High-Precision Moisture Sensing in Tetrahydrofuran with Dual-Emissive Carbon Dots: Leveraging Ratiometric Strategy and Aggregation-Induced Emission

Carbon dots (C-dots) are known for their exceptional fluorescence properties, particularly when they form aggregates influenced by solvent characteristics. Herein, we synthesize intrinsic dual emissive C-dots (DC-dots) using monosaccharide via microwave technique. A judicious combination of acids resulted in the formation of intrinsic DC-dots. Under a UV lamp, these DC-dots emit green and yellow colors with an average lifetime of 0.14 and 0.47 ns, respectively. Transmission electron microscopy results confirmed the C8 structure of the prepared DC-dots with an average size of 4 nm. The DC-dots with tetrahydrofuran (THF) demonstrated attenuation of the long emission band compared with the short emission band. This distinctive behavior is associated with increased nonradiative transitions at the long emission wavelength (Knr = 0.32–0.58 ns). In response to DC-dots' unusual behavior, we investigated the effects of THF moisture interference. The experimental studies showed that successive addition of H2O in the range of (0–5%) volume fractions leads to turning on the long emissive band with redshifts w.r.t. short-range emission due to the aggregation-induced emission (AIE). In addition, these findings aid in developing a ratiometric approach to trace moisture in THF, using detection thresholds of 0.08 and 0.18%. High sensitivity of DC-dots to the trace limit of moisture has opened an avenue for cost-effective, ecofriendly intrinsic dual-emissive nanomaterials in developing moisture-sensing devices.