Environmental Engineering Reference
In-Depth Information
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-0.1
(i)
(f)
(g)
0.15
GQDs
GQDs
UV
FL
Abs
800
GQDs + 20 µm Cl
600
GQDs + 20 µm Cl
0.1
400
0.05
200
0
0
300
400
500
600
700
Wavelength (nm)
Common ions
Heavy metal ions
(h)
(j)
800
R
2
= 0.992
0.6
2000 a.u.
0.4
a
b
0.2
400
c
d
e
0
0
2
4
6
8
10
C
Cl
(µM)
400
800
1200
1600
2000
0
500
600
Wavelength (nm)
700
Raman shift (cm
-1
)
FIGURE 34.5 (Continued)
(f and g) TEM images of the GO/PDDA/Ag NPs at different magniications. (h) SERS spectra of 9 nM folic acid obtained in the GO/PDDA/Ag NP solutions with
(
a
) 0.02 mg/mL, (
b
) 0.01 mg/mL, (
c
) 0.004 mg/mL, (
d
) 0.0025 mg/mL, and (
e
) 0.002 mg/mL graphitic carbon. (Adapted from Ren, W. et al.,
ACS Nano
,
5, 6425, 2012.
With permission.) (i) Plot illustrating the selectivity of the GQD-based sensor for chlorine over other ions in pH 8 solution. Inset shows the UV and luorescence (FL)
spectrum of 0.14 mg/mL GQD solution in the absence and presence of 20 μM free chlorine. Inset shows the FL photos of 0.7 mg/mL GQD solution in the absence
(right) and presence (left) of 100 μM free chlorine illuminated by an UV beam of 365 nm. (j) FL response of 0.14 mg/mL GQDs upon addition of various concentrations
of free chlorine in a pH 8 solution (from top: 0, 0.05, 0.1, 0.3, 0.5, 0.7, 1, 2, 4, 6, 8, and 10 μM). Inset: Stern-Volmer plot of FL quenching of the GQDs by free chlorine.
(Adapted from Dong, Y. et al.,
Anal. Chem.
, 84, 8378, 2012. With permission.)
