Low Temperature Oxygen Research Articles

Tuning oxygen vacancy concentration of MnO2 through metal doping for improved toluene oxidation

Oxygen vacancy acts an important role in adjusting the chemical properties of MnO2. In this paper, two-dimensional MnO2 catalysts with different oxygen vacancy concentration are obtained by doping Cu2+. It is researched that the K+ species in the interlayer of birnessite-type MnO2 can be substituted during the Cu2+ doping process. Meanwhile, this process will generate the oxygen vacancy. Interestingly, the formation of an appropriate numbers of oxygen vacancy in MnO2 distinctly enhances the low-temperature reducibility and oxygen species activity, which improves the catalytic activity for the toluene oxidation (T100 = 220 °C, Ea=43.6 kJ/mol). However, an excessive concentration of oxygen vacancy in MnO2 sample performs against the activity improvement for toluene oxidation. In situ DRIFTS are applied to elucidate the main intermediates and conversion pathway on MnO2-OV3 with moderate concentration of oxygen vacancy. The results demonstrate that the adsorbed toluene can interact with oxygen species of catalyst to form physisorbed benzaldehyde, aldehydic adsorbate and benzoate species. In addition, it is found that the oxygen vacancy concentration plays an important effect on the oxidation of benzoate species owing to the acceleration effect of oxygen vacancy in the activation of gaseous oxygen.

冻融循环对川西亚高山森林土壤酶活性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 冻融循环对川西亚高山森林土壤酶活性的影响 DOI: 10.5846/stxb201902250355 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金青年项目（31700542）；重点实验室开放基金（四川省科技厅）（ESP1704） Effects of the freeze-thaw cycle on soil enzyme activities in a sub-alpine forest in western Sichuan Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤酶活性的研究有助于认识植物-微生物-土壤有机质之间的相互关系，土壤酶的生产遵循"经济法则"，冻融循环将会改变生产土壤酶的资源分配，最终影响土壤的有机质分解过程。亚高山森林土壤具有明显的季节性冻融循环，为深入研究亚高山森林冬季土壤生态过程，以川西亚高山针阔混交林、针叶林以及阔叶林土壤为研究对象，通过室内培养研究冻融循环对6种与碳（C）、氮（N）、磷（P）相关土壤酶活性的影响。结果表明，与N和P相关的土壤β-N-乙酰葡萄糖苷酶、磷酸酶活性受冻融循环影响显著，其中，β-N-乙酰葡萄糖苷酶活性在整个冻融处理过程中表现出先升高后降低并趋于平稳的趋势，磷酸酶活性在后期明显增加。与C相关的土壤纤维素酶、β-葡萄糖苷酶、过氧化物酶、多酚氧化酶在冻融循环过程中没有显著变化。林型对土壤酶活性产生了显著影响。其中，阔叶林的土壤纤维素酶活性显著低于针叶林；阔叶林的土壤过氧化物酶活性显著低于针阔混交林和针叶林；针叶林的土壤磷酸酶活性显著高于针阔混交林和阔叶林。冻融循环和林型的交互作用对土壤酶活性没有显著影响。结果表明，该地区土壤酶活性对冻融循环响应存在差异，气候变化引起的冻融循环将进一步影响川西亚高山森林土壤生态系统的有机质分解过程。 Abstract:Research on soil enzyme activities is beneficial to identify relationships between plants, microbes, and soil organic matter. Freeze-thaw cycles will change resource allocations for the production of soil extracellular enzymes, which affects organic matter decomposition processes in the soil. Based on the pre-recognition of sub-alpine seasonal freeze-thaw cycles and considering typical coniferous-broadleaf mixed forest, coniferous forest, and broadleaf forest soil in the sub-alpine region of western Sichuan, we controlled the freeze-thaw environment and analyzed the effects of freeze-thaw cycles on enzyme activities in the soil, including carbon, nitrogen, and phosphorus. According to the results, the freeze-thaw cycles had a significant impact on β-N-acetylglucosidase and phosphatase activities associated with soil N and P. The activity of β-N-acetylglucosidase was elevated at the beginning of freeze-thaw period and then decreased with an increase in freeze-thaw frequency. The phosphatase activity increased significantly in the later portion of the freeze-thaw cycle. However, the freeze-thaw cycle had no significant effect on C-related soil enzyme activities. The changes in C-related soil enzyme activities in this study were more determined by litter decomposition processes and forest types. Among them, cellulase and β-glucosidase activities were significantly correlated with the decomposition process of organic matter. The limiting factors of peroxidase and polyphenol oxidase and low temperature and low oxygen were still present in this test, so the activities of these two enzymes did not change significantly. On the other hand, the effect of forest types on cellulase, peroxidase and phosphatase activities was significant. The soil cellulase activity of broadleaf forest was significantly lower than that of coniferous forest. The peroxidase activity of broadleaf forest soil was significantly lower than that of coniferous-broadleaf mixed forest and coniferous forest. The soil phosphatase activity of coniferous forest soil was significantly higher than that of coniferous-broadleaf mixed forest and broadleaf forest. Our results indicate that the effects of the freeze-thaw cycles on extracellular enzyme activities in the soil vary in this area. Freeze-thaw cycles that result from climate change will further influence the organic matter decomposition processes of the soil ecology system in the sub-alpine forest in western Sichuan. 参考文献 相似文献 引证文献

Stable hetero-metal doped Co-based catalysts prepared by electrodeposition method for low temperature combustion of toluene

A series of hetero-metal (Ni, Mn, and Cu) doped Co-based catalysts were prepared by a unipolar pulse electro-deposition (UPED) method and applied for the catalytic combustion of toluene. It is found that hetero-metal doping significantly influenced the morphology and surface elemental compositions of Co-based catalysts, and the increase in the contents of Ni and Mn elements made a negative influence on the catalyst structure. H2-TPR and O2-TPD analysis results suggested that the hetero-metal doping enhanced the low temperature reducibility and resulted in the formation of lattice defects, which were favorable to generate more easily reducible species and facilitate the oxygen mobility, thereby improved the performance for the catalytic combustion of toluene. Especially, the Co-Cu/NF catalyst performed the best catalytic activity with the lowest toluene conversion temperature of T90 at 248 °C, which should be contributed by its low-temperature reducibility, increased surface and lattice oxygen species, and high content of active Co3+ species promoted by the interaction of the mixed metal oxides. Moreover, the Co-Cu/NF also performed excellent catalytic stability and high selectivity to CO2 in the presence and absence of water vapor for the catalytic combustion of toluene for a long term.

Improved Surface Properties of Copper/PolyMethylMethacrylate nanocomposite films using DC O2 Plasma

Films of Polymethylmethacrylate with copper nanofiller were prepared and treated with low temperature oxygen DC glow discharge plasma. FTIR spectroscopy, AFM, water contact angle (WCA) measurements and UV-Vis spectroscopy were used to detect the produced chemical, morphological and optical changes as a function of plasma treatment time. The FTIR spectra, showed a decreasing value of the main characterizing signals of the composite films in addition to the creation of an oxygen containing functional group. The surface morphology of the treated samples was altered according to the increased values of the average surface roughness, obtained from the AFM images. The WCA also, decreased noticeably with increasing treatment time. The UV-Vis spectroscopic analysis showed a decreasing value of the optical absorption in the wave length range 190-270 nm which is an indication to the loss of carbonyl group. The value direct and inddirect optical band gap decreased with treatment time meanwhile, values of the band tail width were significantly increased.

Effect of oxygen on the properties of Ga2O3:Si thin films

The results of studies of electrical and gas-sensitive characteristics of thin films Ga2O3:Si on exposure to oxygen in the range from 0 to 100 vol. % and operating temperatures from 25 to 700 °C were presented. Samples were obtained by HF magnetron sputtering. The possibility of developing low-temperature oxygen sensors was shown. A model of oxygen interaction with Ga2O3:Si films was proposed. The mechanism of Si influence on gas-sensitive properties of thin films of gallium oxide was proposed.

LaMnO3 perovskites via a facile nickel substitution strategy for boosting propane combustion performance

The B-site substitution by other metals is a feasible and efficient strategy to modulate the physicochemical properties and catalytic behaviors of perovskite-type metal oxides. Herein, series of LaMn1-xNixO3 (x = 0, 0.1, 0.2 and 0.3) catalysts were prepared for catalytic combustion of propane. The maintenance of perovskite structures but the occurrence of lattice shrinkage was observed after nickel substitution. Superior redox properties (i.e. low-temperature reducibility and surface oxygen mobility), higher average oxidation states of manganese and surface oxygen abundance were identified to be the key factors for the remarkable activity improvement. LaMn0.9Ni0.1O3 presented reversible partial deactivation under water vapor or carbon monoxide-containing atmosphere due to the surface completive adsorption/oxidation phenomenon of various gaseous components. Kinetics investigation revealed the different reaction orders towards propane and oxygen over LaMn0.9Ni0.1O3 and LaMnO3, which was of strong reflection about the surface adsorption behaviors of reactants molecules.

Preparation of Silver-Plated Para-Aramid Fiber by Employing Low-Temperature Oxygen Plasma Treatment and Dopamine Functionalization

Direct electroless silver plating of para-aramid (PPTA) is difficult due to its extremely low surface chemical energy. In order to facilitate the deposition of silver nanoparticles and to enhance the washing fastness, oxygen plasma treatment and dopamine modification were conducted before silver plating of PPTA fibers. Various techniques including scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffractometer (XRD) and thermogravimetric analyzer (TGA) were used to characterize the surface morphology, chemical composition and thermal stability of the silver-plated PPTA fibers. Electrical resistance and silver content of the silver-coated PPTA fibers before and after standard washing were also studied. The results showed that silver nanoparticles were successfully coated onto the surface of PPTA fibers with and without plasma treatment, but the coating continuity and the electrical conductivity of the silver-coated PPTA fibers were greatly enhanced with the assistance of plasma treatment. It was also demonstrated that the washing fastness of silver-coated PPTA fibers was improved after plasma treatment as indicated by electrical resistance and continuity of the silver nanoparticles after various washing cycles. It was found that the electrical resistance of plasma-treated PPTA-PDA/Ag fibers prepared at an AgNO3 concentration of 20 g/L reached 0.89 Ω/cm and increased slightly to 0.94 Ω/cm after 10 standard washing cycles. The silver-coated PPTA fibers also showed stable electrical conductivity under 250 repeated stretching-releasing cycles at a strain of 3%.

In Situ Encapsulated Pt Nanoparticles Dispersed in Low Temperature Oxygen for Partial Oxidation of Methane to Syngas

Highly dispersed ultra-small Pt nanoparticles limited in nanosized silicalite-1 zeolite were prepared by in situ encapsulation strategy using H2PtCl6·6H2O as a precursor and tetrapropylammonium hydroxide as a template. The prepared Pt@S-1 catalyst was characterized by X-ray diffraction (XRD), inductively coupled plasma (ICP), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), N2 adsorption-desorption, CO adsorption, and TGA techniques and exhibited unmatched catalytic activity and sintering resistance in the partial oxidation of methane to syngas. Strikingly, Pt@S-1 catalyst with further reduced size and increased dispersibility of Pt nanoparticles showed enhanced catalytic activity after low-temperature oxygen calcination. However, for Pt/S-1 catalyst, low-temperature oxygen calcination did not improve its catalytic activity.

The estimation of metabolism in the mesopelagic zone: Disentangling deep-sea zooplankton respiration

Respiration in the mesopelagic layer is rather difficult to estimate but is of paramount importance to assess active flux, the downward carbon transport carried out by diel vertical migrants in the ocean. Migrant biomass and respiration in the mesopelagic zone are required to estimate respiratory flux, an important component of active flux. Three main approaches were used in the past to assess respiration in the mesopelagic zone: (1) The use of Q10 values, (2) published equations relating respiration, body mass, and temperature, and (3) the electron transfer system (ETS) enzymatic activity, calibrated to obtain respiration rates. The latter method is also a commonly used approach for measuring mesopelagic community respiration. Here we report respiration rates and ETS activity of migrant copepods captured at night in the epipelagic layer. The estimated mesopelagic respiration obtained from conversion of epipelagic respiration at night using a Q10 value for mesopelagic zooplankton was compared to the estimated respiration obtained using the equations given by Ikeda (1985), Ikeda (2014), and ETS activity using a respiration to ETS (R/ETS) ratio of 1. They were not statistically different. However, differences were observed between those latter values and the R/ETS ratio of 0.5. These results show that the commonly used R/ETS ratio of 0.5 promotes quite conservative values of the respiratory flux, and the equation of Ikeda (2014) displayed values in the middle of both R/ETS ratios, and it may be used with confidence. Relatively high specific ETS activities were observed in the mesopelagic zone, also coinciding with a previous observation in Eastern Equatorial Pacific. We discuss this observation as an adaptation of migrant zooplankton to endure the adverse conditions of low temperature and low oxygen in deep waters.

Investigating modification on electronic properties of bilayer MoS2 field-effect transistor by low-temperature oxygen plasma treatment

Two-dimensional layer materials have been of great interest in the promising application of novel nano-electronics in recent years. In this study, we demonstrated the modification on electronic properties of bilayer MoS2 field-effect transistor (FET) by low-temperature oxygen plasma treatment with different radio frequency (RF) power. According to the I-V measurement with Cascade semi-automatic probe station, it was observed that the electronic properties of bilayer MoS2 FET could be improved effectively after low-power oxygen plasma treatment. The analysis of transport properties in MoS2 revealed the modification mechanism of sulphur (S) vacancies by low-power oxygen plasma. Nevertheless, electronic properties of MoS2 FET were degenerated after high-power oxygen plasma treatment for the increase of defect in MoS2, which has been characterized by Raman spectrum and XPS spectrum. Furthermore, it was found that the signal distributions of surface contact potential difference (CPD) and capacitance of MoS2 mono-crystal samples prepared by chemical vapor deposition (CVD) were heterogeneous, which demonstrates that the edge region of MoS2 can be interacted by oxygen plasma more easily owing to the defect and active sites. This study will provide a theoretical basis in the research of next-generation high-performance electronic device.

Effect of Plasma Surface Treatment on the Impact Behavior of Basalt/Epoxy Composites

In this study, the effects of surface treatment of a low-temperature atmospheric oxygen plasma on basalt/epoxy composites were investigated to improve the hydrophobility of the composite surface. After the plasma treatment, the unmodified and surface treated composite laminates have been experimentally characterized by performing contact angle measurements, low-velocity impact tests and indentation depth on the impacted laminates. Results have showed a dependence of such composite properties on the plasma coating deposition and on the treatment parameters outlining the need to optimize both the plasma power and exposition time to plasma in order to assess the efficiency of the plasma treatment and establish the optimal processing conditions.

Factors determining gasoline soot abatement over CeO2–ZrO2-MnOx catalysts under low oxygen concentration condition

Soot oxidation under a low concentration O2 (0.5% O2/N2) was investigated using CeO2–ZrO2-MnOx mixed oxides with varied amounts of MnOx, in order to gain low temperature catalytic activity and find out the main factors affecting the soot oxidation. The catalytic activity was remarkably improved over these catalysts compared to that of non-catalyst in such a low concentration of O2. In particular, CeO2–ZrO2-MnOx with 10% MnOx doping (M10-CZ) showed the highest catalytic activity with its T50 values of 340 °C under tight contact condition. The results of N2 adsorption-desorption and X-ray diffraction (XRD) indicated that the textural and structural properties were not positive correlation with soot oxidation, are not the main factors affecting the catalytic activity of CeO2–ZrO2 and CeO2–ZrO2-MnOx catalysts. The results of oxygen storage capacity (OSC), hydrogen-temperature programmed reduction (H2-TPR), O2 temperature program desorption (O2-TPD), UV Raman spectroscopy (UV Raman) and X-ray photoelectron spectroscopy (XPS) testified that redox ability, oxygen storage capacity, oxygen desorption capacity at low temperature and surface active oxygen species are more important for soot oxidation. The enhancements of the catalytic behavior after MnOx addition can be due to the improving of the adsorbed, activation and mobility of reactive oxygen species. In this work, these factors about generation and movement of reactive oxygen species are crucial for soot oxidation in a low oxygen concentration condition.

High-Index Faceted Platinum Nanoflowers Catalysts for Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cells (PEMFCs) have tremendous potential to be the preferred power sources for many emerging technologies, from electric vehicles to portable/mobile devices and smart grids, because of their numerous inherent advantages such as high efficiency, high energy density, low emissions, and fast start-up and shut-down capability. While PEMFCs are expected to use platinum group metal (PGM)-based catalysts in the near-term, the cost of the Pt-based catalyst alone constitutes over 40% of the fuel cell stack cost. Enormous efforts have been devoted to reducing the high cost of catalyst. To date, the catalysts can be classified into three groups according to the active component used: PGM-based catalyst (supported on carbon or other supports); PGM-based catalysts that are modified or alloyed with other metals such as Cu, Co, and Ru; and PGM-free catalysts such as non-noble metals and organometallic complexes. PGM-free catalysts are attractive for cost reduction of PEMFC technology, however, in reality is still a long way to go to before they can be used to run actual fuel cell application. Here in, we are proposing a facile, one-step, synthesis of Pt-based alloy nanoparticles for cost effective low temperature oxygen reduction reaction electrocatalysis at industrial scale.Direct Pt nanoparticles synthesis is performed under room temperature to form a branched triple and quadruple-pods particles with an average size of ~3.5 nm, as confirmed by X-ray diffraction (XRD) and Scanning transmission electron microscope (STEM) analysis. Rotating disc electrode (RDE) setup is used to probe ORR. Results showed that synthesized Pt-nanoparticles superior catalytic activity for oxygen reduction reaction compared to state of the art Pt-XC/72R commercial catalyst. Pt-nanoparticles periphery are conformed of high index family crystallographic planes, as observed by STEM analysis. High index planes contain lower density of kinks, which optimize the adsorption/desorption energies to be neither too weak nor too strong. Pt-nanoparticles under accelerated durability testing (ADT) outperform their state of the art commercial catalyst counterparts, surviving 81% of electrochemical active surface area (ECSA) after 10,000 testing cycles.Using a catalyst coated membrane (CCM) technique membrane electro assembly (MEA) was prepared to test Pt nanoparticles under actual PEMFC operation conditions (i.e. temperature and humidity). MEA prepared using the synthesized Pt-nanoparticles outperformed their counterparts prepared by Pt-XC/72R state of the art commercial catalyst with 27% enhancement factor. The reported Pt-based nanoparticles propose a competitive and more efficient synthesis route to prepare large scale commercial catalyst without the need of sophisticated apparatus or special heating conditions.

Low-temperature plasma modification of carbon nanofillers for improved performance of advanced rubber composites

In modern polymer industry, there still is a room for new generations of fillers capable of enhancing the performance of composite materials. Currently, much effort is being put into a process of improving mechanical properties of elastomer materials. In this work, multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GnPs) were modified with silane, titanate, or zirconate using plasma treatment, in order to apply them as fillers for styrene/butadiene rubber. Following its modification, filler surface was analyzed: Surface free energy (SFE) was measured with tensiometry, and micromorphology and chemical composition were studied with scanning electron microscopy–energy-dispersive spectroscopy (SEM–EDS), while elemental composition and bonding were assessed with X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Low-temperature oxygen plasma activation of MWCNT fillers leads to a significant increase in the SFE polar component, with the same effect being much weaker for GnP fillers. Grafting silanes, zirconates, and titanates on activated filler surface results in a decrease in SFE polar component—surface oxygen-containing active groups react with silane/zirconate/titanate molecules. Fillers modified in this way exhibit different micromorphology and surface chemical composition what is revealed with the SEM–EDS, ToF-SIMS, and XPS techniques. As the ultimate step, either MWCNT or GnP rubber nanocomposites were manufactured using the modified fillers with their mechanical properties and cross-link density being studied. Filler modification resulted in substantial changes both in composite performance, and in its cross-linking density. In the case of modified filler containing composites, improved tensile strength and elongation at break were observed.

Air separation and selective oxygen pumping via temperature and pressure swing oxygen adsorption using a redox cycle of SrFeO3 perovskite

The achievement of low oxygen partial pressures is beneficial in a number of applications, including the production of nitrogen for the Habor-Bosch process, one of the largest industrial chemical processes. It has been suggested in the literature that a redox cycle can be utilized for selective oxygen adsorption, with the potential for application in oxygen separation and compression processes. In this work we demonstrate this concept and show the feasibility of using a temperature and pressure swing redox cycle to chemically absorb oxygen gas at a low partial pressure of 10−6 bar. The redox material used was the perovskite oxide SrFeO3, chosen for its relatively low reduction temperature and strong oxygen affinity. The material's intrinsic thermodynamics and low temperature kinetics were both investigated using thermogravimetric analysis. Multiple reduction and oxidation experiments were conducted, with oxidation performed under both synthetic air and inert gas with 1% O2 concentration. The results show successful trials of oxygen removal resulting in inert gasses with ppm level oxygen impurities and no degradation of the material over multiple cycles. Thermodynamic considerations suggest that with further development this technology could offer a very attractive, reversible cycle for the removal of oxygen impurities from gas streams, particularly in combination with conventional pressure swing adsorption.

Spray, Combustion and Soot of Water-in-Fuel (n-Dodecane) Emulsions in a Constant Volume Combustion Chamber; Part II: Effects of Low Temperature Conditions and Oxygen Concentrations

The application of water-in-fuel (n-dodecane) emulsions (WFE) with a fixed water mass fraction of 10 wt% has been investigated in an optically accessible constant volume combustion chamber (CVCC) at varying low ambient temperatures conditions (Tgas=760–800K/ρgas=22.8kg/m3) such as found in direct-injection (DI) Diesel engine operations with (extreme) “Miller”-timing. Furthermore, oxygen concentrations have been decreased to 18 vol% and 15 vol% in order to emulate exhausRd in DI engines.As in Part I two injection strategies have been employed: first, a constant injection pressure case as for neat fuel and prolonged injection duration (strategy (A)), second, the injection pressure has been increased to keep a constant energy input flow, therefore, with constant injection duration (strategy (B)).Spray parameters and combustion characteristics have been assessed by Schlieren imaging, Mie-scattering, diffused back-illumination extinction imaging (DBIEI) and OH∗-chemiluminescence, respectively. Furthermore, the spray flame’s soot formation has been investigated through the detection of soot incandescence signals.For the WFE liquid lengths (LL) penetrate farther downstream the respective LOL at all ambient conditions, whereas, utilizing neat n-dodecane LLs remain upstream the LOL. The interaction between LL and the high-temperature reaction zone dominates the soot behaviour of WFE resulting in decreased dwell times between ignition and first soot occurrence. Decreasing gas temperatures at atmospheric oxygen concentrations generally decrease dwell times, even though, ignition delays and LOLs increase by the utilization of neat n-dodecane.Soot incandescence signal amplitudes decrease strongly employing WFE (150–270 times lower maximum signal values) compared to neat n-dodecane injections. During mixing-controlled combustion phase apparent heat-release rate (aHRR) amplitudes increase for WFE with injection strategy (B) compared to the neat fuel sprays. At the gas temperature of 760 K non-sooting lifted flames have been detected for both fuels. Calculated fuel-to-air ratios Φ evaluated at the respective LOL agree well with soot occurrences for both fuels. Utilizing WFE, the additional latent heat introduced by the water increases LOLs and to a further extent the liquid fuel core which is found within the spray flame and therefore, a fuel rich combustion zone is suggested to surround the liquid-phase WFE. Hence, soot formation persists for calculated fuel-to-air ratios Φ<2 at the LOL, although, detected soot incandescence signals were on very low amplitude levels injecting the WFE.

Effect of oxygen plasma treatment on bonding strength of epoxy coating on steel substrate

In this work, the surface of Q235 steel was pretreated by low-temperature atmospheric pressure oxygen plasma in order to improve the bonding strength between the epoxy coating and the metal substrate. The epoxy coating was prepared by electrostatic spraying. The bonding strength between the epoxy coating and the Q235 steel was characterized by a coating peeling experiment. XRD, laser scanning microscope were employed in this research to characterize the chemical and physical properties of the Q235 surface before and after treatment. The experimental results showed that oxidize occurred on the surface of the Q235 steel after oxygen plasma pretreatment, which improved the surface roughness and free energy. Meanwhile, polar groups were introduced on the steel surface. With the increase in treatment time, the bonding strength increased first and then decreased. When the treatment time was 2 min, the bonding strength reached the highest (7.51 MPa), which was an increase of 3.5 times compared with the untreated sample (1.67 ± 0.48 MPa).

Enhance flotation separation of arsenopyrite and pyrite by low-temperature oxygen plasma surface modification

The flotation separation efficiency of pyrite and arsenopyrite can be enhanced by low-temperature oxygen plasma pretreatment. In this study, the plasma modification mechanism on arsenopyrite and pyrite and the effect on the flotation performance of pyrite and arsenopyrite were investigated. The results showed that plasma modification preferentially starts at the edges and rough areas of the arsenopyrite particles and results in substantial enrichment of O and depletions of Fe, As, and S on the mineral surface. After plasma modification, the concentration of sulfate species on the arsenopyrite surface increased significantly, which promoted the dissolution of the mineral surface and further reduced the number of collector adsorption sites (Fe). Flotation experiment results indicated that plasma modification has excellent selectivity, the arsenopyrite particles were completely hydrophilic and pyrite still exhibited excellent flotation performance.

Low-temperature oxygen plasma treatment of single-layer molybdenum disulfide

Two-dimensional (2D) molybdenum disulfide (MoS2) is considered a promising candidate for next-generation electronic devices because of its non-zero band-gap, mechanical flexibility, and optical transparency. In this study, the structural, mechanical, and surface potential characteristics of single-layer MoS2 films subjected to oxygen plasma treatment were investigated. Comparison of the Raman spectra of single-layer MoS2 films before and after plasma treatment revealed that plasma treatment caused mechanical stripping. The difference between and A1g peaks and the position of the longitudinal acoustic mode changed considerably following oxygen plasma treatment. Atomic force microscopy was used to explore the changes of the structure, mechanical behavior, and surface potential of the MoS2 films induced by plasma treatment. Root mean square values were used to analyze the changes of surface roughness, adhesion, and surface potential of the MoS2 films induced by oxygen plasma treatment. The root mean square roughness of the films first increased and then decreased with increasing plasma treatment duration. The defect content of the MoS2 films was increased by oxygen plasma treatment and the surface potential decreased considerably. These finding could be important for producing two-dimensional dichalcogenide-based electrical and optoelectronic devices.

Photosensitized TiO2 films on polymers – Titania-polymer interactions and visible light induced photoactivity

Photocatalytic coatings at polymers, showing a visible light induced photoactivity, can be synthesized using a low temperature oxygen plasma treatment of the polymer (PP) followed by deposition of TiO2 nanoparticles and their sensitization with organic ligands. The whole process consists of three major steps: surface activation involving its partial oxidation, immobilization of TiO2 nanoparticles and photosensitization of titania film by impregnation with the solution of organic ligands forming surface Ti(IV) charge transfer complexes. XPS and IR analysis revealed the formation of oxygen-containing groups at the polymer surface upon plasma treatment. These groups participate in the formation of TiOC bonds which ensure a very good adhesion of titania films to polymeric surface. The dip-coating process using an aqueous colloidal solution of TiO2 nanoparticles allows to synthesize a compact coating with a thickness of 100–300 nm. Coordination of catechol-like ligands to surface Ti(IV) centers results in formation of colored charge transfer complexes responsible for absorption of visible light and an effective photoinduced charge separation. Photogenerated electrons and holes can take part in surface redox reactions responsible for degradation of pollutants. Tests with various organic ligands (catechol, 2,3-naphthalenediol, pyrogallol and rutin) revealed, that the titanium dioxide coating modified with catechol was the most photoactive one when visible light irradiation was applied. Presented photocatalytic coatings can be effectively used as self-sterilizing surfaces activated by visible light.