Active, Hybrid, and Horizon Nanomaterials

Robert J. Hamers Department of Chemistry

University of Wisconsin-Madison rjhamers@wisc.edu

NSF Nanoscale Science and Engineering Center (2007-2014) (Thrust 4) Goal: To elucidate an understanding of biological response to nanoparticles, using Zebrafish (Danio Rerio) as a model organism

Center for Sustainable Nanotechnology (Phase I CCI, 2012- 2015) Goal: The goal of the Center for Sustainable Nanotechnology is to develop and utilize a molecular-level understanding of nanomaterial-biological interactions to enable development of sustainable, societally beneficial nanotechnologies.

Background: Environmental Safety and Health Impacts of Nanomaterials

Hamers (UW), Pedersen (UW), Murphy (UIUC), Haynes (Minn.) Klaper (Milwaukee) Geiger (Northwestern), Orr (PNNL)

Size

O O

surface chemical groups

shape

\

aggregation state

Surfaces often dominate the interaction of nanomaterials with their environment and with each other

•  Electrostatic interactions (aggregation, NP-membranes interactions) •  Electron-transfer processes •  Catalytic reactions

Environmental Safety and Health Impacts of Nanomaterials

Lewicka, Colvin, et al. Photochemical behavior of nanoscale TiO2 and ZnO sunscreen ingredients J. Photochem. Photobiol. 2013, 263, 24

Linsebigler and Yates, Photocatalysis on TiO2 surfaces: Principles, Mechanisms, and Selected Results Chemical Reviews 1995, 3, 735-758.

Cai, Fujishima, et al, J. Induction of Cytotoxicity by Photoexcited TiO2 Particles Cancer Research 1992, 52, 2346

What is the impact of these processes on the environmental health and safety of NPs?

Fujishima and Honda, Electrochemical Photolysis of Water at a Semiconductor Electrode Nature 1972, 238, 37.

Light-activated nanoparticles

vb

cb O2

O2-

H2O

H+ + •OH

hν>Egap

Alex Weir, Paul Westerhoff*, Lars Fabricius, Kiril Hristovski, and Natalie von Goetz, Titanium dioxide nanoparticles in food and personal care products, ES&T 2012, 46, 2242.

Redox-active nanomaterials

Surface-driven redox processes have a strong influence on the biological response and toxicity of many types of nanoparticles

2Zhang, Nel, et al. ACS Nano 2012, 22, 4349-4368.

-1.0

0.0

1.0

2.0

O2-/O2

Cellular respiration

Semiconducting nanoparticles

Chemical redox

Biological redox

Nanoparticle Electronic structure

E v

s. N

HE

(Vol

ts)

1Bar-Ilan, Pedersen, Heideman, Peterson, Hamers, et al., Nanotoxicology 2012, 6 , 670-679; Environ. Sci. Technol. 2013, 47, 4726-4733.

Phototoxicity1 Redox hijacking2

vb

cb O2

O2-

H2O

H+ + •OH

hν>Egap

Photo-induced creation of ROS species

NP-induced alteration of cellular redox potential

vb

cb EF

NAD+/NADH Cyt c O2/H2O

1Cai, Fujishima et al., J. Cancer Research, 1992, 52, 2346

Redox-active nanomaterials

Reactive Oxygen Species Production Particle and Ligand Degradation

Uptake: Internal ROS Generation

ROS-induced ligand degradation

ROS

ROS

External ROS Generation

Toxicity to aquatic organisms

There is a tight interplay between ROS generation and the presence of surface ligands and/or other organic material

Ligand mitigation of ROS

Days post-fertilization

Phototoxicity of oxide nanoparticles (TiO2), chronic exposure

àSignificant mortality observed at concentrations of ~ 1 ng/ml (=1 part-per-billion) à  Comparable to of lower than environmental concentrations predicted to result from

result of widespread use of TiO2 nanoparticles

Surv

ival

pro

babi

lity

(%)

0.01 ng/ml 1.0 ng/ml 10 ng/ml 100 ng/ml 1000 ng/ml 10,000 ng/ml 10,000 ng/ml dark

5 10 15 20 25 0 0

25

50

75

Embryo Larvae Juvenile

1Bar-Ilan, Pedersen, Hamers, et al., Environ. Sci. Technol. 2013, 47, 4726-4733. doi: 10.1021/es304514r

100 Danio rerio (zebrafish)

TiO2 itself is not toxic (in the dark) à Toxicity arises from active creation of reactive oxygen species

Kim, Louis, Pedersen, Hamers, Peterson, Heideman, Analyst 2013, accepted

There may be new routes of entry for very small (<15 nm ) particles that are not accessible to larger particles

Are all “nano” particles equivalent? Effects of size…

Proposed relationship of band gap energy to the cellular redox potential (−4.12 to −4.84 eV). Conduction band (Ec) and valence band (Ev) were calculated according to eqs 1 and 2 described in Materials and Methods. Band gap energy (Eg) was measured by UV–vis spectroscopy, and absolute electronegativities (χoxide) were calculated using a set of equations reported by Portier et al.(59) Point of zero zeta-potential (PZZP) was determined by measuring zeta-potentials of each nanoparticle suspension over a wide pH range (typically 2–11). According to this band gap profiling, six of the 24 nanomaterials (TiO2, Ni2O3, CoO, Cr2O3, Co3O4, and Mn2O3) showed potential overlap of Ec with the cellular redox interval and were therefore predicted to participate in electron transfers between the particle surfaces and the cellular redox couples. These band gap predictions are very close to those predicted by Burello, who calculated Ec and Ev by using the theoretical Eg,(60) χoxide derived from Portier’s studies,(59) as well as the PZZP reported in the literature.(61) The toxicological predictions for TiO2, Ni2O3, CoO, Cr2O3, Co3O4, Mn2O3, CuO, and Fe2O3, according to the latter set of calculations, are shown in Figure S10.(21)‏

Published in: Haiyuan Zhang; Zhaoxia Ji; Tian Xia; Huan Meng; Cecile Low-Kam; Rong Liu; Suman Pokhrel; Sijie Lin; Xiang Wang; Yu-Pei Liao; Meiying Wang; Linjiang Li; Robert Rallo; Robert Damoiseaux; Donatello Telesca; Lutz Mädler; Yoram Cohen; Jeffrey I. Zink; Andre E. Nel; ACS Nano 2012, 6, 4349-4368.

What is the relationship between nanoparticle electronic structure and toxicity?

What are the important questions and challenges??

To what extent do NPs induce toxicity via creation of ROS species, or but direct coupling to cellular respiration processes ?

What are the surface ligands doing? How do surface ligands impact uptake of NPs by organisms? Are the original surface ligands displaced/covered/destroyed ? What kind of molecular “coronas” are formed, and what do they do?

vb

cb O2

O2-

H2O

H+ + •OH

hν>Egap

How is nanoparticle toxicity correlated with rates of bulk processes (e.g., recombination) vs. surface photocesses (redox chemistry)?

Can we generate a set of “design rules” that will allow ability to predict the toxicity of a NP of given chemical composition, surface

ligands, and size?

Multicomponent nanosystems: Nanoparticle Heterojunctions

Arabatzis, et al., Appl. Cat. B 2003, 42, 187-201. P. Kamat, J. Phy. Chem. C 2008, 112, 18737

Key factors affecting performance Bandgaps of individual materials Alignments of bands (notoriously difficult to predict) Lifetimes of excited states (recombination times)

+

-

+

hν -

+

-

A B Discontinuity at hetero-junctions can facilitate charge separation, visible absorption à Enhanced photcatalytic activity à Improvements in solar energy conversion efficiencies (QD-sensitized TiO2)

Ag activation of TiO2

Ag TiO2 TiO2

+

-

Quantum dot-sensitized solar cell -

+

CdSe-QD TiO2 CdSe-QD

Red Ox

Redox

Shuttle

vb

cb

vb

cb

vb

cb Irreversible

charge separation

1Au:TiO2 Zanella, Giorgio, Henry, and Louis, J. Phys. Chem. B 2002, 106, 7634 2Pt: TiO2 Zhang, et al., J. Phys. Chem B 1998, 102, 10871-10878 3Strained: Mavrikakis and Norskov, Phys. Rev. Lett. 1998, 81, 2819 4Core-shell NPs: Adzic, Advances in Physical Chemistry 2011, Article ID 530397

Au/TiO2

Au

TiO2

O

Bimetallic, trimetallic Supported catalysts

Strained surface layers lead to new emergent behavior

“Designer catalysts”: Multicomponent & core/shell NPs Strained metal layers and

Core-shell structures

“Horizon” Nanomaterials I: Redox-variable nanomaterials Example: Battery cathode, anode materials in renewable energy

Co4+ (O2-)2 LiC6

Li+Co3+ (O2-)2

e-

Li+

Battery materials have variable redox potentials spanning from – 3 V to ~ 1 V vs. NHE

Charged: E = -3.0 V

Discharged Eanode=Ecathode

Charged:E=~ +1V

Anode Li+ + C6 + e- à LiC6

Cathode Li+ + CoO2 + e- à LiCoO2

Co4+/3+

Co: 4s0 -3.0

-2.0

-1.0

0.0

1.0

2.0 DOS

Ele

ctro

chem

ical

pot

entia

l (E

vs.

NH

E),

Volts

http://www1.eere.energy.gov/vehiclesandfuels/avta/pdfs/fsev/battery_leaf_0356.pdf

http://www.iea.org/topics/transport/electricvehiclesinitiative/EVI_GEO_2013_FullReport.PDF

Redox-active NPs: Battery cathode materials

Nissan Leaf:1 LiMn2O4 with LiNiO2/Graphite Battery pack = 294 kg, delivers 24 kWh @ 3.8 V

à 38 pounds of active cathode material in a small EV

How much material? LiNixMnyCo1-x-yO2 materials have capacity of ~ 275 mAh/g

X 1,000,000 EVs estimated by 2020 = 19,000 tons of material (US only)

400 million laptops + tablets, 2013 Ipad battery = 11,666 mAh

LiCoO2 à 140 mAh/g

~83 g LiCoO2/device ~37 tons/year in 2013

Exposure routes: Crashes, fires, recycling, “throwaway” electronics

(x) Li2MnO3 + (1-x) Li Mn0.33Ni0.33Co0.33O2 Silicon nanowires

•  Variable redox potential (lithiated / delithiated) •  Mixed phases on nanometer length scales •  Additional surface coatings (nanometer thickness)

Silicon/Germanium/Tin/Carbon Nickel, Manganese, Cobalt oxides

Hamers, et al., Nanotechnology 2005, 16, 1868-1873 and and unpublished work

Next-generation battery cathode, anode materials)

Toward monodisperse, redox-active nanomaterials

CoO2 NPs in dendrimers

Hang, Hamers (UW-Madison), in collaboration with Michael Curry (Tuskegee)

à Monodisperse, few-nanometer metal oxide nanoparticles

CoO2 NP

dendrimer carcasses

Environmental Corona

Starting “Engineered” Nanomaterial

Protein (Biological)

Corona

An ideal nanoparticle “tracking agent” would have stable surface chemistry and be trackable in the environment

Emerging Nanoparticles: Toward corona-free nano-probes

Humic substances

biopolymers

Chemical Oxidants/reductants

Core alteration

17

290 286

C1s

H-UNCD 1 hr Fib

EG6-UNCD 1 hr Fib

EG6-UNCD 28 days Fib

H-UNCD x 0.5

N1s

404 402 400 398 %

Fib

rinog

en M

onol

ayer

0

2

4

6

8

28 days

1 hour

7 days

H H H

Glycol-functionalized (planar) nano-diamond surfaces are almost completely resistant to fibrinogen adhesion under continuous exposure for 1 month

Can nano-diamond used as non-reactive probes of nanoparticle behavior?

Nano-diamond: an ideal protein-resistant surface?

Stavis, Hamers, et al., in prep

Binding energy, eV

Fibrinogen-exposed nano-diamond

“1 Monolayer”

Emerging Nanoparticles of interest: Nano-diamond (Ultra-stable probes)

D=6.7 nm

ms=0

ms=+1 ms=-1

2.87 GHz

TEM image N N

N V

V V

Single-particle Fluorescence imaging

à Coupling ultra-stable surface chemistry with single-molecule fluorescence tracking and (possibly) even spin detection

Torelli, Goldsmith, Orr, in prep

De-aggregation and

“Activation”

Summary

Redox-active NPs are rapidly increasing in commercial use à Complex crystal structures, multi-component à Variable electrochemical potentials from -3 V to + 2 V vs. NHE

Carbon-based materials (e.g., nanodiamond) provide a potential pathway for ultra-stable nanoparticle probes in the environment

à Highly stable surface chemistry à Strongly protein-resistant à NV center provides fluorescence tag

Surface chemical groups play a major role in NP stability, aggregation, and uptake. Yet there is little understanding (and much opportunity) for using surface chemistry to manipulate the properties of next-generation nanoparticles.

NSF Nanoscale Science and Engineering Center (2007-2014) (Thrust 4) DMR 0832760

NSF Chemistry Division, Center for Chemical Innovation Program (Center for Sustainable Nanotechnology), CHE-1240151

NSF Chemistry, Environmental Chemical Sciences Program #1152604

Acknowledgments Joel Pedersen Richard Peterson Warren Heideman Cathy Murphy Franz Geiger Christy Haynes Rebecca Klaper Galya Orr (PNNL) Richard Curry (Tuskegee)

Marco Torelli Arielle Mensch Mimi Hang Sam Lohse Ariane Vartanian Jamie Wheeler Ofek Bar-Ilan Min-Sik Kim Jared Bozich Ian Gunsolus Gustavo Dominguez