Colossal Stability of SiB11 (BO)12 - : An Implication as Potential Electrolyte in High-Voltage Alkali-ion Battery

High-voltage alkali metal-ion batteries (AMIBs) require a non-hazardous, low-cost, and highly stable electrolyte with a large operating potential and rapid ion conductivity. Here, we have reported a halogen-free high-voltage electrolyte based on SiB11 (BO)12 - . Because of the weak π-orbital interaction of -BO as well as the mixed covalent and ionic interaction between SiB11 -cage and -BO ligand, SiB11 (BO)12 - has colossal stability. SiB11 (BO)12 - possesses extremely high vertical detachment energy (9.95 eV), anodic voltage limit (∼10.05 V), and electrochemical stability window (∼9.95 V). Furthermore, SiB11 (BO)12 - is thermodynamically stable at high temperatures, and its large size allows for faster cation movement. The alkali salts MSiB11 (BO)12 (M=Li, Na, and K) are easily dissociated into ionic components. Electrolytes based on SiB11 (BO)12 - greatly outperform commercial electrolytes. In short, SiB11 (BO)12 - -based compound is demonstrated to be a high-voltage electrolyte for AMIBs.

Manganese substitution induced magnetic transformation and magnetoelectricity in SrFe12O19

In this study, manganese substituted strontium hexaferrite (SrFe_12-xMn_xO₁₉; x = 0, 3, 5, and 7) prepared by the sol-gel auto-combustion method are studied. We observed that the substituted Mn preferentially goes to the 2a and 12k sites of Fe. Raman modes related to the 12k site suggest the stiffening of the lattice. The transformation of the grain's shape from hexagonal (x = 0 and 3) to rhombohedral (x = 7) was observed, as shown in the micrographs obtained from FESEM. The thermomagnetic curves show the shift of T_C to lower temperatures with the increase in the Mn content. From x = 5 onwards, the growth of another magnetic phase (FiM2) of lower coercivity apart from the parent phase (FiM1) of higher coercivity is seen. The FiM2 phase was found to increase with the Mn content in the sample (16.4(3)% for x = 5 but 66.2(5)% for x = 7). Although the magnetization for both FiM1 and FiM2 decreases with the increase in temperature, both magnetic phases behave in contrast to each other for x = 5 and x = 7. The study suggests a transformation of the compound from high magnetic anisotropy (x = 0) to low magnetic anisotropy (x = 7). The x = 5 composition sample displays the highest value of the first-order ME coefficient (0.83(2) mV × cm^-1 × Oe^-1). The observed value for x = 5 composition is ∼2.5 times higher than that of the parent x = 0 composition sample (0.33(2) mV × cm^-1 × Oe^-1). The studies thus suggest that the x = 5 composition is one of the viable candidates for magnetoelectric applications.

Functional Pyromellitic Diimide as a Corrosion Inhibitor for Galvanized Steel: An Atomic-Scale Engineering

Corrosion of metal/steel is a major concern in terms of safety, durability, cost, and environment. We have studied a cost-effective, nontoxic, and environmentally friendly pyromellitic diimide (PMDI) compound as a corrosion inhibitor for galvanized steel through density functional theory. An atomic-scale engineering through the functionalization of PMDI is performed to showcase the enhancement in corrosion inhibition and strengthen the interaction between functionalized PMDI (F-PMDI) and zinc oxide (naturally existing on galvanized steel). PMDI is functionalized with methyl/diamine groups (inh1 (R = -CH₃, R' = -CH₃), inh2 (R = -CH₃, R' = -CH₂CH₂NH₂), and inh3 (R = -C₆H₃(NH₂)₂, R' = -CH₂CH₂NH₂). The corrosion inhibition parameters (e.g., orbital energies, electronegativity, dipole moment, global hardness, and electron transfer) indicate the superior corrosion inhibition performance of inh3 (inh3 > inh2 > inh1). Inh3 (∼182.38 kJ/mol) strongly interacts with ZnO(101̅0) compared to inh2 (∼122.56 kJ/mol) and inh1 (∼119.66 kJ/mol). The superior performance of inh3 has been probed through charge density and density of states. Larger available states of N and H (of inh3) interact strongly with Zn and O_surf (of the surface), respectively, creating N-Zn and H-O_surf bonds. Interestingly, these bonds only appear in inh3. The charge accumulation on O_surf, and depletion on H(s), further strengthens the bonding between inh3 and ZnO(101̅0). The microscopic understanding obtained in this study will be useful to develop low-cost and efficient corrosion inhibitors for galvanized steel.

Sculpting Artificial Edges in Monolayer MoS2 for Controlled Formation of Surface-Enhanced Raman Hotspots

Hotspot engineering has the potential to transform the field of surface-enhanced Raman spectroscopy (SERS) by enabling ultrasensitive and reproducible detection of analytes. However, the ability to controllably generate SERS hotspots, with desired location and geometry, over large-area substrates, has remained elusive. In this study, we sculpt artificial edges in monolayer molybdenum disulfide (MoS₂) by low-power focused laser-cutting. We find that when gold nanoparticles (AuNPs) are deposited on MoS₂ by drop-casting, the AuNPs tend to accumulate predominantly along the artificial edges. First-principles density functional theory (DFT) calculations indicate strong binding of AuNPs with the artificial edges due to dangling bonds that are ubiquitous on the unpassivated (laser-cut) edges. The dense accumulation of AuNPs along the artificial edges intensifies plasmonic effects in these regions, creating hotspots exclusively along the artificial edges. DFT further indicates that adsorption of AuNPs along the artificial edges prompts a transition from semiconducting to metallic behavior, which can further intensify the plasmonic effect along the artificial edges. These effects are observed exclusively for the sculpted (i.e., cut) edges and not observed for the MoS₂ surface (away from the cut edges) or along the natural (passivated) edges of the MoS₂ sheet. To demonstrate the practical utility of this concept, we use our substrate to detect Rhodamine B (RhB) with a large SERS enhancement (∼10⁴) at the hotspots for RhB concentrations as low as ∼10^-10 M. The single-step laser-etching process reported here can be used to controllably generate arrays of SERS hotspots. As such, this concept offers several advantages over previously reported SERS substrates that rely on electrochemical deposition, e-beam lithography, nanoimprinting, or photolithography. Whereas we have focused our study on MoS₂, this concept could, in principle, be extended to a variety of 2D material platforms.

Tuning the Electrocatalytic Activity of Co3O4 through Discrete Elemental Doping

To gain constructive insight into the possible effect of doping on the electrocatalytic activity of materials, a catalytic framework with a discrete distribution of dopants is an appropriate model system. Such a system assures well-defined active centers, maximum atom utilization efficiency, and hence enhanced selectivity, catalytic activity, and stability. Herein, a comprehensive investigation of the electrocatalytic activity of iron-doped cobalt oxide (Fe-Co₃O₄) nanosheets is presented. In order to understand the contribution of dopants, a series of materials with controlled doping levels are investigated. By controlled iron inclusion into the structure of Co₃O₄, an apparent improvement in the oxygen evolution reaction activity which is reflected in the decrease of 160 mV in the overpotential to reach the current density of 10 mA/cm² is manifested. Additionally, it is shown that there exists an optimum doping content above which the catalytic activity fades. Further investigation of the system with density functional calculations reveals that, along with the optimization of adsorption energy toward the reaction intermediates, substantial downshift of the Fermi level and delocalization of electron density occurs on introducing iron ions into the structure.

Chemical constituents and biological studies of Origanum vulgare Linn

Bioassay-guided isolation of methanolic extract of the leaves of Origanum vulgare Linn., yielded two protocatechuic acid ester derivatives, origanol A (1) and origanol B (2) along with ursolic acid (3), oleanolic acid (4), β-sitosterol (5), and triacontanol (6). Structures of the compound were established based on physical and spectral data (UV, IR, ¹H and ¹³C NMR and mass). Origanol A (1) showed significant mushroom tyrosinase inhibition activity.