Copper(II) ion-sensitive electrode using chemical vapor deposited Nb–Ge superconducting films Original Research Article

A kind of thin multi-layer Nb–Ge superconducting film has been prepared on the Hastelloy B substrate (2.5 mm in width and 0.04–0.045 mm in thickness) by chemical vapor deposition and used for the fabrication of an all-solid-state copper(II) ion potentiometric sensor. The sensors made from films with different Nb/Ge ratios show linear response ranges with an upper limit of 10−2 mol l−1 and lower limits of 10−5–10−7 mol l−1. The detection limit ranged from 5.0×10−6 to 1.0×10−7 mol l−1 and the slope ranged from 33.3 to 40.7 mV dec−1. The sensor made from a film with Nb/Ge ratio of 3.04 showed an excellent potentiometric selectivity for copper(II) ion with respect to many common divalent cations such as Mn2+, Zn2+, Cd2+, Ca2+, Sr2+, Mg2+, Ba2+, Pb2+, Ni2+ and Co2+. Hg2+ does interfere and causes deterioration of the electrode function. The potential drift was less than 3 mV as measured for 2 h in a stirred 10−3 mol l−1 copper(II) ion solution at room temperature. When the sensor made from a film with Nb/Ge ratio of 3.04 was alternately measured in the solution of 10−3 and 10−4 mol l−1 copper(II), the standard deviation estimated for five measurements was about 0.62 and 0.65 mV, respectively.