Fluorescent fiber-optic device sensor based on carbon quantum dot (CQD) thin films for dye detection in water resources.

Industrialization, especially in textile industries, has led to increased use of dyes and pigments to impart colours to fabrics. Textile dyes are one of the chief emerging pollutants of water resources as industrial effluents. In the current research, we report the development and utilization of pH-sensitive carbon quantum dots (CQDs) immobilized in polymer thin films acting as sensors for textile dye detection. The CQDs and CQD-containing polymer films were characterized by various techniques like XRD, TEM, XPS, and CLSM. The synthesized CQD thin films possess a unique pH-sensitive property that can be used to detect various model acidic and basic dyes that are important components of industrial effluents from textile dyes. The detection capability of the sensor films was evaluated by spiking dyes in various water matrices, like household tap water and river water. The results indicate that pH-sensitive CQD thin film was able to detect three acidic dyes, namely methyl red, methyl orange, and bromocresol green, and one basic dye, methylene blue, in a linear range of 0-100 μM with a response time of 1 minute. The CQD thin-film sensors have a limit of detection of 26.4 ppb, 214.5 ppb, 46.2 ppb, and 29.7 ppb for methyl red, methyl orange, bromocresol green and methylene blue, respectively. The accuracy of detection performed by spiking studies in water resources indicated an ∼100% recovery value in all tested acidic and basic dyes. The sensor films were compared for analytical parameters using UV-visible-fluorescence spectroscopy and HPLC.