Colorimetric sensor for identifying organic solvent based on mobile phone assistance and preparation method of colorimetric sensor

Abstract

The invention discloses a colorimetric sensor for identifying an organic solvent based on mobile phone assistance and a preparation method of the colorimetric sensor, and relates to the technical field of chemical sensing. The chemical colorimetric sensor based on the F-P stacked structure comprises a microstructure of a selection layer, a dielectric layer and a reflecting layer which are prepared from top to bottom, wherein the bottommost layer of the microstructure can be made of any planar material. Wherein the color on the sensor is collected and analyzed by means of the smart phone. According to the invention, the type of the organic solvent can be identified outdoors without large precision equipment, and the sensor also has the advantage that the minimum range is not limited, which is not possessed by a traditional sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical sensing, and in particular to a colorimetric sensor for identifying organic solvents based on the assistance of a mobile phone and a preparation method thereof. Background Art

[0002] The demand for rapid and accurate monitoring and identification of chemical solvents has shown a rapid growth trend, which has effectively promoted the progress of chemical sensor technology. Among them, organic solvents are often widely used in industrial cleaning, coatings, and pharmaceutical extractants, given their good solubility for some extremely difficult-to-dissolve substances (grease, wax, rubber, fuel, etc.). For this reason, it is particularly important to carry out necessary calibration and characterization work for such solvents in the process of reagent preparation and extraction. At present, organic solvents have been identified and classified by means of chemical methods, gas chromatography, infrared spectroscopy, terahertz time-domain spectroscopy, etc. However, these methods have many significant limitations. Not only do they require numerous operating steps, but they also involve expensive equipment, bulky instruments, and difficulties in operation and maintenance. More importantly, the above detection process must be used by professionals in a specific environment. In addition, organic solvents are often some dangerous solutions that are easy to volatilize, which will inevitably cause harm to users in complicated operating procedures. The above factors limit their application in effective detection. Facing the above problems, it is particularly important to develop a portable sensor with identification function. In order to transmit signals conveniently, efficiently and accurately, a chemical colorimetric sensor with a simple preparation process and more intuitive color response to different types and concentrations of organic solvents is needed. This technology also has the ability to monitor organic solvents in real time with the help of a mobile phone camera. The convenient and compact colorimetric chemical sensor meets the needs of fast and convenient detection and can safely calibrate organic solvents during the experiment. Summary of the invention

[0003] The main purpose of the present invention is to provide a scalable chemical colorimetric sensor based on a FP three-layer nano-stacked structure that is sensitive to organic solvents, which solves the dangers and complexity of traditional measurements and can more intuitively use colors to reflect the differences between different organic solvents (such as alcohol, tetrahydrofuran, acetone, n-hexane, n-heptane and other solvents that can dissolve PDMS).

[0004] To achieve the above-mentioned purpose, the present invention provides a reflective structural color chemical sensor based on a FP three-layer stacking structure, characterized in that it includes a microstructure of a selection layer, a dielectric layer and a reflective layer stacked in sequence from top to bottom, and the structure can be attached to any planar substrate; the reflective layer is bonded to the planar substrate.

[0005] Further, the material used for the reflective layer includes but is not limited to a metallic silver layer, and the thickness is set to be 50 nm or more, such as 100 nm, to ensure that light of visible wavelengths is reflected. Further, on a planar substrate (such as any planar material such as glass, silicon wafer, or a bendable flexible sample), a nanometer-thick material is attached to the selected substrate using a magnetron sputtering method.

[0006] Furthermore, the material of the dielectric layer is selected from a transparent material of polydimethylsiloxane (PDMS), and the thickness is set between 50nm-500nm to ensure that light of visible wavelengths is refracted and reflected.

[0007] Furthermore, the material of the selection layer is selected from germanium antimony telluride alloy (GST) and scandium antimony telluride alloy (SST) materials, and the thickness is set between 3nm-15nm to ensure that light of visible wavelengths is refracted and reflected.

[0008] The method for preparing the above-mentioned chemical colorimetric sensor based on FP microstructure comprises the following steps:

[0009] Step 1: Clean the flat substrate with acetone, alcohol, and deionized water, and blow it dry;

[0010] Step 2: Use a magnetron sputtering instrument (power 40W, vacuum degree 5×10 -4 Pa, deposition rate is 0.45nm / s), a reflective layer, such as a silver layer, is deposited on a planar substrate.

[0011] Step 3: Mix the material corresponding to the dielectric layer, polydimethylsiloxane, with glue A and glue B in a volume ratio of 10:1;

[0012] Step 4: dissolving and diluting the mixed glue with hexane solvent, preferably the corresponding mass percentage of polydimethylsiloxane is 3.2wt%;

[0013] Step 5: After being fully dissolved, use a coating machine to spin-coat the solution onto a flat substrate on which the dielectric layer has been deposited; preferably, the spinning speed is 2500 rpm and the time is 1 minute;

[0014] Step 6: After spin coating, place it in a drying oven for solidification at 60°C for 4 hours;

[0015] Step 7: Use a magnetron sputtering instrument (power 100 W, vacuum degree 5×10 -4 Pa, the deposition rate is 0.2nm / s), and the selective layer is deposited on the dielectric layer.

[0016] The structure obtained in step 7 is subjected to an organic solvent immersion experiment, and the results are analyzed and compared.

[0017] The application of reflective structural color chemical sensors based on the FP three-layer stacking structure is used to detect different solvents, and more intuitively use color reactions to distinguish different organic solvents (such as alcohol, tetrahydrofuran, acetone, n-hexane, n-heptane and other solvents that can dissolve PDMS). Or distinguish or measure the size of the corresponding solvent that can dissolve PDMS when the solvent that can dissolve PDMS is mixed with the solvent that does not dissolve PDMS.

[0018] In the present invention, the reflective layer and the selective layer are made of coating materials, which are non-toxic and have stable structures. The transparent PDMS material used in the dielectric layer is sensitive to organic solvents, and will produce different thickness changes in the same time with the dissolution rate of the organic solvent, thereby producing changes in structural color;

[0019] 1. The preparation process of the transparent dielectric layer used in the present invention is simple and cheap, and the thickness can be adjusted by the concentration and spin speed in the spin coating method. Secondly, the thickness of the upper and lower film structures can be adjusted as needed. Therefore, the structure has a strong scalability, and we can obtain various desired structural colors and identify organic solvents.

[0020] 2. The color change principle adopted by the present invention is generated according to the change in the thickness of the dielectric layer. Therefore, as long as the immersion time is increased, the problem of minimum range limitation will not occur like traditional sensors, and types of organic solvents with very small differences in dissolution rates can be distinguished.

[0021] 3. The structure of the present invention can be attached to any parallel plane, so it can be prepared into a bendable and flexible sample similar to pH test paper as needed, which is convenient for outdoor measurement.

[0022] 4. To ensure the accuracy of recognition and avoid errors in human eye observation, the present invention relies on the camera color recognition function of the smartphone to perform color analysis on the sensor that produces color changes and establishes a small database. After the sensor after immersion is color-recognized, it is compared with the database to obtain the specific type of organic solvent.

[0023] The present invention solves the minimum range limitation of traditional sensors and uses more direct and clear color signals as the result expression of the sensor. It solves the problems of various complicated processes and the harm to human health caused by the careless use of organic solvents in traditional measurement. The three parallel thin film stacking structures not only avoid the problem of difficult preparation of microstructures, but also only the thickness determines the type of color, and it is relatively simple and convenient to control the structural color. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a color display principle diagram of a colorimetric sensor for identifying organic solvents in an embodiment of the present invention;

[0025] Figure 2 Preparation flow chart and physical flow chart of the colorimetric sensor for identifying organic solvents in an embodiment of the present invention;

[0026] Figure 3 is a thickness measurement diagram of the dielectric layer PDMS in one embodiment of the present invention;

[0027] Figure 4 is a corresponding relationship diagram between the dilution concentration and the thickness when preparing the PDMS layer in the present invention;

[0028] Figure 5 Application flow chart for sensor identification of organic solvents.

[0029] Figure 6 Schematic diagram of the structural color change after the sensor is immersed in an organic solvent;

[0030] Figure 7 is a reflectivity graph of a colorimetric sensor for identifying organic solvents in a visible light band in one embodiment of the present invention;

[0031] Figure 8 This is an ED diagram of a colorimetric sensor identifying different organic solvents measured by a mobile phone in one embodiment of the present invention (immersion and identification for 10 minutes);

[0032] Fig. 9 This is an ED graph of a colorimetric sensor identifying different concentrations of the same organic solvent measured by a mobile phone in one embodiment of the present invention (immersion and identification for 90 minutes). DETAILED DESCRIPTION

[0033] The following will describe the embodiments of the present invention in detail with reference to the accompanying drawings. It should be emphasized that the following explanation is only exemplary and is not intended to limit the scope and application of the present invention.

[0034] like Figure 1 The figure shows the color display principle diagram of the colorimetric sensor for identifying organic solvents. When a beam of natural light is incident on the surface selection layer, the GST layer can transmit light in the visible light range due to its optical refractive index and transmittance to natural light. Subsequently, the transmitted light is transmitted inside the dielectric layer and reflected after encountering the silver layer. Due to the different refractive indices, the light waves will be reflected by the upper and lower interfaces of the film (the film refers to the dielectric layer) respectively. Finally, the reflected light that is initially incident and the light generated by refraction and reflection interfere with each other and finally produce color. The refractive index of the middle layer in the figure is n, the thickness is d, the refraction angle is θ, m is an integer, and λ is the wavelength of the incident natural light. Therefore, when interference occurs, the constructive light that interferes will remain, and the destructive light that interferes will disappear. The specific formula is as follows:

[0035] 2n d cosθ=mλ (1)

[0036]

[0037] When the thickness of the middle layer changes, that is, when d changes: the initial thickness is fixed. When detecting the solvent, the sensor is immersed in the detection solvent and then taken out. Due to the different dissolution rates of the detection solvent on the dielectric layer, different detection solvents correspond to different thicknesses d at the same time; visible light is used to irradiate the selection layer (before immersion in the solvent, it can be represented by its own color signal, and different detection solvents will show different colors after immersion), and the interference phenomenon of the internal light will also change, resulting in a change in the wavelength reflected by the entire structure. Therefore, when the reflected light of different wavelengths is reflected into our eyes, we will receive different color signals. In order to change the value of d, we use organic solvents with different dissolution rates to dissolve the PDMS layer. In the same time, the PMDS layer immersed in different types or concentrations of organic solvents will show different d values, and the sensor will eventually show different structural colors.

[0038] like Figure 2 As shown, the preparation method of the chemical colorimetric sensor provided by the example of the present invention includes: S101, acetone, alcohol, and deionized water are placed in a glass cup respectively, and then placed in an ultrasonic cleaning machine for ultrasonic cleaning for 2 minutes. After the ultrasonicated glass piece is taken out with tweezers, its surface is quickly blown dry with a hair dryer to avoid water stains and make the surface uneven.

[0039] S102, using a magnetron sputtering instrument (power 40 W, vacuum degree 5 × 10 -4 Pa, the precipitation rate is 0.45nm / s), the rotation speed of the tray in the chamber is 10 rpm, and a 100nm silver film is plated on the glass substrate. During this process, the glass sheet should be kept stable;

[0040] S103, mixing polydimethylsiloxane (PDMS) A glue and B glue with each other. In order to ensure the stability of the layer structure, the optimal ratio is 10:1, and the two glues are fully stirred for half an hour to promote uniform mixing.

[0041] S104, the mixed PDMS is mixed with n-hexane to a solvent concentration of 3.5 wt % as required. The glass sheet is adsorbed on a gelling machine, 1 ml of the prepared solution is taken with a syringe, and dripped onto the surface of the silver layer. The rotation speed is 2500 rpm and the time is 1 minute.

[0042] S105, placing the spin-coated glass sheet in a drying oven and heating it at 60°C for 4 hours.

[0043] S106, after heating and solidification, a magnetron sputtering apparatus (power 100 W, vacuum degree 5 × 10 -4Pa, the precipitation rate is 0.2nm / s), the rotation speed of the tray in the chamber is 10 rpm, and a 5nm GST film is deposited on the glass substrate. During this process, the glass sheet should be kept stable;

[0044] S107, immersing the prepared sensor in a beaker containing an organic solvent for identification, and finally obtaining a color.

[0045] like Figure 3 The figure shows the thickness of the PDMS layer measured by white light interferometry. During spin coating, a portion of the glass sheet was taped to prepare a PDMS layer with pits, and then the surface morphology was measured by white light interferometry to measure the height of the PDMS layer surface from the silver layer. This figure shows the measurement data of a PDMS layer with a thickness of 70nm, and the PDMS has a good flatness above the Ag layer.

[0046] like Figure 4 As shown in the figure, the PDMS film thickness corresponding to different dilution concentrations is measured after the spin coating speed and time of the PDMS dilution solution are fixed. The curve shows a linear characteristic. As the dilution concentration increases, the film thickness gradually increases.

[0047] As shown in Table 1, the colorimetric sensor structures of different materials and different thicknesses are compared. Due to the different interference paths and material refractive indices, the colors displayed by the final structures are also different. When the structures are Ag, PDMS (thickness is 50-500nm), and GST / SST, the structures will display colors, so these structures can be used for color applications.

[0048] Example 1

[0049] like Figure 5 As shown, the prepared sensor is placed in an organic solvent as a whole, and after waiting for 10 minutes, it is taken out and the color is recognized by the human eye and the mobile phone.

[0050] like Figure 6 Figure 2 shows the structural color changes of the sensor after it was immersed in an organic solvent. After the sensor was immersed in the organic solvent for ten minutes, the thickness d of the PDMS decreased. The color of the sensor changed from the initial purple-red to light yellow. The five colors correspond to the five solvents.

[0051] Figure 7This is a reflectivity graph in the visible light range measured by the colorimeter for the sensor that produces the color change in order to more accurately analyze the color change. The graph shows the effect of different organic solvents on the reflectivity of the sensor at the same time. From the reflectivity graph, it can be seen that the reflection peak and the absorption valley shifted to the left at the same time. Therefore, it also explains the color change, from initially reflecting only the light in the purple-red band to later reflecting only the light in the light yellow band.

[0052] Figure 8 In order to avoid the error of human eye recognition, the ED diagram of the type and concentration of organic solvents measured by the color recognition function of the mobile phone is shown in the example (the color is determined by the three stimulus values ​​of R, G, and B. In order to better contrast the color difference, the RGB value is converted into a single ED value for comparison). The conversion formula of the ED value is as follows:

[0053]

[0054] Among them, R0=250, G0=250, B0=250, and ΔRGB value is the ED value. As can be seen from the figure, the color data of the sensor recognized by the mobile phone are different when immersed in different organic solvents, so various organic solvents can be distinguished according to the ED value.

[0055] in Fig. 9 The concentration ED diagram can illustrate that for the same solvent with a concentration difference of 0.01 (a mixture of a solvent that can dissolve PDMS and another solvent that cannot dissolve PDMS, where the concentration is the solvent that can dissolve PDMS), the colorimetric sensor can solve the minimum range limitation problem and distinguish the two as long as the immersion time is increased to 90 minutes.

[0056] Table 1 compares the colorimetric sensor structures of different materials and thicknesses (their own colors when not immersed in solvents at the beginning)

[0057] project Reflective layer Dielectric layer Select Layer Dielectric layer thickness Is there any obvious color Example 1 Ag PDMS GST 10nm none Example 2 Ag PDMS GST 50nm have Example 3 Ag PDMS GST 100nm have Example 4 Ag PDMS GST 250nm have Example 5 Ag PDMS GST 500nm have Example 6 Ag PDMS GST 600nm none Example 7 Ag PDMS GST 700nm none Example 8 Ag PDMS SST 250nm have Example 9 Ag PDMS Al 250nm none Example 10 Cu PDMS GST 250nm none

[0058] To sum up, the above is only one of the specific examples of the present invention, but the protection scope of the present invention is not limited to this. Any technician familiar with the technical field can easily make any modifications, equivalent substitutions and improvements within the technical scope disclosed in this patent, which should be covered by the protection scope of the present invention.

Claims

1. A reflective structural color chemical sensor based on a three-layer FP stacking structure. It is characterized in that The microstructure comprises a selection layer, a dielectric layer and a reflective layer stacked in sequence from top to bottom, and the structure is attached to an arbitrary planar substrate; the reflective layer is attached to the planar substrate.

2. A reflective structural color chemical sensor based on a FP three-layer stacking structure according to claim 1, It is characterized in that The materials used for the reflective layer include but are not limited to a metal silver layer, and the thickness is set to be 50 nm or above, such as 100 nm, to ensure that light of visible wavelengths is reflected.

3. A reflective structural color chemical sensor based on a FP three-layer stacking structure according to claim 1, It is characterized in that The material of the dielectric layer is selected from a transparent material of polydimethylsiloxane (PDMS), and the thickness is set at 50nm-500nm to ensure that light of visible wavelengths is refracted and reflected.

4. A reflective structural color chemical sensor based on a FP three-layer stacking structure according to claim 1, It is characterized in that The material of the selection layer is selected from germanium antimony telluride alloy (GST) and scandium antimony telluride alloy (SST), and the thickness is set between 3nm and 15nm to ensure that light of visible wavelengths is refracted and reflected.

5. A method for preparing a reflective structural color chemical sensor based on a FP three-layer stacking structure according to any one of claims 1 to 4, It is characterized in that The following steps are involved: Step 1: Clean the flat substrate with acetone, alcohol, and deionized water, and blow it dry; Step 2: Using a magnetron sputtering device, a reflective layer is deposited on a planar substrate; Step 3: Mix the material corresponding to the dielectric layer, polydimethylsiloxane, with glue A and glue B in a volume ratio of 10:1; Step 4: Dissolve and dilute the mixed glue with hexane solvent; Step 5: After being fully dissolved, use a coating machine to spin-coat the solution onto a flat substrate on which the dielectric layer is deposited; Step 6: After the spin coating is completed, place it in a drying oven to solidify; Step 7: Use a magnetron sputtering device to deposit a selective layer on the dielectric layer.

6. Application of a reflective structural color chemical sensor based on a FP three-layer stacking structure as described in any one of claims 1 to 4, for detecting different solvents that can dissolve PDMS.

7. The use according to claim 6, It is characterized in that It is more intuitive to use color reactions to distinguish different organic solvents, including alcohol, tetrahydrofuran, acetone, n-hexane, and n-heptane (solvents that can dissolve PDMS).

8. The use according to claim 6, It is characterized in that Distinguish or measure the size of the corresponding solvent that can dissolve PDMS when the solvent that can dissolve PDMS is mixed with the solvent that does not dissolve PDMS.

9. The use according to claim 6, It is characterized in that The ED graph of organic solvent types and concentrations measured using the color recognition function of a mobile phone. The color is determined by the three stimulus values ​​of R, G, and B. In order to better contrast the color difference, the RGB value is converted into a single ED value for comparison. The conversion formula of the ED value is as follows: Where R 0 =250, G 0 =250, B 0 =250, ΔRGB value is the ED value. As can be seen from the figure, the color data of the sensor recognized by the mobile phone are different when immersed in different organic solvents, so various organic solvents can be distinguished according to the ED value.

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