A revolution in novel nanoparticles and colloidal building blocks has been enabled by recent breakthroughs in particle synthesis These new particles are poised to become the ‘atoms’ and ‘molecules’ of tomorrow’s materials if they can be successfully assembled into useful structures Here, we discuss the recent progress made in the synthesis of nanocrystals and colloidal particles and draw analogies between these new particulate building blocks and better-studied molecules and supramolecular objects We argue for a conceptual framework for these new building blocks based on anisotropy attributes and discuss the prognosis for future progress in exploiting anisotropy for materials design and assembly

/pdf/anisotropy-of-building-blocks-and-their-assembly-into-2quept9gqn.pdf

Anisotropy of building blocks and their assembly into complex structures

A general method to coat colloids with silica is described. The amphiphilic, nonionic polymer poly(vinylpyrrolidone) (PVP) was adsorbed to various colloidal particles such as small gold colloids, gold-shell silica-core particles, small and large silver colloids, boehmite rods, gibbsite platelets, and positively or negatively charged polystyrene. After this functionalization the stabilized particles could be transferred to a solution of ammonia in ethanol and directly coated with smooth and homogeneous silica shells of variable thickness by addition of tetraethoxysilane in a seeded growth process. The length of the polymer used strongly influences the stability of the colloids and the homogeneity and smoothness of the initial silica coating. This method is especially useful for colloidal particles that cannot be covered directly with SiO2 by a Stober-like growth process. Compared to methods known from the literature for the coating of such particles, this new method is faster and requires neither the use o...

/pdf/a-general-method-to-coat-colloidal-particles-with-silica-340pnf9yn2.pdf

A General Method To Coat Colloidal Particles with Silica

Reference LPI-ARTICLE-1999-017View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

/pdf/metal-oxide-surfaces-and-their-interactions-with-aqueous-22jt31pax0.pdf

Metal Oxide Surfaces and Their Interactions with Aqueous Solutions and Microbial Organisms.

Although many recent reviews emphasize a uniformity in granulite pressure–temperature (P–T) conditions and paths, granulites in reality preserve a spectrum of important petrogenetic features which indicate diversity in their modes of formation. A thorough survey of over 90 granulite terranes or occurrences reveals that over 50% of them record P–T conditions outside the 7.5 ± 1 kbar and 800 ± 50 °C average granulite regime preferred by many authors. In particular, an increasing number of very high temperature (900−1000 °C) terranes are being recognized, both on the basis of distinctive mineral assemblages and geothermobarometry. Petrogenetic grid and geothermobarometric approaches to the determination and interpretation of P–T histories are both evaluated within the context of reaction textures to demonstrate that the large range in P–T conditions is indeed real, and that both near-isothermal decompression (ITD) and near-isobaric cooling (IBC) P–T paths are important. Amphibolite–granulite transitions promoted by the passage of CO2-rich fluids, as observed in southern India and Sri Lanka, are exceptional and not representative of fluid-related processes in the majority of terranes. It is considered, on the contrary, that fluid-absent conditions are typical of most granulites at or near the time of their recorded thermal maxima.ITD granulites are interpreted to have formed in crust thickened by collision, with magmatic additions being an important extra heat source. Erosion alone is not, however, considered to be the dominant post-collisional thinning process. Instead, the ITD paths are generated during more rapid thinning (1−2 mm/yr exposure) related to tectonic exhumation during moderate-rate or waning extension. IBC granulites may have formed in a variety of settings. Those which show anticlockwise P–T histories are interpreted to have formed in and beneath areas of voluminous magmatic accretion, with or without additional crustal extension. IBC granulites at shallow levels (< 5 kbar) may also be formed during extension of normal thickness crust, but deeper-level IBC requires more complex models. Many granulites exhibiting IBC at deep crustal levels may have formed in thickened crust which underwent very rapid (5 mm/yr) extensional thinning subsequent to collision. It is suggested that the preservation of IBC paths rather than ITD paths in many granulites is primarily related to the rate and timescale of extensional thinning of thickened crust, and that hybrid ITD to IBC paths should also be observed.Most IBC granulites, and probably many ITD granulites, have not been exposed at the Earth's surface as a result of the tectonic episodes which produced them, but have resided in the middle and lower crust for long periods of time (100−2000 Ma) following these events. The eventual exhumation of most granulite terranes only occur through their incorporation in later tectonic and magmatic events unrelated to their formation.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756800022330

The origins of granulites: a metamorphic perspective

The sol−gel encapsulation of labile biological materials with catalytic and recognition functions within robust polymer matrices remains a challenging task, despite the considerable research that has been focused on this field. Herein, we describe a new class of precursors, based around polyol silicates and polyol siloxanes, especially those derived from glycerol, that addresses problems faced with traditional bioencapsulation protocols. Poly(glyceryl silicate) (PGS) was prepared and employed for sol−gel bioentrapment, in an approach distinguished by a high biocompatibility and mild encapsulation conditions, and which enables the reproducible and efficient confinement of proteins and cells inside silica. The methodology was extended to metallosilicate, alkylsiloxane, functionalized siloxane, and composite sol−gels, thereby allowing the fabrication of a physicochemically diverse range of bio-doped polymers. The hybrid materials display activities approaching those of the free biologicals, together with the...

Encapsulation of Biologicals within Silicate, Siloxane, and Hybrid Sol−Gel Polymers: An Efficient and Generic Approach

Preferential leakage of H2O from fluid inclusions containing multiple gas components has been suspected in natural metamorphic rocks and has been demonstrated experimentally for synthetic H2O-CO2-rich inclusions in natural quartz. Knowledge of the physical and chemical characteristics of the leakage mechanism, which may be very complex, increases the value of natural fluid inclusions to metamorphic geology. It is proposed that crystal defects play a major role in nondecrepitative preferential H2O leakage through quartz, and remain effective during metamorphism. Inclusions with either an internal overpressure or underpressure produce strain in the adjacent quartz crystal via the nucleation of many dislocations and planar defects (like Dauphine twin boundaries). These defects allow preferential loss of H2O from H2O-CO2-rich inclusions at supercritical conditions. The transport capacity of this leakage mechanism is enhanced by nucleation of small bubbles on defect structures. The nucleation of these bubbles seems to be a recovery process in strained crystals. Solubility gradients of quartz in water in a crystal with internally underpressurized inclusions may result in optical visible implosion halos in a three dimensional spatial arrangement, caused by the growth of small bubbles at the expense of the larger original fluid inclusion. Natural fluid inclusions from Naxos (Greece) are always associated with numerous interlinked dislocations. These dislocations may have been produced by plastic derormation or by crystal growth related processes (e.g. crack healing). The presence of small bubbles on these dislocations indicates that a similar leakage mechanism for H2O must have occurred in these rocks.

/pdf/a-mechanism-for-preferential-h-2-o-leakage-from-fluid-312h20u7fj.pdf

A mechanism for preferential H 2 O leakage from fluid inclusions in quartz, based on TEM observations

Carbon, hydrogen, and oxygen isotope studies of the regional metamorphic complex at Naxos, Greece

Fairly monodisperse colloidal boehmite fibrils with a high aspect ratio were synthesized by hydrothermal treatment at 150°C of an acidified aqueous alkoxide solution, prepared by adding an aqueous HCl solution to an aluminum alkoxide precursor. The average particle length could be controlled between about 100 and 500 nm by varying the initial amounts of alkoxide and acid. Using two different alkoxides in a 1:1 molar ratio yielded the most needlelike product, having a particle length standard deviation of 40%. The boehmite particles were polycrystalline and contained 0.14 mol of excess H2O per mol of AlOOH, bound to the particle surface.

/pdf/preparation-of-colloidal-boehmite-needles-by-hydrothermal-mazin03hci.pdf

Preparation of Colloidal Boehmite Needles by Hydrothermal Treatment of Aluminum Alkoxide Precursors

https://fluids.unileoben.ac.at/Publications_files/BakkerJansen1991.pdf

Experimental post-entrapment water loss from synthetic CO2-H2O inclusions in natural quartz

THE fluid density, carbon dioxide content, and therefore the pressure-temperature conditions derived from fluid inclusions in meta-morphic rocks are commonly inconsistent with coexisting mineral assemblages Here we report hydrothermal experiments mimicking isobaric cooling and isothermal decompression, which indicate changes in density and composition without significant change in volume of H2O–CO2 inclusions in quartz A simultaneous change to CO2-rich compositions and lower densities indicates that water is leaking from the inclusions We argue that preferential water leakage is made possible by microscopic unmixing of the H2O–CO2 mixture caused by physical and chemical interactions with the inclusion wall Water transport then occurs by the movement of water-saturated dislocations through the hydrothermally recrystallizing quartz

J. Ben H. Jansen

Papers

A mechanism for preferential H 2 O leakage from fluid inclusions in quartz, based on TEM observations

Carbon, hydrogen, and oxygen isotope studies of the regional metamorphic complex at Naxos, Greece

Preparation of Colloidal Boehmite Needles by Hydrothermal Treatment of Aluminum Alkoxide Precursors

Experimental post-entrapment water loss from synthetic CO2-H2O inclusions in natural quartz

Preferential water leakage from fluid inclusions by means of mobile dislocations