Abstract:We performed an extensive characterization of an electrospinning process to evaluate how the process parameters and precursor solution characteristics affect the fibers morphology. The work was conducted using precursor solutions with different concentrations of polyacrylonitrile (PAN) diluted in a fixed amount of N,N dimethylformamide (DMF). Fibers obtained with this process can find important applications in the field of nanosensors. The characteristics of the electrospun fibers were analyzed as a function of the solution viscosity, applied voltage and distance between the needle tip (positive electrode) and the collector plate (grounded electrode). The electrical current was monitored during the deposition process and its behavior was correlated with the characteristics of the fibers obtained. Our results demonstrate that the diameter of the fibers increases with increasing viscosity and applied voltage. The number of deposited fibers also increases with the applied voltage. Also, viscosity and applied voltage strongly affect the shape, length and morphology of the fibers. Of particular interest, we demonstrated that by monitoring the electrical current it is possible to control the fibers morphology and bead concentration. The distance between tip and collector plate determines the way the fibers arrive on the collector plate. A main contribution of this study was the definition of conditions to controllably obtain fibers that are smooth and that present diameters in the range between 140 and 300 nm.

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Copper phthalocyanine particles were added to polymer solution of Polyacrylonitrile (PAN) 6.0 wt % and to Polyvinylidene Fluoride (PVDF) 20.0 wt %. Using electrospinning process we obtained composite PAN/CuPc and PVDF/CuPc fibers. As copper phthalocyanine has sensitivity to ammonia, it was possible depositing nanofibers on the substrate of a micro device constructed with an Piezoelectric Quartz Crystal (PQC) for detection of ammonia.

O presente trabalho busca articular a música e o conhecimento geográfico a partir da leitura do lugar através dos movimentos musicais brasileiros, mais especificamente a relação local/global nas obras musicais de Chico Science e Mano Brown expoentes da cena contemporânea das artes nos respectivos movimentos: “Mangue Beat E Hip Hop”. As proposições dos geógrafos sobre o lugar são  colocadas em perspectiva para traçarmos uma relação entre a linguagem cientifica e a linguagem  musical que e a possível aplicação desta no processo de ensino/aprendizagem e também para a pesquisas de fenômenos espaciais engendrados pelas expressões sócio/culturais.

The main objective of this work is the incorporation of different particles in order to electrospun polymeric nanofibers of polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF), aiming at applications in sensor devices. Initially, solutions of PAN pure 6 wt% and PVDF pure 20 wt% were prepared and these solutions were mixed with carbon black (NF) particles and copper phthalocyanine (CuPc), obtaining solutions of PAN/NF, PVDF/NF, PAN/CuPc and PVDF/CuPc. The absolute viscosity of the solutions was determined. The electrospinning was performed to obtain nanofibers that were characterized according to the diameter and morphology, using optical microscope and scanning electron microscopy. To evaluate the polymer-polymer and polymer-particle interactions, FITR and Raman spectroscopy were performed. The resistance and conductance of the membranes electrospun from PAN/NF solution were analyzed using a digital picoammeter, and an increase in the resistance was measured. This result shows that the membrane is suitable to be applied as electrostatic filter. A channel was constructed on the silicon wafer using a laser beam for the deposition of fibers inside the channel using the electrodynamic focusing technique. The quartz crystal microbalance technique was used to determine the applicability of the membranes as sensor layer. The results of PAN/CuPc and PVDF/CuPc membranes suggests that these membranes are promising to act such as ammonia vapor sensors.