Preparation of Polyethylene Composites Containing Silver(I) Acylpyrazolonato Additives and SAR Investigation of their Antibacterial Activity.

Novel composite materials PEn (n = 1-9) have been prepared by an easily up-scalable embedding procedure of three different families of Ag(I) acylpyrazolonato complexes in polyethylene (PE) matrix. In details, PE1-PE3 composites contain polynuclear [Ag(QR)]n complexes, PE4-PE6 contain mononuclear [Ag(QR)(L)m] complexes and PE7-PE9 are loaded with mononuclear [Ag(QR) (PPh3)2] complexes, respectively (where L = 1-methylimidazole or 2-ethylimidazole, m = 1 or 2, and HQR = 1-phenyl-3-methyl-4-RC(═O)-5-pyrazolone, where in detail HQfb, R = -CF2CF2CF3; HQcy, R = -cyclo-C6H11; HQbe, R = -C(H)═C(CH3)2). The PEn composites, prepared by using a 1:1000 w/w silver additive/polyethylene ratio, have been characterized in bulk by IR spectroscopy and TGA analyses, which confirmed that the properties of polyethylene matrix are essentially unchanged. AFM, SEM, and EDX surface techniques show that silver additives form agglomerates with dimensions 10-100 µm on the polyethylene surface, with a slight increment of surface roughness of pristine plastic within 50 nm. However, the elastic properties of the composites are essentially the same of PE. The antibacterial activity of all composites has been tested against three bacterial strains (E. coli, P. aeruginosa and S. aureus) and results show that two classes of composites, PE1-PE3 and PE4-PE6, display high and persistent bactericidal and bacteriostatic activity, comparable to PE embedded with AgNO3. By contrast, composites PE7-PE9 exhibit a reduced antibacterial action. Contact and release tests in several conditions for specific migration of Ag+ from plastics, indicate a very limited but time persistent release of silver ions from PE1-PE6 composites, thus suggesting that they are potential antibacterial materials for future applications. Instead, PE7-PE9 almost do not release silver, only trace levels of silver ions being detected, in accordance with their reduced antibacterial action. None of the composites is toxic against higher organisms, as confirmed by D. magna test of ecotoxicity.

Removing aromatic and oxygenated VOCs from polluted air stream using Pt-carbon aerogels: assessment of their performance as adsorbents and combustion catalysts.

Two series of Pt-catalysts were prepared by impregnation or doping of carbon aerogels and different porous textures and Pt-dispersion were obtained. The performance of the samples in the elimination of organic compounds (VOCs) by adsorption and catalytic combustion was studied and compared with the characteristics of both the VOCs and the catalysts and the interactions between them. Toluene, xylenes and acetone were selected as representative aromatic or oxygenated VOCs. The adsorption of VOCs is favoured at room temperature in the case of meso/microporous materials, but at the higher catalytic reaction temperature, the micropores volume is more important. Adsorption and catalytic combustion occur simultaneously, and are both dependent on temperature, albeit in opposite directions. The combustion of aromatic compounds takes place at a lower temperature than that required for acetone combustion, so favouring the accumulation of adsorbed VOC, something that should be avoided to minimize risks. Catalytic performance improves with the contact time and is independent of oxygen content above 5% v/v, but declines significantly below this limit.

Textural and mechanical characteristics of carbon aerogels synthesized by polymerization of resorcinol and formaldehyde using alkali carbonates as basification agents.

Five organic aerogels were prepared simultaneously by polycondensation of resorcinol and formaldehyde using different alkali carbonates (M(2)CO(3), M = Li, Na, K, Rb and Cs) as basification agents. The gelation time depended on the carbonate used, increasing from Li(2)CO(3) to Cs(2)CO(3). The porosity of the samples is defined during this process, when the three-dimensional packing of primary particles is formed. The slower the gelation, the greater the overlapping of primary particles and the formation of clusters, leading to a mechanical reinforcement of the samples and the progressive displacement of their pore size distribution (PSD) towards larger pores. Carbonization produces certain shrinkage of the structure and increases the microporosity and the Young modulus of the samples. Carbon aerogels change from mesoporous to macroporous materials as the counter-ion size of the carbonate increases.

Development of carbon coatings for cordierite foams: an alternative to cordierite honeycombs.

Cordierite foams were prepared by replication of polyurethane foams and were coated with three types of carbon xerogels. The dip coating and synthesis conditions were optimized, and the coated foams were characterized exhaustively. The composition of the starting solution, coat loading, and carbonization temperature are the most important parameters determining both textural and mechanical properties. Carbon xerogel coatings obtained from aqueous solutions of resorcinol (R) and formaldehyde (F) are macro-, meso-, and microporous but present the greatest shrinkage, which causes a loss of adhesion between ceramic foams and carbon coatings. The coatings from polyfurfuryl alcohol (PFA) and RF-poly(vinyl butyral) (Butvar) resin are highly microporous and present very good adhesion even after carbonization. In all cases, coatings induce the improvement of the mechanical properties, which is related to the fact that the coating fills the defects present in the cordierite foams, thereby affecting both the rigidity and the way cracks propagate through the coated samples. These materials, due to the synergetic role of the highly porous coatings and the tortuous channels of the ceramic foams, are suitable materials for adsorption or catalytic treatments of fluids.