NER: Nanostructured Multilayers as Sensing Materials for Long Period Gratings

Miami University, Oxford OH

Investigators

Abstract

The program goal is to develop chemical sensors based on nanostructured assemblies on surfaces. The change of refractive index of selective coatings on long period gratings (LPGs) is the sensing mode. We hypothesize that nanostructured composites fabricated by layer-by-layer (LBL) electrostatic binding of polymers, supramolecules, and/or monolayer-protected, functionalized metal nanoclusters will serve as elements that will impart selectivity and sensitivity to LPGs. The LBL-fabricated nanocomposites will replace the cast films or adsorbed layers traditionally used as the selectivity or preconcentration material on these devices. Conventional coatings, e.g. polymers cast films, require a compromise between providing enough reactive sites to produce a useful signal and having too much bulk for facile transport of the analyte. By using nanostructured multilayers comprised of alternating monolayers of functional components and spacers, we optimized coatings can be fabricated. Moreover, anchoring the functionality to monolayer-protected metal nanoclusters and using these assemblies as components of the nanocomposites is proposed as a route to improving, sensitivity, selectivity, and linear dynamic range of such sensors. The LBL method yields multilayer composites with controlled nanoscale dimensions. Reactive centers within a given layer have a controlled spatial distribution in accord with the properties of the polymers, supramolecules, or nanoclusters that comprise that component of the assembly. The nature of the layers influences mass transport within the assembly. The trade-off is that selectivity must be achieved by control of the interaction between the cladding and the analyte (partition constant and/or kinetics). We hypothesize that the control of such interactions will be enhanced by the LBLs. The results of this study, in particular the transport through nanostructured multilayers, also can contribute to research in other fields such as surface acoustic wave sensors, fabrication of biomimetic media, catalysis, electric energy production/storage, quantum dots as reagents and nanoscale "bar coding". Our graduate and undergraduate students will utilize the findings of their research, thereby improving their knowledge of nanotechnology and materials science.