*
Corresponding authors
a
Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
E-mail:
ychai@polyu.edu.hk
b
School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, P. R. China
c
Institute of Surface Micro and Nano Materials, Xuchang University, Xuchang, Henan 461002, P. R. China
d
Czech Advanced Technology and Research Institute, Regional Centre of Advanced Technologies and Materials, Palacký University Olomouc, Šlechtitelů 27, 78371 Olomouc, Czech Republic
e
Nanotechnology Centre, VŠB–Technical University of Ostrava, 17. listopadu 2172/15, 70800 Ostrava-Poruba, Czech Republic
f
Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic