solvothermal

Solvothermal synthesis refers to chemical reactions conducted in a solvent at elevated temperature and pressure within a sealed vessel, typically an autoclave. While the term is often used interchangeably with hydrothermal synthesis when water is the solvent, solvothermal explicitly emphasizes non-aqueous or mixed-solvent systems. The approach is widely used to produce crystalline solids, nanomaterials, and coordination polymers under controlled conditions that influence solubility and reaction kinetics.

Reactions are carried in closed reactors at temperatures from about 100 to 350°C, with pressures corresponding to the sealed solvent’s vapor pressure. Common solvents include water-rich mixtures, alcohols, ethylene glycol, DMF, DMSO, and other organic media. The choice of solvent and additives can direct crystal phase, particle size, and morphology, enabling materials that are difficult to obtain under conventional conditions. Microwave-assisted solvothermal methods can accelerate heating and reactions.

Applications include the synthesis of metal oxides, sulfides, and nitrides; metal-organic frameworks and coordination polymers; and various nanostructured materials such as nanorods, nanosheets, and quantum dots. Solvothermal routes are used in catalysis, energy storage, electronics, and optics.

The method offers broad solvent compatibility and tunable thermodynamics, enabling unusual polymorphs or metastable phases. Limitations include solvent toxicity and environmental concerns, challenges for scaling up, and sometimes long reaction times. Safety concerns center on high-pressure operation and handling of reactive precursors.