UV Treatment Time Research Articles

Effect of Ultraviolet Light on Mn3O4 Thin Films that are Grown Using SILAR for Room-Temperature Ozone Gas Sensors

Successive ionic layer adsorption and reaction (SILAR) is a promising technique to fabricate gas sensors at room temperature. However, the quality of the films is poor, leading to reduced surface area and increased defects within the film structure, thus decreasing the overall gas response. Inferior film quality also negatively affects the stability and reproducibility of the gas sensors over time. This study determines the effect of UV treatment on the structural, morphological, and ozone (O3) gas-sensing properties of p-type Mn3O4 thin films. As UV treatment time increases, the O3 gas-sensing characteristics increase because a porous structure with a higher surface area is formed and electrical conductivity is increased. Under a UV intensity of 20 mW cm−2, the Mn3O4 sensor exhibits gas response, response time, and recovery time of 1.62, 58, and 39 s, respectively, against 5 ppm concentration of O3 gas. Moreover, the Mn3O4 gas sensor exhibits excellent long-term stability showing around 3% variation in gas response over 60 d. This strategy allows the deposition of high-quality p-type Mn3O4 thin films using SILAR for applications in flexible gas sensors.

ВИЗНАЧЕННЯ ОПТИМАЛЬНИХ ПАРАМЕТРІВ ФОТОКАТАЛІТИЧНОЇ ДЕСТРУКЦІЇ МЕТИЛЕНОВОГО СИНЬОГО В ПРИСУТНОСТІ МАГНЕТИТУ

Використання математичного моделювання для розробки нових технологій очищення стічних вод є дуже важливим, оскільки дає змогу скоротити кількість дослідів, визначити оптимальні умови процесу, побудувати математичну модель. Багатофакторні залежності, які, наприклад, отримують за допомогою методів планування експерименту – це потужні статистичні інструменти, які дозволяють визначити сумарний вплив досліджуваних змінних, який можливо оцінювати одночасно, провести статистичну обробку результатів, що будуть використані, проводити оптимізацію з використанням математичних моделей, щоб отримати найкращі експериментальні умови проведення процесу очищення. Для оцінки впливу обраних факторів використовувався метод центрального композиційного рототабельного планування експерименту. Визначали вплив таких параметрів, як концентрація фотокаталізатора (x1), об’єм Н2О2 (x2) та час обробки УФ опроміненням (x3) на деградацію метиленового синього(МС). Представлені результати показують, що магнетит є ефективним каталізатором розкладу МС під дією УФ-випромінювання. Встановлено, що більшість ефектів є статистично значущими щодо функції відгуку. Високі значення коефіцієнтів при x3, x1, x2 вказують на те, що вони є найбільш впливовими на процес фотокаталітичної деструкції. Коефіцієнт при x3 не тільки має найвище значення з усіх ефектів, а ле й приблизно в 2 рази більше, ніж коефіцієнт при x3. Коефіцієнти відповідні взаємодіям x1x2 (1,32) і x1x3 (5,24) представлені значеннями, що в 5,84 і 1,5 разів менше відносно коефіцієнту при x3. Значення коефіцієнта детермінації (R2) становить приблизно 0,998, що підтверджує тісний взаємозв'язок між незалежними факторами і функцією відгуку. Високі значення коефіцієнтів в лінійних доданках (x2, x3) в порівнянні з іншими коефіцієнтами означають, що вони є найбільш впливовими у рівнянні. Встановлено, що підвищення часу обробки призводить до збільшення ступеню деградації МС. Вплив концентрації перекису водню та каталізатору має екстремальний характер. Значимість факторів змінюється наступним чином: tоб> mадс> Vн2о2. Крім того, дисперсійний аналіз показав узгодженість між експериментальними даними та теоретично визначеними, тобто отримана математична модель адекватна.

Development and evaluation of a point-of-use UV appliance for fresh produce decontamination

In-house treatment strategy for fresh produce decontamination has not been emphasized as much as industrial washing. The most common treatment for fresh produce decontamination and cleaning at home and other point-of-use places such as cafeteria is rinsing and/or soaking in a sink. In this study, an appliance utilizing UV and agitated water to decontaminate fresh produce was developed and its effectiveness was investigated in an aim to identify optimum processing parameters. Grape tomato and spinach representing two different surface smoothness were dip-inoculated in a four-strain Salmonella cocktail to reach a final population of 5–8 log CFU/g and air-dried. The produce samples were then washed in 1 gallon tap water under varying conditions, water agitation speed (0–190 RPM), sample size (50–400 g), UV intensity (0–30 mW/cm2) and treatment time (2, 5 and 10 min). In general, increasing the agitation speed and UV intensity enhanced Salmonella inactivation for both grape tomato and spinach. Sample size significantly affected the UV inactivation of Salmonella on grape tomato, but not on spinach. The effect of extending treatment time from 2 to 10 min was insignificant for almost all the UV treatments and the controls. The effect of UV intensity and treatment time on inactivation of Salmonella on spot-inoculated grape tomato and spinach was also determined. The most severe treatment used in this study, 30 mW/cm2 UV for 10 min, resulted in >4 log reductions of Salmonella dip- or spot-inoculated on grape tomato (200 g sample size and 190 RPM agitation speed) and 3.5 log reductions of Salmonella dip- or spot-inoculated on spinach (100 g sample size and 110 RPM agitation speed). We foresee that the UV appliance developed and evaluated in this study could be further fine-tuned and optimized to eventually construct a point-of-use UV appliance that can be used at home, cafeteria, restaurants, and hospitals for fresh produce decontamination and cleaning. The UV appliance could be an inexpensive and effective tool to improve fresh produce safety.

OPTIMIZACIÓN DE LA REMOCIÓN DE COMPUESTOS ORGÁNICOS PERSISTENTES MEDIANTE EL PROCESO FOTO-FENTON

La metodología de superficie de respuesta se aplicó para evaluar la condición óptima experimental a fin de remover los compuestos orgánicos persistentes de un agua residual textil sintética usando un reactor fotoquímico en lote a escala laboratorio. Cuatro factores a tres niveles fueron estudiados: relación de reactivos Fenton H2O2/Fe2+ (11,25, 18,75, 26,25 mg/L/mg/L), potencia de lámpara UV (4, 11, 18 W), pH (2, 3, 4) y tiempo de tratamiento (60, 120, 180 min). Los niveles óptimos encontrados para los cuatro factores fueron: relación de reactivos Fenton H2O2/Fe2+ igual a 17 mg/L/mg/L, potencia de lámpara UV igual a 4 W, pH igual a 3 y tiempo de tratamiento de 180 min. Se encontró que el proceso foto-Fenton es muy efectivo para tratar el agua residual textil sintética, encontrándose una remoción de un 86 %, respecto al DQO.

Decontamination of irrigation water using a combined sand filtration and UV‐C light treatment

AbstractSurface irrigation water is a food safety risk due to susceptibility to contamination and varying turbidity that affects chlorination efficacy. Effectiveness of a combined high‐throughput, commercially available sand filter and UV‐C system to inactivate Escherichia coli (K12, and attenuated O157:H7) in simulated irrigation water of varying turbidity and actual irrigation water was investigated. Sand filtration reduced the water turbidity from ~600 nephelometric turbidity units (NTU) to ~200 NTU but did not effectively filter out E. coli (K12) [<1 log colony forming units (CFU)/ml]. UV‐C‐induced inactivation of E. coli (attenuated O157:H7) was modeled for various levels of turbidity (0–500 NTU), and the relationship between the D value for inactivation and turbidity was found to be linear (R2 > .97). Predicted UV treatment time to achieve 5 log reduction in water with turbidities of 100 and 300 NTU was 110 and 370 s, respectively. Validation performed with irrigation water (turbidity of 330 ± 82 NTU) showed that sand filtration reduced turbidity to 180 ± 57 NTU. Based on this, the duration of UV treatment required for 5 log reduction of E. coli O157:H7 was calculated (average of 237 s). Observed levels of inactivation, 4.7 ± 0.31 log CFU/ml, were not significantly different (p > .05) from the predicted level, 5 log CFU/ml, indicating a good model fit.

The Relationship between Bulk Silicone and Benzophenone-Initiated Hydrogel Coating Properties.

Polydimethylsiloxane (PDMS) is a silicone elastomer-based material that is used in various applications, including coatings, tubing, microfluidics, and medical implants. PDMS has been modified with hydrogel coatings to prevent fouling, which can be done through UV-mediated free radical polymerization using benzophenone. However, to the best of our knowledge, the properties of hydrogel coatings and their influence on the bulk properties of PDMS under various preparation conditions, such as the type and concentration of monomers, and UV treatment time, have never been investigated. Acrylate-based monomers were used to perform free radical polymerization on PDMS surfaces under various reaction conditions. This approach provides insights into the relationship between the hydrogel coating and bulk properties of PDMS. Altering the UV polymerization time and the monomer concentration resulted in different morphologies with different roughness and thickness of the hydrogel coating, as well as differences in the bulk material stiffness. The surface morphology of the coated PDMS was characterized by AFM. The cross section and thickness of the coatings were examined using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The dependence of coating development on the monomer type and concentration used was evaluated by surface hydrophilicity, as measured by water contact angle. Elongation-until-break analysis revealed that specific reaction conditions affected the bulk properties and made the coated PDMS brittle. Therefore, boundary conditions have been identified to enable high quality hydrogel coating formation without affecting the bulk properties of the material.

Treatment of water contaminated with methyl tertiary butyl ether using UV/chlorine advanced oxidation process

Methyl tertiary butyl ether (MTBE) is a widely used gasoline additive to improve the air quality by increasing the oxygen content of the fuel. After extensive use for some years in the USA, it was recognized as a groundwater contaminant. Several remediation techniques are available for the removal of MTBE from contaminated water systems. However, the inherent limitations of each removal technique makes further research promising. The aim of this study was to investigate the MTBE degradation in water with chlorine-based advanced oxidation process (AOP). A bench scale study was carried out by varying the experimental conditions such as UV radiation intensity, pH, chlorine doses, and treatment time. Free chlorine was used as a chemical oxidant in combination with low-pressure (LP) and medium-pressure (MP) mercury lamps to degrade MTBE in water. LP and MP UV/chlorine were able to degrade more than 99% of MTBE in deionized water within 15–30 min at pH 5 and 7, respectively. The MTBE removal in groundwater sample with LP UV/chlorine and MP UV/chlorine is greater than 99 and 90% after 30 min respectively. The electrical energy per order estimated for LP UV/chlorine and MP UV/chlorine to treat ground water sample was 4.01 and 54.67 kW h/m3 respectively. Chlorine-based AOP could be a promising technique for treating water contaminated with MTBE.

Selective, Spontaneous One-Way Oil-Transport Fabrics and Their Novel Use for Gauging Liquid Surface Tension

Thin porous materials that can spontaneously transport oil fluids just in a single direction have great potential for making energy-saving functional membranes. However, there is little data for the preparation and functionalities of this smart material. Here, we report a novel method to prepare one-way oil-transport fabrics and their application in detecting liquid surface tension. This functional fabric was prepared by a two-step coating process to apply flowerlike ZnO nanorods, fluorinated decyl polyhedral oligomeric silsesquioxanes, and hydrolyzed fluorinated alkylsilane on a fabric substrate. Upon one-sided UV irradiation, the coated fabric shows a one-way transport feature that allows oil fluid transport automatically from the unirradiated side to the UV-irradiated surface, but it stops fluid transport in the opposite direction. The fabric still maintains high superhydrophobicity after UV treatment. The one-way fluid transport takes place only for the oil fluids with a specific surface tension value, and the fluid selectivity is dependent on the UV treatment time. Changing the UV irradiation time from 6 to 30 h broadened the one-way transport for fluids with surface tension from around 22.3 mN/m to a range of 22.3-56.7 mN/m. We further proved that this selective one-way oil transport can be used to estimate the surface tension of a liquid simply by observing its transport feature on a series of fabrics with different one-way oil-transport selectivities. To our knowledge, this is the first example to use one-way fluid-transport materials for testing the liquid surface tension. It may open up further theoretical studies and the development of novel fluid sensors.

Transparent and flexible conducting hybrid film combined with 3-Aminopropyltriethoxysilane-coated polymer and graphene

A simple approach to fabricate graphene hybrid film consisted of Graphene/3-aminopropyltriethoxysilane (APTES)/polyethylene terephthalate (PET) is presented, using self-assembled monolayers (SAMs) for enhancement of conductivity. The SAMs of APTES was prepared on ultraviolet-ozone (UVO)-irradiated PET films via wet chemical technique. The density of APTES was saturated after UV treatment time of 1h for PET films; the carrier density and the optical transmittance were 9.3×10 12/cm2 and 82% for pristine graphene and 1.16×1013/cm2 and 86% for graphene hybrid films, respectively, and experienced at inflection point at 30min in UV treatment time. This behavior can be explained by surface morphology transition due to coalescence or clustering of mobile and low-molecular-weight oxidized components of PET.

Immobilization effect of bone morphogenetic protein-2 on collagen membrane via photoreactive gelatin derivatives: Biocompatibility and preservability of osteoinductive activity

To photo-immobilize bone morphogenetic protein-2 (BMP-2), UV light-reactive gelatin (azidophenyl gelatin, Az-gel), which is introduced with an N-(4-azidobenzoyloxy) succinimide-containing an azide group, was prepared as a carrier of BMP-2. Characterization of the photo-reactivity of Az-gel was evaluated by the curing ratio and it was micropatterned using a photomask. The cross-linking ratio and an enzyme-linked immunosorbent assay, enzymelinked immunospecific assay (ELISA)-based BMP-2-release test were used to determine the optimal density of Azgel (1, 3, and 5%) and UV treatment time (10, 30, 60 s) of the BMP-2 carrier in collagen matrix. The results showed that 5% Az-gel with 60 s of UV treatment was the most efficient condition for cross-linking. Cytotoxicity assays using the C2C12 mouse myoblast cell line showed that there were no cytotoxic effects of Az-gel. Alkaline phosphatase activity and calcium ion detection assays to evaluate the osteoinductive activities were conducted in assumed optimal condition of Az-gel (5% and 60 s UV treatment) 14 days post-treatment. In our study, the osteoinductive activities were the highest in cells treated with BMP-2 and the photo-reactive Az-gel carrier compared to BMP-2 alone or untreated control cells in collagen matrix at all time points (3, 7, and 14 days).

Nanomechanical Analysis of a UV Treated Ag Thin Film Based on a Three-Step Oxidation Model.

Nanoindentation was used as the main method to measure the change in nanomechanical properties on the surface of an Ag thin film due to UV treatment. The 4-point probe method, X-ray diffraction (XRD), and atomic force microscopy (AFM) were used to measure the electrical, crystallographic, and morphological properties, respectively. During a UV treatment time of between 1 and 3 minutes, the sheet resistance increased dramatically to 0.55 Ω/sq. (the sheet resistance was 0.16 Ω/sq. prior to UV treatment) and these results were supported by a proportional decreased in XRD intensity. Thereafter, the sheet resistance decreased and the XRD intensity increased in response to increases in UV treatment time. These results were related to a change in crystal structure from Ag to AgOx, which could also have caused the change in sheet resistance. Based on these results, we propose a 3-step oxidation model of an Ag thin film according to UV treatment time. This proposal has been proven by nanoindentation testing.

UV-Heat Treatments for the Control of Foodborne Microbial Pathogens in Chicken Broth.

This investigation established the process criteria for using UV-C light and mild heat (UV-H treatment) to inactivate 5-Log10 cycles (performance criterion) of common foodborne pathogen populations, Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus, when inoculated in chicken broth. To define the target microorganism and the proper UV-H treatment conditions (including UV dose, treatment time, and temperature) that would achieve the stated performance criterion, mathematical equations based on Geeraerd's model were developed for each microorganism. For the sake of comparison, inactivation equations for heat treatments were also performed on the same chicken broth and for the same microorganisms. L. monocytogenes was the most UV-H resistant microorganism at all temperatures, requiring a UV dose between 6.10 J/mL (5.6 min) and 2.26 J/mL (2.09 min) to achieve 5-Log10 reductions. In comparison with UV treatments at room temperatures, the combination of UV and mild heat allowed both the UV dose and treatment time to be reduced by 30% and 63% at 55°C and 60°C, respectively. Compared to heat treatments, the UV-H process reduced the heating time for 5-Log10 reductions of all the investigated microorganisms in chicken broth from 20-fold to 2-fold when the operating temperature varied from 53 to 60°C.

Inactivation of Bacillus anthracis in water by photocatalytic, photolytic and sonochemical treatment

Bacillus anthracis is one of the most dangerous and pathogenic bacterial species and its intrusion in aquatic environments is a serious threat to public health. The aim of the present study was to investigate inactivation rates of B. anthracis in water by means of photocatalytic (UVA/TiO2), photolytic (UVC) and sonochemical treatment. The effect of various operating conditions such as bacterial concentration, TiO2 loading, UV irradiation source, ultrasound power and treatment time was examined. The reference strain of B. anthracis proved to be highly resistant during photocatalytic and sonochemical treatment of aquatic samples, even in the presence of hydrogen peroxide solution, which is considered among the chemical disinfectants recommended for B. anthracis removal from aqueous suspensions. UVC irradiation was far more effective, as it achieved total inactivation in short treatment time (10 min) and at high initial concentrations (10(6) CFU mL(-1)). The effectiveness of UVC irradiation is also reinforced by the fact that no photoreactivation occurred even after 72 h of exposure under sunlight after the end of the treatment. Furthermore, the virulence of residual cells was investigated, targeting two genes carried in the plasmids pXO1 and pXO2, respectively, which are required for a fully virulent type. Interestingly, the plasmid pXO2 seems to be lost from the host after photocatalytic and photolytic disinfection, resulting in apathogenic residual strains contained in the treated sample. Overall, our results highlight the importance of B. anthracis efficient inactivation in water, as it shows considerable resistance towards effective and reliable disinfection techniques.

The Effect of UV Treatment on the Degradation of Compostable Polylactic Acid

Though many compostable plastics have entered the market, they often require lengthy treatment processes to degrade. Polylactic acid (PLA) has the greatest potential to replace petroleum-based plastics due to its comparable cost with generic plastics. The aims of this study were the following: 1) evaluate the effectiveness of UV treatment on the degradation of PLA; 2) examine the influence of mechanical chopping on its degradation; and 3) propose an economic alternative composting process. PLA samples were treated with UVC light for 30, 60, and 90 minutes. Half of the PLA sample was chopped, and the other half was left unchopped. The extent of PLA degradation was measured using mass loss and molecular weight analyses (i.e., gel permeation chromatography or GPC). After 90 minutes of treatment, the chopped pieces lost 3.95% of their original mass, while the unchopped pieces lost 8.97%. The mass decreased linearly as UV treatment time increased. The PLA average molecular weight decreased from 113,500 g/mol (untreated PLA) to approximately 10,000 g/mol after UV treatment. Based on the experimental results, it was concluded that UV light significantly shortens the time of PLA degradation in comparison to the current process of hydrolysis. However, the results regarding mechanical degradation were inconclusive. As a result of the study, a new process for PLA composting is proposed, which may shorten the current process from days to hours. In this new process, PLA materials would undergo a 3-step continuous process made up of: 1) mechanical chopping, 2) UV treatment, and 3) disposal in a compost facility.

Surface potential behaviors of UV treated of Ag anode for high-performance T-OLED by nanotribology

A high reflective bottom anode is essential for high-performance top-emitting organic light emitting devices (OLEDs). Ag has high reflectivity for visible light but its electronic properties are not ideal for anodes of OLEDs. Thus, we investigated the UV treatment effect of Ag film with a thin silver oxide layer at the surface for application of top-emitting OLEDs. In this study, we measured the change of potential difference between Ag film and ITO (indium tin oxide) films, according to UV treatment time and the mechanical properties by KPFM (Kelvin Probe Force Microscope) method and nano-indenter system, respectively. The KPFM and nano-indenter results show that the differences of surface potential and surface volume change according to UV treatment time.

Quality attributes of starfruit (Averrhoa carambola L.) juice treated with ultraviolet radiation

Starfruit juice were exposed to ultraviolet (UV-C) light for 0, 30 and 60min at room temperature (25±1°C). On exposure, the titratable acidity significantly decreased, while the decrease in °Brix and pH were not significant. With regard to colorimetric parameters, L∗ value increased significantly with a subsequent decrease in a∗ and b∗ values corresponding to UV treatment time. Except for the ascorbic acid, other antioxidants measured (% DPPH inhibition, total phenols, flavonols, flavonoids and antioxidant capacity) showed enhancement on expsoure to UV (significant at 60min). Microbial studies showed reduction in APC, yeasts and mould counts by 2-log cycle on UV treatments. These results supports the application of UV as a measure of non-thermal and physical food preservation technique for starfruit juice that can be explored commercially to benefit both the producers and consumers.

UV 처리된 유리기판위에 RF-스퍼터된 PTFE 박막들의 발수 특성

Surface properties of polytetrafluoroethylene(PTFE) films fabricated by rf-magnetron sputtering system with UV surface treatment were investigated to increase water contact angle for their hydrophobic property. We found that the surface morphology and water contact angles of PTFE film modified as a function of the UV treatment times using UV-irradiation were influenced. The water contact angle of PTFE film with optimized UV treatment time for 15 minute showed a high hydrophobicity compared with the film without any surface treatment. We thought that it was due to the energy change of PTFE surface with an adhesion improvement to the glass surface as a smoothing a rough surface with needle-shape and/or the enhancement of an interface property as a removing some defects on the surface like a cleaning effect.

Photocatalytic properties of Au/TiO 2 thin films prepared by RF magnetron co-sputtering

Au/TiO 2 thin films with various Au doping contents were deposited on quartz substrates by radio frequency (RF) magnetron co-sputtering. The as-deposited Au/TiO 2 films were characterized by energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), XRD, and UV–vis techniques. Au doping and UV treatment enhanced the photocatalytic efficiency of TiO 2 thin films. The optimal RF power of the Au target and UV treatment time were 5 W and 1 h, respectively. The enhanced photoactivity of Au(5 W)/TiO 2 thin films with UV treatment is found to result from the increased hydroxyl concentration.

Formation of Porous Organosilicate Glasses Produced by PECVD and UV Treatment

ABSTRACTThe deposition and post-treatment processes involved in the production of porous organosilicate glasses (OSGs) by plasma-enhanced chemical vapor deposition (PECVD) with ultraviolet light (UV) treatment are investigated through the use of a deuterated organic porogen precursor using infrared spectroscopy and solid-state nuclear magnetic resonance spectroscopy. Infrared analysis provides evidence for hydrogen-deuterium scrambling between the chemical species during the deposition process, which is exacerbated by the UV treatment process. Analysis of 13C cross-polarized magic angle spinning (CP-MAS) NMR suggests that the porogen exists in domains relatively isolated from the network, in agreement with short UV treatment time morphological data that indicates the pore size is relatively constant from the early stages of UV treatment process. The chemical and morphological information provides further support for a deposition controlled morphology and has implications towards enhanced chemical processing of porous organosilicate glass (OSG) films for back-end-of-line integrated circuit manufacturing.

C-Jun regulates cell cycle progression and apoptosis by distinct mechanisms.

c-Jun is a component of the transcription factor AP-1, which is activated by a wide variety of extracellular stimuli. The regulation of c-Jun is complex and involves both increases in the levels of c-Jun protein as well as phosphorylation of specific serines (63 and 73) by Jun N-terminal kinase (JNK). We have used fibroblasts derived from c-Jun null embryos to define the role of c-Jun in two separate processes: cell growth and apoptosis. We show that in fibroblasts, c-Jun is required for progression through the G1 phase of the cell cycle; c-Jun-mediated G1 progression occurs by a mechanism that involves direct transcriptional control of the cyclin D1 gene, establishing a molecular link between growth factor signaling and cell cycle regulators. In addition, c-Jun protects cells from UV-induced cell death and cooperates with NF-kappaB to prevent apoptosis induced by tumor necrosis factor alpha (TNFalpha). c-Jun mediated G1 progression is independent of phosphorylation of serines 63/73; however, protection from apoptosis in response to UV, a potent inducer of JNK/SAP kinase activity, requires serines 63/73. The results reveal critical roles for c-Jun in two different cellular processes and show that different extracellular stimuli can target c-Jun by distinct biochemical mechanisms.