graphene, graphene oxide chemistry aplications

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GRAPHENE OXIDE Properties and Applications BY : GROUP 6

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Page 1: Graphene, graphene oxide chemistry aplications

GRAPHENE OXIDEProperties and Applications

BY : GROUP 6

Page 2: Graphene, graphene oxide chemistry aplications

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

Page 3: Graphene, graphene oxide chemistry aplications

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

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

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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.

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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.

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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.

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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.

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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

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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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Page 12: Graphene, graphene oxide chemistry aplications

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.

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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.

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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.

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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

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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.

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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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Its a Wonder material that could revolutionize the world

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Page 19: Graphene, graphene oxide chemistry aplications

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

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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…

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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…

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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

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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

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

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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

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

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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

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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)

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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

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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

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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

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Page 34: Graphene, graphene oxide chemistry aplications

Different types of functionalization

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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

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Pic-reduced graphene oxide

GO – Graphene OxiderGO – Reduced Graphene Oxide