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magnetism, and the physical properties of nanosize structures
into one entity. Thus, fluorescent–magnetic composites are
widely used in magnetic separation,28 bioimaging,29 medicine
delivery,30 tumor cell localization,31 and cancer treatment.32
The use of CPs as optical reporters combined with magnetic
nanoparticles improves the comprehensive properties of such
composites. Given this consideration, some CP-based fluores-
cent–magnetic nanocomposites have been successfully
obtained by electrostatic coassembly,33 surface-active agent-
assisted coencapsulation,34 and covalent binding processes.35
Compared with other protocols, covalently binding CPs onto
magnetic particles exhibits strong associations between two
key matrixes. The fluorescence quenching provided by the Fe-
based magnetic substrates can be weakened significantly by
the introduction of a blocking interlayer such as silica to sepa-
rate the magnetic core from the fluorescent shell.36–38
Instrumentations
IR spectra were recorded on an EQUINOX 55 FTIR spectrom-
eter with KBr pellets. 1H NMR and 13C NMR spectra were
collected on a VARIAN INOVA-400 spectrometer operating
respectively at 400 MHz (for 1H) and 100 MHz (for 13C) in
deuterated chloroform solution with tetramethylsilane as ref-
erence. Number-average (Mn) and weight-average (Mw) mo-
lecular weights were determined by UltiMate3000 in THF
using a calibration curve of polystyrene standards. UV–visi-
ble absorption spectra were recorded on a SHIMADZU UV-
2450 UV–vis spectrophotometer. Photoluminescence (PL)
spectra were recorded on HITACHIF-4500 spectrophotome-
ter. Transmission electron microscopy (TEM) was conducted
on JEM-2100 (JEOL). Energy-dispersive X-ray spectroscopy
and scanning electron microscopy (SEM) were conducted on
a Leo1430VP microscopy. Magnetic characterization was per-
formed on a Lakeshore 7404 vibrating sample magnetometer
at 300 K.
Previous reports have shown that small carbazole-based
molecules and CPs can be used as sensitive and selective op-
tical probes for I2. The heavy-atom effect of I2 on the N-
atom in a carbazole ring is the presumable reason for their
fluorescence quenching.39–41 Such interaction between the I2
and the N-atom is transient and weak,39 suggesting that the
quenched fluorescence can be recovered if I2 is distracted
from the I2-N complex. High association constants and com-
position ratios exist between Hg21 and I2 (i.e., 8.3 3 1023
for HgI2 and 6.31 3 1029 for [HgI4]22).25,42 By taking
advantage of such strong associations, trials have been con-
ducted to realize the reciprocal detection of these two
ions.25,42–44 These finding indicate that Hg21 has the poten-
tial to act as a suitable I2 abstractor.
Synthesis
Synthetic route of monomers and polymers is shown in
Scheme 1. 9-(4-Iodophenyl) carbazole,45 3,6-dibromo-9-(4-
iodophenyl) carbazole,46 9-(4-(4-methoxyphenylethynyl)-
phenyl) carbazole,47 1-(4-(3,6-dibromo carbazol-9-yl)phenyl)-
2-(4-methoxyphenylethane)-1,2-dione,48 2,7-bis(4,4,5,5-tetra-
methyl-1,3,2-dioxaborolan-2-yl)-9,9-dioctylfluorene,49 and 3,6-
dibromo-9-(4-triisopropylsilyl-phenylacetylene)
were prepared and purified via similar procedures in the
reported literatures.
carbazole50
The synthetic route of magnetic nanoparticles is shown in
Scheme 2. Fe3O4 nanoparticles, 3-azidopropyltriethoxysi-
lane51 and Fe3O4@SiO2-N3 nanoparticles,36 were fabricated
by following the literatures.
On the basis of these findings, a type of acetylene bared car-
bazole-based CP (P-2) was synthesized and P-2 was covered
onto azide-terminated silica-coated magnetic iron oxide
nanoparticles (Fe3O4@SiO2–N3) by high-reactive Cu1-cata-
lyzed click reaction to obtain a novel fluorescent–magnetic
nanocomposite (Fe3O4@SiO2@P-2). The influence of the opti-
cal properties of Fe3O4@SiO2@P-2 by I2, as well as further
turn-on detection of Hg21 by using this complex as a prob-
ing substrate, was investigated systematically in this study.
Intrinsic magnetic properties of Fe3O4@SiO2@P-2 facilitate
probe recovery by simple magnetic separation. Results show
that such nanocomposites can act as sensitive, selective, and
Synthesis of 9-(4-(3-(4-Methoxyphenyl)
quinoxaline)phenyl)-3,6-dibromo carbazole (5)
Monomer
5 was synthesized according to the method
reported previously.48 Diketone-containing intermediate (4)
(0.563 g, 1 mmol) was refluxed with 1,2-phenylenediamine
(0.321 g, 2.92 mmol) in 50 mL of acetic acid under nitrogen
atmosphere overnight. The reaction mixture was cooled to
room temperature and poured into a large amount of cold
water. The yellow precipitate was filtered and washed sev-
eral times with hot water. The crude product was purified
by column chromatography to afford the target compound as
bright yellow solid (0.510 g, 80%).
reversible optical probes for Hg21
.
EXPERIMENTAL
All reagents, unless otherwise specified, were purchased from
Aldrich, Acros, and TCI Chemical and used without further pu-
rification. Diisopropylamine, toluene, and tetrahydrofuran
(THF) were distilled from sodium in the presence of benzo-
Fourier transform infrared spectroscopy (FTIR) (KBr,
cm21): 3059, 2837, 1602 (C@N), 1512 (C@N), 1466, 1435,
1340, 1256, 1170, 1053, 1024, 975, 835, 801, 764, 633,
596, 544. 1H NMR (CDCl3, ppm) d: 8.20–8.17 (m, 4 H),
7.81–7.79 (m, 4 H), 7.58–7.50 (m, 6 H), 7.31–7.26 (m, 2
H), 6.95–6.93 (m, 2 H), 3.86 (s, 3 H). 13C NMR (CDCl3,
ppm) d: 160.48, 152.93, 152.12, 141.50, 140.99, 139.54,
139.04, 137.20, 131.57, 131.44, 131.10, 130.30, 129.96,
129.50, 129.2316, 126.53, 124.12, 123.29, 113.91, 113.31,
111.48, 55.39.
phenone and degassed before use. Solutions of Al31, Pb21
,
Cu21, Mg21, Ni21, Cd21, Fe31, Ag1, Ba21, and Zn21 were pre-
pared from their nitrate salts; Hg21 was prepared from its ac-
etate salts; Fe21, Co21, and Sr21 were prepared from their
chloride salts. Concentrations of metal solutions were con-
trolled at 1021 M in deionized water and were diluted subse-
quently to different concentration stocks for next use.
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JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2013, 00, 000–000