Photochemical degradation of trypan blue.

PURPOSE: To investigate the photochemical degradation of trypan blue (TB) and to identify decomposition products. METHODS: Defined solution samples of TB and a mixture with lutein/zeaxanthin were exposed to blue light. Thermal degradation processes were ruled out using controls not subjected to irradiation. All samples were analyzed using optical microscopy, UV/Vis spectroscopy, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and nuclear magnetic resonance (NMR) spectrometry. Degradation kinetics were determined based on changes in absorbance; intermediates were identified by analyzing mass differences of characteristic fragment ion peaks within the fragmentation patterns, and assignments were verified by NMR. RESULTS: TB demonstrated a photochemical degradation, which can be triggered by lutein/zeaxanthin. Intermediates vary depending on the presence of lutein/zeaxanthin. The self-sensitized photodegradation of TB occurs under generation of dimethyl sulfate and presumed formation of phenol. In contrast, within the presence of lutein/zeaxanthin the decomposition of TB indicates the formation of methoxyamine and sulfonyl arin. Thermal degradation processes were not observed. CONCLUSIONS: TB demonstrated a photodegradation that may be triggered by lutein/zeaxanthin and results in the formation of cytotoxic decomposition products. Our findings contribute to understand degradation mechanisms of TB and may elucidate previous clinical and experimental observations of cellular toxicity after TB application.

Nano Cu metal doped on TiO2-SiO2 nanoparticle catalysts in photocatalytic degradation of direct blue dye.

The photo-assisted deposition (PAD) and impregnation (Img) synthesis of nano-sized Cu metal on TiO2-SiO2 are reported. The prepared catalysts were characterized by different techniques such as XRD, EXAFS, TEM and nitrogen adsorption analysis. Photocatalytic reactivity using Cu-TiO2-SiO2 catalysts under visible-light condition on the oxidation of direct blue dye with O2 reaction was evaluated. The results have shown notable photocatalytic activity of PAD-Cu/TiO2-SiO2 which was 1.6 and 10 times higher than that of Img-Cu/TiO2-SiO2 and TiO2-SiO2, respectively.

Enhancement of titania by doping rare earth for photodegradation of organic dye (Direct Blue).

Lanthanide ions (La(3+), Nd(3+), Sm(3+), Eu(3+), Gd(3+), and Yb(3+))/doped TiO2 nanoparticles were successfully synthesized by sol-gel method. Their photocatalytic activities were evaluated using Direct Blue dye (DB53) as a decomposition objective. The structural features of TiO2 and lanthanide ions/TiO2 were investigated by XRD, SEM, UV-diffuse reflectance, and nitrogen adsorption measurements. Our findings indicated that XRD data characteristic anatase phase reflections and also XRD analysis showed that lanthanides phase was not observed on Lanthanide ions/TiO2. The results indicated that Gd(3+)/TiO2 has the lowest bandgap and particle size and also the highest surface area and pore volume (V(p)) as well. Lanthanide ions can enhance the photocatalytic activity of TiO2 to some extent as compared with pure TiO2 and it was found that Gd(3+)/TiO2 is the most effective photocatalyst. The photocatalytic tests indicate that at the optimum conditions; illumination time 40 min, pH approximately 4, 0.3g/L photocatalyst loading and 100 ppm DB53; the dye removal efficiency was 100%. Details of the synthesis procedure and results of the characterization studies of the produced lanthanide ions/TiO2 are presented in this paper.