2014年6月英语四级作文真题附范文(第2套):A Beautiful City in China

Take the newly prepared AuNPs 100uL, adjust the pH to the anti-CB isoelectric point with K2CO3, add different concentrations of anti-CB solution, mix and shake for 2h, add 6uL 0.1 mmoL/LNaCl and mix at room temperature. The change in color is observed (Fig. s2), and then the optimum concentration is determined using an ultraviolet spectrophotometer and zata-potential.