The pure PVA and HSNs/PVA nanocomposites with 10 wt% HSNs have been successfully prepared by the solution blending method and they have the similar transparency in the visible region (Fig. S4, Supporting Information). UV-vis transmittance spectra (Fig. 4a) present optic
Fig. 4 (a) UV-visible transmittance spectra with and without HSNs (b) Transmittance and haze of HSNs/PVA nanocomposites at 580 nm. (c) TEM image of HSNs/PVA nanocomposites with 22 wt% HSNs. (d) Refractive index of HSNs/PVA nanocomposites at 580 nm.
performance of neat PVA and HSNs/PVA nanocomposites. The transmittance of visible light is increased remarkably with the increase in HSNs content, which illustrates that HSNs indeed have an excellent antireflection effect on the nanocomposite films. The visible light transmittance and haze of them at 580 nm are clearly presented in Fig. 4b. When HSNs content increases from 0 to 33 wt%, the visible light transmittance increases from 91.5% to 97.9%, because that the well-dispersed HSNs can decrease surface reflectivity and boost total luminous flux of nanocomposites due to their low refractive index. However, as we know, the existence of nanoparticles in polymer matrix can change the optical path more or less and cause the light diffuse scattering, leading to the increase in reflectivity on the contrary. Although the total reflectivity of nanocomposites may be declined and anti-reflection effect may be realized, the haze of nanocomposite must be increased remarkably, which is a huge obstacle for the application of antireflection transparent composite films.9, 16 When the particles size is bigger and particles aggregation is more, the haze of composites is raised more obviously. To our surprise, the haze of prepared HSNs/PVA nanocomposite is increased slightly with the addition of HSNs, indicating the excellent dispersion state of HSNs in PVA matrix. As shown in Fig. 4c, HSNs with 22 wt% content have a homogeneous dispersion in PVA matrix without any aggregation. Light diffuse scattering (Rayleigh scattering) does not happen because the particles have the size of much less than 40 nm and are monodispersed in optical polymer matrix basically. 16 In this way, it gives full play to the function of anti-reflection and remarkably improves optical performance of nanocomposites without diffuse reflection. Moreover, HSNs can reduces refractive index of organic matrix obviously (Fig. 4d). It is decreased nonlinearly from 1.535 to 1.458 with increased HSNs volume content from 0 to 21%, which is not consistent with the theoretical calculation results,26because the addition of inorganic nanoparticles would reduce the crystallinity of the organic substrate.29 All these indicate that the HSNs/PVA composite materials have outstanding optical performance with considerable application prospect. Of course, by changing the types of modifiers, the HSNs can be incorporated into the different organic substrates to form nanocomposites with excellent optical properties, which has the widespread application prospect in many different domains.