Supersaturation driven tailoring of photoluminescence efficiency and size distribution: A simplified aqueous approach for producing high-quality, biocompatible quantum dots

Supersaturation was found to play a pivotal role during nanoparticle-synthesis and its subtle variation helped achieve two prime objectives: (a) high photoluminescence quantum efficiency (PLQE) and (b) narrow size distribution, thereby obviating the need for post-preparative treatments. Degree of supersaturation of initial synthetic mixture was varied by changing the concentration of reagents while keeping their molar ratio constant at 1:2.5:0.5 for [Cd2+]:[cysteine]:[chalcogenide]. An eight-fold increase in supersaturation caused a sharp focusing of size distribution by 64% for CdS quantum dots (QDs). The as-prepared CdS and CdTe QDs were found to have size distribution as low as 4% at higher supersaturation. For a four-fold increase in supersaturation, PLQE of as-prepared CdTe QDs (4.3 nm) rose by 5 times to a remarkably high value of 54%. The focusing of size distribution with increasing supersaturation was found to work well even in the absence of any stabilizer. A substantial overlap of nucleation and growth was found at low supersaturation (0.5SCdTe0.5SCdTe), whereas a good separation of the two events is achieved at a higher supersaturation (4SCdTe4SCdTe). This study provides a simplified aqueous route for producing highly monodisperse, photoluminescent and biocompatible nanoparticles.

Graphical abstractDegree of supersaturation has been found to be an effective tool to achieve two prime objectives of nanoparticle synthesis: (1) high photoluminescence quantum efficiency (PLQE) and (2) narrow size distribution.Figure optionsDownload full-size imageDownload as PowerPoint slide