Scientific Reports 6: Article number: 24002; published online: 07 April 2016; updated: 09 February 2017

He Ren and Chuanmao Zhang were omitted from the author list in the original version of this Article. This has been corrected in the PDF and HTML versions of the Article, as well as the Supplementary Information that now accompanies the Article.

The Author Contributions section now reads:

Q.P.S., W.D., Y.S., L.Y. and J.L. designed the research; Q.P.S., W.D., Q.J., Y.Z. and D.J. performed the research experiments; H.R. and C.Z. performed the FEISEM experiments. Q.P.S., W.D. and B.X. analyzed the data; Q.P.S., Y.S., L.Y. and J.L. wrote the manuscript.