The dynamic surface chemistry of colloidal metal chalcogenide quantum dots

Grisorio, Roberto; Quarta, Danila; Fiore, Angela; Carbone, Luigi; Suranna, Gian Paolo; Giansante, Carlo

doi:10.1039/c9na00452a

Cited by 37 publications

(28 citation statements)

References 34 publications

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“…Diffusion-ordered spectroscopy (DOSY) can provide information regarding the interaction between ligands and the NC surface [3,16,[43][44][45][52][53][54]. DOSY measures the diffusion coefficient of molecules in solution: (i) tightly bound ligands yield diffusion coefficients ascribable to objects having roughly the size of the NCs; and (ii) non-tightly bound ligands are in dynamic exchange with the surface of the NCs (i.e., there exists fast exchange between the bound and free states), yielding diffusion coefficients between those of the free ligands and those of objects having the size of the NCs.…”

Section: Surface Characterizationmentioning

confidence: 99%

Guidelines for the characterization of metal halide nanocrystals

Trizio

Infante

Abdelhady

et al. 2021

Trends in Chemistry

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Section: Surface Characterizationmentioning

confidence: 99%

Guidelines for the characterization of metal halide nanocrystals

Trizio

Infante

Abdelhady

et al. 2021

Trends in Chemistry

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“…The static representation of colloidal NCs as discrete entities was indeed demonstrated as fallacious: the NCs are dynamic chemical species with their (metal−)organic ligand shell showing an intrinsic lability, which results in equilibrium structures that largely depend on the surroundings, as sketched in Figure for PbS NCs. Colloidal ME NCs thus exist in the solution phase as equilibrium mixtures with their (metal−)organic ligands depending on their size, their concentration, and the solvent. , A dynamic surface chemistry was also suggested for metal lead halide NCs. , Albeit the NC surface coordination mainly relies on the ligand binding group, ligation is also related to solubility, with the rationale that, for highly soluble ligands, solvation may compete with surface coordination. This confirms the importance of considering ligand–solvent (and ligand–ligand) interactions, which largely depend on the ligand pendant moiety.…”

Section: On the Design Of Ligand Libraries For The Nc Surfacementioning

confidence: 99%

“…Such a steric repulsion may be enhanced by increasing both the deformability and the permeability of the ligand shell . In this regard, unsaturated aliphatic pendant moieties may lessen the rigidity of the ligand shell compared to saturated chains (as it could be for the oleyl moiety compared to its saturated analog, the stearyl chain); in addition, the permeability of the ligand shell solvents may depend on the surroundings with, for example, aliphatic solvents (such as hexane) that were demonstrated to penetrate into an aliphatic ligand shell more deeply than aromatic solvents (such as toluene), as shown by NMR studies on line width and diffusion coefficient. , This conventional conception of sterically stabilized colloidal dispersions, however, neglects intra- and interligand interactions. The use of a ligand library was fundamental to suggest that an increase of intraligand conformational degrees of freedom at the expense of interligand packing interactions may drastically enhance NC dispersibility .…”

Section: Ligand Libraries and Nc Interactions With The Surroundingsmentioning

confidence: 99%

“…Colloidal ME NCs thus exist in the solution phase as equilibrium mixtures with their (metal−)organic ligands depending on their size, their concentration, and the solvent. 3,16 A dynamic surface chemistry was also suggested for metal lead halide NCs. 2,17 Albeit the NC surface coordination mainly relies on the ligand binding group, ligation is also related to solubility, with the rationale that, for highly soluble ligands, solvation may compete with surface coordination.…”

Section: ■ Introductionmentioning

confidence: 99%

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Library Design of Ligands at the Surface of Colloidal Nanocrystals

Giansante

2020

Acc. Chem. Res.

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Conspectus Surfacesand interfacesare ubiquitous at the nanoscale. Their relevance to nanoscience and nanotechnology is therefore inherent. Colloidal inorganic nanocrystals (NCs), which can show more than a half of their atoms at the surface, are paradigmatic of the role of surfaces in determining materials’ form and functions. Therefore, colloidal NCs may be regarded as soluble surfaces, allowing convenient study of ensemble structure and properties in the solution phase. Colloidal NCs commonly bear chemical species at their surface. Such species (generally referred to as ligands) are introduced already in the synthetic procedures and are added postsynthesis in surface chemistry modification (ligand exchange) reactions. Ligands (i) affect the reactivity and diffusion of the synthetic precursors, (ii) mediate NC interactions with the surroundings, and (iii) contribute to the overall electronic structure. In principle, a vast amount of ligands, as large as our imagination, could be used to coordinate the surface of colloidal NCs. In practice and despite the plethora of studies on NC surface chemistry, a relatively limited number of ligands have been explored. In addition, the importance of designing a set of ligands with tailored features (a ligand library), which may permit comprehensive discussion and explanation of the role of surfaces in the NC structure and properties, is often overlooked. Ligand libraries may also foster heuristic access to novel, unexpected observations. Here, the rational design of ligand libraries is discussed, suggesting that it may be a general method to advance knowledge on colloidal NCs and nanomaterials at large. First, a general ligand framework is introduced. The main subunits are identified: ligands are constituted by a binding group and a pendant moiety, bearing functional substituent groups. On this basis, ligand binding at the NC surface is discussed borrowing concepts from coordination chemistry. Dynamic equilibria at the NC surface are highlighted, revealing the compromise between forming and breaking bonds at interfaces and its intricate interplay with the surroundings. Tailoring of the ligand subunits may impart functions to the whole ligand, eventually transposable to the ligated NC. On these bases, it is shown how ligand design may be exploited to (i) exert control on the size and shape of the NCs, (ii) determine NCs’ dispersibility in a solvent and affect their self-assembly, and (iii) tune the NCs’ optical and electronic properties. These observations point to a description of colloidal NCs as un-decomposable species: ligands may be conceived as an integral part of the overall chemical and electronic structure of the colloidal NC and should not be considered as mere appendages that weakly perturb the inorganic core features. Finally, a perspective on the ligand library design is given. Function-oriented design of the ligand subunits is foreseen as an effective strategy to explore the chemical diversity space. High-throughput screening processes by using computation may...

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“…[ 17 , 18 , 26 , 31 , 50 ] For the effective design of ligand exchange reactions and the evaluation of their outcomes, an accurate description of the QDs and their relevant facets based on morphological, structural, and compositional analyses is fundamental. Among other experimental observations that advanced an atomic level description of the colloidal QDs, it is worth mentioning the demonstration of the non‐stoichiometric, metal rich composition of metal chalcogenide QDs, [36] the displacement of metal complexes from the QD surface induced by two‐electron donor ligands (such as amines), [46] and the intrinsic lability of the (metal‐)organic ligands of both metal chalcogenide[ 51 , 52 ] and lead halide perovskite QDs. [53] On these bases, the ligand‐induced effects on the light absorption by colloidal QDs can be reliably evaluated.…”

Section: Ligand Exchange At the Qd Surfacementioning

confidence: 99%

Surface Chemistry Impact on the Light Absorption by Colloidal Quantum Dots

Giansante

2021

Chemistry A European J

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At the size scale at which quantum confinement effects arise in inorganic semiconductors, the materials’ surface‐to‐volume ratio is intrinsically high. This consideration sets surface chemistry as a powerful tool to exert further control on the electronic structure of the inorganic semiconductors. Among the materials that experience the quantum confinement regime, those prepared via colloidal synthetic procedures (the colloidal quantum dots – and wires and wells, too –) are prone to undergo surface reactions in the solution phase and thus represent an ideal framework to study the ensemble impact of surface chemistry on the materials’ electronic structure. It is here discussed such an impact at the ground state by using the absorption spectrum of the colloidal quantum dots as a descriptor. The experiments show that the chemical species (the ligands) at the colloidal quantum dot surface induce changes to the optical band gap, the absorption coefficient at all wavelengths, and the ionization potential. These evidences point to a description of the colloidal quantum dot (the ligand/core adduct) as an indecomposable species, in which the orbitals localized on the ligands and the core mix in each other's electric field. This description goes beyond conventional models that conceive the ligands on the basis of pure electrostatic arguments (i. e., either as a dielectric shell or as electric dipoles) or as a mere potential energy barrier at the core boundaries.

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The dynamic surface chemistry of colloidal metal chalcogenide quantum dots

Abstract: Probing the interactions of ligands at the surface of colloidal quantum dots by NMR measurements of diffusion coefficients and spectral line widths.

Cited by 37 publications

References 34 publications

Guidelines for the characterization of metal halide nanocrystals

Guidelines for the characterization of metal halide nanocrystals

Library Design of Ligands at the Surface of Colloidal Nanocrystals

Surface Chemistry Impact on the Light Absorption by Colloidal Quantum Dots

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