Increased Crystallization of CuTCNQ in Water/DMSO Bisolvent for Enhanced Redox Catalysis

Controlling the kinetics of CuTCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) crystallization has been a major challenge, as CuTCNQ crystallizing on Cu foil during synthesis in conventional solvents such as acetonitrile simultaneously dissolves into the reaction medium. In this work, we address this challenge by using water as a universal co-solvent to control the kinetics of crystallization and growth of phase I CuTCNQ. Water increases the dielectric constant of the reaction medium, shifting the equilibrium toward CuTCNQ crystallization while concomitantly decreasing the dissolution of CuTCNQ. This allows more CuTCNQ to be controllably crystallized on the surface of the Cu foil. Different sizes of CuTCNQ crystals formed on Cu foil under different water/DMSO admixtures influence the solvophilicity of these materials. This has important implications in their catalytic performance, as water-induced changes in the surface properties of these materials can make them highly hydrophilic, which allows the CuTCNQ to act as an efficient catalyst as it brings the aqueous reactants in close vicinity of the catalyst. Evidently, the CuTCNQ synthesized in 30% (v/v) water/DMSO showed superior catalytic activity for ferricyanide reduction with 95% completion achieved within a few minutes in contrast to CuTCNQ synthesized in DMSO that took over 92 min.

Effect of water activity on the functional, colloidal, physical, and microstructural properties of infant formula powder

We report on the physicochemical changes of infant formula (IF) powder and its macronutrients (lactose, fat, and proteins) under given storage conditions. Colloidal (particle size distribution, emulsion stability and sedimentation), morphological (scanning electron microscopy), thermal (differential scanning calorimetry), structural (synchrotron X-ray diffraction) as well as surface and chemical (X-ray photoelectron and Fourier transform infrared spectroscopies) data were used to elucidate the main cause-effect relationships for microstructural, functional, and other properties of the IF powder. The wetting behavior of the powder was found to be significantly affected by water activity (a_w) during storage (a_w in the range between 0.24 and 0.42). At the highest a_w (a_w = 0.42), lactose crystallization and fat migration took place, leading to changes on the surface of the particles that reduced powder wettability. We propose possible mechanisms to explain the observations, associated with changes in protein conformation. Interestingly, no major changes in the pH and colloidal characteristics, including particle size and distribution, stability, and sedimentation were observed in the reconstituted IF powder upon storage for 6 weeks. The results indicated a negligible contribution from possible Maillard reactions. We propose leading microstructural and wetting characterization to troubleshoot changes in the quality of IF powder, most relevant from the perspective of reconstitution after storage.

A Self-Growing Strategy for Large-Scale Crystal Assembly Tubes

Assembled tubular materials have attracted widespread attention due to their potential applications in catalysis, bionics, and optic-electronics. Many versatile methods, including template assistance and self-assembly, have been developed for fabrication of tubular materials. Here we demonstrate a self-growing strategy to prepare large-scale crystal assembly tubes. Addition of the template and the need for the sophisticated equipment are avoided with this method. The sidewall of the tubes is composed of a layer of polyhedral crystals that are connected together through grain coalescence. We demonstrate that the assembled tubular structure is obtained by the synergetic effect of the passivation layer and the dissolution-recrystallization process. This facile one-step strategy and the formation mechanism will offer guidance for fabrication of new superstructures.