Self-assembled halide perovskite quantum dots in polymer thin films showing temperature-controlled exciton recombination.

Rationally assembled supramolecular structures of organic chromophores or semiconductor nanomaterials show excitonic properties different from individual molecules or nanoparticles. We report polymer-assisted assembly formation and thermal modulation of excitonic recombination in self-assembled formamidinium lead bromide perovskite quantum dots.

Highly Luminescent and Stable Halide Perovskite Nanocrystals by Interfacial Defect Passivation and Amphiphilic Ligand Capping.

Halide vacancies cause lattice degradation and nonradiative losses in halide perovskites. In this study, we strategically fill bromide vacancies in CsPbBr3 perovskite nanocrystals with NaBr, KBr, or CsBr at the organic-aqueous interface for hydrophobic ligand-capped nanocrystals or in a polar solvent (2-propanol) for amphiphilic ligand-capped nanocrystals. Energy-dispersive X-ray spectra, powder X-ray diffraction data, and scanning transmission electron microscopy images help us confirm vacancy filling and the structures of samples. The bromide salts increase the photoluminescence quantum yield (98 ± 2%) of CsPbBr3 by decreasing the nonradiative decay rate. Single-particle studies show the quantum yield increase originates from the poorly luminescent nanocrystals becoming highly luminescent after filling vacancies. Furthermore, we tune the optical band gap (ultraviolet-visible-near-infrared) of the hydrophobic ligand-capped nanocrystals by halide exchange at the toluene-water interface using saturated NaCl or NaI solutions, which completes in about 60 min under continuous mixing. In contrast, the amphiphilic ligand accelerates the halide exchange in 2-propanol, suggesting ambipolar functional groups speed up the ion-exchange reaction. The bromide vacancy-filled or halide-exchanged samples in a toluene-water biphasic solvent show higher stability than amphiphilic ligand-capped samples in 2-propanol. This strategy of defect passivation, ion exchange, and ligand chemistry to improve quantum yields and tune band gaps of halide perovskite nanocrystals can be promising for designing stable and water-soluble perovskite samples for solar cells, light-emitting diodes, photodetectors, and photocatalysts.

Smoke-free status of homes and workplaces among Indian people: Evidence from Global Adult Tobacco SurveyData-2016/2017.

AIMS: This study aimed to determine the impact of correlates on tobacco control/smoke-free status of homes and workplace among Indian people. To assess the magnitude of the problem, the relationship between smoke-free status and secondhand smoke (SHS) exposure was also explored. METHODS: Data was extracted from the Global Adult Tobacco Survey Data (GATS)-2017. It was a household survey that included people aged 15 years or older and covered all 30 states and 2 Union Territories (UTs) of India. A logistic regression model was used to determine the correlates of smoke-free status of homes and workplaces. Additionally, the Pearson correlation was used to explore the relationship between smoke-free status and the proportion of participants exposed to SHS both at homes and in the workplaces. RESULTS: The overall prevalence of smoke-free status in the home and workplace was 62.8% and 51.7%, respectively. Results of multivariate analysis (Logistic regression) illustrated that indicators like tobacco smoking status, place of residence, region, education, occupation, wealth quintile, and knowledge status about children's illness were significantly associated with the respondent's intention to live in a completely smoke-free environment both at home and in the workplace in India. This study revealed that SHS exposure was significantly negatively associated with a smoke-free status. CONCLUSION: This study will help the policymakers to promote efficient policies for improving smoke-free status and to ensure a better environment both at home and in the workplace in India.

Mental Health of Physicians During COVID-19 Outbreak in Bangladesh: A Web-Based Cross-Sectional Survey.

There have been numerous studies about the health implication of COVID-19 on patients, but little attention has been paid to the impacts of the pandemic on physicians. Our paper attends to this gap by exploring the mental health of physicians in Bangladesh during the COVID-19 pandemic. This is particularly important since the mental health of physicians impacts not only on themselves, but also their professional performance and hence the care of patients. This study examined physicians' mental health outcomes by evaluating the prevalence and associated potential risk factors of anxiety and depression. Using a web-based cross-sectional survey, we collected data from 114 physicians. Seven-item Generalized Anxiety Disorder (GAD-7) scale and Nine-item Patient Health Questionnaire (PHQ-9) were used to measure the anxiety and depression, respectively. Multivariate logistic regression models were used to explore the potential risk factors related to anxiety and depression. The prevalence of anxiety and depression were 32.5 and 34.2%, respectively. Findings revealed that marital status, work per day and current job location were the main risk factors for anxiety while sex, age, and marital status were the main risk factors for depression. Our results highlight the need to implement policies and strategies for positively impacting the mental health of physicians during and after the COVID-19 pandemic.