Nitrogen-rich Surface Research Articles

Human mesenchymal stromal cell adhesion and expansion on fluoropolymer surfaces modified with oxygen and nitrogen-rich plasma polymers

Fluorinated ethylene propylene (FEP) vessels are of significant interest for therapeutic cell biomanufacturing applications due to their chemical inertness, hydrophobic surface, and high oxygen permeability. However, these properties also limit the adhesion and survival of anchorage-dependent cells. Here, we develop novel plasma polymer coatings to modify FEP surfaces, enhancing the adhesion and expansion of human mesenchymal stromal cells (hMSCs). Similar to commercially available tissue culture polystyrene vessels, oxygen-rich or nitrogen-rich surface chemistries can be achieved using this approach. While steam sterilization increased the roughness of the coatings and altered the surface chemistry, the overall wettability and oxygen or nitrogen-rich nature of the coatings were maintained. In the absence of proteins during initial cell attachment, cells adhered to surfaces even in the presence of chelators, whereas adhesion was abrogated with chelator in a protein-containing medium, suggesting that integrin-mediated adhesion predominates over physicochemical tethering in normal protein-containing cell seeding conditions. Albumin adsorption was more elevated on nitrogen-rich coatings compared to the oxygen-rich coatings, which was correlated with a higher extent of hMSC expansion after 3 days. Both the oxygen and nitrogen-rich coatings significantly improved hMSC adhesion and expansion compared to untreated FEP. FEP surfaces with nitrogen-rich coatings were practically equivalent to commercially available standard tissue culture-treated polystyrene surfaces in terms of hMSC yields. Plasma polymer coatings show significant promise in expanding the potential usage of FEP-based culture vessels for cell therapy applications.

Controlling Nano-to-Microscale Multilevel Architecture in Polymeric Microfibers through Polymerization-Induced Spontaneous Phase Separation.

Hierarchically structured polymeric fibers, composed of structural nanoscale motifs that assemble into a microscale fiber are frequently found in natural fibers including cellulose and silk. The creation of synthetic fibers with nano-to-microscale hierarchical structures represents a promising avenue for the development of novel fabrics with distinctive physical, chemical, and mechanical characteristics. In this work, we introduce a novel approach for creating polyamine-based core-sheath microfibers with controlled hierarchical architectures. This approach involves a polymerization-induced spontaneous phase separation and subsequent chemical fixation. Through the use of various polyamines, the phase separation process can be manipulated to produce fibers with diverse porous core architectures, ranging from densely packed nanospheres to segmented "bamboo-stem" morphology. Moreover, the nitrogen-rich surface of the core enables both the chemisorption of heavy metals and the physisorption of proteins and enzymes. Our method offers a new set of tools for the production of polymeric fibers with novel hierarchical morphologies, which has a high potential for a wide range of applications such as filtering, separation, and catalysis.

Highly fluorescent composite of boron nitride quantum dots decorated on cellulose nanofibers for detection and removal of Hg(II) ions from waste water

To address the challenge of heavy-metal ions in wastewater, boron nitride quantum dots (BNQDs) were synthesized in-situ on rice straw derived cellulose nanofibers (CNFs) as substrate. The composite system exhibited strong hydrophilic-hydrophobic interactions, as corroborated by FTIR, integrated the extraordinary fluorescence properties of BNQDs with fibrous-network of CNFs (BNQD@CNFs) yielding a surface of 35.147 m2 g−1 of luminescent fibers. Morphological studies revealed uniform distribution of BNQDs on CNFs due to hydrogen bonding, according high thermal stability with peak degradation occurring at 347.7 °C and quantum yield of 0.45. The nitrogen-rich surface of BNQD@CNFs exhibited strong affinity for Hg(II), quenching the fluorescence intensity due to combined inner-filter effect and photo-induced electron transfer. The limit of detection (LOD) and limit of quantification (LOQ) were 4.889 nM and 11.1 5 nM, respectively. BNQD@CNFs concomitantly exhibited adsorption of Hg(II) owing to strong electrostatic interactions, confirmed by X-ray photon spectroscopy. Presence of polar BN bonds favoured 96 % removal of Hg(II) at 10 mg L−1 with maximum adsorption capacity of 314.5 mg/ g. Parametric studies corresponded to pseudo-second order kinetics and Langmuir isotherm with R2 ≈ 0.99. BNQD@CNFs exhibited recovery rate between 101.3 %–111 % for real water samples and recyclability upto 5 cycles, demonstrating high potential in wastewater remediation.

Wetland plant development overrides nitrogen effects on initial methane emissions after peat rewetting

Growing productive wetland species on rewetted peatland (paludiculture) is a promising solution to offset carbon loss from drained peatlands. The inlet of nitrogen (N) rich surface water, a proposed method to improve productivity of vegetation, may affect methane (CH4) emissions. This study aims to compare initial CH4 emissions from newly rewetted peat with different types of vegetation and N loading simulating diffuse N inlet. Diffusive CH4 emissions were measured in peat mesocosms during one growing season. Peat cores were either planted with Typha latifolia or Phragmites australis or they were left bare. Mesocosms received 0, 50, 150 or 450 kg ha−1 year−1 N. Plants affected CH4 emissions from rewetted peat soil, leading to stable fluxes over time of 133 mg m−2 day−1 CH4 at 20 °C. Biomass harvesting lead to a 153% increase of CH4 emissions. With increasing N load, CH4 emissions from mesocosms with Typha and Phragmites decreased up to a load of 150 kg ha−1 N, but this was only significant for the Phragmites treatment. Emissions of unvegetated mesocosms increased with increasing N load but not significantly. In conclusion, our mesocosm study suggests that vegetation can reduce or prevent an increase in CH4 emissions from rewetted peatlands compared to only rewetting, possibly due to an increased oxygenation of the sediments by macrophyte roots preventing excessive CH4 formation, while added N does not provoke great changes in emissions at N concentrations up to 150 kg ha−1.

Performance of tungsten nitride compound surfaces to resist sputtering under intense irradiation in nuclear fusion reactors

The formation of tungsten nitride (WNx) films has been experimentally detected on the surface of tungsten divertors in fusion reactors after seeding cooling systems using nitrogen, and hence the sputtering resistance of the WNx film is crucial for the stable operation of the fusion reactor. By performing first-principles calculations, we investigated the sputtering resistance of W2N1, W1N1, and W2N3 surfaces, respectively. It was found that the tungsten nitride surfaces have good sputtering resistance. Especially, the sputtering resistance of the nitrogen-rich (001) surface of W1N1 is better than that of pure tungsten. However, hydrogenation at surface N atoms will weaken the chemical bonds between the N atoms and their own nearest-neighbors in the surface, facilitating the escape of the N atoms from the irradiated surface, even forming ammonia molecules. Our efforts not only reveal the performance of sputtering resistance of WNx surfaces, but also show the influence of hydrogen on the sputtering-resistant properties of WNx, which are valuable for assessing the state and stability of WNx films on divertor surfaces.

Pico-molar level detection of copper ion with extraordinarily high response by Ti-doped copper nitride fabricated via high power impulse magnetron sputtering

Various specific methods have been exercised in recent years to detect heavy metal ions in drinking water or body fluids for environmental as well as health safety. Likewise, development of a simple, fast, and robust method for copper ion (Cu2+) sensing is of paramount importance. Here, we demonstrate an effective Cu2+ sensor by exploiting the change in electrical conductivity of Ti-doped copper nitride (Cu3N) in presence of Cu2+ in solution. The Cu2+ sensor was fabricated with a Ti-doped Cu3N film deposited on indium-tin-oxide (ITO) coated quartz glass substrate by co-deposition method using high-power impulse magnetron sputtering (HiPIMS) and DC magnetron sputtering system simultaneously. DC sputtering power of Ti source was tuned from 0 W to 200 W with 50 W steps to achieve the Cu3N film with doping concentrations of 0, 0.19, 0.33, 0.87, and 1.6 at% respectively. Application of a diluted Cu2+ solution on the Ti-doped Cu3N film increases its electrical conductivity dramatically as manifested in the increase in current measured between two consecutive ITO electrodes beneath the thin film. The extraordinarily high copper sensitivity of the Ti-doped Cu3N film (1.6 at%) originated from the nitrogen-rich surfaces leads to detection of Cu2+ in water at as low as 8 pM concentration. The sensor exhibits not only high response but also a large linear dynamic range of 8 pM to 80 nM well below the maximum contaminant level goal for copper ion in drinking water. The high selectivity and reasonable cross-sensitivity of the sensor show potential commercialization in near future.

Egg-yolk core-shell mesoporous silica nanoparticles for high doxorubicin loading and delivery to prostate cancer cells.

Mesoporous silica-based nanoparticles (MSNs) have gained rapid interest as a drug delivery system (DDS) and demonstrated their versatility in delivering drugs for the treatment of various cancers. However, the drug loading efficiency of MSNs is low and is usually improved by improving textural properties through complicated synthesis methods or by post synthesis modification of the surface that can result in the loss of surface area and modify its drug release properties. In this study, we report a direct single-step synthesis of MSNs with a unique egg-yolk core-shell morphology, large pore volume and a hydrophilic surface, decorated with nitrogen rich surface functionalities for increasing its drug loading capacity. This combination of excellent textural properties and surface functionalisation was achieved by a simple soft templating method using dual surfactants and the silica sources assisted by employing either triethylamine (TEA) or triethanolamine (TEO) as the hydrolysis agent. The morphology and well-ordered mesoporous structure can simply be tuned by changing the pH of the synthesis medium that affects the self-assembly mechanism of the micelles. HRTEM image of samples clearly revealed an egg-yolk core-shell morphology with a thin mesoporous silica shell. The optimised MSN samples synthesized at a pH of 11 using either TEA or TEO depicted a higher doxorubicin (Dox) loading capacity of 425 μg mg-1 and 481 μg mg-1 respectively, as compared to only 347 μg mg-1 for MSN samples due to the uniform distribution of nitrogen functionalities. The anticancer activity of Dox loaded MSNs evaluated in two different prostate cancer cell lines (PC-3 and LNCaP) showed a higher cytotoxicity of the drug loaded on optimised MSN samples as compared to pristine MSNs without affecting the cellular uptake of the particles. These results suggest that the unique single-step synthesis and functionalisation method resulted in successfully achieving higher drug loading in egg-yolk core-shell nitrogen functionalised MSNs and could be implemented as an effective carrier of chemotherapeutic drugs.

Rapid Functionalization of Polytetrafluorethylene (PTFE) Surfaces with Nitrogen Functional Groups.

The biocompatibility of body implants made from polytetrafluoroethylene (PTFE) is inadequate; therefore, the surface should be grafted with biocompatible molecules. Because PTFE is an inert polymer, the adhesion of the biocompatible film may not be appropriate. Therefore, the PFTE surface should be modified to enable better adhesion, preferably by functionalization with amino groups. A two-step process for functionalization of PTFE surface is described. The first step employs inductively coupled hydrogen plasma in the H-mode and the second ammonia plasma. The evolution of functional groups upon treatment with ammonia plasma in different modes is presented. The surface is saturated with nitrogen groups within a second if ammonia plasma is sustained in the H-mode at the pressure of 35 Pa and forward power of 200 W. The nitrogen-rich surface film persists for several seconds, while prolonged treatment causes etching. The etching is suppressed but not eliminated using pulsed ammonia plasma at 35 Pa and 200 W. Ammonia plasma in the E-mode at the same pressure, but forward power of 25 W, causes more gradual functionalization and etching was not observed even at prolonged treatments up to 100 s. Detailed investigation of the XPS spectra enabled revealing the surface kinetics for all three cases.

High surface area nitrogen-functionalized Ni nanozymes for efficient peroxidase-like catalytic activity.

Nitrogen-functionalization is an effective means of improving the catalytic performances of nanozymes. In the present work, plasma-assisted nitrogen modification of nanocolumnar Ni GLAD films was performed using an ammonia plasma, resulting in an improvement in the peroxidase-like catalytic performance of the porous, nanostructured Ni films. The plasma-treated nanozymes were characterized by TEM, SEM, XRD, and XPS, revealing a nitrogen-rich surface composition. Increased surface wettability was observed after ammonia plasma treatment, and the resulting nitrogen-functionalized Ni GLAD films presented dramatically enhanced peroxidase-like catalytic activity. The optimal time for plasma treatment was determined to be 120 s; when used to catalyze the oxidation of the colorimetric substrate TMB in the presence of H2O2, Ni films subjected to 120 s of plasma treatment yielded a much higher maximum reaction velocity (3.7⊆10−8 M/s vs. 2.3⊆10−8 M/s) and lower Michaelis-Menten coefficient (0.17 mM vs. 0.23 mM) than pristine Ni films with the same morphology. Additionally, we demonstrate the application of the nanozyme in a gravity-driven, continuous catalytic reaction device. Such a controllable plasma treatment strategy may open a new door toward surface-functionalized nanozymes with improved catalytic performance and potential applications in flow-driven point-of-care devices.

Evaluation of CO2 and CH4 adsorption using a novel amine modified MIL-101-derived nanoporous carbon/polysaccharides nanocomposites: Isotherms and thermodynamics

The high efficiency organic-inorganic nanocomposites were fabricated by the simple impregnation of polysaccharides such as alginate, cellulose and chitosan on the MIL-101-derived nanoporous carbon (MDC) for gas adsorption from natural gas. The volumetric method was employed to investigate CO2 and CH4 uptake at the different temperatures and P < 21 bar. The incorporation of polysaccharides can enhance the CO2 binding affinity and lead to improved CO2 adsorption capacity. Structural analyses of the samples were characterized by N2 isotherms, FT-IR, TEM, TGA, XRD, FESEM and EDS with mapping analysis. Despite promising advances in the synthesis of MIL-101 as an excellent adsorbent in recent decades, this adsorbent has not yet been commercialized due to the toxic and expensive synthesis procedure of MIL-101. In this work, MIL-101 was synthesized from waste Cr source and without using hydrofluoric acid as a mineral agent. The highest uptake was observed for the nanocomposites of chitosan-MDC (MDC@CT). This behavior of MDC@CT can be explained by the presence of surface NH2-groups which act as primary adsorption sites for CO2. This study also assesses the potential effect of amine-based nitrogen-rich surface functional group loads on MDC@CT on gas adsorption properties. Tris(3-aminoethyl)amine was selected as the amine source in the preparation of amine-modified MDC@CT. The CO2 adsorption was best fitted by Langmuir model, while the CH4 adsorption followed the Freundlich models. The respective negative values of ΔG and ΔH revealed that the adsorption of both the gases were spontaneous and exothermic.

Effect of different surface functional groups on carbon supports toward methanol electro-oxidation of Pt nanoparticles

With an increased demand for efficient energy conversion system, nanoscale electrocatalysts have been intensively studied for high activity and stability. However, carbon support for nanoparticulate electrocatalyst has been generally thought to be inert for reaction pathway on metal nanocrystals. Therefore, material design for carbon support has mainly focused on development of high surface area with engineered pore structure, while surface state of the support has been largely neglected. Here, we demonstrate that surface functionalization of carbon support can modulate catalytic performance of Pt nanoparticle toward methanol electro-oxidation. Vulcan carbon (VC) surface was successfully modified by either acid oxidation or urea annealing, resulting in oxygen-rich (O-VC) and nitrogen-rich (N-VC) surface states, respectively. Modified surface state of carbon supports were investigated with XPS spectra. With controlled experiments, uniform Pt nanoparticles (d ~ 5 nm) were deposited on each carbon support for the same electrochemical surface area. Through high-resolution XPS analysis, electronic transfer from nitrogen to Pt was monitored in Pt/N-VC. With electron-enriched surface, Pt/N-VC reveals less oxophilic surface property compared to Pt/VC and Pt/O-VC. Notably, methanol electro-oxidation reaction largely depended on types of functional groups. Compared to Pt/VC, methanol oxidation decreased 30% in oxygen-rich Pt/O-VC after surface oxidation, while reaction rate increased double in nitrogen-rich Pt/N-VC. From CO bulk oxidation result, improved MOR activity of Pt/N-VC is attributed to larger number of available Pt active sites from attenuated adsorption of oxygen species. Therefore, this study highlights the importance of surface engineering in carbon supports for electrocatalysis.

Highly Efficient and Chemoselective Reduction of Nitroarenes Using Hybrid Ni@g‐C3N4 as Reusable Catalyst

AbstractHybrid Ni@g‐C3N4‐catalyzed highly chemoselective reduction of nitroarenes with high turnover frequency has been demonstrated using NaBH4 as source of hydrogen. Here, g‐C3N4 provides excellent stability to Ni(0) nanoparticles on its nitrogen rich surface and also facilitates the dissociation of NaBH4 resulting formation of active Νi‐H+ and Νi‐H‐ via cooperative effect.

Pluto’s ocean is capped and insulated by gas hydrates

Many icy Solar System bodies possess subsurface oceans. On Pluto, Sputnik Planitia’s location near the equator suggests the presence of a subsurface ocean and a locally thinned ice shell. To maintain an ocean, Pluto needs to retain heat inside. On the other hand, to maintain large variations in its thickness, Pluto’s ice shell needs to be cold. Here we show, by thermal evolution and viscous relaxation calculations, that the presence of a thin layer of clathrate hydrates (gas hydrates) at the base of the ice shell can explain both the long-term survival of the ocean and the maintenance of shell thickness contrasts. Clathrate hydrates act as a thermal insulator, preventing the ocean from completely freezing while keeping the ice shell cold and immobile. The most likely clathrate guest gas is methane, derived from precursor bodies and/or cracking of organic materials in the hot rocky core. Nitrogen molecules initially contained and/or produced later in the core would probably not be trapped as clathrate hydrates, instead supplying the nitrogen-rich surface and atmosphere. The formation of a thin clathrate hydrate layer cap to a subsurface ocean may be an important generic mechanism to maintain long-lived subsurface oceans in relatively large but minimally heated icy satellites and Kuiper belt objects. Pluto’s subsurface ocean and thickness variation in its ice shell may be maintained by a layer of methane clathrates forming an insulating cap to the ocean, according to calculations of thermal evolution and viscous relaxation.

Confined growth of NiCo2S4 nanosheets on carbon flakes derived from eggplant with enhanced performance for asymmetric supercapacitors

Transition metal oxides and compounds have been extensively investigated as electrode materials for high-performance supercapacitors. However, the poor rate performance and cyclic stability of these materials have hindered their practical applications. Herein, carbon flakes with an ultrahigh surface area (3608.4 m2 g−1) prepared from eggplant were used as substrates to enhance the electrical conductivity and overall capacitive performance of NiCo2S4 nanosheets. The composite exhibited a high specific capacitance (1394.5 F g−1 at 1 A g−1) which was 50% higher than that of the bare NiCo2S4 (989.8 F g−1 at 1 A g−1) and four times that of the eggplant-derived carbon (327 F g−1 at 1 A g−1). It also exhibited excellent rate capability (80.2% retention from 1 to 20 A g−1) and cyclic stability (124% retention after 10,000 cycles). These results were achieved by optimizing the pyrolysis of eggplant and the hydrothermal process which led to the confined growth of NiCo2S4 nanosheets on the carbon flakes due to coordination of Ni2+ and Co3+ cations to the polar groups of the carbon. The flake morphology, oxygen and nitrogen-rich surface and the ultrahigh surface area of the eggplant-derived carbon were found to be crucial for the well separation of NiCo2S4 nanosheets and consequently the excellent overall performance. Furthermore, asymmetric supercapacitors were constructed using the composite as the cathode and eggplant-derived carbon as the anode, which delivered a maximum energy density of 46.5 W h kg−1 at a power density of 801 W kg−1 and retained an energy density of 26.2 W h kg−1 at a maximum power density of 16 kW kg−1.

Origin of Life's Building Blocks in Carbon- and Nitrogen-Rich Surface Hydrothermal Vents.

There are two dominant and contrasting classes of origin of life scenarios: those predicting that life emerged in submarine hydrothermal systems, where chemical disequilibrium can provide an energy source for nascent life; and those predicting that life emerged within subaerial environments, where UV catalysis of reactions may occur to form the building blocks of life. Here, we describe a prebiotically plausible environment that draws on the strengths of both scenarios: surface hydrothermal vents. We show how key feedstock molecules for prebiotic chemistry can be produced in abundance in shallow and surficial hydrothermal systems. We calculate the chemistry of volcanic gases feeding these vents over a range of pressures and basalt C/N/O contents. If ultra-reducing carbon-rich nitrogen-rich gases interact with subsurface water at a volcanic vent they result in – concentrations of diacetylene (C4H2), acetylene (C2H2), cyanoacetylene (HC3N), hydrogen cyanide (HCN), bisulfite (likely in the form of salts containing HSO3−), hydrogen sulfide (HS−) and soluble iron in vent water. One key feedstock molecule, cyanamide (CH2N2), is not formed in significant quantities within this scenario, suggesting that it may need to be delivered exogenously, or formed from hydrogen cyanide either via organometallic compounds, or by some as yet-unknown chemical synthesis. Given the likely ubiquity of surface hydrothermal vents on young, hot, terrestrial planets, these results identify a prebiotically plausible local geochemical environment, which is also amenable to future lab-based simulation.

Microstructure and corrosion resistance of nitrogen-rich surface layers on AISI 304 stainless steel by rapid nitriding in a hollow cathode discharge

Nitriding treatments have been successfully applied to austenitic stainless steels to improve their hardness and tribological properties. However, at temperatures above 450 °C, conventional plasma nitriding processes decrease the corrosion resistance due to the formation of CrN phases within the modified layer. In this work, AISI 304 austenitic stainless steels were efficiently treated by rapid plasma nitriding at a high temperature of 530 °C in a hollow cathode discharge. The enhanced ionization obtained in the hollow cathode configuration provided a high current density and, consequently, a high temperature could be attained in a short time. The nitrided layers were characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results indicated that the dual-layer structure of the nitrided layer consists of a high-N face-centered cubic structure with a free CrN precipitate outer (top) layer and a nitrogen-expanded austenite S-phase bottom layer. The rapid nitriding-assisted hollow cathode discharge technique permits the use of high temperatures, as high as 530 °C, without promoting degradation in the corrosion resistance of stainless steel.

Enhanced Thermochemical Stability of CH3NH3PbI3 Perovskite Films on Zinc Oxides via New Precursors and Surface Engineering

Hydroxyl groups on the surface of ZnO films lead to the chemical decomposition of CH3NH3PbI3 perovskite films during thermal annealing, which limits the application of ZnO as a facile electron-transporting layer (ETL) in perovskite solar cells. In this work, we report a new recipe that leads to substantially reduced hydroxyl groups on the surface of the resulting ZnO films by employing polyethylenimine (PEI) to replace generally used ethanolamine in the precursor solutions. Films derived from the PEI-containing precursors are denoted as P-ZnO and those from the ethanolamine-containing precursors as E-ZnO. Besides the fewer hydroxyl groups that alleviate the thermochemical decomposition of CH3NH3PbI3 perovskite films, P-ZnO also provides a template for the fixation of fullerene ([6,6]-phenyl-C61-butyric acid methyl ester, PCBM) owing to its nitrogen-rich surface that can interact with PCBM. The fullerene was used to block the direct contact between P-ZnO and CH3NH3PbI3 films and therefore further enhance the thermochemical stability of perovskite films. As a result, perovskite solar cells based on the P-ZnO/PCBM ETL yield an optimal power conversion efficiency (PCE) of 15.38%. We also adopt P-ZnO as the ETL for organic solar cells that yield a remarkable PCE of 10.5% based on the PBDB-T:ITIC photoactive layer.

Pre-nitridation induced In incorporation in InxGa1−xN nanorods on Si(111) grown by molecular beam epitaxy

We address the issue of obtaining high quality green emitting InGaN nanorods without any phase separation. Role of pre-nitridation of the Si(111) substrate and growth, temperature on the morphology, structural and optical properties of InxGa1−xN films grown by plasma assisted molecular beam epitaxy, has been studied. The nitrogen rich growth environment and surface nitridation results in the formation of vertically well-aligned single crystalline nanorods that are coalesced and isolated at 400 °C and 500 °C, respectively. In incorporation is also seen to be enhanced to ≈28% at 400 °C to yield a stable green emission, while the nanorods grown at 500 °C show blue band-edge emission. The orientation, phase separations, and optical properties characterized by Reflection High Energy Electron Diffraction, Field Emission Scanning Electron Microscopy, high resolution x-ray diffraction, x-ray photoelectron spectroscopy, and photoluminescence are corroborated to understand the underlying mechanism. The study optimizes conditions to grow high quality catalyst-free well-aligned InGaN rods on nitrided Si surface, whose band-edge emission can be tuned from blue to green by sheer control of the substrate temperature.

Multifunctional Plasma-Polymerized Film: Toward Better Anticorrosion Property, Enhanced Cellular Growth Ability, and Attenuated Inflammatory and Histological Responses.

Over the past few decades, plasma surface modification technique has been widely used to selectively improve surface properties and biocompatibility of materials. In this paper, at first a simple and effective method for the deposition of plasma-polymerized allylamine films onto 316L stainless steel (SS) from an allylamine/nitrogen gas mixture was developed. These amine-rich films were characterized by grazing incidence attenuated total reflection Fourier transform infrared spectroscopy (GATR-FTIR) and X-ray photoelectron spectroscopy (XPS), and the anticorrosion properties were demonstrated by electrochemical analysis. Micro-BCA and quartz crystal microbalance with dissipation (QCM-D) results showed that the higher density of amine groups of the allylamine-nitrogen plasma-polymerized film contributes to more serum protein adsorption which may enhance the adhesion and growth of cells on biomaterials. The in vitro and in vivo anti-inflammatory evaluation was performed and it has been confirmed that these nitrogen-rich surfaces could inhibit the activation of macrophages by down-regulation of the pro-inflammatory cytokines TNF-α and IL-6, and exhibit acceptable tissue-compatibility. It was found that with the help of nitrogen, plasma-polymerized allylamine films presented superior biological properties and provided a high potential application in surface modification of biomedical substrate with desirable clinical performance.

Obtenção de austenita expandida (fase S): Nitretação por plasma em baixa temperatura x SHTPN - Parte 2

Corpos de prova de aço inoxidável austenítico ISO 5832-1 apresentando camada superficial rica em nitrogênio (fase S), obtidas pelos processos de nitretação por plasma em baixa temperatura e SHTPN (Solution Heat Treatment after Plasma Nitriding), caracterizadas em trabalho anterior, além de amostras na condição de fornecimento, ou seja, solubilizadas, e amostras nitretadas por plasma em 750 ºC por 3 horas foram testadas quanto à resistência a corrosão. A resistência a corrosão foi avaliada com base no método de polarização potenciodinâmica e obtenção de potencial de circuito aberto (Ecorr vs tempo) em uma solução de 0,5 M NaCl. Os resultados comprovaram o ganho na resistência a corrosão localizada proveniente do nitrogênio em solução sólida, tanto para nitretação em baixa temperatura quanto no processo SHTPN, bem como o efeito deletério proveniente da precipitação do nitreto de cromo.