Thin films of calix-4-resorcinarene deposited by spin coating and Langmuir–Blodgett techniques: determination of film parameters by surface plasmon resonance

Amphiphilic calix-4-resorcinarene (C-4-RA) has been deposited as thin films using both spin coating and Langmuir–Blodgett (LB) techniques. Both LB and spin-coated films were studied by surface plasmon resonance (SPR) using Kretschmannʹs prism configuration, and their optical parameters have been evaluated. LB film thickness d obtained from SPR curve fitting procedure was plotted as a function of the number of layers and from this, a bi-layer thickness of 2.34 nm was determined. The thickness of spun films produced at a spinning speed of 2000 rpm is found to be equivalent to that of six to eight monolayer LB films. Both types of films were found to have a similar refractive index value of about 1.47. Using SPR technique, LB and spun films of C-4-RA of comparable thickness were found to respond in a similar manner when exposed to 400 ppm toluene vapour, indicating a structural similarity between films produced by “wet” techniques, such as LB and spin coating.