Optimizing a dynamic infrared emitter by tailoring titanium carbide MXene surface chemistry

Ti3C2Tx MXene has become a highly promising material in nanophotonics because of its exceptional optical and thermal properties, which can be tailored through surface terminations. For the first time, we examine how Ti3C2Tx MXene without (N) and with different surface terminations (-F, -O-, or -OH) affects the performance of a thermal emitter with negative differential emissivity. This emitter is composed of Tungsten doped VO2 (W-doped VO2) composite/SiO2/Ti3C2Tx MXene. W doping in VO2 enables reversible-hysteresis emissivity behavior at a low critical temperature (~ 315 K), accompanied by negative differential emissivity between high- and low-temperature phases. While the threshold temperature for emissivity remains consistent across all terminations, the average differential emissivity varies considerably. Comparative analysis shows notable differences in differential average emissivity across surface terminations: -0.51 (W-doped VO2/SiO2/Ti3C2(OH)2), -0.49 (W-doped VO2/SiO2/Ti3C2F2), -0.46 (W-doped VO2/SiO2/Ti3C2), and − 0.32 (W-doped VO2/SiO2/Ti3C2O2), with hydroxyl termination demonstrating superior performance. This work highlights how engineering MXene surface terminations can enable tunable negative emissivity modulation at low temperatures, offering promising applications in thermal control devices, light modulation, infrared tagging and identification, solar energy harvesting systems, and other fields.