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Martin HassellMartin Hassellöövv
Environmental Nanochemistry group,Environmental Nanochemistry group,
Department of Chemistry,Department of Chemistry,
University of Gothenburg, SwedenUniversity of Gothenburg, Sweden
Reference material needs to support Reference material needs to support
nanometrology and risk assessment nanometrology and risk assessment
of engineered nanoparticlesof engineered nanoparticles
OutlineOutline
Nanotechnology and nanomaterials
Brief intro and definitions
Benefits and risks
Nanometrology
Measurement needs in risk assessment
Physico-chemical characterization and analysis
• Which properties and measurands?
Reference nanomaterials
Needs in nanometrology
• Calibration artifacts and reference nanoparticles
• State-of-the-art - what´s special about nano-CRMs
• Future needs
Reference material needs for toxicology
NanotechnologyNanotechnology
Solid matter change properties and behavior at the small nanometer scale
Optical, electronic, interfacial, crystalline properties often change
Specific surface area, reactivitiy, catalitic activity
Can be utilized in novel functional materials
Energy production & storage, IT, paint & coatings, cosmetics, food, health & medicin
Nanotechnology is also much more than new nanomaterials
Incl. instrumentation to study these small scales
©F
elice F
ran
kelCadmium
Selenide “Quantum Dots”
Smallest
Largest
Property change as function of sizeProperty change as function of size
Some ISO definitionsSome ISO definitions
Nanotechnology:application of scientific knowledge to manipulate and
control matter in the nanoscale in order to make use of size- and structure-dependent properties and
phenomena, as distinct from those associated with individual atoms or molecules or with bulk materials
Nanomaterials:material with any external dimension in the nanoscale
(~1-100nm) or having internal structure or surface structure in the nanoscale
Nanostructured materials
• Aggregates, nanoporous, ceramics, surface nanostructured etc
Nanoobjects
• Nanoparticles (all three dimensions in nanoscale)
• Nanofibres (2 dimensions in nanoscale)
• Nanoplates
BenefitsBenefits
Nanotechnologies are forecasted to have a major impact in all areas of the future society
Contribute to solve the grand challenges
Energy production (e.g. Photovoltaics)
Energy storage (e.g. Batteries and fuel cells)
Carbon capture
Lighter and stronger vehicles
Faster and smaller computers (e.g quantum or spintronics)
Water treatment
Greener chemical production
Efficient healthcare (e.g. better treatments and diagnostics)
But you have to know what you are producing
Measure, image, analyse
Tasks for the Nanometrology field
NanometrologyNanometrology
Nanometrology is the science of measurement at the nanoscale level.
“Nanometrology must be seen as indispensable part of all kinds of nanotechnology”
Novel subfield of metrology that has large expectations from the needs of nanotechnol. and nanomanufacturing
Accurate, high-precision, traceable measurements of size, length and other physicochemical properties at the nanoscale
Reference materials and methods
Critical for nanometrology
Also standard methods, protocols, strategies all through the
analytical chain are needed
AUS NMI 3 slides
Enhanced reactivity compared to bulk
Reactivity may give adverse biological effects
Small enough to be mobile
in air, water and organisms
Some have been shown to penetrate biological barriers
Nanomaterials comparable in size to many protein structures in cells
Peristent nature
Toxic potential of nanomaterialsToxic potential of nanomaterials
Measurement needs in risk assessment Measurement needs in risk assessment
of engineered nanoparticlesof engineered nanoparticles
Environmental and human health risk assessmentconsists of Hazard assessment (how toxic) and
Exposure assessment (how high concentration of X)
Both requires analysis and physicochemical characterization
Nanometrology needs in environmental risk assessment Nanometrology needs in environmental risk assessment
At a recent horizon scanning workshop with ~60 international experts, metrology development was put at highest importance and where current knowledge were lacking, thus one of the most urgent priorities
(Alvarez et al. Research Priorities to Advance Eco-Responsible Nanotechnology. ACS Nano, Vol 3, p 1616-1619 (2009)
++
+
++
Concentration Shape
Size
Size
Distribution
Composition
Structure /
Crystallinity
Porosity /
Surface Area
Surface
Functionality
Surface
Speciation
Surface
Charge
Agglomeration State
Hassellöv and
Kaegi, 2009
Similar chemistry (all ZnO) –
potentially different behavior (benefits & risks)
Physicochemical CharacterizationPhysicochemical Characterization
Essential to link hazard to physical structure or chemical composition or surface chemistry
Structure-Activity-Relationships!
There are currently a number of standardization organizations and initiatives try to agree on descriptors/properties
OECD working party on nanomaterials
ISO TC 229 - Nanotechnologies
Informal: www.characterizationmatters.org
Characterization is not only staticCharacterization is not only static
Diffusion
Collisions
Attachement
Detachement
Dissolution
Sedimentation
Agglomeration
”Dete
rmin
e Rate
s of C
hange”
”Dete
rmin
e Rate
s of C
hange”
Battery of available methods Battery of available methods
in the analytical toolbox, e.g:in the analytical toolbox, e.g:Size
TEM, SEM, AFM, SLS, DLS, FFF, NTA, SEC, LasDiff,...
ShapeMicroscopy or DLS-SLS
AgglomerationSame as size
CompositionBulk: ICPMS, spectroscopy, MSSingle particle comp: EM-EDX, EM-EELS
Particle concentrationMass conc: e.g. FFF-spectroscopyNumber conc: Microscopy, NTA, LIBD
Crystal structureBulk: XRDSingle particle: TEM-SAED
Surface areaPowders: Nitrogen adsorption with BET sorption isotherm calculation
Surface charge/potentialSurface charge: Potentiometric titrationsZeta-potential: Elektrokinetic measurements
Surface redox stateXPS
Surface functionalizationSPR
For further reading:
Hassellöv, M., Readman, J., Ranville, J. and Tiede, K.
Nanoparticle analysis and characterization methodology
in environmental risk assessment of engineered nanoparticles. Ecotoxicology 2008. Vol. 17, p. 344–361
Tiede, K., Boxall, A., Lewis, J., David, H., Tear, S. and
Hassellöv M. Detection and characterization of
engineered nanoparticles in food and the environment – a
review. Food Additives and Contaminants 2008, Vol. 25,
p. 1-27.
Hassellöv M. and Kaegi, R. Analysis and Characterization of Manufactured Nanoparticles in Aquatic Environments.
In: Nanoscience and Nanotechnology: Environmental and
human health implications. (Eds. Lead J.R. and Smith E.)
Wiley 2009, p. 211-266
But...for complex environmental or But...for complex environmental or
biological samples...biological samples...
Free nanoparticles, aggregates, mixed agglomerates of engineered NP with background nanomaterials (e.g. proteins or humic substances), dissolved ions of the same element, biological cells...
Broad size distributions
Heterogeneity in several physicochemical properties
Such samples has very different requirements on sample preparation and analysis methods than typical nanomaterial analysis.
Method Size (nm)
1 10 100 1000
PSD
capability
ShapeA
capability
Agglomeration
state
capabilityB
Concentr.
range
AFM
ppb − ppm
BET powder
Centrifugation
det. dep.
Dialysis
det. dep.
DLS
ppm
Electrophor.
ppm
EELS/EDX ppm in sp
ESEM
ppb − ppm
Filtration
det dep
Flow FFF
Sed FFF
UV: ppm,
ICPMS: ppb
HDC
det. dep.
ICP-MS ppt − ppb
LIBD
ppt
NTA
ppb-ppm
SEC
det dep
SEM
ppb − ppm
SLS
ppm
SAED
Spectrometry
ppb − ppm
TEM
ppb − ppm
Turbidimetry
ppb − ppm
Ultrafiltration det. dep.
XPS powder
XRD powder
Surface
Chemistry /
Charge / Area
Structure /
Crystallinity
Single
part./
population
Dynamics
capabilityC
Level of
perturbation
+
+
+
++
++
+
++ sp
medium
pp high
pp
low
pp low
pp
minimum
++
+
++
++
+
++ pp
minimum
sp high
sp
medium
pp
low-medium
pp
low
pp
low
pp N/A
sp
minimum
sp
minimum
pp
medium
sp
high
pp
minimum
sp high
pp
minimum
(HR) sp
high
pp
minimum
pp medium
pp
pp high
SSASSA
From Hassellöv and Kaegi, 2009
Electron microscopy detection modes
TEM interaction volume
Electron beam (parallell in
TEM, focussed in S-TEM and
SEM
Characteristic
X-rays
Inelastically
scattered electrons
Electron energy loss
spectroscopy
Secondary
electrons
Back scattered
electrons
Elastically scattered
electrons
Transmitted beam
SEM interaction volume
ESEM ESEM –– Backscattered electron detectionBackscattered electron detectionBSE detection: high contrast for high atomic numbers
Selectivity for heavy metal NPs
Example: Characterization of earthworm toxicity test 10 nm Ag NP
Yields aggregates in 50 - 4000 nmsize range ESEMESEM--BSEBSE ESEMESEM--SESE
NP Emissions (Samsung silver washing machine)Scanning TEM-High Angle Annular Dark Field: high contrast for heavy elements
Nanoparticle tracking analysisNanoparticle tracking analysis
Nanoparticle tracking analysisNanoparticle tracking analysis
Nanoparticle Tracking AnalysisNanoparticle Tracking Analysis
Advantages
Miminum perturbing
Sensitive
Not as biased by scattering intensity of largerparticles as DLS
Limitations
Not fully validated
Sizes below ~20-40nm (depending on mtrl) is invisible
Results are biased by subjective choice of optimum conditions
Conc. responses to some extent material-dependant
Diffu
sio
n
Flow
Fie
ld
To Detector
Diffu
sio
n
Flow
Fie
ld
To Detector
FieldField--FlowFlow Fractionation (FFF)Fractionation (FFF)
0 10 20 30 400.00
0.01
0.02
0.03
0.04
0.05
Dete
cto
r re
sponse
Retention time (min)
PS
33nm
PS
82nm
PS
196nm
Separates according to hydrodynamic diameter (diffusion)
Size range ~1nm - 800 nm
Suitable for fractionations of complex samples
Limitations mainly in compatiblity of sample, membrane & eluent
Coupling of FFF to different detectorsCoupling of FFF to different detectors
FFF channel (side view)FFF channel (side view)accumulation wallaccumulation wall
cross flowcross flow
diffusiondiffusion
widthwidth
~ 0.25 mm~ 0.25 mm
Diagramutanplot
fluorescencefluorescence UV absorbanceUV absorbance
FeFe
AgAg
CuCu
FieldField--Flow Fractionation Flow Fractionation –– UV UV –– FLUO FLUO ––
MALS MALS –– ICPMSICPMS
FFF size fractionates
Optical detector characterize size fractions
Light scattering inidependant size measurements and fractionation validation
ICPMS determines elemental distribution over size fractions
Diffu
sio
n
Flow
Fie
ld
To Detector
Diffu
sio
n
Flow
Fie
ld
To Detector
Diffu
sio
n
Flow
Fie
ld
To Detector
Diffu
sio
n
Flow
Fie
ld
To Detector
Using FlFFF and aTEM to determine trace metal –
nanoparticle associations in riverbed sediment
K. Plathe, F. Von der Kammer, M. Hassellöv et al.
Environmental Chemistry (accepted)
Calibrating FFF with size standards
FFFFFF--UVUV
Independant size measurements (rg)
with on-line static light scattering
FFFFFF--UVUV--MALSMALS
FFFFFF--ICPMSICPMS
Needs for Certified reference nanomaterialsNeeds for Certified reference nanomaterials
CRMs important for validation
Validation: experimentally proving that the method performs according to set-up criteria
For both new methods and
For quality assurance of standard method
Estimate total measurement uncertainty by comparing with CRM or interlab comparisons
Nanoparticle CRMs availableNanoparticle CRMs available
Size
NIST certified (BBI) citrate stabilized gold 10, 30& 60nm (also tested for z-pot)
IRMM ~40 nm silica RM (CRM candidate)
Z-potential
Goethite iron oxide dispersion from NIST with certified positive zeta potential value
Many non certified size standards exists
e.g. Polystyrene (from 20nm upwards)
Reference nanomaterialsReference nanomaterials
Thermodynamically unstable nature
May be kinetically stable against aggregation or cold sintering, ostwald ripening, phase transformations etc
Stability is sensitive to environmental factors
Temp, pressure?, shaking/stirring, pH (CO2)
These factors may influence shelf life
Nanoscale calibration artifacts
Nanoscale objects defined in 1, 2, or 3D
Used for calibration of microscopes and as transfer standards from one microscope to another
Variations of measurands
e.g. Size and Size distributions
Only a perfect sphere can be described with only one number
Various equivalent spherical diameters
Hassellöv and Kaegi, 2009
Comparability and harmonizationComparability and harmonization
Different types of averagesDifferent types of averages
Hassellöv and Kaegi, 2009
Future needs of Reference nanomaterialsFuture needs of Reference nanomaterials
Certified for a larger variety of physicochemical properties
E.g. validation of certain methods need CRMs with certified shape (aspect ratio) and density, and core-shell type of chemical composition, and multimodal distributions
++
+
++
Concentration Shape
Size
Size
Distribution
Composition
Structure /
Crystallinity
Porosity /
Surface Area
Surface
Functionality
Surface
Speciation
Surface
Charge
Agglomeration State
Reference nanomaterial needs in toxicologyReference nanomaterial needs in toxicology
Interlaboratory comparisons of the same toxicants(bench-marking) is important in toxicology studies.
Homogeneity and shelf-life important criteria
Lesser degree of certification has been suggested, but still thorough physicochemical characterization
JRC (IHCP) is hosting and distributing the OECD sponsorship programme batches
Some FP7 projects MARINA, Qnano will also contribute to this work
Interlaboratory comparisonsInterlaboratory comparisons
Issued by international measurement institutesand sometimes others
To compare methods
For proficiency testing of laboratories
For certifying reference materials
A few have been issued (e.g. by NIST and IRMM onanomaterials)
Interlaboratory comparison / proficiency testing
A few words on method comparisonsA few words on method comparisons
A valuable validation tool, but...
Must compare the correct measurandse.g. hydrodynamic vs volumetric diameter
Type of distribution or average (e.g. Number, volume, scattering intensity) must be comparable
Consider shape effects
Otherwise ....apples and pears...
When interpreting the comparison inherent limitations of the methods must be considered
Loss in
sensitivity for
smaller sizes
Size distribution method comparison (IRMM SiO2)
0 10 20 30 40 50 60 70 80 90 100
Particle diameter (nm)
NTA (number)
DLS (intensity)
FFF (volume)
No
rma
lized
fre
qu
en
cy
fu
nc
tio
n
FFF (number)
DMA (number)
TEM (number)
DLS (number)
AcknowledgementsAcknowledgements
Present and former PhD students and visitors
Julian Gallego
Jenny Perez-Holmberg
Jani Tuoriniemi
Kajsa Baumann
Björn Stolpe
Karen Tiede
Other contributorsJan Herrman, Australian Government NMI
Stefan Gustafsson, Microscopy and Microanalysis, Chalmers Univerof Technology
Karen Tiede, University of York
Frank von der Kammer, Univ of Vienna
Thank you for your attention!