An enhanced photoelectrochemical biosensor for colitoxin DNA based on HKUST-1/TiO2 and derived HKUST-CuO/TiO2 heterogeneous composites

HKUST-1 MOFs and its derivative HKUST-CuO were coupled with TiO 2 nanoparticles to form the heterogeneous composites of HKUST-1/TiO 2 and HKUST-CuO/TiO 2 based on their well-suitable bandgap energies (Eg). Compared with mono-component HKUST-1 or HKUST-CuO, the prepared composites displayed photoelectrochemical (PEC) response due to the synergistic effect from their heterogeneous structure. Higher photocurrent response was obtained on HKUST-CuO/TiO 2 -modified ITO electrode (HKUST-CuO/TiO 2 /ITO), which could be attributed to the hollow structure with a thin shell of HKUST-CuO greatly enhancing visible spectra harvesting. The CuO component in HKUST-CuO not only could accelerate electron transfer on the heterojunction interface but also effectively separate the photo-generated charge carriers (e −1 /h + ). Based on the excellent PEC performance of prepared photoactive composite material, under visible-light excitation ( λ  ≥ 420 nm) and with a working potential of 0 V (vs. Ag/AgCl), the S1 (probe DNA)/HKUST-CuO/TiO 2 /ITO PEC platform was successfully fabricated for colitoxin DNA detection without using ascorbic acid (AA) as an electron donor. Compared with the analysis results on S1/HKUST-1/TiO 2 /ITO electrode, S1/HKUST-CuO/TiO 2 /ITO displayed a wider linear response range from 1.0 × 10 −6 to 4.0 × 10 −1  nM with a lower detection limit of 3.73 × 10 −7  nM (S/ N  = 3), the linear regression equation was Δ I (10 −6 A) =0.5549–0.1858 log ( C S2 /M), which confirmed the HKUST-CuO could improve sensitivity because of its prominent PEC property. The relative standard deviation (RSD) of the PEC sensor for target DNA detection of 2.0 × 10 −4  nM was 7.4%. The proposed DNA biosensor also possessed good specificity and stability. Hence, this reported work was a promising strategy for molecular diagnosis in the bio-analysis field. Graphical abstract (A) Schematic illustration of the preparation process of the proposed PEC biosensors for colitoxin DNA detection. (B) The preparation process of HKUST-1 and HKUST-CuO.