Nano-porous sol-gel derived hydrophobic glass coating for increased light transmittance through greenhouse

This paper reports an acid catalyzed sol-gel formulation with tetraethyl orthosilicate (TEOS) as a precursor for developing nano-porous anti-reflective coating on glass. The novelty of this formulation lies in judicious choice of ingredients. Oxalic acid, an unconventional acid catalyst created nano-pores of average diameter 1.25 μm due to entrapped carbon dioxide, which in turn increased the light transmittance by 7.01%. Carboxymethyl cellulose, a biopolymer fiber of 221 nm diameter imparted stability as well as hydrophobicity, without the need for high temperature annealing and hazardous trimethylchlorosilane (TMCS) treatment respectively. The fibrous stabilizer formed a top layer over two or three stacked silica nanoplates. The nanoplates had an average thickness 537 nm and inter-plate gaps of 119 nm, which also increased anti-reflectance property. The hardest pencil 9H failed to make any scratches on this coating, proving complete scratch-resistance. The invented formulation is eco-friendly and similar to solar cell technology.