In the present study, highly sensitive and high-throughput optical waveguidebiosensors were fabricated by using the sensing membranes containing dye andpolymer-enzyme complex. Optical light waveguide can detect the optical change inthe vicinity of the guide surface with high sensitivity due to the evanescentwave scattering. The glucose sensing membranes, composed of dye, enzymes, andbiocompatible polymers were prepared by solution processing on the opticalwaveguide. Herein, we used 3, 3’, 5,5’-tetramethylbenzidine (TMBZ) as a dye, glucose oxidase (GOD) andperoxidase (POD) as enzymes, phosphatide polymer for protection of biologicalactivity of enzyme, and carboxymethyl cellulose (CMC) as a binder. Then wefocused on the optimal composition and structure of sensing membranes for theenhancement in the sensitivity and response speed. The developed glucose sensorsdemonstrated 20 times higher sensitivity than the conventional light waveguideglucose sensors and the low-detection limit of 0.1g/L glucose within thedetection time of 60 sec. For further improvement in the sensitivity,microporous sensing membranes were fabricated by using electrosprayingtechnique. The electroprayed sensing membranes gave 40 % higher sensitivity thannonporous sensing membranes. These results show that both the composition andstructure of sensing membrane are crucial factors for highly sensitive andhigh-throughput optical waveguide biosensors.

Crosslinked or non-crosslinked ultrathin semipermeable membranes based on the N-butylated and N-butylsulfonated polybenzimidazole (BPBI and BSPBI) were successfully prepared by spin-coating method. Structural characterization by FTIR and WAXD revealed that the N-substitution and the crosslinked structure of PBI suppressed the hydrogen bonding and increased the d-spacing. Furthermore, positron annihilation lifetime spectroscopy (PALS) clearly showed the pore radius change from 0.27-0.29 nm to 0.33 nm by crosslinking. As a result, the enhancement of water flux and NaCl rejection was achieved by the crosslinking of the BPBI and BSPBI. Especially, the crosslinked N-butylsulfonated PBI (CL-BSPBI) membrane significantly improved not only salt rejection but also water flux (NaCl rejection : 46 %, water flux : 22.1 L m-2 h-1) compared to those of non-crosslinked BSPBI one (NaCl rejection : 11 %, water flux : 1.88 L m-2 h-1) due to both the Donnan effect and the formation of larger pores in the membrane, respectively.

Thermal-stable, conductive, and flexible carbon fabric (CF), which is composed of thin carbon fibers prepared by electrospinning, was used for the substrate of carbon nanotube (CNT) field emitter arrays. The field emitter arrays were prepared by chemical vapor deposition (CVD). The current density-electric field characteristics revealed that the CNT field emitter arrays on CF produced a higher current density at a lower turn-on voltage compared to ones on a Si substrate. This emitter integrated with a gate electrode based on hierarchy-structured carbon materials, CNTs on CF, can be used for light sources, displays, and other electronic devices.

In this paper we report new excitation method of surface plasmon polariton (SPP) at air/gold interface with electrospun nanofibers. Nanofibers of polyvinylpirrolidone were electrospun onto the surface of a gold film. The observations by scanning electron microscopy and optical microscopy indicated that the average diameters of the nanofibers were about 300 nm and average sizes of pores were about 30-40 μm. Optical response of the nanofibers on gold surface was investigated by polarized reflection absorption spectroscopy (RAS). The RAS spectrum with p-polarized light showed two absorption bands while the spectrum with s-polarized light only one band. One is a band at about 520 nm that also found in the spectrum with s-polarized light. Another is a broad band in the near-infrared region which found only with p-polarized light. The peak intensity of the latter band increases with increase of incident angle of the polarized light and the peak wavelength of the band shifted to longer wavelength. These responses suggested that SPP at air/gold interface was excited with the scattering light from the electrospun nanofibers. We also found that the peak wavelength of the absorption band in near-infrared region changed with the increase of the amount of the nanofibers. This may be due to the fact that the sizes of the pores on gold surface became smaller than the propagation length of SPP, which resulted in scattering and interference of SPP.

In this paper, we report on the preparation and applications of nanofiber networks, particularly in the area of optelectronics. The major topics are (i) carbon nanotubes grown on carbon nanofibers for a field emitter, (ii) dye-sensitized ZnO nanowires grown on carbon nanofibers for a photoelectrochemical cell, (iii) nanofiber coatings for coloring, and (iv) nanofiber coatings on gold substrate for surface plasmon resonance. The results presented here reveal the potential use of nanofiber networks for various optoelectronic devices.