Abstract
Carbon dots (CDs) have a wide range of applications in chemical, physical and biomedical research fields. We are particularly interested in the use of CDs as fluorescence nanomaterials for targeted tumor cell imaging. One of the important aspects of success is to enhance the fluorescence quantum yields (QY) of CDs as well as increase their targetability to tumor cells. However, most of the reported CDs are limited by relative low QY. In the current study, for the first time, one-step synthesis of highly luminescent CDs by using folic acid (FA) as single precursor was obtained in natural water through hydrothermal method. The as-prepared CDs exhibited QY as high as 94.5% in water, which is even higher than most of organic fluorescent dyes. The obtained CDs showed excellent photoluminescent activity, high photostability and favorable biocompatibility. The FA residuals in CDs led to extraordinary targetability to cancer cells and promoted folate receptor-mediated cellular uptake successfully, which holds a great potential in biological and bioimaging studies.
Highlights
Folic acid (FA), one of the B vitamins, is an essential dietary component that can effectively decrease the risk of several diseases[21,22], such as neural-tube defects and congenital heart defects
folic acid (FA) was directly dissolved in ultrapure water without addition of any additives and followed by a hydrothermal treatment at melting point 240 °C for 6 h, and ultra-bright FA-derived N-Carbon dots (CDs) with quantum yields (QY) up to 94.5% in water were obtained successfully
Excitation-independent FL behavior reflects that the surface state of these CDs are mainly single energy level, and almost all excited electrons return to the ground state via a radiative route[27,28], which can enhance the passivation degree of traps on CDs and increase the fluorescence QY29–31
Summary
Haifang Liu[1], Zhaohui Li1,2, Yuanqiang Sun[1], Xin Geng[1], Yalei Hu1, Hongmin Meng[1], Jia Ge1 & Lingbo Qu1. FA was directly dissolved in ultrapure water without addition of any additives and followed by a hydrothermal treatment at melting point 240 °C for 6 h (see Fig. 1 and the experiment section), and ultra-bright FA-derived N-CDs with QY up to 94.5% in water were obtained successfully. These CDs showed instinctive targetability to cancer cells without the requirement of any additional surface modifications
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