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Nanoscale Res Lett. 2017 Nov 29;12(1):611. doi: 10.1186/s11671-017-2369-1.

A Simple Approach for Synthesizing of Fluorescent Carbon Quantum Dots from Tofu Wastewater.

Author information

1
School of Physics and Astronomy and International Joint Research Center for Optoelectronic and Energy Materials, Yunnan University, Kunming, 650091, People's Republic of China. zhangjin96@aliyun.com.
2
School of Physics and Astronomy and International Joint Research Center for Optoelectronic and Energy Materials, Yunnan University, Kunming, 650091, People's Republic of China.
3
Department of Physics, China University of Mining and Technology, Xuzhou, 221116, People's Republic of China.
4
School of Physics and Astronomy and International Joint Research Center for Optoelectronic and Energy Materials, Yunnan University, Kunming, 650091, People's Republic of China. wenxu_issp@aliyun.com.
5
Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, 230031, People's Republic of China. wenxu_issp@aliyun.com.

Abstract

We present an investigation on carbon quantum dots (CQDs) synthesized from wastewater induced during the production of tofu. We find that tofu wastewater is a good source of raw material in making fluorescent CQDs. The corresponding CQDs can be fabricated simply via hydrothermal reaction to carbonize the organic matter in the yellow serofluid of tofu wastewater. Two sorts of CQDs can be obtained within the deionized water and NaOH solution, respectively, where the CQDs in water (NaOH solution) can emit blue (green) light under the UV irradiation. It is found from X-ray photoelectron spectroscopy (XPS) that the basic difference between these two sorts of CQDs is the contents of C-O and C=O bonds on the surface of the CQDs. This difference can cause different features of the photoluminescence (PL) spectra of the CQDs. On the basis of the obtained results from the XPS and PL measurements, we propose a mechanism in understanding and explaining the photon-induced light emission from CQDs. This study is relevant to the fabrication and application of fluorescent CQDs as, e.g., light display materials.

KEYWORDS:

Carbon quantum dots; Fluorescence; Hydrothermal reaction; Tofu wastewater

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