Morphology Effect of One-Dimensional MnO 2 Nanostructures on Heteroatom-Doped Carbon Dot-Based Biosensors for Selective Detection of Glutathione.

Structural versatility of MnO 2 nanostructures plays a significant role in biosensing applications. So, we have prepared simple and selective "turn-off-on" sensing probes for the detection of glutathione (GSH), based on nitrogen, sulfur codoped carbon dots (N, S-Cdots) and different morphologies of one-dimensional (1-D) MnO 2 nanostructures. N, S-Cdots with a high fluorescence quantum yield (73.42%) were prepared by a green approach through high-temperature pyrolysis in just 5 min. The different morphologies of 1-D MnO 2 nanostructures (nanowires with varying aspect ratios and nanorods) were synthesized through a hydrothermal method by varying the reaction period (8, 10, and 12 h). MnO 2 nanowires prepared at 8 h showed a high specific surface area (34 m 2 g -1 ) with a large aspect ratio. They showed significant fluorescence quenching, Stern-Volmer constants, and binding constants in the presence of N, S-Cdots. Further, ultraviolet-visible absorption, zeta potential, and time decay studies showed that the quenching mechanism of the developed sensing system was the inner filter effect, which was further confirmed by using the Parker equation. The N, S-Cdots-MnO 2 nanowire (with a high aspect ratio) sensing system showed the best limit of detection, i.e., 28.5 μM for GSH. This fast, simple, eco-friendly, and cost-effective sensing system can be further used for real-time biosensing and bioimaging application.