Carbon dots (CDs)
as new fluorescent materials with excellent fluorescence properties
have shown enormous potential applications, especially in anticounterfeiting
and cell imaging. Herein, nitrogen-doped CDs (NCDs) with excellent
biocompatibility were prepared by a simple thermal sintering method.
An extremely large red shift (∼130 nm) of the emission peak
was observed when the excitation wavelength changes from 355 to 550
nm, indicating that NCDs are excellent fluorescent labeling materials
for multiple cell imaging. On the other hand, NCDs showed obvious
changes of emission intensity and peak position when the temperature
increased from 223 to 323 K and the pH values changed from 1 to 13,
respectively, which has been demonstrated by the “horse”
pattern printed with NCD water-soluble fluorescent inks. The nontoxic
NCDs dispersed in a multiple matrix are highly sensitive to excitation
wavelength, temperature, and pH, indicating their great potential
application in multiple anticounterfeiting and multiple cell imaging.
The N-modified carbon dots/graphitic carbon nitride (NCDs/g-C3N4) aerogel was successfully prepared by simple electrostatic self-assembly of NCDs and g-C3N4 nanosheets without any harmful solvents or cross-linking agents. The prepared aerogel...
Nitrogen-doped
carbon dots (NCDs) synthesized by the low-temperature
sintering method show electronegativity rich in −COO–,
−CO–NH–, −NH–, and −OH.
The structure, morphology, and fluorescence performance of NCDs were
successively characterized by Fourier-transform, infrared, X-ray photoelectron
spectroscopy, scanning electron microscopy, transmission electron
microscopy, photoluminescence, ultraviolet (UV), and X-ray fluorescence
analyses. On the one hand, NCDs can sensitively detect Pb2+ in water with a detection limit of 3 ppb through the dual response
of fluorescence emission spectra and UV absorbance spectra. On the
other hand, the negatively charged NCDs combine with various positively
charged heavy metal ions (Pb2+, Cu2+, Ni2+, Co2+, and Cd2+) through charge attraction
and coordination to form a hydrogel, thereby removing heavy metal
ions from the water. Among them, the removal rate of Pb2+ by NCDs is as high as 94.8%. It is the first time that pure NCDs
have been used to remove heavy metal ions quickly and easily in the
form of a reversible hydrogel. A simple way is to achieve ultrasensitive
detection and high-efficiency removal of heavy metal ions in water
with unitary NCDs.
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