Research Article pubs.acs.org/journal/ascecg
Nitrogen-Doping Enhanced Fluorescent Carbon Dots: Green Synthesis and Their Applications for Bioimaging and Label-Free Detection of Au3+ Ions Jie Liao, Zehong Cheng, and Li Zhou* Guangxi Ministry-Province Jointly-Constructed Cultivation Base for State Key Laboratory of Processing for Nonferrous Metal and Featured Materials, MOE Key Laboratory of New Processing Technology for Nonferrous Metal and Materials, and College of Materials Science and Engineering, Guilin University of Technology, Guilin 541004, P. R. China S Supporting Information *
ABSTRACT: Fluorescent carbon dots (CDs) hold great promise for a myriad applications due to their fascinating attributes. However, the development of CDs with high fluorescence quantum yield (QY) and unique surface property is still in its infancy. Herein, we report a simple and green strategy to produce water-soluble nitrogen-doped CDs (N-CDs) via the one-pot hydrothermal carbonization of the mixture of natural peach gum polysaccharide (PGP) and ethylenediamine. The resulting N-CDs exhibit a remarkably enhanced QY (28.46%) as compared with that of undoped CDs (5.31%). In addition, the N-CDs show stable fluorescence against ionic strength variation and pH change. Preliminary biological studies reveal that N-CDs possess low cytotoxicity and high fluorescent contrast in cells. Moreover, we present here for the first time that the obtained N-CDs can exhibit a fast and highly sensitive and selective fluorescence quenching effect toward Au3+ ions. The detection limit can reach 6.4 × 10−8 M, which compares favorably to other reported fluorescent probes. We have also demonstrated that the N-CDs can be employed to sense Au3+ ions in real river water. Considering the easy synthetic process and excellent performance of the N-CDs, this investigation opens up new opportunities for preparing high-quality fluorescent CDs to meet the requirement of many applications. KEYWORDS: Nitrogen-doped carbon dots, Fluorescence, Bioimaging, Sensing of Au3+ ions, Selectivity
■
INTRODUCTION Since the pioneering work by Sun et al., fluorescent carbon dots (CDs) have captured intensive attention from many researchers due to their fascinating features, which include excellent watersolubility, high photostability, unique excitation-dependent fluorescence, and superior biocompatibility.1−5 The applications of CDs in bioimaging, sensing, catalysis, and lightemitting devices have been widely investigated.6−16 To date, a myriad techniques such as chemical oxidation, laser ablation, electrochemical synthesis, ultrasonic synthesis, microwave pyrolysis, and hydrothermal carbonization have been reported for fabricating fluorescent CDs.17−24 Among them, one-pot hydrothermal carbonization of natural biomass to afford CDs is an attractive route due not only to the facile and eco-friendly reaction process but also to the cheap and sustainable raw material. We and other groups have employed natural biomass to prepare fluorescent CDs via the hydrothermal carbonization technique.25−28 However, the obtained CDs showed low fluorescence quantum yield (QY) (
