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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.
- Tailored 3D foams decorated with nanostructured manganese oxide for asymmetric electrochemical capacitorsPublication . Siwek, K. I.; Eugenio, S.; Aldama, I.; Rojo, J. M.; Amarilla, J. M.; Da Costa Ribeiro, Ana Paula; Moura E Silva, Teresa; Montemor, M.F.Tailored 3D (Ni and NiCo) metallic foam architectures were produced by electrodeposition and decorated via electrochemical routes with manganese oxide (MnOx) to serve as positive electrodes for supercapacitors. For comparative purposes, an electrode made of commercial Ni foam was also prepared. The foam-based electrodes were paired with a carbon cloth electrode and used to assemble asymmetric electrochemical cells. The electrochemical response of these cells was studied by applying different electrochemical techniques. In addition, two different protocols (cycling and floating) were applied to assess cells durability and fade. Despite the significant differences in the decorated foams morphology and structure their electrochemical responses revealed similar trends. The electrodes made of tailored foams showed higher specific capacitance, better capacitance retention at high current load and enhanced cycling stability compared to the electrodes made of commercial foam. The asymmetric cells made with the tailored foams revealed higher (maximum) specific energy (11-14 Wh kg(-1)) and specific power (1.3-1.4 x 10(4 )W kg(-1)) compared to cells assembled with commercial foams (8.4 Wh kg(-1) and 6.3 x 10(3) W kg(-1)). The durability tests evidenced that corrosion of the NiCo electrodeposited foams and electrochemical dissolution of MnOx are possible causes of cells degradation.
- 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.
- Mechanochemical preparation of Pd(II) and Pt(II) composites with carbonaceous materials and their application in the Suzuki-Miyaura reaction at several energy inputsPublication . Soliman, Mohamed Mostafa Aboelhassan; Peixoto, Andreia F.; Da Costa Ribeiro, Ana Paula; Kopylovich, Maximilian; Alegria, Elisabete; Pombeiro, ArmandoPd(II) and Pt(II) composites with activated carbon (AC), graphene oxide, and multiwalled carbon nanotubes were prepared by ball milling and used as catalysts for the Suzuki-Miyaura reaction, under several energy inputs (mechanical grinding, conventional heating, and microwave irradiation). The catalytic composites were characterized by ICP-MS, BET, XPS analyses, TEM, and SEM. The average particle size of the prepared composites was estimated to be in the range of 6-30 nm, while the loadings of Pd and Pt did not significantly affect the surface area of the AC support due to the tendency to agglomerate as observed by the TEM analysis. The Pd/AC composites exhibit high mechanochemical catalytic activity in cross-coupling of bromobenzene and phenylboronic acid with molar yields up to 80% with TON and TOF of 222 and 444 h(-1), respectively, achieved with Pd(4.7 wt%)-AC catalyst under the liquid assisted grinding for 0.5 h at ambient conditions, using cyclohexene as an additive.
- Characterization of AuNPs+rGO as a functionalized layer for LSPR sensorsPublication . Fantoni, Alessandro; Stojkovic, Vladan; Carvalho, Ana; Da Costa Ribeiro, Ana Paula; Alegria, ElisabeteGraphene-based materials have been extensively explored in recent years as valuable candidates as the key material for novel structures in the field, among many other applications, of sensing devices. This work reports a study about the applicability of rGO as a support for gold nanoparticles (AuNPs) prepared with an economic and eco-friendly method using phytochemicals present in tea extract at room temperature. The overall analysis is supported by simulation results about the LSPR effect in AuNPs-rGO, obtained by Mie theory and FDTD method. The residual phytochemicals are analysed as capping agent of the nanoparticles and their influence on the LSPR properties of the nanoparticles is outlined. The resulting composite is suitable for application as a low-cost sensing layer in biomedical LSPR sensor devices.
- ZnO nanoparticles: An efficient catalyst for transesterification reaction of alpha-keto carboxylic estersPublication . Soliman, Mohamed Mostafa Aboelhassan; Karmakar, Anirban; Alegria, Elisabete; Da Costa Ribeiro, Ana Paula; Rubio, Guilherme; Saraiva, Marta S.; Guedes Da Silva, M. Fátima C.; Pombeiro, ArmandoPure ZnO nanoparticles were synthesized by a sustainable precipitation method using zinc nitrate and sodium hydroxide in aqueous medium at room temperature. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis) spectroscopy and Brunauer-Emmett-Teller (BET) analysis. The XRD patterns indicate the formation of the hexagonal wurtzite phase with high purity and SEMEDS analysis confirm the purity and a homogenous distribution of the nanostructures. The ZnO nanostructures present plate-like agglomerates, resulting in a quasi-spherical morphology. The catalytic activity of the formed ZnO nanoparticles was evaluated towards the transesterification reaction of different carboxylic esters in the presence of various alcohols. This catalyst is highly selective for the transesterification of alpha-keto carboxylic ester (methyl benzoylformate) and leads to ca. 97% of product yield within 24 h of reaction time.
- Green synthesis of zinc oxide particles with apple-derived compounds and their application as catalysts in the transesterification of methyl benzoatesPublication . Soliman, Mohamed Mostafa Aboelhassan; Alegria, Elisabete; Da Costa Ribeiro, Ana Paula; Alves, Marta M; Saraiva, Marta S.; Montemor, M.F.; Pombeiro, ArmandoZnO nanoparticles (ZnONPs) were successfully synthesized using bravo-de-esmolfe apple extract in aqueous medium at room temperature. ZnO microparticles, prepared with a pure apple phytochemical, quercetin (ZnOq), or without phytochemicals (ZnO) were studied for comparative purposes. The re-use of apple waste for highly efficient catalyst production, based on green synthetic routes, can be added to the concept of a circular economy. The synthesized ZnO particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N-2 adsorption/desorption Brunauer- Emmett-Teller (BET) theory. The XRD patterns indicated the formation of a hexagonal wurtzite phase with high purity and SEM and TEM analyses revealed the morphology of the particles. The apple extract produced spherical ZnONPs composed of round lamina-like structures, similar to the micro sized lamina-like shape of ZnOq and dissimilar to the flower-like shape of ZnO. The green synthesized ZnO nanoparticles (ZnONPs) led to a high product yield of ca. 96% within 24 h of reaction time in the transesterification reaction of different carboxylic esters.