Plasticized pectin-based gel electrolytes

Pectin is a natural polymer present in plants and, as all natural polymers has biodegradation properties. Chemically, pectin is a polysaccharide composed of a linear chain of 1 -> 4 linked galacturonic acids, which is esterified with methanol at 80%. The pectin-based gel electrolytes in a transparent film form were obtained by a plasticization process with glycerol and addition of LiClO(4). The films showed good ionic conductivity results, which increased from 10(-5) S/cm for the samples with 37 wt.% of glycerol to 4.7 x 10(-4) S/cm at room temperature for the sample with 68 wt.% of glycerol. The electrochemical behaviors of the samples were studied by electrochemical impedance spectroscopy (EIS), and Nyquist graphs are showed and discussed. The obtained pectin-based samples also presented good adherence to the glass, flexibility, homogeneity (SEM) and transparency (about 70% in the vis) properties. They are good candidates to be applied as gel electrolytes in electrochromic devices. (C) 2009 Elsevier Ltd. All rights reserved.

Integrated analysis of halogenated organic pollutants in sub-millilitre volumes of venous and umbilical cord blood sera

A rapid, robust and economical method for the analysis of persistent halogenated organic compounds in small volumes of human serum and umbilical cord blood is described. The pollutants studied cover a broad range of molecules of contemporary epidemiological and legislative concern, including polychlorobiphenyls (PCBs), polychlorobenzenes (CBs), hexachlorocyclohexanes (HCHs), DDTs, polychlorostyrenes (PCSs) and polybromodiphenyl ethers (PBDEs). Extraction and clean-up with n-hexane and concentrated sulphuric acid was followed with analysis by gas chromatography coupled to electron capture (GC-ECD) and GC coupled to negative ion chemical ionisation mass spectrometry (GC-NICI-MS). The advantages of this method rest in the broad range of analytes and its simplicity and robustness, while the use of concentrated sulphuric acid extraction/clean-up destroys viruses that may be present in the samples. Small volumes of reference serum between 50 and 1000 μL were extracted and the limits of detection/quantification and repeatability were determined. Recoveries of spiked compounds for the extraction of small volumes (≥300 μL) of the spiked reference serum were between 90% and 120%. The coefficients of variation of repeatability ranged from 0.1-14%, depending on the compound. Samples of 4-year-old serum and umbilical cord blood (n = 73 and 40, respectively) from a population inhabiting a village near a chloro-alkali plant were screened for the above-mentioned halogenated pollutants using this method and the results are briefly described. © 2010 Springer-Verlag.

Nanopartículas de CeO2 modificadas com Er obtidas pelo método hidrotermal microondas: estudo fotoluminescente

The development of nanostructured materials have aroused great interest of the industries all over the country, since they enable the development of devices that can be used as gate insulators on silicon transistors, electrochromic devices, solid electrolyte oxygen sensors and as a photoluminescent materials . In this project, it is proposed to investigate the optical properties of CeO2 modified with rare earth Er processed in hydrothermal-microwave. The synthesis of one-dimensional nanostructures (1D) was measured from dilute aqueous solutions of acids and salts of starting reagents in the presence of chemical basis, after these aqueous solutions were processed on hydrothermal-microwave to particle growth. The particles obtained after processing were characterized by X-ray Diffraction, Rietveld Analysis and Raman Spectroscopy. The particle morphology was observed by scanning electron microscopy with field emission gun. The synthesis of 1D nanostructures are evaluated for different surfactants and starting precursors (ceria different salts), pH, temperature and pressure which can modify the morphology of the nanostructures. Combining laboratory experiments and theoretical calculations it was desired to understand the organization of the nanoparticles and their resulting structure. Strict control of chemical homogeneity, crystal structure, microstructure and interaction of the CeO2 cluster with different surfactants using the Hartree-Fock method, was intended to obtain properties compatible with their use in catalysts and optical devices. The use of mineralizer agent KOH and 8 minutes of processing time synthesis conditions were chosen to evaluate the effect of Er dopant. It has been proved that this doping with rare earth increases the photoluminescent properties of the compound obtained without change the structural and morphological propreties of ceria

Nanopartículas de CeO2 modificadas com Er obtidas pelo método hidrotermal microondas: estudo fotoluminescente

The development of nanostructured materials have aroused great interest of the industries all over the country, since they enable the development of devices that can be used as gate insulators on silicon transistors, electrochromic devices, solid electrolyte oxygen sensors and as a photoluminescent materials . In this project, it is proposed to investigate the optical properties of CeO2 modified with rare earth Er processed in hydrothermal-microwave. The synthesis of one-dimensional nanostructures (1D) was measured from dilute aqueous solutions of acids and salts of starting reagents in the presence of chemical basis, after these aqueous solutions were processed on hydrothermal-microwave to particle growth. The particles obtained after processing were characterized by X-ray Diffraction, Rietveld Analysis and Raman Spectroscopy. The particle morphology was observed by scanning electron microscopy with field emission gun. The synthesis of 1D nanostructures are evaluated for different surfactants and starting precursors (ceria different salts), pH, temperature and pressure which can modify the morphology of the nanostructures. Combining laboratory experiments and theoretical calculations it was desired to understand the organization of the nanoparticles and their resulting structure. Strict control of chemical homogeneity, crystal structure, microstructure and interaction of the CeO2 cluster with different surfactants using the Hartree-Fock method, was intended to obtain properties compatible with their use in catalysts and optical devices. The use of mineralizer agent KOH and 8 minutes of processing time synthesis conditions were chosen to evaluate the effect of Er dopant. It has been proved that this doping with rare earth increases the photoluminescent properties of the compound obtained without change the structural and morphological propreties of ceria

Novel polymer electrolytes based on gelatin and ionic liquids

This study describes the results of the characterization of polymer electrolytes using gelatin matrix doped with europium triflate and/or different ionic liquids. Samples of solvent-free electrolytes were prepared and characterized by ionic conductivity measurements, thermal analysis, electrochemical stability, X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy. Electrolyte samples are thermally stable up to approximately 220 degrees C. All the materials synthesized are totally amorphous. The room temperature conductivity maximum of this electrolyte system is based on ionic liquid 1-ethyl-3-methylimidazolium acetate, (C(2)mim)(OAc) (1.18 x 10(-4) S cm(-1) at 30 degrees C). The electrochemical stability domain of all samples is about 2.0 V versus Li/Li+. This new series of materials represents a promising alternative in polymer electrolytes research field. The preliminary studies carried out with electrochromic devices (ECDs) incorporating optimized compositions have confirmed that these materials may perform as satisfactory multifunctional component layers in the field of "smart windows". This new materials, will open a land of promising applications in many areas: optics, energy, medicine for example as membranes and separation devices, ECD-based devices, sensors, etc. (C) 2012 Elsevier B.V. All rights reserved.

Nanochromics: old materials, new structures and architectures for high performance devices

Due to the development of nanoscience, the interest in electrochromism has increased and new assemblies of electrochromic materials at nanoscale leading to higher efficiencies and chromatic contrasts, low switching times and the possibility of color tuning have been developed. These advantages are reached due to the extensive surface area found in nanomaterials and the large amount of organic electrochromic molecules that can be easily attached onto inorganic nanoparticles, as TiO2 or SiO2. Moreover, the direct contact between electrolyte and nanomaterials produces high ionic transfer rates, leading to fast charge compensation, which is essential for high performance electrochromic electrodes. Recently, the layer-by-layer technique was presented as an interesting way to produce different architectures by the combination of both electrochromic nanoparticles and polymers. The present paper shows some of the newest insights into nanochromic science.

Dual-phase inkjet printed electrochromic layers based on PTA and WOX/TiO2 nanoparticles for electrochromic applications

Thesis submitted in Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa for the degree of Master in Materials Engineering

Electrostatic layer-by-layer and electrophoretic depositions as methods for electrochromic nanoparticle immobilization

The present paper describes the immobilization of nanoparticles onto conducting substrates by using both electrostatic layer-by-layer and electrophoretic deposition (EPD) methods. These two techniques were compared in high-performance electrochromic electrodes based on mixed nickel hydroxide nanoparticles. In addition to easy handling, EPD seems to be the most suitable method for the immobilization of nanoparticles, leading to higher electrochromic efficiencies, lower response times and higher stability upon coloration and bleaching cycling. (C) 2008 Elsevier Ltd. All rights reserved.

Gelatin-based protonic electrolyte for electrochromic windows

Proton-conducting gel polymer electrolytes based on gelatin plasticized with glycerol and containing acetic acid were investigated, characterized, and applied to electrochromic window. For glycerol contents varying from 7% to 48%, the conductivity of the uniform and predominantly amorphous gel electrolyte was found to follow a Vogel-Tamman-Fulcher behavior with the temperature. Typically, for the electrolyte chosen to make 7 x 2 cm(2) electrochromic smart window with the configuration: glass/fluor-doped tin oxide (FTO)/WO(3)/gelatin electrolyte/CeO(2)-TiO(2)/FTO/glass and containing 28% of glycerol, the conductivities were found to be of the order of 5 x 10(-5) S/cm at room temperature and 3.6 x 10(-4) S/cm at 80 A degrees C. The device was characterized by spectroelectrochemical techniques and was tested up to 10,000 cycles showing a fast coloring/bleaching behavior, where the coloring process was achieved in 10 s and the bleaching in 2 s. The transmission variation at the wavelength of 550 nm was about 15%. The cyclic voltammograms showed a very good reversibility of the cathodic/anodic processes, and the charge density was about 3.5 mC/cm(2). The memory tests showed that the transmittance in the colored state increased by 8% in 90 min after removing the potential.

Optical Characterization and Optimization of Display Components : Some Applications to Liquid-Crystal-Based and Electrochromics-Based Devices

This dissertation is focused on theoretical and experimental studies of optical properties of materials and multilayer structures composing liquid crystal displays (LCDs) and electrochromic (EC) devices. By applying spectroscopic ellipsometry, we have determined the optical constants of thin films of electrochromic tungsten oxide (WOx) and nickel oxide (NiOy), the films’ thickness and roughness. These films, which were obtained at spattering conditions possess high transmittance that is important for achieving good visibility and high contrast in an EC device. Another application of the general spectroscopic ellipsometry relates to the study of a photo-alignment layer of a mixture of azo-dyes SD-1 and SDA-2. We have found the optical constants of this mixture before and after illuminating it by polarized UV light. The results obtained confirm the diffusion model to explain the formation of the photo-induced order in azo-dye films. We have developed new techniques for fast characterization of twisted nematic LC cells in transmissive and reflective modes. Our techniques are based on the characteristics functions that we have introduced for determination of parameters of non-uniform birefringent media. These characteristic functions are found by simple procedures and can be utilised for simultaneous determination of retardation, its wavelength dispersion, and twist angle, as well as for solving associated optimization problems. Cholesteric LCD that possesses some unique properties, such as bistability and good selective scattering, however, has a disadvantage – relatively high driving voltage (tens of volts). The way we propose to reduce the driving voltage consists of applying a stack of thin (~1µm) LC layers. We have studied the ability of a layer of a surface stabilized ferroelectric liquid crystal coupled with several retardation plates for birefringent color generation. We have demonstrated that in order to accomplish good color characteristics and high brightness of the display, one or two retardation plates are sufficient.

Electrochromic Properties of a Metallo-supramolecular Polymer Derived from Tetra(2-pyridyl-1,4-pyrazine) Ligands Integrated in Thin Multilayer Films

The electrochromic behavior of iron complexes derived from tetra-2-pyridyl-1,4-pyrazine (TPPZ) and a hexacyanoferrate species in polyelectrolytic multilayer adsorbed films is described for the first time. This complex macromolecule was deposited onto indium-tin oxide (ITO) substrates via self-assembly, and the morphology of the modified electrodes was studied using atomic force microscopy (AFM), which indicated that the hybrid film containing the polyelectrolyte multilayer and the iron complex was highly homogeneous and was approximately 50 nm thick. The modified electrodes exhibited excellent electrochromic behavior with both intense and persistent coloration as well as a chromatic contrast of approximately 70%. In addition, this system achieved high electrochromic efficiency (over 70 cm(2) C-1 at 630 nm) and a response time that could be measured in milliseconds. The electrode was cycled more than 10(3) times, indicating excellent stability.

Microfluidic Paper-based Devices For Bioanalytical Applications.

Paper has become increasingly recognized as a very interesting substrate for the construction of microfluidic devices, with potential application in a variety of areas, including health diagnosis, environmental monitoring, immunoassays and food safety. The aim of this review is to present a short history of analytical systems constructed from paper, summarize the main advantages and disadvantages of fabrication techniques, exploit alternative methods of detection such as colorimetric, electrochemical, photoelectrochemical, chemiluminescence and electrochemiluminescence, as well as to take a closer look at the novel achievements in the field of bioanalysis published during the last 2 years. Finally, the future trends for production of such devices are discussed.

Triboelectric Effect As A New Strategy For Sealing And Controlling The Flow In Paper-based Devices.

We reported here for the first time that triboelectric charges on PET sheets can be used to seal and control the flow rate in paper-based devices. The proposed method exhibits simplicity and low cost, provides reversible sealing and minimizes the effect of sample evaporation.

Eletrodos modificados por hidróxido de níquel: um estudo de revisão sobre suas propriedades estruturais e eletroquímicas visando suas aplicações em eletrocatálise, eletrocromismo e baterias secundárias

The present review paper describes the main features of nickel hydroxide modified electrodes covering its structural and electrochemical behavior and the newest advances promoted by nanostructured architectures. Important aspects such as synthetic procedures and characterization techniques such as X-Ray diffraction, Raman and Infrared spectroscopy, Electronic Microscopy and many others are detailed herein. The most important aspect concerning nickel hydroxide is related to its great versatility covering different fields in electrochemical-based devices such as batteries, electrocatalytic systems and electrochromic electrodes, the fundamental issues of these devices are also commented. Finally, some of the newest advances achieved in each field by the incorporation of nanomaterials will be shown.

Nanostructured thin films obtained by electrodeposition over a colloidal crystal template: applications in electrochemical devices

Colloidal particles have been used to template the electrosynthesis of several materials, such as semiconductors, metals and alloys. The method allows good control over the thickness of the resulting material by choosing the appropriate charge applied to the system, and it is able to produce high density deposited materials without shrinkage. These materials are a true model of the template structure and, due to the high surface areas obtained, are very promising for use in electrochemical applications. In the present work, the assembly of monodisperse polystyrene templates was conduced over gold, platinum and glassy carbon substrates in order to show the electrodeposition of an oxide, a conducting polymer and a hybrid inorganic-organic material with applications in the supercapacitor and sensor fields. The performances of the resulting nanostructured films have been compared with the analogue bulk material and the results achieved are depicted in this paper.