ReferenceReference materialmaterial needsneeds toto supportsupport nanometrologynanometrology andand riskrisk assessmentassessment ofof engineeredengineered nanoparticlesnanoparticles

MartinMartin HassellHassell öövv EnvironmentalEnvironmental NanochemistryNanochemistry group,group, DepartmentDepartment ofof Chemistry,Chemistry, UniversityUniversity ofof Gothenburg,Gothenburg, SwedenSweden 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 “QuantumDots” Cadmium Selenide Smallest Property change as function of size Propertyof changeas function Property change as function of size Propertyof changeas function Largest

©Felice Frankel SomeSome ISOISO definitionsdefinitions

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

ToxicToxic potentialpotential ofof nanomaterialsnanomaterials

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 MeasurementMeasurement needsneeds inin riskrisk assessmentassessment ofof engineeredengineered nanoparticlesnanoparticles

Environmental and human health risk assessment consists of Hazard assessment (how t oxic) and Exposure assessment (how high concentration of X)

Both requires analysis and physicochemical characterization 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) Agglomeration State Concentration Shape

Surface Speciation Size Surface

Charge + + + + +

Surface Size Functionality Distribution

Porosity / Structure / Hassellöv and Surface Area Composition Crystallinity Kaegi, 2009 Similar chemistry (all ZnO) – potentially different behavior (benefits & risks) PhysicochemicalPhysicochemical CharacterizationCharacterization

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 CharacterizationCharacterization isis notnot onlyonly staticstatic

” ee ” Diffusion gg ann Collisions hha Agglomeration CC Attachement off s o Detachement tees aat Dissolution RR ee Sedimentation iinn mm err ette D e ””D BatteryBattery ofof availableavailable methodsmethods inin thethe analyticalanalytical toolbox,toolbox, e.g:e.g: Size TEM, SEM, AFM, SLS, DLS, FFF, NTA, SEC, LasDiff,... Shape For further reading: Microscopy or DLS-SLS Hassellöv, M., Readman, J., Ranville, J. and Tiede, K. Agglomeration Nanoparticle analysis and characterization methodology in environmental risk assessment of engineered Same as size nanoparticles. Ecotoxicology 2008. Vol. 17, p. 344–361 Composition Bulk: ICPMS, spectroscopy, MS Tiede, K., Boxall, A., Lewis, J., David, H., Tear, S. and Single particle comp: EM-EDX, EM-EELS Hassellöv M. Detection and characterization of engineered nanoparticles in food and the environment – a Particle concentration review. Food Additives and Contaminants 2008, Vol. 25, Mass conc: e.g. FFF-spectroscopy p. 1-27. Number conc: Microscopy, NTA, LIBD Crystal structure Hassellöv M. and Kaegi, R. Analysis and Characterization Bulk: XRD of Manufactured Nanoparticles in Aquatic Environments. Single particle: TEM-SAED In: Nanoscience and Nanotechnology: Environmental and human health implications. (Eds. Lead J.R. and Smith E.) Surface area Wiley 2009, p. 211-266 Powders: Nitrogen adsorption with BET sorption isotherm calculation Surface charge/potential Surface charge: Potentiometric titrations Zeta-potential: Elektrokinetic measurements Surface redox state XPS Surface functionalization SPR But...forBut...for complexcomplex environmentalenvironmental oror biologicalbiological samples...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) PSD Shape A Agglomeration Concentr. Surface Structure / Single Dynamics Level of 1 10 100 1000 capability capability state range Chemistry / Crystallinity part./ capability C perturbation capability B Charge / Area population

+ − + AFM ppb ppm + sp medium + + SSA BET powder pp high

Centrifugation det. dep. pp low

Dialysis det. dep. pp low

DLS ppm pp minimum

Electrophor. ppm + + + pp minimum + + EELS/EDX ppm in sp sp high ESEM − ppb ppm sp medium

Filtration det dep pp low-medium

Flow FFF UV: ppm, pp low Sed FFF ICPMS: ppb HDC det. dep. pp low

− ICP-MS ppt ppb pp N/A

LIBD ppt sp minimum

NTA ppb-ppm sp minimum

SEC det dep pp medium

SEM ppb − ppm sp high

SLS ppm pp minimum

SAED sp high Spectrometry ppb − ppm pp minimum

TEM ppb − ppm (HR) sp high

Turbidimetry ppb − ppm pp minimum

Ultrafiltration det. dep. pp medium

XPS powder pp

From Hassellöv and Kaegi, 2009 XRD powder pp high Electron microscopy detection modes

Electron beam (parallell in Characteristic TEM, focussed in S-TEM and X-rays Back scattered SEM electrons

Secondary electrons

TEM interaction volume

SEM interaction volume Elastically scattered Inelastically electrons scattered electrons Electron energy loss Transmitted beam spectroscopy ESEMESEM –– BackscatteredBackscattered electronelectron detectiondetection BSE 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 nm size range ESEM -BSE ESEM -SE NP Emissions (Samsung silver washing machine) Scanning TEM-High Angle Annular Dark Field: high contrast for heavy elements NanoparticleNanoparticle trackingtracking analysisanalysis NanoparticleNanoparticle trackingtracking analysisanalysis NanoparticleNanoparticle TrackingTracking AnalysisAnalysis Advantages Miminum perturbing Sensitive Not as biased by scattering intensity of larger particles 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 Flow membrane & eluentmembrane & sample, of in compatiblity mainly Limitations samples complex of fractionations for Suitable nm 800 - rangeSize~1nm (diffusion) diameter to hydrodynamic Separatesaccording Field Field - - Flow Flow

Fractionation (FFF)Fractionation Fractionation (FFF)Fractionation

Field Diffusion Field

Detector response 0.00 0.01 0.02 0.03 0.04 0.05 02 040 30 20 10 0 33nm PS 82nm PS To DetectorTo Retention time (min)Retention time 196nm PS CouplingCoupling ofof FFFFFF toto differentdifferent detectorsdetectors

fluorescence UV absorbance

Diagramutanplot Fe cross flow Ag

Cu

width ~ 0.25 mm

accumulation wall FFF channel (side view)

diffusion FieldField --FlowFlow FractionationFractionation –– UVUV –– FLUOFLUO –– MALSMALS –– ICPMSICPMS

FFF size fractionates Optical detector characterize size fractions Light scattering inidependant size measurements and fractionation validation ICPMS determines elemental distribution over size fractions Field

Flow To Detector Diffusion Diffusion Diffusion Diffusion Calibrating FFF with size standards

FFF -UV

Independant size measurements (rg) FFF -ICPMS with on-line static light scattering

FFF -UV -MALS

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) NeedsNeeds forfor CertifiedCertified referencereference nanomaterialsnanomaterials

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 NanoparticleNanoparticle CRMsCRMs availableavailable

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) ReferenceReference nanomaterialsnanomaterials

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 (CO 2) 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 ComparabilityComparability andand harmonizationharmonization

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 DifferentDifferent typestypes ofof averagesaverages

Hassellöv and Kaegi, 2009 FutureFuture needsneeds ofof ReferenceReference nanomaterialsnanomaterials 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 Agglomeration State Concentration Shape

Surface Speciation Size Surface Charge + + + + +

Surface Size Functionality Distribution

Porosity / Structure / Surface Area Composition Crystallinity ReferenceReference nanomaterialnanomaterial needsneeds inin toxicologytoxicology 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 InterlaboratoryInterlaboratory comparisonscomparisons

Issued by international measurement institutes and 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 o nanomaterials) Interlaboratory comparison / proficiency testing AA fewfew wordswords onon methodmethod comparisonscomparisons

A valuable validation tool, but... Must compare the correct measurands e.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 Size distribution method comparison (IRMM SiO 2)

TEM (number)

DLS (intensity)

DLS (number)

DMA (number)

FFF (volume)

FFF (number) Normalizedfrequency function Loss in NTA (number)

sensitivity for smaller sizes 0 10 20 30 40 50 60 70 80 90 100 Particle diameter (nm) AcknowledgementsAcknowledgements Present and former PhD students and visitors Julian Gallego Jenny Perez-Holmberg Jani Tuoriniemi Kajsa Baumann Björn Stolpe Karen Tiede Other contributors Jan Herrman, Australian Government NMI Stefan Gustafsson, Microscopy and Microanalysis, Chalmers Univer of Technology Karen Tiede, University of York Frank von der Kammer, Univ of Vienna Thank you for your attention!