Adsorption Induced Indirect-to-Direct Band Gap Transition in Monolayer Blue Phosphorus

In this work, we systematically studied adsorption induced indirect-to-direct band gap transition in monolayer blue phosphorus from first-principles calculations by combining one-shot GW approximation and the Bethe-Salpeter equation. Our results revealed that surface adsorption (i.e., O₂, −OH, −COOH, and −CN) strongly modifies the conduction and valence band edges, resulting in an indirect-to-direct band gap transition. More importantly, the direct band gap can be dramatically tuned by either the in-plane strain or the coverage ratio of adsorbates, which enables monolayer blue phosphorus to efficiently adsorb visible light. The mechanism of strain effect and surface adsorption on band gap tuning was deeply discussed. Moreover, our results clearly showed that the adsorbates have an important influence on the exciton binding energies (EBE), while the coverage of adsorbates play a crucial role in the linear scaling behavior between EBE and quasi-particle band gap. Our findings suggest that monolayer blue phosphorus has potential applications in electro-optical devices

The Enhancement of Surface Reactivity on CeO₂ (111) Mediated by Subsurface Oxygen Vacancies

Surface reactivity on metal oxide surfaces and its enhancement play important roles in heterogeneous catalytic reactions. In this work, the interactions of O₂ and H₂O with reduced CeO₂ (111) surface are studied by density-functional theory calculations. The corresponding adsorption geometries, adsorption energies, and reaction barriers are reported. It is found that the diffusion of subsurface oxygen vacancies toward surface can be promoted by the adsorption of O₂ on the CeO₂ (111) surface. Then those oxygen vacancies diffused onto surface sites will be healed by the adsorbed O₂, leaving behind an O adatom on the surface. Interestingly, at moderate temperatures, the surface O adatom will swap positions with surface lattice O dynamically. The adsorption of H₂O may also induce the diffusion of oxygen vacancies from subsurface to surface, leading to the formation of two hydroxyls on the CeO₂ (111) surface. In addition, the interaction between the paired hydroxyl groups and O₂ will result in the formation of water and oxygen adatom on the surface. Our results have revealed important roles played by the subsurface oxygen vacancies in the enhancement of surface reactivity, especially when involving the adsorption of water and oxygen

Maternal mortality due to knowledge, attitude, resource and management.

<p>Maternal mortality due to knowledge, attitude, resource and management.</p

Frequency and percent of maternal deaths in provincial/municipal hospitals, county hospitals township hospitals, private clinics, homes and 2001–2012.

<p>Frequency and percent of maternal deaths in provincial/municipal hospitals, county hospitals township hospitals, private clinics, homes and 2001–2012.</p

The maternal mortality ratios in 2001–2012 for Wuhan and all cities in China combined.

<p>The maternal mortality ratios in 2001–2012 for Wuhan and all cities in China combined.</p

Relative importance of 6 different direct causes of maternal death in Wuhan during 2 periods between 2001 and 2012.

<p>A: Obstetric haemorrhage, B: Pregnancy complications, C: Amniotic fluid embolism, D: Gestational hypertension, E: Anesthetic accident, Ectopic pregnancy, Other.</p

ORs for LBW by weight gain and pre pregnant BMI.

<p>*Adjusted for maternal age, maternal education, infant gender. Smoking was not one confounding factor because of no smoking women.</p><p>ORs for LBW by weight gain and pre pregnant BMI.</p

The differences between IOM and Chinese-recommended weight gain by BMI Categories.

<p>The differences between IOM and Chinese-recommended weight gain by BMI Categories.</p

Total maternal weight gain in Chinese women of different pre pregnancy BMI.

<p>Total maternal weight gain in Chinese women of different pre pregnancy BMI.</p

Characteristics of women and infant.

<p>Characteristics of women and infant.</p