All-inorganic Pb-free bismuth (Bi) halogen perovskite quantum dots (PQDs) with distinct structural and photoelectric properties provide plenty of room for selective photoreduction of CO 2 . However, the efficient conversion of CO 2 -to-CO with high selectivity on Bi-based PQDs driven by solar light remains unachieved, and the precise reaction path/ mechanism promoted by the surface halogen-associated active sites is still poorly understood. Herein, we screen a series of nontoxic and stable Cs 3 Bi 2 X 9 (X = Cl, Br, I) PQDs for selective photocatalytic reduction of CO 2 -to-CO at the gas−solid interface. Among all the reported pure-phase PQDs, the assynthesized Cs 3 Bi 2 Br 9 PQDs exhibited the highest CO 2 -to-CO conversion efficiency generating 134.76 μmol g −1 of CO yield with 98.7% selectivity under AM 1.5G simulated solar illumination. The surface halogen-associated active sites and reaction intermediates were dynamically monitored and precisely unraveled based on in situ DRIFTS investigation. In combination with the DFT calculation, it was revealed that the surface Br sites allow for optimizing the coordination modes of surfacebound intermediate species and reducing the reaction energy of the rate-limiting step of COOH − intermediate formation from • CO 2 − . This work presents a mechanistic insight into the halogen-involved catalytic reaction mechanism in solar fuel production.

Lead (Pb) halide perovskite quantum dots (PQDs) are promising candidates for the photochemical reduction of CO 2 . However, the intrinsically weak adsorption and activation toward inert CO 2 molecules have seriously hindered their practical application. This study reports alternative Cs 2 CuBr 4 PQDs for gas−solid phase photocatalytic CO 2 reduction under simulated solar irradiation. Cs 2 CuBr 4 PQDs exhibited CO 2 photoreduction performance with CH 4 and CO yields of 74.81 and 148.98 μmol g −1 , respectively. In situ diffuse reflectance infrared Fourier transform spectra and density functional theory calculations cooperatively revealed the synergistic strengthening of microelectronic polarization in Cs 2 CuBr 4 PQDs induced by surface-frustrated Lewis pair-like properties and intrinsic Cu d-band properties facilitated robust CO 2 adsorption and activation. This study demonstrated the potential of Cs 2 CuBr 4 PQDs as a platform for highly efficient CO 2 photoreduction and provided a distinct concept for CO 2 adsorption and activation based on the catalytic mechanism of Cu-based PQDs. KEYWORDS: photocatalytic CO 2 reduction, Cs 2 CuBr 4 , perovskite quantum dots, CO 2 adsorption and activation, catalytic mechanism

Background: Corona virus disease (COVID-19) is an infectious respiratory disease that has spread rapidly across the world. Many studies have already evaluated the clinical features of COVID-19, but how it compares with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-negative community-acquired pneumonia (SN-CAP) is still unclear. Moreover, COVID-19 mortality is correlated with disease severity, but indicators for severity grading have not been specified. We aimed to analyze the clinical characteristics of COVID-19 in comparison with SN-CAP and find indicators for disease severity in COVID-19. Methods: Patients diagnosed with COVID-19 and SN-CAP were enrolled. Clinical, radiological, and laboratory data were analyzed. Results: The numbers of COVID-19 and SN-CAP patients enrolled were 304 and 138, respectively. The age of the patients was not significantly different between the groups. Compared with SN-CAP, COVID-19 patients had more symptoms of fever and dyspnea; and showed significant difference in blood count results. Computed tomography (CT) imaging of COVID-19 patients showed patchy ground-glass opacities that correlated with disease severity, whereas the CT imaging of SN-CAP patients showed patchy high-density shadows. COVID-19 patients were classified into moderate, severe, and critically severe groups. The severe and critically severe groups had elevated levels of white blood cells (WBC), neutrophils, platelets, C-reaction protein (CRP), lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), troponin-I, creatinine, and blood urea nitrogen (BUN). However, they had decreased levels of lymphocytes, lymphocyte ratio, and albumin. Compared with the younger patients, the older COVID-19 individuals had more chronic diseases and significantly elevated levels of WBC, neutrophil, and CRP levels. Conclusion: SN-CAP showed more inflammatory reaction than COVID-19. Old people with chronic diseases are more susceptible to COVID-19 and have a high likelihood of developing severe and critically severe infection. Levels of WBC, lymphocytes, neutrophils, CRP, NLR, PLR, troponin-I, creatinine, and BUN are important indicators for severity grading in COVID-19.

CO 2 photoreduction currently faces two challenges: low photoreduction efficiency and poor product selectivity. Ultrathin twodimensional bismuth oxyhalide, with a large number of surface vacancies (active sites), is an ideal material for regulating CO 2 photoconversion. However, surface vacancies in this catalyst are easily deactivated during the reaction. CO 2 photoreduction relies on sufficient active sites; hence, we synthesized ultrathin Bi 4 O 5 Cl 2 nanoplates via a water-assisted self-assembly process with sufficient photoswitchable surface Cl vacancies for solar-driven CO 2 -to-CO reduction. The surface Cl vacancies were generated under light irradiation and filled again with migrated Cl − under an O 2 atmosphere after turning off the irradiation. These photoswitchable vacancies enabled Bi 4 O 5 Cl 2 to produce 58.49 μmol g −1 CO after 4 h of irradiation with high stability and lowered the energy barriers of the rate-determining (CO 2 -to-COOH − ) and selectivity-determining steps (COOH − -to-CO), enabling 100% product selectivity. The reversible, photoswitchable Cl vacancies have a higher potential as active sites for CO 2 photoreduction than synthetically introduced static surface vacancies, which could provide a feasible strategy for the creation of highly dynamic, active-defective catalysts for solar-energy conversion.

Tooth movement is a biological process of bone remodeling induced by mechanical force. Sclerostin secreted by osteocytes is mechanosensory and important in bone remodeling. However, little is known regarding the role of sclerostin in tooth movement. In this study, models of experimental tooth movement were established in rats and mice. Sclerostin expression was investigated with immunohistochemistry staining, and osteoclastic activity was analyzed with tartrate-resistant acid phosphatase (TRAP) staining. MLO-Y4 osteocyte-like cells underwent uniaxial compression and tension stress or were cultured in hypoxia conditions. Expression of sclerostin was assessed by RT-qPCR and ELISA. MLO-Y4 cells were cultured with recombinant human sclerostin (rhSCL) interference and then co-cultured with RAW264.7 osteoclast precursor cells. Expressions of RANKL and OPG were analyzed by RT-qPCR, and osteoclastic activity was assessed by TRAP staining. During tooth movement, sclerostin was expressed differently in compression and tension sites. In SOST knock-out mice, there were significantly fewer TRAP-positive cells than in WT mice during tooth movement in compression sites. In-vitro studies showed that the expression of sclerostin in MLO-Y4 osteocyte-like cells was not different under a uniaxial compression and tension force, whereas hypoxia conditions significantly increased sclerostin expression in MLO-Y4 cells. rhSCL interference increased the expression of RANKL and the RANKL/OPG ratio in MLO-Y4 cells and the osteoclastic induction ability of MLO-Y4 cells in experimental osteocyte-osteoclast co-culture. These data suggest that sclerostin plays an important role in the bone remodeling of tooth movement.