ABSTRACT
Ni-doped TiO2 nanoparticles have been synthesized by a modified sol-gel method. The crystal phase composition, particle size, and magnetic and optical properties of the samples were comprehensively examined using x-ray diffraction analysis, transmission electron microscopy, Brunauer-Emmett-Teller surface area analysis, Raman spectroscopy, magnetization measurements, and ultraviolet-visible (UV-Vis) absorption techniques. The results showed that the prepared Ni-doped TiO2 samples sintered at 400°C crystallized completely in anatase phase with average particle size in the range from 8 nm to 10 nm and presented broad visible absorption. The bactericidal efficiency of TiO2 was effectively enhanced by Ni doping, with an optimum Ni doping concentration of 6% (x = 0.06), at which 95% of Escherichia coli were killed after just 90 min of irradiation. Density functional theory (DFT) calculations revealed good agreement with the experimental data. Moreover, the Ni dopant induced magnetic properties in TiO2, facilitating its retrieval using a magnetic field after use, which is an important feature for photocatalytic applications.
ABSTRACT
OBJECTIVES: Despite the proximity and high travel flows with China, Vietnam has been able to contain the spread of coronavirus disease 2019 (COVID-19). This study describes the characteristics of COVID-19 infections in Vietnam and policy responses to identify potential factors contributing to the relative success of Vietnam in containing this pandemic. METHODS: Narrative analyses were applied to describe the pandemic and policy responses. Descriptive statistics, generalized linear regression, and a susceptible-infected-recovered model were used to explore the effectiveness of Vietnamese policy responses to COVD-19. RESULTS: To date, Vietnam is one of the few countries that have successfully control the spread of COVID-19. As of 26 October 2020, Vietnam has had 1169 cases of COVID-19, of which 1061 people recovered and 35 people died from the disease. COVID-19 infected patients in Vietnam were relatively younger than those in other countries with an average age of 36. Most of the infected cases were from international travels. Policy responses in Vietnam were implemented early and strictly. CONCLUSIONS: Despite the proximity to China, where COVID-19 emerged, Vietnam has experienced a small number of COVID-19 infections and fatalities compared with other countries. Most infected patients were relatively young, and exposure was attributed to international travel. Early policy interventions were the main factors that contributed to the success of Vietnam to date.
