Abstract
Highly fluorescent carbon dots (CDs) exhibiting molecular fluorescence were synthesized and successfully used for sensing ferricyanide based on fluorescence quenching. We conducted dialysis to purify the CDs and found that the dialysate is also fluorescent. From the mass spectra and quantum yield analyses of the dialysate, it is demonstrated that molecular fluorophores were also synthesized during the synthesis of CDs. By the comparison of fluorescence spectra between CDs and dialysate, it is established that the fluorescence emission of CDs partly originates from fluorophores that are attached to CDs’ surface. The fluorescence quenching caused by ferricyanide is proved to be the overlap of absorption spectra between ferricyanide and CDs. The changes of the absorbance and fluorescence spectra are combined to enhance the detection sensitivity, and the limit of detection is calculated to be 1.7 μM. A good linear response of fluorescence-absorbance combined sensing toward ferricyanide is achieved in the range of 5–100 µM. This method is highly selective to ferricyanide among other common cations and anions, and it is also successfully applied in detecting ferricyanide in real water samples.
Highlights
Carbon dots (CDs), as carbon-based fluorescent nanomaterials, have attracted extensive attention due to their outstanding properties such as facile synthesis, low toxicity and high quantum yield since the discovery in 20041
It is found that molecular fluorophores were synthesized, and they led to the fluorescence emission of carbon dots (CDs)
The CDs were successfully synthesized via microwave assisted heating of citric acid monohydrate (CA)
Summary
Carbon dots (CDs), as carbon-based fluorescent nanomaterials, have attracted extensive attention due to their outstanding properties such as facile synthesis, low toxicity and high quantum yield since the discovery in 20041. It can be supposed that fluorophores were synthesized during the synthesis of CDs. Positive mass spectra (MS) measurement confirms the existence of small molecules in dialysate, and the most prominent peak at 344 m/z suggests a molecular weight of 343 (Fig. 3a).
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