A novel multisensing optical approach based on a single phthalocyanine thin films to monitoring volatile organic compounds

This paper reports the use of optical trasduction techniques to characterise solid state chemo-optical sensors prepared by Langmuir–Sch¨afer technique (LS) in thin film form based onto Cu(II) tris-(2,4-di-t-amylphenoxy)-(12-hydroxy-1,4,7,10-tetraoxadodecyl)-phthalocyanine macromolecules CuPcOH as active layers. The study consists in the UV–vis optical absorption monitoring of the active LS layers in the presence of specific five volatile organic compounds (VOCs) mixed in dry air in controlled atmosphere; in particular tert-butylamine, methanol, ethanol, hexane and ethyl acetate, all analytes of interests in the food quality control. The UV–vis spectra have been monitored by recording the dynamic variation in the integral of the absorbance curves in well defined spectral regions: 300–400 nm, 550–600 nm, 600–640 nm, 640–700 nm, covering the whole spectrum and centred around the typical absorption bands of phthalocyanine thin films. This simultaneous UV–vis four channel monitoring allowed to use only one active layer as sensing element where each selected spectral region generates independent sensors. The dependency of the above mentioned outputs towards the analytes has been discussed. A base optical characterisation of the investigated LS thin films has been performed.