The effects of DMAEMA polyelectrolyte and TiO2 photocatalyst on the tartrazine quenching of N-doped carbon dot immobilized in PVA/microfibrillated cellulose film

Abstract

The quenching of carbon dots (CDs) is affected by surface functional groups and other factors. Since CDs were also immobilized into thin films as a sensor, the effects of film properties on their photoluminescence should be investigated. In this work, N-doped CDs (NCDs) were immobilized in polyvinyl alcohol (PVA) thin films for tartrazine detection. Using a microwave-assisted hydrothermal method, amorphous NCDs were successfully produced. NCDs were blended into the PVA dope solution containing microfibrillated cellulose (MFC). An excessive amount of NCDs caused the undesired interaction and mutual reabsorption between the NCDs, resulting in self-quenching. Dimethylaminoethyl acrylate (DMAEMA) was added as copolymer to reduce the swelling ratio by about 50%. The reduction of water uptake subsequently reduced the tartrazine adsorption and the quenching of NCDs. Contradictory, the addition of TiO2 nanoparticles improved the tartrazine adsorption and the NCDs quenching. The thin film also exhibits photocatalytic properties for analyte removal. The linear ΔF and the unchanged absorbance spectra of PVA/DM3/NCD/TiO2 thin film indicate dynamic quenching at low tartrazine concentration (< 10 µM), attaining a limit of detection of 4.66 µM. The overlapping spectrum between the analyte absorbance and NCDs film emission spectra showed possible inner filter effects or fluorescence resonance energy transfer quenching mechanism.