In situ control of the oxide layer on thermally evaporated titanium and lysozyme adsorption by means of electrochemical quartz crystal microbalance with dissipation.

ACS Appl Mater Interfaces

Research Group Electrochemical and Surface Engineering, Department of Materials and Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels, Belgium.

Published: February 2009

Electrochemical (EC) quartz crystal microbalance with dissipation monitoring (ECQCM-D) is a new and powerful technique for the in situ study of adsorption phenomena, e.g., as a function of the potential of the substrate. When titanium (Ti) is employed as the substrate, its oxidation behavior needs to be taken into account. Ti is always covered with a native oxide layer that can grow by, e.g., thermal oxidation or under anodic polarization. For biomolecular adsorption studies on oxidized Ti under applied potential, a stable oxide layer is desired in order to be able to distinguish the adsorption phenomena and the oxide growth. Therefore, the oxidation of thermally evaporated Ti films was investigated in phosphate-buffered saline by means of ECQCM-D, using a specially designed EC flow cell. Upon stepping the potential applied to Ti up to 2.6 V vs standard hydrogen electrode (SHE), a fast increase of the mass was observed initially for each potential step, evolving slowly to an asymptotic mass change after several hours. The oxide layer thickness increased as a quasi-linear function of the oxidation potential for potentials up to 1.8 V vs SHE. The growth rate of the oxide was around 2.5-3 nm/V. No changes in the dissipation shift were observed for potentials up to 1.8 V vs SHE. The composition of the oxide layer was analyzed by X-ray photoelectron spectroscopy (XPS). It was mainly composed of TiO(2), with a small percentage of suboxides (TiO and Ti(2)O(3)) primarily at the inner metal/oxide interface. The amount of TiO(2) increased, and that of TiO and Ti(2)O(3) decreased, with increasing oxidation potential. For each oxidation potential, the calculated thickness obtained from ECQCM-D correlated well with the thickness obtained by XPS depth profiling. A procedure to prepare Ti samples with a stable oxide layer was successfully established for investigations on the influence of an electric field on the adsorption of biomolecules. As such, the effect of an applied potential on the adsorption behavior of lysozyme on oxidized Ti was investigated. It was observed that the adsorption of lysozyme on oxidized Ti was not influenced by the applied potential.

Download full-text PDF

Source
http://dx.doi.org/10.1021/am800029yDOI Listing

Publication Analysis

Top Keywords

oxide layer
24
applied potential
12
oxidation potential
12
potential
9
oxide
8
thermally evaporated
8
electrochemical quartz
8
quartz crystal
8
crystal microbalance
8
microbalance dissipation
8

Similar Publications

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!