Malachite green derivative-functionalized single nanochannel: Light-and-pH dual-driven ionic gating

Article abstract of DOI:10.1002/adma.201202673

A highly efficient and perfectly reversible ionic gate that can be activated by pH or UV light is demonstrated. Switching between the OFF state and the ON state is mainly dependent on the surface charge transition brought about by a malachite green derivative attached to the interior surface of an ion track-etched conical nanochannel, which makes it suitable for confined spaces. Applications in electronics, actuators, and biosensors can be foreseen.

Full text of DOI:10.1002/adma.201202673

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Malachite Green Derivative–Functionalized Single
Nanochannel: Light-and-pH Dual-Driven Ionic Gating
Liping Wen, Qian Liu, Jie Ma, Ye Tian, Cuihong Li, Zhishan Bo,* and Lei Jiang*
Biological nanochannels that can open and close in response to
ambient stimuli play key roles in the proper performance of cel-
lular and biological processes.[1] However, such kinds of nano-
channels and their embedding lipid bilayers are susceptible to
deterioration in changing external environments.[2] To overcome
these difficulties, much effort has been focused on developing
“abiotic” analogues, solid-state synthetic nanochannels that
exhibit properties similar to those of the biological nanochannels
but would be stable in a variety of conditions, such as tempera-
ture, pH, and mechanical stress.[2,3] So far, a variety of approaches
and techniques have been used to prepare solid-state nanochan-
nels: anodic oxidation,[4] focused-ion-beam etching,[5] electron
beam technology,[6] track etching and so on.[7] The fabricated
nanochannels, however, do not respond to external stimuli and
they are not fully compatible with the application requirements.
Functional groups that are introduced into synthetic nanochan-
nels can respond to environmental stimuli, such as pH,[8] ions,[9]
temperature,[10] ligands,[11] light,[12] and even electric fields,[13]
and some of these responsive nanochannels have been used in
sensing,[14] fi ltering,[15] and energy-conversion systems.[16]
In a nanochannel system with a fixed geometric structure and
a given electrolyte, ionic transport properties are mainly con-
trolled by the physical and chemical properties of the functional-
izing stimuli-responsive materials inside the nanochannels, such
as their configuration, charge, and wettability.[3b,17] In most cases,
one stimulus-responsive molecule can respond to only one kind
of external stimulus and realize a mono-responsive nanochannel.
For example, a pH-gating ionic transport nanodevice has been
developed by inserting the pH-sensitive polymer poly(acrylic acid)
(PAA) into a synthetic nanochannel;[8b] thermally activated macro-
molecular gates have been produced by grafting temperature-
responsive poly(N-isopropylacrylamide) (PNIPAM) into a syn-
thetic nanochannel.[10] To obtain a dual-responsive nanochannel,
two kinds of smart materials or one material with two functional
groups are needed to modify the same nanochannel. Recently,
a series of pH-and-temperature dual-responsive ionic gates were
developed by employing two kinds of responsive materials, such
as PAA and PNIPAM,[17a] or one material with two functional
groups, such as poly(NIPAM-co-AA)[18] or homopolymer poly[2-
(dimethylamino) ethyl methacrylate] (PDMAEMA),[19] in a single
nanochannel. However, the sensitivity and reversibility of these
gates, which result mainly from configuration changes in a con-
fined space, are not very efficient.[2]
In this Communication, we demonstrate an artificial func-
tional nanochannel system as an ionic gate whose transport
properties can be controlled by UV irradiation and pH, sepa-
rately, while exhibiting ionic current rectifying behavior. This
rectification is caused by an intrinsic asymmetry of the electro-
chemical potential of the channel.[20] For a cone-shaped nano-
channel with permanent surface charges, the asymmetric shape
allows the system to exhibit ionic current rectification because
such a channel preferentially transports cations/anions from
the small opening (tip) towards the large opening (base) side
of the channel, even when the electrolyte is the same.[21] In this
system, UV irradiation or reduction of the environmental pH
can transform the surface from neutral (nonselective) to posi-
tively charged (anion-selective),[22] which changes the channel
from the OFF state to the ON state. When UV irradiation was
cut off or the environmental pH was increased, the channel
became non-selective, and the OFF state was entered again.
Even after several cycles there was no any decay in the ionic
gating behavior; the functionalized nanochannel shows good
reproducibility and reversibility and can be used as a switch in
areas such as electronics, actuators, and biosensors.
This function can be realized by grafting a novel, newly
synthesized, pH-and-light dual-responsive molecule, mala-
chite green derivative (MG-OH-NH2), onto the inner surface
of a conical nanochannel. This channel was fabricated by a
well-developed asymmetric ion track-etching technique on a
polyimide film (PI, Hostaphan RN12 Hoechst, 12 μm thick,
with a single ion track in the center); the diameters of the
channel were conducted by a commonly used electrochemical
method.[21a] The opening at the base was ≈550 nm, as was
observed by scanning electron microscopy, and the diameter at
the tip side was calculated to be ≈15 nm by an electrochem-
ical measurement. The detailed procedure is described in the
Experimental Section. MG-OH-NH2 was added to the interior
surface of the nanochannel by a two-step coupling reaction
with 1-ethyl-3-(3-dimethyllaminopropyl) carbodiimide (EDC)
and N-hydroxysuccinimide (NHSS). As shown in Scheme 1,
the MG-OH-NH2 originally added to the nanochannel is neu-
tral and hydrophobic, and the ions cannot be transported
across the channel easily, resulting in an OFF state. When the
Dr. L. P. Wen, Dr. J. Ma, Dr. Y. Tian, Prof. L. Jiang
Beijing National Laboratory for
Molecular Sciences (BNLMS)
Key Laboratory of Organic Solids
Institute of Chemistry
Chinese Academy of Sciences
Beijing 100190, P. R. China
E-mail: jianglei@iccas.ac.cn
Q. Liu, Dr. C. H. Li, Prof. Z. S. Bo
College of Chemistry
Beijing Normal University
Beijing 100875, P. R. China
E-mail: zsbo@bnu.edu.cn
DOI: 10.1002/adma.201202673
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Figure 1. A,B) Current–voltage (I–V) curves of the single nanochannel
before (A) and after (B) modification of the inner channel wall with
MG-OH-NH2. I–V characteristics were recorded under symmetric elec-
trolyte conditions (UVirradiationfilteredout) at pH 2.9 (black squares),
pH 7.0 (dark gray circles), and pH 10.2 (gray triangles). C,D) Explanation
of the pH-tunable ionic gating before (C) and after (D) modification as
being induced by the different polarities of the excess surface charge.
E) Current rectification ratios RD that were calculated as the current
changes between–2V and +2 V divided by the current measured at –2 V
in the single conical nanochannel before (black) and after (gray) modi-
fication with MG-OH-NH2 in different pH environments. The electrolyte
solution was 0.1 M KCl with different pH values in both half-cells sepa-
rated by the film. (Sample: base ≈550 nm, tip ≈15 nm, before chemical
modification).
Scheme 1. Light-and-pH dual-driven ionic gate. A) The pH- and light-
dependent equilibrium of malachite-green derivatives (MG-OH-NH2)
that occurs on the inner surface of a polyimide single nanochannel.
B) Simplified illustration indicating the charge changes occurring in the
MG-OH-NH2 layer upon variations in the environmental pH or light.
C) The experimental setup of the electrochemical cell. D) Scanning elec-
tron microscopy (SEM) image, from the base side, of the conical nano-
channel without MG-OH-NH2 attached.
MG-OH-NH2-functionalized nanochannel system (MFNS) was
put into an acid environment, or the MFNS was irradiated with
UV light, the inner channel’s surface became positively charged
by releasing hydroxide ions, which resulted in an anion-
selective, hydrophilic state. In this case, the anions prefer to
flow from the tip to the base side of the channel, resulting in an
ON state. If we put the MG cation-nanochannel system in an
alkali environment or store the system in darkness, the gener-
ated MG cations will take up hydroxide ions and revert to the
original neutral and hydrophobic MG-OH-NH2; in this case the
OFF state will be recovered.
Ionic transport properties of the single nanochannel before
and after MG-OH-NH2 chemical modification have been exam-
ined by current measurements. Figure 1A shows current–
voltage (I–V) properties of the nanochannel before chemical
modification, measured in darkness or with UV irradiation fil-
tered out. Reducing the pH changed the ionic current from rec-
tifying to linear curves, owing to the anionic carboxyl (–COO−)
groups at pH 7.0 and pH 10.2 and the neutral protonated
state (–COOH) at pH 2.9; these results are similar to previous
studies.[20a] After modification, the ionic transport behavior of
the MFNS was observed as symmetric linear I–V curves (pH 7.0
and pH 10.2), owing to the neutral MG-OH-NH2, which dimin-
ished the negative charge inside the channel wall and led to an
OFF state (Figure 1B). However, there was a remarkable differ-
ence: a tremendous increase in the ionic current rectification
could be observed when the MFNS was placed in an acid envi-
ronment (pH 2.9), giving the ON state. In this case, protons
can combine with hydroxide ions coming from MG-OH-NH2
and produce MG cations, thus the surface charge changes from
neutral to positively charged. At the same time, the surface wet-
tability transformed from hydrophobic to hydrophilic, and both
surface charge and wettability contribute greatly to the ionic
conductance.[2a,17f ] This behavior can be explained by the mech-
anism shown in Figures 1C and D. The values can be quan-
tified by the current rectifying ratio R, which was calculated
as the current changes measured between two given voltages
( 2 V) divided by the current measured at –2 V. The ratios that
corresponded to a variation in the environmental pH only, in
darkness (no UV), were defined as RD, while the values meas-
ured in a neutral electrolyte, corresponding to a change in light
irradiation only, were defined as RN. As shown in Figure 1E, RD
of the naked nanochannel stayed around 1 for pH from 2.9 to
10.2. After modification, RD of the MFNS at pH 10.2 was 1.62
0.28, which is much lower than the 8.05 0.68 calculated at
pH 2.9. This result verified that the asymmetric-response ionic
transport property is caused by MG-OH-NH2, the charge of
which changes in response to the ambient environmental pH.
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in UV irradiation was 6.56 0.64, which is larger than 1.55
0.47 calculated for in the dark (Figure 2E). However, at pH 2.9
the channel is always positively charged regardless of UV irra-
diation, because hydroxide ions in MG-OH-NH2 can be easily
released in an acid environment. At pH 10.2, the channel is
always in the neutral state regardless of UV irradiation of the
MFNS, because more hydroxide ions in the alkali environment
can react with MG cations and revert to the original neutral
MG-OH-NH2 (Figure S4 in the Supporting Information). Com-
pared with the ratios calculated from the pH-stimulus system,
there is a small decrease for the UV-stimulus system, which
may be ascribed to the difference in driving mechanism, in that
control is not as efficient for a remote noncontact technique as
for a contact-mode technique in a confined space.
To determine the stability and the responsive switching ability
of the MFNS, further studies have been done, which are shown
in Figure 3. Before modification (naked; gray circles), there was
Figure 2. A,B) I–V curves of the single nanochannel before (A) and after
(B) modification with MG-OH-NH2 on the inner channel wall. I–V char-
acteristics were recorded under symmetric electrolyte conditions (pH
7.0) in darkness (black squares) and under UV irradiation (gray circles).
C,D) Explanation of the light-driven ionic gating before (C) and after
(D) modification induced by the different polarities of the excess surface
charge. E) Current rectification ratios that were calculated from the cur-
rents measured at 2 V in the single conical nanochannel before (black)
and after (gray) modification with MG-OH-NH2 under UV irradiation or
without.
This pH-responsive property can also be characterized by con-
tact angle measurements (Figure S3, Supporting Information)
and X-ray photoelectron spectroscopy (XPS) analysis (Tables S1
and S2, Supporting Information).
In addition to being driven by the pH of the environment,
the ionic current rectification property of this channel can also
be activated by UV irradiation. As demonstrated in Figure 2A,
before modification, UV irradiation had no influence on the
rectification of the ionic current, which remained, even in a
high conductivity neutral 0.1 M KCl solution. Having achieved
closure of the MFNS, we set out to open the gate by UV irradia-
tion (300–400 nm). When the UV lamp is off, the MFNS is in
an OFF state in the neutral electrolyte regardless of the polarity
of the voltage. After being irradiated with light from the UV
lamp for ≈5 min, MG-OH-NH2 will release hydroxide ions and
produce MG cations, making the channel positively charged.
Hence, the high conductance state is obtained as the anions are
driven from the tip to the base by electrophoresis (Figure 2B).
After 30 min in darkness, the MG cations have taken up the
hydroxide ions completely and reverted to the original neutral
and hydrophobic MG-OH-NH2; the low conductivity OFF state
is obtained again. This behavior can be explained by the mech-
anism shown in Figures 2C and D. As shown in Figure 2E,
RN of the naked nanochannel stayed around 1 regardless of the
irradiation of the channel. After modification, RN of the MFNS
Figure 3. Stability and responsive switching ability of the dual-driven
nanochannel system for variation of the pH (A) and light (B): reversible
variation of the ionic current rectification ratios of the single nanochannel
before (gray circles) and after (squares) modification under stimulation
with pH and UV irradiation.
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Figure 4. The synthetic route to MG-OH-NH2, molecule 5 (Pinacol: 2,3-dimethyl-2,3-butanediol).
almost no change in the current ratio regardless of variation of
Experimental Section
pH and UV irradiation; it is stable. Thus, such a material can
be used as an ideal platform for developing smart nanochannel
systems. The responsive switching ability of the MFNS (black
squares) upon cyclic variation of either the pH or UV irradia-
tion reflects good reproducibility and reversibility of the asym-
metric responsive nanochannels. The time scale of each cycle of
the responsive switching experiment was about 35 min, a result
of the behavior of MG-OH-NH2, which is much faster than
the previously reported biomimetic systems, because surface
charges generated by smart materials are much easier to realize
in a confined region than a change in configuration when acti-
vated by external stimuli. Therefore, the sensitivity and revers-
ibility of the MFNS are highly efficient compared with those of
systems based on conformation changes in confined regions.
In summary, we have demonstrated the construction of
a highly efficient and perfectly reversible pH-and-light dual-
driven ionic gate based on a single conical nanochannel fabri-
cated in a PI membrane. MG-OH-NH2 as the active element
was first synthesized and then incorporated into the channel
by directly exploiting the carboxyl groups generated during the
track-etching process. The switching between the OFF state and
the ON state is mainly dependent on the surface charge transi-
tion brought about by MG-OH-NH2 activated by the variation of
pH and UV irradiation, which makes it easy to realize in con-
fined spaces. Moreover, compared with fragile biological nano-
channels in living systems, this “abiotic” equivalent is robust
and has the advantage that it does not have to work in the lipid
environment. Therefore, such a pH-and-light dual-driven ionic
gate can be used as a switch and may find applications in areas
such as electronics, actuators, and biosensors.
Materials: The malachite green derivative MG-OH-NH2 shown in
Figure 4 was synthesized and used for the functionalization of track-
etched nanochannel. This compound was purified and characterized
by 1H NMR, 13C NMR, and matrix-assisted laser desorption ionization
time-of-flight mass spectrometry (MALDI-TOF-MS). The synthesis
of malachite green derivative 5 was performed as given below. The
absorption spectra of MG-OH-NH2 and its corresponding product
are shown in Figure S1 (Supporting Information). Other chemicals
were analytical-grade reagents and were used as received. All aqueous
solutions were prepared with deionized water.
Synthesis of tert-Butyl 3-chloropropylcarbamate (1) : Et3N (12.9 mL,
0.092 mol) was added slowly into a solution of 3-chloropropan-1-amine
hydrochloride (10 g, 0.076 mol) in dichloromethane (DCM; 50 mL). The
resulting solution was cooled to 0 °C with an ice bath, then a solution of
di-tert-butyl dicarbonate ((Boc)2O; 16.8 g, 0.077 mol) in DCM (50 mL)
was added dropwise and the reaction was stirred at 0 °C overnight. After
the reaction, the mixture was washed with a solution of HCl (pH 1) three
times and dried with anhydrous MgSO4. Removal of the solvent by rotary
evaporator afforded compound 1 as a yellow oil (14 g, 98%). 1H NMR
(CD3Cl, 400 MHz): δ 5.15 (s, 1H), 3.61–3.57 (t, 2H), 3.29-3.25 (m, 2H),
2.00–1.94 (m, 2H), 1.44 (s, 9H); 13C NMR (100 MHz, CDCl3): δ 156.07,
79.22, 42.32, 37.83, 32.61, 28.32.
Synthesis of tert-Butyl 3-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)
phenoxy)propylcarbamate (3): A mixture of 1 (3.16 g, 0.016 mol), 2 (3.00 g,
0.014 mol), 2-butanone (150 mL), 18-crown-6 (3.95 g, 0.015 mol),
KI (2.49 g, 0.015 mol), and K2CO3 (5.64 g, 0.041 mol) was heated at
reflux and stirred under nitrogen for 24 h. The solvent was removed
under reduced pressure, the residue was partitioned between water and
CH2Cl2, the organic layer was separated, the aqueous layer was extracted
with CH2Cl2, and the combined organic layers were dried over anhydrous
Na2SO4 and evaporated to dryness. The residue was chromatographically
purified on silica gel, eluting with petroleum ether/ethyl acetate (4:1, v:v),
to afford 3 as a white solid (3.47 g, 67.5%). 1H NMR (CD3Cl, 400 MHz):
δ 7.75–7.73 (d, 2H), 6.89–6.87 (d, 2H), 4.06–4.03 (t, 2H), 3.34–3.32 (m,
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2H), 2.00–1.96 (m, 2H), 1.44 (s, 9H), 1.33 (s, 12H); 13C NMR(100 MHz,
CDCl3): δ 161.40, 156.11, 136.60, 136.56, 113.81, 83.61, 79.23, 65.58,
37.95, 29.52, 28.45, 24.90.
ionic track-etching process was effected by the following procedure. The
first step was the activation of these groups into amine-reactive esters
by means of carbodiimide coupling chemistry. Then, these reactive
esters were further condensed with malachite green derivatives through
the formation of covalent bonds. For the activation of carboxyl groups
into NHSS-ester, the PI film containing a single channel was exposed
to an aqueous solution of 15 mg EDC and 3 mg NHSS for 1 h at room
temperature. After they had been washed with distilled water, the
samples were further treated with 5 mM malachite green derivatives
overnight. Finally, functionalized channels were washed several times
with distilled water.
Current–Voltage Recordings: The properties of the system were
studied by measuring the ionic current through unmodified (naked) and
modified channels. The ionic current was measured by a Keithley 6487
picoammeter (Keithley Instruments, Cleveland, OH). A single channel in
the center of the PI membrane was mounted between the two chambers
of the etching cell, which can be irradiated from the sidewall. Ag/AgCl
electrodes were used to apply a transmembrane potential across the film
(anode facing the base of the nanochannel), and both halves of the cell
were filled with 0.1 M KCl. The main transmembrane potential used in
this work was a scanning voltage that varied from –2 V to +2 V with
a period of 40 s. The process and conditions of all the measurements
mentioned in this Communication were the same, unless stated
otherwise, and each test was repeated 8 times to obtain the average
current value at different voltages.
Synthesis of Malachite Green Derivative 4: A mixture of 3 (500 mg,
1.33 mmol), (4-bromophenyl)bis(4-(dimethylamino)phenyl)methanol
(511 mg, 1.20 mmol), tetrahydrofuran (THF; 50 mL), H2O (10 mL),
tetrabutylammonium bromide (TBAB; 386 mg, 1.19 mmol), and
NaHCO3 (1.01 g, 12.02 mmol) was degassed before and after Pd(PPh3)4
(40 mg, 0.03 mmol) was added. The mixture was then heated at reflux
and stirred under nitrogen for 2 days. After cooling to room temperature,
the mixture was partitioned between water and diethyl ether, the organic
layer was separated, the aqueous layer was extracted with diethyl
ether (100 mL × 3), and the combined organic layers were dried over
anhydrous MgSO4 and evaporated to dryness. The residue was purified
chromatographically on silica gel to afford 4 as a green oil (331 mg,
40%). 1H NMR (CD3Cl, 400 MHz): δ 7.52–7.45 (m, 4H), 7.36–7.34 (d,
2H), 7.16–7.13 (d, 4H), 6.95–6.93 (d, 2H), 6.68–6.66 (d, 4H), 4.07–4.04
(t, 2H), 3.35–3.32 (m, 2H), 2.94 (s, 12H), 2.00–1.96 (m, 2H), 1.45 (s,
9H). 13C NMR (100 MHz, CDCl3): δ 158.22, 156.07, 149.50, 146.49,
138.91, 135.60, 128.81, 128.03, 125.87, 114.73, 111.76, 81.41, 79.21,
67.93, 40.55, 38.07, 29.55, 28.41.
Synthesis of Malachite Green Derivative 5: A mixture of 4 (300 mg,
0.50 mmol), THF (30 mL), and HCl (8 mL, 36%) was stirred at room
temperature for 12 h, and the resulted precipitate was collected by
filtration. The crude product was chromatographically purified on silica
gel, eluting with CH2Cl2, increasing to CH2Cl2/CH3OH (1:1, v/v) to afford
the crude product. The crude product was dissolved in CH2Cl2 (100 mL)
and filtered through filter paper; the collected filtrate was evaporated to
dryness to afford the desired malachite green derivative 5 as a green oil.
1H NMR (CD3Cl, 400 MHz): δ 7.51–7.45 (m, 4H), 7.35–7.33 (d, 2H),
7.16–7.14 (d, 4H), 6.96–6.94 (d, 2H), 6.69–6.67 (d, 4H), 4.08–4.06 (m,
2H), 3.35–3.32 (m, 2H), 2.94 (s, 12H), 2.00–1.96 (m, 2H); 13C NMR
(100 MHz, CDCl3): δ 153.35, 149.03, 135.66, 132.78, 130.28, 128.91,
128.30, 126.20, 114.84, 111.77, 81.45, 58.93, 45.90, 42.27, 40.80. MS
(MALDI-TOF) m/z 478.4 [(M−OH)+, the cation of lost hydroxide].
Nanochannel Fabrication and Characterization: The single conical
nanochannel was prepared with a polyimide (PI, 12 μm thick) membrane,
which was irradiated with single swift heavy ions (Au) of energy
11.4 MeV per nucleon at the UNILAC linear accelerator (GSI, Darmstadt,
Germany). Then the ion track polymer membrane was chemically
etched at a fixed temperature (about 333 K) from one side with 13%
NaClO, whereas the other side of the cell contained 1M KI to neutralize
the etchant as soon as the pore opened. After etching had finished, the
film was soaked in MilliQ water (18.2 MΩ) to remove residual salts. The
diameter D of the large opening (base) of the conical nanochannel was
determined by scanning electron microscopy (SEM) in parallel etching
experiments; the diameter dtip of the small opening (tip) was evaluated
from an electrochemical measurement of the ionic conductance of the
nanochannel filled with 1 M potassium chloride solution as electrolyte by
means of (Figure S2, Supporting Information)
Supporting Information
Supporting Information is available from the Wiley Online Library or
from the author.
Acknowledgements
The authors thank the Material Science Group of GSI (Darmstadt,
Germany) for providing the ion-irradiated samples. This work was
supported by the National Research Fund for Fundamental Key Projects
(2011CB935703, 2011CB935704, 2010CB934700), National Natural
Science Foundation (21171171, 91127025, 20920102036, 21121001),
and the Key Research Program of the Chinese Academy of Sciences
(KJZD-EW-M01).
Received: July 2, 2012
Revised: September 18, 2012
Published online:
[1] a) X. Hou, H. Zhang, L. Jiang, Angew. Chem. Int. Ed. 2012, 51,
5296; b) X. Hou, L. Jiang, ACS Nano 2009, 3, 3339; c) B. Hille,
Ion Channels of Excitable Membranes, 3rd Ed., Sinauer Associates,
Sunderland, MA 2001; d) E. Perozo, D. M. Cortes, P. Sompornpisut,
A. Kloda, B. Martinac, Nature 2002, 418, 942; e) E. Gouaux,
R. MacKinnon, Science 2005, 310, 1461.
[2] a) X. Hou, W. Guo, L. Jiang, Chem. Soc. Rev. 2011, 40, 2385;
b) L. Wen, Y. Tian, J. Ma, J. Zhai, L. Jiang, Phys. Chem. Chem. Phys.
2012, 14, 4027.
[3] a) S. Howorka, Z. Siwy, Chem. Soc. Rev. 2009, 38, 2360; b) M. Ali,
B. Yameen, J. Cervera, P. Ramírez, R. Neumann, W. Ensinger,
W. Knoll, O. Azzaroni, J. Am. Chem. Soc. 2010, 132, 8338.
[4] W. Lee, K. Schwirn, M. Steinhart, E. Pippel, R. Scholz, U. Gösele,
Nat. Nanotechnol. 2008, 3, 234.
4L I
π k(c)UD
dtip
=
(1)
where dtip is the tip diameter; D is the base diameter (≈550 nm); k(c) is
the specific conductivity of the electrolyte (for 1 M KCl solution at 25 °C
k(c) = 0.11173 Ω−1 cm−1 ); L is the length of the channel, which can be
approximated to the thickness of the membrane after chemical etching
(≈12 μm); and U and I are the applied voltage and measured ionic
current in the pore conductivity measurement, respectively. In this work,
the applied voltage and measured ionic current were 0.2 V and 1.2 nA,
respectively. From Equation (1) and the corresponding parameters we
can estimate the tip diameter of the ion track-etched nanochannel; it is
around 15 nm. The etching and characterizing conductivity cell with an
I–V characterization of the naked nanochannel in the PI membrane are
shown in Figure S2 (Supporting Information).
[5] J. Li, D. Stein, C. McMullan, D. Branton, M. J. Aziz, J. A. Golovchenko,
Nature 2001, 412, 166.
[6] A. J. Storm, J. H. Chen, X. S. Ling, H. W. Zandbergen, C. Dekker,
Nat. Mater. 2003, 2, 537.
Nanochannel Functionalization: The chemical functionalization of
carboxyl (–COOH) groups generated on the channel surface during the
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DOI: 10.1002/adma.201202673
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[7] a) J. Wu, A. Eisenberg, J. Am. Chem. Soc. 2006, 128, 2880; b) Y. Lu,
R. Ganguli, C. A. Drewien, M. T. Anderson, C. J. Brinker, W. Gong,
Y. Guo, H. Soyez, B. Dunn, M. H. Huang, J. I. Zink, Nature 1997,
389, 364; c) Z. S. Siwy, M. Davenport, Nat. Nanotechnol. 2010, 5,
697.
Chem. Soc. 2011, 133, 18312; e) Z. Chen, Y. Jiang, D. R. Dunphy,
D. P. Adams, C. Hodges, N. Liu, N. Zhang, G. Xomeritakis,
X. Jin, N. R. Aluru, S. J. Gaik, H. W. Hillhouse, C. J. Brinker, Nat.
Mater. 2010, 9, 667; f) D. K. Lathrop, E. N. Ervin, G. A. Barrall,
M. G. Keehan, R. Kawano, M. A. Krupka, H. S. White, A. H. Hibbs,
J. Am. Chem. Soc. 2010, 132, 1878; g) C. Dekker, Nat. Nanotechnol.
2007, 2, 209; h) B. Zhang, Y. Zhang, H. S. White, Anal. Chem. 2004,
76, 6229; i) A. Mara, Z. Siwy, C. Trautmann, J. Wan, F. Kamme,
Nano Lett. 2004, 4, 497; j) J. Li, M. Gershow, D. Stein, E. Brandin,
J. A. Golovchenko, Nat. Mater. 2003, 2, 611; k) A. J. Storm,
C. Storm, J. Chen, H. Zandbergen, J.-F. Joanny, C. Dekker, Nano Lett.
2005, 5, 1193; l) C. R. Martin, Z. S. Siwy, Science 2007, 317, 331;
m) L.-Q. Gu, O. Braha, S. Conlan, S. Cheley, H. Bayley, Nature
1999, 398, 686; n) E. C. Yusko, J. M. Johnson, S. Majd, P. Prangkio,
R. C. Rollings, J. Li, J. Yang, M. Mayer, Nat. Nanotechnol. 2011, 6,
253.
[8] a) F. Xia, W. Guo, Y. Mao, X. Hou, J. Xue, H. Xia, L. Wang, Y. Song,
H. Ji, Q. Ouyang, Y. Wang, L. Jiang, J. Am. Chem. Soc. 2008, 130,
8345; b) X. Hou, Y. Liu, H. Dong, F. Yang, L. Li, L. Jiang, Adv.
Mater. 2010, 22, 2440; c) Z. S. Siwy, P. Apel, D. Baur, D. D. Dobrev,
Y. E. Korchev, R. Neumann, R. Spohr, C. Trautmann, K.-O. Voss,
Surf. Sci. 2003, 532–535, 1061; d) I. Vlassiouk, Z. S. Siwy, Nano
Lett. 2007, 7, 552; e) B. Yameen, M. Ali, R. Neumann, W. Ensinger,
W. Knoll, O. Azzaroni, Nano Lett. 2009, 9, 2788; f) B. Yameen, M. Ali,
R. Neumann, W. Ensinger, W. Knoll, O. Azzaroni, J. Am. Chem. Soc.
2009, 131, 2070; g) M. Wanunu, A. Meller, Nano Lett. 2007, 7, 1580;
h) R. Fan, S. Huh, R. Yan, J. Arnold, P. Yang, Nat. Mater. 2008, 7,
303; i) G. Wang, B. Zhang, J. R. Wayment, J. M. Harris, H. S. White,
J. Am. Chem. Soc. 2006, 128, 7679; j) M. Ali, P. Ramirez, S. Mafé,
R. Neumann, W. Ensinger, ACS Nano 2009, 3, 603; k) G. Wang,
A. K. Bohaty, I. Zharov, H. S. White, J. Am. Chem. Soc. 2006, 128,
13553.
[9] a) X. Hou, W. Guo, F. Xia, F.-Q. Nie, H. Dong, Y. Tian, L. Wen,
L. Wang, L. Cao, Y. Yang, J. Xue, Y. Song, Y. Wang, D. Liu, L. Jiang,
J. Am. Chem. Soc. 2009, 131, 7800; b) Y. Tian, X. Hou, L. Wen,
W. Guo, Y. Song, H. Sun, Y. Wang, L. Jiang, D. Zhu, Chem.
Commun. 2010, 46, 1682; c) M. R. Powell, M. Sullivan, I. Vlassiouk,
D. Constantin, O. Sudre, C. C. Martens, R. S. Eisenberg, Z. S. Siwy,
Nat. Nanotechnol. 2008, 3, 51; d) Y. He, D. Gillespie, D. Boda,
I. Vlassiouk, R. S. Eisenberg, Z. S. Siwy, J. Am. Chem. Soc. 2009, 131,
5194; e) O. Braha, L.-Q. Gu, L. Zhou, X. Lu, S. Cheley, H. Bayley,
Nat. Biotechnol. 2000, 18, 1005.
[15] a) B. Corry, J. Phys. Chem. B 2007, 112, 1427; b) L. A. Baker,
S. P. Bird, Nat. Nanotechnol. 2008, 3, 73; c) E. N. Savariar,
K. Krishnamoorthy, S. Thayumanavan, Nat. Nanotechnol. 2008, 3,
112; d) H. Gu, S. Faucher, S. Zhu, AIChE J. 2010, 56, 1684.
[16] a) L. Wen, X. Hou, Y. Tian, J. Zhai, L. Jiang, Adv. Funct. Mater.
2010, 20, 2636; b) W. Guo, L. Cao, J. Xia, F.-Q. Nie, W. Ma, J. Xue,
Y. Song, D. Zhu, Y. Wang, L. Jiang, Adv. Funct. Mater. 2010, 20, 1339;
c) F. H. J. van der Heyden, D. Stein, C. Dekker, Phys. Rev. Lett. 2005, 95,
116104; d) F. H. J. van der Heyden, D. J. Bonthuis, D. Stein, C. Meyer,
C. Dekker, Nano Lett. 2006, 6, 2232; e) F. H. J. van der Heyden,
D. J. Bonthuis, D. Stein, C. Meyer, C. Dekker, Nano Lett. 2007,
7, 1022; f) P. Banerjee, I. Perez, L. Henn-Lecordier, S. B. Lee,
G. W. Rubloff, Nat. Nanotechnol. 2009, 4, 292; g) L. Cao, W. Guo,
W. Ma, L. Wang, F. Xia, S. Wang, Y. Wang, L. Jiang, D. Zhu, Energy
Environ. Sci. 2011, 4, 2259.
[10] a) B. Yameen, M. Ali, R. Neumann, W. Ensinger, W. Knoll,
O. Azzaroni, Small 2009, 5, 1287; b) W. Guo, H. Xia, F. Xia, X. Hou,
L. Cao, L. Wang, J. Xue, G. Zhang, Y. Song, D. Zhu, Y. Wang, L. Jiang,
ChemPhysChem 2010, 11, 859.
[11] a) C. Han, X. Hou, H. Zhang, W. Guo, H. Li, L. Jiang, J. Am.
Chem. Soc. 2011, 133, 7644; b) E. A. Heins, L. A. Baker, Z. S. Siwy,
M. O. Mota, C. R. Martin, J. Phys. Chem. B 2005, 109, 18400;
c) A. E. Abelow, O. Schepelina, R. J. White, A. Vallee-Belisle,
K. W. Plaxco, I. Zharov, Chem. Commun. 2010, 46, 7984.
[17] a) X. Hou, F. Yang, L. Li, Y. Song, L. Jiang, D. Zhu, J. Am. Chem.
Soc. 2010, 132, 11736; b) P. Ramírez, V. Gómez, J. Cervera,
B. Schiedt, S. Mafé, J. Chem. Phys. 2007, 126, 194703; c) K. Zhou,
M. L. Kovarik, S. C. Jacobson, J. Am. Chem. Soc. 2008, 130, 8614;
d) D. Stein, M. Kruithof, C. Dekker, Phys. Rev. Lett. 2004, 93, 035901;
e) C. C. Striemer, T. R. Gaborski, J. L. McGrath, P. M. Fauchet,
Nature 2007, 445, 749; f) S. N. Smirnov, I. V. Vlassiouk, N. V. Lavrik,
ACS Nano 2011, 5, 7453; g) R. Karnik, K. Castelino, R. Fan, P. Yang,
A. Majumdar, Nano Lett. 2005, 5, 1638.
[12] a) L. Wen, J. Ma, Y. Tian, J. Zhai, L. Jiang, Small 2012, 8, 838;
b) N. Liu, D. R. Dunphy, P. Atanassov, S. D. Bunge, Z. Chen,
G. P. López, T. J. Boyle, C. J. Brinker, Nano Lett. 2004, 4, 551;
c) A. Koçer, M. Walko, W. Meijberg, B. L. Feringa, Science 2005, 309,
755; d) I. Vlassiouk, C.-D. Park, S. A. Vail, D. Gust, S. Smirnov, Nano
Lett. 2006, 6, 1013; e) G. Nagel, T. Szellas, W. Huhn, S. Kateriya,
N. Adeishvili, P. Berthold, D. Ollig, P. Hegemann, E. Bamberg,
Proc. Natl. Acad. Sci. USA 2003, 100, 13940; f) M. Zhang, X. Hou,
J. Wang, Y. Tian, X. Fan, J. Zhai, L. Jiang, Adv. Mater. 2012, 24, 2424.
[13] a) E. Kalman, O. Sudre, I. Vlassiouk, Z. S. Siwy, Anal. Bioanal. Chem.
2009, 394, 413; b) C. C. Harrell, P. Kohli, Z. Siwy, C. R. Martin, J.
Am. Chem. Soc. 2004, 126, 15646.
[18] W. Guo, H. Xia, L. Cao, F. Xia, S. Wang, G. Zhang, Y. Song, Y. Wang,
L. Jiang, D. Zhu, Adv. Funct. Mater. 2010, 20, 3561.
[19] L.-X. Zhang, S.-L. Cai, Y.-B. Zheng, X.-H. Cao, Y.-Q. Li, Adv. Funct.
Mater. 2011, 21, 2103.
[20] a) Z. Siwy, A. Fulin´ski, Phys. Rev. Lett. 2002, 89, 198103;
b) R. D. Astumian, Science 1997, 276, 917.
[21] a) P. Y. Apel, Y. E. Korchev, Z. S. Siwy, R. Spohr, M. Yoshida, Nucl.
Instrum. Methods Phys. Res., Sect. B 2001, 184, 337; b) Z. Siwy, Y. Gu,
H. A. Spohr, D. Baur, A. Wolf-Reber, R. Spohr, P. Apel, Y. E. Korchev,
Europhys. Lett. 2002, 60, 349; c) Z. S. Siwy, Adv. Funct. Mater.
2006, 16, 735; d) J. Cervera, A. Alcaraz, B. Schiedt, R. Neumann,
P. Ramirez, J. Phys. Chem. C 2007, 111, 12265; e) Z. Siwy,
´
´
[14] a) E. A. Heins, Z. S. Siwy, L. A. Baker, C. R. Martin, Nano Lett.
2005, 5, 1824; b) R. E. Gyurcsányi, Trends Anal. Chem. 2008, 27,
627; c) Z. S. Siwy, M. Davenport, Nat. Nanotechnol. 2010, 5, 174;
d) S. Wen, T. Zeng, L. Liu, K. Zhao, Y. Zhao, X. Liu, H.-C. Wu, J. Am.
I. D. Kosinska, A. Fulinski, C. R. Martin, Phys. Rev. Lett. 2005, 94,
048102.
[22] a) Y. Jiang, P. Wan, M. Smet, Z. Wang, X. Zhang, Adv. Mater. 2008,
20, 1972; b) M. Irie, J. Am. Chem. Soc. 2002, 105, 2078.
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DOI: 10.1002/adma.201202673