Article pubs.acs.org/Langmuir
Electrosynthesis of Layered Organo-Manganese Dioxide FrameworkDoped with Cobalt for Iodide Sensing Kimiko Nakagawa,† Kanon Suzuki,† Misa Kondo,‡ Shinjiro Hayakawa,‡ and Masaharu Nakayama*,† †
Department of Applied Chemistry, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, Japan ‡ Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan S Supporting Information *
ABSTRACT: Aqueous Mn2+ ions were anodized at 70 °C with Co2+ in the presence of cationic surfactant, cetyltrimethylammonium (CTA). X-ray diffraction (XRD) analysis revealed that the deposited film possesses a layered structure of MnO2, the interlayer of which is occupied with the assembled CTA molecules. Inclusion of Co ions in the MnO2 film was evidenced by X-ray photoelectron spectroscopy (XPS). They were located in the MnO2 framework, not in the interlayer. The thus-obtained film, CTA-intercalated Co-frameworkdoped layered MnO2 (CTA/Co-MnO2), was applied as an electrochemical sensor toward iodide (I−), a hydrophobic anion. The organic phase between MnO2 layers could extract I− ions from solution, providing a better sensitivity than a film consisting of layered MnO2 with hydrated alkali metals. On the other hand, the Co-doped layers of MnO2 achieved faster electron transfer kinetics for the oxidation of I−, which resulted in a drastic reduction in response time compared to the nondoped CTA/MnO2.
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potentiostatic oxidation of aqueous Mn2+ ions in the presence of organic cations such as tetra-alkylammonium,12 cationic polymers,11,13 and cationic surfactants,14,15 yielding a transparent thin film adhered well to an electrode substrate. The thus-obtained films were applied to the sorption of organic dyes15 and the electrooxidation of hydroquinone.14 On the other hand, iodine is an essential element in thyroid hormones that play an essential role in biological activities. Both a deficiency and an excess of iodine can cause thyroidrelated diseases, such as goieter, hyperthyroidism, and hypothyroidism.16 In seawater, iodine exists as mainly iodide (I−), iodate (IO3−), and dissolved organic iodine with a total concentration of 4.5−76.2 ng mL−1.17 The fission of uranium235 produces radioactive isotopes of iodine such as 129I and 131 129 I. I has an extremely long half-life (1.57 × 107 years) compared to 131I (8.02 days) or many other radioactive elements. Iodide is highly soluble in water and is hardly adsorbed onto soil. This can allow I− to diffuse over a long period of time in the hydrosphere, including groundwater and seawater. In fact, the ratio of 129I to 127I (stable isotope) can reach values of 10−10−10−4 in the environment, in contrast to values of 10−12 in the prenuclear era (before 1945).18 The concentration of iodine in organisms and environment is extremely low, requiring technologies to capture and detect it from the complicated matrix with high selectivity, sensitivity, and short response time. A number of analytical method,
INTRODUCTION Diversity of manganese oxides (especially MnO2) has been brought about by their oxidation states, crystalline structures, morphologies, and the strategies for incorporation of different metals and carbonaceous materials. As a result, the products have found a wide variety of applications in a number of industries and are the subject of intense research. For example, MnO2-based materials combined with nanoscale carbon such as carbon nanotubes and graphene are recognized as one of the most promising electrode materials for supercapacitors.1 Although the number is limited, a combination of MnO2 with organic substances also created a unique research area. That is, MnO2-based nanocomposites with two-dimensional structure were synthesized particularly in the late 1990s to early 2000s,2−10 where organic molecules charged positive were accommodated between MnO2 layers having negative charge arising from the existence of Mn3+ in the Mn4+ matrix. The process involves ion-exchange,2 layer-by-layer manner,3−5 and self-assembly of organic cations during the formation of negative surfaces of MnO2.6−8 Tetra-alkylammoniums,2,6,7 polycations,3−5 and cationic surfactants8−10 were submitted as the guest cations to be incorporated. The products were utilized for catalytic oxidation of styrene5 as well as removal of organic pollutants such as benzoic acid9 and dyes10 from wastewater. Their structure is similar to that of organoclays because it is composed of a two-dimensional, inorganic host (MnO2) and an organic guest species, and therefore, the composite materials can be termed “organo-MnO2”. An electrochemical approach to build layered organo-MnO2 was first demonstrated by Nakayama et al.11 The process involves © XXXX American Chemical Society
Received: February 7, 2017 Revised: April 21, 2017 Published: May 2, 2017 A
DOI: 10.1021/acs.langmuir.7b00419 Langmuir XXXX, XXX, XXX−XXX
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Langmuir including spectroscopic19−23 and electrochemical methods, have been proposed to determine trace amounts of iodine. Electrochemical methods include polarography,24 voltammetry,25,26 amperometry,27−29 and a variety of potentiometric sensors based on ionophores.30−34 In our previous study, the layered MnO2 film intercalated with hexadecylpyridinium cations (HDPy+) was utilized for the sorption of iodide anions.35 The inherent advantages of an electrochemically grown film over conventional powdered sorbents are (i) thin film sorbent is much less bulkier than powder-type sorbent, (ii) the electrode-supported film can be easily separated from the solution being treated and does not need the secondary collection, and (iii) the oxidation state of the film sorbent can be controlled by an external electrical circuit. The HDPy/MnO2 film selectively captured iodide from the major components of seawater through hydrophobic (organophilic) interaction between the interlayer organic phase of the MnO2 film and iodide ions in solution. This is because the free energy (−275 kJ mol−1) of hydration of iodide ion is lower than other anionic components of seawater, that is, SO42− (−1080 kJ mol−1), Cl− (−340 kJ mol−1), and CO32− (−1315 kJ mol−1),36,37 and therefore, it is more favorable to exist in a hydrophobic environment. Moreover, we found that the sorbed I− ions were anodically oxidized by an external electrical circuit, being removed from the interlayer as I2 molecules.38 A common drawback in Mn oxides as an electrode material is their poor electrical conductivity (10−6−10−5 S cm−1).39 This problem has been addressed by incorporation of different transition metals such as Pb, Ni, Co, Mo, and Fe, especially in the application of MnO2-based materials to supercapacitors.40 The framework doping of layered alkaline MnO2 was accomplished through hydrothermal reaction, where the conductivity increased 2 orders of magnitude when 4% of Mn ions in the oxide framework were substituted by Co.41 To the best of our knowledge, however, there is no report on the layered organo-MnO2 composites having the framework doped with different transition metals. In the present study, we attempted to dope Co atoms into the framework of layered organo-MnO2 by coexisting Co2+ ions during the anodization of aqueous Mn2+ ions at elevated temperature. The improved electron transfer kinetics in the Co-doped MnO2 layers was reflected in a drastic reduction in response time in the sensing process of iodide.
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potential had yielded a product with high crystallinity in the electrodeposition of organo-MnO2 in the absence of Co2+ ions.14 The temperature of a bath was kept using a ribbon heater. In each case, the deposited film was rinsed thoroughly with water, immersed in water for 1 h to remove soluble impurities, and then subjected to structural characterization and electrochemical tests including iodide sensing. Structural Characterization. X-ray diffraction (XRD) patterns were recorded on a Rigaku Ultima IV diffractometer, using Cu Kα radiation (λ = 0.154051 nm). The data were collected over the 2θ range from 1 to 50° at a scan rate of 1° min−1, applying a beam voltage of 40 kV and a beam current of 40 mA. X-ray photoelectron spectroscopy (XPS) was performed using a Thermo Scientific K-Alpha spectrometer with an Al Kα (1486.6 eV) monochromatic source (1805 V, 3 mA). Wide- and narrow-range spectra were acquired with a pass energy of 50 eV and channel widths of 1.0 and 0.1 eV, respectively. The binding energy scale was calibrated with respect to the C 1s (284.8 eV) signal. Semiquantitative estimates of the relative atomic concentrations were obtained from the peak area ratios by considering the sensitivity factors provided by the instrument software. Field emission scanning electron microscopy (FE-SEM) data were obtained using a Hitachi S-4700Y microscope operating at 10 kV. Samples were observed directly without any coatings. Cross-sectional transmission electron microscope (TEM) observation was made via JEOL JEM-CX 200 microscope at an accelerating voltage of 200 kV. UV−vis spectra were collected using a Jasco V-6700S spectrometer for the sample films deposited on an indium-doped tin oxide (ITO)coated glass slide (R = 10 Ω·cm) with an active area of 0.9 cm × 2.0 cm. The ITO surface was degreased with acetone, ultrasonicated in ethanol, and then washed thoroughly with water. Iodide Sensing. Chronoamperometry was carried out for sensing iodide on a glassy carbon (GC) rod (5 mm in diameter) embedded in a Teflon cylinder. Prior to the modification with MnO2 films, the GC surface was polished with 0.5 μm alumina powder and cleaned by ultrasonication in HCl solution for 10 min and then in distilled water for 10 min. For application as an amperometric sensor, the current responses of the modified and unmodified GC electrodes were measured upon successive addition of NaI every 180 s, while the electrode was polarized at a constant potential of +1.0 V. For comparison purposes, a layered alkali MnO2 film (Na/Co-MnO2) was similarly prepared at 70 °C by using the same concentration of NaCl, instead of CTACl. A series of experiments were conducted within a concentration range of 2−20 μM of NaI and were repeated in triplicate for each measurement.
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RESULTS AND DISCUSSION Electrodeposition of Layered Organo-MnO2 with and without Co2+ Ions. Figure 1 shows current density-potential (i−E) curves taken in various solutions kept at 25 and 70 °C, in which 50 mM of CTACl was contained in all the solutions. In a CoSO4 solution without Mn2+ at 25 °C (curve a), no significant
EXPERIMENTAL SECTION
Materials. All chemicals were of reagent grade and used without further purification. MnSO4·5H2O (99.9%), CoSO4·7H2O (99.5%), cetyltrimethylammonium chloride (CTA+Cl−, 95.0%), and NaI (99.5%) were purchased from Wako Pure Chemicals. All solutions were prepared with doubly distilled water and were deoxygenated by bubbling with purified nitrogen gas for at least 20 min prior to use. Electrodeposition of Layered Manganese Dioxide. All electrochemical experiments were performed in a standard threeelectrode cell connected to a potentio/galvanostat (HZ-5000, Hokuto Denko). A platinum mesh with a large surface area and a standard Ag/ AgCl electrode (in saturated KCl) served as the counter and reference electrodes, respectively. Unless otherwise noted, a polycrystalline platinum foil (1.0 × 1.0 cm; thickness 0.5 mm; Niraco) was used as the working electrode on which electrodeposition was conducted. The Pt surface was ultrasonically cleaned in diluted HCl solution for 10 min and then in water for another 10 min. The deposition baths used consisted of 2 mM MnSO4 and 50 mM CTACl with and without 1 mM CoSO4. A constant potential of +1.0 V was applied to the working electrode, while a fixed charge of 200 mC cm−2 was delivered. This
Figure 1. i−E curves taken at (dashed lines) 25 and (solid lines) 70 °C in solutions containing 50 mM CTACl and (black) 1 mM CoSO4, (blue) 2 mM MnSO4, and (red) 1 mM CoSO4 + 2 mM MnSO4. Scan rate, 10 mV s−1. B
DOI: 10.1021/acs.langmuir.7b00419 Langmuir XXXX, XXX, XXX−XXX
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Figure 2. Absorption spectra of the electrodeposited films from 2 mM MnSO4 + 50 mM CTACl solutions (a) with and (b, c) without 1 mM CoSO4, kept at (a, b) 70 and (c) 25 °C. The electrical charge consumed during the film preparation was 45 mC cm−2.
Figure 4. (A) XRD patterns and (B) XPS spectra of the films deposited on a Pt substrate (a) before and (b) after immersion for 24 h in an aqueous solution of 0.5 M CaCl2. The film was prepared at 70 °C in a solution containing 2 mM MnSO4, 1 mM CoSO4, and 50 mM CTACl by applying a constant potential of +1.0 V. The electrical charge consumed during the film preparation was 200 mC cm−2.
were not oxidized directly at the Pt surface, but mediated by the oxidation of Mn species.43 Hereafter, the electrodeposition was carried out by applying a constant potential of +1.0 V in MnSO4 and CTACl solutions with and without Co2+, where the Co2+ oxidation can take part in the growth of MnO2 deposition at 70 °C. In contrast, it is obvious that the same reaction occurs at 25 °C, regardless if it is with or without Co2+ ions. Figure 2 shows the absorption spectra in the visible region of a thin film deposited at 70 °C on an ITO substrate from the MnSO4 + CTACl solution containing CoSO4, along with those made without Co2+ at 25 and 70 °C. The delivered charge for the film preparation was fixed at 45 mC cm−2. Inclusion of Mn in all the deposited films was confirmed by the broad d−d* absorptions lying between 400 and 600 nm.44 In the case of the absence of Co2+, no significant difference was seen between the films prepared at 25 and 70 °C. On the other hand, the absorption spectrum of the film deposited with Co2+ was raised in the higher wavelength region. The absorption peaked at 650 nm can be ascribed to the O2− (2p) to Co3+ (eg) charge transfer
Figure 3. (A) XRD patterns and (B) XPS spectra of the electrodeposited films on a Pt substrate from 2 mM MnSO4 + 50 mM CTACl solutions (a) with and (b, c) without 1 mM CoSO4, kept at (a, b) 70 and (c) 25 °C. The electrical charge consumed during the film preparation was 200 mC cm−2.
current was observed until near +1.2 V, while at 70 °C, this current was enhanced at positive potentials. Also, in a solution containing MnSO4 alone, the current due to oxidation of aqueous Mn2+ became larger at the elevated temperature, as seen from the comparison between curves c and d, since high temperature enables fast electron transfer kinetics.42 The current profile (curve e) obtained in a mixed solution of Mn2+ and Co2+ ions at 25 °C is the same as that (curve c) in the Mn2+ solution without Co2+. This demonstrates that Co2+ ions were not involved in the anodic oxidation of Mn2+ ions at room temperature. At the elevated temperature, however, an enhanced current was clearly observed at least from +0.7 V, as shown in curve f. The increased current, compared to curve d, can be ascribed to a catalytic effect, meaning that Co2+ ions C
DOI: 10.1021/acs.langmuir.7b00419 Langmuir XXXX, XXX, XXX−XXX
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Figure 5. (A) Steady-state CVs of CTA/Co-MnO2 film electrode taken in an aqueous 0.1 M Na2SO4 solution at a scan rate of 20 mV s−1 with different negative potential limits, and (B) XRD patterns of the films after being subjected to the CV cycling in (A).
transition.45 As shown in the images taken by a digital camera, the film deposited with Co2+ appeared more black, rather than brown, like the film without Co2+. The films labeled a, b, and c in Figure 2 were next subjected to XRD analysis, and the results are displayed in Figure 3A. In all patterns, the same set of diffraction peaks was observed, composed of evenly spaced seven peaks, which are diagnostic of a layered structure. The observed peaks are indexable to the 001 plane and its second (002)- to seventh (007)-order diffractions from multilayers of MnO2.14 No new peaks assignable to the Co oxide phase were detected for the film (a) made with Co2+. The d-spacing of the 001 plane (=d001) corresponds to the interlayer distance and was estimated to be 3.26 nm according to the Bragg equation. Considering the crystallographic thickness of a single MnO2 layer of 0.45 nm,46 the gallery spacing between MnO2 layers is calculated to be 2.36 nm, which is capable of accommodating a CTA molecule (2.17 nm)47 in the manner perpendicular to the layers. It is worth noting that the full width at half-maximum (fwhm) of the 001 peak is larger for film a compared to films b and c; that is, 1.0 × 10−2, 9.1 × 10−3, and 9.3 × 10−3 radians, respectively. Combined with the absence of the Co oxide phase in Figure 3A(a) and the appearance of Co 2p XPS peaks, as will be described below, it is strongly suggested that Co atoms were doped into the MnO2 layers that sandwich the organic phase consisting of assembled CTAs. The microstructure of the film deposited with Co2+ was investigated by top-view SEM and cross-sectional TEM measurements (Figure S1), where a sheetlike morphology and evenly spaced stripes were detected, characteristic of the layered MnO2 film intercalated with CTA that was similarly grown without Co2+.14
Figure 6. (a) i−t curves for unmodified and CTA/Co-MnO2-, CTA/ MnO2-, and Na/Co-MnO2-modified GC electrodes upon successive addition of iodide at an applied potential of +1.0 V in 0.1 M Na2SO4, (b) enlarged view of (a), and (c) calibration curves.
Figure 3B shows Mn 3s and Co 2p XPS spectra taken for the same set of films. The energy separation (ΔE) of the doublet peaks in the Mn 3s region is dependent on the oxidation state of Mn involved in the oxide.48 From the figure, the ΔE value was estimated to be 5.11, 4.67, and 4.74 eV for films a, b, and c, respectively. According to a linear relationship between the oxidation state of Mn and ΔE reported in the literature,49 the values correspond to average oxidation states of 3.18, 3.73, and 3.65, respectively. The existence of Co in film a is clearly evidenced by the peaks in the Co 2p region, which are of course absent in films b and c. The fact that the oxidation state of Mn was lower in film a than those in the others, despite all the films being deposited at the same applied potential, can be recognized by considering that some Mn sites in film a were replaced by Co ions. The main peaks appearing at 798.6 and 780.7 eV can be ascribed to the doublet peaks due to trivalent Co atoms.50 This agrees with the result in Figure 1 that Co2+ ions in the deposition bath were catalytically oxidized. Deconvoluted peaks at 775.4 and 795.8 eV can be associated with the minor contribution of remaining Co2+.51 The atomic ratio of Co/Mn for film a was 0.18. On the other hand, there is no difference between the layered organo-MnO2 films (b and c) deposited at different temperatures (70 and 25 °C). D
DOI: 10.1021/acs.langmuir.7b00419 Langmuir XXXX, XXX, XXX−XXX
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Langmuir Table 1. Comparison of the Performances of the Electrodes Examined for Iodide Sensing electrode CTA/Co-MnO2/GC CTA/MnO2/GC K/Co-MnO2/GC GC
sensitivity (A M−1 cm−2)
response time (s for 90% change)
1.288 0.944 0.403 0.061
19 105 9 8
detection limit (M) 6.62 1.08 1.15 1.04
× × × ×
−9
10 10−8 10−8 10−7
R2 0.999 0.994 0.999 0.999
that of unmodified GC. The data were obtained when NaI was successively added every 180 s to a Na2SO4 electrolyte, while the electrode was polarized at a constant potential of +1.0 V. The I− concentration was changed from 2 to 20 μM. All anodic currents observed are ascribed to the oxidation of I− anions in solution to molecular I2 (2I− → I2 + 2e−).54 CTA/Co-MnO2 and CTA/MnO2 electrodes exhibited much larger current than Na/Co-MnO2 or unmodified GC, which indicates that I− ions were accumulated in the organophilic phase of the interlayer and then oxidized. As shown in the enlarged view (Figure 6b), when 2 μM NaI was added, the time required for 90% of the maximum current decreased dramatically from 105 s for CTA/MnO2 to 19 s for CTA/Co-MnO2. This can be related to the improved electrical conductivity of the MnO2 layers by the doping of Co atoms55 and strongly suggests that the electron transfer from I− to the GC substrate is mediated by the MnO2 layers. Based on the steady-state currents in the i−t curves, calibration curves were created in the concentration range of 2−20 μM (Figure 6c). Five repeated measurements for the detection of 2 μM iodide gave a relative standard deviation of 2.9%. This indicates a repeatability of the modified electrode. In order to study the influence of various species on the determination of iodide, the current−time curve was recorded upon successive addition of other anions (NO3−, F−, Cl−, and Br−) and cations (Mg2+ and Ca2+) at a 100-fold higher concentration than I−, while the modified electrode was polarized at +1.0 V in 0.1 M Na2SO4 solution. The resulting data is shown as Figure S2, where no significant interference was observed. Table 1 summarizes the main performances of unmodified and modified GC electrodes, which demonstrates an enhancement in sensitivity and a drastic decrease in response time by the incorporation of CTAs and Co atoms into the interlayer and framework of MnO2, respectively. In addition, the electrode modified with CTA/Co-MnO2 provided better or comparable sensitivity27,28,56 and lower detection limit25,29,57,58 than most electrodes reported for amperometric measurements of iodide (Table S1).
To further evidence the doping of Co into the framework of layered organo-MnO2, the MnO2 film made in the presence of Co2+ was subjected to ion exchange with divalent Ca2+ ions. We previously reported that monovalent cations such as Na+ do not replace the CTA molecules accommodated between MnO2 layers.14 After immersion in a CaCl2 solution, however, the characteristic evenly spaced peaks of the as-deposited film with Co2+ completely disappeared, as shown in Figure 4A. Instead, two peaks occurred at 8.69 and 17.59°. Note that the latter angle is almost equal to twice the former, which is diagnostic of a layered structure, and the diffractions can be attributed to buserite-type layered MnO2 which possesses two layers of water molecules in addition to divalent cations with higher hydration energy, such as Mg2+ and Ca2+.52 The 8.69° peak indicates that the interlayer distance (=d001) was reduced from 3.26 to 1.02 nm after immersion, as a result of the ion exchange between the cationic surfactants in the interlayer and Ca2+ ions in solution. The same films were subjected to XPS analysis, and the results are shown in Figure 4B. Here, all the spectra were normalized with respect to the intensity of Mn 2p peaks, allowing an easy comparison. The N 1s peak due to the cationic nitrogen belonging to CTA disappeared after immersing the asdeposited film in CaCl2 solution, which is in good agreement with the above XRD data. At this time, the doublet peaks due to Ca2+ occurred, while the Co 2p peaks remained. Thus, there is no doubt on the doping of Co ions into the framework of layered MnO2 and not into the interlayer. Hereafter, the film thus-prepared will be denoted as CTA/Co-MnO2. Electrochemical Behavior of CTA/Co-MnO2. We investigated electrochemical properties of CTA/Co-MnO2 film in an aqueous solution containing supporting electrolyte (Na2SO4) alone. As reported previously, the CTA ions intercalated during electrodeposition cannot be replaced by Na+ ions in solution but remain immobilized, as a result of the lateral interaction between the hydrophobic tails of surfactants.14 Figure 5A shows steady-state CVs of the CTA/Co-MnO2-modified Pt electrode recorded with different negative limits (0.7, 0.6, 0.4, and 0.3 V) at a scan rate of 20 mV s−1, along with the XRD patterns of the films after the respective CV cycles. They were obtained after 50 cycles. A capacitive feature, due to the pseudocapacitance arising from the Mn3+/Mn4+ redox couple, was observed with different sizes in all CVs. In Figure 5B, the patterns obtained after CV cycling with the limiting potentials of +0.6 and +0.7 V were the same as that of the as-deposited CTA/Co-MnO2 film. However, the cathodic scanning to +0.3 V provided another XRD pattern composed of two peaks at 12.03 and 24.01°, which is typical of birnessitetype layered MnO2 intercalated with Na+ ions and one layer of water molecules.53 Clearly, the layered organo-MnO2 doped with Co lost its original structure at the cathodic potentials as a result of the replacement of the intercalated CTAs and electrolyte cations (Na+). Figure 6a shows i−t curves collected for the GC electrodes modified with CTA/Co-MnO2, CTA/MnO2, and Na/CoMnO2 films, all of which were deposited at 70 °C, along with
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CONCLUSIONS Aqueous Mn2+ ions were anodized at 70 °C with Co2+ in the presence of cationic surfactant, cetyltrimethylammonium (CTA). The deposited film possesses a layered structure of MnO2, the interlayer of which is occupied with the assembled CTA molecules. Inclusion of Co ions in the MnO2 film was evidenced by XPS, and they were located in the MnO2 framework, not in the interlayer. The CTA-intercalated Coframework-doped layered MnO2 could extract iodide anions into its organic phase between MnO2 layers from solution, providing an improved sensitivity, compared to layered alkali MnO2 film. The Co-doped layers of MnO2 enabled faster electron transfer kinetics for the iodide oxidation, yielding a drastic reduction in response time compared to the nondoped MnO2. E
DOI: 10.1021/acs.langmuir.7b00419 Langmuir XXXX, XXX, XXX−XXX
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(12) Nakayama, M.; Konishi, S.; Tagashira, H.; Ogura, K. Electrochemical Synthesis of Layered Manganese Oxides Intercalated with Tetraalkylammonium Ions. Langmuir 2005, 21, 354−359. (13) Nakayama, M.; Tagashira, H. Electrodeposition of Layered Manganese Oxide Nanocomposites Intercalated with Strong and Weak Polyelectrolytes. Langmuir 2006, 22, 3864−3869. (14) Nakayama, M.; Shamoto, M.; Kamimura, A. Surfactant-Induced Electrodeposition of Layered Manganese Oxide with Large Interlayer Space for Catalytic Oxidation of Phenol. Chem. Mater. 2010, 22, 5887−5894. (15) Mori, K.; Iguchi, S.; Takebe, S.; Nakayama, M. A Thin Film Sorbent of Layered Organo-MnO2 for the Extraction of p-Aminoazobenzene from Aqueous Solution. J. Mater. Chem. A 2015, 3, 6470− 6476. (16) Shelor, C.; Dasgupta, P. Review of Analytical Methods for the Quantification of Iodine in Complex Matrices. Anal. Chim. Acta 2011, 702, 16−36. (17) Wong, G. T. F. The Marine Geochemistry of Iodine. Rev. Aquat. Sci. 1991, 4, 45−73. (18) Hou, X.; Hansen, V.; Aldahan, A.; Possnert, G.; Lind, O. C.; Lujaniene, G. A Review on Speciation of Iodine-129 in the Environmental and Biological Samples. Anal. Chim. Acta 2009, 632, 181−196. (19) Bermejo-Barrera, P.; Fernandez-Sanchez, L. M.; Aboal-Somoza, M.; Anllo- Sendin, R. M.; Bermejo-Barrera, A. Indirect Atomic Absorption Spectrometry (IAAS) as a Tool for the Determination of Iodide in Infant Formulas by Precipitation of AgI and Redissolution with Cyanide. Microchem. J. 2001, 69, 205−211. (20) Pienpinijtham, P.; Han, X. X.; Ekgasit, S.; Ozaki, Y. Highly Sensitive and Selective Determination of Iodide and Thiocyanate Concentrations Using Surface-Enhanced Raman Scattering of StarchReduced Gold Nanoparticles. Anal. Chem. 2011, 83, 3655−3662. (21) Arena, M. P.; Porter, M. D.; Fritz, J. S. Rapid, Specific Determination of Iodine and Iodide by Combined Solid-Phase Extraction/Diffuse Reflectance Spectroscopy. Anal. Chem. 2002, 74, 185−190. (22) Shanga, Z. B.; Wang, Y.; Jin, W. J. Triethanolamine-Capped CdSe Quantum Dots as Fluorescent Sensors for Reciprocal Recognition of Mercury (II) and Iodide in Aqueous Solution. Talanta 2009, 78, 364−369. (23) Ito, K. Determination of Iodide in Seawater by Ion Chromatography. Anal. Chem. 1997, 69, 3628−3632. (24) Takayanagi, K.; Wong, G. T. F. The Oxidation of Iodide to Iodate for the Polarographic Determination of Total Iodine in Natural Waters. Talanta 1986, 33, 451−454. (25) Lefevre, G.; Bessiere, J.; Walcarius, A. Cuprite-Modified Electrode for the Detection of Iodide Species. Sens. Actuators, B 1999, 59, 113−117. (26) Tomčík, P.; Bustin, D. Voltammetric Determination of Iodide by Use of an Interdigitated Microelectrode Array. Fresenius' J. Anal. Chem. 2001, 371, 562−564. (27) Phokharatkul, D.; Karuwan, C.; Lomas, T.; Nacapricha, D.; Wisitsoraat, A.; Tuantranont, A. AAO−CNTs Electrode on Microfluidic Flow Injection System for Rapid Iodide Sensing. Talanta 2011, 84, 1390−1395. (28) Chailapakul, O.; Amatatongchai, M.; Wilairat, P.; Grudpan, K.; Nacapricha, D. Flow-Injection Determination of Iodide Ion in Nuclear Emergency Tablets, Using Boron-Doped Diamond Thin Film Electrode. Talanta 2004, 64, 1253−1258. (29) Tian, L.; Liu, L.; Chen, L.; Lu, N.; Xu, H. Electrochemical Determination of Iodide on a Vanadium Oxide−Polypropylene Carbonate Coated Glassy Carbon Electrode. Talanta 2005, 66, 130−135. (30) Zhou, W.; Chai, Y. Q.; Yuan, R.; Wu, X.; Guo, J. X. Potentiometric Iodide Selectivity of Polymer-Membrane Sensors Based on Co(II) Triazole Derivative. Electroanalysis 2008, 20, 1434−1439. (31) Ghaedi, M.; Shojaie, A. F.; Montazerozohori, M.; Karami, B.; Gharaghani, S. Iodide-Selective Electrodes Based on Bis[N(2-methyl-
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.langmuir.7b00419. SEM and TEM images, influence of impurities, and comparison with other electrodes (PDF).
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Masaharu Nakayama: 0000-0002-5308-0126 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The present work is under the support by the following organizations: Japan Society for the Promotion of Science (Grant No. 16K05938), Electric Technology Research Foundation of Chugoku, and Yamaguchi University OptEnergy Research Center. We gratefully acknowledge all of these supports.
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REFERENCES
(1) Simon, P.; Gogotsi, Y. Materials for Electrochemical Capacitors. Nat. Mater. 2008, 7, 845−854. (2) Gao, Q.; Giraldo, O.; Tong, W.; Suib, S. L. Preparation of Nanometer-Sized Manganese Oxides by Intercalation of Organic Ammonium Ions in Synthetic Birnessite OL-1. Chem. Mater. 2001, 13, 778−786. (3) Liu, Z. -h.; Yang, X.; Makita, Y.; Ooi, K. Preparation of a Polycation-Intercalated Layered Manganese Oxide Nanocomposite by a Delamination/Reassembling Process. Chem. Mater. 2002, 14, 4800− 4806. (4) Wang, L.; Omomo, Y.; Sakai, N.; Fukuda, K.; Nakai, I.; Ebina, Y.; Takada, K.; Watanabe, M.; Sasaki, T. Fabrication and Characterization of Multilayer Ultrathin Films of Exfoliated MnO2 Nanosheets and Polycations. Chem. Mater. 2003, 15, 2873−2878. (5) Espinal, L.; Suib, S. L.; Rusling, J. F. Electrochemical Catalysis of Styrene Epoxidation with Films of MnO2 Nanoparticles and H2O2. J. Am. Chem. Soc. 2004, 126, 7676−7682. (6) Luo, J.; Suib, S. L. Formation and Transformation of Mesoporous and Layered Manganeseoxides in the Presence of Long-Chain Ammonium Hydroxides. Chem. Commun. 1997, 1031−1032. (7) Brock, S. L.; Sanabria, M.; Suib, S. L.; Urban, V.; Thiyagarajan, P.; Potter, D. I. Particle Size Control and Self-Assembly Processes in Novel Colloids of Nanocrystalline Manganese Oxide. J. Phys. Chem. B 1999, 103, 7416−7428. (8) Chen, C.-H.; Crisostomo, V. M. B.; Li, W.-N.; Xu, L.; Suib, S. L. A Designed Single-Step Method for Synthesis and Structural Study of Organic−Inorganic Hybrid Materials: Well-Ordered Layered Manganese Oxide Nanocomposites. J. Am. Chem. Soc. 2008, 130, 14390− 14391. (9) Wang, N.-H.; Lo, S.-L. Sorption of Benzoic Acid from Aqueous Solution by Cetyltrimethylammonium Bromide Modified Birnessite. Water Sci. Technol. 2012, 65, 1863−1868. (10) Zhou, J.; Yu, L.; Sun, M.; Ye, F.; Lan, B.; Diao, G.; He, J. WellOrdered Organic−Inorganic Hybrid Layered Manganese Oxide Nanocomposites with Excellent Decolorization Performance. J. Solid State Chem. 2013, 198, 371−378. (11) Nakayama, M.; Tagashira, H.; Konishi, S.; Ogura, K. A Direct Electrochemical Route to Construct a Polymer/Manganese Oxide Layered Structure. Inorg. Chem. 2004, 43, 8215−8217. F
DOI: 10.1021/acs.langmuir.7b00419 Langmuir XXXX, XXX, XXX−XXX
Article
Langmuir
Graphene/Ni Foam for High-Performance Supercapacitors. RSC Adv. 2015, 5, 100106−100113. (52) Post, J. E. Manganese Oxide Minerals: Crystal Structures and Economic and Environmental Significance. Proc. Natl. Acad. Sci. U. S. A. 1999, 96, 3447−3454. (53) Golden, D. C.; Chen, C. C.; Dixon, J. B. Transformation of Birnessite to Buserite, Todorokite, and Manganite under Mild Hydrothermal Treatment. Clays Clay Miner. 1987, 35, 271−280. (54) Hanson, K. J.; Tobias, C. W. Electrochemistry of Iodide in Propylene Carbonate I. Cyclic Voltammetry Monitored by Optical Spectroscopy. J. Electrochem. Soc. 1987, 134, 2204−2210. (55) Tang, C.-L.; Wei, X.; Jiang, Y.-M.; Wu, X.-Y.; Han, L.-N.; Wang, K.-X.; Chen, J.-S. Cobalt-Doped MnO2 Hierarchical Yolk−Shell Spheres with Improved Supercapacitive Performance. J. Phys. Chem. C 2015, 119, 8465−8471. (56) Kosminsky, L.; Bertotti, M. Determination of Iodate in Salt Samples with Amperometric Detection at a Molybdenum Oxide Modified Electrode. Electroanalysis 1999, 11, 623−626. (57) Kwak, M.−K., I.; Park, D.−S.; Won, M.−S.; Shim, Y.−B. Anodic Differential Pulse Voltammetric Analysis of Iodide with a CinchonineModified Carbon Paste Electrode. Electroanalysis 1996, 8, 680−684. (58) Švancara, I.; Konvalina, J.; Schachl, K.; Kalcher, K.; Vytřas, K. Stripping Voltammetric Determination of Iodide with Synergistic Accumulation at a Carbon Paste Electrode. Electroanalysis 1998, 10, 435−441.
phenyl) 4-Nitro-thiobenzamidato]mercury(II) and Bis[N-phenyl 3,5Dinitro-thiobenzamidato]mercury(II) Carriers. Electroanalysis 2005, 17, 1746−1754. (32) Jeong, D. C.; Lee, H. K.; Jeon, S. Polymeric Iodide-ion Selective Electrodes Based on Urea Derivative as an Ionophore. Bull. Korean Chem. Soc. 2006, 27, 1985−1988. (33) Lizondo-Sabater, J.; Martínez-Máñez, R.; Sancenón, F.; Seguí, M.-J.; Soto, J. Cobalt(II) and Nickel(II) Complexes of a Cyclam Derivative as Carriers in Iodide-Selective Electrodes. Anal. Chim. Acta 2002, 459, 229−234. (34) Rastegarzadeh, S.; Pourreza, N.; Saeedi, I. An Optical Redox Chemical Sensor for Determination of Iodide. Talanta 2009, 77, 1032−1036. (35) Nakayama, M.; Sato, A. Effective and Selective Sorption of Iodide by Thin Film of Multilayered MnO2 Intercalated with Cationic Surfactants. Anal. Sci. 2013, 29, 1017−1020. (36) Behnsen, J.; Riebe, B. Anion Selectivity of Organobentonites. Appl. Geochem. 2008, 23, 2746−2752. (37) Marcus, Y. Thermodynamics of Solvation of Ions. Part 5. Gibbs Free Energy of Hydration at 298.15 K. J. Chem. Soc., Faraday Trans. 1991, 87, 2995−2999. (38) Nakayama, M.; Sato, A.; Nakagawa, K. Selective Sorption of Iodide onto Organo-MnO2 Film and Its Electrochemical Desorption and Detection. Anal. Chim. Acta 2015, 877, 64−70. (39) De Guzman, R. N.; Awaluddin, A.; Shen, Y.-F.; Tian, Z. R.; Suib, S. L.; Ching, S.; O’Young, C.-L. Electrical Resistivity Measurements on Manganese Oxides with Layer and Tunnel Structures: Birnessites, Todorokites, and Cryptomelanes. Chem. Mater. 1995, 7, 1286−1292. (40) Wei, W.; Cui, X.; Chen, W.; Ivey, D. G. Manganese Oxide-Based Materials as Electrochemical Supercapacitr Electrodes. Chem. Soc. Rev. 2011, 40, 1697−1721. (41) Sharma, P. K.; Moore, G. J.; Zhang, F.; Zavalij, P.; Whittingham, M. S. Electrical Properties of the Layered Manganese Dioxides MxMn1−yCoyO2, M = Na, K. Electrochem. Solid-State Lett. 1999, 2, 494−496. (42) Bard, A. J.; Faulkner, L. R. Kinetics of Electrode Reactions. Electrochemical Methods: Fundamentals and Applications, 2nd ed.; Harris, D., Swain, E., Aiello, E., Eds.; John Wiley & Sons: New York, 2001; Chapter 3, pp 87−136. (43) Nakayama, M.; Suzuki, K.; Okamura, K.; Inoue, R.; Athouël, L.; Crosnier, O.; Brousse, T. Doping of Cobalt into Multilayered Manganese Oxide for Improved Pseudocapacitive Properties. J. Electrochem. Soc. 2010, 157, A1067−A1072. (44) Wang, L.; Omomo, Y.; Sakai, N.; Fukuda, K.; Nakai, I.; Ebina, Y.; Takada, K.; Watanabe, M.; Sasaki, T. Fabrication and Characterization of Multilayer Ultrathin Films of Exfoliated MnO2 Nanosheets and Polycations. Chem. Mater. 2003, 15, 2873−2878. (45) He, T.; Chen, D.; Jiao, X.; Wang, Y.; Duan, Y. SolubilityControlled Synthesis of High-Quality Co3O4 Nanocrystals. Chem. Mater. 2005, 17, 4023−4030. (46) Post, J. E.; Veblen, D. R. Crystal Structure Determinations of Synthetic Sodium, Magnesium, and Potassium Birnessite Using TEM and the Rietveld Method. Am. Mineral. 1990, 75, 477−489. (47) Wallin, T.; Linse, P. Monte Carlo Simulations of Polyelectrolytes at Charged Micelles. 3. Effects of Surfactant Tail Length. J. Phys. Chem. B 1997, 101, 5506−5513. (48) Toupin, M.; Brousse, T.; Belanger, D. Influence of Microstucture on the Charge Storage Properties of Chemically Synthesized Manganese Dioxide. Chem. Mater. 2002, 14, 3946−3952. (49) Beyreuther, E.; Grafström, S.; Eng, L. M.; Thiele, C.; Dörr, K. XPS Investigation of Mn Valence in Lanthanum Manganite Thin Films Under Variation of Oxygen Content. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 73, 155425−155433. (50) Chen, Y.; Zhao, S.; Liu, Z. Influence of the Synergistic Effect Between Co−N−C and Ceria on the Catalytic Performance for Selective Oxidation of Ethylbenzene. Phys. Chem. Chem. Phys. 2015, 17, 14012−14020. (51) Wang, Y.; Wang, L.; Wang, B.; Miao, Q.; Yuan, Y.; Yang, Z.; Fei, W. Electrodeposited Nickel Cobalt Sulfide Nanosheet Arrays on 3DG
DOI: 10.1021/acs.langmuir.7b00419 Langmuir XXXX, XXX, XXX−XXX
