•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 interkal_1 •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 interkal_mech •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 graph_st •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 graph_k •Intercalates •15 http://www.nature.com/nphys/journal/v8/n2/images_article/nphys2181-f1.jpg Li-ion Cells •16 http://www.jmbatterysystems.com/JMBS/media/JMBS/Technology/How/how-cells-work.jpg 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 novoselov.jpg geim_postcard.jpg •K. Novoselov •A. Geim Graphene_cropweb.jpg •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 id25744_1.jpg •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 https://cdn.shopify.com/s/files/1/0191/2296/files/graphene_bandgap.jpg?735 •22 Graphene • •Preparation: • • 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 Between the Graphene Sheets •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) theory-vs-experiment Graphene family •30 •Graphene •hBN •BCN •Fluorographene •graphene oxide •C3N4 Graphene oxide •More reactive than graphene •Presence of oxygen groups: -OH, -COOH, =O, -O- hydrophilic character •Electric insulator •Specific SA (theoretically): 1700-1800 m2g-1 •Hummers method go.gif •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) fluorografen.jpg •33 Graphyn, graphydiyn •Predicted •‘‘Non-derivatives‘‘ of graphene •Semiconductors •Movement of electrons as in graphene but only in one direction • •34 Triazine-based graphitic carbon nitride (TGCN) •35 •‘‘graphitic carbon nitride’’ (‘‘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) •36 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 http://www.diamond.ac.uk/Science/Research/Highlights/Layered-phosphates/base/0/text_files/file/Laye red%20phosphates%20figure%201.jpg •37 Layered Compounds - Zirconium Phosphates •α-zirconium phosphate • •Zr(HPO4)2.H2O • •interlayer spacing 7.6 Å http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageSer vice/Articleimage/2014/DT/c4dt00613e/c4dt00613e-f1_hi-res.gif •38 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 •39 Clay Minerals silicate •2:1 •1:1 •kaolinite •montmorillonite •40 Montmorillonite •(Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·10H2O •41 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 •42 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 •43 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 •44 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 •45 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 •46 Hydrotalcite •The layered structure of LDH is closely related to brucite Mg(OH)2 • •a brucite layer, Mg2+ ions octahedrally surrounded by six OH- •the 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 • • •[MII1-xMIIIx (OH)2]x+(Am-)x/m]·nH2O • • •x = 0.25 Mg6Al2(OH)16CO3 • • •x = 0 Mg(OH)2 • •47 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 • •48 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. •49 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 •50 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] •51 Layered Compounds •LDH = layered double hydroxides •hydrotalcites •mineral Mg6Al2(OH)16CO3.4H2O • •Brucite layers, Mg2+ substituted partially by Al3+ •52 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. • •53 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- •54 The anionic exchange capacity (AEC) •55 Types of the composite structures Li Intercalation Compounds •56 •57 Li Intercalation •x Li + TiS2 ® LixTiS2 • •58 Li Intercalation •Li/C ® e + Li+ + C • • •Li+ + e + FePO4 ® LiFePO4 • •59 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 • • •60 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 •61 0D Intercalation Compounds •C60 = FCC • •K3 C60