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Abstract: A novel photoelectrochemical immunosensor based on TiO2/CdS hybrid modified electrode was developed. The TiO2/CdS hybrid modified electrode was obtained by alternately dipping the TiO2 modified indium–tin oxide (ITO) electrode into the [Cd(NH3)4]2+ and S2− solution repeatedly. Compared with the routine method using Cd2+ solution for CdS deposition, the as obtained TiO2/CdS electrode showed enhanced photocurrent intensity with fewer coating times. After the ITO/TiO2/CdS electrode was coated with chitosan (CS), α-fetoprotein (AFP) antibodies were covalently conjugated on the surface of the electrode. Thus, a label-free photoelectrochemical immunosensor for the detection of AFP was developed by monitoring the changes in the photocurrent signals of the electrode resulting from the immunoreaction. The immunosensor displayed a linear response to AFP in the ranges from 50pg/mL to 50ng/mL with a relatively low detection limit of 40pg/ml. The photoelectrochemical results for the detection of AFP in five human sera showed acceptable accuracy. The method is simple, sensitive and specific. Moreover, the studied immunosensor possessed acceptable reproducibility and storage stability. The proposed methodology was potentially attractive for clinical immunoassay. [Copyright &y& Elsevier]

Abstract: Dopamine-coordinated photoactive TiO2 nanoporous films with a wide excitation range of light in the visible region (up to 580nm) were prepared and used for sensitive detection of NADH. Colloidal TiO2 was firstly covered on an indium–tin oxide (ITO) electrode surface and sintered at 450°C to form a nanoporous TiO2 film, then the electrode was dipped in a dopamine solution to form a dopamine–TiO2 charge transfer complex via coordinating dopamine with undercoordinated titanium atoms on the electrode surface. This charge transfer complex provided an anodic photocurrent under visible light and the photocurrent could be largely enhanced by NADH. The photocurrent enhancement might be due to the electron transfer between NADH and the holes localized on dopamine. A new photoelectrochemical methodology for sensitive detection of NADH at a relatively low potential was developed. The detection limit of NADH was 1.4×10−7 M, and the detection range could extend up to 1.2×10−4 M. The dopamine–TiO2 modified electrode exhibits its major advantages such as effective electronic transducer, fast response and easy fabrication for photoelectrochemical determination of NADH. This strategy largely reduces the destructive effect of UV light and the photogenerated holes of illuminated TiO2 to biomolecules and opens a new avenue for the applications of TiO2 in photoelectrochemical biosensing. [Copyright &y& Elsevier]

Abstract: The coupling of biocatalytic precipitation (BCP) to photoelectrochemical (PEC) biosensing for the development of rapid PEC sensors with ultrahigh sensitivity and excellent anti-interference ability is successfully realized. Horseradish peroxidase (HRP) was immobilized on the matrix of TiO2/CdS and 4-chloro-1-naphthol (4-CN) was chosen for the BCP-amplified PEC detection of H2O2. The HRP accelerated oxidation of 4-CN by H2O2 would yield insoluble product on the photoelectrode surface, on the basis of which the photocurrent be influenced. The detection limit of 5.0×10−10 M (S/N=3) for the determination of H2O2 was achieved. [Copyright &y& Elsevier]