Fig. 2. Paper-based colorimetric sensor based on the catalytic etching mechanism of the CTAB/AgNPls with S2O3
2 for measurement of Cu2+ at (a) image of paper-based
deviecs; image of paper-based devices after measurement of Cu2+ (b) 0 ngmL1, (c) 50 ngmL1 and (d) 100 ngmL1 of Cu2+; the SEM images of paper-based sensor at the
detection zone (e) without CTAB/AgNPls (f) with CTAB/AgNPls (g) CTAB/AgNPls in the presence of 100 ngmL1 Cu2+; the TEM images of S2O3
2/CTAB/AgNPls without Cu2+ (h)
and with 100 ngmL1 of Cu2+ (i).