Core-Shell Covalently Linked Graphitic Carbon Nitride-Melamine-Resorcinol-Formaldehyde Microsphere Polymers for Efficient Photocatalytic CO2 Reduction to Methanol.

Photocatalytic reduction of CO2 with light and H2O to form CH3OH is a promising route to mitigate carbon emissions and climate changes. Although semiconducting metal oxides are potential photocatalysts for this reaction, low photon efficiency and leaching of environmentally unfriendly toxic metals limit their applicability. Here, we report metal-free, core-shell photocatalysts consisting of graphitic carbon nitride (g-C3N4, CN) covalently linked to melamine-resorcinol-formaldehyde (MRF) microsphere polymers for this reaction. Covalent linkage enabled efficient separation of photo-generated carriers and photocatalysis. Using 100 mg of a photocatalyst containing 15 wt % CN, a CH3OH yield of 0.99 µmol·h-1 was achieved at a reaction temperature of 80 °C and 0.5 MPa with external quantum efficiencies ranging from 5.5% at 380 nm to 1.7% at 550 nm. The yield was about 20 and 10 times higher than that of its components CN and MRF, respectively. Characterization with X-ray photoelectron spectroscopy, transmission electron microscopy, and bulk and surface elemental analyses supported the formation of a core-shell structure and the charge transfer in the C-N bond at the CN-MRF interface between the methoxy group in the 2,4-dihydroxylmethyl-1,3-diphenol part of MRF and the terminal amino groups in CN. This enhanced ligand-to-ligand charge transfer resulted in 67% of the photo-excited internal charge transferred from CN to the hydroxymethylamino group in MRF, whose amino group was the catalytic site for the CO2 photocatalytic reduction to CH3OH. This study provides a series of new metal-free photocatalyst designs and insights into the molecular-level structure-mediated photocatalytic response.

Preparation of soft magnetic Fe-Ni-Pb-B alloy nanoparticles by room temperature solid-solid reaction.

The Fe-Ni-Pb-B alloy nanoparticles was prepared by a solid-solid chemical reaction of ferric trichloride, nickel chloride, lead acetate, and potassium borohydride powders at room temperature. The research results of the ICP and thermal analysis indicate that the resultants are composed of iron, nickel, lead, boron, and PVP, and the component of the alloy is connected with the mole ratio of potassium borohydride and the metal salts. The TEM images show that the resultants are ultrafine and spherical particles, and the particle size is about a diameter of 25 nm. The largest saturation magnetization value of the 21.18 emu g(-1) is obtained in the Fe-Ni-Pb-B alloy. The mechanism of the preparation reaction for the Fe-Ni-Pb-B multicomponent alloys is discussed.

Calcium citrate: a new biomaterial that can enhance bone formation in situ.

OBJECTIVE: To investigate the effect of a new biomaterial combining calcium citrate and recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone regeneration in a bone defect rabbit model. METHODS: Totally 30 male New Zealand white rabbits were randomly and equally divided into calcium citrate-rhBMP-2 (CC-rhBMP-2) group and rhBMP-2 only group. Two 10 mm-long and 5 mm-deep bone defects were respectively created in the left and right femoral condyles of the rabbits. Subsequently 5 pellets of calcium citrate (10 mg) combined with rhBMP-2 (2 mg) or rhBMP-2 alone were implanted into the bone defects and compressed with cotton swab. Bone granules were obtained at 2, 4 and 6 weeks after procedure and received histological analysis. LSD t-test and a subsequent t-test were adopted for statistical analysis. RESULTS: Histomorphometric analysis revealed newly formed bones, and calcium citrate has been absorbed in the treatment group. The percent of newly formed bone area in femoral condyle in control group and CC-rhBMP-2 group was respectively 31.73%+/-1.26% vs 48.21%+/-2.37% at 2 weeks; 43.40%+/-1.65% vs 57.32%+/-1.47% at 4 weeks, and 51.32%+/-7.80% vs 66.74%+/-4.05% at 6 weeks (P less than 0.05 for all). At 2 weeks, mature cancellous bone was observed to be already formed in the treatment group. CONCLUSION: From this study, it can be concluded that calcium citrate combined with rhBMP-2 signifcantly enhances bone regeneration in bone defects. This synthetic gelatin matrix stimulates formation of new bone and bone marrow in the defect areas by releasing calcium ions.

Using polyethylene glycol to facilitate the absorption of NO2 in sulfite solutions: Kinetics and mechanism.

A new method was developed to scrub NOx compounds in flue gases during the integrated technology of WFGD associated with ozone oxidation, among which polyethylene glycol (PEG) was utilized initially as an additive to facilitate the absorption of NO2 by sulfite solution. Notably, absorption was significantly facilitated with adding PEG into absorbent. Compared to absorption by sulfite solution alone, NO2 removal efficiency with PEG addition increased from 58.75% to 89.17%. Furthermore, the favorable role of PEG was considered to be ascribed to the its improvement on the rate-determining step among absorption process ── mass transfer of NO2 into the liquid phase. A potential chemical transformation pathway between NO2, SO32- and PEG was proposed, and based on the hydrogen bonding between the various compounds. Additionally, a kinetic model was established based on various operating parameters that included adsorbent pH, ionic strength of S species, temperature, flow rate, and inlet SO2 concentration. This model provides theoretical support for practical engineering.