Reaction Chemistry/Nanocrystal Property Relations in the Hot Injection Synthesis, the Role of the Solute Solubility

Abstract

Various literature studies show that increasing the concentration of free acid in the hot injection synthesis of colloidal nanocrystals raises the diameter of the resulting nanocrystals. We analyze this reaction chemistry/nanocrystal property relation by combining reaction simulations with an experimental study on a particular CdSe nanocrystal synthesis. We find that increasing the free acid concentration has the same effect on a real synthesis as raising the solute solubility in the simulations. Both lead to larger sizes and a deterioration of the size dispersion at constant reaction rate. Since free acids are used to coordinate the cation precursors in these syntheses, this leads to a meaningful link between a parameter in reaction simulations and the composition of an experimental reaction mixture. We thus explain the increase of the nanocrystal size with the acid concentration as resulting from an enhanced consumption of the solute by nanocrystal growth, which reduces the number of nanocrystals formed. This link between a simulation parameter and the composition of the reaction mixture provides a rational basis to further explore and understand reaction chemistry/nanocrystal property relations in the hot injection synthesis.

Real-Time in Situ Probing of High-Temperature Quantum Dots Solution Synthesis

“…Our experimental results can be compared to recent work by the Hens group 24,36,41 who used both UV/vis ex-situ experiments and numerical resolution of nucleation and growth equation to unravel the formation mechanism of quantum dots in similar conditions. Remarkably, the evolution of the nanocrystal concentration in their simulations reproduce very well the trends observed in our experiments, where a brief nucleation phase is followed by a decrease in nanocrystal concentration.…”

Large‐Scale Programmable Synthesis of PbS Quantum Dots

“…Reactions of lead chalcogenide QDs made with secondary phosphines have distinct differences from QDs synthesized with tertiary phosphines. In both reactions, the QD size initially increases continually with reaction time, as evidenced by absorbance and photoluminescence red‐shifts . However, importantly, we observe that in reactions made with secondary phosphines, the QDs quickly stop growing in size.…”

Size-controlled growth of spherical nanoparticles of Y-doped BaZrO3 perovskite

“…As the molar concentration of cations increases, the number of nuclei formed also increases, and thus, a higher nucleation rate results in finer particles [34,35]. Kwon et al [36] and later Abe et al [37,38] developed a model for nucleation and growth of colloidal particles from solutions following the classical nucleation and growth theory, in which they proposed a precursor to monomer (P ? M) transition model for nucleation of nanocrystals.…”

“…Moreover, as super saturation (S) increases, nucleation rate (J N ) also increases according to Eq. (2) [37,38]. The monomer in the present case can be taken as the hydrolyzed complexes that form in the base solution as described above.…”