Down and Upconversion NGQDs and CuInS/ZnS QDs Nanocomposite for Ascorbic Acid Sensing

Copper indium sulfide/zinc sulfide (CuInS/ZnS) QDs and Nitrogen graphene quantum dots (NGQDs) were synthesized via aqueous solution methods and facile hydrothermal, respectively. Herein, according to the photoluminescence (PL) properties of QDs, a fluorescent nanocomposite of CuInS/ZnS QDs and NGQDs was synthesized. This nanocomposite was characterized by high-resolution transmission electron microscopy (HRTEM) and PL spectroscopy. This fluorescent nanocomposite was developed as a highly sensitive and selective ascorbic acid optical biosensor based on the luminescent quenching in the range from 10 to 500 μM with a correlation coefficient (R2) of 0.9964 and limit of detection (LOD) of 16.8 µM. HRTEM micrographs confirmed the preparation of CuInS/ZnS QDs with an average diameter size of 3 nm and NGQDs with an average diameter size of 5 nm.