Calcium ion-selective electrode based on the facile synthesis of CuO over Cu wires

Photoelectrochemical Detection of Calcium Ions Based on Hematite Nanorod Sensors

“…Figure b shows the calibration curve of this amperometric response plotted using an average photocurrent for each concentration at a potential of 1 V. A limit of detection (LOD) of 0.42 μM was obtained from the concentration corresponding to the intersection of the linear fit of the calibration data and a line through data points in a concentration range where the sensor shows no response to calcium ions (Figure S9). The diameter of solvated calcium ions (7 Å) is too large to be accommodated in the cavity of DB18C6 (4 Å), but the high charge on the oxygen atoms of DB18C6 allows the complexation of Ca 2+ with DB18C6, known as the ion–dipole interaction; − thus, a PVC film with DB18C6 has previously shown good selectivity to calcium ions in ion-selective electrodes. ,, While the uncoated hematite device clearly showed a mixed potentiometric and amperometric response mechanism to pH, for the PVC-coated sensor, a potentiometric response could be expected as the insulating properties of PVC can block faradaic currents making this into a LAPS device. However, this only applies to low potentials.…”

“… 41 The diameter of solvated calcium ions (7 Å) is too large to be accommodated in the cavity of DB18C6 (4 Å), but the high charge on the oxygen atoms of DB18C6 allows the complexation of Ca 2+ with DB18C6, known as the ion–dipole interaction; 42 − 44 thus, a PVC film with DB18C6 has previously shown good selectivity to calcium ions in ion-selective electrodes. 23 , 24 , 45 While the uncoated hematite device clearly showed a mixed potentiometric and amperometric response mechanism to pH, for the PVC-coated sensor, a potentiometric response could be expected as the insulating properties of PVC can block faradaic currents making this into a LAPS device. However, this only applies to low potentials.…”