1. Key Laboratory of Materials Physics of Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Daxue Road 75, Zhengzhou 450052, China
2. Nanochemistry, Istituto Italiano di Tecnologia, via Morego 30, Genova 16163, Italy
3. Dipartimento di Scienza dei Materiali, Università degli Studi Milano-Bicocca, via R. Cozzi 55, Milano 20125, Italy
4. Dipartimento di Chimica e Chimica Industrial, Università degli Studi di Genova, Via Dodecaneso 31, Genova 16146, Italy
5. International Doctoral Program in Science, Università Cattolica del Sacro Cuore, 25121 Brescia, Italy
6. The State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques, School of Physics and Optoelectronics, South China University of Technology, Guangzhou 510641, P. R. China