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CHIMIE DOUCE: SOFT CHEMISTRY. Synthesis of new metastable phases Materials not usually accessible by other methods Synthesis strategy often involves precursor method Often a close relation structurally between precursor phase and product Topotactic transformations.

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chimie douce soft chemistry
CHIMIE DOUCE: SOFT CHEMISTRY
  • Synthesis of new metastable phases
  • Materials not usually accessible by other methods
  • Synthesis strategy often involves precursor method
  • Often a close relation structurally between precursor phase and product
  • Topotactic transformations
chimie douce soft chemistry1
CHIMIE DOUCE: SOFT CHEMISTRY
  • Tournaux synthesis of a new form of TiO2
  • Beyond Rutile, Anatase, Brookite and Glassy form!!!
  • KNO3 (ToC)  K2O (source)
  • K2O + 4TiO2 (rutile, 1000oC)  K2Ti4O9
  • K2Ti4O9 + HNO3 (RT)  H2Ti4O9.H2O
  • H2Ti4O9.H2O (500oC) 4TiO2 (new slab structure) + 2H2O
kirkendall effect in tournaux synthesis of slab form of tio 2
KIRKENDALL EFFECT IN TOURNAUX SYNTHESIS OF SLAB FORM OF TiO2
  • 16K + - 4Ti4+ + 36TiO2 8K2Ti4O9
  • 4Ti4+ - 16K+ + 9K2O  K2Ti4O9
  • Overall reaction stoichiometry
  • 9K2O + 36TiO2  9K2Ti4O9
  • RHS/LHS = 8/1 Kirkendall Ratio
slide6

NEW METASTABLE POLYMORPH OF TiO2 BASED ON K2Ti4O9 SLAB STRUCTURE - (010) PROJECTION SHOWN

1

Topotactic loss of H2O from H2Ti4O9 to give “Ti4O8” (TiO2 slabs) plus H2O, where two bridging oxygens in slab are protonated (TiOHTiOTiOH)

1

1/2

1/2 x2

1

1/3 x2

1

1/3

1/3 x2

1/3

1/2

1/3 x2

1/3

K+ at y = 3/4

1/2

K+ at y = 1/4

Different to rutile, anatase or brookite forms of TiO2

chimie douce soft chemistry2
CHIMIE DOUCE: SOFT CHEMISTRY
  • Figlarz synthesis of new WO3
  • WO3(cubic form) + 2NaOH  Na2WO4 + H2O
  • Na2WO4 + HCl (aq)  gel
  • Gel (hydrothermal) 3WO3.H2O
  • 3WO3.H2O (air, 420oC) WO3 (hexagonal tunnel structural form of tungsten trioxide)
  • More open tunnel form than cubic ReO3 form of WO3
slide8

Slightly tilted cubic polymorph of WO3 with corner sharing Oh WO6 building blocks, only protons and smaller alkali cations can be injected into cubic shaped voids in structure to form bronzes like NaxWO3 and HxWO3

1-D hexagonal tunnel polymorph of WO3 with corner sharing Oh WO6 building blocks, can inject larger alkali and alkaline earth cations into structure to form bronzes like RbxWO3 and BaxWO3 as well as HxWO3 a 1D proton conductor having mobile protons diffusing from O site to site along channels

slide9

Apex sharing WO6 Oh building blocks

Hexagonal tunnels

Injection of larger M+ cations like K+ and Ba2+ than maximum of Li+ and H+ in c-WO3

Structure of h-WO3 showing large 1-D tunnels

slide10

Functional device, LED, laser, sensor, biolabel

Ligand capping arrested growth of nanocluster core

Growth and ligand capping of nanocluster core

High T solvent, ligand, protection, amphiphilic amines, carboxylic acids, phosphines, phosphine oxides, phosphonic acids

Inorganic precursor, oxides, sulphides, metals, nucleation of nanocluster seed

slide11

Arrested nucleation and growth synthetic method for making semiconductor nanoclusters in a high-boiling solvent. Adding a non-solvent causes the larger nanocrystals to precipitate first, allowing size-selective precipitation and nanocluster scaling laws to be defined

nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

arrested growth of monodispersed nanoclusters
ARRESTED GROWTH OF MONODISPERSED NANOCLUSTERS
  • Hydrophobic sheath of alkane chains of surfactant make the nanoclusters soluble in non-polar solvents - crucial for achieving purification and size selective crystallization of the nanoclusters.
  • nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P
  • Tributylphosphine selenide in a syringe is rapidly injected into a 300C solution of dimethyl cadmium in trioctylphosphine oxide surfactant-ligand-solvent, known as TOPO.
size selective crystallization of ligand capped nanoclusters
SIZE SELECTIVE CRYSTALLIZATION OF LIGAND CAPPED NANOCLUSTERS

Gradually add non-solvent acetone to a toluene solution of capped nanoclusters

Causes larger crystals to precipitate then smaller and smaller crystals as the non-solvent concentration increases.

Smaller ones more soluble because of easier solvation of less dense packed alkanethiolate chains.

size selective crystallization of ligand capped nanoclusters1
SIZE SELECTIVE CRYSTALLIZATION OF LIGAND CAPPED NANOCLUSTERS

When non-solvent added, nc-nc contacts become more favorable than nc-solvent interactions.

Larger diameter capped nanoclusters interact via the chains of the alkanethiolate capping ligands more strongly than the smaller ones due to the smaller curvature of their surface and the resulting greater interaction area.

As a result they are caused to flocculate that is aggregate and crystallize first.

size selective crystallization of ligand capped nanoclusters2
SIZE SELECTIVE CRYSTALLIZATION OF LIGAND CAPPED NANOCLUSTERS

Process repeated to obtain next lower size nanoclusters and procedure repeated to obtain monodispersed alkanethiolate capped gold nanoclusters.

Further narrowing of nanocluster size distribution achieved by gel electrophoresis – an electric field driven size exclusion separation stationary phase.

basics of nanocluster nucleation growth crystallization and capping stabilization

Addition

of reagent

BASICS OF NANOCLUSTER NUCLEATION, GROWTH, CRYSTALLIZATION AND CAPPING STABILIZATION

Gb > Gs

supersaturation

nucleation

aggregation

capping and stabilization

nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

slide17

EgC = EgB + (h2/8R2)(1/me* + 1/mh*) - 1.8e2/R

Quantum localization term

Coulomb interaction between e-h

CAPPED MONODISPERSED SEMICONDUCTOR NANOCLUSTERS

nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

slide20

SIZE DEPENDENT OPTICAL ABSORPTION SPECTRA OF CAPPED CDSE NANOCLUSTERS, SYNTHESIS AND CHARACTERIZATION OF NEARLY MONODISPERSE CdE (E = S, Se, Te) SEMICONDUCTOR NANOCRYSTALLITES, MURRAY CB, NORRIS DJ, BAWENDI MG, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 115 (19): 8706-8715 SEP 22 1993)

slide21

SIZE AND COMPOSITION DEPENDENCE OF THE OPTICAL EMISSION SPECTRA OF CAPPED InAs (RED), InP (GREEN) AND CdSe (BLUE), BRUCHEZ, M.JR; MORONNE, M.; GIN, P.; WEISS, S.; ALIVISATOS, A.P. SEMICONDUCTOR NANOCRYSTALS AS FLUORESCENT BIOLOGICAL LABELS, SCIENCE 1998, 281, 2013

slide22

PXRD, MALDI-MS, TEM CHARACTERIZATION OF CLUSTER CORE, CLUSTER SEPARATION LIGAND SHEATH,

Nanocluster Synthetic Control – size, shape, composition, surface chemical and physical properties, separation, amorphous, crystalline

Do it yourself quantum mechanics – synthetic design of optical, electrical, magnetic properties

slide23

ARRESTED GROWTH OF MONODISPERSED NANOCLUSTERSCRYSTALS, FILMS AND LITHOGRAPHIC PATTERNS

nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P

monodispersed capped cluster single crystals
MONODISPERSED CAPPED CLUSTER SINGLE CRYSTALS

Rogach AFM 2002

methanol

2-propanol

toluene

slide25

TRI-LAYER SOLVENT DIFFUSION CRYSTALLIZATION OF CAPPED NANOCLUSTER SINGLE CRYSTALS. MeOH TOP LAYER, TOLUENE BOTTOM LAYER, 2-PROPANOL MIDDLE BUFFER LAYER - OMITTING THE BUFFER LAYER CREATED ILL-DEFINED CRYSTALS, A NEW APPROACH TO CRYSTALLIZATION OF CdSe NANOPARTICLES INTO ORDERED THREE-DIMENSIONAL SUPERLATTICES, TALAPIN DV, SHEVCHENKO EV, KORNOWSKI A, GAPONIK N, HAASE M, ROGACH AL, WELLER H, ADVANCED MATERIALS, 13 (24): 1868, 2001

slide26

GOLD ATOMIC DISCRETE STATES

GOLD CLUSTER DISCRETE MOLECULE STATES

GOLD QUANTUM DOT CARRIER SPATIAL AND QUANTUM CONFINEMENT

GOLD COLLOIDAL PARTICLE SURFACE PLASMON – 1850 MICHAEL FARADAY ROYAL INSTITUTION GB PIONEER OF NANO!!!

BULK GOLD PLASMON

self assembling aurothiol clusters
SELF-ASSEMBLING AUROTHIOL CLUSTERS

Diagnostic cluster size dependent optical plasmon resonance originating from dipole oscillations of conduction electrons spatially confined in nanocluster – wavelength plasmon depends on size, type of capping ligand and nature of the environment of nanocluster – also size dependent electrical conductivity – hopping from cluster to cluster - useful in nanoelectronic devices and nanooptical sensors – Faraday would be pleased!!!

HAuCl4(aq) + Oct4NBr (Et2O)  Oct4NAuCl4 (Et2O)

nOct4NAuCl4(Et2O) + mRSH (tol) + 3nNaBH4 Aun(SR)m (tol)

size selective crystallization of self assembling aurothiol clusters au n sr m
SIZE SELECTIVE CRYSTALLIZATION OF SELF-ASSEMBLING AUROTHIOL CLUSTERS Aun(SR)m

Gradually adding a non-solvent such as acetone to a toluene solution of capped gold nanoclusters first causes larger crystals to precipitate, then smaller and smaller crystals, as the non-solvent concentration increases.Smaller ones more soluble because of easier solvation of less dense packed alkanethiolate chains.

When non-solvent added, nc-nc contacts become more favorable than nc-solvent interactions. Larger diameter capped gold nanoclusters interact via the chains of the alkanethiolate capping ligands more strongly than the smaller ones due to the smaller curvature of their surface and the resulting greater interaction area. As a result they are caused to flocculate that is aggregate and crystallize first.

Process repeated to obtain next lower size nanoclusters and procedure repeated to obtain monodispersed alkanethiolate capped gold nanoclusters.

slide30

CAPPED METAL CLUSTER CRYSTAL

CLUSTER SELF-ASSEMBLY DRIVEN BY HYDROPHOBIC INTERACTIONS BETWEEN ALKANE TAILS OF ALKANETHIOLATE CAPPING GROUPS ON GOLD NANOCRYSTALLITES

surface plasmon resonance mie theory
SURFACE PLASMON RESONANCE MIE THEORY
  • Extinction coefficient from Mie theory is the exact solution to Maxwell’s electromagnetic field equations for a plane wave interacting with a homogenous sphere of radius R with the same dielectric constant as bulk metal (scattering and absorption contributions).
  • em is the dielectric constant of the surrounding medium
  • e = e1 + ie2 is the complex dielectric constant of the particle.
  • Resonance peak occurs whenever the condition e1 = -2em is satisfied – sensitive to change in em of environment hence use as a surface plasmon sensor
  • This is the SPR peak which accounts for the brilliant colors of various metal nanoparticles – form factors can be introduced to account for non-spherical shape – Gans modification of Mie theory.
slide32
Extinction spectra calculated using Mie theory for gold nanospheres with diameters varying from 5 nm to 100 nm.
au nanorods shape selective additives aspect ratio tunes longitudinal not transverse spr modes
Au Nanorods – Shape Selective AdditivesAspect Ratio Tunes Longitudinal NOT Transverse SPR Modes

(a) L = 46 nm, w = 20 nm; (b) L = 61 nm, w = nm; (c) L = 73 nm, w = 22 nm; (d) L = 75 nm, w = 22 nm; (e) L = 89 nm, w = 22 nm; (f) L = 108 nm, w = 22 nm. The right panel shows a representative TEM image of the sample corresponding to spectrum-f.

Calculated Gans Theory Gold Nanorod w = 20 nm

slide35

Gold NanorodsAspect Ratio Tunes Longitudinal NOT Transverse SPR Modes

NANOCHEMISTRY CURES CANCER

CANCER CELL TARGETED GOLD NANOROD ATTACHMENT

BURN AWAY THOSE NASTY CANCER CELLS BY NANORODS ABSORBING NIR PLASMON AND TRANSFERING HEAT TO CANCER CELL – PHOTOTHERMAL CANCER THERAPY

slide37

CAPPED FePt FERROMAGNETIC NANOCLUSTER SUPERLATTICE HIGH-DENSITY DATA STORAGE MATERIALS

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