Papers by Keyword: Surface Functionalization

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Authors: Md Hosnay Mobarok, Tapas K. Purkait, Jonathan G.C. Veinot
Abstract: The preparation and surface chemistry Si quantum dots (SiQDs) are currently an intense focus of research because of their size dependent optical properties and many potential applications. SiQDs offer several advantages over other quantum dots; Si is earth abundant, non-toxic and biocompatible. This account briefly highlights recent advancements made by our research group related to the synthesis, functionalization, surface dependent optical properties and applications of SiQDs.
Authors: Matthias Schnabelrauch, Manuela Dubs, Armin R. Kautz, Juergen Weisser, Claudia Bergemann, Henrike Rebl, Jürgen Schmidt, Carolin Witt, Thomas Oberbach, Diana Imhof, J. Barbara Nebe
Abstract: Surface biofunctionalization is a common strategy to improve the material-tissue interface of inert implant surfaces. In this context we coated alumina-toughened zirconia (ATZ) ceramics after titanium plasma spraying with two different porous calcium phosphate layers and subsequently functionalized the obtained surfaces either with an RGD containing cell adhesion peptide sequence or a bone morphogenetic protein (BMP)-glycosaminoglycan complex. We studied initial cell adhesion densities, integrin expression, and alkaline phosphatase activity as an osteogenic marker of the coatings in vitro in comparison to the non-functionalized ATZ ceramics to evaluate the bone ingrowth potential of these biofunctionalized implant coatings.
Authors: Odilio B.G. Assis, Leonardo G. Paterno
Abstract: The present work deals with cold plasma organosilicon treatment of glass powder surfaces. The treated material underwent subsequent chemical derivations by storing samples inside an evacuated chamber, allowing chemical penetration at controlled pressures. The radicals’ inductions were characterized by XPS within each stage of modification. The enzyme peroxidase was immobilized using functionalized materials to check the resultant biocompatibility. A sequence of surface tailoring is proposed suggesting the anchoring of enzyme via C = O groups implanted on the glass surface. The experimental results demonstrate that the proposed process is suitable for the functionalization of materials with irregular shapes.
Authors: Yan Yan Lu, Hua Li, He Zhou Liu
Abstract: Electron beam (EB) has been used in curing of polymers in view of its advantages over conventional curing processes including short curing time, lower thermal stress, reduction of hazardous chemical volatiles, higher production flexibility. Carbon nanotubes have been recognized as promising filler that can be used to change the mechanical, thermal and electrical properties of the polymer matrix composites. In this paper, EB curing of epoxide modified multi-walled carbon nanotubes (MWNTs)/epoxy composite has been investigated, and a bisphenol-A epoxy resin was used as matrix. MWNTs were chemical functionalized with epoxide monomer and the epoxide functionalized MWNTs were characterized by TG and FTIR. The gel content and Vicker’s hardness of the EB cured pure epoxy resin and the epoxide functionalized MWNTs/epoxy composites were measured and discussed as function of the concentration of the functionalized MWNTs. With the addition of epoxide modified MWNTs, both the gel content and Vicker’s hardness of the composites showed enhancement compared with EB cured pure epoxy.
Authors: Annabel Braem, Bram Neirinck, Omer Van der Biest, Jef Vleugels
Abstract: A new powder metallurgical processing route for porous Ti coatings on Ti-6Al-4V substrates based on the electrophoretic deposition (EPD) of TiH2 suspensions is presented. After dehydrogenation and sintering in vacuum, coatings with a fully interconnected porosity (up to 51%, interconnective pore channels (IPC) of 2-50 µm) and high adhesion strength (up to 47 MPa) are obtained. Further evaluation of these coatings for potential use in biomedical implants shows that EPD Ti coatings are significantly less prone to bacterial adhesion compared to state-of-the-art vacuum plasma sprayed (VPS) coatings, while still allowing substantial bone ingrowth. Using EPD, the coating process can easily be transferred to complex-shaped implant components.
Authors: Anurag Gupta, Bruce C. Kim, Eugene Edwards, Christina Brantley, Paul Ruffin
Abstract: In this work, we demonstrate the functionalization of zinc oxide nanowires with carboxylic acid moieties and investigate their potential application as p-nitrophenol sensors. First, synthesis of high quality zinc oxide nanowires along with appropriate characterization results is discussed. Subsequently, oleic acid, as a model system, is used to examine functionalization behavior of nanowire surface. Vibrational spectroscopic techniques are employed to determine nature of bonding and orientation of oleic acid molecule at nanowire surface. Photoluminescence properties of modified- and unmodified ZnO nanowires with oleic acid were investigated. Based on these results, an appropriate receptor capable of sensitive optical detection of p-nitrophenol is proposed. In addition, results on sensing mechanism of the receptor based on fluorescence quenching are reported, which highlight the capability of selective and sensitive detection of p-nitrophenol analyte using the receptor.
Authors: Alice Mesnage, Pardis Simon, Guy Deniau, Nathalie Herlin-Boime, Serge Palacin
Abstract: This document aims at presenting and explaining the mechanism of a simple green process, called Graftfast©, recently developed in order to graft polymer films onto any type of materials. This process is of great interest as it works in a short one step reaction at room temperature, atmospheric pressure in water. Particularly since this method is a redoxinduced process consisting in the reduction of diazonium salts into aryl radicals in presence of vinylic monomer, the involvement of such radicals was investigated. Moreover, this work demonstrates the efficiency of such process for the preparation of functionalized TiO2 nanoparticles. The composition and the grafted polymer quantities were investigated showing the successful grafting of the polymer onto the nanoparticles while conserving their morphology.
Authors: Ingo Ross, André Temmler, Moritz Küpper, Stephan Prünte, Marco Teller, Jochen M. Schneider, Reinhart Poprawe
Abstract: Liquid lubrication guarantees high precision and surface quality of workpieces in industrial forming processes. In the case of aluminum cold extrusion, wear and cold welding due to direct contact of tool and workpiece are usually prevented by the extensive use of lubricants. Since the use of lubricants is economically and ecologically unfavorable, surface treatments of tools by, e.g. laser polishing and/or coatings are in the focus of current investigations to substitute these lubricants and establish so called “dry metal forming” processes. The material AISI D2, a ledeburitic 12% chromium steel which is known to have a significant amount of chromium carbide precipitations, is widely used in cold extrusion for forming tools. The large fraction of chromium carbide precipitations, however, hinder the formation of a dense self-assembled monolayer (SAM) that is necessary to avoid direct contact of reactive aluminum with surface oxides of the tool. Therefore, a homogeneous distribution of the chemical elements with a smaller fraction or no chromium carbides in the steel matrix, particularly in the tool surface, is aimed for. Using laser polishing, the surface layer is molten by continuous or pulsed laser radiation. Within the melt pool, the elementary distribution is homogenized as a result of thermal convection and diffusion processes, as well as a smoothed surface and a grain refinement are achieved. Consequently, the effects of the surface treatment by laser polishing on the area coverage of self-assembled monolayers are investigated. Thus, a combined surface treatment by laser polishing and functionalization with a dense self-assembled monolayer shall reduce overall adhesive wear. For this investigation, several specimens of conventional manufactured and powder metallurgical molten AISI D2 are laser polished using continuous or pulsed laser radiation or a combination of both. The resulting surfaces are investigated by microscopy and spectroscopic techniques to analyze the surface topography and the elemental distribution near to the surface. These results are compared to those of conventionally hand-polished specimens. Furthermore, the influence of the element homogenization and grain refinement on the area coverage of self-assembled monolayers is explored. First results show that laser polishing of AISI D2 is suitable to achieve a reduction of grain size and a more homogeneous distribution of chromium carbides within the surface layer.
Authors: Julienne Charlier, Federico Grisotto, Achraf Ghorbal, Cédric Goyer, Serge Palacin
Abstract: Electronic, biology and chemical biology have pushed the scientists to develop new techniques to graft locally organic molecules on surfaces. The objective of the work was to develop a cheap and lithography-free technique by combining Scanning Electrochemical Microscopy (SECM) and electrografting processes in view of tuning locally chemical and physical surface properties on initially homogeneous substrates. The electrografting process was carried out with diazonium salts Plots, lines or more complex 2D-patterns have been “imprinted” on conducting substrates.
Authors: Wei Wei Ye, Mo Yang
Abstract: This study shows the study of optimal surface functionalization of nanoporous alumina membrane for "label-free" DNA detection. Single stranded DNA was first covalently immobilized on the nanopore walls via silane-PEG-NHS linker. The remained NHS group was hydrolyzed to form PEG layer to minimize the unspecific DNA binding during hybridization process. Optimal PEG-silane linker was achieved for better DNA immobilization efficiency. Using this optofluidic device, both ss-DNA immobilization and ds-DNA hybridization were successfully monitored via UV-Vis spectrum montoring. The nanopore size effect on DNA binding efficiency of membranes were also studied. With the increase of nanopore size, the DNA binding efficiency increased due to the increased reacted surface area. This portable optofluidic device integrated with nanoporos alumina membrane has the potential for nucleic acid in field detection in the application of food screening and environmental monitoring with high sensitivity
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