Viviane Dalmoro

Sol–gel hybrid films based on organosilane and montmorillonite for corrosion inhibition of AA2024

The present work reports the production of films on AA2024-T3 composed of vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) with incorporation of montmorillonite (sodium montmorillonite and montmorillonite modified with quaternary ammonium salt, abbreviated Na and 30B, respectively), generated by the sol-gel process. According to FT-IR analyses the incorporation of montmorillonite does not affect silica network. Electrochemical characterization was performed by electrochemical impedance spectroscopy measurement in 0.05 mol L(-1) NaCl solution. Results indicate that montmorillonite incorporation improves the corrosion protection compared to the non-modified system. Scanning electron microscopy micrographs reveal that high concentrations of montmorillonite provide agglomerations on the metallic surface, which is in detriment of the anticorrosive performance. The VTMS/TEOS/30B films with the lowest concentration (22 mg L(-1)) of embedded clay provide the highest corrosion protection.

Imprinted silicas for paracetamol preconcentration prepared by the sol–gel process

Paracetamol-imprinted silicas were prepared by three sol–gel routes, including two basic-catalyzed gelification and precipitation routes, and an acid-catalyzed route. The resulting materials from basic gelification were subjected to Soxhlet, ultrasound and thermal extractions, and characterized by infrared spectroscopy, elemental analysis, nitrogen porosimetry, scanning electron microscopy, and atomic force microscopy. Ultrasound was shown to be the most efficient for template extraction. The resulting materials showed surface areas between 30 m2 g−1 (for the precipitation route) and 200 m2 g−1 (for the acid-catalyzed route). After paracetamol extraction, the resulting surface area was between 30 m2 g−1 and 290 m2 g−1. The presence of paracetamol was confirmed by the presence of an infrared absorption band at 1546 cm−1, which is assigned to ν(C=O). The adsorption of paracetamol from aqueous and urine matrixes on the imprinted materials produced by the acid-catalyzed route was ca. 60% of the nominal concentration present in such matrixes. In the silica without molecular imprints, the preconcentration was ca. 20%.Graphical Abstract

Biodiesel water in oil microemulsions: ferrocene as a hydrophobic probe for direct analysis by differential pulse voltammetry at a Pt ultramicroelectrode

Aimed at monitoring biodiesel oxidation stability, a reproducible, simple and rapid procedure for the determination of ferrocene (Fc) as a probe in water in oil microemulsions (W/O MEs) has been successfully developed. Electrochemical measurements have been performed in microemulsions, ME1, containing 10% water, 60% biodiesel (B100) and 30% pseudo-phase, and ME2, containing 9% water, 28% biodiesel and 63% pseudo-phase, in mass, using sodium dodecyl sulphate (SDS) and n-pentanol as surfactant and co-surfactant, respectively. The so prepared MEs have been characterized through viscosity, conductivity and small angle X-ray scattering (SAXS) measurements. Ferrocene oxidation at a Pt ultramicroelectrode (ume), both in ME1 and ME2, has been evidenced either by linear and differential pulse voltammetry (DPV). As compared to ME1, the higher conductivity of ME2 favours carrying electrochemical measurements in this medium. The DPV results indicate a linear relationship between ip and the Fc concentration with a correlation coefficient of 0.999. Thus, the proposed methodology may ultimately be employed for quality control in the biodiesel production line.

Smart Coatings for Corrosion Protection

The investigation of coatings that can be used to reduce corrosion rates is mandatory because the degradation of metallic structures engenders severe economic, environmental, and social consequences. The primary action of most typical corrosion protection coatings occurs as a result of barrier properties or inhibitive process that is carried out by a corrosion inhibitor incorporated into the coating. Nevertheless, these coatings offer protection over a limited time. Thus, smart coatings have been investigated in the recent years, which possess an active component that releases with an environmental stimulus, for example, corrosion inhibitors to compensate the coating damage. This technology extends the lifetime of coatings. Different attempts have been made to produce coatings with self-healing properties, which allow the inhibitor or healing agent to be released on demand at the coating/metal surface. The most important triggers reported for releasing these agents are local pH gradients, mechanical damage, and ion-exchange processes, all of which are reviewed in the present chapter. Despite numerous researches in this field, the production of smart coatings for corrosion protection on an industrial scale remains a challenge.

Encapsulation of sensors for intelligent packaging

Abstract Traditional packaging for food offers containment and protection; nevertheless it does not provide information about the product degradation. Thus, in recent years the concept of intelligent packaging has emerged that can sense environmental changes and notify consumers that the product to be consumed is in a harmful condition. Different technologies have been employed to produce intelligent packaging, the foremost being the encapsulation of sensors/indicators. Among them, indicators sensitive to pH alteration, caused by degradation of food products, such as, acid or alkaline gases, are the most promising ones. Examples of pH indicators, free or encapsulated in silica-based materials, are discussed and exemplified. Legal aspects dealing with the regulation of the use of such devices in food are also discussed.