Aspects described herein generally relate to a sol-gel that is the reaction product of an organosilane, a metal alkoxide, an acid, and chromium (III) salt and/or a lanthanide salt having a solubility of about 1 gram or greater per gram of sol-gel at 23° C. The lanthanide salt includes a cation and a ligand. The cation can be lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, cobalt, calcium, strontium, barium, and zirconium. A ligand can be a nitrate, a trifluoromethane sulfonate, a sulfate, a phosphate, a hydroxide, or hydrate forms thereof. The chromium (III) salt includes a cation and a ligand. The cation is chromium (III) and the ligand can be a nitrate, a trifluoromethane sulfonate, a sulfate, a phosphate, a hydroxide, or hydrate forms thereof.