Study of the durability and sustainability of fluorescent nanosensors based on cellulose nanocomposites incorporated with various carbon dots

Paper-based analytical devices are promising options for lab-on-chip and other biodetection applications. Among various nanomaterials, carbon quantum dots (CQDs) are famous for their significant and stable photoluminescence (PL) properties, as well as their fast and cost-effective gram-scale synthesis techniques. However, studies on the durability and sustainability of their performance as fluorescent composites are very limited and not systematic. Therefore in this investigation, the PL emission intensity of cellulose papers containing various types of CQDs, including pure, N-, S-, P-, N/S-, and N/P-doped CQDs, were studied over two months, at three different storage temperatures, namely, 4 °C, 10 °C, and 25 °C, and four pH settings as to be 5, 6, 7 and 8. The results show that the environmental keeping conditions, as well as the chemical structure of the embedded CQDs, have significant impacts on the durability and sustainability of the produced sensors. All the fluorescent composites investigated in this study proved to have very high performances, sustaining from above 60–90% of their PL emission intensities over time. Although 4 °C is proved to be generally the best keeping temperature for all the fluorescent nanocomposites, the best pH, in which the PL is most sustained, depends strongly on the chemical nature of the embedded CQDs. The CQDs/cellulose composites were kept for additional longer durations, above six months, in their best keeping conditions, and their performance was checked, showing the reliability of the proposed setup for further industrial promising applications.