H 2 O 2 production with a yield of 6.21 mM h−1, which is 6 times higher than that of bulk CN. Moreover, the H 2 O 2 yield can be further increased to 13.95 mM h−1 by adjusting the pH value. The significantly enhanced photocatalytic property is mainly attributed to the introduction of K+, which is conducive to tuning the electronic structure, extending π conjugated system, passivating trap states and enhancing photocatalytic activity. The result has provided a facile and effective strategy for the modification of ACN to significantly boost its photocatalytic activity. [Display omitted] • K-ACN photocatalyst was synthesized via Ar plasma treatment to the modified melamine and KCl powder mixture. • The as-synthesized K-ACN exhibits 6-fold photocatalytic H 2 O 2 production relative to pristine carbon nitride. • The passivated trap states were observed in K-ACN and result in faster transport of light-induced active electrons. • K doping is conducive to tuning the electronic structure and enhanceing photocatalytic activity of ACN. [ABSTRACT FROM AUTHOR]

A study was done on the effect of temperature and catalyst pre-treatment on CO hydrogenation over plasma-synthesized catalysts during the Fischer–Tropsch synthesis (FTS). Nanometric Co/C, Fe/C, and 50%Co-50%Fe/C catalysts with BET specific surface area of ~80 m2 g–1 were tested at a 2 MPa pressure and a gas hourly space velocity (GHSV) of 2000 cm3 h−1 g−1 of a catalyst (at STP) in hydrogen-rich FTS feed gas (H2:CO = 2.2). After pre-treatment in both H2 and CO, transmission electron microscopy (TEM) showed that the used catalysts shifted from a mono-modal particle-size distribution (mean ~11 nm) to a multi-modal distribution with a substantial increase in the smaller nanoparticles (~5 nm), which was statistically significant. Further characterization was conducted by scanning electron microscopy (SEM with EDX elemental mapping), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The average CO conversion at 500 K was 18% (Co/C), 17% (Fe/C), and 16% (Co-Fe/C); 46%, 37%, and 57% at 520 K; and 85%, 86% and 71% at 540 K respectively. The selectivity of Co/C for C5+ was ~98% with 8% gasoline, 61%, diesel and 28% wax (fractions) at 500 K; 22% gasoline, 50% diesel, and 19% wax at 520 K; and 24% gasoline, 34% diesel, and 11% wax at 540 K, besides CO2 and CH4 as by-products. Fe-containing catalysts manifested similar trends, with a poor conformity to the Anderson–Schulz–Flory (ASF) product distribution.