10th Annual Session of Students’ Chemical Engineering Congress (SCHEMCON – 2014)

GRAPHENE THE WONDER MATERIAL AND IT’S APLICATIONS

PROMOD KUMAR DASH1, SHANTANU KUMAR PRADHAN2, 1,2DEPARTMENT OF CHEMICAL ENGINEERING

INDIRA GANDHI INSTITUTE OF TECHNOLOGY, SARANG, ODISHA, INDIA, 759146

1pk.dash162@gmail.com 2

S C H E M C O N - 2 0 1 4 1 | P a g e

Abstract: Graphene, The wonder material and aninvention of 21st century .An allotrope ofcarbon a two-dimensional, single-layeredsheet of sp2 hybridized carbon atoms. Thiswonder material e material has attractedmuch attention from researchers due to itsinteresting mechanical, thermal, optical,electrochemical and electronic properties.This is not only a good conductor, havingresistivity: 10−6 Ω·cm and mobility 200,000cm2 V-1 s-1 but also it is stronger thandiamond having Maximum Young's modulus: ~1.3TPa and a million times thinner than paper,The interlayer spacing: 0.33~0.36 nm. Theseexceptional properties have opened up newopportunities for the application of thisnanomaterial in the future devices andsystems. This paper is written to give aconsolidated view of the synthesis, theproperties with an aims to present anoverview of the advancement of research inapplications of graphene and its derivativesin different areas such as field emission,sensors, energy storage, electronics,catalysis, and biomedical field as well as abrief discussion on the challenges andperspectives for future research.

Keywords—Graphene, preparation,characteristics, properties, potentialapplication.

I. INTRODUCTIONGraphene is pure carbon in the form ofa very thin, nearly transparent sheet,one atom thick. It is remarkably strongfor its very low weight (100 timesstronger than steel) and it conductsheat and electricity with greatefficiency. Technically, graphene is acrystalline allotrope of carbon with 2-dimensional properties. Graphene hasattracted much attention fromresearchers due to its interestingmechanical, electrochemical andelectronic properties. Graphene, asingle atomic layer of sp2-bondedcarbon atoms tightly packed in a twodimensional (2D) honeycomb lattice, has

evoked great interest throughout thescientific community since itsdiscovery. While scientists hadtheorized about graphene for decades,it was first produced in the lab in2004.

In 2004: Andre Geim and KostyaNovoselov at Manchester Universitymanaged to extract single-atom-thickcrystallites (graphene) from graphite:And won the Nobel Prize in Physics in2010.

As a novel nanomaterial, graphenepossesses unique electronic, optical,thermal, and mechanical properties.Graphene and its derivatives have shownoutstanding potentials in many fieldssuch as Nano electronicsengineering ,Nano composite materials,energy storage, field effect transistor(FET),organic light emission diode(OLED),sensors catalysis and biomedicalapplications (biosensor, bio devices,drug and gene delivery, cancer therapyetc.) .

An easy way to comply with theconference paper formattingrequirements is to use this document asa template and simply type your textinto it.

Figure-1

II. PREPARATIONOver the last forty years, variousunsuccessful attempts have been made toachieve large-scale production of pure,defect-free graphene sheets recently,the method of epitaxial growth on metalcarbide, the CVD method, has shownpromise for production of graphene.Various methods have been devised andcategorized into “top-down” and“bottom-up” processes. The followingsections describe synthesis routes forgraphene.

A. Top DownTop-down approaches commence with an

existing form of the bulk material andprocess it to create the final product.This approach may be cost efficient,depending on the material used. Ingeneral, it is limited to a lab scaleand has limited quality control .Inthis approach, graphene or alteredgraphene sheets are produced by eitherseparation, peeling, cleaving, orexfoliation of graphite or itsderivatives (graphite oxide (GO) andgraphite fluoride

Researchers have been successful infabricating a few layers of free-standing graphene sheets on both microand Nano scales. Various mechanicalprocesses have been involved inproducing high-quality, defect-freegraphene: mechanical exfoliation ofgraphite, sonication,functionalization, electrochemicalexfoliation, super acid dissolution ofgraphite, alkylation of graphenederivatives, chemical reduction ofaqueous/organically treated grapheneoxide (GO), thermal exfoliation, andchemical reduction of GO

B. Bottom UPThe bottom-up approach consists of

standard techniques such as epitaxialgrowth using metallic substrates bymeans of CVD or organic synthesis,which depend on the choice of precursorchemicals and thermal degradation anddecomposition of the SiC . Severalother processes, such as arcdischarge , chemical conversion , COreduction , CNT unzipping, and self-organization of surfactants have alsobeen tried for synthesis of grapheneand its derivatives. Of all theseprocesses, CVD and epitaxial growth,which produce bantam quantities offlawless graphene sheets with largersize, may in future be attractive formass-scale graphene production, incontrast to mechanical cleaving. UsingCVD and epitaxial methods, graphenesheets find their way into fundamentalresearch with a multitude ofapplications ranging from electronicsto polymeric Nano composites.

Electro chemical exfoliation method: High-quality graphene can be effectivelysynthesized on a large scale viathe electrochemical exfoliation ofgraphite and/or electrochemicalreduction of exfoliated GO employing a

selected electrolyte solution. Ingeneral, electrochemical exfoliationtakes place in a mixture of solventscontaining liquid with a narrowelectrochemical window (e.g. water) andliquid with a large electrochemicalwindow. The theory behind theelectrochemical exfoliation process toproduce graphene is as follows:

• Electrolysis of water at theelectrode produces hydroxyl and oxygenradicals;

• The oxygen radicals initiatecorrosion at the graphite anode on edgesites resulting in the opening up ofedge sheets;

• The liquid with largeelectrochemical window is thenintercalated within the edge sheetscausing the electrode to expand;

• Finally, precipitation of the sheetsresults in the formation of graphenesheets in solution.

FIGURE-2

GRAPHENE SHEETS IONIC-LIQUID-MODIFIED BYELECTROCHEMISTRY USING GRAPHITE ELECTRODES.

The electrolyte used in this processis poly (sodium 4-styrenesulfonate).

Figure-3Time evolution of IL electrolyte and highlyoriented pyro lytic graphite (HOPG) anodeduring exfoliation in 60 wt%Water/[BMIm][BF4] electrolyte. Stages I, II,and III are shown in panels (b), (c), and (d),respectively. The heavily expanded HOPG isshown in panel (f).

The exfoliation mechanism and theassociated reactions are summarized inthe following steps:

[1] Anodic oxidation of water producedhydroxyl and oxygen radicals. Thehydroxylation or oxidation of graphiteby these radicals generally took placeat the edge and thus resulted in thedissolution of fluorescent carbon Nanocrystals from the anode.

H2O +

[2] Oxidation opened up the routefor intercalation by the anionic which led to the depolarization andexpansion of the graphite anode.

[3] Oxidative cleavage of theexpanded graphene sheets generatedgraphene Nano ribbons and some expandedsheets precipitated as graphene sheets.

Epitaxial graphene formed by intercalation:Graphene sheets interact weakly withtheir substrate by van der Waalsinteraction. Thus, insertion ofmolecules or atoms into the graphene–substrate interface or intercalation isenergetically favourable and is observedboth on SiC and metal substrates.

On SiC substrates, intercalation isaccompanied by additional chemicalinteractions. The atoms intercalatedbetween Interfacial Graphene (IG) andSiC substrate can react with Sidangling bonds at the interface andrelease Interfacial Graphene (IG) toform an additional graphene layer. Thereactive intercalation occurs with orwithout the top graphene layer. Itprovides an opportunity to reversiblychange the Interfacial Graphene (IG)layer into graphene and eliminate then-type doping effect of InterfacialGraphene (IG) on to Epitaxial Graphene(EG). Many intercalated atoms are foundto react with silicon atoms, includinghydrogen, oxygen, fluorine, gold, iron,lithium, germanium and even siliconitself. However, exceptions have alsobeen found. Cs and Rb do notintercalate into epitaxial grapheneprobably because of their large atomicradius.

Intercalation is usually completed intwo steps.i First atoms are deposited (afew atomic layers) on the graphenesurface. Second, the surface isannealed to cause the adsorbed atoms todiffuse and intercalate through defectsor grain boundaries and to react withinterfacial silicon atoms. Theannealing temperature varies with theelement used. For Ge, the annealingtemperature is as high as 920 °Cwhereas for Li, intercalation occurs atroom temperature although annealing at330 °C helps Li atoms distribute

uniformly. Table I summarizes thetemperature needed to intercalatevarious atoms. For gas molecules,intercalation can be done using atomicsources (hydrogen), high-pressureannealing (oxygen, 1 bar 250 °C) 53 orby molecular decomposition (C 60 F 48 ,fluorine).

Table I Annealing temperature forintercalation of solid atoms atgraphene surface.

Figure-4 Schematic diagram showing the intercalation and exfoliation process to produce slab of graphite potassium is inserted between layers andreacted violently with alcohol. The exploited slab are ~30 layer thick

ELEMENTS TEMPRETURE

Au 727 °C

Fe 600 °C

Li -

Ge 720–920 °C

Si 800 °C

Chemical Vapour Deposition: The large-scaleproduction of graphene for electronicdevices relies on catalytic chemicalvapor deposition (CVD). Therefore, ourfocus is on understanding the mechanismof graphene formation and also oncontrolling the growth process. Despitemuch effort having been put intographene CVD research, there are stillmany challenges to be solved. Cu or Niare the most widely used catalystsowing to their low cost, etch abilityand large grain size.

Although it is worth noting that othermetals can be successfully used forCatalyzing CVD graphene growth, e.g. PtCo, Ir or Ru, but Cu and Ni arecurrently the most promising candidatesfor up scaled graphene production withdirect links to applications in opticsor electronics.

In general, during chemical vapordeposition of graphene, the precursorin a gas phase is injected into areaction chamber, where it reacts witha catalyst at elevated temperature andgraphene is formed on the Catalyst’s surface. The precursor isusually a small hydrocarbon, e.g.methane or ethylene, but vaporized low-molecular-weight alcohols can be usedas well. The growth temperatures rangefrom several hundred degrees Celsius upto the melting point of the catalystmetal.

Figure-5Nickel-grown Graphene. (A) Optical image of apre-pattern Ni film on Sio2/ Si. CVD Graphenegrown on the surface of Ni pattern (b) opticalimage of the grown graphene transferred intactfrom the Ni surface in (a) to another Sio2/Sisurface.

III. PROPERTIES

The various properties of Grapheneare-

A. Structural property The atomic structure of isolated,single-layer graphene was studied bytransmission electron microscopy (TEM)on sheets of graphene suspended betweenbars of a metallic grid. Electrondiffraction patterns showed theexpected honeycomb lattice. Suspendedgraphene also showed "rippling" of theflat sheet, with amplitude of about onenanometer. These ripples may beintrinsic to the material as a resultof the instability of two-dimensionalcrystals, or may originate from theubiquitous dirt seen scanning tunnelingmicroscopy. Photoresist residue, whichmust be removed to obtain atomic-resolution images, may be the"adsorbates" observed in TEM images,

and may explain the observed rippling.Rippling on SiO2 is caused byconformation of graphene to theunderlying SiO2, and is notintrinsic.in all TEM images ofgraphene. Atomic resolution real-spaceimages of isolated, single layergraphene on SiO2 substrates areavailable via

Graphene sheets in solid form usuallyshow evidence in diffraction forgraphite's (002) layering. This is trueof some single-walled nanostructures.However, unlayered graphene with only(hk0) rings has been found in the coreof presolar graphite onions. TEMstudies show faceting at defects inflat graphene sheets and suggest a rolefor two-dimensional crystallizationfrom a melt.

B. Electronic properties Graphene is a semi-metal or zero-gapsemiconductor. Four electronicproperties separate it from othercondensed matter systems.

- High electron mobility (at roomtemperature ~ 200.000 cm2/(V·s),,ex. Si at RT~ 1400 cm2/(V·s),carbon nanotube: ~ 100.000cm2/(V·s), organic semiconductors(polymer, oligomer): <10 cm2/(V·s)

Where υd is the drift velocity in m/s(SI units)E is the applied electric field in V/m,µ is the mobility in m2/ (V·s), in SIunits.

- Resistivity of the graphene sheet~10−6 Ω·cm, less than theresistivity of silver (Ag), thelowest resistivity substanceknown at room temperature(electrical resistivity is alsoas the inverse of theconductivity σ (sigma), of thematerial

Electrons propagating throughgraphene's honeycomb latticeeffectively lose their mass, producingquasi-particles that are described by a2D analogue of the Dirac equationrather than the Schrödinger equationfor spin-1/2 particles.

C. Thermal properties Graphene is a perfect thermalconductor. Its thermal conductivity wasmeasured recently at room temperatureand it is much higher than the valueobserved in all the other carbonstructures as carbon nanotubes,graphite and diamond (> 5000

). The ballistic thermal

conductance of graphene is isotropic,i.e. same in all directions. Similarlyto all the other physical properties ofthis material, its 2 dimensionalstructure make it particularly special.Graphite, the 3 D version of graphene,shows a thermal conductivity about 5times smaller (1000 ). The

phenomenon is governed by the presenceof elastic waves propagating in thegraphene lattice, called phonons. Thestudy of thermal conductivity ingraphene may have importantimplications in graphene-based

i

electronic devices. As devices continueto shrink and circuit densityincreases, high thermal conductivity,which is essential for dissipating heatefficiently to keep electronics cool,plays an increasingly larger role indevice reliability.

D. Mechanical properties The flat graphene sheet isunstable with respect to scrolling i.e.bending into a cylindrical shape, whichis its lower-energy state. As of 2009,graphene appeared to be one of thestrongest materials known with abreaking strength over 100 timesgreater than a hypothetical steel filmof the same (thin) thickness, [111]with a Young's modulus (stiffness) of 1TPA (150,000,000 psi). The Nobelannouncement illustrated this by sayingthat a 1 square meter graphene hammockwould support a 4 kg cat but wouldweigh only as much as one of the cat'swhiskers, at 0.77 mg (about 0.001% ofthe weight of 1 m2 of paper). However,the process of separating it fromgraphite, where it occurs naturally,requires technological development tobe economical enough to be used inindustrial processes. The springconstant of suspended graphene sheetshas been measured using an atomic forcemicroscope (AFM). Graphene sheets, heldtogether by van der Waals forces, weresuspended over SiO2 cavities where anAFM tip was probed to test itsmechanical properties. Its springconstant was in the range 1–5 N/m andthe stiffness was 0.5 TPa, whichdiffers from that of bulk graphite.These high values make graphene verystrong and rigid. These intrinsicproperties could lead to using graphenefor NEMS applications such as pressuresensors and resonators. As is true ofall materials, regions of graphene aresubject to thermal and quantumfluctuations in relative displacement.

Although the amplitude of thesefluctuations is bounded in 3Dstructures (even in the limit ofinfinite size), the Mermin–Wagnertheorem shows that the amplitude oflong-wavelength fluctuations growslogarithmically with the scale of a 2Dstructure, and would therefore beunbounded in structures of infinitesize. Local deformation and elasticstrain are negligibly affected by thislong-range divergence in relativedisplacement. It is believed that asufficiently large 2D structure, in theabsence of applied lateral tension,will bend and crumple to form afluctuating 3D structure. Researchershave observed ripples in suspendedlayers of graphene, [25] and it hasbeen proposed that the ripples arecaused by thermal fluctuations in thematerial. As a consequence of these dynamicaldeformations, it is debatable whethergraphene is truly a 2D Structure.

E. Optical properties Graphene's unique opticalproperties produce an unexpectedly highopacity for an atomic monolayer invacuum, absorbing πα ≈ 2.3% of whitelight, where α is the fine-structureconstant. This is a consequence of the"unusual low-energy electronicstructure of monolayer graphene thatfeatures electron and hole conicalbands meeting each other at the Diracpoint... which is qualitativelydifferent from more common quadraticmassive bands". Based on theSlonczewski–Weiss–McClure (SWMcC) bandmodel of graphite, the interatomicdistance, hopping value and frequencycancel when optical conductance iscalculated using Fresnel equations inthe thin-film limit. Although confirmedexperimentally, the measurement is notprecise enough to improve on other

techniques for determining the fine-structure constant.

Graphene's band gap can be tuned from 0to 0.25 eV (about 5 micrometrewavelength) by applying voltage to adual-gate bilayer graphene field-effecttransistor (FET) at room temperature.The optical response of graphene Nanoribbons is tuneable into the terahertzregime by an applied magnetic field.Graphene/graphene oxide systems exhibitelectro chromic behaviour, allowingtuning of both linear and ultrafastoptical properties. A graphene-basedBragg grating (one-dimensional photoniccrystal) has been fabricated anddemonstrated its capability forexcitation of surface electromagneticwaves in the periodic structure byusing 633 nm He–Ne laser as the lightsource.

F. Anomalous quantum Hall effectThe quantum Hall effect is a quantummechanical version of the Hall Effect,which is the production of transverse(perpendicular to the main current)conductivity in the presence of amagnetic field. The quantization of theHall effect at integer multiples (the"Landau level") of the basic quantity(where he is the elementary electriccharge and h is Planck's constant) Itcan usually be observed only in veryclean silicon or gallium arsenidesolids at temperatures around 3 K andvery high magnetic fields. Grapheneshows the quantum Hall effect withrespect to conductivity-quantization:the effect is anomalous in that thesequence of steps is shifted by 1/2with respect to the standard sequenceand with an additional factor of 4.Graphene's Hall conductivity is, whereN is the Landau level and the doublevalley and double spin degeneraciesgive the factor of 4. These anomalies

are present at room temperature, i.e.at roughly 20 °C.

This behaviour is a direct result ofgraphene's massless Dirac electrons. Ina magnetic field, their spectrum has aLandau level with energy precisely atthe Dirac point. This level is aconsequence of the Atiyah–Singer indextheorem and is half-filled in neutralgraphene, leading to the "+1/2" in theHall conductivity. [22] Bilayergraphene also shows the quantum HallEffect, but with only one of the twoanomalies. In the second anomaly, thefirst plateau at N=0 is absent,indicating that bilayer graphene staysmetallic at the neutrality point

Figure-6

IV. APPLICATIONS

The advancement of new-foundnanomaterials provides a fascinatingopportunity for development indifferent fields because of theirstructures, components and properties.In comparison with its precursor,carbon nanotube (CNT), grapheneexhibits some merits like low cost, twoexternal surfaces, facile fabricationand modification and absence of toxicmetal particles. Thus graphene and itsderivatives are expected to findapplications in many fields such as

Nano electronic devices, chemical andbiological sensors, energy storage andbiomedical fields

A. Electronic Nano devicesBecause of high electrical conductivity, mechanical flexibility and low cost, graphene and its derivatives have got wide spread applications in light emitting diode (LED), field effect transistor (FET), memory and photovoltaic devices.

Due to unique band structure, thecarriers in graphene are bipolar, withelectrons and holes that can becontinuously tuned by a gateelectrical field. The observation ofelectric field effect in graphene wasfirst reported by Novoselov et al. in2004. According to this report,graphene based FETs .Demonstratedambipolar characteristics withelectron and hole concentration of10^13 sq.cm with mobilities up to10,000 sq.cm per volt. Sec. at roomtemperature. Graphene FET devices witha single back gate have beeninvestigated by several otherworkers .For the application astransistor, graphene should be in theform of quasi one dimensional (1D)structure with narrow width andatomically smooth edges termed asgraphene Nano ribbons (GNRs). TheseGNRs exhibits band gap useful or FETapplication with excellent switchingspeed and high carrier mobility atroom temperature. Thus the quasi 1DGNRs become semiconductors with finiteenergy band gap. Although band gaphave been demonstrated in GNRs, thesewere quite different from those ofgraphene in terms of carrier mobilityand fabrication. Several workers have

demonstrated various methods tofabricate GNR including chemical andlithographic methods severaltheoretical studies have been reportedto predict the performance of GNR FETsas function of their edge roughness,chirality, chemical doping, carrierscattering and contact. Various modelshave also been developed to predictthe performance of GNR FETs. Thus theycan be valuable tools for designingefficient FETs. Lu et al. fabricated ahigh mobility flexible graphene field-effect transistor with self-healinggate dielectrics for a wide range ofapplications in flexible electronics.Szafranek and his co-workers havedemonstrated current saturation andvoltage gain in bilayer graphene fieldeffect transistor.

B. Transparent conductive films With high electrical conductivity,high carrier mobility and moderatelyhigh optical transmittance in thevisible range of spectrum, graphenematerial show promise for transparentconductive films (TCFs) and is expectedto be one of the mostly sought materialfor future optoelectronic devices .Graphene TCFs have been used aselectrodes for dye-sensitized solarcells, liquid crystal devices (LCDs)and organic light emittingdiodes(OLEDs) . The high hole transportmobility, large surface area andinertness against oxygen makes graphenea promising candidate for photovoltaicapplications. Graphene has been used asa novel acceptor for bulk hetrojunctionpolymer photovoltaic cells, showingremarkably reduced photoluminescenceand efficient energy transfer. The highmobility and excellent mechanical

properties of transparent graphenefilms makes it a suitable candidate formicroelectronic applications. Kim etal. evaluated the fold ability ofgraphene films, transferred to apolyethylene terephthalate (PET)substrate coated with a thin PDMS layerby measuring resistance as a functionof bending radii . Liu et al.fabricated flexible graphene film onPET substrate from large size GO bythermal annealing and the greenproduction of rGO films had potentialapplication in flexible electronics.Kang and his co-workers developedgraphene films grown on metal substrateby chemical vapor deposition method andsafely transferred onto desiredsubstrate for its application fordisplay and solar cells.

C. Energy Storage Devices: Due to its high theoretical surfacearea of and ability tofacilitate electrons or hole transferalong its two-dimensional surface,graphene has been a promising materialfor electrode. There have been severalreports on graphene based electrodesfor both rechargeable lithium ionbatteries (RLBs) and electrochemicaldouble layer capacitors (EDLCs).Graphite, the most commonly used anodematerial in RLBs has been replaced bygraphene for its superior electricalconductivity, high surface area andChemical tolerance.

D. Lithium Ion Battery Lithium ion battery has been a keycomponent of hand-held devices due to

its renewable and clean nature. To meetthe increasing demand for lithium ionbatteries with higher energy densityand durability, new electrode materialswith higher capacity and stability havebeen developed. Peak et al. hasprepared graphene Nano sheets decoratedwith SnO2 nanoparticles. The SnO2-Graphene exhibits reversible capacityof 810mAh/g and its cycling performanceis drastically enhanced in comparisonto that of bare SnO2 nanoparticles.Wang et al. have demonstrated self-assembled TiO2-graphene hybridnanostructure to enhance high rateperformance of electrochemical activematerial.

E. Ultra capacitor EDLCs are non-faradic ultracapacitor which store charges inelectric double layers formed at theinterface between a high surface areaelectrode and an electrolyte. Activatedcarbon with high specific surface areais extensively used as electrodematerial in EDLCs. Chemically modifiedgraphene (CMG) has been a potentialmaterial for the use as an Electrode inultracapacitors.

F. Fuel cell and Solar cell Graphene materials have also beenused in fuel cells and solar cells.Graphene has been identified as acatalyst support for oxygen reductionand methanol oxidation in case of afuel cell configuration. Conductivegraphene scaffolds for platinumnanoparticles facilitates efficientcollections and transfer of electronsto electrode surface.

G. Sensors Due to its conductance changing as afunction of extent of surfaceadsorption, large specific surface areaand low Johnson noise, recentexperimental and theoretical researchhas demonstrated monolayer graphene asa promising candidate to detect avariety of molecules, such as gases tobiomolecules. The charge transferbetween the adsorbed molecule andgraphene is proposed to be responsiblefor the chemical response.

H. Bio-medical application The application of the principlesof biology to nanotechnology provides avaluable route for furtherminiaturization and improvement ofperformance of artificial devices. Thesynergetic future of Nano graphene andbiotechnology holds great promise forits applications in the fields likegene and drug delivery, Tissueengineering and cancer therapy.

V. CONCLUSION Graphene is a multifunctionalmaterial with unique physical andchemical properties. Betterunderstanding of physics and chemistryat the surface of graphene andinteraction of chemicals andbiomolecules at the interface ofgraphene will play an important role inapplying graphene as Nano scaffold incatalysis, chemical/biosensing, imagingand drug delivery. In addition grapheneis an excellent electrode material forelectroanalysis and electrocatalysis,and there is still much room for thescientific research and applicationdevelopment of graphene-based theory,materials, and devices. As well as theGS nanocomposites could be promisinglyapplied in many fields such as

nanoelectronics, ultracapacitors,sensors, nanocomposites, batteries andgas storage. However, in spite of theconsiderable advances, substantialfundamental research is still necessaryto provide a basic understanding ofthese materials to enable fullexploitation of their nanoengineeringpotential.

Graphene-based nanomaterial’s thesedays have led to an explosive growth ofthe research works on their biomedicalapplications can be observed from theliterature in the past few years,especially in the areas of biosensors,bioelectronics and cancer therapy.Owing to the progress in graphenechemistry, fabrication of water-soluble, well-defined graphene or itsderivates with high quenchingcapability becomes feasible, and willbenefit the development of novel FRETsensors. Graphene based sensingplatform demonstrated high sensitivityand low detection threshold owing toits large specific surface area andfast electron transfer kinetics. Forcancer therapy, graphene based drugdelivery has combined with othertechniques, including photothermaltherapy and gene delivery, to improvethe overall therapeutic efficacy.Although a lot of effort has alreadybeen put together to utilize each andevery property of graphene for thedevelopment and welfare of mankindstill there is much to be done. Forexample, taking electrochemical sensinginto consideration, there is an urgentneed in this area to fabricatereliable, reproducible, and low-costsensors with high detection sensitivityusing well-defined graphene. There isstill much to be done for thescientific research and technologicaldevelopment of graphene-related theory,materials, and applications. We wouldlike to conclude by stating that

opportunities and challenges coexistwith regard to the applications ofgraphene-based nanomaterials.

Reference

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[3] Graphene – A rising star in view ofscientometrics by Andreas Barth* and WernerMarx**.

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