Ethanol-Precipitation-Assisted Highly Efficient Synthesis of Nitrogen-Doped Carbon Quantum Dots from Chitosan

Abstract

Nitrogen-doped carbon quantum dots (NCQDs) were prepared from chitosan through a hydrothermal reaction. When ethanol precipitation was used as the purification method, a high product yield of 85.3% was obtained. A strong blue fluorescence emission with a high quantum yield (QY) of 6.6% was observed from the NCQD aqueous solution. Physical and chemical characteristics of the NCQDs were carefully investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), Raman spectra, X-ray photoelectron spectroscopy (XPS), and transient fluorescence spectra. Experimental results showed that diameters of the NCQDs were in the range of 2–10 nm. The carbon quantum dots possess good water dispersibility and precipitation by ethanol. When used for metal ion detection, the detection limit of the NCQDs for Fe3+ was as low as 1.57 μM. This work proposed a facile method to synthesize NCQDs from chitosan with high yield and demonstrated that carbon quantum dots derived from chitosan were promising for ion detection.

A pseudohomogeneous nanocarrier based on carbon quantum dots decorated with arginine as an efficient gene delivery vehicle

“…To determine presence of functional groups on the surface of CQDs, FT-IR spectroscopy was used for Arginine-CQDs. The FT-IR spectrum of chitosan exhibit strong bond at 3445 cm −1 attributed to O–H and N–H stretches bond 20 , 21 , 24 . The C=O stretching and N–H bending of residual N-acetyl groups appear at 1640 and 1590 cm −1 , respectively.…”

“…The chitosan-based CQDs represent the maximum emission at around 435 nm when excited with 340 nm. The stability of fluorescence properties of CQDs vs time, are investigated by examining the change of fluorescence intensity of Arginine-CQDs sample over 3 months 19 – 21 , 24 . The results proved that the CQDs derived from chitosan polymer are stable during this period and about 7% of their fluorescence intensity is reduced.…”

“…Furthermore, the CQDs derived from chitosan have good solubility in various solvents due to sub-nanometric size, high accumulation of different functional groups on the surface of CQDs as well as doping of nitrogen atoms in the carbon lattice which increases the fluorescence nature of CQDs 19 , 20 . Approaches in order to preparing fluorescent chitosan-based CQDs can be generally classified into two main groups: Hydrothermal and Microwave synthesis methodology 21 , 22 . Zhao and co-workers synthesized N-doped CQDs from chitosan using hydrothermal carbonization method with a high degree of carbonization.…”

Biomass‐derived Carbon Quantum Dots – A Review. Part 1: Preparation and Characterization

“…In the NCQDs chitosan‐citrate, a complex is formed by the interactions between the positive charged protonated amino groups of chitosan and the negative charged carboxylate groups of citric acid. At the first instance, a polymer‐like structure is formed and then it is carbonized to obtain NCQDs with carboxyl, hydroxyl and amino groups on their surface 288.…”

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“…Besides, CDs exhibited a 26% quantum yield with less toxicity against L929 and MG-63 cell lines, proving its candidature in cellular imaging applications. In the same way, Zhan et al prepared nitrogen-doped carbon quantum dots (N-CQDs) with 85.3% yield from chitosan as a precursor via the hydrothermal method [ 82 ]. The synthesized N-CQDs exhibited a smaller size (2–10 nm) with a 6.6% quantum yield.…”