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Photoresponsive polyvinylidene fluoride (PVDF) fibers doped with naphthopyran-functionalized silica nanoparticles (SiO2@NPT) were successfully prepared by dry–jet wet spinning. The incorporated photochromic nanomaterials, SiO2@S1 and SiO2@S2, were previously prepared by covalent post-grafting of the silylated NPTs – 2H-naphtho[1,2-b]pyran derivatives, S1 and S2 – onto nano-sized SiO2 (15 ± 3 nm). The morphological and chemical characterization of the resulting doped fibers PVDF@SiO2@S1 and PVDF@SiO2@S2 was evaluated by scanning electron microscopy with energy dispersive spectroscopy and Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). Both PVDF@SiO2@S1 and PVDF@SiO2@S2 fibers presented average diameters of 133 ± 8 μm and 98 ± 7 μm, respectively, and a porous outer surface. The presence of the SiO2@NPT within the fibers was confirmed through the observation of dense clusters embedded within the polymeric matrix. Furthermore, the FTIR-ATR spectra of the fibers revealed that the PVDF matrix was composed of α and β crystalline and amorphous phases. The PVDF@SiO2@S1 and PVDF@SiO2@S2 fibers showed photoresponsive properties under UV and sunlight irradiation, exhibiting fast coloration kinetics and good optical contrast (ΔE*ab = 7.2 and 15.1, respectively), and changing from a pale orange and an off-white color to a more intense yellow-orange and purple coloration, respectively, in less than 1 min. Moreover, they showed an initial fast bleaching, losing half of their color in less than 30 min (t1/2 = 28 and 20 min for PVDF@SiO2@S1 and PVDF@SiO2@S2 fibers, respectively), but displaying a residual coloration that took 1 and 2 h to return to the initial uncolored state (t3/4 = 95 and 49 min, respectively). The PVDF@SiO2@S2 fibers presented the best photochromic performance.

Coal fly ash (CFA) from different sources (CFA 5, 10, 13) and different size fractions (> or < 75 μm) were characterized and used as inorganic supports for sulfonic acid functionalization by two methodologies including one-pot organosilylation (CFA_CSPTMS) and two-step benzyl alcohol condensation followed by sulfonation (CFA_BnSO3H). The as-prepared organosulfonic CFAs were characterized by solid-state 1H, 13C and 29Si NMR spectroscopy, XPS, S content was quantified by elemental analysis and the intrinsic acidity was determined by potentiometric titration; the highest –SO3H content was obtained for CFA13_BnSO3H. All the functionalized CFAs were tested for the first time as acid solid catalysts in the esterification of levulinic acid (LA) a biomass platform molecule, in the presence of n-butanol. n-Butyl levulinate was the only product with conversions of 100% after 40 min. reaction and using the CFA13_BnSO3H as catalyst. This catalyst also exhibited the highest TOFs (447 h−1) and showed to be the most stable and reusable for 5 consecutive catalytic cycles. Fil: Peixoto, Andreia F.. Universidad de Porto; Portugal Fil: Silva, Sónia M.. No especifíca; Fil: Costa, Paula. No especifíca; Fil: Santos, Ana Claúdia. Universidad de Porto; Portugal Fil: Valentim, Bruno. Universidad de Porto; Portugal Fil: Lazaro Martinez, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentina Fil: Freire, Cristina. Universidad de Porto; Portugal

The conversion of nitroarenes to aminoarenes is of great industrial interest since they are prevalent pollutants in water and aminoarenes are important intermediates in the synthesis of pharmaceuticals, natural products and in bulk chemical production. In this work, two new catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) were prepared by immobilization of gold nanoparticles onto the surface of K10 montmorillonite clay (K10) functionalized with two new l -serine derivative organosilanes. Transmission electron microscopy showed the presence of 4–5 nm gold nanoparticles after catalysis. The reduction reaction of 4-NP to 4-AP at 25 °C, using NaBH4 as reducing agent, led to nearly 100% conversion in only 1 minute, presenting pseudo-first-order rate constants normalized for Au loading of K = 630 and 430 mmol−1 s−1. The catalysts showed high stability, leading to substrate conversions of 95–100% after 10 consecutive cycles, with negligible Au leaching.

Hydrothermal liquefaction (HTL) is a promising technology for the production of biocrude oil from microalgae. Although this catalyst-free technology is efficient under high-temperature and high-pressure conditions, the biocrude yield and quality can be further improved by using heterogeneous catalysts. The design of robust catalysts that preserve their performance under hydrothermal conditions will be therefore very important in the development of biorefinery technologies. In this work, we describe two different synthetic routes (i.e., impregnation and cyclodextrin-assisted one-pot colloidal approach), for the preparation in aqueous phase of six high surface area CoMo/γ-Al2O3 catalysts. Catalytic tests performed on the HTL of Nannochloropsis gaditana microalga indicate that solids prepared by the one-pot colloidal approach show higher hydrothermal stability and enhanced biocrude yield with respect to the catalyst-free test. The positive effect of the substitution of the block copolymer Tetronic T90R4 for Pluronic F127 in the preparation procedure was evidenced by diffuse reflectance UV-visible spectroscopy, X-ray diffraction, N2-adsorption-desorption, and H2-temperature-programmed reduction measurements and confirmed by the higher quality of the obtained biocrude, which exhibited lower oxygen content and higher-energy recovery equal to 62.5% of the initial biomass. © 2018 American Chemical Society.

Photochromic silica nanoparticles (SiO2@NPT), fabricated through the covalent immobilization of silylated naphthopyrans (NPTs) based on 2H-naphtho[1,2-b]pyran (S1, S2) and 3H-naphtho[2,1-b]pyran (S3, S4) or through the direct adsorption of the parent naphthopyrans (1, 3) onto silica nanoparticles (SiO2 NPs), were successfully incorporated onto cotton fabrics by a screen-printing process. Two aqueous acrylic- (AC-) and polyurethane- (PU-) based inks were used as dispersing media. All textiles exhibited reversible photochromism under UV and solar irradiation, developing fast responses and intense coloration. The fabrics coated with SiO2@S1 and SiO2@S2 showed rapid color changes and high contrasts (ΔE*ab = 39–52), despite presenting slower bleaching kinetics (2–3 h to fade to the original color), whereas the textiles coated with SiO2@S3 and SiO2@S4 exhibited excellent engagement between coloration and decoloration rates (coloration and fading times of 1 and 2 min, respectively; ΔE*ab = 27–53). The PU-based f...

Hybrid nanomaterials based on the covalent of silylated naphthopyrans (NPTs) onto silica nanoparticles (SiO2 NPs) were successfully prepared and studied as new photochromic materials. They were prepared by a two-step protocol consisting of (i) NPTs (derivatives from 2H-naphtho[1,2-b]pyran (2H-NPT) and 3H-naphtho-[2,1-b]pyran (3H-NPT)) silylation by a microwave-assisted reaction between hydroxyl-substituted NPTs and 3(triethoxysilyl)propyl isocyanate, followed by (ii) covalent post-grafting onto SiO2 NPs. In order to study the role-of the silylation step, the analogous non-silylated nanomaterials were also prepared by direct adsorption of NPTs. The characterization techniques confirmed the successful NPTs silylation and subsequent grafting to SiO2 NPs. All SiO2-based nanomaterials revealed photoswitching behavior, following a biexponential decay. The SiO2 NPs functionalized with silylated 3H-NPTs (SiO2@S3 and SiO2@S4) presented the most promising photochromic properties, showing fast coloration/decoloration kinetics (coloring in 1 min under UV irradiation and fading in only 2 min) and high values of total color difference (Delta E-ab* = 30-50). Also, the 2H-NPTs-based SiO2 NPs (SiO2@S1 and SiO2@S2) presented fast coloration and good color contrasts (Delta E-ab* = 54); but slower fading kinetic rates, taking more than 2 h to return to their initial color. In contrast, the SiO2 NPs functionalized with non-silylated NPTs (SiO2@1 and SiO2@3) showed weaker color contrasts (Delta E-ab* = 6-10) and slower fading kinetics, proving that the NPT silylation step was crucial to enhance the photochromic behavior of SiO2 NPs based on NPTs. Furthermore, the silylated-based nanomaterials showed good photostability upon prolonged UV light exposure) keeping their photochromic performance unchanged for at least 12 successive UV/dark cycles, anticipating interesting technological applications in several areas.