A CNC amino acid film, preparation method and application thereof in aldehyde-based VOCs detection

Abstract

The present invention belongs to the technical field of organic volatile gas detection, and relates to a CNC amino acid membrane, a preparation method and its application in the detection of aldehyde-based VOCs. In view of the technical problem that the sensitive membrane used for VOCs detection in the prior art has response selectivity, low responsiveness and sensitivity to aldehyde-based organic volatile gases, and low resolution of the detection sensor, the present application provides a method for preparing a CNC amino acid membrane. The amino group of the prepared sensitive membrane can react with the aldehyde group to produce a Schiff base reaction, and can detect concentrations as low as 0.08 mg / m 3 The present application also provides an application of a CNC amino acid membrane. The sensitive membrane is used for aldehyde-based VOCs gases, which can produce a specific response and has high selectivity. The response efficiency to formaldehyde and acetaldehyde is as high as 21.7 and 12.7 nm / (1 mg / m 3 ), achieving color resolution discernible to the naked eye.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic volatile gas detection, and in particular, relates to a CNC amino acid film, a preparation method and application thereof in aldehyde-based VOCs detection. Background Art

[0002] Since the 21st century, mankind has entered a new era of environmental governance and sustainable development of ecological civilization. With the increasing number of laws on the atmospheric environment in various countries, people's attention to air quality has gradually increased, and volatile organic compounds (VOCs) have attracted widespread attention from all walks of life. VOCs released into the air will participate in atmospheric photochemical reactions to produce harmful substances. They are important precursors of ozone and secondary organic particulate matter (such as PM2.5), and are also one of the potential causes of environmental pollution such as photochemical smog and haze. In particular, aldehyde-based VOCs have more seriously aggravated the degree of indoor air pollution, causing damage to human nerves and organs, and inducing systemic diseases. The Ministry of Environmental Protection has identified it as one of the largest pollutants other than particulate matter. Therefore, how to effectively control and manage aldehyde-based VOCs has become the focus of research for many scholars. Among them, the detection of these pollutants, as an important basic link, has always been a hot and difficult issue in indoor environmental testing. At present, the detection of aldehyde VOCs is still mostly done by laboratory methods, that is, the gas in the space to be tested is first collected through methods such as climate chamber method and laboratory small space release method, and then sent to the laboratory for professional analysis through gas, liquid or a combination of both methods. Although these traditional detection methods are relatively mature, with high sensitivity and good selectivity, they have many restrictions or poor anti-interference, cannot reflect the VOCs content level of the gas to be tested in real time, and are complex to operate, have high analysis requirements, and are not easy to popularize.

[0003] VOCs real-time detection technology and system based on sensors and the Internet of Things is a new field of rapid development in indoor VOCs detection science in recent years because of its advantages such as real-time, sensitive, remote monitoring and early warning, and intelligence. The sensing device of this system is the VOCs sensor, of which the core component is the sensitive membrane. The Chinese invention patent application publication number CN104198401A, the application date is September 15, 2014, and the name is: Preparation of alcohol-responsive cellulose photonic crystal membrane. The disclosed method combines cellulose and photonic crystal technology to prepare a responsive optical material, namely cellulose photonic crystal (CPCF), and uses it for the detection of alcohols. Compared with traditional gel materials, cellulose has excellent biodegradability and good optical properties, and is an environmentally friendly material. However, the material in this scheme only responds to ethanol with a color change. Another example is the Chinese invention patent application publication number CN106353257A, the application date is July 17, 2015, and the name is: Visual detection of volatile aldehydes by amino-functionalized photonic crystal film sensor. The disclosed method modifies the amino group on the inverse opal photonic crystal film by spin coating a polymer containing amino groups or by chemical bonding, and utilizes the reversible reaction of amino groups with aldehyde groups and the three-dimensional macroporous structure of the inverse opal photonic crystal. Through the reversible chemical and physical action of the sensing film on the volatile aldehyde gas, the average refractive index of the sensing film is changed, so that the reflection spectrum moves and the appropriate photonic crystal is selected to move the reflection spectrum within the visible light range, which eventually causes the color of the film to change, and realizes highly sensitive and reversible visual detection of volatile aldehyde gas. However, most of the current sensitive films have the disadvantage that the response selectivity and sensitivity cannot be achieved at the same time, which affects the resolution of the sensor. Therefore, finding a sensitive film material with specific functional groups and rich binding sites has become an effective way to solve the low resolution of VOCs sensors. Summary of the invention

[0004] 1. Technical problem to be solved by the invention

[0005] In view of the technical problem that the sensitive membrane used for VOCs detection in the prior art has response selectivity, low response and sensitivity to aldehyde-based organic volatile gases, and low resolution of the detection sensor, the present application provides a method for preparing a CNC amino acid membrane. The amino group of the prepared sensitive membrane can react with the aldehyde group to produce a Schiff base reaction, and the concentration can be detected as low as 0.08 mg / m 3 The present application also provides an application of a CNC amino acid membrane. The sensitive membrane is used for aldehyde-based VOCs gases, which can produce a specific response and has high selectivity. The response efficiency to formaldehyde and acetaldehyde is as high as 21.7 and 12.7 nm / (1 mg / m 3 ), achieving color resolution discernible to the naked eye.

[0006] 2. Technical solution

[0007] In order to achieve the above purpose, the technical solution provided is:

[0008] A method for preparing a CNC amino acid film of the present invention comprises the following steps:

[0009] The steps of preparing the CNC amino acid composite colloid are as follows: amino acid, sulfuric acid and cellulose nanocrystal colloid are mixed in a mass ratio of (2-8):(0.02-0.1):10 to obtain the CNC amino acid composite colloid;

[0010] The step of preparing the CNC amino acid film is as follows: evaporating the CNC amino acid composite colloid to induce self-assembly to obtain the CNC amino acid film.

[0011] Cellulose nanocrystals (CNC) prepared by sulfuric acid hydrolysis have negative charges on the surface of sulfonic acid groups. At a certain concentration, they can form a chiral nematic ordered liquid crystal phase between liquid and crystalline states. CNC rainbow films with chiral nematic helical structures can be prepared by evaporation-induced self-assembly (EISA). The color of the film can be controlled according to the size of the pitch structure. Therefore, the structural color of CNC chiral nematic organization can be used to prepare optically sensitive film materials for special responses. On the other hand, CNC surface contains a large number of hydroxyl groups, which can react with other substances to undergo oxidation, esterification, etherification, graft copolymerization, etc. It is easy to modify CNC to introduce other functional groups. In addition, CNC has a high specific surface area and a multi-level pore structure, which can provide channels and abundant binding sites for gas response. Amino acids are organic compounds containing two functional groups, amino and carboxyl. Due to their inherent chiral properties and easily modifiable groups, they have attracted much attention in the field of biosensing. The present invention applies the chirality of CNC and the functional group advantages of amino acids to the response of aldehyde-based VOCs, improves the resolution of aldehyde-based VOCs sensors, and expands the application scope of CNC and amino acid biomass materials.

[0012] Furthermore, the amino acid includes one or more of glycine, alanine, glutamic acid, tyrosine, glutamine or aspartic acid.

[0013] Furthermore, the concentration of the sulfuric acid is 90-98wt%.

[0014] Furthermore, the cellulose nanocrystal colloid is prepared by the following steps: weighing cellulose nanocrystals and 64% sulfuric acid aqueous solution at a mass ratio of 8 to 12:1, mixing, diluting, centrifuging, dialyzing to a neutral pH value, and ultrasonically crushing to obtain the cellulose nanocrystal colloid.

[0015] Furthermore, the temperature of the evaporation-induced self-assembly is 25°C.

[0016] Furthermore, 3 to 5 mL of the CNC amino acid composite colloid is poured into a polystyrene culture dish with a diameter of 3.5 to 5.0 cm to induce self-assembly by evaporation.

[0017] Furthermore, after the amino acid, sulfuric acid and cellulose nanocrystal colloid are uniformly mixed, the mixture is stirred at 70-80° C. for 2-3 h, centrifuged for 3-4 times, and ultrasonicated for 5-20 min.

[0018] Preferably, the ultrasonic power is 200-500W.

[0019] A CNC amino acid film is prepared using the method described.

[0020] The invention discloses an application of a CNC amino acid membrane, and applies the CNC amino acid membrane to the detection of aldehyde-based VOCs.

[0021] Furthermore, the aldehyde VOCs are formaldehyde or acetaldehyde.

[0022] Preferably, the concentration of formaldehyde or acetaldehyde is ≥ 0.08 mg / m 3 .

[0023] 3. Beneficial effects

[0024] Compared with the existing known technology, the technical solution provided by the present invention has the following beneficial effects:

[0025] (1) A method for preparing a CNC amino acid film of the present invention comprises first mixing amino acids, sulfuric acid and cellulose nanocrystal colloids in a mass ratio of (2-8):(0.02-0.1):10 to prepare a CNC amino acid composite colloid, and then evaporating the CNC amino acid composite colloid to induce self-assembly to obtain a CNC amino acid film. The present invention utilizes the chiral nematic liquid crystal structure of cellulose nanocrystal colloid and the carboxyl and amino functional group structures of amino acids through hydroxyl and carboxyl esterification reactions to prepare a CNC amino acid film. The amino groups carried by the film react with the aldehyde groups carried by aldehyde-based VOCs to produce Schiff bases, which can specifically respond to aldehyde-based VOCs gases and have high selectivity. The response efficiencies to formaldehyde and acetaldehyde are as high as 21.7 and 12.7 nm / (1 mg / m 3 ), which is much higher than the response efficiency to methanol and ethanol, and reaches the resolution of color recognition by the naked eye.

[0026] (2) A CNC amino acid membrane of the present invention can detect concentrations as low as 0.08 mg / m 3 It has excellent sensitivity in detecting aldehyde-based VOCs gases. It also has certain detection performance for alcohol-based VOCs gases.

[0027] (3) Compared with ordinary aldehyde-based VOCs sensors, the aldehyde-based VOCs sensor prepared from the CNC amino acid film of the present invention does not require a capacitor or resistor system and can simply and directly reflect the concentration of aldehyde-based VOCs in the environment by observing the color of the CNC amino acid film, thus having the advantages of real-time and convenient detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 UV-Vis spectrum of CNC amino acid film.

[0029] Figure 2 This is a graph showing the wavelength response capability of the CNC amino acid film prepared in Example 4 when used for formaldehyde, acetaldehyde, methanol and ethanol gas detection.

[0030] Figure 3 This is a diagram showing the color change when the CNC amino acid film prepared in Example 4 is used for formaldehyde, acetaldehyde, methanol and ethanol gas detection. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with specific embodiments.

[0032] The technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] A method for preparing a responsive sensitive membrane for highly selective and sensitive detection of aldehyde-based VOCs comprises the following steps: adding a certain amount of amino acids to cellulose nanocrystal colloid, performing an esterification reaction, obtaining a CNC amino acid composite colloid, and then drying the CNC amino acid composite colloid through evaporation-induced self-assembly (EISA) to form a CNC amino acid membrane; placing the colorful CNC amino acid membrane in an environment of aldehyde-based VOCs gas with different concentrations; the color of the membrane responds to changes in the gas concentration, thereby achieving visual detection.

[0034] The performance of the sensitive film (CNC amino acid film) prepared in each embodiment or comparative example of the present invention is judged by the response efficiency. The response efficiency refers to the maximum reflection wavelength difference divided by the concentration difference of the detected gas [unit: nm / (1 mg / m 3 VOCs)], the higher the ratio, the higher the efficiency, the greater the difference in color change, and the easier it is to distinguish with the naked eye.

[0035] Example 1 (CNC / Gly20, amino acid: cellulose nanocrystal colloid is 2:10)

[0036] A method for preparing a CNC amino acid film in this embodiment comprises the following steps:

[0037] (1) Technical solution of the present invention:

[0038] The specific preparation method is as follows:

[0039] (1) Weigh cellulose nanocrystals and 64% sulfuric acid aqueous solution at an acid-to-slurry ratio (mass ratio) of 8 to 12:1, mix them thoroughly, dilute, centrifuge, and dialyze the above acid hydrolyzate to a neutral pH value, and then use an ultrasonic cell disruptor to ultrasonically disrupt the cellulose nanocrystals to obtain cellulose nanocrystal colloid.

[0040] (2) In the cellulose nanocrystal colloid of step (1), amino acids and 98 wt % concentrated sulfuric acid are weighed in a mass ratio of amino acids: 98 wt % concentrated sulfuric acid: cellulose nanocrystal colloid of 2:0.02:10, and are added to the cellulose nanocrystal colloid in sequence, and stirred at 70-80° C. for 2-3 h to obtain a composite colloid, which is then diluted and centrifuged 3-4 times, and ultrasonicated for 5-20 min using an ultrasonic cell disruptor at an ultrasonic power of 200-500 W to obtain a CNC amino acid composite colloid.

[0041] The amino acid used in this example is glycine.

[0042] (3) 3-5 mL of the CNC glycine (GLy) composite colloid of step (2) was measured and poured into a polystyrene culture dish with a diameter of 3.5-5.0 cm, and then placed at room temperature of 25° C. to allow the CNC / GLy composite colloid to undergo evaporation-induced self-assembly during natural evaporation and drying to form a CNC amino acid film.

[0043] (4) The CNC / GLy rainbow film obtained in step (3) is placed in an environment with a VOCs gas concentration of 0.08 to 5.0 mg / m 3 In the well-sealed test chamber for 30 to 180 min, the color of the CNC / GLy rainbow film was observed to change from blue to yellow-green.

[0044] The VOCs gas tested in this embodiment is formaldehyde.

[0045] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 17.3 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 480~565nm.

[0046] Example 2 (CNC / Gly20, amino acid: cellulose nanocrystal colloid is 2:10)

[0047] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98 wt % concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98 wt % concentrated sulfuric acid: cellulose nanocrystal colloid of 2:0.05:10, and are added to the cellulose nanocrystal colloid in sequence.

[0048] The VOCs gas tested in this example is formaldehyde, and the color of the CNC amino acid film changes from blue to yellow-green.

[0049] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 15.2 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 480~565nm.

[0050] Example 3 (CNC / Gly20, amino acid: cellulose nanocrystal colloid is 2:10)

[0051] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98 wt % concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98 wt % concentrated sulfuric acid: cellulose nanocrystal colloid of 2:0.1:10, and are added to the cellulose nanocrystal colloid in sequence.

[0052] The VOCs gas tested in this embodiment is formaldehyde, and the color of the CNC amino acid film changes from blue to orange-yellow.

[0053] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 15.9 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 512~590nm.

[0054] Example 4 (CNC / Gly40, amino acid: cellulose nanocrystal colloid is 4:10)

[0055] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98wt% concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98wt% concentrated sulfuric acid: cellulose nanocrystal colloid of 4:0.02:10, and are added to the cellulose nanocrystal colloid in sequence.

[0056] The VOCs gas tested in this embodiment is formaldehyde, and the color of the CNC amino acid film changes from cyan to red.

[0057] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 21.7 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 543~650nm.

[0058] Example 5 (CNC / Gly40, amino acid: cellulose nanocrystal colloid is 4:10)

[0059] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98 wt % concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98 wt % concentrated sulfuric acid: cellulose nanocrystal colloid of 4:0.1:10, and are added to the cellulose nanocrystal colloid in sequence.

[0060] The VOCs gas tested in this embodiment is formaldehyde, and the color of the CNC amino acid film changes from cyan to red.

[0061] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 1.2 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 540~600nm.

[0062] Example 6 (CNC / Gly80, amino acid: cellulose nanocrystal colloid is 8:10)

[0063] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98wt% concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98wt% concentrated sulfuric acid: cellulose nanocrystal colloid of 8:0.02:10, and are added to the cellulose nanocrystal colloid in sequence.

[0064] The VOCs gas tested in this example is formaldehyde, and the color of the CNC amino acid film changes from blue to yellow-green.

[0065] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m3 The detection has excellent sensitivity at a concentration of 16.3 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 480~560nm.

[0066] Example 7 (CNC / Gly80, amino acid: cellulose nanocrystal colloid is 8:10)

[0067] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98 wt % concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98 wt % concentrated sulfuric acid: cellulose nanocrystal colloid of 8:0.1:10, and are added to the cellulose nanocrystal colloid in sequence.

[0068] The VOCs gas tested in this example is formaldehyde, and the color of the CNC amino acid film changes from cyan to blue-green.

[0069] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 11.2 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 485~540nm.

[0070] Example 8 (CNC / alanine)

[0071] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98wt% concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98wt% concentrated sulfuric acid: cellulose nanocrystal colloid of 4:0.02:10, and are added to the cellulose nanocrystal colloid in sequence.

[0072] The amino acid used in this example is alanine.

[0073] The VOCs gas tested in this example is formaldehyde, and the color of the CNC amino acid film changes from blue-green to yellow-green.

[0074] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 13.4 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 520~586nm.

[0075] Example 9 (CNC / tyrosine)

[0076] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98wt% concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98wt% concentrated sulfuric acid: cellulose nanocrystal colloid of 4:0.02:10, and are added to the cellulose nanocrystal colloid in sequence.

[0077] The amino acid used in this example is tyrosine.

[0078] The VOCs gas tested in this example is formaldehyde, and the color of the CNC amino acid film changes from blue-green to orange.

[0079] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 1.27 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 530~592nm.

[0080] Example 10 (CNC / glutamic acid)

[0081] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98wt% concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98wt% concentrated sulfuric acid: cellulose nanocrystal colloid of 4:0.02:10, and are added to the cellulose nanocrystal colloid in sequence.

[0082] The amino acid used in this example is glutamic acid.

[0083] The VOCs gas tested in this example is formaldehyde, and the color of the CNC amino acid film changes from blue-green to orange.

[0084] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 11.6 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 545~602nm.

[0085] Example 11 (CNC / glutamine)

[0086] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98wt% concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98wt% concentrated sulfuric acid: cellulose nanocrystal colloid of 4:0.02:10, and are added to the cellulose nanocrystal colloid in sequence.

[0087] The amino acid used in this example is glutamine.

[0088] The VOCs gas tested in this example is formaldehyde, and the color of the CNC amino acid film changes from yellow to red.

[0089] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 14.2 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 580~650nm.

[0090] Example 12 (CNC / aspartic acid)

[0091] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 1, except that amino acids and 98wt% concentrated sulfuric acid are weighed according to a mass ratio of amino acids: 98wt% concentrated sulfuric acid: cellulose nanocrystal colloid of 4:0.02:10, and are added to the cellulose nanocrystal colloid in sequence.

[0092] The amino acid used in this example is aspartic acid.

[0093] The VOCs gas tested in this embodiment is formaldehyde, and the color of the CNC amino acid film changes from red to purple-red.

[0094] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 1.0 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 653~712nm.

[0095] Embodiment 13

[0096] The preparation method of a CNC amino acid film in this embodiment is basically the same as that in Example 4, except that the VOCs gas tested in this embodiment is acetaldehyde, and the color of the CNC amino acid film changes from cyan to flax.

[0097] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 1.277 nm / (1 mg / m 3VOCs), the maximum reflection wavelength is 539~600nm.

[0098] Comparative Example 1

[0099] The preparation method of a CNC amino acid film in this comparative example is basically the same as that in Example 4, except that the VOCs gas tested in this example is methanol, and the color of the CNC amino acid film changes from cyan to brown-blue.

[0100] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 The aldehyde VOCs gas is between 0.08 and 5.0 mg / m 3 The detection has excellent sensitivity at a concentration of 7.3 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 534~570nm.

[0101] Comparative Example 2

[0102] The preparation method of a CNC amino acid film in this comparative example is basically the same as that in Example 4, except that the VOCs gas tested in this example is ethanol, and the color of the CNC amino acid film changes from lake blue to brown-green.

[0103] The CNC amino acid film prepared in this example can detect concentrations as low as 0.08 mg / m 3 Alcohol-based VOCs gas, 0.08~5.0mg / m 3 The detection has excellent sensitivity at a concentration of 9.1 nm / (1 mg / m 3 VOCs), the maximum reflection wavelength is 536~581nm.

[0104] Comparative Example 3

[0105] The preparation method of a CNC film in this comparative example is basically the same as that in Example 4, except that the cellulose nanocrystal colloid prepared directly from CNC is used to test the VOCs gas formaldehyde, and the color of the film changes from blue to blue-green.

[0106] The CNC film prepared in this example can detect concentrations as low as 0.08 mg / m 3 Alcohol-based VOCs gas, 0.14~14.0mg / m 3 At a concentration of 1 mg / m 3 VOCs), the maximum reflection wavelength is 378~470nm.

[0107] Table 1 Performance data of sensitive membranes prepared in Examples and Comparative Examples in response to VOCs

[0108]

[0109] The data results obtained from the examples and comparative examples are shown in Table 1. It can be seen from the examples and comparative examples that Example 4 is the best example. The CNC amino acid film prepared from glycine corresponds to visible light with a wavelength of 468 to 682 nm at 0.08 to 5.0 mg / m 3 After 30 to 180 minutes in a well-sealed test room, the color of the CNC amino acid film was observed to change from cyan to red, corresponding to visible light with a wavelength of 480 to 650 nm, especially for formaldehyde, with a response efficiency of up to 21.7 nm / (1 mg / m 3 ), achieving color resolution that can be recognized by the naked eye and realizing visual detection. When the amino acid is alanine, tyrosine, glutamic acid, glutamine or aspartic acid, the obtained CNC amino acid film corresponds to visible light with a wavelength of 482 to 702 nm. After testing, the response wavelength to formaldehyde is 520 to 712 nm.

Claims

1. A method for preparing a CNC amino acid film, characterized in that: The following steps are involved: The steps of preparing CNC amino acid composite colloid are as follows: amino acid, sulfuric acid and cellulose nanocrystal colloid are mixed in a mass ratio of (2-8): (0.02-0.1): 10, wherein the concentration of the sulfuric acid is 90-98wt%, to obtain CNC amino acid composite colloid; The step of preparing the CNC amino acid film is as follows: evaporating the CNC amino acid composite colloid to induce self-assembly to obtain the CNC amino acid film.

2. The method for preparing a CNC amino acid film according to claim 1, characterized in that: The amino acids include one or more of glycine, alanine, glutamic acid, tyrosine, glutamine or aspartic acid.

3. The method for preparing a CNC amino acid film according to claim 1, characterized in that: The cellulose nanocrystal colloid is prepared by the following steps: weighing cellulose nanocrystals and 64% sulfuric acid aqueous solution at a mass ratio of 8-12:1, mixing, diluting, centrifuging, dialyzing until the pH value is neutral, and ultrasonically crushing to obtain the cellulose nanocrystal colloid.

4. The method for preparing a CNC amino acid film according to claim 1, characterized in that: The temperature of the evaporation-induced self-assembly is 25°C.

5. The method for preparing a CNC amino acid film according to claim 4, characterized in that: 3-5 mL of the CNC amino acid composite colloid was poured into a polystyrene petri dish with a diameter of 3.5-5.0 cm and evaporated to induce self-assembly.

6. The method for preparing a CNC amino acid film according to claim 1, characterized in that: After the amino acid, sulfuric acid and cellulose nanocrystal colloid are mixed, they are stirred at 70-80°C for 2-3 h, centrifuged 3-4 times, and ultrasonicated for 5-20 min.

7. A CNC amino acid film, characterized in that: It is prepared by the method described in any one of claims 1 to 6.

8. An application of CNC amino acid film, characterized in that: The CNC amino acid membrane in claim 7 is applied to the detection of aldehyde-based VOCs.

9. The use of a CNC amino acid film according to claim 8, characterized in that: The aldehyde VOCs are formaldehyde or acetaldehyde.

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