Browse
Submit Data
Databases
API
Help

Dataset Information

13 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Dynamic deformability of individual PbSe nanocrystals during superlattice phase transitions.

ABSTRACT: The behavior of individual nanocrystals during superlattice phase transitions can profoundly affect the structural perfection and electronic properties of the resulting superlattices. However, details of nanocrystal morphological changes during superlattice phase transitions are largely unknown due to the lack of direct observation. Here, we report the dynamic deformability of PbSe semiconductor nanocrystals during superlattice phase transitions that are driven by ligand displacement. Real-time high-resolution imaging with liquid-phase transmission electron microscopy reveals that following ligand removal, the individual PbSe nanocrystals experience drastic directional shape deformation when the spacing between nanocrystals reaches 2 to 4 nm. The deformation can be completely recovered when two nanocrystals move apart or it can be retained when they attach. The large deformation, which is responsible for the structural defects in the epitaxially fused nanocrystal superlattice, may arise from internanocrystal dipole-dipole interactions.

SUBMITTER: Wang Y

PROVIDER: S-EPMC6555630 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Melting and Sintering of a Body-Centered Cubic Superlattice of PbSe Nanocrystals Followed by Small Angle X-ray Scattering.

Project description:The structural evolution of a body-centered cubic (bcc) superlattice of 6.6 nm diameter organic ligand-coated PbSe nanocrystals was studied in situ by small angle X-ray scattering (SAXS) as it was heated in air from room temperature to 350°C. As it was heated above room temperature, the superlattice contracted slightly, but maintained bcc structure up to 110°C. Once the temperature rose above 110°C, the superlattice began to disorder, by first losing long-range translational order and then local positional order. At temperatures exceeding 168°C, the nanocrystals sintered and oxidized, transforming into PbSeO(3) nanorods.

| S-EPMC3090084 | biostudies-literature

Ligand-Induced Shape Transformation of PbSe Nanocrystals.

Project description:We present a study of the relation between the surface chemistry and nanocrystal shape of PbSe nanocrystals with a variable Pb-to-Se stoichiometry and density of oleate ligands. The oleate ligand density and binding configuration are monitored by nuclear magnetic resonance and Fourier transform infrared absorbance spectroscopy, allowing us to quantify the number of surface-attached ligands per NC and the nature of the surface-Pb-oleate configuration. The three-dimensional shape of the PbSe nanocrystals is obtained from high-angle annular dark field scanning transmission electron microscopy combined with an atom counting method. We show that the enhanced oleate capping results in a stabilization and extension of the {111} facets, and a crystal shape transformation from a truncated nanocube to a truncated octahedron.

| S-EPMC5425942 | biostudies-literature

Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals.

Project description:Nanostructured lithium metal orthosilicate materials hold a lot of promise as next generation cathodes but their full potential realization is hampered by complex crystal and electrochemical behavior. In this work Li2FeSiO4 crystals are synthesized using organic-assisted precipitation method. By varying the annealing temperature different structures are obtained, namely the monoclinic phase at 400°C, the orthorhombic phase at 900°C, and a mixed phase at 700°C. The three Li2FeSiO4 crystal phases exhibit totally different charge/discharge profiles upon delithiation/lithiation. Thus the 400°C monoclinic nanocrystals exhibit initially one Li extraction via typical solid solution reaction, while the 900°C orthorhombic crystals are characterized by unacceptably high cell polarization. In the meantime the mixed phase Li2FeSiO4 crystals reveal a mixed cycling profile. We have found that the monoclinic nanocrystals undergo phase transition to orthorhombic structure resulting in significant progressive deterioration of the material's Li storage capability. By contrast, we discovered when the monoclinic nanocrystals are cycled initially at higher rate (C/20) and subsequently subjected to low rate (C/50) cycling the material's intercalation performance is stabilized. The discovered rate-dependent electrochemically-induced phase transition and stabilization of lithium metal silicate structure provides a novel and potentially rewarding avenue towards the development of high capacity Li-ion cathodes.

| S-EPMC4341213 | biostudies-literature

Photoinduced, reversible phase transitions in all-inorganic perovskite nanocrystals.

Project description:Significant interest exists in lead trihalides that present the perovskite structure owing to their demonstrated potential in photovoltaic, lasing, and display applications. These materials are also notable for their unusual phase behavior often displaying easily accessible phase transitions. In this work, time-resolved X-ray diffraction, performed on perovskite cesium lead bromide nanocrystals, maps the lattice response to controlled excitation fluence. These nanocrystals undergo a reversible, photoinduced orthorhombic-to-cubic phase transition which is discernible at fluences greater than 0.34 mJ cm-2 through the loss of orthorhombic features and shifting of high-symmetry peaks. This transition recovers on the timescale of 510 ± 100 ps. A reversible crystalline-to-amorphous transition, observable through loss of Bragg diffraction intensity, occurs at higher fluences (greater than 2.5 mJ cm-2). These results demonstrate that light-driven phase transitions occur in perovskite materials, which will impact optoelectronic applications and enable the manipulation of non-equilibrium phase characteristics of the broad perovskite material class.

| S-EPMC6353988 | biostudies-literature

Energy landscape of self-assembled superlattices of PbSe nanocrystals.

Project description:Self-assembly of nanocrystals (NCs) into superlattices is an intriguing multiscale phenomenon that may lead to materials with novel collective properties, in addition to the unique properties of individual NCs compared with their bulk counterparts. By using different dispersion solvents, we synthesized three types of PbSe NC superlattices--body-centered cubic (bcc), body-centered tetragonal (bct), and face-centered cubic (fcc)--as confirmed by synchrotron small-angle X-ray scattering. Solution calorimetric measurements in hexane show that the enthalpy of formation of the superlattice from dispersed NCs is on the order of -2 kJ/mol. The calorimetric measurements reveal that the bcc superlattice is the energetically most stable polymorph, with the bct being 0.32 and the fcc 0.55 kJ/mol higher in enthalpy. This stability sequence is consistent with the decreased packing efficiency of PbSe NCs from bcc (17.2%) to bct (16.0%) and to fcc (15.2%). The small enthalpy differences among the three polymorphs confirm a closely spaced energy landscape and explain the ease of formation of different NC superlattices at slightly different synthesis conditions.

| S-EPMC4078835 | biostudies-other

Revealing extreme twin-boundary shear deformability in metallic nanocrystals.

Project description:[Figure: see text].

| S-EPMC8442924 | biostudies-literature

Dynamic phase transitions in freestanding polymer thin films.

Project description:After more than two decades of study, many fundamental questions remain unanswered about the dynamics of glass-forming materials confined to thin films. Experiments and simulations indicate that free interfaces enhance dynamics over length scales larger than molecular sizes, and this effect strengthens at lower temperatures. The nature of the influence of interfaces, however, remains a point of significant debate. In this work, we explore the properties of the nonequilibrium phase transition in dynamics that occurs in trajectory space between high- and low-mobility basins in a set of model polymer freestanding films. In thick films, the film-averaged mobility transition is broader than the bulk mobility transition, while in thin films it is a variant of the bulk result shifted toward a higher bias. Plotting this transition's local coexistence points against the distance from the films' surface shows thick films have surface and film-center transitions, while thin films practically have a single transition throughout the film. These observations are reminiscent of thermodynamic capillary condensation of a vapor-liquid phase between parallel plates, suggesting they constitute a demonstration of such an effect in a trajectory phase transition in the dynamics of a structural glass former. Moreover, this transition bears similarities to several experiments exhibiting anomalous behavior in the glass transition upon reducing film thickness below a material-dependent onset, including the broadening of the glass transition and the homogenization of surface and bulk glass transition temperatures.

| S-EPMC7568329 | biostudies-literature

Hybrid Oleate-Iodide Ligand Shell for Air-Stable PbSe Nanocrystals and Superstructures.

Project description:A postsynthetic treatment is presented to improve the air stability of PbSe nanocrystals (NCs) and PbSe square superstructures. The addition of z-type Pb(oleate)2 ligands together with x-type iodide ligands creates a hybrid ligand shell containing both ligands. The air stability of the PbSe NCs is checked by enduring absorption spectroscopy under ambient conditions. With a combined NaI + Pb(oleate)2 treatment, the absorption spectrum remains unchanged for several days under ambient conditions. Fourier transform infrared spectroscopy shows that the surface coordination of the oleate ligands changes by the chemical treatment: from mixed chelating bidentate + bridging to Pb for the pristine nanocrystals to almost exclusive chelating bidentate coordination after chemical passivation. The shift of the C-H stretching vibration shows that the oleate hydrocarbon layer is in a more liquidlike state after the chemical treatment, suggesting that oleate and iodide ligands are often present on adjacent surface positions.

| S-EPMC6694723 | biostudies-literature

Efficient Steplike Carrier Multiplication in Percolative Networks of Epitaxially Connected PbSe Nanocrystals.

Project description:Carrier multiplication (CM) is a process in which a single photon excites two or more electrons. CM is of interest to enhance the efficiency of a solar cell. Until now, CM in thin films and solar cells of semiconductor nanocrystals (NCs) has been found at photon energies well above the minimum required energy of twice the band gap. The high threshold of CM strongly limits the benefits for solar cell applications. We show that CM is more efficient in a percolative network of directly connected PbSe NCs. The CM threshold is at twice the band gap and increases in a steplike fashion with photon energy. A lower CM efficiency is found for a solid of weaker coupled NCs. This demonstrates that the coupling between NCs strongly affects the CM efficiency. According to device simulations, the measured CM efficiency would significantly enhance the power conversion efficiency of a solar cell.

| S-EPMC6150730 | biostudies-literature

Hybrid Growth Modes of PbSe Nanocrystals with Oriented Attachment and Grain Boundary Migration.

Project description:The growth of nanocrystals has widely been researched recently through an in situ high-resolution transmission electron microscopy technique, which reveals the process of morphological and structural evolutions. For nanocrystals, the underlying growth modes are mostly determined by growth environment and crystal morphology. Here, the direct growth process of the PbSe nanocrystals via controlling the temperature is clearly observed. The results show that the PbSe nanocrystals start growth following oriented attachment growth mode, and then change to growth with grain boundary migration at moderate temperature as the heat activated nanocrystals gather together with decreased degree of freedom for crystal rotation. During the grain boundary migration, the smaller nanocrystals are inclined to be assimilated by larger ones through interfacial atom reconfigurations, which are observed to take place through strain mediated atom migration. The growth mode changes in different growth states with a hybrid growth mode of oriented attachment and grain boundary migration during the whole growth process.

| S-EPMC6498134 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data