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- Ultrasound and radiation-induced catalytic oxidation of 1-phenylethanol to acetophenone with iron-containing particulate catalystsPublication . Soliman, Mohamed Mostafa Aboelhassan; Kopylovich, Maximilian N.; Alegria, Elisabete; Da Costa Ribeiro, Ana Paula; Ferraria, Ana Maria; Rego, Ana; Correia, Luís M. M.; Saraiva, Marta S.; Pombeiro, ArmandoIron-containingparticulatecatalystsof0.1–1 µmsizewerepreparedbywetandball-milling procedures from common salts and characterized by FTIR, TGA, UV-Vis, PXRD, FEG-SEM, and XPS analyses. It was found that when the wet method was used, semi-spherical magnetic nanoparticles were formed, whereas the mechanochemical method resulted in the formation of nonmagnetic microscale needles and rectangles. Catalytic activity of the prepared materials in the oxidation of 1-phenylethanol to acetophenone was assessed under conventional heating, microwave (MW) irradiation, ultrasound (US), and oscillating magnetic field of high frequency (induction heating). In general, the catalysts obtained by wet methods exhibit lower activities, whereas the materials prepared by ball milling afford better acetophenone yields (up to 83%). A significant increase in yield (up to 4 times) was observed under the induction heating if compared to conventional heating. The study demonstrated that MW, US irradiations, and induction heating may have great potential as alternative ways to activate the catalytic system for alcohol oxidation. The possibility of the synthesized material to be magnetically recoverable has been also verified.
- Processing of poly(ionic liquid)-ionic liquid membranes using femtosecond (fs) laser radiation: Effect on CO2 separation performancePublication . Gouveia, Andreia S.L.; Oliveira, Vitor; Ferraria, Ana Maria; Rego, Ana; Ferreira, Maria João; Tomé, Liliana C.; Almeida, Amélia; Marrucho, I. M.Femtosecond (fs) laser micromachining on polymeric materials is a single-step, and contactless manufacturing technology. Knowing the potential of poly(ionic liquid)s (PILs) and their derived composite materials incorporating ionic liquids (PIL-IL) to design membranes with improved CO2 separation, we here explore for the first time the creation of microchannels on the surface of PIL-IL materials by laser ablation using femtosecond laser radiation. PIL-IL membranes composed of pyrrolidinium-based PILs containing the [NTf2](-) and [C(CN)(3)](-) anions and different amounts of their corresponding ILs (40 and 60 wt%) were prepared and micromachined using fs laser pulses varying the pulse repetition rate, scanning speed, and pulse energy. The morphology of the fs laser modified PIL-IL samples was investigated through scanning electron microscopy (SEM), while the influence of the fs laser processing on the membranes structure was analyzed by solid-state nuclear magnetic resonance (ssNMR), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The CO2/N-2 and CO2/H-2 separation performances of the irradiated membranes were also evaluated and compared to those of the non-irradiated. Depending on the parameters used, fs laser processing was successful in modifying the surface of PIL-IL membranes through the formation of microchannels around 55-60 mu m deep. Significant improvements in CO2, N-2 and H-2 permeabilities were achieved for the irradiated PIL-IL membranes, maintaining their CO2/N-2 and CO2/H-2 permselectivities.
- Effect of graphene vs. reduced graphene oxide in gold nanoparticles for optical biosensors: a comparative studyPublication . Carvalho, Ana P. G.; Alegria, Elisabete; Fantoni, Alessandro; Ferraria, Ana Maria; Rego, Ana; Da Costa Ribeiro, Ana PaulaAiming to develop a nanoparticle-based optical biosensor using gold nanoparticles (AuNPs) synthesized using green methods and supported by carbon-based nanomaterials, we studied the role of carbon derivatives in promoting AuNPs localized surface plasmon resonance (LSPR), as well as their morphology, dispersion, and stability. Carbon derivatives are expected to work as immobilization platforms for AuNPs, improving their analytical performance. Gold nanoparticles (AuNPs) were prepared using an eco-friendly approach in a single step by reduction of HAuCl4·3H2O using phytochemicals (from tea) which act as both reducing and capping agents. UV–Vis spectroscopy, transmission electron microscopy (TEM), zeta potential (ζ-potential), and X-ray photoelectron spectroscopy (XPS) were used to characterize the AuNPs and nanocomposites. The addition of reduced graphene oxide (rGO) resulted in greater dispersion of AuNPs on the rGO surface compared with carbon-based nanomaterials used as a support. Differences in morphology due to the nature of the carbon support were observed and are discussed here. AuNPs/rGO seem to be the most promising candidates for the development of LSPR biosensors among the three composites we studied (AuNPs/G, AuNPs/GO, and AuNPs/rGO). Simulations based on the Mie scattering theory have been used to outline the effect of the phytochemicals on LSPR, showing that when the presence of the residuals is limited to the formation of a thin capping layer, the quality of the plasmonic resonance is not affected. A further discussion of the application framework is presented.
- New trendy magnetic C-scorpionate iron catalyst and its performance towards cyclohexane oxidationPublication . Da Costa Ribeiro, Ana Paula; Matias, Inês; Alegria, Elisabete; Ferraria, Ana Maria; Rego, Ana; Pombeiro, Armando; Martins, LuisaFor the first time, a magnetic C-scorpionate catalyst was prepared from the iron(II) complex [FeCl2{_3-HC(pz)3}] (pz = pyrazol-1-yl) and ferrite, using the sustainable mechanochemical synthetic procedure. Its catalytic activity for the cyclohexane oxidation with tert-butyl hydroperoxide (TBHP) was evaluated in different conditions, namely under microwave irradiation and under the effect of an external magnetic field. The use of such magnetic conditions significantly shifted the catalyst alcohol/ketone selectivity, thus revealing a promising, easy new protocol for tuning selectivity in important catalytic processes.
- Effect of phenolic compounds on the synthesis of gold nanoparticles and its catalytic activity in the reduction of nitro compoundsPublication . Alegria, Elisabete; Da Costa Ribeiro, Ana Paula; Mendes, Marta; Ferraria, Ana Maria; Rego, Ana; Pombeiro, ArmandoGold nanoparticles (AuNPs) were prepared using an eco-friendly approach in a single step by reduction of HAuCl4 with polyphenols from tea extracts, which act as both reducing and capping agents. The obtained AuNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). They act as highly efficient catalysts in the reduction of various aromatic nitro compounds in aqueous solution. The effects of a variety of factors (e.g., reaction time, type and amount of reducing agent, shape, size, or amount of AuNPs) were studied towards the optimization of the processes. The total polyphenol content (TPC) was determined before and after the catalytic reaction and the results are discussed in terms of the tea extract percentage, the size of the AuNPs, and their catalytic activity. The reusability of the AuNP catalyst in the reduction of 4-nitrophenol was also tested. The reactions follow pseudo first-order kinetics.
- Comparison of microwave and mechanochemical energy inputs in the catalytic oxidation of cyclohexanePublication . Da Costa Ribeiro, Ana Paula; Alegria, Elisabete; Kopylovich, Maximilian; Ferraria, Ana Maria; Rego, Ana; Pombeiro, ArmandoThe effect of microwave and mechanochemical ball milling energy inputs was studied for the peroxidative oxidation (with aqueous H2O2) of cyclohexane to cyclohexanol and cyclohexanone, over CoCl2 and/or V2O5 dispersed (μm scale) catalysts. A maximum total yield of cyclohexanol and cyclohexanone of 43% after 1 h of reaction at 30 °C, in acetonitrile and under microwave irradiation (5 W), was achieved over the CoCl2–V2O5 (3 : 1) catalyst prepared by ball milling. Cyclohexanol is the main final product with a selectivity of up to 93% over cyclohexanone. Conducting the oxidation reaction under microwave irradiation under the same conditions but without any mechanochemical treatment of the catalyst prior to use resulted in a lower total yield of 30% with a lower selectivity (69%) towards cyclohexanol over cyclohexanone. The sole application of mechanochemical treatment for the catalyst preparation and the catalytic oxidation of cyclohexane allowed to reach yields of 29% after 1 h of reaction, at room temperature, without microwave irradiation and any additive and in the absence of any organic solvent. Ball milling is shown to provide a convenient, solvent-free method to disperse these solid catalysts and to promote the above cyclohexane oxidation, although, in the latter case, not so effectively as microwave irradiation.
- Luminescent carbon dots from wet olive pomace: structural insights, photophysical properties and cytotoxicityPublication . Sousa, Diogo A.; Ferreira, L.F. Vieira; Fedorov, Alexander A.; Rego, Ana; Ferraria, Ana Maria; Cruz, Adriana; Berberan-Santos, Mario; Prata, José V.Carbon nanomaterials endowed with significant luminescence have been synthesized for the first time from an abundant, highly localized waste, the wet pomace (WP), a semi-solid by-product of industrial olive oil production. Synthetic efforts were undertaken to outshine the photoluminescence (PL) of carbon nanoparticles through a systematic search of the best reaction conditions to convert the waste biomass, mainly consisting in holocellulose, lignin and proteins, into carbon dots (CDs) by hydrothermal carbonization processes. Blue-emitting CDs with high fluorescence quantum yields were obtained. Using a comprehensive set of spectroscopic tools (FTIR, Raman, XPS, and 1H/13C NMR) in combination with steady-state and time-resolved fluorescence spectroscopy, a rational depiction of WP-CDs structures and their PL properties was reached. WP-CDs show the up-conversion of PL capabilities and negligible cytotoxicity against two mammalian cell lines (L929 and HeLa). Both properties are excellent indicators for their prospective application in biological imaging, biosensing, and dynamic therapies driven by light.
- Processing of poly(ionic liquid)-ionic liquid membranes using femtosecond (fs) laser radiation: Effect on CO2 separation performancePublication . Gouveia, Andreia S.L.; Oliveira, Vitor; Ferraria, Ana Maria; Rego, Ana; Ferreira, Maria João; Tomé, Liliana C.; Almeida, Amélia; Marrucho, I. M.Femtosecond (fs) laser micromachining on polymeric materials is a single-step, and contactless manufacturing technology. Knowing the potential of poly(ionic liquid)s (PILs) and their derived composite materials incorporating ionic liquids (PIL-IL) to design membranes with improved CO2 separation, we here explore for the first time the creation of microchannels on the surface of PIL-IL materials by laser ablation using femtosecond laser radiation. PIL-IL membranes composed of pyrrolidinium-based PILs containing the [NTf2](-) and [C(CN)(3)](-) anions and different amounts of their corresponding ILs (40 and 60 wt%) were prepared and micromachined using fs laser pulses varying the pulse repetition rate, scanning speed, and pulse energy. The morphology of the fs laser modified PIL-IL samples was investigated through scanning electron microscopy (SEM), while the influence of the fs laser processing on the membranes structure was analyzed by solid-state nuclear magnetic resonance (ssNMR), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The CO2/N-2 and CO2/H-2 separation performances of the irradiated membranes were also evaluated and compared to those of the non-irradiated. Depending on the parameters used, fs laser processing was successful in modifying the surface of PIL-IL membranes through the formation of microchannels around 55-60 mu m deep. Significant improvements in CO2, N-2 and H-2 permeabilities were achieved for the irradiated PIL-IL membranes, maintaining their CO2/N-2 and CO2/H-2 permselectivities.
- Processing of poly(ionic liquid)-ionic liquid membranes using femtosecond (fs) laser radiation: Effect on CO2 separation performancePublication . Gouveia, Andreia S.L.; Oliveira, Vitor; Ferraria, Ana Maria; Rego, Ana; Ferreira, Maria João; Tomé, Liliana C.; Almeida, Amélia; Marrucho, I. M.Femtosecond (fs) laser micromachining on polymeric materials is a single-step, and contactless manufacturing technology. Knowing the potential of poly(ionic liquid)s (PILs) and their derived composite materials incorporating ionic liquids (PIL-IL) to design membranes with improved CO2 separation, we here explore for the first time the creation of microchannels on the surface of PIL-IL materials by laser ablation using femtosecond laser radiation. PIL-IL membranes composed of pyrrolidinium-based PILs containing the [NTf2](-) and [C(CN)(3)](-) anions and different amounts of their corresponding ILs (40 and 60 wt%) were prepared and micromachined using fs laser pulses varying the pulse repetition rate, scanning speed, and pulse energy. The morphology of the fs laser modified PIL-IL samples was investigated through scanning electron microscopy (SEM), while the influence of the fs laser processing on the membranes structure was analyzed by solid-state nuclear magnetic resonance (ssNMR), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The CO2/N-2 and CO2/H-2 separation performances of the irradiated membranes were also evaluated and compared to those of the non-irradiated. Depending on the parameters used, fs laser processing was successful in modifying the surface of PIL-IL membranes through the formation of microchannels around 55-60 mu m deep. Significant improvements in CO2, N-2 and H-2 permeabilities were achieved for the irradiated PIL-IL membranes, maintaining their CO2/N-2 and CO2/H-2 permselectivities.