Development of a Template-Free Microwave-Assisted Metal Sulfide Nanoparticles Synthesis Method and Film Deposition with Formulated Inks

Developing efficient and green materials for solar cells is of the utmost importance. In the pursuit of attempting to harvest all of the solar spectrum energy, from the ultra-violet to the near-infrared, metal sulfide nanoparticles were deemed as the most promising materials, due to their low toxicity, low cost, chemical stability, and band gap tunability, compared to the oxide, selenide and telluride counterparts. A microwave-assisted sustainable synthesis protocol was developed to obtain metal sulfide nanoparticles. Using solely 1-dodecanethiol as the sulfur source, solvent, and particle stabilizer, coupled with a metal salt precursor systematically, binary and ternary metal sulfide nanoparticles were synthesized using relatively abundant elements from group 2 to group 15 of the periodic table. Pure ternary alloys were obtained, but syntheses performed with some elements instead resulted in the binary sulfides, influenced by the final phase of each other. Quaternary metal sulfide syntheses were also attempted. Control of the synthesis was attained through video recording and post-analysis of the color profiles, crossed with the temperature and pressure profile, to pinpoint relevant transformations, such as the sulfide formation. The influence of reaction time, temperature, precursors type and concentration, and the presence of light on the size, morphology, material phase, and optical properties of the nanoparticles were evaluated. Changing the concentration of the precursor resulted in the same phase of the metal sulfide but using a higher concentration required less energy input to achieve the same temperature since the thiol weakly absorbs the microwave radiation. In contrast, the salts absorb it more efficiently. Two temperature control modes were tested, one automated and another at constant power. The automated temperature mode was chosen since the temperature profiles were more reproducible between syntheses, but the constant power mode allowed to see if a particular reaction was exothermic. A lower synthesis temperature usually resulted in a metal-thiol complex, while a higher temperature resulted in metal sulfide. The synthesis time was directly correlated to the size of the particles; for example, zinc sulfide particles with an average length of 3 nm with a 5-minute synthesis at 300 °C, up to 8 nm with a synthesis time of 25 minutes. The presence of light paired with light-sensitive precursors, such as silver salts, results in smaller particles. In the dark bigger particles were obtained when silver nitrate was used. When the synthesis was performed with silver oxide, both the metal sulfide and metallic silver were obtained in the dark, while metallic silver was the primary product in the presence of light. Precursors not sensitive to light, such as zinc acetate, revealed no changes in the final material with or without light. A library of metal sulfide nanomaterials was obtained with band gaps of 0.51 eV (copper iron sulfide) that absorbs infrared photons, to 2.56 (indium sulfide) to absorb visible photons, and to 3.54 eV (zinc sulfide) to absorb ultra-violet photons, as well a metallic-like material (NbS2). Stable inks were formulated with the synthesized nanoparticles in isopropanol, with no additives. Slot-die coating and spray deposition methods were tested. Like the synthesis protocol, a simple spray method was developed using a relatively low deposition temperature. As a result, the inks could be used throughout the whole deposition with minimal sedimentation. Thin films of zinc sulfide, tin sulfide, and copper iron sulfide were obtained with the desired optical properties to use in solar cells. The possibility to choose between 2D nanoparticles shape, controllable structure modification with temperature and luminescence properties make this work an important source of metal sulfides nanoparticles syntheses for a vast range of applications from solar cells, batteries, capacitors, photonic devices, and other not yet discovered applications.Desenvolver materiais eficientes e verdes para as células solares é da maior importância. Na tentativa de captar toda a energia do espectro solar, do ultra-violeta ao infravermelho, as nanopartículas de sulfureto de metal foram consideradas como os materiais mais promissores, devido à sua baixa toxicidade, baixo custo, estabilidade química e possibilidade de afinar a banda proibida, conhecida em inglês como band gap, em comparação com os homólogos óxido, selenieto e telureto. Foi desenvolvido um protocolo de síntese sustentável com assistência de microondas para obter nanopartículas de sulfureto de metal. Usando sistematicamente apenas 1-dodecanotiol como fonte de enxofre, solvente, e estabilizador de partículas, associado a um precursor de sal de metal, as nanopartículas binárias e ternárias de sulfureto de metal foram sintetizadas usando elementos relativamente abundantes do grupo 2 ao grupo 15 da tabela periódica. Foram obtidas ligas ternárias puras, mas as sínteses realizadas com alguns elementos resultaram nos sulfuretos binários, influenciados pela fase final uns dos outros. Foram também tentadas sínteses de sulfuretos metálicos quaternários. O controlo da síntese foi alcançado através de gravação vídeo e análise posterior dos perfis de cor, cruzados com o perfil de temperatura e pressão, para identificar transformações relevantes, tais como a formação de sulfuretos. A influência do tempo de reacção, temperatura, tipo e concentração dos precursores, e a presença de luz no tamanho, morfologia, fase material, e propriedades ópticas das nanopartículas foi avaliada. A alteração da concentração do precursor resultou na mesma fase do sulfureto de metal mas a utilização de uma concentração mais elevada requereu menos energia para atingir a mesma temperatura uma vez que o tiol absorve menos a radiação de microondas. Em contraste, os sais absorvem-na de forma mais eficiente. Dois modos de controlo de temperatura foram testados, um automático e outro com potência constante. O modo de temperatura automatizado foi escolhido porque os perfis de temperatura eram mais reprodutíveis entre sínteses, mas o modo de potência constante permitiu ver se uma determinada reacção era exotérmica. Uma temperatura de síntese mais baixa geralmente resultou num complexo metal-tiol, enquanto que uma temperatura mais alta resultou num sulfureto de metal. O tempo de síntese foi directamente correlacionado com o tamanho das partículas; por exemplo, foram obtidas partículas de sulfureto de zinco com um tamanho médio de 3 nm com uma síntese de 5 minutos a 300 °C, até 8 nm com um tempo de síntese de 25 minutos. Finalmente, a presença de luz em conjunto com precursores sensíveis à luz, tais como sais de prata, resulta em partículas mais pequenas. No escuro, foram obtidas partículas maiores quando se utilizou nitrato de prata. Quando a síntese foi realizada com óxido de prata, foram obtidos tanto o sulfureto de prata como a prata metálica na ausência de luz e maioritariamente o metal na presença de luz. Precursores não sensíveis à luz, tais como o acetato de zinco, não revelaram alterações no material final com ou sem luz. Uma biblioteca de nanomateriais de sulfureto de metal foi obtida com band gaps de 0,51 eV (sulfureto de ferro de cobre) que absorve fotões infravermelhos, a 2,56 (sulfureto de índio) para absorver fotões visíveis, e a 3,54 eV (sulfureto de zinco) para absorver fotões ultra-violetas, bem como um material semelhante ao metal (NbS2). Foram formuladas tintas estáveis com as nanopartículas sintetizadas em isopropanol, sem aditivos. Os métodos de deposição revestimento por extrusão de matriz e pulverização foram testados. Tal como o protocolo de síntese, foi desenvolvido um método simples de pulverização usando uma temperatura de deposição relativamente baixa. As tintas foram usadas durante toda a deposição com o mínimo de sedimentação. Foram obtidas filmes finos de sulfureto de zinco, sulfureto de estanho e sulfureto de ferro de cobre com as propriedades ópticas desejadas para uso em células solares. A possibilidade de escolher entre forma de nanopartículas 2D, modificação da estrutura controlável com propriedades de temperatura e luminescência fazem deste trabalho uma importante fonte de síntese de nanopartículas de sulfuretos metálicos para uma vasta gama de aplicações desde células solares, baterias, condensadores, dispositivos fotónicos, e outras aplicações ainda não descobertas

Solution processed quantum dot photodetectors

To find sustainable solutions for the production of energy, it is necessary to create photovoltaic technologies that make every photon count. To pursue this necessity, in the present work photodetectors of zinc oxide embedded with nano-structured materials, that significantly raise the conversion of solar energy to electric energy, were developed. The novelty of this work is on the development of processing methodologies in which all steps are in solution: quantum dots synthesis, passivation of their surface and sol-gel deposition. The quantum dot solutions with different capping agents were characterized by UVvisible absorption spectroscopy, spectrofluorimetry, dynamic light scattering and transmission electron microscopy. The obtained quantum dots have dimensions between 2 and 3nm. These particles were suspended in zinc acetate solutions and used to produce doped zinc oxide films with embedded quantum dots, whose electric response was tested. The produced nano-structured zinc oxide materials have a superior performance than the bulk, in terms of the produced photo-current. This indicates that an intermediate band material should have been produced that acts as a photovoltaic medium for solar cells. The results are currently being compiled in a scientific article, that is being prepared for possible submission to Energy and Environmental Science or Nanoscale journals

Microwave Synthesis of Silver Sulfide and Silver Nanoparticles: Light and Time Influence

UIDB/50025/2020 UIDP/50025/2020 UID/CTM/50025/2019 .Silver sulfide (Ag2S) is a low band gap material, which absorbs near-infrared light and is of great importance in areas such as nanotechnology and biomedicine. We report the influence of the starting reagents, synthesis time, and light radiation on the geometry and size of silver sulfide nanoparticles and on the fraction of metallic Ag obtained in a microwave reactor. The X-ray diffraction diffractograms confirmed that Ag2S is the main product if the reaction's precursor contains silver in the oxidation state of +1 and mostly metallic silver (Ag°) when it is +2. Small nanoparticles (∼6 nm) of spherical geometry are present in the transmission electron microscopy images for the synthesis performed with the lamp light ON, while with the light switched OFF, wider and hundreds of nanometers longer particles are observed. This discriminative effect occurs with shorter synthesis time duration (<10 min) but when the time of reaction is extended, the particles coalesce for both light and dark conditions. Overall, it was observed by photoluminescence that crystalline Ag and Ag2S 4-8 nm nanoparticles obtained in 15 min and light irradiation during synthesis have a clear relative increase of the radiative recombination channels of the charged carriers, which are typical of materials characterized by the involvement of low density of states inside the band gap.publishersversionpublishe

Interviews of Children in a Portuguese Special Judicial Procedure

Since 2007, alleged victims of child sexual abuse in Portugal have provided evidence in a mandatory “Declarações para Memória Futura” (DMF; English transl. ‘Statement for future use’) proceeding. In order to protect children from having to testify in court, interviews conducted at the DMF can be used later as trial evidence because the hearings are conducted by judges. The present study examined 137 interviews with 3- to 17-year-olds conducted in several Portuguese criminal courts. Detailed examination of interview transcripts showed that 69% of all questions asked were option-posing questions, 16% were directive questions, 11% were suggestive questions, and only 3% were open-ended prompts. The vast majority of details provided by children were thus obtained using the risky recognition-based prompts (i.e., option posing and suggestive questions) associated with the risks of contaminating and limiting children's informativeness, both potential threats to the credibility of their testimony. There is an urgent need to address this issue and consider the implementation of a scientifically validated structured interview protocol in Portugal.info:eu-repo/semantics/publishedVersio

Resistance profile of osimertinib in pre-treated patients with EGFR T790M-mutated non-small cell lung cancer

Background: Osimertinib efficacy in pre-treated patients with epidermal growth factor receptor (EGFR) T790M-mutated non-small cell lung cancer (NSCLC) has been demonstrated in clinical trials, but real-world data, particularly regarding resistance profile, remains limited. This study aims to analyze the resistance mechanisms acquired after treatment with Osimertinib. Methods: Clinical outcomes and molecular results from re-biopsies at the time of osimertinib progression of EGFR T790M-mutated NSCLC patient were analyzed. Results: Twenty-one patients with stage IV adenocarcinoma were included [median 69 years; 57.1% female; 85.7% never-smokers; 23.8% ECOG performance status (PS) >= 2]. Median PFS and OS were 13.4 (95% CI: 8.0-18.9) and 26.4 (95% IC: 8.9-43.8) months, respectively. At the time of analysis, 10 patients had tumor progression (47.6%). T790M loss occurred in 50%, being associated with earlier progression (median PFS 8.1 vs. 21.4 months, p = 0.011). Diverse molecular alterations were identified, including C797S mutation (n = 1), PIK3CA mutation (n = 2), MET amplification (n = 1), CTNNB1 mutation (n = 1), and DCTN1-ALK fusion (n = 1). Histological transformation into small cell carcinoma occurred in one patient. Conclusions: This real-world life study highlights the relevance of re-biopsy at the time of disease progression, contributing to understand resistance mechanisms and to guide treatment strategies

Rarity of monodominance in hyperdiverse Amazonian forests.

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors

ASPECTOS EPIDEMIOLÓGICOS E PREVALÊNCIA DE ENTEROPARASITOSES EM CRIANÇAS DO BAIRRO JAMBEIRO, SÃO LUÍS, MA

A carência de condições básicas de higiene e saneamento, aliadas à falta de limpeza dos reservatórios de água e a não utilização de água fltrada ou fervida, intensifcam a ocorrência de problemas de saúde pública. Com o intuito de contribuir para a conscientização da população acerca dos problemas de saúde decorrentes da contaminação da água, realizou-se no Bairro do Jambeiro, localizado nas mediações da Universidade Federal do Maranhão, um projeto interdisciplinar que visou, pela divulgação dos dados da pesquisa científca, avaliar a água utilizada pelos moradores através de análise físico-química, microbiológica e parasitológica, de modo que os resultados permitissem a conscientização, através de atividades educacionais dos moradores. Os resultados endossam a precariedade de condições sanitárias encontradas nessa comunidade. Os poços, as torneiras e o córrego apresentam níveis de contaminação acima do recomendável pela Resolução CONAMA e ANVISA, sendo, portanto, impróprias para o consumo. Os exames parasitológicos revelaram alta prevalência (91%) de enteroparasitoses nas crianças. A partir desses resultados os integrantes do projeto e seus parceiros realizaram palestras destinadas à comunidade sobre os meios de tratamento da água, biologia dos parasitas e medidas profláticas das principais verminoses. Concomitante, ocorreu a entrega e esclarecimentos dos laudos da análise físico-química, microbiológica e parasitológica, onde houve a distribuição de remédios às crianças que estavam infectadas.Descritores:  Enteroparasitos; Epidemiologia; Prevalência.Abstract: The lack of basic conditions hygiene and sanitation, allied to grubbiness of water reservoirs and no use of fltered or boiled water, enhance the occurrence of health public problems. With the aim of contribute to awareness of the population about the health problems resulting from the water contamination, was held in the District of the Jambeiro, located near the Federal University of Maranhão, an interdisciplinary project the aimed, by disclosure of scientifc research, to evaluate the water used by population through physico-chemical, microbiological and parasitological analyses, so that the results allow awareness through educational activities of population. The results comproved the precarious sanitary conditions found in this community. The level contamination of the wells, taps and stream is higher than recommended by Resolution CONAMA and ANVISA, therefore, unft for consumption. The parasitological revealed a high prevalence (91%) of intestinal parasites in children. Based on these results the members of the project and its partners held talks for the community about the water treatment, biology of parasites and worms and of the main prophylactic measures. Concomitantly, there was the delivery and clarifcation of reports of physico-chemical, microbiological and parasitological, where there was the distribution of drugs to children who were infected.Descriptors: Enteroparasites; Epidemiology; Prevalence

Actin-interacting and flagellar proteins in Leishmania spp.: Bioinformatics predictions to functional assignments in phagosome formation

Several motile processes are responsible for the movement of proteins into and within the flagellar membrane, but little is known about the process by which specific proteins (either actin-associated or not) are targeted to protozoan flagellar membranes. Actin is a major cytoskeleton protein, while polymerization and depolymerization of parasite actin and actin-interacting proteins (AIPs) during both processes of motility and host cell entry might be key events for successful infection. For a better understanding the eukaryotic flagellar dynamics, we have surveyed genomes, transcriptomes and proteomes of pathogenic Leishmania spp. to identify pertinent genes/proteins and to build in silico models to properly address their putative roles in trypanosomatid virulence. In a search for AIPs involved in flagellar activities, we applied computational biology and proteomic tools to infer from the biological meaning of coronins and Arp2/3, two important elements in phagosome formation after parasite phagocytosis by macrophages. Results presented here provide the first report of Leishmania coronin and Arp2/3 as flagellar proteins that also might be involved in phagosome formation through actin polymerization within the flagellar environment. This is an issue worthy of further in vitro examination that remains now as a direct, positive bioinformatics-derived inference to be presented

Geographic patterns of tree dispersal modes in Amazonia and their ecological correlates

Aim: To investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser-availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource-availability hypothesis). Time period: Tree-inventory plots established between 1934 and 2019. Major taxa studied: Trees with a diameter at breast height (DBH) ≥ 9.55 cm. Location: Amazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield. Methods: We assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree-inventory plots across terra-firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We performed an abundance-weighted mean pairwise distance (MPD) test and fit generalized linear models (GLMs) to explain the geographic distribution of dispersal modes. Results: Anemochory was significantly, positively associated with mean annual wind speed, and hydrochory was significantly higher in flooded forests. Dispersal modes did not consistently show significant associations with the availability of resources for constructing zoochorous fruits. A lower dissimilarity in dispersal modes, resulting from a higher dominance of endozoochory, occurred in terra-firme forests (excluding podzols) compared to flooded forests. Main conclusions: The disperser-availability hypothesis was well supported for abiotic dispersal modes (anemochory and hydrochory). The availability of resources for constructing zoochorous fruits seems an unlikely explanation for the distribution of dispersal modes in Amazonia. The association between frugivores and the proportional abundance of zoochory requires further research, as tree recruitment not only depends on dispersal vectors but also on conditions that favour or limit seedling recruitment across forest types

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe