A dual-mode probe for colorimetric and fluorometric detection of cysteine based on phosphorus/nitrogen co-doped CQDs and gold nanorods

• Published in: Sensors and actuators. B, Chemical Vol. 273; pp. 1627 - 1634
• Main Authors: Wang, Yanying, Liang, Ruoxuan, Liu, Wei, Zhao, Qingbiao, Zhu, Xiaoyan, Yang, Li, Zou, Ping, Wang, Xianxiang, Ding, Fang, Rao, Hanbing
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10.11.2018
• Subjects: Cysteine; Dual-signal senor; Gold nanorods; Inhibit reaction; Non-aggregation sensor; Non-aggregation sensor; Cysteine; Gold nanorods; Inhibit reaction; Dual-signal senor
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2018.07.084

The fluorescent of phosphorus/nitrogen co-doped CQDs (PNCQDs) was quenched by gold nanorods (AuNRs). under the catalytic of Fe3+, AuNRs were effectively etched by OH·, with the increase of etching depth, the absorbance of AuNRs gradual decrease as well as the fluorescence of PNCQDs recovery. However, Cys can forcefully suppress this etching reaction by means of coordination effect between hydrosulfide group (-SH) in Cys and Fe3+, thus, a dual-mode probe was established for colorimetric and fluorometric detection of cysteine. [Display omitted] •A dual-signal biosensors based on phosphorus/nitrogen co-doped CQDs and gold nanorods was established.•The strategy has wider linear range and lower detection limit for cysteine detection.•The proposed strategy demonstrated a potential for detecting cysteine in original urine samples.•The detection strategy was based on the fluorescence change of PNCQDs/AuNRs etches before and after. In this study a novel method was developed for the fluorescent and colorimetric determination of cysteine (Cys). The fluorescent determination was designed based on surface plasmon-enhanced energy transfer (SPEET), and phosphorus/nitrogen co-doped CQDs (PNCQDs) were employed as the donor, of which the fluorescence was quenched by gold nanorods (AuNRs) (acceptor). For the colorimetric assay, under the catalytic effect of Fe3+, AuNRs were effectively etched by OH· that was generated by the Fenton reaction. The etch of the AuNRs lead to the decrease in the absorbance intensity, the blue shift of longitudinal surface plasmon resonance (LSPR) absorption peak of AuNRs as well as the fluorescence of PNCQDs recovery. However, Cys can suppress this etching reaction by coordination effect between hydrosulfide group (SH) in Cys and Fe3+, leading to red shift of the LSPR absorption peak. Similarly, the fluorescence will change with the absorbance. The peak shift and the fluorescence change can be applied to monitor of Cys. Under the optimal operation conditions, highly sensitive determination of Cys was achieved, with the fluorescent detection limit of 1.2 nM and the colorimetric detection limit of 0.9 nM. The linearity of the system towards Cys was in the range of 0.005–25 μM. The highly sensitive determination of Cys in urine samples demonstrates that this method possesses high potential for on-site and visual detection of urine Cys.