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The simple Schiff base (Z)-N-benzylidenenaphthalen-1-amine (L) acts as an effective fluorescence sensor for Al(3+) by "off-on" mode, and ca. 42 times enhancement in fluorescence intensity is observed. The detection limit of L towards Al(3+) is observed to be 5 × 10(-5) M. UV/Visible and fluorescence data as well as DFT calculations confirm 1:3 coordination between Al(3+) and L through N atoms in a pyramidal shape. L is employed for imaging the Al(3+) ion in living biological cells and for the determination of the Al(3+) ion in bovine serum albumin.

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The redox potential of heme undecapeptide from cytochrome c (microperoxidase 11) in aqueous sodium dodecyl sulfate (sds), hexadecyltrimethylammonium bromide, and Triton X-100 surfactant micelles varied from ϩ2 mV at pH 3.0 to Ϫ222 mV at pH 9.0. The potentials at pH 7.0 were Ϫ114, Ϫ122, and Ϫ166 mV vs. the normal hydrogen electrode in the three surfactants. The nature of the axial ligands, spin state of iron, apolar nature of the local heme environment, and pH influence the potential in the micelles. Binding of histidine (HisH) of the peptide chain gave a negative shift of Ϫ60 mV, and deprotonation of co-ordinated HisH to histidinate gave a Ϫ100 mV shift of the potential in aqueous sds. At pH 5.0-6.0 the axial ligands to iron are H 2 O and HisH; deprotonation of coordinated H 2 O gave Ϫ65 mV shift of the potential. Interaction of hemin with surfactant gave a positive shift of the potential with respect to that in water. The diffusion coefficient of the undecapeptide (2.4 × 10 Ϫ7 cm 2 s Ϫ1 ) at pH 7.0 in the micelles is an order of magnitude smaller than that in water, indicating solubilisation of heme in surfactant solutions. The potential is strongly dependent on pH and is controlled by the uptake/release of protons at three sites: the unco-ordinated HisH of the peptide chain, the axially co-ordinated H 2 O and HisH ligands. The pK a values of these redox state-dependent ionisations in the iron() state are ca. 4.3, 6.3, and 8.3. The change in potential per unit change of pH (∆E/∆pH) was ca. Ϫ59 mV, which indicates proton-coupled electron transfer involving one electron and one proton.

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