A tetraethoxyorthosilicate (TEOS)-based stone protective coating containing functional 3-glycidoxypropyltrimethoxysilane (GPTMS) has been prepared in order to reduce gel crack formation during the drying phase using 𝑛-octylamine as a catalyst. The effect of gel time and viscosity on GPTMS concentration were studied.We have demonstrated that the addition of GPTMS accelerated the gel process and improve viscosity of sol. It was found that GPTMS was chemically incorporated into the gel matrix via Si–O bonds by Fourier transform infrared spectroscopy (FTIR) analysis. Nitrogen adsorption–desorption isotherms of xerogels were measured, they showed that the pore size of xerogels decreased with the addition of GPTMS. Atomic force microscopy (AFM) showed the surface roughness increased as content of GPTMS was higher. The Scotch Tape test and the hardness values showed improvement of cohesion and consolidation ability of hybrid sol. The protective performance evaluation of the treated stones with hybrid sol indicated its acid rain resistance.

Ethylene glycol (EG)-based hybrid nanofluids containing graphene oxide–silver nanosheets (GO–Ag) were simply prepared without using any surfactant. The graphene oxide–silver composites were characterized using X-raydiffraction analysis, transmission electron microscope, infrared and UV–visible spectroscopy. The stability of GO–Ag nanofluids was estimated by UV–visible spectroscopy. The GO–Ag/EG hybrid nanofluids has good stability withoutsignificant sedimentation for 60 days. A few thermophysical properties of GO–Ag/EG nanofluids with 0.1, 0.2 and 0.3 wt% nanosheets were analysed experimentally at different temperatures ranging from 20 to 50$^{\circ}$C.