Fig. 2. XPS survey spectra showing quantitative peaks of constituting elements in (A) acid washed DE, (B) GA-PEI-DE and (C) GA-PEI resin after the 6th day of etching. The quantified peak areas of elements were used to determine (D), the relative Si/N ratio for GA-PEI resins reported with respect to the duration of etching (no. of days). Error bars indicate (±)S.D. between measurements over spots per sample (n = 2).
