Violet Irradiation Research Articles

Co-doped titanium dioxide nanoparticles decrease the cytotoxicity of experimental hydrogen peroxide gels for in-office tooth bleaching.

To evaluate the efficacy and cytotoxicity of experimental 6% and 35% hydrogen peroxide gels (HP6 or HP35) incorporated with titanium dioxide nanoparticles (NP) co-doped with nitrogen and fluorine and irradiated with a violet LED light (LT). Bovine enamel-dentin disks adapted to artificial pulp chambers were randomly assigned to bleaching (n = 8/group): NC (negative control), NP, HP6, HP6 + LT, HP6 + NP, HP6 + NP + LT, HP35, HP35 + LT, HP35 + NP, HP35 + NP + LT, and commercial HP35 (COM). Color (ΔE00) and whiteness index (ΔWID) changes were measured before and 14days after bleaching. The extracts (culture medium + diffused gel components) collected after the first session were applied to odontoblast-like MDPC-23 cells, which were assessed concerning their viability, oxidative stress, and morphology. The amount of HP diffused through the disks was determined. Data were analyzed by generalized linear models orKruskal Wallis Tests (α = 5%). RESULTS: HP6 + NP + LT exhibited ΔE00 and ΔWID higher than HP6 (p < 0.05) and similar to all HP35 groups. HP6 + NP + LT showed the lowest HP diffusion, and the highest cell viability (%) among bleached groups, preserving cell morphology and number of living cells similar to NC and NP. HP6 + LT, HP6 + NP, and HP6 + NP + LT exhibited the lowest cell oxidative stress among bleached groups (p < 0.05). HP35, HP35 + LT, and HP35 (COM) displayed the lowest cell viability. HP6 achieved significantly higher color and whiteness index changes when incorporated with nanoparticles and light-irradiated and caused lower cytotoxicity than HP35 gels. The nanoparticles significantly increased cell viability and reduced the hydrogen peroxide diffusion and oxidative stress, regardless of HP concentration. Incorporation of co-doped titanium dioxide nanoparticles combined with violet irradiation within the HP6 gel could promote a higher perceivable and acceptable efficacy than HP6 alone, potentially reaching the optimal esthetic outcomes rendered by HP35. This approach also holds the promise of reducing cytotoxic damages and, consequently, tooth sensitivity.

Diversity of Methylobacterium species associated with New Zealand native plants.

Methylobacterium species are abundant colonizers of the phyllosphere due to the availability of methanol, a waste product of pectin metabolism during plant cell division. The phyllosphere is an extreme environment, with a landscape that is heterogeneous and continuously changing as the plant grows and is exposed to high levels of ultraviolet irradiation. Geographically, New Zealand (NZ) has been isolated for over a million years, has a biologically diverse flora, and is considered a biodiversity hotspot, with most native plants being endemic. We therefore hypothesize that the phyllosphere of NZ native plants harbor diverse groups of Methylobacterium species. Leaf imprinting using methanol-supplemented agar medium was used to isolate bacteria, and diversity was determined using ARDRA and 16S rRNA gene sequencing. Methylobacterium species were successfully isolated from the phyllosphere of 18 of the 20 native NZ plant species in this study, and six different species were identified: M. marchantiae, M. mesophilicum, M. adhaesivum, M. komagatae, M. extorquens, and M. phyllosphaerae. Other α, β, and γ-Proteobacteria, Actinomycetes, Bacteroidetes, and Firmicutes were also isolated, highlighting the presence of other potentially novel methanol utilizers within this ecosystem. This study identified that Methylobacterium are abundant members of the NZ phyllosphere, with species diversity and composition dependent on plant species.

Highly stable quantum dot light-emitting diodes with improved interface contacting via violet irradiation

The relatively low stability of quantum dot light-emitting diodes (QLEDs) caused by unbalanced carrier injection has not been completely solved. Among various influencing factors, interface contacting is one of the important factors affecting the carrier injection equilibrium. Herein, we proposed a method to improve the carrier injection equilibrium for QLEDs. We investigated and explored the effects of violet irradiation on the efficiency and operating stability of MoO3-based inverted QLEDs. Specifically, violet irradiation on the interface of MoO3/Mg:Ag is carefully analysed. Further research shows that the interfacial reaction between Mg:Ag anode and MoO3 hole injection layer accounts for such improvement. During violet irradiation, the Mg:Ag quickly reacts with the oxygen from MoO3, leading to the formation of Mo-O-Mg:Ag interlayer. The hole injection is effectively enhanced, resulting from the reduction of the electrons extraction barrier at MoO3/Mg:Ag interface and the improvement of the interface contacting. By optimizing the violet irradiation dosage and violet wavelength, the maximum current efficiency (CE) is increased from 20.2 cd/A to 31.1 cd/A. Moreover, devices exhibit a highly stable operation lifetime of 44161 h (T95@1000 nits), which is much longer than non-violet irradiation QLEDs and meet the stringent industrial requirements for display applications.

Photodegradation of Bamboo: A Study on Changes in Mechanical Performances.

One of the main concerns in using natural materials in construction, such as bamboo, regards their durability. Ultra violet (UV)irradiation is claimed as a damaging agent; therefore, it is important to study its effect. Several studies have shown that bamboo components such as lignin are subjected to photochemical degradation, but it is not well understood how this affects the mechanical properties of bamboo. The aim of this paper is to explore the correlation between photodegradation and bamboo mechanical performance. Bamboo samples were exposed to accelerated UV ageing for different times (from 6 to 360 h) and then subjected to a four-point bending test. Since one of the ways to stabilize bamboo is to thermally treat it, the tests were conducted on natural untreated bamboo and treated bamboo with a traditional flame treatment. Modifications of the chemical features of the material were analyzed with Fourier Trasform Infra Red (FTIR) spectroscopy, while modifications of the morphological features were analyzed byEnvironmental Scanning Electron Microscopy ESEM and optical microscopy observations. The results show that the bending behavior of bamboo is not compromised by UV exposure up to 360 h. In fact, although a progressive degradation of lignin is reported and cracks in the fiber walls are highlighted from micrographs, no effects were found on the fiber length.

Green synthesis of iron nanoparticles and photocatalytic activity evaluation for the degradation of methylene blue dye

Abstract The present study focuses on iron nanoparticles (Fe NPs) biosynthesis, characterization and photocatalytic activity (PCA) appraisal for methylene blue dye degradation. A green rapid biogenic synthesis route was employed for synthesis of Fe NPs using banana peel extract. The synthesized Fe NPs was characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy) and EDX (energy dispersive X-ray) techniques. These analysis confirmed the synthesis of zero valent Fe NPs with high crystallinity, purity and semi spherical in shape. The photocatalytic activity was assessed under ultra violet irradiation and under optimum conditions, 87% degradation of MB dye was obtained for 72 min of irradiation, which revealed promising catalytic efficiency of the Fe NPs. The result shows that photocatalytic activity of Fe NPs is promising and could possibly be used to treat dyes in industrial effluents and the use of green synthetic protocol is suggested due to its ecofriendly nature.

Dehydration rate of the glycine‐MgSO4·5H2O complex and the stability of glycine expelled from the complex by in situ Raman spectroscopy under Mars‐relevant conditions

AbstractIn this work, we studied the dehydration process of the glycine‐MgSO4·5H2O complex under Mars‐relevant conditions (99% CO2 and 0.6% H2O under ultra violet (UV) irradiation exposure at 7‐mbar pressure and high vacuum conditions: 8 × 10−5 and 5 × 10−5 mbar) by in situ Raman spectroscopy inside a planetary atmosphere and surface chamber (PASC). This work provides quality Raman spectra taken under simulated planetary conditions (to be integrated in a database), as Raman spectroscopy forms part of the current and upcoming NASA and ESA Mars planetary missions. The results demonstrate that Raman spectroscopy can be used to calculate rates of dehydration of the glycine‐MgSO4·5H2O compound to study the chemical stability with respect to photodecomposition (1) of metal‐bound glycine molecules forming the complex and (2) glycine expelled from the complex, both under Mars‐simulated conditions; finally, Raman spectroscopy can also be used to quantify intermolecular interactions in terms of local pressures. Importantly, advanced detection of water molecules as part of a complex with astrobiological interest under planetary conditions plays a crucial role in planetary missions.

The effects of violet and blue light irradiation on ESKAPE pathogens and human cells in presence of cell culture media

Bacteria belonging to the group of ESKAPE pathogens are responsible for the majority of nosocomial infections. Due to the increase of antibiotic resistance, alternative treatment strategies are of high clinical relevance. In this context visible light as disinfection technique represents an interesting option as microbial pathogens can be inactivated without adjuvants. However cytotoxic effects of visible light on host cells have also been reported. We compared the cytotoxicity of violet and blue light irradiation on monocytic THP-1 and alveolar epithelium A549 cells with the inactivation effect on ESKAPE pathogens. THP-1 cells displayed a higher susceptibility to irradiation than A549 cells with first cytotoxic effects occurring at 300 J cm−2 (405 nm) and 400 J cm−2 (450 nm) in comparison to 300 J cm−2 and 1000 J cm−2, respectively. We could define conditions in which a significant reduction of colony forming units for all ESKAPE pathogens, except Enterococcus faecium, was achieved at 405 nm while avoiding cytotoxicity. Irradiation at 450 nm demonstrated a more variable effect which was species and medium dependent. In summary a significant reduction of viable bacteria could be achieved at subtoxic irradiation doses, supporting a potential use of visible light as an antimicrobial agent in clinical settings.

Enhanced phytase production by Aspergillus niger mutants in solid state fermentation

The present research work was conducted to improve the phytase production by genetic alteration of Aspergillus niger with induced mutagenesis using solid state fermentation. Strain improvement was carried out in the presence of ultra violet (UV) irradiation and ethylmethane sulphonate (EMS) [0.5% v/v] treatments for various time intervals. We reported an improved strain of Aspergillus niger designated as UV-3 mutant producing a zone of hydrolysis of about 40 mm, in comparison to wild strain (26 mm). The highest enzyme activity was found to be 547.64 IU/g for UV-3 mutant followed by EMS-4 mutant (492.23 IU/g)compared to wild strain which showed 406.45 IU/g of enzyme activity. There was 1.35 fold increase in phytase production after mutation studies of Aspergillus niger. Phytase was applied as poultry feed additive and given to broiler chickens for 5 weeks. The results exhibited that there was increase in body weight gain (BWG) of chicks for experimental group (2028 g) in comparison to control group (1903 g). Thus, physical and chemical mutagenesis was proved as an effective technique for the improvement of strain and ultimately for enhanced and economical phytase production for different industrial applications.

Kinetic studies of photocatalytic degradation of an Azo dye by titania nanoparticles

Purpose Dyeing and printing are important steps in textile manufacturing. After the process completion, these dyes are released in the effluent. These dyes impart an unacceptable appearance but are also toxic to the soil and water bodies. The present research has been carried out to study the rate of photocatalytic degradation of an azo dye, namely, CI Direct Green 26, using titania nanoparticles under ultra violet (UV) irradiation as a function of temperature and time. Azo dyes account for the majority of all dyestuffs are produced and extensively used in the textile, paper, food, leather, cosmetics and pharmaceutical industries. Titania nanoparticles have been found to successfully degrade these dyes in the presence of UV light. The purpose of the present paper was to study the photodegradation of azo dyes using titania nanoparticles at different temperatures and time periods. Design/methodology/approach Titania nanoparticle concentration of 0.1% (w/v) was dispersed in distilled water by sonication for 1 h in sonication bath. The of rate of degradation of Direct Green 26 dye in the titania nanoparticle dispersion, under UV-A exposure was studied at different temperatures ranging from 25°C to 65 °C for time periods ranging from 1 h to 6 h. Photocatalytic degradation tests were performed in a specially designed UV reactor chamber. Raman spectroscopy of Titania nanoparticles, dye and titania/dye mixture before and after UV exposure was carried out using Confocal Laser Dispersion Raman Microscope (Renishaw, UK) with 785 nm excitation laser. Findings Titanium dioxide is an efficient photocatalyst for decolourisation of direct dye. The photodegradation of the direct Green dye was found to follow the pseudo first-order reaction. The Arrhenius activation energy was found to be 24.8 kJ/mol with A value of 0.0013 for the photocatalytic degradation of the dye. Raman spectroscopy also confirmed the adsorption of dye on titania nanoparticle and its complete degradation on exposure to UV light. Practical implications This research highlights the application of titania nanoparticles for the effective degradation of dye in the effluent from textiles, clothing, paper and any kind of dyeing process. Azo dyes account for the majority of all dyestuffs are produced and extensively used in the textile, paper, food, leather, cosmetics and pharmaceutical industries. Titania nanoparticles have been found to successfully degrade these dyes in the presence of UV light which can be very beneficial for the effluent treatment plants in textile and other industries. Originality/value Azo dyes are one of the harmful pollutants released in textile waste water. The degradation and removal of the coloured waste in the textile effluent is an important environmental concern and needs to be investigated. The research is one of the first to investigate and understand the mechanism of the degradation of an azo dye in the presence of titania nanoparticles by Raman spectroscopy.

Emamectin benzoate nanogel suspension constructed from poly(vinyl alcohol)-valine derivatives and lignosulfonate enhanced insecticidal efficacy

To reduce the negative impact of nanopesticide carriers of on the environment, a greener nanodelivery system is necessary. Nanogels are nontoxic and degradable carriers, however, the potential of nanogels for delivering pesticides has not been proven. In this study, poly(vinyl alcohol)-valine, an ecofriendly polymer, was synthesized and used to fabricate emamectin benzoate nanogel suspension (EB NS). The nanoformulation showed favorable stability at low temperature, high temperature or one year storage, and in water with different hardnesses. The retention of the EB NS solution on leaves was higher than that of an EB emulsifiable concentrate (EC) by approximately 9% at a concentration of 10 mg L−1. The half-life of EB nanogels under Ultra Violet irradiation was prolonged by 3.3-fold. Moreover, the bioactivity of the EB NS against Plutella xylostella was higher than that of the EB EC. These advantages resulted in a relatively long duration of pest control. The response of nanogels to laccase, a digestive enzyme in the digestive tract of lepidopteran pests, enables pesticide release on demand. Nanogels have the advantages of being ecofriendly carriers, exhibiting higher utilization, and prolonged pest control periods, and they have a brilliant future in pesticide delivery.

Colorimetric evaluation after in-office tooth bleaching with violet LED: 6- and 12-month follow-ups of a randomized clinical trial.

To evaluate the long-term outcomes of in-office bleaching with violet LED light (LED) alone or combined with carbamide (CP) or hydrogen (HP) peroxides. Volunteers of a previous short-term study were recalled for 6- and 12-month follow-ups, according to the following interventions (n = 18/group): LED, CP, LED/CP, HP, and LED/HP. The objective color (ΔEab, ΔE00) and whiteness index (ΔWID) changes were calculated applying the CIELab coordinates' values obtained using a spectrophotometer. A visual shade guide determined the tooth's subjective color change (ΔSGU). Data were submitted to one-way ANOVA or Welch's ANOVA, following appropriate post hoc tests (α = 5%). The LED and CP groups exhibited the lowest ΔEab, ΔE00, and ΔSGU (p < 0.05), but the LED group displayed a significantly lower ΔWID. After 12months, the LED/CP group presented a higher ΔEab and ΔE00 than the CP group (p < 0.05). ΔEab, ΔE00, ΔSGU, or ΔWID means did not differ statistically between the LED/CP and HP groups. The LED/HP group presented a higher ΔE00 than the HP group, regardless of the time. The bleaching efficacy of LED alone was significantly lower compared to the LED/CP and HP-containing protocols. After 12months, the LED/CP and HP groups did not differ in bleaching efficacy. LED irradiation only increased the objective color change of bleaching gels. LED alone promoted a long-term perceptible bleaching, but not compatible with that of high-concentrated HP. The bleaching outcomes of violet irradiation to 37% CP were maintained over time, with LED/CP demonstrating comparable results to HP even after 12months. RBR-5t6bd9.

Antibacterial, self-cleaning and UV blocking of wool fabric coated with nano Ce/ZnO and Ce/ TiO2

Ultrasonic method has been used in order to load nano Ce, ZnO and TiO 2 on the surface of wool fabric. Three types of nano composite fabric have been prepared (wool /Ce, wool /Ce/ZnO, and wool /Ce/ TiO 2 ) and their physical properties are examined. Field emission scanning electron microscope images of the samples show a good distribution of nano material, and EDX and XRD findings prove the amount usage of nano materials. On the other hand, elemental mapping is used to study separately the distribution of each nano material. Antibacterial property of the samples shows excellent result against both Gram-negative and Gram-positive bacteria. Also, UV blocking of treated samples shows low transmission from all samples, when exposed to ultra violet irradiation. Self-cleaning property of wool samples illustrates that doping of nano materials on the surface of wool fabric has an excellent effect on increasing the self-cleaning efficiency.

In-situ observation of photocatalysis of gaseous trichloroethylene using a fourier transform infrared in the presence of a visible light responding homemade oxynitride doped TiO2 under blue LED and violet LED irradiations

A visible light responding TiO2 photocatalyst was prepared by the hydrolysis of TiCl4 with ammonia. Its structures were characterized to anatase with doping of oxynitride by XRD and XPS followed by drying and heat treatment at 400 °C for 2 h (TiON400). The primary particle size observed by TEM was ~10 nm, and the BET surface area was 320 m2/g. Photocatalytic degradation of trichloroethylene (TCE) over TiON400 under blue light emitting diode (BLED) and violet light emitting diode (VLED) irradiation was tested using a Fourier transform infrared (FTIR) spectrometer. The collected FTIR spectra verified the decrease in TCE concentration and the formation of intermediates such as dichloroacetyl chloride (DCAC) and COCl2 during the photocatalysis of TCE. It is concluded that in-situ FTIR analysis can be a useful and reliable tool to evaluate the photocatalytic performance of materials. A new ISO standard for photocatalysis testing method with FTIR analysis under ultraviolet, visible, or violet irradiation is possible to propose.

Synthesis, growth mechanism and photocatalytic properties of nickel oxide (NiO) nanoflower: a hydrothermal process

The present report explores the synthesis strategy of flower like Nickel Oxide (NiO) nanostructures from nanosheets as their building blocks in the presence of citric acid as surfactant. An easy and inexpensive hydrothermal technique was designed for the synthesis of NiO nanoparticles. The structural, morphological and compositional analyses were done by the techniques such as X-ray Diffraction, Field Emission Scanning Electron Microscopy and Energy Dispersive X-ray Analysis respectively and growth mechanism of the NiO nanostructure was also dealt in detail. Diffraction pattern confirms that the prepared NiO is belongs to the face cantered cubic structure. The average crystalline size was obtained by Debye Scherrer formula and the values (8 nm, 9 nm, 7 nm and 7.5 nm for NiO nanoflowers synthesized with 0.5 g, 1 g, 1.5 g and 2 g of citric acid respectively) are comparable with the size obtained by the Williamson Hall plot method. Morphological analysis confirms the formation of nanosheets constituted floral microspheres with a diameter ranging from 750 nm to 850 nm. Elemental analysis proves the presence of Ni and O and its purity. The 750 nm sized, regularly arranged NiO nanoflowers were subjected to photocatalytic degradation of Methylene Blue (MB) and Rhodamine 6G (Rh 6G) under Ultra Violet irradiation and bestow the effective degradation efficiency (76.5% and 92.6% respectively). The photodegradation mechanism was discussed based on the position of conduction and valence bands.

Effect of ultraviolet irradiation on beef carcass yield

The results of testing the use of ultraviolet radiation (UVR) spectrum C (wavelength 253.7 nm) to reduce the contamination of chilled beef in half carcasses are presented. It is determined that the efficiency of UVR with a wavelength of 253.7 nm is directly proportional to the distance between meat half-carcasses in the cooling chamber: if the distance is longer than the efficiency of processing is higher. The efficiency of UVR processing of beef half-carcasses is proved by placing them in a chill chamber and storing them at 17 cm distance one from the other. This condition and the exposure of UVR for 45 min, gives a decrease in the number of mesophilic aerobic and facultative-anaerobic microorganisms on the carcasses surface to 95.15 ± 0.23%. An ecological regime to storage of chilled cattle in half carcasses (suspension) was developed using a UVR with a wavelength of 253.7 nm at 45 minutes exposure and 17 cm distance between the carcasses without breaking the technological process. The developed mode allows to double the shelf life of the raw meat in the chilled state. For efficient UVR processing of slaughtered animals (cattle) the half-carcasses are needed to be placed in a cooling and storage chamber (air temperature – 6.0 ± 2.0°C, relative humidity – 85.0 ± 0.5%) at 17 cm distance one from other. In this condition and 45 minutes exposure the number of mesophilic aerobic and facultative-anaerobic microorganisms on the surface of the experimental half-carcasses decreased from (4.45 ± 0.17) × 103 CFU/cm2 at the beginning of the experiment to (0.22 ± 0.01) × 103 CFU/cm2 after UVR treatment. Keywords: Muscle tissue; half-carcasses; ultraviolet irradiation; air-recirculator; temperature; exposure; microorganisms References Begum, M., Hocking, A. D., & Miskelly, D. (2009). Inactivation of food spoilage fungi by ultra violet (UVC) irradiation. Int. J Food Microbiol., 129, 74-77. Degala, H. L., Mahapatra, A. K., Demircib, A., & Kannana, G. (2018). 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Sanitary-hygienic evaluation of meat processing enterprises productions and their sanation. Ukrainian Journal of Ecology, 8(2), 81-88. doi: 10.15421/2018_313 Rodionova, K. O., & Paliy, A. P. (2016). The effectiveness of application ultraviolet radiation for the sanitation of production premises of meat processing enterprises. Journal for Veterinary Medicine, Biotechnology and Biosafety, 2(4), 20-24. Rodionova K. А., & Paliy A. P. (2019). Analysis of contemporary meat and meat products’ processing methods. Journal for Veterinary Medicine, Biotechnology and Biosafety, 5(2), 32-40. Sommers, C., Sheena, S., Scullena, O. J., & Mackayb, W. (2017). Inactivation of Staphylococcus saprophyticus in chicken meat and purge using thermal processing, high pressure processing, gamma radiation, and ultraviolet light (254 nm). Food Control, 75, 78-82. doi: 10.1016/j.foodcont.2016.12.020 Stefanova, R., Vasilev, N. V., & Spassov, S. L. (2010). Irradiation of Food, Current Legislation Framework, and Detection of Irradiated Foods. Food Analytical Methods, 3(3), 225-252. doi: 10.1007/s12161-009-9118-8 Yeh, Y., de Moura, F. H., Van Den Broek, K., & de Mello, A. S. (2018). Effect of ultraviolet light, organic acids, and bacteriophage on Salmonella populations in ground beef. Meat Science, 139, 44-48. doi: 10.1016/j.meatsci.2018.01.007 Zhou, G. H., Xu, X. L., & Liu, Y. (2010). Preservation technologies for fresh meat - A review. Meat Science, 86(1), 119-28. doi: 10.1016/j.meatsci.2010.04.033

Effect of Ultra Violet (UV) Irradiation as an Environmentally Friendly Pre-Treatment on Dyeing Characteristic and Colorimetric Analysis of Wool

Low-energy UV lamps were used for the pretreatment of wool yarns and its effects were investigated in terms of surface morphology, tensile strength, and percentage dye uptake. Subsequently, raw and UV-treated wool yarns were dyed with Cochineal dye and the essential parameters affecting the dyeing process (i.e., temperature, pH, duration) were determined. The results showed that the color strength of the samples increased by (a) increasing the pre-treatment effectiveness (i.e., UV irradiation strength and its duration), and (b) increasing the influential dyeing parameters (i.e., higher temperature, higher initial dye concentration in the dye bath, longer dyeing time, and acidic pH). The UV irradiation pretreatment also enhanced the color fastness properties of the dyed samples under the same dyeing conditions. The results suggested that an eco-friendly, acid-free, and relatively cheaper dyeing process could be developed for the wool fibers pretreated with scalable and straightforward UV irradiation pretreatment.

Photolysis of hexamethylenediaminetetra(methylenephosphonic acid) (HDTMP) using manganese and hydrogen peroxide

Abstract Aminophosphonates such as hexamethylenediaminetreta(methylene phosphonic acid) (HDTMP) are categorised as persistent substances. They are commonly used as scale inhibitors in cooling water systems and desalination processes. After utilisation, they are often discharged into aquatic environment without pre-treatment. Advanced oxidation processes (AOP) are promising pre-treatments for industrial wastewater treatments. We investigated the photodegradation of HDTMP with or without addition of manganese (Mn2+) and/or H2O2. Similar to results of our former photodegradation studies, we found that HDTMP also undergoes conversion with or without additives during the ultra violet (UV) irradiation. The reaction rate was most affected by the addition of H2O2, i.e. the HDTMP degradation was accelerated by a factor 3.85 compared with UV treatment without additives. The addition of Mn2+ accelerated the degradation of HDTMP only by a factor 1.53 compared with the UV treatment without additives. The combined addition of Mn2+ and H2O2 accelerated the HDTMP degradation by a factor 2.81. Interestingly, the initial cleavage is not initiated as expected at the C–N bond but at the C–P bond of the methyl carbon and the phosphorus of the methylenephosphonic acid group of HDTMP. This initial cleavage was independent whether the UV treatment was performed with or without additives. Therefore, we conclude that the degradation mechanism is similar independent of the four tested treatment conditions. We identified amino(methylenephosphonic acid) AMPA, dimethylamino(methylenephosphonic acid) DAMP and iminodi(methylenephosphonic acid) IDMP as the major breakdown products by performing LC/MS analyses. The major mineralisation products were ortho-phosphate, ammonium and carbon dioxide. The mass balances of unknown breakdown products allowed us to speculate about the molecular size of the unknown organic breakdown products.

Investigation into the surface chemical analysis and luminescent properties of La7O6(BO3)(PO4)2:Dy phosphor

The exploitation of high-quality borophosphate-based phosphor products is currently garnering a significant research focus in solid-state light source. The interest is due to its low-cost and environment-friendly synthesis. In this paper, a new La7O6(BO3)(PO4)2 (LBP):Dy phosphor was developed via sintering at 1673 K for 3 h under an air atmosphere. Structural characterization indicates that all of the prepared products are the monoclinic phases with the space group P21/n. A comparison of the surface chemical states of the elemental compositions for the LBP host versus optimal LBP:13%Dy product was conducted via X-ray photoelectron spectroscopy. Optical characterization shows that the Dy-doped products exhibited visible light emissions of Dy3+ from 4F9/2 to 6H15/2, 6H13/2, and 6H11/2 upon exposure to 348 nm near-ultra violet irradiation. The dominant emission (yellow, 576 nm) belongs to the 4F9/2 → 6H13/2 transition. The best Dy content for doping was 13 mol%, and content quenching occurred due to dipole – dipole interaction. The measured decay lifetime and calculated chromatic properties together manifest that the optimal LBP:13%Dy phosphor shows potential as a yellow ingredient in solid-state lighting.

Synthesis of rutile TiO2 nanowires by thermal oxidation of titanium in the presence of KOH and their ability to photoreduce Cr(VI) ions

Rutile TiO2 nanowires were fabricated by thermal oxidation of titanium foil in the presence of potassium hydroxide, KOH. The fabrication process consisted of two parts; first as to deposit and liquefy KOH into droplets, done at 400 °C for 10 min, followed by ramping the furnace to a desired oxidation temperature (500–800 °C) for oxide growth. The presence of KOH was found to be beneficial in the formation of “shells” that induced anisotropic TiO2 growth (hence nanowires were observed under scanning electron microscope) as oppose to compact, planar oxide. Nevertheless, there exist a temperature window in which the anisotropic growth can be achieved: 550–750 °C. Above or below this temperature range, the oxide is compact without any noticeable nanostructures. Within the temperature window, the nanowires grown were dense with length of 500–600 nm and diameter averaged at 50 nm. The TiO2 nanowires were then used as catalyst to reduce Cr(VI) to Cr(III) in aqueous solution at pH 2.10 mg/L of Cr(VI) was able to be reduced completely within 90 min under ultra violet (UV) irradiation on TiO2 nanowires fabricated at 750 °C.

Deterioration rate of renewable polyurethanes composites prior to ultra violet irradiation exposure

Polyurethanes (PU's) made from renewable and sustainable materials are one of the most important groups of polymers because of their versatility with wide range of grades, densities and stiffness. In this project, polymers based on renewable materials such as rapeseed (RS) and sunflower oil (SF) were synthesized and cross-linked to form polyurethanes. The effect of prolonged exposure up to 1000 h upon UVB light, in general promotes photodegradation for both RS and SF-based polyurethanes, both neat and also composites loaded with TiO2. The addition of 10% Degussa P25 TiO2 pigment, gives the greater degradation while PUs loaded with 5% Kronos 2220 show the slowest rates of degradation due to the effect of the coating of this pigment. The photostabiliser Tinuvin 770 offers high protection from UVB, thus lead the combination of Tinuvin 770 with Degussa P25 promotes the highest protection from UVB exposure. Moreover, addition of Tinuvin 770 at the stage of preparation of the PUs also greatly reduced the undesirable yellow colouration prevalent during PU synthesis.