5
18
L. Zhang et al. / Chinese Chemical Letters 25 (2014) 517–522
Cl
Br
Br
O
O
O
O
Reflux
HOCH CHOHCH Cl
3
CH COONa, DMSO
2
2
NaOCH3, CuO, KI
10 - 115 o
C
PTSA, Toluene
1
S
S
S
Yield: 88.02%
Yield: 61.96%
O
O
O
OH
OH
O
O
O
O
H2O, NaOH
Reflux
O
O
O
O
O
O
O
DMAP, DCC, CH Cl
2
2
S
S
S
Yield: 97.58%
Total yield: 39.98%
Yield: 88.84%
Yield: 84.80%
Fig. 1. The five-step synthesis route of C4-EDOT-COOH.
single-walled carbon nanotubes/b-cyclodextrin conjugate modified
LLC. BPA stock solution was prepared with absolute ethanol and
GCEandmulti-wallcarbonnanotubes/melaminewerefabricatedfor
the sensitivity and selective determination of BPA by Li and
coworkers [21,22]. Sun et al. reported a chitosan–graphene compos-
ite modified carbon ionic liquid electrode for the voltammetric
detection of BPA [23]. Recently, poly(3,4-ethylenedioxythiophene)
stored at 277–281 K. Lithium perchlorate trihydrate (LiClO
disodium hydrogen phosphate dodecahydrate (Na HPO
ꢀ12H
and sodium dihydrogen phosphate dihydrate (NaH PO
were obtained from Sinopharm Chemical Reagent Co., Ltd. 0.1 mol/L
Phosphate-buffered solution (PBS, pH 7.0) was prepared from
4
ꢀ3H
2
O),
O),
2
4
2
2
4
ꢀ2H
2
O)
(
PEDOT) alone was also reported for the direct electrochemical
0.1 mol/L NaH
ylic group functionalized SWCNT (f-SWCNT) suspension (SWCNT
content 0.835 wt%, diameter 1–2 nm, length 5–30 m) was
purchased from Chengdu Institute of Organic Chemistry, Chinese
Academy of Sciences. All reagents were of analytical grade and used
without further purification. All solutions were prepared using
deionized distilled water.
Electrochemical experiments were carried out by using
CHI660B connected to a conventional one-compartment three-
electrode electrochemical cell. A conventional three-electrode
system was employed: the working electrode was the f-SWCNT/
PC4/GCE, a platinum wire was used as the auxiliary electrode, and
the saturated calomel electrode SCE was used as the reference
electrode. Scanning electron microscopy (SEM) measurements
were taken using VEGA\\TESCAN Digital Microscopy Imaging. All
potentials were given vs. SCE. The pH values of solutions were
measured with a Delta 320 pH meter (Mettler-Toledo Instrument,
Shanghai, China).
2
PO
4
ꢀ2H
2
O and 0.1 mol/L Na
2
HPO
4
ꢀ12H
2
O. Carbox-
detection of BPA [24].
PEDOT, one of the most stable conducting polymers, has been
the main subject of extensive research in the past quarter century
due to its versatile properties such as high electrical conductivity,
low band gap, good redox activity, high thermal stability, and
excellent transparency in the doped state, and it has been of
particular significance because of its potential applications in
rechargeable batteries, electrochromic display devices, organic
light emitting diodes, supercapacitors, antistatic coatings, corro-
sion inhibitors, printed circuits, smart windows, microwave
absorbing materials, and chem/bio sensors [25–29]. Simultaneous-
ly, in its well-known study, one of most attractive properties of
PEDOT is that its properties can be tuned by grafting various
functional groups. Carboxylic group functionalized 3,4-ethylene-
dioxythiophene (EDOT) derivatives were synthesized by Yu’s
group, and electropolymerized corresponding thin polymer film
m
(PC4) exhibited good biocompatibility, very low intrinsic cytotox-
icity, and displayed no inflammatory response upon implantation,
making them ideal for diode devices, ionic exchanges, cell
capturing, biosensing, and bioengineering applications [30–36].
Owing to their high electrical catalytic properties, high
chemical stability, and extremely high mechanical strength,
SWCNT has been used in the field of modification of electrode
surface. Moreover, as an electrode material, SWCNT not only
enhances the electron transfer rate, selectivity, and sensitivity, but
also minimizes overpotential and decreases the separation
between the oxidation and reduction peaks [37–42].
2.2. Synthesis of C4-EDOT-COOH monomer
In a previous work, we chose 3,4-dibromothiophene as the
starting material for the synthesis of 2 -hydroxymethyl-3,4-
ethylenedioxythiophene (EDOT-MeOH) through a five-step pro-
0
cess [43]. Then,
a solution of succinic anhydride (1.231 g,
12.301 mmol), triethylamine (1.088 mL), and 4-dimethylamino-
pyridine (53.51 mg, 0.438 mmol/L) in 21 mL anhydrous dichlor-
omethane was added dropwise into
0
a
solution of 2 -
In this work, 4-((2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)-
methoxy)-4-oxobutanoic acid (C4-EDOT-COOH) with good solu-
bility in water was synthesized by an efficient five-step sequence
hydroxymethyl-3,4-ethylenedioxythiophene (1 g, 5.807 mmol/L)
in 54 mL anhydrous dichloromethane and stirred at room
temperature overnight. The mixture was treated with 70 mL of
an aqueous 10% hydrochloric acid solution thrice, 70 mL deionized
water five times, and 70 mL saturated sodium chloride aqueous
solution twice. The remaining organic layer was dried by
anhydrous sodium sulfate. C4-EDOT-COOH was obtained (2.19 g,
(
Fig. 1). Subsequently, a fast and easy method for the detection of
BPA at the f-SWCNT/PC4/GCE has been developed. Electrochemical
properties of the modified electrode for the voltammetric
detection of BPA were studied in detail. It was found that the
electrode exhibited excellent electrocatalytic activity to the
oxidation of BPA.
l
97.58%) as a white solid under reduced pressure. H NMR
(400 MHz, CDCl
3
): d 6.36 (s, 2H), 4.01–4.39 (overlapping m, 5H),
2.66–2.72 (m, 4H).
2
. Experimental
2.3. Preparation of modified electrode
2.1. Reagents and Apparatus
Prior to electrodeposition, the GCE (
polished with chamois leather containing 0.05 m
F
= 3 mm) was carefully
m alumina slurry
and ultrasonically cleaned with deionized distilled water, absolute
BPA was obtained from Aladdin Chemistry Co., Ltd. and sodium
dodecyl sulfate (SDS, 95%) was purchased from Sigma–Aldrich Co.
Zhang, Long
