RU2818998C1 - Gas analytical multisensor chip based on macromolecular composites of functionalised graphenes, modified with dyes, and method of its production - Google Patents

Abstract

FIELD: measurement.

SUBSTANCE: gas analytical multisensor chip based on macromolecular composites of functionalised graphenes, modified with dyes, includes a dielectric substrate, on which a gas-sensitive layer is formed by at least two segments made of macromolecular composites based on functionalised graphenes, covalently modified with dye molecules in concentration of not less than 1 at.%, dyes are selected from a group comprising dyes paradimethylaminobenzylidene rhodanine, "Acridine yellow", "Pararosaniline", "Bismarck brown", "Neutral red" and "Azur A". Method of manufacturing a gas analytical multisensor chip includes applying on the surface of a dielectric substrate a set of coplanar strip electrodes from a noble metal, heaters and thermistors, aerosol deposition on at least part of surface of electrodes and on surface of substrate between electrodes of layer of gas-sensitive material, using mask for formation of separate segments of gas-sensitive layer from different macromolecular composites. Gas-sensitive material is formed by chemical modification of graphene oxide and reduced graphene oxide with covalent bonding of dye molecules in concentration of not less than 1 at.%, dyes are selected from a group comprising dyes paradimethylaminobenzylidene rhodanine, "Acridine yellow", "Pararosaniline", "Bismarck brown", "Neutral red" and "Azur A".

EFFECT: invention provides high sensitivity and selectivity of detecting gases without the need to heat the gas-sensitive layer and a simplified method of making said layer.

13 cl, 18 dwg

Description

Technical field

This group of inventions relates to the field of sensor technology and nanotechnology, in particular to gas sensors and gas analytical multisensor lines of the chemoresistive type and methods for their manufacture. Gas sensors of the chemoresistive (or conductometric) type are widely used to detect impurities in the surrounding atmosphere, primarily toxic and flammable gases.

State of the art

Currently, chemoresistive type gas sensors are the cheapest and easiest to operate and are widely used to detect impurities in the surrounding atmosphere, primarily flammable gases. The basic structure of such sensors, as a rule, includes a substrate on which measuring electrodes are applied, between which a sensor (or gas-sensitive) material is placed. The most popular materials for making chemoresistors are wide-gap metal oxide and sulfide semiconductors, which are characterized by high gas sensitivity and long-term stability when operating in the low concentration range of gases and volatile organic compounds (VOCs).

Thus, a gas sensor based on metal oxide is known (see CN 111272825, IPC G01N 27/12, publ. 06/12/2020), containing a substrate on which interdigitated electrodes made of gold or silver are sequentially applied, and a layer of metal oxide selected from the group: CuO, ZnO, CoO, NiO. The metal oxide layer contains noble metal particles with a radius of 20 nm to 100 nm. Metal oxide particles are deposited on the metal oxide layer and on the noble metal particles.

There is a known method for manufacturing a gas sensor based on metal oxide (see CN 109709163, IPC G01N 27/12, publ. 04/20/2021), including mixing (0.14-0.16) wt. % bacterial hydrogel with (0.1-1.0) mmol/l metal salt solution, incubated for (12-48) hours, the precipitate is washed with deionized water and freeze-dried for (1-2) days to obtain a dry cellulose gel containing metal ions adsorbed on it. The dry cellulose gel is calcined at a temperature of (400-800)°C for (1-5) hours to obtain flaky metal oxide particles. Metal oxide particles are mixed with a volatile reagent and further crushed. The resulting suspension of metal oxide nanoparticles with a size of (10-80) nm is applied to a ceramic substrate with an electrode fixed on it and kept at a temperature of (250-400)°C for at least 5 days.

A fundamental limitation of the use of wide-bandgap semiconductor metal oxides in the field of gas sensing is the almost complete lack of selectivity when detecting various gases and VOCs. One potential technical solution to improve selectivity is to combine chemoresistors into sets or multisensor arrays, the combined signal of which is selective when the sensor elements are selected accordingly.

Thus, a gas multisensor of a chemoresistive type based on titanium sulfide whiskers is known (see RU 2684429, IPC G01N 27/12, G01N 27/125, publ. 04/19/2019), in which a matrix layer of titanium sulfide whiskers TiS ₃ is used as a gas-sensitive material , placed on a dielectric substrate between the measuring electrodes, whose resistance at room temperature changes under the influence of impurities of organic vapors or water vapor in the surrounding air. The number of measuring electrodes is more than three, on top of which a matrix layer of titanium sulfide whiskers of various densities is applied; in this case, the layer enclosed between each pair of electrodes forms a sensor element, and the entire set of sensor elements forms a multisensory line.

A multisensor chip is known (see US 5783154, IPC G01N 25/16, G01N 27/12, G01N 33/00, publ. 07/21/1998), containing a set of chemoresistive strip segments deposited on a substrate by magnetron sputtering, consisting of a semiconductor film of metal oxide, segmented by coplanar electrodes and doped in such a way that its composition changes continuously between coplanar electrodes. On the opposite side of the substrate, heating electrodes are formed in the shape of a meander.

There is a known method for manufacturing a conductometric type gas multisensor based on tin oxide (see EA 032236, IPC G01N 27/407, B82Y 15/00, published on April 30, 2019) by electrochemical deposition in a container equipped with a reference electrode and a counter electrode and filled with a solution containing nitrate anions and tin cations from the salts SnCl ₂ and NaNO ₃ . A layer of tin oxide in the form of nanocrystals is deposited using a cyclic electrochemical process onto a dielectric substrate equipped with strip sensor electrodes that act as a working electrode. A cyclic sequence of potential changes is applied repeatedly, but not less than three times, until the peak on the voltammetry curve corresponding to the dissolution of metallic tin disappears.

There is a known method for manufacturing a multielectrode gas analytical chip based on a membrane of titanium dioxide nanotubes (see EA 033789, IPC G01N 27/407, published November 26, 2019), according to which titanium dioxide nanotubes are formed by the method of electrochemical anodization of titanium in an electrochemical cell in an electrolyte with the addition of ammonium fluoride up to 1 wt. % at constant voltage for 20-300 minutes until the formation of nanotubes with a height of up to 10 μm and a wall thickness of up to 100 nm is completed. The remains of the titanium sublayer are removed in a solution of methyl alcohol with the addition of bromine in a volume ratio of 1:8-1:10 at room temperature. The resulting membrane of titanium dioxide nanotubes is sequentially washed in alcohol solutions until traces of the etching solution are removed and transferred to a container where it is placed on the surface of distilled water, from where the membrane of titanium dioxide nanotubes is deposited onto the surface of the chip substrate by pulling out of the solution and dried in air at room temperature until water is removed.

The general disadvantages of the presented technical solutions and, in general, the use of wide-gap semiconductor metal oxides and sulfides are both the complexity of the synthesis of metal oxide structures, which leads to an increased cost of the final device, and the need to heat them during operation to temperatures T = 300-350°C, which leads to high power consumption (more than 250 mW), limiting their use in self-powered gas detectors, and does not allow their use in devices with increased requirements for fire and explosion safety. In addition, metal oxides have low resistance to poisoning by a number of gases and VOCs, such as hydrogen sulfide and ammonia, which limits the use of these materials in gas sensors for detecting leaks of a wide range of gases and VOCs.

The identified disadvantages have led to the development of the use of other gas-sensitive materials for the formation of gas sensors, in particular graphene and its derivatives - graphene layers, the edges and basal plane of which are modified with a given functional group, such as carboxyl (-COOH), ketone (>C=O), amine (-NH2), aldehyde (-CHO), etc. Graphene derivatives do not require heating during operation, are resistant to poisoning when exposed to high concentrations of gases and VOCs, and have low intrinsic electrical noise. In addition, the use of graphene derivatives makes it possible to widely adjust the sensitivity and selectivity of gas sensors and multisensor arrays based on them, selecting the type and parameters of modification of the graphene layer with functional groups.

Today, many designs of chemoresistive gas sensors based on a graphene layer and its derivatives are known from the state of the art. A gas sensor is known (see CN 111307876, IPC G01N 27/12, publ. 06/19/2020) in the form of a multilayer film structure containing a silicon-based substrate, an electrically insulating layer, an electrode layer and a gas-sensitive composite layer. The gas-sensitive composite layer consists of graphene and a MoS ₂ film on the graphene surface.

The disadvantage of the known gas sensor is the complex multi-stage manufacturing protocol, which requires the use of expensive equipment.

There is a known method for manufacturing a sensor for gaseous toxic substances based on graphene films (see RU 2659903, IPC G01N 27/26, H01L 21/02, publ. 07/04/2018), including obtaining a graphene film on the surface of silicon carbide by thermal destruction, chemical treatment of the graphene film and application ohmic contacts. The graphene film is etched by ion-beam etching using a photoresist mask, then the electrodes are metallized using explosive photolithography, a nickel coating is sputtered, the reinforcement topology of the contact pads is formed, and then finishing chemical treatment is carried out.

The disadvantage of the known gas sensor is the low yield of the technique for producing graphene by heat treatment of silicon carbide, complex technology and high manufacturing cost.

There is a known method for manufacturing a ceramic gas sensor (see CN 109896499, IPC B81C 1/00, G01N 27/00, publ. 02/09/2021), including cleaning the ceramic substrate with an aqueous solution of concentrated sulfuric acid and potassium dichromate, and boiling it for 30- 60 minutes, washing with deionized water, formation of a heating resist and signal output electrodes with a thickness of 500-1500 nm by lithography, application of a seed layer of NiAl ₂ O ₄ or CuAl ₂ O ₄ by chemical vapor deposition, annealing of the substrate in a reducing atmosphere at a temperature of 800- 1100°C and the formation of Ni or Cu clusters on the surface of the substrate. Next, a layer of graphene is grown by chemical vapor deposition using CH ₄ or C ₂ H ₄ as a carbon source at a growth temperature of 800-1100 ° C, functional chemical modification of graphene is carried out with silver oxide or an organic solution with a concentration ranging from 0.05 mg/ ml to 2 mg/ml, followed by drying at a temperature of 50-200°C.

The disadvantage of the known gas sensor is the complex multi-stage manufacturing protocol, which requires the use of expensive equipment.

A gas sensor for nitrogen dioxide is known (see US 20170016867, IPC G01N 33/00, H01B 1/04, publ. 01/19/2017), including a silicon substrate with a polyimide coating, on which a layer is formed of a mixture of multi-walled carbon nanotubes, partially reduced graphene oxide and tungsten trioxide nanoparticles located between two Au comb electrodes.

The known gas sensor has a narrow scope, since it is intended only for the detection of nitrogen dioxide.

There is a known method for manufacturing a gas sensor (see US 20170016867, IPC G01N 33/00 H01B 1/04, publ. 01/19/2017), which includes forming two Au comb electrodes on a polyimide-coated silicon substrate, mixing multi-walled carbon nanotubes and partially reduced powder graphene oxide, taken in a mass ratio of 3:1, with α-terpeniol, adding tungsten trioxide nanoparticles, taken in relation to reduced graphene oxide in a mass ratio of 2:1, to the solution, and applying the resulting mixture to a silicon substrate between comb electrodes, drying and annealing at a temperature of 200°C.

A gas sensor manufactured in a known manner is intended only for detecting nitrogen dioxide, which narrows its scope of application.

A gas analytical multisensor chip based on graphene is known, which is functionalized with carbonyl groups (see RU 2745636, IPC G01N 27/12, publ. 03.29.2021), which coincides with the present solution in the largest number of essential features and is accepted as a prototype . The well-known gas analytical multisensor chip prototype includes a dielectric substrate on which a layer of gas-sensitive material, coplanar strip electrodes made of noble metal, a layer of gas-sensitive material up to 120 nm thick, segmented by coplanar strip electrodes, thermistors and heaters are formed. The gas-sensitive material is made of graphene functionalized with carbonyl groups. In this case, each pair of coplanar strip electrodes forms a sensor segment of a graphene matrix layer functionalized with carbonyl groups, the resistance of which changes under the influence of vapors and gases adsorbed from the air at room temperature.

The disadvantage of the known technical solution is the low sensitivity when detecting alcohols and aldehydes.

There is a known method for manufacturing a gas analytical multisensor chip based on graphene (see RU 2745636, IPC G01N 27/12, publ. 03.29.2021), which coincides with the present solution in the largest number of essential features and is accepted as a prototype. A known prototype method for manufacturing a gas analytical multisensor chip involves applying to the surface of a dielectric substrate a set of coplanar strip electrodes made of noble metal with a thickness of (0.1-1) microns and a width of (50-200) microns with a gap between the electrodes of (10-100) microns, heaters and thermistors, carrying out liquid-phase modification of a graphene oxide suspension by adding graphene oxide with a concentration of (1-5) wt. to an aqueous or organic suspension. % weighed sodium silicate powder in a ratio of (1.3-3.3) g/l and heating for (48-52) hours at a temperature of (75-85) ° C. Next, the resulting suspension is purified by repeated centrifugation at a speed of (12000-12500) rpm, diluting the resulting sediment with deionized water and obtaining graphene functionalized with carbonyl groups. A suspension containing graphene functionalized with carbonyl groups is applied in the form of a thin film up to 120 nm thick onto the surface of a sensor or chip substrate containing a set of coplanar strip electrodes, the resulting structure is dried for (10-12) hours at room temperature and when heated to ( 70-80)°C for (1-2) hours.

The disadvantage of the known prototype method is the possibility of modifying graphene only with carbonyl groups.

The objective of the present invention was to develop a gas analytical multisensor chip based on macromolecular composites of functionalized graphenes, covalently modified with organic dye molecules, with increased sensitivity and selectivity for gas recognition without the need to heat the gas-sensitive layer, simplify the method of its manufacture, expand the range of gas detectors based on gas-sensitive materials operating at room temperature.

The task is solved by a group of inventions united by a single inventive concept.

In terms of the device, the problem is solved in that a gas analytical multisensor chip based on macromolecular composites of functionalized graphenes, covalently modified with molecules of organic dyes, includes a dielectric substrate on which coplanar strip electrodes are formed from a noble metal, thermistors and heaters, while at least part of the surface of the electrodes and on the substrate between the electrodes a layer of gas-sensitive material is applied in the form of a layer of macromolecular composite, the resistance of which changes at room temperature under the influence of impurities of organic vapors or water vapor in the surrounding air. What is new is that the gas-sensitive layer is divided into two or more segments, each of which is represented by a macromolecular composite (Gr-Dye) based on functionalized graphene, covalently modified with dye molecules in a concentration of at least 1 at. %, selected from the group consisting of paradimethylaminobenzylidenorodanine, Acridine Yellow, Pararosaniline, Bismarck Brown, Neutral Red and Azur A dyes.

In one of the particular embodiments of the invention, the gas-sensitive layer is made of three segments formed on the basis of macromolecular composites “Functionalized graphene - Azur A” (Gr-AzurA), “Functionalized graphene - Neutral Red” (Gr-NeR), “Functionalized graphene - Acridine yellow" (Gr-AkY).

The layer of each macromolecular composite can be made with a variable thickness from 100 nm to 2000 nm, preferably from 100 nm to 1000 nm.

In each section of a layer of macromolecular composites ranging in size from 20% to 40% of the total area of the segment, there can be a change in layer thickness from 20% to 40%.

In part of the method, the problem is solved in that the method of manufacturing a gas analytical multisensor chip based on macromolecular composites of functionalized graphenes, covalently modified with molecules of organic dyes, includes applying a set of coplanar strip electrodes, heaters and thermistors to the surface of a dielectric substrate, followed by the formation of at least parts of the surface of the electrodes and on the surface of the substrate between the electrodes a layer of gas-sensitive material represented by macromolecular composites based on functionalized graphene, covalently modified with dye molecules. What is new in the method is that the production of macromolecular composites is carried out by chemical modification of graphene oxide (GO) and reduced graphene oxide (rGO) with the covalent addition of dye molecules in a concentration of at least 1 at. %, selected from the group including paradimethylaminobenzylidenorodanine, Acridine Yellow, Pararosaniline, Bismarck Brown, Neutral Red and Azur A dyes.

The application of macromolecular composites to the surface of the electrodes and the surface of the substrate between the electrodes is carried out with the formation, after drying, of at least two segments of the gas-sensitive layer of variable thickness differing from each other from 100 nm to 2000 nm, preferably from 100 nm to 1000 nm.

The preparation of macromolecular composites “Functionalized graphene - Azur A” and “Functionalized graphene - Neutral Red” is carried out

(1) at the first stage, by obtaining the diazonium salt of the dye “Azur A” or “Neutral Red” by adding a sample of the dye Azur-A or Neutral Red to distilled water in a ratio of 6-7 g/l, adding concentrated hydrochloric acid to the resulting solution in a ratio of 0 ,02-0.03 l/l, cooling the resulting reaction mixture to a temperature of 0-2°C in a cooling bath, stirring, adding sodium nitrite solution to the reaction medium in a ratio of 3-4 g/l, stirring the resulting solution until the color of the solution changes from blue to black;

(2) at the second stage by adding a weighed portion of reduced graphene oxide powder to distilled water in a ratio of 3-3.5 g/l, processing in an ultrasonic bath with an ultrasound frequency of 20-40 kHz and an ultrasonic emitter power in the range of 110-170 W, cooling the resulting the reaction mixture to a temperature of 0-2°C in a cooling bath;

(3) at the third stage, adding a solution of diazonium salt of the “Azur A” or “Neutral Red” dye to a suspension of reduced graphene oxide in a ratio of 0.5-0.75 l/l, stirring and simultaneous treatment with ultraviolet radiation for 3-3.5 hours;

(4) at the fourth stage, cleaning the resulting composite by repeated washing on a Schott filter connected through a Wurtz nozzle with a drain flask and a vacuum station using a 3% solution of hydrochloric acid and distilled water until the wash water becomes discolored, drying the sediment at room temperature for 30-40 minutes to obtain the macromolecular composite “Functionalized graphene - Azur A” or “Functionalized graphene - Neutral Red”.

The preparation of the macromolecular composite “Functionalized graphene - Acridine yellow” is carried out

(1) at the first stage, adding a sample of graphene oxide powder to thionyl chloride in a ratio of 3-3.5 g/l, heating the resulting suspension to a temperature of 70-80°C for 60-80 minutes, vacuum distillation of the resulting suspension for 6 -7 hours to remove thionyl chloride and fill the flask with the suspension with argon;

(2) at the second stage by adding the “Acridine yellow” dye to acetonitrile in a ratio of 4.5-5.5 g/l and a pyridine solution in a ratio of 0.045-0.055 l/l, adding a portion of thiolated graphene oxide obtained in the first stage, in ratio of 0.2-0.25 g/l, stirring the resulting reaction mixture for 3-4 hours;

(3) at the fourth stage, cleaning the resulting composite by repeated washing on a Schott filter connected through a Wurtz nozzle with a drain flask and a vacuum station using acetonitrile and isopropyl alcohol until the wash water is discolored, drying the precipitate at room temperature for 30-40 minutes to obtain a macromolecular composite "Functionalized graphene - Acridine yellow".

The suspension is applied by aerosol spraying using a mask with a window 6-10 mm long and 1.5-2 mm wide at a suspension consumption of 1-50 ml/cm ² . To obtain the base suspension used for aerosol application, a sample of the nanocomposite is added to propylene glycol in a ratio of 10-20 μg/ml, followed by sonication for 7-10 minutes and stirring for 15-20 minutes.

Aerosol application is performed after preheating the dielectric substrate to a temperature of 120-150°C.

After applying each graphene segment with a given thickness, the mask is shifted by 1.5-2 mm in the direction perpendicular to the strip electrodes, and the aerosol deposition procedure is repeated.

Drying is carried out at room temperature for 4-5 hours until the remaining solvent is completely removed.

The presence of covalently bonded dye molecules on the graphene layer ensures the specificity of the sorption of molecules of different gases, due to differences in their chemical affinity (affinity) in relation to a given dye molecule. This makes it possible to significantly increase the selectivity of gas analytical chips, increasing the efficiency of recognizing gases, in particular alcohols, compared to the use of pure graphene, graphene oxide or carbonylated graphene.

The presence of covalently bonded dye molecules in the gas-sensitive layer also leads to n- or p-doping of the graphene layer, which provides a pronounced and excellent chemoresistive response of each segment of the gas-sensitive material upon adsorption of gas molecules.

When the content of dye molecules is less than 1 at. %, sufficient selectivity in the adsorption of gas molecules with different affinities to dye molecules on the graphene surface is not achieved, as well as a decrease in the value of n and p-doping of the graphene layer, which leads to a decrease in the selectivity of recognition of various gases and a decrease in the sensitivity of the device.

Making segments of the gas-sensitive layer from various macromolecular Gr-Dye composites, as well as having different and variable thicknesses, makes it possible to achieve an increase in the variation of the chemoresistive response in different areas of the gas sensor (in the form of a multisensor chip) to different gases due to the inhomogeneities that arise in the structure of the layers of macromolecular composites Gr-Dye. As a result, the total vector response of the entire system of sensor elements located on the chip turns out to be sensitive to the type of test gas, which makes it possible to significantly increase the selectivity of their detection after processing the vector signals of the chip using pattern recognition methods (Sysoev V.V., Musatov V.Yu. Gas analytical devices “electronic nose” // Saratov: Sarat State University - 2011. - 100 p. This allows not only to detect gases (sensor function), but also to identify them (gas analyzer function).

Moreover, if the layer thickness is less than 100 nm, then uniform coverage of the surface of coplanar electrodes and the space (zones) between them with macromolecular Gr-Dye composites is not achieved, and the electrical resistance of the gas-sensitive layer is above 100 MOhm.

Increasing the thickness of the layer of macromolecular Gr-Dye composites to values greater than 2000 nm leads to a deterioration in the access of the analyzed gas or analyte vapor to the lower layers (volume) of the material directly in contact with the measuring electrodes, which causes a decrease in the sensitivity of the multisensor chip.

The use of an application method other than aerosol does not allow the formation of a gas-sensitive layer of several segments represented by various macromolecular Gr-Dye composites.

Lack of heating of the substrate during aerosol deposition leads to the retention of residual solvent (isopropyl alcohol), the presence of which leads to a decrease in the sensitivity of the multisensor chip.

Drying suspensions of macromolecular Gr-Dye composites in the stated modes after aerosol application ensures the removal of solvent residues, as well as the formation of stable electrical contact between the measuring electrodes and segments of the gas-sensitive layer. The use of temperatures above room temperature can lead to degradation of the gas-sensitive layer with partial removal of dye molecules.

The present invention is illustrated by drawings, where:

In fig. 1 shows a schematic representation of a gas analytical multisensor chip;

In fig. Figure 2 shows a section along line A-A of the gas analytical multisensor chip shown in Figure 1;

In fig. Figure 3 shows a diagram of the first stage of obtaining macromolecular composites “Functionalized graphene - Azur A” and “Functionalized graphene - Neutral Red”;

In fig. Figure 4 shows a diagram of the second stage of obtaining macromolecular composites “Functionalized graphene - Azur A” and “Functionalized graphene - Neutral Red”;

In fig. Figure 5 shows a diagram of the third and fourth stages of obtaining macromolecular composites “Functionalized graphene - Azur A” and “Functionalized graphene - Neutral Red”;

In fig. Figure 6 shows a diagram of the first stage of obtaining the macromolecular composite “Functionalized graphene - Acridine yellow”;

In fig. Figure 7 shows a diagram of the second and third stages of obtaining the macromolecular composite “Functionalized graphene - Acridine yellow”;

In fig. Figure 8 shows a diagram of the manufacture of a gas analytical multisensor chip;

In fig. Figure 9 shows a cross-section of the manufactured gas analytical multisensor chip in the area with the minimum thickness of the gas-sensitive layer made of the Gr-Dye macromolecular composite, obtained using an electron microscope, magnification ×80000;

In fig. Figure 10 shows a cross-section of the manufactured gas analytical multisensor chip in the area with the maximum thickness of the gas-sensitive layer made of the Gr-Dye macromolecular composite, obtained using an electron microscope, magnification ×40000;

In fig. Figure 11 shows a survey X-ray photoelectron spectrum of a layer of the macromolecular composite “Functionalized graphene - Azur A”;

In fig. Figure 12 shows a survey X-ray photoelectron spectrum of the macromolecular composite layer “Functionalized graphene - Neutral Red”;

In fig. Figure 13 shows a survey X-ray photoelectron spectrum of the macromolecular composite layer “Functionalized graphene - Acridine Yellow”;

In fig. 14 shows a diagram of the experimental setup used in the example to measure the chemoresistive response of a gas analytical multisensor chip based on Gr-Dye macromolecular composites;

In fig. Figure 15 shows the current-voltage characteristics of three typical sensor elements of gas-sensitive segments, represented by macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow”, a sample of a manufactured gas analytical multisensor chip during operation at room temperature in dry air atmosphere;

In fig. 16-fig. Figure 17 shows the change in the resistance of three typical sensor elements of gas-sensitive segments represented by the macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow” of a sample of a manufactured gas analytical multisensor chip during operation at room temperature when exposed to vapors of methanol (Fig. 16) and acetone (Fig. 17) mixed with dry air in the concentration range (4-10)×10 ³ ppm;

In fig. Figure 18 shows the results of processing the vector signal of a sample of a manufactured gas analytical multisensory chip, operating at room temperature, to the effects of methanol and acetone vapors mixed with dry air using the linear discriminant analysis (LDA) method, where the dots show experimental multisensory signals, ellipses limit the areas of signal clusters to the effects of analytes plotted around the center of gravity, according to a normal distribution with a confidence level of 0.80.

The positions in FIG. 1-fig. 18 are marked:

1 - dielectric substrate; 2 - coplanar strip electrode, 3 - thermistor, 4 - heater, 5 - segment of the gas-sensitive layer based on the macromolecular composite "Functionalized graphene - Azur A", 6 - segment of the gas-sensitive layer based on the macromolecular composite "Functionalized graphene - Neutral Red", 7 - segment of the gas-sensitive layer based on the macromolecular composite “Functionalized graphene - Acridine Yellow”, 8 - stage of forming a reaction mixture containing Azur A or Neutral Red dye and distilled water, 9 - stage of adding concentrated hydrochloric acid (HCl) to the reaction mixture, 10 - stage cooling the resulting reaction mixture to a temperature of 0-2°C, 11 - the stage of adding sodium nitrate solution ( _NaNO3 ) to the cooled reaction mixture, 12 - the stage of stirring the resulting reaction mixture, 13 - the stage of forming a working suspension of reduced graphene oxide in distilled water, 14 - stage of ultrasonic treatment of the working suspension, 15 - stage of cooling the resulting working suspension to a temperature of 0-2°C, 16 - stage of forming a reaction mixture by mixing a base suspension of reduced graphene oxide and diazonium salt of the dye “Azur A” or “Neutral Red”, 17 - stage of processing the reaction mixture with UV radiation while stirring, 18 - stage of purification of the composite "Functionalized graphene - Azur A" or "Functionalized graphene - Neutral Red" by repeated washing on a Schott filter, 19 - stage of forming a working suspension of graphene oxide in thionyl chloride, 20 - heating stage working suspension of graphene oxide in thionyl chloride, 21 - stage of vacuum distillation with removal of thionyl chloride and obtaining thiolated graphene oxide, 22 - stage of filling the flask with thiolated graphene oxide with argon, 23 - stage of forming the reaction mixture by adding a sample of Acridine yellow dye to acetonitrile, 24 - stage adding thiolated graphene oxide to the reaction mixture and stirring it, 25 - stage of purification of the "Functionalized graphene - Acridine yellow" composite by repeated washing on a Schott filter, 26 - stage of obtaining base suspensions of macromolecular composites "Functionalized graphene - Azur A" / "Functionalized graphene - Neutral"Red" / "Functionalized graphene - Acridine Yellow", 27 - stage of homogenization of suspensions of macromolecular composites "Functionalized graphene - Azur A" / "Functionalized graphene - Neutral Red" / "Functionalized graphene - Acridine Yellow" using ultrasound treatment, 28 - aerosol stage applying macromolecular composites “Functionalized graphene - Azur A” / “Functionalized graphene - Neutral Red” / “Functionalized graphene - Acridine Yellow” onto the surface of a multielectrode substrate through a mask to form a separate segment of the gas-sensitive layer from one of the nanocomposites, 29 - stage of drying the gas-sensitive layer on based on macromolecular composites “Functionalized graphene - Azur A” / “Functionalized graphene - Neutral Red” / “Functionalized graphene - Acridine Yellow” on the surface of a gas analytical multisensor chip, 30 - carbon peak C 1s, 31 - oxygen peak O 1s, 32 - nitrogen peak N 1s; 33 - sulfur peak S 2p, 34 - compressor that takes air from the environment, 35 - filter-drier, 36 - gas flow controller, 37 - two-way solenoid valve, 38 - three-way solenoid valve, 39 - relay module for opening control /by closing the valves, 40 - a bubbler that introduces water vapor and organic analytes into the measuring system; 41 - Faraday cage with a chip (gas sensor) placed inside in a sealed stainless steel chamber; 42 - data collection platform; 43 - measuring multimeter; 44 - PID controller; 45 - power supply for heaters; 46 - chamber containing a control commercial semiconductor sensor for alcohols and a humidity sensor; 47 - personal computer.

Below is a more detailed description of the implementation of this group of inventions, which does not limit the scope of the claims of the inventions, but demonstrates the possibility of their implementation with the achievement of the above technical result.

This gas analytical multisensor chip (Fig. 1-Fig. 2) includes a dielectric substrate 1 coated with a set of coplanar strip measuring electrodes 2 made of noble metal, for example, gold or platinum, width (1-100) microns, thickness (50-1000) nm and interelectrode gap (1-100) µm. The substrate 1 can be made of quartz, glass, ceramics, silicon with a thermally grown layer of silicon oxide with a thickness of 300 nm or more, or any other dielectric material known in the art. The number of coplanar strip measuring electrodes can be 3 or more. Also applied to the front surface or back side of the substrate are thin-film thermistors 3 and heaters 4 made of noble metal, for example, platinum, gold or silver. At least part of the surface of the electrodes 2 and, accordingly, the substrate 1 between the electrodes 2 is covered with at least three separate segments of the gas-sensitive layer 5-7 (sensor elements based on the gas-sensitive layer), each of which covers at least 30% of the total surface area of the electrodes 2 and substrates between them 1. Macromolecular composites based on functionalized graphenes covalently modified with dye molecules in a concentration of at least 1 at. are selected as materials for segments of the gas-sensitive layer 5-6. %, selected from the group consisting of paradimethylaminobenzylidenorodanine, Acridine Yellow, Pararosaniline, Bismarck Brown, Neutral Red and Azur A dyes.

Segments of the gas-sensitive layer 5-7 are made of different thicknesses from 100 nm to 2000 nm with a change in the thickness of the layer within each segment by at least 20%. The change in layer thickness can be monotonic with a given law of thickness distribution depending on the geometric dimensions of the film (gradient) and non-uniform, with a chaotic distribution of zones of different thicknesses. The thickness of the segments can be considered different if the distribution of the thickness of the gas-sensitive layer within different segments differs in the law describing the thickness distribution, while the boundary values (minimum or maximum) of the intervals for changing the thickness of various segments may coincide or differ from each other.

In one of the particular embodiments of the invention, the gas-sensitive layer is made of three segments formed on the basis of macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow”. In this case, each of the segments covers, for example, 33% of the total surface area of the electrodes and the substrate between the electrodes and has a variable thickness in the range from 200 nm to 1000 nm.

A gas analytical multisensor chip based on macromolecular composites of functionalized graphenes modified with dyes is manufactured as follows.

A set of coplanar strip electrodes 2 made of a noble metal, for example, platinum or gold, width (1-100) microns, thickness 50-1000 nm and interelectrode gap (1-100) microns, using a mask or lithographic methods. The indicated dimensions of electrodes 2 are determined by the availability of masks and the resolution of standard microelectronic equipment for their manufacture. Also, on the front side of the dielectric substrate 1 along the edges, thin-film thermistors 3 and meander heaters 4 are applied by cathode, magnetron, ion-beam or thermal sputtering using masks or lithographic methods, either from the same material as coplanar strip electrodes 2, or from any another noble metal. Next, suspensions of Gr-Dye macromolecular composites are applied to the surface of strip electrodes 2 and the dielectric substrate 1 between the electrodes to form individual segments of the gas-sensitive layer 5-7. Organic or aqueous suspensions of macromolecular composites based on functionalized graphenes covalently modified with dye molecules in a concentration of at least 1 at. are used as suspensions. %, selected from the group consisting of paradimethylaminobenzylidenorodanine, Acridine Yellow, Pararosaniline, Bismarck Brown, Neutral Red and Azur A dyes.

In one of the private embodiments of the invention, the macromolecular composites “Functionalized graphene - Azure A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow” are selected as Gr-Dye macromolecular composites.

Macromolecular composites “Functionalized graphene - Azur A” and “Functionalized graphene - Neutral Red” are obtained by liquid-phase modification of reduced graphene oxide. At the first stage, the diazonium salt of the dye “Azur A” or “Neutral Red” is obtained. To do this, add a sample of Azur-A or Neutral Red dye 8 to distilled water in a ratio of 6-7 g/l, after which concentrated hydrochloric acid is added to the resulting solution in a ratio of 0.02-0.03 l/l. The resulting reaction mixture is cooled 10 to a temperature of 0-2°C in a cooling bath and set to stirring using a magnetic or mechanical stirrer at a speed of 100-200 rpm. While stirring, add 11 portions of sodium nitrate, reaching a ratio of 3-4 g/l, after which the reaction mixture is left to stir for another 20-30 minutes until the color of the solution changes from blue to black.

At the second stage, a working suspension of reduced graphene oxide is obtained, for which a sample of reduced graphene oxide powder is added 13 to distilled water in a ratio of 3-3.5 g/l, after which the resulting suspension is treated 14 in an ultrasonic bath with an ultrasound frequency of 20-40 kHz and ultrasonic emitter power in the range of 110-170 W for 2-3 minutes and cool 15 to a temperature of 0-2°C in a cooling bath.

At the third stage, covalent immobilization of the selected dye Azur A or Neutral Red is performed, for which the solution of the diazonium salt of the dye obtained in the first stage is added 16 to the working suspension of reduced graphene oxide obtained in the second stage in a ratio of 0.5-0.75 l/l. The resulting reaction mixture is stirred using a magnetic or mechanical stirrer at a speed of 100-200 rpm and exposed to ultraviolet radiation 17 for 3-3.5 hours, using a deuterium lamp with an electric power of 10 W to 30 W with a spectral maximum intensity , lying in the wavelength range from 210 nm to 260 nm.

At the fourth stage, the resulting composites are cleaned by repeated washing on a glass filter. To do this, the resulting suspension is filtered 18 on a Schott filter with a pore size of 16-40 μm. To create a vacuum in the filter, a chemical vacuum station is used, for example, VACUUBRAND PC 3001 VARIO. The set pressure is 45-55 Pa. During filtration, the precipitate, which is the final product, is washed with a 2-3% solution of hydrochloric acid until the wash water becomes discolored (visual control), after which it is washed three times with 20-40 ml of distilled water. The sediment remaining on the filter after the described cleaning procedures is dried in air at room temperature for 30-40 minutes, obtaining the macromolecular composite “Functionalized graphene - Azur A” or “Functionalized graphene - Neutral Red” in powder form.

The macromolecular composite “Functionalized graphene - Acridine Yellow” is obtained by liquid-phase modification of graphene oxide. To do this, at the first stage, thiolation of graphene oxide is performed. A weighed portion of graphene oxide powder is added 19 to thionyl chloride in a ratio of 3-3.5 g/l, the resulting suspension is heated 20 to a temperature of 70-80°C for 60-80 minutes, after which vacuum distillation 21 of the resulting suspension is carried out for 6 -7 hours to remove thionyl chloride. The flask with the resulting thiolated graphene oxide is filled with 22 argon gas.

At the second stage, a reaction mixture is formed based on the Acridine Yellow dye. To do this, add 23 portions of the Acridine Yellow dye to acetonitrile in a ratio of 4.5-5.5 g/l and a pyridine solution in a ratio of 0.045-0.055 l/l. A 24-piece sample of thiolated graphene oxide is added to the resulting reaction mixture in a ratio of 0.2-0.25 g/l and the resulting mixture is set for stirring using a magnetic or mechanical stirrer at a speed of 100-200 rpm for 3-4 hours.

At the fourth stage, the resulting composites are cleaned by repeated washing on a glass filter. To do this, the resulting suspension is filtered 18 on a Schott filter with a pore size of 16-40 μm. To create a vacuum in the filter, a chemical vacuum station is used, for example, VACUUBRAND PC 3001 VARIO. The set pressure is 45-55 Pa. During filtration, the precipitate, which is the final product, is washed with acetonitrile until the wash water becomes discolored (visual control), after which it is washed three times with 20-40 ml of isopropyl alcohol. The sediment remaining on the filter after the described cleaning procedures is dried in air at room temperature for 30-40 minutes, obtaining the macromolecular composite “Functionalized graphene - Acridine Yellow” in powder form.

The application of Gr-Dye nanocomposites to the surface of strip electrodes 2 and the dielectric substrate 1 between the electrodes with the formation of separate segments of the gas-sensitive layer is performed, for example, as follows. A base suspension 26 is formed by adding a sample of the applied Gr-Dye nanocomposite to propylene glycol in a ratio of 10-20 μg/ml, treating the resulting working suspension in an ultrasonic bath 27 with an ultrasound frequency of 20-40 kHz and an ultrasonic emitter power in the range of 60-110 W for 7-10 minutes and then stirring the suspension using a magnetic or mechanical stirrer at a speed of 100-200 rpm for 15-20 minutes.

Next, an aerosol application of the resulting base suspensions 28 is performed. To do this, the substrate 1 is placed on a heating table, a mask is fixed above the substrate on a tripod or otherwise at a distance of 1-5 mm, which is a metal or plastic substrate with a thickness of 1 to 2 mm, dimensions exceeding the dimensions of the dielectric substrate by 2-5 mm, in which a rectangular through slot is made with a length of 6 mm (which corresponds to the distance between the welding points of the strip electrodes), for example, 6-10 mm, and a width of 1.5-2 mm. The width of the slot is adjusted based on the specified width of the applied segment of the gas-sensitive layer from the selected nanocomposite. The mask is fixed on one of the edges of the zone with strip electrodes 2. Above the mask, at a distance of 100-200 mm, an airbrush (for example, JAS 1142 or an analogue) is fixed, into which a working suspension of the selected Gr-Dye nanocomposite is poured. The temperature of the heating stage is set to 120-150°C, wait until the chip substrate is heated to the specified temperature, and spray the working suspension. Dry purified air is used as the carrier gas, obtained, for example, using a compressor with a drying system that provides the amount of solid particles of no more than 0.1 microns without oil content, with a dew point temperature of -70°C. Operating pressure ranges from 2 atm. up to 4 atm., and the carrier gas consumption is 0.5-1 l/min. These values are set based on the characteristics of the spray unit used and the configuration of the spray nozzle, the diameter and shape of the needle, taking into account preliminary test measurements. The required volume of the applied suspension is determined by the selected thickness of the gas-sensitive layer segment in an amount of 1-50 ml/cm ² .

The described aerosol application procedure is repeated for all suspensions of selected Gr-Dye nanocomposites, moving the mask along the axis perpendicular to the strip electrodes at a distance equal to the width of the formed segment, ensuring that there are no gaps between the formed segments.

After applying all the working suspensions of Gr-Dye nanocomposites, the substrate 1 with segments of the gas-sensitive layer 5-6 is dried 29 in air at room temperature for 4-6 hours. The indicated temperature and time ranges are sufficient for stabilization and final formation of segments 5-7 of Gr-Dye macromolecular composites on the chip with good adhesion and the formation of ohmic electrical contact with the measuring electrodes 2 in the absence of changes in the chemical composition of the material. The resulting continuous film of at least three segments of a gas-sensitive layer based on Gr-Dye 5-7 nanocomposites has a variable thickness in the range from 100 nm to 2000 nm, preferably from 200 nm to 1000 nm, and in each section of the Gr-Dye nanocomposite layer with a size ranging from 30% to 40% of the total segment area, a change in layer thickness of at least 10% is achieved.

In this way, a gas detector is obtained - a gas analytical multisensor chip of the chemoresistive type, in which several macromolecular Gr-Dye composites, synthesized by the method of chemical modification of graphene oxide and reduced graphene oxide, by covalent binding of organic dye molecules, are used as a gas-sensitive material on the surface and between strip electrodes 2 in a concentration of at least 1 at. %, selected from the group including paradimethylaminobenzylidenorodanine, Acridine Yellow, Pararosaniline, Bismarck Brown, Neutral Red and Azur A dyes, in which the resistance at room temperature changes under the influence of alcohol or acetone impurities in the ambient air. The difference in the modifying dye molecules in different segments of the chip and the thickness of the gas-sensitive layer for different chemoresistive elements of the chip allows the formation of a vector signal that differs when exposed to different test analyte gases, which makes it possible to selectively detect them.

The concentration of dye molecules in the gas-sensitive layer of the manufactured detector is determined based on the analysis of the integral intensity of spectral components 30-34 (peaks) in the survey X-ray photoelectron spectra (Fig. 11 - Fig. 13), corresponding to the core line C 1s 30, O 1s 31, N 1s 32 and S 2p 33.

A multisensor chip containing a sensor layer of phosphorylated graphene is welded with a microwire of Au or Al, for example, using ultrasonic welding, into a holder in the form of a board made of ceramic or glass or polymer, for example, dimensions (32x45) mm, equipped with a rectangular window for the chip and a set contact pads with a deposited metal layer of Au or Pt or other metal to form a mechanical and electrical connection between the chip and the holder using microwires. In this case, the chip is located in the holder window and is held suspended by microwires. Metal tracks are applied to the holder board for electrical connection, on the one hand, of coplanar strip electrodes, thin-film thermistors and meander heaters of the chip, and on the other hand, a multi-pin connector, the number of pins of which is not less than the number of all elements of the multisensor chip for connection to external electrical devices. In this case, the tracks are made, for example, from a thin film of Au, Pt, Ag or other metals by screen printing or lithography, and the multi-pin connector complies with well-known standards, for example, Erni SMC with a pitch of 1.27 mm or IDC with a pitch of 2, 54 mm, or others. The electrical tracks of the holder are passivated on top with a dielectric layer.

To measure gas-sensitive characteristics, the housing with the chip boiled into it (Fig. 1) is placed in a chamber, for example, made of stainless steel or polymer, and exposed to test analyte vapors. As a measuring signal, the resistance of segments of the gas-sensitive layer 5-7 of Gr-Dye nanocomposites between strip electrodes 2 is used, which is recorded using standard circuits using a divider or using a Winston bridge, using the corresponding electrical measuring unit from the data collection platform 42, measuring multimeter 43, PID controller 44 and power supply for heaters 45 (Fig. 14). A multiplexer is used to sequentially interrogate the resistances of the chemoresistive elements of a multisensor chip. The operating temperature of the multisensor chip based on Gr-Dye macromolecular composites corresponds to room temperature. At low temperatures, a multisensor chip based on Gr-Dye macromolecular composites is heated and the temperature is maintained at T=25°C using heaters 4, controlling the value by signals from thermistors 3.

On a multisensor chip, each section of segments of the gas-sensitive layer 5-7 made of macromolecular composites Gr-Dye, which is located between each pair of measuring strip electrodes 2, forms a separate sensor or chemoresistive element, and the entire set of chemoresistive elements forms a multisensor line of i∈{1,n } elements. The number of chemoresistive elements on a chip is determined by the geometric dimensions of the chip and power consumption restrictions, as well as the capabilities of computing processors to process all signals. The resistance _{Ri of} the sensor elements of the chip or their chemoresistive response _Si are components of the vector {R ₁ , R ₂ , R ₃ , ..., R _n } or {S ₁ , S ₂ , S ₃ , ..., _Sn }, different for different test gases. The magnitude of the chemoresistive response S is determined as the relative change in resistance in the test gas R _g relative to the resistance in the reference atmosphere R _b in percent:

- if the resistance in the test gas increases relative to the resistance in the reference atmosphere,

- if the resistance in the test gas decreases relative to the resistance in the reference atmosphere.

The chemoresistive effect (receptor function) in macromolecular Gr-Dye composites under normal conditions in a normal oxygen-containing atmosphere is determined by the presence on the edges and surface of the graphene lattice of covalently immobilized molecules of organic dyes, which have a high specific affinity for gas molecules and VOCs, and also have a pronounced electron-acceptor or electron-donating effect, which leads to p- and n-doping of the material. When dye molecules interact with molecules of gases and organic vapors, an electron-acceptor or electron-donor interaction occurs between a dye molecule and a gas molecule or organic vapor. This leads to a redistribution of the electron density in the graphene layer in the dye molecule, which reduces its electron acceptor or electron donor, and can also lead to charge transfer from the dye molecule to graphene. Together, these two processes lead to a change in the resistance of the macromolecular composite, as shown in the example in FIG. 16-fig. 17.

An additional important factor in the chemoresistive response in sensor elements formed from a layer of macromolecular complexes based on functionalized graphenes with covalently bound organic dye molecules is that they are represented by an array of platelets. Potential barriers are formed at the sites where such plates are applied, which significantly affects the transport of charge carriers or the signal conversion function and also contributes to the chemoresistive response of the sensor element. Moreover, their values for plates of different sizes and different concentrations of immobilized molecules are different, leading to differences in the chemoresistive response of various sensor elements of the chip within one segment of the gas-sensitive layer.

When using a gas detector based on macromolecular Gr-Dye complexes in the form of a gas sensor, the absence of hysteresis in the current-voltage characteristics of the measuring segments is checked (Fig. 15). If it is necessary to recognize the type of gas mixture, a gas detector is used in the form of a multisensor ruler formed on a chip, in which differences in the gas response of chemoresistive elements in the multisensory line of the chip are used to construct a vector multisensory signal. The resulting multisensory signal forms an “image” of the detected gas or gas mixture. For the task of selective recognition of the type of gas mixture, the vector signal of a gas analytical multisensor chip based on Gr-Dye macromolecular composites when exposed to different gases is processed by pattern recognition methods, for example, the principal component method, and/or linear discriminant analysis (LDA) and/or correlation analysis, and/or artificial neural networks to identify “phase” characteristics or features corresponding to the calibration gas environment. At the same time, for each recognition method, its own features are generated, for example, in LDA - these are the so-called LDA components. At the stage of calibrating the multisensor chip to the effects of known test gaseous media, the obtained signs are recorded in a database stored in a personal computer or other computing system. At the stage of measuring an unknown gaseous medium using a multisensor chip, the procedure for obtaining a vector signal from chemoresistive elements is carried out in the same way as at the calibration stage. In this case, the phase characteristics obtained using the pattern recognition method when exposed to an unknown gaseous medium are compared with the phase characteristics available in the database based on the calibration results, and a decision is made to classify the unknown gaseous medium as the gas for which the calibration was carried out, which allows “recognizing »composition of the gaseous medium (Fig. 18).

Example. A gas detector was manufactured - a multisensor chip based on macromolecular composites "Functionalized graphene - Azur A", "Functionalized graphene - Neutral Red" and "Functionalized graphene - Acridine Yellow" with a content of organic dye molecules of at least 1 at. %. As a base platform, we used a chip made on the basis of a silicon substrate with a size of (9×10) mm and a thickness of 640 μm with a layer of silicon oxide grown on it with a thickness of 320 nm (Fig. 1). A set of coplanar strip gold electrodes in an amount of 39, with a width of 50 μm, a thickness of about 100 nm and an interelectrode gap of 50 μm, was deposited on the front side of the substrate using a magnetron sputtering method (Emitech K575X installation, UK), according to a pre-formed photolithographic pattern. Also, on the front side of the substrate 1, thin-film thermistors 3 and meander heaters 4 made of gold with a thickness of about 100 nm were applied along the edges using the same method and the same technological process. The track width of the thermistors was 20 μm, and that of the meander heaters was 50 μm. A gas-sensitive layer of three segments 5-7, represented by macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow” was applied in the form of an aerosol to the surface of coplanar electrodes and the surface of the substrate between the electrodes.

Macromolecular composites “Functionalized graphene - Azur A” and “Functionalized graphene - Neutral Red” were synthesized by adding a weighed portion of the Azur-A or Neutral Red dye to distilled water in a ratio of 6 g/l, followed by adding concentrated hydrochloric acid to the resulting solution in a ratio of 0. 03 l/l. The resulting reaction mixture was cooled to a temperature of 0-2°C in a cooling bath and set to stirring using a magnetic stirrer at a speed of 200 rpm. While stirring, a portion of sodium nitrate was added, reaching a final ratio of 3.5 g/l, after which the reaction mixture was left to stir for another 30 minutes until the color of the solution changed from blue to black. While stirring the reaction mixture, a working suspension of reduced graphene oxide was prepared by adding a sample of reduced graphene oxide powder to distilled water in a ratio of 3.5 g/l, after which the resulting suspension was treated in an ultrasonic bath with an ultrasound frequency of 40 kHz and the power of an ultrasonic emitter in the range of 150 W for 3 minutes, followed by cooling the suspension to a temperature of 0-2°C in a cooling bath. Next, a solution of diazonium salt of the dye was added to the resulting working suspension of reduced graphene oxide in a ratio of 0.55 l/l, the resulting reaction mixture was set to stirring using a magnetic stirrer at a speed of 100 rpm and exposed to ultraviolet radiation from a deuterium lamp with an electric power of 30 W and a spectral maximum intensity near 248 nm for 3 hours. After the specified time, the reaction mixture was poured into a glass Schott filter with a pore size of 16 μm.

At the fourth stage, the resulting composites are cleaned by repeated washing on a glass filter. To do this, the resulting suspension is filtered 18 on a Schott filter with a pore size of 16 μm. To create a vacuum in the filter, a chemical vacuum station VACUUBRAND PC 3001 VARIO with a set pressure of 50 Pa was used. During filtration, the precipitate, which is the final product, was washed with a 3% solution of hydrochloric acid until the wash water became discolored (visual control), after which it was washed three times with 25 ml of distilled water. The sediment remaining on the filter after the described cleaning procedures was dried in air at room temperature for 40 minutes, obtaining the macromolecular composite “Functionalized graphene - Azur A” or “Functionalized graphene - Neutral Red” in powder form.

Macromolecular composite "Functionalized graphene - Acridine Yellow" was prepared as follows. Thiolation of graphene oxide was carried out by adding a sample of graphene oxide powder to thionyl chloride in a ratio of 3.5 g/l, followed by heating the resulting suspension to a temperature of 80°C for 60 minutes. After the specified time, vacuum distillation of the resulting suspension was performed for 6 hours in order to remove thionyl chloride, followed by filling the flask with the resulting thiolated graphene oxide with argon gas to prevent contact with oxygen and water vapor from the air. Next, a reaction mixture was formed based on the “Acridine Yellow” dye by adding a sample of the “Acridine Yellow” dye and a solution of pyridine to acetonitrile in ratios of 4.5 g/l and 0.045 l/l, respectively. A sample of thiolated graphene oxide was added to the resulting reaction mixture in a ratio of 0.2 g/l, and the resulting mixture was stirred using a magnetic stirrer at a speed of 100 rpm for 4 hours.

After the specified time, the resulting material was purified by repeated washing on a Schott filter with a pore size of 16 μm. To create a vacuum in the filter, a chemical vacuum station VACUUBRAND PC 3001 VARIO with a set pressure of 50 Pa was used. During filtration, the precipitate, which is the final product, was washed with acetonitrile until the wash water became discolored (visual control), after which it was washed three times with 40 ml of isopropyl alcohol. The sediment remaining on the filter after the described cleaning procedures was dried in air at room temperature for 40 minutes, obtaining the macromolecular composite “Functionalized graphene - Acridine Yellow” in powder form.

For aerosol application, basic suspensions of Gr-Dye macromolecular composites were formed by adding a sample of the applied macromolecular composite powder to 100 ml of propylene glycol in a ratio of 20 μg/ml. The resulting working suspension was treated in an ultrasonic bath for 10 minutes at an ultrasound frequency of 40 kHz, with an ultrasonic emitter power of 110 W, after which the suspension was left to mix on a magnetic stirrer at a speed of 100 rpm for 20 minutes.

For aerosol application, a dielectric substrate with a system of strip electrodes was placed on the surface of the heating table and a metal mask with a rectangular window (slot) measuring 6 × 1.7 mm was placed on a stand at a distance of 2 mm from its surface on a stand. An airbrush (JAS 1142) connected to a compressor with a drying system was vertically fixed at a distance of 150 mm from the surface of the mask. The heating stage temperature was set to 150°C, after which a working suspension of the selected Gr-Dye macromolecular composite, namely “Functionalized graphene - Azur A”, was applied at a pressure of 2 atm. and a carrier gas flow rate of 1 l/min, forming the first segment of the chip. Next, the mask was shifted by 1.7 mm in the direction perpendicular to the coplanar electrodes and the aerosol application procedure was performed using a working suspension of the “Functionalized graphene - Neutral Red” nanocomposite, and the process was repeated using a working suspension of the “Functionalized graphene - Acridine Yellow” nanocomposite. The suspension consumption was 40 ml/ ^cm2 .

After application, the substrate with the applied suspension was kept for 4 hours at room temperature, which was sufficient to remove residual solvent and improve the adhesion of the composite layer to the chip. As a result, a three-segment gas-sensitive layer was obtained, represented by the nanocomposites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow”.

The morphology of the gas-sensitive layer based on segments of Gr-Dye macromolecular composites was analyzed using scanning electron microscopy (Jeol JSM-7001F). The obtained scanning electron microscopy images showed that the thickness of the gas analytical layer from the segments “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow” varies from 200 nm to 1000 nm (Fig. 9- Fig. 10).

The chemical composition of macromolecular composites was studied by X-ray photoelectron spectroscopy (XPS, Thermo Fisher ESCALAB 250Xi XPS system). The presence of covalently bound dye molecules was confirmed based on the presence in the survey X-ray photoelectron spectra of lines N 1s 32 and S 2p 33 in the case of the macromolecular composite “Functionalized graphene - Azur A” (Fig. 11) and line N 1s 32 in the case of macromolecular composites “Functionalized graphene” - Neutral Red" (Fig. 12) and "Functionalized graphene - Acridine Yellow" (Fig. 13). The concentration of covalently bound dye molecules in the macromolecular composites of the gas-sensitive layer of the manufactured detector was determined based on the analysis of the integrated intensity of spectral components 30-33 (peaks) in the survey X-ray photoelectron spectra corresponding to the core line C 1s 30, O 1s 31, N 1s 32 and S 2p 33 According to the analysis, the concentration of covalently attached molecules of organic dyes was 2.6 at. %, 3.1 at. % and 1.8 at. %.

The multisensor chip thus obtained, containing a three-segment layer of macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow”, was welded into a 50-pin ceramic holder having a rectangular window for the chip and a set of gold-plated contact pads, and equipped with an Erni SMC connector with a pitch of 1.27 mm, the pins of which corresponded to individual electrodes, thin-film meander thermistors and Au heaters. The welding was carried out with gold microwire, 38 µm in diameter, using ultrasonic welding (WEST Bond 747677E, USA). In this case, the chip was placed in the holder window and held suspended by microwires; There was a gap of about 1 mm between the perimeter of the case window and the chip.

To measure the chemoresistive response, a multisensor chip based on macromolecular composites was placed in a 41 stainless steel chamber (Fig. 14), consisting of two parts held together by screws with silicone heat-resistant sealing rings. Each half of the chamber is equipped with a gas tube: the upper one is for supplying a gas flow with a hole in the chamber facing the front side of the chip, on which there is a three-segment layer of macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized Graphene - Acridine Yellow”, and the bottom one is for removing the gas mixture from the chamber. The chip holder was clamped between two parts of the camera so that the connector was on the outside, and the O-rings tightly pressed the window with the chip. Thus, a sealed volume approximately equal to 2 cm ³ was formed around the chip. A gas mixture supplied through an inlet tube located in the upper half of the chamber was blown onto the front side of a multisensor chip with a three-segment layer of macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow” through the gap between the chip and the holder window. The gas mixture was discharged through an outlet tube at the bottom of the chamber into a fume hood through exhaust 46. The multisensor chip was exposed, for example, to test vapors of methanol and acetone mixed with dry air at a concentration of (4-10)×10 ³ ppm. Gas mixtures were generated by bubbling solutions of the corresponding analytes and mixed with dry air in specified proportions using a gas mixing unit (Fig. 14). The gas mixing unit contained a compressor with air intake from the surrounding atmosphere with a preliminary moisture separator 34, an adiabatic type air dryer 35, gas mass flow controllers 36, two-way software-controlled solenoid valves 37, a three-way software-controlled solenoid valve 38, a relay module for opening/closing control valves 39, bubbler with solutions of organic analytes 40.

The resistances of the sensor elements in the multisensor line (chip) of the gas detector sample were measured sequentially using an electrical measuring system, including a data acquisition platform 42, a measuring multimeter 43, a PID controller 44, a power supply for heaters 45 (RF patent No. 182198), controlled by a personal computer 47 based on developed software (Certificate of state registration of computer program No. 2015611599). The operating temperature of the multisensor gas analytical chip based on macromolecular composites corresponded to room temperature.

In fig. Figure 15 shows the current-voltage characteristics of typical sensor elements of gas-sensitive layer segments made of macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow” in an atmosphere of dry air. It can be seen that, although there is some nonlinearity in the current-voltage characteristics of the gas-sensitive layer segments, in all cases there is no hysteresis between the forward and reverse branches of the current-voltage characteristic. In fig. 16-fig. Figure 17 shows a typical chemoresistive response of typical sensor elements of segments of a gas-sensitive layer made of macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow” as a change in resistance when exposed to methanol (Fig. 16) and acetone (Fig. 17) in a mixture with dry air in the concentration range (4-10)×10 ³ ppm. It can be seen that when exposed to analytes in dry air, the resistance of the chemoresistive elements increases and decreases reversibly. Higher concentrations of analytes lead to more significant changes in resistance.

The response is reproducible, stable and exceeds 3 times the amplitude of electrical noise. This allows us to consider these chemoresistive elements suitable for practical use as gas sensors. The resulting chemoresistive response is explained by a change in the conductivity of the graphene layer when molecules of organic dyes come into contact with molecules of gases and vapors of analytes, as well as by a change in the value of potential barriers at the points of contact of graphene plates with each other in the layer when the composition of the atmosphere surrounding the chip changes. In this case, variations in the thickness of the graphene layer and the concentration of covalently immobilized dye molecules affect the change in its chemoresistive response from one sensor element of a multisensor gas analytical chip to another.

As follows from the type of chemoresistive response, by analyzing the typical sensor elements of the segments of the gas-sensitive layer from the macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow” it is impossible to distinguish the effects of different vapors by type/ the magnitude of the change in resistance. However, they can be distinguished by analyzing the vector signal of the multi-sensor chip. For this purpose, the cumulative vector response of a gas analytical multisensor chip based on a three-segment gas-sensitive layer made of macromolecular composites “Functionalized graphene - Azur A”, “Functionalized graphene - Neutral Red” and “Functionalized graphene - Acridine Yellow” was formed from the responses of 14 chemoresistive elements of the multisensor chip when exposed to log-pretreated analytes and processed by linear discriminant analysis (LDA). To construct the samples, 20 vector signals were used, obtained by recording stationary values of R(t) in each gaseous medium after a change in atmosphere. The results are presented in Fig. 18; As an example, the difference in responses to analytes at concentrations of 10,000 ppm is shown. The constructed data clusters corresponding to the vector responses of the multisensor chip to the effects of various analyte vapors are significantly removed from each other - the average distance between the centers of gravity of the analyte cluster is 118.2 rel. units - and at the same time sufficiently distant from the cluster corresponding to dry air - the average distance corresponds to 117.1 rel. units and 11.5 rel. units for acetone and methanol, respectively. The results obtained indicate the high gas sensitivity and efficiency of gas recognition by the proposed detector. The present invention allows not only to detect these gases, that is, to perform the function of a sensor, but also to identify them, that is, to perform the function of a gas analyzer.

Claims (20)

1. A gas analytical multisensor chip, including a dielectric substrate, coplanar strip electrodes located on the substrate, thermistors and heaters, wherein at least part of the surface of the electrodes and the substrate between the electrodes is covered with a gas-sensitive layer, the resistance of which changes at room temperature under the influence of impurities of organic vapors or water vapor in the ambient air, characterized in that the gas-sensitive layer is formed by at least two segments made of macromolecular composites based on functionalized graphenes, covalently modified with dye molecules in a concentration of at least 1 at. %, selected from the group including paradimethylaminobenzylidenorodanine, Acridine Yellow, Pararosaniline, Bismarck Brown, Neutral Red and Azur A dyes, wherein the gas-sensitive layer segments are made with a variable and different thickness from 100 nm to 2000 nm. 2. Gas analytical multisensor chip according to claim 1, characterized in that the gas-sensitive layer is formed by three segments made of macromolecular composites based on functionalized graphenes with covalently immobilized dyes “Azur A”, “Neutral Red”, “Acridine Yellow”. 3. Gas analytical multisensor chip according to claim 1, characterized in that each of the segments of the gas-sensitive layer covers at least 30% of the total surface area of the electrodes and the substrate between the electrodes. 4. Gas analytical multisensor chip according to claim 1, characterized in that the segments are made with a thickness varying in the range from 200 nm to 1000 nm. 5. Gas analytical multisensor chip according to claim 1, characterized in that macromolecular composites based on functionalized graphene are synthesized by the method of liquid-phase chemical modification of graphene derivatives. 6. A method for manufacturing a gas analytical multisensor chip, including applying a set of coplanar strip electrodes, heaters and thermistors to the surface of a dielectric substrate, followed by applying a suspension containing particles of a gas-sensitive material to the surface of the electrodes and the substrate between the electrodes, and drying the resulting structure, characterized in that the surface of the electrodes and the substrate between the electrodes are coated with at least two different suspensions containing macromolecular composites based on functionalized graphene, covalently modified with dye molecules in a concentration of at least 1 at. %, selected from the group including dyes paradimethylaminobenzylidenorodanine, “Acridine yellow”, “Pararozaniline”, “Bismarck brown”, “Neutral red” and “Azur A”, while applying suspensions to the surface of the electrodes and the surface of the substrate between the electrodes is carried out with the formation of drying at least two segments of the gas-sensitive layer of variable and different thickness from 100 nm to 2000 nm. 7. A method for manufacturing a gas analytical multisensor chip according to claim 6, characterized in that three different suspensions of macromolecular composites based on functionalized graphene are applied to the surface of the electrodes and the substrate between the electrodes to form three segments of the gas-sensitive layer, while suspensions of macromolecular compounds are used as suspensions of graphene derivatives composites based on functionalized graphene with covalently immobilized dyes “Azur A”, “Neutral Red”, “Acridine Yellow”. 8. A method for manufacturing a gas analytical multisensor chip according to claim 6, characterized in that the macromolecular composites “Functionalized graphene – Azur A” and “Functionalized graphene – Neutral Red” are produced (1) at the first stage, obtaining diazonium salt of the dye “Azur A” or “Neutral Red” by adding a sample of the dye “Azur-A” or “Neutral Red” to distilled water in a ratio of 6-7 g/l, adding concentrated hydrochloric acid to the resulting solution acid in a ratio of 0.02-0.03 l/l, cooling the resulting reaction mixture to a temperature of 0-2°C in a cooling bath, stirring, adding sodium nitrite solution to the reaction medium in a ratio of 3-4 g/l, stirring the resulting solution until the color of the solution changes from blue to black; (2) at the second stage, adding a weighed portion of reduced graphene oxide powder to distilled water in a ratio of 3-3.5 g/l, processing in an ultrasonic bath with an ultrasonic frequency of 20-40 kHz and an ultrasonic emitter power in the range of 110-170 W, cooling the resulting the reaction mixture to a temperature of 0-2°C in a cooling bath; (3) at the third stage, adding a solution of diazonium salt of the “Azur A” or “Neutral Red” dye to a suspension of reduced graphene oxide in a ratio of 0.5-0.75 l/l, stirring and simultaneous treatment with ultraviolet radiation for 3-3.5 hours; (4) at the fourth stage, cleaning the resulting composite by repeated washing on a Schott filter connected through a Wurtz nozzle with a drain flask and a vacuum station using a 3% solution of hydrochloric acid and deionized water until the wash water becomes discolored, drying the sediment at room temperature for 30-40 minutes to obtain the macromolecular composite “Functionalized graphene – Azur A” or “Functionalized graphene – Neutral Red”. 9. The method of manufacturing a gas analytical multisensor chip according to claim 6, characterized in that the macromolecular composite “Functionalized graphene - Acridine Yellow” is produced (1) at the first stage, adding a sample of graphene oxide powder to thionyl chloride in a ratio of 3-3.5 g/l, heating the resulting suspension to a temperature of 80°C for 60-80 minutes, vacuum distillation of the resulting suspension for 6-7 hours to remove thionyl chloride and fill the flask with the suspension with argon; (2) at the second stage by adding the “Acridine yellow” dye to acetonitrile in a ratio of 4.5-5.5 g/l and a pyridine solution in a ratio of 0.045-0.055 l/l, adding a portion of thiolated graphene oxide obtained in the first stage, in ratio of 0.2-0.25 g/l, stirring the resulting reaction mixture for 3-4 hours; (3) at the fourth stage, cleaning the resulting composite by repeated washing on a Schott filter connected through a Wurtz nozzle with a drain flask and a vacuum station using acetonitrile and isopropyl alcohol until the wash water is discolored, drying the precipitate at room temperature for 30-40 minutes to obtain a macromolecular composite “Functionalized graphene – Acridine yellow”. 10. A method for manufacturing a gas analytical multisensor chip according to claim 6, characterized in that the suspension is applied by aerosol spraying using a mask with a window 6-10 mm long and 1-5 mm wide at a suspension flow rate of 0.5-5 ml/ ^cm2 . 11. A method for manufacturing a gas analytical multisensor chip according to claim 6, characterized in that drying is carried out in air only at room temperature for 4 hours until the remaining solvent is completely removed. 12. A method for manufacturing a gas analytical multisensor chip according to claim 6, characterized in that the suspension is applied to form a layer of variable thickness after drying, varying in the range from 200 nm to 1000 nm within each segment. 13. A method for manufacturing a gas analytical multisensor chip according to claim 6, characterized in that the suspension is applied to ensure that the layer thickness after drying changes by at least 10% within each segment.