Using these optimal conditions, attention now turns to
study another important parameter, reproducibility, of the
SWCNT/PyCD PCB-77 sensor. Firstly, the reproducibility of
three independently fabricated SWCNT/PyCD electrodes
shows a satisfactory value of 1.9% (Relative Standard Deviation).
And the intraassay precision of the SWCNT/PyCD electrode
was evaluated by assaying one PCB-77 level for reduplicate
measurements, in which the SWCNT/PyCD electrode can be
regenerated by soaking it in an ethanol saturated solution of
sodium acetate for 1 h with magnetic stirring after included by
PCB. It may be that the self-aggregation behavior of PCB was
promoted by sodium acetate. Only 3.2% loss of DRet was
found from 10 mM PCB-77 in the intraassay precision
measurements (Fig. S7a, ESIw), suggesting satisfactory precision
and reproducibility. Furthermore, the DRet towards guest
PCB-77 molecules almost remains unchanged despite the
modified electrode being stored in air for more than one week.
In addition, after continuously scanning for 200 cycles, only
5.74% (at 0.388 V) for the current densities of the peaks in the
same potential region was observed. These results provide
evidence that the SWCNT/PyCD electrode exhibits a high
stability and could be perfectly renewed in sodium acetate
solutions. Secondly, for a control, the same intraassay precision
measurements were carried out with the SWCNT/CD (without
pyrenyl group) electrode. The Ret was shown to be significantly
reduced by almost 71% after transferring the electrode to an
ethanol saturated solution of sodium acetate (Fig. S7b, ESIw),
suggesting that without the pyrene units the CWCNT/CD has
poor reproducibility, some CD molecules were peeled off with
magnetic stirring.
Fig. 3 Interference studies of a SWCNT/PyCD system. Nine organic
compounds were employed as the guests for the sensing test.
solutions. The method offers considerable simplicity and
economy of determination of polychlorinated biphenyl as
compared to the redox reaction-based electrochemical methods.
This work was supported by the One Hundred Person
Project of the Chinese Academy of Sciences, China, the
National Key Scientific Program-Nanoscience and Nano-
technology (2011CB933700), the National Natural Science
Foundation of China (20875004 and 21075002), and Young
Program of Anhui Province (2010SQRL179).
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In summary, we have demonstrated an electrochemical
impedance sensor for determination of polychlorinated biphenyl,
such as PCB-77, based on the concept of host–guest molecular
recognition with an SWCNT/PyCD modified electrode. This
system is highly sensitive and selective to PCB-77 without any
interference. Also, the SWCNT/PyCD electrode exhibits a
high stability and could be perfectly renewed in sodium acetate
c
5342 Chem. Commun., 2011, 47, 5340–5342
This journal is The Royal Society of Chemistry 2011