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11 pages, 2607 KiB

Open AccessArticle

Processing and Formulation Optimization of Mandarin Essential Oil-Loaded Emulsions Developed by Microfluidization

by Jenifer Santos, Nuria Calero, Luis Alfonso Trujillo-Cayado, María José Martín-Piñero and José Muñoz

Materials 2020, 13(16), 3486; https://doi.org/10.3390/ma13163486 - 7 Aug 2020

Cited by 12 | Viewed by 2298

Abstract

Emulsions can be used as delivery systems for bioactive ingredients for their incorporation in food products. Essential oils are natural compounds found in plants that present antioxidant and antimicrobial activity. Therefore, the main goal of this work was to develop emulsions, containing mandarin essential oil stabilized by two food-grade surfactants and guar gum, and to evaluate their physical stability. The initial droplet size of emulsions developed by microfluidization was optimized, obtaining diameters below one micron regardless of the processing conditions. However, the emulsion processed at 25,000 psi and one pass exhibited the lowest mean droplet sizes and polidispersity, and therefore, a higher stability. Different ratios of Tween 80 and Span 80 were assessed as stabilizers. Results obtained indicated that the ratio of surfactants had a significant effect on the mean droplet sizes, physical stability, and rheological properties. Thus, we found that the optimum ratio of surfactants was 75/25 (Tween80/Span80) on account of the lowest droplet mean diameters, lack of coalescence, and a low creaming rate. The rheological characterization of the stable emulsions showed a shear thinning flow behavior, and G″ (loss modulus) values higher than G′ (storage modulus) values, in all the frequency range. The rheological behavior may be governed by the guar gum, which was confirmed by field emission scanning electron microscopy (FESEM). This research can be considered as the starting point for future applications of mandarin essential oil in emulsions, which can be incorporated in products as food preservatives. Full article

(This article belongs to the Special Issue Advanced Research on Electrical, Optical, and Magnetic Nanoparticles, Nanowires, and Thin Films)

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15 pages, 4414 KiB

Open AccessFeature PaperArticle

Citrate and Polyvinylpyrrolidone Stabilized Silver Nanoparticles as Selective Colorimetric Sensor for Aluminum (III) Ions in Real Water Samples

by Paula Ruíz del Portal-Vázquez, Germán López-Pérez, Rafael Prado-Gotor, Cristina Román-Hidalgo and María Jesús Martín-Valero

Materials 2020, 13(6), 1373; https://doi.org/10.3390/ma13061373 - 18 Mar 2020

Cited by 4 | Viewed by 2330

Abstract

The use of silver nanoparticles stabilized with citrate and polyvinylpyrrolidone as a sensor for aluminum ions determination is proposed in this paper. These non-functionalized and specific nanoparticles provide a highly selective and sensitive detection system for aluminum in acidic solutions. The synthesized nanoparticles were characterized by transmission electron microscopy. Surface plasmon band deconvolution analysis was applied to study the interaction between silver nanoparticles and aluminum ions in solution. The interaction band in the UV-visible region was used as an analytical signal for quantitation purposes. The proposed detection system offers an effective AND wide linearity range (0.1–10³ nM), specificity for Al(III) in THE presence of other metallic ions in solution, as well as high sensitivity (limit of detection = 40.5 nM). The proposed silver-nanoparticles-based sensor WAS successfully used for detecting Al(III) in real water samples. Full article

(This article belongs to the Special Issue Advanced Research on Electrical, Optical, and Magnetic Nanoparticles, Nanowires, and Thin Films)

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10 pages, 4435 KiB

Open AccessArticle

Facile Synthesis of Sandwich-Like rGO/CuS/Polypyrrole Nanoarchitectures for Efficient Electromagnetic Absorption

by Bing Zhang, Shaofeng Lin, Jingjing Zhang, Xiaopeng Li and Xiaodong Sun

Materials 2020, 13(2), 446; https://doi.org/10.3390/ma13020446 - 17 Jan 2020

Cited by 14 | Viewed by 2125

Abstract

Currently, electromagnetic pollution management has gained much attention due to the various harmful effects on wildlife and human beings. Electromagnetic absorbers can convert energy from electromagnetic waves into thermal energy. Previous reports have demonstrated that reduced graphene oxide (rGO) makes progress in the electromagnetic absorption (EA) field. But the high value of permittivity of rGO always mismatches the impedance which results in more electromagnetic wave reflection on the surface. In this work, sandwich-like rGO/CuS/polypyrrole (PPy) nanoarchitectures have been synthesized by a facile two-step method. The experimental result has shown that a paraffin composite containing 10 wt.% of rGO/CuS/PPy could achieve an enhanced EA performance both in bandwidth and intensity. The minimum reflection loss (RL) value of −49.11 dB can be reached. Furthermore, the effective bandwidth can cover 4.88 GHz. The result shows that the as-prepared rGO/CuS/PPy nanoarchitectures will be a promising EA material. Full article

(This article belongs to the Special Issue Advanced Research on Electrical, Optical, and Magnetic Nanoparticles, Nanowires, and Thin Films)

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