Combined Effect of Poly(hydroxybutyrate) and Plasticizers on Polylactic acid Properties for Film Intended for Food Packaging

Poly(lactic acid) PLA, and poly(hydroxybutyrate) PHB, blends were processed as films and characterized for their use in food packaging. PLA was blended with PHB to enhance the crystallinity. Therefore, PHB addition strongly increased oxygen barrier while decreased the wettability. Two different environmentally-friendly plasticizers, poly(ethylene glycol) (PEG) and acetyl(tributyl citrate) (ATBC), were added to these blends to increase their processing performance, while improving their ductile properties. ATBC showed higher plasticizer efficiency than PEG directly related to the similarity solubility parameters between ATBC and both biopolymers. Moreover, ATBC was more efficiently retained to the polymer matrix during processing than PEG. PLA–PHB–ATBC blends were homogeneous and transparent blends that showed promising performance for the preparation of films by a ready industrial process technology for food packaging applications, showing slightly amber color, improved elongation at break, enhanced oxygen barrier and decreased wettability.

Electrochemical reactions of catechol, methylcatechol and dopamine at tetrahedral amorphous carbon (ta-C) thin film electrodes

The electrochemical reactions of dopamine, catechol and methylcatechol were investigated at tetrahedral amorphous carbon (ta-C) thin film electrodes. In order to better understand the reaction mechanisms of these molecules, cyclic voltammetry with varying scan rates was carried out at different pH values in H2SO4 and PBS solutions. The results were compared to the same redox reactions taking place at glassy carbon (GC) electrodes. All three catechols exhibited quasi-reversible behavior with sluggish electron transfer kinetics at the ta-C electrode. At neutral and alkaline pH, rapid coupled homogeneous reactions followed the oxidation of the catechols to the corresponding o-quinones and led to significant deterioration of the electrode response. At acidic pH, the extent of deterioration was considerably lower. All the redox reactions showed significantly faster electron transfer kinetics at the GC electrode and it was less susceptible toward surface passivation. An EC mechanism was observed for the oxidation of dopamine at both ta-C and GC electrodes and the formation of polydopamine was suspected to cause the passivation of the electrodes.

Improving the photoactivity of bismuth vanadate thin film photoanodes through doping and surface modification strategies

Currently, one of the most attractive and desirable ways to solve the energy challenge is harvesting energy directly from the sunlight through the so-called artificial photosynthesis. Among the ternary oxides based on earth–abundant metals, bismuth vanadate has recently emerged as a promising photoanode. Herein, BiVO4 thin film photoanodes have been successfully synthesized by a modified metal-organic precursor decomposition method, followed by an annealing treatment. In an attempt to improve the photocatalytic properties of this semiconductor material for photoelectrochemical water oxidation, the electrodes have been modified (i) by doping with La and Ce (by modifying the composition of the BiVO4 precursor solution with the desired concentration of the doping element), and (ii) by surface modification with Au nanoparticles potentiostatically electrodeposited. La and Ce doping at concentrations of 1 and 2 at% in the BiVO4 precursor solution, respectively, enhances significantly the photoelectrocatalytic performance of BiVO4 without introducing important changes in either the material structure or the electrode morphology, according to XRD and SEM characterization. In addition, surface modification of the electrodes with Au nanoparticles further enhances the photocurrent as such metallic nanoparticles act as co-catalysts, promoting charge transfer at the semiconductor/solution interface. The combination of these two complementary ways of modifying the electrodes has resulted in a significant increase in the photoresponse, facilitating their potential application in artificial photosynthesis devices.

Film noir: análise e identificação das características, padrões e clichés do film noir clássico

O film noir, embora seja reconhecido sem dificuldade na cultura cinéfila e até na cultura contemporânea de massas em geral, não pode ainda assim ser definido instantaneamente pelo seu ambiente ou pela presença de determinadas personagens. Por muito difícil que seja captar a essência do noir, tendo em conta apenas fatores estilísticos ou temáticos, é necessário focar a atenção em dados mais concretos e consistentes e tentar encontrar as singularidades que definam o film noir de forma mais objectiva e, ao mesmo tempo, matizada. Para desenvolver a investigação e a sua aplicação projetual associada ao cinema/ vídeo, foi este género cinematográfico e as suas influências, que foi o escolhido, por estar balizado num curto período temporal(de 1941 a 1958)mas com evidentes marcadores que subsistem para além deste período. O objetivo deste projeto é identificar e analisar os padrões e estereótipos do film noir, procurando seguir e interpretar a respectiva influência no universo da cultura visual atual. Para além de uma recolha preliminar de informação que permitiu elaborar uma definição concreta sobre o problema a estudar e as suas origens, analisou-se um número considerável de filmes referenciados como pertencentes ao modelo do film noir. O projeto de investigação culmina no vídeo “Film noir” que é uma recolha de sequências e imagens de diferentes filmes da era do film noir clássico, onde a junção destas cria uma história nova que se enquadra no estilo narrativo dos filmes noir. Por fim, o trabalho é ainda uma ode ainda uma ode e homenagem ao cinema noir.