Controlling the Size of Hot Injection Made Nanocrystals by Manipulating the Diffusion Coefficient of the Solute

Abstract

We investigate the relation between the chain length of ligands used and the size of the nanocrystals formed in the hot injection synthesis. With two different CdSe nanocrystal syntheses, we consistently find that longer chain carboxylic acids result in smaller nanocrystals with improved size dispersions. By combining a more in-depth experimental investigation with kinetic reaction simulations, we come to the conclusion that this size tuning is due to a change in the diffusion coefficient and the solubility of the solute. The relation between size tuning by the ligand chain length and the coordination of the solute by the ligands is further explored by expanding the study to amines and phosphine oxides. In line with the weak coordination of CdSe nanocrystals by amines, no influence of the chain length on the nanocrystals is found, whereas the size tuning brought about by phosphine oxides can be attributed to a solubility change. We conclude that the ligand chain length provides a practical handle to optimize the outcome of a hot injection synthesis in terms of size and size dispersion and can be used to probe the interaction between ligands and the actual solute.

Ultrastable CsPbBr3 Perovskite Quantum Dot and Their Enhanced Amplified Spontaneous Emission by Surface Ligand Modification

“…We think that the short length of chain carboxylic is the main reason for this size increase. The similar phenomenon has also been reported in the previous literatures . The influence of the ligand chain length on the nanocrystal diameter is due to the change of interaction between the ligand and QDs, i.e., the short ligand chain length could improve the high diffusion coefficient and solubility of the solute, resulting in larger size of CsPbBr 3 ‐DA QDs.…”

Aqueous synthesis of PEGylated copper sulfide nanoparticles for photoacoustic imaging of tumors

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“…HS-PEG was serving as a capping agent to ensure the water solubility of the NPs. Owing to the long chain of HS-PEG ligands, 34 the overall size of the NPs from the current reaction is much smaller than those prepared by using small molecular surface capping agents such as sodium citrate. Figure 1 presents the TEM images of the resultant NPs obtained at the reaction time of 1 h, 5 h, and 17 h. The NPs are uniform with average particle size of 2.7 nm, 4.8 nm, and 7.2 nm, respectively.…”

Aminophosphines: A Double Role in the Synthesis of Colloidal Indium Phosphide Quantum Dots

“…[21][22][23] In this respect, mechanistic studies have addressed both the chemical reactions involved in monomer formation and the relation between the monomer formation rate and the size of the resulting nanocrystals. [24][25][26][27] Especially in the case of CdSe QDs synthesized using trioctylphosphine selenium (TOP-Se), precursor conversion was investigated in great detail and found to consist of two essential steps, i.e., a coordination of TOP-Se to the Cd center, followed by the cleavage of the Se=P bond. Moreover, this precursor conversion was found to be limiting the overall rate of CdSe formation.…”