UV-A Lamp Research Articles

Evaluation of Painted Steels for Transmission Towers Under Accelerated Deterioration Tests

Painted transmission towers are repainted after removing the former paint film and corrosion products, because the deterioration of paint film and under-film corrosion take place with time. To judge the appropriate timing to repaint for transmission towers, it is of great importance to estimate the deterioration of painted steels. While atmospheric exposure tests can provide the deterioration behavior close to the actual environment, considering the lifetime of paintings, it takes a long time to obtain data. Thus, it is necessary to establish a test method that can evaluate a variety of painting specifications in a short period of time. The accelerated deterioration tests have been performed using salt spray and ultraviolet (UV) irradiation for various painted structures. However, these test conditions are diverse, and the relationship between them and the degree of deterioration remains to be elucidated.In this study, the deterioration behavior of painted steels for transmission towers was investigated by electrochemical impedance spectroscopy (EIS) and paint film analysis during the accelerated deterioration test.The painted specimens were prepared with the paint film thickness of 100 μm or less using a type of paint that has been widely used for transmission towers in recent years. The painting specifications were the double-layer paint with polyurethane resin for primer and topcoat (PP), single-layer paint with acrylic modified alkyd resin (A), double-layer paint with epoxy resin for primer and polyurethane resin for topcoat (EP), and single-layer paint with polyurethane resin for primer (P). The accelerated deterioration test of each painted specimen was performed using combined corrosion test (CCT) consisting of salt spray, dry, and wet processes, and artificial UV weathering test with fluorescent UVA lamps (UVT). This test was repeated alternatively 50 cycles of CCT and 50 cycles of UVT as one set until 10 sets. The upper area of specimens was exposed to CCT and UVT environments, and the other area was exposed to only CCT environment by shielding UV radiation. The deterioration behavior of painted steels was monitored by measuring EIS each one set. In addition, the surface condition of paint film was observed, and evaluated by measuring of gloss and thickness.The paint film resistance R f was obtained by analyzing impedance spectra, assuming an equivalent circuit for painted metals. In the area exposed to CCT and UVT environments, the R f of A-painted steel decreased significantly at the earliest timing, followed by P-painted steel. On the other hand, the R f of PP-painted steel after 10 sets was almost same as that before tests. The gloss retention of all painted steels in the area exposed to CCT and UVT environments decreases to about 50 %, and that in the area exposed to only CCT environment decreases to 70-80 %. The R f of PP-painted steel kept a high value even when the gloss was decreased. Accordingly, it was showed that the slight initial change in surface roughness did not significantly affect the environmental barrier properties. For all painted steel except P-painted steel, there was almost no change in the paint film thickness after the test with or without UV irradiation. The R f, gloss retention, and paint film thickness of P-painted steel in the area with UV irradiation were lower than in the area without UV irradiation. Moreover, many blisters and corrosion products were observed on the surface of P-painted steel only in the area with UV irradiation. These results revealed that the paint film was accelerated to deteriorate by UV radiation, and under-film corrosion progressed.In conclusion, the initial paint deterioration for painted steels in some specifications was clarified through the accelerated deterioration tests combining CCT and UVT. However, the deterioration of painted steels was not accelerated enough to decrease the paint film thickness and R f of the double-layer painted steel in this test condition.

Thin, disposable, antibacterial, heat-pressed photocatalytic plastic films

The production of several different thin, highly flexible, disposable, antibacterial, photocatalytic plastic films is described. A thin layer of a semiconductor photocatalyst, SC, powder is partially embedded in a thin (ca. 30 μm), highly flexible film of low-density polyethylene, LDPE, by heat-pressing the two together. The resulting SC/LDPE film is then tested for photocatalytic activity, via the photo-oxidised bleaching of methylene blue, MB, and photocatalysed antibacterial activity, via its inactivation of Escherichia coli, E. coli. The SCs tested include, P25 TiO2, high surface area Tronox rutile TiO2, low surface area rutile TiO2, ZnO and WO3. The MB test results reveal photocatalytic activities of the SC/LDPE films are, P25 TiO2 > ZnO > rutile TiO2 ≈ Tronox rutile TiO2 > WO3, which suggest the kinetics depend largely on the redox potential of the photogenerated conductance band electrons. In contrast, the E. coli deactivation results show that the order of activities of the SC/LDPE films, in the dark and (with an increased rate) upon illumination, are, Tronox rutile TiO2 > P25 TiO2 > ZnO > WO3 > rutile TiO2, which is similar to the variation in roughness factor, Rf. It appears that rough films are better at deactivating E. coli, not only under illumination, via both a photocatalytic and thermal mechanism, but also in the dark, via a ‘bed-of-nails’/shear stress physical mechanism. Encouragingly, in most cases, the photocatalysed antibacterial activity exhibited by the SC/LDPE films is not much (ca. 74 %) lower when a cool white fluorescent rather than UVA lamp is used (UVA irradiance = 47 μW/cm2 and 1.5 mW/cm2, respectively). The Tronox rutile TiO2 film was also found to be effective in deactivating another Gram-negative bacterium and, to a lesser extent, two Gram-positive bacterial species. The potential of these thin plastic films with a notable antibacterial activity under room light and in the dark is discussed briefly.

Methylxanthine and Flavonoid Contents from Guarana Seeds (Paullinia cupana): Comparison of Different Drying Techniques and Effects of UV Radiation.

Guarana seeds are typically processed using one of three drying methods: traditional sun exposure, greenhouse drying, or the alguidar oven technique. In our research, we evaluated the contents of methylxanthines and flavan-3-ols in sun- and alguidar-dried guarana seeds from Bahia State's Low Sul Identity Territory. Caffeine, theobromine, catechin, and epicatechin were determined by high-performance liquid chromatography with UV-visible detection (HPLC/UV-vis). Statistical tools, including analysis of variance (ANOVA), Tukey's test, and exploratory analysis, were employed to analyze the obtained data. Our findings indicated that the flavan-3-ols content in sun-dried guarana samples was lower compared to those dried using the alguidar oven, possibly due to exposure to ultraviolet radiation from solar energy. Conversely, we observed no significant differences (p > 0.05) in the average contents of methylxanthines between the two drying methods. Our supplementary experiments involving UV-A and UV-C radiation lamps revealed a decreasing trend in methylxanthines and flavan-3-ols contents with increasing duration of UV radiation exposure.

UV lamp spectral effects on the aging behavior of encapsulants for photovoltaic modules

Polymer encapsulants used in photovoltaic (PV) modules experience severe UV aging during more than 25 years of module’s operation. However, the current standard qualification tests cannot provide a sufficient solution able to mimic the UV exposure in the field. IEC 61215 defines the requirements for UV stability of PV modules with very low cumulative UV dosage. While the new IEC 62788-7-2 imposes higher UV dosages on polymers films, the used UV testing procedure allows the use of either UV-A fluorescence lamps or xenon lamps, yielding different spectra. The given work compares the effect of different lamp spectra, based on IEC 62788-7-2, on the aging behavior of the encapsulant. For this purpose, coupons (glass/encapsulant/busbar/encapsulant/backsheet) using the common encapsulant ethylene-vinyl acetate copolymer (EVA) and the emerging encapsulants polyolefine (POE) and thermoplastic polyolefine (TPO) were manufactured. The samples were weathered under different UV conditions for a total duration of 2500 h with extraction times of 250 h. Photodegradation was observed for all encapsulants and weathering types. However, in general the weathering with UV-A lamps inflicted significantly less damage. The formation of unsaturated carbon bonds because of polymer backbone decomposition was only reported for xenon lamp weathering. The carried out experiments suggest that xenon lamps, providing more realistic accelerated aging, should be predominately used in the UV weathering standards in the PV industry, whose current versions are to be accordingly reconsidered.

Sequential use of a continuous-flow electrocoagulation reactor and a (photo)electro-Fenton recirculation system for the treatment of Acid Brown 14 diazo dye

The decolorization and TOC removal of solutions of Acid Brown 14 (AB14) diazo dye containing 50 mg L−1 of total organic carbon (TOC) have been first studied in a continuous-flow electrocoagulation (EC) reactor of 3 L capacity with Fe electrodes of ∼110 cm2 area each. Total loss of color with poor TOC removal was found in chloride, sulfate, and/or hydrogen carbonate matrices after 18 min of this treatment. The best performance was found using 5 anodes and 4 cathodes of Fe at 13.70 A and low liquid flow rate of 10 L h−1, in aerated 39.6 mM NaCl medium within a pH range of 4.0–10.0. The effluent obtained from EC was further treated by electro-Fenton (EF) using a 2.5 L pre-pilot flow plant, which was equipped with a filter-press cell comprising a Pt anode and an air-diffusion cathode for H2O2 electrogeneration. Operating with 0.10–1.0 mM Fe2+ as catalyst at pH 3.0 and 50 mA cm−2, a similar TOC removal of 68 % was found as maximal in chloride and sulfate media using the sequential EC-EF process. The EC-treated solutions were also treated by photoelectro-Fenton (PEF) employing a photoreactor with a 125 W UVA lamp. The sequential EC-PEF process yielded a much higher TOC reduction, close to 90 % and 97 % in chloride and sulfate media, respectively, due to the rapid photolysis of the final Fe(III)-carboxylate complexes. The formation of recalcitrant chloroderivatives from generated active chlorine limited the mineralization in the chloride matrix. For practical applications of this two-step technology, the high energy consumption of the UVA lamp in PEF could be reduced by using free sunlight.

Synthesis of ZnO-Al:TiO<sub>2 </sub>Materials and their Characterization as Photocatalyst Compounds

Photocatalyst activity relates to the active surface area between pollutants and catalyst compounds. The insertion of Al atoms as a substantial defect in ZnO structures can reduce the particle size thus the active surface area increases. Another way to raise the photocatalytic activity of ZnO is by combination with other oxide materials such as TiO2 (Titanium dioxide). In this study, the ZnO-Al:TiO2 powder was successfully prepared via the sol-gel method using zinc acetate dihydrate as a precursor, 0.5wt% of aluminum nitrate nonahydrate as a dopant precursor, and TiO2 anatase. In order to understand the role of the combination of these two metal oxides, the concentration ratio of ZnO-Al and TiO2 was varied by 1:1 (ZAT) and 4:1 (ZA4T) under low (150°C) and high (450°C) temperature calcination. Photocatalytic testing was carried out using a 3.2 ppm methylene blue (MB) solution under UV-A lamp irradiation for 120 minutes. The high calcination temperature facilitates the growth of ZnO-Al. Besides that, the different ratio concentrations and calcination temperatures produce different defect states in each sample. The most optimum results in the photocatalytic activity performed by ZnO-Al:TiO2 150°C (ZAT 15) with degradation rate constant (k) of 0.033/min and efficiency of 97% for MB removal. The unexpected zinc vacancies defect is estimated produce at the samples in high-temperature calcination. This defect type can accelerate electron-hole pair recombination. In Addition, samples with high-temperature calcination were considered to have lower hydroxyl/oxygen bonds on the surface thus affecting the photocatalytic performance.

Biochemical and functional characteristics of stored (double-dose) buffy-coat platelet concentrates treated with amotosalen and a prototype UVA light-emitting diode illuminator.

Pathogen reduction of platelet concentrates (PCs) using amotosalen and broad-spectrum UVA illumination contributes to the safety of platelet transfusion by reducing the risk of transfusion-transmitted infections. We evaluated the in vitro quality of stored buffy-coat (BC) PCs treated with amotosalen and a prototype light-emitting diode (LED) illuminator. Double-dose BC-PCs collected into PAS-III/plasma or SSP+ /plasma (55/45%) were treated with amotosalen in combination with either conventional UVA lamps (INT100 Illuminator 320-400 nm) or LED illuminators at 350 nm. Platelet quality and function were evaluated over 7 days. Platelet counts were conserved during storage in all groups, as was platelet swirling without appearance of macroscopic aggregates. Integrin αIIbβ3 and glycoprotein (GP) VI expression remained stable, whereas GPIbα and GPV declined similarly in all groups. UV lamp- and LED-treated PCs displayed similar glucose consumption, lactate generation, and pH variation. Comparable spontaneous and residual P-selectin and phosphatidylserine exposure, activated αIIbβ3 exposure, mitochondrial membrane potential, lactate dehydrogenase release, and adhesive properties under flow conditions were observed during storage. The use of SSP+ /plasma compared with PAS-III/plasma better preserved most of these parameters, especially during late storage, irrespective of the type of illuminator. Replacing the UVA lamp for photochemical treatment by LED illuminators had no impact on platelet metabolism, spontaneous activation, apoptosis or viability, or on the in vitro function of BC-PCs stored for 7 days in SSP+ or PAS-III/plasma. These findings support improved procedures for the pathogen reduction and storage of PCs, to ensure transfusion safety and retention of platelet functional properties.

Inactivation of E. coli and S. aureus by novel binary clay/semiconductor photocatalytic macrocomposites under UVA and sunlight irradiation

The disinfection efficiency of several novel photocatalytic macrocomposites made of Ecuadorian clay mixed with two semiconductor materials (TiO2, ZnO) has been evaluated with Staphylococcus aureus and Escherichia coli as target bacteria. They have been tested under two irradiation sources (UVA lamp and sunlight) in different configurations. Two different semiconductor/clay ratios (60/40 and 80/20) were tested at 10–20 g·L–1 (with UVA) and 20–40 g·L–1 (with sunlight) composite loadings. With the presence of the photocatalyst, a four- to five-fold increase in the inactivation rate by UVA was observed with respect to single UVA inactivation, while the performance with sunlight reaches up to six-fold. The particular effect of nature, ratio and loading on the inactivation kinetics depends on the specific bacterial species tested. In this case, the inactivation of S. aureus was faster in comparison with E. coli, probably due to the interaction between bacteria and the catalytic material and the associated ζ-potential. In general, the 80% ZnO composites at maximum loading show the highest efficiency, comparable to that of nanosized semiconductors. The ability of these composites to maintain a high disinfection efficiency after three uses, together with their low cost and ease of recovery, make these composites an attractive option for wider use in water disinfection facilities.

Luminescent Papers with Asymmetric Complexes of Eu(III) and Tb(III) in Polymeric Matrices and Suggested Combinations for Color Tuning.

Complexes of lanthanide ions, such as Eu(III) (red light emission) and Tb(III) (green light emission), with proper ligands can be highly luminescent and color-tunable, also attaining yellow and orange emission under UV radiation. The ligands employed in this work were poly(sodium acrylate), working as polymeric matrix, and 1,10-phenanthroline, taking advantage of its antenna effect. Possibilities of color display were further enhanced by incorporating a cationic polyfluorene with blue emission. This strategy allowed for obtaining cyan and magenta, besides the aforementioned colors. Uncoated cellulose paper was impregnated with the resulting luminescent inks, observing a strong hypsochromic shift in excitation wavelength upon drying. Hence, while a cheap UV-A lamp sufficed to reveal the polyfluorene's blue emission, shorter wavelengths were necessary to visualize the emission due to lanthanide ions as well. The capacity to reveal, with UV-C radiation, a full-color image that remains invisible under natural light is undoubtedly useful for anti-counterfeiting applications. Furthermore, both lanthanide ion complexes and polyfluorenes were shown to have their luminescence quenched by Cu(II) ions and nitroarenes, respectively.

An energy autonomous and portable pilot unit for the photocatalytic treatment of wastewater

An energy-autonomous and portable pilot unit was designed and manufactured. The unit was placed on a wheeled support consisting of a photovoltaic panel, four (4) metallic photo-reactors, each equipped with 6 W UV-A lamps, two (2) peristaltic pumps of 5 W, and an external recirculation tank. The annular space of reactors was packed with ZnO-coated Duranit spheres. The pilot unit was assessed with regard to the degradation capacity of phenol solution and effluents collected from wastewater treatment plant (WWTP). Measurements of the UV-light intensity were combined with the 2-flux radiation model to determine the radial profile of UV-radiant flux across the annular photoreactor. The experimentally measured transient responses of phenol concentration, total organic, and inorganic carbon were fitted with one-dimensional (1D) numerical models to estimate the apparent 1st order kinetic constant of photo-degradation processes. On average, the energy demand of the unit was counterbalanced by the electric power generated by the photovoltaic panel. The repeated use of the same photocatalysts in all experiments confirmed the long-term energy efficiency of the unit. The apparent kinetic constants of phenol, intermediates species, and total organic carbon (TOC) degradation were found to be governed by the corresponding mass-transfer coefficients of relevant species from the bulk liquid to the active catalyst surface. At early times, the total inorganic carbonates (TIC) concentration increases, and at late times the fast mass-transfer of dissolved CO2 to gas phase compensates for the production of inorganic carbon. Preliminary tests showed that the photocatalytic unit is capable of reducing the COD and TOC of WWTP effluents and occasionally, the concentration of nitrates and ammonia may also decrease.

UV-A Radiation: Safe Human Exposure and Antibacterial Activity.

UV radiation is used for sterilization but has adverse health effects in humans. UV-A radiation has lower antimicrobial effect than UV-B and UV-C but constitutes a lower health risk, opening up the possibility to sanitize environments with human presence in controlled exposure conditions. We investigated this possibility by identifying safe exposure conditions to a UV-A lamp along with efficient sanitization of the environment. The human exposure limits were calculated following the guidelines provided by the International Commission on Non-Ionizing Radiation Protection and the International Commission on Illumination. Antibacterial activity was evaluated on Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The maximum human exposure duration has been identified at different irradiation distance and angle, increasing with the increase of both parameters. Bactericidal activity was observed in all microorganisms and was higher with higher exposure time and at lower distance from the source. Noteworthily, in equal conditions of radiant exposure, the exposure time impacts on the bactericidal activity more than the distance from the source. The modulation of factors such as distance from the source, exposure time and irradiation angle can enable effective antibacterial activity and human safety. Prolonged direct irradiation of the surfaces associated with indirect human exposure represents the condition of greater efficacy and safety.

The electrical, and photosensitive behavior of diodes with rare earth elements (Yb and Er) doped sodium yttrium fluoride interfacial layer

This study presents the morphological, electrical, and photosensitive behavior properties of the Al/(NaYF 4 :Yb,Er)/p-Si structure. The (NaYF 4 :Yb,Er) used as an interfacial layer was deposited on a p-Si semiconductor using the thermal evaporation method. The surface morphological properties of the evaporated interfacial layer were examined using scanning electron microscopy and atomic force microscopy. The ideality factor of the structure increases from 3.58 at 320 K to 8.16 at 100 K with decreasing temperature, while the barrier height decreases from 0.80 eV at 320 K to 0.31 at 100 K with decreasing temperature in the same temperature range. The photosensitive behavior of the fabricated structure were investigated using UV-A lamp with 350 nm wavelength. The spectral responsivity, photosensitivity, and detectivity values for the Al/(NaYF 4 :Yb,Er)/p-Si structure were found to be 0.525 A.W−1, 2841.38, and 2.16 × 1011 Jones, respectively.

Photocatalytic Degradation of Psychiatric Pharmaceuticals in Hospital WWTP Secondary Effluents Using g-C3N4 and g-C3N4/MoS2 Catalysts in Laboratory-Scale Pilot

Today, the pollution caused by a multitude of pharmaceuticals used by humans has been recognized as a major environmental problem. The objective of this study was to evaluate and compare the photocatalytic degradation of ten target psychiatric drugs in hospital wastewater effluents using g-C3N4 and 1%MoS2/g-C3N4 (1MSCN) as photocatalytic materials. The experiments were performed using real wastewater samples collected from hospital wastewater treatment plant (WWTP) secondary effluent in spiked and inherent pharmaceutical concentration levels. The photocatalytic experiments were performed in a laboratory-scale pilot plant composed of a stainless-steel lamp reactor (46 L) equipped with ten UVA lamps and quartz filters connected in series with a polypropylene recirculation tank (55–100 L). In addition, experiments were carried out in a solar simulator apparatus Atlas Suntest XLS+ at a 500 Wm−2 irradiation intensity. The analysis of the samples was accomplished by solid-phase extraction, followed by liquid chromatography-Orbitrap high-resolution mass spectrometry. Results showed that the photocatalytic degradation of pharmaceutical compounds followed first-order kinetics. In all cases, 1MSCN presented higher photocatalytic performance than g-C3N4. The removal rates of the pharmaceutical compounds were determined above 30% and 54% using g-C3N4 and 1MSCN, respectively. Parallel to kinetic studies, the transformation products (TPs) generated during the treatment were investigated.

PS-B02-12: EFFECTS OF ULTRAVIOLET LIGHT ON BLOOD PRESSURE AND LEFT VENTRICULAR FUNCTION

Ultraviolet light (UV), induces the activation of constitutive nitric oxide synthases, which produces nitric oxide (NO) of vascular relaxation factor. We hypothesize that UV-induced production of NO could have beneficial effect on hypertension. Twelve 6-week-old salt-sensitive hypertensive rats (Dahl-Iwai salt-sensitive DIS/Eis, Japan Society for the Study of Hypertension, Shizuoka, Japan) were used in this study. These rats were fed a high-salt diet containing 8%NaCl until 10 weeks of age and were then randomly divided into three groups i.e. baseline group (group non-UV), 0 h post UV (group UV 0 h), and 6 h post UV (group UV 6 h). The rats were irradiated with UVA and UVB lamps at an intensity of 100 mJ/cm2. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured by using tail-cuff method (BP-98A; Softron Co., Ltd., Tokyo, Japan). We evaluated left ventricular (LV) systolic and diastolic function using echocardiography with a 12 MHz transducer connected to a Xario ultrasound system (Toshiba Medical Systems Co., Tochigi, Japan). Interventricular septal thickness, LV posterior wall thickness, and LV end-diastolic and end-systolic diameters (LVDd and LVDs) were obtained from a short-axis view. Percent LV fractional shortening (%LVFS) was calculated as an index of LV systolic function. Peak flow velocities at the mitral level during rapid filling (E) and deceleration time (Dct), and peak early diastolic mitral annular velocity which indicate LV diastolic function, were measured using pulsed and tissue Doppler echocardiography. Histological skin tissue sections were fixed with 4% paraformaldehyde phosphate buffer solution for 24 h at room temperature, embedded in paraffin, sectioned transversely (thickness, 3 μm), and stained with hematoxylin-eosin to evaluate the impairments of skin. The SBP and DBP were lower in group UV 6 h than group non-UV and group UV 0 h. In contrast, there were no significant differences in heart rate and body weight among the three groups. The peak early diastolic mitral annular velocity was greater in group UV 6 h than group non-UV and group UV 0 h. LVDd, LVDs, and %LVFS were not significantly different among the three groups. We did not find the impairments in skin after UV irradiation. UVA and UVB may play an important role in regulating not only blood pressure but also LV function.

Degradation of the persistent organic pollutant-lindane in fixed-bed photoreactor packed with immobilized Zinc Oxide and Iron oxide-doped Zinc Oxide photocatalysts

The potential for the photocatalytic degradation of lindane, used as agricultural insecticide and pharmaceutical product, is investigated. Two types of photocatalysts, immobilized on 5 mm sodalime beads are synthesised using an easy and economical process: (1) Zinc Oxide (ZnO) nanoparticles and (2) Iron oxide-doped Zinc Oxide (Fe-ZnO). Tests of lindane degradation under continuous flow conditions are conducted on a stainless steel fixed bed photoreactor using a 6W UV-A lamp operating at 375 nm. The lindane sorption onto photocatalysts is examined with equilibrium and kinetic tests at batch mode. The experimental datasets are fitted with a 1-dimensional advection-dispersion-sorption-reaction numerical model to estimate the parameters controlling the lindane degradation rate: the apparent sorption capacity of the catalyst, and the surface reaction kinetic constant. Based on estimated parameter values, a comparative analysis of the performance of the two catalysts is done.

Total Synthesis of Arylnaphthalene Lignans through a Photochemical Key Step

AbstractThe total syntheses of three arylnaphthalene lignans (ANLs) were developed: Vitrofolal E (1), Noralashinol C (2), and Ternifoliuslignan E (3). These natural products have in common a missing substituent in 2‐position of the naphthalene moiety (2H‐ANLs). The key step of these syntheses is a regioselective intramolecular Photo‐Dehydro‐Diels‐Alder (PDDA) reaction with (1,7)naphthalenophanes as primary products. A further improvement of the photochemical step was achieved by triplet sensitization with xanthone, allowing the use of more efficient UVA lamps. It should be noted that this work is a continuation of a previous publication about the total synthesis of lignans using the PDDA reaction.[1]

Triplet Sensitized Photo‐Dehydro‐Diels‐Alder Reaction

AbstractWe report on the triplet sensitization of the intramolecular Photo‐Dehydro‐Diels‐Alder (PDDA) reaction of two diaryl suberates bearing methyl propiolate chromophors. Compared with the non‐sensitized irradiation, considerably increased yields could be observed. Moreover, it is possible to use the more efficient UVA lamps instead of UVB lamps. Among three investigated sensitizers (xanthone, benzophenone, thioxanthone) xanthone gave the best results.

TL response evaluation for UVA and UVC of LaAlO3:Pr3+ powder

Thermoluminescence properties of lanthanum aluminum oxide (LaAlO3) doped with optically active rare earth ions have been investigated for ultraviolet dosimetry purposes. LaAlO3:Pr3+ powder samples were doped with 2% of Pr3+, for the first research they show two thermoluminescent (TL) peaks at 215±5 °C and 340±4 °C which can be sensitized after 1 min to 12 min of UVA exposure. The material shows TL output and linear response for UVA lamp in 365 nm wavelength light. On the other hand, the powder samples that were irradiated with a UVC lamp at 254 nm, it also shows one peak and a shoulder, the maximum peak in a range that goes from 195 °C to 220 °C, in which the exposure time was varied from 5 to 30 seconds and the shoulder remains stable at 345± 8 ° C. The experiments demonstrates that LaAlO3: Pr3+ powders are very attractive to be investigated as UVA and UVC dosimeters.

Synthesis and Characterization of N and Fe-Doped TiO2 Nanoparticles for 2,4-Dimethylaniline Mineralization.

The present study aimed to evaluate the feasibility of developing low-cost N- and Fe-doped TiO2 photocatalysts for investigating the mineralization of 2,4-dimethylaniline (2,4-DMA). With a single anatase phase, the photocatalysts showed high thermal stability with mass losses of less than 2%. The predominant oxidative state is Ti4+, but there is presence of Ti3+ associated with oxygen vacancies. In materials with N, doping was interstitial in the NH3/NH4+ form and for doping with Fe, there was a presence of Fe-Ti bonds (indicating substitutional occupations). With an improved band gap energy from 3.16 eV to 2.82 eV the photoactivity of the photocatalysts was validated with an 18 W UVA lamp (340–415 nm) with a flux of 8.23 × 10−6 Einstein s−1. With a size of only 14.45 nm and a surface area of 84.73 m2 g−1, the photocatalyst doped with 0.0125% Fe mineralized 92% of the 2,4-DMA in just 180 min. While the 3% N photocatalyst with 12.27 nm had similar performance at only 360 min. Factors such as high surface area, mesoporous structure and improved Ebg, and absence of Fe peak in XPS analysis indicate that doping with 0.0125% Fe caused a modification in TiO2 structure.

Whiteness Perception under LED Source with High Content of UV Radiation

Whiteness is an attribute of color perception with high brightness and low colorfulness. In this study, the correlation between instrumental measurement and visual assessment of whiteness of 40 optically brightened white samples was investigated under a LED light source of correlated color temperature (CCT) 5000K combined with Wood's UV-A lamp. Due to over exposure of UV radiation, tested samples were outside of CIE limit. In those cases, standard CIE whiteness formula show significant shift in whiteness interval scale. A high correlation was identified between visual assessment and modified Vik-Viková whiteness formula. The investigations have also shown that the existing CIBA plastic whiteness scale needs to be expanded.