Optochemical properties of gas-phase protonated tetraphenylporphyrin investigated using an optical waveguide NH₃ sensor

Abstract

5,10,15,20-Tetraphenylporphyrin (TPP) was synthesized, and a glass optical waveguide (OWG) was coated with a gas-phase protonated TPP thin film to develop a sensor for NH3 gas detection.

Advances in designs and mechanisms of semiconducting metal oxide nanostructures for high-precision gas sensors operated at room temperature

“…Therefore, development of high-precision gas sensors with high sensitivity, fast response, good selectivity, low limit of detection (LOD), as well as in situ and real-time monitoring capabilities is paramount. 1,2 For this purpose, various types of gas sensors have been developed, mainly including resistive, [3][4][5] optical, [6][7][8][9] ultrasonic and acoustic wave, 10-12 thermoelectric 13,14 and electrochemical [15][16][17] ones.…”

Substituent Effect on Porphyrin Film-Gas Interaction by Optical Waveguide: Spectrum Analysis and Molecular Dynamic Simulation

“…Gas chamber with 2 cm 3 volume was used as an interaction room; gas injection was controlled with a flowmeter connected to the gas chamber at one end and the other to a plastic syringe with 20 cm 3 volume, which was replaced with a new one for each gas to avoid cross-influence. After each gas exposure, ammonia gas (saturated) was injected to recover the film to the initial state according the typical bands in absorption spectrum [ 25 ]. Dry air was used as carrier gas and as diluter in the flowing system.…”

“…Several dyes and pH indicators were studied to detect organic volatiles and inorganic vapors using optical waveguide system [ 16 , 17 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. Herein, influence of substituents on porphyrin molecules to the sensitivity and selectivity has been analyzed with molecular dynamic simulation (MDS).…”

“…Substitute types on porphyrin molecules, central metallic atoms, protonation, or deprotonation degrees are the main factors that depend on the main interactions and sensitivities [ 25 ]. State of porphyrin molecules is also affected by film forming methods [ 30 ], solvent types [ 31 ], and substituted groups [ 32 ].…”

“…In OWGS, film-analyte interaction dynamics are recorded by following the evanescent transformation, which was excited by laser light with certain wavelength, which is generally chosen based on the highest absorption intensity divergence between pure film and gas-exposed-film. When sensing film exposed to analyte gases, several properties of the film such as the thickness, refractive index, molar absorption coefficient [ 39 ] suffer changes following with color transformation, leading to attenuation or enhance of the evanescent absorbance intensity within the film [ 25 ]. Herein, molecular dynamic simulations offer theoretical proof for the sensing behavior in OWGS, in terms of the number of analyte molecules adsorbed in the vicinity of porphyrin molecules.…”