JP5399101B2 - Sample holding member - Google Patents

Description

The present invention relates to a sample holding member for holding a sample to be subjected to infrared spectroscopic analysis in a surface enhanced infrared absorption method .

  The total reflection measurement (ATR) method is widely known as one type of infrared spectroscopic analysis method capable of identifying an organic compound, for example. As shown in FIG. 15, a sample holding member 1 used in this ATR method has a prism 2 having a shape in which a cylindrical body is cut in half, and a metal thin film 3 formed on a flat surface of the prism 2. .

  The metal thin film 3 is made of, for example, a gold plating film or a silver deposition film having a thickness of 5 to 16 nm, and microscopically is an aggregate of things scattered in an island shape. That is, when the metal thin film 3 is observed with a scanning electron microscope (SEM), the flat surface of the prism 2 is not covered over the entire area, but a spot exposed in the form of dots is recognized.

  A solution in which a sample to be measured is dissolved is attached to the metal thin film 3. In this state, the infrared light IR emitted from the light source 4 enters the prism 2, and the infrared light IR is totally reflected at the interface of the metal thin film 3.

  On the other hand, some evanescent light is observed on the sample side. By measuring the reflection of the evanescent light, it is possible to obtain information on what structure the sample has and identify the sample.

  An ATR-SEIRA method combining an ATR method and a surface enhanced infrared absorption (SEIRA) method has also been proposed (see, for example, Patent Document 1). In this case, as shown in FIG. 16, the solution holding cell 5 is joined to the sample holding member 1. Further, a part of the Ag / AgCl reference electrode 6 is inserted into the solution holding cell 5, and the entire counter electrode 7 made of platinum is inserted. In this case, the metal thin film functions as a working electrode.

  In the ATR-SEIRA method, it is possible to examine the electrochemical change of the sample. That is, an electric potential is applied between the working electrode and the counter electrode, and the sample causes an electrochemical reaction in the solution holding cell 5 accordingly. While this electrochemical reaction is in progress, infrared light IR emitted from the light source 4 is incident on the prism 2, and the infrared light IR is totally reflected at the interface of the working electrode (metal thin film 3). The By detecting and measuring the infrared absorption spectrum of the total reflected light with the detector 8, so-called in-situ observation can be performed on the structural change of the sample accompanying the electrochemical reaction occurring on the working electrode (metal thin film 3). Done. According to Patent Document 2, the intensity of the infrared photoelectric field is amplified on the surface of the metal thin film (working electrode) as described above, and as a result, the infrared absorption is sufficiently performed. It can be acquired.

JP 2007-78487 A JP-A-4-105044

  In order to obtain more accurate information about the structure of the sample and what kind of electrochemical reaction is progressing, it is necessary to improve the sensitivity in the measurement as described above. As a measure for this, it is conceived to increase the surface area of the metal thin film (working electrode), that is, to fill the gaps between the island-spotted ones to form a layer.

  However, it is difficult to obtain a layer having a very small thickness of about 5 to 16 nm by any method such as plating or vapor deposition. As can be understood from this, in the surface-enhanced infrared absorption method, there is a problem that it is not easy to increase the surface area of the working electrode and thus improve the measurement sensitivity.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a sample holding member capable of improving the measurement sensitivity in the surface enhanced infrared absorption method.

In order to achieve the above object, the present invention provides a sample holding member for holding a sample to be measured by the surface-enhanced infrared absorption method,
A prism on which infrared light is incident;
A conductive polymer film formed on one end surface of the prism and having a reflecting surface for reflecting infrared light incident on the prism;
With
The conductive polymer film has open pores on the back surface of the reflective surface,
Holding the sample that has entered the open pores in the open pores ;
The conductivity of the conductive polymer constituting the conductive polymer film is in the range of 10 ⁻³ to 10 ⁴ S / cm, and interacts with the evanescent light that oozes out on the back surface side of the reflecting surface to generate an electromagnetic field. characterized in der Rukoto causing a.

  When a conductive polymer film having open pores, in other words, a conductive polymer film that is a porous body, a chemical species (sample) to be measured is adsorbed and held in the open pores. Since the substance having open pores has a large surface area, this conductive polymer film also has a large surface area. Therefore, a large amount of sample is held on the conductive polymer film. For this reason, since the sensitivity at the time of measuring with respect to this sample becomes large, identification etc. become easy.

A metal film may be interposed between the conductive polymer film and the prism. That is, the present invention is a sample holding member for holding a sample to be measured by the surface enhanced infrared absorption method,
A prism on which infrared light is incident;
A metal film formed on one end surface of the prism and having a reflection surface for reflecting infrared light incident on the prism;
A conductive polymer film formed on the back surface of the reflective surface of the metal film;
With
The conductive polymer film has open pores on the back surface of the end face facing the reflective surface of the metal film,
Holding the sample that has entered the open pores in the open pores ;
The conductivity of the conductive polymer constituting the conductive polymer film is in the range of 10 ⁻³ to 10 ⁴ S / cm, and interacts with the evanescent light that oozes out on the back surface side of the reflecting surface to generate an electromagnetic field. characterized in der Rukoto causing a.

  In this case as well, a large amount of the chemical species (sample) to be measured is adsorbed and held in the open pores of the conductive polymer film as described above. Therefore, the sensitivity when performing measurement on the sample can be improved.

The conductive polymer constituting the conductive polymer film preferably has a conductivity in the range of 10 ⁻³ to 10 ⁴ S / cm.

  Moreover, as a conductive polymer which comprises a conductive polymer film, what has at least any one of a radical cation or a dication in a polymer chain is suitable. In this case, if the measurement target (sample) is a negatively charged chemical species such as sulfate ion, nitrate ion, sulfonate ion, carboxylate ion, etc., the measurement target is efficiently conducted by electrostatic interaction of the conductive polymer. Can be attracted to the conductive polymer membrane. Eventually, the holding amount of the measurement object further increases. In addition, in this case, the conductivity of the conductive polymer is increased. For this reason, the sensitivity is further improved.

  Another preferred example of the conductive polymer constituting the conductive polymer film includes one having at least one substituent selected from the group of sulfonic acid group, carboxyl group, hydroxyl group and amino group. . Among these, a sulfonic acid group and a carboxyl group attract an ion (for example, amine) having a positive charge by electrostatic interaction. The amino group attracts negatively charged ions, and the amino group and the hydroxyl group form a complex with the metal ion through a coordination bond. For these reasons, it is possible to improve sensitivity when measuring various chemical species.

  In any case, a solution holding cell that holds the solution in which the sample is dissolved may be further provided so as to be connected to the prism so that the open end faces the one end surface of the prism. In this case, the sample may be dissolved in the solution accommodated in the solution holding cell, and this sample may enter the open pores of the conductive polymer film.

  According to the present invention, since the conductive polymer film that is a porous body is formed on the prism, the sample to be measured enters and is held in the open pores of the conductive polymer film. Since the porous body has a large surface area, a large amount of sample is held in the conductive polymer film. For this reason, the sensitivity at the time of performing infrared spectroscopic analysis can be improved.

  Therefore, for example, it is easy to obtain accurate information on the structure of the sample and to obtain accurate information about what reaction is proceeding.

It is a schematic block diagram of the infrared spectroscopy analyzer which comprises the sample holding member which concerns on 1st Embodiment. It is a principal part expanded view which shows typically the growth direction of the conductive polymer which comprises a conductive polymer film. FIG. 3 is a fragmentary enlarged view schematically showing a state in which a sample is adsorbed and held in open pores in the conductive polymer film of FIG. 2. It is a horizontal sectional view of the sample holding member concerning a 1st embodiment provided with a solution holding cell. It is a principal part cutting enlarged view which shows typically the growth direction of the conductive polymer in the sample holding member which concerns on 2nd Embodiment. FIG. 6 is a fragmentary enlarged view schematically showing a state in which a sample is adsorbed and held in open pores in the conductive polymer film of FIG. 5. It is horizontal direction sectional drawing of the sample holding member which concerns on 2nd Embodiment provided with the solution holding cell. 2 is a SEM photograph of a polyaniline thin film obtained by the operation of Example 1. FIG. From each of the infrared surface enhanced absorption spectrum of pure water and methanesulfonic acid solution after the formation of the thin film of polyaniline is a spectrum obtained by subtracting the respective infrared absorption spectra of pure water and methanesulfonic acid solution before formation. 3 is a SEM photograph of a thin film of polypyrrole obtained by the operation of Example 3. From the infrared surface enhanced absorption spectra of ethanol after formation of a thin film of polypyrrole is a spectrum obtained by subtracting the infrared absorption spectrum of the ethanol before forming. 4 is a SEM photograph of a polyaniline thin film obtained by the operation of Example 4. FIG. 4 is a SEM photograph of a polyaniline thin film obtained by the operation of Example 4. FIG. Obtained using a sample holding member in which a porous polyaniline thin film was formed on a metal thin film, a sample holding member in which only a metal thin film was formed, and a sample holding member in which a flat polyaniline thin film was formed on a metal thin film It is an infrared surface enhancement absorption spectrum of methanesulfonic acid aqueous solution. It is a schematic block diagram of the infrared spectroscopy analyzer which comprises the sample holding member which concerns on a prior art. It is horizontal direction sectional drawing of the sample holding member which concerns on the prior art provided with the solution holding cell.

  Hereinafter, preferred embodiments of the sample holding member according to the present invention will be described and described in detail with reference to the accompanying drawings. Components corresponding to those shown in FIGS. 15 and 16 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 1 shows a schematic configuration diagram of an infrared spectroscopic analyzer 12 including a sample holding member 10 according to the first embodiment. The sample holding member 10 is shown as a cross-sectional view in a direction orthogonal to the longitudinal direction.

  The sample holding member 10 includes a semi-cylindrical prism 2 and a conductive polymer film 14 formed on a flat surface of the prism 2.

The material of the prism 2 is silicon, germanium, zinc selenide, zinc sulfide, thallium bromoiodide, thallium bromochloride, calcium fluoride, lithium fluoride, magnesium fluoride, barium fluoride, sodium chloride, potassium bromide, Examples include potassium chloride, optical synthetic quartz (SiO ₂ ) glass, cesium iodide, LaSFN15, sapphire, SF59 and the like, and in particular, silicon, germanium, zinc selenide, zinc sulfide, thallium bromoiodide, thallium bromochloride Is excellent in moisture resistance and has a high refractive index and is suitable. 1 illustrates a semi-cylindrical prism 2, the shape of the prism may be a hemispherical shape, a triangular prism shape, or a trapezoidal shape. A prism having such a material and shape is readily available as a commercial product.

  On the other hand, as shown schematically in FIG. 2, the conductive polymer constituting the conductive polymer film 14 covers the flat surface of the prism 2 with a thickness of about 20 nm and then extends the flat surface of the prism 2. Growing so as to be continuous in a direction substantially orthogonal to the existing direction, the conductive polymer row 15 is formed. That is, the conductive polymer has anisotropy in the growth direction.

  For this reason, in the conductive polymer film 14, there are gaps (open pores 16) between the adjacent conductive polymer rows 15 and 15. As will be described later, a chemical species (sample S) to be measured is adsorbed and held in the open pores 16. Since the surface area of the conductive polymer film 14 is increased due to the presence of the open pores 16, the amount of the sample S held is increased. Therefore, the sensitivity when measuring the sample S is increased.

The conductive polymer is not particularly limited as long as it is a polymer exhibiting conductivity, but the conductivity is preferably in the range of 10 ⁻³ to 10 ⁴ S / cm. Preferable examples of such a conductive polymer include polyaniline, polypyrrole, poly (3,4-ethylenedioxythiophene), polyphenylene, polyphenylene vinylene and the like.

  In addition, the polymer chain preferably has at least one of a radical cation and a dication. Here, the radical cation means a state having one radical and one positive charge formed as a result of one electron being extracted from the polymer main chain. That is, it is a state indicated as “radical cation” in the following structural formulas (1) and (2).

  A dication is defined as a state in which radicals form a bond when two radical cations are bonded to each other, and two positive charges remain. That is, it is a state indicated as “diccation” in the above structural formulas (1) and (2).

  Thus, an electrostatic interaction occurs in the conductive polymer having a radical cation or a dication. For this reason, when the sample S is a chemical species having a negative charge such as sulfate ion, nitrate ion, sulfonate ion, or carboxylate ion, the sample S is efficiently attracted to the conductive polymer film 14. This, combined with the increase in the conductivity of the conductive polymer, improves the sensitivity.

  The conductive polymer has at least one substituent selected from the group consisting of a sulfonic acid group, a carboxyl group, a hydroxyl group, and an amino group, such as those represented by the following structural formulas (3) to (5) It may be.

The sulfonic acid group (—SO ₃ H) and the carboxyl group (—COOH) attract an ion having a positive charge, such as an amine, by electrostatic interaction. Conversely, an amino group (—NH ₂ ) can attract negatively charged ions. Furthermore, an amino group (—NH ₂ ) and a hydroxyl group (—OH) form a complex with a metal ion through a coordination bond. For these reasons, it is possible to improve sensitivity when measuring various chemical species.

  Such a conductive polymer film 14 can be formed as follows.

  First, a solution holding cell is connected to the flat surface of the prism 2, and a solution in which a monomer such as polyaniline, polypyrrole, poly (3,4-ethylenedioxythiophene), polyphenylene, or polyphenylene vinylene is dissolved is accommodated in the solution holding cell. To do. Next, a polymerization agent such as an oxidizing agent is added to this solution. As a result, the monomer undergoes chemical oxidative polymerization and grows as a conductive polymer, and as a result, a conductive polymer film 14 is formed.

  When the material of the conductive polymer film 14 is polyaniline, when the thickness of the conductive polymer film 14 is 20 nm or more, the portion exceeding 20 nm is substantially orthogonal to the extending direction of the flat surface of the prism 2. It grows so as to stretch in the direction.

  In order to obtain a conductive polymer having a radical cation or a dication in the polymer chain, a chemical oxidative polymerization or an electrochemical oxidative polymerization is performed by adding a dopant such as an aromatic sulfonic acid anion to the solution in which the monomer is dissolved. Can be advanced. In this oxidation reaction, one electron is extracted from the polymer chain, and as a result, the conductive polymer film 14 made of a conductive polymer having at least one of a radical cation and a dication in the polymer chain is obtained. It is formed.

  A suitable thickness of the conductive polymer film 14 configured as described above is about 1 nm to 5 μm. The thickness of the conductive polymer film 14 is defined as the distance from the flat surface of the prism 2 to the maximum growth end point of the conductive polymer, and is represented as T in FIG.

  The sample holding member 10 according to the first embodiment is basically configured as described above. Next, the function and effect will be described.

  When infrared spectroscopic analysis is performed using the sample holding member 10, the sample S is dissolved in a solvent to form a solution, and this solution is attached to the conductive polymer film 14. The solution, that is, the sample S is held by being adsorbed by the open pores 16 of the conductive polymer film 14. As described above, the open pores 16 exist in the conductive polymer film 14, and thus the surface area is large. Therefore, as shown in FIG. 3, the amount of the sample S held on the conductive polymer film 14 increases.

  Next, infrared light IR is emitted from the light source 4. As the infrared light IR reaches the interface between the prism 2 and the conductive polymer film 14, the evanescent light E oozes out to the conductive polymer film 14 side. An electromagnetic field is generated by the interaction between the evanescent light E and the conductive polymer, thereby improving the surface enhancement effect in infrared absorption. That is, the infrared absorption of the sample S can be detected with high sensitivity.

  In addition, in this case, since the amount of the sample S held on the conductive polymer film 14 is large, this also improves the sensitivity.

  Furthermore, when the conductive polymer constituting the conductive polymer film 14 has radical cations or dications, the sample S having a negative charge such as sulfate ion, nitrate ion, sulfonate ion, carboxylate ion or the like. Draws efficiently. When the conductive polymer has a sulfonic acid group and a carboxyl group, it attracts positively charged ions such as amine, and when it has an amino group, it attracts negatively charged ions. In addition to the above, when the conductive polymer has an amino group or a hydroxyl group, the conductive polymer forms a complex with a metal ion via a coordination bond. This pulling or formation of coordination bonds also improves the sensitivity during measurement.

As described above, according to the first embodiment, by forming the conductive polymer film 14 having the open pores 16 on the prism 2, the sensitivity when performing the infrared spectroscopic analysis in the surface-enhanced infrared absorption method is facilitated. Can be improved.

  In the above description, the case where the sample S is attached to the conductive polymer film 14 is exemplified. However, as shown in FIG. 4, the flat surface side of the prism 2 on which the conductive polymer film 14 is formed. The solution holding cell 5 may be provided, and the solution holding cell 5 may contain a solution in which the sample S is dissolved.

  Next, the sample holding member 22 according to the second embodiment will be described. The components shown in FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 5 is a schematic cross-sectional view of the sample holding member 22 according to the second embodiment. The sample holding member 22 is shown as a cross-sectional view in a direction orthogonal to the longitudinal direction.

  In the sample holding member 22, a metal thin film 26 is interposed between the flat surface of the prism 2 and the conductive polymer film 14. Suitable materials for the metal thin film 26 include platinum, gold, palladium, silver, copper, nickel, or two or more alloys selected from these. Gold, palladium or silver is preferably selected. In particular, platinum and gold are particularly suitable because they have excellent acid resistance and are stable during electrochemical measurement.

  The thickness of the metal thin film 26 is preferably set to 5 to 300 nm. If the thickness is excessively small, it is not easy to form an island structure, and if it is excessively large, the amount of transmitted infrared light IR decreases. A more preferable thickness of the metal thin film 26 is 10 to 30 nm.

  The sample holding member 22 can be produced by forming the metal thin film 26 on the flat surface of the prism 2 by electroless plating or vapor deposition, and then forming the conductive polymer film 14 in accordance with the above.

  Or, the metal thin film 26 may be used as a working electrode, and the electrochemical oxidative polymerization may proceed. In this case, a solution holding cell is connected to the flat surface of the prism 2 on which the metal thin film 26 is formed, and the counter electrode 7 and the Ag / AgCl reference electrode 6 are inserted into the solution holding cell. Next, after storing the solution in which the monomer is dissolved in the solution holding cell, an appropriate voltage is applied for a predetermined time according to the type of the monomer. By applying and holding this voltage, electrochemical oxidative polymerization starts and proceeds, the monomer changes to a conductive polymer, and the conductive polymer film 14 grows.

  Even when infrared spectroscopic analysis is performed using the sample holding member 22 according to the second embodiment, the sample S is adsorbed by the open pores 16 of the conductive polymer film 14 as shown in FIG. Retained. Of course, also in this case, since the surface area of the conductive polymer film 14 is large, the amount of the sample S held on the conductive polymer film 14 increases.

  Thereafter, in the same manner as described above, the infrared light IR emitted from the light source 4 reaches the interface between the prism 2 and the conductive polymer film 14, and the evanescent light oozed out to the conductive polymer film 14 side with this. An electromagnetic field is generated by the interaction between E and the conductive polymer. Thereby, the surface enhancement effect in infrared absorption is improved. That is, the infrared absorption of the sample S can be detected with high sensitivity. Of course, the sensitivity is also improved by increasing the amount of the sample S held on the conductive polymer film 14.

  Also in the second embodiment, as shown in FIG. 7, the solution holding cell 5 may be provided on the flat surface side of the prism 2 on which the conductive polymer film 14 is formed. Here, in order to observe the structural change of the sample S in situ, a part of the Ag / AgCl reference electrode 6 may be inserted into the solution holding cell 5 and the entire counter electrode 7 made of platinum may be inserted.

  In this configuration, the metal thin film 26 functions as a working electrode. That is, a potential is applied between the metal thin film 26 and the counter electrode 7. Along with this, the sample S dissolved in the solution in the solution holding cell 5 causes an electrochemical reaction.

While this electrochemical reaction proceeds, the infrared light IR emitted from the light source 4 is incident on the prism 2, and the infrared light IR is totally reflected at the interface of the working electrode (metal thin film 26). . By detecting and measuring the infrared surface-enhanced absorption spectrum of the total reflected light with the detector 8, in-situ observation can be performed on the structural change of the sample S accompanying the electrochemical reaction occurring on the working electrode. it can.

  An infrared absorption spectrum of a silicon prism having a semi-cylindrical shape (diameter 20 mm × height 25 mm) manufactured by Pier Optics was measured and used as a reference spectrum. Hereinafter, the reference spectrum is subtracted from the infrared absorption spectrum and the infrared surface enhanced absorption spectrum obtained using the sample.

  Next, a rectangular parallelepiped solution holding cell having a side of 20 mm and a height of 25 mm and having one side and one bottom as openings was provided on the flat surface of the silicon prism. 10 ml of pure water was accommodated in this solution holding cell, and the infrared absorption spectrum of pure water was measured.

  Meanwhile, 0.93 g of aniline monomer was dissolved in 50 ml of pure water to obtain an aniline monomer solution having a concentration of 0.2 mol / l. Further, 4.81 g of methanesulfonic acid was dissolved in this aniline monomer solution to adjust its concentration to 1.0 mol / l.

  After 10 ml of this aniline monomer solution was placed in the solution holding cell, 5 mg of ammonium peroxodisulfate as an oxidant was added to the aniline monomer solution, and the mixture was stirred and uniformly dissolved with a stirring rod.

  It was observed that the polymerization of the aniline monomer started and proceeded with the addition and dissolution, the solution had a bluish green color, and a polyaniline thin film was formed on the inner wall of the solution holding cell and the flat surface of the prism.

  Five minutes after the polymerization was confirmed, the entire solution was extracted with a pipette, and the inside of the solution holding cell was washed with pure water. Then, when the thickness of the polyaniline thin film present on the flat surface of the prism was measured, it was 100 nm.

  FIG. 8 is an SEM photograph (magnification is 2000 times) of the obtained polyaniline thin film, which represents a flat layer portion of a black portion, and a white portion where granular shapes are densely represents a conductive polymer row. From FIG. 8, it can be seen that in the thin film, a large number of gaps, that is, open pores exist between the polymer rows. In other words, this thin film is a porous body.

Next, it accommodates pure water 10ml in a solution holding cell and measuring the infrared surface enhanced absorption spectrum was compared with the infrared absorption spectrum of the pure water before forming a thin film of polyaniline. From the infrared surface enhanced absorption spectrum of the pure water after formation of a thin film of polyaniline, it shows a spectrum obtained by subtracting the infrared absorption spectrum of the pure water before forming in FIG. From FIG. 9, it can be understood that the peak is large at 3000 to 3450 cm ⁻¹ , which is the wavelength of the portion showing hydrogen bonds, in other words, the component having hydrogen bonds is increasing. This means that water molecules are adsorbed to the polyaniline thin film through hydrogen bonds.

  From the above, it is clear that the surface enhancement effect can be obtained by forming a polyaniline thin film on the flat surface of the prism.

The infrared absorption spectrum and the infrared surface of the aqueous methanesulfonic acid solution before and after the formation of the polyaniline thin film in the same manner as in Example 1 except that the measurement object (sample) was changed from pure water to a methanesulfonic acid aqueous solution. The enhanced absorption spectrum was contrasted. From the infrared surface enhanced absorption spectra of aqueous methanesulfonic acid after formation of a thin film of polyaniline, it shows a spectrum obtained by subtracting the infrared absorption spectrum of the aqueous methanesulfonic acid before forming in conjunction with FIG. From this result, it is clear that the absorption strength of the sulfonic acid group in the vicinity of 1050 cm ⁻¹ and 1200 cm ⁻¹ is increased, that is, methanesulfonic acid is attracted to the polyaniline thin film.

  An infrared absorption spectrum of a germanium prism having a semi-cylindrical shape (diameter 20 mm × height 25 mm) manufactured by Pier Optics was measured and used as a reference spectrum. Hereinafter, the reference spectrum is subtracted from the infrared absorption spectrum and the infrared surface enhanced absorption spectrum obtained using the sample.

  Next, a rectangular parallelepiped solution holding cell having a side of 20 mm and a height of 25 mm and having one side and one bottom as openings was provided on the flat surface of the germanium prism. 10 ml of ethanol was placed in this solution holding cell, and the infrared absorption spectrum of ethanol was measured.

  Meanwhile, 0.50 g of pyrrole monomer was dissolved in 50 ml of pure water to obtain a pyrrole monomer solution having a concentration of 0.15 mol / l. Further, 1.94 g of sodium paratoluenesulfonate was dissolved in this pyrrole monomer solution to a concentration of 0.2 mol / l.

  After 10 ml of this pyrrole monomer solution was placed in the solution holding cell, 5 mg of the pyrrole monomer solution ammonium peroxodisulfate (oxidant) was added and stirred to stir with a stir bar to uniformly dissolve.

  It was observed that the polymerization of the pyrrole monomer started and proceeded with this addition / dissolution, the solution turned blue, and a thin film of polypyrrole was formed on the inner wall of the solution holding cell and the flat surface of the prism.

  Five minutes after the polymerization was confirmed, the entire solution was extracted with a pipette, and the inside of the solution holding cell was washed with pure water. Then, when the thickness of the polypyrrole thin film present on the flat surface of the prism was measured, it was 50 nm.

  The SEM photograph (10,000 times) of the obtained polypyrrole thin film is shown in FIG. As in FIG. 8, the black portion indicates a flat layer portion, and the white portion indicates a conductive polymer row. From FIG. 11, it can be seen that the polypyrrole thin film obtained as described above is also a porous body having a large number of gaps (open pores).

Then, to accommodate ethanol 10ml in a solution holding cell and measuring the infrared surface enhanced absorption spectrum was compared with the infrared absorption spectrum before ethanol to form a thin film of polypyrrole. From the infrared surface enhanced absorption spectra of ethanol after formation of a thin film of polypyrrole, showing a spectrum obtained by subtracting the infrared absorption spectrum of the ethanol before forming in FIG.

From FIG. 11, it is clear that the absorption intensity derived from ethanol increases in the vicinity of 3000 cm ⁻¹ and 1000 cm ⁻¹ .

  A gold thin film having a thickness of 20 nm was formed by electroless plating on a flat surface of a semi-cylindrical silicon prism (diameter 20 mm × height 25 mm) manufactured by Pier Optics.

  On the other hand, 0.93 g of aniline monomer is dissolved in 50 ml of pure water to make the concentration 0.2 mol / l, and 4.81 g of methanesulfonic acid is dissolved to make the concentration 1.0 mol / l. A prepared solution was prepared.

  Next, the silicon prism, the Ag / AgCl reference electrode, and the platinum counter electrode were immersed in this solution, and each of the gold thin film and the platinum counter electrode was electrically connected to a potentiostat. Then, electrochemical oxidation polymerization was advanced by sweeping 18 cycles at 50 mV / sec with the metal thin film as a working electrode and a potential of −0.1 to 0.85 V. As a result, a polyaniline thin film having a thickness of about 100 nm was obtained on the gold thin film.

  12 and 13 are SEM photographs of a polyaniline thin film. As in FIGS. 8 and 10, since each of FIGS. 12 and 13 has a black portion and a white portion, a flat layer portion in close contact with the metal thin film is formed on the polyaniline thin film, and on the layer portion. It can be seen that the porous portion formed in

  Next, a rectangular parallelepiped solution holding cell having a side of 20 mm and a height of 25 mm and having one side and one bottom as openings was provided on the flat surface of the silicon prism. In this solution holding cell, 10 ml of a 0.1 mol / l methanesulfonic acid aqueous solution was accommodated, and an infrared surface enhanced absorption spectrum was measured.

  For comparison, a solution holding cell is provided on a silicon prism having only a gold thin film formed on a flat surface, and 10 ml of a 0.1 mol / l methanesulfonic acid aqueous solution is accommodated in the solution holding cell, and infrared surface enhanced absorption is performed. The spectrum was measured.

  Further, in the same manner as described above except that the polyaniline thin film having only a flat layer portion having a thickness of 20 nm was formed on the gold thin film with 8 sweep cycles, 0.1 mol contained in the solution holding cell. Infrared surface-enhanced absorption spectrum was measured for 10 ml of an aqueous methanesulfonic acid solution of 1 liter.

The results are also shown in FIG. FIG. 14 clearly shows that the absorption peak intensities of methanesulfonic acid and H ₂ O are improved by providing a porous polyaniline thin film.

  As described above, the sensitivity in infrared spectroscopic analysis can be improved by forming the conductive polymer film having open pores on the prism.

DESCRIPTION OF SYMBOLS 1, 10, 22 ... Sample holding member 2 ... Prism 3, 26 ... Metal thin film 4 ... Light source 5 ... Solution holding cell 6 ... Ag / AgCl reference electrode 7 ... Counter electrode 8 ... Detector 12 ... Infrared spectroscopy analyzer 14 ... Conductivity Conductive polymer film 15 ... conductive polymer array 16 ... open pore IR ... infrared light S ... sample

Claims (5)

A sample holding member for holding a sample to be measured by the surface enhanced infrared absorption method,
A prism on which infrared light is incident;
A conductive polymer film formed on one end surface of the prism and having a reflecting surface for reflecting infrared light incident on the prism;
With
The conductive polymer film has open pores on the back surface of the reflective surface,
Holding the sample that has entered the open pores in the open pores ;
The conductivity of the conductive polymer constituting the conductive polymer film is in the range of 10 ⁻³ to 10 ⁴ S / cm, and interacts with the evanescent light that oozes out on the back surface side of the reflecting surface to generate an electromagnetic field. sample holding member, characterized in der Rukoto causing a. A sample holding member for holding a sample to be measured by the surface enhanced infrared absorption method,
A prism on which infrared light is incident;
A metal film formed on one end surface of the prism and having a reflection surface for reflecting infrared light incident on the prism;
A conductive polymer film formed on the back surface of the reflective surface of the metal film;
With
The conductive polymer film has open pores on the back surface of the end face facing the reflective surface of the metal film,
Holding the sample that has entered the open pores in the open pores ;
The conductivity of the conductive polymer constituting the conductive polymer film is in the range of 10 ⁻³ to 10 ⁴ S / cm, and interacts with the evanescent light that oozes out on the back surface side of the reflecting surface to generate an electromagnetic field. sample holding member, characterized in der Rukoto causing a. The sample holding member according to claim 1 or 2 , wherein the conductive polymer film is
A sample holding member comprising a conductive polymer having at least one of a radical cation and a dication in a polymer chain. 3. The sample holding member according to claim 1, wherein the conductive polymer film has at least one substituent selected from the group consisting of a sulfonic acid group, a carboxyl group, a hydroxyl group, and an amino group. A sample holding member comprising a conductive polymer. The sample holding member according to any one of claims 1 to 4 , wherein an opening end portion is provided continuously to the prism so as to face one end surface of the prism, and holds the solution in which the sample is dissolved. Further comprising a cell,
A sample holding member that holds the sample dissolved in the solution stored in the solution holding cell and entering the open pores by the open pores.

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