Biomedical Engineering Reference
In-Depth Information
calculations with the GGA approximation [46] showing that only
NH
enhances appreciably the AGNRs conductance after chemical
adsorption; in this case a semiconducting metallic transition occurs
thus suggesting that, in principle, a GNR-based junction can be used
to detect NH
3
: indeed, without adsorption the GNR sensor exhibits
a semiconducting behavior showing a zero current even with a bias
of 0.5 V; on the contrary, after NH
3
adsorption a metallic behavior
emerges and the current increases linearly with the voltage as
reported in Fig. 8.9.
3
Figure 8.9
I
-
V
curves for the GNR sensor before and after the adsorption
bias
of NH
. In the inset it is sown a schematic drawing
of the GNR sensor (consisting of one 10-AGNR (detection
region) and two metallic 7-ZGNRs leads). The gas molecule
can be adsorbed around the DB defects of GNR sensor. From
Ref. [46].
and CO
3
2
Vacancies in nanostructured graphene have been investigated as
a possible sites for sensoring; in this case, indeed, the adsorption
properties are expected to be very similar to those of the GNRs.
Sanyal and co-workers [87] have studied the passivation of di-
vacancies in graphene layers using several possible gaseous species,
such as O
, N
, B
, CO, and H
O, in the framework of DFT
ab initio
2
2
2
2
electronic structure calculation. In the particular case of N
, for
instance, the molecule undergoes a dissociation and subsequent
chemical adsorption onto the graphene layer. The adsorbed N atoms
occupy substitutional lattice positions in the graphene honeycomb
structure, thus introducing extra carriers with a consequent
modification of the charge transport properties.
2
