Hierarchical Superstructures of l‑Glutathione

The formation of hierarchical structures of organic crystals has great potential for many chemical and medical applications in various areas such as pharmaceuticals, food, pigments, and organic catalysis. In this paper, we describe the synthesis of l-glutathione spherical hierarchical structures using an anti-solvent precipitation method. The crystallization of l-glutathione hierarchical structures under various experimental parameters such as temperature, solvent composition, and l-glutathione concentrations is thoroughly studied. The hierarchical organic structures are studied using several techniques including X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. It is found that the hierarchical structures and the polymorphs of l-glutathione depend mainly on the anti-solvents used during the anti-solvent precipitation process. On the basis of these results and on kinetic measurements of the crystallization course, we propose a possible mechanism for the formation of the l-glutathione superstructures based on the self-assembly principle. In this work, we investigate the formation of l-glutathione spherical hierarchical structures as a model system of crystallization of organic hierarchical crystals. We believe that the results of this study and the synthesis described here, for the formation of organic hierarchical structures, can be further extended to numerous organic hierarchical crystal systems

Formation of Hierarchical Structures of l‑Glutamic Acid with an l‑Arginine Additive

Formation of hierarchical structures of organic crystals has great potential for many applications in various areas including pharmaceuticals, food, pigments, and organic catalysis. In this paper, we investigate the formation of hierarchical structures of glutamic acid using arginine as a charged additive to control the formation of the hierarchical structures. We used a reprecipitation method as a route to crystallized hierarchical structures of glutamic acid. The crystallization of hierarchical structures of glutamic acid under various experimental parameters, such as solvent compositions, arginine concentrations, and the chirality of the additive were thoroughly studied using several techniques including X-ray diffraction, scanning electron microscopy, and polarized microscopy. It was found that the formation of the hierarchical structures and their size, morphology, and porosity depend strongly on the arginine concentration. On the basis of our results, we propose a possible mechanism for the formation of hierarchical structures of glutamic acid based on the self-assembly principle. Overall, in this work we used the crystallization of l-glutamic acid hierarchical crystals in the presence of arginine as an additive as a model system to better understand the effects of polyelectrolyte additives on the crystallization of organic hierarchical crystals

Induced Crystallization of Amorphous Biosilica to Cristobalite by Silicatein

In nature it is known that silicatein (silica protein) controls the mineralization of a wide range of biosilicas. In this paper we present our results on the induced crystallization of biosilica to cristobalite, which is the thermodynamically most stable crystalline form of silica at a relatively low temperature and ambient pressure. The phase transformation of biosilica from marine sponges to cristobalite under thermal treatment was investigated by a variety of methods, e.g., X-ray diffraction, high-resolution electron microscopy–electron diffraction, and optical methods such as Fourier transform infrared (FTIR) spectroscopy. Our results show that biosilica from marine sponges exhibits a direct phase transformation to cristobalite structure at a relatively low temperature (850 °C). Furthermore, it is shown that porous silica templated with silicatein proteins extracted from sponges also exhibits a phase transformation to cristobalite structure at a relatively low temperature. The surprising discovery that silicatein filaments can induce direct crystallization of biosilica to cristobalite highlights the role of silicatein in governing the synthesis and the hierarchical structure control of biosilica minerals

Liquid-Mercury-Supported Langmuir Films of Ionic Liquids: Isotherms, Structure, and Time Evolution

Ionic liquids have been intensively developed for the last few decades and are now used in a wide range of applications, from electrochemistry to catalysis and nanotechnology. Many of these applications involve ionic liquid interfaces with other liquids and solids, the subnanometric experimental study of which is highly demanding, and has been little studied to date. We present here a study of mercury-supported Langmuir films of imidazolium-based ionic liquids by surface tensiometry and X-ray reflectivity. The charge-delocalized ionic liquids studied here exhibit no 2D lateral order but show diffuse surface-normal electron density profiles exhibiting gradual mercury penetration into the ionic liquid film, and surface-normal structure evolution over a period of hours. The effect of increasing the nonpolar alkyl chain length was also investigated. The results obtained provide insights into the interactions between these ionic liquids and liquid mercury and about the time evolution of the structure and composition of their interface

Characterization of Crystal Chirality in Amino Acids Using Low-Frequency Raman Spectroscopy

We present a new method for differentiating racemic crystals from enantiopure crystals. Recently, developments in optical filters have enabled the facile use of Raman spectroscopy to detect low-frequency vibrational (LFV) modes. Here, for the first time, we use Raman spectroscopy to characterize the LFV modes for crystalline organic materials composed of chiral molecules. The LF-Raman spectra of racemic and enantiopure crystals exhibit a significant variation, which we attribute to different hydrogen-bond networks in the chiral crystal structures. Across a representative set of amino acids, we observed that when comparing racemic versus enantiopure crystals, the available LFV modes and their relative scattering intensity are strong functions of side chain polarity. Thus, LF-Raman can be used as a method that is complementary to the currently used methods for characterizing crystal chirality due to simpler, faster, and more sensitive measurements, along with the small sample size required, which is limited by the laser-beam diameter in the focus

Chiral Metal-Oxide Nanofilms by Cellulose Template Using Atomic Layer Deposition Process

In this article, we describe an advance approach for the fabrication of chiral metal-oxide nanofilms. Our approach is based on the atomic layer deposition of titania and alumina nanofilms onto cellulose microfibers, used as chiral templates, leading to the formation of chiral nanofilms with a spatial fibrous structure. The chiral nanofilms were extensively characterized by X-ray photoelectron spectroscopy and high-resolution electron microscopy. The chiral property of the produced titania nanofilms was studied by enantioselective adsorption experiments using circular-dichroism spectroscopy and chiral high-performance liquid chromatography. We demonstrate the application of the titania chiral nanofilms for enantioselective crystallization. Overall, the basic principle for the preparation of chiral nanofilms by atomic layer deposition is demonstrated, as well as their uses for several enantioselective applications

Potential of Hazardous Waste Encapsulation in Concrete Compound Combination with Coal Ash and Quarry Fine Additives

Coal power plants are producing huge amounts of coal ash that may be applied to a variety of secondary uses. Class F fly ash may act as an excellent scrubber and fixation reagent for highly acidic wastes, which might also contain several toxic trace elements. This paper evaluates the potential of using Class F fly ashes (<20% CaO), in combination with excessive fines from the limestone quarry industry as a fixation reagent. The analysis included leaching experiments (EN12457–2) and several analytical techniques (ICP, SEM, XRD, etc.), which were used in order to investigate the fixation procedure. The fine sludge is used as a partial substitute in concrete that can be used in civil engineering projects, as it an environmentally safe product