Multifunctional mesoporous silica nanoparticles in poly(ethylene-co-vinyl acetate) for transparent heat retention films

Abstract

Transparent inorganic‐polymer nanocomposite films are of tremendous current interest inemerging solar coverings including photovoltaic encapsulants and commercial greenhouse plastics, but suffer from significant radiative heat loss. This work provides a new and simple approach for controlling this heat loss by using mesoporous silica/quantum dot nanoparticles in poly(ethylene‐co‐vinyl acetate) (EVA) films. Mesoporous silica shells were grown on CdS‐ZnS quantum dot (QDs) cores using a reverse microemulsion technique, controlling the shell thickness. These mesoporous silica nanoparticles (MSNs) were then melt‐mixed with EVA pellets using a mini twin‐screw extruder and pressed into thin films of concentration variable controlled thickness. The results demonstrate that the experimental MSNs showed improved infrared and thermal wavebands retention in the EVA transparent films compared to commercial silica additives, even at lower concentrations. It was also found MSNs enhanced the quantum yield and photostability of the QDs, providing high visible light transmission and blocking of UV transmission of interest for next generation solar coatings. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 851–859

Supercritical Fluid Assisted Dispersion of Nano-Silica Encapsulated CdS/ZnS Quantum Dots in Poly(ethylene-co-vinyl acetate) for Solar Harvesting Films

“…These peaks match with previous reports for EVA. 8,39 All these significant peaks were also observed after nanocomposite formation, indicating successful integration of the QDs into the EVA polymer matrix. A new band appearing at 1090 cm −1 and a small peak at 782 cm −1 (indicated with blue star in Figure 1b(iv)) are attributed Si−O−Si vibrations, justifying the silica presence in the EVA nanocomposites.…”

“…The lowering of this UV transmission is because of the absorption of higher energy UV radiation by CdS/ZnS QDs that can be efficiently converted into desirable lower energy visible light through emission, and silica shell is transparent on UV−vis transmission of EVA nanocomposites. 8 It is attributed that the uniform distribution of the QDs throughout the polymer network as shown in Figures 4 and 5 enhances UV blocking by absorption. The UV shielding performance can be further tuned by changing film thickness.…”

“…Here, the individual NPs formation was because of the thin ZnS shell that minimizes the aggregation tendency and surface crystal defects of bare CdS. 8 As shown in Figure 4b, the silica encapsulated CdS/ZnS QDs after vinyl functionalization forms uniform nanospheres with narrow size distribution. The average diameter of the nanospheres was 60 ± 5 nm shown in the histogram data with a core size (mostly QDs) 35−40 nm.…”

“…5−7 However, controlling light and heat selective properties and stability are the major challenges of the neat EVA films. 8 Recently, semiconductor nanocrystals, also known as quantum dots (QDs), have attained intense interest for their light harvesting properties. 6,9,10 The most intriguing feature about QDs is that their absorption, emission, and band gaps can be tuned by changing the type, size, and shape of the QDs.…”

“…16,19 Recently, we have reported QDs-EVA nanocomposite films with improved optical and heat retention properties by using an extrusion approach which is a simple and convenient way suitable for large scale industrial application. 6,8,9 However, due to the high surface energy of the QDs and low compatibility with polymer, it becomes difficult to maintain good dispersibility of QDs within the polymer matrix. This can lead to decrease of the toughness and stability of the prepared composites for long span applications of nanocomposite films and coatings.…”