Optical carbon dioxide sensor based on the colorimetric change of α-naphtholphthalein and internal reference fluorescent CIS/ZnS QDs

A new optical carbon dioxide sensor based on the colormetric change of pH indicator a-naphtholphthalein with the internal reference fluorescent CIS/ZnS quantum dots (QDs) was developed. The luminescence intensity of CIS/ZnS QDs increased with increasing carbon dioxide concentration. The sensing films consisting of a-naphtholphthalein in polyIBM and CIS/ZnS QDs in polystyrene layer. The sensitivity of optical carbon dioxide sensor is quantified in terms of the ration I
₁₀₀
/I
₀
, where I
₁₀₀
and I
₀
represent the detected luminescence intensities in pure carbon dioxide and pure nitrogen environments, respectively. The experimental result reveals that the new optical carbon dioxide sensor has sensitivity of I
₁₀₀
/I
₀
= 13.4.