Self inorganic precursors

Figure 10. An electrostatic self-assembly process for forming mesoporous materials. (A) Organic and inorganic precursor solutions.

The early preparations of mesoporous silica film were conducted by growth from solution.[20,276]. The basic principle for the synthesis of ordered mesoporous films by growth from solution is to bring the synthesis solution (including a solvent, surfactant, and inorganic precursor) into contact with a second phase, e.g. solid (ceramic), gas (air), or another liquid (oil). The two-phase system is kept under specific conditions and the ordered film is formed at the interface. When the second phase is solid, it is the support on which the ordered film or membrane is grown. When the second phase is air or oil, the solid films are self-standing. 

Fig. 2 A schematic illustrating various routes used to synthesize mesostructured materials. Route I A cooperative self-assembly route relying on the interaction between the surfactant molecules and the inorganic precursors. Route II TLCT route. The inorganic framework condenses around preformed surfactant micelles in this case.

The formation of self-assembled materials is governed by a number of experimental parameters the choice of inorganic precursors and surfactants, the inorganic to surfactant ratio, amount of water and other solvents used, pH during synthesis, additives, reaction time and temperature, treatments used to stiffen the inorganic framework, and treatments to remove surfactant and obtain porosity, all decide the final ordering, porosity and surface area. It is well known that successful... 

Use of Dilute Solutions, The reactivity of the inorganic precursors can also be controlled by using low concentrations to lower the reaction rates. Consequent evaporation of solvent results in the formation of organized structure. This approach, introduced by Brinker et al. and termed as evaporation induced self-assembly. (EISA), allows the formation of powders, films, gels, and monoliths. 

RuOj nanotubes have been synthesized by the thermal decomposition of Ru3(CO)j2 inside anodic alumina membranes [248]. Transition metal oxide nanotubes have been prepared in water using iced hpid nanotubes as the template [249]. Self-assembled cholesterol derivatives act as templates as well as catalysts for the sol-gel polymerization of inorganic precursors to give rise to double-walled tubular structures of transition metal oxides [250]. Hydrothermal synthesis of single-crystalline y-Fefi ... 

A simple molecular model was used to simulate the equilibrium phase behaviour of hybrid materials for different inorganic precursors. Although some physical and chemical properties are not explicitly included in the model, it is possible to detect the general behaviour of the system such as the phase separation and the self-assembly of surfactants in hexagonal, lamellar or perforated lamellar structures. 

One proposal is that RNA molecules formed first. Somehow, the necessary inorganic precursors at random managed to produce the first RNA molecules, and these RNA molecules were self-repUcating. It is an intriguing theory. It is not my purpose here to affirm or rebut it, but simply to present it and state that it has not yet been proven. 

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