AgNPls [27] were obtained from the Sensor Research Unit at the
Department of Chemistry, Faculty of Science, Chulalongkorn
University. Briefly, the AgNPls were synthesized by reduction of
AgNO3 using NaBH4 and the shape transformation using a 30%
H2O2 solution [27]. First, the NaBH4 was added into the AgNO3
under vigorously magnetic stirring. The solution turned light
yellow, indicating the formation of NPs. The shape transformation
reaction was done by an injection of the 30% H2O2 solution at the
rate of 13.45 mL min1 into AgNs. After the complete addition of
the H2O2 solution, the colloid was further stirred for 10 min to
complete the shape conversation process. The solution turned
color from light yellow to the blue of AgNPls. For the modification
of AgNPls hexadecyltrimethylammonium bromide (CTAB) capped
AgNPls were prepared by the dilution of AgNPls to 200 mg mL1 in
a total final volume of 1000 mL with a 0.1 M ammonia buffer at pH
11. Then, 10 mL of 0.1 M CTAB was added to produce the CTABcapped AgNPls. Sequentially, 5 mL of 1.0 M Na2S2O3 was added to
the CTAB-capped AgNPls followed by incubation of the mixture for
5 min at room temperature.