Surface Functionalization of Face Masks with Cold Plasma and Its Effect in Anchoring Polyphenols Extracted from Agri-Food.

To improve the capability of non-woven polypropylene-based fabric (NWF-PP) used for face mask production to retain active biomolecules such as polyphenols, the surface functionalization of NWF-PP-directly cut from face masks-was carried out by employing cold plasma with oxygen. The nature/structure of the functional groups, as well as the degree of functionalization, were evaluated by ATR-FTIR and XPS by varying the experimental conditions (generator power, treatment time, and oxygen flow). The effects of plasma activation on mechanical and morphological characteristics were evaluated by stress-strain measurements and SEM analysis. The ability of functionalized NWF-PP to firmly anchor polyphenols extracted from cloves was estimated by ATR-FTIR analysis, IR imaging, extractions in physiological solution, and OIT analysis (before and after extraction), as well as by SEM analysis. All the results obtained converge in showing that, although the plasma treatment causes changes-not only on the surface-with certain detriment to the mechanical performance of the NWF-PP, the incorporated functionalities are able to retain/anchor the active molecules extracted from the cloves, thus stabilizing the treated surfaces against thermo-oxidation even after prolonged extraction.

Conversion of the Propane-Butane Fraction into Arenes on MFI Zeolites Modified by Zinc Oxide and Activated by Low-Temperature Plasma.

The effect of modification of MFI zeolite 1-5 wt.% ZnO activated by plasma on acid and catalytic properties in the conversion of the propane-butane fraction into arenes was investigated. The high-silica zeolites with silicate module 45 were synthesized from alkaline alumina-silica gels in the presence of an 'X-oil' organic structure-forming additive. The modification of the zeolite with zinc was carried out by impregnating the zeolite granules in the H-form with an aqueous solution of Zn(NO3)2. The obtained zeolites were characterized by X-ray phase analysis and IR spectroscopy. It is shown that the synthesized zeolites belong to the high-silica MFI zeolites. The study of microporous zeolite-containing catalysts during the conversion of C3-C4 alkanes to aromatic hydrocarbons made it possible to establish that the highest yield of aromatic hydrocarbons is observed on zeolite catalysts modified with 1 and 3% ZnO and amount to 63.7 and 64.4% at 600 °C, respectively, which is 7.7-8.4% more than on the original zeolite. The preliminary activation of microporous zeolites modified with 1-5% ZnO and plasma leads to an increase in the yield of aromatic hydrocarbons from the propane-butane fraction; the maximum yield of arenes is observed in zeolite catalysts modified with 1 and 3% ZnO and activated by plasma, amounting to 64.9 and 65.5% at 600 °C, respectively, which is 8.9-9.5% more than on the initial zeolite. The activity of the zeolite catalysts modified by ZnO and activated by plasma show good agreement with their acid properties. Activation of the zeolites modified by 1 and 3% ZnO and plasma leads to an increase in the concentration of the weak acid sites of the catalyst to 707 and 764 mmol/g in comparison with plasma-inactivated 1 and 3% ZnO/ZKE-XM catalysts at 626 and 572 mmol/g, respectively.

Intrinsic Kinetics of Dimethyl Ether Synthesis from Plasma Activation of CO2 Hydrogenation over Cu-Fe-Ce/HZSM-5.

CO2 is activated in a plasma reactor followed by hydrogenation over a Cu-Fe-Ce/HZSM-5 catalyst, and the intrinsic kinetics of the plasma catalytic process are studied. Compared with CO2 hydrogenation using Cu-Fe-Ce/HZSM-5 alone, the CO2 conversion and the dimethyl ether selectivity for the plasma catalytic process are increased by 16.3 %, and 10.1 %, respectively, indicating that the CO2 was activated by the plasma to promote hydrogenation. A study of the intrinsic kinetics shows that the activation energies of methanol formation, the reverse water-gas shift reaction, and methanol dehydration to dimethyl ether are 149.34, 75.47, and 73.18 kJ mol-1 , respectively, which are lower than if Cu-Fe-Ce/HZSM-5 is used without plasma, indicating that the activation of CO2 in the plasma reduces the activation energy of the hydrogenation reaction and improves the yield of dimethyl ether.

Electrospun microcrystalline cellulose/chitosan porous composite nanofibrous membranes modified by non-thermal plasma for gaseous formaldehyde adsorption.

To develop a green and facile adsorbent for removing indoor polluted formaldehyde (HCHO) gas, the biomass porous nanofibrous membranes (BPNMs) derived from microcrystalline cellulose/chitosan were fabricated by electrospinning. The enhanced chemical adsorption sites with diverse oxygen (O) and nitrogen (N)-containing functional groups were introduced on the surface of BPNMs by non-thermal plasma modification under carbon dioxide (CO2) and nitrogen (N2) atmospheres. The average nanofiber diameters of nanofibrous membranes and their nanomechanical elastic modulus and hardness values decreased from 341 nm to 175-317 nm and from 2.00 GPa and 0.25 GPa to 1.70 GPa and 0.21 GPa, respectively, after plasma activation. The plasma-activated nanofibers showed superior hydrophilicity (WCA = 0°) and higher crystallinity than that of the control. The optimal HCHO adsorption capacity (134.16 mg g-1) of BPNMs was achieved under a N2 atmosphere at a plasma power of 30 W and for 3 min, which was 62.42 % higher compared with the control. Pyrrolic N, pyridinic N, CO and O-C=O were the most significant O and N-containing functional groups for the improved chemical adsorption of the BPNMs. The adsorption mechanism involved a synergistic combination of physical and chemical adsorption. This study provides a novel strategy that combines clean plasma activation with electrospinning to efficiently remove gaseous HCHO.

Optimization of Laminated Bio-Polymer Fabrication for Food Packaging Application: A Sustainable Plasma-Activated Approach.

The current level of packaging consumption imposes a need to fabricate single-use food packaging with renewable and compostable materials, such as bio-polyesters (e.g., polylactic acid, PLA and polybutylene succinate, PBS) or cellulose, but their use is still problematic. Fabrication of bio-compostable composites can specifically address impeding challenges, and adhesive lamination, achieved with compostable glue, is becoming more and more popular with respect to the less versatile hot lamination. In this context, plasma activation, a chemical-free oxidation technique of a material's surface, is used to increase the affinity of three different biomaterials (cellulose, PLA and PBS) toward a compostable polyurethane adhesive to decrease its amount by gluing bio-polyesters to cellulose. Optical Microscopy reveals activation conditions that do not affect the integrity of the materials, while Water Contact Analyses confirm the activation of the surfaces, with contact angles decreased to roughly 50 deg in all cases. Unexpectedly, ζ-potential analyses and subtractive infrared spectroscopy highlight how the activation performed superficially etches cellulose, while for both PLA and PBS, a general decrease in surface potential and an increase in superficial hydroxyl group populations confirm the achievement of the desired oxidation. Thus, we rationalize continuous activation conditions to treat PLA and PBS and to glue them to neat cellulose. While no beneficial effect is observed with activated PLA, bi-laminate composites fabricated with activated PBS fulfill the benchmark for adhesion strength using less than before, while oxygen permeation analyses exclude plasma-induced etching even at a nanoscale.

Effect of non-thermal plasma treatment and resin cements on the bond strength of zirconia ceramics with different yttria concentrations.

OBJECTIVES: To investigate the effect of different surface treatments and resin cements on the shear bond strength of zirconia ceramics with different yttria concentrations. METHODS: Zirconia blocks characterized by different yttria concentrations [Vita YZ HT (HT), Vita YZ ST (ST) and Vita YZ XT (XT)] were used to prepare disc-shaped specimens (n=252). Specimens prepared to investigate shear bond strength (SBS), water contact angle and surface roughness (Ra) were divided into four subgroups; control (C), sandblasting (S), sandblasting + nonthermal plasma treatment (SNTP) and nonthermal plasma treatment (NTP). For SBS testing, specimens were further divided into two groups (n=108) according to the luting cement used [Panavia F2.0 (P) and Rely X U200 (R)]. The water contact angles were determined by sessile drop technique and Ra was analyzed with optical profilometer. SBS tests were performed in a universal testing machine at a crosshead speed of 0.5 mm/min. The data sets were statistically analyzed with two and three-way ANOVAs followed by post-hoc comparisons (α=0.05). RESULTS: The water contact angle and Ra data were significantly affected by surface treatments. The mean Ra values of ST and XT were significantly lower than HT for the surface treatment groups of C and NTP. The SBS values were significantly different among the groups subjected to different surface treatments. The mean SBS values of surface treatment groups (S, SNTP and NTP) when cemented with R were significantly higher than the groups of C (p<0.05). CONCLUSIONS: For the tested zirconia ceramics with different yttria concentrations, non-thermal plasma activation helps to improve SBS and is a promising tool in practical use.

Glass-to-Glass Fusion Bonding Quality and Strength Evaluation with Time, Applied Force, and Heat.

A bonding process was developed for glass-to-glass fusion bonding using Borofloat 33 wafers, resulting in high bonding yield and high flexural strength. The Borofloat 33 wafers went through a two-step process with a pre-bond and high-temperature bond in a furnace. The pre-bond process included surface activation bonding using O2 plasma and N2 microwave (MW) radical activation, where the glass wafers were brought into contact in a vacuum environment in an EVG 501 Wafer Bonder. The optimal hold time in the EVG 501 Wafer bonder was investigated and concluded to be a 3 h hold time. The bonding parameters in the furnace were investigated for hold time, applied force, and high bonding temperature. It was concluded that the optimal parameters for glass-to-glass Borofloat 33 wafer bonding were at 550 °C with a hold time of 1 h with 550 N of applied force.

Direct Bonding Method for Completely Cured Polyimide by Surface Activation and Wetting.

Polymer adhesives have emerged as a promising dielectric passivation layer in hybrid bonding for 3D integration, but they raise misalignment problems during curing. In this work, the synergistic effect of oxygen plasma surface activation and wetting is utilized to achieve bonding between completed cured polyimides. The optimized process achieves a void-less bonding with a maximum shear strength of 35.3 MPa at a low temperature of 250 °C in merely 2 min, significantly shortening the bonding period and decreasing thermal stress. It is found that the plasma activation generates hydrophilic groups on the polyimide surface, and the wetting process further introduces more -OH groups and water molecules on the activated polyimide surface. The synergistic process of plasma activation and wetting facilitates the bridging of polyimide interfaces to achieve bonding, providing an alternative path for adhesive bonding in 3D integration.

Silanization of Plasma-Activated Hexamethyldisiloxane-Based Plasma Polymers for Substrate-Independent Deposition of Coatings with Controlled Surface Chemistry.

Plasma polymerization has emerged as an appealing technique for surface modification because of its advantages over a variety of conventional techniques, including ease-of-use and the possibility to modify nearly any substrate. One of the main challenges of plasma polymer-based surface modification, however, is having control over the coating chemistry, as plasma deposition generates a diversity of chemical structures. Therefore, this study presents an alternative plasma-based method for the fabrication of coatings that contain selective functionalities. In a first step, hexamethyldisiloxane (HMDSO) plasma polymerization is performed in a medium-pressure dielectric barrier discharge (DBD) to deposit polydimethylsiloxane (PDMS)-like coatings. In a second step, this coating is exposed to an air plasma in a similar DBD setup to introduce silanol groups on the surface. These groups are used in a third and final step as anchoring points for grafting of (3-aminopropyl)triethoxysilane (APTES) and (3-bromopropyl)trichlorosilane (BrPTCS) to selectively introduce amino or bromo groups, respectively. X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) measurements indicated that the first two steps were successful. Moreover, the coating could be synthesized on three different surfaces, namely, glass, ultrahigh-molecular-weight polyethylene, and polytetrafluoroethylene, indicating the wide applicability of the developed procedure. Afterward, XPS also proved that the APTES and BrPTCS grafting resulted in the formation of a coating containing primary amines and alkyl bromides, respectively, in combination with an organosilicon matrix containing silanol groups as remaining reactive groups, proving the successful synthesis of selective functional plasma-based coatings. The intermediate air-plasma-activation step was demonstrated to be necessary for successful and stable grafting of the final layer. In conclusion, this study established a general procedure for the development of coatings with selective functionality that can be applied on a wide variety of substrates for, e.g., biosensor applications, biomolecule, or polymer immobilization or for the synthesis of antibacterial coatings.

Electrostatic self-assembly approach in the deposition of bio-functional chitosan-based layers enriched with caffeic acid on Ti-6Al-7Nb alloys by alternate immersion.

Tailoring surface properties by layer-by-layer (LBL) deposition directed on the construction of complex multilayer coatings with nanoscale precision enables the development of novel structures and devices with desired functional properties (i.e., osseointegration, bactericidal activity, biocorrosion protection). Herein, electrostatic self-assembly was applied to fabricate biopolymer-based coatings involving chitosan (CSM) and alginate (AL) enriched with caffeic acid (CA) on Ti-6Al-7Nb alloyed surfaces. The method of CA grafting onto the chitosan backbone (CA-g-CSM) as well as all used reagents for implant functionalization were chosen as green and sustainable approach. The final procedure of surface modification of the Ti-6Al-7Nb alloy consists of three steps: (i) chemical treatment in Piranha solution, (ii) plasma chemical-activation of the Ti alloy surface in a RF CVD (Radio Frequency Chemical Vapour Deposition) reactor using Ar, O2 and NH3 gaseous precursors, and (iii) a multi-step deposition of bio-functional coatings via dip-coating method. Corrosion tests have revealed that the resulting chitosan-based coatings, also these involving CA, block the specimen surface and hinder corrosion of titanium alloy. Furthermore, the antioxidant layers are characterized by beneficial level of roughness (Ra up ca. 350 nm) and moderate hydrophilicity (59°) with the dispersion part of conducive surface energy ca. 30 mJ/m2. Noteworthy, all coatings are biocompatible as the intact morphology of cultured eukaryotic cells ensured proper growth and proliferation, while exhibit bacteriostatic character, particularly in contact with Gram-(-) bacteria (E. coli). The study indicates that the applied simple sustainable strategy has contributed significantly to obtaining homogeneous, stable, and biocompatible while antibacterial biopolymer-based coatings.

Determination of cytotoxicity following oxidative treatment of pharmaceutical residues in wastewater.

Pharmaceutical residues are released in the aquatic environment due to incomplete removal from wastewater. With the presence of multiple chemicals in sewage waters, contaminants may adversely affect the effectiveness of a wastewater treatment plant (WWTP). In certain cases, discharged metabolites are transformed back into their pristine structure and become bioactive again. Other compounds are persistent and can withstand conventional wastewater treatment. When WWTP effluents are released in surface waters, pristine and persistent chemicals can affect the aquatic environment. To complement WWTPs and circumvent incomplete removal of unwanted chemicals or pharmaceuticals, on-site wastewater treatment can contribute to their removal. Advanced oxidation processes (AOPs) are very powerful techniques for the abatement of pharmaceuticals, however, under certain circumstances reactive toxic by-products can be produced. We studied the application of on-site AOPs in a laboratory setting. It is expected that treatment at the contamination source can eliminate the worst polluters. Thermal plasma and UV/H2O2 oxidation were applied on simulation matrices, Milli-Q and synthetic sewage water spiked with 10 different pharmaceuticals in a range of 0.1 up to 2400 µg/L. In addition, untreated end-of-pipe hospital effluent was also subjected to oxidative treatment. The matrices were activated for 180 min and added to cultured HeLa cells. The cells were 24 h and 48 h exposed at 37 °C and subsequently markers for oxidative stress and viability were measured. During the UV/H2O2 treatment periods no toxicity was observed. After thermal plasma activation of Milli-Q water (150 and 180 min) toxicity was observed. Direct application of thermal plasma treatment in hospital sewage water caused elimination of toxic substances. The low cytotoxicity of treated pharmaceutical residues is likely to become negligible if plasma pre-treated on-site wastewater is further diluted with other sewage water streams, before reaching the WWTP. Our study suggests that AOPs may be promising technologies to remove a substantial portion of pharmaceutical components by degradation at the source. Further studies will have to be performed to verify the feasibility of upscaling this technology from the benchtop to practice.

Low Temperature Hydrophilic SiC Wafer Level Direct Bonding for Ultrahigh-Voltage Device Applications.

SiC direct bonding using O2 plasma activation is investigated in this work. SiC substrate and n- SiC epitaxy growth layer are activated with an optimized duration of 60s and power of the oxygen ion beam source at 20 W. After O2 plasma activation, both the SiC substrate and n- SiC epitaxy growth layer present a sufficient hydrophilic surface for bonding. The two 4-inch wafers are prebonded at room temperature followed by an annealing process in an atmospheric N2 ambient for 3 h at 300 °C. The scanning results obtained by C-mode scanning acoustic microscopy (C-SAM) shows a high bonding uniformity. The bonding strength of 1473 mJ/m2 is achieved. The bonding mechanisms are investigated through interface analysis by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). Oxygen is found between the two interfaces, which indicates Si-O and C-O are formed at the bonding interface. However, a C-rich area is also detected at the bonding interface, which reveals the formation of C-C bonds in the activated SiC surface layer. These results show the potential of low cost and efficient surface activation method for SiC direct bonding for ultrahigh-voltage devices applications.

Argon and Argon-Oxygen Plasma Surface Modification of Gelatin Nanofibers for Tissue Engineering Applications.

In the present study, we developed a novel approach for functionalization of gelatin nanofibers using the plasma method for tissue engineering applications. For this purpose, tannic acid-crosslinked gelatin nanofibers were fabricated with electrospinning, followed by treatment with argon and argon-oxygen plasmas in a vacuum chamber. Samples were evaluated by using scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle (CA) and X-ray diffraction (XRD). The biological activity of plasma treated gelatin nanofibers were further investigated by using fibroblasts as cell models. SEM studies showed that the average diameter and the surface morphology of nanofibers did not change after plasma treatment. However, the mean surface roughness (RMS) of samples were increased due to plasma activation. ATR-FTIR spectroscopy demonstrated several new bands on plasma treated fibers related to the plasma ionization of nanofibers. The CA test results stated that the surface of nanofibers became completely hydrophilic after argon-oxygen plasma treatment. Finally, increasing the polarity of crosslinked gelatin after plasma treatment resulted in an increase of the number of fibroblast cells. Overall, results expressed that our developed method could open new insights into the application of the plasma process for functionalization of biomedical scaffolds. Moreover, the cooperative interplay between gelatin biomaterials and argon/argon-oxygen plasmas discovered a key composition showing promising biocompatibility towards biological cells. Therefore, we strongly recommend plasma surface modification of nanofiber scaffolds as a pretreatment process for tissue engineering applications.

Insight into the Properties of Plasmonic Au/TiO2 Activated by O2/Ar Plasma.

The performance of CO oxidation over plasmonic Au/TiO2 photocatalysts is largely determined by the electric discharge characteristics and physicochemical properties of discharge gas. To explore the activation mechanism of Au/TiO2, an O2 and Ar mixture gas as a discharge gas was employed to activate Au/TiO2. The photocatalytic activity in CO oxidation over activated Au/TiO2 was obtained, and the electric discharge characteristics, Au nanoparticle size, surface chemical state, optical property and CO chemisorption were thoroughly characterized. As the O2 content increases from 10% to 50%, the amplitude of the current pulses increases, but the number of pulses and the discharge power decrease. The photocatalytic activity of Au/TiO2 rises rapidly at first and then remains constant at 75% when the O2 content is above 50%. Compared with the discharge gas of 10% and 30% O2/Ar, the sample activated by 50% O2/Ar plasma possesses less metallic Au and more surface oxygen species and carbonate species by X-ray photoelectron spectroscopy, which is consistent with UV-vis diffuse reflectance spectra and CO chemisorption. The CO chemisorption capacities of the activated samples are the same at a long exposure time due to the approximate Au nanoparticle size observed by transmission electron microscopy. An increase in carbonate species generated from the oxygen species on the surface of TiO2 is discovered.

Effectiveness of Plasma-Treated Hydrogen Peroxide Mist Disinfection in Various Hospital Environments.

Hospital environments are associated with a high risk of infection. As plasma-treated hydrogen peroxide mist disinfection has a higher disinfection efficacy, we tested the efficacy of plasma-treated hydrogen peroxide mist disinfection on several surfaces in various hospital environments. Disinfection was performed in 23 rooms across different hospital environments, including hospital wards, outpatient departments (OPDs), and emergency rooms. A total of 459 surfaces were swabbed before/after disinfection. Surfaces were also divided into plastic, metal, wood, leather, ceramic, silicone, and glass for further analyses. Only gram-positive bacteria were statistically analyzed because the number of gram-negative bacteria and mold was insufficient. Most colony-forming units (CFUs) of gram-positive bacteria were observed in OPDs and on leather materials before disinfection. The proportion of surfaces that showed a percentage decrease in CFU values of more than 90% after disinfection were as follows: OPDs (85%), hospital wards (99%), and emergency rooms (100%); plastic (97%), metal (83%), wood (84%), leather (81%), and others (87%). Plasma-treated hydrogen peroxide mist disinfection resulted in a significant decrease in the CFU values of gram-positive bacteria in various environments. Plasma-treated hydrogen peroxide mist disinfection is an effective and efficient method of disinfecting various hospital environments.

Surface activation with oxygen plasma promotes osteogenesis with enhanced extracellular matrix formation in three-dimensional microporous scaffolds.

Various types of synthetic polyesters have been developed as biomaterials for tissue engineering. These materials commonly possess biodegradability, biocompatibility, and formability, which are preferable properties for bone regeneration. The major challenge of using synthetic polyesters is the result of low cell affinity due to their hydrophobic nature, which hinders efficient cell seeding and active cell dynamics. To improve wettability, plasma treatment is widely used in industry. Here, we performed surface activation with oxygen plasma to hydrophobic copolymers, poly(l-lactide-co-trimethylene carbonate), which were shaped in 2D films and 3D microporous scaffolds, and then we evaluated the resulting surface properties and the cellular responses of rat bone marrow stem cells (rBMSC) to the material. Using scanning electron microscopy and Fourier-transform infrared spectroscopy, we demonstrated that short-term plasma treatment increased nanotopographical surface roughness and wettability with minimal change in surface chemistry. On treated surfaces, initial cell adhesion and elongation were significantly promoted, and seeding efficiency was improved. In an osteoinductive environment, rBMSC on plasma-treated scaffolds exhibited accelerated osteogenic differentiation with osteogenic markers including RUNX2, osterix, bone sialoprotein, and osteocalcin upregulated, and a greater amount of collagen matrix and mineral deposition were found. This study shows the utility of plasma surface activation for polymeric scaffolds in bone tissue engineering.

Aluminum Nitride to Silicon Direct Bonding for an Alternative Silicon-On-Insulator Platform.

The next generation of microelectromechanical systems (MEMS) requires new materials and platforms that can exploit the intrinsic properties of advanced materials and structures, such as materials with high thermal conductivity, broad optical transmission spectra, piezoelectric properties, and miniaturization potential. Therefore, we need to look beyond standard SiO2-based silicon-on-insulator (SOI) structures to realize ubiquitous MEMS. This work proposes using AlN as an alternative SOI structure due to several inherent material property advantages as well as functional advantages. This work presents the results of reactively sputtered AlN films on a Si handle wafer bonded with a mirror-polished Si device wafer. Wafer bonding was achieved by using hydrophilic wafer bonding processes, which was realized by appropriate polymerization of the prebonding surfaces. Plasma activation of the AlN surface included O2, Ar, SF6, SF6 + Ar, and/or SF6 + O2, which resulted in a change in the chemical and topography state of the surface. Changes in the AlN surface properties included enhanced hydrophilicity, reduced surface roughness, and low nanotopography, components essential for successful hydrophilic direct wafer bonding. Wafer bonding experiments were carried out using promising surface activation methods. The results showed a multilayered bonding interface of Si(Device)/SiO2/ALON/AlN/Si(Handle) with fluorine in the aluminum oxynitride layer from the proceeding AlN surface activation process. More notably, this work provided wafer bonding tensile strength results of the AlN alternative SOI structure that compares with the traditional SiO2 SOI counterpart, making AlN to Si direct bonding an attractive alternative SOI platform.

Characteristics of hybrid chitosan/phospholipid-sterol, peptide coatings on plasma activated PEEK polymer.

In this paper, we propose a method of obtaining multi-component surface coatings on PEEK polymer, which is becoming increasingly interested in a very wide branch of medicine - orthopedics. Thanks to the plasma techniques used and due to the presence of chitosan, the materials obtained are characterized by sterility, antisepticity, can accelerate wound healing, and serve as a drug delivery system directly to the tissues in need. In addition, the use of ternary Langmuir-Blodgett (lipid-sterol, peptide) films has resulted in significant change of surfaces polarity. The physico-chemical properties of the ternary Langmuir films obtained on the water subphase were tested exploiting Langmuir trough and a Brewster angle microscope. Then they were transferred to the modified surfaces of the solid PEEK polymer, where changes in wettability as well as surface free energy were determined by the type of substrate/coating and the hybrid composition. Additionally, surface chemistry was studied applying time of flight secondary ion mass spectrometry.

The Wafer-Level Integration of Single-Crystal LiNbO3 on Silicon via Polyimide Material.

In situ measurements of sensing signals in space platforms requires that the micro-electro-mechanical system (MEMS) sensors be located directly at the point to be measured and in contact with the subject to be measured. Traditional radiation-tolerant silicon-based MEMS sensors cannot acquire spatial signals directly. Compared to silicon-based structures, LiNbO3 single crystalline has wide application prospects in the aerospace field owing to its excellent corrosion resistance, low-temperature resistance and radiation resistance. In our work, 4-inch LiNbO3 and LiNbO3/Cr/Au wafers are fabricated to silicon substrate by means of a polyimide bonding method, respectively. The low-temperature bonding process (≤100 °C) is also useful for heterostructure to avoid wafer fragmentation results from a coefficient of thermal expansion (CTE) mismatch. The hydrophilic polyimide surfaces result from the increasing of -OH groups were acquired based on contact angle and X-ray photoelectron spectroscopy characterizations. A tight and defect-free bonding interface was confirmed by scanning electron microscopy. More importantly, benefiting from low-temperature tolerance and radiation-hardened properties of polyimide material, the bonding strength of the heterostructure based on oxygen plasma activation achieved 6.582 MPa and 3.339 MPa corresponding to room temperature and ultra-low temperature (≈ -263.15 °C), which meets the bonding strength requirements of aerospace applications.

Reactive Plasma N-Doping of Amorphous Carbon Electrodes: Decoupling Disorder and Chemical Effects on Capacitive and Electrocatalytic Performance.

Nitrogen-free amorphous carbon thin films prepared via sputtering followed by graphitization, were used as precursor materials for the creation of N-doped carbon electrodes with varying degrees of amorphization. Incorporation of N-sites was achieved via nitrogen plasma treatments which resulted in both surface functionalization and amorphization of the carbon electrode materials. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to monitor composition and carbon organization: results indicate incorporation of predominantly pyrrolic-N sites after relatively short treatment cycles (5 min or less), accompanied by an initial etching of amorphous regions followed by a slower process of amorphization of graphitized clusters. By leveraging the difference in the rate of these two processes it was possible to investigate the effects of chemical N-sites and C-defect sites on their electrochemical response. The materials were tested as metal-free electrocatalysts in the oxygen reduction reaction (ORR) in alkaline conditions. We find that the introduction of predominantly pyrrolic-N sites via plasma modification results in improvements in selectivity in the ORR, relative to the nitrogen-free precursor material. Introduction of defects through prolonged plasma exposure has a more pronounced and beneficial effect on ORR descriptors than introduction of N-sites alone, leading to both increased onset potentials, and reduced hydroperoxide yields relative to the nitrogen-free carbon material. Our results suggest that increased structural disorder/heterogeneity results in the introduction of carbon sites that might either serve as main activity sites, or that enhance the effects of N-functionalities in the ORR via synergistic effects.