UV Irradiation Time Research Articles

Hydrothermal synthesis of bright blue-emitting carbon dots for bioimaging and fluorescent determination of baicalein

Bright blue-emitting CDs (B-CDs) with a considerable QY of 66 % were synthesized from precursors of cysteine, trisodium citrate dehydrate and ethylenediamine by a simple hydrothermal method. Excellent luminescence stability with various pH, salt concentrations, storage time and UV radiation time is found with excitation-independent emission. Based on the good biocompatibility, B-CDs was successfully used for fluorescence imaging of human ovarian cancer cells. Moreover, the B-CDs were confirmed to be capable of baicalein sensing with a good linear relationship in range of 0–30 μM and the limit of detection of 33 nM. The corresponding sensing mechanism was proved to be fluorescence internal filtration effect and the static quenching effect. All results demonstrate that the B-CDs have good potential of the versatile utilization in biology-relevant fields.

Multi-Level Evaluation of UV Action upon Vitamin D Enhanced, Silver Doped Hydroxyapatite Thin Films Deposited on Titanium Substrate

Hydroxyapatite Ca10(PO4)6(OH)2 (HAp) is an important bioactive material for bone tissue reconstruction, due to its highly thermodynamic stability at a physiological pH without bio-resorption. In the present study, the Ag:HAp and the corresponding Ag:HAp + D3 thin films (~200 nm) coating were obtained by vacuum deposition method on Ti substrate. The obtained samples were exposed to different UV irradiation times, in order to investigate the UV light action upon thin films, before considering this method for the thin film’s decontamination. The effects of UV irradiation upon Ag:Hap + D3 are presented for the first time in the literature, marking a turning point for understanding the effect of UV light on composite biomaterial thin films. The UV irradiation induced an increase in the initial stages of surface roughness of Ag:HAp thin film, correlated with the modifications of XPS and FTIR signals. The characteristics of thin films measured by AFM (RMS) analysis corroborated with XPS and FTIR investigation highlighted a process of recovery of the thin film’s properties (e.g., RMS), suggesting a possible adaptation to UV irradiation. This process has been a stage to a more complicated UVA rapid degradation process. The antifungal assays demonstrated that all the investigated samples exhibited antifungal properties. Moreover, the cytotoxicity assays revealed that the HeLa cells morphology did not show any alterations after 24 h of incubation with the Ag:HAp and Ag:HAp + D3 thin films.

РЕЗУЛЬТАТЫ ИССЛЕДОВАНИЙ ПО ОЦЕНКЕ ВЛИЯНИЯ ПРЕДПОСЕВНОЙ УФ-ОБРАБОТКИ И РЕЖИМОВ ИСКУССТВЕННОГО ОСВЕЩЕНИЯ ПРИ ПРОРАЩИВАНИИ ЛЮПИНА НА ВИТАМИННЫЙ КОРМ

One of the ways to increase the nutritional value of feed is the use of a biologically active additive based on sprouted grain. The positive use of sprouted grain of wheat and barley has been reliably established. At the same time, the possibilities of using sprouted grain of lupine are considered much less frequently. The authors have described technique and presented the results of experimental studies on assessing the eff ect of pre-sowing UV treatment and artifi cial illumination modes during lupine germination on vitamin feed. The time of UV treatment aimed at disinfection before germination and the time of grain illumination with a phytolamp during germination were chosen as the variable factors, and the length of the shoots was chosen as the response function. The range of seed illumination was from 4 to 10 h, and the UV irradiation time was from 60 to 300 s. The germination period was 5 days. Samples exposed to natural light served as control. According to the experimental data, a regression equation was obtained that describes the eff ect of UV disinfection and illumination time during growth on the length of the shoots, and graphical dependences of the change in the response function in the intervals of variation of the infl uencing factors were constructed. Experimental data have shown that an increase in the time of UV disinfection of seeds has a positive eff ect on the length of the shoots. It was revealed that on the fi fth day of germination, the maximum length of shoots (25 mm at 11 mm in control samples) was obtained with preliminary UV disinfection of germinating seeds for 300 s and 4-hour artifi cial illumination with a phytolamp. The expediency of using this technique when germinating lupine seeds for vitamin feed for animals has been experimentally confi rmed.

Antibiotic Spectrum and Stability of Crude Extract of Extracellular Metabolites from Bacillus mageterium LB01-17

Crop pathogens including fungi and bacteria seriously affect the quality and yields of agricultural products. The purpose of this study was to detect the antibiotic spectrum of the crude extract of extracellular metabolites produced by Bacillus megaterium LB01-17 and its stability to heat, acid, alkali and ultraviolet light. The methods of mycelium growth rate and inhibitory zones were used to test the antimicrobial activity of the crude extract on 13 kinds of crop pathogenic fungi and 6 kinds of bacteria. The activity stability of the crude extract was determined under different pH values, acid-base environment and UV radiation time with Colletotrichum gloeosporioides in postharvest mango as the indicator strain. The crude extract displayed broad spectrum activity against all tested fungi with the inhibition rate on 5 kinds of fungi more than 83 %. Inhibitory effects of the crude extract on the growth of 6 kinds of bacteria were also observed and strongest inhibition to Xanthomonas oryzae pv.oryzae in rice was showed (inhibitory zone diameter 22.37 mm). By the detection of stability of the crude extract to acid, alkali, heat and UV, the results demonstrated that the inhibition rate of the crude extract against Colletotrichum gloeosporioides was stable at pH 2-8 and 77.13 % of inhibition rate was still kept after treated at 140 ºC for 20 min and the crude extract had a stable activity to UV, and the inhibition rate was almost unchanged after 6 h.

One-step Oxidation of Total Organic Carbon, Total Nitrogen, and Total Phosphorous using Wet Chemical Oxidation

Objective:This study proposed the simultaneous multi-oxidation of total organic carbon, total nitrogen, and total phosphorous using modified wet chemical oxidation method.Methods:The multi oxidation process was based on the dual radical system with sulfate and hydroxyl radicals. The sodium persulfate (Na2S2O8) and sodium hydroxide (NaOH) were activated at 40℃ and UV irradiation with 254 nm to generate the sulfate radical and hydroxyl radical. The organic matters were oxidized by the dual radicals, and TOC, TN, and TP values were compared with the control group.Results and Discussion:The dual radical system oxidized organic carbon to carbon dioxide effectively, and the TOC values were similar to the value obtained from the high-temperature combustion technique. However, the residual persulfate after oxidation process interfered the absorbance for TN and inhibit the complexation in TP measurement. The residual persulfate was effectively converted to sulfate by longer heating and UV irradiation, and the interferences were more sensitive to reaction temperature than UV irradiation time. As a result, a higher temperature condition was more effective and enhanced the applicability of multi-oxidation.Conclusions:The multi oxidation of TOC, TN, and TP was demonstrated by wet chemical oxidation, and the proposed method is expected to secure the sample and reduce the analytic time. However, the more suitable condition to enhance the accuracy of TOC, TN, and TP in the multi-oxidation system should be studied further.

Semi-convertible Hydrogel Enabled Photoresponsive Lubrication

Summary A semi-convertible hydrogel with reversible photoresponsive supramolecular lubricating ability is demonstrated by integrating a responsive supramolecular system of α-cyclodextrins/polyethylene glycol (α-CD/PEG) and competitive guest 1-[p-(phenylazo)benzyl]pyridinium bromide (AzoPB) within a poly(vinyl alcohol) (PVA) and polyacrylamide (PAAm) framework. The competitive host-guest interaction between α-CD/PEG supramolecular network and AzoPB after UV and visible-light irradiation enables the appearance and disappearance of the sol-state layer on the hydrogel surface while the PVA and PAAm consistently keeps the framework. This semi-convertible process realizes the reversible photoresponsive lubricating ability and variable toughness. We envision that this finding will offer a possible way for fabricating novel smart devices far beyond lubrication, leading to an emerging branch of interdisciplinary materials science that integrates supramolecular chemistry, hydrogel, and surface science.

Process optimization of biodiesel production from waste cooking oil by esterification of free fatty acids using La3+/ZnO-TiO2 photocatalyst

In this study, a highly active and reusable La3+/ZnO-TiO2 photocatalyst was prepared by sol–gel method. The production of biodiesel from waste cooking oil by a two-step method. In the first step, under the UV irradiation, La3+/ZnO-TiO2 photocatalytic esterification of ethanol with free fatty acids (FFA) in waste cooking oil (WCO) was studied. In the second step, NaOH catalyzed the transesterification of triglycerides with ethanol. La3+/ZnO-TiO2 photocatalysts were characterized by TG, XRD, SEM-EDS, HRTEM, BET, UV–vis spectroscopy and Raman spectra. The optimum conditions were obtained by orthogonal design. At 35 °C, the ethanol/oil molar ratio is 12:1, the catalyst dosage is 4 wt%, the UV irradiation time is 3 h, the reaction time is 3 h, and the conversion of FFA reaches 96.14%. After 5 cycles of experiments, the conversion rate of FFA is more than 87%, which indicates that the catalyst has stable activity and simple recovery. The reaction mechanism of photocatalytic esterification was proposed and the kinetics of esterification was studied. Through the analysis of the characteristics of biodiesel, it is proved that the biodiesel by the method mentioned in this study conforms to GB 25199-2017 and EN 14214 standards. Therefore, La3+/ZnO-TiO2 as a new photocatalyst opens up a new way for biodiesel production.

Photocurable Polymeric Blends for Surgical Application.

The preparation of photocrosslinkable bioadhesives synthesized from oligomers of lactic acid and polycaprolactone (PCL), both functionalized with 2-isocyanoethyl acrylate (AOI), were studied. The obtained modified macromers of LA-AOI (mLA) and PCL-AOI (mCL) were chemically characterized by 1H NMR and used to formulate polymeric blends with different mass proportions, 1:1, 1:2 and 2:1, respectively. Subsequently, the produced blends were crosslinked, considering two UV irradiation times: 30 and 120 s. After their production, the thermal and mechanical properties of bioadhesives were assessed, where upon the rheology, gel content, hydrolytic degradation and dynamic contact angles were determined. Furthermore, the cytotoxic profile of bioadhesives was evaluated in contact with human dermal fibroblasts cells, whereas their antibacterial effect was studied monitoring Escherichia coli and S. aureus growth. Overall, flexible and resistant films were obtained, presenting promising features to be used as surgical bioadhesives.

Ultraviolet Photodissociation of Protonated Peptides and Proteins Can Proceed with H/D Scrambling.

Ultraviolet photodissociation (UVPD) has recently been introduced as an ion activation method for the determination of single-residue deuterium levels in H/D exchange tandem mass spectrometry experiments. In this regard, it is crucial to know which fragment ion types can be utilized for this purpose. UVPD yields rich product ion spectra where all possible backbone fragment ion types (a/x, b/y, and c/z) are typically observed. Here we provide a detailed investigation of the level of H/D scrambling for all fragment ion types upon UVPD of the peptide scrambling probe P1 (HHHHHHIIKIIK) using an Orbitrap tribrid mass spectrometer equipped with a solid-state 213 nm UV laser. The most abundant UVPD-generated fragment ions (i.e., b/y ions) exhibit extensive H/D scrambling. Similarly, a/x and c/z ions have also undergone H/D scrambling due to UV-induced heating of the precursor ion population. Therefore, dominant b/y ions upon UVPD of protonated peptides are a strong indicator for the occurrence of extensive H/D scrambling of the precursor ion population. In contrast to peptide P1, UV-irradiation of ubiquitin did not induce H/D scrambling in the nonfragmented precursor ion population. However, the UVPD-generated b2 and a4 ions from ubiquitin exhibit extensive H/D scrambling. To minimize H/D scrambling, short UV-irradiation time and high gas pressures are recommended.

Transformation of Contaminants of Emerging Concern (CECs) during UV-Catalyzed Processes Assisted by Chlorine

Every compound that potentially can be harmful to the environment is called a Contaminant of Emerging Concern (CEC). Compounds classified as CECs may undergo different transformations, especially in the water environment. The intermediates formed in this way are considered to be toxic against living organisms even in trace concentrations. We attempted to identify the intermediates formed during single chlorination and UV-catalyzed processes supported by the action of chlorine and hydrogen peroxide or ozone of selected contaminants of emerging concern. The analysis of post-processing water samples containing benzocaine indicated the formation of seven compound intermediates, while ibuprofen, acridine and β-estradiol samples contained 5, 5, and 3 compound decomposition by-products, respectively. The number and also the concentration of the intermediates decreased with the time of UV irradiation. The toxicity assessment indicated that the UV-catalyzed processes lead to decreased toxicity nature of post-processed water solutions.

Screw-Dislocation-Driven Hierarchical Superstructures of Ag-Ag2O-AgO Nanoparticles

Constructing multi-dimensional hierarchical superstructures has been, for a longtime, regarded as a promising strategy for modifying the physiochemical properties of nanomaterials. Guided by this rule, this work reports the synthesis of hierarchical superstructures of Ag-Ag2O-AgO nanoparticles (HSANs) using a convenient and surfactant-less photochemical method under 254 nm UV-irradiation. The formation of the HSANs superstructures is dominated by screw-dislocation-driven growth mechanism at low supersaturation condition. The structural evolution of the HSANs superstructures has been systematically investigated. The average size of the HSANs superstructures increased with prolonged 254 nm UV-irradiation. The step density on the superstructure surfaces also increased along with the 254 nm UV-irradiation time.

Photooxidation of atrazine and its influence on disinfection byproducts formation during post-chlorination: effect of solution pH and mechanism

Partial photooxidation of micropollutants may lead to various degradation intermediates, obviously affecting disinfection byproducts (DBPs) formation during the post-chlorination process. The photooxidation of atrazine (ATZ) in aqueous solutions with low-pressure mercury UV lamps in UV, UV/H2O2 and UV/TiO2 treatment system and the formation of chlorinated disinfection byproducts (DBPs) during subsequent chlorination processes including dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), 1,1,1-trichloro-2-propanone (TCP), trichloromethane (TCM) and chloropicrin (CHP) were investigated in this study. The effect of solution pH on the oxidation pathway of ATZ in three UV photooxidation treatment process and the impact of photooxidation on the DBPs formations were assessed. Based on UPLC-ESI–MS/MS analyses, identification of main oxidation intermediates was performed and the plausible degradation pathways of ATZ in photooxidation system were proposed, indicating that photooxidation of ATZ in UV/H2O2 and UV/TiO2 process system was significantly pH-dependent processes. Dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), 1,1,1-trichloro-2-propanone (TCP), trichloromethane (TCM) and chloropicrin (CHP) were detected in photooxidized ATZ solutions. Compared to the other three DBPs, TCM and TCP were the main DBPs formed. The DBPs formations were greatly promoted in oxidized ATZ solutions. Solution pH and UV irradiation time exhibited obvious impact on the DBPs formation on the basis of DBP species. The variation tendency of DBPs observed relates to the combustion of ATZ in photooxidation system and the production oxidation intermediates.

Quantitative relation between thickness and grafting density of temperature‐responsive poly(N‐isopropylacrylamide‐co‐acrylamide) thin film using synchrotron‐source ATR‐FTIR and spectroscopic ellipsometry

Poly(N‐isopropylacrylamide‐co‐acrylamide) (PNIAM‐co‐AM) grafted onto tissue culture polystyrene surfaces (TCPSs) with different thicknesses and grafting densities were prepared by varying the spin‐coating speed and UV irradiation time for use in cell sheet engineering. The thickness of the PNIAM grafted surface, less than 30 nm, was believed to influence protein adhesion and cell attachment. However, methods for determining the thicknesses of a thin surface (nanometer scale) are still a challenge. In this study, a model was developed to relate the thickness of the PNIAM‐co‐AM film to its grafting density. Spectroscopic ellipsometry (SE) and attenuated total reflection‐Fourier transform infrared spectroscopy (ATR‐FTIR) with synchrotron radiation were used to quantify the thickness and the grafting density, respectively. The amount of the grafted copolymer was determined from quantitative ATR‐FTIR by relating the signals at wavenumber 1,654 to 1,600 cm−1 (A1,654/A1,600) to the known grafting density. A combination of SE and ATR‐FTIR was used to construct a linear model (h = 6.29σ + 2.24), to obtain the grafting density (σ) from the film thickness (h) with R2 = 0.93. To validate the model, random samples were prepared with different thicknesses and grafting densities. The linear model was used to predict the grafting density, which was nearly equal to the measured values.

The Influence of UV Irradiation on Dielectric Properties of Biocomposites

This work deals with the preparation of biocomposites from low-density polyethylene modified by bio-fillers such as fish bones and fish scale and with the study of their dielectric permittivity and dielectric loss depending on the temperature and on the amount of bio-fillers, before and after irradiation with ultraviolet rays. The studies were carried out under the following conditions: a temperature range of 290–390 K. (The dielectrical parameters were carring out before and after UV radiation in temperature range 290–390 K.) UV rays at a dose of 150 Mnit, and duration of 50, 70, 100, and 150 h, in composites with 3, 5, 7, 10, and 15 vol % bio-fillers. The samples were irradiated at room temperature (300 K), with a DRSh-500 lamp. It was found that the dielectric constant of obtained biocomposites during irradiation increases while the dielectric loss decreases. It was revealed that the observed changes in the dielectric constant and in the dielectric loss depending on the temperature and on the volume content of bio-fillers, and UV irradiation time, can be accounted for by a change in the physical structure of the polymer matrix and in the boundary layer of the composition components under the influence of external factors.

Green synthesis of zinc sulfide nanophotocatalysts using aqueous extract of Ficus Johannis plant for efficient photodegradation of some pollutants

In this work, a green and plant-mediated approach based on the aqueous extract of the Ficus Johannis plant was presented for synthesis of zinc sulfide (ZnS), as efficient and eco-friendly nanophotocatalysts (NPCs). In the first phase, after identification, collection, and drying of the plant, the aqueous extract of the plant fruits was prepared by microwave-assisted extraction (MAE) technique. The characterization of the as-prepared ZnS NPCs was carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution scanning electron microscopy (HR-SEM), Fourier-transform infrared spectroscopy (FT-IR), fluorescence, and UV–Vis absorption spectroscopy. The fluorescence and UV–Vis absorption investigations showed an obvious emission peak between 420 and 440 nm with a broad absorption band between 290 and 320 nm. From SEM and TEM images, the particle size of the ZnS NPCs was estimated to be smaller than 20 nm. In the next step, the application of the as-prepared ZnS NPCs was examined as for photodegradation of some industrial pollutants including naphthalene (Naph), anthracene (AnT), 4- chlorophenol (4-CP), and 4- nitrophenol (4-NP). The effect of experimental parameters on photodegradation percentage of the pollutants such as NPCs dosage, initial pollutant concentration, UV-irradiation time, scavenger type was studied. Under optimum conditions, high-degradation efficiency was obtained using a low amount of ZnS NPCs, after 120 min UV irradiation. Finally, the probable mechanism of the presented heterogeneous photodegradation approach was discussed, too.

Bactericidal Activity of TiO2 Nanotube Thin Films on Si by Photocatalytic Generation of Active Oxygen Species.

The photocatalytic bactericidal activity of titanium dioxide (TiO2) thin films has been extensively studied. In this study, we investigated the bactericidal activities of TiO2 nanotube (NT) thin films using Escherichia coli and Staphylococcus aureus cells as the model bacteria. Metallic titanium (Ti) thin films were anodized on a silicon (Si) wafer substrate to form TiO2 NT thin films. To evaluate the bactericidal activity of the TiO2 NT thin films, bacteria on the TiO2 NT thin films were irradiated with near-ultraviolet light (UV-A) at a wavelength of 365 nm. The bactericidal activity was estimated by the survival rate derived from the number of live cells, which form colonies on the cell culture medium. We demonstrated that the survival rate of the two types of bacteria investigated in this study was significantly reduced by UV light irradiation and that there was a difference in the temporal change in the survival rate between the two types of bacteria. Furthermore, we investigated the generation of reactive oxygen species (ROSs) by UV light irradiation of TiO2 NT thin films using electron spin resonance spectroscopy and fluorescence analysis. We found that the main ROS generated on the surface of the TiO2 NT film was the hydroxyl radical, OH•. In addition, the generation of ROSs increased with an increase in the UV irradiation time. We proposed a kinetic model that reproduces the dependence of bacterial viability on the UV light irradiation time by considering the temporal change in the amount of ROSs generated by UV light irradiation. A comparison of the calculated and experimental results revealed that the bactericidal effect consisted of the direct photolysis of bacteria and the photocatalysis via the generation of hydroxyl radicals, with the latter exhibiting a stronger bactericidal effect than the former.

Photografting of p-anisidine-glycidyl methacrylate onto polymeric substrate for developing free-radical scavenging films

In this study, we present a facile approach for the development of a non-migratory antioxidant film via photografting of a conducing polymer (p-anisidine (PA)) onto polypropylene (PP). Initially, the surface of the PP film was functionalized via UV grafting (365 nm) of glycidyl methacrylate (GMA) in the presence of benzophenone (BP) into the methanol or mixed solvents (methanol and water). The addition of 40 v/v% of water into the coating solution led to an increase in grafting density, a reduction in UV-irradiation time, and changes in the grafting morphology. Scanning electron microscopy and atomic force microscopy were used in the identification of the breath figure array structure and brush-like grafting configuration on the surface of the films that were grafted in the mixed solvent (40 v/v % water). Subsequently, PA was immobilized onto the PP-g-GMA films via a ring-opening reaction wherein the PP-g-GMA films developed in the mixed solvent (40 % water) immobilized a higher amount of PA (2.114 ± 0.0013 μM), compared with those developed in methanol (1.760 ± 0.0070 μM). Fourier-transform infrared spectroscopy and solid state 13C nuclear magnetic resonance showed the chemical structure of the grafted surface and identified the grafting mechanism. Moreover, PP-g-GMA-g-PA films presented a strong free-radical scavenging activity using the DPPH assay. Furthermore, cyclic voltammetry analysis exhibited strong oxidation and reduction potential peaks, which proved the antioxidant activity of the films. Therefore, this newly developed free-radical scavenging film can be used as a non-migratory antioxidant film for a variety of applications, such as biomedical, cosmetic, and packaging.

Positive/Negative Phototropism: Controllable Molecular Actuators with Different Bending Behavior

Herein, a series of molecular actuators based on the crystals of (E)-2-(4-fluorostyryl)benzo[d]oxazole (BOAF4), (E)-2-(2,4-difluorostyryl)benzo[d]oxazole (BOAF24), (E)-2-(4-fluorostyryl)benzo[d]thi...

Photocatalytic Assessment of Selective Distribution of Product Arising from Methanol Oxidation on Platinum-deposited TiO2 Mesoporous Layer in a Fixed-film UV Reactor

The photocatalytic assessment of methanol conversion through cross-coupling reaction of methanol with its products was studied in a UV reactor consisting of platinum nanoparticles deposited onto a mesoporous TiO2 film. The temperature-programmed desorption (TPD) analysis showed excess methanol can affect the selective formation of formaldehyde, formic acid, and methyl formate (MF). The TPD results showed the methanol surface coverage, UV photon energy and irradiation time have mutual effects on the oxidation products. At saturated fraction of methanol coverage, formaldehyde was converted to MF and the desorption temperature of MF shifts to lower value. At 266 nm, the photooxidation reaction was more than two orders of magnitude faster than at 355 nm, suggesting that the selectivity of MF increases by the saturated fraction of methanol and increasing photon energy, while the formation of formaldehyde decreases at the same conditions. The formaldehyde conversion to formic acid gradually increases with increasing irradiation time.

Synthesis, spectroscopic investigation and bactericidal effect of Poly (vinyl alcohol) (PVA) - iron nanoparticles (Fe NPs)

This study aimed to synthesize Poly (vinyl alcohol) - iron nanoparticles (PVA-Fe NPs) via two different methods, the green electrochemical technique in presence of (PVA) which rapid and eco-friendly and by adding different ratios of (Fe-NPs) to PVA, then exposed to different time of UV-irradiation. Characterization of the resulting PVA-Fe NPs was performed using many spectroscopic and analytical techniques including, UV–Vis spectrophotometry, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Production of the Fe NPs was verified by appearance of absorbance peaks at about 457 – 462 nm in UV spectra which attributed to surface plasmon resonance. The band gap energy values show decrease with increasing Fe NPs. FTIR spectra confirm the interaction between PVA polymer and Fe- nanoparticle. All the developed PVA-Fe NPs displayed antibacterial efficiency against both Staphylococcus aureus and Escherichia coli bacteria. Moreover, the antibacterial efficiency enhanced by increasing Fe content and UV irradiation time.