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Transparent Coatings Made from Spray Deposited Colloidal Suspensions

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journal contribution
posted on 22.05.2012, 00:00 by B. Fleury, G. Dantelle, S. Darbe, J. P. Boilot, T. Gacoin
The goal of this study is to elaborate few-micrometer thick optically active coatings based on nanoparticles spray-deposited onto a substrate and to control their scattering properties through a progressive suppression of the coffee-ring effect. The modification of the aggregation state of the nanoparticles to be sprayed induces a change of the surface roughness of the films and consequently of their optical transmission. We draw the counterintuitive conclusion that a nonstable colloidal solution gives a smoother coating than a highly stabilized colloidal solution, leading to a more transparent coating. This phenomenon is demonstrated in the case of commercial TiO2 nanoparticles, as well as of homemade luminescent YVO4:Eu nanoparticles, and seems to be generalized to a large range of systems.