Use Of Ultraviolet Light Research Articles

An investigation on the use of ultraviolet light emitting diodes (UV LEDs) in a plug‐flow reactor for water treatment

In this study, a small bench‐scale plug‐flow reactor was designed and characterized to demonstrate the feasibility of using UV/LEDs as a UV source in flow‐through advanced oxidation processes. The plug‐flow reactor was characterized by investigating the effects of residence time, H2O2/methylene blue molar ratio, and initial methylene blue concentration on methylene blue decolorization in water. Methylene blue was selected as a witness dye, because it does not degrade with H2O2 or with UV alone, and it has reduced absorption in the visible spectrum when reacted with OH radicals. UV/LEDs have been employed successfully in AOPs for water treatment in research‐scale systems, as demonstrated in this study. However, they currently have low optical output, which limits their applicability for water treatment to small point‐of‐use systems. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 857–863, 2017

Impact of Ultraviolet Light on Vitiligo.

Vitiligo is a disorder of the melanocytes that results in a dynamic spectrum of skin depigmentation. Its etiology is complex and multifactorial, with data supporting several different hypotheses. Given its prominent phenotype, vitiligo has a significant negative impact on quality of life. Coupled with the chronic and incurable nature of the disease, this presents a formidable treatment challenge. Several treatment modalities have been instituted over the years, with varying efficacy. This chapter focuses on the use of ultraviolet light in vitiligo as an established therapeutic option.

UV Disinfection of Wastewater and Combined Sewer Overflows.

Municipal wastewater contains bacteria, viruses, and other pathogens that adversely affect the environment, human health, and economic activity. One way to mitigate these effects is a final disinfection step using ultraviolet light (UVL). The advantages of UVL disinfection, when compared to the more traditional chlorine, include no chlorinated by-products, no chemical residual, and relatively compact size. The design of most UV reactors is complex. It involves lamp selection, power supply design, optics, and hydraulics. In general, medium pressure lamps are more compact, powerful, and emit over a wider range of light than the more traditional low pressure lamps. Low pressure lamps, however, may be electrically more efficient. In UV disinfection, the fraction of surviving organisms (e.g. E. coli) will decrease exponentially with increasing UV dose. However, the level of disinfection that can be achieved is often limited by particle-associated organisms. Efforts to remove or reduce the effects of wastewater particles will often improve UV disinfection effectiveness. Regrowth, photoreactivation, or dark repair after UV exposure are sometimes cited as disadvantages of UV disinfection. Research is continuing in this area, however there is little evidence that human pathogens can photoreactivate in environmental conditions, at doses used in wastewater treatment. The UV disinfection of combined sewer overflows, a form of wet weather pollution, is challenging and remains largely at the research phase. Pre-treatment of combined sewer overflows (CSOs) with a cationic polymer to induce fast settling, and a low dose of alum to increase UV transmittance, has shown promise at the bench scale.

Modular and Adaptable Tumor Niche Prepared from Visible Light Initiated Thiol-Norbornene Photopolymerization.

Photopolymerized biomimetic hydrogels with adaptable properties have been widely used for cell and tissue engineering applications. As a widely adopted gel cross-linking method, photopolymerization provides experimenters on-demand and spatial-temporal controls in gelation kinetics. Long wavelength ultraviolet (UV) light initiated photopolymerization is among the most popular methods in the fabrication of cell-laden hydrogels owing to its rapid and relatively mild gelation conditions. The use of UV light, however, still causes concerns regarding its potential negative impacts on cells. Alternatively, visible light based photopolymerization can be used to cross-link cell-laden hydrogels. The majority of visible light based gelation schemes involve photoinitiator, co-initiator, and comonomer. This multicomponent initiation system creates added challenges for optimizing hydrogel formulations. Here, we report a co-initiator/comonomer-free visible light initiated thiol-norbornene photopolymerization scheme to prepare modular biomimetic hydrogels suitable for in situ cell encapsulation. Eosin-Y was used as the sole initiator to initiate modular gelation between synthetic macromers (e.g., thiolated poly(vinyl alcohol) or poly(ethylene glycol)) and functionalized extracellular matrices (ECMs) including norbornene-functionalized gelatin (GelNB) or thiolated hyaluronic acid (THA). These components are modularly cross-linked to afford bioinert (i.e., purely synthetic), bioactive (i.e., using gelatin), and biomimetic (i.e., using gelatin and hyaluronic acid) hydrogels. The stiffness of the hydrogels can be easily tuned without affecting the contents of the bioactive components. Furthermore, the use of naturally derived biomacromolecules (e.g., gelatin and HA) renders these hydrogels susceptible to enzyme-mediated degradation. In addition to demonstrating efficient and tunable visible light mediated gelation, we also utilized this biomimetic modular gelation system to formulate artificial tumor niche and to study the effects of cell density and gel modulus on the formation of pancreatic ductal adenocarcinoma (PDAC) spheroids.

The Use of Ultraviolet Light as a Non-destructive Method for Revealing Fragments of Lost Pigmentation in Faded Alcohol-preserved Collection Specimens

A method for visualizing previously pigmented areas of the body with the employment of black-light spectrum bulbs is described. Under ultraviolet (UV) light, fish musculature fluoresces, whereas melanophores absorb incident light, revealing nearly lost contrast between once strongly and poorly pigmented areas of the body that has faded over time. Although a yet unknown extent of melanophore preservation is necessary to expose such contrast, the method was successful on a partially faded holotype of Characidium fasciadorsale Fowler, a nearly completely faded holotype of Characidium etheostoma Cope, and most remarkably for the blackened, previously mold-infested and nearly destroyed holotype of Holotaxis laetus Cope. In the latter case, the method also allowed better recognition of scale pockets on the skin.

Non-contact tunable damping of a cantilever beam structure embedded with photo-rheological fluids

This research presents an introduction to non-contact tunable damping using a new class of photo-rheological fluids (PRFs) whose rheological behavior can be changed by using ultraviolet (UV) light. When the PRF is irradiated by UV light, its viscosity decreases; the viscosity recovers to its initial value when UV light is switched off, implying that the viscosity of PRF is reversible and tunable. We demonstrate that UV light can be used to induce the changes in the viscosity of PRFs, and that the proposed method can be successfully applied to realize non-contact tunable damping of vibrating structures. The additional advantages of PRF include no deposition associated with the single-phase solution of PRF and no electro-magnetic interference shielding.

Converting Volatile Organic Compounds to CO<sub>2</sub> and Water

This paper discusses a novel method to clean VOC from any sources. Photocatalysis surpasses any other technologies in air purification for absorption of volatile organic compounds. A key component is the use of ultraviolet light to activate a photo-catalysis process that can also disinfect microorganisms including bacteria, viruses, moulds and even infectious diseases. The by-products of the photocatalytic process is only carbon dioxide and water. Results as tested by the Chinese government agency for its VOC removal efficacy at several factories is most encouraging. In conclusion, we have found a technology that can help clean the increasing air pollution in China to improve public health.

Study on the abrasion mechanism of ultraviolet cured resin bond diamond wheel

Based on an extensive review of traditional machining technologies, a novel method to manufacture abrasive tools using ultraviolet (UV) light curing technique was proposed to achieve the economy and accuracy for machining ceramic materials. The UV cured resin bond tools have been proven to have substantial advantages in machining performance. However, there has been limited research on the abrasion mechanism of such tools. In this paper, the mechanism of such resin bond tools is proposed as a hybrid of conventional grinding and lapping, and called as a grinding/lapping (G/L) process. In order to verify the proposed mechanism, three resin bond diamond wheels cured by UV light were used to conduct lapping, grinding, and G/L process, respectively, under the same experimental set-up. The experimental results like surface roughness (RA) and surface profiles of the workpieces undertaking the three operations were compared and showed good agreement with the proposed mechanism.

Study on the abrasion mechanism of ultraviolet cured resin bond diamond wheel

Based on an extensive review of traditional machining technologies, a novel method to manufacture abrasive tools using ultraviolet (UV) light curing technique was proposed to achieve the economy and accuracy for machining ceramic materials. The UV cured resin bond tools have been proven to have substantial advantages in machining performance. However, there has been limited research on the abrasion mechanism of such tools. In this paper, the mechanism of such resin bond tools is proposed as a hybrid of conventional grinding and lapping, and called as a grinding/lapping (G/L) process. In order to verify the proposed mechanism, three resin bond diamond wheels cured by UV light were used to conduct lapping, grinding, and G/L process, respectively, under the same experimental set-up. The experimental results like surface roughness (RA) and surface profiles of the workpieces undertaking the three operations were compared and showed good agreement with the proposed mechanism.

Understanding the torsion effects on optical properties of azobenzene derivatives

Most azobenzene derivatives require the use of ultraviolet light for photoisomerization, this limits the utilization of them in biological systems, energy-storing material fields and so on. It’s useful to develop azo-based photo-switches triggered with visible light. Three synthesized azobenzene derivatives (tetra-o-methoxyl-4,4′-diacetamidoazobenzene, 5,6-dihydrodibenzo[c,g][1,2]diazocine and 3,5-dimethyl-bisazo) who can be driven by visible light were studied by DFT calculations in this article. We found that they all have the same structural features of the twisted azobenzene trans geometries. The planarity of azobenzene, which can be reflected by ϕCNNC (the dihedral angle connecting the azo moiety and two phenyl rings) and θCCNN (the dihedral angle connecting the azo moiety and one of the phenyl rings). To better understand the relationship between structure and optical properties, absorption spectra of azobenzene in vacuum as the function of ϕCNNC and θCCNN rotation were investigated by using DFT and TDDFT methods. Calculations demonstrated that distorting ϕCNNC and θCCNN can both result in the red shift of the absorption bands to the visible light wavelength, and ϕCNNC has a greater impact than θCCNN. Furthermore, the influence of twisted structure on the absorption band of 4-(4-aminophenylazo) nitrobenzene (a D-π-A type azobenzene derivative) in DMSO solution was also studied. Our results indicated that both ϕCNNC and θCCNN(NH2) rotation decreased the HOMO–LUMO gap, causing a red shift of the S0→S1 absorption band. However, the θCCNN(NO2) rotation increased the HOMO–LUMO gap slightly, resulting in a little blue shift of the whole bands. This work may provide useful theoretical foundation for fabricating of new visible light driven azobenzene-based photo-switches.

Investigation of photo-induced diffusion of oxygen into carbon nanotube for oxidation process

A controlled and less destructive way of purification of as-grown carbon nanotube (CNT) is a challenging task for the scientific community. A new approach for oxidation of as-grown CNTs using ultraviolet (UV) light lamp is investigated in this paper. For this purpose, the experiment was conducted in a UV lamp chamber consists of a layer of reflective aluminum foil inside to ensure the entire sample would have an even exposure to UV. The experiments were performed under ambient condition. In this study, we vary the exposure time of oxidation. The removal of non-nanotube material after UV light exposure is confirmed by field emission scanning electron microscopy and Raman spectroscopy. Raman spectra show that D band becomes narrow which is consistent with highly purified nanotube. We observed that the intensity of G and D* bands increased rapidly with increasing the UV light exposure time for oxidation. Intensity ratio I D*/I D increases continually with increasing the oxidation time which confirms the reduction of impurities from the MWNTs. Fourier transform infrared spectroscopy confirms the presence of defect sites where some oxygenated functional groups are attached.

Surface Coating of Acrylate Polymer on Sengon Wood (Paraserianthes falcataria L. Nielsen) Using UV Irradiation

SummaryAn experiment on surface coating of sengon wood (Paraserianthes falcataria L. Nielsen) using ultra violet (UV) irradiation has been conducted. Epoxy acrylate and urethane acrylate resins were used as coating materials after addition of tripropylene glycol diacrylate and a photoinisiator, Darocure 1173. Irradiation was conducted using UV light at the conveyor speed of 2, 3, 4, and 5 m/min. Parameters observed were glossyness, adhesion, hardness, abrasion resistance and chemical, solvent and stain resistance. The superior results of the epoxy acrylate films were obtained to show excellent adhesion on the surface of wood meeting with the standard because of greater remaining values than 50% (ASTM 2571‐71), together with the high degrees of abrasion, hardness, glossyness and torelance against chemicals, solvent, and stain except against 10% NaOH solution.

Visible light crosslinking of methacrylated hyaluronan hydrogels for injectable tissue repair.

Tissue engineering hydrogels are primarily cured in situ using ultraviolet (UV) radiation which limits the use of hydrogels as drug or cell carriers. Visible green light activated crosslinking systems are presented as a safe alternative to UV photocrosslinked hydrogels, without compromising material properties such as viscosity and stiffness. The objective of this study was to fabricate and characterize photocrosslinked hydrogels with well-regulated gelation kinetics and mechanical properties for the repair or replacement of soft tissue. An anhydrous methacrylation of hyaluronan (HA) was performed to control the degree of modification (DOM) of HA, verified by (1) H-NMR spectroscopy. UV-activated crosslinking was compared to visible green light activated crosslinking. While the different photocrosslinking techniques resulted in varied crosslinking times, comparable mechanical properties of UV and green light activated crosslinked hydrogels were achieved using each photocrosslinking method by adjusting time of light exposure. Methacrylated HA (HA-MA) hydrogels of varying molecular weight, DOM, and concentration exhibited compressive moduli ranging from 1 kPa to 116 kPa, for UV crosslinking, and 3 kPa to 146 kPa, for green light crosslinking. HA-MA molecular weight and concentration were found to significantly influence moduli values. HA-MA hydrogels did not exhibit any significant cytotoxic effects toward human mesenchymal stem cells. Green light activated crosslinking systems are presented as a viable method to form natural-based hydrogels in situ. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1229-1236, 2016.

Usage of Ultraviolet Test Method for Monitoring the Efficacy of Surgical Hand Rub Technique Among Medical Students

Adequate hand movements are essential in surgical hand rub, so it is important for medical students to learn it correctly. To assess its efficacy, we aimed to use ultraviolet (UV) light test after applying fluorescent solution. Digital images of the hands of 253 medical students were analyzed during "Basic Surgical Techniques" course on the 10th (Survey 1) and 14th (Survey 2) week of the curriculum to check the process and the skills development. The last step of the surgical hand rub was performed with a fluorescent solution, and then the hands were placed under UV light. Photographs were taken and analyzed. Every uncovered area was considered an error. Number and the localization of missed spots and its extent was determined. For evaluation, palmar (P) and dorsal (D) sides of the hands were divided into regions of interest (1-distal phalanxes, 2-thumb and first metacarpus, 3-second to fifth fingers, and 4-second to fifth metacarpals). Various magnitude and number of failure occurred in 123 (48.61%) students in survey 1 and in 65 (25.69%) in survey 2. The most frequent sites of the missed spots were D/2 and P/4 region in survey 1 and D/1 and P/4 in survey 2. There was an improvement seen in survey 2, as shown by a decrease in the number and extent of missed spots. Right-handed students made fewer mistakes on their nondominant hands than left-handed students (n = 23) did. The method was suitable to monitor the efficacy of surgical hand rub technique and identify the mistakes and the critical sites. The main advantage of the UV test was the immediate feedback, which resulted in a distinct improvement. Applying the UV test to the medical education and training may contribute to improvement in the compliance and the efficacy of the technique of surgical hand rub among the students.

Paper-Based ZnO Oxygen Sensor

In this paper, we report the development of an oxygen sensor using a simple device made from a film of ZnO crystals dispersed over a paper surface. Due to the high porosity of this kind of device made from paper and ZnO, a large photoconductive effect is observed as result of the fast absorption and desorption of oxygen from the ZnO surface. To detect oxygen, we propose to use ultraviolet (UV) illumination over the photoconductive surface of the sensor, the applied UV light produces oxygen desorption causing current variations through the sensor that are proportional to the oxygen presence nearby the sensor surface. The sensor developed in this paper is attractive because it is remarkably easy to fabricate, employs only very low-cost materials for its construction, and shows a better sensitivity at low concentration of oxygen at partial vacuum environments.

Advances in cataract surgery: preserving the corneal endothelium.

Cataract surgery is known to lead to some degree of corneal endothelial cell loss (ECL). The purpose of this review is to describe how recent technological advancements such as femtosecond laser-assisted cataract surgery (FLACS) affect corneal endothelium during cataract surgery. It has been suggested that FLACS may reduce the amount of required ultrasound energy used in cataract surgery, a factor known to be directly related to ECL. Several recent studies demonstrate either no difference or less ECL with FLACS than with standard phacoemulsification 1-3 months after surgery. However, results at 6 months show comparable ECL between the two techniques. Other recent advancements in surgical technique, such as biaxial microincision surgery, result in similar ECL rates to that of standard phacoemulsification. The use of ultraviolet light in the newly developing light-adjustable intraocular lenses does not increase ECL. Studies show either similar results or less ECL with the use of the newer viscous-dispersives when compared with other viscoelastic devices. Other aspects such as the use of intracameral injections have no adverse effects on corneal endothelium. Newly emerging cataract surgical techniques cause comparable ECL to that of conventional phacoemulsification. Femtosecond laser-assistance may reduce ECL, but likely only in the early postoperative period. Further studies are needed to better elucidate short and long-term effects of FLACS on the corneal endothelium. Viscous dispersives may offer equal or increased protection of the corneal endothelium during surgery compared with viscoelastic devices currently in wide use, but further studies are required to support these results.

Influence of the carrier concentration on the piezotronic effect in a ZnO/Au Schottky junction.

The piezotronic effect, which utilizes the piezopotential to engineer the interface characteristics, has been widely exploited to design novel functional device or to optimize the device performance, which is intimately related to the carrier concentration. Here, by constructing a general Schottky diode, the piezotronic effect dependence on the carrier concentration was investigated systematically using ultraviolet (UV) illumination. Scanning Kelvin Probe Microscopy was employed to quantify the carrier concentration in ZnO nanorods under UV illumination. The results showed that the carrier concentration increases with increasing light intensity and an average value of up to 5.6 × 10(18) cm(-3) under 1.2 mW cm(-2) light illumination was obtained. Furthermore, with increasing UV light intensity, an increasingly imperceptible variation in the current-voltage characteristics under strain was observed, which finally disappeared under 1.2 mW cm(-2) light illumination. This phenomenon was attributed to the weakened modulation ability of the piezopotential due to the strengthened screening effect. In addition, the gradual disappearing in the barrier also contributed to the gradual disappearance of the piezotronic effect. This study provides an in-depth understanding of piezotronics, which could be extended to other piezoelectric devices and guide the design and optimization of piezotronic and even piezophototronic devices.

Alkali‐responsive membrane prepared by grafting dimethylaminoethyl methacrylate onto ethylene vinyl alcohol copolymer membrane

ABSTRACTAn alkali‐responsive membrane was prepared by grafting dimethylaminoethyl methacrylate (DMAEMA) onto ethylene vinyl alcohol copolymer (EVAL) membrane using ultraviolet (UV) irradiation graft polymerization. A subtranslucent state of EVAL membrane swelling in the DMAEMA solution was observed, and such a state enabled the passage of UV light through all the pores, inducing graft polymerization inside the pores and on the back. Attenuated total reflectance Fourier‐transform infrared spectrometer (ATR‐FTIR), X‐ray photoelectron spectroscopy (XPS), field‐emission scanning electron microscopy (FESEM), and energy‐dispersive X‐ray spectroscope (EDX) confirmed that the poly(DMAEMA)‐grafted chains existed not only on the top surface, but also inside the pores and on the back. Atomic force microscopy (AFM) and nitrogen adsorption analysis confirmed that the grafted chains collapsed in air, and decreased the surface roughness, surface area, and pore size of the grafted membranes. Alkali‐responsive properties of the poly(DMAEMA)‐grafted EVAL membrane (i.e., contact angle, permeability, and selectivity) were observed in the pH range of 9–10. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41775.

Quantifying ultraviolet inactivation kinetics in nearly opaque fluids

The use of ultraviolet light for inactivation of pathogens is an engrained, low-cost, eco-friendly method for disinfection of nearly transparent (UVT254 > 30%/cm) contaminated fluids for which a standard-collimated beam apparatus is typically used for measurement of intrinsic inactivation kinetics. However, such a device cannot be used for low ultraviolet transmittance (UVT254 < 30%/cm) and nearly opaque (UVT254 < 10%/cm) fluids because of the lack of sufficient mixing and intrinsic inactivation kinetics controlled by dose distribution and mass-transfer effects. In this paper, a computational fluid dynamics (CFD) model was used to determine the validity regime for accurate ultraviolet inactivation kinetics studies in low transmittance and nearly opaque fluids when a new Taylor–Couette collimated beam apparatus, which exploits flow instability through the formation of toroidal counter-rotating vortices, is used for irradiations. A Taylor number of ∼ 46,500 was sufficient to overcome the very short UV light penetration at UVT254 ∼ 0.001%/cm as long as the log10 reduction value was used as controlling parameter. Specifically, it was identified that, in case of first-order inactivation kinetics, the applied average dose (AD) should not be higher than three times the dose required for one log10 inactivation (also known as D10) in order to generate data for accurate kinetic studies.

Design of a UV-responsive microactuator on a smart device for light-induced ON-OFF-ON motion

Combining a stimuli-responsive material and the Marangoni effect, a microactuator containing a ultraviolet (UV)-light-responsive photoresist and surfactant is fabricated. The locomotion of a functionally cooperating device loaded with the microactuator can be initiated by irradiation with 365 nm UV light, ceased by the removal of the UV light and restarted by re-exposure to the UV light. Moreover, the device exhibits good direction control via selective irradiation of photoresponsive microactuators at designated locations. This work is the first example using the chemical Marangoni effect to produce photoresponsive ON-OFF-ON motion of a macroscopic object on water surfaces with little impact on the experimental environment and opens up new opportunities for the design of novel advanced functional materials with controlled properties. Feng Shi and colleagues in China have fabricated a smart device that can be pushed along a water surface by the use of ultraviolet light. The researchers from Beijing University of Chemical Technology make use of the Marangoni effect, which creates a force when liquids of different surfaces tension mix — for example, during the expansion of an oil droplet on water. The device consists of a boat made from superhydrophobic metal foam. Silicon chips covered with photoresist and a surfactant are attached at the sides. Shining ultraviolet light on the chips dissolves the photoresist and releases the surfactant, which begins to spread on the surface of the water and pushes the boat. The motion can be stopped by turning the ultraviolet light off, and the direction of movement determined by using silicon chips on different sides of the boat. Combining a stimulus-responsive material and the Marangoni effect, a smart microactuator consisting of UV-responsive photoresist and surfactant was fabricated. The locomotion of a device loaded with the microactuator was initiated upon irradiation with 365-nm UV light, stopped when the light was turned off, and restarted when the light was turned back on. This work is the first example using the chemical Marangoni effect to produce photoresponsive motion on a water surface.