Crystal dissolution by particle detachment

The Influence of Ionizing Radiation on Quantification for In Situ and Operando Liquid-Phase Electron Microscopy

The ionizing radiation harnessed in electron microscopes or synchrotrons enables unique insights into nanoscale dynamics. In liquid-phase transmission electron microscopy (LP-TEM), irradiating a liquid sample with electrons offers access to real space information at an unmatched combination of temporal and spatial resolution. However, employing ionizing radiation for imaging can alter the Gibbs free energy landscape during the experiment. This is mainly due to radiolysis and the corresponding shift in chemical potential; however, experiments can also be affected by irradiation-induced charging and heating. In this review, the state of the art in describing beam effects is summarized, theoretical and experimental assessment guidelines are provided, and strategies to obtain quantitative information under such conditions are discussed. While this review showcases these effects on LP-TEM, the concepts that are discussed here can also be applied to other types of ionizing radiation used to probe liquid samples, such as synchrotron X-rays.

Heterogeneous interfaces in confined microdomains of glycyrrhizic acid for polymorphism selection: Mechanisms and applications

Understanding the mechanisms of heterogeneous nucleation to improve the precision and applicability of polymorphism selection remains challenging. In this study, the formation of confined microdomains with heterogeneous interfaces in the micelle and gel systems were reported based on the supramolecular self-assembly of glycyrrhizic acid. The polymorph with high-purity preparation of isonicotinamide and nicotinamide was achieved due to the high degree of supersaturation and diverse nucleation pathways. In situ spectroscopy and molecular simulations provided insights into the mechanism of polymorphism selection in molecular migration and cluster aggregation, revealing the influence of a heterogeneous templated effect and protonation effect during nucleation and growth. The selective induction of dominant polymorph with chain structure (Form II of isonicotinamide and Form ε of nicotinamide) validated the efficacy and applicability of this approach. Furthermore, the effective loading (up to 4-fold), enhanced stability (up to 2 months), and pH-responsive release of the dominant polymorphs exhibited the potential of glycyrrhizic acid systems for drug delivery. This study provides a promising approach for the selective induction and efficient delivery of dominant polymorphs, which contributes to a deeper understanding of heterogeneous nucleation.

Cell-Membrane-Inspired Ultrathin Silica Nanochannels Coating for Long-Term Stable Photoelectrocatalysis with Enhanced Performance

Photoelectrocatalysis has attracted significant attention for water splitting and contaminant degradation. However, the lifetime of photoelectrocatalysis devices is hampered by the severe instability and photocorrosion of the photo-active nanomaterial on the photoelectrode, which is a key limitation to realizing industrialization. Typically, the conventional protection strategy of photoelectrodes usually suffers from the trade-off between the photoelectrocatalytic activity and stability. Inspired by biological cell membrane with water channels, here a highly permeable and ultrathin silica coating with ultrasmall straight nanochannels is in situ grown that stabilizes the photoelectrode. These ultrasmall channels boost photoelectrocatalysis by accelerating water transport and reducing the reaction energy within the confined nanochannels. Specifically, the ultrathin coating imparts significant mechanical and structural stability to the photo-active nanomaterial, thereby preventing its detachment, dissolution, and crystal damage without compromising performance. As a result, the protected photoelectrode exhibits enhanced water splitting activity and excellent stability over 120 h, whereas the photocurrent of the unprotected photoelectrode degrades rapidly. Meanwhile, the coated photoelectrode also exhibits superior photoelectrocatalytic degradation efficiency (>97%), even after the 10th cycle. This strategy is facile and universal and can be extended to construct other stable and high-performance electrodes for promoting photoelectrocatalysis in practical applications.

Influence of Mechanical Loading on the Process of Tribochemical Action on Physicochemical and Biopharmaceutical Properties of Substances, Using Lacosamide as an Example: From Micronisation to Mechanical Activation

Many physical and chemical properties of solids, such as strength, plasticity, dispersibility, solubility and dissolution are determined by defects in the crystal structure. The aim of this work is to study in situ dynamic, dispersion, chemical, biological and surface properties of lacosamide powder after a complete cycle of mechanical loading by laser scattering, electron microscopy, FR-IR and biopharmaceutical approaches. The SLS method demonstrated the spontaneous tendency toward surface-energy reduction due to aggregation during micronisation. DLS analysis showed conformational changes of colloidal particles as supramolecular complexes depending on the loading time on the solid. SEM analysis demonstrated the conglomeration of needle-like lacosamide particles after 60 min of milling time and the transition to a glassy state with isotropy of properties by the end of the tribochemistry cycle. The following dynamic properties of lacosamide were established: elastic and plastic deformation boundaries, region of inhomogeneous deformation and fracture point. The ratio of dissolution-rate constants in water of samples before and after a full cycle of loading was 2.4. The lacosamide sample, which underwent a full cycle of mechanical loading, showed improved kinetics of API release via analysis of dissolution profiles in 0.1 M HCl medium. The observed activation-energy values of the cell-death biosensor process in aqueous solutions of the lacosamide samples before and after the complete tribochemical cycle were 207 kJmol-1 and 145 kJmol-1, respectively. The equilibrium time of dissolution and activation of cell-biosensor death corresponding to 20 min of mechanical loading on a solid was determined. The current study may have important practical significance for the transformation and management of the properties of drug substances in solid form and in solutions and for increasing the strength of drug matrices by pre-strain hardening via structural rearrangements during mechanical loading.

Silica Polymerization Driving Opposite Effects of pH on Aqueous Carbonation Using Crystalline and Amorphous Calcium Silicates

The aqueous carbonation of calcium silicate (CS), a representative alkaline-earth silicate, has been widely explored in studies of carbon dioxide (CO2) mineralization. In this context, we conducted a specific comparison of the carbonation behaviors between the crystalline calcium silicate (CCS) and amorphous calcium silicate (ACS) across a pH range from 9.0 to 12.0. Interestingly, we observed opposite pH dependencies in the carbonation efficiencies (i.e., CaO conversion into CaCO3 in 1 M Na2CO3/NaHCO3 solution under ambient conditions) of CCS and ACS─the carbonation efficiency of CCS decreased with increasing the solution basicity, while that of ACS showed an inverse trend. In-depth insights were gained through in situ Raman characterizations, indicating that these differing trends appeared to originate from the polymerization/depolymerization behaviors of silicates released from minerals. More specifically, higher pH conditions seemed to favor the carbonation of minerals containing polymerized silica networks. These findings may contribute to a better understanding of the fundamental factors influencing the carbonation behaviors of alkaline earth silicates through interfacial coupled dissolution and precipitation processes. Moreover, they offer valuable insights for selecting optimal carbonation conditions for alkaline-earth silicate minerals.