Reducing the Toxicity of Carbon Nanotubes and Fullerenes Using Surface Modifi cation Strategy - Management of Natural Resources in a Changing Environment - page 176

Table 1 Reported LD 50/LC 50 values
Derivative LC 50/LD 50 References

Fullerene LC 50-0.25 ʼ g/ml Isakovic et al.

( 2006 )

C60(OH)n LC 50-800-1,000 ʼ g/ml Isakovic et al.

( 2006 )

SWCNT LD 50 from acute oral toxicity

studies >1,000 mg/kg bw in mice

Kolosnjaj-Tabi
et al. ( 2010 )

(1) Ultrashort (diam. ~1 nm,
length ~20-80 nm, Fe <1.5 %);
(2) Raw (diam. ~1 nm,
length ~1-2 m, Fe 25 %);

(3) Purifi ed (diam. ~1 nm,
length ~1-2

ʼ

m, Fe <4 %)
MWCNT (mean diameter 10-15 nm;
mean length ~200-1,000 nm;
Co 0.53 %)

ʼ

LD 50 from acute oral toxicity
studies >5,000 mg/kg bw in rats

Pauluhn ( 2010 )

LC Lethal Concentration, LD Lethal Dose

are being widely applied in electronics, automotive, fi ltration and storage devices,
OLEDs, computer RAM, cosmetics, computer hardware and sporting good products.
As of March 2011, a total of 91 products are available worldwide that contains
carbon-based nanomaterials (Inventory done under Project on Emerging
Nanotechnologies, www.nanotechproject.org ) . The number is more than double
when compared to the fi gure given in the 2006 inventory.
Following sections compare toxic effects of fullerenes and carbon nanotubes
with their derivatives, functionalized with groups, such as hydroxyl, carboxyl, etc.
The available information about LC50 of some nanoparticles (i.e., nanoparticles
concentration causing 50 % lethality to exposed species) supports the use of func-
tionalized nanomaterials with more value of LC50/LD50 (where LD50 = nanoparticles
dose causing 50 % lethality to exposed species) (Table 1 ).

Carbon Nanotubes

Synthesis, Substitution and Modifi cation

Carbon nanotubes are cylindrical macromolecules, which have a radius of only a
few nanometres and can be grown in different lengths. The cylinders are usually
capped at the ends by a fullerene-type molecule. The common synthesis procedures
for CNTs with average diameter 1-1.4 nm are Electric arc discharge, Laser ablation,
Catalytic decomposition of gaseous hydrocarbons (maximum production rate), etc.
(Balasubramanian and Burghard 2005 ). There are two major types of CNTs