Ag-Doped Free-Standing 2D TiO₂ Sheets: Electronic, Optical, Magnetic, and Self-Healing Behaviour

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Silver-doped 2D titanium dioxide (ATO) sheets are promising flexible transparent conductors.
• Challenges exist in controlling doping levels and preventing structural defects during synthesis.
• Existing methods struggle with surface energy control, leading to material degradation.

Purpose of the Study:

• To report a surface energy-controlled synthesis method for silver-doped 2D titanium dioxide (ATO) sheets.
• To achieve controlled doping levels and large lateral dimensions in ATO materials.
• To explore the optoelectronic and physical properties of synthesized ATO for device applications.

Main Methods:

• Liquid phase exfoliation of TiO2 followed by hydrothermal Ag-doping using Hexamethylenetetramine (HMTA).
• Electron microscopy (SEM, TEM) and atomic force microscopy (AFM) for structural and morphological characterization.
• Band gap tuning via controlled Ag doping up to ~10%.

Main Results:

• Synthesized 2D ATO sheets with large lateral dimensions and controlled Ag doping.
• Identified multiple crystallographic phases (6-fold, 4-fold, strain-mediated) using high-resolution electron imaging.
• Achieved band gap tuning down to ~2 eV, with demonstrated electrical, optical, optoelectronic, photoluminescence, and ferromagnetic properties.
• Observed a self-healing effect under AFM tip-generated mechanical stress.

Conclusions:

• The surface energy-controlled synthesis provides a robust method for producing high-quality 2D ATO.
• Tunable doping enables the creation of visible light-sensitive, thermally and structurally robust semiconductor/conductor materials.
• These findings pave the way for flexible and wearable device applications, including optoelectronics and sensors.