This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/policies/article-withdrawal). This article has been retracted at the request of the Editors-in-Chief. A journal-wide investigation by Elsevier's Research Integrity & Publishing Ethics team identified violations of the journal's policies on conflict of interest related to the submission and review of this paper. Review of this submission was handled by Guest Editor Daniel Tsang despite an extensive recent record of collaboration, including co-publication, with one of the paper co-authors (Deyi Hou). Acceptance of the article was partly based upon the positive advice of a reviewer who was closely linked to one of the authors (Hou) and of Tsang, who also acted as a reviewer. This compromised the editorial process and breached the journal's policies. The authors disagree with this retraction and dispute the grounds for it.