scholarly journals Cation Dynamics in Hybrid Halide Perovskites

2021 ◽  
Vol 51 (1) ◽  
Author(s):  
Eve M. Mozur ◽  
James R. Neilson
Keyword(s):  
Neutron Scattering ◽  
Degrees Of Freedom ◽  
Materials Science ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Annual Review ◽  
Publication Date ◽  
Elastic Neutron ◽  
Halide Perovskites ◽  
Spectroscopy Studies

Hybrid halide perovskite semiconductors exhibit complex, dynamical disorder while also harboring properties ideal for optoelectronic applications that include photovoltaics. However, these materials are structurally and compositionally distinct from traditional compound semiconductors composed of tetrahedrally coordinated elements with an average valence electron count of silicon. The additional dynamic degrees of freedom of hybrid halide perovskites underlie many of their potentially transformative physical properties. Neutron scattering and spectroscopy studies of the atomic dynamics of these materials have yielded significant insights into their functional properties. Specifically, inelastic neutron scattering has been used to elucidate the phonon band structure, and quasi-elastic neutron scattering has revealed the nature of the uncorrelated dynamics pertaining to molecular reorientations. Understanding the dynamics of these complex semiconductors has elucidated the temperature-dependent phase stability and origins of defect-tolerant electronic transport from the highly polarizable dielectric response. Furthermore, the dynamic degrees of freedom of the hybrid perovskites provide additional opportunities for application engineering and innovation. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is August 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Optical Force-Induced Chemistry at Solution Surfaces

2021 ◽  
Vol 72 (1) ◽  
Author(s):  
Hiroshi Masuhara ◽  
Ken-ichi Yuyama
Keyword(s):  
Materials Science ◽  
Continuous Wave ◽  
Optical Force ◽  
Annual Review ◽  
Publication Date ◽  
Fundamental Study ◽  
Periodic Arrays ◽  
Emission Enhancement ◽  
Promising Application ◽  
Halide Perovskites

When an intense 1,064-nm continuous-wave laser is tightly focused at solution surfaces, it exerts an optical force on molecules, polymers, and nanoparticles (NPs). Initially, molecules and NPs are gathered into a single assembly inside the focus, and the laser is scattered and propagated through the assembly. The expanded laser further traps them at the edge of the assembly, producing a single assembly much larger than the focus along the surface. Amino acids and inorganic ionic compounds undergo crystallization and crystal growth, polystyrene NPs form periodic arrays and disklike structures with concentric circles or hexagonal packing, and Au NPs demonstrate assembling and swarming, in which the NPs fluctuate like a group of bees. These phenomena that depend on laser polarization are called optically evolved assembling at solution surfaces, and their dynamics and mechanisms are elucidated in this review. As a promising application in materials science, the optical trapping assembly of lead halide perovskites, supramolecules, and aggregation-induced emission enhancement–active molecules is demonstrated and future directions for fundamental study are discussed. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 72 is April 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals Correlation of the dynamics of native human acetylcholinesterase and its inhibited huperzine A counterpart from sub-picoseconds to nanoseconds

2014 ◽  
Vol 11 (97) ◽  
pp. 20140372 ◽  
Author(s):  
M. Trapp ◽  
M. Tehei ◽  
M. Trovaslet ◽  
F. Nachon ◽  
N. Martinez ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Neutron Scattering ◽  
Molecular Dynamics Simulations ◽  
Inelastic Neutron Scattering ◽  
Thermal Fluctuations ◽  
Inelastic Neutron ◽  
Huperzine A ◽  
Relaxation Dynamics ◽  
Elastic Neutron ◽  
Dynamics Simulations

It is a long debated question whether catalytic activities of enzymes, which lie on the millisecond timescale, are possibly already reflected in variations in atomic thermal fluctuations on the pico- to nanosecond timescale. To shed light on this puzzle, the enzyme human acetylcholinesterase in its wild-type form and complexed with the inhibitor huperzine A were investigated by various neutron scattering techniques and molecular dynamics simulations. Previous results on elastic neutron scattering at various timescales and simulations suggest that dynamical processes are not affected on average by the presence of the ligand within the considered time ranges between 10 ps and 1 ns. In the work presented here, the focus was laid on quasi-elastic (QENS) and inelastic neutron scattering (INS). These techniques give access to different kinds of individual diffusive motions and to the density of states of collective motions at the sub-picoseconds timescale. Hence, they permit going beyond the first approach of looking at mean square displacements. For both samples, the autocorrelation function was well described by a stretched-exponential function indicating a linkage between the timescales of fast and slow functional relaxation dynamics. The findings of the QENS and INS investigation are discussed in relation to the results of our earlier elastic incoherent neutron scattering and molecular dynamics simulations.

Neutron Scattering in Structural Biology and Biomolecular Materials

MRS Bulletin ◽  
1999 ◽  
Vol 24 (12) ◽  
pp. 40-47 ◽  
Author(s):  
J. Kent Blasie ◽  
Peter Timmins
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Biological Systems ◽  
Inelastic Neutron ◽  
Hydrogen Atoms ◽  
Length Scales ◽  
Elastic Neutron ◽  
Neutron Sources ◽  
Structure And Dynamics ◽  
Scattering Technique

The substantial power of both elastic and inelastic neutron-scattering techniques for the investigation of the structure and dynamics of biological systems and related biomolecular-based materials—as with soft matter in the previous article by Lindner and Wignall—arises primarily from the essentially isomorphous nature of the substitution of deuterium for selected hydrogen atoms in these systems, coupled with the exquisite sensitivity of neutron scattering to this isotopic substitution. Since these systems are comprised of large macromolecules and supramolecular assemblies thereof, their essential structures and dynamics extend from the atomic scale up to very large length scales of the Order of 101–104 Å. Hence neutron sources and neutron-scattering spectrometers optimized for longer wavelength (or “cold”) thermal neutrons are necessary in order to most effectively address the structure and dynamics at the longer length scales inherent to these Systems.The large majority of previous neutron-scattering experiments on biological systems have been performed with reactor neutron sources. Some of the more significant of these are briefly summarized in the following sections. They may be categorized in terms of the nature of the intermolecular order, both orientational and positional, within the System of interest and either the elastic neutron-scattering technique employed to investigate their time-averaged structures or the inelastic neutron-scattering technique employed to investigate their dynamics.

scholarly journals Proton Dynamics in Palladium–Silver: An Inelastic Neutron Scattering Investigation

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5587
Author(s):  
Daniele Colognesi ◽  
Franz Demmel ◽  
Alessandra Filabozzi ◽  
Antonino Pietropaolo ◽  
Alfonso Pozio ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Jump Diffusion ◽  
Inelastic Neutron ◽  
Spectroscopic Techniques ◽  
Spallation Neutron Source ◽  
Complementary Information ◽  
Elastic Neutron ◽  
Proton Dynamics ◽  
Vibrational Density

Proton dynamics in Pd77Ag23 membranes is investigated by means of various neutron spectroscopic techniques, namely Quasi Elastic Neutron Scattering, Incoherent Inelastic Neutron Scattering, Neutron Transmission, and Deep Inelastic Neutron Scattering. Measurements carried out at the ISIS spallation neutron source using OSIRIS, MARI and VESUVIO spectrometers were performed at pressures of 1, 2, and 4 bar, and temperatures in the 330–673 K range. The energy interval spanned by the different instruments provides information on the proton dynamics in a time scale ranging from about 102 to 10−4 ps. The main finding is that the macroscopic diffusion process is determined by microscopic jump diffusion. In addition, the vibrational density of states of the H atoms in the metal lattice has been determined for a number of H concentrations and temperatures. These measurements follow a series of neutron diffraction experiments performed on the same sample and thus provide a complementary information for a thorough description of structural and dynamical properties of H-loaded Pd-Ag membranes.

Quasi-elastic neutron scattering (QENS) studies on the 1:1 tetramethylpyrazine–1,2,4,5-tetracyanobenzene complex

2009 ◽  
Vol 74 (1) ◽  
pp. 73-84 ◽  
Author(s):  
Jan Krawczyk ◽  
Małgorzata Nowina Konopka ◽  
Jerzy A. Janik ◽  
Olav Steinsvoll ◽  
Grażyna Bator ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Crystalline State ◽  
Inelastic Neutron Scattering ◽  
Blue Shift ◽  
Inelastic Neutron ◽  
Methyl Groups ◽  
Elastic Neutron ◽  
Stretching Vibration ◽  
Elastic Neutron Scattering ◽  
The Difference

The quasi-elastic neutron scattering (QENS) spectra over the temperature range 10–270 K were studied. The activation energies for the stochastic jumps of methyl groups in neat tetramethylpyrazine (TMP) and in the complex TMP·TCNB (tetracyanobenzene) were estimated to be equal to 5.0 ± 1.2 and 2.2 ± 1.1 kJ/mol, respectively, which means that the methyl groups behave in the complex more freely than in TMP. This conclusion is in good agreement with frequencies of the CH3 torsional modes recorded in the inelastic neutron scattering (INS) spectra. They are also confirmed by the DFT calculations for the crystalline state of TMP and TMP·TCNB, although the calculations overestimate the effect of the crystalline state on the CH3 torsional frequencies. The difference in the behavior of the methyl groups in neat TMP and TMP·TCNB is also reflected in the blue-shift of the ν(CH) stretching vibration modes.

Anomalous vibrational modes in acetanilide as studied by inelastic neutron scattering

1992 ◽  
Vol 2 (10) ◽  
pp. 1929-1939 ◽  
Author(s):  
Mariette Barthes ◽  
Juegen Eckert ◽  
Susanna W. Johnson ◽  
Jacques Moret ◽  
Basil I. Swanson ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Vibrational Modes
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