Rational design of the gram-scale synthesis of nearly monodisperse semiconductor nanocrystals

Abstract

We address two aspects of general interest for the chemical synthesis of colloidal semiconductor nanocrystals: (1) the rational design of the synthesis protocol aiming at the optimization of the reaction parameters in a minimum number of experiments; (2) the transfer of the procedure to the gram scale, while maintaining a low size distribution and maximizing the reaction yield. Concerning the first point, the design-of-experiment (DOE) method has been applied to the synthesis of colloidal CdSe nanocrystals. We demonstrate that 16 experiments, analyzed by means of a Taguchi L16 table, are sufficient to optimize the reaction parameters for controlling the mean size of the nanocrystals in a large range while keeping the size distribution narrow (5-10%). The DOE method strongly reduces the number of experiments necessary for the optimization as compared to trial-and-error approaches. Furthermore, the Taguchi table analysis reveals the degree of influence of each reaction parameter investigated (e.g., the nature and concentration of reagents, the solvent, the reaction temperature) and indicates the interactions between them. On the basis of these results, the synthesis has been scaled up by a factor of 20. Using a 2-L batch reactor combined with a high-throughput peristaltic pump, different-sized samples of CdSe nanocrystals with yields of 2-3 g per synthesis have been produced without sacrificing the narrow size distribution. In a similar setup, the gram-scale synthesis of CdSe/CdS/ZnS core/shell/shell nanocrystals exhibiting a fluorescence quantum yield of 81% and excellent resistance of the photoluminescence in presence of a fluorescent quencher (aromatic thiol) has been achieved.PACS: 81.20.Ka, 81.07.Bc, 78.67.Bf

Quenching Dynamics in CdSe Nanoparticles: Surface-Induced Defects upon Dilution.

“…Spherical CdSe QDs (diameter ≈ 4,8 nm) were synthesized using a 2-L reactor according to the procedure described in references 1,41 . In brief, 8 mmol of cadmium stearate CdSt 2 , 184 mmol of SA, 0.85 mol (280 mL) of oleylamine (OA) and 186 mL of 1-octadecene (ODE) are introduced in the 2-L reactor which is thereafter degassed for 45 min filled with argon and heated to 250°C.…”

In-situ synthesis of high stable CdS quantum dots and their application for photocatalytic degradation of dyes

“…Optical properties of CdS QDs have been investigated and described in many publications [12,21,23,[31][32][33]. Variables such as concentration of precursors and temperature that might be influenced on the synthesis method were selected from these papers.…”

“…These optimization methods are not only time consuming and more expensive, also these conventional methods of experimentation neglect the effect of interaction between factors, and leading to low efficiency in optimization process [22,23]. Fractional factorial design (FFD) approach is one of the experimental design methods that can be used as an alternative for one-factor-at-a-time optimization methods.…”

Design of a live biochip for in situ nanotoxicology studies: a proof of concept

“…The commercial anatase TiO 2 NPs used in Fig. The preparation of 7 nm QDs of CdSe/CdS/ZnS is described in Protiere et al 35 They were spotted at 20 nM. Rhodamine B labeled -TiO 2 NPs were used to observe translocation in eukaryotic cells as it appears in Fig.…”