abstract
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.
keywords
BOMBYX-MORI SILK; IONIC LIQUIDS; THERMAL-CONDUCTIVITY; HEAT-CAPACITIES; NANOFLUIDS; IMIDAZOLIUM; EFFICIENT; BEHAVIOR; HYDROLYSIS; ABSORPTION
subject category
Chemistry; Materials Science
authors
Duarte, TAG; Pereira, RFP; Medronho, B; Maltseva, ES; Krivoshapkina, EF; Varela-Dopico, A; Taboada, P; Fu, LS; Ferreira, RAS; Bermudez, VD
our authors
Lianshe Fu
Junior Researcher
Maria Rute de Amorim e Sá Ferreira André
Full professoracknowledgements
R.F.P.P. acknowledges FCTUMinho for his contract in the scope of Decreto-Lei 57/2016 57/2017. E.S.M. is grateful for the Erasmus+ grant that funded her stay at CQ-VR. E.F.K. thanks state task no. FSER-2022-0002 within the framework of the National Project "Science and Universities". P.T. thanks Agencia Estatal de Investigacion (AEI) by project PID2019-109517RB-I00 and Xunta de Galicia by grant ED431C 2022/18. ERDF funds are also acknowledged. Vicente Dominguez, Francisco Rivadulla, and Carmen Alvarez-Lorenzo, from USC, are acknowledged for their helpful assistance during heat capacity, thermal conductivity, and thermal imaging acquisition measurements, respectively. Sandra Correia, from IT, is acknowledged for recording the emission spectra.