Multiwall Carbon Nanotubes (MWCNTs) composites fabricated in the form of fibers with large surface areas were used
in the development of important technological applications such as photoactuators. MWCNT-polymer fibers can be
prepared with the simple and fast technique of electrospinning. The precursor for electrospinning was prepared by
adding dispersed MWCNTs to a polymeric solution of Poly(dimethylsiloxane) and Poly(methylmethacrylate) dissolved
in Tetrahydrofuran (THF) and Dimethylformamide (DMF). The dispersion of the carbon nanotubes in Sodium Dodecyl
Sulfate (SDS)/water is expected to enhance the photoactuation properties of the Polymer CNT Composites. The
dispersion of the MWCNTS in SDS and the properties of the precursor solution were analyzed using Scanning Electron
Microscopy (SEM), Ultraviolet-Visible Spectroscopy (UV-Vis), and X-Ray Diffraction (XRD) techniques.
Electrospun polymer-MWCNTs fibers were prepared using a precursor solution that consists of multiwall carbon
nanotubes (MWCNTs), Poly(dymethylsiloxane) and Poly(methylmethacrylate) in Tetrahydrofuran (THF) and
Dimethylformamide (DMF). Before adding them into the precursor, the MWCNTs were dispersed in Sodium Dodecyl
Sulfate (SDS) and water. We report evidence of UV photo-conduction and photo-actuation in electrospun
PDMS/PMMA-CNT composite fibers.
We have reported earlier progress in producing polycrystalline wurtzite-polymorph and photo-conductive GaN
nanofibers by electrospinning. This paper shows grain stacking during heat treatment and suggests the need to
understand nucleation and grain growth following electrospinning. Transmission Electron Microscopy (TEM) analysis of
GaN shows brittle fibers, grain stacking, and unfinished grain nucleation. X-Ray Diffraction analysis confirmed
dominant hexagonal 101-wurtzite preferential overall orientation and the incipient grains are of high crystalline quality
as seen by high resolution TEM.
GaN nanofibers were sintered by electrospinning and analyzed by electron microscopy techniques to study morphology
and grain size. After heat treatment, the fibers showed thinner mats with polycrystalline grains with size on the order of
10 nm. For the first time in electospun GaN, optical properties were investigated by room temperature
cathodoluminescence. Despite polycrystallinity, the fibers produced a luminescence signal. The NBE might be blueshitfted
(by 1.1 eV) by the electron-confinement effect of excitons in the nm-sized grains. The origin of the other two
emissions is also compared to GaN fibres sintered by alternative techniques. The existence of a NBE signal from GaN
nanofibres could open the door to applications in nanophotonics.
The simple and inexpensive technique of electrospinning was used for the production of long GaN nanofibers. The fibers
were made using a precursor solution composed of pure Gallium Nitrate dissolved in dimethylacetamide (DMA) and a
viscous solution of Cellulose acetate dissolved in a mixture of DMA and acetone. Using a tube furnace, they were
sintered under a Nitrogen atmosphere to decompose the polymer and to reduce Oxygen contamination. This process was
followed by sintering under a NH3 flow to complete the synthesis of wurtzite GaN. XRD, ESEM, and FTIR analysis
were used to verify the chemical and structural composition of the samples. The I-V characteristics of a device
constructed using a single GaN nanofiber showed the formation of ohmic contacts.
Tin oxide is a binary semiconductor with a wide band gap (Eg = 3.6 eV at 300 K) and has been used, mostly in the form
of thin films, as the active element in gas sensing applications. As a fiber it is expected to have improved sensitivity as
the surface-to-volume ratio increases. The authors fabricated undoped tin oxide and antimony-doped tin oxide
nanofibers using electrospinning and metallorganic decomposition techniques. The precursor solution for the undoped
fibers was based on a tin (IV) chloride and a viscous solution based on poly(ethylene oxide) (PEO). The antimonydoped
precursor solution had an additional antimony trichloride solution made from isopropanol to obtain a Sb
concentration of 1.5 %. To study the sensitivity of the fibers to gas exposure, both single nanofibers and nanofiber mats
were electrospun onto Si/SiO2 wafers. The changes in the nanofiber resistance with exposure and removal of methanol
were measured as a function of time and gas concentration. In both configurations, the undoped nanofibers show higher
sensitiviy to the presence and removal of methanol. Both the undoped and antimony-doped tin oxide single nanofibers
show faster response times than the nanofiber mats. Of all the configurations tested, the antimony-doped single fiber
gives more stable and faster response.