Integrated heterojunction and photothermal effect multiple enhanced ratiometric electrochemiluminescence immunosensor based on calcination controlled and tunable TiO 2 mesocrystals

Stratifin (SFN) is considered to be a new biomarker of cancers. In clinical medicine, combining tissue chip technology and immunohistochemical methods qualitatively prove that the abnormal expression of SFN is related to cancer. However, the quantitative detection of SFN is rarely performed. Herein, an ultrasensitive ratiometric ECL immunosensor was constructed to realize SFN determination. A polyvinylpyrrolidone (PVP)-assisted synthesis of TiO 2 (PVP-TiO 2 )@Poly[(9,9-dioctyfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadia-zol-4,8-diyl)] (PFBT) nanomaterial with anodic ECL signal and carbon-coated TiO 2 (C-TiO 2 )-loaded graphitic carbon nitride quantum dots (g-C 3 N 4 QDs) with cathodic ECL signal were firstly used as a pair of luminophores to generate two potential-resolved ECL signals. PVP-TiO 2 provided a substrate for the immobilization of biomolecules. C-TiO 2 due to the high specific surface area loaded a large amount of g-C 3 N 4 QDs, thereby increasing the ECL intensity. Not only that, the heterojunction formed by semiconductors could also further enhance ECL signal. Impressively, PFBT-C-TiO 2 conjugation possessed outstanding photothermal property, which could serve as photothermal convertor device and accelerate the electrochemical mass transfer on the electrode surface, further amplified ECL signal. The ratiometric biosensor showed good linear response for SFN from 10 −6 ng mL –1 to 0.1 ng mL –1 with a detection limit of 0.33 fg mL –1.