Yang, Sui
Ni, Xingjie
Yin, Xiaobo
Kante, Boubacar
Zhang, Peng
Zhu, Jia
Wang, Yuan
Zhang, Xiang
Article History
Received: 23 January 2014
Accepted: 16 September 2014
First Online: 2 November 2014
Change Date: 20 May 2016
Change Type: Correction
Change Details: In the version of this Letter originally published, the following sentence was not included in the Acknowledgements: 'Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract no. DE-AC02-05CH11231.' This has been added in the online versions of the Letter.
Competing interests
: The authors declare no competing financial interests.