Irradiation Step Research Articles

Direct laser photo-induced fluorescence determination of bisphenol A

Classical photo-induced fluorescence methods are conducted in two steps: a UV irradiation step in order to form a photo-induced compound followed by its fluorimetric determination. Automated flow injection methods are frequently used for these analyses. In this work, we propose a new method of direct laser photo-induced fluorescence analysis. This new method is based on direct irradiation of the analyte in a fluorimetric cell in order to form a photo-induced fluorescent compound and its direct fluorimetric detection during a short irradiation time. Irradiation is performed with a tuneable Nd:YAG laser to select the optimal excitation wavelength and to improve the specificity. It has been applied to the determination of bisphenol A, an endocrine disrupter compound that may be a potential contaminant for food. Irradiation of bisphenol A at 230 nm produces a photo-induced compound with a much higher fluorescence quantum yield and specific excitation/emission wavelengths. In tap water, the fluorescence of bisphenol A increases linearly versus its concentration and, its determination by direct laser photo-induced fluorescence permits to obtain a low limit of detection of 17 μg L(-1).

Surface modification of amorphous substrates by disulfide derivatives: A photo-assisted route to direct functionalization of chalcogenide glasses

A novel route for chalcogenide glass surface modification is disclosed. The formation of an organic monolayer from disulfide derivatives is studied on two different glasses of formula GexAsySez by water contact angle measurement, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR). The potential anchoring group is the disulfide functionality. Since thioctic acid derivatives absorb around 335nm, an irradiation step is included, in order to favor S–S disruption. Three types of disulfide compounds are grafted onto small glass breaks for contact angle and XPS analyses. The results show effective changes of surface state. According to contact angle measurement, the deposited organic layer functionalized by a small polyethylene glycol chain leads to a more hydrophilic surface, long alkyl chain or a perfluorinated carbon chain leads to a more hydrophobic surface. XPS shows the presence at the surface of an organic layer with sulfur and ethylene oxide chains, or augmentation of organic carbons or fluorine and CF bonds. The photo-assisted grafting of the disulfides onto an ATR prism made of chalcogenide glass shows that this surface modification process does not affect infrared transparency, despite UV treatment, and accurate structural analysis can be performed.

Development of stresses in grain-oriented electrical steel during laser treatment

Variation of magnetic losses in grain-oriented electrical steel subjected to single and multiple laser treatments has been investigated. It is shown that successive application of laser barriers in several passes through a laser unit leads to a deterioration of magnetic properties accompanied by a bending of the sample. The surface subjected to the laser treatment proves to be concave. The magnitude of stresses arising in the metal after each step of laser irradiation was calculated.

Preparation of AgCl Nanoparticles@Ancient Textile with Antibacterial Activity under Ultrasound Irradiation

The growth of silver chloride nanoparticles on ancient textile was achieved by sequential dipping steps in alternating bath of potassium chloride and silver nitrate under ultrasound irradiation. The effect of ultrasound irradiation and sequential dipping steps in growth of the AgCl nanoparticles has been studied. These systems depicted a decrease in the particles size accompanying a decrease in the sequential dipping steps. The samples were characterized with powder X-ray diffraction (XRD) and scanning electron microscopy. XRD analyses indicated that the prepared AgCl nanoparticles on fiber were crystalline. The textile samples containing AgCl nanoparticles were tested for their antibacterial efficacy against Escherichia coli and were found to possess significant antibacterial activity.

Accurate and Precise Measurement of Selenium by Instrumental Neutron Activation Analysis

An accurate and precise measurement of selenium in Standard Reference Material (SRM) 3149, a primary calibration standard for the quantitative determination of selenium, has been accomplished by instrumental neutron activation analysis (INAA) in order to resolve a question arising during the certification process of the standard. Each limiting factor of the uncertainty in the activation analysis, including the sample preparation, irradiation, and γ-ray spectrometry steps, has been carefully monitored to minimize the uncertainty in the determined mass fraction. Neutron and γ-ray self-shielding within the elemental selenium INAA standards contributed most significantly to the uncertainty of the measurement. An empirical model compensating for neutron self-shielding and reducing the self-shielding uncertainty was successfully applied to these selenium standards. The mass fraction of selenium in the new lot of SRM 3149 was determined with a relative standard uncertainty of 0.6%.

REUSE OF DOMESTIC WASTEWATER FOR IRRIGATION: CONCEPTUAL AND BASIC DESIGN ELEMENTS

In Iraq, water shortages and drought, especially during the hot summer months, necessitates that municipal authorities adopt water reuse projects like reusing treated domestic wastewater for crop irrigation. This work gives the conceptual and basic design elements for the necessary steps of filtration, UV irradiation and chlorination to make such a wastewater fit for agricultural use. A typical rural community of 50,000 people is considered as an example case for which functionality and relative simplicity of the proposed designs are prime factors. The objectives are 1) to show what is required and 2) that the presented information may be utilized to embark on the following phases of detailed design and execution of such projects.

The influence of temperature on the synthesis of molecules on icy grain mantles in dense molecular clouds

Context. Infrared observations show the presence of icy mantles along the line of sight toward young stellar objects (YSOs), where a temperature gradient is expected and indirectly observed. In this environment, icy mantles are affected by ion and UV irradiation. Laboratory experiments show that molecules are formed after irradiation of icy mixtures. However, most of the experiments done so far have been performed in the temperatures range of 10-20 K. Aims. To extend previous work we irradiated some icy mixtures, namely H 2 O:CO=10:1, H 2 O:CH 4 =4:1, and H 2 O:CO 2 =3:1 at two different temperatures (12 K and 40 or 60 K) to study the effects of temperature on the synthesis of molecules and the decrease in their parent species after ion irradiation. Methods. The experiments were performed in a high-vacuum chamber (P < 10 ―7 mbar), where icy samples were irradiated with 30 keV He + ions and analyzed by a FTIR spectrophotometer. Infrared spectra of the samples were recorded after various steps of irradiation. Results. We found that the temperature affects the behavior of the volatile species (i.e., CO and CH 4 ) during irradiation. As a consequence, the production of molecular species is generally more prevalent at 12 K than at either 40 or 60 K, while the decrease in their parent volatile species is faster at high temperature. Conclusions. We conclude that the behavior of each species depends on the value of its sublimation temperature with respect to the temperature of the sample. If this latter is higher than the sublimation temperature of a given species, then the effects of thermal desorption compete with those due to irradiation.

A New Route for Mass Production of Uniform Metal Nanoparticles in Water by Means of Laser Light Induced Processes

In this contribution, we report a new route for mass fabrication of metal nanoparticles with monodisperse shape and narrow size distribution in water applying exclusively physical processes. For this purpose, we have combined pulsed laser ablation with the technique of selective laser tailoring. For example, pulsed laser ablation from a gold plate in water results in a large amount of nanoparticles with radii in the range of R = 75 nm with a relatively broad size distribution of sigma = 31%. This broad size distribution has been subsequently narrowed in a single irradiation step to sigma = 20% without a significant change of the mean nanoparticle radius utilizing selective laser tailoring. The main advantage of the laser based process, besides rapid processing, is that no chemicals, which are undesired for many applications, are necessary. Hence, mass production of nanoparticles with narrow size and monodisperse shape distribution in water becomes feasible.

The single-process biochemical reaction of Rubisco: A unified theory and model with the effects of irradiance, CO2 and rate-limiting step on the kinetics of C3 and C4 photosynthesis from gas exchange

Photosynthesis is the origin of oxygenic life on the planet, and its models are the core of all models of plant biology, agriculture, environmental quality and global climate change. A theory is presented here, based on single process biochemical reactions of Rubisco, recognizing that: In the light, Rubisco activase helps separate Rubisco from the stored ribulose-1,5-bisphosphate (RuBP), activates Rubisco with carbamylation and addition of Mg2+, and then produces two products, in two steps: (Step 1) Reaction of Rubisco with RuBP produces a Rubisco-enediol complex, which is the carboxylase–oxygenase enzyme (Enco) and (Step 2) Enco captures CO2 and/or O2 and produces intermediate products leading to production and release of 3-phosphoglycerate (PGA) and Rubisco. PGA interactively controls (1) the carboxylation–oxygenation, (2) electron transport, and (3) triosephosphate pathway of the Calvin–Benson cycle that leads to the release of glucose and regeneration of RuBP. Initially, the total enzyme participates in the two steps of the reaction transitionally and its rate follows Michaelis–Menten kinetics. But, for a continuous steady state, Rubisco must be divided into two concurrently active segments for the two steps. This causes a deviation of the steady state from the transitional rate. Kinetic models are developed that integrate the transitional and the steady state reactions. They are tested and successfully validated with verifiable experimental data. The single-process theory is compared to the widely used two-process theory of Farquhar et al. (1980. Planta 149, 78–90), which assumes that the carboxylation rate is either Rubisco-limited at low CO2 levels such as CO2 compensation point, or RuBP regeneration-limited at high CO2. Since the photosynthesis rate cannot increase beyond the two-process theory's Rubisco limit at the CO2 compensation point, net photosynthesis cannot increase above zero in daylight, and since there is always respiration at night, it leads to progressively negative daily CO2 fixation with no possibility of oxygenic life on the planet. The Rubisco-limited theory at low CO2 also contradicts all experimental evidence for low substrate reactions, and for all known enzymes, Rubisco included.

Poling-inhibited ridge waveguides in lithium niobate crystals

Ultraviolet laser irradiation of a lithium niobate +z polar surface enables the production of ridge waveguides. Ultraviolet laser induced inhibition of poling is used to define an inverted domain pattern which transforms into a ridge structure by differential etching in hydrofluoric acid. The laser irradiation step also induces a refractive index change that provides the vertical confinement within the ridge structure. Furthermore, it was observed that poling-inhibition results in a significant enhancement of the refractive index contrast between the bulk crystal and the ultraviolet irradiated tracks.

Ultrasound-assisted coating of silk yarn with silver chloride nanoparticles

The growth of silver chloride nanoparticles on silk yarn was achieved by sequential dipping steps in alternating bath of potassium chloride and silver nitrate under ultrasound irradiation. The effects of ultrasound irradiation, concentration and sequential dipping steps in growth of the AgCl nanoparticles have been studied. Particle sizes and morphology of nanoparticle are depending on power of ultrasound irradiation. Results show a decrease in the particles size as increasing power of ultrasound irradiation. Increase in concentration and sequential dipping steps result an increase particle size. The physicochemical properties of the nanoparticles were determined by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and inductive coupled plasma (ICP).

Two‐ and Three‐Dimensional Micro‐ and Sub‐Micrometer Periodic Structures Using Two‐Beam Laser Interference Lithography

AbstractIn this study, we present different approaches for the fabrication of two and three dimensional structures using two‐beam interference lithography. The advantages of using more than one irradiation step for the fabrication of complex structures are theoretically demonstrated by avoiding the introduction of line effects. For the fabrication of 3D structures, two alternatives are discussed including a layer by layer approach as well as a multidimensional (non‐orthogonal) interference exposure setup. Finally, an example of biomimetic patterning is given. In all cases, numerical calculations showed a good agreement with the experimental results, being able to explain the shape of the fabricated structures.

The COLIPA in vitro UVA method: a standard and reproducible measure of sunscreen UVA protection

There is a continuing need to measure and communicate reliably the UVA protection offered by commercial sunscreens. To that end, the COLIPA (European Cosmetics Trade Association) 'In Vitro Sun Protection Methods' group has developed a new in vitro method for measuring UVA protection in a standardized, reproducible manner. The method is based on in vitro UV substrate spectrophotometry and convolution of resulting absorbance data with the action spectrum for the in vivo Persistent Pigment Darkening (PPD) endpoint to provide an in vitro UVA protection factor (UVAPF) which is correlated with an in vivo measure. This method has been published as a COLIPA guideline, used currently in European geographies for testing and labelling sunscreen products. This article summarizes two 'ring' studies, involving eight separate testing laboratories, which both defined critical parameters for the method and validated it. In Ring Study 1, eight laboratories tested the in vitro UV transmission of a total of 24 sunscreens and, from the data, a unit dose of UVA (D(0) of 1.2 J cm(-2)) was defined to provide a single irradiation step which, by taking into account potential sunscreen photo-instability, gave the closest agreement with in vivo UVAPF values. In Ring Study 2, eight laboratories tested the in vitro UV transmission of a total of 13 sunscreens using this single irradiation step and established a very good correlation (r(2) = 0.83; slope = 0.84, P < 0.0001) between resulting in vitro UVAPF values and corresponding values derived from the in vivo PPD method. This new method, therefore, can be used to provide a reliable in vitro metric to describe and label UVA efficacy in sunscreen products, in line with the EU Commission recommendation 2006/247/EC.

Properties of isotactic polypropylene irradiated in various atmospheres

In this paper, changes in structure and physical properties of stabilized isotactic polypropylene (iPP) were created by gamma irradiation, up to a dose of 700 kGy, in different media: air, deionized distilled (DD) water and acetylene. Two main effects occur when polyolefins, such as iPP, are subjected to ionizing radiation: crosslinking and scission of macromolecules. The domination of one or the other of these competitive processes is determined by both the structural peculiarities of the polymers and the experimental irradiation conditions. Gel and infrared (IR) spectroscopy measurements were used to determine the changes in the degree of network formation and oxidative degradation, respectively. Sol-gel analysis was studied in detail using the Charlesby-Pinner (C-P) equation. The radiation-induced changes in the structure and evolution of oxygen-containing species were also studied through dielectric loss (tan ?) analysis in a wide temperature and/or frequency range. Evolution of low temperature dielectric relaxations with gamma irradiation was investigated. The results showed that degradation was the major reaction in the initial step of irradiation, no matter what the atmosphere was. The C-P equation seemed applicable when stabilized iPP was irradiated within a certain dose range in various atmospheres. The iPP irradiated in acetylene/air had the lowest/highest values for oxidation level, dielectric losses, Dg and G(s)/G(x) values. The calculated Dg values are 1.5 and 5 times larger for the irradiation in DD water and air than for the acetylene. Furthermore, our data confirm that oxidation strongly affects the gel point but has a much lower effect on the G(S)/G(X) ratio. In the case of dielectric relaxation measurements, the connection between the oxidative degradation and dielectric properties is well established and is in good agreement with IR spectroscopy measurements. The amount of carbonyl, hydroperoxide and other polar groups is much higher for the irradiation in air than in other media, leading to higher dielectric losses. Disappearance of low temperature (? and ?) relaxations with gamma radiation confirmed great sensitivity of iPP structure to radiation-induced changes. Complete ?vanishing? of the ? relaxation in iPP samples irradiated in air is connected with a large radiation-induced oxidative degradation in this medium. Similar crosslinking, oxidation and dielectric behaviour was observed for the samples irradiated in water and acetylene, indicating DD water as a good crosslinking medium.

Colour removal of three reactive dyes by UV light exposure after electrochemical treatment

This study applies UV light irradiation after a low current density electrochemical treatment to degrade reactive dyes to remove wastewater colour. The combination of these two techniques improves the quality of the treated effluent with respect to only an electrochemical treatment. Synthetic dyeing effluents containing a reactive dye (C.I. Reactive Orange 4, C.I. Reactive Black 5 or Procion Navy H-EXL) and Na 2SO 4 were studied. Ti/Pt oxides electrodes and UV irradiation lamp (6 W, 254 nm maximum emission) were used. Kinetic constants of the UV irradiation step were calculated. The influence of chloride ion at 3 and 6 mA/cm 2 was evaluated. Results showed that, with a very small Cl − concentration (in the order of the net water content) the combined techniques provided full decolourization. The possible presence of 25 organic halogenated compounds was studied by gas chromatography–mass spectrophotometry (GCMS). Only four of them were detected after the electrochemical treatment at low intensity, mainly chloroform. Its concentration was found to be highly dependent of the Cl − concentration, being much lower when reducing the amount of chloride ion. In all cases, the chloroform concentration was dramatically reduced by further UV irradiation which destroyed it up to a 75%.

The fate of S-bearing species after ion irradiation of interstellar icy grain mantles

Context. Chemical models predict the presence of S-bearing molecules such as hydrogen sulfide (H2S) in interstellar icy grain mantles in dense molecular clouds. Up to now only two S-bearing molecules, namely sulfur dioxide (SO2) and carbonyl sulfide (OCS), have been detected in the solid phase towards young stellar objects (YSOs), while upper limits for solid H2S have been reported towards the same lines of sight. The estimated abundance of S-bearing molecules in icy grain mantles is not able to account for the cosmic S abundance. Aims. In this paper we studied the effects of ion irradiation on different icy targets formed by carbon monoxide (CO) and SO2 or H2S as mixtures and, for the first time, as layers. Methods. We carried out several irradiation experiments on ices containing SO2 or H2S mixed or layered with CO. The samples were irradiated with 200 keV protons in a high-vacuum chamber (P < 10 −7 mbar) at a temperature of 16‐20 K. IR spectra of the samples were recorded after various steps of irradiation and after warm-up. Results. We have found that the column density of H2 Sa nd SO2, as well as CO, decreases after irradiation, and the formation of new molecular species is observed. In the case of CO:SO2 samples, OCS, sulfur trioxide (SO3), ozone (O3), and carbon dioxide (CO2 )a re the most abundant species formed. In the case of CO:H2S samples the most abundant species formed are OCS, SO2, carbon disulfide (CS2), hydrogen persulfide (H2S2), and CO2. The profile of the OCS band formed after irradiation of the CO:H2S mixture compares well with the profile of the OCS band detected towards the high mass YSO W33A. Conclusions. Our results show that on a time scale comparable to the molecular cloud lifetime, the column density of H2S is strongly reduced and we suggest that this could explain the failure of its detection in the solid phase in the lines of sight of YSOs. We suggest that the solid OCS and SO2 detected in dense molecular clouds are formed after ion irradiation of icy grain mantles.

Coupled Electrochemical/Photochemical Patterning and Erasure of Ag0 Nanoclusters on Au Surfaces

A nitrospiropyran (1a) monolayer-modified Au electrode provides an active surface for the photolithographic patterning of an electrode with Ag(0) nanoclusters. Illumination of the monolayer-modified Au surface through a mask yields nitromerocyanine (1b)-patterned domains on the Au electrode that bind Ag(+) ions. The electrochemical reduction of the Ag(+) ions yields stable Ag(0) nanoclusters on the patterned domains, and this enables the SEM imaging of the resulting microstructures. The photoisomerizable and electroactive nitromerocyanine/Ag(0) nanoclusters exhibit several important features: (i) By the electrochemical oxidation of Ag(0) nanoclusters to Ag(+) ions, the patterned metallic nanoclusters are erased but stored in the form of Ag(+) ions, confined to the patterned monolayer. The stored information can be retrieved by the electrochemical reduction of the Ag(+) ions. (ii) The photoisomerization of the nitromerocyanine (1b)-modified domains to the nitrospiropyran (1a) state (lambda > 475 nm) coupled to the electrochemical oxidation of the Ag(0) nanoclusters to Ag(+) enables the removal of Ag(+) from the surface and its restoration for new patterning. (iii) The orthogonal patterning of the Au surface with Ag(0) nanocluster structures is accomplished by the stepwise coupled photochemical/electrochemical patterning of the surface by two (or more) irradiation steps through the mask.

Ultrashort laser subsurface micromachining of three–dimensional microfluidic structures inside photosensitive glass

AbstractA laser direct writing technique was used successfully to carry out subsurface micromachining of three-dimensional microfluidic structures. It involves simple steps of femtosecond laser irradiation to project a latent image of channels or chambers of various dimensions into a photosensitive Foturan glass, thermal annealing to produce crystallites of lithium metasilicates in the laser-irradiated regions, and use of a diluted hydrofluoric acid solution to remove the crystallized structures through selective chemical etching. The etched surfaces may be smoothened significantly through a secondary thermal annealing process. A microfluidic reagent mixer and reactor consisting of four cubic chambers and multiple channels was produced inside a single piece of glass to demonstrate that the technique can be used for rapid device fabrication without recourse to the cumbersome and expensive processes of alignment, stacking, bonding or assembly of the individual microcomponents. The direct writing technique makes it easy to integrate micro–optical and microfluidic components into a single chip.

Method of simulation of low dose rate for total dose effect in 0.18 μm CMOS technology

Three methods for simulating low dose rate irradiation are presented and experimentally verified by using 0.18 μm CMOS transistors. The results show that it is the best way to use a series of high dose rate irradiations, with 100 °C annealing steps in-between irradiation steps, to simulate a continuous low dose rate irradiation. This approach can reduce the low dose rate testing time by as much as a factor of 45 with respect to the actual 0.5 rad (Si)/s dose rate irradiation. The procedure also provides detailed information on the behavior of the test devices in a low dose rate environment.

YBCO Coated Conductors for Fusion Magnets

Coated conductors (CCs) are considered as an alternative to low temperature superconductors in fusion magnets. High magnetic fields are needed to confine the plasma, which can be generated by YBCO coated conductors at relatively high temperatures (50-77 K). The critical current densities of CCs improved continuously during the last few years and the production was scaled up. The conductors will be exposed to neutron radiation in a fusion magnet, which could potentially improve or degrade their properties. Industrial YBCO coated conductors were characterized by magnetization and direct transport measurements in magnetic fields of up to 15 Tesla and at temperatures between 50 and 85 K. The critical current, its anisotropy and the irreversibility line were determined. The measurements were performed on different samples, which were sequentially irradiated up to a fluence of 2 times 1022 m-2 (two times the ITER specification). The measurements were repeated after each irradiation step to investigate the change in the superconducting parameters. Depending on the production process of the CC and on the actual operation conditions, an increase or a decrease of the critical current density is observed. The measurements show that the performance of the CC nearly reaches the required specification for ITER conductors at present. Neutron irradiation generally does not degrade their properties in the operating range of fusion magnets.