Analytical Ultracentrifugation of Nanoparticles s d r u s ω2 = t ln(r/r ) s 2 m ω = 1 step means 1...
Transcript of Analytical Ultracentrifugation of Nanoparticles s d r u s ω2 = t ln(r/r ) s 2 m ω = 1 step means 1...
Analytical Ultracentrifugation of Nanoparticles
Analytical Ultracentrifugation Analytical Ultracentrifugation of of NanoparticlesNanoparticles
Helmut Cölfen
Max-Planck-Institute of Colloids and Interfaces,Colloid Chemistry, Am Mühlenberg 2, D-14424 Potsdam
Email: [email protected]
Why fractionating analytics in solution ?Why fractionating Why fractionating analytics in analytics in solutionsolution ??
AUC / FFFAUC / FFFAUC / FFF
Sensitive to bigger particles /
dust asI ∼ r 66
Problem:Problem:Big Big particlesparticlesAbsorptionAbsorption
multiple multiple scatteringscattering
Light ScatteringLight ScatteringLight Scattering
EveryEvery particle isdetected,
simultaneousmultiple detection
possible
MicroscopyMicroscopyMicroscopy
Counting ofparticles
Drying artifacts
Problem: Problem: StatisticsStatistics
NoNo fractionationfractionation FractionationFractionation
Svedbergs Colloid ResearchSvedbergs Colloid Svedbergs Colloid ResearchResearch• T. Svedberg, J.B. Nichols, J.
Amer. Chem. Soc. 45 (1923) 2910
• T. Svedberg, H. Rinde, J. Amer. Chem. Soc. 45 (1923) 943
• T. Svedberg, H. Rinde, J. Amer. Chem. Soc. 46 (1924) 2677
• T. Svedberg, Kolloid-Z. Zsigmondy Festschrift, Erg.-Bd. Zu 36 (1925) 53
1926: First 1926: First protein workprotein work
1925: Nobel 1925: Nobel prizeprize forforcolloidcolloid workwork
h
ϕ
rr r r
t m
VapourSolution
ω
b
Radial Detection
Rayleigh Interference optics UV/VIS Absorption opticsΔn
Abs
.
r r
Light
Detector
Principle of AUCPrinciple Principle of AUCof AUC
Experiments very simple, evaluation not always
Sedimentation Sedimentation velocityvelocity
Sedimentation Sedimentation equilibriumequilibrium
Density gradientDensity gradient
High centrifugal forceSedimentation stronger than back diffusion
50000 RPMScaninterval10 min
6.2 6.4 6.6 6.8 7.0 7.2
0.0
0.5
1.0
Abs
orba
nce
Radius (cm)
6.7 6.8 6.9 7.0 7.10.0
0.5
1.0
1.5
2.0
Abs
orba
nce
Radius (cm)
Moderate centrifugal forceSedimentation in the order of back diffusion
Sedimentation
Diffusion
10000 RPM
6.2 6.4 6.6 6.8 7.0 7.20.0
0.2
0.4
0.6
0.8
1.0A
bsor
banc
e
Radius (cm)
50 % CH2Cl2 + 50 % CHCl360000 RPM
Different AUC experimentsDifferent AUC Different AUC experimentsexperiments
High centrifugal force for distributionof a low molecular salt or a second solvent
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
ω−=∂∂
43421321 termentationdimSe
22
termDiffusion
crsdrdcDr
drd
r1
tc
Lamm equationLamm Lamm equationequation
Experiment Effective term in the Lamm equation
Characteristics
Sedimentationvelocity
Sedimentation term much bigger than diffusion term
High rotational speed
Synthetic boundary experiment for the determination of D
Only diffusion term effective
Synthetic boundary cell,low rotational speed
Sedimentationvelocity
Sedimentation and diffusion term effective / equilibrium between sedimentation and diffusion
Moderate / low rotational speed
Density gradient(special case ofsedimentation equilibrium)
Sedimentation and diffusion term effective / equilibrium between sedimentation and diffusion
Moderate / highrotational speed,locally dependent solution density
50000 RPMScaninterval 10 min
6.2 6.4 6.6 6.8 7.0 7.2
0.0
0.5
1.0
Abs
orba
nce
Radius (cm)
Basic evaluation important for nanoparticles
Basic Basic evaluation important for evaluation important for nanoparticlesnanoparticles
a) Determine distance travelled in given time intervalb) Calculate sedimentation coefficient s or its distributionc) Calculate particle size or distribution
ρ−ρη
=2
ii
s18dr
us 2ω=
t)r/rln(s 2
m
ω=
1 step means1 component
Flat baseline indicates purity
( )MsRT
D v=
−1 ρf
RTN DA
=
Sedimentation velocitySedimentation Sedimentation velocityvelocity
ρ−ρη
=2
ii
s18d
Sedimentation velocity depends on:
Molar Molar mass mass / / particle sizeparticle sizeDensityDensityShape Shape / / FrictionFrictionChargeCharge
for given exptl. parameters (temperature, solvent density & viscosity etc.)
Particle size distributions calculated Particle size distributions calculated on a on a hard sphere basishard sphere basis
Sedimentation velocitySedimentation Sedimentation velocityvelocity
6.0 6.2 6.4 6.6 6.8 7.0 7.2
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
a)
Abs
orba
nce
Radius [cm]4.00E+008 6.00E+008 8.00E+008
1.820
1.825
1.830
1.835
1.840
1.845
1.850
b)
sw = 480 S
Data for individual boundaries Regression line
ln(r
/r m)
ω2t
0 200 400 600 8000.0
0.2
0.4
0.6
0.8
1.0
1.2
c) g*(s) c(s) diffusion corrected
g*(s
) res
p. c
(s)
sedimentation coefficient [S]
6.0 6.2 6.4 6.6 6.8 7.0 7.20.0
0.2
0.4
0.6
0.8
1.0 d)
g*(d
)
Diameter [nm]
t)r/rln(s 2
m
ω=
ρ−ρη
=2
ii
s18d
Gold in H2O at 5000 RPM, 25 °C
a) Raw data
b) S-evaluation
c) s-distribution
d) d-distribution
Common ProblemsCommon ProblemsCommon Problems• Extremely broad s-distributions, Big aggregates or small
impurities are not detected• Colloids aggregate or grow during centrifugation
(concentration dependent aggregation)• Density of hybrid colloids is unknown to access particle
size• Electrostatic stabilization complicates analysis due to
charge contributions• Particle polydispersity in size, shape, density and
hydration• High particle density often makes density gradients or
density variation methods impossible• Often multicomponent mixtures
Fractionation of heterogeneous samplesFractionation Fractionation of of heterogeneous samplesheterogeneous samples
6,0 6,2 6,4 6,6 6,8 7,00
1
2
3
4
5 Carrageenan
+ iron oxyhydroxide
Large aggregates
Free
Carrageenan
Carrageenan + iron oxyhydroxide
2.72 fringes
0.55 fringes
40000 RPM, 25 °C
Absorption optics
Interference opticsA
bsor
banc
e / F
ring
e sh
ift
Radius [cm]pH 2, κ-carrageenan
pH > 5
pH 2, Fe3+ crosslinking of κ-carrageenan
Hollow space
Protected partiallymobile FeOOH
Hydrolized Fe3+
+ OH-+ Fe3+ Fe3+
Fe3+
Fe3+
F. Jones
1 0 0 1 0 0 0
0 .0
0 .2
0 .4
0 .6
0 .8
1 .0
d H [μ m ]
3 4 0 0 n m
3 8 9 n m
1 6 4 n m
1 0 0 n m6 0 n m
Σci/c
0
given reproducedd [nm] % d [nm] %
60 20 60 20103 20 100 20160 20 164 18347 20 389 202800 20 3400 22
Latex mixtureLatex Latex mixturemixture
LMP
s18dρ−ρη
=
•• Particles analyzed over colloidal Particles analyzed over colloidal range range in in one experimentone experiment
A. Völkel
1.5 2.0 2.5 3.0
0.00
0.07
0.14
0.21
Species 1: 1.84 +/- 0.15 nm (48.7 %)Species 2: 1.95 +/- 0.20 nm (26.0 %)Species 3: 2.34 +/- 0.32 nm (25.3 %)
Expt. Data Sum Gauss Fit Ind. Gauss Fit
g(d H
) [A
.U.]
dH [nm]
Au55[P(Phe)3]12Cl6AuAu5555[P([P(PhePhe))33]]1212ClCl66Reported Reported to to bebe definitedefinite cluster cluster withwith 55 Au, 55 Au, Transition betweenTransition between
metal andmetal and moleculemolecule1530 counts
Very small colloidsVery small colloidsVery small colloids
6.0 6.2 6.4 6.6 6.8 7.0 7.20.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
60000 RPM, 25 °C, 380 nmScanint. 2 min
Abso
rban
ce
Radius (cm)
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.00.0
0.2
0.4
0.6
0.8
1.0
1.92
nm
1.77
nm
1.68
nm
1.59
nm
1.50
nm
1.40
nm
1.30
nm
0.83 nm
Integral Differential
Sum
of m
ass
frac
tions
Particle diameter [nm]
High resolution PSD
High High resolutionresolution PSDPSDPt colloid in MeOH / HAc
Baseline resolution > 1 Angström
0.1 nm Baseline resolution
Problem: Elimination of diffusion broadening by self-sharpening effectsis not common
Particles slightly bigger than from Particles slightly bigger than from AUC (AUC (DensityDensity))
0.80.8 1.21.2 1.61.6 2.02.0 2.42.4 2.82.8 3.23.2 3.63.600
55
1010
1515
2020350350 countscounts
particle diameterparticle diameter [nm][nm]
Num
ber f
requ
ency
%TEMTEMTEM
Pt-Colloid growthPtPt--ColloidColloid growthgrowth
Critical crystal
nucleus
Coalescence until particles are stabilized
Further growth through reduction of PtCl4 at the
crystal surfacedrdt
const= . DifferencesDifferences in in thethe particleparticle sizesize afteraftercoalescence are conservedcoalescence are conserved
Mechanism in G.A. Braun, Ph-D dissertation, Aachen 1997
= Stabilizer = Pt-Particle
CoalescenceCoalescence GrowthGrowth
0 2 4 6 8 10 12 1450
100150
200250300
0
5
10
Arbi
trar
y un
its
Reac
tion
time [
min
]
Particle diameter [nm]
Growing ZnO ColloidGrowing ZnO ColloidGrowing ZnO Colloid
Zn(Ac)2 (1 mmol/l)+ 20 mmol/l NaOHin water freeIsopropanol
Dilution 1 : 5 andHeating to 65 °C
Start of heating defines start of the reaction
Problem: AUC has a Problem: AUC has a lowlow time time resolutionresolution T. Pauck
0 2 4 6 8 10 12
etched + transferred to waterattached to protein
Diff
eren
tiald
istr
ibut
ion
Particle size (nm)
AuAu
AuAu
S
SCOO
COO
+BSA
D.I.Gittins and F.Caruso
Bio-labelingBioBio--labelinglabeling
0 500 1000 1500 20000.0
0.2
0.4
0.6
0.8
1.0 Au particles in toluene Au particles in water BSA labeled Au particles in water
s25,w [S]
g(s)
Phase transfer agent: 11-Mercaptoundecanoic acid(MUA)
Phase transfer and bio-labelingPhase Phase transfer transfer and bioand bio--labelinglabeling
D.I.Gittins and F.Caruso
Dopamine functionalized TiO2DopamineDopamine functionalizedfunctionalized TiOTiO22
200 250 300 350 400 450 500 550 6000
1
2
3
Abs
orpt
ion
Wavelength [nm]
3 4 5 6 7 8 90.04
0.05
0.06
0.07
0.08
0.09
0.10
g (d
)dH (nm)Particle sizeParticle size
decreasesdecreases Spectra taken at different
positions indistribution
M. Niederberger
Concept of turbidimetric immunoassayConceptConcept of of turbidimetricturbidimetric immunoassayimmunoassay
Antibody(low reactivity)
221 nm
Antibody(high reactivity)
Latex particle
127 nmLatex particle
Antigen
Concept of turbidimetric immunoassayConceptConcept of of turbidimetricturbidimetric immunoassayimmunoassay
Big Big particlesparticlesaggregateaggregate firstfirst, , then thethen the small small
onesones
TEM of ImmunoassayTEM ofTEM of ImmunoassayImmunoassay
0 mg/L CRP 4.28 mg/L CRP
25 mg/L CRP 156 mg/L CRP
Scale bars 500 nm
StatisticsStatistics,, drying artifactsdrying artifacts ??
0.1 1 100
20
40
60
80
100
50 mg/L CRP
0 min 2 min 5 min 7 min 11 min 15 min
G(d
H)
dH [μm]
0.1 1 100
20
40
60
80
100
171 mg/L CRP
0 min 2 min 4 min 7 min 11 min 15 min
G(d
H)
dH [μm]
SLS of ImmunoassaySLS ofSLS of ImmunoassayImmunoassay• Fast measurement
without equilibration needs
• Kinetic measurements possible
• Ambient conditions without any pressure effects
• Low resolution in particle size
• Low statistical resolution(No fractionation)
92 92 wtwt--%% small laticessmall latices
0.0 0.5 1.0 1.5 2.0 2.5 3.00.0
0.2
0.4
0.6
0.8
1.0
25 °C
Latex mixture + 4.28 mg/L CRP + 50 mg/L CRP + 156 mg/L CRP
G(d
H)
dH [μm]
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.20.0
0.2
0.4
0.6
0.8
1.0
37 °C
Latex mixture + 5 mg/L CRP + 10 mg/L CRP + 20 mg/L CRP + 30 mg/L CRP + 40 mg/L CRP + 50 mg/L CRP
G(d
H)
dH [μm]
AUC of ImmunoassayAUC ofAUC of ImmunoassayImmunoassay
• AUC has equilibration time > 10 min before experiment
• Fractionation enables to determine correct particle quantities and sizes by turbidity detection (MIEcorrection) with speed profile even over decades of s-values
• 92 wt-% small latices inmixture correctly detected
Figure from:H.G. Müller, A. Schmidt, D. Kranz; Progr. Colloid Polym. Sci. 86, 70 (1991)
MicrogelsMicrogelsMicrogels
3η⋅ρ−ρ
⋅⋅
=18s
dbQ sP2h b = mass ratio of soluble parts
Fringe shift of crosslinked part: 7.90 76%Fringe shift of free chains : 2.37 24%
6.0 6.2 6.4 6.6 6.8 7.0 7.20
2
4
6
8
10
Fr
inge
shi
ft
r [cm]
7,50
PNIPAM MicrogelsPNIPAMPNIPAM MicrogelsMicrogels
Crosslinked 10000 rpm
6.3 6.6 6.90
1
2
3
4
Fr
inge
shi
ft
r [cm]
2,37
Not crosslinked60000 rpm
D. Kuckling
0 5 10 15 20 25 30 35 400.0
0.2
0.4
0.6
0.8
1.0
low crosslinking degree high crosslinking degree
G(Q
)Q
Swelling degree distributionSwelling degree distributionSwelling degree distribution
0 200 400 600 800 1000 12000.0
0.2
0.4
0.6
0.8
1.0
Deswollen (40 °C) Swollen (25 °C)
G(s
)
s [Svedberg]
3
swollen
unswollen
ssQ ⎟⎟
⎠
⎞⎜⎜⎝
⎛=
η⋅ρ−ρ
⋅⋅
=18s
dbQ sP2h
In principle also possible with soluble fraction b
D. Kuckling
Solvent density variationSolvent Solvent density variationdensity variationPS123-P4VP145 in toluene resp. d-toluene
•• DensityDensity in good agreement in good agreement withwith valuesvalues fromfrom densitydensity metermeter•• Particle size Particle size in agreementin agreement with results from with results from DLS DLS or viscosity measurementsor viscosity measurements•• Same Same resultresult forfor corecore crosslinked crosslinked micellesmicelles
40 60 80 1000,0
0,2
0,4
0,6
0,8
1,0
dH [nm]In
tegr
aldi
strib
utio
n
0,0
0,5
1,0
1,5
2,0
ρ[g
/cm
³]
0 100 200 300 400 5000.0
0.2
0.4
0.6
0.8
1.0ρTdT for the following data:==============================low density:PS-P4VP in toluenehigh density:PS-P4VP in tol/tol-d8
lower densityhigher density
inte
gral
dist
ribut
ion
sedimentation coefficient [S]
LMP
s18dρ−ρη
=
CombinationCombination of 2 sof 2 s--distributions distributions in 2 in 2 chemically identical chemically identical solvents yields solvents yields particle sizeparticle size and and density distributiondensity distribution
K. Schilling
s22s11
s1s22s2s11ηη
ρηρηρ ss
ssp −
−=
s2s1
s11s22 )(18ρρ
ηη−−
=ss
d
0 50 100 150 200 250 300 350 400 4500,0
0,2
0,4
0,6
0,8
1,0
ρP = 1.054 g/mlnP = 1.6b = 38.5%
ρP = 1.188 g/mlnP= 1.460b = 61.5%
integral psddifferential psd
PS-PMAA Latex mixture 40 : 60PSPS--PMAA Latex PMAA Latex mixture mixture 40 : 6040 : 60
A. Völkel
A: StarA: Star like crystalslike crystals//whiskerwhisker, d = 17 nm, l = 184 nm, d = 17 nm, l = 184 nmB: Transversal growth,B: Transversal growth, destabilizationdestabilization ofof filamentsfilaments,, further further
densificationdensification ofof corecoreC: CompactC: Compact aggregates with periodicityaggregates with periodicity („(„ChrysanthemunChrysanthemun““ structurestructure))
100 nm200 nm
200 nmA B CSynthetic hybrid colloidsSyntheticSynthetic hybridhybrid colloidscolloids Brushite CaHPO4 * 2H2O
TG 18% Mineral
M. Breulmann
0 10 20 30 40 50 60 700
100
200300
400
0.0
0.2
0.4
0.6
0.8
1.0
g(s*
)
time [
h]
s* [S]
Synthetic hybrid colloidsSyntheticSynthetic hybridhybrid colloidscolloidswhiskerwhisker
dense structuredense structure
• Superposition of particle sizeand density distribution
• Densities can exceed 2 g/ml
Synthetic hybrid colloidsSynthetic Synthetic hybrid hybrid colloidscolloids
0 5 10 15 20 25 30 35 400.0
0.2
0.4
0.6
0.8
1.0 PEG-PMAA-C12
PEG-PMAA-C12 + Ca2+
"Chrysanthemum" 1 week
g(s*
)
s* [Svedberg]
density increasedensity increase
polydispersitypolydispersityincreaseincrease
Combination Combination of AUC of AUC with with DLS DLS or better or better FlFl--FFF FFF is highly is highly desirabledesirable
Diameter(DLS) = 150 nmDiameter(DLS) = 150 nm
•• Clear monitoringClear monitoringof of density density increase uponincrease uponCaCa2+2+ complexationcomplexation
•• Global AnalysisGlobal Analysiscould reveal could reveal densitydensity andand molar molar massmass
1 10
0,00
0,01
0,02
0,03
r*d(
r) [a
.u.]
2 r [nm]200 250 300 350 400 450
01234
I [a.
u.]
λAbs [nm]
Particle size and densityParticle size and densityUV : d = 1.65 nmDLS : d = 1.6 nmAUC: „ d = 1.25 nm“ (s = 3.6 S)calculated with ρCdS = 4.83 g/cm3
dtotal = 1.6 nmdcore = 1.1 nmdshell = 0.5 nm(Lit.: dshell = 0.4 nm)
ρρparticleparticle = 3.2 g/cm= 3.2 g/cm33
ddparticleparticle = 1.6 nm= 1.6 nm
UVUV DLSDLS
s2p
p ds18
ρ+η
=ρ Density core andshell are known
WithWith independentindependent size measurementsize measurement,,hybrid hybrid particle is fully characterizedparticle is fully characterized
CdS
Hybrid ColloidsHybrid Hybrid ColloidsColloids
Ferrihydrite Fe2O3
. x H2O
• Iron storage protein Ferritin forms robust hollow sphere from 24 dimeric subunits
• Ferritin oligomerizes• Different amounts of
ferrihydrite inside the core (up to 4500 Fe)
•• Simultaneous particle sizeSimultaneous particle size andanddensity distributiondensity distribution
•• SizeSize andand amountamount ofof oligomers oligomers ??
•• AmountAmount ofof ferrihydrite inside ferrihydrite inside the corethe core for the for the different different oligomersoligomers ??
FerritinFerritinFerritin
0 20 40 60 80 100 120 140 1600,0
0,2
0,4
0,6
0,8
1,0
Diffusion corrected g(s*) Sum of Gauss Fits Individual Gauss Fits
g(s*
)
s* [S]0 2 4 6 8 10 12 14 16 18 20 22
2.29x10-7cm2s-1
2.93x10-7cm2s-1
4.35x10-7cm2s-1
t0 = 0.455minSign
al [a
.u.]
tret
[min]
Fl-FFF AUCMonomer
Dimer
Trimer
FlFl--FFF separates FFF separates only according only according to to particle sizeparticle size, AUC , AUC according according to to particle sizeparticle size andand densitydensity
AUC noAUC no baseline separationbaseline separation ofof oligomersoligomers ((density distributiondensity distribution))
A. Völkel
Monomer Dimer Trimer
s* at 25 °C (AUC) 59.8 S 96.9 S 127.9 S
D* at 25 °C (Fl-FFF) 3.68 x 10-7 cm2/s 2.41 x 10-7 cm2/s 1.90 x 10-7 cm2/s
dH (Fl-FFF) 11.9 nm 18.1 nm 23.0 nm
ρP 1.764 g/cm3 1.531 g/cm3 1.436 g/cm3
Mw 586,700 g/mol 954,100 g/mol 1,367,400 g/mol
Oligomer amount 69.4 wt.-% 19.5 wt.-% 11.1 wt.-%
n Fe3+ 1476 667 34
Global Global analysisanalysis
0 20 40 60 80 100 120 140 1600,0
0,2
0,4
0,6
0,8
1,0
Diffusion corrected g(s*) Sum of Gauss Fits Individual Gauss Fits
g(s*
)
s* [S]0 100 200 300 400 500 600 700 800
0.0
0.2
0.4
0.6
0.8
1.0
g (s
)
s (S)
Ferritin low Fe3+ content
Ferritin high Fe3+ content
Ferritin with higher
Ferritin with higher FeFe 3+3+
content
content has different
has different
sedimentation behaviour
sedimentation behaviour
First direct observation of near critical size clusters by AFM
First direct observation of near critical size clusters by AFM
Molecules that are missing in the next frame
Molecules that appeared after captureof the previous frame
S.T. S.T. YauYau, P.G. , P.G. Vekilov Vekilov „Quasi„Quasi--planar nucleus structure planar nucleus structure in in apoferritin crystallizationapoferritin crystallization“, Nature “, Nature 406406, 494 , 494 -- 497; 3 August 2000497; 3 August 2000
CrystallizationCrystallization
DissolutionDissolution
D.W. D.W. OxtobyOxtoby „„CatchingCatching crystalscrystals at at birthbirth“, Nature “, Nature 406406, 464 , 464 -- 465; 3 August 2000:465; 3 August 2000:
„„Although the first small crystallites involved Although the first small crystallites involved in in nucleationnucleation form in form in the bulkthe bulk ofof the the solutionsolution, , YauYau andand Vekilov Vekilov can observe them only once they have can observe them only once they have fallen to fallen to the bottomthe bottomofof the vesselthe vessel andand attached themselves attached themselves to to the surface therethe surface there. . How can the authors be How can the authors be sure that they are observing the critical early stagessure that they are observing the critical early stages ofof crystallization described by crystallization described by nucleation nucleation ?“?“
σ = 1.1
Capillaries
Reservoir
Reactant ( ) containing solution is layered onto thesecond reactant via the capillary ( )
Formation of a sharp reaction boundary
Synthetic boundary cell of the Vinograd TypeSynthetic boundary cellSynthetic boundary cell ofof the Vinogradthe Vinograd TypeType
L. Börger
Particle formation in a synthetic boundary cellParticle formation in a synthetic boundary cell
2 Generation
N-th Generation
1 Generation
Rea
ctio
n zo
ne1) Formed particles sediment out of the reaction zone, reaction is quenched
2) Particles diffuse back into the reaction zone, further growth
3) Sedimentation time >> reaction time
Sedimentation of Sedimentation of particlesparticlesaccordingaccording to to sizesize, Determination , Determination of of particleparticle sizesize distributiondistributionpossiblepossible
Transformation of a Transformation of a timetime distribution intodistribution into a a radialradial distributiondistribution
0.4 0.8 1.2 1.6 2.00.0
0.2
0.4
0.6
0.8
1.0 8 exptl. Scans Sum Gauss Fit Individual Gauss Fits
g(d H
)
dH [nm]
Synthetic boundary crystallization Synthetic boundary crystallization ultracentrifugationultracentrifugation
All All known stable CdSknown stable CdS growthgrowth species simultaneously accessiblespecies simultaneously accessible in in one one experimentexperiment. Even. Even subcritical clusters detectable subcritical clusters detectable in in solutionsolution
[CdSR[CdSR44]]22--
0.3 nm0.3 nm
[Cd[Cd44SRSR1010]]22--
0.5 nm0.5 nm
[Cd[Cd1010SS44SRSR1616]]44--
1.0 nm1.0 nmStructure unknownStructure unknown
literatureliterature 1.3 nm1.3 nmCdCd1717SS44SRSR2626
1.4 nm1.4 nm
CdCd3232SS1414SRSR36361.8 nm1.8 nm
Structure unknownStructure unknownliteratureliterature 1.6 nm1.6 nm
CdSCdS+ + thiothio--glyceringlycerin
• AUC is a very versatile instrument for colloid chemistry (Range of possible methods still not fully explored !!!)
• Fractionation allows the investigation of complex mixtures or very polydisperse samples with s ranging over decades (speed profile)
• High statistical accuracy• Critical crystal nuclei and subcritical clusters can be resolved• Crystal growth reactions can be investigated by transformation
of time distribution into radial distribution
ConclusionConclusionConclusion
BUT:BUT:• Colloids can express various unfavourable properties which
makes them problematic to investigate• Fast multidetection systems together with global analysis can
potentially adress even most complex mixtures with particle size and VBAR distribution but role of charge still unadressed
Future PerspectivesFutureFuture PerspectivesPerspectives• Fast speed profiles and detectors to suppress
diffusion broadening • Multi-detection systems (RI, UV-Vis, SLS and others)• Global Analysis (promising with SEDVEL &
SEDEQUIL + DLS & Fl-FFF) to obtain s, M, D & VBAR distributions
• New ultracentrifugation methods could allow to access new quantities Surface tension from phase transfer, particle charge determination via sedimentation in pH or charge gradient,Conformational changes in solvent quality gradients, new synthetic boundary techniques for membrane / crystal growthinvestigations or chemical reactions in the AUC, etc.
Recommended readingRecommended readingRecommended reading
. Svedberg, K.O. Pedersen, The ultracentrifuge, Clarendon Press, Oxford (1940)
he classical textbook about analytical ultracentrifugation still with much impact today
.K. Schachman, Ultracentrifugation in biochemistry, Academic Press, New York (1959)
compact and useful book covering experimental and theoretical aspects
.E. Harding, A.J. Rowe and J.C. Horton; Analytical ultracentrifugation in biochemistry and polymer science, The royal society of chemistry, Cambridge, ISBN 0-85186-345-0 (1992)
he most comprehensive modern book about analytical ultracentrifugation. A verygood overview about methods & techniques of analytical ultracentrifugation and avaluable source of modern applications.