Effect of Pt Decoration on the Optical Properties of Pristine and Defective MoS2: An Ab-Initio Study.

Using structural relaxation calculations and first-principles molecular dynamics (FPMD), we performed numerical simulations to explore the interaction of a 2D MoS2 surface and a platinum atom, calculating the optical properties of the resulting material. We explored three initial positions for the interaction of the Pt atom and the pristine MoS2 surface, plus another position between Pt and the MoS2 surface with a sulfur vacancy VS. The surface absorbed the Pt atom in all cases considered, with absorption energies ranging from -2.77 eV to -5.83 eV. We calculated the optical properties and band structure of the two cases with the largest absorption energies (-3.45 eV and -5.83 eV). The pristine MoS2 is a semiconductor with a gap of around 1.80 eV. With the adsorption of the Pt atom (the -3.45 eV case), the material reduces its band gap to 0.95 eV. Additionally, the optical absorption in the visible range is greatly increased. The energy band structure of the 2D MoS2 with a sulfur vacancy VS shows a band gap of 0.74 eV, with consequent changes in its optical properties. After the adsorption of Pt atoms in the VS vacancy, the material has a band gap of 1.06 eV. In this case, the optical absorption in the visible range increases by about eight times. The reflectivity in the infrared range gets roughly doubled for both situations of the Pt-absorbed atom considered. Finally, we performed two FPMD runs at 300 K to test the stability of the cases with the lowest and highest absorption energies observed, confirming the qualitative results obtained with the structural relaxations.

Ab Initio Study of the Interaction of a Graphene Surface Decorated with a Metal-Doped C30 with Carbon Monoxide, Carbon Dioxide, Methane, and Ozone.

Using DFT simulations, we studied the interaction of a semifullerene C30 and a defected graphene layer. We obtained the C30 chemisorbs on the surface. We also found the adsorbed C30 chemisorbs, Li, Ti, or Pt, on its concave part. Thus, the resulting system (C30-graphene) is a graphene layer decorated with a metal-doped C30. The adsorption of the molecules depends on the shape of the base of the semifullerene and the dopant metal. The CO molecule adsorbed without dissociation in all cases. When the bottom is a pentagon, the adsorption occurs only with Ti as the dopant. It also adsorbs for a hexagon as the bottom with Pt as the dopant. The carbon dioxide molecule adsorbs in the two cases of base shape but only when lithium is the dopant. The adsorption occurs without dissociation. The ozone molecule adsorbs on both surfaces. When Ti or Pt are dopants, we found that the O3 molecule always dissociates into an oxygen molecule and an oxygen atom. When Li is the dopant, the O3 molecule adsorbs without dissociation. Methane did not adsorb in any case. Calculating the recovery time at 300 K, we found that the system may be a sensor in several instances.

Invisibility of social vulnerability and social rights to a comprehensive health care in Chile / (in)visibilidade da vulnerabilidade social e do direito ao cuidado integral da saúde no Chile / In-visibilidad de la vulnerabilidad social y el derecho al cuidado de salud integral en Chile

ABSTRACT Objective: To estimate the magnitude of perception of invisibility of social vulnerability and its impact on the access to universal and specific services of the Comprehensive Childhood Protection System in Chile. Method: Cross-sectional study in 50 vulnerable dyads, who were registered in a family health care center (Metropolitan Region, Chile; 2012). After the informed consent, mothers were interviewed using a structured questionnaire. A correspondence analysis model was applied. Results: The invisibility of social vulnerability estimated for mothers (92.0%) and children (86.0%), and a better access was observed to universal services by children and to specific services by mothers. Conclusion: The invisibility of vulnerability limits the opportunities of social protection for disadvantaged groups. Therefore, public policy does not correct social inequalities, which deserve attention by the public health managers in Chile.

RESUMO Objetivo: estimar a magnitude da percepção da invisibilidade da vulnerabilidade social e suas consequências no acesso aos serviços universais e específicos do Sistema de Proteção Integral à Infância no Chile. Método: estudo transversal em 50 díades vulneráveis, registrados em um centro de saúde familiar (Região Metropolitana, Chile; 2012). Depois do consentimento informado, as mães foram entrevistadas usando um questionário estruturado. Um modelo de análise de correspondência foi aplicado. Resultados: a invisibilidade da vulnerabilidade social foi estimada para mães (92.0%) e filhos (86.0%), observando-se um melhor acesso aos serviços universais pelas crianças e aos específicos pelas mães. Conclusão: a invisibilidade da vulnerabilidade limita as oportunidades de proteção social a grupos em desvantagem. Consequentemente, a política pública não corrige as desigualdades sociais, que merecem a atenção dos gestores da saúde pública chilena.

RESUMEN Objetivo: estimar la magnitud de la percepción de la in-visibilidad de la vulnerabilidad social y sus consecuencias en el acceso a servicios universales y específicos del Sistema de Protección Integral de la Infancia en Chile. Método: estudio transversal en 50 díadas vulnerables, registradas en un centro de salud familiar (Región Metropolitana, Chile; 2012). Después de la firma de consentimiento informado, las madres fueran entrevistadas usando un cuestionario estructurado. Se aplicó un modelo de análisis de correspondencias. Resultados: la in-visibilidad de la vulnerabilidad social fue estimada para madres (92.0%) y hijos (86.0%), observándose un mejor acceso a los servicios universales a los infantes y específicos a las madres. Conclusión: la in-visibilidad de la vulnerabilidad limita las oportunidades de protección social a grupos desventajados. Como consecuencia, la política pública no corrige las desigualdades sociales, que merecen atención de los gestores de la salud pública chilena.