Chemical doping with foreign atoms is an effective method to intrinsically modify the properties of the host materials. In this paper, we report a facile strategy to prepare nitrogen and boron doped monolayer graphene by using urea and boric acid as solid precursors. By adjusting the elemental precursors, the nitrogen content could be modulated from 0.9 to 4.8% for nitrogen doped graphene and the boron content from 0.7 to 4.3% for boron doped graphene respectively, as estimated by X-ray photoelectron spectroscopy. The mobilities of the nitrogen and boron doped graphene-based back-gate field-effect transistors are about 350-550 cm 2 V À1 s À1 and 450-650 cm 2 V À1 s À1 respectively. Our results are better than plasma treated nitrogen and boron doped graphene. Therefore the synthesis of nitrogen and boron doped graphene sheets by a solid doping elemental precursor method is considered to be an efficient approach to producing graphene with excellent optical and electrical performances at relatively low cost.

Polycaprolactone (PCL) has been widely adopted as a scaffold biomaterial, but further improvement of the hemocompatibility of a PCL film surface is still needed for wide biomedical applications. In this work, the PCL film surface was functionalized with zwitterionic poly(3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate) (P(DMAPS)) brushes via surface-initiated atom transfer radical polymerization (ATRP) for enhancing hemocompatibility. Kinetics study revealed an approximately linear increase in graft yield of the functional P(DMAPS) brushes with polymerization time. The blood compatibilities of the modified PCL film surfaces were studied by platelet adhesion tests of platelet-rich plasma and human whole blood, hemolysis assay, and plasma recalcification time (PRT) assay. The improvement of hemocompatibility is dependent on the coverage of the grafted P(DMAPS) brushes on the PCL film. Lower or no platelet and blood cell adhesion was observed on the P(DMAPS)-grafted film surfaces. The P(DMAPS) grafting can further decrease hemolysis and enhance the PRT of the PCL surface. With the versatility of surface-initiated ATRP and the excellent hemocompatibility of zwitterionic polymer brushes, PCL films with desirable blood properties can be readily tailored to cater to various biomedical applications.

We demonstrate a new strategy for improved stabilization of polydiacetylene micelles. They show temperature-induced color changes, which are fully reversible even at varying pH. A novel azo chromophore-functionalized amphiphilic diacetylene molecule is synthesized and used to prepare self-assembled cylindrical micelles. The micelles can be polymerized by 254 nm light irradiation. The azo chromophores form H- and J-like aggregates in the polydiacetylene micelles and increase the stability of the micelles, which leads to fully reversible thermochromism of the micelles in the temperature range between 20 and 90 °C and the pH range between 5.6 and 9.6.

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ABSTRACT:The antibacterial activity of a series of soluble pyridinium-type polymers with different compositions against Escherichia coli (E. coli ) suspended in sterilized distilled water was investigated by a colony count method. The results show that the antibacterial activity of the soluble pyridinium-type polymers is characterized by their activity to kill bacterial cells and this activity can be enhanced as the content of the pyridinium group ( C q ) in the polymers increases. The species of the bacteria has a great influence upon the antibacterial activity of the soluble pyridinium-type polymers. The polymers possess a strong ability to kill Gram-positive and Gram-negative bacteria, and yeasts, excepting Bacillus subtilis, having gemmae and fungi. The toxicity of this kind of polymer has also been appraised. In the acute stimulation and allergy experiments, the red maculae, edema, and abnormal phenomena of an allergy on the skin of the tested animals were not observed. The acute toxicity experiment shows that the LD 50 of the polymer is 2330 mg/kg, implying that this kind of polymer has only very weak toxicity. This is significant for the application of soluble pyridinium-type polymers.

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The antibacterial activity of insoluble pyridinium‐type polymers with different structures against Escherichia coli suspended in sterilized and distilled water was investigated by a colony count method. The results show that the antibacterial activity of insoluble pyridinium‐type polymers, except for one containing I−, is characterized by an ability to capture bacterial cells in a living state by adsorption or adhesion, with the process of capturing bacterial cells being at least partially irreversible. This feature differs from the antibacterial activity of the corresponding soluble polymers, which is characterized by the ability to kill bacterial cells in water. In addition, insoluble pyridinium‐type polymers can also capture dead bacterial cells. This implies that insoluble pyridinium‐type polymers possess broad prospects for development in new water treatment techniques and whole‐cell immobilization techniques. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 676–684, 2000

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