- Email: [email protected]
A Novel Electrochemical Behavior Research in Micro Interface Based on Sol-gel Modified Electrode
CHINESE JOURNAL OF ANALYTICAL CHEMISTRY Volume 41, Issue 8, August 2013 Online English edition of the Chinese language journal
Cite this article as: Chin J Anal Chem, 2013, 41(8), 1249–1253.
RESEARCH PAPER
A Novel Electrochemical Behavior Research in Micro Interface Based on Sol-gel Modified Electrode RU Jing, DU Jie, HE Hong-Xia, LU Xiao-Quan* Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou 730070, China
Abstract:
The multi-dimension network of sol-gel SiO2 was immobilized on an electrode surface employing sol-gel and
electrochemical impedance spectroscopy (EIS) techniques under the optimal experimental conditions. Then, the multi-dimension network structure of sol-gel was used to simulate electron transfer in cell membrane of micro interface. The electron transfer model was constructed successfully on the multi-dimension micro interface. These SiO2 materials exhibited tunable porosity, high thermal stability and chemical inertness. Key Words: Sol-gel; Electrochemical impedance spectroscopy; Electrochemistry deposition; Cell biological membrane; Electron transfer
1
Introduction
Sol-gel silica, via hydrolysis and condensation polymerization reactions using organic or inorganic compounds as raw materials, is a kind of multi-dimensional network gel formed by sol state gradually solidified. Sol-gel technology was well established and developed for a long time[1], which was widely used for the application of biosensors[2,3]. Sol-gel method provides a unique way to prepare a multi-dimensional network, and sol-gel materials can be prepared under ambient conditions and exhibited various advantages such as simple designing[4,5], low cost, tunable porosity, high thermal stability, chemical inertness and so on[6], sol-gel also presents considerable application prospect in the fields of electronic, ceramics, optical, thermal, chemical, biological and composite materials[7,8]. Additionally, sol-gel materials are homogeneous with a large number of hydrogen bonds, which not only maintains the multidimensional structure, but also promotes electron transfer as a modified electrode. Therefore, it is helpful to improve the stability of the electrochemical modified electrode[1,9].
In this study, the multi-dimensional network structure of sol-gel was immobilized on an electrode surface, which was used to simulate electron transfer in the cell membrane of micro interface by thin layer cyclic voltammetric technique[10–12]. Compared with traditional method[10–12] that can only describe the overall reaction occurring in electrode, sol-gel silica was used as the carrier to distinguish the reaction in specific area of electrode. In this study, a multi-dimensional microchannel electron transfer model was constructed and the electron transfer under the micro environment in cell membrane was investigated.
2 2.1
Experimental Chemicals and reagents
Tetraethyl orthosilicate was purchased from Aladdin (TEOS, Shanghai, China). Hexadecy ltrimethyl ammonium bromide was purchased from Aladdin (CTAB, Shanghai, China). Nitrobenzene (NB) (Shanghai chemical Reagent Co. Ltd.) was the highest purity. KCl, NaClO4 and K3Fe(CN)6 was
Received 28 November 2012; accepted 23 January 2013 * Corresponding author. Email: [email protected] This work was supported by the National Natural Science Foundation of China (Nos. 21175108, 21165015) and the National Natural Science Foundation of Gansu province, China (No. 090GKCA036). Copyright © 2013, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. Published by Elsevier Limited. All rights reserved. DOI: 10.1016/S1872-2040(13)60674-X
RU Jing et al. / Chinese Journal of Analytical Chemistry, 2013, 41(8): 1249–1253
purchased from Beijing Chemical Reagent Co. Ltd., China. HCl, NaOH and LiCl was purchased from Shanghai chemical Reagent Co. Ltd. China, Tetrabutylammonium perchlorate (TBAClO4)was purchased from Wuhan, China); ferrocene (Fc) was purchased from Aldrich (Shanghai, China), 0.1 M phosphate (KH2PO4/K2HPO4) buffer solution (PBS, pH 7.0, containing 0.1 M KCl) was used as supporting electrolyte. 0.3 and 0.05 μm α-Al2O3 powder (Shanghai chemical Reagent Co. Ltd.). Aqueous solutions were prepared with doubly distilled water, and solutions were deoxygenated by bubbling with nitrogen for 10 min. All experiments were performed at room temperature (22 ± 2) ºC. 2.2
Characterization
Cyclic voltammetry (CV) measurement was carried out by a CHI832 electrochemical workstation (CH Instrument Company, Shanghai, China). Electrochemical impedance spectroscopy (EIS) was conducted on a VMP2 Multipotentiostat (Princeton Applied Research, USA). A three-electrode system of a working glass carbon electrode (GCE, 2.0 mm diameter), a saturated calomel reference electrode (SCE) and a platinum wire counter electrode, was employed. Solution pH was measured with a Sartorius basic pH meter PB-10 (RenHe Instrument Co. Ltd., Shanghai, China). SEM images were taken using a field-emission scanning electron microscope (SEM, JEOL JSM-6701F) operated at an accelerating voltage of 5 kV. 2.3
Preparation of sol-gel precursor
The sol-gel precursor was prepared using a sol-gel method. The 0.2 M NaH2PO4/Na2HPO4 (PBS, pH 4.8, containing 0.1 M KCl) solution was added in a beaker, and 151 μL TEOS was added into the solution, then 1088 μL 0.2 M CTAB was dropped under vigorous stirring. Then, the solutions were stirred in a closed state for 12 h at room temperature. In this way the sol-gel SiO2 precursor was prepared. The process of hydrolysis and condensation are shown as following[2, 3]:
H → 4C 2 H 5OH + SiO 2 ( C 2 H 5O )4 Si + 2H 2O ⎯⎯⎯ H O +
2
(1)
(2) 2.4
Preparation of sol-gel modified electrode
The sol-gel film was first electrochemically deposited on a well polished work electrode following a process previously reported[6,13]. A three-electrode system was used with a working glass carbon electrode, a saturated calomel reference electrode (SCE) and a platinum wire counter electrode. Firstly, the working electrode was inserted in an electrolytic cell consisting of 5 mL prepared sol-gel, and a constant potential of –2.0 V was applied for 110 s. After the deposition, the modified electrode was rinsed with water and dried under ultraviolet light irradiation. The morphologies of prepared sol-gel SiO2 film were characterized by SEM. As shown in Fig.1, the SiO2 nanoparticles were clearly seen in the scale of 1 μm, indicating that the sol-gel SiO2 film was immobilized successfully on the electrode surface. 2.5
Construction of electronic delivery model with sol-gel modified electrode
Via thin layer cyclic voltammetry method, the working electrode used in Section 2.4 was modified with sol-gel and the saturated calomel reference electrode (SCE) and platinum wire counter electrode were placed in the solutions. The sol-gel modified electrode held in an upside-down position when thin layers of NB solutions containing interest reactants (Fc) and supporting electrolytes (TBAClO4) were appliedin Fig.2. 1 μL of NB solution was transferred with a microsyringe, so the organic liquid spread spontaneously across the surface of the modified electrode. The electrode was then turned over and immediately immersed in the aqueous solution. An interface between two immiscible electrolyte solutions (ITIES) was then formed.
Fig.1 SEM images of so-gel modified on glassy carbon electrode (GCE).
RU Jing et al. / Chinese Journal of Analytical Chemistry, 2013, 41(8): 1249–1253
Fig.2 Schematic diagram of modified electrode used in thin-layer voltammetry measurement.
3 3.1
Results and discussion Effect of deposition time from different sol-gel modified electrodes
In the process of electrodeposition sol-gel silica, a constant potential was applied to the glassy carbon and platinum electrodes, respectively. Meanwhile, 5 mM K3Fe(CN)6 was used as probe molecules, depositing sol-sol silica at the electrode surface investigated by potential electrochemical impedance spectroscopy (PEIS). The deposition times were set as following: 70, 80, 90, 100, 110, 120 and 130 s, respectively. The doposition was conducted at the potential of –2.0 and –0.9 V, respectively. As shown in Fig.3 and Fig.4, with the increase of deposition time, the impedance increased as well. With the increase of the thickness of sol-gel silica film, the sol-gel transparency was significantly reduced. With 110 s deposition time, Sol-gel has the best transparency and appropriate thickness. Therefore 110 s was selected as the optimum deposition time of the deposition for the sol-gel films. 3.2
3.3
Electron transfer in structure of multi-dimension tiny interference
The electron transfer model was constructed, and the
Fig.3
Electrochemical impedance plots of glass carbon electrode with different deposition time for using sol-gel in 5 mM K3Fe(CN)6 (containing 0.1 M KCl) solution
The different deposition time from a to h is 0 s, 70 s, 80 s, 90 s, 100 s, 110 s, 120 s, 130 s
Effect of deposition potential from different sol-gel modified electrodes
In the process of electrodeposition sol-gel silica, constant potentials were applied to the glassy carbon and platinum electrode, respectively. 5 mM K3Fe (CN)6 was used as probe molecules, and depositing sol-sol silica at the electrode surface was investigated by potential electrochemical impedance spectroscopy (PEIS). Different deposition potential was set: –1.8, –2.0, –2.2 and –2.4 V with the same deposition time 110 s. As shown in Fig.5 and Fig.6, with the increasing of the deposition potential, the impedance increased. The maximum impedance was reached at the potential of –2.0 V, implying the formation of sol-gel silica film with highest thickness. Hence potential of –2.0 V was chose for the experiment to fabricate the sol-gel films on glass carbon electrode.
Fig.4
Electrochemical impedance plots of Pt electrode with different deposition time for using sol-gel in 5 mM K3Fe(CN)6 (containing 0.1 M KCl) solution
The different deposition time from a to h is 0 s, 70 s, 80 s, 90 s, 100 s, 110 s, 120 s, 130 s
RU Jing et al. / Chinese Journal of Analytical Chemistry, 2013, 41(8): 1249–1253
Fig.5 Electrochemical impedance plots of the GC electrode with different deposition potential using sol-gel in 5 mM K3Fe(CN)6 (containing 0.1 M KCl) solution The different deposition potentials are: –1.8 V (curve b), –2.0 V (curve a), –2.2 V (curve c), –2.4 V (curve d)
spontaneously across the surface grid of multi-dimensional micro-channel; aqueous solution was K3Fe(CN)6 (containing 0.1 M NaClO4 as supporting electrolyte). It can be found that Fe2+/Fe3+ redox peaks disappeared, and the redox couple was no longer transferred to the electrode surface of sol-gel. Fig.7c shows the cyclic voltammograms (CVs) of 1 μL NB solutions containing interest reactants (Fc) and supporting electrolytes (TBAClO4). It can be found that a pair of redox peaks appeared at 0.427 V/0.588 V. The results indicated that this pair of redox peaks was the Fc redox peaks. Fig.7d shows the CVs of 1 μL NB solutions containing interest reactants (Fc), supporting electrolytes (TBAClO4) as organic phase and aqueous phase as K3Fe(CN)6 (containing 0.1 M NaClO4 as the supporting electrolyte). The results showed that the oxidation peak of Fc dramatically was increased and reached a steady state, and the peak current platform appeared at 0.315 V. So it can be found that the process of electron transfer between an aqueous phase and an organic phase on sol-gel modified electrode, and the electron transfer model was constructed successfully interfacial in the micro system. A possible reaction mechanism is proposed as follows: Fc (o) + Fe(CN) 3-6 (w) ⎯⎯ → Fc - (o) + Fe(CN) 64- (w) (3)
4
Fig.6
Electrochemical impedance plots of the Pt electrode with different deposition potential using sol-gel in 5 mM K3Fe(CN)6 (containing 0.1 M KCl) solution
The different deposition potentials are: –0.8 V (curve a), –0.9 V (curve b), –1.0 V (curve c), –1.1 V (curve d)
thickness and resistance of sol-gel SiO2 film increased with the extension of deposition time that the thickness and resistance of sol-gel SiO2 film increased with the extension of deposition time. To investigate the thickness, load capacity and permeability of the sol-gel SiO2, deposition time and potential of sol-gel SiO2 film were optimized with different modified electrodes. Under the optimized conditions, sol-gel modified glassy carbon electrode (GC) was used as working electrode. Electron transfer at the interface between two immiscible electrolyte solutions (ITIES) in microchannel model was investigated by thin layer cyclic voltammetry. As shown in Fig.7a, Fe2+/Fe3+ redox pairs of the modified multi-dimensional network structure of sol-gel film GC electrode in 10 mM of K3Fe(CN)6 (containing 0.1 M NaClO4 as the supporting electrolyte) was clearly observed by CVs. Figure 7b shows that the thin layers of NB solutions are applied to the sol-gel modified electrode held in an upside-down position by transferring 1 μL of the solutions to the modified electrode surface; the organic liquid spread
Conclusions
The work presents that the sol-gel is prepared in the absence of ethanol. The three-dimensional network structure of sol-gel SiO2 film is potentiostatic electro-deposited on the electrode surface, and a model of multi-dimensional microchannel interface electron transfer is constructed using the special characteristics of the sol-gel. Therefore, the sol-gel material can be immobilized on the electrode surface. It can be used to simulate electron transfer in cell membrane of micro interface based on the characteristics of their network structure.
Fig.7 Voltammetric observation of electron-transfer model from modified sol-gel thin film Gelectrode between Fc and K3Fe(CN)6 (a) Cyclic voltammogram of modified sol-gel thin film GC electrode in 10 mM K3Fe(CN)6 (containing 0.1 M NaClO4); (b) Repeat of part a after the modified sol-gel thin film GC electrode surface was covered with 1 μL of NB; (c) Cyclic voltammogram with the modified sol-gel thin film GC electrode covered with 1 μL of NB containing 1 mM Fc (containing 0.1 M TBAClO4 as supporting electrolyte) in 0.1 M NaClO4 solution; (d) Repeat of part c in 10 mM K3Fe(CN)6 (containing 0.1 M NaClO4) solution, and 1 μL NB containing 1 mM Fc (containing 0.1 M TBAClO4 as supporting electrolyte). Scan rate: 5 mV s–1
RU Jing et al. / Chinese Journal of Analytical Chemistry, 2013, 41(8): 1249–1253
References
[7]
[1]
[8]
Ju H X. Analysis of Chemical and Biological Sensing Technology. Beijing: Science Press, 2006: 230
Mishira A, Ma C Q, Bauerle P. Chem. Rev., 2009, 109(3):
[2]
Wang B Q, Li B, Wang Z X, Xu G B, Wang Q, Dong S J. Anal.
[9]
Debecker D P, Bouchmella K, Poleunis C, Eloy P, Bertrand P,
[10] Lu X, Sun P, Yao D, Wu B, Xue Z, Zhou X, Sun R, Li L, Liu X H. Anal. Chem., 2010, 82(20): 8598–8603
Gaigneaux E M, Mutin P H. Chem. Mater., 2009, 21(13): 2817–2824 [4]
Gill I. Chem. Mater, 2001, 13(10): 3404–3421
[5]
Suhaxini k, Vu T, Maggie K M H. Journal of Chemical
[6]
Ievgen M, Mathieu E, Rainer O, Smarsly Bernd M., Oksana T, Vladimir Z, Alain W, Langmuir, 2011, 27(11): 7140–7147
Chem., 1999, 71(10): 1935–1939 [3]
Chang S, Hsu Y, Chan T. J. Phys. Chem. C, 2011, 115(5): 2005–2013
1141–1276
[11] Liu X, Hu L N, Zhang L, Liu H, Lu X. Electrochimica Acta, 2005, 51: 467–473
Education, 2010, 87(9): 958–960
[12] Shi C N, Anson F C. Anal. Chem., 1998, 70(15): 3114–3118
Liang R P, Jiang J L, Qiu J D. Electroanalysis, 2008, 20(24):
[13]
2642–2648
Walcarius
A,
Sibottier
E,
Etienne
Naturematerials, 2007, 6: 602–608
M,
Ghanbaja
J.
Cite this article as: Chin J Anal Chem, 2013, 41(8), 1249–1253.
RESEARCH PAPER
A Novel Electrochemical Behavior Research in Micro Interface Based on Sol-gel Modified Electrode RU Jing, DU Jie, HE Hong-Xia, LU Xiao-Quan* Key Laboratory of Bioelectrochemistry & Environmental Analysis of Gansu Province, College of Chemistry & Chemical Engineering, Northwest Normal University, Lanzhou 730070, China
Abstract:
The multi-dimension network of sol-gel SiO2 was immobilized on an electrode surface employing sol-gel and
electrochemical impedance spectroscopy (EIS) techniques under the optimal experimental conditions. Then, the multi-dimension network structure of sol-gel was used to simulate electron transfer in cell membrane of micro interface. The electron transfer model was constructed successfully on the multi-dimension micro interface. These SiO2 materials exhibited tunable porosity, high thermal stability and chemical inertness. Key Words: Sol-gel; Electrochemical impedance spectroscopy; Electrochemistry deposition; Cell biological membrane; Electron transfer
1
Introduction
Sol-gel silica, via hydrolysis and condensation polymerization reactions using organic or inorganic compounds as raw materials, is a kind of multi-dimensional network gel formed by sol state gradually solidified. Sol-gel technology was well established and developed for a long time[1], which was widely used for the application of biosensors[2,3]. Sol-gel method provides a unique way to prepare a multi-dimensional network, and sol-gel materials can be prepared under ambient conditions and exhibited various advantages such as simple designing[4,5], low cost, tunable porosity, high thermal stability, chemical inertness and so on[6], sol-gel also presents considerable application prospect in the fields of electronic, ceramics, optical, thermal, chemical, biological and composite materials[7,8]. Additionally, sol-gel materials are homogeneous with a large number of hydrogen bonds, which not only maintains the multidimensional structure, but also promotes electron transfer as a modified electrode. Therefore, it is helpful to improve the stability of the electrochemical modified electrode[1,9].
In this study, the multi-dimensional network structure of sol-gel was immobilized on an electrode surface, which was used to simulate electron transfer in the cell membrane of micro interface by thin layer cyclic voltammetric technique[10–12]. Compared with traditional method[10–12] that can only describe the overall reaction occurring in electrode, sol-gel silica was used as the carrier to distinguish the reaction in specific area of electrode. In this study, a multi-dimensional microchannel electron transfer model was constructed and the electron transfer under the micro environment in cell membrane was investigated.
2 2.1
Experimental Chemicals and reagents
Tetraethyl orthosilicate was purchased from Aladdin (TEOS, Shanghai, China). Hexadecy ltrimethyl ammonium bromide was purchased from Aladdin (CTAB, Shanghai, China). Nitrobenzene (NB) (Shanghai chemical Reagent Co. Ltd.) was the highest purity. KCl, NaClO4 and K3Fe(CN)6 was
Received 28 November 2012; accepted 23 January 2013 * Corresponding author. Email: [email protected] This work was supported by the National Natural Science Foundation of China (Nos. 21175108, 21165015) and the National Natural Science Foundation of Gansu province, China (No. 090GKCA036). Copyright © 2013, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. Published by Elsevier Limited. All rights reserved. DOI: 10.1016/S1872-2040(13)60674-X
RU Jing et al. / Chinese Journal of Analytical Chemistry, 2013, 41(8): 1249–1253
purchased from Beijing Chemical Reagent Co. Ltd., China. HCl, NaOH and LiCl was purchased from Shanghai chemical Reagent Co. Ltd. China, Tetrabutylammonium perchlorate (TBAClO4)was purchased from Wuhan, China); ferrocene (Fc) was purchased from Aldrich (Shanghai, China), 0.1 M phosphate (KH2PO4/K2HPO4) buffer solution (PBS, pH 7.0, containing 0.1 M KCl) was used as supporting electrolyte. 0.3 and 0.05 μm α-Al2O3 powder (Shanghai chemical Reagent Co. Ltd.). Aqueous solutions were prepared with doubly distilled water, and solutions were deoxygenated by bubbling with nitrogen for 10 min. All experiments were performed at room temperature (22 ± 2) ºC. 2.2
Characterization
Cyclic voltammetry (CV) measurement was carried out by a CHI832 electrochemical workstation (CH Instrument Company, Shanghai, China). Electrochemical impedance spectroscopy (EIS) was conducted on a VMP2 Multipotentiostat (Princeton Applied Research, USA). A three-electrode system of a working glass carbon electrode (GCE, 2.0 mm diameter), a saturated calomel reference electrode (SCE) and a platinum wire counter electrode, was employed. Solution pH was measured with a Sartorius basic pH meter PB-10 (RenHe Instrument Co. Ltd., Shanghai, China). SEM images were taken using a field-emission scanning electron microscope (SEM, JEOL JSM-6701F) operated at an accelerating voltage of 5 kV. 2.3
Preparation of sol-gel precursor
The sol-gel precursor was prepared using a sol-gel method. The 0.2 M NaH2PO4/Na2HPO4 (PBS, pH 4.8, containing 0.1 M KCl) solution was added in a beaker, and 151 μL TEOS was added into the solution, then 1088 μL 0.2 M CTAB was dropped under vigorous stirring. Then, the solutions were stirred in a closed state for 12 h at room temperature. In this way the sol-gel SiO2 precursor was prepared. The process of hydrolysis and condensation are shown as following[2, 3]:
H → 4C 2 H 5OH + SiO 2 ( C 2 H 5O )4 Si + 2H 2O ⎯⎯⎯ H O +
2
(1)
(2) 2.4
Preparation of sol-gel modified electrode
The sol-gel film was first electrochemically deposited on a well polished work electrode following a process previously reported[6,13]. A three-electrode system was used with a working glass carbon electrode, a saturated calomel reference electrode (SCE) and a platinum wire counter electrode. Firstly, the working electrode was inserted in an electrolytic cell consisting of 5 mL prepared sol-gel, and a constant potential of –2.0 V was applied for 110 s. After the deposition, the modified electrode was rinsed with water and dried under ultraviolet light irradiation. The morphologies of prepared sol-gel SiO2 film were characterized by SEM. As shown in Fig.1, the SiO2 nanoparticles were clearly seen in the scale of 1 μm, indicating that the sol-gel SiO2 film was immobilized successfully on the electrode surface. 2.5
Construction of electronic delivery model with sol-gel modified electrode
Via thin layer cyclic voltammetry method, the working electrode used in Section 2.4 was modified with sol-gel and the saturated calomel reference electrode (SCE) and platinum wire counter electrode were placed in the solutions. The sol-gel modified electrode held in an upside-down position when thin layers of NB solutions containing interest reactants (Fc) and supporting electrolytes (TBAClO4) were appliedin Fig.2. 1 μL of NB solution was transferred with a microsyringe, so the organic liquid spread spontaneously across the surface of the modified electrode. The electrode was then turned over and immediately immersed in the aqueous solution. An interface between two immiscible electrolyte solutions (ITIES) was then formed.
Fig.1 SEM images of so-gel modified on glassy carbon electrode (GCE).
RU Jing et al. / Chinese Journal of Analytical Chemistry, 2013, 41(8): 1249–1253
Fig.2 Schematic diagram of modified electrode used in thin-layer voltammetry measurement.
3 3.1
Results and discussion Effect of deposition time from different sol-gel modified electrodes
In the process of electrodeposition sol-gel silica, a constant potential was applied to the glassy carbon and platinum electrodes, respectively. Meanwhile, 5 mM K3Fe(CN)6 was used as probe molecules, depositing sol-sol silica at the electrode surface investigated by potential electrochemical impedance spectroscopy (PEIS). The deposition times were set as following: 70, 80, 90, 100, 110, 120 and 130 s, respectively. The doposition was conducted at the potential of –2.0 and –0.9 V, respectively. As shown in Fig.3 and Fig.4, with the increase of deposition time, the impedance increased as well. With the increase of the thickness of sol-gel silica film, the sol-gel transparency was significantly reduced. With 110 s deposition time, Sol-gel has the best transparency and appropriate thickness. Therefore 110 s was selected as the optimum deposition time of the deposition for the sol-gel films. 3.2
3.3
Electron transfer in structure of multi-dimension tiny interference
The electron transfer model was constructed, and the
Fig.3
Electrochemical impedance plots of glass carbon electrode with different deposition time for using sol-gel in 5 mM K3Fe(CN)6 (containing 0.1 M KCl) solution
The different deposition time from a to h is 0 s, 70 s, 80 s, 90 s, 100 s, 110 s, 120 s, 130 s
Effect of deposition potential from different sol-gel modified electrodes
In the process of electrodeposition sol-gel silica, constant potentials were applied to the glassy carbon and platinum electrode, respectively. 5 mM K3Fe (CN)6 was used as probe molecules, and depositing sol-sol silica at the electrode surface was investigated by potential electrochemical impedance spectroscopy (PEIS). Different deposition potential was set: –1.8, –2.0, –2.2 and –2.4 V with the same deposition time 110 s. As shown in Fig.5 and Fig.6, with the increasing of the deposition potential, the impedance increased. The maximum impedance was reached at the potential of –2.0 V, implying the formation of sol-gel silica film with highest thickness. Hence potential of –2.0 V was chose for the experiment to fabricate the sol-gel films on glass carbon electrode.
Fig.4
Electrochemical impedance plots of Pt electrode with different deposition time for using sol-gel in 5 mM K3Fe(CN)6 (containing 0.1 M KCl) solution
The different deposition time from a to h is 0 s, 70 s, 80 s, 90 s, 100 s, 110 s, 120 s, 130 s
RU Jing et al. / Chinese Journal of Analytical Chemistry, 2013, 41(8): 1249–1253
Fig.5 Electrochemical impedance plots of the GC electrode with different deposition potential using sol-gel in 5 mM K3Fe(CN)6 (containing 0.1 M KCl) solution The different deposition potentials are: –1.8 V (curve b), –2.0 V (curve a), –2.2 V (curve c), –2.4 V (curve d)
spontaneously across the surface grid of multi-dimensional micro-channel; aqueous solution was K3Fe(CN)6 (containing 0.1 M NaClO4 as supporting electrolyte). It can be found that Fe2+/Fe3+ redox peaks disappeared, and the redox couple was no longer transferred to the electrode surface of sol-gel. Fig.7c shows the cyclic voltammograms (CVs) of 1 μL NB solutions containing interest reactants (Fc) and supporting electrolytes (TBAClO4). It can be found that a pair of redox peaks appeared at 0.427 V/0.588 V. The results indicated that this pair of redox peaks was the Fc redox peaks. Fig.7d shows the CVs of 1 μL NB solutions containing interest reactants (Fc), supporting electrolytes (TBAClO4) as organic phase and aqueous phase as K3Fe(CN)6 (containing 0.1 M NaClO4 as the supporting electrolyte). The results showed that the oxidation peak of Fc dramatically was increased and reached a steady state, and the peak current platform appeared at 0.315 V. So it can be found that the process of electron transfer between an aqueous phase and an organic phase on sol-gel modified electrode, and the electron transfer model was constructed successfully interfacial in the micro system. A possible reaction mechanism is proposed as follows: Fc (o) + Fe(CN) 3-6 (w) ⎯⎯ → Fc - (o) + Fe(CN) 64- (w) (3)
4
Fig.6
Electrochemical impedance plots of the Pt electrode with different deposition potential using sol-gel in 5 mM K3Fe(CN)6 (containing 0.1 M KCl) solution
The different deposition potentials are: –0.8 V (curve a), –0.9 V (curve b), –1.0 V (curve c), –1.1 V (curve d)
thickness and resistance of sol-gel SiO2 film increased with the extension of deposition time that the thickness and resistance of sol-gel SiO2 film increased with the extension of deposition time. To investigate the thickness, load capacity and permeability of the sol-gel SiO2, deposition time and potential of sol-gel SiO2 film were optimized with different modified electrodes. Under the optimized conditions, sol-gel modified glassy carbon electrode (GC) was used as working electrode. Electron transfer at the interface between two immiscible electrolyte solutions (ITIES) in microchannel model was investigated by thin layer cyclic voltammetry. As shown in Fig.7a, Fe2+/Fe3+ redox pairs of the modified multi-dimensional network structure of sol-gel film GC electrode in 10 mM of K3Fe(CN)6 (containing 0.1 M NaClO4 as the supporting electrolyte) was clearly observed by CVs. Figure 7b shows that the thin layers of NB solutions are applied to the sol-gel modified electrode held in an upside-down position by transferring 1 μL of the solutions to the modified electrode surface; the organic liquid spread
Conclusions
The work presents that the sol-gel is prepared in the absence of ethanol. The three-dimensional network structure of sol-gel SiO2 film is potentiostatic electro-deposited on the electrode surface, and a model of multi-dimensional microchannel interface electron transfer is constructed using the special characteristics of the sol-gel. Therefore, the sol-gel material can be immobilized on the electrode surface. It can be used to simulate electron transfer in cell membrane of micro interface based on the characteristics of their network structure.
Fig.7 Voltammetric observation of electron-transfer model from modified sol-gel thin film Gelectrode between Fc and K3Fe(CN)6 (a) Cyclic voltammogram of modified sol-gel thin film GC electrode in 10 mM K3Fe(CN)6 (containing 0.1 M NaClO4); (b) Repeat of part a after the modified sol-gel thin film GC electrode surface was covered with 1 μL of NB; (c) Cyclic voltammogram with the modified sol-gel thin film GC electrode covered with 1 μL of NB containing 1 mM Fc (containing 0.1 M TBAClO4 as supporting electrolyte) in 0.1 M NaClO4 solution; (d) Repeat of part c in 10 mM K3Fe(CN)6 (containing 0.1 M NaClO4) solution, and 1 μL NB containing 1 mM Fc (containing 0.1 M TBAClO4 as supporting electrolyte). Scan rate: 5 mV s–1
RU Jing et al. / Chinese Journal of Analytical Chemistry, 2013, 41(8): 1249–1253
References
[7]
[1]
[8]
Ju H X. Analysis of Chemical and Biological Sensing Technology. Beijing: Science Press, 2006: 230
Mishira A, Ma C Q, Bauerle P. Chem. Rev., 2009, 109(3):
[2]
Wang B Q, Li B, Wang Z X, Xu G B, Wang Q, Dong S J. Anal.
[9]
Debecker D P, Bouchmella K, Poleunis C, Eloy P, Bertrand P,
[10] Lu X, Sun P, Yao D, Wu B, Xue Z, Zhou X, Sun R, Li L, Liu X H. Anal. Chem., 2010, 82(20): 8598–8603
Gaigneaux E M, Mutin P H. Chem. Mater., 2009, 21(13): 2817–2824 [4]
Gill I. Chem. Mater, 2001, 13(10): 3404–3421
[5]
Suhaxini k, Vu T, Maggie K M H. Journal of Chemical
[6]
Ievgen M, Mathieu E, Rainer O, Smarsly Bernd M., Oksana T, Vladimir Z, Alain W, Langmuir, 2011, 27(11): 7140–7147
Chem., 1999, 71(10): 1935–1939 [3]
Chang S, Hsu Y, Chan T. J. Phys. Chem. C, 2011, 115(5): 2005–2013
1141–1276
[11] Liu X, Hu L N, Zhang L, Liu H, Lu X. Electrochimica Acta, 2005, 51: 467–473
Education, 2010, 87(9): 958–960
[12] Shi C N, Anson F C. Anal. Chem., 1998, 70(15): 3114–3118
Liang R P, Jiang J L, Qiu J D. Electroanalysis, 2008, 20(24):
[13]
2642–2648
Walcarius
A,
Sibottier
E,
Etienne
Naturematerials, 2007, 6: 602–608
M,
Ghanbaja
J.