a Palladium-graphene nanostructures (PdGO) with high-quality-graphene layers and well monodispersed palladium nanoparticles (PdNPs) were synthesized by the hydrothermal microwave exfoliation method. The structural and morphological characteristics of PdGO were investigated, and the results indicate that the hydrothermal-microwave method allows both the reduction of the metal precursors and their anchorage on highly exfoliated graphene layers. The synthesized PdGO was then deposited as active layers for sensing hydrogen gas (H2). PdGO-based sensors with gas concentrations from 0.01 to 5 vol. % in air exhibited a very reproducible performance with fast response times (~30 seg) and recovery behavior at room temperature. Impedance response results as a high sensitive feasible sensor technique. Our results show that it is feasible to obtain an efficient H2-sensor with reliable and reproducible sensing properties by means of a simple and cost-effective preparation method under real atmospheric conditions.

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In this work, chitosan (CS)/poly (vinyl alcohol) (PVA) nanofibers were prepared by using the electrospinning method. Different CS concentrations (0.5, 1, 2, and 3 wt %), maintaining the PVA concentration at 8 wt %, were tested. Likewise, the studied electrospinning experimental parameters were: syringe/collector distance, solution flow and voltage. Subsequently, the electrospun fibers were collected on a reticulated vitreous carbon (RVC) support for 0.25, 0.5, 1, 1.5, and 2 h. The morphology and diameter of the CS/PVA nanofibers were characterized by scanning electron microscopy (SEM), finding diameters in the order of 132 and 212 nm; the best results (uniform fibers) were obtained from the solution with 2 wt % of chitosan and a voltage, distance, and flow rate of 16 kV, 20 cm, and 0.13 mL/h, respectively. Afterwards, a treatment with an ethanolic NaOH solution was performed, observing a change in the fiber morphology and a diameter decrease (117 ± 9 nm).

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Cellulose is a natural polymer formed by chains of polysaccharide carbohydrates. Traditional processes for extraction of cellulose are expensive and require solvents with high ionic strength and stringent conditions. In this paper, we propose the extraction of cellulose from Bougainvillea spectabilis by using a traditional procedure, such as alkaline and acidic hydrolysis extraction, as well as the Vieira extraction method with the aid of two ionic liquids (ILs), with the purpose of using a solvent that allows reducing the harmful impact on the environment and human health. The obtained fibrous materials were analyzed by FTIR spectroscopy and the gravimetric method. According to gravimetric measurements, the results show an efficiency of 99.3% for the proposed extraction method and of 42.97% for acid hydrolysis. These results show that the proposed method allows adequate extraction using ionic solvents.

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