Graphene history preparation prperties structure applications

1. GRAPHENE OXIDE
Properties and Applications
BY : GROUP 6

2. A modern material with unique
physical and electrical properties
that could reshape our future.

3.  Graphite oxide, formerly called graphitic oxide or graphitic
acid, is a compound of carbon, oxygen, and hydrogen ,
obtained by treating graphite with strong oxidizers.
 The bulk material disperses in basic solutions to yield
monomolecular sheets, known as graphene oxide by analogy
to graphene, the single-layer form of graphite.
INTRODUCTION

4. BEFORE UNDERSTANDING GRAPHENE
OXIDE,
LET’S FIRST TALK ABOUT GRAPHENE.

5. Introduction
 Graphene can be described as a
one-atom thick layer of graphite.
 It is the basic structural element of
other allotropes, including graphite,
charcoal, carbon nanotubes and
fullerenes.
 Graphene is the strongest, thinnest
material known to exist.
Graphene is an atomic-scale honeycomb
lattice made of carbon atoms.

6. Graphene is a 2D crystal of carbon
atoms, arranged in a honeycomb
lattice
Each carbon atom is sp2 hybridized
and it is bound to its three
neighbors.

7. History
 One of the very first patents pertaining to the production of
graphene was filed in October, 2002 entitled, "Nano-scaled
Graphene Plates“.
 Two years later, in 2004 Andre Geim and Kostya Novoselov at
University of Manchester extracted single-atom-thick crystallites
from bulk graphite
 Geim and Novoselov received several awards for their pioneering
research on graphene, notably the 2010 Nobel Prize in Physics.

8. Structure
 Graphene is a 2-dimensional network of carbon atoms.
 These carbon atoms are bound within the plane by strong bonds into a
honeycomb array comprised of six-membered rings.
 By stacking of these layers on top of each other, the well known 3-
dimensional graphite crystal is formed.
 It is a basic building block for graphitic materials of all other
dimensionalities.
 It can be wrapped up into 0D fullerenes, rolled into 1D nanotubes or
stacked into 3D graphite.
 Thus, graphene is nothing else than a single graphite layer.

10. Chemical Properties
 Graphene is chemically the most reactive form of
carbon.
 Only form of carbon (and generally all solid materials)
in which each single atom is in exposure for chemical
reaction from two sides (due to the 2D structure).
 Carbon atoms at the edge of graphene sheets have
special chemical reactivity.
 graphene burns at very low temperature (e.g., 350 °C).
 Graphene has the highest ratio of edgy carbons (in
comparison with similar materials such as carbon
nanotubes).
 Graphene is commonly modified with oxygen- and
nitrogen-containing functional groups

11. Electronic Properties
 It is a zero-overlap semimetal (with both holes and electrons as charge
carriers) with very high electrical conductivity.
 Electrons are able to flow through graphene more easily than through even
copper.
 The electrons travel through the graphene sheet as if they carry no mass, as
fast as just one hundredth that of the speed of light.
 High charge carrier mobility, for which values of 10,000 cm2/Vs, in some cases
even 200,000 cm2/Vs were reported.
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12. In an insulator or semiconductor, an electron bound to an atom can break free only
if it gets enough energy from heat or passing photon to jump the ‘band gap’.
But in graphene the gap is infinitesimal. This is the main reason why graphene’s
electron can move easily and very fast.

13. Mechanical Properties
 To calculate the strength of graphene,
scientists used a technique called Atomic
Force Microscopy.
 It was found that graphene is harder than
diamond and about 300 times harder than
steel.
 The tensile strength of graphene exceeds
1 TPa.
 It is stretchable up to 20% of its initial
length.

14. It is expected that graphene’s
mechanical properties will find
applications into making a
new generation of super
strong composite materials
and along combined with its
optical properties, making
flexible displays.

15. Thermal Properties
 Graphene is a perfect thermal conductor
 Its thermal conductivity is much higher than all the other carbon
structures as carbon nanotubes, graphite and diamond (> 5000
W/m/K) at room temperature
 Graphite, the 3 D version of graphene, shows a thermal
conductivity about 5 times smaller (1000 W/m/K)
 The ballistic thermal conductance of graphene is isotropic, i.e.
same in all directions

16.  The material's high
electron mobility and high
thermal conductivity
could lead to chips that
are not only faster but
also better at dissipating
heat.
 This schematic shows a
three-dimensional stacked
chip with layers of
graphene acting as heat
spreaders.

17. Optical Properties
 Graphene, despite it is only 1 atom
thick, is still visible to the naked
eye.
 Due to its unique electronic
properties, it absorbs a high 2.3%
of light that passes through it.
Photograph of graphene in transmitted light. This one-atom-
thick crystal can be seen with the naked eye.

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19. Graphene Oxide , the monomolecular sheets of graphite oxide is
a compound of carbon, oxygen, and hydrogen in variable ratios,
obtained by treating graphite with strong oxidizers.
Graphene oxide sheets have been used to prepare a strong
paper-like material, and have recently attracted substantial
interest as a possible intermediate for the manufacture of
graphene.
GRAPHENE OXIDE

20. Graphene oxide was first prepared by Oxford chemist Benjamin
C. Brodie in 1859, by treating graphite with a mixture
of potassium chlorate and fuming nitric acid.
In 1957 Hummers and Offeman developed a safer, quicker, and
more efficient process called The Hummers' Method, using a
mixture of sulfuric acid (H2SO4), sodium nitrate (NaNO3),
and potassium permanganate (KMnO4) which is still used.
A Little History…

21. Graphene oxide (GO) has also been prepared by using a "bottom-
up" synthesis method (Tang-Lau method) in which the sole source
is glucose, the process is safer, simpler, and more environmentally
friendly.
A Little History…

22. The structure and properties of graphite oxide depend on
particular synthesis method and degree of oxidation. It typically
preserves the layer structure of the parent graphite.
Besides oxygen epoxide groups (bridging oxygen atoms), other
functional groups experimentally found are : carbonyl (C=O),
hydroxyl (-OH) and phenol(PhOH).
Structure

23. Graphene oxide layers are about 1.1 ± 0.2 nm thick.
Scanning tunneling microscopy shows the presence of local
regions where oxygen atoms are arranged in a rectangular
pattern.
The edges of each layer are terminated with carboxyl and
carbonyl groups.
Structure

24. Structure proposed in 1998 with
functional groups.
A: Epoxy bridges,
B: Hydroxyl groups,
C: Pairwise carboxyl groups

26. XRD, FTIR, Raman, XPS, AFM, TEM, etc. are some common
techniques to characterize Graphene Oxide samples.
Since the distribution of oxygen groups on GO sheets is disperse,
fractionation method using stabilization can be used to
characterize Graphene Oxide sheets.
Characterization

27. (A) Image of fractionated
GO, (B) XRD, (C) Raman,
and (D) FTIR spectra of
GO (black), GOw fraction
(blue), and GOe fraction
(red).

28. Graphite oxides absorb moisture proportionally to humidity and
swells in liquid water.
The amount of water absorbed by graphite oxides depends on
the particular synthesis method and shows a strong temperature
dependence.
Membranes prepared from graphene oxide are vacuum tight and
impermeable to nitrogen and oxygen, but are permeable to water
vapors.
Relation to water

29. Exfoliation of graphene oxide at high temperature.
Exfoliation results in tenfold increase of sample volume and formation of carbon
powder with grains of few graphene layers thickness.
(Exfoliation : to remove the surface of a substance)

30. 1. One of the advantages of the gaphene oxide is its easy
dispersability in water and other organic solvents due to the
presence of the oxygen functionalities.
This helps when mixing the material with ceramic or polymer
matrixes when trying to improve their electrical and
mechanical properties.
Properties

31. 2. Graphene oxide is often described as an electrical
insulator, due to the disruption of its sp2 bonding networks.
In order to recover the honeycomb lattice, and with it the
electrical conductivity, the reduction of the graphene oxide
has to be achieved.
The reduced graphene oxide obtained is more difficult to
disperse.
Properties

32. 3. Functionalization of graphene oxide can fundamentally change
graphene oxide’s properties.
There are many ways in which graphene oxide can be
functionalized, depending on the desired application. For
optoelectronics, biodevices or as a drug-delivery material.
Eg.-It is possible to substitute amines on graphene to increase
the dispersability of chemically modified graphenes in organic
solvents.
Properties

34. Different types of functionalization

35. 4. It is important to develop an oxidization and reduction process
that is able to separate individual carbon layers and then isolate
them without modifying their structure.
Chemical reduction of graphene oxide is currently seen as the
most suitable method of mass production of graphene.
Properties

36.  Pic-reduced graphene oxide
GO – Graphene Oxide
rGO – Reduced Graphene Oxide