ZB 16 - Dynamics of nanocrystal structure induced by surface chemistry (Z.Kaszkur)

Short history of the laboratory.

The group was established on the basis of XRD laboratory existing within Department V (Catalysis on Metals) since 1960-ties and headed by dr A.Janko and later by prof. J.Pielaszek. The laboratory developed projects involving widely understood phase analysis and Rietveld refinement of structural data based on laboratory and synchrotron powder diffraction patterns as well as dynamical and kinetic studies in situ in variable, controlled atmosphere and programmed temperature (from R.T.upto~600 ^oC). Since the last 20 years the group specializes in in situ powder diffraction of nanocrystalline solids and especially of nanometals, focusing on subtle surface phenomena via monitoring peaks position, intensity and width.

The laboratory specialized also in the analysis of the state of organization of quasi-amorphous materials. Our long time experience and expertise was focused on the studies of such materials using wide angle X-Ray Powder Diffraction as well as Radial Distribution Function method (RDF). We have contributed to the method developing the most accurate to date convolutional method of normalization of the scattering pattern (Kaszkur, J.Appl.Crystall.,23 ,180-185 (1990)). Quality of the method was later confirmed by Cumbrera et al.,J.Appl.Cryst.28, 408-415 (1995) in the paper entirely devoted to our method. We have also developed many numerical techniques to study highly dispersed solids (transition metals) deposited on supports (SiO₂,Al ₂O₃). These techniques include reliable background estimation in the XRD pattern, data smoothing procedures and quantitative analysis oriented towards in situ studies.

During the last 20 years we were developing powder diffraction in situ method merged with mass spectroscopy (nanopowder diffraction) to follow subtle evolution of nanometals (catalysts) surface during chemical (catalytic) reaction. It aims at monitoring of the reaction even if no phase transition occur and interprets subtle changes of diffraction pattern with atomistic simulations. The method allowed e.g. showing Au mobility and lack of ceria (CeO₂) oxygen exchange in a low temperature CO oxidation reaction on Au/CeO₂ catalyst (Zieliński et al., Scientific Reports, 2023,  https://doi.org/10.1038/s41598-023-28557-5) and proved non-applicability of the Mars-vanKrevelen reaction mechanism.

The developed by us programme suite CLUSTER allowed constructing tools to analyze domain structure of 3D crosstwinned FCC crystallites, with the domains being perfect FCC fragments. Such structures are common for FCC metals obtained via chemical reduction ( Nanoscale (2023), 15, 8633).

The key achievements during last decades included:

1.  Discovery and structure determination of a new PdC phase - saturated C solution within fcc Pd lattice (Kaszkur, Stachurski, Pielaszek, Phys. Chem. Solids Vol. 47. No. 8. pp. 795-798. 1986).
2. Convolutional method of normalization of the scattering pattern- the most accurate to date for PDF study (Kaszkur, J.Appl.Crystall.,23 ,180-185 (1990))
3. Development of atomistic simulation suite (CLUSTER) for convenient model creation, constrained simulation and interpretation of exp.results (Kaszkur, Mierzwa, Philos.Mag.A, 1998, 77:3, 781-800).(Available from https://kaszkur.net.pl/index.php/cluster/ ).
4. Development of EXAFS data analysis tools (merged with program CLUSTER)(J.Alloys and Compounds 286 (1999) 93–97)    - project discontinued.
5. Building of the XRD Laboratory local network driven measuring system enabling full in situ experiment controll via Linux client-server architecture and Bash scripts, including MS, Temp.controllers, gas feed system, flow controllers etc. (from 2000 onwards).
6. New method of analysis of diffraction pattern series and new ways of the in situ pattern evolution interpretation- reaching beyond Bragg's law and employing large scale atomistic simulations (Kaszkur, J. Appl. Cryst. (2000). 33, 87–94; J. Appl. Cryst. (2000). 33, 1262–1270)  .
7. An XRD method to detect surface reconstruction of metal-catalyst during reaction (proof of the concept Rzeszotarski, Kaszkur, Phys. Chem. Chem. Phys., 2009, 11, 5416–5421).
8. New insight into diffusion in metals based on monitoring of a repeatable, reversible surface segregation in PdAg nanoalloy (Kaszkur, Juszczyk, Łomot, Phys. Chem. Chem. Phys.2015, 17, 28250, see -> RESEARCH).
9.  Peak profile analysis method enabling detection of the atom Column Length Distribution and of the crystallites shape change during chemical process at their surface (Kaszkur,   Zieliński, Juszczyk,J. Appl. Cryst. (2017). 50, 585–593 -> see RESEARCH)
10. In situ diffraction monitoring of nanocrystals structure evolving during catalytic reaction at their surface,  Zieliński, Kaszkur, Juszczyk, Sobczak, Scientific Reports (2023), https://doi.org/10.1038/s41598-023-28557-5.
11. Development of nanoparticle bulk morphology analysis: a multidomain XRD approach. Smirnov, Kaszkur, Hoell, Nanoscale (2023), 15, 8633; https://doi.org/10.1039/d3nr00456b.

Current focus.

The group engages in studies of nanocrystal structure and dynamics of its change during chemical reaction and other physico-chemical processes. The principal methods are in situ powder diffraction complemented with mass spectrometry. The studied materials are mostly catalysts with focus on the structure of small metallic nanoclusters. The developed methods allow detection of surface reconstruction of metal nanocrystals, monitoring of surface segregation phenomena in nanoalloys and interpretation of non periodic structures like icosahedra. A very general review of the developed approach is given at address https://kaszkur.net.pl/index.php/project/ (Zbigniew Kaszkur home page). The list of principal methodology publications is given at RESEARCH section.

The Group activity in instrumental part overlaps with activities of the Laboratory of X-Ray Powder Diffractometry and Spectrometry  (old webpage) .