In this work, we investigate the suitability of Electrospinning as a manufacturing technique to produce CNT-polymer
composites with a response to light. This objective is explored by way of developing a precursor solution comprised of a
polymeric blend, suitable of CNT dispersion and further electrospinning. The MWCNTs were dispersed using Sodium
dodecyl sulfate (SDS) and added to a polymeric solution consisting of Polydimethylsiloxane (PDMS) and
Polymethyl methacrylate (PMMA) in Tetrahydrofuran (THF) and Dimethylformamide (DMF). The dispersion of the
CNTs during synthesis was studied using UV-VIs and XRD techniques. Fibers electrospun out of this precursor and
their response to irradiation will also be discussed. Fiber morphology was characterized by SEM and the response to
irradiation was examined by photoelectric conductivity.
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.
In the current information age, scientists and educators are urged to disseminate scientific findings in a prompt manner for
increased public acceptance, later on, in the market place. Customer acceptance of highly novel technologies is an
education-driven effort that requires attention early-on during the stage of technology development. Prompt attention is
particularly needed in technologies where nanoparticles are employed, such as those being developed within the Nano-
Optical Mechanical Systems (NOMS) project. Another driving force to disseminate photoactuation is to generate interest
and curiosity amongst the K-12 population that could eventually lead to increased enrollment of students in the physical
sciences. In this paper, we present a work plan for the dissemination of photoactuation to society at large; from K-12 to
the general public. The work plan will be designed in accordance with the logic model, following indications of the
National Academy of Sciences, and will include a proposal for evaluating translational research following a process
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.
Porous SnO2 nanoribbons, with their width and thickness of around 20&mgr;m and 20nm, respectively, have been fabricated
from the metallo-organic dimethyldineodecanoate tin using electrospinning and thermal decomposition techniques. The
electrical conductance of one synthesized single ribbon has been measured using the two-probe method in atmosphere
following a cycle of heating from 300 to 660K and subsequent cooling from 660K to 300K. During the heating, the
conductance, G is not so sensitive to the temperature below 380K and, above that, follows an Arrhenius relation with a
thermal activation energy of 0.918±0.004 eV until 660K; upon cooling, G follows the same Arrhenius relation until
570K and, below that, observes another Arrhenius relation with its activation energy decreasing to 0.259±0.006eV down
to 300K. After a cycle of heating and cooling, G returns to a value higher than its initial one. The Arrhenius relations are
attributed to the surface adsorption and desorption of moisture and oxygen, and the G hysteresis between 300 and 380K
is attributed to the partial replacement of adsorbed oxygen by moisture because of the porous nature of the surface.
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.
Ultrafine tin oxide (SnO2) fibers in the rutile structure, with diameters ranging from 60nm to several microns, were synthesized using electrospinning and metallorganic decomposition techniques. In this work we use a precursor solution which is a mixture of a pure SnO2 sol made from SnCl4 : H2O : C3H7OH : 2-C3H7OH at a molar ratio of 1:9:9:6, and a viscous solution made from poly(ethylene oxide) (PEO) (molecular weight 900,000) and chloroform CHCl3 at a ratio of 200mg PEO/10mL CHCl3. This solution allows obtaining an appropriate viscosity for the electrospinning process. The as deposited fibers were sintered at 400, 500, 600, 700 and 800°C in air for two hours. Previous results using this method and characterizing the fibers with scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman microspectrometry and x-ray photoelectron spectroscopy (XPS) showed that up to the sintering temperature of 700°C, the synthesized fibers are composed of SnO2. Further analysis using SEM, Profilometry, Atomic Force Microscopy (SPM), Auger Spectroscopy and I/V analysis is presented in this paper. The results show that the fibers are composed of tin oxide and that smooth and continuous fibers in different shapes (straight, curved, ribbon-like, and spring-like) can be obtained using this method. The change in resistivity as a function of the annealing temperature can be attributed to the thermally activated formation of a nearly stoichoimetric solid.
We have measured the electronic transport properties of PAN based nano-fibers obtained by electrostatic deposition from 1.9 K to room temperature and carefully fitted the temperature and magnetic field dependence of these measurements to pertinent theoretical models
It is noteworthy that the anomalous temperature and magnetic field dependence of conductivity have been found in carbon fibers with diameter larger than 10 microns, and mostly, carbonized at heat treatment temperature (HTT) higher than 1000°C. It is interesting to evaluate the scaling of such effects that is, if similar effects exist after the diameter is reduced into the nano scale. This paper reports such an attempt after the authors obtained carbon nano-fibers by electro-spinning and measured their electronic transport properties. Single carbon nano-fibers were deposited on silicon oxide coated silicon wafer, and with a lithographed gold contact pattern array. The length and cross-section area of the fibers was measured using an optical microscope and a scanning probe microscope (SPM) operated in tapping mode. Four-probe resistance measurement was conducted continuously 300K down to 1.9K, without any applied magnetic field. Resistance was also measured at 1.9, 3, 5 and 10K when the applied magnetic field, perpendicular to the fiber, increasing and decreasing continuously between -9 and 9 Tesla twice. To suppress the possible heating effect, the total measuring power was limited to 5nW. At all the four investigated temperatures, MR is negative. Its magnitude increase with B and decrease with T. It is noteworthy that MR=-0.75 at T=1.9K and B=9T, the highest MR for such system as far as the authors knowledge.