UV and visible light active aqueous titanium dioxide colloids stabilized by surfactants

Area of Science:

• Materials Science
• Nanotechnology
• Photocatalysis

Background:

• Titanium dioxide (TiO2) nanoparticles are crucial for photocatalysis but often lack stability in aqueous solutions across a wide pH range.
• Developing stable nanodispersion systems is essential for efficient TiO2-based photocatalytic applications.

Purpose of the Study:

• To enhance the stability of photocatalytically active titanium dioxide (TiO2) nanodispersions.
• To evaluate the effectiveness of different stabilizing agents, including polyethylene glycols (PEGs) and Tween® 80, for TiO2 nanoparticles.
• To assess the photocatalytic activity of stabilized TiO2 colloids, particularly when photosensitized with naphthol derivatives, under UV and visible light.

Main Methods:

• Dynamic Light Scattering (DLS) measurements were used to assess nanoparticle stability and aggregation.
• TiO2 nanoparticles were stabilized using various molecular weights of polyethylene glycols (PEGs) and polyoxyethylenesorbitan monooleate (Tween® 80).
• Photosensitization of Tween® 80-stabilized TiO2 colloids was performed using 2,3-naphthalenediol (nd), 2-hydroxy-3-naphthoic acid (hn), or catechol (cat).
• Photocatalytic activity was evaluated by monitoring the degradation of azure B dye under UV and visible light irradiation.

Main Results:

• Tween® 80 demonstrated a significant stabilizing effect on TiO2 nanoparticles, preventing aggregation in aqueous solutions (pH 3-10).
• Systems stabilized with PEGs showed a tendency to aggregate in neutral solutions, indicating lower stability compared to Tween® 80.
• The nd@TiO2 + Tween® 80 colloid exhibited particularly high photoactivity under visible light irradiation.
• Comparison revealed that the photosensitized nd@TiO2 + Tween® 80 nanodispersion significantly outperformed both the non-photosensitized TiO2 + Tween® 80 and PEG-stabilized systems under both UV and visible light.

Conclusions:

• Tween® 80 is a highly effective stabilizing agent for titanium dioxide (TiO2) nanoparticles, ensuring stability across a broad pH range.
• Photosensitization of Tween® 80-stabilized TiO2 with 2,3-naphthalenediol (nd) significantly enhances photocatalytic activity, especially under visible light.
• The enhanced performance is attributed to differences in micelle structures formed between TiO2 and photosensitized TiO2 stabilized with Tween® 80.