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Stimuli Responsive Electronic Reconfiguration in Benzo ghi perylene TCNQ Donor Acceptor Crystalline Networks
No full textTemplate assisted crystal engineering provides a powerful strategy for constructing ordered networks tailored to organic electronic applications. We introduce a solution based strategy to fabricate crystalline needle like arrays of charge transfer complexes CTCs between electron donating benzo ghi perylene BP and electron accepting TCNQ. Well defined square crystals of BP polymorphs were employed as templates for the spatially controlled anisotropic growth of CTC needle like arrays. By tuning concentration and deposition rates, we modulated BP crystal dimensions and hence controlled the growth of needle networks mimicking the template spatial scale. In solution, these free standing flexible meshes were detached from the BPs and redeposited onto variable substrates, while the BP templates remain undissolved, enabling repeated fabrication cycles. CTC formation induces an electronic redistribution with thermally reversible modulation of characteristic electronic states. Such transformation modifies the BP luminescence character while bare BP exhibits a strong green emission, it is quenched in the presence of TCNQ and replaced by a weaker blueish CTC emission, establishing a charge transfer mediated photonic response. Our study provides a combination of crystal engineering with microspectroscopic insights offering a highly sensitive handle for elucidating charge redistribution and modulation of electronic states in CTC upon external stimul
Interplay at PMMA Dielectric and C13 BTBT Semiconductor Interface
Full text linkA growing interest towards all organic electronics emphasized the importance of interfaces between the functional components of such devices. In particular, the interaction between the dielectric and semiconductor plays a critical role in device functionality, with strong dependency of charge carrier accumulation and mobility on semiconductor molecular arrangement. We report on the beneficial adsorption conformation with a nearly upright standing molecular orientation of a 2 tridecyl [1]benzothieno[3,2 b][1]benzothiophene C13 BTBT semiconductor monolayer deposited on Langmuir Blodgett prepared polymethyl methacrylate PMMA dielectric films. Such an alignment favors a smooth transfer of charge carriers due to the optimal orbital overlap between amp; 960; conjugated BTBT units. Atomistic insights into the C13 BTBT PMMA system through molecular dynamics revealed an advantageous direct contact of the charge transporting BTBT unit with PMMA, while the alkyl chain is pointing outwards. Compared to non alkylated BTBT, we demonstrate a 43 lower stiffness for surface exposed alkyl chains of a C13 BTBT monolayer, as determined by force distance analysis, highlighting the advantage for flexible device applications. These insights open new perspectives for further engineering of advanced interfaces, paving the way for innovations in efficient carbon based electronic
Fluctuating local polarization a generic fingerprint for enhanced piezoelectricity in Pb based and Pb free perovskite ferroelectrics
Full text linkUnderstanding the atomistic mechanism underlying high piezoelectricity has long been a central focus in research of functional ferroelectric materials. Despite decades of research across various perovskite piezoelectric systems, a clear consensus on the underlying mechanisms remains elusive. We propose a new concept?fluctuating local polarization?a critical factor that effectively correlates with piezoelectricity and could serve as a generic fingerprint for enhanced piezoelectricity. This is achieved by quantitatively capturing the local polarization characteristics of 16 compositions from classical piezoelectric systems. Our findings show that greater fluctuating local polarization, considering both the magnitude and the orientation disorder of local polar displacement vectors, yields improved piezoelectric performance. High fluctuating local polarization value, corresponds to a reduced local potential energy stiffness, thereby facilitating polarization variations and resulting in an amplified piezoelectric response. The concept can further explain the performance gap between Pb based and Pb free ferroelectrics arising from the distinct A site polar displacement characteristics. Overall, our concept offers an atomic level insight into the enhanced piezoelectricity of perovskites and provides a theoretical framework for designing high performance piezoelectric material
Spectroscopy of ionic iron compounds with astrochemical relevance
No full textIron is the most abundant transition metal in the interstellar medium ISM , and is thought to be involved in a variety of astrochemical processes. It has also attracted attention in astrochemical research, particularly because of its high abundance in the interstellar environment. Despite the abundance of iron, relatively few iron containing molecular species have been detected. To date, only FeO and FeCN have been conclusively identified in the ISM. Other iron bearing complexes, in particular FeH , have been predicted to exist in the cold interstellar environment. Due to the lack of laboratory spectroscopic data, it has not been identified yet. Spectroscopy is the cornerstone of astrochemical research, which provides spectroscopic characteristics on molecular level from laboratory. Two valuable spectroscopic methods are discussed in this dissertation, which is infrared multiple photon dissociation IRMPD spectroscopy and X ray absorption spectroscopy XAS on L edge. The former investigates the vibrational transition of molecules and low lying electronic states, the latter analyzes the electron transit from the 2p core shell to the 3d valence shell. Utilizing both methods contributes to a better understanding of the molecular properties of iron bearing molecules. In this dissertation, FeH , an elusive molecule with high astrochemical interest, is studied using Argon tagging IRMPD spectroscopy. The experiment analyzes Argon tagged FeH in the Fe H stretching fundamental and overtone region. Combined with high level quantum chemistry calculation, the Fe H fundamental stretching and its first overtone in bare FeH is expected in the 1790 1840 cm 1 and 3525 3619 cm 1 region, respectively. Comparing laboratory data to the Cygnus X 1 absorption spectrum, the XAS study implies that FeH cannot be ruled out as a component of the absorbing medium. Another iron bearing molecule, Fe H2 , whose neutral form FeH2 is also predicted to be synthesized on grains in the cold stellar environment, has been measured using IRMPD spectroscopy and analyzed to provide a semi quantitative pictur
Boon and Bane of Local Solid State Chemistry on the Performance of LSM Based Solid Oxide Electrolysis Cells
Full text linkHigh temperature solid oxide cells are highly efficient energy converters. However, their lifetime is limited by rapid deactivation. Little is known about the local, atomic scale transformation that drive this degradation. Here, reaction induced changes are unraveled at the atomic scale of a solid oxide electrolysis cell SOEC operated for 550 h by combining high resolution scanning transmission electron microscopy with first principles and force field based atomistic simulations. We focus on the structural evolution of lanthanum strontium manganite LSM yttria stabilized zirconia YSZ regions and the corresponding solid solid interface. It is found that the strong inter diffusion of cations leads to the additional formation and growth of a multitude of localized structures such as a solid solution of La Mn, nano domains of secondary structures or antisite defects in the YSZ, as well as a mixed ion and electron conduction region in the LSM and complexion. These local structures can be likewise beneficial or detrimental to the performance, by either increasing the catalytically active area or by limiting the supply of reactants. The work provides unprecedented atomistic insights into the influence of local solid state chemistry on the functioning of SOECs and deepens the understanding of the degradation mechanism in SOECs, paving the way towards nanoscopic rational interface design for more efficient and durable cell
Beyond material recovery Exergy and environmental analysis of silicon solar panel recycling
Full text linkThe recycling of silicon solar panels is vital to ensure critical material recovery and to sustain the manufacturing of new panels in line with the United Nations Sustainable Development Goals. While various recycling methods based on thermal, chemical, or mechanical separation of the solar panel layers have been studied, a comprehensive thermodynamic and environmental analysis is required to allow holistic comparison within the circular economy framework. Here, such an analysis is performed for four different silicon solar panel recycling processes. First, the processes were simulated in HSC chemistryTM to analyse the flows of exergy. Subsequently, a Life Cycle Assessment LCA was conducted to understand the environmental benefits and drawbacks of each method. Combined Exergy LCA analysis showed that a slightly less exergy efficient process, namely pyrolysis can ultimately has the lowest environmental impact out of the four processes. In contrast chemical treatment of the encapsulant exhibited comparably worse performance due to its increased resource consumption. On the material level, high value material recovery, if realized, could be thermodynamically and environmentally advantageous. The recovery methods presented here could be further improved if heat integration or the use of natural solvents would be considered. These unique findings demonstrate that weighing exerg
Corrigendum In situ synchrotron x ray photoelectron spectroscopy study of medium temperature baking of niobium for SRF
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Lattice Driven Gating in a Cu Based Zeolitic Imidazolate Framework for Efficient High Temperature Hydrogen Isotope Separation
Full text linkFor the separation of hydrogen isotopes H2 D2 , traditional kinetic quantum sieving KQS takes advantage of the diffusion barriers created by the flexibility of organic linkers and the breathing frameworks in porous solids. While the phenomena have been observed typically below 77 K, in this study, we present that a copper based zeolite imidazolate framework Cu ZIF gis can show KQS above 120 K. Since Cu ZIF gis has narrow channels with ca. 2.4 in aperture, the small pore size itself acts as a diffusion barrier. This barrier changes with temperatures, leading to pore contraction or expansion through lattice driven gating LDG . The H2 adsorption isotherms measured at 40 150 K reflect the temperature sensitivity of the pore properties. Quasi elastic neutron scattering QENS experiments indicate a notable difference in the molecular mobility of H2 and D2, even at temperatures exceeding 150 K. Temperature variation powder X ray diffraction measurements at 20 300 K show a small but gradual increase in the unit cell volume, indicating that LDG gives rise to the KQS at temperatures above 120 K. These findings can be applied to develop sustainable isotope separation technologies using existing LNG cryogenic infrastructur
Reassessing anionic redox in conventional layered oxide cathodes for Li ion batteries ionic and covalent mechanisms
No full textEfforts to improve the specific capacity and energy density of lithium nickel cobalt manganese oxide NCM cathodes focus on operating at high voltages or increasing nickel content. However, both approaches necessitate a thorough understanding of the charge compensation mechanism. Traditional ionic bonding models which separate transition metal TM and oxygen redox processes prove inadequate as anionic redox becomes significant, ignoring crucial metal oxygen interactions. In this study, we systematically investigate the charge compensation process in low nickel and high nickel NCMs under high voltage conditions. Here, the involvement of oxygen is critical in redox, as it shares electrons with TM to form a strong TM O covalent bond. Compared to low Ni NCMs, high Ni NCMs exhibit an oxygen dimerization stage with trapped O2, which leads to the aggregation of vacancies in the transition metal layer, thereby accelerating structural destabilization. This variation in oxygen dimerization behavior among NCMs is closely correlated with differences in elemental composition, spin states, and stacking faults. Our findings comprehensively reveal the redox behaviors of transition metals and oxygen, particularly highlighting oxygen behavior at each delithiation state, helping to optimize the utilization of oxygen redox reactions in commercial NCM compounds for high capacity and high energy density lithium ion batterie
Carbon Thin Film Electrodes as High Performing Substrates for Correlative Single Entity Electrochemistry
Full text linkCorrelative methods to characterize single entities by electrochemistry and microscopy spectroscopy are increasingly needed to elucidate structure function relationships of nanomaterials. However, the technical constraints often differ depending on the characterization techniques to be applied in combination. One of the cornerstones of correlative single entity electrochemistry SEE is the substrate, which needs to achieve a high conductivity, low roughness, and electrochemical inertness. This work shows that graphitized sputtered carbon thin films constitute excellent electrodes for SEE while enabling characterization with scanning probe, optical, electron, and X ray microscopies. Three different correlative SEE experiments using nanoparticles, nanocubes, and 2D Ti3C2Tx MXene materials are reported to illustrate the potential of using carbon thin film substrates for SEE characterization. The advantages and unique capabilities of SEE correlative strategies are further demonstrated by showing that electrochemically oxidized Ti3C2Tx MXene display changes in chemical bonding and electrolyte ion distributio