2.1 Carbonaceous Quantum Dots
17
Fig. 2.1 Synthesis procedures of GF supported GQDs-coated VO 2 nanobelts array. TEM and
Scanning TEM images of nanosized S on GQDs electrode in Li 2 S 8 cathode electrolyte when
cycling 20 cycles in the state of charged: a low and high magnification images of nanosulfur
in GQD. Lumps represent nanosulfur-containing GQDs electrodes, and the small black particles
are nanosulfur, b GQDs coated on nanosulfur particles, d High-resolution transmission electron
microscope (HRTEM) image displaying the lattice fringes of the nanosulfur as well as the GQDs,
e The fast Fourier transform (FFT) of the initial HRTEM image is c in the middle of the filtered
image. The two bright spots indicate sulfur particles, and the other spots represent the GQDs lattice
plane. a Reprinted from Ref. Chao et al. (2015), copyright 2014, with permission from American
Chemical Society. b–e Reprinted from Ref. Park et al. (2016), copyright 2016, with permission
from Nature
collapse of little vacuum bubbles, which produce intense hydrodynamic shear forces
and high-speed liquid jets in order to decompose the carbon with layer structure
into GQDs (Tan et al. 2012). In recent, Prasad et al. prepared GQD-like quantum
dots through the ultrasonic desquamation of polythiophene in DMF (Prasad et al.
2014). Fascinatingly, these QDs don’t need to photobleach under consecutive laser
irradiation. In the meantime, laser irradiation with high power can ablate carbon
materials to obtain C-dots. Nevertheless, this method needs sophisticated equipment.
2.1.2 Bottom-Up Method
Stepwise Organic Synthesis. GQDs with well-defined monodispersed structures
can be synthesized by solution chemistry approach, despite with low-throughput
and trouble to avoid aggregation aroused by π-π interaction. For example, Yan
et al. revealed that aryl groups oxidative condensation of polyphenylene dendritic
precursor via stepwise solution chemistry brought about melt graphene moieties and
ultimate formation of GQDs including 168, 132, and 170 carbon atoms that are
conjugated (Yan et al. 2010b) Covalent interaction between 2
, 4, 6
-trialkyl phenyl
groups and the edges of graphene-based materials stabilizes GQDs in liquid. More
recently, homogeneous GQDs (with different dimensions and different colors) could
be produced, with unsubstituted hexa-peri-hexabenzocoronene acting as precursor
(Liu et al. 2011).
Pyrolysis or Carbonization of Organic Precursors. It has been extensively
reported that C-dots and GQDs can be synthetized via thermally decompose or
carbonize small organic molecules. With small organic molecules heated above their
smelting point, they condensate, nucleate, and subsequently form larger C-dots or
GQDs. The used precursors contain organic salts (e.g., diethylene glycolammonium
citrate or octadecylammonium citrate), (Bourlinos et al. 2008) coffee grounds, (Hsu
et al. 2012) glycerol, (Lai et al. 2012) l-glutamic acid, (Wu et al. 2013) ascorbic acid,
(Jia et al. 2012) citric acid, (Dong et al. 2012a; Ju and Chen 2014) and ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) (Deng et al. 2013). Other than
17
Fig. 2.1 Synthesis procedures of GF supported GQDs-coated VO 2 nanobelts array. TEM and
Scanning TEM images of nanosized S on GQDs electrode in Li 2 S 8 cathode electrolyte when
cycling 20 cycles in the state of charged: a low and high magnification images of nanosulfur
in GQD. Lumps represent nanosulfur-containing GQDs electrodes, and the small black particles
are nanosulfur, b GQDs coated on nanosulfur particles, d High-resolution transmission electron
microscope (HRTEM) image displaying the lattice fringes of the nanosulfur as well as the GQDs,
e The fast Fourier transform (FFT) of the initial HRTEM image is c in the middle of the filtered
image. The two bright spots indicate sulfur particles, and the other spots represent the GQDs lattice
plane. a Reprinted from Ref. Chao et al. (2015), copyright 2014, with permission from American
Chemical Society. b–e Reprinted from Ref. Park et al. (2016), copyright 2016, with permission
from Nature
collapse of little vacuum bubbles, which produce intense hydrodynamic shear forces
and high-speed liquid jets in order to decompose the carbon with layer structure
into GQDs (Tan et al. 2012). In recent, Prasad et al. prepared GQD-like quantum
dots through the ultrasonic desquamation of polythiophene in DMF (Prasad et al.
2014). Fascinatingly, these QDs don’t need to photobleach under consecutive laser
irradiation. In the meantime, laser irradiation with high power can ablate carbon
materials to obtain C-dots. Nevertheless, this method needs sophisticated equipment.
2.1.2 Bottom-Up Method
Stepwise Organic Synthesis. GQDs with well-defined monodispersed structures
can be synthesized by solution chemistry approach, despite with low-throughput
and trouble to avoid aggregation aroused by π-π interaction. For example, Yan
et al. revealed that aryl groups oxidative condensation of polyphenylene dendritic
precursor via stepwise solution chemistry brought about melt graphene moieties and
ultimate formation of GQDs including 168, 132, and 170 carbon atoms that are
conjugated (Yan et al. 2010b) Covalent interaction between 2
, 4, 6
-trialkyl phenyl
groups and the edges of graphene-based materials stabilizes GQDs in liquid. More
recently, homogeneous GQDs (with different dimensions and different colors) could
be produced, with unsubstituted hexa-peri-hexabenzocoronene acting as precursor
(Liu et al. 2011).
Pyrolysis or Carbonization of Organic Precursors. It has been extensively
reported that C-dots and GQDs can be synthetized via thermally decompose or
carbonize small organic molecules. With small organic molecules heated above their
smelting point, they condensate, nucleate, and subsequently form larger C-dots or
GQDs. The used precursors contain organic salts (e.g., diethylene glycolammonium
citrate or octadecylammonium citrate), (Bourlinos et al. 2008) coffee grounds, (Hsu
et al. 2012) glycerol, (Lai et al. 2012) l-glutamic acid, (Wu et al. 2013) ascorbic acid,
(Jia et al. 2012) citric acid, (Dong et al. 2012a; Ju and Chen 2014) and ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) (Deng et al. 2013). Other than