ORCID Profile
0000-0002-5055-5843
Current Organisation
Universidad Industrial de Santander
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Publisher: Wiley
Date: 06-11-2019
Abstract: Holey 2D metal oxides have shown great promise as functional materials for energy storage and catalysts. Despite impressive performance, their processing is challenged by the requirement of templates plus capping agents or high temperatures these materials also exhibit excessive thicknesses and low yields. The present work reports a metal-based coordination polymer (MCP) strategy to synthesize polycrystalline, holey, metal oxide (MO) nanosheets with thicknesses as low as two-unit cells. The process involves rapid exfoliation of bulk-layered, MCPs (Ce-, Ti-, Zr-based) into atomically thin MCPs at room temperature, followed by transformation into holey 2D MOs upon the removal of organic linkers in aqueous solution. Further, this work represents an extra step for decorating the holey nanosheets using precursors of transition metals to engineer their band alignments, establishing a route to optimize their photocatalysis. The work introduces a simple, high-yield, room-temperature, and template-free approach to synthesize ultrathin holey nanosheets with high-level functionalities.
Publisher: American Physical Society (APS)
Date: 09-08-2011
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/B918523B
Abstract: The far-red fluorescent protein HcRed was investigated using molecular dynamics (MD) and combined quantum mechanics/molecular mechanics (QM/MM) calculations. Three models of HcRed (anionic chromophore) were considered, differing in the protonation states of nearby Glu residues (A: Glu214 and Glu146 both protonated B: Glu214 protonated and Glu146 deprotonated C: Glu214 and Glu146 both deprotonated). SCC-DFTB/MM MD simulations of model B yield good agreement with the available crystallographic data at ambient pH. Bond lengths in the QM region are well reproduced, with a root mean square (rms) deviation between experimental and average MD data of 0.079 A the chromophore is almost co-planar, which is consistent with experimental observation and the five hydrogen bonds involving the chromophore are conserved. QM/MM geometry optimizations were performed on representative snapshot structures from the MD simulations for each model. They confirm the structural features observed in the MD simulations. According to the DFT(B3LYP)/MM results, the cis-conformation of the chromophore is more stable than the trans-form by 9.1-12.9 kcal mol(-1) in model B, and by 12.4-19.9 kcal mol(-1) in model C, consistent with the experimental preference for the cis-isomer. However, in model A when both Glu214 and Glu146 are protonated, the stability is inverted with the trans-form being favored. The different protonation states of the titratable active-site residues Glu214 and Glu146 thus critically influence the manner in which the relative stability and degree of planarity of the cis- and trans-conformers vary with pH. Coupled with the known correlation of chromophore conformation with fluorescence efficiency, this work provides a detailed structural basis for the observed phenomenon that red fluorescent proteins such as HcRed, mKate and Rtms5 show bright fluorescence at high pH.
Publisher: American Chemical Society (ACS)
Date: 05-01-2022
Abstract: Dedicated hierarchical structuring of functional ceramics can be used to shift the limits of functionality. This work presents the manufacturing of highly open porous, hierarchically structured barium titanate ceramics with 3-3 connectivity
Publisher: American Physical Society (APS)
Date: 20-04-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CP41217A
Abstract: To understand how the protein achieves fluorescence, the isomerization mechanism of the HcRed chromophore is studied both under vacuum and in the solvated red fluorescent protein. Quantum mechanical (QM) and quantum mechanical/molecular mechanical (QM/MM) methods are applied both for the ground and the first excited state. The photoinduced processes in the chromophore mainly involve torsions around the imidazolinone-bridge bond (τ) and the phenoxy-bridge bond (φ). Under vacuum, the isomerization of the cis-trans chromophore essentially proceeds by τ twisting, while the radiationless decay requires φ torsion. By contrast, the isomerization of the cis-trans chromophore in HcRed occurs via simultaneous τ and φ twisting. The protein environment significantly reduces the barrier of this hula twist motion compared with vacuum. The excited-state isomerization barrier via the φ rotation of the cis-coplanar conformer in HcRed is computed to be significantly higher than that of the trans-non-coplanar conformer. This is consistent with the experimental observation that the cis-coplanar-conformation of the chromophore is related to the fluorescent properties of HcRed, while the trans-non-planar conformation is weakly fluorescent or non-fluorescent. Our study shows how the protein modifies the isomerization mechanism, notably by interactions involving the nearby residue Ile197, which keeps the chromophore coplanar and blocks the twisting motion that leads to photoinduced radiationless decay.
Publisher: AIP Publishing
Date: 14-12-2015
DOI: 10.1063/1.4937470
Abstract: The microscopic contributions to the electric-field-induced macroscopic strain in a morphotropic 0.93(Bi1/2Na1/2TiO3)−0.07(BaTiO3) with a mixed rhombohedral and tetragonal structure have been quantified using full pattern Rietveld refinement of in situ high-energy x-ray diffraction data. The analysis methodology allows a quantification of all strain mechanisms for each phase in a morphotropic composition and is applicable to use in a wide variety of piezoelectric compositions. It is shown that during the poling of this material 24%, 44%, and 32% of the total macroscopic strain is generated from lattice strain, domain switching, and phase transformation strains, respectively. The results also suggest that the tetragonal phase contributes the most to extrinsic domain switching strain, whereas the lattice strain primarily stems from the rhombohedral phase. The analysis also suggests that almost 32% of the total strain is lost or is a one-time effect due to the irreversible nature of the electric-field-induced phase transformation in the current composition. This information is relevant to on-going compositional development strategies to harness the electric-field-induced phase transformation strain of (Bi1/2Na1/2)TiO3-based lead-free piezoelectric materials for actuator applications.
Publisher: Elsevier BV
Date: 02-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8TA09353A
Abstract: High energy density was achieved in lead-free La-doped AgNbO 3 antiferroelectric ceramics.
Publisher: AIP Publishing
Date: 07-12-2020
DOI: 10.1063/5.0029659
Abstract: The ferroelectric, ferroelastic, and dielectric properties as well as the crystal structure were investigated for polycrystalline donor doped lead zirconate titanate (PZT) with grain sizes ranging from 0.25 to 5 μm, which were prepared using a novel zirconium titanium hydrate precursor (ZTH) with a specific surface area of 310 m2/g. Piezoforce microscopy was used to investigate the change in the domain structure, revealing a change in the domain configuration from a complex 3D structure to a simple lamellar domain formation at a 1 μm grain size that corresponded to a rapidly increasing internal mechanical stress observed with in situ synchrotron x-ray experiments. The correlation between the change in domain configuration, increasing internal stresses, effects of poling on the crystal structure, and the macroscopic ferroelectric and ferroelastic properties are discussed in detail, allowing a deeper understanding of size effects in polycrystalline donor doped PZT ceramics.
Publisher: American Physical Society (APS)
Date: 15-05-2019
Publisher: International Union of Crystallography (IUCr)
Date: 20-04-2016
DOI: 10.1107/S1600577516005075
Abstract: When studying electro-mechanical materials, observing the structural changes during the actuation process is necessary for gaining a complete picture of the structure–property relationship as certain mechanisms may be meta-stable during actuation. In situ diffraction methods offer a powerful and direct means of quantifying the structural contributions to the macroscopic strain of these materials. Here, a s le cell is demonstrated capable of measuring the structural variations of electro-mechanical materials under applied electric potentials up to 10 kV. The cell is designed for use with X-ray scattering techniques in reflection geometry, while simultaneously collecting macroscopic strain data using a linear displacement sensor. The results show that the macroscopic strain measured using the cell can be directly correlated with the microscopic response of the material obtained from diffraction data. The capabilities of the cell have been successfully demonstrated at the Powder Diffraction beamline of the Australian Synchrotron and the potential implementation of this cell with laboratory X-ray diffraction instrumentation is also discussed.
Publisher: Springer Science and Business Media LLC
Date: 08-2018
DOI: 10.1557/MRS.2018.156
Publisher: AIP Publishing
Date: 21-02-2018
DOI: 10.1063/1.5017934
Abstract: Lanthanum strontium cobalt ferrite La1-xSrxCo1-yFeyO3-δ (LSCF) is one of the most studied mixed ionic-electronic conductor materials due to electrical and transport properties, which are attractive for intermediate temperature solid oxide fuel cells (SOFCs), oxygen permeation membranes, and catalysis. The integration of such materials, however, depends on the thermal as well as mechanical behavior. LSCF exhibits nonlinear hysteresis during compressive stress-strain measurements, marked by a remanent strain and coercive stress, i.e., ferroelasticity. However, the origin of ferroelastic behavior has not been investigated under high compressive stress. This study, therefore, investigates the microscopic origin of stress-induced mechanical behavior in polycrystalline (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ using in situ synchrotron x-ray diffraction. The data presented here reveals that the strain response originates from the intrinsic lattice strain as well as the extrinsic domain switching strain without any apparent change in crystallographic symmetry. A comparison of the calculated microscopic strain contribution with that of a macroscopic measurement indicates a significant change in the relative contributions of intrinsic and extrinsic strain depending on the applied stress state, i.e., under maximum stress and after unloading. Direct evidence of the microscopic origin of stress-strain response outlined in this paper may assist in guiding materials design with the improved mechanical reliability of SOFCs.
Publisher: Wiley
Date: 14-09-2018
DOI: 10.1111/JACE.16014
Publisher: Springer Science and Business Media LLC
Date: 07-2016
DOI: 10.1038/SREP28742
Abstract: Coupling of order parameters provides a means to tune functionality in advanced materials including multiferroics, superconductors and ionic conductors. We demonstrate that the response of a frustrated ferroelectric state leads to coupling between order parameters under electric field depending on grain orientation. The strain of grains oriented along a specific crystallographic direction, 〈h00〉, is caused by converse piezoelectricity originating from a ferrodistortive tetragonal phase. For 〈hhh〉 oriented grains, the strain results from converse piezoelectricity and rotostriction, as indicated by an antiferrodistortive instability that promotes octahedral tilting in a rhombohedral phase. Both strain mechanisms combined lead to a colossal local strain of (2.4 ± 0.1) % and indicate coupling between oxygen octahedral tilting and polarization, here termed “rotopolarization”. These findings were confirmed with electromechanical experiments, in situ neutron diffraction and in situ transmission electron microscopy in 0.75Bi 1/2 Na 1/2 TiO 3 -0.25SrTiO 3 . This work demonstrates that polar and non-polar instabilities can cooperate to provide colossal functional responses.
Publisher: AIP Publishing
Date: 20-10-2014
DOI: 10.1063/1.4898573
Abstract: An electric-field-induced paraelectric cubic to ferroelectric tetragonal phase transformation has been directly observed in prototypical polycrystalline BaTiO3 at temperatures above the Curie point (TC) using in situ high-energy synchrotron X-ray diffraction. The transformation persisted to a maximum temperature of 4 °C above TC. The nature of the observed field-induced transformation and the resulting development of domain texture within the induced phase were dependent on the proximity to the transition temperature, corresponding well to previous macroscopic measurements. The transition electric field increased with increasing temperature above TC, while the magnitude of the resultant tetragonal domain texture at the maximum electric field (4 kV mm−1) decreased at higher temperatures. These results provide insights into the phase transformation behavior of a prototypical ferroelectric and have important implications for the development of future large-strain phase-change actuator materials.
Publisher: AIP Publishing
Date: 09-11-2021
DOI: 10.1063/5.0070594
Abstract: Na1/2Bi1/2TiO3 (NBT) with varying Bi content has gained significant interest as a potential new material for solid-oxide fuel cells and oxygen separation membranes because of its excellent oxygen-ion conductivity. In this work, the effect of varying Bi content in NBT ceramics of compositions Na1/2BixTiO2.25+1.5x, where x = 0.485–0.510, on the temperature-dependent mechanical and dielectric properties and the crystal structure has been investigated, as these applications expose the components to high thermal and mechanical fields. The effects of Bi variation on phase compositions and structural transitions were systematically investigated by scanning electron microscopy-energy dispersive x-ray analyses and neutron diffraction at room temperature, in situ high-temperature x-ray diffraction, dielectric permittivity, and mechanical measurements. In-depth analysis of the temperature-dependent data shows that the Bi content of the s les does not alter the average crystal structure of the NBT however, the temperature-dependent behavior of the latter depend on variations in Bi content and the associated oxygen vacancy concentration. This change in phase transition temperature displays a good correlation with the temperature-dependent ferroelastic response and with the Bi content.
No related grants have been discovered for Manuel Hinterstein.