Nanoscopic Materials Atoms' Nanoscale Condensed Molecules Particles Matter 1 125 70,000 6*106 °° N° Atoms 1 ^ 10 100 oo Diameter(nm) Quantum v Solid State Chemistry ■ ■ Physics Nanomaterials i 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 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 your small finger. And there is a device on the market, they 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 Nanoscale writing with an AFM (Mirkin et al.) 60 nm Rs soan I men* Tor t,h"&_ peopJe t.?] I mp otoj"*^ rrrfnlcrt-ur Fzo*Ton, and fiov/ r ar T* ^as narl j.-i SfTOi I r"nj '.h-jt'& *,He ^^s*^ rr,t-#na ta d*ic<-^i. i& a srü^1" '^'y smo1 f wor'd iE bwJovJ* In ^ear 20GÜ, v.'hen lock bo>_rk qv thi'Lj ',jr 11 wonJp«' .jh^ 1^ was not unti I th? y#^ir rnoue in thns (ftrtfCVtOfti NU Prchard R Feynmür., Nanomaterials 4 Nanoscopic Materials Size is another variable to change physical and chemical properties Each physical property or fenomenon has a characteristic length When particle size is comparable to the characteristic length, property start to depend on th«PSfz^ials Nanoscopic Materials Negligible light scattering - New optics Quantum size effects - Information technology, Storage media High surface area - Catalysts, Adsorbents Large interfacial area - New composites Surface modifications - Targeted drug delivery Nanomaterials Nanoscopic Materials Nanoscale regime Size 1 - 100 nm (traditional materials >. 1 ^im) 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 Nanoscopic Materials Nanoparticles 1 - 100 nm Traditional materials > 1 jli 1 nm = 10-9 m 1 nm = 10 A 1 iim 1 u.m 'da" Nanomaterials STM Scanning Tunelling Microscopy Current Feedback Position Amplifier Control Control > Piezoelectric Transducer -30 nm Tip Atoms coodcSxxxxx^cccco Surface Atoms Bias Voltage Binning and Rohrer Nobel 1986 Nanomaterials 9 Size 10 |±rľi 4 (iní 10 nm Microscopic Entities tticrostope Refolulion Profozoa (1 £-40 (im) Bl d c el I f (o - S |im ) 5faphyl o: o;c uí tat ter iuim Light 9 9 (1-3(1™) microfcope Poí V irui [££0-400 nm) Hirpií simplex ľirui [1 50-200 nm) t I nf I ľ en za r irui (SO- 1 2 0 nm) E I4í fron m icrůscope Pol ior iru j (25-30 nm) Wacromolicultí 0.1 ran 1 nm 10 nm 1(H) nm 1 jim JOfn* 100pm I itl i t i^iijl, ^j^^j—1 x,|jjjiJ_i i """[^- ' ' """J_......"í—t., i i in, < tlj_* i L.i.J.m-L 1 t _Cl Light microscope___ Atoms Protein Small molecules Chloroplast j? bacteria Plant and animal cells The largest known bacterium - Thiomargarita namibiensis - 100-750 microns Nanomaterials 11 Microns to Nanometers - Biological/Chemical/Atomic fi^S lode] Plant, Animal Cell 100 \xm LlO jam 1 |Lim 100 nm Protein { 10 ^ DNA "turn" 1 nm DNA base O.lnm Dimension } Bacteria j^Virus [ Simple Molecules } Atoms • t 4 ^» i # • 4 The Nano-Family At least one dimension is between 1 -100 nm 0-D structures (3-D confinement): AFM 1 |jm x 1 |jm InAs on GaAs/lnP Nanomaterials The Nano-Family 1-D structures (2-D confinement): CARBON NANOTUBES A single-shell nanotube image (Source from Dr. P. M. Aayan) Amuki-srell nanotube image (Ebbesen, T. W., 33^. Annu. Rev. Mater. Sci. 24:;35-64 courtesy of NEC/Handa) 1. A unlquo apaclaaaomawnari brtwaan tradUonal carbon (bera ind nevil formi of carbon uch aa fullerenee. 2. A aaamlaae oylndrloal ahaat of iraphtta whoaa damatar li ea amall and rte ea-p«et rvJo (dlamatarve. lang*) li ap graattriBtlt ean bi conaldarad fromtha tlač-tronle point of vlrw ai i ono-dlmomlontl abuctura. Thara ara two aorta ofearbon narwbibea. On* la muH-ahall nanotubaa ind lha othor la alngle-ahell nanotubaa. Tria formar hivo two oř mora layara aueh u tha laft-alda figura bilow and about 2 to 20 nm dlamatar whlla tha lanař nava on ty ona layar and about 1 to 2 nm dlamatar. Both ara a faw tana of mlcrona long. In murU-ahall nanotaibaa, tht Intar layar epactig la -0.34 nm In both ceaae, aaeh earben ■tom la eomplatály bondad to nalnhbortno carbon ttoma through ap* hybrldlia-Hon to form ■ aoimlaaa ahalL In tha abaanea of oxtamal atraJn, carbon nahotu ba* ilght unleea carbon rlnga hawlng a numbar of carbona daflant trom i.nopl ala (pantáfloni, naptagona, aebigona, atc.) ara praaant In tha haxagonri natworii. Elektrospinning The Nano-Family 2-D structures (1-D confinement): ■ •Thin films • Planar quantum wells ^ , ... Si/Ge/Si/Ge • SuperlattlCeS Superlattice • Graphene •SAM Nano 111UIV1 it Coherence Length XRD patterns of iron oxide nanocrystals a) of 4, 6, 8, 9,10,11,12,13, and 15 nm (311) 15 nm 13 nm 12 nm 11 nm 10 nm 9nm 40 —i-1-1-1-1-1-1 32 33 34 3S 3E 37 3« 39 29 2» Nanomaterials 18 Surface Effects Decreasing grain size = Increasing volume fraction of grain boundaries (50% for 3 nm particles) Particle Size(nm) Nanomaterials 19 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 r>j _ r>j r**j - r**j 1.0 1 0.5-1 i o jfl 0.4- 0.2- 0.0 \ -1-1-1- 20 40 n = N —I-1- 1/3 BE -i-1— 10C n = number of atoms at the cube edge Nanomaterials 20 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 > Mossbauer spectroscopy, quadrupole splitting distribution broadened >Diffusivity enhanced by up to 20 orders of magnitude !! Si > 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 ISlanomaterials 21 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 22 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 23 coordination number Surface Effects 10 9 h v a 309 —l— N 103 55 23 6 I-1-1--*-"-1-1-1-1-1_i_ ■ 0.1 0.15 0.2 0.25 0.3 0.35 0.4 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 Surface Effects Atom binding (vaporization) energies lower in nanoparticles, fewer neighbors to keep atoms from escaping Plasticity of nanocrystalline ceramics Nanomaterials Melting Point Depression AT = Thulk _ T (r\ — m mV ./ 2T bulk m Tj bulk ■■: . Hm Psr (j -a L ( ^ ^3 Ps_ [plJ Sn - 0,5wt%Cu - 4wt%Ag Nano alloy particles 220 210 TJ 200 u SP 190 £ 180 1 170 ^ 160 150 140 20 40 60 GO 100 120 140 160 Particle dinmeter|nm} TJr)- 2* Gibbs-Thomson Equation bulk ' l In nanopartiql hi .confui %d. in „po,re,s., molY si m bulk m Tm(r) = mp of the cluster with radius r Xmbuik = mp of the bulk Vmolf = the molar volume of the liquid y sl = the interfacial tension between the s and 1 surface AHmbulk = the bulk latent heat of melting Nanomaterials DSC b.) d—101 nim b)d=34,3 nm (J lk ■'---------.............1..............■.........' m 375 365 395 405 415 425 435 445 Temperature (K) Phase Transitions Phase transitions = collective phenomena With a lower number of atoms in a cluster a phase transition is less well defined and broadened Small clusters behave more like molecules than as bulk matter 435 g ""-'—T ---------bulk • Id CPG e In VytXir i 0,05 0 IC 0.15 1/d (1/iim) 0.20 0 a) d-101 nm 1 : b)d=34,3 nm i : : c)d-]2,8nm 1 1 : bx d) (1 = 5,6 nm Ilk i ■'---------'-..................1..............■.........' m 375 365 395 405 415 425 435 445 Temperature (K) Surface Effects Reduction in particle size •metal particles usually exhibit a lattice contraction •oxide particles exhibit a lattice expansion A 12.410 A 0 ~1M~ ~M0 WO 400 500 M#an ?i&e (run) Nanomaterials 29 Surface Effects Correlation between the unit-cell volume (cubic) and the XRD particle size in y-Fe203 nanoparticles The smaller the particle size the larger the unit cell volume. I_■ I_1_I_I_I-1-u 80 120 160 200 XRD particle size Nanomaterials 30 Surface Effects The inter-ionic bonding in nanoparticles has a directional character ions in the outermost layer of unit cells possess unpaired electronic orbitals Associated electric dipole moments, aligned roughly parallel to each other point outwards from the surface The repulsive dipolar interactions increase in smaller particles reduced by allowing unit cell volume to increase Nanomaterials 31 Quantum Confinement Effects Physical and chemical properties depend on the size !! (D Finite-size effects MO to Band transition •f- sp- Atomic Hybrid Or bit a 15 Si Atom + - Local Bond Basis LUMO HOMO SIN Molecular Orbitals Si2 Diatonic SiN Nanomaterials Conduction Band Density of States Crystallina Si 32 Metal-to-Insulator Transition 6 = 0 SkT 6» kT bulk metal metallic dusters insulating dusters atoms & & particles & particles molecules increasing diameter nucte arity decreasing Nanomaterials 33 Bulk Metals B'l c LU Nanocrystal Isolated atom Unoccupied :Fernni Occupied Density of states s 7 i 1 Semiconductors E? z LU ^ Unoccupied ■'Fermi Occupied Density of states Nanomaterials Metal-to-Insulator Transition Band gap increases with decreasing size 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 iNaiioniaieriais 35 Metal-to-Insulator Transition The increase in the core-level binding energy in small particles poor screening of the core charge the size-induced metal-nonmetal transition in nanocrystals W 2.0 3.0 4.0 5-0 6^0 Variation of the shift, AE, in the core-level binding energy (relative to the bulk metal value) of Pd with the nanoparticle diameter Nanomaterials 36 Electrical Conductivity Bulk value rrr -I- -i— -r -I- — - HH W.+++. +tt- .-Hfc. tt« +tt- .+++. +« HH. Particle size , Nanomaterials 6s HOMO q to i "re c E u i O 6p LUMO n=f 3 V ~ 6 \ 10 30 65 100 180 250 L 1 0 Binding Energy/eV Photoelectron spectra of Hg clusters of nuclearity n The 6p peak moves gradually towards the Fermi level the band gap shrinks with increase in cluster size Nanomaterials a) Absorption spectra of CdSe nanocrystals (at 10 K) of various diameters b) Wavelength of the absorption threshold and band gap as a function of the particle diameter for various semiconductors. The energy gap in the bulk state in parenthesis a) r 21 A diameter ■—i— 2.0 2,4 2,B Energy /&V -i ■ 3.2 - b) 300 - 1.5 /PbS[0.4l eV) 200 20 Ni 40 60 80 Quantum Confinement Effects (b) Fluorescence of CdSe-CdS core-shell nanoparticles with diameter of 1.7 nm (blue) up to 6 nm (red) Smaller particles have a wider band gap Nanomaterials Bohr Radii quantum confinement -particles must be smaller than the Bohr radius of the electron-hole pair semiconductor rB(Ä) Es (eV) CdS 28 2.5 CdSe 53 1.7 CdTe 75 1.5 GaAs 124 1.4 PbS 180 0.41 Nanomaterials 41 Quantum Confinement Effects (g> Optical properties nc-Ti02 is transparent Blue shift in optical spectra of nanoparticles 300 400 500 600 Wavelength (nm) a) Variation of the nonmetallic band gap with nanocrystal size b) in CdS nanocrystals a) ■j 5 □ a + □ b) 2 2 2 14 M i i i oa fl.M1 0.1 TO SO 100 150 2OT 250 Volume /rim1 Sr ■ i i i n UJ 3- d/nm 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 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 component assemble into supramoJecuigr macrocytic NANOSTRUCTURAL MATERIALS Bottom-up Synthesis $t Atom Aggregation Method GEM - gas evaporation method evaporation by heating - resistive, laser, plasma, electron beam, arc discharge *❖* the vapor nucleates homogeneously owing to collisions with the cold gas atoms *❖* condensation in an inert gas (He, Ar, lkPa) 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 $t 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-► 0-SiC (CH3SiHNH)n (1) -► Si3N4 + SiC laser 300-400°C M(BH4)4 (g) _^ borides MB2+X (M = Ti, Zr, Hf) Si(OEt)4 + Ag+ or Cu2+ + H20 -► Si02/Ag7Cu2+ H2,550 °C -► Si02/Ag/Cu Nanomaterials NANOSTRUCTURAL MATERIALS Bottom-up Synthesis 3* 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 HC1 + 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 50 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 Bottom-up Synthesis Nanomaterials 52 Two-dimensional array of thiol-derivatised Au particles (mean diam 4.2 nm) 250r 2 00 150 100 50 0 J! m, 1 H 5.2 6.8 diameter (nm) Q (degrees) Nanomaterials 53 TEM micrograph of hexagonal arrays of thiolized Pd nanocrystals: a) 2.5 nm, octane thiol b) 3.2 nm, octane thiol Nanomaterials 54 Crt it tim rf/nm C4/O.8 C&/1.2 C,2/1J Cis/2-1 The 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 55 NANOSTRUCTURAL MATERIALS Alkali Metal Reduction in dry anaerobic diglyme, THF, ethers, xylene NiCl2 + 2 K -> Ni + 2 KC1 A1CL + 3 K Al + 3 KC1 Reduction by Glycols or Hydrazine "Organically solvated metals" k + Mg Nanomaterials Alkalide Reduction 13 K+(15-crown-5)2Na- + 6 FeCl3 + 2CBr4 Nanomaterials 57 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 NANOSTRUCTURAL MATERIALS Bottom-up Synthesis 3t Gel or Polymer Matrices X Sol-Gel Method Aerogels, supercritical drying $C 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 Synthesis o H20 + octane iiiiiiiiiiiiii """"0Ô0"' O H20 O' Se2- \Q o 0,...- ..............O (CdSe)0............ PhSeSiMe3 Nanomaterials Bottom-up Synthesis »**# •♦•V•• • • 9 nm Number of counted particles: 204 Average size: 9.04 nm Standard deviation: 0.33 nm (3.7%) 7-7.5 7.5-8 3-8.5 6.5-9 9-9.5 9.5- 10- 10.5- 10 10.5 11 Size {nrn} Nanomaterials 61 Bottom-up Synthesis Phase Control [N*Bu4]2[Fe4S4(SPh)4] ,/ry Fe-- —\ pyrrhotite Fe7Sg 180°C in octylamine 200 °C in dodecylamine 35 40 45 2e (degrees) 55 greigite Fe3S4 thiospinel, the sulfide analogue of magnetite Polymerie Nanoparticles from Rapid Expansion of Supercritical Fluid Solution Nanomaterials 63 Polymerie Nanoparticles from Rapid Expansion of Supercritical Fluid Solution homogeneous supersaturation • t • • precursor t « critical nuclei aggregation growth Nanomaterials 64 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 um) 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 NANOSTRUCTURAL MATERIALS Properties on Nanostructured Materials ® Metallic behavior Single atom cannot behave as a metal nonmetal to metal transition : 100-1000 atoms ® 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 Watzky-Finke mechanism Slow continuous nucleation Fast autocatalytic surface growth Nanomaterials Seed-mediated mechanism Au nanoclusters as seeds Bi, Sn, In, Au, Fe, Fe304 Nanomaterials Other mechanisms Digestive rippening Surfactant exchange Nanomaterials Thermal Decomposition of Precursors 350 °C, 1 h Fe(CO) oleic acid trioctylamine - Fe 350 °C, 1 h Me3NO * Fe203 6 nm Separation of nucleation and growth Fe(CO)5 thermal decomposition at 100 °C contributes to nucleation fflm Fe(oleate) thermal decomposition at 350 °C contributes to growth Nanomaterials 71 Top-down Synthesis: Bulk Down $C Introduction of Crystal Defects (Dislocations, Grain Boundaries) ^High-Energy Ball Milling final size only down to100 nm, contamination 4* Extrusion, Shear, Wear -^High-Energy Irradiation 4> Detonative Treatment Crystallization from Unstable States of Condensed Matter 4* Crystallization from Glasses -^Precipitation from Supersaturated Solid or Liquid Solutions Nanomaterials 72 XRD patterns of iron oxide nanocrystals , i-1 i—«—i—>—i—i—i—i 30 .m 60 32 33 34 3S 36 17 38 39 2ť>-1* 26-► Nanomaterials 73 Nanocatalysis Morphologies of bimetallic nanoparticles ä) parlk!ť-in-particle b) pa r tide-on-parlick e| ajmrtj-aled particle d i core-shell particle e) alloy particle g) super core-shell particle Metal A Metal B □ Nanomaterials f) separate particle O#°o®o^o o o A B Alloy [T] Nanocatalysis Polymers used as metal NP supports for catalysis —f-C-CH?—I- l H J* PVP poly (v i ny I pyrrol id one) PPO po ly (2,5 - d í methy Ipheny le rie ox id ^VOH H2 + j?^QW - Pd° no rio particle Nanomaterials Nanocatalysis Catalysis by nanoparticles encapsulated in PAMAM or PPI dendrimers Nanomaterials 76 Nanocatalysis Nanomaterials Hollow Nanoparticles formation of hollow spheres SH SH SH Sll (CH30)Si(CH2)3SH » SH Toluene Silica sphem Toluo1 SiOi-Kugel Atrung SH SH gH SH 1) Pd(acac)2 2) A IIF Etching Nanomaterials Applications Destruction of dangerous organic compounds (organophosphates - VX, chlorinated - PCB) 400 °C 800 °C 850°C HEAT 7S0°C HEAT Figure 3. Cleavages of bonds in (C2HsO)sP(0) and DMMP under thermal decomposition condition. 170°C \ c2H5 600°c 17CTC 17CTC MgO CH; Figure 4. Cleavages of bonds of (CsH50)3P(0) and DMMP on MgO. Nanomaterials Nanoengine 20 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