ELFT HÍRADÓ

[tcsaba <tcsaba AT eik.bme.hu>]

                 M E G H Í V Ó - I N V I T A T I O N

    Seminar Series of the Department of Theoretical Physics at the
           Budapest University of Technology and Economics


                       Zoltán Erdélyi
                  (University of Debrecen)

     Bimetallic and porous metal/metal oxide hybrid nanoparticles


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. 
[1] Theoretical explanation will be given for the composition dependence 
of the phase separation tendency and demonstrated by computer 
simulations (Stochastic Kinetic Mean Field model [2]). 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. [3]
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.

[1]	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)
[2]	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)
[3]	Erdélyi, Z ; Schmitz, G, Reactive diffusion and stresses in 
spherical geometry, ACTA MATERIALIA 60 : 4 pp. 1807-1817. , 11 p. (2012)
[4]	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)
[5]	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)
[6]	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


Időpont: 2018. november 9. péntek, 10:15
Helyszín: BME Fizikai Intézet, Elméleti Fizika Tanszék,
Budafoki út 8. F-épület, III lépcsőház, szemináriumi szoba