Revelation of the Nature of the Ligand–PbS Bond and Its Implication on Chemical Functionalization of PbS

Abstract

Chemical functionalization of metal sulfides by adsorption of specially designed ligands is of primary importance in efficiently manipulating the physicochemical properties of the target surface. Despite the widely studied ligand–metal molecular systems and the generally used binding energy concept, reports on the bond character of ligand–metal sulfide and its implication on the design of ligands with enhanced functionalities are rather scarce. Herein, using density functional theory calculations, we studied the intrinsic binding mechanism of the typical S/O-terminated ligands and (100) surface of lead sulfide (PbS), with a particular emphasis on the ligand–PbS(100) bond character. Strikingly, the ligand–PbS(100) bond is found to be predominantly ionic with minor covalency, completely different from the conventional perception of covalent interaction. Further insights into the specific hydrophobization of PbS led us to demonstrate that the ligand electronegativity, rather than the commonly used binding energy, allows more accurate prediction of the relative hydrophobic functionality of the ligand toward PbS. Therefore, this study not only advances our fundamental understanding on the ligand–PbS(100) interaction but also provides new perspectives on the first-principles design of ligands.

Strong Coupling of Colloidal Quantum Dots via Self‐Assemble Passivation for Efficient Infrared Solar Cells

“…For both the CQD‐AI and CQD‐PbI 2 (SAP) surfaces with pronounced charge redistribution after structure convergence, the interaction between the passivation layer and the CQD surface exhibits strong ionic bonding characteristics. [ 44 ] The electrons mainly accumulate on the top layer of the PbS bonding region and I atoms in the CQD‐AI system, whereas the electrons uniformly distribute in the PbI 2 passivation layer in the CQD‐PbI 2 (SAP) system. Figure 5c presents the planar average charge density difference that is perpendicular to the direction of constructed models, and the Bader charge was analyzed.…”

Regulating Thiol Ligands of p-Type Colloidal Quantum Dots for Efficient Infrared Solar Cells

“…Therefore, these important theoretical results indicate that the ABT ligands may result in strong electronic coupling between the CQD and surface ligand, facilitating charge transfer between the CQD and surface ligand . Additionally, hybridization at a slightly deeper level may benefit light absorption and carrier delocalization of CQDSCs. ,, …”

“…The results reveal that the electrons accumulated intensively mainly around the S ligand atoms, and the electrons in the intermediate region between the CQD and surface ligand were mostly depleted. Therefore, charge transfer between the CQD and surface ligand is favorable for these systems, and the interaction between the CQD and surface ligand exhibits strong ionic bonding characteristics …”

“…Therefore, charge transfer between the CQD and surface ligand is favorable for these systems, and the interaction between the CQD and surface ligand exhibits strong ionic bonding characteristics. 36 Charge transfer between the CQD and surface ligand was further quantified by using the Bader charge scheme based on the charge density difference, and the calculated charge states of the ligands are summarized in Figure 1f. The value of the Bader charge is determined by the attractive abilities of binding ions toward the valence electrons.…”

“…39 Additionally, hybridization at a slightly deeper level may benefit light absorption and carrier delocalization of CQDSCs. 36,40,41 Monodispersed CQDs capped with long-chain oleic acid (OA) ligands were synthesized using the conventional hotinjection method, and the CQD size is highly uniform at ∼3 nm (Figure S2). During the preparation of p-type CQD solid films, the CQD-OA solid film was treated with thiol ligand solutions for ligand exchange.…”