colloid chemistry · 2019-05-05 · solvo/hydrothermal synthesis mari-ann einarsrud and tor grande,...

Silvia Gross – Chimica dei Colloidi – Laurea Triennale in Chimica

Istituto di Scienze e Tecnologie Molecolari

ISTM-CNR, Università degli Studi di Padova

e-mail: [email protected]

Silvia Gross

La chimica moderna e la sua comunicazione

Dipartimento di Scienze Chimiche

Università degli Studi di Padova

e-mail: [email protected]

http://www.chimica.unipd.it/silvia.gross/

Silvia Gross

Colloid Chemistry


1) Sol-gel and nonaqueous sol-gel processes (also MW-assisted)

2) Pechini and citrate method

3) Coprecipitation from an aqueous solution

4) Polyol-assisted synthesis

5) Thermal and photochemical decomposition

6) Hydro- and solvothermal synthesis

7) Nucleation from solutions/ reduction to metal colloids

8) Decomposition of precursors

9) Colloidal methods

10) Micro- and miniemulsion

11) Sonochemical synthesis

12) Templated synthesis

13) Chemical bad deposition

S. Diodati, P. Dolcet, M. Casarin and S. Gross

Pursuing the Crystallization of Mono- and Polymetallic Nanosized Crystalline Inorganic Compounds by Low-Temperature Wet-

Chemistry and Colloidal Routes, Chem. Rev., 2015, 115, 11449–11502

S. Gross, “Sustainable and very low temperature wet-chemistry routes for the synthesis of crystalline inorganic compounds”

Chapter 1 in in “Green Processes in Nanotechnology” V. A. Basiuk and E. V. Basiuk, eds, Springer, 2015.

Wet chemistry/colloidal syntheses


1) Hydro- and solvothermal synthesis

strictly speaking, not a colloidal route, but in many cases

involves a suspension as starting system to achieve:

1. Colloidal monodisperse particles

2. Nanoscopic materials which can be post-functionalised

and redispersed

Wet chemistry synthesis routes


Solvo/hydrothermal synthesis



Critical point

The temperature and pressure at which the liquid and vapour

intensive properties (density, heat capacity, etc.) become equal. It is

the highest temperature (critical temperature) and pressure (critical

pressure) at which both a gaseous and a liquid phase of a given

compound can coexist.

IUPAC Goldbook: http://goldbook.iupac.org/C01396.html

hydro/solvothermal synthesis

- supercritical

- subcritical

http://goldbook.iupac.org/H02753.html

http://goldbook.iupac.org/C01402.html

http://goldbook.iupac.org/C01397.html



Mari-Ann Einarsrud and Tor Grande, Chem. Soc. Rev., 2014, 43, 2187-2199

A. Rabenau, Angew. Chem., Int. Ed. Engl., 1985, 24, 1026–1040

Definition of hydrothermal reaction

Heterogeneous chemical reaction in aqueous media above room

temperature (normally above 100 °C) and at a pressure greater

than 1 atm

- supercritical

- subcritical



Published items in each year (left) and citations in each year (right) on the “hydrothermal synthesis

of nanostructures” (used keywords: “hydrothermal synthesis” and “nanostructures”).

Source Web of Science Dec 2014.


Why hydrothermal synthesis

Fig. 1 Density, dielectric constant and ionic product, Kw, of pure water at 30 MPa as a function of temperature.

Figure: M.A. Einarsrud , T. Grande

Chem. Soc. Rev., 2014, 43, 2187-2199

ionic product tends to increase with rising

temperature and pressure

viscosity decreases (diffusion enhanced)

dielectric constant of water varies in

dependence to the specific operative

conditions since it increases with higher

pressures, but decreases with rising

temperatures.

Water:

-Solvent

-Pressure-transmitting medium


Why hydrothermal synthesis?

(closed container)

Temperature/ °C State Density/

kg·m-3

Viscosity/

µPa·s

Dielectric

Constant

Pressure equal to 0.1 MPa

27 Liquid 996.56 853.82 80.20

52 Liquid 987.19 530.32 69.32

77 Liquid 973.73 368.80 61.79

102 Gas 0.590 12.339 1.006

135 Gas 0.543 13.285 1.005

177 Gas 0.484 15.426 1.004

Properties of water and vapor as a function of temperature and pressure [CRC; NIST Database –

http://webbook.nist.gov/cgi/fluid.cgi?ID=C7732185&Action=Page]



Feedstock

preparation

Reagents

Growth control agents

Oxides/Hydroxides/salts

Gels /Organics/Acids/Bases

ReactorTemperature (100 to 350oC)

Pressure ( < 15 MPa)

Residence Time (10 min-48 h)

Pressure Let-down

crystalline powderFiltrating/washing/drying



AUTOCLAVE

Control on:

- temperature

- pressure

BOMB/HYDROTHERMAL REACTOR

Control on:

- temperature

(pressure is autogenous)



Byrappa K.; Yoshimura M.; Handbook of Hydrothermal Technology; 2001; Noyes Publications, park Ridge, New Jersey, U.S.A

• Reactants are dissolved (or placed) in water or

another solvent (solvothermal) in a closed

vessel

• Typically alkaline conditions

• Bomb is heated above BP

• Conventional or MW oven

• Commercially:

– Tons of zeolites daily

– Several nanomaterials


Parameters you can play with

Nature of the precursors, solvent

Nominal molar ratios among reagents

Treatment times and temperatures → operating pressure

Filling of the vessel

Peptizing agents, additives, surfactants

Purification steps S. Diodati, PhD Thesis,

Università degli Studi di Padova, 2013


Crystallisation under hydrothermal conditions:

dissolution/precipitation proposed two-step mechanism

1. in situ transformation: the precursor ions are dissolved in the reaction mixture → tiny

quantities of the target compound are able to form (as solutes) in the liquid phase.

2. due to the low solubility, even at high pressure and temperature, of the final compound,

the second phase (diffusion, precipitation and growth) takes place. In this phase,

nucleation centers are formed throughout the system around which crystal growth can

occur.

A. Holden and P. Singer, Crystals and Crystal Growing, Anchor Books Doubleday & Company Inc., Garden

City, New York, 1971.

N. Modeshia, R.I. Walton, Chem. Soc. Rev., 2010, 39, 4303–4325

X. Chen, H. Fan and L. Liu, J. Cryst. Growth, 2005, 284, 434-439.

I. MacLaren and C. B. Ponton, J. Eur. Ceram. Soc., 2000, 20, 1267-1275.

Crystallisation under hydrothermal conds


Crystallisation under hydrothermal

Hydrothermal dissolution/precipitation: basic mechanism

for the hydrothermal formation of ceramic oxide particles

Dissolution

Precipitation

Modeshia, Walton, Chem. Soc. Rev., 2010, 39, 4303–4325


Hydrothermal synthesis of nanomaterials

BaTiO3 Nanoparticles

• Ba(OH)2 + TiO2 BaTiO3 nanoparticles

• 300 - 450°C, HT

• Two proposed mechanisms:

– Dissolution-recrystallization

– In situ crystallization

Hakuta, R., Ura, H. Hayashi, H, and Arai, K. Ind.

Eng. Chem. Res. 2005, 44, 840-846



hydrothermal crystallization

Hydrothermal crystallisation mechanisms

proposed for barium titanate.

1. the case of heterogeneous nucleation where

BaTiO3 growth occurs on the surface of

undissolved TiO2 particles by reaction with

dissolved barium ions to yield core–shell

type intermediates before the complete

consumption of the remaining solid reagents

2. the case where homogeneous nucleation

occurs, i.e. the dissolution of both Ba and Ti

sources under reaction conditions followed

by the direct formation of BaTiO3 from

solution or at the surface of remaining TiO2

particles




BaTiO3 Nanoparticles: in-situ crystallization

Eckert, J.O., Hung-Houston, C.C., Gersten, B.L., Lencka,

M.M., Riman, R.E., J. Am. Ceram. Soc. 1996, 79, 2939.



playing with morphologies

Morphologies of BaTiO3 crystallites formed by one-step

hydrothermal reactions.

(a) Dendritic particles.

(b) Plate-like crystallites.

(c) Spherical nanocrystallites.




Transformation of titanates into TiO2 NSs

Mao, Y., T.-J. Park, et al. (2007).

"Environmentally Friendly

Methodologies of Nanostructure

Synthesis." Small 3(7): 1122-1139.


Control on shape and morphology

Different hydroxyapatite crystalline nanostructures obtained through hydrothermal synthesis

depending on parameters.

Sadat-Shojai, M.; Khorasani, M.-T.; Dinpanah-Khoshdargi, E.; Jamshidi, A.

Synthesis methods for nanosized hydroxyapatite with diverse structures

Acta Biomater. 2013, 9, 7591-7621.


Metal oxide hollow spheres



Metal oxide hollow spheres by hydrothermal

templated approach


Hollow spheres of crystalline metal oxides were

synthesized in a simple one-pot synthesis via a

hydrothermal approach. Various metal salts were

dissolved together with carbohydrates in water,

and the mixtures were heated to 180 °C in an

autoclave. During the hydrothermal treatment,

carbon spheres are formed with metal ions

incorporated into their hydrophilic shell. The

removal of carbon via calcination yields hollow

metal oxide spheres. Using this process, a wide

range of metal oxide hollow spheres was

prepared that are not accessible via sol−gel

chemistry: Fe2O3, NiO, Co3O4, CeO2, MgO, and

CuO hollow spheres that are composed of

nanoparticles. The surface area and thickness of

the shell can be varied or controlled by the

carbohydrate:metal salt concentration.


Metal oxide hollow spheres by hydrothermal

templated approachSEM image of carbon spheres

obtained from the hydrothermal

treatment of glucose



Metal oxide hollow spheres

SEM images of (a) NiO, (b) Co3O4,

(c) CeO2, and (d) MgO hollow

spheres



Hydrothermal synthesis of nanostructured

crystalline ferrites and manganites

andSynthesis of nanocrystalline CoFe2O4, MnFe2O4, NiFe2O4, ZnFe2O4,

ZnMn2O4, ZnMnO3, CuMnO2, ZnO, ZnS

combining coprecipitation of oxalates and hydrothermal treatment

• Crystallisation at very low temperature (100-180°C)

• Using water as solvent: greenest solvent!

• Very easy and reproducible procedure

• Very common, cheap and safe precursors

• Effective control over the products stoichiometry

• Compounds obtained in highly crysyalline form

• Small crystallite size (15-40 nm, depending on conditions)

• High yields (60-90%)

• Very pure compounds (clean decomposition of oxalates)

• Magnetic properties assessed

Diodati S.; Pandolfo L.; Caneschi A.; Gialanella S.; Gross S.; Green, very low temperature hydrothermal assisted synthesis

of nanocrystalline transition metal spinel ferrites, Nano Res., 2014, 7, 1027-1042

Minelli, A.; Dolcet,P., Pandolfo, L; Gross S. et al. Pursuing the stabilisation of crystalline nanostructured magnetic

manganites through a green low temperature hydrothermal synthesis, submitted


Perovskites

MFeO3

• Properties dependant on M metal

• Iron in an oxidation state (III) or (IV)

• Ionic conduction

Applications

• Organic compounds decomposition

• Fuel cells, SOFC

Berenov A.V.; MacManus-Driscoll J.L.; Kilner J.A.; International Journal of Inorganic Materials; 2001; 3,

1109–1111

Yang Y.; Jiang Y.; Wang Y.; Sun Y.; Journal of Molecular Catalysis A: Chemical; 2007; 270, 56–60



Spinels

MFe2O4

• Properties vary with M

• Hard/soft magnetic material

• Normal or inverse structure

• Degree of inversion γ

Applications

• Catalysis – Water splitting

• Ferrofluids

• Hyperthermia

• Diagnostic medicine

Carta D.; Casula M. F.; Falqui A.; Loche D.;

Mountjoy G.; Sangregorio C.; Corrias A.; J.

Phys. Chem. C; 2009; 113, 8606–8615

A. Z. Simoes, F. G. Garcia and C. d. S. Riccardi,

Mater. Chem. 90 Phys., 2009, 116, 305-309.

L. Malavasi, C. A. J. Fisher and M. S. Islam,

Chem. Soc. Rev., 2010,

39, 4370-4387.



Outline

Coprecipitation of oxalates (high T)

Polycrystalline oxide powders

I.

Fe3+

M2+

H2C2O4

TENOHPrecursor salts

solution

Basification

II.

III.

Metal oxalates

suspension

Purification

IV.

V.

Calcination

Diodati S.; Nodari L.; Natile M.M.; Russo U.; Tondello E.; Lutterotti L; Gross S.; Dalton Trans. 2012; 41, 5517–5525

Coprecipitation of oxalates: an easy and reproducible wet-chemistry synthesis route for transition metal ferrites

S. Diodati, L. Nodari, M. M. Natile, A. Caneschi,, S. Gross et al. European Journal of Inorganic Chemistry (2013) 875-887

Fe3+ + M2+ H2C2O4 + NaOH → Fe2(C2O4) 3↓ + M(C2O4)↓ 600-900°C



Hydrothermal synthesis: very low T!

Nanosized crystalline oxides

I. II. III.

Metal oxalates

suspension

Hydrothermal

treatmentCentrifugation

Byrappa K.; Yoshimura M.; Handbook of Hydrothermal Technology; 2001; Noyes Publications, park Ridge, New Jersey, U.S.A

70-120 °C


Hydrothermal synthesis: crystallinity

XRPD patterns and XPS spectra of a) CoFe2O4; b) MnFe2O4; c) NiFe2O4 d) ZnFe2O4

Cou

nts

/a.u

.

8070605040302010

Bragg Angle/°

b

a(111)(220)

(311)

(400)(422)

(511) (440)

(111)(220) (400)

(422)

(440)(511)

(311)

(311)

(440)(511)(400)

(311)

(220)(111)

c

(111) (220)(400) (511)

(440)

d

Co

un

ts/a

.u.

1200 1000 800 600 400 200 0

B.E./eV

C1s

O1sFe2pMn2p

Fe LMM

Mn LMM

O KLL

Na1s

Fe3p

C KVV

C KVV

O KLL

Fe LMM

Ni LMM

Fe2p

Ni2p

C1s

O1s

Fe3p

c

Fe3pC1s

O1s

Na1sFe2pCo2p

Fe LMMCo LMM

b

a

Fe3p

d

C1s

O1sFe2pFe LMM

O KLL

Zn2pC KVV

Zn LMM

e

Zn2p

O KLL

C KVV

Fe LMM Fe2pO1s

Zn LMM C1s Fe3p


Hydrothermal synthesis: TEM

TEM micrographs of a) CoFe2O4; b) MnFe2O4; c) NiFe2O4 d) ZnFe2O4


Coprecipitation

500 nm

CoFe2O4

Method Fe/Co

(Theoretical)

Fe/Co (XPS) Fe/Co

(ICP-AES)

Sol-gel 2.0 2.1 2.0

Coprecipitation 2.0 2.1 2.0

Hydrothermal 2.0 2.0 1.9

Hydrothermal


MnFe2O4

Pure phase through

hydrothermal and

nonaqueous sol-gel

Rapid synthesis

Crystallite sizes in the 10 -

40 nm range

Co

un

ts/a

.u.

8070605040302010Bragg Angle/2

(111)

(220)

(311)

(400)(511)

(440)

(422) (533) (a)

(b)

(c)

Optimisation of the hydrothermal synthesis for shorter times

Diodati S.; Pandolfo L.; Caneschi A.; Gialanella S.; Gross S.; Green, very low temperature hydrothermal assisted

synthesis of nanocrystalline transition metal spinel ferrites; Nano Research, 2014

Nonaqueous sol-gel

Hydrothermal

Hydrothermal

MnFe2O4: comparison


role of the pressure: hydro vs reflux

possible to reproduce the syntheses under reflux conditions (i.e. in an open system):

crystallinity

BUT:

- lower purity

- lower yields

This can be likely attributed to the pressure involved (which is possibly further enhanced

during hydrothermal synthesis by decomposition of the oxalate precursors to CO2).

Diodati S.; Pandolfo L.; Caneschi A.; Gialanella S.; Gross S.; Green, very low temperature hydrothermal assisted

synthesis of nanocrystalline transition metal spinel ferrites; Nano Research, 2014


Following crystallisation (time-resolved)

X-ray powder diffraction patterns of CoFe2O4, MnFe2O4, NiFe2O4 and ZnFe2O4 nanoparticles. Straight lines represent the corresponding MFe2O4 pattern

Dolcet, Smarsly, Mascotto, Gross et al. Green Chem, 2018, 20, 2257

Cyrstalline materials already after 1 hour→ strong energy consumption reduction


Following crystallisation (time-resolved)

X-ray powder diffraction patterns of CoFe2O4, MnFe2O4, NiFe2O4 and ZnFe2O4 nanoparticles. Straight lines represent the corresponding MFe2O4 pattern

Dolcet, Smarsly, Mascotto, Gross et al. Green Chem, 2018, 20, 2257

Not relevant changes in crystallite size upon treatment


Representative TEM images of ZnFe2O4 particles after 1h

(A,B), 9h (D,E), 18h (G,H) and 24h (J,K) and the respective

SAED patterns for 1h (C), 9h (F), 18h (I) and 24h (L).

Main outputs:

particle shape and size remain almost constant

throughout the different synthesis times

particles exhibit diameters in the range of 5-8 nm:

nearly independent of the synthesis time.

single-crystalline particles are present

high crystallinity is achieved even after only one hour

of synthesis time at very low temperature (135°C)

Following crystallisation time-resolved


Synthetic approach: hydrothermal (180°C)

Water based

Good yield and purity

Fast, reproducible

Low cost

Low temperature

Good control on experimental parameters Precursors

Molar ratios

Time and temperature

(t: 1, 3, 6, 9,12, 24, 48 h; T: 150 – 180 °C)

Coprecipitation of

oxalates

Hydrothermal

synthesis

Crystalline

nanostructured

oxides

Pursuing the stabilization of crystalline nanostructured magnetic manganites through a green low

temperature hydrothermal synthesis

A. Minelli, P. Dolcet., S. Diodati, L. Pandolfo, A. Caneschi, S. Gross et al. submitted

Unraveling the very fast copper manganite crystallisation at very low temperature: a combined

spectroscopic and diffractometric approach

P. Dolcet, A. Minelli, F. Zorzi, P. Vöpel, H. Amenitsch, B. Smarsly, F. Nestola, B. Sartori, and S. Gross, in

preparation


Synthetic approach: hydrothermal (180°C)

ZnNO3 + Mn(OAc)2 + 2 H2C2O4 ZnMn2O4

Cu(NO3)2 + Mn(OAc)2 + 2 H2C2O4 CuMnO2

ZnCl2 + MnCl2 + 2 H2C2O4 ZnMnO3

1.Metal oxalates precipitation 3. Nanostructured oxides

2. Hydrothermal

conditions


ZnS Hydrothermal

Vessel sealed and treated at

135 °C ( P = 476 kPa)

Na2S 0.2 M + Zn(acetate)2 0.1 M

Variation of density, viscosity, dielectric

constant, and ionic product of water

+ redissolution reactions

Different crystallization pathways


ZnS Hydrothermal

Pure sphalerite-phase ZnS NPs

21 nm (TEM & size-strain analysis)


ZnS Hydrothermal

Thermodynamic equilibrium shape

(Wulff construction)

Rhombic dodecahedron

Only (110) face

Rhombic dodecahedron

projections found in the

TEM images


Hydrothermal synthesis of nanostructured

crystalline ferrites, manganites, sulfides

andSynthesis of nanocrystalline CoFe2O4, MnFe2O4, NiFe2O4, ZnFe2O4, MgFe2O4,

quaternary ferrites ZnxCo1-xFe2O4, ZnMn2O4, ZnMnO3, CuMnO2, ZnO, ZnS,

CuS, Ag2S, PbS (not yet FexSy…)

• At very low temperature (100-150°C) within very short processing time

• Using water as solvent: greenest solvent

• Very easy and reproducible procedure

• Earth abundant, cheap and safe precursors

• Effective control over the products stoichiometry

• Compounds obtained in highly crystalline form

• Small crystallite size (5-40 nm, depending on conditions)

• High yields (70-90%)

• Very pure compounds (clean decomposition of oxalates)

Diodati S.; Pandolfo L.; Caneschi A.; Gialanella S.; Gross S.; Green, very low temperature hydrothermal

assisted synthesis of nanocrystalline transition metal spinel ferrites, Nano Res., 2014, 7, 1027-1042

Minelli, A., Dolcet, P., L. Pandolfo, Gross S. et al. Pursuing the stabilisation of crystalline nanostructured

magnetic manganites through a green low temperature hydrothermal synthesis, J. Mater. Chem. C, 2017, 5,

3359-3371



Pros & contra

• Pros:

– New materials

– Same materials in milder conditions

– Explores unconventional crystallisation paths

– Easy, relatively cheap

– Water based

– Mild conditions of synthesis



Pros & contra

• Contra:

– Difficult to control morphology, size

– Not for all materials

– May obtain variation in size

– Black box (but….)

colloid chemistry · 2019-05-05 · solvo/hydrothermal synthesis mari-ann einarsrud and tor grande,...

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