Kangwon National University

In this study, heterogeneous biochar catalysts derived from spent coffee grounds (HCBCs) and walnut shells (HWBCs) were synthesized at three pyrolysis temperatures (500 °C (HCBC500, HWBC500), 650 °C (HCBC650, HWBC650), and 800 °C (HCBC800, HWBC800)) to elucidate effects of changes in the aromatization degree determining electron exchange capacity (EEC) of heterogeneous biochar catalysts on the degradation of naproxen (NPX) via the electron transfer-mediated activation of peroxydisulfate (PDS). The greater EEC values of highly aromatic HCBCs and HWBCs produced at higher pyrolysis temperatures led to increased degradation efficiencies of NPX by the HCBCs/PDS and HWBCs/PDS systems. The HCBC800/PDS system achieved the highest degradation efficiency of NPX, at 80.9%, compared to 16.4-48.1% for other systems. These observations highlight that the EEC relying on the aromatization degree of heterogeneous biochar catalysts is a key factor governing the degradation of NPX via the electron transfer-mediated activation of PDS. In the HCBC800/PDS system, electrophilic decarboxylation induced by superoxide-derived singlet oxygen was mainly responsible for the degradation of NPX rather than hydroxyl radical-driven electrophilic hydroxylation. Moreover, the HCBC800/PDS system exhibited excellent reuse efficiency (≥73.2%) for the degradation of NPX over four consecutive cycles. Although increases in bioaccumulation potential and mutagenicity were detected for some degradation intermediates of NPX produced via the HCBC800/PDS system, most of them were less harmful to aquatic ecosystems. Therefore, HCBC800 could be a promising option as a carbonaceous material-based heterogeneous catalyst to activate PDS via the electron transfer for eliminating NPX.

The emergence and spread of Plasmodium falciparum resistance to malaria drugs pose a major threat to malaria control efforts. This study assessed the prevalence of molecular markers associated with resistance to key antimalarials in P. falciparum clinical isolates from Mzuzu and Lilongwe in Malawi. These two regions have high human mobility and are strategically located near the border with Zambia and Tanzania, respectively. A total of 1582 blood samples were collected from individuals who visited hospitals for diagnosis between December 2020 and June 2021. P. falciparum infections were confirmed using nested and quantitative PCR, and drug resistance marker genes (pfmdr1, pfcrt, pfk13, pfatp6, pfdhfr, and pfdhps) were sequenced by Sanger sequencing. No resistance-associated mutations were detected in pfk13 and pfcrt genes, supporting continued susceptibility to artemisinin derivatives and chloroquine (CQ). However, the pfmdr1-NFD haplotype, linked to reduced lumefantrine (LUM) susceptibility, was present in 159/371 (42.9%) isolates. Notably, the quadruple pfdhfr-pfdhps mutant haplotype (AIRNVI-SGEAA), associated with high-level sulfadoxine-pyrimethamine (SP) resistance, was found in 287/328 (87.5%) of isolates. These findings highlight the ongoing risk of declining efficacy of LUM partner drugs in artemisinin-based combination therapies (ACT) and reduced SP effectiveness for intermittent preventive treatment in pregnancy (IPTp). The absence of pfcrt mutations, together with the presence of wild-type pfmdr1 alleles lacking CQ-related mutation, suggests the re-emergence of CQ-sensitive parasites. Continuous molecular surveillance, alongside clinical efficacy studies, is essential to inform treatment policies and prevent the spread of drug-resistant malaria in Malawi.

Understanding the dynamic lattice collapse pathways under thermal stress is pivotal for designing stable perovskite and improving the power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, the lack of dynamic molecular-level characterization techniques has limited a comprehensive understanding of the degradation pathways involved. In this study, we use temperature-dependent Raman spectroscopy (25-375 °C) coupled with multimodal characterization to investigate A-site cation-dependent degradation pathways in mixed-halide perovskites, specifically FA_0.85Cs_0.15PbI₃ (FACs) and FA_0.85MA_0.15PbI₃ (FAMA). We identify three distinct stages of thermal decomposition dynamics with molecular-level precision: (1) grain boundary pre-collapse (25-175 °C), (2) halide segregation and PbI framework dynamics (200-325 °C), including PbI₂-defective domains, PbI₂ formation, and PbI₂ degradation, and (3) terminal lattice disintegration (350-375 °C). FACs preferentially stabilizes CsPbI₃ nanorods alongside amorphous β-PbO, whereas FAMA exclusively generates crystalline β-PbO without intermediate phases. Mechanistically, Cs⁺ acts as a lattice "scaffold", facilitating dynamic Pb-I-Cs coordination reconfiguration and delaying the degradation of the perovskite by more than 25 °C. In contrast, MA⁺ induces abrupt structural collapse via methylammonium volatilization, creating vacancy-propagated disintegration channels. By correlating Raman fingerprint (e.g., β-PbO at 139 cm^-1) with XRD/PL decay kinetics, we establish a predictive framework for A-site cation selection. This study not only reveals the mechanism of lattice anchoring and dynamic coordination reconstruction regulated by A-site cations at the molecular level but also clarifies the previously ambiguous Raman band assignments. These findings highlight the potential of Raman spectroscopy as a dynamic roadmap for elucidating degradation mechanisms and guiding the design of thermally resilient perovskites.