Environmentally friendly cleaner water-soluble fluorescent carbon dots coated with chitosan:

Synthesis and its application for sensitivity determination of Cr(VI) ions

Haiyan Wu1,2 · Jie Wang3 · Jicheng Xu1,2 · Yan Jiang1,2 · Tao Zhang3 · Dongya Yang3 · Fengxian Qiu3

* Corresponding author. Fengxian Qiu, fxqiu@ujs.edu.cn1 Zhenjiang Key Laboratory of Functional Chemistry, Institute of Medicine and Chemical Engineering,

Zhenjiang College, Zhenjiang 212003, China

2 School of Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China

3 School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, China

Synthesis of fluorescent carbon dots (CDs)

CDs were synthesized through a simple, convenient and one-step hydrothermal method. Briefly,

cellulose (2 g), (NH4)2CO3 (2.0 g) and water (25 mL) were sealed into a Teflon equipped stainless steel

autoclave, which was then placed in a drying oven followed by hydrothermal treatment at 180 oC for 13

h. After the reaction, the autoclave was cooled to room temperature. The product was treated by

ultrasonic dispersion for 15 min at 99 frequency to separate the filtrate from the residue. And then the

aqueous solution was centrifuged at 8000 rpm for 20 min to dislodge the non-fluorescent deposition.

Finally, the purified fluorescent CDs solution was stored at 4 oC in the refrigerator. The cleaner

production of fluorescent CDs powder was obtained by evaporating the CDs solution for standby.

Characterization of as-prepared CDs

The structure and morphology of as-prepared CDs were characterized by UV-vis absorption,

Fluorescence spectra, transmission electron microscopy and X-ray photoelectron spectroscopy.

Fig. S1 UV-Vis absorption spectrum and fluorescence spectra of CDs

Fig. S2 XPS survey scan (a), C1s spectra (b), O1s spectra (c) and N1s spectra (d) of CDs

Fig. S3 TEM image of the CDs