41.79 wt %), sodium citrate dehydrate (Sigma-Aldrich, >99%), (3-aminopropyl)trimethoxysilane
(APTMS, Alfa Aesar, 97%), sodium silicate (Sigma-Aldrich, reagent
grade), H2SO4 (BDH, Aristar grade), perchloric
acid (BDH, Aristar grade), propargyl alcohol (Sigma-Aldrich, 99%),
and 2-methyl-3-butyn-2-ol (Alfa Aesar, 98%) were used as received
and all aqueous solutions were prepared using ultrapure water (18.2
MΩ cm).