Diffusion dynamics controlled colloidal synthesis of highly monodisperse InAs nanocrystals

Abstract

Highly monodisperse colloidal InAs quantum dots (QDs) with superior optoelectronic properties are promising candidates for various applications, including infrared photodetectors and photovoltaics. Recently, a synthetic process involving continuous injection has been introduced to synthesize uniformly sized InAs QDs. Still, synthetic efforts to increase the particle size of over 5 nm often suffer from growth suppression. Secondary nucleation or interparticle ripening during the growth accompanies the inhomogeneity in size as well. In this study, we propose a growth model for the continuous synthetic processing of colloidal InAs QDs based on molecular diffusion. The experimentally validated model demonstrates how precursor solution injection reduces monomer flux, limiting particle growth during synthesis. As predicted by our model, we control the diffusion dynamics by tuning reaction volume, precursor concentration, and injection rate of precursor. Through diffusion-dynamics-control in the continuous process, we synthesize the InAs QDs with a size over 9.0-nm (1Smax of 1600 nm) with a narrow size distribution (12.2%). Diffusion-dynamics-controlled synthesis presented in this study effectively manages the monomer flux and thus overcome monomer-reactivity-originating size limit of nanocrystal growth in solution.

ZnCl2 Mediated Synthesis of InAs Nanocrystals with Aminoarsine

“…The best parameters were chosen by checking the absorption curves of the resulting products and, in particular, the HWHM of the first excitonic absorption peak. 35,36 Our results indicated that the narrowest size distribution could be achieved when injecting the amino-As and DMEA-AlH 3 at 240 °C and growing the NCs for 15 min at 240 °C (Figure S1).…”

“…We first optimized the synthesis of InAs NCs, starting from the work of Srivastava et al, by systematically varying the reaction temperature (from 240 to 300 °C), the injection temperature of amino-As and DMEA-AlH 3 (from 150 to 240 °C), and the reaction time (from 5 to 30 min) while keeping the other reaction parameters fixed (5 mL of oleylamine, InCl 3 :amino-As:DMEA-AlH 3 precursors molar ratio of 1:1:3; see the Experimental Section and Figure S1 of the Supporting Information). The best parameters were chosen by checking the absorption curves of the resulting products and, in particular, the HWHM of the first excitonic absorption peak. , Our results indicated that the narrowest size distribution could be achieved when injecting the amino-As and DMEA-AlH 3 at 240 °C and growing the NCs for 15 min at 240 °C (Figure S1).…”

“…Yet, improvements are still needed to meet the standards reached with the TMS-As/TMGe-As precursors. For example, the width of the first exciton absorption peak (normally measured as half width at half-maximum, HWHM) of InAs NCs, which is strictly correlated to the size distribution of the sample, can be as narrow as 60 meV or even 40 meV when employing TMS-As/TMGe-As, while in the case of amino-As the best value reported so far is around 100 meV. , Additionally, the PL quantum yields (QYs) characterizing Cd-free InAs-based core@shell NCs made with TMS-As/TMGe-As, such as InAs@InP@ZnSe NCs, can be as high as 23%, while those synthesized with amino-As (i.e., InAs@ZnSe or InAs@ZnS) could only reach ∼10%. ,,, …”

Stable CsPbBr3 Nanoclusters Feature a Disk-like Shape and a Distorted Orthorhombic Structure

“…The use of NCLs as a single-source precursor can avoid the poorly controllable pyrolytic step in which precursors are converted into monomers (typically occurring at high temperatures), thus enabling greater synthetic control . This is particularly relevant in the synthesis of nano-heterostructures (or in general in seeded growth approaches) and of those NC systems in which the reactivity of the available precursors cannot be finely tuned, as in the case of III–V semiconductors (e.g., InP and InAs). , The interest in such compounds has led, in the last decades, to the isolation and characterization of several NCLs of II–VI and III–V semiconductor materials, namely, CdS, ,,, CdSe, ,, CdTe, , ZnS, , ZnSe, , ZnTe, , PbSe, InP, ,, and InAs. ,, Only recently, with the emergence of lead halide perovskites, NCLs of APbBr 3 (A = methylammonium or Cs) materials were discovered. ,,,,, CsPbBr 3 NCLs have been found to form at room temperature in the presence of a high concentration of oleylamine (OLA) and oleic acid (OA), with usually high Pb-to-Cs feed ratios (ranging from 2.5:1 to 6:1). ,, CsPbBr 3 NCLs have been employed as single-source precursors for the synthesis of quantum-confined nanostructures (nanowires, nanoplatelets) and NCs with complex geometries (i.e., CsPbBr 3 hexapods) and heterostructures (i.e., CsPbBr 3 –Pb 4 S 3 Br 2 ) . Instead, conventional metal halide precursors (e.g., Cs-oleate and PbBr 2 or Cs-carbonate, Pb-acetate, and benzoyl bromide) , lead to a fast nucleation and growth of CsPbBr 3 NCs, making it extremely difficult to perform any seeded growth approach or to synthesize heterostructures …”

Boosting and Activating NIR-IIb Luminescence of Ag2Te Quantum Dots with a Molecular Trigger

“…Quantum dots (QDs) with near-infrared (NIR) excitation and NIR-IIb (1500–1700 nm) emission have shown great prospect in luminescence imaging due to the depressed photon absorption and scattering by biological samples, large tissue penetration depth, and high imaging contrast and resolution. − Compared with previously reported NIR-IIb emissive QDs, such as InAs QDs, PbS QDs, HgTe QDs, etc., − Ag 2 Te QDs without any highly toxic elements have recently attracted wide attention due to their decent biocompatibility. − However, the poor luminescence brightness of Ag 2 Te QDs prevents their practical applications. For this matter, shell coating and Au doping methods were reported to enhance the luminescence via improving the photoluminescence quantum yield. , Meanwhile, these methods not only need to meet the challenge of lattice mismatch but also increase the difficulty of synthesis.…”