Chemistry Reference
In-Depth Information
organic bridging groups could result in distinct biomimic performance. However,
many practical detecting or sensing applications require extraordinarily high sen-
sitivities. Optical sensors are molecular receptors whose optical properties can be
changed upon binding to specific guests. Optical sensing and imaging systems
have been intensively investigated for their capability of providing high sensitivity,
fast, and easy detection processing, biocompatibility, and adaptability to a wide
variety of conditions [
126
]. Since lanthanide-based hybrids are photoluminescent
materials with ease of functionalization, they are a promising class of materials
for applications in sensing and optical imaging. Mesoporous cerium phosphonate
nanostructured hybrid spheres are prepared with the assistance of C
16
TABr while
using EDTMP as the coupling molecule [
127
]. The resulting hybrid is constructed
from the cerium phosphonate nanoparticles, accompanied by high specific sur-
face area of 455 m
2
g
−
1
. The uniform incorporation of rare earth element cerium
and organophosphonic functionalities endows mesoporous cerium phosphonate
with excellent fluorescence properties for the development of an optical sensor
for selective Hg
2
+
detection on the basis of the fluorescence-quenching mecha-
nism. The signal response of mesoporous cerium phosphonate against the Hg
2
+
concentration is linear over the range from 0.05 to 1.5
μ
mol L
−
1
, giving a LOD
of 16 nmol L
−
1
(at a signal-to-noise ratio of 3) (Fig.
5.24
). Most of the common
physiologically relevant cations and anions did not interfere with the detection of
Hg
2
+
. Although lanthanide-based MOFs with valuable luminescent properties,
which can be defined as crystalline organic-inorganic hybrids to some extent, have
been gradually utilized as optical sensing materials [
128
-
130
], nevertheless, there
are still some knotty problems. The major one is the insufficient water solubility
that restricts the further uses in biologic systems, and the emission band usually
contains multipeaks, reducing the monochromaticity and measurement precision.
Hence, the present mesoporous cerium phosphonate hybrid nanostructured spheres
Hg
2+
N
N
N
N
P
P
P
Ce
P
Ce
Ce
Ce
O
O
O
O
Hg
2+
“OFF”
“ON”
Fig. 5.24
Scheme of Hg
2
+
detection by mesoporous cerium phosphonate nanostructured
spheres based on fluorescence-quenching mechanism. Reprinted with permission from Ref.
[
127
]. Copyright 2014, American Chemical Society
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