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.