Double Substitution Research Articles

Design of Anti-Hund Organic Emitters Based on Heptazine.

Hund's rule, which is powerful in governing the first excited states of closed-shell organic materials, can hardly be violated to get inverted singlet-triplet gap (INVEST) molecules with negative singlet-triplet energy gaps (ΔEST), although INVEST materials have shown extraordinary photophysical properties and promising device performance especially in light-emitting diodes. Here, we propose a facile strategy to construct emissive INVEST molecules by introducing different types of substituents to heptazine in various modes, which can effectively tune the ΔEST to be negative with the enlarged oscillator strength (f) for the high fluorescence rate of the heptazine derivatives. Systematic computational studies show that the double substitution of electron-donating units with another nonconjugated substituent in hybrid substitution mode is the most favorable way in achieving slightly negative ΔEST and large f values; the conjugated substituent will compete with heptazine to make the molecule deviate from the INVEST feature. Especially, a series of high-performance heptazine-based INVEST emitters were constructed, exhibiting ΔEST low to -0.362 eV, f up to 0.0436, as well as a wide range emission color from 339 to 716 nm. Also, the designed molecules were predicted to have fluorescence radiative rates up to 106 s-1, along with efficient reverse intersystem crossing rates reaching 108 s-1. Importantly, the figure of merit (FM) was first proposed as a parameter to wholly evaluate the performance of INVEST emitters, and the highest FM of 0.198 was found in the triazine and double nonconjugated amine-substituted heptazine. These results highlight the great potential of the heptazine chromophore in constructing INVEST emitters, revealing fundamental structure-property understandings for the material design of efficient anti-Hund organic molecules with improved emission properties.

A spin-flip study of the diradical isomers of pyrrole, furan, and thiophene.

Heteroaromatic species are commonly found in complex gaseous mixtures, from tobacco smoke to petroleum and asphaltene combustion products. At high temperatures, C-H bond rupture produces various dehydro radical isomers. We have used the spin-flip formulation of equation-of-motion coupled cluster theory with single and double substitutions (EOM-SF-CCSD) to characterize the energies and wave functions of the lowest lying singlet and triplet states of the diradical (2,3), (2,4), (2,5), and (3,4) di-dehydro isomers of pyrrole, furan, and thiophene. In all cases, these diradicals are minima on the broken-symmetry ωB97X-D/cc-pVDZ potential energy surface. In most cases, the diradical geometries distort to enhance through-space or through-bond coupling in the singlet states and to avoid Coulombic or exchange repulsion in the triplet states. EOM-SF-CCSD results indicate that all diradical isomers are two-configurational, closed shell singlet states. The only exceptions to this are for (2,3) and (2,4) thiophene and (2,3) pyrrole, which each contain more than two configurations. In all cases, the leading term in the multiconfigurational diradical wave function doubly occupies the symmetric radical σ orbital, indicative of either through-space or 1,3 through-bond coupling. We utilized the nucleus-independent chemical shift (NICS) approach to qualitatively assess aromaticity and find that this property varies and may be related to the energetic splittings in these diradical isomers.

Clinical Interest in Exome-Based Analysis of Somatic Mutational Signatures for Non-Small Cell Lung Cancer.

Non-small cell lung cancer (NSCLC) remains the leading cause of cancer-related mortality. This study investigates the clinical interest of whole exome sequencing (WES) for analyzing somatic mutational signatures in patients with advanced or metastatic NSCLC treated with the current standard of care. Exome sequencing data and clinical characteristics from 132 patients with advanced or metastatic NSCLC were analyzed. Somatic mutational signatures including single base substitutions (SBSs), double base substitutions (DBSs), and copy number signatures were evaluated. Structural variations including tumor mutational burden (TMB), the number of neoantigens, TCR clonality, homologous recombination deficiency (HRD), copy number alterations (CNAs), and microsatellite instability (MSI) score were determined. The association between these genomic features, NSCLC subtypes, and patient outcomes (progression-free and overall survival) was evaluated. Exome sequencing offers valuable insights into somatic mutational signatures in NSCLC. This study identified specific signatures associated with a poor response to immune checkpoint inhibitor (ICI) therapy and chemotherapy, potentially aiding treatment selection and identifying patients unlikely to benefit from these approaches.

Multicolor Emission in o-Carborane Derivatives Induced by Conformation Diversity through C-C Double Bond Substitution.

Rationally designed molecules with versatile conformations are ideal candidates for creating challenging single component-based multicolor emissive materials. Herein, a new strategy is presented by introducing a C-C double bond in an o-carborane derivative. Compared to a linear connection using a C-C triple bond (CbPyY), a C-C double bond connection (CbPyE) exhibited a zigzag structure and unique fluorescence behavior. Yellow, yellowish orange, and red crystals or films of CbPyE can be obtained, while only orange ones of CbPyY were achieved under the same condition. Single crystal XRD and theoretical calculation studies revealed the zigzag structure brings asymmetry to one arm of CbPyE, which causes conformation diversity and leads to the multicolor emission. Interestingly, different emissions showed different responses to acetone vapor; the yellow one showed much higher sensitivity and faster response than the other two. It is believed that the prepared materials and the proposed strategy would contribute to future advances in single-fluorophore-based multicolor emissive materials.

Bi-doped initiates the crystal structure reconfiguration of Aurivillius, boosts piezoelectric response, and achieve PMS activation and antibiotic degradation in Bi2LaNbTiO9-BiOBr heterojunctions

Piezo-photocatalysis has been widely accepted as a research strategy for environmental treatment. However, the outstanding issues of synergistic pressure response and charge transfer are still the difficulties in this area, so it is crucial to improve these points. Doping modification of piezoelectric materials is a well-established method to enhance the piezoelectric response and promote charge transfer by modulating the crystal structure. In this study, the crystal structure of Bi4Ti3O12 has been reconstructed by double doping substitution at A and B sites, which realizes the layer change of perovskite structure and the structural distortion of MO6 (M = Ti, Nb). This change in crystal symmetry effectively enhances the piezoelectric response of the material and combined with the construction of Bi2LaNbTiO9-BiOBr (BLNT-BOB) heterojunctions, the charge distribution is dramatically improved, and the charge transfer becomes easier. Under the dual effect of heterojunction and piezo-photocatalytic coupling, the catalyst exhibited excellent catalytic performance, and the degradation rate of BhB reached 97.24 % within 20 min, After PMS activation, the degradation rate reached 98.65 % in 16 min, which was higher than that of BLNT (59.13 %) and BOB (46.81 %), and the reaction kinetics were improved by 5.3-fold and 7.4-fold. It also showed good degradation efficiency in the treatment of antibiotics, and the soybean sprout culture experiment provided a strong proof of the applicability of the catalyst in multiple pollutants and biocompatibility. This work provides valuable insights for designing piezoelectric photocatalytic structures and analyzing the activation mechanism of PMS.

Sequential Modification of Pyrrole Ring with up to Three Different Nucleophiles.

An umpolung strategy was used for the preparation of highly functionalized 3-pyrrolin-2-ones. This approach involves dearomative double chlorination of 1H-pyrroles to form highly reactive dichloro-substituted 2H-pyrroles. The resulting intermediate reacts selectively with wet alcohols to form the corresponding alkoxy-substituted 3-pyrrolin-2-ones via double nucleophilic substitution in up to 99% yield. The subsequent reaction with different N-, O-, and S-nucleophiles opens access to highly functionalized pyrrolinones bearing additional functionality. The overall outcome of the reported sequence is step-by-step nucleophilic modification of pyrroles with three different nucleophiles. All steps were found to be highly efficient and 100% regioselective. This transformation proceeds under mild conditions and does not require any catalyst to give final products in very high yields. The obtained experimental results are in perfect agreement with the data obtained by theoretical investigation of these reactions.

A Photoinduced Annulation Strategy Towards a Novel Polycyclic Heteroaromatic Chromophore: Scope, Mechanism, Properties and Applications.

This article reports a detailed mechanistic and kinetic study of an unusual photoreaction leading to the (diazonia)tetrabenzonaphthacene skeleton. The photo‐triggered double intramolecular nucleophilic aromatic substitution (SNAr∗) has been investigated by varying the leaving groups. Photoreaction quantum yields have been determined and mechanistic insights have been supported by theoretical calculations using DFT and TD‐DFT methods. Additionally, we show that this light‐triggered formed diazonia constitutes a potent photosentitizer with a singlet oxygen generation quantum yield of 55 %, both in organic solvents and in water, which is an extremely relevant value in view of PDT applications or use as an oxidation photocatalyst in aqueous media. Once again, the experimental observations were supported by TD‐DFT calculations showing a large density of triplet states below the S1 excited state along with large spin‐orbit couplings. The reaction is not restricted to solutions but can also occur in solid PDMS matrices thus allowing for photochemical encoding of information that will progressively vanish upon prolonged UV‐exposure.

Crystalline-to-Amorphous Transformation and Charge Redistribution Induced by Anion–Cation Double Substitution on 3D Ni(OH)2 Ultrathin Nanosheet Arrays Enable Urea-Assisted Energy-Saving Hydrogen Production

Crystalline-to-Amorphous Transformation and Charge Redistribution Induced by Anion–Cation Double Substitution on 3D Ni(OH)₂ Ultrathin Nanosheet Arrays Enable Urea-Assisted Energy-Saving Hydrogen Production

Investigation of gyrA and parC mutations and the prevalence of plasmid-mediated quinolone resistance genes in Klebsiella pneumoniae clinical isolates

BackgroundThe emergence of fluoroquinolone resistance in clinical isolates of Klebsiella pneumoniae is a growing concern. To investigate the mechanisms behind this resistance, we studied a total of 215 K. pneumoniae isolates from hospitals in Bushehr province, Iran, collected between 2017 and 2019. Antimicrobial susceptibility test for fluoroquinolones was determined. The presence of plasmid mediated quinolone resistance (PMQR) and mutations in quinolone resistance-determining region (QRDR) of gyrA and parC genes in ciprofloxacin-resistant K. pneumoniae isolates were identified by PCR and sequencing.ResultsOut of 215 K. pneumoniae isolates, 40 were resistant to ciprofloxacin as determined by E-test method. PCR analysis revealed that among these ciprofloxacin-resistant isolates, 13 (32.5%), 7 (17.5%), 40 (100%), and 25 (62.5%) isolates harbored qnrB, qnrS, oqxA and aac(6’)-Ib-cr genes, respectively. Mutation analysis of gyrA and parC genes showed that 35 (87.5%) and 34 (85%) of the ciprofloxacin-resistant isolates had mutations in these genes, respectively. The most frequent mutations were observed in codon 83 of gyrA and codon 80 of parC gene. Single gyrA substitution, Ser83→ Ile and Asp87→Gly, and double substitutions, Ser83→Phe plus Asp87→Ala, Ser83→Tyr plus Asp87→Ala, Ser83→Ile plus Asp87→Tyr, Ser83→Phe plus Asp87→Asn and Ser83→Ile plus Asp87→Gly were detected. In addition, Ser80→Ile and Glu84→Lys single substitution were found in parC gene.ConclusionsOur results indicated that 90% of isolates have at least one mutation in QRDR of gyrA orparC genes, thus the frequency of mutations was very significant and alarming in our region.

Complex potential energy surfaces with projected CAP technique: Vibrational excitation of N2.

The projected complex absorbing potential (CAP) technique is one of the methods that allow one to extend the bound state methods for computing resonances' energies and widths. Here, we explore the accuracy of the potential energy curves generated with different electronic structure theory methods in combination with the projected CAP technique by considering resonant vibrational excitation (RVE) of N2 by electron impact as a model process. We report RVE cross sections computed using the boomerang model with potential energy curves obtained with CAP-based extended multistate complete active space perturbation theory (XMS-CASPT2) and equation of motion coupled-cluster method for electron attachment with single and double substitution (EOM-EA-CCSD) methods. We also compare potential energy curves computed with several electronic structure methods, including XMS-CASPT2, EOM-EA-CCSD, multireference configuration interaction with singles (MR-CIS) and singles and doubles (MR-CISD). A good agreement is observed between the experiment and simulated RVE cross sections obtained with the potential energy curves generated with XMS-CASPT2 and EOM-EA-CCSD methods, thus highlighting the potential of the projected CAP technique combined with accurate electronic structure methods for dynamical simulations of the processes that proceed through metastable electronic states.

Compositional-Dependent Structural Parameters and Energetics of Hibonite: Quantum-Chemical Investigation.

One of the first minerals to condense from the early solar nebula was hibonite (CaAl12O19), demonstrating a hexagonal crystal structure. There are five unique aluminum cation sites (M1-M5) in hibonite. Although hibonite contains aluminum, it can also have 3d transitional metals that substitute at aluminum cation sites, such as titanium, and other metals such as magnesium. Titanium can occur in multiple oxidation states, linking to redox conditions. A single substitution occurs when a single aluminum atom is replaced by a single titanium atom, causing the Ti to take on a 3+ oxidation state. On the other hand, Ti achieves an oxidation state of 4+ during a double substitution when a pair of aluminum atoms is replaced by a titanium and a magnesium atom. A density functional theory-based calculation is used to explore the relationship between the number of substitutions and the lattice parameters of the hibonite crystal. The calculated results reveal that the lengths of both unit cells (a and c) increase with an increasing number of single or double substitutions. The rate of increment per substitution depends on the cation sites, M1-M5, and substitution types. Along with the expansion of the unit cell of the hibonite due to the substitution, the substituted unit cell gains energy (and in turn stability) compared to the substituted unit cell without expansion, dependent on the lattice site and substitutions.

New SiS destruction and formation routes via neutral-neutral reactions and their fundamental role in interstellar clouds at low- and high-metallicity values

Context. Among the silicon-bearing species discovered in the interstellar medium, SiS and SiO stand out as key tracers due to their distinct chemistry and variable abundances in interstellar and circumstellar environments. Nevertheless, while the origins of SiO are well documented, the SiS chemistry remains relatively unexplored. Aims. Our objective is to enhance the network of Si- and S-bearing chemical reactions for a gas-grain model in molecular clouds, encompassing both low and high metallicities. To achieve this, we calculated the energies and rate coefficients for six neutral atom-diatom reactions involved in the SiCS triatomic system, with a special focus on the C+SiS and S+SiC collisions. Methods. We employed the coupled-cluster method with single and double substitutions and a perturbative treatment of triple substitutions (CCSD(T)) refined at the explicitly correlated CCSD(T)-F12 level. With these computational results in conjunction with supplementary data from the literature, we construct an extended network of neutral-neutral chemical reactions involving Si- and S-bearing molecules. To assess the impact of these chemical reactions, we performed time-dependent models employing the Nautilus gas-grain code, setting the gas temperature to 10 K and the H2 density to 2 × 104 cm−3. The models considered two initial abundance scenarios, corresponding to low- and high-metallicity levels. Abundances were computed using both the default chemical network and the constrained network, enriched with newly calculated reactions. Results. The temperature dependence for the reactions involving SiS were modelled to the k(T) = α (T/300)β exp (−γ/T) expression, and the coefficients are provided for the first time. The high-metallicity models significantly boost the SiS production, resulting in abundances nearly four orders of magnitude higher compared to low-metallicity models. Higher initial abundances of C, S, and Si, roughly ~2, 190, and 210 times higher, respectively, contribute to this. Around the age of 103 yr, destruction mechanisms become relevant, impacting the abundance of SiS. The proposed production reaction S + SiC → C + SiS, mitigates these effects in later stages. By expanding the gas reaction network using a high-metallicity model, we derived estimates for the abundances of observed interstellar molecules, including SiO, SO, and SO2. Conclusions. We demonstrate the significance of both SiC+S and C+SiS channels in the SiS chemistry. Notably, the inclusion of neutral-neutral mechanisms, particularly via Si+HS and S+SiC channels, played a pivotal role in determining SiS abundance. These mechanisms carry a significance level on a par with that of the well-known and fast ion-neutral reactions.

DFT formalism studies on the structural and electronic properties of hexagonal graphene quantum dot with B, N and Si substitutional impurities

The study of carbon-based nanostructured materials is a highly active research field, that has made significant progress in the study of twodimensional materials and nanotechnology. The interest in these materials is mainly attributed to the fascinating properties they exhibit, as seen in the case of graphene as a 2D material, as well as emergence on numerous novel 2D materials and their heterostructures. Additionally, there is important interest in systems such as 2D quantum dots. Therefore, this work focuses on the systematic study of graphene quantum dots of various sizes, all within the framework of first-principles density functional theory. We started with the simplest graphene quantum dot (GQD) structure, benzene (C6H6), which consist of six carbon atoms passivated with hydrogen atoms. We then increased its size by adding more aromatic rings, resulting in the following GQD configurations: C24H12, C54H18, C96H24, C150H30 and C216H36. We report the density of states (DOS) and the imaginary part of the dielectric function (ε2) for the system, analyzing both the pristine configuration and the effect of both single and double (boron, nitrogen and silicon, denoted as Sa). The double substitutional atom study was done considering random, ortho-, meta-, and para-director positions just for the C94H24Sa2 GQD. In general, we can conclude that as the GQD increases in size, the HOMO-LUMO energy decreases. Furthermore, it is observed that boron and nitrogen exhibit their expected n-, and p-type doping characteristics, but this differs between single and double Sa substitutions. Additionally, the imaginary part of the dielectric function is highly sensitive to the positions of single and double substitutional atoms, as well as the polarization of incident light. Therefore, we suggest that these differences can be used to clearly determinate the type of substitutional atoms and their positions from optical measurements.

Synthesis and cytotoxic evaluation of heterocyclic compounds by vinylic substitution of ketene dithioacetals.

N-heterocyclic compounds are important molecular scaffolds in the search for new drugs, since most drugs contain heterocyclic moieties in their molecular structure, and some of these classes of heterocycles are able to provide ligands for two or more biological targets. Ketene dithioacetals are important building blocks in organic synthesis and are widely used in the synthesis of N-heterocyclic compounds. In this work, we used double vinylic substitution reactions on ketene dithioacetals to synthesize a small library of heterocyclic derivatives and evaluated their cytotoxic activity in breast and ovarian cancer cells, identifying two benzoxazoles with good potency and selectivity. In silico predictions indicate that the two most active derivatives exhibit physicochemical properties within the range of drug-like compounds and showed potential to interact with HDAC8 and ERK1 cancer-related targets.

Natural Orbitals and Targeted Non-Orthogonal Orbital Sets for Atomic Hyperfine Structure Multiconfiguration Calculations

Hyperfine structure constants have many applications, but are often hard to calculate accurately due to large and canceling contributions from different terms of the hyperfine interaction operator, and also from different closed and spherically symmetric core subshells that break up due to electron correlation effects. In multiconfiguration calculations, the wave functions are expanded in terms of configuration state functions (CSFs) built from sets of one-electron orbitals. The orbital sets are typically enlarged within the layer-by-layer approach. The calculations are energy-driven, and orbitals in each new layer of correlation orbitals are spatially localized in regions where the weighted total energy decreases the most, overlapping and breaking up different closed core subshells in an irregular pattern. As a result, hyperfine structure constants, computed as expectation values of the hyperfine operators, often show irregular or oscillating convergence patterns. Large orbital sets, and associated large CSF expansions, are needed to obtain converged values of the hyperfine structure constants. We analyze the situation for the states of the {2s22p3,2s22p23p,2s22p24p} odd and {2s22p23s,2s2p4,2s22p24s,2s22p23d} even configurations in N I, and show that the convergence with respect to the increasing sets of orbitals is radically improved by introducing separately optimized orbital sets targeted for describing the spin- and orbital-polarization effects of the 1s and 2s core subshells that are merged with, and orthogonalized against, the ordinary energy-optimized orbitals. In the layer-by-layer approach, the spectroscopic orbitals are kept frozen from the initial calculation and are not allowed to relax in response to the introduced layers of correlation orbitals. To compensate for this lack of variational freedom, the orbitals are transformed to natural orbitals prior to the final calculation based on single and double substitutions from an increased multireference set. The use of natural orbitals has an important impact on the states of the 2s22p23s configuration, bringing the corresponding hyperfine interaction constants in closer agreement with experiment. Relying on recent progress in methodology, the multiconfiguration calculations are based on configuration state function generators, cutting down the time for spin-angular integration by factors of up to 50, compared to ordinary calculations.

Structural and Optical Properties of Bi4Six/2Gex/2V2-xO11-x/2 Compounds: Effect of Double Substitution and Phase Transitions

Structural and Optical Properties of Bi4Six/2Gex/2V2-xO11-x/2 Compounds: Effect of Double Substitution and Phase Transitions

Essential residues in diterpene synthases for biosynthesis of oryzalexins A-F in rice phytoalexin.

Cultivated rice (Oryza sativa) produces a variety of diterpenoid-type phytoalexins. Diterpene synthase genes that are responsible for the biosynthesis of momilactones, phytocassanes, and oryzalexins have been identified in O. sativa cv. Nipponbare. OsKSL10 (Os12t0491800 in RAP and LOC_Os12g30824 in MSU) was previously identified as an enzyme catalyzing the conversion of ent-copalyl diphosphate to ent-sandaracopimaradiene for the production of oryzalexins A to F. Our previous study on Oryza rufipogon, a wild progenitor of Asian cultivated rice, showed that both OrKSL10 and OrKSL10ind from O. rufipogon accessions W1943 and W0106, respectively, closely related to the japonica and indica subspecies, converted ent-copalyl diphosphate to ent-miltiradiene. Thus, the functional conversion of ent-miltiradiene synthase into ent-sandaracopimaradiene synthase is implied to have occurred through natural amino acid mutations, the details of which have not been elucidated. In this study, we show that introduction of A654G substitution into OrKSL10 significantly alters its function into more closely resembling that of OsKSL10. Moreover, double substitution V546I/A654G almost completely converts the function of OrKSL10 into that of OsKSL10. On the other hand, the reversed substitution I546V/G654A was insufficient to convert the function of OsKSL10 into OrKSL10, indicating the introduction of additional substitution S522I is required for the functionality of OsKSL10. Lastly, point mutations atthe 654A residue in OrKSL10 suggest that hydrophobic side chains atthis position have a negative influence on the production of ent-sandaracopimaradiene.

Renal Function and Transporters in the Na/K-ATPase α1S/S Mouse Model of High Affnity for Cardiotonic Steroids

Genetic ablation of ATP1A1 in the mouse renal proximal tubule (RPT) revealed that Na/K-ATPase (NKA) α1 tonically inhibits sodium and water reabsorption. Mechanistically, findings in KO mouse RPT and renal epithelial cells were consistent with a prevalent role of a NKA/Src-dependent downregulation of Na+/H+ exchanger 3 (NHE3). Pharmacologically, functional activation of this pathway has been obtained in vitro and ex vivo using low concentrations of NKA archetypal ligands cardiotonic steroids (CTS). However, the physiological implication of an activation of the endogenous CTS (eCTS)/NKA/Src on renal transporters including NHE3 has not been explored. We assessed the renal impact of CTS/NKA α1 receptor activation by comparing mice expressing the naturally resistant NKA α1 and age-matched mice genetically engineered to express a mutated NKA α1 with high affnity for CTS (R111Q/D122N double substitution). Mice obtained from established colonies at the University of Cincinnati were a gift from Dr. Jerry Lingrel. CTS-sensitive (α1S/S) male mice aged 3-6 months on a C57Bl6 background and age-matched controls (α1R/R) were used. Mice were born with a normal Mendelian ratio, with no observable difference between α1S/S and α1R/R. Renal Na/K-ATPase inhibitory dose-response curve to the CTS ouabain was shifted to the left, as expected, and occurred without detectable change of total renal NKA activity, NKA α1 or β1 protein contents. Metabolic cage studies revealed that increased α1 sensitivity to CTS resulted in a significant increase in urine output in α1S/S mice compared to age-matched α1R/R controls (3.9±0.3 vs. 2.4±0.2 ml/24h; n=6, p<0.01). Consistent with an activation of the NKA/Src receptor by eCTS, western blot analyses of renal cortical preparation revealed an increased phosphorylation of NKA α1 at Y260 (Src target residue) and decreased NHE3 content (43.6 %; n=5, p<0.01). RNA-seq analysis of whole kidneys from α1S/S and α1R/R littermate mice using the Illumina NovaSeq 6000 system (Novogene) and Volcano Plot (DEG data using Python) further showed differential expression of 296 genes (147 upregulated and 149 downregulated). Gene Set Enrichment Analysis (GSEA) using the WebGestalt toolkit showed that the altered pathways were mostly involved in solute transport. Taken together, these results provide genetic evidence of the physiological role of eCTS/NKAα1 on renal function in the intact mouse. Increased affnity to eCTS is suffcient to lead to an activation of NKAα1/Src, a downregulation of NHE3, and transcriptional regulation of renal transporters associated with increased urine output. This work was supported by AHA, Predoctoral fellowship #19PRE34450095, NIH DK129937, and NIH Grant P20GM103434 to the West Virginia IDeA Network of Biomedical Research Excellence. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effect of double substitution on hydrogen absorption-desorption properties of Ti2CrV alloy

Doubly substituted Ti2CrV alloy with composition Ti1.5Sc0.3CrVNi0.2 was prepared by arc melting method followed by annealing. The annealed alloy exists in body centred cubic (BCC) structure and shows fast kinetics for hydrogen absorption and desorption at room temperature. BCC phase of the alloy undergoes phase transformation to face centred cubic (FCC) hydride phase with H atoms occupying tetrahedral sites in the lattice, reaching an overall H/M ratio >2.2 (storage capacity ∼ 4 wt%). Storage capacity decreases by 40% in the 2nd cycle and then stabilizes at a value of ∼2.5 wt% for the subsequent 10 cycles. A drastic reduction in hydride desorption temperature upon double substitution (Sc and Ni substitution in Ti2CrV alloy) has been confirmed by DSC studies. Furthermore, the change in isotope effect in doubly substituted Ti2CrV alloy is discussed in light of thermal stabilities of the hydrides and deuterides.

Improvement of the Thermoelectric Properties of p-Type Mg3Sb2 by Mg-Site Double Substitution.

A P-type Mg3Sb2-based Zintl phase compound has been considered a promising candidate for thermoelectric applications. Alloying, which introduces a high concentration of point defects, is particularly effective in scattering phonons and reducing lattice thermal conductivity. Herein, alloying in p-type Mg2.995Na0.005Sb2 via the introduction of elements like Yb, Eu, Ca, and Ba was realized, and the room-temperature lattice thermal conductivity has been effectively reduced to ∼1.1 W m-1 K-1. To further intensify the phonon scattering, two groups of elements (Eu and Cd, and Yb and Cd) were chosen for heavy alloying at the Mg site, and the lattice thermal conductivity of Mg1.49Eu0.5Cd1Na0.01Sb2 was further reduced to ∼0.45 W m-1 K-1. Eventually, a peak zT as high as ∼1.0 was achieved at 773 K, and the compound outperforms the previously reported p-type Mg3Sb2 compounds.