Surface plasmon resonance on the LB monolayer of solvent-soluble silicon phthalocyanine

Thin films of bis-(p-chlorophenoxy) (tetra-4-nitrophthalocyaninato)silicon, TNPcSi(OPhCl-p)₂, were prepared by using Langmuir-Blodgett techniques and the morphology of the film was investigated by AFM (atomic force microscope) analysis. It has been found that the LB films were successfully transferred onto substrates like mica, gold deposited glass, and pure glass with domains aggregated on the substrates. Surface plasmon resonance has been used to investigate the interaction between sulfur dioxide and a monolayer of TNPcSi(OPhCl-p)₂ LB film. It has been found that the monolayer of LB film transferred onto gold deposited glass gave a 0.55° shift of resonant angle and an additional 0.45° shift of resonant angle after exposion in sulfur dioxide atomospheric ambient for twenty minute. The UV-visible absorption spectrum of the LB films of TNPcSi(OPhCl-p)₂ showed that there is chemical changes in the film after the exposure to the sulfur dioxide ambient. This work has shown a promising application as an optical gas sensor.