Simple and selective sensing of cysteine using gold nanoparticles modified by ruthenium(II) complexes.

A simple and selective luminescence sensing method for the cysteine detection was developed based on gold nanoparticles modified by the new ruthenium(II) complexes. The intense emission of the modified ruthenium(II) complexes was quenched efficiently by gold nanoparticles due to the energy and charge transfer between the ruthenium(II) fluorophores and gold nanoparticles. Upon addition of cysteine, the emission of the ruthenium(II) complexes was enhanced significantly by the release of the ruthenium(ll) complexes from the surface of the gold nanoparticles. Therefore, cysteine could be detected by this gold nanoparticles-ruthenium(II) complexes based probes. The synthesis of gold nanoparticles and the modification based fluorophores probed could be accomplished successfully within one step, which simplified the preparation of luminescence sensors. Moreover, since metal-to-ligand charge transfer transition (3MLCT) emission band of the ruthenium(II) complexes was in the visible region, this approach was available for biomolecular sensing applications, and its relatively long life time made it suitable for the biological process studies.

Selective recognition of homocysteine and cysteine based on new ruthenium(II) complexes.

A series of the new ruthenium(II) complexes with different number of aldehyde groups have been synthesized and characterized for the simple and selective sensing of homocysteine (Hcy) and cysteine (Cys). The reaction of these ruthenium(II) complexes with Hcy and Cys afforded thiazinane or thiazolidine derivatives which resulted in the obvious changes in the UV-visible spectra and strong enhancement of the luminescence intensity of the system. The luminescence enhancement of [Ru(dmb)(2)(L2)](2+) (dmb: 4,4'-dimethyl-2,2'-bipyridine) showed a good linearity in the concentration of 4.2-350 µM and 6-385 µM with the detection limits of 0.3 µM and 1 µM for Hcy and Cys, respectively. The absorption and emission bands from metal-to-ligand charge transfer transition in the visible region and the large Stokes shift of the ruthenium(II) complex chromophore made it suitable for biological applications.