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Tilen Švarc

University of Maribor

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Melting point of dried gold nanoparticles prepared with ultrasonic spray pyrolysis and lyophilisation

Nanotechnology Reviews (2023)

Žiga Jelen Marcin Krajewski Franc Zupanič Peter Majerič Tilen Švarc

Abstract A coupled process of ultrasonic spray pyrolysis and lyophilisation was used for the synthesis of dried gold nanoparticles. Two methods were applied for determining their melting temperature: uniaxial microcompression and differential scanning calorimetry (DSC) analysis. Uniaxial microcompression resulted in sintering of the dried gold nanoparticles at room temperature with an activation energy of 26–32.5 J/g, which made it impossible to evaluate their melting point. Using DSC, the melting point of the dried gold nanoparticles was measured to be around 1064.3°C, which is close to pure gold. The reason for the absence of a melting point depression in dried gold nanoparticles was their exothermic sintering between 712 and 908.1°C.

Exothermic reaction

Melting-point depression

10.1515/ntrev-2022-0568

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Citations (8)

Synthesis of Ni/Y2O3 Nanocomposite through USP and Lyophilisation for Possible Use as Coating

Materials (2022)

Tilen Švarc Srečko Stopić Žiga Jelen Matej Zadravec Bernd Friedrich

The Ni/Y2O3 catalyst showed high catalytic activity. Based on this, the aim of this study was to create Ni/Y2O3 nanocomposites powder with two innovative technologies, Ultrasonic Spray Pyrolysis (USP) and lyophilisation. In the USP process, thermal decomposition of the generated aerosols in an N2/H2 reduction atmosphere caused a complete decomposition of the nickel (II) nitrate to elemental Ni, which became trapped on the formed Y2O3 nanoparticles. The Ni/Y2O3 nanocomposite particles were captured via gas washing in an aqueous solution of polyvinylpyrrolidone (PVP) in collection bottles. PVP was chosen for its ability to stabilise nano-suspensions and as an effective cryoprotectant. Consequently, there was no loss or agglomeration of Ni/Y2O3 nanocomposite material during the lyophilisation process. The Ni/Y2O3 nanocomposite powder was analysed using ICP-MS, SEM-EDX, and XPS, which showed the impact of different precursor concentrations on the final Ni/Y2O3 nanocomposite particle composition. In a final step, highly concentrated Ni/Y2O3 nanocomposite ink (Ni/Y2O3 > 0.140 g/mL) and test coatings from this ink were prepared by applying them on a white matte photo paper sheet. The reflection curve of the prepared Ni/Y2O3 nanocomposite coating showed a local maximum at 440 nm with a value of 39% reflection. Given that Ni is located on the surface of the Ni/Y2O3 nanocomposite in the elemental state and according to the identified properties, tests of the catalytic properties of this coating will be performed in the future.

Polyvinylpyrrolidone

Thermogravimetric analysis

10.3390/ma15082856

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Citations (6)

Synthesis and characterization of magnetically-active nickel-yttrium oxide (Ni-Y2O3) nanocomposite particles prepared with modified ultrasound spray pyrolysis device

Journal of Materials Science (2024)

Marcin Krajewski Rebeka Rudolf Tilen Švarc Peter Majerič Kamil Sobczak

Abstract The synthesis of magnetically-active nickel-yttrium oxide (Ni-Y 2 O 3 ) nanocomposite particles is described in this work. The investigated material is produced with a modified ultrasound spray pyrolysis (USP) device which differs from a common USP setup in terms of use of three independently heating zones. They provide a direct feed of H 2 to the second reaction zone and allow controlling the formation of the nanocomposite particles and facilitating their post-reaction stabilization with polyvinylpyrrolidone (PVP). According to the morphological and structural studies, the Ni-Y 2 O 3 material takes a form of nanoparticles whose sizes are not homogeneously distributed as well as shapes are not smooth due to the successful formation of composite material with two interpenetrating phases. Moreover, the organic layer is detected on the surface of the nanoparticles which confirms the presence of PVP stabilizer. The magnetic investigations confirm that the Ni-Y 2 O 3 nanocomposite reveals a spin glass-like behavior in which a collective freezing of magnetic moments might occur due to the interparticle interactions between Ni nanocrystallites presented in the sample.

Characterization

Spray pyrolysis

Nickel oxide

10.1007/s10853-024-10517-7

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Study of the Application of Recycled Gold Nanoparticles in Coatings for Eyewear Lenses

Peter Majerič Djuro Koruga Zorana Njegovan Žiga Jelen Tilen Švarc

The surface plasmon resonance of gold nanoparticles causes visible light absorption and scattering effects that may be used in optical coatings for eliminating blue light emission from display monitors, blocking UV light and for decorative applications. This study examines the achievement of functional properties provided by gold nanoparticles in a commercially established C60 fullerene-coated eyewear product. The gold nanoparticles used were sourced from recycling rapid lateral flow tests (LFIA), which use gold nanoparticles as test markers. After the gold`s recovery Ultrasonic Spray Pyrolysis (USP) with freeze-drying was used for the synthesis of new gold nanoparticles, to be used in optical coatings. The gold nanoparticles were examined with SEM, TEM, DLS, zeta potential, BET, and Vis-NIR for characterising their shapes and sizes, required for determination of the surface plasmon resonance effect. After applying the newly produced gold nanoparticles with fullerene C60 in a combined coating for eyewear lenses, the absorption and transmission of the lenses was determined for establishing changes in the coating functionality. The results show that enhancing the fullerene C60 coating with gold nanoparticles improves light absorption and reflectance for blue and UV light further, which may be evaluated as beneficial for the eyewear user, as the reduction of eye strain is improved due to the coating.

Eyewear

10.20944/preprints202308.1488.v1

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Citations (4)

Physicochemical Properties of Gold Nanoparticles for Skin Care Creams

Materials (2023)

Peter Majerič Zorana Jović Tilen Švarc Žiga Jelen Andrej Horvat

Gold nanoparticles (AuNPs) have now been used in skin care creams for several years, with marketed anti-aging, moisturizing, and regenerative properties. Information on the harmful effects of these nanoparticles is lacking, a concern for the use of AuNPs as cosmetic ingredients. Testing AuNPs without the medium of a cosmetic product is a typical method for obtaining this information, which is mainly dependent on their size, shape, surface charge, and dose. As these properties depend on the surrounding medium, nanoparticles should be characterized in a skin cream without extraction from the cream's complex medium as it may alter their physicochemical properties. The current study compares the sizes, morphology, and surface changes of produced dried AuNPs with a polyvinylpyrrolidone (PVP) stabilizer and AuNPs embedded in a cosmetic cream using a variety of characterization techniques (TEM, SEM, DLS, zeta potential, BET, UV-vis). The results show no observable differences in their shapes and sizes (spherical and irregular, average size of 28 nm) while their surface charges changed in the cream, indicating no major modification of their primary sizes, morphology, and the corresponding functional properties. They were present as individually dispersed nanoparticles and as groups or clusters of physically separated primary nanoparticles in both dry form and cream medium, showing suitable stability. Examination of AuNPs in a cosmetic cream is challenging due to the required conditions of various characterization techniques but necessary for obtaining a clear understanding of the AuNPs' properties in cosmetic products as the surrounding medium is a critical factor for determining their beneficial or harmful effects in cosmetic products.

10.3390/ma16083011

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Citations (13)

Correction: Majerič et al. Study of the Application of Recycled Gold Nanoparticles in Coatings for Eyewear Lenses. Coatings 2023, 13, 1666

Coatings (2025)

Peter Majerič Djuro Koruga Zorana Njegovan Žiga Jelen Tilen Švarc

In the original publication [...]

Eyewear

10.3390/coatings15030251

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Citations (0)

Study of the Application of Recycled Gold Nanoparticles in Coatings for Eyewear Lenses

Coatings (2023)

Peter Majerič Djuro Koruga Zorana Njegovan Žiga Jelen Tilen Švarc

The surface plasmon resonance of gold nanoparticles causes visible light absorption and scattering effects that may be used in optical coatings for eliminating blue light emission from display monitors, for blocking UV light, and for decorative applications. This study examines the achievement of functional properties provided by gold nanoparticles in a commercially established C60 fullerene-coated eyewear product. The gold nanoparticles used were sourced from recycling rapid lateral flow tests (LFIA), which use gold nanoparticles as test markers. After the gold’s recovery, Ultrasonic Spray Pyrolysis (USP) with freeze-drying was used for the synthesis of new gold nanoparticles, to be used in optical coatings. The gold nanoparticles were examined with SEM, TEM, DLS, zeta potential, BET, and Vis-NIR for characterising their shapes and sizes, as is required for determination of the surface plasmon resonance effect. After applying the newly produced gold nanoparticles with fullerene C60 in a combined coating for eyewear lenses, the absorption and transmission of the lenses were determined for establishing changes in the coating’s functionality. The results show that enhancing the fullerene C60 coating with gold nanoparticles improves light absorption and reflectance for blue and UV light further, which may be evaluated as beneficial for the eyewear user, as the reduction in eye strain is increased due to the coating.

Eyewear

10.3390/coatings13101666

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Citations (0)

Optical Characteristics of Directly Deposited Gold Nanoparticle Films

Jordi Sancho Parramon Tilen Švarc Peter Majerič Žiga Jelen Rebeka Rudolf

The manuscript presents the optical properties of directly deposited films of gold nanoparticles (AuNPs) prepared by ultrasonic spray pyrolysis technology. Four samples were produced, with an AuNPs deposition time of 15 min, 30 min, 1h and 4h on the glass substrate. The morphological characterization of the deposited films showed that the size of the first deposited AuNPs is between 10 and 20 nm, while with a longer duration of the deposition process, larger clusters of AuNPs grow by coalescence and aggregation. The prepared layers were optically characterised with Ultraviolet–visible spectroscopy (UV-vis) and ellipsometry. The ellipsometric measurements showed an increasingly denser and thicker effective thickness of the AuNPs layers. The extinction spectra display a clear local surface plasmonic resonance (LSPR) signature (peak 520-540 nm), indicating the presence of isolated particles in all samples. For all AuNPs layers, the imaginary part of both ε// and ε⏊ is dominated by a central peak around 2.2 eV corresponding to the LSPR of isolated particles and a high-energy shoulder due to Au interband transitions. It is shown that, as the density of particles increases, the extinction cross section grows over the whole spectral range where measurements are taken. Thus response can be explained with an enhanced electromagnetic response among AuNPs, that can be connected to the increase of particle density but also by the formation of clusters and irregular structures.

10.20944/preprints202403.0408.v1

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Preparation of Ni/Y2O3/Polylactic Acid Composite

Tilen Švarc Matej Zadravec Žiga Jelen Peter Majerič Blaž Kamenik

This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the Ultrasonic Spray Pyrolysis technique. The particle size was predicted accurately using a modified equation, and they were collected in a water suspension with Polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with Transmission Electron Microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a Polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was successfully extruded successfully, so that a 3D printed technology Fused Filament Fabrication could be used further for the production of tensile test tubes. The tensile tests showed that the addition of lyophilised Ni/Y2O3 into the PLA matrix decreased the tensile strength by 21.8 %, while the tensile modulus was not influenced. Dynamic Mechanical Analysis (DMA) showed that the addition of the Ni/Y2O3 particles increased the glass transition temperature by 5 °C, and increased the storage modulus in the glass transition range significantly. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in 3D printing applications, and warrant further exploration of their mechanical properties and potential applications in various fields.

Polylactic Acid

Tensile testing

Polyvinylpyrrolidone

10.20944/preprints202305.2242.v1

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Citations (3)

Optical Characteristics of Directly Deposited Gold Nanoparticle Films

Surfaces (2024)

Jordi Sancho Parramon Tilen Švarc Peter Majerič Žiga Jelen Rebeka Rudolf

The manuscript presents the optical properties of directly deposited films of gold nanoparticles (AuNPs) prepared by the Ultrasonic Spray Pyrolysis (USP) technology. Four samples were produced, with AuNP deposition times on the glass substrate of 15 min, 30 min, 1 h and 4 h. The morphological characterisation of the deposited films showed that the size of the first deposited AuNPs was between 10 and 30 nm, while, with a longer duration of the deposition process, larger clusters of AuNPs grew by coalescence and aggregation. The prepared layers were characterised optically with Ultraviolet–visible spectroscopy (UV–vis) and ellipsometry. The ellipsometric measurements showed an increasingly denser and thicker effective thickness of the AuNP layers. The extinction spectra displayed a clear local surface plasmonic resonance (LSPR) signature (peak 520–540 nm), indicating the presence of isolated particles in all the samples. For all AuNP layers, the imaginary part of the parallel and perpendicular components of the anisotropic dielectric function was dominated by a central peak at around 2.2 eV, corresponding to the LSPR of isolated particles, and a high-energy shoulder due to Au interband transitions. It was shown that, as the density of particles increased, the extinction cross-section grew over the whole spectral range where measurements are taken. Thus, the response can be explained with an enhanced electromagnetic response between the AuNPs that can be connected to the increase in particle density, but also by the formation of clusters and irregular structures.

10.3390/surfaces7020023

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Citations (0)