The Optical Properties of MTPyP Film for HCl Gas Sensor
Date Issued
2012
Date
2012
Author(s)
Lin, Yu-Hui
Abstract
The work presented a simple way to prepare a meso-tetra (4-pyridyl) porphyrin (MTPyP) film for optical gas sensor called dip-dry coating method. The MTPyP molecule of inner nitrogen core of porphyrin ring and the four substituents at the meso positions could conjugate hydrogen ions leading to spectral changes. Therefore, MTPyP molecule could be applied to detect the acid gases. In our study, hydrogen chloride (HCl) gas was chosen to test response of the optical sensor. The MTPyP powder was dissolved in 1%, 10%, 30%, and 50% toluene solutions those were a mixture of ethanol, respectively. The MTPyP solution in 30% toluene solvent shows a stronger absorption band at 427nm than the other MTPyP solutions. Hence, we decided to use MTPyP solution in 30% toluene solution to prepare MTPyP films in our research. The MTPyP multilayer thin films were made by repeating the dip-dry coating method six times which was used to detect HCl gas compare to the one cycle MTPyP film. From the results, the six cycles films shows the better ability to detect HCl gas. Therefore, the six cycles films were chosen to detect the different concentration of 0.064, 0.64, 3.2, 4.8 ppm HCl gas in our study. A linear response was observed when the concentration of HCl was plotted against a difference in absorbance(ΔA491). And the detection limit of the solid state sensor was found to be 0.064ppm. The MTPyP thin film shows good sensitivity to HCl gas. In addition, the MTPyP thin films were used to detect other gases which were 163ppm toluene, 186 ppm acetone, and 99ppm ethanol gases. The values of ΔA491 were approximately 0.001. However, the values ofΔA491 were up to approximately 0.004, when the films exposure to 0.064ppm HCl gas whose the concentration is very low compare to toluene, acetone, and ethanol gases. According to the results, the
v
MTPyP film shows low sensitivity to high concentrations of toluene, acetone, and ethanol gases. In our study, the MTPyP films were also used to detect other common acid gases, such as H2SO4 and H3PO4. But there are no significant changes in the absorption spectra of MTPyP thin films. The reasons to cause these results are H2SO4 and H3PO4 with low values of vapor pressure that are not easy vaporizing to atmosphere.
Subjects
MTPyP film optical gas sensor
hydrogen chloride
Ultraviolet–visible spectroscopy
dip-dry coating
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
index.html
Size
23.49 KB
Format
HTML
Checksum
(MD5):fff63fadd9fc84b1195bd506089b9eb2