The effects of electrospinning parameters in a wider range on the morphology and diameters of polyacrylonitrile (PAN) fibers are studied in detail. The fibers’ diameter increases from 288 to 3469 nm swiftly with the increasing PAN concentration. With the increasing voltage or prolonging gap distance, the diameter increases primarily and decreases later. The combined effects of surface tension, splitting and stretching, electric force, viscosity, and solvent volatilization are the main reasons. Ultrasonic etching method, Atomic force microscope (AFM), Scanning electron microscope (SEM) and X-ray diffraction (XRD) technology have been utilized to verify the nature structure of electrospun PAN fibers. Combining all the results, it is deduced that there are many grooves arranging nearly perpendicular to the fiber axis on the surface of electrospun PAN fibers. The thickness of relative ordered region is 40 to 190 nm and the thickness of amorphous region is 20 to 35 nm. 相似文献
A sense of cell‐being : Single‐walled carbon nanotubes (SWNTs) are functionalized with bioactive monosaccharides to enable their use as biosensors. The glycosylated nanotube network is biocompatible and can interface with living cells (see scheme) to electronically detect biomolecular release with high temporal resolution and high sensitivity.
Transparent phosphate glass ceramics co-doped with Er3+ and Yb3+ in the system P2O5Li2OCaF2TiO2 were successfully synthesized by melt-quenching and subsequent heating. Formation of the nanocrystals was confirmed by X-ray powder diffraction. Judd–Ofelt analyses of Er3+ ions in the precursor glasses and glass ceramics were performed to evaluate the intensity parameters Ω2,4,6. Under 975 nm excitation, intense upconversion (UC) and infrared emission (1545 nm) were observed in the glass ceramics by efficient energy transfer from Yb3+ to Er3+. The luminescence processes were explained and the emission cross section was calculated by Fuchtbauer–Ladenburg (F–L) formula. The results confirm the potential applications of Er3+/Yb3+ co-doped glass ceramics as laser and fiber amplifier media. 相似文献