1. Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
2. Biomolecular and Organic Electronics, IFM, Linköping University, SE-581 83 Linköping, Sweden
3. Key Laboratory for Ultrafine Materials of the Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Mei Long Road 130, Shanghai 200237, China