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

Abstract

Despite recent advances, the synthesis of colloidal InSb quantum dots (QDs) remains underdeveloped, mostly due to the lack of suitable precursors. In this work, we use Lewis acid−base interactions between Sb(III) and In(III) species formed at room temperature in situ from commercially available compounds (viz., InCl 3 , Sb[NMe 2 ] 3 and a primary alkylamine) to obtain InSb adduct complexes. These complexes are successfully used as precursors for the synthesis of colloidal InSb QDs ranging from 2.8 to 18.2 nm in diameter by fast coreduction at sufficiently high temperatures (≥230°C). Our findings allow us to propose a formation mechanism for the QDs synthesized in our work, which is based on a nonclassical nucleation event, followed by aggregative growth. This yields ensembles with multimodal size distributions, which can be fractionated in subensembles with relatively narrow polydispersity by postsynthetic size fractionation. InSb QDs with diameters below 7.0 nm have the zinc blende crystal structure, while ensembles of larger QDs (≥10 nm) consist of a mixture of wurtzite and zinc blende QDs. The QDs exhibit photoluminescence with small Stokes shifts and short radiative lifetimes, implying that the emission is due to band-edge recombination and that the direct nature of the bandgap of bulk InSb is preserved in InSb QDs. Finally, we constructed a sizing curve correlating the peak position of the lowest energy absorption transition with the QD diameters, which shows that the band gap of colloidal InSb QDs increases with size reduction following a 1/d dependence.

Solution-Processed InSb Quantum Dot Photodiodes for Short-Wave Infrared Sensing

“…The reaction time was fixed to 15 min at 240 °C in every case because above 230 °C the reduction rate of both In and Sb precursors is sufficiently fast to allow coreduction of both elements. 24 In Figure 2a, once the molar ratio of the precursor is set to 1:1, three peaks appearing at 2θ = 23.8°, 39.3°, and 46.3°are characteristic of ( 111 secondary phase, while the intensity of these peaks weakens with increasing molar ratio. A further increase of the molar ratio showed the appearance of metallic indium as a secondary phase instead of the absence of antimony.…”

“…21 Another possible reason could be that the size dependences of the bandgaps of the QDs not only depended on 1/R 2 (quantum confinement effect) but also depend on 1/ R (electron and hole Coulomb interaction) which has been neglected in parabolic EMA. 24,37,38 Nevertheless, the magnitude of the optical bandgap increases with a reduction in diameter of InSb QDs based on the effect of quantum confinement, suggesting that the wavelengths of the firstexciton peak can be tuned from 1200 to 1400 nm by adjusting the QD size between 5.1 and 7.8 nm on the assumption that the size distribution should be narrowed with a relative standard deviation of 10%.…”

Magic-Size Semiconductor Nanostructures: Where Does the Magic Come from?

“…From this standpoint, the study recently published by Hsieh and co-workers 44 is of particular interest. The authors used a combination of nondestructive characterization techniques (TEM, SAXS, wide-angle X-ray scattering (WAXS), EXAFS, XRD, X-ray photoelectron spectroscopy, magic-angle spinning NMR spectroscopy) and computational approaches to study the shape, size, local bonding, and chemical environments of octylamine-capped MSNSs that have been previously 28 assigned to (CdSe) 13 MSCs. 44 The isolated solids are observed to consist of 1.6 nm diameter clusters entrained into selfassembled sheet-like triangular lamellae.…”

“…28 The transformation process was significantly accelerated in mixtures rich in a primary alkylamine. 28 The assignment of the starting and final species to (ME) 34 MSCs and (ME) 13 MSCs was done primarily on the basis of absorption spectra, by analogy with spectra that had been previously assigned to those species. 28 Transformations involving II−VI (CdS, CdSe, CdTe) MSNSs in colloidal dispersion have been extensively investigated by Yu and co-workers, 45,54 who reported that the absorbance of the original species continuously decreased while that of the final species increased.…”

“…of the best developed colloidal NCs, which are based on Cdand Pb-chalcogenides, and the relatively large polydispersity of ensembles of NCs of alternative semiconductors. This has driven both the development of alternative colloidal NCs based on nontoxic (or less toxic) elements (for example, InP, 2,12 InSb, 13 or CuAX 2 , 2,14 with A = In, Ga and X = S, Se) and a quest for atomically precise synthesis, yielding monodisperse ensembles of NCs. 15−17 In this Perspective, we address topics that are relevant to the latter, which remains a formidable challenge.…”