Application Of Ultraviolet Light Research Articles

Synergistic inhibition effect of ultraviolet irradiation and benzalkonium chloride on the corrosion of 316L stainless steel caused by Aspergillus terreus

Microbiologically influenced corrosion (MIC) is a key factor that damages engineering materials in marine environments. One of the major concerns in this regard is the corrosion protection of stainless steel (SS) caused against fungal attacks. This study investigated the effect of ultraviolet (UV) irradiation and benzalkonium chloride (BKC) on the corrosion of 316L stainless steel (316L SS) induced by marine Aspergillus terreus in 3.5 wt% NaCl solution. This was accomplished by employing microstructural characterisations and electrochemical analysis to analyse the synergistic inhibition behaviour of the two methods. The results indicated that while UV and BKC demonstrated individual abilities to suppress the biological activity of A. terreus, their inhibitory effects were not significant. The combination of UV light and BKC was found to cause a further decline in the biological activity of A. terreus. The analysis revealed that the combination of BKC and UV significantly decreased the sessile cell counts of A. terreus by more than three orders of magnitude. The fungal corrosion inhibition effect of individual application of UV light or BKC did not yield satisfactory results owing to the low intensity of UV and low concentration of BKC. Furthermore, the corrosion inhibition of UV and BKC occurred mainly during the early stages. The corrosion rate of the 316L SS declined rapidly when the combination of UV light and BKC were used, indicating that UV light and BKC exert a good synergistic inhibitory effect on the corrosion of the 316L SS caused by A. terreus. Therefore, the results suggest that the combination of UV light and BKC can be an effective approach to control the MIC of 316L SS in marine environments.

Possibilities of using the continuous type of UV light on the surface of lor (whey) cheese: impacts on mould growth, oxidative stability, sensory and colour attributes during storage.

This research paper addresses the hypothesis that the optimum doses of a continuous type of ultraviolet (UV) light applied to the surface of lor (whey) cheese needs to be identified to maximize mould inactivation and shelf life while minimizing quality deterioration. Therefore, the mould inactivation, protein and lipid oxidation products, sensory and colour attributes of lor cheese subjected to different doses of UV light (1.617, 4.018, and 36.832 kJ/m2) in a continuous type of UV system were evaluated. UV treated samples presented mould counts lower than those of untreated ones. UV treatment at more than 4.018 kJ/m2 allowed around 0.7-2.7 log reductions on mould growth during storage. The increase in UV light dose caused significant increases in primary and secondary lipid oxidation products. In particular, the highest doses applied to the surface of cheese samples had the highest values of protein carbonyls, as well as lipid oxidation products. Strong positive correlations were recorded between lipid and protein oxidation markers. Exposure to the highest doses of UV light increased foreign flavour perception, probably due to the oxidative reactions. The results indicated that the application of UV light to the lor cheese surface allowed delaying mould growth during storage but extreme doses could induce lipid and protein oxidation reactions, leading to quality deterioration.

UV Light Application as a Mean for Disinfection Applied in the Dairy Industry

Thermal treatment is the most popular decontamination technique used in the dairy industry to ensure food protection and prolong shelf life. But it also causes nutrient and aroma degradation, non-enzymatic browning, and organoleptic changes of dairy products. Non-thermal solutions, on the other hand, have been extensively explored in a response to rising market demand for more sustainable and safe goods. For a long time, the use of ultraviolet (UV) light in the food industry has held great promise. Irradiation with shortwave UV light has excellent germicidal properties, which can destroy a variety of microbial pathogens (for example bacteria, fungi, molds, yeasts, and viruses), at low maintenance and installation costs with minimal use of energy to preserve food without undesirable effects of heat treatment. The purpose of this review is to update the studies made on the possibilities of UV-C radiation while also addressing the essential processing factors involved in the disinfection. It also sheds light on the promise of UV light-emitting diodes (UV-LEDs) as a microbial inactivation alternative to conventional UV lamps.

Realization of Flexible Ultraviolet Organic Light‐Emitting Diodes: Key Design Issues

While organic light‐emitting diodes (OLEDs) have seen huge success as light sources in high‐end displays, efforts are being made to extend their spectral coverage beyond the visible region. Among such endeavors, the development of ultraviolet (UV) OLEDs is particularly of interest due to the unique applications of UV light in a variety of areas such as security, sterilization, phototherapy, etc. However, OLEDs that emit UV light are very challenging to realize due to limitations such as high‐energy‐induced molecular instability, the rarity of adequate emitting layers, and material optical properties that are very different from those of visible OLEDs. Herein, UV OLEDs are realized using 3‐(Biphenyl‐4‐yl)‐5‐(4‐tert‐butylphenyl)‐4‐phenyl‐4 H‐1,2,4‐triazole (TAZ) as emitters in both top‐emitting and bottom‐emitting configurations. High absorption of common plastic substrates is carefully considered, and semitransparent refractory characteristics of metals under UV are exploited to form flexible dielectric−metal−dielectric electrodes with high transparency in UV. As a result, highly flexible UV OLEDs with a peak wavelength of 371 nm and a full width half maximum as small as 13 nm are realized.

UV-photofunctionalization of a biomimetic coating for dental implants application.

Photofunctionalization mediated by ultraviolet (UV) rays changes the physico-chemical characteristics of titanium (Ti) and improves the biological activity of dental implants. However, the role of UV-mediated photofunctionalization of biofunctional Ti surfaces on the antimicrobial and photocatalytic activity remains unknown and was investigated in this study. Commercially pure titanium (cpTi) discs were divided into four groups: (1) machined samples without UV light application [cpTi UV-]; (2) plasma electrolytic oxidation (PEO) treated samples without UV light application [PEO UV-]; (3) machined samples with UV light application [cpTi UV+]; and (4) PEO-treated samples with UV light application [PEO UV+]. The surfaces were characterized according to their morphology, roughness, crystalline phase, chemical composition and wettability. The photocatalytic activity and proteins adsorption were measured. For the microbiological assay, Streptococcus sanguinis was grown on the disc surfaces for 1h and 6h, and the colony forming units and bacterial organization were evaluated. In addition, to confirm the non-cytotoxic effect of PEO UV +, human gingival fibroblast (HGF) cells were cultured in a monolayer onto each material surface and the cells viability and proliferation evaluated by a fluorescent cell staining method. PEO treatment increased the Ti surface roughness and wettability (p<0.05). Photofunctionalization reduced the hydrocarbon concentration and enhanced human blood plasma proteins and albumin adsorption mainly for the PEO-treated surface (p<0.05). PEO UV+ also maintained higher wettability values for a longer period and provided microbial reduction at 1h of bacterial adhesion (p=0.012 vs. PEO UV-). Photofunctionalization did not increase the photocatalytic activity of Ti (p>0.05). Confocal microscopy analyses demonstrated that PEO UV+ had no cell damage effect on HGF cells growth even after 24h of incubation. The photofunctionalization of a biofunctional PEO coating seems to be a promising alternative for dental implants as it increases blood plasma proteins adsorption, reduces initial bacterial adhesion and presents no cytotoxicity effect.

Capacitance-Voltage Characteristics Analysis of Indium Zinc Oxide Thin Film Transistors Based Ultraviolet Light Irradiation.

The mechanism of solution-processed indium zinc oxide (IZO) thin film transistors (TFTs) made by simultaneous spin coating and ultraviolet (UV) light irradiation was investigated by capacitance-voltage (C-V) measurement. The application of UV light on the IZO TFTs was found to improve the thin film surface structure, and pledge to receive low degree of roughness. Meanwhile, electrical characteristics indicated that the TFT prepared at the UV light irradiation with 90 s exhibits the best performance with field-effect mobility 5.6 cm²/Vs, threshold voltage ═ -0.13 V, subthreshold gate swing 0.64 V/decade and on/off ratio ═ 1.7 × 106. In the C-V contrastive analysis with different UV light irradiation time by 60 s and 90 s, the frequency was varied from 100 Hz to 10 kHz to investigate low as well as high frequency C-V.

Effectiveness of ultraviolet (UV) insect light traps for mosquitoes control in coastal areas of Samut Songkhram province, Thailand

This study aimed to investigate the effectiveness of ultraviolet (UV) insect light traps for mosquito control and to study the relationship between this effect and weather factors in coastal areas of Samut Songkhram province, Thailand. The study sites were divided into two areas, approximately 2and4 km from the sea. The trap was placed less than one meter away from the house, where it could reach electrical plugs. The effectiveness of UV light trap was tested from September to October 2017 between 6:00 p.m. and 6:00 a.m., for a total of 30 days. A total of 2,605 adult mosquitoes within four species belonging to two genera were collected, including Anopheles epiroticus Linton & Harbach, Culex quinquefasciatus Say, Cx. sitiens Wiedmann and Cx. gelidus Theobald. The effectiveness of UV insect light traps in area 2 km from the sea trapped 45.96 ± 42.13 mosquitoes per night and area 4 km from the sea trapped 40.83 ± 33.61 mosquitoes per night. While, effectiveness comparison of the UV insect light traps 2 and 4 km from the sea of were shown to be statistically significantly different (p < 0.05). These results of this study are useful for planning and application of UV light traps to control mosquito populations in coastal areas of Samut Songkhram province, Thailand and other coastal areas.

The impact of postharvest ultra-violet light irradiation on the thiol content of Sauvignon blanc grapes

Sauvignon blanc grapes were exposed to an ultra-violet (UV) light source post-hand harvest (whole bunches) or post-machine harvest. The thiol precursors S-3-(hexan-1-ol)-l-cysteine (Cys-3MH) and S-3-(hexan-1-ol)-l-glutathione (GSH-3MH) were quantified in the juices before and after UV treatment. Results showed that irradiation of the grapes with UV light had little to no effect on the thiol precursors. Wines were fermented from the corresponding juices and 18 aroma compounds were quantified. Differences were found between UV treatments of the wines for 3-mercaptohexanol, hexan-1-ol, ethyl butanoate, ethyl hexanoate, ethyl octanoate and phenylethyl alcohol. However, these changes were not significant (p < 0.05) for both grape media trialled. Future studies involving larger sample sizes and replicate numbers should be completed in order to ascertain any changes in aroma chemistry as a result of UV light application to grapes postharvest.

Biofilms: Microbial Strategies for Surviving UV Exposure.

Biofilm communities are an ingenious form of protection of microbial cells which have been evolving for billion of years. In general, ultraviolet (UV) radiation presents poor penetration in the matrix of biofilms and only the first few top layers of microbial cells are exposed to its deleterious effects. For further protection against UV radiation, exposed cells can produce specialized compounds such as mycosporine-like amino acids and carotenoid pigments. In this chapter, the adaptation mechanisms presented by biofilms against UV radiation are presented, as well as the application of UV light to monitor and destroy biofilms in man made surfaces.

The Influence of Ultraviolet Irradiation on Polarization Fatigue in Ferroelectric Polymer Films

In this letter, we report the influence of ultraviolet (UV) irradiation on electrical fatigue in ferroelectric polymers. Experiments indicate that ferroelectric polymer films exposed to UV irradiation show degraded fatigue endurance. However, simultaneous application of UV light and bias voltage ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bias</sub> ) can partially recover the electrical polarization in fatigued films. In our present work, a combination of UV (365 nm) and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bias</sub> ( -51 V) has resulted in the restoration of remanent polarization up to 85.3% of its original value in 1200 s. The influence of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bias</sub> on polarization restoration is also reported. UV effects are explained based on the understanding of charge influence on ferroelectric fatigue.

Sensitivity of oral bacteria to 254 nm ultraviolet light

To explore the sensitivity of bacteria commonly found in root canals to 254 nm ultraviolet (UV) light, either as individual cells or as participants of a bacterial multilayer. The sensitivity of oral bacteria, as individual cells, to UV light was tested by subjecting plates streaked with bacteria to 254 nm UV, at a fluence of 1-20 mJ cm(-2). An experimental model was designed to produce a bacterial multilayer and to study absorption of UV light by bacteria in an outer layer and its effect on the elimination of bacteria in the inner layer. Direct exposure to relatively low doses of UV light (2-7 mJ cm(-2)) effectively eliminated all bacterial strains tested. Furthermore, an Enterococcus faecalis strain, partially resistant to a 24 h exposure to calcium hydroxide, was effectively eliminated within several seconds of exposure to UV light (P < 0.001). UV was absorbed by a multilayer of bacteria. When 4 bacterial cells microm(-2) were present in the light path, the UV light dose had to be increased by a factor of x10 to achieve 100% elimination of the bacteria in an inner layer. The application of UV light to eliminate endodontic pathogens may be possible. Nevertheless, its absorbance by outer layers of bacteria should be considered and the UV light dose adapted accordingly.