title: Mechanistic studies on the reversible photophysical properties of carbon nanodots at different pH.
abstract: The pH-dependent photoluminescence (PL) behavior of carbon nanodots (C-dots) and its mechanism has been exhaustively studied in this work. The PL and UV-vis absorption spectra are reversible in the pH between 3 and 13. We speculate that two kinds of reactions (fast and slow) occurring at the surface of C-dots may contribute to this pH-dependent PL behavior. When C-dots solutions are switched to acidic conditions, they will quickly self-assembled aggregate into larger particles and surface oxygen-related groups of C-dots would be slowly oxidized at room temperature. Moreover, it should be noted that this is the first direct observation of self-assembled aggregation of C-dots under acidic conditions. In addition, the optimal PL spectra of C-dots blue-shift while their sizes increase, so-called 'inverse PL shift' phenomenon is also observed. Meanwhile, as the solution is adjusted to alkaline conditions, a structural tautomerization of C-dots rapidly takes place and hydrogenation/deoxygenation reaction proceeds in a much slower rate. Furthermore, through distinct decay dynamics as well as the characterizations of C-dots at different pHs, the PL properties are proposed to be mainly related to the surface states of C-dots.
authors.affiliation: State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine (MOE), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.
authors.forename: Zi-Qiang
authors.initials: ZQ
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine (MOE), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.
authors.forename: Jia-Yi
authors.initials: JY
authors.lastname: Lan
authors.affiliation: State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine (MOE), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.
authors.forename: Jian-Cheng
authors.initials: JC
authors.lastname: Jin
authors.affiliation: State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine (MOE), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.
authors.forename: Tian
authors.initials: T
authors.lastname: Gao
authors.affiliation: Center Hospital of Huangshi City, Huangshi, Hubei 435002, PR China.
authors.forename: Ling-Li
authors.initials: LL
authors.lastname: Pan
authors.affiliation: State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine (MOE), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China. Electronic address: fljiang@whu.edu.cn.
authors.forename: Feng-Lei
authors.initials: FL
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Virology & Key Laboratory of Analytical Chemistry for Biology and Medicine (MOE), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China; College of Chemistry and Material Science, Hubei Engineering University, Hubei 432000, PR China. Electronic address: yiliuchem@whu.edu.cn.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
mesh_terms: D002244:Carbon / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D049449:Luminescence; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D056951:Photoelectron Spectroscopy; D045663:Quantum Dots / Q000737:chemistry*; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D002244:Carbon
keywords: Carbon nanodots; Mechanism; pH dependent PL