The comparative effects of visible light and UV-A radiation on the combined toxicity of P25 TiO2 nanoparticles and polystyrene microplastics on Chlorella sp.

The objective of this study was to determine the sublethal toxicity of TiO 2 nanoparticles (TiO 2 -NPs) on common carp ( Cyprinus carpio ) under visible light and dark conditions. Blood sampled was collected after 21 days and biochemical parameters, including glucose, total protein, albumin, globulin, creatinine, triglyceride and cholesterol levels, and aspartate aminotransferase (AST), alanine aminotransferase (ALT), γ-glutamyl transferase (GGT), lactate dehydrogenase (LDH), creatine kinase (CK), and alkaline phosphatase (ALP) activities were measured. The results showed that TiO 2 -NPs is caused a significant effect on blood biochemical parameters of C. carpio . By changing lighting conditions from darkness to light, significant differences were observed in certain blood biochemical parameters, including AST, ALT, LDH, ALP and CK activities, glucose, cholesterol and triglyceride levels in fish exposed to TiO 2 -NPs under light conditions as compared with fish exposed to TiO 2 -NPs under dark conditions. Cholesterol and triglyceride levels in fish exposed to 0.0 mg L -1 TiO 2 -NPs under darkness conditions were significantly higher than the control. The results revealed that toxicity of TiO 2 -NPs under visible light conditions was more than darkness conditions.

This study evaluated the toxicity potential of ZnO and TiO2 nanoparticles under pre-UV-A irradiation and visible light condition on Artemia salina. The nanoparticle suspension was prepared in seawater medium and exposed under pre-UV-A (0.23mW/cm2) and visible light (0.18mW/cm2) conditions. The aggregation profiles of both nanoparticles (NPs) and dissolution of ZnO NPs under both irradiation conditions at various kinetic intervals (1, 24, 48h) were studied. The 48-h LC50 values were found to be 27.62 and 71.63mg/L for ZnO NPs and 117 and 120.9mg/L for TiO2 NPs under pre-UV-A and visible light conditions. ZnO NPs were found to be more toxic to A. salina as compared to TiO2 NPs. The enhanced toxicity was observed under pre-UV-A-irradiated ZnO NPs, signifying its phototoxicity. Accumulation of ZnO and TiO2 NPs into A. salina depends on the concentration of particles and type irradiations. Elimination of accumulated nanoparticles was also evident under both irradiation conditions. Other than ZnO NPs, the dissolved Zn2+ also had a significant effect on toxicity and accumulation in A. salina. Increased catalase (CAT) activity in A. salina indicates the generation of oxidative stress due to NP interaction. Thus, this study provides an understanding of the toxicity of photoreactive ZnO and TiO2 NPs as related to the effects of pre-UV-A and visible light irradiation.

Nitrogen doped titanium dioxide as an aesthetic antimicrobial filler in dental polymers

Remarkable bactericidal traits of a metal-ceramic composite coating elated by hierarchically structured surface.

The main drawback of conventional palm oil mill effluent (POME) treatment is that the process is time and space-consuming. Besides, the treatment produces highly polluted wastewater that pollutes the environment if discharged directly. Photocatalytic process has significant potential to degrade recalcitrant organic pollutants and has recently attracted tremendous attention. However, current approaches mainly focus on visible light condition, which is still an ineffective treatment for POME. In this study, POME was successfully degraded using graphitic carbon nitride (g-C3N4) photocatalyst synthesised by calcination. The prepared photocatalyst was characterised by ultraviolet-visible diffuse reflectance (UV-Vis DRS) spectroscopy and scanning electron microscopy (SEM). The SEM results revealed the morphology of g-C3N4 photocatalyst. g-C3N4 could act as a visible-light-driven (VLD) photocatalyst with the highest photocatalytic efficiency of 71% under visible light. The present work highlights the potential of g-C3N4 towards the degradation of POME under visible light and dark condition. The highly enhanced photocatalytic performance is attributed to g-C3N4, but it does not work well in round-the-clock photocatalysis. However, g-C3N4 can work as the band alignment to drive separate photogenerated charge carriers, leading to effective photocatalytic degradation. g-C3N4 photocatalyst may be considered as an ideal candidate for treating POME.

The aim of the research was to investigate the possibility of using the methods of neural image analysis and neural modeling to determine the content of dry weight of compost based on photographs taken under mixed visible and UV-A light conditions. The research lead to the conclusion that the neural image analysis may be a useful tool in determining the quantity of dry matter in the compost. Generated neural model RBF 30:30-8-1:1 characterized by RMS error 0,076378 and this networks is more effective than RBF 19:19-2:1:1 which works in visible light conditions.

Cytotoxicity of titania nanoparticles towards waste water isolate Exiguobacterium acetylicum under UVA, visible light and dark conditions

Graphitic carbon nitride (g-C3N4) and titanium dioxide (TiO2) were chosen as a model system to investigate photocatalytic abilities of heterojunction system under UV and visible light conditions. The use of g-C3N4 has been shown to be effective in the reduction in recombination through the interaction between the two interfaces of TiO2 and g-C3N4. A simple method of preparing g-C3N4 through the pyrolysis of melamine was employed, which was then added to undoped TiO2 material to form the g-C3N4–TiO2 system. These materials were then fully characterized by X-ray diffraction (XRD), Brunauer Emmett Teller (BET), and various spectroscopic techniques including Raman, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), diffuse absorbance, and photoluminescence analysis. Photocatalysis studies were conducted using the model dye, rhodamine 6G utilizing visible and UV light irradiation. Raman spectroscopy confirmed that a composite of the materials was formed as opposed to a mixture of the two. Using XPS analysis, a shift in the nitrogen peak to that indicative of substitutional nitrogen was detected for all doped samples. This is then mirrored in the diffuse absorbance results, which show a clear decrease in band gap values for these samples, showing the effective band gap alteration achieved through this preparation process. When g-C3N4–TiO2 samples were analyzed under visible light irradiation, no significant improvement was observed compared that of pure TiO2. However, under UV light irradiation conditions, the photocatalytic ability of the doped samples exhibited an increased reactivity when compared to the undoped TiO2 (0.130 min−1), with 4% g-C3N4–TiO2 (0.187 min−1), showing a 43.9% increase in reactivity. Further doping to 8% g-C3N4–TiO2 lead to a decrease in reactivity against rhodamine 6G. BET analysis determined that the surface area of the 4% and 8% g-C3N4–TiO2 samples were very similar, with values of 29.4 and 28.5 m2/g, respectively, suggesting that the actual surface area is not a contributing factor. This could be due to an overloading of the system with covering of the active sites resulting in a lower reaction rate. XPS analysis showed that surface hydroxyl radicals and oxygen vacancies are not being formed throughout this preparation. Therefore, it can be suggested that the increased photocatalytic reaction rates are due to successful interfacial interactions with the g-C3N4-doped TiO2 systems.

Mercury (Hg) is assumed to be predominantly methylated by microorganisms in the environment. However, the mechanisms and extent of abiotic methylation are poorly appreciated. The understanding of the mechanisms leading to abiotic methylation and demethylation in the aquatic environment is of special concern since methylmercury (MeHg) biomagnifies in the food web. Bioaccumulating organisms have also been found to preserve specific Hg isotopic signatures that provide direct insight into aquatic Hg transformations. In this study we investigated the influence of chloride on the magnitude of Hg isotope fractionation during abiotic methylation of inorganic Hg (Hg(II)) using methylcobalamin as methyl donor compound. Coupling of gas chromatography with multi-collector inductively coupled plasma mass spectrometry has allowed to determine simultaneously isotopic ratios of inorganic and methyl-Hg species. Kinetic experiments demonstrated that the presence of chloride not only slowed the chemical alkylation of Hg(II) by methylcobalamin, but also decreased the extent of the methylation, which it is especially significant under visible light conditions due to the enhancement of MeHg photodecomposition. Abiotic methylation of Hg(II) by methylcobalamin in the presence of chloride caused significant Hg mass-dependent isotope fractionation (MDF) for both Hg(II) substrate (δ202Hg(II) from −0.74‰ to 2.48‰) and produced MeHg (δ202MeHg from −1.44‰ to 0.38‰) both under dark and visible light conditions. The value of this MDF under such saline conditions was higher than that previously reported (δ202MeHg from −0.73‰ to 0.09‰) in the absence of chloride and appeared mainly related to inorganic Hg speciation in solution, which is predominantly mercuric chloro-complexes (i.e. HgCl42−). Different isotopic signatures were observed for the different Hg species at the same time of reaction for either dark or visible light (450–650nm wavelengths) conditions. However, no significant mass-independent fractionation (MIF) was induced under any conditions within the analytical uncertainties (−0.17±0.31<∆201Hg<0.17±0.28‰), suggesting that photo-induced demethylation does not always involve MIF. These results also suggest that methylation by methylcobalamin can be an experimental model to study Hg isotope fractionation extent during elementary reaction of methyl transfer in biotic systems.

Fabrication of SnSO4-modified TiO2 for enhance degradation performance of methyl orange (MO) and antibacterial activity

Adsorption behavior of triclosan by different microplastics and the impact of water chemistry.

Self-motivated photoaging of microplastics by biochar-dissolved organic matter under different pyrolysis temperatures

Aging process does not necessarily enhance the toxicity of polystyrene microplastics to Microcystis aeruginosa

Toxicity of TiO2, in nanoparticle or bulk form to freshwater and marine microalgae under visible light and UV-A radiation

Photocatalytic effect of N–TiO2 conjugated with folic acid against biofilm-forming resistant bacteria