Hollow Nanostructured Materials

1
Hollow Nanostructured Materials

• Applications include
• drug delivery
• encapsulation and controlled release
• contaminated waste removal,
• catalysis.
• Template structure can lead to modified hollow
  nanostructured materials

2
Gold Nanoshells Prepared by Templating Against
Silver Nanoparticles
Adv. Mater. 2003, 15, 641
3
Difference in SPR of Au Nanoparticles
A comparison between the UV-vis extinction
spectra of gold solid colloids and gold
nanoshells with a core diameter 50 nm and wall
thickness of 4.5 nm
Plot of the dependence of peak shift on the
refractive index
Adv. Mater. 2003, 15, 641
4
Metal Nanostructures with Hollow Interiors
TEM Au nanotubes
TEM Pt nanotubes
TEM Pd nanotubes
SEM Pd nanotubes
Adv. Mater. 2003, 15, 641
5
Coupling Phenylboric Acid and Iodobenzene
Reaction catalyzed by Pd nanotubes
Adv. Mater. 2003, 15, 641
6
Template Synthesis by Electroless Plating Method
Sn (II) surf 2 Ag (I) aq ? Sn (IV)surf a Ag
(0)surf
Au (I ) aq Ag (0) surf ?Au (o)surf Ag (I)aq
7
Allotropes of Carbon
8
Synthesis of Carbon Nanotubes
1993, Nature 1993, 363, 603 Iijima an coworkers
first synthesized carbon nanotubes via the
thermal decomposition of hydrocarbons. High
temperature decomposition of vapors such as
benzene or acetylene, in the presence of Co, Fe,
or Ni catalysts, formed single walled carbon
nanotubes. 1996, Science 1996, 273, 483 Laser
Ablation method (Smalley and coworkers) Method
produced nanotubes formed into ropes of 100-500
carbon nanotubes, at yields of more than 70.
2002, Nano Lett. 2002, 2, 1043 Catalyst-free
synthesis (Avouris and coworkers) Method
developed for carbon nanotube synthesis on a
silicon surface. Advantage is that catalyst
removal is not necessary for purification.
Synthesis of carbon nanotubes involves high
temperature approaches
Carbon nanotubes are cylindrical structures
consisting of rolled-up graphene sheets with half
fullerene caps.
9
Properties of Carbon Nanotubes

• Youngs Modulus 1.2 terra Pascals
• Light weight
• Thermal conductivity
• Electrical conductors

Potential Applications

• Transistors
• Materials strengthener
• Electronic devices
• Ion storage for batteries
• Biological encapsulation

10
Carbon Arc-Chamber
Arc Chamber at PSU
11
Electron Microscopy Images of Carbon Nanotubes
TEM image of carbon nanotubes
SEM image of carbon nanotubes
12
Laser Ablation (Smalley)
Intense laser pulses ablate a carbon target
Catalysts used Ni, Co
Inert gas
Oven temperature 1200 oC

• Yield 70
• Typical by-products are fullerenes, polyhedrons,
  amorphous
• carbon

13
Exposure and Characterization Carbon Nanotubes
What is the nature of exposures to (invisible)
particles capable of entering the lungs when
inhaled?
14
Toxicity of Carbon Nanotubes
Chiu-Wing Lam NASA Johnson Space Center

• Groups of mice were exposed to 4 substances
• Newly made SWNTs mixed with the metal catalyst
• SWNT treated to remove the catalyst
• Carbon black
• Nanosized quartz particles

15
Experimental Design
injected

• Newly made SWNTs mixed with the metal catalyst
• SWNT treated to remove the catalyst
• Carbon black
• Nanosized quartz particles

Mice Lungs
All particles made their way into the alveoli and
remained intact for 90 days.
The nanotubes resulted in gramulomas (a
combination of dead and live tissue surrounding)
16
Light micrograph of lung tissue from a rat
exposed to 5 mg/kg CNT (a few hours after
exposure). The major airways are mechanically
blocked by the CNT instillate. This lead to
suffocation in 15 of the CNT-exposed rats and
was not evidence of pulmonary toxicity of CNT.
Warheit 2004
17
Light micrograph of lung tissue from a rat
exposed to 5 mg/kg CNT (a few hours after
exposure). The major airways are mechanically
blocked by the CNT instillate. This lead to
suffocation in 15 of the CNT-exposed rats and
was not evidence of pulmonary toxicity of CNT.
Warheit 2004
18
Incidental Nanoparticles are not Benign

• Dogma
• Particulate matter causes lung disease
• Particle type key for toxicity
• Emerging (Gunter Oberdorster, 2004)
• Dlt100 nm translocate into brain, CNS
• Challenges (Warheit, 2004)
• Nano isnt more toxic than bulk

19
Disposition of Inhaled Nano-sized Particles

• Not efficiently scavenged by Alveolar Macrophages
• To Lymph Nodes--even more pronounced than
  predicted from larger-sized particles
• To Blood Circulation and then liver, spleen,
  kidney, bladder, heart etc. w/in 24 hours
• Depends on chemistry
• To Brain via olfactory neurons and/or trigeminal
  nerve

20
CleanupNano Size, Big Deal
B. Karn 2004
21
Deposition of Iron ParticlesFollowing Inhalation
Warheit 2004
22
Many Semiconductor Nanomaterials are Redox Active

• metal Qdots are redox active
• (ex Derfus et al. 2004. NanoLett 4(1)11-18
  Joo et al. 2004. Environ Sci Technol.
  38(7)2242-2247)
• nano TiO2 causes inflammation, Severe Acute Lung
  Injury, Thrombus formation
• (several studies by G. Oberdörster)
• ambient or laboratory-produced ultrafine
  particles (of various chemistries) cause
  oxidative stress in vitro
• (Li et al 2003 EHP 111(4)455-460 Brown et al.
  2000 OEM 57685-691, Brown et al. 2001 TAP
  175191-199 Donaldson et al 1998 J Aerosol Sci
  29553-560, to list a few)
• Ultrafine Carbon Black (ufCB) produce ROS in
  cell-free media and
• in the presence of mouse macrophages
• ufCB depleted glutathione (GSH) and ATP in cell
  culture
• ufCB induced inflammatory response in cell
  culture and rat lung
• Wilson et al. 2002. TAP 184(3)172-179.

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Nano TiO2 is Redox Active Under UV
TiO2 hn ? e- h e- O2 ? O2- h -OH ?
OH
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Interrelationship Between Oxyradicals and Some
Proteins in the Anti-oxidant Defense System
Metallothionein Induction
DNA strand breaks, covalent modification of DNA
Protein oxidation
metals or nanomaterials
Redox Cycle
OHOH-
Lipid Peroxidation
produced by nanomaterials produced by
inflammation reactive intermediate of
organic toxicant metabolism
superoxide O2.
SOD
catalase
H2O O2
H2O2
O2
Intermediates from oxyradical attacks
GSH
RH2 GS
RH
GPx
GSH Reductase
GSSG.
O2
GS-
H2O O2
GSSG
GR
GST
ROH GSH
GSSG
RSG H2O
25
Engineered Nanostructures and Cells
Bruchez, Alivisatos et al Science 281 (1998) p.
2013
10 nm particles, inside cell

• Receptor mediated endocytosis
• d gt 100 nm colloids dont
• d lt 50 nm do
• High reactivity of nanoparticle surfaces
• Strong oxidizing/reducing agents
• Free radical activity

26
Toxicity of CdSe Quantum Dots in Liver Culture
Model
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Toxicity of CdSe
Cultures exposed to QDs. Exhibit granular
cytoplasm, indistinct intercellular boundaries,
undefined nuclei
Cultures before exposure to QDs. Exhibit distinct
intercellular boundaries, well-defined nuclei,
Nano Lett. 2004, 4, 11
28
Toxicity of QDs correlates with surface
oxidation, decrease of QD size, and disruption of
crystal lattice
Nano Lett. 2004, 4, 11
Increased exposure to air of TOPO-capped QDs
correlates with surface oxidation as indicated by
a blue-shift in the first quantum confinement
peak and decrease in peak amplitude of absorbance
spectra (in chloroform). Observable changes in
color of QD solutions due to changes in
absorbance spectra (white light - shift from
red/orange to yellow) and fluorescence spectra
(UV light - loss of fluorescence) are also
consistent with surface oxidation.
Exposure to air of TOPO-capped QDs produces
changes in fluorescence spectra (blue-shift of
fluorescence peak by 10 nm after 30 min)
consistent with a decrease in QD size due to
removal of surface atoms. For comparison, the
amplitude of the 30 min TOPO curve has been
increased 20-fold to compensate for the loss in
quantum yield
29
Surface Oxidation Leads to Release of Cadmium
Ions
Proposed mechanism of Cd release from the QD
surface via either TOPO-mediated or UV-catalyzed
surface oxidation
Inductively coupled plasma optical emission
spectroscopy (ICP/OES) measurements of free
cadmium in 0.25 mg/mL solutions of QDs,
indicating higher levels of free cadmium in all
oxidized samples and increasing Cd levels with UV
exposure time, correlating with cytotoxicity
observed in Figure 1A.
Nano Lett. 2004, 4, 11
30
Effects of ZnS Surface Coating on Surface
Oxidation, Release of cadmium, and Cytotoxicity
Cell viability
12 h Air
8h UV
No oxidation
1h UV
ZnS capping of CdSe QDs eliminates
TOPO/air-induced cytotoxicity and reduces
photooxidation-mediated cytotoxicity as indicated
by viability of QD-treated hepatocytes
Nano Lett. 2004, 4, 11
31
Toxic Warnings

• 1997 TiO2 and ZnO2 nanoparticles from sunscreen
  are found to cause free radicals in cells,
  damaging DNA
• March 2002 Rice University researchers report
  to USEPA that engineered nanoparticles accumulate
  in the organs of lab animals and are taken up by
  cells
• March 2003 NASA researchers report that studies
  on effects of nanotubes on the lungs of rats
  produced toxic response
• March 2003 - Toxicopathologist Vyvyan Howard
  concludes that the smaller the particle, the
  higher its likely toxicity and that nanoparticles
  have various routes into the body and across
  membranes such as the blood brain barrier
• July 2003 Mason Tomson (CBEN) shows that
  buckyballs can travel unhindered through the
  soil.

32
Toxic Warnings

• January 2004 - Research by Dr. Gunter Oberdörster
  shows that nanoparticles cause brain damage
• January 2004 Vyvyan Howard presents initial
  findings that gold nanoparticles can move across
  the placenta from mother to fetus
• February 2004 UCSD researchers discover that
  CdSe can break down in the human body potentially
  causing cadmium poisoning
• March 2004 Eva Oberdörster (ACS) reports that
  buckyballs cause brain damage in juvenile fish
  along with changes in gene function

33
Addressing Occupational Impact
34
Potential Health Risk/ToxicityNanomaterials

• Critical factors (inhaled insoluble
  nanoparticles)
• Surface Area
• Surface Chemistry
• Size - deposition probability and translocation
• Shape?

35
Characterizing Environmental Impact
Exposure ? Health Effects Risk
Biodegradation
Bioaccumulation
Yes
Available in water?
Toxicology
Soil Association
Contaminant sorption
No
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Controlling Technology ImpactThe accepted model?
with nanotechnology, we still have the chance to
make a difference before the train leaves the
station