7 research outputs found
Recommended from our members
Impact of Mesoporous Silicon Template Pore Dimension and Surface Chemistry on Methylammonium Lead Trihalide Perovskite Photophysics
© 2020 Wiley-VCH GmbH In influencing fundamental properties—and ultimately device performance—of lead halide perovskites, interfacial interactions play a major role, notably with regard to carrier diffusion and recombination. Here anodized porous Si (pSi) as well as porous silica particles are employed as templates for formation of methylammonium lead trihalide nanostructures. This allows synthesis of relatively small perovskite domains and comparison of associated interfacial chemistry between as-prepared hydrophobic hydrideterminated functionalities and hydrophilic oxide-terminated surfaces. While physical confinement of MAPbBr3 has a uniform effect on carrier lifetime, pore size (7–18 nm) of the silicon-containing template has a sensitive influence on perovskite photoluminescence (PL) wavelength maximum. Furthermore, identity of the surface functionality of the template significantly alters the PL quantum efficiency, with lowest PL intensity associated with the H-terminated pSi and the most intense PL affiliated with the oxideterminated pSi surface. These effects are explored for green-emitting MAPbBr3 as well as infrared-emitting MAPbI3. In addition, the role of silicon surface chemistry on the time-dependent stability of these perovskites packaged within a given mesoporous template is also evaluated, specifically, a lack of miscibility between MAPbI3 and the H-terminated pSi template results in a diffusion of this specific perovskite composition eluting from this porous matrix over time
Recommended from our members
Template Pore Size and A-Site Cation Management Dictate Luminescence Efficiency, Stability, and Wavelength in Confined Perovskite Nanostructures
A-site cation composition is a useful lever in optimizing the photophysical properties and stability of metal halide perovskites (MHPs). Independent of this, straightforward preparative routes to MHP nanostructures that employ a single solid-state template with modest thermal requirements are also in demand. Here we employ both strategies in the fabrication and evaluation of luminescence properties of mixed formamidinium / cesium (CsxFA1-xPbBr3) and methylammonium / cesium (CsxMA1-xPbBr3) nanostructures formed within confining mesoporous silica of 4 nm and 7 nm average pore diameter. Use of such small pore oxide- terminated templates produce perovskite nanostructures in the strongly confined regime, with broadly tunable emission from green to sky blue (g). It is found that the smallest nanostructures that are formamidinium-rich exhibit the largest photoluminescence quantum efficiency values, but such values diminish by more than 50% in a 10-day period. In contrast, the same nanostructures formed within a 7 nm porous template retain their efficiency values over the same time window. The likely origins of this size-dependent behavior are discussed in terms of pore size-dependent capillary forces. Such routes may ultimately lead to improved light emitting diode designs composed of controlled quantum-confined perovskites of greater intrinsic stability than other emitters such as ligand-based colloidal nanocrystals
Cartografia do cuidado na saúde da gestante Cartography of healthcare for pregnant women
Utilizou-se a cartografia como método para mapear a trajetória do cuidado à gestante no serviço da atenção básica. O campo de estudo foram nove Unidades Básicas de Saúde do MunicÃpio de Juazeiro do Norte (CE). Participaram 15 mulheres que estavam entre 37 e 39 semanas de gestação, com as quais foram realizadas entrevistas nos meses de janeiro a junho de 2010. Os achados da cartografia foram descritos em etapas no fluxograma e revelaram lacunas no serviço do pré-natal, tais como o número reduzido da realização do exame da citologia oncótica e o déficit de atividades educativas. Observou-se, entretanto, certa resolubilidade na assistência à gestante, pois vários depoimentos demonstraram satisfação em relação ao serviço. A boa relação desenvolvida com o profissional foi o principal motivo que as levou a continuar o tratamento. Este fato reforça a importância do vÃnculo e do diálogo entre profissionais e gestantes para a adesão e sucesso do pré-natal.<br>This work uses cartography as a method for mapping the trajectory of primary healthcare provided to pregnant women. The scope of the study comprises 9 Basic Healthcare Units located in the city of Juazeiro do Norte in the State of Ceará. In all, fifteen women in the 37th to 39th week of pregnancy were selected. Interviews were conducted with these women during the period from January to June 2010. The cartographic findings were depicted in stages in the flowchart, which exposed lacunas in prenatal healthcare, such as the low number of oncotic cytology exams conducted and the lack of educational counseling. Nevertheless, in the interviews, a significant number of pregnant women expressed satisfaction with the prenatal care provided. The good relationships developed between the healthcare professionals and the pregnant women were the main reason that led them to continue the treatment. This fact reinforces the importance of dialogue between these two actors for the success of prenatal healthcare