Figure 4 depicts the UV–Vis absorption peak of the
AgNP released by the NRL membranes. The UV–Vis
spectra of the sample NRL–AgNp_0.1 % do not
display a clear plasmon absorption band in the first
24 h (Fig. 4a). This suggests that the AgNP were not
released from the NRL–AgNP membranes or the
concentration of the AgNP released was too low to be
detected. In fact, plasmon band with a very low
intensity could only be detected after 48 h, thereby
suggesting that the AgNP are strongly bound to the
NRL matrix. The binding of AgNP to the NRL matrix
probably occurs via the cis-isoprene molecules (Guidelli
et al. 2011b).