Spectrally selective single layered Ag@CuO nanocermet coatings for photothermal application: Green synthesis method

Abstract

Herein, green synthesized single-layered Ag@CuO nanocermet coatings deposited using spin coating on stainless steel (SS) substrates at 700, 800, 900 and 1000 rpm as solar selective absorbers is reported. The solar absorbing coatings consist of plasmonic silver (Ag) nanoparticles (NPs) embedded in a semiconductor matrix of CuO. The morphological, structural, compositional, and thickness of the coatings were characterized using Scanning electronic microscopy (SEM), X-ray diffraction (XRD), Energy dispersive X-ray spectroscopy (EDX), and Rutherford backscattering spectrometry (RBS). The SEM images of Ag@CuO nanocermet confirms the presence of better dispersibility of Ag NPs in the nanorod-like morphology of CuO. XRD patterns revealed well-crystalline nature of monoclinic CuO, and face centered cubic of Ag metal, and EDX spectra confirms the compositions of the coatings. RBS determined thicknesses of the coatings, and are found to be 1416 × 1015 atoms/cm2 (298.2 nm), 1296 × 1015 atoms/cm2 (272.8 nm), 1153 × 1015 atoms/cm2 (242.7 nm), and 998 × 1015 atoms/cm2 (210.2 nm) at 700, 800, 900, and 1000 rpm, respectively. The optical properties of the obtained coatings were analyzed using UV–Vis–NIR, and FTIR spectrophotometers in the wavelength range of 0.3–2.5 μm, and 2.5–20 μm, respectively. The Ag@CuO nanocerment coatings exhibit a solar absorptance (α = 0.93), and emissivity (ε = 0.23) at RS of 700 rpm. The embedded Ag NPs are responsible for enhancing the intrinsic absorption properties of CuO, due to the concentrated free electrons whose particle sizes are comparable to or smaller than the wavelength of incident light.