UV-LED Exposure Research Articles

Oxone activated TiO2 in presence of UV-LED light for the degradation of moxifloxacin: A mechanistic study

This work provides new insight into the development of the TiO 2 /Oxone/UV-LED process for organic contaminant degradation as well as hospital waste management. The Moxifloxacin (MOX) degradation using Oxone activated TiO 2 under UV-LED was studied. The TiO 2 /Oxone/UV LED process was carried out by the addition of Oxone (0.025, 0.05, 0.1 and 0.2 mM) activated by TiO 2 different concentrations 0.0125, 0.025, 0.05, 0.1 and 0.5 g/L. The degradation efficiency was studied by HPLC having UV/Vis detector, C18 column (5µ, 4.6 × 250 mm 2 ). The complete removal of 10 ppm of MOX occurred at 0.1 g/L TiO 2 and 0.1 mM Oxone with UV-LED exposure time of 12 min. The TOC analysis was performed and 55% TOC reduction was observed at described procedure. The parameters such as drug initial concentration, Oxone, TiO 2 dosages and pH were optimized and their effects on degradation were noted. The pseudo-first order reaction kinetics was observed for MOX degradation. It was revealed from the mechanism of activation that S O 4 - . and O H . have played a key role in the degradation. The effect of pH (3.6–11) was observed to evaluate the degradation rate of Moxifloxacin. The pH 9.4 achieved the maximum degradation. The UPLC-ESI-MS analysis was performed to identify the intermediates and degraded end-products.

In situ growth and crystallization of TiO2 on polymeric membranes for the photocatalytic degradation of diclofenac and 17α-ethinylestradiol

TiO2in situ growth on three commercial membranes (polysulfone – PS, polyvinylidene fluoride – PVDF and polytetrafluoroethylene – PTFE) and its hydrothermal post-crystallization to transform TiO2 into a photocatalytically-active phase, were investigated under mild synthesis conditions to preserve the textural properties of the supports. The membranes were successfully prepared and characterized by scanning electron microscopy, thermogravimetry analysis, N2 physisorption, X-ray diffraction, and water contact angle measurements, among other techniques. Membrane supports with a more opened porosity and high hydrophilicity allowed to enhance the content and distribution of the anatase TiO2 nanoparticles on the membrane surface. The efficiency and the permeate flux of the developed membranes were investigated to simultaneously remove diclofenac (DCF) and 17α-ethinylestradiol (EE2) from water by adsorption and UV–LED (light-emitting diode) photocatalysis under continuous recirculating mode. All TiO2 membranes achieved removal efficiencies above 90% for both contaminants, EE2 being always preferentially adsorbed over DCF due to electrostatic repulsions between the DCF molecules and the surface of these membranes. The permeate flux of TiO2 membranes was enhanced after UV-LED exposure as a consequence of the degradation of the contaminants adsorbed on the membrane surface during the dark phase. Moreover, the stability of TiO2 nanoparticles on these membranes was studied by static tests under sonication and several consecutive reaction cycles. The TiO2 membrane prepared with PVDF was the most stable, also presenting a high photocatalytic activity.

Characterization and flexibility properties of UV LED cured acrylic pressure-sensitive adhesives for flexible displays

The era of the Internet of Things (IoT) is becoming a reality, and the display equipment is at its center. The display device is the window that connects the IoT and humans, and is evolving into various form factors convenient to human use, such as foldable mobile phone, flexible wearable device, paper-like display, and rollable TV. Even though transparent flexible electrodes and substrates have been developed, their assembly remains a challenge. Therefore, the importance of optically clear acrylic pressure-sensitive adhesives (PSAs) that ensure device integrity by easily stretched and mitigating the stress during repeated stretching and bending process is being emphasized. In this study, elongation and recovery features were identifiable as key flexible properties of PSAs. These properties were estimated by measuring shear strain and strain recovery using a universal testing machine and by dynamic mechanical analytics respectively. Compared to conventional UV metal halide curing, a newly introduced ultraviolet light-emitting diode (UV LED) curing process resulted in different PSA property variables, namely UV exposure intensity and UV exposure time. Fully cured acrylic PSA realized under UV LED exposure level 30 for 8 s demonstrated the highest shear strain with excellent strain recovery of ~23,500% and 94% respectively. Under these conditions, effective material adhesion performance was achieved while retaining optical transparency and thus fulfilling the dual property requirement for non-opaque material adhesiveness necessary for use in flexible displays.

Naphthalimide derivatives containing benzyl-sulfur bond as cleavable photoinitiators for near-UV LED polymerization

Three naphthalimide aryl benzyl sulfide derivatives (NABSs) cleavable photoinitiators (PIs) containing benzyl-sulfur bonds were designed and prepared. The effect of the benzyl-sulfur moiety and substituents located on benzene ring of the benzyl group on photochemical behavior, involving the light absorption properties, potential mechanisms of the photolysis of NABSs under UV LED at 405 nm, and the electron transfer reaction between NABSs and diphenyliodonium hexafluorophosphate (Iod) were investigated in detail. The NABSs have different photolysis mechanisms as compared to PIs containing only an aryl-sulfur bond. NABS3 is most efficient for initiating free radical photopolymerization of acrylate monomers under UV LED exposure at 405 nm. Furthermore, NABSs/Iod systems can initiate the cationic photopolymerization of epoxides. Interestingly, the polymers prepared by using NABSs as the PI exhibit a great photoluminescence band at about 460 nm under UV LED irradiation at 405 nm.

Fabrication of 3D-Printed Fish-Gelatin-Based Polymer Hydrogel Patches for Local Delivery of PEGylated Liposomal Doxorubicin.

3D printing technology has been applied to various fields and its medical applications are expanding. Here, we fabricated implantable 3D bio-printed hydrogel patches containing a nanomedicine as a future tailored cancer treatment. The patches were prepared using a semi-solid extrusion-type 3D bioprinter, a hydrogel-based printer ink, and UV-LED exposure. We focused on the composition of the printer ink and semi-synthesized fish gelatin methacryloyl (F-GelMA), derived from cold fish gelatin, as the main component. The low viscosity of F-GelMA due to its low melting point was remarkably improved by the addition of carboxymethyl cellulose sodium (CMC), a pharmaceutical excipient. PEGylated liposomal doxorubicin (DOX), as a model nanomedicine, was incorporated into the hydrogel and liposome stability after photo-polymerization was evaluated. The addition of CMC inhibited particle size increase. Three types of 3D-designed patches (cylinder, torus, gridlines) were produced using a 3D bioprinter. Drug release was dependent on the shape of the 3D-printed patches and UV-LED exposure time. The current study provides useful information for the preparation of 3D printed nanomedicine-based objects.

Design of a collimated UV-LED exposure unit based on light spread function method.

A collimated and uniform UV-LED exposure unit (EU) applied in a printed circuit board is investigated by the light spread function (LSF) method. To accurately calculate the source-to-source distance of collimated UV-LED sources and achieve uniform irradiance in the exposure area, we propose a regional maximally flat condition for the LSF. This regional maximally flat condition contains irradiance information from multiple positions in two dimensions. To verify the design results, we built this parameter into optical simulation software and used it in our LSF method calculations. The obtained collimated UV-LED EU results show uniformity and average irradiance values of 98.23% and 43.32 mW/cm2, respectively. Thus, we can conclude that the proposed LSF method is effective for achieving a uniform irradiance distribution.

Photocatalytic decomposition of organic micropollutants using immobilized TiO2 having different isoelectric points

Organic micropollutants found in the environment are a diverse group of compounds that includes pharmaceuticals, personal care products, and endocrine disruptors. Their presence in the aquatic environment continues to be a concern as the risk they pose towards both the environment and human health is still inconclusive. Removal of these compounds from water and wastewater is difficult to achieve and often incomplete, but UV-TiO2 is a promising treatment approach. In this study, the efficiency of titanium dioxide (TiO2) immobilized on porous supports were tested for treatment of target pharmaceuticals and their metabolites under UV-LED exposure, a potential low energy and cost effective alternative to conventional UV lamps. Immobilization was completed using two different methods: (1) dip coating of TiO2 onto quartz fiber filters (QFT) or (2) thermal-chemical oxidation of porous titanium sheets (PTT). Comparison against experimental controls (dark QFT, dark PTT, and photolysis using UV-LED only) showed that UV-LED/PTT and UV-LED/QFT treatments have the potential to reduce the concentrations of the target compounds. However, the treatments were found to be selective, such that individual pharmaceuticals were removed well using QFT and PTT but not both. The complementary treatment behavior is likely driven by electrostatic interactions of charged compounds with the membranes. QFT membranes are negatively charged at the experimental pH (4.5–5) while PTT membranes are positively charged. As a result, cationic compounds interact more with QFT while anionic compounds with PTT. Neutral compounds, however, were found to be recalcitrant under any treatment conditions suggesting that ionic interactions were important for reactions to occur. This behavior can be advantageous if specificity is required. The behavior of pharmaceutical metabolites is similar to the parent compounds. However, isomeric metabolites of atorvastatin with functional groups in para and ortho configurations behave differently, suggesting that the positioning of functional groups can have an impact in their interaction with the immobilized TiO2. It was also apparent that PTT can be reused after cleaning by heat treatment. Overall, these newly synthesized membrane materials have potential applications for treatment of trace organic contaminants in water.

Investigation of the effect of UV-LED exposure conditions on the production of vitamin D in pig skin

The dietary intake of vitamin D is currently below the recommended intake of 10–20μg vitamin D/day. Foods with increased content of vitamin D or new products with enhanced vitamin D are warranted. Light-emitting diodes (LEDs) are a potential new resource in food production lines. In the present study the exposure conditions with ultraviolet (UV) LEDs were systematically investigated in the wavelength range 280–340nm for achieving optimal vitamin D bio-fortification in pig skin. A wavelength of 296nm was found to be optimal for vitamin D3 production. The maximum dose of 20kJ/m2 produced 3.5–4μg vitamin D3/cm2 pig skin. Vitamin D3 produced was independent on the combination of time and intensity of the LED source. The increased UV exposure by UV-LEDs may be readily implemented in existing food production facilities, without major modifications to the process or processing equipment, for bio-fortifying food products containing pork skin.

In-situ 도핑량이 다공성 3C-SiC 박막의 특성에 미치는 영향

This paper describes the elecrtical and optical characteristics of <TEX>$N_2$</TEX> doped porous 3C-SiC films. Polycrystalline 3C-SiC thin films are anodized by <TEX>$HF+C_2H_5OH$</TEX> solution with UV-LED exposure. The growth of in-situ doped 3C-SiC thin films on p-type Si (100) wafers is carried out by using APCVD (atmospheric pressure chemical vapor deposition) with a single-precursor of HMDS (hexamethyildisilane: <TEX>$Si_2(CH_3)_6)$</TEX>. 0 ~ 40 sccm <TEX>$N_2$</TEX> was used for doping. After the growth of doped 3C-SiC, porous 3C-SiC is formed by anodization with <TEX>$7.1\;mA/cm^2$</TEX> current density for anodization time of 60 sec. The average pore diameter is about 30 nm, and etched area is increased with <TEX>$N_2$</TEX> doping rate. These results are attributed to the decrease of crystallinity by <TEX>$N_2$</TEX> doping. Mobility is dramatically decreased in porous 3C-SiC. The band gaps of polycrystalline 3C-SiC films and doped porous 3C-SiC are 2.5 eV and 2.7 eV, respectively.