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!