UACH > Homepage-en > Research > New materials for a sustainable environment > Nanocrystalline reactive metal oxides

Nanocrystalline reactive metal oxides

Contact person: Jiří Henych

Nanostructured oxides of various metals (e.g., Ti, Ce, Mn, or Fe) show exceptional spontaneous or light-induced reactivity and catalytic activity enabling many chemical reactions and transformations taking place on their surface. This is due to unique physico-chemical properties (e.g., acid-base or redox), which are often very closely related to the size of the individual crystals.
These properties can be used in many environmentally and biologically oriented nanotechnologies, e.g., for fast and effective removal and decontamination of toxic substances from water or air. These oxides show high reactivity, for example, towards organophosphate chemical warfare agents (Soman, Sarin) and pesticides (e.g., chlorpyrifos), but also towards other substances such as drugs in water (e.g., sulfonamide antibiotics, see Fig. 1a) or substances that disrupt the hormonal functions of animals and humans (bisphenol S).

Fig. 1: (a) Ceria-catalyzed hydrolytic cleavage of sulfonamide antibiotic yielding various degradation products, (b) dephosphorylation of p-nitrophenyl 5'-thymidine monophosphate on the surface of CeO2 nanoparticle.

The high reactivity of nanooxides is also very interesting for biological and medical applications. For example, cerium oxides exhibit so-called multi-enzymatic mimetic activity, i.e., that they are able to catalyze reactions that catalyze natural enzymes in biological systems, such as oxidases, peroxidases, catalases, superoxo-dismutases or phosphatases as shown in Fig. 1b.
For the preparation of reactive nanooxides, we develop undemanding synthesis procedures and study their properties and reactivity in detail with the aim of describing and clarifying the mechanism of selected environmentally and biologically relevant reactions. In addition to single-component and mixed oxides, we also prepare nanocomposite and hybrid materials, such as those with carbon nanostructures (graphene, graphene oxide, nanodiamonds), 2D materials, or photoactive molecular clusters.

Fig. 2: TEM images of CeO2 nanoparticles grown on graphene oxide.

We are fully equipped for hydrothermal, solution, microwave, sonochemical and solid-state laboratory syntheses, but we also use high-volume reactors (15, 50, 100 L) when scaling up selected syntheses. We use two high-power ultrasound systems (1kW and 2kW) with water-cooled reactors and temperature control to prepare low-dimensional structures (including graphene or quantum dots) by the top-down method and sonochemical syntheses.

Fig. 3: (a) 1 KW sonicator with water-cooled reactor with temperature control for sonochemistry and delamination of 2D nanomaterials, (b) TEM of graphene sheet prepared by ultrasonication.

To study nanomaterials, we use high-end electron microscopes (SEM and TEM) with elemental mapping, a modern atomic force microscope (AFM), or various spectroscopic methods (FTIR, Raman, UV-Vis). We combine the methods of HPLC/DAD, GC-MS and in situ/Operando DRIFT spectroscopy to study the reaction mechanisms of (photo)degradation reactions.

Fig. 4: Operando DRIFTS setup, enabling a comprehensive study of catalytic processes and reactions on the surface of solid substances with subsequent analysis and quantification of gaseous products.

We cooperate closely with the Institute of Physics of the Academy of Sciences of the Czech Republic (nanodiamond research), with J.E. Purkyně University in Ústí nad Labem (degradation of environmental pollutants and new applications of cerium dioxide), Military Research Institute in Brno and the National Institute for NBC Protection (degradation of chemical warfare agents), Uppsala University (study of photoinduced surface chemical reactions in situ), Bulgarian Academy of Sciences (nanostructured oxides), University of Alcalá (catalytic decontamination materials) etc.

References

  1. Henych, M. Šťastný, S. Kříženecká, J. Čundrle, J. Tolasz, T. Dušková, M. Kormunda, J. Ederer, Š. Stehlík, P. Ryšánek, V. Neubertová, P. Janoš. Ceria-catalyzed hydrolytic cleavage of sulfonamides. Inorg. Chem.2024, 63, 2298-2309.
  2. Henych, M. Šťastný, Z. Němečková, M. Kormunda, Z. Šanderová, Z. Žmudová, P. Ryšánek, Š. Stehlík, J. Ederer, M. Liegertová, J. Trögl, P. Janoš. Cerium-bismuth oxides/oxynitrates with low toxicity for the removal and degradation of organophosphates and bisphenols. ACS Appl. Nano Mater.2022, 5, 17956-17968.
  3. Henych, M. Šťastný, J. Ederer, Z. Němečková, A. Pogorzelska, J. Tolasz, M. Kormunda, P. Ryšánek, B. Bażanów, D. Stygar, K. Mazanec, P. Janoš. How the surface chemical properties of nanoceria are related to its enzyme-like, antiviral and degradation activity. Environ. Sci.:Nano2022, 9, 3485-3501.
  4. Henych, M. Šťastný, Z. Němečková, K. Mazanec, J. Tolasz, M. Kormunda, J. Ederer, P. Janoš. Bifunctional TiO2/CeO2 reactive adsorbent/photocatalyst for degradation of bis-p-nitrophenyl phosphate and CWAs. Chem. Eng. J.2021, 414, 128822.
  5. J. Henych, Š. Stehlík, K. Mazanec, J. Tolasz, J. Čermák, B. Rezek, A. Mattsson, L. Österlund. Reactive adsorption and photodegradation of soman and dimethyl methylphosphonate on TiO2/nanodiamond composites. Appl. Catal. B-Environ. 2019, 259, 118097.