After a short introduction of the department and its traditional topics, we will show some of our more recent activities with focusing on nanoparticles.
Nanoparticles are of considerable interest as they often possess size-dependent properties different from those of bulk materials. In the last few years many investigations have focused on bimetallic nanoparticles owing to their promising characteristics. Both one-phase and two-phase alloy as well as hybrid nanoparticles are of great interest for their improved chemical, catalytic, optical, biological and plasmonic properties over their single-component counterparts.
For revealing interesting internal atomic processes in bimetallic nanoparticles, we will show that in individual hemispherical Ag-Cu alloy particles grown by direct current (DC) magnetron sputtering, the phase separation of particles was found to be size- and composition-dependent.  Theoretical explanation will be given for the composition dependence of the phase separation tendency and demonstrated by computer simulations (Stochastic Kinetic Mean Field model ). Moreover, we will show that in Al/Cu/Al and Cu/Al/ Cu triple layered spherical nanoparticles the growth rate of intermetallic products can depend significantly on the stacking order. This was shown experimentally by Atom Probe Tomography and we have developed a complete set of analytical equations to describe reactive diffusion in spherical core shell nanostructures to interpret the observations. 
Porous nanoparticles are very popular because of their high surface/volume ratio. Often, they have unique, more beneficial properties than their solid counterparts. We will show that e.g. nanoporous gold nanoparticles (NPG-NPs) exhibit greater plasmonic tunability and significantly higher local field enhancement as compared to solid NPs. We will demonstrate that the surface of porous gold nanoparticles can be passivated with a thin and conformal metal oxide (Al2O3, TiO2) layers produced by the plasma-enhanced atomic layer deposition method. This passivation results in significant improvement of the thermal stability of the nanoporous morphology. Moreover, the passivation provides further tunability of the plasmon in the hybrid NPs due to the change of the environmental refractive index. [4-6] The high tunability of the plasmonic resonances in the NPG-NPs and the hybrid porous NPs can be very useful for many applications in sensing biological and organic molecules.
 G., Radnóczi ; E., Bokányi ; Z., Erdélyi ; F., Misják, Size dependent spinodal decomposition in Cu-Ag nanoparticles, ACTA MATERIALIA 123 pp. 82-89. , 8 p. (2017)
 Erdélyi, Z ; Pasichnyy, M ; Bezpalchuk, V ; Tomán, JJ ; Gajdics, B ; Gusak, AM, Stochastic kinetic mean field model, COMPUTER PHYSICS COMMUNICATIONS 204 pp. 31-37. , 7 p. (2016)
 Erdélyi, Z ; Schmitz, G, Reactive diffusion and stresses in spherical geometry, ACTA MATERIALIA 60 : 4 pp. 1807-1817. , 11 p. (2012)
 Anna, Kosinova ; Dong, Wang ; Eszter, Baradács ; Bence, Parditka ; Thomas, Kups ; Leonid, Klinger ; Zoltán, Erdélyi ; Eugen, Rabkin, Tuning the nanoscale morphology and optical properties of porous gold nanoparticles by surface passivation annealing, ACTA MATERIALIA 127 pp. 108-116. , 9 p. (2017)
 Rao, Wenye ; Wang, Dong ; Kups, Thomas ; Baradács, Eszter ; Parditka, Bence ; Erdélyi, Zoltán ; Schaaf, Peter, Nanoporous Gold Nanoparticles and Au/Al2O3 Hybrid Nanoparticles with Large Tunability of Plasmonic Properties, ACS APPLIED MATERIALS & INTERFACES 9 : 7 pp. 6273-6281. , 9 p. (2017)
 Laura Juhász, Bence Parditka, Shenouda Shenouda Fam, Misumi Kadoi, Kei-ichi Fukunaga, Zoltán Erdélyi, Csaba Cserháti, Comparing the Morphology and Optical Properties of Porous Gold Nanoparticles Surface Passivated by Al2O3 and TiO2, submitted to SCIENTIFIC REPORTS -NATURE