Transcript SOLID-STATE MATERIALS SYNTHESIS METHODS

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
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)
Relationship between alkanethiolate polymer,
nanocluster and self-assembled monolayer
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
U.Landman AM 1996
Plasmonics Basics – Size Effects
Plasmonics Basics – Size Effects
•
•
What is the the surface plasmon resonance of gold nanostructures. On the top
left corner is shown how the electron cloud of free-electrons in the gold
respond to an oscillating electromagnetic field, depending on the shape and
orientation of the particle. The formation of a dipole causes the emergence of a
resonance at a specific wavelength, as shown on the right by the representative
absorbance spectra. In the case of spherical particles the plasmon resonance
occur at a single frequency, while for elongated nanocrystals you can have two
resonance frequencies related with the two dipole oscillation modes
(longitudinal or transverse).
In the bottom part of the Figure is shown the origin of the absorbance features
according to the Mie theory. The absorbance A is expressed as the product of
two terms. The first term is scattering-related and has a 1/l dependence, while
the second term is exclusively dependent on the dielectric constants of the
metal and the surrounding medium. This last term represent the resonant
plasmon mode which is shown as a peak centered at the surface plasmon
resonance wavelength lSPR. The product of the two terms is the spectrum
observed experimentally.
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 – sensitive to environment
•
 = 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 m 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.
Detecting Biomolecules with Gold Nanocrystals
Self Assembly and Plasmon Coupling
Detecting Biomolecules with Gold Nanocrystals
Self Assembly and Plasmon Coupling
•
•
The coupling of plasmons can be used for the detection of oligonucleotides in
solution. Gold nanocrystals can be produced with thiol-functionalized
oligonucleotides bound to their surface – a construct which we call the probe.
The oligonucleotides on the nanocrystals are synthesized to be complementary
to the ones one wants to detect. The ultraspecific binding of oligonucleotides
for their complementary strand allows the particles to bind very efficiently to
the analytes in solution. Such binding of two nanocrystals to the same analyte
brings the nanocrystals very close together thus enabling the coupling of the
plasmons.
As shown in the diagram below, once the nanocrystals are close the dipole can
extend over the ensemble of the two nanocrystals (as in resonance r2) while
for single isolated particle the dipole is confined to the particle itself
(resonance r1). The simultaneous presence of r1 and r2 resonances leads to an
effective red shift of the absorbance peak of the nanocrystals thus changing
their color, as shown in the photos thereby enabling detection of a specific
oligonucleotide which shows complementary Watson-Crick base pairing.
Gold Nanocrystals to Gold Nanorods
• Gold nanocrystal ncAu seed mediated growth of gold
nanorods nrAu
• ncAu seeds obtained by aqueous sodium borohydride
reduction of HAuCl4 with sodium citrate surface
stabilization
• nrAu obtained by surfactant (trimethylcetylammonium
bromide CTAB) directed re-growth of ncAu seeds using
ascorbic acid mild reducing agent of HAuCl4
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 = 22 nm; (b) L = 61 nm, w = 22 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
Nano Medicine - Photothermal Cancer Therapy Using Gold Nanorods
Nano Medicine
Photothermal Cancer Therapy Using Gold Nanorods
•
In the top part of the Figure you can see how the plasmons relax back to the equilibrium
state after being excited at their resonance. The relaxation occurs through emission of
heat that can be used for killing cells to which they are selectively attached.
•
In the middle part of the Figure is shown from the left the absorption/scattering
spectrum of the biological tissues and water; the windows of low absorbance are
indicated by the pink areas. In the next spectrum is shown how the different absorbances
of the tissues at different wavelengths affect the intensity of light propagating in them;
as it is shown in the graph the light with wavelength 1000 nm will propagate further
than light 500 nm, which is instead strongly absorbed. On the right is a representative
absorbance spectrum of gold nanorods highlighting how the second resonance peak can
be made to fit in the biological window, thus increasing its potential for photothermal
therapy.
•
In the bottom part of the Figure are shown three different lines of cells (nonmalignant
HaCat, malignant HSC and malignant HOC cells) after having exposed them to a strong
NIR laser light (the circle highlights the area of exposure). The gold nanorods were
made to bind selectively to the malignant cells thanks to an active targeting protocol. As
you can see the nonmalignant cells were not harmed since they were not targeted by the
nanorods. The malignant cells instead suffered strong damage because they were
targeted by the nanorods and because the nanorods heated up upon irradiation with the
laser.
CAPPED FePt FERROMAGNETIC
NANOCLUSTER SUPERLATTICE
HIGH-DENSITY DATA STORAGE MATERIALS
NANOMAGNETIC
SEPARATIONS OF
BIOLOGICAL MOLECULES