Abstract

Despite the rising technological interest in the use of calcium-modified TiO2 surfaces in biomedical implants, the Ca/TiO2 interface has not been studied in an aqueous environment. This investigation is the first report on the use of in situ scanning tunneling microscopy (STM) to study calcium-modified rutile TiO2(110) surfaces immersed in high purity water. The TiO2 surface was prepared under ultrahigh vacuum (UHV) with repeated sputtering/annealing cycles. Low energy electron diffraction (LEED) analysis shows a pattern typical for the surface segregation of calcium, which is present as an impurity on the TiO2 bulk. In situ STM images of the surface in bulk water exhibit one-dimensional rows of segregated calcium regularly aligned with the [001] crystal direction. The in situ-characterized morphology and structure of this Ca-modified TiO2 surface are discussed and compared with UHV-STM results from the literature. Prolonged immersion (two days) in the liquid leads to degradation of the overlayer, resulting in a disordered surface. X-ray photoelectron spectroscopy, performed after immersion in water, confirms the presence of calcium.

Highlights

  • Metal oxide surfaces (in particular titanium dioxide (TiO2) surfaces) covered by an alkaline-earth-metal overlayer have been investigated in recent years in experiments [1,2,3,4,5] and theoretical studies [6], considering applications ranging from nanotechnology [7] to gas sensing [8], as well as catalysis [9] and biomedicine [10,11]

  • This investigation is the first report on the use of in situ scanning tunneling microscopy (STM) to study calcium-modified rutile TiO2(110) surfaces immersed in high purity water

  • The TiO2(110) surface was prepared in ultrahigh vacuum (UHV) with sputtering/ annealing cycles, as described in detail in the Experimental section, and the surface quality was examined using Low energy electron diffraction (LEED)

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Summary

Introduction

Metal oxide surfaces (in particular titanium dioxide (TiO2) surfaces) covered by an alkaline-earth-metal overlayer have been investigated in recent years in experiments [1,2,3,4,5] and theoretical studies [6], considering applications ranging from nanotechnology [7] to gas sensing [8], as well as catalysis [9] and biomedicine [10,11]. This investigation is the first report on the use of in situ scanning tunneling microscopy (STM) to study calcium-modified rutile TiO2(110) surfaces immersed in high purity water.

Results
Conclusion

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