Reeling them in: Ph 2 PSiMe 2 fosters low temperature, acid-free growth of ever larger InP nanocrystals Theodore Anthony Gazis, Peter D. Matthews Keele University, UK The quantum dot (QD) projected market value is 8.1 billion dollars by 2026. 1 Driving growth in this area is the versatility of these nanomaterials. 2 The high commercial interest, alongside concerns over heavy metal use in traditional QDs, 3,4 has accelerated the necessity for alternatives. InP QDs are promising candidates due to their excellent optoelectronic properties and their cheap, earth-abundant character. 4 However, their exacting synthesis has hampered their adoption. 5 P(SiMe 3 ) 3, the phosphorus precursor of choice, is rapidly consumed to form the QD nuclei thus impeding monodisperse growth. Previous efforts to temper this reactivity have been met with limited success. 6-9 Moreover, recent mechanistic studies have cast doubt on the importance of precursor conversion rate as QD size distribution did not improve. Most importantly, the majority of the literature mentioned above relied upon the use of In carboxylates, substrates notorious for their oxophilicity. 10 These acids are incompatible with the P 3- precursor, as deleterious side reactions with carboxylic acids are widely reported. Therefore, removal of oxygen containing species is of utmost importance to achieve highly pure QDs. The protocol we have developed utilizes commercially available Ph 2 PSiMe 3 as an effective growth promoter. Adjusting the ratio of Ph 2 PSiMe 3 to P(SiMe 3 ) 3 : In(X) 3 (X=Cl, I) allowed for ever-larger nanoparticles to be isolated. These approached the size of QDs as evidenced by UV-vis spectroscopy. Remarkably, the above system was receptive to growth at 100 °C using volatile toluene as the reaction solvent. This is the lowest reported temperature for InP QDs. Mechanistic studies utilizing FTIR, and in-situ NMR have confirmed the incorporation of Ph 2 PSiMe 3 on the surface of the QD and explained its role in our system. Crucially, the results achieved add another layer of control over InP QD growth under acid-free mild reaction conditions.
Figure 1. Use of Ph 2 PSiMe 3 supports the growth of ever larger nanoparticles. References 1. Purba, N. S.; Nooraeni, R. In Proceedings of the International Conference on Trade 2019 (ICOT 2019); Atlantis Press, 126–130. 2. Cotta, M. A. ACS Appl. Nano Mater. 2020, 3 (6), 4920–4924. 3. Oh, E.; Liu, R.; Nel, A.; Gemill, K. B.; Bilal, M.; Cohen, Y.; Medintz, I. L. Nat. Nanotechnol. 2016, 11 (5), 479–486. 4. Xu, G.; Zeng, S.; Zhang, B.; Swihart, M. T.; Yong, K. T.; Prasad, P. N. Chem. Rev. 2016, 116 (19), 12234–12327. 5. Tamang, S.; Lincheneau, C.; Hermans, Y.; Jeong, S.; Reiss, P. Chem. Mater. 2016, 28 (8), 2491–2506. 6. Ramasamy, P.; Ko, K. J.; Kang, J. W.; Lee, J. S. Chem. Mater. 2018, 30 (11), 3643–3647. 7. Chandrasiri, H. B.; Kim, E. B.; Snee, P. T. Inorg. Chem. 2020, 59 (21), 15928–15935. 8. Joung, S.; Yoon, S.; Han, C. S.; Kim, Y.; Jeong, S. Nanoscale Res. Lett. 2012, 7, 1–8. 9. Gary, D. C.; Glassy, B. A.; Cossairt, B. M. Chem. Mater. 2014, 26 (4). 10. Koh, S.; Eom, T.; Kim, W. D.; Lee, K.; Lee, D.; Lee, Y. K.; Kim, H.; Bae, W. K.; Lee, D. C. Chem. Mater. 2017, 29 (15), 6346–6355.
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