Synergistic antimicrobial effect of lactocin AL705 and nisin combined with organic acid salts against Listeria innocua 7 in broth and a hard cheese

The effectiveness of antimicrobial mixtures against Listeria innocua 7, used as a L. monocytogenes surrogate, was investigated in broth and a food system. Synergistic effects were found for nisin (Nis), potassium sorbate (PS), calcium propionate (CP) and sodium lactate (SL), Nis + PS being the most effective binary mixture that exhibited listericidal activity in broth. To assess the effect of adding lactocin AL705 (AL705) to Nis + organic acid salt combinations, tridimensional isobolograms were generated. Sub-MIC combinations of the antimicrobials exerted bactericidal activity against L. innocua 7 after AL705 addition to the binary mixtures. However, when applied on Sardo cheese contaminated with L. innocua 7 (initial inoculum 4.45 ± 0.06 CFU g⁻¹), only Nis + PS + AL705 produced count reductions respect to the control, reaching 3.04 ± 0.35 CFU g⁻¹ counts after 15 days at 15 °C. Ternary combinations containing AL705 showed potential to reduce antimicrobial usages for L. innocua 7 inhibition.     

水热法制备Sr_2FeNiO_6催化剂及其催化性能研究

采用水热法制备双钙钛矿催化剂Sr_2FeNiO_6,考察不同浓度KOH溶液(4 mol·L~(-1)、6 mol·L~(-1)、8 mol·L~(-1)、10 mol·L~(-1)、12 mol·L~(-1)、14 mol·L~(-1))对催化剂性能的影响,利用X射线衍射、比表面积测定、程序升温还原和扫描电镜等对样品进行性能表征,并以催化甲烷燃烧为目标,考察催化剂催化性能。结果表明,矿化剂KOH浓度对样品性能影响较大,当浓度为10 mol·L~(-1)时,起燃温度最低,T_(10%)为430℃;浓度为8 mol·L~(-1)时,样品比表面积最大,为19.0 m~2·g~(-1),完全燃烧温度最低,T_(90%)为610℃。     

Preparation and photocatalytic activity of g-C3N4/TiO2 heterojunctions under solar light illumination

The solar light sensitive g-C₃N₄/TiO₂ heterojunction photocatalysts containing 20, 50, 80, and 90 wt% graphitic carbon nitride (g-C₃N₄) were prepared by growing Titania (TiO₂) nanoparticles on the surfaces of g-C₃N₄ particles via one step hydrothermal process. The hydrothermal reactions were allowed to take place at 110 °C at autogenous pressure for 1 h. Raman spectroscopy analyses confirmed that an interface developed between the surfaces of TiO₂ and g-C₃N₄ nanoparticles. The photocatalyst containing 80 wt% g-C₃N₄ was subsequently heat treated 1 h at temperatures between 350 and 500 °C to improve the photocatalytic efficiency. Structural and optical properties of the prepared g-C₃N₄/TiO₂ heterojunction nanocomposites were compared with those of the pristine TiO₂ and pristine g-C₃N₄ powders. Photocatalytic activity of all the nanocomposites and the pristine TiO₂ and g-C₃N₄ powders were assessed by the Methylene Blue (MB) degradation test under solar light illumination. g-C₃N₄/TiO₂ heterojunction photocatalysts exhibited better photocatalytic activity for the degradation of MB than both pristine TiO₂ and g-C₃N₄. The photocatalytic efficiency of the g-C₃N₄/TiO₂ heterojunction photocatalyst heat treated at 400 °C for 1 h is 1.45 times better than that of the pristine TiO₂ powder, 2.20 times better than that of the pristine g-C₃N₄ powder, and 1.24 times better than that of the commercially available TiO₂ powder (Degussa P25). The improvement in photocatalytic efficiency was related to i) the generation of reactive oxidation species induced by photogenerated electrons, ii) the reduced recombination rate for electron-hole pairs, and iii) large specific surface area.     

白藜芦醇丙烯酸酯的合成及抗氧化活性研究

以白藜芦醇为先导化合物,合成了白藜芦醇丙烯酸酯,以获得具有更好抗氧化活性的白藜芦醇衍生物。以白藜芦醇和丙烯酰氯为原料,酯化法得到白藜芦醇丙烯酸酯。以维生素C为阳性对照,研究白藜芦醇丙烯酸酯对2,2-联苯-1-苯基肼(DPPH)自由基的清除活性和抗氧化活性。用NMR和HRLC-MS对白藜芦醇丙烯酸酯进行了表征。目标产物白藜芦醇丙烯酸酯收率为30.2%。白藜芦醇丙烯酸酯的抗氧化活性高于白藜芦醇,但低于维生素C。合成得到了白藜芦醇丙烯酸酯,其反应路线简单易行,条件温和,产物抗氧化活性较先导化合物有所提高。     

Laser induced formation of copper species over TiO2 nanotubes towards enhanced water splitting performance

We proposed fast and scalable route where the ordered TiO₂ nanotubes coated with thin copper layers were annealed by the laser beam of 355 nm wavelength at different fluencies in the range of 15–120 mJ/cm². As a result, copper species are integrated with the titania substrate and the formed material exhibits unique optical absorption bands in the visible range. Moreover, X-ray photoelectron spectroscopy analysis reveals the formation of Cu₂O while the 4⁺ oxidation state of titanium is preserved. According to the electrochemical results, the material treated by laser exhibits outstanding photoelectrochemical activity comparing to the pristine titania or the one only covered by the thin copper film. In particular, when the fluence of 60 mJ/cm² was used for the modification of the titania decorated with Cu film, the current density recorded in KOH electrolyte reaches nearly 4.5 mA/cm² at +2.0 V vs. Ag/AgCl/0.1 M KCl upon visible light.     

Fabrication of magnetically recoverable Fe3O4/CdS/g-C3N4 photocatalysts for effective degradation of ciprofloxacin under visible light

Photocatalytic technology is an environmentally safe method of eliminating organic pollutants and antibiotics in wastewater. In this research, the performance of Fe₃O₄/CdS/g-C₃N₄ (FCN) photocatalyst for degradation of antibiotics was studied. The composite photocatalysts with different concentrations of g-C₃N₄ were prepared. FCN has better photocatalytic activity than degradation dyes in removal of antibiotics under visible light. This indicates that FCN could effectively hinder the recombination of carriers, and the addition of g-C₃N₄ increases the optical response range of CdS. At the same time, the introduction of Fe₃O₄ magnetic nanoparticles overcomes the problem of difficulty in recovery of the powder photocatalyst. The photocatalytic activity is not reduced to any significant after three cycles of use.     

Tuning morphology and structure of Fe–N–C catalyst for ultra-high oxygen reduction reaction activity

Exploring efficient and durable non-precious metal catalysts for oxygen reduction reaction (ORR) has long been pursued in the field of metal-air batteries, fuel cells, and solar cells. Rational design and controllable synthesis of desirable catalysts are still a great challenge. In this work, a novel approach is developed to tune the morphologies and structures of Fe–N–C catalysts in combination with the dual nitrogen-containing carbon precursors and the gas-foaming agent. The tailored Fe–N₁/N₂–C-A catalyst presents gauze-like porous nanosheets with uniformly dispersed tiny nanoparticles. Such architectures exhibit abundant Fe-N_x active sites and high-exposure surfaces. The Fe–N₁/N₂–C-A catalyst shows extremely high half-wave potential (E_1/2, 0.916 V vs. RHE) and large limiting current density (6.3 mA cm⁻²), far beyond 20 wt% Pt/C catalyst for ORR. This work provides a facile morphological and structural regulation to increase the number and exposure of Fe-N_x active sites.     

One-step fabrication of highly self-hydroxylated TiO2 mesocrystals and photocatalytic behavior towards water splitting

TiO₂ mesocrystals have been considered as an efficient photocatalyst due to the effective charge transport. Introducing hydroxyls in TiO₂ is respected to reduce the energy barrier of hydrogen formation. Herein, a simple one-step fabrication of highly self-hydroxylated TiO₂ mesocrystals (MCs) for enhancing photocatalytic hydrogen evolution is proposed. TiO₂ single crystals (SCs), polycrystals (PCs) and MCs are obtained via regulating the pH of the precursor during hydrothermal treatment. Results indicate that the moderate alkaline condition is favorable for the synthesis of highly self-hydroxylated TiO₂ MCs. Compared with SCs, PCs and commercial P25 TiO₂ nanoparticles, MCs exhibit the best photocatalytic activity in H₂ evolution. Specifically, the maximum hydrogen evolution rate under solar light illumination (22.8 mmol/h/g) is 10.5 times higher than that of P25. Moreover, the MCs exhibit excellent catalytic stability and the hydrogen evolution rate can be maintained at 20.8 mmol/h/g under solar illumination after five cycles of reactions. The highly self-hydroxylated TiO₂ MCs are constructed from crystallographically oriented nanocrystals with abundant hydroxyls. The unique superstructure and large surface area of MCs enable the effective charge separation and transport. Moreover, the high density of hydroxyls can reduce the recombination rate of photo-generated free charges and energy barrier for hydrogen formation while facilitate light absorption. The synthesis of highly self-hydroxylated TiO₂ MCs and the underlying mechanism offer interesting insights for modifying the structure and properties of TiO₂ towards high-performance hydrogen evolution.     

Enhanced photocatalytic activity of graphene oxide/titania nanosheets composites for methylene blue degradation

In the present work, we report enhanced photocatalytic degradation of methylene blue dye in aqueous solution by using ultra-thin anatase TiO₂ nanosheets (NSs) combined with graphene oxide (GO) as a photocatalyst. The two-dimensional ultra-thin anatase TiO₂ NSs are fabricated via chemical exfoliation. By completely delaminating a lepidocrocite-type layered protonic titanate H_xTi_2−x/4□_x/4O₄·H₂O (x=0.7, □: vacancy) into individual layers through ion exchange with tetrabutylammonium (TBA⁺) cations, well-dispersed ultra-thin colloidal Ti_0.91O₂ NSs with a lateral size up to a few micrometers are obtained. Subsequent acid treatment induces colloidal Ti_0.91O₂ to reassemble and precipitate into a gelation form, followed by thermal annealing to convert the Ti_0.91O₂ gelation into anatase TiO₂ nanosheets as photocatalyst for methylene blue degradation. TiO₂ NSs show a high photocatalytic degradation efficiency of 53.2% due to the ultra-thin thickness for facile electron transfering and large surface area for methylene blue absorption. Moreover, photocatalytic effect can be further improved by simply adding GO suspension to achieve colloidal self-assembly of GO and TiO₂ NSs. An optimal GO content of 3 wt% further increases the photocatalytic degradation efficiency to 91.2% due to faster electron–hole seperation and improved surface area provided by GO. This work provides a simple but effective approach by combing graphene oxide with TiO₂ nanosheets synthesized via the exfoliation method for methylene blue degradation.