Nitrogen and sulfur co-doped carbon quantum dots as "on-off-on" fluorescence probes to detect Hg2+ and MnO4- and improving the photostability of Rhodamine B

Wensu Gao; Shurong Zhang; Guiqiao Wang; Jinzhi Cui; Yaxin Lu; Xing Rong; Yawen Luo; LiChao Zhang; Zhongfa Cheng; Canzhu Gao

doi:10.1016/j.aca.2023.341683

Nitrogen and sulfur co-doped carbon quantum dots as "on-off-on" fluorescence probes to detect Hg²⁺ and MnO₄^- and improving the photostability of Rhodamine B

Anal Chim Acta. 2023 Oct 9:1277:341683. doi: 10.1016/j.aca.2023.341683. Epub 2023 Aug 2.

Authors

Wensu Gao¹, Shurong Zhang², Guiqiao Wang³, Jinzhi Cui⁴, Yaxin Lu⁵, Xing Rong⁶, Yawen Luo⁷, LiChao Zhang⁸, Zhongfa Cheng⁹, Canzhu Gao¹⁰

Affiliations

¹ School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China. Electronic address: 202112894@mail.sdu.edu.cn.
² School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China. Electronic address: 184016467@qq.com.
³ School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China. Electronic address: wguiqiao@mail.sdu.edu.cn.
⁴ School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China. Electronic address: 18713865889@163.com.
⁵ School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China. Electronic address: 1132489979@qq.com.
⁶ School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China. Electronic address: 202132960@mail.sdu.edu.cn.
⁷ School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China. Electronic address: 2679487021@qq.com.
⁸ School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China. Electronic address: 1071704630@qq.com.
⁹ Shandong Taihe Technologies Co, Ltd, Zaozhuang, Shandong, China. Electronic address: 3022661706@qq.com.
¹⁰ School of Environmental Science and Engineering, Shandong University, Qingdao, Shandong, China. Electronic address: gaocz@sdu.edu.cn.

PMID: 37604617
DOI: 10.1016/j.aca.2023.341683

Abstract

Background: Carbon quantum dot (CQDs) are zero-dimensional carbon nanomaterials with a size of less than 10 nm CQDs are widely used in the field of ion detection by virtue of their fluorescence characteristics such as strong fluorescence intensity, good optical stability and tunable emission wavelength. Although the traditional atomic absorption method, electrochemical method and other metal ion detection methods are highly sensitive, the operation is complex, expensive and limited by the site. Therefore, we prepared the N, S-CQDs capable of detecting Hg²⁺ and MnO₄^- in water with the advantages of simple operation, low cost, and direct visual signal.

Results: N, S-CQDs with high-quantum yield (77.68%), uniform particle size (0.4 nm-2.6 nm) and green fluorescence were created utilizing a one-pot hydrothermal process with the precursors ASDA-Na4 and m-phenylenediamine. N, S-CQDs has good optical properties such as high fluorescence intensity, wavelength independence, up-conversion luminescence and fluorescence stability. We examined 27 common ions in water and found that the fluorescence of N, S-CQDs could be selectively quenched by Hg²⁺ and MnO₄^-, and the detection limits are 0.41 μM and 1.2 μM, respectively. The mechanism of quenching is further investigated. The fluorescence of N, S-CQDs-Hg²⁺ system can be restored by halogen ions (Cl^-, Br^-, I^-), while the fluorescence of N, S-CQDs-MnO₄^- system can be partially restored by Fe²⁺. This forms an "on-off-on" mode of fluorescent probes. In addition, we also studied that trace amounts of N, S-CQDs can improve the photostability of RhB.

Significance: The N, S-CQDs are fluorescent probes in an "on-off-on" mode. N, S-CQDs with green fluorescence (on) can be quenched by Hg²⁺ and MnO₄^- (off). The fluorescence quenched by Hg²⁺ can be restored by halogen ions again, while the fluorescence quenched by MnO₄^- can partially be restored (on). This ion detection method can be used to visually detect the two ions in the field, with the advantages of low cost, simple operation and visual intuition.

Keywords: Fluorescence sensor; Ion detection; Light stability; N; S-CQDs.