METHOD FOR THE DETECTION OF AMINATE COMPOUNDS IN THE AIR

Description

technical field

[0001] The present invention relates to a new method for detecting and optionally quantifying amine-type compounds, in particular hydrazine (N2H4), in air.

[0002] Hydrazine is a substance classified as CMR (IARC 2B-EU 1B). In 2011, it was added to the Candidate List of Substances of Very High Concern (CVHC) under the REACH Regulation. In 2017, the European Union lowered its 8-hour occupational exposure limit (OEL) by a factor of 10, imposing a new threshold of 10 ppb (0.013 mg / m³), applicable no later than January 17, 2020. In addition to its health risks to humans, hydrazine is classified as very toxic to aquatic organisms (EU classification H400 and H410).

[0003] Because of its CMR nature, hydrazine is no longer an oxidizer for rockets, but remains used in many fields, notably as an intermediate in organic synthesis in the pharmaceutical and chemical industries, or as a blowing agent for polymer foams, or as a reducer of metal salts or as a corrosion inhibitor in the water circuits of industrial boilers, for example.

[0004] Due to its toxicity, the assessment of risks associated with environmental hydrazine releases is important and requires the ability to detect and optionally quantify the presence of hydrazine in the environment.

[0005] The assessment of these risks is currently severely limited by the metrology associated with this substance, particularly regarding direct in-situ measurement. Indeed, despite the existence of relatively sensitive and specific analytical methods (final reading by HPLC-UV), these cannot be easily implemented or be compatible with industrial practices. "Instantaneous response" analytical methods are neither sufficiently selective nor sufficiently precise and sensitive to allow for the assessment of expected gaseous hydrazine concentrations in final discharges.

[0006] The detection and quantification of hydrazine are currently performed using an indirect method. This method involves collecting ambient air to be analyzed and trapping the hydrazine in an acidified cartridge, then desorbing it and reacting it with a reagent solution. The resulting addition compounds are then separated by liquid chromatography and analyzed optically.

[0007] Besides the length of this method, which involves several steps that are difficult to carry out directly at the sampling site, the potential interferences with other nitrogen gases are unknown, particularly in the potential presence of interfering compounds used to alkalize water or resulting from the degradation of hydrazine, such as ethanolamine (NH2EtOH), morpholine, or ammonia (NH3). It is important to be able to selectively measure hydrazine directly in a concentration range of 1 to 100 ppb in dry to very humid air and in the presence of interfering compounds whose concentration can be 50 to 100 times higher than that of hydrazine.

[0008] The process that is the subject of the present invention provides a solution to these problems.

[0009] Indeed, the method according to the invention allows for the detection and optional selective quantification of hydrazine in the presence of water vapor, volatile organic compounds, and other nitrogenous compounds such as ethanolamine (NH₂EtOH), morpholine, or ammonia. Upon contact with hydrazine, the sensor changes color, and the intensity of the color change is proportional to the hydrazine content, thus enabling the detection and potential quantification of this compound. Previous technique

[0010] The detection of hydrazine has been the subject of numerous studies, and the detection methods are as numerous as they are varied due to the high chemical reactivity of this compound. Therefore, only methods proposed in the literature, capable of covering the target concentration range of 1.3 to 130 µg.m-3 (i.e., 1 to 100 ppb), are described here.

[0011] Methods for measuring hydrazine in air are less numerous than those for the liquid phase, particularly in the targeted range of 1.3 to 130 µg.m⁻³ (i.e., 1 to 100 ppb). The current measurement method is described in INRS Fact Sheet 21. It relies on the use of benzaldehyde [1]. Hydrazine is collected by aspirating air through a tube filled with an inert adsorbent (Chromosorb P NAW or equivalent) with a particle size of 3060 Mesh, impregnated with sulfuric acid. The contents of the cartridge are desorbed with deionized water, and a benzaldehyde derivatization is performed. The addition compound, benzalazine, is measured by high-performance liquid chromatography (HPLC) coupled with optical detection in the UV [2, 3]. This method allows the detection of 30 ppb of hydrazine in 15 sampling minutes.

[0012] A variation of this method uses a cassette containing two glass fiber filters impregnated with sulfuric acid. Hydrazine is extracted with an EDTA buffer solution, and derivatization is performed with benzaldehyde. The benzalazine formed is measured by liquid chromatography coupled with optical detection in the UV range [4]. This assay method proves sensitive, as it is possible to detect 0.017 ppb of N₂H₄.

[0013] These two methods do not allow direct measurement at the sampling site and the interference of ammonia or other amines at high concentrations 50 to 100 times greater than that of hydrazine is not known.

[0014] Direct measurement methods are also available. For monitoring worker exposure to hydrazine, monomethylhydrazine (MMH), and 1,1-dimethylhydrazine (UDMH), used as rocket fuels at air bases and space centers in the United States, several colorimetric dosimeters have been developed and marketed by laboratories [5, 6]. The principle is based on incorporating an aromatic aldehyde such as vanillin, para-dimethylaminobenzaldehyde (pDMAB), or 2,4-dinitrobenzaldehyde onto filter paper or an inert surface. Hydrazine and MMH react with vanillin or 2,4-dinitrobenzaldehyde to form a yellow compound, while the product formed with pDMAB is orange. UDMH reacts with 2,4-Dinitrobenzaldehyde to form a yellow-colored compound and there is no reaction with vanillin and pDMAB.Colorimetric dosimeters based on vanillin and para-dimethylaminobenzaldehyde are marketed by DODTEC [7] and CHEMSEE [8]. They do not allow for exact quantification but only for estimating the concentrations of hydrazine and monomethylhydrazine in air from 25 ppb up to 1.2 ppm.

[0015] In patent US005719061A [9], Rose-Pehrsson et al. propose a method for the selective detection and quantification of liquid or gaseous hydrazine, monomethylhydrazine, and 1,1-dimethylhydrazine by derivatization with aromatic carboxyaldehydes and fluorimetric analysis. Selectivity is based on the reactivity of three derivatizing agents—orthophthalaldehyde (OPA), naphthalene 2,3-dicarboxaldehyde (NDA), and anthracene 2,3-dicarboxaldehyde (ADA)—with hydrazine, monomethylhydrazine, and 1,1-dimethylhydrazine, depending on the pH of the reagent solution. These authors developed a complex device that pumps ambient air through a reagent solution whose composition (OPA, NDA, or ADA) and pH must be modified to achieve selectivity.Even though the detection limit is reached in the ppb range, analyzing the gaseous mixture requires numerous steps involving changing reagents and pH, followed by fluorimetric analyses. Furthermore, there is no interference study, particularly with other amines at concentrations 50 to 100 times higher, which could alter the solution's pH. US2012295363A1 discloses a solid-state chemical sensor based on a porous sol-gel material doped with 4-(dimethylamino)cinnamaldehyde (DMABA) probe molecules. This sensor enables the detection and quantification of chemical compounds such as indole and its derivatives, as well as amines such as hydrazine and urobilinogen.

[0016] For precise measurements, several commercial devices are available. The Interscan portable electrochemical detector, model 4180-100b [10<], can detect hydrazine in the 10–100 ppb range in less than 1 second, with a high detection limit of 10 ppb. Furthermore, the method is not selective, as the sensor also detects NH3, NOx, CO, and other organic amines.

[0017] High sensitivity can be achieved using instruments equipped with a photoionization detector (PID) such as the ppbRAE 3000 from RAE

[11] . The photoionization detector, equipped with a 10.6 eV lamp, ionizes hydrazine and measures a few ppbs in 3 seconds. However, the detection is not selective, as many volatile organic compounds present in the air with an ionization potential below 10.6 eV are also detected, such as NH3, ethanolamine, and morpholine.

[0018] Ionization of hydrazine followed by measurement of ion mobility using ion mobility spectrometry, in English Ion Mobility Spectrometer (IMS) makes it possible to reach levels on the order of tens of ppb (20 - 30 ppb) while being selective with the choice of carrier gas. When using a radioactive source, IMS (such as the SABRE 4000 portable detector [12<] or the ChemPro100i from Environics [13<]) must be operated by a qualified radiation protection expert. This technique is preferred by the armed forces and police for the detection of chemical weapons and illicit substances. Its application in the public sector has developed more recently with the development of new non-radioactive ionization sources (Corona effect) such as the PAIMS portable detector from MaSaTECH [14<] or the LCD 3.3 from Smiths Detection [15<].

[0019] The state of the art in hydrazine measurements shows that the only currently adopted simple method, using benzaldehyde as a reagent, can be used with good selectivity and sensitivity. However, measuring hydrazine in the air compartment requires adsorption, desorption, and derivatization steps followed by optical analysis, which are difficult to perform on-site. Furthermore, the interference from high concentrations of gaseous NH3, ethanolamine, or morpholine in the atmosphere is unknown for this method.

[0020] There is therefore a real need for a method of direct detection and optional direct quantification of hydrazine in the air, selective for hydrazine, compatible with the presence of high concentrations of interfering substances, easy to implement in the field.

[0021] The process according to the invention addresses these problems. Summary

[0022] A first object of the invention is a nanoporous sensor composed of a nanoporous silicate sol-gel matrix containing a reagent composition, said reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid.

[0023] Another object of the invention is a method for preparing a nanoporous sensor according to the invention, said method comprising the following steps: a. Synthesis of a sol from an organosilyl precursor, the synthesis being carried out in a solvent, said solvent comprising water, in the presence of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid; b. Gelation of the sol obtained in step a), so as to obtain a gel; c. Drying of the gel obtained in step b), so as to obtain a nanoporous sensor.

[0024] The present invention also relates to a method for detecting at least one amine-type compound, said compound being selected from hydrazine, ethanolamine, ammonia, and morpholine, using a nanoporous sensor according to the invention, said method comprising the steps of: a. bringing a gaseous sample to be analyzed into contact with said nanoporous sensor, b. detection of said amine-type compound(s) on said nanoporous sensor.

[0025] Another object of the invention is the use of a nanoporous sensor according to the invention, for the detection and / or quantification of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine.

[0026] The present invention also relates to a device for detecting at least one amine-type compound, said compound being selected from hydrazine, ethanolamine, ammonia, and morpholine, in a gaseous sample to be analyzed, said device comprising a cell containing a nanoporous sensor according to the invention and comprising: a gas inlet; a gas outlet; an optical inlet; an optical outlet. Brief description of the drawings

[0027] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which: Fig. 1 [ Fig. 1 ] shows the scheme of the reaction between N 2 H 4 and DMACA catalyzed in acid medium with formation of DMACA-N 2 H 4 (compound 3) and 2DMACA-N 2 H 4 (compound 4). Fig. 2 [ Fig. 2[ ] shows the differential spectra obtained at different times showing the evolution of the absorbance of the DMACA-N 2 H 4 and 2DMACA-N 2 H 4 complexes in the nanoporous sensor Hy3 during the exposure of the sensor to a gas mixture flux containing 14 ppb of N 2 H 4 . A spectrum is collected every 5 min from 0 to 60 min. Fig. 3 [ Fig. 3 [ ] shows the differential spectra obtained at different times showing the evolution of the absorbance of neutral DMACA in the nanoporous sensor Hy1 during the exposure of the sensor to a gas mixture flow containing 5 ppm of NH3. A spectrum is collected every 5 min from 0 to 50 min. Fig. 4 [ Fig. 4 ] shows the diagram of an example of a device according to the invention. Fig. 5 [ Fig. 5 ] shows the diagram of an example of gas flow circulation around the nanoporous sensor placed in the cell according to a particular embodiment of the invention. Fig. 6 [ Fig. 6] shows the diagram of an example cell of the device according to the invention. Fig. 7 [ Fig. 7 [shows: on the left the evolution of the absorption spectrum of the Hy1 sensor exposed to 5 ppm of NH3, a spectrum is collected every 5 minutes for 50 minutes; on the right the variation of the rate of formation of neutral DMACA as a function of the concentration of NH3. Flux = 200 ml·min-1, %RH = 50%.] Fig. 8 [ Fig. 8 [ ] shows the calibration curve of the Hy3 sensor for the detection of N2H4. Variation of the formation rate of the 1DMACA-N2H4 complex at 388 nm as a function of the concentration of N2H4. Flux = 200 mL·min-1, %RH = 50%. Fig. 9 [ Fig. 9 ] shows the effect of the relative humidity of the gas mixture on the rate of formation of the 1DMACA-N 2 H 4 complex as a function of the concentration of N 2 H 4 . Flux = 200 mL·min -1< . Fig. 10 [ Fig. 10This shows the effect of the presence of a potential interfering agent, NH₂EtOH, on the response of the Hy3 sensor to hydrazine. Flux = 200 mL·min⁻¹, RH = 50%. Fig. 11 [ Fig. 11 This shows the effect of the presence of a potential interfering agent, morpholine, on the response of the Hy3 sensor to hydrazine. Flux = 200 mL·min⁻¹, RH = 50%. Fig. 12 [ Fig. 12 This shows the effect of the presence of a potential interfering agent, NH3, on the response of the Hy3 sensor to hydrazine. Flux = 200 mL·min⁻¹, RH = 50%. Fig. 13 [ Fig. 13 This shows the effect of the presence of two potential interferents, NH3 and NH2EtOH, on the response of the Hy3 sensor to hydrazine. Flux = 200 mL·min⁻¹, RH = 50%. Fig. 14 [ Fig. 14 This shows the effect of the presence of two potential interferents, NH3 and morpholine, on the response of the Hy3 sensor to hydrazine. Flux = 200 mL·min⁻¹, RH = 50%. Fig. 15 [ Fig. 15] shows the comparison of the responses of sensors Hy1, Hy2 and Hy3 at 30 ppb of N2H4. Flux = 200 mL·min-1, %RH = 50%. Fig. 16 [ Fig. 16 ] shows the comparison of the responses of the Hy8 and Hy9 sensors at 40 ppb of N2H4. Flux = 200 mL·min-1, %RH = 50%. Fig. 17 [ Fig. 17 ] shows the comparison of the responses of sensors Hy4, Hy5, Hy6 and Hy7 at 25 ppb of N2H4. Flux = 200 mL·min-1, %RH = 50%. Detailed description

[0028] The present invention relates to a nanoporous sensor composed of a nanoporous silicate sol-gel matrix containing a reagent composition, said reagent composition comprising a mixture of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid.

[0029] For the purposes of the present invention, a silicate sol-gel matrix is ​​understood to be a material obtained by a sol-gel process consisting of using as precursors silicon alkoxides of formula Si(OR)x where R is an alkyl group.

[0030] In the sol-gel process, alkoxy (OR) groups are hydrolyzed in the presence of water to silanol (Si-OH) groups. These silanols then condense, forming siloxane (Si-O-Si-) bonds. This results in the formation of small particles, generally less than 1 µm in size, which aggregate and form clumps that remain suspended without precipitating, thus forming a sol. The growth of these clumps and their subsequent condensation increase the viscosity of the gelling medium. A porous solid material is obtained by drying the gel, with the solvent being expelled from the polymer network formed (syneresis). Sol-gel matrices obtained from silicon alkoxides of the formula Si(OR)x are referred to as silicate sol-gel matrices in this application.

[0031] For the purposes of the present invention, the term nanoporous means: having pores with a size of less than 100 nm.

[0032] According to a particular embodiment, the nanoporous matrix of the invention is an essentially microporous matrix. Thus, according to this embodiment, the sensor can also be described as essentially microporous. An essentially microporous material (essentially microporous sensor or essentially microporous matrix) is understood to be a material in which at least 80% of the pores are micropores.

[0033] Micropores are characterized, according to the IUPAC definition, by a width not exceeding 2 nm (IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A.D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S.J. Chalk. ISBN 0-9678550-9-8. https: / / doi.org / 10.1351 / goldbook ).

[0034] Upon contact with an amine-type compound, and in particular gaseous hydrazine, the nanoporous sensor according to the invention changes color due to the formation of DMACA-N₂H₄ and 2DMACA-N₂H₄ complexes by reaction between hydrazine (N₂H₄) and 4-(dimethylamino)cinnamaldehyde (DMACA) in the presence of polystyrene sulfonic acid, which catalyzes this reaction. The absorbance variations are correlated with the hydrazine concentration in the air.

[0035] The reaction between hydrazine (N₂H₄) and 4-(dimethylamino)-cinnamaldehyde (DMACA) is advantageously catalyzed by a polymer-derived acid, particularly polystyrene sulfonic acid. The choice of this type of acid, and especially polystyrene sulfonic acid, has numerous advantages.

[0036] First, this acid is a high molecular weight polymer that has an SO3H acid group for each styrenic monomer. As a result, the number of available protons is particularly high and allows the acidity of the pores to be adjusted to catalyze the reaction between DMACA and N2H4.

[0037] Furthermore, inorganic acids and low molecular weight organic acids present the disadvantage of potential acid vapor release during the drying stage of the sol-gel matrix, meaning the acid is also likely to evaporate in this process. Thus, a volatile inorganic acid such as HCl (or an organic acid such as acetic acid) could evaporate from the sol-gel matrix, reducing the sensor's efficiency or even preventing it from functioning. This drawback does not exist for polymer-derived acids, such as polystyrene sulfonic acid, as these are not volatile.

[0038] Finally, another major advantage of polymer-derived acids lies in the deployment of acidic polymer chains within the small pores of the sol-gel matrix. This deployment of acidic functional groups within the pores allows, on the one hand, for the acidification of each pore and, on the other hand, for the strong restriction of polymer diffusion within the porous network, preventing it from migrating to the sensor surface. The advantages of this method compared to the one currently used with trapping hydrazine in cartridges followed by delayed derivatization with the benzaldehyde reagent are numerous. The sensor according to the invention allows: the direct measurement of hydrazine on site; the measurement of hydrazine, in particular via the measurement of the absorbance of the addition compound DMACA-N2H4 at 388 nm ( Figure 1); the measurement of hydrazine by sampling the air to be analyzed with a flow rate that can vary from 10 to 600 mL·min⁻¹, for example a flow rate of 200 mL·min⁻¹, the sampling time being able to vary according to the concentration of the gas to be detected, for example between 60 min and 5 min, here respectively for 1 and 100 ppb of hydrazine detected; the selective measurement of hydrazine in the concentration range of 1-85 ppb in the presence of interfering substances such as NH₃, ethanolamine (NH₂EtOH) or morpholine, when the total concentration of potential interfering substances is less than 200 times the concentration of hydrazine ([N₂H₄]); the selective measurement of hydrazine in gas mixtures with a relative humidity varying between 25 and 100%.

[0039] Advantageously, the nanoporous sensor according to the invention is characterized by a large specific adsorption surface area. Indeed, it has a specific adsorption surface area of ​​700 to 2500 m².g⁻¹, preferably of 800 to 2000 m².g⁻¹.

[0040] The specific adsorption surface area, pore volume, and pore size distribution are determined by liquid nitrogen adsorption-desorption isotherm analysis using the Density Functional Theory (DFT) model. The Brunauer-Emmett-Teller (BET) method is an analytical method that allows the specific adsorption surface area to be deduced.

[0041] The nanoporous sensor according to the invention preferably has a pore volume of 0.1 to 0.9 cm³ g⁻¹, more preferably 0.2 to 0.8 cm³ g⁻¹, and even more preferably 0.2 to 0.6 cm³ g⁻¹. The pore volume represents the volume occupied by the pores per gram of sensor. The pore volume of the material is obtained from the adsorption isotherm of nitrogen at the temperature of liquid nitrogen.

[0042] Advantageously, the nanoporous sensor according to the invention has a proportion of micropores greater than 75%, preferably greater than 80%, preferably ranging from 85% to 95%, the remainder at 100% corresponding to the proportion of mesopores.

[0043] According to the IUPAC definition (IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by AD McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by SJ Chalk. ISBN 0-9678550-9-8. https: / / doi.org / 10.1351 / goldbook ), Micropores are defined as pores with a width not exceeding 2 nm, and mesopores as pores with a width between 2 and 50 nm. Pores with a width greater than 50 nm are macropores according to the same IUPAC reference.

[0044] The nanoporous sensor according to the invention preferentially has a proportion of mesopores less than 25%, preferably less than 20%, more preferably ranging from 5% to 15%, the remainder at 100% corresponding to the proportion of micropores.

[0045] In particular, the nanoporous sensor according to the invention may have micropores having a diameter ranging from 0.3 to 2 nm, preferably from 0.5 to 2 nm.

[0046] The nanoporous sensor according to the invention can also be characterized in that it advantageously presents mesopores having a diameter between 2 and 20 nm, preferably between 2 and 15 nm.

[0047] The nanoporous sensor according to the invention preferably has a ratio r of the concentrations of polystyrene sulfonic acid and 4-(dimethylamino)-cinnamaldehyde of 1 to 20, preferably of 2 to 15, even more preferably 10.

[0048] This ratio is calculated from the molar concentrations of polystyrene sulfonic acid and 4-(dimethylamino)-cinnamaldehyde (r = [H+] / [DMACA]). For this calculation, the molar mass of the polystyrene sulfonic acid monomer (M = 184 g / mol) is used to convert the mass concentration of polystyrene sulfonic acid (PSS) to a molar concentration. For example, a PSS concentration of 9.2 g L⁻¹ corresponds to a concentration of 0.05 mol L⁻¹ (= 9.2 / 184). Thus, with a DMACA concentration of 5 × 10⁻³ mol L⁻¹ and a PSS concentration of 9.2 g L⁻¹ (0.05 mol L⁻¹), the ratio r is equal to 10.

[0049] The ratio of polystyrene sulfonic acid and 4-(dimethylamino)-cinnamaldehyde concentrations can also be expressed as a ratio r' of the mass concentrations of the two species (r' = [H+] / [DMACA]), this ratio r' ranging from 1 to 20, preferably from 2 to 15, and even more preferably 11. For example, with a DMACA concentration of 5.10-3 mol.L-1 corresponding to 0.876 gL-1 (with M = 175.23 g.mol-1) and a PSS concentration of 9.2 gL-1, the ratio r' is equal to 10.5.

[0050] The present invention also relates to the method for preparing the nanoporous sensor according to the invention, said method comprising the following steps: a. Synthesis of a soil from a chosen organosilyl precursor, the synthesis being carried out in a solvent, said solvent comprising water, in the presence of 4-(dimethylamino)-cinnamaldehyde and polystyrene sulfonic acid; b. Molding of the soil obtained in step a), followed by its gelation so as to obtain a gel; c. Drying of the gel obtained in step b), followed by its demolding so as to obtain a nanoporous sensor.

[0051] According to a preferred embodiment of the process according to the invention, the organosilylated precursor is selected from precursors with rapid hydrolysis and condensation and lacking long hydrophobic chains, such as tetramethoxysilane Si(OCH3)4, methyltrimethoxysilane CH3Si(OCH3)3, ethyltrimethoxysilane (C2H5)Si(OCH3)3, 3-aminopropyltriethoxysilane (C3H6NH2)Si(OC2H5)3, 3-aminopropyltrimethoxysilane (C3H6NH2)Si(OCH3)3), (3-(methylamino)propyl)trimethoxysilane (C3H6NHCH3)Si(OCH3)3, 3-Carboxypropyltriethoxysilane (C3H6CO2H)Si(OC2H5)3, 3-carboxypropyltrimethoxysilane (Si(C3H6CO2H)(OCH3)3), tetraethoxysilane, and mixtures thereof. The precursor is preferably chosen from tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and mixtures thereof.

[0052] Step a) of the process according to the invention is preferably carried out in a solvent which may be water or a water / alcohol mixture, the alcohol preferably being a C1 to C6 aliphatic alcohol, more preferably methanol or ethanol, or a mixture of water with a solvent selected from acetone, formamide, methyl ethyl ketone.

[0053] In the process according to the invention, step a) of soil synthesis is advantageously carried out initially by mixing an organosilyl precursor selected from tetramethoxysilane Si(OCH3)4, methyltrimethoxysilane CH3Si(OCH3)3, ethyltrimethoxysilane (C2H5)Si(OCH3)3, 3-aminopropyltriethoxysilane (C3H6NH2)Si(OC2H5)3, 3-aminopropyltrimethoxysilane (C3H6NH2)Si(OCH3)3), (3-(methylamino)propyl)trimethoxysilane (C3H6NHCH3)Si(OCH3)3, 3-carboxypropyltriethoxysilane (C3 H6CO2H)Si(OC2H5)3, 3-carboxypropyltrimethoxysilane (Si(C3H6CO2H)(OCH3)3), tetraethoxysilane and their mixture, with 4-(dimethylamino)-cinnamaldehyde in the solvent, said solvent comprising water, and then polystyrene sulfonic acid added in a second step.

[0054] The addition of polystyrene sulfonic acid is preferably carried out dropwise, as the dissolution of the acid in the mixture is exothermic. Alternatively, the polystyrene sulfonic acid solution can be added by adding the organosilyl precursor and 4-(dimethylamino)-cinnamaldehyde to the solvent mixture, maintaining this mixture at a temperature below 10°C.

[0055] According to a preferred embodiment, step a) of the process according to the invention is characterized in that the molar ratio of the organosilylated precursor to the solvent ranges from 1 / 20 to 1 / 2, preferably from 1 / 18 to 1 / 3, even more preferably from 1 / 16 to 1 / 4.

[0056] Advantageously, step a) of the process according to the invention is carried out at room temperature, the term room temperature being defined as a temperature of about 20-22°C.

[0057] According to a preferred embodiment, the mixture obtained at the end of step a) is kept under agitation before step b) of gelation. Preferably, this agitation is carried out at room temperature for a period of 2 to 48 hours, preferably 24 hours.

[0058] Step b) of gelation can be carried out after pouring into a mold the mixture obtained at the end of step a). When a mold has thus been used, the process according to the invention can then include, after step c) of drying, a step of demolding the nanoporous sensor.

[0059] Step b) of gelation can advantageously be carried out under a relative humidity of 100%, at a temperature between 20 and 25°C, preferably 22°C. This step b) preferably has a duration of 1 to 15 days, preferably 1 to 5 days, even more preferably 2 days.

[0060] Step c) of drying can advantageously be carried out in a closed chamber, for example a desiccator, in which the humidity and temperature are preferably controlled.

[0061] Step c) of drying is advantageously carried out by sweeping the closed chamber with a flow of inert, humid gas, preferably argon. The relative humidity of the applied gas flow can advantageously be controlled, starting at 100% and then decreasing in steps to approximately 25%. The humidity in the closed chamber can thus decrease during the drying step to reach 25 to 28% relative humidity.

[0062] This step c) preferably has a duration of 15 to 60 days, preferably 20 to 40 days.

[0063] After drying, the resulting nanoporous sensor is preferably stored away from light, at a temperature ranging from 2 to 10°C, preferably from 4 to 8°C, even more preferably 6°C.

[0064] The nanoporous sensor according to the invention, which can be obtained by the process according to the invention, advantageously has a parallelepiped shape. It advantageously has dimensions on the order of a millimeter, for example, a height of 7.5 to 10.3 mm, a width of 4.8 to 6.4 mm, and a thickness of 1 to 1.3 mm.

[0065] The present invention also relates to a method for detecting at least one amine-type compound in a gaseous sample to be analyzed, said compound being selected from hydrazine, ethanolamine, ammonia, and morpholine, using a nanoporous sensor according to the invention, said method comprising the steps of: a. bringing said gaseous sample to be analyzed into contact with said nanoporous sensor, b. detection on said nanoporous sensor of said amine-type compound(s) in the gaseous sample to be analyzed.

[0066] This process advantageously allows for the selective measurement of an amine-type compound, in particular hydrazine, directly, in a concentration range of 1 to 100 ppb in dry to very humid air and in the presence of interfering substances whose total concentration can be up to 200 times higher than that of the amine to be detected, in particular hydrazine.

[0067] For the purposes of the present invention, dry air means air with a humidity level of 25% or less.

[0068] Thus, the method according to the invention makes it possible to carry out measurements on a gaseous sample whose relative humidity varies between 25 and 100%, preferably from 30 to 100%.

[0069] The method according to the invention therefore presents real advantages compared to the prior art methods which do not allow this measurement to be carried out directly, regardless of the humidity level, over this concentration range and in the presence of interfering substances.

[0070] In addition to detection, the method according to the invention can also enable the determination, in a gaseous sample to be analyzed, of the concentration of at least one amine-type compound, said compound being selected from hydrazine, ethanolamine, ammonia, and morpholine. Thus, according to a particular embodiment, the present invention relates to a method for detecting and quantifying, in a gaseous sample to be analyzed, at least one amine-type compound, said compound being selected from hydrazine, ethanolamine, ammonia, and morpholine, using a nanoporous sensor according to the invention, said method comprising the steps of: a. bringing said gaseous sample to be analyzed into contact with said nanoporous sensor, b. detection and quantification on said nanoporous sensor of said amine-type compound(s) in the gaseous sample to be analyzed.

[0071] Step b) of the process according to the invention may in particular include a step of measuring the absorbance of the nanoporous sensor as a function of time.

[0072] The analytical method which allows the detection and determination of the contents of hydrazine and interferants carrying a primary or secondary amine function by absorbance measurements as a function of time involves knowledge of the absorption spectra of the mixture 4-(dimethylamino)-cinnamaldehyde (DMACA) / polystyrene sulfonic acid (PSS) in the presence of the targeted amine-type compounds for different concentrations of said amine compounds.

[0073] From these absorption spectra, calibration curves representing the temporal evolution of absorbance as a function of the concentration of each of the said amine-type compounds can be established.

[0074] Thus, when the sensor according to the invention is brought into contact with a gaseous sample to be analyzed, the absorbance measurement result obtained as a function of time can be correlated with the calibration curves previously established, which leads to the determination of the presence or absence of an amine-type compound and optionally to the determination of its concentration.

[0075] The detection and optionally the quantification of hydrazine, ethanolamine, ammonia or morpholine by absorbance measurements is made possible by the reaction taking place between these compounds and 4-(dimethylamino)-cinnamaldehyde (DMACA) in the presence of polystyrene sulfonic acid (PSS) which acts as a catalyst and which results in the formation of complexes which exhibit detectable absorption spectra in the UV-visible range, for example using a spectrophotometer.

[0076] Thus, the reaction between N₂H₄ and DMACA catalyzed in the presence of polystyrene sulfonic acid gives rise to the formation of the addition complexes, 1DMACA-N₂H₄ and 2DMACA-N₂H₄ according to the equations represented in the Figure 1 .

[0077] The formation of these two complexes 1DMACA-N 2 H 4 and 2DMACA-N 2 H 4 can be visualized by the absorbance peaks at 388 and 558 nm respectively ([ Fig. 2 ]).

[0078] In the context of the present invention, the 388 nm peak is used to detect and quantify hydrazine because, of the two peaks formed, it offers the best sensitivity. Indeed, the 2DMACA-N₂H₄ complex is formed more slowly and in smaller quantities than the DMACA-N₂H₄ complex for steric and kinetic reasons.

[0079] With regard to ammonia, DMACA(H+) deprotonates in the presence of a strong base such as NH3, to form neutral DMACA which absorbs intensely at 420 nm ([ Fig.3 ]). The detection and measurement of the concentration of NH3 can therefore be carried out via the measurement of the deprotonation rate (corresponding to the ratio of the change in absorbance over time) as a function of the concentration of NH3 in the gas mixture ([ Fig. 7 ]).

[0080] The present invention also relates to the use of a nanoporous sensor according to the invention for the detection, or the quantification, or the detection and quantification of at least one amine-type compound, said compound being selected from hydrazine, ethanolamine, ammonia, and morpholine.

[0081] The nanoporous sensor according to the invention can be used in dynamic or static mode. Thus, the nanoporous sensor can be placed in a gas stream to be analyzed and circulated by a fluidic circuit, or alternatively, the sensor can be placed in a chamber containing the gas sample to be analyzed.

[0082] The present invention also relates to a device (1) for detecting at least one amine-type compound, said compound being selected from hydrazine, ethanolamine, ammonia, and morpholine, in a gaseous sample to be analyzed, said device comprising a cell (11) containing a nanoporous sensor according to the invention, said cell comprising: a gas inlet (111); a gas outlet (112); an optical inlet (113); an optical outlet (114).

[0083] Advantageously, the device according to the invention includes a fluidic circuit adapted to circulate the gaseous sample to be analyzed through the cell (11) by generating a gas flow from the gas inlet (111) to the nanoporous sensor and then to the gas outlet (112).

[0084] According to a preferred embodiment, the fluidic circuit according to the invention comprises a flow regulator (2) adapted to regulate the flow rate of the gas stream. The flow regulator (2) may consist of a shut-off valve (21) and a regulating needle valve (22).

[0085] Advantageously, the device according to the invention further comprises a light source (3) and a spectrophotometer (4), wherein the optical input (113) of the cell is connected to the light source (3) and the optical output (114) of the cell is connected to the spectrophotometer (4). The light source (3) and the spectrophotometer (4) can thus constitute the optical analysis portion of the device.

[0086] According to a preferred embodiment, the fluidic circuit of the device according to the invention further includes a temperature probe adapted to measure the temperature of the gas flow.

[0087] Advantageously, the device according to the invention further includes a humidity probe adapted to measure the humidity of the gas flow.

[0088] Advantageously, the device according to the invention further includes a flow meter (5) adapted to measure the flow rate of the gas stream.

[0089] The fluidic circuit can therefore take into account: of the gas mixture flow required for sensor exposure, this flow being able to vary for example between 50 and 600 mL / min depending on the sensor, of the measurement of the temperature and relative humidity of the gas mixture, of a purge mode of the measurement circuit.

[0090] The device according to the invention can thus operate as follows: the air or gaseous sample to be analyzed can be drawn in using a pump (6), which may be miniature, and initially passed through an inlet distributor (7) where the temperature and humidity of the gaseous sample are measured. The distributor (7) can then distribute the gaseous sample to two outlets. The pump may, in particular, have a flow rate ranging from 50 to 1100 ml / min.

[0091] The first outlet can direct air towards the cell (11) containing the nanoporous sensor. The cell can be placed upstream of a flow meter (5) connected to an outlet distributor (8), which is itself connected to the pump (6). The flow meter allows the gas flow velocity in the exposure cell to be set.

[0092] The second outlet of the inlet manifold (7) can be connected to the outlet manifold (8) via a shut-off valve (21) and a regulating needle valve (22). This assembly then forms a leakage circuit. This configuration allows the sensor exposure flow rate to be varied (when using different types of sensors) because the pump operates continuously at a fixed flow rate, for example, 1.1 L / min. The shut-off valve allows the leakage circuit to be closed to purge the measurement circuit when necessary.

[0093] The optical analysis section includes a light source (3) that can probe the sensor and a spectrophotometer (4), which can be miniature, that collects the light transmitted by the sensor and converts it into an electrical current. The spectrophotometer (4) can operate at wavelengths ranging from UV to IR, including visible light, the wavelength being chosen according to the measurement to be performed.

[0094] The light source (3) can consist of two LEDs connected by optical fibers or a miniature lamp. The light source can be UV, visible, or UV-visible.

[0095] For the detection of hydrazine at 388 nm, NH3 at 420 nm, ethanolamine at 474 nm, or morpholine at 490 nm, the combination of a UV LED and a visible LED provides the wavelength range of 380–800 nm. Other LED options are possible depending on the sensor's optical response. The light is transmitted to the exposure cell, for example, using an optical fiber. From the exposure cell, the transmitted light is directed to the miniature spectrophotometer (4), which has a wide response range, for example, from 337.5 to 822 nm.

[0096] An example of a device according to the invention is shown in [ Fig. 4 ].

[0097] According to a preferred embodiment, the device according to the invention is characterized in that the cell comprises a nanoporous sensor support and a parallelepiped-shaped housing, preferably cubic, comprising 4 lateral faces and a front face forming in its center a housing for receiving the nanoporous sensor support, two opposing lateral faces presenting the gas inlet and outlet, two opposing lateral faces presenting the optical inlet and outlet, the front face presenting an opening for the insertion of the nanoporous sensor support into its housing ( Figure 6 ).

[0098] The cell of the device according to the invention can thus comprise two elements.

[0099] The first element is its body, which can consist of a square block ( Figure 6) made of reinforced brass, for example with an internal layer of stainless steel, which can be hollowed out in the center and drilled on all four sides. Two perpendicular tunnels can thus be created to serve as passages for the gas flow and the probe light. This block can therefore be equipped with an optical inlet and outlet as well as a gas inlet and outlet.

[0100] The second element could be a removable part, for example made of stainless steel ( Figure 6and which can also be perforated on all four sides to allow the passage of gas flow and light. The two tunnels between the external block and the removable part can be sealed using O-rings. The removable part can house the nanoporous sensor at its center, which can be, for example, a transparent monolithic block with maximum dimensions on the order of tens of millimeters, for example, 11 x 6.5 x 2 mm. The optical input and output can each include a lens to collimate the analytical light beam. The optical input can be connected via an optical fiber to a UV or visible light source, or a combination of both UV and visible, and the optical output can be connected via a second optical fiber to the UV, visible, or UV-visible spectrophotometer required for the analysis and compatible with the lamp.

[0101] An example of a cell of the device according to the invention is shown in [ Fig. 6 ].

[0102] The sensor can be exposed to the gas flow along its entire length and on both sides. The probe's light beam, originating from the light source and carried by an optical fiber, arrives perpendicularly at the gas flow and is focused onto the sensor at the fiber's output. The probed area can be a circle with a cross-section of 5.7 mm² (2.7 mm in diameter). The optical path length for analysis, which can vary from 1 to 2 mm, corresponds to the thickness of the inserted nanoporous sensor.

[0103] Depending on the geometry of the sensor, for example a disc or a parallelepiped, the removable part can be designed for good positioning of the sensor and its exposure to the gas flow over its largest surface area.

[0104] According to a preferred embodiment, the sensor is placed between two half-cylinders, hollowed out to facilitate the passage of the gas flow above and below the sensor ([ Fig. 5 ] And [ Fig. 6The sensor is positioned at the intersection of a vertical hole that allows the probe light to pass through.

[0105] According to a preferred embodiment, the device according to the invention is characterized in that the nanoporous sensor support comprises two diametrically opposed passage orifices optically connected to the optical input and output.

[0106] Advantageously, the device according to the invention further comprises a computer and a battery to provide power to said device and thus make the device energy self-sufficient.

[0107] The device according to the invention may also include a screen allowing the user to interact with the elements of the system by computer.

[0108] The device according to the invention may also include a power supply and power control board.

[0109] The device components, including the fluidic circuit and the optical analysis section, can be positioned within a compartment of a portable unit. This portable unit could then include a second compartment containing a computer for monitoring measurements and a third compartment containing a power supply to operate the entire device.

[0110] Thus, according to a particular embodiment, the device according to the invention can be integrated into a case comprising several levels, in particular 3 levels. The computer can, for example, be located on the top level of the case, the device according to the invention on the middle level, and the power supply on the bottom level.

[0111] According to a preferred embodiment, the device according to the invention is characterized in that it is portable.

[0112] Advantageously, the device according to the invention allows the quantification of said amine-type compound(s) in the gaseous sample to be analyzed. Examples Example 1 : Synthesis of nanoporous sensors according to the invention. Reagents used :

[0113] Tetramethyl orthosilicate (TMOS), 99% purity, CAS: 681-84-5, Molar mass = 152.22 g·mol⁻¹ and density d = 1.023 g·cm⁻³ 4-(Dimethylamino)cinnamaldehyde (DMACA) Purity ≥98%, CAS: 6203-18-5, Molar mass = 175.23 g·mol⁻¹ < Polystyrene sulfonic acid (PSS) 30% aqueous solution, CAS: 28210-41-5, Molar mass = 75,000 g·mol⁻¹ and density d = 1.1 g·cm⁻³. Para-toluenesulfonic acid (C7H7-SO3H), purity ≥98%, CAS: 6192-52-5, Molar mass = 190.22 g·mol -1< Ultra-pure deionized water. Example 1.1 : Hy1 Sensor

[0114] In a 1 L bottle, 14.2 mg of DMACA, 40.969 mL of H₂O, and 84.598 mL of TMOS are mixed. The solution is kept under stirring at room temperature, and 0.449 mL of 30% PSS is added dropwise, as the dissolution of PSS in the mixture is exothermic. The molar ratio of the silylated precursor to water in the mixture is TMOS / H₂O = 1 / 4. The respective final concentrations of DMACA and PSS are 6.25 x 10⁻⁴ M and 1.18 g·L⁻¹, or [H⁺] ≈ 6.25 x 10⁻³ M.

[0115] The soil is agitated for 24 hours at room temperature and then poured into a polypropylene mold containing 350 wells with a volume of 0.3 cm³. The mold is placed in a 10 L desiccator maintained at 100% relative humidity until the soil gels. This step takes 2 days at 22°C for Hy1. The gels are then dried by sweeping the desiccator with a flow of wet argon at 300 mL / min. The relative humidity of the argon flow, initially 100%, is gradually decreased to 80%, 50%, and then 0%. The drying time is approximately 1 month at 22°C, during which the humidity in the desiccator decreases to between 25% and 28% relative humidity. The mold is then removed from the desiccator. After demolding, parallelepiped-shaped sensors measuring 9.6(H)*6.0(L)*1.26(thickness) mm were obtained from an initial solution of 0.3 mL. The final volume of the resulting sensors decreased by a factor of 4.2.The sensors are kept cool at 6°C, away from light. Example 1.2: Hy2 Sensor

[0116] The same procedure as Hy1 was used, with 14.2 mg of DMACA, 84.598 mL of TMOS, 40.969 mL of deionized H₂O, and 0.673 mL of 30% PSS. The molar ratio of the silylated precursor to water in the mixture was TMOS / H₂O = 1 / 4. The respective final concentrations of DMACA and PSS were 6.25 x 10⁻⁴ M and 1.77 g·L⁻¹, corresponding to [H⁺] ~ 9.38 x 10⁻³ M. The gelation time of the sensors in the desiccator maintained at 100% RH was 2 days at 22°C. The drying process, which involves incremental changes from RH = 80% to 50%, takes approximately 40 days at 22°C. During this time, the humidity in the desiccator decreases to between 25% and 28% relative humidity. After demolding, the resulting sensors measure 9.7(H) x 6.1(L) x 1.26(thickness) mm and have a shrinkage factor of 4. The sensors are stored in a cool, dark place at 6°C. Example 1.3: Hy3 Sensor

[0117] The same procedure as Hy1 was used, with 28.5 mg of DMACA, 84.598 mL of TMOS, 40.969 mL of deionized H₂O, and 0.898 mL of 30% PSS. The molar ratio of the silylated precursor to water in the mixture was TMOS / H₂O = 1 / 4. The respective final concentrations of DMACA and PSS were 1.25 x 10⁻³ M and 2.34 g·L⁻¹, or [H⁺] ≈ 1.25 x 10⁻² M. The gelation time of the sensors in the desiccator maintained at 100% RH was 2 days at 22°C. The drying process, which involves step-by-step drying from RH = 80%, 50%, to 0%, takes approximately one month at 22°C. During this time, the humidity in the desiccator decreases to between 25% and 28% relative humidity. After demolding, the resulting sensors measure 9.5(H) x 6.1(L) x 1.24(thickness) mm and have a shrinkage factor of 4.2. The sensors are stored in a cool, dark place at 6°C. Example 1.4: Hy4 Sensor

[0118] The same procedure as Hy1 was used, with 113 mg of DMACA, 81.496 mL of H₂O, 43.91 mL of TMOS, and 3.563 mL of 30% PSS. The molar ratio of the silylated precursor mixture to water was TMOS / H₂O = 1 / 16. The respective final concentrations of DMACA and PSS were 5 x 10⁻³ M and 9.2 g·L⁻¹, meaning [H⁺] ≈ 5 x 10⁻² M. The sensors gelled in the desiccator maintained at 100% RH after 5 days at 22°C. The drying process, which involves incremental changes from RH = 80% to 50%, takes approximately 1.5 months at 22°C. During this time, the humidity in the desiccator decreases to between 25% and 28% relative humidity. After demolding, the resulting sensors measure 8.37(H) x 4.94(L) x 1.03(thickness) mm and have a shrinkage factor of 7. The sensors are stored in a cool, dark place at 6°C. Example 1.5: Hy5 Sensor

[0119] The same procedure as Hy1 was used, with 87.9 mg of DMACA, 33.777 mL of TMOS, 13.587 mL of H₂O, and 2.77 mL of 30% PSS. The molar ratio of the silylated precursor to water in the mixture was TMOS / H₂O = 1 / 4. The respective final concentrations of DMACA and PSS were 1 × 10⁻² M and 18.4 g·L⁻¹, or [H⁺] ~ 1 × 10⁻¹ M. The gelation time of the sensors in the desiccator maintained at 100% RH was 5 days at 22°C. The drying process, which involves step-by-step drying from RH = 80%, 50%, to 0%, takes approximately one month at 22°C. During this time, the humidity in the desiccator decreases to between 25% and 28% relative humidity. After demolding, the resulting sensors measure 10.2(H) x 6.4(L) x 1.3(thickness) mm and have a shrinkage factor of 3.5. The sensors are stored in a cool, dark place at 6°C. Example 1.6 : Hy6 Sensor

[0120] The same procedure as Hy1 was used, with 226 mg of DMACA, 43.91 mL of TMOS, 77.933 mL of water, and 7.126 mL of PSS. The molar ratio of the silylated precursor to water in the mixture was TMOS / H₂O = 1 / 16. The final concentrations of DMACA and PSS were 1 × 10⁻² M and 18.4 g·L⁻¹, respectively, which corresponds to [H⁺] ~ 1 × 10⁻¹ M. The gelation time of the sensors in the desiccator maintained at 100% RH was 3 days at 22°C. The drying time, in stages from 80.5% to 0% RH, took approximately 49 days at 22°C, during which the humidity in the desiccator decreased to 25%–28% relative humidity. After demolding, we obtain sensors with dimensions of 8.4(H)*5.0(L)*1.05(thickness) mm with a shrinkage factor of 6.7. Example 1.7: Hy7 Sensor

[0121] In a 1 L bottle, 56.5 mg of DMACA, 21.258 mL of H₂O, and 10.974 mL of TMOS are mixed. The solution is kept under stirring at room temperature while slowly adding 613 mg of para-toluenesulfonic acid, C₇H₇SO₃H. When the acid is added to this mixture, heat is released. The molar ratio of the silylated precursor to water is TMOS / H₂O = 1 / 16. The final concentrations of DMACA and para-toluenesulfonic acid are 1 × 10⁻² M and 1 × 10⁻¹ M, respectively.

[0122] The soil is stirred for 3 hours at room temperature and then poured into a polypropylene mold. The mold is placed in a 10L desiccator maintained at 100% relative humidity until the soil gels. This step takes 5 days at 22°C. Drying is carried out by sweeping the desiccator with an Ar flow of 300 mL / min, progressively decreasing the relative humidity in the desiccator from 100% to 80%, 50%, and finally 0% RH. The drying time takes approximately 1 month at 22°C, during which the humidity in the desiccator decreases to between 25% and 28% relative humidity. The mold is then removed from the desiccator. After demolding, parallelepiped-shaped sensors with dimensions of 7.57(H)*4.8(L)*1.0(thickness) mm are obtained, with a shrinkage factor of 8.2. The sensors are kept cool at 6 °C, protected from light. Example 1.8 : Hy8 sensor

[0123] The same procedure as Hy1 was used, with 1.139 g of DMACA, 84.598 mL of TMOS, and 5.054 and 35.916 mL of 30% PSS. The final concentrations of DMACA and PSS were 5 x 10⁻² M and 95.2 g·L⁻¹, respectively, meaning [H⁺] ≈ 5 x 10⁻¹ M. The gelation time of the sensors in the desiccator maintained at 100% RH was 4 days at 22°C. The drying process, with the RH decreasing from 80.5% to 0%, took approximately 1 month at 22°C, during which the humidity in the desiccator decreased to between 25% and 28% relative humidity. After demolding, we obtain sensors with dimensions of 11.2(H)*6.4(L)*1.2(thickness) mm with a shrinkage factor of 3.4. Example 1.9 : Hy9 sensor

[0124] The same procedure as Hy1 was used, with 596.5 mg of DMACA, 84.598 mL of TMOS, 23.012 mL of water, and 17.958 mL of 30% PSS. The molar ratio of the silylated precursor to water was TMOS / H₂O = 1 / 4. The respective final concentrations of DMACA and PSS were 2.5 x 10⁻² M and 47.6 g·L⁻¹, or [H⁺] ≈ 2.5 x 10⁻¹ M. The gelation time of the sensors in the desiccator maintained at 100% RH was 2 days at 22°C. The drying process, which involves stages from RH = 80.5% to 0%, takes approximately one month at 22°C. During this time, the humidity in the desiccator decreases to between 25% and 28% relative humidity. After demolding, the resulting sensors measure 10.24(H) x 6.5(L) x 1.25(thickness) mm and have a shrinkage factor of 3.6.

[0125] The porosity properties of nanoporous sensors, such as the specific adsorption surface area, pore volume, and the size distributions of micropores and mesopores, were determined by establishing adsorption-desorption isotherms of N₂ at the liquid N₂ temperature. The table below summarizes these data. [Table 1] Sensor Formulation (TMOS / H2O) Concentration of reactants in the soil (mol.L⁻¹) V sol V solide Porosity properties [DMACA] [PSS monomer] = [H +< ] H + DMACA S DFT / m 2< .g -1< V pore / cm 3< .g -1< % of pore size in Å % of mesopore Size in Å Hy1 1 / 4 in mole 6,25 x 10 -4< 6,25 x 10 -3< 10 4,2 1794 0,33 100% 0% 5< d <19 Hy2 1 / 4 in mole 6,25 x 10 -4< 9,38 x 10 -3< 15 4,0 1929 0,44 95% 5% 5< d <20 20< d <88 Hy3 1 / 4 in mole 1,25 x 10 -3< 1,25 x 10 -2< 10 4,2 1878 0,4 97% 3% 5< d <20 20< d <65 Hy4 1 / 16 in moles 5 x 10 -3< 5 x 10 -2< 10 7,0 1478 0,51 82% 18% 5< d <12 20< d <131 Hy5 1 / 4 in mole 1 x 10 -2< 1 x 10 -1< 10 3,5 1593 0,42 90% 10% 5< d <20 20< d <102 Hy6 1 / 16 in moles 1 x 10 -2< 1 x 10 -1< 10 6,7 1414 0,42 86% 14% 5< d <20 20< d <88 Hy7 1 / 16 in moles 1 x 10 -2< 1 x 10 -1< 10 8,2 853 0,24 88% 12% (C7H7-SO3H) 6< d <20 20< d <61 Hy8 1 / 4 in mole 5 x 10 -2< 5 x 10 -1< 10 3,4 1778 0,52 89% 11% 8< d <13 20< d <131 Hy9 1 / 4 in mole 2,5 x 10 -2< 2,5 x 10 -1< 10 3,6 1608 0,49 87% 13% 5< d <20 20< d <107

[0126] The percentages of micropores and mesopores given here correspond to the distribution of adsorption surface area as a function of pore diameter. This percentage would be different if we considered the distribution of pore volume as a function of pore diameter. Example 2: Response of sensor Hy1 to NH3

[0127] The Hy1 sensor was exposed to a humid gas mixture (RH = 50%) containing 5 ppm of NH3. NH3 does not react with DMACA(H+) but induces deprotonation of DMACA(H+) to form neutral DMACA. In the porous material, neutral DMACA exhibits a broad absorption band in the near-UV visible range with the maximum centered at 420 nm. (Error! Reference source not found.) The calibration curve of the Hy1 sensor, corresponding to the rate of formation of neutral DMACA as a function of NH3 concentration, is shown in the Figure 7 . Example 3: Response of sensor Hy3 to N₂H₄. Establishment of a calibration curve for gaseous N₂H₄

[0128] The Hy3 sensors are exposed to different concentrations of N₂H₄ over a wide concentration range from 1 to 114 ppb. The relative humidity of the gas mixtures was kept constant at 50%. For each exposure to a given concentration of N₂H₄, the rate of formation of the 1DMACA-N₂H₄ complex at 388 nm was deduced. By plotting the rate of formation of the 1DMACA-N₂H₄ complex as a function of the N₂H₄ concentration, a calibration curve for the detection of N₂H₄ at 388 nm is obtained. An example of an N₂H₄ calibration curve established for the Hy3 sensor is given in the Error! Reference source not found.

[0129] There Error! Reference source not found.This shows the calibration curve of N₂H₄ obtained by exposing Hy3 sensors with storage durations ranging from five to fifteen months. A linear variation in the formation rates of the 1DMACA-N₂H₄ complex is observed as a function of the N₂H₄ concentration. The detection limit is 1 ppb for a probe volume of 12 L (60 minutes, 200 mL·min⁻¹, and ΔAbs = 0.02). The exposure time can be reduced by increasing the flow rate of the gas mixture being analyzed. Example 4: Response of Hy3 sensors to N2H4 at different relative humidities

[0130] The effect of the relative humidity of gas mixtures on the calibration curve of N2H4 of the Hy3 sensor is studied ([ Fig. 9 ]). For this purpose, the Hy3 sensors are exposed to different concentrations of N2H4 in gas mixtures at 30, 50 and 80% RH. Example 5: Response of sensor Hy3 to N2H4 in the presence of a potential interfering agent, NH2EtOH

[0131] The response of sensor Hy3 to N2H4 in the presence of NH₂EtOH is studied ([ Fig. 10]). For this purpose, the Hy3 sensors are exposed to gaseous mixtures containing N2H4 + NH2EtOH. Example 6: Response of sensor Hy3 to N2H4 in the presence of a potential interfering agent, morpholine

[0132] The response of the Hy3 sensor to N2H4 in the presence of morpholine is studied ([ Fig. 11 ]). For this purpose, the Hy3 sensors are exposed to gas mixtures containing N2H4 + morpholine. Example 7: Response of sensor Hy3 to N2H4 in the presence of a potential interfering agent, NH3

[0133] The response of the Hy3 sensor to N2H4 in the presence of NH3 is studied ([ Fig. 12 ]). For this purpose, the Hy3 sensors are exposed to gaseous mixtures containing N2H4 + NH3. Example 8: Response of sensor Hy3 to N2H4 in the presence of the two potential interfering substances, NH3 and NH2EtOH

[0134] The response of the Hy3 sensor to N2H4 in the presence of the two potential interfering substances, NH3 and NH2EtOH, is studied ([ Fig. 13 ]). For this purpose, the Hy3 sensors are exposed to gaseous mixtures containing N2H4 + NH3 + NH2EtOH. Example 9: Response of sensor Hy3 to N2H4 in the presence of two potential interferents, NH3 and morpholine

[0135] The response of the Hy3 sensor to N2H4 in the presence of the interfering agents, NH3 and morpholine, is studied ([ Fig. 14 ]). For this purpose, the Hy3 sensors are exposed to gaseous mixtures containing N2H4 + NH3 + morpholine. Example 10: Comparison of the responses of sensors Hy1, Hy2 and Hy3 at 30 ppb of N2H4

[0136] The responses of sensors Hy1, Hy2 and Hy3 to N2H4 are studied ([ Fig. 15 ]). For this purpose, the Hy1, Hy2 and Hy3 sensors are exposed to 30 ppb of N2H4. Example 11: Comparison of Hy8 and Hy9 sensors at 40 ppb of N2H4

[0137] The responses of sensors Hy8 and Hy9 to N2H4 are studied ([ Fig. 16 ]). For this purpose, the Hy8 and Hy9 sensors are exposed to 40 ppb of N2H4. Example 12: Comparison of sensors Hy4, Hy5, Hy6 and Hy7 at 25 ppb of N2H4

[0138] The responses of sensors Hy4, Hy5, Hy6 and Hy7 to N2H4 are studied ([ Fig. 17 ]). For this purpose, the Hy4, Hy5, Hy6 and Hy7 sensors are exposed to 25 ppb of N2H4. List of documents cited

[0139] [1] Toxicological Data Sheet No. 21 INRS http: / / www.inrs.fr / publications / bdd / fichetox / fiche.html?reflNRS=FICHETOX_21 [2] Air Quality. Workplace Air. Sampling and Analysis of Organic Vapors. Sampling by Pumping on an Adsorption Tube and Solvent Desorption. Standard NF X 43-267. La Plaine Saint Denis: AFNOR; 2004. [3] Hydrazine M-7 Data Sheet, Métropole, http: / / www.inrs.fr / publications / bdd / metropol / fiche.html?refINRS=METROPOL_7 [4] Hydrazine. Method 108 In: Sampling and Analytical Methods. OSHA, 1997 (https: / / www.osha.gov / dts / sltc / methods / organic / org108 / org108.html) ) [ 5< ] BJ Meneghelli, A review of hydrazine sensors: The state of the art, ASRC Aerospace Corp., Cocoa Beach, FL, United States, 2004. [ 6< ] KP Brenner, SL Rose-Pehrss on, Performance Evaluation of a Colorimetric Hydrazine Dosimeter, 1994 . [ 7< ] https: / / dodtec.com / hydrazine-mmh-dose-estimator.html[ 8< ] https: / / www.chemsee.com / commercial / toxic-gas / available-products / dosimeters / hyd-009-dosimeter-for-hydrazine / [ 9< ] Rose-Pehrsson et al., patent US005719061A [ 10< ] http: / / catalog.gasdetection.com / item / search-by-gas-type-hydrazine-s- / nalyzer-4000-series-with-digital-display-hydrazine / 4180-100b [ 11< ] https: / / www.raefrance.fr / produit / detecteur-cov-capteur-pid-ppbrae-3000 / [ 12< ] https: / / www.cbrnetechindex.com / p / 3525 / Smiths-Detection-Inc / Sabre-4000 [ 13< ] https: / / www.environics.fi / product / chempro100i / [ 14< ] https: / / www.masatech.eu / portable-advanced-ion-mobility-spectrometer [ 15< ] https: / / www.smithsdetection.com / products / lcd-3-3 /

Claims

1. Nanoporous sensor composed of a silicate sol-gel matrix containing a reagents composition, said reagents composition comprising a mixture of 4-(dimethylamino)cinnamaldehyde and polystyrenesulfonic acid.

2. Nanoporous sensor according to Claim 1, characterized in that it has a specific surface area for adsorption of 700 to 2500 m2.g-1, preferably of 800 to 2000 m2.g-1.

3. Nanoporous sensor according to Claim 1 or 2, characterized in that it has a pore volume of 0.1 to 0.9 cm3.g-1, preferably of 0.2 to 0.8 cm3.g-1, even more preferentially of 0.2 to 0.6 cm3.g-1.

4. Nanoporous sensor according to one of Claims 1 to 3, characterized in that it has a proportion of micropores of greater than 75%, preferably greater than 80%, more preferentially ranging from 85% to 95%, the remainder to 100% corresponding to the proportion of mesopores.

5. Process for preparing a nanoporous sensor according to one of Claims 1 to 4, said process comprising the following steps: a. synthesis of a sol from an organosilyl precursor, the synthesis being performed in a solvent, said solvent comprising water, in the presence of 4-(dimethylamino)cinnamaldehyde and polystyrenesulfonic acid; b. molding of the sol obtained in step a), followed by gelation to obtain a gel; c. drying of the gel obtained in step b), followed by its demolding to obtain a nanoporous sensor.

6. Process according to Claim 5, characterized in that the organosilyl precursor is chosen from tetramethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, (3-(methylamino)propyl)trimethoxysilane, 3-carboxypropyltriethoxysilane, 3-carboxypropyltrimethoxysilane, tetraethoxysilane and mixtures thereof.

7. Process for detecting in a gas sample to be analyzed at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine, using a nanoporous sensor according to one of Claims 1 to 4, said process comprising the steps of: a. placing said gas sample to be analyzed in contact with said nanoporous sensor, b. detecting on said nanoporous sensor said amine-type compound(s) in the gas sample to be analyzed.

8. Process according to Claim 7, in which step b) also comprises quantification on said nanoporous sensor of said amine-type compound(s) in the gas sample to be analyzed.

9. Use of a nanoporous sensor according to one of Claims 1 to 4, for the detection or quantification or the detection and quantification of at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine.

10. Device (1) for detecting in a gas sample to be analyzed at least one amine-type compound, said compound being chosen from hydrazine, ethanolamine, ammonia and morpholine, said device comprising: - a cell (11) enclosing a nanoporous sensor according to one of Claims 1 to 4 and comprising: - a gas inlet (111); - a gas outlet (112); - an optical input (113); - an optical output (114).