JP5028612B2 - Method for producing viologen nano / microwire and viologen nano / microwire - Google Patents

Description

  The present invention relates to a method for producing a viologen nano / microwire and a viologen nano / microwire.

  Viologen is a general term for 4,4'-bipyridyl salts and is one of the most prominent chemical species capable of redox. The viologen is reversibly subjected to one-electron reduction and two-electron reduction, and the one-electron reduced form becomes a color former (typically blue or purple) having a large molecular extinction coefficient. The former property is used in electron accepting reagents for various chemical reactions (for example, see Non-Patent Document 1 below), and numerous examples of research are reported every year. On the other hand, the latter has recently been used as an electrochromic display (for example, Non-Patent Documents 2 to 4).

G. J. et al. By Kavamos, edited by Hiroshi Kobayashi, photoelectron transfer, Maruzen, 1997 R. Cinnsealach, G.M. Boschloo, S.M. N. Rao, D.D. Fitzmaurice, Solar Energy Materials & Solar Cells, 57, 107-125, 1999 D. Cummins, G.M. Boshloo, M .; Ryan, D.C. Corr, S .; N. Rao, D.D. Fitzmaurice, Journal of Physical Chemistry B, 104, 11449-11459, 2000 H. Pettersson, T.W. Gruszecki, L.M. -H. Johansson, M.C. O. M.M. Edwards, A.D. Hagfeldt, T .; Matuszczyk, Displays, 25, 223-230, 2004

  The reports on the viologen compounds described in Non-Patent Documents 1 to 4 are all about the use of viologen having a molecular form, and the form of viologen nano / microwire is controlled at the nano level / micro level. It is not a report on usage. Moreover, there is no example in which a form such as viologen nano / microwire has been produced. If a viologen nano / microwire is realized, the chemical reaction field can be limited to a one-dimensional fine wire, for example, for use with an electron-accepting reagent. Applications to systems or microreactors (MEMS) (an application of Micro Electro Mechanical Systems) are opened. A wire that is a nano- or micro-sized reaction field forms a special chemical reaction field, so the reaction rate and products are very different from those of conventional reaction fields. Pioneering and efficient reaction are expected. On the other hand, when used for an electrochromic display, the nano / microwire color develops from colorless to blue (or purple), so that it is possible to form an ultra-high-definition electrochromic display composed of very small pixels. Considering that the size of one pixel of a conventional display is about 100 micrometers, the ultra-high definition of the new display having a pixel size of several micrometers to several tens of nanometers is obvious.

  In view of the above problems, an object of the present invention is to provide a novel viologen compound and a method for producing a viologen nano-microwire that is the novel viologen compound.

  In the method for producing a viologen nano / microwire according to one means for solving the above-mentioned problem, a viologen film is formed, and a negative potential is applied to the film.

  In this means, although not limited, as a method for forming a viologen film, any of a micelle electrolysis method, a vacuum deposition method, and a method of forming a film by complexing Nafion and viologen containing a negative ion site. Among these, the micelle electrolysis method is more preferable.

  In this specification, the “micellar electrolysis method” means that a water-insoluble substance (hereinafter referred to as “water-insoluble substance”) is dispersed in a solution containing a surfactant and a supporting electrolyte, and then the surfactant is electrode oxidized. This means a method of forming a film of a water-insoluble substance on the electrode substrate. The surfactant is not limited to this, but is particularly preferably a surfactant having ferrocene.

  Moreover, in this means, although not limited, it is preferable that the negative potential is performed by a potential sweep process or a constant potential application process. In the case of the potential sweep process, although not limited, when an Ag / AgCl reference electrode is used, the electrolytic potential is preferably −1.50 V or more and lower than 0 V with respect to the reference electrode. The speed of the sweep is not limited, but is preferably in the range of 1 mV / s to 1000 mV / s. In the case of the constant potential application treatment, although not limited, when an Ag / AgCl reference electrode is used, the electrolytic potential is preferably -1.50 V or higher and lower than 0 V with respect to the reference electrode. The potential application time is preferably in the range of 1 second to 1 hour.

  Moreover, in this means, although it is not necessarily limited, it is preferable that a negative electric potential is below the electric potential at which a viologen is reduced by one electron.

  Moreover, in this means, although it does not necessarily limit, it is preferable that the negative electric potential applied exists in the range of -1.50V or more and less than 0V.

  Moreover, the other means for solving the said subject is a viologen nanomicrowire. Here, “viologen nano / microwire” is a micro- or nano-sized rod-like / string-like or beard-like microstructure, and is a quasi-one-dimensional structure realized by regular arrangement of viologen molecules. This refers to a structure, including a hollow tube structure.

  As described above, a viologen nano-microwire that has not been prepared in the past can be manufactured. The viologen nano / microwire obtained by the present invention has not been reported so far, and can be expected to be the beginning of the development of a nano / micro size electron transfer chemical reaction system and the development of a new ultra high definition display.

  Hereinafter, embodiments of the present invention will be described in detail. Note that the present invention can be implemented in many different forms, and is not limited to the following embodiments and examples.

  The viologen nano / microwire manufacturing method of the present embodiment is characterized in that a viologen film is formed, and a potential sweep process or a constant potential electrolytic process is performed on the viologen film.

  The step of forming a viologen film can be produced by various methods, and is not limited, but a method obtained by a micellar electrolysis method is preferable. In particular, the micellar electrolysis method can be performed at room temperature and normal pressure, and can be more suitably used for a viologen compound that is unstable to heat.

  The micelle electrolysis method is a technique in which a water-insoluble substance is dispersed in a solution containing a surfactant and a supporting electrolyte, and this solution is electrolyzed using an electrode to form a film of the water-insoluble substance on the electrode. . Although it does not necessarily limit as a micelle decomposition method, For example, (1) K. Hoshino, T .; Saji, Journal of The American Chemical Society, 109, 5881-5883, 1987, (2) K. et al. Hoshino, T .; Saji, Chemistry Letters, pages 1439-1442, 1987, (3) K. et al. Hoshino, M .; Goto, T .; Saji, Chemistry Letters, 547-550, 1988, (4) T. et al. Saji, K .; Hoshino, Y .; Ishii, M .; The method described in Goto, Journal of The American Chemical Society, 113, 450-456, 1991 can be employed.

  In the micellar electrolysis method, when the surfactant is dissolved in water, about 100 molecules of the surfactant are associated to form a spherical molecular aggregate called a micelle. When viologen is added to this solution and subjected to dispersion treatment, viologen molecules are solubilized in the micelles. When a potential at which the surfactant is oxidized is applied to the electrode, the surfactant is ionized and the hydrophilicity increases, so that the micelle no longer forms and the micelle is cleaved. Then, the solubilized viologen molecule is released from the micelle. However, since the viologen molecule is insoluble in water, it is deposited on the electrode substrate to form a film.

  The surfactant used in the micelle electrolysis method is not particularly limited, but is particularly preferably a surfactant containing ferrocene, and for example, polyoxyethylene glycol, alkylammonium salt or pyridinium salt containing ferrocene is preferred. The higher the concentration of the surfactant, the larger the amount of solubilization of the water-insoluble substance, so that it is high for forming a film of the water-insoluble substance in a short period of electrolysis (at a realistic rate). It is desirable. However, if the concentration of the surfactant is too high, the solution viscosity increases and the rate of electrolytic deposition decreases, so the practical upper limit of the surfactant concentration is preferably about 1M.

  The supporting electrolyte is an essential component in the electrolysis, and is preferably a cation or anion that is sufficiently dissolved in water and difficult to electrolyze, and is not limited. It is preferable to use at least one of a salt, a sodium salt, a potassium salt, and a calcium salt. When attention is paid to the anion, for example, at least one of a halide, a sulfate, a nitrate, or a phosphate is preferably used. In the case of lithium salt and sodium salt, perchlorate is also preferable. The concentration of the supporting electrolyte is not limited, but is preferably 0.001 M or more and solubility or less, and more preferably 0.01 M or more and 1 M or less.

  As a solvent used in the micellar electrolysis method, it is convenient and highly preferable to contain water, but other organic solvents that are compatible with water (for example, ethanol, methanol, acetonitrile, γ-butyrolactone, N-methylpyrrolidinone). Mixed solvents are also preferred.

The water-insoluble substance used in the present embodiment is a viologen, and the viologen is not particularly limited except that it is hardly soluble in water, and a commercially available one can also be used. The general formula (1) of viologen is described below. In general formula (1), R _{1 to} R ₁₀ may be the same as or different from each other, and represent a hydrogen atom or a substituent. Further, they may be connected to each other to form a ring.

  The dispersion amount (solubilization amount) of the viologen used in the micellar electrolysis method can be increased in proportion to the concentration of the surfactant having ferrocene used in the micelle electrolysis method. Although not limited, if the realistic upper limit of the surfactant concentration is about 1M as described above, the viologen dispersion amount (solubilization amount) is about 75 mM.

  As an electrolytic cell for the micelle electrolysis method, a three-electrode cell using three electrodes, that is, a working electrode for film formation, a counter electrode facing the working electrode, and a reference electrode serving as a potential reference, or a working electrode A two-electrode cell using only the counter electrode can be used. Note that a three-electrode cell in which the potential of the working electrode can be strictly defined with respect to a reference electrode serving as a reference is more preferable in that a viologen film can be manufactured with good reproducibility.

  The working electrode may be any material that is stable against electrode oxidation in any of the three-electrode type electrolytic cell and the two-electrode type cell. For example, indium tin oxide (hereinafter referred to as “ITO”) is not limited. And a transparent glass electrode, a platinum electrode, a gold electrode, and a glassy carbon electrode coated with tin oxide can be suitably used. Further, as the counter electrode, in addition to these electrode materials, a metal electrode such as stainless steel or a copper plate can be suitably used. The reference electrode is not limited, but for example, a silver / silver chloride electrode (Ag / AgCl electrode) or a saturated calomel electrode can be preferably used.

  When a viologen film is formed using a three-electrode electrolytic cell, the potential applied to the working electrode is not limited. For example, when a silver / silver chloride electrode (Ag / AgCl electrode) is used as the reference electrode , + 0.1V or more and + 1.5V or less is preferable, and + 0.28V or more and + 1V or less is more preferable. If it is +0.1 V or more, the oxidation of the surfactant can be sufficiently advanced, and if it is +0.28 V or more, this becomes more remarkable. Moreover, by making it + 1.5V or less, the electrolytic reaction of water can be prevented and the efficiency of film formation can be maintained favorably, and by making it + 1V or less, this effect becomes more remarkable.

  When a viologen film is formed using a two-electrode electrolytic cell, the potential applied to the working electrode is not limited, but may be in the range of +0.4 V to +3 V with respect to the counter electrode, for example. Preferably, it is in the range of + 0.5V or more and + 1V or less. By setting it to +0.4 V or more, the oxidation of the surfactant can be sufficiently advanced, and at +0.5 V or more, this effect becomes more remarkable. Moreover, the electrolytic reaction of water can be prevented by setting it to +3 V or less, and the efficiency of film formation can be maintained favorably, and this effect becomes more remarkable at +1 V or less.

  The time for electrolysis in the micellar electrolysis method (deposition time for the viologen film) is not limited as long as the viologen film can be deposited, but it is 1 minute or more and 5 hours or less within the range of the applied voltage. It is preferably performed within the range, and more preferably within the range of 10 minutes to 2 hours.

  The electrolysis temperature is not limited as long as the viologen film can be deposited, but is preferably in the range of 0 ° C. or more and 60 ° C. or less.

  Moreover, since this electrolysis is performed at a very low potential, it can be performed in the atmosphere. From the viewpoint of avoiding the possibility of contaminating the formed film, such as oxidation of impurities in the electrolytic solution, it is preferable to carry out in a nitrogen gas or argon gas atmosphere, but there is almost no fear of contamination.

  When forming a viologen film in the micellar electrolysis method, if there is a large amount of oxygen in the solution, the electrode reaction may be affected. Therefore, bubbling with an inert gas (nitrogen gas or argon gas) may be performed. Useful.

  Moreover, the process of forming the viologen film | membrane which concerns on this embodiment can also mention the method of forming into a film by compounding Nafion and a viologen containing a negative ion site | part other than a micelle electrolysis method, for example.

  The method by the vacuum deposition method is not limited, but for example, “Aki Yasuda and Jun'etu Seto, Electrochemical properties of Vvacum-evaporated organic thin film Part3. of Electroanalytical Chemistry, 283, 197-204, 1990 ”.

  In addition, a method for forming a film by forming a complex of Nafion containing a negative ion site and viologen and forming a film is not limited. , Siqing Xia, Janfu Zhao, Development of a conductive metricate biosensor based on Methylviogen / Nafion composite film, 201

Moreover, the manufacturing method of the viologen nano microwire which concerns on this embodiment can convert into the nanomicrowire structure by applying a negative electric potential with respect to the produced viologen film | membrane. This negative potential varies depending on the type of viologen, but when the viologen represented by the general formula (1) is V ²⁺ , a one-electron reduction reaction represented by V ²⁺ + e → V ⁺ occurs. The potential is preferably equal to or lower than the electric potential. Specifically, it is preferably −1.50 V or higher and lower than 0 V. A method for applying a negative potential is not limited, but a potential sweep process or a constant potential application process is preferable.

  The potential sweep process is a process in which a pair of electrodes is immersed in a solution containing the supporting electrolyte and applied while changing the potential at a constant rate. The constant potential application process is a pair of electrodes in the solution containing the supporting electrolyte. Is applied, and a constant potential is applied for a certain period of time.

  As for the supporting electrolyte and the solvent contained in the solution used in the potential sweep process and the constant potential application process, the same ones as in the above micelle electrolysis method can be adopted, and the same applies in the electrolytic cell used. Further, the same applies to the electrodes, except that one having a viologen film formed thereon is used. However, the solution for the potential sweep process and the constant potential application process needs to be a solution containing water and a solvent compatible with water. Although this ratio is not limited, the volume ratio is preferably in the range of 1: 9 to 9: 1, more preferably in the range of 1: 5 to 5: 1.

  In addition, when the micelle electrolysis method is used as the step of forming the viologen film, the system used in the micelle electrolysis method can be used as it is for the potential sweep process or the constant potential application process, but another solution is prepared and used. It is also more preferable. In the potential sweep process and the constant potential application process, it is necessary to be a solution containing water and a solvent compatible with water, but in the micellar electrolysis method, it is preferable to use only water as a solvent. .

  As described above, the viologen nano / microwire manufactured for the first time by this method has a controlled structure, in other words, the direction of electron transfer is limited to one dimension. For example, a microreactor or a microchemical analysis system (MEMS) Can be deployed. In addition, since the color change in the nano-micro area can be controlled by oxidation-reduction reaction, it can be used as an ultra-fine electrochromic display.

  Using the method for producing a viologen nano / microwire according to the above embodiment, a viologen nano / microwire was actually produced, and the effect of the present invention was confirmed. This will be described below.

Example 1
In this example, a viologen derivative film was formed by a micellar electrolysis method, and a viologen nano-microwire was produced by applying a potential sweep process to the viologen derivative film.

(Determination of composition of viologen dispersion)
First, a highly hydrophobic 1,1′-didododecyl 4,4′-bipyridinium dibromide (hereinafter referred to as “didiamide”) by the method described in “K. Hoshino, T. Saji, Chemistry Letters, pages 1439-1442, 1987”. It was called “dodecyl viologen” and abbreviated as “DDV ²⁺ ”). DDV ²⁺ was synthesized by charging and dissolving 4,4′-bipyridine and didodecyl bromide in a 1: 3.5 molar ratio in a dimethylformamide solvent and refluxing for 6.5 hours. After completion of the reaction, the reaction mixture was cooled to room temperature, filtered, and the residue was washed with acetone to obtain DDV 2 ⁺ · 2Br ⁻ . The yield was 91%.

Next, the above-mentioned DDV ²⁺ is 10 mM, a commercially available nonionic type surfactant having ferrocene (ferrocenylundecyl polyethylene glycol, hereinafter abbreviated as “FPEG”) is 2 mM, and LiBr is 0.1 M as a supporting electrolyte. Then, the mixture was poured into water and stirred with a stirrer for 10 minutes, and then dispersed with a ball mill (ball mill disperser model: Planetary micromill pulse verifye 7 manufactured by Fritsch) to obtain a dispersion. The obtained dispersion is allowed to stand for 24 hours in the dark at room temperature, and the secondary coarse particles of the viologen compound that cannot be dispersed are settled and separated, and 20 ml of the supernatant is taken out from the heat-resistant glass. It was put into the main room of a two-room type electrolysis cell (the two rooms were divided into a main room and a sub-chamber, which were separated by sintered glass). Then, a glass electrode coated with 170 nm of ITO film and a platinum plate electrode were immersed in this main chamber. On the other hand, the above supernatant liquid was also placed in the sub chamber, and a silver / silver chloride reference electrode (Ag / AgCl electrode) was further immersed therein.

  Thereafter, an Ag / AgCl electrode is used as a reference electrode and connected to an electrolysis power source (potentiostat model 750A manufactured by ALS). The potential was swept in s), and the composition of the dispersion was determined from the value of the electrolysis current that flowed. In addition, since the electrolysis current of oxygen dissolved in the electrolyte flows when the potential is swept in the negative direction, nitrogen gas is bubbled for 30 minutes before electrolysis in this example to remove dissolved oxygen, and measurement A nitrogen atmosphere was maintained by flowing nitrogen gas over the aqueous solution.

FIG. 1 shows a current-potential characteristic (cyclic voltammogram) obtained by the above-described potential sweep experiment (this experimental method is called cyclic voltammetry). The positive oxidation current seen in the vicinity of +0.5 V is the oxidation current of FPEG (FPEG → FPEG ⁺ + e), and the negative current seen in the vicinity of +0.2 V is the reduction current of the FPEG oxidant (FPEG ⁺ ) generated by the above oxidation. ^{(FPEG + + e → FPEG)} , - 0.4V negative current seen in the vicinity of the ^{DDV 2+} of reduction current ^{(DDV 2+ + e → DDV +} ), and positive current seen -0.3V vicinity, the reduction The oxidation current (DDV ⁺ → DDV ²⁺ + e) of DDV ⁺ generated by the above is shown. Note that FPEG exists in the form of micelles associated with about 100 molecules, and some DDV ²⁺ is solubilized in the micelles.

Further, when the current value is analyzed in detail using the method described in “Masawa Watanabe, Seiichiro Nakabayashi, Electron Transfer Chemistry, Asakura Shoten, pp. 166-171, 1996”, the solubilization amount of DDV ²⁺ is calculated. The value was determined to be about 150 μM. This shows that, on average, about 5 DDV ²⁺ molecules are solubilized in one micelle made by FPEG.

The method for determining the solubilized amount will be described in detail. Cyclic peak current i _p observed in voltammetry (the n = 1 the electron is not only one involved both in the case of the above reaction) molecules interact number of electrons n that when the redox , Electrode area S (geometric area where the electrode is in contact with the solution), diffusion coefficient D of the material to be oxidized / reduced, concentration C of the material to be oxidized / reduced, and potential sweep rate v Is done.

Therefore, the _{i p} was measured by changing the sweep speed v, a straight line passing through the origin is obtained by plotting the _{i p} against ^{v 1/2.} If the values of S and C are known, D can be calculated from the slope of the straight line. Further, when the values of S and D are known, the value of C can be calculated.

Here, attention is focused on the positive oxidation peak current (FPEG oxidation current: FPEG → FPEG ⁺ + e) seen in the vicinity of + 0.5V. This current is a current that flows when FPEG micelles having some solubilized DDV ²⁺ diffuse toward the electrode and oxidize FPEG when reaching the vicinity of the electrode (DDV ²⁺ does not participate in the reaction). When this oxidation peak current was measured while changing the sweep rate v and the oxidation peak current was plotted against v1 ^{/ 2} , a linear relationship passing through the origin was obtained, and the slope of the straight line was 2.6 × 10 ^−4. A value of AV ^−1/2 sec ^1/2 (Amper Volts− ¹ / ² · sec ^1/2 ) was obtained. Since the feed concentration of FPEG is 2 × 10 ⁻³ mol / l and S is 1.0 cm ² , a value of 2.3 × 10 ⁻⁷ cm ² sec ⁻¹ is obtained as the diffusion coefficient D of FPEG micelles.

Next, attention is paid to a negative reduction peak current (DDV ²⁺ reduction current: DDV ²⁺ + e → DDV ⁺ ) seen in the vicinity of −0.4V. This current is a current that flows when DDV ²⁺ is reduced when some FPEG micelles solubilized in DDV ²⁺ diffuse toward the electrode and reach the vicinity of the electrode (FPEG does not participate in the reaction). When this reduction peak current was measured while changing the sweep rate v and the oxidation peak current was plotted against v1 ^{/ 2} , a linear relationship passing through the origin was obtained, and the slope of the straight line was 2.0 × 10 ^{− A value of 5} AV ^−1/2 sec ^1/2 (Amper Volts− ¹ / ² · sec ^1/2 ) was obtained. Since the diffusion coefficient is equal to the value 2.3 × 10 ⁻⁷ cm ² sec ⁻¹ obtained above and S is 1.0 cm ² , the solubilization amount C of DDV ²⁺ is 1.5 × 10 ⁻⁴ mol / A value of l (150 μM) is obtained.

(Production of viologen membrane by micellar electrolysis)
Next, the potential was fixed at +0.5 V, which is the potential at which FPEG is oxidized, the dispersion was subjected to constant potential electrolytic oxidation, and a viologen film was formed on the ITO electrode using the principle of micelle electrolysis. The experimental system and dispersion were the same as above. However, since no negative potential was applied in this step, bubbling was not performed because the electrolytic atmosphere does not necessarily have to be a nitrogen gas atmosphere. The electrolysis time was 30 minutes.

As a result of this constant potential electrolytic oxidation, a colorless and transparent film was formed on the glass electrode on which the ITO film was formed. The glass electrode on which the colorless transparent film was formed was washed with distilled water and deionized pure water, and observed with a scanning microscope (SEM, ABT-32 manufactured by Topcon Corporation). FIG. 2 shows a photograph of the colorless transparent film obtained here, and FIG. 3 shows a scanning electron micrograph (SEM image) of the film (the length of the bar below the photograph indicates a scale of 20 μm). FIG. 2 shows that the DDV ²⁺ film is colorless and transparent. Further, the SEM image of FIG. 3 includes an image of a part where the end of the film is peeled off. From this part, it can be seen that the form of the continuous film is surely maintained. Furthermore, the membrane was dissolved in methanol, and its ultraviolet-visible absorption spectrum was measured to confirm that the constituent molecule of the membrane was DDV ²⁺ . In addition, when the amount of DDV 2 ⁺ · Br ⁻ deposited per unit area is calculated from the ultraviolet-visible absorption spectrum, it is 6.3 nmol / cm ² , which is 41 nm when converted to a film thickness.

(Formation of viologen nano / micro wires)
Next, a potential sweep process was performed on the DDV ²⁺ film obtained here to form viologen nano-microwires. As the electrolyte solution used for the potential sweep process, a solution in which 0.1 M lithium perchlorate (LiClO ₄ ) was dissolved as a supporting electrolyte in a mixed solvent in which acetonitrile and water were mixed at a volume ratio of 1: 4 was adopted. . Then, the electrolytic solution was put into a main chamber of a two-room type electrolytic cell made of heat-resistant glass. Then, an ITO electrode on which a viologen film is formed and a platinum plate electrode are immersed in this main chamber, the above aqueous solution is also placed in the sub chamber, and a silver / silver chloride reference electrode (Ag / AgCl electrode) is further immersed. .

  Thereafter, an Ag / AgCl electrode is used as a reference electrode and connected to an electrolysis power source (potentiostat model 750A manufactured by ALS), and a constant speed (20 mV / s) in a potential range of 0 V to -1.0 V with respect to the reference electrode. The potential was swept with. The number of potential sweeps was 10.

FIG. 4 shows current-potential characteristics (cyclic voltammograms) obtained by the above-described potential processing. One-electron reduction of ^{DDV 2+} around ^{-0.6V (DDV 2+ + e → DDV} +) showed a reduction wave due to, the current value is gradually decreased. In addition, it is involved in the one-electron reduction reaction by the potential treatment of the first sweep by handling according to “Akira Fujishima, Masuo Aizawa, Toru Inoue, Electrochemical Measurement Method (bottom), Gihodo Publishing, pp. 442-444, 1984”. was calculated the ratio of DDV ^2+, among ^{DDV 2+} constituting the membrane, ^{DDV 2+} molecules of about 50% was found to be involved in the reduction reaction.

A method for calculating the ratio of DDV ²⁺ involved in the one-electron reduction reaction will be described in detail. In the adsorbed species of the cyclic voltammetry adsorbed on the electrode, the observed peak current i _p is the case molecule of reducing the number of electrons n (DDV ²⁺ exchanging when redox electrons have only one involved N = 1), electrode area S (geometric area where the electrode is in contact with the solution), supported amount Γ (mol / cm ² ) of what is oxidized / reduced, Faraday constant F, gas constant R, The measurement temperature T and the potential sweep rate v are used to express the following equation.
Therefore, if the value of Γ is known, it is possible to calculate the current i _p flowing at a constant sweep rate v. As described above, the value of Γ in ^{DDV 2+} film used in the experiment is ^{6.3 × 10 -9 mol / cm 2} , also, since it is v = 0.020V / sec, 120μA as the value of _{i p} Is obtained. However in practice the current value observed in the vicinity of -0.6V of the first sweep since it is about 60 .mu.A (see FIG. 4), among the ^{DDV 2+} constituting the membrane, the reduction ^{DDV 2+} molecules of about 50% It turns out to be involved in the reaction.

  After this potential sweep, the ITO electrode on which the viologen film was formed was taken out of the electrolytic solution, washed with a mixed solvent of acetonitrile and water, and then subjected to SEM observation. FIG. 5 shows a structure formed by the potential sweep process. A number of microwire-like structures were formed on the ITO surface. In addition, there was a nano-sized diameter (FIG. 6). Moreover, the cross-sectional shape of the wire was observed by SEM observation from an oblique direction. As a result, it was found that the cross section had a hexagonal shape (FIG. 7) and a rectangular shape (FIG. 8). Furthermore, when a partially broken wire structure was searched and the cross-sectional structure was observed, a wire suggesting a hollow tube-like structure was also observed (FIG. 9).

Moreover, since the above structure is dissolved in methanol similarly to the DDV ²⁺ membrane, the ultraviolet-visible absorption spectrum of the methanol-dissolved solution was measured. And it confirmed that the structure consisted of DDV2 ⁺ .

As described above, according to the present embodiment, a DDV ²⁺ film is deposited by micellar electrolysis, and a potential sweep process is performed on the DDV ²⁺ film to thereby form a nano / micro wire (including a nano / micro tube) made of DDV ^2+. The structure could be obtained.

(Comparative Example 1: Potential sweep process in water)
The present comparative example was different from the mixed solvent consisting of acetonitrile and water in that a potential sweep process was performed in water, but the rest was performed in the same manner as in Example 1.

First, an aqueous solution in which 0.1 M of lithium perchlorate was dissolved was prepared as an aqueous solution, and each was put into a main chamber and a sub chamber of a two-room type electrolytic cell made of heat-resistant glass. And the ITO glass electrode in which the DDV2 ⁺ film | membrane formed using the process similar to Example 1 was formed was immersed with the platinum plate electrode in the main chamber. An Ag / AgCl electrode was immersed in the sub chamber. The ITO glass electrode is the working electrode, the platinum plate electrode is the counter electrode, and the Ag / AgCl electrode is the reference electrode. The potential is applied at a constant speed (20 mV / s) in the potential range of 0 V to -1.0 V with respect to the reference electrode. Swept. The number of potential sweeps was 10.

As a result, almost no electric current flows (the electric current hardly flows because the hydrophobicity of the membrane is high and the affinity with the water electrolyte solution is extremely low), and the DDV ²⁺ membrane partially peels due to the high surface tension of water. It has been confirmed that.

(Comparative Example 2: Potential sweep process in acetonitrile)
In this comparative example, the potential sweep process was performed in acetonitrile instead of the mixed solvent composed of acetonitrile and water, but the other methods were performed in the same manner as in Example 1.

First, an acetonitrile solution in which 0.1 M of lithium perchlorate was dissolved was prepared and placed in a main chamber and a sub chamber of a two-room type electrolytic cell made of heat-resistant glass. And the ITO glass electrode in which the DDV2 ⁺ film | membrane formed using the process similar to Example 1 was formed was immersed with the platinum plate electrode in the main chamber. An Ag / AgCl electrode was immersed in the sub chamber. The ITO glass electrode is the working electrode, the platinum plate electrode is the counter electrode, the Ag / AgCl electrode is the reference electrode, and the potential is applied at a constant speed (20 mV / s) in the potential range of 0 V to -1.0 V with respect to the reference electrode. Swept. The number of potential sweeps was 10.

As a result, it was confirmed that the DDV ²⁺ membrane gradually eluted into the acetonitrile electrolyte during the potential sweep.

  As described above, according to this comparative example, in the method for obtaining viologen nano-microwires, it was confirmed that a solvent having an appropriate hydrophilicity-hydrophobicity balance with respect to the viologen compound was required as the solvent for the potential sweep treatment.

(Example 2)
This example is the same as Example 1, except that the deposition time of the DDV ²⁺ film by the micelle electrolysis method is set to 60 minutes. The film thickness of the DDV ²⁺ film obtained at that time is 74 nm. As a result, as in Example 1, it was confirmed that viologen nano-microwires (including a hollow tube structure) could be obtained.

(Example 3)
This example is the same as Example 1, except that the deposition time of the DDV ²⁺ film by the micelle electrolysis method is 90 minutes. The film thickness of the DDV ²⁺ film obtained at that time is 67 nm. The film thickness was reduced compared with the deposition time of 60 minutes because the longer the deposition time, the longer the time that the generated DDV ²⁺ film was exposed to the electrolytic solution, and the deposition of DDV ²⁺ in the electrolytic solution was increased. This is probably because the rate of dissolution of DDV ²⁺ in the film was superior. However, a DDV ²⁺ film was formed, and as a result, it was confirmed that viologen nano-microwires (including a hollow tube structure) could be obtained as in Example 1.

Example 4
This example is the same as Example 1, except that the deposition time of the DDV ²⁺ film by the micelle electrolysis method is 120 minutes. The film thickness of the DDV ²⁺ film obtained at that time is 65 nm. In this case as well, the film thickness was reduced as compared with the deposition time of 60 minutes. The reason is that the longer the deposition time, the longer the time that the generated DDV ²⁺ film is exposed to the electrolytic solution. This is presumably because the rate of dissolution of DDV ^{2+ in} the film was superior to the deposition of DDV ²⁺ in the liquid. However, a DDV ²⁺ film was formed, and as a result, it was confirmed that viologen nano-microwires (including a hollow tube structure) could be obtained as in Example 1.

  As mentioned above, the effect of the manufacturing method of the viologen nano micro wire which concerns on the said embodiment can be confirmed by Example 1 thru | or 4, As a more desirable electrolysis time in a micellar electrolysis method, about 60 minutes of potential sweep processing It was found that a solvent having an appropriate hydrophilic-hydrophobic balance suitable for a viologen compound is necessary as an electrolyte solution.

The viologen nano / microwire can be industrially used as a microchemical analysis system or a microreactor (an application form of MEMS (Micro Electro Mechanical Systems)) or an ultra-high-definition electrochromic display. Naturally, it can be used industrially.

2 is a current-potential characteristic (cyclic voltammogram) of the viologen dispersion in Example 1. FIG. 2 is a photograph (drawing substitute) of a viologen film obtained in Example 1. FIG. 2 is a SEM photograph (drawing substitute) of a viologen film obtained in Example 1. FIG. 2 is a current-potential characteristic (cyclic voltammogram) of the viologen film in Example 1. FIG. 2 is a SEM photograph (drawing substitute) of the viologen microwire obtained in Example 1. FIG. 2 is a SEM photograph (drawing substitute) of a viologen nanowire obtained in Example 1. FIG. 2 is a cross-sectional SEM photograph (drawing substitute) of a viologen microwire having a hexagonal column structure obtained in Example 1. FIG. 2 is a cross-sectional SEM photograph (drawing substitute) of a viologen microwire having a quadrangular prism structure obtained in Example 1. FIG. 2 is a cross-sectional SEM photograph (drawing substitute) of a viologen microtube having a hexagonal column structure obtained in Example 1. FIG.

Claims (5)

A viologen film represented by the following general formula (1) is formed on the electrode, and the pair of electrodes including the electrode includes a supporting electrolyte of 0.001M to 1M and has a volume ratio of 1: 9 to 9: 1. In the case where an Ag / AgCl reference electrode is used by immersing it in a solution containing water and a solvent compatible with water in a range, and performing a potential sweep process or a constant potential application process on the viologen film, A method for producing a viologen nano-microwire in which a negative potential of −1.50 V or higher and lower than 0 V is applied
  The method for producing a viologen nano-microwire according to claim 1, wherein the negative potential is equal to or lower than a potential at which the viologen is reduced by one electron.   The method for producing a viologen nano-microwire according to claim 1, wherein the viologen film is formed by any one of a micelle electrolysis method, a vacuum deposition method, and a method of forming a film of Nafion and a viologen containing a negative ion site. . The method for producing a viologen nano- microwire according to claim 1, wherein the viologen film is formed by a micelle electrolysis method. A viologen nano-microwire produced by the method according to claim 1 .