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In this paper, we report a robust and a low-cost spin coating approach for fabrication of large area flexible piezoelectric nanocomposite generator device for harvesting biomechanical motions. In order to develop the piezoelectric nanocomposite, ZnO and BaTiO3 were used as filler materials for realization of piezoelectric nanogenerator. Serial stretching and bending tests over these devices illustrated generation of maximum open-circuit voltage of similar to 237 and similar to 736 mV for ZnO and BaTiO3, respectively. Furthermore, we also demonstrated a 2 x enhancement in output voltage performance of nanogenerator by adding graphene platelets to these diphasic piezoelectric nanocomposite systems.

Electrospinning (e-spinning) is a versatile technique to fabricate ultrathin fibers from a rich variety of functional materials. In this paper, a modified e-spinning setup with two-frame collector is proposed for the fabrication of highly aligned arrays of polystyrene (PS) and polyvinylidene fluoride (PVDF) nanofibers, as well as PVDF/carbon nanotube (PVDF/CNT) composite fibers. Especially, it is capable of producing fibrous arrays with excellent orientation over a large area (more than 14 cm × 12 cm). The as-spun fibers are suspended and can be easily transferred to other rigid or flexible substrates. Based on the aligned fibrous arrays, twisted long ropes are also prepared. Compared with the aligned arrays, twisted PVDF/CNT fiber ropes show enhanced mechanical and electrical properties and have potential application in microscale strain sensors.

Flexible lead-free piezoelectric nanofibers, based on BNT-ST (0.78Bi0.5Na0.5TiO3-0.22SrTiO3) ceramic and poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) copolymers, were fabricated by an electrospinning method and the effects of the degree of alignment in the nanofibers on the piezoelectric characteristics were investigated. The microstructure of the lead-free piezoelectric nanofibers was observed by field emission scanning electron microscope (FE-SEM) and the orientation was analyzed by fast Fourier transform (FFT) images. X-ray diffraction (XRD) analysis confirmed that the phase was not changed by the electrospinning process and maintained a perovskite phase. Polarization-electric field (P-E) loops and piezoresponse force microscopy (PFM) were used to investigate the piezoelectric properties of the piezoelectric nanofibers, according to the degree of alignment—the well aligned piezoelectric nanofibers had higher piezoelectric properties. Furthermore, the output voltage of the aligned lead-free piezoelectric nanofibers was measured according to the vibration frequency and the bending motion and the aligned piezoelectric nanofibers with a collector rotation speed of 1500 rpm performed the best.

Vertical single-walled carbon nanotubes (v-SWCNTs) are synthesized within highly ordered porous anodic alumina (PAA) templates supported on Si substrates. A process for obtaining thin-film PAA with long-range ordered nanopores is presented in this paper. Each nanopore contains at most one v-SWCNT that is supported by a dielectric and addressed by electrochemically formed Pd nanowire source contacts and evaporated Pd drain contacts. Characteristics of these completely vertical, two-terminal nanotube devices are presented. Control of the v-SWCNT length is demonstrated using a straightforward etching process with lengths of less than 100 nm achieved without the need for complex/expensive lithography. This effective nanoscale length control of highly ordered v-SWCNTs provides a practical basis for the realization of CNT-based nanoelectronics.

We report measurements of the molecular first hyperpolarizability, thermal stability, photophysical, piezoelectric and ferroelectric properties of a benzothiazole derivative bearing an arylthiophene π-conjugated bridge both in solution and when embedded into a poly (L-lactic acid) (PLLA) matrix in the form of electrospun fibers with an average diameter of roughly 500 nm. The embedded nanocrystalline phenylthienyl-benzothiazole derivative, with crystal sizes of about 1.4 nm resulted in a good piezoelectric response from these functionalized electrospun fibers, indicative of a polar crystalline structure., Fundação para a Ciência e a Tecnologia (FCT)

Extremely high field effect mobility together with the high surface coverage makes graphene a promising material for high frequency electronics application. We investigate the intrinsic high frequency performance limit of graphene field effect transistors limited by the charge impurity scattering. The output and transfer characteristics of graphene field effect transistors together with the high frequency performance are characterized as a function of impurity concentration and dielectric constant of the gate insulator. Our results reveal that graphene transistors could provide power gain at radio frequency band. (C) 2010 American Institute of Physics. [doi:10.1063/1.3506506]

A novel methodology to fabricate highly aligned array of equilateral gold NTs on ITO substrates was demonstrated. The ITO glass substrate was cleaned with a mild detergent solution, sonicated with deionized water and soaked in 10 % HCl solution for activation. They were then washed with water, dried and annealed at 450�C for 7 h and cooled in a desiccator. The glass slides were dipped in 30 mM APTMS solution in methanol for 1 h. Afterwards, they were washed with methanol and water in sequence and kept at 110�C for 2h. Seed coated substrate and an identical blank ITO glass plate were kept at 5 mm apart such that the conducting surfaces faced each other and were connected to the -ve and +ve terminals of a DC power supply. Contact mode AFM measurements were carried out using a reflux coated nanosensors silicon cantilever. It was observed that at higher potentials, irregular shapes are obtained.