Antioxidative, low-concentration MXene inks with high-viscosity for infrared encryption and thermal energy harvesting†

Abstract

MXene-based inks exhibit great potential in direct writing, extrusion printing, and multifunctional coatings. However, achieving high-viscosity processing of low-concentration MXene inks remains a significant challenge due to the poor rheological properties of MXene. Here, we report high-viscosity processing of MXene inks at extremely low concentrations using a gel-assisted strategy through the formation of a three-dimensional network between MXene, water, and glycyrrhizic acid (GA). This network not only enhances oxidation resistance but also imparts a remarkably high viscosity of 31 283 Pa s, long-term stability, and thixotropic behavior to MXene inks at a concentration as low as 0.5 mg ml⁻¹. The unique rheological performance of MXene/GA inks enables multi-mode processing within wide viscosity ranges. Furthermore, the addition of gradient GA mass enables the composite ink to exhibit a wide infrared emissivity regulation capacity (Δ73%, from 19% to 92%), showing great potential in infrared color imaging and information encryption. Meanwhile, the composite inks incorporating 1 wt% GA have a remarkable solar spectral absorptivity of 90.1%, demonstrating their feasibility for solar thermal energy harvesting and conversion. This work provides a feasible strategy to realize multi-mode high-viscosity processing of low-concentration MXene inks, paving the way for multifunctional applications of MXene inks in various scenarios.