ASPECTS OF THE RELATIVE CONTRIBUTION OF PARTICLE SIZE VERSUS PARTICLE COMPOSITION IN THE OVERALL TOXICITY OF NANOCRYSTALLINE MATERIALS

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ASPECTS OF THE RELATIVE CONTRIBUTION OF PARTICLE
SIZE VERSUS PARTICLE COMPOSITION IN THE OVERALL
TOXICITY OF NANOCRYSTALLINE MATERIALS
Speranta Tanasescu, Cornelia Marinescu Institute
of Physical Chemistry of the Romanian
Academy Splaiul Independentei 202, 060021
Bucharest, ROMANIA
Seminar national nano - 2 martie 2006
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This work is part of the FP6 CA
Project, Improving the understanding of the
impact of nanoparticles on human health and the
environment - ImPart

• The project brings together research institutes,
  universities, toxicologists, environmental
  specialists, manufacturers and ethicists in order
  to elucidate the state of the art, reduce
  duplication of effort and improve the current
  level of understanding of the impact of
  nanoparticles on health and the environment.

ImParts Goal

• Not simply hazard identification
• Identify key parameters important for evaluating
  safety/toxicity
• - Role of composition, size
• - Shape, conformation, deformability
• - Surface coatings
• - Physico-chemical properties
• Best practices for safety evaluation
• By what routes do UFPs get into the body and then
  where do they travel to
• Guidance for development of safe nanomaterials

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This work is part of the FP6 CA
Project, Improving the understanding of the
impact of nanoparticles on human health and the
environment - ImPart

• The contribution is based on the former research
  experience existing in the Laboratory of Chemical
  Thermodynamics as concerns the large
  potentialities offered by the Applied Chemical
  Thermodynamics to characterize and investigate
  from the energetic point of view the advanced
  materials involved in the complex modern systems
  and the new technologies

Critical size assessments and general
consideration on Nanocrystalline Materials

• Contribution to the ImParts data base with
  respect to nano-metal oxides, emphasizing on the
  following topics

Questions about the relative contribution of
particle size versus particle composition in
the overall toxicity of ultrafine particles
(UFP)
Particle size versus energetics of nanomaterials
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Critical size assessments
Particle Category

Size

Coarse

lt
m
Particle
s with an average diameter of
10
m

m
(
m micron)

Fine

lt
m
Particles with an average diameter of
2.5
m

Ultrafine
lt
m
lt
Particles with an average diameter of
0.1
m (
100nm)

(Nanoparticles)


Ultrafine
UFP

Approx.
Potential Entry Po
int
(Nanoparticles)

size


70 nm

alveolar surface of the lung


50 nm

cells


30 nm

central nervous system


lt
no comprehensive scientific data
20 nm

as yet


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Potential Applications/Features and Benefits

• Cosmetics, Environmental remediation,
  Demilitarization of chemical and biological
  warfare agents, Gas sensors (for ozone and
  nitrogen dioxide),Thermaly conductive adhesives,
  Ultra-fine abrasives
• Transparent conducting oxide materials Advanced
  ceramic components
• Permanent memory DRAM (Dynamic Random Access
  Memory), FRAM (Ferroelectric Random Access
  Memory)
• Infrared detectors, mechanical and electrical
  micro-actuators, electro-optic, pyroelectric
  sensor, thin films capacitors and surface
  acoustic wave devices, Thermistors. Varistors.
• High-density optical data storage,
  Micro-capacitors, Nonlinear optical devices
• On-chip programmable devices, Optical computing,
  Optical image processing Pattern recognition
• Phase conjugated mirrors and lasers,
  Piezoelectric devices, Pyroelectric sensors,
  Semiconductive ceramics, Refractory ceramics,
  SOFC, sensors
• Nitrogen storage material, Semiconductors, Solar
  energy absorbers nding wheels, Heterogeneous
  catalysts, Fluorescent powder
• Transparent conductive electrodes in electronic
  devices for liquid crystal, displays,solar cells,
  solid electrolyte cells, photovoltaic devices
• UV lasers and detectors, CRT display of color
  television and personal computer, Electrochromic
  mirrors,Flat-panel displays,Heat shields
• Ceramic Magnets, Additives in plastics,
  Agglomerates for thermal sprays, Air/fuel ratio
  controller in automobile
• Catalysts and catalyst supports, Electrode
  materials in lithium batteries, Energy converter
  in solar cells,Inks, Inorganic membranes
• Photochemical degradation of toxic chemicals,
  Piezoelectric capacitors, Pigment for paints,
  Planarization, Polishing agent, Porcelain Solid
  oxide fuel cell, UV protection, Waste water
  purification

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What is so special about nanoscale?

• Every property has a critical length scale
  where the fundamental physics of
• that property starts to change
• Nanoscale building blocks are within these
  critical length scales
• Building blocks impart to the nanostructures
  new and improved properties
• and functionalities
• Essentially any material property can be
  engineered through the controlled
• size-selective synthesis and assembly of
  nanoscale building blocks
• For multifunctional applications, more than one
  property and one length scale
• must be considered.

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Small Particles Impact
Small Particles and Nano-structures have impact
in each of these areas and some topic cross
several areas
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Precaution on nano-scale
The exploitation of the properties associated
with the nanoscale is based on a number of
discrete differences between features of the
nanoscale and those of more conventional sizes,
namely the markedly increased surface area of
nanoparticles compared to larger particles of the
same volume or mass, and also quantum effects.
Questions naturally arise as to whether these
features pose any inherent threats to humans and
the environment. Bearing in mind that naturally
occurring processes, such as volcanoes and fires,
in the environment have been generating
nanoparticles and other nanostructures for a very
long time, it would appear that there is no
intrinsic risk associated with the nanoscale per
se. As noted above, there is also no reason to
believe that processes of self assembly, which
are scientifically very important for the
generation of nanoscale structures, could lead to
uncontrolled self perpetuation. The real issues
facing the assessment of risks associated with
the nanoscale are largely concerned with the
increased exposure levels, of both humans and
environmental species, now that engineered
nanostructures are being manufactured and
generated in larger and larger amounts, in the
new materials that are being so generated, and
the potentially new routes by which exposure may
occur with the current and anticipated
applications.
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Questions about UFPs
Precaution on nano-scale
What is the relative contribution of particle
size versus particle composition in the overall
toxicity of UFPs?
What is the mechanism of toxic action and how
does the reactive surface of UFPs interacts with
wet biochemistry in the body?
By what routes do UFPs get into the body and
then where do they travel to?
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Particle size versus particle composition

• Reduction in size to the nanoscale level results
  in an enormous increase of surface to volume
  ratio, so relatively more molecules of the
  chemical are present on the surface, thus
  enhancing the intrinsic toxicity (Donaldson et al
  2004). This may be one of the reasons why
  nanoparticles are generally more toxic than
  larger particles of the same insoluble material
  when compared on a mass dose base. The dose
  expressed as surface area or number of particles
  administered shows a better relationship with
  biological and/or toxic effects than dose
  expressed as mass (toxicity ofTiO2 and BaSO4 -
  Tran et al 2000).

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Particle size versus particle composition

• The chemical composition and the intrinsic
  toxicological properties of the chemical are of
  importance for the toxicity of particles
  (Donaldson et al 2004). For micron sized
  biomaterial particles, the in vivo distribution
  was dependent on the composition of the material.

Donaldson et al. (2004) comparatively have
discussed the effect of transitional metals
oxides / ultrafine carbon black as a source of
oxidative stress. For micron sized particles the
effect of carbon black has been shown to be more
severe than that of titanium dioxide (Renwick et
al 2004), while for both compounds the
nanoparticles induced lung inflammation and
epithelial damage in rats at greater extent than
their larger counterparts. UFPs are able to
transport transition metals, which have been
implicated in the proinflammatory effects and
toxicity. For several different nanoscale
particles (polyvinyl chloride, TiO2, SiO2, Co,
Ni), differences in cytotoxicity are obtained due
to size difference at the nanoscale, as the
particle size ranged from a mean diameter of 14nm
to 120 nm and even clusters of 420 nm (Peters et
al 2004). Conclusion The contribution of size
vs. the contribution of material composition to a
particles toxicity has not been clearly
established. However, it does seem, in the light
of current knowledge, that the size effect is
considerably more important to UFP toxicity than
the actual composition of the material. The
biological behaviour of nanoparticles is
determined not only by the chemical composition,
including coatings on the surface, but also by
the corresponding shifts in chemical and physical
properties, associated to the increase in surface
to volume ratio.
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Contribution to answer the following
topics are expected ? Which are the general
implications for nanophase stability
relations? ?Are there compositional or crystal
chemical systematics in the energetics of
polymorphism and surface energies? ? To what
extent can the energetic properties of
nanocomposites be predicted from properties of
the nanoscale end-members? ? Which is the
influence of different compositional variables on
the nanophase energetics? ?What environments are
likely to harbor nanoscale phenomena, and how
would thermodynamic modelling be affected? ? How
do environmental effects alter nanoparticle
structures and change reactivity? ? Are the
existent thermochemical databases enough
comprehensible to prevent or for diminution of
ecological hazards? ?Are the previously proposed
defect structure models suitable to explain the
generation of the defects in nanomaterials?
Particle size versus energetics of nanomaterials
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Nanoparticles are often polymorphs of bulk
material with different physical and chemical
properties
11 nm
11-35 nm
gt35 nm
Interrelationships among bulk structure and
defects, surface structures, the environment and
reactivity mean the nanoparticle properties
depend on size, environment and history.
Enthalpy of nanocrystalline samples with respect
to bulk rutile (kJ/mol) versus surface area
(m2/mol)
Ranade, M. R. et al. (2002) Proc. Natl. Acad.
Sci. USA 99, 6476-6481
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Laboratory of Chemical Thermodynamics
The size effect on the energetics of the complex
perovskites
The variation of the and log pO2 with the
temperature for the doped lanthanum manganites
prepared by Solid state reactions (d ? 5 ?m)
and ? Sol-gel method (d ? 40 nm)
The changes of the thermodyamic data can be
explained as a consequence of truly grain-size
dependent properties
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Laboratory of Chemical Thermodynamics
Nano-, micro- and oxygen stoichiometry
Nanostructure -significant changes in the
overall defect concentration -a reduced energy of
oxygen vacancies formation
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Laboratory of Chemical Thermodynamics
Estimation of the contribution made by oxygen
vacancies in balancing the local charge by
correlation of the results obtained from EMF
coulometric titration redox titration
measurements

• S. Tanasescu, D. Berger, A. Orasanu, J.
  Schoonmann, International Journal of
  Thermophysics, 26, 2, 2005
• S. Tanasescu, C. Marinescu, F. Maxim, Solid State
  Phenomena, 99-100, 2004, p. 117-122
• S. Tanasescu, D. Berger, D. Neiner, N.D. Totir,
  Solid State Ionics, 157, 2003, p. 365 370

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Laboratory of Chemical Thermodynamics
Comparative results of the relative partial molar
thermodynamic data of oxygen in the
nonstoichiometric compounds prepared by two
different methods (1173-1273 K)
Nanostructure the increase in the binding energy
of oxygen and an increase of order in the oxygen
sublattice of the perovskite-type structure
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Characteristic Sizes for Physical and Chemical
NANO Effects
Lattice
For metals Pt, Pd, Fe and Ta
Constants
Break down of Hall Petch Grain-Size Hardening
Metal Layer Structures
Oxide Phase Stability
Rutile
Anatase
Brookite
Goethite
Hematite
CuO
Lattice Parameter and Neel Temperature
Oxide Layers on Fe
Air exposed bulk metal
Oxygen exposed nanoparticles
1
10
100
Critical or Characteristic Particle Sizes nm
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Summary and Concluding Thoughts

• Small particle and nanostructured materials
  chemistry is relevant to many subjects, including
  health and environmental topics
• There are many different types of small particle
  and nano-materials effects as well as many
  delightful opportunities and scientific
  challenges
• In contrast to macrothermodynamics, the
  thermodynamics of a small system will usually be
  different in different environments
• More and better tools and their use are
  essential to characterize the properties and
  environmental effects of/on nanoparticles
  (multidisciplinary analysis is required). Theory
  and modeling are useful to successful work in
  this area