Defect engineered N-S codoped TiO₂ nanoparticles for photocatalytic and optical limiting applications: Experimental...

Area of Science:

• Materials Science
• Nanotechnology
• Photocatalysis
• Spintronics

Background:

• Titanium dioxide (TiO2) is a widely studied semiconductor with applications in photocatalysis and optics.
• Enhancing TiO2's visible light absorption and introducing novel functionalities like ferromagnetism remain key research challenges.
• Doping TiO2 with non-metals like nitrogen (N) and sulfur (S) is a promising strategy to modify its electronic and optical properties.

Purpose of the Study:

• To synthesize and characterize nitrogen-sulfur (N-S) codoped TiO2 nanoparticles (NPs).
• To investigate the impact of N-S codoping on the structural, optical, magnetic, and photocatalytic properties of TiO2.
• To explore the potential applications of N-S doped TiO2 in photocatalysis and optical limiting.

Main Methods:

• Sol-gel cum hydrothermal synthesis of N-S codoped TiO2 NPs using ammonium sulfate.
• Characterization using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Electron paramagnetic resonance (EPR), UV-Vis, photoluminescence (PL), and vibrating sample magnetometry (VSM).
• Photocatalytic degradation experiments using Rhodamine B (RhB), Methylene Blue (MB), and Congo Red (CR) dyes under visible light.
• Density Functional Theory (DFT) calculations to understand electronic structure modifications.

Main Results:

• N-S codoping shifted the phase of TiO2 to pure anatase and introduced N-H vibrations and S-O complexation.
• EPR and PL confirmed the creation of oxygen defects (Ti3+ signals) in N-S doped TiO2.
• N-S doped TiO2 exhibited room-temperature ferromagnetic behavior attributed to oxygen vacancies.
• Significantly enhanced photocatalytic degradation of organic dyes under visible light compared to pristine TiO2.
• Improved two-photon absorption (TPA) properties, indicating potential for optical limiting applications.

Conclusions:

• N-S codoping effectively modifies the electronic band structure of TiO2, enhancing visible light absorption and photocatalytic efficiency.
• The presence of oxygen vacancies in N-S doped TiO2 is crucial for both its ferromagnetic properties and optical limiting behavior.
• N-S codoped TiO2 nanoparticles show great promise for applications in environmental remediation and advanced optical devices.