Excellent Protein Immobilization and Stability on Heterogeneous C-TiO₂ Hybrid Nanostructures: A Single Protein AFM...

Enhancing molecular interaction is critical for improving the immobilization and stability of proteins on TiO₂ surfaces. In this work, mesoporous TiO₂ materials with varied pore geometries were decorated with phenyl phosphoric acid (PPA), followed by a thermal treatment to obtain chemically heterogeneous C-TiO₂ samples without changing the geometry and crystalline structure, which can keep the advantages of both carbon and TiO₂. The molecular interaction force between the protein and the surfaces was measured using atomic force microscopy by decomposing from the total adhesion forces, showing that the surface chemistry determines the interaction strength and depends on the amount of partial carbon coverage on the TiO₂ surface (∼40-80%). Samples with 58.3% carbon coverage provide the strongest molecular interaction force, consistent with the observation from the detected friction force. Surface-enhanced Raman scattering and electrochemical biosensor measurements for these C-TiO₂ materials were further conducted to illustrate their practical implications, implying their promising applications such as in protein detection and biosensing.