Lokeshwar, H.Lakshmi Praveen, L.Mandal, S.Shakti, N.2026-02-032025Ceramics International, 2025, 51, , pp. 53681-536932728842https://doi.org/10.1016/j.ceramint.2025.09.113https://idr.nitk.ac.in/handle/123456789/20004This study explores the novel and eco-friendly chemical etching of bulk Cr<inf>2</inf>AlC MAX phases using a deep eutectic solvent (DES) mixture of choline chloride (ChCl) and anhydrous ferric chloride (FeCl<inf>3</inf>) to synthesize chromium carbide (Cr<inf>2</inf>CT<inf>x</inf>) MXene nanolayers. ChCl-FeCl<inf>3</inf>enables a fluoride-free transformation approach to synthesize Cr<inf>2</inf>CT<inf>x</inf>MXene via selective etching of aluminium interlayers, resulting in mixed surface terminations (-O, -OH, -Cl) confirmed from bond vibrations observed in FTIR transmittance spectra. Also, the FESEM micrographs confirm the formation of Cr<inf>2</inf>CT<inf>x</inf>nanolayers with successful cleavage of Cr<inf>2</inf>AlC MAX phase nanolaminates identified from a distinct red shift of D-band with the highest I<inf>D</inf>/I<inf>G</inf>ratio peak intensity ratio, confirming the presence of high defect concentration in Cr<inf>2</inf>CT<inf>x</inf>MXene. The hydrothermally synthesized SnO<inf>2</inf>powders exhibiting a rutile tetragonal phase average particle size of 35.8 ± 0.8 nm were mixed with Cr<inf>2</inf>CT<inf>x</inf>to formulate screen-printable inks for the fabrication of Cr<inf>2</inf>CT<inf>x</inf>, SnO<inf>2</inf>, and their composite Cr<inf>2</inf>CT<inf>x</inf>-SnO<inf>2</inf>gas sensors. The addition of Cr<inf>2</inf>CT<inf>x</inf>demonstrated a detrimental effect on the gas-sensing performance of the SnO<inf>2</inf>sensor, which was further supported from XPS analysis. However, the SnO<inf>2</inf>sensor recorded the highest gas-response of ?452 towards 100 ppm of ammonia gas among all sensors, highlighting the role of oxygen defects confirmed from photoluminescence spectra. This work paves the way for a novel and eco-friendly etching approach of MAX-phases and helps in their research towards the development of ultra-sensitive gas sensors. © 2025 Elsevier Ltd and Techna Group S.r.l. All rights are reserved, including those for text and data mining, AI training, and similar technologies.Aluminum compoundsAmmoniaCarbidesChemical detectionChemical sensorsChlorinationChlorine compoundsChromium compoundsDefectsEutecticsFluorine compoundsFourier transform infrared spectroscopyGas detectorsGas sensing electrodesIron compoundsPhotoluminescenceRed ShiftSynthesis (chemical)Ammonia gasCholine chlorideCr2CTxDeep eutectic solventsEco-friendlyGas-sensorsMAX-phaseNano layersOxygen defectSnO 2Etching