No abstract

Chitosan (CS) is a linear polysaccharide with good biodegradability, biocompatibility and antimicrobial activity, which makes it potentially useful for biomedical applications, including an antimicrobial agent either alone or blended with other polymers. However, the poor solubility of CS in most solvents at neutral or high pH substantially limits its use. Quaternary ammonium CS, which was prepared by introducing a quaternary ammonium group on a dissociative hydroxyl group or amino group of the CS, exhibited improved water solubility and stronger antibacterial activity relative to CS over an entire range of pH values; thus, this quaternary modification increases the potential biomedical applications of CS in the field of anti-infection. This review discusses the current findings on the antimicrobial properties of quaternized CS synthesized using different methods and the mechanisms of its antimicrobial actions. The potential antimicrobial applications in the orthopedic field and perspectives regarding future studies in this field are also considered.

Flexible free-standing hollow Fe 3 O 4 /graphene (H-Fe 3 O 4 /GS) films were fabricated through vacuum filtration and thermal reduction processes, in which graphene formed a three-dimensional conductive network, with hollow and porous Fe 3 O 4 spindles being captured and distributed homogeneously. Using the films as binder-free and free-standing electrodes for lithium-ion batteries, H-Fe 3 O 4 /GS with 39.6 wt % graphene exhibited a high specific capacity (1555 mA h g À1 at 100 mA g À1 ), enhanced rate capability and excellent cyclic stability (940 and 660 mA h g À1 at 200 and 500 mA g À1 after 50 cycles, respectively). The superior electrochemical performance of this novel material can be attributed to two factors. One is that the three dimensional (3D) graphene network formed is very helpful for keeping H-Fe 3 O 4 in good electrical contact. Another is the short transport length for both lithium ions and electrons due to the porous nature which accommodates volume change and favors electrolyte penetration. It is believed that the strategy for preparing free-standing H-Fe 3 O 4 /GS films presented in this work will provide new insight into the design and synthesis of other metal oxide/GS electrodes for flexible energy storage devices.

Coal is the most abundant fossil fuel in the world and is likely to outlast gas and oil for centuries. However, with global issues like climate change at the forefront of public attention there is a trend towards the development of a carbon constrained economy. As a result, research has intensified in the last decade on modes of operating coal fired power plants with carbon capture and storage (CCS). In particular, pre-combustion options via coal gasification, especially integrated gasification combined cycle (IGCC) processes, are attracting the attention of governments, industry and the research community as an attractive alternative to conventional power generation. It is possible to build an IGCC plant with CCS with conventional technologies however; these processes are energy intensive and likely to reduce power plant efficiencies. Novel ceramic membrane technologies, in particular molecular sieving silica (MSS) and pervoskite membranes, offer the opportunity to reduce efficiency losses by separating gases at high temperatures and pressures. MSS membranes can be made preferentially selective for H 2 , enabling both enhanced production, via a water-gas shift membrane reactor, and recovery of H 2 from the syngas stream at high temperatures. They also allow CO 2 to be concentrated at high pressures, reducing the compression loads for transportation and enabling simple integration with CO 2 storage or sequestration operations. Perovskite membranes provide a viable alternative to cryogenic distillation for air separation by delivering the tonnage of oxygen required for coal gasification at a reduced cost. In this review we examine ceramic membrane technologies for high temperature gas separation and discuss the operational, mechanical, design and process considerations necessary for their successful integration into IGCC with CCS systems.