Pre-nucleation clusters as solute precursors in crystallisation

Crystallisation is at the heart of various scientific disciplines, but still the understanding of the molecular mechanisms underlying phase separation and the formation of the first solid particles in aqueous solution is rather limited. In this review, classical nucleation theory, as well as established concepts of spinodal decomposition and liquid–liquid demixing, is introduced together with a description of the recently proposed pre-nucleation cluster pathway. The features of pre-nucleation clusters are presented and discussed in relation to recent modifications of the classical and established models for phase separation, together with a review of experimental work and computer simulations on the characteristics of pre-nucleation clusters of calcium phosphate, calcium carbonate, iron(oxy)(hydr)oxide, silica, and also amino acids as an example of small organic molecules. The role of pre-nucleation clusters as solute precursors in the emergence of a new phase is summarized, and the link between the chemical speciation of homogeneous solutions and the process of phase separation via pre-nucleation clusters is highlighted

Materials Fundamentals of Gate Dielectrics

This book presents materials fundamentals of novel gate dielectrics that are being introduced into semiconductor manufacturing to ensure the continuous scalling of the CMOS devices. This is a very fast evolving field of research so we choose to focus on the basic understanding of the structure, thermodunamics, and electronic properties of these materials that determine their performance in device applications. Most of these materials are transition metal oxides. Ironically, the d-orbitals responsible for the high dielectric constant cause sever integration difficulties thus intrinsically limiting high-k dielectrics. Though new in the electronics industry many of these materials are wel known in the field of ceramics, and we describe this unique connection. The complexity of the structure-property relations in TM oxides makes the use of the state of the art first-principles calculations necessary. Several chapters give a detailed description of the modern theory of polarization, and heterojunction band discontinuity within the framework of the density functional theory. Experimental methods include oxide melt solution calorimetry and differential scanning calorimetry, Raman scattering and other optical characterization techniques, transmission electron microscopy, and x-ray photoelectron spectroscopy. Many of the problems encounterd in the world of CMOS are also relvant for other semiconductors such as GaAs. A comprehensive review of recent developments in this field is thus also given. The book should be of interest to those actively engaged in the gate dielectric research, and to graduate students in Materials Science, Materials Physics, Materials Chemistry, and Electrical Engineering

Effect of the Composition of Copolymers Based on Glycidyl Methacrylate and Fluoroalkyl Methacrylates on the Free Energy and Lyophilic Properties of the Modified Surface

This study proposes to use reactive copolymers based on glycidyl methacrylate and fluoroalkyl methacrylates with a low fluorine content in the monomer unit as agents to reduce the surface free energy (SFE). This work reveals the effect of the structure and composition of copolymers on the SFE and water-repellent properties of these coatings. On a smooth surface, coatings based on copolymers of glycidyl methacrylate and fluoroalkyl methacrylates with fluorine atoms in the monomer unit ranging from three to seven are characterized by SFE values in the range from 25 to 13 mN/m, which is comparable to the values for polyhedral oligomeric silsesquioxanes and perfluoroalkyl acrylates. On textured aluminum surfaces, the obtained coatings provide time-stable superhydrophobic properties with contact angles up to 170° and sliding angles up to 2°. The possibility of using copolymers based on glycidyl methacrylate and fluoroalkyl methacrylates for the creation of self-cleaning polymer coatings is shown

The Energetics of Surfactant‐Templating of Zeolites

Mesoporosity can be conveniently introduced into zeolites by treating them in basic surfactant solutions. The apparent activation energy involved in the formation of mesopores in USY by surfactant‐templating was determined using a combination of in situ synchrotron X‐ray diffraction and ex situ gas adsorption. Additionally, techniques such as pH measurement and thermogravimetry/differential thermal analysis were employed to determine OH− evolution and cetyltrimethylammonium ion (CTA+) uptake during the development of mesoporosity, thereby providing information about the different steps involved. The combination of both in situ and ex situ techniques has allowed determination of the apparent activation energies of the different processes involved in the mesostructuring of USY zeolites for the first time. Apparent activation energies are of the same order of magnitude (30–65 kJ mol−1) as those involved in the crystallization of zeolites. Hence, important mechanistic insight into the surfactant‐templating method was obtained.This work was supported by the Spanish MINECO (PCIN-2013-164) and the EC through the ERA-NET CAPITA(AEI/FEDER, project WAVES, EP7-NMP-266543) and the ALBA Synchrotron (refs. 2016021622 and 2016021729). E.S. thanks the Spanish MINECO and AEI/FEDER, UE (CTQ2015-74494-JIN). E.S. and N.L. acknowledge the University of Alicante support (UATALENTO16-03 and UATALENTO17-05, respectively)

Fetuin-A Is a Mineral Carrier Protein: Small Angle Neutron Scattering Provides New Insight on Fetuin-A Controlled Calcification Inhibition

Clinical studies and animal experiments have shown that the serum protein fetuin-A is a highly effective inhibitor of soft tissue calcification. This inhibition mechanism was elucidated on the basis of an in vitro fetuin-A-mineral model system. In a previous study, we found that in a two-stage process ∼100-nm sized calciprotein particles (CPPs) were formed whose final stage was stabilized by a compact outer fetuin-A monolayer against further growth. Quantitative small-angle neutron scattering data analysis revealed that even at a fetuin-A concentration close to the stability limit, only approximately one-half of the mineral ions and only 5% of the fetuin-A were contained in the CPPs. To uncover the interplay of the remaining supersaturated mineral ion fraction and of the 95% non-CPP fetuin-A, we explored the fetuin-A monomer fraction in solution by contrast variation small-angle neutron scattering. Our results suggest that the mineral ions coalesce to subnanometer-sized clusters, reminiscent of Posner clusters, which are stabilized by fetuin-A monomers. Hence, our experiments revealed a second mechanism of long-term mineral ion stabilization by the fetuin-A that is complementary to the formation of CPPs