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ASPECTS OF THE RELATIVE CONTRIBUTION OF PARTICLE SIZE VERSUS PARTICLE COMPOSITION IN THE OVERALL TOX

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Title: ASPECTS OF THE RELATIVE CONTRIBUTION OF PARTICLE SIZE VERSUS PARTICLE COMPOSITION IN THE OVERALL TOX


1
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
2
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

3
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
4
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


5
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

6
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.

7
Small Particles Impact
Small Particles and Nano-structures have impact
in each of these areas and some topic cross
several areas
8
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.
9
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?
10
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).

11
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12
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.
13
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
14
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
15
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
16
Laboratory of Chemical Thermodynamics
Nano-, micro- and oxygen stoichiometry
Nanostructure -significant changes in the
overall defect concentration -a reduced energy of
oxygen vacancies formation
17
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

18
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
19
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
20
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
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