N-modified carbon quantum dot in 3D-network of microfibrillated cellulose for building photoluminescent thin film as tartrazine sensor

Carbon quantum dot (CDs) dispersed in aqueous solution has been widely studied, this work developed photoluminescent thin film as tartrazine sensor by incorporating nitrogen modified CDs (NCDs) dispersed in three-dimensional network of microfibrillated cellulose (MFC) in polyvinyl alcohol (PVA) thin film. CDs and NCDs was synthesized using microwave assisted hydrothermal method. MFC enhanced the dispersion of quantum dot and improved the luminescence intensity as shown in transmission electron microscopic images and ImageJ analysis results. The LOD of CDs was slightly impaired but the LOD of NCDs was slightly improved by MFC in tartrazine quenching. After drying and crosslinking, PVA/CD, PVA/CD-MFC, PVA/NCD, PVA/NCD-MFC thin films formed without defects and thickness less than 200 nm as shown in scanning electron microscopic images. However, the light transmittance of PVA/CD-MFC thin film was reduced comparison to PVA/CD thin film, resulting the smallest changes of fluorescence intensity during tartrazine quenching. PVA/NCD-MFC thin film showed the greatest reduction in photoluminescence which can be detected using image analysis. It offers data storage, transfer and analysis without liquid sample.