Improvement of the stability of plasma polymerized acrylic acid coating deposited on PS beads in a fluidized bed reactor

The present study deals with the deposition of plasma polymerized acrylic acid (PPAA) coatings on the surface of polystyrene beads. XPS analysis showed that the COOH content of the unwashed surface decreased by increasing the power, whereas the resistance to washing was improved weakly. The results showed that the use of an argon pretreatment of PS beads before plasma deposition of AA leads to a strong adhesion between PPAA coating and the underlying PS, reinforcing its stability. The study of the influence of the plasma deposition time clearly showed that the COOH content increased with the plasma treatment time, due to a better coverage of the PS beads. However, the stability of such coatings decreased inversely with the plasma treatment time due to their delamination

Stable Polymerized Acrylic Acid coating deposited on Polyethylene (PE) films in a low frequency discharge

Plasma polymerized acrylic acid (PPAA) coatings were deposited on PE films, in a 70 kHz low pressure plasma reactor, at various plasma powers. The COOH retention of PPAA coatings and its stability to washing in water were investigated by XPS, WCA (water contact angle), FTIR, ellipsometry and SEM analyses. The results have shown that the use of higher powers leads to an increase of the stability of the coating due to a high degree of cross-linking. Under optimized conditions, it is possible to obtain stable PPAA coatings which resist to washing with a COOH retention rate of 15% on PE, which is much higher than the coating deposited in a 13.56 MHz discharge. This high stability of the coatings observed in the low frequency discharge, which is somewhat similar to DC glow discharges, is probably due to the ions which play an important role in the cross linking process of the coatings. Optical emission spectroscopy measurements (OES) have shown good correlation between the CO density in the gas phase and the carboxylic content of PPAA coating

Adhesion, wettability and mechanical properties of ammonia - and helium - plasma - treated polypropylene

The physicochemical modifications of ammonia-treated polypropylene (PP) films have been studied and characterized in terms of acid-base properties using the contact angle titration method and X-ray photoelectron spectroscopy in conjunction with a molecular probe technique using chloroform as a reference lewis acid. These techniques have shown that PP that have been treated for between 0.7 - 1 are basic in character. For longer treatment times, the basic character of the surfaces decreases, as shown by the above techniques and confirmed by time of flight - secondary ion mass spectroscopy (tof - SIMS). On the other hand, for such treatment times, a degradation of the adhesion and mechanical properties was observed. The ageing of an ammonia-plasma-treated PP was limited by a helium (He) plasma pretreatment known to crosslink the surface, stabilizing in this way the wettability, adhesion and mechanical properties. Tof-SIMS was perdormed on helium treated high Density Polyethylene (HDPE) in order to point out the structural modifications

Development of oligonucleotide microarray from plasma polymerized acrylic acid

This paper presents the manufacturing of biochips by using the COOH– derived polymer coating deposited by plasma polymerization of acrylic acid. This technology is based on depositing a thin layer obtained by plasma polymerization of acrylic acid which allows a further covalent immobilization of biomolecules on glass substrates. The plasma power value was optimized to maximize the stability of plasma polymerized acrylic acid (PPAA) coatings in water, which has a very important role for such applications. In order to obtain a covalent immobilization of DNA probes on the PPAA coated surface, the activation protocol of carboxylic function was carried out with the help of N-Hydroxy Succinimide and 1-Ethyl-3-(3-DimethylAminopropyl) Carbodiimide. The efficiency of PPAA coated in microarray applications was compared with two types of commercial slides. Such surfaces have shown very interesting results in terms of relative density of attached DNA probe molecules and signal-to-background ratio measured for target DNA hybridization. Nonspecific DNA bonding measurements showed only a small amount of nonspecific physisorption between the DNA probe and the PPAA-activated surfaces. This work shows that the plasma polymerization technique can be successfully applied to produce a high-quality glass surface for the manufacturing of DNA arrays

Catkin liked nano-Co3O4 catalyst built-in organic microreactor by PEMOCVD method for trace CO oxidation at room temperature

In this paper, tricobalt tetraoxide (Co3O4) catalyst was coated on the polydimethylsiloxane microchannel by the plasma-enhanced metal-organic chemical vapor deposition technology. The obtained Co3O4 film was characterized by SEM, XRD, XPS, and TEM, and the results show that the as-deposited Co3O4 film was initially composed of many cauliflowers-shaped microclusters. Also, the microcauliflower was transformed from an amorphous phase to a crystal phase when the Co3O4 film was treated by Ar and O2 plasma for more than 20 min, and the crystal lattice line occurred on the surface of nano-sized-Co3O4 particles. Meanwhile, the interface of Co3O4 particles with diameter between 3 and 12 nm became obvious and some nano-catkin structures were also formed on the Co3O4 film. The ratio of Co3+/Co2+ in the spinel-type Co3O4 was nearly 2, and the nano-particles predominantly expose their {311}, {111}, and {220} planes. These morphologies and structure characteristics were found to be ideal for increasing the catalytic activity efficiency of Co3O4 for CO oxidation, and the catalytic stability of Co3O4 coated on the organic microreactor lasted nearly 85 h for trace CO oxidation at room temperature

Silver nanocluster catalytic microreactors for water purification

A new method for the elaboration of a novel type of catalytic microsystem with a high specific area catalyst is developed. A silver nanocluster catalytic microreactor was elaborated by doping a soda-lime glass with a silver salt. By applying a high power laser beam to the glass, silver nanoclusters are obtained at one of the surfaces which were characterized by BET measurements and AFM. A microfluidic chip was obtained by sealing the silver coated glass with a NOA 81 microchannel. The catalytic activity of the silver nanoclusters was then tested for the efficiency of water purification by using catalytic ozonation to oxidize an organic pollutant. The silver nanoclusters were found to be very stable in the microreactor and efficiently oxidized the pollutant, in spite of the very short residence times in the microchannel. This opens the way to study catalytic reactions in microchannels without the need of introducing the catalyst as a powder or manufacturing complex packed bed microreactors

Study of the Stability and Hydrophilicity of Plasma-Modified Microfluidic Materials

Polymers among new classes of materials such as polydimethylsiloxane (PDMS), cyclic olefin copolymer (COC), Norland optical adhesive (NOA), and THV (fluoropolymer) were evaluated as surface-modified microfluidic materials, including investigating the incorporation of silica-like functional groups onto these surfaces. The functionalization of these materials was performed using a hybrid reactor equipped with magnetron sputtering using a silica target and with a PECVD apparatus starting from hexamethyldisiloxane as a chemical precursor. Coated microfluidic materials were then evaluated in terms of wettability, stability, composition, and structure. The deposited coatings were proved to be stable up to 2 month in air and water storage for these materials, with COC providing the most stable substrate