Fig xA PL spectra variations of functionalized ZnO NWs

During the last decade, bismuth-based materials electrodes have been evidenced as a successful alternative to the traditional mercury electrodes for heavy metals trace detection. Being environmentally friendly and biocompatible Bi represents a very attractive material for sensors construction. In order to get fast electrode kinetics and low detection limit required for heavy metals detection, two important aspects were considered. One of this concerns the conductive material used as substrate for Bi deposition. Because it is well-known that the structure and the properties of the supporting material may exert major influences on the Indirubin behavior, various carbonaceous materials (glassy carbon [15], graphite [16], carbon fibers [17], carbon ink [18] and [19]), metals (Ag [14] and [20], Cu [21]), zeolite [22], polymers ((3-mercaptopropyl) trimethoxysilane [23], cyclic olefin copolymer [24], poly(p-aminobenzene sulfonic acid) [25], and polyaniline [26]) were used as substrate. However, the above mentioned substrates, especially the conventional ones, exhibit important drawbacks such as low active surface, easy inactivation or expensiveness. The second aspect, affecting strongly the size and the activity of the sensor working surface, is related to the method used for the Bi deposition on the substrate: (i) “ex-situ” plating or pre-plated material [24], [27] and [28], (ii) “in-situ” plating [5], [17], [25], [27], [29] and [30], (iii) “bulk” method [16], [18] and [27].