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[求助]
谁可以告诉下我这个改进hummer的方法具体是怎样的。
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Kovtyukhova, N. I.; Ollivier, P. J.; Martin, B. R.; Mallouk, T. E.; Chizhik, S. A.; Buzaneva, E. V.; Gorchinskiy, A. D. Chem. Mater. 1999, 11, 771. 很多文章都是用这个方法，可是我找不到原文，如果有，万分感谢 |
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【答案】应助回帖
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感谢参与，应助指数 +1
蒋青松: 金币+1, 鼓励下 2012-07-25 07:53:39
感谢参与，应助指数 +1
蒋青松: 金币+1, 鼓励下 2012-07-25 07:53:39
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Experimental Section Materials. GO was synthesized from natural graphite powder (325 mesh, GAK-2, Ukraine) by the method of Hummers and Offeman.18 It was found that, prior to the GO preparation according to ref 18, an additional graphite oxidation procedure was needed. Otherwise, incompletely oxidized graphite-core/GO-shell particles were always observed in the final product. The graphite powder (20 g) was put into an 80 °C solution of concentrated H2SO4 (30 mL), K2S2O8 (10 g), and P2O5 (10 g). The resultant dark blue mixture was thermally isolated and allowed to cool to room temperature over a period of 6 h. The mixture was then carefully diluted with distilled water, filtered, and washed on the filter until the rinse water pH became neutral. The product was dried in air at ambient temperature overnight. This preoxidized graphite was then subjected to oxidation by Hummers’ method. The oxidized graphite powder (20 g) was put into cold (0 °C) concentrated H2SO4 (460 mL). KMnO4 (60 g) was added gradually with stirring and cooling, so that the temperature of the mixture was not allowed to reach 20 °C. The mixture was then stirred at 35 °C for 2 h, and distilled water (920 mL) was added. In 15 min, the reaction was terminated by the addition of a large amount of distilled water (2.8 L) and 30% H2O2 solution (50 mL), after which the color of the mixture changed to bright yellow. The mixture was filtered and washed with 1:10 HCl solution (5 L) in order to remove metal ions. The GO product was suspended in distilled water to give a viscous, brown, 2% dispersion, which was subjected to dialysis to completely remove metal ions and acids. The resulting 0.5% w/v GO dispersion, which is stable for a period of years, was used to prepare exfoliated GO. Exfoliation was achieved by dilution of the 0.5% GO dispersion (1 mL) with deionized water (24 mL), followed by 15 min sonication. The resulting homogeneous yellow-brown sol, which contained 0.2 g/L GO, was stable for a period of months and was used for film preparation. An aqueous solution (0.01 M) of poly(allylamine hydrochloride), PAH, (Aldrich, MW ) 50 000-65 000) was adjusted to pH 7 with NH3 and was used for growth of polycation layers. An aqueous solution of doped polyaniline (PAN) was made from a saturated solution of the emeraldine base form in dimethylformamide. A 3 mL portion of this solution was slowly added with stirring to 26 mL of water, which had been acidified to pH 3.5 with aqueous HCl. The pH of the final PAN solution was then adjusted to 2.5 by addition of aqueous HCl. The aluminum Keggin ion Al13O4(OH)24(H2O)12 7+ was prepared trom Al13O4(OH)25(H2O)11(SO4)3ax(H2O), which was available from a previous study.5 Briefly, 0.102 g of the sulfate salt was added to a solution of 0.042 g of BaCl2 in 200 mL of water and stirred overnight. The resulting 0.3 mM solution of the chloride salt of the aluminum Keggin ion was filtered using a 0.2 ím filter. Polished (100) Si wafers were sonicated in CCl4 for 15 min and then rinsed with 2-propanol and water. Their surface was then hydroxylated by 30 min sonication in “piranha” solution (4:1 concentrated H2SO4:30% H2O2) (CAUTION: piranha solution reacts violently with organic compounds!) and was rinsed sequentially with water, methanol, and 1:1 methanol/ toluene before the surface derivitization steps began. Aluminum foil, Al-coated glass, both bearing a native oxide, and ITO glass were cleaned by washing with hexane for 15 min prior to GO adsorption. Multilayer GO/PAH Film Growth. Hydroxylated silicon wafers were primed with one of three different types of cationic monolayers in order to initiate the growth of the GO films. This was achieved either by (1) reacting with 4-((dimethylmethoxy) silyl)butylamine (15 h treatment with a 5% toluene solution under dry Ar, over KOH at ambient temperature) or by (2) adsorbing a monolayer of aluminum Keggin ions (5 min adsorption from aqueous solution of the chloride salt at 80 °C19) or by (3) adsorbing PAH (15 min adsorption from a 0.01 M aqueous solution at pH 7 and ambient temperature). The primed Si substrates (1, 2, and 3) are designated hereafter as Si(NH2), Si(OH)/Al-Kg, and Si(OH)/PAH, respectively. The primed substrates were immersed in an aqueous (pH 5) or aqueous ammonia (pH 9) GO sol (0.2 g/L) for 15 min and then rinsed with deionized water and dried in flowing Ar. The samples were then immersed in aqueous PAH solutions for 15 min, rinsed with deionized water, and dried in flowing Ar. Multilayer GO/PAH films were grown by repeating these adsorption cycles. Preliminary experiments had shown that the thickness of a deposited layer (estimated by ellipsometry) does not depend on the substrate/solution contact time in the range from 2 min to 2 h. For electronic measurements, multilayer (GO/PAH)14 and (GO/PAN)30 films were grown on ITO in similar adsorption cycles. For comparison purposes, a GO colloid film (ca. 90 nm thick) was prepared by dip-coating the ITO/glass in the GO colloidal dispersion. |
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