UV Light Exposure Time Research Articles

Extraction and characterization of carotenoid pigments with antioxidant and antibacterial potential from marine yeast Rhodotorula sp. KSB1.

Pigments are coloring agents used widely in different industrial sectors. There is a demand for using natural pigments rather than synthetic dyes because of the health hazards caused by synthetic dyes. Many natural pigments have different medicinal activities which can contribute to the nutritional value of the product. This study was carried forward with marine yeasts which can produce pigments. A total of 4 marine yeast isolates were recovered from the mangrove area of Sundarbans, West Bengal, India. Among them, the isolate KSB1 produced 856µg/g total concentration of carotenoid pigment and the dry mass weight was 3.56g/L. The stability of the extracted pigments was checked using temperature, pH, UV light exposure time, and different saline conditions. The pigments were characterized using HPLC and FTIR analysis. All of the extracted pigments showed good antioxidant activity in DPPH, metal chelating, and reducing power assay. The pigments were also found to have good antibacterial activity against the bacterial pathogens Staphylococcus aureus, Listeria monocytogenes, and Escherichia coli. Carotenoid pigment from KSB1 was found to have maximum activity in all the pathogens. The cytogenotoxicity using onion roots and phytotoxicity analysis indicated that the pigments were non-toxic and safe for cells. Finally, the potential marine yeast was identified using 18s rRNA sequencing and identified as Rhodotorula sp. KSB1 (Accession no. MH782232).

Mesomorphism of (E)-4-[(4-propyloxyphenyl)diazenyl]phenyl alkanoates (3OABOOCm)

Several compounds from the group of (E)-4-[(4-propyloxyphenyl)diazenyl]phenyl alkanoates (3OABOOCm, for m = 1 – 19) were synthesized, with the derivatives for m ≥ 8 being reported for the first time. The phase situation was investigated by polarizing optical microscopy, thermo-optical analysis, and differential scanning calorimetry methods. The enantiotropic nematic mesophase was noted for compounds where m = 2 – 13, whereas the monotropic nematic phase was observed for m = 1, 14, and 15. Multiple crystalline phase were noticed in selected derivatives (for m = 1 – 3, 9, 13, and 14). The X-ray powder diffraction confirmed the polymorphism of the crystalline phase for the 3OABOOC2 compound. The trans-cis photoisomerization process is attributed to the presence of the diazenyl (azo) group. Absorption spectra, collected as a function of UV light exposure time, indicated a first-order reaction comprising two components. The determined values of the kinetic constant k were of the order of 10-2s − 1.

Effect of microneedles shape on skin penetration and transdermal drug administration

Microneedle (MN) patches are highly efficient and versatile tools for transdermal drug administration, in particular for pain-free, self-medication and rapid local applications. Diffraction ultraviolet (UV) light lithography offers an advanced method in fabricating poly(ethylene glycol)-based MNs with different shapes, by changing both the UV-light exposure time and photomask design. The exposure time interval is limited at obtaining conical structures with aspect ratio < 1:3, otherwise MNs exhibit reduced fracture load and poor indentation ability, not suitable for practical application. Therefore, this work is focused on a systematic analysis of the MN's base shapes effects on the structural characteristics, skin penetration and drug delivery. Analyzing four different base shapes (circle, triangle, square and star), it has been found that the number of vertices in the polygon base heavily affects these properties. The star-like MNs reveal the most efficient skin penetration ability (equal to 40 % of -their length), due to the edges action on the skin during the perforation. Furthermore, the quantification of the drug delivered by the MNs through ex-vivo porcine skin shows that the amounts of small molecules released over 24 h by star-like MNs coated by local anesthetic (Lidocaine) and an anti-inflammatory (Diclofenac epolamine) drugs are 1.5× and 2× higher than the circular-MNs, respectively.

KEBERHASILAN DUA JENIS STERILAN DAN LAMA PENYINARAN LAMPU UV (ULTRA VIOLET) PADA STERILISASI EKSPLAN BONGGOL PISANG TALAS (Musa paradisiaca L. var. sapientum)

The technique of cultivating talas bananas through tissue culture with corm explants can produce a large number of seedlings with uniform height and in a short time compared to conventional methods. However, it has a higher level of contamination, so it uses HgCl2 as the sterilant which is classified as hazardous and toxic (B3) chemical. The use of UV light exposure which is able to nonactivate contaminants can be recommended to replace the B3 material. The purposes of this study were to investigate the difference between the control and the UV light exposure time nested in sterilant types on the success of sterilization of talas banana (Musa paradisiaca L.var. Sapientum) corm explant; and to investigate the effects of sterilant types on the success of sterilization of talas banana (Musa paradisiaca L.var. Sapientum) corm explant. This study is an experimental study arranged in a Nested Completely Randomized Design with separate control repeated 3 times. The UV light exposure time (t1 = 1.0 hours; t2 = 1.5 hours; t3 = 2.0 hours; t4 = 2.5 hours and t5 = 3.0 hours) was nested in a type of sterilant (s1 = UV light; s2 = 0.2% Fungicide + 0.2% Bactericide + 70% Alcohol + 30% Bayclin + 20% Bayclin + Betadine + UV light). The results of the study show that the sterilization of talas banana corm explants (s1 type), without using B3 HgCl2 and only using UV light, can be recommended to be applied in the propagation of talas bananas through in vitro culture.

Shape-Tunable UV-Printed Solid Drugs for Personalized Medicine.

Several recent advances have emerged in biotherapy and the development of personal drugs. However, studies exploring effective manufacturing methods of personal drugs remain limited. In this study, solid drugs based on poly(ethylene glycol)diacrylate (PEGDA) hydrogel and doxorubicin were fabricated, and their final geometry was varied through UV-light patterning. The results suggested that the final drug concentration was affected by the geometrical volume as well as the UV-light exposure time. The analysis of PEGDA showed no effect on the surrounding cells, indicating its high biocompatibility. However, with the addition of doxorubicin, it showed an excellent therapeutic effect, indicating that drugs inside the PEGDA structure could be successfully released. This approach enables personal drugs to be fabricated in a simple, fast, and uniform manner, with perfectly tuned geometry.

Dual-wavelength volumetric stereolithography of multilevel microfluidic devices.

Microfluidic devices are typically fabricated in an expensive, multistep process (e.g., photolithography, etching, and bonding). Additive manufacturing (AM) has emerged as a revolutionary technology for simple and inexpensive fabrication of monolithic structures-enabling microfluidic designs that are challenging, if not impossible, to make with existing fabrication techniques. Here, we introduce volumetric stereolithography (vSLA), an AM method in which polymerization is constrained to specific heights within a resin vat, allowing layer-by-layer fabrication without a moving platform. vSLA uses an existing dual-wavelength chemistry that polymerizes under blue light (λ = 458 nm) and inhibits polymerization under UV light (λ = 365 nm). We apply vSLA to fabricate microfluidic channels with different spatial and vertical geometries in less than 10 min. Channel heights ranged from 400 μm to 1 mm and could be controlled with an optical dose, which is a function of blue and UV light intensities and exposure time. Oxygen in the resin was found to significantly increase the amount of dose required for curing (i.e., polymerization to a gelled state), and we recommend that an inert vSLA system is used for rapid and reproducible microfluidic fabrication. Furthermore, we recommend polymerizing far beyond the gel point to form more rigid structures that are less susceptible to damage during post-processing, which can be done by simultaneously increasing the blue and UV light absorbance of the resin with light intensities. We believe that vSLA can simplify the fabrication of complex multilevel microfluidic devices, extending microfluidic innovation and availability to a broader community.

Accumulation of chiral pharmaceuticals (ofloxacin or levofloxacin) onto polyethylene microplastics from aqueous solutions

Drug chirality is attracting increasing attention because the enantiomers of the same chiral pharmaceutical usually exhibit different biological activities, metabolic pathways, and toxicities. The ubiquitous presence of microplastics (MPs) can enrich organic pollutants commonly found in the environment. However, knowledge about the enrichment of pharmaceutical enantiomers to MPs is relatively limited. We investigated the occurrence of enantioselectivity of ofloxacin (OFL) and levofloxacin (LEV) in the adsorption processes on polyethylene (PE) and the interactions influenced by environmental factors. The results showed that the adsorption efficiency of OFL was generally 3–5% (p < 0.05) higher than that of LEV, indicating the different affinities of the enantiomers to PE, but the adsorption process of OFL and LEV on PE was both well described by pseudo-first-order kinetics and liner isotherm models. The chirality of OFL and LEV was not affected by sizes of PE particles and solution salinity due to the identical physicochemical properties. An examination of pH effect indicated that OFL showed better acid-base adaptability than LEV. Moreover, the differences in enantiomeric enrichment between OFL and LEV on PE were promoted with increasing UV light exposure time and natural organic matter (NOM) concentrations. Using Fourier transform infrared spectroscopy (FTIR), we demonstrated that the constituents of the functional groups in chiral NOM were greatly related to the enantiomer stereoselectivity of OFL, subsequently affecting their adsorption in a chiral environment. The excitation-emission matrix (EEM) spectra confirmed the enantioselective behaviors of chiral pharmaceuticals under UV light due to the different optical activity and humic acid-like and fulvic acid-like molecular structure of the enantiomers. These findings imply that the enantioselectivity of drug enantiomers should be considered in presence of microplastics, leading to a more accurate environmental fate and risks assessments of chiral pharmaceuticals.

Stability of SARS-CoV-2 and other airborne viruses under different stress conditions.

Viral stability under stress conditions may directly affect viral dissemination, seasonality, and pathogenesis. We exposed airborne viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), mumps virus, coxsackievirus B5, human rhinovirus A16, and respiratory syncytial virus, to different temperatures, UV light exposure time, pH values, and osmotic pressures and measured the remaining viral infectivity. Reduced thermal stability was observed for coxsackievirus B5 at 45 °C, while SARS-CoV-2 demonstrated residual infectivity at 55 °C. UV light exposure was an efficient means of viral inactivation but was less efficient for non-enveloped viruses. Rhinovirus A16 and respiratory syncytial virus demonstrated extreme sensitivity to acid conditions, while SARS-CoV-2, rhinovirus A16, and respiratory syncytial virus were unstable in an alkaline environment. The information obtained in this study will be useful for the development of viral inactivation methods and may be correlated with epidemiological and seasonal viral characteristics.

A Sulfhydryl Azobenzene-Modified Polyaniline/Silver Electrode and Its Photoswitching Electrochemical Performance.

In this work, a sulfhydryl-functionalized azobenzene derivative (Azo) was synthesized and polyaniline/silver was modified (PANI/Ag) to make a nanocomposite (PANI/Ag/Azo). A series of characterization techniques like1HNMR, UV–vis absorption spectra, Raman spectra, FT-IR, XRD, SEM, TEM, and TGA was employed to study Azo, PANI/Ag, and PANI/Ag/Azo. Electrochemical properties were measured by cyclic voltammetry (CV) and galvanostatic charging/discharging (GCD). CV showed that UV and blue light had hardly any effect on PANI/Ag. However, with the prolonged exposure time of UV light, the maximum CV current density of PANI/Ag/Azo rose from 1.24 to 2.72 A g–1. Then, after 20 min of blue light irradiation, the maximum current density gradually recovered (from 2.72 to 1.26 A g–1). The GCD also obtained similar results. After formula calculation, the specific capacitance of PANI/Ag/Azo also presented a reversible trend under the alternating irradiation of UV light and blue light. All the results show that PANI/Ag/Azo has a good photoelectric response, and its electrochemical performance can be reversibly adjusted by light. This result provides a new design idea for developing electrode materials with real-time electrochemical properties.

An Optically Reconfigurable Förster Resonance Energy Transfer Process for Broadband Switchable Organic Single-Mode Microlasers

An Optically Reconfigurable Förster Resonance Energy Transfer Process for Broadband Switchable Organic Single-Mode Microlasers

Development and characterization of photo-responsive cinnamoly modified alginate

A photo-crosslinkable hydrogel derived from cinnamoyl modified alginate (Alg-CN) was prepared via hydrazide intermediate and employed as an efficient drug carrier using the painkiller drug paracetamol. Methyl ester of the alginic acid was first prepared and converted into the corresponding hydrazide intermediate (Alg-Hyd) and then the cinnamoyl units were incorporated using cinnamoyl chloride. The synthesized derivatives were characterized by spectral and instrumental methods to confirm their suggested chemical structures. The obtained Alg-CN derivatives displayed initiator-free crosslinking capabilities upon the UV exposure for adequate periods of time, which was demonstrated due to the formation of cyclobutane bridges connecting the alginate polysaccharide chains through the [2π+2π] cycloaddition reaction carried out by the CHCH units of the inserted cinnamoyl moieties. The cross-linking of the Alg-CN was monitored by observing the lowering of the UV spectral band related to the cinnamoyl units and then the gelation efficiency along with the swelling degree was investigated over the UV light exposure time. Moreover, the developed hydrogel derivatives present considerable potentials as drug carriers that enable the control of the drug release by varying the degree of hydrogel cross-linking either by cinnamoyl functionalization or UV light exposure time.

Analysis of the influence of UV light exposure time on hardness and density properties of SLA models

The article analysis the effect of exposure to ultraviolet light on the hardening process of the model made in the SLA technology. Research samples were created with the SLA additive technique using a 10s exposure time. In this experiment, the change in item hardness and density over a 96-hour period was analysed. Light exposure time for details of an item made in SLA technology results in an increase in hardness. At the same time are observed, changes in density and stabilization of both parameters with increasing exposure time to UV light.&#x0D; .

Theoretical prediction and experimental validation of the digital light processing (DLP) working curve for photocurable materials

Abstract To achieve high-precision printing results in the digital light process (DLP), the Jacobs working curve (the relationship between the absorbed UV light energy and the cured thickness of the photocurable material during UV light exposure) is of great importance in obtaining accurate printing parameters for a particular photocurable material. However, conventional experimental measurements of the variation of cured thickness under UV light exposure for each individual photocurable material are extremely time-consuming and wasteful of material. In this current research, an analytical model based on differential analysis is developed to analytically obtain the relationship between UV light exposure time and the cured thickness of a single layer. In this model, the analytical Jacobs working curve can be described as depending only on three physical properties of photocurable materials: solid absorbance, liquid absorbance, and gelation time. Moreover, adjusting the concentration of UV absorber in the photocurable materials leads to a good agreement between the analytical Jacobs working curve and the experimental data. The analytical Jacobs working curves of polyethylene (glycol) diacrylate (PEGDA) hydrogel and gelatin methacrylate (GelMA)/decellularized extracellular matrix (dECM) bioink were utilized to predict DLP printing parameters, which were demonstrated to be accurate enough to print 3D complex structures, i.e., three periodic minimal surfaces (TPMS), a triangle cone, and a diamond grid overlaid spherical shell. This theoretical model of the DLP Jacobs working curve lays the foundations for appropriate DLP printing parameters, and in particular makes possible high-precision DLP printing of photocurable materials.

Realization of Microlens Array on Flat Encapsulant Layer for Enhancing Light Efficiency of COB-LEDs

The conventional chip-on-board light-emitting diodes (COB-LEDs) with flat encapsulant layer present low light efficiency due to the total internal reflection (TIR) happens at the encapsulant-air interface. In this study, microlens array was realized on the flat encapsulant layer of COB-LEDs to diminish the TIR at the encapsulant-air interface. The microlens array was fabricated by selectively exposing the UV glue film in UV-light through a pre-designed photomask. Micro-pillars form after the UV-light exposure and microlens array forms spontaneously due to the wetting process of uncured UV glue on the micropillars. The geometry of the microlens array was experimentally optimized, and the light efficiency enhancement of COB-LEDs by the microlens array was analyzed. The results show that optimal geometry of microlens array with curvature of ~41° and base diameter of ~87 μm can be realized by adjusting the UV-light exposure time as >40 s and UV glue film thickness as >80 μm. Compared to the traditional flat encapsulant layer, the microlens array with optimal geometry increases the light efficiency of blue and ~5000 K white COB-LEDs by 50.9% and 9.31%.

Surface modification of polytetrafluoroethylene thin films by non-coherent UV light and water treatment for electrowetting applications

HypothesisThe electrowetting on dielectric or EWOD phenomenon is used in a wide range of applications, such as Liquid Lenses, Lab-on-Chip devices, or EWOD displays, among others. Its chemical resistance, electrical stability, ease of application, and low cost make polytetrafluoroethylene (PTFE) the preferred hydrophobic dielectric layer for such applications. However, the hydrophobic behaviour represents a challenge for spin coating other layers over its surface. As a consequence, several techniques are implemented to modify the surface of PTFE. These methods are complex, time-consuming, and produce morphology changes over the surface that are difficult and sometimes impossible to recover. In this work, we propose a new surface modification method that is based on a non-coherent UV light exposition method and a specific water treatment, that lead to a change from hydrophobic to hydrophilic, and a perfect recovery from hydrophilic to hydrophobic behaviour. ExperimentsIn this work, the fabrication of the hydrophobic layer treatment starts with the creation of a thin layer of alumina (Al2O3) over a glass substrate using an atomic layer deposition technique (ALD). A mixture of 10:1 FC40 solvent and Teflon Dupont AF1600 was coated over the alumina layer. The Teflon film was exposed to UV light produced by a low-pressure mercury (Hg) lamp for a period that ranges from 3−6 min. The results were analysed by scanning electron microscopy, x-ray spectroscopy, and static deionized water contact angle measurements. FindingsContact angles dependent on UV light exposure time were observed. From the scanning electron microscopy analysis, it was confirmed that the UV treatment does not produce morphology changes over the surface. Nevertheless, the x-ray spectroscopy revealed that the UV exposed samples react when they are brought into contact with deionized water, improving the adhesion of the surface. The original hydrophobic behaviour of the surface is recovered (up to 98 %) after 3 h of thermal treatment. Furthermore, the thermal recovery analysis reveals a correlation between the recovery percentage and the applied temperature.

Curing Kinetic Analysis of Acrylate Photopolymer for Additive Manufacturing by Photo-DSC.

In this research, the curing degree of an acrylate-based monomer using direct UV-assisted writing technology was characterized by differential photo calorimetry (Photo-DSC) to investigate the curing behavior. Triggered by the UV light, the duo function group monomer 1,6-Hexamethylene diacrylate (HDDA), photoinitiator 1173 and photoinhibitor exhibit a fast curing process. The exothermal photopolymerization reaction was performed in the isothermal mode in order to evaluate the different thermal effects that occurred during the photopolymerization process. The influences of both UV light intensity and exposure time were studied with single-factor analysis. The results obtained by photo-DSC also allow us to perform the kinetic study of the polymerization process: The results show that, for the reaction, the higher the UV intensity, the higher the curing degree together with faster curing speed. At the same time, the effect of the heat released during the exothermic reaction is negligible for the polymerization process. When increasing the exposure time, limited improvement of curing degree was shown, and the distribution is between 65–75%. The reaction enthalpy and related curing degree work as a function of time. The Avrami theory of phase change was introduced to describe the experimental data. The functions of a curing degree with light intensity and exposure time were achieved, respectively.

Effective Removal of Levofloxacin from Pharmaceutical Wastewater Using Synthesized Zinc Oxid, Graphen Oxid Nanoparticles Compared with their Combination

The presence of antibiotic traces in the aquatic system due to the inefficient treatment of the pharmaceutical wastewater represented threats, such as bioaccumulation and antibiotic-resistance, to the environment and human health. Accordingly, for the first time, the current work utilized the photocatalytic degradation and the adsorption approach for Levofloxacin (LEVO) in pharmaceutical wastewater using new designed nano aspects. Therefore, spherical Zinc oxide nanoparticles (ZnONP) sized 17 nm and ultrathin sheet-like structure graphene oxide nanosheets (GONS) with layer thickness ~5 nm were fabricated separately or in a combination between them then characterized via Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Fourier Transforms Infrared Spectroscopy (FTIR), absorption spectra (UV-Vis) and Brunauer-Emmett-Teller (BET). Additionally, several parameters were investigated to evaluate the potential of the removal process, such as pH, the exposure time to UV radiation, the type and concentration of the nanoparticles (NPs) and the initial concentration of the drug using a mixed fractional factorial design. The most effective parameter for LEVO removal was the NPs type followed by the initial drug concentration. Furthermore, an RP-HPLC/UV method was developed and validated for measuring the percentage of removal for LEVO drug. The highest percentage removal for both 50 and 400 µg mL−1 LEVO was 99.2% and 99.6%, respectively, which was achieved using ZnONP/GONS combination at pH 9 ± 0.05 and UV light exposure time 120 min. In addition, the negative antibacterial activity of the treated wastewater sample confirmed the drug removal. The established protocol was successfully applied on wastewater samples collected from a pharmaceutical company that encouraged researchers to mainstream this design to be applied on other pharmaceutical wastewater drugs.

Investigation of the influence of exposure time on the dual-curing reaction of RPU 70 during the DLS process and the resulting mechanical part properties

Photo-differential scanning calorimetry (Photo-DSC), standard DSC and tensile testing are used in order to investigate the influence of different exposure times on the dual-curing reaction and mechanical properties of RPU 70 specimens produced by the additive manufacturing technology Digital Light Synthesis (DLS). A comparison of reaction enthalpies measured with a Photo-DSC of different exposure times followed by thermal curing and DSC experiments with different exposed DLS green products shows that the degree of thermal cross-linking of the two-component resin RPU 70 is determined by the preceding cross-linking reaction during photo-polymerization. A shorter exposure time of UV-light enhances the subsequent thermal cross-linking, while increased exposure reduces the effect of thermal curing in the second process step.Tensile testing results of specimen produced with custom-made print profiles on the DLS Carbon M2 with different exposure times show that mechanical characteristics such as tensile strength and elongation at break are strongly dependent on the degree of UV-cross-linking. The mechanical characteristics of DLS parts produced with the RPU 70 resin system can therefore be adapted to specific requirements and applications using these customized print profiles with different exposure times.

Enhancement of catalytic activity by UV-light irradiation in CeO2 nanocrystals

Ultraviolet (UV) light irradiation on CeO2 nanocrystals catalysts has been observed to largely increase the material’s catalytic activity and reactive surface area. As revealed by x-ray absorption near edge structure (XANES) analysis, the concentration of subvalent Ce3+ ions in the irradiated ceria samples progressively increases with the UV-light exposure time. The increase of Ce3+ concentration as a result of UV irradiation was also confirmed by the UV-vis diffuse reflectance and photoluminescence spectra that indicate substantially increased concentration of oxygen vacancy defects in irradiated samples. First-principle formation-energy calculation for oxygen vacancy defects revealed a valence-hole-dominated mechanism for the irradiation-induced reduction of CeO2 consistent with the experimental results. Based on a Mars-van Krevelen mechanism for ceria catalyzed oxidation processes, as the Ce3+ concentration is increased by UV-light irradiation, an increased number of reactive oxygen atoms will be captured from gas-phase O2 by the surface Ce3+ ions, and therefore leads to the observed catalytic activity enhancement. The unique annealing-free defect engineering method using UV-light irradiation provides an ultraconvenient approach for activity improvement in nanocrystal ceria for a wide variety of catalytic applications.

Interfacially-mediated oxygen inhibition for precise and continuous poly(ethylene glycol) diacrylate (PEGDA) particle fabrication

Hydrogels based on poly(ethylene glycol) diacrylate (PEGDA) have been engineered for a variety of biomedical applications including drug delivery, cell delivery, and tissue engineering. The miniaturization of these materials to nanoscale and microscale particles has been a subject of intense activity, and promises to extend their range of applicability. In general, however, these efforts have been frustrated by the inhibition of chain growth polymerization by oxygen, an effect that is exacerbated as target length scales are reduced. Here, we report a method that exploits the undesirable oxygen-inhibited photopolymerization to produce size-controlled PEGDA hydrogel particles. The role of initial solution composition in determining the relative particle to droplet size ratio is reported, and is found to contribute through its influence on the polymerization rate, as well as the diffusivity of oxygen. Facile control of photopolymerization kinetics via UV light intensity and/or exposure time, allowed PEGDA particles to be produced with dimensions independent of the parent spherical droplets formed by conventional microfluidic emulsification.