Antifouling properties of zinc oxide nanorod coatings

Abstract

In laboratory experiments, the antifouling (AF) properties of zinc oxide (ZnO) nanorod coatings were investigated using the marine bacterium Acinetobacter sp. AZ4C, larvae of the bryozoan Bugula neritina and the microalga Tetraselmis sp. ZnO nanorod coatings were fabricated on microscope glass substrata by a simple hydrothermal technique using two different molar concentrations (5 and 10 mM) of zinc precursors. These coatings were tested for 5 h under artificial sunlight (1060 W m⁻² or 530 W m⁻²) and in the dark (no irradiation). In the presence of light, both the ZnO nanorod coatings significantly reduced the density of Acinetobacter sp. AZ4C and Tetraselmis sp. in comparison to the control (microscope glass substratum without a ZnO coating). High mortality and low settlement of B. neritina larvae was observed on ZnO nanorod coatings subjected to light irradiation. In darkness, neither mortality nor enhanced settlement of larvae was observed. Larvae of B. neritina were not affected by Zn²⁺ ions. The AF effect of the ZnO nanorod coatings was thus attributed to the reactive oxygen species (ROS) produced by photocatalysis. It was concluded that ZnO nanorod coatings effectively prevented marine micro and macrofouling in static conditions.

Keywords:

• antifouling
• zinc oxide
• nanotechnology
• bacteria
• bryozoa
• photocatalysis

Acknowledgements

The authors would like to acknowledge the partial financial support of the Chair in Nanotechnology, The Research Council (TRC). The work of SD and MF was supported by the HM Sultan Qaboos Research Trust Fund SR/AGR/FISH/10/01. The authors would also like to thank the Physics Department, College of Science, Sultan Qaboos University for allowing the use of XPS facilities. The help of Mrs Yousra Al-Habsi in identification of the bacterium is acknowledged. The authors thank Prof. Dan Rittschof for fruitful discussions.