Toward greener nanomaterials: Lessons from integrating design, synthesis and evaluation

Jim Hutchison, University of OregonONAMI Safer Nanomaterials and Nanomanufacturing Initiative

(SNNI) - http://www.greennano.org

Why not just wait until commercialization to worry about the health and safety implications of a product?

Green design as innovation

Will they be ready to react or have the ability to be proactive?

Design rulesMechanismsToolbox

Feedback needs to be rapid and inexpensive

Actively pursuing greener products

Reasons to take a proactive, mechanistic approach to understanding effects of nanoparticles

These products typically lack diversity of structural variation needed to develop SARs

Characterization for product QC doesn’t (usually) address EHS issues – very different metrics

Often easier to understand a deliberately functionalized surface

Product testing focuses on materials nearer to commercialization

How can we design greener nanoparticles?

Avoid incorporation of toxic elements(Cd2+, Ag+, Zn2+)

Analogies to materials with similar attributes(CNM vs. PAHs and soot)

Use SARs to design effective, safer materials that possess desired physical properties

Design of safernanomaterials

(P4,P12)

Chem. Rev. 2007, 107, 2228ACS Nano 2008, 2, 395

Can we develop design rules that we can use to guidematerial selection and nanomaterial design?

Nanomaterials are different than traditional “molecular” species or larger particles

Pronounced heterogeneity – size, shape, surface coating, purity

Larger size and novel 3-D structure (polyvalency)

Much higher surface areas than larger particles

Purification is critical, challenging due to high surface area and reactivity

Characterization “bottleneck”

Richman and Hutchison ACS Nano 2009, 3, 2441-2446

Integrated approach to designing greener nanoparticles

Nanomaterial-Biological Interactions

Hutchison, J.E. ACS Nano 2008, 2, 395-402

Key themes

Integrate application/innovation with implications research

Molecular-level designMaximize performance/benefitReduce hazards and exposure across the lifecycle

Feedback to design – early interventionWhat do we need to know?Role of the materials chemist in this process

Importance of characterization and material description

Why gold nanoparticles as a model?

Goal: Use model materials to develop extendable design rules

•No toxic elements released – probe nanoscale features•Precision-engineered cores and surface coatings•Diversity of structural variation

Key questions: Nano-specific impacts? Generalizable findings?

Diverse families of functionalized nanoparticles can be prepared by ligand exchange

R = -(CH2)17CH3

-(CH2)15CH3

-(CH2)11CH3

-(CH2)9CH3

-(CH2)8CH3

-(CH2)7CH3

-(CH2)5CH3

-(CH2)2CH3

-(CH2)2Si(OMe)3

-(CH2)2SO3-Na+

-(CH2)3SO3-Na+

-(CH2)2N+HMe2Cl-

-(CH2)2N+Me3Cl-

-(CH2)2O(CH2)2N+Me3-OTs

-(CH2)2O(CH2) 2O(CH2)2 N+Me3-OTs

-(CH2)2O(CH2) 2O(CH2)2 N+Et3-OTs

-CH2COO-Na+

-(CH2)2COOH

-(CH2)11COOH

-(CH2)2OH

-(CH2)2PO(OH)2

-[(CH2)2O]2(CH2)2OH

-(CH2)2O(CH2)2OH

-[(CH2)2O]2CH2COOH

-(CH2)2COGlyGlyOH

-(CH2)2CONH(CH2)14CH3

OH

J. Am. Chem. Soc. 2005, 127, 2172 and Inorg. Chem. 2005, 44, 6149

Core d =0.8 nm,1.5 nm,3 nm15 nm

Surface Functionalization

Neutral: 2-(2-mercaptoethoxy)ethanol (MEE)

Neutral: 2,2,2-[mercaptoethoxy(ethoxy)]ethanol (MEEE)

Anionic: 2-mercaptoethanesulfonate (MES)

Cationic: N,N,N-trimethylammoniumethanethiol (TMAT)

RSH

Wat

erbo

rne

Exp

osur

eC

once

ntra

tion

(µg/

mL)

0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100

50

2

0.4

0.08

0

10

250

0.016

Percent of Total (%)Mortality Malformation Unaffected

MES-AuNPs MEEE-AuNPsTMAT-AuNPs

Biological response at 120 hpf for 1.5nm TMAT-, MES- and MEEE-AuNPs

Hypo-locomotor Activity

0 10 20 30 40 50 60

100

80

60

40

20

0

Tota

lDis

tanc

e(m

m)

120

140

Time (Alternating 10 mins Dark/Light)

160

180 MES TMAT MEEE50 µg/mL 10 µg/mL 50 µg/mL

Control

Hypo-locomotor Activity

Materials matter: Purity is a parameter critical to relating impacts to specific structures

Sweeney, Woehrle, Hutchison J. Am. Chem. Soc. 2006, 128, 3190.

Purity can be more significant for nanomaterials

1% impurity by weight of small molecule impurity

15 nm gold NP sample

>350 times molar excess of the impurity

Materials innovators may not know or care about impurities at this level

Materials matter: Small structural differences can lead to completely different reactivity

Integrative characterization is essential to link impacts with structures

and impurities

TEM

UV/vis

NMR

a

c

b

300 400 500 600 700 800

Wavelength (nm)

Abs

orba

nce

(AU

)

t=0 ht=18 ht=114 h

0% EM

300 400 500 600 700 800

Wavelength (nm)

Abs

orba

nce

(AU

)

t=0 ht=18 ht=114 h

100% EM

0.0

0.4

0.2

0.8

1.0

0.6

0.0

0.4

0.2

0.8

1.0

0.6

HO SH

O

Materials matter: Characterizing behavior in exposure media is also essential

Ionic strength influences aggregation

10 (µg/mL) 50 (µg/mL)Percentage ofEmbryo Media (%)

1.5 nm Au 3-MPA

Biological responses altered by aggregation

Percent of Total (%)Mortality Malformation Unaffected

Wat

erbo

rne

Expo

sure

Con

cent

ratio

n(µ

g/m

L)

50

2

0.4

0.08

0

0 20 40 60 80 100

10

0 20 40 60 80 100 0 20 40 60 80 100

50

2

0.4

0.08

0

0 20 40 60 80 100

10

0 20 40 60 80 100 0 20 40 60 80 100

100% EM 20% EM 4% EM

0.8% EM 0.16% EM 0% EM

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*

*

*

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Materials matter: Particles integrated into products may behave in unexpected ways

t = 0 t = 1 t = 3 t = 5

Beyond applications and implications:Collaboration is needed to advance greener materials

Pioneering NanotechApplications

Pioneering NanotechApplications

Nano EHSImplications

Pioneering NanotechApplications

Greener Nano

Nano EHSImplications

A strong bridge between applications and implications is the key toanticipating new problems and developing proactive solutions

Hutchison, J.E. ACS Nano 2008, 2, 395-402