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Markus Niederberger
Laboratory for Multifunctional Materials
Department of Materials
ETH Zü[email protected]
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(Co(Co--))PrecipitationPrecipitation
SolSol--GelGelChemistryChemistry MicroMicro--
emulsionsemulsions
HydroHydro-- & & SolvothermalSolvothermalProcessingProcessing
BiomimeticBiomimeticSynthesisSynthesis
TemplateTemplateSynthesisSynthesis
OverviewOverview
MicrowaveMicrowaveSynthesisSynthesis
LiquidLiquid--Phase Phase RoutesRoutes to to InorganicInorganic
NanopowdersNanopowders
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AdvancesAdvances inin……
HotHot--InjectionInjection MethodMethod
Times Cited: 26151) Injection of a „cold“ precursor solution to a hot (molten) surfactant or surfactant/solvent
mixture
2) Nucleation and growth
3) Surfactant controls size, shape, and surface properties
4) Precipitation by addition of a „nonsolvent“
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„„ConsequencesConsequences““ of of thethe HotHot--InjectionInjection MethodMethod::
SurfactantSurfactant--DirectedDirected NonhydrolyticNonhydrolytic RoutesRoutes
AdvancesAdvances inin……
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SynthesisSynthesis
Metal Salts: Chlorides MCln, Acetates M(OOCCH3)n, Nitrates M(NO3)n,…
Metal Organic Compounds: Metal Alkoxides M(OR)n,..
Organometallic Compounds: Metal Carbonyls M(CO)n,…
„Molecular“ Precursor(s) +Molten Surfactant(s)
Surfactant(s)/High Boiling Solvent(s)
T = 100 – 350 °C
Inorganic Nanoparticles
Diphenyl ether (C6H5)2O
Boiling Point: 259 °C
Trioctylphosphine oxide (TOPO)
Melting point: 201 °C
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ShapeShape ControlControl
ButBut:: No No PredictionPrediction possiblepossible!!
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SizeSize ControlControl
Fe(CO)5 + dioctylether + oleic acid at 100 °C: Formation of Fe nanoparticle seeds (4 or 8 nm)
Addition of Fe(CO)5 solutionto the preformed seeds
Oxidation in air: γ-Fe2O3 (maghemite)
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SizeSize ControlControl
6 nm
11 nm10 nm
9 nm8 nm7 nm
13 nm12 nm
Hyeon et al., Angew. Chem. Int. Ed. 2005, 44, 2872
PredictionPrediction possiblepossible!!
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„„MolecularMolecular““PrecursorPrecursor
OrganicOrganicSolventSolvent
TemperatureTemperatureTreatmentTreatment
Metal Oxide Metal Oxide NanoparticlesNanoparticles
Without Surfactants!!!
OurOur ResearchResearch
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„„MolecularMolecular““PrecursorPrecursor
OrganicOrganicSolventSolvent
TemperatureTemperatureTreatmentTreatment
Metal Oxide Metal Oxide NanoparticlesNanoparticles
Without Surfactants!!!
OurOur ResearchResearch
+ Low amount of organic impurities
Nontoxic solvent vs. toxicity of surfactants
Simple, robust, and generally applicable synthesis protocol
Small number of initial components: Study of the mechanisms!
Good accessibility of the nanoparticle surface
- Less control over size and shape
Broader size distribution
Formation of agglomerates, limited redispersibility
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BENZYL ALCOHOLBENZYL ALCOHOL
Metal Chlorides:Metal Chlorides:TiO2, VO1.52(OH)0.77,
WO3·H2O, SnO2, HfO2, Ta2O5, Nb2O5
Metal Metal AcetylacetonatesAcetylacetonates::Fe3O4, Mn3O4, ZnO, Co-doped ZnO
Metal Metal AcetatesAcetates::CoO, Fe3O4, MnO, ZnO
Alkoxides + Alkoxides + AcetylacetonatesAcetylacetonates::Indium Tin Oxide (ITO), Mn-doped ZrO2,
Co/Fe-doped TiO2
AcetatesAcetates + + AcetylacetonatesAcetylacetonates::MnFe2O4, CoFe2O4, NiFe2O4
Metal Alkoxides:Metal Alkoxides:TiO2, V2O3, W18O49, SnO2, HfO2, In2O3, Ln2O3, CeO2, ZrO2, ZnO,
Ta2O5, Nb2O5, NaNbO3, NaTaO3, BaTiO3, SrTiO3, (Ba,Sr)TiO3,
LiNbO3, BaZrO3
AcetylacetonatesAcetylacetonates + Chlorides:+ Chlorides:InNbO4, MnNb2O6, YNbO4
OurOur ResearchResearch
AcetatesAcetates + + Alkoxides:Alkoxides:
CdIn2O4
Angew. Chem. Int. Ed. 2008, 47, 5292
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BinaryBinary Metal Oxide Metal Oxide NanoparticlesNanoparticles
Metal ChloridesMetal ChloridesT = 60-220 °C
Metal AlkoxidesMetal AlkoxidesT = 200-250 °C
BENZYL ALCOHOLBENZYL ALCOHOL Metal Metal AcetylacetonatesAcetylacetonates
T = 80-200 °C
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TernaryTernary Metal Oxide Metal Oxide NanoparticlesNanoparticles
M(acac)M(acac)33 and and NbClNbCl55 BENZYL ALCOHOLBENZYL ALCOHOL Alkoxides and Alkoxides and
AcetylacetonatesAcetylacetonates
Indium Tin Oxide 10 wt% SnO2
Metal AlkoxidesMetal AlkoxidesT = 200-250 °C
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Chemical Formation Chemical Formation MechanismsMechanisms
ExampleExample::Formation Formation MechanismMechanism of BaTiOof BaTiO33
No No waterwater TwoTwo mainmain questionsquestions::
1) Where does the oxygen come from?
2) How is it transferred from the source to themetal center?
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Chemical Formation Chemical Formation MechanismsMechanisms
? =
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Chemical Formation Chemical Formation MechanismsMechanisms
O-TiOH
C-C Bond Formation!
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Chemical Formation Chemical Formation MechanismsMechanisms
The oxygen isprovided by the „OH“
group of benzylalcohol!
J. Am. Chem. Soc. 2004, 126, 9120
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Chemical Formation Chemical Formation MechanismsMechanisms
Chem. Eur. J. 2006, 12, 7282
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Chemical Formation Chemical Formation MechanismsMechanisms
To understand nanoparticle formation on a molecular level (i.e., crystallization and size- and shape-determining parameters), all the organic species (initially present as
well as formed in-situ) have to beconsidered!
J. Mater. Chem. 2008, 18, 1171
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AssemblyAssembly
NanoparticlesNanoparticles as Building Blocks (as Building Blocks (LegoLego BricksBricks))
Shevchenko, Talapin, Murray, O’Brien: J. Am. Chem. Soc. 2006, 128, 3620
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AssemblyAssembly
NanoparticlesNanoparticles as Building Blocks (as Building Blocks (LegoLego BricksBricks))
Nature, 439, 55-59 (2006)
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AssemblyAssembly
NanoparticlesNanoparticles as Building Blocks (as Building Blocks (LegoLego BricksBricks))
Chaudret et al. Science 2004, 303, 821
500 nm 10 nm
New Properties?
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ApplicationsApplications
Metal Oxide Metal Oxide NanoparticlesNanoparticles forfor Gas Gas SensingSensing
3 mm 3 mm
6 m
m
Front sidegold electrodes
Back sideplatinum contacts
Cross section
0.38
mm
Alumina substrate
Sensing layer
50 μm
In2O3
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ApplicationsApplications
Metal Oxide Metal Oxide NanoparticlesNanoparticles forfor Gas Gas SensingSensing
100 150 200 250 300
10
100
I Air/I NO
2
Temperature (°C)
2 ppm NO2
a)
2 4 6 810-9
10-7
10-5
10-3
T= 250°C
Cur
rent
(A)
T ime (h)
b)
0
10
20
30
40
50
60
[NO
2] (pp
m)
1 1010
100
slope= (0.49±0.06) ppm -1
lower detection limit ~ 1 ppb
T= 250°C
I Air/I NO
2
[NO2] (ppm)
c)
(a) Response to 2 ppm of NO2 versus operating temperature of the In2O3 sensor: Maximum sensitivity around 200°C
(b) Dynamic response at 250°C to different and successive concentration pulses of NO2 (2-20 ppm): Fast response time (less than 60 s)
(c) Calibration curve at 250°C: Detection limit of about 1 ppb for NO2 in air
Cross-sensitivity tests with CO and CH4 show no response (T = 100-400°C)
Angew. Chem. Int. Ed. 2004, 43, 4345
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ConclusionsConclusions -- OutlookOutlook
Metal Oxides Metal Oxides NanoparticlesNanoparticles
Synthesis in Benzyl Alcohol:
General (> 30 Compositions)
Large Variety of Crystal Sizesand Shapes: Wires, Rods,
Platelets, Cubes, Spheres,…
SynthesisSynthesis
AssemblyAssembly
But: Doping, Multi Metal Oxides, Heteronanostructures!
But: No Prediction! No Rational Synthesis Planning!
1, 2 and 3D Architectures in Selected Cases
But: Dispersions of Nanoparticles on
Primary Particle Level!
But: Nanoparticles as Artificial Atoms
(Directed Bonding)
Nanocomposites / Organic-Inorganic Hybrid Structures
But: Study of Collective Properties
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MultifunctionalMultifunctional MaterialsMaterials
2007