Nanofluid Based on Glucose‐Derived Carbon Dots Functionalized with [Bmim]Cl for the Next Generation of Smart Windows

Abstract

The design of new advanced materials and technologies is essential for the development of smart windows for the next generation of energy-efficient buildings. Here, it is demonstrated that the functionalization of glucose-derived carbon dots with 1-butyl-3-methylimidazolium chloride results in a self-standing, water-soluble, viscous, reusable nanofluid with self-improving conductivity, thermotropy around 30-40 °C, and ultraviolet blocking ability. Its synthesis is straightforward, clean, fast, and cheap. At 36 °C (hot summer day), a sunactuated thermotropic (TT) device incorporating a 95% w/w nanofluid aqueous solution exhibits a transmittance variation (ΔT) of 9% at 550/1000 nm, which is amplified to 47/31% via the surface plasmon resonance effect. An integrated self-healing system enabling independent sun-actuated TT and voltage-actuated electrochromic (EC) operation is also produced. The low-energy EC device offers bright hot and dark cold modes (ΔT = 68/64%), excellent cycling stability, unprecedented coloration efficiency values (−1.73 × 10 6 /−1.67 × 10 6 cm 2 C −1 (coloring) and +1.12 × 10 7 /+1.08 × 10 7 cm 2 C −1 (bleaching) at ±2.5 V), and impressive memory effect. The disruptive design and sustainable synthesis of the new nanofluid proposed here will foster the agile development of novel products with improved ecological footprint.

Nanofluid Based on Carbon Dots Functionalized with Ionic Liquids for Energy Applications

“…Ma et al [25] reported a novel electrolyte based on poly(ethylene oxide) (PEO) nanocomposite with oxygen-rich Cdots that exhibited a conductivity of 0.139 mS•cm −1 , a value significantly lower than that obtained here using ILs as the surface groups. Moreover, these nanofluids present a self-improving feature upon cycling [17,18], which is evident in Figure 3c. Upon four consecutive heating/cooling cycles, the % increase in the conductivity in Cdots/ [17,18].…”

“…Moreover, these nanofluids present a self-improving feature upon cycling [17,18], which is evident in Figure 3c. Upon four consecutive heating/cooling cycles, the % increase in the conductivity in Cdots/ [17,18]. Usually, electrolytes tend to degrade upon consecutive cycling; however, in these nanofluids, we noted precisely the opposite trend (Figure 3b,c).…”

“…The synthesis of the nanofluids was performed according to the procedure reported elsewhere (Figure 1) [17,18] exhibited an orange color. Both these materials were transferred into a dialysis cellulose tubing membrane with a molecular weight cutoff of 500 Da, and dialyzed against ultrapure water for at least 72 h. The resulting solution was centrifuged for 10 min at 5000 rpm, and the supernatant was extracted and centrifuged again.…”

“…The high-resolution transmission electron microscopy (HR-TEM) and dynamic light scattering (DLS) data [17,18] proved that the produced Cdots had spherical morphologies and different size distributions depending on the ILs used and the raw carbon material they originated from. The smaller NPs (mean size of 3 nm) were found in the Cdots/[Bmim]Cl nanofluid, as expected for NPs obtained with a low water content IL [17]. In this particular case, Cdots were only functionalized with solely one IL.…”

“…Indeed, the thermal and electrochemical stability of ILs along with the increase in conductivity when associated with NPs makes them especially appealing to solve fundamental problems, such as the development of rechargeable lithium metal batteries where the uneven deposition of lithium hampers their stability along the repeated charge/discharge cycles [15]. Quite recently, our research group developed unique sustainable nanofluids based on synthetic polysaccharide [17] or waste biomass-derived [18] carbon dots (Cdots) functionalized with imidazolium-based ILs.…”