Facile and Efficient Fabrication of Bandgap Tunable Carbon Quantum Dots Derived From Anthracite and Their Photoluminescence Properties

Jianbo Jia; Yue Sun; Yaojie Zhang; Quanrun Liu; Jianliang Cao; Guangxu Huang; Baolin Xing; Chuanxiang Zhang; Lina Zhang; Yijun Cao

doi:10.3389/fchem.2020.00123

Facile and Efficient Fabrication of Bandgap Tunable Carbon Quantum Dots Derived From Anthracite and Their Photoluminescence Properties

Front Chem. 2020 Feb 28:8:123. doi: 10.3389/fchem.2020.00123. eCollection 2020.

Authors

Jianbo Jia^{1

2}, Yue Sun¹, Yaojie Zhang¹, Quanrun Liu¹, Jianliang Cao¹, Guangxu Huang^{1

2}, Baolin Xing^{1

2}, Chuanxiang Zhang^{1

2}, Lina Zhang¹, Yijun Cao²

Affiliations

¹ Henan Key Laboratory of Coal Green Conversion, College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo, China.
² Henan Province Industrial Technology Research Institute of Resources and Materials, Zhengzhou University, Zhengzhou, China.

Abstract

Low-cost and earth-abundant coal has been considered to have a unique structural superiority as carbon sources of carbon quantum dots (CQDs). However, it is still difficult to obtain CQDs from raw coal due to its compactibility and lower reactivity, and the majority of the current coal-based CQDs usually emit green or blue fluorescence. Herein, a facile two-step oxidation approach (K₂FeO₄ pre-oxidation and H₂O₂ oxidation) was proposed to fabricate bandgap tunable CQDs from anthracite. The K₂FeO₄ pre-oxidation can not only weaken the non-bonding forces among coal molecules which cause the expansion of coal particles, but also form a large number of active sites on the surface of coal particles. The above effects make the bandgap tunable CQDs (blue, green, or yellow fluorescence) can be quickly obtained from anthracite within 1 h in the following H₂O₂ oxidation by simply adjusting the concentration of H₂O₂. All the as-prepared CQDs contain more than 30 at% oxygen, and the average diameters of which are <10 nm. The results also indicate that the high oxygen content only can create new energy states inside the band gap of CQDs with average diameter more than 3.2 ± 0.9 nm, which make the as-prepared CQDs emit green or yellow fluorescence.

Keywords: anthracite; bandgap engineering; carbon quantum dots; coal; photoluminescent.