Solvothermal growth

Solvothermal growth of single crystals or poly crystalline aggregates from hydro-thermal or ammonothermal solution. 

The most important nanomaterial synthesis methods include nanolithography techniques, template-directed syntheses, vapor-phase methods, vapor-liquid-solid (VLS) methods, solution-liquid-solid (SLS) approaches, sol-gel processes, micelle, vapor deposition, solvothermal methods, and pyrolysis methods [1, 2]. For many of these procedures, the control of size and shape, the flexibility in the materials that can be synthesized, and the potential for scaling up, are the main limitations. In general, the understanding of the growth mechanism of any as-... 

The preparation of ZnSe materials is an area of interest and study. The coordinating ability of the solvent used in the solvothermal synthesis of zinc selenide was demonstrated to play an important role in the nucleation and growth of nanocrystalline ZnSe.604 Thermolysis of bis [methyl( -hexyl)di-seleno]carbamato]zinc gave highly monodispersed particles characterized by electronic spectroscopy, photoluminescence, X-ray diffraction, and electron microscopy.605... 

The major drawbacks to standard sol-gel synthesis include slow growth rate and the typically amorphous product, rather than defined crystals, which requires crystallization and post annealing steps. Growth rate and crystallization of the fabricated hybrid can be improved via solvothermal, reflux [224], sonication, and microwave [225] treatment. However, the air oxidation of CNTs (600 °C) and graphene (450 °C) may still be lower than MO crystallization temperature. Moreover, it has been shown that the MO coatings on CNTs can drastically affect their thermal oxidation, particularly with easily reducible metal oxides (e.g. TiOz = 520 °C, Bi203 = 330 °C) [180]. It appears that metal oxides can catalyze the oxidation of CNTs via a Mars van Krevelen mechanism, limiting the maximum temperature of their synthesis as well as applications (i.e. catalysis, fuel cells). 

Crystallization of TiO occurs during solvothermal treatment at high pressure, and the crystals grow to primary particle size through homo-coagulation. At this point, excess solvent partially suppresses further crystal growth as a result, the particle size becomes smaller than that in the sol-gel method. However, hydrolysis and condensation reactions occur very rapidly in sol-gel synthesis of transition metal oxides, therefore uniform and ultrafme products are difficult to obtain. 

Synthesis of ZnO Nanorods. In order to carry out the growth study in the absence of any capping agent, ZnO nanorods were prepared by the reaction of zinc acetate dihydrate (Zn(CH3-C00)2 2H20) and sodium hydroxide in ethanol at 100 °C under solvothermal conditions. The reaction was stopped at different times (I, 2, 3, 6, 12, 18, and 24 h), and the products were analyzed by TEM and SAXS. In a typical synthesis, Zn(CH3-... 

Kiebach et al. (2005) SEM Organogermanates Multiple kinetics of nucleation and growth + + n.a. Solvothermal synthesis... 

By using polymer-controlled growth in ethylenediamine at 170°C, very long CdS nanowires (100px40 nm) were synthesized (Fig. 9a) [36]. Cadmium sulfide with different morphologies, such as nanoparticles and nanorods (Fig. 9b) [39], peanut-like nanostructures [37] and hollow nanospheres [38] (Fig. 9c) were prepared via solvothermal routes. 

Various compounds have been prepared by solvothermal reactions metals, metal oxides, chalcogenides, - ° nitrides, - -" phosphides, open-framework structures, - oxometalate clusters, - organic-inorganic hybrid materials, - - and even carbon nanotnbes. - Most of the solvothermal products are nano- or microparticles with well-defined morphologies. The distribution of the particle size of the prodnct is nsnally qnite narrow, and formation of monodispersed particles is freqnently reported. - When the solvent molecules or additives are preferentially adsorbed on (or have a specific interaction with) a certain surface of the products, growth of the surface is prohibited and therefore products with unique morphologies may be formed by the solvothermal reaction. - - Thus nanorods, wires, tnbes, and sheets of various types of products have been obtained solvothermally. 

As a result of using organic phosphorus starting material, crystal growth was appropriately controlled. Nanowires of sphalerite-type GaP and InP (Figure 7.13) were prepared, suggesting a promising method for the solvothermal synthesis of one-dimensional III-V nanocrystallites. 

The en molecules play an important role in controlling the nucleation and growth of the CdS nanorods. As a bidentate ligand, en molecules may react with Cd + ions and form relatively stable complexes. Under appropriate solvothermal conditions, the complexes become unstable and decompose, which results in the formation of CdS nanorods [lOOj. A mono-dentate ligand, n-butylamrne, was found to be a shape controller for nanorods of CdS and MSe (M = Zn, Cd or Pb) [101]. Similarly, the precursor of ZnE(en)o.s (E = S, Se) could also form in en which then is converted to ZnSe nanopartides via pyrolysis in solvothermal conditions [102]. The coordinating ability of the solvent was found to play an important role in the nucleation and growth of nanocrystallites [103]. 

So far, hydrothermal and solvothermal synthesis have been widely used in the 1) modification, 2) crystal growth and morphology control, 3) phase-transition study, and 4) discovery of new species of zeolites and porous materials. 

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