Detection of Silver(I) Ion Based on Mixed Surfactant-Adsorbed Cds Quantum Dots

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Electronic Supplementary Material

Detection of silver(I) ion based on mixed surfactant-adsorbed CdS quantum dots

Nutthaya Butwonga, Wittaya Ngeontaea, Rodjana Burakhama, Supalax Srijaranaia,*

aMaterials Chemistry Research Unit, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand

* Corresponding author: Tel. +6643202222 41 ext. 12243, Fax. +66 43 202373,

E-mail: (S. Srijaranai)

Figure S1 Effect of surfactant concentration on fluorescence intensity of CdS QDs after extraction

a) Effect of TTAB on the extraction of CdS QDS in the surfactant-rich and the surfactant-dilute phase

b) Effect of SDS on the extraction of CdS QDS in the surfactant-rich and the surfactant-dilute phases

Conductivity behavior

Collective representative conductivity plots of pure TTAB (a) and TTAB plus SDS mixtures (b) are shown in Fig. S2. The studied concentrations of TTAB in this work were lower than its critical micelle concentration (CMC; 4 mmol L-1); therefore, the intersection point of conductivity plots in pure TTAB was not observed (Fig. S2a) [1]. In the case of TTAB/SDS (Fig. S2b), there was intersection point between the two straight lines which corresponding to the optimum concentration of TTAB and SDS for the extraction of CdS QDs. The electrostatic binding between oppositely charged groups in mixed anionic/cationic micelles allow an additional stabilizing force resulting in a decrease in the CMC values of mixed surfactant systems [2]. From this evident, it can be concluded that SDS act as the associate surfactant in the phase separation process by binding the defect sites on surface of CdS QDs.

Figure S2 Conductivity versus concentration of surfactant in CdS QDs colloidal solution as in the experiment; a) TTAB in 3 replicated measurements and b) TTAB 4.75×10-4 mol L-1 plus SDS in 3 replicated measurements

References

1.  Rami AR (2008) The influence of hydrophobic counterions on micellar growth of ionic surfactants. Adv Colloid Interface Sci 14 :24

2.  He R, Qian XF, Yin J, Xi HA, Bian LJ, Zhu ZK (2003) Formation of monodispersed PVP-capped ZnS and CdS nanocrystals under microwave irradiation. Colloids Surf A 220:151