Influence of lattice distortion on the Curie temperature and spin-phonon coupling in LaMn0.5_{0.5}Co0.5_{0.5}O3_{3}

Two distinct ferromagnetic phases of LaMn$_{0.5}$Co$_{0.5}$O$_{3}$ having monoclinic structure with distinct physical properties have been studied. The ferromagnetic ordering temperature $\textit{T}_{c}$ is found to be different for both the phases. The origin of such contrasting characteristics is assigned to the changes in the distance(s) and angle(s) between Mn - O - Co resulting from distortions observed from neutron diffraction studies. Investigations on the temperature dependent Raman spectroscopy provide evidence for such structural characteristics, which affects the exchange interaction. The difference in B-site ordering which is evident from the neutron diffraction is also responsible for the difference in $\textit{T}_{c}$. Raman scattering suggests the presence of spin-phonon coupling for both the phases around the $\textit{T}_{c}$. Electrical transport properties of both the phases have been investigated based on the lattice distortion.Comment: 9 figure

Brillouin Light Scattering Study of Microscopic Structure and Dynamics in Pyrrolidinium Based Ionic Liquids

Pyrrolidinium based ionic liquids are known to be good ionic conductors even in solid-state around room temperature, which is attributed to the highly disordered plastic crystalline phase. Moreover, these ionic liquids are characterized by multiple phase transitions which include plastic, structural glass, and glassy crystal phases with varying levels of molecular disorder. Temperature-dependent Brillouin light scattering is used to investigate the phase transitions in a series of alkylmethylpyrrolidinium Bis(trifluoromethanesulfonyl) imides (P1nTFSI, n=1,2,4). Brillouin spectral features such as the number of acoustic modes, their shape, and linewidth provide the picture of different disordered phases resultant of dynamics at the microscopic scale. The longitudinal and transverse acoustic velocities in different phases are determined from the corresponding acoustic mode frequencies (Brillouin shift). Extremely low acoustic velocities in the solid phase of P11TFSI and P12TFSI are a consequence of a high degree of disorder and plasticity present in the system. Anomalous temperature-dependent behavior of linewidth and asymmetric (Fano) line shape of acoustic modes observed in certain phases of P1nTFSI could be due to the strong coupling between the Brillouin central peak and the acoustic phonons. The present results establish that the Brillouin light scattering technique can be efficiently used to understand the complex phase behavior, microscopic structure, and dynamics of ionic liquids.</p

Single amino acid bionanozyme for environmental remediation.

Enzymes are extremely complex catalytic structures with immense biological and technological importance. Nevertheless, their widespread environmental implementation faces several challenges, including high production costs, low operational stability, and intricate recovery and reusability. Therefore, the de novo design of minimalistic biomolecular nanomaterials that can efficiently mimic the biocatalytic function (bionanozymes) and overcome the limitations of natural enzymes is a critical goal in biomolecular engineering. Here, we report an exceptionally simple yet highly active and robust single amino acid bionanozyme that can catalyze the rapid oxidation of environmentally toxic phenolic contaminates and serves as an ultrasensitive tool to detect biologically important neurotransmitters similar to the laccase enzyme. While inspired by the laccase catalytic site, the substantially simpler copper-coordinated bionanozyme is ∼5400 times more cost-effective, four orders more efficient, and 36 times more sensitive compared to the natural protein. Furthermore, the designed mimic is stable under extreme conditions (pH, ionic strength, temperature, storage time), markedly reusable for several cycles, and displays broad substrate specificity. These findings hold great promise in developing efficient bionanozymes for analytical chemistry, environmental protection, and biotechnology

Superionic phase transition in KHSO<SUB>4</SUB>: a temperature-dependent Raman investigation

Temperature-dependent Raman spectroscopic studies have been carried out on KHSO<SUB>4</SUB> single crystals in the temperature range 298-493 K. A structural phase transition driven by the lattice and molecular disorder is observed at 473 K. The spectral data enable an understanding of the nature of the lattice disorder across the phase transition leading to the superionic phase. The disorder in the HSO<SUB>4</SUB><SUP>&#8722;</SUP> polymeric hydrogen-bonded chain leading to a higher symmetry in the high temperature phase is clearly captured from our Raman results. The internal S-OH and S-O stretching modes and, to a limited extent, the external modes throw light on the disorder mechanism and the enhancement of conductivity after transition