GAS MULTISENSOR AND DEVICE FOR ANALYZING A MULTI-COMPONENT GAS MIXTURE

Abstract

The invention relates to the field of measuring equipment, and more particularly, to gas analysis sensors/chemical sensors designed to analyze the composition of gas mixtures and to detect and quantify toxic chemical gaseous compounds in an environment. The gas multisensor includes an array of N organic field-effect transistors, each of which consist of at least a source electrode and a drain electrode separated by an organic semiconductor layer, a gate electrode, a dielectric layer, and an additional receptor layer based on a metalloporphyrin of general formula 1 or 2 and completely or partially covering the organic semiconductor layer, while a metal ion M of metalloporphyrin is a transition metal, and each of the N organic field-effect transistors contained in the array differs from the other organic field- effect transistors in the array by the chemical structure of the receptor layer. The technical result is lowering the limit of detection of an electronic nose device based on chemosensors.

##STR00001##

Claims

1. A gas multisensor, comprising an array of N organic field-effect transistors, each comprising at least “drain” and “source” electrodes separated by an organic semiconductor layer, a “gate” electrode, a dielectric layer and a receptor layer based on metalloporphyrin of general formula 1 or 2, completely or partially covering the organic semiconductor layer in a structure of the N-th organic field-effect transistor: ##STR00008## wherein the metal-ion M of metalloporphyrin is a transition metal, and each of the N organic field-effect transistors included in the array differs from other field effect transistors of the array by chemical structure of the receptor layer.

2. The gas multisensor according to claim 1, wherein the metal-ion M of metalloporphyrin is a transition metal ion selected from the following group: Cu, Zn, Co, Fe, Ni, Cr, Mn, Ti or V.

3. The gas multisensor according to claim 1, wherein the array of N organic field-effect transistors is formed on a single substrate.

4. The gas multisensor according to claim 1, wherein it determines the presence of one of the following gases: ammonia, hydrogen sulfide, nitrogen dioxide, ethyl mercaptan.

5. The gas multisensor according to claim 1, wherein the organic semiconductor layer of the organic field-effect transistor is a self-assembled monolayer made of chemically inert organosilicon derivatives of oligothiophene, benzothienobenzothiophene or diphenylbitiophene soluble in organic solvents.

6. The gas multisensor according to claim 1, wherein thickness of the organic semiconductor layer of the organic field effect transistor is 2-20 nm.

7. A gas multisensor, comprising an array of N organic field-effect transistors, each comprising at least “drain” and “source” electrodes, separated by an organic semiconductor layer, a gate electrode, a dielectric layer and a receptor layer based on metalloporphyrin of general formula 1 or 2, completely or partially covering the organic semiconductor layer in a structure of the N-th organic field-effect transistor: ##STR00009## where the metal-ion M of metalloporphyrin is a transition metal, and each of the N organic field-effect transistors included in the array differs from other organic field-effect transistors in the array by chemical structure of the receptor layer, wherein the array of N organic field-effect transistors further comprises at least one organic field-effect transistor not having the receptor layer and suitable for quantitative determination of concentration of several low molecular weight toxic gases in atmospheric air or in a gas mixture.

8. The gas multisensor according to claim 7, wherein the metal-ion M of porphyrin is a transition metal ion selected from the following group: Cu, Zn, Co, Fe, Ni, Cr, Mn, Ti or V.

9. The gas multisensor according to claim 7, wherein after the array of N organic field-effect transistors is formed on a single substrate, organic field-effect transistors with the receptor layer are placed along perimeter of the substrate, and an organic field-effect transistor that does not have a receptor layer is located in central parts of the substrate.

10. The gas multisensor according to claim 7, wherein the receptor layers of metalloporphyrins are deposited using the Langmuir-Blodgett method by partially dipping the substrate into a subphase.

11. The gas multisensor according to claim 7, wherein the organic semiconductor layer of the organic field-effect transistor is a self-assembled monolayer made of chemically inert organosilicon derivatives of oligothiophene, benzothienobenzothiophene or diphenylbitiophene soluble in organic solvents.

12. The gas multisensor according to claim 7, wherein thickness of the organic semiconductor layer of the organic field effect transistor is 2-20 nm.

13. The gas multisensor according to claim 7, wherein it determines presence and concentration of one of the following gases: ammonia, hydrogen sulfide, nitrogen dioxide, ethyl mercaptan.

14. An “electronic nose” device for analyzing a multicomponent gas mixture, comprising: a gas multisensor made according to claim 1 or claim 7; a measuring unit connected to each of the organic field-effect transistors in the gas multisensor, the measuring unit being configured to measure current values in each of the N organic field-effect transistors included in the array depending on time; a microprocessor connected to the measuring unit and configured to analyze response of each of the N organic field-effect transistors and determine a type of low molecular weight toxic gas present in the gas mixture, as well as its concentration; a tight chamber with gas inlet and outlet, where the gas multisensor is located.

15. The device according to claim 14, wherein it determines presence and concentration of one of the following gases: ammonia, hydrogen sulfide, nitrogen dioxide, ethyl mercaptan.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] An example of implementation of the invention is confirmed by the following drawings.

[0038] FIG. 1 is a diagram of a gas multisensor device based on organic field-effect transistors.

[0039] FIG. 2 is a diagram of a gas multisensor based on organic field-effect transistors placed on different substrates.

[0040] FIG. 3 is a diagram of a gas multisensor based on organic field-effect transistors manufactured on a single substrate.

[0041] FIG. 4 is a graph illustrating volt-ampere curves of an organic field-effect transistor before metalloporphyrin deposition.

[0042] FIG. 5 is a graph illustrating volt-ampere curves of an organic field-effect transistor after deposition of metalloporphyrin.

[0043] FIG. 6 is a diagram of an “electronic nose” device based on a gas multisensor.

[0044] FIG. 7 is a graph illustrating the dependence of the current value on time for an organic field-effect transistor with a receptor layer of TiO-TPP metalloporphyrin at different concentrations of one gas (ammonia).

[0045] FIG. 8 is a graph illustrating the the dependence of the current value on time for an organic field-effect transistor with a receptor layer of TiO-TPP metalloporphyrin for different gases of the same concentration.

[0046] FIG. 9 is a graph illustrating the dependence of the current value on time for an organic field-effect transistor with various receptor layers of metalloporphyrins.

[0047] FIG. 10 illustrates the results of recording the response of a gas multisensor based on organic field-effect transistors by the linear discriminant analysis (LDA) method.

[0048] FIG. 11 illustrates dependence of the relative value of the current in the organic field-effect transistor without the receptor layer on the gas concentration for a gas mixture containing ammonia (NH.sub.3).

[0049] FIG. 12 illustrates dependence of the relative value of the current in the organic field-effect transistor without the receptor layer on the gas concentration for a gas mixture containing hydrogen sulfide (H.sub.2S).

[0050] FIG. 13 illustrates dependence of the relative value of the current in the organic field-effect transistor without the receptor layer on the gas concentration for a gas mixture containing nitrogen dioxide (NO.sub.2).

[0051] FIG. 14 illustrates dependence of the relative value of the current in the organic field-effect transistor without the receptor layer on the gas concentration for a gas mixture containing ethyl mercaptan (Et-SH).

[0052] In the drawings, the positions have the following designations:

[0053] 1—gas sensor based on organic field-effect transistor with a receptor layer;

[0054] 1.sup.1—substrate of each organic field-effect transistor;

[0055] 1.sup.2—single substrate for placing an array of organic field-effect transistors;

[0056] 1.sup.3—organic field-effect transistor without a receptor layer;

[0057] 2—drain electrode;

[0058] 3—source electrode;

[0059] 4—organic semiconductor layer;

[0060] 5—gate electrode;

[0061] 6—dielectric layer;

[0062] 7—receptor layer;

[0063] 8—gas multisensor based on organic field-effect transistors;

[0064] 9—sealed chamber;

[0065] 10—power supply;

[0066] 11—measuring unit;

[0067] 12—microprocessor.

DETAILED DESCRIPTION OF THE INVENTION

[0068] The gas multisensor 8 shown in FIG. 1 is an array of N organic field-effect transistors 1, each of which includes at least electrode 2—“drain”, electrode 3—“source”, separated by an organic semiconductor layer 4, electrode 5—“gate”, dielectric layer 6 and receptor layer 7, completely or partially covering the organic semiconductor layer 4 in the structure N of the organic field-effect transistor.

[0069] In a preferred embodiment of the invention, the receptor layer 7 is made on the basis of a metalloporphyrin of the general formula 1 or 2:

##STR00004##

where the porphyrin metal ion M is the ion of transition metal, such as Cu, Zn, Co, Fe, Ni, Cr, Mn, Ti or V. In a preferred embodiment of the gas multisensor shown in FIG. 2, an array of N organic field-effect transistors 1, used for a qualitative analysis of the composition of atmospheric air or a gas mixture, may contain at least one organic field-effect transistor 1.sup.3 having no receptor layer, which can be used to quantify the concentration of low molecular weight toxic gas in atmospheric air or gas mixture, containing ammonia (NH.sub.3), hydrogen sulfide (H.sub.2S), nitrogen dioxide (NO.sub.2), ethyl mercaptan (Et-SH).

[0070] In a preferred embodiment of a gas multisensor, an array of N organic field-effect transistors 1 is formed on a single substrate 1.sup.2 (FIG. 3), while the receptor layers 7 of metalloporphyrins are transferred using the Langmuir-Blodgett method by partially dipping the substrate 1.sup.2 into a subphase. If there are N organic field-effect transistors 1 in the array of at least one organic field-effect transistor 1.sup.3 that does not have a receptor layer, it is preferable to place such a transistor in the central part of the substrate 1.sup.2, and N organic field-effect transistors 1 with a receptor layer 7 are placed mainly along the perimeter of the substrate 1.sup.2. The proposed arrangement of N organic field-effect transistors 1 allows the transfer of each subsequent receptor layer 7 without damaging the receptor layers 7 of other transistors in the array.

[0071] In a preferred embodiment of the gas multisensor 8, the organic semiconductor layer 4 is a self-assembled monolayer and can be made of chemically inert organosilicon derivatives of oligothiophenes, benzothienobenzothiophenes or diphenylthiophenes, such as 1,3-bis[11-(5′″-hexyl-2,2′:5′,2″:5″,2′″-quatrothiophen-5-yl)undecyl]-1,1,3,3-tetramethyldisiloxane, 1,3 -bis[11-([1]benzothieno [3,2-b][1]benzothien-2-yl)undecyl]-1,1,3,3-tetramethyldisiloxane, 1,3 bis[11-(7-hexyl[1]benzothieno[3,2-b][1]benzothien-2-yl)undecyl]-1,1,3,3 -tetramethyldisiloxane, 1,3-bis[11-(4-{5-[4(trimethylsilyl)phenyl]-2,2-bitien-5-yl}phenyl)undecyl]-1,1,3,3 -tetramethyldisiloxane. The implementation of the organic semiconductor layer 4 is not limited to the aforementioned examples.

[0072] Organic semiconductor layer 4 can be obtained by any of the known methods, in particular, by the Langmuir Blodgett method [Sizov A. S., Agina E. V., Gholamrezaie F. [et. al.] Oligothiophene-Based Monolayer Field-Effect Transistors Prepared by Langmuir-Blodgett Technique/Applied Physics Letters.-2013.-V. 103, No 4.-P. 043310], by the Langmuir-Schaefer method [Tanese M. C., Farinola G. M., Pignataro B. [et. al.] Poly(Alkoxyphenylene-Thienylene) Langmuir-Schäfer Thin Films for Advanced Performance Transistors/Chemistry of Materials.-2006.-V. 18, No 3.-P. 778-784], by spin coating method [Hall D. B., Underhill P., Torkelson J. M. Spin Coating of Thin and Ultrathin Polymer Films/ Polymer Engineering and Science.-1998.-V. 38, No 12.-P. 2039-2045], by doctor blade method [Yan Y., Huang L. B., Zhou Y. [et. al.] Self-Aligned, Full Solution Process Polymer Field-Effect Transistor on Flexible Substrates/Sci Rep.-2015.-V. 5.-P. 15770], by drop-casting method [Diao Y., Shaw L., Bao Z., Mannsfeld S. C. B. Morphology Control Strategies for Solution-Processed Organic Semiconductor Thin Films/Energy Environ. Sci.-2014.-V. 7, No 7.-P. 2145-2159].

[0073] In a preferred embodiment of the gas multisensor 8, the thickness of the organic semiconductor layer 4 can be from 2 to 20 nm, which provides high sensor sensitivity. Since the electric current in the N organic field-effect transistor, which is part of the gas multisensor 8, is localized in a thin near-surface layer at the boundary “organic semiconductor layer 4—dielectric layer 6”, the thickness of the organic semiconductor layer 4 in the range from 2 to 20 nm provides a direct effect of the receptor layer 7 on the current-carrying part of the semiconductor layer 4. The lower limit of the specified range of 2 nm corresponds to the minimum thickness of the organic semiconductor layer 4, at which the organic field-effect transistors 1 exhibit electrical and gas-sensitive properties. The upper limit of the specified range of 20 nm provides the ability to detect low concentrations of target gases in the concentration range of less than 1 ppm. With an increase of the thickness of the organic semiconductor layer 4, the sensitivity of the gas multisensor in the ppb range decreases.

[0074] In a preferred embodiment of the gas multisensor 8, the receptor layer 7 is a monolayer, which provides a high sensitivity of the device. When the detected toxic gas interacts with the surface of the receptor layer 7, local dipole moments arise, creating electrostatic fields. Since the magnitude of the field decreases with distance, the small thickness of the receptor layer 7 of metalloporphyrin provides the greatest influence of the receptor surface on the conducting channel of the transistor.

[0075] The necessity to use separate semiconductor 4 and receptor 7 layers stems from the fact that the receptor layer 7 with a small thickness has extremely low electrical characteristics, insufficient for the gas sensor operation. The principal factor for achieving the technical result is the preservation of high electrical characteristics of the monolayer organic field-effect transistor 1 during the transfer of the receptor layer 7. This result is achieved due to the fact that the receptor layer 7 is transferred to the substrate 1.sup.1 or 1.sup.2, containing N organic field-effect transistors 1, using the Langmuir-Blodgett method or Langmuir-Schaeffer method [Wei Z. M., Cao Y., Ma W. Z., Wang C. L., Xu W., Guo X. F., Hu W. P., Zhu D. B. Langmuir-Blodgett Monolayer Transistors of Copper Phthalocyanine/Applied Physics Letters.-2009.-V. 95, No 3], which excludes the ingress of the organic solvent into the organic semiconductor layer 4 and violation of its integrity. To illustrate the result, FIG. 4 shows the electrical characteristics of the organic field-effect transistor before applying the receptor layer 7, and FIG. 5 shows the electrical characteristics of the organic field-effect transistor after applying the receptor layer 7.

[0076] In a preferred embodiment of the gas multisensor 8, the dielectric layer 5 can be made of thermally grown dry silicon dioxide modified with a self-assembled monolayer (SAM-self-assembled monolayer) of octyldimethylchlorosilane (ODMS) or another alkylchlorosilane providing a sufficiently low surface roughness (<0.5 nm) of the dielectric layer 5.

[0077] The production of a gas multisensor 8 based on organic field-effect transistors 1 shown in FIG. 2 and FIG. 3 is preferably carried out as follows.

[0078] By known methods, for example, [Sizov A. S., Anisimov D. S., Agina E. V. [et. al.] Easily Processable Highly Ordered Langmuir-Blodgett Films of Quaterthiophene Disiloxane Dimer for Monolayer Organic Field-Effect Transistors/Langmuir.-2014.-V. 30, No 50.-P. 15327-34], on a single substrate 1.sup.2 or on separate substrates 1.sup.1 an array of N organic field-effect transistors 1 is formed, each of which includes at least electrode 2—“drain”, electrode 3—“source”, separated by layer 4 of organic semiconductor, electrode 5—“gate” and dielectric layer 6. Then, over the layer 4 of the organic semiconductor of each of the N organic field-effect transistors sequentially using the Langmuir-Blodgett or Langmuir-Schaeffer methods a receptor layers 7 of metalloporphyrins of various chemical structures are transferred.

[0079] As an example, the following compounds were used to form the receptor layer 7 based on metalloporphyrins:

##STR00005## ##STR00006##

[0080] The technical result is achieved by using a number of 4-6 different metalloporphyrins having a general formula 1 or 2:

##STR00007##

where the porphyrin metal ion M is the transition metal ions Cu, Zn, Co, Fe, Ni, Cr, Mn, Ti or V.

[0081] The choice of these metalloporphyrins is due to two factors. The first is the simplicity of their chemical formula, which does not contain side substituents, which simplifies their synthesis and reduces the cost of final materials and devices based on them. The second factor is that the porphyrins used are readily soluble in common organic solvents, such as toluene, and are capable of forming large area uniform monolayers on the water surface, which can be then transferred onto a solid substrate by the Langmuir-Blodgett method. The formation of a homogeneous large area receptor monolayer provides a high sensitivity of this layer to the presence of toxic gases, while any defects in the layer, especially its thickening, increase the sensor limit of detection.

[0082] At the same time, an increase in the amount of organic field-effect transistors 1, having different receptor layers 7, in the composition of the gas sensor array 8 increases the reliability of the qualitative analysis of the composition of atmospheric air or gas mixture.

[0083] In the case of the creation of an array of N organic field-effect transistors 1 on a single substrate 1.sup.2 (FIG. 3), the receptor layers of metalloporphyrins are transferred using the Langmuir Blodgett method by partially dipping the substrate into a subphase.

[0084] The “electronic nose” for analyzing a multicomponent gas mixture, shown in FIG. 6, includes a gas multisensor 8 based on organic field-effect transistors 1 and 1.sup.3 according to any of the embodiments described above, a microprocessor 9, a measuring unit 10 connected to electrodes 2 «drain», 3 «source» and 5 «gate» of each of the N organic field-effect transistors 1 and 1.sup.3 as part of the gas multisensor 8 and the microprocessor 12, a sealed chamber 9 with gas inlet and outlet, where the gas multisensor 8 is located, power supply 10, connected to electrodes 2 “drain”, 3 “source” and 5 “gate” of each of the N organic field-effect transistors 1 and 1.sup.3.

[0085] The operation of an “electronic nose” for analyzing a multicomponent gas mixture based on a gas multisensor 8, including an array of N organic field-effect transistors 1, is carried out as follows.

[0086] A gas mixture containing one of the detectable gaseous toxic compounds in concentrations from 10 ppb to 1 ppm is supplied to the sealed chamber 9. A constant negative potential V of the value selected so that the electric field in the dielectric layer 6 is at least 50 kV/mm and the electric field in the layer 4 of the organic semiconductor is at least 0.5 kV/mm, is supplied to the electrodes 2 “drain” and electrodes 5 “gate” of each of the N organic field-effect transistors 1 with receptor layers 7, which are part of the gas multisensor 8 (FIG. 2 or FIG. 3), using the power supply 10. Furthermore, the values of the current I.sub.k (k=0 . . . N-1) are measured using the measuring unit 11 for each of the N organic field-effect transistors 1 with receptor layers 7 included in the multisensor 8, depending on the time t.

[0087] Furthermore, using software, the relative changes in current in N organic field-effect transistors are calculated in the microprocessor 12 according to the formula (1):

I.sub.rel.sup.k=I.sup.k/I.sub.0.sup.k,   (1)

where I.sub.rel.sup.k—relative current, relative units; [0088] I.sup.k—current in the channel of the N-th organic field-effect transistor at a given time, A; [0089] I.sub.0.sup.k—initial current in the channel of the N-th organic field-effect transistor, A.

[0090] The resulting series of values I.sub.rel.sup.k (k=0 . . . N-1) is used as an input data for one of the known methods of data analysis, implemented using the microprocessor 12 according to a given algorithm. As such a method, well-known methods of data processing for “electronic nose” systems can be used: the method of principal components analysis (PCA), the method of linear discriminants analysis (LDA), a neural network, etc. [Jurs P. C., Bakken G. A., McClelland H. E. Computational Methods for the Analysis of Chemical Sensor Array Data from Volatile Analytes/Chemical Reviews.-2000.-V. 100, No 7.-P. 2649-2678; Pedregosa F., Varoquaux G., Gramfort A., Michel V., Thirion B., Grisel O., Blondel M., Prettenhofer P., Weiss R., Dubourg V., Vanderplas J., Passos A., Cournapeau D., Brucher M., Perrot M., Duchesnay E. Scikit-Learn: Machine Learning in Python/Journal of Machine Learning Research.-2011.-V. 12.-P. 2825-2830].

[0091] The possibility of using known methods for the analysis of the data obtained and for a qualitative analysis of the composition of atmospheric air or gas mixture is due to a combination of the following factors. First, the values I.sub.rel.sup.k for each of N organic field-effect transistors 1 with a receptor layer 7 of metalloporphyrin in the gas sensor 8 depend on the content and concentration of low-molecular-weight toxic gases in the atmospheric air or gas mixture. In this case, the values I.sub.rel.sup.k in dry air without ammonia and with its content of 200 ppb-1 ppm differ significantly (see FIG. 7).

[0092] Secondly, the values I.sub.rel.sup.k for each of the N organic field-effect transistors 1 with a receptor layer 7 of metalloporphyrin depend on the type of low molecular weight toxic gas present in the atmospheric air or gas mixture. This fact is due to various properties of toxic gas molecules, such as size, magnitude of the dipole moment, donor-acceptor properties, etc. For example, FIG. 8 shows the dependence of the current value on time for an organic field-effect transistor with a receptor layer 7 of metalloporphyrin TiO-TPP for different gases of the same concentration.

[0093] Third, the values I.sub.rel .sup.k for each of N organic field-effect transistors 1 with a receptor layer 7 of metalloporphyrin, in the presence of a low molecular weight toxic gas, depend on the central atom of the metalloporphyrin molecule. This fact is due to differences in the kinetics of sorption of the same gas on the surface of a layer of metalloporphyrins of different chemical structure. For example, in FIG. 9 shows the dependence of the current value on time for an organic field-effect transistor with different receptor layers 7 of metalloporphyrins with an ammonia content of 200 ppb in the gas mixture.

[0094] As an example, FIG. 8 shows the result of applying the LDA method for gas mixtures containing one of the gases: NH.sub.3, H.sub.2S, NO.sub.2, Et-SH. The points corresponding to different gases are grouped into regions on the LDA diagram, and the indicated regions are separated. In accordance with the specified algorithm in the microprocessor 12, for the obtained set I.sub.rel.sup.k, a point is calculated on the LDA diagram and the type of the detected connection is determined in relation to one of the regions.

[0095] At the last step, according to the value I.sub.rel.sup.k obtained for the N organic field-effect transistor 1.sup.3 without a receptor layer, the concentration of the detected compound is determined according to calibration curves (FIGS. 11-14), previously stored in the memory of the microprocessor 12, according to the following algorithm. On the calibration curve of the current value versus concentration (FIG. 11-14), corresponding to the previously defined type of the detected compound, there is a point whose ordinate lies closest to the obtained value I.sub.rel.sup.k, and its abscissa is considered the measured concentration value. The established class of the detected compound, as well as its concentration measured in accordance with the algorithm, is then displayed to the user.