Fabrication, gradient extraction and surface polarity-dependent photoluminescence of cow milk-derived carbon dots

Shuai Han; He Zhang; Jian Zhang; Yujie Xie; Liangliang Liu; Hangxing Wang; Xiangkai Li; Weisheng Liu; Yu Tang

doi:10.1039/C4RA09520K

Fabrication, gradient extraction and surface polarity-dependent photoluminescence of cow milk-derived carbon dots†

Shuai Han,^a He Zhang,^b Jian Zhang,^c Yujie Xie,^a Liangliang Liu,^a Hangxing Wang,^a Xiangkai Li,^a Weisheng Liu^a and Yu Tang*^a

Author affiliations

* Corresponding authors

^a Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
E-mail: tangyu@lzu.edu.cn
Fax: +86-931-891-2582

^b School of Life Sciences, Lanzhou University, Lanzhou 730000, P. R. China

^c Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE 68588-0304, USA

Abstract

Cow milk-derived carbon dots (CMCD) were separated using a simple and cheap “gradient extraction” method, which was applied for the first time in nanomaterials' separation. The surface polarity of the extracted CMCD correlates well with the polarity of the extraction solvent. Interestingly, the surface polarity also affects the photoluminescence (PL) of CMCD: a red-shift of PL was observed as the surface polarity increased, which was attributed to the increasing amount of polar functional groups on the surface as auxochromes which are bound to graphitic sp² clusters and reduce their energy gaps. Furthermore, as the surface polarity of CMCD increases, their PL exhibits longer lifetimes and a stronger excitation-dependency, which are attributed to the more efficient “internal” energy transfer from the auxochrome-poor sp² clusters to the auxochrome-rich sp² clusters of the CMCD.

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DOI: https://doi.org/10.1039/C4RA09520K
Article type: Paper
Submitted: 30 Aug 2014
Accepted: 28 Oct 2014
First published: 29 Oct 2014

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RSC Adv., 2014,4, 58084-58089

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Fabrication, gradient extraction and surface polarity-dependent photoluminescence of cow milk-derived carbon dots

S. Han, H. Zhang, J. Zhang, Y. Xie, L. Liu, H. Wang, X. Li, W. Liu and Y. Tang, RSC Adv., 2014, 4, 58084 DOI: 10.1039/C4RA09520K

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Fabrication, gradient extraction and surface polarity-dependent photoluminescence of cow milk-derived carbon dots†

Abstract

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Fabrication, gradient extraction and surface polarity-dependent photoluminescence of cow milk-derived carbon dots

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