Synthesis of Metal, Oxide, Alloy, and intermetallic Nanocrystals for Catalysis

The synthesis of nanocrystals is the core of the nanoscience. The highly controlled nanomaterials are desirable for the studies of catalysis, in order to unambiguously correlate the catalytic properties with the structure and composition of catalysts. In this thesis, highly controlled nanocrystals are synthesized through solution phase synthesis. Shape controlled nanocrystals can be synthesized as cubes, octahedra, icosahedra, truncated cubes, cuboctahedra tetrapods, octapods and spheres. The nanocrystals with these morphologies selectively expose {100} and/or {111} facets as well as high-index facets, thus enabling various investigations of structure sensitive catalysis at the nanoscale. In addition to the shape control, the composition of metal catalysts is also tunable by making alloy or intermetallic nanocrystals. The nanocrystals of Pt-Mn, Pt-Fe, Pt-Co, Pt-Ni, Pt-Cu, Pt-Zn, Pt-Pb, Pt3Mn, Pt3Fe, Pt3Co, Pt3Ni, Pt3Zn, Pt3Pb, FePt, and etc. allow the fundamental exploration of catalysis. Oxides, heterostructures, as well as artificial crystals which have a long range ordered crystalline structure, are also prepared. These highly controlled nanomaterials have been demonstrated as ideal model materials for studies of catalysis. In this thesis, formic acid and methanol electrooxidation, oxygen reduction reaction, oxygen storage, CO oxidation, and enhanced stability are discussed

Online teaching self-efficacy of Chinese university teachers amidst Covid-19: its changes and the moderation of adaptability and administration quality

Teacher self-efficacy is among the most valued teacher motivational constructs. However, little is known about university teachers’ self-efficacy and even less about changes to it throughout the Covid-19-related online teaching. This study applied a retrospective pre- and post-design to investigate changes in online teaching self-efficacy (OTSE) during Covid-19. Participants included 160 Chinese university teachers, who reported their OTSE before and after the COVID-19 lockdowns, adaptability and administration quality together with demographic information. The self-efficacy for online instruction failed to increase significantly over this period (β=.21, p = .083), whereas that for online technology applications increased significantly (β=.329, p < .01). Individual adaptability and administration quality significantly moderated the changes in OTSE. The implications and limitations of the study are discussed

Mineralizer-Assisted Shape-Control of Rare Earth Oxide Nanoplates

Rare earth oxides are important emerging materials because of their unique properties. Nanosized, two-dimentional (2D) materials have received increasing attention due to their high surface-to-volume ratios and ultrathin layered structures. Here, we synthesize 2D rare earth (RE) oxide nanoplates in the presence of a mineralizer. The use of a mineralizer not only facilitates the synthesis of RE oxide nanoplates (i.e., increases the yield and allows mild reaction parameters), but also allows for shape-control. To emphasize the importance of RE oxide nanoplates in materials science and engineering, we demonstrate that (1) ceria nanoplates can be used in a ceria/Cu inverse catalyst to enable an enhanced CO oxidation activity, and (2) Y₂O₃ nanoplates doped with Eu³⁺ enable photon energy down-conversion

Improving Teacher Effectiveness: Designing Better Assessment Tools in Learning Management Systems

Current-generation assessment tools used in K-12 and post-secondary education are limited in the type of questions they support; this limitation makes it difficult for instructors to navigate their assessment engines. Furthermore, the question types tend to score low on Bloom’s Taxonomy. Dedicated learning management systems (LMS) such as Blackboard, Moodle and Canvas are somewhat better than informal tools as they offer more question types and some randomization. Still, question types in all the major LMS assessment engines are limited. Additionally, LMSs place a heavy burden on teachers to generate online assessments. In this study we analyzed the top three LMS providers to identify inefficiencies. These inefficiencies in LMS design, point us to ways to ask better questions. Our findings show that teachers have not adopted current tools because they do not offer definitive improvements in productivity. Therefore, we developed LiquiZ, a design for a next-generation assessment engine that reduces user effort and provides more advanced question types that allow teachers to ask questions that can currently only be asked in one-on-one demonstration. The initial LiquiZ project is targeted toward STEM subjects, so the question types are particularly advantageous in math or science subjects

Polycycl. Aromatic Hydrocarbon Exposure of Children in Typical Household Coal Combustion Environments: Seasonal Variations, Sources, and Carcinogenic Risks

Polycyclic aromatic hydrocarbon (PAH) emissions from the combustion of household solid coal for cooking and heating cause great harm to public health in China, especially in less developed areas. Children are one of the most susceptible population groups at risk of indoor air pollutants due to their immature respiratory and immune systems. However, information on PAH exposure of children is limited due to limited monitoring data. In this study, we aimed to assess the seasonal differences of PAHs in classrooms, analyze the pollutant sources, and calculate the incremental lifetime cancer risk attributable to PAHs in Shanxi Provence. A typical school using household coal combustion in Shanxi Province was selected. Fine particulate matter (PM2.5)samples were collected by both individual samplers and fixed middle-flow samplers during the heating and non-heating seasons in December 2018 and April 2019. The PAH concentrations in PM2.5 samples were analyzed by a gas chromatograph coupled to a mass spectrometer. The results showed that PAH concentrations in PM2.5 varied between 89.1 ng/m3 in the heating season and 1.75 ng/m3 in the non-heating season. The mean concentrations of benzo[a]pyrene (BaP), a carcinogenic marker of PAHs, were 10.3 and 0.05 ng/m3 in the heating and non-heating seasons, respectively. Source allocation analysis of individual portable and passive samplers revealed that the main contributors during heating and non-heating seasons were coal combustion and gasoline sources, respectively. According to the results of a Monte Carlo simulation, the incremental lifetime cancer risk values from the inhalation of PAHs in the heating and non-heating seasons were 3.1 &times; 10&minus;6 and 5.7 &times; 10&minus;8, respectively. The significant increase in PAHs and the incremental lifetime cancer risk in the heating season indicates that children are more exposed to health threats in winter. Further PAH exposure control strategies, including reducing coal usage and promoting clean fuel applications, need to be developed to reduce the risk of PAH-induced cancer