Formation and characterization of mixed polyelectrolyte-surfactant Langmuir layer templates for silver nanoparticle growth

The hydrophilic characteristic of the polyelectrolyte, poly(4-styrenesulfonic acid) (PSS), was modified by associating with the surfactant, dodecyltrimethylammonium bromide (DTMAB), to form polyelectrolyte-surfactant (PSS-DTMA) Langmuir layers at air/liquid interfaces. The interfacial behavior of the PSS-DTMA complexes was investigated with the Langmuir trough technique. The mixed PSS-DTMA Langmuir layers were then used as the two-dimensional templates to incorporate with silver precursors from the subphase, and were transferred onto mica substrates with the Langmuir-Blodgett (LB) deposition technique. The silver nanoparticles were fabricated in the resulting LB films with UV irradiation, and the morphology of the silver nanoparticle structures was analyzed by atomic force microscopy (AFM). The results indicated that increasing the DTMA⁺ content in the mixed PSS-DTMA system would enhance the hydrophobic characteristic of the complexes and then form stable PSS-DTMA Langmuir layers at interfaces. In addition, by varying the DTMA⁺ content, one could adjust the charge density in the Langmuir layer templates and thus control the association behavior between the two-dimensional templates and the silver precursors in the subphases. The AFM images demonstrated that the formation of the silver nanoparticle structures in the UV-treated LB films could be regulated with the DTMA⁺ content in the Langmuir layer templates. It is inferred that the polyelectrolyte-surfactant template offers a potential of designing structures of polyelectrolyte-nanoparticle materials with a template-synthesis procedure.