A new avenue for analyzing Ru deposition solution and depositing uniform nano-sized Ru structures on Pt substrates with enhanced reproducibility is shown in this work. UV-vis spectrophotometry in conjunction with electrochemical analysis shows that the deposition has a 5-day stability period between 2 and 6 days of its aging. During this stability period, UV-vis spectra showed that Ru(Ill) and Ru(IV) complexes of [Ru(H2O)Cl-5](2-), [RuH2O(OH)(2)Cl-3](-) and Ru-sulfates are in equilibrium. Electrochemical and in situ STM analysis also revealed that Ru nano-structures can be reproducibly deposited onto Pt using a diffusion control potential range of -0.47 to -0.32 V/MSE found in this work. The presence of both metallic Ru and Ru oxides within the deposit from XPS analysis suggests that the different Ru complexes present in the aged solution are involved in multiple parallel reduction processes for Ru deposition. (C) 2008 Elsevier B.V. All rights reserved.