Efficient Red/Near‐Infrared‐Emissive Carbon Nanodots with Multiphoton Excited Upconversion Fluorescence. - Liu, Kai‐Kai; Song, Shi‐Yu; Sui, Lai‐Zhi; Wu, Si‐Xuan; Jing, Peng‐Tao; Wang, Ruo‐Qiu; Li, Qing‐Yi; Wu, Guo‐Rong; Zhang, Zhen‐Zhong; Yuan, Kai‐Jun; Shan, Chong‐Xin (Advanced Science, 2019)