Antiviral efficacy of nanomaterial-treated textiles in real-life like exposure conditions

We thank the following people and institutions for their contribution to our investigation. Toomas Varjund from TAD Logistics OÜ for providing the textiles. Ülis Sõukand from Estonian Environmental Research Center for his help with methods of chemical analysis. Estonian Research Council projects COVSG2, PRG629, PRG1496, PRG1154 and European Commission project STOP (Grant agreement ID: 101057961) for their financial support. The Center of nanomaterials technologies and research (NAMUR+) for core facility funded by project TT13 which was used conducting the research.Due to the growing interest towards reducing the number of potentially infectious agents on critical high-touch surfaces, the popularity of antimicrobially and antivirally active surfaces, including textiles, has increased. The goal of this study was to create antiviral textiles by spray-depositing three different nanomaterials, two types of CeO2 nanoparticles and quaternary ammonium surfactant CTAB loaded SiO2 nanocontainers, onto the surface of a knitted polyester textile and assess their antiviral activity against two coronaviruses, porcine transmissible gastroenteritis virus (TGEV) and severe acute respiratory syndrome virus (SARS CoV-2). Antiviral testing was carried out in small droplets in semi-dry conditions and in the presence of organic soiling, to mimic aerosol deposition of viruses onto the textiles. In such conditions, SARS CoV-2 stayed infectious at least for 24 h and TGEV infected cells even after 72h of semi-dry deposition suggesting that textiles exhibiting sufficient antiviral activity before or at 24 h, can be considered promising. The antiviral efficacy of nanomaterial-deposited textiles was compared with the activity of the same nanomaterials in colloidal form and with positive control textiles loaded with copper nitrate and CTAB. Our results indicated that after deposition onto the textile, CeO2 nanoparticles lost most of their antiviral activity, but antiviral efficacy of CTAB-loaded SiO2 nanocontainers was retained also after deposition. Copper nitrate deposited textile that was used as a positive control, showed relatively high antiviral activity as expected. However, as copper was effectively washed away from the textile already during 1 h, the use of copper for creating antiviral textiles would be impractical. In summary, our results indicated that antiviral activity of textiles cannot be predicted from antiviral efficacy of the deposited compounds in colloid and attention should be paid on prolonged efficacy of antivirally coated textiles.--//-- Alexandra Nefedova, Kai Rausalu, Eva Zusinaite, Vambola Kisand, Mati Kook, Krisjanis Smits, Alexander Vanetsev, Angela Ivask, Antiviral efficacy of nanomaterial-treated textiles in real-life like exposure conditions, Heliyon, Volume 9, Issue 9, 2023, e20067, ISSN 2405-8440, https://doi.org/10.1016/j.heliyon.2023.e20067. Published under the CC BY-NC-ND licence.Estonian Research Council projects COVSG2, PRG629, PRG1496, PRG1154; European Commission project STOP (Grant agreement ID: 101057961); the Institute of Solid State Physics, University of Latvia has received funding from EU CAMART2 project (European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017 TeamingPhase2 under grant agreement No. 739508

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

Modern microwave methods in solid state inorganic materials chemistry: from fundamentals to manufacturing

No abstract available

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

Relaxation of electronic excitations in K2GeF6 studied by means of time-resolved luminescence spectroscopy under VUV and pulsed electron beam excitation

Highly crystalline K2GeF6 micropowders were prepared by co-precipitation in the hydrofluoric acid-water-alcohol solution and studied by means of the cathodoluminescence and time-resolved luminescence spectroscopy under synchrotron radiation excitation at 7 K. The nature of various intrinsic emissions was revealed. The luminescence band at 510 nm detected under excitation by photons with the energy above 9 eV is related to the radiative decay of self-trapped excitons. Fast emission bands with ~400 ps decay time found in the spectral range from VUV to visible (8–2.4 eV) are assigned to the cross-luminescence transitions from K 3p hole states and intraband luminescence transitions due to the presence of the Ge 4s, 4p valence states. The creation of cation excitons was detected in the energy range 18–20 eV. Their non-radiative decay results in the formation of hole states in the Ge energy bands, which finally recombine with electrons from the above lying valence states and provide fast intraband luminescence. Important electronic band structure parameters including the energy gap width of 11 eV, cation exciton formation energy 18.1 eV and ionization energy of cation states 20.0 eV were determined from the luminescence excitation spectra

Time-resolved luminescence spectroscopy of ultrafast emissions in BaGeF6

Phase-pure crystalline micropowder samples of BaGeF6 were prepared and studied under excitation by tuneable synchrotron radiation and 10 keV electron beam. Time-resolved photoluminescence emission and excitation spectra and a set of single emission decay curves were recorded at 7 K for the exciting photon energy region of 4.3–45 eV. Several intrinsic emissions were revealed in BaGeF6 and their origin investigated. A single broad emission band peaking at 455 nm is assigned to be of excitonic origin due to its long decay time in the μs range and due to the presence of an intense excitation peak at 10.1 eV right in the region of the host absorption onset. The energy gap width of BaGeF6 was determined experimentally from the photoluminescence excitation spectra of the 455 nm emission to be 10.9 eV. Several emission bands, including distinct peaks at 270 and 455 nm, with the main decay component of ∼180 ps were revealed across the wavelength range of 200–500 nm. The revealed ultrafast emissions were studied by means of time-resolved photoluminescence spectroscopy and their origin was assigned to cross-luminescence resulting from radiative transitions between the Ba 5p core level and sub-bands of the valence band (Ge 4s, Ge 4p and F 2p hybridized states) and to intraband luminescence between the valence band sub-bands. Photoluminescence excitation spectra of the ultrafast emissions revealed a gently sloping onset at 17 eV, related to transitions from the Ge 4s states. It is followed by a distinct peak at 19.4 eV, which corresponds to the ionization of the Ba 5p cation states and is related to the excitation threshold of cross-luminescence

Stable Aqueous Colloidal Solutions of Nd³⁺: LaF₃ Nanoparticles, Promising for Luminescent Bioimaging in the Near-Infrared Spectral Range

Two series of stable aqueous colloidal solutions of Nd3+: LaF3 single-phase well-crystallized nanoparticles (NPs), possessing a fluorcerite structure with different activator concentrations in each series, were synthesized. A hydrothermal method involving microwave-assisted heating (HTMW) in two Berghof speedwave devices equipped with one magnetron (type I) or two magnetrons (type II) was used. The average sizes of NPs are 15.4 ± 6 nm (type I) and 21 ± 7 nm (type II). Both types of NPs have a size distribution that is well described by a double Gaussian function. The fluorescence kinetics of the 4F3/2 level of the Nd3+ ion for NPs of both types, in contrast to a similar bulk crystal, demonstrates a luminescence quenching associated not only with Nd–Nd self-quenching, but also with an additional Nd–OH quenching. A method has been developed for determining the spontaneous radiative lifetime of the excited state of a dopant ion, with the significant contribution of the luminescence quenching caused by the presence of the impurity OH– acceptors located in the bulk of NPs. The relative quantum yield of fluorescence and the fluorescence brightness of an aqueous colloidal solution of type II NPs with an optimal concentration of Nd3+ are only 2.5 times lower than those of analogous Nd3+: LaF3 single crystals

Neodymium-doped nanoparticles for infrared fluorescence bioimaging: The role of the host

The spectroscopic properties of different infrared-emitting neodymium-doped nanoparticles (LaF3:Nd 3+, SrF2:Nd3+, NaGdF4:Nd3+, NaYF4:Nd3+, KYF4:Nd3+, GdVO4:Nd3+, and Nd:YAG) have been systematically analyzed. A comparison of the spectral shapes of both emission and absorption spectra is presented, from which the relevant role played by the host matrix is evidenced. The lack of a universal optimum system for infrared bioimaging is discussed, as the specific bioimaging application and the experimental setup for infrared imaging determine the neodymiumdoped nanoparticle to be preferentially used in each case. (C) 2015 AIP Publishing LLC