We present a carbon paste electrode (CPE) modified using the electron mediator bis(1,10-phenanthroline-5,6-dione) (2,2′-bipyridine)ruthenium(II) ([Ru(phend) 2+ exhibited luminescence even at low concentration. Modified CPEs were constructed and analyzed using cyclic voltammetry. The intercalated mediator remained electroactive within the layers (E°′ = −38.5 mV vs. Ag/AgCl, 3.5 M NaCl) and electrocatalysis of NADH oxidation was observed. The kinetics of the modified CPE shows a Michaelis -Menten behavior. This CPE was used for the oxidation of NADH in the presence of Bakers' yeast alcohol dehydrogenase. A calibration plot for ethanol is presented.

The direct intercalation reaction of ferrocene (bis(eta5-cyclopentadienyl)iron(II), Fc) with a highly hydrated layered zirconium phosphate (ZrP) resulted in the formation of the ferrocenium ion (Fc+) within the ZrP material. The Fc+-intercalated ZrP material has an interlayer distance of 10.7 A. The intercalated material was used as an electron acceptor for the oxidation of both ferro-cytochrome c and the excited state of tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)3]2+). Upon contact of the material with a 1.5 x 10(-5) M solution of ferro-cytochrome c, the UV-vis absorption spectrum shows the successful formation of ferri-cytochrome c. Luminescence spectroscopy shows that the Fc+-intercalated ZrP material quenches the luminescence of [Ru(bpy)3]2+. The excited-state quenching mechanism of [Ru(bpy)3]2+* by Fc+-intercalated ZrP follows a dynamic plus sphere of action model. The second-order dynamic quenching rate constant kq is 2.2 x 10(8) M(-1) s(-1).

The direct intercalation reaction of [Co(tpy)(2)](2+) with the highly hydrated θ phase of layered zirconium phosphate (θ-ZrP) resulted in the formation of the oxidized [Co(tpy)(2)](3+) ion within the ZrP material. The X-ray powder diffraction patterns showed that the interlayer distance increases from 10.3 Å in θ-ZrP to 14.9 Å in the dry [Co(tpy)(2)](3+)-intercalated ZrP {[Co(tpy)(2)](3+):ZrP} phase. The complex remains electroactive within the layers of ZrP. The formal potential of a carbon paste electrode (CPE) modified with [Co(tpy)(2)](3+):ZrP (E°' = 40.8 mV versus Ag/AgCl, 3.5 M NaCl) is non-pH-dependent. However, the sensitivity of the [Co(tpy)(2)](3+):ZrP-modified CPE for the detection of reduced nicotinamide adenine dinucleotide (NADH) electrooxidation was lower than that of a previously reported CPE modified with [Ru(phend)(2)bpy](2+)-intercalated ZrP. (1) To improve the characteristics of NADH electrooxidation of the [Co(tpy)(2)](3+):ZrP-modified CPE, we included the enzyme diaphorase in solution, which increased the electrocatalytic current for NADH oxidation. A bienzymatic lactate biosensor was constructed and used for lactate sensing.