School of Science;
Xi'an Polytechnic University;
Xi'an 710048;
China;
School of Science;
Xi'an Polytechnic University;
Xi'an 710048;
China;
School of Science;
Xi'an Polytechnic University;
Xi'an 710048;
China;
School of Science & Technology;
Middlesex University;
London NW4 4BT;
UK;