Browsing by Keyword "Electrospinning"
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Item Enhanced photostability and sensing performance of graphene quantum dots encapsulated in electrospun polyacrylonitrile nanofibrous filtering membranes(2018-06-01) Ruiz, Virginia; Pérez-Marquez, Ana; Maudes, Jon; Grande, Hans-Jürgen; Murillo, Nieves; Tecnalia Research & Innovation; PRINTEXWe report a method to encapsulate graphene quantum dots (GQD) in polyacrylonitrile (PAN) nanofibrous membranes to manufacture robust filtering membranes by electrospinning. GQD-PAN membranes with different nanofiber diameter were prepared tuning the electrospinning parameters, all exhibiting the characteristic fluorescence fingerprint of the GQD probes. The photoluminescence (PL) stability of GQD embedded in the PAN fibers was significantly enhanced with respect to that of water dispersed GQD luminescent probes. The PL of GQD-PAN filtering membranes showed remarkable time stability, both stored dry and immersed in phosphate buffer solutions (PBS), as well as exposed to continuous light irradiation. However, the PL intensity of GQD-PAN membranes was irreversibly quenched by highly oxidant free chlorine solutions. Thus, electrospun GQD-PAN membranes exhibited excellent performance as turn-off fluorescence sensing platforms for free chlorine detection in PBS 0.1 M pH 7. The analytical performance of GQD-PAN membranes was comparable to that of GQD solutions with optimal concentrations, displaying a fast (no need of incubation time) and linear response to chlorine concentration in the 10–600 μM range, a low detection limit of 2 μM, high sensitivity, reproducibility and selectivity. Moreover, the sensing performance of the membranes was very stable after being immersed in PBS for months, outperforming the stability of GQD solutions.Item Evaluation of the electrochemical performance of electrospun transition metal oxide-based electrode nanomaterials for water CDI applications(2019-06-20) Santangelo, Saveria; Pantò, Fabiola; Triolo, Claudia; Stelitano, Sara; Frontera, Patrizia; Fernández-Carretero, Francisco; Rincon, Inés; Azpiroz, Patxi; García-Luis, Alberto; Belaustegui, Yolanda; Tecnalia Research & Innovation; TECNOLOGÍAS DE HIDRÓGENO; VALORIZACIÓN DE RESIDUOSComposite fibrous materials based on (graphene-enriched) nitrogen-doped carbon/transition metal oxides were produced by electrospinning and their physicochemical properties were thoroughly investigated by a combination of characterisation techniques. The electrochemical behaviour of the electrodes prepared with them was evaluated in view of their use in the capacitive deionisation of saline water. The morphology of the materials reminded of usnea florida lichens, wheat ears, sea sponges and noodles and depended on the transition metal (Mn, Fe, Ti or Zn). The morphology and the relative amount (14.1–22.2 wt%) of the surface nitrogen and carbon-bonded oxygen functional species, beneficial to wettability and involving pseudocapacitive processes, had strong impact on the specific capacitance (43.7–67.4 F g−1, at 5 m V s−1 scan rate), whereas also the specific micropore volume (0.4–5.6 mm3 g−1) affected the effective areal capacitance of the electrodes (1.2–6.0 F m−2, at 5 mV s−1). Ion storage in the composite materials occurred via a mixed capacitive/pseudocapacitive process. Hence, increasing the content of the oxide (from 24.6 to 56.7 wt%), thanks to the fast-reversible redox reactions at or near surface it involves, partly compensated for the growing hindrance to diffusion encountered by the ions (hampered electrostatic adsorption) as the scan rate increased from 5 to 100 mV s−1.Item Optical sensors based on polymeric nanofibers layers created by electrospinning(2018) Ponce-Alcántara, S.; Martín-Sánchez, D.; Pérez-Márquez, A.; Maudes, J.; Murillo, N.; García-Rupérez, J.; PRINTEX; Tecnalia Research & InnovationPorous materials have become ideal candidates for the creation of optical sensors that are able to reach extremely high sensitivities, due to both the possibility to infiltrate the target substances on them and to their large surface-to-volume ratio. In this work, we present a new alternative for the creation of porous optical sensors based on the use of polymeric nanofibers (NFs) layers fabricated by electrospinning. Polyamide 6 (PA6) NFs layers with average diameters lower than 30 nm and high porosities have been used for the creation of Fabry-Pérot optical sensing structures, which have shown an experimental sensitivity up to 1060 nm/RIU (refractive index unit). This high sensitivity, together with the low production cost and the possibility to be manufactured over large areas, make NFs-based structures a very promising candidate for the development of low-cost and high performance optical sensors.Item PS/PMMA-CdSe/ZnS Quantum Dots Hybrid Nanofibers for VOCs Sensors(2018-12) De San Luis, Alicia; Aguirreurreta, Ziortza; Pardo, Leticia M.; Perez-Marquez, Ana; Maudes, Jon; Murillo, Nieves; Paulis, María; Leiza, Jose Ramon; Tecnalia Research & Innovation; PRINTEXHybrid nanofibers containing CdSe/ZnS quantum dots have been produced by electrospinning of hybrid latexes to characterize the electro‐optical behavior of this novel luminescent sensing material. The latexes are synthesized by seeded semi‐batch emulsion polymerization yielding cross‐linked core‐shell PS/QDs/PMMA particles with efficiently encapsulated quantum dots guaranteeing a good optical stability. Addition of polyvinyl alcohol (PVA) or polyethylene oxide (PEO) to the latexes is necessary to produce polymeric dispersions suitable for electrospinning manufacture of the nanometric fibers. The optimized polymeric dispersions are successfully electrospun obtaining fluorescent nanofibers in both cases. The hybrid nanofibers are sensitive to selected solvents (acetone, methanol and THF) and present positive response making them good candidates for the production of VOC sensors.