7
Solvothermal Synthesis of Non-Oxide
Nanomaterials
Y. T. Qian, Y. L. Gu, and J. Lu
7.1
Introduction
Inorganic non-oxide materials, such as III–V and II–VI group semiconductors,
carbides, nitrides, phosphides, and borides, are traditionally prepared by solid state
or gas-phase reactions. They have also been prepared via the pyrolysis of organometallic precursors but the products may be amorphous or poorly crystalline and a
crystallization treatment at higher temperature is necessary. This treatment, however, may result in the crystalline size being beyond the nanometer scale. Exploration of milder techniques for preparing non-oxide nanomaterials with controlled
shapes and sizes is very important for material science.
Hydrothermal synthesis is one of the important methods for producing fine
powders of oxides. A hydrothermal system is usually maintained at a temperature
beyond 100
C and the autogenous pressure of water exceeds the ambient pressure, which is favorable for the crystallization of products. Recent research indicates that the hydrothermal method is also a practical means for preparing chalcogenide and phosphide nanomaterials, and hydrothermal treatment is an effective
method for passivating porous silicons. Similar to hydrothermal synthesis, in a
solvothermal process, a non-aqueous solvent, which is sealed in an autoclave and
maintained in its superheated state, is the reaction medium, where the reactants
and products are prevented effectively from oxidation and volatilization and the
reaction and crystallization can be realized simultaneously. Furthermore, organic
solvents may be favorable for the dispersion of non-oxide nanocrystallites and may
stabilize some metastable phases.
In this chapter, we briefly review our recent progress in the solvothermal preparation of non-oxide nanomaterials. g-ray irradiation and room temperature synthesis of chalcogenide nanocrystallites are also briefly described but first we present
some progress in hydrothermal synthesis.
In different hydrothermal conditions, TiO 2 nanocrystallites (anatase and rutile)
with nine kinds of morphologies have been prepared [1, 2]. CdWO 4 nanorods [3],
which showed very strong photoluminescence at 486 nm (l ex ¼ 253 nm) at room
temperature, were prepared by a hydrothermal method at 130
C. Lead tungstate
170
Solvothermal Synthesis of Non-Oxide
Nanomaterials
Y. T. Qian, Y. L. Gu, and J. Lu
7.1
Introduction
Inorganic non-oxide materials, such as III–V and II–VI group semiconductors,
carbides, nitrides, phosphides, and borides, are traditionally prepared by solid state
or gas-phase reactions. They have also been prepared via the pyrolysis of organometallic precursors but the products may be amorphous or poorly crystalline and a
crystallization treatment at higher temperature is necessary. This treatment, however, may result in the crystalline size being beyond the nanometer scale. Exploration of milder techniques for preparing non-oxide nanomaterials with controlled
shapes and sizes is very important for material science.
Hydrothermal synthesis is one of the important methods for producing fine
powders of oxides. A hydrothermal system is usually maintained at a temperature
beyond 100
C and the autogenous pressure of water exceeds the ambient pressure, which is favorable for the crystallization of products. Recent research indicates that the hydrothermal method is also a practical means for preparing chalcogenide and phosphide nanomaterials, and hydrothermal treatment is an effective
method for passivating porous silicons. Similar to hydrothermal synthesis, in a
solvothermal process, a non-aqueous solvent, which is sealed in an autoclave and
maintained in its superheated state, is the reaction medium, where the reactants
and products are prevented effectively from oxidation and volatilization and the
reaction and crystallization can be realized simultaneously. Furthermore, organic
solvents may be favorable for the dispersion of non-oxide nanocrystallites and may
stabilize some metastable phases.
In this chapter, we briefly review our recent progress in the solvothermal preparation of non-oxide nanomaterials. g-ray irradiation and room temperature synthesis of chalcogenide nanocrystallites are also briefly described but first we present
some progress in hydrothermal synthesis.
In different hydrothermal conditions, TiO 2 nanocrystallites (anatase and rutile)
with nine kinds of morphologies have been prepared [1, 2]. CdWO 4 nanorods [3],
which showed very strong photoluminescence at 486 nm (l ex ¼ 253 nm) at room
temperature, were prepared by a hydrothermal method at 130
C. Lead tungstate
170