particle characterization at the nanoscale · 2011. 8. 3. · particle characterization at the...

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Particle Characterization at the Nanoscale

Greg MeyersDow ChemicalDow Chemical

G. F. Meyers NNI Workshop Nanomaterials and the Environment, Oct 6-7, 2009

22

Outline

• Experience with an Interlaboratory Study for Nanoparticle (NP) Sizing

• New NP Sizing TechnologyNew NP Sizing Technology

M h i l P ti t th N l• Mechanical Properties at the Nanoscale


33

Interlaboratory Study• ASTM Sponsored ILS#166 in 2008

(basis for ASTM E 2490-09, published June 2009)

• Evaluation of Photon Correlation Spectroscopy (PCS) • with comparison by direct methods (AFM, TEM, SEM)y ( )• 26 participating laboratories

• NIST Au colloid reference materialsNIST Au colloid reference materials

RM 8011 – nominal 10 nm RM 8012 – nominal 30 nmRM 8013 – nominal 60 nm


44Our Results with Au NPs

12141618

M 8

011 TEMSEMAFMPCS

68

10RM

A A A A40

6 7 8 9 10 11 12 13 14 15 16 17 186 7 8 9 10 11 12 13 14 15 16 17 186 7 8 9 10 11 12 13 14 15 16 17 186 7 8 9 10 11 12 13 14 15 16 17 18Particle diameter (nm)

There are statistically significant

25

30

35

RM

801

2

There are statistically significant differences between all techniques

for the smallest particles

60

70

13

20

B B B B

TEM of 8013 AFM of 8011

30

40

50

60

RM

801


AFM

_C

DLS

_C

SEM

_C

TEM

_C All PairsTukey-Kramer0.05

55

Interlaboratory Study• ILS 166 average data is average ofeach laboratory’s mean

• Quite good agreement across many10

15

20

amet

er (n

m)

DowILS 166 ave.

RM 8011 (10 nm)

• Quite good agreement across manylabs, primarily due to clear instructionsfor sample prep, data acquisition, andreporting

0

5

PCS (90º) TEM SEM AFM

mea

n di NIST ROI

40

• Recognition that different techniquescan give statistically different values20

30

40

diam

eter

(nm

) RM 8012 (30 nm)

0

10


mea

n d

80

From NIST RM8011 documentation...

40

60

diam

eter

(nm

) RM 8013 (60 nm)


0

20


mea

n

66Current Challenges• Differences between techniques – this is acceptable

– Different interactions are measured– Different assumptions are made– Different models may be appliedDifferent models may be applied– Sampling statistics variable

• Real systems can be more complexM b lti d l l di i– May be multimodal, large dispersion

– May have primary, aggregated, or agglomerated populations– May be heterogeneous in structure/composition

• Quality of test methods used across laboratories are being addressed through interlaboratory studies

• Accurate sizing of particles that are non-spherical using indirect methods• Accurate sizing of particles that are non-spherical using indirect methods

• Relevant size, shape, surface area metrics for risk assessment


• Lack of standards for broader compositions, shapes, surface chemistries and physical properties

77Mass Selective Particle SizingSuspended Microchannel Resonator (commercialized as Archimedes*)

f

For each particle, relate buoyant mass to density, Spherical equivalentBuoyant mass

sizesizemassmass

mass, and size via:

* Affinity Biosensors

(density)

sizesize Affinity Biosensors


88NP Sizing Needs & Timing• Additional NIST particle standards mirroring

manufactured NPs (1-3 years)– SiO2 and CeO2 (slurry), TiO2 (cosmetic, paint), Ag (antimicrobial), ( y) ( p ) g ( )

CNT or graphene (fillers), dendrimer (drug delivery)

• Techniques or algorithms to deal with non-spherical h (1 3 )shapes (1-3 years)– Fund research into new analysis methods– Improved throughput for direct imaging/analysis (microscopy)

• More interlaboratory studies including both routine and developmental instrumentation for sizing, surface area (ongoing in standards bodies)(ongoing in standards bodies)– Need to advertise participation opportunities more widely– Surface area techniques should be evaluated near term– Consider inversion algorithms for indirect methods as part of


Consider inversion algorithms for indirect methods as part of interlaboratory studies

99NP Sizing Needs & Timing (con’t)• Heterogeneous NP particle development (3-5 years)

– Physically heterostructured NPs• Porous (closed/open cell), core/shell( p ),

– Chemically heterogeneous NPs• Hydrophobic/hydrophilic (surface functionalized particles)• Compositionally heterogeneous on the surface (Janus particles)

• Particles for physical property testing (5-10 years)– Sized NP series for mechanical, thermal, optical, magnetic

propertiesproperties


1010Nanoscale Mechanical PropertiesDow – Veeco NIST ATP Program 2004-2007

Quantitative Nanoindentation in the AFM


1111

Lateral ForcesBefore Force Volume After Force Volume


• solid 700nm PS latex particles dislodged from surfactant rings

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Lateral ForcesThe problem

120%

Deflection Error vs. Sample Modulus

80%

100%

ngle

err

or

k = 0.1 N/m

k = 1 N/m

20%

40%

60%

efle

ctio

n an

k 1 N/m

k = 10 N/m

k = 100 N/m

0%

20%

1.0E+06 1.0E+07 1.0E+08 1.0E+09 1.0E+10 1.0E+11 1.0E+12

Sample modulus [Pa]

D

k = 1000 N/m

X

p [ ]

Errors can be reduced using • passive levers with stiffer springs• active levers


active levers

1313

Lateral ForcesDeflection Lateral Compensation (DLC)*– works with any cantilever

Sample

X-piezoX=cDef

Use the cantilever deflection signal to control the AFM’s X-piezo and compensate for the lateral motion

Improved accuracy on homogeneousmaterial standards


compensate for the lateral motion material standards*L Huang, C Meyer and C Prater, Journal of Physics: Conference Series 61, 805–809 (2007)

1414

Regimes of Deformation

180nN

• Hollow Latex Used in Coatings• Understanding deformation of

nanostructured particles at the ElasticResponse of shell

8 0

particle level • Requires very stable AFM

platform2.0

3.04.0

5.0

6.07.08.0

Mod

ulus

(GPa

)

Type 1Type 2

Spherical tip(K = 32.9 N/m, apex R~60 nm)

550nNElastic-Plastic

0.0

1.0

0.00 0.10 0.20 0.30 0.40

t/R

3Response of shell

3

350nm t/R=0.2

1.1uN

‘Kink’ at point where shell buckles

12


1 um x 1um

1515In-situ TEM Deformation of CdS NP

YouTube video


1616Needs for NP Mechanics & Timing• Accessible methods for calibrating spring constant of high stiffness

probes (40-1000N/m) of arbitrary cross-section for AFM indentation into materials with E>10 GPa (1-3 years)

• Alternative tip geometries including flat punch for AFM indentation (1-3 years)

• Libraries of NPs of various sizes on rigid substrates (3-5 years)– Metal cluster deposition; centrifugal force deposition/separation by spin

coating

• Develop nanoscale test for NP adhesion in biological, ceramic, or polymeric material matrix (3-5 years)

• Models and simulation to support experimental deformation and fracture regimes for NPs (ongoing)

I l b di AFM b d i d i f NP


• Interlaboratory studies on AFM based indentation of NPs are needed (ongoing)

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Acknowledgements• NIST ATP

– NIST Program Award # 70NANB4H3055• Dow• Dow

– Steve Rozeveld, Cliff Todd, Stew Wood (sizing) – Hamed Lakrout, Valeriy Ginzburg, Bob McIntyre (ATP)

• Affinity Biosensors– Ken Babcock

• Hysitrony– Oden Warren, Mike Okerlund, Julia Nowak

• Veeco– Sergei Belikov1 Sergei Magonov2 Natalia Erina Lin Huang– Sergei Belikov , Sergei Magonov , Natalia Erina, Lin Huang,

Chanmin Su, Charles Meyer, Craig Prater3

1 current affiliation 3M Corporation2 current affiliation Agilent Technologies


current affiliation Agilent Technologies3 current affiliation Anasys Instruments

particle characterization at the nanoscale · 2011. 8. 3. · particle characterization at the...

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