Functionalization of graphene and stoichiometric graphene derivatives
Author(s)
Advisor
Çıracı, SalimDate
2011Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
Re
ent developments in experimental te
hniques have made the design and
produ
tion of materials at nanos
ale possible. In parti
ular, graphene has been
the fo
us of resear
h in diverse elds owing to high mobility
arrier transport and
other ex
eptional properties. Over the past four years experimental studies have
demonstrated that
hemi
al
onversion of graphene to its stoi
hiometri
derivatives
is possible by hydrogenation, uorination and
hlorination. The aim of this
thesis is to predi
t stable stoi
hiometri
graphene derivatives and explore their
me
hani
al, ele
troni
and magneti
properties. Moreover, the fun
tionalization
of graphene and its derivatives are a
hieved, whereby their physi
al properties
are modi ed to derive novel materials. Our predi
tions revealing stable 2D single
layer
onformers, whi
h
an be used as novel nano
oeting materials, are obtained
from state-of-the art rst-prin
iples Density Fun
tional
al
ulations of total energy,
phonons, transition state analysis and ab-initio mole
ular dynami
s.
An extensive theoreti
al study on the stability of hydrogenated graphene
(CnH), fully hydrogenated graphane i.e graphane (CH), and their quasi onedimensional
nanoribbons is performed. The formation of meshes of dehydrogenated
domains on graphane resulted in geometry spe
i
magneti
stru
tures
showing interesting magneti
intera
tions. Creation of H and CH va
an
ies,
as well as adsorption of transition metal atoms give rise to signi
ant spinpolarization
in graphane nanoribbons. It is shown that as a result of one-sided
or two-sided uorination of graphene one
an obtain nanostru
tures with diverse
ele
troni
and magneti
properties. Fully uorinated graphene or uorographene
CF is a stable, sti and non-magneti
semi
ondu
tor. Additionally, this
onformer
of bu
kled graphene is fun
tionalized by alkali, non-metal, metalloid and
transition metal atoms, and ea
h group leads to diverse adsorption properties.
Adsorption of
hlorine to graphene is dramati
ally di erent from those of
hydrogen and uorine. While the binding energy of
hlorine is signi
ant, its
migration on the surfa
e of perfe
t graphene takes pla
e almost without barrier.
This is
ru
ial for energy harvesting on graphene surfa
e. Energy optimization
and phonon
al
ulations indi
ate that the
hair
on guration of fully
hlorinated
graphene (
hlorographene) is energeti
ally most favorable and stable. It is a
nonmagneti
semi
ondu
tor with 1.2 eV dire
t band gap, whi
h
an be tuned by
applied uniform strain.
Graphene by itself
an be fun
tionalized by
reating meshes of va
an
ies
or adatoms
onserving spe
i
symmetries. Under these
ir
umstan
es linearly
rossing bands and hen
e the massless Dira
Fermion behavior
an be maintained.
Finally, it is demonstrated that multilayer, even single layer graphene
onstitute
an ex
ellent nanos
ale
oating, whi
h
an prevent a rea
tive metal surfa
e
from oxidation without
hanging the size and other physi
al properties. Graphene
an sti
k to at metal surfa
es and hinders free oxygen atom and mole
ule from
penetrating to the metal surfa
e. Single layer uorographene
an be used also for
the same purposes.
Design of novel nanomaterials, in parti
ular biologi
al mole
ules and
omplexes
using rst-prin
iples methods derived from quantum theory indi
ates a
new dire
tion in theory, whi
h promises a produ
tive hybridization with experimental
studies.
Keywords
GrapheneStoihiometri Graphene Derivatives
Nanooating
Fluorographene
Graphane
Chlorographene