Noble-Metal High-Entropy-Alloy Nanoparticles: Atomic-Level Insight into the Electronic Structure.

The compositional space of high-entropy-alloy nanoparticles (HEA NPs) significantly expands the diversity of the materials library. Every atom in HEA NPs has a different elemental coordination environment, which requires knowledge of the local electronic structure at an atomic level. However, such structure has not been disclosed experimentally or theoretically. We synthesized HEA NPs composed of all eight noble-metal-group elements (NM-HEA) for the first time. Their electronic structure was revealed by hard X-ray photoelectron spectroscopy and density function theory calculations with NP models. The NM-HEA NPs have a lower degeneracy in energy level compared with the monometallic NPs, which is a common feature of HEA NPs. The local density of states (LDOS) of every surface atom was first revealed. Some atoms of the same constituent element in HEA NPs have different LDOS profiles, whereas atoms of other elements have similar LDOS profiles. In other words, one atom in HEA loses its elemental identity and it may be possible to create an ideal LDOS by adjusting the neighboring atoms. The tendency of the electronic structure change was shown by supervised learning. The NM-HEA NPs showed 10.8-times higher intrinsic activity for hydrogen evolution reaction than commercial Pt/C, which is one of the best catalysts.

Chemical and Electronic Investigation of Buried NiO1-δ, PCBM, and PTAA/MAPbI3-xClx Interfaces Using Hard X-ray Photoelectron Spectroscopy and Transmission Electron Microscopy.

Identification and profiling of molecular fragments generated over the lifespan of halide perovskite solar cells are needed to overcome the stability issues associated with these devices. Herein, we report the characterization of buried CH3NH3PbI3-xClx (HaP)-transport layer (TL) interfaces. By using hard X-ray photoelectron spectroscopy in conjunction with transmission electron microscopy, we reveal that the chemical decomposition of HaP is TL-dependent. With NiO1-δ, phenyl-C61-butyric acid methyl ester (PCBM), or poly(bis(4-phenyl) (2,4,6-trimethylphenyl)amine) (PTAA) as TLs, probing depth analysis shows that the degradation takes place at the interface (HaP/TL) rather than the HaP bulk area. From core-level data analysis, we identified iodine migration toward the PCBM- and PTAA-TLs. Unexpected diffusion of nitrogen inside NiO1-δ-TL was also found for the HaP/NiO1-δ sample. With a HaP/PCBM junction, HaP is dissociated to PbI2, whereas HaP/PTAA contact favored the formation of CH3I. The low stability of HaP solar cells in the PTAA-TL system is attributed to the formation of CH3I and iodide ion vacancies. Improved stability observed with NiO1-δ-TL is related to weak dissociation of stoichiometric HaP. Here, we provide a new insight to further distinguish different mechanisms of degradation to improve the long-term stability and performance of HaP solar cells.

Correction: On the electronic structure and hydrogen evolution reaction activity of platinum group metal-based high-entropy-alloy nanoparticles.

[This corrects the article DOI: 10.1039/D0SC02351E.].

On the electronic structure and hydrogen evolution reaction activity of platinum group metal-based high-entropy-alloy nanoparticles.

We report the synthesis of high-entropy-alloy (HEA) nanoparticles (NPs) consisting of five platinum group metals (Ru, Rh, Pd, Ir and Pt) through a facile one-pot polyol process. We investigated the electronic structure of HEA NPs using hard X-ray photoelectron spectroscopy, which is the first direct observation of the electronic structure of HEA NPs. Significantly, the HEA NPs possessed a broad valence band spectrum without any obvious peaks. This implies that the HEA NPs have random atomic configurations leading to a variety of local electronic structures. We examined the hydrogen evolution reaction (HER) and observed a remarkably high HER activity on HEA NPs. At an overpotential of 25 mV, the turnover frequencies of HEA NPs were 9.5 and 7.8 times higher than those of a commercial Pt catalyst in 0.05 M H2SO4 and 1.0 M KOH electrolytes, respectively. Moreover, the HEA NPs showed almost no loss during a cycling test and were much more stable than the commercial Pt catalyst. Our findings on HEA NPs may provide a new paradigm for the design of catalysts.

[Factors predictive of the probable occurrence of traumatic lesions at the level of the incisors. A case-control study of Senegalese adolescents]. / Facteurs prédictifs de survenue de lésions traumatiques au niveau des incisives. Etude cas-témoins chez des adolescents sénégalais.

INTRODUCTION: Knowledge of the factors influencing traumatic injuries of the anterior teeth is useful to prevent their occurrence. The aim of this case control study is to test the relationship between intrinsic and extrinsic factors and dental traumatism in adolescents. MATERIALS AND METHODS: Cases are 32 adolescent consulting for dental traumatism at the University Dental Clinic Dakar (Senegal). Control subjects (49) are derived from the same population but were free from any dental traumatism. Logistic regression analyses are performed to identify factors that best predict the occurrence of incisor traumatism. RESULTS: Stepwise logistic regression analysis identifies the angle between upper incisor axis to palatal plane (OR = 1.10; 95% CI; 1.01-1.19) and variables related to lip position as best predictors of incisors traumatism. Insufficient lip coverage in rest position increases eight times the odds of having incisors injury. CONCLUSION: Early orthodontic management of the identified factors may help preventing the occurrence of traumatic incisor injuries.

[Clinical trials in Dakar: survey on knowledge, attitudes and practices of key actors on the period from 2003 to 2007]. / Essais cliniques à Dakar: enquête sur les connaissances, attitudes et pratiques des principaux acteurs sur une période allant de 2003 à 2007.

AIM: The general objective of this study was to agree an inventory of fixtures of clinical trials done in Dakar, in order to make recommendations to improve the quality of clinical trials in Senegal. METHOD: We have done a survey from mars to may 2007, with investigators of the two biggest Senegalese university teaching hospitals and to the pharmacy management and the ethical committee. RESULTS: Our key results showed: 1) a small participation rate of teachers to clinical trials (11 on 37 interviewed); 2) that the principal sponsor is pharmaceutical industry; 3) that most of investigators have not degree in clinical trials; 4) that most pathologies concerned were malaria and AIDS; 5) that there are regulations related to clinical trials in Senegal. CONCLUSION: This study shows the necessity to integrate, in Senegal, clinical trials in the curricula of students training.

[Not Available]. / Essais cliniques à Dakar : enquête sur les connaissances, attitudes et pratiques des principaux acteurs sur une période allant de 2003 à 2007.

AIM: The general objective of this study was to agree an inventory of fixtures of clinical trials done in Dakar, in order to make recommendations to improve the quality of clinical trials in Senegal. METHOD: We have done a survey from mars to may 2007, with investigators of the two biggest Senegalese university teaching hospitals and to the pharmacy management and the ethical committee. RESULTS: Our key results showed: 1) a small participation rate of teachers to clinical trials (11 on 37 interviewed); 2) that the principal sponsor is pharmaceutical industry; 3) that most of investigators have not degree in clinical trials; 4) that most pathologies concerned were malaria and AIDS; 5) that there are regulations related to clinical trials in Senegal. CONCLUSION: This study shows the necessity to integrate, in Senegal, clinical trials in the curricula of students training.