Transcript K 2 O - 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 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 TiO2
• 16K + - 4Ti4+ + 36TiO2  8K2Ti4O9
• 4Ti4+ - 16K+ + 9K2O  K2Ti4O9
• Overall reaction stoichiometry
• 9K2O + 36TiO2  9K2Ti4O9
• RHS/LHS = 8/1 Kirkendall Ratio
RUTILE CRYSTAL STRUCTURE
z
y
x
SEEING THE 1-D CHANELS IN RUTILE
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
1/3
1
1/3 x2
1/3
1/3 x2
1/2
1/3
1/2
K+ at y = 3/4
K+ at y = 1/4
Different to rutile, anatase or
brookite forms of TiO2
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
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
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
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 Inorganic precursor, oxides, sulphides,
amines, carboxylic acids, phosphines,
metals, nucleation of nanocluster seed
phosphine oxides, phosphonic acids
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
• 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
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 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 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
Gb > Gs
supersaturation
nucleation
Addition
of reagent
aggregation
capping and
stabilization
nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P
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
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)
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
PXRD, MALDI-MS, TEM
CHARACTERIZATION OF
CLUSTER CORE,
CLUSTER SEPARATION
LIGAND SHEATH,
Do it yourself quantum
mechanics – synthetic design
of optical, electrical,
magnetic properties
Nanocluster Synthetic
Control – size, shape,
composition, surface
chemical and physical
properties, separation,
amorphous, crystalline
ARRESTED GROWTH
OF MONODISPERSED
NANOCLUSTERS
CRYSTALS, FILMS
AND LITHOGRAPHIC
PATTERNS
nMe2Cd + nnBu3PSe + mnOct3PO  (nOct3PO)m(CdSe)n + n/2C2H6 + nnBu3P
Rogach
AFM 2002
methanol
2-propanol
toluene
MONODISPERSED
CAPPED CLUSTER
SINGLE CRYSTALS
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 THREEDIMENSIONAL SUPERLATTICES, TALAPIN DV, SHEVCHENKO EV, KORNOWSKI A, GAPONIK
N, HAASE M, ROGACH AL, WELLER H, ADVANCED MATERIALS, 13 (24): 1868, 2001
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
Relationship between alkanethiolate polymer,
nanocluster and self-assembled monolayer
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 SELFASSEMBLING 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.
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
•
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).
•
m is the dielectric constant of the surrounding medium
•
 = 1 + i2 is the complex dielectric constant of the particle.
• Resonance peak occurs whenever the condition 1 = -2m 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.
Extinction spectra calculated using Mie theory for gold
nanospheres with diameters varying from 5 nm to 100 nm.
Non-Spherical
Shapes -Gans
Modified Mie
Theory
Au Nanorods – Shape Selective Additives
Aspect Ratio Tunes Longitudinal NOT Transverse SPR Modes
Calculated Gans Theory
Gold Nanorod w = 20 nm
(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.
Gold Nanorods
Aspect 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
CAPPED FePt FERROMAGNETIC
NANOCLUSTER SUPERLATTICE
HIGH-DENSITY DATA STORAGE MATERIALS
NANOMAGNETIC
SEPARATIONS OF
BIOLOGICAL MOLECULES