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Silvia Gross - Chimica Inorganica III, Laurea Magistrale 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
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], [email protected]
http://www.chimica.unipd.it/silvia.gross/
Silvia Gross, Marta Maria Natile
Chimica Inorganica III
Lezioni propedeutiche al laboratorio
a.a. 2018-2019
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Experiments
0.Procedure speciali nell’attività di laboratorio (tecnica di Schlenk, polimerizzazione UV,
sintesi solvo- ed idrotermale)
1.Sintesi di oxocluster tetranucleari di zirconio Zr4
2.Sintesi di materiali ibridi organici-inorganici reticolati da oxocluster di zirconio Zr4
3.Sintesi di ferriti mediante coprecipitazione di ossalati e mediante sintesi idrotermale
4.Sintesi e caratterizzazione spettroscopica dei complessi di vanadile V(IV) (d1)
5.Chimica di coordinazione del Cu(II)
6.Sintesi di colloidi di oro e di argento
7.Complesso polinucleare termocromico di Cu(I)
8.Polimeri di coordinazione a base di Cu(II)
9.Sol colloidali di zolfo
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Hystorical background
“Die Welt der vernachlässigten Dimensionen”
“Il mondo delle dimensioni trascurate”
Wolfgang Ostwald, 1914
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloid: ethimology
From the Ancient Greek κόλλα: glue-like (Thomas Graham, 1861)
He defines a colloid in terms of inabilty to pass through a fine membrane
important related concept:
dimensions of the species relevant in defining the colloidal region
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloid: definition
The term refers to a state of subdivision, implying that the molecules or
polymolecular particles dispersed in a medium have at least in one
direction a dimension roughly between 1 nm and 1 mm, or that in a
system discontinuities are found at distances of that order.
IUPAC GOLDBOOK, http://goldbook.iupac.org/
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloid: definition
The concept of colloid entails:
-Polymers (105-106 monomers): form aggregates, widely used as dispersion
-Nanomaterials (at least one dimension in the 1-100 nm range)• bottom-up synthesis of nanosystems
• nanoparticles, by definition, are colloids and association colloids (micelles, vesicles, monolayers)
• employed as templates and/or nanoreactors for the in situ generation of nanoparticles
• biomineralization, Mother Nature's construction of nanostructured materials
(Biomineralization is the process by which living organisms produce minerals. It often leads to
the hardening or stiffening of the mineralized materials. This includes the formation of silicates
in algae and diatoms, carbonates in invertebrates, and calcium phosphates and carbonates in
the hard tissues of vertebrates. http://www.nature.com/subjects/biomineralization)
- Soft matter (also of biological nature)
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Hystorical background
Vaso di Licurgo
British Museum, IV secolo a.C.
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Hystorical background
Cortesia Prof. Paolo Mazzoldi+, Dip. di Fisica Universitá di Padova
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Hystorical background
Lustri di Gubbio e Deruta (Italia)
Nanocluster metallici
(~ 5-10 nm) di Ag o Cu
Ricetta di preparazione del Lustro
( Mastro Giorgio , Gubbio, XVI sec.)
Deposizione di ossidi o sali di Ag o di Cu in soluzione
con aceto
Riscaldamento a 600 °C in forno con fascine di ginestra
secca (atmosfera riducente)
Cortesia Prof. Paolo Mazzoldi+, Dip. di Fisica Universitá di Padova
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Hystorical background
Berzelius (1779-1848): introduce the term “polymer”
Robert Brown (1773-1858): typical motion of small particles
→ A. Einstein (1879-1955) and M Smouluchowski (1872-1917)
Francesco Selmi (1840) pseudo-solutions in water of AgI or sulphur
(for Overbeek the birth of colloid science)
Michael Faraday (1791-1867): synthesis of gold colloids and scattering of
light from colloids (with J. Tyndall (1820-1893): Tyndall effect)
Thomas Graham (1805-1869) introduce the word colloid, sol, gel, dialysis
Begin of XIX century: existence of colloidal particles accepted
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Hystorical background
Discovery of ultramicroscope by R. Zsigmondy (1865-1929)
Wolfgang Ostwald (1883-1943): classification of dispersions
H. Schulze (1853-1892) - W.D. Hardy (1864-1934): isolectric point and
Schulze-Hardy rule on critical coagulation concentration
Hermann Staudinger (1881-1965): dispersion colloids, molecular
colloids, association colloids
Lev Landau, J. Overbeek, E. Verwey, B. Derjagin: DLVO Theory
XX Century: E. Matijevic: synthesis of tailor-made colloids
XXI century: Horst Weller, L. Liz-Marzan, F. Caruso, P. Alivisatos, M.
Antonietti, K. Landfester, J. Estoae, P. Mulvaney etc.
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloids: Nobel Prizes
Richard Zsigmondy, Germany, 1925
“for his demonstration of the heterogenous nature of colloid solutions
The (Theodor) Svedberg, Sweden, 1926
“for his work on disperse systems”
Arne Wilhelm Kaurin Tiselius, Sweden, 1948
“for his research on electrophoresis and adsorption analysis”
Hermann Staudinger, 1953
“for his discoveries in the field of macromolecular chemistry”
Paul John Flory, 1974
"for his fundamental achievements, both theoretical and experimental, in the
physical chemistry of the macromolecules"
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloid: definition
The term refers to a state of subdivision, implying that the molecules or
polymolecular particles dispersed in a medium have at least in one
direction a dimension roughly between 1 nm and 1 mm, or that in a
system discontinuities are found at distances of that order.
IUPAC GOLDBOOK, http://goldbook.iupac.org/
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloids
non necessariamente tutte e tre le dimensioni devono
trovarsi nell’intervallo definito per i colloidi
1 D 2 D 3 D
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal domain
Description of behaviour of matter
based on a set of physical laws
(less effective descriptors at the
extremes):
- molecular/atomic properties
- kinematics/wetting phenomena
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloids
1 mm
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloid domain: “phases”
Phase a: dispersing phase
Phase b : dispersed phase
CAVEAT:
1. non –equilibrium states kinetically stable also for decades
2. phase (as physical state of the colloidal systems) can be complex (gel-like particles, or
particle dispersed in a gel)
Phase (according to IUPAC)
An entity of a material system which is uniform in chemical composition and physical state.
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Classification/nomenclature
Medium (a) →
Dispersed phase (b) ↓
Gas (fluid) Liquid Solid
Gas (bubbles) ---- foam solid foam
Liquid (droplets) liquid aerosol liquid emulsion solid emulsion/gel
Solid (particles) solid aerosol sol solid sol
Adapted from Cosgrove
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
dispersed phase medium dispersion type examples
gas liquid foam whipped cream
gas solid solid foam pumice, aerogels
liquid gas liquid aerosol fog, clouds
liquid liquid emulsion milk, mayonaisse, salad dressing
liquid solid gel Jell-O, lubricating greases, opal, cheese
solid gas solid aerosol smoke
solid liquid sol paints, some inks, blood
solid solid solid sol bone, colored glass, many alloys
Classification/nomenclature
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: nomenclature
Source: IUPAC
An emulsion is denoted by the symbol O/W if the continuous phase: is an aqueous solution and by
W/O if the continuous phase is an organic apolar liquid (an `oil'). More complicated emulsions such
as O/W/O (i.e. oil droplets contained within aqueous droplets dispersed in a continuous oil phase)
are also possible. In an emulsion liquid droplets and/or liquid crystals are dispersed in a liquid. In
emulsions the droplets often exceed the usual limits for colloids in size.
In a suspension solid particles are dispersed in a liquid; a colloidal suspension is one in which the
size of the particles lies in the colloidal range.
A latex (plural = latices or latexes) is an emulsion or sol in which each colloidal particle contains a
number of macromolecules.
A foam is a dispersion in which a large proportion of gas by volume in the form of gas bubbles, is
dispersed in a liquid, solid or gel. The diameter of the bubbles is usually larger than 1 μm, but the
thickness of the lamellae between the bubbles is often in the usual colloidal size range.
Gel
Non-fluid colloidal network or polymer network that is expanded throughout its whole volume by a fluid.
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: nomenclature
Aerosols are dispersions in gases. In aerosols the particles often exceed the usual size limits for
colloids. If the dispersed particles are solid, one speaks of aerosols of solid particles, if they are
liquid of aerosols of liquid particles. The use of the terms solid aerosol and liquid aerosol is
discouraged. An aerosol is neither `solid' nor `liquid' but, if anything, gaseous. A great variety of terms
such as dust, haze, fog, mist, drizzle, smoke, smog are in use to describe aerosols according to their
properties, origin, etc. Of these only the terms fog and smoke are included in this nomenclature.
A fog is an aerosol of liquid particles, in particular a low cloud.
A smoke is an aerosol originating from combustion, thermal decomposition or thermal evaporation.
Its particles may be solid (magnesium oxide smoke) or liquid (tobacco smoke).
Source: IUPAC
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Classification (Freundlich, 1926)
→ is the dispersion process occurring?
Lyophobic:
no affinity
with solvent
Lyophilic:
affinity with
solvent
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Classification (Freundlich, 1926)
Lyophobic:
no affinity
with solvent
(irreversible)(hydrophobic if solvent
is water)
Lyophilic:
affinity with
solvent
(reversible)(hydrophilic if solvent
is water)
extent and degree of interaction between solvent and atoms
of suspended particles (even if the surface atoms interact
strongly with the solvent)
→ depends upon the structure of the suspended particles
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloids: Staudinger classification
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Tyndall effect
diffusione della luce che attraversa
una soluzione colloidale
soluzione molecolare
dispersione
scoperto da Faraday nel 1857
studiato da Tyndall nel 1868
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Concept of colloidal stability
Colloidal stability relates to the physical state of the system: it is
stable if it remains well dispersed
Colloidally stable means that the particles do not aggregate at a
significant rate: the precise connotation depends on the type of
aggregation under consideration.
http://old.iupac.org/reports/2001/colloid_2001/manual_of_s_and_t/no
de35.html
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Relevance of colloidal stability
- cosmetics, pharmaceuticals, detergents formulation
- paints, inks, liquid toners
- water treatment
- separation processes (electrostatic stability): filtration of wastewater
- use of coagulants
- cooking
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Hystorical background
Ink in Ancient Egypt made by dispersing carbon in water
Flocculation, sedimentation
Addition of arabic gum: steric stabilisation of the dispersion
Courtesy Prof. Smarsly, JLU Gießen
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Collod stability
Stability: ability of a dispersion to resist coagulation
Aggregation is the process or the result of the formation of aggregates.
When a sol is colloidally unstable (i.e. the rate of aggregation is not
negligible) the formation of aggregates is called coagulation or
flocculation.
coagulation, implying the formation of compact aggregates, leading to
the macroscopic separation of a coagulum;
flocculation, implying the formation of a loose or open network which may
or may not separate macroscopically. In many contexts the loose
structure formed in this way is called a floc.
http://old.iupac.org/goldbook/C01119.pdf
Colloidal stability
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
DLVO theoryColloidal stability
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: stability
stabilità di un sistema colloidale è un complesso gioco di forze
attrattive/repulsive
caricamento superficiale repulsione
forze di van der Waals tra le particelle “nude” flocculazione
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: stability
teoria DLVO: electrostatic repulsion vs. van der Waals attraction
DLVO
Deryaguin B. V. and Landau L. D.
(1941) A theory of the stability of
strongly charged lyophobic sols and of
the adhesion of strongly charged
particles in solutions of electrolytes.
Acta Physicochim. USSR 14, 633
Verwey E. J. W. and Overbeek J. Th.
G. (1948) Theory of
the Stability of Lyophobic Colloids.
Elsevier,
Amsterdam.
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Stability of colloidal dispersion:
kinetics or thermodynamics?
barrier along the path
to coagulation
coagulation
Kinetic stability: consequence of a
energy barrier against collision and
eventually coagulation (favoured,
thermodynamically, by reduction of
DG)
But:
Interaction energy barrier >> kBT
Thermodynamic stability
Example: related to the possibility of
the particle to assembly to give
ordered networks or association
colloids
Colloidal stability
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: stability
A. processi di aggregazione
B. processi di coalescenza e crescita delle particelle
raggiungimento stato termodinamicamente stabile
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: stability
A. processi di aggregazione
flocculazione: aggregazione di particelle senza che
perdano la loro individualità/forma
spontanea se comporta diminuzione energia libera
formazione agglomerati/coaguli
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: coagulation
sistema colloidale gel coagulazione
peptizzazione
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
deflocculation/peptization
deflocculation (peptization)
The reversal of coagulation or flocculation, i.e. the dispersion of aggregates to form a colloidally
stable suspension or emulsion.
http://goldbook.iupac.org/D01555.html
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: stability
B. processi di coalescenza e crescita delle particelle
decremento energia libera attraverso riduzione superficie di separazione
tra particelle:
• sinterizzazione o coalescenza di particelle
• crescita di particelle (maturazione di Ostwald = Ostwald ripening)
• coalescenza di gocce
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: coalescence
coalescenza di due
particelle solide con
sinterizzazione (a T = 2/3
Tfus) mobilità atomica
sufficiente
coalescenza di due particelle solide
coinvolgente l’assottigliamento
dello strato interparticellare e
formazione di una particella più
grande
coalescenza di particelle di eguali dimensioni: riduzione 41% area superficiale
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Colloidal dispersions: ripening
se particelle solide leggermente solubili nel mezzo disperdente, meccanismo di crescita alternativo
che comporta riduzione area superficiale senza implicare collisione tra le particelle (forza trainante:
differenza in tensioni di vapore)
tendenza molecole a lasciare particelle più piccole e a precipitare su quelle più grandi
barriera energetica: energia necessaria a dissoluzione/evaporazione
scomparsa particelle più piccole, crescita particelle più grandi
MATURAZIONE DI OSTWALD (OSTWALD RIPENING)
dispersioni colloidali di particelle molto solubili o molto volatili sono termodinamicamente molto
instabili
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Coalescence vs. ripening
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Two main types of stabilization
of colloidal dispersions
Electrostatic Stabilization
the repulsive Coulomb forces
acting between the charged
colloidal particles
counterbalance
the attractive van der Waals
forces
a polymer is adsorbed or chemically
attached to the particle surface and
gives rise to particle repulsions
Steric Stabilization
Colloidal stability
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Electric double layer
doppio strato diffuso
superficie
controioni
dovuto a moto termico degli ioni
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Electric double layer (IUPAC)
The Coulombic interaction of interfacial charges (e.g. ions) and the magnetic or
electrostatic interaction of interfacial molecules lead to particularly complex
interfacial structures.
Examples of such approximated complex profiles are: the electrical double-layer
consisting of a surface charge layer (i.e. a two dimensional distribution of one type of
ions) and a diffuse charge layer (counter-ions distributed over the space region next
to the surface)
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Electric double layer: factors
• il pH della sospensione influenza in modo rilevante la carica
superficiale. In prossimità del punto isoelettrico (IEP) non sussiste
alcuna forza repulsiva tra le particelle la sospensione non può più
essere stabilizzata
• forza ionica: elevate forze ioniche riducono il raggio d’azione delle
forze repulsive tra le superfici cariche
• concentrazione ionica (aumento c.i. diminuzione spessore d.s.e.)
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Literature
Letteratura rilevante
Die Welt der vernachlässigten Dimension, Wolfgang Ostwald, 1919
M. Faraday, Phil. Trans. Roy. Soc. 147 (1857) 145
W. Ostwald, Colloid Zeitschrift 1 (1907) 291
Colloid Science
D. H. Everett, Basic Principles of Colloid Science, The Royal Society of Chemistry, London, 1988
Jim Goodwin, Colloids and Interfaces with Surfactants and Polymers- An Introduction -Wiley
D.J. Shaw, Colloid and Surface Chemistry, Butterworth-Heinemann Ltd. Oxford 1992, R.J. Hunter
Foundation od colloid science, Hunter, Robert J., Clarendon Press Oxford 1989
Grundrisse der Kolloidchemie , Wolfgang Ostwald, 1910
Hans-Dieter Dörfler: Grenzflächen und kolloid-disperse Systeme, Springer Verlag, Berlin 2002
M. J. Schwuger: Lehrbuch der Grenzflächenchemie, G. Thieme, Stuttgart 1996.
R. D. Vold, M. J. Vold: Colloid and Interface Chemistry, Addison-Wesley Publ. Co., London 1983.
T. Allen: Particle Size Measurements, vols. 1 + 2, Chapman and Hall, London 1997.
R.J. Hunter: Introduction to Modern Colloid Science, Oxford Sci. Publ, 1993
D.J. Shaw: Introduction to colloid and surface chemistry, Butterworths, London 1980.
Silvia Gross - Chimica Inorganica III, Laurea Magistrale in Chimica
Pane & colloidi
"Ich weiß keinen Zweig der heutigen Naturwissenschaften, der derartig viele
und verschiedenartige Interessenkreise berührt, wie die Kolloidchemie. Gewiß,
auch Atomtheorie und Radioaktivität interessieren heute jeden intellektuell
wachen Menschen. Aber dies sind geistige Delikatessen verglichen mit der
Kolloidchemie, die für viele theoretische und praktische Gebiete heute nötig ist
wie das liebe Brot."
Non conosco alcun ramo dell‘odierna scienza che stimoli così tanti e così
diversi ambiti di interesse come la chimica dei colloidi. Certo, anche la teoria
atomica e la radioattività solleticano l‘interesse di persone intellettualmente
vivaci. Ma queste sono Delikatessen per lo spirito, se confrontate con la
chimica dei colloidi, che per molti ambiti, sia teorici che pratici, è oggi
indispensabile come l‘amato pane“
Wolfgang Ostwald, 1922