RO137257A2 - Oxy-fluoro-nanocarbon sensitive layers for resistive detection of humidity - Google Patents

Abstract

The invention relates to a resistive sensor based on sensitive oxy-fluoro-nanocarbon layers to be used in monitoring relative humidity in closed spaces of many fields of activity, such as domestic activity and also industrial, namely wood and paper industry, pharmaceutical industry, electronics, agriculture and the like. According to the invention, the sensor comprises the following components: a. a dielectric substrate consisting of Si/SiO2, with a thickness in the range of 50 μ m...5 mm, b. metal electrodes with linear or interdigitated configuration, made of the same material, Cr or Al, or of different materials, which are deposited onto the surface of the dielectric substrate by direct printing, cathode sputtering or evaporation, and c. a sensitive layer consisting of a thin film of ox - CNHs - F or ox - CNOs - F, where the mass percentage of F varies between 2...5% and the oxygen percentage between 10...15%, which can be synthesized from CNHs in the following sequences: 1. treatment in Ar-O2 plasma and 2. treatment in F2-N2 plasma, and the sequences: 3. treatment in F2-N2 plasma and 4. treatment in Ar-O2 plasma, respectively, or a sensitive layer made of binary nanocomposites of the type ox - CNHs - F/ox - CNOs - F in which the two oxy-fluorinated nanocarbon structures are in equimass ratio, the sensitive layer deposition onto the Si/SiO2 dielectric substrate being made from an isopropyl alcohol solution, by drop casting.

Description

Humidity is one of the most frequently monitored physical parameters and is of great importance in multiple areas of domestic and industrial activity such as indoor air quality control, meteorology, wood processing industry, transport (food, medicine), pharmaceutical industry, agriculture (silos , soil moisture control), chemical industry (dryers, chemical gas purification, furnaces) automotive industry (oil moisture control, engine assembly lines), electronic industry (plates, chips), etc. [1-5] Along with polyelectrolytes [6-9], semiconductor metal oxides [10-13], nanocarbon materials [14-18], fluorinated materials (polymers, nanocarbon materials, synthetic minerals) have raised interest in their use as layers sensitive in monitoring relative humidity[19],

Leng et al publish a study[20, 21] on the use of a modified graphene oxide (MGO)/Nafion hybrid film as a sensitive layer in moisture detection. The functionalization of the hydrophilic nanocarbon material was carried out with 1,6 diamino hexane in the presence of a coupling agent of the type 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. The performance evaluation of the humidity sensor was carried out either by modulating the impedance spectra to extract the charge transfer resistance (Ret), or by measuring the impedance below a certain frequency. Both graphene functionalized with 1,6 diamino hexane and its composite with Nafion present good sensitivity to RH in both test methods. The addition of Nafion decreases the charge transfer resistance and increases the sensitivity of the MGO-based sensor. The linearity of the sensor is improved by using MGO/Nafion nanocomposite compared to MGO.

Chen et al[22] use a carbon nanotube/Nafion nanocomposite in the gravimetric detection of humidity, using a QCM (quartz crystal microbalance) sensor. The detection limit of this detection system was approximately 15.76 ppmv. The CNT / Nafion sensing layer exhibited excellent sensitivity, linearity and short recovery time (less than 5 s) at the test point of 15.76 ppmv. The TiO2/Nafion type nanocomposite[23], the chemically modified Teflon[24 ], asymmetric zinc phthalocyanines containing fluoro and alkynyl groups[25] were used as sensitive layers in moisture detection.

US patent 4,681,855 with the title "Humidity sensing and measurement employing halogenated organic polymer membranes" (Peter H. Huang) refers to the synthesis of a Teflon-type fluorinated polymer membrane on which carboxylic and sulfonic groups are grafted in -a molar ratio that can vary from 1:100 to 100:1. The claimed polymeric membrane can be used as a sensitive layer both in the design of conductive sensors and as a component of optical or gravimetric structures. when using a conductive type detection, the optimal ratio of carboxyl groups/sulfonic groups, in order to obtain adequate conduction and low hysteresis, is 1:2.

The invention patent EP 3 211 408 Bl entitled "Relative humidity sensor and method" (Bogdan-Cătălin Serban, Mihai Brezeanu, Octavian Buiu, Cornel P. Cobianu) refers to a capacitive humidity sensor using as a sensitive layer a composite of the type hydrophilic polymer/hydrophobic filler. The selected hydrophilic polymer is cellulose acetate butyrate (with masses

molecular weights between 12,000 g/mol and 70,000 g/mol), while the hydrophobic filler used is an organic fluorinated material (Viton) or inorganic (small fluorinated synthetic). The presence of the fluorinated component in the sensitive layer (5-10% in mass percentage) has the role of modulating the hydrophobicity, improving the performance of the sensor by reducing the hysteresis.

US patent 5,045,828 entitled "Fluoropolymer humidity sensors" (BM Kulwicki, RT McGovern, TC Conlan) refers to a resistive humidity sensor using Nafion as a sensitive layer in which protons ( H ⁺ ) are replaced by ions of the NH ⁴⁺ and Li ⁺ type. The new relative humidity sensitive film has the advantage of a predictable change in electrical parameters without significant drift.

On the other hand, oxidized carbon nanotubes, hydrophilic nanomaterials with high specific surface area and excellent conductivity [26–28], have recently been used in relative humidity monitoring. Thus, resistive humidity sensors using oxidized carbon nanohorns[29], binary polyvinylpyrrolidone-oxidized carbon nanohorns[30, 31] or ternary nanocomposites of the oxidized carbon nanohorns-polyvinylpyrrolidone-oxide have been reported in the literature. graphene [32], oxidized carbon nanohorns- ZnO-PVP [33], oxidized carbon nanohorns- SnO ₂ -PVP [34], in all cases mentioned above, the increase in the level of relative humidity led to a proportional increase in the measured resistance value .

Patent application RO 134261A2 with the title "Chemiresistive humidity sensor based on nanocomposite matrices containing hydrophilic carbon nanohorns" (Bogdan-Cătălin Șerban, Octavian Buiu, Cornel Cobianu, Viorel Avramescu, Ionela Cristina Pachiu, Octavian Narcis lonescu, Maria Roxana Marinescu ) refers to a resistive humidity sensor using nanocomposite sensitive films consisting of oxidized carbon nanohorns /carboxymethylcellulose and oxidized carbon nanohorns /agarose. The proposed sensor is made up of a dielectric substrate such as Lexan, electrodes (chrome, aluminum, copper, etc.) and the moisture-sensitive film, deposited by the "spin coating" or "drop casting" methods.

The invention patent application RO 134263A2 with the title "Chemiresistive humidity sensor based on nanocarbon composites" (Bogdan-Cătălin Șerban, Octavian Buiu, Cornel Cobianu, Viorel Avramescu, Octavian Narcis lonescu, Maria Roxana Marinescu) refers to a resistive sensor humidity using as sensitive layers nanocomposite materials consisting of oxidized carbon nanohorns/polyvinylpyrrolidone (PVP) and oxidized carbon nanohorns/polyvinyl alcohol (PVA). The proposed sensor is made of a dielectric substrate such as glass, PET, Kapton electrodes (aluminum, copper, chrome, etc.) and the film sensitive to humidity, deposited by the methods of electrospinning (electrospinning), spin coating, drop casting.

Last but not least, carbon nano-onions (CNOs), nanocarbon materials consisting of quasi-spherical or polyhedral graphitic layers [35], are used in the design of chemical sensors [36,37],

Invention patent EP2154520B1 with the title "Gas sensor, gas measuring system using the gas sensor, and gas detection method" (Yasuhiko Kasama, Kenji Omote, Kuniyoshi Yokoo, Yuzo Mizobuchi, Haruna Oizumi, Morihiko Saida, Hiroyuki Sagami, Kazuaki Mizokami, Takeo Furukawa , Yasuhiko Kasama, Kenji Omote, Kuniyoshi Yokoo, Yuzo Mizobuchi, Haruna Oizumi Morihiko Saida, Hiroyuki Sagami, Kazuaki Mizokami, Takeo Furukawa) refers to a resistive gas sensor in which the sensitive layer can be made of a nanocarbon material such as nanoonions, carbon nanotubes, fullerenes, The conductivity of the sensitive layer varies proportionally with the concentration of the gas to be analyzed.

The sensitive layers described in this invention, which can be used to obtain resistive relative humidity sensors, are oxyfluorinated carbon nanohorns (generically labeled ox-CNHs-F, Fig.l), oxyfluorinated onion-type nanocarbon materials (generically labeled ox-CNOs -F, Fig.2), as well as binary ox-CNHs-F/ox-CNOsF type nanocomposites From the point of view of the detection principle, the resistance of the sensitive layer varies with the level of relative humidity.

The use as sensitive layers of ox-CNHs-F, ox-CNOs-F, as well as binary nanocomposites of the type ox-CNHs-F/ ox-CNOs-F several significant advantages:

- the presence of oxygenated functions, generated by the Ar-O ₂ plasma treatment, ensures a degree of hydrophilicity necessary for interaction with water;

- fluorine atoms, through the electron-attracting effect, increase the number of carriers both in carbon nanohorns and in onion-type nanocarbon materials. As in both nanocarbonic structures conduction is achieved through gaps (p-type carriers), the material's sensitivity to water molecules increases;

- the presence of fluorine atoms reduces the hysteresis through their hydrophobic effect;

- due to the increased electronegativity, the fluorine atoms increase the polarity of the surface of the nanocarbon material, creating temporary dipoles that facilitate the interaction with water molecules.

- chemical and thermal stability;

- superior mechanical properties;

- detection at room temperature;

The functionalization of nanocarbon materials in plasma of F ₂ -N ₂ / and Ar-O ₂ has the advantage (by varying the type of plasma, the exposure time, as well as its power) that it can ensure an optimal C:F:O ratio, giving synchronously a corresponding sensitivity as well as a decrease in hysteresis.

The sensor substrate is made of Si/SiO ₂ and has a size of 5 mm, the electrodes being made of gold. The width of the electrodes is about 200 microns, with a separation of 6 mm between them. They can be linear (Fig.3) or have an interdigitated configuration (Fig.4). The relative humidity monitoring capability is investigated by applying a constant current between the two electrodes and measuring the voltage at different values of the relative humidity level to which the sensitive layer of ox-CNHs-F, ox-CNOs-F and binary nanocomposites is exposed of the ox-CNHs-F/ox-CNOs-F type.

In the following, the necessary steps are presented for obtaining relative humidity sensitive layers, as well as for obtaining relative humidity resistive sensors.

Example 1

The necessary steps to obtain the sensitive layer made of ox-CNOs-F are the following:

1) Onion-type nanocarbon materials (CNOs) are synthesized from nanodiamond, by thermal treatment at 1650°C, in a helium atmosphere.

2) The synthesis of fluorinated onion-type nanocarbon materials (CNOs-F) is carried out by plasma treatment of F ₂ and N ₂ (equimolecular mixture) at a pressure of 0.5 bar, in a nickel reactor, at room temperature. The injection time is 4 minutes, the exposure time varying between 1 and 3 minutes.

3) CNOs-F oxidation is carried out by treatment in Ar-Οτ plasma (volumetric mixture 2/1), in a quartz tube, at a pressure of 3 torr, at room temperature. The injection time is 5 minutes, the exposure time varying between 2 and 4 minutes.

4) The dispersion of ox-CNOs-F is prepared by dissolving 2 mg of ox-CNOs-F in 5 mL of isopropyl alcohol, under magnetic stirring for 30 minutes, at room temperature.

5) The obtained dispersion is deposited by the drop casting method using a Si/SiO ₂ substrate with linear electrodes or with interdigitated electrodes (after masking the contact area beforehand).

6) The sensitive layer obtained is subjected to a heat treatment at 90°C, for two hours, in a vacuum.

Example 2

The necessary steps to obtain the sensitive layer made of ox-CNOs-F are the following:

1) Onion-type nanocarbon materials (CNOs) are synthesized from nanodiamond, by thermal treatment at 1650°C, in a helium atmosphere.

2) The synthesis of onion-type oxidized nanocarbon materials (οχ-CNOs) is carried out by treatment in Ar-O ₂ plasma (volumetric mixture 2/1), in a quartz tube, at a pressure of 3 torr, at room temperature. The injection time is 5 minutes, the exposure time varying between 2 and 4 minutes.

3) Ox-CNOs fluorination is carried out by plasma treatment of F ₂ and N ₂ (equimolecular mixture) at a pressure of 0.5 bar, in a nickel reactor, at room temperature. The injection time is 4 minutes, the time of exposure varying between 1 and 3 minutes.

4) The dispersion of ox-CNOs-F is prepared by dissolving 2 mg of ox-CNOs-F in 5 mL of isopropyl alcohol, under magnetic stirring for 30 minutes, at room temperature.

5) The obtained dispersion is deposited by the drop casting method using a Si/SiO ₂ substrate with linear electrodes or with interdigitated electrodes (after masking the contact area beforehand).

6) The sensitive layer obtained is subjected to a heat treatment at 90°C, for two hours, in a vacuum

Example 3

The necessary steps to obtain the sensitive layer οχ-CNHs-F are the following:

l) The synthesis of CNHs-F is carried out by plasma treatment of F ₂ and N ₂ (equimolecular mixture) at a pressure of 0.5 bar, in a nickel reactor, at room temperature. The injection time is 4 minutes, the exposure time varying between 2 and 4 minutes.

2) The oxidation of CNHs-F is carried out by plasma treatment of Ar/O ₂ (volumetric mixture 2/1), in a quartz tube, at a pressure of 3 torr, at room temperature. The injection time is 5 minutes, the exposure time varying between 2 and 4 minutes.

3) The οχ-CNHs-F dispersion is prepared by dissolving 1 mg of CNHs-F in 3 mL of isopropyl alcohol, under magnetic stirring for three hours, at room temperature.

4) The obtained dispersion is deposited by the drop casting method using a Si/SiO ₂ substrate with linear electrodes or with interdigitated electrodes (after masking the contact area beforehand).

5) The sensitive layer obtained is subjected to a thermal treatment at 90°C, for two hours, in a vacuum.

Example 4

The necessary steps to obtain the sensitive layer οχ-CNHs-F are the following:

l) The synthesis of ox-CNHs is carried out by plasma treatment of Ar-O ₂ (volumetric mixture 2/1), in a quartz tube, at a pressure of 3 torr, at room temperature. The injection time is 5 minutes, the exposure time varying between 2 and 4 minutes.

2) The fluorination of ox-CNHs is carried out by plasma treatment of F ₂ and N ₂ (equimolecular mixture) at a pressure of 0.5 bar, in a nickel reactor, at room temperature. The injection time is 4 minutes, the exposure time varying between 2 and 4 minutes.

3) The οχ-CNHs-F dispersion is prepared by dissolving 1 mg of CNHs-F in 3 mL of isopropyl alcohol, under magnetic stirring for three hours, at room temperature.

4) The obtained dispersion is deposited by the drop casting method using a Kapton substrate with linear electrodes or with interdigitated electrodes (after masking the contact area beforehand).

5) The sensitive layer obtained is subjected to a thermal treatment at 90°C, for two hours, in a vacuum.

Example 5

The steps required to obtain the ox-CNH-F/ox-CNOs-F sensitive layer are as follows:

1) 1) Onion-type nanocarbon materials (CNOs) are synthesized from nanodiamond, by heat treatment at 1650°C, in a helium atmosphere.

2) The synthesis of oxidized onion-type nanocarbon materials (ox-CNOs) is carried out by treatment in Ar-O2 plasma (volumetric mixture 2/1), in a quartz tube, at a pressure of 3 torr, at room temperature. The injection time is 5 minutes, the exposure time varying between 2 and 4 minutes.

3) Ox-CNOs fluorination is carried out by treating CNOs in F2 and N2 plasma (equimolecular mixture) at a pressure of 0.5 bar, in a nickel reactor, at room temperature. The injection time is 4 minutes, the exposure time varying between 1 and 3 minutes.

4) The synthesis of CNHs-F is carried out by the treatment of simple carbon nanohorns in F2 and N2 plasma (equimolecular mixture) at a pressure of 0.5 bar, in a nickel reactor, at room temperature. The injection time is 4 minutes, the exposure time varying between 2 and 4 minutes.

5) The oxidation of CNHs-F is carried out by treatment in Ar-O2 plasma (volumetric mixture 2/1), in a quartz tube, at a pressure of 3 torr, at room temperature. The injection time is 5 minutes, the exposure time varying between 2 and 4 minutes.

6) The dispersion of ox-CNOs-F/ ox-CNHs-F is prepared by dissolving 2 mg of oxCNOs-F and 2 mg of οχ-CNHs-F in 10 mL of isopropyl alcohol, under magnetic stirring for six hours, at temperature the room.

7) The obtained dispersion is deposited by the drop casting method using a Si/SiO2 substrate with linear electrodes or with interdigitated electrodes (after masking the contact area beforehand).

8) The sensitive layer obtained is subjected to a thermal treatment at 90°C, for two hours, in a vacuum.

reference

1. Serban, B. C., Buiu, O., Dumbravescu, N., Cobianu, C., Avramescu, V., Brezeanu, M., ...

& Nicolescu, C. M. (2020). Optimization of Sensing Layers Selection Process for Relative Humidity Sensors. Science and technology 23(1),93-104.

2. Cobianu, C., Serban, B., & Mihaila, Μ. N. (2013). US. Patent No. 8,479,560. Washington, DC: US. Patent and Trademark Office.

3. Alwis, L., Sun, T., & Grattan, K. T. V. (2013). Optical fiber-based sensor technology for humidity and moisture measurement: Review of recent progress. Measurement, 46(10), 40524074.

4. Blank, T. A., Eksperiandova, L. P., & Belikov, K. N. (2016). Recent trends of ceramic humidity sensors development: A review. Sensors and Actuators B: Chemical, 228, 416-442.

5. Cobianu, C., Stratulat, A., Serban, B., Buiu, O., Bostan, C. G., Brezeanu, M., ... & Davis, R. (2020). U.S. Patent No. 10,585,058. Washington, DC: US. Patent and Trademark Office..

6. Lee, C.W., Kim, Y., Joo, S.W., & Gong, M.S. (2003). Resistive humidity sensor using polyelectrolytes based on new-type mutually cross-linkable copolymers. Sensors and Actuators B: Chemical, 55(1), 21-29.

7. Lee, C.-W.; Gong, M.-S. Resistive Humidity Sensor Using Phosphonium Salt-Containing Polyelectrolytes Based on the Mutually Cross-Linkable Copolymers. Macromol. Res. 2003, 11, 322-327.

8. Son, S. Polymeric Humidity Sensor Using Phosphonium Salt-Containing Polymers. Sense. Actuators B Chem. 2002, 86, 168-173.

9. Lee, C. W„ Park, H. S., Kim, J. G„ Choi, B. K„ Joo, S. W„ & Gong, M. S. (2005). Polymeric humidity sensor using organic/inorganic hybrid polyelectrolytes. Sensors and Actuators B: Chemical, 109(2), 315-322.

10. Qi, Q., Zhang, T., Yu, Q., Wang, R., Zeng, Y., Liu, L., & Yang, H. (2008). Properties of humidity sensing ZnO nanorods-base sensor fabricated by screen-printing. Sensors and Actuators B: Chemical, 133(2), 638-643.

11. Gao, N., Li, H. Y., Zhang, W., Zhang, Y., Zeng, Y., Zhixiang, H., ... & Liu, H. (2019). QCM-based humidity sensor and sensing properties employing colloidal SnO2 nanowires. Sensors and Actuators B: Chemical, 293, 129-135.

12. Eroi, A., Okur, S., Comba, B., Mermer, O., & Ankan, M. C. (2010). Humidity sensing properties of ZnO nanoparticles synthesized by sol-gel process. Sensors and Actuators B: Chemical, 145(\), 174-180.

13. Hsueh, H. T., Hsueh, T. J., Chang, S. J., Hung, F. Y., Tsai, T. Y., Weng, W. Y., ... & Dai, B. T. (2011). CuO nanowire-based humidity sensors prepared on glass substrate. Sensors and Actuators B: Chemical, 156(2), 906-911.

14. Ding, X., Chen, X., Chen, X., Zhao, X., & Li, N. (2018). A QCM humidity sensor based on fullerene/graphene oxide nanocomposites with high quality factor. Sensors and Actuators B: Chemical, 266, 534-542.

15. Radeva, E., Georgiev, V., Spassov, L., Koprinarov, N., & Kanev, S. (1997). Humidity adsorptive properties of thin fullerene layers studied by means of quartz micro-balance. Sensors and Actuators B: Chemical, 42(\), 11-13.

16. Borini, S., White, R., Wei, D., Astley, M., Haque, S., Spigone, E., ... & Ryhanen, T. (2013). Ultrafast graphene oxide humidity sensors. ACS nano, 7(12), 11166-11173.

17. Yao, YChen, X., Guo, H., Wu, Z., & Li, X. (2012). Humidity sensing behaviors of graphene oxide-silicon bi-layer flexible structure. Sensors and Actuators B: Chemical, 161(\), 1053-1058.

18. Han, J.W., Kim, B., Li, L, & Meyyappan, M. (2012). Carbon nanotube based humidity sensor on cellulose paper. The Journal of Physical Chemistry C, 176(41), 22094-22097.

19. Adamska, M., & Narkiewicz, U. (2017). Fluorination of carbon nanotubes - a review. Journal of Fluorine Chemistry, 200, 179-189.

20. Leng, X., Luo, D., Xu, Z., & Wang, F. (2018). Modified graphene oxide/Nafion composite humidity sensor and its linear response to the relative humidity. Sensors and Actuators B: Chemical, 257, 372-381

21. Leng, X., & Wang, F. Modified graphene oxide/Nafion composite humidity sensor and its linear response to the relative humidity. In 2017 IEEE SENSORS (pp. 1-3). IEEE.

22. Chen, H.W., Wu, R.J., Chan, K.H., Sun, Y.L., & Su, P.G. (2005). The application of CNT/Nafion composite material to low humidity sensing measurement. Sensors and Actuators B: Chemical, 104(\), 80-84.

23. Wu, R. J., Sun, Y. L., Lin, C. C., Chen, H. W., & Chavali, M. (2006). Composite of TiO2 nanowires and Nafion as humidity sensor material. Sensors and Actuators B: Chemical, 115(1), 198-204.

24. Dake, S. B., Bhoraskar, S. V., Patil, P. A., & Narasimhan, N. S. (1986). Chemically modified Teflon as an effective humidity sensor. Polymer, 27(6), 910-912.

25. Ahmetali, E., Karaoglu, Η. P., Urfa, Y., Altindal, A., & Koyak, Μ. B. (2020). A series of asymmetric zinc (II) phthalocyanines containing fluoro and alkynyl groups: Synthesis and examination of humidity sensing performance by using QCM based sensor. Materials Chemistry and Physics, 254, 123477.

26. Zhang, J., Lei, J., Xu, C., Ding, L., & Ju, H. (2010). Carbon nanohorn sensitized electrochemical immunosensor for rapid detection of microcystin-LR. Analytical chemistry, 82(3), 1117-1122.

27. Serban, B. C., Bumbac, M., Buiu, O., Cobianu, C., Brezeanu, M., & Nicolescu, C. (2018). Carbon nanohorns and their nanocomposites: Synthesis, properties and applications. Concise review. Ann. Acad. Rom. Sci. Ser. Math. Appl, 11, 5-18.

28. Marinescu R., Șerban, B. C. „ Dumbravescu N., Avramescu V., Cobianu C. & Buiu O., (2019). CARBON-BASED MATERIALS FOR HEALTHCARE M1CRO-DEVICES. Journal of Unconventional Technologies, 23(4), 72-77.

29. Serban, B. C., Buiu, O., Dumbravescu, N., Cobianu, C., Avramescu, V., Brezeanu, M., ... & Nicolescu, C. M. (2020). Oxidized Carbon Nanohorns as a Novel Sensing Layer for Resistive Humidity Sensor. Acta Chimica Slovenica, 67, 1-7.

30. Serban, B. C., Buiu, O., Dumbravescu, N., Cobianu, C., Avramescu, V., Brezeanu, M., ... & Nicolescu, C. M. (2020). Oxidized Carbon Nanohorn-Hydrophilic Polymer Nanocomposite as the Resistive Sensing Layer for Relative Humidity. Analytical Letters, 114.

31. Bogdan-Catalin Serban, Cornel Cobianu, Niculae Dumbravescu, Octavian Buiu, Viorel Avramescu, Marius Bumbac, Cristina-Mihaela Nicolescu, Cosmin Cobianu Mihai Brezeanu, Electrica! Percolation Threshold In Oxidized Single Wall Carbon Nanohorn Polyvinylpyrrolidone Nanocomposite: A Possible Application For High Sensitivity Resistive Humidity Sensor, Proceedings CAS, 2020, pp 239-242, Sinaia Romania, IEEE event

32. Șerban, B. C., Buiu, O., Cobianu, C., Avramescu, V., Dumbrăvescu, N., Brezeanu, M., ... & Marinescu, R. (2019). Ternary Carbon-Based Nanocomposite as Sensing Layer for Resistive Humidity Sensor. Multidisciplinary Digital Publishing Institute Proceedings, 29(1), 114.

33. Bogdan-Catalin Șerban, Cornel Cobianu, Octavian Buiu, Nicolae Dumbrăvescu, Viorel Avramescu, Mihai Brezeanu, Maria-Roxana Marinescu, Ternary hydrophilic carbon nanohorn / ZnO/ PVP nanohybrid structure for room temperature resistive humidity sensing. , 3 ^rd International conference on emerging technologies in materials engineering, pp 8429-30 October 2020, Bucharest, Romania,.

34. Bogdan-Catalin Șerban, Cornel Cobianu, Octavian Buiu, Nicolae Dumbrăvescu, Viorel Avramescu Mihai Brezeanu Maria-Roxana Marinescu Ternary oxidized carbon nanohorn based nanohybrid as sensing layer for resistive humidity sensor, ^3rd International conference on emerging technologies in materials engineering, pp .83, October 29-30, 2020, Bucharest, Romania

35. Bartelmess, J., & Giordani, S. (2014). Carbon nano-onions (multi-layer fullerenes): chemistry and applications. Beilstein journal of nanotechnology, 5(1), 1980-1998.

36. Mohapatra, J., Ananthoju, B., Nair, V., Mitra, A., Bahadur, D., Medhekar, N. V., & Aslam, M. (2018). Enzymatic and non-enzymatic electrochemical glucose sensor based on carbon nano-onions. Applied Surface Science, 442, 332-341.

37. Kumud Malika Tripathi, et. al., From the traditional way of pyrolysis to tunable photoluminescent water soluble carbon nano-onions for cell imaging and selective sensing of glucose. RSC Advances, 2016 ,6, 37319-37329

Claims (18)

demand 1. Resistive relative humidity monitoring sensor that is characterized by the fact that it consists of a dielectric substrate, metal electrodes and a sensitive layer made of a thin film of ox-CNHs-F or ox-CNOs-F or binary nanocomposites of the type ox-CNHs-F/ ox-CNOs-F. 2. ox-CNHs-F and ox-CNOs-F used under the conditions of claim 1 are characterized in that the mass percentage of fluorine varies between 2-5%, and that the mass percentage of oxygen varies between 10-15%. 3. The binary nanocomposite ox-CNHs-F/ ox-CNOs-F used under the conditions of claim 1 is characterized by the fact that the two oxyfluorinated nanocarbonic structures are found in chemical ratio. 4. ox-CNHs-F used under the conditions of claim 1 are characterized by the fact that they can be synthesized from CNHs by the sequence: l) ArO2 plasma treatment; 2) F2-N2 plasma treatment. 5. ox-CNHs-F used under the conditions of claim 1 are characterized by the fact that they can be synthesized from CNHs by the sequence: 1) F2N2 plasma treatment.2) Ar-O2 plasma treatment 6. ox-CNOs-F used under the conditions of claim 1 are characterized by the fact that they can be synthesized from CNHs by the sequence: l) ArO2 plasma treatment; 2) F2-N2 plasma treatment. 7. ox-CNOs-F used under the conditions of claim 1, characterized by the fact that they can be synthesized from CNHs by the sequence: 1) F2-N2 plasma treatment; 2) Ar-O2 plasma treatment 8. The dielectric substrate used under the conditions of claim 1 is characterized in that it can be made of Si/SiO2 and can have a thickness between 50 microns and 5 millimeters. 9. The electrodes used in the conditions of claim 1 are characterized in that they are deposited on the surface of the dielectric substrate by direct printing, cathodic spraying or evaporation. 10. The electrodes used in the conditions of claim 1 are characterized by the fact that they can be made of the same material (aluminum, chrome) or of different materials. 11. The electrodes used in the conditions of claim 1 are characterized in that they can be linear or have an interdigitated configuration. 12. The deposition of the sensitive layer consisting of οχ-CNHs-F is characterized by the fact that it is made from isopropyl alcohol solution by the "drop casting" method on the Si/SiO ₂ substrate with linear electrodes. 13. The deposition of the sensitive layer consisting of οχ-CNHs-F is characterized by the fact that it is made from isopropyl alcohol solution by the "drop casting" method on the Si/SiO ₂ substrate with interdigitated electrodes. 14. The deposition of the sensitive layer consisting of ox-CNOs-F is characterized by the fact that it is made from isopropyl alcohol solution by the "drop casting" method on the Si/SiO ₂ substrate with linear electrodes. 15. The deposition of the sensitive layer consisting of ox-CNOs-F is characterized by the fact that it is made from isopropyl alcohol solution by the "drop casting" method on the Si/SiO ₂ substrate with interdigitated electrodes. 16. The deposition of the sensitive layer consisting of the ox-CNHsF/ox-CNOs-F binary nanocomposite is characterized by the fact that it is made from isopropyl alcohol solution by the "drop casting" method on the Si/SiO ₂ substrate with linear electrodes. 17. The deposition of the sensitive layer consisting of ox-CNHs-F/ ox-CNOs-F is characterized by the fact that it is made from isopropyl alcohol solution by the "drop casting" method on the Si/SiO ₂ substrate with interdigitated electrodes. 18. The use of chemiresistive sensors obtained according to claims 1217 for humidity monitoring is characterized in that a constant current is applied between two electrodes and the electrical voltage that crosses the sensitive layer is measured at various relative humidity values.