Spin-coated fluorinated PbS QD superlattice thin film with high hole mobility
Abstract not provided
Xia, Pan↗
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The three-way junction structure of the HIV-1 PBS-segment binds host enzyme important for viral infectivity
HIV-1 reverse transcription initiates at the primer binding site (PBS) in the viral genomic RNA (gRNA). Although the structure of the PBS-segment undergoes substantial rearrangement upon tRNALys3 annealing, the proper folding of the PBS-segment during gRNA packaging is important as it ensures loading of beneficial host factors. DHX9/RNA helicase A (RHA) is recruited to gRNA to enhance the processivity of reverse transcriptase. Because the molecular details of the interactions have yet to be defined, we solved the solution structure of the PBS-segment preferentially bound by RHA. Evidence is provided that PBS-segment adopts a previously undefined adenosine-rich three-way junction structure encompassing the primer activation stem (PAS), tRNA-like element (TLE) and tRNA annealing arm. Disruption of the PBS-segment three-way junction structure diminished reverse transcription products and led to reduced viral infectivity. Because of the existence of the tRNA annealing arm, the TLE and PAS form a bent helical structure that undergoes shape-dependent recognition by RHA double-stranded RNA binding domain 1 (dsRBD1). Mutagenesis and phylogenetic analyses provide evidence for conservation of the PBS-segment three-way junction structure that is preferentially bound by RHA in support of efficient reverse transcription, the hallmark step of HIV-1 replication.
59 BASIC BIOLOGICAL SCIENCES↗
Colloidal Dispersions of Sterically and Electrostatically Stabilized PbS Quantum Dots: Structure Factors, Second Virial Coefficients, and Film-Forming Properties
Electrostatically stabilized nanocrystals (NCs) and, in particular, quantum dots (QDs) hold promise for forming strongly coupled superlattices due to their compact and electronically conductive surface ligands. However, studies of the colloidal dispersion and interparticle interactions of electrostatically stabilized sub-10 nm NCs have been limited, hindering the optimization of their colloidal stability and self-assembly. In this study, we employed small-angle X-ray scattering (SAXS) experiments to investigate the interparticle interactions and arrangement of PbS QDs with thiostannate ligands (PbS-Sn2S64-) in polar solvents. The study reveals significant deviations from the ideal solution behavior in electrostatically stabilized QD dispersions. Our results demonstrate that PbS-Sn2S64- QDs exhibit long-range interactions within the solvent, in contrast to the short-range steric repulsion characteristic of PbS QDs with oleate ligands (PbS-OA). Introducing highly charged multivalent electrolytes screens electrostatic interactions between charged QDs, reducing the length scale of the repulsive interactions. Furthermore, we calculated the second virial (B2) coefficients from SAXS data, providing insights into how surface chemistry, solvent, and size influence pair potentials. Finally, we explore the influence of long-range interparticle interactions of PbS-Sn2S64- QDs on the morphology of films produced by drying or spin-coating colloidal solutions. The long-range repulsive term of PbS-Sn2S64- QDs promotes the formation of amorphous films, and screening the electrostatic repulsion by the addition of an electrolyte enables the formation of crystalline domains. These findings highlight the critical role of NC-NC interactions in tailoring the properties of functional materials made of colloidal NCs.
SAXS↗
Valence Disproportionation of GeS in the PbS Matrix Forms Pb 5 Ge 5 S 12 Inclusions with Conduction Band Alignment Leading to High n-Type Thermoelectric Performance
Converting waste heat into useful electricity using solid-state thermoelectrics has a potential for enormous global energy savings. Lead chalcogenides are among the most prominent thermoelectric materials, whose performance decreases with an increase in chalcogen amounts (e.g., PbTe>PbSe>PbS). Herein, we demonstrate the simultaneous optimization of the electrical and thermal transport properties of PbS-based compounds by alloying with GeS. The addition of GeS triggers a complex cascade of beneficial events as follows: Ge 2+ substitution in Pb 2+ and discordant off-center behavior; formation of Pb 5 Ge 5 S 12 as stable second phase inclusions through valence disproportionation of Ge 2+ to Ge0 and Ge 4+ . PbS and Pb 5 Ge 5 S 12 exhibit good conduction band energy alignment that preserves the high electron mobility; the formation of Pb 5 Ge 5 S 12 increases the electron carrier concentration by introducing S vacancies. Sb doping as the electron donor produces a large power factor and low lattice thermal conductivity (κ lat ) of ~0.61 Wm -1 K -1 . The highest performance was obtained for the 14% GeS-alloyed samples, which exhibited an increased room temperature electron mobility of ~121 cm 2 V -1 s -1 for 3 × 10 19 cm -3 carrier density, and a ZT, of 1.32 at 923 K. This is ~ 55% greater that the corresponding Sb-doped PbS sample and is one of the highest reported for the n-type PbS system. Moreover, the average ZT (ZT avg ) of ~0.76 from 400 to 923 K is the highest for PbS-based systems.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Embedding PbS Quantum Dots (QDs) in Pb-Halide Perovskite Matrices: QD Surface Chemistry and Antisolvent Effects on QD Dispersion and Confinement Properties
Hybrid materials of metal chalcogenide colloidal quantum dots (QDs) embedded in metal halide perovskites (MHPs) have led to composites with synergistic properties. Here, we investigate how QD size, surface chemistry, and MHP film formation methods affect the resulting optoelectronic properties of QD/MHP “dot-in-matrix” systems. We monitor the QD absorption and photoluminescence throughout synthesis, ligand exchange, and transfer into the MHP ink, and we characterize the final QD/MHP films via electron microscopy and transient absorption. In addition, we are the first to globally map how PbS QDs are distributed on the micrometer scale within these dot-in-matrix systems, using three-dimensional (3D) tomography time-of-flight secondary ion mass spectrometry. The surface chemistry imparted during synthesis directly affects the optical properties of the dot-in-matrix composites. Pb-halide passivation leads to QD/MHP dot-in-matrix samples with optical properties that are well-described by a theoretical model, based on a Type I finite-barrier heterostructure between the PbS QD and the MHP matrix. Samples without Pb-halide passivation show complicated size-dependent behavior, indicating a transition from a Type I heterostructure between the PbS QD wells and MHP barriers for small-sized QDs to PbS QDs that are electronically decoupled from the MHP matrix for larger QDs. Furthermore, the choice in perovskite antisolvent crystallization method leads to a difference in the spatial QD distribution within the perovskite matrix, differences in carrier lifetime, and photoluminescence shifts of up to 180 meV for PbS in methylammonium lead iodide. This work establishes an understanding of such emerging synergistic systems relevant for technologies such as photovoltaics, infrared emitters and detectors, and other unexplored technological applications.
92 SC - Basic Energy Sciences (BES) (SC-22)↗
GaSb doping facilitates conduction band convergence and improves thermoelectric performance in n-type PbS
P-type lead chalcogenides have superior thermoelectric performance because they exhibit the energy convergence of several valence bands. However, despite the existence of two conduction bands, there has been no report about conduction band (CB) convergence for n-type counterparts because of the large energy difference between them. Therefore, new strategies are required to manipulate the CBs if enhancing the electrical transport performance of n-type lead chalcogenides is to be achieved. PbS is a highly attractive member of the lead chalcogenides because of its high earth-abundance and low cost. Here, we report that the introduction of GaSb can successfully dope the PbS matrix with Ga and Sb atoms occupying the Pb site in its rock salt structure. GaSb doping leads to conduction band convergence and enlarged effective density of state mass for n-type PbS. This effect results in superior power factor and decreased lattice thermal conductivity caused by the soft phonon modes and point defect scattering of phonons. Consequently, a record-high average power factor PF avg of ~20.4 μW cm –1 K –2 and figure of merit ZT avg of ~0.84 in the temperature range of 400 K to 923 K were obtained, higher than any n- and p-type PbS-based thermoelectric materials.
36 MATERIALS SCIENCE↗
Materials Data on PbS by Materials Project
PbS crystallizes in the orthorhombic Aem2 space group. The structure is two-dimensional and consists of one PbS sheet oriented in the (0, 0, 1) direction. Pb2+ is bonded to five equivalent S2- atoms to form a mixture of edge and corner-sharing PbS5 square pyramids. There are a spread of Pb–S bond distances ranging from 2.70–3.10 Å. S2- is bonded in a single-bond geometry to five equivalent Pb2+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on PbS by Materials Project
PbS crystallizes in the orthorhombic Cmc2_1 space group. The structure is two-dimensional and consists of two PbS sheets oriented in the (0, 0, 1) direction. there are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded to five S2- atoms to form a mixture of distorted corner and edge-sharing PbS5 square pyramids. There are a spread of Pb–S bond distances ranging from 2.69–3.06 Å. In the second Pb2+ site, Pb2+ is bonded to five S2- atoms to form a mixture of distorted corner and edge-sharing PbS5 square pyramids. There are a spread of Pb–S bond distances ranging from 2.69–3.01 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a single-bond geometry to five Pb2+ atoms. In the second S2- site, S2- is bonded in a single-bond geometry to five Pb2+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on PbS by Materials Project
PbS crystallizes in the orthorhombic Cmcm space group. The structure is two-dimensional and consists of two PbS sheets oriented in the (0, 1, 0) direction. Pb2+ is bonded to five equivalent S2- atoms to form a mixture of corner and edge-sharing PbS5 square pyramids. There are one shorter (2.71 Å) and four longer (3.01 Å) Pb–S bond lengths. S2- is bonded to five equivalent Pb2+ atoms to form a mixture of corner and edge-sharing SPb5 square pyramids.
36 MATERIALS SCIENCE↗
Materials Data on PbS by Materials Project
PbS crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of one PbS sheet oriented in the (0, 0, 1) direction. Pb2+ is bonded to five equivalent S2- atoms to form a mixture of edge and corner-sharing PbS5 square pyramids. There are a spread of Pb–S bond distances ranging from 2.69–3.01 Å. S2- is bonded in a single-bond geometry to five equivalent Pb2+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on PbS by Materials Project
PbS crystallizes in the orthorhombic Pma2 space group. The structure is two-dimensional and consists of one PbS sheet oriented in the (1, 0, 0) direction. there are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 3-coordinate geometry to three S2- atoms. There are one shorter (2.61 Å) and two longer (2.71 Å) Pb–S bond lengths. In the second Pb2+ site, Pb2+ is bonded in a 6-coordinate geometry to three S2- atoms. There are one shorter (2.66 Å) and two longer (2.82 Å) Pb–S bond lengths. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded to four Pb2+ atoms to form distorted edge-sharing SPb4 trigonal pyramids. In the second S2- site, S2- is bonded in a distorted bent 120 degrees geometry to two Pb2+ atoms.
36 MATERIALS SCIENCE↗
Materials Data on PbS by Materials Project
PbS crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of one PbS sheet oriented in the (0, 0, 1) direction. Pb2+ is bonded to five equivalent S2- atoms to form a mixture of distorted edge and corner-sharing PbS5 square pyramids. There are a spread of Pb–S bond distances ranging from 2.69–3.02 Å. S2- is bonded in a single-bond geometry to five equivalent Pb2+ atoms.
36 MATERIALS SCIENCE↗
Exciton-Phonon Coupling and Carrier Relaxation in PbS Quantum Dots: The Case of Carboxylate Ligands
Some ligand-nanocrystal combinations exhibit rapid cooling of highly excited electronic states while other nanocrystal/shell combinations do not appear to have this effect. There remains a need to identify the distinguishing properties of ligand-nanocrystal interactions that avoid such rapid relaxation processes to guide the design of colloidal quantum dots (QDs) that take advantage of multiple exciton generation or hot-carrier extraction processes. Here, we use mid-infrared transient absorption spectroscopy to investigate the influence that carboxylate ligands with distinct excited state surface chemistries has on exciton-phonon coupling and hot exciton relaxation in PbS quantum dot (QD) films. Our findings reveal that despite significant differences in the excited state surface chemistry of oleate (OA) and iodide/mercaptopropionic acid (I-/MPA) ligands, PbS QD films passivated with both ligand types exhibit identical electronic relaxation rates and exciton-phonon coupling strengths within experimental precision. The data suggest that the inorganic lattice is the principal source of exciton-phonon coupling that influences hot exciton relaxation, rather than the vibronic modes of carboxylate ligands. The size-dependent nature of the exciton-phonon coupling strength is consistent with the localization of charge on the QD surfaces, which enhances the mixing of electronic and nuclear coordinates particularly when the electronic states are more quantum confined in smaller nanocrystals.
14 SOLAR ENERGY↗
Pyroelectricity of Lead Sulfide (PbS) Quantum Dot Films Induced by Janus-Ligand Shells
Asymmetry is an essential property to control. To do that in nanocrystalline systems we have developed methods to produce Janus-ligand shells on otherwise symmetric PbS quantum dots (QDs). In this work, we demonstrate that control by constructing a system that exhibits pyroelectricity built from spherical PbS QDs. We observed a pyroelectric current in two different configurations. In one configuration, the QDs are self-assembled into close-packed arrays while in the second configuration, the QDs are dispersed into an electro-inactive polymer, polydimethylsiloxane. Both exhibit a pyroelectric response. In the first configuration we estimate a lower limit of the pyroelectric coefficient to be 1.97 × 10 -7 C/m 2 K, which is likely limited by the degree of QD alignment during film formation but is already on par with common pyroelectric systems. Compared with inorganic ceramic-like and polymeric pyroelectric materials, pyroelectric films self-assembled from polar QDs are easier to prepare, responsive to light with different energies based on QD exciton energy, and the polarization of each QD could be easily tuned by constructing different Janus-ligand shells.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Strong Structural and Electronic Coupling in Metavalent PbS Moiré Superlattices
Moiré superlattices are twisted bilayer materials in which the tunable interlayer quantum confinement offers access to new physics and novel device functionalities. Previously, moiré superlattices were built exclusively using materials with weak van der Waals interactions, and synthesizing moiré superlattices with strong interlayer chemical bonding was considered to be impractical. Here, in this study, using lead sulfide (PbS) as an example, we report a strategy for synthesizing moiré superlattices coupled by strong chemical bonding. We use water-soluble ligands as a removable template to obtain free-standing ultrathin PbS nanosheets and assemble them into direct-contact bilayers with various twist angles. Atomic-resolution imaging shows the moiré periodic structural reconstruction at the superlattice interface due to the strong metavalent coupling. Electron energy loss spectroscopy and theoretical calculations collectively reveal the twist-angle-dependent electronic structure, especially the emergent separation of flat bands at small twist angles. The localized states of flat bands are similar to well-arranged quantum dots, promising an application in devices. This study opens a new door to the exploration of deep energy modulations within moiré superlattices alternative to van der Waals twistronics.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Atomic Alignment in PbS Nanocrystal Superlattices with Compact Inorganic Ligands via Reversible Oriented Attachment of Nanocrystals
Nanocrystals (NCs) serve as versatile building blocks for the creation of functional materials with NC self-assembly offering opportunities to enable novel material properties. Here, in this work, we demonstrate that PbS NCs functionalized with strongly negatively charged metal chalcogenide complex (MCC) ligands, such as Sn 2 S 6 4– and AsS 4 3– , can self-assemble into all-inorganic superlattices with both long-range superlattice translational and atomic-lattice orientational order. Structural characterizations reveal that the NCs adopt an unexpected edge-to-edge alignment, and numerical simulation clarifies that orientational order is thermodynamically stabilized by many-body ion correlations originating from the dense electrolyte. Furthermore, we show that the superlattices of Sn 2 S 6 4– -functionalized PbS NCs can be fully disassembled back into the colloidal state, which is highly unusual for orientationally attached superlattices with atomic-lattice alignment. The reversible oriented attachment of NCs, enabling their dynamic assembly and disassembly into effectively single-crystalline superstructures, offers a pathway toward designing reconfigurable materials with adaptive and controllable electronic and optoelectronic properties.
Landau-Ginzburg theory↗
Size-Dependent Janus-Ligand Shell Formation on PbS Quantum Dots
We studied the size-dependent Janus ligand shell formation on PbS QDs employing an X-type ligand exchange reaction between native oleate ligands and two substituted cinnamic acid ligands, trifluoromethyl- and dimethyl amino-cinnamic acid, representing electron donating and electron withdrawing ligands. The exchange reactions become significantly more favorable for both electron donating and withdrawing ligands (..delta..G becomes more negative) in the smaller QDs compared to the larger QDs likely because the ligand density is smaller on the larger QDs reducing the strength of the ligand-ligand interactions. We found that Janus-ligand shells form more readily on smaller QDs than on bigger QDs with electron donating ligands. We also observed a dependence on the QD concentration that should be considered when forming Janus-ligand shells. Two-dimensional solution nuclear magnetic resonance spectroscopy (2D-NMR) shows evidence of pronounced phase segregation between oleate and electron donating ligands on the smaller QDs consistent with the enhanced ligand-ligand interactions. This study broadens our understanding of how to construct Janus and patchy ligand shell morphologies on small QDs.
14 SOLAR ENERGY↗
Materials Data on Rh3(PbS)2 by Materials Project
Rh3(PbS)2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Rh is bonded in a distorted linear geometry to four Pb and two equivalent S atoms. There are two shorter (2.89 Å) and two longer (2.91 Å) Rh–Pb bond lengths. Both Rh–S bond lengths are 2.34 Å. There are two inequivalent Pb sites. In the first Pb site, Pb is bonded to six equivalent Rh and two equivalent S atoms to form corner-sharing PbRh6S2 hexagonal bipyramids. Both Pb–S bond lengths are 3.08 Å. In the second Pb site, Pb is bonded in a hexagonal planar geometry to six equivalent Rh atoms. S is bonded in a 4-coordinate geometry to three equivalent Rh and one Pb atom.
36 MATERIALS SCIENCE↗