Transparent Coatings Made from Spray Deposited Colloidal Suspensions

Abstract

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 TiO(2) nanoparticles, as well as of homemade luminescent YVO(4):Eu nanoparticles, and seems to be generalized to a large range of systems.

Gold Nanoparticle Internal Structure and Symmetry Probed by Unified Small-Angle X-ray Scattering and X-ray Diffraction Coupled with Molecular Dynamics Analysis

“…Destabilizing the colloidal solution using poor cosolvents such as ethanol was used to reduce coffee ring effect and allowed homogeneous deposition. 52 Direct comparison between XRD measurement on gold nanoparticle solution in 3 mm capillary and dry sample on coverslip allowed us to conclude that there was no visible structural evolution for those particles through drying (see Figure S19). Scaling of the data was done using references such as tetradecanol and gold foil for q-scaling.…”

“…For the three samples Au33, Au54, and Au63, we were able to fit with populations of small and large spheres as pictured in Figure 4, panels b and c. Without any assumption on the defects inside the nanoparticles, a main conclusion emerges: the samples contain different kind of particles. We concluded that twothirds of nanoparticles were made of small crystals (∼15 Å in diameter for all three samples), and one-third contained larger crystals (33,52, and 63 Å, respectively) ( Figures S15−S18).…”

Nanoparticulate Coatings with Efficient Up-Conversion Properties

“…This explanation is reinforced by the study of single drop spraying ( Figure S9, Supporting Information) which reveals that the solution made of P800G behaves like a colloidal solution of nanoparticles, forming rings when reaching the substrate. 23 Qualitatively, the mechanical properties of the film made of P800G particles, and especially the particle adhesion onto the glass substrate, appear greatly improved as compared to those of the film made of P1200G particles. Note that spraying non annealed nanoparticles and performing a thermal treatment after the deposition is not an appropriate choice as we face cracks and problems with the substrate thermal resistance.…”

Nanophosphor Coatings: Technology and Applications, Opportunities and Challenges

“…Sol-gel coatings and pastes can be applied by dip-coating (Pang et al, 2003;Wu et al, 2007) or spin-coating (Bedekar et al, 2010;Buissette et al, 2006;Huang et al, 2012a;Khan et al, 2008;Klausch et al, 2012;Psuja et al, 2009;Revaux et al, 2011b;Song et al, 2011). Wet spraying, known for many decades (Sadowsky, 1949), could be adopted for the deposition of nanophosphors as well (Fleury et al, 2012;Revaux et al, 2011a).…”