Diapositive 1

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SOLVOTHERMAL PROCESSES A ROUTE TO NOVEL
MATERIALS, WELL DEFINED NANOPARTICLES and HYBRID
NANO-SYSTEMS. Gérard DEMAZEAUEmeritus
Professor, ICMCB, CNRSUniversity BORDEAUX
1 Sciences and Technologies Vice-Président of
ISHA(International Solvothermal Hydrothermal
Association)
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SOLVOTHERMAL PROCESSESBucarest ,october 5-7 ,2007

• Dear Colleagues
• I apologize to be absent during this important
  Meeting organized by my friend Prof. Radu
  PITICESCU.
• After strong efforts for organizing a specific
  Session devoted to  Solvothermal Reactions 
  during the international High Pressure Conference
  (AIRAPT/EHPRG) in Catania (sept.15-23, 2007)
• and
• the participation to the XVIIIth Mendeleev
  Conference in Moscow (sept.22sept.28,2007) for
  presenting an invited lecture on  Solvothermal
  Processes 
• I was obliged due to health problems- to stop
  during one week my activity!!!
• All my best wishes for the success of this
  Meeting .
• Nevertheless ,I shall try to do the best for
  supporting your scientific project

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.
SOLVOTHERMAL REACTIONS
A solvothermal reaction can be defined as a
chemical reaction (or a transformation) between
precursor(s) in a solvent (in a close system) at
a temperature higher than the boiling temperature
of this solvent and under high pressure ?
autogeneous pressure or imposed pressure. ?
Subcritical or supercritical domain. ?
Homogeneous or heterogeneous system.
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WHAT ARE THE MAIN FACTORS CHARACTERIZING HIGH
PRESSURES

• Pressure is always involved in Solvothermal
  Processes( autogeneous our imposed pressure)
  consequently it is necessary to take into account
  the different factors induced by such a parameter
• The weak energy involved by pressure,
• The negative ?V value leading to the denser
  phases,(?V being the volume difference between
  the final state and the starting state)
• The improvement of the reactivity.

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• FIRST FACTOR THE ENERGY WHAT IS THE DIFFERENCE
  BETWEEN PRESSURE AND TEMPERATURE FROM AN
  ENERGETICAL POINT OF VIEW?
• 1)Comparison of the energy conveyed by HIGH
  PRESSURES and the energy of a CHEMICAL REACTION

Pressure (en bar) Medium Energy (en cal/mol)
1000 Gas 3000
1000 Solid 1
10000 Solid 5
100000 Iron 20
100000 H2O 1000
1 Chemical Reaction 20000
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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• 2) ? Comparison between Pressure and
  Temperature
• ? 1 liter of water, T20 ?T25C, P1bar
  (constant)
• Energy 20kJoules
• Using a constant temperature (T20C) what is
  the pressure value able to be reached with this
  energy ???
• P4000bar (400MPa)
• CONSEQUENTLY Due to the small energy conveyed by
  pressure
• such a parameter can be developed in
  Biosciences.

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• Brief history
• - Hydrothermal reactions (using aqueous
  solutions) have been developed at the end of the
  XIX Century ? ?objective to prepare geomaterials.
• - Development of hydrothermal crystal growth
  SPEZIA 1898-1909
• - Industrial crystal growth of ?-quartz and
  piezo-electric materials
• - Development of hydrothermal synthesis of new
  materials
• - 1990 Development of non-aqueous
  solvents hydro H2O Solvo
  solventProposition of solvothermal reactions(G.
  Demazeau-Bordeaux)
• for developing non-oxides. systems

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• DEVELOPMENT OF SOLVOTHERMAL REACTIONS
• Main types of chemical reactions involved in
  Solvothermal processes
• - oxidation/reduction, - hydrolysis,
• - thermolysis, - complexation, - metathesis
• The control of such reactions associated to the
  formation of the target material implies
• ?to improve the knowledge of the chemistry
  in non-aqueous solvents

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• Different research fields are implied in
  solvothermal processes
• ? MATERIALS CHEMISTRY and MATERIALS SCIENCE
• ? Synthesis of novel materials
• ? Research of low-cost
• processes
• ? Preparation of micro- or nano-crystallites
• ? Growth of single crystal of functional
  materials
• ? Low-temperature sintering processes
• ? Thin film deposition
• ? DEVELOPMENT OF RESEARCH DOMAINS AT THE
  INTERFACE BETWEEN DIFFERENT DISCIPLINARIES.
• ? Hybrid Materials (inorganic
  chemistry/Organic chemistry).
• ? Hybrid Systems (nano-chemistry/Biosciences)

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• Main parameters involved in Solvothermal
  Reactions
• -The nature of the reagents
• Chemical composition, size of the crystallites
• - The chemical composition of the solvent-
• Such a parameter is able to open new research
  areas concerning the composition of the expected
  materials
• Synthesis of intermetallic compounds, oxides,
  nitrides, phosphides, borides..
• - The mild temperature conditions-
• Temperature is mainly used for improving the
  diffusion of chemical species,
• The mild temperature conditions allow- if the
  reaction is kinetically controlled- to prepare
  metastable materials.
• - The pressure in liquid phase is limited (10
  ltPlt500 MPa)
• Pressure is developed in order-
• (i) through the interactions between liquid/solid
  phases or between solvated chemical species (in
  solution) to improve the reactivity,
• (ii) through the densification effect to
  orientate the structure of the expected
  materials.

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.
ROLE OF THE REAGENTS IN SOLVOTHERMAL
PROCESSES SYNTHESIS OF A NEW-CLASS OF
BI-DIMENSIONNAL OXIDES ISOSTRUCTURAL TO
PHYLLOSILICATES THE PHYLLOSILOXYDES. (P. REIG ,
G. DEMAZEAU ,R. NASLAIN) ICMCB ,LCTS, University
Bordeaux 1
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SOLVOTHERMAL SYNTHESIS OF PHYLLOSILOXIDES
? The thermal stability of phyllosilicates is
limited by OH groups. 2OH-
O2-H2O?? ? Anionic substitution OH-?O2- in the
phyllosilicates lattice.But correlated with
cationic substitutions
?
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SOLVOTHERMAL SYNTHESIS OF PHYLLOSILOXIDES

• The anionic sustitution OH-?O2- leads to an
  increase of the anionic charges
• Consequently such an anionic substitution is
  correlated with cationic substitutions.
• One possibility
• Al3(Td) ? Si4 (Td)
• Mg2(Oh) ? Al3 (Oh)

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SOLVOTHERMAL SYNTHESIS OF PHYLLOSILOXIDES
SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.
D

• sol-gel process sol ? gel
  aerogelConventional Solid State Solvothermal
  processProcess (500 ?1000C) solvent
  methoxy-ethanol precursor aerogelMixture
  of 3D silicates T500C, 50?P?150MPa, t?24h
  
• single phase

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

I.R. Spectroscopy
K Mg3 (Si3Al)O10(OH)2
K(Mg2Al) Si4 O12
X. Ray Diffraction
Scanning Electron Microscopy
H.R.T.M.
K(Mg2Al) Si4 O12
K Mg3 (Si3Al)O10(OH)2
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SOLVOTHERMAL SYNTHESIS OF PHYLLOSILOXIDES

• X-ray diffraction analysis
• The X-ray spectrum of the resulting single phase
  is similar to that of the initial  mother
  phase  mica with the phlogopite structure.
• ? Ir spectroscopy
• K Mg3 (Si3Al) O10(OH)2 ? strong absorption band
  due to OH group ( 3700 3800 cm-1).
• K (Mg2Al) Si4O12 ? NO absorption band
  corresponding to OH groups.
• Electronic Microscopy.
• SEM platelets (l? 0.2 µm)
• TEM layered structure (interlayer distance
  corresponding to the phlogopite structure)

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.
ROLE OF THE SOLVENT IN SOLVOTHERMAL PROCESSES (A)
Synthesis of metastable compounds The
solvent, can induce the formation of very stable
complex ions and such complex ions can act as
template for stabilizing metastable
compounds. Example LI J., CHEN Z., WANG R.J.,
PROSERPIO D.M. Coordination Chem. Rev. (1999)
190-192 p. 707. Ethylenediamine has a strong
coordination ability towards the divalent
transition metals (Mn2, Fe2, Co2, Ni2,
Zn2)M2 3en ? M(en)32 M(en)32 characterized
by an octahedral geometry can act as template for
building new metastable materials.
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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.
ROLE OF THE SOLVENT IN SOLVOTHERMAL PROCESSES (B)
Orientation to a metastable structural
form LU J., QI P., PENG Y., MENG Z., YANG Z., YU
W., QIAN Y. Chem. Mater. (2001) 13 p.
2169. precursors MnCl2, 4H2O and SC(NH2)24
solvents have been evaluatedH2O or
ethylenediamine able to form a stable Mn
complex ? a-MnS rocksaltnon polar C6H6 ?
g-MnS wurtzite (Metastable)tetrahydrofuran (THF)
? b-MnS zinc-blende (Metastable)when no stable
complexes are stabilized? the solvothermal
reaction is kinetically controlled leading to the
stabilization of two metastable forms.
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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.
ROLE OF THE SOLVENT IN SOLVOTHERMAL PROCESSES (C)
The oxidation-reduction properties
inducing a specific composition. PANDA S.K.,
GORAI S., CHAUDURI S. Mater. Sci Eng. B. (2006)
129 p. 265.have underlined the role of the
oxidation-reduction process induces by the
solvent during the solvothermal synthesis of SnS
crystallites from Sn metal. Such a solvothermal
process can be described through three
steps(1) Sn0 (few amounts of H2O) ? Sn2
2e-(2) Sn2 n en. ? Sn(en)n2(3) Sn(en)n2
S2- ? SnS.
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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.
ROLE OF THE SOLVENT IN SOLVOTHERMAL PROCESSES (D)
Preparation of nano-crystallites
with a specific morphology. Solvothermal
preparation of nanocrystallites with a specific
morphology has attracted a strong interest during
these last years. Different compositions of
nanocrystallites have been developed but
recently intermetallic nanocrystallites have been
investigated. The preparation of nanoparticles of
intermetallic FePt nanowires has been selected as
example.
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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• (D) ROLE OF THE SOLVENT IN THE PREPARATION OF
  INTERMETALLIC FePt NANOWIRES
• Interest of such FePt nanoparticlesIntensive
  Research due to its potential applications in
  high density storage and high performance
  permanent magnets. ? WELLER D., DOERWER M.F.
  Annu. Rev. Mater. Sci. (2000) 30 p. 611.? SUN
  S., MURRAY C.B., WELLER D., FOLKS L., MOJER A.
  Science (2000) 287 p. 1989.Conventionally FePt
  particles were synthesized via thermal
  decomposition of Fe(CO)5, reduction of Platinum
  acetylacetonate Pt(acac)2 and co-reduction of
  iron salt and Pt(acac)2. ?difficulty to
  control the morphology of FePt nanoparticles.

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• ROLE OF THE SOLVENT IN THE SOLVOTHERMAL
  PREPARATION OF INTERMETALLIC FePt NANOWIRES
• In order to control the size and the morphology
  of PtFe nanoparticles
• Development of a solvothermal process.
• Precursors Pt(acac)2 Fe(CO)5 (en) as solvent
• (160 lt T lt 200C , autogeneous pressure)
• Pt(en)22 inducing self organization leads to
• the formation of FePt Nanowires.
• MAO C.B., SOLIS D.J., REISS B.D., KOTTMANN S.T.,
  SWEENEY R.Y., HAYHUST A., GEORGIOU G., IVERSON
  B., BELCHER A.M. Science (2004) 303 p. 213.

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• Potentialities of solvothermal processes
• for developing hybrid systems

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.
Low temperature solvothermal processes allow to
stabilize original hybride materials (inorganic/
organic components) as an example ?
Solvothermal synthesis of Zincophosphite
(C6H16N2)Zn3(HPO4)3
FU et al. Solid State Sciences 6, 225 (2004)
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At the interface between BIOSCIENCES and
NANO-SCIENCES
SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• PEPTIDE ENGINEERING FOR BIO-INSPIRED MATERIALS
• (M.UMETSU et al. Tohoku University)
• J. Materials Science (in press)
• Peptides have affinity for non-biological
  materials and could mineralized inorganic
  materials.
• ZnO semi-conductor with a direct band gap
  ....fabrication of ZnO nano-structures.
• Peptide can bind the ZnO particles (but no ZnS)
  and further the ZnO-binding peptide selectively
  catalyses the synthesis of a highly anisotropic
  ZnO particles from a Zn(OH)2 solution at room
  temperature and medium pressure conditions

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SOLVOTHERMAL PROCESSES FROM NOVEL MATERIALS TO
HYBRID NANO-SYSTEMS.

• MAIN CHALLENGES FOR THE FUTURE ???
• Why and How to reduce Temperature
• WHY? ? FOR PRESERVING SPECIFIC COMPONENTS
• (in order in particular to prepare hybrid
  inorganic/organic or inorganic/biological
  systems)
• ? FOR INDUCING METASTABLE PHASES
• (but it is necessary to improve the
  kinetical effects)
• ? FOR SAVING ENERGY
• (sustainable development)
• HOW ?
• TO IMPROVE THE CHEMICAL REACTIVITY ? TROUGH THE
  OPTIMIZATION
• -PRECURSORS
• -SOLVENT,
• -PRESSURE.

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MAIN OBJECTIVES OF SOLVOTHERMAL PROCESSES

• ? To open a route through new  soft chemical
  processes
• Kinetically controlled for stabilizing
  metastable systems,
• To help the synthesis of specific structures
  using templates,
• To control the nucleation/ crystal growth
  processes for the preparation of nanocrystallites
  well defined in size and morphology,
• To facilitate ,through the improvement of the
  chemical reactivity and the development of mild
  temperature conditions, the synthesis of hybrid
  nano-systems.

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CONCLUSIONS

• All the objectives of SOLVOTHERMAL PROCESSES
• require to optimize
• The physico-chemical properties of the
  precursors,
• The physico-chemical properties of the solvent,
• The thermodynamical parameters P, T.
• Solvothermal processes appear to be important in
  the near future, not only for developing Basic
  Science
• But also
• for developing new industrial processes in mild
  P,T conditions.
• THANK YOU FOR YOUR ATTENTION.