Methods of Chemical Synthesis in the Synthesis of Nanomaterial and Nanoparticles by the Chemical Deposition Method: A Review

Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality and high-performance solid materials. The process is often used in the semiconductor industry to produce thin films. Microfabrication processes widely use CVD to deposit materials in various forms, including monocrystalline, polycrystalline, amorphous, and epitaxial. These materials include silicon (dioxide, carbide, nitride, oxynitride), carbon (fiber, nanofibers, nanotubes, diamond, and graphene), fluorocarbons, filaments, tungsten, titanium nitride, and various high-k dielectrics. Chemical deposition takes advantage of the chemical reaction where the product self-assembles and deposits on a suitable substrate. Chemical deposition is commonly used for generating thin nanostructured blend films of crystalline inorganic materials, such as ZnS, CuSe, InS, CdS, etc. Depending on the deposition conditions, several terms have been used, such as chemical bath deposition, CVD, and ECD. Depending on the material and the deposition conditions, different surface morphologies have been obtained, from nanopins to nanotubes to nanorods. Reagents in sedimentary reactions are usually water-soluble ionic compounds. When these compounds are dissolved in water, they separate from each other to form anion and cation ions. If a cation of one compound forms an insoluble compound with an anion of another compound, precipitation occurs. Applications of this method include the removal of heavy metals and anions from wastewater, reducing water hardness, and metal recovery. Synthesis processes occur by chemical deposition based on deposition reactions (substitution), co-precipitation, oxidation–reduction, thermolysis, hydrolysis, polymerization, and condensation. The control of various variables in a synthetic system plays an important role in controlling particle size and morphology. The products of sedimentary processes under various synthetic conditions range from coarse crystals to nanostructured colloidal particles. Co-precipitation chemical methods allow the synthesis of metal nanoparticles, metal oxides, as well as many metal semiconductor compounds. Also, a wide range of properties and characteristics can be achieved by changing the synthesis conditions. The basis of these methods is the preparation of products from soluble precursors using different systems such as electrochemical equipment, microwave radiation, ultrasound, and high-energy beams.