1 Layered Compounds Graphite Clay Minerals Layered Double Hydroxides (LDHs) Layered α-Zirconium Phosphates and Phosphonates Layered Manganese Oxides Layered Metal Chalcogenides Alkali Silicates and Crystalline Silicic Acids Two-dimensional layers 2 Layered Compounds 3 Host-Guest Structures TOPOTACTIC SOLID-STATE REACTIONS = modifying existing solid state structures while maintaining the integrity of the overall structure Host dimensionality 3D 2D 1D 0D 4 Host-Guest Structures Exfoliation Host + Guest Staging 5 Exfoliation 6 Intercalation Intercalation Insertion of molecules between layers 7 Graphite ABABAB Graphite sp2 sigma-bonding in-plane p-p-bonding out of plane Hexagonal graphite = two-layer ABAB stacking sequence SALCAOs of the p-p-type create the valence and conduction bands of graphite, very small band gap, metallic conductivity properties in-plane, 104 times that of out-of plane conductivity 8 Graphite GRAPHITE INTERCALATION G (s) + K (melt or vapour) → C8K (bronze) C8K (vacuum, heat) → C24K → C36K → C48K → C60K C8K potassium graphite ordered structure Ordered K guests between the sheets, K to G charge transfer AAAA stacking sequence reduction of graphite sheets, electrons enter CB K nesting between parallel eclipsed hexagonal planar carbon six-rings 9 Graphite Intercalates 10 Graphene High electric conductivity (metallic) Optically transparent – 1 layer absorbs 2.3% of photons High mechanical strength 11 GraphenePreparation: • Scotch tape – layer peeling, flaking • SiC pyrolysis – epitaxial graphene layer on a SiC crystal • Exfoliation • CVD from CH4 on Ni, Cu surfaces 12 Scotch tape – Layer peeling Mechanical exfoliation 13 SiC pyrolysis • Annealing of the SiC crystal in a vacuum furnace (UHV 10-10 Torr) • Sublimation of Si from the surface at 1250 - 1450 °C • The formation of graphene layers by the remaining carbon atoms 14 Exfoliation Chemical exfoliation (surfactant) Sonochemical exfoliation 15 CVD from CH4 / H2 on Metal Surfaces (A) SEM - graphene on a copper foil (B) High-resolution SEM - Cu grain boundary and steps, two- and three-layer graphene flakes, and graphene wrinkles. Inset (B) TEM images of folded graphene edges. 1L, one layer; 2L, two layers. Graphene transferred onto (C) a SiO2/Si substrate (D) a glass plate 16 Clay Minerals 2:1 1:1 kaolinitemontmorillonite 17 Montmorillonite (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·10H2O 18 Clay Minerals A clay [Si4O10]4- tetrahedral (T) sheet in (a) top view and (b) side view A clay octahedral (O) sheet (c) top view and (d) side view The [Al4O12]12- dioctahedral top view is shown in (c) [Mg6O12]12- trioctahedral top view would show a continuous sheet of octahedral units 19 Clay Minerals N2 sorption isotherms (a) TMA- and Ca- montmorillonite (b) An Italian sepiolite (c) Natural SHCa-1 Na-hectorite (d) synthetic laponite and Li-(silane)-hectorites Closed symbols = adsorption Open symbols = desorption H3 H4 H4 H2 20 Surface Area nonpolar guest molecules N2 do not penetrate the interlayer regions Na+ forms of smectites and vermiculites – no penetration larger ions (Cs+ and NH4 + keep the basal planes far enough) - limited penetration the most important parameters of clays with respect to catalytic applications 21 Layered Double Hydroxides LDH = layered double hydroxides HT = hydrotalcites Natural mineral hydrotalcite Mg6Al2(OH)16CO3.4H2O Brucite layers, Mg2+ substituted partially by Al3+ Layers have positive charge Interlayer spacing d(003) = 0.760 nm Hydrotalcite Mg6Al2(OH)16CO3.4H2O the brucite-like layer = 0.480 nm gallery height = 0.280 nm 22 Hydrotalcites Brucite layers, Mg2+ substituted partially by Al3+ Layers have positive charge (a) [Ca2Al(OH)6]2SO4.6H2O (b) [LiAl2(OH)6]Cl (c) [Mg2.25Al0.75( OH)6]OH 23 Hydrotalcite The layered structure of LDH is closely related to brucite Mg(OH)2 a brucite layer, Mg2+ ions octahedrally surrounded by six OHthe octahedra share edges and form an infinite two-dimensional layer the brucite-like layers stack on top of one another either rhombohedral (3R) or hexagonal (2H) sequence Hydrotalcite Mg6Al2(OH)16CO3.4H2O - 3R stacking [MII 1-xMIII x (OH)2]x+(Am-)x/m]·nH2O x = 0.25 Mg6Al2(OH)16CO3 x = 0 Mg(OH)2 24 Hydrotalcite The interlayer spacing c′ is equal to d003, 2d006, 3d009, etc.; c′ = (d003 + 2d006 + … + nd00(3n)) / n The cell parameterc is a multiple of the interlayer spacing c′ c = 3c′ for rhombohedral (3R) c = 2c′ for hexagonal (2H) sequences 25 Hydrotalcite Hydrotalcite Mg6Al2(OH)16CO3.4H2O - 3R stacking unit cell parameters a = 0.305 nm c = 3d(003) = 2.281 nm the interlayer spacing: d(003) = 0.760 nm the spacing occupied by the anion (gallery height) = 0.280 nm a thickness of the brucite-like layer = 0.480 nm the average M—O bond = 0.203 nm the distance between two nearest OH- ions in the two opposite side layers = 0.267 nm shorter than a (0.305 nm) and indicative of some contraction along the c-axis. 26 XRD Patterns of LDH XRD patterns of layered double hydroxides synthesized by coprecipitation method with various cations composition: A – Mg/Al; B- Mg/Co/Al; C- Mg/Ni/Al * = Reflections from Si crystal used as a reference 27 XRD Patterns of LDH rhombohedral structure the cell parameters c and a The lattice parameter a = 2d(110) corresponds to an average cation–cation distance The c parameter corresponds to three times the thickness of d003 c = 3/2 [d003+2d006] 28 Layered Compounds LDH = layered double hydroxides hydrotalcites mineral Mg6Al2(OH)16CO3.4H2O Brucite layers, Mg2+ substituted partially by Al3+ 29 Intercalation to LDH the intercalation of methylphosphonic acid into Li/Al LDH (a) [LiAl2(OH)6]Cl.H2O (b) second-stage intermediate, alternate layers occupied by Cl and MPA anions (c) first-stage product with all interlayer regions occupied by MPA. 30 Intercalation to LDH LDH = layered double hydroxides hydrotalcites mineral Mg6Al2(OH)16CO3.4H2O Brucite layers, Mg2+ substituted partially by Al3+ Layers have positive charge Intercalate anions [Cr(C2O4)3]3- 31 Memory Effect 32 Calcination to Spinels 33 The anionic exchange capacity (AEC) 34 Types of the composite structures 35 Layered Compounds MPS3 (M = V, Mn, Fe, Co, Ni, Zn) TiS2 α-Zr(HPO4)2.H2O 36 Layered Compounds x Li + TiS2 → LixTiS2 37 3D Intercalation Compounds Cu3N and Mn3N crystallize in the (anti-) ReO3-type structure the large cuboctahedral void in the structure can be filled By Pd to yield (anti-) perovskite-type PdCu3N By M = Ga, Ag, Cu leading to MMn3N 38 3D Intercalation Compounds Tungsten trioxide structure = WO6 octahedra joined at their corners = the perovskite structure of CaTiO3 with all the calcium sites vacant The color and conductivity changes are due to the intercalation of protons into the cavities in the WO3 structure, and the donation of their electrons to the conduction band of the WO3 matrix. The material behaves like a metal, with both its conductivity and color being derived from free electron behavior. The coloration reaction used in electrochromic displays for sun glasses, rear view mirrors in cars Zn + 2 HCl → 2 H + ZnCl2 WO3 + x H → HxWO3 39 0D Intercalation Compounds C60 = FCC K3 C60