Liquid-phase preparation method

Liquid-phase preparation methods use metal-organic precursors which are converted to inorganic materials, either in water or in an organic solvent. The sol-gel process has a long history in the preparation of silicate systems and other oxides. 

The primary goal of the researchers has been to produce Q-dots possessing all of the attributes of the Q-dots prepared using liquid-phase synthetic methods (that is adjustability of the nanocrystal identity and diameter and size monodispersity) and also the technological utility of Q-dots prepared by MBE (specifically, the deposition of nanocrystals with a defined orientation and an electrical output contact). It was shown that the E/C-synthesized 5-CuI and CdS Q-dots were indeed epitaxial with narrow size distribution and strong photoluminescence tunable by the particle size. Qne of the advantages of the E/C method is that it can be made size selective. The key point is that the size as well as the size dispersion of product nanoparticles are directed actually by the corresponding properties of the metal nanoparticles therefore the first deposition step assumes special importance. 

The liquid-phase reduction method was applied to the preparation of the supported catalyst [27]. Virtually, Muramatsu et al. reported the controlled formation of ultrafine Ni particles on hematite particles with different shapes. The Ni particles were selectively deposited on these hematite particles by the liquid-phase reduction with NaBFl4. For the concrete manner, see the following process. Nickel acetylacetonate (Ni(AA)2) and zinc acetylacetonate (Zn(AA)2) were codissolved in 40 ml of 2-propanol with a Zn/Ni ratio of 0-1.0, where the concentration of Ni was 5.0 X lO mol/dm. 0.125 g of Ti02... 

The authors concluded that using the gas-phase preparation method leads to better control of variables during preparation and to higher dispersions of the active component over the conventional liquid phase impregnation method. 

Catalytic hydrogenation of nitriles has long been used for the preparation of various amines. It is performed over metallic catalysts mostly in the liquid phase. The method is also of industrial importance and has been applied to the commercial production of various amines, for example, various aliphatic amines from fatty acid nitriles, hexa-methylenediamine (1,6-hexanediamine) from adiponitrile, and xylene-a,a -diamines [bis(aminomethyl)benzenes] from the corresponding phthalonitriles. 

Highly dispersed Rh nanoparticles were successfully loaded on GaN ZnO without aggregation by adsorbing Rh nanoparticles that were stabilized by 3-mercapto-1-propanesulfuric acid (prepared by a liquid-phase reduction method) onto GaN ... 

In emulsion polycondensation, the polymer formation reaction occurs in the bulk of one of the liquid phases. This method is employed for irreversible, exothermic polycondensations, accompanied by the liberation of a side product. Highly reactive monomers (e.g., dichlorides or dicarboxylic acids, diamines, etc.) are most suitable for emulsion polycondensation. To date, the number of step-growth polymers that are prepared using emulsion or mini-emulsion polymerization methods is small, and the technological aspects of this technique... 

Thin films prepared using the sol-gel method are usually amorphous before heat treatment. High-temperature heat treatment is generally required for the films crystallization and densification of the films. For application of thin films to substrates with low thermal stability such as polymer substrates, lowering of the crystallization temperature is necessary. Consequently, many researchers have recently reported formation of oxide crystals, such as T1O2, Sn02 and ZnO, at low temperatures [1, 2]. For example, the preparation of various oxide thin films from aqueous metal-fluoro complex solutions using the liquid phase deposition method... 

We consider vapor phase preparation methods in the following categories (1) reactions between a gas and a solid, (2) reactions between a gas and a liquid, and (3) reactions between two or more gases. 

Dldeoxylnosine has been prepared by Barton deoxygenation of the 5 -0-benzoyl-2 -deoxy compound. Liquid-liquid and solid-liquid phase transfer methods have been used to prepare 2 -deoxyribofuranosides of pyrrolol2,3-dlpyrimidlnes (7-deazapurines). which have been converted to 2, 3 -dideo3Qrcompounds by Barton-type procedures amongst the... 

Alkyl cyanides have been prepared by three major variations of the phase transfer method. These include the liquid-liquid phase transfer method (including catalysis by quats and amines), the crown catalyzed solid-liquid method and the tri-phase catalytic method. Each of these methods has been discussed with reference to the mechanism in the preceding section and it remains largely to exemplify these approaches. It should be noted, however, that numerous stoichiometric syntheses of aliphatic nitriles are available, including those involving dipolar aprotic solvents [12]. 

This chapter reviewed recent advances in the preparation of hollow oxide nanoparticles by liquid-phase deposition methods. Hollow particles with various compositions, controlled shell structures, and controlled shapes and sizes have successfully been obtained by employing either template or template-free method, and many interesting properties arising from their unique structural features have been reported. Large-scale and low-cost production by environment-friendly processes promises practical applications in many fields. 

Figure 1.11 summarizes the general procedure of the liquid-phase synthesis method used in the preparation of perovskite oxides with a large surface... 

Diethylene glycol method. Place 0-5 g. of potassium hydroxide pellets, 3 ml. of diethylene glycol and 0 5 ml. of water in a 10 or 25 ml. distilling flask heat the mixture gently until the alkali has dissolved and cool. Add 1-2 g. of the ester and mix well. Fit the flask with a thermometer and a small water-cooled condenser in the usual way. Heat the flask over a small flame whilst shaking gently to mix the contents. When only one liquid phase, or one hquid phase and one solid phase, remains in the flask, heat the mixture more strongly so that the alcohol distils. Identify the alcohol in the distillate by the preparation of the 3 5 dinitrobenzoate (Section 111,27,2). 

The major method for preparing the monomer commercially since the early 1960s has been the so-called balanced process from ethylene. In the first stage of the reaction, 1,2-dichloroethane is prepared by reacting ethylene with chlorine in either the vapour or the liquid phase Figure 12.2). In a typical liquid phase... 

Liquid-liquid extraction is a basic process already applied as a large-scale method. Usually, it does not require highly sophisticated devices, being very attractive for the preparative-scale separation of enantiomers. In this case, a chiral selector must be added to one of the liquid phases. This principle is common to some of the separation techniques described previously, such as CCC, CPC or supported-liquid membranes. In all of these, partition of the enantiomers of a mixture takes place thanks to their different affinity for the chiral additive in a given system of solvents. 

Commercially available poiybrominated aromatic ethers have been analyzed by reversed phase high performance liquid chromatography. NMR spectra of material isolated by preparative methods served to identify the observed peaks as congeners of tetrabromo to nonabromo diphenyl ether. A bromination pathway was clearly indicated. 

Borides have been prepared as single crystals by making use of gas-phase, liquid-phase and flux methods, depending on the thermal stability of the boride and on the required size and perfection of the single crystals. 

Modified hotocatalysts were prepared using commercial and synthesized Ti02. The modification was carried out in two different methods, i.e. platinization with H2PtCl6 solution and metallization with leached solution from wasted catalytic converter. They were characterized by UV-DRS, BET, and XRD and tested their catalytic performance for decomposition and oxidation of TCE in liquid phase. 

Solid solutions generally form in one of two ways, both of which involve forming the solid flxim the liquid phase. One way is to heat the solid solvent until it melts, add the solutes into the molten material, and then cool the melt until it solidifies. Solid solutions of one metal in another, such as brass and steel, are prepared in this way. A second method is to dissolve the solid solvent and solutes in an appropriate liquid, then cool or evaporate the liquid until a solid precipitates. Solid solutions of organic substances can form in this manner. 

The reverse ME technique provides an easy route to obtain monodispersed metal nanoparticles of the defined size. To prepare supported catalyst, metal nanoparticles are first purified from the ME components (liquid phase and excess of surfactant) while retaining their size and monodispersity and then deposited on a structured support. Due to the size control, the synthesized material exhibits high catalytic activity and selectivity in alkyne hydrogenation. Structured support allows suitable catalyst handling and reuse. The method of the catalyst preparation is not difficult and is recommended for the... 

The main advantage of the salt reduction method in the liquid phase is that it is reproducible and allows colloidal nanoparticles with narrow size distribution to be prepared. 

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