Voltammetry of [Re(DMPE)(3)](+) at ionomer-entrapped composite-modified electrodes

Nation or sodium poly(styrenesulfonate) (NaPSS) entrapped in either sol-gel -derived silica or cross-linked poly(vinyl alcohol) (PVA) composite coating s on spectroscopic graphite electrodes were investigated electrochemically with [Re-I(DMPE)(3)](+), where DMPE = 1,2-bis(dimethylphosphino)ethane. Amo ng these composite coatings, Naftion-entrapped sol-gel-derived silica (Nafi on-silica) exhibited a sensitivity for [Re-I(DMPE)(3)](+) similar to 4 time s higher than that of NaPSS-entrapped sol-gel-derived silica or NaPSS-entra pped PVA. When Nafion was entrapped in cross-linked PVA matrix, however, th e voltammetric response was found to be only similar to 14% of that of Nafi on and Nafion-silica composite coatings. Dispersing Nafion in sol-gel-deriv ed silica matrix improves the slow diffusion of [Re-I(DMPE)(3)](+) in Nafio n, thus leading to a higher sensitivity than Nafion in a shorter preconcent ration time. Such a Nafion-silica composite is promising for both electroch emical and spectroelectrochemical sensing of [Re-I(DMPE)(3)](+). It was als o found that increasing the high potential of a cyclic voltammetric scan gr eatly reduces the amount of [Re-II(DMPE)(3)](2+) available for reduction in the reverse potential scan, suggesting that the electrochemically generate d [Re-II(DMPE)(3)](2+) was consumed in the more positive potential region.