Photonics of DNA/ruthenium(II) complexes

In this review, we describe the investigation of a ruthenium [Ru(II)] complex-based, AC voltage-driven, electrochemiluminescent (ECL) device first. The ECL turn-on response time and intensity were dramatically improved by introducing the AC method. The turn-on response time was speeded up by increasing the applied frequency: 4 ms response time was achieved at 200 Hz, which was much faster than when using the DC method (1.5 s). We also introduced rutile-type titanium dioxide nanoparticles (TiO2 NPs) in a Ru(II) complex-based AC-ECL device. The ECL intensity and the lifetimes of the ECL device with TiO2 NPs were greatly improved compared to those of the device without nanoparticles. Then we tried to improve photoelectrochemical properties of the Ru(II) complex by combining it with DNA molecules. We fabricated a novel DNA/Ru(bpy)(3)(2+) hybrid film that could immobilize the ECL-active Ru(bpy)(3)(2+) onto the electrode surface through electrophoretic migration. The hybrid film contained unique micrometer-scale aggregates of Ru(bpy)(3)(2+) in the DNA matrix. Surprisingly, by using the DNA/Ru(bpy)(3)(2+) hybrid film for the ECL device, luminescence could be obtained at frequencies as high as 10 kHz, which corresponds to a response time shorter than 100 mu s.