Raquel Diana Carneiro Alves

Study and Characterization of a Novel Polymer Electrolyte Based on Agar Doped with Magnesium Triflate

In the present work one host natural matrix – agar – has been doped with magnesium triflate (Mg(CF3SO3)2) with the goal of developing electrolytes for the fabrication of solid-state devices. The resulting samples have been represented by the notation AgarnMg(CF3SO3)2, where n represents the percentage of the magnesium triflate salt proportion in the electrolyte samples. The samples investigated, with n between 0.00% and 37.56%, have been obtained as transparent and thin films. The samples have been characterized by conductivity measurements, thermal analysis, cyclic voltammetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The agar-based electrolytes were also tested as ionic conductor in an electrochromic device with the following configuration: glass/indium tin oxide (ITO)/WO3/agar-based electrolyte/CeO2–TiO2/ITO/glass.

The Influence of Glycerol and Formaldehyde in Gelatin-Based Polymer Electrolytes

In the present work, one host natural matrix – gelatin – has been doped with magnesium triflate (Mg(CF3SO3)2). Using gelatin as host polymer and magnesium triflate as salt, thin films were produced by varying the amount of glycerol and formaldehyde. The behavior of the samples produced was evaluated using techniques such as thermal analysis (thermogravimetric analysis – TGA and differential scanning calorimetry – DSC), complex impedance spectroscopy, and electrochemical stability. The electrolyte films produced were obtained as transparent and amorphous samples with encouraging electrochemical and thermal properties.

Luminescent polymer electrolytes based on chitosan and containing europium triflate

Abstract Solid polymer electrolytes based on chitosan and europium triflate were prepared by solvent casting and characterized by X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM), and photoluminescence spectroscopy. The X-ray diffraction exhibited that the samples were essentially amorphous with organized regions over the whole range of the salt content studied. The AFM analysis demonstrated that the smoother sample had roughness of 4.39 nm. Surface visualization through SEM revealed good homogeneity without any phase separation for more conductive samples and the less conductive showed some imperfections on the surface. The emission and excitation spectra displayed the characteristic bands of Eu(CF 3 SO 3 ) 3 in addition to broad bands corresponding to the polymer host. The excited state 5 D 0 lifetime values ranged from 0.29–0.37 ms for the studied samples.

Eco-friendly luminescent hybrid materials based on EuIII and LiI co-doped chitosan

Biopolymer-based materials have been of particular interest as alternatives to synthetic polymers due to their low toxicity, biodegradability and biocompatibility. Among them, chitosan is one of the most studied ones and has recently been investigated for the application as solid state polymer electrolytes. Furthermore, it can serve as a host for luminescent species such as rare earth ions, opening up the possibility of combined electro-optical functionality, of particular interest for electroluminescent devices. In this study, we perform a fundamental, initial, investigation of chitosan based luminescent materials doped with EuIII and LiI triflate salts, from the structural, photophysical and conducting points of view. Because the host presents a broad emission band in the blue to green, while EuIII emits in the red, fine-tuning of emission colour and/or generation of white light is proven possible, by proper combination of optimized composition and excitation scheme. Europium lifetimes (5D0) are in the range 270-350 µs and quantum yields are up to 2%. Although LiI does not interfere with the luminescent properties, it grants ion-conducting properties to the material suggesting that a combination of both properties could be useful in the development of electro-luminescent devices.

Natural Membranes for Application in Biomedical Devices

Polymers from natural sources are particularly useful as biomaterials for medical devices applications. In this study, the results of characterization of a gelatin network electrolyte doped with europium triflate (Eu(CF3SO3)3) are described. The unusual electronic properties of the trivalent lanthanide ions make them well suited as luminescent reporter groups, with many applications in biotechnology. Samples of solvent-free electrolytes were prepared with a range of guest salt concentration. Materials based on Eu(CF3SO3)3 were obtained as mechanically robust, flexible, transparent, and completely amorphous films. Samples were characterized by thermal analysis (thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC), electrochemical stability, scanning electron microscopy (SEM), and photoluminescence spectroscopy.