Opening experiments: synthesis, purification, and characterization of polyethyleneimine-modified carbon dots

doi:10.3724/SP.J.1123.2023.12017

Abstract

Abstract:

Open experiments are an effective means of cultivating top-notch innovative talents. Based on student interests, research hotspots and our laboratory conditions, an experimental scheme was designed. In this experiment, polyethyleneimine modified carbon dots (PEI-CDs) were prepared via a one-step hydrothermal method using citric acid (CA) as the carbon source and PEI as the surface passivator. First, CA and PEI were completely dissolved in 0.1 mol/L HCl and transferred into an autoclave. The autoclave was heated to 130 ℃ for 2 h. PEI-CDs solution was obtained. After cooling to room temperature, the solution was concentrated to 2 mL by rotary evaporation. Finally, the PEI-CDs were precipitated, washed with ethanol, and dried under vacuum at 70 ℃ for 12 h. The obtained PEI-CDs were characterized by fluorescence spectrophotometry, absorption spectrophotometry, infrared spectrometry, and transmission electron microscopy. The results indicated that anhydrous-ethanol precipitation is a simple, rapid, economical, and green purification method. The as-prepared PEI-CDs had unique properties, such as good water solubility, high luminescence, uniform particle sizes, and good stability. Through this open experiment, students can not only master the operation of large-scale instruments but also enhance their interest in scientific research.

Key words: open experiment, polyethyleneimine (PEI), carbon dots (CDs), fluorescence, purification method

CLC Number:

O658

LI Rui, XU Guanhong, YU Hailin, CEN Yao, PENG Yan, SHEN Fanli, WEI Fangdi. Opening experiments: synthesis, purification, and characterization of polyethyleneimine-modified carbon dots[J]. Chinese Journal of Chromatography, 2024, 42(4): 393-398.

Figures/Tables 8

Fig. 1 (a) Fluorescence and (b) UV-vis absorption spectra of polyethyleneimine modified carbon dots (PEI-CDs) in ultrapure water

Fig. 2 Photoluminescent quantum yield (PLQY) standard curves of quinine sulfate and PEI-CDs

Fig. 3 FT-IR spectrum of PEI-CDs

Fig. 4 XPS spectra of PEI-CDs a. Full survey XPS spectrum; b,c,d. high-resolution XPS peaks of C 1s, N 1s, O 1s, respectively.

Table 1 Element contents of PEI-CDs

Name	Peak/eV	Element content/%
C 1s	284	60.15
N 1s	398	18.91
O 1s	531	20.94

Fig. 5 TEM images of PEI-CDs

Fig. 6 Size distribution histogram of PEI-CDs

Fig. 7 Evolution of fluorescence intensities of PEI-CDs under (a) irradiation with ultraviolet light and (b) 4 ℃ (n=3)

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