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pH controlled synthesis of porous graphene sphere and application to supercapacitors
Ha, Taehyeong,Kim, Sun Kyung,Choi, Jeong-Woo,Chang, Hankwon,Jang, Hee Dong VSP 2019 Advanced powder technology Vol.30 No.1
<P><B>Abstract</B></P> <P>Graphene (GR) has excellent physical and chemical properties, making it promising for application in supercapacitors. In this study, we report the synthesis of spherical GR (SGR) composed of tens of GR sheets and its application in supercapacitors. Graphene oxide (GO) was first reduced in the liquid phase by using L-ascorbic acid (L-AA), an environmentally friendly reducing agent, and then SGR was prepared using the reduced GO colloid by aerosol spray drying. The reduction of GO in the liquid phase was completed in 1 h. The SGR fabricated by the aerosol process ranged from 2 to 4 μm in diameter. The as-prepared SGR fabricated from GO at pH 2 showed a densely packed spherical morphology and porous structure with a specific surface area of 150 m<SUP>2</SUP>/g. The SGR fabricated from the GO colloid at pH 10 showed an improved specific surface area (216 m<SUP>2</SUP>/g) and a higher specific capacitance (182 F/g) than the SGR fabricated at pH 2. Considering the environmentally friendly process, the as-prepared SGR is a highly promising material for supercapacitors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Graphene oxides (GO) were reduced using L-ascorbic acid at different pH. </LI> <LI> Spherical graphene (SGR) was fabricated from reduced GO by aerosol process. </LI> <LI> SGR fabricated at pH 10 showed enhanced electrochemical performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Soon Hee,Ha, Hyun Jung,Ko, Youn Kyung,Yoon, Sun Jung,Rhee, John M.,Kim, Moon Suk,Lee, Hai Bang,Khang, Gilson VSP 2007 Journal of Biomaterials Science. Polymer Edition Vol.18 No.5
<P>In order to find a correlation between cell adhesion, growth and biological response with different wettability, NIH/3T3 fibroblast cells were cultured on plasma-treated low-density polyethylene (LDPE) film generated with radio frequency. Different surface wettabilities (water contact angle 90-40 degrees ) were created by varying the duration of plasma treatment between 0 and 15 s, respectively. Growth and proliferation rate of cells on LDPE surfaces was evaluated by MTT assay, and cell morphology, by means of spreading and adhesion, was characterized by scanning electron microscopy (SEM). The expression of particular genes in cells contacted on films with different wettability was analyzed by RT-PCR. Using the MTT assay, we confirmed that the amount of cell adhesion was higher on surface of film with a water contact angle of 60 degrees than with other water contact angle. Also, the proliferation rate of cells was highest with a water contact angle of 60 degrees . It was confirmed by SEM that the morphology of cells adhered with a water contact angle of 50-60 degrees was more flattened and activated than on other surfaces. Furthermore, c-fos mRNA in cells showed maximum expression on the film with contact angle range of 50-60 degrees and c-myc mRNA expressed highly on the film with a contact angle of 50 degrees . Finally, p53 gene expression increased as wettability increase. These results indicate that a water contact angle of the polymer surfaces of 50-60 degrees was suitable for cell adhesion and growth, as well as biological responses, and the surface properties play an important role for the morphology of adhesion, growth and differentiation of cells.</P>