O uso da espectroscopia óptica na diferenciação e caracterização de microalgas

Dissertação (mestrado)—Universidade de Brasília, Instituto de Física, Programa de Pós-Graduação em Física, 2020.Nesse trabalho as espectroscopias Raman ressonante e FTIR foram usadas com sucesso na diferenciação e caracterização bioquímica de três espécies diferentes de microalgas: Chlamydomonas sp. (CA), Chlorella sorokiniana (CO) e Nannochloropsis oceanica (NN). As características dos espectros Raman e de FTIR, juntamente com a análise por compontes principais, permitiram diferenciar as três espécies de microalgas com precisão superior a 96%. Além do mais, os dados espectroscópicos permitiram estimar os teores relativos de carotenoides, lipídios e carboidratos nas diferentes espécies de microalgas. A precisão dessas estimativas foi validada por técnicas convencionais. A espectroscopia Raman determinou que o teor de carotenoides com relação ao teor de clorofilas a e b é 53 % maior na microalga NN, quando comparada com a microalga CO e 37 % superior com a observada na microalga CA. Por sua vez, a espectroscopia de FTIR mostrou que a espécie NN apresentou o maior teor lipídico relativo, seguido pela espécie CO. O menor teor lipídico foi observado para a espécie CA. Um comportamento semelhante foi observado para os teores relativos de carboidratos.In this work, resonant Raman and FTIR spectroscopies were used successfully to differentiating and biochemical characterization of three different microalgae species: Chlamydomonas sp. (CA), Chlorella sorokiniana (CO) and Nannochloropsis oceanica (NN). The characteristics of the Raman and FTIR spectra, together with the Principal Component Analysis, allowed differentiating the three microalgae species with an accuracy greater than 96%. Furthermore, the spectroscopic data allowed to estimate the relative levels of carotenoids, lipids and carbohydrates in the different microalgae species. The accuracy of these estimates has been validated by conventional techniques. Raman spectroscopy determined that the content of carotenoids in relation to the content of chlorophylls a and b is 53% higher in microalgae NN, when compared with microalgae CO and 37% higher than that observed in microalgae CA. On the other hand, FTIR spectroscopy showed that the NN species had the highest relative lipid content, followed by the CO species. The lowest lipid content was observed for the CA species. A similar behavior was observed for the relative levels of carbohydrates

Investigation of the effects of GaAs substrate orientations on the electrical properties of sulfonated polyaniline based heterostructures

In this work we present a detailed study of the influence of the GaAs substrate orientation on the electrical properties of heterojunctions based on GaAs and sulfonated polyaniline (SPAN) using Current-Voltage (I-V), Capacitance-Voltage (C-V), Deep-Level Transient Spectroscopy (DLTS) and Laplace DLTS techniques. Three different GaAs substrate orientations have been investigated, namely (1 0 0), (3 1 1)A and (3 1 1)B. The I-V results revealed that the turn-on voltage (Von) of SPAN/(3 1 1)B GaAs heterojunction is higher than that for SPAN/(1 0 0) GaAs and SPAN/(3 1 1)A GaAs heterojunctions. The DLTS results showed that the number of electrically active defects present in devices based on the lower index (1 0 0) plane of GaAs substrate is higher than those of higher index (3 1 1)A and (3 1 1)B GaAs substrates, corroborating with I-V results. In order to investigate the role of interface states, capacitance-frequency measurements were performed in forward bias on all three devices

The feasibility of recycled micro polyethylene terephthalate (PET) replacing natural sand in hot-mix asphalt

Microplastic pollution is contaminating the human food chain worldwide. At the same time, construction excessively exploits natural sand, requiring the incorporation of alternative materials to achieve sustainable development. From this scenario, the study evaluates the potential of recycled micro-PET replacing natural sand on hot-mix asphalt (HMA) mechanical behavior by weight and volume. The materials’ characterization occurred via XDR, XRF, TGA/DTG, FTIR, SEM, and AFM tests. The Superpave mix design, X-ray micro-tomography (μ-CT), indirect tensile strength (ITS), resilient modulus (RM), and moisture damage tests were performed in conventional and PET-incorporated mixtures, considering 2% (in wt.), 4% (in wt.), and 8% (in wt. and vol.) substitutions. The 8% PET replacing sand by volume showed no significant change in the mixture’s optimum asphalt content (OAC) due to the binder absorption equivalence between the materials’ surfaces. For the same binder content, the increase in PET content in weight decreased the binder film thickness and increased the volume of voids, visualized as non-permeable micropores in μ-CT. Although adding and incrementing PET reduced the mixtures’ ITS and RM values, its most significant contribution was enhancing the resistance to moisture damage, especially for regions where the pavement deterioration process is associated with an intensive rainfall regime, thus demonstrating this application’s practical feasibility in concrete asphalt paving