Surface plasmon polariton studies of 18-crown-6 metal-free phthalocyanine

Abstract

In this work surface plasmon resonance studies have been used to characterize the response of a thin film of 18-crown-6 metal-free phthalocyanine upon exposure to NO2. The phthalocyanine was deposited by spin coating onto a gold film which supported the surface plasmon resonance. By fitting angle dependent reflectivity data to the Fresnel theory for a range of wavelengths it has been possible to obtain the real and imaginary parts of the optical permittivity of the material over the visible part of the spectrum. This procedure has been conducted both before and after exposure to the gas giving an accurate characterization of the changes brought about by the NO2. Thereby the wavelength at which the system's sensitivity to NO2 is an optimum has been calculated. As a secondary measure, the optical parameters derived from the surface plasmon resonance experiments have been compared to data obtained by ultraviolet-visible spectroscopy.

Surface Plasmon Resonance: Theoretical Evolutionary Design Optimization for a Model Analyte Sensitive Absorbing-Layer System

“…20 Thin absorbing phthalocyanine films spin-coated onto thin gold layers have shown broadening in the SPR curve and an increase in the resonance angle and reflectivity 21,22 as predicted from theoretical models. 6,7,23 Upon exposure of such films to nitrogen dioxide, the resonance reflectivity was seen to decrease (consistent with the decrease in absorbance at the excitation wavelength), with only a small shift in the resonance angle 24 modulated according to metal and by peripheral substitution.…”

“…Analogues of phthalocyanine are a common reagent for nitrogen dioxide detection and have been extensively studied in the last 30 years. , Metal phthalocyanines have strong absorbance bands , in the range of 620−855 nm, with variations in the location due to coordinated metal, morphology, or peripheral substitutions . Thin absorbing phthalocyanine films spin-coated onto thin gold layers have shown broadening in the SPR curve and an increase in the resonance angle and reflectivity , as predicted from theoretical models. ,, Upon exposure of such films to nitrogen dioxide, the resonance reflectivity was seen to decrease (consistent with the decrease in absorbance at the excitation wavelength), with only a small shift in the resonance angle modulated according to metal and by peripheral substitution.…”

The optical gas-sensing properties of an asymmetrically substituted porphyrin

“…8,9 However, recent developments based on spectral changes in the optical properties of the organic materials have shown a number of advantages in terms of selectivity, sensitivity and response time. 10,11 In particular, porphyrin thin films have shown promise as useful optical gas-sensing materials. 12,13a A successful sensor must be capable of providing an easily measurable signal in response to the interaction of the sensing agent with the ion or molecule to be detected.…”

Optical transduction of chemical sensing by thin films of colour reagents and molecular receptors using piezo-optical and surface plasmon resonance methods

“…For example, the thickness and relative permittivities of copper tetra(21-crown-7) phthalocyanine ®lms spin-coated on gold from chloroform solution have been determined by computer modelling of experimental SPR data. 15 Sambles and co-workers 16 measured SPR as a function of exciting wavelength for spun ®lms of metal-free tetra(18-crown-6)phthalocyanine in air and after exposure to nitrogen dioxide. By modelling the data they were able to show that the derived changes in real and imaginary refractive indices as a function of wavelength were in good agreement with data from directly measured spectroscopic changes due to the interaction of nitrogen dioxide.…”