ZnO Quantum Dots Coupled with Graphene toward Electrocatalytic N2 Reduction: Experimental and DFT Investigations.

Electrochemical reduction of N2 to NH3 is a promising method for artificial N2 fixation, but it requires efficient and robust electrocatalysts to boost the N2 reduction reaction (NRR). Herein, a combination of experimental measurements and theoretical calculations revealed that a hybrid material in which ZnO quantum dots (QDs) are supported on reduced graphene oxide (ZnO/RGO) is a highly active and stable catalyst for NRR under ambient conditions. Experimentally, ZnO/RGO was confirmed to favor N2 adsorption due to the largely exposed active sites of ultrafine ZnO QDs. DFT calculations disclosed that the electronic coupling of ZnO with RGO resulted in a considerably reduced activation-energy barrier for stabilization of *N2 H, which is the rate-limiting step of the NRR. Consequently, ZnO/RGO delivered an NH3 yield of 17.7 µg h-1 mg-1 and a Faradaic efficiency of 6.4 % in 0.1 m Na2 SO4 at -0.65 V (vs. RHE), which compare favorably to those of most of the reported NRR catalysts and thus demonstrate the feasibility of ZnO/RGO for electrocatalytic N2 fixation.

Boosted Electrocatalytic N2 Reduction on Fluorine-Doped SnO2 Mesoporous Nanosheets.

The development of highly active and durable electrocatalysts toward the N2 reduction reaction (NRR) holds a key to ambient electrocatalytic NH3 synthesis. Herein, fluorine (F)-doped SnO2 mesoporous nanosheets on carbon cloth (F-SnO2/CC) were developed as an efficient NRR electrocatalyst. Benefiting from the combined structural advantages of mesoporous nanosheet structure and F-doping, the F-SnO2/CC exhibited high NRR activity with an NH3 yield of 19.3 µg h-1 mg-1 and a Faradaic efficiency of 8.6% at -0.45 V (vs RHE) in 0.1 M Na2SO4, comparable or even superior to those of most reported NRR electrocatalysts. Density functional theory calculations revealed that the F-doping could readily tailor the electronic structure of SnO2 to render it with improved conductivity and increased positive charge on active Sn sites, leading to the lowered reaction energy barriers and boosted NRR activity.

Using 2003-2014 U.S. NHANES data to determine the associations between per- and polyfluoroalkyl substances and cholesterol: Trend and implications.

Exposure to per- and polyfluoroalkyl substances (PFASs) is a major concern due to their widespread occurrence and adverse health outcomes. The possible binding of PFASs to peroxisome proliferator-activated receptors (PPARs) and nuclear receptors raises concerns that PFASs may impact cholesterol levels in human. In this study, the U.S. National Health and Nutrition Examination Survey (NHANES) data were employed to address the temporal trend for PFAS concentrations in biomonitoring and associations between cholesterol levels and PFAS exposure. Compared to the PFAS levels in 2003-2004, the median perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS) and perfluorononanoic acid (PFNA) levels in human serum in 2013-2014 decreased from 3.7 to 1.8 ng/mL, 19.2-4.7 ng/mL, 1.7 ng/mL to 1.3 ng/mL and 0.8 ng/mL to 0.6 ng/mL, respectively. Also, an estimate of 1.5 ±â€¯0.7 mg/dL (95% confidence interval: 0.2 - 2.8) and 0.4 ±â€¯0.2 mg/dL (95% confidence interval: 0.1 - 0.6) total cholesterol increases for unit PFOA and PFOS increase (ng/mL), respectively. By using hybrid approach, RfDs were estimated to be 2.0 ng PFOS/kg per day and 0.8 ng PFOA/kg per day. However, it should be cautious when using proposed RfDs based on data obtained from cross-sectional datasets, especially evidence based on data originating from experimental or animal studies is still controversial.

Two-dimensional (2D)/2D Interface Engineering of a MoS2/C3N4 Heterostructure for Promoted Electrocatalytic Nitrogen Fixation.

The electrochemical nitrogen reduction reaction (NRR) is a very efficient method for sustainable NH3 production, but it requires effective catalysts to expedite the NRR kinetics and inhibit the concomitant hydrogen evolution reaction (HER). Two-dimensional (2D)/2D interface engineering is an effective method to design powerful catalysts due to intimate face-to-face contact of two 2D materials that facilitates the strong interfacial electronic interactions. Herein, we explored a 2D/2D MoS2/C3N4 heterostructure as an active and stable NRR catalyst. MoS2/C3N4 exhibited a conspicuously improved NRR performance with an NH3 yield of 18.5 µg h-1 mg-1 and a high Faradaic efficiency (FE) of 17.8% at -0.3 V, far better than those of the individual MoS2 or C3N4 component. Density functional theory calculations revealed that the interfacial charge transport from C3N4 to MoS2 could enhance the NRR activity of MoS2/C3N4 by promoting the stabilization of the key intermediate *N2H on Mo edge sites of MoS2 and concurrently decreasing the reaction energy barrier. Meanwhile, MoS2/C3N4 rendered a more favorable *H adsorption free energy on S edge sites than on Mo edge sites of MoS2, thereby protecting the NRR-active Mo edge sites from the competing HER and leading to a high FE.

Electronically Coupled SnO2 Quantum Dots and Graphene for Efficient Nitrogen Reduction Reaction.

Electrocatalytic N2 reduction reaction (NRR) provides an effective and renewable approach for artificial NH3 production, but still remains a grand challenge because of the low NH3 yield and Faradaic efficiency (FE). Herein, we reported that the SnO2 quantum dots (QDs) supported on reduced graphene oxide (RGO) could efficiently and stably catalyze NRR at ambient conditions. The NRR performance of resulting SnO2/RGO was studied by both experimental techniques and density functional theory calculations. It was found that the ultrasmall SnO2 QDs (2 nm) grown on RGO could provide abundant sites for efficient N2 adsorption. Significantly, the strongly electronically coupled SnO2 QDs and RGO brought about the enhanced conductivity and the decreased work function, which led to a considerably lowered energy barrier of *N2 → *N2H that was the rate-determining step of the NRR process. Meanwhile, the SnO2/RGO exhibited inferior hydrogen evolution reaction activity. As a result, the SnO2/RGO delivered a high NH3 yield of 25.6 µg h-1 mg-1 (5.1 µg cm-2h-1) and an FE of 7.1% in 0.1 M Na2SO4 at -0.5 V (vs RHE), together with the outstanding selectivity and stability, endowing it as a promising electrocatalyst for N2 fixation.

[Open-wedge high tibial osteotomy and unicomartmental knee arthroplasty in treating medial compartment osteoarthritis of the knee: a Meta analysis].

OBJECTIVE: To systematic evaluate the outcome of open-wedge high tibial osteotomy(OWHTO) and unicomartmental knee arthroplasty (UKA) in treating medial compartment osteoarthritis of the knee. METHODS: According to the retrieval strategy made by the Cochrane collaboration, a computer-base research of Medline, Pubmed, EMbase, Cochrane Library, CBM, CNKI, and Wanfang databases was performed and search deadline was March 2018. Related Chinese and English orthopedic journals and conference papers were manually searched. Controlled studies of OWHTO and UKA in the treatment of medial knee osteoarthritis were included. The quality of included researches was evaluated, and the data of postoperative knee function, complications, total knee arthroplasty(TKA) revision rates, and postoperative pain were extracted. Meta analysis was performed using the RevMan 5.0 software. RESULTS: A total of 8 articles that met the criteria were included containing a total of 675 patients. Meta-analysis showed that there was no significant difference in postoperative HSS score, knee score, functional score, and Lysholm score between the OWHTO and UKA groups(P=0.32, P=0.87, P=0.22, P=0.53). The range of joint motion in the OWHTO group was better than that in the UKA group, and the difference was statistically significant(P=0.009). There was no significant difference in postoperative complications and the rates of revision to TKA between the two groups(P=0.81, P=0.23). There was no difference in postoperative knee pain between the two groups. CONCLUSIONS: In the treatment of medial compartmental osteoarthritis of the knee that meets the surgical indications, OWHTO had better postoperative joint mobility. The results were similar in postoperative knee score, postoperative complications, and postoperative TKA revision rates between OWHTO and UKA groups.

[Ectopic osteogenesis of tissue engineered bone with slow-released bioactive factors].

OBJECTIVE: To study the ectopic osteogenesis of tissue engineered bone with recombinant human bone morphogenetic protein/transforming growth factor-beta (rhBMP/TGF-beta) or WO-1 slow-released factors. METHODS: Partial demineralized freeze-dried bone (PDFDB) of pig was used as scaffold material. rhBMP/TGF-beta or WO-1 were pre-coated on the surface of material by means of vacuum negative pressure absorption, and then coated with polylactic acid (PLA) to make slow-released material. There were six group: PDFDB material (group A); PDFDB combined with osteoblasts (group B); PDFDB material with rhBMP/TGF-beta slow-released system (group C); PDFDB material combined with rhBMP/TGF-beta slow-released system osteoblasts (group D); PDFDB with WO-1 slow-released system (group E); PDFDB material combined with WO-1 slow-released system and osteoblasts (group F) were implanted in bilateral lower limbs of 36 Newzealand rabbits respectively (6 rabbits in each groups). Histological, histochemical and biochemical analysis were detected 2, 4, 6, 8 weeks after operation. RESULTS: Within the observation periods, no osteogenesis was observed in group A. The osteogenesis in group B, D, F were superior to that of group C and E (P < 0.05). The osteogenetic activity in group C and E was delayed. The quantity and quality of osteogenesis in group D and F were 2 weeks ahead of time compared with group B, and 4 weeks to that of group C and E. The newborn calcification content was superior to that of group A, C, and E (P < 0.05). CONCLUSIONS: The osteogenesis of PDFDB materials with BMP/TGF-beta or WO-1 is slower than that of which combined with osteoblasts. Simple material PDFDB has no ectopic osteogenesis.

[Experimental study of periosteal osteoblasts coculture with freeze-dried demineralized bone matrix].

OBJECTIVE: To investigate the feasibility of freeze-dried demineralized bone matrix (FDBM) as scaffold material in bone tissue engineering. METHODS: Osteoblasts which were isolated from cranial periosteum of New Zealand rabbits were cultured as the seeding cells, then the cells were cocultured with heterogenous FDBM in vitro. The cell-material complex was observed under phase microscope, light microscope and electronic scanning microscope in order to evaluate the interaction between cells and FDBM. RESULTS: Eight hours after coculture, the osteoblasts adhered to FDBM scaffolds. Seven days later, the osteoblasts differentiated and proliferated in FDBM network. Extracellular matrix was secreted and calcium nodes were formed among osteoblasts. CONCLUSION: FDBM is a good scaffold material for the bone tissue engineering.