Furthermore, the sizes of the little pieces do not become smaller even if the reaction time is beyond 48 h. Meanwhile, there were two kinds of nanoscale GO existing in the mixture: one is the pure nanoscale GO pieces in Figure 2b, and the other is the silver-GO composite pieces in Figure 2c. In addition, the nanoscale GO film cannot be conductive using C-AFM testing (see Additional file 1: Figure S3). Figure 2 Tapping-mode AFM image of nanoscale GO pieces using 0.5 mM silver ions for 24 h. a)nanoscale GO; (b) and (c) the high- resolution images of the labeled area in (a). Influence of the reaction time on the sizes and properties

of nanoscale GO pieces was monitored AZD8931 mw by UV-vis spectroscopy (Figure 3a). The UV-vis spectra of GO display two characteristic peaks at 230 and 303 nm, corresponding to π → π* transition of aromatic C-C bond and n → π* transition of C=O bond, respectively [23]. From Figure 2d, it can be found that the two characteristic GW3965 cost peaks of GO red-shift to approximately 250 and approximately 310 nm after Barasertib cell line adding 0.5 mM Ag+ ions into the GO solution for 0.5 h, due to the interaction of GO and silver ions. The peak intensities decayed gradually with prolonged reaction time. Especially the peak intensity in the region approximately

310 nm decreases dramatically after 48 h, providing a first hint that some functional groups in GO may decrease [24]. Similar results can be further achieved by changing the concentration of Ag+ ions in Figure 3b. We can find that there is a distinct difference in wavelengths and intensities of the characteristic peaks of GO with the different concentrations of Ag+ ions in the system after approximately 24 h. At lower concentration, the signal at 310 nm nearly disappears and that at 250 nm becomes distinct, which may mean that the Ag+ ions preferentially

attack the sites of sp 3 carbon clusters or defective regions on the basal planes and partially restore the sp 2 carbon framework. When a higher proportion of Ag+ ions (5 or 0.5 mM) are added into the reaction system, the peak intensity (at approximately 310 nm) of GO seems to be obvious and accompanies a larger red shift with increasing Ag+ ion concentration, gradually close to 360 nm which is for silver Morin Hydrate plasmon absorption bands [24]. It can be explained that the number of silver nanoparticles fabricated on the GO surface or solution becomes large with the increasing proportion of Ag+ ions in the mixture, which also provides more change for the interaction of Ag nanoparticles and GO. At the same time, we also find that even if the Ag+ concentration is increased to 5 mM, there still exists some nanoscale GO with smooth edges in the mixture. Figure 3 UV-vis absorption and FTIR spectra of nanoscale GO. (a) UV-vis change with reacting time, (b) UV-vis change with adding Ag+ concentration; (c) FTIR spectra of nanoscale GO by adding 0.5mM Ag+ after reacting 12h.