The COVID-19 pandemic has caused the loss of many lives and transformed the global educational system. This has resulted in a rapid transition from face-to-face classroom meetings to online education delivery. Online education provides another opportunity to engage students during crises, such as pandemics. However, during the transition to online education, both students and educators faced tremendous challenges, especially at rural locations. To shed light on these experiences, we conducted a survey to learn more about student learning and engagement in two similarly sized institutions in Dhule, India, and St. Cloud, USA. The data collected provides an insight into student engagement and their learning during the crisis. About 49% of participants from Dhule reported that internet issues were a major challenge they faced, while 19% of participants reported a financial burden as a major challenge met during the pandemic. In comparison, 63% of participants from St. Cloud reported that internet issues were a major challenge they faced, while 11% of participants reported financial burden as a major challenge they faced. However, only 22% and 9% of the students from Dhule and St. Cloud, respectively, rated the level of chemistry learned during the crisis as exceptional. Through analysis of these results, strategies to overcome some of the challenges and improve student learning outcomes are presented.

To create general awareness among students and assess their level of chemical safety knowledge and attitudes, an online chemical safety survey was completed by chemistry students at Jai Hind Educational Trust's (JET's), Z.

Lanthanides are routinely incorporated into quantum dots to act as down-shifting and up-converting phosphors in display and lighting applications due to their high photoluminescence quantum yields (PLQY). Recent efforts in the field have demonstrated that trivalent lanthanide, Ln­(III), incorporated into ZnAl2O4 spinel nanocrystals can achieve PLQYs of 50% for down-shifting nanophosphors using earth abundant materials. The high PLQY is surprising as the Al­(III) site in a spinel is centrosymmetric, which should lead to poor performance for these nanophosphors. However, spinels are prone to formation of an admixture of inverse and normal spinel lattices when the cation size ratio is not optimal. Such behavior can produce local cation disorder that can influence the phosphor performance. Herein, we describe the use of Tb­(III) as an optical probe to evaluate the fractional population of the inverse and normal spinel structures within Tb x ZnAl2‑x O4. The experimental data exhibits a Tb­(III) concentration dependent change in the fractional population that results in a maximum PLQY of 37% with 3.56% Tb­(III) incorporation. A decrease in the degree of inversion (cation disorder) leads to larger amounts of the cubic Fd m phase resulting in the observed photoluminescence behavior. The correlation of NMR, pXRD, and optical methods provides direct insight into the high PLQY behavior for this class of nanophosphor.

Latva’s empirical rule states that the energy separation between a molecular sensitizer and a lanthanide ion excited state must lie within 2000 to 4000 cm–1 for optimal energy transfer. At energies below 2000 cm–1, back energy transfer will impact the process resulting in the reduction of the photoluminescence quantum yield (PLQY). The role of excited triplet state (3π*) energy and intralanthanide ion energy hopping is assessed for a series of β-diketonate molecular sensitizers coordinated to the surface of a 2 nm 3.56% Tb­(III):ZnAl2O4 nanospinel. It is observed that energy transfer from the β-diketonate to a 2 nm nanospinel lies within the critical radii for energy transfer and the presence of efficient energy hopping minimizes back energy transfer contributions. In contradiction to Latva’s rule, the highest PLQY of 39% is achieved following sensitization by hexafluoroacetylacetonate, with an energy difference (3π*-5D4) of only 1534 cm–1. The measured PLQY is consistent with other reports of Tb­(III) doped nanocrystal hosts lattices, suggesting that energy hopping within the lattice enhances the Tb­(III) phosphor performance. Although not measured, the energy gap plot suggests that a PLQY approaching 58% may be achievable by ligand design.

Abstract:We prepared pyridine-2,6-bis(ethyl)ester [BEP] and pyridine-2,6-bis(diethylamide) [BDP] polymers with polycarbonate backbones by ring-opening polymerization of the pyridinebis(ethyl)ester and pyridine-bis(diethylamide) units appended to a cyclic carbonate via a glycol chain. The polymers were characterized by FTIR, NMR, UV/Vis absorption and fluorescence spectroscopy, as well as SEC, powder XRD, DSC, and TGA. The measured glass transition temperature (T g ) of the BEP polymer was shifted from -32°C to -7 and -8°C after coordination of the Eu III and Tb III ions, respectively. Similarly, the T g of the BDP