Printed electronics, PE, is one of the fastest growing technologies in the world; it allows the construction of electronic devices in low-cost flexible substrates by printing techniques (e.g., screen, gravure, offset, flexography and inkjet printing) traditionally used in several industries (e.g., graphics arts, textiles, polymers). In PE, ink pigments are replaced by metallic particles or precursors that impart the electrical conductivity to the resultant printed patterns. This work reviews the available solid metal formulations used for conductive inks and pastes, focusing on both metallic particles and polymeric components. The influence and technical requirements of most commonly used printing techniques, along with the postprocessing treatments to reach the aim performance in the resultant inks has been addressed. Considering that PE is an emerging profitable field with novel applications in radio frequency identification (RFID) tags, thin-film transistors (TFT), light-emitting diodes (LED), transparent conductive electrodes (TCE) and organic solar cells (OSC), among others, it is crucial to know how printed formulations work and how they can be molded to fulfill the applications requirements. In this review, apart from metallic solid particles that has been widely reviewed in the past, the chemistry of polymer matrices has been focused in order to elucidate its important role in resultant inks performance. Novel outstanding formulations, such as reactive or metal-organic-decomposition (MOD) inks, have been presented.

This work presents the preparation, optimization, and testing of an enzymebased optical biosensor for catechol determination. The sensing area is attached to a glass support and contains: anionic polyamide 6 (PA6) porous microparticles supporting laccase from Trametes Versicolor, embedded in a Pebax ® MH1657 polymer binder that contains the optical indicator dye 3-methyl-2-benzothiazolinone hydrazone (MBTH), responsible for the optical transduction. The catechol analyte, after its enzymatic oxidation, forms o-benzoquinone that can be detected by oxidative coupling with MBTH giving rise to a colored product. The latter can be quantified measuring the UV/VIS absorbance at 500 nm. The PA6 microparticles performed as useful laccase carriers reaching high immobilization yields of up to 99.8% and preserving the enzyme catalytic activity. This permitted the preparation of a new biosensor presenting a detection limit of 11 μM and responding linearly to up to 118 μM of catechol. Biosensor applicability was tested in spiked natural water samples from river and spring. The recovery rates observed were in the range of 97-108% that proves the good accuracy of the proposed biosensor.

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