478931-41-8Relevant academic research and scientific papers
Fast, reversible optical sensing of NO2 using 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-21H,23H-porphine assemblies
Dooling,Worsfold,Richardson,Tregonning,Vysotsky,Hunter,Kato,Shinbo,Kaneko
, p. 392 - 398 (2001)
The optical absorbance spectrum of LB film assemblies of 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-21H,23H-porphine (EHO) is highly sensitive to low concentrations of NO2 in nitrogen. LB films prepared at much faster than conventional deposition rates (～ 1000 mm min-1) yield t50 response and recovery times of 25 s and 33 s respectively and show a sensitivity of 60% relative absorbance change (at 430 nm) for 4.4 ppm NO2. The morphology of these films is revealed using atomic force microscopy to contain isolated micron-size domains which are themselves composed of grains of several nm in diameter. This unconventional structure leads to a useful sensing material as a result of the molecular functionality of the porphyrin coupled to the enhanced surface area of the porous film assembly. The EHO film shows a gradually diminishing optical response as its temperature is increased, resulting from the shift in the adsorption-desorption equilibrium towards desorption as expected. The UV-visible spectrum recovers fully after exposure to NO2. The rate of recovery is slow at room temperature but can be accelerated dramatically with gentle heating (～ 350 K) for a few seconds. The concentration dependence of the optical response over the range 0.8-4.4 ppm follows a Langmuir model.
Nitrogen dioxide sensing characteristics at elevated temperature of sol-gel glass thin films containing substituted porphyrin dyes
Worsfold,Dooling,Richardson,Vysotsky,Tregonning,Hunter,Malins
, p. 399 - 403 (2001)
An optical gas sensor device based on tetra-substituted porphyrin dye entrapped in sol-gel glass displays greatly improved signal strength (1400% at 295 K) on exposure to 4.4 ppm nitrogen dioxide (in N2) gas compared to a multilayer Langmuir-Blodgett film fabricated from the same porphyrin. Temporal response was found to be similar, but differences in the two deposition methods were observed in terms of signal strength and response/recovery times. This behaviour is explained in terms of the differing nature of the two film types. A room temperature sensitivity of 176 ppb was measured and the response obeyed Langmuir adsorption kinetics.
