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 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 jum) Physical and chemical properties depend on the size !! Natural examples: © Human teeth, 1-2 nm fibrils of hydroxyapatite Ca5(P04)3(OH) + collagen © Asbestos, opals, calcedon © Primitive meteorites, 5 nm C or SiC, early age of the Solar system Nanoscale objects have been around us, but only now we can observe them, manipulate and synthesize them. 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): • Nanowires • Nanorods • Nanotubes CdTe NPs 2-D structures (1-D confinement): • Thin films Superlattice • Planar quantum wells • Superlattices tö:st*.i —Jl—< 100 nm IUI Nanomaterials 10 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 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 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 16 Surface Effects A = Atoms at surfaces (one layer) - fewer neighbours, lower coordination, unsatisfied (dangling) bonds B = Atoms close to surface (several layers) - deformation of coordination sphere, distorted bond distances and angles C = Bulk atoms - not present in particles below 2 nm Nanomaterials 17 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 18 Surface Effects Atom binding (vaporization) energies lower in nanoparticles, fewer neighbors to keep atoms from escaping Plasticity of nanocrystalline ceramics Nanomaterials 19 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 27 Bulk Metals LU Nanocrystal isolated atom r\ Unoccupied ^^B ^^H Occupied Density of states ■ _ • Semiconductors E? ÜJ D- ■'Fermi Occupied Density of states Nanomaterials 28 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 29 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 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 39 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 42 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 43 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 44 Bottom-up Synthesis Arrested growth Growth j ^ X m X J , - H j, ~<> Quenching -=!> Stabilization S Hi Nanomaterials 45 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 46 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 47 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 48 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 50 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 51 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 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 53 Bottom-up Synthesis ■ 9 nm Ém%^lÄÄ^* ■'* ■■■* •*■<" i Number of counted particles: 204 Average size: 9.04 mn Standard deviation: 0.33 mn (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 Bottom-up Synthesis Phase Control [N«Bu4]2[Fe4S4(SPh)4] Ph£^ / Fe------- Fh^Fe- 7 A Ch 7 Npí pyrrhotite Fe7S8 180°C in octylamine 200 °C in dodecylamine 35 40 45 2e (degrees) 55 greigite Fe3S4 thiospinel, the sulfide analogue of magnetite 55 30 nm t 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 56 Polymerie Nanoparticles from Rapid Expansion of Supercritical Fluid Solution homogeneous ... , . . * . precursor critical nuclei aggregation growth supersatiiration * • • •-• • t " Nanomaterials 57 Spinning Disc Processing (SDP) A rapidly rotating disc (300-3000 rpm) Ethanolic solutions of Zn(N03)2 and NaOH, polyvinylpyrrolidone (PVP) as a capping agent Very thin films of fluid (1 to 200 \xm) on a surface Synthetic parameters = temperature, flow rate, disc speed, surface texture influence on the reaction kinetics and particle size Intense mixing, accelerates nucleation and growth, affords monodispersed ZnO nanoparticles with controlled particle size down to a size of 1.3 nm and polydispersities of 10% Nanomaterials Product 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 60 Watzky-Finke mechanism Slow continuous nucleation Fast autocatalytic surface growth Nanomaterials 61 Seed-mediated mechanism Au nanoclusters as seeds ■ ■ Bi, Sn, In, Au, Fe, Fe304 Nanomaterials 62 Other mechanisms Digestive rippening Surfactant exchange Nanomaterials 63 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 64 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 65 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 66 Nanocatalysis Morphologies of bimetallic nanoparticles a) purl k Itiji-[Kirlkli Id partkle-un-partide c) Ji^rt^alťd purlklt: rl i ťíiTť-slull particle e k alloy particle g) super core-shell particle Metal A ľl separate partiele o°o.o o o Metal H □ AB Alloy Nanomaterials 67 Nanocatalysis Polymers used as metal NP supports for catalysis \ ■!=0 hr-CH'1r PVP poly (v i n y I pyrrol id one) o PFÜ poly(2,5-dimethylpheny]ene oxid ^-^OH Hj 4 ^ŕ^OH = Pd°na no partie k OH + Hj ô = Pd" = Pd° nanoparticlc Nanomaterials 68 Nanocatalysis Catalysis by nanoparticles encapsulated in PAMAM or PPI dendrim Pd/Rfi bimetallic est D2 2) A HF Etching Nanomaterials 71 Applications Destruction of dangerous organic compounds (organophosphates - VX, chlorinated - PCB) 400 °C 800 °C 850°C O 750°c O í í HEAT HEAT Figure 3. Cleavages of bonds in (CaHB0)aP(0) and DMMP under thermal decomposition condition. 170°c c2H5 600°c \ 0 O^2 5 " ^V^CHa \ A. o* 2>> C2H5 H3C>1 X II .-mAT CH3 170°C' ^ 170°C Figure 4. Cleavages of bonds of (C2H50)3P{0) and DMMP on MgO. Nanomaterials CNT growth 73 Nanoengine 20 \itn H* / Fließrichtung 0; + 2H* H,Q„ 2H.0 Hp: + ÍH* Nanomotor funguje díky katalýze (viz obr.) U platinové části tyčinky se štěpí peroxid vodíku (H202) na kyslík (02) a protony (H+). Přebytečné elektrony se přesunují k stříbrozlaté části tyčinky, čímž nastartují redukční reakci H202 a protonů a vzniká voda. Uvolnění kyslíku a vody vytváří slabé proudění, které žene nanotyčinku kapalinou, a to platinovou částí napřed. Slovo Fliessrichtung na obrázku znamená směr proudění. Slitina zlata a stříbra se postará o to, že se k ní elektrony přesunují rychleji. Tím se urychlí i rozpad pohonné látky a tyčinky jsou o to rychlejší. 150 mikrometrů za sekundu Josepha Wanga z Kalifornské univerzity v San Diegu a Arizonské státní univerzity Nanamaterials