1. Shenzhen Key Laboratory of Advanced Thin Films and Applications Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Physics and Optoelectronic Engineering Shenzhen University Shenzhen 518060 P. R. China
2. Australian Institute for Bioengineering and Nanotechnology The University of Queensland Brisbane Queensland 4072 Australia
3. School of Chemistry and Physics Queensland University of Technology Brisbane Queensland 4001 Australia