1. Nanotechnology and Bio-Engineering Research Group, Department of Environmental Science, School of Science, Institute of Technology Sligo, Ash Lane, Sligo F91YW50, Ireland
2. Centre for Precision Engineering, Materials and Manufacturing Research (PEM), Institute of Technology Sligo, Ash Lane, Sligo F91YW50, Ireland
3. Department of Materials Science, University of Milano-Bicocca, Milan I-20125, Italy
4. The Surface Analysis Laboratory, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, U.K.