Monodisperse silica-coated polyvinylpyrrolidone/NaYF(4) nanocrystals with multicolor upconversion fluorescence emission.

[*] Prof. Y. Zhang Division of Bioengineering Faculty of Engineering, Blk, EA-03-12 National University of Singapore 9 Engineering Drive 1, Singapore 117576 (Singapore) Fax: (+65)6872-3069 E-mail: [email protected] and Nanoscience and Nanotechnology Initiative National University of Singapore 9 Engineering Drive 1, Singapore 117576 (Singapore) Dr. Z. Li Singapore–MIT Alliance National University of Singapore 4 Engineering Drive 3, Singapore 117576 (Singapore) [**] The authors thank the Singapore–Massachusetts Institute of Technology Alliance (SMA) for a postdoctoral fellowship for Z.L. and the National University of Singapore for research funding. Supporting information for this article is available on the WWW under http://www.angewandte.org or from the author. Communications