Abstract
Transparent nanocomposite films containing quantum dots are popular because of their extensive applications. However, nanoparticles tend to aggregate, resulting in phase separation of the nanoparticles in the polymer matrix. Herein, we present a bulk thermo-curing copolymerization method to fabricate poly(methyl methacrylate)-based nanocomposite films with ultra-high-loading ZnS quantum dots (ZnS/PMMA), utilizing polymerizable group-capped ZnS and monomer of methyl methacrylate (MMA). We found that the nanocomposite film is highly transparent, although the transmittance decreases with the ZnS content, especially at the wavelength between 300 nm and 400 nm. The results from X-ray diffraction (XRD), transmission electron microscopy (TEM), and dynamic mechanical thermal analysis (DMTA) show that the ZnS quantum dots maintain their original crystal structure, and are uniformly dispersed in the nanocomposite films, even with a very high ZnS content (41 wt %, determined by thermogravimetric analysis). The thermogravimetric analysis shows that the nanocomposite films possess a better thermal stability than that of pure PMMA film. The photoluminescence measurements show that ZnS/PMMA nanocomposite films have good optical properties. The fluorescence intensity increases with the increment of free ZnS content to 30 wt %, and then decreases due to self-reabsorption at a higher ZnS content. The transparent ZnS/PMMA nanocomposite films have a potential application as photoluminescence material.
Highlights
Quantum dots (QDs) possess attractive properties, such as narrow tunable emission and a high photoluminescence quantum yield (PLQY), making them promising candidates for numerous applications, including light-emitting diodes (LEDs) [1], photodetectors [2], biological labeling and imaging [3,4], lasers [5], and energy harvesting [6]
Researchers used to think that incorporation of a small amount of QDs is enough for photoluminescence, because self-reabsorption usually happens when the content of quantum dots is high in the nanocomposite films
The synthesis route of transparent high QD-loading nanocomposite films was shown in Scheme 1
Summary
Quantum dots (QDs) possess attractive properties, such as narrow tunable emission and a high photoluminescence quantum yield (PLQY), making them promising candidates for numerous applications, including light-emitting diodes (LEDs) [1], photodetectors [2], biological labeling and imaging [3,4], lasers [5], and energy harvesting [6]. Polymers 2018, 10, 1217 in-situ nanoparticle formation [7] or the bulk polymerization of monomer solution to fill premade quantum dots The latter approach is usually more advantageous because of the controllable size and size distribution of premade quantum dots, enlarging their unique size-dependent properties. Researchers used to think that incorporation of a small amount of QDs is enough for photoluminescence, because self-reabsorption usually happens when the content of quantum dots is high in the nanocomposite films. They prepared ultra-high-loading quantum/polymer nanocomposites with lower-band-gap organic dyes, resolving the problem of severe light yield deterioration, and the nanocomposite films exhibited simultaneous improvements in both light yield and gamma attenuation. The effect of ZnS incorporation into the nanocomposites on the material characterization was studied, indicating a potential application as photoluminescence material
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