Search

Although deterioration of silicone maxillofacial prostheses is severely accentuated in smoking patients, the phenomenon has not been systematically studied. To address a gap in the literature concerning the stability of maxillofacial prostheses during service, in this contribution, the effect of cigarette smoke on the aspect and physical properties of M511 silicone elastomer was evaluated. The aspect, surface, and overall properties of the silicone material, pigmented or not, were followed by AFM, color measurements, FTIR, water contact angle measurements, TGA‐DTG and DSC, hardness and compression stress–strain measurements. The types of the contaminants adsorbed were assessed by XRF, ESI‐MS, MALDI‐MS, and NMR spectral analyses. Important modifications in color, contact angle, surface roughness, local mechanical properties, and thermal properties were found in the silicone material for maxillofacial prostheses after exposure to cigarettes smoke. The presence of lead, nicotine, and several other organic compounds adsorbed into the silicone material was emphasized. Slight decrease in hardness and increase in Young's modulus was found. The combined data show important impact of cigarette smoke on the silicone physical properties and could indicate chemical transformations by secondary cross‐linking. To our knowledge, this is the first study making use of complementary physical methods to assess the effect of cigarette smoke on the aspect and integrity of silicone materials for maxillofacial prostheses. [ABSTRACT FROM AUTHOR]

Ailanthus altissima, a highly invasive species, contains valuable compounds in different plant parts, indicating great practical potential. This paper proposes the use of non-polar (n-hexane) and polar (ethanol) solvents for the extraction of antioxidant compounds from A. altissima (family Simaroubaceae) leaves in a sequential two-step process. Fresh and dried leaves were examined for their microstructure by scanning electron microscopy, and for color changes in the CIELAB color space co-ordinates. An investigation of the harvesting season, processing (freezing and drying), and solvent indicates ethanol can be used for the highly efficient extraction of phenolics, flavonoids, tannins, and carotenoids. Statistically significant differences were found between the autumn and summer samples for phenolic content, and between dried and frozen samples for tannin content. The HPLC phenolic profile indicates more phenolics (nine polyphenols) in dried leaves harvested in both seasons compared to those in frozen ones (five to six polyphenols). Frozen leaves showed a higher antioxidant activity in a ferric-reducing antioxidant power assay than that of the dried samples, which exhibited a higher antioxidant activity using the 1, 1-diphenyl-2-picryl-hydrazyl assay, but it was not statistically significant. The phenolic, flavonoid, and carotenoid contents significantly influenced the antioxidant activities. Among the ethanolic extracts, those from dried leaves showed better antibacterial activity, in particular, on Staphylococcus aureus and Enterococcus faecalis. The high bioactive content and activity of A. altissima leaves make them suitable natural raw materials for various applications. [ABSTRACT FROM AUTHOR]

Isocyanides (isonitriles) are unique organic compounds that contain a formally divalent carbon. Herein, the synthesis of 1,3‐bis(isocyanopropyl)tetramethyldisiloxane was performed by a modified carbylamine method, using a phase transfer agent. Spectral methods (nuclear magnetic resonance [NMR], Fourier transform infrared spectroscopy [FT‐IR], and electrospray ionization mass spectrometry [ESI‐MS]) were used to confirm the structure. Energy gap of 1.86 eV (measured by diffuse reflectance spectroscopy [DRS]), high dielectric permittivity (15 at 10 kHz), and conductivity value in the order of 10−7 S·cm−1 place this compound in the range of wide‐bandgap semiconductors. The synthesis of Pt, Ag, and Fe metal complexes without organic co‐ligands and their catalytic activity were also investigated. The Pt complex was active in hydrosilylation reaction and in reduction of p‐nitrophenol, whereas the Ag complex was found effective in alkaline decomposition of hydrogen peroxide. The Fe complex is a new and cheap heterogeneous hydrosilylation catalyst and also showed very good catalytic behavior in heterogeneous Fenton‐like photodecomposition of Congo Red in various photo‐irradiation conditions, with 100% color removal efficiency after 60 min under sunlight. Thus, a simple path for siloxane‐containing materials with promising applications is open. [ABSTRACT FROM AUTHOR]