measurement of nanomaterials - standards australia...measurement challenges for nanomaterials vast...
Post on 05-Feb-2021
5 Views
Preview:
TRANSCRIPT
-
Jan HerrmannNanometrology Section, Physical Metrology Branch
National Measurement InstituteFood and Grocery Nanotechnology Forum, 26 February 2013
Measurement of Nanomaterials
-
NMI Nanometrology
“To measure is to know.” (Lord Kelvin)
People making decisions about [nano]technologiesmanufacturersresearchersregulatorsconsumers
require [nanoscale] measurements that arefit‐for‐purposeaccuraterecognised
Certification Report EUR 24620 EN for ERM®‐FD100, EU (2011)
0 5 10 15 20 25 30 35 400
5
10
15
20
particle cou
nt / 103
area equivalent particle diameter / nm
Total numberof particles:156606
-
NMI Nanometrology
Why are we measuring ?What is the purpose of the measurement ?
What should be measured ?What is the quantity that matters ?
How accurate does the result need to be ?How is the purpose affected by the accuracy ?
What can actually be measured ?What methodology/infrastructure is available ?
How accurate is the measurement result ?What is the uncertainty budget of the measurement ?
How comparable is the measurement result ?Is the measurement traceable to a reference ?
Measurement questions
100 nm
ZnO
SiO2/PSL
-
NMI Nanometrology
NMI nanometrology activitiesDevelop nanometrology infrastructure
traceable nanoscale length measurementsnanomaterials characterisation
Investigate and comparemeasurement instrumentationmeasurement methodologyreference materials
Provide measurement and calibration services
Disseminate nanometrology expertisepublications, consultancy, workshops,interlaboratory studies, research collaborations,student internships, …
Contribute to developmentof international nanometrology system andof documentary standards
NMI mSPM
20 nm SiO2
-
NMI Nanometrology
NMI nanomaterials measurement activitiesLaboratory comparisons
– VAMAS TWA34 round robin on sizingof airborne nanoparticles (2011/12)• Transmission Electron Microscopy• Atomic Force Microscopy
– APMP Supplementary Comparisonon Nanoparticle Size (2011/12)• Transmission Electron Microscopy• Atomic Force Microscopy• Dynamic light scattering
– Australian inter‐laboratory studyon nanoparticle sizing (2012)• Organised by NMI• 27 participants• 66 measurements (EM, AFM, DLS, DCS, AF4, PTA, …)
• Mono‐modal and bi‐modal Au(20 nm and 100 nm)
Application‐drivenmethod development– Sunscreens, cosmetics
– WastewaterEvaluation of instrumentation
– Sedimentation FFF– Single‐particle ICP‐MS
Contribution to development of documentary standards– SA/NT001– ISO/TC229– VAMAS
TiO2
-
NMI Nanometrology
Measurement challenges for nanomaterialsVast variety of nanomaterials and characterisation techniques.
Relevant properties for applications, e.g., for risk assessment.
Definition of measurand; measurement model.
Complex descriptors required for complex systems.
Ensemble vs single particle methods:averaging vs limited statistical relevance.
Sampling.
Primary particles vs agglomerates/aggregates.
Engineered vs naturally occuring/incidental nanomaterials.
Detection + identification + quantification.
Intensity vs volume vs number weighted size distributions.
Influence of nanomaterial interaction with environment.
Limited number of methods available for nanomaterialsin complex matrices (e.g., food, soil, tissue).
60 nm Au
ZnO
-
NMI Nanometrology
Measurands — what should be measured?quantity intended to be measured
(VIM, 3rd edition, JCGM 200:2008)
Several published lists of physical/chemical propertiesrelevant for safety testing of nanomaterials:
• EC / SCENIHR (2009)“Risk Assessment of Products of Nanotechnologies”
• OECD WPMN Sponsorship program (2010)Series on the Safety of Manufactured Nanomaterials,No. 27
• ISO/TR 13014:2012 “Nanotechnologies – Guidanceon physico‐chemical characterization of engineered nanoscale materials for toxicologic assessment”
Set of physical‐chemical properties
Agglomeration/aggregationWater solubilityCrystalline phaseDustinessCrystallite sizeRepresentative TEM picture(s)Particle size distributionSpecific surface areaZeta potentialSurface chemistryPhotocatalytic activityPour densityPorosityOctanol‐water partition coefficient Redox potentialRadical formation potential
-
NMI Nanometrology
++
+
++
Concentration Shape
Size
Size Distribution
CompositionStructure / Crystallinity
Porosity / Surface Area
Surface Functionality
Surface Speciation
Surface Charge
Agglomeration State
Hassellöv and Kaegi, 2009
Particle characterisation
-
NMI Nanometrology
What is the ‘right’ particle diameter?Sphere of same
2D projection areaSphere of same hydrodynamic mobility
Sphere of same surface area
Sphere of same sieve aperture
Sphere of same sedimentation rate
Sphere of same mass
Sphere of same volume
dec
ds
dsieve
dsed
dw
dv
dh
Choose a measurand that matches the application.Be aware of limitations of methodology/infrastructure.
-
NMI Nanometrology
How to describe ensembles of nano‐objects?
Complex particle systems require complex descriptors.
“Size” is (almost) never enough.Guidance: ISO 9276 Series, e.g., ISO 9276‐6:2008 “Representation of results of particle size analysis ‐‐ Part 6:
Descriptive and quantitative representation of particle shape and morphology”
30 nm
AuV Coleman
Al2O3T Tsuzuki
ZrOT Tsuzuki
CeO2T Tsuzuki
100 nm
ZnOV Coleman
-
NMI Nanometrology
High surface energies associated with nanoparticles
→ tendency to agglomerate/aggregate
Important: Dispersion stability; agglomeration/aggregation dynamics
Primary particles: Energy input required to break up agglomerates
In many situations, nanoparticles are not present as individual nanoparticles!
Transmission electron microscopy image of Au, Ag and TiO2 nanoparticles (V Coleman).
Primary particles or agglomerates?
-
NMI Nanometrology
How comparable are different techniques?
NIST Report of Investigation, RM 8012, Dec‐2007.
Method divergence!
-
NMI Nanometrology
NMI particle measurement infrastructure
Dynamic light scattering
Disk centrifuge
FFF
Dimensional properties (‘size’)– Light scattering
• Dynamic light scattering• Laser diffraction• Particle track analysis
– Size classification• Disk centrifuge• X‐ray sedimentation• Field flow fractionation• Microsieving
– Microscopy• Atomic force microscopy• Electron microscopy*• Optical microscopy(static & dynamic)
– Electrical zone sensing– Single‐particle ICP‐MS*
Surface area / porosity– Gas adsorption– NMR
Mass / density– Microchannel resonator
Surface charge– Zeta potential fromelectrophoretic mob.
light scatteringparticle tracking
– Streaming currentpotential
Chemical identity– Thermogravimetricanalysis
– FT‐IR spectroscopy– ICP‐MS*
-
Dynamic Light Scattering (DLS)
Size range ~0.1 nm ~ 6 µm.
Measurand Autocorrelation function of the scattered light intensity; average hydrodynamic diameter.
Advantages Fast and accurate for monomodal suspensions. An ensemble measurement technique, providing a good statistical representation of the sample.
Limitations Particles must be in suspension and undergoing Brownian motion. Large particles scatter much more light (I� (diameter)6); even a small number of large particles will obscure the contribution from smaller particles.
-
Atomic Force Microscopy (AFM)
Aerosolised SiO2 (M. Lawn) Samples: R Goreham / U South AustraliaImages: M Lawn
1 µm × 1 µm scansVertical scale: (a) 0…2 nm; (b)–(f) 0…25 nm.
• Excellent for visualizing the surface morphology of a sample
• Particle shape• Size• Size distribution• Degree of aggregation/agglomeration• Surface forces and interactions
• Poor statistical representation of a sample• Time consuming• Tip‐sample convolutions• Sample preparation can be challenging
-
Differential Centrifugal Sedimentation(DCS)
Size range
-
Transmission Electron Microscopy (TEM)
30 nm Au (V Coleman)
ZnO (V Coleman)
• Excellent for visualizing the sample• Representative EM images• Particle shape• Size• Size distribution• Degree of aggregation/agglomeration• Crystalline phase• Chemical analysis
• Poor statistical representation of a sample• Time consuming• Sample preparation can be challenging.
Aerosolised SiO2 (Å. Jämting)
-
Mix of 100 nm PS and 100 nm Au (Å Jämting)
Size range ~20 nm ~ 1 µm.
Measurand Diffusion length. 2‐D tracking of particles moving with Brownian motion.
Advantages Qualitative differentiation between particles of different composition based on scattering intensity, allows measurements of particle number concentration (particles/mL). Single particle measurement technique.
Limitations Strong dependence on operator through choice of settings for imaging and analysis. Limited statistical relevance due to limited number of particles analysed.
Particles scatter in the laser beam
Particles to be viewed are suspended in liquid
Laser beam (approx 50 mm wide)
Glass Metallised surface
Liquid
Particle Track Analysis (PTA)
JH4
-
Slide 18
JH4 Acknowledge Nanosight Ltd.JH, 12/11/2012
-
Microchannel Resonator
Size range60 nm – ~5µm
Lower limit is dependant on particle density. Instrument sensitivity is ~1 Femtogram.
MeasurandBuoyant mass determined by a shift in the resonant frequency of an oscillating cantilever with a buried microfluidic channel
Advantages Measures particle mass – orthogonal method. Can be used to measure density.Can measure ‘floating’ or ‘sinking’ particles. Single particle measurement technique.
Limitations Sample needs to have homogeneouscomposition, density, porosity. Sensitivity is dependant on the channel size Smallest channel currently available: 2 x 2 µm. Dilute suspensions required.
50 100 1500.0
0.5
1.0
Nor
mal
ized
vol
ume
dist
ribut
ion
(arb
. uni
ts)
Equivalent spherical diameter (nm)
Micro-channel resonator (1000 particles)
DCS
100 200 300 400 5000.0
0.2
0.4
0.6
0.8
1.0 DLS
Nor
mal
ized
volu
me
dist
ribut
ion
(a.u
.)
Equivalent spherical diameter (nm)
-
Characterization techniques ‐ AFFFF
Size range ~ 0.1 nm ~ 2 µm.
Measurand Detector dependent, often equipped with light scattering detectors measuring static and dynamic light scattering. Elution time can also be used to provide a measure of particle size. Can be hyphenated with chemical analysis instrumentation, e.g., mass spectrometry.
Advantages A separation measurement technique. Very high resolution for both high and low molecular weight particles. Provides sequential separation of particles based on a size dependent interaction of the particles with an applied force field (flow). Fractions can be collected for off‐line processing.
Limitations Complex method development required to optimise particle separation.
-
NMI Nanometrology
Comparison of particle sizing techniques
mixture
Å Jämting
DCSmixture
Sample: Mixture of six aqueous of gold nanoparticleswith nominal diameters of 5 nm, 10 nm, 20 nm,30 nm, 40 nm and 50 nm (BB International, UK).
DLS individual suspensions TEM individual suspensions TEM mixture
AF4mixturePTA
mixture
-
NMI NanometrologyReference MaterialsNISTAu•AFM• DLS• TEM• SEM• SAXS
JRC‐IRMMSiO2• DLS• DCS• TEM/SEM• SAXS
PSL• DMA
Thermo ScientificPSL• DLS (20‐50 nm)• TEM (> 50 nm)
www.nano‐refmat.bam.de/en/
-
NMI Nanometrology
ConclusionAccurate, fit‐for‐purpose and recognised nanoscalemeasurements support both the development of nanotechnologies and their effective regulation.
There many challenges in nanomaterials metrology.The application determines the measurand[s].The measurand determines the technique.Complex systems require complex descriptors.
Agree on definitions and terminology.Understand and model your measurement.Use reference materials to validate/calibrate.
Separation + sizing + chemical analysis:promising approach for complex matrices such as food.
-
Jan Herrmann
Nanometrology
National Measurement Institute
Bradfield Road, West Lindfield NSW 2070
Email: jan.herrmann@measurement.gov.au
Phone: (02) 8467 3784
NMI Nanometrology team:
Malcolm Lawn, Jan Herrmann,John Miles, Bakir Babic,Chris Freund;Heather Catchpoole,Victoria Coleman, Maitreyee Roy,Åsa Jämting
And many students…
top related