Although there have been many reports on the preparation and applications of various polymer nanofibers with the electrospinning technique, the understanding of synthetic parameters in electrospinning remains limited. In this article, we investigate experimentally the influence of solvents on the morphology of the poly(vinyl pyrrolidone) (PVP) micro/nanofibers prepared by electrospinning PVP solution in different solvents, including ethanol, dichloromethane (MC) and N,N‐dimethylformamide (DMF). Using 4 wt % PVP solutions, the PVP fibers prepared from MC and DMF solvents had a shape like a bead‐on‐a‐string. In contrast, smooth PVP nanofibers were obtained with ethanol as a solvent although the size distribution of the fibers was somewhat broadened. In an effort to prepare PVP nanofibers with small diameters and narrow size distributions, we developed a strategy of using mixed solvents. The experimental results showed that when the ratio of DMF to ethanol was 50:50 (w/w), regular cylindrical PVP nanofibers with a diameter of 20 nm were successfully prepared. The formation of these thinnest nanofibers could be attributed to the combined effects of ethanol and DMF solvents that optimize the solution viscosity and charge density of the polymer jet. In addition, an interesting helical‐shaped fiber was obtained from 20 wt % PVP solution in a 50:50 (w/w) mixed ethanol/DMF solvent. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3721–3726, 2004

Self-assembled crystalline porous organic salts (CPOSs) formed by an acid-base combination and with one-dimensional polar channels containing water molecules have been synthesized. The water content in the channels of the porous salts plays an important role in the proton conduction performance of the materials. The porous salts described in this study feature high proton conductivity at ambient conditions and can reach as high as 2.2×10 S cm at 333 K and under high humid conditions. This is among the best conductivity values reported to date for porous materials, for example, metal-organic frameworks and hydrogen-bonded organic frameworks. These materials exhibiting permanent porosity represent a group of porous materials and may find interesting applications in proton-exchange membrane fuel cells.

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A combined XRD and XPS study showed that the Au1/ZSM-5 zeolite (Au 4f7p,5p = 85.6 and 89.2 eV) can be prepared by spontaneous monolayer dispersion of AuCl3 in ZSM-5 followed by reductive carbonylation with CO at 343 K. The in-situ FTIR shows that the intrazeolite Aul in ZSM-5 provides Aul carbonyl (YCO = 2170 cm-') and nitrosyl ( y~o = 1817 cm-l) on chemisorption of CO (5-350 Torr) and N O (5-50 Torr) at 300 K, respectively. The interaction of CO and NO on Au1/ZSM-5 results in surface intermediates such as Au1(N0)2 NO = 1837 and 1741 cm-l) and AuIN02 (1620 and 1302 cm-l), which are catalytically active in NO reduction with CO producing N2O and C02 at 293-373 K.

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