Understanding of nanoparticle nucleation and growth is critical for further progress in material design. Nevertheless very often, their synthesis is empirical. Common practice is to reconstruct the mechanism of the nanoparticle formation using either the detailed characterization of the final material and/or conduct the in situ studies under “compromised” conditions (e.g. in capillaries, lower temperature, less toxic reagents, etc). 

To investigate the contribution of different parameters that control synthesis of NPs, we focus to perform in situ x-ray studies of the synthesis of single component and multicomponent nanoparticles under realistic conditions. I will discuss the formation and doping process of iron and iron oxide NPs in real time by in situ synchrotron X-ray absorption spectroscopy. In our study we revealed that the mass flow of the metal triggered by oxidation is responsible for the internalization of the dopant (molybdenum) adsorbed at the surface of the host iron NPs. The new oxidation induced doping mechanism allows control over the doping levels by varying the amount of dopant precursor. Our in situ studies also showed that the dopant precursor substantially changes the reaction kinetics of formation of iron and cobalt nanoparticles and their oxidized formed. I will also present in situ studies on the nucleation and growth kinetics and the temporal changes in the crystal structure of the metal dumbbell NPs (e.g. CoPt3/Au, Pt/Au and PtFe/Au). Using synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS) techniques, we were able to catch the transient stages of structural and volumetric changes of NPs. We found that in the early stage of the reaction intermediate core/shell heterostructure is formed prior to dumbbells. The transition of the core/shell into the dumbbell occurs via strain relaxation of the pseudomorphic Au shell resulting in the nucleation of a strain-free Au domain. In addition, I will present the data on synthesis of semiconductor/noble metal heterostructures that are of interest for application as photocatalysts. I will demonstrate how the proper understanding the mechanism of the nanoparticle formation can expedite the material’s discovery. I will discuss the optical, catalytic and electrochemical properties of the synthetized multicomponent nanoparticles.