### 基于混酸回流制备碳点的中和过程

1. 1 山东大学化学与化工学院，胶体与界面化学教育部重点实验室，济南 250100
2 中国日用化学工业研究院，太原 030000
• 收稿日期:2020-05-05 录用日期:2020-06-05 发布日期:2020-06-11
• 通讯作者: 李洪光,郝京诚 E-mail:hgli@sdu.edu.cn;jhao@sdu.edu.cn
• 基金资助:
国家自然科学基金(21875129)

### Toward the Neutralization of Carbon Dots Prepared by Mixed Acid Reflux

Ning Feng1,2, Hongguang Li1,*(), Jingcheng Hao1,*()

1. 1 Key Laboratory of Colloid and Interface Chemistry, School of Chemistry and Engineering, Shandong University, Jinan 250100, China
2 China Research Institute of Daily Chemical Industry, Taiyuan 030000, China
• Received:2020-05-05 Accepted:2020-06-05 Published:2020-06-11
• Contact: Hongguang Li,Jingcheng Hao E-mail:hgli@sdu.edu.cn;jhao@sdu.edu.cn
• About author:Email: jhao@sdu.edu.cn (J.H.), Tel.: +86-531-88363963 (J.H.)
Email: hgli@sdu.edu.cn (H.L.)
• Supported by:
the National Natural Science Foundation of China(21875129)

Abstract:

Carbon dots (C dots) are relatively novel carbon nanomaterials that have attracted significant interest due to their unique photoluminescence, good biocompatibility, and stability. The preparation methods of C dots was usually summarized into "top-down" and "bottom-up", and mixed acid reflux is a top-down strategy that can be used to synthesize C dots, during which neutralization is a necessary step that can significantly influence the properties and potential applications of the final product. Previously, this research area mainly focused on tuning the properties of C dots by changing the starting materials and/or varying the reaction conditions; the influence of the reagents used during neutralization has been largely ignored. As the previously reported C dots prepared by mixed acid reflux were obtained from different starting materials under varied conditions, a meaningful comparison is difficult. Herein, yellow-emitting C dots were prepared by mixed acid-refluxing a carbon-rich material derived from fullerene carbon soot. For the same batch of as-prepared C dots, the influences of four reagents, i.e., NaOH, Na2CO3, K2CO3, and NH3·H2O, during neutralization on the structures and photoluminescence of the resulting C dots were investigated in detail. The results of thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy clearly showed that the reagent used during neutralization can affect the degree of dissociation of the acidic functional groups on the C dots. This is further supported by examination of the C dot/surfactant mixtures where subtle changes in the phase behavior were observed. Structural changes of the C dots cause variations in their surface states, ultimately altering the optical characteristics, including UV-vis absorption and fluorescence. Among the treated C dots, the sample prepared with Na2CO3 showed the strongest emission under the same excitation wavelength, while that prepared with NH3·H2O exhibited a distinct red shift (~8 nm) in the emission curve. The results presented herein provide clear evidence that neutralization reagent selection is important for optimizing the properties of the resulting C dots obtained by mixed acid reflux. In addition, the photoluminescence of the C dots can be influenced by their counterions, providing a novel method for tuning the properties of C dots while explaining their behavior in saline solutions. In short, the basicity of the neutralizing reagent and the type of counterions affect the structure of the C dots surface, which brings different performances. This work reminds researchers that it is necessary to use the type of neutralizing reagent as an experimental condition when preparing C dots in the future.

MSC2000:

• O648