Optical Characterization of an N,N′-Dicyclohexyl-3,4:9,10-Perylene bis(Dicarboximide) Langmuir–Blodgett Film for the Determination of Volatile Organic Compounds

ABSTRACT

Langmuir–Blodgett thin-film fabrication and gas-sensing properties of a novel N,N′-dicyclohexyl-3,4:9,10-perylene bis(dicarboximide) material are reported. Surface plasmon resonance was used to study the deposition process. Fitted data were used to evaluate the refractive index and the thickness of the material. Thickness of a single layer and refractive index were determined to be 0.43 ± 0.04 nm and 1.52 ± 0.07, respectively. Responses of films to chloroform, benzene, and toluene were measured by surface plasmon resonance. Changes in reflectivity implied swelling of the perylendiimide film during adsorption and may be explained by the capture of organic molecules. Fick’s law for early-time diffusion was used to characterize the swelling processes. Diffusion coefficients for swelling were proportional to the square root of time and were correlated with volatile organic compounds. Responses of N,N′-dicyclohexyl-3,4:9,10-perylene bis(dicarboximide) films to volatile organic compounds were characterized based on the physical properties of solvents. Films were more sensitive to chloroform compared to other volatile organic compounds.

KEYWORDS:

• Chemical sensors
• optical properties
• surface properties
• thin films