Silver nanoparticels obtained by sonochemical route

Poster presented at Adriatic School of Nanoscience – ASON-1, Dubrovnik, Croatia, September 19–23, 201

Hydrothermal synthesis of magnetic nanoparticles and fabrication of magnetic composite particles using poly(L – lactide)

Magnetic iron oxide nanoparticles ranging from 5 to 20 nm were synthesized using hydrothermal approach. Syntheses were carried out starting from non toxic chemicals at mild reaction temperatures. Different surfactants such as sodium oleate, oleic acid/oleyl amine and PEG are used as in situ surface modifiers for nanoparticles. Also, by varying the type and concentration of precursors and surfactants the size and habitus of the obtained nanocrystals was adjusted. Furthermore, prepared particles are used for fabrication of hydrophilic nano and micro composite particles using biodegradable poly(L-lactide). The qualitative analysis of the synthesized magnetic particles and composites were carried out by XRD. The particle morphology, size and structure were determined TEM, while size distribution was measured by laser diffraction. The phase composition of composite particles, in particular, surface modification was investigated by FT−IR spectroscopy. Morphology of composite particles was observed by SEM

Surface modification of graphitic carbon nitride with copper nanoparticles

Two different synthetic routes were employed to modify surface of graphitic carbon nitride (g- CN) with copper nanoparticles (CuNPs). Structure, morphology and CuNPs distribution on presynthesized g-CN surface are characterized by FT-IR, XRD and TEM. Results suggested that the simpler method based on mixing of precursors in inert atmosphere and room temperature, resulted in better CuNPs distribution compared to method which used refluxing as a step in synthesis.29th International Symposium on Analytical and Environmental Problems : November 13-14, Szeged, Hungary, 2023

Influence of Synthesis-Related Microstructural Features on the Electrocaloric Effect for 0.9Pb(Mg1/3Nb2/3)O3−0.1PbTiO3 Ceramics

Despite having a very similar electrocaloric (EC) coefficient, i.e., the EC temperature change divided by the applied electric field, the 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 (PMN-10PT) ceramic prepared by mechanochemical synthesis exhibits a much higher EC temperature change than the columbite-derived version, i.e., 2.37 °C at 107 °C and 115 kV/cm. The difference is due to the almost two-times-higher breakdown field of the former material, 115 kV/cm, as opposed to 57 kV/cm in the latter. While both ceramic materials have similarly high relative densities and grain sizes (>96%, ≈5 µm) and an almost correct perovskite stoichiometry, the mechanochemical synthesis contributes to a lower level of compositional deviation. The peak permittivity and saturated polarization are slightly higher and the domain structure is finer in the mechanochemically derived ceramic. The secondary phases that result from each synthesis are identified and related to different interactions of the individual materials with the electric field: an intergranular lead-silicate-based phase in the columbite-derived PMN-10PT and MgO inclusions in the mechanochemically derived cerami

Multifunctional Cantilevers as Working Elements in Solid-State Cooling Devices

Despite the challenges of practical implementation, electrocaloric (EC) cooling remains a promising technology because of its good scalability and high efficiency. Here, we investigate the feasibility of an EC cooling device that couples the EC and electromechanical (EM) responses of a highly functionally, efficient, lead magnesium niobate ceramic material. We fabricated multifunctional cantilevers from this material and characterized their electrical, EM and EC properties. Two active cantilevers were stacked in a cascade structure, forming a proof-of-concept device, which was then analyzed in detail. The cooling effect was lower than the EC effect of the material itself, mainly due to the poor solid-to-solid heat transfer. However, we show that the use of ethylene glycol in the thermal contact area can significantly reduce the contact resistance, thereby improving the heat transfer. Although this solution is most likely impractical from the design point of view, the results clearly show that in this and similar cooling devices, a non-destructive, surface-modification method, with the same effectiveness as that of ethylene glycol, will have to be developed to reduce the thermal contact resistance. We hope this study will motivate the further development of multifunctional cooling devices

Analysis of the Phase Transition and the Domain Structure in K\u3csub\u3e0.5\u3c/sub\u3eBi\u3csub\u3e0.5\u3c/sub\u3eTiO\u3csub\u3e3\u3c/sub\u3e Perovskite Ceramics by \u3cem\u3eIn Situ\u3c/em\u3e XRD and TEM

The local crystal and domain structures of K0.5Bi0.5TiO3 ceramics were investigated by transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). The individual grains showed a lamellar domain structure, and on the basis of spot splitting along the characteristic crystallographic directions, 90°a–a- and 90°a–c-type domains were identified. Furthermore, lamellar features within the 90° domains were observed, which we presumed were 180° domains; however, in the case of P4mm structures they cannot be distinguished by SAED. The 90° domain boundaries were (011) and (101) twin planes, typical for tetragonal perovskites. The domains could be designated as rotation twins, where the symmetry element describing the relationship between two twin domains is a twofold twin axis [011]/[101] and the symmetry operation is a 180° rotation. In order to determine the dynamics and the temperature of the phase transformation from the tetragonal to the cubic structures, high-temperature XRD and in situ heating TEM analyses were performed. The results showed a gradual phase transformation in the temperature range from ~280° to ~450°C, where some grains lost their polar domains at a lower temperature than others. These findings confirmed the existence of a binary stability field in which the cubic and tetragonal structures coexist

Combining silver, polyaniline and polyvinylpyrrolidone for efficient electrocatalysis of borohydride oxidation reaction

The catalytic activity of five silver-polyaniline-polyvinylpyrrolidone (Ag@PANI@PVP1–5) nanocomposites for borohydride oxidation reaction (BOR) was thoroughly examined. The nanocomposites were synthesized by an in situ chemical oxidative polymerization of aniline monomer by Ag+ ions in the presence of accelerator – PVP and physicochemical properties were determined prior their use in electrocatalysis. Ag@PANI@PVP3 with 35.4 wt% Ag delivered the highest current density and specific current density during BOR. Evaluation of the order of reaction < 1 suggested indirect BOR mechanism. Furthermore, Ag@PANI@PVP3 also delivered the highest current density and stable performance during chronoamperometric study of BOR. Its apparent activation energy of 15 kJ mol−1 was found to be the lowest among the studied materials accounting for the high current densities. © 2023 The Author(s

ANTIBACTERIAL ACTIVITY OF COPPER/POLYPYRROLE NANOCOMPOSITE

A novel and favorable antibacterial agent as a combination of copper nanoparticles (CuNPs) and polypyrrole (PPy) is presented. By simple in situ polymerization method, copper/polypyrrole (Cu/PPy) nanocomposite with spherical CuNPs, around 25 nm in diameter, uniformly dispersed throughout PPy matrix with granular morphology, was characterized and subjected to determination of antibacterial activity toward bacteria Escherichia coli and Staphylococcus aureus. Knowing that when acting alone, CuNPs and PPy have already shown antimicrobial responce, their mutual and synergetic engagement against bacteria in this survey is somewhat expected. After a twenty-four-hour interaction with S. aureus, already 2 ppm of Cu/PPy with only 9.45 wt% content of Cu is acting almost completely cidal, with 99.17% of bacterial growth inhibition. Such nanocomposite could easily find application in water disinfection, soil sterilization and food preservation