Evolution of crystallinity during nanoparticle formation
Besides the classical nucleation pathway based on supersaturation, non-classical nucleation pathways have been established for various nanoparticle systems (ZnO, CdS, CdTe,…). Crystalline particles do not directly nucleate, but only form after several steps.
For ZnO, we have shown that initial, tetrahedrally coordinated precursor complexes form in solution, which assemble to internally disordered particles. Only gradually those particles become crystalline, see scheme. The crystallization kinetics depend on the organic ligands, which stabilize the final particle sizes.
The interesting applicational properties, i.e. photoluminescence in case of CdS, result from its internal structure. Quite often, final products are well characterized, but the evolution of internal particle structures is insufficiently understood.
We run in-situ nucleation experiments to follow the particle formation and watch the crystallization as it happens. The impact of organic ligands or the role of solvents during the nucleation can be assessed.
Zobel, M., Windmüller, A., Schmidt, E., et al. The evolution of crystalline ordering for ligand-ornamented zinc oxide nanoparticles, CrystEngComm 18 (2016) 2163-2172.
Zobel, M., Chatterjee, H., Matveeva, G., et al. Room-temperature sol-gel synthesis of organic ligand-capped ZnO nanoparticles, Journal of Nanoparticle Research 17 Issue 5 (2015)