SiO 2 /TiO 2 /Ag multilayered microspheres: Preparation, characterization, and enhanced infrared radiation property

Abstract SiO 2 /TiO 2 /Ag core–shell multilayered microspheres were successfully synthesized by the combination of anatase of TiO 2 modification on the surfaces of SiO 2 spheres and subsequent Ag nanoparticles deposition and Ag shell growth with face-centered cubic (fcc) Ag. The composites were characterized by TEM, FT-IR, UV–vis, Raman spectroscopy and XRD, respectively. The infrared emissivity values during 8–14 μm wavelengths of the composites were measured. The results revealed that TiO 2 thin layers with the thickness of ∼10 nm were coated onto the SiO 2 spheres of ∼220 nm in diameter. The thickness of the TiO 2 layers was controlled by varying the amount of TBOT precursor. Homogeneous Ag nanoparticles of ∼20 nm in size were successfully deposited by ultrasound on the surfaces of SiO 2 /TiO 2 composites, followed by complete covering of Ag shell. The infrared emissivity value of the SiO 2 /TiO 2 composites was decreased than that of pure SiO 2 . Moreover, the introduction of the Ag brought the remarkably lower infrared emissivity value of the SiO 2 /TiO 2 /Ag multilayered microspheres with the lowest value down to 0.424. Strong chemical effects in the interface of SiO 2 /TiO 2 core–shell composites and high reflection performance of the metal Ag are two decisive factors for the improved infrared radiation performance of the SiO 2 /TiO 2 /Ag multilayered microspheres.