Optical fiber carbon dioxide sensor based on colorimetric change of α-naphtholphthalein and CIS/ZnS quantum dots incorporated with a polymer matrix

• Published in: Optical materials express Vol. 9; no. 7; p. 2937
• Main Authors: Chu, Cheng-Shane, Hsieh, Meng-Wei
• Format: Journal Article
• Language: English
• Published: Washington Optical Society of America 01.07.2019
• Subjects: Carbon dioxide; Carbon fiber reinforced plastics; Colorimetry; Emission; Luminescence; Optical fibers; Quantum dots; Sensors; Zinc sulfide
• ISSN: 2159-3930; 2159-3930
• DOI: 10.1364/OME.9.002937

This paper presents a new optical fiber carbon dioxide (CO2) sensor based on the emission wavelength shift of CuInS2/ZnS quantum dots (CIS/ZnS QDs) due to changes in the absorption of a pH indicator (α-naphtholphthalein) with a changing CO2 concentration. Using an LED with a central wavelength of 375 nm as the excitation source, it is shown that using the red emission of CIS/ZnS QDs allows for the detection of CO2 concentration over the range of 0-100%, and the associated wavelength shift was found to be 630 pm/%CO2. Moreover, the observed luminescence intensity from CIS/ZnS QDs at 578 nm increases as the CO2 concentration increases. The observed luminescence intensity change by CO2 is expressed as I100/I0, which I0 is used to represent the sensitivity of the optical fiber sensor, where I100 and I0 represent the steady-state luminescence intensities in pure carbon dioxide and pure nitrogen environments, respectively. The ratio I100/I0 of this optical fiber sensor is estimated to be 100. These results of the optical sensing method can be used in practice for detection of CO2 and could offer a new approach for developing novel types of optical fiber sensor.