Alkoxide-based precursors for direct drawing of metal oxide micro- and nanofibres

12 páginas, 13 figuras, 3 tablas.-- et al.The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO2, TiO2, ZrO2, HfO2 and CeO2) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol–gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.The work was supported by the Estonian Science Foundation (grant nos. 7603, 8377, 7612, JD69, JD120, SF0180073s07 and SF0180058s07) and ESF FANAS program NANOPARMA.Peer reviewe

Antiviral efficacy of cerium oxide nanoparticles

The authors gratefully acknowledge the financial support by the Estonian Research Council Grants (COVSG2, PRG629, PRG1496), Estonian Centre of Excellence in Research project “Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelectronics” TK141 (2014-2020.4.01.15-0011) and University of Tartu Development Fund (PLTFYARENG53). The research was partly conducted using the NAMUR+ core facility funded by projects “Center of nanomaterials technologies and research” (2014-2020.4.01.16-0123) and TT13.Nanomaterials are prospective candidates for the elimination of viruses due to their multimodal mechanisms of action. Here, we tested the antiviral potential of a largely unexplored nanoparticle of cerium dioxide (CeO2). Two nano-CeO2 with opposing surface charge, (+) and (−), were assessed for their capability to decrease the plaque forming units (PFU) of four enveloped and two non-enveloped viruses during 1-h exposure. Statistically significant antiviral activity towards enveloped coronavirus SARS-CoV-2 and influenza virus was registered already at 20 mg Ce/l. For other two enveloped viruses, transmissible gastroenteritis virus and bacteriophage φ6, antiviral activity was evidenced at 200 mg Ce/l. As expected, the sensitivity of non-enveloped viruses towards nano-CeO2 was significantly lower. EMCV picornavirus showed no decrease in PFU until the highest tested concentration, 2000 mg Ce/l and MS2 bacteriophage showed slight non-monotonic response to high concentrations of nano-CeO2(−). Parallel testing of antiviral activity of Ce3+ ions and SiO2 nanoparticles allows to conclude that nano-CeO2 activity was neither due to released Ce-ions nor nonspecific effects of nanoparticulates. Moreover, we evidenced higher antiviral efficacy of nano-CeO2 compared with Ag nanoparticles. This result along with low antibacterial activity and non-existent cytotoxicity of nano-CeO2 allow us to propose CeO2 nanoparticles for specific antiviral applications. © 2022, The Author(s). --//-- This is an open access article Nefedova A, Rausalu K, Zusinaite E, Vanetsev A, Rosenberg M, Koppel K, Lilla S, Visnapuu M, Smits K, Kisand V, Tätte T, Ivask A., "Antiviral efficacy of cerium oxide nanoparticles", Scientific Reports (2022); 12(1):18746, doi: 10.1038/s41598-022-23465-6 published under the CC BY 4.0 licence.Estonian Research Council Grants (COVSG2, PRG629, PRG1496); Estonian Centre of Excellence in Research TK141 (2014-2020.4.01.15-0011); University of Tartu Development Fund (PLTFYARENG53); Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2

Atomic layer deposition of titanium oxide films on As-synthesized magnetic Ni particles : Magnetic and safety properties

Spherical nickel particles with size in the range of 100-400 nm were synthesized by non-aqueous liquid phase benzyl alcohol method. Being developed for magnetically guided biomedical applications, the particles were coated by conformal and antimicrobial thin titanium oxide films by atomic layer deposition. The particles retained their size and crystal structure after the deposition of oxide films. The sensitivity of the coated particles to external magnetic fields was increased compared to that of the uncoated powder. Preliminary toxicological investigations on microbial cells and small aquatic crustaceans revealed non-toxic nature of the synthesized particles.Peer reviewe

Rheological Properties of MWCNT-Doped Titanium-Oxo-Alkoxide Gel Materials for Fiber Drawing

A strategy of doping by multi-walled carbon nanotubes (MWCNT) to enhance mechanical strength and the electrical conductivity of ceramic fibers has nowadays attracted a great deal of attention for a wide variety of industrial applications. This study focuses on the effect of MWCNTs on rheological properties of metal alkoxide precursors used for the preparation of nanoceramic metal oxide fibers. The rheological behavior of MWCNT-loaded titanium alkoxide sol precursors has been evaluated via an extensional rheometry method. A substantial decrease in elongational viscosity and relaxation time has been observed upon an introduction of MWCNTs even of low concentrations (less than 0.1 wt.%). A high quality MWCNT/nanoceramic TiO2 composite fibers drawn from the specified precursors has been validated. The MWCNT percolation, which is mandatory for electrical conductivity (50 S/m), has been achieved at 1 wt.% MWCNT doping

Rheological Properties of MWCNT-Doped Titanium-Oxo-Alkoxide Gel Materials for Fiber Drawing

A strategy of doping by multi-walled carbon nanotubes (MWCNT) to enhance mechanical strength and the electrical conductivity of ceramic fibers has nowadays attracted a great deal of attention for a wide variety of industrial applications. This study focuses on the effect of MWCNTs on rheological properties of metal alkoxide precursors used for the preparation of nanoceramic metal oxide fibers. The rheological behavior of MWCNT-loaded titanium alkoxide sol precursors has been evaluated via an extensional rheometry method. A substantial decrease in elongational viscosity and relaxation time has been observed upon an introduction of MWCNTs even of low concentrations (less than 0.1 wt.%). A high quality MWCNT/nanoceramic TiO2 composite fibers drawn from the specified precursors has been validated. The MWCNT percolation, which is mandatory for electrical conductivity (50 S/m), has been achieved at 1 wt.% MWCNT doping

Alkoxide-based precursors for direct drawing of metal oxide micro- and nanofibres

The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO2, TiO2, ZrO2, HfO2 and CeO2) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol–gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems