ABSTRACT:We present synthesis protocols, based on indium halide and aminophosphine precusors, that allow for the economic, up-scaled production of InP Quantum Dots (QDs). The reactions attain a close to full yield conversion -with respect to the indium precursor -and we demonstrate that size tuning at full chemical yield is possible by straightforward adaptations of the reaction mixture. In addition, we present ZnS and ZnSe shell growth procedures that lead to InP/ZnS and InP/ZnSe core/shell QDs that emit from 510 nm to 630 nm with an emission linewidth between 46 nm and 63 nm. This synthetic method is an important step towards performing Cd-free QDs, and it could help the transfer of colloidal QDs from the academic field to product applications.Colloidal QDs have rapidly evolved from a lab-scale invention of academic interest to new, useful building blocks widely applied in various fields of nanoscience and technology research.1 This is mainly due to high precision, synthetic schemes developed for cadmium chalcogenide QDs, 2 which have made available monodisperse QD ensembles that preserve the unique, size-tunable optoelectronic properties of individual QDs. The restrictions several countries have imposed on the use of cadmium however question the long term feasibility of product applications relying on cadmium-chalcogenide based QDs, hence the quest for Cd-free alternatives.3 This search has mainly focused on CuInS2 and InP where, similar to CdSe, size quantization enables the bandgap transition to be tuned across most of the visible spectrum. Especially InP QDs combine a reduced toxicity with emission characteristics close to those of CdSe-based QDs. 4 The strategies developed to produce colloidal InP QDs can be roughly divided in two groups. The first group includes high reactivity P(-III) precursors such as tris(trimethylsilyl)phosphine [(TMS)3P] 5-7 or phosphine [PH3], 8 and the second group utilizes lower reactivity P(0) and P(+III) precursors such as trioctylphosphine (TOP), 9 P4, 10 or PCl3. 11 Based on size dispersion -a key parameter to be minimized for most QD-based applications -P(-III) precursors give the best results. In particular, (TMS)3P has been the most commonly used phosphorous precursor, where optimized protocols yield emission lines with a full width at half maximum (FWHM) of 40-60 nm.12 Unfortunately, (TMS)3P is a costly and pyrophoric precursor that tends to decompose and forms lethally toxic PH3 in contact with air. This renders upscaled (TMS)3P-based InP production elusive and may explain why InP QDs are far less studied than CdSe QDs. Opposite from the high reactivity P(-III) precursors, protocols to synthesize InP QDs with low reactivity precursors yield QDs with too large a size-dispersion for most of the potential applications.Recently, an innovative and potentially efficient alternative to make InP QDs has been published by Song et al.. 13 These authors use tris(dimethylamino)phosphine [(DMA)3P] as a phosphorous precursor, which can be classified as a low-reactive P(+III) precurso...

We present the synthesis and the optical properties of a new type of two-dimensional heterostructure: core/crown CdSe/CdS nanoplatelets. They consist of CdSe nanoplatelets that are extended laterally with CdS. Both the CdSe core and the CdS crown dimensions can be controlled. Their thickness is controlled at the monolayer level. These novel nanoplatelet-based heterostructures have spectroscopic properties that can be similar to nanoplatelets or closer to quantum dots, depending on the CdSe core lateral size.

Aminophosphines have recently emerged as economical, easy-to-implement precursors for making InP nanocrystals, which stand out as alternative Cd-free quantum dots for optoelectronic applications. Here, we present a complete investigation of the chemical reactions leading to InP formation starting from InCl3 and tris(dialkylamino)phosphines. Using nuclear magnetic resonance (NMR) spectroscopy and single crystal X-ray diffraction, we demonstrate that injection of the aminophosphine in the reaction mixture is followed by a transamination with oleylamine, the solvent of the reaction. In addition, mass spectrometry and NMR indicate that the formation of InP concurs with that of tetra(oleylamino)phosphonium chloride. The chemical yield of the InP formation agrees with this 4 P(+III) → P(-III) + 3 P(+V) disproportionation reaction occurring, since full conversion of the In precursor was only attained for a 4:1 P/In ratio. Hence it underlines the double role of the aminophosphine as both precursor and reducing agent. These new insights will guide further optimization of high quality InP quantum dots and might lead to the extension of synthetic protocols toward other pnictide nanocrystals.