To understand the mechanism of the catalytic etching of AgNPls
by S2O3
2 for the measurement of Cu2+, the SPR absorption was
investigated as shown in Fig.1. The CTAB/AgNPls in 0.1Mammonia
buffer at pH 11 exhibited an absorption maximum (lmax) of
563nm (curve a). After the addition of 1M Na2S2O3 at 1.5mL in
3mL of CTAB/AgNPls the lmax of the CTAB/AgNPls was decreased
(curve b) and blue shifted to 522 nm. This is due to the decreased
AuNPls size through oxidation of AgNPls with oxygen (O2). By the
addition of Cu2+, the color of the solutions changed from violet-red
to colorless within 5 min. The absorbance peak at 522nm
decreased with an increase in concentration of Cu2+ from 50 to
200 ngmL1 (curves c–e). The insets of Fig.1 show the color change
of CTAB/AgNPls caused by the catalytic etching of CTAB/AgNPls by
S2O3
2 in the presence of Cu2