Copyright WILEY-VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2012.
Supporting Information
for Adv. Mater., DOI: 10.1002/adma.201202673
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*
Submitted to
DOI: 10.1002/adma. 201202673
Supporting Information for
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*
Experimental
Chemicals and Instruments. Polyimide (PI, 12 µm thick) (GSI, Darmatadt, Germany). 3Chloropropan-1-amine hydrochloride, 18-crown-6, tetrabutylammonium bromide, bis(1,1dimethylethyl) dicarbonate [(Boc)2O], 4-hydroxyphenylboronic acid, potassium iodide (KI),
potassium carbonate (K2CO3), 1-Ethyl-3-(3-dimethyllaminopropyl) carbodiimide (EDC), Nhydroxysulfosuccinimide (NHSS), sodium hydroxide (NaOH), potassium chloride (KCl), and
formic acid (HCOOH) were purchased from Sinopharm Chemical Reagent Beijing Co., Ltd.
(SCRC, China). THF was distilled from Na-benzophenone under nitrogen atmosphere before
use. Pd(PPh3)4 was prepared according to the literature procedures.1 Dichloromethane (DCM)
was distilled from CaH2 before use. All solutions were prepared in MilliQ water (18.2 MΩ).
Current-voltage curves were measured by a Keithley 6487 picoammeter (Keithley
Instruments, Cleveland, OH). The light source for illumination of the above special PEC was
a 300 W xenon lamp (PLS-SXE300, Trusttech ltd Co., Beijing) combination with an infrared
cutoff filter. The intensity was measured with an optical power/energy meter (Model 842-PE).
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Optical properties: UV-vis absorption spectra provided some information on the occurrence
of chemical reaction and their corresponding transition process. Figure S1 displayed the
normalized absorption of MG-OH-NH2 and their corresponding products. In the absence of
UV light, MG-OH-NH2 had little dissociation and showed strength absorption at about 350
nm. After irradiation, MG-OH-NH2 released hydroxide ions easily and transformed into
another substance that absorption spectra were different from the original MG-OH-NH2
molecule, there was another absorption peak at 613 nm. And these results were recorded with
a JASCO V-570 spectrophotometer.
Figure S1. Optical properties: Shown was the optical absorption, measured with 10-6 M
malachite green derivative solutions. Before irradiation, the normalized absorption spectra of
MG-OH-NH2 showed an apparent absorption at about 350 nm (black); under irradiation, a
new absorption peak at 613 nm appeared (red).
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Electrochemical Measurement: The ionic current was measured by a Keithley 6487
picoammeter (Keithley Instruments, Cleveland, OH). A naked single conical nanochannel in
the center of PI membrane was mounted between two chambers of the etching cell that was
similar to Figure S 2A. Ag/AgCl electrodes were used to apply a transmembrane potential
across the film (anode facing the base of the nanochannel), and both half of the cell were
filled with 1 M KCl. The main transmembrane potential used in this work was fixed at 0.2 V
and the measurement ionic current was around 1.2 nA (Figure S 2B).
Figure S2. A). Schematic of an etching and characterizing conductivity cell; B). Ionic current
was recorded at the potential of 0.2 V.
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Contact angle measurements of the mercury (II) responsive surfaces. Contact angles were
measured using an OCA20 machine (DataPhysics, Germany) contact-angle system at ambient
temperature and saturated humidity. In each measurement, an about 2 µL droplet of water was
dispensed onto the substrates under investigation. The average contact angel value was
obtained at five different positions of the same sample. The original PI film for contact angle
measurement was treated with NaClO (13 %) for 3 hours. The sample was then removed from
the etching solution and treated with a stopping solution (1 M KI) for 30 min. After that, the
sample was treated with deionized water overnight. Before the contact angle test, the sample
was blown dry with N2. For the flat PI film, the mean water contact angle was 76 ± 1.5°
(Figure S 3A). Once the PI film was modified with MG-OH-NH2, the sample exhibited
hydrophobic property, and the mean water contact angle increased to 98 ± 1.9 ºC (Figure S
3B). We wondered if this MGD-functionalized film can behave as pH-responsive surface. In
order to address this issue, contact angle measurements were employed to observe the
differences in wetting properties as a function of pH. Although the changes of the contact
angles observed on flat surfaces modified with MGD under different pH conditions are not
very large. When a pH = 10.2 water droplet was dispensed onto the pH-responsive surface, a
contact angle of about 104 ± 2.1 ºC (Figure S 3C), that is, a hydrophobic behavior was
observed; instead, when a pH = 2.9 water droplet was dispensed onto the pH-responsive
surface, a decreasing contact angle of about 83 ± 1.2 ºC (Figure S 3D), that is, hydrophilic
behavior was observed. The reason for this remarkable change should be the pH-induced
transformation of the MG-OH-NH2 from an electrically neutral form to a net positive
delocalized charged triphenylmethyl cation form, which is responsible for hydrophilicity. We
have also confirmed that the above-mentioned surface can show UV-controlled wetting
properties. The wetting properties can be controlled and fine-tuned by the UV irradiation,
from hydrophobicity to hydrophilicity. As the malachite green group undergoes
photoionization by loss of a hydroxide anion to the corresponding carbocation with high
quantum efficiency as a result of UV irradiation, the hydrophobic malachite green group of
MG-OH-NH2 is converted into the MG cation; the wetting behavior of the surface becoming
hydrophilic accordingly, the contact angle is about 88 ± 2.6 ºC (Figure S 3E). After removal
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of UV irradiation, the MG cations largely recover to the electrically neutral MG-OH-NH2
form, that is, the fraction of MG-OH-NH2 is smaller than the one in the above-mentioned
reversible pH-responsive process, and so the contact angle is a little lower than the
hydrophilic surface, the contact angle is about 99 ± 2.7 ºC (Figure S 3F) .
Figure S3. pH and light dual-responsive wettability for a flat malachite green derivative
functionalized PI surface: Changes of water drop profile when the etched PI film (A) were
modified with MG-OH-NH2 (B) A pH = 10.2 water droplet was dispensed onto the surface
(C) A pH = 2.9 water droplet was dispensed onto the surface (D) MG-OH-NH2-functionalized
surface was irradiated with UV light (E) And putting the irradiation surfaces in darkness
conditions (F) with water contact angles of 76 ± 1.5°, 98 ± 1.9°, 104 ± 2.1°, 83 ± 1.2°, 88 ±
2.6°and 99 ± 2.7°, respectively.
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X-ray photoelectron spectra characterization. X-ray photoelectron spectra (XPS) data were
obtained with an ESCALab220i-XL electron spectrometer from VG Scientific using 300W Al
Kα radiation. All peaks were referenced to C 1s (CHx) at 284.8 eV in the deconvoluted high
resolution C 1s spectra, and the analysis software used was provided by the manufacturer.
Table S1 and S2 showed the XPS data from PI film before and after MG-OH-NH2
modification, respectively. The changes of element content confirm the successful
immobilization of MG-OH-NH2 molecules on the surface of PI film.
Table S1 The XPS data from PI film before MG-OH-NH2 immobilization
Name
Start BE
Peak BE
End BE
Height CPS
FWHM eV
Area (P) CPS. eV
At. %
C1s, 284.8 eV
294.43
284.81
278.84
35304.23
1.89
98072.71
70.5
N1s, 399.7 eV
407.32
399.73
394.2
1323.12
1.82
3284.35
1.39
O1s, 532 eV
538.86
532.3
525.37
28288.71
3.03
92877.91
26.17
Table S2 The XPS data from PI film after MG-OH-NH2 immobilization
Name
Start BE
Peak BE
End BE
Height CPS
FWHM eV
Area (P) CPS. eV
At. %
C1s, 284.8 eV
291.7
284.91
278.99
20295.38
1.6
40042.91
53.26
N1s, 399.7 eV
406
399.4
391.83
515.52
0.55
1944.49
1.53
O1s, 532 eV
538.45
532.28
524.81
23818.14
1.55
44492
23.19
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Figure S4. Current-voltage (I-V) curves of the Naked and the MG-OH-NH2-functionalizd
nanochannels in darkness and under UV irradiation. At pH 2.9, the ionic current of the naked
nanochannel (A) was in linear curves for the neutral state, while the MG-OH-NH2functionalizd nanochannels (B) was positively charged no matter in darkness or under UV
irradiation and positive charges were the majority carries. The anions preferred to flow from
the tip to the base to maintain the lower resistance, leading to current flowing in the same
direction. At pH 10.2, the ionic current of the naked nanochannel (C) was rectifying for the
negative charges, while the MG-OH-NH2-functionalizd nanochannel (D) was neutral state no
matter in darkness or UV irradiation. The electrolyte solution was 0.1 M KCl with adjusted
pH in both half cells separated by the membrane (Sample: base ~550 nm, tip ~15 nm, before
chemical modification).
Reference:
(1) Tolman, C. A.; Seidel, W. C.; Gerlach, D. H. J. Am. Chem. Soc. 1972, 94, 2669.
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