Effect Of Irradiation Time Research Articles

Synthesis of anisotropic gold nanoparticles in a water-soluble polymer

Anisotropic gold nanoparticles have been synthesized by a UV irradiation technique through the interaction of HAuCl 4 and a stabilizing agent, poly (vinyl pyrrolidone) (PVP). The effect of irradiation time on the size and shape of gold nanoparticles was investigated by UV–visible spectroscopy and Transmission Electron Microscopy (TEM). The absorption spectra of all samples show a broad band with the characteristic surface plasmon resonance (SPR) peak visible at around 530 nm. The presence of an additional low intensity absorption peak at a longer wavelength suggests the presence of non-spherical nanoparticles. The TEM measurements show evidence of particle shapes such as spheres, hexagons, decahedrons and truncated triangles as the reaction proceeded from 5 min to 24 h. The variation in particle shape is probably due to the effect of the reduced gold to PVP ratio as the reaction proceeds.

Photo‐induced chemiluminescent method for determination of reducing sugars

In the present study, a simple and sensitive photo-induced chemiluminescence (CL) method for the quantitation of reducing sugars, including fructose, glucose, sucrose and lactose, was developed. This method was based on the on-line photocatalytic reaction of the reducing sugars, using a home-made photoreactor consisting of PTEF tube helically coiling around a high-pressure mercury UV lamp. Reducing sugars were detected by direct CL emission resulting from the reaction between the photoproducts and luminol. To maximize the signal intensity, the effects of irradiation time, flow rate, luminol concentration, buffer pH and concentration were tested. Under optimum conditions, the linear dynamic ranges were all 0.36-18 mg/L and the relative standard deviations (RSDs) were 1.8-2.3%, with limits of detection (3sigma) of 0.06 mg/L for fructose, glucose, sucrose and lactose. Finally, interference effects from ascorbic acid, amino acids (alanine, glycine, serine, leucine and methionine) and some metal ions and anions were also investigated.

Surface characteristics of UV-irradiated polyurethane elastomers extended with α, ω-alkane diols

Polyurethane elastomers (PUEs) based on 4,4′-diphenylmethane diisocyanate (MDI), poly (ɛ-caprolactone) (PCL) and extended with series of chain extender (CE) were synthesized via two step polymerization technique. The synthesized samples were irradiated for 50, 100 and 200 h in an UV exposure unit as such the spectral distribution of the light is good match for terrestrial solar radiation. The modifications in the chemical structures of the PU before and after irradiation were characterized using Fourier transform infrared (FT-IR) technique. The effect of irradiation time and chain extenders length on surface properties were studied and investigated. Photo-oxidation of PU surface leads to fast increase in surface free energy and its polar component. Simultaneously, the work of water adhesion to polymer increases significantly during UV-irradiation. The higher changes in surface properties, observed by water absorption (%), equilibrium degree of swelling, as well as monitored by ATR-FT-IR and contact angle measurement, were found for the PU samples extended with higher number of methylene unit and irradiation time.

Porphyrin with amino acid moieties: A tumor photosensitizer

A porphyrin with amino acid moieties was synthesized in this work, which may be a latent photosensitizer for photodynamic therapy (PDT). Adler's strategy was used to synthesize meso-tetra (4-nitrophenyl) porphyrin ( TNPP) through cyclolization of 4-nitrobenzaldhyde and pyrrole in refluxed nitrobenzene. Reduction of TNPP yielded meso-tetra(4-aminophenyl) porphyrin ( TAPP). The synthesis was improved by employing lactic acid as a catalyst. Based on TAPP, porphyrin with valine ( TAPP-4Val) was obtained. The application of the resultant TAPP-4Val as tumor photosensitizer on human breast tumor cells for photodynamic therapy (PDT) was preliminarily explored. Dark-toxicity evaluations showed that, under a concentration at up to 6 × 10 −6 M, the survival of MCF-7 cells was larger than 90%, which means TAPP-4Val is almost of non-cytotoxicity. However, TAPP-4Val showed remarkable phototoxicity after visible light irradiation. Effects of irradiation time on the survival of cells under typical concentrations of TAPP-4Val were also studied. The new porphyrin with amino acid moieties, TAPP-4Val, is of high phototoxicity but minimal or no dark-toxicity, which can be used as an effective photosensitizer for PDT.

Decoloration of chitosan by UV irradiation

Decoloration of chitosan by UV irradiation, which was used to replace a bleaching step during chitosan preparation, was evaluated under four separate treatments (effect of irradiation time, chitosan/water ratio, stirring speed, and UV light source). The optimal decoloration condition was defined as that producing white chitosan with higher viscosity. Decoloration of chitosan could be achieved effectively using a UV-C light by stirring unbleached chitosan in water (1:8, w/v) for 5 min at 120 rpm. UV irradiation applied under the optimal conditions could be used to produce chitosan with desirable white color ( L ∗ = 76.95, a ∗ = −0.37, and b ∗ = 14.04) and high viscosity (1301.7 mPa s at 0.5% w/v in 1.0% v/v acetic acid).

Ultrasound emulsification: Effect of ultrasonic and physicochemical properties on dispersed phase volume and droplet size

Ultrasonic emulsification of oil and water was carried out and the effect of irradiation time, irradiation power and physicochemical properties of oil on the dispersed phase volume and dispersed phase droplet size has been studied. The increase in the irradiation time increases the dispersed phase volume while decreases the dispersed phase droplets size. With an increase in the ultrasonic irradiation power, there is an increase in the fraction of volume of the dispersed phase while the droplet size of the dispersed phase decreases. The fractional volume of the dispersed phase increases for the case of groundnut oil–water system while it is low for paraffin (heavy) oil–water system. The droplet size of soyabean oil dispersed in water is found to be small while that of paraffin (heavy) oil is found to be large. These variations could be explained on the basis of varying physicochemical properties of the system, i.e., viscosity of oil and the interfacial tension. During the ultrasonic emulsification, coalescence phenomenon which is only marginal, has been observed, which can be attributed to the collision of small droplets when the droplet concentration increases beyond a certain number and the acoustic streaming strength increases.

Activation analysis of tritium breeder materials in the FDS-II fusion power reactor

Lithium lead (Li 17Pb 83) is presently considered as a primary candidate tritium breeder for fusion power reactors because of its attractive properties. Its induced radioactivity by D–T fusion neutrons was calculated with the fusion power reactor (FDS-II) as the reference reactor. The results were compared with the activation levels of other tritium breeders, such as Li 4SiO 4, Li 2TiO 3, Li 2O, Li, etc., under the same irradiation conditions. Furthermore, the dominant nuclides to dose rate of Li 17Pb 83 and the effects of irradiation time on the activation characteristics of Li 17Pb 83 were analyzed.

Synthesis and characterization of carboxyl‐functionalized magnetic nanogel via “green” photochemical method

AbstractCarboxyl‐functionalized magnetic nanogel was synthesized by facile “green” photochemical method. A possible mechanism of photochemical synthesis was proposed. Effects of irradiation time and volume of monomer dropped on the hydrodynamic diameter of the magnetic nanogel were investigated by photo correlation spectroscopy. The image of atomic force microscopy presented that the magnetic nanogel was with loosed structure. X‐ray diffraction analysis showed that UV irradiation did not induce phase change of Fe3O4. Superparamagnetic behaviors were retained for Fe3O4 while slightly reducing the value of saturation magnetization for surface coating. High magnetic content of (as high as 85%) and strong magnetization of Fe3O4 guaranteed that the magnetic nanogel was susceptive to external applied magnetic field. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Monomer conversion and cytotoxicity of dental composites irradiated with different modes of photoactivated curing

The aim of the study was to compare the monomer conversion and cytotoxicity of two resin composites, Tetric Ceram (TC) and Heliomolar (HM), irradiated with a halogen light-curing unit (Optilux 501) using a number of curing modes, boost (OB), ramp (OR), and conventional (OC), as well as a light-emitting diode (LED) curing unit (LEDemetron; LEDe). The effects of irradiation times (10, 20, 30, and 40 s) were also investigated. The monomer conversion of resin composites was measured using Fourier transform infrared (FTIR) analysis. Resin samples were preimmersed in Dulbeco's modified engles medium (DMEM) for 24 h, and the periodontal ligament cells (PDL) were cultured with aged medium for 72 h to evaluate the cytotoxic effects of resin samples using the microtiter-tetrazolium (MTT) method. The spectral outputs of the curing units were also compared. After irradiation using the same curing mode, the TC monomer conversion was higher than the HM analog. The TC conversion value was lower after OC and LEDemetron irradiation for 10 s compared to exposures of 30 and 40 s. The HM conversion value was lowest for the 10-s OC irradiation, and highest for the 40-s OC exposure. In cytotoxicity tests, the negative control group was without irradiation. The succinate dehydrogenase (SDH) activities of the OB and OR-irradiated TC samples were significantly lower than analogs irradiated with LEDemetron for 40 s; however, no significant differences were demonstrated between OB, OR, and control groups. Further, no significant differences in SDH activity were demonstrated for OB, OR, and control groups of the HM.

Microwave-accelerated derivatization for the simultaneous gas chromatographic–mass spectrometric analysis of natural and synthetic estrogenic steroids

A rapid microwave-accelerated derivatization process for the GC–MS analysis of steroid estrogens, estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2) and mestranol (MeEE2), was developed. Under microwave irradiation, the five estrogenic hormones studied were simultaneously derivatized with N, O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) + trimethylchlorosilane (TMCS) in pyridine solution. Effects of irradiation time (15–120 s) and power level (240–800 W) on the yield of the derivatization were investigated. The derivatization under the irradiation of 800 W microwave for 60 s produced comparable results when compared with the conventional heating process in a sand bath for 30 min at 80 °C in terms of derivatization yield, linearity and precision for all steroid hormones tested. The calibration curves are linear between 3.00 and 3.00 × 10 2 μg mL −1. The square of the regression coefficients ( R 2) range from 0.979 to 1.000. The applicability of the method was evaluated on spiked river and distilled water samples at two concentrations, 25.0 and 2.00 × 10 2 ng mL −1. The recoveries obtained by using microwave heating (60 s, 800 W) were similar to those by conventional heating. When combined solid-phase extraction (SPE) with the application of the microwave-accelerated derivatization proposed here, the detection limits of 0.02–0.1 ng L −1 for the steroid hormones have been achieved. The results demonstrated that microwave-accelerated derivatization is an efficient and suitable sample preparation method for the GC–MS analysis of estrogenic steroids.

Surface modification of cardo polyetherketone ultrafiltration membrane by photo-grafted copolymers to obtain nanofiltration membranes

Hydrophilic nanofiltration membranes were prepared by grafting hydrophilic copolymers onto surface of ultrafiltration membranes. The method consists of a UV irradiation followed by an in situ graft co-polymerization of water soluble monomers on the membranes made of cardo polyetherketone (PEK-C). The effect of irradiation time and monomer nature on the membrane performance was investigated. Analysis by Fourier transform infrared in attenuated total reflection mode, contact angles and scanning electron microscopy of the membrane surface showed that the grafting degree and their hydrophilicity increase with irradiation time. The co-polymerization of hydrophilic monomers yielded better nanofiltration membranes, i.e. with higher permeation flux. The water flux through a membrane grafted for 10 min at a 5.2 mW cm −2 UV-irradiation power changed from 1.46 L m −2 h −1 for poly(acrylic acid) to 9.69 L m −2 h −1 poly(acrylic acid-co-sodium allyl sulfonate) under a driving pressure of 0.2 MPa, for the sodium sulfate retention of 75%.

Hypofractionation in radiotherapy

Major changes in cancer radiotherapy have followed a greater understanding of the biological effects of radiation on tumours and normal tissues. Clinical radiotherapy is today a solid body of knowledge with well defined scientific foundations. Key concepts in current radiobiology include lethal and sublethal injuries, dose-effect coefficients, alpha/beta ratios, acute and late response, biologically equivalent dose, fraction dose, irradiation time and tumour regeneration between others. Effects of irradiation time and dose per fraction on tumours versus normal tissues are of special importance. Dose per fraction must be considered for analysis of effects in normal late-responding tissues. In contrast, both dose per fraction and irradiation time influence the response to radiation of malignant tumours and acute-responding tissues. Finally, the ability to quantify relationships between radiation dose and biological effect has been of particular value in the development of radiotherapy. This is illustrated by the growing use of high doses per fraction for the treatment of some cancers.

Nanoscale surface roughening of mulberry silk by monochromatic VUV excimer lamp

AbstractSurface treatment of mulberry silk was carried out using a VUV excimer lamp (172 nm). The changes occurring in morphology and physical properties of silk were studied. The nanopores created on the surface of treated samples were quantitatively analyzed using a high resolution scanning electron microscope. The physical and chemical changes taking place in silk fabric on irradiation were studied through measurement of wetting and wicking time, weight loss, crystallinity, and strength. Effect of irradiation time and distance from the lamp on these properties was also studied. Results show that wettability and wickability of silk improved significantly on exposure before stabilizing at 5 min irradiation time while the weight loss continued to increase. The effect of irradiation was negligible when the distance of the sample from the lamp became >15 mm. The effect of irradiation on tensile strength was found to be insignificant. Presence of moisture in silk hindered the effect of irradiation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4102–4106, 2007

Nanofiltration membrane preparation by photomodification of cardo polyetherketone ultrafiltration membrane

Hydrophilic nanofiltration membranes were prepared by UV-assisted graft polymerization of hydrophilic monomers onto the surface of ultrafiltration membranes made of cardo polyetherketone (PEK-C). The effect of irradiation time and monomer nature on the membrane performances was investigated. Analyses by Fourier transform infrared in attenuated total reflection mode, contact angles of the modified-membrane surface showed that the grafting degree and the hydrophilicity increase with the irradiation/grafting time or irradiation intensity. It was found that the UV-assisted grafting can be performed on the PEK-C chains with or without benzophenone (BP). The grafting inside the pores of the UV sensitive PEK-C membrane is demonstrated by the change of the membrane retention characteristic from that of an UF membrane to that of a nanofiltration membrane. The retentions to sodium chloride and sodium sulfate of the membrane with poly(acrylic acid) grafted for 90 min. UV irradiation under a 1.6 mW/cm 2 irradiation were 36 % and 94.1%, respectively, while the water flux through the membrane was ca. 31.3 L m −2 h −1, at 0.4 MPa.

05/02188 Photovoltaic cell characteristics for high-intensity laser light

Olive mills wastewater (OMW) is characterized by its high organic content and refractory compounds. In this study, an advanced technology for the treatment of the recalcitrant contaminants of OMW has been investigated. The technique used was either photo-Fenton as homogeneous photocatalytic oxidation or UV/semi-conductor catalyst (such as TiO2, ZrO2 and FAZA) as heterogeneous photocatalytic oxidation for treatment of OMW. For both the processes, the effect of irradiation time, amounts of photocatalysts and semi-conductors, and initial concentration of hydrogen peroxide has been studied. At the optimum conditions, photo-Fenton process achieved COD, TOC, lignin (total phenolic compounds) and total suspended solids (TSSs) removal values of 87%, 84%, 97.44% and 98.31%, respectively. The corresponding values for UV/TiO2 were 68.8%, 67.3%, 40.19% and 48.9%, respectively, after 80 min irradiation time. The biodegradability expressed by BOD5/COD ratio for treated wastewater was ranged from 0.66 to 0.8 compared to 0.19 for raw wastewater indicating enhancement of biodegradation.

Cinnamic carbohydrate esters: new polymeric supports for the immobilization of horseradish peroxidase

Several crosslinking photopolymers were used to cover 3 mm diameter glass beads for immobilising HRP. These immobilization supports were prepared from the totally cinnamoylated derivatives of 4-hydroxybenzaldehyde, glycerine (GLICN), d-sorbitol (SOTCN), d-manitol (MNTCN), 1,2- O-isopropylidene- α- d-glucofuranose (IPGSCN), d-glucuronic acid (GLUCNA), d-gulonic acid (GULCNA), sucrose (SSCN), d-glucosone (GSOCN), d-arabinose (ASCN), d-fructose (FSCN), d-glucose (GSCN), ethyl- d-glucopyranoside (EGSCN), maltose (MSCN), inuline (INCN), dextrine (DXICN), dextrane (DXACN) and polyvinylic alcohol (PVCN). The following partially cinnamoylated derivatives were also used: 2,3,4,6-tetracinnamoyl- d-glucopyranose (GPSTCN), obtained by partial hydrolysis of EGSCN in acid medium, and 3,5,6-tricinnamoyl- d-glucofuranose (GFSTCN), which was obtained by the acid hydrolysis of IPGSCN. The derivatives obtained were cross-linked by irradiation in the ultraviolet region, where these prepolymers show maximum sensitivity. The enzyme was immobilized by adsorption on to the support. The immobilized enzymatic activity varied with the length of incubation (2–21 h) and depended on the chemical nature of the support used. The effect of irradiation time on initial enzymatic activity and on that remaining after storage of the samples with immobilized enzyme was studied; both were seen to be related with the cross-linking density of the final polymer. The immobilized enzyme was more resistant than the soluble enzyme to inactivation by H 2O 2 at neutral pH, and provided good yields after thermal treatment at this pH value. The results show that the cinnamic esters described are suitable supports for immobilising peroxidase and can be used for different applications of the enzyme on an industrial scale.

Degradation of benzene, toluene ethylbenzene and p‐xylene (BTEX) in aqueous solutions using UV/H2O2 system

AbstractThe homogeneous degradation of benzene (B), toluene (T), ethylbenzene (E) and p‐xylene (X) (BTEX) was studied in aqueous solutions, at pH 3.0, of hydrogen peroxide (5.8 mM) under UV irradiation in a photoreactor equipped with a 300 nm lamp of light intensity 3.5 × 10−5 Ein L−1 min−1. BTEX was substantially degraded by the H2O2/UV system, with >90% disappearing in 10 min of irradiation. The decomposition of BTEX was studied either as single or as multi‐component systems. The effects of irradiation time, amounts of H2O2 in molar ratios, rate of degradation and competition between components were thoroughly examined. It can be stated that the rate of BTEX degradation in mixture was higher than those for the individual components due to external effects of the absorption of UV light by the mixture, and their effects on enhancing the formation of OH• radicals. The appropriate figure of merit, the electrical energy per mass (EE/M), was estimated at various molar ratios and it was confirmed that the best value was the one depicted for p‐xylene (0.065 kWh kg−1). A theoretical model for the degradation pathway was proposed. Copyright © 2004 Society of Chemical Industry

Surface modification of poly(propylene) by photoinitiators: Improvement of adhesion and wettability

AbstractDifferent benzophenone‐type photoinitiators were photografted onto poly(propylene) (PP). The polymer surfaces were analyzed by means of contact angle measurements, UV spectroscopy, and FTIR‐ATR. The modified samples showed a better wettability and higher surface energies, increasing from 26 mN/m for pure PP to 36 mN/m for the modified samples. The UV spectrum of the modified PP films showed two absorption bands that could be related to the grafted initiator. The effect of irradiation time and photoinitiator concentration was investigated. Different acrylates were grafted efficiently onto the modified polymer surfaces. FTIR‐ATR and contact angle measurements confirmed the presence of the grafted chains. The surface energy of the grafted surfaces of samples increased to 70 mN/m, depending on the type of acrylate used. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2341–2350, 2004

Photobleaching of humic rich dissolved organic matter

Humic rich dissolved organic matter (DOM) from a bog lake in the Northern Black Forest was treated with simulated solar UV-light. The effects of irradiation time, initial pH values, and dissolved iron and copper on photobleaching were investigated. The DOC concentration and the UV/VIS absorption decreased with increasing amounts of absorbed light energy. The wavelengths of the maximum bleaching effect and of the maximum amount of absorbed energy were found to coincide. A decrease in the average hydrodynamic radii of the DOM was shown by size-exclusion chromatography. Furthermore, evidence was given that hydrophilic moieties of the DOM were preferentially photodegraded while hydrophobic ones remained relatively unaffected or were even formed. Iron was an important factor of DOM photobleaching in the bog lake. However, copper, another redox active metal ion, inhibited the bleaching processes.

Desulfurization of Tabas coal with microwave irradiation/peroxyacetic acid washing at 25, 55 and 85 °C

Tabas coal sample from Iran was desulfurized with combination of microwave irradiation and peroxyacetic acid washing in a batch reactor. The effect of irradiation time and power, peroxyacetic acid reaction time and temperature and particle size on reduction of sulfur was investigated. For microwaved/acid washed samples, depending on desulfurization conditions, the reduction in pyritic, organic and total sulfur ranged from 26 to 91, 2.6 to 38.4 and 17 to 65%, respectively. Microwave irradiation had positive effect on desulfurization with peroxyacetic acid. For <300 μm size fraction, after irradiation, the reduction enhanced from 49.9 to 86.6% in pyritic sulfur, 23.8 to 35% in organic sulfur and 36 to 61.9% in total sulfur. FT-IR spectroscopy of coal structure before and after desulfurization has shown significant changes in the peak corresponding to pyrite whiles the bands related to coal organic matrix have not changed significantly. The results prove that this method can use as secure process on removal of inorganic and organic sulfur without destruction of coal organic matrix.