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[en] In this paper, we report the generation of Poly-vinyl-pyrrolidone (PVP) microfibers doped with two types of polydiacetylene (PDA): 10, 12-tricosadyinoic acid (TCDA) and 10,12-pentacosadiynoic acid (PCDA). The colorimetric transition behavior of the fibrous samples upon exposure to acetone stimulus is evaluated and compared to PVP layers doped with TCDA and PCDA. The quasi-instantaneous color shift of PVP-PDA microfibers and layers is quantitatively characterized by mean of UV-visible spectrometry and the colorimetric response (CR) is calculated from the absorption spectrums. The results show that PVP can be successfully used as a low cost host matrix for the development of PDA chemo and biosensors. In addition, the chemosensors exhibit sigmoidal behavior upon exposure to different acetone solutions and samples doped with TCDA present a higher sensitivity than samples doped with PCDA due to the length of their alkyl tail. Finally, the fibrous structure significantly enhance the sensors sensitivity by 1.6 times for TCDA samples and 10 times for PCDA samples highlighting the importance of the high surface to volume ratio provided by the electrospun fibers. (paper)
[en] Furthering the development of nanocomposite structures, namely membranes for water treatment applications, requires that methods be developed to ensure nanoparticle dispersion in polar and non-polar solvents, as both are widely used in associated synthesis techniques. Here, we report on a two-step method to graft polyvinylpyrrolidone (PVP), and a one-step method for octadecylphosphonic acid (OPA), onto the outer surfaces of imogolite nanotubes. The goal of these approaches was to improve and maintain nanotube dispersion in polymer compatible polar and non-polar solvents. The PVP coating modified the imogolite surface charge from positive to weakly negative at pH ≤ 9; the OPA made it weakly positive at acidic pH values to negative at pH ≥ 7. The PVP surface coating stabilized the nanotubes through steric hindrance in polar protic, dipolar aprotic, and chloroform. In difference to the PVP, the OPA surface coating allowed the nanotubes to be dispersed in n-hexane and chloroform, but not in the polar solvents. The lack of miscibility in the polar solvents, as well as the better dispersion in n-hexane, was attributed to the stronger hydrophobicity of the OPA polymer relative to the PVP. .
[en] Highlights: • A highly selective morphology formation of Cu-Ni nanocrystals is developed. • Nanocrystals evolve from nanoplates to nanowires with increasing PVP amount. • Nanoplates/nanowires are well dispersed and have high crystallinity and uniformity. • A mechanism is proposed for the formation of Cu-Ni nanocrystals. • Nanoplates/nanowires show better catalytic activities than conventional catalyst.
[en] The helical micro/nanofiber arrays of polyvinylpyrrolidone (PVP) were successfully prepared by Near-field electrospinning(NFES) with different concentrations of PVP and different voltages by a gradient of per 0.5 kV from 1 kV to 2.2 kV. It is found that the morphology of the arrayed fibers evolved with regularity with the increase of the working voltage, and the uniformity of the fiber arrays also increased. The formation mechanism of the arrayed helical micro/nanofibers was analyzed. This may be a cost-effective method for the large-scale production of morphologically controllable spiral fibers, which opens up an effective way for the precise and controlled deposition of electrospun helical fibers and the integration of single or array spiral fibers with functional devices. (paper)
[en] Shape and size controlled gram level synthesis of tin/indium (SnIn) alloy nanoparticles and nanobundles is reported. Poly(N-vinylpyrrolidone) (PVP) was employed as a capping agent, which could control the growth and structure of the alloy particles under varying conditions. Transmission electron microscopy showed that unique SnIn alloy nanobundles could be synthesized from the bulk materials above a certain concentration of PVP and below this concentration, discrete spherical nanoparticles of variable size were evolved. The morphology and the composition of the as-synthesized SnIn alloy nanobundles were investigated by high-resolution transmission electron microscopy (TEM). The possible mechanisms on the formation of these structures were discussed
[en] The study of the polymeric mixture compatibility by nuclear magnetic resonance was performed aiming to evaluate the molecular mobility of the title system and its compatibility. It was observed that the system is compatible up to 60% weigh/weigh proportion
[en] Pb(Zr0.52Ti0.48)O3 nanocrystals were synthesized by a hydrothermal method. The poly(vinyl pyrrolidone) (PVP) was used as the surfactant to control growth of the Pb(Zr0.52Ti0.48)O3 nanocrystals. The effect of PVP concentration, reaction temperature and time on morphologies and crystallinity of Pb(Zr0.52Ti0.48)O3 nanocrystals were investigated. The tetragonal PbZr0.52Ti0.48O3 grains were obtained, as they were prepared at 200 °C for 4 h with PVP concentration from 0.1 to 10.0 g/L. With increasing the PVP concentration from 0.1 to 10.0 g/L, the size of PbZr0.52Ti0.48O3 grains decreased. When the PbZr0.52Ti0.48O3 grains were prepared at 200 °C for 12 h with PVP concentration of 6.0 g/L, the PbZr0.52Ti0.48O3 nanocrystals with average diameter of 30 nm were formed.
[en] The core–shell nanofibers from Poly(ε-caprolactone) (PCL) and Polyvinylpyrrolidone (PVP) with variety in percentage of consisting material at core (PCL or PVP) and shell (PVP: PCL with proportions of 100:0, 50:50, 30:70, 10:90, and 0:100) were electrospun at two different shell flow rates (0.2 and 0.4 ml h−1). In the first phase, the properties of samples were studied in terms of viscosity changes of the polymer solutions, morphology, stability of the material structure during production, tensile strength properties, and degradation behavior. In the second phase, drug release percentage was measured through spectroscopy method. Results showed that increasing PVP in the core and shell of the nanofibers increased solution viscosity and fiber diameter and decreased tensile strength of the nanofibers. Also, the degradation behavior of samples was influenced by the amount and the location of PVP. Weight loss percentage of the samples varied from 17 to 71%. Also, initial burst release was controlled and reduced with the use of core–shell structure. Finally, it was revealed that by engineering the proportion of polymers in core–shell structure, the release rate of the 5-FU for each target fiber could be adjusted based on diagnosing and treatment protocol. (paper)