Luminescent Colloidal InSb Quantum Dots from In situ-Generated Single-Source Precursor

Despite recent advances,\nthe synthesis of colloidal InSb quantum\ndots (QDs) remains underdeveloped, mostly due to the lack of suitable\nprecursors. In this work, we use Lewis acid–base interactions\nbetween Sb­(III) and In­(III) species formed at room temperature <i>in situ</i> from commercially available compounds (<i>viz.</i>, InCl₃, Sb­[NMe₂]₃ and a primary\nalkylamine) to obtain InSb adduct complexes. These complexes are successfully\nused as precursors for the synthesis of colloidal InSb QDs ranging\nfrom 2.8 to 18.2 nm in diameter by fast coreduction at sufficiently\nhigh temperatures (≥230 °C). Our findings allow us to\npropose a formation mechanism for the QDs synthesized in our work,\nwhich is based on a nonclassical nucleation event, followed by aggregative\ngrowth. This yields ensembles with multimodal size distributions,\nwhich can be fractionated in subensembles with relatively narrow polydispersity\nby postsynthetic size fractionation. InSb QDs with diameters below\n7.0 nm have the zinc blende crystal structure, while ensembles of\nlarger QDs (≥10 nm) consist of a mixture of wurtzite and zinc\nblende QDs. The QDs exhibit photoluminescence with small Stokes shifts\nand short radiative lifetimes, implying that the emission is due to\nband-edge recombination and that the direct nature of the bandgap\nof bulk InSb is preserved in InSb QDs. Finally, we constructed a sizing\ncurve correlating the peak position of the lowest energy absorption\ntransition with the QD diameters, which shows that the band gap of\ncolloidal InSb QDs increases with size reduction following a 1/<i>d</i> dependence.