A new highly sensitive and selective fluorescent cadmium sensor

Condensation product (L) of salicylaldehyde and semicarbazide behaves as a fluorescent sensor for Cd(2+) ion, in 1:1 DMSO:H(2)O, over Mn(2+), Fe(2+), Ni(2+), Co(2+), Cu(2+), Pb(2+) and Hg(2+) ions. The emission peak of L at λ(max) = 520 nm, on excitation with 420 nm wavelength photons, showed an enhancement in intensity of ca 60-fold when interacted with Cd(2+) ion. The intensity was however found to remain unaltered when interacted with metal ions--Mn(2+), Fe(2+), Ni(2+), Co(2+), Cu(2+), Pb(2+) and Hg(2+). The intensity increases by approximately 20 fold on interaction with Zn(2+) ion. The increase in the fluorescent peak can be explained on the basis of photo induced electron transfer (PET) mechanism. A 1:1 complexation between Cd(2+) and L with log β = 4.25 has been proved.