Electrochemical deposition behavior and characterization of Pd-Ag-HAp nanoparticles on ultra-fine TiO2 nanotubes

The deposition of ultra-fine Pd/Ag/HAp nanoparticles onto TiO2 nanotubes has been performed by an electro-chemical method using a mixed electrolyte solution. Electrochemical deposition was carried out under constant voltage, and Pd/Ag/HAp nanoparticles were carefully added in the mixed electrolyte of 1.7 M (NH4)H2PO4 + 0.4 M NH4F, which was slowly rotated by a magnetic stirrer on a hot plate in order to increase the diffusion rate of electrolyte ions. The electrochemical deposition behavior, chemical bonding state, and surface characteristics of the Pd/Ag/HAp nanoparticles have been investigated by FE-SEM, EDS, and XPS. The Pd/Ag/HAp nanoparticles were uniformly electrodeposited onto the whole top surface and around the tube walls, including the inner side and outer side, of the ultra-fine TiO2 nanotubes. The ordered tubular structure was well-maintained without destruction during the electrochemical deposition process. With excessive activation up to a deposition time of 7200 s, continuous granular Pd/Ag/HAp nanoparticles gradually formed with a rough surface around the top of the TiO2 nanotube layer. From the XPS and EDS analyses, Ti, Ca, P, Pd, and Ag were detected in the nanopartides on the electrochemically deposited surfaces. The surface morphology after soaking in SBF exhibited hydroxyapatite-like precipitates, which consisted of the four elements Ti, O, Ca, and P, and having a Ca/P atomic ratio of 1.67. (C) 2016 Elsevier B.V. All rights reserved.