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A series of porous carbon nitrides modified by different polyoxometalates (POMs) were prepared by the ultrasonic method. POMs were assembled on the surface of mpg-C3N4 via electrostatic attraction. The catalyst has visible light degradation activity for phenol (λ > 420 nm). mpg-C3N4 modified by H4SiW12O40 with a mass ratio of 1 : 5 showed the highest catalytic activity, which was 3.5 times higher than that of mpg-C3N4. As an electron acceptor, polyoxometalate can capture the photoelectron of C3N4, which can promote the separation of photocharge and improve the photocatalytic activity. ESR also confirmed that the superoxide radicals play a major role in degradation. The results show that the charge separation efficiency and catalytic activity can be enhanced by polyacids.

The time-consuming assembling process of the traditional photonic crystals (PCs) and non-water-dispersibility of the reported magnetic responsive PCs (MRPCs) have greatly limited the application especially in the biotechnological fields. Herein, the hydrophilic and size-controllable Fe3O4@poly(4-styrenesulfonic acid-co-maleic acid) (PSSMA)@SiO2 MRPCs were fabricated by orderly assembling of the core–shell colloidal nanocrystal clusters via a two-step facile synthesis approach. Due to the rich carboxyl and hydroxyl groups of PSSMA, the obtained MRPCs have excellent properties of hydrophilicity, high surface charge which presented magnetically tunable photonic structural colors, and rapid reflection signal in aqueous solution under external magnetic field within 1 s. The diffraction color of the MRPCs in the entire visible range could be tuned by adjusting the magnetic strength or the nanoparticle size, which bring a clear change of the structure color from brilliant red to modena by the naked eye. Thus, th...

Birnessite-type MnO2 materials are widely studied as electrodes for pseudocapacitors. However, the poor cycling stability limits their applications. Here, wrinkle birnessite-type MnO2 nanosheet array has been synthesized and taken as an example to discover the reason of capacity fading for pseudocapacitors. It is discovered that in the the galvanostatic charge-discharge process, the smalle nanosheets blocking the macropores of the array framework have been dissolved and recrystallized on the large wrinkle birnessite nanosheet array framework, finally forming a hierarchical structure of nanosheets@nanosheets of birnessite. The recrystallizaion of the small birnessite nanosheets may decrease the specific capacity through the decreasement of the surface area of the electrode.

A novel label-free fluorescence assay for detection of Hg2+ was developed based on the Hg2+-binding single-stranded DNA (ssDNA) and SYBR Green I (SG I). Differences from other assays, the designed rich-thymine (T) ssDNA probe without fluorescent labelling can be rapidly formed a T-Hg2+-T complex and folded into a stable hairpin structure in the presence of Hg2+ in environmental drinking water samples by facilitating fluorescence increase through intercalating with SG I in one-step. In the assay, the fluorescence signal can be directly obtained without additional incubation within 1 min. The dynamic quantitative working ranges was 5–1000 nM, the determination coefficients were satisfied by optimization of the reaction conditions. The lowest detection limit of Hg2+ was 3 nM which is well below the standard of U.S. Environmental Protection Agency. This method was highly specific for detecting of Hg2+ without being affected by other possible interfering ions from different background compositions of water samples. The recoveries of Hg2+ spiked in these samples were 95.05–103.51%. The proposed method is more viable, low-costing and simple for operation in field detection than the other methods with great potentials, such as emergency disposal, environmental monitoring, surveillance and supporting of ecological risk assessment and management.

The extreme thermophilic bacterium Caldicellulosiruptor kronotskyensis can use hemicelluloses and cellulose as carbohydrate source. The gene Calkro_0081 encoded a novel GH11 xylanase (Xyn11A) with a catalytic domain (GH-CD) and a carbohydrate binding module (CBM6). The native Xyn11A and two corresponded truncations Xyn11A-CD (catalytic domain of Xyn11A) and Xyn11A-CBM (carbohydrate binding module of Xyn11A) were respectively cloned, heterologously expressed, and biochemically characterized. The recombinant Xyn11A is active in a wide temperature range from 40 to 95 degrees C with the highest activity at 75 degrees C. Xyn11A was completely stable at 70 degrees C for 6 h and more than 50% activity was retained after incubation for 6 h at 75 degrees C. The optimum pH of Xyn11A was 6.0, and it retained 100% activity after 15 h incubation in pH 5.5-7.5 at 70 degrees C. As for Xyn11A-CD, the optimal pH value and temperature were 6.0 and 65 degrees C, the residual activity retained 30% after 6h at 60 degrees C. The respective specific activities of Xyn11A, Xyn11A-CD, and Xyn11A-CBM were 1752.0, 986.8, and 0 IU/mg on beechwood xylan (BWX) at optimum conditions. The activity of Xyn11A is the highest among the reported thermostable xylanases at 75 C. Using BWX as substrate, the final products were xylose and xylobiose after hydrolysis with Xyn11A or Xyn11A-CD. No hydrolytic activity of CBM6 was found, while which shows crucial functions on thermostability and activity for Xyn11A. The characteristics of thermostability and high activity make Xyn11A a potential enzyme for industry application. (C) 2014 Elsevier B.V. All rights reserved.

In 2001-2002, 14 maize cultivars in Liaoning Province were used for the analysis of their entophytic bacteria population. The entophytic bacteria strains with a higher frequency in maize roots were Bacillus spp., Enterobacter spp., Serratia spp., Pseudomonas spp., Xanthomonas spp., Clavibacter spp., Bacillus spp., Enterobacter spp. and Serratia spp. Comparatively, Bacillus spp. was the most prevalent entophytic bacterium, including 8 species, B. subtilis, B. megaterium, B. cereus, B. licheniformis, B. anthracis, B. mycoides, B. pumilus and B. circulans, and with an average isolation frequency of 75.5% at seedling stage and 77.6% at adult stage. There existed significant differences in the population and dynamics of endophytic bacteria among maize cultivars and growth periods, and a significant correlation was found between maize genetic background and entophytic bacteria population.