Optical, structural and adsorption properties of zinc peroxide/hydrogel nanohybrid films
ABSTRACT Hybrid nanofilms from zinc-peroxide/poly(acrylamide) (ZnO2/PAAm) and zinc-peroxide/poly(N-isopropyl-acrylamide) (ZnO2/PNIPAAm) were prepared using the photopolymerization procedure. The thin layers were prepared by the combination of the Layer-by-Layer (LbL) self-assembly method and photopolymerization using UV light in every step of the procedure. The hybrid multilayer films consisting of layers of zinc peroxide nanoparticles and hydrogel alternating in a sandwich-like fashion with thicknesses of 65–246 nm. The chemical structures of the hybrid films were investigated by FTIR spectroscopy, their morphology was studied by atomic force microscopy (AFM). The build up of the films was studied by measuring the optical reflection spectrum, and we have calculated the refractive index and layer thickness of the hybrid layers using simulating software. The adsorption properties of the ZnO2/hydrogel nanohybrid composite networks were investigated by measuring water and ethanol vapour adsorption by a quartz crystal microbalance (QCM). It was established that on partially hydrophobic ZnO2/PNIPAAm hybrids the adsorbed amounts were lower, against the hydrophilic ZnO2/PAAm film the vapour amount was higher. These results correspond to those of the bulk gel swelling results.
Chapter: Fundamentals of Optics01/1958; McGraw-Hill Book Company, Inc..
- [Show abstract] [Hide abstract]
ABSTRACT: We have recently reported on the consecutive physisorption of anionic and cationic bipolar amphiphiles onto charged surfaces, adsorbed out of aqueous solutions . Here, we extend our previous concept to multipolar compounds such as polyelectrolytes. In contrast to the bipolar amphiphile system, it is not necessary to separate single charges by a rigid unit, when the polyelectrolyte is adsorbed from sufficiently concentrated solutions. In this case the physisorbed layer does not bind with all ionic groups to the surface and exposes free ionic groups at the new film/solution interface. Therefore a polyelectrolyte layer can replace a layer of bipolar amphiphiles in the consecutive buildup of a multilayered assembly. The buildup of multilayers can then be described as follows: A solid substrate with a positively charged planar surface is immersed in the solution containing the negatively charged bipolar amphiphile, a monolayer of the amphiphile is adsorbed and due to its bipolar structure the surface charge is reversed. After rinsing in pure water the substrate is immersed in the solution containing the positively charged polyelectrolyte. Again a monolayer is adsorbed but now the original surface charge is restored. By repeating both steps in a cyclic fashion alternating multilayer assemblies of both compounds are obtained. In the same way multilayer assemblies can be prepared by using negatively charged polyelectrolytes and positively charged bipolar amphiphiles. It is demonstrated that multilayer films composed of at least 39 consecutively alternating layers, which corresponds to a total film thickness of 151 nm, can be assembled.Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 95(11):1430 - 1434.
- [Show abstract] [Hide abstract]
ABSTRACT: A previously unknown rigid helical structure of zinc oxide consisting of a superlattice-structured nanobelt was formed spontaneously in a vapor-solid growth process. Starting from a single-crystal stiff nanoribbon dominated by the c-plane polar surfaces, an abrupt structural transformation into the superlattice-structured nanobelt led to the formation of a uniform nanohelix due to a rigid lattice rotation or twisting. The nanohelix was made of two types of alternating and periodically distributed long crystal stripes, which were oriented with their c axes perpendicular to each other. The nanohelix terminated by transforming into a single-crystal nanobelt dominated by nonpolar (0110) surfaces. The nanohelix could be manipulated, and its elastic properties were measured, which suggests possible uses in electromechanically coupled sensors, transducers, and resonators.Science 10/2005; 309(5741):1700-4. · 31.20 Impact Factor