Device and method for detecting elemental iodine in solution

Abstract

The invention discloses a device and a method for detecting elemental iodine in a solution, and the device is configured as follows: when p-type silicon is contacted with the solution containing the elemental iodine, electrons flow from the p-type silicon to the solution to reduce the elemental iodine into iodide ions due to different Fermi level positions of p-type silicon and elemental iodine / iodide ion redox couple, so that the elemental iodine in the solution is reduced into the iodide ions. Therefore, a hole accumulation layer is formed on the surface, in contact with the solution, of the p-type silicon, the conductivity of the p-type silicon is increased, and the elemental iodine in the solution is dynamically detected by measuring the conductivity of the p-type silicon. According to the device and the detection method, signals are stable, response is rapid, operation is simple and easy, and portable detection can be achieved.

Description

Technical Field

[0001] The invention relates to semiconductor electrochemical technology, and is a device and method for detecting iodine element in a solution. Background Art

[0002] Iodine is closely related to human survival activities. The iodine content not only has a huge impact on human health, but is also closely linked to the sustainable development of the ecological environment. At present, the main analytical methods for detecting elemental iodine include chemical titration, spectral analysis, electrochemical analysis, chromatography and mass spectrometry. These methods have unstable signals, slow response speed, cumbersome operation, limited anti-interference ability, and high requirements for operators. In addition, the current traditional electrochemical method requires an electrolyte as a supporting solution to be carried out, which increases the complexity of the entire system. Summary of the invention

[0003] The purpose of the present invention is to disclose a device and method for detecting iodine in a solution. The method overcomes the problems of unstable signals and cumbersome operation in the prior art, and provides a new method for detecting iodine in a solution with stable signals, rapid response, simple operation and portable detection.

[0004] To achieve the above object, the technical solution of the present invention is:

[0005] When low-concentration doped high-resistance p-type silicon contacts a solution containing iodine (the solution is not required to be conductive), due to the difference in the Fermi level positions of the two, that is, the Fermi level position of p-type silicon is higher than that of iodine / iodide ions (I2 / I - ) The electrode potential of the redox couple, electrons will flow from p-type silicon to the solution to reduce iodine to iodide ions. Finally, the Fermi levels on both sides of the interface are equal and the whole system reaches equilibrium. This directional movement of electrons from p-type silicon to the solution containing iodine will lead to the formation of a hole accumulation layer and a corresponding built-in electric field on the surface of p-type silicon in contact with the solution, causing the p-type silicon surface energy band to bend upward, thereby increasing the conductivity of p-type silicon. According to the Nernst formula, I2 / I - The electrode potential of the redox couple is related to the concentration of iodine. When the concentration of iodine in the solution changes, I2 / I - The electrode potential of the redox couple changes accordingly. At this point, the original balance is broken, and electron transfer due to inconsistent Fermi levels occurs at the interface, causing corresponding changes in the hole concentration and band bending degree on the surface of p-type silicon, ultimately leading to changes in p-type conductivity. The present invention utilizes this principle to achieve the purpose of dynamically detecting iodine in a solution by measuring changes in the conductivity of p-type silicon. Thus, the present application provides a method for detecting iodine in a solution, comprising the following steps:

[0006] Step 1: Make an ohmic contact electrode on p-type silicon to measure its conductivity; (See: S. Li, H. M. Ayedh, M. Yli-Koski, V. Vahanissi, H. Savin, J. Oksanen, Chemical excitation of silicon photoconductors by metal-assisted chemical etching, J. Phys. Chem. C 127 (2023) 4072–4078.);

[0007] Step 2: Encapsulating the p-type silicon with ohmic contact electrodes;

[0008] Step 3: Expose the packaged p-type silicon to the test liquid and measure its conductivity.

[0009] The purpose of the present invention is to disclose a device for detecting iodine in a solution, wherein the device is configured as a constant potential instrument connected to p-type silicon through two wires, the p-type silicon is exposed to a test solution containing iodine, the p-type silicon is packaged and contains two ohmic contact electrodes, the ohmic contact electrodes are used to accurately measure the conductivity of the p-type silicon, the p-type silicon is a high-resistance silicon wafer doped with low concentration of boron, and its resistance is greater than 0.01Ωcm. The packaging material is an insulating material that does not penetrate the solution, and the test solution is an organic solution or aqueous solution containing iodine.

[0010] Compared with other existing methods, the present invention has the following advantages:

[0011] At present, the detection of elemental iodine in the solution mainly adopts chemical titration, spectral analysis, chromatography and mass spectrometry. These methods, especially the spectral measurement method, have unstable signals, cumbersome operation, expensive equipment, limited anti-interference ability, and high requirements for operators. The present invention detects the iodine element in the solution by measuring the conductivity of p-type silicon. The method has stable signals, rapid response, simple and easy operation (only IV test is required), low requirements for testers, and can realize portable detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of a device for detecting iodine in a solution according to the present invention;

[0013] Figure 2 The current-voltage curve measured when the p-type silicon in Example 1 of the present invention is exposed to methanol solutions containing iodine at different concentrations;

[0014] Figure 3 The current-time curve measured when the p-type silicon in Example 1 of the present invention is exposed to methanol solutions containing iodine at different concentrations;

[0015] Figure 4 This is a current-voltage curve measured when the p-type silicon in Example 2 of the present invention is exposed to an aqueous solution of potassium iodide containing elemental iodine. DETAILED DESCRIPTION

[0016] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0017] The present application is illustrated below with reference to specific embodiments to provide a further understanding.

[0018] Embodiment 1:

[0019] Step 1: Make an ohmic contact electrode on p-type silicon to measure its conductivity (see: S. Li, H. M. Ayedh, M. Yli-Koski, V. Vahanissi, H. Savin, J. Oksanen, Chemical excitation of silicon photoconductors by metal-assisted chemical etching, J. Phys. Chem. C 127 (2023) 4072–4078.);

[0020] A boron-doped high-resistance (>10KΩcm) p-type (100) silicon wafer was selected. The silicon wafer was first cleaned by standard RCA. Then, the silicon wafer was wet-oxidized at 1000°C for 84 minutes to grow an oxide layer several hundred nanometers thick as a barrier layer for subsequent ion implantation. Standard photolithography and BHF etching steps were used to open the barrier layer on one side of the silicon wafer. Boron ions were implanted in the opening area to form a heavily doped p + The ion implantation energy is 20 KeV and the dose is 5×10 15 cm -2 , with an angle of 7°. Subsequently, a drive annealing treatment at 1050°C was performed in a N2 atmosphere for 20 minutes. Then, the thermal oxide layer was completely removed by BHF etching. + A 1-micron thick aluminum film is deposited on one side of the region, and then all the deposited aluminum outside the heavily doped p+ region is removed by photolithography and aluminum etching. After that, the entire silicon wafer is annealed in a reducing atmosphere at 425°C for 20 minutes. Finally, the silicon wafer is cut into 1.2×1.2 cm 2 Each chip contains two aluminum contact electrodes with a length of 10 mm and a width of 0.4 mm, and a spacing of 10 mm between the electrodes;

[0021] Step 2: Encapsulate p-type silicon with ohmic contact electrodes

[0022] Use conductive silver glue to connect two copper wires to the two aluminum contact electrodes on the sample, cover the ohmic contact electrode area with hot melt glue, and leave the other areas as exposed areas;

[0023] Step 3: Detection of iodine in organic (taking methanol as an example) solution

[0024] Connect two copper wires to a potentiostat. Expose the sample to pure methanol and methanol solutions containing different concentrations (0.1M, 0.01M) of iodine, and measure the current-voltage (IV) curve. A simplified schematic diagram of the entire setup is shown in the attached figure. Figure 1 Attached Figure 1 This is just an example description. Figure 1 In the process, the side with the ohmic contact electrode and the side are all covered with hot melt adhesive, leaving only an exposed area of ​​about 1 square centimeter on the side without the ohmic contact electrode (or, only the area with the ohmic contact electrode is covered with hot melt adhesive, leaving the other area as the exposed area). The IV curves measured in different solutions are shown in the attached figure. Figure 2 As shown. When exposed to pure methanol solution, the IV curve has the lowest slope, that is, the conductivity is the lowest. When exposed to a methanol solution containing iodine, the conductivity increases, and the conductivity increases with the increase of iodine concentration. In addition, a voltage of 0.5V is applied between the two electrodes of the sample to observe the change in current when the sample is exposed to methanol solutions containing different concentrations of iodine. The results are shown in the attached Figure 3 When the sample is exposed to a methanol solution containing iodine, the current increases, and the higher the iodine concentration, the greater the current.

[0025] Embodiment 2:

[0026] Except that the solvent of the solution to be tested is replaced with water, the implementation steps are the same as those in Example 1 and will not be repeated here. Figure 4 As shown in Figure 2, when exposed to an aqueous solution of potassium iodide containing elemental iodine (0.1 M), the conductivity of the sample also increased. The purpose of using potassium iodide is to allow elemental iodine to form an iodide ion in the aqueous solution. 3- ions, thereby increasing the solubility of iodine in water.

[0027] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0028] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting iodine in a solution, characterized in that: The p-type silicon is exposed to a test solution containing iodine, and the iodine in the solution is detected by measuring the change in the conductivity of the p-type silicon when the p-type silicon is in contact with the test solution.

2. The method according to claim 1, characterized in that The following steps are involved: Two ohmic contact electrodes are made on the surface of p-type silicon, and the ohmic contact electrodes are used to accurately measure the conductivity of p-type silicon; Encapsulating p-type silicon with ohmic contact electrodes; The packaged p-type silicon is exposed to a test liquid to measure the conductivity of the p-type silicon.

3. The method according to claim 2, characterized in that The p-type silicon used is a high-resistance silicon wafer doped with low concentration of boron, and its resistance is greater than 0.01Ωcm.

4. The method according to claim 2, characterized in that: The method for making two ohmic contact electrodes on the surface of p-type silicon is as follows: firstly, the selected area of ​​p-type silicon is heavily doped with impurity boron, and then metal aluminum is deposited in the heavily doped area.

5. The method according to claim 2, characterized in that: The packaging material is an insulating material that is impermeable to the solution.

6. The method according to claim 2, characterized in that The test solution is an organic solution or an aqueous solution containing iodine.

7. The method according to claim 5, characterized in that The packaging method is to cover two ohmic contact electrodes on the surface of p-type silicon with packaging materials, leaving other areas for detecting iodine element.

8. A device for detecting iodine in a solution, characterized in that: The invention comprises a constant potential instrument and p-type silicon, wherein the constant potential instrument is connected to the p-type silicon through two wires, the p-type silicon is exposed to a test liquid containing iodine, and the p-type silicon is packaged and contains two ohmic contact electrodes.

9. The device according to claim 8, characterized in that The ohmic contact electrode is used to measure the conductivity of p-type silicon, and the p-type silicon is a high-resistance silicon wafer doped with low concentration of boron, and its resistance is greater than 0.01Ωcm.

10. The device according to claim 8, characterized in that The packaging material is an insulating material that is impermeable to the solution, and the liquid to be tested is an organic solution or a water solution containing iodine.

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