One-step and green synthesis of nitrogen-doped
carbon quantum dots for multifunctional
electronics†
Zhan Wang, Lijun Cao, Yamei Ding, Rui Shi, Xiangjing Wang, Hang Lu, Zhengdong Liu,
Fei Xiu, Juqing Liu
*
and Wei Huang
*
A facile one-step and green synthesis method was developed to prepare water soluble, environmentally
friendly, and highly nitrogen-doped carbon quantum dots (CQDs) with tunable properties. As a proof-of-
concept application, a multifunctional electronic device with the configuration of PEDOT:PSS/s-
CQD@SWCNT/PEDOT:PSS was fabricated through a full-solution process, which exhibits memory and
current limiting behavior, with the merit of stable operation and reliable endurance.
Carbon electronic materials, including carbon quantum dots
(CQDs), fullerenes, carbon nanotubes (CNTs), graphene, and
graphdiyne, have aroused extensive attention due to their novel
structures, and unique electrical and optical properties.
1–4
Among them, CQDs have attained a prominent position in the
eld of nanoscience and nanotechnology owing to their large
specic surface area, low toxicity, excellent solubility and highly
tunable properties.
5–7
Several attempts, such as laser irradia-
tion,
8
microwave irradiation,
9
electrochemical,
10
chemical
cutting,
11
and hydrothermal routes,
12
have been reported to
realize the controllable synthesis of CQDs with tunable prop-
erties. So far, compared with other mentioned methods,
hydrothermal approach is one of the most efficient and effective
methods to prepare CQDs, with the merit of simple process,
large-scale production, and potential low cost. The properties of
CQDs can be tuned via doping or surface functionalization,
13–20
but some of the most common challenges faced by multi-step
synthesis, expensive carbon sources, low yield, complex prepa-
ration and post-treatment associating with toxic chemicals.
Utilization of one-step synthesis, nontoxic chemicals, environ-
mentally benign solvents, and renewable source materials are
highly desirable in the synthesis of doped CQDs.
Because of their outstanding physical and chemical proper-
ties, CQDs and their derivatives, especially for doped CQDs,
have been used successfully in the eld of bioimaging, catalysis
and sensor issues.
21–23
Recently, doped and undoped CQDs also
show promising applications in the next generation of organic
electronic and optoelectronic devices, such as solar cells for
energy conversion, light-emitting devices for display and
lighting, memories for data storage, and photodetectors for
information collection.
24–27
However, most of the CQDs-based
organic electronics focus on the actualization of single func-
tion in a single device, but there has been a lack of break-
throughs in the multifunctional electronic devices. Therefore,
how to realize CQDs-based multifunctional devices is extremely
important.
In this work, we present a facile one-step and green approach
for the synthesis of nitrogen-doped CQDs via asimplehydro-
thermal method. Our strategy is renewable, inexpensive,
nontoxic, and environmentally friendly since sustainable vegeta-
bles and deionized water are the choice of self-doped carbon
sources and solvent medium, respectively. Importantly, this
method is a general process and can be used to prepare various
nitrogen-doped CQDs from different precursors. As a proof of
concept, the hybrid nitrogen-doped CQDs and single-walled
carbon nanotubes (SWCNTs) lm is employed as active mate-
rials in carbon electronics with PEDOT:PSS lm as both of the
electrodes, the solution processable device does not exhibit vola-
tile memory effect, but also features a current limiting behavior.
Self-doped carbon sources, including spinach, Guangdong
cabbage, and brassicachinensis l, were purchased from local
markets as precursor. In order to synthesize CQDs, 100 g
precursor and 20 mL deionized water were squeezed and added
into a 50 mL Teon-lined stainless steel autoclave, then main-
tained at 180
C for 12 h. Aer the reaction and cooling process,
dark brown solution was ltered with a 0.22 mm membrane
followed by dialyzing using 1 kDa dialysis membrane for 1 day
to remove the large particles. Finally, CQDs were collected from
the light yellow aqueous solution and stored at 4
C for further
characterization and device fabrication.
Fig. 1a shows the transmission electron microscopy (TEM)
image, which displays that the spinach-CQDs (referred as s-
Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials
(IAM), Jiangsu National Synergistic Innovation Center for Advanced Materials
(SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing
211816, P. R. China. E-mail: iamjqliu@njte ch.edu.cn; iamwhuang@njtech.edu.cn
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c7ra03840b
Cite this: RSC Adv.,2017,7, 21969
Received 4th April 2017
Accepted 13th April 2017
DOI: 10.1039/c7ra03840b
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