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Chloride Double Perovskites Doped With Sb3 Er3 as Stable and Effective Luminescence Material in the Vis NIR Region
Get PDFThe luminescence properties of stable chloride double perovskites Cs2BIInCl6, where BI is 4 at. Ag, 6 at. Na, doped with Sb3 and Er3 were investigated for the first time in the 250 1600 nm region and revealed significant potential for advanced application. We employed XPS and ToF SIMS for chemical analyses, while SEM, XRD, and Raman spectroscopy provided insights into the morphology, crystal structure, and vibrational characteristics of the samples. The crystal structures of Cs2Ag0.292Na0.708InCl6, Cs2Ag0.285Na0.715In0.971Er0.029Cl6, Cs2Ag0.16Na0.84In0.893Er0.017Sb0.09Cl6 were examined using singlecrystal methods. The excited Sb3 ions emitted blue light at 450 nm due to electronic absorption at sub band gap levels, facilitating energy transfer to Er3 ions. Notably, the Er3 emitted radiation at 1540 nm, a wavelength particularly useful for optical communication applications. Additionally, emissions at 525 nm, 552 nm, 665 nm, and 805 nm were observed, corresponding to f f transitions of Er3 ions. These compelling results were supported with calculations based on the Modified Crystal Field Theory, explaining the effects of varying concentrations of Sb3 and Er3 on the crystal structure and luminescent properties. By using the synthesized materials, we successfully developed an LED prototype that utilized a UV chip 320 nm combined with the Cs2Ag0.4Na0.6In0.9Er0.01Sb0.09Cl6 powder as a stable and effective luminophore for possible application in optoelectronic
Neutralization of Multiply Charged Ground State Ions by Collective Electron Transfer from an Environment
Get PDFHighly charged cations are omnipresent species after the interaction of high energy or high intensity light with matter. When embedded in environments, the mechanism and outcome of the redistribution of the cation s charge are crucial for the further fate of the whole system. Generally, ground state cations can decay by charge transfer, proceeding radiatively, through nuclear dynamics, or by electron transfer mediated decay ETMD . ETMD causes electron emission from a remote neighbor and appears ubiquitous in loosely bound systems. It remained unclear how multiply charged ions decay if conventional ETMD channels are closed. Here, we show that a yet undiscovered variant of ETMD is possible, where multiple electrons are collectively transferred. Explicitly, we observe ETMD in which two electrons from two distinct neighbors partially neutralize a multiply charged ion, and an electron from a fourth site is emitted. According to the established nomenclature, we suggest naming the process ETMD
Morphology Engineering in Cobalt Free Li Rich Oxides for High Capacity and Strain Tolerant Cathodes
No full textMorphology engineering plays a critical role in enhancing ionic diffusion kinetics and activating oxygen redox activity in cobalt free lithium rich layered oxides LROs , addressing their intrinsic limitations for high energy density batteries. Herein, a morphology engineering strategy is proposed to synthesize cobalt free LRO cathodes with radially arranged primary grains LRO RA and short rod like grains LRO SR . The radial architecture of LRO RA establishes fast Li diffusion pathways, as evidenced by its near identical Li diffusion coefficient to LRO SR despite dominating oxygen redox contributions. This accelerated ion transport facilitates reversible anionic redox, yielding a 79 mAh g amp; 8722;1 higher initial discharge capacity 0.1C and a 50.6 mV lower O oxidation potential compared to LRO SR. Advanced spectroscopic and diffraction analyses confirm that the radial morphology stabilizes anionic redox, minimizes MnO6 distortion, and mitigates strain accumulation. Consequently, LRO RA achieves a 94.8 capacity retention after 400 cycles 1C , far exceeding LRO SR 75.6 , with mitigated voltage decay. Post cycling analysis confirms that the dense radial grains resist electrolyte infiltration and phase transformation, preserving structural integrity. This work elucidates how morphology driven ion transport optimization amplifies oxygen redox reversibility, offering a universal design principle for high capacity Li rich cathode
Overcoming Thickness Limitations of Polymer Dielectrics with Langmuir Blodgett Prepared PMMA Films
No full textSolution processing of high structural quality organic thin films offers access to the production of sustainable, flexible, and low cost carbon based electronic devices. We report on the preparation of well defined poly methyl methacrylate PMMA dielectric films by means of the Langmuir Blodgett LB method in the mono and multilayer regimes. The sequential multilayer fabrication in separate LB compressions involves a reimmersion of the produced layers into the water subphase. This results in a modification of the PMMA film morphology due to water absorption. With the benefit of real time control via compression isotherms, fabrication of defined multilayer films in a single step by high degree compression allows avoidance of a forced presence of the polymer inside water. Unlike previously proposed polymer dielectrics that exceed 100 600 nm in thickness to compensate for potential morphological defects, we demonstrate that LB prepared PMMA films of only about 35 nm thickness serve as insulating layers in organic field effect transistors. Fabricated C13 BTBT based devices demonstrate a high charge carrier mobility and low voltage operation due to negligible electrical shorts within the insulating PMMA fil
Tuning Reactivity in Cu TEMPO Catalyzed Alcohol Oxidation Reactions
No full textA dinuclear copper I complex Cu2L22 L2 3,3 dimethyl 1 1 methyl 1H benzo[d]imidazole 2 yl N propan 2 ylidene butan 2 amine containing benzimidazole and imino donors was previously reported by some of us as an efficient catalyst for the aerobic oxidation of alcohols to aldehydes in presence of TEMPO 2,2,6,6 tetramethylpiperidinyloxyl and an external base NMI N methyl imidazole . Cu III 2 bis amp; 956; oxo and Cu II 2 bis amp; 956; hydroxo cores were trapped as viable intermediates in the reaction, which provided deeper mechanistic insights. Here, we report two new ligand systems L3 N isopropyl 3,3 dimethyl 1 1 methyl 1H benzol[d]imidazole 2 yl butane 2 amine and L4 Z 2,4 di tert butyl 6 3,3 dimethyl 1 1 methyl 1H benzol[d]imidazole 2 yl butane 2 yl imino methyl phenol , which are designed to perturb the overall electronics of the complexes and the resulting effects on their O2 activation mechanisms. The stronger donation of the secondary amine group stabilizes a mononuclear CuIL3 core, which nevertheless follows a dinuclear O2 activation mechanism as in Cu2L22. Notably, the CuIL3 TEMPO catalyst system performs the aerobic oxidation of alcohols to aldehydes with good yields and turnover numbers, even in the absence of NMI. The dinuclear CuI2L42 complex involving a non innocent phenolate group, in contrast, exhibits depleted catalytic activity, because of the instability of the Cu III 2 bis amp; 956; oxo core against intramolecular H atom abstraction to form an alkoxo bridged dicopper II comple
Strongly Entangled Kondo and Kagome Lattices and the Emergent Magnetic Ground State in Heavy Fermion Kagome Metal YbV6Sn6
No full textApplying angle resolved photoemission spectroscopy and density functional theory calculations, we present compelling spectroscopic evidence demonstrating the intertwining and mutual interaction between the Kondo and kagome sublattices in heavy fermion intermetallic compound YbV6 amp; 8290;Sn6 . We reveal the Yb 4 amp; 8290; amp; 119891; derived states near the Fermi level, along with the presence of bulk kagome bands and topological surface states. We unveil strong interactions between the 4 amp; 8290; amp; 119891; and itinerant electrons, where the kagome bands hosting the Dirac fermions and van Hove singularities predominate. Such findings are well described using a amp; 119888; amp; 8722; amp; 119891; hybridization model. On the other hand, our systematic characterization of magnetic properties demonstrates an unusually enhanced antiferromagnetic ordering, where the kagome derived van Hove singularities near amp; 119864; amp; 119865; play a vital role in determining the unconventional nature of the Ruderman Kittel Kasuya Yosida interaction and Kondo coupling. These unique kagome state mediated exchange interactions have never been reported before and could lead to a novel phase diagram and various quantum critical behaviors in YbV6 amp; 8290;Sn6 and its siblings. Our results not only expand the family of exotic quantum phases entangled with kagome structure to the strongly correlated regime, but also establish YbV6 amp; 8290;Sn6 as an unprecedented platform to explore unconventional many body physics beyond the standard Kondo pictur
Generation and Nitric Oxide Reactivity of a Cobalt II Superoxide Complex via Ligand Based Redox Non Innocence
Get PDFA novel guanidine based NNN pincer cobalt II complex, Co1, was investigated for dioxygen O2 activation. Upon reaction with O2 at room temperature, a amp; 956; hydroxo bridged CoII OH CoII complex Co2 was isolated as the final oxygenated product. In depth spectroscopic investigation revealed that the formation of Co2 occurs via an intermediate superoxide species Co1 O2 , by taking advantage of the redox non innocence behavior of the ligand 3,3 amp; 8242; pyridine 2,6 diyl bis 1 methyl N phenylimidazolidin 2 imine , and therefore keeping the cobalt oxidation state unchanged at 2. Interestingly, the zinc analogue, Zn1, was also shown to yield a similar amp; 956; hydroxo bridged ZnII OH ZnII complex Zn2 as the final product under the same aerobic conditions, providing further confirmation of the ligand influence on metal oxidation and spin states during O2 activation. Further reactivity studies demonstrated that Co1 O2 reacts with nitric oxide NO to form a CoII peroxynitrite Co1 ONO2 intermediate, which performs an unprecedented intramolecular nitration of the phenyl moieties of the ligand at the para positio
An Oxoiron IV Complex Supported by an N alkylated Cyclam Ligand System Containing a Pendant Alcohol Moiety
Get PDFThe effect of a pendant neutral alcohol moiety in the N alkylated cyclam 1,4,8,11 tetraazacyclotetradecane ligand backbone is examined for the non heme mononuclear oxoiron IV unit in [FeIV Osyn TMC HOR NCCH3 ]2 1 syn TMC HOR 2 4,8,11 trimethyl 1,4,8,11 tetraazacyclotetradecan1 yl ethan 1 ol . Unlike in the related [FeIV Oanti TMC SR ] 3 anti TMC SR 1 mercaptoethyl 4,8,11 trimethyl 1,4,8,11 tetraazacyclotetradecane complex, bearing an axial mono anionic thiolate ligand trans to the oxo unit, the alcohol moiety in 1 syn stays protonated and does not axially coordinate to iron. The protonation of the alcohol moiety is a prerequisite for the stabilization of the oxoiron IV core; it presumably serves as a hydrogen bonding donor to the oxoiron IV unit, which is positioned syn to the three methyl groups. Comparative reactivity studies reveal 1 syn to be a stronger hydrogen atom abstraction but weaker oxygen atom transfer agent relative to the [FeIV Osyn TMC NCCH3 ]2 2 syn complex, bearing the N tetramethylated cyclam TMC ligan
The relationship between Sm alloying and structure sensitivity of ceria 111 and 100 oriented nanoislands on Cu 111
No full textWe have investigated the complex dynamics of samarium deposition on ceria islands of different orientations, namely 111 and 100 , grown side by side on a Cu 111 single crystal substrate, followed by post oxidation and annealing under ultra high vacuum conditions. Only the 100 oriented ceria islands undergo substantial initial reduction upon samarium deposition at 740 K via a pathway similar to the strong Ce ceria interfacial interaction, while the 111 oriented islands remain in the Ce4 oxidation state. This remarkable structure sensitivity is explained by the different energies required for oxygen vacancy formation for both oxide orientations. Subsequent mild re oxidation with O2 results in the complete recovery of the Ce4 oxidation state in the 100 oriented islands, indicating the complete healing of oxygen vacancies. In contrast, extended annealing at moderate temperatures likely induces persistent samarium incorporation into the cerium oxide matrix. Our results provide new insights into the complex structure activity relationships in mixed rare earth metal oxide systems and have promising implications for optimizing catalytic reactions over such compounds in reducing environment
Statistical analysis of grains and pores within polycrystalline Al2TiO5 ceramics, based on X ray computed tomography
Get PDFAdvanced statistical image analysis workflows were developed to segment and quantitatively evaluate 2D electron backscatter diffraction EBSD maps and 3D synchrotron X ray computed tomography SXCT volumes of a polycrystalline AlTiO refractory composite that contains microcracks and pores. Several size, shape, and further geometric descriptors were determined for both the solid phase AlOTi grains and the pore space. The resulting pore size distribution is distinctly bimodal coarse pores tens to hundreds of micrometers , traced to incomplete powder compaction, coexist with fine pores generated during sintering. The two pore populations appear to be correlated with grain growth and crystallographic orientation in different ways. Finally, the descriptors obtained from the 2D EBSD and 3D SXCT data sets are internally consistent but complementary, highlighting the value of characterizations based on EBSD and SXCT in the microstructural study of refractory ceramic