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In this work, γ-irradiation was used as an effective and environmentally friendly technique for the synthesis of superparamagnetic iron oxide/Ag (SPION/Ag) and iron oxide/Au nanostructures (SPION/Au). Such hybrid particles have promising applications and advantageous properties due to combination of unique magnetic, electric and optical properties. Alkaline iron(III) precursor solutions, with addition of 2- propanol and DEAE dextran, were purged with nitrogen and γ-irradiated to doses of 14 and 75 kGy, resulting in the reduction of Fe3+ to Fe2+ ions and formation of magnetite (14 kGy, 33% reduction) or Fe(OH)2 (75 kGy, 100% reduction). After irradiation, gold (AuNPs) or silver (AgNPs) nanoparticles were attached to the surface of the magnetic NPs by in situ reduction of Au3+ or Ag+ with radiolytically formed Fe2+. At 75 kGy, the simultaneous oxidation of Fe(OH)2 formed on irradiation and reduction of Au3+ or Ag+ (as confirmed by additional irradiation experiments) led to the formation of superparamagnetic feroxyhyte (δ-FeOOH) nanodiscs decorated with well distributed small AuNPs or AgNPs. The synthesized SPION/Au and SPION/Ag showed high catalytic efficiency in reducing the highly toxic organic pollutant 4-nitrophenol to the commercially important substance 4 aminophenol. The catalytic activity depended on concentration and size of Au (Ag) NPs on the surface. The synthesized hybrid NPs also showed promising SERS activity for the detections of low concentrations of organics in aqueous solutions. δ-FeOOH/Ag NPs enabled good SERS enhancement and detection of up to 10-6 M of 4-MBPA. Acknowledgments: This work has been supported by the Croatian Science Foundation under the project UIP-2017-05-7337 (POLRADNANOP), and Croatian-Slovenian project “Radiolytic synthesis of magnetic δ-FeOOH@Au designed for biomedical applications“

Nanocomposite gels are usually synthesized by two- step methods, while the one step synthesis of nanocomposite hydrogels is much less investigated. One-step synthesis takes an advantage of simultaneous crosslinking of polymer chains and reduction of metal cations, which is quicker and simpler, but finding optimal conditions for these reactions to occur simultaneously is crucial. The aim of this study was to investigate the influence of various experimental factors on the ability of the irradiation technique to synthesize PEO/Ag and PEO/Au nanocomposite hydrogels in a single-step, and thus on the properties of synthesized gels. PEO and Ag+ or Au3+ aqueous solutions were γ- irradiated without addition of a scavenger. The dose, atmosphere, pH, concentration of metal salts, and polymer molecular mass and concentration were varied and optimised. The pH and concentration of metal salts were crucial factors in determining the formation of nanocomposite gels vs. suspensions. Neutral pH let to the formation of stable AuNPs colloid solutions, whereas unstable suspensions and bigger AuNPs were obtained at acidic pH. Alkaline conditions and lower metal salt concentrations favored the formation of Ag and Au nanocomposite hydrogels. Synthesis at elevated pH (pH 11 vs. 9), more concentrated PEO solution and inert atmosphere enabled the formation of hydrogels with higher NPs concentration. AgNPs (AuNPs) were embedded within PEO network with homogenous distribution. Smaller NPs were formed at lower concentration of metal salt, higher pH (pH 11 vs. 9) and under nitrogen atmosphere. In addition to the above, dose was significant factor affecting the PEO crosslinking density ; influence of atmosphere was also visible. At 100 kGy nearly amorphous composite gels with significantly reduced melting and crystallization temperatures were obtained. Smaller amount of NPs did not significantly affect the polymer network, with composite gels having slightly higher degree of crystallinity compared to pure PEO gels. The optimal amount was 1 wt% Au3+ to incorporate AuNPs into the gel and maintain or even improve the rheological properties (firmer gels, higher storage moduli, higher yield points and flow points and better recovery) compared to pure PEO gel. Higher amount of AuNPs (5 wt%, 10 wt%) lead to deterioration of gel properties and significant weakening of gel. The synthesized gels were also tested for their catalytic activity for the degradation/reduction of organic contaminants. The gels were showed to be promising catalysts for the reduction of toxic pollutant 4 nitrophenol to 4- aminophenol. Depending on the amount of NPs synthesized within gels the reduction can be completed almost instantaneously. Acknowledgments: This work has been supported by the Croatian Science Foundation under the project UIP-2017-05- 7337 (POLRADNANOP).

Polymer hydrogels embedded with magnetic nanoparticles are a novel class of composite materials and they gained a lot of attention in the last two decades due to their interesting properties which combine the viscoelasticity of the polymeric network and the sensitivity of magnetic nanoparticles to the external magnetic field. Although γ- irradiation method is highly suitable for generation of nanoparticles (NPs) in a solution as well as for the formation of three-dimensional polymer network, i.e. hydrogels, the radiolytic syntheses of iron oxide/polymer nanocomposite gels are rarely investigated, especially in the case of one-step synthetic approaches, such as the one used in this work. The radiolytic one-step synthesis resulted in the simultaneous crosslinking of the PEO polymer and the reduction of iron (III) salt. In this work, we performed electron microscopy, XRD, SQUID (ZFC and FC, magnetization-temperature measurements), ac susceptometry and Mössbauer measurements (external magnetic field) to elucidate the structural and magnetic properties of synthesized ferrogels. The particles were identified as magnetite/maghemite and showed that they were < 5 nm in size, superparamagnetic and that there was a significant contribution of surface effects on the magnetic properties of the nanoparticles embedded in the hydrogel. Mössbauer measurements showed that the samples consist of core-shell magnetic structure and large spin canting (32-36°) on the outer layer of the particles. Furthermore, a significant contribution of spin-glass behavior and/or dipole-dipole interactions between the nanoparticles was seen from ac susceptometry and SQUID magnetometry. Acknowledgments: This work has been supported by the Croatian Science Foundation under the project UIP-2017-05-7337 (POLRADNANOP).

The Pt/SnO2 (SP-samples) and Pt/α-Fe2O3 (FP- samples) with platinum loadings between 1 and 10 mol% were synthesized mechanochemically starting from platinum(II) acetylacetonate dissolved in toluene and from SnO2 and α-Fe2O3 powders obtained from tin(II) and iron(II) acetates. The STEM results show that the ultrasmall platinum nanoparticles (PtNPs) are well dispersed on the SnO2 and α-Fe2O3 supports. The PtNPs size distributions calculated with lognormal functions ranged from 1.0 to 1.3 nm. The results of temperature programmed reduction in hydrogen showed maxima at 120-160 oC due to the reduction of PtOx to Pt0. The Pt-4f-XPS results showed that the dispersed platinum on the SnO2 and α-Fe2O3 supports consisted of all three oxidation states of platinum: Pt4+, Pt2+ and Pt0. The average oxidation state of platinum as a function of molar fraction of Pt loading in the SP samples varies from 1.69 to 2.11, whereas the oxidation state of Pt in the FP samples varies more linearly and steeply from 1.42 to 2.58. The synthesized samples showed high catalytic activity for the reduction of 4-nitropenol (4-NP) to 4-aminophenol (4-AP), which can be explained by the high dispersion of non-aggregated ultrasmall PtNPs with a size of about 1 nm on the SnOx and FeOx supports.

In this work we have used γ-irradiation as an efficient and environmentally friendly technique for the synthesis of magnetic nanoparticles. The γ-irradiation has the advantage of inducing electrons and other reducing species uniformly in the sample. The alkaline aqueous iron(III)chloride solutions were purged with nitrogen and γ-irradiated with the addition of 2-propanol. DEAE-dextran was used as a growth and stabilizing agent for MNPs in suspensions. The phase composition, stoichiometry, and morphology of MNPs were controlled by adjusting the γ-irradiation dose. Irradiation with doses of 10-36 kGy resulted in the formation of 4 nm spherical sub-stoichiometric magnetite NPs, while at higher doses (50 kGy or more) the main phase was magnetic δ-FeOOH (feroxyhyte) in the form of nanodiscs. Magnetic measurements revealed superparamagnetic behavior of magnetite NPs and exceptional intrinsic magnetic properties of δ-FeOOH nanostructures at room temperature with a Curie temperature above 300 K. Reduction of Fe3+ to Fe2+ ions was quantitatively determined using 1, 10-phenanthroline spectrophotometric method. The reduction is rapid in the initial stages of irradiation (~65% of Fe3+ is reduced up to 30 kGy), then slows down and reaches 100% at ~75 kGy. The reduction power of Fe2+ in irradiated suspensions was explored to synthesize iron oxide/Au nanostructures by adding aqueous HAuCl4 solutions to the irradiated suspensions. Microstructural and morphological analysis showed that the simultaneous oxidation of Fe(OH)2 and reduction of Au3+ led to the formation of δ-FeOOH nanodiscs decorated with small spherical Au nanoparticles. The density and size of AuNPs on the surface of nanodiscs depended on the concentration of added aqueous HAuCl4 solution. The same procedure was used for the synthesis of δ-FeOOH nanodiscs with AgNPs on the surface. The synthesized magnetic nanoparticles were tested for their SERS and catalytic activity.

The only gamma irradiation facility in Croatia is a panoramic batch-type dry storage 60Co gamma irradiator, located at the Radiation Chemistry and Dosimetry Laboratory (RCDL) at Ruđer Bošković Institute (RBI) in Zagreb. This irradiator is used for the synthesis of magnetic and noble metal nanoparticles (NPs), as well as their nanocomposite hydrogels. Gold and superparamagnetic iron oxide NPs have been used in various fields in biomedicine: as contrast agents in diagnostics, in drug delivery, as radiosensitization agents, biosensors, for hyperthermia cancer treatments etc. On the other hand, ferrogels (magnetic-field-sensitive gels) and Au and Ag NPs containing hydrogels have potential applications as wound dressings, artificial muscles, for bone and cardiac tissue regeneration etc. The applications of NPs depend on physicochemical parameters such as NPs size, surface, phase composition and stability, which can be controlled by synthesis method. At RCDL different g-irradiation assisted methods for the synthesis of NPs in the presence of polymers and small organic molecules, and in microcompartments, were used to control NPs size and stability. Superparamagnetic magnetite and gold NPs were synthesized by microemulsion method, and the reducing conditions, NPs size, composition and stoichiometry controlled by γ-irradiation dose, dose rate, atmosphere and pH. AuNPs were synthesized by a citrate-radiolytical method and compared to the classical citrate method. Polymer present and its ability to stabilize Fe(III) precursor NPs strongly influenced the reduction of Fe(III). High reduction, in the case of DEAE-dextran, resulted in superparamagnetic magnetite NPs at lower doses, and superparamagnetic δ-FeOOH nano-discs at above 50 kGy. In addition, Au, Ag and magnetic nanocomposite hydrogels were synthesized by one step g-irradiation technique, by simultaneous crosslinking of polymer chains and reduction of metal cations/metal oxide precursors, with promising thermal and rheological properties for further application.

Magnetic iron oxides are used for various applications, such as pigments, catalysts, in drug delivery, and hyperthermia cancer treatments. The chemistry of iron oxides is very diverse, due to the high versatility of iron in aqueous media. Two stable oxidation states (+2 and +3) and their relative concentrations and properties in aqueous media profoundly affect the end product of the synthesis. Although the chemistry of iron oxides is relatively complex, there are numerous works concerning their synthesis and characterizations. On the other hand, the radiolytic synthesis of magnetic iron oxide nanoparticles is much less investigated. Generally, γ-irradiation synthesis is an attractive and ecologically friendly technique for the synthesis of various nanomaterials including magnetic ones. It has the advantage of inducing electrons and other reducing species homogeneously throughout the system. The properties of the final magnetic material crucially depend on the particle size, dispersion, and aggregation. Various polymers can be used as stabilizers of magnetic nanoparticles in suspensions and as growth and surface modifiers. In this work, iron(III) chloride deaerated alkaline aqueous suspensions were γ-irradiated in the presence of 2-propanol and polymer stabilizer. We investigated the effect of different polymers (dextran and its cationic (DEAE-dextran) and anionic (dextran sulfate) derivatives, poly(ethylene oxide) (PEO), polyvinylpyrrolidone (PVP) and poly(vinyl alcohol) (PVA). Furthermore, the effect of irradiation dose, pH, polymer molecular mass and concentration, iron(III) precursor and 2-propanol concentration on the reduction of iron(III) to iron(II) upon irradiation, as well as the accompanied phase transformation of iron(III) precursor was investigated. The variation of experimental conditions strongly influenced the amount of reduced iron(III), and subsequently the phase composition, morphology, and size of formed nanoparticles. The higher pH values (12 vs. 9) contributed to a better reduction of Fe(III) in the presence of PEO, while the opposite behavior was observed for all other polymers. The initial concentration of DEAE- dextran significantly affected the reduction ; complete reduction occurred at 0.35% polymer concentration, whereas it decreased by ~40% when DEAE-dextran concentration was 10%, at the same dose. Average molecular mass had almost no effect in the case of dextran (40.000 vs. 500.000), whereas a small improvement of reduction was observed for lower molecular mass PEO (35.000 vs. 400.000). Iron(III) precursor and 2-propanol concentration also influenced reduction and phase composition. Furthermore, dextran polymers, especially DEAE-dextran, completely stabilize the precursor particles forming colloidal solutions before irradiation. In the case of DEAE-dextran, the phase composition of formed nanoparticles was predominantly magnetite or magnetic δ-FeOOH nanoparticles depending on the absorbed dose. In the case of dextran sulfate, a multiphasic system was obtained in all cases. On the other hand, upon irradiation in the presence of PEO, PVP, and PVA, the magnetic suspensions or magnetic nanocomposite hydrogels were formed depending on the initial conditions. Due to the lower reduction achieved in the case of PEO and PVP, magnetite and goethite were the predominant phases even at very high doses.

Targeting cancer stem cells (CSC) is significant because they are considered responsible for metastasis formation and relapse after conventional chemotherapy. Ascorbic acid (AA) has been thoroughly investigated as an anticancer agent due to its specific cytotoxic effect on CSC. Because of the instability of ascorbic acid, its derivatives are often used to improve delivery bioavailability. As an alternative, we have used the ascorbyl palmitate (AP), a lipophilic derivative of AA. But for utilization in aqueous environments, AP has to be incorporated in carriers, due to its lipophilic nature. For that purpose, we have synthesized solid lipid nanoparticles with AP (SLN-AP) using the microemulsion technique (water in oil). They were analyzed by measuring their size and polydispersity by DLS and zeta-potential by ELS. Also, for evaluation of morphology, they were visualized on TEM. Cellular uptake of SLNs containing fluorescent dye coumarin-6 was analyzed on HEK 293, U2OS and patient-derived sarcoma CSC by fluorescent microscope during 48h. The effect of SLN-AP on the viability of patient-derived sarcoma CSC (n=5) was determined by the MTT test. DLS analysis of SLN-AP showed that nanoparticles have a diameter of 414 nm, the zeta potential of 0 mV and polydispersity of 0, 228. TEM revealed round morphology and confirmed the size of nanoparticles. SLN containing coumarin-6 are successfully and gradually uptaken by cell lines HEK293, U2OS and patient-derived sarcoma CSC. However, the high exosome/vesicle activity was noticed on the CSC membranes suggesting possible efflux of SLN. Viability assays show that sarcoma CSC have diverse sensitivity to SLN-AP treatment and they are sensitive to up to 33 µM concentration of ascorbate delivered by SLN-AP. In conclusion, we have successfully synthesized and characterized ascorbyl palmitate-incorporated solid lipid nanoparticles. The SLN-AP gradually enter the cells and affect the viability of sarcoma CSC. Therefore, our research confirms the potential of SLN-AP for targeting sarcoma CSC.

Superparamagnetic iron oxide nanoparticles (MNPs) due to their unique magnetic and electrical properties have applications as biosensors, contrast agents, in drug delivery and for hyperthermia cancer treatments. For these uses, the surface of the particles should be modified with a suitable coating. Gold is one of the favored coatings because it is non-toxic, biocompatible, chemically inert, can protect MNPs from oxidation without significantly reducing magnetic properties and enables surface functionalization. It also has special optical properties. Such composite nanostructures have promising applications and advantageous properties compared to individual Au and MNPs. In this work we have used γ-irradiation as an efficient and ecologically friendly technique for the synthesis of magnetic nanoparticles. γ-irradiation has an advantage of inducing electrons and other reducing species homogeneously throughout the sample. The iron(III) chloride alkaline aqueous solutions were purged with nitrogen and γ-irradiated with addition of 2-propanol. DEAE-dextran was used as growth and stabilizing agent of MNPs in suspensions. The phase composition, stoichiometry, and morphology of MNPs were controlled by adjusting γ-irradiation dose. Irradiation with doses 10-36 kGy resulted in the formation of 4 nm spherical substoichiometric magnetite NPs, whereas at higher dose (50 kGy or more) the major phase was magnetic δ-FeOOH (feroxyhyte) in the form of nanodiscs. The reduction of Fe3+ to ferrous Fe2+ ions was quantitatively determined using the 1, 10 phenanthroline spectrophotometric method. The reduction proceeds fast in the beginning stages of irradiation (up to 30 kGy, ~65% Fe3+ reduced), slows down, and reaches 100% reduction at ~75 kGy. The reducing power of Fe2+ in irradiated suspensions was explored to synthesize composite iron oxide/Au nanostructures by the addition of aqueous solutions of HAuCl4 into the irradiated suspensions. Microstructural and morphological analysis showed that the simultaneous oxidation of Fe(OH)2 and reduction of Au3+ resulted in the formation of composite δ-FeOOH nanodiscs decorated with spherical Au nanoparticles. The density and size of Au NPs depended on the amount of added HAuCl4 aqueous solution.

Magnetic iron oxide nanoparticles (MNPs) due to their unique magnetic and electrical properties have applications as sensors, contrast agents, in drug delivery, hyperthermia cancer treatments, etc. For these uses, the surface of the particles should be modified with a suitable surface coating that can easily bind the appropriate biomolecules for the selected application. Gold has become one of the favored coatings because it is non-toxic, biocompatible, chemically inert, and can protect MNPs from oxidation without significantly reducing magnetic properties. Gold enables the surface functionalization with various organic species (due to strong Au-S bond). Magnetic composite or core@shell Fe-oxide/Au nanoparticles have an advantage in the applications due to the combined magnetic properties of the core and the unique optical properties of the Au coating. However, the properties, functionality, and thus the application of magnetic iron oxide/Au NPs, depends on their size, shape, magnetic properties, and colloidal stability. In addition, the quality and homogeneity of the gold coatings significantly depend on the coating process, in this case, the radiolytic process. γ-irradiation has an advantage of inducing electrons and other reducing species homogeneously through the sample. In this work, we have used γ-irradiation as an attractive and ecologically friendly technique for the synthesis of magnetic composite nanoparticles at room temperature. We have systematically studied the influence of γ-irradiation dose. The MNPs were synthesized from N2-purged, iron(III) chloride alkaline aqueous suspensions by γ- irradiation up to doses of 130 kGy (27 kGy/h) with the addition of 2-propanol, while the composite iron oxide/Au nanostructures were synthesized by the addition of HAuCl4. DEAE-dextran was used as a growth and stabilizing agent of MNPs in suspensions. During irradiation, iron(III) reduces to iron(II) depending on the absorbed dose. This radiolytic reduction is accompanied by phase transformations of the iron oxide precursor suspension. The addition of HAuCl4 aqueous solution induced the formation of Au nanoparticles on the surface of MNPs. The phase composition, stoichiometry, and morphology of MNPs were controlled by adjusting the γ-irradiation dose. Irradiation with doses 10– 36 kGy resulted in the formation of very small 4 nm spherical superparamagnetic substoichiometric magnetite NPs, whereas at a higher dose (50 kGy or more) the major phase was magnetic δ-FeOOH (feroxyhyte) in the form of nanodiscs. The magnetic measurements showed superparamagnetic behavior of magnetite NPs and exceptional intrinsic room-temperature magnetic properties of δ-FeOOH nanostructures with the Curie temperature above 300 K. The Au nanoparticles formed were spherical ; the quantity and size of Au nanoparticles depended on the amount of initially added HAuCl4 aqueous solution. Au nanoparticle size ranged from 6 nm to 27 nm, established by UV- Vis spectroscopy and electron microscopy. In this way, it was possible to obtain magnetic spherical magnetite and spherical Au nanoparticles, and thin disc δ-FeOOH/Au nanostructures from the same starting suspension by varying just one experimental factor: the absorbed dose.

Superparamagnetic iron oxide nanoparticles (SPIONs) due to their unique magnetic (superparamagnetism and high saturation field) and electrical properties have applications as sensor, contrast agents, in drug delivery and for hyperthermia cancer treatments. These nanoparticles (NPs) can be modified with noble metal NPs, which combines the magnetic and biocompatible properties of SPIONs and the optical properties of noble metal NPs. In this work we used -irradiation as an attractive and ecologically friendly technique for the synthesis of magnetic NPs at room temperature. -irradiation has an advantage of inducing electrons and other reducing species homogeneously through the sample. The FeCl3 alkaline aqueous solutions were purged with N2 and irradiated with addition of 2- propanol. DEAE-dextran was used as growth and stabilizing agent of MNPs. The phase composition, stoichiometry and morphology of MNPs were controlled by adjusting γ-irradiation dose and dose rate. Doses 10-36 kGy resulted in the formation of small 4 nm spherical substoichiometric magnetite NPs, whereas at higher dose (50 kGy or more) the major phase was magnetic -FeOOH (feroxyhyte) in the form of nanodiscs, as confirmed by SEM, HRTEM, XRD and electron diffraction. The magnetic measurements revealed superparamagnetic behaviour of magnetite NPs and exceptional intrinsic room-temperature properties of -FeOOH with Curie temperature above 300 K. The reduction of Fe3+ to Fe2+ ions was determined using 1, 10-phenanthroline spectrophotometric method. Reduction proceeds fast in the beginning stage of irradiation (up to 30 kGy, 65% Fe3+ reduced), slows down and reaches 100% reduction at 75 kGy. The reducing power of Fe2+ in irradiated suspensions was explored to synthesize composite nanostructures by addition of aqueous solutions of HAuCl4 or AgNO3 in irradiated suspensions. Microstructural and morphological analysis showed that simultaneous oxidation of Fe(OH)2 and reduction of Au3+ or Ag+ resulted in the formation of composite δ-FeOOH nanodiscs decorated with spherical Au or Ag nanoparticles.

Iako je vitamin C prvenstveno otkriven kao antiskorbutski faktor, od njegove izolacije provedeno je više istraživanja kako bi se utvrdilo može li se koristiti u terapiji tumora. Međutim, razlike u primjeni vitamina C su dovele do oprečnih rezultata i nepovjerenja u njegovu sposobnost antitumorskog djelovanja. Također, njegova slaba stabilnost pri izlaganju svjetlosti, povišenoj temperaturi i kisiku otežava njegovu primjenu. Zbog toga smo sintetizirali čvrste lipidne nanočestice u koje smo ugradili askorbil palmitat, stabilniji lipidni derivat askorbinske kiseline. Po sintezi, nanočestice smo karakterizirali mjerenjem veličine, polidisperziteta (DLS) i zeta potencijala korištenjem (ELS), a i morfologiju evaluirali na TEM-u. Pratili smo ulazak nanočestica s ugrađenom fluorescentnom lipidnom bojom coumarin-6 u stanice tokom 48h. Kako bismo usporedili citotoksičnost askorbata dopremljenog nanočesticama i u slobodnom obliku, proveli smo MTT testove na tumorskim matičnim stanicama (engl. cancer stem cells, CSC) izoliranim iz uzoraka sarkoma. Po odabiru optimalnog izvora askorbata, kvantitativnom lančanom reakcijom polimeraze smo ispitali njegov učinak na ekspresiju markera diferencijacije CSC kao mogući mehanizam citotoksičnog djelovanja. Ovim istraživanjem želimo rasvijetliti djelovanje askorbata na matične stanice sarkoma te tako doprinijeti u razumijevanju ove kontroverzne teme.

Magnetic iron oxide nanoparticles (MIONPs) and their magnetic gels are versatile materials, but their radiolytic synthesis has hardly been studied. We have used γ-irradiation as a powerful technique for the synthesis of MIONPs of controlled size, shape and phase composition, as well as for one-step synthesis of magnetic gels. To control the size and stability of MIONPs, the synthesis was carried out in a microemulsion and in the presence of polymers. The γ-irradiation dose and dose rate affected the stoichiometry and size of the magnetite NPs synthesized in the microemulsion. The polymer had a pronounced effect on the reduction conditions and the final product obtained upon irradiation of Fe(III) precursor suspensions. In the presence of DEAE-dextran highly concentrated ferrofluids with 4 nm spherical, superparamagnetic magnetite NPs were produced at 10-36 kGy. At 75 kGy, the complete reduction of Fe3+ to Fe2+ resulted in the magnetic δ-FeOOH nanodiscs. The reducing power of Fe2+ formed was explored to synthesize composite iron oxide/Au and Ag nanostructures. The simultaneous oxidation of Fe(OH)2 and reduction of Au3+ or Ag+ led to the formation of δ-FeOOH nanodiscs decorated with Au or Ag NPs. The synthesized NPs were tested for SERS and catalytic activity. On the other hand, when irradiated in the presence of PEO and PVP, a lower reduction was obtained and magnetic suspensions or magnetic nanocomposite hydrogels were formed depending on the initial conditions. This result is the first report of γ- irradiation synthesis of magnetic hydrogels in a single step. More amorphous and stronger gels were formed at higher dose and Fe(III) precursor concentration. The synthesized MIONPs acted as reinforcing agent and additional crosslinkers of polymer chains. The gels exhibited good self- recoverable properties and superparamagnetic behavior even at very low temperatures. Acknowledgments: This work has been supported by the Croatian Science Foundation under the project UIP-2017-05-7337 (POLRADNANOP).

Magnetic polymer gels are a new promising class of nanocomposite gels with numerous potential applications as effective absorbents of toxic ions in water, in soft actuators such as artificial muscles, in tissue engineering, drug delivery, hyperthermia applications, etc. In this work, the magnetic and rheological properties of radiologically synthesized magnetic PEO/iron oxide hydrogels were systematically investigated. Magnetic PEO/iron oxide nanocomposite hydrogels were for the first time synthesized by a one-step γ-irradiation method starting from poly(ethylene oxide) (PEO) and iron(III) suspensions, followed by the simultaneous crosslinking of PEO chains and reduction of Fe(III) precursor. Magnetic hydrogels with embedded magnetite nanoparticles were obtained with 2-propanol and at high doses, as confirmed by XRD, SEM, TEM and Mössbauer spectroscopy. Rheological measurements confirmed the formation of a well-structured network. The rheological properties of the gels depended on the dose, PEO concentration and the amount of nanoparticles synthesized in the gels (initial Fe3+ content). Stronger gels with higher degree of intermolecular crosslinking were formed at higher dose and higher nanoparticle content. Magnetic iron oxide nanoparticles acted as reinforcing agents and additional crosslinkers of PEO chains facilitating gel formation in one step. All gels exhibited very good self-recoverable properties. SQUID magnetization measurements and Mössbauer spectroscopy showed that the samples exhibited superparamagnetic behavior even at very low temperatures. However, preliminary ac susceptibility measurements showed a deviation from Arrhenius' law ; the relaxation times of the composite hydrogels are unphysically small, suggesting that the particles interact with each other. Furthermore, in-field Mössbauer spectroscopy showed that the samples exhibit spin- canting phenomenon, presumably at the nanoparticle surface, forming a magnetically disordered shell with a ferrimagnetically ordered core.

Solid state dispersions of platinum in the SnO2 nanomaterials

γ-irradiation is an attractive and environmentally friendly technique for the synthesis of magnetic iron oxide nanoparticles at room temperature. In this work, deaerated alkaline aqueous suspensions of iron(III) chloride were irradiated in the presence of 2- propanol and a polymer stabilizer to synthesize magnetic iron oxide nanoparticles (MIONs). We studied the effect of different polymer stabilizers (DEAE-dextran, poly(ethylene oxide)) and the effect of γ-irradiation dose on the synthesis of MIONs. The magnetic properties of the samples were studied by SQUID magnetometry and 57Fe Mössbauer spectrometry, and their structural and morphological properties were analyzed by XRD and electron microscopy. The samples showed significantly different phase compositions, morphologies and exhibited superparamagnetic behavior even at very low temperatures, depending on the polymer and absorbed dose. In-field Mössbauer spectrometry showed that the samples exhibited spin-canting phenomenon, presumably at the nanoparticle surface. Acknowledgments: This work has been supported by the Croatian Science Foundation under the project UIP-2017-05-7337 (POLRADNANOP).

Honeycomb silicon structure (HCSi) was prepared by magnesiothermic reduction of the synthesized SiO2 and investigated as a potential anode material for Li-ion batteries. The characterization of HCSi powder showed the mean particle size of ≈30-40 nm and BET surface area of 102.22 m2/g. In order to increase the conductivity of HCSi, Ag nanoparticles were deposited on HCSi in different amounts. Sample HCSi10, which had the highest Ag content, showed the highest conductivity of 1.379 × 103 S/cm and lower BET surface (34.04 m2/g) which is suitable for anode material. These three materials were investigated as anode material in Li-ion cells and their electrochemical properties were investigated by chronoamperometry, cyclic voltammetry and electrochemical impedance spectroscopy. The enhanced electrochemical performance of sample HCSi10 is attributed to the lowest impedance, highest intercalation intensity and current which results in specific capacity of 3333 mAh/g at 0.067 A/g.

Mechanochemical synthesis and characterisation of Pt-Fe2O3 nanomaterials

Po ugrađivanju askorbata u čvrste lipidne nanočestice, ispitana je njihova citotoksičnost na tumorskim matičnim stanicama izoliranim iz uzorka sarkoma.

Sintetizirane su čvrste lipidne nanočestice s ugrađenim askorbil palmitatom i testirano je njihovo citotoksično djelovanje na tumorskim matičnim stanicama dobivenim iz uzoraka sarkoma pacijenata.

Magnetic iron oxide nanoparticles (MNPs) due to their unique magnetic and electrical properties have applications as sensors, contrast agents, in drug delivery, hyperthermia cancer treatments, etc. For these uses, the surface of the particles should be modified with a suitable surface coating that can easily bind the appropriate biomolecules for the selected application. Gold has become one of the favored coatings because it is non-toxic, biocompatible, chemically inert, enables additional functionalization and can protect MNPs from oxidation without significantly reducing magnetic properties. In this work, we have used γ- irradiation as an attractive and ecologically friendly technique for the synthesis of magnetic composite nanoparticles at room temperature. The phase composition, stoichiometry, and morphology of MNPs were controlled by adjusting the γ- irradiation dose. Irradiation with doses 10–36 kGy resulted in the formation of very small 4 nm spherical magnetite NPs, whereas at a higher dose (50 kGy or more) the major phase was magnetic δ- FeOOH (feroxyhyte) in the form of nanodiscs. The Au nanoparticles formed were spherical ; the quantity and size of Au nanoparticles depended on the amount of initially added HAuCl4 aqueous solution. In this way, it was possible to obtain magnetic spherical magnetite/Au and thin nanodisc δ-FeOOH/Au nanostructures (Figure 1) from the same starting suspension by varying just one experimental factor: the absorbed dose.

The success of Li-ion batteries in the early 1960s took years of research and contribution of many scientists and engineers. Since then there are several electronic revolutions and still lithium-ion (Li-ion) cells are the most widely used as rechargeable battery system for portable electronic devices and electrical vehicles. It has many advantages like high energy density, long storage life, small volume, light weight, low self-discharge efficiency and non-memory effect. The most widely used anode is graphite whose lithiated compounds have stable phases up to the LiC6 stoichiometry corresponding to a theoretical specific capacity of 372 mAh / g[1]. In contrast, silicon possesses a very high theoretical capacity of 4200 mAh / g and can intercalate 4.4 Li into Si at high temperature to form Li15Si4[2]. Silicon also features a working potential around 0.4 V vs. Li+/Li which is safer than operating potential of graphite (0.05 V vs. Li+/Li). Although silicon possesses all of these advantages, silicon based anodes suffer from huge volume expansion upon cycling (≈400%) causing electrode fracture and electrical isolation during repeated cycling [3]. Continuous volume changes cause the breaking-reformation of the solid electrolyte interphase (SEI) film which leads to consumption of lithium-ions and electrolyte. Exhaustion of the electrolyte causes the degradation of conductivity and induces fast capacity loss. The porous structure can provide lithium-ion transport from electrolyte to silicon. The commercial micrometer silicon (Si) powder, ball-milled Si powder, and silicon nanowires generated by metal-assisted chemical etching method were investigated as a potential anode materials for Li-ion batteries.

γ-irradiation is an attractive and ecologically friendly technique for the synthesis of magnetic nanoparticles (MNPs) at room temperature. It has the advantage of inducing electrons and other reducing species homogeneously throughout the reaction vessel. Unlike radiolytic synthesis of noble metal NPs, the radiolytic synthesis of iron oxide NPs is much less investigated. One of the reasons is a very complex iron oxide chemistry that produces numerous phases. Furthermore, MNPs have a high tendency for agglomeration and due to these reasons, various polymers are used that act as dispersants and stabilizers of MNPs in suspensions as well as growth and surface modifiers. We investigated the effect of 3 different polymers (DEAE- dextran, dextran sulfate and poly(ethylene oxide)), as well as the effect of absorbed dose of γ-irradiation on the synthesis of iron oxide MNPs. The results have shown that dextran polymers, especially DEAE-dextran, completely stabilize the precursor particles forming colloidal precursor solutions before irradiation. Irradiation of such colloidal solutions resulted in the synthesis of stable magnetic suspensions. In the case of DEAEdextran, the phase composition of formed NPs was predominantly magnetite or δ- FeOOH depending on the absorbed dose [1]. In the case of dextran sulfate, a multiphasic system was obtained in all cases [2]. On the other hand, on irradiation in the presence of PEO a completely different kind of product forms - PEO/Fe-oxide magnetic nanocomposite hydrogel. Due to the nature of the PEO polymer, a simultaneous crosslinking of the polymer and reduction of precursor NPs to single-phase iron oxide nanoparticles (magnetite in most cases) occurred. Mössbauer spectroscopy was used to investigate the hyperfine interactions of the materials. Samples generally exhibited superparamagnetic relaxation phenomena, and in some cases, samples were not completely magnetically blocked even at 77 K (Fig. 1). Acknowledgments: This work has been supported by the Croatian Science Foundation under the project UIP-2017-05-7337 (POLRADNANOP). References: [1] I. Marić, G. Drazić, G. Štefanić, K. Zadro, M. Gotić, T. Jurkin, Materials Characterization, Vol. 159, 110038 (2020) [2] I. Marić, G. Štefanić, M. Gotić, T. Jurkin, Journal of Molecular Structure, Vol. 1183, p. 126 (2019)

The enhancement in the morphology of anode materials leads to better capacitance properties. Nanostructure design is an effective way to improve battery cycling because nanostructures provide short diffusion length for Li+ ions and electrons with better resistance to fracture [1]. The most widely used anode is graphite whose lithiated compounds have stable phases up to the LiC6 stoichiometry corresponding to a theoretical specific capacity of 372 mAh / g [2]. In contrast, silicon possesses a very high theoretical capacity of 4200 mAh / g and can intercalate 4.4 Li into Si at high temperature to form Li15Si4 [3]. Silicon also features a working potential around 0.4 V vs. Li / Li+ which is safer than operating potential of graphite (0.05 V vs. Li / Li+). Although silicon possesses all of these advantages, silicon-based anodes suffer from huge volume expansion upon cycling (≈400%) causing electrode fracture and electrical isolation during repeated cycling [4]. Continuous volume changes cause the breaking-reformation of the solid electrolyte interphase (SEI) film which leads to the consumption of lithium-ions and electrolyte. There are two strategies to avoid this problem, first one is combining Si with different kinds of carbon materials such as amorphous carbon, conductive carbon black, carbon nanotubes and graphene and secondly, by designing nanoscale silicon with different structures. In the present work, we represent nanostructured composite anodes. Structural and microstructural changes in silicon nanomaterials were examined using several methods: X-ray powder diffraction combined with the results of Raman spectroscopy, FT-IR spectroscopy, UV-Vis spectrometry, Nitrogen adsorption measurements, and TEM analysis. Electrochemical performances were investigated by cyclic voltammetry and galvanostatic charge- discharge measurements.

Magnetic polymer gels are a new promising class of nanocomposite gels with numerous potential application as effective absorbents of toxic ions in water, in soft actuators such as artificial muscles, in tissue engineering, drug delivery, hyperthermia applications etc. The aim of this work was to explore the ability of γ-irradiation technique for a one-step synthesis of magnetic hydrogels. Magnetic PEO/iron oxide nanocomposite hydrogels were successfully synthesized using one-step γ- irradiation method starting from poly(ethylene oxide) (PEO) and iron(III) suspensions followed by simultaneous crosslinking of PEO chains and reduction of Fe(III) precursor. γ-irradiation dose and concentrations of Fe3+, 2-propanol and PEO in the initial suspensions were varied and optimized. With 2-propanol and at high doses magnetic hydrogels with embedded magnetite nanoparticles were obtained, as confirmed by XRD, SEM and Mössbauer spectroscopy. The quantitative determination of γ-irradiation generated Fe2+ was performed using the 1, 10- phenanthroline method. DSC and rheological measurements confirmed the formation of well- structured network. The thermal and rheological properties of the gels depended on the dose, PEO concentration and amount of nanoparticles synthesized inside gels (initial Fe3+ content). Both enthalpies and temperatures of melting and crystallization of gels decrease with the dose and the amount of formed magnetic NPs. More amorphous and stronger gels were formed at higher dose and higher nanoparticle content. The properties of the synthesized gels were determined by the presence of magnetic iron oxide nanoparticles, which acted as reinforcing agents and additional crosslinkers of the PEO chains thus facilitating one-step gel formation.

Magnetic iron oxide nanoparticles (NPs) have applications as sensor, as contrast agents for MR imaging, in drug delivery and for hyperthermia cancer treatments. γ-irradiation is an attractive and ecologically friendly technique for the synthesis of magnetic nanoparticles at room temperature. It has an advantage of inducing electrons and other reducing species homogeneously through the sample. Unlike radiolytic synthesis of noble metal NPs, the radiolytic synthesis of iron oxide NPs is much less investigated. One of the reasons is a very complex iron oxide chemistry that produces numerous phases. Furthermore, magnetic NPs have a high tendency for agglomeration and due to these reasons various polymers are used that act as dispersants and stabilizers of magnetic NPs in suspensions as well as growth and surface modifiers. In this work we investigated the effect of 3 different polymers (DEAE-dextran, dextran sulfate and PEO), as well as the effect of absorbed dose of γ-irradiation on the synthesis of magnetic iron oxide nanoparticles. It was shown that the polymers completely stabilize the precursor particles before irradiation. The type of polymer, as well as the dose applied, had a strong influence on phase composition, morphology, and size of the formed nanoparticles, and in the case of PEO polymer, a completely different kind of product forms (hydrogel/Fe oxide nanocomposite material). In the case of DEAE dextran polymer, the phase composition was dominated by either magnetite or δ-FeOOH depending on the dose absorbed. In the case of dextran sulfate, a multiphasic system was obtained in all cases, with up to 4 different phases for each product obtained. Due to the nature of the PEO polymer, a simultaneous crosslinking of the polymer and the formation of single-phase iron oxide (magnetite in most cases) nanoparticles was observed.