Crown-Porphyrin Ligand for Optical Sensors Development

A novel porphyrin ligand, Zn(II)TPP-BPI-crown (ZnPC), functionalized with two dibenzo-crown-ether moieties was synthesized and tested as cation-sensitive ionophore. Fluorescence studies on ligand sensitivity towards a number of different metal cations (Na+, K+, Li+, Ca2+, Mg2+, Co2+, Cd2+, Pb2+, Cu2+, Zn2+ and NH4+) were carried out first in solution and then inside polymeric membrane optodes. Emission light signal was sufficiently brilliant to be captured by a low-cost computer webcam, while a commercial blue-light LED served as monochromic excitation light source. The influence on the ZnPC optode response of the lipophilic sites functionalization was investigated. The visibly (naked eye) observed color change of sensing material from green to red demonstrated the suitability of the ZnPC-based optodes to perform fast monitoring of Cu(II) ions in the concentration range between 6.6 × 10−7 and 2.4 × 10−2 mol/L with a low detection limit (estimated by s/n = 3 method) of 0.3 mg/L, which is lower than WHO guideline value of 2 mg/L.