CN104897663A - Thin film sensor for detecting carbon dioxide and application of thin film sensor - Google Patents

Abstract

The application discloses a thin film sensor for carbon dioxide detection, which includes a porous film and an indicator and a carrier complex attached to the pores of the porous film; the indicator can react with hydrogen ions, and when protonated and deprotonated The two states show different colors; the carrier complex contains cations and basic anions, and the cations can be chemically linked with the deprotonated indicator in the solid phase; the basic anions make the pH value in the channel more indicative when there is no contact with carbon dioxide The agent has a high pKa value. The film sensor of the present application is the first to use a porous film as a carrier, and utilizes its large specific surface area to allow carbon dioxide to fully contact with the indicator, improve sensor sensitivity, and reduce response time. The sensor of the present application is simple in structure, easy to use, easy to carry, low in cost, has the advantages of accuracy, speed, resistance to water vapor interference, and reversible response, and can meet the demand for rapid detection of carbon dioxide.

Description

A thin film sensor for carbon dioxide detection and its application

technical field

This application relates to the field of carbon dioxide detection, in particular to a thin film sensor for carbon dioxide detection and its application.

Background technique

Medical carbon dioxide monitoring and environmental carbon dioxide monitoring are two fields where carbon dioxide monitoring is widely used. Among them, medical carbon dioxide monitoring, that is, clinical end-tidal carbon dioxide detection, including end-tidal carbon dioxide detection, inhaled carbon dioxide detection, etc., is one of the important monitoring parameters for critical patients in clinical ICU, OR and other key departments. Environmental carbon dioxide detection includes atmospheric carbon dioxide detection, water carbon dioxide detection, greenhouse vegetable carbon dioxide detection and indoor carbon dioxide detection, etc. Whether it is medical carbon dioxide monitoring or environmental carbon dioxide monitoring, high accuracy and fast response are the keys to carbon dioxide detection.

Existing carbon dioxide detection methods mainly include solution measurement and gas phase measurement. The principle of solution measurement is that carbon dioxide dissolves in water to generate weakly acidic carbonic acid, which causes the pH value of the water to drop, which can be detected by an acid-base pH indicator, and the degree of pH drop is related to the partial pressure and concentration of carbon dioxide Related, therefore, carbon dioxide in solution can be detected by acid-base pH indicators. Acid-base pH indicator is one of the three types of indicators in chemical analysis, which can undergo reversible chemical reactions with hydrogen ions or hydronium ions; the carbonic acid solution formed after carbon dioxide is dissolved in water is hydrogen ions, bicarbonate ions and An equilibrium system of the three ions of the carbonate ion. The existence of a small amount of pH indicator in the solution can cause a visual color change or fluorescence change when the pH value of the solution changes at a specific point, so that the change of the absorption spectrum or emission spectrum can be observed by the naked eye or an instrument, that is, carbon dioxide detection can be realized.

However, for medical and environmental carbon dioxide monitoring, it is very difficult to directly measure carbon dioxide in solution. First of all, the measured carbon dioxide sample must be compressed and pumped into water, which requires a lot of additional equipment, such as catheters, liquid chambers, pumps, etc., which is inconvenient to carry; and there is a risk of liquid overflow in the liquid chamber, and there is also a risk of inhalation during medical use. Secondly, due to the process of bubbling and gas dissolution, the color change usually occurs after the carbon dioxide is pumped into the water for 3-5 seconds; when medical carbon dioxide is detected, the human breathing rate is 16-44 times/min, therefore, Solution monitoring carbon dioxide cannot observe the reversible change of color with respiratory rate in real time, so it is not suitable for clinical use.

In gas phase measurement, non-dispersive infrared spectroscopy (NDIR) is currently a commonly used carbon dioxide detection technology. The principle is that carbon dioxide has an absorption peak in the 2600nm and 4300nm regions, while other components in the air, such as oxygen and nitrogen , carbon monoxide, etc. have no obvious absorption; and, the infrared absorption of carbon dioxide at 2600nm and 4300nm is proportional to the concentration and partial pressure of carbon dioxide; therefore, the change of carbon dioxide concentration can be monitored through the change of infrared absorption spectrum. Non-dispersive infrared spectroscopy technology, if part of the respiratory gas is introduced into the sample chamber of the infrared detector for measurement, the function of carbon dioxide concentration and time can be obtained, that is, the capnogram (capnogram), its peak is at the end of the breath, and the volume content is about 5% ; The characteristic carbon dioxide waveform contained in the capnogram is very valuable clinical information. However, the use of non-dispersive infrared spectroscopy to monitor carbon dioxide requires high equipment requirements. The relevant equipment is expensive, bulky, and is subject to large interference from water vapor, which is prone to high noise and unstable measurement results. Moreover, due to the complex structure and bulky size of the instruments and equipment, it takes a long time to install the monitoring platform for patients during medical carbon dioxide monitoring, which can easily delay the critical timing of monitoring and rescue; therefore, it is not suitable for applications that require rapid carbon dioxide monitoring.

Contents of the invention

The purpose of this application is to provide a new thin film sensor for gas phase detection of carbon dioxide and its application.

The application adopts the following technical solutions:

The application discloses a film sensor for carbon dioxide detection, including a porous film and an indicator and a carrier complex attached to the pores of the porous film; the indicator is capable of reacting with hydrogen ions, and is Chromogenic dyes that exhibit different colors in two states; the carrier complex contains cations and basic anions that can be chemically linked to deprotonated indicators in the solid phase; basic anions are used to balance charges and regulate porosity The pH in the pores of the membrane, such that the pH in the pores of the porous membrane without exposure to carbon dioxide is higher than the pKa value of the indicator.

It should be noted that the key point of this application is to use the characteristics of large specific surface area of the porous film to attach the indicator and the carrier complex in the pores, so that the carbon dioxide can fully contact the indicator, so that the sensor has better sensitivity and higher sensitivity. short response time. It can be understood that the key point of this application is to use the specific surface area of the porous film to increase the contact between carbon dioxide and the indicator; the specific material of the porous film is not specifically limited in this application, such as organic polymer porous membrane, inorganic ceramic porous membrane or mixed Materials such as porous membranes can be used in this application. However, in a preferred embodiment of the present application, a hydrophobic porous film is preferably used. In addition, it can also be understood that the indicator of the present application is actually a conventional display dye that can react with carbon dioxide to produce a color change, such as cresol red, phenol red, neutral red, rhodic acid, bromothymol blue, p- Nitrocresol, m-nitrocresol, alizarin, xylenol blue, thymol blue, bromocresol green, m-cresol purple, bromocresol purple, naphthol purple, phenolphthalein or thymolphthalein, etc., No specific limitation is made here.

When the thin film sensor of the present application is used, there will be water vapor in both breathing gas monitoring and environmental carbon dioxide monitoring. Water vapor forms a water layer in the pores of the film sensor. The solubility of carbon dioxide at room temperature and standard atmospheric pressure is water: the volume ratio of carbon dioxide is 1:0.759. Before reaching saturation, the partial pressure of carbon dioxide in the gas phase increases, and the dissolved in the water film As the concentration of carbon dioxide increases, the hydrogen ions produced by the equilibrium reaction with water increase, and the pH value of the water film decreases, and vice versa. Based on this, the film sensor of the present application adjusts the pH value in the pores of the porous film through the anion of the carrier complex, so that the pH value when not in contact with carbon dioxide is higher than the pKa value of the indicator; Before carbon dioxide, it remains deprotonated and remains connected to the cation. In the presence of carbon dioxide, carbon dioxide dissolves in water to produce carbonate and bicarbonate ions. In the buffer system of the carrier complex, the cation forms a complex with carbonate or bicarbonate to release the indicator. The indicator and Hydrogen ions are combined to be in a protonated state, and the color of the indicator changes from the color of the deprotonated state to the color of the protonated state. It can be understood that as long as the cation can be connected with the deprotonated indicator, and can cooperate with carbonate or bicarbonate in the presence of carbon dioxide to release the indicator; while the anion can balance the charge and adjust the pH value in the pores of the porous film The role; such carrier complexes composed of cations and anions can be used in this application, and are not specifically limited here.

It should be noted that, compared with the non-dispersive infrared spectroscopy technology, an important difference between the thin film sensor of the present application is that the breath gas or the water vapor in the environment not only will not adversely affect the detection, but will be beneficial to the detection; In terms of dispersive infrared spectroscopy technology, due to the interference of water vapor, the water vapor removal part has to be added to perform accurate detection, while the thin film sensor of the present application does not need a water vapor removal device at all. Moreover, the existence of water vapor is unavoidable in the actual detection process, so there is no need to deliberately increase water vapor to form a water layer during detection; in one implementation of the application, dry pure carbon dioxide and dry anhydrous The mixed gas of carbon dioxide and nitrogen is tested, and good detection results can also be obtained.

Preferably, the basic anion adjusts the pH value in the pores of the porous film, so that the pH value in the pores of the porous film is 0-5 pH units higher than the pKa value of the indicator when there is no contact with carbon dioxide. More preferably, the pH is 0.5-2 pH units higher than the pKa.

Preferably, the porous film has open channels, and its pore size is larger than the mean free path of carbon dioxide molecules.

It should be noted that, in order to facilitate the flow and diffusion of carbon dioxide, the porous film of the present application has a pore size larger than the mean free path of carbon dioxide molecules; and the open pores can facilitate the observation of color changes on the other side of the measurement sample, for example, in the patient's In the detection of carbon dioxide in the trachea, the sensor of the present application can not affect the patient's respiration or gas exchange, thereby facilitating the realization of remote measurement.

Preferably, the pore diameter of the porous matrix film is 0.05-100 microns; preferably, the pore diameter of the porous matrix film is 0.1-50 microns.

It should be noted that the dynamic diameter of carbon dioxide molecules is 0.34 nanometers, and the diffusion coefficient of carbon dioxide molecules increases exponentially with the increase of the aperture of the porous film. The pore size of the macroporous membrane is larger than the mean free path of carbon dioxide diffusion, and the mass transfer resistance of carbon dioxide in it is almost negligible; however, if the pore size is too large, the compound uniformity and mechanical strength of the thin film sensor will decrease. Therefore, it is preferable to use a pore size of 0.05 - Porous film of 100 microns, preferably a porous film with a pore size of 0.1-50 microns. It can be understood that the flow or diffusion of carbon dioxide in a porous film with a pore size of less than 0.05 microns will be affected, thereby affecting the sensitivity and response time of the sensor. Therefore, in the case where the sensitivity or response time is not high, the pore size can also be used Porous films smaller than 0.05 microns, even in more secondary applications, may not require porous films with pore sizes larger than the mean free path of carbon dioxide molecules. Likewise, in the case where the mechanical strength of the thin film sensor does not depend on the porous film, for example, where a thin film, sheet or glass plate is additionally provided as a substrate or base, the mechanical strength of the thin film sensor mainly depends on the substrate or base The pore diameter of the porous film can also exceed 100 microns; or in some special applications, when the mechanical strength requirements of the film sensor are relatively low, a porous film with a pore diameter greater than 100 microns can also be used.

Preferably, in the carrier complex, the cation is at least one selected from metal ions, quaternary ammonium ions and phosphonium cations; preferably, the cation is a quaternary ammonium ion. More preferably, the quaternary ammonium ions are tetraalkyl quaternary ammonium ions.

Preferably, in the carrier complex, the basic anion is selected from at least one of halide ion, hydroxide ion, carbonate ion, bicarbonate ion and acetate ion; preferably, the basic anion is hydroxide ion .

It should be noted that the anion of the carrier complex not only plays the role of balancing the charge, but also plays the role of adjusting the pH, so that the pH value of the thin film sensor is higher than the pKa value of the chromogenic dye when it is not exposed to carbon dioxide. Higher values are related to the characteristic groups of the chromogenic dye, the chemical structure of the support complex, and the choice of the porous film. Chromogenic dyes, carrier complexes, and porous films with different pKa values can undergo different color changes in the presence of carbon dioxide, and the response is reversible; that is, when the concentration of carbon dioxide increases, it shows a protonated color, and when the concentration decreases, it shows a detonated color. Protonized color, and can be used repeatedly. The color change and response CO2 sensitivity are determined by the compositional match of the thin-film sensor, which can change color from blue to yellow, violet to yellow, or blue to red. Therefore, in order to achieve a better color rendering effect, the present application further limits the cations and anions of the carrier complex.

Preferably, the porous film is a hydrophobic macroporous film.

It should be noted that the porous film of the present application may be hydrophilic or hydrophobic. The heat of adsorption of water by hydrophobic materials is much smaller than that of hydrophilic materials, which means that the influence of humidity in carbon dioxide on the sensor is minimized, that is, the thin film sensor has a faster response. And the hydrophobic porous film has faster water desorption, which means that the reverse recovery response of the carbon dioxide sensor is significantly improved for the water layer formed by carbon dioxide detection under dry conditions. What's more beneficial is that the hydrophobic material has strong anti-dust, anti-fouling, and anti-bacterial capabilities, which is helpful for the storage and quality assurance of thin-film sensors. Therefore, in a preferred implementation of the present application, a hydrophobic porous matrix film is used. It should also be noted that according to the classification standard of the International Union of Pure and Applied Chemistry (IUPAC) according to the pore size of membrane materials, membrane materials can be divided into microporous, mesoporous and macroporous materials. The pore diameter of the porous material is between 2-50nm, and the pore diameter of the macroporous material is greater than 50nm; therefore, in the preferred solution of the present application, a hydrophobic macroporous film is used, that is, a hydrophobic porous film with a pore diameter greater than 50nm.

Another aspect of the present application discloses a carbon dioxide detection device equipped with the thin film sensor of the present application.

It can be understood that the thin film sensor of the present application can monitor the change of carbon dioxide very intuitively, therefore, it can be installed in various instruments or devices that monitor carbon dioxide through color change or fluorescence change.

Another aspect of the present application discloses a medical endotracheal intubation, in which the film sensor of the present application is installed.

The medical tracheal intubation in this application mainly refers to the tracheal intubation used in the anesthesiology department. During anesthesia, it is usually necessary to place a tracheal intubation in the patient's trachea; using the tracheal intubation equipped with a thin film sensor of the present application, it is easy to determine whether the tracheal intubation has been placed correctly. This is because the thin film sensor of the present application can easily distinguish the carbon dioxide in the exhaled breath and the ambient air, there is only about 0.03% carbon dioxide in the atmosphere, and the end-tidal carbon dioxide content of a normal person is about 5%; If the level of carbon dioxide consistent with the concentration and frequency of exhaled breath is detected, the endotracheal tube is placed correctly; if only persistently low levels of carbon dioxide are detected, the endotracheal tube may have been placed incorrectly in the esophagus and the endotracheal tube needs to be removed and replaced. Reinsert correctly. Furthermore, if it is determined that the endotracheal tube has been properly placed in the patient's trachea, but the concentration of carbon dioxide in the exhaled breath becomes low, this may indicate a problem with perfusion. Continuous exhaled capnography can indicate whether the endotracheal tube has been removed and whether breathing and perfusion are normal.

Another aspect of the present application discloses a food packaging container, in which the film sensor of the present application is arranged.

It should be noted that in environmental testing applications, especially in food packaging environments, aerobic bacteria and anaerobic bacteria can grow with the increase of storage time no matter in air or nitrogen packaging, and the microbial growth process Carbon dioxide will be produced, and the degree of food deterioration can be indicated by monitoring the concentration of carbon dioxide; the thin film sensor of the present application can respond quickly to the carbon dioxide produced by the microbial growth process, therefore, the thin film sensor of the present application is placed in the food packaging container, Before eating, you can visually see the degree of carbon dioxide increase in the food packaging container, so as to judge whether the food in it has deteriorated.

It should also be noted that the food packaging containers used in this application include, but are not limited to, conventionally used food packaging bags, food packaging boxes, and the like.

In order to observe the change of the film sensor directly from the outside of the food packaging container, it is preferred in the present application that the food packaging container is transparent or has at least one transparent window, and the film sensor is arranged in the transparent food packaging container or the transparent window of the food packaging container Inside.

The beneficial effect of this application is:

The film sensor used for carbon dioxide detection of the present application is the first to use porous film as a carrier, and utilizes the characteristics of large specific surface area of the porous film, so that the carrier complexes and indicators filled in the porous film can fully contact with carbon dioxide, thereby improving the performance of the film sensor. sensitivity and reduce response time. The thin film sensor of the present application is simple in structure, easy to use, easy to carry, low in cost, has the advantages of being accurate, fast, visible to the naked eye, resistant to water vapor interference, reversible in response and reusable, and can meet the needs of rapid detection of carbon dioxide.

Description of drawings

Fig. 1 is the principle and roadmap for carbon dioxide detection in the embodiment of the present application, D ^- is the dye of deprotonation, Ct ⁺ is the cation in the carrier complex, An ( ^- ) is the anion in the carrier complex, DH For protonated dyes, due to the structural changes of protonation and deprotonation of dyes caused by the increase and decrease of carbon dioxide concentration, color changes are brought about. The color changes are related to the chemical structure properties and carbon dioxide concentration of the thin film sensor of this application;

Fig. 2 is a thin film sensor for carbon dioxide detection prepared in the embodiment of the present application, and its surface scanning electron microscope photo;

Fig. 3 is the graph of the relationship between the absorption spectrum of the film sensor used for carbon dioxide detection prepared by the embodiment of the present application and the concentration of carbon dioxide contacted, the absorption peak of 620nm in the figure, that is, the curve from top to bottom of the second absorption peak is respectively Test curves with carbon dioxide concentrations of 0%, 0.06%, 0.1%, 0.25%, 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30% and 100%;

Fig. 4 is the linear relationship diagram between the spectral response amplitude and the carbon dioxide concentration of the film sensor for carbon dioxide detection prepared by the embodiment of the present application;

Fig. 5 is a capnogram of the rapid reversible detection of the thin film sensor under the pulse condition of nitrogen and 5% carbon dioxide in the embodiment of the present application;

Fig. 6 is a capnogram of the fast reversible detection of the thin film sensor under the condition of pulse of nitrogen and 5% carbon dioxide in the presence of saturated water vapor in the embodiment of the present application;

Fig. 7 is the graph of the relationship between the absorption spectrum of the thin film sensor used for carbon dioxide detection prepared in another embodiment of the present application and the concentration of carbon dioxide contacted, the absorption peak of 604nm in the figure, that is, the curve of the second absorption peak from top to bottom Test curves for carbon dioxide concentrations of 0%, 0.03%, 0.1%, 0.5%, 1%, 3%, 5%, 10%, 30% and 100%, respectively;

Fig. 8 is a graph showing the relationship between the absorption spectrum of the thin film sensor for carbon dioxide detection prepared in another embodiment of the present application and the concentration of carbon dioxide in contact with, the absorption peak at 580nm in the figure, that is, the curve of the second absorption peak from top to bottom Test curves for carbon dioxide concentrations of 0%, 0.03%, 0.1%, 0.5%, 1%, 3%, 5%, 10%, 30% and 100%, respectively.

Detailed ways

The film sensor of the present application is mainly composed of a porous film and an indicator and carrier complex attached to the pores of the porous film. Among them, the function of the porous film is to provide a porous and loose carrier with a large specific surface area, so that the carbon dioxide can fully contact with the indicator. The material of the porous film can be organic polymer material, inorganic ceramic material or mixed material, and the prepared porous film can be either hydrophilic or hydrophobic. In the preferred solution of the present application, a hydrophobic porous film is used. Specifically, in the implementation of the present application, the hydrophobic porous film is polyethersulfone membrane, polyvinylidene fluoride membrane, polyamide membrane, polytetrafluoroethylene membrane, polypropylene membrane, polystyrene membrane, nylon 6, nylon 66 or silicon oxide film. Hydrophobic porous films can also be modified or prepared by chemically grafting hydrophobic groups or by physically encapsulating hydrophobic particles. Hydrophobic particles need to be monodisperse, have uniform nanometer size and pore size, stable chemical properties, and high mechanical strength, including but not limited to monodisperse porous silica microspheres, monodisperse porous carbon spheres, and monodisperse zirconia microspheres. The spheres are preferably monodisperse porous silica microspheres.

The indicator of the present application is a commonly used acid-base indicator, or pH indicator, which is a weakly acidic natural color-developing dye that can react with hydrogen ions to produce a color change. Every acidic compound has a different value for the acid dissociation constant, pKa, which is a quantitative measure of the acid strength of that compound in solution. The acid-base indicating dye shows the color of the deprotonated form when the pH value is greater than the pKa value, and the color of the protonated form when the pH value is less than the pKa value. There are many such pH indicators, including but not limited to cresol red, phenol red, neutral red, bromocresol purple, bromothymol blue, p-nitrocresol, m-nitrocresol, alizarin, dimethyl Phenol Blue, Thymol Blue, Bromocresol Green, Meta-Cresol Violet, Naphthol Violet, Phenolphthalein, Rosebic Acid, Thymolphthalein. Their mutual combination will also produce more adjustable pKa values and discoloration ranges, which can be used in this application and are not specifically limited here. In the examples of the present application, thymol blue, m-cresol violet, and mixed chromogenic dyes of thymol blue and phenol red are used as indicators; , such as cresol red, phenol red, etc., the principle of color development is the same as that of thymol blue and m-cresol violet, so they can also be used in this application.

The main function of the carrier complex is to provide a buffer environment for the protonation and deprotonation of the indicator. In the solid phase, the cation of the carrier complex is chemically linked with the deprotonated indicator, and the anion balances the charge, adjusts the pH value of the whole system, and keeps the indicator in a deprotonated state. Until carbon dioxide exists, carbonate and bicarbonate ions coordinate with cations, and the released deprotonated indicator reacts with hydrogen ions, and the indicator shows a protonated state. It can be considered that the cations in the carrier complex play a role in promoting the transfer of carbon dioxide in the gas phase to the solid phase porous film substrate attached with the indicator.

In addition, in a preparation method of the film sensor of the present application, it is specifically adopted that the indicator and the carrier complex are dispersed in a solvent, and then the porous matrix film is soaked in the solvent, so that the indicator and the carrier complex naturally Adsorbed on the surface of the inner wall of the pores of the porous matrix film; it can be understood that the thin film sensor prepared in this way may also contain some residual solvents, or other additives that are conducive to dispersion or adsorption, as long as these solvents or additives do not interfere with the thin film sensor. The pH value of the surface may not affect the color response of carbon dioxide, and is not specifically limited here. Taking the examples of this application as an illustration, the solvent can be colorless, transparent, and neutral, such as methanol, ethanol, ethylene glycol, propylene glycol, glycerol, diethylene glycol, triethylene glycol, polyethylene glycol, toluene , cyclohexane, or a combination thereof; additives mainly include thickeners, viscosifiers or plasticizers, such as acrylate, polyacrylate, methylcellulose, ethylcellulose, hydroxyethylcellulose, polyurethane , silica, tributyl phosphate, bis(2-ethylhexyl) phthalate, dioctyl phthalate, diethyl phthalate, diisodecyl phthalate, or its combination.

It can be understood that, as a new carbon dioxide detection sensor with high sensitivity and rapid response, the thin film sensor of the present application can not only be used for the aforementioned medical carbon dioxide monitoring and environmental carbon dioxide monitoring, but also for any occasions that require rapid and sensitive detection of carbon dioxide can be used. Moreover, the thin film sensor of the present application is simple in structure, easy to use, can be used alone, and can quickly and intuitively observe changes in carbon dioxide concentration; it can also be used as a part of other carbon dioxide monitoring devices, or installed in other instruments and equipment as a carbon dioxide detection device. part.

The present application will be described in further detail below through specific examples. The following examples only further illustrate the present application, and should not be construed as limiting the present application.

Embodiment one

In this example, thymol blue is used as the indicator, the cation of the carrier complex is quaternary ammonium ion, the anion is hydroxide ion, and the porous film is nylon 6 material. The specific preparation is as follows:

Dissolve 5.0g of tetraoctylammonium bromide and 0.74g of hexadecyltrimethylammonium bromide in methanol into a 15ml solution, put it into a 50ml flask, and slowly add 1.82g of silver oxide under vigorous stirring powder. Vigorously stirred at room temperature for one hour and then filtered to obtain a methanol solution of mixed alkylammonium hydroxides, which was colorless or pale yellow. Dissolve 0.02g of thymol blue solid powder in 2ml, 0.7mol/L methanol buffer solution of mixed alkylammonium hydroxide, shake slightly to fully dissolve the solid, and the solution is dark blue at this time. In another flask, 5ml of toluene was added, and 1g of ethyl cellulose powder was slowly added to the flask under vigorous stirring to make it fully dissolved, and then 1g of monodisperse porous silica microspheres were added to obtain ethyl cellulose oxidation Methanol solution of silicon microspheres. After mixing 1.5ml of the above-mentioned thymol blue methanol buffer solution and 2.5ml of methanol solution of ethylcellulose silica microspheres, 0.5ml of tributyl phosphate and 7ml of toluene were added thereto to form an indicator formula solution.

Place a square hydrophobic porous membrane matrix material with a side length of 2cm horizontally on a square glass plate with a side length of 5cm, then add 2ml of the indicator formula solution dropwise to the center of the porous membrane material, and after the solution is automatically covered with the membrane material, infiltrate After 90 seconds, the excess solution was sucked dry, and after 2 hours of natural drying, the thin film sensor for carbon dioxide detection of this example was obtained.

The prepared thin film sensor for carbon dioxide detection was subjected to topographic electron microscope inspection, and the results are shown in Figure 2. It can be seen that the thin film sensor prepared in this example has a continuous open pore structure with a pore size ranging from 0.2 to 1.2 microns.

The surface of the thin-film sensor had a pH of 9.3 without exposure to carbon dioxide, about 0.5 pH units above the pKa of 8.8 for the chromogenic dye.

When the film sensor prepared in this example is placed under the airflow of exhaled air from the human body, the color change from blue to yellow can be seen with the naked eye, while under the airflow of inhaled air, the color change from yellow to blue can be seen with the naked eye; the thin film prepared in this example can be seen The sensor can quickly detect changes in carbon dioxide levels. The principle and roadmap of the thin film sensor detecting carbon dioxide when the human body breathes are shown in Figure 1, where D ^- is a deprotonated dye, Ct ⁺ is the cation in the carrier complex, and An( ^- ) is the cation in the carrier complex Anion, DH is a protonated dye, because the concentration of carbon dioxide is high when exhaled, and the concentration of carbon dioxide is low when inhaled, the increase and decrease of carbon dioxide concentration will cause the structural change of protonation and deprotonation of the dye, resulting in color change.

Experiment 1 Determination of Optical Response of Thin Film Sensors to Carbon Dioxide

A Shimadzu UV-2600 ultraviolet-visible spectrophotometer was used to measure the spectrum of the thin film sensor prepared in this example. Firstly, the porous matrix film and the thin film sensor are cut into a suitable size that can be put into the cuvette; the ultraviolet test wavelength range of the spectrophotometer is set to 350nm-750nm, and the data collection interval is 1nm, and the two pieces are cut A good porous matrix film is placed vertically into two cuvettes respectively, and then the cuvettes are placed on the cuvette slots for testing to obtain baseline data. Subsequently, take out a cuvette, take out the porous matrix film, put the cut thin film sensor vertically, and blow into the cuvette containing 0.06% _CO Nitrogen gas, seal it with the cuvette cover, Put it into the card slot for testing and get a set of UV data. Repeat the above experimental steps and change the concentration of _CO2 gas in the blown nitrogen, respectively 0%, 0.06%, 0.1%, 0.25%, 0.5%, 1%, 2%, 3%, 4%, 5%, 10% , 20%, 30% and 100%, respectively to obtain the ultraviolet test data under different carbon dioxide gas concentrations.

All the data are comprehensively arranged to obtain the spectrum shown in Figure 3, which is the relationship between the absorption spectrum and the concentration of carbon dioxide in contact. It can be seen from the spectrum that the thin film sensor prepared in this example, with the increase of the _CO gas concentration, its The absorption peak at 620nm gradually decreases, and the absorption peak at 435nm gradually increases, and the position of the absorption peak shifts from 620nm to 435nm, which shows that the response of the thin film sensor prepared in this example to the _CO2 gas concentration can be read by a spectrometer.

Experiment 2 Regression fitting of carbon dioxide detection signal

According to the absorption spectrum data of the thin film sensor at 620nm, calculate the ratio R between the realized absorption spectrum change range and the unrealized absorption spectrum change range of the thin film sensor when the carbon dioxide concentration is x%, as shown in formula 1. in is the absorption spectrum value at 620nm of the carbon dioxide detection porous sensor film when the carbon dioxide concentration is 0, When the carbon dioxide concentration is x%, the carbon dioxide detection porous sensor film absorbs the spectrum value at 620nm, The absorption spectrum value of the porous sensor film at 620nm is measured for carbon dioxide when the concentration of carbon dioxide is 100%.

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Abs</span>}}_{{\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \%</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Abs</span>}}_{{\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \%</span>}}{{\mathrm{<span\; class="notranslate">\; Abs</span>}}_{{\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; \%</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Abs</span>}}_{{\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 100</span>}<span\; class="notranslate">\; \%</span>}}$

Between 0.03% of the inhaled air and 5% of the exhaled air of the human body, the R calculated by the ultraviolet-visible spectrophotometer series spectrum is plotted against the carbon dioxide concentration, and Figure 4 is obtained, which is the linear relationship between the spectral response range and the exposed carbon dioxide concentration; It can be seen that within the range of respiratory gas carbon dioxide concentration, the ratio R between the realized and unrealized absorption spectrum change range has a linear relationship with the carbon dioxide concentration, and the coefficient of determination r ² of the regression is 99.58%.

Experiment 3 Response change of thin-film sensor under dry simulated breathing pulse carbon dioxide flow

Cut the porous matrix film for preparing the thin film sensor and the thin film sensor into a suitable size that can be placed in the cuvette, and put the two cut porous matrix films vertically into the cuvette. Set the UV test wavelength to 620nm, and the data collection time to 100s. Place two cuvettes both equipped with porous matrix films on the cuvette slots for UV testing to obtain baseline data. Take out the porous matrix film in a cuvette, put the cut film sensor vertically, and then place the cuvette on the cuvette slot. The gas mass flowmeter is used to realize the alternate pulse change between 5% CO ₂ plus 95% N ₂ balance gas and 0% CO ₂ plus 100% N ₂ balance gas, the used 5% CO ₂ plus 95% N ₂ balance gas The pulse time is 5s, the pulse time of 0% _CO2 plus 100% _N2 balance gas is 5s, the two gases are continuous but uninterrupted, and the total pulse time is 100s. Under the condition of this pulse sequence, the pulse gas is blown into the cuvette, and the ultraviolet test is carried out on the thin film sensor, and the data collection interval is 100ms. Fit the UV data obtained from the test according to the formula of Experiment 2, and calculate the concentration of _CO2 through the UV data, so as to obtain the concentration of _CO2 measured by the thin film sensor over time under the condition of pulsed 5% _CO2 , namely The capnogram is shown in Figure 5; it can be seen that the peak value of the thin film sensor prepared in this example is on a horizontal line in the test of all pulses of 5% _CO2 gas, and the holding time is basically equal to the pulse duration. Fully reversible with no loss of accuracy during round-robin testing. The response time to the simulated exhaled CO ₂ is less than 0.5s, and the recovery time is less than 1s, which proves that its detection speed is very fast and meets the needs of rapid detection such as respiratory gas detection.

Experiment 4 Response change of film sensor under humid simulated breathing pulse carbon dioxide flow

Use a gas mass flow meter to achieve 5% _CO2 plus 95% _N2 balance gas, and 0% _CO2 plus 100% _N2 balance gas, alternate pulse changes between the two, and bubble through distilled water at 25 ° C, the rest Same as Trial 3. The capnogram measured under the condition of saturated water vapor is shown in Figure 6; it can be seen that in saturated water vapor, its detection ability is not affected by water vapor, which proves that the film sensor has a high tolerance to water vapor , in the presence of water vapor without any special treatment, very suitable for the monitoring of respiratory gas. It should be noted that, on the one hand, the thin-film sensor of this application adopts a hydrophobic film, which can realize fast reversible recovery and effectively improve the ability to resist water vapor interference; on the other hand, this application detects the absorption spectrum of the indicator in the ultraviolet-visible light range changes, while water vapor is transparent and has no absorption in the visible-ultraviolet region; in contrast, for traditional non-dispersive infrared spectroscopy techniques, water vapor has strong and messy absorption in the infrared region to interfere with the measurement; therefore, the thin film sensor of the present application Has a strong ability to resist water vapor interference.

Test 5 endotracheal intubation

One end of the endotracheal tube was inserted into the airway of the patient, and the other end was installed with the thin film sensor prepared in this example. In use, if the endotracheal tube is placed correctly, as the patient breathes, a blue to yellow color change is visible to the naked eye when exhaling, and a yellow to blue color change is visible to the naked eye when inhaling; if the endotracheal tube is not placed correctly Into the trachea, the aforementioned color change will not occur; or, if the endotracheal tube is displaced midway, the above color change will be terminated accordingly.

Test 6 food packaging bags

Install the film sensor prepared in this example into an opaque food packaging bag with a transparent window, and the film sensor is pasted in the transparent window. At the same time, after the LB solid medium was inoculated with a small amount of common food bacteria, it was packaged into a food packaging bag pasted with a film sensor; it was placed in an incubator to observe and record the color change of the film sensor every 24 hours.

The results showed that with the growth of microorganisms, the color of the thin-film sensor gradually changed from blue to yellow, and the thin-film sensor completely turned yellow after 3 days; it can be seen that the microorganisms grew rapidly in the sealed food packaging bags and produced a large amount of carbon dioxide. However, the thin film sensor of the present application can reflect the growth of microorganisms in the sealed packaging bag in real time; accordingly, it can be judged whether the food in the sealed food packaging bag is polluted or deteriorated by bacteria.

Embodiment two

In this example, m-cresol violet is used as the indicator, the cation of the carrier complex is quaternary ammonium ion, the anion is hydroxide ion, and the porous matrix film is nylon 6 material. The specific preparation is as follows:

Dissolve 5.74g of dodecyltrimethylammonium bromide with methanol to a solution of 15ml, put it into a 50ml flask, and add 1.82g of silver oxide powder under vigorous stirring. Stir at room temperature for one hour and then filter to obtain a methanol solution of dodecyltrimethylammonium hydroxide, which is colorless or light yellow. Dissolve 0.02g m-cresyl violet solid powder in 2ml, 0.7mol/L methanol solution of dodecyltrimethylammonium hydroxide, shake slightly to fully dissolve the solid, and the solution is now purple. In another flask, 5ml of toluene was added, and 1g of ethyl cellulose powder was slowly added to the flask under vigorous stirring to make it fully dissolved, and then 1g of monodisperse porous silica microspheres were added to obtain ethyl cellulose oxidation Methanol solution of silicon microspheres. After mixing 1.5ml of the above m-cresyl violet methanol buffer solution and 2.5ml of methanol solution of ethylcellulose silica microspheres, add 0.5ml of tributyl phosphate and 7ml of toluene to it to form an indicator formula solution. The remaining steps are the same as in Embodiment 1.

The surface electron microscope inspection of the prepared thin film sensor shows that the thin film sensor prepared in this example has a continuous open pore structure with a pore size ranging from 0.2 to 1.2 microns.

The surface of the thin-film sensor had a pH of 9.0 without exposure to carbon dioxide, 0.7 pH units above the pKa of the chromogenic dye of 8.3.

When the film sensor prepared in this example is placed under the air flow of exhalation, the color change from purple to yellow can be seen with the naked eye. When the film is removed from the air flow of exhalation or inhalation, the color change from yellow to purple can be seen with the naked eye; The sensor can quickly detect changes in carbon dioxide levels.

In addition, a Shimadzu UV-2600 ultraviolet-visible spectrophotometer is also used to measure the spectrum of the thin film sensor prepared in this example. Test procedure is identical with the test 1 of embodiment one, obtains _CO When the concentration of gas is 0.00%, 0.03%, 0.1%, 0.5%, 1%, 3%, 5%, 10%, 30% and 100% respectively, The absorption spectrum data of the thin film sensor of this example is shown in Figure 7; it can be seen that the thin film sensor prepared in this example, with the increase of _CO2 gas concentration, its absorption peak at 604nm gradually decreases, and its absorption peak at 440nm gradually decreases. Increased, the position of the absorption peak shifted from 604nm to 440nm. Compared with the thin film sensor prepared in Example 1, the absorption of the thin film sensor in this example has a blue shift, which proves that the porous sensor thin film of the present application can change the chemical structure according to the requirements, and realize the change of different colors.

Embodiment Three

In this example, thymol blue and phenol red were used as indicators, quaternary ammonium ions were used as cations of the carrier complex, hydroxide ions were used as anions, and nylon 6 material was used for the porous matrix film. The specific preparation is as follows:

Dissolve 5.74g of tetraoctylammonium bromide with methanol to a solution of 15ml, put it into a 50ml flask, and add 1.82g of silver oxide powder under vigorous stirring. Stir at room temperature for one hour and then filter to obtain tetraoctyl ammonium hydroxide methanol solution, which is colorless or light yellow. Dissolve the solid powder of 0.01g thymol blue and 0.01g phenol red in 2ml, 0.7mol/L methanol solution of tetraoctyl ammonium hydroxide, and shake slightly to fully dissolve the solid. At this time, the solution is blue-purple. That is, the indicator methanol buffer solution. In another flask, 5ml of toluene was added, and 1g of ethyl cellulose powder was slowly added to the flask under vigorous stirring to make it fully dissolved, and then 1g of monodisperse porous silica microspheres were added to obtain ethyl cellulose oxidation Methanol solution of silicon microspheres. After mixing 1.5ml of the methanol buffer solution of the above-mentioned indicator and 2.5ml of the methanol solution of ethylcellulose silica microspheres, add 0.5ml of tributyl phosphate and 7ml of toluene to it to form an indicator formula solution. The remaining steps are the same as in Embodiment 1.

The surface electron microscope inspection of the prepared thin film sensor shows that the thin film sensor prepared in this example has a continuous open pore structure with a pore size ranging from 0.2 to 1.2 microns.

The surface of the thin film sensor had a pH of 9.1 without exposure to carbon dioxide, about 1 pH unit higher than the pKa of 8.1 for the chromogenic dye.

When the thin film sensor prepared in this example is placed under a gas flow composed of 10% carbon dioxide and 90% nitrogen balance gas, the color change from blue to yellow can be seen with the naked eye, and the color change from yellow to blue can be seen with the naked eye when the gas flow stops.

Similarly, a Shimadzu UV-2600 ultraviolet-visible spectrophotometer is used to measure the spectrum of the thin film sensor prepared in this example. Test procedure is identical with the test 1 of embodiment one, obtains _CO When the concentration of gas is 0.00%, 0.03%, 0.1%, 0.5%, 1%, 3%, 5%, 10%, 30% and 100% respectively, The absorption spectrum data of the thin-film sensor of this example is shown in Figure 8; it can be seen that the thin-film sensor prepared in this example, with the increase of _CO gas concentration, its absorption peak at 580nm gradually decreases, and its absorption peak at 435nm gradually decreases. increase, the position of the absorption peak shifts from 580nm to 435nm, compared to the thin film sensor made in Example 1, its response sensitivity to carbon dioxide changes from <0.06% to ~1%, which proves that the porous sensor of the present invention The chemical structure of the thin film can be changed according to the needs, so as to realize the carbon dioxide response of the porous sensor thin film with different sensitivities.

On the basis of the above examples, the present application has further studied different carrier complexes. Specifically, metal ions and phosphonium positive ions are used to replace quaternary ammonium ions as the cations of the carrier complexes; Hydroxide ions, bicarbonate ions and acetate ions were used as the anions of the carrier complexes in place of the hydroxide ions. Essentially, these carrier complexes with positive onium ions or alkali metal ions have the functions of reducing the Coulomb interaction between cations and indicator active anions, and solubilizing and stabilizing reactive ion pairs in polar proton environments; The decoulombic force and solubilization stabilization are related to the size and charge density of the carrier complex cations. Therefore, according to the above-mentioned matching principle of surface pH and indicator pKa, according to the required response sensitivity, or response time, or response color change, or parameters such as quality assurance requirements, an appropriate carrier complex anion and cation pair can be selected; in general, The cation needs to be able to chemically connect with the deprotonated indicator in the solid phase, and has a phase transfer effect, which can transfer carbon dioxide in the gas phase to the solid phase of the composite acid-base indicator, while the anion is mainly to balance the charge and adjust pH effect. According to the above principles, the application respectively adopts typical sodium carbonate, sodium bicarbonate, sodium acetate, potassium chloride, and tetrabutylphosphonium hydroxide as carrier complexes; the test results show that m-cresyl violet and carbonic acid Sodium is compounded on porous polypropylene, which can realize the reciprocating change from purple to yellow under simulated gas, where sodium carbonate can be replaced by sodium bicarbonate, sodium acetate, potassium chloride; cresol red + bromothymol blue and sodium carbonate Compounded on porous nylon 6, it can realize the reciprocating change from bright blue to bright yellow under simulated gas, in which sodium carbonate can be replaced by sodium bicarbonate, sodium acetate, potassium chloride; thymol blue and tetrabutylphosphine hydroxide Onium compounded on porous nylon 6 can realize the reciprocating change from blue to yellow under simulated gas.

The above content is a further detailed description of the present application in conjunction with specific implementation modes, and it cannot be considered that the specific implementation of the present application is limited to these descriptions. For those of ordinary skill in the technical field to which this application belongs, some simple deduction or substitutions can be made without departing from the concept of this application, which should be deemed to belong to the protection scope of this application.

Claims (10)

1. A film sensor for carbon dioxide detection, characterized in that: comprise a porous film and an indicator and a carrier complex attached to the pores of the porous film; The indicator is a chromogenic dye capable of reacting with hydrogen ions and exhibiting different colors in the protonated and deprotonated states; The carrier complex contains cations and basic anions, and the cations can be chemically linked to the deprotonated indicator in the solid phase; The basic anion makes the pH value in the pores of the porous film higher than the pKa value of the indicator when there is no contact with carbon dioxide. 2. The film sensor according to claim 1, characterized in that: the porous film has open channels, and its pore size is larger than the mean free path of carbon dioxide molecules. 3. The film sensor according to claim 2, characterized in that: the porous film has a pore diameter of 0.05-100 microns; preferably, the porous film has a pore diameter of 0.1-50 microns. 4. The film sensor according to claim 1, characterized in that: in the carrier complex, the cation is selected from at least one of metal ions, quaternary ammonium ions and phosphonium positive ions; preferably, the cation is a quaternary ammonium ion ; Preferably, the quaternary ammonium ions are tetraalkyl quaternary ammonium ions. 5. The film sensor according to claim 1, characterized in that: in the carrier complex, the basic anions are selected from the group consisting of halide ions, hydroxide ions, carbonate ions, bicarbonate ions and acetate ions. At least one; preferably, the basic anion is hydroxide ion. 6. The film sensor according to any one of claims 1-5, characterized in that: the porous film is a hydrophobic macroporous film. 7. A carbon dioxide detection device equipped with the thin film sensor according to any one of claims 1-6. 8. A medical endotracheal tube, wherein the film sensor according to any one of claims 1-6 is arranged in the endotracheal tube. 9. A food packaging container, characterized in that the film sensor according to any one of claims 1-6 is arranged in the food packaging container. 10. The food packaging container according to claim 9, characterized in that: the food packaging container is transparent or has at least one transparent window, and the film sensor is arranged in the transparent food packaging container or the transparent window of the food packaging container. inside the window.