1. Development of a gold nanoparticle dispersion for plasma jet printing on solid substratesLan Kresnik, Peter Majerič, Darja Feizpour, Rebeka Rudolf, 2025, original scientific article Abstract: Gold nanoparticles (AuNPs) were synthesised using ultrasonic spray pyrolysis (USP) with the addition of polyvinylpyrrolidone (PVP) as a stabilising agent and subsequently dried via lyophilisation. The resulting dried AuNPs were redispersed in ethanol and homogenised to ensure uniform dispersion. This AuNP dispersion was then deposited onto a ceramic substrate - aluminum oxide (Al2O3) - using plasma jet printing. Comprehensive characterisation of the dispersion, AuNPs, and the resulting printed lines was performed using the following methods: inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning transmission electron microscopy (STEM), energy dispersive X-ray spectroscopy (EDS), ultraviolet-visible spectroscopy (UV–Vis), dynamic light scattering (DLS), measurements of dispersion viscosity and printed line roughness. ICP-OES confirmed consistent gold content in the AuNP dispersion, while the SEM and EDS analyses revealed predominantly spherical AuNPs with minimal aggregation and similar size distributions. TEM, SAED, and STEM/EDS confirmed that the crystalline structure and elemental composition of the AuNPs had diverse morphologies and strong gold signals. The UV–VIS, DLS, and zeta potential measurements indicated moderate colloidal stability, and thermogravimetric analysis (TGA) verified the AuNPs dispersion’s composition. The AuNP dispersion exhibited thixotropic behaviour favourable for printing applications, while confocal microscopy confirmed smooth, uniform printed traces, with an average surface line roughness of 1.65 μm. The successful use of plasma printing with the AuNP dispersion highlights its potential for functional material applications in electronics.
Keywords: gold nanoparticles, ultrasonic spray pyrolysis, dispersion, plasma jet printing
Published in DiRROS: 19.06.2025; Views: 130; Downloads: 65
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2. Hybrid nanostructures of ▫$Fe_3O_4$▫ and Au prepared via coprecipitation and ultrasonic spray pyrolysisLan Kresnik, Peter Majerič, Darja Feizpour, Klementina Pušnik Črešnar, Rebeka Rudolf, 2024, original scientific article Abstract: The coupled processes of coprecipitation and ultrasonic spray pyrolysis (USP) were used to synthesize Fe3O4-Au hybrid nanostructures. The first coprecipitation method enabled the synthesis of Fe3O4 nanoparticles by mixing iron salts’ ions (Fe2+ and Fe3+) and ammonia as the base, and USP was used as the coating process of the Fe3O4 nanoparticles with Au. The formatted hybrid nanostructures consist of Fe3O4 nanoparticles that have Au on their surface in the form of gold nanoparticles (AuNPs). AuNPs have a crystalline structure and range in size from 10 to 200 nm. Additional characterization techniques, including ICP-OES, TEM, SEM, EDS, DLS, zeta potential, and room temperature magnetic hysteresis loops, were used to determine the chemical, physical, and magnetic properties of the Fe3O4 nanoparticles and hybrid nanostructures. It was found that USP produces separate AuNPs too (not just on the Fe3O4 surface), suggesting a bimodal formation of AuNPs. The zeta potential of the Fe3O4 nanoparticles showed poor stability (−15 mV), indicating a high tendency to aggregate, and the zeta potential of the hybrid nanostructures was also very low (≅0), which, comparatively means even worse stability. The saturation magnetization of the Fe3O4 nanoparticles was 35 emu/g, which is relatively lower than that of bulk Fe3O4, while the saturation magnetization of the hybrid nanostructures was significantly lower (0.1 emu/g) compared to the Fe3O4 nanoparticles.
Keywords: magnetic NPs, gold NPs, transmission electron microscopy, magnetic properties
Published in DiRROS: 08.01.2025; Views: 502; Downloads: 293
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3. Development of the recycling procedure for rapid antigen testsRebeka Rudolf, Darja Feizpour, Žiga Jelen, Peter Majerič, Tilen Švarc, Matej Zadravec, Timi Gomboc, Aleksandra Kocijan, 2024, original scientific article Keywords: rapid antigen tests, recycling, characterization, nanogold, plastic
Published in DiRROS: 28.02.2024; Views: 989; Downloads: 458
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4. Evaluation of the impact and fracture toughness of a nanostructured bainitic steel with low retained austenite contentMihael Brunčko, Peter Kirbiš, Ivan Anžel, Leo Gusel, Darja Feizpour, Tomaž Irgolič, Tomaž Vuherer, 2023, original scientific article Keywords: evaluation of fracture toughness, impact toughness, nanostructured bainite, natural aging, low retained austenite content, kinetically activated bainite KAB
Published in DiRROS: 02.02.2024; Views: 946; Downloads: 481
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5. Recovery study of gold nanoparticle markers from lateral flow immunoassaysTilen Švarc, Peter Majerič, Darja Feizpour, Žiga Jelen, Matej Zadravec, Timi Gomboc, Rebeka Rudolf, 2023, original scientific article Abstract: Lateral flow immunoassays (LFIAs) are a simple diagnostic device used to detect targeted analytes. Wasted and unused rapid antigen lateral flow immunoassays represent mass waste that needs to be broken down and recycled into new material components. The aim of this study was to recover gold nanoparticles that are used as markers in lateral flow immunoassays. For this purpose, a dissolution process with aqua regia was utilised, where gold nanoparticles were released from the lateral flow immunoassay conjugate pads. The obtained solution was then concentrated further with gold chloride salt (HAuCl4) so that it could be used for the synthesis of new gold nanoparticles in the process of ultrasonic spray pyrolysis (USP). Various characterisation methods including scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and optical emission spectrometry with inductively coupled plasma were used during this study. The results of this study showed that the recovery of gold nanoparticles from lateral flow immunoassays is possible, and the newly synthesised gold nanoparticles represent the possibility for incorporation into new products.
Keywords: gold nanoparticles, recovery, LFIA, ultrasonic spray pyrolysis, characterisation
Published in DiRROS: 02.02.2024; Views: 878; Downloads: 421
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6. The impact of Al2O3 particles from grit-blasted Ti6Al7Nb (alloy) implant surfaces on biocompatibility, aseptic loosening, and infectionBoštjan Kocjančič, Klemen Avsec, Barbara Šetina, Darja Feizpour, Matjaž Godec, Veronika Kralj-Iglič, Rok Podlipec, Andrej Cör, Mojca Debeljak, John T. Grant, Monika Jenko, Drago Dolinar, 2023, original scientific article Keywords: Ti6Al7Nb implant alloy cementless hip endoprostheses, roughness, Al2O3 grit blasting, surface and subsurface implant contamination, cytotoxicity, aseptic loosening, infection, osseointegration
Published in DiRROS: 01.02.2024; Views: 1053; Downloads: 521
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8. Impact and fracture toughness of nano-bainitic steel with low retained austeniteMihael Brunčko, Peter Kirbiš, Tomaž Irgolič, Darja Feizpour, Tomaž Vuherer, 2021, published scientific conference contribution abstract Keywords: nanostructured bainite, retained austenite, low temperature baite formation, impact toughness, fracture toughness
Published in DiRROS: 06.05.2022; Views: 1220; Downloads: 384
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