Photochemical reaction of organosilane self-assembled monolayer as studied by scanning probe microscopy

The interaction of water with freshly cleaved BaF(2)(111) surfaces has been studied using scanning force microscopy operated in different modes at room temperature and under controlled humidity. The Kelvin probe microscopy (KPM) mode has been used to study the evolution of the surface potential differences (SPDs). In the 20%-50% relative humidity (RH) range, adsorbed water forms two-dimensional solidlike bilayers (islands). The SPD between water islands and the bare substrate surface exhibits a sign crossover from negative ( approximately -30 mV) at low RHs to positive ( approximately +50 mV) at higher RHs, evidencing a cooperative and irreversible flipping of the preferential orientation of water dipoles, from pointing toward the surface evolving into the opposite direction. The KPM results suggest that the classical hexagonal (I(h)) bilayer configuration is not the most favorable structure.

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Article:Gentile, P., Frongia, M.E., Redon, M.C. et al. (4 more authors) (2015) Functionalised nanoscale coatings using Layer-by-Layer assembly for imparting antibacterial properties to polylactide-co-glycolide surfaces. Acta Biomaterialia.https://doi.org/10.1016/j.actbio.2015.04.009 eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. AbstractIn order to achieve high local biological activity and reduce the risk of side effects of antibiotics in the treatment of periodontal and bone infections, a localised and temporally controlled delivery system is desirable. The aim of this research was to develop a functionalised and resorbable surface to contact soft tissues to improve the antibacterial behaviour during the first week after its implantation in the treatment of periodontal and bone infections. Solvent-cast poly(D,L-lactide-coglycolide acid) (PLGA) films were aminolysed and then modified by Layer-by-Layer technique to obtain a nano-layered coating using poly(sodium4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) as polyelectrolytes. The water-soluble antibiotic, metronidazole (MET), was incorporated from the ninth layer. Infrared spectroscopy showed that the PSS and PAH absorption bands increased with the layer number. The contact angle values had a regular alternate behaviour from the ninth layer. X-Ray Photoelectron Spectroscopy evidenced two distinct peaks, N 1s and S 2p , indicating PAH and PSS had been introduced. Atomic Force Microscopy showed the presence of polyelectrolytes on the surface with a measured roughness about 10 nm after 20 layers deposition.The drug release was monitored by Ultraviolet-visible spectroscopy showing 80% loaded-drug delivery in 14 days. Finally, the biocompatibility was evaluated in vitro with L929 mouse fibroblasts and the antibacterial properties were demonstrated successfully against the keystone periodontal bacteria Porphyromonas gingivalis, which has an influence on implant failure, without compromising in vitro biocompatibility. In this study, PLGA was successfully modified to obtain a localised and temporally controlled drug delivery system, demonstrating the potential value of LbL as a coating technology for the manufacture of me...

The interaction of water with freshly cleaved BaF(2)(111) surfaces at ambient conditions (room temperature and under controlled humidity) has been studied using scanning force microscopy in different operation modes. The images strongly suggest a high surface diffusion of water molecules on the surface indicated by the accumulation of water at step edges forming two-dimensional bilayered structures. Steps running along the 110 crystallographic directions show a high degree of hydrophilicity, as evidenced by small step-film contact angles, while steps running along other directions exhibiting a higher degree of kinks surprisingly behave in a quite opposite way. Our results prove that morphological defects such as steps can be crucial in improving two-dimensional monolayer wetting and stabilization of multilayer grown on surfaces that show good lattice mismatch with hexagonal ice.