CHIMIE DOUCE: SOFT CHEMISTRY

1
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

2
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

3
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

4
RUTILE CRYSTAL STRUCTURE
5
SEEING THE 1-D CHANELS IN RUTILE
6
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
1/2
1/3
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
7
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

8
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
9
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
10
Functional device, LED, laser, sensor, biolabel
Growth and ligand capping of nanocluster core
Ligand capping arrested growth 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
11
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
12
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.

13
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.

14
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.

15
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.

16
BASICS OF NANOCLUSTER NUCLEATION, GROWTH,
CRYSTALLIZATION AND CAPPING STABILIZATION
?Gb gt ?Gs
supersaturation
nucleation
aggregation
capping and stabilization
nMe2Cd nnBu3PSe mnOct3PO ? (nOct3PO)m(CdSe)n
n/2C2H6 nnBu3P
17
EgC EgB (h2/8R2)(1/me 1/mh) - 1.8e2/?R
Coulomb interaction between e-h
Quantum localization term
CAPPED MONODISPERSED SEMICONDUCTOR NANOCLUSTERS
nMe2Cd nnBu3PSe mnOct3PO ? (nOct3PO)m(CdSe)n
n/2C2H6 nnBu3P
18
(No Transcript)
19
(No Transcript)
20
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)
21
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
22
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
23
ARRESTED GROWTH OF MONODISPERSED NANOCLUSTERS
CRYSTALS, FILMS AND LITHOGRAPHIC PATTERNS
nMe2Cd nnBu3PSe mnOct3PO ? (nOct3PO)m(CdSe)n
n/2C2H6 nnBu3P
24
MONODISPERSED CAPPED CLUSTER SINGLE CRYSTALS
Rogach AFM 2002
methanol
2-propanol
toluene
25
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
26
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
27
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)
28
Relationship between alkanethiolate polymer,
nanocluster and self-assembled monolayer
29
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.

30
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
31
Plasmonics Basics Size Effects
32
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.

33
SURFACE PLASMON RESONANCE MIE THEORY

• Extinction coefficient from Mie theory is the
  exact solution to Maxwells 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 sensitive to environment
• 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.

34
Extinction spectra calculated using Mie theory
for gold nanospheres with diameters varying from
5 nm to 100 nm.
35
Detecting Biomolecules with Gold
NanocrystalsSelf Assembly and Plasmon Coupling
36
Detecting Biomolecules with Gold
NanocrystalsSelf 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.

37
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 (trimethylcetylammoni
  um bromide CTAB) directed re-growth of ncAu seeds
  using ascorbic acid mild reducing agent of HAuCl4

38
Non-Spherical Shapes -Gans Modified Mie Theory
39
Au Nanorods Shape Selective AdditivesAspect
Ratio Tunes Longitudinal NOT Transverse SPR Modes
(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.
Calculated Gans Theory Gold Nanorod w 20 nm
40
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
41
Nano Medicine - Photothermal Cancer Therapy Using
Gold Nanorods
42
Nano MedicinePhotothermal 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.

43
(No Transcript)
44
CAPPED FePt FERROMAGNETIC NANOCLUSTER
SUPERLATTICE HIGH-DENSITY DATA STORAGE MATERIALS
45
NANOMAGNETIC SEPARATIONS OF BIOLOGICAL MOLECULES
46
(No Transcript)