An inorganic titanium oxide (TiO) gel sensor was demonstrated for convenient detection of ascorbic acid (AA). It is composed of TiO (PI–TiO) functionalized with a perylene diimide derivative containing carboxylic groups as a new soft dopant material. A traditional solvothermal reaction is adopted to prepare the PI–TiO composite, which exhibits a different spectrum according to the reaction time. The final gel possesses a strong chelating affinity with AA molecules, in which phenol hydroxyl groups are shown to compete with those already present in PI. We further utilize the functionalized gel to prepare a series of films with a simple and portable AA response. A visual colour variation can be recognized by the naked eye, together with obvious fluorescence changes for selective and sensitive AA detection. Finally, the as-prepared gel film displays good stability and reproducibility for real sample responses with satisfying results.