Well aligned Pt/Au alloy nanowire arrays are successfully synthesized and used as the substrate for the construction of phosphate biosensors. Pyruvate oxidase is immobilized onto the nanowire surface together with co-factors via cross linking approach. Morphology, composition, structure and chemical state of the nanowires are characterized by SEM, TEM, EDS and XPS, and the electrochemical behaviors of the as-prepared phosphate biosensors are investigated by cyclic voltammogramic and chronoamperometric techniques. Especially, the influence of the composition and aspect ratio of Pt/Au alloy nanowire arrays on the response of phosphate biosensors are studied as well. The present phosphate biosensor shows a high sensitivity of 50.5 μA • cm −2 • mM −1 and a wide linear range between 248 and 1456 μM toward the detection of phosphate. In addition, the biosensor also exhibits good selectivity and stability, which promises great potential in phosphate detection applications.

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The article describes a method for rapid and visual determination of Hg(II) ion using unmodified gold nanoparticles (Au-NPs). It involves the addition of Au-NPs to a solution containing Hg(II) ions which, however, does not induce a color change. Next, a solution of lysine is added which induces the aggregation of the Au-NPs and causes the color of the solution to change from wine-red to purple. The whole onsite detection process can be executed in less than 15 min. Other amines (ethylenediamine, arginine, and melamine) were also investigated with respect to their capability to induce aggregation. Notably, only amines containing more than one amino group were found to be effective, but a 0.4 μM and pH 8 solution of lysine was found to give the best results. The detection limits for Hg (II) are 8.4 pM (for instrumental readout) and 10 pM (for visual read-out). To the best of our knowledge, this LOD is better than those reported for any other existing rapid screening methods. The assay is not interfered by the presence of other common metal ions even if present in 1000-fold excess over Hg(II) concentration. It was successfully applied to the determination of Hg(II) in spiked tap water samples. We perceive that this method provides an excellent tool for rapid and ultrasensitive on-site determination of Hg(II) ions at low cost, with relative ease and minimal operation.

A polypyrrole based potentiometric phosphate biosensor has been fabricated by entrapment of pyruvate oxidase in a polypyrrole film.