A Glance at Novel Ionanofluids Incorporating Silk-Derived Carbon Dots

One of the hallmarks of the current efforts in the field of thermal energy is heat transfer enhancement. Ionanofluids (INFs), a combination of nanomaterials and ionic liquids (ILs), are an appealing category of thermal fluids. In this work, we introduce sustainable INFs composed of carbon dots derived from Bombyx mori silk fibroin (SF) dispersed in a mixture of 1-butyl-3-methylimidazolium chloride (IL1) and 1-(4-sulfobutyl)-3-methylimidazolium triflate (IL2). The syntheses were performed at mild conditions, with reaction times of 3, 4, and 5 h, and without purification steps. The INFs display room-temperature emission in the visible spectral range with quantum yield values up to 0.09 and are essentially viscous fluids (G″ > G′). A marked shear thinning behavior is observed at high shear rates, particularly for the systems SFIL1IL2-3h and SFIL1IL2-4h. The INFs demonstrate relatively high heat capacity and thermal conductivity values in comparison to state-of-the-art INFs. Under suitable illumination conditions, the INFs can convert light into heat in an efficient manner, with photothermal conversion efficiencies of up to 28%, similar to other reported INFs. SFIL1IL2-5h exhibits remarkable stability over time within the range of working temperatures. This work paves the way for the development of new thermal fluids for enhanced heat transfer technologies using sustainable synthesis routes and natural raw precursor materials.