The presence of domains is an intrinsic feature of ferroelectric materials and is essential for their many functional properties. However, the characterization of individual domains and the motion of domain walls, both in static conditions and under external stimuli, remains a challenging task. Here, we use the in-situ high-resolution single-crystal X-ray diffraction to investigate the thermally driven domain rotations in the tetragonal and monoclinic phases of PbZr0.52Ti0.48O3 single crystal. By establishing a precise correspondence between the domains and their specific X-ray diffraction peaks, we traced the rotation of individual domains as a function of temperature. Our results demonstrate a direct correlation between the domain size and its rotation angle towards the neighbors in a multidomain state. These findings provide new insights into understanding the behavior of complex domain patterns at the morphotropic phase boundary of piezoelectrics, and potentially shed light on the development of advanced materials with enhanced electromechanical properties.
Gold's importance in various industries, the ever-rising demand for electronics, and shrinking gold reserves all underscore the pressing need to develop effective gold recovery methods from waste. In this study, we systematically evaluate several large-pore Zirconium-carboxylate Metal-Organic Frameworks (Zr-MOFs) having slightly varied internal surface functionality (-H, -CH3, -NH2, and -NO2) in gold recovery from acidic, simulated e-waste solutions. We compare two Zr-MOFs constructed from oligophenylene ligands with four MOFs built from structurally analogous piperazine-based ligands, including two unreported frameworks. The piperazine-based frameworks offer a critical sustainability advantage: by replacing the central benzene core with piperazine, they eliminate the need for expensive Pd-catalyzed coupling chemistry required for oligophenylene synthesis. In this work, we demonstrate for the first time that Zr-piperazine MOFs exhibit stability in acidic conditions, significantly surpassing their oligophenylene-based counterparts. One developed Zr-piperazine MOF, functionalized with both amine and methyl groups, substantially outperforms all analogs, displaying the highest stability alongside a gold adsorption capacity of up to 1826 mg/g and rapid adsorption kinetics in a 40 ppm gold solution. X-ray Absorption Near-Edge Structure (XANES) studies reveal distinct gold adsorption mechanisms for primary versus tertiary amines. These findings establish piperazine-based building blocks as promising candidates for designing selective gold adsorbents for e-waste recovery applications.
Three novel Zn(II) coordination compounds derived from chrysin and 1,10-phenanthroline were synthesized using microwave-assisted methodology: a mononuclear complex (1), a two-dimensional coordination polymer (2), and a tetranuclear cluster (3). Fine-tuning of reaction parameters enabled selective access to these distinct architectures, with single-crystal X-ray diffraction confirming the structures of 1 and 3. Positive-ion nanospray mass spectrometry showed that complexes 1 and 2 predominantly generate well-defined mononuclear Zn-chry-phen units upon ionization, a behavior consistent with the formation of such units under the experimental conditions, whereas cluster 3 undergoes extensive fragmentation into Zn-phen-based dicationic species, limiting biological evaluation to complexes 1 and 2. Both compounds displayed enhanced, though moderate, radical-scavenging activity relative to free chrysin, consistent with electronic modulation and stabilization of phenoxyl radicals upon metal coordination. Their anticancer properties were assessed in vitro against human melanoma (A375), hepatocellular carcinoma (HepG2), and non-tumoral keratinocyte (HaCaT) cell lines. Complexes 1 and 2 exhibited pronounced time- and dose-dependent cytotoxicity, with IC50 values in A375 and HepG2 markedly lower than those of free chrysin and comparable to phen. Cytotoxicity in HaCaT keratinocytes occurred within the same micromolar range, indicating modest selectivity while still providing meaningful insight into the biological behavior of Zn(II)-chrysin-phen systems. Mechanistic studies indicated S phase cell cycle arrest and increased reactive oxygen species (ROS) generation, suggesting oxidative stress as a key contributor to cytotoxicity against the tumor cell-lines. Overall, these findings highlight the versatility of microwave-assisted synthesis for generating structurally diverse Zn(II)-flavonoid architectures and advance understanding of their coordination chemistry and structure-activity relationships.
