[show abstract][hide abstract] ABSTRACT: It is an essential issue in graphene based nanoelectronic and optoelectronic devices to tune the electrical properties of graphene layers while preserving its unique band structure. Here we report the tuning of electronic properties of single, bi and tri layer mechanically exfoliated graphenes by p-toluenesulfonic acid (PTSA) molecular doping. Raman spectroscopy and charge transport measurements revealed that PTSA molecule imposes n-doping to single, bi and tri layer graphenes. The shift of G and 2D peak frequencies and intensity ratio of single, bi and tri layer graphenes are analyzed as a function of reaction time. The Dirac point is also analyzed as a function of reaction time indicates the n-type doping effect for all single, bi and tri layer graphenes. Our study demonstrates that chemical modification is a simple approach to tailor the electrical properties of single, bi and tri layer graphenes while maintaining the important electrical assets.
[show abstract][hide abstract] ABSTRACT: It is essential to tailor the electronic properties of graphene in order to apply graphene films for use in electrodes. Here we report the modification of the electronic properties of single layer chemical vapor deposition (CVD) grown graphene by molecular doping without degrading its transparency and electrical properties. Raman spectroscopy and transport measurements revealed that p-toluenesulfonic acid (PTSA) imposes n-doping on single layer CVD grown graphene. The shift of G and 2D peak wave numbers and the intensity ratio of D and G peaks are analyzed as a function of reaction time. In the gate voltage dependent resistivity measurement, it is found that the maximum resistivity corresponding to the Dirac point is shifted toward a more negative gate voltage with increasing reaction time, indicating an n-type doping effect. We have also made single layer graphene p–n junctions by chemical doping and investigated the current–voltage characteristics at the p–n junction.
Journal of Materials Chemistry 06/2012; · 5.97 Impact Factor
[show abstract][hide abstract] ABSTRACT: Polyaniline/SnO<sub>2</sub> nanoflber based surface acoustic wave (SAW) gas sensor has been investigated towards hydrogen (H<sub>2</sub>) gas. Chemical oxidative polymerization of aniline was employed to synthesize polyaniline nanofibers with SnO<sub>2</sub> nanoparticles. The nanocomposite was deposited onto a layered ZnO/64deg YX LiNbO<sub>3</sub> SAW transducer. The sensor was exposed to various concentrations of H<sub>2</sub> gas and operated at room temperature. The sensor response was found to be 7 kHz towards 1% of H<sub>2</sub> in synthetic air. A fast response and recovery with good repeatability in a stable baseline condition were observed at room temperature.
Optoelectronic and Microelectronic Materials and Devices, 2006 Conference on; 01/2007
[show abstract][hide abstract] ABSTRACT: The effect of iron oxide nanoparticle addition on the physicochemical properties of the polypyrrole (PPy) was investigated.
In the presence of iron oxide nanoparticles, PPy was observed in the form of discrete nanoparticles, not the usual network
structure. PPy showed crystalline structure in the nanocomposites and pure PPy formed without iron oxide nanoparticles. PPy
exhibited amorphous structure and nanoparticles were completely etched away in the nanocomposites formed with mechanical stirring
over a 7-h reaction. The thermal stability of the PPy in the nanocomposites was enhanced under the thermo-gravimetric analysis
(TGA). The electrical conductivity of the nanocomposites increased greatly upon the initial addition (20wt%) of iron oxide
nanoparticles. However, a higher nanoparticle loading (50wt%) decreased the conductivity as a result of the dominance of
the insulating iron oxide nanoparticles. Standard four-probe measurements indicated a three-dimensional variable-range-hopping
conductivity mechanism. The magnetic properties of the fabricated nanocomposites were dependent on the particle loading. Ultrasonic
stirring was observed to have a favorable effect on the protection of iron oxide nanoparticles from dissolution in acid. A
tight polymer structure surrounds the magnetic nanoparticles, as compared to a complete loss of the magnetic iron oxide nanoparticles
during conventional mechanical stirring for the micron-sized iron oxide particles filled PPy composite fabrication.
Journal of Nanoparticle Research 11(6):1441-1452. · 2.18 Impact Factor