RO138575A2 - RESISTIVE FORMALDEHYDE SENSOR - Google Patents

Abstract

The invention relates to a resistive sensor for monitoring formaldehyde concentration. The sensor according to the invention is made up of a dielectric substrate made of Si/SiO2, some metallic electrodes (1, 2) and a sensitive layer made up of a thin binary nanohybrid film of the nitrogen-doped carbon nanohorns (CNHs-N)/copper oxide (CuO) type, the sensor being based on the detection principle according to which the resistance of the sensitive layer increases with the level of formaldehyde concentration.

Description

Description

STATE OFFICE FOR INVENTION Application for _Invention

Deposit date

Resistive formaldehyde sensor

Inventors:

Bogdan-Cătălin Șerban, Octavian Buiu, Marius Bumbac, Cristina Mihaela Nicolescu

Formaldehyde is a volatile organic compound (VOC), flammable, colorless, with a strong odor, being a valuable intermediate in the chemical industry, light industry, etc. Formaldehyde is used as a raw material in the synthesis of compounds such as urea-formaldehyde resins, melamine resins, 1,4 butanediol, polyoxymethylene, etc. Last but not least, it is used as a fungicide, germicide, disinfectant, and as a preservative for anatomical preparations [1,2].

Traditional sources of formaldehyde include forest fires, exhaust fumes and cigarette smoke. Pressed wood products, particle boards, materials frequently used as a base for furniture, contain urea-formaldehyde resins which, over time, emit significant amounts of formaldehyde [3,4]. The release of this volatile organic compound into buildings is a major component of the phenomenon called “indoor pollution”. Formaldehyde is associated with many health risks (watery eyes, burning sensations in the eyes and throat, nausea and difficulty breathing) and has been identified as a major cause of sick building syndrome (SBS) [5]. It is worth noting that the International Agency for Research on Cancer (IARC) classifies formaldehyde as a human carcinogen. Thus, the National Institute for Occupational Safety and Health (NIOSH) in the USA has established a maximum long-term exposure limit of 0.016 ppm (TWA) [6,7].

Given the multitude of formaldehyde sources, as well as its high toxicity, interest in the manufacture of formaldehyde sensors has experienced remarkable development in recent decades [8].

Various materials such as semiconducting metal oxides [9-18] and nanocarbon materials [19-24] have been used as sensing layers in the design of resistive formaldehyde sensors due to their high sensitivity, good selectivity, low cost.

The patent _JP6774127B2 entitled "Formaldehyde detection and system using it" (77 77 7 7 , fpjife ΦΜ, ) 4 ³ ¾) refers to a sensor for the detection and monitoring of formaldehyde, based on the modification of the electrical resistance of a nanocarbon material. The process leading to the change in conductivity consists of the reaction of hydroxylamine salts with formaldehyde. The acid generated in this reaction represents the key element in the variation of the electrical resistance. The selected nanocarbon materials can be carbon nanotubes, carbon nanohemes, graphene, fullerenes, etc. The carbon material can be mixed with a dispersant which can be a surfactant, polymer, supramolecular polymer. The formed sensitive film can detect 0.05 ppm of formaldehyde in air, at room temperature. The sensor of the described invention can be used repeatedly by simply removing the adsorbed on the carbon material by purging it with a gas flow. // /$

77sTl-7

The patent CN106290488B “Amino-functionalized carbon nanotube resistance type formaldehyde gas sensor and preparation method thereof” (refers to the resistive detection of formaldehyde using carbon nanotubes functionalized with tannic acid and polyethyleneimine. The formaldehyde sensor comprises a flexible substrate, interdigitated electrodes, and a sensitive film. The flexible substrate is made of polyethylene terephthalate (PET), while the interdigitated electrodes can be made of gold, silver, copper, or graphene. The gas sensor can detect formaldehyde at normal temperature, is insensitive to humidity, has strong anti-interference ability, high sensitivity, and fast response. The manufacturing method of the gas sensor is simple, easy to control, and suitable for mass production.

The patent CN 104 198321B entitled “QCM (quartz crystal microbalance) formaldehyde sensor with Chemical and physical adsorption effects and preparation method thereof’ ( ^-¾¾¾^¾) refers to a gravimetric formaldehyde sensor. The sensitive layer is made of organic polymer nanocomposites (PVP, PMMA, P3HT) - graphene or polymer - carbon nanotubes. The claimed sensor has the advantages of simple manufacturing, low cost, high sensitivity, the ability to operate at room temperature.

On the other hand, carbon nanotubes are materials with a tubular structure, related to carbon nanotubes [25]. They can be synthesized by laser ablation of graphite. The advantage of the synthesis of carbon nanotubes, compared to obtaining carbon nanotubes, is that the technological process does not require the presence of a metal catalyst. Oxidized carbon nanotubes have a hydrophilic character, are easily dispersible in water and organic solvents (ethanol, isopropyl alcohol) and have a large specific surface area (1300-1400 m ² /g) [26].

Despite the wide range of applications, there are relatively few studies on the use of carbon nanotubes (simple and oxidized) as sensing layers for various types of gases [27]. In recent years, chemiresistive detection of ethanol has been achieved using ternary and quaternary nanohybrids of the oxidized carbon nanotubes/semiconductor metal oxide/polymer type [2829],

The patent application RO133637A2 entitled Ethanol sensor and method of obtaining it (Bogdan Cătălin Șerban, Octavian Buiu, Comei Cobianu, Octavian Narcis lonescu, Dragoș-Alexandru-Cristian Varsescu, Maria Roxana Marinescu, Niculae Dumbrăvescu) refers to a resistive sensor for monitoring ethanol concentration using as sensitive layers nanocomposite matrices Sm2O3 / oxidized carbon nanocomposites, InjOa / oxidized carbon nanocomposites, Gd20a / oxidized carbon nanocomposites, the sensor resistance varies proportionally to the ethanol concentration in the analyzed gas.

Patent application A/00477.31 entitled "Essay sensitive layer,

^(%inescu) refers to a sen: r^i dc patent, it is derived from Si/SiO2, pol

Marian Av concentrate^] from a s

on resistant nzor of tallow, Viorel itorization constituted phthalate or

Kapton. The metal electrodes (linear or with interdigitated configuration) are made of the same material (Al, Cr, Cu or Au), or of different materials and are deposited on the substrate by direct printing. The sensitive layer is made of a thin film of ternary nanocomposite of the type oxidized carbon nanotubes / SnO2 / polyvinylpyrrolidone, polyvinylpyrrolidone having a molecular mass between 10000 ... 40000 Da.

The technical problem solved by the present invention consists in obtaining new layers sensitive to the variation of formaldehyde concentration, used in the design of resistive sensors. The sensitive film described in this invention, which is used to obtain resistive formaldehyde sensors, is a binary nanohybrid of the nitrogen-doped carbon nanohomes (NCNHs) - copper oxide (CuO) type. The mass percentage of the nanocarbon material in the sensitive layer varies between 70 and 90%. From the point of view of the detection principle, the resistance of the sensitive layer increases with the level of formaldehyde concentration. The decrease in conductivity is explained by the fact that formaldehyde donates electrons to the sensitive layer, decreasing the concentration of holes.

The use of the binary nanohybrid nitrogen-doped carbon nanotubes - copper oxide as a sensitive layer presents several undeniable advantages:

nitrogen-doped carbon nanotubes provide a high specific surface area/volume ratio, affinity for formaldehyde molecules, as well as a variation in the resistance of the sensitive layer upon contact with them;

copper oxide is a p-type semiconductor and exhibits a synergistic effect with nitrogen-doped carbon nanotubes, also p-type semiconductors, upon contact with formaldehyde molecules;

CuO changes the pore distribution at the interface with nitrogen-doped carbon nanotubes, increasing their specific surface area;

room temperature detection;

chemical and thermal stability;

superior mechanical properties.

Nitrogen-doped carbon nanotubes are synthesized by initial fluorination in F2Ar plasma and then defluorination in NH3 atmosphere at 500 °C (Fig.l)

The sensor substrate is made of Si/SiO2 and has a size of 5 mm, the electrodes being made of gold. The width of the electrodes is approximately 200 microns, with a separation of 6 mm between them. The electrodes can be linear (Fig.2) or can have an interdigitated configuration (Fig.3). The formaldehyde monitoring capacity is investigated by applying a constant current between the two electrodes and measuring the voltage at different values of the formaldehyde concentration to which the sensitive layer of the binary nanohybrid type carbon nanohombres doped with nitrogen - copper oxide is exposed.

The steps required to obtain N-CNHs are as follows:

1) The synthesis of nanohoms of <Kh^nÎfciUflî^^ is carried out in and Ar (mixture volume^Tă^ 0.4 bar, in the chamber. The time of deljîft^ the time of exp

1.1 m of F2 temperature for 2^i ^minutes.

2) Heating the fluorinated carbon nanohomes to 500 °C in an NH3 atmosphere leads to their defluorination with the formation of vacancies in the structure of the nanocarbon material. Nitrogen atoms occupy these vacancies with the formation of N-CNHs.

The mass percentage of nitrogen in the composition of nitrogen-doped carbon nanotubes varies between 5 and 10%.

The raw materials required for the synthesis of the CuO/N-CNHs sensitive film are: Cu(CH3COO)2 2H2O, mixture of isopropanol (solvent) and diethanolamine (stabilizer), and nitrogen-doped carbon nanotubes N-CNHs. The molar ratio of Cu(CH3COO)2 2H2O - isopropanol is 1:3, while the mass ratio of acetate/stabilizer is 1/1.

The raw materials are mixed by magnetic stirring, which is carried out sequentially, in two stages:

- first stage - at a temperature of 60 °C, for 1h;

- second stage - at a temperature of 70 °C, for 2 hours.

Nitrogen-doped carbon nanotubes N-CNHs are added in the second stage of magnetic stirring.

The obtained dispersion is subjected to magnetic stirring for three hours at room temperature.

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

Densification of the sensitive layer is achieved sequentially, in two stages, by thermal treatment, as follows:

1) in a nitrogen atmosphere, for 10 minutes, at a temperature of 300 °C;

2) in a nitrogen atmosphere, for 1 h, at a temperature of 400 °C.

reference

Title:

Resistive formaldehyde sensor

Inventors:

Bogdan-Cătălin Șerban, Octavian Buiu, Marius Bumbac, Cristina Mihaela Nicolescu

1. Korpan, Y. I., Gonchar, Μ. V., Sibimy, A. A., Martelet, C., El'skaya, A. V., Gibson, T. D., & Soldatkin, A, P, (2000). Development of highly selective and stable potentiometric sensors for formaldehyde determination. Biosensors and Bioelectronics, 75(1-2), 77-83.

2. Chung, P.R., Tzeng, C.T., Ke, Μ. T., & Lee, C. Y. (2013). Formaldehyde gas sensors: a review. Sensors, 75(4), 4468-4484.

3. Wang, L., Gao, J., & Xu, J. (2019). QCM formaldehyde sensing materials: Design and sensing mechanism. Sensors and actuators B: Chemical, 293, 71-82.

4. Dirksen, J. A., Duval, K., & Ring, T. A. (2001). NiO thin-film formaldehyde gas sensor. Sensors and Actuators B: Chemical, 80(2), 106-115.

5. Kawamura, K.; Kerman, K.; Fujihara, M.; Nagatani, N.; Hashiba, T.; Tamiya, E. Development of a new hand-held formaldehyde gas sensor for the rapid detection of sick building syndrome. Sense. Actuators B Chem. 2005,105, 495-501.

6. Bemardini, L., Barbosa, E., Charao, M.F., & Brucker, N. (2022). Formaldehyde toxicity reports from in vitro and in vivo studies: a review and updated data. Drug and Chemical Toxicology, 45(3), 972-984.

7. Marsh, G. M., Morfeld, P., Collins, J. J., & Symons, J. M. (2014). Issues of methods and interpretation in the National Cancer Institute formaldehyde cohort study. Journal of Occupational Medicine and Toxicology, 9(1), 1-9.2012, 163, 186-193.

8. Air Quality Guidelines, 2nd ed.; WHO Regional Office for Europe: Copenhagen, Denmark, 2001.Occupational Safety and Health Guideline for Formaldehyde Potential Human Carcinogen·, U.S. Department of Health and Human Services: Washington, DC, USA, 1998.

9. Lou, C., Lei, G., Liu, X., Xie, J., Li, Z., Zheng, W., ... & Zhang, J. (2022). Design and optimization strategies of metal oxide semiconductor nanostructures for advanced formaldehyde sensors. Coordination Chemistry Reviews, 452, 214280

10. Park, H.J., Choi, N.J., Kang, H., Jung, Μ. Y., Park, J.W., Park, K.H., & Lee, D.S. (2014). A ppb-level formaldehyde gas sensor based on CuO nanocubes prepared using a polyol process. Sensors and Actuators B: Chemical, 203, 282-288.

11. Peng, X., Liu, J., Tan, Y., Mo, R., & Zhang, Y. (2022). A CuO thin film type sensor via inkjet printing technology with high reproducibility for ppb-level formaldehyde detection. Sensors and Actuators B: Chemical, 362, 131775.

12. Zhu, L.Y., Yuan, K., Yang, J.G., Ma, Η. P., Wang, T., Ji, X. M., ... & Lu, H. L. (2019). Fabrication of heterostructured p-CuO/n-SnO? core-shell nanowires for enhanced sensitive and selective formaldehyde detection. Sensors and Actuators B: Chemical, 290^^^3^1^^^

13. Meng, D., Liu, D., Wang, G., San, X., Shen, Y., Jin, Q., & Meng, F. (2017). CuO hollow microspheres self-assembled with nanobars: Synthesis and their sensing properties to formaldehyde. Vacuum, 144, 272-280.

14. Yang, L., Yang, J., Dong, Q., Zhou, F., Wang, Q., Wang, Z.,... & Xiong, X. (2021). One-step synthesis of CuO nanoparticles based on flame synthesis: As a highly effective non-enzymatic sensor for glucose, hydrogen peroxide and formaldehyde. Journal of Electroanalytical Chemistry, 881, 114965.

15. Dirksen, J. A., Duval, K., & Ring, T. A. (2001). NiO thin-film formaldehyde gas sensor. Sensors and Actuators B: Chemical, 80(2), 106-115.

16. Lee, C.Y., Chiang, C.M., Wang, Y.H., & Ma, R.H. (2007). A self-heating gas sensor with integrated NiO thin-film for formaldehyde detection. Sensors and Actuators B: Chemical, 122(2), 503-510.

17. Xu, Y., Tian, X., Fan, Y., & Sun, Y. (2020). A formaldehyde gas sensor with improved gas response and sub-ppm level detection limit based on NiO/NiFe2O4 composite nanotetrahedrons. Sensors and Actuators B: Chemical, 309, 127719.

18. Fomekong, R.L., Kamta, Η. T., Lambi, J.N., Lahem, D., Eloy, P., Debliquy, M., & Delcorte, A. (2018). A sub-ppm level formaldehyde gas sensor based on Zn-doped NiO prepared by a coprecipitation route. Journal of Alloys and Compounds, 731, 1188-1196.

19. Liu, C., Hu, J., Wu, G., Cao, J., Zhang, Z., & Zhang, Y. (2021). Carbon nanotube-based field effect transistor-type sensor with a sensing gate for ppb-level formaldehyde detection. ACS Applied Materials & Interfaces, 13(M), 56309-56319.

20. Zhao, B., Zhou, Y., Qu, J., Yin, F., Yin, S., Chang, Y., & Zhang, W. (2022). Preparation and performance of CNTs-Pt formaldehyde sensor and CNTs-Au glucose sensor. Sensor Review, (ahead-of-print).

21. Xie, H., Sheng, C., Chen, X., Wang, X., Li, Z., & Zhou, J. (2012). Multi-wall carbon nanotube gas sensors modified with amino-group to detect low concentration of formaldehyde. Sensors and Actuators B: Chemical, 168, 34-38.

22. Lu, Y., Meyyappan, M., & Li, J. (2010). A carbon-nanotube-based sensor array for formaldehyde detection. Nanotechnology, 22(5), 055502.

23. Shi, D., Wei, L., Wang, J., Zhao, J., Chen, C., Xu, D., ... & Zhang, Y. (2013). Solid organic acid tetrafluorohydroquinone functionalized single-walled carbon nanotube chemiresistive sensors for highly sensitive and selective formaldehyde detection. Sensors and Actuators B: Chemical, 177, 370-375.

24. Yang, M., & He, J. (2016). Graphene oxide as quartz crystal microbalance sensing layers for detection of formaldehyde. Sensors and Actuators B: Chemical, 228, 486-490.

25. Zhu, S., & Xu, G. (2010). Single-walled carbon nanohomes and their applications. Nanoscales, 2(12), 2538-2549.

26. Serban, B. C., Buiu, O., Dumbravescu, N., Cobianu, C., Avramescu, V., Brezeanu, M., ... & Nicolescu, C. M. (2020). Oxidized carbon Nanocomposites as a novel sensing layer for humidity sensor. Acta Chimica Slovenica, 67(2).

27. Șerban, B. C., Cobianu, C., Buiu, O., Bumbac, M., Dumbrăvescu, N., Avramescu, V., ... & Comănescu, F. (2021). Quatemary Oxidized Carbon Nanohoms - Based Nanohybrid as Sensing Coating for Room Temperature Resistive Humidity Monitoring. Coatings, 77(5), 530.

28. Cobianu, C., Șerban, B. C., Dumbrăvescu, N., Buiu, O., Avramescu, V., Pachiu, C., ... & Cobianu, C. (2020). Organic-inorganic temary nanohybrids of single-walled carbon nanohoms for room temperature chemiresistive ethanol detection. Nanomaterials, 70(12), 2552.

29. Cobianu, C., Șerban, B. C., Dumbrăvescu, N., Buiu, O., Avramescu, V., Bumbac, M., ... & Cobianu, C. (2020, October). Room temperature chemiresistive ethanol detection by temary nanocomposites of oxidized single wall carbon nanohom (ox-SWCNH). In 2020 International Semiconductor Conference (CAS) (pp. 13-16). IEEE.

Claims (3)

demand Title: Resistive formaldehyde sensor Inventors: Bogdan-Cătălin Șerban, Octavian Buiu, Marius Bumbac, Cristina Mihaela Nicolescu 1. Resistive sensor for monitoring formaldehyde concentration, characterized in that it consists of a dielectric substrate, metal electrodes and a sensitive layer consisting of a thin binary nanohybrid film of the nitrogen-doped carbon nanotubes CNHs-N / copper oxide CuO type. 2. Resistive sensor for monitoring formaldehyde concentration according to claim 1, characterized in that the electrodes used can be made of the same material (aluminum, chromium) or of different materials. 3. The electrodes used in the conditions of claim 1 are characterized in that they may be linear or may have an interdigitated configuration.