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In the present work, we explored the reactivity of HS− with a family of fluorescent metal complexes via a variety of spectroscopic techniques. The complexes under investigation are obtained by complexation of zinc or nickel with pyridoxal-based ligands. More specifically complexes 1 and 2 are zinc complexes namely L1Zn(II) and L2Zn(II) where L1 stands for N,N′-phenylenebis(pyridoxyliminato) and L2 is N,N′-binaphthylenebis(pyridoxyliminato), whereas complex 3 is a nickel complex (L3Ni(II)) where L3 is N,N′-ethylenebis(pyridoxyliminato). A combination of NMR, ESI-MS, UV–vis and fluorescence experiments provide evidence that HS− binds the metal center in the case of complexes 1 and 3 whereas for complex 2, ZnS precipitation and hydrolysis of the organic ligand occur. Fluorescence experiments indicate that in the presence of HS− complex 1 undergoes a consistent fluorescence enhancement whereas for complex 3 the parent fluorescence exhibits a visible quenching. The results highlight the potential of complex 1 to be implemented as a HS− fluorescent sensor via a coordinative-based approach.

The DNA molecule, recognized as the carrier of genetic information in vivo, can function as an efficient organocatalyst for Michael additions of 1,3-dicarbonyl compounds to activated alkenes in aqueous media. The procedure described here is environmentally benign and offers several advantages in terms of simplicity, generality and efficiency. We have used fluorescence spectroscopy to evaluate the catalytic activity of a molecule of DNA.

Fluorescently labeled type-3 copper proteins have been proposed previously as solution oxygen sensors by using a FRET mechanism. Herein, we describe how this principle can be adapted to sense O 2 by means of proteins immobilized in optically transparent silica matrices. Specifically, the protein, hemocyanin from Octopus vulgaris N-terminally labeled with Cy5, is immobilized in two different kinds of optically transparent silica matrices, which appear to be a promising platform for enzyme encapsulation. The presented results provide proof of principle that fluorescently labeled proteins immobilized in a silica matrix can be implemented in a reusable, biocompatible and stable oxygen measuring device that might lead to new developments in the field of optical biosensing.