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α-Synuclein (α-SYN) is a very important neuronal protein that is associated with Parkinson's disease. In this paper, we utilized Au-doped TiO(2) nanotube arrays to design a photoelectrochemical immunosensor for the detection of α-SYN. The highly ordered TiO(2) nanotubes were fabricated by using an electrochemical anodization technique on pure Ti foil. After that, a photoelectrochemical deposition method was exploited to modify the resulting nanotubes with Au nanoparticles, which have been demonstrated to facilitate the improvement of photocurrent responses. Moreover, the Au-doped TiO(2) nanotubes formed effective antibody immobilization arrays and immobilized primary antibodies (Ab(1)) with high stability and bioactivity to bind target α-SYN. The enhanced sensitivity was obtained by using {Ab(2)-Au-GOx} bioconjugates, which featured secondary antibody (Ab(2)) and glucose oxidase (GOx) labels linked to Au nanoparticles for signal amplification. The GOx enzyme immobilized on the prepared immunosensor could catalyze glucose in the detection solution to produce H(2)O(2), which acted as a sacrificial electron donor to scavenge the photogenerated holes in the valence band of TiO(2) nanotubes upon irradiation of the other side of the Ti foil and led to a prompt photocurrent. The photocurrents were proportional to the α-SYN concentrations, and the linear range of the developed immunosensor was from 50 pg  mL(-1) to 100 ng  mL(-1) with a detection limit of 34 pg  mL(-1). The proposed method showed high sensitivity, stability, reproducibility, and could become a promising technique for protein detection.

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A highly ordered titanium dioxide nanotube arrays (HOTDNA) electrode was prepared in hydrofluoric acid solution by electrochemical anodization technique on a pure titanium sheet. The HOTDNA electrode was characterized by FE-SEM microscopy, X-ray diffraction, and UV-vis spectra. The linear-sweep photovoltammetry response on the HOTDNA electrode is presented in this work. The photogenerated current of 0.3 mA/cm2 was observed significantly upon illumination with applied potential of 0.5 V in the UV regions at the central wavelength of 253.7 nm. Photoelectrocatalytic (PEC) and photocatalytic (PC) activities of the HOTDNA electrode were evaluated in the degradation of methyl orange (MeO) in aqueous solution. A set of optimized conditions such as anodic potential, calcinations temperature, and MeO concentration on the PEC activity was investigated. The PEC and PC activities of HOTDNA electrode were compared. We concluded that the HOTDNA electrode was an effective photoelectrode for achieving an enhanced MeO degradation.

Multiwall carbon nanotubes were dispersed in Nafion (MWCNTs-NA) solution and used in combination with bismuth (MWCNTs-NA/Bi) for fabricating composite sensors to determine trace Pb(II) and Cd(II) by differential pulse anodic stripping voltammetry (DPASV). The electrochemical properties of the MWCNTs-NA/Bi composites film modified glassy carbon electrode (GCE) were evaluated. The synergistic effect of MWCNTs and bismuth composite film was obtained for Pb(II) and Cd(II) detection with improved sensitivity and reproducibility. Linear calibration curves ranged from 0.05 to 100 mg/L for Pb(II) and 0.08 to 100 mg/L for Cd(II). The determination limits (S/N ¼ 3) were 25 ng/L for Pb and 40 ng/L for Cd, which compared favorably with previously reported methods in the area of electrochemical Pb(II) and Cd(II) detection. The MWCNTs-NA/Bi composite film electrodes were successfully applied to determine Pb(II) and Cd(II) in real sample, and the results of the present method agreed well with those of atomic absorption spectroscopy.