José Carlos Germino

Ag Nanoparticles-Based Zinc Hydroxide-Layered Hybrids as Novel and Efficient Catalysts for Reduction of 4-Nitrophenol to 4-Aminophenol

Silver nanoparticles and zinc hydroxide-layered hybrid materials (AgNPs/ZHL) have been successfully developed as efficient catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with sodium borohydride. A facile and rapid visible-light assisted green route was used for the deposition of silver nanoparticles (AgNPs) on the external surface of ZHL material. The resulting AgNPs/ZHL hybrids contained AgNPs with spherical morphology and uniform size distribution. Moreover, the AgNPs/ZHL compounds exhibited excellent catalytic performance (the reduction reaction was finished within 4 min) and reusability (three cycles) toward the reduction of 4-NP to 4-AP in presence of sodium borohydride. The reduction reaction obeyed the pseudo-first-order kinetics. The rate constants increased with the increase of amount of the AgNPs deposited into the hybrid materials. These results suggest that the as-prepared catalysts (AgNPs/ZHL) have great potential for heterogeneous catalytic applications.

Electronic and Magnetic Properties of the [Ni(salophen)]: an Experimental and DFT Study

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Color tunable hybrid light-emitting diodes based on perovskite quantum dot/conjugated polymer

Inorganic organic metal halide perovskite materials have been investigated for several technological applications, such as photovoltaic cells, lasers, photodetectors and light emitting diodes (LEDs), either in the bulk form or as colloidal nanoparticles. Recently, all inorganic Cesium Lead Halide (CsPbX3, X=Cl,Br, I) perovskite quantum dots (PQDs) were reported with high photoluminescence quantum yield with narrow emission lines in the visible wavelengths. Here, green-emitting perovskite quantum dots (PQDs) prepared by a synthetic method based on a mixture of oleylamine and oleic acid as surfactants were applied in the electroluminescent layer of hybrid LEDs in combination with two different conjugated polymers: polyvinylcarbazole (PVK) or poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO). The performance of the diodes and the emission color tuning upon dispersion of different concentrations of the PQDs in the polymer matrix is discussed. The presented approach aims at the combination of the optical properties of the PQDs and their interaction with wide bandgap conjugated polymers, associated with the solution processing ability of these materials.

Exfoliation of zinc-layered hydroxide by luminescent conjugate polyelectrolyte: synthesis and photophysical aspects

Exfoliation of layered materials is of significant interest for both the fundamental scientific studies and technological applications. In this work, the π-conjugated polymer, poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene] potassium (MSP-PPV), was intercalated/exfoliated between the lamellae of the zinc-layered hydroxide (ZHL) to produce luminescent hybrid materials. This process is highly attractive because the intercalation/exfoliation of the MSP-PPV polymer in the sheets of zinc-layered hydroxide was realized by anionic exchange at room temperature. Depending on the amount of polyelectrolyte used in the preparation of the hybrid compounds (MPS-PPV/ZHL), the intercalation reaction was followed by exfoliation of the zinc-layered hydroxide layers. At higher MSP-PPV concentration used in the experiment, the resulting material presented a high degree of exfoliation of the zinc-layered hydroxide sheets, as suggested by both the X-ray diffraction and scanning electron microscopic images. Elemental analysis, nuclear magnetic resonance and Fourier transform infrared spectroscopy also confirmed the interaction between MSP-PPV anionic polyelectrolyte and the sheets of zinc-layered hydroxide matrix. In addition, in order to better understand the photoluminescent behavior, a complete characterization of optical properties of the MSP-PPV/ZHL hybrids was also performed. Due to the MPS-PPV presence, all hybrid materials showed absorption bands in the visible region (≈450 m) with emission band in the green region (≈560 m). Moreover, the photophysical properties of the MSP-PPV intercalated/exfoliated can be easily tuned by changing their concentration demonstrating that the zinc-layered hydroxide material plays an important role in preventing the aggregation and photostability of the anionic polyelectrolyte.Graphical Abstract