There are several stabilizing agents such as "diethanolamine", "glacial acetic acid " and "acetylacetone (acacH)" for deposited the TiO2 using sol-gel spinning technique.
I would use a polymer, because polymers stabilize NPs usually better than "small" molecules. For TiO2 I would recommend Polystyrene sulfonate, which is negatively charged at any pH. It binds strongly to the TiO2 surface which is positively charged at low pH values . This has been used for example here: 10.1002/smll.201200738