A Brief Overview on Graphene based Sensors

2. WHAT IS GRAPHENE ???
It is a two-dimensional planar sheet of sp2-bonded carbon atoms
that are densely packed in a honeycomb crystal lattice.
Andre Geim and Konstantin Novoselov at the University of
Manchester won the Nobel Prize in Physics in 2010

4. Properties which makes graphene useful in sensors
 Large surface-to-volume ratio,
 Unique optical properties, excellent electrical conductivity.
 remarkably high carrier mobility , high carrier density
 high thermal conductivity, room temperature Hall effect,
 ambipolar field-effect characteristics, high signal-to-noise
ratio.
 extremely high mechanical strength (200 times greater than
steel, tensile modulus of 1 TPa).

5. Graphene sensing requires functionalization…
 To endow graphene with sensing capabilities, it is often
necessary to functionalize it with recognition elements that
bring the detection targets onto the graphene surface through
specific interactions and sometimes also assist in signal
transduction.
 Graphene may also be functionalized in order to enhance its
sensitivity, specificity, loading capacity, biocompatibility
 Covalent and Non- covalent methods followed

7. Electrochemical Sensors.
 graphene has a large electrochemical potential window
 detection of molecules that have high oxidation or reduction potential (e.g.,
nucleic acids) become feasible.
 edges and defects on graphene provide a high electron transfer rate
 RGO sheets or small flakes of pristine graphene are superior for electrochemical
detection
 Electron transfer can be enhanced also because small graphene flakes are able
to providedirect electrical wiring between the electrode and the active centers
of the redox enzymes
 RGO has intrinsic catalytic activity towards some small enzymatic products such
as H2O2 and NADH, making it attractive for enzyme-based sensors
 Useful in detection of glucose , protein biomarkers , other biomolecules

8. Optical sensor
 Graphene oxides exhibit interesting optical properties.
 Unlike zero-gap graphene or other carbonaceous materials, GO can fluoresce in a
wide range of wavelength (from near-infrared to ultraviolet)
 GO has the potential to serve as a universal fluorescence label for optical imaging
 GO is also capable of quenching fluorescence
 The quenching efficiency of GO is superior to the conventional organic quenchers
 On the basis of its fluorescence and quenching abilities, GO can serve as either an
energy donor or acceptor in a fluorescence resonance energy transfer (FRET) sensor.
 Graphene materials may also assist to enhance the performance of optical sensors,
 graphene materials can be used to reduce fluorescence interference in Raman
spectroscopy

9. QUENCHING FL. DONOR

10. NANOPORE SENSOR
 A nanopore, which resides on an insulating membrane and has a molecular diameter, can be used as a molecular
detector with exquisite (single molecule or even intra-molecular) sensitivity.
 When a molecule passes through a narrow pore that connects two separated electrolyte solutions, the ionic
current flowing through the pore is partially blocked,
 producing a current signature influenced by the charge state and subtle molecular structure of the occupying
molecule or its segment
 Protein nanopores embedded within a lipid bilayer have been used for detection of DNA and RNA molecules
 solid-state nanopores created on dielectric membranes (e.g., Si3N4 or SiO2) have been developed.