1 Layered Compounds Graphite and Graphene Clay Minerals Layered Double Hydroxides (LDHs) Layered Zirconium Phosphates and Phosphonates Layered Metal Oxides Layered Metal Chalcogenides - TiS2, MPS3 (M = V, Mn, Fe, Co, Ni, Zn) Alkali Silicates and Crystalline Silicic Acids Two-dimensional layers 2 Layered Compounds 3 Host-Guest Structures Host dimensionality 3D 2D 1D 0D TOPOTACTIC SOLID-STATE REACTIONS = modifying existing solid state structures while maintaining the integrity of the overall structure 4 Intercalation Intercalation Insertion of molecules between layers 5 Intercalation 6 Intercalation Exfoliation Host + Guest Staging Intercalate APB = advancing phase boundary 7 Exfoliation APB = advancing phase boundary 8 APB = advancing phase boundary 9 Staging Hendricks-Teller effect 10 HT = galleries are filled randomly Intercalation 11 Dependence of the basal spacing of the intercalates of the alkylamines (circles) and alkanols (crosses) on the number of carbon atoms nC in SrC6H5PO3·2H2O 12 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 13 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 14 Graphite Intercalates 15 Li-ion Cells 16 Graphene • Discovery – 2004 • Exotic properties: – Firm structure – Inert material – Hydrofobic character – Electric and thermal conductivity – High mobility of electrons – Specific surface area (theoretically): 2630 m2g-1 K. Novoselov A. Geim http://www.synchrotron.org.au/ 17 Sythesis of graphene • Top down – Mechanical exfoliation – Chemical exfoliation • Bottom up – CVD, epitaxial growth, … • Defects • Application: diodes, sensors, solar cell, energy storage, composites, … 18 http://www.nanowerk.com/what_is_graphene.php 19 20 Graphene High electric conductivity (metallic) Optically transparent – 1 layer absorbs 2.3% of photons High mechanical strength HRTEM 21 Graphene LCAO-band structure of graphene 22 GraphenePreparation: • Scotch tape – layer peeling, flaking • SiC pyrolysis – epitaxial graphene layer on a SiC crystal • Exfoliation of graphite (chemical, sonochemical) • CVD from CH4, CH2CH2, or CH3CH3 on Ni (111), Cu, Pt surfaces 23 Scotch tape – Layer peeling Mechanical exfoliation 24 25 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 26 Exfoliation Chemical exfoliation (surfactant) Sonochemical exfoliation 27 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 28 Graphene on SiO2 29 Pseudo-magnetism Graphene on platinum grown from ethylene at high temperatures. Cooled to low temperature to measure STM to a few degrees above absolute zero. Both the graphene and the platinum contracted – but Pt shrank more, excess graphene pushed up into bubbles, size 4-10 nm x 2-3 nm The stress causes electrons to behave as if they were subject to huge magnetic fields around 300 T (record high in a lab, max 85 T for a few ms) Graphene family 30 Graphene hBN BCN Fluorographene graphene oxide C3N4 Graphene oxide • More reactive than graphene • Presence of oxygen groups: -OH, -COOH, =O, -Ohydrophilic character • Electric insulator • Specific SA (theoretically): 1700-1800 m2g-1 • Hummers method 31 Graphane – hydrogenated graphene • 2009 (graphene + cold hydrogen plasma) • Two conformations: chair x boat • Calculated binding energy = most stable compound with stoichiometric formula CH • Chair type graphane insulating nanotubes 32 Fluorographene • Monolayer of graphite fluoride • Chair type x boat type-strong repulsion • Sythesis: – Graphene + XeF2/CF4 (room temperature) – Mechanical or chemical exfoliation of graphite fluoride – By heating graphene in XeF2 gas at 250 °C • Graphene + XeF2 at 70 °C – high-quality insulator, stable up to 400 °C (resemblence with teflon) 33 Graphyn, graphydiyn • Predicted • ‘‘Non-derivatives‘‘ of graphene • Semiconductors • Movement of electrons as in graphene but only in one direction 34 Graphitic carbon nitride 35 Temperature- induced condensation dicyandiamide NH2C(=NH)NHCN In a LiCl/KCl melt 1834 Berzelius, Liebig Graphitic carbon nitride 36 (a) triazine and (b) tri-s-triazine (heptazine) Graphitic carbon nitride 37 (‘‘g-C3N4’’) band gap 1.6 - 2.0 eV small band gap semiconductors Si (1.11 eV), GaAs (1.43 eV), and GaP (2.26 eV) Phosphorene 38 Semiconductor - direct band gap bulk BP 0.3 eV monolayer phosphorene 1.5 eV N -methyl-2-pyrrolidone Black phosphorus Orthorhombic a = 3.31 Å, b = 4.38 Å, c = 10.50 Å = 90 Space group Bmab Exfoliation Phosphorene 39 Height-mode AFM images single-layer phosphorene ca. 0.9 nm Phosphorene 40 Black phosphorus 12 lattice vibrational modes 6 Raman active modes 3 vibrational modes A1 g , B2g , and A2 g can be detected when the incident laser is perpendicular to the layered phosphorene plane: 361 cm1, 438 cm1, 465 cm1 As the number of phosphorene layers increases, the three Raman peaks red-shift 41 Layered Compounds - Zirconium Phosphates (a) α-zirconium phosphate = Zr(HPO4)2.H2O interlayer spacing 7.6 Å (b) γ-zirconium phosphate = Zr(PO4)(H2PO4)2H2O interlayer spacing 12.2 Å 42 Layered Compounds - Zirconium Phosphates α-zirconium phosphate Zr(HPO4)2.H2O interlayer spacing 7.6 Å 43 Layered Compounds - Zirconium Phosphates (a) α-zirconium phosphate = Zr(HPO4)2.H2O interlayer spacing 7.6 Å (b) γ-zirconium phosphate = Zr(PO4)(H2PO4)2H2O interlayer spacing 12.2 Å 44 Clay Minerals 2:1 1:1 kaolinitemontmorillonite 45 Montmorillonite (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·10H2O 46 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 47 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 48 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 49 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 50 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 51 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 52 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 53 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. 54 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 55 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] 56 Layered Compounds LDH = layered double hydroxides hydrotalcites mineral Mg6Al2(OH)16CO3.4H2O Brucite layers, Mg2+ substituted partially by Al3+ 57 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. 58 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- 59 The anionic exchange capacity (AEC) 60 Types of the composite structures Li Intercalation Compounds 61 62 Li Intercalation x Li + TiS2  LixTiS2 63 Li Intercalation Li/C  e + Li+ + C Li+ + e + FePO4  LiFePO4 64 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 65 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 66 0D Intercalation Compounds C60 = FCC K3 C60