Turning built-in electric field of porphyrin on Ti3+ self-doped blue-TiO2 hollow nanospheres boosts peroxidase-like activity for high-performance biosensing

Abstract

The four well-designed porphyrins are synthesized with different electronegativity groups at the meso-substituted phenyl groups to turn the built-in electric field of the porphyrins. Among them, the meso-tetrakis(meta-hydroxyphenyl) porphyrin (mTHPP) with the largest diploes is revealed to form the strongest built-in electric field on the surface of Ti3+ self-doped blue TiO2 hollow nanospheres (b-TiO2). The b-TiO2 with Fenton-like activity couple mTHPP with a mass ration (the mass of mTHPP to the total sample mass) of 29% by stable hydrogen and electrostatic bonding, resulting in b-TiO2/29mTHPP. A synergistic effect of strong built-in electric field and the well-matching energy levels between mTHPP and b-TiO2 promotes the rapid multi-channel transmission of photo-generated electrons from mTHPP to b-TiO2. Consequently, the outstanding peroxidase (POD) -like activity achieved for b-TiO2/29mTHPP with the fast oxidation of TMB (3,3′,5,5′-tetramethylbenzidine) by H2O2 to form the blue product (oxTMB) only in 10 s under visible light. Furthermore, the b-TiO2/29mTHPP combined with cholesterol oxidase (Chox) can quantitatively determine cholesterol in the range of 0.005–10 mM with a limit of detection (LOD) of 1.2 μM within 1 min. The present sensing performance represents one of the best results for the cholesterol colorimetric sensor reported so far. Furthermore, this colorimetric biosensor has been used for accurately determining the levels of total cholesterol in serum samples, indicating the great potential in clinical medical detection. The present work provides new perspectives to design various POD-like nanozyme for biosensing applications.