CN201034936Y - A surface-enhanced infrared spectroscopy optical device - Google Patents

Abstract

The utility model belongs to the infrared spectrum technology field, in particular to a surface enhanced infrared spectrum optical device, which comprises an electrolytic cell, a reference electrode, a counter electrode, a metal nanometer film electrode, a silicon wafer and a zinc selenide semicircular cylinder. The metal nanometer film electrode is plated on the silicon wafer, a water film is provided between the lower surface of the silicon wafer and the zinc selenide semicircular cylinder, which is sealed by the paraffin in the surrounding gaps to form a working electrode. The electrolytic cell is arranged on the upside of the metal nanometer film electrode, in the middle of which is a silicone rubber ring sealed. The metal nanometer film electrode is conducted by a conductor copper membrane. The counter electrode and the reference electrode are arranged in the electrolytic cell to form an electrode system of electrochemical spectrum testing. The device is simple in structure and convenient to operate, can detect the site and the off-site electrochemical spectrum infrared signals below the 1000cm <-1> wave band conveniently, which can be used stably for a longer time.

Description

A surface-enhanced infrared spectroscopy optical device

technical field

The utility model belongs to the technical field of infrared spectroscopy, in particular to a surface-enhanced infrared spectroscopy optical device, which can be used in the research and application of electrochemical on-site and off-site surface-enhanced infrared spectroscopy, and can lower the lower limit of the signal interval from the usual 1000cm ^-1 The wavenumber extends to 700cm ^-1 wavenumber.

Background technique

Surface-enhanced infrared spectroscopy (SEIRAS) ^[1] is an important analytical tool for studying molecular structure information at electrode interfaces. Surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) with attenuated total reflection (ATR) mode has strong surface signal and simple surface selection law, which can avoid the problems faced by traditional external reflection infrared absorption spectroscopy (IRAS), such as insufficient surface signal , Uneven electric field distribution, mass transfer replenishment hysteresis, solution background interference, etc. In the past 10 years, ATR-SEIRAS technology has been developing continuously: first, the research electrode system has expanded from Au and Ag electrodes to Pt and Fe family electrodes; Evaporation, sputtering, electron beam deposition) to simple and reproducible wet preparation (including electroless plating, electrodeposition and self-assembly methods).

Especially with semi-cylindrical (spherical) silicon as the infrared window, it is relatively mature to grow nano-metal thin film electrodes on the reflective bottom surface by electroless plating and electroplating methods, which can replace the traditional dry method to prepare membrane electrodes. For example, the Osawa group obtained Au and Pt nano-film electrodes with SEIRA activity on the infrared window silicon by electroless plating ^[2] , and this group used a two-step wet method (electroless plating + electrodeposition or self-assembly + electroless plating) as General strategies to obtain Pt and Fe nano-film electrodes with strong SEIRA effect ^{[3, 4]} and Au and Ag nano-film electrodes with tunable SEIRA effect ^[5] .

The infrared windows commonly used in surface-enhanced infrared spectroscopy devices are silicon, germanium, and zinc selenide columns. Silicon pillars have strong absorption signals below 1000cm ^-1 and cannot give corresponding infrared signals; germanium and zinc selenide have weak absorption below 1000cm ^-1 , but the metal films on the surface of these two substrates are prepared by vacuum dry method , what is more serious is that the germanium and zinc selenide substrates are unstable in acidic solutions, which may easily cause the metal film to fall off during use, and the electrochemical response of the metal film on it often deviates from the characteristics of the bulk metal electrode, which is not suitable for field spectroscopy Electrochemical research. The Adzic group ^[6] proposed the concept of combining zinc selenide cylinders and silicon wafer infrared windows, but did not give the relevant parameters. According to the knowledge of physical optics, this combination must have high requirements for the smoothness of the interface. In fact, in the spectrum It is difficult to realize the design concept of the device in electrochemical experiments.

The utility model is different from the experimental device of the Adzic group: according to the principle of decay wave penetration, an ultra-thin water layer is introduced between two zinc selenide cylinders with different refractive indices and the infrared window of the silicon chip to develop a simple and easy Apparatus for electrochemical internal reflection SEIRAS.

1.M.Osawa, In Handbook of Vibrational Spectroscopy; Chalmers J.M., Griffiths, P.R., Eds.; John Wiley&Sons: Chichester, UK, 2002; Vol.1, p.785.

2.Y.-X.Chen.; A.Miki.; S.Ye.; M.Osawa.J.Am.Chem.Soc., 125(2003) 3680.

3.S.-J.Huo.;X.-K.Xue.;Y.-G.Yan.;Q.-X.Li.;M.Ma.;W.-B.Cai ^* .;Q. -J.Xu.; M.Osawa.J.Phys.Chem.B 110(2006)4162.

4.Y.-G.Yan.;Q.-X.Li.;S.-J.Huo.;M.Ma.;W.-B.Cai ^* .;M.Osawa.J.Phys.Chem. B 109(2005) 7900.

5.S.-J.Huo.;Q.-X.Li.;Y.-G.Yan.;Y.Chen.;W.-B.Cai ^* .;Q.-J.Xu.;M. Osawa. J. Phys. Chem. B 109 (2005) 15985.

6.M.-H.Shao.; P.Liu.; R.-R.Adzic.J.Am.Chem.Soc., 126(2006)7408.

Contents of the invention

The purpose of this utility model is to propose a new type of surface-enhanced infrared spectrum optical device, which is required to be simple and easy to operate, can be used stably for a long time, and is convenient to detect on-site and off-site electrochemical spectral signals in the band below 1000cm ^-1 .

The surface-enhanced infrared spectrum optical device proposed by the utility model is composed of an electrolytic cell, a reference electrode, a counter electrode, a metal nano-film electrode, a silicon chip and a zinc selenide half cylinder. Its structure is shown in Figure 1. Wherein, the metal nano film electrode 8 is plated on the silicon chip 9, and the water film layer 5 is provided between the lower side of the silicon chip 9 and the zinc selenide semi-cylinder 10, and the water film layer is sealed by the stone ring 4 at the gap around it, Constitute the working electrode; above the metal nano film 8 is the electrolytic cell 6, with a silicon rubber ring 7 sealing in the middle, and the metal nano film 8 is drawn out by the wire copper film 3; the counter electrode 1 and the reference electrode 2 are placed in the electrolytic cell 6 to form an electrolytic cell Three-electrode system for chemical spectroscopic testing.

In the utility model, a water thin film layer is added between the bottom surface of the zinc selenide semi-cylindrical and the silicon chip, and the extrusion is controlled to make it thinner to several microns (generally 0.1-5 microns), and the "coupling waveguide" theory is used to make the incident The infrared light attenuation wave can pass through the silicon wafer layer, so as to detect the infrared signal of the adsorbed species adsorbed on the surface of the metal thin film electrode. The above metal film electrodes on silicon wafers are prepared by chemical wet method.

"Coupled waveguide" theory: In two slab waveguides that are far apart, the field distributions of the two waveguide modes do not overlap each other, and they propagate independently in their respective waveguides. However, when the two slab waveguides are very close to each other, the field distributions of the two waveguide modes overlap each other, and they can be coupled through the so-called optical tunneling effect to exchange power with each other. If the incident light enters the bottom from the top, when the upper and lower optical windows are squeezed with a fixture, the two windows are separated from each other by a very thin water medium, whose refractive index is higher than that of air, which is conducive to the penetration of infrared light, which constitutes coupling waveguide system. The thinner the thickness of the liquid film layer, the greater the proportion of incident infrared light transmitted through the layer.

In fact, after adding the water film layer, the infrared signal of the adsorbed species on the thin film electrode increases with the increase of the incident angle, and the experimental results show that the incident angle is 70° which is ideal. In contrast, a very weak infrared signal can only be detected at an incident angle of 20° without adding water, and the infrared signal of the adsorbed species cannot be detected when the incident angle is increased, indicating that the incident infrared light is at the ZnSe bottom surface/air interface Most of the reflections cannot effectively pass through the Si sheet. The stability of the water film layer has a great influence on the strength of the detection signal, and the use of paraffin to seal the water film at the gaps around the interface can improve the stability of the water film.

The beneficial effect of the novel device is that the on-site and off-site electrochemical spectrum infrared signals between 4000cm ^-1 and 700cm ^-1 can be expanded to be measured, the structure is simple and stable, and it is convenient and easy to operate.

Description of drawings

The following is a further description of the new surface-enhanced infrared spectroscopy research device in conjunction with the accompanying drawings and specific examples.

Fig. 1 is a schematic diagram of the structure of the novel surface-enhanced infrared spectroscopy optical device.

Fig. 2 is a spectrogram of an example (manually modulated potential) of the device of the present invention.

Fig. 3 is a spectrogram of Fig. 2 at different electrode potentials.

Fig. 4 is a diagram of the relationship between the central wave number and integral intensity of CO adsorption in Fig. 3 and the potential.

Fig. 5 is a spectrogram of another example (manually modulated potential) of the device of the present invention.

Numbers in the figure: 1: counter electrode; 2: reference electrode; 3: wire copper film; 4: paraffin; 5: water film layer; 6: electrolytic cell; 7: silicone rubber ring; 8: metal nano film electrode; 9 : Silicon wafer; 10: ZnSe half cylinder.

Detailed ways

The specific structure of the device is mainly composed of an electrolytic cell, a reference electrode, a counter electrode, a metal nano-film electrode, a silicon wafer and a zinc selenide half cylinder. The size of the silicon wafer is 20mm×25mm, and the thickness is 50-200 microns; the diameter of the zinc selenide half cylinder is 20mm, and the height is 25mm. Concrete use steps are as follows: 1. at first on the surface of silicon chip 9 plate metal nano-film 8, then the silicon rubber ring 7 that diameter is 8-14mm is covered on the surface of metal nano-film, and pack in the electrolytic cell 6, then in Add the water layer to the other side of the silicon wafer 9 and squeeze the water layer with the zinc selenide half cylinder 10, and finally seal the water film 5 in the gaps around the interface with paraffin 4, which constitutes the working electrode. ② Insert the reference electrode 2 and the counter electrode 1 into the electrolytic cell, which forms a three-electrode system for electrochemical spectroscopy.

Figure 2 is the surface-enhanced infrared spectrum of the Pt electrode in a 0.1mol/L HClO ₄ solution containing saturated CO. The sample spectrum was collected at -0.2V (vs. SCE), and the reference spectrum was collected at 0.8V. Curve a is the surface-enhanced infrared spectrum when no water film layer is added to the device, and curve b is the spectrum after adding a water film layer to the device. Obviously, the signal of adsorbed CO (2072cm ^-1 , vCO _L ; 1857cm ^-1 , vCO _B ) was greatly enhanced in curve b, and the signal of co-adsorbed water (3656cm ^-1 , vOH; 1634cm ^{- 1} , δHOH).

Fig. 3 and Fig. 4 are graphs showing the relationship between the signal of CO adsorption on Pt surface and the change of different electrode potentials. In Fig. 4, the Stark slope of the central wave number of vCO _L is 31cm ^-1 ·V ^-1 , and the integrated intensity of vCO _L increases with the positive potential The shift tends to become weaker, indicating that the more positive the potential is, the easier it is for the CO adsorbed on the surface of the Pt electrode to be oxidized.

Figure 5 is the surface-enhanced infrared spectrum of the Pt electrode in a 0.1mol/L HClO ₄ solution saturated with p-nitrobenzoic acid (PNBA). The sample potential was collected at 0.6V, and the reference potential was collected at -0.1V. The spectrum not only detects the characteristic spectrum peaks of PNBA between 2000cm ^-1 and 1000cm ^-1 , but also detects the characteristic spectrum peaks of 866cm ^-1 (δCO ₂ ⁾ and 835cm ^-1 (δNO ₂ ) between 1000cm ^-1 and 700cm -1 .

Claims (2)

1. A surface-enhanced infrared spectrum optical device is characterized in that it is made up of electrolytic cell, reference electrode, counter electrode, metal nano film electrode, silicon wafer and zinc selenide half cylinder, wherein, metal nano film electrode (8) is plated On the top of the silicon wafer (9), a water film layer is provided between the lower side of the silicon wafer (9) and the half cylinder of the zinc selenide (10), and the water film layer is sealed at the surrounding gaps by stone pegs (4) to form a Working electrode; above the metal nano film (8) is the electrolytic cell (6), with a silicon rubber ring (7) sealing in the middle, and the metal nano film (8) is drawn out by the wire copper film (3); the counter electrode (1) and the reference The electrode (2) is placed in the electrolytic cell (6) to form an electrode system for electrochemical spectroscopic testing. 2. The surface-enhanced infrared spectroscopy optical device according to claim 1, characterized in that the thickness of the water film layer is 0.1-5 microns.

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