Synthesis of Ti3C2 and Ti2C MXenes

Ti₃C₂ MXenes were synthesized
by a two-step exfoliation process
according to the literature.^{53 (link)} Generally,
2.0 g of Ti₃AlC₂ MAX powder (Forsman Scientific
Co., Ltd., Beijing, China) was immersed in 30 mL of 40% HF aqueous
solution (Aladdin Co., Ltd., Shanghai, China) and electromagnetically
stirred for 24 h at room temperature to completely remove Al atoms
in the Ti₃AlC₂ MAX phase. For
Ti₂C, the synthesis process is quite simpler, and the concentration
of HF is only 20%. The etched Ti₃C₂ or Ti₂C MXene powders were collected by centrifugation process and
washed with water and ethanol for 4–5 times. Then, the prepared
Ti₃C₂ or Ti₂C MXene powders were
dispersed in 30 mL of TPAOH (tetrapropylammonium hydroxide 25 wt %
aqueous solution, Macklin Co., Ltd., Shanghai, China) and electromagnetically
stirred for three days at a speed of about 800 rpm/min to delaminate
the etched nanosheets. Then, Ti₃C₂ or Ti₂C MXene powders were collected by centrifugation process and
washed with ethanol and water three times to remove the residual TPAOH.
Finally, the prepared Ti₃C₂ or Ti₂C MXene powders were collected for Raman detection. The Au–Ti₃C₂ nanosheets were synthesized by reducing HAuCl₄ to Au nanoparticles on Ti₃C₂ MXene
nanosheets.^{54 (link)}