Biomedical Engineering Reference
In-Depth Information
Fig. 4.2
CV (
a)
and ECL intensity versus potential (
b)
: (
black
) 0.1 M NaClO
4
and PBS only;
(
red
) with addition of 13 mM TPrA; (
blue
) expanded scale of ECL intensity of curve 1. Potential
scan rate
=
20 mV/s at an HOPG electrode (area
=
0.07 cm
2
).
c
Photoluminescence in air of an
HOPG electrode after ECL experiments. Excitation wavelength is 430 nm (
black
) and 440 nm
(
red
).
d
ECL spectrum of HOPG in 0.1 M NaClO
4
, PBS (pH 7.0) containing 13 mM TPrA.
Reprinted with permission from Ref. [
46
]. Copyright 2009 American Chemical Society
electrodes. Similar phenomenon was observed by Yuan's group [
48
] using hemin-
graphene nanosheets (H-GNs) as the ECL amplification. Owing to the superior
electrical conductivity of H-GNs, they were able to promote electron transfer, so
as to amplify the luminol ECL signals of the prepared biosensor.
In the author's group, a series of graphene QD (GQD) and its nanocompos-
ites were synthesized and studied. Via the electrostatic interactions between
negatively charged thioglycolic acid (TGA)-modified CdSe QDs and positively poly
(diallyldimethylammonium chloride) (PDDA)-protected graphene, the P-GR-CdSe
composites were successfully prepared and used to construct an ECL immu-
nosensor [
49
]. With the help of the excellent conductivity, extraordinary electron-
transport properties and large specific surface area, the interfusion of PDDA-protected
graphene (P-GR) with CdSe QDs film not only improved the ECL intensity, response
speed, and stability, but also held high levels of protein loading, which resulted in
extreme sensitivity.
Later, we prepared the greenish-yellow luminescent graphene quantum
dots (gGQDs) with a quantum yield (QY) up to 11.7 % through the assistance
of microwave irradiation [
50
]. As shown in Fig.
4.3
, ECL is observed from the
gGQDs for the first time in 0.05 M, pH 7.4 Tris-HCl buffer solution (TBS)
with 0.1 M K
2
S
2
O
8
as coreactant. The possible ECL mechanism was proposed
as follows: firstly, strongly oxidizing SO
4
radicals and GQDs
·−
radicals were
produced by electrochemical reduction in S
2
O
8
2
−
and GQDs, respectively.
·−
