Abstract
A concept for the fundamental science of nanoparticle synthesis, thermodynamic equilibrium-driven formation
of colloidal single-sized nanoparticle ensembles, is proposed and demonstrated in this manuscript, which
addresses the controlled formation of CdSe magic-sized and regular quantum dots (MSQDs and RQDs).
During formation, the former are magic-sized nuclei without further growth in size, while the latter experience
nucleation and growth. Both MSQDs and RQDs exhibit bandgap emission, while the former have homogeneous
spectra broadening only and the latter both homogeneous and inhomogeneous spectra broadening. The former
are single-sized and the latter have size distribution. With continuous and homogeneous nucleation, the
thermodynamically driven formation of MSQDs was realized via our one-pot noninjection approach, which
features highly synthetic reproducibility and large-scale capability. With the proper tuning of the synthetic
parameters, such as the nature of the reaction medium, that affect the thermodynamic equilibria, various
CdSe MSQDs and RQDs were synthesized discriminately under otherwise identical synthetic formulation
and reaction conditions; the reaction media were noncoordinating 1-octadecene, coordinating trioctylphosphine,
and mixtures of the two. The nature of Cd precursors, affected also by the reaction media, plays a major role
in the formation of MSQDs versus RQDs. The present investigation on the thermodynamically driven formation
of CdSe single-sized nanoparticles via tuning of the reaction medium, mainly, brings novel insights into the
formation mechanism and into the surface ligands of the resulting colloidal nanocrystals. More importantly,
the present study provides novel experimental design and approaches to single-sized nanoparticles desired
for various applications.