title: Electron-tunneling modulation in percolating network of graphene quantum dots: fabrication, phenomenological understanding, and humidity/pressure sensing applications.
abstract: The two-dimensional (2D) electron cloud, flexible carbon-carbon bonds, chemical modifiability, and size-dependent quantum-confinement and capacitance makes graphene nanostructures (GN) a widely tunable material for electronics. Here we report the oxidation-led edge-roughening and cleavage of long graphene nanoribbons (GNRs) (150 nm wide) synthesized via nanotomy (nanoscale cutting) of graphite (with 2 nm edged diamond knife) to produce graphene quantum dots (GQD). These GQDs (~100-200 nm) selectively interfaced with polyelectrolyte microfiber (diameter = 2-20 μm) form an electrically percolating-network exhibiting a characteristic Coulomb blockade signature with a dry tunneling distance of 0.58 nm and conduction activation energy of 3 meV. We implement this construct to demonstrate the functioning of humidity and pressure sensors and outline their governing model. Here, a 0.36 nm decrease in the average tunneling-barrier-width between GQDs (tunneling barrier = 5.11 eV) increases the conductivity of the device by 43-fold. These devices leverage the modulation in electron tunneling distances caused by pressure and humidity induced water transport across the hygroscopic polymer microfiber (Henry's constant = 0.215 Torr(-1)). This is the foremost example of GQD-based electronic sensors. We envision that this polymer-interfaced GQD percolating network will evolve a new class of sensors leveraging the low mass, low capacitance, high conductivity, and high sensitivity of GQD and the interfacial or dielectric properties of the polymer fiber.
authors.affiliation: Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506, United States.
authors.forename: T S
authors.initials: TS
authors.lastname: Sreeprasad
authors.forename: Alfredo Alexander
authors.initials: AA
authors.lastname: Rodriguez
authors.forename: Jonathan
authors.initials: J
authors.lastname: Colston
authors.forename: Augustus
authors.initials: A
authors.lastname: Graham
authors.forename: Evgeniy
authors.initials: E
authors.lastname: Shishkin
authors.forename: Vasanta
authors.initials: V
authors.lastname: Pallem
authors.forename: Vikas
authors.initials: V
authors.lastname: Berry
mesh_terms: D004583:Electrons; D006108:Graphite / Q000737:chemistry*; D006813:Humidity; D037742:Nanotubes, Carbon / Q000737:chemistry; D010316:Particle Size; D011108:Polymers; D011312:Pressure; D045663:Quantum Dots / Q000737:chemistry*
chemical_list: D037742:Nanotubes, Carbon; D011108:Polymers; D006108:Graphite