The hydrogenation of nitrobenzene into aniline is one of industrially important reactions, but still remains great challenge due to the lack of highly active, chemo-selective and eco-friendly ...catalyst. By using extensive density functional theory (DFT) calculations, herein we predict that single Pt atom decorated g-C
3
N
4
(Pt@g-C
3
N
4
) exhibits excellent catalytic activity and selectivity for the conversion of nitrobenzene into aniline under visible light. The overall activation energy barrier for the hydrogenation of nitrobenzene on single atom Pt@g-C
3
N
4
catalyst is even lower than that of the bare Pt(111) surface. The dissociation of N–O bonds on single Pt atom is triggered by single hydrogen atom rather than double hydrogen atoms on the Pt(111) surface. Moreover, the Pt@g-C
3
N
4
catalyst exhibits outstanding chemoselectivity towards the common reducible substituents, such as phenyl,–C=C,–C≡C and–CHO groups during the hydrogenation. In addition, the doped single Pt atom can significantly enhance the photoconversion efficiency by broadening the light absorption of the pristine g-C
3
N
4
to visible light region. Our results highlight an interesting and experimentally synthesized single-atom photocatalyst (Pt@g-C
3
N
4
) for efficient hydrogenation of nitrobenzene to aniline under a sustainable and green approach.
Display omitted
•The CO2RR on precise number of Fe atoms is systematically investigated.•Fe dimer and Fe trimer exhibit the highest catalytic performance toward CO2-to−CH4 and CO2-to−HCOOH ...conversion, respectively.•The catalytic activity and selectivity can be significantly tuned by controlling the number of Fe atoms.
Single atom catalysts have become a hot frontier in heterogeneous catalysis due to the low cost and high catalytic efficiency. However, a general question is whether a single atom active site is the most optimal to deliver the highest catalytic activity and selectivity or not? By using ab initio studies, herein we report a systematic investigation of the active-site dependent activity/selectivity for CO2 electrochemical reduction over a few Fe atoms (Fen, n = 1–4) doped graphdiyne. We find that Fe dimer and Fe trimer exhibit the highest catalytic activity and selectivity with the remarkably low rate determining step of 0.29 and 0.35 eV toward CO2-to−CH4 and CO2-to−HCOOH conversion, outperforming many reported catalysts to date. Moreover, the catalytic activity and selectivity can be significantly tuned by controlling the number of Fe atoms. The modulation of performance is attributed to the broken linear scaling relationship on different active-site structures that can significantly tune affinities to the key intermediates such as *CO, *CHO, *OCHO and*OCHOH, thus leading to efficient CO2 reduction over catalyst size. Our work is the first report of catalyst size effects for precise number of atoms (Fe1-4) which may open a new avenue for nanocatalyst design for electrochemical reduction of CO2.
The oxygen evolution reaction (OER) represents the rate-determining step of electrocatalytic water splitting into hydrogen and oxygen. Creating oxygen vacancies and adjusting their density has proven ...to be an effective strategy to design high-performance OER catalysts. Herein, a hydrogenation method is applied to treat a two-dimensional (2D) iron-cobalt oxide (Fe
1
Co
1
O
x
-origin), with the purpose of tuning its oxygen vacancy density. Notably, compared with Fe
1
Co
1
O
x
-origin, the iron-cobalt oxide hydrogenated at 200 °C and 2.0 MPa optimized conditions exhibits a markedly improved OER activity in 1.0 M KOH (with an overpotential
η
of 225 mV at a current density of 10 mA·cm
–2
) and a rapid reaction kinetics (with a Tafel slope of 36.0 mV·dec
–1
). Moreover, the OER mass activity of the hydrogenated oxide is 1.9 times that of Fe
1
Co
1
O
x
-origin at an overpotential of 350 mV. The experimental results, combined with density functional theory (DFT) calculations, reveal that the optimal control of oxygen vacancies in 2D Fe
1
Co
1
O
x
via hydrogenation can improve the electronic conductivity and promote OH
–
adsorption onto nearby low-coordinated Co
3+
sites, resulting in a significantly enhanced OER activity.
Retraction is a self-cleaning activity done in the global science community. In this study, the retraction of global scientific publications from 2001 to 2010 was quantitatively analyzed by using the
...Science Citation Index Expanded
. The results indicated that the number of retractions increased faster compared to the number of global scientific publications. Three very different patterns of retraction existed in each field. In the multi-disciplinary category and in the life sciences, retraction was relatively active. The impact factor strongly correlated with the number of retractions, but did not significantly correlate with the rate of retraction. Although the increases in the number of publications in China, India, and South Korea were faster, their retraction activities were higher than the worldwide average level.
2D black phosphorus (BP) is one promising electrocatalyst toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysis. The too strong adsorption of oxygen intermediates ...during OER, while the too weak adsorption of hydrogen intermediate during HER, however, greatly compromise its practical water splitting applications with overpotentials as high as 450 mV for OER and 420 mV for HER to achieve 10 mA cm−2 under alkaline conditions. Herein, by rationally introducing the nanosized iridium (Ir) modifier together with optimized exposing surface toward electrolytes, an efficient Ir‐modified BP electrocatalyst with much favorable adsorption energies toward catalytic intermediates possesses an outstanding pH‐universal water splitting performance, surpassing the nearly all reported BP‐based catalysts and the commercial noble‐metal catalysts. The Ir‐modified BP catalyst with the optimized exposed surfaces only requires an overall cell voltage of 1.54 and 1.57 V to achieve 10 mA cm−2 in acidic and alkaline electrolysers, respectively. This design uncovers the potential applications of 2D BP in practical electrocatalysis fields via decreasing reaction intermediate adsorption energy barriers and promoting the interfacial electron coupling for heterostructured catalysts, and offers new insights into the surface‐dependent activity enhancement mechanism.
An efficient iridium‐modified 2D black phosphorus electrocatalyst is rationally designed to achieve the desired adsorption energies toward catalytic intermediates, and the resultant catalyst demonstrates outstanding pH‐universal water splitting performances, surpassing the commercially dominating catalysts. Furthermore, an interesting surface‐dependent activity enhancement mechanism is identified.
Background This study aimed to investigate the effect of bone marrow mesenchymal stem cell (BMSC)-derived exosome injection on cartilage damage and pain relief in both in vitro and in vivo models of ...osteoarthritis (OA). Methods The BMSCs were extracted from rat bone marrow of the femur and tibia. Chondrocytes were treated with IL-1beta to establish the in vitro model of OA. Chondrocyte proliferation and migration were assessed by CCK-8 and transwell assay, respectively. A rat model of OA was established by injection of sodium iodoacetate. At 6 weeks after the model was established, the knee joint specimens and dorsal root ganglion (DRG) of rats were collected for histologic analyses. For pain assessment, paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were evaluated before model establishment and at 1, 2, 4, and 6 weeks after model establishment. Results Exosomes can be endocytosed with the chondrocytes in vitro. Exosome treatment significantly attenuated the inhibitory effect of IL-1beta on the proliferation and migration of chondrocytes. Exosome pre-treatment significantly attenuated IL-1beta-induced downregulation of COL2A1 and ACAN and upregulation of MMP13 and ADAMTS5. In the animal study, exosome treatment significantly upregulated COL2A1 protein and downregulated MMP13 protein in the cartilage tissue of the OA rat. At weeks 2, 4, and 6, the PWL value was significantly improved in the exosome-treated OA rats as compared with the untreated OA animals. Moreover, exosome treatment significantly alleviated the upregulation of CGRP and iNOS in the DRG tissue of OA rats. Conclusion BMSC-derived exosomes can effectively promote cartilage repair and extracellular matrix synthesis, as well as alleviate knee pain in the OA rats. Keywords: Osteoarthritis, Chondrocytes, BMSC-derived exosomes, Pain relief
The fabrication of electrocatalysts that are active for more than one of the water splitting reactions has gained significant momentum. Here we demonstrate such a material produced via an ...electrochemical process that is based on amorphous cobalt sulfide films doped with oxygen which are active for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline conditions. The optimum electrochemical protocol was found to be a repetitive potential cycling approach rather than a constant potential to create an amorphous CoS x film containing oxygen. Samples with a Co : S ratio of 1.56 : 1 were found to be active for the HER in 0.5 M H 2 SO 4 , phosphate buffer and 0.1 M NaOH. Significantly this activity is comparable to highly crystalline nanomaterials of cobalt sulfide. Density functional theory calculations indicated that a reduced S–Co coordination number, as encountered in amorphous materials, leads to an optimum binding energy for hydrogen adsorption on the material which facilitates good electron transfer kinetics. In addition, this material was also active for the OER in alkaline conditions with evidence of conversion to cobalt oxide which gave a low overpotential of 370 mV for an applied current density of 10 mA cm −2 with a Tafel slope of 67 mV dec −1 . This simple approach shows promise for the fabrication of a dual action electrocatalyst for electrochemical water splitting under alkaline conditions.
PKC-δ is an important molecule for B-cell proliferation and tolerance. B cells have long been recognized to play a part in osteoimmunology and pathological bone loss. However, the role of B cells ...with PKC-δ deficiency in bone homeostasis and the underlying mechanisms are unknown. We generated mice with PKC-δ deletion selectively in B cells by crossing PKC-δ-loxP mice with CD19-Cre mice. We studied their bone phenotype using micro-CT and histology. Next, immune organs were obtained and analyzed. Western blotting was used to determine the RANKL/OPG ratio in vitro in B-cell cultures, ELISA assay and immunohistochemistry were used to analyze in vivo RANKL/OPG balance in serum and bone sections respectively. Finally, we utilized osteoclastogenesis to study osteoclast function via hydroxyapatite resorption assay, and isolated primary calvaria osteoblasts to investigate osteoblast proliferation and differentiation. We also investigated osteoclast and osteoblast biology in co-culture with B-cell supernatants. We found that mice with PKC-δ deficiency in B cells displayed an osteopenia phenotype in the trabecular and cortical compartment of long bones. In addition, PKC-δ deletion resulted in changes of trabecular bone structure in association with activation of osteoclast bone resorption and decrease in osteoblast parameters. As expected, inactivation of PKC-δ in B cells resulted in changes in spleen B-cell number, function, and distribution. Consistently, the RANKL/OPG ratio was elevated remarkably in B-cell culture, in the serum and in bone specimens after loss of PKC-δ in B cells. Finally, in vitro analysis revealed that PKC-δ ablation suppressed osteoclast differentiation and function but co-culture with B-cell supernatant reversed the suppression effect, as well as impaired osteoblast proliferation and function, indicative of osteoclast-osteoblast uncoupling. In conclusion, PKC-δ plays an important role in the interplay between B cells in the immune system and bone cells in the pathogenesis of bone lytic diseases.
Osteoarthritis (OA) is a high‐morbidity skeletal disease worldwide and the exact mechanisms underlying OA pathogenesis are not fully understood. Casein kinase 1 epsilon (CK1ε) is a serine/threonine ...protein kinase, but its relationship with OA is still unknown. We demonstrated that CK1ε was upregulated in articular cartilage of human patients with OA and mice with experimentally induced OA. Activity of CK1ε, demonstrated by analysis of phosphorylated substrates, was significantly elevated in interleukin (IL)‐1β‐induced OA‐mimicking chondrocytes. CK1ε inhibitor or CK1ε short hairpin RNA (shRNA) partially blocked matrix metalloproteinase (MMP) expression by primary chondrocytes induced by IL‐1β, and also inhibited cartilage destruction in knee joints of experimental OA model mice. Conversely, overexpression of CK1ε promoted chondrocyte catabolism. Previous studies indicated that CK1ε was involved in canonical Wnt/β‐catenin signaling and noncanonical Wnt/c‐Jun N‐terminal kinase (JNK) signaling pathway. Interestingly, the activity of JNK but not β‐catenin decreased after CK1ε knockdown in IL‐1β‐treated chondrocytes in vitro, and JNK inhibition reduced MMP expression in chondrocytes overexpressing CK1ε, which illustrated that CK1ε‐mediated OA was based on JNK pathway. In conclusion, our results demonstrate that CK1ε promotes OA development, and inhibition of CK1ε could be a potential strategy for OA treatment in the future.
PDF
