Abstract

One of the most critical issues in the design of oxide semiconductors is the capability to design optical functionality at ultralow additive concentrations. In this case, prove that a single interfacial process enables trace Ti3C2Tx MXene (0.01-0.05 wt%) to reorganize the structural, electronic, and photonic space of TiO2. XRD and FT-IR examinations demonstrate that development of coherent Ti-O-C interfacial-heterophase and characteristic 2D -> 3D elastic confinement occurs, which minimizes crystal size (36 -> 24 nm), elevates microstrain (1.8 -> 3.0 x10- 3), and leads to controlled reduction of Ti4+-Ti3+. Optical disorder is strongly inhibited despite greater strain and density of dislocation, with an increase in the steepness parameter of Urbach threefold and a sharp reduction in tail-state energy (Eu: 5.65 -> 1.95 e V). Band-gap tunability (3.00 -> 2.71 eV) and increased optical conductivity, as well as the development of direct excitonic luminescence, is observed by optical characterization. The X-ray photoelectron spectroscopy also offers direct data of Ti-O-C interfacial bonding and a progressively growing concentration of Ti3+ species with a rise in MXene concentration. Photoluminescence and CIE chromaticity measurements verify color-tunable emission (lambda dom=430-530 nm) and high color purity (60-80 %), which is attributed to MXene-induced conduction-band shifts (similar to 0.5-1.0 eV) and interfacial orbital hybridization. These findings define that ultralow MXene loadings are not conductive additives, but programmable interfacial architectures which program band alignment, defect self-compensation, and excitonic pathways. This work introduces MXene-based interfacial orbital engineering as a versatile methodology to highperformance optoelectronic material development, which can be used to make colorimetric sensors, applications in tunable light emitters.