Bacterial nanocellulose and CdTe quantum dots: assembled nanopaper for heavy metal detection in aqueous solution

Abstract

The urgent requirements for rapid identification and quantification of heavy metals worldwide has spurred the development of methods that enable rapid and selective detection and quantification. Among these methodologies, nanomaterials have shown particular promise, with chemosensors made of quantum dots that modify their luminescence in response to the presence and concentration of certain heavy metals. The properties of these sensors can be enhanced using support materials such as nanocellulose, making them promising candidates for the in situ identification of heavy metals in water effluents. In this study, a nanocomposite chemosensor composed of bacterial nanocellulose (BNC) as a support material and photoluminescent CdTe quantum dots (QDs) and/or dithizone (DTZ) as sensitizing agents was fabricated to obtain portable optical sensing nanopaper via immobilization. Several loadings of BNC:QDs ratios were evaluated. The chemosensor and its components were structurally and morphologically characterized by UV-Vis, fluorescence, IR, XRD, TEM, SEM, and XPS techniques. The results indicated a QD particle size of 2.4 nm, a nucleus with a CCC crystalline structure, and a homogenous dispersion on the BNC fibers. The chemosensor was sensitive to heavy metals such as copper, mercury, and lead, exhibiting variations in the sensor's fluorescence. Remarkable results are shown for mercury sensing under optimal conditions with a limit of detection (LOD) of 1 nM. Finally, the results were subjected to RGB analysis (red, green, and blue composition), which enabled correlation of the chemosensor's green color composition with a numerical value corresponding to the amount of green in each evaluated spot before and after the fluorescence decrease. This application demonstrates BNC-based sensors to be valuable, fast, and easy-to-use tools for rapid heavy-metal sensing.