Investigation of near infrared reflectance by tuning the shape of SnO2 nanoparticles

Different shaped SnO2 nanoparticles have been prepared via a sol–gel method. We investigate the relationships between morphology, crystal size and reflectance of as-prepared products. In addition, we also demonstrate the different shaped nanoparticles have different crystal sizes, namely 5.9, 7.5, 10.2 nm by XRD. And the calculated results are consistent with the TEM. Furthermore, the UV–vis–NIR results show that the reflectance is tightly related with the crystal size and its morphology. With the enhanced alkaline, the reflectance values decreased to 84% along with the square shaped particle sizes increased to 10.2 nm. According to S ∝ 1/d, the particle size (d) decreases, while the scattering coefficient (S) increases. The absorption of samples in the near-infrared region increased to 0.07 which led to the depth of penetration enhancing caused the reflectance decreased. This matches well with the Kubelka–Munk (KM) theory.