Fingerprint plots of Hirshfeld surfaces were used to locate and analyze the deficiencies in various methodologies employed in the determination of the relative energies of five polymorphs of 1,8-dihydroxyanthraquinone. Nine crystallographically independent molecules were characterized by X-ray crystallography and Hirshfeld surfaces were derived from the X-ray structures. The space groups and number of independent molecules (Z′) for each of the polymorphs (1−5) is as follows: (1) P41 (or P43),Z′ = 1; (2) Pca21, Z′ = 2; (3) P1, Z′ = 4; (4) P21/n, Z′ = 1; (5) P41212 (or P43212), Z′ = 0.5. Form 1 is the most thermodynamically stable among the reproducible structures, as established by competitive solubility tests, followed by 2 and then 4. The unrestrained structures of the five polymorphs were computed using the CVFF and COMPASS force fields as well as with the density functional code, SIESTA.

Hirshfeld surfaces identify inadequacies in computations of intermolecular interactions in crystals: pentamorphic 1,8-dihydroxyanthraquinone

Development of renewable energy technologies has been a significant area of research amongst scientists with the aim of attaining a sustainable world society Solar thermal fuels that can capture, convert, store, and release solar energy in the form of heat through reversible photoisomerization of molecular photoswitches such as azobenzene derivatives are currently in the limelight of research Herein, we provide a state-of-the-art account on the recent advancements in solar thermal fuels based on azobenzene photoswitches We begin with an overview on the importance of azobenzene-based solar thermal fuels and their fundamentals Then, we highlight the recent advances in diverse azobenzene materials for solar thermal fuels such as pure azobenzene derivatives, nanocarbon-templated azobenzene, and polymer-templated azobenzene The basic design concepts of these advanced solar energy storage materials are discussed, and their promising applications are highlighted We then introduce the recent endeavors in the molecular design of azobenzene derivatives toward efficient solar thermal fuels, and conclude with new perspectives on the future scope, opportunities and challenges It is expected that continuous pioneering research involving scientists and engineers from diverse technological backgrounds could trigger the rapid advancement of this important interdisciplinary field, which embraces chemistry, physics, engineering, nanoscience, nanotechnology, materials science, polymer science, etc

Azobenzene-based solar thermal fuels: design, properties, and applications

A systematic multi-step screening of numerous salt hydrates for low temperature thermochemical energy storage

Langmuir-Blodgett films

Structure and order in thermal dehydrations of crystalline solids

Recent advances in microscope techniques have been used in a reinvestigation of the kinetics of the formation and the growth of nuclei developed during dehydration of cleaved (111) faces of relatively perfect crystals of the alums KAl(SO 4 ) 2 . 12H 2 O and KCr(SO 4 ) 2 . 12H 2 O , and solid solutions of five intermediate compositions, KAl x Cr 1-x (SO 4 ) 2 . 12H 2 O. There was observational evidence that nuclei are usually produced at sites of identifiable surface imperfection and that such sites are not randomly distributed across the reactant surfaces. Nucleation is a deceleratory process and, during the later stages, the continued generation of new reaction sites was associated with surface cracking. The rates of interface advance are constant at the boundaries of established nuclei, though this stability sometimes followed an initial period of either more or less rapid growth. The implications of these observations are discussed for the formulation of yield-time kinetic expressions for solid state decomposition. The activation energies determined for the constant rate of interface advance during dehydrations of chrome alum and the solid solutions were between 70 and 93 kJ mol -1, with no systematic dependence on composition discerned, and the value for aluminium alum was greater (108 kJ mol -1 ). Textural examinations of partially reacted surfaces give evidence that exposure to vacuum results in modification, attributable to water loss, of all the reactant surface and that dehydration is not restricted to the interface comprising the reactant-product contact zone. It is believed that each growth nucleus arises as a consequence of a local recrystallization and this is promoted at the interface by water temporarily retained within cracks and pores of the reactant and between the finely divided product particles. We also conclude that local surface stresses exert a more significant control upon these reactions than has hitherto been generally realized. This model contrasts with many mechanistic features of the accepted theory of the subject. Rates of nucleus growth in the five solid solutions (mixed alums) were less than those of the pure end members, a minimum reactivity was found at the composition 2Al:1Cr. There were no significant changes in activation energy with composition and we discuss the significance of the Arrhenius parameters calculated for these reactions.

Nucleation and Growth Processes Occurring During the Dehydration of Certain Alums: The Generation, the Development and the Function of the Reaction Interface

The importance of the study of the collapse phenomenon both for low molecular weight and macromolecular substances has been shown by several authors (1). I t is known and it has often been stressed that the collapse pressure and area strongly depend upon the rate and the modality of compression even for substances which are simple and very stable at the W/A interphase (2). Here we report a study on the collapse rates of a carboxylic acid at the W/A interphase, undertaken partially to ascertain the reproducibility conditions for the kinetics of substance separation from the monolayer, but chiefly to understand the mechanism and the energies of this process. Arachidic acid was selected for its great stability at the W/A interphase and also because it had previously been used by one of us in a study, at the same interphase, of its mixtures with a polypeptide (3). These components showed surface incompatibility. An understanding of the mechanism of the collapse of arachidic acid may be helpful in determining the reasons of such an incompatibility. Surface pressure measurements as a function of time were performed and ellipsometry was used mainly to obtain the thickness of the bidimensional layer at various stages of collapse. EXPERIMENTAL

On the mechanism of collapse of arachidic acid films at the water/air interface

Some particular methods of collecting and treating DSC data for the determination of kinetic parameters in thermal decompositions of solids are suggested. These are mainly concerned with an extrapolation method to avoid the effect of the sample mass; with an approximate method to obtain the activation energy and the exponent of the decay-law for runs at constant temperature in which the total area under the thermal curve is not known with accuracy; and with a method to ascertain whether a particular decomposition takes place by a single mechanism or by a sequence of different mechanisms.

Some experimental aspects of DSC determination of kinetic parameters in thermal decompositions of solids

Low temperature study of w/o microemulsions by

By means of thermal analysis (DSC) applied to water-in-oil microemulsions, the experimental evidence is presented that, in the above systems, the water may exist in at least two different configurations, namely: interphasal and free, distinguished by the melting temperatures of respectively 263 K and 273 K. The role of both water and interphase in governing the microemulsion stability and structural changes upon water addition, are analysed. It is also shown that the enthalpic contribution associated with the thermal events ascribed to the dispersed phase (interphasal chorona + water core of the spherical droplet), are not particularly affected by the change of the continuous, hydrocarbon dispersing medium, provided that all the other components of the system as well as their mutual proportions are kept unchanged. The title system is, therefore, presented as a useful tool for studying the properties of water and interphasal water from both a scientific and a practical point of view, with particular regard to the forms of water in biosystems.

http://iopscience.iop.org/article/10.1209/0295-5075/2/6/008/pdf

Giulio G. T. Guarini

Papers

Nucleation and Growth Processes Occurring During the Dehydration of Certain Alums: The Generation, the Development and the Function of the Reaction Interface

On the mechanism of collapse of arachidic acid films at the water/air interface

Some experimental aspects of DSC determination of kinetic parameters in thermal decompositions of solids

Low temperature study of w/o microemulsions by

Experimental Evidence of Interphasal Water in Water-in-Oil Microemulsions