Biomedical Engineering Reference
In-Depth Information
are currently being studied for use in nanomedicine and in tissue engineering as
nanovectors.
169-171
The CNTs are synthesized by rolling sheets of carbon into
hollow tubes that can be in the form of single-walled (0.4- to 2-nm diameter),
double-walled (1- to 3.5-nm diameter), or multiwalled (2- to 100-nm diame-
ter).
142
Although multiwalled CNTs have not resulted in proliferative or cyto-
kine changes in vitro, CNT size and composition must be carefully controlled
to promote intracellular delivery of these nanotubes and to prevent immune
reaction to them.
172
Functionalization and alteration of CNT and other graphite
nanoplatform surface chemistry can reduce or eliminate complement activation
while making the CNTs more biocompatible.
166-168,173,174
2.4.1 Protocol for the Synthesis of CNTs
There are numerous publications about CNTs in journals and in topics.
Only a simple method is described in this topic using catalytic decomposi-
tion to form CNTs.
175
The following method was derived from Gao's group
publication.
175
(1)
LaNi alloy is prepared by arc-melting an argon atmosphere.
(2)
Alloy ingot is ground mechanically into its powder form to a particle size
between 15 and 20 µm.
(3)
Soak the powder with 6 N KOH solution at 70 °C for 8 h.
(4)
Rinse thoroughly with running distilled water and dry in vacuum.
(5)
Place the dried powder in a ceramic boat.
(6)
Introduce into the flow reactor (quartz tube with an inner diameter of 3 cm
and a length of 60 cm) for the CNT synthesis.
(7)
Treat the alloy powder at 600 °C with flowing H
2
at 50 cm
3
/min for 30 min
to reduce nickel oxides at the particle surface.
(8)
Introduce methane at 80 cm
3
/min at atmospheric pressure, temperature of
670 °C for 30 min over the LaNi particle catalyst to synthesize the CNTs
by catalytic decomposition.
(9)
Collect the CNTs and characterize with SEM and TEM.
Another method was published by the group of Nasibulin who investigated CNT
formation in two experimental setups as shown in their paper.
176
The two pro-
cesses differ in the location of the catalyst particle generator that is outside (ex
situ) or inside (in situ) the flow reactor. Both setups consisted of a hot wire gen-
erator (HWG) and a heated vertical tubular furnace and a ceramic tube, with an
internal diameter of 22 mm inserted inside the furnace (Entech, Sweden; 44 or
90-cm long) was used as the reactor that was operated at ambient temperature.
176
The laminar flow conditions inside the reactor were maintained. The HWG was
a resistively heated thin iron or nickel wire (0.25 mm in diameter) protected
from the environment with either glass shielding (ex situ) or with a ceramic
tube (in situ) through which a carrier gas was passed.
176
The particles formed
by the HWG were transferred into the reactor by a carrier gas that consisted
