Sn and Ag doped ZnO quantum dots with PMMA by in situ polymerization for UV/IR protective, photochromic multifunctional hybrid coatings

Abstract

A facile multilayer hybrid coating with multifunctional characteristics like UV shielding, IR reflectance, photochromic and photoluminescence are designed with doped ZnO quantum dots [ZQDs] in PMMA polymer and proposed to fabricate solar radiation control active-interface layers. Sn and Ag doped ZnO quantum dots [ZQDs] were initially synthesized via a simple microwave assisted sol-gel strategy in the presence of 3-aminopropyl trimethoxy silane, a known organic capping agent. Doped ZQDs were assessed for the size, morphology, chemical nature, crystallinity and optical qualities. ZQDs were subsequently dispersed in methyl methacrylate monomer and polymerized in situ to obtain PMMA/ZQDs coating precursor sol. Multilayer hybrid coatings were then fabricated and examined for NIR shielding and UV absorbance efficiencies. Results indicated that the doped ZQDs/PMMA hybrid coatings have blue emission under UV light. With regard to NIR reflectance, the undoped PMMA/ZQDs hybrid coatings exhibit only < 14% NIR reflectance. It is enhanced to 30% and 23% upon doping with Ag and Sn in PMMA/ZQDs hybrids. The hybrid is redesigned with the inclusion of rare earth phosphate dispersoids by which the NIR reflectance is wisely enhanced to ~ 36%. A photochromic organic dye, spiropyran, is introduced in the doped ZQDs/PMMA hybrids, to display photochromic functionality with red emission. It is concluded that ZQDs doped with Sn and Ag ions once treated with organic dye molecule and inorganic co-activators, can result in an innovative photochromic, UV/NIR shielding solar-control interface coatings.