Intercalant MApproach' Soft Chemistry reactions are carried out under ning that structural elements of M Involves inserting ions into an existing structure this leads to a reduction (cations inserted) nts are preserved in the product, but the oxidation (anions inserted) of the host istry Methods ar u Typically carried out on layered materials(strong .Modifying the electastable compounds(structural motif can type bonding between layers, i.e. graphite, clays De selected by choice of precursor, may have unusual dicalchogenides, etc.) Performed via electrochemistry or via chemical in heparin reactive andor high surface area materials used eagents as in the n-butyl Li technique dIsadvantages: First of all, one must find the appropriate n Examples EmDr如mpm8 Chemistry. Secondly TiS2+ nBu-Li→LiTs2 I high temperatures are used or single crystals are needed De-intercalation Dehydration a The reverse of intercalation, also performed using chemical chemical methods or with reactiv ving wa de groups fror compound, you can often perform redox iMoS4→MopS4 chemistry and maintain a structural framework In,Mo S6+6HCI(g)- Mog Se 2InCl, (g)+3H,(g) not accessible using conventional synthesis approaches a This approach can often lead to new phases (polymorphs)of previously known compounds a Examples CuT2S4→ cubic Tis 02OH2nH2O→TiO2(B)(500°C) KCrSe→ layered CrSe 2KTiO3(OHnH2O→K2TisO17(500°C) Li,FeS,→FeS Molten salt fluxes Ion Exchange Solubilize reactants-> Enhance diffusion- Reduce reaction temperature Exchange charge compensating, ionically,ions) Synthesis in a solvent is the common approach to bonded cations (easiest for monovalent synthesis of organic and organometallic compounds This approach is not extensively used in solid state syntheses, because many inorganic solids are not LiNbo6+HO→ HNbWO6+L le in water or organic solvents. However, molten CubickSbo. Na+- Cubic- NaSbo +K+ salts turn out to be good solvents for many Often slow cooling of the melt is done to grow crystals however if the flux is water soluble and the produet is be made in this separated from the excess flux by washing with water.14 Soft Chemistry Approach : Soft Chemistry reactions are carried out under moderate conditions (typically T < 500°C). Soft Chemistry reactions are topotactic, meaning that structural elements of the reactants are preserved in the product, but the composition changes. Advantages : Soft Chemistry Methods are very useful for the following applications: Modifying the electronic structure of solids (doping) Design of new metastable compounds (structural motif can be selected by choice of precursor, may have unusual properties) Preparing reactive and/or high surface area materials used in heterogeneous catalysis, batteries and sensors Disadvantages : First of all, one must find the appropriate precursor in order to carry out Soft Chemistry. Secondly, metastable products are often unstable in applications where high temperatures are used or single crystals are needed Intercalation Involves inserting ions into an existing structure, this leads to a reduction (cations inserted) or an oxidation (anions inserted) of the host. Typically carried out on layered materials (strong covalent bonding within layers, weak van der Waals type bonding between layers, i.e. graphite, clays, dicalchogenides, etc.). Performed via electrochemistry or via chemical reagents as in the n-butyl Li technique. Examples : TiS2 + nBu-Li → LiTiS2 De-intercalation The reverse of intercalation, also performed using either electrochemical methods or with reactive chemical species Examples : NiMo3S4→ Mo3S4 In2Mo6S6 + 6HCl (g) → Mo6S6 + 2InCl3 (g) + 3H2 (g) This approach can often lead to new phases (polymorphs) of previously known compounds CuTi2S4 → cubic TiS2 KCrSe2 → layered CrSe2 Li2FeS2 → FeS2 Dehydration By removing water and/or hydroxide groups from a compound, you can often perform redox chemistry and maintain a structural framework not accessible using conventional synthesis approaches Examples : Ti4O7 (OH)2*nH2O→ TiO2 (B) (500°C) 2KTi4O8 (OH)*nH2O→ K2Ti8O17 (500°C) Ion Exchange ß Exchange charge compensating, ionically bonded cations (easiest for monovalent cations) ß Examples : LiNbWO6 + H3O+ → HNbWO6 + Li+ Cubic-KSbO3 + Na + → Cubic-NaSbO3 + K+ Molten Salt Fluxes Solubilize reactants®Enhance diffusion ® Reduce reaction temperature Synthesis in a solvent is the common approach to synthesis of organic and organometallic compounds. This approach is not extensively used in solid state syntheses, because many inorganic solids are not soluble in water or organic solvents. However, molten salts turn out to be good solvents for many ionic￾covalent extended solids. Often slow cooling of the melt is done to grow crystals, however if the flux is water soluble and the product is not, then powders can also be made in this way and separated from the excess flux by washing with water