Nanoscopic Materials Atomď Molecules 1 Nanoscale Particles 125 70,000 Condensed Matter 6*106 oc N° Atoms ' Quantum Chemistry 1 ^ 10 ■ 100 oc Diameter(nm) Solid State Physics Nanomaterials 1 Nanostructural Materials "Prey", the latest novel by Michael Crichton, author of "Jurassic Park". The horrible beasties threatening humanity in this new thriller are not giant dinosaurs, but swarms of minute "nanobots" that can invade and take control of human bodies. Last summer, a report issued by a Canadian environmental body called the action group on erosion, technology and concentration took a swipe at nanotechnology. It urged a ban on the manufacture of new nanomaterials until their environmental impact had been assessed. The group is better known for successfully campaigning against biotechnology, and especially against genetically modified crops. The research, led by a group at the National Aeronautics and Space Administration's Johnson Space Centre in Houston, has found in preliminary studies that inhaling vast amounts of nanotubes is dangerous. Since they are, in essence, a form of soot, this is not surprising. But as most applications embed nanotubes in other materials, they pose little risk in reality. Nanomaterials 2 Room at the Bottom •■-'■. i' ■.,..'..' -: ■' š ,.. ..: -:' -. š ,.. ..: -:' l š ,.. '■■ What I want to talk about is the problem of manipulating and controlling things on a small scale ... As soon as I mention this, people tell me about miniaturization, and how far it has progressed today. They tell me about electric motors that are the size of the nail on vour small finger. And there is a device on the market, thev tell me, by which you can write the Lord's Prayer on the head of a pin. But that's nothing; that's the most primitive, halting step in the direction I intend to discuss. It's a staggeringly small world that is below. In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction...... Prof. Richard Feynman in "There's plenty of room at the bottom", lecture delivered at the annual meeting of the APS, Caltech, 29 December. 1959. Nanomaterials 3 Nanoscale Writing lp*Pen Nanolithögraphy AFM Tip ^ Wrllthfl direction Nanoscale writing with an AFM (Mirkin et al.) ■5 sijan as I ment Tor, th"s. peopie t?] I me aba a*.- miníg+rdr řiiať*un, and fiov.j r or T progí-^r.ied Ť OíJoy. Ti ry t. ŕ I' m* ubouť ptř-ctríc rno'T; "^ho^ or ŕ t tip s:?e c í* *he T. he r»' rrl-.et. L^eu »r(.fl ttk«, bL, '...'h";h 2on uTlte T.hr L3rd"s Prayer on vhe head a pTri. Bw+ŕ r Hq-i; ' e no^hinjjí v ho t a t-He- ^as** V I C t* L>" prím" i. íuf, hoít^ínrj *;tori In t h»? dľr*»c^íco X Tf.%f0í>a ta d?£CL--5a. T t ii o bt aqq»?r 1 rtg ' u srna1 v^or'd tifiort« i5 be*low. In the year 2QSG. -.-.-hen *n*?y took bavrk at ťh?*i uo*. they will WCftdw .jhij í T' u»QS nor. urvi I the gear 1^0 "that orybodu. b «aar serTo^afu to mou* ľn t,h"s airei.Mün. 400 nm R:chord P. Feynrr.on. ÍRBO Nanomaterials 4 Nanoscopic Materials How big is nano? 10 million times ----------------► smaller What Changes? smaller d = 10 nm i Size is another variable to change physical and chemical properties Nanomaterials 5 0�7763 Nanoscopic Materials Small Negligible light scattering New optics Quantum size effects Information technology, Storage media ■ ■ High surface area Catalysts, Adsorbents Large Interracial area New composites Surface modifications Targeted Drug Delivery Nanomaterials 6 Nanoscopic Materials Nanoscale regime Size 1-100 nm (traditional materials > 1 |um) Physical and chemical properties depend on the size !! Natural examples: © Human teeth, 1-2 nm fibrils of hydroxy apatite Ca5(P04)3(OH) + collagen © Asbestos, opals, calcedon © Primitive meteorites, 5 nm C or SiC, early age of the Solar system Nanomaterials 7 Nanoscopic Materials Nanoparticles 1 - 100 nm .; ■ « * - 5 um Traditional materials > 1 |um • * * '-----------1 1—t ŽjiíTI Nanomaterials 8 texture / morphology V 0.1 iiiii U,5 Dim 1.0 Dm 1.5 am 3.0 am 8.0 nm O.äum lOOfini NMR EXAFg XftíJ TEM STftí XANES ESR UV SAXS SEM OM Nanomaterials The nano-Family At least one dimension is between 1-100 nm 0-D structures (3-D confinement): • Quantum dots • Nanoparticles 1-D structures (2-D confinement): • Nano wires • Nanorods • Nanotubes 2-D structures (1-D confinement): • Thin films • Planar quantum wells • oUperlattlCeS Nanomaterials Si/Ge/Si/Ge Superlattice CARBON NANOTUBES A «Hfl» afip|i ■- .noiutie rti'-íqo (Stajiŕ* h*fr> Dr P M Ajiy*ll) A ÍRÍIII-íii?ll ^aridl UÜS uralit (Ebbewn.f W., (94*. Aww Ňlff «riff. Sil 2Í-235ÍJ 1. A unique specks somewhere between traditional carbon fibers and revel forms of carbon such as fulrerenes 2. A seamľess cylindrical sheet of graphite whose diameter is so small and its aspect raus (diameter vs. length) Is so great (hat it can be considered from the electronic point of view as a. one.dimensional structure. There are two sorts of carbon nandu bes. One Is multi-shell nanotubes andthe other is single-shell nanotubes. Tne former rave two or more layers such as the left-side figura ba low and about 2 to 20 nm diameter while the latter have only ona layer and about 1 to 2 n m diameter. Both are a few tens of moons long. In multi-shell nanotube s. the Inter layer spacing Is -0.34 nm. In both cases, each earb on atom is completely bonded Co neighboring carbon atoms through sp! hybridization to form a sea ml es t shell. In We absence of external sdajrv carbon nanotube* are atways straight unless carbon rings having a number of carbons defiant from si x (pentagons, h eptagons, octagons, etc) are present i n the hexagonal network. Afnckjie nf a lypic-*' mjlli-rMĽll nan^lU^B Taken using TEH (Símitŕ frum [< P M Ajiyün) ASEMiŕnage Dfmul1*Lh*'t cartran nanaltémx ard pmlicka (Soule* Ircm Dr P. M. Aujini Nanomaterials Coherence Length frei XRD patterns of iron oxide nanocrystals a) of 4, 6, 8, 9,10,11,12,13, and 15 nm (311) <1,1> T J ■-*.—.----------^^A—'X^_/^ >^vA -1- 20 -í-JO 15 nm 13 nm 12 nm -11 nm IUI.';. Önm b) 011) _ — 4nm 1 r 1 r 6nm — flnm - 9nm -10nm — 11 nm — 12nnn — 13nm " 15nm A - ŕ tf ■■Í1 1 I"' Cjo 1 U ■KU fctt ^r RH 32 33 U 35 3Ě 17 3ft 39 2B 2ii Nanomaterials 12 Surface Effects Decreasing grain size = Increasing volume fraction of grain boundaries (50% for 3 nm particles) É&č&ó Ru particle diameter 2.9 nm 20 ■ Nanomáterials Bulk Atoms Surface Atoms '*-•**. ******** 10 15 20 25 30 Particle Size(nm) 3S 13 Surface Effects Dispersion F = the fraction of atoms at the surface F is proportional to surface area divided by volume N = total number of atoms V ~ r3 ~ N F 1 1 IÍŇ F g o Cl. ill n = N iH n = number of atoms at the cube edge Nanomaterials 14 Surface Effects Atoms at surfaces have fewer neighbours than atoms in the bulk lower coordination and unsatisfied bonds surface atoms are less stabilized than bulk atoms The smaller a particle the larger the fraction of atoms at the surface, and the higher the average binding energy per atom. the melting and other phase transition temperatures scale with surface-to-volume ratio and with the inverse size Example: the melting point depression in nanocrystals 2.5 nm Au particles 930 K bulk Au 1336 K Nanomaterials 15 coordination number 10 9 ■ 6 Surface Effects N 309 103 55 23 i i i - S^A - - *Vs . A - - D.I Q.15 0.2 0.25 0.3 0.35 N -U3 D.4 Calculated mean coordination number as a function of inverse radius, represented by N~1/3 for Mg clusters (triangles = icosahedra, squares = decahedra, diamonds = hep Nanomaterials 16 Surface Effects Atom binding (vaporization) energies lower in nanoparticles, fewer neighbors to keep atoms from escaping Plasticity of nanocrystalline ceramics Nanomaterials 17 Surface Effects Properties of grain boundaries >Lower coordination number of atoms >Reduced atomic density (by 10 - 30 %) >Broad spectrum of interatomic distances Experimental evidence >HREM ■ >EXAFS, reduced number of nearest and next-nearest neighbors > Raman spectroscopy > Mössbauer spectroscopy, quadrupole splitting distribution broadened >Diffusivity enhanced by up to 20 orders of magnitude !! > Solute solubility in the boundary region Ag (fee) and Fe (bec) immiscible in (s) or (1), but do form solid solution as nanocrystalline alloy >EPR, nano-Si gives a sharp signal Nanomaterials Melting Point Depression AT = jbulk _ J , . = m m \ J IT. bulk m Tj-bulk -^ , Hm PS (J. -kT S»kT bulk metal mete 11 ic cl u ste rs insu lati ng duste rs atů ms & & particles & particles molecules increasing diameter nuclearity decreasing Nanomaterials 26 Bulk Metals LU Nanocrystal isolated atom r\ Unoccupied ^^B ^^H Occupied Density of states ■ _ • Semiconductors E? ÜJ D- ■'Fermi Occupied Density of states Nanomaterials 27 Metal-to-Insulator Transition Band gap increases with decreasing size A/K 105 104 < 1°3 i 102 O) c c 1 10-1 - | 10-2 - o 10^ _ 10-4 ; 10"5 10-6 i—r i r Surface atom fraction - 1 10 - IQ"2 -1 r 3 c o £ 1 e 3 TO'3 Z C O 10"^ 2 10"5 10 100 1000 Particle diameter (d/A) 10.000 Metallic behavior Single atom cannot behave as a metal nonmetal to metal transition 100-1000 atoms Magnetic behavior Single domain particles large coercive field iNaiiumaieiiais 28 Metal-to-Insulator Transition 1-0- \good sinterability >high catalytic activity > difficult handling > adsorption of gases and impurities >poor compressibility PREPARATION METHODS Top-down: from bulk to nanoparticles Bottom-up: from atoms to nanoparticles Nanomaterials a) Variation of the nonmetallic band gap with nanocrystal size b) in CdS nanocrystals a) 2.E U 1Í r DD 3 14 3 □ S -r "J i i i i b) i ř ■ aus 0.M1 0-1 10 SO IDO 150 200 250 Volume /nm1 Sr _ O Au n Píj J__i uj 4 3- . _ £ 1 ďJnm Nanomaterials Nanoscopic Materials NANO -particles, crystals, powders -films, patterned films -wires, rods, tubes -dots Nanostructured materials = nonequilibrium character >good sinterability >high catalytic activity > difficult handling > adsorption of gases and impurities >poor compressibility ■ PREPARATION METHODS Top-down: from bulk to nanoparticles Bottom-up: from atoms to nanoparticles Nanomaterials Bottom-up Synthesis: Atom Up Sixteen componenls assemble into supnamoiemiar macrocyde + !?:>,■ ObCu' Nanomaterials 38 NANOSTRUCTURAL MATERIALS Bottom-up Synthesis St Atom Aggregation Method GEM - gas evaporation method -v* evaporation by heating - resistive, laser, plasma, electron beam, arc discharge -v* the vapor nucleates homogeneously owing to collisions with the cold gas atoms 4- condensation in an inert gas (He, Ar, IkPa) on a cold finger, walls - metals, intermetallics, alloys, SiC, C60 in a reactive gas 02 Ti02, MgO, A1203, Cu20 N2, NH3 nitrides ■ in an organic solvent matrix Nanomaterials NANOSTRUCTURAL MATERIALS Bottom-up Synthesis SMAD - the solvated metal atom dispersion 1 - 2 g of a metal, 100 g of solvent, cooled with liquid N2 more polar solvent (more strongly ligating) gives smaller particles Ni powder: THF < toluene < pentane = hexane Carbide formation 77 to 300 K 180 °C> octane Ni(g) + pentane ------------► NixCyHz -------------► Ni3C Nanomaterials NANOSTRUCTURAL MATERIALS Bottom-up Synthesis ^ Thermal or Sonocative Decomposition of Precursors Fe(CO)5 ---------► nc-Fe + 5 CO sono [Co(en)3]W04 _____► nc-WC - 23% Co Ar, 1500 °C PhSi(OEt)3 + Si(OEt)4 + H20 --------► gel----------------► ß-SiC (CH3SiHNH)n (1) ---------► Si3N4 + SiC laser 3on-4nn°c M(BH4)4 (g) ___________^ borides MB2+X (M = Ti, Zr, Hf) Si(OEt)4 + Ag+ or Cu2+ + H20 --------► Si02/Ag+/Cu2+ H2,550°C -------------------► Si02/Ag/Cu Nanomaterials 41 NANOSTRUCTURAL MATERIALS Bottom-up Synthesis K Reduction of Metal Ions Borohydride Reduction - Manhattan Project Aqueous, under Ar 2 Co2+ + 4 BH4 + 9 H20 -----► Co2B + 12.5 H2 + 3 B(OH)3 ■ Under air 4 Co2B + 3 02 ---------► 8 Co + 2 B203 Nonaqueous Co2+ + BH4 + diglyme ---------► Co + H2 + B2H6 TiCl4 + 2 NaBH4------------► TiB2 + 2 NaCl + 2 HCl + H2 MXn + n NR4[BEt3H]---------► M + NR4X + n BEt3 + n/2 H2 M = group 6 to 11; n = 2,3; X = CI, Br mixed-metal particles Nanomaterials 42 NANOSTRUCTURAL MATERIALS Bottom-up Synthesis Au colloidal particles HAuCl4 + NaBH4 in toluene/H20 system, TOABr as a phase transfer agent, Au particles in the toluene layer, their surface covered with Br, addition of RSH gives stable Au colloid Nanomaterials 43 Bottom-up Synthesis Arrested growth Growth j ^ X m X J , - H j, ~<> Quenching -=!> Stabilization S Hi Nanomaterials 44 Two-dimensional array of thiol-derivatised Au particles (mean diam 4.2 nm) 250 - 2 DO - - 150 r '00 ■ fl ™ 50 0 -, 0. .0 m 2 iJl i 5.2 6.8 diameter (nm) d =5rim 9 (degrees) Nanomaterials 45 TEM micrograph of hexagonal arrays of thiolized Pd nanocrystals: a) 2.5 nm, octane thiol b) 3.2 nm, octane thiol Nanomaterials ir ^'S 2r/*«S 46 C it nm The d-l phase diagram for Pd nanocrystals thiolized with different alkane thiols. The mean diameter, d, obtained by TEM. The length of the thiol, /, estimated by assuming an a\\-trans conformation of the alkane chain. The thiol is indicated by the number of carbon atoms, Cn. The bright area in the middle encompasses systems which form close-paced organizations of nanocrystals. The surrounding darker area includes disordered or low-order arrangements of nanocrystals. The area enclosed by the dashed line is derived from calculations from the soft sphere model Nanomaterials 47 NANOSTRUCTURAL MATERIALS Alkali Metal Reduction in dry anaerobic diglyme, THF, ethers, xylene NiCl2 + 2 K -+ Ni + 2 KCl AICI3 + 3K^ Al + 3 KCl Reduction by Glycols or Hydrazine "Organically solvated metals" k + Mg Nanomaterials Alkalide Reduction 13 K+(15-crown-5)2Na- + 6 FeCl3 + 2CBr4 THF -30 °C 2 Fe3C (nano) + 13 K(15-crown-5)2Cl0 43Br0 57 + 13 NaCl Anealed at 950 °C / 4 h Fe3C: 2-15nm Nanomaterials 49 NANOSTRUCTURAL MATERIALS Bottom-up Synthesis $<: Reactions in Porous Solids - Zeolites, Mesoporous materials Ion exchange in solution, reaction with a gaseous reagent inside the cavities M2+ + H2E --------► ME M = Cd, Pb; E = S, Se Ship-in-the-Bottle Synthesis Ru3+ + Na-Y--------► Ru(III)-Y Ru(III)-Y + 3 bpy---------► Ru(bpy)32+ reduction of Ru(III) Conducting carbon wires Acrylonitrile introduced into MCM-41 (3 nm diam. channels) Radical polymerization Pyrolysis gives carbon filaments Nanomaterials 50 NANOSTRUCTURAL MATERIALS Bottom-up Synthesis SC Gel or Polymer Matrices # Sol-Gel Method Aerogels, supercritical drying Ik Aerosol Spray Pyrolysis Aqueous solution, nebulization, droplet flow, solvent evaporation, chemical reaction, particle consolidation, up to 800 °C 3Gd(N03)3 + 5 Fe(N03)3 --------► Ga3Fe5012 + 6 02 + 24 N02 MnCl2 + 2 FeCl3 + 4 H20 ---------► MnFe204 + 8 HCl Mn(N03)2 + Fe(N03)3 no go, why? Nanomaterials 51 NANOSTRUCTURAL MATERIALS *§(: Inverse Micelles Bottom-up Synthesi o H20 + octane ( ) __ .,„»" lllllllllllllll lllllllllllllll Se2" "O ° o......... O H20 O1 PoQ. lllllllllllllll. Illlllllllllll oJšp....... O (cdSeJO Iiiiiiiiiiiiiii PhSeSiMe3 Nanomaterials is 52 ■ ■ ■ 9 nm Ém%^lÄÄ^* ■'* ■■■* •*■<" i Number of comired particles: 204 Average size: 9.04 mn Standard deviation: 0.33 nm (3.7%) 7-7.5 7.5-8 8-8.5 8.5-9 9-9.5 9.5- 10- 10 10.5 Size (nm) 10.5-11 Nanomaterials Polymerie Nanoparticles from Rapid Expansion of Supercritical Fluid Solution Water or Aqueous Solution •••• PHDľDA Nanoparticles '■ " i ^^ Syringe ^1 Pump Tube Furnace HHDr'DAinCO, S' 1000 100 10 t? r i S S °-1 o Micro-orifice 001 A SMPS.UCPC i A APS W 10 100 1000 Partide Diameter (nm) Homogeneous solution under h 19h pressure Nanomaterials 54 Polymerie Nanoparticles from Rapid Expansion of Supercritical Fluid Solution homogeneous ... , . . * . precursor critical nuclei aggregation growth supersatiiration * • • •-• • t " Nanomaterials 55 NANOSTRUCTURAL MATERIALS Properties on Nanostructured Materials ® Metallic behavior Single atom cannot behave as a metal nonmetal to metal transition : 100-1000 atoms (g) Magnetic behavior Single domain particles, large coercive field © Depression of melting points in nanocrystals bulk Au mp 1064 °C 10 nm Au 550 °C Nanomaterials LaMer mechanism Supersaturated solution Burst of nucleation Slow growth of particles without additional nucleation Separation of nucleation and growth Nanomaterials 57 Watzky-Finke mechanism Slow continuous nucleation Fast autocatalytic surface growth Nanomaterials 58 Seed-mediated mechanism Au nanoclusters as seeds Bi, Sn, In, Au, Fe, Fe304 Nanomaterials 59 Other mechanisms Digestive rippening Surfactant exchange Nanomaterials 60 Thermal Decomposition of Precursors Fe(CO) 350 °C, 1 h ' oleic acid trioctylamine Fe 350 °C, 1 h Me3NO * Fe203 6 nm ónm Separation of nucleation and growth Fe(CO)5 thermal decomposition at 100 °C contributes to nucleation Fe(oleate) thermal decomposition at 350 °C contributes to growth ■.'O*.::., - Nanomaterials 61 Top-down Synthesis: Bulk Down $<: Introduction of Crystal Defects (Dislocations, Grain Boundaries) -^High-Energy Ball Milling final size only down to 100 nm, contamination -♦■ Extrusion, Shear, Wear *v*High-Energy Irradiation "♦■ Detonative Treatment ^ Crystallization from Unstable States of Condensed Matter ^ Crystallization from Glasses -^Precipitation from Supersaturated Solid or Liquid Solutions Nanomaterials 62 XRD patterns of iron oxide nanocrystals a) of 4, 6, 8, 9,10,11,12,13, and 15 nm (311) (440) t1"» T J *» ■ — — Ji.. Jf {«0) 15 nm 12 nm -r-20 JO 20 Nanomaterials b) I311. 4nm 6nm -■ -- finm — — Snm 10nm — — 11 nm — - I2nnn 13nrn 15nm 32 33 3J 35 3S 17 3« 39 2fl 63 Nanocatalysis a) pujiklť-iii-purtk'k b) partide-ujl-partide ej aiyjrtnattd part kle d) t ore-íhell particle e) alloy particle g) super core-shell particle Metal A f) separate particle O o Metal« □ ABAUoy morphologies of bimetallic nanoparticles Nanomaterials Nanocatalysis _ . ft-cHsiľ PVP poly (v i ny I py rrol id one) PPO polyí2,5-dímethylpheny]ene o: polymers used as metal NP supports for catalysis ^-^OH H2 + jf^OH = Pd°nai» partie to Ô = Pď OH + H4 s Pd° nanoparticle Nanomaterials 65 Nanocatalysis Pd/Rfi bimelallic eat. DíPtíŕ/Rh,3*) D(Pd^Rhy°) catalysis by nanoparticles encapsulated in PAMAM or PPI dendrimers Nanomaterials 66 Nanocatalysis Asymmetric heterogeneous catalysis on nanoparticles ■ ■ ■ + CH3N02 Nanomaterials Hollow Nanoparticles (CH30)Si(CH2)3SH -----------------*~ SH Silica spherd SiCh-Kugd Toluene Toluol Atmung HF l)Pd(acaĽ>2 2) A Etching Nanomatenals formation 0f holloW Sphéfes Applications Destruction of dangerous organic compounds (organophosphates - VX, chlorinated - PCB) 400 °C 800 °C H yQ 17(TC 17CTC imED MgO CH; Figure i. Cleavages of bonda of (C2H50)3P{0) and DMMP on MgO. JNanomatenals CNT growth 70