Atmospheric air-phase singlet oxygen generator for practical multifunctional applications

Singlet oxygen is a metastable reactive oxygen species involved in numerous biochemical reactions and physiological processes. This suggests its potential applicability in addressing practical challenges in medicine and human safety. Due to its oxidative properties, singlet oxygen effectively eliminates pathogenic organisms, including bacteria, fungi, and viruses, and is utilized in photodynamic therapy for the treatment of various diseases, including oncological and dermatological pathologies. Traditionally, photosensitizers are employed for its generation; however, they exhibit significant drawbacks, such as toxicity, low selectivity toward affected cells, and the requirement for high-intensity optical radiation. One promising solution involves the use of photocatalytic materials capable of generating singlet oxygen in both liquid and gaseous phases. The lifetime of singlet oxygen molecules in the gas phase is substantially longer than in liquids. Investigating methods for generating singlet oxygen in the gas phase represents a pressing scientific challenge. Currently, there is a lack of publications in scientific literature describing the qualitative and quantitative characteristics of air mixtures enriched with reactive oxygen species. The development of singlet oxygen generators in the gas phase of atmospheric air is an urgent task with multiple functional applications in medicine and safety technologies. This study presents and examines an experimental prototype of a device designed for generating singlet oxygen in the gas phase of atmospheric air. The design incorporates the authors’ research on the development of an original photocatalytic nanocrystalline coating based on ZnO-SnO₂-Fe₂O₃, capable of producing singlet oxygen under irradiation with optical radiation near the visible spectrum (405 nm). A novel device model has been developed, featuring a reusable photocatalyst. The materials were characterized using X-ray diffraction analysis and atomic force microscopy. Singlet oxygen generation activity was assessed via electron paramagnetic resonance spectroscopy. The achieved photogeneration rate of singlet oxygen was 100 (μmol/L)/min. The calculated concentration of singlet oxygen in the air at the device outlet under normal conditions, determined based on the photodegradation rate of rhodamine 6G dye in porous glass, reached 10 (μmol/L)/min. The presented prototype exhibits low energy consumption, environmental safety, cost-effective materials, utilization of near-visible spectrum radiation, and the ability to generate singlet oxygen without toxic oxidizing byproducts. The developed prototype allows for the creation of multiple modifications, enabling a range of multifunctional devices for individual or group therapeutic use as well as for engineering solutions aimed at ensuring a safe living environment. Selective singlet oxygen generation permits the application of these devices in medical settings, both for direct tissue contact and for establishing breathable air environments conducive to human life.

1. Correia J.H., Rodrigues J.A., Pimenta S., Dong T., Yang Z. Photodynamic Therapy Review: Principles, Photosensitizers, Applications, and Future Directions. Pharmaceutics, 2021, vol. 13, no. 9, pp. 1332. https://doi.org/10.3390/pharmaceutics13091332

2. Martusevich A.A. Metabolic and hemodynamic effects of singlet oxygen. Dissertation for the search of the academic degree of candidate of biological sciences. Kazan, 2019, 167 p. (in Russian)

3. Lundberg J., Lindgård A., Elander A., Soussi B. Improved energetic recovery of skeletal muscle in response to ischemia and reperfusion injury followed by in vivo 31P-magnetic resonance spectroscopy. Microsurgery, 2002, vol. 22, no. 4, pp. 158–164. https://doi.org/10.1002/micr.21744

4. Samosiuk I.Z., Chukhraev N.V., Pisanko O.I., Didenko A.A., Bondarenko L.N., Kurik L.M. О.И. Singletno-oxygen therapy. apparatus “MIT — С”. Biomedical Radioelectronics, 2007, no. 1, pp. 67–75. (in Russian)

5. Gunaydin G., Gedik M.E., Ayan S. Photodynamic Therapy—Current Limitations and Novel Approaches. Frontiers in Chemistry, 2021, vol. 9, pp. 691697. https://doi.org/10.3389/fchem.2021.691697

6. Wang K.-K., Song S., Jung S.-J., Hwang J.-W., Kim M.-G., Kim J.-H., Sung J., Lee J.-K., Kim Y.-R. Lifetime and diffusion distance of singlet oxygen in air under everyday atmospheric conditions. Physical Chemistry Chemical Physics, 2020, vol. 22, no. 38, pp. 21664–21671. https://doi.org/10.1039/d0cp00739k

7. Sun X., Xu K., Chatzitakis A., Norby T. Photocatalytic generation of gas phase reactive oxygen species from adsorbed water: remote action and electrochemical detection. Journal of Environmental Chemical Engineering, 2021, vol. 9, no. 2, pp. 104809. https://doi.org/10.1016/j.jece.2020.104809

8. Khomutinnikova L., Evstropiev S., Meshkovskii I., Bagrov I., Kiselev V. Ceramic ZnO-SnO2-Fe2O3 powders and coatings — effective photogenerators of reactive oxygen species. Ceramics, 2023, vol. 6, no. 2, pp. 886–997. https://doi.org/10.3390/ceramics6020051

9. Ronald Dehmlow. Activating and energising water-satured inhaled air. Available at: http://www.holmevalleywellbeing.com/files/image/files/ActivatedOxygenTherapy/DrRonaldDehmlowStudy.pdf (accessed: 10.12.2024).

10. Li B., Lin L., Lin H., Wilson B.C., Photosensitized singlet oxygen generation and detection: Recent advances and future perspectives in cancer photodynamic therapy. Journal of Biophotonics, 2016, vol. 9, no. 11-12, pp. 1314–1325. https://doi.org/10.1002/jbio.201600055

11. Gavrilova D.A., Gavrilova M.A., Khomutinnikova L.L., Evstropiev S.K., Meshkovskii I.K. Optimization of chemical composition and structure of the photocatalyst. Optics and Spectroscopy, 2024, vol. 132, no. 4, pp. 380–386. https://doi.org/10.61011/EOS.2024.04.58882.6016-24

12. Lachheb H., Ajala F., Hamrouni A., Houas A., Parrino F., Palmisano L. Electron transfer in ZnO-Fe2O3 aqueous slurry systems and its effects on visible light photocatalytic activity. Catalysis Science and Technology, 2017, vol. 7, no. 18, pp. 4041–4047. https://doi.org/10.1039/c7cy01085k

13. Evstropiev S.K., Karavaeva A.V., Vasilyev V.N., Nikonorov N.V., Aseev V.A., Dukelskii K.V., Lesnykh L.L. Bactericidal properties of ZnO-SnO2 nanocomposites prepared by polymer-salt method. Materials Science and Engineering B, 2021, vol. 264, pp. 114877. https://doi.org/10.1016/j.mseb.2020.114877

14. Saratovskii A.S., Senchik K.Yu., Karavaeva A.V., Evstropiev S.K., Nikonorov N.V. Photo-oxygenation of water media using photoactive plasmonic nanocomposites. The Journal of Chemical Physics, 2022., vol. 156, no. 20, pp. 201103. https://doi.org/10.1063/5.0094408

15. Shelemanov A.A., Nuryev R.K., Evstropiev S.K., Kiselev V.M., Nikonorov N.V. The influence of polyvinylpyrrolidone on the structure and optical properties of ZnO-MgO nanocomposites synthesized by the polymer-salt method. Optics and Spectroscopy, 2021, vol. 129, no. 12, pp. 1300–1305. https://doi.org/10.1134/s0030400x21090198

16. Kraljić I., El Mohsni S. A new method for the detection of singlet oxygen in aqueous solutions. Photochemistry and Photobiology, 1978, vol. 28, no. 4-5, pp. 577–581. https://doi.org/10.1111/j.1751-1097.1978.tb06972.x

17. Evstropiev S.K., Lesnykh L.L., Nikonorov N.V., Karavaeva A.V., Kolobkova E.V., Oreshkina K.V., Mironov L.Yu., Bagrov I.V. Transparent ZnO-SnO2 photocatalytic nanocoatings prepared by polymer-salt method. Optics and Spectroscopy, 2019, vol. 126, no. 4, pp. 431–438. https://doi.org/10.1134/S0030400X19040064

18. Yi S., Cui J., Li S., Zhang L., Wang D., Lin Y. Enhanced visible-light photocatalytic activity of Fe/ZnO for rhodamine B degradation and its photogenerated charge transfer properties. Applied Surface Science, 2014, vol. 319, no. 1, pp. 230–236. https://doi.org/10.1016/j.apsusc.2014.06.151

19. Guo L., Yang S., Yang C., Yu P., Wang J., Ge W., Wong G.K.L. Highly monodisperse polymer-capped ZnO nanoparticles: Preparation and optical properties. Applied Physics Letters, 2000, vol. 76, no. 20, pp. 2901–2903. https://doi.org/10.1063/1.126511

20. Khomutinnikova L.L., Evstropiev S.K., Meshkovskii I.K., Moskalenko I.V., Bagrov I.V., Skorb E.V. Intensive singlet oxygen photogeneration and photocatalytic activity of Sn,Fe-doped ZnObased composites. Journal of Photochemistry and Photobiology, A: Chemistry, 2025, vol. 462, pp. 116254. https://doi.org/10.1016/j.jphotochem.2024.116254

21. Herman J., Neal S.L. Efficiency comparison of the imidazole plus RNO method for singlet oxygen detection in biorelevant solvents. Analytical and Bioanalytical Chemistry, 2019, vol. 411, no. 20, pp. 5287–5296 https://doi.org/10.1007/s00216-019-01910-2

22. Zhuravskii S.G., Meshkovskii I.K., Podiacheva E.Iu., Shulmeister G.A., Zelinskaia I.A., Pliastcov S.A., Khomutinnikova L.L., Evstropev S.K., Baindurashvili A.G., Vasilev V.N. Systemic effects of chronic inhalation of air mixture with singlet oxygen in rats. Medical Academic Journal, 2025, vol. 25, no. 2, pp. 41–50. (in Russian)