Single-Crystal and Electronic Structure of a 1.3 nm Indium Phosphide Nanocluster

Abstract

Magic-sized nanoclusters have been implicated as mechanistically relevant intermediates in the synthesis of group III-V quantum dots. Herein we report the single-crystal X-ray diffraction structure of a carboxylate-ligated indium phosphide magic-sized nanocluster at 0.83 Å resolution. The structure of this cluster, In37P20(O2CR)51, deviates from that of known crystal phases and possesses a non-stoichiometric, charged core composed of a series of fused 6-membered rings. The cluster is completely passivated by bidentate carboxylate ligands exhibiting predominantly bridging binding modes. The absorption spectrum of the cluster shows an asymmetric line shape that is broader than what would be expected from a homogeneous sample. A combination of computational and experimental evidence suggests that the spectral line width is a result of multiple, discrete electronic transitions that couple to vibrations of the nanocrystal lattice. The product of reaction of this nanocluster with 1 equiv of water has also been structurally characterized, demonstrating site selectivity without a drastic alteration of electronic structure.

Quantifying Ligand Exchange Reactions at CdSe Nanocrystal Surfaces

“…Cossairt and co-workers have recently shown that carboxylic acids bind to InP nanoclusters in 4 modes, one of which involves symmetric bridging of two indium atoms. 63 If this bridging binding mode is also present for native oleate ligands on CdSe, the increased coverage of thiol ligands could result from displacement of carboxylic acids binding in this bridging motif. In order to maintain charge balance in these various ligand exchange processes, the ligands binding to open coordination sites are likely doing so as neutral thiols, while those displacing the native oleate ligands undergo a proton transfer reaction and bind as thiolates.…”

Templated Growth of InP Nanocrystals with a Polytwistane Structure

“…Thes ynthesis was carried out at 100 8 8C, at emperature at which the cluster does not spontaneously thermally decompose (t 1/2 > 5h at 150 8 8C), but where any added P(SiMe 3 ) 3 immediately reacts,t hus allowing for aq uantitative relation between the equivalents of P(SiMe 3 ) 3 added and the evolution of the NCs via their optical spectra. Closer inspection of the optical change versus time (Figure 1, inset) reveals that the growth occurred across three distinct regimes.Regime Iis an apparent induction period wherein the optical spectra show no appreciable shift, slowly accelerating by the addition of approximately 5equivalents of P(SiMe 3 ) 3 .G iven that the lowest energy cluster transitions have been previously assigned to molecular orbitals that reside primarily in the core of the cluster, [11] this observation does not discount the possibility of significant, surface-localized reactions.R egime II shows an extended period of nanocrystal growth with astrong correlation to the amount of P(SiMe 3 ) 3 added to the solution. During this period, nanocrystal polydispersity was maintained as indicated by the change in full width at half maximum (FWHM) of the excitonic transition ( Figure S2).…”

“…[12,[18][19][20] Theexistence of nonclassical cluster intermediates during crystal growth has been shown to have profound implications on the growth kinetics of NCs. [23] Specifically,c lose examination of ar ecently discovered InP magicsized cluster,I n 37 P 20 (O 2 CR) 51 , [11] reveals ah igh-symmetry In 13 P 14 core fragment displaying as tructure of multiple polytwistane units helically intersecting in three dimensions. [7,9,14] This last feature has made magic-sized clusters intriguing synthons for templated nanomaterial synthesis and suggests that exploiting their unique structural properties can facilitate the synthesis of new nanoscale phases.…”

“…Thea bility to define structure at the nascent stage of nanocrystal (NC) nucleation has enabled the synthesis of awide variety of non-thermodynamic structures,including Al, Ge,and Au clusters, [1][2][3][4][5] metal chalcogenide superlattices, [6][7][8][9] allotropic phases such as e-Co, [10] and molecule-like crystals of InP and CdSe, [11][12][13][14] many of which exhibit unique surface chemistry and optical properties,a nd all of which redefine the classical ideas of material phase and crystal synthesis.Controlling the synthesis of these non-thermodynamic materials using soft-chemical methods presents ap articular challenge.E fforts in the field of semiconductor NC synthesis have revealed colloidal routes to,for example,new allotropes of Si [15] as well as metastable phases of CuInSe 2 [16] and SnS. Thea bility to define structure at the nascent stage of nanocrystal (NC) nucleation has enabled the synthesis of awide variety of non-thermodynamic structures,including Al, Ge,and Au clusters, [1][2][3][4][5] metal chalcogenide superlattices, [6][7][8][9] allotropic phases such as e-Co, [10] and molecule-like crystals of InP and CdSe, [11][12][13][14] many of which exhibit unique surface chemistry and optical properties,a nd all of which redefine the classical ideas of material phase and crystal synthesis.Controlling the synthesis of these non-thermodynamic materials using soft-chemical methods presents ap articular challenge.E fforts in the field of semiconductor NC synthesis have revealed colloidal routes to,for example,new allotropes of Si [15] as well as metastable phases of CuInSe 2 [16] and SnS.…”

Identifying short surface ligands on metal phosphide quantum dots

“…3–6 The point of convergence of these works is the surface of the QDs. In contrast to the now well-known surface chemistry of the lead and cadmium chalcogenides nanocrystals (NCs), 7 that of phosphide QDs is much less understood and displays a diversity that does not seem to exist for selenides or sulfides.…”