Abstract
Optical and magneto-optical surface plasmon resonance (MOSPR) characterization and preliminary sensing test onto single- and multi-layers of two organic macrocycles have been performed; TbPc2(OC11H21)8 phthalocyanine and CoCoPo2 porphyrin were deposited by the Langmuir-Schäfer (LS) technique onto proper Au/Co/Au magneto-optical transducers. Investigations of the MOSPR properties in Kretschmann configuration by angular modulation, gives us an indication about the potential discrimination of two organic macrocycles with absorption electronic transition in and out of the propagating plasmon energy spectral range. An improved molecular vapors sensitivity increase by the MOSPR sensing probe can be demonstrated depending on the overlap between the plasmonic probe energy and the absorption electronic transitions of the macrocycles under investigation. If the interaction between the plasmon energy and molecular HOMO-LUMO transition is preserved, a variation in the complex refractive index takes place. Under this condition, the magneto-plasmonic effect reported as 1/|MOSPR| signal allows us to increase the detection of molecules deposited onto the plasmonic transducer and their gas sensing capacity. The detection mechanism appears strongly enhanced if the Plasmon Wave/HOMO-LUMO transitions energy are in resonance. Under coupling conditions, a different volatile organic compounds (VOC) sensing capability has been demonstrated using n-butylamine as the trial molecule.
Highlights
The interaction mechanism taking place between organic macrocycles such as metallatedphthalocyanines and metallated-porphyrins and surface plasmons has been investigated to describe how plasmonic materials can interact with nearby molecules by enhancing their spectroscopic signatures, allowing for plasmon-enhanced sensing and detection [1,2,3,4]
A sensitivity increase was detected by magneto-optical surface plasmon resonance (MOSPR) sensing probe if an overlap
Characterizations between plasmonic probe energy and the electronic transitions of the PC ring free have electrons been performed on layers of two are organic macrocycles—TbPc
Summary
The first class of proposed macromolecules are ubiquitous in Nature and can be regarded as derivatives of the heterocycle porphyrin and differ in the chemical groups on the periphery and central metal atom, in our study cobalt The latter are highly colored and the substitution of the central hydrogen atoms by metal ones, in our case terbium, results in the changes of the optical properties in the UV-VIS spectral range. By this strategy they can be deposited by chemical deposition methods like the Langmuir-Blodgett deposition technique onto a proper transducer [12,13,14] The interest in these macrocycles is due to the peculiar properties of the large family of tetrapyrrolic functional molecular materials, above all their high chemical and thermal stability. In our case well organized monolayers have been deposited by using the horizontal lifting or Langmuir-Schäfer (LS) technique [22,23,24] a well-established method of controlling thickness and molecular orientation within thin organic film [25,26]
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